EPA-670/2-73-064
August 1973
Environmental Protection Technology Series
Pilot - Demonstration Project For
Industrial Reuse Of Renovated
Municipal Wastewater
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
Environmental Protection Agency, have been grouped into five
series. These five broad categories were established to facili-
tate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and method-
ology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides
the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality
standards.
-------
EPA-670/2-73-064
August 1973
PILOT-DEMONSTRATION PROJECT FOR
INDUSTRIAL REUSE OF RENOVATED MUNICIPAL WASTEWATER
By
G. A. Horstkotte, Jr.
Contra Costa County Water District
Central Contra Costa Sanitary District
Walnut Creek, California 94596
Project No. 17080 FSF
Project Officer
Carl A. Brunner
U.S. Environmental Protection Agency
National Environmental Research Center
Cincinnati, Ohio 45268
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
JTnr salaJiitJJui Snnnrlntr-ndent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.
65
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EPA REVIEW NOTICE
This report has been reviewed by the Office of
Research and Development, EPA, and approved for
publication. Approval does not signify that the
contents necessarily reflect the views and
policies of the Environmental Protection Agency,
nor does mention of trade names or commercial
products constitute endorsement or recommendation
for use.
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ABSTRACT
Three pilot plant treatment sequences were operated during this study
to produce various grades of effluent for subsequent testing as industrial
water sources. The testing was conducted in pilot-sized test loops con-
sisting of small cooling towers and heat exchangers. At the same time
the renovated waters were tested, Contra Costa Canal water, which is
presently used by industry in the study area, was also investigated in a
test-loop identical to those used for the renovated water.
The study results illustrated that the wastewater investigated can be
treated satisfactorily for reuse in industrial applications. Corrosion
rates and fouling factors observed with renovated water were equal to or
less than found with the canal water. Precipitation of phosphorous was
the major source of scale formation while using renovated water for
cooling purposes, thus indicating the need for phosphorous removal.
Biological oxidation of organic materials and ammonia in a multistage
treatment system resulted in renovated water suitable fcfr industrial re-
use. Filtration and phosphorous removal in association with biologi cal
treatment were also advantageous. Physical-chemical treatment pro-
cesses can produce suitable renovated water provided that a suitable
method is developed to prevent the generation of noxious odors in the acti-
vated carbon process.
Costs for the alternative treatment systems ranged from approximately
25^/1000 gal for conventional activated sludge treatment to 50^/1000 gal
for a three-stage biological treatment system with filtration and alum
addition for phosphorous removal. Physical-chemical treatment costs,
including the cost for nitrogen removal, ranged from about 38 to 45^/1000
gal. The costs for renovated water should be significantly less than the
above costs in those cases where high degrees of treatment are required
to discharge the treated effluent to a receiving body of water.
This report was submitted in fulfillment of Project Number 17080 FSF,
by the Contra Costa Water District and the Central Contra Costa
Sanitary District, under the partial sponsorship of the Environmental
Protection Agency.
111
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CONTENTS
Section Page
I INTRODUCTION 1
Motivation 1
Objectives 4
II CONCLUSIONS AND RECOMMENDATIONS 5
Conclusions 7
Recommendations 13
III EXPERIMENTAL PROGRAM 15
Description of Facilities 15
Operating Program ZZ
Sampling and Analysis Program Z4
IV RESULTS OF WASTEWATER TREATMENT STUDIES 29
Phase I : Biological-Physical Treatment System Z9
Phase II : Biological Nitrification-Denitrification 39
Phase III: Chemical-Physical Treatment System 58
Evaluation of Treatment Processes 71
Heavy Metals 79
V RESULTS AND DISCUSSION OF INDUSTRIAL
TEST LOOP STUDIES 81
Heat Exchanger Fouling Data 81
Corrosion Rates* 88
Algal Growth Potential 92
Toxicity Analysis 95
Evaluation of Industrial Test Loop Results 98
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Section Page
VI ESTIMATED WASTEWATER TREATMENT COSTS 103
Phase I: Activated Sludge 105
Phase II: Biological Nitrification 105
Phase II A: Biological Nitrification-Denitrification 106
Phase III: Physical-Chemical Treatment 107
Phase III A: Combined Physical-Chemical-
Biological Treatment 108
VII ACKNOWLEDGMENTS 111
VIII REFERENCES 113
IX APPENDICES 115
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ILLUSTRATIONS
Figure Page
1-1 Geographic Location of Project Area 2
2-1 Process Flow Diagram for the Pilot-Demonstration
Facility 6
2-2 Approximate Treatment Costs'for 30-mgd Plants 12
3-1 Perspective Drawing of Pilot-Demonstration
Facilities 16
3-2 Pilot-Plant Filtration Media 18
3-3 Pilot-Demonstration Plant Operating Schedule 21
3-4 Sampling Points in the Pilot-Demonstration Facility 26
4-1 Activated Sludge Process Operating Characteristics 30
4-2 Activated Sludge Process Quality Characteristics 31
4-3 Filtration Data Using Activated Sludge Process
Effluent 34
4-4 Performance Data of Activated Carbon Treatment
of Activated Sludge and Nitrification Process Effluents 37
4-5 Nitrification Process Data 41
4-6 Nitrification-Denitrification Process Data 44
4-7 Denitrification Process Data 47
4-8 Filtration Data Using Denitrification Process
Effluent 52
4-9 Performance Data of Activated Carbon Treatment
of Nitrification and Denitrification Process Effluents 54
4-10 Lime Requirements for Chemical Treatment 59
4-11 Chemical Treatment Plant Lime. Requirement
and pH Values 60
4-12 Hardness and Alkalinity of Raw Wastewater and
First-Stage and Second-Stage Chemical Treatment
Effluents 62
vn
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Figure Page
4-13 Orthophosphate and Suspended Solids Removal
in the Two-Stage Chemical Treatment Process 64
4-14 Total and Soluble Organic Carbon Removals in
the Two-Stage Chemical Treatment Process 65
4-15 Filtration Data Using Chemical Treatment Effluent 67
4-16 Performance Data of Activated Carbon on Chemical _ ;
Treatment Process Effluent 69
5-1 Average Fouling Factor Data 86
5-2 Algae Growth in Renovated Waters 94
6-1 Flow Diagrams and Treatment Costs for 30-mgd
Plants 104
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TABLES
Table Page
3-1 Analytical Procedures 27
4-1 Activated Sludge/Nitrification Data 33
4-2 Summary of Filtration Performance Using
Activated Sludge Process Effluent 35
4-3 Summary of Activated Carbon Performance Data
During Treatment of Filtered Activated Sludge
Effluent 38
4-4 Average Monthly Suspended Solids Concentrations
of the Biological Effluents (mg/1) 45
4-5 Phosphorous Removal Using Ferric and Aluminum
Additions to the Denitrification System 50
4-6 Summary of Filtration Performance Using Denitri-
fication Process Effluent 53
4-7 Summary of Activated Carbon Performance Data
During Treatment of Filtered Nitrification and
Denitrification Process Effluents 57
4-8 Chemical Treatment Average Hardness and
Alkalinity Data 6l
4-9 Average Performance Data of Activated Carbon
on Chemical Treatment Process Effluent 70
4-10 Pilot Plant Average Effluent Quality Compared to
the Raw Wastewater 72
4-11 A Comparison of Single-Stage Activated Carbon
Performance for Various Pilot Plant Effluents 77
4-12 Removal of Heavy Metals 80
5-1 Fouling Factors and Scale Analyses 82
5-2 Typical Fouling Factors 87
5-3 Corrosion Rates and Circulating Water Quality 89
IX
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Table Page
5-4 Comparison of Corrosion Rates 91
5-5 Sample Analysis for Algae Growth Potential Tests 93
5-6 Summary of Toxicity Results 96
5-7 Industrial Test Loop Toxicity Results 97
5-8 Typical Quality Characteristics of Wastewater
and Canal Water 100
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Section I
INTRODUCTION
This report presents the results of a pilot-demonstration investigation
on wastewater renovation conducted by Bechtel Corporation under a con-
tract dated July 27, 1970, with the Contra Costa County Water District
(CCCWD) and Central Contra Costa Sanitary District (CCCSD). The in-
vestigation was partially funded by a Class IV Research and Development
Grant from the Environmental Protection Agency. Figure 1-1 shows the
project area location. This location is adjacent to industries generally
located along the south shore of Suisun Bay.
MOTIVATION
In 1969, during a feasibility study conducted by Bechtel for the CCCWD,
it was concluded that "it is technically feasible to produce renovated water
for the CCCWD for a wide range of irrigational and industrial uses"
(Reference 1). As a result, it was recommended that (1) a sampling and
analysis program be established to characterize local waters and waste-
waters, (2) a pilot-demonstration program be initiated, and (3) a master
plan for water renovation be developed. It was also recommeded that
an agreement be established for cooperation between the CCCWD and
CCCSD in undertaking additional wastewater renovation investigations.
The CCCWD and CCCSD, on December 3, 1969, entered into a memo-
randum of understanding which:
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INTERSTATE STATE 4
680
SAN FRANCISCO BAY
Figure 1-1. Geographic Location
of Project Area
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Recognized the basic water supply function of the
CCCWD and water pollution control function of
the CCCSD
Established the intent of both Districts to cooperate
in future water renovation and reuse activities
Outlined the following six-phase program:
Phase Activity
I Water Renovation Feasibility Study
(sponsored by CCCWD and complet-
ed September 1969)
II Solid Waste Disposal Investigation
(sponsored by CCCSD and completed
March 1970)
III Sampling and Analysis Program
(jointly sponsored by CCCWD and
CCCSD and completed November
1971)
IV Pilot Plant Program (jointly spon-
sored by CCCWD and CCCSD)
V Demonstration Program (jointly
sponsored by CCCWD and CCCSD)
VI Implementation Plan for waste -
water renovation and solid wastes
disposal
Because of the national significance associated with Phases IV and V,
the CCCWD and the CCCSD applied for, and were granted on February
19, 1970, a Class IV research and demonstration grant from the Fed-
eral Water Pollution Control Administration (now Environmental Protec.
tion Agency) to carry out the pilot-demonstration program.
The motivation for this investigation stems from the activities listed
above, which reflect the CCCWD's and the CCCSD's desire to conserve
our water resources by water reuse.
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OBJECTIVES
Objectives of the pilot-demonstration program using various wastewater
treatment process sequences were to;
Allow investigation of the removal of various impurities
in wastewaters by certain treatment processes
Produce various grades of renovated waters whose
properties will be tested for factors of importance in
industrial water use
Provide process data that, along with other available
information, will be used in orde r-of-magnitude cost
comparisons of various water renovation processes
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Section II
CONCLUSIONS AND RECOMMENDATIONS
Three pilot plant treatment sequences were investigated during this study
to determine the suitability of various grades of renovated wastewater
for industrial reuse (Figure 2-1). In the Phase I treatment sequence,
primary effluent from the existing CCCSD treatment plant was given bio-
logical treatment in the pilot plant. The biologically treated effluent,
before and after filtration, was chlorinated and used as cooling water
makeup for the industrial test loops.
In the Phase II pilot plant sequence, primary and activated sludge treatment
was provided in the CCCSD treatment plant, while ammonia was biolo-
gically oxidized to nitrate in the pilot plant nitrification process. The
nitrate was subsequently removed biologically as nitrogen gas in the
denitrification process (Figure 2-1). Filtration and activated carbon
adsorption were used as additional treatment steps on a portion of the
effluents from the nitrification and the denitrification processes. Ni-
trified, filtered nitrified, and activated-carbon-treated nitrified ef-
fluents were used as makeup water for the industrial test loops. Simi-
lar combinations of denitrified effluents were also used in the cooling
towers.
The Phase III treatment sequence incorporated only chemical and physical
processes. Wastewater was given preliminary treatment for the removal
of grit, rags, and large suspended materials in the existing CCCSD plant
before being conveyed to the pilot plant, where lime was added to remove
suspended solids and phosphorous in the first stage flocculation-sedi-
mentation processes. Carbon dioxide was then added to reduce the pH
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PRIMARY EFFLUENT
(PHASE I) OR ACTIVATED
SLUDGE EFFLUENT
(PHASE II)
rrrfrj
PILOT
BIOLOGICAL
STAGE
CARBON
ADSORPTION
STAGES
SEDIMENTATION
RAW J
INFLUENT
PHASE III FLOCCULATION
CARBON
ADSORPTION
WET STAGES
WELL FILTRATION ^~~\ S~~\
f-^*l
+ ^
TEST LOOPS
LEGEND
RENOVATED
WATER
RENOVATED
WATER
PHASE
PHASE II
PHASE III
SLOWDOWN
SLOWDOWN
HEAT
EXCHANGER
CONDENSATE
SLOWDOWN
Figure 2-1. Process Flow Diagram for the Pilot
Demonstration Facility
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prior to the removal of excess calcium in the second stage flocculation-
sedimentation processes. Filtration followed for the removal of the re-
maining suspended solids, and activated carbon treatment was used to re-
duce the organic carbon content of the filtered effluent. After chlorination,
a portion of the treated wastewater was used as makeup water for the in-
dustrial test loops. Filtered chemically treated effluent was also used as
cooling water makeup.
In addition to testing various grades of renovated water in the industrial
test loops, the Contra Costa Canal water that is presently used by indus-
tries in the area was also tested. Such tests permitted direct comparison
of the renovated waters with the existing water source.
Conclusions regarding industrial reuse and the various treatment se-
quences investigated in this study are discussed in this section. Re-
commendations based on the pilot-demonstration investigations are also
presented.
CONCLUSIONS
Industrial Reuse
Based on the industrial test loop studies, wastewater
can be treated satisfactorily for reuse in industrial
applications. Major areas of concern for cooling
water reuse are calcium, sulfate, phosphate, and
silicate as they relate to scaling, and the maximum
cycles of concentration one can maintain without
excessive maintenance costs. Organics and total
dissolved solids (TDS) are the most important
factors affecting boiler feed water treatment costs.
The corrosion rate of carbon steel as determined
with corrosion coupons, for all renovated waters
tested without the use of corrosion inhibitors,
ranged from 2.0 to 31 mils/year, which was less
than that for untreated canal "water ( 12. 5 to 37
mils/year). Canal water with the addition of a
-------
corrosion inhibitor was observed to have a corrosion
rate of 2. 7 mils/year. Based on these results, it
can be concluded that renovated water can be pro-
duced that is substantially less corrosive than un-
treated canal water.
Fouling of heat exchanger surfaces by renovated
wastewater was approximately equal to that of
the untreated canal water. The fouling factors
ranged from 0. 0005 to 0. 004 hr-°F-sq ft/Btu
for. the renovated waters and 0. 0005 to 0. 003
hr- F-sq ft/Btu for the untreated canal water.
Based on these results, it can be concluded that
renovated water can be produced that will not
cause any greater fouling problems than un-
treated canal water.
Precipitation of phosphorous was the major source
of scale formation while using renovated wastewater
for cooling purposes, thus indicating the need for
phosphate removal. The phosphorous concentration
in the renovated water should be 0. 5 mg/1 as P or
less in order to minimize scaling problems.
Where chlorine is used in cooling water systems for
the control of biogrowth, it would be desirable to
remove ammonia from renovated water used for
makeup purposes in order to reduce chlorine re-
quirements. An effective removal procedure is
the biological nitrification process in which ammonia
is converted to nitrate.
Since nitrate does not limit the cycles of concentration
attainable in the operation of cooling towers, the need
for denitrification cannot be justified on such a basis.
However, lower algal growth anticipated with denitri-
'fied effluent compared to nitrified effluent suggests
that denitrification may be helpful.
Filtration of renovated water not only improves the
water quality but also reduces potential problems
arising from the deposition of suspended solids in
industrial heat exchanger equipment. With filtered
renovated water, this problem would not be as great
as normally encountered during the use of canal water.
Activated carbon treatment would not be required for
biologically treated wastewater for its reuse as in-
dustrial cooling water. If renovated water is to be
used for boiler feedwater, it may be more economical
for industry to provide any additional treatment, such
as activated carbon, for that portion of the water used
for such purposes.
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Biological Treatment
Biological nitrification in a conventional single-
stage activated sludge system, can be achieved
provided the sludge age is greater than 10 days
and the dissolved oxygen is maintained at greater
than 2. 0 mg/1. A two-stage biological system
designed to achieve nitrification is significantly
more reliable and less difficult to control than
a single-stage system.
The presence of a limited concentration of organic
materials in the nitrification reactor influent of a
two-stage biological system is necessary to promote
a required synergistic relationship between the nitri-
fying bacteria and the heterotrophic bacteria. These
organic materials should have a total organic carbon
(TOC) concentration of approximately 30 to 50 mg/1.
Reduction of organic materials in typical municipal
wastewaters to this level can be achieved with a high
rate activated sludge system, a trickling filter, or a
chemical-primary treatment process.
The pilot plant denitrification data were quite variable
due to difficulties encountered with the methanol feed
system and solids separation. Effluent nitrate con-
centrations ranged from less than 1 mg/1 to 20 mg/1
and averaged about 3. 2 mg/1, indicating an average
removal of 82 percent. With an improved methanol
feeding system and an aeration step between the de-
nitrification reactor and the final clarifier, as found
necessary in subsequent studies to improve solid
separation, the denitrification process can be ex-
pected to perform satisfactorily.
Physical-Chemical Treatment
Chemical treatment resulted in the most consistent
effluent quality of all the pilot plant processes in-
vestigated during the study. Total phosphorous re-
movals averaged about 97 percent, and about 70
percent of the total organic carbon (TOC) was re-
moved in the chemical treatment system.
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e Ferric chloride at a concentration of approximately
15 mg/1 enhanced the coagulation of insoluble pre-
cipitates formed in the second-stage flocculation unit.
In a large-scale treatment plant, recycling lime sludge
or using coagulant aids would be expected to perform
as well as the ferric chloride for this purpose and would
thus minimize potential sludge handling problems.
e Because of the organic carbon concentration remaining
after chemical treatment, either activated carbon or
biological oxidation is required to lower the concentration
of total organic carbon in the effluent to about 10 mg/1.
The chemically treated effluent turbidity was approximately
5 JTU. This turbidity was reduced by only 20 to 40 percent
by filtration. Improved filter performance may be expected
if a polyelectrolyte or alum is added to the filter influent.
Filtration following biological treatment increases process
reliability, improves effluent quality, and should enhance
disinfection as a result of significant decreases in the
effluent suspended materials.
« Chlorination of the filtration process influent should be
provided to prevent biological growths and subsequent
clogging of the filter media.
» The data obtained in this study indicate that if activated
carbon treatment is employed, a carbon contact time of
approximately 15 minutes would be suitable for biologically
treated effluents and 30 minutes for chemically treated
effluents. Organic carbon removals averaged only about
2 or 3 mg/1 in the second stage of the activated carbon
process when the contact time in each carbon stage was
25 to 30 minutes.
« The pilot plant data indicated that approximately 410 pounds
of activated carbon per million gallons of water treated would
be required for biologically treated effluents, and 690 pounds
per million gallons would be required for chemically treated
effluents.
While activated carbon reduced the total organic carbon
concentration of the biological effluents to values as low as
2. 0 mg/1, the reduction generally represented less than 10
percent of the total organic carbon removed from the raw
wastewater. Since only 70 percent'of the total organic carbon
is removed by chemical treatment, activated carbon treatment
of chemically treated effluents would be required.
10
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Related Studies
Various units in the treatment sequences of the pilot
plant were spiked with poliovirus and monitored to
determine the degree of inactivation resulting from
each treatment step. Essentially all of the poliovirus
was inactivated within five minutes of exposure in the
first-stage lime flocculation unit when the pH was 11
or above. Contact with the lime sludge at an operating
pH between 10 and 11 and with biological sludges re-
duced the active viral count by three to four orders of
magnitude. Activated carbon treatment removed about
75 percent of the virus, whereas little or no viral removal
occurred during filtration or sedimentation.
Results of Provisional Algae Assay Procedure (PAAP)
tests demonstrated that there was little or no growth of
the test algae for at least 15 days in the chemical treat-
ment effluent, indicating that algal growth can be mini-
mized by the removal of phosphorous. Denitrified effluent
resulted initially in a logarithmic growth of algae, although
after approximately five days the rapid growth stopped,
thus suggesting that nitrogen became the limiting nutrient.
Cooling tower circulating water which had approximately
five cycles of concentration was not toxic to fish (stickle-
back) after 96 hours of exposure, when canal water, nitrified
effluent, filtered nitrified effluent, filtered chemical treat-
ment effluent, and activated carbon chemical treatment
effluent were used as cooling water makeup.
Heavy metals and trace organics, including pesticides,
phenols, and detergents, are generally reduced by 50 to
99 percent in the biological, chemical, and physical
treatment-renovation processes.
Treatment costs for the various sequences investigated are
summarized in Figure 2-2 for 30-mgd plants. All of
the costs are based on mid-1972 prices as discussed
in Section 6. The treatment costs range from approxi-
mately 25^/1000 gal for conventional activated sludge
treatment to 50^/1000 gal for a three-stage biological
treatment system with filtration and alum addition for
phosphorous removal Chemical treatment preceding
biological nitrification, biological denitrification, and
filtration costs approximately 41^/1000 gal. This treat-
ment cost was within the range of costs associated with
physical-chemical treatment including nitrogen removal
(i.e., approximately 38 to 45^/1000 gal).
11
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CENTS/1000 GAL
S 8 o S S
-
1
2
3
4
1
2
5
6
3
4
1
2
5
7
6
3
4
2
8
5
9
10
1
2
5
7
6
9
10
-
s § « §
DOLLARS/AC RE- FOOT
PHASE I
PHASE II
PHASE IIA PHASE HI PHASE IIIA
1 - SLUDGE
2 - CI2
3 - ACTIVATED SLUDGE
4 - PRIMARY
5 - FILTRATION
6 - NITRIFICATION
7 - DENITRIFICATION
8 - ACTIVATED CARBON
9 - CHEMICAL TREATMENT CALCINATION
10 - INFLUENT WORKS
Figure 2-2. Approximate Treatment Costs for 30-mgd Plants
12
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RECOMMENDATIONS
The following recommendations are offered for consideration:
Additional investigations should be conducted on the
biological denitrification process in order to develop:*
Improved control of the methanol feed. (A con-
tinuous TOC analyzer or a selective nitrate probe
may be satisfactorily used for this purpose. )
Improved solids separation of mixed liquor sus-
pended solids. (Intermediate aeration between
the denitrification reactor and the sedimentation
basin may be desirable. Dissolved air flotation
may also be worthy of further study. )
Further studies on the activated carbon process are
recommended to:
Optimize the carbon contact times required for
biologically and chemically treated effluents
Evaluate the necessity of filtration preceding
activated carbon treatment
Further investigate methods to eliminate the
generation of noxious odors in carbon columns
Investigate the advantages and disadvantages of
using two carbon stages in series versus a single
stage, as well as the expanded bed mode of operation
versus the packed bed
Sludge disposal methods should be evaluated to:
Determine optimum dewatering methods such as
vacuum filtration and centrifugation
Ascertain fuel requirements and product recovery
values associated with incineration and recalcination
Establish the market value of digested sludge as a
liquid fertilizer and, after drying, as a soil condi-
tioner
Since the time the pilot plant results presented in this report were
completed, CCCSD has conducted additional large-scale studies on
the denitrification process.
13
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Section III
EXPERIMENTAL PROGRAM
DESCRIPTION OF FACILITIES
A process flow diagram of the wastewater renovation pilot plant facili-
ties and the industrial test loops are presented in Figure 2-1. The pilot
plant facilities consist of biological processes (activated sludge, nitri-
fication, and denitrification), physical treatment processes (filtration
and activated carbon adsorption), and the chemical treatment processes
of lime coagulation and flocculation. The industrial test loops used during
this study were designed to simulate the use of cooling water in industrial
applications. Figure 3-1 is a perspective drawing showing the relative
locations of the pilot plant facilities and the industrial tests loops.
Pilot Plant Facilities
In Figure 3-1, the rectangular basin labeled biological stage was 8 feet
wide, 16 feet long, 11 feet deep, and contained 32 submerged air diffusion
units (Chicago Pump). This vessel was initially used as a conventional
activated sludge basin treating primary effluent from the CCCSD plant.
Later the active volume of this vessel was reduced by baffling, and the
vessel was used as a nitrification basin treating activated sludge effluent
from the CCCSD 1 -mgd plant.
The biological denitrification basin was 5 feet 6 inches in diameter and
11 feet deep. During the testing period on biological denitrification, this
basin was continuously stirred with a submersible pump. Methyl alcohol
15
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CLEAR WELL
SLUDGE STORAGE
FLOCCULATION
HEAT EXCHANGERS
AND COOLING TOWERS
BACKWASH WATER
WET WELL
PRIMARY OR ACTIVATED
SLUDGE EFFLUENT
BIOLOGICAL
DENITRIFICATION
SLUDGE
STORAGE
WET
WELL
Figure 3-1. Perspective Drawing of Pilot-Demonstration Facilities
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was added continuously to the denitrification basin using a variable-
speed diaphragm pump. For a short period of time, the denitrification
basin was used for biological nitrification since it was initially equipped
with air diffusers.
All sedimentation basins used in the pilot facilities were designed identi-
cally. These basins were 6 feet in diameter and 9 feet 11 inches deep with
an external peripheral effluent channel near the overflow weir. A 60-de-
gree cone bottom, constructed in each basin, was connected to a horizon-
tal pipe located near the bottom of the basin for sludge withdrawal.
Lime addition to the physical-chemical pilot plant influent (i. e. , partially
settled raw wastewater) was regulated by a. preset pH controller (Uniloc
Model 1000). The pH sensor was located in the first stage flocculation tank,
and the pH was continuously recorded in the laboratory trailer.
The flocculation tanks in the physical-chemical system were each Z feet
6 inches in diameter and 3 feet 4 inches deep. Three flocculation tanks
were provided for each stage of treatment. Inlet and outlet piping was
provided to facilitate removing any one or all of the flocculation tanks
from the operation. Each operating flocculation tank was equipped with a
clamp-mount variable-speed mixer (Lighting Model ND-1YM) with a flat
blade turbine impeller.
Recarbonation between the first and second stage of the chemical treatment
system was provided in a tank Z feet 6 inches in diameter and 10 feet deep.
Bottled carbon dioxide gas was introduced through a diffuser into the bottom
of the recarbonation tank, countercurrent to the liquid flow. Following re-
carbonation, precipitated calcium carbonate was flocculated with ferric
chloride used as a coagulant. The ferric chloride was added continuously
(using a diaphragm pump) to the flocculator in the second stage of the
chemical treatment system.
17
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The effluents from the biological processes and the chemical treatment
process were given additional physical treatment of filtration follow-
ed by two stages of activated carbon adsorption. The filtration equip-
ment consisted of three 20-inch diameter pressure filters (Bruner,
Model AG20), each containing different media, as illustrated in Figure 3-
Filters No. 1 and No. 2 contained anthracite coal (0. 68 to 0. 77 mm effec
tive size, 1.75 uniformity coefficient) and graded sand (0.45 to 0.55 mm
effective size, 1. 50 uniformity coefficient). Filter No. 3 contained mixec
media (Neptune Microfloc; MF-152) consisting of anthracite, sand, and
garnet. Each stage in the activated carbon system included a pressurizec
36-inch diameter vessel (Bruner, Model AC36) containing granular carboi
(Filtrasorb 400, Calgon Corporation) at a depth of 2. 5 feet. Graded grave
was used to support the filtration media as well as the activated carbon.
Backwash rates of approximately 20 gpm/sq ft and 6 gpm/sq ft were used
for the filters and the carbon columns, respectively. Surface wash mecha
isms were installed in each filter and carbon column.
FILTER
NO. 1
r 1
ANTHF
N
CN
CO
(ACITE
SAND
GRADED
GRAVEL
-JU
20"
. .
FILTER
NO. 2
r i
ANTHRACITE
n
^ SAND
GRADED
: GRAVEL
r^
20"
. .
FILTER
NO. 3
-------
Existing Treatment Plant
The existing treatment plant at CCCSD provides primary treatment to the
incoming wastewater preceded by screening and grit removal. Approxi-
mately 30 minutes detention time is provided in the aerated grit chamber
thus providing pre-aeration as well as grit removal. The design detention
time in the primary sedimentation tanks for a 30-mgd average daily flow
is 1-1/2 hours.
Sludges from the primary sedimentation tanks are anaerobically digested,
dewatered on drying beds, and sold as a soil conditioner. The grit removed
from the wastewater is dewatered and buried on the plant site. Gas pro-
duced during anaerobic digestion is used for fuel to operate gas engines used
for generation of electricity. Digester supernatant is returned to the plant
influent.
Pre-chlorination and post-chlorination of the wastewater is practiced, and
the chlorinated effluent is discharged to Suisun Bay through an outfall pipe-
line. The primary effluent used in the pilot plant study was pumped to the
pilot facilities before post-chlorination.
In addition to the 30-mgd primary treatment plant, a conventional activated
sludge plant having a nominal capacity of 1 mgd is located at CCCSD. Pri-
mary effluent is treated in this plant and used for surface sprays and ir-
rigational needs at the plant site. The activated sludge basin is rectangular
in shape and is aerated using blowers connected to a diffused aeration
system. A detention time of approximately 6 to 8 hours is provided in this
basin. The sedimentation basin is also rectangular in shape providing a
detention time of about 2 hours.
19
-------
Industrial Test Loops
Three industrial test loops, each consisting of a small cooling tower,
heat exchanger, and appurtenances, were included in the pilot-demon-
stration facilities. The cooling towers were 3 feet by 4 feet in plan with
20 inches of packing, which was constructed of 1 /4 inch by 1-1/2 inch
redwood splash bars having 2 inch horizontal spacing and 1-5/16 inch
vertical spacing (Marley Model 4411).
Each heat exchanger consisted of a steel shell, with 1/2 inch steam inlet
and outlet, having an outside diameter of 4- 1 /2 inches (Schedule 40 pipe)
and a length of 3 feet. The heat exchanger shell contained two 5/8 inch
OD carbon steel removable tubes, each having a wall thickness of 0.065 inch
(Calgon, Model Test Heat Exchanger).
The industrial test loops were equipped with appropriate valves, steam
traps, strainers, rotometers, pressure gauges, and thermometers to
facilitate their operation. Also, a corrosion probe (Magna) for instantaneous
corrosion rate measurements and a corrosion test specimen bypass loop
(Betz, Model No. 35D000110) were located in the circulating water on the
heat exchanger tube outlet of each industrial test loop.
Two sources of steam were used in the industrial test loops. Excess steam
available at 15 psi from the CCCSD plant was piped to the pilot plant area to
serve as one source. The other source was produced at the pilot plant site
using a vertical firetube boiler (Eclipse, Type Z). This boiler was rated
at 173 Ib steam/hour with a maximum operating pressure of 150 psig.
Boiler feed water was filtered using cartridges and softened using ion ex-
change (Culligan Mark 5 Model CF-28-40).
20
-------
PHASE
1
II
II
l&ll
III
III
TEST
LOOP
1
2
3
BOILER
1971
JAN
FEB
I I
MAR
I I
APR
1 |
MAY
ACTIVATED SLUDGE SYSTEM
JUNE
|
JULY
|
AUG
|
SEPT
| |
OCT
|
NOV
NITRIFICATION SYSTEM
DENITRIFICATION SYSTEM
FILTRATION^ACTIVATED FILTRATION & ACTIVATED CARBON
ACTIVATED SLUDGE EFFLUENT ^EFf?'
T
DENITRIFIED EFFLUENT
CHEMICAL TREATMENT SYSTEM (LIME)
REATME
FILTRATION & ACTIVATED CARBON
CHEMICAL TREATMENT EFFLUENT
ENT PLA
NT OPE
RATION
CANAL WATER
ACTIVATED SLUDGE EFFLUENT ^EFF""'
ACTIVATED SLUDGE w-i.pj.Ar
& FILTRATION IN-I-I-I-W,
SCHEDl
JLE
CANAL WATER _ iC 1
& Cl C +F I
DENITRIFIED EFFLUENT C+F+AC
DENITRIFICATION C+F+
& FILTRATION AC+CI
CANAL WATER PLANT STEAM CANAL PLANT D+F+AC PLANT STEAM
INDUSTRIAL TEST LOOP OPERATION SCHEDULE
1
LEGEND: NITRIF
Cl CORROSION INHIBITOR EFF.
C CHEMICAL TREATMENT (LIME) AC
F FILTRATION N
D
I I
I I I
_LJ_
1 1
_L_LJ
_L
NITRIFIED EFFLUENT
ACTIVATED CARBON
NITRIFICATION
DENITRIFICATION
m
1 I 1
J_
J_
Figure 3-3. Pilot-Demonstration Plant Operating Schedule
21
-------
OPERATING PROGRAM
Operation of the pilot facilities was divided into three phases. In addition
to process evaluation, the major purpose of the experimental program was
to test the use of the various renovated product waters in the industrial test
loops. Activated sludge, nitrification-denitrification, and physical-
chemical treatment processes were tested and evaluated, in Phases I
through III, as discussed below. Figure 3-3 summarizes the operating
schedule for the entire period of the pilot plant study. The upper portion
of the figure refers to the operation of the treatment plants and the lower
portion refers to the periods when treated wastewaters were fed to the
industrial test loops.
Phase I
The treatment system adopted during Phase I consisted of activated
sludge, filtration, and activated carbon adsorption, as shown by the
solid line in Figure 2-1. The operation extended from January 6, 1971,
through May 18, 1971. On May 3, 1971, effluent from the activated sludge
process was used to start the second-stage biological (nitrification)
culture. At the same time, the detention time in the activated sludge
aeration basin was reduced by approximately one-half. The test loop
operation started on January 20, 1971, with Loop 1 receiving the
Contra Costa Canal water, Loop 2 receiving activated sludge effluent,
and Loop 3 receiving filtered activated sludge effluent. The canal
water was also used for boiler feed after it was treated with cartridge
filters and softened by zeolite resin.
22
-------
Phase II
During the operation of Phase II, the CCCSD activated sludge effluent
was used as the influent to the pilot plant facilities (dotted line Figure
2-1). The Phase I activated sludge basin was used for the biological
nitrification basin, and the denitrification reaction was carried out in
the basin that was used for nitrification during Phase I. Nitrified
effluent from the Phase II treatment system was filtered and treated
with activated carbon from May 20 through June 30, 1971. From July 1
until November 4, 1971, the filters and activated carbon units were used
for treatment of the denitrified effluent.
Chemical addition for phosphate removal was investigated during this
phase. The denitrification reactor was dosed with ferric chloride from
June 16 through September 2, 1971 and with alum from September 3
through October 26, 1971. In addition, during the week of September 20,
polymer was added to the influent of the denitrification sedimentation
basin.
During this phase, Loop 1 continued to receive Contra Costa Canal
water and, until June 30, Loops 2 and 3 received nitrified effluent be-
fore filtration and after carbon adsorption, respectively. On July 1
and until October 29, Loops 2 and 3 received the denitrified effluent
before and after filtration, respectively. The boiler continued opera-
tion as in Phase I until June 15, at which time CCCSD plant service
steam was used in the industrial test loops. From July 15 through
August 15, denitrified effluent after carbon adsorption was used as the
boiler feedwater. The 15-psi CCCSD plant, service steam was utilized
during the remainder of the project.
23
-------
Phase III
An evaluation of the physical-chemical treatment system was made ,
from March 15 through November 23, 1971. After approximately 10
minutes of sedimentation, the partially settled raw wastewater was
flocculated with lime at a pH value of approximately 11.0 and recarbon-
ated to pH 9 to 9. 5. The calcium carbonate formed after recarbonation
was flocculated with approximately 30 to 40 mg/1 of ferric chloride to
improve floe formation before final sedimentation. During the period
from October 29 through November 23, the industrial test loops were
used to investigate effluents from the physical-chemical treatment system.
The filtered effluent from the two-stage chemical treatment plant was fed
directly to Loop 1, whereas Loops 2 and 3 received the filtered water
that had the additional benefit of treatment with activated, carbon. An
average of about 25.0 mg/1 of zinc-chromate (Nalco 370) was added to
the influent water of Loop 3 to determine its impact on any fouling or
corrosion that might develop.
SAMPLING AND ANALYSIS PROGRAM
A sample collection and analysis program was established to monitor
the performance of the pilot facilities. Descriptions of the laboratory
facilities, sampling program, and analytical methods are presented below.
Laboratory Facilities
A trailer laboratory located at the pilot plant site served as the center
for the sample preparation and analysis. The CCCSD Laboratory and
Bechtel Environmental Laboratory at Belmont were used for special
analyses such as fish toxicity studies and algae growth tests. The trailer
laboratory was equipped to handle the routine analyses.
24
-------
Sampling Program
Samples were collected at several points in the treatment system during
each phase of the pilot plant studies, as indicated in Figure 3-4. The
composited samples were collected daily and were analyzed for specific
constituents on a daily basis. Additional analyses were performed
either three times a week or weekly. Appendix A summarizes the
sampling frequencies. Automatic samplers, which collected approxi-
mately 250 ml of sample each hour, were generally used to provide the
daily composited sample for all analyses except for mixed-liquor solids
in the biological units. The latter samples were daily "grab" samples
since the concentration of these solids did not greatly change during a
24-hour period.
Because of clogging problems encountered with the automatic samplers
handling the influent raw waste to the physical-chemical pilot plant,
samples were taken manually every 8 hours and composited for analyses
for this particular stream.
Analytical Procedures
Analytical methods used in the program generally followed References 2,
3, and 4 (the 12th Edition of Standard Methods and ASTM procedures).
Table 3-1 summarizes the methods used and the source references for
the procedures. Some modification of certain methods was necessary
to assure thorough analytical coverage. Appendix A gives a detailed
description of the procedures and instrumental methods used in this study
that are not available in the 12th Edition of Standard Methods. Rigorous
sample preparation techniques stressing acid digestion and blending were
developed for the heavy metal analyses.
25
-------
PRIMARY EFFLUENT
(PHASE II OR ACTIVATED
SLUDGE EFFLUENT
[PHASE III -
PILOT PLANTS
CHEMICAL
FEEDER
BIOLOGICAL
STAGE V
AIR
RETURN SLUDGE
BIOLOGICAL DENITRIFICATION
T i
s
RETURN SLUDGE |
A
'SEDIMENTATION
CARBON
ADSORPTION
STAGES
CARBON
ADSORPTION
STAGES
RAW '
INFLUENT
PHASE III FLOCCULATION
TEST LOOPS
RENOVATED
WATER
RENOVATED
PHASE I
PHASE II
PHASE III
SAMPLING POINT
H HEAT
* EXCHANGER
CONDENSATE
Figure 3-4. Sampling Points in the Pilot-Demonstration Facility
26
-------
Table 3-1
ANALYTICAL PROCEDURES
Determination
Method
Reference
Conductivity
pH
Turbidity
Total Solids
Dissolved Solids
Suspended Solids
Biochem Oxy. Dem. (BOD)
Detergents (MBAS)
Carbon Chloroform Extr.
Total Organic Carbon (TOC)
Soluble Organic Carbon (SOC)
Organic Nitrogen
Phenol
Pesticides
Alkalinity
Ammonia
Boron
Calcium
Chloride
Chromium, Hexavalent
Copper
Hardness
Iron
Magnesium
Nitrate
Phosphate, Ortho
Phosphate, Total
Potassium
Silica, Dissolved
Silica, Total
Sodium
Sulfate
Trace Metals (Dissolved)*
Trace Metals (Total)*
Mercury
Selenium
Wheatstone Bridge
Glass Electrode
Photometric
Gravimetric
Gravimetric
Gravimetric
5-day Incubation
Methylene Blue
Direct CHC13 Extr.
Combustion-IR (Sample Unfiltered)
Combustion-IR (Sample Filtered)
Kjeldahl
Colorimetric - Distillation
Electron Capture G/l Chrom.
Titration
Nessler
Cur cumin
EDTA Titration
Mohr
Colorimetric
Cuprethol
EDTA Titration
o - Phenanth r oline
EDTA Titration
Reduction
Colorimetric
Colorimetric
Atomic Absorption
Colorimetric
Emiss, Spectrograph
Atomic Absorption
Gravimetric
Atomic Absorption
Emiss. Spectrograph
Colorimetric
Colorimetric
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
4
3
2
4
4
2
2
*Trace Metals include aluminum, arsenic, barium, boron, cadmium, chromium (tot;
chromium (hex. ), cobalt, copper, iron, lead, lithium, manganese, mercury, molyb-
denum, nickel, silver, strontium, tin, titanium, vanadium, zinc, and zirconium.
27
-------
Section IV
RESULTS OF WASTEWATER TREATMENT STUDIES
The results from Phases I, II, and III of the pilot plant studies at the
CCCSD treatment plant are presented and evaluated in this Section. A
description of the experimental results from the industrial test loops is
presented in the following section.
PHASE I: BIOLOGICAL-PHYSICAL TREATMENT SYSTEM
The biological treatment system was operated initially as a conventional
activated sludge plant and later as a multistage plant for biological
nitrification and denitrification (Figure 2-1). Physical treatment con-
sisted of filtration through dual or mixed-media filters followed by activa
ted carbon adsorption. At different times during the study, the effluent
from the various biological-physical process steps was conveyed to the
industrial test loops for evaluation of its suitability for industrial use.
Pilot Plant Activated Sludge
The activated sludge process was in operation from January 6 through
May 18, 1971. Figure 4-1 indicates the flow and general characteris-
tics of the activated sludge system. The mixed-liquor suspended-solids
concentration during the first month was approximately 2000 mg/1 and
then increased to a steady-state concentration of about 3000 mg/1 during
the remaining periods. The volatile suspended solids (VSS) in the
mixed liquor averaged 80 percent, whereas the sludge volume index
(SVI) averaged 250 ml/gm during the test period.
29
-------
The net growth rate in the system, defined as the mass of solids pro-
duced per unit time per unit mass of solids in the reactor, was quite
variable during the first part of January and then remained at a steady-
state value of approximately 0. 04 day dujring the latter part of
January and February (Figure 4-1). Although the net growth rate was
relatively low for activated sludge (typical values are 0. 05 to 0. Z day )
during this period, the degree of nitrification was also low, as indicated
by the influent and effluent ammonia concentrations shown in Figure 4-2.
This is believed to have resulted from the 0. 5 mg/1 minimum DO con-
centration maintained in the activated sludge mixed liquor.
NET GROWTH RATE
SUBSTRATE REMOVAL RATE
o8
- >
60
40
0
%vs§__~^_^-v-
' MLSS
. ."'
%A_
'"' '"-''' " '" '-....
L. _^-
*~"
JAN
FEB
MAR
1971
APR
Figure 4-1.
Activated Sludge Process
Operating Characteristics
30
-------
As indicated in Figure 4-2, the activated sludge influent ammonia con-
centration was usually between 20 and 30 mg N/l. Some nitrification
did occur in the activated sludge unit as indicated by the increase in
nitra'te-N during January and again in March. However, this single-
stage system was not consistently nitrifying, and thus rather high efflu-
ent ammonia concentrations were observed for a significant amount of
the time. During the latter part of March and early April, the DO was
increased to 2. 0 mg/1 and the effluent ammonia-N concentration was very
low. However, the concentration increased somewhat by early April
and remained at approximately 10 mg/1 N thereafter. The data plotted
in Figure 4-2 suggest that by maintaining a DO of about 2. 0 mg/1, in
Su "°
§ S 30
h- ? M
2 10
0
120
2 > 100
O E
5 § 80
a. 60
-------
conjunction with a net growth rate of about 0. 1 days (Figure 4-1), it
is possible to obtain consistently a 50 percent reduction in the influent
ammonia-N concentration with the activated sludge process.
The effluent suspended solids concentrations were found to be quite
variable, primarily because of floating materials in the secondary sedi-
mentation tanks. These materials did not appear to be typical floating
activated sludge. Instead, the materials appeared to consist of small
globules with attached activated sludge floe and filimentous organisms.
This problem indicated the need for permanent skimming equipment on
the secondary sedimentation tanks. The influent suspended solids aver-
aged 80 mg/1 and the effluent 33 mg/1 during this testing period.
The activated sludge influent TOC concentration averaged about 80 mg/1
with a minimum of 55 mg/1 and a maximum of 130 mg/1 (Figure 4-2).
While the SOC concentrations in the activated sludge effluent were nearly
constant at about 9 mg/1, the effluent TOC varied in relationship to the
effluent suspended solids and averaged about 26 mg/1.
In May, the loading on the activated sludge system was increased by block-
ing off a portion of the aeration basin volume. The effluent was then split
with one stream going to the filtration and activated carbon systems and
the other stream to a separate nitrification basin. A nitrifying culture
had been established a few weeks earlier.
The activated sludge and nitrification proces s data for this operating period
are summarized in Table 4-1. The degree of nitrification obtained during
this short period of time indeed suggested that multistage biological treat-
ment had much greater potential of nitrification than a single-stage biologi-
cal process. The pilot plant operation was thus modified to a three-stage
system to provide carbonaceous BOD removal in the first stage, nitrifica-
tion in the second stage, and denitrification in the third stage, as des-
cribed in Section 3 for the Phase II operation.
32
-------
Table 4-1
PRELIMINARY ACTIVATED SLUDGE/NITRIFICATION DATA
Flow, gpm
Activated Sludge
Influent
SS, mg/1
TOC, mg C/l
SOC, mg C/l
Ammonia, mg N/l
MLSS, mg/1
Effluent
SS, mg/1
TOC, mg C/l
SOC, mg C/l
Ammonia, mg N/l
Nitrate, mg N/l
Nitrification Effluent
TOC, mg C/l
SOC, mg C/l
Ammonia, mg N/l
Nitrate, mg N/l
May
10,
1971
16
163
102
22
21
1840
12. 8
16
9.5
13
3
4
23
May
12,
1971
16
128
82. 5
20. 3
26
1750
120 6
20
11.6
20
4
15
7.2
0. 6
24
May
13,
1971
16
148
'92
20
20
1980
62. 5
35
7.0
11
8
17
5. 3
1. 5
30
May
14,
1971
16
118
80
16
23
2180
51.0
29
6,2
9
9
11
4.6
0.6
31
May
17,
1971
16
77
64
16
29
1930
35.6
33
24
24
2
13
5
8
23
May
18,
1971
9. 3
2230
10
4.8
5
21
33
-------
Filtration
Effluent from the biological treatment processes generally contained 10 to
30 mg/1 of suspended solids. These solids contributed significantly to the
effluent total organic content. Filtration of this effluent can, however, in-
crease the plant reliability and result in a much more consistent effluent
quality. Figure 4-3 summarizes the influent and effluent TOG and turbidity
data for the three types of filter media investigated during this study at a
filtration rate of 5. 0 gpm/sq ft. The TOG concentration of the filtered ef-
fluent approached that of the SOC (10 to 20 mg/1), indicating that the filters
were removing most of the suspended organic material. The filtered ef-
fluent turbidity was generally less than Z JTU, and it was much better in
quality than the unfiltered activated sludge effluent.
Z
O
m
DC
O S
Z^
< ?
O *-
QC
O
H
Q
m
o:
D
I-
50
40
30
20
10
0
40
30
20
10
0
INFLUENT TOC
EFFLUENT TOG
FILTER IN OPERATION
^INFLUENT
EFFLUENT
JAN
FEB
MAR
APR
Figure 4-3. Filtration Data Using Activated
Sludge Process Effluent
The average percent removals of TOC and turbidity are summarized
in Table 4-2. The removals observed indicate very small difference
in the three types of filter media tested. Filter No. 3, the mixed media,
appeared to have somewhat higher removal efficiencies than Filter Nos.
1 and 2. However, the influent TOC and turbidity concentrations to
34
-------
Table 4-2
SUMMARY OF FILTRATION PERFORMANCE USING
ACTIVATED SLUDGE PROCESS EFFLUENT
Filter
No. 1 (Dual Media)
20 Percent Sand
80 Percent Anthracite
No. 2 (Dual Media)
45 Percent Sand
55 Percent Anthracite
No. 3 (Mixed Media)
25 Percent Garnet
30 Percent Sand
45 Percent Anthracite
Average Percent Removal
TOC
35
39
50
Turbidity
JTU
75
73
79
Filter No. 3 during the testing period were generally higher than for
Filter Nos. 1 and 2. Thus, one would anticipate somewhat higher re-
movals. The cycle time between backwashings for a 20 psi pressure
drop was approximately the same for Filter Nos. 1 and 3, with shorter
times observed for Filter No. 2. For an influent suspended solids
concentration of about 100 mg/1, the time between backwashings was
only one to three hours. At an influent suspended solids concentrations
of about 40 mg/1, filter runs were 10 to 15 hours, and, with an in-
fluent suspended solids of 10 mg/1, filter runs of approximately 30 hours
were observed. Based on this information, normal filter runs for a
typical plant may be in the range of 12 to 24 hours. However, during
periods of relatively high solids in the filter influent (i.e., approxi-
mately 50 mg/1), filter runs as low as four hours may be expected.
35
-------
Although the filtration process generally worked satisfactorily, prob-
lems were encountered with biological growth in the filter media. This
growth resulted in what appeared to be channeling through the filter
along with excessive head losses. Extended backwashing and the addi-
tion of heavy doses of chlorine did not eliminate the problem, and, con-
sequently, the filter media were replaced. As a result, facilities were
installed to chlorinate the feedwater to the filtration process. This proce-
dure eliminated biological growth problems. Approximately 5 mg/1 of
chlorine was fed into the water before filtration, resulting in a post-
filtration residual of approximately 0. 5 mg/1 Cl_. Based on these ob-
Lf
servations, the ability to chlorinate the filter influent in a full-scale
filter plant would be advantageous.
Activated Carbon
Two identical activated carbon columns were operated in series to treat
the filtered effluent from the activated sludge units from January 6
through May 25, 1971. The empty-bed contact time for each column,
calculated from the total bed volume and the volumetric flow rate, was
about 11 minutes. Backwashing every four or five days at about 6.5
gpm/sq ft was required to keep the head loss below 10 psi. Figure 4-4
indicates the TOC and SOC concentrations for the first-stage influent
and effluent and the second-stage effluent. The average activated car-
bon influent TOC was about 14 mg/1, while the activated carbon effluent
TOC averaged about 8 mg/1. The data plotted in Figure 4-4 indicate
that the first stage of the activated carbon system was removing the
bulk of the material during most of the treatment period. The higher
TOC removals observed in the first stage can be attributed partly to
the filtration of suspended materials remaining in the filtered influent
feed.
By May, the removal efficiency of the first stage in the activated carbon
process had decreased significantly. Its effluent concentrations of TOC
36
-------
INFLUENT - tft STAGE
EFFLUENT- t« STAGE
EFFLUENT - 2nd STAGE
700 800 900 1000
CUMULATIVE VOLUME TREATED - lOOO'i gal
1100 1200
1500 1600
JANUARY 6 - MAY 17 ACTIVATED SLUDGE EFFLUENT
MAY 18-MAY 26 NITRIFIED EFFLUENT
INFLUENT- 1ft STAGE
EFFLUENT- 1st STAGE
EFF LUENT - 2nd STAGE
700 BOO 900 1000
CUMULATIVE VOLUME TREATED - loco's gal
1300 1400 1500 1600
Figure 4-4. Performance Data of Activated Carbon Treatment of
Activated Sludge and Nitrification Process Effluents
-------
and SOC were nearly the same as the influent concentrations. On.May
25, 1971, the first-stage column was replaced with fresh carbon and re-
installed as the second stage of treatment.
Approximately 1.7 x 10 gallons of filtered activated sludge effluent
were treated by activated carbon before the first stage approached ex-
haustion. At this point, the activated carbon removed O.cl7 Ib TOC/
Ib activated carbon in the first stage. Based on an influent TOC con-
centration of 14 mg/1, a 60 percent removal, and a removal of 0. 17
Ib TOC/lb carbon, approximately 410 Ib of activated carbon would
be required for each million gallons of water treated.
Average performance data for the carbon units are summarized in
Table 4-3. The first-stage carbon unit removed approximately 40
Table 4-3
SUMMARY OF ACTIVATED CARBON PERFORMANCE DATA DURING
TREATMENT OF FILTERED ACTIVATED SLUDGE EFFLUENT
.Item
Average Influent mg/1
Average Effluent mg/1
Total Pounds Applied Ibs
Total Pounds Removed Ibs
Ibs OC removed
Ibs act. carbon
Average Removal percent
Average Flow gpm/sq ft
Total Throughput Volume gal
Average Empty Bed
Contact Time min
First .Stage
Organic- Carbon
Total
14, 0
8. 3
192
77
0. 17
40
1.4
1.7 x I0(>
11.2
Soluble
8, (i
5.8
120
40
0.07
33
Second Stage
Organ if C;t rbnn
Total [Soluble
8 3
5, 7
1 H.
3(.
0.081-
31
14
17
11.2
T. «
3 (,
81
30
0.068
37
Overall
Carbon Removal
Total 1 Soluble
_._ j
192
111
59
120
I''1.'
5K
*Carbon adsorption was terminated before breakthrough of the activated carbon column.
Operation of the first stage: January 6 - May 25, 1971
Activated carbon bed repacked: May 25, 1971
38
-------
and 33 percent of the influent TOC and SOC, respectively, whereas the
second stage removed 31 and 37 percent of the remaining TOC and SOC.
Removal percentages of the organic carbon were nearly identical in
each stage of carbon treatment, indicating that the organic carbon which
passed through the first stage was readily adsorbed by the second car-
bon column. The combined two-stage activated carbon treatment process
achieved a 59 percent reduction in the organic carbon concentration of
the activated sludge effluent during the five months of operation. These
removals, combined with those resulting from the activated sludge pro-
cess resulted in an overall TOC removal of 93 percent, 82 percent of
which occxirred in the conventional activated sludge stage. Although
the activated carbon treatment removed almost 60 percent of the organ-
ic carbon in the activated sludge effluent, this only amounted to about
7. 5 percent of the TOC in the raw wastewater. This small but significant
increase in effluent quality resulted in an appreciable increase in the
complexity and expense of the treatment process. Thus, in cases where
biological systems are able to operate at high efficiencies, it may not
be necessary to utilize activated carbon treatment unless very high quality
effluents are required.
PHASE II: BIOLOGICAL NITRIFICATION-DENITRIFICATION
Phase II of this study started on May 20, 1971, at which time activated
sludge effluent from the CCCSD 1 -mgd plant was used as the influent to
the pilot plant nitrification reactor. The average influent flow rate into
the treatment process was approximately 17 gpm, resulting in a four-
hour detention time in the nitrification basin followed by two hours of
sedimentation. The settled nitrified effluent was then fed into a hydrau-
lically mixed reactor where methanol was added in a 3:1 methanol:
nitrate-N weight ratio for biological denitrification under anaerobic
39
-------
conditions. Flow in this basin averaged 10 gprn initially for a deten-
tion time of about three hours and a settling time of two and a half hours.
This overall operation resulted in a three-stage biological system which
provided carbonaceous BOD removal in the activated sludge, ammonia
oxidation in the nitrification basin, and nitrate removal in the denitrifi-
cation basin.
The main emphasis during this phase of the work was on the nitrifica-
tion and denitrification studies. However, additional investigations
were conducted using the physical treatment processes of filtration
and activated carbon adsorption. Nitrified effluent was fed to the
filtration and activated carbon units from May 20 until June 30. From
July 1 until project complation on November 4, the denitrified efflu-
ent was filtrated and treated with activated carbon.
Nitrification
The influent and effluent ammonia concentrations, nitrification mixed
liquor suspended solids (ML.SS) concentrations, and the ammonia re-
moval rates are presented in Figure 4-5.
The ammonia content in the nitrification process influent was usually 10
to ZO mg/1; however, at times, lower ammonia values were observed.
These lower values resulted from varying degrees of nitrification occur-
ring in the activated sludge stage preceding the nitrification stage. Often,
the ammonia concentration in the nitrification-stage effluent was less
than 1 mg N/l. Ammonia concentrations greater than this value gener-
ally corresponded to periods when the MLSS in the nitrification reactor
were significantly reduced in concentration.
40
-------
INFLUENT
z
01
I
Z
o
20
10
0
-5
EFFLUENT
2,000 -
1,000 -
MAY
JUN
JUL
AUG
SEP
OCT
NOV
Figure 4-5, Nitrification Proces s Data
41
-------
During about the first three months of operation of the nitrification
stage, as shown in Figure 4-5, the MLSS concentration was quite
variable. The sudden increases in MLSS resulted from the addition
of settled activated sludge solids from the activated sludge mixed
liquor. Following each addition of solids, however, the nitrification
MLSS decreased with time until the nitrification efficiency decreased,
and, consequently, the effluent ammonia concentration increased.
During the latter three months of operation, activated sludge solids
were added to the nitrification reactor at more frequent intervals so
that the MLSS did not decrease below about 500 to 1000 mg/1. The
effluent ammonia concentrations observed during this period were
consistently quite low. However, in October, the effluent ammonia
concentrations increased to values around 10 mg/1. For about one
week prior to this period, the influent ammonia concentrations to
the nitrification stage were quite low since the ammonia was being
oxidized in the activated sludge stage. It is possible that because
of the low influent ammonia, the viability of the nitrifying culture
decreased resulting in the reduction of nitrification efficiency.
The ammonia removal rates, expressed as the mass of ammonia re-
moved per unit time per unit mass of suspended solids in the nitrifica-
tion reactor (Figure 4-5), were initially quite variable as a result of
the changing MLSS concentrations. These rates, however, were more
stable during the latter two months of operation. The data indicate
that, with an ammonia removal rate of 0.05 mg NH -N/mg MLSS-day,
a MLSS of 3000 mg/1, and 20 mg/1 of ammonia oxidized, a detention
time of 3. 2 hours would be required in the nitrification reactor. It
should be noted that this ammonia removal rate is based on pH values
42
-------
of about 7. 0. If somewhat higher pH values of around 8. 0 to 8. 5 could
be maintained in the nitrification reactor, then a higher ammonia re-
moval rate would be expected, providing the potential of reducing the
required detention time.
The results obtained during this study suggest that high removal efficien-
cies of organic materials and suspended solids in the first biological
stage preceding the nitrification stage are not required, and indeed are
not desireable. If relatively high removal efficiencies are obtained in
the first biological stage, then, at times, some nitrification may occur
which could be detrimental to the nitrifying culture in the second stage.
Also, in order to maintain a desireable MLSS concentration in the
nitrification reactor, the data indicate that it is necessary to have some
carbonaceous oxidation in the nitrification reactor in conjunction with
the oxidation of ammonia to nitrate, thus establishing a synergistic
effect between the heterotrophic and autotrophic microorganisms.
The average and range of suspended solids observed monthly in the
CCCSD 1-mgd activated sludge effluent and the effluents from the pilot
plant nitrification and denitrification stages are summarized in Table 4-4.
The TOC and SOC concentrations for these effluents are illustrated in
Figure 4-6. Suspended solids in the activated sludge effluent averaged
9 mg/1 less than observed in the nitrified effluent. The decrease in nitri-
fied MLSS discussed earlier can be largely attributed to this increase in
solids concentration.
In the denitrified effluent, the suspended solids averaged approximately
ZO mg/1 higher than the nitrified effluent. This increase resulted from
problems encountered with the denitrification stage MLSS floating in the
sedimentation tank. At times, a layer of solids several inches thick would
accumulate on the surface of the sedimentation tank. The floating nature
of these solids is discussed in more detail later.
43
-------
55
50
45
-40
OJ
~~ ACTIVATED SLUDGE EFFLUENT
NITRIFICATION EFFLUENT
DENITRIFICATION EFFLUENT
35
30
03
20
15
10
i i i
j i
25
E
I 20
z
O
CO
QC
< 15
o
o
§10
(T
O
ao
D
O
CO
ACTIVATED SLUDGE EFFLUENT
NITRIFICATION EFFLUENT
DENITRIFICATION EFFLUENT
Jii 1 1i I i i i
MAY
JUN
JUL
AUG
SEPT
OCT
1971
Figure 4-6. Nitrification-Denitrification Process Data
44
-------
Table 4-4
AVERAGE MONTHLY SUSPENDED SOLIDS CONCENTRATIONS
OF THE BIOLOGICAL EFFLUENTS (mg/1)
Month
June
July
August
September
October
Average
Activated Sludge '
Average
10
7
6
14
29
14
Range
8-13
2-10
2-12
4-50
6-87
Nitrification
Average
34
23
18
19
25
23
Range
22-42
12-50
8-26
11-37
8-56
Denitrification
Average
45
35
25
56
61
42
Range
30-70
21-62
5-37
33-95
13-116
CCCSD 1 mgd plant
Effluent TOC concentrations, as shown in Figure 4-6, averaged 14 mg/1
in the activated sludge effluent and 15 mg/1 in the nitrified effluent. In
the denitrified effluent, the TOC averaged 20 mg/1 with this higher value,
compared to the nitrified effluent, resulting primarily from the loss of
floating solids mentioned above.
The SOC concentrations shown in Figure 4-6 for the activated sludge and
nitrification-stage effluents indicate slightly lower values for the latter.
Generally, the denitrified effluent SOC concentration was nearly the
same as the nitrified effluent except for three peak concentrations.
These peaks probably resulted from the methyl alcohol which was not
completely metabolized in the denitrification reactor.
45
-------
De nitrification
Nitrate removal rates expressed as the mass of nitrate-nitrogen re-
moved per unit time per unit mass of suspended solids in the denitrifi-
cation reactor, influent and effluent nitrate-nitrogen concentrations,
and denitrification MLSS concentrations are presented in Figure 4-7.
The nitrate removal rates were quite variable during the first two
months of operation, but, during the latter three months, the rates
were more stable. The removal rates were quite high during the
month of July, primarily as a result of low concentrations of MLSS
(Figure 4-7). Very good removals were observed at rates up to about
0. 15 mg nitrate removed/mg MLSS-day, indicating that the detention
time in the denitrification reactor could be as low as approximately
one hour. The residence time in the denitrification reactor may, how-
ever, need to be longer in order to assure that sufficient time is avail-
able for the denitrification reaction to be completed, thus minimizing
any additional denitrification in the final sedimentation tank.
During the pilot plant denitrification studies, problems were encounter-
ed with poor settling of the denitrification MLSS. Apparently, either the
denitrifying organisms were continuing to produce nitrogen gas in the
sedimentation basins or the suspended solids from the denitrification
basin were carrying entrained nitrogen gas bubbles into the sedimen-r
tation basin, thereby buoying up the settled solids and causing them to
float on the surface of the sedimentation tank. The inlet to the sedimen-
tation tank was modified so the mixed liquor would be exposed
46
-------
0.7
0.6
0.5
0.4
0.3
i
0.2
0.1
0
40
! 30
I
gE 20
uu
o
-.868
10
<
H
Z
4000
t/J
Q
Q
LLI
Q
Z
LU
Q.
2000
1000
.801
0 I ' ' I I i iI I IIl_lIII 1IIL
MAY JUN JUL AUG
I i i i i i I i i i | i I
SEP OCT NOV
Figure 4-7. Denitrification Process Data
47
-------
to atmospheric pressure for a short time before entering the settling
zone. This modification was employed to release the nitrogen gas en-
trapped in the biological floe. Some reduction in suspended solids losses
was achieved by this technique, but the problem was not eliminated. Air
agitation for 3 to 5 minutes in the center of the sedimentation tank inlet
was also tested as a means of stripping out excess nitrogen gas and meth-
anol and to provide a residual DO in the sedimentation tank. Since there
was no apparent improvement in the effluent quality, this procedure
was discontinued. Recent information, from the EPA District of Colum-
bia pilot plant, indicates that aeration of the mixed liquor for about 30
minutes prior to settling reduces the solids separation problems and, at
the same time, reduces the excess methanol carried over from the deni-
trification reaction. Similarly, results obtained from the CCCSD plant,
which was modified to further investigate the problems with denitrifica-
tion discussed above at a scale of about 0. 5 mgd, indicate that aeration oi
the denitrification mixed liquor for approximately one hour prior to sedi-
mentation significantly improves solids separation and effluent quality.
The effluent nitrate concentrations, as shown in Figure 4-7, were quite
variable. However, the rather high nitrate concentrations observed dur-
ing part of July resulted from problems encountered with the methanol
feed pump. The effluent nitrate increases observed in August and the
first part of September are believed to have resulted from the ferric
chloride additions being made to the denitrification reactor during this
time, which caused a decrease in the pH of the mixed liquor. When all
plant functions were properly operating and the denitrification MLSS con-
centration was sufficiently high, effluent nitrate-nitrogen concentrations
of 1 mg/1 or less could be maintained.
Although the denitrification results obtained during this study generally
placed doubt on the adequacy of this process, enough good results were
48
-------
obtained to indicate that, with additional time and development, the pro-
cess can be made to perform satisfactorily. The results from the EPA
District of Columbia pilot plant and the CCCSD "Advanced Treatment
Test Facility, " reported after the data in this report were obtained, illus
trate that the denitrification process can be designed to perform satis-
factorily. Perhaps the most significant finding in these more recent in-
vestigations was the required aeration of the denitrification MLSS for
30 to 60 minutes prior to final sedimentation.
Phosphorus Removal
Ferric chloride and alum were added during different periods of time
to the denitrification system to observe the effect on phosphorus re-
moval. Table 4-5 is a summary of the results.
Ferric chloride was added in three different ratios of iron to phos-
phorus. Removals of phosphorus for Fe/P weight ratios of 1.9 and
5.6 were 57 percent and 63 percent, respectively. Results during
the testing period from June 16 to June 24 indicated only 43 percent
phosphorus removal at an Fe/P ratio of 2. 5. This lower removal re-
sulted in part from problems encountered with the chemical feeding
system. Also, the addition of ferric chloride periodically reduced
the pH of the denitrification MLSS to the extent that the denitrifica-
tion reaction was inhibited.
Alum additions during periods in September and October were main-
tained at an aluminum-to-phosphorus weight ratio of about 1. 2 to
1.3. These ratios resulted in average phosphorus removals of 52
percent across the denitrification system. Based on these results,
it appears that alum would be preferred over ferric chloride for the
49
-------
removal of phosphorus in combination with biological treatment. How-
ever, to obtain a high degree of removal, multiple addition points
would be required.
Table 4-5
PHOSPHOROUS REMOVAL USING FERRIC
AND ALUMINUM ADDITIONS TO THE
DENITRIFICATION SYSTEM
Date
6/16 6/24
7/30 8/20
8/21 - 9/2
9/3 - 9/17
9/20 - 9/27
9/28 - 10/26
Dosage
(Weight Ratio)
Fe/P
2. 5
1.9
5.6
Al/P
1. 2
1. 3
1. 2
Effluent
mg/1 as P
5.2
4. 2
3.6
4.2
4. 2
4.9
Removal
%
43
57
63
55
52
50
50
-------
Filtration
The filtration process data shown in Figure 4-8 for filtration rates of
5. 0 gpm/sq ft indicate that, during the time that nitrified effluent was
being filtered, there was a very good removal of the suspended organic
materials. Effluent turbidities were quite low and showed only minor
variations over the six weeks of operation. Influent turbidities ranged
from Z to 30 JTU, averaging about 14 JTU; whereas effluent turbidities
averaged about Z JTU, for a mean turbidity removal of 85 percent. TOC
removals averaged 70 percent through the filtration process resulting in
an effluent concentration of about 6 to 7 mg/1. Apparently, the effluent
suspended solids in the nitrified effluent formed a strong floe with fil-
terability similar to typical activated sludge floe.
The quality of the filtered, denitrified effluent was considerably more
variable than that of the nitrified effluent. In July and early August,
when the influent turbidity-was relatively low, there was very little
removal of turbidity occurring with Filter No. Z. Removals were
somewhat better in late August and September, when Filter No. 1 was
in operation. This may have been due to the higher solids loading
during this period, since turbidity removals of Filter No. Z appeared
to improve somewhat between August 5 and 15 as the loading increased.
Effluent turbidities from Filter No. 3 appeared to be consistently lower
than observed with Filter Nos. 1 and 2. Table 4-6 summarizes the
average removals for the various filters employed.
The highly variable turbidities of the filter influent attest to the difficul-
ty of attaining consistent solids removals in the denitrification sedimen-
tation tank. The lower quality of the filtered, denitrified effluent may
have been due to the nature of the floe. It appears from the filtration
51
-------
45
40
^ 35
O>
1 30
z
o
m
o: 25
o
^20
10
5
0
NITRIFICATION-*
EFFLUENT
Fl
*« 1
FILTER IN OPERATION
MAY
JUN
JUL
AUG
SEPT
OCT
NOV
Figure 4-8. Filtration Data Using Denitri-
fication Process Effluent
52
-------
Table 4-6
SUMMARY OF FILTRATION PERFORMANCE USING
DENITRIFICATION PROCESS EFFLUENT
Filter
No. 1 (Dual Media)
20 Percent Sand
80 Percent Anthracite
No. 2 (Dual Media)
45 Percent Sand
55 Percent Anthracite
No. 3 (Mixed Media)
25 Percent Garnet
30 Percent Sand
45 Percent Anthracite
Average Percent Removals
TOC
58*
37
27
38
Turbidity
JTU
84*
53
37
61
* Nitrified Effluent
data that this floe was more fragile than that developed in the first two
biological stages. If this is the case, it may be necessary to reduce the
filtration rate when filtering denitrified effluent. Also, aeration of the
denitrification MLSS prior to sedimentation, as discussed earlier, may
improve the filterability; however, this was not studied.
Activated Carbon
The results of the two-stage carbon adsorption studies for the Phase II
pilot plant are shown in Figure 4-9. Nitrified effluent was filtered and
passed through the columns from May 20 until June 30, 1971. From July
1 until November 4, the denitrified effluent was used as the influent to
the activated carbon adsorption system. The 1.7 million gallons which
the first-stage carbon column had been exposed to at the start of the study
53
-------
NITRIFIED EFFl UENT
DENITRIFIED EFFLUENT
2300 0 100 200
CUMULATIVE VOLUME TREATED - lOOCTsgal
Figure 4-9. Performance Data of Activated Carbon Treatment of
Nitrification and Denitrification Process Effluents
-------
represents the amount of water treated during Phase I, when this column
acted as the second-stage for the activated sludge effluent. The new
second-stage column was freshly repacked activated carbon.
The TOG concentration in the first-stage effluent as shown in Figure 4-9
was generally Z to 4 mg/1 less than the influent TOG, representing about
a 30 percent reduction in the TOG concentration. The very high TOG con-
centrations resulting when the denitrified effluents was fed to the carbon
columns were due to suspended solids from the denitrification process.
However,, these materials were effectively removed in the carbon column.
The second stage of the activated carbon system was operating more ef-
fectively than the first during this period, as is evident from Figure 4-9,
This column was generally removing 3 to 5 mg/1 of TOG, or about 50 per-
cent of the influent TOG.
SOC concentrations in the activated carbon influent were usually between
5 and 10 mg/1, while the second-stage effluent was generally between 1
and 2 mg/1. This reduction represented approximately 80 percent re-
moval of the SOC through the activated carbon process.
During much of July and early August, the organic carbon content of the
first-stage effluent was nearly the same as. the influent. On August 17, the
first-stage was removed from service after treating approximately 2. 2 miL
lion gallons, repacked with fresh activated carbon and reinserted as the
second stage of the carbon treatment system. The former second stage
was installed as the first stage. (Note in Figure 4-9 the discontinuity
in the abscissa on August 17, when the treated volume of the first stage
changes from 2.2 million gallons to about 500,000 gallons, signifying the
interchange of columns). Removal efficiencies improved appreciably.
Except for two high TOC concentrations in the first-stage effluent in late
September, each column appeared to remove about the same amount of
TOC and SOC, resulting in a treated effluent having a TOC concentration
of 2 to 3 mg/1.
55
-------
The activated carbon adsorptive capacity was determined from, the time
freah carbon was initially contacted with the influent until the time the car-
bon was exhausted. This was done by calculating the masses of TOC and
SOC removed and relating them to the mass of activated carbon contacted.
A summary of the data is shown in Table 4-7 for the period between January
6 and August 16, 1971. The average removal efficiency during this period
was 30 percent and the average carbon loading, through exhaustion, was
0. 11 Ib total organic carbon removed per pound of activated carbon.
Also shown in Table 4-7 are performance data for the activated carbon
column that served as the second stage in the process from May 26 to
August 17 and then the first stage from August 17 through October 31, 1971.
The data, as shown in Figure 4-9, indicate that this carbon column was not
completely exhausted through the end of October. The average TOC re-
moval efficiency for this column was 50 percent and the carbon loading
was 0. 13 Ib TOC removed per pound of activated carbon. Since the carbon
"was not exhausted, this removal efficiency was greater than observed with
the column operated between January 6 and August 16. However, the car-
bon loading on the column operated from May 26 through October 31, with-
out being exhausted, was actually higher than that of the previous observa-
tions. This difference in carbon loading was due to the differences in the
influent suspended TOC concentrations. The activated sludge and nitri-
fication proces s effluents, which were readily filtered, resulted in lower
TOC concentrations than the denitrification process effluent.
TOC removals in the activated carbon columns generally ranged between
6 and 12 mg/1. Based on an average TOC concentration of about 80 mg/1
in the treatment plant influent, the activated carbon system removed only
56
-------
Table 4-7
SUMMARY OF ACTIVATED CARBON PERFORMANCE DATA
DURING TREATMENT OF THE FILTERED NITRIFICATION
AND DENITRIFICATION PROCESS EFFLUENTS
Jan 6 - Aug 16, 1971
Total Applied
Total Removed
Average Removal
Carbon Loading
.Average Flow
Detention Time
May 26 - Oct 31, 1971
Total Applied
Total Removed
Average Removal
Carbon Loading
Average Flow
Detention Time
Ibs
Ibs
percent
Ibs TOC removed
Ibs act. carbon
gpm/sq ft
min
Ibs
Ibs
percent
Ibs TOC removed
Ibs act. carbon
gpm/sq ft
min
Organic Carbon
Total Soluble
166 109
49 36
30 33
0.11 0.08
0. 7
27
112 63
56 38
50 60
0.13 0.086
0.9
21
57
-------
about 10 percent of the organic materials. Thus, although the activated
carbon treatment resulted in very low effluent organic carbon concentra-
tions, the preceding biological treatment processes were responsible for
the removal of the bulk of the organic materials.
PHASE III: CHEMICAL-PHYSICAL TREATMENT SYSTEM
The two-stage chemical treatment system which began operation in late
April and continued until November consisted of lime coagulation and
settling in the first stage followed by recarbonation and settling of the
calcium carbonate precipitate in the second stage. The effluent from
this treatment process was then filtered and treated with activated
carbon.
Lime Treatment
Preliminary laboratory data were obtained on the chemical treatment of
wastewater to determine the approximate operating pH to use in the pilot
plant studies. As shown in Figure 4-10, apHof 10.5 to 11.0 appeared to
be near the optimum value with regard to minimizing the lime require-
ments and obtaining appreciable reductions in TOC, phosphorus, and tur-
bidity. Approximately 350 to 500 mg/1 of lime (as CaO) were required to
maintain a pH of 10. 5 to 11.0, while only 250 mg/1 of lime were required
to obtain an operating pH of 10. 0.
The lime dosage requirements, and the operating influent and effluent
pH values for the chemical treatment system are shown in Figure 4-11.
The amount of lime used in the chemical process was controlled by a pH
feedback controller to maintain a predetermined pH value. Daily lime
requirements ranged from 200 to 500 mg/1 CaO, averaging about 390 mg/1,
From mid-September until the end of November, the lime dose was about
58
-------
12
11
10
TOC
30 -
25 -
I
20 -
o
URB
60
50
01
40 g
O
O
30 <
O
cc
O
_!
<
20 £
K
10
10
8 _
Q.
6 I
O
5 I
O
X
Q.
200 400 600 800 1000 1200
LIME CONCENTRATION - mg CaO/l
Figure 4-10. Lime Requirements for
Chemical Treatment
450 mg/1, resulting in an operating pH of about 11.0. Initial studies
indicated little difference in the quality of the treated effluent between
flocculation times of 30 and 20 minutes, so the shorter flocculation time
was adopted throughout the study. After recarbonation and second stage
flocculation and sedimentation, the pH of the lime treated effluent was
about 9. 5. It was observed that the dispersed nature of the calcium car-
bonate precipitate formed after recarbonation made it difficult to separate
by gravity settling. The addition of ferric chloride to coagulate the dis-
persed material resulted in better separation, but light flocculant materials
59
-------
were observed in the effluent. By returning a portion of the calcium
carbonate sludge to the second-stage flocculator, the effluent quality
was improved, most likely as a result of improved particle growth.
However, recycling of lime sludge to the first-stage flocculator did not
appear to significantly improve the performance of that stage.
700
600
500
400
SE 300
a
£ 200
UJ
1 100
,st,
1SI STAGE EFFLUENT
RAWWASTEWATER
2^ STAGE EFFLUENT
I I
MAY
JUN
JUL
AUG
SEPT
OCT
NOV
Figure 4-11. Chemical Treatment Plant
Lime Requirements and pH
Values
60
-------
Hardness and Alkalinity
The hardness and alkalinity data for the chemical treatment system are
shown in Figure 4-12. Average influent and effluent data are summarized
in Table 4-8. Generally, the alkalinity of the second stage effluent was
less than in the raw wastewater, its decrease averaged 18 mg/1 as CaCO
or 9. 1 percent. The total hardness of the treated effluent was not signif-
icantly changed. An average increase in hardness of 6 mg/1 as CaCO or
3. 3 percent was observed.
Table 4-8
CHEMICAL TREATMENT AVERAGE HARDNESS
AND ALKALINITY DATA
First Stage Influent, mg/1
Second Stage Effluent, mg/1
Concentration Change, mg/1
Concentration Change (%)
Alkalinity
198
179
18
9. 1
(Decrease)
Hardness
152
158
+ 6
3. 3
(Increase)
Concentrations expressed as CaCO
The increase in hardness most likely resulted from incomplete precipi-
tation of calcium carbonate following the recarbonation step. The typical
chemical reactions associated with water softening were not directly ap-
plicable because of the likely interference of organic materials in the raw
wastewater with the calcium. Improved performance of the chemical
treatment system may have been obtained if sludge recycling was effec-
tively used.
61
-------
350
^300
<3 250
O)
, 200
Z 150
_i
<
j 100
<
50
0
RAW WASTE WATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED EFFLUENT
/r
210
190
150
130
110
90
70
1 WASTEWATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED EFFLUENT
JUN
JUL
AUG
SEPT
OCT
NOV
Figure 4-12. Hardness and Alkalinity of Raw Wastewater and
First-Stage and Second-Stage Chemical Treat-
ment Effluents
62
-------
Suspended Solids
The suspended solids concentrations for the various stages in the chemical
treatment plant are shown in the upper portion of Figure 4-13. Although
the suspended solids concentration in the influent to the first-stage floccu-
lation basin varied from about 100 mg/1 to as high as 350 mg/1, the sus-
pended solids content of the effluent from the second stage of the process
was nearly constant. The variability in the suspended solids content of
the raw wastewater was largely removed in the first stage of the chemi-
cal treatment process. During the 7 months of operation of the chemi-
cal treatment plant, the suspended solids removal averaged 87 percent.
The chemically treated effluent suspended solids ranged from 5 to 40
mg/1, with an average concentration of 19 mg/1.
Phosphorus
The total phosphorus contents of the influent, first-stage effluent, and
second-stage effluent of the chemical treatment plant are shown in the
lower portion of Figure 4-13. The total phosphorus content of the influent
water was generally about 7.4 mg P/l, whereas after the first stage of
lime treatment, the total phosphorus was reduced to an average value of
about 1.6 mg/1. This reduction represented about 80-percent removal
of the total phosphorus content of the raw wastewater. The total phos-
phorus concentration in the effluent from the first-stage flocculation ba-
sin was higher during August due to the decrease in operating pH from
10. 7 to 10.'2 (Figure 4-11).
The phosphorus concentrations in the first-stage effluent were further
reduced in the second stage of the chemical treatment process. Effluent
from the second stage contained approximately 0.4 mg/1 of total phos-
phorus, making the overall phosphorus reduction in the chemical treatment
63
-------
300
250
200
150
Q
01
Q
Z
LU
Q.
C/3
100
RAW WASTEWATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED EFFLUENT
JUN
/ \ ' \ * ^
/ \ ' * A * *
" X A A - / V'
,' ^ ^ ^ AV v V-\/__.
JUL
AUG
SEPT
OCT
NOV
35
30
E 25
I
C/3
i 20
O
O
Q_
O
15
10
RAW WASTEWATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED EFFLUENT
A
x ; \
Figure 4-13. Orthophosphate and Chemical Suspended Solids Re-
moval in the Two-Stage Chemical Treatment Process
process approximately 95 percent. During October and November, when
the pH of the first stage was between 11 and 11. 5, the total phosphorus
concentration of the effluent was generally about 0. 16 mg/1, indicating a
98-percent removal.
Organic Carbon
Figure 4-14 illustrates the TOG contents of the influent wastewater, which
had been settled for about 10 minutes in the CCCSD primary sedimentation
64
-------
140
^120
E
I
Z100
o
00
cc
< 80
o
60
20
RAW WASTE WATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED
EFFLUENT
50
40
30
20
1.0
CO
RAWWASTEWATER
RECARBONATED EFFLUENT
SETTLED RECARBONATED
EFFLUENT
JUN
JUL
AUG
SEPT
OCT
NOV
Figure 4-14. Total and Soluble Organic Carbon Removals
in the Two-Stage Chemical Treatment Process
basin to remove large suspended materials and rags, the first-stage ef-
fluent, and the second-stage effluent of the chemical treatment plant.
The influent TOC varied from a low of 60 mg/1 to a maximum value of
125 mg/1. The average influent TOC was approximately 90 mg/1 dur-
ing this study, whereas the concentration of TOC in the recarbonated
effluent was usually between 25 and 30 mg/1, indicating that nearly
70 percent of the TOC was removed in the chemical treatment process.
65
-------
There was very little change in the SOC concentration as & result of the
chemical treatment, as is apparent from th6 data plotted in the lower
half of Figure 4-14. The SOC concentration in the effluent from the first-
stage flocculation basin was usually greater than that in the influent
water. Apparently, the high pH of the first stage was causing the TOG
to undergo alkaline hydrolysis, converting some particulate organic
carbon to soluble organic material. Some of the SOC was removed during
the second-stage flocculation reaction so there was little or no net in-
crease in SOC, and at times the SOC showed a moderate decrease1 through
the system. Overall, SOC removals averaged about 5. 0 percent for the
7-month operation of the two-stage system.
Filtration
Figure 4-15 summarizes the turbidity data from the influent and effluent
of the filtration process. The settled effluent from the second stage of
the chemical treatment plant was filtered at a rate of 2. 5 gprn/sq ft, and
the filters were backwashed at a rate of 20 gpm/sq ft.
The effluent turbidity from the chemical treatment process was generally
about 5 JTU (Figure 4-15), but there were periods when much higher tur-
bidity resulted. Filtration reduced the average turbidity by about 50 per-
cent, producing a filtered effluent having a turbidity of 2 to 3 JTU. How-
ever, when the turbidity of the filter influent increased substantially above
5 JTU, the filters usually were able to control the turbidity, indicating
that for the most part the chemical floe was readily filterable. The TOC
data shown in Figure 4-15 from the filter influent and effluent indicate
that there was very little removal of TOC in the filters. This was not
surprising since about 70 percent of the TOC was in the soluble form
(SOC). Filter No. 1 appeared to show the best performance during
these tests.
66
-------
25
15
9 10
CQ
CC
FILTER INFLUENT
FILTER EFFLUENT
2 *~
FILT
^ 1
ER IN OPERATION
35
, 30
25
20
15
o
o
cc
o 10
O 5
0
FILTER INFLUENT
FILTER EFFLUENT
JUN
JUL
AUG
SEPT
OCT
NOV
Figure 4-15. Filtration Data Using Chemical Treatment Effluent
67
-------
Activated Carbon
The results of the activated carbon adsorption studies are shown in
Figure 4-16. For the two stages of carbon treatment, the average
empty bed contact time was about 25 minutes per stage with an average
How of 0. 76 gpm/sq ft. Influent TOC concentrations averaged about
24 mg/1, whereas the first-stage effluent averaged about 13 mg/1 and the
second-stage about 11 mg/1. The second stage of carbon treatment
appeared to have little influence on the organic carbon removal, indi-
cating that these materials could not be readily adsorbed with activated
carbon.
In early September, the effluent TOC and SOC from the carbon adsorp-
tion system began to approach the influent concentration, signifying
that the columns were approaching exhaustion. Surprisingly, it was the
second stage which had the greatest effluent concentration at this time,
even though it had only received a very light loading of organic carbon
compared to the first stage. This apparent inefficiency of the second
stage may have been due to anaerobic conditions interfering with the
organic carbon adsorption process. On September 9, the two carbon
columns were interchanged, and the former first-stage carbon column
was repacked and replaced as the second stage. After this interchange,
the TOC and SOC of the effluent generally remained below 10 and 6
mg/1, respectively.
The overall performance of the activated carbon columns is summarized
in Table 4-9, showing approximately 52 and 60 percent removal of TOC
and SOC for the two-stage system. At the time the first stage became
exhausted, 0. 14 Ibs of organic carbon had been removed per pound of
activated carbon, and this occurred after a volume of 640, 000 gallons
had been treated. Based on the observed loading rates for the first stage,
68
-------
INFLUENT - 1st STAGE
EFFLUENT - 1st STAGE
EFFLUENT - 2nd STAGE
|700 [750 [BOO 860 |900 |950 1000 in STAGE
50 100 150 200 260 300 350 2nd STAGE
NOTE
FIRST STAGE REMOVED ON SEPT 7. 1971, REPACKED AND REPLACED
AS NEW STAGE 2. OLD STAGE 2 BECOMES NEW STAGE 1
CUMULATIVE VOLUME TREATED - lOOO'i 93
CUMULATIVE VOLUME TREATED - 1000*1 g«l
llOOO 1st STAGE
360 2nd STAGE
Figure 4-16. Performance Data of Activated Carbon on Chemical
Treatment Process Effluent
-------
it would require about 690 Ib of activated carbon to treat one million
gallons of chemically treated wastewater for the removal of about 50
percent of the influent TOG at a concentration of 24 mg/1.
Table 4-9
AVERAGE PERFORMANCE DATA OF ACTIVATED CARBON
CHEMICAL TREATMENT PROCESS EFFLUENT
Item
Influent Carbon mg/1
F'ffluent Carbon mg/1
Total Applied Ibs
I'otal Removed Ibs
1 b '! OC removed
Ib af t. ea rbon
Avrraur Removal percent
Avorauc Flow gpm/.sq ft
[oial Ihrouuhput Volume gallon*
Average Kmpty Bed
Contact Time minutes
First Stage
Organic Carbon
Total
23.8
12.6
131
62
0. 14
47
0. 76
0. 64 v 10(>
24 5
Soluble
15. 2
7.2
82
43
0. 10
52
. 76
Second Stage
Organic Carbon
Total
12,6"
11.0
69
8
0.019
12
0. 76
0.64 x 10f'
24, 5
Soluble
7. 2
6. 1
40
(,
0. 014
15
0. 76
Overall
Organic Carbon
Total
131
70
52
Soluble
82
49
60
70
-------
One major difficulty that arose during the activated carbon processing of
the chemically treated wastewaters was the noxious odors that were gen-
erated in the carbon columns. Since little or no aeration occurred dur-
ing chemical treatment, the influent to the carbon columns was devoid
of oxygen. As the amount of adsorbed organics increased, bacteria be-
gan to attack these materials, producing odors through putrefaction
(production of hydrogen sulfide). Injection of oxygen and chlorine ahead
of the filters was not sufficient to overcome the anerobic conditions that
had developed in the filters and the carbon columns. It is possible that
if aeration and chlorination had been practiced from the start of the ex-
perimental runs, the anerobic conditions might never have developed.
The use of diffused air aeration ahead of activated carbon treatment
would most likely be impracticable; it would undoubtedly result in con-
siderable foaming due to the high concentrations of MBAS (Methylene
Blue Active Substances, surfactants) that had not been removed by chem-
ical treatment alone. Additional studies are required to develop a suit-
able means of eliminating these problems.
EVALUATION OF TREATMENT PROCESSES
The average physical and chemical quality parameters of the treated ef-
fluents from the various pilot plant studies are summarized in Table 4-10,
Where applicable, average removal efficiencies are also presented. In
this section, these parameters are discussed along with a comparison of
the results from the filtration and activated carbon adsorption studies.
Also, results from separate virus and trace metal removal investiga-
tions are presented.
Organic Carbon
The average TOC and SOC of the various effluents differed only moder-
ately during the study. Nitrification reduced the TOC and SOC of the
71
-------
Table 4-10
PILOT PLANT AVERAGE EFFLUENT QUALITY
COMPARED TO THE RAW WASTEWATER
Parameter
TOG
mg/1
% removal
SOC
mg/1
% removal
Suspended Solids
mg/1
% removal
pH
mg/1
Conductivity
jumhos /cm
Ammonia -N
mg/1
% removal
Nitrate-N
mg/1
% removal
Or tho- Phosphate
mg/1 P
% removal
Total Phosphate
mg/1 P
% removal
Activated
Sludge
(1 Stage)
26
82
9
61
33
86
7.4
982
7.4
70
16. 5
7. 7
8.6
Nitrified
Effluent
(2 Stage)
15
89
6. 0
83
23
90
7. 1
846
2.9
88
19. 3
9.3
9. 7
Denitrified
Effluent
(3 Stage)
20
85
7. 2
79
42
82
7. 0
767
2. 1
3. 5
82
7. 3
7.4
Chemical
Effluent
(2 Stage)
26
70
18
5
19
87
9.2
827
16
20
0. 1
0.2
98
0.4
95
72
-------
activated sludge effluent by 11 mg/1 and 3 rng/1, respectively. Following
denitrification, both the TOG and the SOC increased, the former due pri-
marily to the carryover of suspended solids from the settling basin and
the latter probably from excess methanol in the treated effluent.
The average TOC and SOC of the chemically treated effluent (without ac-
tivated carbon treatment) was somewhat greater than that resulting from
biological treatment, primarily due to the poor removal of soluble organic
material in the lime treatment operation. Alkaline hydrolysis of particu-
late organic carbon apparently released as much as new soluble organic
material as was adsorbed by the insoluble calcium floe formed during the
chemical treatment process, leading to an average SOC reduction of less
than 5 percent. Although the quality of the chemically treated effluent was
poorer than that of the biological process, chemical treatment demonstrated
less variability than was observed with the biological processes.
Suspended Solids
The average suspended solids concentrations for the biologically treated
settled effluents in the pilot plant decreased in proceeding from activated
sludge through nitrification and then increased through the denitrification
process. The activated sludge effluent observed in the pilot plant, with a
suspended solids concentration of 33 mg/1, was significantly higher than
observed in the CCCSD 1-mgd plant, which had an average concentration
of 8. 7 mg/1. This difference can be attributed to (1) poorer efficiencies
normally associated with small scale sedimentation basins and (Z) the
relatively low overflow rates in the CCCSD plant. Also, problems were
encountered in the activated sludge pilot plant with floating sludge that
significantly increased the effluent suspended solids concentration. The
effluent suspended solids from the nitrification proces s at Z3 mg/1 were
generally lower than observed with the activated sludge pilot plant but were
higher than observed with the CCCSD 1-mgd activated sludge plant.
73
-------
The nitrified effluent quality further degenerated after denitrification,
primarily due to the buoying of settled solids by nitrogen gas bubbles.
Thus, the combined treatment of activated sludge, nitrification, and de-
nitrification removed only about 82 percent of the suspended solids with
respect to the raw wastewater. As noted earlier, recent information
illustrates that significant improvement in denitrification MLSS separation
can be achieved by aerating these solids for 30 to 60 minutes prior to fi-
nal sedimentation.
Chemical treatment of the partially settled raw wastewater removed 87
percent of the suspended material, producing an effluent having 19 mg/1.
Since the chemical treatment process resulted in the precipitation of
soluble materials during the flocculation reaction, a significant portion
of the 19 mg/1 suspended solids in the effluent was calcium carbonate
rather than suspended organic materials. Contrary to the biological pro-
cesses, chemical treatment consistently produced a moderately low sus-
pended solids concentration in the effluent.
Inorganic Nitrogen
The data listed in Table 4-10 indicate that the activated sludge process
oxidized 70 percent of the ammonia -N to nitrate. However, this did not
represent the conversion efficiency desired, particularly since only
about 50 percent of the ammonia could be consistently oxidized in this
single-stage system. By using a two-stage biological treatment system,
the average ammonia concentration was reduced to 2. 9 mg/1 for an over-
all ammonia conversion of 88 percent. This higher efficiency was attained
despite the difficulties of maintaining an adequate MLSS in the second-
stage nitrification basin. Although the average effluent ammonia -N was
2.9 mg/1, much of the time concentrations of 1 mg/1 or less of ammonia
-N were observed. The data indicate that by maintaining an adequate
74
-------
MLSS concentration in the nitrification reactor very low effluent am-
monia concentrations can be consistently obtained.
On the average, 82 percent of the influent nitrate -N was reduced to ni-
trogen gas in the denitrification reaction, resulting in an average effluenl
concentration during the study period of 3. 5 mg/1 nitrate -N (Table 4-10)
As with the nitrification process, the major difficulty encountered during
the operation of the denitrification process was in maintaining the MLSS
at a desired level.
A small amount of ammonia was lost during chemical treatment, re-
ducing the ammonia -N content by approximately 20 percent. These
losses probably resulted from the high surface-area-to-volume ratio in
the pilot plant in conjunction with the high pH. It is doubtful that the
ammonia removal would be this great in a full-scale plant.
Phosphorus Removal
Between 95 and 98 percent of the phosphorus was removed in the chemi-
cal treatment system, resulting in effluent concentrations of about
0.4 mg/1 of phosphorus. While this is enough phosphorus to stimulate
algal growths, potential problems in industrial cooling towers could be
controlled by periodic shock doses of chlorine.
Filtration
Results of the filtration studies indicated that the average turbidity of
the effluents from the activated sludge, nitrification, and chemical treat-
ment proces ses could be maintained at 5 JTU or less. Apparently, the
floe formed during these operations had a high shear strength and was
readily removed during filtration.
75
-------
Floe from the denitrification basin did not exhibit the same filterability
characteristics. Solids frequently broke through the filters during opera-
tion with this effluent. Thus, the denitrification process floe was either
finer than floe from the other processes or had a lower shear strength.
In either case, filtration of denitrification process effluent most likely
will require the use of filter aids (polyelectrolyte) in order to produce a
desirable effluent quality. Aeration of the denitrification MLSS prior to
settling may also be expected to improve the solids filterability.
Since the filters were not operated in parallel on the same effluents, it is
very difficult to compare their performance. There was no significant
difference in the effluent quality from the three filters during all operations
except that of denitrification, where there appeared to be a reduction in
the variability of the effluent turbidity when the mixed media filter was
used instead of the dual media. Further evaluations of filterability would
be necessary before the optimum media could be selected.
During the operation of the filtration process, biological growths developed
in the filter media. To prevent this problem from occurring, a suitable
means of disinfection should be provided ahead of the filters. In general,
filtration significantly improved the effluent quality and process reliability
of all the pilot plant systems investigated.
Activated Carbon
The results for the first stage of carbon adsorption of filtered activated
sludge, denitrification, and chemical effluents are summarized in Table
4-11. The carbon used with the activated-sludge-treated wastewater had
76
-------
a slightly greater adsorption capacity than that determined with the other
two effluents. Carbon adsorption of the denitrified effluent produced the
lowest organic carbon concentrations in the treated effluent, despite the
fact that the influent TOC was greater than that from the activated sludge
unit. These lower concentrations in the denitrified effluent were probably
due to the increased detention time in the carbon column which was neces-
sitated by the need for a lower hydraulic loading in the denitrification re-
actor and settling basin. The chemically-treated wastewater, which had
the highest influent TOC and SOC, also had the highest effluent organic
carbon concentration. Removal efficiencies in the first-stage treatment
of the chemical effluent were nearly equivalent to those in the denitrified
effluent and somewhat better than those for activated sludge, although
increased contact time for the activated sludge effluent would be expected
to improve the removal efficiency.
Table 4-11
COMPARISON OF SINGLE-STAGE ACTIVATED CARBON
PERFORMANCE FOR VARIOUS PILOT PLANT EFFLUENTS
Parameter
Effluent
TOC mg/1
SOC mg/1
Ibs TOC Removed
Ib Activated Carbon
Average Removal
TOC %
SOC %
Contact Time (min)
Ibs Carbon required
to treat 1 mg
Activated
Sludge
8. 3
5.8
0. 17
40
33
11
410
Denitrified
Effluent
7.2
3.4
0. 13
50
60
21
Chemical
Effluent
12. 6
7.2
0. 14
47
52
24. 5
690
77
-------
Because of the higher influent TOC and SOC concentrations to the acti-
vated carbon columns in the chemical treatment plant effluent, more
activated carbon per unit volume treated was required to adsorb the
organic carbon. Thus, it would require 690 pounds of activated carbon to
treat 1 mg chemically treated effluent, about 1.7 times the amount required
to treat the activated sludge effleunt.
While having two activated carbon columns in series increased the re-
liability of the adsorption system during the pilot plant studies, the
second carbon stage generally removed no more than 2 to 4 mg/1 of or-
ganic carbon. It is possible that the activated carbon treatment could
be optimized either by decreasing the carbon contact time in each stage
or by having only a single-stage treatment system to provide sufficient
contact time. The type of system which would actually be employed
would depend on the water quality requirements for each specific reuse ap-
plication and the relative cost of the two-stage versus single-stage system.
Virus Removal
The viral content of the treated wastewater is important from a public
health point of view, especially if the water is to be reused or dis-
charged to a waterway which may be used for body contact recreation.
Because of the potential hazards of virus in the treated waters, a
separate study was sponsored by CCCSD/CCCWD and Bechtel Corporation
to determine virus removals in the pilot plant processes. A brief sum-
mary of the results of the study conducted by Cooper et al. (Reference 5)
is presented here.
Since the viral content of treated wastewater was anticipated to be at or
near the detection limit of available analytical procedures, it was deemed
necessary to add a known amount of attenuated virus (poliovirus type 1,
strain LSc) to the wastewater and then measure the concentration of
78
-------
virus after various steps in the treatment process. Tracer studies
through the various processes were made so that effluent concentrations
with respect to time could be predicted and compared with actual mea-
surements.
Results of experiments in the biological treatment systems indicated
that the viral concentration was reduced from one-one hundreth to one-
one thousandth of its initial concentration in the treatment units contain-
ing high MLSS concentrations. When the pH of the chemical treatment
system was maintained at 11 or above, there was no virus found in the
effluent. The results indicated a very rapid reduction in the viral con-
centration in the lime reactor so that after just three minutes, the viral
concentration was reduced to about one-five hundredth of its original
concentration. Limited removal of virus occurred in the filtration pro-
cess, while the activated carbon reduced the influent viral concentra-
tions by about 75 percent.
HEAVY METALS
Table 4-12 illustrates the removal of heavy metals in the activated sludge,
filtration, activated carbon, and chemical treatment processes. Atomic
absorption spectroscopy and emission spectrography analyses were made
on 24-hour composites of the influent and effluent streams. Removal
efficiencies were generally better in the chemical treatment process than
they were in the activated sludge process, except for copper and nickel.
However, since the influent concentrations were generally quite low, ana-
lytical variance makes it difficult to compare the results directly.
Appendix B contains a summary of data from a series of experimental
runs using the chemical treatment plant in which a solution of soluble
metal salts was added to the influent stream. Removals ranged between
79
-------
85 and 99 percent for all metals except hexavalent chromium, which was
reduced by an average of only about ZO percent. Filtration generally re-
moved between 60 and 99 percent of the metals, indicating that most of
the metals were associated with the particulate material in the waste
streams. Similar results were achieved using activated carbon, where
adsorption of organometallic compounds as well as straining of particu-
late metallic materials were undoubtedly taking place.
Table 4-12
REMOVAL OF HEAVY METALS
Ha riLim
Chromium
Copper
I. pad
\Unjjanoic
\UkH
SiKer
Titanium
/inc
Biological-Physical Treatment
Activated Sludce
Pi
In
rnn/1
Nil
0. 12
1). 12
0. 09
11. 21
a. 07
0. 012
0. 035
Nil
ot Plant
Out
mg/1
Nil
0. Of,
0 03
0 02
0. 24
i). 02
0. 006
0. Old
Nil
rem
50
73
78
11
7 1
50
54
CCCSD 1 mgd
In
mg/1
0, 50
0. 05
0.8
0. 1 15
0. 39
0. 085
0. 007
0. 27
0. 33
Out
mg/1
Nil
0. 01
0. 19
0. 008
0. 32
0 021
0. 001
0. 01
0. 10
rem
99 i
SO
70
93
18
75
85
9B
70
Filtration
In
mg/1
Nil
0.42
0.033
Nil
0. 017
0. 01
Nil
0. 01
Nil
Out
mg/1
Nil
0. 01
0, 023
Nil
0. 015
0. 006
Nil
Nil
Nil
rem
_
98
30
-
12
dO
-
99 t
Activated Carbon
In
mg/1
Nil
Nil
0. 023
0. 040
0. 060
0. 010
Nil
0. 34
0. 020
Out
me /I
Nil
Nil
0. 015
0. 001
0. 001
0. 005
Nil
0. 01
0. 001
rem
.
-
35
98
9?
50
-
98
98
Chemical Treatment
mg/1
0.43
0. 17
0. 14
0. 13
0. 33
0. 015
0. 013
Nil
Nil
Out
mg/1
Nil
0. 07
0. 05
Nil
0.02
0. 004
0. 002
Nil
Nil
Rem
99^
59
64
99.
94
67
85
-
-
80
-------
Section V
RESULTS AND DISCUSSION OF
INDUSTRIAL TEST LOOP STUDIES
Three industrial test loops and a test boiler received Contra Costa Canal
water and various grades of renovated water during the pilot-demonstra-
tion project to evaluate the feasibility of using renovated wastewater for
industrial purposes in relationship to the present water source. Data
on the scaling potential, corrosion rate, algal growth potential, and
toxicity of the circulating water in the test loops are presented and dis-
cussed in this section.
HEAT EXCHANGER FOULING DATA
During the normal operation of heat exchangers, there may be scale
formed on the walls of the heat exchanger tubes. This scale may reduce
corrosion, but, if it becomes excessive, a significant loss in heat trans-
fer occurs. During this study, reduction in the rates of heat transfer
and the related fouling factors were used as one means of evaluating
the various renovated waters and canal water. Knowing the temperature
of the water and steam at the inlet and outlet of the heat exchanger, the
flow (contact time), surface area, and type of heat exchanger tubes, it
was possible to calculate the heat transfer coefficient,, Any reduction
from the original value indicated that fouling was occurring and a fouling
factor could be calculated.
Heat exchanger tube fouling may result from precipitation of calcium
phosphate or carbonate, corrosion products (rust), dirt, and other for-
eign materials which accumulate on the heat exchanger surfaces. Table 5
81
-------
Table 5-1
FOULING FACTORS AND SCALE ANALYSES
Exchanger Tube Exposure Period
Corrosion Inhibitor
Phosphorus Removal
Fouling Faclor lhr-°F-sq ft/Btu]
pll
Cy. les of Concentration
rempi-ralure IHeal Exchange
Oiitlell I°F)
Aluminum
Huron
Gallium
Chromium
Cobalt
Copper
Lead
Magnesium
Manganese
Molybdenum
N'u-kel
Phosphorous
Si lii-on
Silver
Strom ium
Tin
Titanium
\anaclium
/ mi
Other Hindis
Contra Costa Canal
5/18-6/8
6/9-7/1
No No
No I No
0.001 0.003
8.5
8.0
9.8 ! 7.0
125
0.08
140
O.I-
Nil , Nil
7't-7/30 's/1-8/31
No 1 Yes
No 1 No
0.0005 0.002
H. 5 7. 5
8.9 ' 6.5
IOS I 134
Nitrification
Effluent
5/18-6/8
No
No
0.0005
6/9-7/1
No
No
0.0005
8.4 7.8
5.6 6.7
100
I 1 5
0. 3 i 0.6 0. 03 0. 02
Nil Nil Nil 0.03
0.01 0.3 0. 06 ; 0.2 16' 30
0.01 ' 0 . 0 1
0.002 0.003
0. 08 0.10
65 60
Nil ! 0.01
0. 3
0.2
0.01
0.002
Nil
Nil
Nil
0.002
Nil
0. 7
0.2
0. 59 j 1.5 0. 0 1 | 0. 005
Nil ' Nil Nil Nil
0.09 ! 0.009 0.01
62 54 4. 3
0. 03 0. 2 0. 06
0.2, 1.2 6.1
0. 1 0. 20 0. 5
0.01 j 0.09 : 0.2 Nil
0.007 Nil 0.02 0.006
Nil
^
"Nil Nil ' 22
2.4 3.6 Nil
Nil Nil . Nil Nil
0. 0]
Nil
0.002 Nil
Nil
Nil
3 . n 6.0
Nil
Nil
Nil ' Nil 0. 50
Nil ! Nil Nil
O.OOi. i 0.01 0.01
Nil Nil ! Nil
2.01 7.5' 6.2
:->il I Nil i Nil
0.03
0. 4
0.005
2.0
0. 2
Nil
0.003
1 5
0.05
Nil
0. 1
Nil
Nil
Nil
5.0
Nil
Activated
Carbon/
Nitrification
Effluent
5/18-6/8
No
No
0. 0005
8.0
4. 4
6/9-7/1
No
No
0. 003
7.8
6.2
100 108
0.02 0.01
Nil 0.03
15
0.002
Nil
0. 01
2.4
0.05
4. 3
0.4
Nil
0.001
26
Nil
Nit
0. 30
Nil
Nil
Nil
6. 9
Nil
35
0.008
Nil
0. 04
0.7
0.005
1. 5
0.08
Nil
0.003
15
0.04
Nil
0. 1
Nil
Nil
Nil
6.0
Nil
Effluent
7/6-7/30
No
No
0.002
8. 5
8.0
102
0.02
0. 05
20
0.01
8/1-8/31
No
Yes
0.001
7.9
a. 4
134
0.04
0. 02
4.2
0.024
Nil Nil
Nil
0. 36
0. 1
3. 9
0.4
Nil
0.006
25
0. 7
0. 0007
0. 1
0.011
Nil
Nil
1.7
Nil
0.09
48
0.05
1 . 4
0. 3
0.02
0.01
2.8
2.7
0. 0006
0. 04
Nil
Nil
Nil
6. 3
Nil
Filtered
Effluent
7/6-7/30
No
No
0.004
8. 4
5.7
106
0.6
0.01
23
0.015
Nil
0.006
15
0. 06
2. 5
0. 4
Nil
0.008
6. 1
0.06
0.0009
0. 2
Nil
Nil
Nil
3. 1
Nil
8/1-8/31
No
Yes
0.002
7.4
5.4
134
0.03
0. 009
5. 3
0.02
Nil
0.09
29
0. I
1.0
0.2
0. 01
0.009
I 1
0. 7
0. 0003
0. 04
Nil
Nil
Nil
Filtered
C emica
Effluent
10/29-11/24
No
Yes
0.001
8. 6
10.4
126
0. 15
0.002
0.08
0. 66
Nil
0.08
20
0.02
0. 6
0. 08
0.04
0.005
Nil
0.40
Nil
0. 0 1
Nil
0.003
Nil
16 2.S
Nil Nil
Chemical Treatment
Effluent
10/29-1 1 /24
No
Yes
0.002
8. 1
5. 4
1 17
0. 2
10/29-11/24
Yes
Yes
0.003
8.4
7.4
120
0.2
0.004 , 0.002
0. 5 , 0. 30
0.05 0.009
Nil
0.06
0.002
0.05
17 19
0.06 0.05
0.6
0. 10
0.007
0.4
0. 08
0.006
0.005 ! 0.007
1.6 | 1.0
0. 3
Nil
0.02
Nil
Nil
Nil
5. 2
Nil
0. 3
Nil
0.02
Nil
Nil
Nil
5.0
Nil
-------
summarizes the data for the chemical composition of the scale that
formed during the various test periods of this study. Fouling factors
(see Reference 6 for calculation procedure) and operating data for
each test period are included in the table. Analyses of the scale formed
in the heat exchanger tubes where canal water was used in the test loops
indicated that it consisted primarily of corrosion products (iron)
with some deposition of silica. There was no significant calcium or phos-
phorous scale formed during use of the canal water. The addition of a
corrosion inhibitor (NALCO 370) to the canal water caused a moderate
increase in the amount of zinc-chromate in the scale but had little effect
on the magnitude of the fouling factor. The relatively high levels of zinc
in the scale formed by all of the samples listed in Table 5-1 most likely
resulted from the dissolution of the galvanized coating on the bottom pans
of the cooling towers, since analysis of the influent waters indicated re-
latively low zinc levels.
In contrast to the canal water, the renovated waters that had received bio-
logical-physical treatment generally resulted in scale formation composed
largely of calcium and phosphate. When ferric chloride was added to the
denitrification basin to reduce the phosphorous concentrations in late July
and August, the iron content of the scale formed in using this water in-
creased sharply, whereas the phosphate was appreciably reduced. This
reduction in phosphorous scale was observed even though only about 50
percent of the phosphorous had been removed from the makeup water.
The significance of this scale is further illustrated by the results obtained
with the effluents from the chemical treatment process. With these ef-
fluents, the phosphorous and calcium scale formed in the heat exchanger
tubes was greatly reduced, resulting in a scale composition nearly the
same as found with the canal water. Also, the silicon in the scale was
generally less when using the renovated waters than when using the canal
83
-------
water. Based on these observations, it must be concluded that a high
degree of phosphorous removal is desirable for the use of renovated
water for industrial cooling purposes.
The fouling factors, shown in Table 5.1, ranged from 0.0005 to 0.004
hr-°F-sq ft/Btu for the canal water and the renovated waters. These
factors represent the values observed after 18 days from the time new
heat exchanger tubes were placed in operation for each exposure period.
The nitrified effluents consistently resulted in the lowest fouling factors
observed (i.e., 0.0005 hr-°F-sq ft/Btu). However, nitrified effluent
that was filtered and treated with activated carbon resulted in fouling
factors ranging from 0. 0005 to 0. 003 hr-°F-sq ft/Btu. There is no
apparent reason for the lower fouling factors observed with the nitrified
effluent.
The fouling factor observed for the filtered chemically treated effluent
was 0. 001 hr- F-sq ft/Btu, whereas this effluent that had activated car-
bon treatment resulted in a fouling factor of 0. OOZ hr- F-sq ft/Btu. The
addition of corrosion inhibitor to the carbon-treated effluent further in-
creased the fouling factor to 0.003 hr-°F-sq ft/Btu.
An interesting observation from the tests conducted is that the renovated
waters that were filtered or treated with activated carbon generally had
somewhat higher fouling factors than the same waters without these addi-
tional treatment steps. The scale formed with the filtered and carbon-
treated waters appeared to be considerably harder and adhered to the
heat exchanger surface more tenaciously. It is possible that when organic
and particulate materials were present (i.e. , no filtration or activated
carbon treatment), the scale formed on the heat exchanger tubes was
partially removed because of scouring action of the circulating water.
84
-------
Visual observations made during operation of the test loops indicated
that the rather turbid canal waters and the unfiltered renovated waters
deposited a significantly greater amount of solids in the bottoms of the
cooling towers than the filtered effluents. Although the solids deposition
did not adversely affect the operation of the test loop equipment, such
deposition in heat exchange components used by industry could result
in significant operational problems. These difficulties would be expec-
ted to offset any benefits derived from the softer scale formed without
filtration.
Figure 5-1 summarizes the fouling factor data described above. The
data plotted for the canal water and various process waters represent
average values. The data indicate that the fouling potential of the reno-
vated waters is nearly the same as observed with the canal waters.
Filtered, chemically treated effluent and nitrified effluent had the low-
est fouling potentials.
Control of the pH in the pilot plant treatment processes and the industrial
test loops was limited so that on occasion pH values in the makeup and cir-
culating waters were higher than desired. During these periods, in-
creased precipitation of calcium salts most likely occurred, resulting
in an accelerated decrease in the heat transfer rate over a very short
time period. Although the process difficulties were generally corrected
within a day, the precipitated materials probably remained, thus keep-
ing the heat transfer at a low rate. Because of this, it is felt that the
data presented for the fouling factors represent conservative (high)
values for fouling. In a full-scale treatment plant, operating conditions
would be more closely controlled, thereby eliminating some of the prob-
lems resulting from abnormally high pH values.
Representative fouling factors for various types of waters used in indus-
trial applications are listed in Table 5-2. The fouling factors (corrected
85
-------
FOULING FACTOR
Hr °F ^ Ft
Btu
00
oq
£
i-i
CD
m
I
OQ
n>
o
P
O
r-t-
O
I-t
d
O
8
p
§
ro
p
8
p
8
CANAL WATER
' CANAL WATER (WITH CORROSION INHIBITOR)
NITRIFIED EFFLUENT
CARBON TREATED NITRIFIED EFFLUENT
DENITRIFIED EFFLUENT
FILTERED DENITRIFIED EFFLUENT
DENITRIFIED EFFLUENT (WITH PHOSPHATE REDUCTION)
FILTERED DENITRIFIED EFFLUENT
(WITH PHOSPHATE REDUCTION)
FILTERED CHEMICAL TREATMENT EFFLUENT
J FILTERED AND CARBON-TREATED CHEMICAL EFFLUENT
FILTERED, CARBON TREATED CHEMICAL
EFFLUENT (WITH CORROSION INHIBITOR)
-------
Table 5-2
TYPICAL FOULING FACTORS"
Temperature of Heating Medium
Temperature of Water
Types of Water
Sea Water
Brackish Water
Cooling Tower and Artificial Spray Pond:
Treated Makeup
Untreated
City or Well Water (Such as Great
Lakes )
Great Lakes
River Water:
Minimum
Mississippi
Delaware, Schuylkill
East River Iv New York Bay
Chicago Sanitary Canal
Muddy or Silty
Hard (Over 15 grains/gal)
Engine Jacket
Distilled
Treated Boiler Feedwater
Boiler Blowdown
Up to 240°F
125°F or Less
Water Velocity
3 ft/sec
and Less
. 0005
. 002
. 001
. 003
. 001
. 001
002
. 003
. 003
. 003
. 008
. 003
. 003
. 001
. 0005
. 001
. 002
Over
3 ft/sec
. 0005
. 001
. 001
. 003
. 001
. 001
. 001
. 002
. 002
. 002
. 006
. 002
. 003
.001
. 0005
. 0005
, 002
240°F to 400°F
Over 125°F
Water Velocity
3 ft/sec
and Less
. 001
. 003
. 002
. 005
. 002
. 002
. 003
. 004
. 004
. 004
. 010
. 004
, 005
. 001
, 0005
. 001
. 002
Over
3 ft/ser
. 001
.002
. 002
. 004
. 002
. 002
. 002
. 003
. 003
. 003
. 008
. 003
. 005
. 001
. 0005
. 001
.002
Reference 6
87
-------
to a velocity of 2 ft/sec), observed during this study for various reno-
vated waters compare favorably with the published data. This informa-
tion supports the results obtained and indicates that on the basis of foul-
ing, renovated waters are comparable to many other sources of indus-
trial cooling water being used throughout the United States.
CORROSION RATES
Corrosion rates associated with the use of Contra Costa Canal water and
various grades of renovated water in industrial applications were deter-
mined using two procedures. The first procedure involved the use of a
portable corrosion meter (Magna Corporation) in conjunction with a cor-
rosion probe inserted in the circulating water of each industrial test loop.
Corrosion rates using this procedure could be determined immediately.
The second procedure utilized standard corrosion coupons made from car-
bon steel. Four of these coupons were inserted in a circulating water by-
pass loop during each testing period. Coupon weight loss was determined
after each testing period using ASTM procedures, and a corrosion rate
was calculated. The corrosion probes and the corrosion coupons were lo-
cated on the discharge side of the heat exchangers.
Table 5-3 summarizes the corrosion rates obtained with the corrosion
probes and meter for the various renovated waters and canal water in the
industrial test loops. Chemical characteristics of the circulating waters
are also shown in Table 5-3.
The observed corrosion rates, as determined with the corrosion probes
and meter, for the untreated canal water ranged from 23 to 106 mils/yr
while the corrosion rates for the renovated waters that received biological
treatment ranged from 6. 3 to 14 mils/yr. A corrosion rate of 3 mils/yr
was observed for the filtered chemical treatment effluent. However, a
-------
Table 5-3
CORROSION RATES AND CIRCULATING WATER QUALITY
Source of Water
Exchanger Tube Exposure Period
Corrosion Inhibitor
Phosphorous Removal
Corrosion Rate* mils/yr
Cycles of Concentration
Langelier Index
3/5-
5/4
No
No
106
4. 7
0. 27
Calcium niR/1 CaCO( 1 (,8
Alkalinity nip/I CaCO, 69
pll 8.0
Total Phosphate mc/l PO 0.08
Conductivity Mmhos /cm 1263
o
Kxit Temperature F 104
Suspended Solids mg/I 15.2
Act
Contra Costa Canal Sludge
Eff
5/18-
6/8
No
No
6/9- 7/f>-
7/1 7/30
No
No
68 41
9. 8 7.0
,.42 ,0.83
267 215
88 70
8/1- . 3/5-
8/31 5/4
No Yes l No
No No
23 5.4
8. 0
1.74
6. 5
3.05
No
10
4.0
1. 31
316 230 ' 424
230 .52 112
8.5 K. 0 8.5 7.5
0. 60 0.70 | 1.5
2143
1 19
18
1415 ! 1780
1 14
14
102
48
1.8
1323
123
I. 0
8.0
Filt-
ered
Act
Sludge
Eff
Nitrification
Err
3/5- J5/18-
5/4 6/8
No
No
No
No
6. 3 ; 14
4.7
0.98
496
6/9-
7/1
No
No
7.8
5. 6 6. 7
1.47 0.82
395 ; 471
87 111, 64
At t Carbon
Nitrification
Eff
5/18-
6/8
No
No
10.7
4.4
0.68
6/9-
7/1
No
No
6. 3
6.2
0.77
Dentrifica-
tion
Eff
7/6,
7/30
No
No
12
8.0
,.75
289 426 366
59 52 258
8/1-
8/31
No
Yes
9.2
8.4
0.89
542
74
Filtered
Dentrifica-
tion
Eff
7/6-
7/30
No
No
7.9
5.7
1. 53
338
207
7.9 ' 8.4 ' 7. 8 8.0 . 7. 8 8.5 ' 7.9 8.4
18 15 1 0 ' 24 : 9 11 13 13
3063 4740
1 10
6. 3
107
35
5180 5855
121
1
1 18
3. 6
3944 j 5406 5780 5242
,22
4.7
128 105
2.4 ; . 3
12
5100
127 , 104
13 5.8
8/1-
8/31
No
Yes
11
5.4
0.27
496
49
7.4
Filt-
ered
Chem
Treat-
ment
10/29-
11/24
No
Yes
3.0
10.4
2.7
580
230
Act Carbon
Chemical
Treatment
Eff
10/29-
11/24
No
Yes
72
6. 1
0. 5
260
40
8. 6 8. 1
20 1 1.2 j 1.5
4929
130
11
7610 ' 4400
130 130
7.5 ' 4.0
10/29-
11/24
Yes
Yes
26
7.4
0.93
396
60
8. 3
1. 9
5420
119
3.7
Data obtained from corrosion probes
Noli-: Art Activated
KIT Klfluenl
-------
rate of 72 mils /yr was determined for the chemical treatment effluent that
was also treated with activated carbon. These latter values suggest that
the 3 mils/yr corrosion rate observed with the filtered chemical treatment
effluent may be erroneously low. The addition of a corrosion inhibitor to
the canal water decreased the corrosion rate from an average of 60 mils/
yr to 5.4 mils/yr. A decrease in the corrosion rate from 72 mils/yr to
26 mils/yr was observed when corrosion inhibitor was added to renovated
water having chemical and activated carbon treatment.
Shown in Table 5-4 are the corrosion rates obtained from the corrosion
coupons inserted in the industrial test loop circulating waters. Also shown
in this table are the corresponding corrosion rates observed with the cor-
rosion probes and meter. In all cases the corrosion coupons indicated
lower corrosion rates than determined with the corrosion probes and
meter. Biologically treated renovated waters resulted in corrosion rates
ranging from 2. 0 to 6. 6 mils/yr as determined with the corrosion coupons,
while untreated canal water had corrosion rates of 12. 5 to 37. 2 mils/yr.
The canal water corrosion rate was reduced to 2. 7 mils/yr by the addition
of a corrosion inhibitor. The renovated water receiving chemical and ac-
tivated carbon treatment resulted in a corrosion rate, as determined with
the coupons, of 31.0 mils/yr; this rate was reduced to 11.9 mils/yr with
the use of a corrosion inhibitor.
The data generally indicated that the renovated waters receiving treatment
for the reduction of phosphorous had higher corrosion rates than when
phosphorous was not removed. This observation suggests that either the
phosphorous in the water inhibited corrosion or the phosphate scale that
was formed on the heat exchanger tubes provided a protective coating.
Visual observation of the heat exchanger tubes suggested that the scale
formation most likely was the primary mechanism associated with the re-
duction in the corrosion rate. Also, solubility coefficients for various
calcium and phosphorous compounds indicate that scale formation could
continue to the point that heat exchanger tubes would be severely restricted.
90
-------
Table 5-4
COMPARISON OF CORROSION RATES
Type of Water
Canal Water
Canal Water
Canal Water with Corrosion
Inhibition
Nitrified Effluent
Denitrified Effluent
Denitrified Effluent with Phos-
phorous Reduction
Filtered Denitrified Effluent
Filtered Denitrified Effluent
with Phosphorous Reduction
Chemical and Activated Carbon
Treated Effluent
Chemical and Activated Carbon
Treated Effluent with Corrosion
Inhibitor
Date
6/9 7/1
7/6 7/30
8/1 8/31
6/9 7/1
7/6 - 7/30
8/1 - 8/31
7/6 7/30
8/1 8/31
10/29 11/24
10/29 - 11/24
Corrosion Rate
mils/yr
Coupons
37. 2
12. 5
2. 7
2.9
2. 0
6. 6
2. 2
4.9
31. 0
11.9
Probe""
41. 0
23. 0
5.4
7.8
12. 0
9.2
7.9
11.0
72. 0
26. 0
Data obtained with corrosion coupons
##Data obtained with corrosion probes
91
-------
For the canal water and the renovated waters, the L/angelier Index did not
provide an accurate assessment of the potential for scaling or corrosion.
The chemical characteristics of these waters must have been responsible
for these inaccuracies.
ALGAL GROWTH POTENTIAL
Since many of the problems which arise from the discharge of nutrients
into the environment are associated with the response of algae to the in-
creased nutrient levels, a means of assessing this potential growth would
be useful in evaluating the efficacy of various treatment procedures. The
Provisional Algae Assay Procedure (PAAP) was used for this purpose dur-
ing this investigation in accordance with the methods developed by the
University of California Sanitary Engineering Research Laboratory. This
procedure utilized algae to measure the growth potential of a given sample
of water in much the same way that BOD is used to assess the oxygen con-
suming capacity of a given waste by bacteria. Growth of the test species of
algae Selenastrum capricornutum was assessed using a standard solution
which had all of the nutrients required for the growth of the algae. The
growth of the algae in this standard solution was then compared to the
growth in the sample solutions.
Table 5-5 indicates the phosphorous and inorganic nitrogen concentrations
in the sample waters which were used for the Provisional Algae Assay
Procedure. The denitrified effluent had a high poshphorous content but
relatively low concentrations of nitrate and ammonia, whereas the acti-
vated sludge effluent had both high phosphorous and high inorganic nitro-
gen concentrations. The chemically treated effluent had a very low phos-
phorous concentration and almost all of the nitrogen present was in the
ammonia form. When these process waters were used as the algal growth
9Z
-------
Table 5-5
SAMPLE ANALYSIS FOR ALGAE GROWTH POTENTIAL TESTS
Measured Parameter
pH
Conductivity /j. mho
Orthopho sphate
as P mg /I
Nitrate, as N nig /I
Ammonia, as N nig /I
Process Water
Deni-
trified
Effluent
7.4
630
8. 5
0. 3
0.6
Activated
Sludge
Effluent
7. 5
610
9. 1
9.0
9.0
Lime-
Treated
Effluent
7.8
895
Nil
Nil
17.0
medium, the response curves shown in Figure 5-2 were obtained. The
algae grew rapidly in the standard test medium and, even after six days,
were still in the log growth phase in this medium. There was a lag of about
three to five days in the growth of the algae in the denitrified medium and
the activated sludge medium. The log growth phase in the denitrified effluent
lasted for approximately three days, and after aboutnine days it appeared as
if nitrogen limited further growth of the algae in this medium. Growth in the acti-
vated sludge medium continued for the duration of the experiment after
the initial lag period. Apparently, there was some material in the acti-
vated sludge effluent which inhibited the growth of the algae initially, but,
once the algae became acclimated to the activated sludge effluent, they be-
gan to grow rapidly since they were not nutrient limited. The chemically
treated effluent apparently had a low enough phosphorous concentration so
as to limit the growth of algae in this medium. The data plotted in Figure
5-2 indicated that lime treatment produced an effluent which permitted
little or no growth of the algae, whereas denitrification permitted a limited
93
-------
1.00-
to
fa
o
UI
0.10-
0.01-
STANDARD
ACTIVATED SLUDGE
EFFLUENT
DENITRIFICATION
EFFLUENT, /
LIME-TREATED
EFFLUENT
8
DAYS
i
10
12
I
14
16
Figure 5-2. Algae Growth in Renovated Waters
94
-------
growth of the algae. The high nutrient concentrations in the activated
sludge effluent permitted a rapid and continuous growth of algae for at
least a 15-day period.
With nutrient removals in excess of 95 percent, there will be sufficient
nutrients remaining to support some growth of algae. However, it is an-
ticipated that such growth can be readily controlled in cooling towers using
established techniques.
TOXICITY ANALYSIS
The toxicities of effluent streams receiving primary and activated sludge
j<
treatment and primary with lime treatment are summarized in Table 5-6. ""
The results indicated that primary treatment produced an effluent which,
when diluted to an average value of 47. 5 percent of its initial concentra-
tion with dechlorinated tap water, killed 50 percent of the test species
(stickleback) in 96 hours (96 hr LC-50% = 47. 5). Undiluted effluent from
the activated sludge plant killed less than 50 percent of the test species in
96 hours. Lime precipitation, on the other hand, produced an effluent
which was only slightly less toxic than that resulting from primary treat-
ment alone, so that diluting to 61 and 81 percent of the initial concentra-
tion produced a 50-percent kill after 96 hours in the chemical effluent. By
providing activated carbon adsorption after chemical treatment, the toxi-
city of the effluent was reduced to the point that less than half of the fish
were killed in the undiluted waste after 96 hours. Since the ammonia con-
centration did not change appreciably due to the carbon treatment, some-
thing other than just ammonia must have been contributing to the toxicity.
When the ammonia was removed from the chemical treatment effluent by
ion exchange (clinoptilolite), the survival was again greater than 50 per-
cent after 96 hours in the undiluted waste.
*Toxicity analyses performed by Sanitary Engineering Research Laboratory,
College of Engineering and School of Public Health, University of Cali-
fornia, Berkeley.
95
-------
Table 5-6
SUMMARY OF TOXICITY RESULTS*
(Central Contra Costa oanltary District)
Constituent
Week 1
(April 23-27)
COD v
BOD j
SS >mg/l
NH3-N I
Total P/
pH
96 hour LC-50,
percent
Week 2
(April 27-May 1)
COD \
BOD
SS Trig /I
NH3-N
Total P/
PH
96 hour LC-50,
percent
72 hour LC-50,
percent
Biological Treatment
Primary
Effluent
208
112
96
22. 7
9.3
7. 3
45
217
80
88
24. 8
9.2
7.4
50
Activated
Sludge
Effluent
86
42
37
7. 2
10, 5
7. 2
':-.':'
110
30
32
7. 8
9. 7
7. 3
Physical-Chemical Treatment
Partially
Settled
Sewage
260
112
178
22. 2
12. 8
7. 1
58
299
130
129
20. 9
13. 3
7. 4
71
Chemical
Treat
ment
Effluent
83
29
13
18. 5
1.6
6.8
61
78
20
15
20. 9
1.0
7. 2
81
Chemical Treatment
Effluent After
Activated
Carbon
43
19
11
19. 0
1, 5
6.9
44
13
9
21. 0
1.0
6, 7
'!' '!^
Ammonia
Removal
69
29
13
3. 1
1. 5
7. 0
sV -'-
55
14
8
1. 9
0. 7
7. 6
;!' ;!'
* Average of daily composites
** Less than 50 percent kill in 100 percent waste at 96 hours
Note: The above data were obtained by the Sanitary Engineering Research
Laboratory at the University of California, Berkeley
96
-------
Table 5-7 presents a comparison of the toxicity of activated sludge, nitri-
fied, and filtered nitrified effluents from the pilot plant. After 96 hours
of contact, two of the test species were dead in the undiluted activated
sludge effluent, whereas there was complete survival of the test species
in the nitrified effluents. All of the test species survived after 96 hours
exposure to the circulating waters in the industrial test loops which had
been concentrated by approximately five times. These data indicated that
blowdown from cooling towers using renovated water should not result in
toxicity problems if adequate treatment is provided.
Table 5-7
INDUSTRIAL TEST LOOP TOXICITY RESULTS
CCSD Activated
Sludge Effluent
Pilot Nitrified
Effluent
Pilot Filtered
Nitrified Effluent
Cooling Tower
Circulating Water
Canal
Nitrified
Effluent
Filtered Nitri-
fied Effluent
Filtered Chemically
Treated
Effluent
Filtered Acti-
vated Carbon
Chemically Treated
Effluent
Dilu-
tion
None
None
None
None
None
None
None
None
DO
mg/1
8.2
8. b
9.0
8.6
8. 0
8.8
7.9
9. 5
pH
7. 95
7. 45
7. 55
7. 15
7. 70
7. 60
8. 4
7. 0
Numbor Sur\ ving/Prrrent Survival
Start
10/100
10/100
10/100
10/100
10/100
10/100
10/100
10/100
24 hr
10/100
10/100
10/100
10/100
10/100
10/100
10/100
10/100
4K hr
10/100
10/100
10/100
10/100
10/100
10/100
10/100
10/100
72 hr
8/80
10/100
10/100
10/100
10/100
10/100
10/100
10/100
c'6 hr
8/80
10/100
10/100
10/100
10/100
10/100
10/100
10/100
jr,Temperature 71 F Test Species stickleback Number of fish per test 10
'Slowdown from the cooling towers was about five times the concentration
of the cooling tower feed.
97
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EVALUATION OF INDUSTRIAL TEST LOOP RESULTS
The most significant finding during the investigation of fouling factors and
corrosion rates was that renovated water used as cooling tower makeup
performed at least as well as the Contra Costa Canal water. Precipitation
of phosphorous in the test heat exchanger tubes was observed for the reno-
vated waters not receiving treatment for phosphorous removal. Calcium
precipitation was associated with the precipitated phosphorous. However,
scale formed from the use of lime-treated renovated water with very low
phosphorous concentrations had very small contents of calcium and phos-
phorous. Since the calcium concentrations and pH of the lime-treated
waters were approximately the same as in the biologically treated effluents
not receiving treatment for phosphorous removal, it appears that little
precipitation of calcium carbonate or calcium sulfate would be expected
when the renovated water tested in this study is used as cooling water.
Thus, the chemical constituent in these wastewaters most directly in-
fluencing the scaling of heat exchanger tubes was phosphorous. Removing
the phosphorous increased the corrosion rate of the renovated water, but
this was satisfactorily reduced by the addition of a corrosion inhibitor.
When the above considerations are taken into account, the potential fallacy
of considering only the total dissolved solids content when evaluating a
water's utility for reuse becomes apparent. Water having a high TDS but
a low phosphorous or calcium content generally would not be expected to
result in problems associated with scaling from precipitation. Similarly,
chlorides, which are important with respect to the stresses imposed on
stainless steel heat exchanger tubes, may be relatively low in waters hav-
ing a high TDS if these waters are derived primarily from the dissolution
of calcareous sediments. Thus, TDS concentrations can be used to provide
a preliminary indication of the potential utility of a given water for reuse,
but should not be relied upon as the sole criterion for a given water.
98
-------
The fouling factor results, summarized in Figure 5-1, indicate that nitri-
fied effluent, denitrified effluent with phosphorous reduction, and filtered
lime-treated effluent with and without carbon adsorption have fouling ten-
dencies comparable to canal waters treated with a corrosion inhibitor.
Corrosion rates for these waters were also approximately the same as
canal water with a corrosion inhibitor added. The only exception to this
was the filtered, activated carbon, lime-treated effluent which had a rela-
tively high corrosion rate of 31 mils/yr. When the corrosion rate was
reduced to about 12 mils/yr with a corrosion inhibitor, the fouling in-
creased appreciably. These results indicate that a balance between cor-
rosion and fouling can be achieved by the treatment processes of activated
sludge and nitrification. Denitrification did not appear to improve the
fouling or corrosion rates, so this added process would not be expected
to significantly improve the industrial usability of the treated wastewater.
While it is likely that adding a corrosion inhibitor to the filtered, lime-
treated effluent would produce a water which would have a lower corrosion
rate than the same water receiving activated carbon treatment, there is
no way of knowing how this would affect the fouling factor, since experi-
mental results for this particular test were not obtained.
Table 5-8 summarizes typical concentrations of chemical constituents in the
Contra Costa Canal water and CCCSD primary influent. As is apparent
from this table, there is an appreciable increase in the concentration of
dissolved salts in the wastewater in relationship to the canal water. How-
ever, of major concern in the reuse of this wastewater for cooling water
purposes is the calcium, carbonate, and sulfate concentrations. These
constituents as well as phosphorous are important since they may enter
into precipitation reactions in a cooling water system as the number of
cycles of concentration and the temperature increase. Studies concern-
ing the fouling tendencies of the renovated waters indicated that no signifi-
cant precipitation of calcium salts occurred during the industrial test
loop studies other than that due to precipitation with phosphorous.
99
-------
Table 5-8
TYPICAL QUALITY CHARACTERISTICS
OF WASTEWATER AND CANAL WATER
Chemical Parameters
Na+
K+
Ca++
Mg++
Cl"
S°4
HC03
TDS
Alkalinity (as CaCO )
Hardness (as CaCO )
CCCSD Primary
Influent (mg/1)
106
12
51
17
123
116
205
860
179
197
Canal
Water
(mg/1)
57
2.4
26
15
78
56
103
310
84
129
Thus, no trouble with precipitatioh of calcium salts is expected in using
renovated water for cooling purposes at cycled of concentration of approxi
mately five to eight, if the total phosphorous concentrations are reduced
to 0. 5 mg/1 as P or less.
Chloride concentrations are of concern with regard to stress corrosion
in the heat exchanger tubes fabricated from stainless steel. However,
the chloride concentrations which cause such problems with Stainless
Steel 316 are in excess of those in the renovated wastewater even at
cycles of concentration above ten. Therefore, chlorides are not expected
to be a major problem during the use of renovated water for cooling
purposes.
100
-------
In using renovated water for industrial purposes, limitations on the dis-
charge of blowdown waters to receiving waters must be considered. Of
prime concern is the toxicity of the discharge, to established fish species
and the tendency for the discharge to stimulate algal growths. Fish bio-
assay studies using the blowdown from.the industrial test loops indicated
that 100 percent of the test organisms survived after 96 hours of exposure
to the concentrated canal water, unfiltered and filtered nitrified effluent,
and filtered chemically treated effluent with and without activated carbon
treatment. However, it should be noted that the bioassay studies were
made on the blowdown waters after they had been aerated sufficiently to
increase the DO to greater than 7 mg/1 and cooled to ambient temperatures.
Zinc, which may be toxic to fish at concentrations of 1 mg/1 or less, was
one of the relatively high constituents of the scale formed in the industrial
test loop studies. Although zinc was probably present in the blowdown
water as well as the scale, there was no apparent effect of this toxic
metal on the test organisms during the bioassay studies. As discussed
earlier, the high zinc concentrations were probably due to leaching of
zinc from the galvanized coating on the cooling tower bottom pans. This
source of zinc would be greatly reduced or eliminated in a commercial-
scale cooling tower.
The use of zinc chromate as a corrosion inhibitor in cooling towers, how-
ever, may cause toxicity to fish or other sensitive organisms if they are
exposed to the blowdown water. This effect was not evaluated during this
study but should be reviewed before such water is discharged to receiving
bodies of water. In this respect, the use of renovated wastewaters is
not expected to cause any greater problems than encountered in the use
of canal water.
101
-------
Based on the findings of the industrial test loop studies, the nitrified ef-
fluent produced the most satisfactory water for industrial reuse except
with respect to algal growth potential. This growth potential was signifi-
cant because neither nitrogen nor phosphorous was reduced by this treat-
ment sequence. The nitrified effluent did have a relatively high potential
for phosphorous precipitation, and the scale analysis did show appreciable
amounts of calcium and phosphorous. Despite this scaling, the fouling
factor was surprisingly low for the nitrified effluent. With phosphorous
removal to minimize algae growth and scaling problems, biological
oxidation and nitrification to remove organics and ammonia, and fil-
tration following nitrification to reduce suspended solids and improve
process reliability, a suitable renovated water can be produced for in-
dustrial cooling purposes. In the event that total nitrogen is limited to
receiving bodies of water, biological denitrification may also be necessary,
Activated carbon treatment tended to increase the fouling factors but had
little or no effect on decreasing the corrosion rates of the renovated
waters. Since it did not appear necessary to remove organic materials
to reduce toxicity, the use of activated carbon treatment for general in-
dustrial water supply does not appear to be necessary. Where specific
uses call for low organic carbon in the water, such as may be required
for boiler feedwater, it would probably be most economical for the indus-
try concerned to supply the additional treatment necessary. Biological
denitrification and activated carbon treatment may also be important if
the renovated water is to be demineralized and used for boiler feed or
process purposes.
102
-------
Section VI
ESTIMATED WASTEWATER TREATMENT COSTS
This section presents cost estimates for 30-mgd plants using the treat-
ment processes investigated during the pilot-demonstration studies.
These cost estimates can serve as an aid in the comparison of alternative
treatment procedures; they are based on assumed average conditions for
land, easements, site preparation, and engineering. Actual costs for
specific treatment facilities, such as those for the Central Contra Costa
Sanitary District, will differ somewhat because of factors peculiar to
the individual construction site. The costs discussed below are for treat-
ment facilities only; they do not include the cost of administration and
maintenance buildings, utility tunnels and discharge lines, or storm
water treatment, since these facilities would be common to all of the
treatment systems.
Figure 6-1 indicates the estimated treatment costs, in 1972 dollars, for
each of the three phases of the study. A cost index of 185. 0, as published
by the EPA for wastewater treatment plants, was used to adjust cost data
presented by others (References 7, 8, 9, and 10). Amortization costs
were based on capital recovery at 6-percent interest over a 25-year
period. For the purpose of cost comparison, no federal or state grants
were assumed. It is emphasized that the costs presented in this section
may not be directly related to water renovation costs because in many
cases considerable treatment is required simply to discharge the efflu-
ent to receiving bodies of water. In such cases, the costs associated
103
-------
PHASE NUMBER
1
"JPRIMARY
~\
2 3
1 IU2
ACTIVATED *
~~T SLUDGE
SLUDGE
DISPOSAL
I-CONVENTIONAL TREATMENT
1
* PRIMARY
ii-BIOLOGICAL
NITRIFICATIO
I
* PRIMARY
IIA-B OLOGICAL
NITRIFICAT
DENITRIFY
III - PHYSICAL-
CHEMICAL
TREATMENT
1
^.INFLUENT
WORKS
ALUM (OPTIONAL)
|~ 2 3 ~J 4 5
1 1 1 1
-1*. A(1TIV*J|D P.NITRIFICATlONk-i*-FILTRATlON !-»
_. SLUDGE -.
r ii i
i
6
N SLUDGE DISPOSAL *-
ALUM (OPTIONAL
r~ "5 314 5
i * * 1
1*. ACTIVATED ^ NITR1F CATION -J^DENITR FICATION ^FILTRATION
p, SLUDGE ^ p.
1 II 1 1 1
1 1 1
1
SLUDGE DISPOSAL »-
mnN
L|M£ NH3 REMOVAL IOPTIONALI 3-11V/1C
1 34
1 CHEMICAL ACTIVATED
CALCINATION ^nou«
LIME
1 | 2 3 4 5
INFLUENT
WORKS
1 CHEMICAL
i*- TREATMENT* »- NITRIFICATION * DEN ITRI FICATION «- FILTRATION
CALCINATION
1
I
6
J±
1 »-
WO GAL
_b
J*.
MIA- COMBINATION BIOLOGICAL SLUDGE
DISPOSAL
TREATMENT COSTS {i n 000 gal)
0 & M
1
2
3
4
1
2
3
4
5
6
OPTIONAL
I
2
3
4
5
6
7
OPTIONAL
1
2
3
4
5
1
2
3
4
5
6
7
1.6
6.5
1.7
3.7
13.5
1 6
6 3
35
36
1 7
38
205
267
1 6
63
35
3.5
36
1 7
3.8
24.0
30.2
1.3
101
3.6
3.4
1.7
20.1
1 3
10 1
3 5
35
36
1.7
1.6
253
AMORTIZATION
2 7
4 6
0 1
3 8
1 1 2
2 7
3 8
3 4
1 4
0 1
4.5
15 9
16 5
2 7
3 8
3 4
3 1
1 4
0 1
4 7
19 2
19 8
2.2
4 4
1 .4
6 4
0.1
14.5
2 2
4 4
3 4
3 1
1 4
0 1
0.9
15 5
TOTAL
4 3
I 1 1
1 8
7 5
24 7
4 3
10 1
6 9
5 0
1 8
8.3
36 4
43 2
t 3
10.1
6 9
6 6
5 0
1 8
8.5
43 2
50 0
3 5
14 5
5 0
9 8
1 8
34 6
3 5
14 5
6.9
6.6
5.0
1 8
2.5
40.8
COMMENTS
Least cost solution
Waslewater may be toxic and require more treatment lor
ditcharge
Limited reduction in nutrient content ol wastewater
Additional costs are excessive if nutrient removal is required (see option
Phase II A)
Limited reuse potential tor industrial purposes due to phosphorus and
Undiluted effluent is apparently not toxic
Nitrification reduces the qxygen demand of the effluent
Phosphorus removal coukj be achieved by adding alum at an annual
cost of 634/1000 gal
Limited reuse potential for industrial purposes due to potential
phosphorus precipitation
Filtration will increase the plant reliability and improve effluent
quality
Undiluted effluent is apparently not toxic
Demtnfication may limit the algal growth in the effluent
improve effluent quality
Industrial reuse would be limited by the high phosphorus
If nitrogen and phosphorus removal are required, this is the most expen
Lime treatment was most reliable of the pilot plant systems
About 95 percent phosphorus removal in the lime stages
Requites additional step for SOC reduction
Effluent is apparently not toxic and may be suitable toi industrial use
if odors are controlled
Filtration may not be necessary if activated carbon is used
Ammonia removal could be accomplished with clinoptilolite ( 8 to
lOrf/lOOOgall
Nitrification reduces the organic carbon and oxidizes the ammonia to
nitrate
Filtration increases reliability of treatment and effluent quality
Nitrified lime-treated effluent is probably nontoxic and should be good
for industrial purposes
Demtnfication could be deleted if nitrogen removal is not
required fot discharge into receiving waters
Figure 6-1. Flow Diagrams and Treatment Costs for 30-mgd Plants
-------
with wastewater treatment should be deducted from the water renovation
co.sts.
General process descriptions of the alternatives considered in the cost
estimates are presented below. Advantages and disadvantages of the
various alternatives are also discussed.
PHASE I: ACTIVATED SLUDGE
The first alternative considered was a conventional activated sludge plant
consisting of primary and activated sludge treatment along with sludge
dewatering and incineration. This alternative was the least expensive
treatment sequence having water costs for a 30-mgd plant of approxim-
ately 24. 7 cents per thousand gallons at capacity. Although this plant
should remove approximately 90 percent of the suspended solids and BOD,
the nutrient content of the effluent, especially ammonia and phosphorous,
\vould support appreciable algal growth. Because of the chlorine demands
associated with the ammonia, the potential for algal growth, and the
likelihood of precipitation of calcium phosphate, additional treatment
processes would be required to produce an effluent suitable for direct
industrial cooling water use. It is possible, however, that an industrial
user could provide the additional treatment necessary.
PHASE II: BIOLOGICAL NITRIFICATION
This system includes the basic plant considered in Phase I with the addi-
tion of a nitrification stage to oxidize the ammonia to nitrate, followed by
105
-------
filtration to increase the overall reliability of the plant and improve the
renovated water quality. The detention time in the activated sludge unit
(i. e. , the first stage) would be reduced so there would be a higher organic
carbon concentration in the nitrification reactor influent and the treatment
costs for -this stage can be reduced. As with the Phase I alternative,
sludge disposal would consist of dewatering and incineration. Costs for
this treatment system were estimated at 36. 4 cents per thousand gallons.
For phosphorous removal, it would be possible to use alum in conjunction
with the biological treatment processes, as indicated in Figure 6-1,
Phase II. Annual operating costs for this treatment would be approxim-
ately 6. 8 cents per thousand gallons in addition to the above mentioned
costs, resulting in a total cost of 43. 2 cents per thousand gallons. This
additional cost represents the cost for the alum feeding system as well
as the additional sludge disposal costs.
With phosphorus removal, the effluent produced with this treatment sys-
tem should, in most cases, be suitable for direct reuse by industry for
cooling water makeup. Consideration must be given, however, to the
increase in TDS, specifically sulfate, resulting from the use of alum for
phosphorus removal.
PHASE II A: BIOLOGICAL NITRIFICATION-DENITRIFICATION
This option is identical to that discussed under Phase II except the addi-
tional step of denitrification has been added to remove inorganic nitrogen
from the effluent. The additional cost for this option would be about 6. 6
cents per thousand gallons. Included in these costs would be the denitri-
fication reactor, an aeration basin, and a settling basin. Aeration is pro-
vided to aid in the sedimentation of the denitrification solids and to bio-
logically oxidize any excess methanol.
106
-------
Sludge disposal costs for this three-stage system were increased to
account for the additional sludge produced during the denitrification
reaction. The total cost for this system was estimated to be 43. 2 cents
per thousand gallons. As discussed for biological nitrification, alum
could be added to the treatment system for phosphorous removal at an
additional cost of about 6. 8 cents per thousand gallons.
As with the Phase II alternative, the effluent produced with the treatment
system including biological denitrification should be suitable for indus-
trial reuse. The nitrogen removal step should reduce the algae growth
potential in industrial cooling towers. However, with phosphorous re-
moval and typical industrial cooling water treatment, the need for bio-
logical denitrification does not appear justified. This treatment step
may be necessary in some cases when the effluent is discharged to a re-
ceiving body of water.
PHASE III: PHYSICAL-CHEMICAL TREATMENT
The physical-chemical treatment system considered for the Phase III
alternative consisted of two-stage chemical treatment followed by filtra-
tion and activated carbon adsorption. Lime would be added to the first
chemical treatment stage, the effluent recarbonated, and the precipitated
calcium carbonate removed in the second stage. The sludges produced
would be dewatered, classified, and recalcined or incinerated. Recal-
cined materials would be reused in the first stage of the chemical treat-
ment process.
This treatment sequence has been estimated to cost 34.6 cents per
thousand gallons. For an additional 8 to 10 cents per thousand gallons,
clinoptilolite could be used to remove ammonia, while ammonia strip-
ping would cost between 3 and 5 cents per thousand gallons treated.
Ammonia removal would be very desirable in conjunction with the in-
dustrial reuse of the water produced.
107
-------
Based on the observed limited removals of turbidity and TOG in the
filtration process during the pilot plant studies, it might ' ossible
to eliminate this process step and use the activated carbon Columns to
remove the small amounts of suspended material carried over from
the chemical treatment process. Also, a single-stage chemical treat-
ment process may be satisfactory for wastewater having relatively high
hardness concentrations. If either the filtration process, second-stage
chemical treatment process, or both could be eliminated, the treatment
cost would be significantly reduced.
Noxious odors that developed in the pilot plant activated carbon columns
indicated the need to develop a satisfactory odor control procedure.
The costs for such a procedure would be expected to be less than 1. 0
cent per thousand gallons, but the procedure must be satisfactorily
developed before this alternative becomes suitable.
PHASE III A: COMBINED PHYSICAL-CHEMICAL-BIOLOGICAL
TREATMENT
An alternative to the independent physical-chemical treatment sequence
described for Phase III would be the use of a combined physical-chemical
biological treatment sequence. Based on the results of the pilot plant
and industrial test loop studies, chemical treatment, as described for
the Phase III alternative, preceding biological treatment, could provide
definite advantages. Since chemically treated wastewater is too high
in organic carbon content (BOD) for reuse or discharge, either activated
carbon or biological oxidation is required to reduce the organic carbon
concentration. Biological nitrification in conjunction with oxidation of
the remaining organic materials could be used. Such a system would
also provide the advantage of phosphorous removal. If discharge lim-
itations require inorganic nitrogen removal, this could be accomp-
lished by biological denitrification, as described under Phase II A. To
108
-------
assure effluent quality and increase process reliability, filtration would
also be desirable. Sludge disposal consisting of dewatering, recalcina-
tion, and incineration would also be included.
The cost for the Phase III A alternative described above and shown in
Figure 6-1, is approximately 40.8 cents per thousand gallons. This
cost is nearly the same as that for the Phase III alternative with ammonia
removal included. As discussed for the Phase III alternative, if a single-
stage chemical treatment system can be used, the cost will be reduced.
The effluent produced with this treatment sequence in which phosphorous
nitrogen, organics, and suspended solids are removed should be suit-
able for direct reuse by industry for cooling water makeup.
109
-------
Section VII
ACKNOWLEDGEMENTS
The assistance and cooperation provided by the Boards of Directors and
staffs of the Central Contra Costa Sanitary District and the Contra
Costa County Water District are gratefully acknowledged. The support
of the Environmental Protection Agency and the help provided by Dr.
Carl Brunner, Project Officer, were sincerely appreciated.
Ill
-------
Section VIII
REFERENCES
1- Feasibility Investigation of Water Renovation in Central Contra
Costa County, prepared for Contra Costa County Water District
by Bechtel Corporation, September 17, 1969.
2. Standard Methods for the Examination of Water and Wastewater,
APHA, AWWA, WPCF, 12th Edition, 1965.
3. Annual Book of ASTM Standards, General Test Methods, Part
30, American Society for Testing Materials, 1970.
4. Instruction and Operational Manual, Model 915, Total Organic
Carbon Analyzer, Beckman Instruments, 1969.
5. R. C. Cooper, R. C. Spear, and F. L. Schaffer, Virus Sur-
vival in the Central Contra Costa County Waste Water Renovation
Plant, University of California at Berkeley, School of Public
Health, The Environmental Health Services Division, January
1972.
6. Standards of Tubular Exchanges, Manufacturers Association, Fifth
Edition, New York, 1968.
7. Estimating Costs and Manpower Requirements for Conventional
Wastewater Treatment Facilities, EPA, Water Pollution Control
Research Series, Project No. 17090 DAN, October 1971.
8. R. Smith, "Cost of Conventional and Advanced Treatment of
Wastewater," Journal WPGF, Vol 40, No. 9, pp 1546-1574,
September 1968.
9. Cost and Performance Estimates for Tertiary Wastewater
Treating Process, Robert A. Taft Water Research Center,
Report No. TWRC-D, June 1969.
113
-------
10. Preliminary Cost Estimates for a Blue Plains Advanced Water
Treatment Plant, prepared for FWQA by Bechtel Corporation,
July 10, 1970.
11. Annual Book of ASTM Standards, Volume 23, American Society
of Testing Materials, 1968.
12. Y. Argaman and C. L. Weddle, "The Fate of Heavy Metals in
Physical-Chemical Treatment Processes, " to be published by
AIChE in 1973).
114
-------
Section IX
APPENDICES
Appendix Page
A ANALYTICAL PROCEDURES 117
Determination of Mercury 117
Determination of Selenium in Wastewater 122
Determination of Trace Metal Emission
Spectroscopy 123
Table A-l; Recovery of Mercury from
100 ml of Wastewater 121
Table A-2: Sampling and Analysis Schedule,
Activated Sludge Process 125
Table A-3: Sampling and Analysis Schedule,
Nitrification/Denitrification Processes 126
Table A-4: Sampling and Analysis Schedule,
Physical-Chemical Processes 127
Table A-5: Sampling and Analysis Schedule,
Industrial Test Loops 128
B TRACE METALS 129
Table B-l: Summary of Heavy Metals Testing
Program 130
Table B-2: Removal of Heavy Metals by Lime
Coagulation, Settling, and Recarbonation 131
Table B-3; Removal of Heavy Metals by (Secondary)
Ferric Chloride Coagulation and Settling 132
Table B-4: Removal of Heavy Metals by Filtration
and Carbon Adsorption 133
115
-------
Appendix A
ANALYTICAL PROCEDURES
This appendix includes a description of analytical procedures that differ
from those of Reference 2 and a tabulation of the sampling frequencies
for the various analytical procedures employed. Sample analysis general-
ly followed the schedule outlined in this appendix. On some occasions,
the schedule was modified due to process upsets or analytical backlog.
DETERMINATION OF MERCURY
The emergence of mercury as a significant environmental contaminant
stimulated the need for the development of methods for its extraction or
separation from a wide variety of substances, including reclaimed waste-
water. In view of the fact that it is a cumulative-type poison, mercury
is of particular importance when considering the use of reclaimed sewage
as an eventual source of potable and irrigational waters.
It was the purpose of this analytical program to determine whether mer-
cury was present in sewage and, if so, to what extent it was removed by
conventional sewage treatment processes. Therefore, it was imperative
to develop a reasonable method for the determination of mercury in sew-
age.
Summary of Method
Sewage samples were taken periodically, either as 24-hour composites or
as hourly samples, and placed in a metal-free sulfur ic-nitric acid solution
117
-------
to promote dissolution of metallic compounds and to prevent sorption of
the metals on the walls of the collection vessel. Glass was the preferred
material for the collection vessel, and great care was taken to avoid con-
tamination of the sample. All containers and utensils making contact
with the sample were thoroughly washed, acid cleaned (metal free), and
double rinsed with deionized water.
The acidified sewage sample was blended for 2 minutes or until com-
pletely homogenized. An appropriate aliquot (50 ml) of the sample was
digested in a reflux condenser for at least 30 minutes. Glass beads were
used to prevent bumping and excessive foaming during digestion. The
condenser unit was highly efficient so as to return any mercury that had
been vaporized. After digestion was completed, the condenser was
rinsed thoroughly with dilute nitric acid (50 ml) to remove any mercury
adhering to the walls, and the digest was filtered through a glass-fiber
filter to remove any organic residue. Provision was made for any
dilution with the rinse water.
Mercury was determined by a spectrophotometer procedure where the
sample was wet ashed or digested with nitric acid-chromium trioxide.
Potential interferences were eliminated by adding ethylene glycol mono-
methyl ether and EDTA. An iodide complex was formed that reacted
with crystal violet and was extracted with toluene. The absorbance of
the extracted crystal violet complex was determined at 605 millimicrons
(m^i), and the mercury concentration was determined by comparison with
standard mercury solutions. The detection limit was 0.25 micrograms
of mercury.
118
-------
Proced
ure
The following apparatus and reagents were used:
Apparatus
300-ml standard tapered (24/40) Erlenmeyer flasks
250-ml glass stoppered separatory funnels
~ Reflux condensers
- Hot plate
Spectrophotometer (capable of reading absorbance
in the 600 mpi range)
Reagents
Hydrogen peroxide, 30 percent
Nitric acid, 10 N containing 1-percent chromium
trioxide
Potassium permanganate, 5 percent
Hydrochloric acid, 5 N
Toluene
Sodium metabisulphite Na S O , 20 percent
LJ Lj O
~ Potassium iodide, 2.5 percent
EDTA disodium salt, 5 percent
Crystal violet, 0. 1- and 1-percent solution
(Dissolve 1 g of crystal violet in 1 ml of
ethylene glycol monomethyl ether. This
solution diluted [10-100] with distilled water
was used in the determination. )
Mercury stock solution (Dissolve 135 mg of
HgCl in 100 ml of distilled water, add 2 ml
of concentrated HC1, and dilute to 200 ml
[1 ml = 0. 5 mg]. Working standard was
made by diluting [l ml to 1000] with dis-
tilled water [1ml = 0.5 g]. The working
standard was made fresh daily.)
119
-------
Analysis . Three ml of 10 N nitric acid containing 1-percent chromium
trioxide were added to a 100-ml aliquot of the completely mixed waste-
water sample. The flask was attached to a reflux condenser (or lightly
stoppered with a glass stopper using a Teflon shim) and placed on a hot
plate set at 250 F. After 30 minutes of refluxing, the sample was re-
moved, ZO ml of 5-percent potassium permanganate were added, and
the sample was refluxed again for 15 minutes. The flasks were removed
and 30-percent hydrogen peroxide was added dropwise to react with
excess permanganate and any manganese dioxide formed. One ml of
excess hydrogen peroxide was added, and the digestion was continued
for an additional 30 minutes. The inside walls of the condenser were
rinsed with a small amount of distilled water before the flask was re-
moved and cooled to room temperature. Five ml of 5 N HC 1 and 1 ml
of 2. 5-percent KI were added to the flasks. A few seconds were allowed
for the iodide complex to form, then ZO-percent sodium metabisulphite
was added dropwise to reduce the excess iodine, adding five drops in
excess (should have odor of SO ). Then Z ml of 5-percent disodium
EDTA were added and thoroughly mixed with the sample. The contents of
the flasks were transferred to a 250-ml separatory funnel, where 5 ml of
0. 1-percent crystal violet solution was added and mixed in to form an
emerald green color. If blue or very dark green colors developed, Z to 5
ml of 5 N HC 1 were added. Five ml of toluene were added and the
stoppered flask shaken gently 10 times, repeating the shaking after co-
alescence of drops. After total coalescence of droplets, the bottom
(water layer) was drained out. The stem of the separatory funnel was
dried, and a plug was inserted to remove suspended materials. The
toluene layer was run directly into a 1-cm cell, and the absorbance was
read at 605 m/j within ZO minutes.
A standard curve was prepared according to the above procedure by
adding 0, 0. 5, 1, 2. 5, and 5 ^g of mercury to 100 ml of the wastewater.
120
-------
Discussion. It was found that the amount of nitric acid-chromium tri-
oxide digestion mixture was critical. Too large an excess after digestion
of organic material had a fading effect on the crystal violet-mercury color
complex, with subsequent loss of sensitivity. The 3-ml addition of nitric
acid outlined in the method in conjunction with the 20 ml of 5-percent
permanganate and 30-percent peroxide should be ample for complete
digestion of the organic material found in normal wastewater. If not,
it is recommended that digestion be continued with 30-percent hydrogen
peroxide.
The above procedure can be used for potable water by using 1 ml of
nitric acid-chromium trioxide mixture instead of 3 ml and reducing the
digestion time by one-half.
There were no significant differences observed in the partition effects
when the crystal violet-Hg complex was extracted with toluene from
75 ml instead of 150 ml of total solution.
It is important that glassware used for the mercury determination be
cleaned with either diluted chromic or nitric acid and rinsed with dis-
tilled water before attempting the analysis.
There were no significant mercury losses during the digestion period.
Wastewater samples spiked with increasing amounts of mercury gave
the results listed in Table A-l.
Table A-l
RECOVERY OF MERCURY FROM 100 ML OF WASTEWATER
Mercury Added (/ug)
0.0
0.5
1.0
2. 5
5.0
Mercury Found (fjg)
0.00
0.49
0. 94
2.45
5. 05
% Recovered
98.0
94.0
98.0
101.0
121
-------
DETERMINATION OF SELENIUM IN WASTEWATER*
Summary of Method
The method used involved simultaneous evaporation and oxidation of the
sample with hydrogen peroxide in an alkaline medium. The residue was
further oxidized by taking up with concentrated HNO and evaporated to
dryness. The selenate that was formed was reduced to selenite with
concentrated HC 1. Reaction with diaminobenzidine produced a yellow
colored compound extractable with toluene, and the absorbance was
determined at 420 mp. with a spectrophotometer.
An average standard deviation of - 0. 001 mg/1 was found by spiking five
samples with 10 micrograms of selenium and another five samples with
30 micrograms of selenium.
Procedure (Reference 2)
To 1000 ml of the sample in a 1500-ml beaker were added 5 ml of 0. 1 N
NaOH, 5 ml of calcium chloride solution, and 10 ml of 30 percent HO.
<-. £*
A few boiling chips were added, and the solution was placed on a hot plate
and evaporated just to dryness. Ten ml of concentrated HNO were added
to oxidize any remaining organic material (evaporation to dryness should
take place on a hot plate at low heat or on a steam bath). The sides of the
beaker were rinsed with approximately 10 ml of distilled water, and the
solution was evaporated to dryness. The residue was cooled; 5 ml of
concentrated HC 1 were added, followed by 10 ml NH Cl solution; and
the mixture was heated on a steam bath for 10 0.5 minutes. The warm
solution and precipitate, if any, were transferred to a graduated 100-ml
beaker suitable for pH adjustment; the larger beaker was rinsed with 5
ml of EDTA-sulfate reagent and 5-ml of 5 N NH OH. The pH was adjusted
Modified Diaminobenzidine Method A
122
-------
to 1.5 - 0 3 with NH OH. One ml of diaminobenzidine solution was added,
4
and the mixture was heated on a steam bath for approximately 5 minutes
and cooled and adj
adjusted to 50 ml.
and cooled and adjusted to pH 8 1 with NH OH. The volume was then
The contents were poured into a Z50-ml separatory funnel with 10 ml of
toluene and shaken for approximately 30 seconds. After the lower aqueous
layer was drained, the stem of the separatory funnel was dried and a cotton
plug inserted. The toluene was allowed to run into a 1-cm cuvette, and
the absorbance was determined at 420 mjj.. If there was any difficulty in
obtaining two distinct layers, as much of the bottom layer as possible
was drained. The remaining material was transferred to a centrifuge
tube and centrifuged for approximately 3 minutes, or until a definitely
clear toluene layer was obtained. (If no centrifuge is available, the upper
layer could be filtered through paper containing anhydrous sodium sulfate. )
A calibration curve was made by spiking approximately 500 ml of the
sample with 0, 10, 20, 30, and 40 micrograms of selenium. The stock
selenium solution was made by dissolving an accurately weighed amount
of reagent grade selenium in 5 ml of concentrated HNO . The solution
was heated to dryness and diluted to 1000 ml with distilled water. Ap-
propriate dilutions of the stock solution resulted in a standard solution
such that 1 ml was equivalent to 1. 0 microgram of selenium.
DETERMINATION OF TRACE METALS BY EMISSION SPECTROSCOPY
Summary of Method
Emission spectrography was used as a means of determining total trace
metal concentration. Samples were treated with sulfuric acid and dried
at 600°C before being weighed'and arced using standard spectographic
123
-------
techniques. These analyses, coupled with atomic absorption results,
gave values for both soluble and insoluble metal content necessary for
the investigation of treatment removal efficiencies.
Procedure (Reference ll)
Two ml of concentrated H SO were added to a 400-ml water or waste-
water sample of known total solids concentration. The sample was
partially dried on a water bath. A hot plate was used to dry the sample
completely by heating it under a hood at 600 C. After 30 minutes, the
residue was scraped with a plastic spatula. A 10-mg residue sample
was weighed and analyzed using a DC arc in accordance with ASTM
methods for spectrographic determination of solids.
124
-------
Table A-2
SAMPLING AND ANALYSIS SCHEDULE
ACTIVATED SLUDGE PROCESS
Analysis*
Turbidity
PH
Conductivity
Total organic carbon
Soluble organic carbon
Ammonia
Nitrate
Total Kjeldahl nitrogen
Ortho-pho sphate
Total phosphate
Total hardness
Calcium hardness
Total alkalinity
Chloride
Sulfate
Silica
Settleable solids
Suspended solids
Volatile suspended solids
Dissolved solids
Dissolved oxygen
Coliform count
Chemical oxygen demand
Biochemical oxygen
demand
Temperature
Activated Sludge
Influent
D
D
D
D
D
D
D
W
D
D
W
W
W
W
W
W
D
D
D
W
W
Mixed
Liquor
D
D
D
D
D
Effluent
D
D
D
D
D
D
D
W
D
D
W
W
W
W
W
W
D
D
D
W
W
Filter
Effluent
D
D
D
D
D
D
W
D
D
D
W
Activated Car-
bon Effluent
1st
D
D
D
D
D
W
2nd
D
D
D
D
D
D
D
W
D
D
D
W
W
D = Daily
Three times/week
W
Weekly
All samples were hourly samples composited on a daily basis except for
the mixed liquor sample, which was a daily "grab" sample.
125
-------
Table A-3
SAMPLING AND ANALYSIS SCHEDULE
NITRIFICATION/DENITRIFICATION PROCESSES
Analysis
Turbidity
pH
Conductivity
Total organic
carbon
Soluble organic
carbon
Ammonia
Nitrate
Ortho-phosphate
Total phosphate
Total hardness
Calcium hardness
Total alkalinity
Chloride
Sulfate
Silica
Scttleable solids
Suspended solids
Volatile suspen-
ded solids
Dissolved solids
CCCSD
Primary
Influent
T
T
T
T
T
W
T
W
W
Primary
Effluent
T
T
T
T
r
\\
Nitrification
Influent
D
T
T
T
T
D
D
T
W
T
Mixed
Liquor
"
D
D
W
Effluent
D
D
T
T
D
D
Denitrification
Mixed
Liquor
T
w ;
r
D
U
W
Effluent
D
D
T
T
T
D
D
T
W
W
W
W
T
Filter
Effluent
D
T
' T
W
W
W
W
Activated Car -
bon Effluent
1st
D
T
T
2nd
D
T
T
T
T
W
W
T
W
W
W
W
w
\v
w
w
w
Daily
Three times/week
Weekly
All samples were hourly samples composited on a daily bnsis except for the mixed liquor samples,
which were daily "grab" samples.
126
-------
Table A-4
SAMPLING AND ANALYSIS SCHEDULE
PHYSICAL/CHEMICAL PROCESSES
Analysis-'-
Turbidity
pH
Conductivity
Total organic carbon
Soluble organic carbon
Ammonia
Nitrate
Ortho-phosphate
Total phosphate
Total hardness
Calcium hardness
Total alkalinity
Chloride
Sulfate
Silica
Settleable solids
Suspended solids
Volatile suspended solids
Dissolved solids
Flocculation
Influent
1st
T
T
T
T
W
W
T
W
W
W
W
W
W
W
T
W
W
2nd
D
D
D
T
T
T
W
W
W
W
T
W
W
Effluent
2nd
D
D
D
T
T
W
W
T
W
W
W
W
T
W
Filter
Effluent
D
T
T
T
T
W
W
Activated Car-
bon Effluent
1st
D
T
T
2nd
D
T
T
T
T
W
W
T
W
W
W
W
W
W
W
W
D Daily T = Three time's/week W = Weekly
* All samples were hourly samples composited on a daily basis.
127
-------
Table A-5
SAMPLING AND ANALYSIS SCHEDULE
INDUSTRIAL TEST LOOPS
Analysis*
Turbidity
pH
Conductivity
Total organic
carbon
Ammonia
Nitrate
Ortho-phosphate
Total phosphate
Total hardness
Calcium hardness
Total alkalinity
Chloride
Sulfate
Silica
Sulfite
Suspended solids
Corrator
Temperature
Circulating Water
Tower
No. 1
T
D
D
W
W
W
W
W
W
W
W
W
W
W
W
D
D
Tower
No. 2
T .
D
D
W
W
W
W
W
W
W
W
W
W
W
W
D
D
Tower
No. 3
T
D
D
W
W
W
W
W
W
W
W
W
W
W
W
D
D
Boiler
Blow-
down :
W
W
W
W
W
Softener
. Effluent
W
W
W
W
W
Con-
densate
W
W
W
W
W
Canal
Water
.. W
W
W
W
W
W
W
W
W
W
W
W
D = Daily T = Three times/week W = Weekly
* All samples were hourly samples composited on a daily basis.
128
-------
Appendix B
TRACE METALS
This appendix contains a summary of a separate study concerned with the
removal of heavy metals in the various treatment stages of a physical-
chemical pilot treatment facility. The treatment plant influent was dosed
with a mixture of heavy metals, and their removal was monitored through
the treatment process. Although this study was not within the scope of
work of the project, the results are included here for informational pur-
poses. A complete discussion of the data may be found in a paper by
Yerachmiel Argaman and Clark L. Weddle (Reference 12).
129
-------
Table B-l
SUMMARY OF HEAVY METALS TESTING PROGRAM
Run
No.
Heavy Metals Added
Point of Addition
NTA
Added
1
Zn 10 xng/1, Mn 2. 0 mg/1,
others* 0. 5 mg/1
Zn 10 mg/1, Mn 2. 0 mg/1,
others -2.0 mg/1
Zn 10 mg/1, Mn 2. 0 mg/1,
others 2. 0 mg/1
As, Cd, Cu, Hg 10. 0 mg/1,
Mn 2. 0 mg/1
As, Cd, Cu 10 mg/1, Hg
5 mg/1, Mn 20. 0 mg/1
Zn 10 mg/1, Mn 2. 0 mg/1,
others 2. 0 mg/1
Zn - 10 mg/1, Mn 2. 0 mg/1,
others 2. 0 mg/1
Ahead of lime coagulation
Ahead of lime coagulation
Ahead of lime coagulation
Ahead of lime coagulation
Ahead of lime coagulation
Ahead of ferric coagulation
(2nd stage)
Ahead of filtration
0
10.0mg/l
' Other metals added were: Ag, As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb
130
-------
Table B-2
REMOVAL OF HEAVY METALS BY LIME COAGULATION,
SETTLING, AND RECARBONATION
(In and Out Concentrations in mg/1)
Metal
Ag
As
Ba
Cd
Co
Cr
Cu
Hg
Mn
Ni
Pb
Zn
Run #1
In
0.04
0. 36
0. 54
0.42
0. 45
0.60
2.2k
0. 75
0. 41
9.61
Out
0.01
0.04
0.01
0. 04
0. 30
0.04
0.02
0. 11
0.04
0. 12
%
rem
96
89
98
90
33
93
99
85
90
99
Run t>2
In
1. 51
-1.08
1. 42
1.29
1.40
1.47
1. 37
1.36
1.21
7. 34
Out
0.02
0. 14
0.02
0.05
1.25
0.23
0.01
0. 20
0.05
0. 18
%
rem
99
87
99
96
11
84
99
85
96
97
Run #3 (NTA)
In
1.20
1.48
1.48
2.07
2.95
0.71
2. 37
1.48
1.48
10.00
Out
0.06
0.06
0. 19
1.58
2. 53
0.32
1.27
1.27
0.25
1. 58
%
rem
95
96
87
24
14
55
46
14
83
84
Run #4
In
8.40
4.00
4.60
4.45
Out
0. 30
0. 19
0. 31
0.61
%
rem
96
95
93
86
Run #5
In
7.00
5.78
4.60
3.26
Out
0.20
0. 13
0.20
0.29
%
rem
97
98
96
91
131
-------
Table B-3
REMOVAL OF HEAVY METALS BY (SECONDARY)
FERRIC CHLORIDE COAGULATION AND SETTLING
(In and Out Concentrations in mg/1)
Metal
Ag
As
Ba
Cd
Co
Cr
Cu
HS
Mn
Ni
Pb
7.n
R
In
0. 01
0.04
0.01
0. 04
0. 30
0.04
0.02
0, 11
0.04 '
0. 12
un 11
Out
0.01
0.03
0.01
0.017
0.07
0.03
0.02
0.09
0.04
0. 13
r em
25
58
72
25
18
-R
In
0.02
0. 14
0.02
0.05
1.25
0.23
0.01
0,20
0.05
0. 18
u'n "2
I
Out
0.01
0.07
0.01
0.02
0.63
0,02
0.01
0. 15
0.023
0. 04
rem
50
50
50
60
50
56
25
54
78
R
In
0.06
0.06
0. 19
1. 58
2, 53
0. 32
1.27
1. 27
0. 25
1. 58
un' "3
Out
0,02
0.09
0.01
0. 49.
0.65
0. 29
0. 19
0. 66
0. 12
0. 53
rem
Ij7
95
69
78
9
85
48
52
66
' -R
In
0. 30
0.-19
0. 31
0.61
un M
Out
0.01
0.-04
0. 32
0. 28
. -
rem
97
79
54
' R
'In-
tl. 20
0: 13-
-
'0, 2T)
0,29;
un »5
Out
0.01
-------
Table B-4
REMOVAL OF HEAVY METALS BY
FILTRATION AND CARBON ADSORPTION
(In and Out Concentration in mg/1)
Metal
Ag
Ba
Cd
Co
Cr
Cu
Mn
Ni
Pb
Zn
Dual Media Filtration
Run #6
In
0. 09
0. 23
0.29
1.40
3.40
0. 17
2. 30
1. 10
0,23
00 04
Out
0.02
0. 16
0.01
0. 16
0. 83
0. 24
0. 27
0.41
0.03
0. 03
%
rem
78
30
96
89
76
88
63
87
25
Run #7
In
1.90
1.90
2. 10
1. 90
2. 70
0. 54
2. 70
1.60
1.40
4, 30
Out
0.02
0.05
0.02
0.48
1. 04
0. 28
0.29
0. 51
0. 02
Oo 05
%
rem
99
97
99
75
61
48
89
68
99
99
Activated Carbon Adsorption
Run #6
In
0.02
0. 16
0. 01
0. 16
0. 83
0. 24
0. 27
0.41
0.03
0. 03
Out
0.01
0.02
ND
0.014
Oo 01
0. 01
0. 01
0. 0014
0.04
0, 03
%
rem
50
88
91
99
96
96
97
Run #7
In
0.02
0.05
0. 02
0.48
1. 04
0. 28
0,29
0. 51
0.02
0.05
Out
0.01
0,01
0.01
0. 004
0. 01
0.01
0. 28
0. 12
0.0002
0. 02
%
rem
50
80
50
99
99
96
34
76
90
60
133
fiU.S. GOVERNMENT PRINTING OFFICE:1973 546-310/72 1-3
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FOI?M
t. Report Ho.
ccf.iaiou ffo.
w
4 Tit! a
Pilot-Demonstration Project for Industrial
Reuse of Renovated Municipal Wastewater
Asithor(s)
Mr. G. A. Horstkotte, Jr.
Contra Costa County Water District
Central Contra Cpsta Sanitary District
5. Report Date
6.
9. Perfarmia&Ofgaaizatioa
Report No,
10. Project No.
17080 FSF
11, Contract/Great Nu
13. Type of Report and
Period Covered
12. Sponsoring Organization
Environmental Protection Agency report number,
EgA-670/2-73-064. August 1973. _
IS. Abstract
Three pilot plant treatment sequences were operated during this study"to produce
various grades of effluent for subsequent testing as industrial water sources. The
testing was conducted in pilots-sized test loops consisting of small cooling towers and
heat exchangers. At the same time the renovated waters were tested, Contra Costa
Canal water, which is presently used by industry in the study area, was also investi-
gated in a test-loop identical to those used for the renovated water.
The study results illustrated that the wastewater investigated can be treated satis-
factorily for reuse in industrial applications. Corrosion rates and fouling factors
observed with renovated water were equal to or less than found with the canal water.
Precipitation of phosphorous was the major source of scale formation while using
renovated water for copling purposes, thus indicating the need for phosphorous
removal.
I7a. Descriptors Water reuse , Reclaimed water , Sewage treatment, tertiary treatment,
Waste water
17b. Identifiers
17c. CO WKR Field & Group 05D
IS. Availability
19. Security Class.
(Report)
20. Security Class.
(Page)
27.
1ft. ot
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. ZO24O
Abstractor
[tift'tutton
Central Contra Costa Sanitary District
------- |