oEPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/9-79-039
December 1979
Research and Development
Proceedings
6th
United States/Japan
Conference on
Sewage Treatment
Technology
1978
Cincinnati, Ohio
October 30-31
Washington, D.C:
November 2-3
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/9-79-039
December 1979*
PROCEEDINGS
SIXTH UNITED STATES/JAPAN CONFERENCE ON
SEWAGE TREATMENT TECHNOLOGY
Cincinnati, Ohio: October 30-31, 1978
Washington, D.C.: November 2-3, 1978
Office of International Activities
Office of Water and Waste Management
Washington, D.C. 20460
Office of Research and Development
Washington, D.C. 20460
Cincinnati, Ohio 45268
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
CINCINNATI, OHIO 45268
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DISCLAIMER
These Proceedings have been reviewed by the
U.S. Environmental Protection Agency and approved for
publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement
or recommendation for use.
11
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FOREWORD
Environmental improvement is a worldwide need. Maintaining
clean water supplies and managing municipal and industrial wastes is
a vital element of a quality environment.
The participants in the United States-Japan cooperative project
on sewage treatment technology have completed their sixth conference.
These conferences, held at 18-month intervals, give the scientists and
engineers of the cooperating agencies an opportunity to study and compare
the latest practices and developments in the United States and Japan.
These Proceedings of the Sixth Conference comprise a useful body of
knowledge on sewage treatment, which will be available not only to
Japan and the United States but also to all nations of the world who
desire it.
Aaninistrator
Washington, D.C.
111
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CONTENTS
FOREWORD. . iii
JAPANESE DELEGATION vi
U.S.-CINCINNATI DELEGATION. vii
U.S.-WASHINGTON DELEGATION................... viii
JOINT COMMUNIQUE.
JAPANESE PAPERS.
UNITED STATES PAPERS 409
v
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JAPANESE DELEGATION
DR. TAKESHI KUBO
Co-Chairman of Conference and Head of Delegation,
Vice President, Japan Sewage Works Agency
TOKUJI ANNAKA
Chief, Advanced Waste Treatment Section, Public
Works Research Institute, Ministry of Construction
HIDEO FUJII
Senior Advisor, Sewage Works Bureau, Tokyo
Metropolitan Government
SHIGEKI MIYAKOSHI
Head, Department of Construction, Sewage Works
Bureau, The City of Yokohama
DR. NAGAHARU OKUNO
Assistant Director, Department of Research and
Development, Japan Sewage Works Agency
TSUTOMU TAMAKI
Head, Regional Sewerage Works Division, City
Bureau, Ministry of Construction
KAZUO TANI
Director, Construction Division, Sewerage Bureau,
Osaka Municipal Government
VI
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UNITED STATES/CINCINNATI DELEGATION
FRANCIS M. MIDDLETON
General Chairman of Conference and
Head of Cincinnati U.S. Delegation,
Senior Science Advisor
Municipal Environmental Research
Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
FRANCIS T. MAYO
Director. Municipal Environmental
Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
LOUIS W. LEFKE
Deputy Director, Municipal
Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
DR. CARL A. BRUNNER
Chief, Systems and Engineering
Evaluation Branch
Wastewater Research Division
Municipal Environmental Research
Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
DR. ROBERT L. BUNCH
Chief, Treatment Process
Development Branch
Wastewater Research Division
Municipal Environmental Research
Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
DR. JOSEPH B. FARRELL
Chief, Ultimate Disposal Section
Treatment Process Development
Branch, Wastewater Research
Division, Municipal Environmental
Research Laboratory
U.S. Environmental Protection
Agency
Cincinnati, Ohio 45268
DR. IRWIN J. KUGELMAN
Chief, Pilot and Field Evaluation
Section, Technology Development
Support Branch, Wastewater Research
Division, Municipal Environmental
Research Laboratory
U.S. Environmental Protection
Agency
Cincinnati, Ohio 45268
LAWRENCE K. BARBER
Director of Manufacturing,
A. C. Lawrence Leather Co, Inc.
Hazelwood, North Carolina 28737
RICHARD A. VANDERHOOF
Director, Department of Sewers
Metropolitan Sewer District
of Greater Cincinnati
1600 W. Gest Street
Cincinnati, Ohio 45204
LEO WEAVER
Executive Director £ Chief Engineer
Ohio River Valley Water
Sanitation Commission (ORSANCO)
414 Walnut Street
Cincinnati, Ohio 45202
vn
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UNITED STATES/WASHINGTON DELEGATION
FRANCIS M. MIDDLETON CARMEN GUARINO
General Chairman of Conference Commissioner, City of
Senior Science Advisor Philadelphia Water Department
Municipal Environmental Research 15th § JFK Boulevard
Laboratory Philadelphia, Pennsylvania 19107
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268 ROBERT A. CANHAM
TORN T DHPTT Executive Director,
JOHN l. KHtTT Pollution Control Federation
Head of Washington U.S. Delegation ^Pennsylvania Avenue, N.W.
Deputy Assistant Administrator for ,, " . „' r onn^7
Water Program Operations, OWWM Washington, D.C. 20037
U.S. Environmental Protection Agency ^.r-r-n
Washington, D.C. 20460 DR. DANIEL P- SHEER
Planning Engineer,
ALICE BRANDEIS POPKIN Interstate Commission/Potomac
Associate Administrator for River Basin-ICPRB
International Activities 4359 East-West Highway
U.S. Environmental Protection Agency Bethesda, Maryland 20014
Washington, D.C. 20460
THOMAS P. O'FARRELL ROBERT V. DAVIS
Sanitary Engineer, Office of Executive Secretary,
Water Program Operations, OWWM Virginia State Water Control
U.S. Environmental Protection Agency Board
Washington, D.C. 20460 2111 Hamilton Street
WILLIAM J. LACY Richmond, Virginia 23230
Principal Engineering Advisor,
Office of Research and Development MICHAEL COOK
U.S. Environmental Protection Agency Chief, Facility Requirements
Washington, D.C. 20460 Division, Office of Water Program
Operations, OWWM
DR. STEPHEN J. GAGE U-S> Environmental Protection
Assistant Administrator for Agency
Research and Development Washington, D.C. 20460
U.S. Environmental Protection Agency
Washington, D.C. 20460 GREEN A> JQNES
JAMES V. BASILICO Director, Water Division
Chief, Community Sources Staff Region III
Waste Management Division, OEET U.S. Environmental Protection
U.S. Environmental Protection Agency Agency
Washington, D.C. 20460 Philadelphia, Pennsylvania 19108
KIRK MACONAUGHEY
Japances Coordinator MILLARD H. ROBBINS, JR.
Office of International Activities Executive Director,
U.S. Environmental Protection Agency Upper Occoquan Sewage Authority
Washington, D.C. 20460 Manassas, Virignia 22110
viii
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H-
X
UNITED STATES AND JAPAN DELEGATES TO
THE SIXTH CONFERENCE, CINCINNATI, OHIO
-------
DR. TAKESHI KUBO, JAPANESE TEAM LEADER RESPONDS TO
OFFICIAL OPENING OF SIXTH CONFERENCE, USEPA, CINCINNATI, OHIO
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X
H-
MR. JOHN J. CONVERY, NEWLY APPOINTED GENERAL CHAIRMAN OF THE JOINT
U.S./JAPAN CONFERENCES ADDRESSING DELEGATES OF SIXTH CONFERENCE, WASHINGTON, D.C
-------
ALICE BRANDEIS POPKIN, ASSOCIATE ADMINISTRATOR
FOR INTERNATIONAL ACTIVITIES GREETS JAPANESE DELEGATES
AT SIXTH CONFERENCE, WASHINGTON, D.C,
DR. TAKESHI KUBO AND MR. ROBERT A. CANHAM, EXECUTIVE DIRECTOR,
WATER POLLUTION CONTROL FEDERATION DISCUSS AREAS OF MUTUAL INTEREST
AT SIXTH CONFERENCE, WASHINGTON, D.C.
xii
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JOINT COMMUNIQUE
SIXTH UNITED STATES/JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
WASHINGTON, D.C.
NOVEMBER 3, 1978
1. The Sixth United States/Japan Conference on Sewage Treatment
Technology was held in Cincinnati, Ohio, and Washington, D.C.,
from October 30 through November 3, 1978.
2. The Japanese delegation headed by Dr. T. Kubo, Co-Chairman
of the Conference, Vice President, Japan Sewage Works Agency,
was composed of three National government officials and three
local government officials.
3. Mr. Francis M. Middleton, formerly Senior Science Advisor,
Municipal Environmental Research Laboratory, Cincinnati, Ohio,
US EPA, served as General Chairman and Head of the Cincinnati
delegation which consisted of six US EPA officials and three
representatives of industry, local government and regional water
basin commission.
Mr. John T. Rhett, Deputy Assistant Administrator for Water
Program Operations was Head of the Washington delegation which
consisted of three US EPA, one state and three local government
officials. In addition to government officials, conference
delegates included Mr. Robert A. Canham, Executive Director,
Water Pollution Control Federation and Dr. Daniel P. Sheer,
Planning Engineer- Interstate Commission on the Potomac River
Basin.
4. Prior to the Conference, the Japanese delegation visited
San Jose and Pomona Water Reclamation Plant, Joint Water
Pollution Control Plant, Los Angeles County Sanitation
Districts, R. L. Jackson Sewage Treatment Plant, Clayton County
Water Authority, Dalton County Utility Authority, Georgia, Mill
Creek Sewage Treatment Plant, City of Cincinnati, Ohio and Ohio
River Valley Water Sanitation Commission. In the Washington,
D.C. area, the treatment facilities in Arlington and Alexandria,
Virginia, and the Occoquan Water Reclamation Plant, Upper Occoquan
Sewage Authority were visited.
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5. Principal topics of the Sixth Conference in Cincinnati were
biological nitrogen control, wastewater and sludge research program,
air pollution discharges from sewage sludge incinerators, several
applications of pure oxygen activated sludge systems for treating
mixtures of high organic industrial and domestic wastes, tannery
waste treatment and progress in instrumentation and automation.
Principal topics in the Washington Conference were: Institutional
Structures of Water Pollution Control in Japan; Financing of Sewage
Works Including Sewer User Charge System; Mission and Activities of
Japan Sewage Works Agency at Present and Future; the 1977 Mid-Course
Corrections" to the Federal Clean Water Program; Construction Grants
Program--A Regional Perspective; Water Quality Programs of the
Virginia State Water Control Board; Water Supply and Wastewater
Management Planning in the Washington, D.C. Metropolitan Area;
The Occoquan Watershed Policy--A Comprehensive Program to Save
a Water Supply; and Pretreatment Standards: EPA Strategy to Curb
Hazardous Industrial Discharges.
6. Progress reports of joint research works were presented from
both sides during the conference. Data and findings on the joint
research projects were mutually supportive and provided increased
insights with the nature of the problem and potential solutions.
This was especially true of metal emissions from incinerators and
instrumentation performance.
7. A decision was made to continue the productive joint research
efforts on municipal sludge disposal, agricultural use of sludge
and instrumentation and automation. The fourth area of joint
research, biological nitrogen control, is to be broadened to
include biological removal of specific contaminants including
toxic substances.
8. Recent engineer exchanges included a two-week visit to Japan
by Mr. Richard I. Field, Chief of the Storm and Combined Sewer
Section, Municipal Environmental Research Laboratory, Cincinnati,
and a six-month visit to the U.S.A. by Mr. K. Tanaka and Mr. S.
Hiromoto of the Japan Sewage Works Agency. The parties agreed
in principle to the continuation of the Engineer Exchange Program.
Two nominations for Japanese participation in the Program during
1979 were identified.
9. At the end of the Cincinnati Conference, a ceremony was held
awarding an honor to Mr. F. M. Middleton for his outstanding
contribution to the exchange program between the two countries
since 1971.
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10. Mr. John J. Convery, Director, Wastewater Research Division,
MERL, was named to succeed Mr. Middleton as General Conference
Chairman for the United States.
11. It was proposed by the Japanese side that the Seventh
Conference shall be held in Japan about April 1980.
12. A Proceedings of the Conference will be printed in
English and in Japanese.
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JAPANESE PAPERS
PAPERS FOR THE SIXTH US/JAPAN
CONFERENCE ON SEWAGE
TREATMENT TECHNOLOGY
Cincinnati, Ohio
October, 30-31, 1978
Ministry of Construction
Government of Japan
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CONTENTS
CHAPTER 1 BIOLOGICAL NITROGEN CONTROL 8
by K. Kobori, T. Annaka and K. Sakai, Public Works Research
Institute, Ministry of Construction
I. BIOLOGICAL NITROGEN CONTROL IN ACTIVATED SLUDGE
PLANT (LABORATORY STUDY) 10
II. FIELD SURVEY ON NITRIFICATION AT EXISTING SEWAGE
TREATMENT PLANT 52
III. NITRIFICATION ACCELERATION BY ALUM ADDITION TO
THE PRIMARY SEDIMENTATION TANK 58
IV. STUDIES ON NITRIFICATION PROCESS AT SMALL-SCALE
SEWAGE TREATMENT PLANT 66
CHAPTER 2 PRACTICE OF NITROGEN REMOVAL BY BREAKPOINT
CHLORINATION PROCESS 87
I. PRACTICE OF NITROGEN REMOVAL BY BREAKPOINT
CHLORINATION PROCESS 88
by H. Fujii, and A. Mori, Planning Division, Department of
Sewage Works, Tokyo Metropolitan Government
II. THE PREVENTION OF FORMATION AND REMOVAL OF
CHLORINATED ORGANICS IN WASTEWATER 103
by T. Annaka, and H. Watanabe Public Works Research Insti-
tute, Ministry of Construction
CHAPTER 3 DEWATERING AND INCINERATION OF SEWAGE
SLUDGE WITH PULVERIZED COAL 115
by S. Miyakoshi, Construction^ Division, Sewage Works Bureau,
Yokohama Municipal Goverment
CHAPTER 4 FACTS ABOUT EMISSION CONTROL EQUIPMENTS FOR
SEWAGE SLUDGE INCINERATOR 128
by N. Okuno, R &D Division, Japan Sewage Works Agency
CHAPTER 5 PILOT PLANT STUDY OF TANNARY WASTE TREAT-
MENT BY OXYGEN ACTIVATED SLUDGE PROCESS ... 162
by M. Kashiwaya, R &D Division, Japan Sewage Works Agency
and T. Annaka, Public Works Research Institute, Ministry of
Construction
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CHAPTER 6 SEVERAL APPLICATIONS OF PURE OXYGEN
ACTIVATED SLUDGE SYSTEMS FOR TREATING
MIXTURE OF HIGH ORGANIC INDUSTRIAL AND
DOMESTIC WASTEWATERS 184
by N. Okuno, R &D Division, Japan Sewage Works Agency
CHAPTER 7 REMOVAL OF COLOR FROM MUNICIPAL SEWAGE
CONTAINING TEXTILE WASTEWATER 195
by K. Murakami and T. Annaka, Public Works Research Insti-
tute, Ministry of Construction
CHAPTER 8 DEVELOPMENT AND EVALUATION N OF AUTOMATIC
WATER QUALITY MONITORING EQUIPMENTS 220
by T. Annaka, K. Murakami, and S. Kyosai, Public Works
Research Institute, Ministry of Construction
I. CURRENT STATE OF THE DEVELOPMENT OF AUTOMATIC
WATER QUALITY MONITORS FOR HAZARDOUS
SUBSTANCES IN WASTEWATER 222
II. DEVELOPMENT OF CONTINUOUS WATER QUALITY
MONITORING EQUIPMENTS FOR SEWAGE TREATMENT 234
III. DEVELOPMENT OF AUTOMATED CONTINUOUS P-D,
HYARO AND NH3 ANALYZERS 247
IV ALUM DOSING METHOD IN ALUM PRECIPITATION 255
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CHAPTER 1
I BIOLOGICAL NITROGEN CONTROL
I. BIOLOGICAL NITROGEN CONTROL IN ACTIVATED SLUDGE
PLANT (LABORATORY STUDY) 10
1 C 10
1. Summary
1 "7
2. Succession of Microorganisms in Activated Sludge in Nitrification
2.1 Experiment Method
2.2 Test Results and Discussion 13
2.3 Summary 21
3. Nitrification Study by Continuous Operation 22
3.1 Test Method 22
3.2 Results and Discussion 24
3.3 Summary 35
4. Experiments Concerning Effects of Trace Elements on Nitrification 36
4.1 Test Method 36
4.2 Test Results 38
4.3 Discussion 43
4.4 Summary 45
5. Determination of Nitrification Bacteria and Heterotrophs in Activated
Sludge 46
5.1 Testing Procedure 46
5.2 Result and Discussion 47
5.3 Summary 51
II. FIELD SURVEY ON NITRIFICATION AT EXISTING SEWAGE
TREATMENT PLANT 52
i
1. Method of Survey 52
2. Results of Survey 52
3. Summary 57
Ml. NITRIFICATION ACCELERATION BY ALUM ADDITION TO
THE PRIMARY SEDIMENTATION TANK 58
Introduction 58
1. Outline of the Facilities 58
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2. Influence on Treatment Due to Addition of Alum to Primary
Sedimentation Tank 59
3. Acceleration of Nitrification 62
3.1 Nitrification by Conventional Process 62
3.2 The Effects of pH Adjustment When Adding Alum to Primary
Sedimentation Tank 62
3.3 Nitrification at High Loading 64
3.4 Nitrification in Winter 65
4. Summary 65
IV. STUDIES ON NITRIFICATION PROCESS AT SMALL-SCALE
SEWAGE TREATMENT PLANT 66
1. Introduction 66
2. Outline of the Plant 66
3. Outline of Survey Results 68
3.1 Results of Treatment by Initially Proposed Flow Chart 68
3.2 Proposed Improvement Measures Based on Initial Operational
Condition 70
3.3 Results of Survey of Proposed Improvement Measures 70
4. Summary 86
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CHAPTER 1
BIOLOGICAL NITROGEN CONTROL
I. BIOLOGICAL NITROGEN CONTROL IN ACTIVATED SLUDGE PLANT
(LABORATORY STUDY)
The objectives of th,e study are: 1) to determine physical, chemical and
biological operational conditions for effective nitrification in the conventional
activated sludge process. 2) to define optimum operational variables to maintain
effective nitrification and organic removal at existing sewage treatment plants with
the least modification of the facilities. 3) to develop recovery techniques of organic
carbon from anaerobic digester supernatant, for carbon source of denitrification
process.
Effect of pH and sludge retention time (SRT) on nitrification has been
studied by the laboratory scale plug flow type aerators under the temperature of
20° C, using synthetic sewage with the substrate of dextrin, meat extract, yeast
extract, peptone, ammonium sulfate and other inorganic components.
Effects of seawater, Mg, anions and phosphate buffer on the activities of the
nitrifiers in activated sludge have been studied separately by a shaking culture
method and an aeration method. Synthetic seawater used here was the one devel-
oped by Lyman et al. (1949). Determination of the nitrifiers was followed by IBP
(1968).
1. SUMMARY
Nitrification in activated sludge process: 1) Result of the field survey showed
that numbers of nitrifiers were in the range of 103 to 104N/m (Dec. 1975) and
Nitrobacter was more than Nitrosomonas. 2) Analysis of "Annual Sewage Treat-
ment Plants' Report" indicated: i) Highest degree of nitrification under the
temperature of 18 ~ 23°C. ii) Minimum effluent dissolved oxygen level of 28% of
saturation value for effective nitrification. 3) Generation time of the each organisms
at the temperature of 20°C in mixed culture system was; ammonium oxidizers 7.4
hours, nitrite oxidizers 11.6 hours, activated sludge ciliata 2.5 days, Rotifera 3.5
days and Sarcodina 13.6 days. 4) More than 104N/ml of nitrifiers would be neces-
sary to obtain nitrate in the effluent. 5) Nitrification activity of the biomass was
not likely to be interferred with a shock load of 2 hours when pH was kept within 4
to 11. 6) Above nitrification activity is affected by organic loadings. When pH of
the system goes down from 8, which, is an optimum pH level of nitrification, to the
lower, effect of organic loadings become severe. The long SRT is necessary to ob-
tain the same extent of nitrification.
7) As for the biological fauna, activated sludge ciliata and Rotifera were
dominant when pH was within the range of 7 to 8 and Sarcodina was easily to
appear when it goes down to 6. This tendency was much clearer when STR of the
system was kept longer. 8) Rotifera and Sarcodina could be used as index organisms
to determine whether nitrification could be expected or not in the system.
9) Optimum pH for nitrification was 8. To achieve substantial nitrification, SRT of
10
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the system should be kept more than 3,6, 11 days when pH is 8, 7, 6 respectively
under the temperature of 20°C. 10) Removal efficiency of soluble organics was
more than 97% in all the experimental runs regardless to the pH and SRT. High
solid removal efficiency was obtained when SRT was maintained between 5 and
10 days. However, when SRT was less than 3 days, solid removal was deteriorated
due to the bulking of the sludge and when SRT was more than 10 days, solid
washout was observed due to the deflocculation and floatation of the denitrified
sludge.
Effect of trace inorganics: 1) Growth of fresh water nitrifiers were inhibited
when cultured with more than 40% of sea water, while maximum growth rate was
obtained when no sea water was added at all.
2) Under the case that both sea water and fresh water nitrifiers were
co-inhabited, maximum growth rate were obtained when cultured just in sea water.
However, lag phase was shortest when sea water was added 40 to 60%. This may
indicate that changes in "environment" of the nitrifying bacterias is related to the
length of the lag phase.
3) Results of shaking culture tests indicated that addition of sea water provides
buffer capacity to the system rather than accelerating nitrification by the effects of
trace materials in sea water. In all cases of the run, degree of nitrification was
preceded by the addition of sea water. As pH in the system has kept relatively high
due to the buffur action of sea water, activities of Nitrobacter seemed to be
restrained and nitrite nitrogen be readily to exist in the system.
4) Growth rate on Nitrosomonas in 40% mixture of sea water under the
existence of Tris-buffer was about 1.34 times as much as that in 20% mixture. This
was probably due to the favorable effect of Mg in sea water. However, ammonium
oxidation rate per Nitrosomonas was more in 20% mixture than that in 40%. 5) In a
system in which culture time was less that nitrifiers' generation time, phosphate was
effective to accelerate nitrification. Optimum dose was 13mM for ammonium
oxidation. 6) High dose of anions deteriorates the rate of nitrification under the
existence of phosphate. Deterioration effect of anions is summarized as follows:
NO3-(29mM)>F-(48mM)>SO42-(76mM)>r(80mM)>Br-(140mM)>Cr(170mM).
Numbers in parenthesis are the critical concentrations which deteriorate the rate of
nitrification down to 50%.
Bacteria culture procedure: 1) Dispersion technique of activated sludge for
bacteria determination applied here was ultrasonic shredding. Selected power for
the apparatus was 25 W and 2.5 minutes for shredding. Those are recommended
values. 2) Recommended procedures for bacteria determination for counting are
10 day incubation for heterotrophs in 20°C with Trypton media and for nitrifiers
20 — 40-day when IBP method is applied.
11
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2. SUCCESSION OF MICROORGANISMS IN ACTIVATED SLUDGE
IN NITRIFICATION
It is a well known fact that microorganisms contained in activated sludge differ
in types and compositions with influent quality, organic loads, return sludge rate
and dissolved oxygen and so on.
This particular study was conducted to determine operating conditions that
would promote nitrification at activated sludge treatment facilities by conducting
examinations of the changes of hetrotrophs, nitrification bacteria, protoxoa and
metazoa besides studying organic removal and nitrification rate of the mixed culture
system based on SRT as an indicator of activated sludge. SRT is one of the factors
that is detrimental in dominating the types and compositions of micro organisms
and is an indicator for the generation time of microorganisms.
Studies were also made on the influence of sudden change of the pH against
nitrification.
2.1 EXPERIMENT METHOD
Five Inhoff type cones were used for the experiment. (Fig. 2.1).
Fig.-2.1 Batch Type Testing Apparatus
12
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The synthetic sewage mainly composed of protein such as meat extract,
peptone was fed to the aerators by batch method with aeration time being 22 hours
and sedimentation time 2 hours. Activated sludge obtained from domestic sewage
treatment plant was seeded to the each aerator. The experiment was conducted in a
20°C constant temperature room. pH was controlled at a range between 7 and 8
continuously by automatic regulator, and the SRT was set by controlling MLSS in
the aerators. Namely, influent organic load was kept constant while the MLSS was
adjusted each aerator at 500, 1,000, 1,500, 3,000 and 6,000 mg/1.
Nutrient bacteria, nitrite bacteria, nitrate bacteria, protozoa and metazoa in
mixed liquor were determined beside water quality analysis.
The trypton glucose culture medium was used for determination of hetero-
trophs, culturing at 20°C for 10 days. All colonies emerging from the culture were
counted. The nitrification bacteria determination was followed by the IBP.
2.2 TEST RESULTS AND DISCUSSION
The summary of the results is shown in Table 1. The shortest SRT was about
4 days while the longest 60 days. As to the sludge characteristic, when the F/M ratio
was high, SVI became 125 and growth of filamentous bacteria was observed
resulting in bad sedimentation condition. However, when the F/M ratio maintained
lower, or in the longer SRT condition, protozoa in the sludge became affluent. And
the SVI was easy to be maintained less than 100.
The organic load was estimated to be between 0.2 and 1.5 g/ss.g/day from the
following: TOC-SS load 0.06 - 0.58 g/ss.g/day; and BOD-SS load based on the
relationship between TOC and BOD (observed ratio: BOD = 2.78 TOC).
Table-2.1 Average Values of Analytical Results
Phase
SRT (day)
MLSS (mg/l)
MLVSS (mg/1)
MLVSS/MLSS
TOC Load (mg/ss-g/day)
Removed TOC (mg/ss-day)
Removal Rate (%)
SS (mg/1)
Removal Rate K-N
(%) Org-N
T-N
Nitrification Rate (%)
A
3.65
670
647
0.966
538
489
91.0
49.1
43.6
91.9
35.1
11.6
B
5.82
1,202
1,089
0.906
308
288
93.5
32.4
50.8
95.4
25.7
36.5
C
9.60
1,626
1,465
0.901
213
198
92.5
31.4
59.4
91.3
20.4
55.8
D
18.01
3,083
2,585
0.839
115
107
93.0
39.2
92.1
91.2
3.8
97.1
E
59.3
5,979
4,618
0.772
58.6
54.6
93.1
22.2
93.6
91.5
-0.1
99.0
13
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The SRT in this paper is defined as below.
SRT (days) =-
Vx S
As + ss.q
V: Aerator capacity (liter), S: MLSS (mg/1),
s: Excess activated sludge (mg), ss: effluent SS (mg),
q: flow (1/d).
SRT expresses the retention rate of activated sludge within the system. At
normal condition, the SRT is subjected to sludge production which depends upon
the volume of removed organic matters to be converted into sludge. The conversion
rate to sludge differs according to sewage strength and for the municipal sewage the
rate is about 0.7 while the synthetic sewage used in this test was about 0.21 which
means the sewage is easily degradable. The relation between organic load and SRT
in this study is shown in Fig. 2-2. The longer the SRT the smaller the F/M ratio.
f
n
0.6
0.5
0.4
0.3
0.2
0.1
Fig.-2.2 SRT vs Loading
2345 10 20 30 4050
SRT (day)
0.12
0.10
0.08
0.06
0.04
0.02
0
14
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2.2.1 SRT and Removal Rate
The removal rate of organic substances under each run is in the range of 91 to
93.5 percent, and there was little difference in removal rate.
The removal rate of nitrogen in terms of TKN increased in proportion to SRT
and reached 90% when SRT exceeded 18 days. In each run, organic nitrogen was
removed mostly and removal rate was more than 91%. Total nitrogen removal rate
was 35% at about four days of SRT. The removal rate decreased in proportion to
the increase in SRT while nitrification rate increased. (Fig. 2.3). When SRT is kept
over 18 days, mostly all nitrogen were converted to nitrate. When SRT increased,
self oxidation in the sludge resulted in the release of ammonium to increase the total
amount of nitrogen in effluent. The nitrate concentration, up until the 18 days of
SRT, followed a straight ascending line. And beyond the 18 days, amount of TKN
in the influent served as the limiting factor of nitrification. Since the amount of
nitrite was extremely low in this SRT range, there was a possibility that the
nitrification rate was hindered by nitrite in system.
Fig.-2.3 TOC Removal Rate, Nitrification Rate and SRT
(pH 7-8)
100
80
60
40
20
0
-o-
TOC removal rate /'
Nitrification rate —- A t
(mg/l)
I f *[ I . i i i I I I I I i
345
SRT
10
20 30 40 50
2.2.2 Bacteria Population and SRT
The bacteria growth rate can be described as follows:
dN
d t
or
'= jLlN
N
(D
(2)
NO : Number of bacteria at i±
N: Number of bacteria at t2
IJL: Specific growth rate (1/t)
tg: Average Generation Time (t)
Cn2 0.693
(3)
15
-------
Generally, the growth rate of nitrification bacteria is known to be between 10
and 12 hours, although some species require 20 or 40 hours. When compared to the
growth of heterotrophs, the growth rates of autotrophs are slower owing to energy
efficiency. The numbers of nitrification bacteria in activate sludge also changes in
proportion to the length of SRT.
The relationship between bacteria number and SRT obtained is as shown in
Fig. 2.4. With regards heterotrophs, constant number was maintained between 10
and 109 in this SRT range and thus the substrate in the system was regarded as the
ruling factor. Furthermore, the value was close to the one obtained from the
activated sludge at an existing plant. The nitrite bacteria increased in proportion to
the SRT and reached the maximum value of 107 in number when SRT was 7 days
while the nitrate bacteria were between 105 and 107. The existed number of nitrate
bacteria was less than nitrite bacteria.
Fig.-2.4 Relation between SRT and Bacteria Number
heterotrophs
Nitrite bact.
S- 5
^
OJ •—-
_Q
Nitrate bact.
4 5
SRT (day)
10
20 30 40 50
This fact also was confirmed by the water quality analysis that resulted in low
concentration of NCT2 in effluent. This indicates that the NO~2 have acted as the
ruling factor against the growth of nitrate bacteria.
When nitrification bacteria are to be maintained in maximum concentration
with the substrates being the ruling factors similar to heterotrophs, the system
requires SRT of over 10 days. At existing plants, although it is affected by
operational factors, it is considered possible to designate operating SRT by
estimating the maximum yield of nitrification bacteria by TKN concentration.
Since it is possible to consider that the maximum yield of nitrification bacteria
is maintained at each designated SRT, from the relationship as shown in Fig. 2.4, the
growth rate of nitrification bacteria (ju, I/day) and generation time (tg.h) are
calculated as follows: for nitrite bacteria /u = 2.26, tg = 7.4h and for nitrate bacteria
fi - 1.44, tg = 11.6h respectively. Based on this generation time, from the
relationship between nitrite bacteria and nitrate bacteria (Fig. 2-5), the minimum
16
-------
culture time or SRT can be obtained from Equation (2) (3) on bacteria
multiplication rate after obtaining the nitrification bacterial number based on the
assumption that the nitrification of TKN attained 100 percent.
Fig.-2.5 Nitrification Bacteria and Amount of Nitrification
9 r
8
Nitrite bact.
S Nitrate bact.
(O) (O)
(•) (•)
Nitrification over 97 percent
I
I
I
I
I
0 10 20 30 40 50 60 70 80 90 100
(NO; + NO~3)-N (mg/l)
2.2.3 Protozoa and Metazoa in the System
Table 2.2 shows the microscopic test results. From these results, the growth
condition can be grasped to a certain degree. When organic load is high, the number
of swim type microorganisms is great. And when the load decreases, the population
of swim type diminishes accordingly. In this case, the Pleuromonas is quoted as the
index. When settlerability of activated sludge sedimentation is good, it is generally
regarded that the fix type and worm type microorganisms increase in number. And
similar tendency was observed in this study. In the condition of aerobic digestion or
extended aeration system, Rotifera, Arcella and Euglypha were frequently observed.
In this case, they were observed when load was low. Also filamentous bacterium,
related microorganisms to bulking, appeared in proportion to the load. The
filamentous bacteria that appeared here included those in divided and shredded
forms. Zoogloes also were detected as Z-ramigera and Z-filpendula coexisting.
The observation of the relationship of organic load and biological fauna
indicated that the organic load and SRT are also in relationship and that the species
of fast multiplying rate become dominant when SRT is short and those of slow
growth rate appeared when SRT become longer to increase in variety. The relation-
ship between SRT and biological fauna is shown in Fig. 2.6. Protozoa of fix type
and worm type appeared when SRT was over 3 days, Rotifera over 6 days, and
Sarcodina much longer. Similar to bacteria, the growth rate and generation time are
calculated from Fig. 2.6 as follows: for Protozoa ju = 0.28 I/day, tg = 25 days; for
17
-------
Rotifera //= 0.20 I/day, tg = 35days; and for Sarcodina n = 0.05 I/day,
tg= 13.6 days. Rotifera rank at the top of food chain and are polyphagia thus
showing such tg level.
With regards loricate amoeba, it is often observed when organic loading is
maintained low like in extended aeration or in aerobic digestion processes.
Fig.-2.6 Relation Between SRT and Protozoa Sarcodina, Protozoa
o o-, 400
x102
8
ra -^ 6
o E
°^
ro ^
co— 2
Protozoa
Rotifera
Sarcodina
300
200
o
cc
100
345 10
SRT (day)
20 30 4050
Being loricate, the percentage of such ameoba being preyed upon is low and
their generation time being to the short category.
The microscopic studies of protozoa and metazoa revealed that the organisms
that were identifiable also maintained intimate relationship with SRT in activated
sludge. Furthermore, concerning the Flagellate organisms observed when organic
loading was high, as the substrate became the ruling factor when organic substrate
became low in concentration because they utilize soluble ingredients, they were
handicapped in the race to consume energy. The swim type ciliata appeared were
few when TOC-SS load were in the range of 0.2 — 0.3 mg/ss.g/day, and they were
detected when the load was either higher or lower than this range.
2.2.4 Organism Index Predicting Nitrification Activity
The attempt to grasp activated sludge condition by microscopic study results is
one of the important procedures to maintain and control biological treatment.
To assume nitrification conditions from the results of microscopic studies, the
relationship between nitrification bacteria concentration and protozoa (fix type plus
worm type) shown in Fig. 2.4, Fig. 2.6 and Table 2.2 was used to develop Fig. 2.7.
There is a clear corelation between nitrifier number and protozoa. It is possible to
expect nitrification when protozoa of fix and worm type with comparatively long tg
exist in quantity. This figure shows just an example, and it is necessary to
accumulate data at actual existing plants. With regards Rotifera, Arcelia and
Euglypha, they were often observed in existing treatment plants thus can be
considered an effective index to predict nitrification activity.
18
-------
Table-2.2 Organisms Survey Result
Phase
Sarcodina
Amoeba
Arcella
Euglypha
Flagellate
Pleuromonas
Ciliata
Swim, type
Litonotus
Unknown g.
Worm, type
Aspidisca
Euplates
Fix, type
Vorticella
Epistylis
Cpercuraria
Unknown g.
Rotifera
Filamentous bact. (%)
SRT (day)
A
243
243
30,800
1,267
1,170
97
0
1,215
389
729
97
0
50
3.63
B
29
29
1,409
0
0
340
291
49
4,672
1,321
1,268
437
1,651
49
30
5.82
C
29
29
428
324
324
1,228
1,142
96
6,285
571
1,714
829
3,171
0
5
9.60
D
200
171
29
200
1,200
1,200
1,114
1,000
114
5,877
620
571
143
4,543
400
2
18.01
E
1,622
371
1,257
171
1,000
1,000
486
457
29
1,771
257
200
200
1,114
400
59.3
Fig.-2.7 Relationship between iMitrif ication Bacteria and Protozoa
8
I 5
01
_o
~ 4
Protozoa
(fix+worm.t.)
o NO^ Bacteria
• NO; Bacteria
I
I
I
4567
Prot N x 103/ml
10
19
-------
2.2.5 The Influence of pH on Nitrification Activity
Experiments were conducted to see the effect of pH change on the nitrification
activity. Two procedures were chosen for the experiment. One is that four hour
reaction time aerators were used for each pH condition between 4 and 14. The
other is that after two hours of reaction at a set pH, the pH was adjusted to 7 for
further reaction of four hours.
Concerning the optimum pH for nitrification bacterial activity, although
researchers differ in opinion with regards the optimum pH range, it is generally
regarded best between 7 and 8.5.
The reaction time for these experiments was too short for multiplication of
nitrification bacteria, and the tests were to simply compare the pH effects against
enzyme reaction. Fig. 2.8 shows the relationship between pH and nitrification rate.
Fig.-2.8 Relation between pH and Nitrification
0.8 r
(4 hr. reaction time)
pH
Maximum rate was obtained in the neighborhood of pH 8. It was 0.7 mg.
(NO~2 + NO~3) - N/g.ss/d. The Optimum pH range was 8 ± 0.5. The forms of pH
and nitrogen were as shown in Fig. 2.9. On the acidic side, more ammonium residue
was found, while on the alkaline side, more organic nitrogen was detected. In terms
of total nitrogen amount, it was found increasing on the alkaline side perhaps due to
elution of decomposing inert organisms and cells when pH was above 11.
Fig. 2.10 shows that, the inhibition occurred when contacted with fixed pH for
a short time and then adjusting the pH to 7. Within the range of ph 4 and 11, even
when contact was made with each pH for two hours, little inhibition was observed
against nitrification activity when adjusted to neutral later on. It also became
obvious that there are strong resistance against sudden change in pH shock load
deriving from the inflow of industrial waste water.
20
-------
Fig.-2.9 pH and Form of Nitrogen
100
c 80
CTl
O
| 60
c
ro
| 40
Q.
£ 20
0
Org.N
NHJ-N
I
8
9 10 11 12 13 14
pH
MLSS 2,400-3,000 mg/l
Fig.-2.10 Influence on Nitrification Rate when Adjusted to pH 7 after 2 Hours
Contact with Set pH
0.25
0.20
+ -i?
I C4 C3)
O £
0.15
0.05
0
10 11 12 13 14
pH
MLSS 2,000- 2,700 mg/l
2.3 SUMMARY
It became clear that the biological fauna in activated sludge was subjected to
SRT. The amount of nitrification bacteria for sufficient nitrification was over
104 N/ml. The generation time of the biological fauna in mixed culture was as
follows: Nitrite bacteria 7.4 hours; Nitrate bacteria 11.6 hours; Flagellate of fix and
worm type 2.5 days flotifera 3.5 days and Loricate Ameoba 13.6 days. It is also
effective to expect substantial nitrification by the control of treatment facilities
with SRT required to maintain nitrification bacteria based on generation time. It is
also possible to grasp the nitrification condition of plants by indexing Rotifera and
Loricate Ameoba by microscopic examinations.
Maximum rate of nitrification in short time reaction was obtained at around
pH 8. There were no changes observed in total nitrogen at pH 5 to 9, and the
balance of nitrogen forms was affected by nitrification activity. As organic nitrogen
increased on the alkali side, total nitrogen also increased. In the range of pH 4
to 11, even when contact was made with each pH for two hours, it was possible to
continue nitrification activity after being neutralized.
21
-------
3. NITRIFICATION STUDY BY CONTINUOUS OPERATION
In this study, a continuous testing apparatus of plug flow type aerators were
used to control SRT and pH to determine their influence on nitrification.
3.1 TEST METHOD
In this test, four sets of continuous testing apparatus (A, B, C, D) of 60 liter
aeration tanks and 30 liter sedimentation basins were employed. As shown in
Fig. 3-1, the tests were conducted by continuously feeding synthetic sewage in
constant temperature room of 20° Centigrade. The tests were broken up in three
stages as follows:
I) The pH was set at 8 and SRT was varied in each unit. II) at pH 7, III) and at
pH 6, Furthermore, the air flow was thoroughly controleld to prevent the DO from
becoming a ruling factor in this experiment.
The pH control was done by Automatic pH Regulating Units at 2 points. The
chemicals for pH control were NaOH and HC1 diluted by tap water. SRT was
indirectly controlled by introducing the following method. The concentration and
flow rate of influent to all units were fixed at the same amount. And the MLSS
concentration in each unit was maintained in different level. By this manner, each
unit was fixed to have different organic loadings. SRT was controlled by extracting
the set amount of waste activated sludge. The MLSS in the aeration tank of Unit A
was set at 500 mg/1, B 1,000 mg/1, C 1,500 mg/1, and D 3,000 mg/1.
In the operation care was placed on controlling MLSS because it was necessary
to maintain as constant as possible the organic loadings. Therefore, efforts were
exerted to sludge withdrawal. Further, periodic checks were conducted on the flow
rates of pumps. The daily sampling was made by the 24-hour composite sampling
by analyzing the Transparency, pH, SV30, MLSS, MLVSS, SS, BOD, COD, TKN,
ammonia, nitrite and nitrate. A once weekly determination was conducted of
hetrotrophs, nitrification bacteria, protozoa, and metazoa. The counting method
based on plane culture was employed for hetrotrophs determination while the MPN
Method was introduced to count nitrification bacteria after 100 days of culture.
With regards counting of protozoa and metazoa, the microscopic method was
incorporated. The culture media used for counting the bacteria were as follows:
Hetrotrophs: Trypton glucose culture medium (pH 7)
Tripton: 20g, glucose lOg, and agar 9g are dissolved in one liter
of water.
Bacteria infection: 115°C, 30 minutes.
Nitrification Bacteria Quantitative Culture Medium:
A Solution: KH2PO4 100 mg., MgSO4 50 mg, CaCl2 20 mg.,
NaHCO3 200 mg, EDTA-Fe 6 //g, CaCO3, SiO2 trace
dissolved in one liter of ion exchange distilled water.
Nitrite Bacteria: A Solution plus (NH4)2 SO4 30 mg
Nitrate Bacteria: A Solution plus KNO2 30 mg
(filtered by 0.2 n membrane filter.)
22
-------
Fig.-3.1 Outline of Testing Apparatus
I I
I: Tap Water II: Synthetic Sewage
M _i L M
No.1 No.2
Aeration Tank
P: Pump
M: Stirrer
(
^
T
' /
I
T
Treated Water
•JTimerl
Sedimentation Basin
Table-3.1 Synthetic Sewage
(BOD = 150 mg/1)
Substrate
Dextrin
Meat extract
Yeast extract
Peptone
mg/1
23
49
56
49
Substrate
NaCl
MgSO4
KH2P04
KC1
mg/1
5
3
14
10
23
-------
3.2 RESULTS AND DISCUSSION
Table 3.2 shows the summary of the results. The values represent each
respective testing condition that are considered stable.
The organic load was within the range of BOD-SS Load 0.07 - 0.51 g/ss.g/day
and COD-SS load 0.07 - 0.51 g/ss.g/day. And SRT was within the range between
2.7 and 22.4 days. The pH was successfully controlled in the range neighboring the
set value. The SVI has shown a tendency to be in proportion to the organic load
and marked a maximum 2,350 at high load. This was due to the growth of two or
three species of filamentous bacteria.
3.2.1 Relationship between Organic Load, Removal Rate and SRT
With regards soluble (S) BOD, COD and T-N, Fig. 3.2 shows each relationship
between the organic load per sludge unit and removal rate. The removal rate within
this load range was: BOD, about 98 percent and virtually unaffected by load
changes; and removal rate of total nitrogen increased in proportion to load-increase
and remained virtually unaffected from pH. Similarly, Fig. 3.3 shows the
relationship between loadings and the removed amount for each item. Each has
shown that the removal rate per solid had the tendency to increase in proportion to
the load applied loadings, and the gradients were: BOD, 0,984, COD, 0,853 and
T-N, 0,447. These values express the removal rate per solid.
100
80
~ 60
20
Fig.-3.2 Load and Removal Rate
S-COD
S-T-N
A.V'
^ 1 1 ' 1 1
o - pH 8
A - pH7
a - pH 6
J___, 1 , , ,
0.01 0.02 0.03
0.05 0.1 0.2 0.3
Load (g/SS-g/day)
0.5
24
-------
Fig.-3.3 Load and Removal Per Unit Sludge
o.e r
0.5 -
0.4 -
in
in
0.3
0.2
0.1
ca
/f
o
«*'.A
I I
0.1 0.2 0.3 0.4 0.5 0.6
Load (g/SS-g/day)
Fig.-3.4 Removal Rate and Multiplying Rate Per Unit Sludge
0.5
0.3
t/3
55 0.1
0.05
0.03
0.02
0.01
0.01 0.02 0.03 0.05 0.1 0.2 0.3 0.5
S-COD Removal rate (g/SS-g/day)
25
-------
When examining the relationship between the removal rate of soluble COD per
sludge unit and the amount of sludge production per solid, a positive primary
interrelation as shown in Fig. 3.4 was obtained. If the relation between load and
generating amount can be given, SRT to a certain degree can be predicted. The SRT
can be expressed in the following:
SRT = -^jr- (D
= (1 + a) MLSS. Vp
S
(3)
(4)
SRT: Sludge Retention Time (T)
2SS: Total Solid in the system (M)
AS: Multiplying Rate of Activated Sludge (M.T1 )
MLSS: Activated Sludge Concentration in Aeration
Tank (ML'3)
V0 : Aeration Tank Capacity (L3)
a: Coefficient when Total Solid in the system
is expressed in MLSS.
F(R), F(L): Multiplying Rate (Function of Amount
per Solid (R) a.,d Load (L)) (T'1)
Equation (1) is the fundamental equation of SRT which can be expressed in
Equation (2). Also Equation (2) can be expressed as a function by the inverse
number of the multiplying rate. When the relation between the multiplying rate and
the removal rate per sludge unit and load can be given, SRT can be predicted by
Equations (3) and (4).
F(R) and F(L) are obtained as follows by applying soluble COD.
F(R) = KO .RCOD C0 + (K0 = 0.864, C0 = -0.002) and
F(L)=Ko.K,-LCOD + KoC, + C0 (K, = 0.853, C, =0.009)
SRT = (1 +a).(0.737.LCOD + 0.006)~1 (5)
Thus the SRT was obtained as follows:
SRT = (1 + a).(0.737-LCOD + 0.006)-1 (5)
When a is approximated by the settler capacity of this testing apparatus, a is
0.5. Fig. 3.5 compares the results of SRT calculated by Equation (5) and the
observed value. Fig. 3.5 shows that the values differed slightly. But if a = 0.368 is
used, it coincides with the observed values.
In this test, the effect of pH within the range of 6 — 8 was not clear on the
relationship between organic load and SRT (Fig. 3.5). Perhaps, the pH range was so
close to the optimum range of microorganisms like heterotrophs and protozoa in the
activated sludge.
26
-------
Fig.-3.5 COD-SS Load and SRT
T3
\-
cc
25
20
15
10
SRT = (1+0) • (0.737-LCOD
+ 0.006)"'
I
I
I
0.1 0.2 0.3 0.4 0.5
COD Load (9 /SS- 9 /day )
0.6
3.2.2 SRT and Effluent Quality
Fig. 3.6.1, 2, 3 and 4 are the relationship between SRT and effluent quality
in terms of BOD, COD, SS and Transparency. There is a tendency to deteriorate
in effluent quality when SRT is either kept longer or shorter. As is seen in Fig. 3.6.1
and 2, the soluble BOD and COD were comparatively constant and low in any SRT.
Effluent quality is influenced by effluent solids. Effluent solids increase by the
bulking of filamentous bacteria when SRT is short, and increase of floatable solids
due to denitrification in final settler or micronization of activated sludge when SRT
was long. From this result, the optimum SRT range is to be between 5 and 10 days.
40
30
- 20
Q
o
CD
10
Fig.-3.6.1 SRT and Effluent BOD
o
o IT) _
• (s)
A(T)_
D(T)
• (S)
pH 8
pH 7
pH6
A
I ,
10 20 30 50 100
SRT (day)
27
-------
30r
= 20
D
O
O 10
03
tfl
60 i—
40 -
20 -
Fig.-3.6.2 SRT and Effluent COD
J L
i i i 11
1 1
10
SRT (day)
20 30
50
100
Fig.-3.6.3 SRT and Effluent SS
O
0 A
D 0
0 * D°
A D
I 1 1 1 1 i i i i 1 1 1
O pH 8
A pH7
0 pH6
i 1 i i i i
1
1 2345 10 20 30 50 100
SRT (day)
Fig.-3.6.4 SRT and Effluent Tr
^JU
IE x
CJ
^ 15
0
-
"
! I
?<
>J
' •-
? L
C
,
J
|
J ii «A U 11
]
b
\ , i i i 1
i
i
i
P ^
|
»
l>
1 . 1 , , . ,1
345 10 20 30
SRT (day)
50
100
3.2.3 SRT and Nitrification
Fig. 3.7 and 8 show the relation between SRT and nitrite and nitrate in the
effluent, of each pH condition. From Fig. 3.7, the tendency is that the longer the
SRT, the easier the nitrification. Also the pH greatly affects the whole process.
Required SRT that nitrification start are; the SRT at pH 8 is 3 days; at pH 7, 6 days;
and at pH 6, 11 days. This shows that within the range of these pH, when SRT is
short or when organic loading is high, it is possible to maintain substantial
nitrification by controlling the pH at around 8. When the SRT is maintained at over
15 days, the affects of pH are negligible, thus sufficient nitrification is expected.
28
-------
Fig.-3.7 SRT and Nitrification
14 r-
- , ,• ul i i I I I
235 10 20 30 50 100
Fig. 3.8 shows the relation between SRT and nitrification rate. Of the nitrified
nitrogen, the ratio of existing nitrite and nitrate is reported to change with the pH in
the reaction tank. The condition allowing predominance of nitrate is pH 6—7
while at pH 8.0 — 8.6 there will be more nitrite existing. This explains that the
activity of nitrite bacteria and that of nitrate bacteria change with pH. In this study,
the existing ratio of nitrite of nitrified nitrogen was highest at pH 7 and at
SRT 7 — 8 days, and at pH 8 the abovementioned pattern was not observed. In
comparing the existing ratio of nitrite with SRT, when SRT was shrot or
nitrification rate low, the existence rate was slightly high; and when the SRT was
long the majority existed as nitrate. This tendency was also observed in the two
other experiments. The multiplying rates of nitrite and nitrate bacteria from the
two tests were 7 hours and 12 hours respectively. Accordingly, in a condition when
nitrification rate was low or SRT short, as the existing amount of nitrite bacteria
could not catch up with that of the nitrite bacteria, nitrite increased in amount.
And when the nitrification rate was high or SRT long, the activities of both bacteria
reached the same level allowing nitrified nitrogen to remain more in the form of
nitrate.
Fig. 3.9 shows the relation between the pH and nitrification rate with SRT.
When expecting more than 80 percent of nitrification at pH 6 — 7, the SRT should
be more than 15 days. And it shows that in the neighborhood of pH 8, a reasonably
sufficient nitrification can be expected by setting SRT at around 6 or 7 days.
29
-------
Fig.-3.8 SRT and Nitrification Rate
100
A
n _
< s?
V
A
II
fl
ii
o o
z z
80
60
40
20
1001-
I III
23 5 10 20 30 50
STR (day)
Fig.-3.9 pH and Nitrification Rate and SRT
6 7
pH in Aeration Tank
100
30
-------
Table-3,2 Average Water Quality
SRT (day)
AS (j/day)
PH
SV30 (%)
MLSS (mg/1)
MLVSS (mg/I)
MLVSS „,
MLSS <*>
SVI
BOD (mg/1)
COD (mg/1)
K-N (mg/1)
KH-.-N (mg/1)
Tr (cm)
SS (mg/1)
BOD
(mg/1)
COD
(mg/1)
K-N
(mg/1)
Total
Soluble
Total
Soluble
Total
Soluble
NHi-N (mg/1)
NOi-N (mg/1)
N01-N (mg/1)
BOD
COD
T-N
BOD
COD
T-N
BOD
COD
T-N
Total
Soluble
Total
Soluble
Total
Soluble
Total
Soluble
Total
Soluble
Total
Soluble
I pH 8
A
2.68
14.04
7.81
7.65 ~
8.15
85.4
366
324
88.5
2,350
48.4
15.42
9.41
(9.30) ~
30 < '"
35.7
39.9
17.19
5.81
7.97
6.55
6.25
1.05
2.82
0.513
0.1376
52.3
84.9
27.6
32.4
0.293
0.436
0.0501
0.0574
B
3.06
17.13
7.67
7.44 ~
7.93
85.0
565
508
86.7
1,770
48.9
15.57
9.41
(8.81) ~
30 < '"
46.2
34.2
20.0
5.81
10.48
5.30
5.56
1.02
4.04
0.327
0.1343
40.5
86.5
4.82
34.7
0.1596
0.297
-261
x 10''
0.0508
C
18.27
7.74
7.91
7.80-
8.02
70.7
1,967
1,751
89.0
345
51.2
16.29
9.07
(26.0) ~
30 < "'
18.7
17.13
10.83
4.98
3.10
1.10
0.31
0.06
12.73
0.1065
0.0320
76.0
90.7
9.96
6.99
0.0843
0.0963
4.46
x 10"
2.30
x 10"
D
22.4
8.96
8.19
7.94 ~
8.31
45.0
2,920
2,540
87.2
146
49.9
15.90
8.81
20.5 -
30 < '"
25.1
7.70
9.85
4.58
3.17
1.10
0.51
0.16
12.75
0.0705
0.0218
78.8
89.0
-5.57
7.43
0.0566
0.0641
-0.888
xlO"
2.01
x l
-------
Table-3.2 (continued)
Nitrification
rate (%) |
Income and Outgo
<%>
N(V-N
(NO,>NO,-+NH/)-N
NO.'-N
(NO,"+NOr+NH,*)-N
(NO,-+NO,-)-N
(NN(V)-N
NO.'-N
NCV-N
NH/-N
Soluble Org-N
Total Olg-N
Nitrite Bacteria ( /ml)
Nitrite Bacteria ( /ml)
Heteiotrophic Bacteria ( /ml)
I pH 8
A
9.97
28.2
38.2
78.6
7.87
17.49
38.9
3.13
7.88
4.9x10*
2.4x10'
B
18.25
37.1
55.4
75.4
6.24
26.7
31.8
0.40
24.9
2.8x10'
2.4x10'
C
0.75
95.6
96.3
99.2
0.38
74.2
1.79
6.61
15.19
2.4x10'
2.4x10'
D
0.99
95.3
96.3
98.7
1.01
82.4
3.16
3.79
16.72
4.9x10'
2.4x10'
II pH 7
A
20.1
5.04
25.1
0.31
16.19
0.08
48.5
7.55
19.09
3.3x10'
3.3x10'
7.6x10'
B
24.3
27.2
51.5
51.2
15.1
21.9
41.1
5.80
10.80
1.7x10'
7.9x10'
2.4x10"
C
25.5
22.1
47.6
42.6
15.88
18.93
38.7
6.87
15.67
1.7x10'
7.2x10'
3Jxl
-------
contain any nitrite nitrogen, the existing quantity of nitrite bacteria or the amount
of nitrite was considered to have accelerated the growth of nitrate bacteria.
Fig.-3.11.1 SRT and Metazoa
600
400
; 200
235 10 20 30 50
SRT (day)
100
6r
o
X
Fig.-3.11.2 SRT and Amoeba
23 5 10 20 30 50 100
.E
o
o
Fig.-3.11.3 SRT and Amoeba
I ,mJ.-,-r7VT " I I
2 3
5 10
SRT (day)
20 30 50
100
33
-------
Table-3.3.1 Microscopic Test Results (pH 8 N/ml)
Phase
Sarcodina
Flagellata
Ciliata
Swim, type
Worm. t.
Fix. t.
Rotifera
Nematoda
SRT (d)
A
240
4,305
1,146
200
360
586
67
27
Pleuromonas
27
B
657
3,430
3,199
226
1,143
1,830
244
0
Arcella
Euglypha
Aspidisca
VorticeOa
3.1
C
400
147
3,906
306
2,680
920
227
0
Arcella
Aspidisca
18.3
D
1,510
783
6,270
1,266
3,744
1,260
444
167
Euglypha
Aspidisca
22.4
By classifying the biological fauna in the activated sludge into Metazoa,
Rhizapoda and activated sludge ciliata, Fig. 3.11.1, 2 and 3 show the relationship
between each group and SRT. Table 3.3.1, 2 and 3 show the population of the main
organisms that appeared. Each biological fauna has shown a tendency to increase in
number on the high SRT side. Also when comparing this with pH, Rotifera
increased in number at pH 7. In contrast to other biological fauna, Rotifera
remained formidable against pH influence and proved highly adaptable to pH. In
this pH range, it was amoeba galore in the lower pH area and showed a tendency to
decrease in the higher pH zone. In this study Englypha, Arcella and other loricate
amoeba observed in extended aeration or long SRT system were found in abundant.
Loricate amoeba is one of Protozoas upon which Rotifera find them difficult to
prey and this is why they still exist in this low pH 6.
The activated sludge ciliata, on the otehr hand, unlike amoeba, were found in
less quantity in the lower pH range.
Table-3.3.2 Microscopic Test Results (pH 7 N/ml)
Phase
Sarcodina
Euglypha
Arcella
Amoeba
Flagellata (Pleuromonas)
Ciliata
Swim, type
Litonotus
A
50
86
43
50,840
436
129
307
B
286
407
157
22,293
3,607
2,400
1,207
C
457
422
343
2,382
3,979
514
3,465
D
1,357
793
607
893
750
43
707
34
-------
Table-3.3.2 Microscopic Test Results (pH 7 N/ml) (continued)
Phase
Worm, type
Aspidisca
Fix. type
Vorticella
Zoothamnium
Carchesium
Tokophrya
Rotifera
Nematoda
SRT (d)
A
222
214
8
916
522
300
72
22
0
0
6.3
B
244
222
22
257
50
107
14
86
108
36
8.2
C
1,365
1,179
186
300
43
43
50
164
43
8
8.0
D
5,579
4,300
1,279
386
86
300
872
0
15.3
Table-3.3.3 Microscopic Test Results (pH 6 N/ml)
Phase
Sarcodina
Euglypha
Arcella
Amoeba
Flagellata (Pleuramonas)
Ciliata
Swim, type
Litonotus
Worm, type
Aspidisca
Fix. type
Vorticella
Epistylis
Tokophrya
Rotifera
Nematoda
SRT (d)
A
930
0
550
150
21,780
10
10
40
40
20
20
'0
150
4.3
B
3,180
30
900
380
3,060
0
0
0
0
3,460
1,960
1,350
50
100
370
10.9
C
1,100
190
720
30
10,870
300
100
200
340
340
130
70
0
20
40
110
13.5
D
2,960
240
1,570
120
3,050
200
50
50
100
100
630
200
100
10
320
180
16.4
3.3 SUMMARY
(1) Load and SRT.
The relation between load and SRT was proved to be described by
Equation (5). It is recommended that the coefficient a be the ratio of the settler
capacity to the aerator capacity.
35
-------
(2) SRT and Nitrification.
The study results revealed that at pH 8, nitrification can be expected in only
half of SRT than at pH 7. When applying this to existing conventional treatment
plant operation, either the load should be kept low to maintain long SRT or the pH
in the aeration tank should be kept high. The application of the former to the
existing treatment methods is difficult because capacity is limited at the most
plants. Also the employment of the latter requires installation of the pH adjustment
facilities.
(3) SRT and Microorganisms.
The number of Heterotrophs was 108 per milliliter, and the amount remained
unaffected by SRT changes. The number of nitrification bacteria was between 10s
and 10s per milliliter and was strongly affected by the length of SRT and also by
pH. When SRT was fixed, the amount of nitrification bacteria increased in the order
of pH8, 7 and 6.
In this study, on the slightly alkaline side of the pH, protozoa and activated
sludge ciliata were detected in galore, while on the acidic side more amoeba were
found. On the other hand, under long SRT condition, both had shown a tendency
of increasing. Rogifera and Sarcodina are regarded as useful index organisms of
nitrification condition.
(4) SRT and Effluent Quality.
The optimum SRT was 5 — 10 days. When SRT was kept short, it induced a
bulking condition. When SRT was long, outflow of minute floe and floating of
sludge from settlers perhaps due to denitrification occurred, at the final sedimenta-
tion basins.
4. EXPERIMENTS CONCERNING EFFECTS OF TRACE ELEMENTS ON
NITRIFICATION
There are two procedures to determine effects of trace elements on
nitrification acceleration.
1) Short terms culture method; to determine effects of trace element addition
on nitrification rate within a short period (4-5 hrs) in which growth of nitrifiers is
negligible. Namely, this method is to determine the effect of trace element addition
on the enzyme reaction.
2) Long term culture method; to determine effects of trace elements on growth
of nitrifiers and nitrification activity of nitrifiers by measuring amount of nitrifiers
and nitrified nitrogen in effluent.
In this study, long term contact method has been adopted.
4.1 TEST METHOD
The activated sludge at sewage treatment plants, (chlorine concentration of
40 - 50 mg/1 as Cl) where substantial nitrification achieved was used as nitrification
bacteria. Ultrasonic treatment (50Hz, 25 watt 5-10 minute) was conducted to kill
protozoa to prevent them to prey on nitrifiers. The sludge was washed two or three
times with ion exchange distilled water to release soluble metals.
36
-------
To alleviate the influence of buffer solution and sea water, the analysis was
conducted by diluting samples of 10 to 20 times.
Test 1) The Effects of Sea Water under the Existence of Tris Buffer
Effect of sea water on nitrification was tested adding sea water of 0, 20, 40, 60,
80, and 100% to the influent.
As buffer solution, 50mM Tris buffer (tris hydroxymethyl aminomethane) was
used as it was considered comparatively low in physiological influence. (NH4 )2 SO4
and NaNO2 were added at the concentration of 30 mg.N/1 as sources of ammonia
and nitrite respectively. Under the existence of 50m/M Tris-buffer, activated sludge
collected at sewage treatment plant was used after one week of aeration. The sea
water was prepared according to the Lyman and Fleming Synthetic Seawater
Composition List.
In 3-liter vessels, sea water, Tris-buffer, washed activated sludge (MLSS
adjusted to 520 mg/1) and substrate were added in that order to total 3 liters each
and to reach the designated concentrations respectively. Then the mixtures were
separated in 500 ml flasks by 100 ml transfer pipers, and the flasks were attached to
shaking culture units. The shaking culture was conducted at an amplitude of
50 mm, and shaking frequency of 10 times per minute.
Test 2) Effects of Phosphate Buffer
From the results of Test 1) Tris-buffer, that inhibit nitrification bacteria, was
found inappropriate for use in the nitrification tests. To examine the effects of
phosphate (Na2 HPO4 + NaH2 PO4) which is the alterative buffer solution against
nitrification, the short incubation method was introduced.
To reach the designated concentrations, one-liter cylinders were filled with
phosphate (When NH+4 substrate: 10"4, 5 x 10^, 10~3, lO"2, 25 x 10~2, 5 x 1CT2,
10"1 M phosphate. When NO~2 substrate: 10~6, 10'5, 10~4, 10'3, 10"2, 10~' M
phosphate), 2000 mgN/1 (NH4 )2 SO4 or NaNO~2 ... 25 ml, and washed activated
sludge collected at sewage treatment plant (When NH+4 substrate) 21800 mg/1 . . .
100ml or activated sludge (When NCT2 substrate) 24800 mg/1 . . . 150ml in that
order to total 1 liter each. Then the mixtures were aerated and the pH adjusted
between 7.5 and 8.0 of NaOH. And finally the amount of nitrite bacteria contained
in 0, 0.5, 5, 10 and 20mM solutions of NH substrate 24 hours later were measured.
Test 3) The Effect of Mg2+ on Nitrification under the Existence of Phosphate
Phosphate of 2mM was added to the solution of MgSO4 (002, 0.2, 2, 50mM),
MgCl2 • • 50mM, and (MgCO3 )4 Mg(OH)2 ... 0.04mM (Mg = 0.2mM) to
determine the effects of Mg in short period incubation.
In 1-liter cylinder, 40 ml of 0.5M Phosphate was added. Then Mg compounds
were added to reach the designated concentration. This was followed by the
annexing of 100ml of washed activated sludge (MLSS 19400m/l) and 25 ml of
(NH4 )4 SO4 2000 (mg/1 as N). The mixtures were aerated and five minutes later
amount of ordinary bacteria were measured.
Test 4) Effect of Anion under the Existence of Phosphate
Under the existence of phosphate, NaF, NaCl, NaBr, Nal, Na2 SO4 and NaNO2
of 10~4M, 10~3M, 10~2M and 10"'M were added respectively to examine the affects
of anion against nitrification.
37
-------
4.2 TEST RESULTS
Prior to the buffer addition study, tests to determine the effects of sea water
on nitrification was conducted.
The results are shown in Figs. 4.1, 4.2 to 4.4. Since these tests were conducted
by adjusting the pH only once every day, when the sea water addition rate was low
or the buffer capacity low, the pH also decreased, making it impossible to maintain
optimum pH. The more the pH was lower than the optimum pH, the apparent
nitrification rate decreased. In short, it is assumed that the actual nitrification rate
will increase to the extent of the concentration of sea water as shown in Figs. 4.1
and 4.2: This indicated that the optimum pH must be maintained in this manner to
make comparisons of nitrification rates. Then, the experiments were extended to be
done under the addition of buffer solution to remove the effect of pH change.
Fig.-4.1 Effect of Sea Water on Nitrification Fig.-4.2 Effect of Sea Water on Nitrification
•a
Z 4
Rate (fresh water nitrifiers
CL = 50 mg/l)
-I 9
pH adjusted to 8.0 ome a day
optimal pH
° 3
Rate (Activated Sludge of 6000 -
7000 CL plant)
pH adjusted to 8.0 ome a day
optimum pH
Nitrification rate
20 40 60 80
Cocentration of sea water (%)
100
20 40 60 80
Concentration of sea water (%)
100
38
-------
Fig.-4.3 pH and Nitrification
20
O4
OJ
, n
° 10
z lu
I w
O
z
Q
^.
~ A - > S
0 NO" (mg/B) \ / j /
D NO; (mg/B) V .' /' '
• NO, + NO; (mg/B) -5<4_ _PA_>'
APH .,•' oX^ ~
^SZZ^ \
5 10 15
20
CW
1
i m
° 10
+
b"
z
Q
k
» ^..—f—t — '?'
».x'^ / /
x\ • /
/x>C__\.<*__A/
.7 - \
J/ ... o— ' \
>^-" , . v
5 10 15
20
0<
OJ
~n
§ 10
+
0
Q
•6- ' ^"
(Sea water 0%)
20
*
._ ._B
(Sea water 20%)
i
20
" •
-
A-
•
.
' x**** ^^
X • ^""A~ ,*~ ~
* S^ /o x°
/o »4 '' X
^^ V °
5 10 15
20'
CX
I
i 10
O
z
Q
___ _ X"^ - -* /
// ^l<^\
^--s— °
5 10 15
20
CX
1
i 10
b"
Q
^*" *
j»x'^ X-A ^ A
/o-
-------
Fig.-4.4 Sea Water vs. Percentage of Nitrite
100
50
o
2
+
O
z
n
/ \ "ft
/" < \
x° . \ \
¥ "\
\ •
N
\
.\
X4
\
\
\
1 • A
10 15
Time (day)
o Sea water: 0 (%), °: 20 (%), A: 40 (%), •: 60 (
• : 80 (%), *: 100 (%)
Fig.-4.5 Nitrification in Different Substrat- and Sea Water Conditions
30h
20 \
• (NOi+NOs), Sea water concentration 0%,
Substrate NH*, Tns-buffer not added
NO; Sea water concentration 0%,
Substrate NH5, Tris-buffer not added
NO] Sea water concentration 0%,
Substrate NO;, Tris-buffer not added
; (NO;+NO;l, Sea water concentration 20%,
Substrate NH;, Tns-buffer added
; NO; Sea water concentration 20%
Substrate NH5, Tris-buffer added
; (NO;+NOS), Sea water concentration 40%,
Substrate NHJ, Tris-buffer added
; NO; Sea water concentration 40%
Substrate NHJ , Tris-buffer added
_§
O
10
40
-------
Test 1) Influence of Sea Water under the Existence of Tris Buffer
Figure 4.5 shows the relation between nitrified nitrogen (NO~2, NO~2 +NO~3)
in effluents and reaction time (days), under the different sea water concentration,
fed forms of substrate nitrogen (NH+4 or NO~2).
Similar to the result shown in Fig. 4.1, the inclination was that the nitrification
declined when sea water concentration increased. The rates were 2.38 (mg/l.day) in
20 percent sea water concentration and 1.21 (mg/l.day) in 40 percent sea water
concentration. These values relate that the nitrification rate in 40 percent sea water
was only about 1/2 of that of 20 percent, indicating the fact of sea water inhibition.
Inversely, the growth rate of nitrite bacteria as shown in Fig. 4.6 was higher in
40 percent than in 20 percent sea water with the values being 0.126 (generation
number) and 0.0941 respectively. This means that the growth rate in 40 percent sea
water solution was about 1.34 times faster than in 20 percent. The generation time,
on the other hand, was 2.4 days in 20 percent sea water and 5.5 days in 40 percent.
Test 2) Effect of Phosphate Buffer
The ratios of nitrification rate of phosphate addition and without addition
under the nitrogen substrate of NH+4 and NO~2 are shown in Fig. 4.7. It shows that
the phosphate added as pH buffer had accelerated ammonia oxidation with the
optimum concentration being about 13mM. The rate at this point was about twice
the rate of that phosphate was not added (Control). However, when phosphate
concentration was below 0.1 mM, there was no action observed to accelerate
ammonia oxidation. Also over 13 mM in concentration, the rate suddenly dropped.
And when lOOmM, the rate dropped about 45 percent against Control. The nitrite
bacteria count in 0 — lOmM concentration, 24 hours later, roughly maintained the
same population of 1.5 x 108N/ml. However, the count in 25mM concentration
dropped to about one third of the original level and was 4.9 x 107N/ml.
Test 3) Effect of Mg on Nitrification under the Existence of Phosphate
To see the effect of Mg+2 addition, ratios of nitrification rate of Mg+2 level
against control rate are shown in Fig. 4.8. The figure shows that even in MgSO4
50mM solution (Mg+2 concentration in 96 percent sea water) the effect to
nitrification rate was hardly seen, and also (MgCO3 )4 Mg(OH)2 was similar to
MgSO4. Although there was about 10 mg/1 of ammonia oxydation, there was no pH
drop demonstrating strong buffer strength. Table 4.1 shows the population of
bacteria after five minutes of each chemical addition.
Test 4) Effect of Anion under the Existence of Phosphate
Fig. 4.9 (a) and (b) show the ammonia oxidation rate of halogen concentra-
tion against control. The Figures show that the concentrations that decreased rate
to 50 percent were NCrs(29mM) > F'(48mM) > SO5'(76mM) > r(80mM) > Cl"
(IVOmM) in that order. Cl"6" had shown the least effect.
41
-------
Fig. -4.6 Change in Population of Nitrifiers
10'
104
Nitrite bact. Nitrate bact.
(NHJ Substrate) (NOz Substrate)
10
20
day
30
40
Fig.-4.7 Rate of Ammonia Oxidation, Nitrite
Oxidation vs Phosphate Concentration
° rate of ammonia oxidation
• rate of nitrite oxidation
§1.5
a:
c
o
1.0
0.5
oLi.
10"' 10"6 10~5 10~4 10~3 10~2 10"'
Concentration (M)
42
-------
4.3 DISCUSSION
The Influence of Tris-buffer on Nitrification:
Despite the fact that the generation time of Nitrite bacteria by pure culture is
known to be between 10 and 12 hours, it was 10.6 days in 20 percent sea water
addition, 7.9 days in 40 percent solution or 23 and 17 times respectively longer than
pure culture. Furthermore, from Figures 4.3(a) and 4.5, when comparing the lag
phase of sea water addition of 0 percent and 20 percent, the former showed no
difference, but the latter had shown an excessive difference of 14 days between
0 percent sea water (without Tris-buffer), perhaps, owing to the fact that Tris-buffer
had caused inhibition to nitrite bacteria growth.
By addition of Tris-buffer, as is seen from Fig. 4.3(b), nitrite concentration
increase significantly. The population of nitrate bacteria with NO~2 as substrate in
Fig. 4.6, diminished with the passing of days. From these facts, it is concluded that
Tris-buffer acted to inhibit activity of nitrate bacteria.
Addition of higher sea water had higher bacteria growth rate, and this
phenomenon is reasoned as follows: Either substances contained in the sea water
acted as catalyst to stimulate growth or metal enzyme, engulfed in bacteria, had
been formulated to promote growth. According to Loveless Report (1968), by
addition of MgCl2, the nitrite bacteria hightened in growth. So, this fact in this
study was considered to be due to Mg contained in sea water.
It is regarded that anions such as Cl~ and SCT4 affected to causing the
acceleration of lag phase and nitrification rate in proportion to the increase in sea
water addition. From the fact that the amount of nitrification per nitrite bacterium
was smaller in 40 percent sea water solution, it is necessary to check whether the
amount of nitrification per nitrite bacterium will increase by grafting and
acclimatization.
With regards oxidation of ammonia to nitrite, phosphate proved effective as
accelerators.
The forms when phosphate is pH 7.5 and pH 8.0 are as follows: pH 8 ...
H2PCT4 13.8 percent, and HPO2"4 86.2 percent. pH 7.5 ... H2PCT4 33.9 percent
and HPO2~4 66.5 percent (at 25 degrees centigrate). If H2PO~4 is an accelerator to
promote nitrification, it should increase 2.5 times between pH 7.5 and pH 8, and
HPO 2"4 should decrease more than 20 percent. With this in mind the subject rests
were conducted by setting the pH at about 1.15, a high concentration phosphorous
acid solution in which pH drop is scarce.
By the addition of more than 13mM of phosphate, the activity to convert to
NO"2 suddenly decreased. But despite the fact an equal amount of nitrite bacteria
inhabited in the solution until lOmM, the bacterial population decreased to about
1/3 in 25mM phosphorous acid solution. From these facts, it was considered that
even though the apparent nitrification dropped suddenly, the per bacterium
nitrification inhibition also slightly decreased.
Characteristics of Cation Under the Existence of Phosphate:
It was proved that phosphate is an effective nitrification accelerator. But it
bears a characteristic to form complex or sediments with cation. As an example, the
43
-------
characteristics of phosphate with Mg2 are as shown in Fig. 4.10. The figure shows
the existing form ratio of Mg2+ in 2mM of phosphate. The reaction of phosphate
and Mg2+ is expressed in the following equation:
Mg2+ + HP02-4 ^ NgHP04 (pK = 2.18)
From this equation, the complex formation is influenced by the concentration
of phosphate. If phosphate concentration is maintained constant level, by increasing
Mg+2, the amount of complex increases. In this case, however, MgHOP4/ Total Mg
ratio will decrease.
Fig.-4.10 Mg2+ vs MgHPO4 (Phosphate 2mM, at 25°C)
100 r
10"
Concentration of Mg (M)
When studying the effects of additives such as cation, the addition of buffer
solutions should be with care. Addition of the buffer solutions is held down to the
minimum. For example, in case of phosphate, it should be controlled to about
0.1 /uM. In this case, the nitrogen as substrate, too, must be similarly controlled.
However, it is impossible to conduct the aforementional studies by using
activated sludge. When activated sludge is cultured, NH4 will liberate from the
sludge. And the release rate of NH4 is affected by the composicion and
44
-------
concentration of the culture solution, the condition of the collected activated sludge
(collected time & place), the preservation method of the collected sludge, and so
on. In this study irrelevant to the concentration of phosphate, the increase in T-N
due to the release of NH4 within five hours was not observed. But 24 hours later,
the soluble T-N, when compared to the initial T-N, increased about 5 (mg/1 as N).
Release of NH4 was observed until about four hours in ohter case. But after that
(between 4 and 6 hours) no release was observed. The initial release rate without
any chemical addition was about 1.9 to 2.9 (mg.N/liter/h). Also, in proportion to
the increase in anion addition the release of NHt, showed an inclination to
decrease. In this way, the cause of the large amount of NH^ release in the initial
stage is attributed to the preservation method of activated sludge. In other words, as
the collected activated sludge (MLSS: 10,000 - 20,000 mg/1) was preserved under
an aeration, the released NH!» has nitrified and caused pH to drop. It should be
noted if pH adjustment is conducted only once or twice every day, the nitrification
bacteria will exist in the solution at around pH 5 most of the time. However, in this
test as pH was maintained highly between 7.5 and 8.0, it was concluded that the
release was not triggered by sudden pH changes.
From these results, in the nitrification tests using activated sludge, it is
recommended that a reasonably large amount of nitrogen as substrate be needed.
4.4 SUMMARY
1) Under the existence of Tris-buffer, the population of nitrite bacteria
contained in 20% sea water solution and 40% solution were counted and the growth
rate in 40% solution was about 1.34 times faster than in 20% solution. This was,
perhaps, caused by Mg2~ in the sea water. However, the amount of nitrification
amount per nitrite bacterium was higher in the 20% sea water solution.
2) In short period incubation (under the existence of 2mM phosphate), no
Mg2+nitrification acceleration activity was observed.
3) In short period incubation, nitrification to nitrite was accelerated by
phosphate addition and the optimum concentration was about 13mM.
4) Under the existence of 1 ImM phosphate, when expressing the 50%
nitrification decrease in terms of concentration due to the influence of anion, it can
be as in the following order: NCr3 (29 mM) > F~ (48 mM) > SO^ (76 mM) > T
(80mM)> Br(140mM)> Cl(170mM).
45
-------
5. DETERMINATION OF NITRIFICATION BACTERIA AND HETERO-
TROPHS IN ACTIVATED SLUDGE
The biological composition of activated sludge is: bacteria, protozoa and
metazoa or microorganisms. And bacteria exist in the form of autorotrophs such as
nitrite bacteria, nitrate bacteria. Then there are the heterotrophs. Counting of
protozoa and metazoa population is possible by the microscopic method. On the
other hand, although there are no established measurement methods for bacteria,
Sakurai (1967) and Chida et. al (1971) reported several types of culture media for
the measurement of heterotrophs. With regards the measurement of autorotrophs,
especially nitrite and nitrate bacteria, the plate culture method and the liquid
culture medium are suggested. But concerning the development of the plate culture
method incorporating silica gel, it takes up considerable time in the preparation of
the culture medium and the colony is little too small for counting. Therefore, the
method is considered inconvenient for practical use.
Incubation of nitrification bacteria is generally conducted by the MPN Method
introducing the liquid culture medium. But this medium, too, has many problems
yet to be cleared such as determination of the incubation period, etc.
In this study to bring to light the succession of nitrifiers and heterotrophs in
the biological treatment system, considerations were made on the dispersing
method, incubation period and culture medium of specimens that were considered
fundamental to measure the actual population of existing microotganisms.
5.1 TESTING PROCEDURE
The specimen sludge was activated sludge produced by the indoor experiments
boosting a comparatively high nitrification activity.
The TOMY SEIKO UP200P Ultrasonic Shredding Unit was introduced to
disperse the specimen. The selected power for the apparatus was 25 watts with the
maximum shredding time being 3 minutes. The specimen was a mixed solution of
5 ml in quantity. The cultured temperature was maintained at 20° C and the
incubation periods for heterotrophs maximum 30 days and nitrifiers maximum
130 days.
Considerations of the culture medium were made only on heterotrophs. And
concerning nitrification bacteria, there were no discussions conducted pertaining to
the culture medium incorporating the IBP Method.
The culture media for heterotrophs were: Medium A ... ordinary agar
medium. Medium B . . . ordinary agar medium diluted 10 times. Medium C . . .
Sakurai Culture Medium. Medium D . . Trypton Glucose. Medium E . . . ASE
Culture Medium. And Medium F . . PWRI (Public Works Research Institute)
Culture Medium. There were six types in all. As PWRI culture medium employs
synthetic sewage produced by the indoor experiments, 15 grams of agar was added
to the syncthetic sewage to have the concentration of influent. The population of
heterotrophs was measured by counting all colonies formulated in the medium.
With regards measurement of nitrification bacteria, the counting of nitrite and
nitrate was done to measure nitrite bacteria; while the number of nitrate was
counted and plus and minus judged to measure nitrate bacteria. The measurements
46
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of nitrite and nitrate were conducted by introducing the Technicon Auto Analyzer
based on the Cd-Cu Reduction Method.
5.2 RESULT AND DISCUSSION
5.2.1 Dispersion of Specimen Sludge
Various types of microorganisms are adhered to the activated sludge.
Especially, as nitrification bacteria are microorganisms with a sticking tendency
(fixed type), special methods must be incorporated to disperse them to make way
for easy measurement. And there are many methods developed.
Since the specimen contains live microorganisms, this gives rise to the problem
of dispersion force. Therefore, it is important to confirm the optimum conditions
of each specimen with regards dispersion method and force before implementing
dispersion. Here, the ultrasonic shredding method was implemented and the relation
between shredding time and the number of microorganisms was searched. The
results are shown in Figs. 5.1 and 5.2.
Fig.-5.1 Living Microorganisms and Ultrasonic Shredding Time
0.5
1 1.5 2
shreadding time (min.)
2.5
Until around two minutes of shredding, the number of bacteria continued to
increase and reached a fixed quantity, (two or three minutes.) Similar tendency was
observed of nitrification bacteria. When this apparatus is used, the shredding time
would be about 2.5 minutes. According to Chida (1971), with homogenizers, the
appropriate time was 10 minutes. However, when coping with a number of
specimens, the ultrasonic shredding unit is instrumental to shorten time. When
conducting microscopic observation of specimens subjected to ultrasonic shredding,
protozoa were shredded between 1.5 and 2 minutes leaving no trace of the original
form. With regards shredding of Rotifera, only traces of shells were barely
recognizable. From these observations, it is assumed that shredding can cause the
mortality rate of the microorganisms to increase. Therefore, comparison with other
dispersion methods is necessary. Here the shredding time was set at 2.5 minutes for
activated sludge.
5.2.2 Incubation Period
The growth rate of bacteria is easily subjected to physico-chemical conditions
such as temperature, pH, nutrient source and inhibitors. The growth rate is further
47
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influenced by other microorganisms in the mixed culture system. The culture
temperature was set at 20°C, a temperature requiring longer incubation period.
Concerning activated sludge and heterotrophs, the Gils (1964) at normally 25°C, the
incubation period is 6 days. Tezuka (1968) reports at 30°C, the culture period is
between 6 and 7 days. Chida et al. (1971) statee at 20°C, the incubation requires
10 days. And the IBP Method (1969) insists at 30°C, the period is between 7 and
10 days of incubation.
The relation between incubation period and the number of bacteria in this test
was as shown in Fig.s. 5.3 and 5.4.
Fig.-5.2 Nitrification Bacteria and Ultrasonic Treatment Time
^
E
O)
o
Z
Q_
5
10
8
7
6
5
(83) x
^-"""""^ J|\
>< (44) \
-y^^^^^"^ ___ Q _^ ^_ o X.
— ^^ -— — ~ """ "^* •»*. ^v
^? «^\ O (21) ^v 'V
O 0 * — «~~" " — * *~ ~ a J6
• ^^*
y^
( ) indicates incubation
period (days)
I I I I I I I
0.5 1 1.5 2
Shredding time (min.)
2.5
Fig.-5.3 Number of Bacteria and Incubation Period
40
& X
CD
U ^-
a C
CD -E
4_ 01
0 O
fe " 20
_g x
E z
D
Z
10
0
-
i t t
. A A A
A g « 8
g o
o
-
I I I I I 1 1
A
a
o
Culture Medium
o A
A B
a C
• D
A E
• F
Heterotrophs
1 1 1 1
8 10 12 14
Incubation Period
16 18 20
48
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Fig.-5.4 Incubation Period and Number of Bacteria
10
9
8
7
6
5
4bl
Nitrate bact.
Nitrite bact.
Ultrasonic Wave: 25 Watts
Treatment: 2.5 minutes
Culture Temperature: 20°C
Specimen: Activated Sludge
I
I
I
I
I
10 20 30 40 50 60 70 80 90 100 110 120 130 140
Incubation Period
The heterotrophs, after eight days, haVe shown fixed values. This tendency was
also observed in other specimens. Accordingly, the culture of heterotrophs was
conducted at 20° C and the incubation period being 10 days. With regards
nitrification bacteria, Meikle John (1975) reports 25°C for two weeks. IBP states at
between 20 and 22°C, the period is over 60 days. Matulewich et al. (1975) states
that at 28°C, the incubation period for nitrate bacteria is between 20 and 55 days
and nitrite bacteria between 108 and 113 days. When compared with heterotrophs,
both the nitrate and nitrite bacteria require longer incubation periods. As shown in
Fig. 5.4, at 20°C, the equilibrium condition was reached after more than 60 days.
However, with the passing of days, after the 60th day, the nitrification bacteria
showed a tendency to further increase. This inclination differed with the types of
specimens, thus making the determination of incubation period difficult. Bacteria
that turn positive after 100 days of incubation period, or those with extremely slow
multiplying rate, were found impossible to propagate in the bilogical treatment
system except under special conditions. In optimum condition, the generation time
(tg) of nitrification bacteria is regarded to be between 10 and 12 hours. On the
other hand, to estimate the incubation period by judging the number of days needed
to reach the specified nitrification extent based on the growth rate of nitrifiers and
the actual amount of nitrifiers when nitrites and nitrates produced by nitrification
were detected, it is as follows:
From this study, it became obvious that the nitrification bacteria population
more than about 103 and 104N/ml, and thus the post-culture bacteria was estimated
to be 104N/ml. When incubation is conducted by the MPN Method, the
nitrification bacteria amount would be 1 N/test tube of 5 ml at a certain dilution
stage. From this, when the incubation period is seeked by setting the generation
time at 12 hours, it will be about 8 days. In case of marine nitrification bacteria,
Yoshida (1967) states the generation time would be 40 hours at 20°C while Kimata
and his group (1961) insist that the incubation period will be mroe than 2 months.
When the generation time is 40 hours, the incubation period will be 22 days. By
considering this value and the logarithm derived from the environmental changes in
the test tube by the MPN method, it may be appropriate to define those that turned
49
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positive at about 40 days of incubation as nitrification bacteria. The culture
temperature should be between 25 and 27°C, or the optimum temperature of
nitrification bacteria.
5.2.3 Studies of Culture Media for Determination of Heterotrophs
Various types of culture media are being developed for measurement of
bacteria contained in activated sludge and in streams, lakes and swamps. Here,
comparison of six different types of culture media was conducted. Fig. 5.5 shows
the results of 14 days of incubation period. Except for specimen No.4, no drastic
differences were observed. As shown in Photo. 1, the colonies in media E and F
were small compared to others and made measurements difficult. Here, of the
remaining four specimens, culture medium D enabled easiest measurement.
Therefore, it was decided to introduce culture medium D (Trypton Glucose) for
measurement of heterotrophs.
GO
50
OJ <—
f;
30
20
10
Fig.-5.5 Bacteria Number and Culture Media
Sample
C D
Culture media
Photo-1 Comparison of Colony Size in Tested Culture Medias
50
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5.3 SUMMARY
When conducting measurements of nitrification bacteria and heterotrophs
contained in activated sludge, comparisons and studies of culture media were made
only of dispersion method of sludge, incubation period and heterotrophs. The
ultrasonic shredding unit was introduced to disperse sludge with an output of 25 w
for 2.5 minutes. The incubation period was 10 days at 20°C for heterotrophs.
However, with regards nitrification bacteria, there were difficulties in determining
the incubation period. It was decided that the appropriate incubation period for
nitrification bacteria was between 20 and 40 days based on tg, etc. Among
introduced six different types of culture medium no drastic differences were
observed. However, in view of the fact that the size of the colony was
comparatively large and measurement easy, it is recommended adopting the Trypton
Glucose culture medium.
51
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FIELD SURVEY ON NITRIFICATION AT
EXISTING SEWAGE TREATMENT PLANT
The studies were conducted to clarify the condition of nitrification at an exist-
ing activated sludge plant, in order to acquire a firm grasp of the relationships be-
tween nitrification and various contributing factors in specific reference to labora-
tory tests. Survey items include the nitrification rate, number of nitrifying bacteria,
fauna, etc. in the aeration tank.
The hydraulic load at the plant surveyed is relatively low, and nitrate nitrogen
is detected in its effluent almost throughout the year. The plant has a design capac-
ity for treating 200,000m3 /day of inflow, and its present inflow is approximately
150,000 m3/day. This plant, Arakawa STP is located in Saitama Pref..
1. METHOD OF SURVEY
The survey was conducted using one bay of aeration tanks having a length of
85m, with sampling conducted at four points equidistant from each other between
the inlet and outlet of aeration tank. Sampling time was set at 11:00 hours when
hydraulic load is considered to be relatively stabilized. Operational factors such as
hydraulic load and MLSS were not controlled for this purpose, and survey was made
once a month.
Water temperature, pH, DO, BOD, COD, N, nitrifying bacteria, fauna, are meas-
ured and analyzed.
The nitrifiaction rate was obtained in terms of the yield of nitrate and nitrite
nitrogen per unit time during the period taking the highest rate. The lag time was
taken as the time differential between the inlet of aeration tank and the formation
of nitrate and nitrite nitrogen.
2. RESULTS OF SURVEY
Table 1 shows the summary of the 1977 survey results. As seen in the table,
the water temperature ranged from 12.5 to 24.8° C, and the aeration time from 5 to
7 hours. SRT (sludge retention time) influencing the standing crop of nitrifying
bacteria exceeded 14 days which, however, could have been longer because with-
drawal of excess sludge was conducted not continuously but intermittently at a
rate of once in three days or a week. pH generally maintained at the neutral level.
BOD-SS loading recorded less than 0.1 g/ss-g/day in most cases, although a
maximum of 0.16g/ss'g/day was observed once. The aeration tank is relatively run
at low loadings. However, the hourly variation of BOD-SS is unknown because 24-
hours survey was not conducted. DO registered 0.3 ~ 5.6mg/l. As this value was
obtained by settling the sample for liquid-solid separation and by applying Winkler's
azide modification method to the supernant, it is probable that DO in the aeration
tank was slightly higher.
52
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Judging the degree of nitrification on the basis of the above data, it can be said
that the water temperature worked as the rate determining factor of the activity of
nitrification. Hence, the data shown in Table 1 and 2 are employed as control data
for clarifying other factors of nitrification in respect to water temperature and
season.
Table-1 Sumurary of the Results (1977)
Date
W.T. (°C)
Aeration time (h)
pH
DO (mg/1)
MLSS (mg/1)
MLVSS (mg/1)
MLVSS/MLSS
BOD-SS Loading
COD-SS Loading
Nitrification rate (%)
Nitrite bacteria (N/ml)
Nitrite bacteria (N/ml)
SRT(d)
77
5/10
19.9
5.87
6.2
3.3
4,205
2 405
0.57
0.06
0.02
60.1
4 9x10*
2.3x10'
69
6/13
235
6.59
7 0
0.5
4,700
3,000
0.64
0.02
27.0
11x10*
1.7x10'
15
7/13
23.2
5.48
6.8
0.3
2,237
1,407
0.63
0.16
0.03
21xlOs
13xl06
18
8/11
24.8
5.93
6.5
1.2
3,400
2,210
0.65
0.03
0.02
10x10*
0 8x10'
32
9/13
22.5
4.56
6.9
5.6
1,434
915
0.64
0.06
0.03
14.5
23x10*
0.5x10'
24
10/11
21.5
5.25
6.8
4.4
3,000
1,980
0.66
0.03
0.02
13x10*
4.9x10'
100
11/7
205
6.04
6.6
0.3
3,849
1,680
0.70
0.04
0.02
50.2
23x10*
23x10'
60
12/13
17.0
5.74
6.7
0.3
3,800
2,508
066
0.05
0.02
30.3
13x10'
3.3x10'
24
78
1/9
14.5
6.22
6.8
0.7
3,300
2,300
0.70
0.02
49.5
13x10*
11x10'
20
2/7
12.5
6.84
7.0
1.0
3,714
2,622
0.71
0.07
0.02
25.5
0.2x10*
0.3x10'
26
3/27
16.5
5.86
7.1
3.1
3,000
1,900
0.63
0.09
0.03
12.3
21x10*
4.9x10'
14
Table-2 Summary of the Results (1976)
Date
W.T. (°C)
PH
DO (mg/1)
MLSS (mg/1)
MLVSS (mg/1)
MLVSS/MLSS
BOD-SS Loading
Nitrification rate (%)
Aeration time (h)
SRT (d)
76
5/27
19.3
6.6
6.7
3,500
2,230
0.64
0.047
64.3
5.10
57
6/16
19.3
6.7
4.9
2,000
1,180
0.59
0.094
71.6
5.10
35
7/12
21.8
6.8
6.8
2,000 n
1,300
0.65
0.034
83.8
5.10
71
7/21
22.2
7.0
7.1
3,000
2,040
0.68
0.023
72.1
4.08
53
8/9
24.8
6.9
9.5
2,300
1,580
0.69
0.027
92.4
4.08
31
9/13
21.2
6.9
1.500
880
0.59
0.020
64.9
5.10
62
9/27
21.0
6.7
L!A°°
1,680
0.67
0053
90.2
4.08
94
10/7
21 9
6.8
2,500
1,540
0.62
0.064
82.7
5.10
31
11/24
17.8
6.95
4,490
3,160
0.70
0.032
96.6
4.76
71
11/30
16.7
7.01
1,960
1,350
0.69
0.091
87.1
5.10
49
12/20
15.7
6.99
2,680
1,840
0.69
0.14
55.9
5.10
62
77
1/17
13.6
6.95
2,520
1,900
0.75
0.17
30.5
4.37
134
2/21
12.5
6.97
2,510
1,800
0.72
0.12
31.8
5.31
122
3/16
16.8
7.02
2,330
1,880
0.81
0.22
15.7
5.31
68
As for the population of nitrifying bacteria in activated sludge, Kobori et al.
indicated in their report (1977) that it registered approximately 106 N/ml and
generally maintained itself at this level when SRT was more than 10 days (20°C),
and that the number of heterotrophic bacteria was 108 ~ 109 N/ml.
In the present survey, SRT ranged from 14 to 100 days and the bacterial
number determind, through the year, 106 ~ 107 N/ml for nitrate bacteria and about
106 N/ml for nitrite bacteria (Fig. 1). As shown in Fig. 2, about the same bacterial
numbers were detected from the results of extended aeration process. These facts
indicate that where SRT longer than the generation time of nitrifying bacteria is
maintained, the bacterial number in activated sludge is held at about 106 N/ml
irrespective of SRT. While the number of heterotrophic bacteria in activated sludge
is known to range from 108 ~ 109 N/ml, that of nitrifiers is much smaller, ranging
from 102 to 103 N/ml.
Fig. 3 shows the relationship between nitrification rate and water temperature.
Although it is required to obtain the nitrification rate per unit bacterial number, the
figure indicates the rate per MLSS as the 1976 survey excluded the measurement of
53
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Fig.-1 Seasonal Variation of Nitrifying Bacteria
in Aeration Tank
.2 6
0)
o
ro
CD
o 5
E
z 4
MJJASONDJ FM
1977 1978
Fig.-2 Seasonal Variation of Bacteria in Aeration Tank
(Extended Aeration Plant)
9
1 8
O)
o
- 7
o Heterotrophs
A Nitrite Bacteria
A Nitrate Bacteria
I i i
JASON DJ FM
1976 1977
Fig.-3 Effect of Temperature on Nitrification Rate
5.0
Nr = 0.105 x 1.121* (1976)
r = 0.868
•2 0.5
8
| 0.25
Z
0.1
/ (1977)
Nr'= 0.0319 x 1.1631
r =0.958
10 15 20 30
Temperature (°C)
25
54
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bacterial number. As seen in this figure, the nitrification rate rose slightly when the
operating factors in the aeration tank were controlled. The rate declined under
normal operating condition, which is perhaps assignable to the influences of other
factors than water temperature. The conceivable influences of such other factors are
loading variation and DO level, and they seemed to become greater with the decline
of water temperature. Temperature coefficient obtained on the basis of the ob-
served data was a value of 1.121 under controlled operating condition (1977 survey)
and 1.163 under non-controlled condition (1976 survey). These values show fair
conformity with those in relevant reports.
Observation of nitrification which takes place with the downflow in the aera-
tion tank disclosed that it involved certain time lag. Fig. 4 showing the relationship
between water temperature and lag time indicates that latter tends to become longer
with the decline of the former. The exact reason of this lag time increase is un-
known, but it appears probable that as the activity of nitrifying bacteria becomes
weaker due to the drop of water temperature, the influences of other environmental
factors become stronger. Reduction of lag time which is often evidenced in labo-
ratory tests is essential for efficient utilization of aeration tank, and this is one of
the most important problems to be solved for satisfactory nitrification at an actual
plant.
Fig.-4 Effect of Temperature on Lag Time
.c
I
'£
01
03
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
n
•
•
° 0° 00
° 0°
o
o
o
o
o 1976
• 1977 *
10 15 20 25
Temperature (°C)
30
Table 3 shows the fauna in activated sludge. The fauna was predominated by
activated sludge type maintaining activated sludge in a favourable condition through-
out the year. Euglypha and Rotifera whose propagation is accelerated by the op-
erational condition favourable for nitrification were observed through the year. At
present, studies are being made on the possibility of using Euglypha as an indicator
of nitrification condition in the aeration tank.
55
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Table-3 Protozoa Observed Frequently during the Study
N/ml
Date
Litonotus
Arcella
Euglypha
Aspidsca
Vorticella
Espitylis
Opercularia
Acinata
Rotifera
W.T. (°C)
76
5/10
40
1,060
480
180
1,900
640
220
60
280
199
6/13
40
340
20
60
1,420
140
23.5
7/13
591
617
711
720
231
103
180
51
695
23.2
8/11
100
1,160
1,400
240
2,840
620
60
80
2,900
24.8
9/13
40
460
120
280
840
620
520
20
340
22.5
10/11
21.5
11/7
620
340
640
880
3,480
2,120
220
180
40
20.5
^12/13
400
1,560
380
940
t 1,080
1,960
340
80
340
17.0
77
1/9
820
1,460^
40
1,360
3201
1,060
200
60
340
14.5
2/7
229
7.233
130
3,862
4,123
9,492
164
65
229
12.5
3/27
1,480
^,460
100
j_ 760
140
20
60
60
240
16.5
Fig. 5 shows the effect of nitrification rate and water temperature on the
population of Euglypha which is one of the Protozoa detected when SRT is long.
It was found that the number of Euglypha increased/decreased in proportion to the
nitrification rate and water temperature, its coefficient of correlation with water
temperature being 0.64. From this fact, it was discovered that the number of
Euglypha is directly indicative of the degree of nitrification in the aeration tank.
This relationship also applies to a plant employing extended aeration process as it
was noted that Euglypha was dominant when the NH4-N concentration in the
effluent was less than 1 mg/1.
Fig.-5 Effect of Nitrification Rate and Temperature
on Number of Euglypha
O A
1000
500
100
50 -
• Nitrification Rate
A Temperature
A
A
0
10
Mr
0.5
15
20
25
(mg/h/ss-g) 1.0
30 (°C)
Fig. 6 shows the relationship between water temperature and population of
Arcella. As seen in the figure, the number of this amoeba was inversely proportional
to water temperature at a correlation coefficient of 0.72. Arcella is observed, just as
Euglypha, when SRT is long, but it increases with the decline of water temperature.
It is planned that sutdies on index fauna will be continued as the operation and
maintenance of aeration tanks can be performed with a mininum of time and labour
by the use of such fauna as indicators.
56
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Fig.-6 Relation between Temperature and Number of Arcella
9000
5000
_£
z
1000
500
•
o
o •
•
o
10 15 20 25
Temperature (°C)
30
3. SUMMARY
The findings of the survey introduced above can be summarized as follows.
1) Number of nitrifiers in activated sludge is on the order of 106 N/ml.
2) While there a diversity of factors influencing the nitrification at existing sewage
treatment plants, the nitrification rate can be maintained at a high level by con-
trolling environmental factors affecting it and by operating the plant as con-
stant load as possible.
3) Nitrification reaction in the aeration tank involves a lag time, which is an im-
portant matter to be considered for designing and operating nitrification plant.
4) For the purpose of satisfactory maintenance of aeration tank, its operating con-
dition can be determined by the bacterial population (biomass) and aeration
time on the basis the relationship between nitrification rate and water tem-
perature. Also, as mentioned, the operating condition needs to be determined
with consideration of the lag time involved in the nitrification.
5) There is probability that Euglypha will be used as an indicator of the degree of
substantial nitrification.
57
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NITRIFICATION ACCELERATION BY ALUM ADDITION
TO THE PRIMARY SEDIMENTATION TANK
INTRODUCTION
To induce nitrification, it is necessary to accelerate growth of nitrifying bacteria
in the treatment process. When compared with other bacteria related with water
treatment, nitrifiers are comparatively slow in growth. Therefore, to accelerate the
growth of nitrifying bacteria, it is indispensible to lengthen the retention time of
micro fauna existing in the treatment process to help growth of nitrifiers.
In the activated sludge process, the SRT (Sludge Retention Time) of the
activated sludge process is a significant factor to control. The SRT is expressed as a
ratio between the amount of solids existing in the treatment process and the amount
of solids discharged outside of the treatment process as effluent SS or waste acti-
vated sludge. Therefore, to extend the SRT means either to increase the amount of
solids in the treatment process or to decrease the amount of solids discharged.
To maintain solids in the treatment process, there are means to elevate the re-
turn sludge rate, to prepare a sludge storage tank and others. To decrease discharged
solids, considerations can be made to either lower the influent organic load or the
influent SS load that will in turn decrease the amount of solid production.
This report is a summary of experiments that were aimed at accelerating
nitrification by extending the SRT as a result of suppressing solid production by
lowering the organic load in the aeration tank after adding alum as a coagulation
agent to the primary sedimentation tank.
1. OUTLINE OF THE FACILITIES
The studies were conducted at the Nishiyama Sewage Treatment Plant in
Nagoya city. With treatment capacity of 20, 000 ~ 30,000m3 /day, it is a plant
handling influent composed of only domestic sewage. Fig. 1 shows the facilities
and the flow-diagram.
From the primary sedimentation tank to the final sedimentation tank, it can be
broken up into two independant bays - Bay No. 1 (the lower part of Fig. 1) and
Bay No. 2.
In experimental phases No. 1 and No. 2 alum was added to the preaeration
tank while the primary effluent was supplied to the aeration tank in the Bay No. 1,
and the primary effluent was added with NaOH and its pH values adjusted before
being send into the aeration tank in the Bay No. 2. In phase No. 3, the addition of
alum to the primary sedimentation tank was stopped in the Bay No. 1, and con-
tinued only in the Bay No. 2.
Furthermore, in the Bay No. 1, except during phases No. 1 and No. 2, the
conventional activated sludge phases No. 1 and No. 2, the conventional activated
sludge process was employed in its operation. On the other hand, in the Bay No. 2
prior to the subject experiments, tests were conducted on adding alum to the
aeration tank.
58
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Fig.-1 Flow Diagram of Nishiyama STP
Inflow
/
^"
'
to.
^
Discharge
Preaeration
Grit chamber Primary settler
Aerator
Final settler
Point of alum dose
Point of NaOH dose
I"A\
W
,O|
OL)
©
2.
INFLUENCE ON TREATMENT DUE TO ADDITION OF ALUM TO
PRIMARY SEDIMENTATION TANK
First, the experimental conditions for both bays during the subject experiments
are listed in Table 1. The MLSS values that show a great difference between the two
bays in Table 1 was considered to be the difference in the capacity of the final
sedimentation tanks.
Table-1 Sumary of Operational Conditions
Phase
Bay
Flow(m3/d)
Aeration time (hrs)
Return sludge rate (%)
Air flow (times)
MLSS
MLVSS (mg/1)
SVI
BOD- SS load (kg/kg/d)
SRT (d)
Alum does as Al (mg/1)
NaOH addition
No.l
1977.9.13- 10.15
No. 1
14,570
2.55
20.6
1.6
703
562
97
0.450
6.3
6
No
No. 2
14,570
2.06
49.4
3.3
2125
1382
63
0.149
37.6
6
Yes
No.2
10.15- 11.9
No. 1
13,920
2.65
21.6
1.7
687
502
98
0.688
2.9
3
No
No.2
13,920
2.13
51.7
3.4
1999
1361
69
0.236
13.4
3
Yes
No. 3
11.9- 1978. 1.26
No. 1
12,180
2.96
24.6
2.0
831
643
113
0.666
1.9
0
No
No.2
12,180
2.32
59.1
3.9
2607
1832
90
0.153
13.6
6
Yes
59
-------
With regards the influence of the alum addition to the primary sedimentation
tank, it was divided into two groups: the influence to primary treatment and that to
the secondary process.
Concerning the influence to the treatment at the primary sedimentation tank,
Table 2 summarized the primary sedimentation effluent values and the removal rate
which were based on the data obtained between March 1975 and March 1978.
From this Table, the followings can be pointed out:
a. BOD, COD and TOC removal rates improved. Especially, the removal rate of
soluble matters markedly improved. With regards the removal rate of suspended
matters, there was no significant change.
b. SS removal rate hardly changed.
c. Phosphorous removal rate changed markedly from 17.4% to 51.9%.
d. Although slightly, K-N and NH4-N removal rates increased.
e. pH values dropped around 0.3 and 0.5.
f. Total alkalinity of influent .without alum addition increased slightly. But with
addition, it dropped a little.
Besides the above mentioned points, the increase in primary sludge production
and the improvement of primary influent transparency can be quoted.
Table-2 Changes in Primary Effluent Quality with Alum dose
BOD (T)
BOD (S)
COD (T)
COD (S)
TOC (T)
TOC (S)
K-N
NH4-N
T-P
SS
T-Alkalinity
PH
No addition
Effluent
Quality
73.4
43.7
43.2
22.0
52.2
26.6
23.1
13.5
3.08
46.7
89.6
6.6-7.3
Removal
Rate
42.1 W
14.1
35.5
5.2
30.0
12.2
9.7
-5.9
17.4
67.5
Alum addition
(6mgAl/l)
Effluent
Quality
51.5
29.4
28.6
41.4
22.2
19.2
11.6
1.84
47.1
52.9
6.3-6.8
Removal
Rate
58.4
47.2
51.9
40.2
30.7
25.1
4.6
51.9
66.6
(mg/1)
Concerning the influence to secondary treatment, data obtained between mid
September and mid November were collected and compared. The results of data
60
-------
comparasions are shown in Table 3. However, the 1975 and 1976 data are of op-
erations by the conventional system and 1977 of operations by adding alum to the
primary sedimentation tank.
From Table 3, the followings can be pointed out:
a. The effluent values and the removal rate of BOD and COD did not show much
changes.
At BOD (T), the improvements on the removal rate and the effluent values
were perhaps due to the fact that oxygen consumption by nitrification in a
BOD bottle was small.
b. With regards TOC, the removal rate deteriorated.
The reasons are yet unknown.
c. Nitrification virtually did not occur, and K-N, NH4-N removal rate dropped.
d. With regards phosphorous, both residal concentration and removal rate in-
creased.
e. Due to drop in waste activated sludge production, the SRT became longer.
Table-3 Secondary Effluent Quality when Alum is Added in Primary Settler
Year
BOD (T)
BOD (S)
COD (T)
COD (S)
TOC (T)
TOC (S)
K-N
NH4-N
N02-N + N03-N
T-P
SS
MLSS
SRT (d)
Mode of Operation
1975
Effluent
quality
19.5
3.7
11.1
7.5
11.8
8.2
8.6
5.4
5.5
1.62
9.8
Removal
rate
68.3(%)
89.8
71.7
55.3
65.5
59.7
61.3
58.2
37.7
77.6
1227
Conventional
1976
Effluent
quality
27.2
7.6
13.2
9.3
10.1
7.9
5.4
3.4
1.60
13.2
Removal
rate
55.9(%)
79.5
73.5
57.7
71.9
60.8
56.5
37.3
65.9
730
3.4
Conventional
1977
Effluent
quality
11.8
5.7
10.8
23.0
19.0
14.8
10.7
0.7
0.65
6.8
Removal
rate
77.4 (%)
81.5
62.4
54.0
33.6
24.4
9.5
61.8
82.2
646
4.6
Alum addition
in primary settler
61
-------
3. ACCELERATION OF NITRIFICATION
3.1 NITRIFICATION BY CONVENTIONAL PROCESS
Fig. 2 shows the actual results of the Bay No. 1 demonstrating to what extent
can nitrification be expected in the conventional operating process.
Fig.-2 Seasonal Variation of Nitrogen at Conventional Process
* * Primary Effluent (NH4-N)
a ° Secondary Effluent (NH4-N)
0----0 Secondary Effluent (NO2-N + NO3-N)
1975 1976
10 11 12 1 23
78 9 10 11
456
7
(Month)
The NH4-N concentrations in both the primary sedimentation tank effluent
and the secondary treat ment effluent were higher in winter and lower in summer,
thus showing seasonal changes. The difference between the two, in other words the
NH4-N removal rate (nitrification rate), was approximately 0% in winter and
between 50% and 60% in summer.
3.2 THE EFFECTS OF pH ADJUSTMENT WHEN ADDING ALUM TO
PRIMARY SEDIMENTATION TANK
The SRT during summer when nitrification developed was between 2.5 and 3.5
days by conventional operation. By adding alum to the primary sedimentation tank,
sufficienct length was obtained with regards SRT. But, despite this fact, nitrifica-
tion was insufficient, perhaps, due to the drop of pH value in the aeration tank. It is
known that the activity of nitrifying bacteria reaches its peak when pH are between
7 and 8. But, the pH value in the primary effluent dropped to 6.3 ~ 6.8 when alum
was added, and it is assumed that the value has further dropped owing to nitrifica-
tion activity. Therefore, in the Bay No. 2 tests were conducted by adjusting the pH
values with NaOH for the purpose to highten the pH and to give sufficient alkalinity
for nitrification.
NaOH was added at the primary sedimentation tank, and pH adjustment was
made according to the pH meter installed in the lower stream. The target pH value
was between 7.8 and 8.2. Fig. 3 shows the influence of pH adjustment to the pH
value in the aeration tank. This shows how the pH values changed at the end of the
62
-------
aeration tank with regards non pH adjustment (Bay No. 1) and pH adjustment
(Bay No. 2). The Fig. shows that when pH adjustment was not conducted, the pH
value dropped markedly from night to the following morning. The minimum pH
value recorded was about 5.0. In contrast, when pH adjustment was conducted,
there was no pH value drop at night, and the value was maintained throughout the
day at between 6.0 and 7.0.
Fig.-3 Effect of pH Adjustment
-pH adjusted
7 -
(D
CD
(D
"o
1 6
x5
a
3AM 1° 12 2PM 4 6 8 10 12 2AM 4 6 8 1° 12
9/21 9/22
Date and Time
Fig. 4 shows the daily changes in NRt-N concentration in the effluent of both
the Bay No. 1 and the Bay No. 2. The Fig. summarizes the measurements con-
ducted by the automated continuous colorimetric analyzer. The average of around-
the-clock measurements from 9:00 am to 8:00 am the following morning is plotted
as the value of a single day.
In the Bay No. 2, the daily average of 2 ~ 5 mg/1 of NH4 -N in the effluent con-
tinued until mid-December, and from the latter part of December it gradually in-
creased.
In the Bay No. 1, it can be pointed out that nitrification virtually did not
develop when compared with that in the Bay No. 2 and in the conventional Bay
No. 1.
From these results, even when SRT is sufficient, if the pH is too low, it can be
anticipated that the nitrification will not be achieved. Therefore, an experiment was
conducted. The results of this test are as shown in Fig. 5. As it was not possible to
monitor the effluent in the Bay No. 2 at that time, it was substituted by expressing
the changes of NH4 -N in the effluent of the filters. The influence of suspending pH
adjustment have shown immediate results on the following day as the daily average
of 1.6 mg/1 was boosted to 6.6 mg/1. Also, the recovery after resuming pH adjust
was fast and returned to normal in a signal day. This testified to the fact that the
effects of pH adjustment were great and showed immediate results.
63
-------
Fig.-4 Change in Ammonia Nitrogen
20
"a
i
z
No Alum
A addition
VXX
XX
* No NaOH addition
i
Alum A
6mgAI/l^
Alum
3mgAI/l
0
o
O €0
0
00
n
°0 o
o®0 <
00
Sep.
Oct.
Nov.
Feb.
Month and Date
X Primary effluent 0 Final effluent
(Bay No. 2)
Dec. Jan.
Note) Obtained by 24 hour composit.
Fig.-5 Effect of pH Adjustment on Nitrification
Final effluent
(Bay No. 1)
Stop pH adjustment
20 24 4
10/14
Start NaOH addition
3.3 NITRIFICATION AT HIGH LOADING
The NH4-N concentration in the effluent varied greatly in a signal day. This is
illustrated in Fig. 6. As shown in the Fig., except for the 9 hours between 11 a.m.
and 8 p.m., the NH4-N was totally nitrified and marked 'zero' in the Bay No. 1. The
peak time during 11 a.m. and 8 p.m. came a little later than the peak time of
primary effluent owing to the inflowing NH4-N being discharged without totally
nitrified.
64
-------
30
- 20
I
z
10
Fig.-6 Hourly Variation of Ammonia Nitrogen
Sept 21
(Scale over)
Dec. 20
* A Primary effluent X X Final effluent (No. 1) O G Final effluent (No. 2)
During other hours than the peak time, nitrification was sufficient, thus show-
ing that nitrification was insufficient during hours when either the influent volume
or the influent concentration increased. It is regarded necessary to contrive means
to heighten MLSS at least during high loading time.
This trend remains the same even in winter.
3.4 NITRIFICATION IN WINTER
When studying the Bay No. 2 data as shown in Fig. 4. nitrifiaction continued
even in December and the nitrification rate began to drop from the latter part of
December. Similar to the seasonsal changes observed in Fig. 2, this is considered to
derive from the drop in the water temperature.
In the Bay No. 1 as shown in Fig. 2, it has lost its nitrification ability in
January. In contrast, in the Bay No. 2, it maintained a nitrification rate of between
40 and 50 percent even in the latter part of January showing the strong influence
of the SRT length.
It is considered difficult to prevent drop in nitrification ability due to water
temperature drop despite sufficient SRT and pH adjustment.
4. SUMMARY
The results of the study are summarized as follows:
a. The arganic loading to the secondary process can be decreased and the SRT can
be extended when alum is added to the primary sedimentation tank.
b. To extend SRT is necessary to induce nitrification. When SRT is sufficiently
long, nitrification activity can be kept high even in winter.
c. pH adjustment was necessary to obtain completely nitrified effluent.
d. Control measure to increase MLSS at high loading is nescessary to maintain
substantial nitrification.
65
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IV. STUDIES ON NITRIFICATION PROCESS AT
SMALL-SCALE SEWAGE TREATMENT PLANT
1. INTRODUCTION
The Nasu plant used for this study is located in a coppice of Kuroiso town,
Tochigi Prefecture and is designed for treating wastewater from the service area of
an expressway running through a hilly area. Its operation is subject to seasonal
fluctuation. Users of the service area increase particularly in periods including many
holidays such as early January, May and August. In these periods, raw sewage in-
creases in both volume and strength.
Wastewater comes from the restaurant and water closet in the service area. At
present, only the final effluent from the plant is used as flushing water on the water
closet, although a mixture of effluent and tap water (1:1) was used at the initial
stage of the plant operation.
Sewage treatment at this plant is conducted by the combined application of
activated sludge process and filtration. Final filtered effluent is discharge into a near-
by river through an agricultural waterway. As the effluent is used for irrigation, its
target quality is set at less than 5mg/l for BOD, SS and NHt-N. Considering the
functions of the plant, this target can be attained for BOD and SS. Hence, removal
of NH4 -N or nitrification is the main objective of sewage treatment at the plant.
This report introduces the existing state of the plant facilities, with specific
reference to the nitrification process. As for nitrification denitrification process,
studies are being made to obtain further detailed data.
2. OUTLINE OF THE PLANT
The plant is operated to treat raw sewage from the restaurant and water closet
by the extended aeration process in order to attain the effluent standards shown
below.
A portion of the effluent is reused as flushing water for the water closet, and
the remainder is discharged into the agricultural waterway.
1) Effluent Standards
BOD Less than 5 mg/1
SS - Ditto -
NH4 -N - Ditto -
E. coli group Less than 3,000 N/ml
2) Design Flow and Water Quality of Raw Sewage
Average daily flow 860 m3 /day
Maximum hourly flow 89.6 m3 /h
BOD 200 mg/1
SS 250 mg/1
3) Treatment Process (Fig. 1)
The plant is designed for the combination of extended aeration and filtration.
As shown in Fig. 1 illustrating the initially planned flow chart, the plant is com-
66
-------
posed of balancing tank (flow equalization), aeration tanks and settling tank for
removing organics, nitrification tanks and settling tank for oxidizing nitrogen com-
pounds, filters for removing solids, and chlorination tank.
Retention time of both aeration tanks and nitrification tanks is about 10 hours
at the design flow. Actual flow is about a half of design flow. Dual media filters of
sand and anthracite are used.
Fig.-1 Outline of the Plant
Storage Tank of
Alkali Solution
(No. 2)
1)
2)
3)
/
/
) S
Aeration
Tank 1
Aeration
Tank II
\
-------
provement, intended basically for introduction of a single stage nitrification-
denitrification process, consists of the following main alterations.
The aeration tanks were converted to unaerobic tanks, a denitrification zone
was formed by dosing methanol in the middle portion, of the nitrification tanks,
and end portion of the tank was used for re-aeration.
Studies are in progress on this introduced process.
Method of Survey
The survey, covering a period from January 1976 to March 1977, was con-
ducted in two ways, 24-hour composite sampling and analysis carried out once
week and 24-hour grab sampling conducted once in two months.
The survey points are shown in Fig. 1, and survey items included pH, trans-
parency, alkalinity, SS, BOD, COD, nitrogen in various forms, fauna, bacteria, etc.
3. OUTLINE OF SURVEY RESULTS
3.1 RESULTS OF TREATMENT BY INITIALLY PROPOSED FLOW CHART
As a result of surveys conducted on March 1 and 2, 1976 according to the ini-
tially planned flow chart, the following findings were obtained.
Although organic matters such as BOD and COD were sufficiently removed, the
effluent registered a transparency of 20 ~ 40 cm and contained micro floes which
were not removed by filtration. These particles were of the size small enough to
pass through the filter paper pore size of 12/u.
Residual concentration of NH4-N ranged from 3.3 to 4.4mg/l and averaged
3.7mg/l. In the weekly sampling analysis, it recorded a value of 2 ~ 13mg/l. At
that stage of operation, tap water mixed with effluent as dilution water to meet
standard, and the diluted effluent was resued as flushing water of water closet in
service area.
pH was reduced from 6.8 ~ 7.6 (average : 7.4) to 3.9 ~ 4.0, and alkalinity re-
gistered zero. In the weekly 24-hour survey conducted, however, effluent pH
showed considerable fluctuation, ranging from 3.8 to 6.6. Because of the low pH
of effluent, alkali solution is added at the outflow side of the nitrification tank.
Nitrification rate recorded 13 ~ 78%, which is indicative of the possibility of
conducting sufficient nitrification despite the water temperature of 8 ~ 10°C. Judg-
ing from the decline of pH, it appeared that the nitrification was supressed due to
the shortage of alkali required for oxidation of ammonia.
Scum was formed in large quantities in aeration tanks and nitrification tanks.
Microscopic examination disclosed that the sucm was air bubbles entrapped in oily
film. The scum disappeared after its pH was adjusted to 8 ~ 8.5. Activated sludge
presented a fauna predominated to a substantial degree by Rotifera and Euglypha,
which is characteristic of the extended aeration process.
As for the functional performance of flow balancing tank, aeration tanks and
filters, the following findings were obtained.
1) The balancing tank equiped with diffusers, is a fairly useful facility in that it
can mitigate loading fluctuations by virture of its large capacity and is also
capable of turning raw sewage aerobic (raw sewage in balancing tank contains
68
-------
protozoa).
2) The aeration tanks suffice for removal of organic matters and oxidation of
nitrogen as the aeration time is 24 hours at the present flow. However, the low
pH in the tanks needs to be adjusted.
3) The nitrification tanks are not necessary at present because the aeration tanks
suffice for both removal of organic matters and oxidation of nitrogen (Fig. 2).
4) The filters are indispensable for the extended aeration process like this plant.
Specifically, the extended aeration process brings activated sludge close to the
state of endogenous respiration, often causing floes of activated sludge to be
segmented or nitrified. This results in the denitrification in the settling tank,
whereby nitrogen gas in produced to cause activated sludge to float up and
overflow the weirs. Even in such a case, the filters are useful in improving the
effluent transparency.
From the findings described above, it is concluded that 1) pH in the aeration
tanks should be adjusted to about 8 in order to hold Nrt,-N concentration in the
final effluent at less than 5 mg/1 at all times, and 2) considering the present flow, the
nitrification tanks can be put out of operation without any hindrance to the plant
operation.
Fig.-2 Average Water Quality of Each Process (1) Average Water Quality of Each Process (2)
160
140
_ 120
i, 100
I 80
" 60
40
20
0
0
100
§50
Alkalinity: Sampling Point No 2:47.8mg/l,
No 3.4. 5 Omg/l
Sampling Poing. No. 2 — Influent to
Aeration Tank
No 3 - Effluent of Aeration Tank
No 4 — Effluent of Nitrification Tank
No 5 - Effluent of Filter
P-BOD
NO.-N-;
NH.-N
S-Org-N
P-Org-N
-NOj-N
w\\\\\\\
234
Sampling Point
234
Sampling Point
69
-------
3.2 PROPOSED IMPROVEMENT MEASURES BASED ON INITIAL
OPERATIONAL CONDITION
1) pH Control
For the purpose of controlling pH, NaOH was selected for addition as 25%
solution due to its nature. The injection dosage, about 60 kg/day, was deter-
mined for oxidizing TKN totally to nitrate so that the target pH of 8 ~ 8.5
would be attained by the plant operation.
2) Modification of Treatment Process
The nitrification tank was put out of operation for use as aerobic digestion
tanks, and the treatment process was consequently modified as follows.
Raw sewage -> Balancing tank -> Aeration tank ->•
Settling tank ->• Filters -> Reuse or discharge
After effecting the above two measures, the survey was continued with the dual
purpose of removing organic matters and attaining 100% nitrification efficiency.
3.3 RESULTS OF SURVEY OF PROPOSED IMPROVEMENT MEASURES
3.3.1 Effects of pH Control
Summary of the survey results in shown in Figs. 3.1 ~ 3.3. By effecting pH
control, removal rate of organic matters recorded 93 ~ 98% for BOD and 71 ~ 88%
for COD. Removal of SS at secondary settler was also increased, but these filtered
effluent showed the similar water quality as it did before pH control.
SS concentration in secondary effluent declined after pH control, although it
was unknown whether this was to be ascribed to the increased bio-coagulation of
activated sludge or to the shortening of aeration time. Particularly notable among
the effects of pH control was the fact that the transparenty of final effluent in-
creased to more than about 1 m as a result of augmented SS removal in the filters.
On examining SS in secondary effluent, it appeared that fine segmented particles of
activated sludge flowed out in a sort of colloidal state when pH ranged from 4 ~ 5.
After pH control, however, such fine particles disappeared and secondary effluent
contained particles large enough to be entrapped in the filter, which is perhaps
assignable to the shortening of aeration time by about a half. When pH ranged from
4 to 5 in the aeration tank, micro floes in secondary effluent could hardly be
trapped even if filtered by GFC. It may as well be added here that the minimum
size of particles that can be entrapped by dual media filter of sand and anthracite is
reported to be larger than 7 ~ lOju.
70
-------
Fig. 3-1 Summary of the Results
o Influent
0 Secondary Effluent
A Filtered Effluent
25 r
20 -
Water Temparature
Water Temper
15
10
5
_, (pH Control) cr
•t*
till
3456
1976
I | i
789
1 I 1 1 1
10 11 12 1 2
1977
1
3
345
1976
10 11
12
1
1977
150 r
100
01
in
CO
50
0 1- i
3
1976
-H-
789
(pH Control)
10 11
12
1
1977
71
-------
Fig.-3.1
120
110
100
90
80
^ 70
J
Q 60
O
in
50
40
30
20
BOD
o Influent
D Secondary Effluent
^ Filtered Effluent
10
' —
I I
3 4
1976
I
5
-A
1
6
1
7
-A — _
1 I
8 9
-Cr^
— A —
1
10
A—
1 1
11 12
I
1
1977
^
2
\
-•&
3
(pH Control)
100
80
o>
.§ 60
Q
O
<-> 40
20
COD
£r
I I
3 4
1976
A- _"^
I I i
567
*T1 —
1
8
__
i
9
-9-~
- —Cr
l
10
__ — -• — ""
1
11
— ~u —
i
12
I
1
1977
— D-
l
2
— a
~~"A
3
(pH Control)
72
-------
Fig.-3.3
o Influent
a Secondary Effluent
A Filtered Effluent
(pH Control)
10 11 12 1 2
1977
(pH Control)
60
50
^40
i 30
i 20
N02 + NO3
10 -O
345
1976
9 10 11
12 1
1977
(pH Control)
73
-------
Fig. 4 Results of Survey
^ V
J 1 F 1 M
^
1 tt^^A*, x a [
A | M | J J
/
2 n H r/
J
A
1976
-------
As for nitrogen, TKN and NH4-N in secondary effluent dropped to less than
5 mg/1 and to about 1 mg/1, respectively, indicating that pH control exhibited a high
nitrification efficiency. However, the weekly 24-hour composite survey (Fig. 4)
disclosed that the nitrification rate declined to 30 ~ 40% in August and January
when the aforementioned service area was most frequently utilized, with NH4-N in
final effluent recording 41 mg/1 in August and 25 mg/1 in January. A diversity of
reasons can be conceived of as contributing to this phenomenon, such as the shorten-
ing of aeration time due to increased inflow of wastewater, decline of activated
sludge density, sharp changes in pH, inflow of toxic or harmful substances, etc.
However, since none of them can be identified as the decisive reason, further studies
must be conducted to cast light on this problem.
The plant operating factors are shown in Table 1. The aeration time is as long
as 20 ~ 40 hours. Even if inflow increases to designed 800m3/day, therefore, an
aeration time of about 10 hours can be secured, which is long enough for removal of
organic matters and nitrification under normal condition. Settling time, ranging
from 12 to 24 hours, is also long enough to make the supernatant water consider-
ably transparent, provided that activated sludge is condensed satisfactorily in the
settling tank. MLSS is maintained at 1,200~ 3,400mg/1, averaging 3,000mg/1 as
seen in the table. BOD-SS loading is about 0.02kg/kg/d operational factors dis-
cussed above, it may be said that the plant has considerably large surplus capacity.
Table-1 Operating Factors
1
2
3
4
5
6
Average
Date
1976
3.1-2
5.24-25
7.26-27
9.27-28
11.29-28
1977
2.14-15
Inflow
(m3/d)
380.2
(15.9 m3/h)
223.8
(9.3)
292.1
(12.2)
297.1
(12.4)
401.8
(16.7)
440.6
(18.4)
339.3
Aeration
Time
(hr)
23.5
40.0
30.6
30.1
22.2
20.3
27.8
Settling
Time
(hi)
13.9
23.5
18.0
17.7
13.1
12.0
16.4
Overflow
Rate
(m3/mVd)
5.4
3.2
4.1
4.2
5.7
6.2
4.8
Discharge
Loading
(m'/m'/d)
12.7
7.5
9.8
10.0
13.5
14.8
11.4
MLSS
mg/1
1,670
3,140
2,950
2,620
2,900
2,940
2,703
*(1,910)
Inflow
BOD
Loading
(kg/d)
14.3
14.0
18.9
13.3
26.4
21.2
18.0
Inflow
SS
Loading
kg/d
56.6
23.5
31.3
23.8
43.4
31.5
35.0
BOD-SS
Loading
(kg/ss-kg/d)
0.02
0.01
0.02
0.01
0.02
0.02
0.02
*pH Control
3.3.2 Relationship between pH and Nitrification Rate (Fig. 5)
Optimal pH for nitrobacteria is known to be 8 ~ 8.5. As for the relationship
between the nitrification rate and pH, opinions differ from researcher to researcher,
though to a minor extent.
In one of the papers dealing with this subject, it is reported that a nitrification
rate of more than 90% can be obtained within a pH range of 7 ~ 9, which was con-
firmed by the experiment conducted at the Public Works Research Institute.
During the present survey, a nitrification rate of more than 85% was observed
within a pH range of 7 ~ 9 except in May, August and January. When pH was lower
than 7, the highest nitrification rate observed was about 80%. For satisfactory op-
75
-------
o Average per Week
* Average per two Months
o o
o
eration of the plant, therefore, it is advisable to maintain pH at about 7.5 ~ 8.
Fig.-5 Effect of pH on Nitrification Rate
100 -
90
80
g 70
CO
a: 60
c
o
8 50
Z 40
30
20
10
0
10
pH
3.3.3 Relationship between Water Temperature and Nitrification Rate (Fig. 6)
The effect of water temperature on the nitrification efficiency is not simply
but influenced by the retention time of sludge in the treatment plant (SRT), so that
simple comparison of the two is liable to produce a misleading conclusion.
In the case of this plant where SRT is very long, however, activated sludge
maintains its activity of nitrification at a high level and pH remains constant after its
control. As this makes it possible to regard that all environmental conditions exclud-
ing temperature are free from variation, the nitrification rate was compared with
water temperature.
Before effecting pH control when the water temperature ranged from 8 to
13°C and pH was at a low level, the nitrification rate was subject to a large fluctua-
tion, ranging from 13 to 86%.
After pH control, the nitrification rate recorded more than 90% except in May,
August and January while the water temperature ranged from 8 to 25°C, indicating
that the water temperature had practically nothing to do with the nitrification rate.
Hence, the fluctuation of nitrification rate before pH control can be assigned not to
the influences of water temperature but to the shortage of alkalinity. The survey
also disclosed that the residual concentration of NH4-N held itself at less than
1 mg/1 for the greater part of the year (Fig. 7).
76
-------
100
90
80
70
~ 60
o 50
.S 40
z
30
20
10
Fig.-6 Effect of Temperature on Nitrification Rate
('76. 11-77. Ill)
o ancOo COD°
0 Q
00
o» o
oA
OI/8
, VIII/2-16
Till/21
1 V/10
°l/5
- •
•
1 1 1 1 1 I
A • No pH Control
Ao pH Control
1 |
10 15 20
Water Temperature (°C)
25
30
77
-------
Fig.-7 Effect of Water Temperature on NH4-N in Effluent
o 42
• 39
o 42
• 41
35 r
30
25
20
15
10
No pH Control ' pH Control
O Sampling Point No. 3
• Sampling Point No. 5
\
I
11 /~\
• o
o o
0 I—
0
I -1
Water Temperature (°C)
3.3.4 Relationship between pH and Total Alkalinity, and Effect of Alkalinity on
Nitrification Rate (Figs. 8 and 9)
The relationship between pH and alkalinity as disclosed by the survey indicates
that, unlike the values obtained from the neutralization titration curve, pH changed
only to a limited degree even when alkalinity presented heavy fluctuations. Spe-
cifically, pH maintained a level of about 7.5 ~ 9 when alkalinity ranged from 160 to
400, which indicates that overdose of NaOH will not exert any adverse influence on
biological treatment process. As pH can be helf at 7.5 ~ 8 if alkalinity of about 180
~ 200 is present, it will be possible to save the chemical cost considerably by adding
NaOH so as to maintain this alkalinity.
78
-------
As for the effect of alkalinity on the nitrification rate, a high rate of nitrifica-
tion can be ensured at an alkalinity of more than 160 as shown in Fig. 9.
It is to be noted, however, that if alkalinity declines below 100, pH could de-
crease and the nitrification rate also becomes instable.
Fig.-8 Relation between Alkalinity and pH
10r
I
o.
5
4 -
100
90
80
70
60
50
40
30
20
10
0
s: i o • : •: • 450
- • ' . : • . -440
100 200 300 400
Alkalinity (mg/l as CaCO3)
Fig.-9 Effect of Alkalinity on Nitrification Rate
> O OO^ooooo 0%°6*°° ° 440 '
100 200 300 400
Alkalinity (Sampling Point No. 3) (mg/l as CaCO31
79
-------
3.3.5 Total Sludge Production
As sludge production data before pH control were limited and sludge formation
was subject to a large fluctuation, the total sludge production in the plant was ob-
tained by summing up the sludge volumes recorded from April 1976 to March 1977.
As can be seen in Fig. 10, sludge production through the year depicts two
patterns. Specifically, the volume of sludge varies by temperature as shown below.
High temperature season — May ~ October:
(Water temperature - 15 ~ 20° C) SS - 4.3 kg/day
Low temperature season — November ~ April:
(Water temperature - 8 ~ 15°C) SS - 13.6 kg/day
The coefficient of correlation between sludge production and season was 0.6
for the high temperature season and 0.9 for the low temperature season. Sludge pro-
duction in the low temperature season was about three time as large as that in the
high temperature season.
The increase of MLSS in the aeration tank cannot be estimated with accuracy
only on the basis of sludge production because the respiration and fauna of activated
sluge works as a contributing factor. However, calculation was conducted on the
basis of SS increase and tank capacity, which disclosed that the daily increment of
MLSS is 12mg/l in the high temperature season and 37mg/l in the low temperature
season. Hence, it can be concluded that the monthly increment of MLSS is about
400mg/l in the high temperature season and about l,000mg/l in the low tempera-
ture season.
Fig.-10 Seasonal Variation of Total Sludge
I 2
a.
O
1976 JFMAMJ J ASOND 1977 J F M
3.3.6 SRT
SRT is one of the important incentive factors to maintaining substantial nitri-
fication of activated sludge process. It is generally accepted that the longer SRT,
the higher the activity can be maintained.
Data of weekly survey indicates that SRT increased from about 45 days in
March (before pH control) to 230 ~ 270 days in the May ~ September period, re-
cording about 80 days in the subsequent low temperature season, which is long
enough for the growth of nitrifvino Bacteria.
80
-------
Month
SRT (days)
Mar. May Jul. Sept. Nov.
45.7 272 255 227 79.3
Feb.
80.4
Total volume of activated sludge in the plant
CDT-
Discharged SS + Waste activated sludge
In order to maintain nitrification when the water temperature is about 10°C,
more than 12 days of SRT is reported to be required. From the data given above,
therefore, it can be concluded that year-round nitrification can be expected of the
plant.
3.3.7 Micro Fauna
The fauna of activated sludge is composed of bacteria, Protozoa and Metazoa.
Protozoa is classified into swim t., worm t. and fixed 6., the latter two dominating
when activated sludge is in a condition favourable for their propagation. When ex-
tended aeration is carried out and sludge has high activity of nitrification, on the
other hand, Metazoa and Euglypha of Protozoa prevail. Swim t. dominates when
the organic matter loading is high or the water temperature is low.
The survey revealed that Euglypha, Vorticella, Litanotus and Rotifera were
found relatively frequently through the year. It is known that Vorticella and
Litanotus emerge in the normal activated sludge, and Euglypha and Rotifera when
SRT is long (in extended aeration). In the aerobic digestion tank, it was found that
Englypha was dominant. The frequent occurrence of large numbers of Euglypha
and Rotifera is indicative of the probability that SRT is longer than 20 days.
As for bacteria, those working for removal of organic matters (about 10* N/ml)
and nitrobacteria (about 106 ~ 7 N/ml) were identified, which suggests that the
bacterial activity is maintained at a high level both for removal of organic matters
and for nitrification (See Fig. 11).
Fig.-11 Seasonal Variation of Bacteria in Aeration Tank
I
3 6
•s 5
O
1976
F
1977
81
-------
Installation of filters is very important especially at a plant expecting nitrifica-
tion. The floes of activated sludge entrapped in the filter contained lots of micro-
organisms. Biological examination in November disclosed that these microorganisms
included 73,000 N/ml of Euglypha and 18,000 N/ml of mastigopha, the concentra-
tion of the former being about twice as large as in the aeration tank and that of the
latter about 18 times as large. About 10,000 N/ml of Rotifera was also entrapped,
but the great majority was found dead. Other general bacteria and nitrobacteria
were found alive in the floes in a quantity of about 107 ~ 8 N/ml.
Backwash waste contains a far less quantity of microorganisms than in the
aeration tank as it is returned only about once in 48 hours, so that it may be con-
tributing to the bacterial activity in the aeration tank only to a small degree. How-
ever, it is much more meaningful to return the backwash waste to the aeration tank
than to discharge it outside the nitrification system because of its rich bacterial
activity mentioned above.
3.3.8 Consumption of NaOH
NaOH consumption was estimated from the raw sewage flow, and from alkalin-
ity, TKN and pH of influent.
NaOH wad added at a dosage rate of 170ml/min of 25% solution. With a daily
NaOH consumption of about 61 kg, pH was maintained at 8 ~ 8.5.
Influent TKN as revealed by the survey ranged from 7 to 16 kg- N/day, averag-
ing 9.8 kg/day, The NaOH requirement for nitrifying this inflow TKN completely
turned out to be 56 kg/day. As it was confirmed that nearly 100% of influent TKN
was nitrified, the estimated dosage of 61 kg/day can be considered to be adequate.
After pH control was effected, secondary effluent presented a residual alkalin-
ity of 100- 390 as CaCO3 mg/1. This points to the need for controlling NaOH
desage by checking the residual alkalinity in order to reduce overall NaOH consump-
tion.
Although the optimal pH for the activity of nitrobacteria is 8 ~ 8.5, it is
known that nitrifer in activated sludge exhibits the same high activity at pH 7 ~ 9.
Hence, it is considered possible to maintain a high nitrification rate even if the plant
is run with pH value held at 7.5 ~ 8.
Fig. 12 shows the relationship between (NO3 + NO2 )-N and alkali consumption.
Oxidation of 1 mg of NH4-N calls for the input of 7.1 mg of alkali theoretically, but
the actual alkali consumption is usually smaller than this theoretical value. In this
case of the plant, however, alkali consumption of 7.5 mg.
82
-------
c
o
a
O
O
Fig.-12 Relation between (NO3 + NO2)-N and Alkali Consumption
o
100
A Total Alkali Consumption 975.4 kg/d
B Total Nitrite and Nitrate Produced 130.2kg/d
A=7.49
< 50
o / Theoretical Value
O
I I I
0 5 10 15
(NO3 + NO2) -N (kg/d)
3.3.9 Water Balance
In order to clarify the water balance at the plant, the monthly values of total
tap water consumption, restaurant water consumption, dilution water volume, total
reuse water volume and inflow volume were obtained to determine the average daily
value for each, and the total reuse volume was divided into dilution water volume
and final effluent volume by applying the mixing ratio of dilution water and inflow.
During the period from May to August, inflow ranged from 280 m3 /day to
470 m3 /day. The maximum daily inflow, which is not confirmed yet, will have to
clarified by future studies as it is possible that inflow into the plant is influenced by
daily inflow volume especially in August and January when the residual concentra-
tion of NH4 -N records a high value.
Tap water consumption decreased after pH control was put in practice. This
was due to the dwindled use of tap water for diluting final effluent to meet standard.
Tap water consumption at the restaurant showed a slight upward trend during the
survey period.
Fig. 13 shows the breakdown of influent. As seen in this figure, the inflow
volume showed a tendency to decrease from January to June, increase in July, and
drop again from August to March. From summer to autumn, the inflow was re-
latively large, registering about 400 ~ 450 m3 /day, which is likely to be ascribable to
the increased inflow of reuse water.
83
-------
The share of reuse water in the total in(low started rising from about July when
the water quality was stabilized by pH control, and recorded about 60% from July
to March, accompanied by the increased inflow of dilution water. This will give rise
to augmented volume and concentration of various salts and nitrate in circulating
effluent,
Fig.-13 Wastewater Mass Balance
Breakdown of Wastewater Sources
m3/d
500^ °'429
0.436 0.356
0.455 0.371
0302 0.1570.131 0.037
0.004, . 0.176 0.151 0.161
0.231 0.143
Restaurant
Reuse
Water
Volume of Tap Water Used (m3/day)
Percentage of Tap Water Used
84
-------
3.3.10 Nitrate in Reuse Water and Influent
After effecting pH control, tap water consumption for diluting effluent de-
clined because the effluent transparency increased to more than 100 and its NH4-N
concentration became as low as less than 1 mg/1. As a consequence, effluent reuse
rate became higher, with the result that NO3 -N concentration showed a tendency to
increase both in influent and effluent. Specifically, NO3 -N concentration in final
effluent which was in the neighbourhood of 22 mg/1 before pH control increased
to 40 ~ 100 mg/1. This growing tendency of nitrate nitrogen concentration will pose
itself as a serious problem if restriction is placed on total nitrogen concentration at
some future date.
Fig. 14 shows the relationship between NO3-N flowing into the plant in reuse
water and that carried in the inflow sewage. NO3-N concentration in the influent
kept on rising from June to November, and it is likely that this tendency will con-
tinue in future. The concentration dropped in December but the reason for this is
not known. The concentration in reuse water is far higher than that in influent.
The shaded section in Fig. 14 indicates the unknown portion. Assuming that this
section represents the portion denitrified between the reuse water inlet and the
balancing tank outlet, calculation of the denitrification rate produces the results
shown in Fig. 15 which indicates about 50% denitrification rate for the period from
April to September and 30 ~ 40% rate from October to December. The figure
shows that denitrification did not take place only for a few months in winter.
While the location of the exact denitrifying point calls for an another survey, it
is possible that denitrification has taken place in the inflow pit. This is turn calls for
further studies to be made to clarify the NH3 -N balance.
Fig.-14 Change in Nitrate and Nitrite
(Influent Nitrogen vs. Renovated Water Nitrogen)
kg/d
Nitrogen of
Renovated \
'Water A \ \
85
-------
Fig.-15 Denitrification Rate
n 60
cc
•§40
t 20
Q
M A
1976
M
J F M
1970
4. SUMMARY
By conducting pH control at the plant, the following facts were made clear.
1) Flushing water for water closet can be supplied without diluting effluent with
tap water.
2) Nearly 100% nitrification rate can be maintained through the year. According
to the weekly survey, however, a high ammonia concentration was detected
due to retarded nitrification in May, August and January when the service area
is utilized by many people. It may become necessary to resume the operation
of nitrification tanks depending on the cause of this high residual ammonia
concentration which needs to be cleared up by another aurvey.
3) Daily sludge production is estimated to be 10 ~ 40mg/l. Since the plant is
provided with a filters, frequent sludge with drawal is not considered essential.
Further, the long SRT will make it possible to hold the nitrification activity at
a high level through the year.
4) NaOH Consumption
NaOH was dosed at a rate of 61 kg/day with pH held at 8 ~ 8.5. This dosage
proved to be generally acceptable because the calculation worked out on the
basis of the weekly 24-hour survey produced a dosage of 56 kg/day. Con-
sidering the activity of nitrobacteria in activated sludge, it will be possible to
run the plant with pH value held at 7.5 ~ 8.
5) Nitrogen concentration in the effluent increased as a result of the augmented
share of reuse water in the total inflow (more tahn 50%) and attainment of
100% nitrification rate. It will therefore be found necessary to incorporate
denitrification at a future date.
86
-------
CHAPTER 2
I. PRACTICE OF NITROGEN REMOVAL
BY BREAKPOINT CHLORINATION PROCESS
1. Method 88
2. Chlorine Requirement 89
3. Costs for Chemicals in BPC Process 94
4. Caustic Soda Consumption 95
5. Changes of Water Quality 95
5.1 CODcr 96
5.2 Chloride Ion 97
5.3 Nitrate and Nitrite Nitrogen ... 97
6. pH and Oxidation-Reduction Potential 98
7. Removal of Anionic Surfactants 99
8. CODcr Adsorption Ability of Activated Carbon 100
9. Removal of Chlorinated Organics 100
87
-------
1. METHOD
Pilot plant tests for nitrogen removal by breakpoint chlorination (BPC) process
were performed from October 1977 to March 1978 at Minamitama Municipal
Sewage Treatment Plant in Tokyo. The effluent from the tertiary treatment facilities
consisting of chemical coagulation and sand filtration process was used for the pilot
plant study. A schematic flow diagram of the pilot plant and the dimension of each
unit are shown in Fig. 1 and Table 1 respectively. The influent NH3-N concentra-
tion examined in this study was two concentration levels of 6mg/l and 20mg/l.
Ammonium sulfate was added into the ammonia dosing tank for adjusting the
influent NH3-N concentration for this breakpoint chlorination study. Also, caustic
soda was added to the No. 1 pH adjusting tank for a pH control in which a cascade
control system with a connection of a pH meter in the following chlorine dosing
tank was employed. The effects of pH were studied by varing the pH value of the
sample wastewater in the chlorine dosing tank at pH 6, 7 and 8. Chlorine dosing
rate was automatically controled with aNH3-N meter (TECHNICON MONITOR IV)
and a ratio slider. The ratio of chlorine dosage to nitrogen content was varied in a
range from 4 to 16 and the weight of a chlorine gas cylinder (capacity, 1 ton) was,
further, measured to ascertain the C12 : NH3-N weight ratio.
Three types of activated carbon originated from coconut shell (granular,
crushed), spherical coal (granular) and crushed coal (granular) were evaluated by
installing three carbon adsorbers in parallel. Flow rate through the carbon bed was
always automatically adjusted to be 45 m3 /hr. Except Staturday and Sunday, the
pilot plant was continuously operated in a base of 24 hours per day. One oper-
ational condition was continued at least for two day.
Fig. -1 Schematic Flow Diagram of the Pilot Plant
Receiving Ammonia No. 1 pH Chlorine Chlorination Activated carbon No. 2 pH Effluent
tank
Effluent
from the *
tertiary
treatment
\
dc
ta
sing
nk
ft
C-to
t
c
t
ontrol
ank
T 1
' 1 '
1
i
dosing tank
tank \
i
1
ti
I
effli
No. 1
je
nt tank
Mo. 2 No. 3
o
t
ontrol
ank
w I
I
A
tank
t
?
I
L
T
[A
o the river
m
Table-1 Dimensions of the Test Plant
Equipment
Receiving tank
Ammonia dosing tank
No. 1 pH control tank
Chlorine dosing tank
Chlorination tank
Activated carbon adsorber
Activated carbon adsorber
Quantity
1
1
1
1
1
2
1
Dimensions
(Effective Height)
WxLxH,m
3x 5.5x3.5 (2.9)
2.430x3.07(2.48)
2.430 x 3.07 (2.48)
1.450x 1.85 (1.51)
6 x 7 x 2.5 (2.20)
2.5 x 2.5 x 7.00 (6.00)
2.7 x 2.7x7.00(6.00)
Capacity
m3
48.0
11.5
11.5
2.5
92.0
37.5
43.7
88
-------
Table-1 Dimensions of the Test Plant (Continued)
Equipment
Activated carbon effluent tank
No. 2 pH control tank
Effluent tank
Ammonium sulfate storage tank
Ammonium sulfate dissolution tank
Ammonium sulfate dosing head tank
Caustic soda storage tank
Caustic soda dosing head tank
Caustic soda dosing head tank
Activated carbon storage tank
Quantity
3
1
1
1
1
1
2
1
1
1
Dimensions
(Effective Height)
Wx LxH,m
2.030x3.05 (2.47)
2.430x3.07(2.48)
2.5 x 10x2.50(2.00)
1.150x2.35
1.540x 1.84(1.40)
0.800 x 1.40(1.10)
1.940x2.45(2.20)
0.80 x 1.40(0.99)
1.150X 1.40(0.96)
2.20 x4.00x 3.45
Capacity
m3
8.0
11.5
50.0
1.2
2.6
0.6
6.5
0.5
1.0
16.0
2. CHLORINE REQUIREMENT
Relationships between C12 : NH3-N weight ratio (R) and ammonia nitrogen
removal rate are shown in Fig. 2.1 and 2.2. The concentration of ammonia nitrogen
of the sample wastewater in the ammonia dosing tank and the chlorine dosing tank
was measured to obtain the ammonia nitrogen removal rate. The each average value
in continuous operational condition is plotted in these figures. Caustic soda was
Fig. -2.1 Ammonia Removal by Chlorination
NH3-N Average Concentration 5.9 mg/l
pH Adjusted at 6, 7 and 8
(Figures Denote the Adjusted pH Value)
6 7 6 8 8
0
i
100
90
_ 80
60
50
40
•In the Tank
(pH=7 and 8)
In the Chlorine
Dosing Tank
At the Outlet ot
f -- the Chlorination
Tank
1—-
_l I L
5 10 15
Ratio of Chlorine to Ammonia (CI2/NH3-N)
89
-------
Fig. -2.2 Ammonia Removal by Chlorination
NH3 -N Average Cocentration 20 mg/l
pH Adjusted at 6, 7 and 8
(Figures Denote the Adjusted pH Value)
100
90 -
80
1 70
o
-------
pH value in the No. 1 pH control tank has to be raised previously as shown in Fig.
2.3. In the case of the low concentration of ammonia nitrogen in the sample
wastewater, the almost complete ammonia nitrogen removal in the chlorine dosing
tank can be achieved at C12 : NH3-N weight ratio 9.5. The above results were
observed at every set pH value (6 ~ 8) in the chlorine dosing tank. At the lower
C12 : NH3-N weight ratio in a range from 6.0 to 8.0, however, the ammonia nitrogen
removal was slightly higher at pH 6 than at pH 7 and 8.
In the case of the high concentration of ammonia nitrogen in the sample
wastewater, the ammonia nitrogen removal in the chlorine dosing tank at pH 6 was
significantly different from it at pH 7 and 8. At pH values of 7 and 8, the chlorine
dosage at C12 : NH3-N ratio 9.5 was enough to accomplish the almost complete
ammonia nitrogen removal. But the C12 : NH3 -N ratio 1 1.5 was necessary at pH 6.
No further increase of the ammonia nitrogen removal was observed at the
chlorination tank outlet. So it could be said that the reaction of chlorine and
ammonia nitrogen was already completed in the chlorine dosing tank.
Regarding the pH values in the No. 1 pH control tank, they are increased to
pH 9.5, 10.0 and 10.5 at the lower chlorine dosing ratio and to pH 10.5 at the lower
chlorine dosing ratio and to pH 10.5, 11.25 and 11.50 at the higher chlorine dosing
ratio in order to achieve the set pH values 6, 7 and 8 respectively in the chlorine
dosing tank.
The activated carbon adsorption unit following the chlorination tank has
increased the ammonia nitrogen removal ratio as shown in Fig. 2.4 through 2.6. At
the low concentration of nitrogen of the influent and at the low ammonia nitrogen
removal ratio in the BPC process, the additional activated carbon treatment in-
creased the ammonia nitrogen removal rate by 10 ~ 30% (Fig. 2.4). The ammonia
nitrogen removal effect, however, decreases when achieving the removal rate higher
than 90 ~ 95%. In order to accomplish 100% ammonia nitrogen removal, about 9.5
in C12 : NH3-N ratio is necessary. Then, it means that the required C12 : NH3-N
ratio is same as it in the case of no additional carbon unit.
When the requirement of the ammonia nitrogen removal is assumed to be 95%,
the addition of the activated carbon unit can decrease the C12 : NH3 -N weight ratio
in the BPC unit from 8 to 7. At the high concentration of ammonia nitrogen in the
influent, the pH value has an influence to the ammonia nitrogen removal effect of
the activated carbon. As shown in Fig. 2.5, about 30% increase in the ammonia
nitrogen removal rate observed resulting in a decrease of chlorine dosing ratio from
11.5 to 10 on the complete ammonia nitrogen removal. The increase of the
ammonia nitrogen removal rate by the activated carbon unit was only 10% at pH 7
and 8 and the chlorine requirement could not be decreased in the complete
ammonia nitrogen removal. In the case of the ammonia nitrogen removal rate of
95%, the additional carbon unit decreased the chlorine requirement from C12 : NH3-
N ratio 8.8 to 8.3. For the 100% ammonia nitrogen removal and the high concentra-
tion of NH3-N in the influent, the decrease of the chlorine requirement can not be
expected even with the additional activated carbon adsorption unit.
91
-------
Fig. -2.4 NH3-N Removal by Activated
Carbon
100r Activated
Carbon
No. 1
90
80
•5 70
>
o
0)
rr
Z 60
50
40
NH3-N Average Concentration 5.9mg/l
pH Adjusted at 6, 7 and 8
(Figures Denote the Adjusted pH Values)
7.6 7.6 7.6
6 A .V (^
^Outlet of
Chlorination Tank
(pH=7 and 8>
Outlet of
Chlorination Tank
(pH=6)
Activated Carbon
No. 1 (Daiichi Tanso, WA)
Activated Carbon
' No. 2 (Takeda, X-7000)
Activated Carbon
' No. 3 (Calgon, F-400)
5 10
Ratio of Chlorine to Ammonia (CI2 /NH3-N)
15
Fig. -2.5 NH3-N Removal by Activated
Carbon
Average NH3-N Concentration 20mg/l
pH Adjusted at 6
100
90
-S 80
^
"(D
§ 70
E
0>
f£
Z 60
l"
z 50
40
Activated Carbon
No. 1
Outlet of
Chlorination Tank
oU-
Activated Carbon
No. 1
_ Activated Carbon
No. 2
Activated Carbon
No. 3
5 10 15
Ratio of Chlorine to Ammonia (CI2 /NH3-N)
92
-------
100
90
80
o 70
60
Fig.-2.6 NH3-N Removal by Activated
Carbon
Activated Carbon
No. 1
NH3-N Average Concentration 20mg/l
pH Adjusted at 7 and 8
(Figures Denote the Adjusted pH Values)
7 .
Outlet of the Chlorination Tank
o—--Activated Carbon No. 1
• Activated Carbon No. 2
(•> Activated Carbon No. 3
50-
40
5 10
Ratio of Chlorine to Ammonia (CI2/NH3-N)
15
93
-------
3. COSTS FOR CHEMICALS IN BPC PROCESS
Fig. 3.1 shows the costs of chemicals required for the nitrogen removal by the
BPC process. These costs include liquid chlorine ($375/ton) and caustic soda
(15% liquid $90/m3) used in pH control.
This figure indicates that the chemical cost for the NH3-N removal is $7.2/kg
NH3-N (removed) in all the ranges of the pH values and the influent NH3-N con-
centrations studied in this pilot plant tests. (Changing rate $1=¥200)
Fig.-3.1 Chemicals Costs
34
32
30
28
26
24
I'2
i20
WJ
8 18
E
0)
6 16
14
12
10
8
6
4
Treated Amount
44.375 m3/nr
Ammonia Removal
>95%
Set pH Values
60
(Figures Denote Ration
of Chlorine to Ammonia)
6 8 10 12 14 16 18 20 22
Amount of Ammonia Removed (g-NH3-N Removed/m3)
94
-------
4. CAUSTIC SODA CONSUMPTION
Caustic soda requirement to control the set pH values for the breakpoint
reaction is shown in Fig. 4.1. Mol (weight) ratio of the required caustic soda to
the amount of chlorine added is 1.35 (weight ratio 0.76) at the set pH values of 6,
and also 2.35 (1.33) and 2.50 (1.41) at the set pH values of 7 and 8 respectively.
Fig. -4.1 Consumption of Caustic Soda
300 -
250
200
o
a : Weight Ratio
( ) Mol Ratio
Treated Amount
44.375 m3/HR
-OSet pH Values 6
-A- Set pH Values 7
-a- Set pH Values 8
150
o 100
50
50 100 150 200 250
Concentration of Chlorine Dosage (mg-CI2/l)
The overall reaction of the breakpoint chlorination is represented by the
equation (1). The reaction presented by the equation (2) shows the neutralization
reaction.
2NH3 +3C12 -> 2N2 +6HC1 (1)
6HC1 + 6NaOH -> 6NaCl + 6H2 O (2)
According to the above equations, the mol ratio of caustic soda required to
chlorine added to adjust at the pH value of 7 is 2.0. In this test, it resulted in 2.35.
It is, therefore, considered that the sample wastewater has the buffer effects to the
pH elevation at pH around 7.
5. CHANGES OF WATER QUALITY
Water quality changes at various points through the treatment system, such as
at the receiving tank, the chlorination tank outlet and the activated carbon ad-
sorber (No. 1 to No. 3) were observed.
95
-------
5.1 CODcr
The changes of CODcr along the BPC process at the various C12 : NH3-N
weight ratio are shown in Fig. 5.1. The initial concentration of ammonia nitrogen
does not effect the CODcr behaviour. By adding chlorine, its concentration de-
creased in a certain degree and the further reduction of CODcr was achieved through
the following activated carbon adsorber.
Fig. -5.1 Changes in CODcr Concentration
pH6
CODcr
20.0
15.0
I
o
10.0
5.0
™.*f:::::: IS
R : Ratio of Chlorine
to Ammonia
Receiving Ammonia Outlet of Activated
Tank Dosing Chlorination Carbon
Tank Tank No. 2
CODcr removal effects by chlorination and activated carbon adsorption are
summarized in Table 2. CODcr/CODmn ratio was 3.12 which resulted from 41
samples analysis.
Table-2 CODcr Removal Rate (%)
Influent concen-
tration of NH3-N
Low concentration
(about 6 mg/1)
High concentration
(about 20 mg/1)
(*1)
Chlorination
11.8
5.8
(*2)
Activated Carbon Adsorption
No.l
37
33
No. 2
49
43
No. 3
46
42
96
-------
*1 =
100
_B-C
x 100
A A 1W ^ B
A (mg/1) : CODcr (mg/1) at the ammonia dosing tank
B (mg/1) : CODcr (mg/1) at the chlorination tank outlet
C (mg/1) : CODcr (mg/1) at the carbon absorber outlet
5.2 CHLORIDE ION
The changes of chloride ion at the set pH value of 7 are shown in Fig. 5.2.
A concentration of CT in sample wastewater (secondary effluent) was in a range of
60 and 90 mg/1. The decomposition of added chlorine increases chloride in the
effluent as shown in Fig. 5.2. The concentration of chloride, further, increased at
the activated carbon adsorber outlet. This implies that the decomposition of residu-
al chlorine occurs in the carbon bed.
250-
200-
|l50
o
100
50-
Jc.
Fig. 5-2 Changes in Chloride Concentration pH 7
o Low
. High
R : Ratio of Chlorine
to Ammonia
Receiving Outlet of Activated
Tank Chlorination Carbon
Tank No. 2
5.3 NITRATE AND NITRITE NITROGEN
At a high C12 : NH3-N ratio in the BPC process, hypochlorous acid may oxidize
ammonia nitrogen, which results in the increase of nitrate and nitrite nitrogen. In
this study, however, this increase was not observed as shown in Fig. 5.3.
97
-------
16
15
14
J= 12
c
10
O 9
Z
Fig. -5.3 Changes in (NO2 +NO3 )-N
Concentration
ph=7, R-12III
pH: Adjusted after Chlorine Dosage •
R: Ratio of Chlorine to Ammonia \
(I): Low Influent NH3-N Concentration\
(h): High Influent NH3-N Concentration
Ammonia Chlorine Chlorination Activated
Dosing Dosing Tank Outlet Carbon
Tank Tank No. 2
6. pH AND OXIDATION-REDUCTION POTENTIAL
1000
900
j> 800
700
600
500
Fig. -6 Relationship between pH and
Oxidation-Reduction Potential
O -» Less thi
0 — 80 ~ 85%
A -, 85 ~ 90%
T — 90 - 95%
D -* More than 95%
• Figures Denote R
1 Black Plots Denote High Ammonia Concentration
• White Plots Denote Low Ammonia Concentration
Chlorine Dosing Tank
-
// ' ' '
40 4.5 5.0
5.5 6.0 6.5
pH
\>°
1 1
7.0 7.5
98
-------
Oxidantion-reduction potential value of the solution will increase suddenly
when the reaction reaching at the breakpoint. As shown in Fig. 6, the value in less
than 600 mV before reaching the breakpoint, that is in the lower ammonia nitrogen
removal zone of the breakpoint curve, even at a low pH value of wastewater.
In the zone that C12 and NH3-N reaction is near the breakpoint and the
ammonia nitrogen removal rate is greater than 95%, the potential value increases
suddenly. The potential values at pH 6.0 and 7.0 are in the ranges from 800 to
950 mV and from 750 to 900 mV respectively. This indicates that the lower the pH
value, the higher the oxidation-reduction potential value. It also can be said that the
breakpoint reaction is taking place when the potential value is higher than 700 mV.
7. REMOVAL OF ANIONIC SURFACTANTS
Raw sewage usually contains anionic surfactants in a range of 5 and 6 mg/1.
This concentration of surfactants can be reduced to a range from 0.08 to 0.10 mg/1
either by the secondary treatment alone, plus filtration or coagulation processes
with filtration. As shown in Fig. 7, the additional activated carbon adsorption has
decreased the concentration of anionic surfactant to 0.01 ~ 0.02 mg/1.
Fig. -7 Anionic Surfactant Concentrations
in the Effluents of Minami-Tama
Wastewater Treatment Plant
L.q 0.0874 50mm Cell, 650 nm Wavelength
5.0
4.0
— 0.10
"oi
-§ 0.09
c
S 0.08
CO
I 0-07
0
0 °'06
< 0.05
"o
o 0.04
CO
t 0.03
c
CD
CJ
o 0.02
O
0.01
f
V
I
^
I
^
|
|
^
s
^
I
|
i 0.8486 \ Standard Substance Di-2-Ethylhexyl Sulfosuccinate
0.07971 \°'\
} -r- \
0.0854 f
} 1C
-,
)18 Sodium Salt
aS53. 6. 21 AM 10:00
ESS53. 6. 22 AM 10:00
EZ3S53. 6. 24 AM 10:00
0.0118
\ No. 2
\ X-7000
\ / 0.02057
\ 1^^
nl
C QJ
S £
^
99
-------
8. CODcr ADSORPTION ABILITY OF ACTIVATED CARBON
In Fig. 8, the residual CODcr in the activated carbon treatment effluent is
shown. The leakage of CODcr from the carbon adsorbers is shown as.a ratio of
effluent concentration to the influent concentration,Ci/Co.
Fig. -8 Adsorption of CODcr by Activated
Carbon
No. 1 AC (Daiichi Tanso, WA) 0
17.6m3-AC/Column
_No. 2 AC (Takeda, X-7000) *
16.1 m3 -AC/Column
-No. 3 AC (Calgon, F-400)..-,
,20.2m3-
AC/Column
No. 3 Backwash
•No. 1
Backwash
No. 3 Backwash
No. 2 Backwash
1 No. 1 Backwash
Backwash
1500 2000 2500 3000
3500 4000 4500 5000 5500
Volume Treated (m3/m3-AC)
6000 6500 7000 7500
An apparent reduction of CODcr removal rate was observed when the amount
of wastewater treated by activated carbon became as 1800 times as the volume of
the activated carbon F-400 and 2000 times as it of the activated carbon X-7000 and
WA. After then, however, these activated carbon still show the CODcr removal rate
of 30~ 40%.
9. REMOVAL OF CHLORINATED ORGANICS
The addition of a relatively large amount of chlorine to secondary effluent in
the BPC process will produce chlorinated organics. Activated carbon is able to
remove them. Fig. 9 shows the changes of trihalomethanes through the activated
carbon adsorption process. Trihalomethanes such as chloroform, bromoform,
bromodichloromethane and dibromochloromethane can be quantitatively analysed.
The concentration of trihalomethanes in the activated carbon effluent are plotted
against a volume ratio of the treated wastewater volume (average 1,032 m3/day) to
the amount of activated carbon charged in the adsorber (15.6 m3). The granular
(spherical) virgin activated carbon (X-7000) was employed in this study and the
operational conditions are LV (linear velocity) 6.88 m/hr and SV (space velocity)
2.8 hr'1. The ammonia nitrogen concentration and the pH value of sample waste-
water in the study are adjusted to 6.0 mg/1 and pH 8. Before July 31, the chlorine
dosing ratio is averaged to be 9.2 (C12 : NH3-N ratio) and after August 1, to be
11.2.
100
-------
Fig. 9 Analytical Results of Trihalomethanes
> Chlonnation Effluent CHCI,
Actuated Carbon Effluent CHCI
100 Valuas Regulated by EPA
-ft-
0.01
500
1000
1500
2000
2500
Volume Treated
As shown in Fig. 9, total trihalomethanes produced in the BPC process was
20 ~ 50 ppb, which composition is chloroform of 13 ~ 34 ppb, bromodichloro-
methane of 5 ~ 11 ppb, dibromochloromethane of 1 ~ 8 ppb and bromoform of less
than 1 ppb. This composition was not affected by C12 : NH3 -N ratio. The following
activated carbon adsorption unit can reduce the concentration of total trihalo-
methanes to 0.5 ~ 3 ppb. Most of the residual trihalomethanes were of chloroform
(0.3 ~ 3 ppb) and the others were not detected.
When the volume ratio of activated carbon treatment was increased up to
1700~ 1800 (m3/m3-AC), trihalomethanes removal effect by activated carbon
decreased. Trihalomethanes removal ratio lowered to 40% when the volume ratio
increased up to 2500m3/m3-AC, that resulted in the residual trihalomethanes
concentration of 20 ppb. This increase of the residual trihalomethanes was mostly
contributed by the increase of chloroform. With respect to bromoform, no increase
in its concentration was observed.
101
-------
The low concentration of trihalomethanes obtained on August 10 in the
Fig. 9 was probably caused by the operational trouble of the pH meter in the
chlorine dosing Tank. Incidentally, the concentration of each trihalomethane in the
secondary effluent was of chloroform 0.9 ppb, bromodichloromethane 0.2 ppb and
dibromochloromethane 0.08 ppb. Bromoform was not detectable. The composition
of trihalomethanes in the coagulation and filtration effluent was same as it in the
secondary treatment effluent.
102
-------
II. THE PREVENTION OF FORMATION AND REMOVAL OF
CHLORINATED ORGANICS IN WASTEWATER
1. Introduction 104
2. Reaction of Chlorine and Organics 104
2.1 Identification of Chlorinated Organics 104
2.2 Reaction of Chlorine and Nitrogen-containing Compounds 105
3. Formation of Chlorinated Organics 107
3.1 Chlorine Dose Rate 107
3.2 Reaction Time 109
4. Removal and Prevention of Chlorinated Organics Formation 110
4.1 Removal Precursors 110
4.2 Removal of Chlorinated Organics 112
5. Summary 114
103
-------
THE PREVENTION OF FORMATION AND REMOVAL OF
CHLORINATED ORGANICS IN WASTEWATER
1. INTRODUCTION
Since chlorinated organics such as chloroform had been detected in tap water
and was suspected to be relevant to be carcinogenic, extraordinary attention has
been paid to chlorinated organics centering on trihalomethane. Chloroform is
known to be a product of reaction between chlorine and precursors, and the un-
covering of the identity of precursors seems to be magnetizing the attention of those
concerned. Chlorinated organics are giving rise to many concerns related to water
treatment. And these problems are considered relevant to wastewater treatment as
follows:
1) Chlorination disinfection is also introducted in wastewater treatment.
2) As some water treatment plants are located in the lower reaches of a waste-
water treatment plant, there are possibilities of wastewater effluents being
reused. In this case, there should be a possibility of precursors being contained
in the wastewater effluent.
3) The breakpoint chlorination of sewage has something to do with the produc-
tion of chlorinated organics.
This report deals with the above mentioned problems with special emphasis
placed on 3). The breakpoint chlorination process is one of the processes of remov-
ing ammonia nitrogen, and the process is presently being experimented by the
Puplic Works Research Institute, Ministry of Construction at a pilot plant in the
Toba Sewage Treatment Plant in Kyoto. The pilot plant is equipped with an auto-
matic control unit to control the ratio between ammonium and chlorine, and carbon
column to remove residual chlorine. With the use of the automatic control unit,
over 90 percent of ammonia nitrogen removal has been achieved. However, as there
remained a certain amount of organics in the wastewater effluent, it was expected
that the dosed chlorine reacted with such organics to produce chlorinated organics.
2. REACTION OF CHLORINE AND ORGANICS
2.1 IDENTIFICATION OF CHLORINATED ORGANICS
As the breakpoint chlorination process requires dosing of a large amount of
chlorine, the production of chlorinated organics was anticipated. The identification
of chlorinated organics was conducted by employing a Gas-Chromatograph Mass-
Spectrometer (GC-MS). The identified compounds in the breakpoint chlorination
effluents are listed as follows:
carbon tetrachloride, trichloromethane (chloroform), trichloroethylenne, tetra-
chloroethylene, dibromomethane, dibromochloromethane, tribromomethane
(bromoform), m-p-dichlorobenzene, O-dichlprobenzene, 1.2.4-trichlorobenzene
and 1.2.3-itrichlorobenzene.
104
-------
2.2 REACTION OF CHLORINE AND NITROGEN-CONTAINING
COMPOUNDS
Besides ammonia nitrogen, there are other nitrogen-containing organic com-
pounds that consume chlorine in wastewater.
Although nitrogen-containing organic compounds or organic nitrogens are
found in low concentration in the secondary effluent, they are discovered in the
primary effluent at a ratio of about 1 : 1 with ammonia nitrogen. When primary
effluent is to be discharged after chlorination, there is a possibility that nitrogen-
containing organic compounds react with chlorine to produce organic chloramine.
In Fig. 1, sodium hypochlorite (NaOCl) was added to eight different nitrogen-
containing compounds to draw chlorine dissipation curves. The compounds selected
were:
aniline and cadaverine dihydrochloride as amine, N-l naphtylacetamide and
thymidine as amide, 4-aminoazobenzene as azo, histidine and tyrosine as
amino-acid, and humic acid.
Fig.-1 Chlorine Dissipation Curve of Nitrogenous Compounds
Aniline 20mg/l
NaO Cl dose
10mg-CI/l
5 10 15
Time (hr)
10
1 8
1
1 6
o
^
o 4
CD
D
•0
'"> 9
o> *
DC
Q
\
-
N-1 Naphthylacetamide
20 mg/l
NaO Cl dose
10mg-CI/l
\
\
i i i i »
0 5 10 15 20
Time (hr)
25
•§ 6
_o
± 4
S 1
oc
10
"ro 8
CD
.E 6
_o
JZ
" 4
co
8 2
Cadaverine dihydrochloride
20mg/l
NaOCl dose
10mg-CI/l
5 10 15
Time (hr)
20 25
Thymidine 20mg/l
NaOCl dose 10mg-CI/l
10 15
Time (hr)
20 25
105
-------
Fig.-1 (Continued)
10
.E 6
_o
° 4
I2
10
"ra 8
CD
.E 6
;g
'•& 2
OC
Histidine 20 mg/l
NaOCI dose
10mg-CI/l
50mg-CI/l
50
40
30
10
10 15
Time (hr)
20 25
4-Aminoazobenzen
20 mg/l
NaOCI dose
IOmg-CI/1
5 10 15
Time (hr)
20 25
Legend
15
'12
_o
.c
20 ro 6
(T 3-
Tyrosine 20 mg/l
NaOCI dose
15mg-CI/l
10 15
Time (hr)
20 25
Humic acid 20 mg/l
NaOCI dose
IOmg-CI/1
5 10 15
Time (hr)
•Total residual chlorine
- Free residual chlorine
The measurement of chlorine was based on the DPD method. The difference
between the thick line and the thin line in Fig. 1 is the amount of organic chlora-
mine formed. Organic chloramine is composed of cadaverine dihydrochloride,
histidine and tyrosine. With the reaction time, the residual chlorine in histidine and
tyrosine decreased and was considered to partly have changed into aldehyde.
Thymidine consumed little chlorine. Aniline, N-l naphtylacetamide, 4-amino-
azobenzene and humic acid produce little organic chloramine. As these compounds
have the property of aromaticity, there may be substitution reaction occured with
these compounds and chlorine. The products of reaction between aniline and chlo-
rine have partly become clear by using the GC-MS. When 10mg-Cl/l of sodium
hypochlorite was added to 20 mg/l of aniline solution, three substitutions of O-
chloroaniline, m-p-chloroaniline and 2.4-dichloroaniline and non-reacted aniline
were identified. The ratio of each compound was: O-chloroaniline 2.8%, m-p-
chloroaniline 1.9%, 2.4-dichloroaniline 0.5% and non-reacted aniline 47.4%. All
these total 52.6%. However, it was not possible to identify the remaining 47.4%.
Also, chloroform was identified in the solutions of the above mentioned
compounds 24 hours after addition of chlorine. Namely, 15 Mg/l of chloroform was
detected in 4-aminoazobenzene solution and 60|Ug/l in humic acid solution. Humic
106
-------
acid is known as a precursor in producing chloroform. Chloroform was not detected
from other compounds.
Although the reactivity of chlorine and nitrogen-containing compounds was
high, the reaction velocity was comparatively slow.
Primary effluent contained ammonia nitrogen and nitrogen-containing organic
compounds. It is known that the reaction velocity between ammonia nitrogen and
chlorine is fast. Accordingly, when chlorine is dosed to the primary effluent, it is
considered that the chlorine first reacts with ammonia nitrogen and produces
inorganic chloromine. When compared with chlorine, chloromine is reported to be
inferior in reactivity. Also as the disinfection level of chlorine is only a few mg Cl/1,
free chroline of high reactivity was hardly detected. From the above reasons, it was
concluded that chlorine dosing on a disinfection level rarely produce chlorinated
organics and organic chloramine.
3. FORMATION OF CHLORINATED ORGANICS
The formation of chlorinated organics is reported to be subjected to chlorine
dose rate, reaction time, pH and temperature. In this study, effects of chlorine dose
rate and reaction time was determined.
3-1 CHLORINE DOSE RATE
Tests were conducted to determine to what extent chlorinated organics were
formed by the dosing rate of chlorine on a disinfection level and on a breakpoint
level. The rate of chlorine dose on a disinfection level was 5 mg-Cl/2 and on a
breakpoint level between 100 and 200'mg-Cl/C. The reaction time was about 1
hour. The wastewater were collected from five wastewater treatment plants in
Tokyo and her neighborhood. Analysis were conducted by employing GC equipped
with BCD on compounds with a low boiling point such as chloroform, etc.
Fig. 2 shows the results of tests for the secondary effluent. Totally there were
23 different peaks detected, although not all the secondary effluent samples were
responsible for the 23 peaks. The average number of peaks in the secondary effluent
itself was 9.9. When chlorination was conducted on the secondary effluent on both
the disinfection and breakpoint levels, respectively, each recorded an average of 12.5
peaks.
107
-------
Fig.-2 The Effect of Chlorine Dose on Secondary Effluents
500
100
50
S 10
a
3 5.0
1.0
0.1
Secondary effluent
Chlorine dose on disinfection level
Chlorine dose on breakpoint level
2345678 91011121314151617181920212223
Peak No. (in order of retention time)
Peak
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Compounds
(Unit)
CH2CI2 (mm)
CHCI3 (ppb)
I.l.l-Trichloroethane (ppb)
CCI4
Unknown
Unknown
C2 HCI3
Unknown
CHBrCI2
CH2Br2
Unknown
Unknown
Unknown
Unknown
C2CI4
CHBr2CI
Unknown
Unknown
Unknown
Unknown
CHBr3
Unknown
Unknown
(10"3 ppb)
(mm)
(mm)
(ppb)
(mm)
(ppb)
(ppb)
(mm)
(mm)
(mm)
(mm)
(10"! ppb)
(ppb)
(mm)
(mm)
(mm)
(mm)
(ppb)
(mm)
(mm)
When comparing the secondary effluent and the disinfected effluent, except
for peaks No. 13, 19 and 21, no marked differences were confirmed. The reason
why No. 21 marked a great difference was perhaps due to the large value of 65
Mg/C detected in the effluent of one sewage treatment plant. This sewage treatment
plant is located on a coastal line where its influent contained more than 2,000 mg/C
of chloride ion concentration due to the intrusion of sea water. Therefore, as the
bromide ion concentration was higher than in ordinary wastewater, it was
considered to have resulted in the more formation of bromide compounds. This, on
the other hand, indicates if bromide ion exists, the reactivity between chlorine and
108
-------
organics becomes higher.
When dosing chlorine on a breakpoint level, it has shown a drastic difference in
the height of the peaks when compared with those of the secondary effluent. Those
distinct differences were in peaks No. 1, No. 2, No. 5, No. 6, No. 9, Nos. 12 ~ 14,
and Nos. 16 ~ 21. Of these, the compounds identified were CH2C12, CHC13,
CHBrCl2, CHBr2Cl, and CHBr3. Although confirmed existing in the wastewater,
the compounds that inevitably do not associate with chlorination are CH3CC13,
CCl4,C2HCl3,CH2Br2 andC2C!4.
ECD is a detector which has a peculiar sensitivity to halogenide. Also ECD's
sensitivity differs greatly according to the types of compounds. By ignoring the
differing sensitivity of ECD, chlorinated organics formed on both the disinfection
level and the breakpoint level based on the secondary effluent were estimated from
the heights of peaks. As a result, it was 1.69 times on the disinfection level and
14.8 times on the breakpoint level of the secondary effluent respectively.
In case of the primary effluent, when similar assumptions were made, it
resulted in the same tendency. The results were 1.18 times on the disinfection level
and 16.6 times on the breakpoint level of the primary effluent respectively.
From these results, when chlorine is dosed on a breakpoint level to the waste-
water, although each chemical compounds is not identified, it has become obvious
that a variety of chlorinated organics are formed in short time. Of all the identified
compounds, the concentration of trihalomethane was the highest. And, if the re-
action time is further lengthened , it is assumed that the concentration of trihalo-
methane will increase.
3.2 REACTION TIME
A large amount of chlorine is dosed to remove ammonia nitrogen by the break-
point chlorination process. But as the breakpoint being the border, the forms of the
residual chlorine differ. Inorganic chlorine exists before the breakpoint while free
chlorine is found after the breakpoint. And on the breakpoint, both inorganic
chlorine and free chlorine little exist. To obtain the above three conditions, chlorine
was dosed to the secondary effluent. After chlorine dosing, analysis of chloroform
formed were conducted at the first hour and at the 24th hour. The chloroform
concentration at pre-breakpoint, breakpoint and post-breakpoint changed from 12
to 14, 39 to 43, and 88 to 260 Mg/1, respectively. However, before the breakpoint
and at the breakpoint, there were no marked changes in the chloroform concentra-
tion even after 24 hours. In the post-breakpoint condition, or in a condition when
free chlorine exists, the chloroform concentration increased by three times with the
reaction time. This indicates the fact that the secondary effluent contains a good
amount of precursors that have potential to form chloroform.
109
-------
4. REMOVAL AND PREVENTION OF CHLORINATED ORGANICS
FORMATION
4.1 REMOVAL PRECURSORS
4.1.1 Laboratory Tests
Gel filtration chromatography (GFC) is one type of liquid chromatography and
is used as a means to evaluate the removal effects of soluble organics. Fig. 3 shows
the gelchromatograms of the primary effluent, the secondary effluent, the coagu-
lated secondary effluent and the coagulated and carbon adsorbed secondary effluent.
Fig.-3 Gel-Chromatogram of Wastewater
30r
0.422
0.716
^ 20
E
J5
< 0.1
0.3 L
30
20
25
35
40
Coagulated and adsorbed secondary effluent
The gel conditions are as listed below:
gel bed Sephadex G-15
developer H2O
fraction volume 10ml
The sample used for gel filtration chromatography was filtered by the milipore
filter of 0.45 M and then condensed to 20 times by a rotary evaporator. Concen-
trated organics were separated by gel filtration chromatography after the condensed
solution was filtered by 0.45 n filter. The loss of soluble organics by condensation
was about 50 percent, and the recovery rate of soluble organics by gel filtration
chromatography was over 90 percent.
From the gel filtration chromatography, the soluble organics are divided into
four groups: Group I is composed of organics of over 1,500 molecular weight,
Group II is consisted of organics with 260 nm adsorbance, Group III was organized
110
-------
by organics with no 260 nm adsorbance, and Group IV was made up of organics
colored brown with 260 nm adsorbance.
When studying the gel filtration chromatography, the secondary effluent of the
activated sludge treatment is generally low in TOC when compared with the primary
effluent, and shows that activated sludge process is effective in removing the
organics in Group III. When secondary effluent underwent a chemical precipitation
process, organics in Group I were removed and those in Group II and Group III re-
mained. However, when carbon adsorption is conducted, only a negligible amount
of organics of Group IV was detected.
Table 1 shows the studies made on the chloroform formation in each group
dosing chlorine to the samples divided into four at the gel filtration chromato-
graphy. The amount of chlorine dosed was about 10 mg Cl/C. The reaction time
was about one hour, and sodium sulfite was dosed to stop reaction. From Table 1,
the following facts become clear:
Table-1 Chloroform Formation by Chlorination
Primary effluent
Secondary effluent
Coagulated*
secondary effluent
Coagulated and
adsorbed secondary
effluent**
Not
Chlorinated
0"g/i)
7.8
(40.6)
3.7
(14.8)
1.8
(13.4)
0.8
( 7.7)
Chlorinated
(Mg/1)
61.4
48.6
39.5
4.4
GFC Fraction (%)
Group
I
16.7
10.5
4.9
2.1
Group
II
25.5
14.2
16.2
2.1
Group
III
13.5
11.0
10.3
0
Group
IV
44 .4
43.5
32.9
3.0
Total
100
79.2
64.3
7.2
( ) Soluble TOC, mg/1
* Coagulant Alum, mole ratio Al/p = 3
** Coagulant Alum, mole ratio Al/p = 3
activated carbon Colgon Firtrasorb 300, SV = 5
1) When comparing the primary effluent and the secondary effluent, despite the
TOC removal being 67 percent, the chloroform concentration only dropped by
about 20 percent. Therefore, the removal of precursors can not be expected in
the activated sludge treatment.
2) When comparing the secondary effluent and the coagulated secondary effluent,
the chloroform concentration has dropped by 18.7 percent. Then, the co-
agulation process can not be considered that effective in removing precursors.
3) Carbon adsorption was most effective in the removal of precursors.
4) Group IV was brown in color and was considered to be formed by compounds
resembling humic acid or fulvic acid. Of the chloroform formed in the primary
effluent, the secondary effluent and the coagulated secondary effluent,
111
-------
organics belonging to Group IV occupied nearly half.
5) Group II and Group IV organics with UV 260 nm adsorption produced a
significant amount of chloroform. In the primary effluent, the chloroform
produced by organics in Group II and Group IV accounted for nearly 70 per-
cent of the total. Similarly, in the secondary effluent, they accounted for
about 73% and in the coagulated secondary effluent about 76%.
4.1.2 Pilot Plant Tests
As shown in Table-1, activated carbon is quite effective in removing precursors.
As the pilot plant in Kyoto, studies on carbon capacity were made by feeding
the effluent of the breakpoint chlorination process on the filtered secondary
effluent and the filtered-adsorbed secondary effluent. As the test periods and the
operation conditions of the carbon columns for both effluents differed, accurate
comparison was not possible. The following shows the results of the tests:
Chloroform Concentration after Breakpoint Chlorination (/ig/2)
filtered
filtered-carbon adsorbed
average
36.2
29.7
range
11.9-80.5
9.3-63.8
Studies of the results reveal that the residual chloroform concentration only
dropped by 18 percent in the filtered-adsorbed secondary effluent compared with
the filtered secondary effluent. At the pilot plant, the contact time of the carbon
column was 36 minutes in a six-month continuous operation, and reactivation was
conducted on once per six month basis. Accordingly, in this condition, the pre-
cursors in the wastewater within six month period seem to have broken through.
4.2 REMOVAL OF CHLORINATED ORGANICS
Fig. 4 shows the Freundlich's adsorption formula employing activated carbon
of granulated Takeda X-7100 and Calgon Firtrasorb 300. The initial concentrations
of chloroform and bromodichloromethane were set at 119 and 32 mg/£, respectively.
The temperature was between 24 and 25° centigrade.
From the Fig. 4, the following became clear:
112
-------
1000
100
0 10
I
o
3
.E
x
Fig.-4 Freundlich's Adsorption Formula
1000r
O CHCIj
A CHBrCI,
-e
u
TJ
03
s 100
10
Calgon Firtrasorb 300
log a =— log c + log k
CHCI, — =• 1.012, log k = -0.082
CHBrCI, —=0.977, log k = 0.977
O CHCIj
A CHBrCI,
10 100
Residual concentration (jug/1)
10
Residual concentration (Mg/l)
100
1)
2)
Bromodichloromethane is adsorbed more easily than chloroform.
The adsorption capacity differed a little according to the types of activated
carbon. But the chloroform per 1 gram of activated carbon or the adsorption
capacity of bromodichloromethane (x/m) at the most was lOOAig order.
At the Kyoto pilot plant, to remove the chloroform formed by the breakpoint
chlorination process, tests were conducted by employing Takeda X-7000. The
apparent contact time was 20.7 minutes. From the first week to the fourth week,
the average removal rate of chloroform for each week was 80.0, 55.9, 53.9 and
40.4%, respectively. The chloroform adsorbed in the activated carbon during the
operation in the 4th week was 54.8^g-CHCl3/g. Accordingly, the chloroform
adsorbed by the activated carbon was very small, thus removal of chloroform by
activated carbon can not be highly expected.
The detected dichlorobenzene and trichlorobenzene in the effluents at the
Kyoto plant were as follows:
Concentration
Chlorination
Chlorinated-
adsorbed
m-p-DCB
2.2
0.11
0-DCB
3.2
0.51
1.2.4.-TCB
0.48
0.70
1.2.3-TCB
0.45
0.02
The concentrations of dichlorobenzene and trichlorobenzene were both /ug/8
order. And except for 1.2.4-TCB, it was considered that the chloroform was com-
paratively easily adsorbed into the activated carbon.
113
-------
5. SUMMARY
The chlorinated organics formed by the wastewater breakpoint chlorination
process was low in concentration and polysucrose. Although the identified com-
pounds were limited in number, of those identified trihalomethane (chloroform,
bromodichloromethane, dibromochloromethane and bromoform) had comparative-
ly high concentration.
To prevent the formation of trihalomethane in high concentration in the
process of breakpoint chlorination, the following can be recommended:
1) Conduct carbon adsorption prior to chlorine dosing to remove precursors.
2) The rate of chlorine dosing should not exceed the breakpoint.
3) To shorten as possible the reaction time of chlorine and organics. The residual
chlorine should readily be removed.
It is most effective to adsorb by granular activated carbon to remove precursors
of trihalomethane. However, a long lasting effect of granular activated carbon can
not be expected. According to the gel filtration chromatography method, it was
anticipated that the organics with UV 260 nm adsorbance made up the precursors.
Chlorination on a disinfection level presented no special problems with regards
chlorinated organics although there was possibility of bromine compound forma-
tion when the bromide ion concentration was high in the wastewater.
114
-------
CHAPTER 3
DEWATERING AND INCINERATION OF SEWAGE SLUDGE
WITH PULVERIZED COAL
1 Characteristics of the Dewatering and Fluidized Incineration
Method 116
2 Method of Experiments 116
2.1 Flow Sheet 116
2.2 Experiments on Dewatering 117
2.3 Experiments on Incineration 119
3 Results of Experiments 119
3.1 Experiments on Dewatering 119
3.1.1 Experiments on the Small Pressure Filter 119
3.1.2 Experiments on the Pilot Plant 121
3.2 Experiments on Incineration 121
3.2.1 Critical Limit of Autogeneous Combustion 121
3.2.2 NOx Concentration 122
3.2.3 SOx Concentration 124
3.2.4 Heavy Metal Release from Ash 124
3.2.5 Dust Concentration 125
3.2.6 Material Balance 126
4 Summary of Results 126
115
-------
The dewatering and fluidized incineration method with pulverized coal is an
object of public attention as a sludge incineration system that makes use of pulveriz-
ed coal as dewatering aids, as substituted energy for oil and for prevention of
secondary pollution.
Experiments of this dewatering and fluidized incineration had been carried out
by Yokohama City* on a pilot plant, and fundamental data have been obtained.
The outline of the experiments and the results obtained are reported below.
1. CHARACTERISTICS OF THE DEWATERING AND FLUIDIZED
INCINERATION METHOD
This method is composed of the dewatering process and the incineration pro-
cess, and is said to provide the following features.
In the dewatering process, dewatering is accomplished by making use of poly-
metric coagulant and pulverized coal to the level of moisture content that is identi-
cal to that of dewatered sludge obtained by using conventional inorganic coagulant.
As a result, autogeneous combustion can be made in the incineration process with-
out auxiliary fuel.
In the incinerating process, the fluidized bed is partially turned into a reductive
atmosphere by red-hot pulverized coal, causing nitrogen oxide (NOx) to be reduced
to nitrogen gas (N2). At the same time, oxidization of chromium in the sludge into
sexivalent chrome is prevented. In addition, by the use of cement clinker particles
(major constituent CaO) as the fluidizing medium instead of silica which has been
conventionally used, sulfur oxides (SOx) are retained as calcium compounds to be
removed.
The major operation of this method is composed of operation of the dewaterer
for obtaining autogeneously combustible dewatered sludge cake (control of dosage
of coagulant and pulverized coal), control of the sludge loading rate (dewatered
cake feed rate) and control of the air feed rate.
2. METHOD OF EXPERIMENTS
2.1 FLOW SHEET
A flow sheet of the pilot plant is shown in Figure 1, and specification of the
principle equipment is shown in Table 1.
Thickened sludge (mixture of primary settled sludge and excess activated
sludge) is stored in a storage tank, and is then fed to a mixing tank by a pump.
Soluted polymetric coagulant is added to the thickened sludge and the mixing opera-
tion is carried out in a mixing tank for about 30 seconds to cause formation of floes.
The sludge is then thickened to two times by a rotary screen, and then fed to the
next mixing tank, where the thickened sludge is mixed with pulverized coal in the
form of slurry for about 30 minutes. The blended sludge is dewatered by a dewater-
er of pressure filter type. The dewatered cake is fed to a hopper feeder for storage.
The dewatered cake is charged into the furnace from the top of the furnace at
the standard feed rate of 510 kg/m2-h through a flight conveyor and a cake feeder.
The temperature of the fluidized bed in the furnace is kept at the level of about
800°C, and the furnace outlet gas temperature is kept at about 900°C. The sludge
makes autogeneous combustion. The air that is necessary for combustion is fed
* The City made a contract on the experiment with Babcock Hitachi K.K., and set up a joint committee to carry
out the experiment.
116
-------
Fig. 1 Flow Sheet
Dewaterina Process
Rutarv Screen
Flight Conveyi
Forced Draft Fan Forced Draft Blower
Table 1. Specification of Major Equipment
Process
Dewatering
Process
Incinerating
Process
Major Equipment
Pre-Thickener
Sludge Feed Pump
Dewaterer
Incinerator
Single Cyclone
Air Preheater
Wet Scrubber
Electro Static Precipitator
Forced Draft Blower
Forced Draft Fan
Induced Draft Fan
Specification
Rotary Screen 900 mm0 x 1,770 mmL 0.75kW
Diaphram Pump 80 C/min x 40m 5.5 kW
Pressure i rjOO x 1,000 mm x 10 Chambers 16.7 m2
Filter
Fluidized Bed Furnace 400 kg/h 1,0000 x 5,400 mmH
High Temp. Type 2,400 Nm3/h x 800°C
Tubular Heat Exchanger 16.7 m2
Venturi Scrubber 2,400 Nm3/h
Dry Type ESP 1,320 Nm3/h
Turbo Blower 40 m3/min x 2,000 mmAq 30 kW
Turbo Fan 90 m3/min x 500 mmAq 15 kW
Turbo Fan 190 m3/min x 600 mmAq 37kW
through the air distributor located at the bottom of the fluidized bed. Recircula-
tion of flue gas is made as required for controlling O2 concentration in the furnace.
The majority of the dust in the flue gas is caught by a single cyclone. The flue
gas enters an air preheater, after passing through the single cyclone, where the gas
temperature is quenched to about 300°C, and is then fed to a venturi scrubber for
wet scrubbing or to an electrostatic precipitator for electrostatic dedusting. The
properties of polymetric coagulant, pulverized coal, and cement clinker particles
used for the experiments are shown in Table 2, Table 3 and Table 4 respectively.
Selection of these materials and the method of adding them were determined in
laboratory experiments in advance.
2.2 EXPERIMENTS ON DEWATERING
The sludge used in the experiments was thickened sludge of two kinds of
different VTS (volatile total solid), and the properties are shown in Table 5.
117
-------
Table 2. Properties of Polymetric Coagulant
Molecular Weight
700 x 104
Viscosity of Solution (0.5%)
350 C.P.
pH Available
(9
pH of Solution (0.5%)
3.3
Table 3. Properties of Pulverized Coal
Items
Specific Gravity
Bulk Density
Angle of Rest
Moisture
Ash
Gross Heating Value
C
H
N
S
ce
Unit
-
g/cm3
degree
%
% (D.B)
Kcal/kg
% (D.B)
% (D.B)
% (D.B)
% (D.B)
% (D.B)
Analyzed Value
1.39
0.758
35
5.38
17.64
6,210
60.54
4.66
0.95
0.48
0.01
Table 4. Properties of Fluidizing Medium
Specific
Gravity
(-)
3.20
Bulk
Density
(g/cm3)
1.37
Angle
of Rest
(degree)
28
CaO
(wt. %)
48.7
SiC-2
(wt. %)
12.14
A«203
(wt. %)
5.50
Table 5. Properties of Thickened Sludge
Kinds of Sludge
High VTS Sludge (56%)
Low VTS Sludge (44%)
PH
7.6
6.8
TS
(%)
3.4
4.3
Gross Heating Value
(Kcal/kg)
3,300
2,200
Constituent of Solid (%)
C
36.1
20.7
H
4.0
3.5
N
3.7
1.7
A small pressure filter in the bench scale (178 mm x 178 mm x 1 chamber) and
a pressure filter in the pilot plant (1,000 mm x 1,000 mm x 10 chambers) were
used for the experiments. In the experiments with a small pressure filter, dewater-
ing was attempted with various combinations of coagulant and pulverized coal to
investigate the effect of coagulant and pulverized coal in dewatering. With the
pressure filter in the pilot plant, dewatering was made under the conditions iden-
tical to those with the small pressure filter, and investigation was made as for the
118
-------
scale-up effect of dewaterers. Dewatering conditions were filtration for 8 min-
utes at 4 kg/cm2 and squeezing for 12 minutes at 10 kg/cm2 for both pressure
filters.
2.3 EXPERIMENTS ON INCINERATION
The heating value required for autogeneous combustion of sludge containing
pulverized coal, the correlation between sludge loading rate, air feed rate and NOx
concentration and the correlation between the supply rate of cement clinker parti-
cles and SOx concentration were investigated through the experiments. In addition,
investigations were also made as for properties of ash, release of heavy metals and
dust catching efficiency of electrostatic precipitator and of venturi scrubber.
3. RESULTS OF EXPERIMENTS
3.1 EXPERIMENTS ON DEWATERING
3.1.1 EXPERIMENTS ON THE SMALL PRESSURE FILTER
The results of experiments made with a small pressure filter are shown in
Figure 2 and Figure 3. These figures represent moisture content of dewatered cake
to the pulverized coal dosage (to total solid) for every coagulant dosage (to total
solid). These figures also indicate the range in which removability of dewatered cake
from filter cloth is good. In addition, these figures indicate the range in which
dewatered cake autogeneously combusts, which will be described later.
According to the results of these experiments it is apparent that differences
arise in the dewatering effect by the VTS of sludge.
a. Moisture content of dewatered cake
« For obtaining dewatered cake of identical moisture content, the dosage of
polymetric coagulant and pulverized coal required for the sludge of low
VTS is less than that required for the sludge of high VTS.
« In the case where VTS of sludge is high, the effect of the dosage of pulver-
ized coal over the moisture content of the dewatered cake is not apparent
if the pulverized coal dosage is 100% or less. In this case, however, a large
difference occurs in the moisture content of dewatered cake when the
difference in the dosage of polymetric coagulant is between 0.6% or less
and 0.9% or higher.
Fig. 2 Results of Dewatering Experiment (VTS=56%) Fig. 3 Results of Dewatering Experiment (VTS=44%)
Polymetric Coagulant Dosage
Polymetric Coagulant Dosage
0.3%
0.6% 90
utogeneous Limitation ^ $>,
JQ.3%
0.6%
0.9%
1.2%
-Cake Removable Autogeneous_Lim,m,on
t Limitation
100 200
Coal Dosage (% to TS)
300
0 20 40 60 80 100 120 140
Coal Dosage (% to TS)
119
-------
Where the dosage of pulverized coal is over 100%, the moisture content of
the dewatered cake is reduced when the dosage of pulverized coal increases,
even if the dosage of polymetric coagulant is fixed. In this case, reduction
in the moisture content of dewatered cake due to the difference in the
dosage of each coagulant is apparent to the dosage rate of 1.2%.
In the case where VTS of sludge is low, the effect of pulverized coal over
the moisture content of dewatered cake was observed from the range where
dosage is small. As for polymetric coagulant, a difference in the effect over
the moisture content of dewatered cake was observed between dosage rates
of 0.3% and 0.6%, but no difference was observed in the moisture content
of dewatered cake between other dosages.
What indicates the moisture content of dewatered cake obtained through
calculation by the simple addition of pulverized coal together with meas-
ured values is shown in Figure 4 and Figure 5. If the measured value is less
than the calculated value which is indicated by broken lines, it is meant
that pulverized coal caused reduction in moisture content of dewatered
cake at a rate that is higher than the increase of solid materials, and it indi-
cates that it has an effect as a dewatering aid.
According to these figures it is found that measured values are less than
calculated values and pulverized coal has an effect as a dewatering aid
where VTS of sludge is low.
Cake removability
. As shown in Figure 2 and Figure 3, the removability of dewatered cake
from the filter cloth is good below moisture content of cake of about 65%
in the experiments.
. In the case where VTS of sludge is high, the dosages of pulverized coal
required to obtain dewatered cake with removability are 300%, 150% and
30% at minimum respectively in correspondence to dosage of polymetric
coagulant of 0.6%, 0.9% and 1.2 -v 1.5%.
• In the case where VTS of sludge is low, cake removability is good except
for the cake where dosage rates of polymetric coagulant and pulverized coal
are 0.3% and 30% respectively.
Fig. 5 Effect of Pulverized Coal
as Dewatering Aids (VTS=44%)
Polymetric Coaglant Dosage
Fig 4 Effect of Pulverized Coal
100 ias Dewatering Aids (VTS=56%)
90
Sgol
Fig. 5
100 1-
Polymetric Coagulant Dosage
• 0 3% to TS
O 0.6% to TS
« A 0.9% to TS
w • D 1 .2% to TS
1 2 O 8 • 9 1 .5% to TS
1 °^^- 0
»7oL^>--.
S. T>«*^ A-.
Eo
1 60
I 50
40
30
" M^6 n *A~- ~~ ~
^0>?V° "~~*-/V "•.-•. 03<
Measured
ralculated £ 80
* £ (
"5 70
•g1 C
v5 1
"5 60
O v
" ^^4jL .. ~ ~ ~ ~ - 0-6% ~ 3 50
" " - -~ t~2%:n 40
i .5%- a
30,
k^
t>~~-^
^tf
-
;
80.3% to TS
0.6% to TS
ft, 0.9% to TS
Q 1.2% to TS
U 1.5% to TS
Measured
Calculated
100 200
Pulverized Coal Dosage (% to TS)
300
40 60 80 100 120
Pulverized Coal Dosage (% to TS)
140 160
120
-------
3.1.2 EXPERIMENTS ON THE PILOT PLANT
a. Moisture content of dewatered cake
The results of experiments on the pilot plant which were carried out under
the conditions identical to those of the fundamental experiments are shown
in Figure 6. The moisture content of dewatered cake in the experiments on
the pilot plant was higher in the range of 0 'v. 4% than the results of the
fundamental experiments, but the effect of polymetric coagulant and
pulverized coal over dewatering was identical in both experiments.
b. Filtration rate
What indicates the filtration rate to VTS of sludge is shown in Figure 7.
According to this figure, the filtration rate tends to be reduced as VTS of
sludge increases.
3.2 EXPERIMENTS ON INCINERATION
3.2.1 CRITICAL LIMIT OF AUTOGENEOUS COMBUSTION
a. Limitation of heating value
The results of incineration of cake containing pulverized coal carried out
with dosage of pulverized coal varied for the purpose of obtaining the heat-
ing value required for autogeneous combustion of the cake containing pul-
verized coal are shown in Table 6. The incineration temperature was 800°C
and the excess air ratio was 1.3 at standard.
From Table 6, it was estimated that the critical heating value required for
autogeneous combustion of dewatered cake is 1,100 Kcal/kg of wet cake
because supplemental fuel combustion is required if the heating value is less
than this level.
b. Limitation of moisture content and pulverized coal dosage
The autogeneous limits in said Figure 2 and Figure 3 give the autogeneous
limit moisture content of cake containing pulverized coal to a certain pul-
verized coal dosage. The autogeneous limit moisture content was calculated
based on the heating values of dry solid of sludge and of pulverized coal as
well as pulverized coal dosage, assuming that the heating value required for
Fig. 6 Comparison of Sludge Cake Moisture between Bench
Scale Pressure Filter and Pilot Plant Pressure Filter
Coal Dosage
Fig. 7 Relationship between VTS
of Sludge and Filtration Rate
70
060
f
55
S50
£
I 4
0 10 20 30 40 50 60 70 80 90 100
VTS of Sludge (%)
0.6
0.9 1.2 1.50.6 0.9 1.2
Polymetric Coagulant Dosage (%)
121
-------
Table 6. Relationship between Heating Value and Autogeneous Combustion
Coal Dosage
(% to Sludge TS)
33.7
47.3
51.9
50.9
Moisture of Cake
(%)
56.4
55.0
53.6
55.1
Net Heating Value
(Kcal/kg)
756
908
1,068
1,134
Kerosene
Consumption
(£/h)
14.2
10.3
0
0
Bed Temperature
(°C)
760
790
780
820
note) Thickened Sludge has 34 percents of VTS, 7.1 percents of TS and nearly
1,600 Kcal/kg of dry solid as heating value.
autogeneous combustion of cake containing pulverized coal is l,100Kcal/
kg of wet cake.
From these figures, it is determined that dosages of pulverized coal of 50%
or higher and dosages of polymetric coagulant of 0.9% or higher are re-
quired for sludge of high VTS (VTS 56%), and that dosages of pulverized
coal of 50% or higher and dosages of polymetric coagulant of 0.3% or
higher are required for sludge of low VTS (VTS 44%). Autogeneous com-
bustion of dewatered cake cannot be accomplished if dosage of pulverized
coal is 30% or less in this case. Therefore, from both aspects of removabil-
ity of cake from filter cloth and autogeneous combustion, minimum dosage
of pulverized coal is 50%, and the same of polymetric coagulant is 0.9%
when VTS of sludge is high and 0.3% where VTS of sludge is low.
3.2.2 NOx CONCENTRATION
a. Sludge loading rate, air feed rate and NOx concentration
500 r 20 h
400
I300
g 200
o
c
o
CJ
X
O
100'
15
.210
Fig. 8 Chart of NOX and O2 Concentration
1 HR
Sludge Cake Feed Rate (kg/h)
Sludge Cake Loading. Rate(kg/m2h)
FluidizinR Air (Nm3/m2.h)
400
509
920
300
382
920
300
382
690
200
255
940
122
-------
Fig.
600
The change in the NOx concentration at the furnace outlet when the sludge
loading rate and air feed rate are changed while continuous incineration of
sludge is maintained is shown in Figure 8.
At the beginning of the experiments, the sludge loading rate was 509
kg/m2-h and an air feed rate was 920 Nm3/m2-h, and then the sludge load-
ing rate was reduced by 25% to 382 kg/m2-h with the air feed rate un-
changed. As a result, O2 concentration at the furnace outlet increased and
NOx concentration also increased accordingly. Next, it was attempted to
reduce the air feed rate by 25% to 690 Nm3/m2.h with the sludge loading
rate kept unchanged. As a result, O2 concentration at the furnace outlet
was reduced and NOx concentration was also reduced. Then, the air feed
rate was increased to the original value and the sludge loading rate was
reduced to 50% of the original value. A remarkable increment in the O2
concentration and the NOx concentration occurred as a result.
From these results, it can be said that the NOx concentration is related to
both the sludge loading rate and the air feed rate and that it is possible to
reduce NOx concentration as the sludge loading rate is increased to the air
feed rate, that is, as O2 concentration at the furnace outlet is reduced.
Relationship between O2 concentration and NOx concentration at the fur-
nace outlet
The relationship between O2 concentration and NOx concentration at the
furnace outlet is shown in Figure 9. There is a tendency that the lower the
O2 concentration, the lower the NOx concentration. The relationship be-
tween the air feed rate/sludge loading rate and O2 concentration is shown in
Figure 10. O2 concentration is reduced as the air feed rate/sludge loading
rate is low. It appears to be possible to control the NOx concentration by
regulating the sludge loading rate or the air feed rate.
9 NOX Concentration vs. O2 Concentration
o
O
Fig. 10 O2 Concentration vs.
Air Rate/Sludge Loading Rate
500-
400 •
o 300 •
5 200
100
O O
o>
O Not Controled
O Gas Recirculation
• Fluidizing Air Rate
Reduction
o •;
> Regulated Value 105 ppm
5 10
02 Concentration (%)
15
2 10
CP
O
o 0° o
o
o°o
1 1 j 4
Air Rate (Nm3/m2 h) /Sludge Loading Rate (kg/m2-h)
123
-------
c. Flue gas recirculation and NOx concentration
Experiments were made to control O2 concentration by causing a part of
flue gas released to the atmosphere through a chimney to be recirculated
into cumbustion air and by mixing it with fluidizing air. The relationship
with O2 concentration in the case where flue gas recirculation is made is
shown in said Figure 9. When flue gas recirculation is made, NOx con-
centration is reduced even if O2 concentration remains unchanged. On the
other hand, however, there is a tendency that CO concentration in the flue
gas increases, and that uncombusted matters in the ash increase.
d. Reduction of fluidizing air rate and NOx concentration
For the NOx reduction, the fluidi/ing air is lowered to 0.9 ^ 1.2 of a
theoretical amount of air so that the fluidized bed may become more
reductive atmosphere. In this case, unburnt materials are combusted by
supplement of fresh air supply to the freeboard of the furnace.
As the results shown in Figure 9, when the fulidizing air rate is reduced,
NOx concentration is decreased even if O2 concentration remains on a
same level. Reduction of the fluidizing air rate is effective in NOx removal
as well as flue gas recirculation.
3.2.3 SOx CONCENTRATION
Figure 11 illustrates the change of SOx concentration in the furnace when the
furnace is continuously operated for 50 hours while supplying cement clinker parti-
cles by a fixed rate (0.025 kg per 1 kg of sludge cake). SOx concentration was as
high as 50 ppm when cement clinker particles were initially supplied, but it never
exceeded 10 ppm thereafter.
3.2.4 HEAVY METAL RELEASE FROM ASH
The particle size of ash was 0.5 mm at maximum and 0.1 mm at average. Igni-
tion loss was about 1% in an ordinary case and was 3^4% when flue gas recircula-
tion was made.
According to the results of heavy metal release experiments, even if Cr6+ was
Fig. 11 Relationship between Bed Particle Feed Rate and SOX Concentration
100
50
Regulated Value 205 ppm
SOv Concentration
Bed Particle Feed
10 20 30
Time (h)
100
50
40
50
124
-------
detected partly at 0.19 mg/C, the majority was of the limit of determination (0.02
mg/C) or less. Other heavy metals, i.e., Fe, Mn, Cu, Zn, and Pb were not detected.
Concentration of Hg and As, which are heavy metals of low boiling point is shown
in Table 7. It is noted that these metals are vaporized and dispersed in flue gas,
although the rate is minor.
The ash obtained through these experiments contains Ca by 5 -v 15%. The
extract obtained in the extraction test indicates the pH of 11 ^ 12, and it is con-
sidered that heavy metals are in hardly releasable condition. The results of a test of
releasing of Cr6+, Cd and Pb with pH value varied for the purpose of warranting
safety of ash at the disposal site are shown in Figure 12. According to these results,
releasing of these metals does not occur even if the extract of ash is of weak acidity.
3.2.5 DUST CONCENTRATION
The results of investigation of dust catching efficiency with two kinds of dust
catchers, that is, a dry electrostatic precipitator and a wet venturi scrubber are
shown in Table 8 and Table 9. Dust catching efficiency is higher with the electro-
static precipitator, but dust concentration of both dust catchers satisfies the regulat-
ed value.
Table 7. Hg and As Concentration in Flue Gas
Location
Date
Time
Hg
As
(mg/Nm3)
(mg/Nm3)
Cyclone Outlet
Mar. 30, 1977
9:30
0.18
0.58
10:00
3.05
N.D.
10:30
2.67
0.20
16:45
2.16
0.22
17:15
1.48
0.19
17:40
0.17
0.70
EP Inlet
Mar. 31
15:30
0.15
N.D.
EP Outlet
Mar. 31
15:30
0.19
N.D.
Fig. 12 Relationship between pH of Extract and Metal Release
< Regulated Value 3 mg/C
•3 5 0.2
I
I
CS 1
Regulated Value 0.3 mg
Regulated Value 1.5 mg/C
8 10
pH of Extract (-)
12
125
-------
Table 8. Dust Collecting Efficiency of Venturi Scrubber
Date and Time
Mar. 29 18:15-20:10
1977 Mar. 29 18:50-20:10
Mar. 30 16:23-17:28
1977 Mar. 30 17:30-18:25
Location
Venturi Inlet
Outlet
Venturi Inlet
Outlet
Dust
Concentration
(g/Nm3)
7.6
0.063
6.5
0.021
Collecting
Efficiency
(%)
99.17
99.67
Dust
Concentration
(Regulated Value)
0.2 g/Nm3
note) Dust concentrations shown are mean values found during the time of measurement.
Table 9. Dust Collecting Efficiency of Electro Static Precipitator
Date and Time
1977 Apr. 4 16:15-17:00
1977 Apr. 4 17:10-17:50
1977 Oct. 25 14:00-14:40
1977 Oct. 27 14:10-14:50
Location
EP Inlet
Outlet
EP Inlet
Outlet
EP Inlet
Outlet
EP Inlet
Outlet
Dust
Concentration
(g/Nm3)
2.441
0.0059
4.520
0.0097
5.716
0.0002
7.912
0.009
Collecting
Efficiency
(%)
99.75
99.78
99.99
99.99
Dust
Concentration
(Regulated Value)
0.2 g/Nm3
note) Dust concentrations shown are mean values found during the time of measurement.
3.2.6 MATERIAL BALANCE
Material balance for the case of 100 tons of sludge solid based on the results
obtained through these experiments is shown in Figure 13. According to Figure
13, the weight of ash after being humidified is 1/5.6 of that of dewatered cake and
its weight is 1/6.0 of that of cake. These figures indicate that it is possible to reduce
the weight of dewatered cake through incineration.
4. SUMMARY OF RESULTS
Thickened sludge was dewatered by using pulverized coal and polymetric
coagulant, and it was possible to obtain dewatered cake that combusts without
supplementary fuel. The dosage rates of pulverized coal and of polymetric coagulant
which are matched with this method vary by VTS of sludge, but they are 50% and
0.3 'v 0.9% respectively from the removability of dewatered cake and also from
critical limit of autogeneous combustion.
NOx concentration in the flue gas is reduced as C>2 concentration at the fur-
nace outlet is reduced, and flue gas recirculation and fluidizing air rate reduction
were also found effective in reduction of NOx concentration.
It was possible to control SOx concentration by supplying cement clinker par-
ticles as fluidizing medium.
126
-------
As for heavy metal release from ash, even if Cr6+ was partly detected, other
metals were not detected.
Fig. 13 Material Balance
Polymetnc Coagulanl
Dosage (to TS of Sludge) 12%
Solid I 21
Volume (1% Solution) 120m3
Dosage (lo TS of Sludge) 50%
Solid 501
Volume (25% Slurry) 200 m3
VT.S. 82%
lo Atmosphere 0033 I
127
-------
CHAPTER 4
FACTS ABOUT EMISSION CONTROL EQUIPMENTS
FOR SEWAGE SLUDGE INCINERATOR
1. Outline 129
2. Present Status of Exhaust Gas Generated by Existing Incineration
Systems 129
3. Restriction of NOx (Nitrogen Oxide) Emissions 132
4. Performance of Apparatus for Collection of Particulate Matters 133
4.1 Particulate Emissions from the Furnace Outlets 133
4.2 Performance of Apparatus used for Collection of
Particulate Matters 134
4.3 Comparison of Various Type of Apparatus for Collection
of Particulate Matters 138
5. Controlled Incineration at a Multiple Hearth Furnace 139
(Capacity: 50ton/day)
6. Reduction of NOx at a Fluidized Bed Incinerator 143
(Capacity: 40ton/day)
7. Reduction of NOx by means of Ammonia Injection at a Fluidized
Bed Incinerator Equipped with Pre-drying Hearths 150
(Capacity: 36 ton/day)
8. Reference Materials 161
128
-------
1. OUTLINE
The recent two years survey has shown that the treatment of restricted hazard-
ous materials in the exhaust gas discharged by incineration of sewage sludge is being
dealt with effectively, meeting all the existing standards for restriction of such
materials. For collection and removal of particulate matters and sulfur oxide (SOx),
the used of scrubbers was found to be particularly effective.
It has also been learned that these hazardous materials can be more effectively
eliminated by using an electrostatic precipitator and an "alkaline liquid absorption
system", in conjunction with the scrubbers. This will make it possible to use the
system in areas where more stringent exhaust gas standards are applied.
No specific counter-measurers have yet been proposed to deal with the recent
(June, 1977) restriction of nitrogen oxide (NOx). However, experiments for its
effective elimination have been made and measures which we believe to be effective
have been developed.
This paper is based upon the results of our investigation and reports on the
following items:
(1) Performance of Apparatus for Collection of Particulate Matters
(2) Controlled Incineration at a Multiple Hearth Furnace (Capacity: 50 ton/day)
(3) Restriction of NOx at a Fluidized Bed Incinerator (Capacity: 40 ton/day)
(4) Reduction of NOx by means of Ammonia (NH3) Injection at a Fluidized Bed
Incinerator equipped with Pre-drying Heaters (Capacity: 36 ton/day)
2. PRESENT STATUS OF EXHAUST GAS GENERATED BY EXISTING
INCINERATION SYSTEMS
Table 1 shows the results of analysis made of the exhaust gas discharged by
incineration of sewage sludge at a conventional multiple hearth furnace and a
fluidized bed incinerator. The measurements were taken at the furnace outlets and
then statistically compiled. Data includes actual test data by our Testing Division as
well as those supplied by furnace manufacturers in response to our questionaires.
Three kinds of dewatered cakes were fed to the furnaces; those dewatered with
vacuum filters, filter presses and centrifuges. However, due to scarcity of data for
incineration of centrjfuge-dewatered cakes at multiple hearth" furnaces, they were
excluded from the Table.
129
-------
Table-1 Most Probable Properties Exhaust Gas Broken Down by the Type of Furnace
^^\^ ^
Waste Gas Temp.
Am't of Waste Gas
Moisture Content
o,
C02
Dust Concentration
SOx
HCI
Ch
NOx
Odor Concentration
~ —
\,
°C
Nm'/t Cake
7r
%
%
g /Nm
ppm
ppm
ppm
ppm
-
No of Experiment
Multiple Hearth 1 urnace
Vacuum Filter
Average
Value
270.7
3,673
26.1
13.5
5.3
1.46
126.3
80.8
0.80
100.6
5,597
Standard
Deviation
47.6
641
8.1
2.4
1.9
1.00
161.2
80.6
1.33
39.2
8,346
19 Case
I'ilter Press
Average
Value
235.0
2,778
30.5
10.0
8.6
1.81
313.4
95.3
0.41
48.6
2,241
Standard
Deviation
33.8
431
10.5
3.0
2.3
0.72
201.2
44.3
0.64
37.9
2,852
8 Case
Total
Average
Value
266.7
3,491
27.8
12.6
6.2
1.57
191.2
85.0
0.66
88.7 ,
3,912
Range
247-286
3,211~3,771
24.5-31.1
11.3~13.8
5.1-7.3
1. 20 ~ 1.94
118-264
55-115
0.12-1.2
68- 109
*
I luidized Bed Incinerator
Vacuum Filter
Average
Value
823.8
2,510
33.8
8.3
7.5
38.3
49.6
26.2
0.39
188.0
-
Standard
Deviation
55.0
265
7.8
4.1
2.3
24.4
74.5
47.5
0.74
73.1
-
10 Case
1'iltcr Press
Average
Value
807.1
2,726
33.7
6.5
8.7
79.1
99.3
30.6
3.3
261.6
-
Standard
Deviation
68.5
512
7.7
2.6
1.3
19.1
108.3
47.9
5.8
73.1
-
7 Case
Average
Value
812.5
2,982
36.7
5.9
12.9
15.0
325
-
-
54.7
-
Standard
Deviation
62.9
587
7.8
1.4
1.3
6.2
263
-
-
37.7
-
4 Case
Total
Average
Value
816.5
2,672
34.3
7.4
8.6
44.5
103.4
30.3
1.15
186,4
-
Range
791-842
2,473-2,871
31.0-37.6
5.8-9.0
7.1-10.0
27.6—61.4
32.7-174.1
3.4-57.2
0-3.2
135-238
-
-------
Fig 1 is the illustration of Table 1. It shows that the concentration of particu-
late matters emitted by a fludized bed incinerator is higher than that of the multiple
hearth furnace, as was expected from the differences in their systems. Also, the
cake dewatered by centrifuge using a polymar as filter aid shows lower concentra-
tion at the furnace outlets than cakes make with vacuum filters or filter presses
using inorganic coagulant.
It was found that the emission of SOx and HCI can be greatly reduced if lime
is used as filter aid, because most of the sulfur and chlorine are fixed in the lime.
For example, the residual contents of sulfur and chlorine in the ash were between 77
to 89% and 78 to 88%, respectively, of their initial contents in the cakes. This can
be readily understood from the fact that lime tends to fix sulfur, as evidenced from
the use of magnesium as sulfur fixing agent in the Eschka's method which is used to
measure sulfur contents in the fuel, and also from the fact that chlorine tends to fix
lime.
Fig.-1 Properties of Waste Gas of Multiple Hearth Furnace, Fluidized Bed Incinerater
i 1 Multiple hearth furnace
,!, l ^ Fluidized bed incinerater
^ X Average value
"E
Q
— ,
E
j»
o
y
i
1
0
J
I
Dust
o
0
o
•o-
o
o
o
1 O
3 „,-
DO ^
3
X
^
E§
< °~
o.
1
,
T
1
*
1
Vol.
to
bfl
3
cd
X
X
d>
O
M
rt
a>
O-
5
o
o
ON
O
O
CO
O
o
o
o
o
o
o
*
o
o
(N
I
f
o|
1 Temp.
"c
U
C
o
o
ot
O
0)
rt
^
o
-3"
=
-1
T
Water
I
T
i
02
I
I*
CO2
Concentration of HCI, NOx, SOx
o
o
o
'C
0
o
o
T
1
1
1
1
1
1
1
1
X
SOx
T
1
\
1
1
T
f
1
NOx
T
1
t
L
HCI
T
1
T ^
f ;
a,
0 5 . „ 10 [ppn
Concentration of C12
131
-------
3. RESTRICTION OF NOx (NITROGEN OXIDE) EMISSIONS
The Third Air Pollution Prevention Act, enacted on June 16, 1977, for the first
time set a limit on the emission of NOx generated by sludge incineration, and stipu-
lated that installations which emit more than 40,000 Nm3 /h of exhaust gas must
restrict the amount of NOx emission to be less than 250 ppm (Converted on the
basis of O2 = 12%). For future installations, this goes into effect on June 18, 1977.
Existing facilities which have to be renovated to meet the NOx emission criteria
were given a three-year grace period, and the dead line will be May 1, 1980.
The amount of sludge incineration which corresponds to the above-mentioned
40,000 Nm3/h of exhaust gas can be estimated as follows:
No.
1
2
3
Place
A Sludge
B Sludge
C Sludge
Kind of Sludge
Centrifuge
Dewatered
Cakes
Filter Press
Dewatered
Cakes
Centrifuge
Dewatered
Cakes
Water Content
%W.B
86.58
60.76
78.56
Combustibuls
%W.B
0.16
0.15
0.15
Incineration t/h
Corres. to 40.000
Nm3/h Exhaust Gas
12.3
15.1
11.8
From the table, it can be seen that installations with the design capacity of
burning more than 250 tons/day come under the above restriction. This means that
almost all of the facilities in large cities such as Tokyo, Osaka, Kyoto and Nagoya
fall into this category.
There are, however, municipalities which have enacted more stringent standards
of their own. Kawasaki City, for example, set a limit on the total amount of NOx
emission that may be permitted for a given area, based upon calory values of fuel
used or the sludge incinerated. This municipal code specifies that the amount of NOx
emission per one ton of sludge must be less than 800 g, converted into NO2 for the
existing facilities having a capacity of more than 50 tons/day, and less than 0.19g,
converted into NO2 per 0.15 x 101 ° kcal for future facilities.
Assuming that the concentration of suspended solids in the influent is 250mg/l
and that the entire sludge is conditioned with inorganic coagulant, the above-
mentioned 50 tons/day of the sludge cake would equal to one which is produced
from a sewage plant to handle 40,000 m3 sewage a day. Many existing facilities
come under this category.
0.15 x 1010 kcal is even more strict, extending the coverage to facilities of much
small scale, as illustrated by the following calculation:
Assuming that;
Fuel consumption per one ton of sludge 501
Calorific consumption per one liter of fuel . 8,000 kcal
Then, the calorific consumption per year for an installation with a capacity of
132
-------
combusting 50 tons of sludge/day will be as follows:
50 ton/day x 501 x 8,000 kcal x 365 days/year = 0.73 x 101 ° kcal/year
Thus, the 50 ton/day capacity consumes more calories than 0.15 x 1010 kcal/
year.
As enumerated above, the restrictions on NOx emissions are becoming in-
creasingly stringent.
4. PERFORMANCE OF APPARATUS FOR COLLECTION OF
PARTICULATE MATTERS
4.1 PARTICULATE EMISSIONS FROM THE FURNACE OUTLETS
From the results of the surveys conducted to-date, the present status of the
particulate emissions at the furnace outlets are as follows:
Range of Particulate sizes ju
Range of Medium sized Particles n
True Specific Gravity
Apparent Specific Gravity
Multiple Hearth
Furnace
1- 140
2~10
2.80-2.97
0.50
Fluidized Bed
Incinerator
5- 140
10-60
2.35-3.01
0.61 -0.76
Fig. 2 and 3 show, in Rosin Rammler diagrams, the distribution of particle
sizes, measured from the samples obtained at the outlets of multiple hearth furnaces
and fludized bed incinerators, respectively.
In the case of fluidized bed incinerators (Fig. 3), some similarities in the parti-
cle distribution patterns can be observed from the straight slanting lines, although
the particulate sizes vary. Generally speaking, however, the dispersion patterns vary
in both types of furnaces, indicating no set patterns.
In the Fig. 3, YS denotes the particulate emissions generated by incinerating
cakes which used polymer as a filter aid, whereas HK and GH dennote particulate
emissions from cakes in which lime was used as a filter aid. As noted, YS, which
used polymer, shows finer particle sizes.
In the case of multiple hearth furnace (Fig. 2), all the cakes incinerated used
lime as a filter aid; none used polymar. Generally fine particulate sizes are shown.
The reason why that, in the fluidized bed incinerator, the particle sizes tend to be
coarse when lime was used as filter aid, is because the particulate sizes of the lime
are coarser than those of the sludge itself, thus creating shift of particle sizes to
those of the larger.
On the other hand, the movement of exhaust gas in the case of the multiple
hearth furnace is slower than that of the fluidized bed incinerator. Also, since there
is no crushing of sludge, as in the case of fluidized bed incinerators, only the fine
particulate matters are emitted. These seem to account for emission of finer particu-
late sizes than in the case of fluidized bed incinerator. The typical example of the
above is observed with TS of the multiple hearth furnace.
133
-------
Fig.-2 Rosin-Rammlar Distribution Chart of Dust Fig.-3Rosin-Rammlar Distribution Chart of Dust
at the Outlet of Multiple Hearth Furnace at the Outlet of Fluidized Bed Incinerator
10 20304050 100
Particle Diameter —
99.9
0.1
10
4.2 PERFORMANCE OF APPARATUS USED FOR COLLECTION OF
PARTICULATE MATTERS
Tables 2, 3 and 4 show the performance of apparatus for collection of particu-
late matters used with multiple hearth furnaces and fluidized bed incinerators. The
cakes fed to the multiple hearth furnace (TS) and fluidized bed incinerator (GH)
used lime as a filter aid, whereas those fed to the fluidized bed incinerator (YS) used
polymer.
Table-2 Multiple Hearths Furnace TS
Flow Sheet I
^\^
F- urnace outlet
Fluidized bed scrubber
(outlet)
Fluidized bed absorp-
tion tower (outlet)
E. P. outlet
1
2
1
2
1
2
1
2
Temp, of
exhaust gas
°C
250
306
22
30
15
20
28
32
Static pressure
mm H2O
-38
-57
-925
-571
-1,156
Moisture
%
26.0
33.1
2.9
4 4
1.9
-925 [ 2.5
+45
+82
3.7
4.7
Flow volume
of wet gas
Nm3/hour
46,800
46,000
34,800
39,000
31,000
40,000
35,900
42,000
Dust
concentration
g/Nm3
2.2
2.2
0.13
0.22
0.095
0.14
0.009
0.021
Dust collec-
tion efficiency
%
94
88
-
-
89
84
Remakrs
Am't of
scrubbing water
Wet type
HP
17m3 /ho us
134
-------
Table-3 Fluidized Bed Incinerator GH
Row Sheet
"\^
Furnace outlet
(after secondary
heat exchange)
Cyclon outlet
EP outlet
Spray/scrubber
outlet
1
2
1
2
1
2
1
2
Temp, of
exhaust gas
°C
355
362
240
265
150
176
35
30
Static pressure
mm H2O
-140
-80
-200
-120
-250
-185
-400
-270
Moisture
%
39.0
43.5
37.6
42.0
18.2
19.3
7.6
4.6
1 low volume
of wet gas
Nm3/hour
5,300
5,300
5,400
5,300
7,400
7,400
6,500
5,300
Dust
concentration
8/Nm3
78.9
72.6
6.2
7.1
0.52
0.53
0.008
0.017
Dust collec-
tion efficiency
%
-
91
89
84
85
98
97
Remarks
Dry-type EP
Volume of
scrubbing water
58m3/hour
Table-4 Fluidized Bed Incinerator YS
I low Sheet ( I"
^-\
Furnace outlet
Cyclon outlet
Venturi scrubber
outlet
1
2
1
2
1
2
Temp, of
exhaust gas
°C
525
-
442
482
10
19
Static pressure
mm H2O
-2
-10
-36
Moisture
%
47.2
33.7
35.3
1.0
4.5
Flow volume
of wet gas
Nm3/hour
3,890
3,470
3,490
2,530
1,940
Dust
concentration
g/Nm3
20
3.4
9.7
0.06
0.084
Dust collec-
tion efficiency
%
-
-
81
98
99
Remarks
Volume of
scrubbing water
SSm'/noui
- Heat exchanger
Furnace
Cyclon (Dry type) O^Pj) " Electrostatic precipitator OO : Absorption tower
Scrubber 0 Induction fan (pic) : Fluidized bed scrubber
(1) Cyclon (Dry Type)
Since the participate emissions from the fluidized bed incinerator normally
have higher concentration and larger particle sizes than those from the multiple
hearth furnaces, the use 'fa cyclon (dry type) which employs centrifugal force is
effective for collection and removal of the particulate matters.
Fluidized Bed
Incinerator GH
Fluidized Bed
Incinerator YS
Concentration
of P.M. at
Inlet g/Nm3
73~79
20
True Specific
Gravity
3.01
2.35
Pressure Drop
mm-H2 0
40-60
110
Rate for
Collection
of P.M. %
89-91
(Lime)
81
(Polymar)
Also, as seen from the above table, GH which combusted cakes for which lime
was used as a filter aid shows higher emission concentration but less pressure drop,
as compared with YS which used polymer as a filter aid, and had a higher collection
rate of particulate matters.
135
-------
(2) Scrubbers
Scrubbers play an important role in the purification of exhaust gas generated
by sludge combustion. They not only collect and remove particulate matters, but
also prove to be effective for cooling and absorption of water-soluble gas.
There are several types of scrubbers. The packed tower type scrubber is not
normally used with sludge incineration as it tends to jam. A spray tower type as
well as venturi type scrubbers are normally used with sludge incineration. The table
below shows the performance of each type of scrubbers, based upon the data we
have gathered.
Spray Tower
Venturi Scrubber
Aerotic Floating Bed
Concentration
of P.M. at
Inlet g/Nm3
0.52-0.53
3.4-9.7
2.2
Pressure Drop
mm-H2 0
85- 150
350
500
Rate for
Collection
ofP.M.%
84-85
98-99
88-94
(3 Beds)
Liquid-gas
1/m3
8
24
5
The rate of collection of particulate matters of the spray tower type scrubbers
is lower than that of the venturi type, though this may be attributable to the lower
concentration of particulate matters at the inlet. However, the pressure drop is
small and so is the liquid-gas ratio. The venturi type scrubbers, on the other hand,
shows its suitability for use with particulate matters of high concentration, and the
collection and removal rate is also high. However, its pressure drop is great and
requires a greater quantity of scrubbing water.
The aerotic floating bed scrubbers is the type which fluidizes the packing and is
highly effective for collection of fine particles, requiring only a small quantity of
scrubbing water.
(3) Electrostatic Precipitator
An electrostatic precipitator collects particulate matters in the exhaust gas by
charging the particles electrostatically and then separating them from the gas by an
electrical force. There are two types for this system; wet and dry. The dry type
collects the particles from the collecting electrodes by striking the electrodes inter-
mittently with a hammer. The wet type collects the particles by a stream of water
on the electrode surface.
The effectiveness of the electrostatic precipitation varies depending upon its
inlet condition; viz., the conditions of gas or particulate matters. Hence, a
study of the exhaust gas condition at the inlet is necessary in order to maintain high
efficiency.
Amontg the factors which are present at the inlet, the one which affects the
efficiency of collection of particulate matters and the operational stability is the
electrical resistance of the particles. Generally speaking, the particles having elect-
rical resistance within the range of 10s - 106n cm to 1010 - 10nn cm can be
dealt with rather easily.
Experiments were made to compare the apparent electric resistance of particu-
late emissions from incinerating cake conditioned with inorganic coagulant (No. 1)
136
-------
and with polymer (No. 2). The results were as follows:
Voltage: 2,000 V/cm
Water Content: 0%
Temperature: 150- 200°C
KI(No. 1)
KI(No. 2)
Particulate
Matters
Particulate
Matters
Inorganic
Coagulant
Polymar
Apparent Electric Resistance
2.44 X 10' 2 ~ 1.06X1012 cm
1.30X1011 ~2.38xl010cm
Both of the cases showed apparent electric resistance higher than the desired
1010 ~ 1011 ft cm, though some differences were observed. Some measures to lower
the apparent electric resistance are considered necessary.
Generally speaking, the apparent electric resistance tend to maximize in gas
temperatures of 150 to 200°C, and decrease as the water content increases. With
the dry type electrostatic precipitator, therefore, the adjustment of these two factors
is considered necessary.
Fig. 4 shows dispersion of particulate emissions at inlets of KI (No. 1) and KI
(No. 2). As clearly seen, the particle sizes are smaller with No. 1 (lime).
Dry Type GH
Dry Type KI
(No. 1)
Dry Type KI
(No. 2)
Wet Type TS
Gas Flow
Orientation
Horizontal
Horizontal
Horizontal
Vertical
Press.
Drop
mm-H2 O
50-65
10
10
20-60
WaterC.
Exhausts Gas
at Inlet %
38-42
16
25
2-3
Exhaust
Gas
Temp. °C
240 ~ 270
250
300
15-20
Concent.
ofP.M.
g/Nm3
6.0-7.0
1.6
0.3
0.09-0.14
Collect.
Rate of
P.M. %
84-85
95
86
84-89
Of the dry types, KI (No. 1) shows the best collection rate of 95%. KI (No. 1)
and KI (No. 2) are of identical design and the water content as well as the tempera-
ture of the exhaust gas at the inlet are considered to be approximately the same.
The reason why KI (No. 2) shows a lower collection performance despite its high
efficiency is presumably due to the lower concentration rate of particulate matters
(0.3 g/Nm3), as compared with the concentration rate of KI (No. 1) (1.6 g/Nm3).
Conversely, GH presumably registered a low collection performance, as the con-
centration was at a high level of 6 - 7 g/Nm3
For the wet type, only one example at the TS incinerator is shown. Despite
the low concentration rate of 0.1 g/Nm3 at the inlet, a rather high collection, average
of 86%, was recorded. The wet type seems to have a better collecting performance,
particularly for collection of extremely small particulate matters. This is due to a
constant flow of water on the collecting electrodes, eliminating such disadvantages
as (1) re-flying of the particulate matters that had once stuck to the electrodes, and
(2) the failure of particles to separate from the electrodes, even with hammering,
as is often the case with the dry type precipitators.
137
-------
Fig. 5 shows the dispersion of particulate matters at the inlets and outlets of
the GH (dry type) and the TS (wet type) electrostatic precipitators. It can be seen
that the TS processed extremely fine particles.
Fig.-4 Kl Incinerator Diagram of RRS Particle Sizes
of Particulate Matters of EP Outlet
H 50
99
99.5
99.9
No. 1 Inorganic coagularor true specific gravity polymor
No. 2 True specific gravity
10
100
0.1
Fig.-5 Diagram of Particle Sizes of Particulate
Matters at EP Inlet & Outlet
0.01
50
99
99.5
99.9
Inlet
Multiple hearths TS
--- FluidizedbedGH
Filter aid lime
10
100
MM)
0.1
1.0
4.3 COMPARISON OF APPARATUS FOR COLLECTION OF
PARTICULATE MATTERS
Table 5 shows the summarized comparison of various types of apparatus for
collection of particulate matters.
138
-------
Table-5 Comparison of Apparatus for Collection of Particulate Matters
Method
System
Particles Collection
Rate
Paiticulate Con-
centration at the
Inlet
Pressure Drop
Liquified Gas Ratio
Moisture Content
of Gas Exhaust
Temperature of
Exhaust Gas
Applied to
Merits & Demerits
Cyclon Dry Type
Centrifugal Force
Introduces gas
into the tower
tangentially, and
separates the
particles in the
gas by centrifuge
80 - 90%
20 - 80 g/Nm3
40-110 mmH2O
Fluidized bed
Effective for col-
lection of high
concentration,
large sized particles
relative simplenple
design. Efficienty
drops if diameter
of cyclon is made
larger.
Spray Tower
(Spraying
Chamber)
Scrubbling
Sprays water
into the tower
and induces
the gas to come
in contact with
water at a slow
speed
85%
0.5-2.0g/Nm3
85-150
mmH2O
8 1/m3
-
Multiple hearth/
fluidized bed
Collection ab-
sorption can be
combined. Sim-
ple design.
Spray holes gets
plugged some-
times. Defici-
ency in flow
may hinder
adequate con-
tact of liquid &
gas.
Venturi
Scrubbers
Scrubbling
Injects gas
into throat
portion at a
high speed and
have it mix
with water
98 - 99%,
3 - 10 g/Nm3
350 mmH2O
24 1/m3
-
-
Fluidized bed
Collection by
absorption can
be combined.
Compact but
able to process
large q'ty of ex-
exhaust gas.
Highly efficient
for collection
of particulate
matters.
Fluidized Bed
Scrubbers
Scrubbling
Spraying chamber
& fluidized bed are
integrated; the latter,
consisting of multiple
bed, contains plastic
balls, which forms
fluidized bed, con-
tacting with turbulent
gas
88 - 94%
2. 2 g/Nm3
500 mmH2O
(3 fluidized bed)
5 1/m3
Multiple hearth
Collection by absorp-
tion can be combined.
Suitable for fine parti-
cles not recommended
when gas speed varies.
1
Elec. Sta.
Prccipitator
(Dry Type)
Charging
Particles charged
with electro statics
are separated from
gas by elec. force.
Particles on elect-
rodes are separated
by hammering
(Horizontal type)
84 - 95%
0.3-7.0 g/Nm3
10 - 65 mmH2O
-
16 - 42%
240 - 300°C
Fluidized bed
Performance tends
to vary depending
upon the condi-
tions of gas or of
particulate matters.
Elec. Sta.
Precipitator
(Wet Type)
Charging
Same as the dry
type. Water flow-
ing on electrodes
collects particles
(Vertical type)
85 - 89%
0.1 g/Nm3
20 - 60 mmH2O
2 - 3%
15 -20°C
Multiple hearth
Inlet conditions
not as critical as
the dry type.
Suitable for ex-
tremely fine
particles.
5. CONTROLLED INCINERATION AT A MULTIPLE HEARTH FURNACE
The experiments were made using a multiple hearth furnace with a capacity of
50 tons/day. The exhaust gas generated by combustion was treated by scrubbers
and an electrostatic precipitator and then heated to more than 750° C by an after-
burner. The resultant gas was then further processed by scrubbers and a spray tower
and then discharged into the atmosphere.
In conducting the experiments, some simple renovations were made to reduce
airleaks, such as closure of the air feed port at the drying zone of the furnace as well
as ports for feeding shaft-cooled return air. The feeding of the dewatered cakes was
maintained at the designed capacity, and the feeding of air was controlled so as to
achieve the overall air ratio, while monitoring the O2 concentration in the exhaust
gas.
Experiment No.
Run I
Run II
Run III
Overall
Air Ratio
1.73
1.27
1.00
Year & Date
Aug. 2, 1977
Aug. 6, 1977
Aug. 5, 1977
139
-------
(1) Results
1) The results of the analysis of the dewatered sludge cake feed and ash are
shown in Table 6. The cakes were dewatered with ferric chloride and lime
as filter aid and then pressure filtered.
The analysis of the ash revealed that for Runs I and II, the ignition losses were
6.7 ~ 7.0%, indicating satisfactory combustion of the cakes. For Run III,
however, the 13% ignition loss indicates inadequate combustion. This is
because the volume reduction speed of the combustibles slowed down as the
furnace condition approached the reduced atmospheric condition.
Table-6 Results of Analysis of Dewatered Cake and Ash
^^^^^^^
Moisture content
Fixed residue
Volatile matter
Fixed carbon
Carbon
Hydrogen
Nitrogen
Oxygen
Combustibility/"S"
Incombustibility/"S"
Chlorine
Calcium oxide
Cyanogen
Total chrome
Chromium (VI)
Solubility test of chromium (VI)
Caloric value
%
Wt % D.B.
Wt %D.B.
Wt % D.B.
Wt % D.B.
Wt % D.B.
Wt % D.B.
Wt % D.B.
Wt % D.B.
Wt &D.B.
Wt%D.B.
Wt %D.B.
mg/kg D.B.
mg/kg D.B.
mg/kg D.B.
mg/1
kcal/kg. D.B.
Sludge
Run I
95.4
46.3
47.2
6.5
23.16
3.75
4.01
21.01
1.77
0.96
3.74
-
ND
550
-
-
2,550
Dewatered Cakes
Run I
59.4
54.8
43.9
1.3
20.03
3.20
2.84
19.05
0.12
1.72
0.86
28.3
7.29
510
N D
N D
1,810
Run II
64.0
52.3
46.9
0.8
21.33
3.22
3.18
19.56
0.45
1.71
0.75
19.1
14.30
530
N D
N D
2,030
Run III
63.3
52.5
46.5
1.0
21.52
3.14
3.17
19.22
0.45
1.71
0.89
19.9
14.17
580
N D
N D
2,050
Ash
Run I
0.4
93.5
6.5
0
2.30
0.22
0.02
3.96
0
2.82
1.16
44.8
N D
950
6.6
N D
Run II*
50.5
89.9
7
0
3.49
0.87
0.07
5.65
0.02
2.88
1.16
47.5
ND
1,050
N D
ND
Run III*
41.5
80.8
13
0.1
8.66
0.88
0.50
9.12
0.04
2.51
1.12
38.9
0.56
950
N D
N D
* For Run II, III, Moisture was added to ash.
2) The overall data of the present experiments is shown in Table 7. As can be
seen from the Table, by reducing the overall air feed ratio to; Run I: 1.73:
1.27, Run III: 1.00, the amount of discharged gas (wet gas) was also decreased
to : Run I: 4,897 Nm3, Run II: 3,920 Nm3, Run III: 2,980 Nm3 This de-
crease in the discharged gas brought about a decrease in the amount of the
heavy oil used for combustion of the excess gas as well as the kerosine used for
re-heating, as shown in Fig. 6. Also, due to the drop in the drying speed of
Run II and Run III, the temperature of the eighth hearth, normally a cooling
zone, went up (Fig. 6).
140
-------
Table-7 Results of Experiments
_______
Am't of Dewatered Cake
Properties of Cake
Am't of Kerosine
Used.
Moisture content
Fixed residue
Calorific value
Incinerate
After burning
Total
Ain't of Comb. Air *
Over All Air Ratio
Properties of
Exhaust Gas
(At the Furnace
Outlet)
Ash'
Temperature
Wet gas
Dry gas
Water content *
02 *
CO2 *
Dust
SOx
NOx
HCL,
0,
HCN
NH3
Odor concentration
Am't
Ignition loss
Unit
T/H
W%W.B.
W%D.B.
kcal/kgD.B.
1/H
1/T-Cake
1/H
1/T-Cake
1/T-Cake
kg/H
Nm3/H
-
C
kg/H
Nm3/H
kg/H
Nm3/H
V%
V%
V%
g/Nm3
ppm
ppm
ppm
ppm
ppm
ppm
-
kg/H
%
Designed Value
2.08
70
48
1,700
102
49.0
240
115
164
-
2.3
-
7,360
-
5,100
-
-
-
-
3,000
687
-
-
-
325
-
Run 1
1.97
59.4
54.8
1,810
29
14.7
115
58
73.1
4,060*
3,172*
1.73
245
5,585*
4,897
4,123*
3,078*
37.1*
9.0*
10.3*
1,979
360
25
150
0.2
260
840
5,500
464*
6.5
Run II
1.94
64.0
52.3
2,030
46
23.7
78
40
63.9
2,739*
2,149*
1.27
196
4,320
3,920
2,843
2,082
46.9*
4.4*
14.9*
1,547
530
19
26,48, 118
0.07
39
1,070
1.7 xlO"
392«
7*
Run III
1.95
64.3
52.5
2,050
7
3.6
60
31
34.4
1,551*
1,212*
1.00
186
3,087
,2,980
1,647
1,186
60.2*
0.6*
18.5*
1,666
420
26
120
0.2
230
71
7.7 x 10'
418*
13*
1 Valuer calculated from material balance.
141
-------
Fig.-6 Results of Analysis
(m3N/h)
0.060
0.050
0.040
0.030
(m3N/h)
5,000
4,000
3,000
1/h
130
120
110
100
90
80
70
60
50
40
30
20'
10:
1st
2nd
c 4th
o
I 5th
I 6th
7th
8th
Kerosine used (Incinaration + After burning)
Kerosine (After burning)
/ I
Am't of NOx
Am't of waste gas (Wet)
Kerosine used (Furnace)
_L
J_
•Run I Run II Run III
Over All Air Ratio (%)
Run I (1.73)-
Run II (1.27)-
Run III (1.00)
200 300 400 500 600 700 800 900
Temperature in each hearth C
3) Contrary to our assumption that the concentration rates of the materials con-
tained in the gas would rise with the decrease in the amount of discharged gas,
no marked changes were observed in the concentration rates of SOx and HC1.
This is because large amounts of these materials are fixed in the ash and only
small amounts are gasified due to the large quantity of lime used as filter aid.
142
-------
According to our analysis of Run I, 89% of sulfur contained in the cake was
found in the ash and only 11% had gasified. With Cl, 78% remained in the ash
and 10% gasified. This means that with the decrease of discharged gas, the
gasification of these materials had also decreased.
4) The NOx concentration rates, measured at the furnace outlets, were 25 ppm for
Run I, 19 ppm for Run II and 26 ppm for Run III. When these values are
converted on the basis of O2 concentration = 0%, the figures become; Run I:
0.14Nm3/h, Run II: 0.05Nm3/h, and Run III: 0.03Nm3/h, and show a
definite decrease. Attempts to check the nitrogen contents at various stages of
processes for Run I revealed that the N content in the exhaust gas in the forms
of nitrogen monoxide (NO), Hydrogen cyanide (HCN) and ammonia (NH3)
was 2.3 kg/h, versus 22.7 kg/h originally contained in the cake.
5) The amounts of SOx, HC1, HCN and NH3 can be adequately dealt with through
proper exhaust gas treatments such as scrubbing and absorption, satisfying the
existing codes for restriction of the exhaust gas.
(2) Summary
From the fore-going, it is considered possible to operate existing incinerators at
a reduced air feed rate and with proper supplemental measures such as minimization
of leak air and reinforcement with insular bricks to withstand the increased temper-
atures at the cooling zone, thus reducing NOx formation.
The results of these experiments show that operations at the overall air ratio of
1.4 are possible, and that future operation of multiple hearth furnaces should adopt
this ((controlled combustion" concept, and at the same time, try to scale down
their exhaust gas treatment facilities.
6. REDUCTION OF NOx AT A FLUIDIZED BED INCINERATOR
The experiments made using a fluidized bed incinerator with a design capacity
of 40 tons/day were as follows:
1) Combustion with varied cake feed and air feed quantities.
2) Combustion with varied quatities of fluidized sand.
3) Combustion with hot gas injected by a distributor using a hot wind box (start-
up burner), instead of the conventional method of injection auxiliary fuel (A
heavy oil) into the fluidized bed.
For the combustions d cribed above, the concentrations of O2 and NOx in the
exhaust gas were measured.
(1) Results
1) The results of analysis of the dewatered cakes used in the experiments are
shown in Table 8. No significant differences were observed in the analytic
values, and it is assumed that the combusted cakes were generally of the same
quality and properties. The results of analysis of the ash are shown in Table 9.
The N content in the dewatered cakes averaged 2.5% per D.S, whereas N con-
tent in the combusted ash was 0.01 ~ 0.04%. From this it can be assumed that
almost all of the N content in the cake had volatilized. Supposing that com-
bustion of a D.S 1 kg generates exhaust gas of lONm3 and that all of the N
143
-------
content in the cake, 2.5% per D.S, converted into NO, the resultant concentra-
tion is calculated to be approx. 4,000 ppm. The maximum NOx value by
actual measurement, however, was only 99 ppm (O2 concentration 8%). Judg-
ing from this, it is assumed that almost all of the N content had volatized in
forms other than NOx. According to our experiments, the NO2 content in the
NOx was less than 10%.
Table-8 Results of Analysis of Dewatered Cakes, Sludge
— — _____
Moisture Content
Calorific Value
Volaitle Residue
Fixed Carbon
Fixed Residue
Elementary
Analysis
C
H
N
O
Combustibility "S"
Incombustibility "S"
Ammonia Nitrogen
Calcium
%
kcal/kgD.S.
%
%
%
%D.S.
%D.S.
%D.S.
%D.S.
%D.S.
%D.S.
%D.S.
%D.S.
Dewatered Cake
52-8-23
71.5
2,870
48.4
6.2
51.6
26.83
4.06
2.46
13.32
1.55
0.18
1.5
0.35
52-8-25
72.2
2,870
48.9
5.9
51.1
26.98
4.05
2.22
14.08
1.32
0.25
1.7
0.57
52-8-29
75.2
2,870
50.7
6.6
49.3
28.18
4.19
2.68
14.03
1.31
0.30
1.2
0.65
Average
73
2,870
49.4
6.23
50.6
27.3
4.1
2.52
13.8
1.39
0.243
1.47
0.524
Sludge
52-8-29
99.0
3,080
50.5
-
49.5
27.91
4.19
2.66
14.14
1.25
0.35
-
-
1) Sludge ob tained from Decanter's Tank
2) Dewatering: Centrifuge
3) Filter aid: Diafrock (Cationoid) 0.9~0.95 D.S./D.S.-% Added.
Table-9 Analysis of Ash
^-^^
O R 74
eo o TC
52-8-26
52-8-27
17 ft 78
O 8 7Q
17 R "*n
— - — -__
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
Nitrogen
0.01
0.04
0.02
0.00
0.02
0.02
0.01
0.02
0.01
0.02
0.01
0.02
Carbon (%)
0.01
0.58
0.18
0.22
0.42
0.17
0.73
0.54
0.13
0.28
0.26
0.39
Calcium (%)
0.06
2.08
1.60
1.72
1.15
1.43
1.54
1.84
1.59
1.49
2.29
1.20
144
-------
2)
The results of our experiments are shown in Figs. 7 to 14. It should be noted
that the indicated NOx values have been converted on the basis of a 12%
residual oxygen concentration rate, in keeping with the current standards for
exhaust gas.
Fig.-7
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Fig.-13
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Fig.-14
.2
50
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-8-9_8_L
10
11
12
13
14
15
16
17
Aug. 23 - Aug. 24
Prior to start up, 1.2 tons of sand were removed from the fluidized bed, thus
leaving approx. 5 tons of sand. The cake feeds were 0.7ton/h on August 23, and
l.Oton/h on August 24. On both of these days, approximately an equal amount of
combustion air was supplied to the incinerator.
The exhaust gas on August 23rd, when the cake feed was less, showed higher
NOx concentration than on August 24th, when the cake feed was greater.
148
-------
August 25
1.3 tons of sand were added to the incinerator to restore the bed to its normal
operational condition. The cake feed was 0.7 ton/h. The amount of air feed was the
same as on August 23rd. With the increased fluidized sand, the NOx concentration
was lower than that of August 23rd, when the quantity of sand was less.
August 26
Instead of injecting heavy oil into the fluidized bed as in the case of normal
operation, a hot wind box (start-up burner) was used for hot gas injection. The NOx
concentration values were higher than the values obtained in the normal operational
mode. However, since the quantity of cake feed was small, no clear relationship
between this mode of operation and NOx concentration was obtained.
August 27
Combustion was made at the cake feed rate of 1.1 ton/h. The quantities of air
feed and the sand were the same as on August 25th. With the increased cake feed,
NOx concentration showed lower values than on August 25th, when the cake feed
was less (0.7 ton/h).
August 28
0.7 ton/h of cake was combusted with the air feed restricted to the minimum,
which is possible with this type of incinerator. The gap between the temperature of
the fluidized sand and the free-board was great, despite the small amount of cake fed
to the furnace. Presumably, this was because the combustibles, which had not com-
busted completely in the sand bed, combusted in the free board. The NOx con-
centration was lower than that of August 25th, when the cake feed was the same.
August 29
The cakes were fed at the rate of 0.7 ~ 1.1 ton/h, with the combustion air
restricted to the minimum. The NOx concentration was equal to or slightly lower
than that of August 28th. When the cake feed was increased to more than 1.1 ton/h,
the ash, which is normally brownish in color, turned to black, indicating the pres
ence of residual combustibles.
August 30
1.5tons/h of cakes were combusted with the maximum air feed. Compared
with the runs of August 25th and 27th when the amounts of air feed were the same,
it revealed that the NOx concentration goes down, as the amount of cake feed is
increased.
The O2 and NOx values quoted in the foregoing were obtained by automatic
monitoring. In order to ascertain the accuracy of these figures, samplings were made
every day in the morning and in the afternoon. The values obtained in this manner
coincided with the above-mentioned values.
These values, as well as the operational conditions from which the values were
obtained are summarized in Fig. 15. For convenience of observation, lines were
drawn between the measurements taken in the mornings and those taken in the
afternoons. Since no analysis were conducted in the mornings of August 24th &
27th due to failure of the facilities, values for those dates were not included.
149
-------
(2) Summary
1) When processing sewage sludge in fluidized bed furnaces, NOx generation can
be kept to a minimum by restricting the overall air ratio. When the air feed is
lower than 1.15, however, some detrimental effects from incomplete com-
bustion take place.
2) NOx can be minimized by keeping the amount of cake feed as close as possible
to, but not exceeding, the design capacity of the incinerator.
3) The incinerator used in the experiment showed a tendency that NOx increases
as the amount of fluidized sand decreases.
Accordingly, in processing sewage sludge in a fluidized bed incinerator or in
planning new processing facilities, it is considered advisable to maintain the overall
air ratio at 1.2 for effective control of NOx.
7. REDUCTION OF NOx BY MEANS OF AMMONIA INJECTION AT A FLU-
IDIZED BED INCINERATOR EQUIPPED WITH PRE-DRYING HEARTHS
The fluidized bed incinerator (Capacity: 36 tons/day) used in the experiments
consists of (1) the upper drying zone in the form of a multiple hearth furnace and
(2) the lower combustion zone in the form of a fluidized bed. A portion of the com-
busted gas is led into the drying hearth, and after being used for drying, circulates
back to the fluidized bed via the furnace top.
The experiments were made in the following methods.
1) Method 1: No dewatered cakes were fed and only kerosine was burnt to deter-
mine NOx emission.
2) Method 2: Dewatered cake samples from three different processing plants were
combusted to investigate the resultant NOx emission.
3) Method 3: NH3 was injected into the furnace to see if it decreases NOx emis-
sion.
(1) Results
1) Method 1: The kerosine used had N content of less than 0.01%. The results of
the analysis are shown in Fig. 17. Since excess restriction of air feed raises the
furnace temperature excessively, the oxygen concentration was regulated to
within 10 ~ 15%, so as to maintain the furnace temperature within 800-
900° C. The horizontal axis shows O2 concentration rates at the furnace
outlet and vertical axis shows NOx concentration rates as well as NOx forma-
tion per one (1) liter of kerosine.
O2-NOx concentration curve shows that as the O2 concentration increases,
the NOx concentration shows a downward curve. This is because NOx was
diluted by air. Therefore, the values were converted to the restricted standards
of O2 concentration = 12%. The result shows a nearly horizontal line. If the
NOx formation per one unit of kerosine is illustrated, it also forms a nearly
horizontal line. Thus, there seems to be no clear inter-relationship between the
NOx formed by kerosine combustion and the O2 concentration. It can be
surmissed from the foregoing that the most of the NOx formed by kerosine in
the furnace temperatures of 800 to 900°C is fuel NOx.
150
-------
The Figure indicates that when O2 concentration is high, so is the NOx con-
centration. This interrelationship between O2 and NOx concentration is shown in
Fig. 16.
Fig.-15
Temperature
in furnace
Free board, upper
Free board, middle
Free board, lower
Bed, middle
NOx ppm
-------
Fig.-17 NOx of Perosine Burning
g1 30x10
1 28x10"4
"5 26x10"4
~~ 'a?
«'g 24x10"4
I* 22x10"4
I"x
|0 20x10""
u_m'
x"c
il
14
13
12
11
10
14
12
10
8
6
4
Amount of Kerosine
Temperature of Fluidized Bed
F. B. Temperature
52- 1101/h
850- 920° C
740- 820° C
10 11 12 13 14 15 16
O2 Concentration at Furnace Outlet (%)
2) Method 2: The properties of the dewatered cakes used for this experiment are
shown in Table 10 below. Fig. 18, 19 and 20 show the measurements taken of
each of the dewatered cakes subjected to the experiments. In the Figures, the
FB temperatures denote the temperatures in the free board. RG/EG show the
ratio of circulating gas to the exhaust gas at the furnace outlet in percentage;
RG denotes the amount of circulating gas and EG the amount of discharge gas.
152
-------
Table-10 Properties of Dewatered Cakes Tested
~==5=:=^:;-r_______ Sample Sludge
item — — __ unit \
Drainage System
Digestion
Dewatering
Moisture Content *
Ash Content
Combustibles
HHV
LHV
C
H
N *
S
Cl
-
-
-
%
%
%
kcal/kg-D.S
kcal/kg-D.S
%
%
%
%
%
A
Separate system
No
Centrifuge
80.58
1534
84.66
4,690
4,320
41.86
6.83
1.10
1.08
0.22
B
Combined system
No
Filter press
60.76
61.76
38.24
1,960
1,760
16.65
3.64
0.81
0.73
1.10
C
Combined system
No
Centrifuge
78.56
29.32
70.68
3,810
3,560
36.85
4.73
1.51
1.09
1.70
* Moisture and "N" contents are on "wet base". Others are on "dry base".
(In case of C sludge, however, "N" contents were analysed on the "dry base" and were converted to the
"wet base".)
Fig.-18 NOx Formation by Combustion of
A Dewatered Cakes
£ 3
300
2SO
200
I
.1
a
ISO
u 100
O
z
50
RG/EG=62%
0 2 4 6 8 10
O, Concentration at Furnace Outlet
Am't Processed
Temp, of Fluidized Bed
F.B. Temp.
l,100kg/h
840~950 °C
690~860 °C
153
-------
Fig.-19 NOx Formation by Combustion of
B Dewatered Cakes
18
16
•e 14
12
a
I
o
(J
x
10
8
6
" 4
2
0
1000
800
600
400
200
- RG/EG=40-44%
RG/EG=60%
Fig.-20
NOx Formation by Combustion of
C Dewatered Cakes
J
X
O
100
I
I
x
i
50
RG/EG=50%
246
j Concentration at Furnace Outlet
2468
O2 Concentration at Furnace Outlet
Am't Processed
Temp, of Fluidized Bed
F.B. Temp.
1,500 kg/h
820~890°C
770~840 °C
Am't Processed
Temp, of Fluidized Bed
F.B. Temp.
840 kg/h
880~930°C
780~870°C
154
-------
NOx conversion rate may be defined as follows:
Amount of NOx Generated
NOx Conversion Rate =
The Amount of NOx when all the N Content in the
Sludge is Converted into NOx.
Quality of Dry NOx Concentration
Discharge Gas x (ppm) at the
(Nm3/h) Furnace Outlet
N Content (kg/h) in Sludge x -~-(Nm3 /kg)
x 100%
A common tendency in these types of dewatered cakes is that as the O2 con-
centration (air ratio) decreases, so does the NOx concentration, as can be observed
from these Figures. This coincides with the conclusion of the previous survey that
NOx generation is lower with a lower air ratio. This is because intermediate pro-
ducts such as ammonia, which are formed prior to the combustion of N contenet in
the fuel, exert reducing effects to NOx under the low air feed ratio, causing NOx to
lose its nitrogen oxide.
When the amount of the circulating gas is increased, it accelerates the decom-
position of the residual gases such as NH3 and HCN in the drying zone, and these
residual gases in the circulating gas serve to reduce the NOx in the furnace. This
phenomenon can be observed in the Figure.
The increase of the circulating gas, however, accelerates the mixing in the flu-
idized bed, and sometimes serves to increase the NOx. Since the dewatered cake
feed for these experiments were pure sewage sludge, there was much volatilization of
NH3 and HCN in the drying zone, and it is considered that NOx reducing effect,
entailed by conversion of uncombusted gas, was greater than the increase of NOx by
accelerated mixing. If degested sludge were used instead of pure sludge, the results
would have been different.
3) Method 3: The results of experiments using B dewatered cakes are shown in
Table 11,12 and Fig. 21. As noted in Fig. 21, the NOx concentration shows a
marked decrease with the injection of NH3, and the degree of fluctuations is
also much less. Effects from the O2 concentration are much smaller.
Fig. 22 illustrate, based upon Table 11, the relationship between the concen-
trations of O2 and NOx, as distinguish by the amounts of NH3 injected. The de-
crease of NOx by the NH3 injection can be observed.
To determine the effect of the NH3 injection in removing nitrogen oxide, the
calculation was made using the following formula:
155
-------
Rate for Removal of Nitrogen Oxide = (1 -
NOx Concentration
with NH3 Injection
NOx Concentration
without NH3 Injection
In calculating the second item on the right side of the formula, the values ob-
tained from the actual measurements were used.
The relationships between the O2 concentration at the furnace outlet and the
rate by which the amount of nitrogen oxide is removed under a fixed amount of
NH3 injection are shown in Fig. 23. Calculation was made using a formula which
determines the relationship of NOx and O2 by the amount of NH3"injected.
From Fig. 23, it is understood that if the O2 concentration is more than 4%,
the nitrogen oxide removal reate stays fixed, providing the amount of NH3 injection
is kept constant. This relationship in shown in the Table below:
Table-11 Results of Tests for Removal of Nigrogen Oxide (B Dewatered Cakes)
12/15
12/23
A'mtof
sludge
kg/h
1500
1500
"N" con-
sludge
12.50
12.87
NH3
Nm /h
0
21
0
10
15
21
RG/EG
52
56
EG(DG)
Nm3/h
2381
2521
Cy
5
63
475
5 3
4.25
55
4 5
6.0
4.75
50
6.0
6.0
4.0
7.0
4.3
6 5
7.3
S 3
50
3 8
62
4 7
6 0
7.2
3.6
5.0
4.0
5,5
!on Outlet
NOx
ppm
415
290
335
255
325
260
360
70
80
420
300
140
360
160
280
370
220
165
115
220-250
160
150
160
85
100
85
90
[urn
*'
5.
3.
4
3
4
3
5.3
3.9
4.2
5.3
53
3 2
6.3
3.5
5 8
6.6
4.5
4.2
2 9
55
3 9
53
6.5
2.7
4.2
3 2
4.7
ace Outlet
NOx
ppm
436
305
352
268
341
2 3
3 3
4
4
441
5
7
8
8
4
9
1
3
1
23 -263
68
58
68
89
105
89
95
NOx
7<
5 19
303
4 19
3 19
406
325
4.50
0.88
1 00
5.40
386
1 80
4.63
2.06
3 60
476
2.83
2 12
1.48
2.83~3.22
206
1 93
206
1.09
1 29
1.09
1.16
NOx co-
NHj imec-
299
322
415
229
508
257
462
536
350
322
210
433
294
415
526
191
322
229
369
NH3 injection
Mol Ratio
0
295
27.4
0
9 6
17.3
7 8
15
8
7.
11.
18.
28.
13
20
20.
15.8
436
259
364
226
Rate Tor
Removal
of NOx
0
75
74
0
24
36
66
35
36
27
34
46
42
47-39
43
62
68
53
67
61
74
NH3
ppm
4.0
2.0
28.4
4.2
NH3decom-
7'
9995
99.50
9995
Remarks
Bed Temp
= 830-880°C
F.B Temp.
= 800-840'C
Bed Temp
= 820~880°C
F B. Temp.
NOx concentja-
injeclion of NHj
is calculated by
next equation.
NOx = 88 6 (O, )
-5061
156
-------
Table-12 Furnace Temperature Dispersion and IMOx (w/o NHa Injection)
______JTest Dates
Item "
Drying feaith Temp. 1st furnace
Drying fearth Temp. 2nd furnace
Drying fearth Temp. 3rd furnace
Fluidized bed temp.
Free board temp.
Wind box temp.
Circulating gas temp.
NOx concentration in furnace (Free board, lower)
NOx concentration at the furnace outlet
270°C
405 °C
490 °C
860 °C
780°C
263°C
280 °C
900 ~ 1,250 ppm
350 ppm
250° C
425° C
520°C
850° C
840° C
300° C
285° C
700—1,000 ppm
-
220 °C
425 °C
520°C
850°C
840 °C
285 °C
290 °C
1,500~3,000 ppm
300 ppm
Notes : 1. NOx concentration in furnace were measured by constant electric potential, electrolytic analysis.
2. NOx concentrations at furnace outlet were obt ained from serial records of "Luminescent Chemical
Method" adjusted to furnace outlet concentration at Oi = 4%.
Fig.-21 Changes in NH3 Concentration by NH3 Injection
Changes in NHj
connections by
injection
500
157
-------
Fig.-22
en
00
X
O
6-
4-
2-
o-
- 800
o.
O.
C
'•£ eoo
c
* 400
i
200
Decrease of NOx by NH3 Injection
Kind of sludge
Am't processed
R.G/E.G
Temp, of fluidized bed
F.B. temperature
XK
.
*~-^
B
1500 kg/h
52~56%
820~880 °C
790~840 °C
Am't NH3 Injection
0
10Nm3/h
15Nm3/h
21 Nm3/h
2468
O2 Concentration at the Furnace Outlet
10
Fig.-23 Rate of Decrease of NOx by NH3 Injection
100
80
x 60
O
I 40
b
Q
o
£, 20
-2
Kind of sludge
Am't processed
R.G/E.G
Temp, of fluidized bed
F.B. temperature
P,_
B
1500 kg/h
52~56%
820~880 °C
790 840 °C
Am't NHs Injection
0
10Nm3/h
15Nm3/h
— ^V A - A - A - A — A — A - A -
2 4 6 8
Oz Concentration at the Furnace Outlet
10
-------
NH3 Injection (Nm3/h)
10
15
21
Rate of Removal of Nitrogen Oxide (%)
30
45
70
More than 99% of the NH3 injected disappeared either by the removing of
nitrogen oxide or by its self-decomposition, and the highest NH3 concentration at
the furnace outlet was 30 ppm.
Fig. 24 shows the relationship between the removal rate of nitrogen oxide and
the mol ratio, with NH3 injection. This Figure shows that the mol ratio of 29 is
required to obtain the removal rate of 70%, and the mol ratio of 23 to achieve 50%.
If the reaction between NH3 and NO is improved, however, it is believed that
further reduction of the mol ratio would be possible. This indicates the need to ex-
plore the optimum injection method and the need to protect the NH3 from decom-
posing itself before it is used for decompostion of nitrogen oxide. The optimum
temperature for this process is between 800 ~ 1,000°C. The temperatures used for
the present experiments were between 800 ~ 900° C.
Fig.-24 Mol Ratio NOx Removal Rate
O
z
100
80
60
40
20
^
Kind of Sludge
Amount Processed
R.G./E.G.
Temp, of Fluidized Bed
F.B. Temperature
O2 Concentration
A
1500 kg/h
52 ~56 %
820~880°C
790~810 °C
4%
10 20
Mole Rate NH3/NOx
30
(2)
Operating Cost
To Predict the increase in the operating cost by NH3 injection, the volume in-
crease at the time of injection was calculated at the cake feed rate of 1.5ton/h
against the estimated operating cost with no NH3 injection. The operating cost with
no NH3 injection, based upon our past actual measurements, are as follows:
159
-------
Kerosine
Elec. Power
Caustic Soda
Ind. Water
Fluid. Bed S.
Total
Quality
Used
1101/h
120kw
lkg/h
3.5ton/h
7.5kg/h
Unit Cost
¥34/1
¥15.5/kwh
V65/kg
¥15/ton
¥16/kg
Cost (¥/h)
3,740
1,860
65
52
120
5,837
Cost per
1 1 Cake (¥)
2,493
1,240
43
35
80
3,891
Ratio (%)
64
32
1
1
2
100
Condition: B Sludge, Water Content, 60.76%
Low Calorific Value: 1,760 kcal/kg - D.S
The coast increase by the NH3 injection is estimated as follows:
Case
1
2
3
NH3 Injection
Mol Ratio
13.6
20.4
28.5
Rate of Removal
of Nitrogen Oxide
33
44
67
NH3
Nm3/h
10
15
21
Inject.
kg/h
7.6
11.4
15.9
NH3
U.C (¥/kg)
90
90
90
NH3 Cost
(¥/h)
684
1,026
1,431
From the foregoing, the total cost and the rate of increase for each case are
estimated as follows:
Case
1
2
3
Total Cost
¥5,837 + ¥687 = ¥6,521
¥5, 837 + ¥1,026 = ¥6,863
¥5 ,837 + ¥1,431 =¥7 ,267
Rate of Increase (%)
12
18
25
To achieve 67% nitrogen oxide removal rate, 25% cost increase is necessary.
However, if the injection is made under an optimum condition and if the mol ratio
of NH3 can be kept around 3;
(3)
1)
15.9 kg/h x
= 1.67 kg/h
28.5
1.67 kg/h x ¥90/kg = ¥150/h
¥150/h + ¥5,837/h x 100 = 2.6%
Thus, adequate cost effectiveness can be obtained.
Summary
Combustion of Kerosine Only
a) The amount of NOx generated by burning only kerosine stays the same
regardless of the air-feed ratio, as follows:
NOx concentration (O2 = 12% conversion) = 12ppm
The amount of NOx per 1 liter of kerosine - 2.6 x 10"4 Nm3
160
-------
2) Combustion of Sludge
a) For the three types of dewatered cakes combusted, the NOx concentra-
tion at 4% O2 concentration (O2 =12% conversion) ranged from 30 to
IVOppm, and the NOx conversion rate between 0.5 ~ 5%.
b) The factor which exerts the greatest influence over NOx generation is the
air ratio. As the air ratio increases, NOx also increases. Neither the
amount of sludge feed nor the furnace temperature has a noticeable effect
on NOx.
c) The sludge with a large N content does not necessarily have a high NOx
conversion rate.
d) NOx tends to decrease as the amount of circulating gas is increased. This
is due to the increased volatilization of NH3 and HCN in the drying zone,
which accelerates the NOx reduction function.
3) Non-catalytic removal of nitrogen oxide by NH3 injection.
a) It was confirmed that NOx can be greatly reduced by injecting NH3 into
the sludge incineration. It has therefore been proven that the "non-
catalytic removal of nitrogen oxide by NH3 injection" can also be used
with the sludge incineration.
b) More than 99% of the NH3 injected was consumed either by the removal
of nitrogen oxide or by its self-decomposition, and the highest NH3 con-
centration at the furnace outlet was 30ppm.
c) To achieve 70% and 50% removal of nitrogen oxide, the mol ratios of 29
and 23 are required respectively. Judging from the actual performance of
the boiler, however, operation at a lower mol ratio would be possible,
providing the injection method of NH3 is optimized.
8. REFERNCE MATERIALS
(1) lidani "Apparatus for Collection of Parteculate Matters" 1972
(2) Kato "Journal of the J.S.M.E." Vol. 42, No. 582, 1976
(3) Kurosawa "Problems by NOx from Stationary Sources" ppm, Vol. 4, No. 2,
1973
(4) Toba "Experimental Investigation of NOx Formation in the Fluidized-bed Coal
Combustion" Journal of the Fuel Society Vol. 56, No. 604, 1977
(5) R.C. Hoke, L.A. Ruth, H. Show "Combustion & Desulfurization of Coal in
Fluidized-bed of Limestone" Combustion Jan. 1975
(6) Kasaoka "Reduction Removal of Nitrigen Oxides by Non-catalytic Method"
Chemfactory Vol. 20, No. 7, 1976
(7) Yamanaka "Practicals of Facilitie of Reduction Removal of Nitrigen Oxides by
Non-catalytic Method" Heat Control and Public Niusance
Vol29, No. 2, 1976
(8) "Away to lower NOx in Utility Boiler" Environmental Science & Technology
Vol. 11, No. 3, March 1977
161
-------
CHAPTER 5
PILOT PLANT STUDY OF TANNARY WASTE TREATMENT
BY OXYGEN ACTIVATED SLUDGE PROCESS
1. Introduction 163
2. Studies Conducted in the Past 164
3. Application of Oxygen Activated Sludge Process for Tannary Waste
Treatment 168
4. Experiment Program and Procedure 169
5. Experiment Results and Discussion 180
6. Summary 182
162
-------
CHAPTER 5
PILOT PLANT STUDY OF TANNARY WASTE TREATMENT
BY OXYGEN ACTIVATED SLUDGE PROCESS
1. INTRODUCTION
From old days in Hyogo Prefecture, centering Himeji city, a large number of
tanneries have clustered around specific areas. A total of 9 such tannery communi-
ties are found in the prefecture in Himeji City, Kawanishi city, Tatsuno city and
Taishi town. In Himeji city, there are the Takagi area, Shigo and Gochaku areas,
Kawanishi area, Fukui area and Jippo area with 234, 99, 37, 20 and 9 tanneries
respectively.
From early days, Himeji was noted for its production of 'Himeji Leather',
a white leather finished by its unique tanning process. However, with the passing of
time, vegetable tanning was introduced and also chromic tanning. And today,
the majority of tanneries employ the vegetable-chromic tanning.
The majority of the tanneries are either small-sized enterprises or privately-run
plants. The average number of workers at an enterprise level is 32.6 and 5.6 at a
privately run level. Owing to the fact that it is privately-run plant galore in the city,
the average number of workers of all plants in Himeji is as low as 7.5.
The manufacturing process of tanneries in Hyogo prefecture including Himeji
city can be divided as follows: (a) preparing, (b) tanning, and (c) finishing. Fig. 1.1
shows the process in detail. Tanneries use a great amount of industrial water and
about 70 percent of the water consumed is used up at the preparing stage. Table 1.1
shows the amount of water used at a chromic tannery plant processing about 30
kilograms of raw leather (said capacity), and also the wastewater quality and
organic and other pollutant loads. Waste from chromic tanneries contains a large
amount of suspended solids, organic matters and tri-valent chromium.
Fig.-1.1 Manufacturing Flow-chart of Chromic Tannery
163
-------
Table-1.1 Composition of Waste Water from Chromic Tannery held
300 kg Raw Hide Treatment Capacity
^^---^^ Processing
Items ^^-^^^
Weight of Hide (kg)
Water Consumption (C)
Wastewater Discharged (CO
pM
Total Sobds (mg/S)
Dissolved Solids (mg/e)
Suspended Solids (mg/C)
Ash (mg/S)
Ignitjon Loss (mg/C)
Total Nitrogen (mg/S)
Dissolved Total Nitrogen (mg/8)
Chloride (mg/l!)
Iodine Consumption (mg/C)
Calcium (mg/&)
CODMn (mg/l!)
Cr,0, (mg/l!)
Washing & Soaking
Pre-
para-
tion
330
1,650
1,530
6 3
49,710
47,550
2,515
46,960
2,750
552
403
26,709
43
70
8,881
Mam
Waste
1,650
1,620
7 1
12,420
12,070
350
11,928
493
111
83
4,628
14
38
890
Liming
&
Un-
hainng
1,650
1,610
12.6
25,708
22,960
2,748
15,300
10,408
1,670
1 ,554
2,422
3,184
2,470
13,007
Washing
1st
<& 2nd
Washjng
3,300
3,260
12.4
3,873
3,549
324
1,343
1,530
179
164
843
232
396
1,309
3rd
Washing
270
1,350
1,320
12.3
2,364
2,057
307
1,451
913
132
116
592
54
221
1,148
Retiming
1,350
1,330
12.7
5,687
4,980
707
2,714
2,973
204
182
628
405
1,445
2,162
Washing
4,450
4,500
12.5
817
638
179
419
398
38
19
135
34
160
201
Bating
810
800
9.3
3,882
3,172
710
2,447
1,435
760
712
771
16
243
419
Washing
4,450
4,410
8.9
572
520
52
287
285
73
69
188
52
27
Pickling
270
320
3.0
54,193
53,953
240
50,280
3,913
191
J83
20,824
2
731
1,866
Chromic
Tanning
270
260
3.3
68,503
68,443
60
52,003
16,500
75
67
9,903
157
3,899
7,071
Each city having such groups of tanneries within its administrative area in
Hyogo Prefecture has already constructed pre-treatment facility and is exerting
efforts to treat waste by sedimentation. This pretreatment facility, in most cases,
is composed of grit chamber, screens (coarse and fine screens), pumps (screw pump),
sedimentation tanks provided with track-mounted sludge scraper (some with floccul-
ation basins), sludge thickeners, sludge heat treatment units (heating the sludge
between 90 and 100 degrees centigrade to denaturate the protein contents and
to facilitate dehydration), vacuum filters and deodorization installation to remove
odor.
The industrial waste from tanneries is conveyed to the pre-treatment facility
via covered concrete rectangular sewers or concrete pipes by gravity. Therefore,
it is necessary to prevent organic solids from depositing as possible in the sewers.
And to do this, a rotary fine screen is installed in each factory to receive screened
effluent into the sewer.
The existing pre-treatment facilities were designed to remove about 70 percent
of suspended solids, but in future further studies will be made to increase the design
removal rate of suspended solids.
The sedimentation tank effluent of the pre-treatment facility contains 600 -
800 mg/l of BOD, therefore a biological treatment is envisaged. This study was
conducted to determine its design criteria of the biological treatment facilities.
2. STUDIES CONDUCTED IN THE PAST
Several experiments were conducted in the past concerning biological treatment
of tannary wastes in Himeji city on laboratory scale and pilot plant scale. Results
are summarized as follows;
(1) The experiment of low-rate trickling filter process
This experiment was conducted in 1968 - 69 at the Public Works Research
Institute of the Ministry of Construction. The experiment was conducted in a
164
-------
constant temperature room of 20° C by using a specially prepared laboratory scale
trickling filter apparatus. The influent used in the experiment was (i) chromic
tannery waste only, (ii) mixture of chromic tannery waste and domestic sewage at
a ratio of 4:1, and (iii) mixture of chromic tannery waste and 1 percent vegetable
tannery wastewater.
With regards experiment results, although the pH of the influent changed
on the alkali side between 9 and 12, the pH of the effluent was stable between 8 and
8.5 indicating the existence of a strong buffer action. In other words, it became
obvious that the treatment was possible without any pH control. The BOD removal
against BOD Load and the removed BOD are as shown in Fig. 2.1. The BOD
removal when the BOD Load was below 0.05 kg/m3 .d and when below 0.1 kg/m3 .d
was over 80 percent and between 70 and 80 percent, respectively. However, in the
experiment using chromic tannery waste only as influent, the BOD removal did not
exceed 0.15kg/m3.d. The experiment for mixing chromic tannery waste and
domestic sewage, have shown the most stable treatment results.
Fig.-2.1 BOD Loading vs. BOD Removal at the
Laboratory Test of Low-rate Trickling Filter
0.3
• Chromic Tannery Waste Only
• Combined Chromic Tannery Waste with
Domestic Sewage by the Proportion of 4 to 1
A Combined Chromic Tannery Waste with 1%
of Vegetable Tannery Waste
0.1
0.2 0.3 0.4
BOD Loading (kg/m3/d)
0.5
0.6
(2) Aerated Lagoon Experiment
This experiment was conducted at the same time with the above mentioned
low-rate trickling filter process at the Public Works Research Institute. The influent
used in the experiment was the same as those used in the low-rate trickling filter
process except for increasing the mixing rate from 1 percent to 5 percent of
vegetable tannery waste.
The aerated lagoon test on a laboratory scale was conducted in the constant
temperature room at 10°, 20° and 30° centigrades, respectively. The experiment
results as shown in Fig. 2.2 have shown that the BOD removal was greatly affected
by changes in temperature, and, that the BOD removal dropped markedly in low
water temperatures. Also in the experiment using influent mixed with chromic
tannery waste and domestic sewage, as shown in Fig. 2.3, the best treatment results
were obtained.
165
-------
Fig.-2.2 Detention Time vs. Remaining BOD at the
Laboratory Test of Aerated Lagoon
(Chromic Tannery Waste Only)
1200
1000
A A Aeration at 10°C
• • Aeration at 20°C
•- - -• No Aeration at 20° C
X--—y Aeration at 30°C
0 1 2 3 4 56 7 8 9 10 11 12 13 14 15
Detention Time (days)
Fig.-2.3 Detention Time vs. BOD Removal at the
Laboratory Test of Aerated Lagoon (20°C)
100
80
60
o
O
40
20
Chromic Tannery Waste Only
Combined Chromic Tannery Waste with
Domestic Sewage by the Proportion of 4 to 1
Combined Chromic Tannery Waste with 5%
of Vegetable Tannery Waste
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Detention Time (days)
(3) Experiment of Activated Sludge Process in Extended Aeration
In this experiment, influent containing chromic tannery waste only was used.
And the test was held outdoors employing a small scale pilot plant. At that time,
the pretreatment facility in Takagi area was in operation. Therefore, the effluent
from this pretreatment facility (plain sedimentation) was used for the activated
sludge treatment experiment.
The average quality of pretreated wastewater was BOD 782 mg/1, CODMn
311 mg/1, SS 120 mg/1, total chromium 7.1 mg/1 and pH 8.0 - 11.8. pH was
controlled in advance by dosing sulfiric acid. The aeration tank was operated by
the completely mixing mode at MLSS 3,000 - 4,000 mg/1. And the experiment
was conducted from fall to spring. Fig. 2.4 shows the relations between the BOD
Load and treatment efficiency.
Comparatively favorable treatment efficiency was obtained when the BOD
Load was under 0.1 kg/MISS.kg/d. But the fluctuation in effluent quality was
inevitable and sludge bulking phenomenom was observed.
166
-------
Fig.-2.4 BOD Loading vs. Effluent BOD and BOD Removal
at the Small Scale Pilot Plant Test of
Extended Activated Sludge Process
400
Hi 300
Q
0 200
CO
c
QJ
2 100
t
UJ
0
100
E
| 80
o>
C
Q
O
CQ
60
£*,
•
> '.:••
*
7*
h V
•
•
•
.
• 10°
• 10
•
•
•
C or High Temperature
C or Low Temperature
•
•
•
•
0.2 0.4 0.6
BOD Loading (kg/MLSS • kg/d)
0.8
(4) Preliminary Experiment of Pure Oxygen Activated Sludge Process
This experiment, similar to the experiment in (3), used effluent from the
pretreatment facility of Takagi area and was conducted at a pilot plant mounted
on a trailer. The water quality of the influent was the same as (3) but the experiment
was conducted only limited period of between summer and fall. The experiment
was held as follow: Aeration time: 3.5 - 6 hours; and MLSS 6,500 - 7,600 mg/1.
There was no pH control in this experiment.
Part of the experiment results is shown in Fig. 2.5. As the figure shows, when
the BOD Load was 0.37 - 1.07 kg/MLVSS. kg/d, the BOD removal rate was over
97 percent, thus a linear relationship between BOD Load and BOD removal was
obtained. Furthermore, oxygen consumption in the aeration tank was roughly
the same as BOD removal. The total chromium in the activated sludge changed
greatly from 510 to 31,000 mg/kg, but when SRT was kept long, chrome ac-
cumulated in the activated sludge and have shown a tendency to affect biological
activity.
167
-------
Fig.-2.5 BOD Loading vs BOD Removal
at the Pilot Plant of
Pure Oxygen Activated
Sludge Process
BOD Removal (kg/MLVSS • kg/d)
p o o ->
* en bo b
jf
•
•
3.
0.4 0.6 0.8 1.0
BOD Loading (kg/MLVSS • kg/d)
APPLICATION OF OXYGEN ACTIVATED SLUDGE PROCESS FOR
TANNARY WASTE TREATMENT
From the experiments held in the past, it has become clear that the most
favorable treatment efficiency can be expected from the pure oxygen activated
sludge process. When introducing the pure oxygen activated sludge process, the
following advantages can be expected:
i) pH control is not necessary for the tannery waste treatment.
ii) As it is possible to maintain MLSS in the aeration tank at a high concentration,
it is possible to decrease in aerator capacity or shortening of aeration time.
iii) There is a possibility of preventing the sludge bulking phenomenon.
iv) The oxygen supply deficit that is likely to occur in high organic waste treatment
can be prevented.
Of the reasons cited, it was decided most appropriate to introduce the pure
oxygen activated sludge process in treating tannery waste. Also, as Himeji city is
planning to construct a coastal station for LNG (Liquid Natural Gas) transported
from abroad in the near future, there is a great possibility of obtaining cheap
oxygen produced at this station and conveyed through a pipe line. That was another
reason why oxygen activated sludge process was adopted.
However, in the past oxygen activated sludge process experiments, the test
periods were as short as four months and were held at summer time. Therefore,
at this study, the following problems must be served:
a) Even during day time, the fluctuation of tannery waste quantity and quality
is great. However, at night time and on Sundays, there is virtually no wastewater
coming in.
Therefore, it was requested to determine whether the waste from tanneries
should be treated with diurnal variation or equalized condition.
b) Experiment results of through the four seasons by oxygen activated sludge
process were not available.
Therefore, it was required to conduct experiments in winter to obtain necessary
data to design facilities.
168
-------
c) The effluent from the pretreatment facilities at Takagi area and Shigo &
Gochaku areas are expected to be transported to the Himeji Tobu Wastewater
Treatment Plant located near the coast by an exclusive pipe line extending about 6
kilometers.
The effluent from these pretreatment facilities totals about 28,000m3/d.
It was required to determine whether it is better to separate this effluent from
other domestic sewage for exclusive treatment or should be combined with domestic
sewage and others at a ratio of 1:1.
d) The effluent standard of BOD 20 mg/1 (maximum: 25 mg/1) is to be applied to
the enfluent from the Himeji Tobu Wastewater Treatment Plant. Also in the Seto
Inland Sea water areas, the total emission of wastewater load by CODMn is to be
regulated after 5 years. Presently, the total dischargeable load by CODMn fr°m
this wastewater treatment plant is undecided. Therefore, it is necessary to consider
the removal of CODMn when conducting this experiment.
e) In Japan, three types of oxygen activated sludge processes are put on the
market. They are the UNOX system, the MAROX system and the EBARA-Infilco
system. It is important to study thoroughly the merits and demerits of each system
and select the most economical and effective system for operation when designing
the actual facilities of the Himeji Tobu Wastewater Treatment Plant.
To solve the problems mentioned above, pilot plants of the three companies
were installed in the compound of the Takagi Pretreatment Facility to conduct
15 month experiments. The pilot plants of the three companies were each operated
by engineers from their own. Also, city officials and members of private consulting
firms cross checked the water quality data and the operating data to assure fairness
in giving engineering evaluations of the three systems.
Himeji city, in order to instruct, supervise and evaluate the experiments at the
three pilot plants, has organized the Engineering Evaluation Committee of Tanneries
Waste Treatment Experiment in Himeji. The members of this committee included
officials from the Public Works Research Institute of the Ministry of Construction,
Hyogo Prefectural Industrial Research Laboratory, Public Works Department of
Hyogo Prefectural Government and Environmental Department of Hyogo Prefectural
Government.
4. EXPERIMENT PROGRAM AND PROCEDURE
As the experiments of the pilot plants of three companies were conducted
to obtain fundamental data and to confirm the problems with regards operation and
maintenance to design the Tobu wastewater treatment plant, the following condi-
tion was given:
i) Experiment of constant feed of tannery waste only
ii) Experiment of varied feed of tannery waste only
iii) Experiment of mixed feed of varied tannery waste and constant domestic
sewage.
With regards each experiment listed above, the self-active operation term of
which the operation condition is designated by free judgement of each company
169
-------
(seek operation condition during this period to secure target effluent quality) and
the evaluating operation term of which the treatment results of the designated
operation condition are evaluated.
The aforementioned experiments i) and ii) were held twice in summer and
winter, and the evaluating operation term for each season was instituted.
In experiment i), the pretreatment effluent was supplied by a constant feed
pump. In experiments ii) and iii), the typical influent flow pattern was given from
the measured influent flow results. Furthermore, in experiment iii), without chang-
ing the flow pattern in experiment ii), domestic sewage equivalent to 1/2 of the total
volume was to be fed constantly. Fig. 4.1 and Fig. 4.2 respectively show the flow
patterns used in experiments ii) and iii).
Fig.-4.1 Fluctuation Flow Pattern of Chromic
Tanneries Waste Only
200.
150
I 100
50
Daily Average
Flow (100)
4 6 8 10 12 14 16 18 20 22 24
Time
Fig.-4.2 Fluctuation Flow Pattern of Mixed
Chromic Tanneries Waste with Domestic
Sewage
200
150
o 100
50
00
176% „
tr
145%
113%
Tanneries Waste
81%
Domestic Sewage
0 24 6 8 10 12 14 16 18 20 22 24
Time
170
-------
Prior to the commencement of the experiments, experiment plan for the next
15 months was compiled. But as the start of the experiments was in winter and
too much time was consumed on the aclimation of activated sludge, the initial plan
was postponed. As a result, the experiment was held under experimental conditions
as shown in Fig. 4.3.
Fig.-4.3 Pilot Plant Experimental Plan for Chromic Tanneries Waste Treatment
Jan'77
mr,
Feb
a
i//////
Mar
m
17777
Apr
•linn,
Mjy
nun,
June
'////l/i
July
77771
m
Aug
777777?
Sept.
Oct.
777771
E
Nov
-ez
7777J
Dec
7ZZ7J
£
Jan:?8
p47777
Jza
Feb.
77777^
22 ^
Mar
Item
Domestication of Activated Sludge
Committee Decided Constant Feed
Operation of Tanneries Waste Only
Self -decided Constant Feed
Operation of Tanneries Waste Only
•Evaluation of Kach Operation
Self-decided Varied Feed Operation
of Tanneries Waste Only r
Self-decided Mixed Feed Operation of
Varied Tanneries Waste and Constant
Domestic Sewage
Remarks:
I) Experimental condition for the Committee decided constant feed operation of tanneries waste
only was detention time of six hours and mixed liquor suspended solids of 6,000 mg per
litre in the aeration tanks.
2) Experimental condition for evalution of each operation was decided with understanding of
the Committee on the basis of the proposal of each manufacture. It was the major premise
that the effluent was maintained both BOD of 20 mg per litre or less and CODMn of 50mg
per litre or less.
Of the operating conditions for pilot plants shown in Fig. 4.3, the standard
operating conditions centering in February of 1977 were: detention time 6 hours,
and MLSS over 6,000 mg/1 to operate the pilot plants. Also during the evaluating
operating period, each company, based on the results of the self-active operating
period, was asked to submit its operating conditions to the Committee for approval.
In this instance, the BOD of the effluent was set within 20 mg/1 and CODMn within
50 mg/1 as a target.
Of the three companies, Ataka Kogyo Co. which owns the MAROX system
submitted a proposal in July 1977 to conduct the oxygen activated sludge process
experiment in two stage process to the Committee. And thus, the MAROX system
has employed the two stage process ever since August of 1977.
In Fig. 4.4 (a) and (b), the pilot plant of MAROX system, in Fig. 4.5 the pilot
plant of EBARA-Infilco system and in Fig. 4.6 the pilot plant of UNOX system
and their flow sheets are shown.
Also in the tannery waste only supply experiment, as the phosphorous content
in the raw water was insufficient, phosphorous was added to conduct the experi-
ments.
171
-------
Fig.-4.4(a) Flow-Chart of Pilot Plant
(Single Stage Marox System)
—tx}-
J
Measuring
Device
<
iv
r
em
RAD Aeration Tank RAD
-------
Fig.-4.4(b) Flow-Chart of Pilot Plant
(Two Stage Marox System)
a
DO IRC \ / DO IRC
(
rM—
to Excess Sludge Tank
Excess Sludge \ First Stage
Tank \ Effluent Tank
Return Sludge \
Pump
-------
Fig.-4.5 Flow-Chart of Pilot Plant
(Ebara Infilco System)
Final Settling Tank
Oxygen Supply Gas Meter
Pipe
Aeration Tank Aeration Tank
Oxygen A _
Bomb Air Supply
£f—
Compressor
174
-------
Fig.-4.6 Flow-Chart of Pilot Plant
(Unox System)
-------
Table 5.1 Summary of Experimental Result
Name of
System
OJ
X
C/D
X
O
a
s
Ebara Infilco System
Unox System
Month of Experiment
Committee Decided
Experimental
Condition
Experiment Nos.
Detention Time (hrs.)
MLSS (g/t)
MLVSS/MLSSxlOO(%)
Return Sludge (%)
Sa-t(MLSS-T)xl03
F/M (BOD-kg/
MLVSS-kg/d)
SRT (days)
BOD (mg/C)
COD (mg/C)
Stage
Influent
Effluent
Influent
Effluent
Experiment Nos.
Detention Time (hrs.)
MLSS (g/5)
MLVSS/MLSSxlOO(%)
Return Sludge (%)
Sa-t(MLSS-T)xl03
F/M (BOD-kg/
MLVSS-kg/d)
SRT (days)
BOD (mg/B)
COD (mg/C)
Influent
Effluent
Influent
Effluent
Experiment Nos.
Detention Time (his.)
MLSS (g/C)
MLVSS/MLSSxlOO(%)
Return Sludge (%)
Sa-t(MLSS-T)xlOs
F/M (BOD-kg/
MLVSS-kg/d)
SRT (days)
BOD (mg/2)
COD (mg/S)
Influent
Effluent
Influent
Effluent
Feb. '77
Mar.
Apr.
May
June July
Constant Feed of Tannery Waste Only
Evaluation
1
6.0
13.5
66
143
81.0
0.35
14.1
790
130
434
136
1
6.2
13.3
58
32
82.5
0.39
14.3
763
229
458
183
2 3
6.0 6.0
10.7 8.1
79 84
155 149
62.448.
0.35 0.4
5.1 5.0
4
8.0
8.8
85
257
5 70.
20.3
17.
5
8.0
7.5
84
140
160.0
1 0.34
8.4
6
12.C
10.2
83
222
122
O.H
16.4
7
6.0
7.6
87
124
45.6
0.40
5.8
739 710 761 707 660 656
89.7 107 89.3 154 90.2 89.3
456 405 402 416 392 373
108 115 101 114 107 96.7
2
6.2
11.9
57
42
73.8
0.44
4.2
3
5.9
9.4
84
70
55.5
0.37
9.1
4
8.8
9.7
85
41
85.4
0.22
5.5
753 724 670
144 112 185
424 400 391
120 99.1 116
1
6.0
10.7
73
41
64.2
0.40
5.1
772
115
2
5.0
8.5
84
71
42.5
0.50
4.5
Single Stage Process
5
10.1
9.3
85
48
93.9
0.19
13.1
8
12.0
6.5
86
86
78
0.22
14.5
9
18.0
8.7
84
95
157
0.12
25.9
10
12.C
8.9
84
73
107
0.1S
23. t
Aug. Sept.
Oct. , Nov. , Dec.
Varied Feed of Tannery Waste Only
Evaluation
11
7.
6
5.7
86
163
86.6
0.29
3.
1
598 635 "697 598
44.1 21.8 15.4 35.2
335 350 388 354
80.3 57.4 45.9 66.9
6
8.5
9.6
86
51
81.6
0.22
17.2
632 656
145 28.2
413 375
133 74.6
3
8.6
9.8
86
100
84.3
0.24
13.6
737 710
98.7 83.1
436 405 513
120 105 108
Month of Experiment Feb. '77
Mar.
4
6.0
9.8
87
57
58.8
0.28
6.3
591
96.0
363
99.9
Apr.
5
8.6
10.2
86
80
87.7
0.22
11.7
£87
71.9
412
93.9
May
7
8.5
11.7
85
85
99.5
0.21
18.3
8
11.7
9,6
84
44
112
0.16
13.9
9
12 13
7.6 7.6
5.2 4.9
85 87
148 204
39.5 37.2
0.38 0.43
5.4 5.2
14
5.7
3.6
86
394
20.5
0.72
2.6
Mixed Feed of Varied
Tannery Waste and
Constant Domestic
Sewage
Evaluation
15
3.8
3.6
86
228
14.1
0.66
2.5
16
2.8
3.0
82
171
8.4
1.10
1.4
17
3.9
3.9
75
199
15.2
0.72
1.9
, Jan. '78 , Feb. Mar.
Varied Feed of
Tannery Waste
Only
Evaluation
18
7.6
4.9
73
248
37
2
0.42
9.
8
19
7.6
5.3
84
215
40.3
0.42
4.7
Constant Feed
of Tannery Waste
Only
Evaluation
20
9.0
7.2
86
195
64.8
0.22
13.1
21
9.0
6.0
86
91
54.0
0.28
6.0
530 576 530 330 320 331 476 590 508 536
23.2 15.9 17.8 9.91 32.3 25.2 48.7 29.4 26.7 23.4
304 336 329 215 190 194 299 377 342 408
55.2 50.8 42.7 31.0 42.8 39.4 63.7 59.3 60.1 53.9
22.9
10.9
83
86
250
0.07
25.1
604 641
26.8 17.7
345 344
61.1 54.0
6
12.0
8.5
83
80
102
0.18
12.8
7
10.0 1
8.2
82
67
82.0
0.22 C
16.3
8
2.0
9.3
82
00
12
.18
7.5
626
18.6
370
49.2
9
18.9
8.1
82
158
153
XI 2
28.4
652 628 670 639
25.2 22.017.013.5
10
16.5
10.1
83
67
167
0.08
26.0
11
12.0
9.2
84
100
110
0.15
17.9
12
8.1
9.1
86
114
73.7
0.20
17.5
13
6.2
7.2
85
93
44.6
0.21
22.8
Two Stage Proces
14
4.7
6.1
85
82
28.7
0.32
6.3
15
4.1
5.9
85
64
24.2
0.39
6.6
16
15.8
8.7
84
66
137
0.099
45
.5
17
23.2
9.7
84
66
225
0.075
31.0
18
17.5
10.4
85
71
182
0.076
34.7
19
13.6
11.0
85
95
150
0.097
18.6
476 586 530 340 320 331 476 590 506 536
19.0 19.2 19.9 12.8 16.9 26.7 35.2 42.2 24.5 23.7
276 338 329 224 201 194 299 377 342 408
50.1 48.6 42.6 40.0 32.5 36.8 51.2 63.6 59.5 63.7
10
15.1
8.4
82
126
127
0.15
33
8
11
12.6
8.6
83
105
108
0.13
31.2
12
10.1
8.8
85
84
88.9
0.19
12.6
13
9.0
9.0
85
85
il.O
).16
2.5
638 500 581 582
15.4 9.85 13.6 12.8
412 347 350 376 354 356 338 344
68.4 50.947.045.952.8 38.5 43.8 38.7
June July
Aug. Sept.
14
8.2
9.6
85
78
78.7
0.19
13.2
15
5.1
6.8
85
48
34.7
0.28
7.5
16
4.5
7.0
86
53
31.5
0.28
5.8
17
3.8
6.2
87
64
23.6
0.39
5.4
18
12.0
7.2
85
100
86.4
0.18
9.7
540 340 320 331 544
17.6 12.4 8.95 24.6 30.5
315 224 186 193 322
39.5 34.9 30.0 36.2 51.5
Oct. ' Nov. ' Dec.
19
18.0
5.8
84
150
104
0.14
33.3
20
16.0
9.4
84
133
150
0.11
29.5
21
15.0
10.7
85
100
161
0.06
27.1
22
12.0
11.5
87
108
138
0.11
24.7
408 590 497 536
23.2 24.6 13.7 24.4
266 377 327 366
45.0 49.6 58.2 66.5
Jan. '78 ' Feb. Mar.
-------
Fig. 5.1 Experimental Results of BODS and CODMn (Marox System)
Exparimer
tal Not.
Temperature (°C)
F/M (BOD-kg/MLVSS-kB/d)
Detention
Time Ihrs)
(1)
10.0
0.35
6.0
12)
11.2
0.35
6.0
(31
14.0
0.42
6.0
(4)
14.1
0.31
8.0
Mixed Feed of Varied Tannery Varied Feed Constant Feed
Constant Feed of Varied Feed of Waste and Constant Domestic of Tannery of Tannery Waste
Tannery Waste Only Tannery Wane Only Sewage ^ Waste Only { Only
(5)
15.4
0.34
8.0
16)
17.1
0.16
12.0
(7)
18.9
0.40
6.0
18)
23.7
0.21
12.0
191 110) 111)
25.8 26.7 28 9
0.12 0.19 0.29
18.0 12.0
7.6
1121
26.6
0.38
7.6
113)
25.3
0.43
7.6
1141
21 7
0.72
5.7
115)
21 1
0.66
38
(16)
185
1.10
28
117)
15.0
0 72
3.9
1
118)
11 0
0.42
76
(191
10 4
042
7 6
(20)
94
022
90
(21)
130
0.28
9.0
900
800
700
600
500
400
300
| 200
~c
2
a 180
8
° 160
a"
140
120
100
80
70
60
50
40
30
20
10
0
Operation of Single Stage — — Operat on of Two Stage
. - :." >. .-.
*• ••• x
•
.r. ..
v H •-.•.•.••• •./
• Influent BOD,
A Influent CODfy|n
O Effluent BOD,
A Effluent CODMr,
—•—Effluent BOD, of Intermediate
Settling Tank
P ^ N
-LH
July
-------
Fig. 5.2 Experimental Results of BOD5 and CODMn (Ebara Infilco System)
Experimental Nos
Temperature I°C)
F/M IBOD'kg/MLVSS'ko/dl
Detection Time (hrs.)
900
800
700
600
500
400
Constant
ID
81
039
6.2
12)
12.0
0.44
6.2
(31
13.6
037
5.9
41
14.!
0.2
8.8
Mixed Feed of
Varied Tannery Varied Feed of Constant Feed
Waste and Constant Tannery Waste of Tannery Waste
Feed of Tannery Waste Only | Varied Feed of Tannery Waste Only | Domestic Sewage | Only
IS)
17 4
0.19
10 1
(61
19 8
022
8.5
(7)
24.6
0.21
85
18)
26 2
0 16
11 7
^1
19)
33.1
007
229
(10)
28.3
0.08
165
111)
25.8
0.15
12.0
(12)
23.2
0.20
8.1
(13)
21.2
0.21
6.2
114)
19.0
0.32
4.7
115)
15.5
0.39
4.1
(16) 117)
124 11.1
0.099 0.075
15.8 232
Only
118)
10.7
0.076
175
(191
132
0.097
13.6
1 — 1
00
3
c
£
5
o
§
300
200
180
160
140
120
100
Domestication ^ *** A * • ^ ^4^ ^f A «rf ^^% k 4 4 *^^
of Activated a .% ' A » * «•
Slu*. ., _« \ ^ ' . * ^^^ » *
* ^ "^ J# 4.
^ * A / ^~
ii o « ^ i 4j»^
' '/ o .
: • *
o AA ° * * Influent BOD,
* °c o<^ r\ * * influent CODMn
a, ? O Effluent BOD,
o
-------
Fig. 5.3 Experimental Results of BOD5 and CODMn (Unox System)
Constant Feed ol
Tannery Waste Only
Varied Feed of Tannery Waste Only
Mixed Feed of Varied
Tannery Waste and
Constant Domestic
Sewage
Varied Feed of
Tannery Waste Only
Constant Feed of
Tannery Waste Only
Experimental Not.
Temperature (°C)
F/M (BOD-kg/MLVSS'kg/d)
Detention Time IhnJ
900
800
700
600
500
400
300
200
ID
10.4
0.40
6.0
(21
13.4
0.50
5.0
13)
15.3
0.24
8.6
(4)
18.6
0.28
6.0
(5)
20.9
0.22
8.6
(6)
242
0.18
12.0
171
24.5
0.22
10.0
18)
27.7
0.18
12.0
19)
30 1
0 12
18.9
1101
30.7
0.23
15.1
(111
28.0
0 13
126
1121
27 6
0.19
10.1
(131
24.3
0 16
9.0
(14)
23.4
0 19
8.2
1151
21.6
0.28
5 1
1161
18.8
0.28
4.5
117)
152
039
3.8
118)
I20I
10.7
0 11
16.0
(21)
9.9
0.06
15.0
(221
12.9
0.11
12.0
-v « .*••
v »
.A .
V
Domestication
of Activeted
.^
^f~**^'~
I ISO
o
o
? 160
*-V
• Influent BODj
O 140
120
too
80
70
60
50
40
30
20
10
0
°o * Influent COD^n
° o« O Effluent BOO.
000 C
4.o 4«.e °o0 «<.** o A Effluent CODMn
' ° °'*x>. *%'/ V/Vo** V*'' A
"„ *a ° %° o °° ° *"*'' '»
O (P
°°%> '. *» ' \.^
A a A a
o A tfp * . *^^ ^A*1 aaA AA
^ - '* ^ V^ ^ *\. f ' *
*.f '^ f *£ ^kX^^ \ ^J^»jf^^ V -"o
V 'St"**/*" •» / "o
/ ° o°-S\o «% ^o /" °° "^ V"^* ""V,,0^ '^•°
^= 1 H H M H H N H H 1 H H H H 1 1 H 1 1 H 1 1
,-J , 1 1 1, 1 LJ ! L_l L-L, 1 ip 1 L_l L-jJ 1 I ^-1, 1 1 1 1 1 1, I_J 1 1 ! LJ-L, 1 , LJ 1 ,__! 1
Dec. Jan.'78 Feb.
-------
5. EXPERIMENT RESULTS AND DISCUSSION
The pilot plant experiments continued for 15 months from January 1977
to March 1978. Table 5.1 summarizes the operating results of the pilot plants of
the three companies. And the influent and effluent BOD and CODMn are shown
Fig. 5.1, Fig. 5.2 and Fig. 5.3, respectively.
The first few months after commencement of the operations have seen both
BOD and CODMn in effluent frequently exceeding the 100mg/l level due to low
water temperature. However, after six months, stable operations were obtained.
And by the end of December in all operating conditions, effluent quality of 15 -35
mg/1 of BOD and 40 - 70 mg/1 of CODMn was obtained. Especially, when the
operating conditions were stable, it was possible to maintain the objective effluent
quality of BOD being below 20 mg/1 and CODMm below 50 mg/1. However, after
January, being influenced by the drop in water temperature, both BOD and CODMn
in effluent began to raise again despite keeping the F/M ratio at a low level.
From the resutls of the experiment on constant feed of tannery waste water
only and the experiment on varied feed of tannery waste water only, if the latter is
to be operated with a slightly lower F/M ratio than the former, it was found that
similar effluent can be obtained. However, to ensure stable operation for a long
period of time, it was found appropriate to introduce the influent as constant as
possible by providing a equalization tank.
As the experiment on joint tannery waste and domestic sewage was operated
at a higher F/M ratio than that on tannery waste only, BOD and CODMn con-
centrations in the effluent climbed higher than those in the experiment on tannery
waste water only. Especially, in the latter half of this experiment, the water quality
of the effluent was influenced by the drop in water temperature of the influent.
However, if the F/M ratio can be kept at a lower level in this experiment, it will
obviously bring about stable performance. During this period, although the experi-
ment on mixed feed of constant feed of tannery waste and domestic sewage was not
possible due to time restrictions, it is considered that it would have brought about
good results with regards stable operation and treated water quality when conducted.
To maintain BOD below 20 mg/1 in the effluent in the tannery wastewater only
experiment, it is necessary to constantly maintain BOD removal rate at more
than 97 percent, which is very difficult to sustain in many cases in biological
treatment. On the other hand, in the joint treatment with tannery wastewater and
domestic sewage, BOD removal rate needs to be sustained at about 95%, thus from
this point it is regarded better to select the joint treatment.
The operation of MAROX system pilot plant commenced from August in two
stages. But since the F/M ratio was kept at an extremely high level, its effluent BOD
concentration was higher than the single-stage pilot plant effluent of the other
systems. However, if the F/M ratio can be kept lower in the operation than the
experiment conducted, it is considered possible to sustain the objective BOD value.
When employing the two stage process, although it has the merit of conducting
operations at a higher F/M ratio than the single-stage process, it has the disadvantage
of requiring an intermediate settling tank. Further studies should be made before
180
-------
selecting either the single stage process or the two stage process.
The influent pH was between the range of 9 and 11.5, but pH of pilot plant
effluent even without pH control was maintained between the range of 6.5 and 7.5.
From these facts, when introducing the oxygen activated sludge process, there is
no need of performing pH control. The drop in pH level in the effluent was observed
more markedly in the covered type aeration tank than the open type aeration tank.
SVI of the mixed liquor was in the range of 50 — 160 and was normally kept
at a level between 80 and 110. In either experimental conditions, there was no
bulking of activated sludge observed. Similar values of SVI were obtained in both
the experiment on tannery wastewater only and on the experiment on tannery
wastewater mixed with domestic sewage.
In general, at the pilot plant experiment, both the surface area rate of the final
settling tank and the settling time have shown a tendency of becoming larger than
the full scale actual facility. The return sludge concentration obtained in this
experiment was 15 — 30 g/1 by the single stage tannery wastewater only feed
process and between 11 and 16 g/1 by the two-stage process. The return sludge by
the experiment on mixed feed of tannery wastewater and domestic sludge was
between 14 and 21 g/1 by the single-stage process and 8 and 11 g/1 by the two-stage
process. Also MLSS concentration in the aeration tank was between 8 and 10 g/1 by
the experiment on tannery wastewater only feed, and between 6 and 7 g/1 by the ex-
periment on combined feed of tannery waste and domestic sewage. In the two-stage
process, these was a tendency that the MLSS concentration in the aeration tank
was lower than the single-stage process in both experiments. This is reasoned to the
fact that in the two-stage process the return sludge ratio had to be kept at a high
value of between 257 and 73%.
SRT of the pilot plant showed a marked fluctuation of between 1.4 and 34
days. But, on the average, favorable effluent quality was obtained when SRT was
maintained between 10 and 15 days. Even in these instances the nitrification has
only slightly occurred. The total alkalinity and ammonia nitrogen in the effluent
have shown a tendency of becoming higher than in the influent.
The oxygen consumption in the aeration tank was 0.62 - 1.73 kg O2 per
removed BOD 1 kg. When performing operations to hold excess sludge in the
system, this value had further increased to reach a maximum 1.91 kg. The oxygen
utilization ratio in the aeration tank was between 87 and 99% although actual
measurements were only made of the covered type aeration tank. In general, the
value exceeded 90% showing extremely good efficiency. The use of an oxygen
cylinder was quoted as the reason.
The waste activated sludge volume have shown a great fluctuation of between
0.22 and 1.34 kg per BOD 1 kg. In general, when the oxygen consumption per
removed BOD increased, the sludge production have shown a tendency of decreasing.
In the two-stage process, oxygen consumption per BOD removal was smaller than
in the single-stage process but a tendency of the increase of sludge production
have been recognized.
The accumulation of chromium in sludge is estimated to reach between 40 and
50 mg per 1 kg of dry solids when viewing the results of the experiment on tannery
181
-------
waste only feed. Even in the case of the experiment on the combined feed of tannery
and domestic sewage, the accumulation of chromium compound is estimated
to reach a maximum 40 mg per 1 kg of dry solids of sludge. Viewing from the fact
that chromium compound of high concentration do accumulate in the sludge,
extra care must be exerted to the disposal of such sludge.
Resulting from the accumulation of chromium in sludge, the total chromium
concentration of between 6 and 20 mg/1 contained in the influent have decreased
to below 0.6 mg/1 in the effluent, proving the fact that the oxygen activated
sludge process is also effective in total chromium removal.
6. SUMMARY
The study was performed to compile the results of the oxygen activated sludge
process treating tannery waste flowing into the Tobu Sewage Treatment Plant in
Himeji city. However, detailed analysis of the results of the experiment are not
contained in this report due to lack of ample time after completing the tests.
But it was truely fortunate that Mr. W. J. Lacy and Mr. R. S. Burd who both
represented the American team at the 5th U.S.-Japan Conference on Sewage
Treatment Technology have taken the trouble to extend their field trip to Himeji
to inspect the experimental facilities.
The first stage of construction work of the Sewage Treatment Plant is expected
to start in 1979, and the actual operation to commence during the 1982 fiscal year.
The results obtained from the experiment can be summarized as follows:
(1) It is appropriate to employ the oxygen activated sludge process for tannery
waste. However, extra care must be exerted to the operation and maintenance of
the process. When the F/M ratio is kept at below 0.1 kg.BOD/MLVSS. kg/d, it is
possible to obtain effluent with BOD 20 mg/1 and BOD removal rate 97 percent.
(2) Fluctuation of tannery waste quantity and quality is great. But if the F/M
ratio can be slightly lowered at the time of constant feed, it is possible to obtain
effluent with BOD of below 20 mg/1 even when there is a fluctuation of influent
flow. However, when considering the long period use of the biological treatment
facility for stable operation and maintenance, it is desirable to provide a equalization
tank for constant supply of influent.
(3) It is advisable to introduce the method of supplying tannery waste combined
with domestic sewage for stable treatment. When the mixing ratio of tannery waste
and domestic sewage is 1:1, even when F/M ratio is more than 0.2 kg.BOD/
MLVSS.kg/d, it is possible to maintain effluent BOD below 2Qmg/l.
(4) When the two-stage oxygen activated sludge process is employed, although it is
possible to operate with a high F/M ratio, it requires an intermediate tank. From
the economical standpoint and so forth, further studies should be made before
selecting either the single-stage process or the two-stage process.
(5) In the treatment of tannery waste by the oxygen activated sludge process, pH
control is not necessary. Judging from the experiment results, SVI is maintained
at around 100 and activated sludge is free from bulking. The removal of total
chromium is effectively done, but more than 50 mg of total chrome per 1 kg of
dry solids accumulate in sludge, thus extra care must be exerted in the disposal of
182
-------
the sludge.
(6) The oxygen consumption in the aeration tank was between 0.62 and 1.73
kilogram O2 per 1 kg of BOD removed. Also the sludge production was between
0.22 and 1.34 kg per 1 kg of BOD removed. In general, when the oxygen consump-
tion per BOD removed increased, the sludge production have shown a tendency of
decreasing.
183
-------
CHAPTER 6
SERVERAL APPLICATIONS OF PURE OXYGEN ACTIVATED SLUDGE
SYSTEMS FOR TREATING MIXTURE OF HIGH ORGANIC INDUSTRIAL
AND DOMESTIC WASTEWATERS
1. Over View of Pure Oxygen Activated Sludge Process in Japan 185
2. Covered Oxygen Systems for High BOD Municipal Wastewater
Treatment 186
— Case of Kyoto —
2.1 BOD Removal 186
2.2 Nuisance Free Design 187
3. Covered Oxygen System for Domestic Wastwater Treatment 191
— Cases of 4 Cities —
3.1 BOD Removal 191
3.2 Comments by Each City with Regard Oxygen System 191
4. Power Cost of Covered Oxygen System 191
5. Open Tank Oxygen System 192
- Case of Pilot Plants -
184
-------
1. OVER VIEW OF PURE OXYGEN ACTIVATED SLUDGE PROCESS
IN JAPAN
When compared with the United States, the number of examples of applying
pure oxygen activated sludge process to publicly owned sewage plants is small in
this country (Table-1). This may be reasoned to the fact that people no more think
it necessary to change the air activated sludge system to another method due to the
completion of designing techniques and the rich experiences in management and
operation. Only when waste water can not be treated effectively by the air system,
then the oxygen system is basically used. Until mid 1977, the cases of publicly
owned pure oxygen activated sludge process had been only 4.
In Octover, 1977, the nation's largest UNOX System with a capacity of
40,000m3/day was completed and immediately put in operation. This is the first
unit that was completed by the national construction grant.
The open type activated sludge process is now available in Japan thanks to the
good offices of Ataka Construction Company, K.K. This type is applied at two
industrial waste water treatment plants in 1978 for pretreatment purposes.
With the aim of compiling a manual for the pure oxygen activated sludge
process, we have decided to gather data and the features of this process. Hitherto,
the pure oxygen activated sludge process was considered highly economical only
when the BOD concentration contained in the raw water to be treated was high.
Also, when treating municipal sewage, its power cost was considered higher than
that of the air system. To confirm the reliability of this general idea is also one of
our aims, in this survey.
We have conducted performance tests for both the UNOX system and the
MAROX system by full plant test and pilot plant test respectively based on the
available data.
Table-1-a Unox Plants in Japan in Operation as of August 1978
No.
1
2.
3.
4.
5.
6.
7.
8.
9-
10.
11
12.
13.
Location
Kasuga S.T.P.
Ikuta S.T.P.
Uenodai S.T.P.
Japan Housing Corp.
Gotsu S.T.P.
Kisshoin S.T.P.
Nissho Kayaku
Co., Ltd.
Showa Neoprene K.K.
Sankyo Kokusaku Pulp
Co., Ltd.
Jujo Paper Co., Ltd.
Oji Paper Co., Ltd.
Oji Paper Co., Ltd.
(Expansion)
Oji Paper Co., Ltd.
Mitsubishi Chemical
Industries Ltd.
Oita City,
Oita Pref.
Kawasaki City
Kanagawa Pref.
Kamifukuoka City
Saitama Pref
Katano City
Osaka
Kyoto City
Kyoto
Oita City,
Oita Pref.
Kawasaki City
Kanagawa Pref.
Iwakuni City
Yamaguchi Pref.
Kushiro City
Hokkaido
Kasugai City
Aichi Pref.
Kasugai City
Aichi Pref.
Tomakomai City
Hokkaido
Kurashiki City
Okayama Pref.
Application
Municipal
Raw Degmted
Municipal
1 ry Effluent
Municipal
Raw
Municipal
Degritted
Municipal
with Dye
Wastes 1 ry
Effluent
Petrochemical
Waste
Synthetic
Rubber Waste
Pulp & Paper
Waste
Pulp & Paper
Waste
Pulp & Paper
Waste
Pulp & Paper
Waste
Pulp & Paper
Petrochemical
Waste
Aeration Tank Design
Flow
(m'/day)
1,000
2.300
1,950
2.750
40,000
2.800
3,000
3.360
6.000
70.000
22,000
50,000
7,200
Retention
Time
l(TO)hrs)
1 8
1.57
1.70
2.0
3.0
100
3.6
9.0
8.0
24
2.6
3.7
9.3
BOD,
Inlet
mp/l)
200
140
200
274
220
1,700
190
2,000
2,000
286
380
600
970
Oxygen Supply
Capacity
(tons/day)
04
0.6
0.6
1.1
15.0
50
1.0
8 3
18.4
250
160
27
85
System
PSA
PSA
PSA
PSA
PSA
PSA
Pipe
PSA
PSA
PSA
PSA
Pipe
Pipe
Aerator
SA
SAB
SAB
SA
SAB
SA
SAB
SA
SAB
SA
SA
SA
SA
On Stream
Oct.. 1972
June. 1973
Dec., 1973
May, 1974
Sept.. 1977
Sept., 1972
del., 1972
July, 1973
Sept., 1973
July, 1974
April. 1978
Aug , 1974
Teb., 1975
185
-------
Table-1-b Unox Plants in Japan in Operation as of August 1978
No
14
15.
16
17.
18.
19
20.
21.
22.
23.
24.
Location
Sumitomo Chemical
Co . Ltd
Electro Chemical
Industrial Co . Ltd
Tokiwa Sangyo K K
Mitsubishi Chemical
Industries Ltd
Mitsui Toatsu
Chemicals, Inc.
Sapporo Breweries,
Ltd.
Nippon Kasei
Chemical Co , Ltd
Koa Kogyo K K.
Toyo Pulp Co., Ltd
Otake Shigyo K K.
Sumitomo Chemical
Co , Ltd
Ichihara City
Chiba Pref.
Ichihara City
Chiba Pref
Oware Asahi City
Aichi Pref
Kitakyushu City
hukuoka Pref
Takaishi City
Osaka
Sapporo City
Hokkaido
Iwaki City
Fukushima Pref.
Fuji City
Shizuoka Pref
Kure City
Hiroshima Pref
Otake City
Hiroshima Pref
Niihama City
Ehime Pref.
Application
Petrochemical
Waste
Petrochemical
Waste
Pulp & Paper
Wasle
Dvestuff
Waste
Petrochemical
Brewery Waste
Coke Oven
Waste
Pulp & Paper
Waste
Pulp & Paper
Waste
Pulp A Paper
Waste
Chemical Waste
Waste
Aeration Tank Design
Flow
(m'/day)
3,000
10,000
14,000
11,700
6,480
3,000
3,900
40,000
1 1 ,000
33,000
180
Retention
Time
( (TO) Mrs)
9 1
66
1.8
8 15
5.5
8.0
5.6
20
3.6
2.0
4 0
BOD,
Inlet
(mg/l)
1,320
730
150
830
1,100
1.330
620
220
540
190
300
(BOD,,)
Oxygen Supply
Capacity
(tons/day)
3 7
9 2
24
11 1
7 8
5 0
2.85
33.0
7 2
11 4
0.06
System
Pipe
Pipe
PSA
Pipe
Pipe
PSA
Pipe
PSA
Liquid
PSA
Pipe
Aetator
SAB
SA
SAB
SAB
SA
SA
SA
SAB
SAB
SAB
SAB
On Stream
June, 1975
July. 1975
Oct . 1975
Jan.. 1976
1 eb , 1976
April, 1976
May, 1976
June, 1976
Sept.. 1976
Oct., 1976
April, 1977
Table-1-c Unox Plants in Japan in Construction in Japan as of August 1978
No
I
2
Location
Todoroki S T P
(Phase I)
Ishmomaki-Tobu S T.P.
(Phase I)
Kawasaki City
Kanapawa Pref
Ishmomiiki C'lty
Miyapi Pref.
Application
Municipal
1 ry l-ffluent
Municipal with
I-ish Processing
Wasle
Aeration Tank Design
Flow
(mVday)
60,000
10,000
Retention
Time
((TO) Hrs)
I 93
>5.0
BOD,
Inlcl
(mg/l)
105
700
Oxygen Supply
Capacity
(tons/day)
15
11
System
PSA
PSA
Aerator
SAB
SAB
On Stream
1981
1981
Note S.T.P. Sewage Treatment Plant
PSA On-site pressure swing adsorption oxygen gas generator
Liquid = On-site liquid oxygen storage and vaporization
Pipe PipeliYie transport of oxygen gas from a off-site oxygen generating facility
SA Surface aerators
SAB Surface aerators with bottom mixers
2. COVERED OXYGEN SYSTEM FOR HIGH BOD MUNICIPAL WASTE
WATER TREATMENT
— Case of Kyoto City —
2.1 BOD REMOVAL
In this sewage treatment plant are two trunk sewers, A and B, through which
raw sewage flows in. The A chiefly deals with industrial waste water while the B
handles domestic sewage. The former contains an average 250 mg/l of BOD while
the latter 120 mg/l. By varying the mixing rate of both wastewaters, the BOD con-
centration in the raw sewage can be altered. Under the several different influent
BOD concentrations, UNOX's performance was observed. BOD removal, SVI, and
oxygen consumption were our main concerns. Table 2 shows the summary of
results of the test.
Even in this case when the BOD load is as large as 2 kg/m3/day, the effluent
BOD did not exceed 20 mg/l. SVI registered a low value of 100. And the BOD-SS
load at this time (BOD/kg-SS/day) was 0.38.
At this plant, the air system is also employed in parallel. In the air system,
186
-------
when the BOD load exceeded 1 kg/m3 /day, bulking generated.
Table-2 Performance of Unox in Kyoto
Item
~-~__^
Test
Percentage of Industrial Waste-
Water (%)
Temperature in Reactor (°C)
Aeration
Time
Q(hr)
(Q+R) (hr)
BOD Load in Tank (kg/m3 /day)
BOD SS
Load (kg/m3 /day)
MLSS (mg/1)
MLVSS/MLSS (%)
Concentration of Return Sludge
(mg/1)
SVI
Final Clarifier
(For Q Base) (hr)
Final Clarifier
(Overflow Rate)
(m3/m3day)
(Influent) (mg/1)
(Effluent) (mg/1)
(Influent) (mg/1)
(Effluent) (mg/1)
(Influent) (mg/1)
(Effluent) (mg/1)
Oxygen
BODR/MLVSS(kg/kg)
Used02/BODR
(kg/kg)
(Efficiency) (%)
I
50
17.9
2.8
2.1
1.36
0.31
4.552
80.4
14,976
191
3.5
24.3
163
14
103
35
74
11
0.3,0.4,0.5
1.05,0.86.1.14
95.5
II
100
19.9
3.2
2.1
1.74
0.33
5.308
74.8
12,697
117
3.9
21.4
233
18
173
70
120
22
0.3,0.4,0.5
1.07,1.36,1.17
87.3
III
100
19.9
3.0
2.0
2.01
0.38
5.383
76.7
11,538
116
3.6
23.3
247
18
180
74
136
25
—
2.2 NUISANCE FREE DESIGN
As this plant was constructed in the center of a residential area, extra care was
exerted to finish the facade in plesant apperance in design. The aeration tank and
PSA were totally housed in the structures. Also, to save space of the building lot,
the aeration tank was constructed atop the final Clarifier.
All sources of noise including PSA were housed, thus the noise level of the
sewage treatment plant at the border line was within the standard values.
Odorants contained in the exhaust gas of both the pure oxygen activated sludge
process and the air system were checked. The Offensive Odor Control Law stipulates
187
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5,000
4,000
Q
O
CD
2,000
2.5
2.0
1.5
1.0
0.5
0--fr
-20
6—6 Removed BOD (mg/day)
V X Eff Total BOD (mg/l)
• • Eff Sol BOD (mg/l)
1.0 1.2 1.4 1.6
BOD Load (kg/ma/day)
1.8
2.0
10 -§
0
O
CD
-0
Fig.-1 BOD Load vs Eff BOD and Removed BOD Weight
Primary
Clarified
Effluent
1. Aeration Machinery Room
2. Aeration Tank
3. Final Clarifier
4. Return Sludge Pump
5. Electric Room
6. Oxygen Generating Unit (PSA)
7. Air Compressor Room
8. Ventilation Rook
Fig.-2 Covered Aeration Tank and
188
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Scale: 1/600
® Noise Level Measureing Point
Purr
P
Chan
3 rid
iber
Pump
55- 56 dB
Aeration
Tank &
P.S.A.
1®!
47.5~45dB
48- 49.5 dB
J
Fig.-3 Noise Level
the permissible level of the odor threshold concentration as shown in Table 3.
Table-3 Allowable Maximum Concentration of III Smelling Material
\
V_Odor Density
0 d o ranF~~~~-~----__^^
Ammonia
Hydrogen Sulfide
Methyl Sulfide
Methyl Bisulfide
Trimethylamine
Acetaldehyde
Styrene
Odorant Concentration
2.5
1 .0 ppm
0.02
0.01
0.009
0.005
0.05
0.4
3.0
2.0 ppm
0.06
0.04
0.003
0.002
0.1
0.8
3.5
5.0 ppm
0.2
0.2
0.1
0.07
0.5
2.0
The measuring results of odorants contained in the exhaust gas of the pure
oxygen activated sludge process and the air system are shown in Table 4.
189
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Table-4 III Smelling Material Concentration at Aeration Tank
Hydrogen Sulfide
Methyl Mercaptan
Methyl Sulfide
Dimethyl Sulfide
Acetaldehydle
Ammonia
Trimethylamine
Styrene
Carbon Dioxide
Oxygen
Nitrogen
Carbonyl Sulfide
(Formaline)
Formaldehyde
Air System
(ppm)
0.002
0.003
0.002
0.0003
0.002
0.029
0.0003
0.005
0.9 (%)
19.4 (%)
79.7 (%)
-
0.24 ppm
Oxygen System
(ppm)
ND (Below 0.003)
ND (Below 0.001)
0.003
ND (Below 0.0001)
0.003
0.017
ND (Below 0.0002)
ND (Below 0.005)
5.5 (%)
35.0 (%)
59.5 (%)
-
0.008 ppm
Allowable
Limit
0.002
0.01
0.009
0.05
1.0
0.005
0.4
The concentrations of odorants contained in the exhaust gas of both systems
were below the regulated standard values. And in general the odorant concentration
values of the pure oxygen activated sludge process were more than those of the air
system.
Table 5 expresses the emission volume of odorants in air per unit sewage
volume. This Table shows that when comparing the emission volume of odorants in
the air by the pure oxygen activated sludge process and the air system, the emission
volume by the pure oxygen activated sludge method is smaller from 1/1000th to
1/100th.
Table-5 Volume of Smelling Material in a Unit Volume of Sewage
Ammonia
Methyl Mercaptan
Hydrogen Sulfide
Methyl Sulfide
Demethyl Sulfide
Trimethylamine
Styrene
Oxygen
Carbondioxide
Nitrogen, Argon, etc.
Oxygen
0.191
Below 0.0 11
ND
0.034
ND
0.034
ND
0.004
0.0006
0.0067
Air
170
2.76
15.3
291
2.76
20.3
Below 646
1.46
0.055
5.86
Unit
10-9m3/m3
m3/m3
190
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3. COVERED OXYGEN SYSTEM FOR DOMESTIC WASTE WATER
TREATMENT
-CASES OF 4 PLANTS: Kawasaki City, Katano City, Oita City and
Uenodai —
3.1 BOD REMOVAL
The subject four cities have a long experience in treating municipal sewage with
the pure oxygen activated sludge system. Table 6 shows the performance data ob-
tained at the four cities.
Table-6 Performance Data of Oxygen System Treating Domestic Wastewater
Capacity m3/day
Aeration Time for Q (hr)
Primary Clarifier
Raw BOD (mg/1)
Eff BOD (mg/1)
SVI
Number of Operatior
Kawasaki
2,300
1.6
Yes
130-360
7-18
150
11
Katano
2,750
2
No
130-200
7-16
100
8
Oita
1,300
1.8
No
90-180
9-20
150
5
Uenodai
1,950
1.7
No
20 - 240
5-20
100
1
3.2 COMMENTS BY EACH CITY WITH REGARDS OXYGEN SYSTEM
At Kawasaki-city, the hitherto air system had a slight tendency of causing
bulking of sludge. Therefore, the total performance was instable. However, after
employing the oxygen system, bulking has never occurred. Also, the oxygen system
seems to be flexible against shock loads.
At Katano-city, both the oxygen system and the air system are put into op-
eration in parallel at the same treatment plant. The performance of the oxygen
system is considered much more stable than the air system. But, the concentration
of return sludge in the oxygen system do not reach the designated value of mg/1,
owing to the lack of ability of the rectangular clarifier to condense sludge. There
should be some improvement made with regards the shape of the basin.
As the oxygen system at Uenodai is fully automatic, it is possible to conduct
the central control and monitoring system. That is why only one operator can
mange the plant. Despite the plant being located close to a school and a cluster of
houses, there is no complaint brought against the plant with regards ill smell due to
the smallness of exhaust gas volume.
4. POWER COST
Fig. 4 compares the power costs of the UNOX system and the air system. Both
are the yearly average costs and show no remarkable differences.
191
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1-0
g-
o
0.5
BOD 150- 240mg/l
KAWASAKI -y . __ AirSystem
<£
BOD 150- 360mg/l
/Kyoto
D BOD250mg/l
1000 10000 100000
Volume of Water m3/day
Fig.-4 Comparasion of Power Costs of the Oxygen System and the Air System
5. OPEN TANK PURE OXYGEN ACTIVATED SLUDGE PROCESS
— Case of Pilot Plants —
The function of the open tank pure oxygen activated sludge process was
examined at a pilot plant in three places. Photo 1 shows the total view of the pilot
plant. The plant dimensions are: Depth 2.5 meters, width 1.5 meters, and length
3 meters. The effective capacity is 12m3, the RAD diameter 50 cm (diffusion area
0.0214m2), rotating speed 400 rpm, and the oxygen supplying capacity 12.2
kg/day. The greatest interest in the open tank oxygen activated utility sludge
system was to find out the oxygen utility efficiency. The oxygen utility efficiency
can be obtained from the following equation:
Used O2 + effluent O2 - influent O2 /supplied O2
The amount of used oxygen can be obtained by substracting the oxygen con-
tained in the exhaust gas from the supplied oxygen.
• The collection and measurement of exhaust has were conducted as follow:
As shown on the left, a 30mm funnel and a 1000ml graduate cylinder filled
with water were used to collect the exhaust gas that ascended and released in the air.
The exhaust gas volume was measured by measuring the volume of the exhaust gas
collected in the graduate cylinder and computing the elapsed time.
192
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1000ml graduate
Sylinder
V
The measurement results are show in Table 7.
Table-7 Data for O2 Material Balance in Marox Pilot Plant
02 Supply
(Nm3/day)
(1)16.1
(2) 16.1
(3) 40.8
(4) 40.8
(5) 6.75
(6) 7.67
(7)11.9
(8) 10.3
(9) 14.8
O2 Sup/
std (%)
175
175
443
443
73
83
129
112
161
Off Gas
(Nm3/day)
4.03
3.86
12.2
12.2
0.464
0.518
0.491
1.20
2.05
OffGas/O2
Supply (%)
25.0
24.0
30.0
30.0
6.87
6.75
4.13
11.6
13.9
Composition
of Off Gas
02
C02
Other
(%)
76
76
79
78
35.7
49.6
39.5
43.0
44.4
5
7
4
3
11.0
15.0
12.0
22.5
23.1
19
15
17
18
53.3
35.4
48.5
34.5
32.5
Efficien-
cy (%)
81
81
76
77
98
97
98
95
94
Place
(RAD)
No. 1
No. 2
No. 1
No. 1
No. 2
No. 2
No. 2
No. 1
No. 2
Note: The MLDO at measuring time:
(1) - (4) Both No. 1 and No. 2 were 2-3 mg/1
(5) - (9) Both No. 1 and No. 2 were 3-4 mg/1
193
-------
In Fig. 5, the oxygen consumption efficiency is expressed on the axis of left
ordinates and the exhaust has rate is expressed on the axis of right ordinates. With
the volume of oxygen supply increases, the efficiency drops. When the designated
amount of oxygen supply is given, the efficiency becomes 95 percent.
This value exceeds those of the UNOX method.
90-
0.
a
~ 70-
60-
50-
o/
/
30
20
10
a
a
3
CO
50
100 200 300% Oxygen Supply Ratio
O2 Supply/Std
Fig.-5 Oxygen Utilization vs O, Supply in Open Tank Oxygen System
In Fig. 6, the actual measurement values of the relationship between
BOD-MIVSS Load and required oxygen to remove unit BOD given. For com-
parasion, the values obtained at ENGLEWOOD and the MAROX system is DENVER
were were also shown on the Figure. Our measurement values also showed similar
rusults as those in the United States.
The BOD removing performance by the open tank pure oxygen activated
sludge system have shown similar results with those of the covered oxygen system
with no marked difference.
194
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CHAPTER 7
REMOVAL OF COLOR FROM MUNICIPAL SEWAGE
CONTAINING TEXTILE WASTEWATER
1. Introduction 196
2. Color Measurement 196
3. Color Change of Wastewater by Activated Sludge Process 200
3.1 Experimental Method 202
3.2 Experimental Results 204
4. Removal of Color from Secondary Effluent by Physical Chemical Process . . . 210
4.1 Experimental Method 210
4.2 Experimental Results and Discussion 212
5. Summary and Conclusion 219
195
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CHAPTER 7
REMOVAL OF COLOR FROM MUNICIPAL SEWAGE
CONTAINING TEXTILE WASTEWATER
1. INTRODUCTION
The cleaness or dirtiness of water should be, as a rule, determined by the
amount of specific pollutants contained in the water. However, when a man judges
the cleaness of a river, he is often influenced sensibly by elements which can not be
specified, such as color, smell and foam of the water. Especially with regards color,
there is essentially no direct or indirect regulations in the form of stream, effluent
or pretreatment standards. However, even in the field of sewage treatment, there are
several cases where receiving bodies of water are being offended in appearance due
to the colored effluent from treatment plants which treat municipal sewage
containing textile wastewater and other colored industrial wastes. This situation
makes the study of color removing processes one of the major research projects.
At the present stage, the method to measure the degree of color itself is insufficient.
There remain many economical and technical problems to be solved including
the comparison of the system of treating colored wastewater after receiving into
public sewerage system with that of treating it by pretreatment facilities.
In this study, methods of color measurement are discussed and color removal
from municipal sewage containing textile wastewater by activated sludge process
and physical-chemical processes as tertiary application are investigated.
2. COLOR MEASUREMENT
The methods of measuring color of water can be divided into two categories:
the spectrophotometric method and the visual comparison method. The former
includes the mono-chromatic specification method, and the method to express
the degree of color by the color difference from pure water by improving the
mono-chromatic specification. The latter, however, is varied: a method of expressing
degree of color by making comparison with the color of platinum — cobalt
solution; a method to obtain chroma and luminance based on JIS standard color
plates and to express the extent of color based on these parameters, which is
stipulated in the Anti-Pollution Ordinance of Kawasaki City; and a method of ex-
pressing the degree of color by making comparisons with other suitable color
scales. Furthermore, there are the sensual methods of expressing the degree of
color based on the impression gained by viewing the color of water.
Generally, from the standpoint of pertinently expressing the various colors
resulting from industrial wastewater, the conditions that the method of color
measurement should satisfy can be listed as follows:
(a) Results coincide at least roughly with the visual impression of man.
(b) Reasonable comparisons are possible with regards colors of different hues.
(c) Colors by dissolved substances and by suspended matters are equally evaluated.
(d) Results are qualitative and have a good correlation, preferably linear relation-
ship, with the concentrations of substances causing color, and
196
-------
(e) The measuring method is simple and has a good reproducibility, and personal
error is small.
The above-mentioned conditions are not always perfect, even containing
conditions that would partially contradict with each other. However, tentatively
setting these conditions as the criteria for judgement and by comparing the
various measuring methods aforementioned, the color difference expression by
the spectrophotometric analysis and the method described in the ordinance of
Kawasaki City are considered to be effective. Accordingly, by employing the two
methods, measurements of color of various dye solutions and river waters were
conducted to make preliminary studies for evaluating them. The results have shown
that the two methods were not fully satisfactory but applicable for practical use.
However, the spectrophotometric method was superior in quantitativeness and
measurements at higher concentration, thus, the method based on the color differ-
ence was to be employed in this study.
By slightly modifying the original method, the procedure for color measure-
ment was determined as in Fig. 1. The color difference from pure water calculated
by this method is referred to as 'color intensity' in this paper. The modified points
are: the stricter filteration condition and the emplyment of the newer L*a*b*
system (1975 — UCS1) for calculation of color difference.
Fig.-1 Procedure for Color Intensity Measurement
| Sample [
^
put measurement,
put adjustment
according its necessity
"True" color
"Apparent" color (No filtration)
filtration through
0.45 M membraine filter
Measurement of normal
transmittance value
with 10 and 100 mm
absorption cells
Measurement of total
transmittance value
with 10 mm absorption
cell
Calculating of tristimulus
values X, Y and Z
Calculation of color difference
from pure water, E(L", a*, b")
Color intensity(S)io
Color intensity(S) 100
Color intensity(T)
197
-------
Since the color of water may differ greatly depending on pH of the sample,
it is adjusted to be within the range of stream standard (6.5 - 8.5) by adding 10
N sodium hydroxide solutions, when pH of the sample is outside of the range.
For the measurement of color by soluble substances, the normal transmittance value
of the sample within the wavelengths of 400 - 700 nm is measured after 0.45 M
membrane filtration. With regards color by suspended matters, the total transmit-
tance value of the non-filtered sample is measured within same wavelengths.
The total transmittance value mentioned here is the transmittance value combining
both the transmitted light and the scattered light measured by the spectrophoto-
meter having a photo cell with integrating sphere. The measurement of the
transmittance value is based on JIS Z8722 (Methods of Measurement for Color of
Materials Based on the CIE 1931 Standard Colorimetric System) and is conducted
at 10mm intervals by setting the transmittance value of distilled water as 100
percent, or is performed by 10 or 30 ordinate systems in spectrophotometric
color measurement to calculate the tristimulus values X, Y and Z. From these values,
the color difference from pure water E (L*a*b*) can be obtained from the following
equation:
AE(L*a*b*) = (AL*)2 +(Aa*)2 (1)
Here, AL*, Aa*, and Ab* are the difference between the sample and the pure
water with regards luminance parameter L* and chromaticness parameter a* and b*
which are defined as follows:
L* = 25(100Y/Yo)1/3- 16
a* = 500 (X/Xo)1/3~ (Y/Yo)1/3
b* = 200 (Y/Yo)1/3- (Z/Zo)1/3
In which, Xo, Yo and Zo are the tristimulus of the light source. By using any
spectrophotometer with Type C Light Source, which is designated by JIS Z8720
(Standard Illuminants and Sources for Colorimetry), can be set at 100 (percent).
The influence of dissolved substances and suspended matters to the total
transmittance value is reported to be as follows: Let the total transmittance value
be T, absorption coefficient of solution be K and scattering coefficient be S,
respectively,
log (1) log peid - (p - 1) e-Pd (2)
where,
q =VK(K + 2S)
a =
/K + 2S
d: thickness of solution.
When there is no influence of turbidity or K S, the above equation is reduced
to:
log(l/T)ocKd . . (3)
log(l/T) is in proportion to the concentration. On the other hand, when
198
-------
considering the case when K^O, equation (2) becomes,
1/TocSd . . (4)
(1/T) is in proportion to the concentration. Accordingly, color by dissolved
and suspended substances do not exhibit the same weight. However, while (1/T)
is small, log (1/T) is nearly equal to (1/T), and the combined influence of the
two can be expressed in a single parameter by incorporating the total transmittance
values.
The light paths for measurement of the total transmittance values are 10mm
and 100 mm when measuring normal transmittance value of filtered samples, and
the path is 10 mm when measuring total transmittance value of non-filtered samples.
The color differences obtained from the measurements are referred to as color
intensity (S)i0, color intensity (S)i0o and color intensity (T) respectively. The
reason why the light path is limited to 10 mm when measuring the total transmit-
tance values is the technical difficulty to capture the scattered light when the light
path is long.
Fig. 2 shows examples of results of measuring the relationship between color
intensity and concentration for the Pt-Co color standards and the various dye solu-
tions. The dyes in Fig. 3 and 4 are hydrophilic ones, and thus color intensity (T)
and color intensity (S)10 are the same. The relationship between dye concentration
and color intensity assumes a form resembling the exponential function as expected
by equation (3). However, colors of bright hues such as yellow and green, and
colors of comparatively dark hues including purple, blue and red show a slight
difference in trend. With colors of dark hues color intensity reaches maximum
value at comparatively low concentration. When the concentrations are same, color
intensity of dye solution with darker hue is larger than that with brighter hue.
Although this seems to be reasonable, there still is some room for further studies
on to what extent it coincides with the impression received by visual sense.
Fig.-2 Color Intensity(S) of Pt-Co Color Standards
140 r
120
-r 100
C/3
80
o
o
60
40
20
100 200 300 500
Pt-Co Color Unit
1000
199
-------
Fig.-3 Relationship between Dye Concentration (Yellowish Dye) and Color Intensity
140
10 15
Dye Concentration (mg/l)
20
Fig.-4 Relationship between Dye Concentration (Violet Dye) and Color Intensity
120 r ^ • goloMntenSity(s)100
100r
Dye Concentration (mg/l)
At about 10 different stations in rivers flowing through the city of Hamamatsu,
repeated measurements of color intensity and visual impression surveys were
conducted. The visual impression tests were of simple nature, categorizing the
impressions into three ranks, that is, 'clean', 'normal' and 'dirty'. The average color
intensity of river water was calculated for the stations evaluated visually as 'normal'.
The average color intensity (S)100 was 2.5 and the color intensity (T) was 0.7.
Although the impression of color of river water on site differs depending on water
depth and the surrounding conditions, the abovementioned values give a rough idea
on the limit of color of not making people feel uncomfortable and repugnance.
3. COLOR CHANGE OF WASTEWATER BY ACTIVATED SLUDGE PROCESS
With regards color removal of sewage containing textile wastewaterby activated
sludge process, there are reports confirming decolorization to some extent while
others report no removal of color. Types of dyes and measurement methods are
considered to have significant effects. Laboratory experiments were carried out in
200
-------
Hamamatsu City to investigate color change of wastewater by activated sludge
orocess using overall textile wastewater and process effluent containing specific
type of dye.
Hamamatsu is famous for its production of textile goods with dye works of all
types in the city. At the Chubu Sewage Treatment Plant that covers the major
portion of the city, an average 109,400 m3/day of sewage was handled in 1975.
Nearly 20 percent or roughly 20,000 m3/day (including textile process effluent of
14,720 m3/day) of wastewater was from textile plants. There are 29 textile plants
within its service area of which 28 are located in the drainage area of one of the
pumping stations, the Minami Pumping Station. The Minami Pumping Station
handles about 60,000 m3/day of sewage of which nearly one-third are wastewater
from textile plants. Excluding the non-colored wastewater generated at scouring
and bleaching processes, colored wastewater accounts for roughly 24 percent at the
Minami Plant. The quantity of dyes (including pigments) used by the previously
mentioned 28 plants was about 27.3 tons per month, and as Table 1 indicates,
pigments and reactive dye shared more than half of the total. When pigments are
excluded, reactive dye accounted for over 50 percent of the total. Table 2 shows
the percentage of dyes used in Japan in 1975. Dispersive dye is predominantly used
as a whole.
Table-1 Percentage of Dyes Used in the Drainage Area
of the Minami Pumping Station, Hamamatsu City
Sulphide
6.7
Leuco
9.0
Naphtolic
4.0
Dispersive
0.4
Reactive
35.1
Acid
2.8
Direct
2.9
Mordant
0.8
Basic
0
Pigment
38.3
Table-2 Percentage of Dyes Used in Japan
Sulphide
6.2
Leuco
7.1
Naphtolic
4.3
Dispersive
39.6
Reactive
9.1
Acid
6.6
Direct
5.5
Mordant
2.6
Basic
3.1
Pigment
15.9
Table-3 Color Intensity of Textile Wastewaters and Others
Reactive Dye Waste
Sulphite Dye Waste
Dispersive Dye Waste
Basic Dye Waste
Night Soil
Color Intensity(S),o0
85.0
(35.9-110)
59.8
(9.7-78.9)
73.3
(20.0-100)
122
(77.8-140)
102
(101-103)
Color Intensity(S),0
64.3
(4.3-89.1)
9.6
(0.8-14.8)
16.1
(3.3-34.1)
65.3
(11.6-113)
64.6
(45.1-79.9)
Color Intensity(T)
66.1
(4.8-90.8)
37.7
(27.3-53.5)
38.5
(13.0-59.0)
75.4
(18.5-116)
86.6
(85.2-88.7)
Color Intensity(S),0
Color Intensity(T)
95.5%
(89.6-98.2)
26.4%
(29.~49.3)
39.4%
(8.2-57.8)
82.5%
(60.5-99.5)
73.2%
(52.1-87.0)
The upper figures are the average values and the lower figures show the range.
201
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3.1 EXPERIMENTAL METHOD
3.1.1 Samples Used in the Experiments
The activated sludge treatment experiments conducted here were to examine
removal of color from municipal sewage containing comparatively -small amount of
textile wastewater.
Samples of domestic sewage for the experiment were taken at the Enshuhama
Sewage Treatment Plant in Hamamatsu. This treatment plant is a small one, handling
only domestic sewage with an average flow of 2,500 m3/day. The population served
was 10,600 as of the end of 1975. According to the result of water quality tests
during a whole day, the color intensity and other water quality parameters such as
BOD and SS have shown almost identical time variations by reaching the maximum
at between 8 and 9 am. The range of color intensity (S)100 variation during a day
was from 5 to 25. As the samples collected at around 11 am were considered to
show an average color intensity, the influent taken at 11 am was used as domestic
sewage to be mixed with textile wastewater for the experiment.
As for the samples of textile wastewater, effluent containing various types of
dyes altogether and that containing specific types of dyes were used. The former
was collected at the aforementioned Minami Pumping Station while the latter was
collected from actual dyeing plants.
The range of color intensity variation of sewage at the Minami Station during
a daytime was 20 - 25, marking its peak at between 4 and 6 pm. Thus, sewage
collected at 4.30 pm was used as the samples for the experiment.
Concerning the samples containing single type of dye in each sample, on the
other hand, reactive, sulphide, dispersive and basic dyes were selected as types of
dyes, and wastewaters from actual textile plants were collected as the samples
except for basic dye. Since there are no plants in Hamamatsu using this type of dye,
synthetic wastewater by dissolving basic dye was prepared. Table 3 shows the color
intensity of each wastewater used in the experiment. In the Table, the upper figures
show the average values while the lower figures indicate the range.
The ratio of color intensity (S)10 to color intensity (T) serves as an index
indicating the proportion of the color intensity caused by dissolved substances.
It is quite natural that the reactive and basic dyes that are hydrophilic show larger
values while hydrophobic sulphide and dispersive dyes show smaller values.
In some sewage treatment plants, night soil addition at the sewage treatment
plant can be considered to cause coloring of treated water. Therefore, decoloring
experiments were also conducted by using samples which were prepared by adding
night soil to the domestic sewage. Color intensity of night soil is also shown in Table
3. It shows that night soil, too, has tremendously high color intensity.
3.1.2 Experimental Run, Experimental Apparatus and Experimental Conditions
Twelve experimental runs were carried out. In which, five runs are for textile
wastewater containing various kinds of dyes altogether (hereinafter, these runs are
called 'Mixed Dyes Waste'). For these runs, feed waters were prepared by adding
the sewage taken at the Minami Pumping Station to domestic sewage so that ratios
202
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of the textile wastewater were 1, 2, 4, 8 ' and 16%, respectively. Four runs are for
textile wastewaters, each containing reactive, sulphite, dispersive and basic dyes
separately. In these runs, percentage of textile wastewater in the feed water was
10%. In the experimental run for night soil, one percent of night soil was added to
the domestic sewage to prepare the feed water. And, as controls, domestic sewages
collected at 9 am and 1 1 am were prepared for two different runs. Table 4
summarizes the water quality of each feed water influent for each experimental
run. Due to technical difficulties in the measuring devices, some figures are missing
in Color Intensity (T).
Table-4 Influent Water Quality of Each Experimental Run of Activated Sludge Treatment
Name of Run
Mixed Dyes Waste 1%
Mixed Dyes Waste 2%
Mixed Dyes Waste 4%
Mixed Dyes Waste 8%
Mixed Dyes Waste 16%
Reactive Dye Waste 10%
Sulphite Dye Waste 10%
Dispersive Dye Waste 10%
Basic Dye Waste 10%
Night Soil 1%
Domestic Sewage Taken at
9AM
Domestic Sewage Taken at
11 AM
Turbidity
82
(50-175)
92
(50-250)
89
(33-190)
104
(53-220)
81
(22-160)
114
(51-185)
66
(37-168)
162
(47-368)
108
(45-178)
156
(60-382)
99
(70-230)
102
(42-245)
SS
(mg/ )
81.6
(57.0-108)
78.5
(48.8-146)
80.7
(45.0-190)
94.9
(60.8-218)
93.0
(39.1-214)
89.1
(46.0-139)
73.8
(52.7-108)
173
(73.0-269)
106
(69.0-150)
124
(67.0-335)
122
(7.0-168)
94.7
(25.0-171)
COD
(mg/ )
44.1
(31.7-53.5)
43.6
(30.4-62.1)
42.0
(27.1-52.5)
47.8
(37.6-70.6)
46.3
(35.3-62.7)
50.8
(39.6-60.7)
40.4
(32.4-47.9)
82.0
(38.7-117)
48.1
(36.4-56.2)
64.3
(47.5-113)
52.1
(41.8-61.2)
39.7
(19.4-65.1)
Color
Intensity(S)ioo
15.9
(13.4-20.6)
14.0
(9.9-19.5)
15.1
(10.6-23.6)
18.7
(13.2-37.1)
24.8
(12.9-42.3)
74.1
(12.9-92.6)
15.4
(10.2-22.2)
23.5
(15.5-54.7)
24.5
(9.3-102)
25.1
(20.7-32.6)
17.3
(14.1-24.2)
13.9
(11.1-18.8)
Color
Intensity(T)
15.4
(3.2-22.0)
5.6
(3.6-7.9)
8.9
(4.0-27.5)
13.3
(5.3-48.3)
5.4
(3.1-11.5)
The upper figures are the average values and the lower figures show the range.
Table 3 and Table 4 show some interesting points when compared. In the case
of basic dye, after being mixed with domestic sewage, coloring caused by dissolved
substances dropped markedly. Comparing with the case of reactive dye which is
also hydrophilic, color intensity (S) of basic dye wastewater before mixing with
domestic sewage is a little larger than that of reactive dye wastewater. But after
the wastewaters are mixed with domestic sewage, the color intensity (S) of basic
dyes become much smaller. This is reasoned to the fact that as the basic dye
wastewater is not a real wastewater from plants and a reasonable amount of basic
dyes are absorbed by the SS in the domestic sewage. Therefore, in such decoloring
203
-------
treatment experiments, there is a danger of acquring misleading results when not
employing actual wastewater from textile plants. The apparatus used for the experi-
ment was a laboratory scale one with primary sedimentation tank of 4 liters,
aeration tank of 18 liters, and final settling tank of 7.5 liters. Experimental condi-
tions are shown in Table 5. The feed water was prepared every day from the samples
taken on the same day or one day before. The feed water was mixed slowly and
continuously in the storage tank to prevent sedimentation of suspended matters in
the raw water.
Table-5 Experimental Conditions
Flow Rate
Settling Time of Primary Settler
Aeration Time
Settling Time of Secondary Settler
Water Temperature in Aeration Tank
Experimental Period in Each Run
55 ml/min.
1.2hrs.
5.5 hrs.
2.3 hrs.
20°C
2 weeks
As for seed sludge of activated sludge, the activated sludge at the Chubu Sew-
age Treatment Plant was used for the experimental runs with textile wastewater.
With regards runs with night soil and domestic sewage, the activated sludge of the
Yayoi Sewage Treatment Plant in Hamamatsu that exclusively handles domestic
sewage was used. The experimental period for each run was 2 weeks. With regards
experimental runs with specific dyes, two weeks of acclimation period were given
for each run. No acclimation period was given for other runs since water quality of
feed water was similar to that of the treatment plant where seed sludge was collected.
The raw sludge at the preliminary settling tank was withdrawn arbitrarily depending
upon the generation of sludge. The adjustment of return sludge and the withdrawal
of the excess sludge were conducted at the secondary settling tank by determing
the amount based on the results of measuring the SV, MLSS, etc. of the aeration
tank.
The water temperature in the aeration tank was maintained at 20° C through-
out the experimental period.
The water quality of feed water and treated water was measured daily. pH, SV,
and DO in the aeration tank was also measured daily. MLSS was measured 2 to 4
times during the experimental period.
3.2 EXPERIMENTAL RESULTS
Table 6 shows DO, MLSS, SVI and BOD loading in the aeration tank for each
experimental run. The BOD loading indicated in the table is a rough estimate which
is calculated from COD of feed water since measurement of BOD in feed water was
not performed. Fig. 5 shows the removals of COD, SS and turbidity. According to
Fig. 5, the removals of SS with regards sulphide and basic dyes were slightly bad.
However, SVI in these runs was smaller when compared with runs of the mixed
dyes waste and bulking was not observed. Rather, in runs of mixed dyes waste
204
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there was a tendency of causing bulking. The COD removal was about 65 percent
in runs of specific dye waste and about 75 to 80 percent in runs of domestic
sewage and mixed dyes waste with low ratios. In general, the COD removal
because low when the textile wastewater was mixed. However, in the experimental
runs with low removal rate, the BOD loading was high, therefore it was not clear
whether the difference in treatment conditions or textile wastewater had caused
the drop in the removal rate. Since the aim of the experiment was to investigate
the decolorization effect of activated sludge process, further examinations were
not conducted because the treatment condition of each experimental run was
judged fairly satisfactory.
Table-6 Operating Parameters of Activated Sludge Process of Each Run
Name of Run
Mixed Dyes Waste 1%
Mixed Dyes Waste 2%
Mixed Dyes Waste 4%
Mixed Dyes Waste 8%
Mixed Dyes Waste 16%
Reactive Dye Waste 10%
Sulphide Dye Waste 10%
Dispersive Dye Waste 10%
Basic Dye Waste 10%
Night Soil 1%
Domestic Sewage Taken
at 9AM
Domestic Sewage Taken
at 1 1 AM
PH
7.0
(6.7-7.3)
7.2
(7.0-7.4)
7.2
(7.1-7.4)
7.1
(6.2-7.3)
7.2
(6.8-7.6)
7.4
(7.1-7.6)
6.6
(5.7-7.2)
6.8
(6.2-7.2)
7.3
(6.9-7.8)
7.6
(7.4-7.9)
7.0
(65.-7.0)
7.4
(6.1-7.0)
DO
(mg/ )
0.9
(0.3-1.9)
0.9
(0.3-4.5)
0.4
(0.3-0.6)
0.8
(0.5-1.6)
1.1
(0.3-4.1)
1.2
(0.3-3.1)
1.5
(0.4-2.9)
1.8
(0.8-5.0)
3.2
(0.9-6.9)
1.5
(0.2-3.1)
0.7
(0.3-1.6)
1.5
(0.4-4.7)
SV
(%)
19.3
(9.0-31.5)
20.6
(4.5-31.0)
27.6
(14.5-47.0)
24.2
(10.5-48.0)
25.2
(3.0-73.5)
13.0
(5.0-24.0)
8.0
(5.0-14.0)
12.0
(7.0-15.5)
13.0
(7.0-24.0)
11.5
(2.0-28.0)
18.2
(9.0-30.5)
12.6
(0-24.0)
MLSS
(mg/ )
1330
(1230-1420)
1200
(1070-1330)
1220
(850-1860)
1490
(1170-2300)
1740
(1400-2400)
560
(380-780)
1320
(880-1790)
1110
(980-1270)
1060
(600-1590)
1030
(970-1150)
1540
(1430-1660)
1560
(1380-1740)
SVI
145
170
225
160
145
174
(119-212)
64
(48-78)
99
(78-134)
117
(98-145)
141
(82-183)
120
80
BOD Loading
(kg/SS-kg/d)
0.19
0.21
0.20
0.19
0.15
0.52
0.18
0.42
0.26
0.36
0.20
0.15
The upper figures are the average values and the lower figures show the range.
205
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Fig.-5 Removal of Turbidity, SS and COD in Each Experimental Run of
Activated Sludge Treatment
• Turbidity
o SS
0 COD
Mixed Dyes Waste 1%
Mixed Dyes Waste 2%
Mixed Dyes Waste 4%
Mixed Dyes Waste 8%
Mixed Dyes Waste 16%
Reactive Dye Waste 10%
Sulphide Dye Waste 10%
Dispersive Dye Waste 10%
Basic Dye Waste 10%
Night Soil 1%
Domestic Sewage Taken at 9 AM
Domestic Sewage Taken at 11 AM
^ 60 80 100
o o*
0 •
« o»
00 •
9 o*
0 09
« 0»
-rt
60 80 100
Removal (%)
The removal of color intensity in each experimental run is summarized in
Fig. 6. Since color intensity is not a linear index, the concept of removal may not
be appropriate. But for convenience sake the removal was defined as the ratio of
the difference of color intensities of the feed water and the treated water to the
color intensity of the feed water. The removal of color intensity (T) of runs of
mixed dyes waste and domestic sewage are not listed owing to malfunctioning
of measuring devices.
206
-------
Fig.-6. Removal of Color in Each Experimental Run of Activated Sludge Treatment
o Color lntensity(S)10o
• Color Intensity(T)
0 20 40 60
Mixed Dyes Waste 1%
Mixed Dyes Waste 2%
Mixed Dyes Waste 4%
Mixed Dyes Waste 8%
• o
o
Mixed Dyes Waste 16% r o
Reactive Dye Waste 10% h°
Sulphide Dye Waste 10%
Dispersive Dye Waste 10%
Basic Dye Waste 10%
Night Soil 1%
Domestic Sewage Taken at 9 AM • o
Domestic Sewage Taken at 11 AM "- O
o
o
0 30 40 60
Removaal (%)
The removal of color intensity (S)j00 was about 30 to 40% for runs of do-
mestic sewage. But when textile wastewater was mixed, the removal was about
20% with regards runs of mixed dyes waste and below 10% concerning runs of
specific dye waste excluding that of sulphide dye waste. With regards sulphide
dye waste, substances classified as dissoluble were predominantly in the form of
colloid particles and were absorbed by the activated sludge, thus giving higher re-
moval. Furthermore, it is noteworthy to mention that sewage added with night soil
was very low in removal compared to sewage containing only domestic sewage.
Also, concerning removal of color intensity (T), it was about 60% for the
hydrophobic dispersive and sulphide dyes with the apparent color by suspended
matters considered totally removed. Naturally, the removal of color intensity (T)
for the hydrophilic reactive dye waste water was as low as 25%. With regards basic
dye waste water which is also hydrophilic, the removal of color intensity (T) was
extremely high owing to the reasons mentioned before that actual waste water from
textile plant was not used. In short, as it was a synthetic wastewater by artifically
dissolving dyes in water, the dyestuffs were adsorved by the SS or activated sludge
in the water and thus the apparent removal rate was considered to be high. When
actual wastewater from textile plant is used, it is assumed that the removal of color
intensity (T) is extremely small.
To further study on the removal of color caused by dissolved substances,
chromaticity diagrams were made for samples of filtered feed water and treated
water (0.45 jj. membrane filteration). Figures 7 to 10 show the chromaticity
diagrams for each experimental runs of sewage containing only domestic sewage,
sewage with 16% mixed dyes waste, sewage containing reactive dye and sewage
207
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added with dispersive dye.
Fig.-7. Change in Color through Activated Sludge Process: Influent is the domestic Sewage
Pure
100
80
u 60
CO
c
E
c 40
20
r-0
Water
oo
sic
s
0.34
o 0.33
o
H 0.32 -
0.31 -
570 nm
580 nrn
Pure Water
o Effluent
• Influent
0.31 0.32 0.33 0.34
Trichromatic Coefficient X
0.35
Fig. -8
Change in Color through Activated Sludge Process: Influent is the Sewage
containing 16% of textile waste
100
- 80
60
40
P.W.
0.33
0.32
• Influent
o Effluent
Pure
. Water
0.31
0.30
580 nm
590 nm
600 nm
530 C mm
0.31 0.32 0.33 0.34 0.35
Trichromatic Coefficient X
0.36
208
-------
Fig.-9 Change in Color through Activated Sludge Process: Influent is the Sewage
containing 10% of reactive dye waste
650 nm
700 nm
0.30
0.35 x 0.40^
Trichromatic Coefficient X
Fig.-10 Change in Color through Activated Sludge Process: Influent is the
Sewage Containing 10% of dispersive dye waste
560 nm 570 nm
100- :-
90
80-
70-
60
P.W.
0.35- •
0.31
580 nm
••A Influent
ODA Effluent
Pure Water
590 nm
600 nm
620 nm
0.30 0.35
Trichromatic Coefficient X
Figure 7 shows that the dominant wave length for both feed water and treated
water containing only domestic sewage was 57t nm (yellow). And by applying
the activated sludge process, the excitation purity has decreased while the luminance
has increased, testifying to the fact that decoloring was evident.
On the other hand, Figure 8 shows that the luminance followed a trend of
increase with regards sewage containing 16% of mixed dyes. And also the excita-
tion purity followed a similar trend. In this experimental run, considering the fact
that 80% of the sewage was domestic sewage, color by dissolved substances of the
dyestuffs is considered to be strengthened by the activated sludge process. With
regards this point, Figures 9 and 10 on reactive and dispersive dyes make the matters
clear. Concerning the run of reactive dye waste, the hues of red and purple are
treated and converted to red color in the neighborhood of 620 nm. The excitation
purity, too, increased slightly. Furthermore, in case of the run of dispersive dye
waste, even when the hue of feed water is either red or yellow, the hue of treated
water changes to yellow (about 575 nm) with the excitation purity increasing
greatly.
209
-------
When processing sewage containing only domestic sewage, the excitation
purity drops when treated by the activated sludge process. But as mentioned above,
with regards sewage mixed with dispersive dye, although domestic sewage occupies
about 80 to 90 % of the total, the excitation purity increases when treated by the
activated sludge treatment. Also as the hue changes, the dyestuffs are considered
to undergo changes owing to the activated sludge process and show stronger color.
Although the chromaticity diagram for sewage containing 1% of night soil is
similar to that of sewage containing only domestic sewage, the rate of drop in
excitation purity is smaller. And as understood from the comparisons made in Fig.
6, by the addition of 1% of night soil color removal drops to about 1/4 of the
sewage containing only domestic sewage. Therefore, the color of domestic sewage
that can be removed by activated sludge process is considered to be only that of
miscellaneous drainage and not night soil.
Although not illustrated, the chromaticity diagram of the run of sulphide dye
waste is nearly identical to that of domestic sewage, proving that sulphide dye can
be removed by the activated sludge process.
4. REMOVAL OF COLOR FROM SECONDARY EFFLUENT BY PHYSICAL
CHEMICAL PROCESS
When treating sewage containing textile wastewater by the activated sludge
process, removal of color caused by suspended matters is quite effective. But, on the
other hand, removal of color caused by dissolved substances is poor and sometimes
color is strengthened by the treatment. Therefore, in order to effectively remove
color by such substances, tertiary treatment may be necessary. Thus studies were
made to examine the color removal by ozonation, activated carbon adsorption and
chemical coagulation processes.
4.1 EXPERIMENTAL METHOD
4.1.1 Samples Used for the Experiments
Similar to the activated sludge process experiment, the experiments were
conducted by preparing samples containing various types of dyes altogether and
containing only specific dyes. As the former samples the secondary effluent (before
chlorination) at the Chubu Sewage Treatment Plant in Hamamatsu city were used,
and treated water from the activated sludge experiments was used for the latter
samples.
As mentioned previously, about 20% of the influent at the Chubu Plant is
wastewater from textile plants (about 13% when only colored wastewater), thus
the effluent is considerably colored. Fig. 11 shows an example of the daily variation
of color intensity (S)100 of the secondary effluent. Since visual color evaluation of
river water mentioned before showed that a rough boundary between 'dirty' and
'clean' is about 2.5 in color intensity (S)100, the secondary effluent of the plant is
colored to a good extent. The dominant wave length of light absorption was between
570 and 600 nm with the hue being yellowish orange.
210
-------
Fig.-11 Diurnal Variation of Color Intensity(S)10o of the Secondary Effluent of
the Chubu Sewage Treatment Plant
20
~ 15
03
10
_g
o
U
13
17 21
Time of Day
4.1.2 Experimental Method
(1) Ozonation process
The experiment was based on the batch test with an ozone generator of
maximum capacity of 0.9 g/hour. One-liter of sample was used for each experiment,
and the reacted ozone was calculated from the following equation?
Reacted ozone (mg/1) - [Ozonation per unit time (mg/min) x Elapsed time
(min) — Excess ozone (mg)]
The measurement of ozone contained in the water was conducted by titration
of sodium thiosulfate.
(2) Activated carbon adosrption
The decolorization experiment by the activated carbon adsorption process
was conducted by both the adsorption isotherm test and the continuous column
test.
The experimental process of the isotherm test was as follows:
The activated carbon was crushed in the mortar, and only those passing through
the 100 mesh seive were taken and dried for 2 hours in the drying oven adjusted at
105 - 110°C. 0.01, 0.025, 0.075 and 0.15 grams of the activated carbon were
placed in different 500 ml Erlenmeyer flasks with stopper, respectively. Then the
flasks were added with the water sample which had been filtered through 1 ju
membrane filter, and then thoroughly shaked to be placed in a 20 C constant
temperature room overnight. The color intensity (S)100 of the water sample was
measured prior to and after the adsorption test, and the difference was regarded
as the color intensity adsorbed by the carbon. The adsorption test was repeated
four or five times using the same water sample, and the arithmetical mean was
obtained.
The activated carbons used in the adsorption isotherm test with the secondary
effluent of the Chubu Plant were 12 types of 7 manufacturers. Concerning other
secondary effluents, three types of activated carbons were used. The selection of
three types of carbons were based on the test results with the Chubu plant effluent,
and one type of carbon was chosen from each category evaluated as 'good',
'normal' and 'poor'. The 12 types of activated carbon were all of coal type of which
211
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four were spherical carbons and the rest granular carbons.
The activated carbon column used in the continuous test was made of acrylic
resin with an inner diameter of 34 mm and length 2 m. The operation of the carbon
column was of a pressurized down-flow type. The continuous test was held only
on the filtered secondary effluent of the Chubu treatment plant.
First, to examine the influence of contact time, a single type of activated
carbon was selected. And tests were conducted by setting the condition at LV 100
(m/day) and SV at 2, 4, 6, 8, 10, and 12 (I/hour). Next, the color removal by acti-
vated carbon was compared of the 12 types at conditions of LV 100 (m/day) and SV
4 (I/hour).
(3) Chemical coagulation process
The following chemical coagulants were used in the tests: Four types of metal
coagulants including alum, polialuminum chloride (PAC), ferric chloride and lime.
Twelve types of polymers including eight cationic and four anionic coagulants.
All tests were conducted by jar tests, using coagulants independently and in
combination. The mixing were conducted in three different speeds as follow: rapid
mix (150 rpm), medium mix (80 rpm) and flocculation (40 rpm). When single
coagulant was used, the mixing time was 1.5 minutes for rapid mix, 0.5 minutes for
medium mix and 3 minutes for flocculation. And when the coagulants were com-
bined, the time was 3, 1 and 6 minutes respectively.
4.2 EXPERIMENTAL RESULTS AND DISCUSSION
4.2.1 Ozonation
Ozone's ability to remove color caused by organic substances is well known.
In this experiment, it was also confirmed that the color removal by ozone of
secondary effluent colored by textile wastewater produced extremely good results.
Fig. 12 shows the relationship between the amount of reacted ozone and the color
intensity (S)ioo removal. Here too, the removal is defined as the ratio of the dif-
ference in color intensity of the feed water and the treated water to the color
intensity of the feed water for convenience sake.
Fig.-12 Removal of Color by Ozonation: Samples are filtered secondary
effluent of the Chubu Sewage Treatment Plant
3 100
80
g 60
5
£ 40
tf>
c
CD
- 20
o
o
0 0
9 12 15 18
Reacted Ozonation (mg/l)
21
24 27
30
212
-------
Fig. 13 similarly shows the change in color by ozonation on the chromaticity
diagram. It shows that with the increase in reacted ozone, the luminance increases
and the excitation purity decreases proving that decolorization is progressing.
Also, the dominant wave length changes from 588 nm to 577 nm, and the orange
hue of the feed water changes to a yellowish hue.
Fig.-13 Change in Color by Ozonation; The sample is filtered secondary effluent of
the Chubu Sewage Treatment Plant. Figures in the parentheses show reacted
ozone in mg/
h o
P.W.
(28.7)
'(10.5)0.35
• .5: n T4
J4.6) £ •
°-33
0.32
0.31
560 nm
570 nm 580 nm 590 nm
Feed Water
Pure
Water
600 nm
620 nm
650 nm
Trichromatic Coefficient X
Fig. 14 shows the relationship between reacted ozone and color intensity (S)iQO
removal with regards non-filtered secondary effluent of the Chubu Sewage Treat-
ment Plnat. It shows similar results as shown in Fig. 12, and when ozone of low
concentration is dosed to the secondary effluent of this level of SS (roughly 20
mg/1), ozone consumption or its decoloring effect will not be much affected. Also
concerning removal of color intensity (T), similar results were obtained although
the deviation of data were a little larger.
Fig.-14 Removal of Color by Ozonation: Samples are non-filtered secondary
effluent of the Chubu Sewage Treatment Plant
3 6
Reacted Ozone (mg/l)
213
-------
As to the results of the runs of specific dyes, the relation between reacted
ozone and removal of color intensity (S)100 was as shown in Fig. 15. In Fig. 15, re-
sults of runs of 1 percent night soil addition and domestic sewage alone are also
shown for comparison. The figure indicates that except for the extremely poor
decoloring effect of dispersive dye, there were no significant differences observed of
other dyes. However, they seem to be slightly inferior when compared with
secondary effluent of domestic sewage.
Fig.-15 Removal of Dissolved Color by Ozonation: Samples are secondary effluents
obtained by treatment of sewage containing specific kinds of dye and others
100--
Reactive Dye Waste 10%
Sulphide Dry Waste 10%
Dispersive Dye Waste 10%
Basic Dye Waste 10%
Night Soil 1%
Domestic Sewage
6 8 10
Reacted Ozone (mg/l)
12
14
16
Although not illustrated, relationship between color intensity (T) removal and
reacted ozone was found to be similar to that shown in Fig. 5. In this case, however,
not only dispersive dye but also sulphide dye had a poor color removal. Perhaps,
this is reasoned to the fact that as both dyes are hydrophobic, oxidation by ozone
is not effective in removing color caused by suspended matters.
From Figures 12, 14 and 15, it can be commonly said that decolorization
progresses roughly in proportion to the amount of reacted ozone until the removal
reaches 60 or 70 percent. The color remaining after ozonation, as an example of
which is shown in Fig. 13, is yellowish in most case with the dominant wave length
being in the neighborhood of 575 nm. It is well known that yellowish color often
remains when wastes of high concentration is treated by ozone. Therefore, the
residual color after ozonation of secondary effluent might be caused by oxidation
products of dissolved dye. However, since similar color remains in the ozone treated
effluent when domestic sewage, or domestic sewage and night soil were handled
214
-------
it was considered thfct remaining color was caused mainly by night soil.
4.2.2 Activated Carbon Adsorption
The adsorption at equilibrium state of dissolved organic substances by activated
carbon may be expressed by the following Freundich Equation:
X/M = KC
Here, X is the amount of adsorbed substances. M is the amount of activated
carbon. C is the equilibrium concentration after adsorption. And K and n are con-
stants.
When applying adsorption of color in the equation, concentration of the color
causing substances or a parameter which has a linear relationship with the substance
should be used. But since there is no proper means of measuring the concentration
of color causing substances, the color intensity (S)10o was incorporated to obtain
approximate values.
Adsorption isotherm tests were carried out using the secondary effluent of the
Chubu sewage treatment plant and 12 types of activated carbons, A to L. In some
cases, straight lines were obtained. In most cases, however, knicks appeared and
two straight lines gave closer approximation than single line. An example is shown
in Fig. 16. As mentioned before, this is caused by the fact that the adsorption ex-
pressed by color intensity is not in proportion to the concentration of the color
causing substances and also the substances different in adsorption characteristics
were present.
Fig.-16 Adsorption Isotherm, Carbon A
200 r
100
> .0
£ °
i- .C
_O O)
"o
-------
However, to make rough comparisons, it was judged that single line was pos-
sible for approximation, and, thus, K and 1/n values of the equation were calculated
from the data obtained by the experiments using the secondary effluent of the
Chubu Plant. The result is shown in Table 7. It indicates that the adsorption
ability differs greatly depending on the types of carbons. Activated carbons H, E,
J, I and G have shown high decoloring efficiency while carbonsL, K and B were poor.
Table-7 Constants in Freundlich Equation: Adsorption of Color from
Secondary Effluent containing Mixed Dyes
Name of Carbon
A
B
C
D
E
F
G
H
I
J
K
L
K
14.2
6.8
12.2
12.0
62.0
4.4
45.0
100
46.0
64.0
11.0
2.9
I/n
0.90
1.20
0.75
0.80
0.45
1.10
0.60
0.40
0.55
0.50
0.90
1.20
Based on the assumption that the average color intensity (S)i0o of the feed
water is 22 from Fig. 11 and that 80 percent of this is to be removed, the necessary
quantities of carbon with the largest adsorption capacity and with the smallest
adsorption capacity differ about 10 times.
Adsorption isotherm tests with secondary effluent of the sewage containing
10 percent of textile wastewater of specific dyes and the sewage containing one
percent of night soil were also conducted by using carbons E, H and L. K and 1/n val-
ues obtained from the tests are shown in Table 8. The difference in activated
carbons had similar effect to those obtained from the tests using secondary effluent
of the Chubu treatment plant. However, it should be noted that the adsorption
characteristics differred greatly dependent on the difference in dyes. Reactive dyes
were adsorbed comparatively easily while basic dyes proved most difficult to adsorb
of all tested dyes.
216
-------
Table-8 Constants in Freundlich Equation: Adsorption of Color from
Secondary Effluent containing Specific Types of Dye and Others
\sName of Carbon
Name of Dry"""---^^
Reactive
Sulphide
Disperse
Basic
Night Soil
K
E
123
22.2
9.7
26.0
52.0
H
177
38.0
26.6
22.2
62.0
L
0.45
0.25
0.14
0.83
8.0
I/n
E
0.21
0.89
1.19
1.28
0.42
H
0.18
0.70
0.87
1.48
0.48
L
1.51
0.72
2.48
1.61
0.78
The effect of contact time was investigated by continuous column test using
the carbon A. The filtered secondary effluent of the Chubu Plant was used as the
feed water. As a result, as far as color intensity removals at the same feed water
volume applied to carbon volume was concerned, the removal rate was obviously
large when SV = 2 (I/hour, hereinafter the same). However, within the SV range of
between 4 and 12, there was no significant difference.
Furthermore, to confirm the results obtained from the adsorption isotherm
tests, continuous tests were conducted on all activated carbon employed in the
experiment by using the filtered secondary effluent of the Chubu Plant as feed
water.
In this instance, the LV was set at 100 (m/day) and SV at 4 (I/hour). The
results of the sleeted activated carbons are shown in Fig. 17.
Fig.-17 Comparison of Adsorptive Capacities of Test Carbons for Color Strength(S)ioo
Influent is the secondary effluent of the Chubu Sewage Treatment Plant
1150
1 1 40
o o 30
"o °
" ~ 20
El 10
LU —
200 400 600 800 1000
Volume through Column (m3/m3 of Carbon)
1200
From the adsorption isotherm test, activated carbon E was superior in adsorp-
tion characteristic to carbon A. However, data shown in Fig. 17 are not so. There
were this kind of minor differences in the results of both tests, but as a whole,
continuous column tests gave the similar results to those obtained from the adsorp-
tion isotherm tests.
217
-------
The difference in adsorption capacity owing to the difference in activated
carbons was compared with the characteristics of the carbons themselves. Table 9
shows the characteristics of activated carbons given by each manufacturer. The
blank space in the Table is due to lack of information. Although the values listed in
the Table are not so precise, the activated carbons having greater transitional pores
can be judged to have higher adsorption capacity. Therefore, dyestuff substances
that have undergone biological treatment are likely to be adsorbed in the transitional
pores.
Table-9 Properties of Test Carbons
Test Carbon
Apparent Density g/cc
Hardness %
Ash %
Iodine Adsorption Cap.
mg/g
Methylene Blue Ads. Cap
ml/g
Benzene Ads. Cap %
Specific Surface Area m2 /g
Approximate
Pore Size
Distribution
20 A cc/g
20-10= A
cc/g
lO'-lO4 A
cc/g
A
0.48
<8.0
>900
>9SO
0.12
0.22
B
0.44
<8.5
>1000
1000
-1100
\C
.0.45
4-0.5
>98
900
-1150
900
-1200
D
0.45
-0.5
>98
900
-1150
900
-1200
E
0.4
-0.45
>90
>350
900
1200
F
0.43
97
3.1
1080
36.8
11001
0.24
0.48
G
0.44
90
6.4
924
28.4
1070
0.85
0.43
H
0.41
91
7.2
785
20.3
750
0.92
0.48
I
0.40
99
1014
41.2
0.92
0.30
J
0.4
-0.5
>93
<10
>1000
>28
>1000
L
0.49
-0.51
>99
IS
-16
990
160
900
0.15
0.32
0.42
K
0.44
-0.51
88
-92
3
-5
1000
-1100
200
-220
0.20
0.27
0.11
4.2.3 Chemical Coagulation Process
Various chemical coagulants were used in the jar tests of the secondary effluent
of the Chubu Plant toinvestigate on the decoloring efficiency. In general, only
unsatisfactory results were obtained. As an example, the test results employing
metal coagulants are shown in Fig. 18. The most effective was lime. However, in
order to conduct effective removal, extremely high dose was needed proving im-
practical to serve only for color removal.
Fig.-18 Relationship between Coagulant Dose and Color Strength(S)10o Removal:
Samples are the secondary effluent of the Chubu Sewage Treatment Plant
100
50
o
8
o Alum
0 PAC
a Ferric Chloride
A Lime
25 50
100
200
Alum of Pack (mg/l)
400
0 10 15
50
100
Ferric Chloride (mg/l)
200
400 600
Lime (mg/l)
800
200
-J
1000
218
-------
With regards polymer, anionic coagulants were virtually ineffective. However,
cationic coagulants, when added with over 10 mg/liter, more than 50% of color
caused by dissolved substances was removed, but such a high dose was beyond
practical use. Poor flocc settlability is another defect.
Any combinations of metal salts andt polymers did not give satisfactory result
too.
5. Summary and Conclusion
(1) As a result of examining the existing measurement methods of color,
particularly color due to industrial wastewater, it is considered most appropriate
to express color by color difference with pure water. This can be done by measuring
the normal transmittance value of the filtered sample with regards color by dissolved
substances, and by measuring the total transmittance value with regards suspended
matters. The former is referred to as color intensity (S) and the latter color
intensity (T).
Color intensity of river water and visual impression obtained by looking at the
river were compared. Although the figures are rough, the limits that did not make
people feel uncomfortable or repugnance was 2.5 in color intensity (S)i0o and 0.7
in color intensity (T), respectively.
(2) Experiments on activated sludge treatment of sewage containing about 10
percent of textile wastewater were carried out. The removal of color caused by
suspended matters was quite effective, but removal of color caused by dissolved
substances was generally poor, and color was sometimes strengthened.
Color caused by dissolved substances in domestic sewage was removed 30 — 40
percent by activated sludge process. However, 1 percent of night soil addition to
the domestic sewage, decrease color removal rate considerably.
(3) Experiments on ozonation of secondary effluent was conducted to remove
residual color due to textile wastewater. Color caused by dissolved substances was
effectively removed by ozonation. About 60 and 70 percent removal was obtained
at a dose of less than 10 mg/1. Removal of color was roughly proportional to dose
up to this level. However, when it exceeded this level, the removal of color per
unit of reacted ozone decreased considerably.
Color caused by suspended matters was not effectively removed by ozoniza-
tion. Rather, the suspended matters in secondary effluent was irrelevant to ozone
consumption.
(4) Similarly, experiments on activated carbon adsorption of color remaining in
secondary effluent were conducted.
Adsorption by activated carbon depended greatly on the types of activated
carbons and the types of dyes present in water. It was found that activated carbons
with greater transitional pores were particulary effective to remove residual color.
Within the range of the dyes experimented, color by reactive dye was comparatively
well removed by activated carbon.
(5) Chemical coagulation was considered to be inadequate process when the
purpose is only to remove residual color in the secondary effluent.
219
-------
CHAPTER 8
DEVELOPMENT AND EVALUATION OF AUTOMATIC WATER
QUALITY MONITORING EQUIPMENTS
I. CURRENT STATE OF THE DEVELOPMENT OF AUTOMATIC
WATER QUALITY MONITORS FOR HAZARDOUS SUBSTANCES IN
WASTEWATER 222
1. Introduction 222
2. Problems Related to the Development of Automatic Monitors 222
2.1 Outline 222
2.2 Sampling Unit 223
2.3 Pretreatment Unit 224
2.4 Detecting Unit 227
3. Current Status of Development 230
3.1 Total Cyanide Monitor 231
3.2 Total Chromium Monitor 231
3.3 Hexavalent Chromium Monitor 232
3.4 Cadmium Monitor 232
3.5 Copper Monitoring Unit 232
3.6 Others 232
4. Conclusion 233
II. PERFORMANCE OF CONTINUOUS WATER QUALITY MONITORING
EQUIPMENTS FOR SEWAGE TREATMENT 234
INTRODUCTION 234
1. Sampling Procedure 234
2. Performance of Analyzers, and Problems in Their Maintenance 236
2.1 Turbidimeter 236
2.2 UV (Ultra Violet) Photometer 239
2.3 Automated Colorimetric Analyzer for Phosphorus and Ammonia
Nitrogen 242
2.4 TOC Meter 242
2.5 pH Meter 244
2.6 Sludge Density Meter 244
3. Conclusion 245
220
-------
III. DEVELOPMENT OF AUTOMATED CONTINUOUS P-D, HYARO
AND NH3 ANALYZERS 247
1. P Analyzer 247
2. Colorimetric NH3 Analyzer 252
IV. ALUM DOSING METHOD IN ALUM PRECIPITATION 255
1. Experimental Conditions 255
2. Experimental Results and Discussion 256
221
-------
CHAPTER 8
DEVELOPMENT AND EVALUATION OF AUTOMATIC WATER
QUALITY MONITORING EQUIPMENTS
I.CURRENT STATE OF THE DEVELOPMENT OF AUTOMATIC WATER
QUALITY MONITORS FOR HAZARDOUS SUBSTANCES IN WASTEWATER
1. INTRODUCTION
When a public sewage system receives industrial wastewater, provisions should
be taken to prevent possible adverse effects on facilities or treatment function. It
should not cause any difficulty in meeting the effluent standards applied to the
treatment plant, nor create particular difficulty in treatment and disposal of sewage
sludge. For these purposes, ordinances concerning pretreatment standards are
provided to regulate the quality of wastewater being discharged into a sewerage
system. Especially with regards to hazardous substances, pretreatment standards
can be, and in most cases are, as stringent as the effluent standards applied to indus-
trial wastewater discharged directly into public bodies of water.
To effectuate such ordinances and regulations, it is important not only to
thoroughly guide and supervise the pretreatment facilities of the factories but also
to establish a system to monitor water quality of industrial wastewater being dis-
charged, which the municipalities across the nation are presently eneavoring. How-
ever, by a manual monitoring system, there are limits in the frequency of city
officials inspecting all of the industrial plants, and there are danger of overlooking
the discharge of harmful wastewater either by accident or on purpose. On the
other hand, the current status of automatic monitors is that there are only few
automatic monitors put to practical use to check wastewater being discharged. And
even those put to practice are complicated in structure and require considerable
manpower for operation and maintenance. Therefore, installation of these equip-
ments, if they are installed, are limited to the places such as sewage treatment plants
and pumping stations. However, automatic monitors that are most desirable to be
developed are those highly reliable and free from maintenance, for example, similar
to flight recorders mounted on aircraft and those which can readily be installed in
sewers or outlets of industrial wastewater into sewers. For the past few years,
the Ministry of Construction have entrusted the Association of Electrical Engineer-
ing to conduct researches to boost development of such automatic water quality
monitors for hazardous substances.
This report summarizes on the present situation of the development of auto-
matic water quality monitors for hazardous substances and related problems.
2. PROBLEMS RELATED TO THE DEVELOPMENT OF AUTOMATIC
MONITORS
2.1 OUTLINE
An automatic water quality monitoring device can be divided into several
units as shown in Fig. 1. The structure and system of each unit differ depending
on the characteristics of water handled and substances to be monitored, thus the
222
-------
problems involved are varied. Even when water is comparatively clean and the
constituents are relatively simple, automatic measurement of hazardous substances
is not easy. Since sewage contains wide variety of substances, most of which inter-
fere the measurement, and have the characteristics to easily develope biological
slime, automatic monitoring of harmful substances in sewage is quite difficult.
Fig.-1 Schematic Conf igulation of Automatic Water Quality Monitor
Recording Unit I
Sampling Unit I "-
Pretreating Unit I »
ig Unit
Detec
^ ' '
inc Unit 1C"
,. ., . r^_i
^1 Data Transmitting Unit
f
Major problems involved are as follows:
a) Suspended solids
The sampling pumps and valves in the piping are easily subjected to clogging
in continuous operation as wastewater contains a good amount of suspended
solids and floating substances. Normally, the substances to be measured in
wastewater like heavy metals are contained in suspended solids. However, the
method to detect and analyze substances is generally only possible when the
substances are in dissolved form. Therefore, a process to dissolve substances
contained in suspended solids becomes necessary. Even when this dissolving
process is unnecessary, there are many instances requiring pulverization of
suspended solids to obtain stable data.
b) Interferences
As substances found in wastewater are diversified and varied, when analyzing
hazardous substances such as heavy metals, it is necessary to either eliminate
interferences or mask them. Accordingly, the automatic monitoring devices
must be equipped with a mechanism to eliminate the interferences. These
mechanisms are hard to automate, and even when automation is possible the
mechanical structures will be extremely complicated.
c) Biological slime
Wastewater usually contains a large amount of organics making it ideal for
microorganisms to grow. Therefore, slime easily develops in the inner walls
of the equipment coming in contact with the sample. Slime not only causes
clogging of piping but also obstructs measurement by developing at the surface
of the detector. Also, substances contained in water are often adsorbed on the
slime to change quality of water, or slimes are often detached from the wall
to interfere measurements.
2.2 SAMPLING UNIT
The engineering methods and equipments are available to take samples of
wastewater directly from a sewer either in large rate continuous flow system or
batch system. However, concerning sampling of extremely small continuous flow,
the available methods and equipments are not considered satisfactory, since suction
inlet and piping are liable to clog easily. Submersible pumps (with cutter) and air-
223
-------
lifts are employed for sampling continuous large rate discharge while vacuum suction
sampling or air lifts are used for batch sampling. Generally, strainers of suction
inlets are not useful and at times are harmful by accelerating clogging.
In general, there are two types of automatic monitors, that is, continuous type
and batch type. In case of the continuous type, sampling of large rate flow is taken
at first. And then the necessary amount of sample is supplied to the monitoring
device via a branch tube directly from the main piping or through a head tank. In
this way, the shape of the inlet of a branch tube receiving small rate of flow can be
formed to hydraulically make it difficult to clog. Also it is possible to shorten the
length of tubing with the small rate flow. However, even though employing such
method, it is difficult to maintain a constant flow over a long period of time without
maintenance. Therefore, when quantitative accuracy is demanded, it is necessary to
conduct an appropriate pretreatment before supplying sample to the measuring
equipment.
In case of batch type monitoring device, sample volume is measured at each
detection, thus there is almost no problems on the quantitativeness of the sample.
Therefore, as far as the sampling unit is concerned, the batch type is easier to
operate and maintain.
2.3 PRETREATMENT UNIT
The role of a pretreatment unit differs depending on the substances to be
analyzed and detection methods. But generally, the purposes of a pretreating unit
are (a) to prevent formation of slime, (b) to dissolve substances contained in sus-
pended solids, (c) to remove or mask interferences, and (d) to adjust samples to best
conditions for measurements.
Hazardous substances, particularly heavy metals, in wastewater, are in most
cases present in the form of suspended solids. Whatever analytical method is taken,
the substances must once be put in a dissolved form. And when the analysis is
conducted manually, samples are pretreated by wet oxidation with sulfuric-nitric
acids or nitric-perchloric acids to oxidize and decompose substances. However, as
it is structually and materially difficult to incorporate such powerful oxidizing
process in the automatic monitoring units, pretreatment to merely lower pH of the
sample by dosing acid is normally done. When compared to wet oxidation, mere
lowering of pH values can not be considered a perfect pretreatment method. But it
is effective to a certain degree to dissolve the heavy metals in suspended solids.
Figures 2 ~ 6 show the results of experiments on solubilization of heavy metals
in suspended solids by pH adjustments and heating. Samples are raw sewages taken
at 4 to 8 sewage treatment plants. These samples were added with a hydrochloric
acid for pH adjustment and then filtered. To examine the effect of heating, a part
of the sample was heated prior to the filtration. The concentrations of metals in
the filtered solutions were analyzed and the dissolved fraction of each metal was
calculated. 300°C hot plates were used for heating at about 95°C of water tempera-
ture for five minutes. The analysis was conducted by the atomic absorption spectro-
photometry (direct aspiration) after wet oxidation of the sample. In case when the
metal concentrations in raw sewage was too low to analyze, return sludge was added
224
-------
to the sample to raise the concentrations.
Fig.-2 Solubilization of Heavy Metal in SS in Wastewater by pH Adjustment -Chromium
100
• 5 min. heating at 95°C
O Without heating
Without adjust.
Fig.-3 Solubilization of Heavy Metal in SS in Wastewater by pH Adjustment -Copper
100r
80
c 60
o
40
O 20
O——
0.5 1
-1 tt '
4 " Without adi
Without adjust.
Adjusted pH
225
-------
Fig.-4 Solubilization of Heavy Metal in SS in Wastewater by pH Adjustment -Iron
100r
Without adjust.
Fig.-5 Solubilization of Heavy Metal in SS in Wastewater by pH Adjustment -Zinc
120
100
o
G
60
40
• 5 min. heating at 25 C
O Without heating
0.5 1 2 4
Adjusted pH
'/ Withoi
Without adjust.
Fig.-6 Solubilization of Heavy Metal in SS in Wastewater by pH Adjustment —Nickel
120r
100
_
8
in
Q
80
60
40
20
O
0.5 1 2 4
Adjusted pH
Without adjust.
226
-------
As understood from the data of the samples without pH adjustment in these
figures, a good portion of metals in the sewage was contained in the suspended
solids. Especially, dissolved fractions of chromium and iron in the unadjusted
samples were quite small. Although the dissolved fractions of zinc and nickel were
comparatively high, they were about 50 percent. The lowering of pH is effective
to increase the dissolved fraction as shown in the figures. At pH value of 2, zinc and
nickel were almost totally dissolved. But with regards chromium, copper andiron,
only 80 percent of them were dissolved even when pH value was lowered to 0.5.
Heating together with the lowering of pH was found to be effective, and the dis-
solved fractions of chromium, copper and iron increased to about 90 percent at pH
0.5. Incidentally, the values shown in the figures are average values, and there were
deviations of data between 10 and 30 percent expressed in standard deviation.
The relationship between pH and dissolved fraction might be dependent on
characteristics of wastewater. Therefore, in the process of dissolving substances in
suspended solids, measurement errors to some degree would be produced.
Concerning prevention of slime formation, since disinfection is conducted by
both acid addition and heating, pretreatment for dissolution of metals can prevent
formation of slime.
As to removal of interferences, methods may differ depending on the param-
eters to be measured and methods of measurement, thus making it difficult to
generalize the methods. However, as far as the analysis of heavy metals are con-
cerned, organics are the common interferences. Since it is not wise to automate wet
oxidation process for automatic monitors, the activated carbon adsorption may be
only process to be acceptable. The adsorption of heavy metals contained in the
sample to activated carbon was very small under acidic condition.
2.4 DETECTING UNIT
Measuring methods for automatic water quality monitors for hazardous sub-
stances include automated colorimetry, ion selective electrodes and polargraphy.
Atomic absorption spectrophotometry, high frequency plasma spectrography and
X-ray fluorometry may be included, although they are too sophisticated in mecha-
nism and considered unsuitable for on-site automatic measurement. The possibility
of application of each method is listed in Table 1.
Table-1 Analytical Methods and Their Applicability to Automatic Monitor
^ Substances
M e t ho d s~^~- ^__^_^
Automated Colorimetry
Ion Selective Electrode
Polaiography
Atomic Absorption
Others
CN
0
o
o
Cd
O
o
0
Pb
A
O
O
o
As
A
O
Oig-P
R-Hg
A
T-Hg
O
Cr(VI)
o
A
T-Cr
o
o
Phynols
o
Cu
o
o
o
o
Zn
o
o
D-Fe
o
o
D-Mn
A
O
F
A
O
High Frequency Plusma Spectiophotometry ajid X-ray Fluorometry for
Metals, and UV Absorption for Cr (VI)
Notation O Possible, A : difficult
227
-------
2.4.1 Automated Colorimetry
The most orthodox detecting method in automatic monitoring is automated
colorimetry. When strict quantitative analysis is required, pretreatment is indispen-
sable. However, for actual application, it is considered difficult to develop a
monitoring device having complicated functions, such as wet oxidations, solvent
extraction and so on. Therefore, the analytical methods for monitors are limited to
those with relatively simple procedure, yet giving reasonably accurate results.
The following methods are some examples: Bathocuproin method for cupper,
diphenylcarbazide method for chromium, 4-aminoantipyrine method for phenol,
isonicotinic acid-pyrazolone method of cyanide, etc. Even with these methods it
is necessary to perform pretreatment, such as oxidation of trivalent chromium for
analysis of total chromium, reduction of trivalent iron for measurement of total
iron, reduction of divalent copper for appraisement of total copper, and distillation
of cyanide for valuation of total cyanide.
When employing automated colorimetry, the problems involved are troubles
caused by using wet chemicals and danger of resulting large measurement errors
due to lack of complete pretreatment procedure to eliminate interferences. How-
ever, the latter is a common problem to any measurement method.
Since it is difficult to totally remove suspended solids, the device must have
a mechanism that can correct the sample blank. Although sample blank correction
can be done by the double beam system and others for continuous type monitors,
the batch measurement is easier in this respect.
2.4.2 Ion Selective Electrodes
Ion selective electrodes available on the market are those for cadmium, lead,
copper, cyanide and fluoride measurements. Fluoride electrode has high selectivity
and less interferences. However, as regards other electrodes, they are many and
serious interferences. The well known ones are Hg2+, Ag+, Fe3+ and S2~ for cad-
mium, lead and copper electrodes, and S2~ for cyanide electrode. It is not that
difficult to insert in the unit a process of dosing masking agents or other processes
to eliminate the interferences by these inorganic ions. The greatest problem is the
interferences caused by organics present in the wastewater. Table 2 shows the
selectivity coefficients of selected organic substances. The Table shows that ionized
organics cause extremely large interference. Actually, when measurements are done
without removing the organics, for example using cadmium electrode, the measured
values sometimes are lower by one order than the true concentration. Accordingly,
when employing ion electrodes for the detecting unit, it is imperative to remove
organics by activated carbon and soon.
228
-------
Table-2 Selectivity Coefficients against Selected Organic Substances
^^-•^Electrodes
Substances^^^^
Ethyl Alcohol
Glucose
Sucrose
Acetic Acid
Succinic Acid
Tartaric Acid
Cifric Acid
Linoleic Acid
Oxalic Acid
L-Ascorbic Acid
L-Gultamic Acid
Casein
Peptone
Dextrin
Powdered Cream
Urea
Cadmium
10s <
104<
10s <
2.1
1.9
21 xlO2
2.2 xlO3
104<
0.27
4.8
2.2
3.1 x 102
2.4
1.6 xlO2
18
7.0 x 104
Copper
10s <
104 <
10s <
0.6
28
84
57
104<
1.1
64
103<
8.4
4.9 x 1CT2
6.1
2.1 x 103
l.SxlO2
Lead
104<
104<
104<
1.2
7.2
54
2.1
104<
2.8
21
4.0
54
15
2.3 x 102
34
90
Note : Figures in the table are the averages of the selectivity coefficients at dadmium concentrations
of 0.01, 0.1 and 1.0 mg/1 for the Cd electrode, at copper concentrations of 0.3, 3.0 and 30
mg/1 for the Cu electrode, and at lead concentrations of 0.1, 1.0 and 10 mg/1 for Pb electrode,
respectively.
2.4.3 Polargraphy
Ordinary polargraph with dropping mercury electrode is occasionally used in
the automatic monitors for rivers. But owing to the difficulty in coping with
interferences such as organics, reducing substances, iron and other interfering
substances, and the difficulty in maintaining proper condition of the dropping
mercury electrodes, ordinary polargraph are considered unsuitable for monitors for
wastewater. However, as the anode stripping voltimetry, which is one type of
polargraphy, allow the use of mercury electrodeposited graphite electrode or glassy
carbon electrode, it has a possibility for being applied in automatic monitoring
devices.
There are three heavy metals possible for measurements at the same time by
the anode stripping voltimetry — cadmium, lead and copper. According to a test
employing a mercury electrodeposited graphite electrode, it was possible to obtain
comparatively high precision measurements of lead and copper by dissolving these
metals by acid addition followed by filtration and removal of dissolved oxygen.
Organics contained in wastewater did not cause strong interference. However, with
regards to cadmium measurements, when measurements were conducted in a sample
pretreated in the above mentioned way, the characteristics of the electrode deterio-
rated tremendously thus the removal of organics was considered necessary.
229
-------
The anode stripping voltimetry has given rise to such problems as expensive
maintenance cost due to electrodeposition of electrodes at each 100 or 200 times
of measurement and complicated data processing due to the necessity of obtain
intergal values instead of peak volues of output electric current.
2.4.4 Atomic Absorption Spectrophotometry
The atomic absorption spectrophotometry is the most popular method in
conducting manual analysis of heavy metals in wastewater. And the development
of automatic monitors with this method as detecting unit is advancing to a certain
stage. Especially with regards to mercury analysis, the flameless atomic absorption
spectrophotometry was regarded as the only practical measurement method.
When measurements are conducted by the cold vapor atomic absorption
method, the analysis of inorganic mercury is said to be effectively done by perform-
ing pretreatment of dosing ammonium chloride and heating. It is also reported
that the measurement of total mercury was effectively conducted only by the
oxidation with potassium permanganate under acidic condition.
Concerning other heavy metals, when the flame atomic absorption spectro-
photometry and the flameless atomic absorption spectrophotometry are compared,
it is considered that the flameless method is more appropriate from the view points
of removing interferences by organics and the possibility of on-site installation.
However, in case of the flameless method, it is difficult to automate the sample
injection to the carbon atomizer. At this stage, atomic absorption spectrophoto-
metry is considered to be too sophisticated and complicated for monitors being
installed on-site.
2.4.5 Others
When ignoring complexity of the equipments, difficulty in operation and
maintenance, and economy, the high frequency plasma spectrography and the X-ray
fluorometry would be good methods since they have less interferences than other
methods and have the merits of measuring various elements at the same time.
However, the possibility of putting these methods to practical use at the present
stage is dim.
Hexavalent chromium can be measured by ultraviolet absorption. This method
utilizes the property of hexavalent chromium in alkaline solution that exhibits
ultraviolet absorption at about 370 nm wave length, while trivalent chromium does
not adsorb UV in the area of this wave length. The measurement of the hexavalent
chromium concentration is seeked from the difference in the absorbance before
and after the hexavalent chromium is reduced to trivalent in the sample. The
greatest intereference is ferric ion. When the ferric concentration is high, the it must
be removed.
3. CURRENT STATUS OF DEVELOPMENT
On consignment from the Ministry of Construction, the Association of Elec-
trical Engineering has organized a committee composed of users and manufacturers
within its framework and has so far tried to develop and improve automatic
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monitoring devices for total cyanide, total chromium, hexavalent chromium,
cadmium and copper. In performing these works, specifications of the devices,
such as accuracy of measurement, which are considered achievable, are determined,
and long term field tests are to be conducted to confirm that the specification are
met.
Of automatic monitoring devices, the total cyanide monitor, for the time
being, has been developed, and its standard specifications were already published.
However, concerning others, they are presently under development and are slated
for commencement of field tests by the end of this year.
3.1 TOTAL CYANIDE MONITOR
In the development of total cyanide monitor, the most important thing is to
remove interference by sulfur ion and others. As a result of laboratory and field
tests on the methods of pretreatment, it has been decided to adopt the method to
oxidate sulfur ion by potassium permanganate under acidic condition prior to
distillation and the method to remove sulfur ion by granular lead peroxide after
distillation. The measurement of cyanide is conducted by the cyanide electrode.
The field tests were conducted for about two years at an ordinary municipal
sewage treatment plant and at a treatment plant handling industrial wastewater
mainly consist of metal finishing wastes. And improvements of the devices were
made during the field test. It was found that some kinds of organics could be
transferred into the distillate during distillation and could interfere the measure-
ment. Therefore, activated carbon column is necessary to remove organics in
the distillate when occasions demand. Through these tests, it was confirmed that
the accuracy of measurement was between the range of-0.15pCN and 0.25 pCN
provided that there were no unforeseen interferences contained in the sample.
The larger error on the positive side was due to the fact that the influence of inter-
ferences acted more strongly on the 'plus' side.
There are three types of monitoring devices designated by the standard specifi-
cations: one batch type and two continuous types. Concerning the details, refer to
the "Standard Specifications of Automatic Total Cyanide Monitoring Devices"
issued by the Association of Electrical Engineering in March 1978.
3.2 TOTAL CHROMIUM MONITOR
A few types of automatic total chromium monitors based on the diphenyl-
carbazide method are already being put on the market. However, it is doubtful
whether these monitors can be used for the measurement of chromium in waste-
water which contains organic reducing substances in high concentration. Therefore,
based on the hitherto laboratory tests, a series of field tests to improve and modify
the monitoring devices presently marketed will begin from late this year. The major
purposes of the field tests are to study the effects of preliminary aeration prior to
addition of potassium permanganate and the possibilities of using other oxidizing
agents such as sodium hypobromite instead of potassium permanganate. Based on
the results of these field tests, standard specifications are to be made.
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3.3 HEXAVALENT CHROMIUM MONITOR
With regards to the measurement of hexavalent chromium, a few types of
automatic monitoring devices employing the diphenylcarbazide method are also
on the market. But when these monitors are used for the measurement of Cr (VI)
in the sewage, sample blank becomes extremely large and it often exceeds the
range of automatic correction. Furthermore, direct measurement of Cr (VI) by the
diphenylcarbazide method in samples containing a large amount of reducing
substances may be doubtful, thus gives rise to studies of introducing the afore-
mentioned ultraviolet adsorption method in the monitoring devices. However, the
ultraviolet adsorption method, too, faces interference by iron. Ferric hydroxide
formed in the alkaline solution absorbs ultraviolet, and 10 mg/1 of ferric ion gives the
interference equivalent to about 1.5 m/1 of chromium. Therefore, when this method
is applied to water sample containing a large amount of ferric ion it must first be
removed.
3.4 CADMIUM MONITOR
Concerning cadmium measurement, as there is no appropriate colorimetric
analyzing method for automatic monitoring, studies are presently being advanced to
develop an automatic monitoring device with a detecting unit using ion selective
electrodes. However, as mentioned previously, cadmium electrode has an increasing
large number of interferences. According to the hitherto basic experiments, results
show that interferences by organic were removed to some extent by passing the
sample through activated carbon column under acidic conditions and that inter-
ferences by inorganic ions were eliminated by addition of proper masking agents.
Masking agents to remove metal ions, for example, are phosphates to remove Pb2+,
Ag2+, Fe3+, etc.; L-ascorbic acid as against Cu2+ and oxidizing substances; and sodium
tetraphenyl borate to cope with Ag2+ and Cu2+. For others, by utilizing the nature
of cadmium that it is adsorbed to anion exchange resin under acidic condition with
hydrochloric acid, extraction of cadmium from the sample is being studied.
With regards to studies of cadmium monitoring devices, field tests are slated
to commence at the end of this year to conduct comparasions of effects of the
above mentioned pretreatment methods and to decide on the apt mechanical
structures of the devices considered most appropriate for practical application.
3.5 COPPER MONITORING UNIT
The bathocuprion method with extremely few interferences is a colorimetric
analyzing method of copper and serves as an excellent detecting method for an
automatic monitor. Concerning copper monitoring units employing the bathocuprion
method, field tests are expected to begin from the latter part of this year. And
surveys will be conducted on measurement precision, operation and maintenance of
the devices.
3.6 OTHERS
Besides cooperating in developmental studies of various monitoring devices on
consignment by the Ministry of Construction, manufacturers have their own devel-
opment projects. As mentioned before, mercury monitoring devices employing the
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frameless atomic absorption spectrophotometry are presently marketed, and also
a monitoring device for heavy metals having flame atomic absorption spectrometry
detecting units is on the market. However, as these devices are not always designed
for application to wastewater that contains a large number of interferences, there
are many problems involved when they are to be used for wastewater monitoring.
Presently, automation of X-ray fluorometry and high frequency plasma
spectrophotometry has advanced to a stage of developing laboratory type automatic
instruments. And, depending on the requirement of the users, there is a possibility
of these methods being adopted as detecting units in automatic monitoring devices
in the future.
4. CONCLUSION
The current status of the development of automatic water quality monitoring
devices for hazardous substances in wastewater and its related problems have been
discussed in this report. At the present stage, the only reliable monitoring unit
that has been completed is that for cyanide measurement. As regards chromium,
cadmium and copper, the outlook for developing monitors for these substances is
bright.
The strenous efforts until now has been exerted to develop monitors to give
as accurate data as possible in practical sense. However, generally speaking, as the
measurement accuracy requires complicated mechanism, the accuracy required and
the cost as well as difficulty in operation and maintenance are in a counteracting
relation. Therefore, studies should be made on the 'software' of the monitoring
system, such as the role of automatic monitors in the total monitoring system and
cost benefit relationship. And the results of these studies should be forwarded as
a feed-back information to set the targets to develop automatic monitoring devices.
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PERFORMANCE OF CONTINUOUS WATER QUALITY
MONITORING EQUIPMENTS FOR SEWAGE TREATMENT
INTRODUCTION
Since 1972, the Public Works Research Institute of the Ministry of Construc-
tion has conducted a series of research activities on advanced waste treatment using
a pilot plant constructed' at the existing sewage treatment plant in three cities,
Shitamachi plant in Yokosuka, Toba plant in Kyoto and Nishiyama plant in Nagoya,
with full collaboration from respective municipalities. These researches also cover
the applicability test on the continuous water quality monitoring equipments
available on the market which are indispensable for effective operation and control
of the advanced waste treatment at the said plants.
The evaluation of continuous water quality monitoring equipments is tested
mainly at Kyoto plant and Nagoya plant. Kyoto plant, which is intended to treat
secondary effluent, is provided with the functions essential for that specific purpose
such as chemical precipitation, sand filtration, activated carbon adsorption, and
break point chlorination. Nagoya plant, on the other hand, is an actual plant de-
signed to upgrade the functional aspects of the existing plant by adding coagulant,
and it also has sand filters for experimental purposes.
This paper introduces some of the monitoring equipments installed at the two
plants which are generally applicable for advanced waste treatment, with specific
reference to their performance and problems in their actual operation.
1. SAMPLING PROCEDURE
In automated water quality analysis of sewage, the sampling procedure or the
method of leading sample sewage to the terminal water quality monitoring equip-
ments (hereinafter referred to as the "water quality analyzers" or "analyzers") bears
very closely upon smooth and accurate measurement. This is due to the inherent
characteristics of sewage, especially raw sewage, which contains lots of solids and
organic matters. The solids are prone to be accumulated in the pipes and the organic
matters are liable to cause slime formation, so that the piping system is easily
clogged up and changes in water quality are liable to occur. Particularly in the case
of raw sewage which contains lots of coarse solids, sampling must be carried out
constantly to maintain sample continuity and the whole configuration of the sampl-
ing system must be designed with care taken in the selection of sampling pumps and
valves.
Kyoto plant is a tertiary plant intended mainly to treat secondary effluent, so
that its sampling system is less influenced by the above mentioned characteristics of
sewage than at secondary treatment plants. In addition, as the conveyance distance
is short, it is not confronted with any specific difficulty in leading sample from each
specified sampling point to the analyzer by making use of the head in the convey-
ance route or by means of exclusive sampling pumps.
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In the case of Nagoya plant, however, the applicability test was conducted by
making use of the actual plant, so that it was necessary to drive all effluents, ranging
from raw sewage to final effluent, to the shed designed exclusively for water quality
analysis. For this reason, raw sewage and effluents were pumped up continuously
from each sampling point to specially dsesigned head tanks, and thence to respective
analyzers through pipelines with a suitable head. Further, a centrifuge (8,000rpm)
run by an industrial motor was installed immediately beneath the head tank to send
the sample free from suspended solids to those analyzers whose performance could
be degraded by the inflow of sample containing the solids. A sample changer with
an electromagnetic valve was also used for measurement of a plural number of
samples by a single analyzer. The flow chart of sampling at Nagoya plant is shown
in Fig. 1.
Fig.-1 Flow Chart of Sampling (Nagoya)
Head Tank
Drain
Head 1 anks
\
J
-
;
i
"o Analyzers
©
>ampling Pump
j>
i
1
1
1
I
I
:
1
?
i
Pumps
s-\ 60A
ks-4 .S~*\ 30A r.ti , rttt
To Contrifuge, Sample Changers
or Analyzers
By reason of their functional and structural characteristics, pH meter and
sludge density meter were installed at each measuring point outside the sampling
system described above.
The sampling pumps were of self-contained volute type, with a suction port
diameter of 60 A for raw sewage and primary effluent and 30 A for other effluents,
and the flow form them to the head tanks was adjusted by means of delivery re-
gulating valves to maintain an optimal rate of overflow from the head tanks.
After about two and a half years' operation of the above sampling system, the
following problems were brought to the fore.
1) Scums were formed in the head tanks, and their admixture in the sample
caused dispersion of measured values. This drawback could be coped with by
cleaning the head tank every morning for most effluents but not for raw sewage
which contained lots of solids. Thus, the system proved to insufficient for
sampling raw sewage.
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2) A diversity of troubles were encountered in the pumping of raw sewage. To
cite an example, the strainer of ordinary suction pipe became clogged up rapid-
ly due to the inflow of paper, debirs and dirts contained in raw sewage, often
causing overload of the pump. By introducing a large stainless steel basket type
strainer (400 x 400 x 550mm, 5mm square), this trouble was mitigated to a
substantial extent, but it was still necessary to carry out screening once a week
or so.
3) As the raw sewage sampling pipeline installed at Nagoya plant was long (approx.
70m), it was subjected to frequent clogging, causing gradual decline of the
pump delivery rate. Four solution of this problem, the delivery side piping of
primary effluent pump was connected with the said raw sewage sampling pipe-
line to flush is at suitable intervals with the primary effluent as backwash water.
4) Pretreatment by the centrifuge for removal of solids had to be conducted every
5 to 7 days to remove concentrated solids caught inside the rotor. Neglect of
this pretreatment caused the decline of SS removal rate, which resulted in the
decomposition of concentrated solids and emission of an offensive odour in
summer.
2. PERFORMANCE OF ANALYZERS, AND PROBLEMS IN THEIR
MAINTENANCE
2.1 TURBIDIMETER
The turbidimeter used for water quality monitoring is of the type designed for
measuring scattered lights on the free water surface formed on top of the flow cell
by the overflow of sample effluent. This meter is generally considered to be suited
to the measurement of sewage turbidity for two reasons: it does not come in direct
contact with sewage, and sample volume is usually abundant.
At Kyoto plant, 10 units of this turbidimeter are installed for the purpose of
continuous water quality monitoring of secondary effluent, chemical clarifier
effluent. At Nagoya plant, 6 units are installed for turbidity measurement of raw
sewage, primary effluent, secondary effluent, and filltered effluent. All the 16
units are operated at a high rate of nearly 100%.
As turbidity is not the only or a sufficiently credible index in sewage treatment,
it is important to clearify the turbidity vs. SS relationships which are shown in
Figs. 2 ~ 4 for the two plants. Fig. 2 shows the relationships at Kyoto plant be-
tween the turbidity of secondary and filtered effluents and their SS concentration
obtained by manual analysis. Fig. 3 also shows the turbidity-SS relationships be-
tween effluent. As seen in the two figures, secondary and subsequent effluents
present a marked correlation between turbidity and SS concentration, indicating
that SS concentration can be estimated by turbidity measurement. Fig. 4 shows the
turbidity-SS relationships between raw sewage and primary effluent at Nagoya plant.
This figure indicates that raw sewage does not present any notable correlation be-
tween turbidty and SS concentration, suggesting that it cannot be justified to
represent SS by turbidity. This is assigable to the working principles of the turbidi-
meter which does detect settlable solids of relatively large size.
236
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20
15
O)
.§ 10
to
CO
Fig. 2 Turbidity ~ SS (Secondary Effluent and Its
Filter Effluent)
O Secondary Effluent
• Filter Effluent of Secondary Effluent
SS = 0.976-Turbidity
SS = 0.898-Turbidity
10
Turbidity (mg/l)
15
20
Fig.-3 Turbidity ~ SS (Alum Precipitation Effluent
and Its Filter Effluent
O Effluent from
Alum Precipitation
• Filter Effluent of
Alum Precipitation
Effluent
10 15 20
Turbidity (mg/l)
237
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Fig.-4 Turbidity vs. SS (Nagoya)
100
o
D O
° 0°° °
o o
0°
° o o o
I n
I °r
50
n Q
Jr f O Raw Sewage
O D I
[ D Primary Effluent
50 100 150
SS (mg/l) (Manual)
From the experience obtained at the two plants, the follow proposition can be
advanced in connection with continuous turbidity monitoring.
1) Secondary effluent, chemical clarifier effluent and filtered effluent present a
comparablly high correlation between turbidity and SS concentration. In so
far as these effluents are concerned, therefore, it is feasible to obtain SS con-
centration from the measured values of turbity with a fairly high accuracy.
However, as the relationships betwen these two factors vary according to sam-
ple quality, it is necessary to establish the relationships for each effluents.
2) As for raw sewage, the validity of estimating SS concentration from measured
turbidity values is questionable. At both plants, turbidimeters were used for
quality monitoring of backwash waste of filters which had a higher SS con-
centration than raw sewage. In the case of this backwash waste, the correlation
was rather high, which may be ascribed to the fact that activated sludge floes
which are relatively uniform in size constitute the greater part of suspended
solids of backwash waste.
3) The effluent flow velocity on the surface of flow cell is limited to an extent by
reason of the system's working principles. Hence, raw sewage containing lots
of coarse solids formed a debris film covering the flow cell surface, which
caused dispersion of measured values. Formation of this film was so rapid that
it was not possible to prevent the dispersion by cleaning it away once a day or
so. The debris film was also formed on the flow cell surface of primary effluent
and secondary effluent, making it imperative to clean the cell at least once a
day for stabilized measurement.
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4) Certain minor differences in measured values were observed between respective
turbidimeters, which are likely to have been noted among other analyzers.
Specifically, there were cases where the turbidity of the same sample differed
from turbidimeter to turbidimeter. This is because even if a number of meters
are calibrated all at the same time, the measured value inevitably involves a
deviation from the correct value varying in degree for each meter with the lapse
of time. This fact must be taken into careful consideration when measured
values of low turbidity effluents such as filtered effluent and carbon effluent
are to be sued for absolute turbity comparison between such effluents. Never-
theless, this trouble can be averted by measuring the turbidity of a number of
samples with the same turbidimeter by means of the aforementioned sample
changer.
2.2 UV (ULTRA VIOLET) PHOTOMETER
The abosrbance in the neighbourhood of extinction of 254mm beam in water
contanining organic matters in known to have a certain correlation with the organic
matter concentration measured in terms of COD and BOD. In general, UV photo-
meter is basically designed for measuring absorbance through a flow cell, and it is
simple in structure and easy for maintenance. Where the organic matter concentra-
tion in sewage of treated effluent can be represented by UV absorbance, its measure-
ment can be greatly facilitated by the use of UV photometer.
The UV photometers installed at the two plants are capable for measuring the
absorbance of an extinction of 254 mm beam using a mercuric lamp, and can effect
correction to the influences of turbidity of taking the ratio of transmitted light in-
tensities of ultraviolet rays and visible rays.
At Kyoto plant, 2 units of UV photometers are combined with the sample
changer for continuous quality monitoring of secondary effluent, chemical clarifer
effluent, filter effluent and carbon effluent. At Nagoya plant, on the other hand, 1
unit is installed for combination with the sample changer for measurement of
primary effluent, secondary effluent, and filtered effluent.
Although a period of about one and a half years has elapsed since the com-
mencement of the measurement, a very high operational rate is exhibited by all the
three photometers. In the earlier stage of measurement, however, the following
problems were experienced.
1) Measured values showed fluctuations due to temperature changes in the
neighbourhood of the flow cell.
2) Ozone was generated near the mercuric lamp, emitting its peculiar smell.
The former trouble was solved by improving the measuring unit so as to main-
tain a constant temperature (40° C), and the latter by inserting activated carbon in
the measuring unit to adsorb ozone.
Fig. 5 shows the realtionships between COD (permanganate) and UV absorbance
as obtained by measurement conducted for about half a year (December to June) at
Kyoto plant on effluents at different stages of treatment. The figure presents the
general tendency that both COD and UV absorbance decline with the progress of
sewage treatment from secondary effluent to chemical clarifier effluent, and further
239
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to carbon effluent, but indicates the difficulty in estimating COD from UV ab-
sorbance.
Fig.-5 UV vs. COD
1.5
1.0
0.5
0
(
o
o
• Secondary Effluent
O Chemical Clarified Effluent
O Filtered Effluent
1
a
o o *«
o • «
o ° oV
o ° o a» o
o ••
0 °Q
° ° p 8 °
°
-------
Fig.-6 UV vs COD (Seasonal Change)
• Filtered Effluent
« No. 1 Carbon Column Effluent
o No. 2 Carbon Column Effluent
rr 1.0
ro
3
ra 0.8
8 0.6
c
CD
-9 0.4
o
< 0.2
D 0
C
a
o
o
a
o
a
o
a
o
•
) 10 20 0 10 20 0 10 20 0 10 20 0 10 20 0 10 20 0 10 20 30
4/14 4/27 5/13 5/26 6/22 7/13 8/25
CODMN Date
1 1.0
c
| 0.8
8 0.6
(0
J3
Oo.4
J3
< 0.2
D
Q
a
®
a
o
a
o
0
.
a
o
•
a
o
.
•
o
0 10 20 0 10 20 0 10 20 0 10 20 0 10 20 0 10 20 0 10 20 :
9/8 9/21 10/6 10/19 11/9 12/7 12/14
CODMN Date
Fig.-7 Relationship between UV Absorbance and TOC (Automatic Analyzer)
80-
70-
60-
_ 50-
O
O 40
30-
20-
10-
A Primary Effluent
0 Sencondary Effluent
• Secondary Effluent (Alum Addition)
A Filtered Secondary Effluent
a a
0.5
1.0
UV Absorbance
1.5
2.0
241
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From the results introduced above, it appears questionable to obtain the ab-
solute values of organic matters from UV absorbance by continuous water quality
analyzers, although the abosrbance may be used in setting the control point within a
certain limit, e.g., the point of breakthrough of carbon effluent.
As described already, maintenance of UV photometer is very easy and calls only
for the replacement of the mercuric lamp (one thousand and several hundred hours)
and routine inspection services.
2.3 AUTOMATED COLORIMETRIC ANALYZER FOR PHOSPHORUS AND
AMMONIA NITROGEN
Detailed description on the captioned analyzer is given elsewhere in this report.
2.4 TOC METER
The TOC meter used at the two plants is of the type designed to drop pH value
of continuously supplied sample by adding hydrochloric acid, purge inorganic carbon
therefrom by bubbling in an exclusive scrubber, and then obtain TOC by measuring
CO2 with an infrared analyzer after incinerating the sample at a temperature of
about 800° C. CO2 -free air is used as carrier gas.
By reason of its working principle, TOC meter presupposes instantaneous in-
cineration of sample, so that the sample must be very small in volume and the pipe-
line must also be small in diameter. This makes it inevitable for the meter to be
subjected to strong influences of suspended solids such as the large fluctuation of
measured value resulting from the infiltration of suspended soilds into the furnace,
and the deflection of measured value of total TOC which is caused when part of
suspended solids in introducted in the pipeline running from the sampling point
through the analyzer. Fig. 8 is a comparison between TOC values of primary effluent,
secondary effluent and filtered effluent as obtained by manual analysis (on samples
collected from the outflow point of head tank) and the readings of continuous
analyzer recorded at the same time. In the manual analysis, values of both total
TOC and soluble TOC were obtained. As seen in this figure, the values obtained by
continuous analyzer are close to those of soluble TOC, suggesting that a consider-
ably portion of suspended solids is removed in the sampling line downstream of the
measuring point.
Fig. 9 is a comparison between the TOC values obtained by manual analysis on
the sample collected from the scrubber and the readings of continuous analyser re-
corded at the same time. As can be seen in the figure, the two show a fair con-
formity to each other, indicating that the measured values of continuous analyzer
become stabilized after suspended solids have been removed to some extent.
242
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Fig.-8 Comparison of TOC, Manual and Automatic Analyses
60-
50-
E 40-
_ 30-
o
O 20-
10-
AA
10
—I—
20
—I—
30
40
—I—
50
TOC, Automatic Analysis (mg/l)
A A Primary Effluent
o • Secondary Effluent
n Filtered Secondary Effluent
, • and * Refer to Total TOC ,
Manually Measured.
60
Fig.-9 Comparison of TOC, Manual and Automatic Analyses
- Samples taken at the Outlet of the Scrubber in the TOC Monitor -
10 20 30 40
TOC, Automatic Analysis (mg/l)
50
243
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Prior to its actural application, the TOC meter mentioned above was considered
to be superior to all other continuous TOC analayzers currently available on the
market for the purpose of analyzing samples containing suspended solids. Judging
from the test data, however, it does not seem fully appplicable to continuous
measurement of total TOC including suspended solids. At Nagoya plant, this
problem is coped with by pretreatment using a continuous centrifuge.
Although the following operational troubles and maintenance troubles were
encountered in the past, none were so serious as to invite suspension for a long time
and the TOC meters exhibited a high operating rate.
1) Pipelines developed frequent thermal deterioration especially in the neighbour-
hood of cell of infrared analyzer where the pipe replacement can be done only
by the manufacturer.
2) The carrier gas line was often clogged up due to moisture. Although an
electronic cooler was installed behind the cooling condenser to remove mois-
ture, water collected in the dust filter and often clogged up the carrier line
This trouble was coped with by modifying the shape of dust filter so as to be
able resist the collection of water to an extent.
3) Dehumidifying silica gel had to be replaced frequently due to the high relative
humidity of ambient room air used as carrier gas.
4) The scrubber for removing inorganic carbon has a shape which makes its clean-
ing difficult, and the pipeline supplying sample from the pump to the scrubber
is subjected to frequent clogging.
5) The furnace needs to be replaced in less than two years due to its corrosion,
and the breaking of heater wires must also be assumed to take place after the
lapse of just about the same period.
2.5 pH METER
The pH meters used are of dual sensor type with augmented internal liquid
volume (total length : approx. 2m).
At Nagoya plant, 5 pH meters of this type are installed in the aeration tanks
and primary effluent delivery lines.
By calibrating these pH meters once a week, measured values are stabilized at
present. The sensor surface becomes soiled considerably in a single day if the meter
is installed directly in the aeration tank, but excessive soiling could be prevented by
cleaning it once a week and it did not affect the measured values. By reason of its
functional characteristics, the pH meter needs an amplifier to be fitted near the
extreme end of its sensor. As there were no adequate measures to reduce the
humidity near the amplifier, satisfactory measured values could not be obtained
from some meters. To cope with the high humidity resulting from the tanks being
installed indoors, silica gel filled in a box is replaced at suitable intervals.
2.6 SLUDGE DENSITY METER
Ultrasonic type sludge density meters are installed in designated places in the
pipline at both plants; for density measurement of primary sludge and waste activated
sludge at Nagoya plant and alum sludge at Kyoto plant. The density meter itself is a
virtually maintenance-free instrument, but attention must be directed to the follow-
ing points in order to obtain accurate measured values.
244
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1) As the declining rate of ultrasonic wave varies according to the changes in
sludge properties resulting from the development of bulking and addition of
coagulant, it is necessary to carry out calibration frequently. In the density
measurement of waste activated sludge conducted at Nagoya plant, it was dis-
covered that 20 dB decline at FS 3% when SVI stood around 100 in summer
had to be adjusted to 33 dB decline at FS 3% in winter when SVI rose to about
200 (pipe diameter: 150 mm).
2) The declining rate is high especially for primary sludge. The measured density
of primary sludge once showed a value about 1.5 times as large as that obtained
by manual analysis even near the uppermost limit of adjustable range (FS — 8%,
45 db decline) (pipe diameter : 300mm). As primary sludge is subject to little
fluctuation of properties and consequently presents a high density correlation
between manual analysis and density meter measurement, a predetermined
coefficient is adopted at Nagoya plant to obtain the primary sludge density.
3) As the density meter gives the most reliable value around the centre of the
measuring range, it is not advisable to set the measuring scale extending un-
necessarily far beyond the density range of measured sludge. This caution
needs to be observed particularly for waste activated sludge as its density
changes largely with the lapse of time.
3. CONCLUSION
In the foregoing pages, the continuous water quality monitoring analyzers
installed at Kyoto plant and Nagoya plant have been introduced in outline, together
with the problems entailed in their maintenance as disclosed from the record of their
past operation.
All the analyzers selected for elucidation in this report exhibited a satisfactory
operating rate. Considered from the viewpoint of reliability, however, they can be
divided into two groups, those producing fairly stabilized measured values and those
liable to produce misleading values unless operated with full understanding of
functional and structural characteristics. In terms of maintenance services, too,
some are nearly maintenance-free, others call for simple maintenance only, and still
others demand complicated maintenance services.
The dominant cause of troubles related to the maintenance of all analyzers was,
as anticipated, the clogging of flow lines in the sampling system and measuring
system ensured from the inherent characteristics of sewage. Especially those lines
conveying a small volume of sample were found to be prone to be clogged up readily
because of the limited flow velocity and insufficient sectional area. These lines must
be made as large in diameter as possible up to the measuring point so as to be able to
carry abundant sample, and should also have a structure promising easy flushing
operation. The sampling lines at Nagoya plant are commendable in this respect up
to the head tanks, but all lines at subsequent treatment stages are not immune from
maintenance troubles. If the sampling pipelines are provided with a suitable auto-
matic flushing mechanism, it will certainly contribute to sizable labour-saving.
245
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Continuous water quality monitoring analyzers are often required to be installed
in unfavorable conditions such as high humidity or liability to water intrusion. It
was found that the tested analyzers were not necessarily installed with due regarded
to these unavoidably adverse factors, so that they developed not only electrical
troubles but also disjointing of pipes which caused the flow cell to be filled with
water. In prevention of such troubles, the layout of internal components of mea-
suring unit rack must be designed with special care. Furthermore, for the purpose of
easier and quicker routine inspection, all parts to be checked every day or at short
intervals should be gathered on the front of equipment. It was noted that main-
tenance was made difficult by multitubular piping and by inadequate design, shape
or layout of equipment which force the worker to move around it for calibration or
inspection, and this gave rise to the occurrence of another troubles. Although im-
provement of all equipment for completely maintenance-free operation may not be
possible, it certainly appears possible to reduce manpower requirement by effecting
suitable improvement to various equipment. For easier maintenance and inspection
services and quicker detection of troubles, it is advisable to affix a rough sketch
showing pipelines, measuring methods, signals and power source on the front surface
of each equipment. For all these improvements, cooperation of manufacturers is
indispensable and solicited.
To maintain all analyzers in perfect service condition, it is recommended to
appoint those with some experience in water quality analysis as exclusive operators
of analyzers because nearly all analyzers installed at the two plants call for routine
maintenance and inspection services, and the amount of such services is by no means
small considering the number of analyzers. The changes in water quality of sewage
generally depict the same pattern every day, so that the service condition and
malfunction of each analyzer can be cheked with ease from the daily observation
record if it is operated by an exclusive operator. The need for such exclusive op-
erated by an exclusive operator. The need for such exclusive operators can also be
justified by the fact that some analyzers cannot be operated satisfactorily without
the delicate knock which only the exclusive operators can gain through accumula-
tion of skills.
Maintenance cost of analyzers is by no means small even if personnel cost is
excluded. NH3 analyzer, for example, incurs an annual cost of more than 150
thousand yen merely for consumables such as chemicals and tubes. As another con-
spicuous example of high maintenance cost, it may as well be mentioned that COD
analyzer using the acid process is known to require an annual expenditure of more
than a million yen only for chemicals.
Utilisation of continuous water quality monitoring equipments in sewage treat-
ment produces immeasurable benefits for overall operation and maintenance of
sewage treatment plant in that it makes it possible to know the water quality of raw
sewage and effluents at any time. It is to be noted, however, that such benefits can
be expected not by simply installing necessary automatic analyzers but by operating
each individual analyzer with full understanding of its characteristics and keeping it
in perfect fault-free service condition under a well-planned and integrated system of
routine inspection and maintenance services.
246
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DEVELOPMENT OF AUTOMATED CONTINUOUS
P-D, HYARO AND NH3 ANALYZERS
Pilot or demonstration studies concerning advanced waste treatment are con-
ducted by the Public Works Research Institute of the Ministry of Construction in
Kyoto, Nagoya, and Yokosuka.
Of the three plants, studies are conducted on the practicability of Automated
Continuous Water Quality Analyzer together with development of advanced water
treatment processes in Kyoto and Nagoya.
This report mentions the studies conducted at the plants in Kyoto and Nagoya
on colorimetric P analyzers (hereinafter referred to as "P analyzer") and colori-
metric NH3 analyzer (hereinafter referred to as "NH3 analyzer").
The P analyzers installed in Kyoto and Nagoya are both products of K com-
pany. However, the P analyzers and the NH3 analyzers installed in the Kyoto plant
are the products in the developing stage.
Especially, the P analyzers are the first model ever made. On the other hand, as
the P analyzers and also the NH3 analyzers installed in Nagoya in 1976 are improved
versions of those in Kyoto, this report will mention the analyzers in Nagoya. How-
ever, with regards operating conditions of the analyzers, the report will refer to both
Kyoto and Nagoya.
1. P ANALYZER (PHOTO 1)
Photo-1 P Analyzer (Nagoya)
The flow sheet of the P analyzer is as shown in Fig. 1. This analyzer is a
mechanized version of the manual analyzing method of P-D, hydro. The analyzer
can be divided into three stages: Sample filtration, Pre-treatment and Color ab-
sorbance measuring stages.
247
-------
Fig.-1 Flowsheet of P Analyzer
Colorimeter
820nm
900nm
p) Tube Pump
«^X
V) Valve for Changing
•^r
Sampler
H2S04
Zero Solution
In the Sample filtration stage, the insoluble matters in sample are removed
by filter paper. The rolled sheets of filter paper, after filtration, is continuously
wound after being dried at about 100 degrees centigrade. And the winding speed is
adjustable between 1 and 10mm per minute depending upon the properties of the
insoluble matters. A roll of filter paper is 30 meters long. Therefore, one roll lasts
between 2 and 21 days. Then sulfuric acid is injected into the filtrate to prevent
contamination of the flow passage.
At the Pretreatment stage, the sample from inside a cup is collected by a vertical
movement of a sampler with air which partitions it. Then sulfuric acid is injected
into the sample. After mixing polyphosphate and part of organic phosphorous con-
tained in the sample, is subjected to hydrolysis in an incubater maintained at 90
degrees centigrade.
At the Color Absorbance Measuring stage, after releasing air in the pretreated
sample from the cup, the sample is again subjected to the vertical motion of the
sampler. In a mixing coil, ammonium molibdate is added, and the sample is rolled
and mixed. Then in the 90° C incubator, coloring occurs depending upon the ortho-
phosphate contained in the sample. After complete coloring, the sample is colori-
metrically analyzed in the flow cell. This unit utilizes the two wave type method to
prevent interference caused by color and turbidity in the sample. The P-D, hydro in
the sample, measured in such a manner, is sent to either the controller or the
recorder by the output of 4 ~ 20 mA or 0 ~ 10 mV.
The response time from the Filteration Stage to the Color Absorbance Measur-
ing Stage is about 30 minutes. The maximum concentration can be set at three
ranges of 2.5, 5 and 10mg-p/l. Washing of the flow passage and calibration are auto-
matically conducted at designated time by a 24-hour timer. Fig. 2 shows the
method. After washing, zero solution containing no phosphorous is injected into the
piping. And when the indicating value becomes stable, the value is electrically set to
"0" This is followed by injection of standard solution containing phosphorous of
248
-------
50% full scale concentration, and when the indicator shows a stable value, the
value is electrically set to 50% of full scale. The time required for washing and
calibration is about 110 minutes. About 30 minutes from the start show the sample's
measurement values. When a facility is controlled automaticaly based on output
from the analyzer, and when washing and calibration is in progress, the output
shown immediately before the operation remains unchanged and are transmitted to
the control unit. In case of any abnormalty such as dropping of water level in sampl-
ing tank, ripping of filter paper, or scaling out, the measurement process is sus-
pended and the alarm is sound. The alarm is sound even when it exceeds the
minimim values set in advance.
Daily inspection of flow passage, once weekly regent replenishment, once or
twice weekly filter paper changing, and once in between every 2 weeks and one
month tube chaning are necessary to maintain them.
Fig.-2 Automated Washing and Calibration
100-| i Measuring the color absorbance of sample
2. Washing
3. Measuring the color absorbance of zero solution
4. Calibration of zero solution
5. Measuring the color absorbance of standard solution
6. Calibration of standard solution
1 23456 1
50-
About 80 minutes
The above mentioned P analyzers in Nagoya are improved versions of those
in Kyoto as follows:
1) Filter paper feeding system has become continuous due to simplification of
winding mechanism.
2) The filtering direction changed from upflow to downflow to solve the problem
of sulfuric acid backflow, injected to prevent contamination of flow passage.
The air injection method to divide the sample has been changed form the
glass tube utilization method to the sampler vertical motion method. As a
result, the intervals between the sample and air became consistent and stable.
The colorimeter has been altered from the double beam type to the two wave
type analyzing method, and thus the cell has become single instead of double.
Then the response time has been shortened.
The addition of the Automated Washing Equipment has stabilized measure-
ments. At Kyoto, manual washing is conducted on a twice weekly basis by
using a siringe.
The flow passage that ran back and forth in the front and rear of the equip-
ment has been grouped together in the front of the unit.
Fig. 3 compares the measurement values of the P analyzer and the manual
3)
4)
5)
6)
249
-------
method (After filtration with No. 5 C filterpape-paper, the P-D, hydro was meas-
ured). Sampling was conducted on an once weekly basis during continuous opera-
tion of the P analyzers, and measurements were taken for six-months. On the whole,
the P analyzer results has shown slightly larger values than the manual method. One
of reasons cited can be the sulfuric acid injected to prevent contamination of flow
passage after filtration. Fig. 4 shows the results when identical sample was flown
into two P analyzers of which only one was injected with sulfuric acid. The Fig.
shows that the values of the P analyzer injected with sulfuric acid were higher.
This is reasoned to the fact that a part of the injected sulfuric acid has reached the
filtration stage and dissolved part of the insoluble phosphorous on the filter.
Fig. 5 shows an example of the automated continuous measurement results of
the P analyzer.
Fig.-3 Comparison between P Analyzer and Manual Analysis (Kyoto)
2.2
2.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
N=36
Regression Line
y = 1.079x + 0.0086
r = 0.983
s = 0.121
s Secondary Effluent
°Effluent from Alum
Precipitation
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
P-D, hydro (mg/2, Manual Analysis)
Fig.-4 Effect of H2SO4 for Cleaning on Measuring
Sample: Effluent from Alum Precipitation
I i
0.5 1 1.5 2
P-D, hydro (mg-P/C, without H,S04)
250
-------
Fig.-5 Variation of P-D, hydro (Alum was dosed into the primary clarifier., Nagoya)
Raw Waste
Primary Effluent
• Secondary Effluent
789 10(Sun.) 11 12 13 14 15 1617(Sun.)18 19 20 21 22
(Date)
-Alum Concentration Control (6mg-AC/C)-»f— Molar Control (Mole Ratio 2)
The hitherto developed troubles are as follows:
1) The residual flock containing phosphorous in the alum percipitation effluent
was not removed thoroughly by the original filter paper (20/u), and thus the
filtrate contained a reasonable amount of insoluble phosphorous. And when
supplying paper, the filter paper sometimes was torn. By improving the paper
quality and adjusting the pore size to about \n, the problems were solved.
(Kyoto)
2) Because exchanging and cleaning of tubes at each part were not easy, pro-
ficiency of the facility was deteriorated. However, efforts were made by
exchanging the flow passage to ease cleaning work. (Kyoto)
3) At first, persulfuric solution was used as a washing agent to clean the pipelines,
etc. However, as persulfuric was scattered onto the skin and clothes during
manual washing, it was dangerous. Therefore, the washing agent was changed
to phosphorous free detergent. The new agent has been bringing about good
washing results. ( Kyoto)
On the other hand, in Nagoya, the original design required the use of hydrogen
peroxide. However, when using only hydrogen peroxide in washing, it was not
able to remove scale in the mixing cell immediately before the flow cell. As it
was shown that the scale was removable by an alcaline solution, a caustic soda
solution was used as a washing agent alternating with hydrogen peroxide
solution every week. When using the caustic soda solution, it caused abnormal
coloring (especially when phosphorus concentration was high) until being
totally discharged and sounded the alarm to suspend operation. (Nagoya)
4) Troubles frequently developed in the filtration stage. And virtually all of the
trubles were eliminated by improving the filtration system. Troubles develop-
ing in the filtration stage were as follows:
(1) Improper feeding of filter paper. (Kyoto)
(2) Tearing of filter paper. (Kyoto, Nagoya)
(3) Leaking of sample into the filtrate. (Nagoya)
(4) A hole was made in the filter paper due to backflow of sulfuric acid.
(Nagoya)
Those were the troubles, but, presently, a total of 5 P analyzers are operating
in good conditions both in Kyoto and Nagoya.
251
-------
A single person can service several P analyzers although it takes about a month
for him to be accustomed in handling the units.
Table 1 shows the maintenance costs of the P analyzer and the NH3 analyzer
that are explained later.
Some problems that remain unsolved are as follows:
In case of continuously measuring phosphorous as water quality monitoring, it
is necessary to measure not only soluble phosphorous but also insoluble phos-
phorous. To perform this, development of a unit enabling the measurement of in-
soluble phosphorous is necessary. Though as the ratio of organic phosphorous con-
tained in the total phosphate in wastewater is small, the hydrolyzable phosphorous
is nearly equal to total phosphorus, organic phosphorus can not necessarily ignored
in surface water, so development of a unit enabling measurements of organic phos-
phorous is necessary.
Table-1 Maintenance Costs of P and NH3 Analyzers (YEN/month-unit)
Item
Tube
Filter
Reagent
Total
P Analyzer
8,200
1,200
1,100
10,500
NH3 Analyzer
8,000
1,200
2,800
12,000
Remarks
A exchange/two weeks
A exchange/one weeks
2. COLORIMETRIC NH3 ANALYZER (PHOTO 2)
Photo 2 NH , Analyzer
The measurement principle of this unit is as follow:
After adding salicylic acid to the sample, when the alkaline isosialic acid is
applied, the sample turns green in color. As the degree of the green is proportionate
to the ammonia-nitrogen concentration in the sampe, by measuring the absorbance
of the green color the amonia-nitrogen conceptration in the sample can be deter-
mined. By this method, besides ammonia-nitrogen, mono-chloroamine can also be
252
-------
determined.
The flow sheet of the NH3 analyzer installed in Nagoya is shown in Fig. 6.
The filteration method, washing and calibration methods, and absorbance
measuring method in the NH3 analyzer are the same as the P analyzer. However, as
pretreatment stage is not required in the NH3 analyzer, the response time is only
about 15 minutes, or nearly half of that of the P analyzer.
At maximum measurement concentration of 20 ~ 30mg-N/l, similarly with
the P analyzers, the full scale can be switched into 3 stages and it is possible to op-
erate even at 1/2 or 1/4 of the maximum concentration. When ammonia-nitrogen
concentration is more than 20mg-N/l, a straight calibration line is not obtained.
Therefore, when operating in full scale of over 20mg-N/l, the two fold dilution
equipment is employed. The daily routine operation is the same as that of the P
analyzer.
Fig. 7 compares actual measurement results of the NH3 analyzers and the
manual method (Indophenol blue method). Fig. 7 shows the measurement results
during 18 months of operation, using samples collected at once weekly rate.
Fig. 8 shows an example of continuous measurement results.
Fig.-6 Flowsheet of NH3 Analyzer
[01
Colorimeter
770nm
810nm Di-thlofide iso-cyanuric acid
Salicylic Acid
Overflow
Sample
HCB
Zero Solution
Zero Solution
253
-------
Fig.-7 Comparison between NH3 Analyzer and Manual Analysis (Kyoto)
26
24
22
„ 20
0)
£ 18
I16
10
8
N = 66
Regressin Line
V = 1,019 x + 10.136
r = 0,973
s = 1,458
0 2 4 6 8 10 12 14 16 18 20 22 24 26
NH3-N (mg/8, Manual Analysis)
• Filter Effluent and AC Effluent
of Secondary Effluent
o Carbon Contactor Effluent of
BPC Effluent
• BPC Effluent
Fig.-8 Variation of NH3
— Primary Effluent (Alum was dosed into the primary clarifier.)
;— Secondary Effluent (Alum was dosed into the primary clarifier.)
— Secondary Effluent (Alum was dosed into the primary clarifier,
and pH of the aeration tank was controled
with NaOH.)
8 10 12 14 16 18 20 22 24 Ti
Trouble developed until now are as follows:
The sodium nitroprusside added to expedite rection of coloring regent of
salicylic acid was instable when pH exceeded 8. This deteriorated the meas-
urement accuracy gradually. However, by adjusting the pH correctly, the
problem was solved. (Kyoto)
As the open type standard solution preservation container was used, the water
in the standard solution evaporated. There were times when the 10mg-N/l
standard solution condensed to 13mg-N/l 10 days later, sealedtype containers
are now used. (Kyoto)
Also there were problems similar to those in the P analyzers.
Presently, a total of 6 NH3 analyzers are functioning normally at the plants in
Kyoto and Nagoya. Table 1 shows the daily maintenance costs.
1)
2)
3)
254
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IV. ALUM DOSING METHOD IN ALUM PRECIPITATION
At the Kyoto pilot plant, experiments were conducted to compare the alum
constant dosing method with the molar control method, that is, alum is dosed into
the influent in proportion to the dissolved phosphorous concentration (P-D). The
flow diagram of the precipitation facility is as shown in Fig. 1. And the experi-
mental conditions and results are as shown in Table 1. The influent was effluent
form conventional activated sludge. The influent flow was 300 m3/day (in case of
fluctuations in flow, the daily average influent). The overflow rate of the clairifer
was 30m3 /day.
Fig.-1 Flow Diagram of Alum Precipitation
Rapid Mixer
Flocculation Tank
Clarifier
1,OOOWx 1.000L xSOOD
1,OOOWx 2,000 Lx 3,6000
1,OOOW x 10.000L x 3,600D
I Excess Sludge
EXPERIMENTAL CONDITIONS - See Table 1 -
Experiment numbers 1 ~ 3 were constant doxing method, and experiment
numbers 4 ~ 6 were molar control method.
The amount of alum doze in the constant dosing method was set at 5.9mg-Al/
liter. In case of molar control method, based on the phosphorous monitor output
that continuously measured P-D of the influent, the alum doxing pump was re-
gulated to maintain the molar ratio at 6 of Al against P-D of the influent.
The experiments on the constant dosing method and the molar control method
were diversified as follows:
Experiments 1 and 4: Constant influent flow without return sludge.
Experiments 2 and 5: Constant influent flow with return sludge.
Experiments 3 and 6: Varying influent flow with reutrn sludge.
255
-------
Table -1 Experimental Conditions and Results of Alum Precipitation at Kyoto P.P.
__^_^Number of Experiment
Item " ___
Conditions
P (mg-P/1)
P-D (mg-P/1)
SS (mg/1)
PH
M-Alkalinity
(mg-CaCoj/l)
Temperature
Flow
Alum Dosing Method
Sludge Return Rate (%)
Excess Sludge Rate (%)
Alum Dosing (mg-Al/1)
Mole Ratio (Al/P-D)
Influent
Effluent
Excess Sludge
Mixed Liquor
Removal (%)
Influent
Effluent
Excess Sludge
Mixed Liquor
Removal (%)
Influent
Effluent
Excess Sludge
Mixed Liquor
Influent
Effluent
Influent
Effluent
Effluent
1
Constant
Constant
0
0.6
5.9
4.8
1.69
1.01
26.7
40.2
1.40
0.44
0.19
68.6
9.7
24.8
1690
7.2
6.9
159
135
20.5
2
Constant
Constant
4.2
0.7
5.9
4.6
1.83
1.08
74.7
9.40
41.0
1.48
0.32
0.39
0.87
78.4
7.7
17.6
2190
188
7.1
7.0
145
129
16.1
3
Varying
Constant
5.1
0.7
5.9
5.7
1.44
0.80
35.8
6.27
44.5
1.18
0.23
0.22
0.47
80.5
12.6
16.2
1740
155
7.0
6.9
150
117
19.1
4
Constant
Molar
Control
0
0.7
7.1
6
1.50
0.80
46.7
1.36
0.30
77.9
6.1
13.3
7.1
6.9
144
123
15.1
5
Constant
Molar
Control
4.0
0.7
7.3
6
1.51
1.08
23.9
3.20
28.4
1.39
0.25
0.29
0.66
82.0
5.8
19.7
640
74
7.1
6.9
143
113
13.4
6
Varying
Molar
Control
4.9
0.7
6.8
6
1.44
0.79
37.2
4.95
45.1
1.30
0.26
0.27
0.32
80.0
8.9
15.2
1450
112
7.1
6.9
144
118
16.7
By performing the above mentioned experiments, studies were made on alum
dosing methods, effect of return sludge, influence of variation of influent flow.
The experiment results as shown in Table 1 are average values for each experiment.
Also, the analysis of influent and effluent was conducted by using the composite
samples of each day. Other samples were collected at 10 in the morning everyday.
EXPERIMENTAL RESULTS AND DISCUSSION
According to Table 1, the removal rate of phosphorous (P) was low ranging
between 40 and 45%, except for Experiment 5. In contrast, the P-D removal rate
was about 80%, and in all cases SS in the effluent was higher than SS in the influent.
From these facts, the lowliness of the phosphorous removal rate can be considered
to be caused by the lowliness of the insoluble phosphorous removal rate. Therefore,
it is necessary to conduct studies on the improvement of the clarifier.
Results of P-D removal are shown in Fig. 2 concerning Experiments 1 ~ 3,
and in Fig. 3 concerning Experiments 4 ~ 6.
256
-------
Fig.-2
0.8
0.7
0.6
o?
a: 0.5
o
^ 0.4
v
9
a- 0.3
0.2-
0.1-
Numberof Experiment
X 1
O 2
• 3
0 „ 0° 0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
P-D iff. (mg-P/2)
Fig.-3
0.5
0.4
0.3
0.2
a
a.
0.1
Number of Experiment
X. 4
O 5
• 6
0.2 0.4 0.6 0.8 1.0 1.2
P-D iff. (mg-P/E)
1.4 1.6 1.8 2.0
From Table 1, Fig. 2 and Fig. 3, the fallowings can be considered concerning
the P-D removal:
1) In both the constant dosing method and the molar control method, it was
possible to lower P-D concentration in the effluent by the return sludge.
Also, it lessened the fluctuations of P-D concentration in the effluent. This is
because the alum sludge still had the ability to remove phosphorous.
In Table 1, Mixed Liquor is a combination of influent and return sludge before
alum dosing. In other words, Table 1 shows that between 40 and 75 percent
of P-D in the influent were removed by the return sludge. Accordingly, the
return sludge lowered the P-D concentration in the influent, and as variations
became smaller, it lowered P-D concentration in the effluent to further mini-
mize fluctuation.
2) The molar control method prevented variation of P-D concentration in the
effluent by either daily average (Fig. 2, 3) or continuous measurement (Fig. 4,
5) than the constant dosing method even when sludge was returned. However,
257
-------
3)
according to Fig. 2, 3, the daily average value of P-D concentration in the
effluent did not show any clear differences between the two alum dosing
methods. The molar ratio of P-D/A1 in the constant dosing method was 6 when
P-D concentration of the influent was 1.13 mg-p/1. When the P-D concentra-
tion was about 1.13 mg-p/1, the P-D in the effluent was a little less than 0.3
mg-p/1 in both methods.
Both alum dosing methods with return sludge did not cause increase of the P-D
loading in the effluent owing to the variation in influent flow. (See Table 1
and Fig. 4, Fig. 5) Although this was considered quite natural in the molar
control method, it was worth mentioning in the alum constant dosing method.
So, it can be concluded that with regards P-D removal in alum precipitation,
there is no need to conduct molar control method when sludge is returned.
Fig. -4
EXPERIMENT?
>
'•5
•§1.0
2.0
Influent
Effluent
Mon. Tues.
EXPERIMENTS
J61.0
!5
Wed. Thurs.
Time
Fri.
Sat. Sun.
2.0
— 1.0
9
0.
Influent
Wed.
Thurs.
Fri. Sat.
Time
Sun. Mon. Tues.
258
-------
Fig. -5
EXPERIMENTS
20
f 10
!5
K
400
1 300
1 200
5
2 100
Sat.
EXPERIMENT 6
20 r
•o 10
Xl
400
300
Sat.
.§ 200
o
il 100
0
2.0
1.0
Q
OL
Sun.
Mon.
Tues. Wed. Thurs.
Time
Fir.
259
-------
PAPERS FOR THE SIXTH US/JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
Washington D.C.
November 1 - 2, 1978
Ministry of Construction
Government of Japan
''261
-------
CHAPTER 1
CHAPTER 2
CHAPTER 3
CHAPTER 4
CHAPTER 5
CONTENTS
RECENT TROPICS OF WATER POLLUTION
CONTROL IN JAPAN 263
by T. Hayashi, Water Quality Control Division, Environmental
Agency
INSTITUTIONAL STRUCTURES OF WATER POLLUTION
CONTROL IN JAPAN 278
by T. Tamaki, River-Basin Sewerage Division, Sewerage and
Sewage Purification Department, Ministry of Construction
FINANCING OF SEWAGE WORKS - USER CHARGES
by T. Tamaki, River-Basin Sewerage Division, Sewerage and
Sewage Purification Department, Ministry of Construction
300
SEWER USER CHARGE SYSTEM IN OSAKA CITY 319
by K. Tani, Construction Division, Sewerage Bureau, Osaka
Municipal Government
NEW SUPERVISION AND CONTROL SYSTEM OF
SEWAGE TREATMENT PLANT IN YOKOHAMA
by S. Miyakoshi, Construction Division, Sewage Works
Bureau, Yokohama Municipal Government
351
CHAPTER 6 MISSION AND ACTIVITIES OF JAPAN SEWAGE WORKS
AGENCY AT PRESENT AND FUTURE 364
by T. Kubo, Japan Sewage Works Agency
262
-------
CHAPTER I
RECENT TOPICS OF WATER POLLUTION CONTROL IN JAPAN
1 Current State of the Water Pollution 264
2 Status Quo of Water Pollution Control Law and Seto Inland
Sea Conservation Law in Their Enforcement 264
2.1 Specified Factories 265
2.2 More Stringent Effluent Standards 266
2.3 State of Enforcement of Seto Inland Sea Conservation. 266
3 Amendment of Seto Inland Sea Conservation Law and Water
Pollution Control Law 267
3.1 Amendment of Seto Inland Sea Conservation Law 267
3.2 Amendment of Water Pollution Control Law 268
263
-------
I CURRENT STATE OF THE WATER POLLUTION
In general, the state of water pollution has tended to improve
in recent years, reflecting the vigorous enforcement of effluent
control measures which have been continuously strengthened.
The ratio of samples which met the environmental quality st-
andards relating to human health (cadmium,cyanide and seven other
toxic substances) continued to rise in 1975, as in 1975, reaching
the very high value of 99.91 percent; in neither year was any
alkyl mercury or organic phosphorus detected in samples, in addit-
ion to this, hexavallent chromium was not detected in samples in
1976.
The recent trends in BOD( or COD for lakes and coastal water
bodies) which are major items of the standards relating to the
living environment tend to show an improvement in water pollution
on the whole.
Next, with respect to the attainment of the environmental wat-
er quality standards for BOD or COD in 2,586 water areas (2,024
rivers, 82 lakes and 480 coastal water bodies) categolised by vir-
tue of a Cabinet decision taken in September 1970 and also by vir-
tue of a Cabinet Order issued in May 1971, 60.5 percent (1,164 ri-
vers, 34 lakes and 366 coastal water bodies; total, 1,564 water
areas) had attained the environmental standards as of the end of
1976, showing an improvement over the 59.6 percent attainment of
1975. Specifically, the ratios of attainment in 1976 stood at 57.5
percent of rivers (57.1 percent in 1975), 41.5 percent of lakes
(38.6 percent in 1975) and 76.3 percent of coastal water bodies
(72.4 percent in 1975). Also, the ratio of attainment of the env-
ironmental standards by major rivers which flow through large
cities and coastal water areas which are adjacent to large cities
remained lower than of other water areas, leaving room for still
further improvement.
The Seto Inland Sea is a scenic area of rare beauty and an in-
valuable storehouse of marine resources, and as such pollution
control measures to check the deterioration of its water quality
have become a problem of the utmost importance. The enactment of
the Seto Inland Sea Conservation Law in 1973 and the implementat-
ion of various measures have initiated a tendency toward improvem-
ent, but the still-continuing occurence of "red tides" and cont-
amination by spilled oil caused by accident (for example collision
of crude oil carriers) are evidece of the need for appropriate
countermeasures to meet the different states of pollution.
2 STATUS QUO OF WATER POLLUTION CONTROL LAW AND SETO INLAND SEA
CONSERVATION LAW IN THEIR ENFORCEMENT
Under the reguration of Water Pollution Control Law, the per-
son who discharges effluent from factories or establishment into
the public water area should submit a report, whenever he intends
to install any Specified Facilities, to the prefectural governor
(including Works-Entrusted Mayor of Cities which are designated in
the Cabinet Order).
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Much the same, under the regulation of Seto Inland Sea Conser-
vation Law, the person who discharges effluent from factories or
establishment into the public water area, wihtin the area of Osaka
Prefecture and other ten prefectures relating to Seto Inland Sea
(excluding the area where has no relationship to the water pollut-
ion of Seto Inland Sea such as the geographical portion which
faces to Sea of Japan) shall obtain permission of or should submit
a report to the governor concerned (including works-entrusted may-
or of cities which are designated in the Cabinet Order), whenever
he intends to install any Specified Facilities.
2,1 SPECIFIED FACTORIES
As of March 31,1977, 250,801 Specified Factories had been sub-
mitted reports to the governors of the competent prefectures under
the provision of Water Pollution Control Law (including 4,062
Specified Factories to which the permits had been issued by the
competent governors of prefectures under the provision of Seto
Inland Sea Conservation Law).
The Effluent Standards relating to preservation of living
environment (such as pH) issued by the Ordinance of the Prime
Minister's Office are applied to the Specified Factories which
discharge 50 cubic metres or more effluent per day on an average,
and as of March 31, 1977, 28,254 reports from those factories had
been received by the governors of prefectures.
On the contrary, the Effluent Standards relating to harmful
substances (such as cadmium) are applied to all the Specified
Factories whatever the quantities of their effluent are. Among
the 222,547 Specified Factories which discharge less than 50 cubic
metres per day on an average, those which discharge harmful
substances are 7,338 and this is 3 percent of the total. So at
least, the total number of Specified Factories which are applied
with so called Uniform Effluent Standards is 35,592 and this is 14
percent of the total. Moreover, among the Specified Factories
which discharge 50 cubic metres or more of effluent per day on an
average, those which discharge harmful substances are 3,592 and
this is 1 percent of the total.
Table 1 shows ten major types of industries which hold higher
ranks in number as the Specified Factories as of March 31, 1977.
Also, Table 2 shows " Specified Facilities" under the provis-
ion of the Cabinet Order of Water Pollution Controi'-Law?for refer-
ence.
As to the sewage treatment plants which submitted the reports
to the governors of prefectures according to the regulation of the
Water Pollution Control Law (including nine plants to which perm-
issions issued by the governors of prefectures concerned under the
provisions of Seto Inland Sea Conservation Law) are 467 in number
as of March, 1977.
Several Specified Facilities have been added during the period
from October 1972 to June 1976. Those facilities are as follows.
Livestock breeding (October 1, 1972, No. 1-2)
Desizing facilities of textile industry (December 1, 1974,
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(i) of No. 19)
Lodging service (December 1, 1974, No. 66-2)
Research,determination,measurement or professional educat-
ion for science and technology (Decem
ber 1, 1974, No. 71-2)
Domestic and industrial water supply (June 1, 1976, No. 64-
2)
Central wholesale market of aquatic products (June 1,1976,
No. 69-2)
Also, the Environment Agency intends to add new specified fac-
ilities at need for coming years. For instance, hospitals and
waste treatment facilities will be added in near future.
2,2 MORE STRINGENT EFFLUENT STANDARDS
Under the provision of the Water Pollution Control Law, when
there is any Public Water Area under a prefectural jurisdixion for
which the effluent standards as provided for is recognised to be
insufficient for protecting human health or for preserving the
living environment, the prefecture may establish more stringent
standards than the standards established by the Government ( Water
Pollution Control Law, Article 3).
All of the prefectures (47) have established more stringent
effluent standards as of March 31, 1977.
As to the contents of "more stringent effluent standards",
prefectures which have the standards relating to harmful subst-
ances are 23 prefectures, while the remainder 24 prefectures have
established more stringent standards only for the items relating
to the preservation of living environment, as of March 31, 1977.
Also, as to the factories which discharge less than 50 cubic
metres per day on an average, the effluent standards established
by fche Government are not applied in principle, but 32 prefectures
deal with even those factories as the objects to be controled by
the more stringent standards.
2,3 STATE OF ENFORCEMENT OF SETO INLAND SEA CONSERVATION LAW
Seto Inland Sea Conservation Law was unanimously enacted by
the Diet in 1973 in view of the special importance of this area as
a treasure house of scenic beauty and fishery resources. In line
with the Law, a series of special measures have been taken to pro-
tect the environment of Seto Inland Sea.
These measures include, among others, (a) to make a basic plan
for the conservation of the environment of Seto Inland Sea, (b) to
reduce, within the period of three years, the Chemical Oxygen De-
mand load upon the Seto Inland Sea from the industrial sector to
one half of the level of 1972, (c) to require special permission
for the new setting up of certain types of industrial facilities,
and (d) to ensure special consideration on the peculiar importance
of the Seto Inland Sea.
Initially, this law was planned to lapse after three years in
accordance with the Article 4 of supplementary provisions of this
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law. .Afterwards, in 1976, this limitation of period was prolonged
two more years — until November 1, 1978.
As to the goal for the reduction of COD loadings we have got
a big success beyond the goal. Namely, the goal was to reduce the
COD load upon the Inland Sea from 1,345 tons in 1972 to its one
half, i.e., 673 tons, while the result was 459.5 tons in November
1976. It means 131.7 percent attainment against the aim.
As to the special consideration on land reclamation in Seto
Inland Sea area, before the enforcement of this law, for instance
in the period from January 1, 1970 to November 1, 1973, the aver-
age anual reclamation area was 2,190 hectare, while after the en-
forcement of this law, in the period from November 2, 1973 to Oct-
ober 31, 1977, the average anual reclamation area was 540 hectare,
and this means three quarter reduction of pace.
Also, as to the basic plan for for the conservation of the en-
vironment of Seto Inland Sea, it was made by the Environment
Agency through the discussion of Seto Inland Sea Environmental
Conservation Council and decided by the Cabinet Meeting, in April
1978.
3 AMENDMENT OF SETO INLAND SEA CONCERVATION LAW AND WATER
POLLUTION CONTROL LAW
As stated before, the Seto Inland Sea Conservation Law was ex-
pected to expire in November 1978, strong views have been express-
ed from various sectors calling for necessary legislative action
to extend the validity of the Law.
Inthe meanwhile, the water quality in the public water areas
in Japan has been generally improved as stated before. But it is
still difficult to attain the environmental water quality stand-
ards in some large scale closed/semi-closed water bodies the Seto
Inland Sea, Tokyo Bay and Ise Bay.
Under such circumstances, a new Amendment Bill was proposed to
extend the validity of the Seto Inland Sea Conservation Law and
to establish a Total Mass Effluent Control system for water poll-
ution control in the large size closed/semi-closed water bodies,
under which total amount of pollutant load is to be regulated, as
well as to conserve the environment of the natural beaches.
Thus, on June 7 the National Diet passed the bill for revision
of the Special Law for Conservation Of the Environment of the Seto
Inland Sea and the Water Pollution Control Law.
3,1 AMENDMENT OF SETO INLAND SEA CONSERVATION LAW
The extention of validity of the Law is now realised by the
enactment of this bill, by which the supplemental provisions lim-
iting the implementation period for the Special Law for Conservat-
ion of the Environment of the Seto Inland Sea are abolished.
The highlight of the amendment is as follows:
Firstly, establishment a new provision for Prefectural Plan
was introduced to realise the effectiveness of various countermea-
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sures taken in the competent prefectures according to the geogr-
aphical and social characteristics.
Secondlly, Total Mass Effluent Control system was introduced
for the region of Seto Inland Sea. This is a measure to take over
the measures of reduction of COD load from the industrial sector
(extended for COD load from the domestic sector in the amendment).
Thirdly, new measures, directed to the prevention of damage due
to eutrophication, like the "red tides" in the Seto Inland Sea,
are incorporated in the Water Pollution Control Law. The amendment
makes it possible to regulate the inflow of phosphorus and other
substances which are to be specified by a Cabinet Order as eutro-
phication substances. More specificaly, the prefectural governors
in areas concerned are now empowered to give administrative guid-
ance to factories when it is deemed necessary to reduce the volume
of such eutrophication substances in their effluent. This guidance
is to be given in accordance with guidlines to be set by the Dir-
ector-General of the Environment Agency.
Fourthly, new measures related to the preservation of natural
beaches used for sea bathing and other forms of recreation are
included. The prefectural government bodies concerned are now aut-
thorised to designate such natural beaches as requiring preservat-
ion, to require that the building of structures and other activit-
ies in the area be reported to the prefectural authorities in adv-
ance and to give necessary guidance regarding such activities.
Fifthly, a new provision introduced to prevent oil pollution
in the Seto Inland Sea caused by marine accidents; regulations are
requesting the Government to make efforts to take necessary meas-
ures for strengthening of guide and control, preparation of prev-
enting and removal system, concerning large quantities of oil dis-
charge aused by marine accident and removal of spilled oil.
3,2 AMENDMENT OF WATER POLLUTION CONTROL LAW
As for the revision of the Water Pollution Control Law to set
up a system for regulating the total amount of pollutants in effl-
uent, the Prime Minister is now expected to work out a basic pol-
icy for the reduction of the total pollution load for pollutants
which are to be determined by a Cabinet Order (limited to COD for
the time being), with respect to river basins (Specified Areas) of
arge size closed/semi-closed water bodies where attainment and
maintenance of the environmental water quality standards is diffi-
cult (Seto inland Sea , Tokyo Bay, etc.).
Next, the prefectural governor concerned is to work out a pro-
gramme in line with the said basic policy for the reduction of the
total effluents, and according to this programme, to work out mass
regulation standards to be observed by factories and other work-
shops larger than a certain scale which are located in the Specif-
ied Areas. Unlike the effluent standards enforced heretofore which
regulate only the concentration of pollutants, the mass regulation
standards will set the permissible level of the pollutant load em-
itted by factories and other workshops concerned.
Moreover, if necessary for carrying out the programme for the
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reduction of the effluents, the prefectural governor is authorised
to give guidance even to persons other than the factories and
other workshops which are required to observe the mass regulation
standard.
In order to ensure the effectiveness of the total mass regul-
ation system, the amendment also includes provisions for the issu-
ance of orders to enforce programme change or improvement, and es-
tablishes the obligation to measure and record the pollution load.
The amendment is to take effect at a date within a year from
the day of its promulgation (June 13).
Also, the goal date of the attainment of the aimed level of
water quality in the competent water bodies by this total mass
control system are scheduled five years after the date that this
amendment is to take effect.
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Table 1 Major types of industries hold higher
ranking in number as Specified Factories
Ranking
1
2
3
4
5
6
7
8
9
10
Types of industries
*
Lodging service
( No. 66-2 )
Livestock breeding
( No. 1-2 )
Laundry
( No. 67 )
Bean foods manufac-
turing
(No. 17 )
Automatically wash-
ing facilities of
car (No. 71 )
Sea foods manufact-
uring
( No. 3 )
Night soil treatment
plant
( No. 72 )
Textile industry
(No. 19 )
Acid and alkali
treatment facilities
of metal surface
(No. 65 )
Soft drink manufact-
uring and brewery
(No. 10 )
Number
**
72,908
(29.1%)
36,746
(14.7%)
26,474
(10.6%)
21,889
( 8.7%)
13,463
( 5.4%)
10,518
( 4.2%)
7,703
( 3.1%)
5,091
( 2.0%)
5,049
( 2.0%)
4,683
( 1.9%)
Ratio of exceeding
50 cubic metre per
day of effluent
discharge
5.3 %
1.5 %
1.0 %
0.7 %
1.8 %
9.2 %
87.5 %
31.8 %
33.1 %
11.3 %
Note ; * ( ) shows the number listed in "Table 1"
annexed to the Cabinet Order of Water
Pollution Control Law.
** ( ) shows the percentage of the competent
Specified Factories in number against the
total number of Specified Factories, as
of March 31, 1977.
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Table 2 The list of Specified Facilities
( 1) MINING AND COAL WASHING
(a) ore separation facilities,
(b) coal dressing facilities,
(c) neutrlisation and sedimentation facilities of mine
water,
(d) solids separation facilities from water used for
digging.
( l)-2 LIVESTOCK BREEDING
(a) pig shed facilities (excluding the facilities in-
stalled in the shed with the total area of less
than 50 square metre),
(b) cattle shed facilities (excluding the facilities
installed in the shed with the total area of less
than 200 square metre),
(c) horse shed facilities (excluding the facilities
installed in the shed with the total area of less
than 500 square metre).
( 2) MEAT PACKING AND POULTRY PROCESSING
(a) initial preparation facilities,
(b) washing facilities,
(c) cooking facilities.
(3) SEA FOODS MANUFACTURING
(a) initial preparation facilities,
(b) washing facilities,
(c) dehydration facilities,
(d) screening facilities,
(e) cooking facilities.
( 4) TINNED AND FROZEN VEGETABLES AND FRUITS MANUFACTURING
(a) initial preparation facilities,
(b) cleaning facilities,
(c) pressing facilities,
(d) cooking facilities.
( 5) MISO, SOY-SOURCE, EDIBLE AMINO ACID, GLUTAMIC ACID,
VEGETABLE SOURCES AND VINEGAR MANUFACTURING
(a) initial preparation facilities,
(b) cleaning facilities,
(c) boiling facilities,
(d) concentration facilities,
(e) finishing facilities,
(f) straining facilities.
( 6) WHEAT FLOUR MANUFACTURING
washing facilities
( 7) SUGAR MANUFACTURING
(a) initial preparation facilities,
(b) washing facilities,
(c) filtration facilities,
(d) separation facilities,
(e) refining facilities.
( 8) BAKERY AND CONFEXIONARY
bean-jam processing facilities
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( 9) RICE CAKE AND MALT MANUFACTURING
washing facilities
(10) SOFT DRINK MANUFACTURING AND BREWERY
(a) initial preparation facilities,
(b) cleaning facilities,
(c) extraxion facilities,
(d) straining facilities,
(e) boiling facilities,
(f) stilling facilities.
(11) FEED STAFF AND ORGANIC FERTILISER MANUFACTURING
(a) initial preparation facilities,
(b) washing facilities,
(c) pressing facilities,
(d) vacuum concentration facilities,
(e) water washing deodorisation facilities.
(12) OIL AND FAT MANUFACTURING
(a) initial preparation facilities,
(b) washing facilities,
(c) pressing facilities,
(d) separation facilities.
(13) YEAST MANUFACTURING
(a) initial preparation facilities,
(b) washing facilities,
(c) separation facilities.
(14) STARCH MANUFACTURING
(a) soaking facilities,
(b) washing facilities,
(c) separation facilities,
(d) waste pits.
(15) DEXTROSE MANUFACTURING
(a) initial preparation facilities,
(b) filtration facilities,
(c) refining facilities.
(16) NOODLE MANUFACTURING
boiling facilities
(17) BEAN FOODS MANUFACTURING
boiling facilities
(18) INSTANT COFFEE MANUFACTURING
extraxion facilities
(19) TEXTILE INDUSTRY
(a) scouring facilities,
(b) by-product processing facilities,
(c) soaking facilities,
(d) finishing facilities,
(e) silket machine,
(f) bleaching facilities,
(g) deying facilities, (i) desizing facil-
(h) chemical treatment facilities ities
(20) WOOL SCOURING AND WASHING
(a) wool scouring and washing facilities,
(b) carbonising facilities.
(21) SYNTHETIC TEXTILE MANUFACTURING
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(a) spinning facilities,
(b) chemical treatment facilities,
(c) recovery facilities.
(22) CHEMICAL FINISHING OF WOODS
(a) wet barker,
(b) chemical soaking facilities.
(23) PULP AND PAPER MANUFACTURING
(a) soaking facilities,
(b) wet barker,
(c) chipper,
(d) digester,
(e) accumulator for digester waste,
(f) chip refiner and pulp refiner
(g) bleaching facilities,
(h) paper mill,
(i) cellophane paper mill,
(j) wet fibre plate facilities,
(k) waste gas washing facilities.
(24) FERTILISER MANUFACTURING
(a) filtration facilities,
(b) separation facilities,
(c) water jet breaking facilities,
(d) waste gas washing facilities,
(e) wet dust collector.
(25) SODIUM HYDROXIDE AND POTASSIUM HYDROXIDE MANUFACTURING
(MERCURY ELECTROLYSIS)
(a) electrolyte refining facilities,
(b) electrolising facilities.
(26) INORGANIC PIGMENT MANUFACTURING
(a) washing facilities,
(b) filtration facilities,
(c) centrifuger ( cadmium and its compounds)
(d) water flushing separator (ultra-marine)
(e) waste gas washing facilities.
(27) INORGANIC CHEMICALS MANUFACTURING EXCLUDING ITEMS OF 25
AND 26
(a) filtration facilities,
(b) centrifuger,
(c) sulfur dioxide gas cooling and washing facilities
(sulfuric acid),
(d) washing facilities (activated carbon and carbonated
disulfur),
(e) hydrochloric acid regenerating facilities (silicate
anhydrous),
(f) reactor (cyanides),
(g) absorber and sedimentation facilities (iodines),
(h) sedimentation facilities (saline magnesia),
(i) water flushing facilities (bariumates),
(j) waste gas washing facilities,
(k) wet dust collector.
(28) ACETYLENE DERIVATIVES MANUFACTURING (CARBIDE PROCESS)
(a) wet acetylene generation facilities,
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(b) washing facilities and still (acetate ester),
(c) methyl alcohol still (polyvinyl alcohol),
(d) still (acrylic acid ester),
(e) vinyl chloric monomer washing facilities,
(f) chlorprene monomer washing facilities.
(29) COAL TAR PRODUCTS MANUFACTURING
(a) sulfuric acid washing facilities of benzene relates,
(b) waste pits,
(c) tar sodium sulfonate reactor.
(30) FERMENTATION INDUSTRY EXCLUDING ITEMS OF 5, 10 AND 13
(a) initial preparation facilities,
(b) still,
(c) centrifugal decanter,
(d) filtration facilities.
(31) METHANE DERIVATIVES MANUFACTURING
(a) still (methyl alcohol and 4-chloromethane),
(b) refining facilities (formaldehyde),
(c) washing and filtration facilities,
(32) ORGANIC PIGMENT MANUFACTURING OR SYNTHETIC DYES MANUFACT-
URING
(a) filtration facilities,
(b) water washing facilities,
(c) centrifugal decanter,
(d) waste gas washing facilities.
(33) SYNTHETIC PLASTIC MANUFACTURING
(a) condensation reactor,
(b) water washing facilities,
(c) centrifugal decanter,
(d) settling facilities,
(e) cooling gas washer and still (fluorides plastics),
(f) diluent still (polypropylene),
(g) diluent still (polyethylene),
(h) acid and alkali treatment facilities (polybutane),
(i) waste gas washing facilities,
(j) wet dust collector.
(34) SYNTHETIC RUBBER MANUFACTURING
(a) filtration facilities,
(b) dehydration facilities,
(c) washing facilities,
(d) latex concentration facilities,
(e) sedimentation facilities (styrene-butadiene,nitrile-
butadiene and polybutadiene-gum).
(35) ORGANIC GUM CHEMICALS MANUFACTURING
(a) distilation facilities,
(b) waste gas washing facilities,
(c) wet dust collector.
(36) SYNTHETIC DETERGENT MANUFACTURING
(a) acid washing and separating facilities,
(b) waste gas washing facilities,
(c) wet dust collector.
(37) PETROCHEMICAL INDUSTRIES (CARBOHYDRATE AND ITS DERIVATIVES)
EXCLUDING ITEMS FROM 31 TO 36 AND 51
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(a) washing facilities,
(b) separation facilities,
(c) filtration facilities,
(d) distilation and rapid cooling facilities (acrylo-
nitrile),
(e) distilation facilities (acetoaldehyde, acetone,
terephthalic acid and tolylene diamine),
(f) acid and alkali tratment facilities (alkylbenzene),
(g) distilation facilities and sulphuric acid concentr-
ation facilities (isopropyl alcohol),
(h) distilation and condensation reactor (ethylene
oxide or ethylene glycol),
(i) condensation reactor and distilation facilities
(2-ethyl hexyl alcohol or isobutyl alcohol),
(j) acid and alkali treatment facilities (cyclohexane),
(k) gas cooling and washing facilities (phthalic
anhydride),
(1) acid or alkali treatment facilities and methyl-
alcohol distilation facilities (normal paraffin),
(m) saponification facilities (propylene oxide or
propylene glycol),
(n) steam condenser (methylethyl ketone)
(o) reactor and methyl alcohol recovery facilities
(methyl-meta-acrylate monomer),
(p) waste gas washing facilities.
(38) SOAP MANUFACTURING
(a) initial preparation facilities,
(b) salting out facilities.
(39) HYDROGENATED OIL MANUFACTURING
(a) alkali conditioning facilities,
(b) deodorisation facilities.
(40) FATTY ACIDS MANUFACTURING
distilation facilities
(41) PERFUMERY MANUFACTURING
(a) washing facilities,
(b) extraxion facilities.
(42) GELATINE AND GLUE MANUFACTURING
(a) initial preparation facilities,
(b) lime soaking facilities,
(c) washing facilities.
(43) PHOTO SENSITIVE GOODS MANUFACTURING
washing facilities
(44) NATURAL RESIN MANUFACTURING
(a) initial preparation facilities,
(b) dehydration facilities.
(45) WOODS CHEMICAL MANUFACTURING
furfural distilation facilities
(46) ORGANIC CHEMICALS MANUFACTURING EXCLUDING ITEMS FROM 28
TO 45
(a) water washing facilities,
(b) filtration facilities,
(c) concentrator (hydrazine),
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(d) waste gas washing facilities.
(47) PHARMACEUTICAL MANUFACTURING
(a) initial preparation facilities,
(b) filtration facilities,
(c) separation facilities,
(d) mixing facilities,
(e) waste gas washing facilities.
(48) GUNPOWDER MANUFACTURING
washing facilities
(49) PESTICIDES MANUFACTURING
mixing facilities
(50) REAGENT MANUFACTURING
processing facilities
(51) OIL REFINING INDUSTRY
(a) desalting facilities,
(b) crude petroleum distilation facilities,
(c) desulfurisation facilities,
(d) washing facilities (volatile oil, kerosene or
gasoline),
(e) lubricant washing facilities.
(52) LEATHER MANUFACTURING
(a) washing facilities,
(b) lime soaking facilities,
(c) tannin soaking facilities,
(d) chrome bathing facilities,
(e) dyeing facilities.
(53) GLASS MANUFACTURING
(a) grinding and washing facilities,
(b) waste gas washing facilities.
(54) CEMENT PRODUCTS MANUFACTURING
(a) centrifuger,
(b) moulding facilities,
(c) wet curing facilities (including steam curing
facilities).
(55) READY-MIXED CONCRETE MANUFACTURING
batcher plant
(56) ORGANIC SAND BOARD MANUFACTURING
mixing facilities
(57) SYNTHETIC BLACK LEAD ELECTRODE MANUFACTURING
shaping facilities
(58) RAW POTTERY MATERIALS MANUFACTURING
(a) water jet crusher,
(b) separation facilities,
(c) acid treatment facilities,
(d) dehydration facilities.
(59) MACADAM QUARRYING
(a) water jet crusher,
(b) separation facilities.
(60) GRAVEL QUARRYING
separation facilities
(61) STEEL INDUSTRY
(a) tar and gas separation facilities,
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(b) gas cooling and washing facilities,
(c) rolling facilities,
(d) hardening facilities,
(e) wet dust collector
(62) NONFERREOUS METALS MANUFACTURING
(a) reduction basins,
(b) electrolysis facilities,
(c) hardening facilities,
(d) mercury refinery facilities,
(e) waste gas washing facilities,
(f) wet dust collector.
(63) METALIC GOODS MANUFACTURING AND MACHINERY INDUSTRY
(a) hardening facilities,
(b) surface treatment facilities (electrolysis)
(c) cadmium electrode and lead electrode processing
facilities,
(d) mercury refining facilities,
(e) waste gas washing facilities.
(64) TOWN GAS AND COKE MANUFACTURING
(a) coal-tar and gas-liquid separating facilities,
(b) gas cooling and washing facilities (including
desulfurisation facilities).
(64)-2 DOMESTIC AND INDUSTRIAL WATER SUPPLY
(a) sedimentation facilities,
(b) filtration facilities.
(65) METAL FINISHING INDUSTRY
acid and alkali treatment facilities
(66) ELECTRO-PLATING INDUSTRY
electro-plating facilities
(66)-2 LODGING SERVICE (defined by the provision of paragraph 1
of Article 2 of the Lodging Service Law, excluding board-
ing house service)
(a) cooking facilities,
(b) washing facilities,
(c) bathing facilities.
(67) LAUNDRY
washing facilities
(68) PHOTO DEVELOPING
automatically developing and washing facilities of
film
(69) SLAUGHTER HOUSE
(69)-2 CENTRAL WHOLESALE MARKET OF AQUATIC PRODUCTS
(a) market yard,
(b) intermediate market yard.
(70) WASTE OIL TREATMENT FACILITIES
(71) AUTOMATICALLY WASHING FACILITIES OF CAR
(71)-2 RESEARCH, DETERMINATION, MEASUREMENT OR PROFESSIONAL
EDUCATION FOR SCIENCE AND TECHNOLOGY (excluding human
science)
(a) washing facilities,
(b) hardening facilities.
(72) NIGHT SOIL TREATMENT PLANT (more than 501 population
served)
(73) SEWAGE TREATMENT PLANT
(74) WASTE WATER TREATMENT PLANT (excluding items 72 and 73)
277
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CHAPTER 2
INSTITUTIONAL STRUCTURES
OF WATER POLLUTION CONTROL IN JAPAN
1. Introduction 279
2. Water Pollution Control and Sewerage Administration 280
2.1 Basic Course of Water Pollution Control 280
2.2 Basic Law Against Public Hazard 282
2.2.1 Definition of Public Hazard 282
2.2.2 Basic Policies on Public Hazard Prevention 282
2.3 Water Pollution Prevention Law 288
2.3.1 Object of Discharged Wastewater Control 288
2.3.2 Effluent Standard 288
2.4 Sewerage Law 290
2.4.1 Comprehensive Basin-wide Sewerage Study Program 290
2.4.2 Use of Public Sewerage 290
2.4.3 Management of Public Sewerage 291
2.5 Pollution Load Control System 293
2.5.1 Background of Introducing Pollution Load Control
System 293
2.5.2 Outline of Pollution Load Control System 294
2.5.3 Enforcement of Pollution Load Control and Responsibility
of Sewerage 296
Conclusion 299
278
-------
1. INTRODUCTION
The history of water pollution control in Japan is exceedingly short.
The beginning of public hazard caused by water pollution runs back to the "Ashio
Copper Mine Pollution Incident" of 1880 and problems had already originated
prior to World War II, however, water pollution has gradually expanded since then
into various aspects with the development of postwar industries and concentration
of population into cities. In 1949, the Public Hazard Ordinance of Tokyo Metro-
polis was instituted and this gradually spreaded into various cities. In March 1951,
a recommendation on water pollution prevention was also made by the Government,
however, it did not result in legislation.
In June 10th of 1957, a dispute originated between the fihsermen and the
Honshu Paper Mfg. Co., Ltd. (Honshu Paper Mfg. Co. Incident) due to numerous
fishes being killed in the Edo river (Tokyo) and with this as the momentum, the
Government finally enacted two Laws (Water Quality Preservation Law and
Industrial Wastewater Control Law) in September of 1958. However, there existed
several defects in these Laws. For example, it was an ex post facto control in which
the discharged water quality standard was established by specifying the water body
where water pollution originated, compulsory observance of the effluent standard
were based on the Industrial Wastewater Control Law and other ten laws, actions
taken against violators of the effluent standard were light, etc.
On the other hand, a designated area was established based on Water Quality
Preservation Law for rivers as seen in large cities which were polluted by both
the industrial wastewater and the domestic sewage and a policy for providing
sewerage, etc. by setting the period was formulated. This policy was called the Urban
River System and the obligation of discharging favorably treated water by construct-
ing sewage treatment plants within the designated period originated. This was an
epochal way of doing for sewerage administration and resultantly, it came to place
sewerage in a position of not being merely a facility for improving the living
environment but also a facility for controlling the water pollution of public water
bodies such as rivers, etc.
The Basic Law Against Public Hazard was enacted in 1967 and the Environ-
mental Standard to be established. Moreover, in 1970, the enactment, alteration
and abolition of various Laws related to public hazard were made and the Water
Pollution Prevention Law was newly established in place of the conventional Water
Quality Preservation Law and the Industrial Wastewater Control Law. Furthermore,
the Sewerage Law was also revised for enabling the sewerage to sufficiently serve its
role as a water pollution control facility.
By factors such as the establishment of environmental water quality standards
based on the Basic Law Against Public Hazard, and designation of the sewage
treatment plant as a specified facility under the Water Pollution Prevention Law
and its being subjected to the application of the effluent standard, etc., the role and
responsibility achieved on water pollution control by sewerage have also been clari-
fied from the point of legislation.
279
-------
Furthermore, a pollution load control system is to be newly introduced in
addition to the conventional concentration control system for conducting a more
effective water pollution prevention of closed water bodies such as the Seto Inland
Sea, Tokyo Bay, Ise Bay, etc. For this purpose, the Water Pollution Prevention Law
was revised in June this year and the provision of sewerage came to be placed in a
position where its materialization is the key which controls the success or failure of
this system.
Now, we wish to observe mainly from the standpoint of sewerage administra-
tion the institutional structures of water pollution control in Japan which has
pursued the above-mentioned circumstances and arrived at its condition of today.
2. WATER POLLUTION CONTROL AND SEWERAGE ADMINISTRATION
2.1 BASIC COURSE OF WATER POLLUTION CONTROL
The basic course of water pollution control lies in performing the various
policies necessary for achieving and maintaining the environmental water quality
standard which has been established based on the Basic Law Against Public Hazard
as a goal. Among these policies, the following two constitute the most important
elements.
(1) Control of discharged wastewater into public water bodies by the Water Pollu-
tion Prevention Law.
(2) Expansion of sewerage and sewage treatment facilities.
Firstly, we will relate on the entire institutional framework of water pollution
control and survey the position where sewerage administration is situated within the
framework.
280
-------
Table-2.1 Institutional Structures of Water Pollution Control
1
t Public
as
1
«
Water Pollution Prevention Law
,3
u
Si
Contents of Water Pollution Control
Environmental Water r-Environmental standard concerning human
Quality Standard ~\ health
'-Environmental standard on living environment
Public Hazard
Prevention Plan
Control of
wastewater
Supervision of
water pollution
condition
Comprehensive
age Study Program
' Designation of the type of water body
E Instruction of basic policy
Preparation of plan
Approval of plan
- Effluent standard
~
-Pollution load
control
-Supervision of
factories, etc.
E Uniform standard
Severer standard
Additional standard
-Basic policy for pol-
lution load reduction
-Plan for pollution load
reduction
Standard for pollution
load control
pNotification on estab-
lishment and changes
of specified facilities
-Alteration order of plan
-Improvement order
Report and inspection
-Constant supervision
-Preparation of measuring plan
-Preparation of plan
-Approval of plan
Construction and j-Public sewerage
SE5Tt0f LRegional sewerage
Compulsory use of pObligation for providing drainage equipment
public sewerage [-obligation for remodelling into a flush toilet
Control of industrial
wastewater ~~
-Notification on establishment and changes of
specified facilities
-Alteration order of plan
-Obligation for equipping pretreatment facilities
—Improvement order
-Report and inspection
Responsible Person
National government
National government
Prefectural Governor (National
government is responsible for
interprefectural bodies)
Prime Minister — ^Governor
Governor
Prime Minister
National government
Prefectural government
Prefectural and local government
Prime Minister
Governor
Governor
Dischargers ^-Governor
Governor
Governor
Governor
Governor
Governor
Governor
Minister of Construction (Con-
sult with the Minister of the
Environment Agency)
Municipalities
Prefectural government
Users, etc.
Users
To sewerage superintendent
Sewerage superintendent
Users
Sewerage superintendent
Sewerage superintendent
Other Related Laws:
o Ocean Pollution Prevention Law o River Law o Mining Safety Law o Natural Park Law o Coal Washing
Industry Law o Harbor Regulations Law o Marine Resources Protection Law o Scraps and Wastes Disposal
& Cleaning Law o Poisonous Substances and Powerful Drugs Control Law o Agricultural Medicines Control
Law o Pollution Prevention Law of Land for Agricultural Use o Public Hazard Disputes Disposition Law
o Law for Compensating Health Harms by Public Hazard o Law on Enterpriser's Burden for Public Hazard Pre-
vention Expenses o Public Hazard Prevention Agency Lawo Public Hazard Crime Punishment Law
281
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2.2 BASIC LAW AGAINST PUBLIC HAZARD
The Basic Law Against Public Hazard has been enacted for the purpose of
protecting the health of the people and preserving the integrity of living environ-
ments, and together with clarifying the obligations of the enterpriser, national and
local government on public hazard prevention, this law is for plotting the compre-
hensive promotion of public hazard policy by establishing matters which become
basis of policies on public hazard prevention (Article 1 of the Law).
2.2.1 Definition of Public Hazard
Public hazard referred to the Law means the origination of harms affecting
the health of people or living environments by air pollution, water pollution, soil
pollution, noises, vibrations, sinking of ground and odors which are caused by
industrial activities or other activities of people (Article 2 of the Law).
2.2.2 Basic Policies on Public Hazard Prevention
a. Environmental Standard
In regards to the environmental standard on air pollution, water pollution, soil
pollution and noises, it has been decided to establish a standard which is desirable
for maintaining in protecting the health of the people and preserving the integrity of
the living environment (Article 9 of the Law).
The Environmental Water Quality Standard was decided upon by the Cabinet
in April 21, 1971 and its notification issued in December 26, 1971. In this Standard,
there are both the environmental standard on the protection of people's health and
the environmental standard on the preservation of integrity of living environments
(See Tables 2.2 and 2.3). In the former standard, an uniform standard is established
for all public water bodies on health affecting items such as cadmium, mercury, etc.
In the latter standard, a standard is established for each type of public water body
on environmental items such as pH, BOD, etc., and the designation of the type of
water bodies to which each public water body corresponds is made by the Minister
of the Environment Agency (With the exception of interprefectural public water
bodies, entrusted to prefectural governors).
Table-2.2 Environmental Standard Concerning People's Health
Item
Standard
value
Cyanide
Not to
be de-
tec ted
Alkyl-
meicury
Not to
be de-
tected
Organic
phosphorus
Not to be
detected
Cadmium
Less than
0.01 ppm
Lead
Less
than
0.1
ppm
Sexi-
valent
chrome
Less
than
0.05
ppm
Arse-
nic
Less
than
0.05
ppm
Total
mercury
Less
than
0.0005
Ppm
PCB
Not to
be de-
tected
282
-------
Table-2.3 Environmental Standard Concerning Living Environment
(1) Rivers
\ Item
\
Type\
classi- \
fication \
AA
B
C
Adaptability of
purpose of use
First class waterworks
Preservation of natural
environment and those
listed in columns
below A
Second class waterworks
First class fisheries
Bathing and those listed
in column below B
Third class waterworks
Second class fisheries
and those listed in
columns below C
Third class fisheries
First class industrial
water and those listed
in columns below D
Second class industrial
water
Agricultural water and
those listed in column
E
Third class industrial
water
Environmental preser-
vation
Standard Value
Hydrogen
ion con-
centration
(pH)
More than
6.5 and
less than
More than
6.5
Less than
8.5
More than
6.5 and
less than
8.5
More than
6.5 and
less than
8 <;
More than
6.0 and
8 <;
More than
6.0 and
less than
8.5
Biochemical
oxygen de-
mand
(BOD)
Less than
1 ppm
Less than
2 ppm
Less than
3 ppm
Less than
5 ppm
Less than
8 ppm
Less than
10 ppm
Suspended
solids
(SS)
Less than
25 ppm
Less than
25 ppm
Less than
25 ppm
Less than
50 ppm
Less than
100 ppm
Suspension
of dusts,
etc., not to
be detected
Dissolved
oxygen
(DO)
More than
7.5 ppm
More than
7.5 ppm
More than
5 ppm
More than
2 ppm
More than
2 ppm
More than
2 ppm
No. of
coliform
group
Less than
50MPN/
100ml
Less than
1,000
MPN/100
ml
Less than
5,000
MPN/100
ml
_
_
-
(Notes): 1. Preservation of natural
environment
2. First class waterworks
Second class water-
works
Third class waterworks
3. First class fisheries
Second class fisheries
Third class fisheries
4. First class industrial
water
Second class industrial
water
Third class industrial
water
5. Environment preser-
vation
Preservation of environments of natural sight-seeing sceneries, etc.
Those performing simple purification operations by means of filtration, etc.
Those performing normal purification operations of settling and filtration, etc.
Those performing high-degree purification operations which accompany pre-treatment, etc.
Those for marine creatures in water body of oligosaprobien such as trout and char, and
those for marine creatures of Second and Third class fisheries.
Those for marine creatures in water body of oligosaprobien such as the Oncorhynchus
genus, sweetfish, etc., ari3 those for marine creatures of Third class fisheries.
Those for marine creatures in water basin of p-mesosaprobiens such as carp, roach, etc.
Those performing normal purification operations by sedimentation, etc.
Those performing high-degree purification operations by adding chemicals, etc.
Those performing special purification operations.
Limit which does not originate an unpleasant impression in the daily life of the people
(including strolls at coast).
283
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(2) Lakes & Marshes (Natural lakes & marshes and artificial lakes with a reservoir capacity of more than 10
million cubic meters
\^ Item
TypeX
classi-X
ficationX
AA
A
c
Adaptability of
purpose use
First class waterworks,
First class fisheries
Natural environment
preservation and those
listed in columns
below A
Second and third class
waterworks
Second class fisheries
Bathing and those listed
in columns below B
Third class fisheries
First class industrial
water
Agricultural water
and those listed in
column C
Second class industrial
water
Environmental preser-
vation
Standard Value
Hydrogen
ion con-
centration
(pH)
More than
6.5 and
less than
8 ^
o.o
More than
6.5 and
8.5
More than
6.5 and
less than
8.5
More than
6.0 and
less than
8.5
Chemical oxy-
gen demand
(COD)
Less than
1 ppm
Less than
3 ppm
Less than
5 ppm
Less than
8 ppm
Suspended
solids
(SS)
Less than
1 ppm
Less than
5 ppm
Less than
15 ppm
Suspension
of dusts,
etc., not to
be detected
Dissolved
oxygen
(DO)
More than
7.5 ppm
More than
7.5 ppm
More than
5 ppm
More than
2 ppm
No. of
coliform
group
Less than
50MPN/
100ml
Less than
1,000
MPN/100
ml
(Notes): 1. Natural environment
preservation
2. First class waterworks
Sedond and third class
waterworks
3. First class fisheries
Second class fisheries
Third class fisheries
4. First class industrial
water
Second class industrial
water
5. Environmental preser-
vation
Preservation of environments of natural sight-seeing sceneries, etc.
Those performing simple purification operations by means of filtration, etc.
Those performing normal purification operations by settling and filtration, etc., or those
performing high-degree purification operations which accompany pre-treatment, etc.
Those for marine creatures in water basin of poor nutrition type lakes such as trout, etc.,
and those for marine creatures of second and third class fisheries.
Those for marine creatures in water basin of poor nutrition type lakes such as the
Oncorhynchus genus, sweetfish, etc., and those for marine creatures of third class fisheries.
Those for marine creatures such as carp, char, etc., in water basin of rich nutrition type
lakes.
Those performing normal purification operations by sedimentation, etc.
Those performing high-degree purification operations by adding chemicals,etc., or those
performing special purification operations.
Limit which does not originate an unpleasant impression in the daily life of people (including
strolls at coast).
284
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(3) Seas
\ Item
Typ\
classi- \
ficationX
A
B
C
Adaptability of
purpose use
First class fisheries,
Bathing and those listed
in columns below B
Second class fisheries,
Industrial water and
those listed in column
C
Environmental preser-
vation
Standard Value
Hydrogen
ion con-
centration
(pH)
More than
7.8 and
less than
8.3
More than
7.8 and
less than
8.3
More than
7.0 and
less than
8.3
Chemical
oxygen de-
mand
(COD)
Less than
2 ppm
Less than
3 ppm
Less than
8 ppm
Dissolved
oxygen
(DO)
More than
7.5 ppm
More than
5 ppm
More than
2 ppm
No. of
coliform
group
Less than
1,000
MPN/
100ml
N-hexane
extraction
(Oily mat-
ters)
Not to be
detected
Not to be
detected
(Notes): 1. First class fisheries
Second class fisheries
2. Environmental preser-
vation
Those for marine creature? such as red sea-bream, yellow-tail, Wakame seaweed, etc., and
those for marine creatures of second class fisheries.
Those for marine creatures such as gray mullet, laver, etc.
Limit which does not originate an unpleasant impression in the daily life of people (including
strolls at coast).
b. Policies for Achieving and Maintaining the Environmental Standard
The following policies to be performed by the national and local government
are established.
Control on discharged wastewater, etc. (Article 10 of the Law), Control on
land use and establishment of facilities (Article 11), Promotion of providing facilities
(sewerage, etc.) on public hazard prevention (Article 12), Consolidation of super-
vision and measurement setup (Article 13), Execution of investigations (Article 14),
Furtherance of scientific techniques (Article 15), Diffusion of knowledge (Article
16), and Considerations of public hazard prevention in regional development policies
and protection of natural environment (Section 2 of Article 17).
c. Public Hazard Prevention Plan
The Public Hazard Prevention Plan is a plan concerning policies for public
hazard prevention which is carried out systematically and collectively in specific
areas where public hazards are concentrated. Areas where the public hazard preven-
tion plan is schemed are areas where public hazards are presently extreme or where
there lies a fear of public hazards becoming conspicuous due to the rapid concen-
tration of population and industries and unless policies on public hazard prevention
are collectively adopted, it would become extremely difficult to attain public hazard
prevention. The proceedings on plan scheming are that the Prime Minister decides
the area, indicates the basic policy and instructs the scheming of the plan to the
concerned Governor after listening to the opinions of the prefectural Governor, and
then the concerned Governor prepares the plan and receives the approval of the
Prime Minister (Article 19 of the Law).
285
-------
In the Public Hazard Prevention Plan, the goal is placed on environmental
standard, the discharge control methods necessary for achieving the environmental
standard'within the stipulated period of 5 - 10 years are indicated and the required
amount of public hazard elimination facilities such as sewerage, etc. is estimated as
the bases of the plan. On water pollution, it is impossible to attain the target of the
plan by merely controlling the discharges of wastewater as the pollution load dis-
charged from general households also occupies a considerable percentage. Thus, the
construction of a considerable amount of sewerage facilities is required. The total
amount of necessary public investments is listed in the Public Hazard Prevention
Plan, however, more than 70% of the total amount is for sewerage construction
expenses.
Table-2.4 Actual Conditions of Public Hazard Prevention Plan
Area
classifica-
tion
First
area
Second
area
Third
area
Fourth
area
Name of area
Chiba. Ichihara area
Yokkaichi area
Mizushima area
Tokyo area
Kanagawa area
Osaka area
Chiba Prefecture,
Edo River drainage
basin
Saitama Prefecture,
Ara River system
drainage basin
Kyoto Prefecture,
Yodo River drainage
basin
Nara Prefecture,
Yamato River drain-
age basin
Kashima area
Nagoya, etc., area
Hyogo Prefecture,
Eastern area
Kita-Kyushu area
Oita area
Fuji area
Harima southern area
Otake area
Iwakuni area
Omuta area
Saitama area
Term for
accomplishment
To be included in
Chiba littoral
districts and re-
considered
1977 (4 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
To be included in
Chiba littoral
districts and re-
considered
1981 (5 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
1981 (5 years)
1977 (5 years)
1977 (5 years)
1977 (5 years)
1977 (5 years)
1977 (5 years)
L1984 (9 years)
Expenses for
public hazard
policy (Unit:
100 million
yen)
230
220
22,290
11,120
11,520
4,390
3,580
1,750
190
4,290
3,380
1,830
400
190
1,100
140
130
130
(340)
Plan for sewerage
Served
population
(Unit: 1000
persons)
69
106
8,661
3,380
5,581
1,622
1,213
342
18
2,040
1,433
820
142
154
544
37
44
32
-
Served area
(ha)
1,093
662
66,047
29,885
42,826
25,433
10,074
4,846
2,250
23,196
13,118
8,800
1,305
1,136
5,836
470
473
373
-
286
-------
Table-2.4 Actual Conditions of Public Hazard Prevention Plan (Continued)
Area
classifica-
tion
Fifth
area
Sixth
area
Seventh
area
Name of area
Tomakomai area
Sendai Bay area
Iwaki area
Chiba littoral districts
Toyama, Takaoka area
Koromoura vicinity
area
Kobe area
Bingo area
Shunan area
Toyo area
Muroran area
Hachinohe area
Niigata area
Shizuoka, Shimizu
area
Hiroshima, Kure area
Shimonoseki, Ube area
Kagawa area
Wakayama area
Okayama, Bizen area
Sapporo area
Akita area
Hitachi area
Matsumoto, Suwa
area
East Mikawa area
Gifu, Ogaki area
East Nomi area
Tokushima area
Hiyuga, Nobeoka
area
Term for
accomplishment
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1978 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1979 (5 years)
1980 (5 years)
1980 (5 years)
Expenses for
public hazard
policy (Unit:
100 million
yen)
170
810
820
3,500
450
1,430
1,550
830
490
290
120
230
440
223
990
280
370
290
370
2,050
390
180
320
770
550
120
220
70
Plan for sewerage
Served
population
(Unit: 1000
persons
140
588
124
1,460
211
319
1,552
336
164
79
114
20
142
200
394
167
182
45
200
1,303
190
94
190
434
497
44
87
63
Served area
(ha)
1,751
7,507
1,595
14,196
2,170
11,664
10,780
3,477
1,897
1,378
1,054
273
1,397
1,232
3,148
1,550
1,925
530
1,849
16,285
766
1,397
830
3,209
3,406
331
697
429
Note): The expenses for the Public Hazard Policy is the total expenses which includes the sewerage
construction costs.
Furthermore, on public hazard prevention projects which are based on
this plan, a subsidy of a higher percentage than same projects in other areas is
generally made pursuant to the "Law Concerning the Special Financial
Measures by National Government for Projects on Public Hazard Prevention".
287
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2.3 WATER POLLUTION PREVENTION LAW
The Water Pollution Prevention Law contrives to prevent public water bodies
from pollution by controlling discharged wastewater from factories and the like
and preserves the living environment as well as protecting the health of people, and
aims at promoting the protection of victims by providing the responsibility of
the enterpriser's indemnification for damages caused in the case that damages
originate on the health of the people by wastewater which are discharged from
factories and the like (Article 1 of Water Pollution Prevention Law).
The control of discharged wastewater under the Water Pollution Prevention
Law plots the water pollution control of public water bodies by making the factories
and the like to be provided with specified facilities in discharging wastewater into
public water bodies report on their provision of such specified facilities and whenever
necessary, together with issuing a plan alteration order and having the wastewater
treatment setup consolidated, and assigning the obligation of observing the effluent
standard and applying the penal regulations when there lies a fear of violating the
effluent standard.
2.3.1 Object of Discharged Wastewater Control
The "Discharged Wastewater" which becomes the object of control under the
Water Pollution Prevention Law refers to the water discharged into public water
bodies from factories or the like (specified works) which are provided with specified
facilities (Article 2, Section 3 of Water Pollution Prevention Law).
"Specified Facilities" refers to facilities discharging waste waters which contain
substances such as cadmium and the like affecting health or facilities discharging
wastewater to the extent where there lies a fear of damages affecting living environ-
ments originating on items indicating the water pollution condition such as pH,
BOD, etc., and it is concretely specified in the Government Ordinance. A sewage
treatment facility also corresponds to the specified facilities.
2.3.2 Effluent Standard
The effluent standard is the tolerance limit stipulated for each item on the
polluted condition of the discharged wastewater and is classified into the uniform
standard and the severer standard.
a. Uniform Standard
The uniform standard is decided by the Ordinance of the Prime Minister's
Office and there are the "General Standard" and the "Provisional Standard". The
General Standard is a standard which is applied uniformly for all public water bodies
and for all specified works, however, the Provisional Standard is a tentative and
lenient standard which is applicable for the restricted 5 years period from June 24,
1976 in place of the General Standard of environmental items and is provided for
several specific industrial classifications.
288
-------
Table-2.5 Uniform Standard
(1) Items Concerning Health Protection of People
Item
Standard
value
Cyanide
Max.
1 ppm
Alkyl-
mercury
Not to
be de-
tected
Oiganic
phosphorus
Max. 1 ppm
Cadmium
Max. 0.1
ppm
Lead
Max.
1
ppm
Sexi-
valent
chrome
Max.
0.5 ppm
Arse-
nic
Max.
0.5
ppm
Total
mercury
Max.
0.005
ppm
PCB
Max.
0.003
ppm
(2) Items Concerning Preservation of Living Environments (General Items)
Item
Standard
value
pH
Rivers, lakes
& marshes
5.8 -8.6
Seas
5-9
BOD
Average
daily
120
ppm
Max.
160
ppm
COD
Average
daily
120
ppm
Max.
160
ppm
SS
Average
daily
150
ppm
Max.
200
ppm
Remarks: 1. This standard shall be applied to factories or the like of generally more than
50m3 of discharged wastewater per day. •.
2. The standard of COD shall not be applicable to factories or the like discharging
water into rivers and the standard of BOD shall not be applicable to those dis-
charging water into lakes, marshes and seas.
3. The standard of pH shall not be applicable for the sulphur mining industry (in-
cluding pyrrhotite mining industry which coexists with sulphur).
(3) Items Concerning Preservation of Living Environments (Special Items)
Item
Standard
value
Oily matters
(n-hexane
extraction)
Petro-
leum
group
oily
matter
Max.
5 ppm
Animal
& plant
oils and
fats, etc.
Max.
30 ppm
Phenol
Max.
5 ppm
Copper
Max.
3 ppm
Zinc
Max.
5
ppm
Iron
(Soluble)
Max.
10 ppm
Manga-
nese
(Soluble)
Max.
10 ppm
Chrome
Max.
2 ppm
Fluo-
rine
Max.
15
ppm
No. of
coliform
group
Average
daily
3000/
cm3
Remarks: 1. This standard shall be applied to factories or the like of generally more than
50m 3 of discharged wastewater per day.
2. The standard on iron (soluble) shall not be applicable for the sulphur mining
industry (including pyrrhotite mining industry which coexists with sulphur).
b. Severer Standard
In case that a section which can be recognized as insufficient for protecting
the health of people or for preserving the living environments under the uniform
standard exists in public water water bodies within the territory of prefecture con-
cerned, judging from natural and social conditions, the competent prefecture may
stipulate by Ordinance a severer effluent standard up to the extent that is required
and sufficient for maintaining the environmental water quality standard, for the
discharged wastewater in that section (Article 3 Section 3 of Water Pollution Preven-
tion Law). This standard is called the "Severer Standard".
Since the Severer Standard stipulates a tolerance limit which is severer than the
tolerance limit stipulated in the Uniform Standard, its objective substances and
items shall be limited to substances and items that are the objects under the Uniform
Standard. Discharge control on others besides the objective substances and items
289
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under the Uniform Standard (Additional Control) and discharge control of dis-
charged wastewater from factories or the like other than the specified works (Ex-
tended Control) can be stipulated by the Ordinance of local government according
to Article 29 of the Water Pollution Prevention Law.
2.4 SEWERAGE LAW
The Sewerage Law stipulates the matters concerning the Comprehensive Basin-
wide Sewerage Study Program and standards for the establishement and management
of public sewerage, regional sewerage and urban storm water channel for promoting
sewerage works, and aims at contributing to the sound development and improve-
ment of public health of cities and at the same time, contributing to the water
pollution control of public water bodies (Article 1 of Sewerage Law).
2.4.1 Comprehensive Basin-wide Sewerage Study Program
Among public water bodies with a environmental standard, for water bodies
which produce water pollution by wastewater from more than two municipalities
districts and which can be considered necessary to achieve the environmental water
quality standard by mainly providing sewerage, the prefectural government must
prepare the Comprehensive Basin-wide Sewerage Study Program (Article 2, Item 2
of Sewerage Law).
In this Program, stipulations must be made for the basic policy for providing
sewerage, the area where the sewage should be collected and treated, arrangement,
structure and capacity of basic facilities of sewerage and the executing ranking of
sewerage projects, by taking into consideration the natural conditions of the
competent area, outlook on quantity and quality of wastewater, cost effectiveness
analysis of expenditures for sewerage, etc. The Comprehensive Basin-wide Sewerage
Study Program is so called an -integrated basic plan for sewerage systems and
individual sewerage project shall be carried out in conformity with this Program
(Article 6, No. 5 and Article 25, Item 5, No. 4 of Sewerage Law).
2.4.2 Use of Public Sewerage
When the use of public sewerage is commenced, the landowner (building
owner in case of building sites, public facility manager in case of public facility
sites) within the drainage district must promptly provide necessary drainage
equipment for allowing the sewage of the land to flow into the public sewerage.
However, even though he may be the responsible person for providing drainage
equipment, connections to public sewerage do not have to be made, upon receiving
the permission by the superintendent of public sewerage when the cooling water,
or the like of the factory conforms to the effluent standard to public water bodies
and is approved that the direct discharge to public water bodies is rational (Article
10, Section 1 of Sewerage Law).
When sewage treatment is commenced by the sewage treatment plant of
public sewerage or by the sewage treatment plant of regional sewerage to which the
290
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competent public sewerage connects, the owner of the building where a non-flush
toilet is provided within the treatment district must remodel the toilet into a flush
toilet within three years from the day of treatment commencement (Article 11,
Item 3, Section 1 of Sewerage Law).
2.4.3 Management of Public Sewerage
a. Water Quality Control of Effluent
It is necessary to appropriately perform water quality control of effluent from
sewerage in order for the sewerage to contribute to the water pollution control of
public water bodies. For this purpose, it is defined in the Sewerage Law that the
quality of effluent from public sewerage or regional sewerage into rivers and other
public water bodies must conform to the technical standards stipulated in Govern-
ment Ordinance (Article 8 of Sewerage Law).
Article 6, Section 1 of the Ordinance stipulates the water quality standard of
effluent for each sewage treatment method (See Table 2.6 below).
Table-2.6 Technical Standard of Water Quality of Effluent
Classification
Activated sludge
process
Low-rate trickling
filter process
or the like
High-rate trickling
filter process
Modified aeration
or the like
Sedimentation
PH
5.8 -8.6
5.8 -8.6
5.8 - 8.6
BOD
(mg/1)
Less
than
20
Less
than
60
Less
than
120
SS
(mg/1)
Less
than
70
Less
than
120
Less
than
150
No. of coli-
form group
Less than
3,000
Less than
3,000
Less than
3,000
Moreover, in Section 2 of Article 6 of the Ordinance, when the effluent stand-
ard based on the stipulation of Article 3 of the Water Pollution Prevention Law (to
include severer standard as well as uniform standard) is severer than this water
quality standard or when the additional standard is stipulated by ordinance of local
government, it is made to treat the effluent standard as the standard of effluent
based on the Sewerage Law.
Generally speaking it can be said that a severer standard than the standard of
the Water Pollution Prevention Law is spontaneously placed-on BOD.
b. Control on Dischargers of Hazardous Wastewater
(i) Control of Discharged Wastewater from Specified Works
Those who discharge wastewater from factories or the like (Special Works)
which are provided with specified facilities under the Water Pollution Preven-
tion Law and use public sewerage must not discharge wastewater which do not
conform to a fixed water quality standard (2 of Article 12 of Sewerage Law).
Panel regulations shall be applicable to violators (2 of Article 46 of Sewerage
Law).
291
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As to the fixed water quality standard, an uniform standard is stipulated
(same as the uniform standard of the Water Pollution Prevention Law) by
Government Ordinance for those difficult to treat at sewage treatment
plants such as cadmium, etc., as health items and zinc, etc., as environment
items, and as to other items such as BOD, etc. which are possible of treating
at sewage treatment plants, stipulations are respectively made by municipal
ordinances according to the standards stipulated by the Government Ordinance.
The standard values for the former health itmes, etc. are the same values
as in the case of direct discharge into public water bodies. Therefore, specified
works will be subjected to an entirely same control on these items as in the case
of discharge into public water bodies.
However, it does not mean that all wastewaters from the specified works
will become objects of immediate punishment, but small amount of wastewater
is excluded. As for the wastewater which is not subjected to immediate
punishment but contains a fear of making water quality of effluent from the
sewerage extremely difficult to conform to the technical standard of Article 8
of the Sewerage Law, the superintendent of public sewerage can obligate the
provision of pretreatment facilities by ordinance (10 of Article 12 of
Sewerage Law). Moreover, the provision of pretreatment facilities can be
obligated by ordinance to those who use public sewerage by continuously
discharging wastewater having the fear of extremely obstructing the functions
of sewerage facilities or damaging facilities (Article 12 of Sewerage Law).
Besides the above, the pre-checking system which requests reporting on
establishment of specified facilities and issues a alteration order of plan when-
ever necessary to specified works that uses public sewerage by discharging
wastewater, and the improvement order system which orders improvement of
structures of specified facilities in case that it is recognized that a fear exists
of discharging wastewater which violates the water quality standard are
stipulated.
(ii) Control of Discharged Wastewater from Non-Specified Works
A direct penalty is not imposed on discharged wastewater from works
other than the specified works. However, when the wastewater with a fear of
extremely obstructing the functions of sewerage facilities or damaging facilities
is discharged, or when the wastewater with a fear of making effluent from
sewerage extremely difficult to conform to the technical standard of Article 8
of the Sewerage Law is discharged, establishment of pretreatment facilities
can be obligated by ordinance (Article 12, 10 of Article 12 of Sewerage Law).
The controls by both Water Pollution Prevention Law and Sewerage Law
are compared and illustrated, as shown in Fig. 2.1.
292
-------
Fig.-2.1 Comparison of Controls by Both Water Pollution Prevention Law and Sewerage Law
When discharged to public water bodies
(Water Pollution Prevention Law)
(1) Establishment of septic tank
(Article 3 of Building Stand-
ard Law)
(2) No particular controls on
water quality
Homes
Non-speci-
fied works
Specified
works
(Specified
facilities)
Water quality control is made
for hospitals, etc. by the Extended
Control (Article 29 of Law)
(a)
(i)
(1) Report on specified facilities
(Article 5 of Law)
Permission system for the
Seto Inland Sea
(Article 5 of Special Measures
Law for the Seto Inland Sea)
(2) Control of water quality
Direct penalty system
(Article 12 of Law)
Uniform standard
(Article 3, Section a of Law)
(ii) Provisional standard
(Attached sheet of supple-
mentary provision of Prime
Minister's Office Ordinance)
(iii) Severer standard
(Article 3, Section 3 of Law)
(b) Plan alteration order system
(Article 8 of Law)
The competent system is not
applicable for the Seto In-
land Sea
((Article 12 of Special Meas-
ures Law for the Seto Inland
Sea)
Improvement order system
(c)
Homes
When discharged to sewerage
(Sewerage Law)
(1) Obligation of providing drain-
age equipment
(Article 10 of Law)
(2) Obligation of remodelling to
flush toilet
(3 of Article 11 of Law)
Non-speci-
fied works
Specified
works
(Specified
facilities)
(Article 13 of Law)|Sewerage tr^ment plant]
(1) Obligation of providing drain-
age equipment
(Article 10 of Law)
(2) Control on damage protec-
tion of sewerage functions
(Establishing pretreatment fa-
cilities (Article 12 of Law)
(3) Water quality control
(Establishing pretreatment fa-
cilities)
(10 of Article 12 of Law)
(1) Obligation of providing drain-
age equipment
(Article 10 of Law)
(2) Report on specified facilities
(3 of Article 12 of Law)
(3) Control on damage protec-
tion of sewerage functions
(Establishing pretreatment fa-
cilities) (Article 12 of Law)
(4) Water quality control
(a) Direct penalty system
(2 of Article 12 of Law)
(i) Standard of government ordi-
nance
(ii) Standard of municipal ordi-
nance
(iii) Provisional standard
(b) Plan alteration order system
(5 of Article 12 of Law)
(c) Improvement order system
(3 of Article 37 of Law)
(d) Control on water quality
which does not become ob-
ject of direct penalty
(Establishing pretreatment fa-
cilities)
(10 of Article 12 of Law)
Sea
Control by Water Pollution Prevention Law
2.5 POLLUTION LOAD CONTROL SYSTEM
2.5.1 Background of Introducing Pollution Load Control System
The recent water pollution conditions of pubb'c water bodies in Japan are
relatively in the trend of improvement, however, water pollution is particularly
conspicuous in widely closed water bodies such as Tokyo Bay, Ise Bay, Seto Inland
Sea, etc. where numerous pollution generating sources concentrate. Thus, the
improvement of water quality in these water bodies has become an urgent problem.
In December last year, a report by the Central Council for Public Hazard
Policy has been made on "the way of pollution load control system" and the follow-
ing has been stated in the report.
"It is essential to reduce in overall the pollution load which affects the water
quality of water bodies. For this purpose, together with making all industrial
293
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wastewater and domestic sewage as objects, it is necessary to direct attention
to the establishment of a comprehensive water pollution control policy which
also includes pollution loads from the so-called internal production and non-
point pollution sources."
In other words, for the water quality improvement policy of closed water
bodies, it has been emphasized that it is necessary to collectively carry out the
reduction policy of pollution load from non-point pollution sources as well as from
point sources and the policy for nutritive salts in the water bodies.
Amid such a background, the "Amendment of Seto Inland Sea Environment
Preservation Extraordinary Measures Law and the Water Pollution Prevention Law"
was promulgated on June 13 this year and is subjected to enforcement within a year.
These Laws constitute a portion of the water pollution prevention policy in widely
closed water bodies such as the Seto Inland Sea, etc., and the contents consist of
institutionalizing the pollution load control on point pollution sources of industrial
wastewaters, sewerages, etc. which flow into these water bodies, preparation of
recommended guideline for reducing designated substances such as phosphorus, etc.
in the Seto Inland Sea and other matters.
2.5.2 Outline of Pollution Load Control System
The main points of the Pollution Load Control System are as follows.
(1) For preventing water pollution in widely closed water bodies recognized as
being difficult to maintain the environmental water quality standard under the
present effluent standard only, the Prime Minister shall decide the basic policy
on pollution load reduction (Basic Policy for Pollution Load Reduction) on
districts related to water pollution (designated districts) of water bodies speci-
fied according to chemical oxygen demand (COD) and other designated items
(designated water bodies).
(2) The Prefectural Governor must decide the plan for achieving the reduction goal
(Pollution Load Reduction Plan) based on the above-mentioned Basic Policy
for Pollution Load Reduction.
(3) The Prefectural Governor must decide the Pollution Load Control Standard
based on the Pollution Load Reduction Plan for the discharged wastewater
from a specified works which is above a fixed scale within the designated
district (works within designated district).
(4) The Prefectural Governor shall be able to order measures for improvement,
etc. of wastewater treatment methods when a fear exists of discharged waste-
water not conforming to the Pollution Load Control Standard.
(5) The Prefectural Governor shall be able to give guidance, advice and counsel
which are necessary for reducing the pollution load to dischargers other than
"the works within designated district" for accomplishing the Pollution Load
Reduction Plan.
(6) Persons discharging water from "the works within designated district" must
measure the pollution load and record the results.
The above is the gist of the law revision on the Pollution Load Control System,
and the Seto Inland Sea, Tokyo Bay and Ise Bay are expected to be the "designated
294
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water bodies" which are subjected to pollution load control. The "designated item"
which becomes the object of control is only COD for the time being.
In the "Basic Policy for Pollution Load Reduction", the following are to be
decided.
Fig.-2.2 Flowchart of Pollution Load Control
Designated Items
o COD, etc. (Designated by
Government Ordinance)
Listening opinions •
Designated Water Bodies
o Specific widely closed water bodies
(Designated by Government Ordinance)
Designated Districts
o Districts as a rule possessing pollution sources which flow into
designated water bodies. (Designated by Government Ordinance)
Public Hazard Policy
'
"(After deliberation
- Listening opinions
Notice
Basic Policy for Pollution Load Reduction
° Prime Minister decides for each designated water bodies.
° Establish the goal within the actually possible range
(The concrete method shall be indicated by Government Ordinance.)
(Contents of Policy)
(1) Reduction goal for each pollution sources in designated water bodies.
(2) Allocation of reduction goal to related prefectures.
(3) Basic matters of Pollution Load Reduction (a. Industry b. Domestic c. Others)
(4) Target year
After deliberation
Approval
Related Municipalities
Listening opinion—1
Pollution Load Reduction Plan
(Prepared by Governor of each prefecture)
(Contents of Plan)
(1) Reduction goal for each pollution sources (a. Industry b. Domestic c. Others)
(2) Means of reduction (a. Pollution Load Control Standard b. Construction of
sewerage, etc. c. Others)
u
Pollution Load Control Standard
(Decided by Governor according to guideline indicated in Prime
Minister's Office Ordinance)
(1) Applied for each works
(2) Tolerance limit per day is (Pollution load = Reported quantity of
wastewater x Fixed concentration)
(Water quality standard is parallelly appbed )
Works within designated districts
(Scale is decided by Prime Minister's Office Ordinance)
Specified Works stipulated by Water Pollution Prevention Law
(Factories, sewerage treatment plant, night-soil disposal plant
and purification tank (large-scaled), of more than 50m3 of
discharged wastewater per day)
Works within the designated districts shall perform reporting
of the measuring method of pollution load, measuring and
recording of the pollution load.
(Technical standards, etc. are decided by Prune Minister's
Office Ordinance.)
Observance of Pollution Load Control Standard
(Direct punishment is not to be applied, but applicable for concen-
tration standard )
Punishment shall be apply to the violator to the orders.
Guidance, advice and counsel for pollution sources other
than works within the designated districts are to be made.
(To be performed by the Governor based on the Pollution
Load Reduction Plan.)
(1) Uncontrolled types of industries and discharged
wastewaters of small quantity (Less than 50m3/day)
(2) Small-scale domestic sewage (Less than 501 persons tank)
(3) Culture fisheries
(4) Livestock wastewater
(5) Others
Receiving reports, Spot inspection *
(* Only receiving reports for pollution
sources other than works within the
designated districts)
Setup for pollution load observation
(The Governor shall constantly grasp information on
pollution load, water quality, etc.)
(1) Measuring plan
(2) Telemeter
(3) Others
295
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(1) Amount of reduction goal for each pollution source in designated
water bodies.
(2) Allocation of the amount of reduction goal to related prefectures.
(3) Basic matters of pollution load reduction. (Classified according to
industrial, domestic and others)
(4) Target year: 1984 (Intermediate target year: 1981)
In the "Pollution Load Reduction Plan" which Prefectural Governors are to
prepare based on the Basic Policy for Pollution Load Reduction, the followings are
to be decided.
(1) Amount of reduction goal for each pollution source in each prefecture
(Classified according to industrial, domestic and others).
(2) Means of reduction (Pollution Load Control Standard, construction of
sewerage and others)
Moreover, in the "Pollution Load Control Standard" which the Prefectural
Governor is to decide according to the guideline indicated by the Prime Minister's
Office Ordinance and based on the Pollution Load Reduction Plan, the tolerance
limits of pollution load per day of discharged wastewater for each works is to be
decided and this tolerance limits shall be calculated by multiplying reported amount
of discharged wastewater by fixed concentration. (See Fig. 2.2.)
2.5.3 Enforcement of Pollution Load Control and Responsibility of Sewerage
The revised Law on Pollution Load Control is scheduled for enforcement from
June of 1979. At that time, various proceedings necessary for the performance of
the Pollution Load Control such as the designation of water bodies, determination
of the Basic Policy for Pollution Load Control and the Pollution Load Reduction
Plan, reporting of the amount of discharged wastewater from specified works
within the designated districts, etc., shall be promoted. Based on these factors,
the Pollution Load Control Standard for each works will be established in June,
1980 (1 year after the enforcement of the revised Law) and applied to newly
established works to begin with. In June of 1981, two years after the enforcement
of the revised Law, the Pollution Load Control will be applied extensively to also
cover existing works and in 1984 (5 years after the enforcement of the revised Law),
the target is to be accomplished.
296
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Fig.-2.3 Imaginary Transfer Diagram Towards "Pollution Load Control"
2 years-
J une of
1981
3 years
June of
1984
Promulgation Enforcement of Revised Law
of revised law
» Designation of water bodies
• Determination of basic policy
' Intermediate goal
= Present value
• Goal
• Determination of reduction plan
Acceptance of amount of discharged
wastewater (Reporting)
Establishment of Pollution Load
Control Standard
• Indication of permissible load | ^ £
to works
Intermediate permissible load
Finally permissible load
Application of Pollution Load Control System
Obligation of observance
Obligation of measurement and reporting
£ E
V
<
Legally, "Concentration Control" is applied in principle.
Legally, "Pollution Load Control" is fully applied.
Priority construction of sewerages, etc.
Provision of pollution load measuring apparatuses
Provision of public hazard prevention devices for accomplishing goal.
Provision of telemeter
-------
The Pollution Load Control System will demand on sewerages the responsi-
bility in two aspects; the reduction of pollution load of sewage through its sys-
tematical construction and the control of discharged pollution load from sewage
treatment plant.
First of all, there lies the problem of sewerage contribution in the aspect of
reduction of pollution load. On the establishment of "reduction goal" which
becomes the basis in the application of Pollution Load Control System, although
the revised Law aims at maintaining the environmental water quality standard
concerning the designated items in designated water bodies, the reduction goals
for each pollution source and for each prefecture shall be determined on the
premise that reductions will be planned within possible enforcement limits, by
taking the trend of population and industries in the designated districts, technical
levels of sewage treatment, outlook on sewerage construction, etc. into consider-
ation.
The number of prefectures related to Tokyo Bay, Ise Bay and the Seto Inland
Sea which are scheduled as objects of Pollution Load Control count 20 and since
these areas include the three great urban areas where population and industries are
concentrated (Tokyo Area - Tokyo Metropolis, Kanagawa Prefecture, Saitama
Prefecture, Chiba Prefecture; Nagoya Area — Aichi Prefecture, Mie Prefecture;
Osaka Area — Osaka Prefecture, Kyoto Prefecture, Hyogo Prefecture), about 50% of
the total population of Japan concentrate into these areas. Therefore, the pollution
generating from these areas are extremely great and particularly since the poll-
ution load from domestic sewage must be reduced by sewerage, it is no exaggeration
to say that the systematical construction of sewerage becomes the key of Pollution
Load Control. It is due to such circumstances that the prospect of sewerage construc-
tion is taken into consideration at the establishment of reduction goal. Therefore,
sufficiently investigating the local pollution factors of objective water bodies from
the viewpoint of performing the reduction of pollution load most effectively and
clarifying the positioning of sewerage as a part of the comprehensive water pollution
prevention policy, the reduction goal of which sewerage should take charge must be
established based on the 5—Year Plan for Sewerage Construction and individual
sewerage projects conformed to the Comprehensive Basin-Wide Sewerage Study
Program of the competent area. Particularly, as to the necessity of tertiary treatment
of sewage, it should be decided by taking the pollution factors, conditions of
sewerage construction, etc. into consideration and by carefully studying its effect.
Therefore, in deciding the Basic Policy for Pollution Load Reduction, together
with sufficiently investigating beforehand the actual conditions of pollution load
from objective districts, the Environment Agency shall consult for adjustment with
the Ministry of Construction who is in charge of sewerage administration. Moreover,
as for the preparation of Pollution Load Reduction Plan which prefectural Governor
is to decide based on the Basic Policy for Pollution Load Reduction, the Department
or Bureau in charge of its preparation shall perform sufficient adjustments
beforehand with the Department or Bureau in charge of sewerage or river.
Secondly, there is the problem of responsibility of sewerage for controlling
298
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pollution load discharged from sewage treatment plant. Since sewerage are handled
as specified works similarly as ordinary factories and the like in the Water Pollution
Prevention Law, the Pollution Load Control Standard (Permissible limit of
discharged pollution load) shall be applied similarly as discharged wastewater from
factories and the like for effluent from the sewage treatment plant. Moreover,
the Pollution Load Control Standard is to be decided by the Governor based on
the guideline of the Environment Agency (Ordinance of Prime Minister's Office).
However, if the water quality of effluent is constant, the discharged pollution
load from the sewage treatment plant will enlarge in proportion to the increase of
the quantity of effluent, so it is necessary to enable to change the reported quantity
of effluent according to the expansion of the treatment facilities. Furthermore,
BOD has been mainly used as a pollution index in sewage treatment plant, and COD
has been handled as a resembling item of BOD in the Sewerage Law, however, since
COD is to be the object in this Pollution Load Control, in the application of the
Pollution Load Control Standard for sewage treatment plant, together with
sufficiently investigating the actual conditions of removal in the sewage treatment
plant into which industrial wastewaters with COD of difficult resolvability, it is
also necessary to study the establishment of pre-treatment standard for these COD.
On the other hand, for furthering the effect of Pollution Load Control on the
sewerage side, it is necessary to exert efforts so that the increase of pollution load
generated from the treatment area of sewerage may be controlled to the utmost.
For this purpose, efforts such as providing an incentive on pollution load reduction
to sewerage users by adopting a progressive user charges system for large quantity
dischargers, and by adding a water quality surcharge for wastewater of high concen-
tration, performing enlightenment for pollution load reduction and others become
necessary.
3. CONCLUSION
We have hitherto related on recent trends and the institutional structures of
water pollution control in Japan, and particularly with the introduction of the
Pollution Load Control System, systematical construction of sewerage in designated
districts is to be obligated and the role of sewerage as a water pollution prevention
policy has become increasingly greater.
As a consequence, the necessity of co-operation between Environment Agency
and Ministry of Construction in national level and between Department or Bureau
of Environment and Sewerage in prefectural and municipal levels in promoting
water pollution control has become much more stronger than ever.
299
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CHAPTER 3
FINANCING OF SEWAGE WORKS - USER CHARGES
1. Introduction 301
2. Outline of Sewage Works Financing and its Tendency 301
2.1 Financial Sources for Construction Cost 301
2.1.1 Composition of Financial Sources for Construction Cost .... 301
2.1.2 Tendency of Financial Sources for Construction Cost 304
2.2 Financial Sources for Maintenance and Operation Cost 305
2.2.1 Actual Conditions of Financial Sources for Maintenance
and Operation Cost 305
2.2.2 Actual Conditions of the Amount of Money Transferred
from General Account 306
3. Sewerage User Charges 307
3.1 Existing Systems of User Charges 307
3.1.1 Type of User Charges System 307
3.1.2 Progressive Charges System 308
3.1.3 Water Quality Surcharges System 309
3.1.4 Level of User Charges 309
3.1.5 Sewage Works Expenditures to be covered by User
Charges 310
3.2 What User Charges Should be 311
3.2.1 Basic Principle of User Charges 311
3.2.2 Bases for Calculation of User Charges 312
3.2.3 Method of Calculation of User Charges 313
4. Conclusion 318
300
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1. INTRODUCTION
Financing of sewage works has gradually changed corresponding with the
variety of the function of sewerage.
The principle of financing sewage works had been studied three times by the
Study Committee for Sewage Works Financing organized at Japan City Center in
1960, 1966 and 1973. The recommendations for adequate financing of sewage
works for each period were made by the committee. The recommendation by the
1st committee in 1960 was made from the viewpoint that sewerage was a basic
facility for city and brought about improvement of city environment and public
health by its function of storm water drainage, wastewater drainage and purification.
The 2nd committee in 1966 stressed that the function of sewerage had been
varied and complicated, especially the sewerage provision in large cities had urgently
necessitated for water pollution control. Furthermore, the 3rd committee in 1973
made the recommendation from the viewpoint that reflecting serious water pollution
problems the social demand for sewerage for the purpose of water quality preserva-
tion -of public water bodies and effective use of water resources had more and more
swollen.
Based on these recommendations, the five-year-plans for sewerage construction
and other policies were enforced.
After the recommendation by the 3rd committee in 1973, however, the
circumstances of sewerage administration have remarkablly changed; for instance,
(1) the pollution load control system has come to introduce in order to improve
water quality in widely closed water bodies, (2) the maintenance and operation of
sewerage are becoming an important problem, (3) through the cognizance of
limitation of water resources, the social request for effective use of water including
reuse of wastewater has enhanced.
Under the circumstances, the 4th Study Committee for Sewage Works Fi-
nancing was organized in June this year and is continuing to deliberate the financing
of sewage works for new era, including the policies for systematic and effective con-
struction of sewerage facilities and the principle of managing sewerage systems.
This paper describes the outline of the status quo of sewage works financing in
Japan, and introduces the actual condition and the principle of the user charges
which is closely related to the management of sewerage systems.
2. OUTLINE OF SEWAGE WORKS FINANCING AND ITS TENDENCY
2.1 FINANCIAL SOURCES FOR CONSTRUCTION COST
2.1.1 Composition of Financial Sources for Construction Cost
Sewerage is classified into three types; public sewerage, regional sewerage and
storm water channel, but in this paper the former two are the object for description.
Public sewerage is managed by municipality, while regional sewerage which is
a trunk sewerage covering more than two municipalities is managed by prefectural
government.
The financial sources for construction cost of sewerage facilities consist of
301
-------
national grant, loan, general tax, city planning tax, prefectural grant, beneficial
assessment, etc. The composition of these financial sources for public sewerage and
regional sewerage are shown in Figure 2.1 .
Fig. -2.1 Composition of Financial Sources for Construction Cost in Sewage Works
(1) Public Sewerage
Sewers
Subsidized Self-financed
s- \X^ *
10
Sewage Treatment Plant
^ Subsidized — -^^ Self-financed
1
6
10
\
3.4
10
0.6_^
• National ..
Grant
•'. .'•••' •'.'•
Loan
Loan
^
10
/
J
\
\
2.83
10
OB>
• .
' ' 6
Nation
' ' ' . • • '• . '
al Grant ,'10 '
'• \
' • •'.'. • V
3.4
10
v_
A
10
0.6'
10
City Planning Tax, Beneficial Assessment, Municipal Expenditure, etc.
\s Loan
10
1
'To"
(2) Regional Sewerage
Sewers
^.Subsidized-
^
4
J_
12
Self-financed
(10%)
Sewage Treatment Plant
Subsidized
^
' National Grant
Loan
, Loan
Self-financed
(5%)
. • Nationa Grant . _ .
Loan
.Loan
'10
Perfectural Expenditure, etc.
12
a. National Grant
Since sewerage facilities should be provided as a part of water pollution control
measures from the national point of view, the rate of national grant for sewerage
construction cost has gradually been raised until now. The rate of national grant is
6/10 (2/3 for sewage treatment facilities) for public sewerage, and 2/3 (3/4 for
sewage treatment facilities) for regional sewerage since 1974.
On the other hand, the objects of national grant are confined to main sewer,
pumping station and sewage treatment plant, and are fixed by the rule of Ministry
of Construction. According to this rule, the rate of the construction cost of the
facilities to be subsidized by the national government to the total construction cost
302
-------
is 60% (45% for designated cities, 75% for general cities) for public sewerage in the
4th Five Year Plan for Sewerage Construction.
b. Loan
Loan is permitted for the certain rates of construction cost and compose of
a main financial source for construction cost. Appropriation rates of loan for sewage
works are shown in Table 2.1.
Table -2.1 Appropriation Rate of Loan
Classification
Public Sewerage
Regional Sewerage
>H
u
CO
Sewage
Treatment
Plant
2
0>
I
ffl
1 Sewage
Treatment
Plant
Subsidized
Self-financed
Subsidized
Self-financed
Subsidized
Self-financed
Subsidized
Self-financed
National
Grant
6/10
-
2/3
-
2/3
-
3/4
-
Local
Burden
4/10
10/10
1/3
10/10
1/3
10/10
1/4
10/10
Loan out of Local Burden
4/10x8.5/10 = 3.4/10
10/10x9/10 = 9/10
1/3 x 8.5/10 = 2.83/10
10/10x9/10 = 9/10
1/3 x 3/4 = 1/4
10/10x9/10 = 9/10
1/4x3/4=3/16
10/10x9/10 = 9/10
The funds for sewage works loan are classified into three categories; govern-
mental funds, finance corporation funds and private funds (market collection funds,
bank connection funds). The shares of each category in 1978 are 30% in govern-
mental, 23% in corporation and 47% in private, respectively. This shows that the
governmental funds of low interest tend to decrease while the private funds of high
interest are inclined to increase.
c. Beneficial assessment
The beneficial assessment for sewage works is levied on the owners of land
which is located within the drainage area of a public sewerage, based on a municipal
ordinance in accordance with the City Planning Law.
The number of municipalities that adopt this financial system are 295 out of
547 municipalities which had been approved their projects of public sewerage
systems at the end of 1976, and the unit amount of beneficial assessment is mostly
100 to 300 yen per square meter of assessible land. The total amount of benefisial
assessment in 1976 throughout the country occupied about 1.1% of the total
construction cost, and about 2.5% of the construction cost in the municipalities in
which beneficial assessment had been collected.
303
-------
d. City planning tax
City planning tax can be levied by a municipality on the owners of land and
buildings which are located within a city planning area in order to appropriate to
the cost of city planning projects. Therefore, city planning tax can be appropriated
to other city planning projects than public sewerage. The city planning tax
appropriated to the public sewerage in 1976 occuped about 1.3% of the total
construction cost throughout the country, that is approximately same percentage
as the beneficial assessment.
e. Prefectural grant
The number of prefectural governments that deliver grant to municipalities
that execute public sewerage works is 12 in 1976 (Total number of prefectural
government is 47.)
The percentage of the prefectural grant in the total construction cost of public
sewerage in 1976 was about 0.5% and have tended to decrease since 1974.
Construction cost of a regional sewerage after subtracting national grant is
as a general rule borne fifty-fifty by a prefectural government and related municipal-
ities. Allotting method among related municipalities is generally by the ratio of
planned volume of wastewater or planned drainage area of each municipality.
2.1.2 Tendency of Financial Sources for Construction Cost
The shares of financial sources for sewerage construction cost for each fiscal
year from 1970 to 1976 are shown in Fig. 2.2. Reflecting the public character and
the urgency as water pollution control measures of sewage works, the amount of
construction cost has been increasing year by year. It is noted that since 1974 the
share of local government expenses other than the floation of loan has been
remarkably lightened. This had been caused by the improvement of the rate of
national grant and the appropriation rate of loan in 1974, and furthermore,
the introduction of special loan system in 1975. The special loan system is a financial
system applied to the construction cost of sewage treatment plants of public sewerage
concerning to the public water bodies in which environmental water quality
standards have been established. In order to promote sewage works to attain
environmental water quality standards while national grant to evenly deliver, the
national grant is advanced by the special loan which is paid in installment by
national grant for five years.
304
-------
Fig. -2.2 Actual Conditions of Financial Sources for Construction Cost in Sewage Works
441
(20.7)
Fiscal 1970
2'132 Hundred Million Yen
1971
1972
1973
1974
1975
1976
922
(25.9)
1,757
(49.3)
886
(24.8)
,,. „ , ....... v
3,565 Hundred Million Yen
1,345
(27.5)
2,442
(50.0)
J.096 1
(22.4) |
lYen
1,236
(23.1)
2,858
(53.3)
1,263
(23.6)
1,741
(28.8)
3,310
(54.7)
998
(16.5)
"^^^^^1
(165) 16.050 Hundred Million Yen
2,000
(24.8)
814
(10.1)
4,042
(50.2)
1,196
(16.5)
8,053 Hundred Million Yen
National
Grant
2,410
(28.8)
689
(8.2)
Special Loan
General Loan
4,229
(50.6)
1,032
(12.4)
Others
8,361 Hundred Million Yen
2.2 FINANCIAL SOURCES FOR MAINTENANCE AND OPERATION COST
2.2.1 Actual Conditions of Financial Sources for Maintenance and Operation Cost
The actual conditions of financial sources for maintenance and operation
cost of public sewerage throughout the country are shown in Table 2.2, which
indicates the the maintenance and operation cost has been remarkably increasing
year by year. It is pointed out that the reasons for this are the increase of the
administrative expenditure such as the cost for surveillance and guidance for
pretreatment facilities, the expense for propagation of flush toilet, and the require-
ment of high quality treatment with strengthening of water quality control, in
addition to the increase of sewerage facilities.
Table -2.2 Actual Conditions of Financial Sources for Maintenance and Operation Cost
(Unit: Million Yen)
Fiscal
Yeai
1972
1973
1974
1975
1976
Mainte-
nance and
Operation
Cost
(A)
61,578
83,244
123,007
134,585
257,232
In-
creasing
Rate
100
135
200
219
255
Financial Sources for Maintenance and Operation Cost
User
Charges
(B)
31,246
37,211
41,532
65,354
96,T;j
In-
creasing
Rate
100
119
133
209
309
Money
from General
Account
(C)
24,850
32,038
53,233
60,502
-
In-
creasing
Rate
100
129
214
243
-
Others
5,482
13,995
28,242
8,729
-
(B)/(A)
50.7
44.7
33.8
48.6
61.5
(C)/(A)
40.4
38.5
43.3
45
-
305
-------
The most part of the maintenance and operation cost is covered by user
charges and the money transferred from general account. In spite of the raising
of user charges in many municipalities in 1975 and 1976, the appropriation rate of
user charges to the maintenance and operation cost in 1976 is only 61%. Therefore,
the amount of money transferred from general account had been increasing with the
rate exceeding that of user charges until 1975. With the revision of user charges
in 1975 and 1976, the amount of money transferred from general account in 1976
is estimated to remain on the same level as a previous year and the share of it is
expected to return to the situation of 1973. But the maintenance and operation
cost is presumed to increase in the future, while the revenue from user charges
won't be expected to increase excepting the revenue with the increase of users.
For this reason, the share of the money transferred from general account is anti-
cipated to increase like the condition since 1974.
Table 2.3 shows the actual conditions of the maintenance and operation cost
and the amount of loan redemption. It is noted here that the share of the cost
concerning to wastewater drainage and purification comes up to 43% to 63%.
Table 2-3 Maintenance and Operation Cost in Main Cities
(Fiscal 1976, Unit: Million Yen)
\ Classifi-
\cation
Name\
of city \
Sapporo
Sendai
Kawasaki
Nagoya
Kyoto
Osaka
Okay am a
Hiroshima
Kita-
kyushu
Mainte-
nance and
Operation
Cost for
Wastewater
A
3,046.6
(2,193.6)
1,164.8
(815.1)
2,420.0
(1,621.4)
9,610.0
(6,823.1)
4,757.0
(3,994.2)
16,424.0
(10,628.9)
656.0
(459.2)
2,062.6
(1,443.8)
1,332.8
(1,095.6)
A/D
%
29.3
(48.2)
36.3
(72.2)
49.8
(52.9)
48.3
(59.1)
43.4
(60.5)
55.4
(64.7)
50.4
(70.3)
64.0
(80.6)
22.8
(36.8)
Loan
Redemp-
tion for
Wastewater
B
3,822.4
(1,223.2)
227.5
(68.3)
598.0
(35.8)
2,441.6
(1,123.1)
943.4
(396.2)
2,643.9
(1,208.3)
109.0
(32.7)
197.8
(59.3)
980.2
(409.7)
B/D
%
36.8
(26.9)
7.1
(6-0)
12.3
(11-6)
12.3
(9.7)
8.6
(6.0)
8.9
(7.4)
8.4
(5.0)
6.1
(3.3)
16.8
(13.8)
Loan
Interest
for Waste-
water
C
3,531.1
(1,130.0)
819.1
(245.7)
1,837.8
(1,102.7)
7,839.6
(3,606.2)
5,266.7
(2,212.0)
10,604.7
(4,591.8)
(536.4)
(160.9)
964.2
(289.3)
3,527.1
(1,474.3)
C/D
%
34.0
(24.9)
25.5
(21.8)
37.8
(35.8)
39.4
(31.2)
(48.0)
(33.5)
35.7
(27.9)
41.2
(16.1)
29.9
(16.1)
60.4
(49.5)
Total
for Waste-
water
D
10,400.3
(4,546.8)
2,211.5
(1,129.1)
4,855.8
(3,082.9)
19,891.2
(11,552.4)
10,965.1
(6,602.4)
29,676.8
(16,429.0)
1,301.4
(652.8)
3,224.8
(1,792.4)
5,840.2
(2,979.6)
Cost for
Waste-
water
Total
Cost
%
43.7
51.1
63.5
58.1
60.2
55.9
50.2
55.6
51.0
Loan
Balance
at the End
of Fiscal
1976
55,757.3
14,648.4
33,918.2
115,494.2
89,494.8
157,912.8
8,985.4
14,058.2
48,805.8
2.2.2 Actual Conditions of the Amount of Money Transferred from General
Account
The money transferred from general account to sewage works account is
appropriated not only to maintenance and operation cost but also construction cost
and loan redemption. Table 2.4 shows the actual conditions of the amount of money
transferred from general account for each population rank of municipalities.
306
-------
Table -2.4 Amount of Money from General Account
(Unit: Hundred Million Yen)
Population
Rank of
Municipal!
ties
More than
a Millon
100,000 to
1,000,000
Less than
100,000
Total
Fiscal
Year
1972
1973
1974
1975
1972
1973
1974
1975
1972
1973
1974
1975
1972
1973
1974
1975
Amount of Money from General Account
for Construc-
tion Cost
(100) 320
( 93) 296
( 57) 183
( 80) 256
(100) 252
( 97) 245
( 83) 208
( 71) 178
(100) 162
( 60) 98
( 63) 102
( 62) 101
(100) 734
( 87) 639
( 67) 493
( 73) 535
for Loan
Redemption
(100) 354
(126) 446
(174) 616
(225) 795
(100) 159
(135) 215
(167) 265
(214) 340
(100) 24
(163) 39
(204) 49
(288) 69
(100) 538
(130) 700
(173) 930
(224) 1205
Sub-Total
(100) 674
(110) 742
(119) 799
(156) 1051
(100) 411
(112) 460
(115) 473
(126) 518
(100) 186
( 74) 137
( 81) 151
( 91) 170
(100) 1272
(105) 1339
(112) 1423
(137) 1740
for Mainten-
ance and Opera-
tion Cost
(100) 119
(122) 145
(211) 251
(224) 267
(100) 112
(135) 151
(215) 241
(267) 299
(100) 19
(126) 24
(205) 39
(205) 39
(100) 249
(129) 320
(214) 532
(243) 605
Total
(100) 793
(100) 887
(132) 1050
(166) 1318
(100) 523
(117) 611
(137) 714
(156) 817
(100) 205
( 79) 161
( 93) 190
(102) 209
(100) 1521
(109) 1659
(129) 1955
(154) 2345
Total Cost for
Maintenance
and Operation
I
1
I
I
/
I
/
/
1
(100) 616
(135) 832
(200) 1230
(219) 1346
Remarks
(Note) Figures in the brackets show the increasing rates of each year in case of 100 for fiscal 1972.
This table indicates that the appropriation to the construction cost has
gradually been decreasing, while the appropriation to the loan redemption has
remarkably been increasing, particularly in municipalities of small population
rank. Loan redemption consists of principal and interest, and the share of the
interest is very high as shown in before-mentioned Table 2.3. With the progress
of sewerage construction works hereafter, loan redemption will become a main
oppressing factor for financing of sewage works. As mentioned before in 2.1.1, b,
the tendency t1 the share of governmental funds has been lowering while the
share of private funds has been rising in sewage works loan will further burden
general account.
3. SEWERAGE USER CHARGES
3.1 EXISTING SYSTEMS OF US,_,t CHARGES
3.1.1 Type of User Charges System
Although user charges systems in Japan are various reflecting a special
character of each municipality, these systems are classified into two types.
a. Water charges proportional system
W;< ter charges proportional system is the system in which sewerage user charges
are calculated as a certain percentage of water charges. But in this case a separate
system is usually adopted to the wastewater from other supply of water such as
wellwater.
In the municipalities adopting this system, the identified charges system
307
-------
for both water supply and sewerage is familiar to citizen. In addition to this, water
charges proportional system has considerable merits of collecting convenience and
easy computation of the charges. However, since this system has the defect that
the cost price is not reflected to the user charges, municipalities adopting this
system is decreasing in number (See Table 3.1).
Table 3-1 Classification of User Charges System [1] (Sampled for 85 Cities)
Classification
Wastewater from
Water Supply
Wastewater from
Well water and
Others
(A) Water Charges Proportional System
(B) Wastewater Quantity Conformable
System
Other System
Total
(A) Separate System from One for
Wastewater from Water Supply
(B) Same System as One for Wastewater
from Water Supply
Other System
Total
Average Rate of Sewerage User Charges to Water Charges
Among the Cities Where Water Charges Proportional System
Are Applied (%)
End of
Fiscal
1971
22
55
3
80
17
45
16
78
40.2
End of
Fiscal
1972
20
59
3
82
17
45
18
80
42.0
End of
Fiscal
1973
21
62
2
85
17
51
16
84
40.0
End of
Fiscal
1974
18
66
1
85
16
55
14
85
37.4
End of
Fiscal
1975
17
67
1
85
15
58
12
85
37.2
June of
1976
15
69
1
85
14
61
10
85
39.2
b. Wastewater quantity conformable system
Wastewater quantity conformable system is the system in which sewerage
user charges are calculated in conformity with the quantity of discharged waste-
water. This system has the merits that the cost price corresponding with the quantity
of discharged wastewater can be reflected to the user charges, and furthermore,
by adopting progressive charges system, the promotion of reducing wastewater from
large quantity dischargers can be expected. The quantity of discharged wastewater
for this charges system is recognized by inspecting a water consumption meter in
most cities (See Table 3.1).
3.1.2 Progressive Charges System
Among the municipalities adopting water charges proportional system or
wastewater quantity comformable system, the progressive charges system in which
user charges per unit quantity of discharged wastewater goes up as the quantity
increases, the uniform charges system in which user charges per unit quantity
is constant, and the diminished charges system in which user charges per unit
quantity becomes cheaper for larger quantity dischargers, are adopted. However,
the municipalities adopting the progressive charges system are rapidly increasing
in number (See Table 3.2 and Table 3.3).
308
-------
Table -3.2 Classification of User Charges System [II]
(In case of (A) and (B) for Wastewater
from Water Supply in Table 3-1)
Classification
Without Basic Charges
With Basic Charges
Uniform Charges System
Progressive Charges System
Diminished Charges System
Both Progressive and Diminished
Charges System
Sub-Total
Uniform Charges System
Progressive Charges System
Diminished Charges System
Sub-Total
Total
Average Number of
Progressive Steps
Without Basic Charges
With Basic Charges
End of
Fiscal
1971
16
3
6
1
26
40
8
3
51
77
2.3
2.8
End of
Fiscal
1972
18
4
5
1
28
37
8
3
51
79
2.5
2.8
End of
Fiscal
1973
20
5
5
1
31
37
13
2
52
83
2.8
2.8
End of
Fiscal
1974
20
5
5
1
31
32
19
2
53
84
6.4
3.4
End of
Fiscal
1975
17
9
5
31
25
25
3
53
84
5.9
4.2
June of
1976
8
16
1
25
13
42
4
59
84
6.1
4.8
Table -3.3 Actual Conditions of Application of Progressive
Charges System and Water Quality Surchages System
(End of Fiscal 1976)
Number of Municipalities Applying
Progressive Charges System
End of Fiscal 1972
End of Fiscal 19 74
End of Fiscal 1976
17
40
126
Number of Municipalities Applying
Water Quality Surcharges System
End of Fiscal 1972
End of Fiscal 19 74
End of Fiscal 19 76
9
18
31
3.1.3 Water Quality Surcharges System
Water quality surcharges are the additional user charges which are imposed to
dischargers who dischage wastewater of higher concentration than a certain level.
The merits of adopting water quality surcharges system are that the cost recovery
can be made by fair imposition of user charges in accordance with the conditions of
discharged wastewater, and that the effect of encouraging efforts to improve
the quality of wastewater of high concentration to the dischargers can be expected.
Therefore, the municipalities adopting water quality surcharges system are steadily
increasing in number (See Table 3.3)
3.1.4 Level of User Charges
Since user charges systems are various among municipalities, it is difficult
to simply compare the level of user charges in one municipality with others. Table
3.4 shows the distribution of user charges in ordinary household which discharges
20m3 per month. The table indicates that user charges in average household dis-
tribute in considerably wide range centering from 400 yen to 599 yen throughout
the country and user charges in large cities are generally cheaper.
309
-------
Table -3.4 Distribution of User Charges in Ordinary Household (End of Fiscal 1976)
User Charges for 20m3 per
Month in Ordinary Household (Yen)
Number of Municipalities
(Number of Specified Cities)
-399
88
(8)
400- 599
93
(2)
600— 799
47
(0)
800- 999
11
(0)
1000-
10
(0)
Total
249
(10)
3.1.5 Sewage Works Expenditures to be covered by User Charges
The expenditures to be covered by user charges are a depreciation cost and
a loan interest besides a maintenance and operation cost. The actual conditions of
the expenditures included in the estimation of user charges in the municipalities
which had collected user charges at the end of fiscal 1976 are shown in Table 3.5.
The table indicates that the number of municipalities which include the depreciation
cost and the loan interest besides the maintenance and operation cost in the estima-
tion of user charges are 103 out of 249, and that 28 municipalities include all of
these cost in the estimation of the user charges only for the part of wastewater
exceeding a certain quantity (specified wastewater).
Table -3.5 Actual Conditions of Expenditures Covered by User Charges (End of Fiscal 1976)
Expenditures Covered by User Charges,
Except for Maintenance and Operation Cost
Depreciation Cost and Loan Interest
Depreciation Cost Only
Loan Interest Only
Total
Number of Municipalities
Adopting to Both Ordinary and
Specified Wastewater
58
9
8
75
Number of Municipalities
Adopting only to Specified
Wastewater
26
1
1
28
Total
84
10
9
103
In this case, the standard quantity of specified wastewater is mostly over
1,000m3 or 500m3 per month. The percentage of the quantity of specified waste-
water to the total is about 20%, while in most cases the user charges from specified
wastewater is over 40% of the total revenue of user charges, reflecting the adoption
of the progressive charges system and the water quality surcharges system (See
Table 3.6)
Table -3.6 Amount of Specified Wastewater and Revenue of User Charges
from Specified Wastewater (Fiscal 1976)
Name of City
Definition of Specified Wastewater
(More than Cubic Meter per Month)
a. Total Amount of Specified Wastewater
(Thousand Cubic Meter)
b. Rate of Amount of Specified Wastewater to Total (%)
c. Revenue of User Charges from Specified Wastewater
(Thousand Yen)
d. Rate of Revenue from Specified Wastewater to Total (%)
c/a
d/b
Progressive Charges System
Water Quality Surcharges System
Sapporo
1,000
31,885
32.9
1,899,809
52.0
60
1.6
o
Yokohama
501
37,160
23.6
1,518,426
42.7
41
1.8
o
0
Kobe
500
20,489
18.1
1,521,805
47.2
74
2.6
o
0
Sendai
1,000
9,158
19.9
192,875
26.7
21
1.1
0
310
-------
3.2 WHAT USER CHARGES SHOULD BE
3.2.1 Basic Principle of User Charges
Since the users of sewerage facilities can be distinguished from others, it is
necessary from the viewpoint of effective management of the sewerage facilities
and fair charge of the expenditures to levy user charges in accordance with the
conditions of the use. On the other hand, it is necessary to burden needed cost
to dischargers of wastewater accompanied with enterprising activities in conformity
with 'the pollutor-pay-principle' (PPP). However, since it is difficult to determine
dischargers and their quantities and qualities of wastewater at the beginning of
sewerage construction, it is adequate to burden needed cost through user charges.
Article 20 of Sewerage Law stipulates that the superintendent of the public
sewerage is able to collect user charges prescribed by the municipal ordinance from
its users in conformity with the following principles.
1) To be appropriate in accordance with the conditions of the use such as the
quantity and the quality of wastewater.
2) Not to exceed the reasonable cost price under the efficient management.
3) To be definitely determined with the fixed rate or the fixed amount.
4) Not to unjustly discriminate specific users.
From the above-mentioned point of view, the followings should be the basic
principle of sewerage user charges.
a. Range of expenditures to be covered by user charges
Since the appraisal of the conditions of the use should be made with respect
to the wastewater which is discharged to the sewerage by users, and the construc-
tion cost of sewerage should be paid with public expenditure excepting the beneficial
assessment and the burden to be conformed to PPP, the range of expenditures
to be covered by user charges should be the maintenance and operation cost as for
the ordinary wastewater (the whole of domestic sewage and the part of wastewater
under a certain quantity from industrial and business activities).
As for the specified wastewater (the part of wastewater over a certain
quantity from industrial and business activities), the repayment cost of the
facilities and the loan interest in addition to the maintenance and operation cost
should be included in the expenditures to be covered by user charges.
b. Adoption of water quality surcharges system
In order to aim the thoroughness of PPP and the fairness of the burden among
users, water quality surcharges should be added to water quantity charges.
In this case, the items of water quality and the range of concentration to be
considered in water quality surcharges system should be limited within the bounds
not to extremely obstruct sewerage functions or not to impair sewerage facilities
and to be able to keep the water quality standards for effluent from sewage
treatment plant. The items and the concentration exceeding these limitations and
toxic pollutants should be removed by pretreatment facilities prior to be discharged
into a public sewerage.
311
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c. Adoption of progressive charges system
It is desirable to adopt the progressive charges system in which the unit
charges go up progressively as the quantity of discharged wastewater increases,
within the bounds that the total amount of user charges does not exceed the cost
price.
The progressive charges system together with the water quality surcharges
system acts as the incentive to the efforts for reducing the quantity and for
improving the quality of the wastewater discharged to sewerage, and it is expected to
be useful for saving and effective use of water resources, recovery of resources and
effective management of sewerage facilities.
d. User charges for tertiary treatment
Since the effluent from tertiary treatment should be in principle returned
to a public water body as a part of water management, the cost for tertiary
treatment should be covered by public expenses and be excluded from the expendi-
tures to be covered by user charges, excepting the cost for the specified wastewater.
As for the specified wastewater, the cost for tertiary treatment (including
repayment cost of facilities and loan interest besides maintenance and operation
cost) should be covered by user charges, in conformity with PPP.
3.2.2 Bases for Calculation of User Charges
a. User charges for ordinary wastewater
(1) Water Quantity Charges
Annual Cost for Maintenance and Operation
Average Charges per m3 =- r— : Cf. -r. 777— —-—JT
Annual Quantity of Ordinary Wastewater (m3)
(2) Water Quality Surcharges
None
b. User charges for specified wastewater
(1) Water Quantity Charges (including the user charges for tertiary treatment
for BOD (or COD) and SS)
Average Charges per m3
Part of Construction Cost and Loan Part of Maintenance
Interest for Specified Wastewater and Operation Cost for
to be Covered by Water Quantity Charges Specified Wastewater
~~ T;+ to be Covered by Water
Duration Years
Quantity Charges
Annual Quantity of Specified Wastewater (m3)
312
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(2) Water Quality Surcharges
Average Charges per m3
Part of Construction Cost and Loan
Interest for Specified Wastewater
to be Covered by Water Quality Surcharges
Duration Years
Part of Maintenance
and Operation Cost for
Specified Wastewater
to be Covered by Water
Quality Surcharges
Annual Quantity of Specified Wastewater to be Subjected to Water
Quality Surcharges (m3)
(Note) As to the user charges for tertiary treatment for other items of water
quality than BOD (or COD) and SS, the user charges should be calculated based
on the same idea of the above-mentioned formula, where the water quality
exceeds that of domestic sewage.
Calculation term of user charges is usually set up in the range of three to five
years. At the determination of the calculation term, it is necessary to consider
the equalization of the burden of the initial cost over the future, while the estimation
of the cost price during the calculation term has to be possible.
Where a preceding investment is quite huge, a part of the initial cost which
cannot be covered by the present user charges is advanced by public expenditure
and is to be recovered by the user charges in later years.
3.2.3 Method of Calculation of User Charges
The process of determining user charges in accordance with the above-
mentioned bases of calculation is shown in Figure 3.1.
Fig. -3.1 Process of Determining User Charges
Setting of Calculation Term
Estimation of Expenditures
Investigation and Estimation
of Influent
Calculation of Unit Costs
Calculation of User Charges
Policy Adjustment (Application
of Progressive Charges System, etc.)
Determination of User Charges
313
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a. Estimation of expenditure
The capital cost (depreciation cost and loan interest) and the maintenance and
operation cost of the sewerage facilities are estimated extending over the calculation
term, which should be determined by considering the certainty for estimation of
the cost price and the income and outgo program as well as the administrative
stability, and the reasonable term is about three to five years. In this case, it is
necessary for estimating the stability of user charges to calculate user charges for
several cases of the term.
The total expenditures are classified into some elements indicated in the bases
for calculation of user charges, as shown in Fig. 3.2.
Fig. -3,2 Classification of Expenditures
(Note 1)
Repayment Cost of Facilities
and Loan Interest
•- Maintenance and Operation Cost
Crv
Cmv
Replayment Cost of Facilities
and Loan Interest
•- Maintenance and Operation Cost
Crl
Cml
(Note 1) Cost for Sewers, Pumping Stations and Primary Treatment Facilities
(Note 2) Cost for Secondary Treatment Facilities and Sludge Handling Facilities
b. Investigation and estimation of influent
Sewerage user charges are classified into the charges for ordinary wastewater
and for specified wastewater, and the latter consists of water quantity charges
and water quality surcharges. Therefore, both the quantity and the quality of each
wastewater flowing into a sewage treatment plant should be investigated.
The process of investigation of influent is shown in Fig. 3.3.
314
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Fig. -3.3
(Investigation of Quantity)
Investigation and Estimation of Influent
Quantity of Ordinary
Wastewater
Quantity of Specified
Wastewater
Quantity of Specified Wastewater Subjected
to Water Quality Surcharges
Quantity of Infiltration Inflow
(Investigation of Quality)
Pollution Load of Wastewater not Subjected to
Water Quality Surcharges
Ordinary Wastewater
Specified Wastewater
Pollution Load of Specified Wastewater
Subjected to Water Quality Surcharges
Pollution Load of
Infiltration Inflow
c. Calculation of unit costs
Unit costs mean the cost per cubic meter of wastewater and the cost per
gram of pollution load, and can be calculated by dividing the expenditures estimated
at a. by the quantities and the pollution loads investigated at b. The calculation
formulas of the unit cost for each expenditure are shown in Table 3.7.
315
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Table -3.7 Calculation of Unit Costs
Item of Cost
Cost for Quantity
of Wastewater
Cost for Quality
of Wastewater
Repayment Cost of Facilities
and Loan Interest
Urv = Crv
urv v
UH = Crl
Maintenance and Operation Cost
IImv = Cmv
V
II , = cml
(Notes)
Urv
Umv
Url
mv
Crl
Cml
V
L
Unit Cost for Repayment and Loan Interest out of Cost for Quantity
(Yen/m3)
Unit Cost for Maintenance and Operation out of Cost for Quantity
(Yen/m3)
Unit Cost for Repayment and Loan Interest out of Cost for Quality
(Yen/gr.)
Unit Cost for Maintenance and Operation out of Cost for Quality
(Yen/gr.)
Cost for Repayment and Loan Interest out of Total Cost for Quantity
during Calculation Term
Cost for Maintenance and Operation out of Total Cost for Quantity during
Calculation Term
Cost for Repayment and Loan Interest out of Total Cost for Quality
during Calculation Term
Cost for Maintenance and Operation out of Total Cost for Quality
during Calculation Term
Total Volume of Wastewater Subjected to User Charges during Calculation
Term
Total Pollution Load of Wastewater Subjected to User Charges during
Calculation Term (for Each Item of Water Quality)
d. Calculation of user charges
In accordance with the bases for calculation, the user charges per cubic meter
of ordinary and specified wastewater can be computed by combining the above-
mentioned unit costs. In this case, the expenditures to be covered by the user charges
for ordinary wastewater are restricted to the maintenance and operation cost, and
the depreciation cost and the loan interest are excluded from the expenditures.
The composition of the user charges computed in this manner is illustrated in
Figure 3.4.
316
-------
Fig. -3.4 Composition of User Charges
Cost for Quantity
Maintenance and Operation Cost
Repayment Cost
of Facilities and
Loan Interest
Cost for Quality
Repayment Cost of Facilities
and Loan Interest
/(Yen/m3)/1
Url(Ss-Sd)
Maintenance and
Operation Cost
(Yen/mJ)
Uml(Ss-Sd)
(Note) So : Average Quality of Ordinary Wastewater (ppm)
Ss Quality of Specified Wastewater Subjected to Water Quality Surcharges (ppm)
So : Average Quality of Domestic Sewage (ppm) (Si> =?So)
e. Determination of user charges
At the determination of user charges, the following considerations should be
added to the above-mentioned result of calculation.
1) Measures for Preceding Investment
Since sewage works are occupied their considerable part by a preceding invest-
ment at the initial stage of construction, it is necessary to lighten user charges by
appropriating money of general account to the part of expenditures originated from
the preceding investment.
2) Adoption of Progressive Charges System
Although progressive charges system has been explained at 3.2.1, c, it is
necessary to examine a concrete way of its application. In this occasion, the average
value of user charges under the progressive charges system conforms to the bases for
calculation described in 3.2.2, and the steps and values of progressive charges should
be so determined as to keep balance between the total income of user charges ?nd
the expenditures to be covered by user charges.
3) Same User Charges System for Same Administrative Area
Unit costs for user charges are varied for each sewage treatment area, but it is
desirable for equalization of administration to apply same user charges system for
317
-------
same administrative area. However, in the case that it is reasonable in view of
the actual conditions of the area to adopt an independent user charges system for
the specified area such as a newly developed urban area, it is not always necessary
to apply the same user charges system.
4. CONCLUSION
The outline of financing of sewage works and the actual conditions and the
basic principle of sewerage user charges in Japan have been described as above.
Financing of sewage works should be changed corresponding with the variety of
the role of sewerage as stated at the preface. Particularly, because the role of
sewerage in the aspect of water pollution control and preservation of water resources
are increasingly expected today, proper maintenance and operation of sewerage
facilities has become more and more important problem. For this reason, it is
indispensable to seek sound finance in the aspect of management of sewage works,
and proper application of sewerage user charges system is one of its requirement.
For instance, as to the principle of the cost imposition of tertiary treatment,
it will become necessary to establish more detailed rule in accordance with the
purpose of tertiary treatment, though it is recognized today that the cost for
tertiary treatment shouldn't be covered by user charges excepting the cost for
specified wastewater as stated at 3.2.1, d.
Furthermore, it is required to rescrutinize the range of specified wastewater
the cost of which should be covered by user charges including the capital cost,
in conformity with PPP.
The rule for sewage works financing compatible with the demand of new era
is now being studied in the 4th Committee of Sewage Works Financing as mentioned
in the preface. We wish that the result by the committee could be presented at the
next conference.
318
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CHAPTER 4
SEWER USER CHARGE SYSTEM IN OSAKA CITY
1. Introduction . . . 320
2. Sewerage Works and Finance of Osaka City .. 320
2.1 Present Situation of Sewerage . 320
2.2 Construction Expenses and Their Financial Resources 322
2.3 Operation and Maintenance Expenses and Capital Expenses and Their
Financial Resources. . . 324
2.4 Financial Situation of Osaka City and Sewerage Works. 324
2.5 New Five-year Plan for Sewerage Works 326
3. Sewer User Charges in Osaka City .... . . . . 328
3.1 Transition of Sewer User Charge System. . . 328
3.2 .Provisions of the Sewerage Law and Proposal of the Third Committee
for the Investigation of Sewerage Financing . .. .. 332
3.3 Principle of Sharing Expenses . . ... .... 332
3.4 Calculation of Expenses Share Rate 333
3.5 Fundamental Philosophy Underlying Sewer User Charge System . . . 335
3.6 Cost of General Sewer User Charges . .... 335
3.7 Fundamental Philosophy Underlying Water quality Surcharge . . . 337
3.8 Cost of Water quality Surcharge . 338
4. Recent Trend in Sewer User Charges .... . . 339
4.1 Change in Total Amount of Effluent. . . .... 339
4.2 Change in Quantity and Quality of Effluent Subjected to Water
quality Surcharge . . . . 340
4.3 Discussion. ....... 341
5. Conclusion . . . . ... 343
319
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1. INTRODUCTION
Sewarage is a fundamental facility in cities which protects urban areas from
flood, improves the living environment by the diffusion of flush toilets and the
prevention of the stagnation of waste water, and prevents the pollution of public
water bodies. Various kinds of facilities that systematically constitute the sewerage;
sewer, pumping stations and sewerage treatment plants, must display their effects to
the fullest in an organic manner. The utility and benefit brought by sewerage are
dual in nature, bringing both public and private assets to the people living in the
community.
The construction of sewerage requires a great amount of money. However,
sewerage construction itself is obviously not the objective. In other words, sewerage
cannot achieve its true objective until it is completely maintained and managed.
Consequently, expenses for sewerage easily surpass those for roads and rivers. This
is the reason why the security of financial resources is the key to the execution of
sewerage works and therefore is our important task to grapple with.
2. SEWERAGE WORKS AND FINANCE OF OSAKA CITY
2.1 PRESENT SITUATION OF SEWERAGE
The city of Osaka has a total area of about 21,000 ha, most part of which is
lowlands made of sedimentary earth and sand of Yodo River and Yamato River and
is below the flood level or the high tide level of Osaka Bay. Therefore, it is
necessary to drain sewage with pumps for up to 90% of the city area. Besides, in
addition to the above-mentioned two rivers, there are many other rivers flowing
through the city, to which sewage is discharged. Its environmental water quality
standard is set at 5 - 10 ppm of BOD value. The sewerage plan of Osaka City is
shown in Fig. 1.
The construction of sewerage in Osaka City was commenced in 1894,
prompted by the poor discharge and the prevalence of cholera. Through various
kinds of development since then, the diffusion of sewerage was energetically
promoted especially after the World War II. As a result, the diffusion rate has now
reached 93%. The diffusion of sewerage and outline of facilities are shown in Table
1.
Combined sewerage system is adopted for discharging sewage and about 60% of
the total pumping capacity of the pumping stations is dependent on Diesel pumps to
provide for disasters. The sewage is treated by secondary treatment based on the
activated sludge process (the primary treatment by plain sedimentation is being
improved for secondary treatment) and the sludge is treated and disposed of by
digestion, dewatering, incineration (construction is under way to incinerate all the
sludge) and landfill.
320
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Legends
[ZH
^m
n
o
— »
Public sewerage area
Regional sewerage area
Treatment plant
Pumping station
Sewer (Major trunk line)
Fig. 1 Sewerage Plan in Osaka City
321
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Table 1 Diffusion of Sewerage and the Outline of Facilities in Osaka City
(As of the end of fiscal 1977)
Division
Diffu-
sion
of
sew-
erage
Out-
line
of
facil-
ities
Sewered area (ha)
Population served (1,000)
Number of households
with flush toilets (1,000)
Sewer (km)
Pump-
ing
sta-
tions
Treat-
ment
plants
Number
Pumping capa-
city (m3/sec)
Capacity of
diesel pump
included in the
above (m3/sec)
Number
Treatment
capacity
(1,000m3 /day)
Secondary
treatment
capacity
included in the
above
(1,000m3 /day)
17,118
2,671
670
3,941
77
899.5
504.0
12
2,570
1,128
Remarks
93.0% of total planned area of
18,410 ha
96.1% of total population of
2,779 ,000 as of today
95.8% of total number of
households of 700,000
Inclusive of 1 1 pumping houses in
sewage treatment plants
56% of the total pumping capacity
44% of the total treatment
capacity
2.2 CONSTRUCTION EXPENSES AND THEIR FINANCIAL RESOURCES
In Japan, the construction of sewerage is financed by national expenditure in
the name of national grant and local expenditure including prefectural grant,
beneficial assessment, loan and general municipal expenses. Sewerage works are
divided in two categories; subsidiray works and works financed by municipal funds
and the breakdown of their financial resources is as shown in Table 2. According to
this Table, up to 93% of the construction expenses of the sewerage is financed by
national grant and the issuance of loans. However, the redemption funds for the
issued loans that occupy 65% of the total financial resources in designated cities (10
big cities including Tokyo and Osaka) and 46% in general cities are causing a
difficult problem in the financing of sewerage works.
The constitution of financial resources for sewerage construction and the
balance of issued loans are shown in Tables 3 and 4, respectively. The balance
reached ¥175 billion at the end of fiscal 1977, 1.5 times that for water works (¥120
billion).
322
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Table 2 Breakdown of Financial Resources for the Construction of Public Sewerage in Japan
Division
Designated
cities
General
cities
National
average
Subsidiary
works
Works financed by
municipal funds
Total
Subsidiary works
Works financed by
municipal funds
Total
Subsidiary works
Works funanced by
municipal funds
Total
Working
expenses
45%
55
100
75
25
100
60
40
100
National
grant
28%
-
28
47
-
47
38
-
38
Loans
15%
50
65
24
22
46
19
36
55
General
local funds
2%
5
7
4
3
7
3
4
7
Table 3 Constitution of Financial Resources for Sewerage Construction in Osaka City
(Unit: 100 million yen)
Fiscal year
1966
68
70
72
73
74
75
76
Total
1972- 1976
Working
expenses
72.2
108.0
160.0
240.0
226.1
280.7
324.2
324.0
1,395.0
National
grant
11.4
20.2
31.0
62.1
44.7
80.6
88.5
79.0
354.9
16%
19
19
26
20
29
26
24
25
Issuance
of loans
53.1
73.7
100.6
143.8
148.9
183.6
211.5
213.6
901.4
73%
68
63
60
66
65
67
66
65
General
local funds
7.7
14.1
28.4
34.1
32.5
16.5
24.2
31.4
138.7
11%
13
18
14
14
6
7
10
10
Table 4 Transition of Balances of Issued Loans for Sewerage Construction in Osaka City
(Unit: 100 million yen)
Fiscal
year
Balance
1966
257
1968
379
1970
538
1972
790
1973
923
1974
1,085
1975
1,313
1976
1,527
323
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2.3 OPERATION AND MAINTENACE EXPENSES AND CAPITAL EXPENSES
AND THEIR FINANCIAL RESOURCES
The operation and maintenance expenses and capital expenses for sewerage
comprise (1) personnel expenses and supplies expenses required for the repair of
sewer, dredging, the operation and maintenance of pumping stations and sewage
treatment plants, the disposal of sludge generated in the treatment plants, the
examination and regulation of effluent quality and the collection of sewer user
charges (referred to as operation and maintenance expenses) and (2) depreciation
expenses arid interests for issued loans (referred to as capital expenses). Although
efforts have been continuously made to minimize the operation and maintenance
expenses and capital expenses, they have increased drastically mainly due to the
diffusion of sewerage, the increase in the number of facilities (see Table 5), the rise
in power rate, chemicals cost, sludge disposal cost and personnel expenses, as well as
the ever-increasing amount of interests payable and depreciation expenses. This
situation is well described in Table 6. The impression of the scale of these expences
can rightly be made by the comparison with the 1978 budget of Osaka City. The
operation and maintenance expenses and capital expenses for sewerage is ¥40
billion, or approximately 13% of the sum (¥320 billion) of the municipal tax
revenue arid the revenue from the local allocation tax. Besides, annual expenses
amount to ¥15,000 per capita, or as high as 75% of the individual municipal tax
(¥20,000) in Osaka City.
Yauie 6 Transition of Diffusion of Sewerage and the Outline of Facilities in Osaka City
Division
-------
therefore been making serious efforts to curb its administrative expenses. Despite
such efforts, the financing structure has been necessitating^ the increase in com-
pulsory expenses such as personnel expenses, expenditures for welfare and other
assistance and public bond expenses year after year, ever strengthening the rigidity
of financing. Table 7, which describes the financial situation of Osaka City, shows
the decrease in general financial resources including municipal tax that can be
appropriated for investment and extraordinary expenses, as evidenced by the drop
from 31% in 1970 to 10% in 1978.
Table 6 Transitions of Operation and Maintenance Expenses and Capital Expenses for Sewerage
in Osaka City
(Unit: 100 million yen)
Division
Personnel
expenses
Supplies
expenses
Sub-total
Interests
payable
Depreciation
expenses
Total
1965
8.4
5.6
14.0
11.4
8.5
33.9
1966
10.6
7.7
18.3
14.8
9.3
42.4
1968
15.1
13.6
28.7
22.5
13.8
65.0
1970
20.5
17.7
38.2
30.1
20.7
89.0
1972
31.1
25.9
57.0
44.0
28.5
129.5
1973
40.8
31.6
72.2
52.0
35.0
159.2
1974
58.2
47.6
105.8
64.1
38.6
208.5
1975
72.7
56.3
129.0
82.2
46.8
258.0
1976
81.7
67.8
149.5
101.4
54.5
305.4
Table 7 Change in Financial Structure of Osaka City (General Account)
(Unit: 100 million yen)
^~"~~\^^ Fiscal year
Division ^^^^^^^
Tax revenue A
Ordinary expenses B
Specific funds for the
above C
Taxes revenue covering
ordinary expenses
(B - C) D
Percentage of the above
D/A
Taxes revenue covering
investment and
extraordinary expenses
(A - D) E
Percentage of the above
E/A
Original budget
for fiscal 1978
3,211
4,352
1,472
2,880
90%
331
10%
Settlement of
accounts of
fiscal 1974
2,329
2,410
690
1,720
74%
609
26%
Settlement of
accounts of
fiscal 1970
1,093
1,410
293
749
69%
344
31%
325
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Table 8 Transition of Municipal Tax, General Municipal Expenses Appropriated for Sewerage and
Standard Fiscal Demand
(Unit: 100 million yen)
Division
Municipal
taxes
Growth rate
of the above
General
municipal
expenses
appropriated
for sewerage
Growth rate
of the above
Standard
fiscal
demand
1965
468.7
100
18.2
100
-
1966
520.9
111
26.9
148
25.8
1968
690.7
148
43.5
239
26.3
1970
960.4
205
59.6
327
38.1
1972
1,249.3
267
87.4
480
38.5
1973
1,587.6
339
95.2
523
57.0
1974
2,018.7
431
114.0
626
49.6
1975
2,075.9
443
130.4
716
74.0
1976
2,247.4
480
150.2
825
104.6
Despite such a background, the construction and improvement expenses and
operation and maintenance expenses and capital expenses for sewerage works
require a large amount of money. As a matter of fact, in the fiscal 1978 budget of
Osaka City, a huge amount of ¥19.1 billion from general municipal expenses has
been funneled into the fund for sewerage works. Table 8 shows the transition of
municipal tax, general municipal expenses appropriated for sewerage works and
standard fiscal demand. Even in the midst of the unprecedented crisis of the
financial situation of the municipality, the growth rate of the appropriated general
municipal expenses is much higher than that of the municipal tax. Furthermore, the
appropriation of municipal tax is far larger than the necessary amount for the
construction, maintenance and management of sewerage approved by the national
government (standard fiscal demand).
2.5 NEW FIVE-YEAR PLAN FOR SEWERAGE WORKS
Based on the long history of sewerage works of well over 80 years, the Osaka
Municipality has made strenuous efforts to maintain and manage every facility in
order to achieve the objective of sewerage works. Now the diffusion rate is as high
as 93%, flood is prevented in extensive areas, and the quality of river water in the
city has been considerably improved. However, there are still many districts that are
subjected to flood and the environmental standards for the quality of river water
have not been achieved yet. At present, efforts are being made for the progress of
the 5-year plan started in 1977 with the aim of improving sewerage in Osaka City.
The contents of the 5-year plan follow;
1) Objective of the Plan
° Spread of secondary treatment in all the existing treatment plants and the
introduction of tertiary treatment at Hirano treatment plant, with the aim of
achieving and maintaining the environmental standards of water quality.
326
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° Construction of new trunk sewer and additional pumping stations, with the
aim of eliminating flood.
° Expansion of sewered areas to cover almost all city areas.
° Diffusion of flush toilets to almost all households.
2) Outline of the Plan
Extension of installment of sewer
Construction and expansion of pumping
stations
Expansion of treatment plants
Treatment capacity
Secondary treatment included in the
above
Tertiary treatment included in the
above
Total working expenses
400km
25 places
12 places
2,960,000
m3 /day
2,960,000
m3/day
100,000
m3 /day
¥240 billion
(245km)
(20 places)
(12 places)
(2,696,000
m3 /day)
(2,696,000
m3/day)
( 50,000
m3 /day)
(¥113.8 billion)
* In the parentheses are the figures for the first 3 years.
This 5-year plans is divided into the first phase (3 years from 1977 to 1979)
and the second phase (2 years from 1980 and 1981), to be flexibly executed
depending on the economic and financial situation of the times. The plan is now
under way in compliance with the plan for revenue and expenditure (for the first
three years) described in Table 9. In making this plan for revenue and expenditure,
a lot of efforts were exerted to secure enough financial resources through the
request for the increase in national grant, the security of general municipal funds
and the revision of sewer user charges (double the previous charges in real terms).
All this was done for the following reasons;
1) About two thirds of sewerage construction expeneses. are financed by the
issuance of loans. It is expected that an enormous amount of borrowings
will be necessary in addition to the issuance of loans so far, which means
that the interests payable will increase accordingly.
2) Construction of facilities results in the rise of depreciation expenses.
3) Due to the increased number of secondary treatment plants, the improve-
ment of facilities, and the rise in prices and personnel expenses, the opera-
tion and maintenance expenses including power and sludge disposal expenses
are on the rise.
In the following sections, sewer user charges that occupy about half of the
revenue shall be described, centering on the current charges.
327
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Table 9 New Plan for Revenue and Expenditure (1977-1979)
(Unit: 100 million yen)
1 . Income balance (Management)
Expenditure
Operation and maintenance expenses
Interests payable
Depreciation expenses
Cumulative deficit
Total
608
382
212
58
1,260
Profit
Sewer user charges
General account subsidy
Other revenue
Balance of comulative deficit
Total
611
577
36
36
1,260
2. Capital balance (Construction and improvement)
Expenditure
Construction and improvement
expenses
Redemption for corporate loans
Repayment of general account
borrowings
Fund shortage
Total
1,138
121
21
5
1,285
Revenue
National and prefectural grant
Corporate loans
Reserve fund, etc.
Total
333
706
246
1,285
3. SEWER USER CHARGES IN OSAKA CITY
3.1 TRANSITION OF SEWER USER CHARGE SYSTEM
Osaka City has a long history of sewerage and has long suffered the difficulty in
securing financial resources for construction, maintenance and management of the
sewerage. Osaka City is where the beneficial assessment system was introduced for
the first time in Japan, although that system is prevalent nowadays all over the
country. (It is not adopted at present because the document concerned were
destroyed by fire and so on.)
Sewer user charge was also introduced in Osaka preceding its introduction in
other cities. The study by Mr. Hajime Seki, the then Mayor of Osaka, published in
1928 evoked a hot controversy between the national government and the
municipality over whether the sewer user charge should be borne by public or
private expenses. The sewer user charge was finally approved after this argument.
The approval of sewer user charge is based on the ground that "sewerage works can
be pushed forward and the financing in compliance with the principle of fairness can
be maintained only when people concerned are made to pay the majority of
expenses for the construction, maintenance and management of sewerage in
accordance with the degree of their use. And it is only natural to collect the charge
for the use of sewerage as an establishment from the people who are no more in
need of domestic sewage septic tanks with the completion of the municipal sewage
treatment plant" The revenue that accrues from the collection of sewer user
charges is to be appropriated for the financial resources for the operation and
maintenance of sewerage and the redemption of public loans.
328
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The transition of sewer user charge system in Osaka City is as shown in Table
10-1 and Table 10-2.
The year 1940 when the collection of sewer user charges first began was also
memorable in that the sewage treatment plant was put into operation for the first
time in Osaka City. In that year, diminishing rate system was adopted for the
collection of sewer user charges. Since then until 1965, the unit price had been
revised for several times while no change took place in the sewer user charge system
itself. The meter-rate system was then introduced when the unit price was revised
again in 1965.
In 1968, it was decided to prepare a 5-year plan for the improvement of
sewerage with the objective of securing financial resources for sewerage works
including operation and maintenance expenses and the redemption expenses of
issued loans. By making a clear distinction between stormwater expenses to be
borne by public expenses and waste water expenses to be subjected to the benefit
principle, another revision of sewer user charges was made. This revision which
linked the construction plan and sewer user charges was the first of its kind in Osaka
City.
In 1972, the sewerage works plan was drastically expanded and revised in
pursuit of the diffusion of sewerage in all city areas and the promotion of secondary
treatment at sewage treatment plants. At this time, the diffusion rate of sewerage
exceeded 60%, which in turn necessitated enormous amount of operation and
maintenance expenses and redemption expenses for issued loans. This incident
meant a significant turning point in the financing of sewerage in Osaka City. In
pursuit of the adequate share of expenses and the observance of the Polluter Pays
Principle, the water quality surcharge for various kinds of industries was
established for the first time in Japan as a new sewerage charge system. For general
users, the conventional meter-rate system was replaced by progressive rate system.
Thus, a comprehensive revision of the system was carried out.
In 1974, four ranks were newly established in the conventional system in which
uniform charge had been collected for the sewage exceeding 100m3, thereby
reinforcing the progressive rate system. Furthermore, another revision including the
fractionation of ranks was made in 1977, with the consideration of domestic waste
water and the adequacy of sewer user charges for big users.
329
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Table 10-1 Transition of Sewer User Charge System in Osaka City
Kind
General sewer user charges
1 Sewer user charges
for Hush toilets
Minimum
charge
For public
bathhouse
Other
sewage
For public bathhouse
For general use
Faecal
stool
Urinal
stool
Domestic
use
Business
use
Domestic
use
Business
use
Unit water
quantity
Per month
(up to 300m3)
Exclusive use
(up to 10m )
Common use
(up to 10m3)
per m
up to 500m3
perm
501 -
10,000m3
perm3
10,001m3
or over
per m
per stool
per month
per stool
per month
per stool
per month
per stool
per month
April 1
1940
yen
0.01
0.35
0.20
0.10
0.18
0.18
April 1
1956
yen
600
30
24
2
3
2.40
1.50
(Nov. 1,
1951)
20
40
10
20
Kind
Basic
charges
Extra
charges
Faecal
stool
Urinal
stool
For general
use & public
bathhouse
For common
use
For
general
use
For public
bathhouse
For common
use
Domestic
use
Business
use
Domestic
use
Business
use
Unit water
quantity
up to 8m3
up to 10m
up to 8m3
llm3
or over
per m3
llm or over
per m
9m or over
per m3
per stool
per month
per stool
per month
per stool
per month
per stool
per month
April 2,
1965
30
40
24
5
2.60
3.90
20
40
10
20
Oct. 1,
1968
50
70
24
10
4.50
3.90
20
40
10
20
Kind
Basic
charges
Extra
charges
Faecal
stool
Urinal
stool
For general
use & public,
bathhouse
For common
use
For
general
use
For public
bathhouse
For common
use
Domestic
use
Business
use
Domestic
use
Business
use
Unit water
quantity
up to 8m
up to 10m
up to 8m
11 -20m3
per m3
21 - 30m3
per m
31 -50m3
per m
51 -100m3
per m
101m3 or
over
llm or over
per m
9m or over
per m
per stool
per month
per stool
per month
per stool
per month
per stool
per month
Nov. 1,
1972
50
70
24
10
15
16
17
18
4.50
3.90
Abolished
OO
o
[Reference]
(Note)
(1) Diminishing rate system
(2) Meter-rate system
(3) Progressive rate system
from April 1940 to April 1965
from April 1965 to October 1972
from November 1972
(1) Sewer user charges were revised eight times altogether from 1940 to 1965.
(2) The collection of flush toilet charges had been held in suspense until November 1951, the starting year of the collection.
The flush toilet charge system was later abolished in November 1972.
(3) Industrial waste surcharge was put into effect on April 1,1973.
-------
Table 10-2 Transition of Sewer User Charge System in Osaka City
Kind
Basic
charges
Extra charges
(per m3)
Water quality
surcharge
(per m3)
For general use &
public bathhouse
For common use
For general use
For public
bathhouse
For common use
Division by water
quality (ml/1)
ppm ppm
201 - 300
301 - 450
451 - 600
601 - 850
851 -1,100
1,101 -1,350
1,351-1,600
1,601 - 1,850
1,851 -2,100
2,101 -2,350
2,351 -2,600
Nov. 1, 1974
yen
up to 8m 50
up to 10m3 70
up to 8m3 24
11 -20m3 10
21 -30m3 15
31 -50m3 16
51 -100m3 17
101 -200m3 20
201 -500m3 25
50 1-1, 000m3 30
1,001m3 or
over
llm3 or over 4.50
9m3 or over 3,90
April 1, 1973
B.O.D
(COD)
yen
2
6
13
23
33
42
S.S
yen
2
7
16
27
38
49
April 1, 1977
yen
up to 8m3 100
up to 8m3 50
11 -20m3 20
21 -30m3 27
31 -50m3 30
51 - 100m3 35
101 -200m3 40
201 -500m3 50
501 -1,000m3 60
1,001 -5,000m3 80
5,001 or 9
over
llm or over 5
9m3 or over 10
Nov. 11, 1974
B.O.D
(COD)
yen
4
13
28
50
72
91
S.S
yen
5
16
36
61
86
110
April 1, 1977
B.O.D
(COD)
yen
8
18
30
46
66
86
106
126
146
166
186
S.S
yen
9
21
35
55
79
103
127
152
176
200
225
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3.2 PROVISIONS OF THE SEWERAGE LAW AND PROPOSAL OF THE THIRD
COMMITTEE FOR THE INVESTIGATION OF SEWERAGE FINANCING
The provisions on sewer user pharges and the rules on which the charges shall
be determined are provided in the Sewerage Law. The Committee for the Investiga-
tion of Sewerage Financing has made some proposals with regard to sewer user
charges. The contents of these are explained by Mr. Tamaki, the member of this
conference, in his report.
3.3 PRINCIPLE OF SHARING EXPENSES
The Sewerage Law stipulates that the sewer user charges "should not exceed
the proper sum of cost". But, what on earth is this cost?. Here the problem arises
as to who should bear the expenses for what. Sewerage obviously has a public
nature as it is a fundamental facility of cities. Its function is divided into the
discharge of stormwater and the treatment of waste water, and its expenses into
construction and improvement expenses and operation and maintenance expenses
and capital expenses. Moreover, jt inevitably involves various factors. For example,
conditions of location vary, depending on the situation of each local autonomy. At
the present stage, such a uniform principle is not yet established as to divide
distinctively the portion to be borne by public expenses and that to be borne by
private expenses. The latter should be the basis for the calculation of sewer user
charges.
The first proposal made by the Committee for the Investigation of Sewerage
Financing (in 1961) was instrumental in establishing the principle that both con-
struction and management expenses concerning stormwater must be borne by public
expenses and that those concerning waste water by private expenses. The second
proposal (in 1966) recommended to expand the portion to be borne by public
expenses, placing special emphasis on the importance of stormwater discharge
function of cities. The third proposal (in 1973) suggested the principle that
sewerage construction expenses be borne by public expenses and the operation and
maintenance expenses concerning sewerage by private expenses, as the improvement
of sewerage was regarded as a national task.
Referring to this proposal and the Polluter Pays Principle, the Osaka
Municipality now follows the principle that operation and maintenance expenses
and capital expenses regarding the discharge of stormwater be borne by public
expenses and those regarding the treatment of waste water by private expenses.
However, there exists a problem concerning the share to be borne by public
expenses proposed by the Third Committee. The third proposal meant to the effect
that for specified waste water (discharged by big users such as buildings and
factories), capital expenses for the said waste water must be included in the object
of sewer user charges in addition to operation and maintenance expenses, and that
the waste water falling short of the specified quantity must be borne by public
expenses. Yet, the minimum quantity of this specified waste water in this proposal
(50m3 /day) is too large in quantitative terms. The expense for the waste water in
332
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short of this quantity is not dealt with in the local allocation taxes. Nor is the share
concerning stormwater satisfactorily calculated, as shown in Table 8. It is a hard
fact that the present financial situation of the municipality can not bear such
burden. Besides, as progressive rate system is adopted in the city's sewer user charge
system, the charges for domestic waste water can be kept at a relatively low level.
Under these circumstances, the Osaka Municipality did not accept the aforemen-
tioned proposal.
Although the necessity to attain the national minimum of the capital expenses
borne by public expenses is well recognized, its range should be confined to
domestic waste water (below 20 - 25m3 per month). In the case of Osaka City,
about 54% of total users discharge less than 20m3 per month, and more than 76%
discharge less than 30m3 per month, as can be seen in Table 11. Therefore, it is
considered possible to achieve the above-mentioned purpose.
Table 11 Number of Households and Amount of Effluent Classified by Ranks
(Average of 3 years from 1977 to 1979)
Rank
10m3 or less
1 1 - 20m3
21 -30m3
31 -50m3
51 - 100m3
101 -500m3
501 - 1,000m3
1,001 -5,000m3
5,001m3 or over
Public bathhouse
For common use
Total
Number of households
270,782
281,498
233,352
163,268
50,416
22,235
2,561
1,980
413
1,096
2,290
1,029,891
%
26.3
27.3
22.6
15.8
4.9
2.2
0.3
0.2
0.1
0.1
0.2
100.0
Amount of effluent
1,000m3
21,423
51,444
69,116
73,738
40,295
52,138
21,393
43,836
108,507
19,062
358
501,310
%
4.3
10.2
13.8
14.7
8.0
10.4
43
8.7
21.7
3.8
0.1
100.0
3.4 CALCULATION OF EXPENSES SHARE RATE
The expenditure in the category of the income balance in Table 9 comes to an
enormous amount of ¥120.2 billion for three years from 1977 to 1979 as
mentioned in 2.3.
By clarifying the ratio of the portions of this necessary expenditure to be borne
by public expenses and users, the amount to be borne by users shall be collected as
sewer user charges. The concrete calculation method of this ratio is based upon the
way of thinking described below and the result of the calculation is shown in Table
12. The percentage of share in total expenses is 45.2% for public expenses and
54.8% for users, or ¥54.3 billion and V65.9 billion respectively when converted into
the sum of money. It must be noted that the expenses for tertiary treatment is not
included as that specific treatment will not be put in operation during this period.
333
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1) Operation and Maintenance Expenses
» Expenses for sewer (dredging expenses, etc.)
Inorganic substance and others shall be classified as stormwater and waste
water respectively, by the composition analysis of deposit in sewer.
° Pumping station expenses - To be shared in accordance with the ratio of
pumping capacity for stormwater and waste water.
° Treatment plant expenses - Pumping station expenses shall apply to
pumping facilities. Others shall be shared in accordance with the ratios of SS
quantity, BOD quantity and water quantity.
° Water examination expenses and other expenses
To be shared in accordance with the average share ratio of sewer expenses,
pumping station expenses and treatment plant expenses. However, the
expenses that can be divided clearly shall be shared accordingly.
2) Depreciation Expenses
° Sewer - To be shared according to the ratio of construction expenses in the
case of separate sewerage system.
° Pumping stations — To be shared according to the ratio of the capacity of
stormwater pump and waste water pump.
° Treatment plants - Most of the expenses is concerned with waste water.
3) Interests Payable
The same way of thinking as in the case of depreciation expenses applies to
sewer, pumping stations and treatment plants.
Table 12 Breakdown and Share of Expenditure in Income Balance (for 3 years; 1977 — 1979)
(Unit: million yen)
Division
Operation and maintenance expenses
Sewer expenses
Pumping station expenses
Treatment plant expenses
Water examination expenses
Other expenses
Depreciation expenses
Sewer
Pumping stations
Treatment plants
Interests payable
Sewer
Pumping stations
Treatment plants
Total
Total
60,871
14,671
7,182
31,749
1,407
5,862
21,171
10,065
2,442
8,664
38,209
23,013
3,326
11,869
120,252
Share
Municipal expenses
21,869
10,635
4,785
4,215
670
1,564
11,000
7,236
2,121
1,643
21,486
16,545
2,903
2,038
54,355
35.9%
72.5
66.6
13.3
47.6
26.7
52.0
71.9
86.9
19.0
56.2
71.9
87.3
17.2
45.2%
Sewer user charges
39,002
4,036
2,397
27,534
737
4,298
10,171
2,829
321
7,021
16,723
6,469
423
9,831
65,897
64.1%
27.5
33.4
86.7
52.4
73.3
48.0
28.1
13.1
81.0
43.8
28.1
12.7
82.8
54.8%
334
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3.5 FUNDAMENTAL PHILOSOPHY UNDERLYING SEWER USER CHARGE
SYSTEM
As sewer user charge is the charge for the use of facilities, it must be collected
from the users in accordance with their individual use modes. The Sewerage Law
stipulates that proper sum of cost under the efficient control should be obtained in
calculating expenses and that sewer user charges should be determined in accordance
with the amount of effluent and water quality with the aim of attaing fair share of
burden among users.
Osaka City set the sewer user charges in accordance with the provisions of the
Sewerage Law and the system is divided into general sewer user charges to be
collected according to the amount of effluent and water quality surcharge to be
collected according to the strength of water quality.
The general sewer user charges employ the progressive rate system. The
adoption of this system, coupled with introduction of water quality surcharge,
will definitely result in the decrease in the quantity of sewage discharged into sewer,
the improvement of water quality, the saving and effective utilization of water
resources and the recovery of resources. Moreover, it is rational in terms of cost.
The sewerage works are passive and cannot control actively the quantity of
water that flows in. This is why the facilities are always equipped with maximum
capacity. For this reason, 80% of the total expenses is occupied by the fixed
expenses that is always required irrespective of the presence or absence of the
discharge of waste water, such as basic power charge, personnel expenses, deprecia-
tion expenses for the facilities, interests payable, etc. This readily leads to the
assumption that if the volume of the inflow of waste water into the sewer sould be
the same every day, the highest efficiency of the expenses will be attained but that if
the use of water varies due to the business and seasonal fluctuations, the efficiency
will decrease as much.
The investigation into the actual situation of the use of water has revealed that
the more water is used, the larger fluctuation of the amount of effluent. In this
connection, this progressive rate system is appropriate in terms of cost.
3.6 COST OF GENERAL SEWER USER CHARGES
The comprehensive cost of expenses borne by sewer user charges (Table 12),
that is, the expenditure in the income balance (Table 9) minus the expenses
regarding stormwater borne by public expenses, is ¥45 per m3. This is based on the
calculation that the total amount of effluent for the three years amounts to about
1.5 billion m3. Besides, excluding the amount to be collected as water quality
surcharges that shall be described later, the amount that should be collected as
general sewer user charges comes to ¥44 per m3.
In calculating the cost in the case of progressive rate system, the ratio of
required treatment capacity and the chargeable amount of effluent was figured out,
dividing all the users in Osaka City in three groups in accordance with the amount of
effluent.
335
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° Group A - Users that discharge domestic waste water and small-scale com-
mercial waste water with chargeable amount of effluent of 0- 50
m3 /month.
° Group B Restaurants, hotels, etc. that use relatively large quantity of water
with chargeable amount of effluent of 51 1,000 m3 /month.
» Group C Department stores, buildings, factories, etc. that use especially
large quantity of water with the chargeable amount of effluent of
more than 1,001 m3 /month.
As a result, the ratio turned out to be 1.0 for Group A, 1.3 for Group B and
3.5 for Group C. This means that treatment capacity for 1 m3/day can yield the
revenue for 1 m3 /day in the case of users in Group A whereas fixed expenses
required in the case of Group C will be 3.5 times as much as those for Group A.
The trial unit prices for each rank calculated on the basis of the abovemen-
tioned findings are as shown in Table 13.
The current sewer user charges system (see upper right column of Table 10-2) was
established on this basis through the examination of the total amount of expenses in
each group. To provide more information, the current charge systems -for potable
water and industrial water in Osaka City are shown in Table 14 and Table 15,
respectively.
Table 13 Trial Unit Price Classified by Groups
(Yen/m3)
Group
A (0- 50m3 /month)
B(51 - 1,000m3 /month)
C(0ver 1,00 1m3 /month)
Total
Total amount of effluent
for 3 years (1,000m3)
648,233
347,258
508,438
1,503,929
Transitory
expenses
9.66
9.66
9.66
9.66
Fixed
expenses
18.06
23.48
63.22
34.58
Total
27.72
33.14
72.88
44.24
Table 14
The Current Potable Water
Charges in Osaka City
(Put into effect in
September, 1975)
Basic
charges
¥230 up
to 10m3
¥130 up
to 8m3
Extra
Use
General use
Business use
For public
bathhouse
Common use
charges
Perm3
11
21
31
41
51
101
201
501
1,001
11
31
51
11
9
m3 m3
20
30
40
50
100
200
500
- 1,000
-
30
50
-
-
—
Yen
40
49
58
88
108
137
155
169
180
85
130
180
28
24
336
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Table 15 The Current Charges of Industrial Water
(Put into effect in December, 1977)
Classification
Measured by mercury pressure
difference meter
Measured by meters other
than the above
Contract quantity
When hourly consumption quantity
exceeds hourly contract quantity
(amount of water obtained by dividing
contract quantity by 24 hours)
Contract quantity
In excess of contract quantity
Rate
¥27 per m3
¥54 per m3
¥27 per m3
¥54 per m3
3.7 FUNDAMENTAL PHILOSOPHY UNDERLYING WATER QUALITY
SURCHARGE
Two major merits of water quality surcharge are that (1) coupled with the
progressive rate system of general charges, this system enables the recovery of cost
through fair share of charges consented by users, and that (2) the system will work
as an incentive for the users discharging sewage of high strength in their efforts to
improve water quality, which will eventually facilitate adequate maintenance and
management of sewerage.
In Osaka City, this specific system was introduced in 1972 and has been
employed since then, as mentioned earlier. With BOD or COD and SS to be dealt
with at sewage treatment plants as objects, it was decided that sewage having a
strength over 200 ppm and a monthly discharge of more than 1,250m3 be subjected
to the collection of water quality surcharge for the following reasons;
° Provisions on water quality and those concerning proper sum of cost and the
elimination of unfair discrimination were introduced with regard to sewer
user charges when the Sewerage Law was revised.
° The responsiblities of enterprisers were specified in the Basic Law for
Environmental Pollution Control and the Pollution Control Public Works
Cost Allocation Law.
The responsibilities of enterprisers to share the expenses of pollution pre-
ventive works in accordance of their benefit are strongly sought for.
° In order to realize the prevention of water pollution without delay, the
improvement of sewerage and especially the promotion of secondary treat-
ment at sewage treatment plants are necessary. This will, however, boost the
operation and maintenance expenses and capital expenses, which will in turn
widen the gap between the unit prices for treatment of high strength waste
water and domestic waste water in the above-mentioned expenses.
It goes without saying that such harmful substances as to damage or hamper
the functions of sewerage system shall not be discharged into the sewer until they
are disposed of by pretreatment facilities to meet the regulation values specified in
the Sewerage Law.
1)BOD or COD and SS are considered as objects of water quality surcharge
on the following grounds;
337
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' BOD TJT COD and SS are essentially the items that must be dealt with at
sewage treatment plants. Although it is possible to treat them even if they
are of rather high strength, the treatment becomes comparatively expensive.
From the standpoint of fair share of burden, water quality surcharge was
adopted.
° However, as effluent of very high strength causes an adverse effect on
sewerage system, pretreatment facilities must be installed for such effluent.
Though the maximum strength is set at 2,600 ppm, approval is required for
water quality of 600 ppm of more.
2) Waste water of 200 ppm or more are subjected to the collection of water
quality surcharge for the following reasons;
° In general, the water quality of domestic sewage is 120- 180 ppm, the
maximum being approximately 200 ppm.
° The regulated values in the Water Pollution Control Law are set at 160 ppm
BOD or COD (daily average 120 ppm) and 200 ppm SS (daily average 150
ppm).
° Design criteria of sewage treatment plants are at 200 ppm, as a general rule.
3) Factories with monthly discharge of 1,250m3 or more are subjected to the
collection for the following reasons;
° Factories with monthly discharge of 1,250m3 or more are relatively large-
sized. Most of the small enterprises can, therefore, be excluded from the
object of collection.
° The Sewerage Law and the Enforcement Ordinance of the said law stipulate
that factories with daily discharge of 50m3 or more be required to give
notice of both quantity and quality of their effluent.
° Possible effects on sewerage system and the bearing on business routine
were also taken into consideration.
4) The reason why the unit prices were set, classified by water quality (BOD or
COD and SS) is as follows;
° The relation between the object items of water quality surcharge and unit
prices can be clarified.
° Sewer user charge system becomes easy to understand.
It also conforms to the philosophy underlying Article 20 of the Sewerage
Law.
° Object items of water quality surcharge can be readily distinguished from
other restriction items.
Consequently, the contents of guidance for the installation of pretreatment
facilities can also be clarified.
° The cost accounting of water quality surcharge was performed for each
water quality item.
3.8 COST OF WATER QUALITY SURCHARGE
The expenses borne by sewer user charges as described in 3.4 and 3.6 can be
divided into those concerning amount of effluent (water quantity expenses) and
those concerning quality of effluent (water quality expenses). ¥35.3 billion is
338
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planned for the former and ¥36.4 billion for the latter for the three years from
1977 to 1979.
As a result of the ananlysis of the water quality expenses, ¥8.01 and ¥9.70
were obtained for BOD or COD and SS, respectively, per m3 of inflow quantity and
100 ppm water quality. Sewer user charge was established for each rank based on
these figures as shown in Table 10-2 (lower right part). The analysis method shall be
described later.
It should be noted that only ¥1.8 billion is estimated as the revenue from
water quality surcharge, a meager amount accounting only for 3% of total revenue
from sewer user charges, which is estimated to reach ¥61.1 billion.
1) Analysis of Expenses Borne by Sewer User Charges into Water Quantity
Expenses and Water Quality Expenses
The analysis is based upon the following;
° Water Quantity Expenses -
Expenses for pumping stations, primary settling tanks and chlorine installa-
tions
° BOD or COD Expenses
Expenses for aeration tanks and final settling tanks
° SS Expenses
Expenses for sludge treatment facilities
2) Calculation Method of water quality Surcharge
The total amount of effluent to be treated for the three years from 1977 to
1979 is about 1.5 billion m3. The water quality expenses thereof is ¥36.4
billion, which is analyzed into BOD'(or COD) expenses (¥15.8 billion), SS
expenses (¥20.3 billion) and water examination expenses (¥300 million).
By dividing the BOD or COD and SS expenses by the load of inflow quantity
and quality, unit price per m3 (quantity) per 100 ppm (quality) can be
figured out. These figures will then be multiplied by the difference (actual
strength in ppm figure minus 200 ppm) to make them unit prices for
individual ranks. On the other hand, water examination expenses shall be
divided by the object amount of effluent of water quality surcharge
(83,000 m3) to obtain unit price per m3. In this case, a fixed amount shall
be added irfespective of strength.
4. RECENT TREND IN SEWER USER CHARGES
4.1 CHANGE IN TOTAL AMOUNT OF EFFLUENT
As described so far, Osaka City adopted the progressive rate system and
water quality surcharge (applied in 1973) in its sewer user charge system in 1972.
Later in 1974 and 1977, the revisions of unit prices and the reinforcement of
progressive system were made. The change in the amount of effluent over years
since 1973 is shown in two versions; classified by ranks (Fig. 2) and by sources (Fig.
3). The condition of monthly change is shown, classified by ranks (Fig. 4) and by
sources (Fig. 5).
The total amount of effluent during this time period was 523 million m3 (100)
339
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in 1973, 498 million m3 (95) in 1974, 507 million m3 (97) in 1975, 496 million m3
(95) in 1976 and 492 million m3 (94) in 1977, showing a slight decline over years.
The classification by ranks is characterized by a rising trend in the case of users
with small amount while in the rank of large amount and especially in the rank of
10,001 m3/month or more, the figure represents a drastic decline, 1977's figure only
being 63% of that in 1973. The classification by sources reveals that the potable
water quantity is flattening out whereas the quantity of industrial water and well
and river water which markedly affect sewer user charges almost halved to 62% and
59% respectively. (See Table 17).
4.2 CHANGE IN QUANTITY AND QUALITY OF EFFLUENT SUBJECTED TO
WATER QUALITY SURCHARGE
The monthly changes in the number of factories subjected to the collection of
water quality surcharge and their amount of effluent are shown in Fig. 6. The
yearly change in the amount of effluent and the change in load, both classified by
object items, are shown in Figs. 7 and 8, respectively.
In 1977, amount of effluent decreased to 61% in terms of BOD or COD and to
31% in terms of SS, compared to the figure in 1973. Similarly, the load decreased
to 51% in terms of BOD or COD and to 27% in terms of SS by the same
comparison. The rate of decrease is rather high and worthy of special attention in
the case of SS.
Is it because that SS can be more easily eliminated than BOD? In this general
trend of decrease, high and low ranks indicated decreasing trend, whereas the
intermediate ranks showed an increasing trend.
The shift in the average unit price in the water quality surcharge after the
establishment and revisions of the water quality surcharge is shown in Table 16.
Although the change in the unit price after the second revision is small, it marked a
7% decrease one year after the establishment and a 25% decrease one year after the
first revision.
It is assumed that the water saving resulted in the drop of effluent amount to
lower rank and that efforts had been made in pursuit of the improvement of effluent
quality.
Table 16 Transistion of Average Unit Price of Water Quality Surcharges
\^ Number of
^-. months passed
^\after revision
Establish- ^\
ment and ^^.
revisions ^\
Establish-
ment
1973)
First
revision
(Nov
1974)
Second
revision
1977)
Average unit
price (Yen/m )
Index
Average unit
price (Yen/m )
Index
Average unit
price (Yen/m )
Index
1
8.9
100
15.8
100
26.6
100
2
8.9
100
15.2
96
26.6
100
3
8.8
99
16.1
102
25-1
94
4
10.7
120
12.5
79
24.8
93
5
9-4
106
13.7
87
25,2
95
6
9.4
106
12.5
79
25.8
97
7
9.7
109
12.3
78
25.5
96
8
9.0
101
12.2
77
24.8
93
9
8.4
94
11.6
73
25.8
97
10
8.5
96
12.3
78
26.1
98
11
8.9
100
11.9
75
30.2
114
12
8.3
93
11.9
75
31.5
118
340
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4.3 DISCUSSION
It is somewhat rash to conclude that all these phenomena have been brought by
the sewer user charge system. Many other factors such as the change in economic
environment must be taken into account.
Related to not only factories but also activities of business offices in general,
these factors are intricately entangled, permitting no easy grasp of the situation. As
a trial, we examined the relation between the growth rate of industrial shipment in
the city (adjusted by price index) and the growth rate of sewered area as well as the
fluctuation in total amount of effluent and quantity and quality of effluent
subjected to water quality surcharges. (See Table 17.)
Table 17 Rate of Increase/Decrease over Years of Amount of Effluent, Load,
Industrial Shipment and Sewered Areas
(1973 = 100)
Classification
Total
amount
of
effluent
Object of
water
quality
surcharges
By
ranks
By
sources
Amount
of effluent
Load
Sewered area
Industrial shipment
0- 50m3 /day
51- 1,000m3 /day
1,001 -10,000
m3/day
Over 10,001 m3/day
Total
Potable water
Well and river water
Industrial water
Total
BOD or COD
ss
BOD or COD
SS
1970
98
72
180
37
88
90
87
74
88
83
89
1971
104
73
185
37
91
93
91
77
91
84
88
1972
92
102
104
93
97
98
88
93
97
90
94
1973
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
1974
105
91
90
89
95
97
88
85
95
87
63
78
61
105
89
1975
111
95
94
81
97
101
85
77
97
73
47
58
32
109
82
1976
115
91
91
72
95
100
72
72
95
67
44
56
39
113
84
1977
119
93
91
63
94
102
59
62
94
61
35
51
27
115
According to this Table;
« The sewered area is much larger in 1976 than in 1973.
(An increase of 13%. However, the rate of increase in total amount of
effluent is not so high.)
° Production decreased at a little higher rate (-16%).
° Total amount of effeuent showed a slight decline (-5%).
As many conditions overlap, it is not at all easy to make a conclusion. But it is
suspected that slackened business activities had something to do with the decline in
amount of effluent. Whatever the reason may be, the fact is that the amount of
effluent from big users and that of well and river water and industrial water recorded
a big decline.
341
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Worhty of special note is the radical drop in the quantity and quality of
effluent related to industrial waste surcharges. These phenomena seem to be the
effect of this sewer user charge system.
As many factors such as seasonal fluctuations as shown in Figs. 4 and 5 exist,
more detailed analyses and examinations will be necessary. And to what extent the
amount of effluent will decrease in the future is an interesting problem.
The examples shown in Fig. 9 describe the efforts to reduce the amount and
load of effluent at factories.
It can be easily assumed that the total amount of effluent decreased somewhat
due to the decreased production caused by the oil shock. However, the amount of
effluent was, in fact, reduced to a larger extent and the quality of effluent was
improved likewise.
To cope with this declining trend in the amount of effluent, the following
things are reckoned to be of fundamental importance;
1) Review of the basic discharge per unit of production set at the time of
planning of facilities
It is necessary to check the basic discharge per unit of production
(especially of big users) under the present conditions of the existing
facilities, and seek for the ideal discharge per unit of production (water
saving type) which is most suitable for resources and energy saving policies
and sewer user charge system.
2) Execution of phased expansion of facilities and especially of treatment
facilities
Keeping an eye on the actual increase in the quantity of inflow, it is
necessary to expand the facilities step by step, though such construction
work might be time-consuming.
This phased execution scheme is generally employed for the construction of
treatment plants. The same policy will be applied to the future expansion plan of
sewerage in Osaka City.
The municipality is determined to set fixed expenses (construction work
expenses) which is definitely necessary, grasp accurately the amount of effluent, and
establish proper sewer user charges, thus securing financial resources.
342
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5. CONCLUSION
The sewerage in Osaka City has been continuously constructed over the past 80
years in order to prevent the pollution of public water bodies and to improve the
urban environment. At the same time, the established facilities are given as much
maintenance and management as possible to achieve the objectives of the sewerage
system. Throughout this development, people concerned have been faced with
administrative and technical problems as well as financial problems and have suf-
fered the difficulty in securing financial resources for construction, maintenance and
management. Today, efforts are being made to ask -the national government to
secure financial resources for construction whereas part of municipal tax and sewer
user charges constitute the financial resources for maintenance and management.
Observing the Polluter Pays Principle, the sewer user charges adopt both
progressive rate system and water quality surcharge with proper and reasonable
cost determined in accordance with the use mode including the quantity and quality
of sewage.
This charge system works as an incentive for the reduction of amount and the
improvement of quality of effluent, which then leads to the saving and effective
utilization of water resources, the recovery of resources, and the efficient construc-
tion, maintenance and management of sewerage.
However, the sewerage in Osaka City is not free of problems. Even with regard
to sewer user charges alone, many problems concerning the increase in the national
grant for construction, the improvement of loan issuing conditions and the increase
in the local allocation tax could be cited. Besides, to reduce the operation and
maintenance expenses, it is necessary to develop better technology for water
treatment and sludge treatment and disposal. Furthermore, the increase in the share
of expenses required for the construction, maintenance and management of tertiary
treatment facilities to be borne by the national government is strongly sought for.
Though the financing problem of sewerage has long been existing, it is also a
new problem. We intend to resolve this problem for the sake of better
management of sewerage facilities. The other day, the Fourth Committee for
Investigation of Sewerage Financing was inaugurated to begin examining what the
new sewerage financing should be under the new circumstances. And again, we are
harboring so many expectations for the outcome of this meeting.
343
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Fig. 2 Yearly Change in Amount of
Effluent by Ranks
Fig. 3 Yearly Change in Amount of
Effluent by Sources
200,000-
150,000
100,000
50,000
(1,000m3)
400,000
80,000
0 — 50m3/month
51 — 1,000m3/month
1,001 - 10,000m3/month
* * 10,001 m3/month or over
1973 74
75
76
77
300,000
60,000'
200,000
40,000
(Potable water]
100,000.
20,000
(1000m3)
- Potable water
Well and river water
Industrial water
(Industrial water or
Well and river water)
1973 74
75
76
77
344
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Fig. 4 Monthly Change in Amount of Effluent by Ranks
15,000
0 ~ 50m3/ month 1,001 ~ 10,000m3/month
51 ~1,000m3/month
10,000
5,000-
Establishment
of new
charge
system
(1,000m3)
1973,4
74.4
First
revision
75.4
76.4
Second
revision
77.4
78.4
345
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Fig. 5 Monthly Change in the Amount of Effluent by Sources
80,000 j
8,000
60,000
6,000
\
\
\
1
li
ii
II
Industrial water
A
40,000
4,000
20,000
2,000
Potable
water
0
0
(1,000m 3)
Establishment
of new change
system
First
revision
1973.4
(Industrial water or
Well and river water)
74.4
75.4
76.4
Second
revision
77.4
78.4
346
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8,000
6,000
4,000
2,000
(1,000m 3)
0
0
Fig. 6 Monthly Change in the Number of Factories Subjected to
Water Quality Surcharges and their Amount of Effluent
Amount of Effluent
Establishment
of new charge
system
1973.4
74.4
75.4
76.4
77.4
78.4
347
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30.000J
20,000-
10,000-
(1,000m3)
0
Fig. 7
Yearly Change in Amount of Effluent by Object Items of
Water Quality Surcharges
1973 74
75 76
77
1973 74
76
77
348
-------
30,000
BOD or COD
Fig. 8 Yearly Change in Load by Object Items of
Water Quality Surcharges
SS
1973
74
75
349
-------
150
100
Fig. 9 Example of Yearly Change in Amount of Effluent and
Load (1973 = 100)
Firm B
Firm C
Amount of Effluent
0%
1973 74 75 76 77 1973 74
76 77
350
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CHAPTERS
New Supervision and Control System of Sewage
Treatment Plant in Yokohama
— Effective application of microcomputer —
Introduction 352
1. Centralized Supervision and Control System 352
1.1 Centralized Supervision and Control by Blocks 352
1.2 Centralized Supervision and Control 354
1.2.1 Centralized Supervision and Control of the Whole Sewage
Treatment Plant 354
1.2.2 Remote Supervision and Control of Relaying Pumping Stations
1.2.3 Application of Electronic Computer 355
1.2.4 Programmable Logic Controller and Micro-controller 355
1.2.5 Improvement of Existing Facilities, etc .... 355
2. Centralized Supervision and Distributed Control System 359
2.1 Basic Ideas for Supervision and Control in the Kanagawa Sewage
Treatment Plant 359
2.2 Outline of Supervision and Control System 360
2.2.1 Central Supervision System 360
2.2.2 Control System in Field Blocks 361
2.2.3 DATA-WAY (Multi-data Transmission) System 363
Conclusion . 363
351
-------
Introduction
The municipality of Yokohama has taken up the subject of its sewage projects
in almost all areas of the City, and plans the construction of sewage treatment plants
in eleven locations.
In the 16 years since 1962, when the first sewage treatment plant in The Chubu
district (Chubu S.T.P.) was put into operation, plants in The Nanbu, Hokubu,
Totsuka 2nd, Kohoku, Midori, and Kanagawa districts have been constructed, in
that order, and the seven plants currently are being operated.
The operational system of a sewage treatment plant is based upon the trend
toward centralized supervision and automatic control, but the details have changed
with the lapse of time, keeping pace with the innovations of technology and
development of the equipment.
First, there was a centralized supervision and control system by blocks, whereby
the total process was divided into several blocks. However, thereafter a centralized
supervision and control system, where not only the total process of the plant was
consolidated but also the remote supervision and control of the relaying pumping
stations was included, became available, and this new system has been strengthened
in the sixth plant in the Midori district. The seventh plant, in the Kanagawa district,
has the greatest treatment capacity in the City (572,000 m3/day), and for this plant,
a centralized supervision and distributed control system has been newly applied,
based upon our experience and the rapid progress made in the instrumentation and
data processing devices, and also on the premise of possible technological
developments, and the complications and expansion of the subject to be controlled.
This paper is involved with the progress of the supervision and control systems
in the sewage treatment plants of the City as shown in Fig 1, and an outline of the
centralized supervision and distributed control systems of the Kanagawa Sewage
Treatment Plant.
1. Centralized supervision and control system
The purpose of centralized supervision and control is to concentrate and
automate, as far as possible, monitoring of the processing conditions, process
control, and gathering and recording of the process data, to attain stable processing,
efficient operation of the facilities, man power saving, energy saving, improvement
of the work environment and a reduction of treatment costs.
1.1 Centralized supervision and control by blocks
For control of the Chubu S.T.P which was put into operation for the first time
in the City, the latest technology for automatic control at that time were
applied. The outline was as follows:
a) A centralized supervision and control system by three separate blocks was
applied: a sewage treatment block, sludge transfer block (relevant to return,
excess and concentrated sludge) and a sludge treatment block (as the
treatment of sludge mixed with dipped-up night soil was conducted under
special condition in this country, this process was under the control of the
other bureau).
b) In the sewage treatment block, centralized supervison and manipulation
conducted from a central operation room and automatic operation were
352
-------
Fig. 1 Progress of Supervision and Control System of Sewage Treatment Plant in Yokohama City
tn
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
Plant put into
operation
Chubu
(64,800 m'/day)
Nanbu
(2 34 ,000 m'/day)
Hokubu
(260,800 m'/day)
Totsuka 2nd
(148,000 m'/day)
Kohoku
(439,000 m'/day)
Midori
(44 3, 000 m'/day)
Kanagawa
(5 7 2, 000 m'/day)
Supervision and control systems (S & C)
Chubu '62
Centralized S 4 C
by blocks
Nanbu -55
Centralized S & C
by blocks
1
Hokub
'68
Centralized S & C |
Chubu '70
Remote S & C of
P. s.
Totsuka
^v
\ \
2nd '72 Kohoku '72
(Centralized S & C ] Centralized S & C
Nanbu
'74
Centralized S & C
Midori
Chubu '75
Centralized S & C
including P. S.
'77 Hokubu '77
| Centralized S & C Centralized S 4 C
Kanagawa "78
Centralized supervision
and distributed control
included relaying
pumping station
Instrumentation
Chubu
'62
Motor timer
Controller
Hokubu
'68
Graphical monitoring
panel
Control desk parted
ITV unit
Data logger
Chubu
'70
Cyclic digital type
Remote S & C equipment
Isogo
PS '72
Micro-
controller
Nanbu
Totsuka 2nd
Nanbu '72 Kohoku '72
ProRrammable
logic
controller
'74
Simple super type remote
S & C equipment
Kanagawa
'78
Computer multi-system
Colored CRT display unit
DATA-WAY
Digital instrument
Electric
computer
Chubu '62
Measurement ol quality
1 loating level meter
(selsyn type)
Electromagnetic flowmeter
(sludge volume)
Ventun Dowmetcr
(sewage volume)
Parshall flume flowmeter
(treated water)
Orifice flowmeter
(air volume)
Totsuka 2nd
Xohoku '72
Ultrsonic level mater
Mutsuura P.S '72
Pressure type level meter
Ultrasonic flowmeter
(sing-aroiir.d type)
Kanagawa '78
Ultrasonic flowmeter
(Doppler type)
Electromagnetic
Torihamal.WTP '72
Measurement of quality
pH meter
ORP meter
Midori '77
Turbidity meter
Do meter
Sludge density meter
Kanagawa '78
MLSS meter
Blanket meter
COD meter
S & C = Supervision and Control
P. S. = Pumping station
l.W.T.P = Industrial Wastcwatcr Treatment Plant
-------
adopted for grit chamber equipment, main pumps, blowers, etc.
Control devices:
• A regulator for controlling to keep the air volume constant
• A motor driven timer to control time for the primary, excess and
concentrated sludge withdrawal
• A logic sequence for interlocking motions of the main pumps and
mechanical screens
c) The measuring instrument was used mainly for quantitative measurement.
For water level measurement, a float system (selsyn type) was used, and for
the flow rate measurement, a Parshall flume, venturi meter etc. were used.
In 1965, the monitoring and control of the sludge transfer block in the Chubu
S.T.P. was consolidated into the central operation room.
The Nanbu S.T.P. was put into operation in the same year, and, in this plant
also, a centralized supervision and control system by three separate blocks, i.e.,
sewage treatment block, aeration block and sludge treatment block, was used.
1.2 Centralized supervision and control
1.2.1 Centralized supervision and control of the whole sewage treatment plant
In the Hokubu S.T.P. which was put into operation in 1968, a centralized
supervision and control system taking the whole plant as its subject, was
applied for the first time.
The outline of this system was as follows:
a) Monitoring was conducted through a graphical monitoring panel, to
enhance the monitoring function. The processing system was graphically
indicated on the front of the panel, and indicating meters (flow meter,
opening meter, voltmeter, ammeter, etc.) and indicating lamps were
arranged at key points in the system. In addition, an ITV unit was
installed for monitoring the major site locations (i.e. the grit chamber,
power station and sludge dewatering room).
b) Controls were, in principle, automatic; and in case that the equipment
failed to function automatically, it would be automatically switched to
the spare one.
A control desk was installed, separately from the monitoring panel, and
ON-OFF switches, provided on the desk for the major components of
the equipment (i.e. the influent gates, screens, main pumps and blowers),
also made it possible to operate the equipment manually from the
central operation room.
c) The measured values were indicated on the graphical monitoring panel,
and, in addition, the data necessary for operation and maintenance were
automatically recorded in the operation and maintenance diary, in a
definite format at definite time intervals by a data logger.
The above-mentioned system made a one-man control system available, and
a reduction of operators was visualized, compared with the conventional
supervision and control system by blocks. A reduction of 16 operators was
made, compared with the conventional supervision and control system by
three blocks.
354
-------
1.2.2 Remote supervision and control of relaying pumping station
Remote supervision and control was first introduced, in the newly installed
relaying pumping station for the Chubu S.T.P. in 1970. (The distance
between the pumping station and the plant is 7.5 km.) This system is
dependent upon the Cyclic Digital type remote supervision and control
equipment, using an exclusive cable. The application of this system reduced
the number of staff necessary to operate and maintain the pumping station
to only one for daily work of cleaning around the grit chamber and un-
manned at night, while periodic inspection and maintenance work was
carried out by two members of the staff desptached from the sewage treat-
ment plant. (A conventional pumping station needed nine staff members for
operation and maintenance.)
Also at that time, based upon experience in the Hokubu S.T.P., a data
logger was introduced into the Chubu S.T.P. to prepare operation and
maintenance diaries, for both the sewage treatment plant and relaying
pumping station.
1.2.3 Application of electronic computer
"What can be replaced by the computer, among the works conventionally
conducted by man, are to be conducted by the computer, and what can be
conducted only by the computer are to be practically conducted by the
computer." This is the purpose of the introduction of the computer. The
computer was first used in the Totsuka 2nd S.T.P. and the Kohoku S.T.P.,
both of which were put into operation in 1972, with the purpose of the
stabilization of treatment and rationalization of the operation and main-
tenance. The outline of the supervision and control system in the Kohoku
S.T.P. is as follows:
a) The processes in the sewage treatment plant and relaying pumping
station are continuously supervised by the computer, and occasionally
by the operator.
b) A Mosaic type graphical monitoring panel was applied for an easy
expansion and modification in the future.
c) Recording of process failures, and preparation of daily and monthly
reports on operation and maintenance, are conducted by the computer.
d) The principle of operation in the process is automatic control, while the
speed and number of units of the main pumps are directly controlled by
the computer.
e) The relaying pumping station is, in principle, automatically operated at
site, but occasional supervision and manual operations from the sewage
treatment plant are possible through the remote supervision and control
equipment. (The distance between the pumping station and the sewage
treatment plant is 1.5 km.)
As the result of application of the above-mentioned system, the number of
staff necessary to operate and maintain the process were reduced to 31, a
decrease of 16, compared with the past.
1.2.4 Programable logic controller and micro-controller
The programable logic controller and micro-controller were first installed in
355
-------
the City in 1972, and made it possible to easily cope with modification and
expansion, in the contents of control, in the future.
a) The programable logic controller was adopted for a blanket program
control of feed, transfer, and withdrawal, of the sludge of the nine
digestion tanks in the Nanbu S.T.P.
While the modification of the program is difficult in a conventional
sequential circuit consisting of wired relay, it is-easy in a programable
logic controller which can use any other logic circuit when necessary.
b) The micro-controller was adopted for smooth control of the speed and
number of units of the main pumps in the Isogo pumping station. While
the flow rate control through conventional analog instruments was
complicated, the adoption of the microcontroller having a micro-
computer visualized easy access to optimum control, through arithmetic
operation as well as an easy response to modification in the set flow rate
and modification of or additions to the control program.
1.2.5 Improvement of the existing facilities, etc.
a) Since the management of the sludge treatment facilities in the Chubu
S.T.P. and the Nanbu S.T.P. had been merged with the Sewage Works
Bureau in 1965, the computer system was introduced into the Nanbu
S.T.P. in 1974 and into the Chubu S.T.P. in 1975, with centralized
supervision and control system adopted.
At that time, a simplified remote supervision and control equipment
(simple super) was installed to operate remote monitoring and control of
the sludge treatment facilities, the data logger already installed in the
Chubu S.T.P. was removed, and its functions shifted to the computer.
b) The micro-controller was incorporated into the control of the sludge
treatment facilities of the Kohoku S.T.P., to operate liquid level control
of the digestion tanks, chemical dosage control, control of the number
of units of the press filters, etc., while a programable logic controller was
incorporated in the operation control circuit. The combination of these
two types of equipment was aimed at an optimum process control, the
possible addition of hardware, and modification of the software.
c) In 1977, the computer system was applied in the Hokubu S.T.P. and a
remote supervision and control system was used in the four relaying
pumping stations, making it possible to control the volume of the sewage
inlet flow from each relaying pumping stations into the sewage treatment
plant.
d) In the Midori S.T.P., which was put into operation in 1977, a
micro-controller was adopted for power control, resulting in an
automatic switch from buying power to power station and vice versa, as
with the automatic sequential ON-OFF of high voltage loads.
As stated above, during the period from 1962 to 1977 there was a transition
from centralized supervision and control by blocks, to that in the aggregate,
including the relaying pumping stations. Taking the Chubu S.T.P. as an
example, the situation is as shown in Fig. 2 and Fig. 3.
356
-------
Fig. 2 Centralization of supervision and control in the Chubu Sewage Treatment Plant (1)
C/J
en
Central operation room
Central operation room
Centra) operation room
1: Drum
2: CPU
3 PI/0
4 PI/O
Sewage treatment
M & C panel
Sewage treatment Pumping statior
M & C panel M & C panel
I
Sewage treatment Sludge treatment Pumping station
M & C panel M & C pane] | M 4 C panel
Simple type ,,,
Supervision unit
I Sludge treatment
MAC panel
Sewage treatment bloek | Sludge treatment
block
Sewage treatment Sludge Iran
; Sewage treatment bloek
TM/TC = (Remote Telemetry and Telceontrol unit) M & C = (Monitoring Control)
-------
Fig. 3 Centralization of supervision and control in the Chubu Sewage Treatment Plant (2)
!')(,_' h! 64 I,-; 66 67 6ri M 111 71 n 73 74 75 76 77 7K
tn-alilKiil blink
r hlmk
0°
.c
o „
• o
(Vntral-
i/ution
Kcniolc supervision
und control equip-
ment (Cyclic Digital
~ Computer system
~ Simple type supervision unit
1962 ft 3 M ft 5 66 67 68 69 70 71 72 73 74 75 76 77 78
358
-------
2. Centralized supervision and distributed control system
The supervision and control system of the Kanagawa S.T.P., which has put into
operation in 1978, has a newly developed basic ideas, though it is an extension of
the automation. Briefly, "both supervision and control at center" has proceeded to
"supervision at center, control at site".
2.1 Basic ideas for supervision and control in the Kanagawa Sewage Treatment
Plant
The reason why the supervision and control system in the Kanagawa S.T.P.
has been looked at other than as an extension of the traditional automation is
as follows:
a) This plant has the largest treatment capacity in the City.
b) The equipment for automation and electrical data processing has been
progressively developed, and the actual results have accumulated.
c) Further progress in man power saving has been required.
There has been serious discussion on what should be the optimum supervision
and control system for large plants, resulting in the following policy:
a) The operation of the sewage treatment plant and relaying pumping stations
should be conducted by a small number of operators (ordinarily one or
two) through further promotion of automation and the qualitative
enhancement of control.
b) Measures should be taken to prevent failure of the control at center, or in
any part from having an influence on the whole.
c) The control system should be such that the optimum control mode can be
selected in response to the process conditions, and modification can
readily be made to cope with possible technological developments.
d) The technology for quality control should be progressively introduced.
Based upon the above-mentioned ideas, the monitoring of the processes in the
sewage treatment plant and relaying pumping stations is concentrated into,
and conducted by the computer installed in the central operation room, while
the controls are multiplely conducted by giving a control function to each
field block.
The advantages of this system are as follows:
a) The failure of the central computer does not lead to a stoppage of the
whole plant, as control is continued in the field blocks.
b) As the controls are divided into each field block, it is possible to build a
control program that matches best with the characteristics of each block.
c) When modification or addition is required in the control program, it can be
made in each program, having no influence on the other blocks.
d) It is convenient for inspection and maintenance.
(The number of staff for management of the Kanagawa S.T.P. and
two relaying pumping stations is 43.)
359
-------
2.2 Outline of supervision and control system
The new system, in the Kanagawa S.T.P., is as shown in Fig. 4.
2.2.1 Central monitoring system
The central computer system has the following functions:
Fig. 4 Supervision and control system in the Kanagawa Sewage Treatment Plant
Hodopaja F S
Sakuragi P S.
P I/O (Process input/output)
Central Processor
(192 KB) 96 KW
Hulk store
(Magnetic disk)
2MB \ 4
MS, -M.S. Masier station
RS.-RS,, Remote slat
RS, RS, RS, RS4 RS< RSt RS- RS, RS, RS, „
(I/O-T/W)
II
1°
a. A
-O ~
V ~
1!
— J2
f
a. I
* in future
360
-------
a) All process data for the sewage treatment plant and two relaying
pumping stations are input to the computer, and the process
conditions are continuously monitored.
b) In order to efficiently conduct the supervision and operation of the
process, a greatly consolidated graphic monitoring panel of mosaic
type, showing indicating lamps and system operations at a glance, is
installed.
c) Process values and operating conditions of the equipment are indicated
by colored CRT display equipments, and the instruction for selection
of the control mode of the micro-controller of each field control
block, modification of set values, setting of operation sequence of the
equipment, etc. can be issued after viewing the CRT picture.
d) Process failure is automatically recorded, and daily, monthly and
yearly reports on the operation are automatically prepared. The
automatically measured data for the quality are not only displayed on
the CRT picture, but also automatically listed on the daily, monthly
and yearly reports, including manually analized quality data.
In addition, in order to enhance the reliability of the supervision and
control function, the central computer is consisted of dual-duplex system.
2.2.2 Control system in field blocks
The constitution of the control system in each field block is as shown in
Fig. 5.
a) The control in each field block is perfomed in the minor loop by the
micro-controller, programable logic controller, digital instruments, etc.
For the ON—OFF instructions, set values etc., the control outputs are
issued from the processing unit of the central computer, through the
DATA-WAY described later. Similarly, the data from each field control
block are sent, through the DATA-WAY, to the data processing unit of
the central computer, and annunciation and memory are conducted.
Fig. 5 Block diagram of control system in field block
361
-------
Table 1 Field Block Items in Kanagawa Sewage Treatment Plant
Field Block
1. Receiving and transforming power
block
2. Power station block
3. Main pump block
Main pump
(".ate
Screen
4. Primary sedimentation tank block (1 )
5. Aeration tank and
final sedimentation
tank block (2)
Aeration
Return sludge
pump
Kxccss sludge
pump
6. Blower facilities block
7. Sludge treatment block
8. Chlorination and filtering block
Control Item
1. Interruption and recovery control
2. Power supervision and control
Received power
Generated power
3. Power-factor control
1 . Automatic starting control
2. Generating energy control
Simulated load control
Number of units control
3. Continuous priming control
1. Optimum level control
(Velocity control and Number of units control)
2. Optimum flow control
(Velocity control and Number of units control)
Automatic opening and closing control by sewage
inflow volume
1. Screen control by level difference
2. Time control and interlocking control
Sludge withdrawal control
(Constant volume, proportional to sewage inflow
and primary sedimentation tank sludge level control)
Air volume control
(Constant volume, proportional to sewage inflow,
or set DO control)
Flow rate control
(Constant volume, proportional to sewage inflow,
or final sedimentation tank sludge level control)
1. Intermittent withdrawal
(preset control and timer control)
2. Continuous withdrawal (set MLSS control)
1. Suction air volume control
( Regulating valve control)
2. Number of units control
1 . Sludge volume control
2. Chemical dosing control
3. Dcwaterer optimum process control
1 . Constant dosing volume control
2. Constant dosing rate control
Primary sedimentation tank block (2), an aeration tank and final sedimentation tank block (2)
and sludge treatment block (2) may be added in the future.
362
-------
b) The field blanket panel, installed in each field block, shares the same
functions as the operating function of the central desk and the
condition-indicating function of the colored CRT display equipment,
enabling the operation of the equipment at site, if necessary. The
control items of each field block are given in Table 1.
2.2.3 DATA-WAY (Multi-data transmission) system
This is a system where the master station is located in the central
computer and the remote stations are located in each field control block,
and a great deal of data necessary for monitoring and control can be
voluntarily transferred between the stations at high speed. Since both
stations are connected by a pair of cables, this system is superior to the
conventional control cable system in the following points:
a) No limit is required in the type and quantity of data to be transferred.
b) It is easy to cope with a possible increase in the data to be transferred.
c) A shorter period is required for the design and construction of the
cable.
d) The cost for wiring is greatly reduced.
e) Inspection and maintenance are easier.
f) Remedy of the cable failure is facilitated by doubling the transfer
cable.
Conclusion
In the City of Yokohama, the automatic control and recording of various
processes, and the remote supervision and control of the relaying pumping stations,
have been promoted for the past 16 years, with the aim of a centralized supervision
and control in operation and maintenance of the sewage treatment plants.
This has been supported by the introduction of electronic computers and the
development of related supervision and control equipment. As a result, at present,
normal monitoring, control and recording are all performed by the equipment, the
operators being required to monitor only occasionally.
If the subject of monitoring and control becomes more plentiful and more
complicated, the centralized supervision and distributed control system, where
supervising function and control function are separated is taken to enhance the
reliability, flexibility, and economy of the system. This greatly dues to the advent of
the microcomputer which is suitable in capacity and profitable in the economy of
the number of loops used, from a few to several dozen, and the DATA-WAY, which
makes a high-speed transfer of a great deal of data possible. Thanks to this advanced
technology, a reasonable general management of the whole process has become
available through an automatic control of each block, that composes the whole
system, and a smooth transfer of the data in the whole system.
Up to the present, however, the main subject of supervision and control is
quantitative control, and to obtain the optimum control, technology in the field of
qualitative control must be developed. As a part of such development, the City is
promoting field tests for some of quality sensors, and has already obtained a
practical use for some of them. We plan to steadily accumulate the actual results, as
our theme for the future.
363
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CHAPTER 6
MISSION AND ACTIVITIES OF JAPAN SEWAGE WORKS AGENCY AT
PRESENT AND FUTURE
1. Mission of Japan Sewage Works Agency 365
1.1 Sewerage Systems Built before 1950s 365
1.2 Environmental Pollution after 1960 and its Countermeasures 366
1.3 History of Water Pollution Control and the Sew~erage
Act in Japan 370
1.4 The Background for the Establishment of the Japan Sewage
Works Agency 371
1.5 Legal Aspect of the Japan Sewage Works Agency 372
1.6 Outline of the Functions of the Japan Sewage Works Agency 373
1.7 Financing and Subsidies for the Japan Sewage Works Agency 373
1.8 Policies in Conducting Business at the Japan Sewage Works
Agency 374
1.9 The Role of the Japan Sewage Works Agency and the Procedures of
Operations 375
1.10 The Budget and the Organizational Structure of the Japan Sewage
Works Agency 376
2. Activities of The Japan Sewage Works Agency 379
2.1 Construction of the Main Facilities of Sewerage Systems 379
2.2 Detail Design 381
2.3 Project Planing 384
2.4 Technical Assistance 385
2.5 Training 387
2.6 Engineer Certification 392
2.7 Research and Technology Development 394
2.8 Technological Committee 406
3. The Future of Japan Sewage Works Agency 407
364
-------
1. MISSION OF JAPAN SEWAGE WORKS AGENCY
1.1 SEWERAGE SYSTEMS BUILT BEFORE 1950s
Before taking up the main subject — the background to the establishment of
the JSWA, it would be necessary to briefly review the history of construction of
sewerage systems in Japan. Construction of modern sewerage systems for cities
began with the enactment of the Sewerage Act in 1900. According to this Act,
construction and management of sewerage systems were entrusted with each city,
but when a city wanted to provide its sewerage system, an approval of the plan by
the Minister in charge was necessary. In spite of the enactment of the Sewerage Act,
sewerage systems were not actually built before 1945 except in a limited number of
large cities. As of 1945, only the following six cities had sewage treatment plants in
operation.
After 1945 and during the 1950s, sewage works did not make a development
so much all over Japan, and the rate of provision with sewerage systems remained at
a very low level. This situation was due mainly to the following reasons:
(1) The lavatory at each household was a dipping-up type, and night soil was
carried to a farm land to be used as manure for crops.
(2) Necessity of building sewerage systems was not well recognized.
(3) Municipalities which were responsible to employ their sewerage systems con-
struction were in difficult positions to obtain appropriate funds for the con-
struction of sewerage systems.
(4) In those days, the government's top priority policy was to form the basis of
industries; measures and facilities for environmental protection such as sewer-
age systems were left over.
City
Tokyo
Nagoya
Nagoya
Nagoya
Kyoto
Toyohashi
Gifu
Tokyo
Tokyo
Kyoto
Osaka
Osaka
Name of Sewage
Treatment Plant
Mikawashima
Horidome
Atsuta
Tsuyuhashi
Kisshoin
No da
Chubu
Mikawashima
Shibaura
Toba
Tsumori
Ebie
Treatment System
Trickling Filter Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Activated Sludge Process
Start of
Operation
1923
1928
1930
1932
1934
1935
1937
1937
1937
1938
1940
1940
365
-------
1.2 ENVIRONMENTAL POLLUTION AFTER 1960 AND ITS
COUNTERMEASURES
Environmental pollution rapidly developed in the 1960s. A number of reasons
can be cited for this situation, but the first reason is that Japan attained a remark-
able economic growth in the 1960s, with a shift of its industrial structure from
primary industries to secondary and tertiary industries. Also there was a population
move from agricultural and fishing villages to cities. As seen in Table 1, in 1960, the
ratio of urban population (population in densely populated districts) to the total
population in Japan was 43.3%, but in 1975, this ratio increased to 57%. The total
area of urban districts in Japan was 3,865 km2 in 1960, but this figure also increased
to 8,275km2 in 1975, ushering in the age of urbanization and industrialization.
As is clear from Table 2, the rate of increase of the urban population in Japan is
higher than that of other major countries of the world.
The second reason is that the economic growth rate, especially that of the
industrial sector, was exceptionally high as shown in Table 3.
Table-1 Periodical Change of City (Urban District) Population
1960
1965
1970
1975
Whole Country
Total
Population
(10 thou-
sand A)
9,430
9,920
10,466
11,194
Total
Area
(km2)
374,773
375,070
377,535
377,535
Cities (Urban Districts)
Population
(10 thou-
sand) B
4,083
4,726
5,599
6,382
Area
(km2)
3,865
4,605
6,444
8,275
B/A
(%)
43.3
47.6
53.5
57.0
Other Districts
Population
(10 thou-
sand) C
5,347
5,194
4,867
4,812
Area
(km2)
370,908
370,465
371,091
369,260
C/A
(%)
56.7
52.4
46.5
43.0
Table-2* Ratio of City Population (1970) and Annual Rate of
Increase (1960 ~ 1970)
Japan
U.S.A.
Britain
France
Italy
Sweden
Netherlands
OECD
Ratio of City Popula-
tion to Total Popula-
tion in 1970 (%)
56.3
58.3
71.7
42.6
29.4
32.7
45.2
49.3
Annual Rate of In-
crease for Years
1960-1970 (%)
4.0
2.8
0.5
3.5
2.8
3.5
3.1
2.7
*Environmental Policies in Japan, OECD, Paris 1977
366
-------
Table-3* Growth Rates of Japan and Major Member Countries of OECD
(Annual Rate, 1960 ~ 1970, %)
Japan
U.S.A.
Britain
France
Italy
Sweden
Netherlands
OECD
GNP
10.8
4.2
2.7
5.6
5.5
4.6
5.3
5.0
Industrial
Output
14.8
4.8
2.8
5.9
7.0
6.1
7.3
5.9
Energy
Consumption
11.6
4.5
2.3
5.3
8.9
5.0
8.4
3.0
Number of
Automobiles
in Use
25.3
3.7
6.6
8.2
24.2
6.4
15.7
6.2
*Environmental Policies in Japan, OECD, Paris 1977
What played inportant roles in the economic growth process during 1960s were
such pollution-causing industries as the steel making, power generation, cement
production, paper and pulp manufacturing, foodstuff processing and chemical
synthesizing, all these marking particularly high growth rates. During this period,
there were several incidents in which health of residents in relevant areas was greatly
impaired due to water contamination by local industries.
For example, in 1959, residents in Minamata City, Kumamoto Prefecture,
contracted a disease after they ate fish contaminated by mercury which was dis-
charged into Minamata Bay by a nearby chemical factory. Since then, this disease
has been named "Minamata Disease" In 1965, similar cases to those of Minamata
Disease were found in the area along the Aganogawa River in Niigata Prefecture.
This was also proved as mercury contamination due to discharge of waste water
from a local chemical factory. In 1959, a cadmium contamination case called
"Itai-itai Disease", was found in the basin of the Jintsu River, Toyama Prefecture.
The cause of this social problem was the waste water from a metal mining company
in the area.
The third reason is that the production and consumption activities in Japan
were concentrated in limited areas. Japan is an island country with a population of
more than 100 million, and the population density is very high. A greater part of
the land is mountainous, and the habitable area with a ground surface gradient of
less than 10% is only a quarter of the total land area.
All the production and consumption activities are conducted within this
habitable area, therefore, the activities per km2 of the habitable land area — the
pollution load — are greater than in any other country of the world as shown in
Table 4.
The fourth reason is that historically very little public investment has been
made in Japan for the stock of the social overhead capital. In many cases, the social
367
-------
Table-4* Major Economic Activities per km2 of Habitable Land Area
Japan
U.S.A.
Britain
France
Italy
Sweden
Netherlands
OECD
GNP
(Million
U.S. Dollars)
1975
6.05
0.32
1.04
0.87
0.81
1.67
3.10
0.31
Industrial
Output
(Million
U.S. Dollars)
1974
2.04
0.09
0.26
0.25
0.24
0.44
0.83
Energy
(1,000 tons
in Terms of
Petroleum)
1974
4.12
0.36
1.00
0.47
0.66
1.09
2.38
0.27
Number of
Automobiles
Owned
1974
331
27
80
47
74
69
146
21
*Environmental Policies in Japan, OECD, Paris 1977
Table-5 Comparison between Rate of Provision with Water Supply Facilities and
That of Sewerage Systems
1960
1965
1970
1975
Total
Population A
(10, 000 people)
9,342
9,827
10,372
11,194
Population
Supplied B
(10,000 people)
4,991
6,824
8,375
9,839
Population
Sewered C
(10, 000 people)
519
816
1,630
2,551
B/A
(%)
53.4
69.4
80.8
87.8
C/A
(%)
6.1
8.3
15.7
22.8
Table-6 Periodical Change in GIMP and Investment in Sewerage System
Construction
1960
1965
1970
1975
1977
GNP A
(100 million Yen)
162,070
328,137
730,461
1,495,500
1,860,140
Investment in Sewerage
System Construction B
(100 million Yen)
203
705
1,893
6,975
11,617
Ratio (B/A)
%
0.12
0.21
0.26
0.46
0.62
368
-------
overhead capital contributes to reducing the pollution load, but in Japan, the social
overhead capital was accumulated slower than in other countries. Moreover, the
social overhead capital is not well balanced in its contents, which brings about
environmental pollution. For example, Table 5 shows a comparison between the
rate of provision with water supply facilities and that of sewerage systems. This is
an indication that, as a whole country, water supplied and used is being discharged
without any control and without any proper treatment.
The fifth reason for the environmental pollution is that since 1945 Japan has
regarded industrial development as a matter of prime importance and the govern-
ment policy for the industrial development has resulted in relative negligence of the
quality of the environment. Since 1970, however, there has been a slight change in
its policy, the quality of the environment being given serious consideration. Many
of the countermeasures taken were rather patchy, and no satisfactory results have
been obtained so far. Recently, however, improvement in the environmental quality
has been somewhat felt.
Let's look at the investment made in sewerage systems as a water pollution
control measure. As is clear from Table 6, the ratio of funds invested in sewerage
systems to GNP was 0.12% in 1960, but it increased to 0.62% in 1977. If we look
at the public investment plan included in the government's economic plan, we see
that the investment in the sewerage systems gradually increases, as seen in Table 7,
being given a sufficient consideration along with road construction, housing develop-
ment and flood control.
Table-7 Social Capital Investment and 5-year Construction Plan for
Sewerage System in Government Economic Plan
(Unit: 100 million yen)
\ Economic
\ Plan
Public \
Works \
Road
Construction
Housing
Sewerage
Systems
City Parks
Food Control
Total
Grand Total
5-yeai
Construction
Plan for
Sewerage
Planned
Period
Investment
Economic Plan for
Late 1970s
(1976-1980)
Invest-
ment
195,000
65,000
71,000
15,400
55,000
401,400
1,000,000
Share
(%)
19.5
6.5
7.1
1.5
5.5
40.1
100.0
fourth
1976 ~ 1980
75,000
Basic Economic
and Social Plan
(1973- 1977)
Invest-
ment
190,000
60,800
56,500
13,000
47,000
367,300
900,000
Share
(%)
21.1
6.8
6.3
1.4
5.2
40.8
100.0
New Economic and
Social Development
Plan
(1970- 1975)
Invest-
ment
117,000
39,000
23,000
4,300
29,000
212,300
550,000
Share
(%)
21.3
7.1
4.2
0,8
5.3
38.6
100.0
third
1971 - 1975
26,000
Economi
Social Deve
Plan
c and
opment
(1967-1971)
Invest-
ment
61,500
17,100
9,300
2,070
16,100
106,070
275,000
Share
(%)
22.4
6.2
3.4
0.7
5.9
38.6
100.0
second
1967- 1971
9,300
Economic Plan for
Mid-1960s
(1964 ~ 1968)
Invest-
ment
41,000
11,200
5,792
805
9,000
67,797
178,000
Share
(%)
23.0
6.3
3.3
0.4
5.1
38.1
100.0
first
1963-1967
4,400
369
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1.3 HISTORY OF WATER POLLUTION CONTROL AND THE SEWERAGE
ACT IN JAPAN
Rapid improvement was seen in the I970's for the protection of the environ-
ment, particularly with the sewerage systems of the country. It appreared against
the backdrop of deteriorating living environment of the 1950's and 1960's.
The followings are some of the major developments in chronological order:
1958 The Sewerage Act (April 24)
A Law of Quality Control of Public Water (December 25)
A Law of Industrial Waste Water (December 25)
1959 The Sewerage Section established within the Public Works Research
Institute, Construction Ministry (April 1)
1963 The Act For The Improvement Of The Living Environment And
Facilities (December 24)
The First Five-Year Sewerage Construction Plan (with the estimated
budget of 440 billion Yen)
1967 The Act Of Sewerage Improvement (June 21)
The Basic Law For Environmental Pollution Control (July 21)
1969 The Second Five-Year Sewerage Construction Plan (with the total
budget of 960 billion Yen; February 21)
1970 A Class of the Environmental Water Quality Standard decided by the
Government (April 1)
The Water Pollution Control Act (December 25)
Partial Revision of the Sewerage Act (December 25)
1971 The Establishment of the Department of Sewerage & Sewage Purifica-
tion within the Ministry of Construction (April 1)
The Establishment of the Environment Agency (May 31)
The recommendations by the Central Committee on City Planning,
concerning "Ways and means to execute the promotion of sewerage
construction" (August 16)
The Third Five-Year Sewerage Construction Plan (at the total expense
of 2.6 trillion Yen; August 27)
The First US/Japan Conference On Sewage Treatment Technology
(October 25 ~ 28), Tokyo, Japan
1972 The Sewage Construction Project Center Act (May 29)
The Second US/Japan Conference On Sewage Treatment Technology
(November 27~December8),Cincinnati,Ohio and Washington,D.C.,U.S.A.
1973 The Basic Economic And Social Plan (1973 ~ 1977) approved by the
Government (February 13)
The Seto Inland Sea Conservation Law (October 2)
1974 The Third US/Japan Conference On Sewage Treatment Technology
(February 12 ~ 16), Tokyo, Japan
1975 The Japan Sewage Works Agency Act (February 21)
The Fourth US/Japan Conference On Sewage Treatment Technology
(From October 22 ~ 30), Cincinnati, Ohio and Washington, D.C.,
U.S.A.
370
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1.4 THE BACKGROUND FOR THE ESTABLISHMENT OF THE JAPAN
SEWAGE WORKS AGENCY
In the 1970's, various measures were introduced by the Government to con-
struct and improve the sewerage systems as part of its efforts to control the quality
of water. Particularly, with the start of the third Five-Year Sewerage Construction
Plan in 1971 at the expense of 2.6 trillion Yen, which is a little less than three times
the amount of the second Five-Year Plan, sewerage works increased tremendously,
and as a result, we saw a lack of enough engineers to carry out the work smoothly.
On April 21, 1970, the Government approved a Class of the Environmental
Quality Standard. And consequently, the number of rivers increased, whose water
qualities must meet the government standard. And in order to meet the national
standard to control the water quality of rivers in Japan, the Government had to con-
struct sewerage systems of local municipalities. As shown in Table 8, the govern-
mental emphasis on sewerage construction has been shifted from big cities to smaller-
sized local cities and towns, and this trend will become more so in the future.
It is very important of employ enough well-trained engineers for sewerage
construction. And such engineers are usually concentrated in b'ig cities in Japan.
This is because, in large cities, a fairly large amount of work is available continuously
at higher pay than in smaller cities. On the other hand, in smaller cities and pre-
fectural governments, there are not enough engineers both of them have not con-
ducted sewage works so far and have not employed engineers in charge of these
works. Under these circumstances it would be difficult for them to carry out their
sewerage projects particularly big-scale sewerage construction projects. They are not
well experienced and it is difficult for such local municipalities to employ spe-
cialized engineers, such as sanitary, electric, mechanical engineers, chemists and
biologists in charge of planning, constructing, and maintaining sewage treatment
plants. In addition, each local municipality is an independent organization, per-
sonnel exchanges are virtually impossible between big cities and smaller ones. This
is due mainly to Japan's life-time employment system, under which a person is hired
by an organization for life and he is expected to stay there for life.
Private consulting firms in the field of sewage works in Japan have come into
existence only recently, and generally there are few which have well-experienced,
well-qualified engineers.
Under these circumstances, the Minister of Construction asked the Central
Advisory Committee on City Planning to submit its recommendations on ways to
execute the promotion of sewerage construction. And on August 16, 1971, the
Committee came up with the recommendations that the Government and local
governments must take fundamental measures as soon as possible to provide the
system under which engineers are to be pooled and sent to various organizations as
the need arises. Along the line of the recommendations, the Ministry of Construc-
tion asked the Education Ministry to put more emphasis in providing courses on
sanitary engineering in technical colleges and universities. The Ministry of Construc-
tion also began preparation, with cooperation of local governments, to establish
a sewerage works organization for the purpose of pooling enough engineers to be
dispatched where they are needed, as well as advancing the construction expenses
371
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Table-8 Sewerage Investment In Big
And Smaller-sized Cities
Year
1960
1965
1970
1975
10 big cities
Amount
Invested
(billion
Yen)
"A"
15.0
48.9
112.4
361.4
No. of
cities
10
10
10
10
Smaller-sized cities
Amount
Invested
(billion
Yen)
"B"
5.4
21.6
77.0
336.2
No. of
cities
138
162
239
476
Total
Amount
Invested
(billion
Yen)
"C"
20.4
70.5
189.4
697.6
%
A/C
73.6
69.4
59.3
51.8
B/C
26.4
30.6
40.7
48.2
for the needy local municipalities. And the Sewage Construction Project Center
(SCPC) was set up on November 1, 1972.
Among its many functions, this SCPC's main job is to give various technical
assistance to local governments, including the assessment of sewerage construction
projects, the planning and actual construction works under commission with their
money, as well as other assistance, such as training of engineers and research and
technology development and in making it into practical use in cooperation with
local governments each giving 50% of the total cost. In short, the SCPC has been
working to help local government bodies to promote sewerage works in Japan.
However, since then, the application of the water quality standard by the Govern-
ment was extended to rivers, lakes, bays and coastal waters throughout Japan, and
as a result, the construction of sewerage systems for environmental protection
became to be beyond the boundaries of one local government. It came to be re-
cognized, instead, as the national issue to be immediately dealt with in order to
conserve the nation's water resources as a whole. Consequently, the main function
of the SCPC was being shifted from giving assistance to local governments to taking
over their operations to construct sewerage systems by the SCPC.
With the changes in the nature of the SCPC during the first three years after
its establishment, the Japan Sewage Works Agency Act was enacted on June 19,
1975, which virtually absorbed the SCPC into a new body, the Japan Sewage Works
Agency by enlarging the functions and organizational structure of the former.
1.5 LEGAL ASPECT OF THE JAPAN SEWAGE WORKS AGENCY
The JSWA is a public corporation which has a special status as stipulated by a
special law. Since its operation involves the sewage works which local governments
ought to do, the JSWA must work for the benefit of all these local governments.
Therefore, the establishment of the JSWA is to be initiated by the representatives of
local governments, and the cost of establishing the organ and some operational
expenses are to be borne equally by the central government and local governments,
including the cost for training engineers and for research and technology develop-
ment. Planning and construction of sewerage systems by the JSWA under commis-
372
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sion with a local government is to be paid for by the local government concerned.
However, since the function of the JSWA is not only to promote common interests
among local municipalities by providing sewerage systems to improve the living
environments of the people, but also to attain the national goal to control the
quality of the public water and to secure water resources for the entire nation, the
JSWA is considered to be the same as those established by the central government as
far as the control and financial assistance of the Government is concerned.
1.6 OUTLINE OF THE FUNCTIONS OF THE JAPAN SEWAGE WORKS
AGENCY
The functions of the JSWA are stipulated in the first clause in Article 26 of
the Japan Sewage Works Agency Act. The following are some of the major func-
tions of the organization:
(1) Construction of main sewerage facilities.
Under commission from a local government, the JSWA is to consturct sewage
treatment plants, the trunk sewers to such plants, and the pumping stations.
(2) Designing, construction supervision, and operation and maintenance of the
sewerage systems
Under commission from a local government, the JSWA is to plan sewerage
systems, supervise their construction, operation and maintenance the sewage treat-
ment plants and the pumping stations.
(3) Technical assistance for sewerage construction
By request of a local government, the JSWA is to give technical assistance for
the assessment of the plans, construction, and the operation/maintenance of the
plants.
(4) Tranining of engineers
The JSWA is to give training to national and local civil service personnel who
are in charge of sewage works. Training of those from commercial companies by the
JSWA is prohibited.
(5) Qualification tests
The JSWA is authorized to give qualification tests to those who wish to take
them, including engineers of both national and local governments as well as those
from private companies.
(6) Research and technology development
The JSWA is to conduct research and technology development in the field of
sewerage, sewage treatment and pre-treatment, as well as on the practical applica-
tion of such technology.
(7) Construction of the facilities, and giving technical assistance upon request of
public corporations
Under commission from public corporations which are established by special
laws, the JSWA is to plan and construct the main sewerage facilities, supervise the
actual construction work, and give technical assistance on operation of the facilities.
1.7 FINANCING AND SUBSIDIES FOR THE JAPAN SEWAGE WORKS
AGENCY
The JSWA receives capital fund and subsidies from the central and local govern-
373
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ments. The capital fund covers the costs of land purchase and the construction of
the administration building and the laboratory, as well as the deposit for renting the
office building, housing for staff members, and others. In other words, the capital
fund is used to acquire the fixed property for the operation of the JSWA.
On the other hand, the subsidies are to be spent on personal expenses of the
staff in the planning, general affairs., accounting, training, and research and develop-
ment divisions of the JSWA, as well as travel expenses and operational costs. Sub-
sidies are also used to provide training facilities and testing equipments for training
courses.
In principle, the central government and local governments each contribute
half of the combined total amount of the capital fund and subsidies for the op-
eration of the JSWA. With the half to be paid by the local governments, a group of
prefectural governments and a group of local municipalities (each with more than
80,000 in population) contribute with the 2 to 1 ratio. In other words, the ratio of
contribution to the finances of the JSWA is 50% by the central government, 25% by
prefectural governments, and another 25% by local municipalities. This is based on
the government recognition that the construction and operation of sewerage systems
in controlling the quality of the public water should be carried out jointly by
various governments at different political levels of the nation.
1.8 POLICIES IN CONDUCTING BUSINESS AT THE JAPAN SEWAGE WORKS
AGENCY
(1) Conduct of business
Business is to be conducted according to the Japan Sewage Works Agency Act,
its Enforcement Ordinance, and the detailed enforcement regulations. In practice,
business is carried out according to the operational procedure which is approved by
the Minister of Construction as stipulated in the regulations mentioned above, as
well as according to regulations and official notices issued by the President of the
JSWA.
The JSWA is also bound legally to submit its budget, plant of operation, and
financial program each fiscal year to the Minister of Construction for approval.
This means that the JSWA conducts its business within the regulations specified by
law and others, as well as within its budget. Therefore, the JSWA's operations are
secured both legally and financially. And the organization is expected to conduct
its business most efficiently and properly as an organizational entity.
(2) Conclusion of an agreement
Since the JSWA operates under commission with a local government, the op-
erational procedure manual directs the organ to conclude an agreement of commis-
sion with the local government concerned, the manual also specifically mentions the
details to be agreed upon. This agreement of commission is the basis, on which
other businesses are conducted thereafter. Howver, according to the regulations on
conducting business under commission, an agreement of commission is to be con-
cluded only after the approval of the national budget, the budgetary appropriation
for the JSWA, and the business plans are thoroughly examined. This is because the
operations of the JSWA are costly, such as the construction of a sewage treatment
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plant, and because the cost of such operation is to be financed by subsidies and
other financial assistance of the national government.
After an agreement is reached on the nature of the commissioned operation,
the date of completion, and other details, the JSWA makes a report on the agree-
ment and sends a copy to its local government for approval. If no objection is
voiced or no unexpected circumstances arise, the agreement goes into effect after it
is signed by the representatives of both parties. The formal contract is to be made
by the party which commissions the JSWA for work, bacause that party is primary
responsible to do sewage works, and not the JSWA.
(3) Payment of expences
After the agreemtnt is signed by both parties, the JSWA has an obligation to
complete the work under commission by a certain date specified in the contract.
And the trusting party take responsibility to bear the cost of the work by its trustee,
the JSWA. However, such rights and duties are different from those in ordinary
contracts in that the fiduciary relations between the signatories rest at a much
higher level than those in ordinary business contracts. And this difference is clearly
seen in the payment of expences.
The trusting party pays necessary expenses in advance within the amount
specified in the agreement, as the work advances, and upon completion of the
commissioned work, the JSWA calculates accurately the amount to be borne by the
trusting party. The payment of expenses is in fact a matter of settling accounts,
which means that the amount of payment agreed on in the contract is essentially
either the rough estimate or the ceiling amount of payment.
We are fully aware that the cost of a commissioned work is of primary im-
portance particularly to the trusting party. And the JSWA goes by the detailed
regulations on the payment of expenses, by which the contract amount of payment,
or the rough estimate or the ceiling amount, can be rationally calculated that is
acceptable to the trusting party.
(4) Delivery of completed work and settling accounts
Upon completion of the commissioned work, the JSWA hands the completed
facilities or goods over to the trusting party and settles an account. With such
facilities as sewage treatment plants, the maintenance and the trial run, and the
problem of advance security are involved, and therefore, the JSWA has the special
regulations, besides a contract, when delivering the final products to its trusting
party. Other businesses are conducted according to what a contract stipulates.
1.9 THE ROLE OF THE JAPAN SEWAGE WORKS AGENCY AND THE
PROCEDURES OF OPERATIONS
The JSWA can be regarded as an organ to achieve the central government's
policy of controlling the quality of the public water mainly by constructing sewage
treatment plants under commission with local governments. The role of the JSWA is
stipulated in Article 1 of the Japan Sewage Works Agency Act, which says that
"the JSWA constructs and maintains the main facilities of sewerage systems, gives
technical assistance, trains sewage works engineers by request of local governments,
as well as promoting research and technology development of sewerage systems and
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practical application of new technology development. And in so doing the JSWA is
to promote the betterment of sewerage systems, imporve the living environment,
and control the quality of the public water in Japan".
The procedures of the JSWA's operations are indicated in Table 9.
1.10 THE BUDGET AND THE ORGANIZATIONAL STRUCTURE OF THE
JAPAN SEWAGE WORKS AGENCY
The budget of the JSWA for fiscal 1978 is shown in Table 10. The organi-
zational structure of the JSWA is given in Table 11. The number of staff is 670, and
the ratio of staff by job classification is shown in Table 12.
Table-9 Standard Procedures In Public Sewerage Construction Project
Procedures on Procedures on Procedures on
the part of the part of the part of the Procedures on the
local munici- prefectural central govern- part of the JSWA
palities governments ment
Environmental Quality
Standards
project
k-
r
Preparatory
survey
^
Comprehensive
plan to build
sewerage sys- ^ —
terns according
to areas
Technical assistance
for assessing the
comprehensive pro-
ject of sewerage
systems
Basic plan of
the project
Project plan
Request for
budget
Designing
Construction
Operation
Start-up of the '
facilities
I
Maintenance
and operation
Urban Planning
decided
Urban Planning
approved
Sewerage
project OK'd
Adjustment:
OK'd -^°- Approved
Amount for
new project
indicated
informally
Application for _
subsidy
: Inspection
upon
completion
• Examination:
. Subsidy
" decided
Audit
Plan to be
commissioned;
Technical assistance
in basic survey and
others
Actual plan
commissioned;
Technical assistance
in designing;
Construction to be
commissioned
Supervision of
construction
commissioned;
Technical assistance
in the project
Maintenance
commissioned;
Technical assistance
in maintenance
376
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Table-10 The 1978 Budget of the JSWA
(Million Yen)
Categories
Projects:
Work under
commission
Technical
assistance
Training,
qualification
tests etc.
Management
cost
Management
cost
Refund
TOTAL
Budget:
Capital fund
Central
government
Local
governments
Subsidies
Central
government
Local
governments
Loans
Revenue on
commission
Revenue outside
business
TOTAL
1978
98,953
252
506
17,112
6,481
10,631
116,823
76
38
38
904
452
452
13,635
90,770
11,435
116,820
1977
79,197
290
486
14,759
5,956
8,803
94,732
76
38
38
896
448
448
16,083
68,000
9,677
94,732
Rate of increase
1.25
0.87
1.04
1.16
1.09
1.21
1.23
1.00
1.00
1.00
1.01
1.01
1.01
0.85
1.33
1.18
1.23
377
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Table-11 The organizational Structure (1978)
Trustees (15)
— Headquarters
President
Vice President
Executive Director (5)
Part-time Directors (3)
Auditors (2)
Policy-planning and
general affairs Div.
- Accounting Div.
- Operations Div.
— Planning Div.
— Engineering Div.
Headquarters
on Research
and Training
— Training Div.
Research and Techno-
logy Development
Div.
Tokyo Regional
Office
Deputy chief
(Management)
Deputy chief
(Technical)
Osaka Regional
Office
Deputy chief
(Management)
Deputy chief
(Technical)
Secretary Office
— General Affairs Section
— Personnel Section
— Accounting Section
— Policy Planning Section
— Advisor (Welfare)
— Advisor (Public relations)
E
Accountants' Section
Finance Section
Contracts Section
I— Operations Section
I— Assistance Section
— Planning Section
— Designing Section
— Designer Office
— Advisor (Buildings)
— Advisor
(Systems development)
— Engineering Section
— Building Section
Facilities Section
— Advisor (Facilities)
— Advisor (Inspection)
Management Section
I— Training Section
I— Instructors etc.
Research and Technology
Development Section
Chief Researcher
(Water-quality)
• Chief Researcher (Sludge)
- Chief Researcher
(Basic Structure)
- General Affairs Section
- Construction Section
- First Designing Section
- Second Designing Section
- Building Section
- Electricity Section
- Machinery Section
- Researcher (Test-run)
— Construction Offices
— General Affairs Section
— Construction Section
— First Designing Section
— Second Designing Section
— Building Section
— Electricity Section
— Machinery Section
— Researcher (Test-run)
— Construction Offices
Chief Inspector-Inspector
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Table-12 Breakdown of Type of Work of Personnel in %
Clerical
21.8
Engineers
Civil/
Sanitary
46.6
Archi-
tectural
"
Mechanical
i
1
6.9
12.5
Electrical
10.3
Chemists/
Biologists
1.9
Sub-total
78.2
Total
100
2. ACTIVITIES OF THE JAPAN SEWAGE WORKS AGENCY
2.1 CONSTRUCTION OF THE MAIN FACILITIES OF SEWAGE WORKS
2.1.1 Range of Consignment and Policy
Sewage works are composed of sewage treatment plants, pumping stations,
trunk sewer, branch sewer and other collection system. Of these facilities, the
construction of sewage treatment plants and pumping stations require highly
advanced techniques involving civil & sanitary engineering, architectural engineering,
electrical engineering, mechanical engineering and biological and chemical experitise
supported by long experience. On consignment entrusted by the local governments,
JSWA conducts construction work of the following main sewage facilities that do
require such fully advanced techniques:
(1) Sewage treatment plant.
(2) Trunk sewer directly connected to the treatment plants.
(3) Publicly owned pretreatment plants other than the Sewage treatment
plants described in (1).
(4) Pumping stations.
When the JSWA is entrusted by a local government, it gives top priority to
the project of the water basin whether it concurs with the provisions of the
environmental quality standards related to water pollution. Furthermore, immedi-
ately after completion of work and before commencement of operation, JSWA
makes it a rule to conduct comprehensive starting-up operations to check and
confirm the normal functioning and mechanical conditions of the total plant.
The comprehensive start-up operations are followed by maintenance and operation
work. The JSWA periodically dispatches engineers to the plant as an after care to
offer proper technical guidance to the plant operators.
2.1.2 Cost
Concerning cost, the expenses are based on the standards stipulated by JSWA.
It will be an aggregation of cost of each designed plan. Besides costs, adminis-
trative expenses will also be required. The administrative expenses are computed
on a percentage basis as listed in Table-13.
Concerning payment, JSWA and the local government normally compile the
payment terms after thorough consultation.
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Table-13 Percentage of Administrative Expenses Accompanying Construction Work
Consignment Cost (million yen)
below 500
500 ~ 1 ,000
above 1 ,000
Percentage
5.3%
4.3%
3.3%
2.1.3 Methods of Work Execution
(1) Instructions governing basic plans
Prior to the construction work, JSWA generally conducts planning of schemes
and specifications. But, even in this case, JSWA makes it a rule to submit the
drafted plans for examination to the local government. And based on the inst-
ructions by the local government with regards the blueprints, the construction
work is conducted. Therefore, the construction work by JSWA is based on the
instructions by the local government.
(2) Work execution, supervision and inspection
JSWA invites tenders to execute work by contractors specializing in civil
engineering, architecture, electrical engineering, mechanical engineering, etc. Then
JSWA organizes a team of qualified engineers in civil engineering, architecture,
electrical engineering and mechanical engineering to advance construction work by
repeatedly conducting discussions. Stationed at the work site, the technical
experts supervise the work based on JSWA's 'List of Contract Work Supervision.'
These people are all experts with long experience in organizing and supervising
sewage works construction from the Ministry of Construction, Prefectures and
Municipalities, etc.
(3) Comprehensive start-up test operation
In coordination with the contractor, manufacturer and the local government,
JSWA normally conducts a thorough start-up operation prior to actual maintenance
and operation work of all units of the freshly completed sewage treatment plant
including the sewage treatment, sludge treatment and pumping facilities. To
guarantee continuous and proper functioning of all units, adjustments are made and
trouble shooting performed. This comprehensive start-up run of facilities usually
last for about 30 days concerning sewage treatment and for 10 days with regards
pumping work.
(4) Financial procurement and temporary advances
Work to complete sewerage systems require a tremendous amount of funds.
Although the main facilities of a sewerage system are given government subsidy,
the amount of allotment is limited. However, the financing of preceding work
must be tentatively prepared by the local government (subsidiary body) as advances.
As JSWA considers it an important mission to cover construction of sewage works
requiring prompt and urgent action, JSWA takes special financial measures to
alleviate fund requirements of the local government concerned.
In other words, when JSWA is entrusted by a local government to construct
a sewerage system, JSWA can acquire advances by loans from commercial banks
380
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the amount equivalent to the share to be borne by the local government concerned.
To alleviate the increasing financial requirements, measures can be taken to
relieve the burdens of the local government to repay funds on a five-year deferred
payment basis. This deferred payment method of five years has a grace period
of one year repayable in eight different installments equalizing the incidence of
interests for each six months.
2.1.4 Sewage Treatment Plants in Service Built by JSWA
Table-14 shows the construction projects managed by the Japan Sewage
Works Agency.
Table-14 Construction Projects Managed by JSWA
Municipal Sewage Works
Basin-wide Sewage Works
Total
1972
1
0
1
1973
16
0
16
1974
23
3
26
1975
45
7
52
1976
55
8
63
1977
64
11
75
1978
73
16
89
2.2 DETAIL DESIGN
2.2.1 Range of Consignment and Policy
In compliance with the requests by local governments, JSWA considers the
construction of the main facilities of sewage works as her main business. Accord-
ingly, JSWA is entrusted with the basic designing of the following main facilities.
However, to accepting the consignment, the Agency makes it a rule to receive
instructions in mapping out detail design.
(1) Sewage treatment plant.
(2) Trunk sewer directly connected to the treatment plants.
(3) Publicly-owned pretreatment plants other than the above sewage treat-
ment plants.
(4) Pumping stations.
The detail design is deeply related to the actual construction work. Therefore,
the detail design is generally mapped out as part of a single scheme that encompasses
construction work. The engineering staff of JSWA may partly take part in the
design drafting work which is mainly entrusted to private consultant engineering
firms.
2.2.2 Costs
With regards costs to implement planning, they are computed on the standards
stipulated by JSWA. The sewage treatment capacity, the pumping capacity and
the length of trunk sewer are detrimental in determining the expenses directly
needed. In addition, 10 percent of administrative expense is needed as contract fee.
2.2.3 Execution of Work
Upon signing the consignment contract, the work is implemented by a special
team of experts of JSWA of civil engineering, architecture, mechanical engineering
and electrical engineering organized in either Tokyo or Osaka Regional Office
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Table-15 Sewage Treatment Plants in Service Built by JSWA
City or
basin-wide
Motobu
Imabari
Marugame
Kasugai
Kanuma
Oyama
Sano
Nagaoka
Kure
Kitakyushu
Hohu
Higashimatsuyama
Yokohama
Ashikaga
Itako
Gamagori
Oita
Kawasaki
Machida
Kitakyushu
Fukuoka
Kyoto
Utsunomiya
Muroran
Saga
Kasumigaura
Kannonji
Mure
Numazu
Kawanoe
Nago
Ena
Construction
starts
Jan. 1974
Oct. 1973
Oct. 1973
Oct. 1973
Oct. 1973
Oct. 1973
Oct. 1973
Jul. 1973
Nov. 1975
Aug. 1975
Sep. 1975
Oct. 1973
Jul. 1975
Oct. 1973
Nov. 1973
Oct. 1973
Dec. 1975
Aug. 1975
Jul. 1973
Sep. 1976
Oct. 1975
Jan. 1976
Jun. 1974
Jun. 1974
Aug. 1974
Aug. 1975
Nov. 1973
Oct. 1973
Jul. 1974
Jul. 1975
Jul. 1974
May 1976
Service
begins
Jul. 1975
May 1976
May 1976
May 1976
May 1976
Jun. 1976
Jun. 1976
Sep. 1976
Oct. 1976
Nov. 1976
Jan. 1977
Apr. 1977
Apr. 1977
Jun. 1977
Aug. 1977
Aug. 1977
Aug. 1977
Sep. 1977
Oct. 1977
Oct. 1977
Oct. 1977
Oct. 1977
Jun. 1978
Sep. 1978
Sep. 1978
Oct. 1978
Oct. 1978
Oct. 1978
Nov. 1978
Jan. 1979
Mar. 1979
Feb. 1979
Capital
billion yen
3.5
4.1
3.7
2.6
3.1
3.5
5.1
4.3
1.0
1.0
4.2
4.1
1.7
4.5
1.4
5.7
2.3
2.4
5.9
0.7
1.6
2.2
8.0
4.4
5.5
7.2
2.7
2.4
3.4
2.5
2.7
1.6
Capacity
1,000m3 /day
6
34
17
17
17
34
27
28
23
50
14
10
74
24
2
56
12
64
23
23
10
40
36
24
24
27
16
10
16
3
5
7
depending upon the locality of the local government. The planning of trunk
sewer is entrusted to the specialists in civil engineering of JSWA. However,
prior to the planning work, the special project team confirms the wishes and
views of the local government, carefully studies the contents of the approved
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project plan and makes on-the-spot investigations on the conditions of the work
site before delegating the designing work to a private firm. In the meantime, in
close coordination with the local government based on geological surveys, the
scale of the plant, the model and type of the main equipment and the layout are
decided as the basic plan which is forwarded to the Technological Committee in
JSWA to confirm that no problems are involved and to assure the basic plan as
flawless. This work is entrusted to the engineers in the Design Section of the
Agency Headquarters. Then either at JSWA Tokyo or Osaka Regional Office,
designing of specifications with regards the structure and machinery of each
facility and the execution methods are conducted. And the completed and
finalized plans are submitted to the local government. In this case, when deciding
on the method of sewage treatment, the Design Criteria/Manual of JSWA serves
as a guideline and, at times, pilot plant tests, prior to designing, become necessary.
In this case, engineers in the Research and Technology Development Division of
JSWA cooperate in the work to help incorporate the test results in mapping out
plans.
2.2.4 Detail Design Mapped Out by JSWA
Table 16 shows the number of detail design mapped out by JSWA ever since its
inauguration in 1972.
Table-16 Detail Design Mapped out by JSWA
Municipal Sewage Works
Basin-wide Sewage Works
Total
1972
19
0
19
1973
12
2
14
1974
16
4
20
1975
21
7
28
1976
18
4
22
1977
33
8
41
1978
45
10
55
2.2.5 Evaluation of Detail Design
With regards detail design of sewage treatment plants, to make accurate
evaluations on the observance of the contract by private consultant firms, evalua-
tions are made in three stages of No. 1 (Time of completion of detail design),
No. 2 (While construction is in progress), and No. 3 (Upon completition of
start-up operation). And the evaluation of detail design is done. The results of
the evaluation are recorded and filed to be reflected in the future and to perfect
future designing work.
The evaluations of the sewage treatment plant design should be made in
three stages: Evaluation by those who designed the plans. Evaluation by those
engaged in construction stage concerning solicitude for convenience of execution.
And evaluation from the standpoint of maintenance and operation.
Although depending upon the size, the construction work of a sewage treat-
ment plant executed by JSWA normally takes between 5 and 7 years from the
planning stage, construction work to comprehensive start-up operations. Therefore,
the three stages of evaluation by a project team take more than 5 to 7 years.
Table 17 shows the outline of the three stage evaluation.
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Table-17 Three Stage Evaluation of Design Work
Time of
evaluation
Evaluation
items
Evaluation
made by
First Stage
Upon completion of
designing
Evaluation by those
in charge of designing
plans
oThe results of draw-
ings
o Progress in work un-
der commission
Plan designers
Civil Engineering
Architecture
Mechanical
Engineering
Electrical Engineering
Inspectors
Seond Stage
During construction
work. 3 years after
commencing work on
sewage treatment plant
and two years after
commencing work on
sludge treatment plant.
Evaluation by those
engaged in construc-
tion work
o Accuracy
o Understanding
o Workability
o Adaptability
o Material fitness
o Estimate accuracy
Work supervisors
Civil Engineering
Architecture
Mechanical
Engineering
Electrical Engineering
Chief supervisor
Third Stage
Upon completion of
comprehensive start-up
test operation
Evaluation by those
conducting trial tests
o Consistency of each
unit
o Operation efficiency
o Safety free degree
o Maintenance
Work supervisors
Civil Engineering
Architecture
Mechanical
Engineering
Electrical Engineering
Chief test operator
2.3 PROJECT PLANNING
2.3.1 Scope of Consignment and Policy
On consignment, JSWA commences project planning for sewage works (basic
plan as stipulated in the provisions of Project Plan). In project planning for
sewage works, the population in the drainage area and specifications of sewage
treatment plants, pumping stations and their maintenance programs must be
envisaged. Then they are incorporated into the Basic Plan of the planned sewage
works project as an undertaking plan. JSWA then takes legal steps to have the
sewage works scheme approved by the City Planning Law as it is related to city
planning project and undertaking, and also by the Sewerage Law. JSWA, concern-
ing necessary planning, compiles her undertaking plans in the following three
stages. And depending upon the work scale of the scheme, these three stages of
planning are completed within a year or more than two years.
(1) Basic survey
With regards the projected area of the sewage works, JSWA conducts surveys
on the sewage flows and the conditions of the expected sites of trunk sewer,
pumping stations and sewage treatment plants.
(2) Compilation of undertaking plan (for approval by the City Planning Law)
The total area of the expected draining area of the sewage works, location of
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the trunk sewer, a rough layout plan of the treatment plants, pumping stations and
total sewer system length and other relevant items of sewage works that can be
considered as part of city planning are prepared.
2.3.2 Procedures of Consignment and Expenses
With regards procedures of consignment, a local government first submits a
paper requesting JSWA to construct sewage facilities on consignment. Then
JSWA and the subject local government hold repeated discussions and conclude
an agreement. As the expense to compile the initial planning of the project is
not eligible to the government subsidy, the government or the requesting public
entity must prepare for appropriate budget for the cost. The expense required
to draft the project plan is computed on the bases decided by JSWA. The expense
is inconsistent depending upon the scale of initial plan covering a wide range of
subjects including Basic Survey, Basic Planning, Project Drafting, and Project
Planning. However, the agency also demands expenses directly needed to compile
outline of plan after surveying the geologocial and topographical conditions of the
planned city area, the total area required for sewage treatment and other city
conditions. Presently, most of the expense goes to private consulting firms, as
they are entrusted to conduct the survey work and compilation of the outline of
plan.
In addition, 10% of the total cost agreed upon is needed as administrative
expenses.
2.3.3 Method of Implementation
When JSWA is entrusted by a local government to design plans, the work is
undertaken by JSWA's staff in either Tokyo or in Osaka Regional Office depending
upon the locality of the local government. And prior to the commencement of
planning, JSWA's staff are dispatched to the local government to gather information
on requests and desires and also to survey the actual conditions of the work site.
A part of this work is often delegated to the consultants.
2.3.4 Project Planning Conducted by JSWA
Table-18 Project Planning Conducted by JSWA
Municipal Sewage Works
Basin-wide Sewage Works
Total
1972
1
1
2
1973
11
4
15
1974
25
1
26
1975
12
1
13
1976
13
0
13
1977
12
0
12
1978
6
0
6
2.4 TECHNICAL ASSISTANCE
2.4.1 Scope of Consignment and Policy
JSWA offers technical assistance covering all fields of sewage works including
planning, designing, scheming, constructing, maintenance and operations. The
contents of the technical assistance offered by JSWA are as follows:
(1) Technical assistance regarding planning of sewage works
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Besides analyzing and examining the contents of plans, JSWA offers technical
advice and guidance. JSWA also engages in studies of advanced wastewater
treatment, trouble-shoots problems of inundation, conducts surveys on water
polluting conditions of rivers and researches on drafting a comprehensive basin
planning for each drainage area.
(2) Technical assistance concerning sewage works design
JSWA not only offers technical advice and guidance upon examining plans for
sewage works (structure, appropriateness of construction method and process, and
estimates of costs listed in the plans) but also serves as a consultant for other
aspects of sewage works.
(3) Technical assistance concerning sewerage work
Besides offering general advice and guidance with regards execution of work,
JSWA conducts studies on construction methods when requested.
(4) Technical assistance concerning maintenance and operation of sewage
facilities
JSWA offers general advice and guidance with regards maintenance and opera-
tion of sewage treatment plants, etc; technical diagnosis of operating and manipu-
lating methods and water quality control;and consultation with regards maintenance
and supervision systems.
(5) Other technical assistance
JSWA engages in consultative service by offering advices despite minuteness or
roughness, fineness or coarseness of technical problems concerning operating system
and other matters of sewage works. Furthermore, to positively engage in all
problems concerning sewerage, JSWA dispatches personnel to offer advice and
guidance to cities where prefectural government offices are located.
2.4.2 Consignment Procedure and Expenses
Concerning the procedure of consignment, it is the same as in the case of
entrusting the designing of plans. However, in case of technical assistance, as the
expenses are used to mostly cover administrative costs, they will be appropriated
in the administrative account. The items in the account include salary for
JSWA personnel while being dispatched to conduct on-the-spot studies of work-
sites, their travelling expenses and other expenditures. Although depending on
the contents of technical assistance, if the work involves planning of schemes, the
expenses will be computed on the same basis as scheme planning. However,
with regards simple consultation, it is normally free of charge.
2.4.3 Implementation Method
(1) Technical assistance by dispatching personnel
In compliance with the request rendered by a local government, JSWA
dispatches her personnel to various work-sites to offer technical assistance.
(2) Technical assistance without dispatching personnel
With regards problems requiring technical research, the experts basically
conduct survey at the Headquarters of JSWA or at her Regional Offices. But
when necessary, JSWA personnels visit the work-site to conduct on-the-spot survey
386
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to collect materials and to consult with people concerned. Depending upon the
content of technical assistance, at times, there are needs to involve consultants or
specialists.
2.4.4 Inspection and Technical Service (After Care) at Sewage Treatment Plants
JSWA periodically dispatches her experts to sewage treatment plants con-
structed by the Agency and already in operation to inspect the operating and
functioning conditions of the plants, to offer technical guidance as after care to
the various local governments and to obtain materials that would be of help in
the future designing works.
(1) Inspection and technical guidance
(i) Technical guidance concerning operation and maintenance
(ii) Servicing and trouble shooting of machinery
(in) Matters to be fed-back to future designing of plant in general
(2) Inspection of maintenance & operation conditions
(i) Inspection of actual operating conditions of sewage treatment plant
(ii) Inspection of management and organization of sewage treatment plants
In 1978, JSWA will conduct periodic inspection of sewage treatment plants
completed by the Agency in 7 cities that commenced operation in 1976 and in
7 cities that began service in 1977. However, together with the increase in the
number of sewage treatment plants to be inspected in the future is expected.
Therefore JSWA must cope with the situation by expanding the after care operation.
2.5 TRAINING
2.5.1 Outline
JSWA trains personnel belonging to the various local governments engaged in
sewage work or those who are expected to engage in this field in the future.
Furthermore, JSWA is driven by necessity to conduct highly efficient trainings to
maintain and secure necessary number of engineers in the fields of civil engineering,
architecture, electrical engineering and mechanical engineering to cater to all
demands. According to Article 22 of the Sewerage Law, those engaged in drawing
blueprints and those in charge of maintenance and supervision of sewage treat-
ment plants require special qualifications as stipulated in the Law. The qualifi-
cations are given to only those who have completed the special training courses
designated by the Ministry of Construction and the Ministry of Health and Welfare.
Of all the trainings offered by JSWA, a number of these are those designated by
the two Ministries. JSWA Research and Training Headquarters was built in
Toda City, Saitama Prefecture with funds from both the government and various
local governments. The scale of the Headquarters is as listed in Table-19.
Table-19 Outline of Main Building Housing
The Research and Training Headquarters
Address: 5141, Shimo Sasame, Toda-shi, Saitama-ken
Total land area: About 4,600 square meters
Structure of building
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and number of floors:
Detail of each floor:
1st floor:
2nd floor:
3rd floor:
4th floor:
5th floor:
6th floor:
Reinforced concrete structure, 6 floors
Library, faculty room, reference room
Main office, water quality test laboratory
Classrooms for trainees, drafting room, auditorium, rest room
Dining room, bath room, culture room
Dormitory (38 rooms for 152 people)
Rest room, wash room
2.5.2 Recruiting of Trainee
JSWA requests the mayors of the 10 large cities and the governors of all
prefectural governments in Japan to recommend probable candidates for trainees.
And from those recommended by the mayors and governors, JSWA carefully
examines the past record and qualification of each candidate and selects trainees.
2.5.3 Training Expense
Each trainee bears the expenses for text books and food and accomodation
during the training period. Other expenses are free of charge borne by JSWA.
2.5.4 Training Program
See Table 20.
Table-20 Subjects of Studies for Training
Course
Planning
Design-
ing
Major
Master
Planning
and
Project
Planning
Compre-
hensive
Basin
Planning
Detail
Design
- 1 -
Trainees
Those chiefly en-
gaged in work of
preparing docu-
ments to acquire
approval of pro-
ject planning or
improving sewage
system in a city.
An official at ei-
ther government
or prefectural
governments or
municipalities en-
gaged in compre-
hensive basin
planning.
Those who com-
pleted academic
courses other
than those relat-
ed to civil engi-
neering and who
will newly be as-
signed to sewer-
age works.
Content
1 . Basic matters & points
in planning sewage
facilities.
2. Studies on related
laws and administ-
rative acts.
3. Showing actual exam-
ples of planning work.
(99 hours, 20 days)
1. Basic planning of basin
project.
2. Actual examples of
planning.
3. Methods of water pol-
lution analysis.
(66 hours, 12 days)
1. Introduction to civil
engineering, and basics
of sewage engineering.
2. Designing and laying
of branch sewer.
3. Surveying, flow rate
measuring and design
calculating.
(162 hours, 34 days)
Result
Becomes person
responsible for
preparing papers
to apply for app-
roval and to
offering guidance
to consultants.
Becomes person
responsible for
surveying basin
project, and able
to compile water
plans for public
use.
With the newly
acquired civil en-
gineering knowle-
dge, becomes a
person capable of
designing branch
sewer.
388
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Course
Design-
ing
Major
Detail
Design
— 2 —
Detail
Design
-3-
Trunk
Sewer
— 1 —
Trunk
Sewer
-2-
Treatment
Plant
- 1 -
Treatment
Plant
-2-
Trainees
Those who com-
pleted civil engi-
neering courses
and who will
newly be assigned
to sewerage work.
Engineers in
other fields being
transferred to
sewage works.
Having experi-
ence of over five
years or equiva-
lent.
Engineers of
supervisory class
engaged in design-
ing of trunk sew-
er.
Having experi-
ence of over
5 years or equi-
valent .
Those completing
electrical and me-
chanical engineer-
ing courses or
having experience
of over 5 years or
equivalent experi-
ence.
Content
1. Basics of hydraulics
and soil mechanics.
2. Designing and laying
of branch sewer.
3. Surveying, flow rate
measuring and design
calculating.
(123 hours, 25 days)
1 . Designing of sewage
facilities.
2. Sewage engineering
and planning of sew-
erage.
3. Problems in execution
of plans.
(99 hours, 20 days)
1 . Points on planning
sewage system layout.
3. Points on soil mecha-
nics.
(99 hours, 20 days)
1 . Trends in Sewage Engi-
neering techniques.
2. Recent Execution me-
thod and execu-
tion management.
3. Points on special me-
thods and calculation.
(99 hours, 18 days)
1 . Selection of treatment
methods.
2. Selection of sludge
treatment methods.
3. Layout planning and
capacity calculation.
(99 hours, 20 days)
1 . Designing of electrical
equipments of sewage
treatment plants.
2. Designing of mechani-
cal equipments of
treatment plants.
3. Specifications and
computation of equip-
Result
With the newly
acquired knowle-
dge of basic civil
engineering, be-
comes a person
capable of design-
ing branch sewer.
A person who can
understand the
contents of pro-
ject planning.
Be able to make
decision of trunk
sewer method.
Able to instruct
consultant while
mapping out
plans for execu-
tion.
Be able to design,
execute and inst-
ruct special me-
thods.
Able to make
selection of engi-
neering method
and decision of
basic designs at
treatment plants.
Also able to give
guidance to con-
sultants.
Able to make
designing of elec-
trical and mecha-
nical equipment
at pumping sta-
tions and treat-
ment plant.
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Course
Design-
ing
Manage-
ment of
Execution
Mainte-
nance
and
Opera-
tion
Major
Treatment
Plant
-3-
Manage-
ment of
Construc-
tion
Work
Manage-
ment of
Mainte-
nance and
Operation
- 1 -
Manage-
ment of
Mainte-
nance and
Operation
_ 2 _
Manage-
ment of
Mainte-
Trainees
Chief engineers in
charge of design-
ing or planning
treatment plants.
Those with over
5 years of experi-
ence or equiva-
lent.
Those newly as-
signed to sewage
treatment plant.
Those having en-
gineering experi-
ence in other
fields and newly
engaging in sew-
age treatment
plant.
Those over 5
years of actual
experience or
Content
ment.
(99 hours, 20 days)
1. Technical trends of
sludge treatment at
sewage treatment
plant.
2. Points of designing
sewage treatment
plants & computation.
3. Countermeasures aga-
inst industrial waste
water.
(57 hours, 10 days)
1 . Planning and manage-
ment of execu-
tion work.
2. Points on soil mecha-
nics and work.
3. Disaster prevention
and compensentation.
Measures against local
citizens.
(99 hours, 20 days)
1 . Basics of sewage treat-
ment plant.
2. Basic knowledge of
water quality and ac-
tual examples.
3. Mock tests and machi-
nery handling.
(123 hours, 25 days)
1. Maintenance of elect-
rical and mechanical
units of sewage treat-
ment plant.
2. Symptoms and mea-
sures.
3. Safety management,
water quality contol
and countermeasures.
(First half: 45 hours
10 days
Practical teaching: 3
months
Second half: 78 hours
15 days)
1 . Total management of
sewage treatment
plant and related laws.
Result
Able to plan lay-
outs evaluate
plans and give
guidance of sew-
age treatment
plants.
Be able to con-
duct on-the-spot
supervisory work
concerning work
management.
Understand total
system of operat-
ing sewage treat-
ment plant to en-
gage in mainte-
nance work.
Understand total
system of operat-
ing sewage treat-
ment plant to en-
gage in mainte-
nance work.
Able to make
maintenance and
management of
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Course
Mainte-
nance
and
Opera-
tion
Instruc-
tion
and
Guidance
Major
nance and
Operation
-3 -
Total
Manage-
ment
Water
Quality
- 1 -
Water
Quality
-2-
Water
Quality
-3-
Guidance
- 1 -
Trainees
equivalent.
Those expected
to be head of a
section or sew-
age treatment
plant operator
with experience
on management,
and supervision.
Those engaged in
water quality test
or those expected
to be assigned.
Those complet-
ing studies on
biochemistry and
to be assigned as
leader of labora-
tory and indus-
trial waste water
monitoring.
Section heads
supervising indus-
trial waste water
monitoring.
(Prefectural em-
ployee)
Content
2. Water quality control
and measures against
accident.
3. Mock tests and machi-
nery handling.
(99 hours, 20 days)
1 . Total management of
sewage treatment
plant and related laws.
2. Water quality control
and measures against
accident.
3. Sewage management
and management mea-
sures.
(First half: 45 hours
10 days
Practical teaching: 3
months
Second half: 78 hours
1 5 days)
1. Basic knowledge of
sewage and sludge
treatment.
2. Practical training of
water examination test.
3. Water control practice.
(123 hours, 25 days)
1. Industrial waste water
control and related
laws.
2. Heavy metal analysis,
etc.
3. Water control practice,
etc.
(99 hours, 20 days)
1. Sewerage Law and In-
dustrial waste water
control.
2. Pretreatment plant
and practical training.
3. Waste water control
and administrative
guidance.
(45 hours, 8 days)
1 . Design criteria of sew-
age and planning.
Result
sewage treatment
plant.
Person in charge
of sewage treat-
ment plant with
leadership.
Able to analyze
sewage and sludge
at sewage treat-
ment plant and
also water quality
control.
Able to under-
stand mechanical
analysis necessary
for sewage treat-
ment plant main-
tenance and to
offer guidance
concerning indus-
trial waste water.
Becomes person
in charge to cont-
rol industrial
waste water and
inspect pretreat-
ment plant.
Able to inspect
and instruct work
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Course
Instruc-
tion
and
Gui-
dance
Major
Guidance
-2-
Guidance
-3-
Trainees
Prefectural gov-
ernments' work-
ers supervising
work in related
cities.
(Managerial class)
Those in manage-
rial class in sewer-
age or equivalent.
Those in the
managerial class
being transferred
to sewerage work.
Content
2. Standard application
for approval, and pro-
blems related to appli-
cation for subsidiary.
3. Points concerning con-
struction method and
supplementary work.
(99 hours, 20 days)
1 . Sewerage problems
and financing and
management.
2. Pollution measures of
public waters and
trend.
3. Problems involving ex-
ecution of sewage
works.
(33 hours, 6 days)
1. Problems related to
sewerage and admini-
strative financing and
management.
2. Explanation of sewer-
age facilities.
3. Problems involved in
execution of sewage
work.
(66 hours, 12 days)
Result
to apply for app-
roval and subsidi-
ary.
Understand the
points with re-
gards sewerage
operation to
offer guidance to
personnel.
Thoroughly und-
erstand sewerage
undertaking.
(Notes) 1. The number of years is) based on high school graduates.
2. Those having experience means sewerage experience.
3. Engineering experiance means technical engineering experience in all fields.
2.6 ENGINEER CERTIFICATION
2.6.1 Certification System
JSWA performs certification examinations to those aspiring to become
qualified engineers to engage in designing of sewage treatment facilities and to
those to become authorized managers and supervisers engaged in the construction
work of such facilities. This certification system was inaugurated with the aim
of encouraging capable engineers in other fields such as water supply, river,
harbor, etc. to transfer or being introduced into the sewerage field by enabling
them to obtain certificates stipulated in Article 22 of the Sewerage Law in a
short period of time.
2.6.2 Contents of examination
The method of engineer certification is based on examinations in academic
subjects. The contents and level of examinations for 1st class and 2nd class
engineers are decided by the Ministry of Construction. And the contents and
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level of examinations for 3rd class engineers are decided by both the Ministry of
Construction and the Ministry of Health and Welfare. On October 9, 1975,
notification with regards definite contents of examination was issued as shown in
Table-21.
To ensure fairness in the examinations, the preparation of examination
papers and judgement of results are conducted by five members of the Engineer
Certification Committee nominated by the President of Japan Sewage Works Agency.
Table-21 Academic Subjects and Standards for Engineer Certification Examinations
Classification
First
Class
Engineers
Second
Class
Engineers
Subject
Sewerage
Planning
Sewage
Treatment
Plant
Planning
Management
Methods
of Work
Execution
Sewage
Disposal
Related
Laws
Sewerage
Planning
Management
of Work
Execution
Sewage
Treatment
Examination Standard
To have necessary knowledge to map out plans
concerning layout, structure and capacity of
sewer.
1. To have general knowledge of mechanical
and electrical equipment, their capacities and
their structures installed in the sewerage
system or at sewage treatment plants.
2. To have necessary knowledge to calculate
strength of structure of plant.
3. To have necessary knowledge concerning con-
struction methods of sewerage facilities.
4. To have general knowledge concerning speci-
fications of designs of sewage facilities.
To have general knowledge concerning mapping
out of plans for execution work of sewerage,
supervising of work process, material quality
control, safety control, etc.
To have general knowledge with regards sewage
and sludge.
To have general knowledge concerning related
sewerage laws.
1. To have general knowledge of mechanical
and electrical equipment, their capacities, and
their structures installed in the sewerage
system or at sewage treatment plants.
2. To have necessary knowledge to calculate
strength of plant.
3. To have necessary knowledge concerning con-
struction methods of sewerage facilities.
4. To have general knowledge concerning specifi-
cations of designs of sewage facilities.
To have general knowledge concerning mapping
out of plans for execution work of sewerage,
supervising of work process, material quality
control, safety control, etc.
To have a rough outline of knowledge with
regards sewage and sludge treatment and disposal.
Examination
Method
Descriptive
and
selective
Selective
Selective
393
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Classification
Second
Class
Engineers
Third
Class
Engineers
Subject
Related
Laws
Sewage
Treatment
Industrial
Waste
Water
Maintenance
and
Operation
Safety
Control
Related
Laws
Examination Standard
To have a general knowledge related to sewerage
laws.
To have necessary knowledge in sewage and sludge
treatment and disposal.
1 . To have general knowledge with regards the
influence of industrial waste water to public
sewer.
2. To have general knowledge of function of
pretreatment plant.
To have necessary knowledge concerning mainte-
nance and operation of sewage treatment plants
and pumping stations.
To have general knowledge concerning safety
control of sewage treatment plants and pumping
stations.
To have general knowledge concerning laws and
acts related to sewerage.
Examination
Method
Selective
2.7 RESEARCH AND TECHNOLOGY DEVELOPMENT
2.7.1 Aim
It is important to reinforce research and technology development activities
of JSWA to fulfill its mission. Especially, it is strongly urged to introduce new
technology that are more economical, stable and safe for practical use. To cope
with these demands, JSWA has founded its Research and Technology Development
Division to conduct studies on the following four fields:
(1) Surveys to develop new technology.
(2) Surveys to perform technical consultations with regards designing, plan-
ning and building of sewage facilities.
(3) Surveys to evaluate new technology.
(4) Special surveys in compliance with requests by government and local
governments.
2.7.2 Facilities
The main facilities and experimental facilities and devices employed by the
Research and Technology Development Division are as shown in Table 22.
2.7.3 Evaluation of New Engineering/Equipment
Japan is an attractive market for sewage equipment manufacturers. Many
new products are recently introduced and many companies claim avantages of
their products or process. Their advertisement like a kaleidoscope. This creates
an additional confusion to not only local personnels but also governmental
administrators. Therefore, proper evaluation of the newly introduced engineering
or equipment is required.
Many campanies want that their products are evaluated. Selecting ones among
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Table-22 Tests and Research Facilities and Devices
Research and
Training Center
Major Facilities
(Main Laboratory)
Laboratory for Chemical
Analysis
Laboratory for Instrumental
Analysis
Balance Room
Constant-temperature Room
Bioassey Laboratory
Computer Room
Data Room
(Annex building)
In-door Experimental Station
Sludge Pilot Station
Greenhouse
Mobil Laboratory (Otsu City)
Major Testing Apparatus and Analyzer
High rate chromatograph
Atomic absorption analyzer
T.O.C. analyzer
Calorie meter
Automatic BOD analyzer
CN analyzer
Automatic nitrogen analyzer
Photometer
Gas chromatography
TOC/TOD automatic monitoring
instrument
Secondary treatment pilot plant
X-ray fluorescence analyzer
Eutrophication test tank
Automatic control unit for pilot plant
Wet oxidation pilot plant
Pylolysis pilot plant
Others
Lake Biwa Advanced Waste Pilot
(Semimentation, sand filteration
Composting Unit (Sakado city)
Plant Laboratory
and activated carbon facilities)
many of them is a hard job. Therefore, the subject to be evaluated are selected
from the requests of national government or municipalities. The priority in the
selection is determined by JSWA. Research works for the evaluation (to see how
the equipment performs) are managed by Research and Development Division.
For the purpose of making fair evaluations or uneven conclusions, a special
committee is engaged in this work. It is named "Committee for Evaluation of New
Technology". Members of the Committee are as follows:
Professors of universities:
Engineering chief director of sewage works in municipalities:
Engineering administrator of national government:
Research director of Public Works Research Institute:
Executive director of JSWA:
number
3
4
1
1
1
Conclusions given by the Committee may be refered when the national
government determines whether the equipment/engineering can be subject to the
construction grant, and if yes under what circumstance.
At present, the following topics are under way of the evaluation:
(1) Pure oxygen activated sludge process.
(2) Best selection of anti-air pollution equipment for sludge incinerator.
(3) Economical and technical feasibility of automatic control for activated
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sludge process.
(4) Rotating biological contactor process
2.7.4 Current Research Topics and Findings
2.7.4.1 Evaluation of New Thickening and Dewatering Equipments
for Sewage Sludge
(1) Purpose
The prime importance in sludge treatment is how to decrease sludge volume.
Any costs associated with sludge handling and disposal process are entirely
dependent on moisture concentration. A gravity thickener does not work satis-
factorily in many cases. Therefore recently power drive thickening equipment
appears to attract attentions. They are floatation or centrifuge.
Such new developments as screw press or belt press are introduced and claim a
high performance in dewatering, in this year, their performance were compared
side by side in the field.
(2) Results
By using the advanced dewatering devices, 10 different sludges were applied
to see their performance.
(i) A belt-press type dewatering machine has the characteristics that the
high belt speed dewaters more amount of sludge, but moisture concent-
ration in final cake is high.
(ii) A pressure-filter dewatering machine has the characteristics that wider
slit opening and shorter pressing time increase the capacity at sacrificing
solid concentration.
(iii) The Belt press achieved 96% SS recovery.
(iv) With Cationic polymer at dosage rate 0.6 ~ 0.8%, dewatering performance
of the belt press was good.
2.7.4.2 Evaluation of Sewage Sludge Incinerator
(1) Purpose
At present, multiple hearth type, fluidized bed type and rotary kiln type
are populare for the purpose of municipal sludge incineration. The target of this
research is that performance of the three alternatives are compared in several
ways in actual field.
Thus recommendation is provided to the potential users.
(2) Finding
(i) The actual sludge fed rates and moisture content in the sludge never
meet design value. They always exceeded the design or expected values.
(ii) Usually more diluted sludge is fed, and therefore much auxial fuel is re-
quired to help burning.
The following is an example of least fuel consumption among the
surveyed.
Type Capacity Moisture Fuel Fuel consumption
i) multiple hearth 300 t/D 78.5% A oil 130kg/t-D.S.
ii) rotary kiln 24 t/D 61.2% coal gas 180 Nm3 /t-D.S.
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(iii) Odor components are removed through a process of thermal decomposi-
tion. The fluidized bed type incinerator need not after-burning system
has an advantage in the mean.
Type Capacity Moisture Fuel Fuel consumption
i) multiple hearth 50t/D 79.3% A oil 410kg/t-D.S.
ii) fluidized bed 40 t/D 83% A oil+kerosene320kg+820kg/t-D.S.
(iv) The required air rate concerned with fuel consumption, depended on
type of incinerators. The least air rate is more desirable. The following
were examples.
Type Total air rate Fuel
i) multiple hearth 2.2 ~ 3.5 A oil
ii) rotary kiln 2.3 ~ 3.2 coal gas
iii) fluidized bed 1.4-1.8 A oil
(v) Any incinerator described above did not have difficulties in operation
and monitoring. The rotary kiln type incinerator has the merit that
we can see dry section and burning section of incinerator, if city gas is
supplied as auxial fuel.
(vi) Continuous incinerator operating is best for economy, but in the field,
this practice was rare. For intermittent operation, fluidized bed type
is most suitable due to short warming up time and high heat holding
capacity.
(vii) Because calory which is sent out by exhaust gas is major portion of the
total energy losses, we must reuse it as much as possible.
2.7.4.3 Development of Index for Predicting Eutrophication Potential
(1) Purpose
AGP (Algal Growth Potential) in effluent has been known useful to indicate
eutrophicational potential in natural water course. Our purpose of this study is
to develop a standard procedure for AGP examination.
(2) Results
"Algal Assay Procedure" for fresh water, saline water and sea water has been
developed. The procedure discribed in the report is consisted of (1) Principle,
(2) Apparatus, (3) Test Algae Species, (4) Synthetic Algal Nutrient Medium,
(5) Method of Sampling, (6) Method of Stock Culture, (7) Method of Cultivation
(Temperature, Illumination, Rate of Oscillation and Amount of Inoculum etc.),
(8) Parameters of Algal Growth (Maximum Specific Growth Rate, Maximum
Standing Crop).
2.7.4.4 Design Criteria for Covered Sewage Plant
It is not seldom that a sewage treatment plant is a next door to a school,
houses, or downtown due to land shortage. This situation enforces municipalities
to design fully covered sewage treatment plant.
To the neighbors, the cover may provides good appearance or a nice play
ground. However, to the plant operator it may give miserable working environ-
ment, if exhaust system does not work properly.
Problems being associated with the covered plant will be pointed out through
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this study. The fallowings are findings in this year.
(1) Disadvantage
a. Not only construction cost but also operational cost of the covered plant
are higher.
b. Expantion or improvement of covered one is much difficult.
c. Installing large machineries and taking out them are not easy.
d. High humidity, insufficient light, or bad smell are very common, resulting
in poor working environment.
(2) Improvement for working environment
A double covers is a popular practice to improve the nuisance environment
caused by the primary deck. If the primary setting tank and secondary aeration
tank are covered with a inner deck; and the fumes are vented, the problems are
desolved.
(3) Exhaust goes from the covered space; especially thickeners and sludge
dewatering building, smell bad. Several practice for deodering are applied.
Among them, soil adsorption is in high potential for this purpose.
2.7.4.5 Best Selection of Unit Process for Treating Wastewater for
Small Communities
The unit processes which are operated in large municipalities are not always
successfully operated for small communities. These communities do not afford
skillful plant operators. Their plants are usually suffered from the operational
problems which are associated with sharp and wide variation in influent rate.
A special consideration should be paid to selection in unit process for them.
A foolproof but still high performance is desirable. In this year, specific
biological process were surveyed to see how they meet the requirement for the small
plant. The following two are found potential alternatives to the traditional
sludge process.
(1) Pure Oxygen activated sludge process
The process was less subject to sludge bulking than the activated sludge
process.
A large variation of influent flow rate causes the sludge bulking in the
conventional activated sludge proi s. The Oxygen system is as designed to fully
automatically operate that the si Caller number in operators and less experience
personnels can manage it.
(2) Rotating biological contactor
Rotating the contacting media is all thing to do for wastewater treatment.
Operation itself is quite simple. On the other hand, effluent quality is not so
good as that from air activated sludge. Fine floes can not be removed in a final
clarifier. Due to the floes, the final effluent does not appear sparkling clear
neither high transparency. In addition to this the effluent BOD does just clear
20 mg/C at best. The improvement of this is under the study. Nevertheless, the
process is high potential to the small communities.
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2.7.4.6 Evaluation of Equipment for Sewage Plant Automation and Development
of New Technology
— Automation for Sewage Treatment Plant —
Facilities for constant MLSS and MLDO control are equipped in the pilot
plant in JSWA's laboratory.
2.1 A.I Application of Advanced Construction Methods to Specific Cases of Sewer,
Pumping Station and Sewage Plant Placing
The purpose of this study is to standardize technical and economical feasibility
of such advanced methods for sewage system construction as stabilization of founda-
tion and foundation work.
For this purpose many construction sites are visited and all aspects of the
construction are summerized. In this survey, our major concerns are:
(1) Geographical and foundational condition on construction site.
(2) Stabilization of foundation.
(3) Landslope protection wall and excavation and their auxiliary construction
methods.
(4) Foundation works.
(5) Environmental disruption produced by construction and its counter-
measure.
(6) The problem awaiting solution on construction method of sewerage
systems.
This .study just begings and results are coming up now.
2.7.4.8 Management of Industrial Pre-treatment
(1) Purpose
This research program has two purpose, one of which, is to show the most
suitable operational management requested for the fulfilment of the industrial
pre-treatment facilities. The other purpose is to standardize the reference by
which municiplaties can judge whether proposed pre-treatment facilities are
acceptable or not.
(2) Finding in 1977
(i) Monitoring industrial wastewater
Generally speaking, companies do not like to pay much efforts to their
wastewater handling since it is negative investment.
They neglect the watch or monitor effluent quality, which is discharged
to publicly owned sewer. However, on the other hand, if the wastewater is
reused for some purposes in the plants, they try their best to operate the
treatment facilities. Municipalities or local authority should pay attention in
introduce a policy in which the companies are induced to have recycle system.
(ii) Operation of pre-treatment facility
In general, a selection of unit pre-treatment process is found reasonable
for almost all the cases. Activated sludge system is a good choice for such
food industrial wastewaters as soybean paste product or brewery industry.
Pressurized floatation process is a better application for paper recovery indus-
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trial wastewater than chemical precipitation. The pre-treatment plant which
were surveyed performed satisfactorily.
(iii) Characteristics of industrial effluent
Characteristics of typical industrial wastewater are summerized from the
data in the field survey.
Tile industry; contain such heavy metals as Pb, and much SS
Sanitary toilet bowl industry; high alkaline concentration
Landry and dry cleaning industry; high pH, BOD, oil
(iv) Sludge disposal
Sludge produced from the organic wastewater pre-treatment process is
rich organic content and converted easily to fertilizer after composted.
2.7.4.9 Operating and Improving Existing Sewage Plant (III)
(1) Inflow equalization
Almost common problem appears in air mixed flow equalization tank is
mixing efficiency goes down when the water level lowers, which results in the
deposition of solids. Sometimes several diffusers located at entrace of the basin
were buried under the solids.
(2) Sludge bulking prevention
Dosing alum to the aeration tank was quite effective to cure bulked sludge
into normal one. After getting back to normal, there is no necessity to dose conti-
nuously alum but one or twice a week.
(3) Improved over-loaded aeration tank by marox system
Conventional activated sludge plants have been suffered from serve sludge bulk-
ing due to specific carbon hydrates included in Orange canning industrial wastewater.
During the canning season the final clarifier did not separate bioflocs. SVI
was over 1000. Marox pilot plant had been operated by side. It showed very
good performance. Aeration time was 1/3 of the air system and much better
BOD removal resulted. Marox's economy did not differ much from air system.
2.7.4.10 Improvement of Sludge Handling Process
It is a common practice among many sewage plants that side streams generated
within sludge handling process are recycled to the secondary facilities. There are
many cases that the poor quality of the side stream retarded the secondary
performance. Our survey showed that all most all the thickeners did not perform
so satisfactorily as designers intended, which resulted in poor supernatant quality.
In the thickeners, sludge became septic and floated up; that is most common
phenomenum seen in many thickeners. The following interrelationship between
suspended solid concentration in the sludge and time until floating up are found.
~r = a X Ts + b
t: time until floating up (hr)
Ts: overall solid concentration (%)
The equation says that diluted sludge is less subject to floating. Our experi-
ment showed that dilution with secondary effluent imprqved sludge settability but
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not retarded the underflow concentration. Polymer had effects on preventing the
sludge floating but not on improving underflow concentration chlorine, at 50 ~
100 mg/liter, prevents the sludge from floating.
2.7.4.11 Recovery Energy and Raw Material from Sewage Sludge
(1) Purpose
Under a condition of a little oxygen, a high temperature, and a certain pressure,
sewage sludge is decomposed in a different way from a traditional incineration.
This is a so-called "pylosis or thermal decomposit" process. End products from
this process are high caloric fuel gas, reuseful raw material and inert ash. It will
be a main process for disposing sewage sludge, if the reaction goes efficiently.
We commenced to power much research effort to see what are key factors in
good performance of the pyloysis.
The specific research purpose on this subject was to find optimum process
parameters for wet thermal decomposition and dry type pyloysis.
(2) Dry type pyloysis
(i) Caracteristics of fed sludge cake
moisture content 83.1%, volatile matter 82.3%
calorie potential 4715 kcal/kg, carbon content 43.3%
(ii) Yielding rate of tar and residual ash
Temp(°C) Tar Residual Ash
600 14g/kg-sludge cake 102g/kg-sludge cake
700 30 60
800 26 53
(iii) Specific surface area of residual ash was 1.1 m2 /g at 600°C, 1.2 m2/g at
700° C, and 2.5m2 /gat 800° C
(iv) Caloric value of tar was 4500 ~ 8000 kcal/kg and carbon content of
tar was about 50%
(v) Caloric value of gas was 2500kcal/m3 at 700°C and 3500kcal/m3 at
800°C
(3) Wet thermal decomposition
The higher temperature and more air existed in the reactor, more volatile
solid is removed through the process.
When the process of the wet thermal decomposition is operated at 250°C and
hold for one hour, carbohydrate contained in the fed sludge is completely oxidized
to carbondioxide and water. The protein is decomposed to organic acid which
are relatively stable, and fat is degradated to fatty acid.
2.7.4.12 Application of Sewage Sludge to Agricultural Use
(1) Purpose
The purposes of the research are
(i) to obtain the optimum conditions for composting sewage sludge
(ii) to investigate the moving phenomena of sludge-borne heavy metals in
soils and crops
(2) Findings
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(i) The following optimum conditions were obtained for composting centri-
fuged sludge cake
1) Mixing ratio (Wet weight base)
Rice hull: Sludge cake = 0.3 ~ 0.4 : 1
Rice-straw: Sludge cake = 0.15 ~ 0.3 : 1
Both were composted without adding the returned compost.
2) Moisture
Rice hull mixture: less than 65%
Rice-straw mixture: less than 75%
3) Detention time
Fermentation: 1 ~ 2 weeks
Curing: 2 ~ 3 months
4) Aeration rate
Rice hull mixture: 250C/m3min.
Rice-straw mixture: 150£/m3 min.
5) Turning
Fermentation: every 1 or 2 days
Curing: every 1 or 2 weeks
6) pH
As pH of centrifuged sludge cake ranged 5 ~ 7, it assumed that pH
had no bad effect on fermentation.
(ii) The following indexes are assumed to be useful for composting centri-
fuged sludge cake.
1) Fermentation: BOD, Odour
2) Curing: Carbon, Ignition Loss, Calories, Alog K, Fumic
Materials
(iii) Sludge borne isotope labeled heavy metals were used to investigate the
moving phenomena in soil and crops.
1) Only a little of isotope labeled heavy metals were eluviated into soil
from sludge cake added; e.g. 1.2% of sludge-borne 73As and less than
0.1% of sludge-borne 109 Cd,203 Hg,51 Cr and 65 Zn were eluviated.
2) Amount of sludge-borne heavy metals incorporated into berley was
also a little; e.g. less than 0.1%.
2.7.4.13 Survey of Emission from Sewage Sludge Incineration Process
(1) Purpose
At present there are 50 cities which operate incinerators to burn sewage sludge.
Many municipalities are going to have ones. Public concern to air pollution is
very keen. It is afraid that stack exhaust gas from the incinerators is a new air
pollution source. The main target of this research is to see how it gives impact to
atomospheric environment and, if yes, how to decrease it.
(2) Findings in 1976
From last 2 years surveys, generally, quality of the exhaust gas from the
sewage sludge incinerators were fond to meet local emission standard. If electoric
precipitators were applied, the particle concentration can be reduced as low as
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1/10 of the standard. However, such advanced exhaust gas treatment operation
as EP results in a increase in-operation cost. Therefore a new engineering should
be developed to concentrate to:
(i) decrease in exhaust gas volume
(ii) decrease in NOx
(3) Findings 1977
In order to decrease the exhaust gas rate, the least air supply is desirable.
Without any defficiency, minimum air requirement is tried to find out. All over
air ratio for multiple hearth incinerator is 1.3 and for fluidized bed is 1.2. Under
the least air supply, also NOx concentration is not high.
At the same time, several methods were tried to remove NOx. Among them,
"selective homogeneous gas-phase method with NH3 " was found very effective for
this purpose. More than 75% NOx could be removed.
2.7.4.14 Experimental Study for Establishing Design Parameters of LakeBIWA
Tertiary Treatment Plant
(1) Alum precipitation
(i) Recycling one portion of precipitated alum sludge to the flush mixing
tank results in great improvement of solid settlability in the clarifier.
The improvement is about 80%. When apply this practice, the overflow
rate of the clarifier can be enlarged at 1.8 time for the same SS removal
efficiency.
(ii) If the precipitated sludge is treated at pH 3 with sulfic acid before
recycled, virgin alum requirement can be cut down to a half.
(iii) Pressure floatation can thicken the clarified underflow sludge, up to
3 ~ 4% solid concentration, while a gravity thickener does only 1% at best.
(iv) 80 ~ 90 percent alum can be recovered through selective ionexchange
process. The alum is as effective to P-precipitation as virgin one.
(v) A belt press dewatering process can reduce moisture concentration of the
sludge down to 80%if properly conditioned with polymer.
(2) Sand filteration
(i) The maximum allowable flow rate for the dual mixed media filteration is
between 200 ~ 300 m3 /m2 /day. A greater rate than this causes phospho-
rous leakage to effluent.
(ii) Suspended solid capture through the filteration bed is 2.5 ~ 2.8 kg/m2.
(iii) Back washing of the dual media filter is not perfect without air buffle
agitation.
(3) Activated carbon adsorption
(i) COD adsorption capacity is around 40 ~ 50g/kg AC when COD removal
rate is less than 50%.
(ii) Flow rate, SV10 is for up flow and SV4 for down flow.
2.7.4.15 Performance of Unox System in Kyoto City
Since the Fall 1977, a unox plant has operated in Kyoto City for treating
mixture of dye industrial wastewaters and domestic sewage. The plant has a
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capacity of 40000 cu-meters a day. It is the biggest unox plant in publicly owned
ones in Japan. The whole sewage plant are completely housed in fancy and good
looking building, since it is built in mid residential area. Thus nuisancefree
operation is possible; free from noise, smell and vibration.
At BOD aeration tank loading 2kg/m3/day, BOD removal rate is 1.8kg/m3/day.
BOD in final effluent is 18 mg/C at the loading.
2.7.4.16 Performance of Jet Aerator (Impingment Type) in Deep Aeration Tank
The city of Kitakyushu had to increase suddenly a capacity of Hiagari Sewage
Plant 2 times as much as that of the original design after the air blower room and
main air supply pipes had been completed. There was no available space left over
to extend facilities to cope with the increased quantities, so the only alternatives
were to deepen the aeration tanks and improve the oxygen transfer efficiency
without increasing air supply equipment. The jet aerator was tried to answer the
needs.
The following is average data for its performance:
oxygen utilization rate 20%
kWH/kg.BOD removed 1.08
As compared with traditional diffuser system, air supply requirement to keep
a sufficient DO concentration is about a half. Power requirement to remove unit
BOD is about equal in the both system. The nozzle holes seem subject to clogging
and errosion for a long use. At present no data on this matter are available.
2.7.4.17 Oder Removal of Vented Air from Sewage Treatment Plant
— Soil FiIteration —
Exhaust gas from several sources in a sewage plant is introduced to several
difficult soil filter beds for the purpose of fume removal preliminary findings are
as follows:
(1) A soil bed which contains high concentration of organic matter and has
large void spaces shows good performance.
(2) Moisture content in the bed is critical for optimum operation.
(3) Original odor content 5000 ~ 17000 unit are reduced to 50 ~ 130 unit
after applied to the soil filter. The removal rate is 98 ~ 99%.
2.7.4.18 Solidification of Sludge Cake with Cement
Public concern to environmental pollution is too keen that even sanitary
landfill practiced in many where is not practical in and around Tokyo Metropolitan
area. Fishermen are against sludge ocean dumping even though it is stabilized by
an anaerobic digestion. The sludge cake should be treated with some means before
final disposal regardless it is the sanitary landfill or ocean dumping.
One approach to this is to solidify the sludge cake by blended with ash or
cement. Tokyo Metropolitan Government goes on this line for reclamating sea-
shore by sewage sludge application. Before going deep to this way, Tokyo asked
JSWA to examine how the solidified sludge cake were stable to outer stress and
could keep such toxicants as heavy metals off leakage. Finally how this approach
are economically feasible in our main interest.
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Findings
(1) Portland cement along could not improve characteristics of the sludge
cake to meet the Tokyo's request.
(2) When ash and alminum cement are blended to the sludge cake, the final
products are satisfactory.
Sludge cake (%) Ash (%) Al-Cement (%) One day strength
(kg/cm2)
83 12 5 0.56-0.83
80 10 10 1.09-2.92
70 10 20 1.10-6.76
2.7.4.19 Infiltration-Inflow Survey in Sewer Systems
Purpose
Infiltration-inflow often causes hydraulic overload for sewer systems, which
results in dry weather overflow to streams or wet weather inflow increases in sepa-
rate systems. The purpose of this survey is to accomplish the countermeasure for
infiltration-inflow problem. As the first step, surveys were carried.
Findings
(1) Peak infiltration rate appeared in August or September and recorded from
45.5 to 409 m3 /liner 1000 m/day (or from 7.9 to 92.5 m3 /ha/day)
(2) A total amount of rain water included in sanitary sewer was 1 ~ 6% of
total storm water.
(3) Poor joint between two pipes, manhole wall and inverts poorly const-
ructed caused infiltration. In addition to those, other sourses of inflow
are manhole covers and poor house drain systems.
(4) Countermeasures for infiltration-inflow are following:
a. Check of house drains and correct of cross connection
b. Use of pipes with water tite joint for example PVC pipe, clay pipe
with compressive joint and concrete pipe with high precise socket joint.
c. Chemical grout on leaky sewer section.
d. Upgrade of construction methods, that is, laying and bedding.
2.7.4.20 Process Design of RBC for Koya City Treatment Plant
Koya City is a famous religions city.
A secondary facility in the new treatment is planed to have RBC. A pilotplant
operation concludes the following parameters; at 4°C.
Retention Time 2.8 Hr
Hydraulic Loading 50 litters/sq-meter/day
BOD Loading 5.2 gram/sq-meter/day
2.7.4.21 Process Design of RBC for Shirakaba Treatment Plant
The Shirakaba is a typical resort lake where a new sewage plant is to be built.
The local ordinance requests that the new treatment plant should discharge final
effluent which meet the following qualities: BOD is 18mg/C and SS is 10mg/5.
The requirement of lOmg/C for the suspended solid in the effluent is hard to
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keep. Therefore specific attention is paid to selection of unit process.
clarifier. RBC and rapid sand filtration are the result.
Planning data are as follows:
Primary
BOD
ss
Water quality (mg/£)
Primary
effluent
126
104
RBC
effluent
26
15
Filtrate
18
10
Removal efficiency (%)
RBC
78
86
Filtration
31
33
RBC +
filtration
86
90
A RBC pilot operation resulted in the following design parameter:
Retention Time: 1.4Hr
Hydraulic Loading: 120 litter/sq-meter/day
BOD Loading: 15 gram/sq-meter/day
at temperature 4°C
2.8 TECHNOLOGICAL COMMITTEE
At JSWA, to deliberate, investigate and survey important matters relevant
to technology of sewage works, a special technological committee is organized at
the headquarters. The committee is composed of executive directors in charge of
planning, engineering works and research and technology development; heads of
the planning, engineering works, research and technology development, and training
division; chiefs and deputy chiefs of both Tokyo and Osaka Regional Office. The
chairman of the committee is the Vice President of JSWA.
The committee is entrusted with the responsibility to perform the following
investigations and surveys:
(1) Concerning detail design criteria.
(2) Concerning inspection of construction work and its criteria.
(3) Concerning design of projects requiring judgement of high technical
engineering level.
(4) Concerning application of new technology.
To expedite the committee's deliberations of the above mentioned matters
expertly, the following sub-committee are held:
(1) Design Criteria
(2) Execution Criteria
(3) Project Case Study
Presently three university professors are participating in the committee discus-
sions to survey exclusive technical matters.
Of the various undertakings by JSWA, concerning new techniques to be put
to practical use for the first time or new techniques that are already put to
practical application but pending evaluations of their practicability as sewage treat-
ment plant equipment involving sewage treating methods, treating facilities and
instruments, the committee plans to positively introduce and evaluate such new
techniques and foster practical application in an orderly manner.
When the survey results prove the necessity of practical application of new
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engineering techniques, the committee will designate a demonstration plant to
conduct experiments. In this case, the committee will decide the basic policy of
the application plan and other important matters for the demonstration plant.
The all round appraisement of the operating results the experiments at the
demonstration plant will be put together by the committee.
Presently, the design criteria/manual by the Design Criteria Sub-Committee
divided into civil engineering, architecture, mechanical engineering and electrical
engineering is bringing about good results.
And the committee activities with regards introducing new techniques are
going well.
3. THE FUTURE OF JAPAN SEWAGE WORKS AGENCY
As aforementioned in "The Background for the Establishment of Japan Sewage
Works Agency," JSWA was founded as a group of highly specialized engineers to
supplement the insufficient engineering of each local government to cope with the
rapidly increasing demands to improve its sewerage system. And it was also a
countermeasure to meet the environmental quality standards in rivers, lakes and
coastal waters all over Japan with regards water pollution.
Since establishment, JSWA has been widely participating in all phases of
activities including designing, constructing, research, technology development and
engineer training in the field of sewerage works. Catering to the increasing
demands expected in the future, JSWA will be obliged to continue to expand
its activities.
Presently, the 4th Five Year Sewerage Construction Plan (7,500,000 million
yen) is being implemented. As the Water Pollution Control Law was partly revised,
the Discharge Elimination System in closed water areas such as the Seto Inland Sea,
the Ise Bay and the Tokyo Bay is enforced after one year of preparation period.
In the near future, discharge elimination of phosphorous is to be regulated newly.
The Seto Inland Sea, the Ise Bay and the Tokyo Bay border important land
areas containing large cities and strategic industrial zones. Therefore, sewerage
measures to be implemented in these areas are drawing keen attention as an impor-
tant domestic political problem. These areas are regarded as the core of industrial
and business activities deeply related to our daily lives of Japan where water
consumption is tremendously high. And since water shortage is anticipated in
these areas, it is most urgent to not only prevent their water from pollution but
also to develop methods that would most effectively reuse and recycle effluent
from sewage treatment plants as important water supply. Therefore, sewerage
measures in these areas must be dealt with in close cooperation with the nation,
prefectural governments and municipalities in harmony.
Experts predict that the nation's sewerage undertakings will confront with the
problem of reorganization. In that event, it will become an important task with
regards the position and role JSWA should take.
In closing, JSWA is destined to take on more responsibilities to carry on
sewage works in Japan in the coming years.
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UNITED STATES PAPERS
WASTEWATER AND SLUDGE RESEARCH PROGRAM 411
Dr. R.L. Bunch, Municipal Environmental Research Laboratory,
ORD, USEPA
MEASURING THE DEGREE OF SLUDGE STABILITY 433
Dr. R.L. Bunch, Municipal Environmental Research Laboratory,
ORD, USEPA
PROGRESS IN INSTRUMENTATION AND AUTOMATION 453
Dr. I.J. Kugelman, M.D. Cummins, W.W. Schuk, J.F. Roesler,
Municipal Environmental Research Laboratory; ORD, USEPA
A SYSTEM FOR TANNERY EFFLUENT TREATMENT 499
L.K. Barber, A.C. Lawrence Leather Company, Inc.
THE 1977 "MID COURSE CORRECTIONS" TO THE FEDERAL CLEAN WATER
PROGRAM 513
J. Faier £ M. Cook, Office of Water Program Operations, USEPA
THE CONSTRUCTION GRANTS PROGRAM _ A REGIONAL PERSPECTIVE 529
G.A. Jones £ J.W. Newsom, Water Division, Region III, USEPA
WATER QUALITY PROGRAMS OF THE VIRGINIA STATE WATER CONTROL BOARD 547
R.V. Davis, Virginia State Water Control Board
WATER SUPPLY AND WASTEWATER MANAGEMENT PLANNING IN THE
WASHINGTON, D.C. METROPOLITAN AREA 579
Dr. D.P. Sheer § P.W. Eastman, Interstate Commission
on the Potomac River Basin
THE OCCOQUAN WATERSHED POLICY - A COMPREHENSIVE PROGRAM TO
SAVE A WATER SUPPLY 599
M.H. Robbins, Jr., Upper Occoquan Sewage Authority
OPERATIONAL EXPERIENCE - SURFACT 615
M.D. Nelson, M. Lozanoff, C.F. Guarino, Philadelphia Water
Department and T.E. Wilson, Greeley £ Hansen Engineers
PRETREATMENT STANDARDS: EPA STRATEGY TO CURB HAZARDOUS INDUSTRIAL
DISCHARGES 657
W.J. Lacy, USEPA
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WASTEWATER AND SLUDGE RESEARCH PROGRAM
Robert L. Bunch, Ph.D.
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268 USA
ABSTRACT
In the early 1970's, EPA was heavily involved in advanced wastewater
treatment (AWT). It was believed that physical-chemical treatment would be
needed to solve water quality problems that could not be eliminated by
biological secondary treatment. At that time there was an environmental move-
ment sweeping our country to cleanse our surface water of all pollution. The
focus was predominantly on point sources. The present prevailing attitude is
to use conventional facilities for removal of conventional pollutants (BOD
and suspended solids) and reliance on pretreatment for removal of toxic and
unconventional pollutants. Thus, our research funds are being spent on
sludge disposal on land, toxic substances removal, and improving existing
treatment plants to make them more effective and less costly to operate and
maintain. In recent years our sludge management research has been switched
from energy intensive processes, such as incineration, to obtaining useful
products, such as compost, liquid and gaseous fuels. Our present projects
are associated with the problems concerned with land disposal of sludge and
the conversion of sludge into useful products. In the past, considerable
sums of money were spent on nutrient removal and lagoon upgrading. Today, we
have several processes that can be used for removal of phosphorus and nitrogen.
They appear to be adequate for the time being. The outcome of our lagoon
program has been that today there is more confidence both in the capabilities
of conventional pond systems and in the use of supplementary devices to
upgrade the existing lagoons. The research of the Wastewater Research
Division is continuously changing to be responsive to regulatory changes,
needs of the wastewater treatment community and to shifting world situations.
WASTEWATER TREATMENT PROCESS DEVELOPMENT
Major efforts in the past have been devoted to the development of oxygen
aeration, lagoon performance, control of the nutrients nitrogen and phosphorus,
uprating of existing treatment processes and disinfection. Current efforts
are on approaches that show potential savings in energy and resources. Novel
and innovative treatment concepts will receive more emphasis in the future.
Some of the U.S. Environmental Protection Agency's (EPA) current interest in
wastewater treatment process development are discussed below.
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DEEP SHAFT PROCESS
An EPA demonstration grant to evaluate an innovative biological treatment
concept has been made to the City of Ithaca, New York. The concept is the
Deep Shaft Process, the heart of which is a vertical, activated sludge reactor
consisting of two concentric pipes, an inner downcomer leg and an outer riser
leg. The process was initially developed and piloted in Billingham, England,
by Imperial Chemical Industries (ICI) .
Compressed air is injected into the Deep Shaft downcomer at about one-
third total depth to provide the necessary oxygen for aerobic metabolism.
The different liquid densities thereby created in the two legs cause mixed
liquor to continuously circulate up the riser and back down the downcomer.
Due to the high pressures existing at the bottom of the shaft, the saturation
concentrations of the gases in air plus respiration by-product, carbon dioxide,
are increased many fold at this point. Consequently, supersaturated dissolved
gases, primarily nitrogen and carbon dioxide plus a small amount of unused
oxygen, come out of solution as they travel up the riser leg to the surface.
The natural flotation effect which results from this phenomenon has led to the
development of two alternatives for liquid/solids separation. They are the
standard gravity clarification with a degassing standpipe interposed between
the settler and the reactor, and flotation clarification with polymer addition.
Both modes of clarification will be evaluated at Ithaca. The inventors of
Deep Shaft claim savings in power, volume, overall treatment cost and less
excess sludge production than conventional activated sludge. Most certainly
the land requirements will be less, making it applicable to industrial plants
and municipalities with limited space.
The plant at Ithaca is designed for 760 m3/day (200,000 gal) with a
detention time of 38 minutes in the flotation clarification mode. The shaft
will be 0.5 m x 133 m (18 in. x 435 ft.). Parameters to be evaluated in
addition to process performance, will include power consumption, excess
sludge production, and the economic tradeoff between the larger reactor volume
required in the gravity clarifier mode versus polymer requirements in the
flotation mode. Power consumption is tied directly to oxygen uptake rate and
oxygen utilization. Due to the combination of high intensity mixing and
greatly elevated pressures, oxygen transfer rates up to 2,885 kg/m^/hr
(180 lb/1000 ft-Vhr) and oxygen utilizations of 90 percent or more are
reportedly achieved, yielding an effective power transfer rate in wastewater
of 2.4-3.6 kg C>2/kWh (4-6 Ib C^/hp-hr) . By comparison, conventional air
aeration systems typically achieve 5-15 percent oxygen utilization and
0.6-1.2 kg 02/kWh (1-2 Ib 02/hp-hr) power transfer rate. The potential
economic savings in energy are considerable if the above figures for Deep
Shaft power consumption can be verified.
The unusual cycling environment created by rapid circulation in the shaft
is credited with stimulating high microorganism respiration rates at the
expense of cell synthesis. This phenomenon has led to claims of potential
reductions in excess biological sludge production compared to conventional
activated sludge regimes. Based on pilot plant experiences to date, it is
anticipated full-scale excess sludge production will approximate 0.5 kg TSS/kg
BOD removed at F/M loadings of 0.75-1.0 kg BOD/day/kg MLVSS. Historically,
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sludge production at loading rates of this magnitude would be expected to
approach 1.0 kg TSS/kg BOD removed. Because of the huge capital and operating
costs involved in sludge processing and disposal, this aspect of Deep Shaft
operation also suggests significant potential economic impact.
STANDARD FOR EVALUATING OXYGEN TRANSFER
As the USA continues to search for more effective ways to conserve energy,
greater emphasis is being placed upon the development of energy efficient pro-
cesses in pollution control technology. The evaluation of the efficiency of
oxygen transfer devices and systems will assume greater importance as engineers
seek less energy intensive equipment. In spite of the considerable effort
devoted to oxygen transfer technology, it is evident that unanimity of opinion
has not been achieved in the development of a standard procedure for the eval-
uation of oxygen transfer devices. The areas of disagreement lie not only in
the details of conducting oxygen transfer tests, but also in the methods of
data evaluation.
Presently, manufacturers rely on clean water shop tests (i.e., performance
tests conducted in a test tank at the manufacturing plant), for describing the
oxygen transfer capability of aeration equipment. The chemical constituents
of wastewater vary substantially from one source to another. The concentration
of surface active agents present greatly affects the Alpha factor. Temperature,
tank geometry, and bubble size are other factors which influence the prediction
of oxygen transfer in wastewater or mixed liquor based on clean water test
results. A further complicating feature of this is that oxygen demand in acti-
vated sludge systems is due to a respiring biomass, whereas in the clean water
test it is chemically induced.
ments
Faced with this problem, many consulting engineers have written require-
ment for field performance testing into their specifications for aeration
equipment. Contractors and manufacturers recognize this liability in preparing
bids and will include larger factors of safety; thus, many aeration systems
will be adequate but overdesigned. Some systems, however, may still prove to
be inadequate.
All of the above discussion emphasizes the dilemma that the design
engineer, the municipal decision maker, and the regulatory grant reviewer
face in comparing alternative oxygen transfer systems. With increasing
energy costs stimulating extensive interest in fine-bubble diffusion devices
for the first time in this country, it has become imperative to develop uni
form methods for testing and evaluating oxygen transfer which accurately
assess equipment capabilities and which through repeated usage would assume
the role of a consensus standard. A unified approach to evaluating competi-
tive aeration systems would benefit all involved; the designer and municipal
official in making trade-off decisions and selecting the equipment best suited
for a specific situation.
A 2-year research grant has been awarded to the American Society of Civil
Engineers (ASCE) to develop a tentative standard for evaluating oxygen trans-
fer capacity of aeration and oxygenation equipment in water and wastewater.
The ASCE has established a Subcommittee on Oxygen Transfer under the Committee
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on Environmental Standards. This Subcommittee is chaired by Dr. William
Boyle, University of Wisconsin. The final report for the project will con-
tain a tentative standard, literature review, and recommendation for verifying
the tentative standard in the field.
As an adjunct to developing a standard for evaluating oxygen transfer,
an EPA contract has been awarded to Los Angeles County Sanitation District
to compare seven submerged air aeration devices. The transfer devices will
be tested under strictly controlled conditions ina6mx6mx7.5m
(20 ft. x 20 ft. x 25 ft.) tank filled with clean water. The diffusers to be
tested will include:
1. Fine bubble diffuser system designed for total floor coverage.
(Norton)
2. Fine bubble diffuser system designed for side wall installation.
(FMC, Pearlcomb)
3. Static mixer aerator system. (Kenics)
4. Jet aerator system. (Penberthy)
5. Coarse bubble diffuser system variable orifice. (Bauer)
6. Coarse bubble diffuser system fixed orifice. (Sanitaire)
7. Coarse bubble diffuser system designed for total floor coverage
(Envirex)
Data generated on the test program to date suggest that fine bubble
systems can substantially reduce energy requirements. The second phase of
this project will evaluate the more promising systems under field conditions
in activated sludge systems. The field studies will determine the extent
that operation in wastewater (i.e. mixed liquor) decreases the oxygen transfer
efficiencies observed with fine bubble equipment in clean water. The study
will also determine whether the fine porous media of some of these devices
are subject to rapid headless buildup and unacceptable maintenance require-
ments for cleaning.
ACTIVATED BIO-FILTER
The activated bio-filter (ABF) system is a unique combination of conven-
tional biological processes. Settled activated sludge instead of being
returned to the head of the aerator as in other two-stage systems where an
attached growth unit precedes an activated sludge unit, is first recycled to
the top of the tower for mixing with primary effluent and passage through the
redwood media biocell in trickling filter fashion. There is no intermediate
clarifier. Biocell effluent containing the recycled settled sludge and
sloughed humus is then fed directly to the aeration tank.
Carrying active suspended biomass through the biocell reportedly greatly
increases the organic loading and removal capacity of this unit. The
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recommended design organic loading for the biocell of 3.2 kg/day/m3 (200 Ib
BOD/day/1000 ft^) is 4-7 times higher than for high-rate stone media trickling
filters and 2-4 times higher than for synthetic media trickling filters. BOD
removal for all three of the above at their respective design loading rates
is approximately 65 percent. Due to the high-removal capability of the bio-
cell, advertised nominal detention time requirements for the downstream
aerator to complete secondary treatment are minimal, ranging from 1/2-1 hour
depending on the actual residual BOD concentration from the biocell.
The ABF process as now marketed qualifies as an efficient high-rate
biological treatment system. Broad acceptance and deployment of the technol-
ogy is lagging due to the lack of full-scale confirmation of the claims made
for it. Data at full-design loading exist only at pilot scale. Municipal
treatment plants which have installed ABF systems are in the early part of
their design lives and are typically operating at 1/3 to 1/2 of stipulated
capacity.
Comprehensive cost estimates of biological treatment systems recently
completed by Culp/Wesner/Culp indicate that at the manufacturer's recommended
design conditions, the ABF process is substantially more cost effective than
any of the established pure attached growth biological processes and is cost
competitive with established suspended growth processes at all sizes up to
4.38 m^/sec (100 mgd). Substantiation of the manufacturer's pilot results
on a large-scale municipal installation would stimulate greater consideration
of a potentially cost-effective innovative treatment alternative.
A grant has been awarded to the City of Helena, Montana, to collect and
evaluate full-scale operating and performance data on ABF process under care-
fully controlled loading conditions up to the manufacturer's recommended
design organic loading. Helena's current influent flow is 16,650 m-Vday
(4.4 mgd). Although Helena's current biocell loading is only one-half of
design, the unit's flexibility permits sections to be removed from service
such that several loading rates can be imposed.
WASTEWATER DISINFECTION DEVELOPMENT
The U.S. Federal Water Pollution Control Act Amendments of 1972, Public
Law 92-500, clearly established the responsibility of the Environmental Pro-
tection Agency (EPA) for reducing and controlling the pollution of navigable
waters. The Act established as a National goal that the water quality should
provide for the protection of fish, shellfish and wildlife and for recreation
in and on the water by July 1, 1983. The principal mechanism used to achieve
the objectives of Public Law 92-500 was by implementing effluent standards for
industrial and municipal wastewater dischargers. Included in the effluent
standards were biochemical oxygen demand, suspended solids, pH, and fecal coli-
form bacteria. The limit on fecal coliform bacteria was set at 200 per 100
milliliters. This requirement generally necessitated the use of separate,
continuous disinfection processes in addition to the biological or physical-
chemical processes for BOD and suspended solids removal.
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On July 26, 1976, the EPA deleted the fecal coliform requirement from the
effluent standard. Reliance on the site-specific water quality standards of
each State to set disinfection requirements for municipal wastewater treatment
plants is now the practice. Thus, disinfection will still be required by State
regulation, but no uniform Federal requirement has to be achieved. Some of the
reasons for the change in the regulation are: (1) Toxic effects on the aquatic
environment of residual chlorine, (2) halogenated organic compounds are poten-
tially carcinogenic, (3) continuous disinfection of wastewater is not needed
in certain locations, (4) potential dangers associated with the use of ele-
mental chlorine, and (5) the amendment of the effluent standards provides
flexibility in disinfection requirements. Cost was not considered as a main
factor, because public health and protection of aquatic environment are the
overriding considerations affecting any disinfection requirements. The
unnecessary and excessive use of disinfectants, however, is wasteful both in
terms of available financial resources and energy.
The adverse environmental effects of residual chlorine in chlorinated
wastewaters has prompted EPA to search for alternative disinfection agents
which would satisfy the disinfection requirements and be environmentally
acceptable. The present alternatives currently under investigation are:
chlorination-dechlorination, ozonation, chlorine dioxide and application of
ultraviolet light.
PILOT PLANT DEVELOPMENT OF OZONE DISINFECTION
Ozone is a potent oxidizing agent, and its reaction with oxidizable
material is non-selective. The demand exerted by organic matter in effluents
can have a marked influence on the disinfection efficiency and reliability of
ozone. Care must be exercised in making certain that the ozone produced is
utilized in the most efficient manner; otherwise, the operating costs of
ozonation may be needlessly high due to excessive use of energy resources.
One of the main items influencing the cost is the contactor.
Private industries concerned with supplying ozone generation facilities
have as their objective the most cost-effective package. The package normally
includes air preparation, ozone generation, and ozone contacting. Every
conceivable liquid-gas contacting device is marketed with ozone systems. EPA
has initiated at its pilot plant at the Robert A. Taft Laboratory, Cincinnati,
Ohio, a project to determine the advantages and disadvantages as well as the
economics associated with the contactor. This study has completed evaluating
three generic types of contactors commercially available. It is intended to
evaluate more in the near future. The three contactors evaluated were: (1)
positive pressure injector (PPI), (2) a packed column (PC), and a bubble
diffuser (BD).
All the contactors were designed and fabricated in EPA's pilot plant.
The packed column contactor was a 230 mm diameter glass column packed with
3.1 m of 12 mm ceramic Intalox saddles. Secondary effluent entered the top
of the column and exited at the bottom. The ozone entered at the bottom and
flowed countercurrent to the secondary effluent. Residence time of the
secondary effluent was 20 seconds at a flow rate of 75 1/min. The pressure
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injector was a PVC gas-liquid contactor into which both secondary effluent
and ozone gas were pumped under a positive pressure of 50 to 60 kPa. The gas
and liquid mixed in a specially designed head compartment, then flowed con-
currently downward through an inner cylinder. Upon reaching the bottom of
the inner cylinder, the gas-liquid mixture reversed flow and flowed upwards
through a larger cylinder. At the top the gas and liquid separated, the gas
flowing to the exhaust gas line and the liquid flowing downwards through a
second concentric cylinder. Total liquid residence time in the system was
20 seconds at 75 1/min. The bubble diffuser contactor consisted of three
aluminum columns, each 3.7 m high and 300 mm in diameter, connected in series
by PVC piping. The three columns were staggered vertically so that secondary
effluent which had been pumped to the top of the first column, could flow by
gravity to each of the two successive columns. The ozone enriched gas was
injected through domed ceramic diffusers located at the bottom of each column.
The first column received 50 percent of the total gas flow, while the other
two columns received equal fractions of the remaining 50 percent.
Testing of the different contactor types was performed using a split plot
design where whole plots were arranged in a balanced incomplete block design.
The whole plots were arranged in a balanced incomplete design due to the
physical restriction that only two of the contactors could be set up in
parallel at any given time. Thus, two contactors per day were tested with
both contactors receiving the same applied dose at any given time. The order
of the dose levels was balanced so that each dose level was used first, second,
and third in a day the same number of times for each contactor. Randomization
consisted of randomizing the order in which the pairs of contactors were com-
pared.
The first set of experiments evaluated the percent ozone utilization as a
function of applied ozone dose. The results, as shown in Table 1, indicated
that overall percent ozone utilization was highest in the bubble diffuser,
followed by the packed column, and then the positive pressure injector. As
the dose was increased, percent ozone utilization in all contactors decreased.
In Table 2, the total coliform log reduction (TCLR) in the above experiments
are summarized. The data reveal that overall mean TCLR was higher in the
bubble diffuser than in either the packed column or the positive pressure
injector. The overall mean TCLR in the latter two contactors was not signi-
ficantly different.
The second set of experiments was run to determine the change in percent
ozone utilization and microorganism reduction when the applied dose was
varied by changing the ozone concentration and maintaining a constant gas
to liquid flow ratio. In Table 3, the mean percent ozone utilization data
per contactor at each dose level are summarized. The results indicated that
overall percent ozone utilization was higher in the bubble diffuser than in
the packed column or the positive pressure injector while percent utilization
in the latter two contactors was similar. The rate of decrease in percent
ozone utilization at higher doses was substantially less in the bubble diffuser
than in the other two contactors. The total coliform log reduction data are
shown in Table 4. The overall TCLR in all contactors was similar. Although
the overall utilization of ozone in the bubble column was higher, only 0.5 mg/1
more ozone was absorbed than in the other two contactors. This increase was
not sufficient to cause a marked increase in TCLR.
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TABLE 1. MEAN PERCENT OZONE UTILIZATION AS A FUNCTION OF APPLIED
OZONE DOSAGE (INCREASING QQ/, CONSTANT Y*
Mean Percent Ozone Utilization
(Standard Deviation)
Dose
mg/1
3.3
6.7
10.0
Mean %U,
All Doses
Positive Pressure
Injector
77
(2)
53
(3)
41
(3)
57
(16)
Packed
Column
85
(4)
58
(2)
46
(3)
63
(17)
C% U)
Bubble
Diffuser
90
(2)
86
(2)
81
(3)
86
(5)
Mean % U,
All Contactors
84
(6)
66
(15)
56
(18)
= carrier gas flow rate
= liquid flow rate
= concentration of ozone in the carrier gas
TABLE 2. MEAN TOTAL COLIFORM LOG REDUCTION (TCLR) AS A FUNCTION OF
APPLIED OZONE DOSE (INCREASING Q /Q , CONSTANT Y )*
Vj J_i J.
Mean Total Coliform Log Reduction
(Standard Deviation)
Dose
mg/1
3.3
6.6
10.0
Mean TCLR,
All Doses
Positive Pressure
Injector
2.90
(0.36)
2.94
(0.44)
3.04
(0.34)
2.96
CO. 36)
Packed
Column
2.85
(0.36)
3.13
(0.10)
3.31
(0.11)
3.10
(0.29)
Bubble
Diffuser
3.12
(0.10)
3.56
(0.25)
4.52
(0.55)
3.73
(0.69)
Mean TCLR
All Contactors
2.96
(0.31)
3.21
(0.38)
3.62
(0.75)
*QG = carrier gas flow rate
QL = liquid flow rate
YI = concentration of ozone in the carrier gas
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TABLE 3. MEAN PERCENT OZONE UTILIZATION AS A FUNCTION OF APPLIED
OZONE DOSE (INCREASING Y,, CONSTANT QG/QL)*
Dose
rag/1
1.5
4.5
7.5
Mean % U,
All Doses
Mean
Percent Ozone Utilization
(Standard Deviation)
Positive Pressure Packed Bubble
Injector
84
(4)
68
(5)
62
(4)
71
(10)
Column Diffuser
79 89
(3) (2)
68 80
(4) (4)
62 77
(3) (3)
69 82
(8) (6)
Mean % U,
All Contactors
84
(5)
72
(7)
67
(8)
*Qg = carrier gas flow rate
QL = liquid flow rate
Y, = concentration of ozone in the carrier gas
TABLE 4. MEAN TOTAL COLIFORM LOG REDUCTION (TCLR) AS A
FUNCTION OF APPLIED OZONE DOSE (INCREASING Y, , CONSTANT Q-/QJ*
1 G L
Mean Total Coliform Log Reduction
(Standard Deviation)
Dose
mg/1
1.5
4.5
7.5
Mean TCLR,
All Doses
Positive Pressure
Injector
0.81
(0.68
3.07
(0.43)
3.28
(0.40)
2.39
(1.25)
Packed
Column
0.73
(0.59)
2.90
(0.39)
3.37
(0.30)
2.34
(1.25)
Bubble
Diffuser
0.56
(0.40)
3.24
(0.49)
4.00
(0.49)
2.60
(1.58)
Mean TCLR,
All Contactors
0.70
(0.54)
3.07
(0.44)
3.55
(0.50
= carrier gas flow rate
= liquid flow rate
Y, = concentration of ozone in the carrier gas
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DEMONSTRATION OF ULTRAVIOLET LIGHT DISINFECTION
Ultraviolet has been demonstrated to be feasible under certain conditions,
but reliability is hampered by wastewater quality and inadequate design. Most
UV units available on the market are designed for treating potable water. It
is only recently that equipment manufacturers have focused their attention on
wastewater.
EPA has funded a full-scale demonstration project on ultraviolet disin-
fection at Waldwick, New Jersey. A prototype ultraviolet system is being
tested on a 30,000 m^/d (8 med) conventional activated sludge effluent to ob-
tain cost, reliability of achieving the desired coliform reduction, maintenance
requirements and electrical power needed. The ultraviolet unit which will be
used for this project is a prototype system, the UVS 5000, manufactured by the
Uvoxx Company, Jersey City; New Jersey. The unit has been specifically
designed for treatment of municipal wastewater effluent. It is especially
flexible in operational modes and thus well suited to a research oriented
study. It is characterized by a body having a series of spaced, parallel,
quartz-jacketed mercury lamps (400 in number) extending from end to end. The
placement of the lamps has been engineered to utilize a thin film concept with
a minimal head loss through the unit. Actual water thickness between quartz
jackets is 6.4 mm (0.25 inch). The water flows perpendicular to the UV lamps
to an exit tank, where air which is used to ventilate the UV lamps is injected.
This air contains a small amount of ozone. To insure unimpeded transmission
of ultraviolet radiation through the wastewater, the unit is equipped with an
automatic wiper mechanism adjustable for stroke frequency. The close tolerance
wiping mechanism is designed to prevent scale buildup and solids accumulation
on the quartz sleeves, but its performance has never been evaluated. The
high intensity, short detention time concept needs also to be evaluated. A
dimmer control will be incorporated into the UV unit so that electrical energy
input can be varied without changing detention time. This could eventually
act as a dosage control device. For example, as wastewater quality varies,
changes in UV intensity would send signals to the dimmer to increase or de-
crease the current supplying the lamps. Finally, ozone generated in the
ventilation air will be injected in the exit holding tank to provide additional
disinfectant action. Since the purpose of the ventilation air is to provide
the proper temperature for optimum lamp efficiency, the amount of ozone pro-
duced will vary with the volume of air being circulated, which will, in turn,
vary with seasonal temperature changes. These effects will be closely moni-
tored throughout the project.
Results obtained thus far indicate that approximately 600 UV lamps would
be needed to achieve satisfactory disinfection for a design flow of 30,000 m /d
(8.0 mgd) and a peak flow of 60,000 m3/d (16 mgd). The total cost of ultra-
violet light disinfection computes to approximately $0.008/m3 ($0.03/1000 gal).
This is a very preliminary estimate, but certainly indicates UV to be competi-
tive with chlorination.
UV does not add chemicals to the wastewater, and the dose use for destroy-
ing bacteria is so small, changes in chemical compounds present will be mini-
mal. Bioassay tests with rainbow trout support this hypothesis. Ultraviolet
radiation may prove to be an alternative where wastewater quality is high and
its volume is low.
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CONTROL OF TOXIC COMPOUNDS
WASTEWATER TOXICITY
No discussion of wastewater would be complete without mentioning the
concern for the presence of toxic metals and organics, because most waste-
waters are a variable mixture of domestic and industrial wastewaters. The
Environmental Protection Agency has established a list of 65 priority toxic
pollutants under Consent Decree. The Agency is under court order and legis-
lative mandate (Section 307 b and c of the Clean Water Act Amendments) to
establish standards for these organics for 21 industries. The Office of
Water Programs plans to spend more than $3 million on contracts to survey
municipal wastewater and sludges for the priority pollutants. Unfortunately,
the existing analytical protocol for organics has poor sensitivity in raw
wastewater and sludges. The Wastewater Research Division has a grant with
the University of Washington to improve the protocol and conduct a sampling
survey of 25 municipal wastewater treatment plants. The grant with The
University of Washington at Seattle, Washington, started June 1, 1978, and
will end June 1, 1980. The amount of EPA funding is $400,000. The first
task will be to develop and verify analytical methods to determine toxic
priority pollutants in domestic wastewaters and sludge at a concentration of
less than 1 pg/1. Attempts to apply the presently available industrial proto-
cols to domestic wastewaters have failed because of poor detection limits.
For many of the priority organic compounds, the present limits are 30-50 yg/1.
This is far too large a limit to be of practical use in a survey of municipal
treatment plants. After the test methods have been developed, surveys will
be conducted of 25 municipal plants for toxics (129 priority pollutants) in
the influents, after primary treatment and in the effluent discharge before
and after chlorination, if practiced. Sludges will also be analyzed. A
variety of plants containing various compositions of industrial/domestic flows
and treating the wastewaters by a variety of processes will be surveyed. From
this there will emerge the beginnings of a data base which will provide infor-
mation on influent occurrence and concentration, removals currently being
obtained by a variety of treatment processes and an evaluation of the toxics
in sludges. Certain compounds tend to accumulate in sludge 10 to 1000 fold
higher in concentrations than the influent. A corollary, yet extremely
important objective of this study is to develop and verify the analytical
methods that will be used in the survey. Surrogate tests for toxicity of the
effluents, such as Ames test and acute fish toxicity will complete the study.
A data base on the occurrence and distribution of metals is being devel-
oped. The University, of Tennessee has a grant to locate and tabulate existing
data on influent heavy or toxic metals to POTW. To date, 47 percent of the
cities contacted have stated that data exist that have not been reported. All
these data will be evaluated to determine the reliability and quantity of the
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data. A concerted effort is being made to determine the source of these
metals and what percent is due to domestic source, runoff, and industry. The
grant at The University of Tennessee at Knoxville, Tennessee, started Octo-
ber 10, 1977, and will end August 23, 1979. EPA's contribution is $142,788.
Metals discharged to a treatment plant have a special significance since, in
the absence of proper precautions, they may be cycled from one medium of the
environment to another; since metals cannot be destroyed, they can only be
contained. Thus, removal from the liquid flow in a plant merely concentrates
the metals in the sludges.
A survey of the City of Kokomo, Indiana, is being conducted by Purdue
University on a $137,000 grant from EPA. The City of Kokomo has a
64,350 m^/d (17 mgd) activated sludge wastewater treatment plant that receives
a variety of industrial wastes in addition to the regular domestic waste.
The grant started in November of 1977 and will be finished in September 1979
when the final report is published.
The study will determine sources of toxic metals and cyanide in the
local municipal wastewater and sludges and establish a general protocol for
identifying, quantifying and regulating such toxics in other municipal waste-
waters. The objectives are to be accomplished through a comprehensive
sampling and analysis program for stormwater, residential, industrial, and
total municipal wastewaters and sludge. Elements of interest are those of
greatest significance in land spreading of municipal sludges or the potential
damage to the aquatic environment. They are Cu, Ni, Cd, Zn, Hg, Pb, Cr+3,
total Cr and cyanide.
A 60-day heavy metals mass balance around unit operations of the
municipal treatment plant is nearing completion. High overall removals of
metals, ranging from 68 percent for Ni to 97 percent for Cd, are being
obtained through the plant which consists of activated sludge followed by
tertiary filtration of effluent. These high removals are believed to be due,
in part, to discharges of pickle liquor to the sewer from a steel plant next
to the wastewater treatment plant. The iron which often produces a dark brown
coloration of the wastewater is an effective precipitant for trace metals.
An evaluation of the Zimpro sludge reactor and thickener showed that
relatively little total mass of metal was released from the sludge solids to
be recycled to the plant in the supernatant.
There is a marked decrease in the total mass of metals entering the plant
during weekend periods particularly for Cd, Cr, and Ni, pointing out the
probable industrial origin of these pollutants. Sampling of feeder sewers
containing only residential wastewaters had shown very low concentrations of
Cd, generally less than 0.5 yg/1. Five of the six major trunklines serving
Kokomo have been sampled to date.
Since the main thrust of EPA's efforts for toxics control is source
control and pretreatment before discharge to a municipal treatment plant
(POTW), it is not likely very much of our research funds will be devoted to
process modification to enhance removal of toxics. Under ideal regulatory
422
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conditions POTW should not have any toxics in the influent; however, experi-
ence has shown that toxics do enter treatment facilities from diffuse sources.
Presently, two approaches are concerned with toxics. They are the use of
activated carbon in the aerator of an activated sludge system and the treat-
ability of toxic substances.
One of the potentially useful processes for control of toxic organic
compounds is adsorption on activated carbon. It has the merit that the com-
pounds are destroyed when the carbon is thermally regenerated. Adsorption is
a complex process which involves both the nature of the carbon surface as well
as the characteristic of the molecule. Some of the latter factors include
solubility, molecular weight, polarity, ionization, orientation at the sur-
face, and more. All of these factors contribute to the adsorbability of a
compound which, operationally, can be determined quantitatively by determining
a batch equilibrium adsorption isotherm. During the last year the adsorption
isotherms for 60 organic compounds were determined. These were collected into
a simple publication entitled "Carbon Adsorption Isotherms for Toxic Organics,"
Environmental Research Laboratory, Cincinnati, Ohio, 45268, May 1978.
While carbon is highly effective for the removal of organics, it is
important to point out that the variation of loading on carbon is great. For
example, the adsorption of 60 compounds mentioned above varied from 0-360 mg/g
of carbon at an initial concentration of 1 mg/1 of compound. Relatively small
changes in a molecule can alter the adsorbability of the compound. For
example, unsubstituted benzene is barely adsorbable, 0.7 mg/g. Substituting
an OH group for one of the H in the benzene molecule increases the adsorption
by a factor of 30. When Cl is substituted, this factor increases to 133.
In summary, adsorption (or non-adsorption) depends on many factors, not
the least of which is the substitution on a parent molecule. It is one of
the goals of the research on treatability to discover those factors which
govern adsorption and ultimately to be able to predict adsorption in some
systematic way. Without this capability, laboratories will be burdened with
the need to evaluate adsorption for thousands of compounds.
The treatability of selected toxic compounds is being studied in EPA's
physical-chemical wastewater treatment pilot plant. Five compounds are being
added to the raw sewage prior to treatment by alum clarification, duel media
filtration and granular activated carbon. The first five compounds to be
tested are: dimethylphthaiate, ethylbenzene, carbon tetrachloride, trichloro-
ethylene, and nitrobenzene.
Automatic composite samplers, designed to avoid loss of volatile organics,
collect samples at appropriate locations in the system. The samples are
analyzed by gas chromatographic procedures. Preliminary data indicate that,
from an influent averaging 120-180 yg/1 of each compound, reductions across
the alum-polymer clarification unit range from 11 percent for dimethyl-
phthalate to 66 percent for ethylbenzene. Some of the volatile substances
are undoubtedly lost to the atmosphere during air-liquid contact. No further
removal occurs during dual-media filtration.
423
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A five-minute (empty bed) contact time carbon adsorber operating on
dual media filter effluent maintained the concentration of the five organics
to less than detectable levels for only 1-2 weeks. The order of breakthrough
to 25 percent of influent concentration of the compounds assayed was, first,
carbon tetrachloride, then trichloroethylene, dimethylphthalate, nitrobenzene
and ethylbenzene. Only carbon tetrachloride and trichloroethylene had begun
to break through the carbon at a contact time of 15 min after five weeks on
stream. Complete loading data from the column operation, together with
laboratory equilibrium tests will help to clarify the role of activated
carbon in the removal of toxic organics from municipal wastewaters.
Many times the most economical way to increase the efficiency of a
wastewater treatment process is to add onto or modify the treatment train.
In that activated carbon is effective for removing many of the toxic compounds,
a study has been funded to investigate the addition of powdered activated
carbon to the aeration process in activated sludge. The grant was awarded
to The University of Michigan for a three year study. Dr. Walter Weber will
direct the research. Bench-scale complete-mix activated sludge units will be
used to examine the mechanisms involved and the effects of operational vari-
ables on system performance. It is possible that only a slight amount of
powdered activated carbon would be needed to remove toxic compounds when there
are only trace amounts present in the influent.
In anticipation that process economics may be affected by the cost of
powdered carbon, a study with Stanford University in California was initiated
to seek a cheaper but equivalent powdered carbon to current commercial pro-
ducts. A variety of waste carbonaceous sources, other than coal or wood, are
being treated by processes including pyrolysis and activation to produce a
powdered activated carbon. The two major reactions will be optimized and
the resulting carbons matched by performance against commercial products.
The project is expected to be completed in March 1979.
The second approach to the problem of organic toxics is the determina-
tion of their treatability and biodegradability. Regulations cannot be made
to control toxics unless the knowledge is obtained on how a compound behaves
in the environment and in particular how it reacts in unit wastewater treat-
ment processes. The task is tremendous because of the large number and
variety of compounds now existing and the constant flow of new organic com-
pounds. The task can be simplified if methods are developed to predict the
behavior rather than having to resort to testing each compound under various
environmental conditions. In the investigation of treatability, a variety of
processes must be addressed, such as: adsorption (soils, solids and carbon),
biodegradability (aerobic and anaerobic) volatility and chemical modification
(by oxidation, precipitation, etc.). With enough basic information on the
behavior of many compounds and their molecular characteristics, it may be
possible to develop models which predict the behavior of untested compounds.
Another approach to this kind of research is to observe removals of
compounds across various unit processes such as sedimentation, biological
oxidation, carbon contactors, etc. Much can be learned from this approach
about the unit process, but since many mechanisms operate in most processes,
424
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little fundamental knowledge will be gained about the compound itself. This
research can be characterized as "removability." Because of the need for
both short and long term information, research is taking both approaches of
"treatability" and "removability."
The treatability of carcinogenic compounds is being conducted by Illinois
Institute of Technology under a $69,000 EPA grant. The project will be
finished this year, furnishing data on five compounds and their treatability
by biological oxidation, activated carbon adsorption and chemical oxidation
with ozone. Activated carbon adsorption capacities in mg of compound adsorbed
per gram of carbon were measured. Values obtained for an initial concentra-
tion of 1.0 mg/1 of test compound were: benzidine 170; 3-naphthylamine 170;
naphthalene 170; 4,4'-methylene-bis (2-chloroaniline) 720; and 1,1-dephenyl-
hydrazine 160.
Chemical oxidation with ozone at 1.0 wt % and a flow of 2.4 1/min in a
12-liter reactor gave the following results: (a) an initial concentration of
10 mg/1 of 1,2-diphenylhydrazine was reduced to zero in 6 minutes, (b) an
initial concentration of 11 mg/1 of g-naphthylamine was reduced to 0.01 mg/1
in 4.5 minutes, (3) an initial concentration of 1.52 mg/1 of 4-4'-methylene-bis
(2-chloroaniline) was reduced to zero in 5.0 minutes, (d) an initial concen-
tration of 7.4 mg/1 of naphthalene was reduced to 1.5 mg/1 in 40 minutes.
All of the compounds tested were amenable to biological oxidation. Acti-
vated carbon treatment was effective in removing all but the highly polar
dimethylnitrosamine. Chemical oxidation was not effective for naphthalene
or dimethylnitrosamine. A summary of the treatability data for the systems
investigated is tabulated below. A "+" sign indicates effective removal of
the compound by the treatment process while a "-" sign means little or no
removal.
TABLE 5. TREATABILITY OF CARCINOGENIC COMPOUNDS
Compound
Biological
Oxidation
Oxidation
Activated
Carbon
Naphthalene
1-1-Diphenyl
Hydrazine
3-Naphthy1amine
4-4'-Methylene-bis
(2-chloroaniline)
Dimethylnitrosamine
(a) Reacts slowly with 0^. Some removal by gas-stripping.
425
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Additional biodegradation studies are being done by Purdue University.
They will study a number of representative priority organic pollutants in
both aerobic and anaerobic experimental laboratory systems. It is hoped that
after testing many compounds, the data will be such that one can predict the
fate of organic compounds in biological wastewater treatment systems.
Although the initial grant is for 2 years, it is expected that it will be
continued so that Purdue could furnish quick response for organic compounds
that in the future would be of great concern.
SLUDGE TOXICITY
Application of municipal sewage sludge on agricultural land is, in most
cases, cost effective and ecologically sound. Sludge is a good conditioner
and contains many essential plant nutrients; however, there is some serious
concern about possible crop contamination by the toxic metals and organic
compounds present in sludge. The heavy metal content of sludges, particularly
that of cadmium, tends to inhibit the use of land for final disposal of sludge
solids. The median values of cadmium and zinc for over 200 municipal sludges
in the USA were found to be 16 and 1740 ppm, respectively . For an industrial
city, such as Chicago, the concentration of toxic metals is much higher.
Typical values for Chicago are shown in Table 6.
TABLE 6. TOXIC METAL CONCENTRATIONS IN CHICAGO SLUDGE
Type of metal Cone, in Dry Digested Sludge (ppm)
Cadmium 100
Chromium (total) 1000
Copper 900
Nickel 200
Lead 1800
Zinc 3500
Some toxic metals in sludge can be taken up by food crops after the
sludge is applied to farm land. This contaminates the crops making them
unsuitable for use.
There are two approaches to the problem of metal accumulation in sludge:
(1) confine the metals at their source by pretreatment, (2) remove the metals
from the sludge. Unfortunately to date, there is no practical way of doing
either. Many of the metals come from diffuse sources, rather than from point
discharge. The amino acids found in the microbial cellular proteins of sec-
ondary biological treatment processes form relatively stable complexes.
Typical concentrations of amino acids found in activated sludge ^ and the
stability constants with some metals 3 are shown in Table 7.
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TABLE 7. AMINO ACIDS IN ACTIVATED SLUDGE AND STABILITY CONSTANTS WITH METALS
Amino acids
Concentration
in act. sludge
(% dry wt.)
Stability constant* of
metal-amino acid complexes at
20-25 °C, 0-1 M ionic strength
Arginine
Cystine
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Tyro sine
Glycine
Glutamic Acid
*Symbols ( ) :
r T
1.04
0.18
0.41
0.91
1.58
0.92
4.45
1.20
1.15
0.22
1.18
0.70
1.55
2.89
[MA ] /
- 1.26
- 0.50
- 2.20
- 2.03
- 1.33
- 0.65
-2.00
- 2.20
- 0.34
- 2.77
-1.71
[M][A]2
r»» A n r A n
Cd
3.27
-
5.65
-
3.99
-
3.88
-
-
[8.1]
4.3
-
4.8
4.78
Zn Pb
4.19 4.06
9.86 12.2
6.63 6.84
-
3.99
(7.6)
4.38 4.40
-
-
[9.3]
5.00
{9.1}
5.03 5.47
5.45
Cu
7.34
-
10.56
-
7.00
(13.8)
(14.75)
7.74
{14.54}
[15.9]
7.93
{15.0}
8.22
7.85
Ni
4.92
10.48
8.69
-
5.58
(8.8)
5.56
-
-
[10.2]
5.45
{10.1}
5.97
5.9
{ >:
Otherwise:
Lmrtoj I L1YIrtJ LrtJ
[M(flA)2] / [M][HA]2
[MA] / [M] [A]
The technical and economic feasibility of removing heavy metals from
sludge using a hot acid process has recently been studied under a contract
with Walden Research, Abcor, Inc. The process involves acidification of the
sludge (pH 2-3) and heating to temperatures below boiling (about 95 °C).
Test results show that the process can solubilize the cadmium and the other
heavy metals in varying percentages. In addition, the process improves the
dewaterability of the sludge and destroys all pathogens. A preliminary eco-
nomic analysis of the process indicates that it is cost-competitive with
alternative stabilization and conditioning processes. A demonstration of the
heavy metals removal processes at pilot scale is planned to confirm the
laboratory findings and improve the predictability.
A sizeable portion of MERL's research effort has been devoted to deter-
mining the fate and effects of the nutrients and trace elements in sludge-
treated soils. Copper, nickel and zinc have been identified as metals that
are more likely to accumulate to phytotoxic levels in sludge-treated soils.
Cadmium is the element of most concern because of its potential adverse
effects on human health. It is assimilated by growing plants and is accumu-
lated in the liver and kidneys of the consumer. Lead is of concern if sludge-
427
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contaminated forages are ingested by animals. Nitrates can leach into
ground water, and both nitrates and phosphates can be transported by surface
runoff into streams and reservoirs. Progress has been made in identifying
acceptable sludge application rates and appropriate site management techniques
for application of specific sludges on specific soil-climate-crop combinations.
A grant to the City of Chicago is supporting a study of the accumulative
effects of annual sludge applications over a long period of time. After 10
years, cadmium concentration in grain does not appear to be increasing. No
phytotoxity from metals has been encountered. Corn yields from sludge-
treated soils are equivalent to, or superior to, conventionally fertilized
plots. Pheasants, rats and swine were fed corn from sludge-amended soils.
Metals accumulated in livers and kidneys of pheasants, but not beyond the
range of concentration in wild pheasants. In rats, there was a slight
depression in weight gain of male rats. There were no adverse effects upon
the swine.
With MERL support, the Science and Education Administration of the U.S.
Department of Agriculture at St. Paul, Minnesota, is developing site manage-
ment technology to enable the beneficial use of sludge as a soil amendment.
Conservation practices applied to a 16-hectare watershed include parallel
terraces, grassed waterways, and a runoff detention reservoir. The parallel
terraces divide the watershed into 13 test plots or subwatersheds, each of
which is equipped with surface tile inlets to collect runoff water for analy-
sis. Sludge is applied to subwatersheds growing corn at a rate of about
7.5 cm per year of liquid sludges containing 2 to 5 percent solids. Grass
plots receive about 10 cm per year of the same sludge. Groundwater, soil
water, runoff, soils, and plants are sampled and analyzed to determine the
effects of using sludge. Two sludge storage lagoons are used. One is lined
and the other is not. Sludge is analyzed for total and volatile solids, total
and NH4-N, conductivity, pH, organic matter, total P, K, Ca, Mg, and heavy
metals. Water samples are analyzed for total N, P, and K, NH4, and NO^-N,
P04-P, Na, Ca, Mg, conductivity, pH, and fecal coliform. Plants are analyzed
for nutrients and metals, and soils are analyzed for the same parameters as
the sludge.
Three and one-half hectares are used to produce corn for silage to be
fed to lambs and dairy goats. Sixteen 0.22 hectare plots (4 replications and
1 control) will be treated with sludge at rates of 15, 30, and 45 tonnes per
hectare per year. The control plot will be fertilized at a rate consistent
with maximum corn yields.
The watershed study has involved application of 39 metric tons per
hectare of sludge on corn and 43t/ha on grass. The sludge is low in cadmium
(7 mg/kg) and has not resulted in an increase in Cd in corn. The unlined
sludge lagoon was apparently effectively sealed as evidenced by lack of
increased nutrients in soil water samples taken from under and below the
lagoons.
Corn and grass yields were good on both sludge-treated and fertilized
control areas in 1977. The greatest amount of surface runoff occurred during
428
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the snowmelt period. Nitrogen runoff was highest from sludge-treated corn,
but runoff of phosphorus and potassium was highest on sludge-treated grass
areas. Nitrates were increased in soil water, but could not be detected in
groundwater. Lamb and dairy goat feeding of silage from sludge-enriched soils
is underway.
Numerous efforts have been made to gain a better understanding of toxic
hazards of modern synthetic organic chemicals that find their way into waste-
water and sludge. However, there are many difficult sampling and analysis
problems in concentrating, extracting, and identifying such compounds, many
of which still may be unknown breakdown products of more complex chemicals
that have undergone partial biodegradation. EPA is presently conducting a
study to identify toxic materials in the effluent.
The utilization/disposal of sludge on croplands and pasturelands empha-
sizes the need for definitive data on plant uptake of synthetic organic chemi-
cals. Uptake studies have shown that edible parts of plants contain these
organics, but at levels 5 to 20 percent of the levels in the soils used. In
general, root crops take up more chlorinated organics from the soil than other
types of crops. However, studies have shown that chlordane, heptachlor and
dieldrin are translocated from the soil into soybeans and stored in the oil
of the seed . Although the levels found were low, these data show that
sludge can be a source of recycling of organic contaminants back into the
food chain if sufficient precautions are not observed. An incident that
happened in Bloomington, Indiana, a few years ago, illustrates this point.
A cow was allowed to graze on pasture to which 27 tonnes/ha of sludge had
been applied. It was discovered a few months later that the cow's milk con-
tained 5 ppm of PCB's on a fat basis. Transfer of PCB's to the cow was proba-
bly related to grazing habits resulting in consumption of the contaminant
without uptake of pasturage. Applying sludge to hay crops after cutting may
not present a problem because much of the new growth takes place at the top,
not from the bottom. It is not anticipated that organic toxics in sludge
will be as great a problem as metals to land application of sludge.
SEWAGE SLUDGE PROCESS DEVELOPMENT
The sludge research program is divided into three areas: (1) sludge
processing and treatment, (2) sludge conversion, and (3) beneficial utili-
zation and disposal. Sludge processing and treatment includes all of the
steps from the first appearance of sludge until it enters the disposal step.
Anaerobic digestion is an example. Sludge conversion is any process that
changes the nature of the sludge so that it is no longer recognized as
sludge, for example composting. Beneficial utilization includes any con-
structive use of sludge. Land spreading of sludge on soil to add nutrients
and improve the soil characteristics is an example of constructive use.
In recent years our sludge process development program has been switched
from energy intensive processes, such as incineration, to obtaining useful
products, such as compost, liquid and gaseous fuels. Our sludge management
429
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research program is continuously changing to be responsive to regulatory
changes, needs of the wastewater treatment community and to shifting world
situations.
THERMOPHIL.IC SLUDGE DIGESTION
The need for producing a stabilized sludge that is essentially free of
pathogens is a controversial subject. In some disposal situations, such a
need clearly exists. Thermophilic (ca. 50 °C) digestion processes can
produce relatively pathogen free sludge.
Anaerobic and aerobic digestion processes are well established methods
of stabilizing sludge, but both have certain inherent cost disadvantages. To
achieve reasonable digestion rates, anaerobic digestion requires the addition
of heat, and aerobic digestion requires an adequate supply of oxygen. By
operating an aerobic digestion process in tandem with an anaerobic digestion
process, these costs could conceivably be greatly reduced. If high purity
oxygen is used for aerobic digestion, the temperature of the reactor can be
raised to 60 °C, and at this temperature pathogenic organisms will be killed,
and it will not be necessary to provide additional heat to the anaerobic
digester. The methane produced can be used to meet other energy needs,
offsetting the cost of oxygen. This concept is being tested by the City of
Hagerstown, Maryland, on an EPA grant.
The Hagerstown, Maryland, wastewater treatment plant employs an activated
sludge treatment process with a design flow of 30,000 m^/d (8 mgd). The muni-
cipal utility in cooperation with the research personnel of the Union Carbide
Corporation, Linde Division, will perform the study. The process was con-
ceived by Union Carbide Corporation.
The anaerobic digestion process is a well-established solids handling
system and used in sewage treatment plants throughout the country. It is,
however, subject to upsets either due to overloading or buildup of toxic
substances. On the other hand, the aerobic digestion process is more resist-
ant to upset, but retention times for adequate stabilization are long, gener-
ally in excess of 20 days. In cold weather, the sludge temperature falls, and
aeration for as long as 60 days is needed for adequate stabilization. Aerobic
digestion can be made much more effective by using oxygen as the aeration
medium instead of air. The operation can proceed at thermophilic temperatures
(ca. 55 °C) without the need for supplementary fuel and is accomplished in
less than 10 days. Oxygen costs, however, can be substantial.
The Union Carbide process takes advantage of the best features of both
aerobic and anaerobic digestion. The rugged aerobic digestion process moder-
ates the effect of shock loads and increases alkalinity, which stabilizes the
subsequent anaerobic digestion step. No extra heat is needed for digestion
and gas production is approximately the same, winter or summer. Because there
is only one day of oxygen supply, cost of oxygen is low.
In operating the demonstration plant, the sludge in the aerobic digester
will be treated with pure oxygen with a retention time of one day. The sludge
will then be pumped into the anaerobic digester where it will be digested
anaerobically for 8 days.
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USE OF SOLAR ENERGY TO HEAT DIGESTERS
Digester gas is commonly used as fuel for digester heating. If solar
energy could be substituted as the prime heat source for anaerobic digestion,
then the methane produced could be freed for higher grade energy requirements.
The technical and economic feasibility of providing this alternative heat
source was evaluated by Environmental Systems, Incorporated, by the aid of an
EPA contract.
The study showed that solar digester heating is economically feasible at
all locations in the USA. The degree of economic attractiveness at any given
location is directly proportional to the average annual solar radiation multi-
plied by the difference between the digester design operating temperature,
35 °C, and the average annual air temperature. The study, also, showed that
optimum flat plate solar collectors can provide from 82 to 97 percent of the
total annual digester heat load, the higher percentages being applicable to
areas of higher solar radiation intensity. Specific guidelines have been
developed for determining the optimum size and design of a solar heating
system for any size of sludge digester at any location.
The town of Wilton, Maine, with the support of a construction grant from
EPA and the State of Maine, is presently building a 1700 m^/d (0.45 mgd)
wastewater treatment plant that is designed to minimize the need of off-site
energy. This project will demonstrate innovative energy savings concepts
that will make use of an integrated energy system of solar energy, digester
gas, and heat pump.
PARASITES IN SLUDGE
Public Law 92-500 emphasizes returning wastewater and sewage sludges to
the land in an ecologically acceptable manner with minimal health risks. A
1977 Federal law prohibits ocean dumping of sewage sludge after 1981; there-
fore, more consideration is being given to land disposal. The potential for
spreading of disease by poorly managed land application of sludge is real.
The occurrence of bacteria and viruses in wastewater and sludges and their
survival in the soil have be^n the subject of considerable research. Apparent-
ly, less interest has been stimulated for the occurrence of the larger patho-
genic organisms. Few studies have includedthe surveillance of protozoa and
helminths. This is a significant omission because some of these organisms
can apparently survive wastewater treatment processes and land application
better than any of the bacteria or viruses. Because of their weight, most
cysts and eggs are found in the sludge.
A research grant was awarded to Tulane University to survey sludges from
municipal wastewater treatment plants in the Southeastern USA. The first
sampling has been completed. The first survey covered 38 municipal treatment
plants. Of the 34 samples from drying beds sampled, 23 were positive for
As caris lumbricoides (roundworm), 7 for Trichuris trichiura (whipworm) and
17 for Toxocara spp. The results indicated a much more general contamination
of municipal sludges with Ascaris than had previously been expected. The
study will be extended to other parts of the USA. Future studies will also
include a mass balance study of parasites in conventional wastewater treatment
431
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systems and investigation of the effectiveness of parasite destruction by
anaerobic and aerobic digestion and the effect of lime treatment.
As an adjunct to the survey for parasites, EPA has a grant with the
College of Veterinary Medicine, University of Illinois, to study the trans-
mission of helminth to livestock. In this investigation, anaerobically
digested sludge containing ova of several nematodes, specifically As car is
will be applied on strip mined soil which has not been contaminated by live-
stock. After variable quantities of sludge have been applied to plots, worm-
free pigs will be placed on these experimental plots and will live in the
natural environment with the ova-contaminated sludge. The rate of survival
and transmission of parasitic helminths, and heavy metal accumulation in soil,
feed, and swine tissues will be determined.
The first experiment with swine exposed on sludge-amended soils has been
completed and parasites, heavy metals, and organic uptake are being measured.
One swine from each pen (each pen contained 5 swine, 4 swine to be held for
about 3 months) was necropsied after 3 weeks of exposure. The exposure in
the pens was as follows: sludge and embryonated ova of Ascaris lumbricoides
suum, embryonated ova of A._ lumbricoides suum, and a control plot with no
sludge or ova. A single larva was found in the lungs of the necropsied pig
in the first and second case - the pens containing added embryonated ova.
The second series of swine tests on sludge plots is underway.
REFERENCES
1. Sommers, L. E., "Chemical Composition of Sewage Sludges and Analysis of
Their Potential Use as Fertilizers," J. Environ. Qual. 6_, 225 (1977).
2. Hurwitz, E., "The Use of Activated Sludge as an Adjuvant to Animal Feeds,"
Proc. 12th Ind. Waste Conf. Purdue Univ., Ext. Ser. 94, 1957, page 395.
3. Sillen, L. G., and A. E. Martell, Stability Constants of Metal-Ion
Complexes, The Chem. Soc. Spec. Pub., No. 17, Metcalf § Cooper, Ltd.,
London (1964).
4. Moore, S., H. B. Petty, and W. N. Bruce, "Insecticide Residues in
Soybeans in Illinois, 1965-1974," 28th Illinois Custom Spray Operators
Training School, Summary of Presentation 226-230 (1976).
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MEASURING THE DEGREE OF SLUDGE STABILITY
Robert L. Bunch, Ph.D.
Municipal Environmental Research Laboratory
U.S. Environmental Proctection Agency
Cincinnati, Ohio 45268 USA
ABSTRACT
There are several parameters that are applicable in the operation and
control of sludge stabilization processes. Only a few have the potential of
being useful in evaluating the degree of stability. The degree of stability
required will depend on the method of ultimate disposal. Before a standard
for determining the degree of stability of sludge can be established, more
correlation studies are needed.
DEFINITION OF SLUDGE STABILITY
There are many definitions of "stable sludge." To most, stability is the
antonym of putrescibility. To others, it means it can be applied to the soil
without causing problems. The definition of stability implies the resistence
to change. For sludge to be useful in land application, it is desirable that
the sludge decomposes to a certain extent in the soil. Thus, ultimate stabili-
ty is not desired, but rather a degree of stability in which the readily de-
composable constituents have been degraded and only the more biologically
resistant, decomposable compounds remain. The degree to which a sludge must
be stabilized will depend on the location and the method of final disposition.
A sludge can be stabilized by biological, chemical or physical means.
MEASUREMENT OF SLUDGE STABILITY
Several parameters have been used to measure the degree of sludge
stability during stabilization processes. Thus, by taking a series of
measurements during a sludge stabilization process, it is possible to
determine when the parameter approaches a constant value, and the sludge
becomes resistant to change. For example, reduction in volatile solids (VSS)
could be used. Different control parameters could be used, depending on the
unit process, e.g., aerobic digestion, anaerobic digestion, composting, etc.
It is much more difficult to determine if a sludge is stable, based only
on terminal analyses. The control parameter VSS suggested above would have
little meaning if only determined on the final product. A sludge with a high
percentage of VSS is not necessarily unstable.
433
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If standards are to be set for sludge stability, it is necessary to
specify measurements and criteria that sludges must meet. For land spreading,
aerobic activity would be the main consideration as an indicator of stability.
While unsafe concentrations of metals, toxic compounds and pathogenic organ-
isms are important in land spreading, they are not necessarily related to
stabilization.
The literature is not uniform in discussing sludges. Should standards
be based on only sludge solids or on the total sludge (liquid and solids)?
The characteristics of the two are very different, especially in the case of
anaerobic and aerobic.
The following are parameters that have been suggested as applicable to
the measurement of the stability of sludges:
1. Aerobic Activity
The aerobic activity has been used as a method for calculating the BOD
of a substance and for determining the respiration of an activated sludge.
The value is usually given as mg of oxygen used by a gram of sludge per hour.
High oxygen use per gram of solids would indicate a very active, viable sludge.
A very low uptake rate would indicate a sludge that has been stabilized or
that the sludge contains a toxic substance that inhibits the respiration of
the sludge. Values between 0.5 and 1.0 mg C^/g VSS-hr have been suggested for
stabilized, aerobic digested sludge. The criteria used was that the sludge
did not putrefy when left unaerated. The oxygen uptake rate of sludge will
vary with temperature; therefore, the temperature of the test condition must
be specified.
Oxygen uptake measurements offer a potential method of evaluating the
degree of stability of aerobic digested sludges. More correlations are
needed for different sludges, temperatures and ultimate disposal methods.
2. Reduction in Volatile Suspended Solids
In both aerobic and anaerobic digestion as the processes proceed, there
is a drop in the percent VSS until a relatively constant value is reached.
The reduction in volatile solids is a useful parameter for controlling the
operation of digesters and will give an indirect indication of sludge stabili-
ty if a series of measurements are taken. In general, aerobic and anaerobic
digestion lowers the VSS by 50 percent. The reduction in VSS is a more reli-
able indicator in batch processes than continuous operations because of the
periodic fluctuations in the volatile fraction of the sludge wasted to the
digester. A complete mass balance would be necessary to determine accurately
the sludge stability based on solids reduction. It is not a very useful
parameter for determining the degree of stability of sludges when only the
final product is analyzed. A sludge high in percent VSS is not necessarily
unstable unless the solids are easily decomposed.
434
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3. Odor Production
Odors created during the storage of sludge are of prime importance. Not
only is the odor intensity important, but also the type of odor. Unfortunate-
ly, people disagree on what odors are offensive. What may smell unpleasant to
one person may not be offensive to another. The most readily identifiable
odor associated with sludges is that of hydrogen sulfide. Test procedures
have been proposed for relating to the stability of sludges with production of
hydrogen sulfide. A strip of lead acetate is hung in a bottle containing a
sample of sludge. The time required for the paper to turn black is noted.
The test period is generally 25 - 30 days. The long test period would limit
its use for practical purposes, but it could be used to establish a process
for stabilization. It would allow a direct comparison of aerobic digested
processes, regardless of reaction conditions or feed sludge type. The environ-
mental conditions of the test method would not necessarily reflect the condi-
tions of actual field disposal. The test might be applicable to anaerobically
digested sludge if modified. The hydrogen sulfide normally present in an-
aerobic digested sludge would first have to be destroyed or removed.
The Commission of the European Communities have defined a fully aerobic
sludge as a sludge "where the Odor Intensity Index (Oil) does not exceed 11 at
any time prior to or during 14 days of storage at 20 °C unless the odor can be
classified as a typical soil odor." Methods for determining Odor Intensity
Index are given in "Standard Methods." The duration of the test does not make
it a very practical parameter to use as a measure of sludge stability. Except
for small treatment plants, the sludges are usually disposed of before 14 days.
Although Oil is an important parameter, for practical use some other parameter
should be tied to Oil.
Oil probably would not be applicable to lime stabilized sludges. When
lime is added to sludges, the odor usually changes from a rotten, offensive
one to an ammonia or manure type and becomes more intense with time. Ammonia
tends to disappear if the sludge is exposed to air.
4. Adenosine Triphosphate (ATP)
ATP is present in all living cells and has received some attention as a
measurement of the biomass in the activated sludge process. In general, it is
proportional to the mixed liquid suspended solids (MLSS). Unfortunately, wide
variations can occur without significant changes in MLSS or COD in the system
due to population shifts and changes in the phase of growth.
The test equipment is not available in many laboratories and requires a
special firefly enzyme. The major drawback to the use of ATP for determining
sludge stability is that the organic material need not be living to cause
nuisances in the environment.
5. Total Organic Carbon and COD
It is possible to estimate the stability of a sludge by these parameters,
but high values do not necessarily mean easily decomposable organic matter.
435
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Some difficulty can be experienced in getting the sample comminuted so that
it will not clog the total organic carbon analyzer.
6. Nitrification
Nitrification takes place during the latter stage of aerobic stabilization.
The degree of nitrification is a fairly good indicator of the stability of
aerobic stabilized sludge. Nitrification as a measure of stability would not
be of any value for anaerobically digested sludge because the end product of
the nitrogen cycle is ammonia.
7. Caloric Value
The fuel value of sludges is indirectly related to the VSS and TOC. There
would be no advantage to using this parameter because VSS and TOC are more
easily measured.
8. Other Suggested Parameters
For controlling the operation of an anaerobic digester, gas production
can be used. Total carbohydrate, total protein, dewatering properties also
have been suggested as suitable for describing the course of stabilization in
an anaerobic digester. All of the values vary greatly depending on the type
of sludge fed.
As a rough indicator for stabilization of both aerobic and anaerobic
digested sludges, pH, specific resistance, BOD, orthophosphate and ammonia
content of the sludge liquor can be used.
436
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AIR POLLUTION FROM SEWAGE SLUDGE INCINERATORS:
A PROGRESS REPORT
by Joseph B. Farrell, Howard 0. Wall, and Barbara A. Kerdolff
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268, U.S.A.
ABSTRACT
Air pollution tests are being carried out at ten wastewater sludge in-
cinerators to determine the quantity, particle size distribution, and composi-
tion of the particulate discharges. Results are now available for three in-
cinerators.
The incinerators tested were equipped with low-intensity water scrubbers.
Particulate discharges exceeded Federal standards for new sources. Percent-
age losses of lead and cadmium were much higher than losses of other metals.
Lead and cadmium are concentrated in the fine particulate fraction leaving
the incinerator. Since the scrubbers were inefficient in removing this frac-
tion, concentrations of lead and cadmium were higher in the particulates
leaving the scrubber than in those leaving the incinerator.
Maximum ground level concentrations of lead calculated from a plume dis-
persion model were approximately the same magnitude as local ambient concen-
trations. For cadmium, which has a much lower ambient concentration than
lead, calculated maximum ground level concentrations were much higher than
ambient concentrations. Use of high intensity scrubbers could reduce the
local impact of lead discharges from sludge incinerators on ambient concen-
trations to a negligible value, but this may not be true for cadmium.
INTRODUCTION
In October of 1970, the Council on Environmental Quality recommended
that ocean dumping of sludge be phased out as an ultimate disposal process
for municipal sludge. With this recommendation in mind, the U. S. EPA
undertook an investigation to determine whether this action would unreason-
ably limit sludge disposal options. A task force was set up in the Spring
of 1971 to determine whether incineration, a potentially important disposal
method for East Coast cities, was an environmentally acceptable disposal
procedure. The task force investigated a number of sites where incineration
was practiced and equipment was reasonably modern and working properly.
Particulate discharge rates were measured, and particulate composition was
determined. The task force concluded (1) that properly operated incinera-
tors produced acceptable stack emissions of particulate matter, nitrogen
437
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oxides, sulfur oxides, and odor. On the basis of the task force work, stan-
dards for particulates were set.
The only EPA standards for sludge incineration are shown in Table 1
(2,3,4). No standards were set for oxides of nitrogen and sulfur, because
quantities and concentrations were low compared to other sources.
TABLE 1: FEDERAL STANDARDS APPLICABLE
POLLUTANT STANDARD
Particulates 0.65 g/kg dry sludge fed
Opacity 20%
Beryllium 10 g/24 hr.
Mercury 3200 g/24 hr.
The analytical determinations made on the particulate samples collected
during the air pollution testing of the sludge incinerators indicated that
there was a higher concentration of lead and possibly cadmium in the par-
ticulates than in the original sludge (on a combustibles-free basis) and the
ash (1,5). Mercury was essentially all lost to the stack gases. Data ob-
tained in a series of air pollution tests carried out in Japan (6) indicated
that concentrations of some metals were markedly higher in the particulates
collected from the gases leaving the gas cleaning equipment than in the
original sludge (combustibles-free basis). A portion of these data has been
recalculated and is presented in Table 2. The term Cp/Cs in the table is the
ratio of the concentration of the metal in the particulates (Cp) to its con-
centration in the sludge on a volatiles-free basis (Cs). Examination of
these ratios shows that cadmium and lead are greatly concentrated in the par-
ticulates, whereas iron and nickel show no concentration effect.
The cumulative effect of this information encouraged us to undertake
additional studies of the air pollutants from incinerators. The objective of
the investigation was primarily to determine whether the increased concentra-
tion of heavy metals in the particulates that was observed in Japan also
occurred in sludge incinerators in the United States, and, if so, whether
this condition might cause substantial environmental degradation. Tests
have been inaugurated in two steps: four multiple hearth incinerators have
been tested in the first step, and in the second step, six more incinerators,
four multiple hearth and two fluid bed, will be tested. Results obtained on
three of the first set of four incinerators tested are now available and are
discussed in this presentation.
438
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TABLE 2: METALS CONCENTRATION IN PARTICIPATES RELATIVE
TO FEED SLUDGE--JAPANESE INCINERATORSl
PLANT TOTAL METAL
EMISSIONS
(g/Nm3)
K-l 0.0295 Cd
(% ash
= 27.5) Pb
£ Fe
<£>
Ni
E-2 0.1075 Cd
(% ash
= 52.0) Pb
Fe
Ni
CONCN .
TOTAL
18
335
40000
70
13.6
231
24500
48.2
IN SLUDGE (yg/g)
VOLATILES-FREECC,;)
65.4
1218
145500
254
26.1
444
47115
92.7
CONCN. IN
yg/Nm^
160
2700
140
40
125
1095
3850
10
PARTICULATES
yg/g(Cp)
5424
91525
4746
1356
1163
10186
35814
93.0
RATIO
Cp/Cs
82.9
75.1
0.03
5.3
44.6
22.9
0.76
1.00
1. Calculated from data obtained from personal communication with Dr. A. Sugiki.
-------
EXPERIMENTAL PROCEDURES
The four incinerators selected were multiple hearth furnaces of commer-
cial size (ca. 20 ft. diameter) which receive sludges from municipal waste-
water treatment plants with a high proportion of industrial waste. The
stacks were sampled for particulates at the inlet to the particle collection
device and at its outlet. Sludge, bottom ash, and water into and out of the
scrubbers were sampled (all incinerators used wet scrubbers). It was desired
to determine the particle size distribution of the particulates so a large
sample was needed. This necessitated long sampling times. It was not possi-
ble to supply two sampling crews at each site, so the samples at the scrubber
inlet and outlet were not taken simultaneously.
The sampling was accomplished using an Aerotherm* high volume Source
Assessment Sampling System (SASS) train. The equipment is illustrated in
Figure 1. In this system, the stack gas stream passes through a series of
three centrifugal collectors followed by a filter, which segregates the
particles into the following four fractions: greater than 10 ym, 10 to 3.5 ym,
3.5 to 1 ym, and 1.0 to 0.1 ym. For the sample at the scrubber inlet, where
the quantities in each fraction were plentiful, sufficient material was col-
lected to permit a further separation of the 10 to 3.5 ym fraction. This
separation, which was carried out in a Bahco* classifier (7), divided the
sample into a 10 to 5.6 ym and a 5.6 to 3.5 ym fraction.
The SASS train is described in detail by Harris et al. (8). The section
following the heated oven (see Figure 1) consists of a cooler and a series of
impingers contained in an ice bath, where the stack gases can be reacted with
adsorbents or liquid reagents to determine organic or inorganic gaseous sub-
stances. In the air pollution experiments conducted in this study, the
impingers were filled with water. Analysis of the solids deposited in the
impingers has not yet been completed.
Analyses for eleven metals were performed on each individual particle
size range. Each fraction was digested and then trace metal analyses were
performed using a Jarrell-Ash* spectrometer system with an inductively
coupled argon plasma source for all of the elements except arsenic and mer-
cury. These elements were analyzed by conventional atomic absorption. The
results presented in this progress report are restricted to four metals:
cadmium, lead, iron, and nickel. The important conclusions of the investiga-
tion are made clear with this abbreviated presentation. However, information
on all of the metals will be presented when a comprehensive report of our
investigation is published.
RESULTS AND DISCUSSION
The results of the stack testing are presented in Table 3. Although
these incinerators were installed before Federal regulations went into effect,
it is startling to note that none of them meet the Federal emission standard
of 0.65 g/kg dry sludge solids for new stationary sources. As can be seen in
the table, they all have low intensity scrubbers.
* Trade name. Use of trade names does not indicate EPA endorsement.
440
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SOURCE ASSESSMENT SAMPLE COLLECTOR
Heated Oven (205°C)
Heated Probe
Gas
Stream
Organic and Volatile
Metal Collection
i
Cooler
To Vacuum Pump
FIGURE 1.
-------
TABLE 3: RESULTS OF AIR POLLUTION
STACK TESTS
PLANT
TEST AT SCRUBBER
PARTICULATES
Flow (kg/hr)
Cone, (g/dry Nm^)
SLUDGE FEED
Flow (dry, kg/hr)
% Volatile Solids
SCRUBBER Ap(cm H20)
SOLIDS LOSS (g/kg DSS)
OUTLET INLET OUTLET INLET OUTLET INLET
0.918
1.825
1282
55.5
10.2
0.72
69.86
70.96
1736
42.2
14.0
1.632
0.017
2443
50.2
19.0
0.67
17.35
0.19
1999
51.7
17.8
2.03
0.124
162.3
4.94
1174 720
40.6 29.4
16.5
1.73
15.2
Stack samples were taken at the outlet of the incinerator before the
scrubber and at the outlet of the scrubber. The data permit calculation of a
removal efficiency for the scrubber. It should be noted, however, that sam-
ples were not run concurrently but followed one another. Consequently, the
efficiency calculation is approximate, although every effort was made to keep
conditions constant.
The calculated efficiencies for Plant C and D are presented in Table 4.
On the basis of the total particulates collected, the scrubber for Plant C
is much less efficient than the Plant D scrubber. Examination of the
efficiencies for each particle size fraction indicates much better agreement
between the two units. Evidently-, Incinerator C was underloaded relative to
Incinerator D. Fewer particles were carried out of the incinerator, and they
were smaller in size and harder to capture.
In the stack testing, rates of flow of solids entering the incinerator,
and of particulates and gases before and after the scrubber were measured,
and the solids collected were analyzed for the principal heavy metals. Con-
sequently, the flow of solids at scrubber inlet and outlet can be related to
the rate of sludge input. These results are presented for total particulates
and four metals in Table 5. It is evident that the recovery of lead and
cadmium is much poorer than for total particulates, iron, and nickel. Note
that results appear inconsistent between scrubber inlet and outlet in some
cases (for instance, in Test C only 7.2% of the total cadmium fed to the
furnace escapes from the furnace and enters the scrubber, whereas 36% of the
total fed to the furnace escapes from the scrubber). It should be recalled
442
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TABLE 4: EFFICIENCY OF COLLECTOR FOR
DIFFERENT SIZE FRACTIONS
PARTICLE SIZE
PERCENT REMOVAL
RANGE (pm)
Total Sample
> 10
3.5 - 10
1 - 3.5
0.1 - 1
Inlet Loading
Pressure Drop
(g/dNm3)
(cm HjO)
PLANT C
90.60
99.0
99.8
98.4
65.3
0.192
17.8
PLANT D
98.75
> 99.9
99.9
99.5
49.7
4.94
15.2
TABLE 5: PERCENTAGE OF METALS FED THAT LEAVE
IN THE PARTICULATE STREAM
COMPONENT
Non-Vclatiles (N.V.)
Cd
Fe
Ni
Pb
SCRUBBER INLET
SCRUBBER OUTLET
% REMAINING1 METAL/N.V. % REMAINING1 METAL/N.V.
1.80
7.2
0.57
0.80
0.73
(1.0)
4.0
0.32
0.44
0.96
TEST C
0.34
36
0.028
0.14
3.6
(1.0)
270
0.21
1.03
27
TEST D
Non-Volatiles
Cd
Fe
Ni
Pb
32
88
14
15
94
(1.0)
2.8
0.43
0.47
2.9
0.17
4.2
0.12
0.97
32
(1.0)
14.4
0.41
3.3
109
TEST A
Non-Volatiles
Cd
Fe
Ni
Pb
1.43
23
4.2
6.6
5.2
(1.0)
16.2
2.9
4.6
3.6
0.16
29
0.21
0.39
3.8
(1.0)
174
1.27
2.4
23.5
1. Percent of this component originally in the feed that is still
not removed.
443
-------
(see above) that the inlet and outlet samples were not taken at the same time.
Composition of the sludge changed drastically halfway through Test C, evi-
dently causing markedly different particulate compositions.
The results in Table 5 indicate the same kind of increase in concentra-
tion of lead and cadmium in the particulates when compared with the feed that
was noted in the Japanese work (Table 2). It is perhaps more important to
note that under some conditions over 30 percent of the lead and of the
cadmium fed to the incinerator is discharged in the form of fine particulate
matter even after wet scrubbing.
A part of the reason for the kind of effect noted in Table 5 is the
relationship between particle size and composition in the particulates. The
composition of cadmium, iron, nickel, and lead in the particulates entering
the scrubber is shown as a fraction of particle size in Figures 2 and 3.
Both cadmium and lead are concentrated in the finest fraction. When the par-
ticulates pass through the scrubber, the coarse particles are effectively
removed, whereas the fine particles are not well removed. For iron and
nickel, the composition in the various fractions is relatively uniform. Con-
sequently, a concentration effect can occur for lead and cadmium, but not for
iron and nickel, as a result of wet scrubbing. (Despite the concentration
effect, total outflow of lead and cadmium is reduced by the scrubber.)
The selective removal of coarse particles in the scrubber is only part
of the reason for the high proportion of cadmium and lead escaping from in-
cineration. These metals and some of their salts are relatively volatile.
Metal particles can vaporize, compounds can be reduced to pure metal in
oxygen-deficient parts of the burning sludge and volatilized, and volatile
salts can be vaporized. Oxidation of the metals probably occurs in the vapor
phase, but the oxide particles are doubtlessly very small and remain en-
trained in the combustion gas stream, eventually to pass out of the incin-
erator.
The degree of contamination of the surrounding air from incinerator dis-
charges can be calculated from plume models, which predict the ground level
concentrations of particulates from a knowledge of the nature, quantity, and
temperature of the discharge, and conditions of discharge such as velocity
and stack height. The plume model used was supplied by EPA's Meteorology
Laboratory, Research Triangle Park (8). The program assumes that the parti-
cles are of neutral buoyancy and essentially act like a gas.
The dispersion of a plume is illustrated schematically in Figure 4. The
particle concentration is highest at the center of the plume and lower near
the edges (Curves I-h in Figure 4). Curve I-L shows the longitudinal parti-
cle concentration distribution at ground level. The maximum concentration
occurs some distance farther along after the plume first touches the ground.
The plume dispersion model calculates the distance at which this maximum
occurs and the value of the maximum concentration. The distance and the
value of the maximum concentration shift with wind speed and atmospheric con-
ditions. Plume dispersion models necessarily give approximate results
because of the intrinsic difficulty of the problem as well as the fluctuations
444
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*>.
•Pa.
Pb
10.0
1.0
0.1
Fe-MO
Ni
0 5 10 0 5 10
PARTICLE SIZE (jim) PARTICLE SIZE (pm)
FIGURE 2. VARIATION IN CONCENTRATION OF METALS
WITH PARTICLE SIZE: PLANT C
-------
10.0
O)
I
z
g
t-
QC
I-
z
HI
o
o
o
1.0
0.1
1 i I
10.0
Pb
1.0
Cd
0.1
Fe
- .... i .... i
0 5 10
PARTICLE SIZE
0 5 10
PARTICLE SIZE (urn)
FIGURE 3. VARIATION IN CONCENTRATION OF METALS
WITH PARTICLE SIZE: PLANT D
-------
WIND DIRECTION
HEIGHT
ABOVE
GROUND
(h)
I., I,=Particulate
Concentration
Distribution,
with height (h),
with distance (L)
DISTANCE FROM STACK (L) >
FIGURE 4. EFFECT OF PLUME DISPERSION ON PARTICULATE
CONCENTRATIONS IN AIR AND AT GROUND LEVEL
-------
of conditions that appear in nature. Nevertheless, they are useful in pre-
dicting the approximate magnitude of effects.
The results of these calculations are presented in Figure 5 for Plants A,
C, and D for total particulates. The ambient conditions chosen were those
that would contribute to a high ground level concentration—high solar radia-
tion (a sunny day) and low wind velocity (0.5 meter per second was selected
as a practical minimum velocity). The figure shows the maximum ground level
concentration of total particulates as a function of wind velocity. The
highest maximum ground level concentration depends on the site-specific con-
ditions and, for the three cases, occurs at wind speeds that vary from
0.5 m/s to about 2 m/s.
In Table 6, the highest maximum ground level concentrations of lead and
cadmium are shown along with the annual average ambient concentrations ob-
tained in the cities where the plants were located. The ground level con-
centrations of lead are seen to be of the same order of magnitude as the
ambient concentrations found in these cities. For cadmium, the ground level
concentrations are far higher than the ambient concentrations in the cities.
TABLE 6: COMPARISON OF HIGHEST MAXIMUM GROUND
LEVEL CONCENTRATIONS WITH AVERAGE
CONCENTRATIONS IN TEST CITY
HIGHEST MAXIMUM CITY A CITY C CITY D
CONCENTRATION PLANT AMBIENT PLANT AMBIENT PLANT AMBIENT
(yg/m3) A C C
Total Particulates 6.24 -- 8.31 -- 15.4
Pb 0.59 1.71 0.33 0.65 0.70 1.50
Cd 0.085 0.0086 0.64 0.008 0.026 0.004
Estimation of the degree of hazard from a pollutant in an air-shed is an
extremely complex process that requires site-specific information such as
relative magnitude of regional and local discharges and meteorology. However,
some general observations can be made. For lead, the highest maximum concen-
trations will under some conditions elevate ambient concentrations signifi-
cantly, but these occasions will be rare and the area affected will be small.
However, EPA has set a standard (9) for lead of 1.5 microgram per cubic meter
average value. Many cities exceed this value. It is clear that there will
be pressure to reduce lead discharges. There will probably be pressure to
reduce lead discharges from sludge incinerators by using higher pressure drop
scrubbers. This type of corrective action will very likely achieve the
desired reductions.
448
-------
CO
O
CO
E
o>
<
DC
UJ
O
z
O
O
20
15
10
o PLANT D
o PLANT C
n PLANT A
0123
WIND SPEED (m/s)
FIGURE 5. MAXIMUM PARTICULATE CONCENTRATION
AS A FUNCTION OF WIND SPEED
449
-------
For cadmium, the highest maximum concentrations greatly exceed ambient
levels. No EPA standard for cadmium exists, so it is not possible to estab-
lish whether this situation is not in conformance with standards or is
hazardous. However, with the serious attention being given to cadmium as a
hazardous pollutant, these results will receive prompt attention. The pres-
sure to improve performance of scrubbers will be substantial. Use of higher
pressure drop wet scrubbers may not reduce discharges to a point that ground
level concentrations from incinerator plumes will not exceed ambient concen-
trations. A radical change in the method of particulate removal or a change
in the method of thermal processing from incineration to starved-air combus-
tion or pyrolysis may be needed.
CONCLUSIONS AND RECOMMENDATIONS
The low pressure drop scrubbers used at the sites examined allow par-
ticulate concentrations in the discharges to exceed EPA standards for new
stationary sources. In addition, under some conditions, as much as 30 per-
cent of the lead or cadmium in the sludge can escape as fine particulate
matter. The use of high pressure drop scrubbers is strongly recommended to
reduce total particulate discharge and the losses of heavy metals.
Calculations of ground level concentrations of lead indicate that
occasionally discharges of lead from sludge incinerators will noticeably in-
crease local ambient lead concentrations. Use of higher intensity wet scrub-
bers would probably make this likelihood remote. Cadmium discharges from
sludge incinerators can noticeably increase local ambient concentrations.
High intensity scrubbers may not solve the problem completely.
The method used to calculate ground level concentrations of cadmium and
lead gives "worst case" estimates. An alternative approach is to calculate
the maximum annual average ground level encountered in the vicinity of the
incinerator, based on the emission data and available data on wind velocity
and atmospheric stability. This figure should be better related to long
term impact on people living near an incinerator than the "worst case"
estimate. This alternative approach will be used in future presentations.
More experimental work is needed to identify the reasons why lead and
cadmium are so poorly retained in incinerators, and to develop means to
retain them.
450
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LITERATURE CITED
1. "Sewage Sludge Incineration," by EPA Task Force, EPA-R2-72-040, pub. Aug.
1972 (NTIS No. PB 211 323).
2. Code of Federal Regulations (CFR), Title 40, Part 60, "Standards of Per-
formance for New Stationary Sources, Subpart 0, Standards of Performance
for Sewage Treatment Plants," 60.150 to 60.154.
3. CFR, Title 40, Part 61, "National Emission Standards for Hazardous Air
Pollutants, Subpart C, National Emission Standards for Beryllium,"
61.30-61.34.
4. Ibid, Subpart E, "National Emission Standard for Mercury," 61.50-61.55.
5. Farrell, J. B., and Salotto, B. V., "The Effect of Incineration on Metals,
Pesticides and Polychlorinated Biphenyls in Sewage Sludge," pp. 186-198,
Proc. of National Symposium, "Ultimate Disposal of Wastewater Residuals,"
Apr. 26-27, 1973, Pub. by Water Resources Research Institute, North
Carolina State Univ., 1973.
6. Sugiki, Dr. A., Personal communication from Dr. Sugiki, Japan Sewage
Works Agency, Aug. 20, 1977, "Concentration of Materials Leaving Stacks
of Burning Sewage Sludge."
7. "Micro Particles Classified Centrifugally," 7 pp, describes the Bahco of
Particle Size Classifier, manuf. Harry W. Dietert Co., 9330 Roselawn Ave.,
Detroit, Michigan 48204.
8. Program DBTSI, "Calculates concentration from multiple point sources and
average concentrations for the time period," by D. B. Turner- Research
Meteorologist, Model Applications Branch, Meteorology Laboratory, U.S.EPA,
Room 3168, NCHS Bldg., Research Triangle Park, N. C. (Tel. 919-549-8411,
Ext. 4564).
9. Federal Register, 42, pp. 63076-63094, Dec. 14, 1977, "Lead, Proposed
National Ambient Air Quality Standard."
451
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PROGRESS IN INSTRUMENTATION AND AUTOMATION
by
Irwin J. Kugelman, Sc.D. Chief, P^FES
Michael D. Cummins Sanitary Engineer
Walter W. Schuk Engineering Technician
Joseph F. Roesler Sanitary Engineer
Presented at the
Sixth U.S./Japan Conference on Sewage Treatment Technology
Cincinnati, Ohio
October 28-31, 1978
U.S. EPA/ORSD/MERL
Cincinnati, Ohio 45268
453
-------
Introduction
One of the primary goals of U.S. EPA research and development activities
is to devise methods to improve control of treatment processes and systems.
Improved process control will result in cost reduction and discharge of
effluents with lower pollution potential. One of the primary methods of
achieving improved process control is through the application of instrumentation
and automation. Instrumentation and automation provides for much closer
monitoring of treatment systems and allows for much more rapid response to
upsets than can generally be achieved with manual operation.
In order to tap the potential advantages of this area of technology
the U.S. EPA has for several years sponsored a program of research and
development on instrumentation and automation for control of wastewater
treatment systems. A review of the activities of this program was given
at the Fourth United States/Japan Conference on Sewage Treatment Technology (1).
Some of the more recent studies will be covered in this presentation. The
information presented will be devided into several distinct areas including:
instrumentation testing, process control strategy development, and digital
computer applications to plant and areawide control.
I. Instrumentation Development and Testing
A recent survey by EPA of performance and acceptance of instrumentation
at wastewater treatment plants identified numerous instances of unacceptably
high failure rates and unsatisfactory operation (2). Among the several
contributing factors identified were the absence of proven performance
criteria and" technical specifications for the instrumentation, and accepted
methods for field maintenance and testing of instruments.
a) Testing and Certification Laboratories
In order to remedy this situation on Inter-Agency Agreement was
established with the National Bureau of Standards to develop performance
criteria, specifications and test methodologies of on-line instrumentation
for use in wastewater treatment. The project will deal with fluid flow
instruments and chemical instrumentation. Table 1 lists the instrumentation
which will be investigated.
For each instrument or group of instruments three levels of reports
will be produced. The first level will deal with the performance
specifications of the instrument as a function of its intended use, the
essential procedures for maintenance of the equipment in a wastewater
treatment plant, and factors required to maintain compatibility of the
instrument with other electronic or pneumatic components of automatic process
control systems. These data will generally be available from vendors
literature, ISA and ASTM specifications and knowledge of the level of
confidence in a measurement needed to achieve control in a wastewater treatment
plant.
454
-------
TABLE 1
INSTRUMENTATION INVESTIGATED IN NBS STUDY
Flow
Venturi Type Meters
Magnetic Flow Meters
Acoustic Flow Meters
Flumes
Chemical
Residual Chlorine
Dissolved Oxygen
Total Organic Carbon
Suspended Solids
PH
455
-------
The second level report will deal primarily with development of a
"Test Protocol" i.e. methods of testing to determine if the performance
specifications for an instrument are being met. The test protocol will
include: installation procedures, test procedure to generate baseline data,
calibration procedures, maintenance during test, and other operational
guides.
For the most part the "test protocol" described above will address
bench testing of the instrument. A test protocol referred to as a
Measurement Assurance Program dealing with field evaluation and calibration
procedures will be the subject of the third level report.
The first level reports were submitted within the last month. The
second and third level reports will not be complete for 1 to 2 more years.
Extensive bench and field testing will be necessary to prove out the test
protocols.
A second effort in this area, which has just been started, is a
Feasibility Study on Establishing an Instrumentation Testing and Certification
Institute. In this project which has been undertaken by Public Technology
Inc. a study will be made of the legal, institutional, financial, techno-
logical, and market factors involved in establishment of such an independent
institute [3). Particular attention will be paid to the experiences of similar
types of institutions in the United Kingdom (Sira Inc.) and the Netherlands
(W.I.B.). These institutes conduct tests at the request of manufacturers or
potential users of instrumentation to determine if an industry wide or
manufacturers specification can be met by the instrument. All reports on
results are confidential. It is expected that the results of the NBS study
will form the base testing program for use by an type of testing and
certification center.
b) Field Evaluations of Instruments
Recently evaluation of several on-line analysers was conducted on
EPA projects. These included a TOG analyser used in conjunction with an
F/M control strategy for activated sludge systems, and a sludge blanket
level monitor and a solids concentration monitor used in conjunction with
control of a thickener.
The EPA instrumentation and automation program has had only limited
experience in making first hand evaluations of instrumentation, because
basic policy is to refrain from conducting specific instrument evaluation
under government auspices. However in the course of conducting evaluations
of specific control strategies of treatment processes evaluations of some
equipment are conducted. These evaluation are in the context of the control
strategy being evaluated i.e. the performance of the instrument must be
good enough so that the automated control strategy can be properly implemented.
Thus, even if an instrument performs its basic sensor function properly
it may not be acceptable if its response time is inadequate to the control
strategy.
456
-------
The TOC analyser evaluated was a Dohrmann/Envirotech, Model DC-60.
The operating principles of the DC-60 are analogous to laboratory techniques
for the determination of organic carbon as described in Standard Methods,
13th edition, except the sample is not homogenized, and the carbon content
is equated to the area under the peak rather than the amplitude of the peak(4).
As shown in the system plumbing diagram, Figure 1, a sample of the stream
to be monitored is diverted to a small, (500 ml), overflow tank adjacent to
the analyzer. The sample is pumped from the overflow tank at 25 ml/min to a
baffled chamber where it is continuously acidified to a pH less than 2 and
air sparged to remove inorganic carbon. The conditioned sample is pumped at
20 ml/min past an automatic syringe (injector valve) to drain. At a selectable
interval, 5, 10, 15, 30, 60, 120 minutes, a 250 micro-liter portion is drawn
from the 20 ml/min sample stream and injected into the top of a combustion
chamber, Figure 2. Here the 250 micro-liter sample is vaporized at 900°C in
an air stream. Under the influence of a catalytic heat transfer medium,
(cobalt oxide) carbon compounds are converted to carbon dioxide. The
resultant sample is cleaned of non-gaseous material and passed through an
infrared detector. The carbon dioxide content of the sample gas is measured
by comparing the infrared light passed through the sample gas to the infrared
light passed through a reference cell.
The resulting electrical signal is amplified, integrated, and displayed
on a strip chart recorder. The recorder is calibrated to read directly in
milligrams per liter of total organic carbon. An electronic sample sensing
device automatically shuts down all three pumps upon loss of sample flow,
and furnace temperature runaway is prevented by a thermostatic power cut-off.
An adjustable high level alarm signals when TOC exceeds a selected level, a
predetermined number of times in succession. Connections are available at
the rear of the analyzer for remote monitoring of; the high TOC level alarm
signal, the sample loss alarm signal, the furnace overtemperature alarm
signal, and an isolated output signal proportional to the TOC value.
During a 1 month continuous evaluation at the Blue Plains Pilot Plant
the TOC analyser sampled and analysed primary effluent once every 5 minutes.
During this period TOC varied from 30 to 100 mg/1. Comparison of the analyser
results to samples analysed manually on a Beckman Model 915 TOC analyser
indicated a maximum deviation of - 2.5 mg/1 TOC. A similar successful
evaluation for use on tertiary effluent in the TOC range of 0 mg/1 to 10 mg/1
was conducted. Here the maximum deviation was - 0.5 mg/1. The only
difficulty encountered was the need to recalibrate the instrument span once
during each evaluation.
In order to use the analyser out-put to implement F/M control strategies
it was necessary to introduce a smoothing routine. The analyser tracked small
changes in influent TOC so closely that direct use of the out-put would have
introduced oscillations in the activated sludge reactor solids. An inexpensive
microprocessor can be used to automatically implement the smoothing routine.
The sludge blanket level detector (Biospherics Model 56) was installed
in a thickener at the MWCC of Minneapolis-St. Paul Metro Plant. The unit,
consists of two submersible probes "A" and "B" suspended, by individual
457
-------
NTEG./T-ROG. INJECTION
MODULE PLATE
IS-2 TS-1
I 2:
REACTION ZONE
PRESSURE
BULKHEAD UNION
% IN - BRASS
IGYROLOK)
ACID
INLET
on
oo
REACTANT
ADJUST BUIKHEAD UNKJN
1/8IN - BRASS (GYROLOK)
GAS
BULKHEAD
UNION 1/8M - BRASS
(GYROLOK)
INFRA RED CO2
DETECTOR
VENT TO
ATMOSPHERE
FIGURE 1
TOC ANALYSER PLUMBING
OUT
OWJO 1 COOLING
WATER
BULKHEAD UNION (T)
'/.IN BRASS
(GYROLOK)
-------
SALT COLLECTOR
TO CONDENSER
NOTES:
1. ITEMS 1A, IB AND 1C ARE ALL CUSTOM
FIT, AND ARE NOT INDIVIDUALLY
REPLACEABLE (NOTE 3).
2. ITEMS IB AND 1C ARE MATCHED TO
THEIR RESPECTIVE ENDS OF THE REACTION
TUBE, AND MAY NOT BE INTERCHANGED.
3. ITEMS 1A, IB 1C, 2 AND 3, ARE AVAILABLE
AND STOCKED UNDER PART NO. 835-275.
NOTES
1,2,3
BILL OF MATERIAL
ITEM
1A
IB
1C
2
3
4
5
6
7
8
9
10
11
12
13
14
PART NO.
030-400
835-281
835-282
835-244
835-285
835-276
835-284
030-402
080-834
080-836
100-472
100-473
100-474
100-475
511-735
511-870
DESCRIPTION
REACTION TUBE
CUSTOM TOP TUBE NUT
CUSTOM BOTTOM END PLUG
END PLUG JACKET
END PLUG NUT
HASTELLOY LINER
PERFORATED CERAMIC DISC
CERAMIC INSERT
TEFLON FRONT FERRULE
STAINLESS BACK FERRULE
O-RING -028
O-RING -029
O-RING -030
O-RING -031
QUARTZ WOOL
OXIDIZER GRANULES
FIGURE 2
TOC ANALYSER COMBUSTION
CHAMBER
459
-------
waterproof cables, from a control box. Each probe consists of a light source
and photocell separated by a 3/4 in. sensing gap. The light transmitted to
the photocell is a function of the concentration and characteristics of the
solids slurry in the sensing gap. When in service each sensor is suspended
in the thickener from its cable which also provides power to the light
emitting diodes and photocell and transmits the photocell output to the control
unit.
The control unit is housed in a NEMA 4 enclosure mounted on the thickener
handrail and consists of control circuits, power supplies and output relays.
A two position response switch is provided for fast or delayed response to
changes in photocell output. Three indicating lights labeled, LOW, MEDIUM,
HIGH, are mounted on the enclosure to indicate the sludge blanket position as
below, between or above the two sensors.
When probe "A" is located above probe "B" in the thickener basin the
control unit functions as follows. The energy source in each probe emits
radiation through the optical sensing gap to the photocell which senses the
amount of energy transmitted through the liquid and produces a signal related
to the suspended solids concentration of the liquid in the gap. This signal
is compared in the control circuit to an adjustable density threshold setting.
When the signal representing the concentration of solids in the liquid at
probe "A" exceeds the threshold setting an electronic 15 min timer is activated.
If the sludge blanket level remains at or above probe "A" at the expiration of
the 15 min interval the output relay is energized and the HIGH lamp on the
control box illuminates. The output relay is used to energize the starter
of the thickener underflow pump motor. After a period of sludge withdrawl
the sludge blanket level drops below probe "A" and the photocell output
drops below the threshold setting. At this time the HIGH lamp is extinguished
and the MEDIUM lamp illuminates. After continued sludge withdrawl the sludge
blanket drops to the level of probe "B" and the signal representing the
concentration of solids falls below the threshold setting. At this point in
time a second 15 min interval timer is activated. If the sludge blanket
level remains below probe "B" at the expiration of the 15 min interval the
output relay is deenergized and the MEDIUM lamp is extinguished and the LOW
lamp illuminated. The underflow pump starter is disengaged when the output
relay is deenergized. When the sludge blanket level rises to probe "B" the
photocell output increases above the threshold setting and the LOW lamp is
extinguished and the MEDIUM lamp illuminated. The above cycle is repeated
as the sludge blanket level rises to probe "A".
A three position switch (HAND, OFF, AUTO) was installed in the control
room to allow the operator to establish the mode of operation. This flexibility
was required to minimize problems associated with instrument failures and high
sludge levels in the holding tanks downstream of the thickeners.
An evaluation of the efficacy of this device was made in terms of blanket
level stability versus an identical thickener receiving identical feed. In
the control thickener periodic manual measurements were used to determine
blanket depth, and underflow pumps were started or stopped manually from a
control center to keep the blanket at the target depth. In the automated
thickener a signal from the blanket level instrument controlled the pumping.
460
-------
Figure 3 illustrates results obtained over a 10 day period. It can be
seen that the unit with the automatic blanket level detector had a much more
stable blanket and that the blanket was kept within 1 foot of the set point.
Deviation from the set point was due to fouling of the sensor. It was found
necessary to clean the probe once per week to avoid problems.
Optical type solids analysers were installed in the inflow, overflow,
and underflow streams of these thickeners to aid in the collection of data
on thickener performance and to more fully evaluate their own performance
characteristics. Biospherics model 52LE suspended solids analysers and
Biospherics model 52H sludge density analysers were utilized. These are
self-cleaning optical types of analysers.
The analysers were installed in the influent and underflow pipes
through a pipe insertion adapter mounted in a 2 in. NPT threaded hole. The
overflow analysers were mounted in the sample sinks in the thickener gallery.
The installation locations are illustrated in Figure 4.
The influent solids analysers consisted of a one foot long sensing head
housing a glass sampling chamber, a motor drive mechanism that operated a
plunger positioned in the sampling chamber, and a control unit connected to
the sensing head by a multi-conductor cable. The sensing head of the analyser
contains a light source that transmits a light beam across the sample chamber
to a photocell. The plunger is equipped with a wiping seal that cleans the
optical surfaces of the photocell and light source with each operating stroke.
The signal from the photocell is linearized in the control unit producing a
meter reading that is designed to be proportional to the suspended solids
concentration of the sample.
The unit completes a sample and analysis cycle every 15 sec. The
plunger retracts and draws a sample into the sampling chamber similar
to the operation of a common laboratory syringe. The light transmission
measurement is made and the sample is expelled. The instrument output
(meter and/or recorder) is maintained constant during each cycle. A range
switch on the face of the control unit provides for operation in the range
of 0 to 3000, 0 to 10,000 and 0 to 30,000 mg/1. An ON/DAMP switch allows
for recording of the actual output fluctuations at 15 sec intervals or only
a portion of the step change when the fluctuations are large.
Zero and span controls are located at the rear of the control unit.
The zero control is used to adjust the output with clear water present in
the sampling chamber. The span control is used to adjust the slope of the
calibration curve. A test plug which consists of two fixed resistors and
a high/low switch can be attached to the control unit in place of the signal
cable. The resistors simulate photocell output in the 0 to 10,000 and
0 to 30,000 mg/1 ranges; and, the meter readings with the test plug in place
can thus be used to identify malfunctions in both the control unit and sensing
head.
The overflow analysers are functionally identical to those used to
monitor inflow, however, the sensing heads are four feet long. The units
were mounted in sample sinks in the thickener basins. Thickener overflow
461
-------
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DATE - NOVEMBER 1977
FIGURE 3 COMPARISON OF BLANKET LEVEL CONTROL
-------
Overflow
parshall
flume
Thickener
influent
well-
East Bank
thickener
inflow
pipe
Overflow ->
sample line
Overflow —
Thickener
sidewall
Underflow
analyzer
.Underflow
sample line
Inflow sample line
analyzer |J |-Sample sink
Underflow
pump
\Underflow
pipe
FIGURE 4 LOCATION OF SOLIDS ANALYZERS AND SAMPLING LINES
-------
is piped from the overflow flumes to the sample sinks and discharges to
sample buckets. The analysers are supported above the sample sinks and
the sensing heads extend into the sample buckets which overflow continuously.
The sensing head of the underflow monitor is externally identical to
the inflow unit, however, the underflow analysers contain three photocells
in the sensing head; one each for measuring light transmittance, 90° light
scatter and color compensation. The parallel combination of the light
transmittance and light scatter photocells provides an output related to the
suspended solids concentration in the sludge sample. The color compensation
photocell adjusts the input current to the control unit amplifier to reflect
changes in sludge color. A linerization module in the control unit corrects
the nonlinear response of the transmittance and light scatter photocells.
The unit completes a sample analysis cycle every 40 sec.
The control units are equipped with the ON/DAMP switches and span
adjustment controls. The instrument range is fixed at 0 to 10% solids and is
calibrated in terms of total solids. A test plug is used to simulate the
output of the sensing head and check for drift in the control circuitry.
The outputs of the six solids analysers along with the output of the
thickened sludge (underflow) flowmeter serving basin 4 were recorded on a
Leeds and Northrup Speedomax W multipoint recorder.
The performance of the solids analysers was monitored during a 4 month
period while they were on-line. The inflow and overflow sensors performed
quite well. The calibration did drift slightly for each of the devices
but the correlation coefficient between the instrument and manual analysis
remained high. For one of the inflow sensors it decreased from 0.998 to .967
and for the other from 0.973 to 0.952 over a range of suspended solids of
0 to 8,000 mg/1. For one of the overflow sensors the correlation coefficient
decreased from .997 to .991 and for the other from .998 to .967 over a range
of 0 to 6,000 mg/1.
For the underflow solids analyses generally poor results were obtained
These were found to be due to changes in the physical properties and color
of the sludge rather than any electronic defects in the sensor. A test
with this same instrument for a limited time about 1 year prior to this
test had given good correlation (r = 0.90).
II. Treatment Process Control Strategy Development
During the past few years EPA research efforts have concentrated on
development of new or verification of existing control strategies for the
activated sludge process and selected sludge handling and stabilization
techniques. Investigation of these was deemed most important because of
the large expenditures scheduled for these processes under the construction
grant regulations of PL 92-500. In conducting these studies emphasis was
placed on demonstration of the control strategy concept, and deliniation
of improvements in process performance and or process cost effectiveness.
464
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a) Activated Sludge
For the activated sludge process emphasis has been placed on strategies
involving dissolved oxygen level control, and instantaneous food to
microorganisms ratio control (F/M). The need to maintain a minimum level
of dissolved oxygen in the aerator of an activated sludge system was
established many years ago, and the potential power savings when this is
automated is self evident. Consequently the major recent effort was to
produce a design hand book which could be used to aid engineers in designing
the most cost effective systems. This manual which was published in 1976
discusses the various activated sludge modifications, aeration methods,
equipment and application techniques, compressors and blowers, D.O. control
methods, and presents an economic analysis of manual versus automatic D.O.
control. The reader is referred to the manual for the findings ( 5 J.
In addition detailed case histories were presented for 12 sites at which
both manual and automatic D.O. control were conducted. Table 2 presents
a summary of the improvements resulting from the use of automatic D.O. control
The value of instantaneous F/M for control of activated sludge has been
a subject of great debate in the environmental engineering field for a long
time. One problem is that F/M control is often confused with Solids Retention
Time (SRT) control. The latter has proven to be a valuable control parameter
Confusion results because the long term average F/M in an activated sludge
is a function of the SRT; indeed these parameters are mathematically related
by a simple equation. Thus various investigators have interchangeably used
these two terms. Instantaneous F/M, however, can vary significantly over
limited time periods while SRT remains constant.
An investigation of the efficacy of instantaneous F/M control was
conducted in a joint EPA-Clemson University study ( 6 ). The Clemson
University staff prepared a model of the activated sludge system and used
this model to simulate events which would occur if an activated sludge system
was subjected to a typical diurnal variation of loading, and an attempt was
made to maintain instantaneous F/M constant. It was found that this was
impossible in a conventional type activated sludge system ( Figure 5a );
because the clarifier can not store sufficient solids to effect good control
while still maintaining good solids-liquid separation. In addition when
increased recycle is used to try to increase the mass rate of return sludge
the sludge concentration in the clarifier and recycle is diluted so that
the mass rate of return does not change. Use of a separate sludge storage
basin between the clarifier and aerator (Figure 5b) was found necessary to
achieve instantaneous F/M control. The mathematical simulation indicated
that a storage basin with a volume equal to 40% of the aerator volume was
sufficient to achieve good instantaneous F/M control. Use of such a storage
chamber essentially converts the flow sheet to the contact stabilization
mode of operation.
An attempt to obtain experimental verification of this model and
determine the specific effect of instantaneous F/M on activated sludge
performance was initiated at the Blue Plains Pilot Plant. Unfortunately
the work had to be terminated before all the planned runs were complete.
Table 3 summarizes a comparison between a run with no control of instantaneous
465
-------
TABLE 2
EFFECT OF D.O. CONTROL ON ACTIVATED SLUDGE
Parameter % Improvement
Air Supplied per Unit of BOD Inflow 21.9
Air Supplied per Unit of Inflow Volume 11.6
BOD Removed per Blower KWH 32.1
BOD Removal Efficiency 3.2
466
-------
F-F
W
F
S
O
Aeration
Basin
>
V
F+FR
s
s ^
•M*
Clar
\
>
FR
ifier
/
f
FW
%
AR AR
FIGURE 5A CONVENTIONAL ACTIVATED SLUDGE
-------
F-F
W
Aeration Basin
Clarifier
00
Storage Basin
FIGURE SB ACTIVATED SLUDGE
WITH SLUDGE STORAGE FOR F/M CONTROL
W
-------
TABLE 3
COMPARISON OF ACTIVATED SLUDGE WITH AND WITHOUT
INSTANTANEOUS F/M CONTROL
Parameter
No Control
Control
SRT days
(Total Sludge Mass)
2.3
3.0
(F/M).
0.98
(Avg.)
0.71
Inflow gpm
20
20
Recycle gpm
10
variable
Effluent TOC mg/1
10.0
15.7
Effluent Turbidity JTU
26.6
53.1
469
-------
F/M and one with control. As only one apparatus was available a truly
controlled study could not be run, rather sequencial runs separated by
several weeks were conducted. Thus parameters such as SRT and F/M could not
be kept the same in both runs. With respect to maintenance of solids
inventory and control of instantaneous F/M the model developed by Clemson
University was verified. However, performance of the system was poorer wh |