&EPA
          United States
          Environmental Protection
          Agency
           Office of Research and
           Development
           Washington, DC 20460
EPA/600/9-90/036
August 1990
Proceedings -Twelfth
United States-Japan
Conference on Sewage
Treatment Technology
          October 12-13, 1989
          Cincinnati, Ohio

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                                EPA/600/9-90/036
                                August 1990
              PROCEEDINGS

TWELFTH UNITED STATES-JAPAN CONFERENCE
                  ON
      SEWAGE TREATMENT TECHNOLOGY
          OCTOBER  12-13,  1989
           CINCINNATI, OHIO
 RISK REDUCTION  ENGINEERING  LABORATORY
 U.S. ENVIRONMENTAL PROTECTION AGENCY
  OFFICE OF RESEARCH AND DEVELOPMENT
        CINCINNATI, OHIO 45268

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                                  DISCLAIMER
     These Proceedings have been reviewed by the U.S. Environmental Protection
Agency and approved for publication.  Approval does not signify that the
contents necessarily reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.

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                         FOREWORD
     The maintenance of clean water supplies and the
management of municipal and industrial wastes are vital
elements in the protection of the environment. 	

     The participants in the United States-Japan cooperative
project on sewage treatment technology have completed their
Twelfth Conference.  These conferences, held at 24-month
intervals, have given the scientists and engineers of the
cooperating agencies an opportunity to study and compare the
latest practices and developments in the United States and
Japan.  These Proceedings of the Twelfth Conference comprise
a useful body of knowledge on sewage treatment, which will be
available not only to Japan and the United States but also to
all nations of the world who desire it.
                         William K. Rei
                           Administrator
Washington, D.C.

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                               TABLE OF CONTENTS
Foreword.		
List of Japanese Delegates and Presentation Topics	
List of United. States Delegates and Presentation Topics
Joi nt Communique 	
Japanese Papers 	f	
United States Papers 		
  VI
v i i i
   1
   3
   5

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                              JAPANESE  DELEGATION
          Delegates

Dr. Ken Murakami (Head of Delegation)
Director, Regional Sewerage Division
Sewerage & Sewage Purification Dept.
City Bureau
Ministry of Construction

Mr. Taigo Matsui
Director, Water Quality Control Dept.
Public Works Research Institute
Ministry of Construction

Mr. Shunsoku Kyosai
Research Coordinator for
  Wastewater Treatment
Water Quality Control Dept.
Public Works Research .Institute
Ministry of Construction

Mr. Eiichi Nakamura
Chief, Water Quality Section
Water Quality Control Dept.
Public Works Research Institute
Ministry of Construction

Dr. Kazuhiro Tanaka
Director, Research & Technology
  Development Division
Japan Sewage Works Agency

Mr. Masanobu Aoki
Deputy Director
Research & Technology Development Division
Japan Sewage Works Agency

Mr. Kazuo Hoya
Director, Engineering Division
Regional Sewerage Center
Sewerage Bureau
Tokyo Metropolitan Government
     Presentation Topics

New Movement in Sewerage
Construction Projects in Japan
Renovation of an Extended
Aeration Treatment Plant for
Biological Nutrient Removal
Process

Innovative Wastewater Treatment
Processes - Interim Results of
Biofocus WT Project
Toxicity Monitoring Method by
Biosensor
Innovative Sludge Handling System
Using Pelletization for
Simultaneous Thickening and
Conditioning

Development of a High Efficiency
Nitrogen Removal System Using
Immobilized Nitrifiers in
Synthetic Resin

Fundamental Study on Application
of High Gradient Magnetic
Separation to Municipal
Wastewater Treatment System
                                      VI

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                      JAPANESE DELEGATION (continued)
Mr. Senji Kaneko
Chief, Research & Development Division
Sewage Works Bureau                 
Yokohama City

Mr. Hirdshi Oniki
Director, Planning Department
Sewage Works Bureau
Fukupka City
 Operation  of Centralized Sludge
"Treatment  Plant
 Development of Sludge  Treatment
 Technology in  Biological
 Phosphorus Removal  Process
Dr. Takeshi Kubo (Advisor)
Counselor, Japan Sewage Works Agency
                                      VI 1

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                           UNITED STATES DELEGATION
             Delegates

Mr. John J. Convery  (Head of Delegation)
Deputy Director
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency

Mr. Dolloff F. Bishop
Chief, Treatment Assessment Branch
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency    .>
  Presentation Topics
Dr. William C. Boyle
Dept. of Civil & Environmental Engineering
University of Wisconsin-Madison

Mr. William F. Brandes
Permits Division
Office of Water Enforcement & Permits
U.S. Environmental Protection Agency
Performance of Fine Pore
Aeration Systems in Process
Water

Current Status and Future
Direction of Organic Toxics
Control in the Water
Environment - Discharge
Regulations and Stream
Standards
Mr. Richard C. Brenner
Environmental Engineer
Treatment Assessment Branch
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Mr. Donald S. Brown
Environmental Engineer
Municipal Wastewater Branch *
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
In-Vessel Composting of
Municipal Wastewater Sludge
Mr. Randall J. F. Bruins
Environmental Scientist.
Environmental Criteria & Assessment Office
U.S. Environmental Protection Agency
The Development of Risk
Assessment Methodologies
for Use in Regulation of
Sewage Sludge Disposal

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                    UNITED  STATES  DELEGATION  (continued)
Dr. Carl A. Brunner.
Acting Chief, Hazardous Waste Treatment Branch
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Dr. Arthur J. Condren
James M. Montgomery Consulting Engineers, Inc.

Dr. 'Richard A. Dobbs
Research Chemist
Treatment Assessment Branch
Water & Hazardous Waste Treatment
  Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency

Dr. Rahesh Govind
Dept. of Chemical and Nuclear Engineering
University of Cincinnati
                                                  A Preliminary Assessment of
                                                  High Biomass Systems

                                                  Partitioning of Toxic
                                                  Organic Compounds Between
                                                  Wastewater and Wastewater
                                                  Solids
                                                  Prediction of Biodegradation
                                                  Kinetics of Toxic Organic
                                                  Compounds
Dr. James A. Heidman
Sanitary Engineer
Municipal Wastewater Branch
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
                        Wastewater Branch
                        Treatment
Mr. James F. Kreissl
Acting Chief, Municipal
Water & Hazardous Waste
  Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency

Dr. Vincent P. Olivieri
Department of Geography and
  Environmental Engineering
The Johns Hopkins University
Dr. 0. Karl Scheible
Hydro-Qual, Inc.
Experience with Intrachannel
Clarifiers in the U.S.A.
Levels and Removal of
Selected Indicator and
Pathogenic Microorganisms
During Conventional  -
Anaerobic Sludge Digestion

UV Disinfection

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                    UNITED STATES DELEGATION (continued)
Mr. Henry H. Tabak
Research Chemist
Treatment Assessment Branch
Water & Hazardous Waste Treatment
  Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Biodegradability and
Biodegradation Kinetics
Assessment for Toxic
Organic Compounds Using
Oxygen Uptake Measurements
Dr. Albert D. Venosa
Microbiologist
Municipal Wastewater Branch
Water & Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency

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      UNITED  STATES AND  JAPANESE DELEGATES TO THE
                  TWELFTH CONFERENCE
DR. KEN MURAKAMI, HEAD OF THE JAPANESE DELEGATION,  AND
MR. JOHN CONVERY, HEAD OF THE U.S. DELEGATION, MAKING
          OPENING REMARKS AT THE CONFERENCE
                          XI

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r
                  DELEGATES OBSERVING PILOT ROTATING BIOLOGICAL CONTACTOR STUDIES AT
                       THE USEPA TEST AND EVALUATION FACILITY,  CINCINNATI,  OHIO
                DELEGATES OBSERVING MECHANICAL COMPOSTING OF SLUDGE AT HAMILTON, OHIO
                                                  xn

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                WASTEWATER  REUSE  PLANT OPERATION AT
           DENVER, COLORADO,  BEING DESCRIBED TO DELEGATES
DELEGATES OBSERVING SEWER RELINING AT LOS ANGELES COUNTY, CALIFORNIA

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DELEGATES OBSERVING THE
COLLECTION AND EVALUATION
OF MARINE LIFE NEAR SEWAGE
OUTFALLS, LOS ANGELES
COUNTY, CALIFORNIA
                                     xiv

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                                JOINT COMMUNIQUE

                   Twelfth United States/Japan Conference on
                          Sewage Treatment Technology

                            Friday,  October  13,  1989

 1.    The  Twelfth  United  States/Japan Conference on Sewage Treatment  Technology
 was  held  in  Cincinnati,  Ohio,  October 12  and  13,  1989.

 2.    The  US  Delegation headed  by Mr.  John J.  Convery,  Deputy  Director,  Risk
 Reduction Engineering Laboratory, U.S.  Environmental  Protection  Agency
 (USEPA),  Cincinnati, Ohio, was composed of  twelve representatives  from  the
 USEPA, two representatives from consulting  engineering  companies,  and three
 representatives from the universities.

 3.    Dr.  Ken Murakami, Director, Regional Sewerage Division,  Sewerage and
 Sewage Purification Department, Ministry  of Construction was  the Head of the
 Japanese  Delegation, which consisted  of four  National Government
 representatives,  three Japan Sewage  Works Agency representatives,  and three
 representatives from'the Tokyo Metropolitan Government, Yokohama City and
 Fukuoka City.

 4.    During  the Conference, papers related  to toxics control  in  municipal
 wastewater,  and sludge treatment and  disposal technologies.were  presented by
 both  sides.  Additional  presentations were made by the  Japanese  side
 concerning sewage construction  projects and innovative  wastewater  treatment
 processes including nutrient removal.   The US side, too, presented additional
 papers related to aeration methods, pathogens and disinfection,  and  innovative
 treatment.  Data  and findings  were useful to the development  of  sewage
 treatment technology for  each  country.                      .

 5.    Field visits in Chicago,  IL, -Denver, CO, and Los Angeles, CA  are planned
 to inspect sewers and wastewater treatment facilities.

 6.   A proceedings of the Twelfth Conference shall be printed in English and
 Japanese.

 7.   Regarding the operation of the Sewage Treatment Technology  Project under
 the United States/Japan  Environmental Cooperation Agreement (hereinafter
 referred to as the Project), both sides agreed that the Project  be amended
 following  .this conference to have a workshop for technology exchanges and
visits in  either country by sending one .or two representatives to the host
country.   Each side would host the workshop at least once every two years
alternatively..

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                         JOINT COMMUNIQUE (continued)
8.   Both sides agreed that engineer exchanges and the cooperative research
program be continued as before.

9.   Summaries of the research projects concerning sewage treatment technology
of each country shall be exchanged every year.

10.  A progress report shall be prepared each year by both the US and Japan to
summarize briefly the activities of the Project.  The progress reports' shall
be exchanged at the time of the workshops discussed in paragraph 7.

11.  The Co-chairmen'of the Project shall be the Branch Chief responsible for
municipal wastewater research, Water and Hazardous Waste Treatment Division,
Risk Reduction Engineering Laboratory, USEPA for the US side and Director,
Sewerage and Sewage Purification Department, Ministry of Construction for the
Japanese side.                                     .              ,

12.  It was proposed by the Japanese side that the forthcoming workshop based
on paragraph 7 of this Joint Communique shall be held in Tsukuba around May
1990.                  -                                   v

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                                JAPANESE  PAPERS
INNOVATIVE WASTEWATER TREATMENT PROCESSES - INTERIM RESULTS OF
BIOFOCUS WT PROJECT	
     Shunsoku Kyosai, Research Coordinator for Wastewater Treatment,
     Yutaka Suzuki, Masahiro Takahashi, Katsumi Moriyama, Masashi
   -  Ogoshi, Toshiyuki Nakajima, Takashi Masuda, Suuichi Ochi, and
     Hiroaki Tanaka, Water Quality Control Department, Public Works
     Research  Institute, Ministry of Construction

FUNDAMENTAL STUDY ON APPLICATION OF HIGH GRADIENT MAGNETIC
SEPARATION TO MUNICIPAL WASTEWATER TREATMENT SYSTEM 	
  ,   Kazuo Hoya, Director, Engineering Division, Regional Sewerage
     Center, Yasuo Tanaka, Ph.D., Researcher of Research and
     Technological Development Section, Planning Division, and Khouichi
     Ishida, Asst. Head of Research and Technology Development Section,
     Planning Division, Sewerage Bureau, Tokyo Metropolitan Government
   59
NEW MOVEMENT IN SEWERAGE CONSTRUCTION PROJECTS IN JAPAN	
     Dr. Ken Murakami, Director, Regional Sewerage Division,
     Sewerage and Sewage Purification Department, City Bureau,
     Ministry of Construction

INNOVATIVE SLUDGE HANDLING SYSTEM USING SLUDGE PELLETIZATION
FOR SIMULTANEOUS THICKENING AND CONDITIONING  	
     Dr. Kazuhiro Tanaka, Director, Shuzo Koike, Research Engineer,
     Research and Technology Development Division, Japan Sewage Works
     Agency, and Naohiro Taniguchi, Director, General Planning Section
     of General Planning Division, City Planning Bureau, Tokyo
     Metropolitan Government
 ,101
,119
OPERATION OF CENTRALIZED SLUDGE TREATMENT PLANT	
     Senji Kaneko, Chief, Research and Development Division,
     Sewage Works Bureau, Yokohama City

DEVELOPMENT OF SLUDGE TREATMENT TECHNOLOGY  IN BIOLOGICAL PHOSPHORUS
REMOVAL PROCESS	
     Hiroshi Oniki, Director,  Planning Department, Sewage Works
     Bureau, Fukuoka.City
,157
,215.
TOXICITY MONITORING METHOD  BY  BIOSENSOR  	
     Eiichi Nakamura,  Chief, and Hiroaki Tanaka, Senior Research
     Engineer, Water Quality Section,  Public Works Research  Institute,
     Ministry of  Construction
.239-

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                           JAPANESE PAPERS (continued)
RENOVATION OF AN EXTENDED AERATION TREATMENT PLANT FOR BIOLOGICAL
NUTRIENT REMOVAL PROCESS	i.	
     Taigo Matsui, Director, K. Sato, K. Moriyama, Water Quality
     Control Department, Public Works Research Institute, Ministry
     of Construction, M. Imamichi and Y. Yarada, Sewage Works
     Division, Hamamatsu City  .            .

DEVELOPMENT OF A HIGH EFFICIENCY NITROGEN  REMOVAL SYSTEM USING
IMMOBILIZED NITRIFIERS  IN SYNTHETIC RESIN  	
     Masanobu Aoki, Deputy Director,-Minoru Tada, Deputy Director,
     Takashi Kimata, Shouji Harada, and Yuhko Fujii,  Research and
     Technology Development Division, Japan Sewage Works Agency
,253
.265

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                              UNITED  STATES  PAPERS

CURRENT STATUS AND  FUTURE  DIRECTION  OF  ORGANIC'TOXICS  CONTROL  IN
THE WATER  ENVIRONMENT  -  DISCHARGE  REGULATIONS AND  STREAM  STANDARDS  	295
     William  F.  Brandes, and  Catherine  Crane, Permits  Division,
     Office of Water Enforcement and Permits, U.S.  EPA, Washington,  DC

PERFORMANCE OF FINE PORE AERATION'SYSTEMS  IN PROCESS WATER	-	303
     Dr. William C. Boyle,  Professor, Department of Civil and
     Environmental  Engineering, University  of Wisconsin,  Madison,
  '   Wisconsin;  Richard  C.  Brenner,  Environmental  Engineer, Water
     and Hazardous Waste Treatment Research Division,  Risk  Reduction
     Engineering Laboratory,  U.S.  EPA,  Cincinnati,  Ohio;  James J. Marx,
     Consulting  Engineer,  Donohue  and Associates,  Milwaukee, Wisconsin;
     and Thomas  C. Rooney,  Consulting Engineer, Waukesha, Wisconsin

BIODEGRADABILITY AND BIODEGRADATION  KINETICS ASSESSMENT FOR TOXIC
ORGANIC COMPOUNDS USING OXYGEN UPTAKE MEASUREMENTS	325
     Henry H. Tabak, Research Chemist,  Water and Hazardous Waste
     Treatment Research Division,  Risk  Reduction Engineering
     Laboratory, U.S.  EPA,  Cincinnati,  Ohio; Senjay Desai, Chemical
     Engineer, and Dr. Rakesh Govind, Professor, Department of Chemical
     and Nuclear Engineering, University of Cincinnati, Cincinnati,
     Ohio                                                                   '

PREDICTION OF BIODEGRADATION KINETICS OF TOXIC ORGANIC COMPOUNDS 	I..383
     Sanjay Desai, Chemical Engineer, Dr. Chao Gao, Visiting Chinese
     Scholar, Dr. Rakesh Govind, Professor, Department of Chemistry
     and Nuclear Engineering, University of Cincinnati, Cincinnati,
     Ohio; and Henry H. Tabak, Research Chemist, Water and Hazardous
     Waste Treatment Research Division, Risk Reduction Engineering
     Laboratory,  U.S.   EPA,   Cincinnati, Ohio

PARTITIONING OF  TOXIC ORGANIC COMPOUNDS BETWEEN WASTEWATER AND
WASTEWATER SOLIDS	'	401
     Dr.  Richard A.  Dobbs,   Research Chemist, Water and
     Hazardous Waste Treatment Research Division,  Risk Reduction
     Engineering Laboratory, U.S.  EPA, Cincinnati,  Ohio

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                       UNITED STATES PAPERS (continued)

LEVELS AND REMOVAL OF SELECTED INDICATOR AND PATHOGENIC MICROORGANISMS
DURING CONVENTIONAL ANAEROBIC SLUDGE DIGESTION 	:	425

     Dr. Vincent P. Olivieri, Professor, Lynne Cox, and Mohammed Sarai,
     Department of Geography and Environmental Engineering,  The Johns
     Hopkins University, Baltimore, Maryland; Dr. Jan L. Sykora,
     Professor, and Patrick Gavagahn, University of Pittsburgh,
     Pittsburgh, Pennsylvania
IN-VESSEL COMPOSTING OF MUNICIPAL WASTEWATER SLUDGE 	..	441
     Donald S. Brown, Environmental Engineer, Water and Hazardous
    Waste Treatment Research Division, Risk Reduction Engineering
     Laboratory, U.S. EPA, Cincinnati, Ohio; John Johnston,  Associate
     Professor, California State University-Fresno, Fresno,  California;
     and Leslie Bayer, Eastern Research Group, Arlington, Massachusetts

THE DEVELOPMENT OF RISK ASSESSMENT METHO*DOLOGIES FOR USE IN
REGULATION OF SEWAGE SLUDGE DISPOSAL 	475
     Randall J. F. Bruins, Physical Scientist, Dr. Norman E. Kowal,
     Research Medical Officer, Cynlthia Sonich-Mullin, Environmental
     Health Scientist, and Steven D. Lutkenhoff, Physiologist,
     Environmental Criteria and Assessment Office, U.S. EPA, Cincinnati,
     Ohio
UV DISINFECTION 	1	
     Dr. 0. Karl Scheible, HydroQual, Inc., Mahwah, New Jersey
                                                                         .485
                                                                         ,515
A PRELIMINARY ASSESSMENT OF HIGH BIOMASS SYSTEMS	
     Dr. Arthur J. Condren, James M. Montgomery Consulting
     Engineers, Inc., Pasadena, California; Dr. Bjorn Rusten,
     Aquateam Norwegian Water Technology Centre AS, Oslo, Norway;
     and Dr. James A. Heidman, Sanitary Engineer, Water and Hazardous
     Waste Treatment Research Division, Risk Reduction Engineering
     Laboratory, U.S. EPA, Cincinnati, Ohio

EXPERIENCE WITH INTRACHANNEL CLARIFIERS IN THE U.S.A...:	531
     James F. Kreissl, Environmental Engineer, Water and Hazardous
     Waste Treatment Research Division, Risk Reduction Engineering
     Laboratory, U.S. EPA, Cincinnati, Ohio; Dr. A. T. Wallace,
     Professor, College of Engineering, University of Idaho, Moscow,
     Idaho; and Jon H. Bender, Environmental Engineer, Technical Support
     Division, Office of Drinking Water, Office of Water, U.S. EPA,
     Cincinnati, Ohio

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      INNOVATIVE WASTEWATER TREATMENT PROCESSES

     - INTERIM RESULTS OF BJOFOCUS WT PROJECT -
                          by
 Shunsoku Kyosai,  Yutaka Suzuki, Masahiro Takahashi,
Katsumi Moriyama,  Masashf Ogoshi,  Toshiyuki  Nakajima,
    Takashi Masuda,  Shuuichi Ochi, Hiroaki Tanaka

           Water Quality Control Department
           Public  Works Research Institute
              Ministry of Construction
       Asahi,  Tsukubashi,  Ibarakiken 305 Japan
  The work described in this paper was not  funded  by
  the U.S. Environmental Protection Agency.  The contents
  do not necessarily reflect the views, of the Agency  and
  no official endorsement should be inferred.
            Prepared for Presentation at:
         12th United States/Japan Conference
                         on
             Sewage Treatment Technology
                     October  1989
                   Cincinnati, Ohio

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1. PREFACE

      The Ministry of Construction of the  Government  of Japan started a five-
year research  project,  "The Development  of New Wastewater  Treatment Systems
Employing Biotechnology",  which is commonly called Biofocus WT, in ffscal year
1985 as  one of  the  comprehensive  research and  development projects  of  the
Ministry.

      By broadly applying  biotechnology,  which is a  technology  that utilizes
the life maintenance  functions of biological organisms,  to  wastewater treat-
ment,  Biofocus WT intends  to  solve the  present and future  problems  in waste-
water treatment listed below.

      a.  lower energy requirement and lower 0 & M costs
      b.  smaller land requirement for wastewater treatment facilities
      c.  better effluent quality
      d.  recovery of valuable resources from wastewater treatment
      e.  easier operation & maintenance of wastewater treatment facilities
      f.  discovery of useful microorganisms for wastewater treatment

      The Public Works Research  Institute  and  the  Building  Research  Institute
of the Ministry of Construction -are the'main organizations carrying out Biofo-
cus WT.  The former  is mainly  in charge  of matters related  to publicly owned
wastewater treatment plants (POWTP), while the latter oversees matters related
to household wastewater treatment tanks.

      Table 1.1 shows the  subjects  of research  and development in Biofocus WT
related  to  POWTP.    This, paper  presents  the interim  results of  Biofocus  WT
being carried out'by the Public Works Research Institute.   :

        Table 1.1  Subjects of Research and Development in Biofocus WT

     a. Study on Microorganism Bank for Wastewater Treatment
     b. Study on Application of Genetic Engineering to.Microorganisms for
        Wastewater Treatment
    *c. Study on Immobilization Methods of Microorganisms for Wastewater
        Treatment
     d. Development of Bioreactors for Wastewater Treatment
     e. Development of Bioreactors for Sludge Treatment
     f. Development of Solid-Liquid Separators for Raw Wastewater
     g. Development of Biosensors for Water Quality Measurement
     h. Development of New Wastewater Treatment Systems

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2. STUDY ON MICROORGANISM BANK FOR WASTEWATER TREATMENT '

2-1 OUTLINE OF MICROORGANISM  BANK

      Recently, environmntal  microbiology has  achieved great progress. Though
there is much  microbiological information useful for wastewater systems, most
sanitary  engineers can  not  fully  utilize such  information.   There  may  be
several reasons for this  situation:   (1) The results of microbiology  research
are too difficult  for  sanitary engineers to utilize.   (2)  The  esults are too
specialized  in a certain field.   (3)  Sanitary  engineers can  not obtain the
information easily.

      A microorganism  bank  for wastewater treatment  has  been investigated  in
or'der to-apply the results  of microbiology research  to wastewater  engineering.
There are several key points  for establishing such a  bank.  A technical opera-
tion  strategy  is  one  of the most  important  issues  as  well as  a financial
operation strategy.  Development  of  the technical operation  strategy would  be
the result of  this research.

      The bank deals with the microorganisms  which are principally related  to
wastewater systems.  A unique feature of the bank is  that  it consists of two
p'arts, a data  bank and a preservation  bank.   The data  bank accumulates data
sheets in which microbiological, and  ecological  data on microorganisms related
to wastewater  systems  are  summarized.   The  preservation bank  is  an ordinary
one.  It wi.ll  not collect every strain  listed in  the  data bank, but only  those
which are not kept at other places.  The  preservation places  where the strains
.are kept are listed in the  data bank.                           

2-2 DATA BANK

      Most microbiological  data on  any  individual  strain  are  obtained from
pure  cultures.   However,  most microbiological phenomena  in  biological waste-
water treatment processes are observed  in mixed cultures of bacteria, protozoa
and other microorganisms.   The results of the pure  cultures are usually dif-
ferent from the phenomena  in the mixed  cultures.   This understanding impedes
                of microbiological  information  for  wastewater  treatment sys-
                bank would  reconcile this situation  by providing the ecologi-
                of each  strain.    It also  employs  special  classification  of
                  All  strains are  classified  by  their  relationship to waste-
                A tentative classification is shown  in Table  2.1.
the utilization
terns.  "The data
cal properties
mi croorgan i sms.
water systems.
      Table 2.2 is the data  sheet  from  the data bank.
information as  well  as ordinal microbiological  data.
water treatment systems are  also summarized.
                                                        It contains ecological
                                                        Data concerning waste-
      Table 2.3  shows  the  list of bacteria species which have 'been registered
in  the  bank.    These  species were  collected from  papers,  or  were  obtained
directly from researchers.

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             Table 2.1   Tentative Classification of Microorganisms
                        in Relation to Wastewater Treatment

                  WASTEWATER TREATMENT
                     Removal ,of  Biodegradable Organics
                     Removal of  Refractory Organics
                     Removal of  Synthetic Hazardous Organics
                     Nitrification
                     Denitrification
                     Phosphorus  Removal
                     Iron, Manganate Removal
                     Removal of  Trace Heavy Metals
                     Removal of.  Soluble Inorganic Materials
                     Oxidation of Sulfur Compounds
                     Reduction of Sulfur Compounds
                     Sedimentation of Suspended Solids
                     Flotation of Suspended Solids
                     Liquefaction of Suspended Solids
                     Odor Control
                     Color Removal
                     Epidemic Risk Control
                  SLUDGE TREATMENT AND DISPOSAL
                     Liquefaction of Sludge
                     Volatilization of Sludge
                     Heavy Metal Removal from Sludge
                     Composting
                     Resource Recovery from Sludge
                          Table 2.3  List of Strains
Strains
Characteristics
Nitrosomonas europaea
Nitrobacter sp.
Thiothrix sp.
Beggiatoa sp.
Thlosheara pantotropha GB17
Rhodopseudomonas sp.
Rhodospirill urn rubrum
Flavobacterium sp., or
Pseudomonas sp.
Alcallgenes eutrophus H850
Aclntobacter sp. GJ70
Rhodococcus sp. TTD-1

Acintobacter calocaeticus
 SH-1
Pseudomonas sp. K172

Pseudomonas sp. S100
Nitrification
Nitrification
Sulfur Oxidation, Bulking
Sulfur Oxidation, Bulking
Sulfur Oxidation
Removal of Organic Material
Removal of Organic Material
Removal of Synthetic Hazardous Organic Material

Removal of Synthetic Hazardous Organic Material
Removal of Synthetic Hazardous Organic Material
Removal of Synthetic Hazardous Organic Material,
Odor Control, Sulfur Oxidation  .
Removal of Synthetic Hazardous Organic Material

Removal of Synthetic Hazardous Organic Material,
Denitrification
Removal of Synthetic Hazardous Organic Material,
Denitrification
                                     10

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                     Table 2.2  Data Sheet of Data Bank
 1.  CODE
  (1) Bank Code
  (2) Scientific Classification:  1) Family 2) Species- 3) Common Name
 2.  RELATION TO WASTEWATER TREATMENT
  (1) Functional Name
  (2) Relationship to Wastewater Treatment
 3.  DATA SHEET WRITER
  (1) Name
  (2) Affiliation
  (3) Date of Register
 4.  RESEARCHER
  (1) Name                                                '       "   .
  (2) Affiliation
 5.  PRESERVATION
  (1) -.Organization
  (2) Code Number in the Organization
 6.  ORIGIN OF .STRAIN
  (1) Purification from Natural  Environment
     a)  Purification Data:  Source of Strain,  Date of Purification,
        Researchers,  Affiliation
     b)  Identification Data:  Researchers,  Affiliation
  (2) Genetic Engineering              .                                 .
   '  a)  Applied Genetic Engineering Method
     b)  Conditions:  Host,  Vector,  Other
   -  c)  Characteristics of Strain
  (3) Other
     a)  Obtained from Other Researcher
     b)  Characteristics of Strain
7.  CHARACTERISTICS  OF STRAIN
  (1) Physiological  Characteristics:  Growth Rate,  Substrate,  Products,
                                     Genetic  Data,  so forth
  (2) Ecological Characteristics:  Environmental  Condition for Growth,
                                  Competition,  Symbiosis, so forth
 8.  NOTES FOR EXPERIMENT
   Epidemic Notes, Hazardous  Products,  Patents,  so  forth
 9.  CONDITION FOR PURIFICATION  .
  (1) Cumulative Cultivation:  Temperature,  Media, Method
  (2) Purification:  Temperature,  Media, Method
 10.  PRESERVATION OF  VIABLE CELL:  Temperature,  Media,  Subculturing  Method
 1.1.  PRESERVATION AND REACTIVATION OF FREEZING  CELL
  (1) Preservation:  Temperature,  Media, Period  of Preservation
  (2) Reactivation:  Temperature,  Media, Reactivation of Specified Nature
 12.  RELATED LITERATURE                                         '
                                    11

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3. STUDY ON APPLICATION OF GENETIC ENGINEERING TO MICROORGANISMS FOR
   WASTEWATER TREATMENT

3-1 ECOLOGICAL AND EVOLUTIONARY STABILITY OF.ENGINEERED MICROORGANISMS

3-1-1 INTRODUCTION
                      ft
      There are  various  technical problems in  the application  of  engineered
microorganisms to wastewater treatment  systems.   From the view  point of sta-
bility of useful genetic traits or genetic  information  of engineered microor-
ganisms, the problems can be divided into three  as to stability at  each level
of the biological system.             *

*     Firstly, the  useful  genes must be  stably retained  in  the cell.   This
stability includes  synchronous  replications of plasmids  with  replications  of
the host cell.  This stability is called physiological stability here.

      Secondly,  a   sufficient  population of  the  cells   with  physiologically
stable  genetic  information is'required to survive  in  a  microbial  community
within a reactor under ecological  interactions  such as  interspecific competi-
tion,  predator-prey interactions  and   so  forth.  .This  stability   is  called
ecological stability of genetic information here.

      Thirdly, various mutants  may arise from an  ecologically  stable popula-.
tion with useful traits  after  a  long period.   Then, intraspecific competition
between the cells of original genotype  with useful  traits and mutants without
useful traits  would occur.   If the fitness of the original  phenotypic cells
are lower than that of mutants, the population  of  the original  genotype would
decrease  and  disappear  from the  reactor.    Thus,  engineered  organisms  are
required to  have higher  fitness  in a  given  reactor than any  other mutants
which might arise  from,themselves.   This stability,  called  evolutionary sta-
bility of the genotype of a microbial  organism here, may be a kind of ecologi-
cal stability, because  evolutionarily  stable  bacteria with  useful  traits  are
able to exist under intraspecific competition with the mutants.   The notion of
evolutionary stability, however, can be useful to differentiate the ecological
stability of a population  in   evolutionary (i.e.,   long)  time  scale  where  the
effects of mutants  can not be ignored  from that  in  ecological  (i.e.,  short)
time scale where there is  no  significant effect of mutants  on  the  population
dynamics.

      In this  study,  from  the view point  of  the  ecological  and evolutionary
stability of  bacterial  populations, a  basic  approach  to the  application  of
genetically engineered microorganisms  to wastewater  treatment  technology  was
done using long term experimental cultures of enteric bacteria.

3-1-2 MATERIALS AND METHODS

      Bacteria used  :  Escherichia vulneris JCM1688,   Escherichia  blattae
OCM1650, Enterobacter cloacae  JCM1232,  Enterobacter aerogenes JCM1235, Citro-
bacter  freundii   IF012681,  Citrobacter freundii   IF013539,  and  Citrobacter
freundii IF013545.   Long term cultures  of  bacteria were  conducted by a serial
transfer culture  illustrated  in Figure  3.1  and changes  in  ecological  traits
related to their fitness in the culture were examined  as .to  specific growth
rate, cell dispersiveness,  biochemical  characteristics,  etc.

                                     12

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                                                                           same
 3-1-3  RESULTS            .

       The  experimental  results are  shown  in Figures 3.2  and 3.3, and  summa-
 rized 'as follows:                                                            

  (1) The fitness  of bacterial  populations, which is expressed by  the  specific
    growth rate in  the  culture,  increased  with the number of transfers.   This
    is  considered to be  caused  by the appearance and increase of  mutants  with
    higher fitness  in the culture.
  (2)  The  fitness  of  a bacterial   population  eventually  came  to  a  plateau
    level.
  (3) The  plateau values of the  fitness of bacteria were  not  changed by  the
    treatment of a chemical mutagen with i\ITG.
  (4) The  plateau values were  different in  species (see  Figure  3.2),  and  in
    case of C._ freundi i the values varied  in strains.
  (5) Genetically  identical  bacterial strains which "were derived from  the
    clone have the same value for the plateau level.
  (6) From  the  experimental results  of mixed  cultures  consisting of two kinds
    of  bacteria,  both of which had reached  each plateau level,' it  was  revealed
    that the  population with  the  lower  plateau  level  decreased  and became
    extinct in the  mixed cultures,  while  that with the  higher  plateau level
    remained (see Figure 3.3).

  3-1-4 DISCUSSION                        "                  ....''

       It  was  revealed  that  ecological  traits  of  bacteria  can  genetically
 change  through  intraspeci.fic competition.    In  addition,  the changes in their
 growth  rates were  limited  to certain values  which- were  depending on species.
 From the view  point of  the application of  engineered microorganisms to waste-
 water treatment,  it  is  important  to use  the bacterial  species or  strains with
 higher  plateau  levels  for  treatment,  whether they  are  selected from  natural
 microbial  communities or genetically modified in laboratories.

 3-2 GENETIC MANIPULATION OF ECOLOGICAL TRAITS OF MICROORGANISMS
    RELATED TO THEIR FITNESS

 3-2-1  INTRODUCTION

      Many  genes  with  useful  traits,  which, are  integrated  into particular
 plasmids,  have been transferred into bacterial  cells  in  order to genetically
modify the bacterial ability for some industrial demands.  This method, howev-
 er, can not  manipulate a number  of  genetic  traits which would  be related to
 ecological  fitness  of the  bacteria  in some way..   It commonly deals  only with
 genes related to some biochemical or physiological traits which are considered
 to be useful for such demands.   For wastewater treatment,  engineered microor-
ganisms should grow  under  various kinds'of ecological  interactions with other
 species in  a given  reactor.    Then,  physiological  and. ecological  traits  of
microorganisms required for  the  stable existence in a reactor should  be
to genetic  modification, if it becomes necessary.
                                                                          open
      In this study, focusing on  how  we  can genetically manipulate such quan-
titative phenotypes as ecological traits  which  are  considered to be expressed
by many  genes on  the  chromosomes,  for  the first  step,  we  investigated  the
genetic changes of ecological traits of bacteria by genetic recombination at a
genomic level.
                                      13

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      Hfr strains of Escherlchia coll K12 are known as conjugational donors of
the chromosome DNA into F~ strains at high  frequency.   When an Hfr cell joins
to a F~ cell, conjugation-induced replication of F~ factor which is integrated
into  the  chromosome  begins,  and  transfer of  the  chromosome DNA  follows.
Complete transfer of  the  chromosome requires about  100 minutes at 37C.   By
breaking apart  the male  (Hfr)  and  female  (F~)  conjugant unions  by violent
agitation at different times, we  can  get various kinds of recombinant strains
which vary in the degree  of recombination  between  parental  strains.   Using
these strains,  we investigated  the genetic changes  of  ecological  traits of
bacteria by genetic reco.mbination at a genomic level.
                                                                              a
3-2-2 MATERIALS AND METHODS

      E. coli K12  JE5879  (sue,  man) and   E.  coli K12  ME7767  (ara,  mal,  xyl,
mtl, lac,  sue, str, gal) were used  as an  Hfr  strain  and an F~ strain, respec-
tively.

      Conjugation  between OE5879 and  ME7767  and  isolation   of  recombinant
strains between  the two were carried out by the method illustrated in Figure
3.4.

      Each strain was cultured in an L-broth medium.   6 ml of JE5879 and 3 ml
of ME7767  suspensions at a stationary phase of their growth were mixed togeth-
er in a 300 ml flask.   The mixture was statically  incubated for 180 minutes at
37C.

      After  30,  60,  and  100 minutes  of  incubation,   1  ml of  the bacterial
suspension were  taken from the  flask.   The samples were agitated' with a vio-
lent blender  for 30 seconds, and plated  onto  three  kinds  of  EMB  agar plates
containing maltose  and  streptomycin, xylose  and  streptomycin,  and galactose
and streptomycin.  After  incubation for 1-2 days, dark-violet bacterial colo-
nies, which   indicated  acid  forming  ability from the  sugars,  were  randomly
isolated from the plates  with  a  loop.    The  ten  strains isolated  from  the
plates  that  were  incubated  for  30 minutes  are  here  referred to  as hy30-l
through hy30-10.  Each isolated strain was purified two  times on the same kind
of EMB agar plate as the  plate  for  the  isolation.  These  isolates were trans-
planted to L-broth slant agar, and  stored at  4C.  To obtain bacterial growth
curves,  optical  densities of bacteria were monitored with a spectrophotometer
in their cultures.

3-2-3 RESULTS

      The  changes of viable  cell  counts  on  the  three kinds of EMB agar plates
during the conjugation experiment are shown in  Figure 3.5.  The growth curves
of  ME7767,  hylOO-7,  hylOO-8, and hylOO-9 are shown  in  Figure  3.6.   Various
types of growth  curves which varied in  the growth rate  and maximum density at
a  stationary phase of the  population  growth were observed.    While  both  the
growth rate  and  the maximum  density of  hylOO-7,  for example, were higher than
those of  parental strains,  the  growth  rate was lower  than that  of hy100-9.
The growth rate  of JE5879 was much  lower  than that of ME7767.

3-2-4 DISCUSSION

      Although  the  ecological  traits of  hy-30  and hy-60  are  not  examined at

                                      14

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this time,  from  the result  of  hy-100 it  is  revealed that  ecological  traits
such as growth rate, maximum density at  a stationary phase  can  .be changed by
genetic recombination at a'genomic DNA level.
                                      15

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4. STUDY ON IMMOBILIZATION METHODS OF MICROORGANISMS FOR WASTEWATER
   TREATMENT

      The  immobilization  of microorganisms  in  bioreactors  for  wastewater
treatment  and  sludge  treatment  is  useful  to  increase  the  concentration  of
microorganisms in the  reactor, and  to maintain a large  amount  of microorgan-
isms  for  specifically removing  particular  pollutants.    Three  immobilization
methods  will  be  discussed: binding method,  entrapping  method  and  self-
immobilization method.

      Microorganisms themselves attach to the surface of media  in the binding
method.  Microorganisms are  immobilized by chemicals in the entrapping method.
Immobilization is made by microorganisms themselves with no other materials in
the self-immobilization method.

4-1 BINDING METHOD

      Suitable shape and materials of attached media depend on the features of
reactors  in  which the media are used.   The  reactors  can be classified  into
fixed bed type or fluidized  bed type and aerobic or anaerobic.

4-1-1 ATTACHED MEDIA FOR FIXED BED TYPE REACTOR

(1)*For Aerobic Treatment
      Attached biomass was  compared  among  eight different media  under  condi-
tions of moderate aeration and synthetic substrate addition.   Figure 4.1  shows
the results.   Though  attached biomass was different between  media,  sufficient
biomass grew after 3 months  on all media tested.

      Table 4.1 is  an example of physical  characteristics of attached  media.
The media with more specific surface  area accumulate more biomass but require
regular washing  due to  clogging.   The  media  with  diameter less  than  1  cm
remove SS,  then  additional   SS removal  is  unnecessary,  though washing is  re-
quired.   On the other hand, washing is not  necessary  for media with  bigger.
diameters but solids separation from the effluent is essential.

       Table  4.1   Examples  of Physical'Characteristics of Attached Media
Media
Ceramics
Ceramics
Polypropylene
Polypropylene
Shape
Saddle
Ball
Cyl inder
Ring
Void
Ratio
77
40
89
89
Size
(cm)
2
 1
5
5
Specific
Surface
Area
(g/cm3)
335
400
76
185
Specific
Gravity
2.64
1.63
0.95
1.45
(2) For Anaerobic Treatment
      A comparison  test of  attached  media for  anaerobic treatment  revealed
that porous media  produce  gas more than  media with smooth  surfaces,  showing
that microorganisms attach to the porous media more than the  smooth.media.   As
no  aeration  results in  insufficient  mixing  in  anaerobic treatment  compared
with aerobic treatment,  it was  necessary  to select and arrange media  so  that
                                     16

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adequate influent distribution was attained.

4-1-2 ATTACHED MEDIA FOR FLUIDIZED BED TYPE REACTOR

      Attached biomass  was compared  among  different media  under  aerobic and
anaerobic conditions.  Table 4.2 shows the results.

           Table 4.2  Results of Comparison Tests of Attached Media      .  .
                      for  Fluidized Bed Type Reactor
Media

Silica
Sil ica
Silica
Zeol ite


Sand
Sand
Sand



A
B
C

Polypropylene
Plastic
Foam

Size
(mm)
0.2-0.3
.074-0.15
0.09-0.25
0.35
2-5
1-2
Specific Aerobic
Gravity or
(g/cm3) Aerobic

2.
2.
2.
1.
1.
1.

65
65
63
98
03
3

Aerobic
Aerobic
Anaerobic
Anaerobic
Aerobic
Aerobic
Attached
Biomass
(mg*VSS/
g%edia
40
1,200
3.5
10-30
26
95-150
)
4
1
0
'1
3
4
Biomass
in
Reactor
(g/i)
.4
2 '
.8
0-20
.8
. 3-6.






7
      Attached biomass and total  biomass  in  reactors  was more for sand B than
A, which has a smaller diameter  under  aerobic conditions.   Comparison of sand
B and  C  shows  that aerobic microorganisms tend  to attach to  media  more than
anaerobic microorganisms.  Zeolite  had  more  biomass  than sand in an anaerobic
condition.   As polypropylene  pellets   have.the . least  specific  gravity,  they
were  fluidized  in a  reactor  with  the  least mixing.   As about 90 %  of the
volume of plastic  foam has  pores with  diameters 0.03 to  1 mm, it accumulates,
many microorganisms.

      Granular activated  carbon  and porous  ceramics  had problems  with abra-
siveness.                               .

4-2 ENTRAPPING METHOD          '   -=  .
                                             >
      Polyvinyl alcohol  (PVA),  acrylic amide (ACAM)  and  polyethylene  glycol
(PEG) were compared as chemicals to entrap microorganisms.

4-2-1 POLYVINYL ALCOHOL (PVA)

(1) PVA-Boric Acid Method
      In this method,  a  mixture  of PVA and  activated sludge  is  dropped into
saturated boric acid  solution, then activated sludge  is entrapped in lattices
of pellets made of PVA and  boric acid.   Appropriate  conditions  of  the  method
were as follows:
  -PVA concentration  in the mixture of PVA & activated sludge: 7.5-10%
  -Activated sludge concentration: 80-90 g/1
  -Contact time of the mixture'with the saturated boric acid  solution:  24
   hours
            *

      Though the  respiration rate of the entrapped activated  sludge was  low at
the beginning of  cultivation,  the rate increased  rapidly  to  3 - 4  times the
initial value after 10 days,  as shown  in Figure 4.2.

                                      17

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(2) PVA-Refrigeration Method
      The mixture of  PVA  and activated sludge  is  refrigerated and  becomes  a
gel.  The activity of microorganisms  is only  slightly  reduced  after the immo-
bilization by this method compared with the method  using  boric  acid,  which is
harmful to microorganisms.

      The appropriate refrigeration temperature was minus  20C.   The strength
of  the gel  did not  increase  at temperatures lower than  the value.   The  PVA
concentration  of  10  % was  not  enough to make  pellets with enough strength..
Pellets of 22.5 % showed  a  lower respiration rate  than that of 15  % as shown
in  Figure 4.3, thus PVA concentration, of about 15 % is suitable.

4-2-2 ACRYLIC AMIDE (ACAM)

      ACAM is  relatively  cheap  and a typical polymer  for entrapping microor-
ganisms.  However, it has the ability to impair the activity of microorganisms
due to a harmful.monomer present during the immobilization.

(1) Agar-ACAM  Monomer Method
      Microorganisms  are  first  immobilized by  agar,  then an ACAM  monomer is
added to the  immobilized  pellets to polymerize and harden them.  The more ACAM
monomer added  resulted in less activity of  microorganisms.  But less additio"
of  monomers  leads  to weak  gels.   The proper concentration  of  ACAM was about
7.5 % as shown in Figure  4.4.

(2) ACAM Monomer Method
      A cross-linking agent and a polymerization agent are added to a  mixture
of  ACAM monomer and  activated sludge  to make gels.   Figure 4.5 shows the test
results.  Proper concentration  of ACAM monomer  was  about  15 % in this method.
Variation  of  concentration of  a  cross-linking agent  had  no  effect  on  the
activity of microorganisms.

4_2-3 POLYETHYLENE 6LYCOL (PEG)

      An immobilization method  by  PEG was  developed as a method to  immobilize
nitrifiers.   Activity of  nitrifiefs  in gels  by  PEG  was higher by 5 times than
those by ACAM, melamine and urethane.

      A  respiration  rate  of gels prepared by PEG after sufficient  cultivation
was 1,100 mg*02/l*hr which  was  higher.by  2 times than those prepared  by other
materials.  This was  mainly because the penetration rate  of  ammonia from water
to gels was the highest  in  PEG  gels among  the chemicals tested.

4-3 SELF-IMMOBILIZATION METHOD

       Immobilization is  made by microorganisms  themselves with no  other mate-
rials  in this method.    Dense  granules  made of microorganisms are  naturally
formed without sludge recirculatidn  in upflow sludge  blanket type bioreactors.
UASB (upflow  anaerobic sludge blanket) process  applied for treatment of waste-
water  with  high organic  concentration has  been  well known as a  process utiliz-
ing this method.    In Biofocus WT,   four  processes using  self-immobilization
methods  have  been  investigated.  There are two UASB processes, an  AUSB (aero-
bic upflow sludge blanket) process and MRB  (multi-stage  reversing-flow biore-
actor).
                                      18

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 4-3-1  UASB  PROCESSES
.(1)  For Municipal  Wastewater Treatment
     .  Anaerobic sludge blanket of  10  g*SS/.l  was obtained under
 temperature TO  to 25C,  linear velocity  (LV)  5  to 6  cm/min
 retention  time 6 to 9 hours.   Biological  granules
 acclimation.   Though  they are small in diameter  (1
 same as  biological  granules  generally  found   in
 wastewater with high-organic concentration.
              conditions  of
              and  hydraulic
have formed  after  6 months
mm), they are basically the
the  UASB process  treating
 (2)  For  Treatment of  Supernatant from Heat Treatment of Sludge
       Anaerobic sludge blanket  shown in  Figure  4.6 was  obtained.
 influent was 5,000 mg/1 and temperature  in the reactor was 35C.
 granules were 0.5  to 2 mm  in  diameter and had  1  to  5  cm/sec  of
 velocity.   Methanothrix seemed  to dominate in  the granules.
                   CODcr  in
                 Biological
                 a  settling
 4-3-2  AUSB  PROCESS
       Aerobic .granules  were  developed in this process.  DO  in  influent  to  the
 reactor is  as  high as  50 to  70 mg*02/l for keeping the  reactor  aerobic.  This
 high  DO concentration  is achieved  by contact  of  wastewater to  pressurized pure
 oxygen as shown  in  Figure 4.7.   Granules of several  milimeters in'  diameter
 have  been observed.   The mechanism of the aerobic granulation  is  under  inves-
 tigation. :,

 4-3-3 MRB

       Multi-stage Reversing-flow Bioreactor (MRB) which utilizes  new  biologi-
 cal  interaction for removal  of organic substrate in  wastewater has  been  de-
 veloped in  Biofocus  WT.

 (1) Principle  of  MRB
       Figure  4.8  is a  flowsheet of  the  MRB.    Influent  is  introduced to  the
 first downflow aeration vessel  (AV).   No suspended solids  remain here.   The
 next  vessel  is a .biological   reaction  vessel  (BV) of upflow without aeration.
 Suspended  solids  with  a  higher settling  velocity  than  the  upflow  velocity
 remain here.   The following  vessels  have  the  same sequences.   The  AV is  merely
 for oxygen  supply^ . In the BV,  suspended  solids and  biomass are  gently mixed
 by  the  upflow,  resulting in  formation  of self-granulated  sludge (SGS) with
 diameters  of 2  to 10  mm.    The primary  effluent of  a municipal wastewater
 treatment plant was  "influent  to the  MRB.   In  the initial period of the  opera-
 tionj  anaerobic  sludge  was accumulated in the first BV  and  then  the sludge  was
 carried over from'the first  BV to  the second  and third  BVs,  the  SGS was  formed
 in  due course as  shown  in  Figure  4.9. '  Once  the sludge blankets, of  SGS were
 built up in these BVs,  the  fourth and fifth  BVs receiving partially treated
 wastewater  became aerobic and developed an aerobic sludge blanket.  The aero-
 bic sludge  blankets  did  not  have the firm SGS,  but could be kept  in these  BVs
 against 144 m/day upflow velocity.   Sludge returning,  liquid circulation and  a
 final  sedimentation  tank were not  required.,

 (2) Mechanism  of  Self-Granulation  of Sludge in MRB
       One of  the  interesting topics  of the MRB  is the  formation of SGS.   The
 SGS is firm enough to be picked up by tweezers,  but is  crushed  by  strong shear
 stress,  such as when it  is pumped  out.  Most  of  the SGS  is covered with  a thin
 white film  as  shown  in  Figure 4.9.  The film consists of  filamentous  bacteria
                                       19

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as shown in Figure 4.10.  The bacteria, having  small sulfur granules in their
cells and showing  active  gliding mobility,  are identified  as  Beggiatoa.   The
inside of the S6S is black and anaerobic.  The  plate count method for sulfate
reducing bacteria  indicated  that there were  10   N/g-SS  of  sulfate reducing
bacteria (SRB).  In the MRB,  oxygen  is supplied at  the AV  where  few microor-
ganisms are present.  DO in  the  AV  is  limited to  the saturation concentration
for  wastewater at  a  given  temperature.   On the other  hand, a significant
amount of microorganisms accumulate  in the BV,  and the DO  supplied  in  the AV
is consumed  rapidly  if  organic substrate in  the  wastewater is high.   Conse-
quently, near-anaerobic  conditions  allowing  the  growth  of  the  SRB are  de-
veloped in the BV.   From  the  above-mentioned observations,  the  mechanism of
self-granulation of sludge in the  BVs  is considered as follows.   Figure 4.11
explains the interaction among the  SRB,  Beggiatoa as sulfide oxidizing  bacte-
ria and other  anaerobic bacteria.  Organic substrate diffusing into the SGS is
hydrolyzed to  organic acids  by  anaerobic bacteria,  then  utilized by the  SRB
resulting in sulfate reduction.
           *
      Sulfide  produced  from  this reaction diffuses  into   bulk  liquid  through
the SGS surface.  Though the oxygen  supply is limited  in  the BV,  there  is  the
chance of the  microorganisms  contacting  oxygen  on the SGS  surface.    Because
an oxygen consumption rate of bacteria oxidizing  sulfide  is  much higher than
that of organic  substrate  oxidizing bacteria, most  the oxygen  is utilized by
the sulfide oxidizing bacteria which are microaerophil ic.   Beggiatoa, which is
one of the most  common bacteria  existing  in  such  an  environment,  increases on
the SGS surface  in a thin film.
                                     20

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5.  DEVELOPMENT OF BIOREACTORS FOR WASTEWATER TREATMENT

      Many municipal sewage systems are being designed or constructed in rural
areas in Japan.  Even in rural areas,  the land for wastewater treatment plants
is limited  in  many cases.   In addition,  small  municipalities tend  not  to be
able to employ enough skilled technicians.

      Many local governments will  have  to reconstruct or to improve their old
wastewater treatment plants in the future.  An increase in treatment capacity,
and/or upgrading removal efficiency of .-nutrients or refractory organic materi-
als might be .required in such cases..                           ,

      Development of bioreactors for wastewater treatment aims to answer these
needs mainly by introducing immobilization of microorganisms.  There are three
targets of  the  development,  in addition  to  develop  bioreactors  with features
of easier 0 & M, phosphorus removal or refractory organic removal.

 (1) To  reduce the  retention  time in reactors  to  1/2 to  1/10  compared with
    the conventional  processes.
 (2) To  reduce the  energy  requirement and/or  sludge production to  1/2 com-
    pared  with conventional  processes.
 (3) To reduce the retention  time  in  reactors  for biological nitrogen removal
    to  6 to 12 hours so that  existing  plants-can be  modified to  remove nitro-
    gen.

      The  first  target would  be  accomplished  mainly  by the development of
aerobic bioreactors.   Anaerobic  bioreactors are  for the second  target.   The
third target would .be concluded by immobilization of microorganisms related to
nitrogen removal.

      In total, 23 bioreactors are under  development.   AIT of the bioreactors
have been  developed  as  joint  researches between the Public Works  Research
Institute  and  private  companies.  Twenty-three pilot plants are  operated at
present.

5-1  AEROBIC BIOREACTOR

      Thirteen aerobic bioreactors have been developed.  They are divided into
three groups: fixed,  bed type, fluidized bed type and  sludge blanket type.

5-1-1 FIXED BED TYPE

       Figure 5.1 shows an example of fixed bed type aerobic bioreactors which.
have been  developed.   The  aerobic  biofilter has several experimental and full
scale trials  in  Japan  and abroad.  Influent is introduced to the  top  of the
fflter.  Air is dispersed from the bottom of the filter.  Wastewater is treat-
ed by  the  biofilm on the surface  of  filter media.    Suspended solids  are re-
moved by a filtration mechanism.

      Suspended solids in  influent is  better to be low  in  order not to cause
clogging in the filter.  The filter is washed by backwashing.  The operational
conditions and the performance are summarized in Table 5.1.

                                      21

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               Table 5.1   Operational  Conditions  and Performance
                          of Fixed Bed Aerobic Bioreactor
CONDITIONS
Linear Velocity, m/day
Hydraulic. Retention Time, hr
BOD Volumetric Load, kg-BOD/m3/day

31
1.65
1.1

' 50
1.01
1.5

70
. 0.7
2.3
  PERFORMANCE

ss
BOD
T-K-N
T-P

mg/1
mg/1 -
mg/1
mg/1
Inf.
42
72
28.8
2.8
Eff.
4
6
4.1
1.9
Inf.
39
62
27.1
2.2
Eff.
4
9
5.7
1.5
Inf.
35
69
24.1
2.1
Eff.
4'
11
11.1
1,5
5-1-2 FLUIDIZED BED TYPE

      Figure 5.2  shows  an example  of fluidized bed  type  aerobic bioreactors
which have been developed.  Air  diffusers  are installed in the reactor.   Fine
sand,  fine  slag,  granulated  activated  carbon,  plastic  media,   and  chemical
media which are made of  polyacryl  amide and poly-ethylenglycol for immobiliz-
ing microorganisms are used as the fluidizing media in these developments.

      Media separation from  liquid is  one  of the engineering problems  to be
solved.   When effluent  from  bioreactors  has  little SS,   final  solid-liquid
separation might  be  accomplished  not  by sedimentation but  by filtration be-
cause settlability of 'the SS is poor.   How to fluidize the media  is another
hurdle.  Lighter and finer media are better for fluidizing, but such media are
difficult to separate from liquid.

               Table  5.2   Operational  Conditions  and  Performance
                          of Fluidizing Aerobic Bioreactor
      RUN
1
CONDITIONS


Hydraulic Retention Time of Reactor, hr 2.0
Linear Velocity of PF,
Linear Velocity of SF,
PERFORMANCE
T-BOD mg/1


S-BOD mg/1


SS g/1


m/day
m/day

Influent
PF Effluent
DF Effluent
Influent
PF Effluent
DF Effluent
Influent
PF Effluent
DF Effluent
80
161

138
20.6
9.4
44.3
'10.9
8.0
109
10.1
3.2

2.0
80
161

91.9
 16.0
11.1
47.0
9.5
8.0
 40.1
7.5
2.6

4.0
53 r"
115

132
17
9.1
44.7
8.5
6.3
102
6.7
2.2
      PF:  Plastic Media Filter
      DF:  Dual  Media Filter
                                      22

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      A  plastic  medium  of 3 to 5 mm in diameter  and  about 1.0 in density  has
been employed  in a development.   It  can  be separated by a screen.  The  opera-
tional conditions and the performance of the plastic media bioreactor  followed
by a two stage filtration process are summarized  in Table  5.2.

5-1-3 SLUDGE BLANKET TYPE

       A flow  diagram of  an aerobic sludge blanket  reactor  developed  in" this
project  is shown in  Figure 5.3.    Influent flows  into a pressurized  oxygen
tank.  Effluent  from  the  tank'with .50  to  70 mg/1 of  DO  is  introduced to  the
bottom of  the.upflow reactor.    At  the beginning of  the   operation,  activated
sludge was  seeded  in  the reactor.   Within several  weeks, aerobic biological
granules formed  in  the  reactor.   The operational  conditions and the  perform-
ance are summarized  in  Table  5.3.   Though the mechanism  of  self-granulation
has  not  been  clear, sludge that, settles  easily  has  been maintained  for  one
year.                                                               _

             Table 5.3  Operational  Conditions and Performance of
                        Sludge Blanket Type Aerobic Bioreactor
                CONDITIONS
                   Hydraulic Retention Time, hr        ,1.72
                   Recirculation Ratio of Effluent       1.57
                   Up Flow Velocity in Reactor, m/day  125
                   Influent DO mg/1                     63
                   Effluent DO mg/1                      4.8

                PERFORMANCE

T-BOD
S-BOD
SS
T-N
T-P

mg/1
mg/1
mg/1
mg/1
mg/1
Influent
112.6
42.4
91.3
30.9
2.7
Effluent
19.9
10.2
9.6
24.6
1.8
5-2 ANAEROBIC BIOREACTOR

      Six anaerobic bioreactors are  under  development.   They are also divided
into 3  groups:  fixed bed  type,  fluidized bed  type  and sludge  blanket type:
Anaerobic wastewater treatment requires the  post-treatment due^to the follow-
ing two reasons.  Effluent from anaerobic treatment can. hardly satisfy the BOD
standard of 20  mg/1 for  secondary treatment.   It  also  contains  sulfide which
causes corrosion and odor problems.

      Most post-treatment  processes  under development are aerobic biological
treatments which require additional  energy and  facilities.  A pilot plant has
installed a modified  trickling .filter  for  post-treatment..   The  filter media
are  cubic  sponges  which' catch up fine  suspended solids.   This  system  can
eliminate further SS  removal  facilities and aeration devices  for post-treat-
ment.

5-2-1 FIXED BED TYPE

      Non-woven fabrics,  saddle-shaped ceramics and plastic braids are used as
                                       23

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media for fixed beds.

      Figure  5.4  shows an example  of a  fixed  bed type  anaerobic bioreactor
under development.   Concentrated anaerobic  sludge can shorten  the hydraulic
retention time to less than 8 hours  for  primary  effluent.   There is no recir-
culation of effluent.

5-2-2 FLUIDIZED BED'TYPE

      One fluidizing anaerobic bioreactor with fine zeolite of 0.5mm in diame-
ter as  media  has been developed.   The  flow  diagram  is shown  in  Figure 5.5.
Recirculation of effluent is required to fluidize the media and the recircula-
tion ratio depends on the fluidized velocity of the media.  The retention time
is less than 3 hours, but this reactor requires energy for recirculation..

5-2-3 SLUDGE BLANKET TYPE '

      An upflow  anaerobic sludge blanket  (UASB)  reactor shown  in  Figure 5.6
has been  applied  for  domestic  wastewater treatment.   Pellets of anaerobic
microorganisms formed  6  months  after seeding digested  sludge  to the reactor.
The effluent  from the  reactor has been  good  as  the  influent  to  the modified
trickling filter  mentioned  before.    The operational  conditions and  the per-
formance are summarized in Table 5.4. The system has  neither liquid recircula-
tion,  nor aeration devices.   If there is enough water  head  difference avail-
able between  influent  and effluent in a  plant,  this  system can be an energy
saving system.

             Table 5.4  Operational Conditions and Performance of
                        Sludge Blanket Type Anaerobic Bioreactor
CONDITIONS
Hydraulic Retention
Hydraulic Retention
Water Temperature,
PERFORMANCE
BOD mg/1
SS mg/1
Sulfide as
S mg/1
Time
Time
C
of
of
Inf.
71-111
45-99
Reactor
MTF, hr
, hr
E'ff.(UASB)
24-40
8-15
6-8
8
2
13-1.6
Eff
7-1
2-7
0

7
(MTF)
              MTF: Modified Trickling Filter for post-treatment

5-3 MULTI-STAGE REVERSING-FLOW BIOREACTOR (MRB).

      The  Multi-stage  Reversing-flow  Bioreactor  (MRB)  which  utilizes  new
biological interaction  for organic substrate  removal  in wastewater  has  been
developed.  As  shown  in Figure 4.8,  MRB   has several stages, one  stage  con-
sists of  a downflow aeration  vessel  (AV) and  an  upflow  biological  reaction
vessel (BV).   Successful  accumulation of self-granulated  sludge  (SGS)  can  be
achieved  in BV.   As  described in  4-3-3,  the biological  interaction  between
sulfate reducing  bacteria  and sulfide oxidizing bacteria  (Beggiatoa) .is  con-
sidered to contribute  to  form SGS with 2 to  10 mm  in  diameter.   SGS  can  be
maintained in BV  with  linear  velocity of  144  m/day.   A  prototype  plant study
was conducted to demonstrate the performance of the MRB.
                                      24

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     'The design parameters,  the operational conditions and the performance of
the prototype MRB are summarized in Tables 5.5 and 5.6

                 Table 5.5  Design  Parameters of Prototype  MRB
           Diameter:   AV
                      Lower part of BV
                      Upper part of BV
           Depth      Average
           Total volume
           Hydraulic retention time
           Up-flow velocity at lower part of BV
 10 cm
 10 cm
 18 cm
220 cm
213 1
3-4.5 hour
144-216 m/day
              Table 5.6  Operational  Conditions of Prototype MRB
Influent
BOD volumetric load for total volume
for BV volume
Hydraulic retention time
Dissolved oxygen concentration in AV
Settled municipal
0.42 kg/m3.day
0.73 kg/m3.day
4.5 hour
5-9 mg/,1
wastewater
        Table 5.7  Typical performance and Sludge Concentration in MRB
No. of BV
Total Solids (mg/1)

BOD (mg/1)
D-BOD (mg/1)
SS (mg/1)
No.l
21,000
Influent
80
50
30
No. 2
14,600
No. 3
8,900
No. 4 No. 5
5,900 14,000
Effluent
14
9
4






      Though the  influent  BOD was  sightly  low,  the  effluent quality was  as
good as  that  of a  conventional  activated sludge process.   The  influent  was
municipal primary effluent.  The total hydraulic retention  time  was  4.5  hours
including  the  final  solid-liquid  separation  in  the  last  BV.    The MRB  has
several advantages over conventional biological wastewater  treatment,  such  as
lower  energy  requirements,  less  sludge  production,  and no  necessity  for  a
final settling tank.

5-4 BIOREACTORS FOR NITROGEN REMOVAL

      This  study  has  been  conducted  to  develop  biological  nitrogen  removal
processes  utilizing immobilization  methods  of microorganisms related  to bio-
logical nitrogen removal in pilot plants.   The immobilization methods used are
a binding method and an entrapping method.

5-4-1 BIOREACTOR FOR NITROGEN REMOVAL WITH BINDING  METHOD

(1) Experimental Conditions of Pilot Plant Study
      The  flowsheet of  the pilot plant is shown in  Figure  5.7.  t The  size  of
the cross  section of  the reactor  is 700  mm by 700  mm and 2,800  mm  in  height.
                                       25

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The volume is 1.37 m3.  Sands with  diameters  of  0.2 mm to 0.3mm constitutes 8
% of  the  reacting volume  in  the reactor.   The  specific surface  area  of the
sand  is  1.5 m^/g.   Sand  was selected  as attaching-media after  a comparison
test among clistobalite, sand and two kinds of light    weight aggregate.

      Influent  flow  was 11.5 m3/day  and the  retention  time in  the  reacting
volume in the reactor was 2.9 hours.  BOD, total nitrogen and ammonia nitrogen
in influent were 110 to 160 mg/1, 40 to 60 mg/1 and 30 to 40 mg/1, respective-
ly.  The water temperature was 28 to 29C. .

      The operation mode of the reactor was intermittent aeration with contin-
uous  inflow.   Both  aeration  time and  anaeration  time were 15 minutes.   The
volumetric loadings  of  BOD  and  total .nitrogen in the  reactor were-0.9  to 1.3
kg/m3/day and 0.3  to 0.5  kg/m3/day,  respectively.   The DO level  was  set to 2
to 3 mg/1 during aeration period.

(2) Results of Pilot Plant Study and Discussion.
     . Total nitrogen in the effluent was  8 to 15  mg/1  as shown  in Figure 5.8.
The fact that ammonia nitrogen and nitrate nitrogen in the effluent were about
2 mg/1 and 8  to 10 mg/1,  respectively,  shows that  it  is  necessary to enhance
denitrification for upgrading nitrogen removal.

      MLVSS in  the reactor  was  7,000 to 9,000 mg/1..   About  90  %  of the MLVSS
was attached  to sands,  which  demonstrates  the effectiveness  of  sand  to in-
crease microorganisms in the reactor.

      The following are necessary to study in order to improve this biological
nitrogen removal process.
  a. optimum combination of aeration time and anaeration time
  b. DO level during aeration time
  c. air flow rate to fluidize sand and to supply DO
  d. solid-liquid  separation'of effluent  from the reactor

5-4-2 BIOREACTOR FOR NITROGEN REMOVAL WITH ENTRAPPING METHOD

(1) Experimental Conditions of Pilot Plant Study
      Figure  5.9  is the  flowsheet  of  the  pilot  plant.   The  volume  of the
nitrification tank is 4 m3 and that of  the denitrification tank  is 6m3.  7.5
% of  the  nitrification tank  volume is filled by  pellets in which activated
sludge taken  from a biological  nitrification-denitrification  plant are en-
trapped.   Polyethylene glycol was selected as a  suitable chemical to make the
pellets with activated  sludge containing  nitrifiers based on a  selection test
among 5 chemicals.   As  it was  revealed  that  chemical  entrapping of denitrifi-
ers for denitrification was not effective, microorganisms including denitrifi-
ers were suspended in the reactor.   Experimental  conditions  are summarized in
Table 5.8.

(2) Results of Pilot Plant Study and Discussion
      Figure 5.10  is  the  performance of  nitrogen removal  in the  pilot  plant.
BOD, TN and  SS  in effluent were  10  mg/1, 7  mg/1 and  7  mg/1,  respectively in
RUN 1  in  which the  total  retention time in  the reactor was  8  hours.    This
performance was satisfactory, considering the water temperature was between 10.
to 12C.   The total retention time was reduced to 6 hours in the following RUN
2 in which BOD and TN in the effluent were less than 20 mg/l and 10 mg/1.

                                      26

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                      Table 5.8  Experimental Conditions
                                                           RUN-1   RUN-2
   Inflow (m3/day)           ,                        .      31.5    42
   Retention Time in Biological Reactor (hr)                86
   Retention Time in Nitrification Tank (hr)                4.8     3.6
   Retention Time in Denitrification Tank (hr)              3.2     2.4
   Percent of Pellets Filled into l\l. Tank by Volume (%)     7.5     7.5
   Air Supplied (Nm3/day)                                 200     230
   Recirculation Ratio of Mixed Liquor (%)                300     300
   Sludge Return Ratio (%)                                 40      40
      This  process  can  be  applied  to  existing  activated  sludge  plants  for
upgrading Tl\l removal.   The  following should be studied in  order  to make this
biological nitrogen removal  process feasible.
  a. 1ife of pel lets
  b. a production method of huge amounts of pellets for full-scale plant
     application                                   -         .
  c. cost of pellets, including disposal
                                      27

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 6.  DEVELOPMENT OF BIOREACTORS FOR SLUDGE  TREATMENT

 6-1  ANAEROBIC SLUDGE DIGESTION

       There  are two  objectives  in this  development.   One  is  to shorten  the
 period of sludge digestion  to less than 10 days, and the other  is to  increase
 the  percentage of solid decomposition for recovering more digested gas  by  1.5
 times that of the conventional  process.   Two  techniques  have been investigated
 in  order to  attain the objectives.   They  are liquefaction  of feed sludge  and
 immobilization of bacteria  related to anaerobic sludge digestion by the  bind-
 ing  method.

       It is  well  known that  liquefaction  of "feed  sludge,  especially  excess
 biological sludge,  is the most limiting factor in the digestion.  As  attempts
 were unsuccessful  to find  bacteria and enzymes which accelerate  the liquefac-
 tion of sludge,  the direction has been changed to use physical-chemical  meth-
 ods.   The  following  three methods  have  been investigated:

  (1) Crushing excess  sludge  by a mill  with  NaOH of  0.05   N  addition	An
    example of the experiment is shown in Table 6.1.
  (2) Heat treatment of excess sludge  with conditions of  60C for 1 hour
  (3) Heat treatment of excess  sludge with conditions of 90C  for  1  hour  and
    protease  addition  to the  heat treated sludge  flowing  to ah  acidification
    process

         Table  6.1   Liquefaction of Excess Sludge by  Crushing with NaOH
Items
(mg/1)


TS
VS
VSS
PH
Sol. Sugars
Sol. Proteins
VFA
formic
acetic
propionic
isobutyric
butyric
isovaleric
valeric
	 CRUSHING  
Control


24,100
19,700
18,400
6.0
. 199
250
'1,836
-
580
425
84
401
' 157
189
Crushed


23,900
18,800
12,500
6.2
. 458
2,420
3,070
114
2,082
-
348
-
526

	 	 CRUSHING WITH
Control


24,800
19,500
18,100
6.1
128
205
1,361

460
346
250
327
119
109
NaOH
Addi ti on

25,000 '
19,300
16,400
7.1
232
1 , 060
3,222
28
1 , 824
350
99
239
169
513
NAOH 	
Crushed
with
NaOH
24,800
18,400
8,100
7.0
554
3,030
3,847
51
3,162
_
__
 .
_
168
      Attached media for bacteria in sludge digestion are different from those
for bacteria in wastewater treatment, because sludge is much more viscous and,
of course, contains more SS  than  wastewater.   Cement  balls  as  attached media
for a fluidized  bed  type  reactor and ceramics as  attached media for  a fixed
bed type reactor have been investigated.

      Three pilot plants are under operation.  Their  flowsheets  are in Figure
                                      28

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 6.1.   In  addition to their  digestion  performance,  dewaterability of  the di-
 gested . sludge,  biodegradability  of the  filtrate  and heat  balance  of  each
 system are scheduled to Be examined.

 6-2 BACTERIA LEACHING OF HEAVY METALS FROM SLUDGE

       The bacteria leaching technique,  which is practiced in recovering metals
 from ores by oxidizing sulfur and lowering pH by sulfur oxidizing bacteria and
 iron oxidizing bacteria,  was applied to sewage sludge in order to remove heavy
 metals from it.

 6-2-1  GROWTH-OF  BACTERIA IN SLUDGE       :

       Thiobacillus thiooxidans and Thiobacillus ferrooxidans  were  selected  as
 sulfur oxidizing bacteria and iron oxidizing bacteria.   The conditions  for the
 two kinds of bacteria to grow  in  sludge were examined.  Results of  the study
 are summarized as follows,:
                               >

  (1) There .was no difference in the growth of the bacteria  in primary  sludge,
     excess  sludge, mixed  sludge or digested sludge.
  (2) Sterilization of  sludge was not necessary for  the growth of the bacte-
     ria.
  (3) Though it  was  indicated  that  Thiobacillus thiooxidans  and Thiobacillus
     ferrooxidans  or  bacteria similar to those  existed  in sludge,  addition -of
     Thiobacillus  thiooxidans  and Thiobacillus  ferrooxidans  accelerated  the
     decrease of pH in sludge.
  (4) Initial pH  of  sludge  had no influence  to  the  growth of the  bacteria  if
     the pH was between 4  to  7.
  (5) Addition  .of powdered sulfur  or ferric  sulfate
     sary for the growth of bacteria.
            as  a  substrate was neces-
 6-2-2  HEAVY  METAL REMOVAL  FROM SLUDGE BY BACTERIA  LEACHING

       Bench  scale tests on the bacteria leaching of mixed  sludge  and  digested
 sludge were  conducted.  Figure  6.2  is the procedure.   The results were  com-
 pared  with those  attained  by sulfuric acid addition  to  sludge.   Results  of the
study  are summarized  as follows.
  (1)  Mixed sludge  and  digested sludge
    after  the  start of the  incubation.   The  pH  values were  1.0  and.1.8  for
    mixed sludge and digested sludge, respectively.
  (2)  Leaching ratios depended  on  heavy metals.   Cd,  Zn  and  Mg were
    more than 80 %.  Little  Hg  was  removed  from the sludge.   Figure 6
    changes of leaching ratios of heavy metals.
  (3)  There was  no  significant difference in the bacteria  leaching and "chemi-
    cal leaching1 as to the leaching ratios of heavy metals.
came to  pH  equilibrium within  7  days
                               leached
                               3 shows
                                      29

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7. DEVELOPMENT OF SOLID-LIQUID SEPARATORS FOR RAW WASTEWATER

      Almost  all  bioreactors  for  wastewater  treatment  being  developed  in
Biofocus WT  incorporate immobilization  methods in the  reactors in  order  to
increase concentration of  microorganisms.    A problem  may exist  in reactor
clogging due  to  SS in influent for  such reactors,  especially fixed  bed type
reactors.  In addition, as dissolved organics are decomposed by microorganisms
faster  than  particulate organics,  removal  of  the  bigger  particles  from raw
wastewater makes bioreactors more efficient.

      Solid-liquid  separators  for raw  wastewater,  of  which SS removal rate is
higher  than  that  of  a conventional  primary  sedimentation  tank,   have been
developed in  this  subject.

7-1 SIZE DISTRIBUTION  OF SUSPENDED SOLIDS IN  RAW WASTEWATER

      Filtrate were prepared  by sieves of 2  and 74 mm  and filter papers of  8
and  1  microns.    SS,  BOD,  COD,  TN and TP  in the  filtrates  were  -analyzed.
Examples  of the study are shown  in Figures  7.1  and 7.2,  and  summarized as
follows:

  CD  Percentage  of particulate BOD  in  raw wastewater was  higher than those of
    particulate  nitrogen and  phosphorus.  Then" C/N and C/P ratios  in influent
    to  bioreactors become  small,  if the removal  rate of SS in  raw  wastewater
    is  high (see Figure 7.1).                                          .    ...
  (2)  Size  distribution  of SS  in   raw  wastewater  is   different  during  high
    influent  loading  and  during low influent loading.   Percentage  of SS  more
    than 8  microns  is higher  during  high  influent  loading  than  during  low
    influent  loading  (see Figure 7.1).                                      .
  (3)  There was  a  possibility  that  influent to small  plants with shorter time
    of  flow contained soluble BOD more  than  that of large plants  with  longer
    time of flow (see  Figure  7.2).

 7-2 BIODEGRADABILITY OF PARTICULATE ORGANICS

       Biodegradability of  particulate  TOC  was  examined under  aerobic  and
 anaerobic conditions.  Examples of the study are shown in Figures 7.3 and 7.4.
 Initial biodegradation rate  of  particulate  TOC  in  particle  size more  than  1
 micron meter was  much lower  than that of smaller than  1  micron meter in both
 aerobic and anaerobic conditions.

 7-3 SOLID-LIQUID  SEPARATORS FOR RAW WASTEWATER ^

        Five  solid-liqui'd   separation  processes  have  been developed in  this
 subject.
        (1) Upflow  sedimentation process
        (2) Floating-bed filtration process
        (3) Filtration  process with tube-shaped  filtration  media
        (4) High  rate  bioflocculation process  with lamella  settler
        (5) Two stage filtration process  with  upflow moving  bed and downflow
           fixed bed

        An upflow sedimentation process  has been  investigated  using  an  experi-
  mental column  of 280 mm  in  diameter  and  1,500 mm in  effective  height and
  mixing paddles.   Figure  7.5  is 'the  result.
                                       30

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      Removal rates  of the processes  of (2),. (3)  and  (4) are  summarized in
Figure 7.6.  Removal.rates of SS  larger  than  8  microns  in raw wastewater were
more than 80 % in these three processes.   On the other hand, SS smaller than 8
microns were difficult to remove by these processes.
                                      31

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8. DEVELOPMENT OF BIOSENSORS FOR WATER QUALITY MEASUREMENT

      Biosensors, which use biomaterials such as enzymes and microorganisms as
detectors to measure  objective  matter,  have been developed  as  for  BOD,  ammo-
nia-nitrogen and organic acids.

8-1 PRINCIPLE OF WATER QUALITY MEASUREMENT BY BIOSENSOR

      Aerobic microorganisms are  applied  to these  biosensors.   Microorganisms
are immobilized  in  a thin biofi1m which  is attached to  an  oxygen  electrode.
When the microbial  electrode  is immersed into  a substrate  solution,  the sub-
strate begins to diffuse  into  the-biofi1m.    If microorganisms  in the biofi1m
metabolize the substrate, they  consume  DO in the biofilm resulting in decline
of oxygen  electrode current.    In a few  minutes  the oxygen  consumption rate
becomes equivalent  to  the oxygen diffusion  rate towards  the biofilm.   Conse-
quently the current of the electrode becomes steady  (peak current).

      When the microbial  electrode .is  removed from the substrate solution and
put into  a solution without substrate, oxygen  consumption  rate decreases the
level  of  endogenous metabolism  (base  current).  An oxygen  consumption rate,
which  is expressed  as the difference between the peak  current  and   base cur-
rent,  is in proportion to substrate  concentration within  a certain range.

      The flow chart  of a system  is  shown in Figure 8.1.   The microbial elec-
trode  attached to the  flow  cell  sends  the current  to a microcomputer (CPU) by
way of an amplifier  and an analog digital (A/D) transfer.  A standard solution
or a sample is injected into the  flow cell  for  calibration or measurement.  DO
in the flow cell  is almost completely eaturated.  The  flow  cell  is .set in an
isothermal water bath  to  maintain a  constant temperature.

8-2 BOD SENSOR

8-2-1  SELECTION OF  BIOFILM FOR  BOD SENSOR

     Microorganisms  and immobilization  methods  to  make  biofilm  for BOD sensor
were experimentally  compared among the  following candidates.
              
  Microorganisms:
    Sacharomyces cerevisiae(yeast)
    Sacharomyces uvarum(yeast)
    Schizosacharomyces pombe(yeast)
    Trichosporon cutuneum(yeast)
    Candida lypolylica(yeast)
    Candida tropicalis(yeast)
    soil microorganisms
    wastewater microorganisms
    activated  sludge
   Immobilization methods:
    entrapping method by  glutaraldehyde treatment
    entrapping method by  PVA-boric  acid
    immobilization  by acetylcellulose  dialysis  membrane absorption method

       Three  combinations of microorganisms  and an  immobilization method  were
 selected  for  further BOD sensor  development based on performance of the  dif-
 ference  between  the peak current and  the base  current, the transient  time  to

                                       32

-------
the peak current and the recovery time to the base current.  They were;
  a) Trichosporon cutuneum + gelatin-glutaraldehyde film,
  b) Trichosporon cutuneum + acetylcellulose film, and
  c) soil microorganisms + PVA "film

8-2-2 PERFORMANCE OF BOD BIOSENSOR

      The three  selected  biofi1ms . were  evaluated.      Glucose-glutamic  acid
(GGA) solution and synthetic wastewater were used as samples.  The results are
shown  in  Figure  8.2.    Each  biofilm  had a'linear  relationship  between  BOD
concentration and the  current difference.   The  most sensible,biofi1m was of
soil microorganisms  immobilized  by  PVA  in  both  GGA  solution  and 'synthetic
wastewater.    The  current difference of  a GGA  solution  shows  larger  than the
artificial sewage in each biofilm.              ,

      A biofilm of soil microorganisms immobilized by PVA was used for further
study in which BOD in  several  kinds  of raw wastewater,  secondary effluent and
polluted  urban  river water was  measured  by the BOD  sensor and  by  a manual
method.   Calibration  curves  were  prepared  with  GGA  solution  and  synthetic
wastewater.    Figure 8.3  shows the  relationship between  the  sensor  BOD  and
manual  6005.

      In  the  case of  raw" wastewater,  the  sensor BOD  showed  enough output
current.   The  sensor  BOD  calibrated  by  the  synthetic wastewater  was  more
agreeable with  the manual BOD on the whole than that by GGA.

      In  cases  of secondary  effluent  and  river water,  however,  the current
difference was so small that the  sensor  BOD  showed much  lower than the manual
BOD.   The difference between  the  two  calibration methods  seemed  very small.
Samples which have been  biologically treated seem difficult to detect by this
BOD sensor  in a short peripd.   We  have been trying to  improve the detection
ability for such refractory organic solution.

8-3 AMMONIA.SENSOR

8-3-1 PERFORMANCE OF AMMONIA BIOSENSOR             ,.

      Nitrosomonas europaea was immobilized between two  porous acetylcellulose
membranes to  make a  biofilm for  an  ammonia biosensor.  The relationship be-
tween ammonia nitrogen concentration  below  10  mg/1 and a current difference
was  linear  as shown in  Figure 8.4.    According  to the  biomass  increase,  the
upper sensible  concentration  became  lower, but  the  resolutionbecame better.
It  takes  7  to 8  minutes  for the sensoring  system to reach the peak current
after sample  injection.   It takes 7  to 12 minutes to return to the  base cur-
rent after stopping  the sample injection.

      Environmental  samples .such- as  river water  and effluent  from* wastewater
treatment .plants  were  measured  by  the  sensor  system  in  batch  bases.   The
sensor  ammonia  agreed  well with  the manual ammonia.   The  sensor system was
tested  as a  monitor  for  effluent from  a wastewater  treatment  plant.   The
monitoring  of ammonia  in the  effluent was conducted  every  15 minutes.   A
stable agreement  between  sensor ammonia and manual ammonia was observed during
more than 3 weeks.   Ammonia nitrogen standard solution with  a glucose  glutamic
acid solution (100mg/l) was .sometimes  injected into the  sensor system  to check
the interference of  other microorganisms.   But  only the  response to the ammo-

                                      33

-------
nia nitrogen  solution was recognized.   Therefore,  the  interference  of other
microorganisms  seemed negligible for this sensor.

8-3-2 APPLICATION OF AMMONIA BIOSENSOR TO TOXIC SENSOR

      As  a  nitrification  bacterium is  said to  be very  sensitive  to toxic
substances,  application  of the developed ammonia biosensor  to  a toxic sensor
has been expected.  Ortho-chlorophenol (OCR) was selected as a .toxic material.
It was  solved in the  ammonia  nitrogen standard  solution  (1 mg/1).   The  re-
sponse of sensor output  was observed when  the  concentration  of OCR was added.
The results are shown in Figure 8.5.  When the OCR concentration was below 0.5
mg/1,  any decrease .of the current difference was not observed.  The inhibitory
effect  of  OCR   to    the ammonia sensor  was recognized over  0.5 mg/1.   The
current difference  of the electrode decreased with  increasing  OCR concentra-
tion.    When the OCR  concentration  was over 4  mg/1,  the   current difference
became almost zero.   After the OCR  solution   was removed,  the current differ-
ence recovered to the initial   current difference.

      This experiment shows tha.t this ammonia sensor has the ability to detect
toxic materials.  Additional  experiments have  been carried out  to  study  the
detective concentration  of other chlorinated organics.

8-4 ORGANIC ACID BIOSENSOR

      A yeast of Trichosporon  brassicae  is  used  as a detector.   The  yeast is
immobilized between two  porous acetylcellulose  membrane filters.   The biofilm
was sandwiched between an oxygen electrode and a gas permeable teflon membrane
filter.  The  yeast  utilizes gasified  organic acid  and  consumes  oxygen in  the
biofilm when  the  microbial electrode is  immersed in^to an organic acid solu-
tion.

      A linear relationship was observed between an organic  acid concentration
below 600 mg/1  and   current difference  as  shown in Figure'  8.6.   The current
difference decreased with  the  ascent  of  pH  from 3 in the sample   and fell to
zero at a pH of 7 or more due to ionization  of acetic  acid.   It shows pH in a
sample must be kept lower than 3.

      The sensitivities  of other  organic  acid  samples  were tested.  ,   The
sensor  could  detect formic acid,  n-butyric acid,  propionic acid as  well as
acetic acid.  However lactic acid,  tartaric acid,  succinic  acid could not be
detected.   That shows it  is difficult  to convert  the  senson value   to   the
actual  acetic acid  equivalent  value  in  solutions containing  a mixture of
organic acids.
             #
      A field test  in an actual digestion  tank  has. been carried  out for  the
check of maintenance .        -
                                       34

-------
9. DEVELOPMENT OF NEW WASTEWATER TREATMENT SYSTEMS

      Bioreactors for wastewater and sludge treatment, liquid-solid separators
and  biosensors  are  being developed  in addition to  the  basic  studies  on the
microorganism bank and genetic engineering in Biofocus WT, as mentioned above.
Systematizing the individual  development to^propose  new wastewater treatment
systems is being  investigated.   Table  9.1  summarizes new wastewater treatment
systems to be proposed based on  results  of  pilot  plant studies.  Table 9.2 is
the  list of pilot plants in Biofocus WT.

  Table  9.1   New Wastewater  Treatment Systems  to be Proposed  in  Biofocus W.T.

            a. Energy-saving Type Wastewater Treatment System
            b. Area-saving Type Wastewater Treatment System
            c. Nitrogen Removal Type Wastewater Treatment System
            d. Simultaneous Nitrogen & Phosphorus Removal Type
               Wastewater Treatment System
            e. Wastewater Treatment System for Small Flow


      A self-sustaining energy system  has  been  proposed  a.s an  ultimate system
of an energy-saving  type  wastewater treatment  system.   The  system  is illus-
trated in Figure  9.1.   Most SS in raw wastewater  are  removed by a high-effi-
ciency liquid solid  separator.   Energy consumption in the secondary treatment
can  be greatly reduced by two means.  One has influent to the secondary treat-
ment containing not  only  less  organics,  but less  particle organics  which are
more  difficult  to decompose  than  soluble  ones.    The  other  is  adopting  an
energy-saving type bioreactor.              ,

      In sludge  digestion,  the  feed  sludge  has  a large  amount of  primary
sludge which  has  higher potential for  generating  digestion  gas  than  that  of
excess sludge.  Also, ah energy-creating type  bioreactor for sludge digestion
is employed,  so that a greater amount of energy can be recovered.  A key point
of the  system  development  is  how  energy  consumption  of  a   high-efficiency
liquid solid separator can be reduced.

10. POSTSCRIPT

      As Biofocus W.T.  is  a research  project  which intends  to broadly apply
biotechnology  to biological  wastewater treatment  for   its  improvement  and
greater understanding,  it includes  various  research subjects from  very basic
ones  to practical ones,  as  mentioned  above.   Therefore,  results  of Biofocus
W.T.  will  be varied,  from  those  of  identifying  further  research  needs  to
practically feasible  technologies  which may  break through  present  technolo-
gies.
                                      35

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  transfer
                                         37

-------
                          ME77B7  JE5879
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Figure 3.4  Schematic  Diagram of the- Relationship between Parental Strains  and
Recombinant Strains
             -10'
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                           TIME [minutes]

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                  05      10      15     20


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                                        38

-------
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Figure   4.4     Effect .of  ACAM  Concentration  on   Respiration   Rate

Microorganisms Immobilized by Agar-ACAM  Monomer Method
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                                                (m)

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Figure  4.6     Distribution   of   Sludge   Concentration  in   UASB  Reactor

for Treatment of Supernatant from Heat Treatment of Sludge
                                       40

-------
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                               41
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-------
Figure 4.9  Self-Granulated Sludge (SGS)
Figure  4.10   Microscopic View of Film
                 42

-------
          Organic
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Figure 4.11   Mechanism  of Self-Granulation
                      43

-------
           Washed Sludge
                                   Bioreactor
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                                   44

-------
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                        "            45

-------
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             Bioreactor       Modified Trickling Filter

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Figure 5.6  Flow, Diagram of UASB with Modified Trickeling Filter

                               46

-------
Influent
                         Sedimentation
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                               Exess Sludge
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   Figure  5.7   Flowsheet of  Pilot  Plant
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         Figure  5.8   Nitrogen Removal
                      47   .

-------
                   Recirculation
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                                              "Exess  Sludge
        Figure  5.9.  Flowsheet of Pilot Plant
    40


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                Effluent  T-N
              RUN-2
                                    : Iuent T-N
                                 Effluent NH4-N
                 Feb.l  10    20  Mar.l 10
                         DATE


     Figure  5.10  Performance of Nitrogen Removal
                            48

-------
[Pretreatment]
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                                 MB.:Complete Mixing Reactor
                                  E^iFluidized  Bed Reactor  (Cement  Ball)
                                 SLS:Solid Liquid Separator
                                  EXrFixed Bed  Reactor (Ceramic)
Figure  6.1 Flowsheets of  Pilot Plants on Anaerobic Sludge Digestion
   Supernatant
                 Sludge
                   4
               Centrifuging
                      i	Deionized  water (make 100 ml  sample)
                      I	Sulfur Ig
                      	Sulfur bacteria
                      	Iron bacteria
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                   I
         30 C for 0.  3. 7, 14 days
                   I
               Centrifuging
       I
    Sludge
    I
LiquoKContaining leached metals)
               Measurement
       Figure 6.2  Procedure of Bacteria Leaching of Sludge
                              49

-------
                      14 (day)      oi  3

                                100
                      14 (day)      oi   3
                                100
                      a
                      14  (day)
              013
                                    14 (day)
14 (day)

01   3
                                           bacteria not added, mixed sludge
                                           bacteria not added, digested sludge
                                           bacteria added,  mixed sludge
                                           bacteria added,  digested sludge
                                .   ,O --- O.pH  = 4
                         chemical /n --- Q pH  = 3
                         leaching I  A^  A pH  = 2
                                           PH  = 1
14 (day)
   Figure 6.3  Changes of Leaching Ratios of Heavy Metals
                                50

-------
                   A nim>
    Concentration(mg/l)
    300  250  200  150   100
50
                                         B MWTP
                                     Concent ration(mg/l)
                                    50   100   150  200
          50   40.   30-  20   10
     6    5.4    3    2    1
        BOD
      week  max.flow
       day  min.flow
      Holi   max.flow
      -day  min.flow

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      week  max.flow
       day  min.flow
      Holi   max.flow
      -day  min.flow

           SS
      week  max.flow
       day  min.flow
      Holi   max.flow
      -day  min.flow

        T-N
      week  max.flow
       day  min.flow
      Holi   max.flow
      -day  min.flow

        T-P
      week  max.flow
       day  min.flow
      Holi   max.flow
      -day  min.flow
Figure  7.1   Distribution  of Particulate  Contaminants in  Raw  Wastewater
                                    10   20   30   40
                                     1    2     34
                  BOD
   s
   L
i  M
\  L
:  L
5  L
   S
   S
   S
                            composition rateCO
                          SO     80     TOO
                                       \~
               S
            uj  L
            5  M
            :-L
            I  L
            -   L
                S
                S
                s
Pl^xsgro^ggpiafl
                              g C '
                                   composition rate(!0
                                40    60     80    100

  D    i
       1~!0  10-74 u 74 <
           particle  size,
             D    i
                   l~10tf 1D~7< 74 u<
                       particle sire
Figure 7.2   Comparison of Distribution of  SS  and  Particulate BOD
                    in Raw Wastewater  by Plant Size
                                       51

-------
                                                   2mm-74>m
                                                  M 74jum- 8>mi
                                                 A 8/mi- IJJITI
                                                 ODissolved
  Figure 7.3  Difference of Biodegradation Rates  of TOC due  to
                      Particle Size of Contaminant in Aerobic  Condition
                                                   2mm-74>m
                                                  74jum- 8}im
                                                 A  8/rni- Ijurn
                                                 ODissolved
                                                           TIME(h)
Figure 7.4   Difference of Biodegradation Rates  of TOC due to
                    Particle Size of Contaminant in Anaerobic  Condition
                                    52

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sa-
ri-
a-
n-
a-
SB-
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                                        upflow rate(cm/min.)
                       (1) SS removal  rate and upflow rate


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                                      *     >1     13
                                      upflow rate(cm/min.)


                      (2) SS concentration in sludge blanket
                         and upflow rate


     Figure  7.5  Performance of Upflow Sedimentation Column
100
90

8 80
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2 60
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 10
 30
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particle size


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                       (2)        (3)        (4)

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Figure 7.6  SS Removal by Three Solid-Liquid  Separation Processes

                                ~ 53

-------
                                  CPU
                                  amplifier
                                  A/D transfer
          Microbial electrode
                        Isothermal water bath
                                              Drainage
          Standard solution    Buffer solution
Figure 8.1   Flow  Chart  of  Biosensoring System
                        54

-------
   200
   150
*>
C
(U
    50
O
u

a
o
CQ    o
       GGA standard  solution
   0.5     1.0     1.5    2.0

current difference  (uA)
                                      2.5
                                           20i
                                  150
                                           100
                                       synthetic wastewater
                                    -  2
                                           50
 0      0-5     1.0     1.5    2.0     2.5

      current  difference  (uA)
                Figure 8.2  Performance of Three Selected Biofilms
                                                   river  water
                                                  A secondary effluent
                        150
                      200
10    20     30    40    50
           sensor  BOD (mg/1)                sensor  BOD (mg/1)
   calibrated  with  GGA solution     calibrated   with artificial sewage


            Figure 8.3  Relationship between Sensor BOD and Manual BOD
                                    55

-------
        0)
        TJ-
        O
        O
        
         i
        
            13

            P
             O

             0)
             Q)
             J-,
                1.0
                  OCP  concentration  (mg/1)
Figure 8.5  OCP concentration and Current  Difference of Ammonia Sensor


                                 56         '

-------
              500T
              400
          4)
          O
             300
         ~tion
more
>s
jy

combustible
gas

Generation
of
electricity


uti nzation or
electricity
Utilization o
waste heat

         Sludge
        Utilization


Figure 9.1   Self-energy Sustaining Wastewater Treatment System

                               57

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-------
FUNDAMENTAL STUDY ON  APPLICATION OF HIGH GRADIENT  MAGNETIC  SEPARATION

               TO  MUNICIPAL WASTEWATER TREATMENT SYSTEM
           Kazuo  HOYA,  Director  of  Engineering  Division,
                         Regional Sewerage  Center
           Yasuo  TANAKA, Ph.D.,  Researcher  of  Research  and
                         Technological  Development  Section,
                         Planning   Division
           Khouichi  ISHIDA, Assist.   Head of Research and
                         Technological  Development  Section,
                         Planning   Division

                            Sewerage  Bureau
                      Tokyo  Metropolitan Government
                The work described in this paper was not  funded by
                the U.S. Environmental Protection Agency.  The contents
                do not necessarily reflect the views of the Agency and
                no official endorsement should be inferred.
                      Prepared  for  Presentation  at:
                  12th  United  States/Japan  Conference
                                     on
                      Sewage  Treatment  Technology

                              October  1989
                            Cincinnati,    Ohio
                                    59

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                                 Abstract             c                

       A research  was carried out  on the development  of small  land
  required   treatment  process  which  is  applicable   for both   combined
  sewer overflows  treatment in wet weather and tertiary  treatment of
  secondary  effluent  in   dry weather using  high  gradient   magnetic
  separator.   Experiments   with   the   bench   scale  and   pilot   scale
  apparatuses of  high  gradient  magnetic   separation process  exhibited
  that  the  pollutants were  removed sufficiently  for  both   combined
  overflow   treatment  and  tertiary  treatment.  The  results  of   the
  experiments suggested that an  optimum  flow  velocity  of  the  magnetic
  separator  was  about 2000  to  3000  m/day  and  appropriate  magnetite
  concentration   was   about   25   mg/1  for   combined  sewer   overflow
  treatment  and about 5  mg/1  for tertiary  treatment. Preseparation of
  large floes by high rate  sedimentation prior  to  magnetic separation
  was considered to be effective measure to lengthen the filter run of
  the  magnetic  separator  for  combined  sewer   overflows  treatment.
  Optimum  overflow  rate of preseparation was about  800  to  900;   mVm2
    day.  Sludge  produced  from the  treatment process could be  thickened
  and  dewatered   easily.   Preliminary   design  was  carried  out  for   a
  demonstration  size plant  with  a  10,000  m   3   /day  treatment flow  and
full scale plant with a  100,000  m3   /day treatment  flow.
                                    60

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                            1.   INTRODUCTION

      In  recent   years, - several   kinds  of   technological  improvements
has   been   required   for   wastewater   treatment   plant    in   Tokyo
Metropolis.   One  is  the  improvement  of effluent  water  quality  at
storm  weather.    Collection  system.  in    the  ward   area   of   Tokyo
Metropolis  is  combined type,  hence large   volume  of  wastewater is
discharged   from  treatment  plants  at   storm  weather   after  only
primary  treatment.  This  causes   the pollution  of  public  water  body
at   storm  weather.   The  other   is  the  introduction  of   advanced
treatments'  far the  prevention of  eutrophication  and for the reuse" of
effluent  for  aesthetic,  recreastional   and  subpotable  water  supply .
purposes.  Removal  of   phosphorus,  BOD,   COD,  turbidity,  chromaticity
and   coliform  bacteria  is  especially  important  for  these  purposes.
However,  treatment   plants  in  Tokyo  do  not .have enough  space  to
install   many  new  facilities,  hence  developement   of  a   treatment
technology  which  is  small  land  required  and applicable to  above all
purposes  is important nowadays.

      High  gradient  magnetic separation   using  seeding  material  seems
suitable  technique  for  satisfying  above  technological  requirements
because  of  its  high processing rate, high effluent water  quality  and
adaptability for  wide  range  of influent water  quality.  The  theory of
"High Gradient  Magnetic   Separation"  was  established  by  Oberteuffer
(Oberteuffer,  1973).  Currently,   a  high   gradient  magnetic .  separator
(HGMS)  based  on  this  theory  is  applied  for  removing   magnetic
suspended  solids  in discharge  from  steel  industry and  for  eliminating
collosion  products  in the  feed  water of  power plant.  High gradient
magnetic  separation  is  also  applicable  to  municipal  and  industrial
wastewater  treatments  for  the removal   of  non-magnetic  contaminants
using   magnetic    seeding    method.  In    this   method,   non-magnetic
pollutants in water are  coagulated  with  magnetic seeding  material  by
coagulant and subsequently  removed  by  HGMS. Magnetite  (Fe3  O 4  )
has   been usually  used  as  seeding material in  the  seeding  method
because  of  its   large magnetic  moment.  Chemical  coagulation of  the
magnetite   and   pollutants   is   made  by  alum   and  polyelectrolyte.
Principal  advantage  of  the  seeding  method  is its  5high  processing
rate  and high removal rate  of suspended  and colloidal  matters.

      Seeding  method has  been  investigated  by many  researchers. Allen
et  al.   (1977)  and  Allen  (1978)    investigated  about   application   of
the  seeding  method  for combined sewer  overflows treatment.  According
to them, the seeding method  was  effective for  reducing most  forms  of
pollutants present  in a  combined sewer  overflows.  They  emphasized
that  the treatment  system  has  several  additional benefits, namely,
high, processing   rate,  small   land requirements, and  lower  chlorine
demand.  Several  studies have been  also carried  out  on the ^removal  of
phytoplankton  in.  eutrophic   seawater  or   freshwater  (Kurinobu  &
Uchiyama,  1982;   Kaneko   et  al.,   1981;  Kaneko,   1982).   These  studies

                                   61                        - '    '     .

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confirmed   the  excellent  efficiency   of  the  seeding   method  for
removing  phytoplankton.

     The   seeding   method,   however,   lias  not   received   practical
application  because  of  following two problems.  First is high  cost of
chemicals,  especially for   magnetite.  Reducing  the concentration  of
magnetite or  using  low  price seeding  material instead of magnetite;
are  important to   reduce the  chemical  cost. In  addition  to  this,
selection  of  the most  suitable polyelectrolyte may be  important for
reducing   the   required  amount   of   seeding    material   because
characteristics  of  polyelectrolyte  strongly  affect  the  mechanical
strength  of   coagulated  floe. Second   is that  filter  run   of  the
magnetic  separator   are  impractically  short  when the   feed  water
contains high  concentration  of   aggregates.  Preseparation  of  large
aggregates  before  magnetic  separation  or increase  in   the  matrix
thickness should  be  required  for  lengthen  the  filter  run.

     Tokyo  Sewerage Bureau has been  carrying out  the  research about
the seeding method since three years ago. The  main objectives  of the
research  are  determination  of  optimum  treatment conditions  at low
magnetite   concentration  and   establishing   the   treatment   flow
applicable  to  both  combined   sewer overflows treatment and  tertially
treatment.   The present paper  outlines  the  results obtained  by this
research.
                                  62

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                       O
                       4
                       ro
                       ro
                       Q_
                       
-------
                  2.  COMBINED SEWER  OVERFLOWS TREATMENT
 2-1.  Bench  Tests
 Scope of  testing
      Bench  tests were carried  out  to obtain  basic data "to  about an
 optimum  dosing  rate and  treatment  conditions.

 Bench test  apparatus
      Fig.2  shows the appearance  of a batch  type  apparatus  used for
 t,he  bench   test.  The  flowsheet  of  the  apparatus  is   indicated  by
 Fig.3. Flocculatiori  tank  was 5   Jitter  in capacity.  Size  of  mixing
 blade in  the  flocculation   tank  was   15  cm  in length  and  6  cm  in
 width. The  matrix  for the   high  gradient  magnetic separator  consists
 of 100  pieces  of  SUS  430  expanded  metal  disc which  were  10  mm  in
 diameter  (Fig.4).  The  matrix  is  80  mm in  thickness  and  80% jn  void
 ratio. Electromagnets are  ori both sides  of the matrix.
      Test  procedures  are  described  as   follows.   Magnetite  powder  (1
 to 4 urn   in diameter)  were  added  to 5   litter  of raw  water in the
 flocculation , tank  and  mixed  by tho mixer at  150 rpm  for one minute.
 Then,  alum  was  added  and   flush  mixed   at  150 rpm   fro  15  seconds
 followed   by   gentle   mixing  at   50   rpm   for   1  minute.   Finally,
 polyelectrolyte  was added  and stirred at  150  rpm   for  15  seconds and
 50  rpm  for  2 minutes  successively. The flocculated slurry  was pumped
 to.  the  magnetic   separator  by  a filter  pump  which  was  .located
 downstream  from  the  magnetic  separator  to  avoid the  disruption of
 the  floes.  Effluent from  magnetic  separator  was sampled continuously
 for    chemical   analysis   untill    the   breakthrough.   After    the
 breakthrough,  matrix was  backflushed  with tap  water.

 Alum  concentration
      Ordinary jar, test was  performed prior  to the  experiments with
 the   test apparatus  to  clarify   the   relationship   between  the  alum
 requirement  and SS  value  of  raw  sewage.  Fig.5  shows  one  of  the
 results of  the  jar  test.   In  this  case, optimum  concentration was
 estimated  for  about 5mg/l   because  the  transparency  of  supernatant
 reached  to  a  plateau  at -tliis  concentration.  Relationship  between SS
 and   optimum  alum  concentration  is  shown   by Fig.6.   Optimum   alum
 concentration  fluctuated  in  narrow  range  (3  to 7 mg Al/1) while the
 SS  values  fluctuated  considerably (100  to  600 mg/1).

 Magnetite  concentration
      Fig.7  shows  relationship  between  the  magnetite   concentration
 and   the   removal   rate   of   totaj  organic  carbon  (TOG).   Magnetite
 concentration  had almost  no  effect  on the removal rate and also  on
 the  filter  run in  the  range between  50  to 400 mg/1, hence magnetite
 requirements should be less  than  or  equal  to  50  mg/1. Further  tests
showed that magnetite  concentration can  be reduced to about  25  mg/1.
This  optimum  value is  considerably lower  than tliat  recontended.  by
Allen  (1978)    (200mg/l).   Lower  flow   velocity   (2000m/day)  comparing
with  that of   Allen  (5000  m/day)  should   be  cause of low  magnetite

                                  64

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demand   in  the  present  study.  In Japan,  price   of  magnetite   is
considerably higher  than  that in  the United  States,  hence,  it  may be
unavoidable  to   reduce  the  flow velocity.  Reduction  of  magnetite
concentration  is also  important  from the  viewpoint  of  cutting down
the  amount of sludge  generated from the process.

Polyelectrolyte   concentration
     To  select  suitable  sort of   polyelectrolyte, ' filter  run and the
transparency  of  effluent   were   compared  for    many   kinds   of
polyelectrolyte.   As . shown  in  Table. 1,  anionic  polyelectrolytes  were
generally  superior   to  amphoteric  and  cationic  ones.  Among  the
anionic    polyelectrolytes,    P-720     had    especially     excellenct
performance, hence it  was  used for all  of  remaining  tests.
     Fig. 8 shows the   effects of   P-720  concentration  on  the  filter
run  and   effluent  water   quality.  Polyelectrolyte'  concentration  had
almost no  effect on  the effluent. water quality  within  the range of
0.5 to 3 mg/1. The filter  run,  however,  decreased markedly  under the
concentration   of  2   mg/1.   It   is   concluded   that   the  optimum
concentration  was 2  mg/1.

Flow velocity  of  high gradient magnetic  separator
     Fig. 9 shows  the  effects  of the flow  velocity  on  the filter run
and  effluent water quality.  There was  no  observable effect  of flow
velocity  on  the  effluent water  quality, except  a  slight  increase  of
total phosphorus over  1500  m/day.  On  the  other   hand,  the filter run
markedly  dropped at  the  velocity  over  1500 m/day.

Magnetic  field  strength
     As  shown  in Fig. 10,  magnetic field  strength  has  little  effect
on  the  effluent water  quality, while  filter run  increased markedly
with the  strength.  Electrical  power consumption 'increases with  the
magnetic  field strength,  hence   optimum   magnetic  field strength must
be  determined  by the consideration  of  total running  cost.

2-2.  Pilot Plant Tests

Scope of testing
     To  obtain  the  fundamental  data for the   design of  full scale
plant,  a  continuous   flow  pilot  plant  was  operated  on  optimum
conditions which had  been determined by  the bench  test.

Pilot  plant   facility
     Fig. 11 and  Fig. 12  s"hows  a  flowsheet   and side  view of  the pilot
plant.  Raw sewage taken  by submerged pump  was  applied  to  automatic
flushing  strainer with  0.5  mm  opening  J,o  remove  rubbish,  and  then
pumped to flush mixing  unit.  After  addition  of magnetite  and  alum,
the  mixture  was stirred  for 3  minutes.  Coagulated  slurry was  fed  to
a  floe   preseparation  tank (preseparator)  after  addition  of  the
polyelectrolyte  (P-720).  Overflow  rate of the  preseparator  was  about

                                    65

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800 m3  /ra2     day.  The  preseparator  consisted  of three  layers;
settling layer  in  which  large  sized  floes  settle  down,  helically
flowing  flocculation  layer   in which  feed  slurry  flew  into   and
flocculation proceed,  and sludge  blanket  layer  by  which  fine  floes
was  removed,  in order   of height.  Remaining  floes  in  the  effluent
from  the   preseparator  were  removed  completely  by  the  magnetic
separator.  Matrix of  the  magnetic separator was  150  mm in  diameter
and  150  mm  in  thickness. SUS  430  expanded  metal  plates which  mesh
size was  13 mm  in length  and  5.1  mm  in width  were  used  for  the
matrix.   Operating  conditions   of  the magnetic  separator  were  2000
m/day for  flow  velocity, 3 KG for magnetic  field  strength and 1  hour
for filter  run.    Backflush  of  the magnetic separator was made with
mixture  of pressurized  water  and   air  for  10  seconds  with   flow
velocity of 2000 to  3000  m/hr.

Optimal parameter runs
     Table  2 shows  the  results from   an optimized pilot  plant run  of
6  hours  continuous  operation  using   raw  sewage  at  dry weather  as
influent.  The  results show  that high removal   rates (more  than  90%)
of  SS,  turbidity,  phosphorus,   coliform bacteria  can be  achieved  by
the seeding method.  Removal  rates  of BOD  and  COD were lower  than
those  values.  However,  it  was  confirmed  by bench   test that higher
removal  rates of  BOD  and  COD  could  be obtained  in  wet  weather,
probably because the  ratio  of soluble COD and BOD  to suspended  ones
decreased   markedly  in  wet  weather.   Fig. 13  shows   the  counts  of
coliform bacteria  in effluent for  19  runs operation. The counts  were
much   lower  than  3000   no./ml, which is  the  regulation   number  in
Japan,  hence   addition   of.   chlorine  to  the  effluent   should  be
avoidable.
     The  approximate amount  of sludge generated  from the process was
estimated  for about  140 to   310 g-dry   weight per  1m3  of  the
influent.  Seventy  eight  .percent  of  the  total  sludge  was generated
from the preseparator and remainings  from the magnetic separator.  As
shown   in  Table  3  and. Fig. 14,  the  generated  sludge  had  excellent
thickenability   and   dewaterability.
     It was confirmed that  about 99%  of  trapped floes in  the matrix
were  washed out by the  backflushing  which was made with the mixture
of  effluent water  and two   times  volume  of  pressurized air.  Little
amount  of  cellulose fiber  however  remained  in the  matrix after the
backflushing.  It  has  not been,  clarified  yet  whether  these  fibrous
materials causes the  clogging  of matrix  after  long time  continuous
operation.  Ball  shaped matrix  seems -to  be  more  convenient than the
expanded   metal  matrix   to   prevent   clogging   because   tangle  of
cellulose  fiber  should not occur.  Test of ball matrix is earring out
now.                               cc
                                   oo

-------
Fig. 2.  Bench  test  apparatus.
                67

-------

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Fig. 4.  Matrix  (16 mm0 x 80  mm H) of  high  gradient  magnetic
        separator   used for  bench test.
                               69

-------
                                          >100
                                           CX
     0
      0
8
10
               Alum   Concentration   (mg-Al/1)
Fig.5.  Effect of  alum concentration on  transparency  and
       SS  of supernatant in jar  test  of raw  sewage.
         (magnetite:  25  mg/1,   polyelectrolyte:  2   mg/1)
                              70

-------
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I    .    I   .   I    .    I
               100     200
       300
       400
500
600
                           SS   (mg/1)

Fig. 6.  Relationship between SS concentration of  raw  sewage
        and  optimum alum  concentration.
                                  71

-------
Removal Rate (%)
80
60
40
20
0

1 1 II
              0      100      200     300     400
                 Magnetite  Concentration  (mg/1)
Fig. 7.  Effect of magnetite  concentration  on  removaJ. rate
        of total  organic  carbon  (TOG).

        Test   conditions
           Magnetic  Field Strength:  5KG
           Flow  Velocity:  2000  m/day
           Alum  Cone.:  8.6  mg/1
           Polyelectolyte   Conc.(C-599-lP):    1   mg/1
           Influent  TOG:  73  mg/1
                              72

-------
Table  1.   Polyelectrolyte  comparison.
          Test  conditions
            Magnetic  Field  Strength : 5KG
            Flow  Velocity :  1400  m/day
            Magnetite  Cone.:  25  mg/l
            Ferrous   Alum  Cone.:  Al-8mg/l,Fe-3mg/l
            Polyelectrolyte  :  2  mg/l
       Table  l-l.   Anionic  Polyelectrolyte

Name
I' - 700
P - 710
P - 713
P - 720
P - 730
P - 790




 :













Characteristics
Chemical composition (mole%)
DMC
80
80
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80
80.
40
40

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A A ii


55
55


55
55
60
60
80
90
90
80
95
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20
5
5
20
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40
40
20
io
10
20
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M.VV.
Mt*)
300
500
300
500
300
500
300
400
21)0
400
500
300
600
700
600
Filter run
(relative
value )
34
34
34
29
- 47-
.28
44
55
.46
66
-9
84
136
29
19
'rarspaierty
relative
value)
-

-
-
85


83
75
89
75
85
60

-
                      73

-------
Table   1-3.  Cationic  Polyelectrolyte

Name
c - 100
c - 200
c - 201
C - 202
C - 252
C - 270
C - 300
C - 301
C - 340
C - 341
C - 343
C - 360
C - 373
C - 380
C - -155
C - 500
CA
DC-802P
UC-753P
1A1-883P
DM -254 P


(D
___
"C~5U9-1P
CP-G58
Characteristics
Chemical composition (mo(e%)
DMC
100
100



70
100

40

20
60
50
~80
100'



100
100


95
~95

DM- Ac


100




100

40
20

20









5
5


A A in




50
30


60
60
60
40
30
20
50






40




'
AAc



























DAC





	







50












others



S3 100
*3 50











*4 100
$5 100
KS 100


*6 60
*7 100




M.W.
Mb*)
100
200
200
200
200
200
300
300
300
300
300
300
300
300
400
500
1
1
8
7
25
500
20
200
400

1000
Filter run
(relative
value )
19
21
23
28
26
32
23
33
60
48
45
50
43
36
71
28
19
13
14
17
25
76
18
12
17
27
73
rrarspaimy
(relative
value)




-
-
-
-
72

-
-
-

83
-


-

-
68
' -

-
68
64
                       74

-------
                  G  20

                  S
                    10
                    80


                 0
                 fi  60
                 0)
                 fc
                 cd
                 ft  40
                 CO
                 G
                 03
                 ti  20
                 H
                   30
                   20
                   10
                   0.3
                 bo
                 cd
                 4->
                   0.2
                                       2
Turbidity
     ss
                __  0
                ^ .  0        1         2         3


                   Polyelectrolyte   Cone.   (mg/1)



Fig. 8.  Effects of  polyelectrolyte  concentration on filter

        run  and  effluent water quality.
  Test   conditions

  =  Magnetic  Field  Strength:5KG

    Flow  Velocity  :  1400m/day

    Magnetite Cone.  : 25mg/l

    Alum  Cone.  :  8mg/l

    Polyelectrolyte  :  P-720

                                75
   InfluentCSettled  Sewage)

     Transparency  :  5.5

      Turbidity  :   95

      SS  :  34 mg/1

      TOG : 77 mg/1

     Total  P : 5.3  mg-P/1

-------
                +3 20


                S 10
             fc,
                   1000
                             1500
                                         2000
C.100
g 50
2  ol
E-,   1000
                  14 -


                  12


                  10
                             1500
                                         2000
             W/i
                      TOC
      Turbidity
     o	o-
                           .55
                   1000
                             1500
                                        2000
            CU -N o.2
                   1000        1500         2000
                      Flow Velocity  (ra/day)
Fig. 9..  Effects  of  flow  velocity  on  filter  run  of  high
        gradient  magnetic separator  and effluent water
        quality.

        Test  Conditions       fj
          Magnetic .Field  Strength  :  5KG
          Magnetite  Cone.  :   25mg/l
          Alum  Cone.  :  8mg/l
          Polyelectrolyte  Cone.   (P-720)  :  2mg/l
        Influent   (Settled  Sewage)
          Transparency  :  5.5,    Turbidity  :  93,  SS  :  62rag/l
          TOC  :  52mg/l,  Total P :  3.8mg/l
                              76

-------
                   30
               C  ^
              <  "$ 20


              I  | 10
                S
M .... 	 . 	 . 	 L 	 _J
^ 0 1 23 4 5
0
150
CB 10u
W 50
c
ca 

.
*
i i i . i r
n i 9 Q .1 c
                   30 r
                   20
                   10
                                  TOC
                             Turbidity
                  0.3


                  0.2


                  0.1
                      012345
                     Magnetic  Field Strength
                              (KG)
Fig.10. Effects of  magnetic  field strength on filter  run of
         high gradient  magnetic  separator  and effluent water
         quality.

     Test  Conditions
       Magnetite  Cone.   :  25mg/l
       Alum  Cone.  : 8mg/l
       Polyelectrolyte   Cone. . (P-720)  :  2mg/l
     Influent   (Settled   Sewage)
       Transparency  :   6,   Turbidity  :  97,  SS  :  41mg/l
       TOC  :  68rag/l,  Total  P :  5.9mg/l
                               77

-------
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              78

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79

-------
Table'2. Results of  continuous  operation  of  pilot
         plant for combined sewer overflows treatment.
Influent
PH
Transparency
Turbidity
Chromatic! ty
SS (mg/1)
COD (mg/1)
BOD (mg/1)
Total P (mg-P/1)
Coliform bacteria
(No. /ml)
7.3 -
r\
o -
81 -
30 -
108 -
74 -
106 -
25 -
2xl05 -

7.8
5
202
50
190
109
177
4.2
3xlOE

Effluent
6.7
more
2
18
1 ess
21
21
0.1
13

- 7.0
than .150
- 7
- 24
than 5
- 50
- 51
- 0.2
- 16

        (Operating conditions)
           Influent :  Raw ,se*wage at dry weather
           Magnetic Field Strength : 3KG
                           2000* m/day
                          6 mg-Al/1
                           :  26 mg/1
                           Cone.  :  1.8 mg/1
Flow Veloci ty
Alum Cone. :  7
Magnetite Cone.
Polyelectrolyte
           Backflush
           Backflush
          cycl e
          T i me :
 1
10
hour
seconds
                              80

-------
 8
T: AOOO
$
0
ca
E


O
  2000
     rv
     0.
      Ln  H
       '88-
                            Regulation  Number   (3000  cells/ml)
                n .n  ,m  n : n
               -'88. '89-
-fi  n  n'n  n.

                              Experimental   Day
Fig. 13.
                  Number  of  coliform  bacteria  in  effluent.


                   (Influent : raw sewage at  dry and wet  weather)
                                  81

-------
Table  3.  Characteristics  of   sludge generated from pilot
               plant for combined sewer overflows treatment.

              Raw sludge
               S3
                         '2000
mg/1
              Thickened sludge
               pH
               TS
               SS
               VSS
               Coarse suspended
                   sol ids
               Calorific value
    6.5
  28600 mg/1
  26600 mg/1
  17290 mg/1
     24%

  3690 Cal/g-dry weight
                 (gravity thickening for 12 hours)
                               82

-------
 I
 3
 IQ
 p.
 i
 %
 H
 0
 
 (!)
                               -
-------
 3.  TERTIARY  TREATMENT OF  ACTIVATED SLUDGE  PROCESS EFFLUENT

 3-1.  Bench  Tests

 Scope of  testing
      The bench test was carried  out to obtain  the basic data
 about     the  best dosing  rate and  treatment  conditions.

 Bench test  apparatus
      The bench test apparatus  described  above  was used for also the
 experiment  of  tertiary  treatment.

 Alum  concentration
      Fig. 15  shows   the  relationship   between  alum  dosing  .rate  and
 removal   rate  of  total  phosphorus.  It  is  obvious' that  the   total
 phosphorus  concentration   became   lower  than  0.2 -mg/1  when  the
 mole-ratio  of alum  to total  phosphorus is higher than  2.5.

 Magnetite  and  polyelectrolyte  concentrations
      Fig. 16  and   17  shows   the   effects   of  the   magnetite  and
 polyelectrolyte  (C-599-1P) concentrations on  the removal  rate of TOC
 and total  phosphorus.  In   the case of  poor  water quality  influent
 (Fig. 16),  removal   rate   increased  markedly  with  concentrations  of
 polyelectrolyte and  magnetite.  On   the other   hand,  in the   case  of
 improved   water   quality  influent   (Fig. 17),  high  removal  rate  -was
 obtained   regardless  of   the  concentrations  of  polyelectrolyte  and
 magnetite.  Optimum magnetite  concentration   should  be ranges  between
 5  to 10 mg/1.
     Fig. 18
shows
the
effect
of
polyelectrolyte
                                                    (P-720)
concentration  on  the filter run  and  effluent  water quality. Effluent
water   quality improved   with  polyelectrolyte   concentration  in  the
ranges  between 0  and 0.5 mg/1,  and  became  stable  in  the ranges from
0.5 to  1  mg/1.  On the  other  hand,  filter run  increased steadily with
polyelectrolyte concentration in  the ranges  between  0  and 1  mg/1.
These  results   suggest  that  appropriate concentration  is  0.5   to 1
mg/1.

Flow velocity  of  high gradient  magnetic  separator
     As. shown. in  Fig. 19,  flow velocity  had  almost  no  effects on the
effluent water quality.  The  filter run however dropped markedly with
increase  of the  -flow velocity.  It   is  estimated that  filter run  will
be  about 30 minutes at  flow  velocity of  2000 m/day  when  using the
matrix  of  15  cm  thickness,   which  is  standard  value  of  full  scale
magnetic  separator.  This filter  run  should  be practical   for   the
operation of full  scale  magnetic  separator, hence  it  is assumed that
optimum  flow velocity is 2000  m/day.

Magnetic  field  strength                                             >
    Fig. 20  shows the effects of the  magnetic field strength on  the

                                   84

-------
effluent water quality and  filter  run.  Though  the effluent * water
quality was  not affected by  magnetic field strength,  filter  run '
increased" considerably with  magnetic  field strength.  Filter  run
became  rather stable  over 3 KG, hence this value should be
appropriate  for  practical operation.

3-2.  Pilot  Plant  Tests
                                                     
Scope  of testing                                            
     A  continuous flow pilot  plant  was operated with  the  optimum
conditions determined  by  the  bench tests to obtain a  design
parameters  of  full-scale plant.

Pilot   plant  facility
     Fig. 21  shows  the  flowsheet  of  the  pilot   plant. Magnetite  and
alum  were   dosed  successively and  mixed  by  a  static  mixer.   The
mixture  was gently  stirred  by  helical flow in  flocculation tank  for
4   minutes.   The  flocculated   slurry  was   fed   to  the   magnetic
separator  after  addition of  polyelectrolyte.  Magnetic separator  was
operated with, the flow  velocity of  2000 m/day and  the 'magnetic field
strength  of  3 KG.  The  matrix  of  magnetic separator was  10 cm in
diameter  and 15 cm  in thickness.  When the turbidity  of the  effluent
increased  markedly,  backflushing was  carried  out  with 40  litter  tap
water   and 120  litter of  pressurized air for  ten   seconds.  Fig. 22
shows  the side view  of  the  pilot plant.

Optimal parameter runs
     Table  4 shows  one  of the  results of  the water quality analyses.
High removal  rate  was   obtained for  SS,   BOD,  total   phosphorus  and
coliform bacteria. Chromaticity  and  COD  also removed  for  about 40%.
These  results  prove that the seeding  method has  high performance  of
tertiary-   treatment.
     The amount  of sludge   generated was  determined  about  30 to 50
g-dry   weight  per   1  m3  of  influent.   This  production  rate  is
one-fifth of  that for combined sewer  overflow treatment. As  shown in
Table  5, the   sludge  was  easy for  thickening  and  dewatering.   The
caloric value  of  the  dewatered  sludge was almost  half  of that  from
the  combined  sewer overflows  treatment.  Incinerated  ash  contained
ferromagnetic material for about 1%, hence   it  seems  possible  to  reuse
the ash  as seeding material  after  ore  dressing by magnetic "separation.
     The  matrix was  washed almost  compfetely  by the  backf lushing
described   above.   In  contrast  to   the   combined  sewer  overflows
treatment,  fibrous material  did not  accumurate  in the matrix.
                                    85

-------
             3
             o
100


 90


80


70
             I
                  60
50
  0          10'         20
  Alum  concentration
       (mg-Al/1) .
Fig. 15.  Effect of  alum concentration on removal  rate  of
         total  phosphorus.

         Test  Conditions
          Magnetic  Field  Strength  :  5KG
          Flow Velocity  :  1000  m/day
          Magnetite  Cone.   :  200  mg/1
          Polyelectrolyte(C-599-lP)    :    lrag/1

         Influent   (activated  sludge  process  effluent)
          Total P  : 4.6 mg/1
                            86

-------
                o
                CO
                I
                0)
                PS
     100

     80


     60

     40

     20
                          Polyelectr olyte:0. 6rag/l
                       0    10   20   30    40   50
a.
"ca
p
5
0
100


80


"60

40
                 f>    20
                 0
                 S    o
                PS    
                         Polyeleotrolyte:0. 6mg/l
                         0.3n/t
                      0    10   20   30    40   50
                   Magnetite   concentration  (rag/1)
Fig. 16.  Effect  of  magnetite and  polyelectrolyte
         concentrations on  removal rates of -TOG and total
         phosphorus.
         (The case of  poor water quality  influent.)

         Test  Conditions
           Magnetic  Field Strength  :  5KG
           Flow  Velocity  :   1000  m/day
           Alum  Cone.  :  8mg/l
           Polyelectrolyte    :   C-599-1P

         Influent    C Activated  sludge  process  effluent)
           TOG  :  28mg/l
           Total  P  :  4.7 mg-P/1
                                87

-------
          8
          H
          I
60


40


20
          10
                                   o Polyeleetrolyte:0.1mg/l

                                         0.3mg/i

                                   *      Q.Gng/l
                   20
                           30
           03

          P

           O
          I
          I
100


80

60


40


20
                0        10       20        30
             Magnetite   concentration  (rag/1)
Fig. 17.  Effect  of  magnetite  and polyelectrolyte *
         concentrations  on  removal rates  of TOG and total
         phosphorus.
    (The  case of the  influent of high grade water quality)

         Test  Conditions
           Magnetic 'Field Strength :  5KG.
           Flow  Velocity  :  1000  m/day
           Alum  Cone.  :  8mg/l
           Polyelectrolyte   :   C-599-1P

         Influent    (Activated  sludge process  effluent)
           TOC  :  13mg/l
           Total  P :  0.57  mg-P/1
                                   88

-------
                      80
                      60
                      40
                      20
Transparency
150
100
50
0
10
0 0.2
[ t T

0 0.2
0.4 0.6 0.8
t 1

0.4 0.6 0.8 
^ TOG
1.0
f

1.0
 60   4

     2

     0

    0.15
1 ,-H.
 ^ 0.10


 1? 0.05
                              0.2
                                  0.4  0.6
                                           0.8
                                                1.0
                         0   0.2   0.4.  OS   0.8   1.0
                       Polyelectrolyte   Conc.(mg/l)

F i g. 18.  Effects  of  polyelectrolyte  concentration  on  filter
         run of  high gradient magnetic separator and  effluent
         water  quality.

         Test  Conditions
          Magnetic  Field  Strength :  5KG
          Flow   Velocity  :  1400m/day
          Magnetite  Cone.  :   10mg/l
          Alum  Cone.  : 4mg/l
          Polyelectrolyte   :  P-720
         Influent  (Activated  Sludge  Process  Effluent)
          Transparency :  65,  Turbidity :  8.7,  SS  :  4.3mg/l
          TOG  :  13rag/l,  Total  P  :   Q.54mg-P/l
                                89

-------
               s
              s
20
                     1000
            2000
                       3000
Transparency
150
100
50
0
1
t- r T

DOO 2000
T t

3000
  txQ   4
  S
      2

      0

fri ""*  .
  C^  6.1
s*
P I1   o
                                   TOG
                       Turbidity
                     1000
            2000
3000
                     1000         2000    .     3000 .
                       Flow  Velocity  (ra/day)

Fig. 19.  Effects  of  flow  velocity on filter  run of high
          gradient magnetic separator and effluent, water
          qual i ty.

         Test   Conditions
           Magnetic  Field  Strength :  5KG
           Magnetite  Cone.  :   10mg/l
           Alum Cone.  :  4mg/l
           Polyelectrolyte    Conc.(P-720)   :   lmg/1
         Influent  (Activated  Sludge   Process  Effluent)
           Transparency  :  36,  Turbidity  :  11.2,  SS   :  9.8mg/l
           TOC   :  18.4mg/l,  Total   P   :  1.3mg-P/l
                               90

-------
            9
            +>  e
            i i  ~~'
            H
                   40
                   20
Transparency
u
150
100
50
0
10
R
0 1
t-

0 1
2 3 ,4
t

2 3.4
TOC
. 	 	 	
5
1

5
__ -
G




O. "^
-V.
la ^
O 
4
2



Turbidity
..ss-

0 1.2 3 4 5

0.04

0.02
n


  

                      012345
                      Magnetic  Field  Strength
         ,                 .   (KG)                            ''

F i g. 2 0.  Effects  of  magnetic  field  strength on  filter  run  of
          high  gradient magnetic separator  and  effluent water
          quality.

         Test   Conditions
           Flow Velocity  :  2200m/day
           Magnetite  Cone,   :  lOmg/1
           Alum Cone.  :  4mg/l
         -  Polyelectrolyte   Conc.(P-720)   :    lmg/1
         Influent  (Activated  Sludge  Process Effluent)
           Transparency  :  42,  Turbidity :  9,  SS :  9mg/l
           TOG   :  13.5mg/l,   Total  P  :   0.67rag-P/l
                               91

-------
                                       Air  tank
                             5"
       Magnetite
         (M)
Alum
Influent _/g>
                          7
                               Flocculation
                                  tank
-KZS	
                   Static  mixer
                                                               Effluent
                                        Sludge
                                     \_y
                                        Polyelectrolyte
         Fig. 21.  Flow  sheet of  the  pilot  plant  for tertiary
                 treatment.
                 (HGMS :  High  Gradient  Magnetic  Separator)
                                   92

-------
 CO

p
 J-l
   -p
                                            ca

                                            5
                                        CO
93

-------
Table 4. Results of  continuous^ operation  of  pilot  plant  for
         tertiary  treatment.

PH
Transparency
Chromatici ty
SS (mg/1)
CODMn (mg/D
BODS (mg/1)
Coliform bacteria
(No. /ml)
Total phosphorus
(mg-P/ml ) 	
In.f luent
7.8
34
29
- 12
19
7.5
340

1.7

Effluent Removal rate
7.4
more than 150
17
3.6
11
2.3
14'

0.33

-

41%
70%
42%
'69%
96%

81%

      (Operating conditions)
         Magnetic Field Strength  : 3KG
         Flow Velocity  : 2000 m/day
         Magnetite Cone. : 10 mg/1
         Alum Cone.  : 4 mg-Al/1
         Polyelectrolyte Cone.  :  1.5 mg/1
                                 94  .

-------
Table 5.
Characteristics  of  sludge  generated  from  tertiary
treatment process.               "                      '

Raw sludge
           PH
           SS
           VSS
           SVI
                 6.9
               440 mg/1
               200 mg'/l
               102
          Thickened sludge
           SS
               9800 mg/1
            (gravity thickening for  30  minutes)

          Dewatered  sludge
           Water  content
           Calorific  value
                       85%
                     2380  cal/g-dry weight
             (Buchner  funnel  test  with  760  mmHg-for  15
               minutes,  no  coagulant  addition)
                              95

-------
4. PRELIMINARY  DESIGN OF  DEMONSTRATION  SIZE  AND  FULL SCALE  PLANTS

     Based  on  the results  of  the  present  study,  preliminary design
was  carried out   for a  demonstration  plant  and a  full  scale  plant
whjLch  are   used  for  combined  sewer   overflows  treatment   in  wet
weather  and tertiary treatment of  activated sludge  process  effluent
in dry weather.
     Fig. 23   shows  the  flowsheet   of  the demonstration  plant  with
capacity  of  10000  m   3   /day.  The  plant  consists  the  apparatus  for
dosing and  flocculation,  two preseparators of 2.75 m  in  diameter,  and
high gradient  magnetic separator of  2.5  m in diameter.  Preseparators
are  used only  for treatment  of  wet  weather  flow.  In  dry weather,
flocculated slurry is fed directly to the  magnetic  separator  through
by-path.  Fig. 24  shows  a  layout  of  the  demonstration  plant.   Land
required  of this  plant is  165 m2.    Fig.25  shows a layout plan of  the
full  scale  plant  with treatment  capacity of  100000  m 3   /day.  The
required  area  of   this plant   is  estimated  about  860  ma.       The
preseparators  occupied large area  in  the plants,  hence omit of  the
preseparator is desirable from  the  view  point  for reduction  of land
required.   Thickness   of  the  matrix  ,   however,  must   be  increased
considerably  to  omitt  the  preseparator,  which  increases electrical
power   consumption  of  the   magnetic   separator.   Furhter   careful
consideration  should  be given  to  determine wheather adoption of sthe
preseparator is  profitable  or not.

5. SEEKING  FOR  LOW  PRICE  SEEDING  MATERIAL

     Seeking for  low price  seeding  material  will  be important from
the   view   point  of  running   cost   reduction.   In   the   present
investigation,  magnetite recovered from  coal ash  was  tested as  one
of   the  promising low  price  seeding  material.  In   power plants  in
Japan, coal was  adopted   as energy  source  in  addition to  oil  and
nucleous. Ash  derived  from  some kinds  of coal  used in  those  power
plants  contains  magnetite   particles.  Recovering   technique of  these
magnetite   particles  by    magnetic   separator   has  t>een    almost
established. Preliminary pilot  plant  test  showed  that  the  coal  ash
magnetite was  suitable  for  seeding  material.  In addition to  the coal
ash  magnetite, industrial  wastes  from magnetite production  plant  and
iron mill are  seemed to be hopeful  for  utilizing as seeding  material.
                                   96

-------
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                                         =  !
                                            1
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                                      CO
    s
97

-------
                             Preseparator
                        22,000
                                               HGMS
Fig-24.  Arrangement  plan of demonstration  scale  plant,.
                  (10000  m3    /day)
                               98

-------
 DDDDDDQD  4.
 DD D  0 D D  D
                                   ' 4-> ,
                                    0)
                                    r^
                                    CO
                                    0
                                    w
                                    c

                                    ft
                                    |
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                                    r
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 to
 cq
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99

-------
6.   CONCLUSIONS

     The  following  conclusions were  obtained from the  bench test  and
pilot plant  test  of  seeding  method  on  the  treatments  of  combined
sewer  overflows and secondaly effluent.
(1)  Seeding  method  was  effective  for   both combined  sewer  overflows
treatment  and  tertially  treatment.
(2)  Optimum  operating conditions  of high  gradient  magnetic separator
were   2000  m/day  for  flow  velocity   and  3   KG  for   magnetic  field
strength.
(3)  Optimum  concentrations  of chemicals for combined  sewer  overflows
treatment  were  25  mg/1 for  magnetite, 3  to 7 mg-Al/1  for alum  and  1
to  2  mg/1  for  anionic  polyelectrolyte.
(4)  Optimum concentrations  of chemicals  for tertially  treatment  were
5 mg/1  for magnetite, 2  to  4 mg-Al/1   for alum  and 0.5 to  1  mg/1  for
anionic   polyelectrolyte.
(5)  Sludge  produced  from  the seeding  process  was easy  for thickening
and  dewatering.
(6)  Magnetite  which  was  recovered  from coal  ash  was  possible  to
utilize- as  seeding   material.

7.   ACKNOWLEDGEMENTS

     The   authors  wish  to  thanks  Mr.  Masao  Kobayashi,  Mr.   Suguru
Katura and Mr.  Hideaki Hakamada  for  their helpful assistance  in the
bench   test.   The   authors  would   also   like   to  acknowledge  the
co-operation  of Hitachi Plant   Engineering &  Construction  and Daido
Steel  Co. Ltd.  for  the pilot  plant test.         ,

                                REFERENCES

Allen,  D.  M.,  Sargent, R.L.  &  Oberteuffer,  J.  A.   (1977)  Treatment
    of  combined  sewer overflows  by high gradient  magnetic
    separation.     EPA-600/2-77-015    (PB-264935).
Allen,  D.  M.  (1978)  Treatment  of combined sewer  overflows  by high
    gradient  magnetic ' separation.  EPA-600/2-78-209.
Kurinobu,  S.  &  Uchiyama,  S.  (1982) Recovery  of  plankton from  red
    tide  by HGMS.    IEEE   Trans.  Magn.,  MAG-18;   1526-1528.
Oberteuffer,  J.  A.  (1973)  High  gradient  magnetic separation.   IEEE
    Trans.,  Magn.,   MAG-9;   303-306.
Kaneko,  M., Kunikane,  S.,   Maehara, R.,  Ishibashi,  T.,  &  Kimura, M.
    (1981)  Journal   of  Water  and  Waste,  Vol.23;   1053-1062.   (In
    Japanese)
Kaneko,  M.  (1982)  Zousui  Gijutu,  Vol.8,  No.3;  49-53.   (In   Japanese)

                                    100

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NEW MOVEMENT IN SEWERAGE CONSTRUCTION PROJECTS IN JAPAN
                          by
                     Ken Murakami
              Regional Sewerage Devision
       Dept. of Sewerage and Sewage Purification
               Ministry of Construction
           . Kasumigaseki, Tokyo 100, Japan
    The work described in this paper was not funded by
    the U.S.  Environmental  Protection Agency.   The contents
    do not necessarily reflect the views of the Agency and
    no official  endorsement should be inferred.
             Prepared for Presentation at:
          12th United States/Japan Conference
                          on
              Sewage Treatment Technology

                     October 1989
                   Cincinnati, Ohio
                          101

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                                  ABSTRACT

     Huge investment in construction of public sewerage systems has been
made in Japan based on the five year programs.  Overall percentage of the
sewered population still remains about 40%, but that in major cities has
reached almost 90%.  Under this situation, the scope of sewage works in
Japan has been expanding to put more emphasis on such problems as more
safety from inundation in urbanized aeras, combined sewer overflow problem,
advanced wastewater treatment, wastewater reclamation and reuse, beneficial
utilization of sewage sludge, multi-purpose utilization of sewers and
treatment plant sites and so, forth.  This paper summarizes these movements
in Japan.
                                      102

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INTRODUCTION

   .  Human wastewater  in Japan  is basically treated by three different
systems.  These are public sewerage, septink tanks and collective human
excreta treatment plants which  treat human excreta collected by tank
trucks.  Public sewerage systems currently covers about 40% of the  total
population.  Human wastewater from approximately 30% of the population is
treated by septic tank systems.  The remaining 30% is treated at collective
excreta treatment plants.  Most of the existing septic tank systems, as well
as collective excreta  treatment plants, treat only human excreta.   Grey
water from households  served by these systems is discharged without any
treatment.                                                   ,

     Therefore, necessity of public sewerage systems is still very  high.
The sixth five year program for construction of sewerage systems plans to
invest 12.2 trillion yen "in construction of public sewerage systems during
the period of five years from 1986 to 1990.  In FY1989, the investment is to
be approximately 2.3 trillion yen.  About one third of the total investment,
800 billion yen is appropriated as a government subsidy.

     In big ten Cities in Japan, percentage of sewered population has
reached almost 90% on  the average, although there still remain problems to
be solved.  One of the problems is storm water discharge including  the
combined sewer overflow problem.  In many places, the capacity for  storm
water discharge is not sufficient, and safety from, inundation needs to be
improved.  Various measures to cope with this problem are beginning to be
undertaken,  in big cities where sewage works have rather long history,
combined sewer systems are generally adopted.  The combined sewer overflow
is another problem which needs to be improved.

     As sewerage systems with a secondary treatment level are installed,  the
next target of providing advanced wastewater treatment has become a
practical one in many areas,  particularly in the highly loaded areas or in
the river basins where wastewater is finally discharged into lakes or other
stagnant bodies of water.  People's wishes to have better water environment
and more water space amenity have been stronger than ever.

     It has also, been required to seek for additional functions in sewerage
systems, such as wastewater reclamation and reuse,  beneficial utilization of
sewage sludge and multi-purpose uses of sewers and treatment plant sites.
Interesting progresses have been made in these fields,  and the movement
toward this direction will be promoted further in the future.

     Wastewater facilities in small communities are generally very poor.   A 
number of small scale facilities will have to be constructed to improve the
situation.  Therefore,  one of the current major concerns is to develop
suitable technology for constructing economical and appropriate facilities
in small communities.
                                     103

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1.  STORMWATER DISCHARGE

1.1  More Safety from Inundation

     Measures to prevent stormwater inundation in cities are generally based
on improving sewer pipes and pumping stations to discharge stormwater to
nearby rivers and the sea as quickly as possible.  However, when such
methods cannot be adopted because of the poor capacity of the river
receiving the discharge and so forth, the following methods have to be
applied.

     (1)  Bypath sewer

     A bypath sewer line functions to divert stormwater flow to a river with
a greater capacity, or directly to the sea, to cut the storm discharge in
the upperstream region.  This occurs when urbanization in the upperstream
region has led to the occurence of inundation, but improvement in the sewer
pipes and in the lower reaches of the river is difficult.  One example is
the Hirao-Takamiya region in Fukuoka City, where rapid urbanization caused
frequent inundation in the lowlands, and it was difficult to improve the
storm trunk sewers and rivers in the downstream region.  However, a portion
equivalent to two-thirds of the basin area, or 212 ha (34 m3/sec), which
equals the deficient capacity, will be cut.  The stormwater is to be
discharged directly to a river through the Hirao-Takamiya Trunk Sewer (3 to
4 m diameter, 2.5 km length) constructed along, an abandoned railway line.
The sewer is currently under construction.                                  

     (2)  Stormwater retention tank

     A stormwater retention tank functions to cut the peak discharge by
holding the stormwater temporarily, and it may be constructed either on the
ground or under the ground.  Stormwater retention reservoirs have been
constructed in many housing complexes in order to control the increase in
storm runoff.  Similar facilities have been built in sewer systems, too.
The Jiyugaoka retention reservoir built in a residential area east of Nagoya
City is a good example.  The reservoir has a capacity of 10,000 m3, and
its top is used as a playing ground for a primary school.  In urban areas
where land use is very intensive, public spaces (such as roads and parks)
are used to construct underground retention tanks.  Good examples are the
Imazu retention tank (26,000 m3 capacity) in Osaka City, which was built
under a baseball ground, and the Takatsuji retention tank (30,000 m3
capacity) in Nagoya City, which was built under a tall residential building
and a park.  In addition to such large facilities, many small retention
tanks have been constructed to cope with localized inundation disasters in
urban areas.
                                     104

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     In an area of Nagoya City, the citizens filed a suit against the city,
claiming that the city did not respond properly.  The court ^case lasted for
9 years.  When a retention tank of 2,000 m  capacity was constructed under "
this street and inundation was successfully prevented, the citizens withdrew
the suit.
     A stormwater retention tank is an extremely effective means of
preventing inundation.  However, there remains the question of whether space
for a stormwater retention tank can be ensured in congested urban areas.  In
the future, it will be necessary to examine the more effective utilization
of public spaces, such as parks and schools.

     (3)  Large-scale storm trunk sewer

     Where inundation is highly likely to occur in catchment basins, and the
capacity of the receiving rivers is critically short, large-scale storm
trunk sewers can be built to both bypass and hold stormwater.  These* may
therefore be called "second rivers".

     In Osaka City, such a facility, called the "Tennoji-Benten Trunk Sewer"
(80,000 in3 capacity), is already in service.  In addition, the
"Hirano-Suminoe Trunk Sewer" is under construction.  Tokyo Prefecture is
planning to construct a large-scale storm trunk sewer under the Loop 7
highway, and is expected to prevent inundation in the Kanda River and
Shakujii River basins.

     (4)  Infiltration of stormwater

     Along with the above measures to reserve and divert .stormwater, various
attempts to reduce stormwater discharge by the infiltration of stormwater
have been made in many municipalities.  This method maximizes infiltration
into the ground by providing infiltration in yards, porous pavements,
infiltration curbs and infiltration inlets.  Furthermore, the runoff of
stormwater flowing into pipes is delayed through pipe storage and pipe route
bypassing.


1.2  Combined Sewer Overflow Problem

     Combined sewer overflow should be basically controled by ensuring an
appropriate intercept volume to a treatment plant.  When this is difficult,
measures based mainly on storage have been adopted.  In addition, since
storage and infiltration as inundation prevention measures are also
effective in reducing the overflow volume, qualitative as well as
quantitative measures are under examination.
                                     105

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     (1)  Sedimentation/storage of stormwater
                                      H
     The first facility for stormwater sedimentation/storage to reduce the
overflow load was constructed at the Nakanoshima Pumping Station in Osaka
City in 1974.  Since then, many such facilities have been constructed.  Most
of them have the capacity to store a 5 mm rainfall, on average, within a
drain basin.

     (2)  Treatment of wet weather sewage

     The water volume and water quality of wet weather sewage fluctuates
enormously and requires intermittent treatment.  Consequently, the
application of a biological treatment process is difficult.  Thus, currently
planned methods are based on physical-chemical treatment processes.

     One of them is a swirl concentrator, which is characterized by having
no moving parts and by ease of maintenance.  Tokyo Prefecture and Matsuyama
City are currently constructing swirl concentrators.

     As for wet weather sewage treatment, plate settlement using chemical
additives, and a super high-rate filtration, are under technological
development.
2.  ADVANCED WASTEWATER TREATMENT

2.1  Necessity of Advanced Wastewater Treatment

     The sewage system plays an important role in preventing water pollution
in public waters, and in preserving precious water resources.  Depending on
the conditions of the basin secondary,treatment is not sufficient to protect
water environment, making advanced treatment necessary.  Currently, advance
wastewater treatment is undertaken mainly in the basins of the rivers which
are used as important sources of water supply, and lakes, in order to meet
the water quality standards as quickly as possible.  Typical lakes in Japan
(including Lake Biwa and Lake Kasumigaura), have become considerably
eutrophicated, so that nutrient removal is required.


2.2  Present state of Advanced Wastewater Treatment

     The advanced treatment is under way at 22 sewage treatment plants
throughout Japan.  Each of them aims to meet or keep meeting the water
quality standards.  In some plants discharging their effluent into Lakes,
biological denitrification and chemical addition into aeration tanks are
practiced to remove nitrogen and phosphorus.  As for advanced treatment
processes in plants discharging their effluent into rivers,  rapid filtration
and chemical clarification are used to get higher removal of biochemical
oxygen demand (BOD) and suspended solids (SS).
                                     106

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2.3  Future Direction

     Advanced wastewater treatment has been practiced in areas where such
treatment is in great demand.  People's wishes, on the other hand, to have a
better water environment and more water space amenity have become stronger
and stronger.  It is considered necessary, therefore, to take a policy to
adopt advanced wastewater treatment more actively.  There will be an
increasing demand for advanced wastewater treatment, particularly at the
following areas:                                                *

     (1)  Improvement of water environment in big cities and their
          surrounding areas

     The sewage service has made great progress in big cities and their
surrounding areas.  However, due to too much concentration of pollutant
loading, some rivers in the urbanized areas cannot be fully restored in
water quality by secondary treatment.  This may necessiate the employment of
advanced treatment in the catchment areas of these rivers.  In addition, in
some big cities where water shortage is always a potential problem, the
treated sewage has become precious water resources.  The necessity of
advanced treatment will further increase in relation to reuse of treated
water.  For example, many urban streams have experienced a reduced flow with
the progress of urbanization.  The. restoration of stream flow to these
rivers is greatly desired.  For this purpose, the utilization of sewage
water treated by the advanced treatment process is being planned in many
municipalities.

     (2)  Protection of water resources for drinking water supply

     In planning a sewerage project and examining the effect of effluent
discharge on the water uses in the downstream reach, special attention has
been paid to water intakes for drinking water supply.  When the receiving
river is used as a source for drinking water supply at the downstream,
advanced treatment of sewage has been practised depending on the necessity.

     Recently, people are demanding more safety in drinking water, and
calling for better "taste" of drinking water.  In this regard, necessity of
advanced treatment is becoming higher.than before.

     (3)  Prevention of eutrophication of lakes and reservoirs

     Preventing eutrophication of lakes and reservoirs has become a
significant problem these days.  Effluent standards regarding phosphorus are
established at 1066 lakes, and those regarding nitrogen at 78 lakes.  Most
of these standards do not necessarily require higher level of treatment than
secondary treatment for domestic sewage.  However, to restore a beautiful
water environment and maintain'good water quality for the lakes and
reservoirs advanced treatment of sewage is the most effective measure to be
taken, and it will be more significant in the future.
                                     107

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      (4)  Control of eutrophication of bays and the inland sea

     Many big cities in Japan including Tokyo, Osaka and Nagoya are situated
on bays and the Seto inland sea where exchange of water is little.
Eutrophication of these seas has already intensified.  To restore the water
quality, nutrient loading should be minimized.  At present, no quality
standards concerning nutrients in the seas have yet been set forth.  And,
therefore, actually no advanced wastewater treatment is practised to remove
nutrients. >

     However, more and more people are considering it quite necessary to
restore water quality in the seas near big cities.  In these areas, too, the
necessity of advanced treatment is advocated.


3.  MULTI-PURPOSE UTILIZATION

3.1  Reclamation and Reuse of Sewage

      (1)  Reclamed sewage as precious water resources

     The annual demand for domestic water in Japan has been increasing by an
average of 3%.  In order to meet the increasing water demand, continual
effort to develop new water resources should be made.  At the same time,
quality of water resources must be ensured.

     The total volume of the effluent from about 700 sewage treatment plants
in Japan reached approximately 8 billion cubic meters in FY1987.  This
volume corresponds to approximately one-fourth of the municipal water supply
(the total of water for domestic and industrial water).  Most of the
effluent is discharged to the rivers and seas, although some is reused for
various purposes.

     With the expansion of industrial activities and the concentration of
population into big citites, the municipal water demand is still increasing
these days.  Consequently, a system to reuse reclaimed sewage is being
introduced as a means to cope with an intensive water demand in urban areas,
and to achieve a stable water supply.  Sewage can be a stable and abundant
water resource obtained in a city, and its volume is expected to increase
with the expansion of the sewerage systems.
                                     108

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      (2)  Model project  for sewage reclamation and reuse

     The Ministry of Construction has  launched a model project for sewage"
reclamation and reuse since FY1979 in  order to facilitate reuse of treated
sewage.  This project aims to supply reclaimed sewage to corporate buildings
in a certain district as toilet flush  water after implementing a necessary
treatment of the reclaimed sewage.  Currently, the projects are under way  in
eight districts throughout Japan.  These include the Tenjin district of
Fukuoka city, where the  citizens suffered severe water shortage for over 287
days in 1978, and the subcenter of Shinjuku in the metropolis of Tokyo,
where skyscrapers are abundant.  Among them, five projects are already'under
operation.  In FY1989, the Tokyo Metropolitan government is planning to
start the project in a coastal subcenter.

     (3)  Flow augmentation, and ornamental streams and lakes

     Many of the urban streams in large cites in Japan lose their flow in
dry weather due to an increase in the  impermeable area within their basins
as the result of urbanization.  On the other hand, people in cities have
come :to put more and more emphasis on a better environment,, particularly an
environment with clean water.  Reclaimed water is a stable water resource
within cities, and thus, there have been many projects to utilize reclaimed
water for restoring live streams and creating clean water bodies within
cities.

     Restoring live streams utilizing reclamed water was practised at 6
locations in 1986.  Among these 6 locations, reclaimed water was discharged
year-round at 4 locations.  The outline of these 4 projects is shown in
Table 1.                           :
          Table 1.  .Typical examples of restration of live streams
                    using reclaimed water
 Name of city    Name of STP
                 Reclaimed
                 Water flow
                 (m'/day)
Name of
stream
Reclamation
process
 Tachikawa     Nishikimachi
                      212
                                            Nekawa
                                            Sand filtration
 Metro. Tokyo  Tamagawa-Jouryu    20,720
                             Nobidome and   Sand filtration
                             Tamagawa
 Osaka
Nakahama
                                   3,000    Outer Moat of  Sand filtration
                                            Osaka Castle
 Osaka
Hirano
                                   7/074
                            Imagawa and
                             Komagawa
            Sand filtration
                                    109

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     In addition, a model project named "restoration of live streams in
stormwater drains" was initiated in 1985.  Most of the open storm sewers
used to be natural storm drains.  This project is to restore live streams in
these storm sewers utilizing reclaimed water.  Currently 8 projects of this
type are being carried out as shown in Table 2.
           Table 2.  Effluent reuse model projects "Restoration of
                     live streams in storm water drains"
Year of
project
start
1985
1985
1986
1986
1987
1987
1988
1988
Name of
prefecture
Kyoto
Oita
kanagawa
Osaka '
Kanagawa
Aichi
Aichi
Hyogo
Name of city
Nagaokakyo
Oita
Yokohama
Toyonaka
Yokahama
Nagoya
Nagoya
Nishinomiya
Name of storm
drains
Shoryu j i
Nakajima No. 1
Saedo
Houno-Nanbu
Terao
Arakogawa
Shirako-Sakae
Edakawa No. 2
Design flow
(m3/S)
0.06
More than 0.1
0.12
0-1
0.12
0.23
0.002

     Furthermore,  reclaimed water  from sewage treatment plants  is used at
many locations  for ornamental  lakes and streams within treatment plants and
in parks nearby.

     (4)   Snow  disposal

     In order to  remove  and dispose of snow  in urban areas  including private
lots,  it is necessary to provide suitable disposal  sites.   Open channels,
including  open  storm sewers,.are often used  for this purpose.   A problem
usually encountered is the lack of sufficient flow  to flush away the.
disposed snow.
                                A              '
     The effluent from sewage  treatment plants has  good characteristics for
this use,  such  as being  stable in  flow, being available within  a city, and
having a relatively high temperature  in. winter.

     A model project named "The rapid removal of  snow in urban  areas using
reclaimed  water"  was initiated in  1985.  Currently  nine projects are being
carried out  in  cities in heavy snow areas, as shown in Table  3.

                                      110                .

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          Table 3.  Model effluent reuse projects "Rapid removal of
                    snow in urban areas .using reclaimed water"
Year of
project
start
1985
1985
1986
1986
1987
1987
1987
1987
1988
Name of
prefecture
Hokkaido
Aomori
Akita
Niigata
Hokkaido
Niigata
Ishikawa
Fukui
Ishikawa
Name of
city
Ebetsu
Aomori
Akita
Tpkaichi
Sapporo
Yuzawa
Kaga
Tsuruga
kanazawa
Name of drains Design reclaimed
storm utilized water flow (m3/S)
Ebetsu No. 32
Namiuchi
Kusouzugawa-
Sagan No. 1
Inaricho and
Honmachi
Yasuharu
Nunoba No. 1
Jougan j i
Maizaki-Shimizu
Ekiura
0.15
0.12
0.12
0.04
0.5
0.238
0.03


     Another project is being planned in Sapporo City to utilize a
stormwater reservoir in winter time as a disposal site for the removed
snow.  The disposed snow is melted away by introducing effluent from a
sewage treatment plant into the reservoir.

     Snow removal in snowy area is equivalent to stormwater drainage in
other areas.  More contributions to sewage works from this field are
expected.
                                     Ill

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3.2  Beneficial Utilization of Sewage Sludge

     (1)  Necessity of effective utilization of sewage sludge

     Wastewater treatment is accompanied by the generation of sewage
sludge.  As the sewered population increases, the volume of sewage sludge
generated increases.  Advanced treatment may increase sludge production^in
the future.  In 1987, when the percentage of sewered population was 39%, the
sludge production in dry solids (DS) was approximately 1.25 million tons,
and the annual volume of sludge disposed of was 2.1 million m3.  When the
percentage of sewered population reaches 50%, it is estimated, that the
sludge production will be approximately 1.7 million tons in DS, and that the
annual volume to be disposed of will be 3.7 million m3.

     On the other hand, the sites for landfill are limited.  As urbanization
progresses, the acquisition of landi.fill sites is getting more difficult.
And the associated costs are increasing.  Therefore, further efforts must be
taken to reduce the volume"of sludge, and to facilitate beneficial .
utilization of sludge as resources.
             Table 4.  Status of sewage sludge disposal.  (1987)
                                                          (Units:  1000 m )
      Disposal
      method

  Treatment
Landfill
           coastal
           Beneficial
           reclamation   utilization
                         Others   Total (%)
  Dewatered        762
  cake

  Incinerated      156
  ash

  Dried sludge      17

  Digested and       7
  thickened
  sludge
              306


              105


                4

                0
              274
               43
              126
            114
             19

            191.
        1,456 (68)


          310 (15)


          166 ( 8)

          198 ( 9)
  Total (%)
  942
  (44)
415
(19)
443
(21)
330
(16)
2,130 ( 9)
 (100)
                                     112

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      Table 5.   Status the beneficial utilization of sewage sludge (1987).
                    Treatment   Dewa-  'incin-
                               tered  erated
   Classification              cake   ash
Green  Committed by         117
farm-  the municipality
land
       Assigned to a        157
     ,  fertilizer company
                                        0
                                                            (Units:   1000 m3)
        Com-

SlUd96  SSgf  Slud9e
                                               15
          80


          24
                                                                0
                                                                0
ouuLutaj. 274 7 22 104 0
Use as a
material
Total
^  . ^_^_
construction
	 	 	

0 36 0 0 0
274 43 . 22 104 0
Total


 204


 203


 407

  36


 443
      (2)   Current status, of beneficial utilization
 spacefor         .   of ^Plications,  such as for farmlands and green
 spaces,  and for construction materials.   Recovery of energy is another
 example  of beneficial utilization.                        9Y    another

      T5eqam"nt f Slud9e  utilized  for farmlands and green spaces in the
       L>^TT^i8lUdOB CakS'  CmPsted Slud9e-  and dried sLdge,  Somes to
 11.5% of the total amount  of sludge generated or 140,000 tons  (DS
 year   The amount  of  sludge (mainly as incinerated ash)  utilized  as
 construction materials  is  estimated to be 6.5% or 85,000 tons.
      (i)  Utilization for farmlands and green spaces
An-7 nnlf f^ of sewage sludge utilized for farmlands and green spaces was
407,000 m /year, in 1987.  The amount has been fairly constant in t2 last

flLllnZ'  Ef f ^ SlUd9S UtllZed fr this P^Pse is applied to
farmlands   Only a sma.ll amount of sewage sludge is used for green spaces
Sewage sludge is mostly used in the state of dewatered sludge cake
However  more and more composted sludge is being utilized recently*  Sewaae
               6ffiCientl* "** 'or farmlands and green- spaces in Europe
                                     113

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      Currently,  21 municipalities are running sewage sludge composting
 plants.  The product is sold in bulk, or 20 kg package.   The retail price
 varies greatly,  depending on the districts.  The heavy metal standards for
 the sludge utilized for farmlands are that the maximum concentrations of
 mercury  arsenic, and cadmium shall be 2,. 50, and 5 mg/kg, respectively.  In
 addition, a tentative guideline has been worked out, specifying .that sludge
 application is allowed in the areas where the zinc content of the soil is
 less than 120 mg per kg dried soil.  These values are rather strict compared
 with those stipulated in European nations.  In particular, the guideline for
 zinc in soil is very strict in terms of the zinc concentration in sludge or
 soil.  This is an obstacle, in a sense, to distributing composted sludge in
 Japan.                                                            ,

       (ii)  Utilization for construction materials
             '                                                       "-v
      There are two utilization methods:  One is the direct utilization of
 incinerated ash  or melted slag, and  the other is to use incinerated ash or
 melted slag as a part of the raw materials to produce building materials.
 Examples of the  former include roadbed material for pavement, back-filling
 material for retaining walls, and  intermediate cover for  sanitary
 landfills.  Recently, incinerated  ash has been used to improve soil
 characteristics  of the excavated material  from sewer construction sites.  In
 order to use the excavated material  for refilling,  it is  often required to
 increase the kinetic strength by mixing an additive.  Incinerated ash has
 good characteristics as an additive  for this purpose.  This  is a newly
* development in  the utilization of. incinerated ash.

       In  the latter utilization of  incinerated ash  or melted  slag,  these
 materials  can be used  as  raw materials  for producing such products as -
 ceramic  pipes,  light-weight  aggregates, bricks,  tiles, and permeable
 blocks.   Some of these raw materials are  manufactured on a commercial
 basis.  The amount of  sludge used for construction materials is limited at
 present, but  is expected to increase with the  encouraged employment  of  the
 melting  process.
                                                                     
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  3.3  Multi-purpose Utilization of Sewers and Treatment Plant Sites



      (1)  Utilization of treatment plant sites




  an ov^rnfT^ Plant SteS and P^P1^ stations are precious open spaces in

  rf ?he Snf  /in7'  MVltlple utili^tion of the area permits effective v    '
  of the land and the realization of pleasant  urban scenery, thus providing

  n]Ln?n? ^rl^0d Wlth a PlaCS f recreation  and relaxation.  This kind of
  planning is becoming popular these days.
 baseblr           ^  Sporting ^cilities including tennis courts and
 baseball grounds,  as well  as parks and green zones are being constructed in
           th                               '                            s
           the covered top of  the  facilities are used as a refuge at the time

 of disaster,  in addition,, buildings such as music halls and mf rtial art

                ^S ^ COnStructed above Plant, sites.  This ne^ tre"nd of
             is becoming noticeable.



      (2)   Effective utilization of sewers
                         carried out at
due
                        Under9rouna seers
sews win                            Ver a
sewers will become more intensive in  the future.
                                               not been used efficiently

                                                    n^rstS.
                                                  - this utilization of
4.  SMALL-SCALE SEWERAGE SYSTEMS
50

the
                     arS 2817 communities with ^ Population. of less than
                     percentage of sewered population is as little as 6% on
              APProxim^^ly 2200 of  these communities have not started

              6           S Y6t-  men Plannin9 Sewera9e system ^ these
    n                     sometimes  encountered with selecting a plant site
because the community is located in  a mountainous area,  or on the sea  or

               "11   ^^ &  CnSenSUS f ^^   In -ch a ^ase,  a
                            Sewa9e treatment plant may be  an  amicable


                                           deveiop
                  Sections wil1 introduce prefabricated treatment plants
              treatment Plants- tunnel-type treatment  plants, and

                                    exampl's of
                                    115

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4.1  Prefabricated Treatment Plants

     The Japan Sewage Work Agency has studied cost-effective methods of
constructing small-scale treatment plants since 1982.  Based on the studies,
a prefabricated treatment plant has been developed and standardized.

     For the prefabricated plant, an oxidation ditch process is adopted.
This is because it can withstand inflow load variations, is easy to
maintain, and generates less sludge.

     The prefabricated treatment plant is a circular structure that a
conventional ditch is laid out as an outer circle, with a secondary
sedimentation tank at its center.  As for the structure  pre-stressed
concrete panels manufactured at the factory are assembled at the site.  For
mechanical and electrical facilities, standardized equipments are used  to
reduce the costs.  To rationalize the design, standardized designs are
prepared for the plants with capacities  from 300  to  1,200 m /day with an
interval of 100 mf/day.  Thus, when a certain number of plants? have been
constructed, the costs of construction as well as design can be considerably
reduced.  Furthermore, the  construction  period can be  shortened, and the
construction work can be easily  performed at the  site.  The first
prefabricated  treatment plant  was  completed in Nakanojo, Gunma Prefecture
 in 1988.  There are  currently  nine plants  in Japan which are under  planning
or construction.


 4.2  Floating-type Treatment Plants (Plants Floating on the Sea)

      A number of  small communities are located on the hilly sea  shores,
 where it is sometimes quite difficult to acquire suitable sites  for
 constructing sewage treatment plants.   In these cases, it has been a common
 practise to create the land by coastal reclamation.   This is sometimes very
 costly and requires the long period of construction.

      The Japan Sewage Works Agency has developed a floating-type treatment
 plant as an alternative technology, and the first, plant of this type was
 constructed in Atami City, Shizuoka Prefecture in 1985.

      Steel made, ark-structure plant constructed at a dockyard is taken in
 tow to the sea site.  The plant is installed at a specified position,
 connected with the  sewer, and then put  into operation.  The floating plant
 can utilize either  the conventional activated sludge process, oxidation
 ditch process, or sequencing batch reactor process.

      There are two  installation methods:  Grounding at the bottom of the
 sea, and moorage at a pier with an anchor.  Compared  with the method of
 constructing  a plant after reclaiming the  sea, the  advantages of the
 floating method are that  the  construction  period can  be shortened  and the
 construction  costs  could  be reduced, particularly for smaller scale plants.
                                      116

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 4.3  Tunnel-type Treatment Plants

      In areas where it is difficult to find a suitable plant site, one
 alternative is a tunnel-type treatment plant.  In Sweden and other
 Scandinavian nations,  the rock bed is tunneled so that a so-called "tunnel
 treatment plant" can be constructed inside,  in Japan, too, feasibility
      Since a treatment plant is built in a tunnel,  the plant has a long
          '       ^     ^ difference comPared to a plant built above the
                       pi PrOCeSS'  n Si^f icant -strictions are
 rrcn         treatmenj Plant  is operated in a tunnel,  no. considerations are
 required regarding the foundation and covers.   In heavy snow areas  where
 coverage of  the  facilities is  required for maintenance  or  to prevent tSe
 water  temperature  from dropping,  the  tunnel method will prove effective.
4.4  Alternative Collection Systems

     The cost for sewers occupies 70% of the total sewage construction costs
of a sewerage system.  Therefore, to. reduce the construction costs, sewer
construction costs must be minimized.

     Conventionally, most Japanese sewer systems are of the gravity type
Now that sewerage systems are constructed in small communities, the gravity
sewers are not necessarily economical due to geographical conditions.
Consequently, the employment of pressure or vapuum sewers has been activelv
investigated.  A pilot project is underway to acquire data concerning the
costs and design.  Based on the results, the pressure or vacuum sewers may
largely be substituted for gravity sewers in the future.
                                    117

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-------
Innovative Sludge Handling System Using Pelletization
                         for
      Simultaneous Thickening and Conditioning
                         by
         Kazuhiro TANAKA, Dr. Eng., Director
           Shuzo KOIKE, Research Engineer
    Research and Technology Development Division
              Japan Sewage Works Agency

             Naohiro TANIGUCHI, Director
General Planning Section of General Planning Division
                City Planning Bureau
            Tokyo Metropolitan Government
  The work described in this paper was not funded by
  the U.S. Environmental Protection Agency.  The contents
  do not necessarily reflect the views of the Agency and
  no official endorsement should be inferred.
            Prepared for Presentation at:
         12th United States/Japan Conference,
                         on
             Sewage Treatment Technology

                    October 1989
                  Cincinnati, Ohio~
                           119

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            Innovative Sludge Handling System Using Pelletization
                                     for
                  Simultaneous Thickening and Conditioning
                     Kazuhiro TANAKA, Dr. Eng., Director
                       Shuzo KOIKE, Research Engineer
                Research and Technology Development Division
                          Japan Sewage Works Agency

                         Naohiro TANIGUCHI, Director
            General Planning Section of General Planning Division
                            City Planning Bureau
                        Tokyo Metropolitan Government
                                  ABSTRACT

     Many sewage treatment plants in Japan have suffered from difficulties
in sludge handling processes, especially in sludge thickening/dewatering
processes, because of the changes in sludge characteristics in the past one
or two decades.
                                                                     *
     This paper introduces an innovative sludge handling system, developed
by the Japan Sewage Works Agency, to solve those difficulties.

     The newly developed sludge handling system employs a metal coagulant
aid and an amphoteric polymer that has the characteristics of flocculants
that are both cationic and anionic.  The .system consists of a sludge-charge
neutralization reactor and a sludge pelletizing thickener.  The sludge from
wastewater treatment process is directly fed to the system.  In the
sludge-charge neutralization reactor, the fed sludge is dosed with the metal
coagulant aid to neutralize anionic sludge charge*  In the pelletizing
thickener, the amphoteric polymer is fed into the charge-neutralized sludge
to pelletize and thicken it.  The small sludge particles form spherical
sludge masses of 1 to 2 cm in diameter, which have excellent mechanical
strength and low water content.                                

     The function of this system as a sludge thickener has eliminated the
necessity of the conventional sludge thickening process.  An SS recovery
efficiency of 90%, or higher, is provided by this system.  Compared with
conventional sludge handling systems, this system achieves a higher
filtration rate of 200 kg-DS/m/h and lower dewatered sludge cake moisture
content of 75%, by using a belt-press filter.

     Phosphate is also physicochemically fixed to the sludge through use of
a metal coagulant aid.  Hence, this system can be also characterized as a
sludge handling system that is suitable for biological phosphorus removal
processes.         
                                     120

-------
            Innovative Sludge Handling System Using  Pelletization
                                     for
                  Simultaneous Thickening and Conditioning
                     Kazuhiro TANAKA, Dr. Eng., Director
                       Shuzo KOIKE, Research Engineer
                Research and Technology Development Division
                          Japan Sewage Works Agency

                         Naohiro TANIGUCHI, Director
            General Planning Section of General Planning  Division
                            City Planning Bureau
                        Tokyo Metropolitan Government
1.  Introduction

     Sludge handling systems have the following objectives:

     1)  to reduce the volume of sludge to economize  land  space for  disposal
         and costs of sludge disposal,
     2)  to improve the ease of handling during disposal,  and
     3)  to change the characteristics of the sludge  to  a  stable form.

     In genreal, the sludge handling systems consist  of  thickening,
digesting, dewatering, and incinerating processes.  In the past one  or  two
decades, the characteristics of sewage sludges have changed  in Japan.
Especially, the VSS/SS ratio of sludge has increased  significantly.  The
causes of these changes,in the sludge characteristics are  due  to the
transition from combined sewer collection systems to  separate  sewer
collection systems, and the changes in our way of life.
                                                                  *

     As a result of the changes in sludge characteristics, many sewage
treatment plants have suffered from difficulties in sludge handling,
especially, in sludge thickening and dewatering processes.

     This paper introduces an innovative sludge handling process,  developed
by the Japan Sewage Works Agency, to solve those problems  in sludge  handling
systems.
2.  Sludge Handling Difficulties in Japanese Sewage Treatment Plants

     1)  Problems Related to Gravitational Thickeners

     The status quo of the sludge handling difficulties are well pointed  out
in a research report prepared by the Tokyo metropolitan government.1'
                                     121

-------
     The chronological changes in the Volatile Suspended Solid to Suspended
Solids (VSS/SS) ratio of excess sludges are shown in Figure 1.  Figure 1
reveals that the VSS/SS ratio of excess sludges in 1965 was around 60%, and
increased to around 80% in 1985.  The chronological changes in the solid
content of thickened sludges are shown in Figure 2, which reveals that the
sludge was thickened to about 5% of the solid content in 1965, and decreased
to 3%, or less, of the solid content in 1985.  The gravitational
thickenability of sewage sludge has decreased as the VSS/SS ratio increased.

     The increase in the volume of thickened sludge caused by the decrease
in solid content means an increase in the volume of the sludge to be
supplied to the dewatering machines.  This is one of the reasons for the
recent deterioration of the dewatering efficiency.

     The chronological changes in-the dewatering rate and in the coagulants
(FeCl3 and CaCO3) dosing ratio (% to DS), for a vacuum-type dewatering
machine, which had been widely employed in Japan are shown in Figure 3.  As
shown in the figure, the dewatering rate has been decreasing, and the dosing
ratio has been increasing.

     The changes in the characteristics of sewage sludges such as those in
Tokyo, have been observed in almost all Japanese sewage treatment plants.
These changes include the gravitational thickenability of sewage sludge, the
dosing ratio of chemicals, the dewatering capacity of the dewatering
processes, and the moisture content of dewatered sludge cakes.
         co
         co
         en
         CO
         CO
         8
         o
         X
         CD
         o
         H
         p
         CO
         CO
         en
         en
90


80


70


60


50


40
I
           I
                       I
                1965
               1970
          1975
          Year
1980
1985
           Figure. 1  Chronological change in the VSS/SS ratio of
                      excess sludges. (Tokyo)
                                     122

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6
o
O

C/3
7.





6





5





4





3





2





1




0
   1965
                            Plant  B


                            Plant  C
                                 _L
                                             j_
                                                          _L
1970
       1975


       Year
1980
1985=
    Figure 2.   Chronological change in the  solid content of

                graviat.ionally thickened sludges.  (Tokyo)
     CO
     Q
      0)
      p
      CO
      i-l
      0)
      p

      
      0)
      Q
    ,25




     20





     15




     10





      5




      0 '
                                           Coagulant

                                           dosing

                                           ratio
                                    Dewatering rate
       _L
                                                       50  *>
                                   40




                                   30




                                   20




                                   10
        1965,
1970  .      1975



      Year
                              1980
                                  o
                                  H
                                  4->


                                 2


                                  (7)


                                  H
                                                           c
                                                           (0
    Figure  3.   Chronological changes in the dewatering rate

                and coagulant dosing ratio  (with vacuum-type

                dewatering machine). (Tokyo)
                             123

-------
       The increase of the moisture  content of dewatered sludge cakes results
  in an increase in fuel consumption in incineration systems.  Thus, to  '
  improve the performance of the  total  sludge handling system, it is very
  important to improve the performance  of  the sludge thickening and dewatering
  processes.  Therefore, municipalities having difficulties with the sludge
  thickening processes have started  to  employ mechanical thickeners, such as
  centrifugal thickeners, instead of the gravitational thickeners.

       2)  Problems Related to Biological  Phosphorus Removal
                                                                              t
       It is known that phosphate is released from sludges when a
  gravitational thickener is employed to handle the excess sludge in a
  biological phosphorus removal process.  This results in a poor total
  phosphorus (T-P) removal efficiency.

       An experimental study cm the  biological phosphorus removal efficiency
  was conducted in the S treatment plant.   A schematic flow diagram of the
  plant is shown in Figure 4.  The results obtained can well explain the
  relationship between the phosphate release in a sludge handling process and
  the effluent T-P.  The operational conditions of the plant during the
  experimental study are as follows.
                                     Back washings
          Return flow
             *
Raw influent
                     Primary
                     settling
                     tank
                     372 m3
Biological reactor
2160 or 4320 ra3
                                                                          Final effluent
                                            Septic tank
                                               sludge
  Deatered
  cake
                                                                Rapid sand filter
           Figure  4.   Schematic flow diagram of the S treatment  plant
       Influent  Flow Rate
       Hydraulic Retention Time
       of the  Biological Reactor
       (1/4 was  operated as anaerobic)
       MLSS
    :  8,000 -  9,500 m3/day

    :  5.5  to 6.5 hours

    :  2,400 to 3,500 mg/L

    124

-------
      The chronological  changes in the sidestream phosphorus load ratio*
 and the effluent T-P  concentration are shown in Figure 5.


      The sidestream phosphorus load ratio:


        Sidestream phosphorus  load
         Influent phosphorus load   x 100% (1)
              150
          o
          H
          4->
          (0
          U
          m
          u
          o
          a
          a
              100 -
                                                            - 1
                                                                   a?
CM

EH

P
G
                                                                   t-i
                                                                   t-i
                                                                   W
     Figure 5.
                                         SidestrearaPhosphorus load ratio
                                                                      
   t!                 rati resulted in an overloaig of the T-P load
   the biologxcal  reactor,  which caused the increase in thl effluent ?-P





etticiency of biological phosphorus  removal,  it is-necessarv to
                              *ich  handles'sludge
                                    125

-------
3.  Targets in This Study                                     ,

     The Japan Sewage Works Agency decided to develop an innovative sludge
handling system to solve the sludge handling difficulties.  The following
are its targets.

(1)  Elimination of conventional sludge thickening systems

     The difficulties in sludge handling systems come from conventional
sludge thickening processes.  One of the targets was the elimination of
conventional sludge thickening processes to achieve a high efficiency  of
sludge handling.

(2)'  Reduction of the moisture content of the dewatered sludge cake with
     belt-press filter dewatering machines

     An 80% moisture content of a dewatered sludge cake is common when the
sewage sludge  is dewatered with a belt-press filter.  The target  was  to
reduce the  sludge cake moisture content of a dewatered  sludge .cake using  a
belt-press  filter, from 80% to less  than 75%.

 (3)  Reduction of phosphate release  from excess sludges

     The  reduction of phosphate  release from the excess sludge to attain  an
efficient biological phosphorus  removal was another  of  the  targets.


 4.  Theory of the Innovative Sludge Handling System

     As  sewage sludge  particles  are  volatile-fraction rich,  they form
hydrophilic'colloids because of  the  anionic charge.   It is  difficult to
 remove water from sludge particles under  such conditions.   In addition, as
 the particles are very small,  there  is high electric repulsion among the
 particles,  and they are poorly agglutinative.   Furthermore,  small particles
 easily cause the filter cloth to be  clogged.

      To  dewater sludges,  usually,  cationic polymer flocculants (cationic
 polymer/polymers)  are dosed to the sludge to neutralize the anionic charge
 of the sludge, and thus the sludge particles are flocculated.  However, as
 the flocculated sludge floe is still small and its mechanical strength is
 still -weak, the moisture content of the dewatered sludge cake will be
 decreased up to 80% when dewatered with a belt-press filter.  Also, poor
 separation of dewatered sludge cakes from the filter cloth is often observed.

      The newly developed  innovative sludge handling system employs a metal
 coagulant aid and a functional .polymer, which has characteristics of
 flocculants that are both cationic and anionic  (the amphoteric polymer).  A
 schematic flow diagram of the system is shown in Figure 6.
                                       126

-------
                       Separated water -
Sludge charge
neutralizing reactor
Fed sludge
               Sludge pelletizing
               thickener
                                                                   To
                                                                   the dewatering
                                                                   machine
                                    Charge-
                                    neutralized
                            Q      sludge
               Metal coagulant aid
               container
Amphoteric polymer
solution tank
                Figure  6.   Schematic  flow diagram of  the system.


      First, raw sludges withdrawn from  sedimentation tanks are fed to the
 sludge-charge  neutralizing reactor. Then, the metal coagulant aid is dosed
 to the sludge.

      Next, the charge-neutralized sludge is fed to the pelletizing thickener
 with an amphoteric polymer.  In the reactor, the sludge will be pelietized
 to spheres of  1 to 2 cm in diameter (the sludge pellets).

      A conceptual model of the pelletization process is shown in Figure 7.
                                     127

-------
                             Cationic
                             conpound

              Nucleus of floe

              Metamorphic
              agglutinative
              layer
                                   Anionic
                                   conpound
                                   (inactive)
      Sludge particles after
      dosing polyaluminum chloride
                  J~
                       o
                 \
                                       STEP I
                                       STEP  II
                                       STEP III
Figure 7.  Conceptual model of the palletization process.
                          128

-------
STEP 2 :
STEP 3 :
      The pelletization is carried out by the following 3 steps.

 STEP 1 :  The amphoteric polymer is fed to the charge-neutralized sludge.
         - The cationic compounds of the amphoteric polymer adhere to the
           sludge particles.  At the same time, inavtive anionic compounds of
           the amphoteric polymer will be charged due to charge in pH.

           The anionic compounds of the amphoteric polymer combine the
           cationic compounds which adhere to the sludge particles.  The
           bridged sludge particles will start to form larger sludge floes.

           The amphoteric polymers which bridge the sludge particles contract
           as the reaction continues,  and the sludge pellets grow and become
           thicker and stronger.   The growth of the sludge pellets will be
           accelerated by contact with growing sludge pellets and sludge
           particles.

     An  increase in the filtration rate,  and a decrease in the moisture
content  of the dewatered sludge  cake are expected,  as a consequence of
strong and thick sludge pellets  being formed with this system.   '

     From these system characteristics,  the system can be explained as a
sludge handling system which makes  sludge particles into Ball-shaped
sludge pellets and  a  very Effective Sludge  Thickening system.   Using
these  initial  letters,  the system has  been  named  the BEST System.
                                                                           -t

5.  Development of the Pelletizing Thickener

     The development  of the  BEST  system was originally begun to develop a
sludge handling system suitable for biological phosphorus  removal
processes.  At that time,  a  sludge handling system  which combined metal
coagulant aid dosing with  polymer flocculant dosing was evaluated  for  the
physicochemical fixation of  phosphorus.  A schematic flow diagram of the
prototype system is shown  in Figure 8.
                                    129

-------
             Primary
             sedimentat ion
             tank
                       Excess sludge
Aeration tank

          V
Secondary
sedimentation
tank
                         Gravitational
                         thickener

                       Sludge
                       charge
                       neatral-
                       ization
                       reacter
             Belt press  filter
     Palletizing
     reacter
           Metal coagulant,   Amphoteric polymer
           aid storage tank   storage tank

           Figure 8.  Schematic  flow diagram of prototype system.


     As can be seen in Figure 8,  the prototype system-consisted of a
sludge-charge neutralization  reactor.and a pelletization reactor.  The
thickened/not thickened primary  sludge and the gravitationally thickened
excess sludge were fed to  the system.   The mixed sludge was
charge-neutralized by the  metal  coagulant aid dosing, and pelletized by the
amphoteric polymer dosing.  The  reason the amphoteric polymer was used is as
follows.  The sludge fed to the  pelletization reactor was conditioned with a
metal coagulant aid which  is  cationic,  and the electrical charge condition
changes to cationic or anionic,  depending on the dosage of the coagulant
aid.  So, the amphoteric polymers were selected to be able to pelletize the
conditioned sludge, regardless of whether it was charged as cationic or
anionic.  In the  prototype system, the sludge thickening process was
indispensable  to  making  the following facilities as compact as possible.
                                      130

-------
     Through the experiments, the development target to reduce phosphate
release waa achieved.  In addition to this success, the observation of quite
fine separation of liquid and solids in the palletizing reactor suggested
another possibility to develop an innovative sludge thickening process.
This led the development of a sludge thickening/conditioning system, by
adding a separated water withdrawer to the sludge pelletization reactor.

     The structure of the separated water withdrawer was examined, using the
following type of screens, which is installed at the bottom..of the separated
water withdrawer.
                              *
     1)  Metal nets,
     2)  Punching plates, and
     3) . Plates with concentric circular slits.

    . These screens are shown in Figure 9.                                    ,
                                                    Separated water
                                                    withdrawer
      Metal net
Punching plate
Plate with
concentric
curcler slits
                         Figure ,9.   Examined screens.
                                      131

-------
     The performance of each screen was examined in terms  of  the SS recovery
efficiencies,  clogging occurrences, and available flow rates  through the
screens.  It was found that the plate with concentric circular slits was the
most suitable  for the separated water withdrawer,  as it showed the best
performance on the SS recovery efficiency, and no clogging troubles were
observed.  The clearance of the slit was 1.5 to 2 mm wide.

     After gathering all the information about the favorable  performances
for the sludge pelletization thickener, the sludge pelletizing thickener
shown in Figure 10 was developed.
Separated
water
                                                                 Sludge
                                                                 pellets
                       TT~D
                 Amphoteric  Charge-neutralized
                 polymer     sludge
          Figure 10.  Structure of sludge  pelletizing thickener.
                                   132

-------
      The sludge from'the sludge charge neutralization reactor is fed to the
 reactor at the bottom  of the reactor,  with an amphoteric polymer.   There are
 two stirring paddles in the sludge pelletizing thickener.   The fed sludge is
 mixed by the lower paddle with the amphoteric polymer.   The lower  paddle
 also establishes an internal recirculation of growing sludge pellets and fed
 sludge particles contact each other.   The upper paddle propels the growing
 sludge pellets along the internal  wall of the reactor.   Then,  the  sludge
 pellets are consolidated and the water contained in the sludge pellets is
 removed from the pellets.   Thus, the strength of the pellets increases.
 This is a benefit not  only for improving dewatering performance, but also
 for improving the SS recovery efficiency of the system.   As the sludge
 pellets contain a small amount of  water,  sludge pellets with a sufficiently
 high solid content will be supplied to dewatering machines.

      The development of this sludge pelletizing thickener has made it
 unnecessary to employ  conventional thickening processes.   This elimination
 has made stable sludge dewatering  possible,  even when sludges were fed which
 showed poor thickenability or poor dewaterability to conventional  sludge
 thickening,  conditioning,  and dewatering processes.

      This system just  requires tanks,  stirring equipment,  and pumps to feed'
 sludges and coagulants.   As all of them are very simple  and compact,  the
 construction cost of this system-can be reduced compared with other
 conventional sludge thickening systems.


 6.  Experimental Procedures

      The following four  kinds of sludge were examined for  the  development  of
 the BEST system.

      (1)  Mixed Raw Sludge of the  Conventional  Activated Sludge Process  (the
          Mixed Raw Sludge),
      (2)  Excess  Sludge  of  the Conventional  Activated Sludge Process,
      (3)  Excess  Sludge  of  the Anaerobic/Oxic  Process, and
      (4)  Excess  Sludge  of  the Oxidation Ditch  Process
           (Sludges  described  in (2) to  (4) will  be referred to as  the  Excess
          Sludges).

     The characteristics of the above sludges are listed in Table  1.   In
general,  the Mixed Raw Sludge is less difficult  to thicken and to  dewater,
compared with other  sludges.   It is said that a moisture content of 80%
would be  the lowest, when  the Mixed Raw Sludge  is dewatered by a belt-press
filter with the available maximum  filtration rate of  130 kg-DS/m/h after
single polymer conditioning.   For  the Excess Sludges, it is said to be very
difficult to reduce  the moisture content of dewatered sludge cake  to less
than 85% with an available maximum filtration rate 'of 50 kg-DS/m/h, when
they are conditioned and dewatered in the same way as the Mixed Raw Sludge.
                                     133

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             Table 1.  Characteristics of four kinds of sludges
  Kind of sludge
                   Characteristics
  Mixed raw sludge
  of conventional
  activated sludge
  process
  Excess sludge of
  anaerobic/aerobic
  process
  Excess sludge of
  convent ional
  activated sludge
  process
The fresher sludge has more fibers and shows better
dewatering efficiency.  However, this kind of sludge
is generally corruptible.  Once corruption
progresses, the thickneability and dewatering
efficiency deteriorate.

Compared with the excess sludge of a conventional
activated sludge process, this sludge shows a
slightly better dewatering efficiency and higher
phosphorus content.  However, when this sludge is
put into the gravitational thickener, or mixed with
primarily sludge, phosphorus release occurs.

In general, this kind of sludge shows poor dewatering
efficiency.  It is said to be very difficult to
treat this sludge, even if the belt-press filtration
is employed.  The moisture content is as high as 85%.
  Excess sludge of
  the oxidation
  ditch process
This sludge is considered to be poorly flocculated by
the single polymer conditioning.
     The characteristics of the sludges used in the experiments- were
measured on the items listed in Table 2.
                                    134

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  Table 2.  Measurement items and methods for the characteristics of sludges
        Item
      . Unit   Notation
                                                     Method
         PH
                 PH
JIS (Note 1)
  Electrical
  conductivity
       us/cm    Cond   JIS
  Methyl orange      mg/
  alkalinity
                 MA    Jis,  Japanese standard method for the
                       examination of wastewater quarity.
         TS
                               TS    Jis,  Japanese standard method for the
                                     examination of wastewater quarity-.
       VTS/TS
               VTS/TS  Japanese standard method for the
                       examination of  wastewater. quarity.
         SS
                               SS     JIS,  Japanese standard method for the
                                     examination of wastewater quarity.
      VSS/SS
              VSS/SS  Japanese standard method  for  the
                      examination of wastewater quarity.
     Fiber/SS
       %     Fiber/SS
        CST
                    sec
               CST
                                    Toriton's CST measuring  instrument and
                                    Wattman filter are employed.
 Total phosphorus  mg-p/2    T-P     (Mixed reagent method)  (Note 2)
 Orthophosphoric
 acid
     mg-P/    o-P    (Mixed reagent method) (Note 2)
     Note 1:
     Note 2:
Japanese Industrial Standards
Methods for chemical analysis of water and and wastes (1971)
of the Environmental Protection Agency.
     Lab tests and pilot scale experiments were conducted to examine the
basic performances of the BEST system with regard to pelletization and
dewatering.  The tests studied the relationship between the moisture
contents of the sludge pellets after gravitational drainage, the achievable
moisture contents of dewatered sludge cakes*5 (AMC), and the operational
conditions, such as chemical dosing ratios, etc.

*) The moisture content of a dewatered sludge cake decreases and the
   clogging level increases, as the dewatering pressure of the belt-press
   filter increases.  Thus,  the most preferable operation of a belt-press
   filter is done with the highest dewatering pressure, and the least filter
   cloth clogging.   The achievable moisture content of the dewatered sludge
   cake is defined as the minimum moisture content of a dewatered sludae
   cake with less than 10% of the clogging area on the filter cloth in batch
   dewatering tests with sludge- compression.
                                    135

-------
     The tests were done to examine the dewatering efficiencies in the
gravitational drainage zone, the primary pressure zone, the secondary
pressure zone, and the final dewatering zone with the shearing force of a
belt-press filter dewatering machine.

     The dosage of the metal coagulant aid was examined by the capillary
suction time technique, searching for the inflection point of the CST versus
chemical dosage curve (the CST procedure).

     The dosage of the amphoteric polymer was decided by examining the SS
recovery efficiency for the sludge pelletization thickener and the
mechanical strength of sludge pellets under various operational conditions.


7.  Results and Discussions

7-1.  Sludge  Pelletization/Thickening Efficiency

     The dosage of the metal coagulant aid, the dosage of  the amphoteric
polymer, the  condensing  ratip  in the sludge pelletizing  thickener, and the
system's solid retention time  in the pelletizing thickener are the
operational conditions of the  BEST  system.  The influence  of these
operational conditions on pelletizing and dewatering performances were
examined.

1)   Dosage of Metal  Coagulant  Aid (Polyaluminum chloride)

     A  metal  coagulant aid is  dosed to  the  fed sludge, with  the  objective of
neutralizing the  anionic sludge charge.   The  dosage of the metal coagulant
aid is  decided by the CST procedure.

     The relationships between the CST  value  and  the  dosage  of  the metal
coagulant  aid for the mixed raw sludge  and  the excess sludges  of a
conventional activated sludge process are shown  in Figure "11 and Figure 12,
 respectively.

      Both Figures 11 and 12 show that the inflection points  lay in almost
 the same dosage range.  This fact suggests that  proper dosage of the metal
 coagulant aid will range from 0.6 to 0.8% as A  to SS.
                                      136

-------
       o
       0)
       W"
      3
      o
           500
           400 -
           300 -
200 -
           100 -
              0   0.2  0.4  0.6  0.8  1.0  1.2  1.4  1.6  1.8


             Dosage of metal coagulant aid  (% as A  to SS)




Figure  11.  Relationship between  the dosage of metal coagulant  aid

            and  the CST  value.  (Mixed raw  sludge  of a conventional

            activated sludge  process.)
           200 -
       8
      I
           100 -
             0    0.2 0.4   0.6   0.8  1.0   1.2  1.4  1.6


             Dosage of metal coagulant aid (% as AS. to SS)



Figure 12.  Relationship between the dosage of metal coagulant aid

            and the CST value.  (Excess sludge of a conventional

            activated sludge process.)

                                137  .

-------
     The relationship between the AMC and the dosage of the metal coagulant
aid is shown in Figure 13.  As shown in the figure, the smallest AMC value
is about 70%, with the metal coagulant aid dosage of 0.6 to 0.8% as A to
SS.  This means that the actual dewatered sludge cake separation will be
satisfactory, when 75% of the moisture content of the cake is achieved,
which was one of the targets.
       75
       70
       65
 SS = 1.06%
 Amphoteric polymer = 1.38% to SS
 SSRT = 12 min
 Condensing ratio = double
                                                              100
                                                              90
                                                              80
0.2
                    0.4     0.6      0.8      1.0      1.2

            Dosage of metal coagulant aid (% as A2 to SS)
                                                         H
                                                          O
                                                         H
                                                                     
-------
thP nh relationship between the SS recovery efficiency and the dosage of

the amphotenc polymer for the Mixed Raw Sludge is shown in Figure 14   ?he


 fU lin^Cate that thS mC ShWed far less than the target vSue of "75%
when the dosage was 0.6% to SS, or more.  And an SS recovery Ifficiencv of

95% or more was achieved with the dosage of 0 7% to SS       e"iciency of
           70
       o
           65
    Figure 14.
SS = 1.76%



      C?agulant aid: '45% as
     = 12 mm


Condensing ratio: double
                                                     to
                                                            100
                                                            95
                                                            90
                 0.5  0.6  0.7  0.8  0.9  1.0  1.1  1.2



                  Dosage of amphoteric polymer (% to SS)
                                                                   B
                                               O

                                              H
                                               _
                                              a)

                                              s
                                              o
                                              
-------
         85 r
         80
         75
  SS  =  1.04%,  CST  =  170 sec
  Metal coagulant,  aid:  0.76% as A to SS
  SSRT  - 12 min
  Condensing ratio:  double
 i  	L	u	:	
0.5            1.0            1.5

  Dosage of amphoteric polymer (% to SS)
                                                                100
                                                                 95
                                                                 90
                                                            2.0
                                                                      H
                                                                      CD
                                                                      H
                                                                      O
                                                                      rl
                                                                       0)
                                                                       
                                                                       8
                                                                       1-1
                                                                      CO
     Figure 15.  Relationship between the dosage of amphoteric polymer,
                 and the mechanical strength of sludge pellet and the SS
                 recovery efficiency.  (Excess sludge of a conventional
                 activated sludge process.)


     From these results, the proper dosage of the amphoteric polymer is
revealed to be 1% to SS, or less.
3)  Condensing Ratio and SSRT of Sludge Pelletizing Thickener

     As one of the functions of the BEST system is a sludge thickening
process, the solid content of the sludge to be supplied to a dewatering
machine from this system is very important.  Therefore,, to estimate the
solid content of the sludge from this system, the condensing ratio and the
SS recovery efficiency are defined as follows.
     CR
     SSRE
            Q
             in
            CA
     where   CR  :
             SSRE:
             Qm  :
             Qt  :
                          x  100%
    the Condensing Ratio  (-)
    the SS Recovery  Efficiency  (%)
    Sludge feeding Rate  (m3/min)
    Separated Water  withdrawal  Rate  at  the  Sludge
    Pelletizing Thickener (m  /min)   '         '  -
                     140                 '    .
                                                         (2)
                                                         (3)

-------
             Cm-

             CA

             Ct
               Solid Content of Supplied Sludge (mg/jg)

               Solid Content in the Reactor (mg/)

               Solid Content of the Separated Water (mg/)
.By  reforming Equation 3,  the following equation is obtained.



CA  =
               x
                 Cin x Oin  =  SSRE
                                                                         (4)
     According to Equation 4, to  increase the solid content of  sludge  fed to

     o     3 maCh^6' the Censing ratio should be kept high  while keeping

of t   recverj efflciency hi9h-  To examine the extent of the  solid coJten?

of the sludge from this system, the relationship between the SS recovery

^  M16n!;Vndo?he Slid content  in the sludge pelletizing thickener when
the Mixed Raw Sludge was fed to the system was examined, and is shown  in

Figure 16.  it is suggested that  the SS recovery efficiency tends to

decrease when the solid content in the reactor exceeds 3 or 4%   This

implies that the opportunity for  the sludge pellets to clash increased  (and

then small sludge particles were produced) as the solid content in the -
        8
        CO
        H
        O
        H
       Q)


       8
       0)
       u

       CO
       CO
           100
       90
       80
Figure 16.
                               _L
                                            J.
              1            2            3            4


        Solid content in the sludge pelletizing thickener (%)




       Relationship between the solid content in the sludge

       pelletizing thickener and the SS recovery efficiency.

       (Mixed raw sludge of a conventional activated sludge process.)
                                   141

-------
     The same investigations were conducted for the Excess Sludges,  and
almost the same trend was observed.  However, the critical solxd content
claXing was slightly smaller than that for the Mixed Raw Sludge.  It  was
found to be about 3%, or less, of solid content.

     From these results, it was  found  that the solid content in the sludge
pelletizing thickener should be  operated  with 3 to  4% when  the Mixed Raw
Sludge is fed, and with 2 to 3%  when the  Excess sludges are fed.

     Next  the relationship between  SSRT*> and  the  moisture content of the
dewaterS'sludge cake was examined.  The  relationship for the Mixed Raw
Sludge is shown in Figure 17.
      dp
      0)
      A:
      
-------
     Figure 17 implies that the mechanical strength of the pellets will be
higher, as the moisture content of a dewatered sludge cake is lowered, when
the PT value   is increased, and that a fine separation will be expected
under these conditions.       ,                 .

     Figure 17 also implies that the mechanical strength of the sludge
pellets increased as the SSRT increased.  However, the sludge cake
separation was sufficient when the SSRT was 6 minutes, or longer.  Thus, the
SSRT in the sludge pelletizing thickener should be kept for a minimum of 6
minutes when the Mixed Raw Sludge is fed.             ..

     Also, it^ was revealed that the SSRT in the sludge pelletizing thickener
should be kept for about 12 minutes for the Excess Sludges.


7-2.  Dewatering Performance with a Batch Tester

     Dewatering examinations were made employing a belt-press filter batch
tester.  Figure 18 describes the tester.  The dewatering performances were
evaluated with the procedure shown in Figure 19.
         Side roll
      Filtered water
      receiver
                                    Press  dewatering  roll

                                                Filter cloth
                                 'Air  cylinder / Filter cloth
                                                 tensidning roll
      Filter cloth
      driving motor
                                                         Compressor
                 Figure 18.  Belt press filter batch tester.
                                    143

-------
                        Feeding pelletized sludge
 Conditions:
Gravitational drainage
 time:  1 min.
Compressing time:
 1 min.
Dewatering^pressure:
 0.03kg/cm2
                                                    Evaluation:
                                                  Pellet diameter
  Filtration
  test
Times of roll compres-
 sions:  3 to 15 times  _
Roll pressure:  0.5kg/cmz
"Filter cloth driving
 rate:  Im/min
Roll commpres-
sion test
                    Gravitational drainage
                    efficiency: *
                      Filtered water volume,
                      Cake volume
                    Preliminary press-
                    dewatering property:
                      Side leak,
                      Filtered water volume,
                      Cake volume
                                                  Moisture content of cake,
                                                  Cake thickness,
                                                  Cake expansion,
                                                  Cake separation,
                                                  SS of filtered water
                                 Analysis
                             Filtration rate,
                             Moisture content  of
                             cake,
                             Others
               Figure 19.   Procedure of  batch dewatering  tests.
      The dewatering performances as a control  were also examined with single
 polymer conditioning after centrifugal sludge  thickening,  to evaluate the
 dewatering performance by the BEST system.


      The characteristics of the applied sludges  are listed in Table  3.
                                    144

-------
























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-------
r
                  The relationship between the,filtration rates and the moisture contents
             of dewatered sludge cakes are shown for both the Mixed Raw Sludge and the
             Excess Sludges are shown in Figure 20 and Figure 21, respectively.
               0)
               0)
               O)
               a
               3
               r-t
               CO
               Q)
               J-i
               0)
               Q)
               P
               C
               0)
               4->
               s
               O
               a)
               u
               -M
               CO
               rt
                    80
                    75
70
                    65
                                     O
                                   D/0
BEST system

Centrifugal thickening
+ Single polymer
conditioning
          Filtration  limit
          for the control
                            0-O
                                          I
                                         I
                                         100                 200

                                         Filtration rate (kg-ds/mhr)
                                                            300
                Figure 20.  Relationship between the filtration rates and the moisture
                            content of dewatered sludge cakes.  (Mixed raw sludge of a
                            conventional activated sludge process.)
                                                  146

-------
        85
   (0
   o
   o
   4->
   O
   0)
   (-1
   3
   H

   i
        80
       75
                                   Arrowed data showed side-leaks.
0             50             100            150

                 Filtration  rate  (kg-DS/m/h)

    BEST :   Conventional, A A/O,  OD

    Contl:   O Conventional, A A/O, D OD
                                                                     200
   Figure 21.  Relationship between the  filtration  rates and  the moisture
               content of dewatered sludge cakes.
               (Excess sludges)


     According to the results in Figure  20 for the  Mixed Raw  Sludge, the
achievable maximum filtration rate for the control  was found  to be less than
130 kg-DS/m/h, as a side leak of sludge  was observed when dewatered with
this rate.  Then, the moisture content of the dewatered sludge cake was 71%.

     On the other hand, when the BEST system was employed, it was possible  -
to dewater the Mixed Raw Sludge with a filtration rate of 220 kg-DS/m/h
without any failure in dewatering.  Then, the moisture content of the
dewatered sludge cake was 71% in the examination.   For the dewatering
performance of a belt-press filter in Japan, it is  generally  said that 78%
of the moisture content will be obtained with a filtration rate of 130
kg-DS/m/h when a gravitationally thickened mixed raw sludge is fed.  The
moisture content attained with he BEST  system was  lower than the
conventional value, and the achieved filtration rate was almost twice that
of the conventional performance.                                     r     
                                     147

-------
     The results for the Excess Sludges in Figure 21, also show that the
BEST system could attain lower moisture content .of the cake and larger
filtration rate compared with the control system.  For example, a sludge
side leak was observed when sludges were dewatered with a filtration rate of
about 50 kg-DS/m/h with the control method, and more than twice the
filtration rate was achieved when the BEST system was used to dewater the
excess sludge of a conventional activated sludge process.  In addition, the
moisture content for the BEST system was 2 to 5% lower than that for the
control method.
7-3.  Full Scale Evaluation of Dewatering Performance

     Full scale run of the BEST system was tested in the T treatment plant
with the operational conditions listed in Table 4.  The BEST system was
incorporated between the sludge storage tank and the belt-press filter as
shown in the schematic flow diagram of Figure 22.
        Primary
        sedimentation  tank
Aeration tank
Secondary
sedimentation tank
             Mixed raw sludge
                                              Belt press  filter
     Gravitational  thickener
                              Sludge storage tank
                                                             External disposal
             Figure 22.  Schematic flow diagram of the T plant.
                                    148

-------
               Table 4.  Operational Conditions of the T Plant.
         Wastewater Collection System
                           Separate Collection System
         Wastewater Treatment Process
                           Conventional Activated Sludge
                           Process
         Influent Rate
                           3,600 to 6,400 m3/day
         BOD-SS Loading
                           0.64 kg-BOD/kg-SS/day
         Sludge Handling System
                           Gravitational Thickening
                           ==> Dewatering
                           (Belt-Press Filter)
                           ==> Disposal
        Solid Content of Sludge
                           Mixed Raw Sludge
                           = 0.8 to 1.6% of SS
                           Thickened Sludge
                           = 0.98 to 1.63% of SS
    7? ?ef rUn WaS Performed for one month, and the characteristics of
betwpS *iUdf*dUling thiS P6"^ are shown in Table 5-  The relationship
between the filtration rates and the moisture content of the dewatered
sludge cakes are shown in Figure 23.  in the figure, the annual average
values of the moisture content of the dewatered cake and the filtration rate
are also shown.
         Table 5.  Characteristics of sludges during the experiment.
     PH
Cond
(uS/cm)
                          SS
           VSS/SS
                                             TS
                    VTS/TS
                                         Fiber/TS
   5.6
   to 6.3
1,560
to 1,900
 0.98
-to  1.63
86.2
to 88.3
1.11
to 2.30
82.3
to 86.4
15.5
to 29.3
                                     149

-------
 0)
 o
 0)
 en
 to
 0)
  0)
 o
  0)
  p
  o
  P
  CO
  H
74
      72
      70
       68
            A
                                 A :
                           O :
                               Annual average with single
                               polymer conditioning
Condensing ratio = 0

Condensing ratio
                                                  1.5
                                                          O
                              _L
                                                              BEST system
         0     100
                       200            300

                   Filtration rate (kg-ds/m-hr)
                                                          400
 Figure 23.  Relationship between the filtration rate and the moisture
             content of dewatered sludge cakes.  (At the D plant; Mixed raw
             sludge of a conventional activated sludge process.)
     As shown in Figure 23, the average filtration rate and the average
moisture content of the cake were 90 kg-DS/m/h and 75%, respectively  when
the single polymer conditioning had been employed.  Improvements in the
molsturJ content decreaseding to 72%, and in the filtration rate increasing
to 150 to 160 kg-DS/m/h are shown in the figure, even when the BEST system
was employed wi?h a condensing ratio of zero.  Also, the further improvement
in the moisture content to 70% decreasing with an increased filtration of
220 kg-DS/m/h are shown when the BEST system was employed with a condensing
ratio of 1.5.                :

     The further improvements  in the moisture content and the filtration
rate are considered to be due  to the following reason.  The mechanical
SrLgth o?  the sludge pellets increased because of  the elongated, SSRT  in
the sludge pelletizing thickener brought about by  the  increase, of  solid
content in Se  reactor as the  result of withdrawing  separated water   Thus
withdrawal of separated water  from the sludge pelletizing  thickener  is  found
to be very effective  in  improving  the  dewatering  efficiency of  the system.
                                      150

-------
      The conventional value of dewatering performance for a belt-press
 filter  is described (in the specification code of  the Japan Sewage Works
 Agency)  as being able to make the moisture content of the dewatered sludge
 cake  75%,  or  less,  of the solid content,  with a filtration rate of
 130kg-DS/m/h,  when  a mixed raw sludge is  fed with  3% solid content after
 gravitational  thickening.   However,  it is said that to attain these values
 have  become extremely difficult in many municipalities in recent years.
 From  these facts, the dewatering performance of the BEST system can be
 described as being  very good.


 7-4.  Phosphate  Fixation     ;

      The relationship between the ortho-phosphate  concentration (O-P)  and
 the dosage of  metal coagulant  aid, when a fresh biological phosphorus
 removal  excess sludge was  fed to the system is shown in Figure 24.
        O-i
        o
CO

8
             10 -
                                                            - 10
             0
                   0.2  0.4   0.6  0.8   1.0  1.2   1.4  1.6

                Dosage of  metal  coagulant  aid (% as A2 to SS)


  Figure 24.  Relationship between the orthophosphate concentration and the
              dosage of metal coagulant aid.  (Fresh excess sludge of an
              anaerobic/oxic process.)
     The results in the figure indicate that O-P was almost completely fixed
within the sludge with a metal coagulant aid dosage of 0.5% as A to SS.  As
discussed in Section 7-1, a metal coagulant aid dosage of about 1% as A to
SS is required for charge neutralization, so the O-P in the sludge liquid
will be almost completely fixed within the solids with this dosage.

                                    151

-------
     Figure 25 shows the relationship between the same  items  shown in
Figure 24, using excess sludge from a biological phosphorus removal
process.  The sludge was stored 5 days under anaerobic  condition prior to
the test.  The results shown in the figure indicate  that  a dosage of  1.5% as
A to SS was required to reduce O-P to the level attained with 0.5% dosage
when the fed sludge was fresh.  From the economic point of view,  the  sludge
should be processed while it is fresh to fix O-P within the sludge.
                 1135
         0.
         6
             20 -
             10 -
                                                           - 400
                                                           - 300
- 200
                                                           - 100.
                                                                    o
                                                                    
-------
                   Table  6.  Conditions of cost estimation
     Kind of Sludge
                  BEST system
Moisture	'
content of _       .
dewatered  Dosa?e of       Dosa9e of
cake (%)   metal           amphoteric
           coagulant aid   polymer
           (% as A to SS) (% to SS)
                      Convent ional
                      system

                        Dosage of
                        cationic
                        polymer
                        (% to SS)
     The Mixed Raw
     Sludge
    70
0.46
0.78
                                          0.60
     Excess Sludge of
     convent ional
     activated sludge
     process
    82
0.89
0.86
                                          1.31
     Excess  Sludge of
     anaerobic/oxic
     process
    82
0.74
                              1.18
            0.63
     Excess  Sludge of.
     oxidation ditch
     process
    82
0.60
                              0.83
                          0.33
     The estimates for the BEST system include costs for the metal coagulant
aid and the amphoteric polymer.  The estimates for the conventional system
include costs for the cationic polymer and electricity for the centrifuge.
Costs for electricity required to operate pumps and stirring equipment were
not included in the estimates, as they were thought to be in significant "in
relation to the total costs.  The results are shown in Figure 26.  In the
figure, operation hours are shown as well.
                                     153

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             Mixed raw sludge of a
             conventional activated
             sludge process
Excess sludge of a
conventional activated
sludge process
Excess sludge of an
anaerobic/aerobic
process
Excess sludge of an
oxidation ditch process
O CO
OP
en 4->
83
H ^x
       30,000
       20,000
       10,000
          10


          12
                                                         Metal coagulant aid


                                                         Amphoteric polymer.

                                                         Electricity for centrifugal
                                                         sludge thickening

                                                         Cationic polymer
Note 1:  The left bar  represents the  BEST system,  and the  right  bar, the
          single  polymer  conditioning  after centrifugal thickening.

Note 2:  The operation hours  for the  conventional  system indicate the
          hours required  to dewater the same  amount of sludge that the
          BEST system dewater  within 7' hours.


                Figure 26.  Comparison  of operational cost.
                                       154

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      According to the results, the estimates for the BEST system are a
 little bit high compared with those for the conventional system when
 handling the Mixed Raw Sludge.  The moisture contents of the dewatered
 sludge cake dewatered with both systems are the same, however, though the
 achievable filtration rates differ significantly between the two.  When
 7-hour operation of a belt-press filter is required to dewater the Mixed Raw
 Sludge with the BEST system, 11.4-hour operation of the same belt-press
 filter will be necessary to dewater the same amount of sludge processed with
 the control system.  '
 9.   Conclusion
 1)
      The following is obtained in this study of the BEST system.

     The BEST system makes it possible to dewater any of the mixed raw sludge
     of the conventional activated sludge process, the excess sludge of the
     conventional activated sludge process, the excess sludge of an
     anaerobic/aerobic process, and the excess sludge of an oxidation ditch
     process sludges, without any of conventional sludge thickening processes.

 2)  The required dosage of the metal coagulant aid for the BEST system
     ranges between 0.6 and 0.8% as A to SS of any sludges examined in this
     study*;

 3)  The dosage of the amphoteric polymer for the BEST system is about 1% to
     SS for any of the fed sludges.   The required dosage of the amphoteric
     polymer is almost the same,  or slightly larger,  compared with that of
     the cationic polymer dosage in a single polymer conditioning system.

. 4)  The sludge pelletizing thickener should be operated with 3 to 4% of the
     solid content,  and with 6 minutes,  or .more,  of SSRT when the mixed raw
     sludge is fed into the system.   When excess sludges are fed into the
     system,  the sludge pelletizing thickener should be operated with 2 to 3%
     of the solid content,  and for 12 minutes,  or more,  of  SSRT.   The system
     is very compact compared with a gravitational thickener.

 5)  The dewatering  performance of the BEST  system revealed that  the  moisture
     content  of  dewatered sludge cake can attain the  target  volume of 75%   or
     less,  with  a filtration  rate  of  200  kg-DS/m/h, when a mixed  raw  sludge
     is fed to the system and dewatered with a  belt-press filter,   when
     excess sludges  are fed to the BEST system,  the dewatering performance
     was improved compared with conventional system.

6)   The running costs  for  this system are-estimated  to be almost  the same
     or  slightly more compared with that for the mechanical  thickening
     dewatering  system, which  employs  a centrifuge  for thickening, and the
     single polymer dosing  to  condition the  sludge.
7)
    The release of phosphate in the system is almost completely cut off by
    dosing the metal coagulant aid.
                                     155

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    For these characteristics of the BEST system, the following applications
are now under consideration.

(1)  Application to sewage treatment plants, where the gravitational sludge
     thickeners do not work efficiently.

(2)  Application to small size sewage treatment plants, as an itinerant
     sludge handling system by trucking a belt-press filter combined with
     this system.

(3)  Application to the sewage treatment plants where biological phosphorus
     removal processes are employed.
Reference                        ,

1.   Annual Technical Report,  Sewage Works Bureau  of  Tokyo Metropolitan
     Government, March,  1989.
                                      156

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Operation of Centralized Sludge Treatment Plant
                         by


                     Senji Kaneko

         Chief, Research & Development Division

                 Sewage Works Bureau

                   City of Yokohama
    The work described in this  paper was not  funded by
    the U.S. Environmental  Protection Agency.  The contents
    do not necessarily reflect  the views of the Agency and
    no official  endorsement should be inferred
             Prepared for Presentation at:

          12th United States/Japan Conference

                        on

            Sewage Treatment Technology
                    October 1989

                  Cincinnati, Ohio
                      157

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                               Abstract


     Th'e construction of sewage works in the city of Yokohama has progressed
at a rapid pace ever since the first wastewater treatment plant went into
operation in 1962. As of 1984, all eleven of the planned wastewater treatment
plants were in operation.  In March of 1989, the percent of sewered population
reached'80 percent, or 2.54 million of the city's total population of 3.15 million.

     The quantity of sludge that has to be, treated and disposed of has, in the
meantime, increased along with this construction.  Recognizing the  crucial
importance of constantly keeping abreast of the ever-increasing quantity of
sludge, the city has been  pursuing technological-development aimed at estab-
lishing more effective and efficient methods of sludge treatment and disposal.

     In view of this city's rapid urbanization and the rising citizen concern for
improving and preserving the environment, the city.decided to modify the
sewerage plan, shifting from the former system of decentralized  sludge
treatment at each of .the  eleven wastewater treatment plants to a centralized
treatment system at two sludge treatment centers constructed within two
waterfront area wastewater treatment plants.

      One of'these sludge treatment centers (Hokubu) began operating in
September 1987. The center contains egg-shaped digesters, the first  of their
kind in Japan.  To insure the efficient operation of these digesters, centrifugal
thickeners are employed during pretreat'ment, enabling high-concentration
digestion. In addition, the digestion gas energy is recovered as electrical power
owing to a gas power generation system that transforms the energy. Further-
more, before incineration, the sludge cake is dried using the heat released from
the incineration system, thus enhancing the efficiency of incinerator opera-
tions. These and similar measures demonstrate the city's efforts to incorporate
technological development into treatment facilities in order to optimize the
total system.

      Full-scale operation records for approximately one year indicated that
power generated from digestion gas supplied 64 percent of the  center's total
 power needs. This figure amounts to an annual savings of  200 million for the
 present volume of sludge treatment, which is one-fifth of the planned  volume.
The record also confirms the advantages of centralized treatment; it was found
 that sludge treatment cost at Hokubu was less than half the sludge treatment
 cost for the same quantity of treatment processed at the individual wastewater
 treatment plants.

      This report presents  the  center's operational record for the  year in
 question, the actual status of energy recovery and recycling, at the center, and
 current modes for effective utilization of incinerated sludge ash.
                                   158
                                                                               if?

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1.   Foreword

     The quantity of sewage sludge generated in cities has been steadily increasing
with the expansion of sewerage systems.  The increase is particularly eminent in
major cities, which not only shoulder the enormous burden of costs required for
treatment and disposal, but also are finding it increasingly difficult to acquire the
needed disposal sites.

     In the city  of Yokohama,  the construction of the sewerage system has
progressed at a rapid pace ever since the first wastewater treatment plant went into
operation in 1962. As of 1984, all eleven of the planned wastewater treatment plants
were in operation. As of March 1989, the sewerage service rate reached 80 percent,
or 2.54 million residents of the entire population 3.15 million.

     The quantity of sludge generated in the city has been expanding each year with
this progress. Efficient and effective treatment and disposal of sludge are becoming
increasingly important issues.  Moreover, the city experienced rapid urbanization
during Japan's recent period of high-level economic growth.  Subsequently,  the
improvement and preservation of the environment have become major concerns of
city residents.  In view of these  factors, the city decided to shift from its former
system of decentralized sludge treatment at each wastewater plant to a new system
of centralized treatment at two sludge  treatment  centers  constructed at two
wastewater treatment plants located in the waterfront area.

     One of these sludge treatment centers (Hokubu) went into operation in
September 1987. This report presents the operational record of this facility and the
effects of centralized sludge treatment.
                                    159

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2.   Current status of sewerage system construction in Yokohama
     Full-scale-construction of sewerage system including waste water treatment
plants in Yokohama dates from 1957. This construction is being promoted in a series
of five-year plans, the sixth of which is now underway, in a program called the Five-
year Program for Sewerage Construction. In the process, the city's sewerage system
has greatly expanded. Initially, the construction was confined to the oldest parts of
the city in the waterfront area; it now covers all areas of the city. At present, the
main priority is an increase in the sewered population in the city as  a whole, and
particularly in suburban areas.

     In the sewerage system plan, the city is divided into nine treatment districts
and includes 11 wastewater treatment plants, as shown in Figure  3-1 in the
following section. With the initiation of the  newest plant in 1984, all eleven of the
planned wastewater treatment plants were in operation 22 years after the start-up of
the first plant in 1962.

     The original plan called for each wastewater  treatment plant to carry out its
own sludge treatment. Subsequently, however, it  was decided to construct sludge
treatment centers at two specific plants in the water front zone, where centralized
treatment of the sludge generated at each of these plants could be  done. This report
concerns the operation of the Hokubu Sludge Treatment Center, which began
operation in September  1987. The other center-the Nambu Sludge Treatment
Centeris scheduled to go into operation during fiscal year  1989.  Table 2-1 shows
the current status of the city's sewerage system construction.

      Table 2-1. Status of Sewerage System Construction (as of March 1989)
City area (ha)
Urbanization promotion area (ha)
Treatment district area (ha)
Total city population (thousands of persons)
Sewered population (thousands of persons)
Percent of sewered population (%)
Extended sewer length (km)
Number of WTPs (in operation)
Treatment capacity (103 m3)
Number of pumping stations (in operation) .
Number of stormwater retention reservoirs (in operation)
43,082
32,473
22,136
3,158
2,542
80
7,906
11
1,844
22
3
                                    160

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 3.   'Centralized sludge treatment plans and an outline of the facilities

 3-1. Plans and outline                   ....

 3-1-1.  Centralized sludge treatment plans

     The city has formulated plans to construct two centralized sludge treatment
 centers in the waterfront area~the Hokubu and Nambu sludge treatment centers.
 As shown in Figure 3-1, the plans call for the treatment of sludge generated from the
 waste water treatment plants in the northern section of the city, namely, the Midori,
 Kokubu, Hokubu No. 1, Hokubu No. 2 and Kanagawa plants, at the Hokubu Sludge
 Treatment Center, and for the treatment of sludge.generated from those plants in
 the southern part, namely, the Chubu, Nambu, Kanazawa, Sakae No. 1, Sakae No.
 2, and Seibu plants, at the Nambu Sludge Treatment Center.  Table 3-1 shows the
 outline of the city's wastewater treatment plants.

     As part of  these plans, sludge is transported to the centers by means of
 pressurized  pipelines.  The sludge is not routed directly from the wastewater
 treatment plants to the centers, however.  Wherever possible, it is routed through
 one or more wastewater treatment plants served by the same center.

     Table 3-2 shows an outline of the sludge treatment center plans. Several
 treatment processes are planned for both centers in order to provide flexibility in
 sludge treatment and accommodate future technological innovation.

 3-1-2.  Current construction status of the centralized sludge treatment plant

     As of March 1989, virtually all of the sludge pipelines had been completed.
 Routes 11 and 12 are still under construction, but routes 1 through 6 are already in
 operation, and routes 7 through 10 are scheduled for operation during fiscal year
 1989.

     Table 3-3 shows the construction status of the sludge treatment facilities at the
Hokubu Sludge Treatment Center. In September 1987, the Center began full-scale
operation based  on a sequence process of thickening, digestion, dewatering, and
incineration. The  Nambu Sludge Treatment  Center is scheduled'for operation
during fiscal year 1989.
                                   161

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Fig. 3-1. Map of Sludge Pipelines
                              \ ,-KanagawaWTP
                                                        HokubuNo. 1WTP
                                                             \
                                                            HokobuNo.2WTP
                                              Hokubu Sludge
                                              Treatment Center
                         Isogo Pumping Station'
\
                                .

                SakaeNo.2WTP  I/
                                                       ChubuWTP
                                                 NambuWTP
                                                   Nambu Sludge]
                                                   Treatment Center
    SeibuWTP
                                               KanazawaWTP
        Legend:
              In operation
        ===> Under construction
                                     162

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        Table 3-1. Sewage Treatment Plants
                                                 (as of March 1986)
Treatment plant
1. Hokubul
2. Hokubu n
3. Kanagawa
4. Chubu
5. Nambu
6. Kanazawa
7. Kohoku
8. Midori
9. Sakael
lO.SakaeH
ll.Seibu
Design treatment capacity
(m3/day) (population) .
196,000 (377,000)
86,400 (166,000)
543,200 (1,074,000)
96,300 (185,000)
255,000 (433,000)
'345,000 (663,000)
439,000 (844,000)
433,000 (833,000)
124,000 (238,000)
206,000 (396,000)
191,000 (367;000)
Current treatment
capacity
(m3/day)
196,000
86,400
380,200 
96,300
225,000
230,000
172,500
126,000 .
62,000
206,000
63,600
Operation
started
July '68
Aug. '84
Mar. '78
July '62
July '65
Oct. '79
Dec. '72
May '77
Dec. '84
Oct. '72
Mar. '83
Table 3-2. Outline of Centralized Sludge Treatment Plans
Center
Hokubu
Nambu
Wastewater
treatment
plants covered
Midori
Kohoku
Hokubu No.l
Hokubu No.2
Kanagawa
Chubu
Nambu '
Kanazawa
SakaeNo.l
Sakae No.2
Seibu
Capacity
(TS: 1%)
44,100
m3/day
30,000
m3/day
Sludge treatment processes
Thickening-* anaerobic digestion* dewateringr-* incineration
(gravity-type/centrifugal) (centrifugal) ^drying
Thickening" wet oxidation" dewatering
(centrifugal) (filter press)
Thickening-^ anaerobic digestion *de watering^- incineration
(centrifugal) (belt press)
Thickening-^- wet oxidation * dewatering
(centrifugal) (filter press)
                      163

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       Table 3-3.  Construction Status of Hokubu Sludge Treatment Center
                 Facilities                   -                  , ,
                                                      (as of March 1989)
Facility
Sludge intake tanks
Thickening tanks
Centrifugal thickeners
Digesters
Centrifugal dehydrators
Incinerators

Gas engine power generators
Gas holders
In operation
1,500 m3X 2
1,260 m3X 8
100m3/hrX3
6,800 m3x 6
50m3/hrX3
lOOwt/dayXl
150wt/dayX2
920kWX3
8,000 m3xl
Under
construction



6,800 m3X 6


150wt/dayXl
920kWXl
8,000 m3 XI
   Note: The abbreviation wt refers to wet ton.
3-2.  Outline of centralized sludge treatment (Hokubu Area)

3-2-1.  Sludge transportation system

     The sludge generated from the primary and final sedimentation basins  at
wastewater treatment plants is transferred, in mixed form, to concentration
conditioning tanks, where the TS concentration is adjusted to about 1 percent. The
sludge is then stored in  a  holding tank and transported through pipelines
pressurized by pumps to the Hokubu Sludge Treatment Center.

     The sludge generated at the Midori plant is first transported via the Kohoku
plant to the Hokubu No. 1 plant.  At each plant, the sludge is mixed with that
generated from the wastewater treatment plant, and then transported to the Center.

     The sludge generated at the Kanagawa plant is  transported  directly to the
Center after its TS concentration has been adjusted.  The sludge generated at the
Hokubu No. 2 plant is also transported directly to the Center, in the form of primary
sludge, i.e., sludge drawn from the primary sedimentation tank.

     Ideally, the operation and management of the sludge transportation and intake
system should be integrated with that of sludge treatment, the two forming a single
system.  Taking this into account, the city has adopted a system of centralized
supervision and decentralized control.
                                    164

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 3-2-2.  Hokubu Sludge Treatment Center

      As shown in Table 3-2, the Center has a daily treatment capacity of 44,100
 cubic meters of sludge (TS: 1%) through a combination of three processes:  anaerobic
 digestion/dewatering/incineration,  digestion/dewatering/drying, and wet  air
 oxidation /dewatering.  At present, only the first process (digestion /dewatering/
 incineration) is in operation.  This section presents an account of the facilities
 involved in this process. Figures 3-2 and 3-3 present the layout of the Center and the
 flow of the digestion/dewatering/incineration process, respectively.

 (a)   Thickening process

      The sludge transported from the wastewater treatment plants first enters  the
 sludge intake tanks and is then transported to thickening tanks. In these tanks  the
 sludge concentration is adjusted to about 2 percent and then increased to about 5
 percent, by means of a centrifugal thickeners. In recent years,  it is presumed that
 the thickening properties of sludge have deteriorated as a result  of the rise of sludge
 VTS and decomposition during long-term  transportation.  Consequently, gravity
 thickening is supplemented with mechanical thickening to provide for the stability
 of, and alleviate the burden on, subsequent processes. The Center has adopted a
 mode of centrifugal thickening for  this purpose, seeing that maintenance is
 relatively simple and the equipment's compact size facilitates installation.

 (b)   Digestion process
                              s
      The Center has adopted an anaerobic digestion process in the interests of
 enhancing the overall flexibility of the facilities and making effective use of the gas
 generated in digestion. The egg-shaped tanks used for this digestion are the first of
 their kind in Japan and offer various advantages; they generate an extremely high
 agitation efficiency, ensure a minimal generation of scum, and facilitate the easy
 removal of sediment.  In addition, the construction cost per unit of treated solids is
 virtually the same as for conventional tanks. There are six such tanks, each with a
 capacity of 6,800 m.3.                                                .

 (c)   Power generation process using digestion gas

     The heat and power, derived as a result of the power generation using digestion
gas,  are effectively utilized for the purposes of heating the digesters and supplying
power for various facilities within the Center.  The  system now consists of three
generators in the 920-kilowatt class.
                                     165

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(d)   Dewatering process                          *

     The Center uses centrifugal dehydrators to dewater the sludge after digestion.
These centrifugal units are easy to maintain and offer a high solids capture rate-and
contribute to efficient operations. There are now three such units in operation, each
with a capacity of 50 cubic meters per hour.

(e)   Incineration process

     To reduce the quantity of sludge for disposal, fluidized bed incinerators are
used to incinerate the entire quantity of sludge cake.  The temperature of the
incinerator exhaust gas is about 800C, and the exhaust gas is used for drying sludge
cake before incineration; thus increasing the efficiency of the operation. There are
now three such incinerators operating in the Center, one with a daily capacity of 100
wt and two with a capacity of 150 wt per day.

(f)   Sidestreams treatment process

     Various types of sidestreams are separated out in  the sludge treatment
processes (e.g.,thickener effluent, supernatant from  digestion tanks, filtrate from
dehydrators, and scrubber drain). There are plans to first pretreat these sidestreams
at facilities constructed for this purpose within  the Center,  and then undergo
secondary treatment process.
Fig. 3-2. Layout of the Hokubu Sludge Treatment Center

    ^^.
                        HokubuNo.2WTP
          Hokubu Sludge
          Treatment Center
             Facilities for
             effective use of
             incinerated ash
washing facilities p
                                                      Power generation
                                          "Digesters
                                             Centrifugal thickeners
                                       166

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 Fig. 3-3 Flow of Anaerobic Digestion/Dewatering/Incineration Process Flow Chart

                                               Gasholder  Desuifurizati0n equipment
                         Gas engine power generator
                                                            h
 Sludge intake tank             Centrifugal
              Thickening tank  thickener
Digestier  Centrifugal
         dehydrator
                                                                    Incinerator
                                                                      Incinerated ash
  iDigestion/drying process
  I Wet air oxidation process -
                                "*{ Sidestreams     1
                                .^treatment process J~
         Wastewater treatment system
                                                              Legend
                                                                 Flow of sludge
                                                              	* Flow of digestion gas
                                                              	* Flowofsidestreams
                                                              L~~~\ Planned
     At present, these plans are at the preliminary stages of process selection.  In
the meantime, the sidestreams generated at the Center are being sent back for
treatment at three wastewater treatment plants (Hokubu No.-l, Hokubu No. 2, and
Kanagawa), distributed according to the load produced by such treatment.

3-2-3.  Instrumentation

(1)  Outline

     The instrumentation systems of the sludge transportation facilities at each
wastewater treatment  plant are linked  to the centralized supervision  and
decentralized control  system at the* Center.  This  facilitates the  integrated
management of the sludge intake facilities, thickening and digestion facilities, and
other sludge treatment facilities.
                                       167

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      The main computer system, which is at the core of this instrumentation
 system, is equipped with a backup system for reliability and safety.  The backup
 system assures operational continuity in the event of an unplanned shutdown or
 planned shutdown in accordance with the maintenance schedule of the other system.
 Even if both systems are shut down, the facilities can be monitored and operated
 through the monitor panel located within the central supervision and control room.

      At the same time, each of the treatment facilities within the Center is equipped
 with a local station, microcontroller, and sequence controller. 'These devices can
 automatically control the facilities and exchange information with  the main
 computer. Utilizing optical fiber cable, information is transmitted between the'main
 computer and local stations through a high-speed dataway.

      Figure 3-4 shows the Composition of Instrumentation at the Hokubu Sludge
 Treatment Center.

 (2)   Sludge transportation facility instrumentation         *>

      The function of controlling sludge  transportation facilities is  to assure the
 smooth transportation of sludge generated at each of the wastewater treatment
 plants to the Center. Sludge from numerous plants is transported through a single
 pipeline in a cascade. For this reason, coordinating the transportation time.sequence
 at each transportation facility is a major part of the operation. To effect such
 coordination, the transportation facilities ar-e controlled by a  daily sludge
 transportation schedule.                                   "

     The schedule is developed in accordance with the Center's general operational
plans, which are based on estimates of the quantity of sludge generated at the
wastewater treatment plants, and is formulated by main computer operators. The
basic goals behind creating the plans are to maximize the total quantity of sludge
transported per day, assure that the minimum  required flow, speed  within the
pipeline is maintained, and that a proper balance between the quantity of sludge
entering the holding tanks and that of the transported sludge is upheld.

     Sludge transportation is automatically initiated when the time specified in the
transportation schedule is reached or when the level of sludge in the holding tank in
the transportation facilities reaches its upper limit. Transportation is automatically
terminated when the quantity specified in the schedule' is reached (as calculated
from the quantity and frequency of sludge transportation for the day in question) or
when the level of sludge in the holding tank reaches its lower limit.

     The sludge transportation facilities are also equipped with a timer control,
which has a sequence controller as a backup system in the event of microcontroller
failure.  In this mode  of control, the  start-up and shutdown of the sludge
transportation pump are based on the  time of transportation initiation and the
duration of pump operation in each case.         .
                                     168

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 Fig. 3-4.  Composition of Instrumentation at the  Hokubu Sludge Treatment
           Center

       ,	 	  Ho^ubu Sludge Treatment Center-Areas of Control
                        Computer
                                   Computer
                                                            Data way
                                                       (Optical fiber cable)
               (STF)
               IOC
                           CTR
                 SQC]
                Sludge _p
             I   JTM/I1VJUL/ llugge p
           VtD|MIiTC'ntake facilities^

RS -


CTR
SQC


RS


h
CTR
SQC

Digesters*
.... RS -.


CTR
SQC

                                 [Thickeners	Dehydrators       Power generators
                      |_ Public telephone circuits
                 
Sludge transportation
          facilities
                                                                        Direct
                                                                        transmission
 Legend
 FD:  
 CB:
 LP:
 IRB:
 TW:
 MS:
 CRT:  ,
 RS:
 SYC:
                                                   Off premises of Hokubu Center
                                                                                  i  i
                                                                         On the premises of
                                                                         Hokubu Center
Flexible disk drive
Central monitor board
Line printer               IOC:
Information retrieval board  CTR:
Output typewriter          SQC:
Master station              MD:
CRT display               IB:
Remote station              TM/TC:
System console              STF:
                  F.low of sludge
            	'- Direct transmission
            "1U1"" Public telephone circuits
            (_   J Data way
Input/output controller
Microcontroller
Sequence controller
Modem
Instrumentation board
Telemeter/telecontrol
Sludge treatment facility
                                       169

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(3)   Detection of pipeline abnormalities

     Blockage:  Sludge transportation pipelines are considered blocked when both
the pump discharge pressure is higher than the set value and the quantity of sludge
flow is lower than the set value or has rapidly decreased. When blockage is detected,
the pump is immediately shut down and a blockage alarm is transmitted.

     Leakage:  Sludge transportation pipelines are deemed leaking when both the
pump discharge pressure is lower than the set value and the quantity; of sludge flow
is higher than the set value or has rapidly increased.  When leakage is detected, the
pump is immediately shut down and a leakage alarm is transmitted.

(4)  Instrumentation of sludge intake facilities

     Because sludge residue within pipelines can cause blockage or generate gas,
they must be cleaned after transportation.  As a general rule, the pipelines are
cleaned once every day. The cleaning is performed by flushing the pipelines with
pressurized water, using the sludge transportation pump.  After the sludge
transportation for the day has  been completed,  the operator in  the central
supervision  and control room in the Center orders  the commencement of the
cleaning.

     On the intake side, separate tanks are used to receive the sludge and cleaning
water. A near infrared-type sludge  -densitometer      is attached to the pipeline
on this side to  constantly measure the concentration.  When the concentration of
fluids transported through the pipeline falls  below the  set level, the intake is
automatically switched to the cleaning water tank. The operation makes use of the
comparatively well-defined interface between sludge and cleaning water within the
pipeline, and of the sharp drop in concentration when sludge is replaced by cleaning
water.
                                     170

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  4.    Operation of Hokubu sludge treatment center facilities

  4-1.  Operation of sludge transportation system

       The Hokubu Sludge Treatment Center treats sludge transported by pipeline
  from five wastewater treatment plants.

      The sludge transportation system consist of transportation facilities (sludge
  holding  tanks and sludge pumps), sludge pipelines, and sludge intake facilities
  (screenings removal units and sludge holding tanks).

      Table 4-1 presents the quantities and the TS and VTS concentrations of sludge
  generated at each of the five wastewater treatment plants during fiscal year 1988.

                Table 4-1. Sludge Quantities and TS and VTS Concentrations
STP
Item
Quantity of sludge
generated (m3/day)
TS(%) '
VTS (%)
Midori
540-870
(680)
1.0-3.4
(2.4)
49-88
(80)
Kohoku
250-600
(360)
1.9-4.0
f (3.4)
51-79
(69)
Hokubu No. 1
630-1,000
(760)
1.5-5.5
(3.3)
52-84 .
(67)
Hokubu No. 2
160-660
(480)
0.8-2.2
(1.4)
. 66-83
(75)
Kanagawa
1,750-2,770
(2,120)
1.4-3.2
(2.0)
62-85
(78)
      valuesoveraone-yearperi^F^^
     The sludge is transported from the Midori plant to the  Kohoku plant and
 further to the Hokubu No. 1 plant with treated wastewater through-a pipeline  In
 order to separate .the sludge from the water, a near infrared reflective-type sludge
 densitometer        (TS meter) is attached to the pipeline in front of the sludge
 intake tank at the latter two plants. The line of separation is a TS concentration of
 0.1 percent; the pipeline is emptied into the sludge intake tank if the concentration is
 over 0.1 percent and into the treatment plant grit chamber if it is under 0.1 percent
 Change m TS concentration within the pipeline is well defined, and the separation of
 sludge and treated wastewater could be effected even at a higher TS concentration
 setting  on the TS meter.  However, a setting of 0.1 percent was decided upon to
 reduce the burden on the wastewater treatment plants.

     Only sludge is transported in the pipelines leading to  the Center from the
Hokubu No. 1, Kanagawa, and Hokubu No. 2 plants. These pipelines are cleaned as
required.
                                    171

-------
     Sludge transportation management is based at the Center, and is a system of
centralized supervision and decentralized control.

4-1-1.  Operation and control of sludge transportation facilities

     The time required for the movement of sludge and the sludge transportation
time schedule are shown in Figures 4-1 and 4-2, respectively.

     Maintenance and inspection of the various transportation facilities is the
responsibility of the Center.

     Sludge transportation is carried out three times per day. As shown in Figure 4-
2, the transportation is initiated at prescribed times and terminated when the
prescribed quantity has been transported or when the level of sludge in the holding
tank reaches the prescribed quantity.  In the event of an increase of sludge due to
storms or other developments, agreements are reached with personnel at the various
wastewater plants to  adjust the aforementioned upper limits and  increase the
quantity of sludge transported.

Fig. 4-1.  Movement of Sludge from Transportation Facilities to the Center
tun j - ;



Hokubu
No.l
6,010m 7,680m
2 hr 40 min 2 hr 32 min
540-870 m3/day 990-1,280 m3/day


4,9E
23 1
1,7(

>0m
ir 27 min
)0~2,170
m3/day


Hokubu
, No. 2
1
160-660 m3/day
On-premise pipes
1 r


                              5,030m
                              9 hr 3 min
                              1,750-2,770 m3/day
                                  \
                                 Kanagawa
  Legend
  First line:   section distance
  Second line:  transportation time
  Third line:   transportation quantity
Hokubu Sludge Treatment
Center intake facilities
                                       172

-------
  Fig/4-2. Sludge Transportation Time Schedule
   Send from
   Midori
W
   Intake at
   Kohoku
  Send from
  Kohoku
       \wm
  Intake at
  HokubuNo. 1
  Send from
  Hokubu No. 1
  Intake at
  Center
  Send from
  Kanagawa
                                                    Legend   Sludge transportation

                                                                Cleaning
4-1-2. Management of sludge pipelines

      The sludge transportation pipeline is basically composed of ductile castiron
pipe (DCIP) in sections that are buried and of fiber glass reinforced plastic mortar
(FRPM)  pipe in sections that are installed in public utility ducts.  As part of the
maintenance work, the operation of the pipeline's air valves, sludge discharge
valves, and other equipment is checked periodically four times a year.

      However  slight, pipeline leaks must be  immediately detected  and repaired
since the effluent is sludge.  Consequently, all sections are equipped with flow
meters on both the sending and receiving sides. Leakage is detected by monitoring
and checking for variation between these meters. Similarly, the correlation between
the quantity sent and the discharge pressure is used to check for leakage  and
blockage. At hourly intervals, the quantities sent and received are integrated to
check for leaks and to check that operation is proper. The Center also maintains a
store  of materials for repairing leaks (e.g., various types of short pipe sections,
connecting bolts,.packing materials, and coupling rings).
                                      173

-------
4-1-3.  Operation of sludge intake facilities

     During fiscal'year 1988, the quantity of sludge received at the Center ranged
from 4,110  to 5,290 m3  per day.  The corresponding ranges for  TS and VTS
concentration were 1.4-3.0 percent and 62-84 percent, respectively.  The trends of
sludge intake quantity and TS and VTS concentrations are shown in Figure 4-3.

Fig. 4-3.  Monthly Trend of Sludge Intake Quantity, and TS and VTS
        Concentrations
 I
    Q)
    ho
    CO
100

 90

 80

 70

 60

 50

 40

 30

 20

 10

 0
            4  5'6   7  8  91011121  2  3

                         Month
                                               O   tUD
                                                  I
                                                  55
Legend
                                                                 Intake quantity
                                                                 Sludge VTS
                                                                 Sludge TS
     As shown in Figure 4-3, the intake quantity gradually increases, and is in
inverse proportion to that of the TS concentration. This is presumably due to the fact
that the quantity transported is increased, in order to maintain the quality of the
treated wastewater at the plants when the sludge thickening properties deteriorate
due to meteorological changes. It can also be seen that the VTS concentration is
lowest during the summer (around August) and highest during the winter (around
January). This trend is thought to stem from sludge decay that accelerates with the
rise in water temperature.

4-1-4.  Changes in sludge properties     *              

     As shown in Figure 4-1, the duration of time from  the start of sludge
transportation to the start of treatment at the Center is longer than one day for the
Midori plant, which is the remotest plant. Table 4-2 indicates  the change in sludge
properties during this time.

-------
            Table 4-2. Changes in Sludge Properties durftig Transportati
on

TS
VTS
SS
DS
Total nitrogen
Ammonia nitrogen
Total phosphorus
Total soluble phosphorus
Volatile organic acid
Total quantity at the five
wastewater plants (t/day)

92.2
69.5
89.3
2,90
6.26
0.47
1.23
0.15
3.20
Intake quantity at Hokubu
Sludge Treatment Center (t/day)

92.0
67.2
73.6
18.4
5.34
0.63
1.16
. 0.28
5.34
Rate of change (%)
(-)/X100
A 0.2
A3.3
A 27.6
534
A 14.7 , '
' 33.8
A 5. 7
84.0
66.9
                                                                          The
      In the course of transportation, the sludge decays and solids within it are
 increasingly dissolved and changed into solubles. As a result, the suspended solids'
 concentration declines and the dissolved solids concentration rises. Naturally, there
 is also a rise in the amount of organic acid, an indicator of the degree of decay
 Nitrogen and phosphorus  also dissolve, leading to a rise in the concentration of
 ammonia nitrogen and total soluble phosphorus.

      With this progressive decay of the sludge over time, the thickening property
 and characteristics of the. sludge deteriorate.  For this reason, great care must be
 taken in the operation and management of the centrifugal thickeners and other
 equipment used in centralized sludge treatment.

 4-2.  Operation record of the Hokubu Sludge Treatment Center

 4-2-1. Outline

     Table 4-3 presents the operation record of the Hokubu Sludge Treatment
 Center during fiscal year 1988. The entire quantity of sludge intake was subjected to
 the sequential process of centrifugal thickening, digestion, dewatering  and
 incineration. The uses of the gas generated during digestion greatly depend on the
 volume of gas generated and the operational status of the incineration facilities
 During fiscal year 1988, about 30 percent of this gas was used as auxiliary fuel for
 the incinerator; the remainder was used as fuel for the gas engine of the electrical
power generator.
                                    175  .

-------
     Table 4-3. Hokubu Sludge Treatment Center Operation Record (FY1988)

Sludge intake
Centrifugal thickeners
Digesters
Digested sludge
Sludge cake
Incineration
Incinerated ash
Digestion gas generated
Electrical power generated
Quantity treated "
1,606 X 103 m3/year
4,110-5,290 m3/D
(4,400)
1,793 X 103 m3/year
4,220-5,560 m3/D
(4,900)
560X103m3/year
1,100-5,650 m3/D
(1,530)
589Xl03m3/year
1,100-2,000 m3/D
(1,560)
76,826 tyear
130-270 t/D
(210)
83,280 t/year
170-360 t/D
(230)
15,270 t/year'
24-55 t/D
(41.8)
10,500 X103 Nm3/year
21400-37000 Nm3/D
(28,800)
13,362 kWh/year
23000-51800 kWh/D
(36,600)
TS (%)
1.4-3.0
(2.0)
1.6-2.3
(1.9)
4.2-6.2
(5.2)
2.6-4.0
(3.2)
18-24
(22)
."

.,"

VTS(%)
62-84
. (74)
64-83
(73)
63-84
(72)
60-65
(56)
50-67
(57)
"



              Note:* The difference between the quantity of sludge cake and the quantity
                  incinerated reflects the transport of sludge cake from other
                  wastewater treatment plants for incineration. Figures in parentheses
                  indicate averages.

4-2-2.  Operation of thickening facilities

     As noted in section 4-1-4, the sludge received ^at the Center is in a state of
advanced decay, which  would seriously lower the effectiveness of gravity-type
thickening.  As  a result, thickening is carried out employing a horizontal-type
continuous centrifugal thickener, after the sludge has been passed through a drum-
screen-type racks. The sludge TS concentration was in the range of 1.6-2.3 percent
before the thickening process and 4.2-6.2 percent after it.  the screenings separated
out through the mechanically cleaned bar racks (amounting to 860 tons for the year)
were first,dewatered using a screw press and,then transported by pneumatic
conveyors to the incinerator for incineration.

     Table 4-4 shows the quantity and TS and VTS concentrations of sludge treated
during fiscal year 1988.  Figure 4-4  presents monthly changes in centrifugal
thickenr operations.          "              .
                                    ,  176

-------
         Table 4-4.  Quantity Treated and TS and VTS Concentrations (FY1988)

Intake sludge
Thickened sludge
Quantity treated per day
(m3)
4,220-5,560
(4,910)
1,100-1,900
(1,530)
TS
(%)
1.6-2.3
(1.9)
4.2-6.2
(5.2)
 VTS
,(%)
64-83
(73)
63-84
(72)
  Fig. 4-4. Monthly Changes in Centrifugal Thickener Operations
o
iH
X

o
'55
   0)
   13
  g? 2
        4  5
                   8  9 10 11 12  1

                      Month
                                 2  3
                                           100
                                          80
                                          60
                                          40
                                              
                                           
                                           u
                                           to
                                           3
                                           'o
                                           CO
                                                      Legend
Intake sludge TS

Thickened sludge TS
Intake sludge VTS

Thickened sludge VTS

Solid capture rate

Rate of dosing
       ;  fC^   gal thickneners recorded an operation rate in the range of 64-84
 percent of ful capacity.  The centrifugal thickeners were operated mainly through
 dosing (chemical feeding), and the target capture rate for SS was 90 percent  In

 plantrtneS1raCte ^* ******  sent back to the wastewater treatment
 plants the rate of dosing with polymer coagulants was controlled appropriately in
 order to improve the properties of the effluent. The centrifugal effect" weir radius,
 and differential speed were adjusted in accordance with the TS concentration of the
 intake sludge The average values for centrifugal effect and differential speed were
 i,Ulb (j and 17.8 rpm, respectively.
tfc   i                                amUnt f intake slud^e' but the quantity of
thickened sludge remained fairly constant. As shown in Figure 4-4, there was 1 ttle

rrduor^nth  Ts;ncrratir f the intake siudge' but the Ws ^1
rose during the winter. Even when the rate of dosing with polymer coagulants was
increased, it was impossible to obtain a stable retrieval of solids during the winter
Ihe average solids capture rate for the year was about 83.3 percent. .
                                    177

-------
4-2-3.   Operation of digestion facilities

     The Center contains egg-shaped digestion tanks, each with a capacity of 6,800
cubicmeters. The tanks are organized in series of three tanks^each  D****
year 1988 two such series (six tanks) were used for anaerobic digestion. All tanks
function as primary tanks. The operation specifications were as follows: a digestion
temperature of 35 degrees centigrade, an average holding time of 27 days,  and an
a^mge ntakeTS concentration of 5.1 percent. For the operation method employed
^ere was high concentration and mesophilic digestion. The agitation was mecham-
X performed using a draft tube, and formed a downward flow within the tube. An
outline of the digesters and their operational conditions are shown in Table 4-5.

              Table 4-5. Outline of Digesters' Operation Condition
  Quantity of sludge
  withdrawn
  Quantity of sludge
  recycled

  Heating
   Agitator
                           Conditions
45
2m3/min

Recycled sludge heated by
means of warm water; the
warm water circulation
pump is started at 34.5C
and shut down at 36C.

400 rpm
         Comments

Automatic control within the
scope of liquid level change

 )ontinuous 24-hour operations
External heating using a heat
exchanger (heat source: waste
heat from gas engine)
 Continuous agitation in form of
 a downward flow within the
 tube; agitating intensity is
 3,000 m3/hr (10 times tank
 volume per day)
       All tanks were operated as primary tanks because of the poor solids-liquid
  separa  on in tL secondary digesters.  This  is probably due to the fact that
  settiab  ity of digested sludge was low and transferring the sludge from the primary
  Tthe secondary tanks,  and with drawing the  sludge out of the secondary tanks
  Its so frequently thai there is not enough time for the sludge to  stil .  And
  also the difference L temperatures of the sludge in the primary tanks and that of the
  secondary tanks is such that heat convection occurs.

       The  intake pump was  used to inject the  thickened sludge into the sludge
  circulation pipe, where it was mixed with the recycled sludge. The average daily
                                      178

-------
 intake  quantity per tank was about 256 m3, and the average quantity of sludge
 withdrawn per tank was about 260 m3 per day.  Scum generation has not been
 detected since the start of operation in September 1987. The average pH values and
 alkalinity within the digestion tanks were about 7.3 and 4,100 mg/1, respectively,
 with little variation.                         .      '   '

      Figure 4-5,4-6 show the monthly trend of digester operation indicators.

 Fig. 4-5. Monthly Trend of Digester Operation Indicators (I)
    . 4,000 r
     3,000
&

1
g-
0)

00
     2,000
     1,000
                    -1	1	'   I   '   '
            4  5  6   7  8  9 . 10  11 12  1  2  3
                        Month
                                                      Legend
                                                          . Intake sludge quantity
                                                           Digested sludge quantity.
                                                          -Intake sludge TS
                                                           Digested sludge TS
Fig. 4-6. Monthly Trend of Digester Operation Indicators (H)
      100
_g   80
 Crf  M
 II
 -*3  ctf
 I  a  60
    2hfl
    
 I "2
 S '  40
   >   20
   O
                                   '  *  . . i..
           4   567  89 10 11 12 12  3

                         Month
                                               40,000
                                               30,000
                                                    I
                                                    1
                                               10,000
                                                    0)
                                                    %
                                                    O
                                                           Legend
                                               20,000  a
                                                      O
                                                     "43  '
                                                                Intake sludge VTS
                                                                Digested sludge VTS
                                                                Solids reduction rate    *
                                                                Organic matter degradation rate
                                                                Gas generation quantity

-------
     As shown in Figure 4-5, 4-6, the trends of both the organic loading and the
intake sludge quantity- exhibit basically the  same patterns of decrease  in the
summer and increase in the winter.  Virtually the same patterns characterizes the
trends of the VTS concentration of intake and withdrawn sludge. By contrast, the
pattern for the TS concentration of intake and withdrawn sludge is one of increase in
the summer and decrease in the winterthe inverse of the VTS concentration
pattern.  The trends of the respective rates of solid reduction and organic  matter
degradation resemble those of VTS concentration. The trend of the quantity of
digestion gas generated resembles that of organic loading, and indicates  that a
sufficiently stable digestion was carried out at that load level.  Since all of the tanks
were operated as primary tanks without supernatant runoff, the quantity of intake
thickened sludge was almost the same as that of withdrawn sludge.
     Table 4-6 presents additional data for the operational record during fiscal year
1988.
                Table 4-6. Digesters' Operation Record for FY1988
Item
Quantity of thickened sludge intake (m3/day)
TS (%)
VTS(%)
Quantity of digested sludge (m3/day)
TS(%)
VTS(%)
Digestion period (number of days)
Digestion temperature (C)
Amount of heat used for heating (1,000 kcaVmS)
Volumetric loading (kgVTS/m3/day)
Solids reduction rate (%)
Digestion ratio (%)
Digestion gas generation quantity (Nm3/day)
Digestion gas generation rate (Nm3/kg-VTS)
Multiplier for digestion gas generation (Nm3/m3-day)
Operation record
1,100-1,900
(1,530)
4.2-6.2
(5.2)
63-84
(72)
1,100-2,000
(1,560)
2.6-4.0
- (3.2)
50-65
(56)
21-36
(27)
35.1-35.3
(35.1)
9.3-28.7
(18.2)
0.96-1.9
(1.4)
28-45 '
(37)
39-61
(51)
21,400-37,000
(28,800)
0.3-0.6
(0.5)
16.7-21.0
(18.7)
                Note: Figures in parentheses indicate yearly averages.
                                    180

-------
      Table 4-7 shows the composition of the  digestion gas.  Hydrogen sulfide
 .contained m the digestion gas was removed using a wet-type desulfurization unit in
 order to enable using it as a source of heat for the incinerator and a source of power
 tor the gas engine-driven power, generator.  The hydrogen sulfide concentration
 averaged 148 (30 - 600) ppm at the unit inlet and 0.9 (0 -12.5) ppm at the unit outlet.

  Table 4-7. Concentration of Digestion Gas Components
Constituent components
Methane
Carbon dioxide 
Hydrogen sulfide
Moisture
Concentration (v/v%)
59-62
34-37
30-600 ppm
2.3-3.2
 4-2-4. Operation of gas engine power generation facilities

     After the digestion gas was removed from the gas holder, a gas booster was
 used to raise its pressure to about 1 kilogram-force per square centimeter. In-this
 form, the gas was used as fuel for the gas engines driving power generators. The
 engines are water-cooled, 12-cylinder, boiling coolant gas models with a horsepower
 of 1,350 ps.  There are directly connected to the generators, which are triphase
 current synchronized models (920 kW,  50 Hz, 6.3 kV).  The generators constantly
 operated parallel with commercial power sources, and supplied a portion of the
 Center's power needs.  The  number  of generators in operation were regulated  in
 accordance with the quantity of digestion gas in the holding tank. The quantity of
digestion gas used for power generation and of the generated power are shown  in
Figure 4-7.

 Fig. 4-7. Monthly Trend of the  Quantity of Digestion Gas  Used for Power
          Generation and of the Generated Power
                                                     Legend
                                                     j|^ Generated electric power
                                                     E_J Purchased electric power
50,000
1
 40,000
Quantity of Electric Power (kV
1-  10 CO
p p o
o "o "o
_ o o o
o o o o







/
[







i




nn
tS
'







%
s







f





y-f
-,:






T"


!




'



* & 6 7 8 9 10 11





>






12
:".
v


1





m
I
^

2





7"
*
^

3
Month
                                   181

-------
     The daily average for the quantity of digestion gas used for power generation
was 21 300 Nm3, of the power so generated, the daily average was 43,000 kWh, and
of the power used for the auxiliary generator unit, this was 6,400 kWh. The effective
quantity of power generated (excluding the power required for  operation of the
auxiliary'unit)  averaged 36,600 kWh per day.  This figure represents  about 64
percent of the power used within the Center during the year in question.

     The lower calorific value of the digestion gas was 5,500 kcal/Nm3. The rate of
power generated was 31.5 percent of the amount of heat supplied to the gas engine
(26.8 percent when  the power consumed by the auxiliary unit is deducted).  The
generated power per digestion gas unit was 2.02 kWh/Nm3.

     The waste heat from the generator (contained in the cooling water for the
engine and in exhaust gas) was retrieved in the form of pressurized steam using a
heat exchanger (the steam temperature averaged 121 degrees centigrade).  The
quantity of heat retrieved was equivalent to about 35 percent of that supplied to the
gas  engine. The pressurized steam was used as a source of heat for warming the
digesters and for air conditioning.  The quantity of heat used for. heating the
digesters ranged from 12,000 to 51,000 Meal (averaged 28,000 Meal) per day; the
average utility rate was equivalent to 23.9 percent of the amount of calories supplied
to the gas engine. The calorific value for heating the digesters per unit volume of
intake sludge,  varied greatly depending on the season.  The respective  maximum
 and minimum values per cubic meter were 28.7 Meal (during March) and 9.3 Meal
 (during August); the average value was 17.7 Meal.

 4-2-5.  Operation of dewatering facilities

     After digestion, the sludge was dewatered using a horizontal-type continuous
 centrifugal dehydrator unit. The TS concentration of the digested sludge before
 dewatering ranged from 2.5 to 4.2 percent. The moisture content of the sludge cake
 ranged from 76 to 82 percent.  Table 4-8 shows 'the operational record of the
 dewatering process  and Figure 4-8, 4-9 shows the monthly trend of dewatering
 operation indicators.
              Table 4-8. Operational Record of Dewatering Processes

Digested sludge
Sludge cake
Daily handling
quantity
1,100-2,000 m3/day
(1,600)
130-270 t/day
(.210)
TS/
moisture content*
(%)
2.6-4.0
(3.2)
76-82*
(78)
VTS
(%)
50-65
(56) .
50-67
(57)
      Note- Figures in parentheses indicate yearly averages.
                                      182

-------
 Fig. 4-8. Monthly Changes in Dewatering Facilities Operations (I)
    o
    1-1
    X

    '
   11
      a
      p.-
     I
   '43 -w
   rt rt

   I!
   0> O
  . bo 4)
   T3 >-<
   r2 -3
   M 03
     '
  Fig. 4-8.


  200
  150
         100
  50
          0'	'	1
                                                             Legend
                                                         bo
                                                 -s
                                                  -
                                                  o
                                                  0)
    O
              4  5  6  7  8   9  10  11  12  1  2  3    

                             Month
                Digested sludge quantity
                Sludge cake quantity
                Sludge cake moisture content
                Solids capture rate
                Rate of dosing
Fig. 4-9.  Monthly Changes in Dewatering Facilities Operations (II)
    3
    s<
    3
    o
    02
100
 90
 80
 70
 60
 50
 40
 30
 20
 10
            -i	1__i	1   i   i
            4  5   6   7  8  9  10 11 12  1   2   3
                           Month
                                                           Legend
   s>
3  -a
   3
   Sw
   O
   $'
   03
2  tf
                                                      B
                                                           Digested sludge TS

                                                           Digested sludge VTS

                                                           Sludge cake VTS
                                                           Solids capture rate
                                                           Rate of dosing
                                         183

-------
     As shown in Figure 4-8, 4-9, there is a basic correlation between the trend of
the intake quantity of digested sludge and that of the sludge cake quantity; both
exhibit a decline in summer. By contrast, the trend of TS concentration of digested
sludge declines in winter. However, the trends of the VTS concentration of digested
sludge and sludge cake both show an increase in winter.

     This decline in TS concentration and rise in VTS concentration during winter
is presumed to be the cause of the rise in the sludge cake moisture content and
decline in the solids retrieval rate during the same season. There is a close correla-
tion between the trend of the sludge cake moisture content and that of the. digested
sludge VTS concentration. When the VTS concentration was high, it proved difficult
to maintain the moisture contents on a constant level even when the dosage was
increased.

     The annual average values for the solids capture rate and of dosage were about
90 percent and 1.06 percent per solid, respectively.

4-2-6. Operation of incineration facilities

      The sludge cake generated at the Center was incinerated along with the sludge
 cake transported from the city's wastewater treatment plants. Incineration facilities
 consist of the incinerator proper (an erect hollow cylindrical structure), a sludge cake
 feeder, cake drier, heat recovery unit, and an exhaust gas treatment unit.  The
 incinerators proper-fluidized bed furnaces-are made of fire-resistant brick  and
 castable materials, which are lined on the outside with a steel sheet shell.

      The ash resulting from incineration is composed of small particles with a
 diameter ranging from  about 50 to 300 microns. The  ash was removed  from  the
 incinerator along with the combustion gas and collected by cyclone separators and
 electrostatic precipitators. The collected ash was moisturized and then disposed of in
 industrial waste disposal sites within the city.

      The quantity of sludge cake fed into the incinerator was  maintained ori a
 constant level. The incinerator was supplied with additional heat using auxiliary
 fuels in order to assure a temperature of about 800C on top of the fluidized bed. The
 incinerator construction proceeded in a sequence (Nos. 1 through 3), and the thermal
  efficiency rises in correspondance with the newness of the incinerator in  question,
  due to the advanced heat recovery.  Table 4-9 shows the respective modes of incinera-
.  tion, heat recovery, and exhaust gas treatment adopted for each.
                                       184

-------
   Table 4-9. Modes of Incineration, Heat Recovery, and Exhaust Gas Treatment for
               Each Incinerator
  Mode of
  incineration
  Auxiliary fuel
  Heat recovery
  Mode of exhaust
  gas treatment

  SO* treatment

  NO* treatment


  Smoke and dust
  reatment
 Fluidized bed incinerator
Pulverized coal, kerosene
Heating of air for fluidization,
waste heat boiler
 3aCO3-based dry desulfurization
 iontrol of internal temperature
and combustion air ratio

Cyclone separator, electrostatic
>recipitator
 Fluidized bed incinerator

 ""                   
 Pulverized coal, kerosene,
 digestion gas
                                           Heating of air for fluidization,
                                           waste heat boiler
                           Heating of air for fluidization,
                           heating of heat medium oil used
 1aCO3-based dry desulfurization
Control of internal temperature
and combustion air ratio

 lyclone separator, electrostatic
>recipitator
 Fluidized bed incinerator (with
 drier)

 Digestion gas, city gas
                                                      NaOH-based wet desulfurization
 :ontrol of internal temperature
and .combustion air ratio

 Cyclone separator, electrostatic
 irecipitator
1 n f     mTTIT1 peration centered around the No. 3 incinerator (capacity of
150 tons per day) offers the best thermal efficiency. Table 4-10 and Figure 410 show
the record of operation and monthly trend of the quantity of sludge cake incinerated,
                                                                                               ^


                  Table 4-10. Incinerator Operation Record (FY1988)

No. 1 incinerator
No. 2 incinerator
No. 3 incinerator
Total
Number of
days in
operation
151
259
297
 ._
Annual quantity of
sludge cake
incinerated
14,510 t/year
24,850 t/year
43,820 t/year
	  	 	 	
83,180 t/year
Annual quantity of
incinerated ash (with
30% moisturization)
3,430 t/year
5,110 t/year
6,730 t/year
15,270 t/year
                                            185

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Fig. 4-10. Monthly Trend of Quantity of Sludge Cake Incinerated
1
 I
 I
 faD
Legend  .
    No. 1 incinerator
HI No. 2 incinerator
    No. 3 incinerator
                                  Month
      The incinerators were operated in accordance with quarterly plans formulated
 on the basis of estimates of the sludge cake quantity to be generated during the
 quarter in question. This enabled each incinerator to  operate continuously for at
 least one month. Repair work was scheduled to coincide with the legally stipulated
 boiler inspection (once annually) and conducted intensively along with preventive
 maintenance work. The repair periods, each lasting about one month, were May-
 June for the No. 1 incinerator, February for the No,. 2 incinerator, and November-
 December for the No. 3 incinerator.

 4-3. Treatment of sidestreams from the sludge treatment facilities

 4-3-4.  Properties of sidestreams

      Figure 4-11 shows the sources  of sidestreams out in the sludge treatment
 process, and Table 4-11, the related quantities and quality.
                                       186

-------
  Fig. 4-11 Sources of Sidestreams
  Intake

  sludge
       J   fn
'hickening Centrifugal
  4-n-nl*  I  ^1.1-   ^     :
tank
  - KanagawaWTP
          I
                                 I
Digester
                                 Centrifugal  Incinerator
                              Thickner effluent
                            Sidestreams receiving tank
                                    (4)
denydrat
1
D
	 j
Dr"

Filtrate 
? tank

, *

\
Scrul
[ Hokubu No. 2 WTP
    Table 4-11. Quantities and Quality of Sidestreams by Source (actual, FY1988)
  OD-Mn (mg/1)
  

 BOD (mg/1)
Note: The quantity for number three Was calculated as  - ( +).
                                    187

-------
     The sidestream sources are centrifugal thickeners, centrifugal dehydrators,
scrubber drains and others.   During fiscal year  1988, the first three sources
accounted for 91 percent of the entire quantity of sidestreams. The single greatest
source was thickener effluent, which accounted for about 45 P^* a*^?X the
can also be noted that the quantity of the central** relatively .high compared to the
conventional-type sludge treatment system. This is due to the fact that the Center
does not remove supernatant during digestion, meaning that the entire quantity
undergoes the dewatering process.

     As shown in Table 4-11, the concentrations  of the thickener effluent are
extremely high in virtually every category of water quality   Regging ritrogen,
however, the centrate concentration (SBOmg/1) is higher than that of me tmcKener
effluent (360 mg/1).  This is because the nitrogen compound is decomposed during
digestion and ammonia is present in the centrate.

    ' Table 4-12 presents the calculation results (based on the above data) of the
sidestreams loading for each category. In virtually  all categories, the percentage of
the total load occupied by thickener effluent is extremely high, from 75 to 90 percent.
     As these percentages suggest, this is the source of the bulk of the sidestreams
load. An exception is in relation to nitrogen, where the centrate accounts fl>r just over
50 percent of the entire load. Since the thickener effluent accounts for another 40
percent these two taken together account for over 90 percent of the total load m this
category. By contrast, scrubber drains account for only a few percentage points of
the entire load in every category, with the exception of TS.

                  Table 4-12.  Composition of Sidestreams' Loads
Classification
Sidestreams
TS
VTS
SS
COD-Mn
BOD
Nitrogen
Phospho

rus
Thickened effluent
(t/day)
13.5
9.6
6.9
4.1
9.0
1.2
0.26
(%)
75
91
87
85
84
 40
76
Centrate
(t/day)
1.8
0.63
0.12
0.24
0.11
1.7
0.07
(%)
10
6
2
5
1
53
21
Other processes
(t/day)
0.2
0.01
0.9
0.4
1.6
0.1
0.01
(%)
2
1
11
9
15
3
3
Scrubber drains
(t/day)
2.4
0.23
0.01
0.06
0.03
0.13
0
(%)'
13
2
0
1
0
4
0
Total
(t/day)
17.9
10.5
7.9
4.8
10.7
3.0
0.34
(%)
100
100
100
100
100
100
100
      For the time being, the Center has been sending the sidestreams (thickener
  effluent filtrate, and miscellaneous drainage) to three wastewater plants (Hokubu
  No.l, Hokubu No. 2, and Kanagawa), where  they are mixed with  wastewater
                                       188

-------
influent and treated. Since scrubber drains account for only a small load (as noted
above) they are not distributed among these three plants.  Instead, it is sent
separately from the other fluids to the Hokubu No. 2 plant (see Figure 4-11). The
distribution ratio of the sidestreams among the three plants in the aforementioned
order was 3:1:6.

     Although the system is only temporary, the Center is currently sending side-
streams out in the course of sludge treatment to the wastewater treatment plants. It
strictly controls the quality of the separated fluid, analyzing it at least threejimes
per week.  A major focus in water quality management is proper operation of the
centrifugal thickener, since thickener effluent accounts for the bulk of  the
sidestream load.               \

4-3-2.  Impact of sidestreams on wastewater treatment

(1)  Treatment properties of sidestreams

     In order to  ascertain the treatment  properties of sidestreams, the Center
conducted gravitational sedimentation tests and biodegradability  tests on it.
Concerning SS, COD, and BOD, the removal  rate by gravitational sedimentation
was low (below 35 percent).  Since the removal rate of SS and BOD in primary
treatment of ordinary influent is generally in excess of 50 percent, this suggests that
the sidestreams contained a large quantity of substances (e.g., coloids) that have low
settleability.

     Similarly, the biodegradability of sidestreams was also found to be low.  The
degree of biodegrada'tion  over a 24-hour period in the case of ordinary municipal
wastewater was in excess of 90 percent for BOD and 70 percent for COD. In the case
of sidestreams, however,  the  respective figures were 61 percent for BOD  and 43
percent for COD after four hours, and 81 and 43 percent .after twenty-four hours.
These figures also indicate the difficulty of treating sidestreams.

(2)  Impact of sidestreams on  waste water treatment

     Table 4-13 shows the share of the total wastewater inflow for  the three
wastewater treatment plants receiving sidestreams from the Center (actual shares
for fiscal year 1988).                               .     .

     Although sidestreams account for only 1.3 percent of the total quantity of water
treated at the plants, they are  the source of an extremely high share of the SS loads
(13 percent), BOD (18 percent), and nitrogen (24 percent).  Regarding quality,
sidestreams contain many ingredients that cannot easily  be  removed through
sedimentation or activated sludge treatment.
                                    189

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                 Table 4-13. Sidestreams' Share of Total Loads

Water quantity
(m3/day)
SS(t/day)
BOD (t/day)
COD (t/day)
Nitrogen (t/day)
Phosphorus (t/day)
Sidestreams

5,730
7.5
11
4.3
2.9
0.43
Total influent at
theSWTPs
442,000
57
61
34
12
1.6
Share
(-e-@)X100
1.3
13
18 
13
24
27
     Table 4-14  supplies estimates of the  extent to which water quality
improvement would be made at the three plants now receiving the sidestreams if
they were no longer receiving this.

     In terms of the average value for the three plants, sidestreams account for an
estimated 42 percent of the BOD, 42 percent  of the COD, and 34 percent of the
nitrogen of the respective secondary effluent load. When this amount is added, the
effect on BOD is  even  greater.  Furthermore,  the figures are estimates based on
annual averages; the  sidestreams' impact  would  presumably increase if the
treatability declines due to the decreased water temperature during winter or the
deterioration state of activated sludge.

     At present, no particular problems are experienced at the plants, in. part,
because the pumping  time and distribution  ratio  among the three plants are
adjusted in accordance with the treatment situation at each plant.
                                             
       Table 4-14. Impact of Sidestreams on Waste water Treatment Plants
Item
BOD
COD (Mn)
Nitrogen
WTP
Hokubu No, 1
Hokubu No. 2
Kanagawa
Average
Hokubu No. 1
Hokubu No. 2
Kanagawa
Average
Hokubu No. 1
Hokubu No. 2
Kanagawa
Average
Treated water
 quality

12
12
19
16
11
11
12
12
15
16
17
16
Sidestreams' shares of
treated water

7.4
5.0
6.7
6.7
5.6
3.8
5.1
5.1
6.1
4.1
5.5
5.5
Separated fluids
. impact (%)
@/XlOO
62 /
42
35
42
51
34 ,
42
42
41
26
32
34
           Note: (1) = actual FY1988 figures: average figures are weighted averages.
                                    190

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 4-4.  Environmental pollution control

 4-4-1.  Background and regulations pertaining to pollution control

      Japan's fast-paced economic development during the postwar period was
 accompanied by an ever worsening environmental pollution resulting from the smoke
 and wastewater discharged by factories and other sources. The pollution eventually
 began  to affect local  communities, stimulating campaigns aimed at winning
 compensation through litigation for those whose health had been affected by it.

      Structuring a regulatory framework to prevent such health  problems began
 with the enactment of the Basdic Law for Environmental Pollution  Control in 1967.
 This law was followed in 1968 by the Air Pollution Control Law (amended most
 recently in 1974) and by regulations pertaining to the enforcement  of the same law,
 and then in 1978 by pollution control bylaws enacted by Kanagawa Prefecture. For
 its part, in  1975, the City of Yokohama devised general plans for administrative
 guideance to curtail the release of SOX, soot and dust and in 1977 of NOX.

      Several laws related to aid for  pollution victims were also enacted.  The
 Pollution-related Health Problem Compensation Law, which was enacted in October
 1973, has played a major role  in providing aid for those suffering  with  health
 problems stemming from pollution.  Revised in  September 1987,  when  it was
 retitled: Law Concerning Compensation and Other Matters Pertaining to Pollution-
 related Health Problems.  This law provides for the  cancellation of so-called first-
 class regions in the event of violation and allows for projects to be carried out
 pertaining to the prevention of health hazards, funded by endowments created for
 that purpose. In accordance with this law, the Center pays pollution load charges as
 well, commensurate with its total quantity of SO* discharged.

     In all,  discharge of soot and dust,  SO* , and NO* are regulated by the Air
Pollution Control Law and pollution control bylaws. The Air Pollution Control Law
contains specific regulations concerning the permissible concentrations of SO* and
NO*. The total quantity of such pollutants is regulated by this law and by pollution
prevention bylaws and regulations.
                                                             5      "
     Industrial waste is regulated by the Waste Disposal and Public  Cleansing Law.
The main sources of industrial waste generated by the Center are incinerated ash,
ash removed from the cyclone separators and electrostatic precipitators.

     The Center's modes of treatment for the substances covered by antipollution
regulations are as follows:   >.     '

     Soot and dust:    Removal by cyclone separators and electrostatic
                     precipitators
                                    191

-------
     SO*:
Desulfurization in exhaust gas treatment units (removal of
S0;e by showering with a caustic soda solvent)
     NO*:
Curtailment of generation through low-oxygen combustion
     Incinerated ash:  Disposal in inland landfill sites after boosting moisture
                     content to 30 percent, to prevent scattering

     Subrubber drain: Treatment with influent wastewater at wastewater
                     treatment plants

     Figure 4-12 shows the flow sheet of Exhaust Gas Treatment Facilities.

 Fig. 4-12. Outline of the Flow of Exhaust Gas Treatment Facilities

Incinerator
re

Waste heat | _^
cdvery facilities
Curtailment of

Cyclone
separator
Desooting

_>Electrostatic_>| Smoke | ^
precipitator treatment unit
Chimney
Removal of SO*
     generation
4-4-2.  Discharge of SO*, NO*, and soot and dust

     Table 4-15 shows the pollutant concentrations and exhaust gas quantities
generated by each incinerator during fiscal year 1988.
 Table 4-15. Concentration of Pollutants Within Incinerator Exhaust Gas
Place of measurement
EP outlet of No. 1
incinerator
EP outlet No.2
incinerator
Treatment unit outlet
of No. 3 incinerator
SO.x concentration
(ppm)
19-39
<5~41
<15~19
NOX concentration
, (pPm)
16-35
34-56
<10~15
Soot concentration
(g/Nm3)
0.018-0.039
0.018-0.039
0.001-0.002
Exhaust gas quantity
(1000 Nm3/hr)
15-17.7
9.2-15.7
10.5-12.5
 Note: The 02 conversion factor for the SO* and NO* concentration was 12 percent.                   "

     As noted in the previous section, SOX and NOX are regulated in terms of the
entire quantity, and soot and dust are regulated in terms of the discharge
concentration. The regulation standards and the maximum discharge levels
recorded during the year in question are shown in Table 4-16.

                                    192

-------
             Table 4-16 Pollutant Regulation Standards and Center Discharge Levels


                      Maximum quantity of SOX
  No. 1 incinerator

  No. 2 incinerator

  No. 3 incinerator

         Total.
                         discharge (Nm3/hr)
 Note: Soot and dust discharge is regulated with reference to concentration.
 Maximum quantity of
NO* discharge (Nm3/hr)
                                                                Soot and dust
                                                                concentration
                                                                  (g/Nm3)
4-4-3.  Odor countermeasures

     Regulatory standards concerning offensive odors as contained in the national
Offensive Odor Control Law and in the City of Yokohama's regulation '
permissible concentrations (Ppm) for eight types of malodorous Lbrt
are also odor concentration standards contained in the city's provisional
tive guidelines concerning malodor countermeasures. The "odor c^nt        s
based on the  odor perceptible .by the human olfacotry sense.  It is expressed as a

                       " to                                               a
      Table 4-17 shows the regulatory standards for the eight types of malodorous
 substances on the boundary line of the Center, which is located in lTtu2ve

           dTff     " ^ PrSPeCtS ^ 10WerIng the o^r eoncentrat"rugh
           1   r? T uncertain> the actu^l deodorization unit design aims for a
        at the odor discharge outlet that is lower than the standards at the
 boundary, for both material and odor concentration.                 ^ne.

     The main malodorous substances of concern at the Center are four
 related-substances:  hydrogen sulfide, methyl  mercaptan, methyl suS

 "tf yTr s seh Tht re:rctive;oncentrations vary ^^ **^
 site   This is shown by the readings for  one of the most typical malodorous
 substances-hydrogen sulfide.  The readings (material and odor  coc
respectively) were  3  ppm and 10,000- 40,000 at the sludge intake a
thickening tank, and  40 ppm and about 100,000 at the centrifugal thickener
                                                                       and
                                   193

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             Table 4-17. Malodorous Substance Standards and Actual Data
Malodorous substances
Hydrogen sulfide (ppm)
Methyl mercaptan
(ppm)
Methyl sulfide (ppm)
Methyl disulfide (ppm)
Ammonia (ppm)
Trimethylamine (ppm)
Acetaldehyde (ppm)
Styrene (ppm)
Odor concentration
Note: Figures with an as
to nlrs and other de
Regulatory
standards (at
premise boundary)
0.02
0.002
0:01
0.009
1
0.005
0.05
0.4
32
Base odor level*
2.06
2.554
0.145
0.068
0.4
	
	
  
23700
Odor level at outlet of
deodorization ,
facilities* .
" 0.0003
0.0049
0.0341
0.025
0



208
terisk indicate an average of four readings taken at sludge thicfcenmg
odorization facilities during fiscal years 1986 and 198 /.
     Efforts are made to completely seal the sources generating offensive odors  and
steps are taken to reduce the deodorization airflow.  In addition  leakage of odors
from such facilities is prevented  by absorbtion. of odors and by maintaining a
negative pressure within them! The deodorization airflow varies depending on the
location; facilities are ventilated anywhere from once to ten times per hour.

     The centralized treatment of sludge has enabled resolution of the problem of
odor transmission to communities in the vicinity of wastewater treatment plants  It
has also enabled centralized treatment of the generated odors  The Center s mam
mode of deodorization is soil deodorization, which also  provides an effetive use of
natural tracts. It is incorporating countermeasures for odors with a high concentra-
tion (50,000 or more) in its plans for pretreatment facilities.
                                      194

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  5.   Effects of centralized treatment

  5-1.  Effective use of energy

       There  are various methods of sludge treatment, ea.ch with their  own
  advantages and disadvantages.  The type of process adopted will depend on the
  disposal method and the purpose. This section presents an account of the effects of
  the sludge treatment process adopted at the Center, based on actual operations for
  fiscal year 1988, focusing on the use of energy, the energy balance, and on
  comparisons with other plants.

  5-1-1. Energy use                                                 '

       One of the  major objectives of tne process adopted by the Center involved both
  the recovery and effective use of the latent energy harbored by sludge  The unit
  processes which make up centralized treatment are organically integrated during
  implementation. The overall flow of energy use and the proportions occupied by each
  process are shown in Figure 5-1 and Table 5-1, respectively.  The  processes in
  question are all those intermediate to and  included in  the  sludge intake  and
 ' incineration processes.

      As shown in Table 5-1, the use of energy by process varies considerably
 depending on whether the focus is electrical power or fuel.  As such, figures for
 electrical power were converted into calories to indicate the total quantity of energy
 use.  It can  be  seen that sludge transportation, centrifugal thickening  and
 dewatermg each account for less than  2 percent of this total.  By contrast  the
 respective percentages occupied by digestion and incineration are roughly 5- and 30-
 fold that level. Incineration fuel accounts for about 50 percent of the total quantity
 of energy use.

     Table 5-1 also takes into account the energy recovered as digestion gas in  the
 centrifugal thickening, digestion, and gas engine generation processes, which form
 the nucleus of the entire treatment process.  These three processes can basically be
.regarded as yielding a positive net energy.  Collectively, these three processes
 generated about  59,000 Meal per day of surplus energy, which can be effectively
 utilized for other uses.                           '  .        .         *
                                     195

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       Fig. 5-1.   Overall Flow of Energy Use
        ,	Sludge-,
        transportation
                       I Sludge sending    t

                                Power supply
                       I
Sludge intake
-.Centrifugal-,
thickening 1
^
Thickene
sludge
      Dewateringunit|
              Commercial power source
                                       Digestion gas.
 Sludge

> Digestion gas

 Electric power
 and other
                                                Gas engine
                                             power generation
                                                     Purchased fuel
                                Sludge cake
             Table 5-1. Allotment of Energy Use by Process


Sludge
transportation
Centrifugal
thickening
Digestion
Gas engine *
power generation
Dewatering
Incineration
Total
Electrical power (kWh/d)
Quantity
used
6,503
(9.8%)
8,432
(12.7%)
7,063
(10.6%)
6',352
(9.6%)
7,855
(11.8%)
30,207
(45.5%)
66,412
(100%)
Quantity used
quantity generated!)
6,503
8,432,
7,063
-36,632
, 7,855
30,207
23,428
Fuel (Mcal/d)
Quantity
used
0
(0%)
0
(0%)
28,079
(7.9%)
117,282
(33.2%)
0
(0%)
207,992
(58.9%)
353,353
(100%)
Quantity used
quantity generated!)
0
0
-130,123
89,203
0
207,992
167,072
Quantity of energy use (Mcal/d)
 +
5,593
(1.4%)
7,252 .
(1.8%)
34,153
(8.3%)
122,745
(29.9%)
6,755
(1.6%)
233,970
(57.0%)
410,468
(100%)
+ 
5,593
7,252
-124,049
57,699
6,755
233,970
187,220
                                    tity generated indicate the difference after the deduction of electrical
                                5 generated by each process from the amount of electrical and thermal Uuel)
   energy (or equivalent) which each used.
2.  Figures in parentheses indicate percentages of total.

                                          196

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 5-1-2.
Unit process energy balance and unit energy consumption
                                K^^vtgt, it is possible to reduce the
^s:i:sj~~?=H?F=d"-"

        Table 5-2. Units of Treatment Energy Use in Each Process
I   		-	
[Sludge transportation
f	"	
Centrifugal thickening
Digestii
Gas engine power
I generation 2)
	~	.
Dewatering
	  	
Incineration (No. 3) 3)
Treated sludge
quantity
DSt/d

Quantity of electrical
power use
kWh/d

Quantity of fuel
use
Mcal/d

Consumption
units of electrical
power
kWh/DSt
Consumption
units of thermal
power
Mcal/DSt
92^0 KK/VJ 1 ' 	  I" 	 1 	 .
             92.0
             78.0
             (21,324)
             50.0
             33.3
                 8,432
                 7,063
                (36,632)
                7,855
                15,967
28,079 1)
                            Total: 24,591
                            Gas:  21,283
70.7
91.7
90.6
(1.72)
        157
        479
                 360
                                        1:  738
                                      3as: 639
                                      qu""ly f


-------
"owmraton fedlities  Therefore, these three processes must always funcbon

as a unit.
     The energy balances of the digesters, gas engine generation facilities,  and
incineration facilities are described below.

(1)  Energy balance of digesters

      Figure 5-2 shows the energy balance of the digesters.


                  Fig. 5-2.  Energy Balance of Digesters

                  Quantity of heat used for warming          .
                  28,079 (Mcayd)    Electrical power use quantity
    (8.6%)
                                    7,063 (kWh/d)
                                    6,074 (Mcal/d)
                                    (1.9%)
                     1,
                     290,500(Mcayd)(89.5%)
                   . _ .V4..  v
       (Digestion tank facilities)
                     Digestion gas generated
                          158,S
                          (48.7%)
                                             (35C)
                                             161 ,025 (Mcayd)
                                             (49.6%)
Sludge :  5, 000 Meal /VS- ton
Digestion gas : 5,500 kcayNmS
                                             Loss 5j426 (Mcal/d) (1.7%)
           shown in Figure 5-
                                               half of the intake sludge calories are
  used for warming).

  (2)   Energy balance of gas engine power generation facilities
   power generation facilities.
   r     '
                                           198

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                 Table 5-3. Energy Use in Power Generation Facilities
Year/
month
'88/4
'88/5
'88/6
'88/7
'88/8
'88/9
'88/10
'88/11
'88/12
'89/1
'89/2
'89/3
Average
Note: Ilnrf
Quantity of
digestion gas
generated
Nm3/d
32,565
31,810
28,013
25,262
23,352
23,313
24,923
29,440
31,140
31,510
32,210
31,530
28,764
(100%)
Digestion gas use quantity
Incinerator
Nm3/d
9,919
11,090
7,675
3,464
4,021
9,265
7,426
7,480
7,720
10,060
3,180
7,980
7,440
<24.9%)
Gas engine generation
facilities
Nm3/d.
22,647
20,720
20,338
21,798
19,331
14,049
17,497
21,960
23,420
21,450
29,030
23,650
.21,324
(74.1%)
Mcal/d
124,557
113,960
111,861
119,889
106,320
77,268
96,234
120,780
128,810
117,975
159,665
130,075
117,283
Gas engine generation facilities
 Quantity
of power
generation
kWh/d
45,694
42,059
41,124
44,175
37,809
28,000
34,619
43,920
47,630
43,610
59,370
47,790
42,984
 Quantity
of power used
kWh/d
6,343
6,093
6,287
6,583
6,871
6,070
5,835
6,410
6,580
5,980
7,560
6,610
6,352
-l)
kWh/d
39,351
35,966
34,837
37,592
30,938
2,930
28,784
37,510'
41,050
37,630
51,810
41,180
36,632
Quantity of
heat used for
warming
digesters
Mcal/d
31,187
22,794
17,765
16,488
12,035
17,264
19,591
30,210
36,450
42,885
39,696
50,583
28,079
      A major factor in the fluctuation of the digestion gas quantity generated
reflects the change in the quantity of organic substances contained in the thickened
sludge.  For the year in question, this latter quantity ranged from a maximum of
about 70 tons (in February) to a minimum of about 50 tons (in September)  and
averaged about 58 tons.  There was a close correlation between this quantity and
that of the dige'stion gas.

      Figure 5-3 shows the balance of energy  in  the gas engine power generation
facilities.

       Fig. 5-3.  Energy Balance of Gas Engine Power Generation Facilities
                                          Effective quantity of power generated
           Power consumed by auxiliary equipment     ^--~\     36,632 (kWh/day)
           Krt(iW^ay!,     ^-.	^1       r   31>504 (Meal/day) (26.9%)
           5,463(Meal/day) (4 &%\/^_
                                        D
                       	__  Total power output
            Quantity of digestion gas use  42,983 (kWh/day)
            (100%)
            (Gas engine generation facilities).
                                         Heating of digesters
                                         28,079 (Mcal/d) (23.9%)
                                     Air-conditioning and heating
                                     12,916 (Mcal/d) (11.0%)
                                            ?.
                                          [uantity not retrieved
                                          4,128 (Mcal/d) (12.0%)
                             Loss 30,652(Mcal/d) (25.9%)
                                        199

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     The generative efficiency obtained from the effective quantity of power
generated amounted to 26.9 percent, but the efficiency of the generator itself was
31 5 percent. The digester's heating needs were met using about one-fourth of the
digestion gas supplied  to the generation facilities.  A certain quantity of energy
(expressed in terms of calories in the figure) was not retrieved, only because  an
effective use for this energy was lacking.  However, this quantity can be effectively
utilized.
(3)   Energy balance of incineration facilities
     As noted in previous sections, the Center operates three incinerators. The first
two (No. 1 and No. 2) began operation before the digesters did, The No. 2 incinerator
can use  both digestion gas and other types of .auxiliary fuel, but the No. 1
incinerator, which is  the oldest, cannot use digestion gas.  By contrast, the No. 3
incinerator, which is the newest, was basically designed to use digestion gas.

     Table  5-4 shows the specific differences among the incinerators regarding
energy use.                                    
                    Table 5-4. Energy Balance of Incinerators
Incinerator
(No.)
No.l
No. 2
No. 3
Sludge incinerated
quantity 
(DSt/d)
22.7
21.3
33.3
Incinerated
ash quantity
(DSt/d)
17.5
15.2 -
17.4
Quantity of energy use
Electrical
power
(kWh/d)
6,191
8,048
15,967
Auxiliary fuel (Mcal/d)
Digestion
gas
0
28,986
21,283
Other auxiliary
fuels
 . 	 	  - 	
62,480
. 49,496
3,308
Subtotal
62,480
78,482
24,591

 Total
(Mcal/d)
67,804
85,403
38,322
/
(Mcal/DSt)
2,987
4,010
1,151
      As  shown in Table  5-4, the  No. 3  incinerator has the lowest energy
 consumption units per DS  tons, and digestion gas can be used to meet about, 87
 percent of its auxiliary fuel needs. In view of this advantage, which suggest that
 incinerators of the No. 3 type will constitute the main mode of incineration in future
 centralized sludge treatment, it was decided to base the consumption units for
 incineration on the values for the No. 3 incinerator for the following discussion.

 5-1-3. Energy balance comparison with other processes

       The aforementioned findings provide the basis for Figure 5-4, which shows the
 energy balance per unit of solids received for treatment at the Center. For  the
 purposes of comparison, calculations were  also made of the energy balance in the
 conventional digestion/incineration process in which a boiler is used to warm the
 tank and effect separation of supernatant and calculations were also made in raw
 sludge dewatering/incineration processes.  In these calculation, the values applied
 for the various units are  based  on  the actual  figures obtained in the Center s
  operation,  with the exception of the  units  for digesters in the conventional
  digestion/incineration process, which are nationwide averages for fiscal year 1986.
                                      200

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                            *"
                                                                             the three above-'
               Fig. 5-4.   Energy Balance per Unit of Treated Solids at the Center
                                           (No. 3 Incinerator)
                 Fuel-
                         .50Mcal
                                                               Commercial electric power
                                                                    134 kWh
                                                                    (24%)


                                                                     *	Fuel and other
                                                                     <    Sludge

                                                                     -3-=- Electric power

                                                                     1    Digestion gas
                                                           Air-conditioning and
                                                           beatingsystems

                                                           562 Meal
                                                           Loss
                        Table 5-5. Energy Balance Comparison
                                U) Digestion/incineration
                                                         Conventional
                                 process in Yokohama
                                                     digestion/incineration
                                                                        dewatering/incinera
                                (Centralized treatment)
Treated sludge quantity
Total energy use
  Electrical power
  Fuel
                         kWh
                         Meal
  Total (in terms of calories) |Mcal

Outside energy introduced
  Electrical power
  Fuel
  Total (in terms of calories)
     ,
                                         201

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     The figures for total energy use reveal that processes (1) and (2) require about
the sa^ne amount of energy for treatment (expressed in terms of calones),but ti
nrocess (3) requires only about one-fourth the energy that processes (1) and (2) do. In
Sis respect process (3) is the most advantageous.  (The calculate for process (3)
SsuSeralgeneouscombustionbacauseitexcludedthedigestaonprocess.)
     TTnwever  process (1) is the most advantageous in respect to outside energy
introotTwherTiSQuantities for processes (2) and (3) are virtually the same. The


ippufddtcttyIn'order to heat the tanks, which rule out the install of power
generation facilities fueled by this gas.
      Process (1) is clearly superior, in view of the fact that it offers energy retrieval
 in the form of both electrical power through power generation using the digestion
 gas aJidTermal power for heating the digesters using the generaUon umt exhaust
 heat.
 5-2. Construction costs
 5-2-1. Hokubu Sludge Treatment Center construction costs
       Table 5-6 shows  the composite construction costs for  the Hokubu Sludge
 Treatment Center by unit process.
           Table 5-6.  Hokubu Sludge Treatment Center Construction Costs
                         Facility

           Sludge intake
           Gravity thickening
           Centrifugal thickening
           Digestion
           Dewatering
           Digestion gas power generation
           Incineration
           Other facilities
Construction costs
 (millions of yen)
      1,330
      1,770
      2,590
      10,490
      2,440
      3,270
      12,990
       7,340
      42,220
                                       202

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 5-2-2.  Comparison: of the construction cost

      It is not possible to make a fair comparison of the construction costs for
 centralized treatment and the conventional method because of the differences in the
 processes themselves and the level of technological development involved.
 Nonetheless, the following may be presented as relevant data calculated on the basis
 of the next three points:

 1)    The evaluation is  based on .a comparison with the Kohoku Wastewater
      Treatment Plant.  This comparison was used because the sludge treatment
      process varies from plant to plant, and the main process of the Kohoku plant
      closely resembles the process at the Center.   -         .

 2)    The process sequence that is the subject of comparison is thickening, digestion,
      dewatering and gas power generation; incineration is not included.

 3)    The cost of land acquisition was not taken into consideration.

      Following is the evaluation method that was employed.  First, a calculation
 was made of the construction costs per  unit  of treatment capacity in each unit
.process, at the Kohoku WTP and the Center. These figures were then totaled. Next,
 the cost of the facilities at Kohoku WTP (conventional decentralized treatment) was
 adjusted to  reflect the rise in prices.  Also, the construction cost of facilities
 associated with  sludge transportation were added into the total for the. Center
 (centralized treatment facilities). The two  figures were then compared.  The
 procedures and results are shown in Table 5-7.

    Table 5-7. Comparison of Construction Costs of Sludge Treatment Facilities


Unit construction costs
Thickening
Digestion
Dewatering
Other.processes
Gas power generation
Subtotal
Deflator
Sludge transportation
facilities
Total construction costs
Conventional treatment
system

6,100
51,810
91,430
7,270
	
156,610
1.440
	
225,520
Centralized treatment
system

39,660
78,280
34,130
17,630 .
42,280
212.-520
rT ^
26,530
239,050
      Note: The deflator is the price increase ratio between 1975-1985.
                                    203

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     It can be seen that the unit construction costs for centralized treatment are
about 6 percent higher than those of a conventional treatment system.  This
difference is due to the inclusion of gas power generation and environmental
protection facilities in the centralized treatment facilities.   If comapred  after
removing the gas power generation facilities' expenses to equalize conditions with
decentralized treatment, the construction costs for centralized treatment are about
13 percent lower, clearly indicating the benefits of centralized treatment.

5-3.  Sludge treatment costs

5-3-1.  Treatment costs at the Center

     Table 5-8 shows the sludge treatment costs for the Hokubu Sludge Treatment
Center during fiscal year 1988.
  Table 5-8.  Treatment Costs at the Hokubu Sludge Treatment Center (FY1988)
                                                        (Unit: thousands of yen)

Personnel
Power
Chemical agents
Fuel
Repair
Other costs
Total treatment costs
Quantity of treated
solids (DSt)
Treatment costs
(thousands of yen/DSt)
Transportation
and intake
34,543
24,377
18
0
9,996
19,077
88,011
28,580
3
Digestor
dewatering
. 132,139
57,830
232,954
0
108,372
55,234
586,579
28,580
21
Incinera-
tion
132,943
46,626
39,181
118,808
77,085
144,728
559,371
28,580
20
Total
299,675
128,833
272,153
118,808
195,453
219,039
1,223,961
(28,580)
44
Breakdown of
treatment costs
(thousands of yen/DSt)
. 10 (6)
5 (3)
10 (8)
4 (0)
7* (4)
8 (3)
44 (24)


 Note: Other costs include comissions and utilities (light, heat, water). Incineration costs do not include
      the incineration cost of cake transported from other treatment plants. Figures in parentheses
      indicate the costs which do not include incineration cost.

     This table presents the breakdown of treatment cost per unit of solids in sludge
transportation and intake, digestion/dewatering,  and incineration, which are the
processes involved in the comparison with the conventional  treatment process
sequence in the next section.  These costs per DS-tons were  3,000 yen for sludge
transportation and intake, 21,000 yen for digestion and dewatering, and 20,000 yen
for incineration, totaling 44,000 yen.
                                      204

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  5-3-2.  Treatment costs in conventional processes

       A calculation was made for the fiscal year 1988 treatment costs in  the
  digestion/dewatermg  process sequence in the  Chubu, Nambu,  and Kohoku
  wastewater treatment plants, in order  to  estimate the  treatment costs in  the
  standard process prior to the introduction of centralized treatment. In the Kohoku
  plant, this cost was obtained by adjusting the treatment costs in fiscal year 1983 bv
                                  intervening period The finding are presented in
            Table 5-9. Treatment Costsin Conventional Processes (FY1988)
           -                                       (Unit: thousands of yen)
       Quantity of treated solids
       (DSt)
       Treatment costs
       thousands of yen/DSt))
                           Chubu
                           (WTP)
1,672
        Nambu
        (WTP)
         7,203
Kohoku
CWTP)
                   2,573
Total
          11,448
   Breakdown of
  treatment costs
(thousands of yen/DSt)
      Note: Other costs include commissions and utilities (light, heat, water). Incineration costs are excluded.

      As shown in Table 5-9, the total quantity of solids treated at these three plants
^solid's          Treatment of this quantity cost  778 million, or  68,000 per ton


5-3-3.  Comparison of sludge treatment cost

     Table 5-10 compares the treatment costs of the Center with the estimated costs
in the conventional sludge treatment system.

                  Table 5-10. Comparison of Sludge Treatment Costs   .-


Treatment costs per ton of treated solids
Treatment costs (up to and including
dewatering)
Quantity of treated solids (DS tons)
Incineration costs per ton of treated solids
Total treatment costs per ton of treated solids
Conventional
system
68
778,416
11,448 
23
91
i yen, JJQ tons;
Centralized
system
24
674,590
28,580
20
44
                   Figures for incineration costs in the conventional process sequence are
                   based on the assumption that a power generation process is not Stflized.
                                      205

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     As shown in Table 5-10, the costs of treatment, up to and including dewatermg
in the conventional system per ton of treated solids, are about three times greater
than the corresponding costs of about 24,000 yen at the Center.

     If the incineration process is also included, the costs per ton of treated solids in
the conventional system would increase to an estimated 91,000 yen. This figure is
almost double that of the corresponding center costs of about 44,000 yen. As such
the benefits of centralized  treatment also appear in the comparison of total
treatment costs, i.e., including the incineration costs.

     These findings indicate that a rise in the expanse of facilities, while involving a
rise in the total maintenance and operational costs, including power, fuel, and other
expenses, also  induces a greater economy of scale  including considerable labor
saving  meaning a decline in the treatment costs .per ton of treated solids. 1 here is
also the benefit derived from a more effective use of energy due to the use of digestion
gas for power generation.                                                  ,

     The benefits of centralized treatment also appear in regards to transportation
 as well The cartage costs of transporting sludge cake by truck are about  2,300 per
 ton  Transportation of the entire sludge cake quantity generated at the Center
 (about 77,000 tons) by truck would therefore cost about  200  million. Transporta-
 tion of the sludge equivalent by pipeline costs only about  88 million.

 5-4.  Improvement of water quality in wastewater treatment plants

 5-4-1.  Improvement of water quality through sludge transportation

      The shift from treating their own sludge to pumping it to the Center through
 pressurized pipelines has improved the quality of treated effluent in the wastewater
 treatment plants. This is due to the fact that the shutdown of the sludge treatment
 facilities has eliminated the load brought about in sidestreams.  However, it is
 difficult to quantify this improvement, for the following reasons.

 1)   The wastewater treatment situation exhibits a broad fluctuation depending on
      such factors as climate, the amount of rainfall, and operating conditions during
      the year in question. Improved quantification would require comparing yearly
      data  for  at least several  years before and after the  shift to pipeline
      transportation.

  2)   The influent load has been fluctuating every year due to increases in the
      quantity of influent wastewater and the expansion of treatment facilities. This
      has made long-term comparisons difficult.
                                      206

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 3)   The Kanagawa and Hokubu No. 1 plants both transport sludge and receive
      sidestream water at the same time, making it difficult to isolate the influences
      of sludge transportation.

   ;   For these reasons, it was decided to compare the treated effluent quality for a
 short period of time before and after sludge transportation at the Midori and Kohoku
 plants, both of which are not subject to the influence of sidestreams loads. The period
 of time in question is about one year, during which the treatment facilities were not
 expanded. The results are shown in Table 5-11, just for reference.

  Table 5-11. Treated Effluent Quality Before and After Sludge  Transportation
WTP
te
Item
Term of data collection
Sludge transportation rate (%)
Number of facility trains
Influent wastewater quantity (m3/d)
BOD load (kg/m3day)
Transparency (cm)
SS (mg/1)
COD-Mn (mg/1)
Midori
Before sludge
transportation
Oct. 1983 -
Apr. 1984
0
2
30000
0.33
56
6
14
After sludge
transportation
Oct. 1984 -
Apr. 1985
100
2
41000
0.32
89
3
12
Kohoku
Before sludge
transportation
July 1984-
June 1985
0
3
65000
0.42
64
6
11
After sludge
transportation
July 1986 -
June 1987
21
5
62000
0.21
83
5
8.9
July 1987 -
June 1988
66
5
84000
0.24
94
4
8.6
 *,^>,^. j.. .my, j..j.iuwii jjiciiinjuiuaLcuBiuuge LImmpui i/auun in vjciooer oot i treatment lacuities were expanded in
      2. The Kohoku plant initiated sludge transportation in September 1985 (treatment facilities were
        expanded in May 1985).

    . The effect of transportation appears most clearly in the figures for the Midori
plant, which show major improvement in transparency, SS, and COD after the shift
to transportation, despite an increased influent.  The effect cannot be clearly grasped
in the case of the Kbhoku plant, due to the fact that the transportation rate  (the
share of the total sludge generated occupied by  that transported to-the Center) was
increased in increments from an initial 21 percent to 100 percent over a three-year
period, during which the facilities were expanded.  Nevertheless,  a comparison  of
water quality  at the transportation rates of 21 and 66 percent, when the BOD load
was virtually the same, reveal a somewhat improved tendency in transparency and
SS.

5-4-2.  Other improvements

     Various  factors, such  as an abnormally .high  influent of stormwater  and
industrial  drainage as well  as bulking, can  impair treatment  in  wastewater
treatment plants.  Unlike the above, however, the deterioration of water quality
                                    207

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associated with sludge treatment trouble is generally not transitory, but exerts a
direct impact on the activated sludge over a long period of time.  For this reason, its
impact on wastewater treatment is fairly serious.

     The shift to centralized treatment has resolved many such problems, owing to
the fact that the sludge is promptly sent off the plant premises for treatment. In this
area as well, centralized sludge treatment is exerting a favorable influence on
wastewater treatment.

5-5. Effective use of sludge.

     In order  to prolong the service life  of Yokohama's existing disposal sites,
virtually the entire quantity of sludge generated in  the city is incinerated at the
Hokubu and Nambu sludge treatment center. Nevertheless, the city has recognized
sewage sludge as a useful resource, and is pursuing various applications of its
effective use, as shown in Figure 5-5.

                             Fig. 5-5. Utilization of Sludge   '
                         Drying	 Particular fertilizer (named HAMAYUKI)
                                   _ Lime ash
                                                 Soft soil improvement material
. Pavement base material
                                                _ Concreat material
                                                _ Pottery material
                                   _ Polymer ash 	
                                                  Agricultural material
                 	Artifical soil
                    (named HAMASOIL)


                   . Earthen square plate

                   _ Earthen block

                   _ Cray pipe
                                                 . Interlocking block (press sintering)

                                                 . Back-filling material
                                       208

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       The following is an outline of the two main types of usage that are the subject of
  the city s promotional efforts: soil improvement and nursery farming.

  5-5-1. Soil improvement

       Incinerated ash can be divided into two categories, lime ash and polymer ash
  A polymer dewatering agent has been adopted for use in both of the city's centralized
  sludge treatment centers (Hokubu and Nambu).  But the ash from the Hokubu
  center has a higher CaO content (approx. 25%).  The reason for this is that the
  Hokubu center adopts a dry-type desulfurization method in which CaCCL is added to
  prevent SO* generation during the incineration of the sludge cake.

  _  ^ Due to its high water absorption capacity and the chemical action of CaO
 incinerated ash with a CaO content in excess of 20 percent can be mixed with soil to
 improve its suitability for uses relevant to civil engineering. It has been confirmed
 that lime-type incinerated ash has sufficient strength for use as material for backfill
 and roadbeds (especially the lower layer). In actual use, however, the powdered form
 o this ash causes handling problems.

     'The disposal of surplus soil resulting from public works projects is growing into
 a major  problem in Japan as  the number of disposal sites  for it  declines
 Consequently, it was decided to promote the use of lime-type ash as  soil improve-
 ment material in order to resolve the problem of the disposal of both this ash and
 surplus soil. Surplus soil generated during sewerage system construction is'disposed
 oi at considerable costs when it is of a poor quality.  However, improving this soil
 mixing it with incinerated ash for reuse as backfill material, would in  effect resolve
 three problems:  it would reduce the quantity of waste surplus soil and incinerated
 ash, and reduce the expenditure for their disposal and backfill use on sand.

     Various tests confirmed the practicality of incinerated ash and raised hopes for
 the use of lime-type ash as soil improvement material. In view of these prospects
 the city constructed a soil improvement plant at the Hokubu No. 2 Plant, adjacent to
 the Center, for effectively utilizing incinerated ash. This plant,  the first of its kind in
 all ot Japan, went into operation in April 1989.

     Operation of this plant at a rated output would yield a savings of about 300
million yen annually in expenditures for disposal of incinerated ash and surplus soil
and for the purchase of sand.

     The plantmay be outlined as follows:

     1)   Capacity: 30 m3/hour (continuous operation)
                                    209

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     2)   Rate of incinerated ash admixture:  no more than 30 percent relative to
         the  dried weight of the base  soil; quicklime  and cement are  used as
         additional agents if necessary

     5)   Quality standard for improved soil: an indoor GBR of at least 10 percent

     6)   Quantity of incinerated ash used: 22,000 m3 per year

     7)   Quantity of improved soil produced: 49,000 m.3 per year

     8)   Construction cost: 1.08 billion yen

5-5-2.  Use as nursery farming    

     Using polymer ash with a low lime content, the city developed the agricultural
materials "hama soil." Production of hama soil begins with the addition and mixture -
of the incinerated ash and polyvinyl alcohol as a binder.  After pelletization and
chemical treatment with an ammonium sulfate solution, the mixture is then washed
and dried. The following can be cited as the major characteristics of Hama Soil.

     1)   Excellent water retention, water absorption, and  aeration qualities for
          plant cultivation.

     2)   A pH of 6-7, ideal for plant cultivation

     3)   Durability; retains structure

     4)   Change of color reflecting degree of dryness/webness, which serves as  a
          guideline for watering

     5)   Lack of odor; sterile

     A pilot plant is now producing about 300 kilograms of this soil per day. Efforts
are being made to reduce the production costs while promoting sample shipments to
the market.

5-6. Evaluation

     The following effects were  anticipated in planning the centralized  sludge
treatment facilities.

(1)  A more  effective system of sludge treatment regarding facility construction,
     maintenance and operation.

(2)  Promotion of retrieval and comprehensive use of the energy generated from
     sludge due to the greater quantities involved in centralized treatment.
                                     210

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(3)   Improvement of the secondary effluent quality at the wastewater treatment
     plants due to the elimination of sidestream water from sludge treatment
     facilities.

(4)   Improvement in the efficiency of sidestream treatment through centralized
     treatment of the same at the Center.

(5)   Alleviation of  the need  for pollution control facilities at the  individual
    . wastewater treatment plants.

     As has already  been noted, to date, the operation of the centralized treatment
facilities has achieved the anticipated degree of success. Effects (1) through (3) have
clearly surfaced. The results regarding efficient retrieval and the comprehensive
use of energy exceeded our expectations.

     This performance rests on several major factors.  First, the combination of the
centrifugal thickeners and the egg-shaped digesters enable.a high-concentration
digestion that yields an increased quantity of digestion gas and enable the amount of
heat for warming the tanks, per load, to be reduced.

     Second, the expanded quantity of digestion gas generated is used on a priority
basis as supplementary fuel  for the incinerators, which need a  considerable
proportion of the energy consumption in the centralized treatment process. Third,
any remaining digestion gas is used as a source of energy for power  generation,
which supplies 64% of the Center's own electrical power needs.

     Finally, energy is conserved in  the operation of incinerators by effectively
using their exhaust  heat to dry the sludge cake before incineration. In short, the
successful operation of centralized treatment was made possible by the  fruits of
much research and extensive developments aimed at optimizing such treatment as a
total system.

     Presently, the Center sends back sidestream generated in the course of sludge
treatment for treatment to certain wastewater treatment plants which send it
sludge. While this system causes no particular problems, the Center is currently
promoting detailed studies for the implementation of the original'plans, which
anticipate centralized treatment of sidestreams  at the Center. This system will be
implemented in the near future.

     Nevertheless, research on the following subjects  is needed to augment the
effects of centralized treatment:

(1)  Studies for operating applications of the centrifugal thickener  during storms
     and in the winter; a concentration of about 5 percent was achieved by the
     thickener in mixed sludge.        911

-------
(2)  More efficient operation of the egg-shaped digesters (digestion periods, organic
     loading, agitation methods, gas generation quantities).

(3)  Study of dewatering units and pretreatment to bring the moisture contents of
     digested sludge to a level permitting autogeneous combustion, and the develop-
     ment of a more efficient incinerator.

(4)  Increase the Center's self-sufficiency rate in electrical power and fuel energy to
     100 percent through promotion of number three above and the promotion of
     energy conservation in facilities.

(5)  Utilization of low-temperature energy produced through cogeneration.

(6)  Facilitation  of sludge transportation,  since the thickening characteristics
     deteriorate during transport.
                                    212

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 6.   Afterword

     The record for the first year of full-scale operation of the centralized treatment
 facilities at the Hokubu Sludge Treatment Center reveals that electrical power
 generated using the digestion gas supplied 64 percent of the total electrical power
 consumed at the Center. This represents an annual savings of about 200 million yen
 in electrical power costs, despite the fact that the Center was still operating at only
 one-fifth of its planned capacity. It also reveals a decline in the amount of energy
 that had to be purchased from outside sources and  labor saing stemming from the
 shift to centralized treatment at the Center.  As a result, the Center's sludge
 treatment costs were less than half those of the same sludge quantity under the
 previous system of treatment at each wastewater treatment plant. These and other
 effects of centralized treatment have been described in the report.

     At the same time, it must be acknowledged that it'has only been a short time
 since the Center went into full-scale operation.  For this  reason,  the current report
 must be termed  an  interim report  as far as the operation and  evaluation of
 centralized sludge treatment facilities are concerned.  It is also clear that there is
 still room  for improvement  in several areas,  including sludge transportation,
 effective incinerator operation, further  energy conservation, and treatment of
 sidestream water. In addition, the Nambu Sludge Treatment Center will begin
 operation before the end of this year.  As such, we are looking forward to preparing
 another report specifically on these developments and subsequent progress, at the
next available opportunity.

     In closing, the author would like to  thank all those who assisted him in the
preparation of this report,  particularly Mr. Hachiro Shimomura and Mr. Tetsuro
Ishii, whose help was instrumental in creating the project.
                                    ###             ''
                                    213

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DEVELOPMENT OF SLUDGE TREATMENT TECHNOLOGY
                          IN
    BIOLOGICAL PHOSPHORUS REMOVAL PROCESS
                          by
                     Hiroshi Oniki
                       Director
                  Planning Department
                 Sewage Works Bureau
                     Fukuoka City
     The work described in this paper was not funded by
     the U.S. Environmental Protection Agency.  The contents
     do not necessarily reflect the views of the Agency and
     no official endorsement should be inferred.
             Prepared for Presentation at:
          12 th United States/Japan Conference
                         on
             Sewage Treatment Technology

                    October 1989
                   Cincinnati, Ohio

                        215

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                                    ABSTRACT
     Fukuoka city has been developing an advanced wastewater treatment, process,
mainly based on the biological phosphorus removal, to remove large amounts of
nutrients.  Biological phosphorus removal process has many advantages as
compared with the other phosphorus  removal processes.  However,  it has one major
disadvantage that phosphorus  absorbed by  the  activated sludge  may be  released
when  the  sludge  is  handled  inadequately, _and  this.makes  it difficult  to  treat
sewage efficiently.   All  the  sewage treatment plants* in  Fukuoka city  are
provided  with  mixed sludge  gravity  thickening process and anaerobic  digestion
process.  Phosphorus absorbed  by the sludge may be released in these  processes.
 In order  for the biological phosphorus  removal plants to run with some stability,
 it is necessary to decrease phosphorus  concentration in the return water from
 sludge treatment process.
      For this reason, Fukuoka city has been  investigating the behavior of .-
 phosphorus in the sludge,  and developing the sludge  treatment  technologies
 for  prevention of phosphorus release.
       This paper  introduces several  results of our  investigation and
 development as  follows.

       1)  Prevention of  phosphorus release by  adopting dissolved air  floatation
          thickening.
       2)  Phosphorus fixation with lime  and ferric chloride in digestion tank.
       3)  Phosphorus fixation with lime and ferric chloride for supernatants.
       4)  Phosphorus fixation by crystallization of Magnesium* Ammonium Phosphate.
                                        216

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1. INTRODUCTION

     Recently, eutrophication or aggravation of closed water with excessive
quantities of. in-flowing nutrients, is increasingly causing social problems.
The sewage systems, which are largely dependent on the conventional
secondary treatment, cannot cope adequately with eutrophication.   This  is
because of the limited capacity of the conventional secondary treatment to
remove nutrients, in particular nitrogen and phosphorus.   However, the
eutrophieation is steadily progressing.   And it is essential to  abate
nutrients flowing into closed water in order to preserve  its quality.
     Sewage,  therefore,  has been increasingly treated from the angle of
solving eutrophication problems.  Several sewage treatment plants around
lakes are- attempting to  remove nutrients drastically, and more advanced
wastewater treatment processes are being developed for cities facing closed
sea water.
     Fukuoka  City has been recently developing an advanced wastewater
treatment process,  mainly based on biological phosphorus  removal, .to remove
large amounts of nutrients from sewage.   This paper describes some of
important developments carried out so far for the sludge  treatment process  
as the core of the  biological phosphorus removal process.
                PHOTO 1.  FUKUOKA CITY AND HAKATA BAY
                                  - 217

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2.  OUTLINE OF EXPERIMENTS OF ADVANCED WASTEWATER  TREATMENT PROCESS

     2-1.'Background of Experiments

     Fukuoka City  is an economic and cultural  center of the Kyushu  Island
located  in the  southwest part of Japan,  and  is  the 8th largest city  in
Japan with a population of 1.2 million.                   ,/...
     The city has  been populated along  the  Hakata Bay with the city  facing
north    Host of the rivers running  through  the city drain into the  bay,  and
treated  water from the 6 sewage treatment  systems operated by Fukuoka  City
flow  into  the bay  either directly or via rivers.   The bay is fairly  closed
with  Unino-nakaniehi peninsula and  Shika Island in the east, and  Itoshima
peninsula  in  the west. Therefore,  the  sea  water exchange  with the  open sea
(Japan  Sea)  requires many days.  As the population and production  volume
increase,  the  bay is increasingly  becoming eutrophic, causing red  tide to
occur more frequently.The sea  water quality of the bay is  improving
gradually  according  to  the  expanded sewage treatment  facilities,  but it is
generally  still behind  the  related  environmental  target  levels of  water
quality preservation.
                                                            Fukuoka City

                                                                 ''JAPAN
                                                      nlanfl Sanitation
                                                      plant]  district Future Pl.esent
                                                           Saitozaki
                                                           Wajiro
                                                           Tobu   E=H3
                                                           Chubu  I** ****!  l-x'v-x-l
                                                           Seibu  II1111II  Illllllllllll
                                                           Nagao
                                                           Nanbu 
          FIGURE 1. LOCATION MAP OF TREATMENT PLANTS AND SEWERAGE DISTRICTS
                                        218

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TABLE 1.  SERVICE OF FUKUOKA CITY
                                          (as of March 1989)
Total area of the city
Total area of urbanizd districts
Total population
Total service area
Service area in urbanized districts
Population in sewage service area
Sewerage service ratio
Treatment capacities (total of 6 plants)
33,818
14,969
1,200,204
11,346
75.8
947,800
79.0
538,000
ha
ha

ha
%

%
m3/day 
 4.0 r
                                          TARGET LEVEL

                                         (EASTERN AREA)
                                         TARGET LEVEL
                                         /CENTRAL AND \
                                         WESTERN AREA;
    79  '80 -'81  '82  '83  '84  '85  '86  '87  '88

                    YEAR



      FIGURE 2. TREND OF WATER QUALITY IN HAKATA BAY

             (COD CONCENTRATION)
                         219

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     The city has decided to develop new advanced wastewater treatment
techniques because the sewer.age systems will expand to cover 79% ot the
city towards the end of 1989, and increasing quantities, of the
eutrophication causing materials cannot be treated efficiently using
secondary treatment processes.

     2-2. Object of Advanced Wastewater Treatment Experiments

     The object of the advanced wastewater treatment experiments is to
develop biological phosphorus removal  techniques.  The advanced .processes
for the prevention of eutrophication are generally designed  to  remove COD,
phosphorus  and nitrogen.  The new treatment process of the  city  is  aimed  at
removal of  phosphorus.  This  is because  the Environmental Bureau of the
city has  found through many  surveys  that phosphorus is the  limiting
material  for eutrophication  in  Hakata  Bay.

     The  phosphorus  removal  processes  are  three  general  and practical
categories:

      The  physico-chemical  process  represented  by  the coagulation
-precipitation  and crystallization  processes;                           _
      The  combination process  in  which the physico-chemical and biological
process are combined.   represented  by  the  activated sludge  process combined
with  alum coagulation;  and  *                        '
      The  biological process represented  by biological  phosphorus removal
process.

      Fukuoka City has selected the biological phosphorus removal approach
 for the following reasons:

      The existing activated sludge  plants can be easily modified into  the
 biological phosphorus removal plants.
      It  is superior to the coagulation-precipitation process  in running

 CSt'It  produces less quantities of  sludge  than that of  the  coagulation
 -precipitation process.

      One of the major disadvantages involved  in  the biological  phosphorus
 removal  process is  that phosphorus  absorbed  by  the activated  s,ludge  may  be
 released when the sludge  is  handled inadequately,  and this  makes  it  _
 difficult  to treat  sewage  efficiently.  The  sludge  treatment  plants  in  all
 of  the sewage  treatment facilities  are provided  with anaerobic digestion
 tanks,  because  the  sludge  is  finally  treated  into  composts for farms
 Therefore, phosphorus  in  the return water from  the  sludge  treatment  plants
 must  be  carefully controlled and  reduced.
                                     220

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 3.  OUTLINE OF ADVANCED  WASTEWATER TREATMENT  EXPERIMENTS

       3-1.  Outline of Experimental Plant
 was mo'SmLlnto ^"^ - sludsf ^  at  the Tob'u sewa^  treatment plant
 was modified into the experimental plant, which  has capacity  of  16,700 nf/day
 Tobu sewage treatment plant  has total capacity  of 100,000  rrf/day  max with
 conventional activated sludge  process.  A schematic diagram  of  experimental
 Phosphorus  removal process is  as shown in Figure 3.  The sludge treaJIent
 Plants consists of the mixed sludge gravity  thickening, two-stage  anaerobic
 digestion,  elutriation, and  filter press dewatering                anaerobic
      In  the experiments,  the aeration tank (herein refferd to as  the'
  consfstin/efaC70r>  ^  ^  ^  ^ biol^ical  Phosphorus  removal  process)
  consisting of  7 compartments,  devided by the partition walles, modified  in
 such way  that  the frrst 2 compartments were made  anaerobic stage by
 stopping  aeration,  the remainder left aerobic stage as  before'  The
 anaerobic stage was  mixed by the agitators and  the openings in the wall  '
 between  the anaerobic and aerobic  tanks  were reduced!  ?o 1 mU   Lf  ow of
 n^rf  tTh* excess  Activated sludge generated at  the experimental line was
 passed  to the preaeration tank  of  another adjacent  line, to prevent  Jelee
 of phosphorus in  the  primary sedimentation tank.   The  return  sludge  was
                                                                 '18
       The target  level  of the phosphorus  removal was 0.5  nig/   or less -as
  he  total phosphorus  in the final sedimentation tank effluent    The target

          hBD                                           ''
                          .
.      The sludge treatment  experiments were  carried out by bench  scale fp
Plants  because quantities  of sludge generated  from the experLerial line
were  too small to be  treated by the commercial  line.
                  Biological Phosphorus Removal Process (Experimental Line)
      Influent
                                     Biological reactor
           to gravity
           thickener
I Primary
J sludge
Return sludge
                                                        Final
                                                        sedimentation
                                                        tank
                                                                 Effluent
      Influent
                      Standard'Activated Sludge Process (Control Line)

                                      Aeration tank
[Excess sludge
    ^ to preaeration tank
     of another line
V V
..V V
V v




                                      Return sludge
                                                        Final
                                                        sedimentation
                                                        tank
                                                                 Effluent
                                      Excess sludg
                                                                 Anaerobic

                                                                 Aerobic
                  FIGURE 3, SCHEMATIC DIAGRAM OF EXPERIMENTAL
                          PHOSPHORUS REMOVAL PROCESS
                                      221

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     3-2. Results of Biological Phosphorus Removal Experiments

     The experimental conditions and results are shown in Table 2 and Table
3, respectively.  Total phosphorus in the treated water was in arrange of
from 0 37 to 0.44 ml & , Well below the target of 0.5 mg/ fi  , and also the
BOD and SS levels were equivalent to those obtainable by  the standard
activated sludge process.  Temporary increases in NOx and decreases  in   _
phosphorus removal efficiency,  caused by decreased substrates concentrations,
were observed during  raining periods, but the plant  conditions recovered
well soon after  rain  stopped.   As a result,  the  target level was  reached
for note than 90% probability  through  experimental  period.
     These favorable  results, however,  were  with 5 to 6  rag/fi as  total
phosphorus in the influent wastewater.   It  was anticipated  by the
calculation  by  material  balance,  when all  the  lines  were  modified  into  the
biological phosphorus removal  process,  that  total  phosphorus  in  the teed
water  would  increase  to  9  mg/fl ,  unless some countermeasures  to  prevent
release  of phosphorus were  taken  in  the sludge  treatment  system    It was
experimental proven  that  increasing  total  phosphorus  in the  feed
wastewater  to 8 mg/fi  resulted total  phosphorus  in the  effluent  from final
sedimentation  tank  to above  1  mg/fi .      ,                '
      In  order for the biological  phosphorus removal  plants  to *run with some
stability,  it  is, therefore,.necessary  to decrease phosphorus concentration
 in the return  water from the sludge treatment process  to a level comparable
with  that generally observed in the standard activated sl.udge process.

     TABLE 2.  EXPERIMENTAL CONDITIONS AT WASTEWATER TREATMENT PROCESS
BPRP '
1986fy 1985fy ,
Flow rate
Aeration/flow ratio
Return sludge ratio
Excess activated sludge
MLSS
SVI
C-BOD-SS loading
SRT
MLDO 3
Reactor water temp.
Anaerobic
HRT A U-
Aerobic
(mVday)

(%)
(mVday)
(mg/0

(kg/kg-day)
(day) .
(mg/.g)
(C)
(hour)
(hour)
12,105
4.7
86
315
2570
140
. 0.16
4.9
3.6
21.5
1.3
3.1
12,139
3.9
82
313
2380
140
0.15
6.1
' 4.0
21.0
1.3
3.3
SASP 2
1986fy
12,143
4.3
77
173
2330
180
0.11
6.8
2.8
21.0 .

.4.7
        Note: 1 Biological Phosuphorus Removal Process
            2 Standard Activated Sludge Process

            3 at the end of reactor
                                       222

-------
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                                       223

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4.  DEVELOPMENT OF SLUDGE TREATMENT TECHNIQUES


     4-1. Sludge Treatment Process
        .
fro. the biological phosphorus remjval plant ntal    phosphorus may  be
than that of the standard  activated sludge Plant      '   ons for a long
released again into water            J^le problem  in the sludge treatment
     havePbeennstudied in the above two stages.


4-2. Composition of Excess Activated Sludges

The co.positioas of the excess acuvate^slu^e far.hthe
   ,
 asrs ss::1.!?: ^1^. %%. ^ f--- --.
 prl.ars sludge,  aad phosphorus conteut is  2.6 *JS       than those  in the
 se        1:1.!-s^..r.n.i"".i:;!.:.,  rt..p,.r..  i. the  .u,,..
TS
VS
PH
T-N
T_p
K
Ca
Mg
Cu
Zn
Fe
Cd
T-Hn
(%)
(%)

(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg)
(mg/kg).
(mg/kg)
. (mg/kg)
r (me/kg)
3.67
70.8
6,53
.67,000
26,200
9,000
11,900
9,000
359
1,000
16,100
1.76
0.94
3.96
63.3
5.94
43,500
10,300
2,980
19,800
6,410 
411
1,300
16,400
1.78
1.52
.93
112
110
110
254
302
60
140
87
77 . ' '
98
99
62
          Note: Excess sludge is one thickend by dissolved air floatation

              Primary sludge is one thickend by gravity thickener
                                   224

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      4-3.  Phosphorus Release in Gravity Thickening
   '"
             f
 storage  ?easSLf    *      s'      o-
 was  collated  in  24 -ho" s  incre ?ni ortn^T \
 liquid to  100  mg/,  acco^pan ed   nL  educ iLP in";
 concentration  in  the  sludge  from 3 7%  to 2 ?o/    ? tOtal
 release  in  12  hours  was  about 60% of th           Amounts of phosphorus
From a standpoint of  phosphorj ^release  rh"0"11^  "^T^ in' 24 hoii>s-
generally has  a detention tile  of  IboJJ'^J ""'^ tMckeninS Process
gravity  thickening  is' not suitab ]/             "'  Which indicates that

in the biological'ph  s h'r r em  a  SarSS  '"  tFeating eice"
                   u    4    8    12    16    20

                             Detention time  (hr)


                   FIGURE 4. RELEASE OF PHOSPHORUS
                           FROM EXCESS SLUDGE
24
                                225

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     4-4. Dissolved Air Floatation
     The  excess sludge which is


difficult to  thicken by S^^^Hf dissolved air  floatation was
concentration technique   The PJ^ntia  o              also  aeroMc

studied for the reason of its shor  thick JJ          Table 5.  The

conditions.  The  operations il r .alt. .re -'     tlon  and 0>23  mg/ I as


                            in the separated water.               '    .
   TABLE 5. RESULTS OF THICKENING TEST,
_
pH
SS'
PCU-P
T-P in sludge

(mg/0
(mg/4)
(%)
6.5
4,840
1.91
3.1
6.3
33,400 .
5.46

6.5
320 '
0.23
_..
.6.2
17,300 
9.80
'"
6.5
1,940
5.64
	 - - 
     Note: 1 Thickened sludge


          2 Thickener effluent




      4-5. Phosphorus Release  in Digestion Process




      The digestion experiments were conducted,  to

  of phosphorus in the Digestion process  where the       floatatlon


  phosphorus  removal process,  thickened by di' ^d^^  (mixing ratio: 3

  r      .   .  i	j,*4-l^TrtTmiYP. nWlTjIlbntJr'J-J-lua'J       ,     .  TII_ICOY^
                                                   are shown  in Table b ana
              Ce  of excess sludge only   the sludge Concentration^
  organic -atter concentration were too high  o be em     Q ^  irapossible.

  the 26 days detention  time, and     "     qothep hand) solid-liquid

                                                          
  ,
   The  phosphorus ^^^""^"^J/afer 2 months.  The phosphorus
   gradually with time, up to J13  mg/ * JJJ   however,  was fairly constant at
   concentration in the case of  ffllf J  sijf ?'   asing for  the experimental

   200  to 250  ^g/fi Witho^wae4rrenthe  supernatant contains very high   .
   period.   In any case, however,  the  f^e"     d directly  to  the waste water

   rr.r syr.! ffi;pi.:"iUt;  r.r rof 10. P^P^. ,....1.1..

   drastically.
                                      226

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 TABLE 6.  EXPERIMENTAL CONDITION OF DIGESTION TEST
 Sludge volume before digestion
             after digestion
 Supernatant volume
 Digestion temperature
 Digestion period
 Digestor gas generation "ratio
. Organic loading
 Digestion rate
                                 (day)
                              (kg/m3  day)
 5.0
 3.03
 1.60
37.0
26
 7.46
 1.05
 5.0
 2.97
 1.72
36.1
26
.7.94
 0.91
34
TABLE 7.  RESULTS OF DIGESTION TEST
Excess sludee

pH (%)
TS (%)
VS ( (%)
T-P (mg/kg)
P04~P (mg/ty
T-N (mg/kg)
M-Alkalinity (mg/^)
VGA (mq/e)
Inf.1
6.5
4.14
66.6
1,130
' 101
2,610
282
12
.Dig.2
7.4
3.35
56.3
960
. 289
2; 670
3,520
112
Sup.3
; 7.4
3.63
56.7
1,040
. 274
2,760
3,520

Mixed sludge
Inf.
6.3
3.18
73.9
791
75.4
2t170,
386
135
Dig.
7.2
3.01
65.2
1,042
245
2,550
2,950
137
Sup.
7.4
0.78
63.0
417
239
, 1,420
2,930

 Note:  1 Influent
       2 Digested sludge
       3 Supernatant
                              227

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                    500
                   400
                  ? 300
                  ~b
                  jj
                  CU
                   *
                  2 200
                    100
                  Excess sludge
                  Mixed sludge
                         40
50   60   70   80   90   100  120
   . Experimental period (day)
                     FIGURE 5. CHANGES OF PHOSPHORUS
                             CONCENTRATION IN SUPERNATANT


     Therefore,  the  phosphorus blockade  is necessary.   In an attempt  to
control phosphorus  concentration in the  return  water from the digestion
process,  the  city  has  studied three approaches  as follows.

     Addition  of  lime (calusium oxide)  and ferric chloride to  the  feed
sludge for  the digestion tank;

    .Addition  of lime and ferric  chloride  to the supernatant,  to  fix
phosphorus  present therein;

     Utilization of crystallization of Magnesium Ammonium  Phosphate (MAP)
                                       228

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     _4-6   Phosphorus Fixation (Preventing  Phosphorus  Release)  with Lime and
 Ferric  Chloride in Digestion Tank

      Figur% 6  illustrates that the pilot plant  with 2  tanks  of 70 liter
 volume  for the phosphorus fixation.  The sludge  used  in'the  experiments was
 the  excess sludge treated by the dissolved air  floatation  process   The
 fixing  chemicals  were lime and ferric chloride.  Four  cases  are.studied
 where the  lime addition "ratio was set at 0, 4.8, 7.4- or  9.8%  of the total
 solid weight,  with neutralization-equivalent quantity  of ferric  chloride,
 to follow  phosphorus fixation and. digestion.
     The results  are shown in Figure 7 and Table 8.  The extent  of
 Phosphorus  fixation ascended in  proportion to lime addition  ratio,  whereas
 that of digestion reached a  maximum at about 0.7 mol/mol as  the  ratio  of
 the  fixing  chemical to  total phosphorus in the feed sludge,  decreasing
 thereafter  with lime addition ratio.   This could be attributed to decreased
 activity of  the digestive bacteria as a result of increased  quantity of  the
 inorganic  coagulant.   It  is  supposed  .that the optimum  addition ratio of  the
fixing chemical will  be around  1.0 mol/mol (about 5%   as feed  lime
concentration) for  the  phosphorus fixation from consideration  of digestion
ratio, limiting the attainable fixing ratio to around  70%  or phosphate
concentration  in  the  digested sludge  to approximately  100 m/&
                            Measurement tank

                                     Gas meter
                                                     > Supernatant

                                                      Digested sludge
        Thickened sludge
        storage tank
Digestion tank 70X2tanks
                    FIGURE 6. FLOW CHART OF DIGESTION
                            EXPERIMENT PILOT PLANT
                                  229

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TABLE 8.  RESULTS OF PHOSPHORUS FIXATION IN DIGESTION TANK
   Dosage   Molar ratio TS

           to T-P

Lime  FeCls
VS   T-P
                                  (mg/kg)
                                             P04-P
                                            Digestion
                                           Con.1  F.R2 ratio
   Note I 1 Concentration
        2 Fix ing ratio
o 
4.8
7.4
9.8
0
5.7
8.9
11.9
0
0.84
1.58
2.10
2.97
3.15
2.90
3.03
66.4
65.5
67.3
68.9
1,170
1,140
970
900
498
208
39.3
11.9
0
59 .
92
98
36
 38
32
22
 100


, 80
          2  60
          a
          i*
          bo  .
          a  40
          fa
  20


   0
                                                150
                                               40 S
                                                  o
                                               30 |

                                                  o
                                               20 'is
                                                  &
                                Fixing ratio
                                Digestion ratio
               0             1.0              2.0
                       Molar ratio to T-P
                                                  0
                   FIGURE 7. PHOSPHORUS FIXATION
                          IN DIGESTION .TANK
                                230

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      4-7.  Phosphorus Fixation with  Lime  and Ferric chloride for  Supernatant

      Next,  lime and ferric chloride  were added to supernatant, to  prevent
phosphorus  release.  Three cases were  studied:

      lime  alone
      ferric  chloride alone                                  '           '   .
      (3)a combination .                                             .

The results  are shown in Figure 8 ~ 10.  Ferric  chloride removed SS and
Phosphorus more efficiently than lime.   The  results  indicated that molar
addition ratio  of the fixing chemical, to keep total  phosphorus  removal
ratio at 90% or  more,  was about i mol/mol  with fe'rrib  chlori-de  and 4 mol/  '
mol with lime.   A combination of these chemical gave  the  most  favorable
results; phosphorus fixation ratio of 90%  or  more was  attained  at a dosage'
ot about 1 mol/mol,  accompanied with improved  compositions  of  both treated
water and also  precipitated sludges.
      100


      75

     *

      50
    I 25
            T-P
            PQ4-P
2   4    6    8
   Molar ratio
                             10
                               100
                             ^ 75
                                           50
25
                                            0
   T-P
-* P04-P
 0    2    4   6    8    10
         Molar ratio
    FIGURE 8. PHOSPHORUS FIXATION
            WITH FERRIC CHLORIDE
                              FIGURE 9. PHOSPHORUS FIXATION
                                      WITH LIME
      100
      75
      50
    "a
    
    e
                    O	0 T-P

                    ** PO4-P
            24    6    8   10
              " Molar ratio
    FIGURE 10. PHOSPHORUS FIXATION WITH
            FERRIC CHLORIDE AND LIME
                                   231

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     4-8. Phosphorus Fixation by Crystallization of Magnesium Ammonium
Phosphate (HAP) -Development of MAP Process

     Many reports said that scales are frequently  deposited  on  supernatant
transfer pipes of digestion tank in a sewage  treatment  plants near  sea,
causing pipe plugging problems.  J, Borgerding  detailes  that these  scales
consist mainly of magnesium ammonium phosphate  (MAP).   Namely,  magnesium in
sea water brought into a digestion tank  reacts  with phos.pha.te and ammonium
ions present in supernatant from a digestion  tank  to  form insoluble MgNH4P04-
6H.O crystals.  Therefore, our  attempts  were- made  to  fix phosphorus by
artificially forming MAP.    -.

     4-8-1. MAP Forming Conditions

     The  nesessary  conditions 'for  the'formation of MAP are:

       presence  of magnesium              .             
       slightly  alkaline  condition  of  the system ,

Supernatant  from  the anaerobic  digestion system contained 207  mg/fi of  a
phosphate,  7.0 mg/fi  of  soluble magnesium, and 756 mg/fi of ammonia nitrogen
'-   As  the molar ratio of  MAP  is  1(P): 1(N): 1 (Mg) from the  moleculer  formula
of MgNH,PO<-6H20, magnesium  was deficient stoichiometerically  to form MAP.
Addition of  magnesium to  the supernatant to a M'g/P ratio of 1.05/1  caused
 formation of MAP crystals, increasing phosphorus  removal ratio.
      Solubility of  MAP declines as pH ascent, as  shown  in Figure 11,  and
 the system should be kept at PH 8 or higher, to reserve  MAP efficiently.
The supernatant alkalinity should be increased by some,  means,  because  its
 pH level was typically within  a range from 7.3 to 7.5.
                           5.000
                           4.000
                         be


                         < 3.000

                         8
                         & 2.000
                           1.000
                              0
                               012345678
                                      pH of solution

                              A                       1)
                            FIGURE 11. EFFECT OF pH ON
                                     SOLUBILITY OF MAP
                                      232

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  The following four methods were studied to increase pH level of the
 supernatant:

      (D addition of sodium hydroxide     '
      (D addition of lime (calusium hydroxide)
      (3) addition of magnesium hydroxide
       aeration to accelerate decarbonization

 Result of lime was less effective than that of sodium hydroxide,  requiring
 3 times more quantity of feed chemical to keep the same pH level.   Result
 ol  magnesium hydroxide failed to increase pH level efficiently    On the
 other hand,  aeration was found to be an effective  method to  remove  carbon
 dioxide dissolved in the supernatant at a high concentration,  to  go up  PH
 level to 8.4 in about 2 hours.   The  pH level adjustment by aeration,  however,
  was accopanied by the odor problems,  and so the exhaust gases  should be
 deodorized because of the presence of  high  concentrations  of  the  materials
 causing offensive odor.   The composition of exhaust  gases  are shown in
 laore 9.                                       '
                 TABLE 9.  COMPOSITION OF EXHAUST GASES
Concentration
Ammonia
Metyl mercaptan
Hydrogen sulfide
Methyl sulfide
Di-methyl di-sulfide*
(ppb)
(ppb)
(ppb)
(ppb)
(ppb)
1,900
, 150
3.6
37
2.3
     Based on the above results,  it has .been found that  MAP  can  be  produced
efficiently by adding magnesium to the supernatant,  and  by  increasing  the
system PH to, at'least 8 with addition of sodium  hydroxide or aeration.   The
MAP process to continuously remove phosphorus  from the supernatant  has  been
then attempted with pilot plant experiments.
                                    233

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     4-8-2.  Pilot Plant Experiments for  the  MAP  Process  (Part 1)

     Figure 12 and Table 10 show  the  flow  diagram  of  the pilot plant and
   'experimental conditions respectively.   The supernatant storage.tank
 uh 2 n? volume was equipped with  an agitator and also  an aeration system
capable of controlling air  ratio  arbitrarily with  a Hertz conver er to
increase pfl'level.  The feed water  pumps was a variable  type, with manual
con ro  covering a flow ratio from, 4  to  0.5 nf/hour   A  NaOH solution was
added automatically to the  feed  water,  to  keep.a PH level in a  range from ,
3 to 9 0   MgCl2 injection  ratio  was  changed' in accordance with the
phosphorus concentration  in the  supernatant.  The  supernatant was passed
from the storage tank  to  the  rapid  stirring tank,  then  transferee! to the
slow stirring  tank for crystallization.   And, finally,  the crystalline
precipitate were separated  -from  the feed water in the settling  tank, and
some part of  the precipitates  were sent  back as the seeds to  the  rapid
stirring  tank.
                           MgC> tank ,  NaOH tank
             Blower
                Storage tank
Slow stirring tank
         Settling tank
            n
                             Rapid stirring
                             tank
                                                       Effluent
                Precipitates
                                           Seed crystal
                                           recycling pump
                     FIGURE 12. FLOW DIAGRAM OF MAP PROCESS
                             PILOT PLANT (No.l)
      TABLE 10.  EXPERIMENTAL CONDITIONS OF PILOT PLANT (PART 1)
Flow rate
Dosage of MgCla solution
Molar ratio to PO4-P
Retention time in stirring tanks
Retention time in settling tank
(nrVhour)
(m^/min.)

(min.)
(min.)
0.5
6 ' >
1.05
24
144
                                       234

-------
      Figure 13 shows the results of pilot plant study continuous  treatment  -
 with capacity of 0.5 rrf/hour of the supernatant fro, the digestion  LnTa
.the Tobu sewage treatment plant.  Ortho-phosphate concentration of  the
 influent fluctuated from 20. to 80 mg/fl ,  but the effluent Ortho-phosphate

 GOT*/1011 na;fdp,fr\5 t0 15 mg/  (1 mg/  n the average),  that  is,
 60  to 70%  as Ortho-Phosphate removal ratio.  The 'crystals, thus, formed
 were very fine,  mostly  deposited on SS surfaces, and sometimes leaked into
 the etliuent  to, cause high  phosphorus concentration   Th'e leaked
 crystalline precipitates may become soluble ortho-phosphate at a stage of
 reduced  PH,_and  increase phosphorus load  of the waste water treatment system
 Therefore,  it is  very important to  control  SS in the settling tank   In  the '
 experiments,  the  effhient water ratio must  have been controlled at 0 5 m3/
 hour (40m/day  as  LV) or less.   Figure 13  includes test  results with'the
 seed crystal  recycling    Recycling  of the  seed  crystals,  though sometimes
increased SS  in  the  effluent water,  was an  effective method of increasing
 size or  magnesium  ammonium  phosphate crystals.
      The  problem  observed in- this pilot plant experiments  were difficulty
 in  aeration to adjust PH of  the water In  the storage tank,  frequently
 causing  precipitation of MAP in the  storage  tank,  and/or  decrease in the
purity of MAP because the precipited MAP was withdrawn together with the -
sludge out  of the  settling  tank.  As a next  step the new  pilot plant was
designed and  constructed to  solve the  above  problems.
   80
   70
^ 60
J50
PH 40
   30
                 C?
                    10

                     0
                        Aug. to Sep.    Oct.
                                                    0 Influent
                                                     Efflueut
                                                    * pH
                          Nov.
                                                9.0
                                                8.5
                                                8.0'
                   FIGURE 13. RESULT OF MAP PROCESS EXPERIMENT
                                   235

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                                                            MAP
     4-8-3. Pilot Experiments for  the MAP Process  (Part.2)

     Figure 14 illustrates the new pilot plant  where  aeration,  stirring,
and crystallization 'are carried out  together  in the  same reactor tank.
precipitates formed in the reactor column,located  in  the middle ol  the
reactor tank, are separated from SS  and  settled by gravity.   The
experiments are still ongoing, but the  results  obtained so far have
indicated a prospe-st of producing  high-purity MAP.  However,  phosphorus
removal ratio is not high so  far,  because  of  low phosphorus  concentration
in the supernatant separated  from  the  digestion tank of standard Activated
sludge process.  As a following experiment,  we will  attempt  the case that
supernatant of higher phosphorus  concentration, is  use'd.
                                            Pump
                                          Effluent
                                         )     >
Supernatant
Storage tank
                Blower      MAp precipitates
        FIGURE 14. FLOW DIAGRAM OF MAP PROCESS
                PILOT PLANT (No.2)
                         236

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 PHOTO 2.
 PILOT PLANT
 (No.2)
PHOTO 3.
MAP CRYSTALS
RECOVERED
IN THE PLANT
                     237

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5.  AFTERWORD

     The pilot experiments are still under way,  and there is room for
further improvement especially in the case of MAP.   Fukuoka City is
planning to improve the sludge disposal process  well-matched the biological
phosphorus removal process.  This sequence consists of mechanical
thickening of excess sludge, anaerobic digestion ,  MAP phosphorus fixation,
dewatering, and compost production processes.
     The MAP process is desirable not only from  the viewpoint of
stabilization of the advanced wastewater treatment process, but also from
the viewpoint of the effective utilization of resources.  Magnesium
ammonium phosphate, rich in phosphorus and nitrogen, is expected to find
use as a product for slow-effect fejtilizers.  As a newer process, MAP
process, therefore, will be  developed further also as a phosphorus
supplier to fully utilize  the limited quantity of natural resources in,Japan,
because the phosphorus of  necessary volume in Japan is covered with 100%
by import  from foreign countries.
  REFERENCE:  1)  J.Borgerding,  Phosphate  deposits  in  digestion  systems,
                              Journal  WPCF,  vol.  44,  No.5,  1972
                                      238

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       TOXICItY MONITORING METHOD BY  BIOSENSOR
                         by
                   Eiichi  Nakamura
            Chief, Water Quality Section
           Public  Works  Research  Institute
              Ministry of Construction
            Tsukuba, Ibaraki   305,  Japan

                         and

                   Hiroaki Tanaka
              Senior Research Engineer
               Water Quality Section
           Public  Works .Research  Institute
              Ministry of Construction
            Tsukuba, Ibaraki   305,  Japan
The .work described in this paper "was not funded by
the U.S. Environmental Protection Agency.  The contents
do not necessarily reflect the. views of the Agency  and
no official endorsement should be inferred.
           Prepared for Presentation at:
        12th United States/Japan Conference
                        on
            Sewage Treatment Technology

                   October 1989
                 Cincinnati, Ohio
                         239

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                                  ABSTRACT

      Use of the ammonia biosensor as a tool to monitor toxicity of water is
 presented.  Since Nitrosomonas are known one of the most sentive classes of
 microorganisms in the biological wastewater treatment processes, respirometry
 measurement (oxygen uptake) using Nitrosomonas gives more information on the
 toxic characteristics of water than using activated sludge.

      Ammnoia biosensor was initially developed using Nitrosomonas europaea
 (ATCC 25978) to monitor the ammnoia concentration of water.  The ammonia
 biosensor consists primarily of a receptor (immobilized nitrifier)  and a
 probe of dissolved oxygen meter (DO probe).  Depending on the concentration
 of ammonia in water, the rate of oxygen uptake in the receptor will  vary.
 Comparison of the measurement of output current of a DO probe with  the
 calibration curve which shows the relationship between the ammonia
 concentaration and the output current gives an estimation of the
 concentration of ammonia of a sample.

      However,  if a sample contains a toxic compound against Nitrosomonas
'europaea,  the output current of a DO probe would be lowered depending on the
 level of toxicity of the compound.  Therefore,  the level  of toxicity can be
 estimated by comparing the expected output current which  is estimated by
 measuring  the ammonia concentration with  the actual  output of a sample which
 contains a toxic compound.

      Time  required to measure the toxicity of a sample is found 10 to 15
 minutes.  According to the experimental results using  ortho-chloro"phenol,
 trichloroethylene  and tetrachloroethylene,  the  ammonia biosensor  detects
 their toxicity with the order of  0.01 mg/1.   Although  it  was  known that
 ammonia  concentration would influence the relative magnitude  of output,  the
 level of toxicity  could be expressed  reasonably by  using the  kinetic
 parameters.  Required time for the  sensor to  recover from the  damage  caused
 by a  toxic  compound is found  to depend on the magnitude of  toxicity
 previously  applied.
                                      240

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                                  INTRODUCTION
       A chemical specific approach to regulate the discharge  of toxic
  compounds can only be possible if the levels of toxicity  of  all chemical
  compounds against selected indicator organisms are understood and al
  cjecal compounds can b* meas"red by available detection methods.  However,
  it is practically impossible to understand  the toxicity levels of  1]uwever'
  S.  /2mp^dS-  i" add1t1on> available detection methods have not yet
  developed for thousands of toxic compounds  (1).   Therefore,  use of the
         VPeClf^.appraCh to contro1  the discharge of toxic compounds is
          to specific group of compounds such as heavy metals.
                   thf  cnemical  specific approach, a biological approach has
  waPr            S^ P"?!  the d1scha^e of toxic compounds to the public
  tollasurl thp   "  f6 ^J10?1?91 approach, living organisms are directly used
  to measure the  level  of  toxicity of a compound, or of water even when the
  amount or name  of compounds contained in the water are completely unknown   A
  variety of biological  testing  methods is already developed from a simSe
  respirometry  test to  a complicated bioassay test (2).  Although ?ox c?ty of a
  compound against, specific living organism does not necessarily mean that ?he
  compound is toxic against all  living organisms including men, use of a
                                       SUre
 tact ^EPA developed tnree types of toxicity test, namely microtox toxicity
 test, respirometry (oxygen uptake) test, and adenosine triphosphate (ATP
 test, to measure the toxicity of wastewater as near real-time and Inexpensive
 monitoring tools (3).  Since the measurement of rate of oxygen uptake  is  a
.routine job for a plant operation, the respirometry test is  the easiest amona
 these methods.  However, activated sludge is not necessarily the most       9
 sensit;>ve 9rouP of microorganisms to toxic compounds.   It is known  on the
 other hand, that nitrification process becomes upset when the influen?
 contains excessive heavy metals or hazardous chemicals (4).   Therefore  use
 of Nitrosomonas as a.tool for a respirometry test may give more sensitive
 result of toxicity test than using activated sludge?            sensitive

 com* Ammonia biosensor is found capable to detect the  level  of  toxicity of
 some toxic compounds,  though the ammonia biosensor was initially  developed to
 .monitor ammonia.  And  also the ammonia biosensor is found to  be potentially
 used as a continuous monitoring tool  of toxicity.   This  paper describes the
 principal  mechanisms of the ammonia biosensor  and introduces  some of the
 experimental  results how the biosensor responds  to a toxic compound!


                       DEVELOPMENT OF'AMMONIA BIOSENSOR

      Structure.  Fundamental  structure  of the ammonia biosensor is shown in
 t^*'<"^"?'V** ?f diss1v*d oxygen meter (DO
 aSfrpn TUnted Khere "^rifyin9 bacteria (nitrifier) are immobi  zed by
 acetyl  cellulose membrane filters. . This sandwich structure of receotor is
 found easier to mount than other immobilizing methods such as qel
 tn7r^oZat 10n $ P^gc^""He.  And also gel  immobilizations are reported
 wLn In8 ane9at]vf.effect on the activities of some microorganisms (5}.
 When a  buffer solution which contains no ammonia is fed to the sensor,  there
 is  a little consumption of oxygen by endogenous  respiration of nitrifier

-------
resulting in rather high and steady  output current of a DO probe.  This
steady output is considered as  the base  output.   In recording the output, the
current is converted to voltage.  When a sample contains ammonia, oxygen is
consumed in the receptor resulting in rather  lower output.  Since the
difference of this output from  the base  output depends on the concentration
of ammonia in the sample, ammonia concentration can be estimated.  The
difference between the sample output and the  base output is simply expressed
as "the output" unless otherwise specified.
      Electrolyte.
      DO probe


      0 - ring

      Teflon
      membrane
      Receptor _
      (immobilized
       nitrifier)
            Figure-'l  Fundamental  Structure  of  the Ammonia Biosensor


      Receptor(mixed culture).  In the initial  stage  of  development of the
 ammonia biosensor, various efforts were made to obtain  nitrifier from
 activated sludge.  Mixed liquors were sampled  from a wastewater treatment
 plant where nitrification was well proceeded.   Activated sludge was cultured
 by feeding substrate containing ammonium chloride and no^organic compounds.
 After three month cultivation, nitrifier seemed well grown  in the sludge.
 The sludge was immobilized by membrane filters and mounted  to a DO probe.
 The results of this prototype sensor are shown in Figure-2.  It seemes that
 the sensor responds quite accurately to the change of ammonia concentration.
 The relationship between the output and the ammonia  concentration is shown in
 Fiqure-3.  Although linearity of the relationship can not be maintained  in
 the region of high ammonia concentration because of  oxygen  limitation, use of
 this prototype sensor seemed possible.  However, the prototype  sensor was
                                      242

-------
found to respond to organic compounds contained  in  a  sample,  because  mixed
culture of microorganisms were applied as a receptor.  Figure-4  shows an
example where the sensor responded to organic compounds.  To  overcome the
effect of organic compounds, efforts were made using  antibiotics  and  other
chemicals in vain.  The initial development became  a  complete failure.
                   s
                                                               v

                                        Numbers in the figure indicate
                                           -N concentration fed in  mg/1.
            Figure-2  Recording Results of the Prototype Sensor:
              200 _
                                     2         3
                                  NH$ - N (mg/l)
     Figure-3  Relationship between  the  Output  and Ammonia Concentration
                                   243

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              140  r
              120  -
                                           O  Glucose
                                           0  Peptone
                   0     '20      40       60      80     100.

                            Organic Concentration as TOC (mg/1)

        Figure-4  Output Response to  Organics Using the Prototype Sensor
     Receptor(pure culture);  Use of pure cultured Nitrosomonas was
considered from tne experience of initial developmentNitrosomonas europaea
(ATCC 25978) was cultured by using Pramer's culture medium (6) as shown in -
Table-!.  Receptor structure is shown in detail in Figure-5.  Although
optimum pH and temperature where the maximum output was gained were found 9.2
and 35*C respectively, the sensor was tested under pH of 8.0 and temperature
of 30"C to save required amount of a buffer solution as well as energy for
heating.  No response to organic compounds was identified by using glucose
and peptone as organics.  The amount of nitrifier was found to affect the
relationship between the output and the ammonia concentration.  Figure-6
shows how the relationship differs by the amount of immobilized nitrifier
expressed in adenosine triphosphate (ATP) density.  It .can be said from
Figure-6 that higher concentration of nitrifier is preferable to measure
lower concentration of ammonia, and lower concentration of nitrifier is
preferable to measure wider range of ammonia concentartion.  Although
durability test is still going on, no deterioration effect is identified for
50 days of use.


              Table-! ; Pramer's Culture Medium for Nitrosomonas
(NH4)2 S04
Na2 H P04
KH2 P04
Na H C03
Mg S04 . 7H20 .
Ca C12 . 2H20
Fe S04 . 7H20
Distilled water
2.5. g
13.5 g
0.7 g
0.5 g
0.1 g
5 mg
30 mg
1 ,000 ml
                                     244

-------
          0
                     membrane



II
'
*
filters Teflon^
/ \ . membrane
   
*\t  9
\Dz  
*   
x
/
x


-,

3lectrol>



v^
te

X-"
                     cathode

                    .anode
                    Nitrosomonas
                                                                  glass
       Figure-5  Detailed Structure of the  Receptor of Ammonia  Biosensor
                     400 r-
                                        o
N1trif1er Concentration

   O 40 ,.g. ATP/mm2
   Q 10 ng.ATP/mm2
   A  2 vg.ATP/imi2
                                           6      8      10
                                         NHj- N (mg/1)
               Figure-6  Effect  of  Nitrifier  Concentration on the
                        Output-Ammonia  Concentration Relationship


     /"lmnif Biosensor System.  To apply the  ammonia biosensor as a
      n            ammonia, supporting  devices should be combined.  Althouqh
sampling  is an  important part of whole  monitoring processes, no effort has
an^fj1"" 3" eX1^t1n Sampl1n9 P^edure maybe app"ed   During the
cSn ta t   IfTsamolf if ?'^frature of^the sample should be mainfL'ned
San5! H     *?    Pi      ack of Oxy9en, oxygen should be supplied
Standard  solut^ns of ammonia should be prepafed for automatic calibration
The output should be expressed in concentartion, which requires themount of
a calculating system as well as a recording system.   Figu?e-7 showl a
schematic system of the monitor using the ammonia biosensor.  A buffer
SnSlS In SUPP  ?d t0 3d^St the PH f a sample automatically.   Air is
supplied to a sample regardless to the dissolved oxyqen concentration nf *
sample.   Figure-8 shows an operational  example of the monitor
                                    245

-------
                    CPU
                    Amplifier


                    DO Probe

                Receptor
          Air Pum
          Air
Sampling Pump
        Sampl e
                                             Recorder
             Display
      er  Bath

           Drainage



    Buffer Pump
                  1      2
     Standard Solutions
Buffer Solution
       Figure-7   Schematic  View of the Monitor
                 Using  the  Ammonia Biosensor
Output Status of the
Sensor
Reco
D
R
I
V
E
rdln
0~l
I
g(analogue)
OmV F. S.
P-l 
3Y-I
 SV-I
SY-3
SY-4
Operation Status



Time
1



S
Stand-by,
Output Stabili-
zation *
_______   



CAL-1
^-~~^~~~-
Call
Zero a
MV^~M^il



Ci
brati
djust
^


CAL-2



Ci
IM^^MKB*


CAL-3



Ci
m(3 poits)-Washing
2 poits calibration




M-OO. OOl*
.*

 ^^"^^
s
Sample dose,
Calculation

   Figure-8  Operational Example of the Ammonia Monitor

                            246

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                            MONITORING OF TOXICITY
      Effects of toxic compounds.  Since the ammonia biosensor uses
 Nitrosomonas europaea as a receptor of the sensor, it is expected to have
 some effects in the output when supplied with a toxic containing sample.
 Three chlorinated organic compounds, ortho-chlorophenol, trichloroethylene
 and tetrachloroethylene, were tested to measure their toxicity against
 Nitrosomonas europaea under the ammonia concentration of 1.0 mg/1   Since
, aeration or a sample is considered to have an effect to change the
 concentration of a test compound, a sample solution was previously aerated
 before dosing a toxic compound to a sample solution.  Necessary time of
 recovery for the ammonia biosensor was examined for ortho-chlorophenol as a
 toxic compound.                                                 K

      Since maximum allowable concentaration (MAC) of each compound below
 which there was no effect on the rate of respiration was not precisely
 detected, the maximum concentration where the output was the same with the
 control  was assumed as MAC.   Figures 9,  10 and 11 show the results of
 experiment for ortho-chlorophenol, trichloroethylene and tetrachloroethylene,
 respectively.  Relative magnitude of output was calculated by comparing
 Sam^n^Utp^ Wlth contro1  output.  For  ortho-chlophenol, MAC was considered
 as 0.034 mg/1.   It can be recognized that there is a substantial  decrease in
 the relative magnitude of output as the  concentration of ortho-chlorophenol
 increases.  Similar tendency is also recognized for other two compounds.

      When the ammonia biosensor is fed with a sample containing toxic
 compounds, time is required  for the sensor to'recover from the effects of
 toxics.   One. of the experimental  results  using  ortho-chlorophenol  as a toxic
 compound is shown  in Figure-!2.   Required time  of recovery is increased
 proportionally  to  the increase in  toxic concentration.
            1.0
        f
        o
           0.5
           0
-* MAC =0.034 mg/1
             0
 0.5
1.0      1.5       2.0

Ortho-chlorophenol (rag/1)
2J5
                 Figure-9  Effect of Ortho-Chlorophenol on
                           Relative Magnitude of Output
                                     247

-------
   1.0 ft
     MAC = 0.015 mg/1
S  0.5
C
O>
m
    0
      0                   0,5        ,          1.0

                     Trichloroethylene (mg/1)


          Figure-10   Effect of Trichloroethylene on
                      Relative Magnitude of Output
                       MAC  = 0.019 mg/1
       s
       01
       
-------
           >>30

           0)
           >
           o
           o
           OJ



           fe 20
           q-

           0)
             10
           3
           CT
           O)
           o;
              0
                                                     i-
                         Concentration of orthochlorophenol (mg/1 )



         Figure-12  Required Time of Recovery for Ortho-Chlorophenol-










             v = Vmax S / (  S + Ks (1  + I / Ki))                    (1)


      where,  Vmax is the maximum rate  of reaction  S is
                                                             of
       v = Vmax S / (S + Ks (1 + (I - MAC) / Ki))


where, (I - MAC) = 0 if I is lower than MAC.
                                                                   (2)
            (I - MAC) / Ki = ((1 - p)/p) ((KS + S) / Ks)          (3)


^    where, p is the relative magnitude of output as shown in Figures 9 to











                                    249

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                                                     c;n   e
  Table-2  Toxicity of Ortho-chlorophenol
Concentration
(mg/1)
0.034
0.068
0.136
0.340
0.680
1.360
2.720
6.800
Relative magnitude
of output, p
1.0
0.932
0.941
0.867
O'.SIO
0.694
0.552
0.185
Toxicity
(I-MAO/K1
0
0.104
0.089
0.219
0.334
0.629
1.157
6.280
   Ki  = 2.184 mg/1,   CV =  0.272


   Table-3  Toxicity of Trichloroethylene
Concentration
   (mg/1)	
Relative magnitude
of output, p	
Toxicity
(I-MAO/K1
   0.015
   0.030
   0.060
   0.120
   0.240
   0.480
   1.20
       1.0
       0.961
       0.741
       0.699
       0.480
       0.305
       0.151
   0
   0.058
   0.498
   0.614
     .544
     .248
1
3.
   8.015
    Ki  = 0.217 mg/1,  CV.= 0.073
    Table-4   Toxicity  of 'Tetrachloroethylene
Concentration
(mg/1)
0.019
0.037 .
0/056
0.074
0.111
0.148
0.370
Ki = 0.120
Relative magnitude
of output, p
1.0
0.977
0.760
0.707
0.566
0.457
0.231
mg/1, CV = 0.074
250
Toxicity
(I-MAC)/Ki
0
0.034
0.450
0.591
1.093
1.694
4.746


-------
                                   CONCLUSION
 the experimental results indicated high potential of practical USP of     *
 ammonia biosensor in the field of toxic Lnagement   practlcal use of
                                    CREDITS
?*
8-
poilutlnu;'
                                  REFERENCES

                                 B10'9lCa'
                                                               toxic wate,
3
4. Hockenbury  M.R.  C.P.L.  Grady(1977)  Inhibition  of nitrification effects
   of selected organic compounds;  JWPCF,  49,  768        '"'ricanon errects
5. Chibata, I. (Ed.) (1981)  Immobilized enzymes; Kodansha, Tokyo
                                             Nitrosomonas in pure culture; j.
  * ISfel!!lSi;.J76rSr'(1958)
                                               J  W.H.Freeman  and  Company,  San

                                    251

-------

-------
   RENOVATION OF AN, EXTENDED AERATION TREATMENT PLANT FOR

             BIOLOGICAL NUTRIENT REMOVAL PROCESS
                            by
            T. Matsui*, K. Sato*, K. Moriyama*,
               M. Imamichi** and Y. Harada**


                 Cf r01 De*>artment' Public Works Research
                                        1, Asahi, Tsukuba-Shi,
** Sewage Works Division, Hamamatsu City Hall, 104-6, Motoshiro
   Hamamatsu-Shi, Shizuoka-Ken, 430- Japan             Motosh2.ro,
    The  work described in  this  paper was not funded by
    the  US.  Environmental  Protection Agency.   The contents
    do not  necessarily reflect  the  views of the Agency and
    no official endorsement  should  be inferred
              Prepared for Presentation at:
           12th United States/Japan Conference
                           on
               Sewage  Treatment Technology


                      October 1989
                   Cincinnati,  Ohio
                          253

-------
 ABSTRACT
                                         F








. INTRODUCTION








   operators .
        Under  these circumstances,  in December 1,982,  the Environment Agency
   obliged to remove nitrogen and phosphorus.









    anoxic tank  is designed with a  total detentxon tune of 12-16  hours.
                                        254  .

-------
                   *i??au? of this Process is in the range of 60-70%



























      All but one of the plants which was newly built, were oricHmv
                                                          of nitrogen and


o Mass balance of alkalinity in this process.


o Re^n KSreen remVal f nitr9en * that of phosphorus.
P Relation between ORP control and DO concentration

o Response of this process to load variations.
PLANT DESCRIPTION AND EXPERIMENTAL PROCEDURE
    A  schematic  flow of the plant is shown in Fig. 1.  The reactor
                                    255

-------
denitrification reaction was assumed  as  "aerobic  denitrification".   The
second basin of 6 hours hydraulic  retention ^i-  was post-denxtrxf.catxon
zone for nitrate nitrogen  leaked out  from basin A.   The last oxic basin or

                                               
the anoxic-oxic process.

Aeration/ORP
Control System

Flow |  Influent-
Equalization
Tank j
tGrit Chamber
Effluent
<
i
 r~
 4-
- 

,gnal- 	 noRp ^^
Basin A |B
Oxic Anox'c3
330m3r 1 250m3
L[MJ 	 [Mi]1[M2]-[M2]J
t air t
1
C
Oxic
80m3
tai
-* Settl
Tank
/^
[ 	 : 	 Keturn aiuoge
discharge
ing
im3)
 ^-*

Wa
to
X
Upf 1 ow
Sand
Filter
tBiological
Effluent
ste Sludge .
other plant
    [MxliSubmerged mixer with air piping
    [M2]Submerged mixer
[Bi]:Blower with frequency converter
[B2]:Blower
                  Pig. 1  Flow chart  of  the  Hitomigaoka- plant
      The experiment was  commenced in Oct.  1987,  and is going on as of Aug.
 1989   This paper analyzed the data obtained from Jan. to, Aug. 1988.  The







                          TABLE 1  Operation Conditions
      Influent flow
      Retention time in the biological reactor
      (Basin A; 8 hours, Basin B; 6 hours, Basin
      Return sludge ratio
      MLSS
      BOD-SS loading
      TN-SS loading
      Sludge retention time
      Sludge aeration time
      ORP value set in Basin A
          900-1100 m /day
          15-17 hours
          C; 2 hours)
          60-90%
          2800-3200 mg/1
          0.05-0.08 kg-BOD/kg-SS/day
          0.01-oTo2 kgTN/kgSS/day
          17-25 days
          10-16 days
          100-125-150--180--115 
          125  mV  (changed stepwise)
                                        256

-------
   RESULTS AND DISCUSSION

   Nitrogen Removal

   Outline of  nitrogen  removal
                                                                   s.
  kept in the best condition n    '         concentration of  the  effluent was
60
50
^40-
Z 20-
10-

Jar
Inf.
0
0 o o . - 	
D D D D aQ o
O
100 .1?-5-/" 	 ' V D a. 125 mV
i^^r*^* S^*,** ^
>. Feb. Mar. Apr. May Jun^Jul'] Au^
T-N +Pff T M t,cff n_ >!.-._ 	
,20
1
0. c*
O ^ir\
200 z
100
Ort
)t. Ja

:::::::::::/:;:^;:i 	 ^ 	
+ 	 / 0 t
^E~~'A*  	 "AA.-  - -d" -......
-*^^..i*C?...*t.r.... 	
..A...* * ' * + + 	
e>* ^ % 	 A"A--f  f----

n. Feb. Mar. Apr. May Jun."

...-. 	


"Tr'&'d
"WSWftTWfl
Jul. Aug.Sep

o.
a:
0 ,
100


0
t.
                      .3-.NH4-N-ORP

   Fig. 2.  Variations of Nitrogen
            concentrations in the
            influent and the effluent
  D-T-N
                          -QRP
Fig. 3.  Variations of nitrogen
         concentrations in Basin A
2 or Fig. 3, ORP control can be easily achieved?       '     "

                                     257

-------
          5   gives the typical behavior of nitrogen  in the process, when the

            value of l^v is adopted.  As mentioned "






shown in Fig. 5.
16-r
14-
12-
1 8-
z 6-
4-
2
n

_ o
 C
 0 *

* a. % 
-------

c
o
r<
.Li
 o
If
J



^

Nitrification
CX7.14
"\^:
Apparent
consumption

c
o
o
  Fig. 7.   Alkalinity balance in the
            simultaneous nitrification-
            denitrification  reactor
                                               250

                                               200

                                               150-

                                               100-

                                                50-

                                                 0
                                                                      CX3.57
                                                  0          20         40
                                                        Nitrified nitrogen,  C mg/s.
                                                                             60
                                     Fig.  8.   Relationship  between nitrified
                                               nitrogen and  consumed
                                               alkalinity in Basin A
  Phosphorus Removal                                       ,           
                                        at different Points in this process are
 all
                        On  the other hand,  during the efficient
                             of     mv  
-------

                                  .
to take place in the  settling tank.


                     ss ^^
higher than 4 mg/1 in the settling tank.
                    Q.

                     a-
12-
10-
8-
6-
4-
2-
ocn D
**
n" 
a a
a +5
a a
n D + . 4
K: o"**
Stf^.^dtD

100 ' 120' 140 160 180
ORP tnV
            PO,-P   + NO,-N
            in-R.S.   in R.S.
                                                NO,-N in
                                                Basin C
        Fig.  11.
Relationships between PO4-P and NO3-N concentrations
 ORP Value and DO Concentration


















  process.
                                        260

-------
                     O
                     O
                     -O 1
                     
                     
                        80   100   120   140   160   180
                                Measured ORP value mV
                                              200
               Fig. 12.  Relationship between the measured ORP
                         value and the measured DO  in Basin A
   30

 2 25
 
-------
bU-
50-
AQ-

30-

zu-
io-
4 A A March 7 to 8, 1989
A A A ORP value set; 120 mV
a,

V*^ 0 + **>^ + 4, ^
 O
200 1~M-
Q. i-
i nn -^ t|
1UU 

a a.
o a:
en o
                       8 10 12 14 16 18  20 22 24  2 4  6
                                    Time
                 -Supplied + Inf. T-N  Inf . BOD * INf .   -ORP
                   air flow
                                            D-TOC
            Fig. 15.  Variations in the influ'ent load and diurnal
                      variations in the supplied air flow
CONCLUSIONS

The following conclusions were obtained in this study:

1)  It has been proved that in this method, the optimum ORP value for
    simultaneous removal of nitrogen and phosphorus exists, and. that ,a
    completely mixed flow single reactor, when its ORP value is kept at this
    proper value, can provide a simultaneous nitrification and
    denitrification reactor, where simultaneous removal of nitrogen and
    phosphorus can be achieved.

2)  Concretely speaking, it was required to put the NO3-N concentration in
    Basin C below 0.5 mg/1 by controlling ORP.  The necessary anaerobic
    condition in the sludge blanket of the settling tank was assured in this
    manner, and phosphorus removal was thus achieved.

3)  Examinations of the relationship between measured ORP values and measured
    DO concentrations showed that ORP values are more suitable than DO
    concentrations, as a control factor in this method.

4)  In the conditions of the optimum ORP value and 16 hours of the retention
    time in the biological reactor during a high water temperature period,  the
    nitrogen removal rate of 90-95%, the effluent T-N of less than 2 mg/1,
    the effluent T-P of 0.5-1.0 mg/1 and the effluent PO4-P of 0.5 mg/1 were
    achieved.

5)  When nitrogen removal is aimed at, then a completely mixed flow single
    reactor with an approximately 8 hour retention time and an ORP control
    system can achieve the effluent T-N of approximately 10 mg/1.
REFERENCES
 1.  Robertson, 'L.A.  and Kuenen,  J.G.,  "Aerobic denitrification - old wine in
    new bottles,"  Antonie van Leeuwenhoek,  50, pp.  525-544,  1984.
                                      262

-------
2.  Kuenen, J.G. and Robertson, L.A., "Ecology of nitrification and
    denitrification," In:  The Nitrogen and Sulphur Cycles.  Society for
    General Microbiology Symposium 42, J.A.  Cole and S. Ferguson (Eds)js
    Cambridge University Press, Cambridge, pp. 161-218, 1987.
                                     263

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-------
Development of a High Efficiency Nitrogen Removal System
     Using Immobilized Nitrifiers in Synthetic Resin
                           by
             Masanobu Aoki,  Deputy Director
              Minoru Tada,  Deputy Director
            Takashi Kimata,  Senior Researcher
             Shouji Harada,  Research Chemist
             Yuhko Fujii, Research Biologist
      Research and Technology Development Division
                Japan Sewage Works Agency
    The work described in this paper was not funded by
    the U.S. Environmental  Protection Agency.   The contents
    do not necessarily reflect the views of the Agency and
    no official  endorsement should be inferred
             Prepared for Presentation at:
          12th United States/Japan Conference
                          on
              Sewage Treatment Technology

                     October 1989
                  . Cincinnati, Ohio
                          265

-------
          Development of a High-Efficiency Nitrogen Removal System
               Using Immobilized Nitrifiers in Synthetic Resin
                       Masanobu Aoki,  Deputy Director
                        Minoru Tada,  Deputy Director
                      Takashi Kimata,  Senior Researcher
                       Shouji Harada,  Research Chemist
                       Yuhko Fujii, Research Biologist
                Research and Technology Development Division
                          Japan Sewage Works Agency


                                  ABSTRACT

     This technology is a biological nitrogen removal process which uses
immobilized nitrifiers (the IN Process) to reduce the reactor volume
required for nitrogen removal.  Nitrifiers are immobilized in 2 to 3 mm
diameter polyethylene-glycol resin.  The immobilized nitrifiers in the resin
(Biopellets) are mixed with activated sludge in the nitrification tanks to
promote quick nitrification.  Since nitrification is completed at shorter
sludge retention times using Biopellets, the reactor volume required for
denitrification is also reduced.  As a result, sufficient nitrogen removal
within the conventional reactor-volume (6-8 HRTs) has become feasible with
this technology.  The IN Process was developed through a joint research
project between the Hitachi Plant Construction, Co., Ltd. and the Japan
Sewage Works Agency (JSWA) under a research contract between the Ministry of
Construction and JSWA.  This paper introduces selection of sythetic polymer,
polymerization methods, nitrifying activity of Biopellets, separation and
fluidization of Biopellets, and applicability of Biopellets to nitrogen
removal processes.

Keywords; biological nitrogen removal, nitrified liquor recycling activated
          sludge process,  immobilized nitrifiers, synthetic polymer,
          polyethylene-glycol
                                     266

-------
            Development of a High-Efficiency Nitrogen Removal System
                 Using Immobilized Nitrifiers in Synthetic Resin
                         Masanobu Aoki, Deputy Director
                          Minoru Tada, Deputy Director
                        Takashi kimata. Senior Researcher
                         Shouji Harada, Research Chemist
                         Yuhko Fujii, Research Biologist
                  Research and Technology Development Division
                            Japan Sewage Works Agency
  Introduction

       Nitrogen removal from municipal wastewater is biologically
  using nitrification and denitrification mechanisms.  Nitrifiers
  r;?^,!!i!r^.n_!0"itrite ^>  *** to nitrate nitrogen.
                      nitrate nitrogen to nitrogen gas.  Two biological
                     scesses have been applied in full-scale plants in Japan
                      the nitrified liquor recycling activated sludge system
                     denitrifying activated sludge system.   Although these  '
                    i effective nitrogen  removal,  the applications  have been
                     larger  reactor volume required.   To maintain a sufficient
                    :s in an activated sludge reactor* during periods of low
                  reactor volume has  to  be *-"-'  --- -^ -
                                                                uses
          for mtrogen removal.  Nitrifiers are immobilized in 2 to 3mm
.
 volume required for denitrif ication is also reduLd wfthout 4ny carSn
 sources,  excepting that in the influent wastewater.  As a result
 nitrogen removal within the conventional reactor-volume (6 - 8
 become feasible with this technology.
                                    267

-------
        IN Process
            Nitrified liquor recycling

                    T
                                                  Biopellets

DN

0  0
N
O O
                        6 to 8 hr

                        Return sludge
        Conventional nitrified liquor recycling system

                         Nitrified liquor recycling
IDenitrif ication
tank
Nitrification
tank
                                  16 hr
                                 Return sludge
      Figure 1.
Difference between the-IN Process and the conventional
nitrified liquor recycling .system.
     a.  The selection of polymer resin suitable for immobilizing nitrifiers,
     b.  Methods for the immobilization of nitrifiers,
     c.  The separation and fluidization of immobilized nitrifiers,
     d.  Secondary effluent nitrification using immobilized nitrifiers,  and
     e.  Biological nitrogen removal using immobilized nitrifiers in
         activated sludge reactors.

     In 1988, a pilot plant study was initiated to evaluate the process
performance of the IN Process.


Selection of the polymer resin, and immobilization method

Polymer resin

     The immobilization of microorganisms  in polymer resin is a widely
applied technique in drug manufacturing and food processing.  The resins
used in those fields are natural polymers  (such as agar and carrageenan),
and  synthetic polymers  (such as acryl-amide and epoxy).  Generally, the
characteristics required of the resin  for  immobilizing microorganisms are:
                                     268

-------
      a.  to be water soluble, and able to gel at ambient temperatures
      b.  to have a low toxicity to the immobilized microorganisms during and
          after gelling,
      c.  to have a high dispersion coefficient for the substrate to be
          treated in the resin,          e
      d.  to have low biodegradability and to be durable,
      e.  to be physically strong,  and
      f.  to be inexpensive.
      Among the resins used for microorganism immobilization,  the natural
 resins are less toxic and less expensive compared to synthetic ones.
 However,  they are physically weak and easily biodegraded within short time
 periods,   in contrast,  synthetic resins  have the opposite characteristics.

      When applying microorganism immobilization to wastewater treatment   the
 resin should have good durability to reduce 'operation and maintenance  '
 costs.  This must be  the  most important  point when selecting  a desirable
 resin.  Therefore,  it was decided that synthetic resins  would be used as the
 immobilizing material early in that  selection process.   The physical
 characteristics of polyethylene-glycol (PEG), acryl-amide (AAm)   epoxy
 (Epx),  urethane,  and  melamine were examined.  The results showed that
 melamine  resin did not  gel  well  at ambient temperatures,  and .that it  was
 gelled1"  ^ Ur&thane  resin to  take on  a'spherical shape, even though it


     The physical,characteristics  and  nitrifying activity of  PEG, AAm, and
 Epx pellets  as  immobilizing nitrifiers (Biopellets) are compared  in Table
if R^^yin9-aCtiVl?,WaS  measured as  the respiration rate per unit volume
of Biopellets  in aerated ammonium nitrogen solution.  The composition of the
solution is  shown in Table  2.  The initial and final respiration rates were
measured just after gelling, and after 80 or more days of acclimation with
ammonium nitrogen solution  (Table 2), repectively.  Those physical
characteristics did not differ .very much.  However, the Biological
characteristics were significantly different.  Both the intitial and final

                                                      amng a11 three resins
                                    269

-------
      Table 1.  Physical characteristics and nitrifying activity
                of pellets immobilizing nitrifiers.
Evaluation item Polyacryl-amide Epoxy Polyethylene-glycol
Compressive strength
(kg/cm2)
Deformation ratio (%)
Degree of swelling (%)
Durability
Initial respiration rate (%)
Final respiration rate
(mgO2/2-pellets/hr)
2.1
49-
101
Good
1 or less
500
2.1 - 5.2
30 - 69
81 - 107
Good
1.8 - 3.3
180 - 500
2.8 - 3.6
33-52
93 - 113
Good
5-15
1100
Note-  The initial respiration rate is the ratio of respiration rates'
       before and after immobilization.  The final respiration rate is
       measured after 80, or more, days of acclimation with ammonium
       nitrogen solution.


          Tablet.  Composition of ammonium nitrogen solution.
                  Chemicals
                                        Concent rat ion
                NH4C2
76.1 mg/2 (20 mg-N/)
                Na2HP04*12H2O
23.1 mg/2
                NaC2
10.1 mg/2
                KC2
4.7 mg/2
                Cac22'2H20
4.7 mg/2
                MgS04-7N2O
16.7 mg/2
                NaHCOa
243.3 mg/2
            Note:   Sodium bicarbonate is  added as  a  pH buffer.
                                    270

-------
      The change in respiration rate with time for PEG and AAm pellets are
 shown in Figure 2.  The  respiration rate of the PEG pellets  increased
 quickly as compared to the AAm pellets.  This means that  PEG provides a more
 suitable environment for nitrifying bacteria than AAm.  As a result of these
 physical and biological  considerations, PEG was chosen as the resin for
 immobilizing nitrifiers.
  1000 r
                          PEG
                                Pellet diameter    :
                                NH4-N Concentration:
                                Nitrification rate :
                                Water temperature  :
2.5 to 3 mm
20 mg/e
150 to 240 itigN/2 pellets/h
20C
                              80
                                    100    120    140

                                     Time (days)
    160
          180
                 200
                       220
      Figure  2.   Change of respiration rates with time for PEG and AAm.


Immobilization method

     Biopelletes  must be produced in large amounts for use in full-scale
treatment plants.   From this point of view, four  immobilization methods were
evaluated.  The methods tested were:

     a.  intra-tube polymerization,
     b.  sheet polymerization,
     c.  drop polymerization,  and                                  ,
     d.  suspension polymerization.
                                     271

-------
     The applicability of each method is  summarized as  follows:
a
Intra-tube
polymerization
Sludge
Immobilizing
material/Gelling
catalyst
L-m^^zzErr-^/jX^


Cylindrical shape
b
Sheet
polymerization
Sludge
Immobilizing
material/Gel 1 ing
catalyst +
L Cutter
Upper belt f^
) - p_Qj>
O  OY- 
Lower belt
Cubic shape
c
Drop
polymerization
Sludge
Immobilizing
material/Gelling
' catalyst +
Sodium alginate
(S>
V
CaCl2 ~4--^^(

Spherical shape
d
Suspension
polymerization
Sludge
Immobilizing
material/Gelling
catalyst
r  r\
l.'ob .-T>  oil
\^y
Spherical shape
                      Figure 3.  Immobilizing methods.
a.  Intra-tube polymerization (Figure 3 a)

     A mixture of activated sludge (nitrifier enriched), PEG prepolymer, and
gelling catalysts (accelerator and starter) is pumped into a tube.  In the
tube gelation of the mixture occurs.  The gelled mixture is extruded from
the tube, and then cut into small, cylindrically shaped pellets.  Several
tubes must be prepared for mass production.  However, there are some
mechanical constraints involved in cutting several bars of gelled mixture at
the same time into a uniform shape.


b.  Sheet polymerization  (Figure 3 b)

     The mixture is cast  between two sheets which are separated by a fixed
distance.  The-mixture gels there, and then the gelled sheet mixture is cut
horizontally and vertically to produce cubic pellets.  Since this process
seems to be easily automated, the sheet polymerization method should be
applicable to mass production.


c.  Drop polymerization  (Figure 3 c)                           ,

     A mixture of activated sludge, PEG prepolymer,  sodium alginate, and
gelling starter is dropped into a calcium chloride solution.  The alginate
and calcium, ions react and produce a thin membrane.  The mixture is covered
with the membrane and gelation proceeds inside the membrane.  An appropriate
sized nozzle producing spherical pellets  with a set  diameter was determined
through experiments.
                                     272

-------
d.   Suspension polymerization (Figure 3 d)

 ^  Amixt"re of activated sludge, PEG prepolymer, and gelling catalysts  is
added  to oil.   The mixture is dispersed and suspended in the oil  and with
agitation  forms small drops.  In such a suspended condition, gelation
proceeds.  This process does not appear to be suitable because the drops
stick  to each  other and become large clusters during suspension.

     It was considered from the above evaluations that only the methods of
sheet  polymerization and drop polymerization were applicable to
immobilization.   The latter method was chosen temporarily for producing
Biopellets to  be used in experiments on treatment performance.  This was
because of its mechanical simplicity.   The procedures for producing
Biopellets by  drop  polymerization are shown in somewhat more detail in
Figure 4.
C     Conditioning of^\
     seed sludge    J
                                                         Gelling catalyst
   C
Preparation of
immobilizing
material
Mixing""')
                     Immobilizing
                     material
                                Gelling^)
                                                         Pellets
    Figure 4.  Procedures to produce Biopellets by drop polymerization.
                                   273

-------
 Acclimation of Biopellets

      The respiration rates of nitrifiers decrease to 5 to 15% of  their
 initial rates just after immobilization in PEG.  Within two months  (or  less)
 acclimation with wastewater, the rates increase, and then plateau.  To
 determine the period required for acclimation, the effects of temperature on
 nitrifying activity, and in which part of a PEG pellet the nitrifiers
 reside, a laboratory study was conducted.

      The effects of activated sludge types on acclimation are shown in
 Figure 5.  Two different types of activated sludge were seeded  in PEG
 pellets.  One was sludge from a nitrified liquor recycling activated sludge
 plant, the other was the same sludge but pre-acclimated for 80  days with
 ammonium nitrogen solution.  The two kinds of pellets were applied  to
 wastewater treatment at 20 and 30C.  As shown  in Figure 5, the respiration
 rate of pellets seeded with acclimated sludge increased rapidly at  a
 temperature of 20C.  By comparison, pellets seeded with the original sludge
 needed a longer period to reach the plateau of  respiration at the same
 temperature.  However, at 30C the pellets did  not require such a long
 period, and were more rapidly acclimated than nitrifier-enriched pellets at
 20C.  The respiration rates after 100 days were 600  to 800
 mg02/-pellets/hr, and there were no differences among the three cases.
 These results mean:
~   1000
I   -
W
%    800
     600
$    .
*   400

8
rt
g    200
U
                                    ___ A	
Sludge from a nitrified
liquor recycling
activated sludge    A
plant (30C)       ,-'' A  . .  t  ,
*                x^re-acclimated
              xx sludge (20
             A
                                          Sludge from a nitrified
                                          liquor recycling activated
                                          sludge plant (20C)
              10     20    30    40  .   50     60     70    80 ,   90

                                          Time (day)
                                                                     100
                                                               110
          Figure 5.  Effects of activated sludge types on acclimation.
                                       274

-------
       a.

       b.

       c.

       d.
the acclimation period  required depends upon the seed sludges and
temperatures,
the final nitrifying activity is not  related to the seed sludge or
temperature,
at higher temperatures,  the sludge type seeded with pellets does
not have a significant  effect on starting up reactors, and
at lower temperatures,  the nitrifier-enriched sludge should be used
as seed sludge for immediate  starting up.
       Microorganism distribution in a pellet was observed using an electron
 microscope.   The observed results over time are shown in
 Figure 6.  The growth of microorganisms in the pellets proceeded  as  follows:

       a.  Microorganisms exit dispersively in a pellet just after
          immobilization.
       b.  Microorganisms form colonies in a pellet during increasing
          nitrifying activity.  The growth of colonies is significantly high
          near the pellet's surface (until the 60th day).
       c.  The density of the colonies increases near the pellet's  surface,
          where the biological environment is better than that  inside,
          colonies inside the pellets tend to fade out (from the 60th'to  the
          200th .day).
       d.  The microbial layer near and/or on the surface grows  to  a thickness
          of  60 urn,  and there seem to be no mircoorganisms inside  the pellets
          (after the 200th day).
            Nitrifying
            bacteria
                               Growth of
                               colonies
                                        Growth of colonies
                                        near the pellet
                                        surface
                                                                          50/
-------
     From the above observations, it was shown that nitrifying bacteria
exist only near and/or on the pellet's surface after sufficient acclimation,
and that the inside of a pellet works merely as a support medium.  This
indicates that smaller pellets produce better nitrification performance when
only a small amount of pellet material is available.  The relationships
between pellet diameters and final respiration rates are shown in Table 3.
Smaller pellets showed higher respiration rates per unit pellet volume.
However, respiration rates per unit pellet surface area were approximately
400 mgO2/m2/hour, and almost the same among pellets with different
diameters.  This result clearly shows that the pellet diameter must be as
small as possible.  The separability of pellets from activated sludge will
determine the suitable diameter for Biopellets.


 Table 3.  Relationships between pellet diameters and final respiration rates.
 Diameter
1.00 - 1.41 1.41 - 1.68 1.68 - 2.00 2.00 - 2.38 2.38 - 2.83
 Respiration rate
 per unit pellet   1,730
 volume
 (mg02//hr)
             1,600
          1,480
          1,260
1,110
 Number of
 pellets per unit  1,105
 pellet volume
 (1000/)
               523
            307
            179
                                                   109
 Surface area per
 unit pellet
 volume
     5.00
  3.90
  3.26
                                         2.73
    2.31
 Respiration rate
 per unit pellet
 surface area
 (mgOz/m2/hr)
   346
411
454
                                       462
                                    481
 Separation and fluidization of Biopellets

 Separation of pellets

      Biopellets have to be separated from treated wastewater or activated
 sludge to maintain them in a reactor.  Two separation methods,  wedge-wire
 separation (Figure 7) and gravity separation,  were tested.   It  was thought
 before the experiments that pellets would be separated from activated sludge
 by a slight difference in the setting velocities of the pellets and the
 sludge.  But the apparent density of the pellets decreased from 1.06 to
 1.03, or less, due to the attached sludge so that stable pellet separation
 was difficult.'  On the other hand, wedge-wire worked well.   It  was found
 that wedge-wire should be installed at an angle of 30 to 60 from the
 water's surface.                       .

-------
              Air bubbles
            'l O '
Biopellets  i'o/ry'
                                                  Mixed liquor
                                           I  Wedge-wire
                                          ^Titling angle
              Figure 7.  Biopellet separation with wedge-wire.


     To determine the conditions for wedge-wire separation of pellets,
several studies were carried out using a 200 Z reactor.  The effects of
wedge-wire opening on the separation of pelltes with different diameters are
shown in Table 4.  Each separation test was continued for one hour.  Both   *
pellet loss ratios and wedge-wire clogging ratios were measured after one
hour operation.  For the combination of a wedge-wire with a 1mm opening and
pellets with 2.00 to 2.83mm diameters, pellet loss was less than 0.1%, and
the clogging ratio was less than 5%.  When a wedge-wire with a 1.5mm
openning and pellets with diameters of more than 2.83mm were used, the
ratios were the same as with the previous combination.  These ratios, 0.1%
loss and 5% clogging, did not cause any operational problems.  This result
indicates that the pallet diameter should be at least two times as large as
the wedge-wire opening.            '
                                     277

-------
         Table 4.  Effects of wedge-wire opening on separation of
                   pellets with different diameters.
    Wedge-wire

    opening (nun)
0.5
1.0
                                 1.5
   Pellet diamter 1.68- 2.00- 2.83 1.68- 2.00- 2.83 1.68- 2.00- 2.83
    (mm)           2.00  2.83 <     2.00  2.83 <     2.00  2.83 <
Pellet loss
ratio (%)
Wedge-wire
clogging
ratio (%)
000 0.4 0.1 0 9.1 1.4 <0.1
0 0 0 20 5 0 40 20 <5
Note:  The pellet  loss ratio is the ratio of the pellet loss measured
       after one hour operation to the pellet volume in the nitrification
       tank.  The  wedgewire clogging ratio is the ratio of the clogged
       area to  the entire wedge wire area.  * .

       Operating conditons:
       Wedge-wire  separation rate = 1.25m3/m2/min.
       Air flow rate = 0.08m3/m3 - tank volume/min.


     The effects of separation rates and air flow rates on pressure loss at
the wedge-wire are shown in Table 5.   Approximately 2m3/hour of air flow
to unit volume of the aeration tank with 3-hour HRT is required for
biological treatment with nitrification.  This is based on 25 mg/e influent
ammonium nitrogen and 15% oxygen transfer efficiency.  The air flow rate is
equivalent to an aeration intensity of 1.28m3/m2-floor area/min at a
water depth of 4m.  Unit area of wedge-wire separated 1.28m /min of mixed
liquor from a aeration tank with 10% pellets by volume at aeration
intensities between 0.08 and 0.16m3/m*/min.  When the pellet volume was
increased to 20%,  the pressure loss increased, and the separating capacity
of unit area wedge-wire decreased considerably.  This means that a larger
wedge-wire area is required for effective separation of mixed liquor at
higher pellet volume ratios.  The mixed liquor flow to be separated is equal
to the sum of the  inflow rate and recycling rate when a nitrified liquor
recycling system is employed.  A IN Process treating 10,000m /day of
wastewater at  a 10% pellet volume ratio and 300% recycling rate requires a
wedge-wire separating system with a 20m  area.
                                      278

-------
          Table 5.  Effects of separation rates and air flow rates on
                    pressure loss at wedge-wire
                                          Inflow rate
     Air flow rate
0.96
                                       1.28         1.60         1.92
                                    m3/m2/min.   m3/m2/min.   m3/m2/min.
     No aeration
             x/x
     0.08 m3/ma/min.
O/A
o/x
x/x
                                                                 x/x
     0.16 m3/m2/min.
o/A
o/x
o/x
     0.24
o/o
                                       p/A
                          x/x
     0.40 m3/m2/min.
             O/A
             O/A
                                                                 x/x
   Note:  Pellet volume ratio of 10% / Pellet volume ratio of 20%
                               &       '
          o:  No operation problem

          A:  Pellets continue attaching and detaching to the wedge-wire
              randomly.  This causes, a sudden increase/release of pressure
              loss.  Due to the fluctuation, the separation'is not be
              maintained at a constant rate.

          x:  Great pressure loss.  Continuous operation is not possible.

          Operating conditions:
              Pellet diamter > 1.68 mm.
              Wedge-wire opening = 0.5 mm
Fluidization of pelJLets

     The fluidization test on the pellets was conducted under whole-floor
aeration in a pilot-scale nitrification tank (effective volume = 4.2m3).
The pellet volume ratio to the nitrification tank was set at 15 and 20%.
Air supplied at 1.25m /hour to unit cubic meter of tank volume fluidized
pellets uniformly under both conditions.  The air requirement for fluidizing
pellets uniformly increased to 2.5m3/m3-tank/hour when the pellet volume
ratio was 30%.  The boilogical air requirement for both BOD removal from and
nitrification of ordinary municipal wastewater is about 2m3/m3/hour at 3
hour HRT in a whole-floor aeration tank.  This means that fluidization will
be achieved with air supply to meet the biological need when the pellet
volume ratio is less than 20%.
                                     279

-------
Application of Biopellets  to  secondary effluent nitrification
                                     *
     Temperature largely influences  the nitrification of wastewater.  In
ordinary activated sludge  plants,  nitrification proceeds to some extent in
summer, but not in winter.  Since  partial nitrification often causes
effluent BOD5 to increase,  nitrification must be carefully monitored even
in plants targeting  only organic removal.  Considering such problems in this
section, the application of Biopellets to secondary effluent nitirification
is discussed.

     A pilot study was carried out using a 200 L reactor nitrifying
secondary effluent.   The pilot plant was as shown in Figure 8.  The treated
secondary effluent was pumped from a secondary settling tank in an activated
sludge plant to the  pilot  plant.  Nitrified wastewater in the reactor
containing  Biopellets was  separated by wedge-wire.
                                            Pellet separator
                                                                         Effluent
        Submerged  Feed
        pump      tank

   Secondary settling tank
                           Pump
                                                compressor
Storage tank
        Figure 8.   Schematic flow diagram of the pilot plant nitrifying
                    secondary effluent.
                                      280

-------
     The operating conditions were as shown in Table 6.  The pellet volume
ratio was 20%,at 2 hour HRT, and 30% at 1 hour HRT.  Water temperatures were
between 10 and 12C.  Influent ammonium nitrogen concentrations were 20 to
30mg/e.  The experimental results are shown in Figure 9.  Complete
nitrification was achieved when the ammonia volumetric loadings were 0.2 to
0.4kg-N/m3/day at 2 hour HRT.  Increasing ammonia loadings to a range
between 0.5 and 0.7kg-N/m3/day caused nitrification to .lightly
deteriorate.  However, effluent ammonium nitrogen concentrations were still
less than 2mg/, and more than 95% of the ammonium nitrogen was removed.
When the dissolved oxygen concentrations in the reactor decreased, the
nitrifying efficiency dropped.  This might have been caused by oxygen
deficiency.

              '                                                      a.
    Table 6.  Operating conditions for secondary effluent nitrification.
Run 1
Water temperature (C) 10 - 12
Pellet volume ratio(%) 20
Retention time (hour) 2
Run 2
10 -12
30
1
             Ammonium nitrogen
             volumetric loading
             (kg/m3/day)
0.2 - 0.4   0.5 - 0.7
                                     281

-------
             Run 1
                                     Run 2
     100

8 ^  9

Si  8

2 3  7
!<*;  6
IB   o =t_
   30
   25
  20

   15
   10
          0000-  00Q  00
                     00    0  ,

                      _o_a
           Influent

                           Dissolved oxygen

                           deficiency
                                               Influent
Dissolved oxygen
deficiency
         Jan/20    25      Feb/1
                                                  15     20
  Figure 9.  Results of  secondary effluent nitrification.
                                282

-------
     The nitrifying rates of the pellets used in the pilot  experiment were
measured in a  small batch reactor.  The pellet volume ratio wS increased by
steps, from 10%,  to 20%,  to 40%.  The results of the batch  stSy are X    *
shown xn Figure  10.   The  nitrifying rates were 147mg-N/L-pellets/hour It 10%
pellet volume  ratio,  140mg-N/L/hour at 20%, and 83mg-N/L/hour at 40%
increasing  the pellet volume ratio means decreasing the nitrifying  rate per'
unit volume of pellets.   Oxygen transfer to liquid may have controlled tnT
nitrifying  rates  of  the pellets.  In-addition,  a larger area of  wedgj-wirj
was required for  pellet separation at higher pellet volume  ratios
Therefore,  the feasible pellet  volume ratio should be limited to 20%
             30
             20
          c
          0)
             10
                               Pellet volume ratio
                              ^40%
Reagent   :
Water     :
temperature
PH       :
Secondary effluent
10 toa2C  .

6.7 to 8
(Jan.- 26, '88, Jan. 27, '88)
                                 Time (hr)
                 Figure 10.   Results of batch'experiment.


        fetent0n *ime  ^quired for'complete nitrification at 20% pellet
         to ^S ?  Y ne hUr'  ^^ n thS *** Stud^  However,^ is
  that    a Sman^/h  OXy9f  Concetration in ^ full-scale reactor as high
                  batCh  react-  Moreover,  maintaining high oxygen
                                    283

-------
Application of Biopellets to nitrogen removal  (the  IN Process)

Preliminary study

     The -application of Biopellets to biological nitrogen removal processes
enables a Significant reduction in the required reactor volume.  To confirm
the treatment performance and-to determine operation  conditions  a
preliminary study was conducted.  Biopellets were applied to the nitrified
liquor recycling activated sludge process.

     The reactor used was as shown in Figure 11.  The reactor consisted of a
denitrification tank, a nitrification tank, and a final  settling tank   In
the nitrification tank, wastewater was mixed with return sludge, and the
nitrified  liquor recycled.  Denitrification occurred in  the tank,  and
simultaneously, some of the organics were consumed  as carbon sources for
S^5Steatt.  The mixed  liquor then flowed into the  nitrification tank,
containing Biopellets.  Organic removal by the activated sludge  and
SSif ication S both  the activated  sludge and Biopellets  proceeded at this
?ime    The wedge-wire  installed near the top of the tank-separated nitrified
Sor  from  thJ pellets.   The separated nitrified liquor was partly recycled
to the  denitrification tank,  and the rest was introduced into a final
settling tank.
Dentrification Nitrification
tank           tank
                                           set
                          0 0
                  Nitrified
               ,.T liquor
                 I recycling
                 L___J^I_
                                                            Kf f 1 tient:
                                                    .Biopellets
                                                    (Pellet volume ratio:10%)
                                                                  sludae
      1.6m/day     Return sludge


          Figure 11.   Flow diagram of IN Process for preliminary study.


       The operating conditions are shown in Table 7.  The treated wastewater
  was the primary effluent of the municipal wastewater.  The retention times
  in the denitrification, nitrification, and final settling tanks were 3
  hours, 3 hours, and 1.8 hours, respectively.  The reactor volume requirement
  was almost the same as that for the conventional activated sludge process.
  The Sludge return ratio was 100%, and the nitrified recycling ratio was
  300%.  Twenty liters of pellets were added to the nitrification tank.  The
  pellet volume ratio was equivalent to 10%.
                                       284

-------
    Table 7.  Operating conditions for preliminary study of the IN Process.
Nitrification tank
Denitrification tank
Final settling tank
Pellet volume ratio
Sludge return ratio
MLSS
Nitrified recycling
ratio
BOD volumetric loading
T-N volumetric loading
Effective volume: 2002, Retention time: 3
Effective volume: 2002, Retention time: 3
Effective volume: 1202, Retention time: 1.
hours
hours
8 hours
10% of the effective volume of the nitrification
tank
100%
2,000 to>3,000 mg/je
300% .
1.46 kg/m3/day to the denitrification tank
0.31 kg/m3/day to the nitrification tank





 Note:  Operating condition during winter: Water  temperature is  15  to 16C.


     The experimental results are  shown in Figure 12.  The influent BOD*
suspended solids,  and total nitrogen were 120 to 300mg/, 120 to SMOg/I'-and
30 to 60mg/, respectively.  The average volumetric loadings during the
experimental period were 1.46kg/m3/day for BOD5/ and 0.31kg/m3/day for
total nitrogen.  During the experiment, both the -BOD and suspended solids
were removed to 20mg/, or less, and .the total nitrogen was reduced to less
than 10mg/2.  The ammonium nitrogen concentrations remaining in the effluent
were less than 2mg/.  These results demonstrated that Biopellets work well
even in activated sludge, and that the IN Process is feasible as a
biological nitrogen removal process.
                                    285

-------
I
P
,s
 0)
 o
 OH
 CP s '
300
     200
     100
               Influent
                   Effluent
          Q   o
                                  .  o ' o
c
o
H
U
P
C
c^
O H
O)
(A E


300
250
200

150
100

50
n
Influent
-
*
A
 
*

Effluent
O r> . n i O i O i
Dec/1 11 21 Jan/1 11 21
Time (day)
c
0
-rl
-P
to
4J
C

O
c
o 
O H
?!
t" -^
60
50

40


30

20
10
n
-
Influent

- * 
& 
 e


Effluent
o 0  o oo
1 1 	 1 	 1 	



1





o
1
                                        o
                                        P
                                        to
                                        I
                                              8"
                                                  30
                                                   20
                                                   10
                                                                   influent
                                                                 Effluent
                                                                   o
                                                               o
                                                                           n  i n
                                                   Dec/1    11    21    Jan/1   11    21

                                                                 Time (day)
                  Average BOD load :   1.46 kg/m3/day  (denitrification tank)
                  Average T-N load :   0.31 kg/m3/day  (nitrification tank)
                  MLSS            :   2,000 to 3,000  mg/Z
                  Water temperature:   15  to 16"C


                Figure 12.  Results of preliminary study on IN Process.


          The sharing of ammonium nitrogen between the  Biopellets and the
     activated sludge in summer and in winter is  shown  in  Figure 13.  The
     nitrification  rates of the Biopellets and activated sludge  were nearly equal
     in summer.   The rate of  the activated sludge decreased in winter, while the
     rate of the  Biopellets increased and supplemented  activated sludge.  The
     nitrification  rate of the Biopellets in winter  was lOOmg-N/L-pellets/hour.
     This rate is not much lower than the figure  obtained  in secondary effluent
     nitrification  (140 mg-N/L-pellets/hour).
                                            286

-------
                H
                P
                s
                
                o
                2
                                  Activated sludge (winter)
                                  (MLSS:2000mg/l)
                                     Activated sludge (summer)
                                     (MLSS:2500mg/l)
(summer)
   ratio:10%)
   (winter)
 volume ratio:10%)
                       0    1    2    34     5

                                  Time (hr)
        Figure 13.  Sharing of ammonium nitrogen between Biopellets and
                    activated sludge.


 Pilot plant study


 .  c^A3pilot  plant study was initiated in November 1988.   The plant capacity
 is 50m /day.  -The primary objectives of this study were:

     a.  to confirm the treatment performance throughout  a year,
     b.  to clarify operational characteristics,  such as  fluidization and
         separation of pellets and nitrified liquor recycling,  and
     c.  to esatablish design and operation/maintenance procedures.

     The pilot plant experiment will last to the  end of this year.  This
section introduces interim results obtained last  winter.
                                      287

-------
     A flow diagram and the specifications of the pilot plant are shown in
Figure 14.  Raw wastewater is pumped up from a municipal wastewater
treatment plant to the experimental yard in the same plant.  After temporary
storage in a feed tank, the raw wastewater is settled in a primary
sedimentation tank.  The primary effluent is treated by a scaled-down pilot
IN Process.  The process configuration is alomst the same as that for the
preliminary study, but excludes the nitrified recycling system.  The
nitrification tank is aerated, making the contents overflow into the
denitrification tank by air-lift effect, to thus recycle the nitrified
liquid.  The volume of Biopellets. added into the nitrification tank is 10%
of the tank's effective volume.
                                 t
     The operating conditions last winter are shown in Table 8.  The
influent BOD5 and total nitrogen concentrations were 100 to 200mg/ and 20
to 30mg/, respectively.  The detention times were 4.8 hours for
denitrification, and 3.2 hours for nitrification at the constant inflow rate
of 31.5m3/day.  The air flow rate, sludge return ratio, and nitirified
liquor recycling ratio were controlled at 140L-air/min, 40%, and 300%,
respectively.  The MLSS concentration fluctuated in the range between 2,000
and 3,OOOmg/2, and the water temperatures were between 10 and 12C.
                                     288

-------
                                       3
                                       (0 -P
                                          CN  10


                                       X  X CN





                                   COfE
                                   c in ro 3
                                   ^  M CO pr)
                                   >
                                   


            S
            rH

            0,
                                                       -H
                                                        a
           s
            
           8
                                                       w  u/

                                                      58
          0)
Ra
289

-------
 Table 8.  Operating conditions for pilot plant study of the IN Process.
 Primary settling tank
 Nitrification tank
 Denitrification tank


 Final settling tank
 Pellet volume ratio
Water surface area: 2.9 m2,
Overflow loading  : 10.9m3/m2/day

Effective volume: 4.2 m3,
Retention time  : 3.2 hours

Effective volume: 6.3 m3,
Retention time  : 4.8 hours

Water surface area: 3.8 m2,
Overflow loading   : 8.3 m3/m2/day
 7.5% of  the effective volume of the
 nitrification tank.
 Nitrified  recycling ratio ,  40%
  BOD volumetric
                                        /day to  the denitrification tank
     The treatment performance is shown in Figure  15.  The average

                                                               -.,

Scarification was almost completed.  The transparency of the final
effluent was not as good as that from the conventional system. More
consideration should be given to, this point.
                                     290

-------
           200 r
           150
           100
           50
                                   Influent
                                   Effluent
             20     Feb/1   10     20    Mar/1   10
Figure 15.   Results of pilot study on IN Process in Winter.
                           291

-------
Initial and 0/M costs for the In Process

     The initial cost and the operation/maintenace costs for the IN Process
were estimated by the interim results, and were compared with those for the
conventional biological nitrogen removal process.  Conditions for the
estimation are shown in Table 9, and the results are shown in Table 10.
Since the reactor volume requirement was reduced to half that for the
conventional system, the initial cost was reduced greatly.  The estimate did
not include land cost.  This means that the saving should be greater in
larger cities, where land costs are extremely expensive.  Furthermore, one
feature on the IN Process is that it can save land area, which is the
biggest advantage for existing treatment plants.  In fact, there is no space
for retrofitting advance treatment in most of the treatment plants in large
cities, nor surround them.
            Table 9.  Conditions for estimation of initial cost,
                      and operation/maintenance costs.
                                                  Conventional biological
                                  IN Process       nitrogen removal
                                                  process
  Flow rate
                10,000 m3/day
  Influent BOD
                  120 mg/
  Effluent  BOD
               20 mg/ or less
  Influent  NH4-N
                   25 mg/
  Effluent T-N
               10 mg/ or less
  Lowest water temperature
                                                 13C
  Nitrification rate
'96 mgN/-pellets/hour    0.67 mgN/gSS/hour
  Denitrificatipn rate
 1.04 mgN/gSS/hour
0.71 mgN/gSS/hour
  MLSS
,3,000 mg/
3,000 mg/
                                      292

-------
Table 10.
Estimates of initial and O/M costs for  the  IN Process.
                                IN Process  Conventional biological
                                            nitrogen removal process
Reactor volume (m3)
Retention time (hour)
Nitrification tank (m3)
. Retention time (hour)
Denitrification tank (m3)
Retention time (hour).
Pellet volume (m3)
Initial cost (yen)
Civil .works (yen)
Installations (yen)
Operation and maintenance
cost (yen/year)
Power requirement (yen/year)
Pellet cost (yen/year)
Repairs (yen/year)
Treatment unit cost (yen/m3)
3,330
8
1,330
3.2
2,000
4.8
. 100 (7.5%)
540,000,000
250,000,000
290,000,000
35,000,000
15,000,000
6,000,000
14,000,000
10
6,670
16.
4,170
10
2,500
6
-
790,000,000
480,000,000
310,000,000
46,000,000
31,000,000
15,000,000
13
Note: It is supposed that the air-lift r^von c,i 	 * _.,. _.i_. _,
           .               	-~ -v,>^jr^j.j.iiv.) oyocciu uj. xiitiririec
   liquor  is employed for the IN Process,  while a pump recycling
   system  for  the conventional  biological  nitrogen removal process.
   Owing to the higher aeration strength of the nitrification tank
   for the IN  process (2.02 mVm3. tank/hour,  versus 0.50 m3/m3
                                   Process),  a greater gas hold up in
                           is achieved.   This simplifies recycling of
             liquor by the air-lift method.   As a result,  the IN  "
   process requires no driving power for recycling.   The estimation
   is made in  terms of  the reactor only.   Therefore,  the above costs
   do not include those for the primary  and  final settling tanks
                              293

-------
     The estimate of O/M costs did not include the cost for personnel.
Therefore, the costs for agitating denitrification tanks, aerating
nitrification tanks, and maintaining mechanical and electrical devices are
dominant in the estimate.  Additionally in the IN Process, the cost for
pellets had to be included because Biopellets would be damaged after a
long-term operation.  The duration of Biopellts was assumed to be 5 years.
The results indicated that the O/M costs for the IN Process is less
expensive, (by 3yen/m3-treated) than that for the conventional process.
This is due mainly to the air lift recycling system of nitrified liquor,
which was applied for the IN Process.  If pumps are employed for recycling,
the costs will be increase by 4yen/m3, and will be slightly more expensive
compared to the conventional system.  From this viewpoint, the establishment
of the air-lift recycling system is important to promote, the application of
the IN Process as well as prolonging the duration of the Biopellets.
     s            *

Acknowledgements

     The authors wish to express their thanks to the following people:  Mr.
Aoyama, Deputy Director  of the Kitano Sewage Treatment Plant of Hachiouji
City, for his valuable suggestions on the pilot study ongoing in his  plant;
Mr. Mizuguchi, Mr. Mori, Mr. Emori, and Mr. Nakamura, co-researchers  from
the Hitachi Plant Construction Co., Ltd., for contributing to the
development of the Biopellets and  the IN Process; and Mr.  Kyosai, Research
Coordinator, Dr.  Sato, Section Chief and Dr. Mbriyama, Senior Researcher of
the Water Quality Control Division, Public Works Research Institute,
Ministry  of Construction, for serving as advisors during the entire project.
                                      294

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CURRENT STATUS AND FUTURE DIRECTION OF ORGANIC TOXICS CONTROL
                 IN THE WATER ENVIRONMENT -
         DISCHARGE REGULATIONS AND STREAM STANDARDS
                             by
                     William  F.  Brandes
                      Catherine Crane
              Environmental Protection Agency
                      Office of Water
                      Permits Division
                      Washington,  D.C.
     This paper has been' reviewed in accordance with
     The U.S. Environmental Protection Agency's peer
     and administrative review policies and approved
             for presentation  and publication.
               Prepared  for presentation at:

          Twelfth United States/Japan Conference
              on Sewage Treatment Technology
                     Cincinnati, Ohio

                   October 12-13, 1989
                           295

-------
I.   INTRODUCTION






















ecosystems.               problems associated with the discharge of






































 the difficulty of obtaining positive identification of these















                        analyses o  eluent an,
  biological  and chemical assessment methods.



  II.  IEGISLATIVE FRAMEWORK
                            ?s ssss
  water pollution control efforts across the country
                                   296

-------
      The emphasis changed from strictly water quality-based
      standards (biological endpoint-based)  to technology-based
      standards (wastewater engineering-based).   The introduction
      of technology-based effluent guidelines shifted the burden
      to the discharger to meet the discharge limits achievable
     "through already existing, defined control technologies.

      The NPDES permit program was established limiting the levels
      of pollutants allowable in effluent discharges.    The
      program is under EPAs'  authority and applies to all direct
      dischargers.    To date,  NPDES permits  have been issued to
      over 65,000 dischargers.    This includes  more than 50,000
      industrial dischargers  and over 15,000 municipal dischargers
      which release wastewater directly to surface waters.   There
      are as many as ah additional 100,000 "indirect"  industrial
      dischargers releasing wastewater to the sewer systems of
      publicly owned treatment works (POTWs).    These  indirect
      dischargers are regulated by the POTW  through the national
      pretreatment program.

      Enforcement authority was succinctly defined by  making
      illegal all discharges  to U.S.  waters  without a  permit, and
      allowed for civil and criminal penalties  in cases of
      noncompliance.

      A  national policy on  toxics  was established which prohibited
      the discharge of toxic pollutants  in toxic amounts.

      o   In 1977 Congress passed the Clean Water Act (CWA)  to refine
some  of the requirements originally set  out in the 1972  law in  order
to emphasize the control of toxic pollutants.    Among the  most
important modifications made to the 1972  requirements were the
revisions to the Effluent  Guidelines and  Pretreatment programs:

      The National  Effluent Limitation Guidelines  program sets
      forth uniform national standards for direct  dischargers,
     -developed  on  an  industry-by-industry basis utilizing
      existing control  technologies.   in  an effort  to stimulate
      advances in toxic control mechanisms the  CWA established a
      list  of  126 "priority pollutants", produced  by 21 categories
      of  industries, which must be specifically addressed in the
     development of effluent limitations  guidelines.   This list
      includes 111  organic compounds,  13 heavy metals, asbestos
     and  cyanide.

     The National  Pretreatment Program regulates the  introduction
     of pollutants from nondomestic sources into sewer systems of
     POTWs.                    ,

    .o  In 1987, amendments were made to the CWA, known as the Water
Quality Act  (WQA), in order to further encourage control of and
research on toxic pollutants and their effects.
                              297

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-    Because Congress recognized that progress on chemical
     specific controls was slow, a dual approach was developed to
     facilitate water quality improvement.   Section 303(c)(2)(A)
     of the WQA requires that States develop water quality
     criteria based on biological monitoring or assessment
     methods.

     Under section 304(1) of the WQA"each State must prepare
     lists of 'its waterways which do not meet water quality
     standards.   The States must develop individual control
     strategies  (NPDES permits), to reduce the amount of toxic
     substances being released by point sources.'

     Increased Congressional concern for toxics is also reflected
     in amendments to section 405 which requires EPA to identify
     toxic substances in sewage sludge and develop numerical
     limits  for maximum allowable concentrations.   A total of 16
     organic chemicals are to be controlled via numeric
     limitations.

  III.  CURRENT  STATUS OF ORGANIC TOXICS CONTROL EFFORTS

 Technology-Based Standards

     The  CWA requires the development of national standards for
 treatment technologies for direct dischargers, which are  implemented
 through the  NPDES. permit program.    Technology-based effluent limits
 define a  minimum level of control and are  imposed at the  point of
 discharge or "end-of-pipe".    Organic toxics  are controlled through
 Best Available Technology Economically Achievable  (BAT).
      The most significant effluent limitation guideline  to be
 developed to date for the control of organic  toxics  is  the organic
 chemicals, plastics,  and synthetic  fibers  (OCPSF) effluent limitations
 guideline issued in November of 1988.   Typically,  organic chemical
 manufacturing facilities discharge  more than  60 toxic  substances in
 their wastestreams.   With at least 400 indirect dischargers  and 300
 direct dischargers  nationally,  organic chemicals facilities affect a
 large number of  receiving waters.

 Water Quality-Based Standards

      Existing technology-based permits require limits  on a specific
 set of known pollutants  which are treated to  a specific level by BAT.
 This approach may not address complex effluents where  combinations of
 chemicals may have additive  effects, or  effluents  containing  toxicants
 not found on EPA's priority pollutant list.    Water quality-based
 permitting is used in cases  where limits  more stringent than
 technology-based are necessary to protect the designated use  (such as
 a fishable river usage)  of the receiving waters.

      Water Quality Criteria and Advisories.   Using experience gained
 by States and EPA Regions in toxic impact analysis, EPA is developing
 new water quality criteria for high priority toxicants as well as
 advisories  for toxicants for which more limited information is
                                 298

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 available.   For example, EPA is issuing a criterion for organotin
 compounds because these compounds have been found to cause toxic
 impacts in harbors where organotin paints are used to protect ship
 ^   ;>,    ?ef c?lteria are bein9 developed for pesticides found: to
 pass through typical treatment systems.

 . .    Whole Effluent Toxi city Toting is often a preliminary step in
 the process of setting water quality-based permit limits for toxic
 pollutants.   Effluent toxicity is measured by exposing test organisms
 to varying concentrations of an effluent/water mix to measure the"
 aggregate toxic effect on living organisms.

  ,_ ,  Toxicity Reduction Evaluation (TRE) .    A TRE is initiated if tho
 whole effluent toxicity test indicates an unacceptable" re"ve"l of
 toxicity.    A TRE is a site-specific study conducted in a step-wise
 process to narrow the search for effective control measures for
 effluent toxicity.    These studies are designed to identify the
 causative agents of effluent toxicity,  isolate the sources of effluent
 toxicity  evaluate the effectiveness of toxicity control options  and
 then  confirm the reduction in effluent toxicity          options, ana
      Whole effluent toxicity tests have been used in detecting
          tn t^/?flu;?ts f POTWs across  the ^tion.   TREs hive then
          identifying the causative agents  of this effluent toxicitv
           6'  ^ nUmbSr ^ a?eS organophosphate pesticides have been
            as the cause of toxicity in  POTW effluents.    One such
 compound,  diazinon,  has been repeatedly identified as  either the
 primary toxicant, or a substantial contributor to the effluent
 t-oxic 1 t
 ad
 aided
     Due to the, unexpected presence of toxic concentrations  of  '
diazinon in diverse effluents, the National Effluent Toxicity
Assessment Center  (NETAC) has conducted a national survey of 28 POTW
inSS;K%b0? *?X1Clty ?aused by diazinon.   The resultsof  this study
indicate that diazinon is present in 61 percent of the POTWs tested
though toxic levels of diazinon tended to be restricted to the
southern region of the nation.   The relatively widespread occurrence
of this compound in POTW effluents would likely have gone undetected
were it not for the use of toxicity testing and TREs.     undetected

Pretreatment

_,., pretreatment programs require that industrial dischargers to
POTWs reduce the level of pollutants in their process wastewaters
Approximately 1500 of the 15,000 POTWs in the 5 . S . Sre ^iqSSed to
implement pretreatment programs as part of their NPOE?

                                                                -der
     Prohibited Discharge Stand^r-ri
 trucral daaae
structural damage;
                                    include both general and specific
                                     include prbh!bi?SJs agaSJ? ^
                     from any nondomestic user which cause pass
                           ^.includes prohibitions agains?
                           V  fir& r exPlosion hazards; 2). corrosive
                      interference due to flow obstruction; 4)
                                299

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interference due to flow rate or concentration; and 5)  interference
due to heat .                                            .

     categorical Pretrea^^-nt standards are incorporated into local
permit requirements to limit potentially hazardous discharges.
Categorical standards are developed from effluent limitations
guidelines and identify what level of a specific Pollutant ^ cause
interference with treatment systems and what amount of the pollutant
is removed by typical treatment processes.

     T.ocal limits are utilized by the POTW because categorical
standards are minimum requirements which apply to broad classes of
industries and do not necessarily address all industrial discharge
problems that might occur at a given POTW.   To prevent site-specific
problems, each POTW must assess all of its industrial discharges and
employ sound technical procedures to develop defensible local limits
that will adequately protect the POTW, its personnel and the  .
                    local  limits a POTW must conduct an industrial
waste  survey to  locate  and  identify all  industrial users as well as
the  character  and volume  of their pollutant discharges.   The POTW
then determines  which pollutants have the potential for interference,
pass through or  sludge  contamination.    Then  for  each pollutant of
concern the POTW must determine the maximum loading which can be
accepted by the  treatment facility without problems.   The POTW must
then implement a system of  local permit  limits  to ensure that the
maximum loadings will not be  exceeded.
                                         t
V.   Future Directions  '

     As environmental monitoring and  detection  capabilities become
more sophisticated, the pervasiveness and consequences of toxic
pollution become increasingly evident.    In  response  to our expanding
awareness of  the impacts  associated with toxic  contamination,  control
efforts have  been refined to greater  levels  of  efficacy and
comprehensiveness.    In order to  continue to progress in  this  area  EPA
 is both building on established programs and developing new
methodologies .

      Technoloav-based effluent limitations guidelines are continuously
 being developed for additional industries.    Two effluent guidelines
 currently under development will  have considerable impact on organic
 toxics discharges.    These guidelines are for the pharmaceutical and
 pesticide industries.   Both of these industries discharge wide
 varieties of organic toxics and few have met BAT control  standards.

      Water quality-based limits will continue to be a major focus of
 pollution control.   Point sources and other sources of pollution such
 as  storm water  discharges will be given limits to protect local water .
 quality.

       Sewage sludge is  produced at the rate of 7.6 million tons per
 year  in the U.S-. ,  and  this rate is expected to double by the year
 2000.   Sludge may  contain  unacceptable  levels of toxic substances,
                                 300

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particularly heavy metals and organics.    When properly treated,
sludge can be beneficially used as a soil conditioner and fertilizer.
EPA encourages beneficial reuse of sludge whenever environmentally
feasible.   To this end, EPA is developing regulations and procedures
for identifying, managing and reducing the amount of toxic pollutants
in municipal sludge based on sludge use and disposal practices.

     Bioconcentratable Contaminants are compounds that have the
ability, due to their chemical properties, to accumulate in fish-and
shellfish tissues in concentrations hazardous to human consumers.
Water quality criteria and effluent guidelines designed to prevent
acute and short-term toxicity to aquatic life may not be sufficient to
protect human health.   EPA is exploring methods that will allow
environmental managers to identify and quantitate bioconcentratable
pollutants in effluents, and develop acceptable ambient criteria,
wasteload allocations and effluent limitations for these pollutants.

     Sediment Assessment is utilized to evaluate toxic contaminants in
the bottom sediments of lakes, rivers and coastal waters for potential
adverse impacts to biota and water quality.   Historically, water
quality-based standards have not been developed to directly protect
sediment quality or the beneficial uses associated with uncontaminated
sediments.   Sediment assessment is being analyzed as a means to
target dischargers and develop more stringent effluent limits.

     Pollution Prevention reflects EPA's policy to reduce the amount
and toxicity of pollutant's being discharged,  either directly or
indirectly through POTWs, to waters of the U.S.    Increasingly
stringent controls and better detection methods encourages dischargers
to begin in-plant recycling programs or to substitute less toxic
compounds in their production processes to reduce the levels or
toxicity of their discharges.
                                301

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PERFORMANCE OF FINE PORE AERATION SYSTEMS IN PROCESS WATER
                                  by

      - ..   WffliamC. Boyle, University of Wisconsin-Madison
      Richard C. Brenner, U.S. EPA, Risk Reduction Research Laboratory
                  James J. Marx, Donohue and Associates
                   Thomas C. Rooney, Sanitary Engineer
         This paper has been reviewed in accordance with the U.S
         Environmental Protection Agency's peer and administrative
         review policies and approved for presentation and publication
                      Prepared for Presentation at:

                 Twelfth United States/Tapan Conference
                    on Sewage Treatment Technology
                           Cincinnati, Ohio

                         October 12-13,1989
                                303

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                                  INTRODUCTION
     cement of less efficient action systems with fine pore aeration devices can save up to 50
.	at in aeration energy costs and has resulted in typical simple pay back periods of two to six
ware As aresult of these very impressive cost savings, more than 1,300 municipal and industrial
Slwater Sent facilities* the United States and Cf ada now use fine pore aeration. In
5 the U S Environmental Protection Agency (EPA) funded a CooperativeResearch
     men
oiifine pore diffused aeration systems in both clean and process waters, conduct field studies at a
number& municipal wastewater treatment facilities employing fine pore aeration and prepare a
comprehensive manual addressing the design, operation, maintenance, control, and economics ot
fine pore aeration systems.

    A Design Manual on Fine Pore Aeration was produced from this effort by U.S. EPA(2).
This presentation summarizes a portion of this manual which discusses the performance of fine
pore aeration systems under process conditions.

    The term "fine bubble" diffused aeration is elusive and difficult to define.  ^ term "fine
tjore" was adopted to more nearly reflect the porous characteristics of the high efficiency diffusers
mariceSoda?Ty^Sy, fine pore diffuserswill produce a headloss due to surface tension m
S^wlterof greater thai about 5 cm water gauge (w.g.).  For the purposes of this paper, fine
pore diffusers are defined as including the following devices:

      Porous ceramic plates, discs, domes, and tubes
      Rigid porous plastic plates, discs, and tubes
      Nonrigid porous plastic tubes
      Perforated membrane tubes and discs

                          FACTORS AFFECTING PERFORMANCE

                                                *

     The performance of diffused aeration systems under process conditions is affected by a
 myriad of factors, some of the more important of which are:

      Changes in performance due to fouling, aging, fatigue, etc.
      Wastewater characteristics
      Loading conditions
       Process type and flow regime
       Basin geometry and diffuser placement
       Diffuser performance and characteristics
       Mixed liquor DO control and air supply flexibility
       Mechanical integrity of the system
       Quality of preventive maintenance
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      Manual of Practice FD-13 (3) is a good general reference on the importance of the above
 tactors  To minimize life-cycle costs of an aeration system, all of these factors must be considered
 during design and some must be controlled during operation.

      The areas of greatest concern in process water oxygen transfer performance of fine pore
 aeration systems are changes in performance due to fouling, aging, etc.; wastewater characteristics;
 process type and flow regime; and loading conditions. In a given case, any combination of these
 these factors can have a significant effect on the alpha (a) profile of a system, DO control and
 changes in aeration system performance with time due to diffuser fouling. Some of these factors
 are discussed in greater detail later in this paper.

                      CALCULATION OF PROCESS PERFORMANCE


     A substantial data base exists on the perforrhance of fine pore diffusers in clean water  In
 designing aeration systems to operate under process conditions, clean water data are corrected to
 account for the influences of process water characteristics,temperature, and pressure. The
 corrections are made using the following equations:
     OTFf = KLa20 OF 0CT-20) (T p

. where,
                                         - Q V
                                                                               (1)
 OTRf
 KLa
 V
 C*oo20     -

 c
 a         =
 P         -
 ecr-^)     =
 T
 a
 Q approx.  =
 Pb
 gamma     =
 PS

PVT       =


C*ST     =
               oxygen transfer rate under process conditions, mass/time
               apparent volumetric mass transfer coefficient in clean water I/time
               KLa at 20C, I/time
               volume of water, length3
               steady-state dissolved oxygen (DO) saturation concentration attained at infinite time
               for a given diffuser at 20<>C and 1 atm, mass/length3
               process water DO concentration, mass/length3
               (process water Ki,a of new diff user)/(clean water KLa of new diffuser)
               (process water C*W(clean water C*oo)
               temperature of process water being treated
               (Pb + gamma dg - P\rr)/(Ps + gamma dg - PVT)
               Pb/Ps (for basin depths <6.1 m or for elevations <600 m)
               atmospheric pressure at aeration system location, mass/Cength x time2)
               weight density of water at the test water temperature, force/length
               standard atmospheric pressure (1.0 atm of air at 100% relative humidity)
               mass/(length x time2)
               saturated vapor pressure of water at temperature T, mass/(length x time2)
               effective depth at infinite time, length
              tabular value of DO surface saturation concentration at temperature T and standard
              total pressure (1 atm at 100% relative humidity), mass/length3
              (process water KLa of a diffuser after a given time in service)/(KLa of a new
              diffuser in the same process water)
Since standard oxygen transfer rate in clean water, SOTR, is:
                                                                              (2)
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Equations 1 and 2 may be combined to calculate the process water oxygen transfer rate, OTRf:


    OTRf = aF(SOTR)0T-20(tpQC*oo20-C)/C*co20                            <3>

This equation can be rearranged as follows:


    OF(SOTR) = (OTRf C*o<,20 e^/Cr P Q C* C = 0).

    Further, since standard oxygen transfer efficiency, SOTE, may be defined as:

    SOTE = SOTR/Wo2                     .                                   (5)

where,

    Wo2 = mass flow rate of oxygen, mass/time

Equation 3 may also be used to describe process water oxygen transfer efficiency, OTEf, by direct
substitution of oF(SOTE), oxygen transfer efficiency under field conditions corrected to.standard
temperature and pressure, and a driving force of C*>20 fc>r ctF(SOTR).

    Although employing clean water SOTR values to estimate oxygen transfer rates in process
water is conceptually straightforward, the estimate of OTRf is subject to considerable doubt
because of the uncertainties contained in a and R These uncertainties are magnified when toe
process water application is based on a basin geometry and process temperature that differ from
 those of the clean water test.

     Table 1 is a guide for applying Equation 3 and indicates the source of information for the
 parameters needed to estimate OTRf.

                                    DIFFUSER FOULING


     All fine pore diffusers are susceptible to waterside buildup of biofilms and/or deposition of
 inorganic precipitates that can alter the operating characteristics of the diffusers. Porous diffuser
 media may also be susceptible to air-side clogging of pores due to particles in the supply air. Air
 diffusion media may also suffer changes in properties, and the integrity of the installation may
 change with time. These changes, which include alteration of diffuser media properties over time
 and leaks in the air piping or around diffuser gaskets, may be caused by type of materials selected,
 poor equipment design, improper installation, or inadequate inspection and maintenance.

      The rate of diffuser fouling has historically been gauged by the change in backpressure while
 in service.  Since significant levels of fouling can take place with little or no increase in
 backpressure but with substantial reductions in OTE, this provided a crude and qualitative measure
 at best.

      Better methods of measuring the degree of diffuser fouling and the effectiveness of diffuser
 cleaning became available in the early 1980s, These methods include dynamic wet pressure
 (DWP), bubble release vacuum (BRV), the ratio of one to the other, and chemical and      
 microbiological analysis (4). The practice of employing pilot diffusers that could be removed from
 the basin and individually analyzed also came into use during this period. DWP is defined as the
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 pressure differential (headless) in cm w.g. across the diffusion element when operating in a
 submerged condition at some specified airflow rate. BRV is a measure of the negative pressure in
 cm w.g. required to form and release bubbles in tap water from a localized point on the surface of a
 thoroughly-wetted porous element Normally, BRV denotes the average of the point BRV values
 for a specific diffuser.

     Concurrently, better methods were being developed to measure the oxygen transfer
 performance of operating aeration systems. These methods permitted better appraisal of the effects
 of fouling and facilitated improved preventive maintenance scheduling. These methods include
 inert gas tracers, off-gas analysis, a nonsteady-state technique that uses hydrogen peroxide, and
 DO and respiration rate profiles (5-8). Off-gas analysis equipment has been effectively used to
 evaluate the adverse effects of fouling on both full-scale diffused air systems and individual
 diffusers (5). For the U.S. EPA/ASCE Cooperative Agreement on fine pore aeration (2), off-gas
 analyses were used in all field studies. All investigators conducting field studies on this project
 were trained in the use of this equipment, all off-gas analyzers were of the same design^ and
 calculation methodology was standardized.

 TYPES OF FOULING

     Fouling can be classified as one of two general types, Type I or Type II. The two types have
 distinct characteristics and can occur alone or in combination with variable dominance from
 treatment plant to treatment plant and within the same treatment plant from time to time.

 Type I Fouling

     Type I fouling is characterized by clogging of the diffuser pores, either on the air side by
 airborne particulates or on the liquid side by precipitates such as metal hydroxides and carbonates.
 In the process of fouling, the areas of the diffusers with the highest local air flux foul more rapidly.
 This serves to reduce the flux in the high flow areas and increase it in low flow areas. The
 combined effect is to improve uniformity of air distribution. As fouling progresses, the BRV
^coefficient of variation  decreases (9).

     Eventually, the accumulation of foulant in the pores reduces the pore size and DWP rises
 correspondingly. The increase in DWP can exceed the capabilities of the air supply system, and
 process air delivery may fall short of requirements.  Also, the reduced effective pore diameters
 produce smaller bubbles such that OTE does not decline and can actually increase slightly. A
 schematic representation of Type I fouling is illustrated in Figure 1. An idealized plot of how OTE
 and DWP change with time is shown in Figure 2.

 Tvoe n Fouling

     Type n fouling is characterized by the formation and accretion of a biofilm layer on the surface
 of the diffuser.

     Figure 3 is a model of Type II fouling proposed by Costerton (10) based on scanning electron
 microscopy data collected on the biofilms that had thicknesses >1 mm. The microscopic work
 showed that the biofilms were composed of bacterial cells enmeshed in a matrix of their own
 amorphous exopolysaccharides.  Inorganic particles were trapped within the bacterial matrix. This
 composition has been observed in other biofilms found in natural and industrial aquatic systems
 (11). When a biofilm of this structure develops on a fine pore diffuser, the bubble release surface
 changes dramatically. Preliminary studies (10) indicate that bubble sizes increase, which may
 significantly reduce OTE.
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    Thin biofilm layers are usually not a problem, but as the biofilm thickness increases, BRV and
its coefficient of variation will increase, DWP will increase slightly or not at all, and OTE will
decrease substantially. The net result of nonuniform bubble release and an increase in bubble size
is a substantial reduction in OTE. Figure 4 is an idealized representation of OTE and DWP
changes with time under Type n fouling conditions.

EFFECTS OF FOULING ON PERFORMANCE

    As indicated above, fouling processes may affect BRV, DWP, and OTE.  Based on fouling
studies at nine municipal plants (12), the effects of diffuser fouling were divided into three
categories as shown in Table 2. the diffusers from the same plant could fit into more than one
category depending on the time in service and operating conditions of the plant.

    Equation (1) introduced a new term, F, that describes the impairment of diffuser performance
caused by diffuser fouling or diffuser media deterioration.  It has been introduced to separate the
effects of wastewater characteristics (a effects) and diffuser fouling (F effects) on the estimateof
process water oxygen transfer. F generally decreases from a value 1.0 with time in service.  The
characteristics of fouling dynamics are site and diffuser specific as hypothesized in Figure 5. At
this time, a linear model describing fouling dynamics has been introduced in the design manual (2)
and that conceptual model is shown in Figure 6.  The slope of the F vs. time curve represents the
fouling rate factor, fp, expressed in terms of a unit decrease per month. Therefore:

    fF = (F-1.0)/t = [cxF(SOTE)o-ocF(SOTE)t]/aF(SOTE)ot                     (6)

    This model assumes that there is a minimum value of F, Fmjn, that occurs after some critical
service period, tc. It may be reasonably assumed that Fmin approaches the ratio of the oxygen
transfer performance of a coarse bubble diffuser  to that of an unfouled fine pore diffuser in
question, both diffusers being in the same physical basin configuration and operating under the
same process loadings.                                      *

    F and its functional relationship with time can be estimated by:

     Conducting full-scale OTE tests in process water over a period of time
     Monitoring aeration system efficiency using operational data
     Conducting OTE tests on fouled and new  diffusers, ex  situ, in an aeration column (2)

    The results of preliminary tests conducted at municipal plants under full-scale monitoring of
 OTE appear in Table 3. It should be emphasized that these data are very preliminary and based on
 a simplified assumption of linear reduction of F with time in service to some minimum value.

 MEDIA EFFECTS ON PERFORMANCE

    Fine pore aeration systems have sometimes  exhibited reductions in OTE that could be
 attributed to mechanical failures or material changes rather than a or fouling effects. A number of
 examples have been cited where oxygen transfer performance decreased due to gasket failures,
 broken support bolts, and cracked plenums and  air piping (2).

     Changes in diffuser media properties can also affect DWP and OTE.  Plasticized PVC (a
 thermoplastic elastomer) and EPDM (a thermoset elastomer), the two principal perforated
 membrane materials in use, can experience various physical property changes with time when used
 as wastewater aeration devices. These changes, however, may differ significantly in nature and
 degree between the two materials.  Specific, comprehensive descriptions of the materials employed
 in media production are therefore essential for prediction of perforated membrane diffuser
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 performance. Conditions that can substantially affect perforated membrane performance and life
 includeaoss of plasticizer, hardening or softening of the material, loss of dimensional stability
 through creep, absorptive and/or extractive exchange with wastewater, and chemical changes
 resulting from environmental exposure. Plasticizer migration can cause hardening and reduction in
 membrane volume, resulting in dimensional changes. Absorption by the membrane of various
 constituents, including oils, can result in softening of the membrane with volumetric increases and
 consequent dimensional changes. Membrane creep, which may be influenced by the above
 factors, will reduce OTE in some cases. It may also be accompanied by a reduction in DWP after
 cleaning to lower than the original value.  This reduction is not recoverable by known maintenance
 procedures.

     Reported data on performance and changes in characteristics of perforated membranes under
 service conditions, although limited, are becoming increasingly available.  Table 4 presents the
 results of some of these data (2).

                    EFFECT OF WASTEWATER ON PERFORMANCE


     The literature is replete with studies on the effects of wastewater characteristics on oxygen
 transier. Both a and the nature and dynamics of fouling are attributed to wastewater properties.
 fcurtactante (surface active agents) are believed to play an instrumental role in the depression (and
 occasionally the increase) of a in wastewaters. The rise in a as treatment progresses down the
 length of plug flow aeration basins has been attributed to surfactant removal from the wastewater
 Other wastewater properties may also have an impact on a, including total dissolved solids and
 transition elements such as iron and manganese (2).

     It is instructive to note that oF values obtained from a significant number of in-process studies
 Ait?    are  wer l   ^^ anticipated for fine pore aeration systems in municipal wastewater
 Although oF values presented in this table are dependent on several process and design variables
 tor ttie specific treatment plants tested, it is apparent that the average mean weighted oF is usually
 ^\J* J -
     The variability of oF is site specific.  Examples of typical variations over a 24-hr period are
 presented in Table 6. A review of oF variations at these sites revealed a maximum oFraverage oF
 of about 1.2, with a range of 1.08-1.47. The average value of minimum oFraverage oF was
 approximately 0.86, with a range of 0.77-0.96.

                               PROCESS LOADING EFFECTS
                 . 

     A review of the dynamics of oF(SOTE) in a variety of activated sludge systems suggests that
 several process variables affecting oxygen transfer are not clearly identifiable based on our current
 knowledge of the process. For example, oF(SOTE) data collected at Madison, WI (13) over an
 UU-day period in the first pass of a three-pass plug flow system demonstrate a significant
 variability in oF(SOTE) with time. Some of this variability may be attributed to the properties of
 the wastewater (i.e., composition and strength), but cannot account for all of it Multiple linear
 regressions of the data including sludge retention times (SRTs), food-to-microorganism (F/M)
 loadings, volumetric organic loadings, mixed liquor volatile solids (MLVSS) concentrations and
 air-flow rates could account for up to about 60-70 percent of the variability. Similar findings were
 1^   ^ Whittier Narrows treatment plant (14), where 30-74 percent of the variability in
 oF(SOTE) could be accounted for by F/M loadings, airflow rates, and time-in-service.

    These studies suggest that elements of process loading may have some impact on diffuser
performance. There are theoretical reasons why oF should be a function of SRT, F/M loading, or
MLVSS concentration. Current biological  treatment models developed for activated sludge predict
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substrate concentration as a function of these parameters.  Since the substtates are partially
comprised of surfactants, lower substrate concentrations imply lower surfactant levels and higher a
values. The dynamics of biomass accumulation and depletion on diffuser surfaces will very likely
influence F. The impact of these process loading factors on aeration system performance may be
short or long term depending on their combined effects on both a and F.

    Data from Table 5 were analyzed to determine whether a relationship between process loading
and oF(SOTE) may exist.  A plot for the ceramic diffuser installations in this table, using SRT as
the loading parameter, is given in Figure 7. Although wide variations in system design and
operation, as well as wastewater characteristics, are evident at these sites, it appears a trend does
exist between process loading and oF(SOTE). Nitrifying treatment plants have been highlighted in
this figure to indicate their relative importance to the relationship.

                                 FLOW REGIME EFFECTS


     Aeration basin flow regime affects the mixing pattern of the basin and, therefore, the residence
time distribution of the influent wastewater. Because wastewater components may have an impact
on oF(SOTE), it is reasonable to expect that mixing patterns will also affect. oF(SOTE). A study
conducted on the Madison, Wisconsin, ceramic dome diffuser system (13) illustrates this concept
(Figure 8)  Single-day oF(SOTE) off-gas profiles are compared as a function of grid position tor
one aeration basin when it was operated first in a step feed mode vs. two months later when it was
operated in a plug flow pattern of three passes in series.  The switch from step feed to plug flow
was made approximately half way between the two off-gas test days. In both cases, SRT was
approximately 2.2 days.

     The oF profile along the length of any aeration basin will depend on the degree of mixing that
exists in that basin. Typical results for a variety of basin geometries are presented m Table 7. The
 site key given in the first column refers to the treatment plants described in Table 5.  In general, it
has been found that treatment plants with high length-to-width ratios, operating as plug flow
 basins, generate significant  oF gradients.  Conversely, treatment plants that are short and wide or
 that employ step feed configurations exhibit much less variability in oF along the basin length.

                              DIFFUSER FLOW RATE EFFECTS


     The OTE of a fine pore diffuser in clean water decreases as the airflow rate jncreases.  Similar
 results are reported for process waters (2). A plot of oF(SOTE) versus airflow rate per unit media
 surface area for selected municipal plants listed in Table 5 shows this trend (Figure 9).  This curve
 should not be used for design purposes, since many other variables, as described above, attect
 oxygen transfer performance.

                                       CONCLUSIONS


     Field research over the last three years has significantly improved our understanding of fine
 pore aeration systems. Based on the information available at this time, the following conclusions
 can be formulated.

       Fine pore aeration system performance is significantly influenced by diffuser fouling as well
       as by changes in media properties.                                         .      ,
       Attempts to quantify the effects of diffuser fouling and media changes have been initiated
       using the fouling factor, F, and fouling rate, fp.
                                           310

-------
                                       w  vaae  omnance rom ste to ste and tim

              r of factors effect the performance of a fine pore aeration system under process
                )Sudf g Ae wa?tewater, process loading, flow regime, and airflow rate.
               (F/M) of an operating plant appears to affect fine pore aeration system
               106* An mcrease in SRT (decrease in F/M) generally will result in an increase
  1.  Wesner, G.M., LJ. Ewing, T.S. Linecfc, Jr., and DJ. Hinrichs.  Energy Conservation in
     Municipal Wastewater Treatment. EPA-430/9-77-01 1, NTIS No. PB81-165391  U S
     Environmental Protection Agency, Washington, D.C., 1977.

 2.  Design Manual, Fine Pore Aeration Systems. EPA/625/1-89/023, U.S Environmental
     Protection Agency, Office of Research and Development, Risk Reduction Engineering
     Laboratory, Cincinnati, Ohio, September 1989.                               6.

 3 '  1988tin' ManUal f Practice FD~13' Water Pollution Control Federation, Washington, D.C.,


 4.  Boyle, W.C. and D.T.Redmon. Biological Fouling of Fine Bubble Diffusers: State-of-Art
     J. Env. Eng. Div., ASCE 109 (EE5):99 1-1005, October 1983.
 5 ' Er^??  DX>T W-'C ?yle' and L' EwinS- Oxygen Transfer Efficiency Measurements in
    Mixed Liquor Using Off-Gas Techniques. JWPCF 55(1 1): 1338- 1347, 1983.

 6 . Boyle, W.C. and H. J. Campbell, Jr.  Experiences with Oxygen Transfer Testing of Diffused
    Air Systems Under Process Conditions. Wat. Sci. and Tech. 16 (10/11):91-106, 1984.

 7* SVJ' J-S-'JJ-  McKeown, D. Krause, Jr., and B.B. Benson. Gas Transfer Rate
    Coefficient Measurement of Wastewater Aeration Equipment by a Stable Isotope
    Krypton/Lithium Technique. In: Gas Transfer at Water Surfaces, Brutsaert, W. and G H
    Jirka, Editors, D. Reidel Publishing Co., Dordrecht, Holland, 1984.

 8.  Mueller, J.A.,R. Sullivan, and R. Donahue. Comparison of Dome and Static Aerators
    Treating Pharmaceutical Wastes.  In: Proceedings of the 38th Industrial Waste Conference
    Purdue University, West Lafayette, IN, May 1983.

 9 .  Rietii, M.O, W.C. Boyle, and L. Ewing. Effects of Selected Design Parameters on the
    K>ulmg of Ceramic Diffusers. Presented at the 61st Annual Conference of the Water
    Pollution Control Federation, Dallas, TX, October 1988.

10. Costerton, J.W. Investigations into Biofouling Phenomena in Fine Pore Aeration Devices
    Study conducted under Cooperative Agreement CR812167, Risk Reduction Engineering
    Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH (to be published).
           lj JAV' et ^ Bacterial Films in Nature and Disease.  Ann. Rev. Microbiol. 41:435-
    464, 1987.
                                       311

-------
19  Raillod C R and K Hopkins  Fouling of Fine Pore Diffused Aerators: An Interplant
1 ' C^ptiS' ^mdy conS under Cooperative Agreement CR812167, Risk Reduction
    Engineering Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio (to be
    published).

13. Boyle, W.C. Oxygen Transfer Studies at the Madison Metropolitan Sewerage District
    Facilities. Stady conducted under Cooperative Agreement CR812167, Risk Reduction
    Engineering Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio (to be
    published).

 14. Stenstrom,M.K. Fine Pore Diffuser Fouling: The Los Angeles Studies. Study conducted
    under Cooperative Agreement CR812167, Risk Reduction Engineering Laboratory, U.S.
    Environmental Protection Agency, Cincinnati, Ohio (to be published).
                                          312

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Parameter
  SOTR
  de
  C
  T
  t
  n
  a
  P
  e
  F
                    TABIJE 1
         Guide to Application of Equation 3

                    Source of Information
Clean water test results.
Clean water test results.
Clean water test results.
Process water conditions.
Process water conditions.
Calculated based on tabulated DO surface saturation values.
Calculated based on site barometric pressure and effective depth data.
Estimated based on experience or on measured values of KJJI in clean and
process'waters using a clean diffuser.
Calculated based on total dissolved solids measurements.
Taken as 1.024 unless experimentally proven to differ.
Estimated based on field experience, field measurements, or laboratory
analysis of diffusers taken from the field.
                                     TABLE2
                       Fine Pore Diffuser Fouling Categories (2)
Condition
Severe
Moderate
Light
BRV
(cm, w.g.)
>100
40-100
<40
DWP/BRV
<0.3
0.3-0.6
>0.6
F (After 1 year in service)
<0.7
0.7-0.9
>0.9
                                       313

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                                         TABLES

        Fouling Rates (fp) and Fouling Factors (F) for Selected Treatment Plants (2)
City  Plan! 	
Frankenmuth. Ml
Green Bay, WI
(2nd operating
period)
Green Bay. Wt
(1st 6 months
rv^K/l
uiuyj
Milwaukee. WI;
Jones Island East
Milwaukee, WI;
South Shore
Madison. WI;
Nine Springs
Monroe. WI
Los Angeles
Comity. CA;
WhitUer Narrows
RkJgewood, NJ
Tmie HI
Service.*
years
3.3
3.0

3.3

6.0

15.0

3.5

3.0
9.3

6.0
Test
Period.
months
13.0
11.7
6.5
6.5

6.0
6.0

30.0

56.7

26.7,

4.5
24.0

5.0
No.
Tests
17
16
9
9

5
5

20

20

37

5
23

48
IF.
month-1
0.029
0
0.064
0.067

0.028
0.046

0.002

QC

oc

0.043
0.027

0.074
Correlation,
r
0.52*>
-0.43
-0.66>

0.56
-0.65&

-0.22

-

-

0.81
-0.82t>

-0.15
F(@1
month)
0.97
1.0
0.94
0.93

0.97
0.95

1.0

1.0

1.0

0.96
0.97

0.93
Comments
Ceramic disc diffusers; Basin 5
Ceramic disc diffusers; Basin 6
Ceramic disc diffusers: contact basin
Ceramic disc diffusers; reaeration basin

Perforated membrane tube diffusers;
contact basin
Perforated membrane tube diffusers;
reaeration basin
Ceramic plate diffusers

Ceramic plate diftusers; various basins

Ceramic disc diffusers

Ceramic disc diffusers during bypass of
aerated flow from equalization basin
Ceramic disc diffusers injected with HCI
gas 5 times about every 3 months

Ceramic dome diffusers cleaned often
by hosing or brushing with HCL solution
As Of 4/1/89.
*> Significant at 95 percent confidence level.
c Zero fouling rale based on visual inspection.
                                               314

-------
 00

 .5
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 S

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          55
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                                   S
                                   
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                          u. u.  U. U.  CL (L   (L (L  n n
                    OJ CO

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              2^  S
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                                    I  I
                                    I  =
                                    I  J
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                                                   I   1
                                                   3
                S5'  o*  o^

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                                   ^  fill  II  II  II  li
                v
                i'
                         1=  H
                       m   o   Q   uj
                                      1   .8
                                         0
                                               b
                                            M
                                            b
                                                              I

                                                                  "   i
                                                              ^o-S E .  5
                                                               .  c = 
                                                                 llf!S*
                                 315

-------
2
(9
'I
u
I
If
"1
A
i
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||
fir-
3

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t
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a. o> e  g

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d d d d d
Io o o o co
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in n 10  r*
d d d d d

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c> r  to h-

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d *- d d d

co to en co CM
o o o o o
O CO CM to O
oo ri co co CM
d d d o o
GO <* ^ CO
v i?) tZ) * .
dodo
o in to *
CO CO CO CM .
o o o o
N CO 0) CO
co * * co .
o o o o
in v- 01  to
d d r^ d ^
co r- *r to r-
in in to ** co
o o o o o


CO *- CO * en
r* r cd to o
d d d d *-

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1 i 1 1 1
gees*
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d d - d r-' d
CO CM O CO -; *l
co CM r en co r^
CM CO CM in  h-
CD co *- - CM o
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t-. S r- i-  - 00
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d d d d d d
h CO C5 O OI t
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d d o d d d
f~ O> - 00
. in r* in in .
d d d d
, S S 5 8 .
d d d d
5  ? ? .
d d d d
*r jf to co ** o
r^ ^ ^ O O "-1
^ ^ N f^- OO CD
 in oi co co o>
d d d d d o


h * * CM ix in
K i^ *- en co CM
d d -' d d -

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g-l n i 1 2- g
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a. -.
d o
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CM" N
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o o

 s

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co in
d d

 CM
O 0
in CM
CM CO
,d o
0 01
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CM r
d d
S Si
d d
S g
d d
d d


CM in
5 2
u o
if t
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si s
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2 si 1 1 1 i il II 1
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CM CO
r- r-
" -


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CM CM
d d



CM *
n o>
rl O

a co
CO CM
d d
S ^
d d
rt
d
o
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d
d
fe o.
d ^
t* CM
CM (O
d d


5 S
d d

 < - t-
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e o o
.2 ." .Sf S
1 1 1 \
S S S S
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O

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CM 0
CM CM
d d

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d d
d d
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o
CM
d
to
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S R
d d
ft 5
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o o

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=) O
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I
                                                                                       O
                                                                                       CD
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                                                                                        <0
                                                                                      Sm <
                                          316

-------
                                       TABLE6
             24-Hr OF and oF(SOTE) Variations at Selected Municipal Treatment Plants
Site
No.
4
g
10
12

12

13

17
17
Cily  Plant
Hartford, CT ~
Madison, Wl;
West
RkJgewood, NJ
Los Angeles'
County. CA;
WhitUer Narrows
Los Angeles'
County, CA;
Whittier Narrows
Los Angeles
County, CA;
Whitlier Narrows
Monroe, Wl
Monroe. Wl
 ' 	 ' __

Average
 i
0.30
0.24
0.46
0.25

0.26

0.4S

0.23
0.39
aF
Minimum
0.23
0.22
0.44
0.21

0.20

0.41

0.19 '
'0.33

Maximum
0.44
0.29
0.59
0.27

0.30

0.50

0.28
0.45

Average
8.3
8.7
10.7
7.8

8.7

12.2



oF(SOTE)
Minimum
6.4
7.7
9.5
6.4

6.6

11.1


.

Maximum
11.2
10.4
13.1
8.7

9.9

13.5


'
Position in Basin
Influent pass
Inlet end
Entire basin weighted
Influent grid

Middle grid

Effluent grid


' Influent pass
Effluent pass
' Date lor 6-hr period.
                                       317

-------
                                        TABLE?
                        oF Profiles for Various Aeration Systems^-6

Site
No. City - Plant
2 Green Bay. Wl

3, Green Bay. Wl
4 Hartford. CT
5 Milwaukee. Wl;
Jones Island East
0 Milwaukee. Wl;
Jones Island West
7 Madison. Wl;
Easl
8 Madison, Wl;
East
9 Madison. Wl;
Wesl
11 Milwaukee. Wl;
Sooth Shore
12 Los Angeles
County. CA;
WNtUjr Narrows
13 Los Angeles
County, CA;
Whittjer Narrows
18 Phoenix, A2;
23rd Ave.
21 Minneapolis, MN;
Metro
22 Minneapolis. MN;
Metro
23 Minneapolis, MN;
Metro
26 Glastonbury, CT



Mean
0.45

0.49
0.37
0.45
0.34
0.32
0.40
0.33
0.64
0.25

0.16

0.29
0.36



0.50
0.59



Mm
0.35

0.41
0.18
0.32
0.18
0.24
0.33
0.26
0.50
0.15

0.09

0.25
0.32

-

-
Max Mean
0.55 0.43

0.68
0.49
0.60
0.46
0.44
0.47
0.40
0.92
0.42

0.27

0.34
0.40

'


0.43 0.69

i  




0.50
0.37
0.58
0.40
0.44
0.64
0.54
0.62
0.30

0.23

0.27
0.36

 "

*
0.54



Znne 3 Total Basin
"Min Max Mean
0.35 0.59 0.40

0.34 0.67
0.28 0.49
0.44 0.79
0.27 0.49
0.29 0.62
0.54 0.78
0.52 0.56
0.47 0.83
0.15 0.40

0.08 0.40

0.23 0.31
t
0.23 0.42



"
0.56 0.77




0.46
0.35
0.60*
0.43
0.52
0.92
0,55
0.64
0.38

0.31

0.25
0.37




0.56



Mm Max Mean
0.31 0.54 0.43

0.30 0.64
0.24 0.45
0.47 0.77
0.25 0.60
0.36 0.76
0.77 1.00
0.52 0.58
0.51 0.83
0.22 0.51

0.17 0.49

0.21 0.30
0.24 0.45




0.37 0.65




0.49
0.36
0.54
0.39
0.43
0.66
0.48
0.63
0.31

0.24

0.27
0.37
0.40

0.52

0.56

.i 
Oiffuser
Flow
Min Max Type Hegirne
0.36 0.53 PVCPeri. Plug
Memo. Flow

0.36 0.64
0.24 0.48
0.44 0.68
0.23 0.52
0.31 0.57
0.56 0.79
0.44 0.51
0.51 0.75
0.21 0.40

0.11 0.39

0.24 0.31,
0.29 0.45
0.34 0.46

0.45 0.59

0.42 0.67



Tubes
Ceramic
Discs
Ceramic
Domes
Ceramic
Plates
Ceramic
Plates
Ceramic
Domes
Ceramic '
Domes
Ceramic
Discs 
Ceramic
Plates
Ceramic
Discs

Ceramic
Domes

Ceramic
Domes
Ceramic
Domes
Ceramic
Domes
Ceramic
Domes
Rigid
Porous
Plastic
Tubes


Plug
Flow
Step
Feed
Plug
Flow
Plug
Flow
Plug
Flow
Plug
Flow
Plug
Flow
Step
Feed
Plug
Flow

Plug
Flow

Step
Feed
Step
Feed
Step
Feed
Step
Feed
Plug
Flow



 Each zone represents 1^ ^J^L*,
*> Reaerntion volume nol mdude-
e SOTE tor plaie ditfusers was i
                                                318

-------
                           FIGURE 1
              Schematic Structure of Type I Fouling
            Precipitated Inorganic
               Foutanl Layer
Small (10.2 mm x 0.6 mm)
    Pores in Rigid Diffuser Surface
                          FIGURE 2
Idealized Plot Showing Effects of Type I Fouling on DWP and OTE
      a.
      I
                            Time
                           319

-------
                          FIGURES

             Schematic Structure of Type H Fouling
                         Large (0.5 x 0.9mm) Round Aperture*
                         *     in Leathery" BtoWm         V

                                                           Structured
                                                          Anastomosing
                                                    0.6 mm) Irregular
                                                   Pores in
                                                   Rigid
                                                  Oiffuser
                                                  Surface
Tight Adhesion
   A Biotilm
                                  Cavernous Spaces
                               	m	     17mm
                             Between Difluser Surface
                                    and Biofilm
                            FIGURE 4

Idealized Plot Showing Effects of Type H Fouling on DWP and OTE
        a.
        1,
                                Ttme
                                  320

-------
        aF(SOTE)
  aF0(SOTE)
   F - 1.0
  QF,(SOTE)
aFmin(SOTE)
                                             FIGURES

                                    Hypothetical Fouling Patterns
                                            Linear Fouling Model
                                                             Note:    Curve Must be Plotted for the Same
                                                                     Operating Conditions and a Values;
                                                                     That Is:
                                                                     F - aF,(SOTE)/aF0(SOTE)
                                                                         F - F,/F0 - F/1
                                    Time Since Diffuser was Cleaned, t
                                                321

-------
                                       FIGURE 6

                               linear Fbuling Factor Model
                       1.0
                                                       I
                               1.0-F  1 .lcF,(SOTE)/aFn(SOTE)
                                   Time Since Diffuser was Cleaned, t
                                          FIGURE 7

                       oF(SOTE) vs. SRT for Ceramic Diffuser Facilities
aF(SOTE)/tt, percant

  1.5 r-
Numbers refer to plant
identifications in Table S
                                                  o  Nitrifying
                                                    Non-nitrifying
                                               SRT, days

                                               322

-------
                                           FIGURES

    
-------

-------
B^DvETG.RAPABII-ITY AND BIODEGRADATION KINETICS ASSESSMENT FOR
 TOXIC ORGANIC  COMPOUNDS  USING  OXYGEN  UPTAKE MEASUREMENTS
                            by

                      Henry H. Tabak
               Biosystems Treatment Section
                Treatment Assessment Branch
   Water and Hazardous Waste  Treatment Research Division
           Risk Reduction Engineering  Laboratory
           U.S. Environmental Protection Agency
                  Cincinnati,  Ohio  45268

                           and

              Sanjay Desai and Rakesh Govind
       Department of Chemical  & Nuclear Engineering
                 University of Cincinnati
                  Cincinnati, OH  45221
   This  paper has  been reviewed in accordance with
   the U.S.  Environmental  Protection  Agency's peer
   and administrative  review policies and  approved
   for presentation  and publication.
              Prepared for Presentation at:

         Twelfth United States/Japan Conference
             on Sewage Treatment Technology
                    Cincinnati, Ohio

                   October 12-13,  1989
                           325

-------
        BIQDEGRADABILITY AND BIQDEGRADATION KINETICS ASSESSMENT FOR
         TOXIC ORGANIC  COMPOUNDS USING OXYGEN UPTAKE MEASUREMENTS
                                *  ABSTRACT

                                                                             !
     Electrolytic respirometry involving natural sewage,-sludge and soil
microbiota is being applied to the fate studies of priority pollutant and
RCRA toxic organics to generate data on their biodegradability and on
biodegradation/inhibition kinetics.  This paper discusses the experimental
design and procedural steps for the respirometry biodegradation and toxicity
testing approach for individual organics or specific industrial wastes.  The
discussion also includes a review of the electrolysis BOD measuring system
inherent in electrolytic respirometry and the factors effecting
respirometric determination and measurement of respiration rate.

     A developed multi-level protocol is presented for determination of the
biodegradability, microbial acclimation to toxic substrates and first order
kinetic parameters of biodegradation  (n and n') and for estimation of the
Monod kinetic parameter  (JL, Ks and Y ) of toxic organic compounds, in  order
to correlate the extent  and rate of  biodegradation of these organics with a
predictive model based on chemical properties and structure of these
compounds.                                                                 >

     Respirometric biodegradability/inhibition  and biodegradation  kinetic
data are provided for representative RCRA alkyl benzenes,  phenolic
compounds, phthalate esters,  and  ketqnes.  Data on the effects of  the  source
of sludge  biomass, temperature, and  concentrations of microbial  inoculum  and
of toxic substrate on the  kinetics of biodegradation, are  also  included.
                                     .326

-------
                                 .INTRODUCTION
      Electrolytic respirometry is attaining prominence in biodegradation
 m^c,1,^ an?k1Su-Somin ?"?.of the more Su1table experimental methods for
 measuring the biodegradability and the kinetics*of biodegradation of toxic
 organic compounds by the sewage, sludge and soil  microbiota and for
 determining substrate inhibitory effects to microorganisms on wastewater
 treatment systems,

      Biodegradation of toxic and hazardous organic compounds holds a great
 promise as an important fate mechanism in wastewater treatment and in soil
 detoxification   Information about the extent and rate of biodegradation  s
 a prerequisite for informed decision making on the applicability^ of the
 Ji2 ^ra?ahrn/Ppr^h:  Unfrtunately,  relatively little quantitative data
 are available from which engineering judgement can be made,  because of the
 large effort required to assess biodegradation kinetics.

      Current research in our laboratories has shown that  it is possible to
 Jhrnnnh Jhfef   fi0? kjne^c parameters  from oxygen uptake data,  obtained
 through the use  of electrolytic respirometry.   This method greatly reduces
 the work and expense  involved in  evaluation of biodegradation kinetics    The
 ongoing biodegradation  studies are concerned with  the  generation  of
 biokinetic database so  that it can be ultimately  used to  establish a
 possible correlation  between molecular substrate  configuration
 (chemical/physical characteristics)  and biomass activity  (kinetic
 parameters)  as an index  of  biodegradation;   The experimental  respirometric
 testing is also  providina data on the mnrpntratinn ipypic  nf tnv-.v  nw,r>^,.
                                                      eveis  OT T.OXIC  organics
 respirometry  as  an  approach to measure the biodegradation of selected
 organic compounds and generate biokinetic data so that these can be
 ultimately used  to  establish a possible correlation between molecular
 substrate configuration  (physical/chemical characteristics) and biomass
 activity (kinetic parameters) as an index of biodegradation/  The
 experimental  respirometry testing is also providing data on the
 concentration levels of toxic organics inhibitory to microbial activity.

     Initially,  the inter-laboratory, ring test,  Organization of Economic
 Cooperation and  Development (OECD) studies at the EPA laboratory,
 Cincinnati, Ohio, were undertaken to develop confirmatory respirometric
 biodegradability testing procedure.   Respirometric biodegradabilitv and
 biokinetic data were provided for the selected non-inhibitory and  non-
 adsorbing compounds, tetrahydrofuran, hexamine,  pentaerythritol,  1-napthol,
 sodium benzene sulphinate,  thioglycolic acid and  the biodegradable reference
compound,  aniline.
tn Hoto            s1"J1l?r electrolytic respirometry studies were initiated
to determine biodegradation kinetic parameters for selected representative
toxic compounds of varied classes of organics included in  the Priority
Pollutant,  RCRA and superfund CERCLA lists,  and to demonstrate presence  of

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any inhibitory effects of these organics of specified concentration levels
on the sludge biomass and on the metabolism of^biogenic compounds.

     The objectives of the present study were to utilize the electrolytic
respirometry oxygen uptake data to:  (1) determine tne'blo^9dability of
selected RCRA alkyl, chloro, and nitrobenzenes,  phenols, phthalates, and
ketones and representative tERCLA leachate toxic organics; (2) generate
information on their acclimated times (t0) and the initiation and
termination time values for the declining growth phase  (t^ and t2);  (3)
determine their first order kinetic parameters of biodegradation  (specific
growth rate constants for the exponential growth phase  (n) and for the
declining growth phase  (JB'); (4) estimate the Monod kinetic parameters  (/ira,
K  and Y) of these compounds without initial growth or growth yield
alsumptions;  (5) demonstrate presence of  any  inhibitory effects of these
compounds on  the metabolism of the biodegradable reference compound,
aniline; and  (6) to  correlate the extent  and  rate of biodegradation of  these
compounds with a predictive model based on  chemical properties and structure
of these compounds.

      The purpose of this  study was to obtain  information  on  biological
treatability  of the benzene, phenol, phthalate  and  ketone organics  and  of
the  Superfund CERCLA organics  bearing wastes  in wastewater treatment  systems
which will  support development  of an EPA  technical  guidance  document  on the
discharge  of the  above organics  to  POTWs.  The  study was  to  generate  basic
 information on the fate of CERCLA leachate organics. during  on-site treatment
 and  biodegradation and inhibition data  for pollutants  found  in Superfund
 site wastewater that could be  discharged  to POTWs.  Respirometric
 biodegradability,  biokinetic and inhibition data  were  generated for the
 selected RCRA benzene, phenolic, phthalate and  ketone  compounds.
                                  BACKGROUND
 Measurement of Oxygen Consumption

      Measurement of oxygen consumption is one of the oldest means of
 assessing biodegradability.  Time consuming manual measurement of oxygen
 uptake  (dilution BOD measurements) was replaced gradually by a more direct
 and continuous respirometric method for measurement of oxygen consumption in
 biochemical reactions, for use  in routine examination of sewage and in
 control of sewage treatment process.

      A  rather comprehensive review of the use of respirometers for the study
 of sewage and industrial waste  and their application to water pollution
 problems was published by Jenkins in 1960 (1).  Montgomery's (2) review of
 respirometric methods summarized the design and application of respirometers
 for determination of BOD.

      The  application of  respirometry was gradually directed to research
  studies to  assess the toxicity  and biodegradation of specific wastes  or
  compounds,  to evaluate factors  affecting biological growth and to provide an
  insight into nitrification  reaction.  Of the  commercial respirometers which
  have been developed for  respirometric studies,  the electrolytic
  respirometers were  shown to be  most  applicable  for measurement and
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quantitation of biodegradation activity because they automatically produce
oxygen as needed, thereby eliminating some of the limitations of other
techniques and allowing output data to be collected automatically for direct
recording and processing (3-9).  A recent detailed review of respirometric
techniques and their application to assess biodegradability and toxicity of
organic pollutants was published by King and Dutka (10).

Respirometric Biodegradability Testing

     Most uses of electrolytic respirometry in biodegradability testing have
been for screening purposes to measure the extent of biodegradation as a
percentage of the theoretical oxygen demand exerted in some time period
(9, 11-17).  A more recent study by Painter and King (18) concluded that-a
procedure based on electrolytic respirometry was reliable for assessing
biodegradability, and could serve as an adequate Level I screening test for
biodegradability (19).

     A considerable number of .studies using electrolytic respirometry to
determine the biodegradability of wastes and specific organics is available
in published literature and significant data on biodegradation of pollutants
based on oxygen uptake have been generated (2, 4, 5, 20-34).

     There are many techniques that have been used to evaluate
biodegradation kinetics and these were reviewed in detail by Howard et al.  ,
(35, 36) and Grady (37).  These techniques utilize continuous, fed-batch and
batch type reactors for providing data from which kinetic parameters can be
evaluated.  The use of batch systems in biotechnology and biological
wastewater treatment represents a less labor intensive, less expensive and
much faster way to model biokinetics.

     Hopefully, the kinetic parameters obtained by the above techniques
would be intrinsic, that is, dependent only on the nature of the compound
and the degrading microbial community and not on reactor system used for
data collection.  If this condition is satisfied, then the parameters
obtained can be used for any reactor configuration and can be used in
mathematical models to estimate the fate of toxic organics.

     Batch techniques have been shown to be successful in obtaining
intrinsic kinetic parameters by applying non-linear curve fitting techniques
to single batch substrate removal curves, provided initial conditions are
selected with proper care (Simkins and Alexander (38, 39), Robinson and
Tiedje (40), Cech et al. (41), and Braha and Hafner (42).  Batch systems can
be used with either  acclimated or unacclimated biomass for providing
kinetic data and require that samples be taken at discrete time intervals
during the course of biodegradation [Tabak et al. (43), Larson and Perry
(24) and Paris and Rogers '(44)].
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Use of Electrolytic Respirometry to Generate Biokinetic Data

      Dojlido (11), Larson and Perry (24), Tabak et al. (45), Oshima et al.
(46), Gaudy et al. (47, 48), Grady et alI (49-51) investigated the use of
respirometry to generate biodegradation kinetic data.  Larson and Perry (24)
showed that the electrolytic respirometer can be used to measure
biodegradation of complex organics in natural waters when specific
analytical methods or radiolabeled materials are unavailable.  However, they
used empirical kinetic expressions which were system specific.

     Dojlido (11) divided the oxygen uptake curve into seven different
phases and then proposed an empirical model for each phase and evaluated the
biodegradability and toxicity of a test compound by measuring empirical rate
constants and time interval associated with each phase.  Various phases were
distinguished by identifying inflection points in the curve through the
plots of the logarithm of the slope versus time.

     Tabak et al. (45) and Oshima et al. (46) sought to capitalize on
Dojlido's method of identifying inflection points in order to quantify more
fundamental rate coefficients.  In order to identify more fundamental (and
therefore intrinsic) kinetic coefficients they used the. generalized concept
of oxygen uptake by Gaudy and Gaudy (52).  Substrate removal was divided
into exponential and declining phases separated by an inflection point, and
the endogenous phase.  They coupled substrate removal and cell growth to
oxygen consumption by imposition of an electron balance and consequently
were able to evaluate p  from oxygen consumption data up to the inflection
point.  They proposed tne use of the lag time as an indicator of how
difficult it is to achieve acclimation to a test compound and their
respirometric studies were carried out with an unacclimated biomass.

     The justification for using respirometry to obtain intrinsic kinetic
lies in the concept of oxygen consumption as an energy balance [Busch et al.
(53); Gaudy and Gaudy (52)].  This concept states that all of the electrons
available in a substrate undergoing biodegradation must either be
transferred to the terminal acceptor or be incorporated into new biomass or
soluble microbial products.  If the concentrations of the substrate, the
products and the biomass are all expressed in units of chemical demand
(COD), then the oxygen uptake can be calculated in a batch reactor from an
equation relating oxygen uptake to substrate, biomass and soluble products
[Grady et al. (49)].  Furthermore, since biomass growth and product
formation are proportional to substrate removal, this suggests that an
oxygen uptake curve can provide the same information as either a substrate
removal curve or a biomass growth curve.  This latter concept has recently
been used by Gaudy et al. (47, 48) to calculate biodegradation kinetics.
Specific growth rates obtained from growth studies as slopes of plots of Ln
(biomass concentration) or Ln(X) versus time at different substrate
concentrations, compared favorably with those obtained from exponential
phase of respirometric oxygen uptake curves as slopes of plots of Ln (d
oxygen uptake)/d time or Ln (dOu/dt) versus time.
                                                            it
     Studies of Grady et al. (49, 50) have demonstrated that it is possible
to determine intrinsic kinetics of single organic compounds by using only
measurements of oxygen consumption in respirometric batch reactors.  With
the use of computer simulation techniques and non-linear curve fitting
                                     330

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methods, intrinsic kinetic parameters were obtained from oxygen consumption
data and were shown to be in agreement with those obtained from traditional
measurement of substrate removal (DOC, SCOD, 14C)  or cell*growth.

                           MATERIALS AND METHODS
Experimental Approach

     The electrolytic respirometry approach to determine the biodegrad-
ability of the organic test compounds in this study was chosen because of
the specific advantages of the respirometric methods over that of manometric
procedures in tracking oxygen utilization during the exertion of biochemical
oxygen demand (BOD).  These advantages are listed in Table 1.  General
classification of respirometers based on principle of operation and on
techniques and applications is presented in Tables 2 and 3.

     The electrolytic respirometry studies were conducted using an automated
continuous oxygen uptake and BOD measuring Voith Sapromat B-12 (12 unit
system) electrolytic respirometer-analyzer:  The instrument consists of a
temperature controlled waterbath, containing measuring units, a recorder for
digital indication and direct plotting of the decomposition velocity curves
of organic compounds; and a cooling unit for the conditioning and continuous
recirculation of waterbath volume.  The recorder shows the digital
indication of oxygen uptake and constructs a graph for these values of each
measuring unit.  The cooling unit constantly recirculates water to maintain
constant temperature in the waterbath.  Each measuring unit as shown in
Figure 1 is comprised of a reaction vessel with a carbon dioxide absorber
mounted in a glass joint flask stopper, an oxygen generator and a pressure
indicator.  This measuring unit is interconnected by hoses, forming an air
sealed system, so that the atmospheric pressure fluctuations do not
adversely affect the results.

     The activity of the microorganisms in the sample creates a vacuum which
is recorded by the pressure indicator, which triggers the oxygen generator.
The pressure conditions are balanced by electrolytic oxygen generation.  The
quantity of the sample, the amperage for the electrolysis and the speed of
the synchronous motor are so adjusted that, with a sample of 250 ml, the
digital counter indicates the oxygen uptake directly in mg/L.  The C02
generated is absorbed by soda lime.  The nitrogen/oxygen ratio in the gas
phase above the sample is maintained throughout the experiment and there is,
no depletion of oxygen.  The recorder-plotter concomitantly constructs an
oxygen uptake graph for the selected values.  The oxygen generators of the
individual measuring units are electrolytic cells which supply the required
amount of oxygen by electrolytic dissociation of a copper sulfate solution
combined with sulfuric acid.
     The nutrient solution used in these studies was an OECD synthetic
medium (19, 56) consisting of measured amounts per liter of deionized
distilled water of (1) mineral salts solution; (2) trace salts solution,
(3) a solution (150 mg/L) of yeast extract as a substitute for vitamin
solution.
and
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     The microbial inoculum was an activated sludge from The Little Miami
wastewater treatment plant in Cincinnati, Ohio, receiving municipal
wastewater.  The activated sludge sample was aerated for 24 hours before use
to bring it to an endogenous phase.  The sludge biomass was added to the
medium at a concentration of 30 mg/L total solids.  Total volumes of the
synthetic medium in the 500 ml capacity reactor vessels were brought up to a
final volume of 250 ml.                                          

     The test and control compound concentrations in the media were 100
mg/L. Aniline was used as the biodegradable reference compound, at a
concentration of 100 mg/L.

     The typical experimental system consisted of duplicate flasks for the
reference substance, aniline, and the test compounds, a single f>ask for the
physical/chemical test (compound control), a single flask for toxicity
control (test compound plus aniline at 100 mg/L each) and an inoculum
control.  The contents of the reaction vessels were preliminarily stirred
for an hour to ensure endogenous respiration state at the initiation of
oxygen uptake measurements.  Then the test compounds and aniline were added
to it.  The reaction vessels were then incubated at 25C in the dark
(enclosed in the temperature controlled waterbath) and stirred continuously
throughout the run.  The microbiota of the activated sludge used as an
inoculum were not pre-acclimated to the substrates.  The incubation period
of the experimental run was between 28 to 50 days.  A more comprehensive
description of the procedural steps of the respirometric tests is presented
elsewhere (45, 55 and 56). ,

     For fully automatic data acquisition, frequent recording and storage of
large numbers of oxygen uptake data, the Sapromat B-12 recorders are
interfaced to an IBM-AT computer via the Metrabyte interface system. The use
of Laboratory Handbook software package allows the collection of data at 15
minute intervals.

     The oxygen utilization by the biomass based on the oxygen uptake
velocity (BOD) curves, consisting of the exponential and declining phases of
microbial growth was the basis for measurement of substrate utilization and
growth rate.  Figure 2 provides a generalized plot of the substrate
concentration, biological solids concentration (biomass), and oxygen
utilization during exertion of BOD, versus time in a respirometric
biodegradability treating vessel system.  A typical relationship between the
BOD and substrate degradation curves as well as between biomass and
substrate concentrations and growth yield is illustrated in Figure 3.

     Possible curves of oxygen uptake attributed to the organic test
substrate that can be generated in a respirometric run and which are
dependent on the acclimation time, the extent and rate of bio-oxidation of
the substrate, the presence of cometabolite(s) and the presence of
biocatalytic additive in the nutrient solution are demonstrated in Figure 4.

     Factors affecting respirometric BOD determination have been taken into
consideration in the study, and are listed in Table 4.
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 Chemical  Analysis

      Indirect analysis of culture samples from respirometric vessels during
 the study included determination of chemical  oxygen demand as soluble and
 total  COD and of dissolved oxidizable carbon  (DOC)  with the use of a Beckman
 Model  915 B system.
                                                        *
      Specific substrate analysis of culture samples for the residual parent
 compound  and the possible intermediate and final  products of metabolism was
 performed with the use of a Gas Chromatograph Varian 3700, equipped with FID
 and EC detectors and with different detector  columns (depending on the
 substrate to be analyzed) and the Finnigan automated GC/EI-CI Mass
 Spectrophotometer system.  Samples were analyzed  as dichloromethane extracts
 of cultures (continuous liquid-liquid extraction) or by direct aqueous
 injection.

      Suspended solids and biomass were measured gravimetrically (solids
 retained  on a 0.45 im filter) and by optical  density determined
 spectrophotometrically (percent transmission  read at 540 nm).

-Determination of Substrate Biodegradability from  Oxygen Uptake Data

      In this study,, biodegradation was measured by  three approaches:  the
 first,  as the ratio of the measured BOD values, in mg/L (oxygen uptake values
 of test compound minus inoculum control  - endogenous oxygen uptake values)
 to the theoretical oxygen demand (ThOD)  of substrate as a percent; the
 second as a percentage of the test compound as measured by dissolved organic
 carbon (DOC) changes [OECD Guidelines for Testing of Chemicals (Method DGXI
 283/82, Revision 5) (56)]; and the third, as  a percentage of the test
 compound  as measured by specific substrate,analysis.

      Graphical  representation of percent biodegradation based on the
 BOD/ThOD  ratio were developed against time for each test compound. The
 experimental DOC data for the initial  samples and samples for reaction
 flasks collected at the end of experimental run were used to calculate the
 percent biodegradation based on the percent of DOC  removal in the culture
 system.

 Determination of Kinetic Parameters of Biodegradation

      The  Monod equation,  relating cell  growth to  biomass and substrate
 concentration and the linear law, relating cell growth to substrate removal
 are the most popular kinetic expressions which can  provide adequate
 description of growth behavior during biodegradation of substrate.  The
 Monod  relation states that cell  growth is first order,with respect to
 biomass concentration (X) and mixed order with respect to substrate
 concentration (S) by tbe equation
                           dX/dt  =  (SumX)/(Ks + S)
(1)
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Cell growth is related to substrate removal by the linear law by the
equation

                             dX/dt = -Y(dS/dt)
                                                                        (2)
     The kinetics of biodegradation were evaluated by quantifying ft ,  Ks  and
Y kinetic parameter's expressed in the equation for the rate of substrate
removal . r^:

                                             '                            (3)

where X is the concentration of biomass capable of utilizing the organic
substrate and Y is the biomass yield coefficient for the compound and in the
Honod equation;
(if the compound is not inhibitory to its own biodegradation) or by he
Haldane equation;

                                   + Ss  + (Ss2/Kr)
                                                                         (5)

if the compound is inhibitory.  In these equations, /^ is the maximum
specific growth rate, Ks is, the half saturation coefficient, KT is the
inhibition coefficient and  S is the concentration of substrate.

     A graphical presentation of the Monod substrate utilization  equation  is
illustrated in Figure 5 which provides a relationship between  rate of
substrate utilization and substrate concentration.

Determination of Rates of Exponential and Declining Growth

     The first order kinetic irate constants  (specific growth rate
parameters) were determined by the linearization of the  BOD curves or
transforming the typical BOD curve to the linear function of time t,  by  the
relationship of log dO /dt  to t, which gives straight lines expressing the
exponential and declining endogenous phases  of the BOD curve as shown  in
Figures 6 and 7.  The slope of the Ln(d oxygen uptake/dt) versus  t  give
specific rate constants of  the exponential growth phase  (n  values) and the
dec-lining growth phase  (/*'  values) of the BOD curve as described  by Dojlido
(11), Tabak et al.  (45), Oshima et al .  (46), and Tabak et al .  (54, 55).

     Acclimation time values  (t0) and the time values for the  initiation and
termination of the declining growth phase (t1 and t2)  for each test compound
were determined from linearized expressions  of BOD curves.

Estimation of Honod Kinetic Parameters

     The estimations of the Monod Kinetic parameters, maximum  specific
growth rate constant, /L, half saturation constant, K  and growth yield
constant, Y were determined directly  from experimental oxygen  uptake  curves
without the consideration of  initial  growth  and growth yield assumption
[Jobbagy, Grady and Tabak  (57)  and Tabak et  al.  (54)].
                         /334

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      If the concentrations of the substrate, the products and the  biomass
 are all expressed in BOD units, then the oxygen uptake  (0  at any time in
 the batch reactor may be calculated from                     **
- (X-XJ  -  (S -SDO)
                                                                          (6)
 where Sso,  Spo and X0 are the concentrations of substrate,  products and
 cells, respectively, at time zero, and S  and S  are the concentrations of
 substrate and product, respectively, at time t.

      To apply equation (4) for the determination of kinetic coefficients,
 equations must be available which express the concentrations of soluble
 substrate (Ss),  soluble product (S )  and  biomass  (X)  as  functions  of time.
 For batch reactors, those equations are:

                         dSs/dt = -(MyY)SsX/Ks + Ss)                       (7)

                       dSp/dt = (Yp/in/Y)SsX/(Ks + Ss)                       (8)

                  dX/dt = 0mSsX/(Ks 4. ss) - KsbX/(Ks + Ss)                  (9)

 where Ss  =  soluble substrate concentration; S  =  soluble product
.concentration;-Yp = product yield; and b = decay coefficient.

      To calculate oxygen uptake in a batch reactor,  equations (7),  (8) and
 (9) must  be solved simultaneously, and the resulting values of Ss, S  and X
 over time are substituted into equation (6).                        p

 Determination of Y Constant

      Y -  the true yield parameter or the ratio of growth of biomass to
 substrate utilization,  can be obtained from the experimental oxygen uptake
 curve at  the initiation of the plateau of the curve  as shown in Figure 8,
 with the  use of equation:
                              Y- d-Oupt/S0)-Y
                                     (10)
      Where Oypt is the cumulative oxygen update value at the initiation of
 plateau,  S0  is  the  concentration  of substrate  at  time  zero,
 product yield.   .
                        and Yp is the
      A vertical  line is drawn at the point of intersection of the tangents
 of the exponential  and plateau phases of the curve.   The oxygen uptake value
 obtained at the  point of intersection of the vertical line (drawn through
 intersection of  tangents)  and oxygen uptake curve is the 0 t value -
 [cumulative oxygen  uptake  value at the initiation of plateau].


      The Oqpt value  is then substituted into equation (10) , for Y
 determination.   Y  is  soluble  product  concentration  formed, divided  by
 initial  substrate concentration.  In this study,  product yield (Y') was
 negligible.                                                      p
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Determination of um Constant
      The initial estimate of nm is obtained by the technique of Gaudy et
al. (47, 48).  If Y  is assumed to be zero, equation (8) is eliminated and
if b (decay constant) is assumed to be zero, equation  (9)  is  simplified  to
                         dX/dt =  (/imSs)C)/(Ks
                                                                         (11)
Combining equation  (7) and  (11) and  integrating from  Sso to Ss and from X0  to
X gives:                                                               -
                           X = X
                                    Y(SSO  -  Ss)
                                                   (12)
If the assumption that S  Ks, the term SS/KS  + S? in equations  (7)  and  (11)
or (1) approaches one, and these systems can be simplified  through  the use
of equation (12) to give equation
                                dX/dt = /imX
                                                :            *
Integrating equation (13) and combining with equation  (2) and than
substituting in equation  (6) with P and P0 both equal to zero .gives
Ln[X0
                                        = Ln(X0)  + /im(est)
                                                                        (13)
                                                                        (14)
The plot of Ln[(X0 + 0U)/((1/Y) - 1)] versus time will give a straight line
with slope /Jm.  The accuracy of /Jm(est) will depend upon the size of Ks,  but
this value is good enough  as an  estimate.

     fim - the maximum specific growth rate  can be determined from
experimental oxygen uptake curve plot  in the  following  manner:

(1)  Values of the change  of Ou with time (dOu/dt) or slopes are determined
     along the entire experimental  oxygen uptake. curve  as  shown in  Figure 9.

(2)  These dOu/dt (slope)  values  are then plotted against  the cumulative  Ou
     values for each time  interval,  as  shown  in  Figure  10.

(3)  The slope of the developed  linearized  form  of  oxygen  uptake curve is
     the estimated nm value.

Determination of K= Constant

     K  - the half saturation  constant  or the substrate concentration  at
which the specific growth  rate is 1/2  the maximum specific growth rate can
be obtained from the experimental oxygen uptake  curve in the following
mariner:

(1)  Value of 0 t can be calculated from the plot of  (dOu/dt) versus Ou
     provided the Ks value is  1  or less (insignificant  in  comparison to S0
     value) and the plot contains a linear  section  with the slope nm,  as
     shown in Figure 11.

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 (2)   Other (dO /dt)  versus 0 plot  in which the  slope deviates  from /j  
      because of larger Ks values (more  significant in  comparison^  Sm)  is
      illustrated in Figure 12.

 (3)   The value of dO/dt  is determined  at the intercept of the  straight  line
      developed from the plot of dOu/dt  versus Ou  (Figure  11) which contains
      a linear section with slope Mm.

 (4)   Beginning with the value of 1/2 the intercept value, another straight
      line (b) is constructed with the slope 1/2 that of the slope of-
      original line (a) whose slope is /Jm.

 (5)   At the point where line (b) intercepts the declining experimental  curve
      of the plot, a vertical line from that point of interception can
      provide the value of Out on the x axis.

 (6)   This Out value is then  used in the determination" of  1C with the use of
      the equation

                          St = S0 -  Out/(l-Yp-Y) = Ks

      where S0 =  initial substrate concentration  and  St =.substrate
      concentration at time t.

 (7)   When the Out, Y, Y ,  and S0  values  are plugged into the equation, the
      value of St  can  be calculated  - which  is  the  value of K  (in systems
      where Ks value is 1 or  less).
                                                        *
      Thus the oxygen  uptake value Out associated with 1/2 of the estimate of
 um is used  in Ks' = S0 - Out/(l-Y -Y) to get the estimate of Ks.   The major
 impact  of Ks  is upon  the shape of the oxygen uptake  curve in the region of
 the plateau.   Comparison  of the  experimental  curves  to  a  family of
 standardized  curves as an  initial estimate provides  an  initial  estimate  of
 Ks that is sufficient for non-linear curve fitting techniques for
 quantitation  of  the kinetic parameters.

 Quantitation  of  Monod Kinetic Parameters

      The  methodology  for  quantitation of  the  Monod kinetic parameters
 requires  the  use  of the above specific methods for estimating them initially
 and subsequently  followed  by computer simulation methods  coupled with non-
 linear  curve  fitting  techniques  and is based  on the  use of measured values
 of initial growth  and growth'yield.  The method requires  the use of the
 kinetic equation  relating growth rate of  biomass  in  presence of substrate,
 the substrate utilization rate,  product formation  rate  and rate of oxygen
 consumption from  02 uptake (BOD)  curves to calculate and use the theoretical
 oxygen consumption data to  quantitate the  biokinetic parameters.

     The determination of the kinetic parameters associated with
 biodegradation requires a series of steps.  The initial substrate (S )  and
 biomass (X ) concentration must be carefully measured in COD units.  sthe
 ratio of the twb values must lie in a certain  range  in order to allow
 independent evaluation of /im, K  and Y  [Simkins and Alexander  (.38, 39)].
Grady's studies  (49,  50) have shown that a SSO/X0 ratio  of around 20 works
                                   337

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well.  The value of Y  may be estimated by determining the residual  stable
SCOD concentration after substrate depletion (plateau area).  It is
numerically equal to the residual SCOD divided by the initial SCOD.  The
value of the decay coefficient, b, may be determined by fitting to the
oxygen consumption curve after the plateau when the only activity
contributing to oxygen consumption is endogenous metabolism and cell decay.
Once X0,  Sso, Y  and b are known, #m,  Ks and Y may be determined  by non-
linear curve fitting techniques [Grady (49, 50)].                       

     The technique involves the calculation of a theoretical oxygen
consumption using oxygen uptake equation  (4) and equations for substrate,
product and biomass concentrations (5) -  (7) with assumed Monod parameters.  .
The residual sum of squared errors (RSSE) associated with the difference in
calculated and experimental oxygen uptake values is used to obtain new
estimates.  The above procedure is repeated until a minimum RSSE is found.

     The Grid Search technique was selected as a most suitable non-linear
curve fitting technique for application in the determination of the'kinetic
parameters from oxygen uptake data, because it can allow easy discrimination
between local minima and the global minimum RSSE.  This technique enables a
comparison between the calculated and experimental oxygen uptake data.  The
value of Y is fixed.  For this value of Y, a pair of nm and K which give
RSSE is found on a /tm:K  plane.   The  above-procedure  is  repeated with other
values of Y.  Values of /i, Ks and Y  which give minimum  RSSE associated  with
the difference in calculated and experimental oxygen uptake data constitute
the best values of fhe kinetic parameters.

     The values of /im,  Ks and Y developed  from  grid  search technique,  which4
when substituted into equations 5-7, will provide X and S values, which  ,
(when substituted into oxygen uptake equation 4) will in turn provide
calculated oxygen uptake values at the region of the plateau, closest to the
experimental oxygen uptake values, with a minimum RSSE, will constitute the
best quantitative kinetic parameter values.

Development of Multi-Level Respirometric  Biodegradation Testing Protocol

     The oxygen consumption data generated with the 'use of electrolytic
respirometry have been adequately utilized for assessing the biodegradative
activity of sludge microbiota, the biodegradability/toxicity of toxic
organic compounds, as well as for the determination of the  intrinisic
kinetic parameters of biodegradation.  Methodologies have been developed for
quantitating biodegradability and biodegradation kinetics of representative
classes of RCRA toxic organics, with the  resultant development of a
comprehensive multi-level respirometric biodegradation testing protocol
based on oxygen consumption data.

     The methods of each successive testing level of the respirometric
protocol are characterized by increased complexity and a consequent  higher
cost for performing the tests pertaining  to each testing level.
Accordingly, the testing levels can be selected as appropriate to the
research needs.
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     Studies to assess the biodegradability and biodegradation rates of
toxic organics by sludge microbiota with the use of respirometric oxygen
uptake data can involve the use of one of more levels of the protocol,
depending on the amount of information needed for assessing the
biodegradability of the organic toxic pollutant or the toxicant bearing
waste for determination of its fate and rate of biotreatment in the
municipal or industrial waste treatment systems.  A logic flow diagram of
the respirometric biodegradation testing protocol, providing a brief
description of each of the testing levels, is shown in Figure 13.
                           RESULTS AND DISCUSSION

     Respirometric biodegradability, biokinetic and Monod  kinetic data for
selected RCRA alkyl benzenes, phenols, phthalates and ketones  are reported
in this paper.  The electrolytic respirometry oxygen uptake data for the
test compounds, the control  reference compound aniline, the inhibition and
endogenous control systems were generated revealing the lag phase
(acclimation phase), the biodegradation  (exponential) phase, the different
bio-reaction rate slopes (characteristic of the test compound)  as well as
the plateau region at which  the biooxidation rate reaches  that  of the
endogenous rate of microbial  activity.   Figure 14 illustrates  a
representative oxygen uptake curve for aniline and the endogenous controls.
Figure  15 shows the replicate pentaerythritol oxygen uptake curves  and the
toxicity control  (pentaerythritol plus aniline) curve, Figure  16 illustrates
a representative graphical treatment of  the percent biodegradation  of
pentaerythritol with time, which was developed for each test compound  (OECD
studies).

     Based on the biokinetic equations relating growth rate of microbiota  in
presence of above compounds, the substrate utilization rate, and rate  of
oxygen  uptake (BOD) curves,  specific growth rate kinetic parameters
(biodegradation rate constants) were derived as slope values of the
linearized plots  (plots  of the  log of DO /dt) of exponential and declining
growth  phases of  the BOD curve.  The acclimation time values (t0),  and time
values  for the  initiation and the termination of the declining  growth  phases
(tj and t2)  for the test compounds and aniline were also generated.

     The estimations of  the  Monod kinetic parameters for benzene, phenol,
phthalate, and  ketone compounds reported here, were determined directly from
experimental oxygen uptake curves without the consideration of initial
growth  and growth yield  assumption.

Respirometric Studies with Selected  RCRA Alkyl Benzene Compounds

     The biodegradation  of benzene,  toluene, ethyl benzene, m- and
p-xylenes, tert-butyl benzene,  sec-butyl benzene,  butyl  benzene,  cumene,  1-
phenyl  benzene  and the reference compound, aniline at  100  mg/L concentration
by  30 mg/L sludge biomass  (as measured by oxygen consumption by sludge
microbiota in mg  02/L) was followed over a period of 20 days.   The
electrolytic respirometry oxygen uptake  and  BOD curves were generated  and
graphical treatment of the percent  biodegradation  was  established  for  each

                                     339

-------
compound.  Figure 17 demonstrates typical oxygen uptake and BOD curves for
p-xylene and p-xylene + aniline and Figure 18 illustrates graphically the %
biodegradation of p-xylene with time.

     The percent biodegradation data based on the BOD/ThOD ratios for
benzene, toluene, ethyl benzene, m- and p-xylene and the reference compound,
aniline, are summarized in Table 5.  All of the above alkyl benzene
compounds were shown to be biodegradable substrates at concentration levels
of 100 mg/L when exposed to 30 mg/L of activated sludge biomass under the
environmental conditions of the respirometric testing procedure, and within
the period of 20 days of incubation.

     The toxicity test control flask respirometric data revealed no
inhibitory effects by these test compounds at the 100 mg/L concentration
levels on the bio-oxidation of aniline by sludge microbiota.

     Table 6 summarizes thefsbio-kinetic data for the benzenes studied,
showing the specific growth rate constants for the exponential growth phase
(p values) and for the declining growth phase (/*' values) of the linearized
form of the BOD curves of these compounds, as well as the tft,  t,  and  to
kinetic parameters.  Figure 19 shows a typical plot of Ln(dOu/dt) vs. time
for toluene, from which the kinetic parameters were determined.

     Table 7 summarizes the Monod kinetic parameter (/im,  Ks, Y ) data for
these benzene compounds.

Respirometric Studies with Selected RCRA Phenolic Compounds

     The biodegradation of phenol, resorcinol, o-, m- and p-cresols,
catechol, 2,4-dimethyl phenol and the reference compound aniline at 100 mg/L
concentration levels and exposed to 30 mg/L biomass was followed over a
period of 20 days.

     All of the phenols were shown to be biodegradable substrates under the
conditions of the respirometric testing procedure.  The toxicity test
control flask respirometric data revealed no inhibitory effects by these
compounds at the 100 mg/L levels on the biodegradation of aniline by the
sludge biomass.

     Table 8 summarizes the bio-kinetic data for the phenols studied,
showing the specific growth rate constants as well as the t0,  t1}  and t2
kinetic parameters.  Table 9 provides the Monod kinetic parameter data for
these phenolic compounds.

Respirometric Studies with Selected RCRA Phthalate Ester Compounds

     Evaluation of the biodegradability and determining of bio-kinetics of
degradation of phthalate compounds, dimethyl phthalate, diethyl phthalate,
dipropyl phthalate and butyl benzyl phthalate was achieved with use of
respirometric oxygen uptake data.
                                     340

-------
  rnnrf-?1-1  f  *h?u above Phthalates were shown to biodegradable under the
  conditions of the respirometric tests and were shown not to exhibit any

  sludge mTcrobTota? at the 10 mg/L levels " "* biodegradation bjrthe


  ann MIabieE-10*and H summarize respectively the biokinetic (first order)
  and Monod kinetic parameter data for the selected phthalate esters under
  S L
 Respirometric Studies with Selected RCRA Ketone Compounds

      Respirometric oxygen uptake data from the studies with the selected
 ketone compounds, acetone, 2-butanone, 4-methyl-3-pentanone and a cyclic
 Ketone, isophorpne were utilized to determine their biodegradability and
 biodegradation kinetic parameters.                                      

      All the ketones were shown to be biodegradable at 100 mg/L
 anvC?n^vnJeVe-?-in fdia C0"tainin9 30 mg/L biomass and did not exhibit
 any toxicity to aniline biodegradation at these concentrations.
      Tables 12 and 13 summarize respectively the first order and  Monod
 kinetic parameter data for these ketones.
                                 CONCLUSIONS
      The experimental  data of respirometric  studies with  several classes of
 organic compounds definitely demonstrate  that  it  is possible to measure the
 SiSS^th11^ (?-rCen $1ode9radation  - as  a ratib of  BOD to ThOD) and to
 determine the  kinetics of degradation  of  single organic compounds by using
 only  measurements of oxygen consumption in respirometric  batch reactors.
 ISre  JlnS ?   +  S kinetic parameters determined from oxygen consumption data
 were  demonstrated to be similar to those  based on the measurements of
 substrate removal  and  those made with  cell growth data.

      The  generated data on  biodegradation, biodegradation rates and
 Siri  Ilihii"!;    in H"et!^s  th^ough  the use of electrolytic respirometry,
 will  enable the  classification of biodegradability of toxic priority
 pollutant and  RCRA toxic  organic compounds and ultimate projection of the
 fate  of organic  compounds of similar molecular structure to those
 experimentally studied  by way of the established predictive treatability
 models  based on  structure-activity relationships.                 ""niy

 nf thW1tl!  the 6lectro1yt1c  resplrometry approach,  a data base on the removal
 of the  above compounds  by biodegradation fate mechanism can be adequately
 generated  to support the development of predictive models on fate and
 removal of toxics in industrial and municipal waste treatment systems.   A
 possible relationship between the kinetic  parameters and the effect of
different factors on these parameters,  as  determined through electrolytic
respirometry and the structural properties of the  organic pollutant? cai
eventually facilitate prediction of the extent and the  rate of
,^dSrafa*10?uf,,organ!c chlmlls In  the field of wastewater treatment
systems from the knowledge of the  structural  properties  of the pollutant
orgamcs.
                                    341

-------
     A preliminary predictive biodegradation - structure/activity model
based on the group contribution approach was developed from the generated
biodegradation kinetic data (first order kinetic parameters) with the use of
electrolytic respirometry.  It is expected that the model will closely_
predict the results found experimentally.  In this way, the fate of other
organic compounds may be anticipated without the time and expense of
experimental work.

     The electrolytic respirometry biodegradation studies will provide basic
pilot scale treatability information and data which will be used to confirm
methods to predict treatability and the need for pretreatment of
structurally related pollutants (e.g., by structure, anticipated
treatability properties, etc.).  This study will thus provide a more
extensive list of pollutants than was covered by experimental data, for
consideration in guiding the Agency to predict the fate of such compounds
without costly experimental testing.

     Studies are currently  in  progress to determine the effect of
temperature, and different  sources of sludge  biomass  (domestic and
industrial wastewater treatment) on the  biodegradation  kinetics derived  from
electrolytic respirometry.

                               ACKNOWLEDGEMENTS


     The  authors wish to  thank Mrs. Rena M.  Howard  and  Mrs.  Diana  L.
Redmond,  secretaries  in the U.S.  Environmental  Protection  Agency's  Risk
Reduction Engineering Laboratory,  Cincinnati,  Ohio,  for their excellent  and
timely wordprocessing skills in preparing this  manuscript  for presentation
at the 12th  U.S./Japan  Conference  on  Sewage Treatment Technology,  October
12-13,  1989  in  Cincinnati,  Ohio.

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                                                                      Water
                                      346

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0
"'
57.

                                   HanometHc

                              347

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                        TABLET
          ADVANTAGES OF RESPFOMETWC
1. oxygan uptaka can ba monitorad oontinuou.ly and eon.tantly and .or.
   pracisaly.
,. Automation provida.  Burical  or binary output aat. for air.et
   recording er procea.ing  (electrolytic).

'  ssx&ss,

- jsgss,
5  Th. anpl.s ar. .ix.fl continuou.ly to provia. uniform  contact of
   microorganism., substrata and orygan.
. xo ebamical titrations ara ratjuirad.
7. * continuou. record of O2 uptake i. provided with .om. unit, having
   automatic recording device..
a. jermit treatment  plant* and in-.tream condition, to be .imulat.d
   more clo.ely than in dilution te.t.


-
   volume and .ource of .ewage .eed and .eed adaptation.

 10.  can b.  u..d to determine  bacterial growth and .ub.trat.  removal
     coefficient..


 -
 
 13. o.afull infor.tion i. oft.n av.ilabl. in vary .uoh 1... than in 5
     day*.


     which variabla. can ba eontrollad.
                                348

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    TABLE 2      GENERAL CLASSIFICATION OF RESPIROMETERS
     Types

1. Manometrk
2. Electrolytic       Same.
3. Dissolved 02
    depletion
        Basic Prinfjply fff O
    Determination of O2 weight changes in a dosed system
    by measuring or responding to O2 pressure chances at
                      and 0lume " 0lume ^ *
   Use   of  dissolved  oxygen   probe   to   make   dir-t
   measurements of depletion of dissolved O2 from
TABLE 3   TYPES OF RESPIROMETERS BASED ON TECHNIQUES AND APPLICATIONS
                        measuring gas

               A. Sfnall constant Preyynr* rSDJromi.t<.r< _
                    Measurements are  made by observing the change in volume of

                    SSHf " ""^ WUh the feSpi""g llquid'  I^ 02 is

               B. Small constant
                                                     2
C.
                                    s

                 Lifgt respirometers mi-astiring e* /-h=.^n -
                   Kecommended especially for studies of treatability.

               D. Electrolvti<;
                                                maintained at a constant value



                                                         ^ 02 ^
                                      349

-------
           Diagram of a measuring
           unit.
           A  reaction vessel
           B  oxygen generator
           C  pressure indicator


           1  magnetic stirrer
           2  sample  (250 ml)
           3  C02 absorber
           4  pressure indicator
           5  electrolyte
           6  electrodes
           7  recorder
SCHEMATIC DIAGRAM OF A MEASURING UNIT

               FIGURE 1
                     350

-------

            
-------
                             Endogenous Phase
X
>;
(/f
  Substrate
  ^
Removal Phase
                           BOD Curve
                            Test Compound
                             Degradation Curve
                      Time
       The schematic diagram for the relationship of S, y and x.
                        FIGURE 3
                             352

-------
                        >      

                       Time (days)

 A - 02 uptake curve of a rapidly oxidizing substrate.

 B -
C  - .Og uptake  curve with an initial lag period

                        ^  miCrbbta  "*
             m      beffre ^atl'0n othe remaining part of
    substrate. Illustration of catabolite repression.
E -
    cumulative  Or uptake attributed  to b
    m (A) and  (B) curves for a substrate
in presence of only the
    control seed organisms.
      1?f!I!LE CURVES OF THE OXYGEN UPTAKE
       ATTRIBUTED TO THE PROBLEM SUBSTRATE
                 FIGURE  4
                          253

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-------
PREDICTION OF BIODEGRADATION KINETICS OF TOXIC ORGANIC COMPOUNDS


                    Sanjay Desai, Chao Gao and Rakesh Govind
                       Department of Chemical Engineering
                             University of Cincinnati
                             Cincinnati, Ohio 45221

                                      and

                                Henry H. Tabak
                      U. S. Environmental Protection  Agency
                       Office of Research and Development
                      Risk Reduction Engineering Laboratory
                             Cincinnati, Ohio 45268
               This paper has been reviewed in accordance with the
                 U. S. Environmental Protection Agency's peer and
                  administrative review policies and approved for
                          presentation and publication.
                          Prepared for Presentation at:

                     Twelfth United States/Japan Conference
                        on Sewage Treatment Technology
                               Cincinnati, Ohio

                             October 12-13,1989
                                      383

-------
 PREDICTION OF BIODEGRADATION KINETICS OF TOXIC ORGANIC COMPUNDS
                                    ABSTRACT

     Biodegradation is the most important mechanism in controlling the concentration
of chemicals  in  an  aquatic system because  it  can mineralize  toxic  pollutants  to
harmless  forms.  So the  fate  of organic  chemicals  in an  aquatic  environment  is
dependent on  the  susceptibility to  biodegradation.  Because of the  large  number  of
chemicals, it would be expensive and  labor intensive to gather this  information' in a
reasonable amount of time. Hence,  there is need for a  prediction method to obtain
these data.

     The paper describes a predictive biodegradationstructure/activity model based on
the group contribution approach  using  biodegradation kinetic data obtained from the
literature  and  through  electrolytic  respirometry  studies.  The  model,  incorporating
chemical  properties  and  structure  of organic  compounds,  predicts  biodegradation
kinetics for  related toxic  compounds.  Biodegradation kinetic data  for  representative
RCRA toxic organics presented in  this paper, were used  to establish  a  pattern  of
predictability for  biodegradation  of  related  compounds  with the  group contribution
predictive model.

     Results are presented  on  the development  of  the  structure-activity  relationship
for biodegradation  using  the  group  contribution  approach. With  the  use  of this
approach,  reported  results  of the kinetic rate constants agree within 20% with the
predicted  values.  Additional compound  studies  are essential to  further  extend the
methodology.
                                         384

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                                   INTRODUCTION

  ,h   i            estimated that 50,000 organic chemicals are commercially  produced in
  the  United States  and a  large number  of  new organic chemicals are  added to  the
  JP/a Sr?nnf   fJ^J^X**?^ **"* of these ^micals in the environment
  disposal\iechn\ues         Problem-  Their presence  could be attributed  to inadequate


  t** -SlnCe  many* f these hazardous  chemicals can  be detected in wastewater,  their
  fate in wastewater  treatment system  is  of  great interest.  Of  the many factors that
  fmnnLn,6  Sf6  2J. theus.eucomPu.nds' mfcrobial  degradation  is  probably  the most
  important   (2).  The   high   diversity  of  species  and   the  metabolic  efficiency  of
  microorganisms suggest that  they  play  a major role in the ultimate degradation of
  these   chemicals   (3).   Biodegradation   can  eliminate  hazardous  compounds   by
  biotransform.ng them  into  innocuous  forms,  degrading them  by  mineralization  to
  carbon  dioxide, water  and other simple and  harmless molecules.  So the  information
  regarding the  extent   and the  rate  of  biodegradation  of  these  chemicals  is  very
  important for  regulation  of their manufacture and  use. Due to the large  number of
 these chemicals, gathering of this information in a reasonable  amount of time would
 be both  expensive and  labor intensive.   Thus, the only practical way out  is to develop
 correlations  and predictive  techniques to  assess  biodegradability (4).  Lack  of  an
 adequate database  on  biodegradation  kinetics has hindered  the development of such
 techniques.

                           EXPERIMENTAL TECHNIQUES

      There  are  many  techniques for collection of biodegradation data and these  are
 reviewed in  great detail by Howard,  et al. (5) and Grady (6). Experimental  techniques
 for biodegradation data collection fall  into three  broad categories  : continuous  fed-
 batch and batch reactor systems.                                              '

      Continuous culture reactors  require an acclimated  biomass.  They also require long
 transitional time intervals for  reaching  quasi steady state condition  (7).  So it  is time
 consuming, tedious  and expensive. However,  the analysis of data obtained  is  simpler
 because the equations  for continuous  reactors, operating at  steady state,  reduce  to
 algebraic equations  that are easily solved. This technique is  used more for evaluating
 parameters  for the design of treatment  systems rather  than for biodegradation kinetics


 ..  ,  Fed-batch reactors have also  been used to estimate  the  kinetic parameters  of
 biodegradation.  In these reactor configurations, a quantity of biomass is  added into a
 reactor  and a substrate  stream is continuously added in negligibly small amounts with
 respect   to  the reactor  volume.  Because  of  small  amounts  of both substrate and
 microorganisms,  a pseudo steady state  is achieved. So  this technique reduces the time
 required and also alleviates  the problems associated with changes in the  composition
 ot the microbial community. This configuration requires  an acclimated biomass  because
 the microbes must be capable of responding instantaneously to the  input of substrate
 This technique cannot be used  to determine the Monod biokinetic parameters, but it  is
an  excellent procedure  to  determine the  parameters   for treatment plant  design  or
operation.                                                          KB

     The use of batch  cultures in biotechnology and biological  wastewater  treatment
represents a  less  expensive and much  faster  way to model  biokinetics in fermenters

                                       385

-------
and  in  activated  sludge  tanks  (7). The batch method  commonly used  for  a large
number of  compounds (10)  is  one in which  the substrate  of interest,  at different
concentrations, is  inoculated with the small amount of biomass. Then the increase in
biomass  concentration  in  each  reactor is  measured  as a  function of time. Another
technique focuses  on the substrate removal rather  than  the microbial  growth. This is
commonly  used in engineering studies. The batch reactors are inoculated with large
quantities of biomass and  the substrate removal  is measured as a function of time.
Both of  these  techniques have been widely used to measure  parameters such  as  five
day  BOD and COD.  Batch reactor can be used with  either acclimated or unacclimated
biomass. It requires that  samples be taken at discrete time intervals during the course
of biodegradation.  If unacclimated  biomass is  used,  the number of samples required
may  be  large  depending  on  the acclimation time. Tabak, et al.  (11)  have collected
degradability  and  acclimation  data on 96  compounds  by  static culture  screening
procedure and culture enrichment process. Larson and  Perry (12) and Paris, et al. (13)
have done biodegradation studies with  unacclimated biomass in  the batch  reactors  and
have evaluated the kinetic parameters.

      In the past, the  number of  data points  obtained was small because of  manual
sampling.  This can  be  avoided by  monitoring oxygen  consumption as  an  indirect
measure of biodegradation using  an   electrolytic  respirometer. The  automatic  data
collection and  recording  allows  sufficient accumulation of data, that  the  reliability of
the kinetic parameters evaluated is maximized.

      In the respirometric methods of BOD measurement, wastewater samples are kept
in contact with the gas phase source of oxygen. Oxygen uptake by the microogramsms
over a  period  of  time is measured by the changes in volume  or pressure of the gas
phase. An alkali is included in the apparatus to absorb carbon dioxide produced during
biodegradation.  Samples  are usually incubated  at  constant temperature  and are kept
away from light.  The latest development in  respirometric techniques has  been the
advent  of an  electrolytic respirometer. It  supplies oxygen, produced  from electrolysis
of water,  to  the  air  space above  the  sample  in  a completely sealed reaction vessel.
The production  of oxygen is triggered due to the  pressure changes in  the reaction
vessel. Studies by Larson and Perry (12), Young and  Baumann  (14), Tabak, et  al.  (15)
and  Dosanjh  and  Wase  (16)  have shown that the electrolytic  respirometer eliminates
most of the technical  difficulties associated with other methods for determining BOD.
It is particularly  useful  for the rate  studies because it provides both, a continuous
record of oxygen  uptake and  it maintains an unchanging atmosphere over the sample
regardless of the length of the test.

                              EXPERIMENTAL SET-UP

      The  electrolytic respirometer Sapromat B-12, consists of a temperature controlled
waterbath, which  contains the  measuring units,  a recorder  for digital indication and
 direct plotting of the oxygen  uptake curves and a cooling  unit.  The waterbath has l/
 reaction  flasks, each  connected  to  the  recorder.  Each  unit  as shown  in  figure,  1
consists of a  reaction vessel  C, with  a carbon diox.de absorber (sodalime) 3 mounted
 in   a stopper,  an  oxygen generator   B,  and  a  pressure  md.cator  A.  The  vessels
 interconnected  by hoses,  form  a sealed  measuring  system  which  assures that  the
 barometric pressure  fluctuations  do  not adversely,  affect the result  The magnetic
 stirrer 1 in the sample 2  to  be analyzed provides vigorous agitation,  thus ensuring an
 effective exchange of gases. The  activity of the microorganisms in the sample creates
 a reduction in the  pressure  which is recorded by the  pressure, indicator  It  controls
 both the electrolytic  oxygen generation and  the indication  and the plotting ot the
 measured values.
                                        386

-------
       Jjl !  nSUmpIIOnA f xyge? by  microorganisms creates a  reduction in  pressure in
            " VeSS?'  ^  a -result'  the level  of  '5%  sulphuric  acid  in  the pressu e
  drrnt      f*  *"*' X"168 '"  C.ntac,t wlth "  platinum  ^trode. This completes  the
  circuit and I  triggers the generation  of oxygen by the electrolytic  cell. The oxyeen  eas
  s  provided  to  the  reaction  vessel,  alleviating  the negative  pressure ^  The fevel  of

          ten  hC     51"
                   ...        -       amount of oxygen supplied  to the sample is
  n RM ATr6CK-lyi, m """w*  Per  t by  the  recorder.  The border is connected to
  an IBM AT which records data from the measuring units every 15 minutes    onnecrea lo
                          Figure 1. Diagram of a Measuring Unit

                      A.   Pressure indicator
                      B.   Oxygen generator
                      C.   Reaction vessel
                      1.   Magnetic stirrer
                      2.   Sample (250ml)
                      3.   C(>2 absorber
                      4.   Pressure indicator
                      5.   Electrolyte
                      6.   Electrodes
                      7.   Recorder
                            BIODEGRADATION KINETICS

     A  considerable  amount  of  information  concerning  biodegradation  kinetics is
aa?Jc   IStr   . P"bl'1!hed literature.  Early  literature  shows  widely differing kinetic
rates in different  studies. The evaluation and  prediction of the  extent  and rate of
biooxidation  is affected by methodological and experimental factors.  Regardless of the
intlSiv-^VS"*  'W '.nLthe measureme"t  of  biodegradation  rates/it is
generally considered associated with microbial cell growth and  so most  of the models

                                        387

-------
for it are the same as those used to model growth and substrate removal.

     Although  many  models  have  been  proposed for microbial  growth, the  Monod
relation is the most popular kinetic  expression (17). The Monod model, in combination
with  the linear  law for substrate  removal  can  provide  an  adequate  description  ot
microbial growth behavior.  It states that the cell growth  is first order with  respect to
the  biomass  concentration  (X) and  mixed  order  with  respect  to  the   substrate
concentration (S)
                            dX/dt = (S n,m X) / (Ks + S)
Cell growth is related to the substrate removal by the linear law
                                dX/dt = - Yg (dS/dt)
(1)
(2)
      The  kinetic parameters of interest are maximum  specific  growth rate u,m,  half
 saturation constant Ks, (it is the  concentration of substrate when P-=0.5u.m), and the
 yield coefficient Ye. The Monod equation has two limiting cases.  When the substrate
 concentration  is  much  greater than  the  saturation  constant  the  term  (5/Ks+b)
 approaches 1.0 and cell  growth and  substrate removal  are zero order with respect to
 substrate  concentration.   When the substrate  concentration is  much  smaller than the
 saturation  constant,  the term  (S/Kc+S)  approaches  (S/KS)  and  cell  growth  and
 substrate  removal are first order with  respect to the  substrate concentration. Many
 researchers  have used  either  of  the  above two approaches.  The characteristics of
 these kinetic expressions have been discussed by Simkms and Alexander (18).

      The  electrolytic respirometer has  been mostly  used  to  measure the extent of
 biodeeradation as a  percentage of the theoretical  oxygen demand over a certain period
 of time.  Several researchers have  tried to  extract  kinetic  parameters from  oxygen
 uptake  data.  Larson and Perry  (12)  used empirical  kinetic expressions  which were
 system  specific.  Dojlido  (19)  divided  the oxygen uptake curve  into  seven different
 phases  and  then proposed  an  empirical  model  for each  phase  and evaluated  the
 biodegradability  and  toxicity  of a test compound by measuring.empirical rate constants
 and  time  intervals associated with each phase. Tabak, et al.  (15) d.v.ded the ?ubstrate
 removal  region  of oxygen uptake curve into  two reg.ons, separated  by  an inflection
 point. The  first  period was called exponential phase where  it was assumed that  the
 substrate was not limiting and cell  growth was occuring, while the second period was
 called declining  phase and  here it was assumed  that  the substrate was  limiting. So
 work done to obtain kinetic parameters from oxygen uptake curve  has been empirical.

                      STRUCTURE-ACTIVITY RELATIONSHIP

      The structure-activity  relationships (SAR) have  been widely used in pharmocology
 and medicinal  chemistry. The different methods  and  models  used are  free energy
 models, Free-Wilson mathematical model, discriminant analysis cluster analysis, pattern
 recognition, topological methods, and quantum mechanical methods.

      The free energy model of Hansch, et al. (20)  is  widely  used They incorporated
 octanol-water coefficient, log  P,  in the linear'free energy relationship as  a measure of
 liooDhilicitv  This provided  a general SAR model for  biological  activity. The success or
 this model has led  many researchers to include  additional phys.cochem.cal Parameters
 and properties   structural, topological and  molecular indices.  Using similar  principles
 other researchers have proposed models to include more complex relationships between
 the bioactivity  and  the chemical  structure or the properties. Martin  (21)  has  dicussed

                                         388

-------
   these models.



   subst,tuted ,n various pos.tions, resulting in a series of linear equation^ of the form

  to bto     to *&*"? ^ "ly srHantl^ or qualitative data  have


                     ..              the location of the substituent groups, Geating
                    aLg0"thtm '. pred!ct  "*>*" quantification is  required

     In the literature, first order rate of biodegradation or five day  BOD of chemicals
    hlhTH  ^"f* wi*  Phsical o' chemical  properties.  Paris,  etal   S,?^)
established  a correlate between  second  order  biodegradation rate constant arid the
                                       389

-------
van der Waal's radius of substituent group for substituted anilines and for a  series  of
para-substituted  phenols. Wolfe, et al. (35) correlated second order alkalme hydrolys
rate constant and biodegradation  rate constants for  selected pesticides  and phthalate
^.fTe^afworkershave observed  a  correlation  between  biodegradabihty  and
     Lilt.:*..   	:n^oii ^anni/watpr nart t on  coefficients  (log Pi. Pans,  et al.  Uoj
of esters  of 2,4-dichlorophenoxy  acetic acid. Banerjee,  et  a       oame  a  si
relationship for chlorophenols. Vaishnav, et al.  (38}  correlated ^degradation of  17
alcohols  and  11  ketones  with octanol-water  coefficients  using  5-day BOD data
pSer(39)  has found  a  dependence of  biodegradation  rate  on e'ectronicnfaf"'  *
Harnmett  substituent constant,  for  a  series  of anilines and  phenols   Dearden  and
Kfcholso"  (40  hav   correlated 5-day BOD with modulus  difference of atomic charge
acrossTselected  bond in  a molecule  for amines, phenols,  aldehydes, car^xyhc acids
haogenated  hydrocarbons   and   amino acids   A  direct  correlat.on   be ween  the
biodfgradability rate constant and the  molecular structure  of  the  chemical has  been
used by  Govind (41) to relate the first order biodegradation  rate constant  with the
first  oLr  molecular  connectivity index  and  by  Boethling  (42) to  "jrfatjthe
biodegradation  rate  constants  with  the  molecular connectives  for  dialkyl  esters,
carbamates, dialkyl ethers, dialkyl phthalate esters and aliphatic acids.

                        GROUP CONTRIBUTION APPROACH

      Using  a  group contribution approach,  a  very  large number  of chemicals of
 interest  can  bl  constituted from perhaps a  few  hundered   functional groups   The
 Drediction of the property  is based  on the structure of the  compound. According to
 tWs  method the ^molecules of a  compound are structurally decomposed into functional
 SouoTor their fragments, each having  unique contribution  towards  the compound
 property   This ^method  is similar to the Free-Wilson  method  used  m  medicinal
 chemistry.
      The  biodegradability rate  constant  k, is  expressed  as  a  series       f
 a)ntribution ai, of each group of the compound. The first order approximation of
      TnctionJ representing biodegradation rate constant can be expressed as
                          Ln (k) =
                                  >
(3)
  where Nj is the number of groups of type j in the compound  a,  is the contribution
  of group of type j and L is the total number of groups in the compound.

  CALCULATION OF GROUP CONTRIBUTION PARAMETER, o
                                                                                s
  using regression analysis.
       If there are n a's and m compounds (n
-------
                           = 2{Ln(kj)-2Njjaj}2.
                            1=1           =lj  JJ
 (4)
The estimates of a's  should  be such that it produces the least  value  of  S.  These
estimates are obtained by  differentiating equation 4 with respect to a and  setting it
equal to zero
                   .    m            n
          dS/dak = - 22 {[ Ln(ki) - 2 Njjaj ] Nki> = 0
(5)
This  will  generate  a  series of n  linear  equations which are solved for a's. If N is the
matrix of coefficients of a's and  Y is the vector  of  Ln(k)  values  then the solution
vector a is given by

                                a=(N>N)-1(N'Y)
                      4
where ' denotes the transpose of matrix.
                              MODEL VERIFICATION
     The  contribution  of  several  different  groups  was  calculated from the  data
obtained from  the  literature (43,44,45).  The data used to calculate these contribution
parameters  is  given  in  Table 1. The groups  and their  contribution  parameters are
given in Table 2.
     The biodegradation experiments were carried out for cresols, phenol, 2,4dimethyl
phenol, 2butanone, acetone, 1phenyl hexane  and butyl benzene using an electrolytic
respirometer Sapromat B-12 (Voith-Morden, Milwaukee, Wl). The chemicals were from
Aidrich chemical  company with  99+% purity. These compounds were used to validate
the model, but were not  used in the calculation of the group contribution parameters.
The experimental conditions  were : temperature 25C, biomass concentration 30 mg/L
and  compound concentration lOOmg^L The biomass was obtained  from Little  Miami
wastewater  treatment  plant  in  Cincinnati,  which  receives 95%  domestic waste. The
biomass  was  aerated  for  24  hours  and  then  used  for  the   experiment.  The
biodegradation  rate  constants  for these  compounds  were  determined  using  the
following simplified Monod form, obtained by assuming  that Ks  S  and change in
biomass concentration is negligible.                                              -
                             dS/dt =. - KX0S.
(6)
where K = (p-rn/Yg Ks) and Xo is initial biomass concentration.  Integrating equation 6
we get
                                S = S0exp(-KX0t)	(7)

In terms of BOD the above equation transforms to

                          BOD = ThOD (1 - exp{-KX0t}). ....  (8)

The  above equation was used  for only the rising  part of the BOD versus time curve,
and initial data and data for endogenous  phase were neglected. Note  that the selection
of the  rising  part of the BOD  curve was arbitrary and was based on visual  inspection
of the BOD  curve. The biodegradation rate constants were  also predicted  using the
group contribution  parameters of Table 1. The comparison of these  values is given in

                                       391

-------
Table 3 and Figure 2.

                            RESULTS AND DISCUSSION

     The prediction values of Ln(K) are within 10% of the experimental  values. It is
important to emphasize that  there are several reasons for  the  rather large discrepancy
between the predicted and experimental values. These reasons are as follows :

1.   The data used for  calculating  the  group contribution  parameters  were obtained
from  the literature (refer  Table 1). The experimental BOD  curves,  obtained  from
electrolytic  respirometry,   were  approximated   by  an   exponential  relation  (refer
equations 6, 7 and 8). The  range  of curve  to which  this equation was  applied was
selected  arbitrarily. This resulted in some error between the experimental data and the
calculated value of the kinetic constant, K.

2.   The group contribution method described  here is the  first  order approximation. It
assumes that the  contributions  of the groups  are independent of each other.  So the
rates predicted are only expected to be within an order of magnitude.

3.   Biomass and experimental  methods  used in the different studies  were different.
The studies, used  for determination  of group contribution  values had acclimated their
biomass to the compound before using  it in the experiment,  while our biomass was
from  domestic wastewater  treatment plant and was not acclimated to the compounds
used in the study.

     Inspite  of  these  errors,  the  prediction  is within an  order of magnitude.  With
availability of more data and  using  a  detailed kinetic model rather than  a  first order
exponential equation, the prediction error may be reduced considerably.

ACKNOWLEDGMENT  :This research  was supported by co-operative  agreement CR
812939-01 from U. S. Environmental  Protection Agency.

                                   REFERENCES

1.    Blackburn, J.W.,  Troxler, W.L. Prediction of the  fates of organic  chemicals in a
      biological treatment process  An overview. Environ. Prog.  3: 163, 1984.
2.    Howard, P.H., Saxena, J.,  Sikka, H. Determining the fate  of chemicals.  Environ.
      Sci. Tech. 12: 398,1978.
3.   Alexander, M. Biodegradation of chemicals of environmental concern.  Science 211:
      132,1980.
4.    Strier, M.P.  Pollutant treatability : A  molecular engineering  approach.  Environ.
      Sci. Tech. 14: 28r 1980.
5.    Howard, P.H.,  Banerjee,  S., Rosenberg,  A. Review  and  evaluation of available
      techniques  for  determining persistence  and  routes  of degradation  of chemical
      substances in environment.  560/5-81-011, U.S. Environmental Protection Agency,
      1981.
6.    Grady,  C.P.L.,  Jr.  Biodegradation  : Its measurement  and microbiological basis.
      Biotech. Bioengg. 27: 660, 1985.
7.    Braha, A., Hafner, F. Use  of lab batch reactors to model kinetics. Wat Res. 21:
      73,1987.
8.    Chudoba,  J., Cech,  J.S.,  Farkac,  J.,  Grau,  P.  Contro  of  activated   sludge
      filamentous bulking ;  Experimental  verification, of  a kinetic selection  theory. Wat,
      Res. 19:191,1985.
9.    Bull,  A.T.,  Slater, J.H. in:  AT. Bull, J.H. Slater (eds.), Microbial  Interaction and

                                        392

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 25.
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 27.
 28.
 29.
 30.
 31.
 32.
33.
34.
   n^T"?leIVVLil:AuCad!m,lc P:ess. New York., NY, 1982.
                                                           f
                                                                   to
   Effects of nutr^VV n tK'netl<; concePts,fo/ measuring microbial  rate constants
  . cnects or nutrients on rate constants. ADpL Env ron Miemhinl M- wi  loa*
  Young, J.C., Baumann, E.R. The electrolytic^ respirome er - II -Use ?n  water
  pollution control plant laboratories. Wat. Res 10-1141  1976
  Tabak,  H.H.,  Lewis. R:F..  Oshima  A  Pi-^olytic'  respi'rometry  biodegradation
                                                method  for  J '    '   '
                                             >. Environmental
                                     ^^

        v
NewYork,  1978".  Quan"tatlve
                                       chemistry. 1. Med Ch.m wfl 1976
                                    Desi*n  :  A  Critical  IntroducJion?  Dekker,
                                                  Chemistry. Vo,.
                                                                            of
                                                            .
                                                             .....
 Dunn, W. J.  Ill, Wold,  S. Structure-activity' analysed  by pattern  recognition  
 The asymmetric case. J. Med. Chm  n-vx 1930            pern  recognition  .
                                         '
Ac?demicBpVessa"NY- ,^6Mole<:ular  Connecti.it, in Chemistry and Drug Research,
                                                 RMltronships  of  Drugs'  Ed-
    .  
      n
                                                              in water- EPA-
                        -  Realtionships between properties of a series of anilines
                          ^act!ria- ADD|- Environ ^irrfthioi  *"."*
                         LL>'  Stecn'  W"  C' Structure-activity  relationships  in
       H  P,       ,baCtf ^ ADDl. Environ Mirmhinl 53:971, 1987.   ?
       D. F., Wolfe,  N.  L,  Steen,  W.  C.,  Baugham  G  L  Effect of
molecular structure on bacterial transformation  rate constants  in  p?nd
                                  393

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39.
40.
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<;amnles  ADD! Environ. Microbiol. 45:1153, 1983.                          .
Wolfe  NLPr Paris,  D.F.,  Steen,  W.C,  Baugham  GL  Correlation of m.crob.a.
degradation rates with chemical structure. Fnv.ron Sc. Tech  U.1 431980
KrSriTKrWoife, N.  L.,  Steen, W.  C.  Microbial transformation of ester of

B^e^                                                A- J-. S^ "
Tullis  D.  L. Development.of a general  kinetic model for  biodegradation and  its
application to chlorophenols and related  compounds.  Fnviron. Sci.  Tech. 18.416,

Vaishnav   D.   D.,  Boethling,  R.  S.,  Babeu,  L.   Quantitative  structure-
biodegradability   relationships   for  alcohols,  ketones  and  alicychc  componds.
Chemosphere. 16:695,1987.                             romnnnnHs and the  rate
Fitter, P.  Correlation between the structure of aromatic compounds ana wei  rate
of their  biological  degradation. Collection Czecoslovak Chemical  Comm. 49.2891,

Dearien, J.C., Nicholson, R.M. The prediction of biodegradabilities by the use of
quantitative structure-activity relationships  :. Correlat.on of  biological  oxygen
demand  with atomic charge difference. Pestici. Sci. 17: 305,1986.          9nfM o.
Govind,  R. Treatability of toxics in wastewater systems. Hazardous Substances 2.
 Boetnnng,  R-S.  Application of  molecular^topology  to  quantitative  structure-
 biodegradability relationships. Environ. Tox. Chem. 5: 797,1986.            MH^n>tr
 Urano,  K.,   Kato,  Z.  Evaluation  of  biodegradation  ranks  of  pr.or.ty  organic
 compounds. J. Hazardous Mtl. 13:147,1986.                                   .
 Stover   E.   L.,  Kincannon,  D.F.  Biological  treatability   of. specific  organic
 compounds  found  in  chemical  industry  wastewater. Paper  presented  at  36th
 SiVduV Industrial Waste Conference. Purdue University, West Lafayette, IN, May
 1214  1981
 Environ  Corporation.   Characterization  of  constituents  *"**  fdaftaA   waste
 streams listed in 40 CFR section 261 DRAFT profiles. Report for EPA, 1984.
                                         394

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TABLE 1. DATA USED TO CALCULATED GROUP CONTRIBUTION PARAMETERS
No. COMPOUNDS Molecular formula
1 Ethyl alcohol C2H50H
2 Butyl alcohol C4H9OH
3 Ethylene glycol C2H4(OH)2
4 Aceticacid CH3COOH
5 Propionic acid C2H5COOH
6 n-Butyric acid C3H7COOH
7 n- Valeric acid C4H9COOH
8 Adipic acid C4H8(COOH)2
9 Methyl ethyl ketone CH3COC2H5
10 HexamethylenediamineC6H12(l\!H2)OH
11 n-Hexylamine C6H13NH2
12 Mono ethanol amine C2H4(NH2)OH
13 Acetamide CH3CONH2
14 Benzene C6H6
15 Benzyl alcohol C6H5CH2OH
16 Toluene C6H5CH3
17 Acetophenone C6H5COCH3
18 Hydroxybenzoic acid C6H4(OH)COOH
19 Aminobenzoic acid C6H4(NH2)COOH
20 Aminophenol C6H4(NH2)OH
21 2-CI phenol CIC6H4OH
22 1,2-Dichlorobenzene C6H4CI2
23 l,2,3-Tri-CI-benzeneC6H3CI3
K(L/Mg.Hr)*E4
5.749
11.10
40.00
22.22
23.14
10.50
- 6.516
2.781
3.071
2.994
4.425
3.720
4.576
288.3
16.34
8.446
6.408
10.50
6.332
4.179
1000.
678.4
446.7
REF.
43
43
43
43
43
43
43
43
43*
43
43
43
43
44
43
43
43
43
43
43
45
45
45
                           395

-------
No. COMPOUNDS
Molecular formula K(L/Mg.Hr)*E4REF.
24 l-Glutamic acid C2H4(COOH)CH(NH2)COOH
25 Glycerol
26 iso Valeric acid
27 Propionaldehyde
28 n-Butylaldehyde
29 Benzaldehyde
30 Acetonitrile
31 Benzonitrile
32 Chloroform
*
33 2,4-Dinitrophenol
34 Nitrobenzene
35 1,2 Dichlorobenzene
36 TriBr methane
37 Br-di-CI-methane
38 DiBrCI methane
CH(CH2OH)2OH
CH(CH3)2COOH
C2H5CHO
C3H7CHO
C6H5CHO
CH3CN
C6H5CN
CHCI3
C6H3OH(N02)2
C6H5N02
C6H4CI2
CHBrS
CHBrCI2
CHBr2CI
24.17
44.78
15.43
4.010
5.106
25.13
1.455
6.326
178.1
93.00
147.3
233.5
1.000
1.000
1.000
43
43
43
43
43
43
43
43
44
44
44
44
45
45
45
396

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TABLE 2. GROUP CONTRIBUTION PARAMETERS
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Group
Methyl
Methylene
Ketone
Amine
Acid
Hydroxy
Aromatic CH
Aromatic C
Chlorine
Methylidyne
Nitro
Aldehyde
Nitrile
Bromine

CHS
CH2
CO
NH2
COOH
OH
ACH
AC
Cl
CH
N02
CHO
CN
Br
aJ
-3.460
-0.1354
-0.9650
-4.061
-3.201
-2.983
-0.8340
1.973
-2.352
3.223
-2.448
-3.909
-5.272
-4.657
             397

-------
r
                    TABLE 3. COMPARISON OF ACTUAL AND PREDICTED Ln(K) VALUES
                       Compound
Actual    Predicted
Ln(K)    Ln(K)
Error % based
on Ln
                       o-Cresol               -6.0890  -5.8330       4.20
                       m-Cresol              -5.7706  -5.8330       -1.08
                       p-Cresol               -5.8659  -5.8330       0.56
                       2,4-Dimethylphenol      -6.2472  -6.4860       -3.82
                       Butylbenzene            -6.5297  -6.0632       7.14
                       1-Phenylhexane         -6.7983  -6.3340       6.83
                                                 398

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                                                                          :LO
                                                                         : CD
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                                       399

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-------
PARTITIONING OF TOXIC ORGANIC COMPOUNDS BETWEEN WASTEWATER
                  AND WASTEWATER  SOLIDS
                            by

                     Richard A.  Dobbs
               Biosystems  Treatment  Section
               Treatment Assessment Branch
  Water and Hazardous Waste Treatment Research Division
          Risk Reduction Engineering Laboratory
          U.S. Environmental  Protection Agency
                 Cincinnati, Ohio  45268
  This paper has been reviewed in accordance with
  the U.S. Environmental Protection Agency's peer
  and administrative review policies and approved
  for presentation and publication.
             Prepared for Presentat i on at:

        Twelfth United States/Japan Conference
            on Sewage Treatment Technology
                   Cincinnati, Ohio

                  October 12-13,  1989
                         401

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        PAPTTTTnMTNfi OF TOXIC ORGANIC COMPOUNDS BETWEEN WASTEWATER
        	:            AND WASTEWATER SOLIDS    "
                                  ABSTRACT


     An experimental protocol  which eliminates the effect  of biodegradation
and volatilization losses on the sorption measurement has  been  developed  and
SJplled to uptake of toxic organics by wastewater solids   Sorption
capacities obtained for primary, mixed-liquor and digested solids  from
municipal wastewater treatment plants have been correlated with
SctaSol/water panition coefficients and with modified Randid indexes.  It
has been shown that the correlations are the same for all  three types .of
wastewater solids if partition coefficients are calculated on the  basis of
organic content of the solids.  The correlations developed are useful for
asSing thi role of sorption in the treatment of toxic or hazardous

                   ^^


                                                          "?'of the

 impact  of toxics  on  sludge  disposal options.
                                      402

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                                  INTRODUCTION
      Sorption on solids  is one of the fundamental processes control linq
 removal of toxic organic compounds in biological wastewater treatment
 {Jin  A  J    a!S f hydrPhobic organic pollutants in wastewater is highly
 dependent upon their sorptive behavior.  The degree of sorption not only
 affects a chemical's mobility, but also is a dominant factor in fate
 processes such as volatilization and biodegradation.  Organics may
 accumulate in sludges at concentrations several orders of magnitude greater
 than the raw wastewater concentrations.  Concentrations factors of 50-39 000
 have been reported (1, 2).                                            ,vuu


 thP nl!!t?l!nnerS0lJ*1ns*w!!1
-------
                                                                     (4)
     The Freundlich equation is a useful method for treatment of sorption
data.  Since X = C0-C ,  for  a given  volume of  solution,  substitution of C0-
Ce for X in Equation (2) yields:

                                  Cr /u   vr n                         fKA
                                 0-Ce/M = KCe                         \*>)

which gives removal of toxic organic as a function of wastewater solids
concentration.  However, to relate the logarithmic form of the Freundlich
equation (Eq. 3) to the equation for the partition coefficient (Eq. 4), one
must assume that the slope  (n) is unity.  In most cases where the
concentration of toxic organics in the aqueous solution are low, the slopes
are generally close to unity.  Deviations can result from difficulties in
measuring the sorption .isotherm caused by biodegradation, volatilization
losses, or analytical problems.

      In the present study,  partition coefficients were  measured for selected
toxic organic compounds on  raw, mixed-liquor, and digested wastewater
solids.  Sorption data were correlated with fundamental properties of the
compounds  studied.

                            MATERIALS AND METHODS
 REAGENTS

      Organic  compounds  were obtained from Eastman  Kodak Co.,  Rochester,  NY;
 Aldrich Chemical  Company,  Inc.,  Milwaukee,  VII;  and Chem Service  Inc.,  West
 Chester,  PA.*

 ANALYTICAL METHODS

      Analytical  methods for analysis of the selected organic  compounds used
 in the validation study are summarized in Table 1.

      Volatile chlorinated organics were analyzed using a Tracer  LSC-2  sample
 concentrator and a Tracer 222 gas chromatograph equipped with a  Tracer 700
 Hall  electrolytic conductivity detector.  Pesticides and the  cresol  were
 analyzed  using a Varian Model 3700 gas chromatograph equipped with a Van an
 CDS-111 chromatographic data system.  Dyes were determined with  a Beckman
 Model 25  spectrophotometer equipped with a clinical sipper system.

 COLLECTION OF WASTEWATER SOLIDS

      Wastewater solids were collected from municipal wastewater treatment
 plants within a fifty mile radius of the Risk Reduction Engineering
 Laboratory, Cincinnati, Ohio.  Wastewater plants were selected to include a
 wide range of domestic/industrial contribution to the total plant flow.
 Samples of primary sludge, mixed-liquor solids, and digested sludge were
 *Mention of trade names or commercial products does not constitute
 endorsement or recommendation for use.

                                     404

-------
                                                              .
  I'eni.rirugation.  The collected solid*: (annw\vima+oii/ i/v>/  ~   j     . .
  wr.^STp.M;c:;?J"v^ s.MSrSj'Knn,
          Borage perioa required for completion of experimental testing for
                                       USED FOR ANALYSE OF TOX.C
      TABLE ,.  SUMMARY OF ANA
  Compound
 Methyl ene chloride
 Chloroform
 1 , 1 -di chl oroethyl ene
 Carbon tetrachloride
 Tetrachloroethylene
 Chlorobenzene
                          Analytical method
                         	.
                          Purge and trap
                          Gas chromatography
  Conditions
  Tenax trap;  3%
  Carbowax 1500 on
  Chromosorb column
 Hall detector
 Lindane
 Heptachlor epoxide
 Dieldrin
                         Hexane extraction
                         Gas chromatography
 1.5% SP-2250/1.9%
 SP-2401 column
 Electron capture
 detector
2,4-dinitro--cresol
                         Freon extraction
                         Gas chromatography
                                               1% SP-1240 DA on
                                               Sepelcoport column
                                               flame ionization
                                               detector
Methylene blue dye
Azo dye 88
Azo dye 151
                        Visible spectroscopy
665 nm
505 nm
512 nm
                              405

-------
EXPERIMENTAL PROCEDURE

Experimental Protocol Development

         issues to be resolved in the development of a Pro*?
-------
 will  be  found In the wastewater solids as a natural  background.  If this
 occurs,  it  is easier to correct analytical values  of the equilibrium
 concentrations in the samples  by a constant amount.
    ' CO
     
     co
     60
     X
1000
100
!

10,




1.0

>
AM





















ETHOD 1 CONSTANT COMPOUND; VARIED SOLIDS
ETHOD 2 CONSTANT SOLIDS: VARIED COMPOU

































































o'.oi ' ' ' 4"6'.i ' '



















I
/












^


T
'
J. K
' poi

1.0



/I





*










,











y





























Kj - 22.2 r - 0.99
K2 - 22.2 r - 0.98
3led - 22.6 r  0.98






10



1 i

ILu
, *




-rr*


1

JT

hrr
100
                        RESIDUAL CONC. (C ),  mg/1


   Figure  1.   Comparison  of  two isotherm  methods

                   for  sorption  capacity measurements.


     A great  deal  of confusion exists  in the literature regarding the rate
of attainment of sorption equilibrium.  Sorption kinetics  for  phenol and
1,4-dichlorobenzene were reported  to  be exceedingly fast .(equilibrium in < 4
minutes) (7).  In  the case of polynuclear aromatic hydrocarbons on natural
sediments 35  to 60% of the equilibrium sorption capacity was achieved in
minutes (mixing limited) with apparent equilibrium after a few hours (8).

     Based on the  conflicting reports  in the literature on the rate of
attainment of equilibrium, kinetic  measurements on the  sorption of methylene
blue dye on mixed-liquor solids were made to determine  the proper contact
time for experimental purposes. Mixed-liquor solids from  three different
municipal wastewater treatment plants were collected.   Rate of sorption of
methylene blue  dye from a 10 mg/L solution was measured at 0.1, 0.2, and 0.5
g/L dry weight  solids.  All  three mixed-liquor solids concentrations from
the same wastewater treatment plant used in the isotherm runs  are presented
in Figure 2.
                                  407

-------
     10
60
B
8
a
M
tn
w
os
1.0
   0.10
                                   0.13g/l  solids

                                   0.20g/l  solids

                                   0.50g/l  solids
        0
           100
200
400
500
                                                           600
                                    300
                                TIME (MIN.)

     Figure  2.   Kinetics of  sorption  of  methylene

                    blue  dye  on  mixed-liquor solids.

     The kinetic data for the sorption  of methylene blue dye are in
aareement with  the two box model  proposed for hydrophobia pollutants  in
water (9).  The two box model described sorption dynamics in terms of a
rapid or "labile" exchange and a highly retarded or "non-labi  e" sorption
requiring days  to weeks to occur.  In the case of methylene blue dye  and 0.5
g/L mixed-liquor solids dose, 92% of the compound was sorbed in
approximately 30 minutes, while the remainder required seve^l hou^.  In
order to minimize biodegradation during the  sorption test, an equilibration
period of 6 hours is recommended.  The remaining organic compounds were
equilibrated for 6 hours.  This avoids overnight contact and permits  samples
to be separated from the solids the same day.

     The third  issue to be resolved in the  protocol development studies
involved methods to eliminate biological degradation of test compounds
during the partitioning process.  It is obvious  that other removal
mechanisms such as biodegradation and volatilization wo" haveto be
controlled if accurate  sorption data are to be  obtained.  9*";, inrl,,rfP
measurements of changing aqueous phase compound  concentrations would include
the  effects of all  removal mechanisms resulting  in  apparent sorption
capacities greater than actually achieved.   Volat   ization can be eliminated
frbm sorption measurements by using completely filled  containers with zero
headspace.  The impact  of  biodegradation on the sorption  measurem^!m;"
more difficult to control.   Lyophilization followed by dry  heat treatment
has  been reported to produce biological solids which had  flpeculation and
settling properties which  were  indistinguishable from live  biomass (7).

                                   408

-------
These authors claimed the batch experimental technique with nonviable
biomass appeared to give realistic results compared to tests with  viable
nJTIXiAniJX   ?" *te r?P?rt!d successful use of lyophi 1 ization for control
of biological activity,  this technique was evaluated.  A batch of  mixed-
liquor solids was collected and separated from the supernatant in  a
perforate  bowl centrifuge.  The moist solids were divided into two portions
One portion was freeze-dried and the other was stored at 4-C.   Sorption
 ,       were measured  using 2,4-dinitro-o-cresol.  The isotherms were
          at pH 3.0 for  two reasons.  First, the low pH would  inhibit or
+h  x     biological  activity in the test with viable biomass.   Secondly,
the decrease in pH would convert the 2,4-dinitro-o-cresol to the
undissociated (sprbable) form (pka = 4.35).   Results of the isotherm
comparison are shown  in  Figure 3.
    to
    to
   S
   pa
   of
   o
   CO
   X
     0.01	
         6.01'  ' '   *'6'

                       RESIDUAL CONC.  (C ) Bg/1


Figure  3.   Comparison  of freeze-dried  and viable

biomass for sorption of  2,4-dinitro-o-cresol
at  pH  3.0.

                                409

-------
     The use of freeze-dried solids in the isotherm procedure  was  not
acceptable based on the results shown in Figure 3.   The viable biomass
clearly has a significantly greater sorption capacity than the freeze-dned
material.  A similar result has been reported for sorption of  azo  and
triphenylmethane dyes on microbial populations (10).

     Alternate'techniques to control biodegradation were evaluated.
Wastewater samples are often preserved prior to analysis by adjusting  pH to
3 or less.  Preliminary experiments indicated that this approach would
minimize biological activity for primary and mixed-liquor solids but did not
completely inhibit digested sludge.  In addition, the technique would  be
limited to neutral organics, since pH change would alter charge and
dissociation of acidic and basic organic compounds which,would impact
partitioning.

     Two  additional methods were evaluated as potential treatments to
eliminate biodegradation during the equilibration period  in the isotherm
test    Pretreatment of the wastewater solids with cyanide was attempted
based  on  the reported potent inhibition of methanogensis  and carbon
Solism by  this aniSn  (11,  12,  13).  Carbon tj^1;"^"""!6^ 3S
a model  compound  to evaluate the  required contact time  to  ^activate the
biomass and the ratio of  cyanide  to dry weight solids  required to minimize
biodegradation over the 6-hour period recommended foreg"1]!1-    11C.
Results indicated that treatment  of the wastewater  solids for 24  hours  using
a cyanide to dry  weight  solids ratio  of 0.1-0.2  was optimum to P^yent
biodegradation of the  easily degradable carbon tetrachlpride.  _In the second
method wastewater solids  were  pasteurized at 85'C  for  thirty  minutes prior
to being used  in  the  isotherm  procedure.   The effectiveness of  the  two
methods for eliminating  biodegradation  is compared  in  Table 2 where whole
 samples (solid and liquid phases) were  analyzed  for five  chlorinated
 solvents initially and after 6 hours of mixing.
   TABLE 2.
EFFECT OF CYANIDE ADDITION AND PASTEURIZATION  ON  BIODEGRADATION
            DURING ISOTHERM EQUILIBRATION
                                    Concentration of toxic.
                             Control
  Compound
             0 hr
        Cyanide addition     Pasteurization

6 hr      0 hr     6 hr     0 hr      6 hr
1,1-dichloroethane
Chi orof orm
Carbon Tetrachl or ide
Tetrachl oroethyl ene
Chlorobenzene
106
100
100
105
100
91
103
49
107
109
113
97
100
102
93
100
94
101
100
97
103
101
- 99
100
97
99
100
95
96
106
                                      410

-------
       Results  in Table 2 demonstrate that both cyanide addition and
        mZa^?n T? effet1ve f'thpcls to eliminate biodegradation during the
  ho     v. ?     ?"ly rbon tetrachloride showed biodegradation losses in
 the control samples after the 6 hour equilibration period.   Pretreatment of
         HV1Ud9eS^nd S11ds by either method will eliminate the effect of
         dation on the sorption isotherm.  The recommended procedure is to
         an5eronin^S ft ^ m*thod Vhoice  separate fromthe supernatant

                                                             ^ fhUld 0t
                          of the preliminary experiments  a  general  overall
 i- o,,tnnoH < c-;   ~;'n    the Petition coefficient  (sorption-isotherm)
  is outlined in Mgure 4.             .

 MEASUREMENT OF SORPTION ISOTHERMS

      In the present study, the following  general procedure was used.  The
 moisture content of the solids from the perforate bowl centrifuge was
 determined by drying a portion to constant  weight at 110'C.  A stock slurrv
 was prepared to give the desired  concentration of solids for the Isothera
 test.  Equal aliquots of the stock slurry were added to a series of
 C^t*;i|uge b?ttlef-   A different  concentration of the organic compound was
 added to each centr fuge bottle from a stock solution of the toxicin
 rnethanol.   The bottles were  completely filled and capped to avoid loss of
 voiatiles  to the headspace or atmosphere. ,  Isotherm samples were mixed on a
 multiple magnetic stirrer at approximately  100 rpm for six hours.  After
 equilibration,, the solid and liquid  phases were separated by high-speed
 centrifugation and analyzed.   Blanks, standards, and whole samples (both
 an'alwP/fn/nMlvf      J  T* also  Processed through the procedure and
 analyzed for quality control  purposes.
 fnr            isotherms were measured using the general  procedure described
 rhla  seleted organic compound on the three types of wastewater solids.   .
 in FigSreS5rU               tOXiC Or9an1c compounds investigated are shown


 are suSarlze'Sln Table's!^ parameters for sorPt1on   -Ixed-llquor solids


 fnr J?hS?ln C?ffi^ents on mixed-liquor solids ranged from 0.056  mg/gm
 for methylene chloride to an extrapolated value of 38.9  mg/gm for dieldrin
 Mn!^11?^11"1 "ncentrat1o"s of 1.0 mg/L.  Slopes (n values)  were generally
 close to 1.0 and ranged-from 0.57 to 1.28 for sorption on mixed-liqSor
 of o ^'to lT?nhfJ f;pj!?? " S011f nave been reported to  range from a low
 of 0.3 to a high of 1.7 (14).   Compiled data on 26 chemicals  (mostly
 Hw0!???* h?J a mean va]ue ?f n of -87 Wlt" a coefficient  of  variation of
 to HP iiSi tlVnmea?UrediValUe 1s  ?ot available,  it is frequently assumed
 'ohtSnSJ *L !n  !;  ^x";ient  correlation coefficients  (r values) were
 obtained for all  the isotherms  measured.

     Isotherms for the chlorinated solvents  listed  in  Table 3 were measured
SiyfnS  ?ry   -d9? and  anaerob1ca1ly  digested  sludge to complete the
testing of municipal wastewater treatment  plant  solids.  Freundlich
parameters obtained are presented  in  Table 4.
                                   411

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                            I ISOLATE SOLIDS
                 FILTRATION
                   CENTRIFDGATION
                         [OPTIONAL  BUFFER WASH
                   CYANIDE OR PASTEURIZATION TREATMENT
                            [EQUILIBRATION |
          VARIED AMOUNTS OF SLUDGE
CONSTANT CONCENTRATION OF COMPOUND
             mNSTANT AMOUNTS OF  SLUDGE
             VARIED CONCENTRATION  OF COMPOUND
               WHOLE SAMPLES
                   SUPERNATANTS
                               [ANALYSIS]
         ^PECTROSCOPY
         UV   VISIBLE
   CHRQMATOGRAPHY_
GAS    LIQUID    GC-MS
   OTHER
TOC TOX TKN etc.
         RATE CONSTANTS Ks
                 FREUNDLICH PARAMETERS X/M, K, n
     Figure 4.  Protocol for sorptlon of toxics on wastewater solids.

                                    412

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                                                                     cr
                     Azo Dye 88
                                                 Methylene Blue
                      e o
                                          NO,S
                                                               MO
                Heptachlor Epoxide
                                                     Azo Dye 151
                 Lindane
       T
    CICH


       ei




Methylene Chloride




      Cl
                                                          Dleldrin
                                                             Cl
V
2,4-dinltro-o-cresol
I1
Cl C H
Cl
Chlorofrom
P
Chlorobenzene
Cl M
Cl C=C M
1  1 *H4 r Vil n V^^^!B*^ ..__
Cl C Cl
Cl
Carbon tetrachloride
Cl Cl
Cl C=C Cl

                                                     Tetrachloroethyl*
Figure 5.  Structures of organic compounds used In sorption
                                       studies.
                                     413

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TABLE 3   SUMMARY OF FREUNDLICH PARAMETERS FOR SORPTION OF TOXIC OR6ANICS
    .    '                  ON MIXED-LIQUOR SOLIDS
Compound
Methyl ene chloride
Chloroform
1,1-dichlorethylene
Carbon tetrachloride
Chlorobenzene
2,4-dinitro-o-cresol
Tetrachl oroethyl ene
Lindane**
Heptachlor epoxide**
Dieldrin**
Methyl ene blue dye
Azo dye 151
Azo dye 88
K, (mg/gm)*
0.056
0.094
0.150
0.497
0.285
0.420
0.897
0.762
17.9
38.9
22.6
8.30
1.35
n+
1.28
0.90
0.71
0.57
0.96
0.90
1.12
1.00
1.09
1.11
0.82
1.00
0.65
r#
0.85
0.98
0.96
0.95
0.96
0.96
0.98
0.99
0.98
0.99
0.98
0.99
0.99
*K  sorption coefficient = X/M at Ce = 1.0 mg/L

*n - slope of isotherm plot
*r  correlation coefficient
**K values extrapolated to Ce - 1.0 mg/L for comparison purposes
                                     414

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    TABLE 4.  SUMMARY OF FREUNDLICH PARAMETERS FOR SORPTION OF CHLORINATED
            SOLVENTS ON PRIMARY AND ANAEROBICALLY DIGESTED SLUDGES
       Compound
Primary sludge
                       K,(mg/gm)     n
Digested sludge
                       K,(mg/gm)   n
Methyl ene chloride
Chloroform

1 , 1 -di chl oroethyl ene
Carbon tetrachloride
Chlorobenzene
Tetrachl oroethyl ene
0.188
0.267

0.142
0.339
0.483
0.596
1.08
0.81

0.54
0.41
1.05
1.31
0.75
0.99

0.93
0.98
1.00
0.98
0.075
0.054

0.130
0.203
0.285
0.698
0.80
0.90.

0.82
1.18
0.76
1.47
0.94
0.61
N. ',
0.96
0.97
0.98
1.00
                            DISCUSSION OF RESULTS
      In  soil  and  sediment  sorption,  the extent to which  an  organic compound
 partitions  itself between  the solid  and solution  phases  is  expressed in
 terms  of a  parameter  K , which is largely independent of the properties of
 the  soil  or sediment  fr!6,  17).  Once.K has  been determined  for  a  soil  or
 sediment, it  is divided  by % organic carbon  (OC)  contained  in the soil or
 sediment  and  multiplied  by 100  to  obtain Koc.  In the case of wastewater
 solids used in the present study,  organic carbon  content was based on  weight
 loss on  ignition  at 600'C  and is defined by  the following equation:
                                     K  ifip_
                                         %VSS
                                        (6)
wctre  ^ " amount sorbed per unit weight of organic matter in solids and
VSS = volatile suspended  solids.  Sorption data are  usually correlated based
on organic carbon or organic matter.  Therefore, the sorption coefficient,
K, must be converted to K  for correlation  purposes.  Thus,  we  can define a
corrected partition coefficient by the following equation:
                                      1000
                                        (7)
     Emphasis on the environmental impact of toxic organic chemicals has
resulted in increased reliance on the physical-chemical properties of these
compounds to assess their environmental behavior.  One such parameter, the
octanol/water partition coefficient (Kow),  has proved  useful  as  a  means  for
predicting soil adsorption (18), biological uptake (19), Tlpophilic storage
(20), and biomagnification (21-24).  Kow  is defined by the  following
equation:                                                           
                                    415

-------
                                                                     (8)

where C  - equilibrium concentration of organic compound in octanol  layer
and Cw - equilibrium concentration of organic compound in water layer.

     Based on the soil-sediment literature, an attempt was made to correlate
sorption on wastewater solids with the octanol/water partition coefficient
for the compounds used in the present study.  Sorption coefficients in
Tables 3 and 4, were converted to K   values using  Equation 6.   The  Kom
values obtained were used to calculate corrected partition coefficients  (K
values) using Equation 7.  Log of the average K '  values for sorption of the
toxic organic compounds on the three different types of wastewater solids
are summarized in Table 5 along with the corresponding octanol/water
partition coefficients.  Log of the average K ' values obtained for the
three types of wastewater solids were used  for each compound for correlation
purposes.  Justification for averaging the  log Kp'  values was based on
replicate isotherms measured for methylene  blue dye on the three kinds/of
solids studied.  Log K.' values measured for sorption of dye on separately
collected replicate samples of wastewater solids averaged  4.35, 4.57, and
4.41 for primary solids, mixed-liquor solids,  and  digested solids,
respectively.  All  individual replicates were  within  0.1 of  the average
values.  Thus, it was concluded that when sorption coefficients are based on


  TABLE 5.  AVERAGE LOG Kp'  VALUES USED TO CORRELATE SORPTION ON WASTEWATER
               SOLIDS WITH OCTANOL/WATER  PARTITION  COEFFICIENTS
       Compound
Log Kp'
Log KQ

Methyl ene chloride
Chl orof orm
1 , 1 -di chl oroethyl ene
Carbon tetrachloride
Chl orobenzene
Tetrachl oroethyl ene
2,4-dinitro-o-cresol *
Lindane
iteptachlor epoxide
Dieldrin
*
2.06
2.15
2.23
2.65
2.64
3.00
2.77
3.41
4.19
4.40

1.26
1.97
2.13
2.64
2.84
2.85
2.88
3.85
5.40
5.48
 *K   values were taken from reference (25)  or were calculated by the
 fragment method from  reference  (26).

                                      416

-------
organic matter in the sorbent,  all three types  of solids are equivalent.
Methylene blue dye is an ideal  model compound for sorption experiments
because it in non-volatile,  non-biodegradable and can be determined
accurately in the complex matrices used in the  isotherm procedure.

     A simple linear regression of log K '  on log Kow yielded a correlation'
coefficient  (r) of 0.963.  A plot of logHK ' versus log  K  is shown in
Figure  6.  The following equation was obtained  for the relationship between
partitioning on wastewater solids and octanol/water partition coefficient:

                       log  Kp' = 1.57  + 0.57 log Kow                (9)

If Kow 1s 9iven in numerical  form, the  equation  can  be written as follows:
 Q)
 O
      6.0
      5.0
      4.0
      3.0
     2.0
      1.0
                            V = 37.2(KOW)
                                         0.57
                        (10)
lnt.-1.57
Slope*.57

r-0.96
1.0      2.0
3.0     4.0
         5.0
                                                           6.0
                              Log i
   Figure  6.   Correlation  of  partition coefficients

          with  octanol-water partition coefficients.
                                 417

-------
     Octane!/water partition coefficients are generally accepted as accurate
estimates of soil sorption coefficients.  However, at least two major
difficulties have been described (27).  First, the precision of available
K  data  is  low;  and  secondly,  a  variety of  quantitative linear models
describing the relationship between Kow and  soil  partition  coefficients  have
been proposed, hence the choice of the model to be used for a given system
becomes difficult.   The same problems are encountered in correlating
sorption on wastewater solids with Kow.

     Methods based on the topology of molecules have been found to predict a
broad range of properties and have found applications beyond simple
predictions of chemical behavior (28).  The Randid molecular-connectivity
index has a wider range of application than others yet devised.  Significant
correlations have been reported between the Randid index and log K   (29).
The index was first  described by Randid  (30) and  has since been applied to
prediction  of soil sorption coefficients for polycyclic aromatic hydro-
carbons, alkylbenzenes, chlorobenzenes, chlorinated alkanes and alkenes, and
halogenated phenols  (27).  Several extensive reviews of both the theory and
calculation of molecular and connectivity indexes have been published (29-
33).  The conventional first-order molecular connectivity  indexes.are
calculated  from  the  non-hydrogen part  of the molecule.  Each non-hydrogen
atom is  described by its atomic  6 value, which is equal to the number of
adjacent non-hydrogen atoms.  This index is then  calculated from, the atomic
values by the following equation:
                                     2(6,6,)
                                           -0.5
                               (ID
where  6, and 6- correspond to the pairs of adjacent non-hydrogen atoms and
summation  is over all  bonds  between  non-hydrogen  atoms.   In  the  present
study  heteroatoms such as oxygen and nitrogen  are included  in  the  analysis
by using the appropriate valence assigned  to the  heteroatom.   Thus,

                                  6,  = Zv-h,            .               (12)

where  Zv is the number of valence electrons  in the  site and  h, is the number
of hydrogen  atoms.  Therefore,  for oxygen  Zv - 6  and  for  nitrogen  Z  - 5.
 In the case  of chlorine, a value of  0.690  has  been assigned  (30).   The  basic
assumption is  that a multiple bond  in a molecule  should  be  represented  by
the endpoint valencies derived from  the formula  for 6, as described earlier.
Double bonds are  counted as double  edges.   To  illustrate, the  modified
 Randid index (lxv) for 1,1-dichloroethylene  is calculated as follows:

 (1)  Determine valence weighted graph (omit hydrogen atoms):
                                  Cl -
i;
                                      418

-------
  (2)  Calculate valence at node or vertex (vertex valence = number of valence
      electrons = number of H atoms):

                                 0.69   4     2
                                  Cl  - C  - C
                                        Cl
                                        0,69

 (3)  Compute product of vertex valencies for each edge:

                                   2.76  8

                                  Cl i C * C
                                2.761
                                       Cl

 (4)  Compute each edge term as the reciprocal  square root product (e.g.,
                                    0.602
                                           0.354/bond
 (5)   Compute  sum  of the  edge  terms.                                  

                Therefore, lxv - 2(0.602)  + 2(0.354)  = 1.912.

Correlation of the  modified Randi  index  with the corrected partition
coefficients  for  sorption on  wastewater solids was attempted using the
average Log Kp' calculated from the Freundlich parameters from Table 5 and
the corresponding values for  log  lxv presented in Table 6.

     A simple linear regression of  log K  ' on lxv yielded a correlation
coefficient (r) of  0.972.  A  plot of logPK ' versus lxv  is shown  in Figure
7.  The following equation was obtained-for the  relationship between
partitioning on wastewater solids and the modified Randic index:
                          log Kn
1.79 + 0.29 lxv
(13)
     Methylene blue dye, and the two azo dyes used for sorption experiments
were not included in the correlation with the modified Randic index because
they were ionic species.  Methods exist to treat polar and ionic compounds
and these will be evaluated in future research work.
                                   419

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       TABLE 6   MODIFIED RANDIC INDEX USED TO CORRELATE SORPTION ON
                             WASTEWATER SOLIDS
Methylene chloride
Chloroform
1,1-dichloroethylene
Carbon tetrachloride
Chlorobenzene
Tetrachloroethylene
2,4-dinitro-o-cresol
Lindane
Heptachlor epoxide
Dieldrin
1.70
2.08
1.91
2.41
2.51
2.91
3.46
6.17
8.52
8.98
                                      420

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. D.
O)
O
7.0


6.0


5.0


4.0


3.0


2.0


1.0
                                                   lnt.= 1.79
                                                   Slope=0.29
                                                   r-0.97
          0    1.0   2.0   3.0   4.0   5.0    6.0   7.0   8.0  9.0  10.0

                                    -   V

                Figure 7.  Correlation of partition coefficients

                        with modified Randic indexes.
                             SUMMARY AND CONCLUSIONS-
       Sorption of toxic organics on primary sludge,  mixed-liquor  solids and
  digested sludge have been correlated with the octanol  water  partition
  coefficient and with modified Randi indexes.  The  same  correlation is valid
  for all types of wastewater solids if results are expressed  on the basis of
  EC* rS?Ulc content of the solids as measured by weight  loss on  ignition at
  550-600 C.  Octanol/water partition coefficients are useful  for  estimating
  uptake of toxic organics on wastewater solids.  However, the modified Randid
  indexes offer a more fundamental  method for assessing  sorption of toxic
  organic compounds based on structural  features  of the  molecule.
  Correlations based on Randic indexes avoid the  problems  of low precision in
  the reported values for Kow and provide at least a  theoretical  basis for
  predicting sorption of complex mixtures of organic  compounds.

       The relationships developed  provides  a basis for  estimating the removal
  of toxic and hazardous organics from wastewater by  the sorption process
  The equations presented can be used to calculate removal of toxic organic
  compounds from wastewater treatment plants if the compounds are non-volatile
  and non-biodegradable.   In addition, toxic organic  compounds sprbed on
                                     421

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wastewater solids can impact treatment and disposal of sludges.  Toxic and
hazardous compounds can affect anaerobic digestion processes,  land
spreading, incineration, and ocean-dumping of sludges.  The correlations
developed provide a basis for assessing the impacts of sorbed  orgamcs on
the sludge disposal options.

                                 REFERENCES
 1.
  4.
    Dobbs,  R.A.,  Jelus,  M.,  and Cheng,  K.Y.   Partitioning of toxic organic
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    Treatment of Toxic Wastewaters, Consortium for Biological Waste
    Treatment Research and Technology.   Arlington, Virginia, 1986.  p.  585.

    Dobbs,  R.A.,  Wang, L., and Govind,  R.  Sorption of organics on
    wastewater solids:  Correlation with fundamental properties.  Accepted
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    1989.

    O'Connor, D.J. and Connoly, J.P.  The effects of concentration of
    adsorbing solids on the partition coefficient.  Water Res..  14: 1517,
    1980.

    Voice, T.C., Rice, C.P., ,and Weber, W,J.   Effects of solids
    concentration on the sorptive  partitioning of hydrophobic pollutants  in
    aquatic  system.  Environ.  Sci. Techno!.   17: 513, 1983.

    Voice, T.C.  and Weber, W.J.  Sorbent concentration effects  In'
    liquid/solid partitioning.  Environ. Scj..  Techno!.   19(9):  789, 1985.

    Gschwend,  P.M. and Wu, S.   On  the constancy of  sediment-water partition
    coefficients of hydrophobic organic  pollutants.   Environ. SCT.. Techno!.
    19(1): 90, 1985.

    Blackburn, J.W. and Troxler, W.L.   Prediction  of the fates  of organic
    chemicals  in a biological  treatment  process.   Environ.  Progress 3(3):
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    Karickhoff,  S.W.   Sorption kinetics  of  hydrophobic  pollutants in
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    Vol.  II.  Ann  Arbor Science, Ann Arbor, MI,  1980.  p.  193.

 9.  Karickhoff,  S.W.  and  Morris, K.R.   Sorption dynamics of hydrophobic
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     1985.

10.  Michaels,  G.B. and Lewis, D.L.  Sorption and toxfcity of azo and
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11.   Smith, M.R., Lequerica, J.L.,  and Hart, M.R.  Inhibition of
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     J. Bact. 162: 67, 1985.
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 Water Techno! . 12: 977, 1980.                                 - a


 Fedorak, P.M., Roberts, D.J., and Hrudey, S.W.  The effects of cyanide
    c  iSo- angen1c de9radation of phenolic compounds.  Water Res. 20:
       1986.
 Hamaker, J W. and Thompson, J.M.  Adsorption.  In:  Organic Chemicals
 in the Soil Environment.  Vol.1.  Marcel Dekker, Inc.  New York, NY,
 * y * C.    p   ^ry ,


 Rao, P.S.C. and Davidson, J.M.  Environmental impact of non-paint
 source pollution.  Ann Arbor Science Publishers, Inc.  Ann Arbor,
 Michigan,  1980.  p. 23.                                            .


 Lambert, S.M.,  Porter, P.E., and Schieferstein,  H.   Weeds 13: 185,
 1965.


 Karickhoff, S.W., Brown, D.S., and Scott,  T.A.   Sorption of hydrophobic
 pollutants on natural  sediments.  Water Res.  13: 241, 1979.

 Briggs,  G.G.   A simple relationship between soil adsorption  of organic
 chemicals  and their octanol/water partition coefficients.   In-
 Proceedings of the 7th British Insecticide and  Fungicide Conference.
 city/state, 1973.

 Kenga,  E.E.  Res. Rev.  44:  73,  1972.

 Davies,  J.E.,  Barquet,  A.,  Freed,  V.  H., Hagve,  R.,  Morgade,  C.,
 Sonneborn,  R.E.,  and Vaclavek,  C.   Human pesticide  poisonings  by a fat-
 soluble  organophosphate insecticide.  Arch.  Environ.  Health  30:  608,
 1975.


 Lu,  P.Y. and Metcalf,  R.L.   Environmental  fate and  biodegradation  of
 benze derivatives as studied  in  a  model aquatic  ecosystem.   Environ.
 Health Persoect.  10: 269, 1975.                             -


 Metcalf, R.L.,  Kapoor,  I. P.,  Lu, P.Y.,  Schuth, C.K.,  and Sherman,  P.
 Model ecosystem studies  of the environmental  fate of  six organochlorine
 pesticides.  Environ. Health  Persoect.  4: 35, 1973.

 Metcalf, R.L., Sanborn,  J.R.,  Lu,  P.Y., and Nye, D.   Laboratory model
 ecosystem studies  of the  degradation and fate of radiolabeled  tri-,
 tetra-, and pentachlorobiphenyl  compared with DDE.  Arch. Environ.
 Cont. Toxicol. 3:  151,  1975.                        -  " -


 Neely,  W.B., Branson, D.R., and  Blan, G.E.   Partition coefficient to
measure bioconcentration  potential of organic chemicals in fish.
 Environ. c_i.. Techno! . 8: 1113,  1974.
                                    423

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25.  Callahan, M.A., Slimak, M.W., Gabel, N.W., May, I.P., and Fowler, C.F.
     Water-related environmental fate of 129 priority pollutants.  EPA-
     440/4-79-029a and 029b.  U.S. Environmental Protection Agency,
     Washington, DC, 1979.
26.  Hansch, C. and Leo, A.  Substituent constants for correlation analysis
     in chemistry and biology.  John Wiley and Sons, Inc., New York, NY,
     1979.  p. 18.
27.  Sabljic, A.  On the prediction of soil sorption coefficients of organic
     pollutants from molecular  structure:  Application of molecular topology
     model.  Environ. Sci. Techno!. 21: 358, 1987.
28.  Rouvray, D.H.  Predicting  chemistry from topology.  Scientific American
     225: 40, 1986.
29.  Kier,  L.B. and Hall,  L.H.  Molecular connectivity in chemistry and drug
     research.  Academic,  New York, NY, 1976.
30.  Randid, M.J.  On characterization of molecular branding.  J. Am. Chem.
     Soc. 97: 6609, 1975.
31.  Balaban, A.T., Motoc,  I.,  Bonchev, D., and Mekenyan, 0.  Top.. Curr.
     Chem.  114: 21, 1983.
32.  Sabljic, A.  and Trinajstic,  N.  'Acta Pharm. Juoosl. 31:  189,  1981.
33.  Trinajstic,  N.  Chemical Graph Theory.  CRC Press, Boca  Raton, Florida,
     1983.
                                     424

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MTrnS!nL'S AND REMOVAL OF SELECTED INDICATOR AND PATHOGENIC
MICROORGANISMS DURING CONVENTIONAL ANAEROBIC SLUDGE DIGESTION
                             by

                     Vincent P.  Olivieri
                Lynne Cox and Mohammed Sarai
                The Johns Hopkins University
                  Baltimore,  Maryland 21218

                             and

             Jan L. Sykora and Patrick Gavaghan
                  University of Pittsburgh
                  Pittsburgh, Pennsylvania
      This  paper  has  been  reviewed  in  accordance  with
      the U.S.  Environmental  Protection Agency's  peer
      and administrative review  policies  and  approved
      for presentation  and publication.
               Prepared  for Presentation  at:

          Twelfth United States/Japan Conference
              on Sewage Treatment Technology
                     Cincinnati,  Ohio

                   October  12-13, 1989
                           425

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?1nditcliorsAPP;hTeraonlyyo 2*10 \    s7en wT/efoSn^fov the streptococci
sS"a'were reduced 1.3 to 3.3Orders of magnitude:.  The^^  og reduct   n  ,









fewer significant correlations were found..
                                      426

-------
                .  .               INTRODUCTION

   Samples were collected at three wastewater treatment plants in the Baltimore
vicinity to  characterize the  levels  of reduction  of selected  indicator and
pathogenic microorganisms  during anaerobic  sludge digestion  to  provide the
necessary  database  to  prepare and support  regulations  for  the  handling  of
domestic wastewater sludge including disposal to  land.  In addition,  the study
investigated the relationship between solids,  microbial indicators and pathogens
in wastewater  and sludge  during conventional  sludge treatment processes  to
evaluate effective monitoring parameters that reflect the pathogen reductions.

                                    METHODS

SAMPLING
      Samples were collected after  thorough  flushing of  the  available sample
lines to insure a representative sample.  Sterile 2 to 5 gal tubs with seal able
tight fitting covers were used for ease of handling and wide mouth to accommodate
the thick  samples.  After  collection, samples  were transported  immediately to
the  Water  and  Wastewater   Microbiology  Laboratories  at The  Johns  Hopkins
University in  Baltimore  and  were processed immediately  upon  arrival.   Typical
travel times to the laboratory after sample collection were 20,  40  and 60 minutes
for Back River, Sod Run and  Blue Plains, respectively.  The routine collection
of samples was  begun  on  August 26,  1987  and  continued through September 1988.
In addition, samples  for the determination of  human  parasites were cooled and
shipped by overnight express to Dr.  Jan Sykpra  at the University of Pittsburgh.
Samples for human enteric viruses were  concentrated  and the concentrates shipped
frozen to Dr. Robert Safferman at the  USEPA laboratory in Cincinnati,  Ohio.
      Each sample was mixed with a "lightning mixer" for 5 minutes at about 200
revolutions  per  minute  prior  to  dispensing.    Samples  were dispensed  with
continuous mixing for analysis.  Microbiological assays that required subsequent
dilutions were  mixed  with  an equal  volume  of  1 % peptone and blended  at high
speed  in  a Waring blender  for 1.0 minute.    Immediately after  blending,  the
samples were diluted and plated.

CULTURE AND RECOVERY METHODS
    A major effort during the preliminary phase was the comparative evaluation
of culture methods  for the  selected indicator and  pathogenic microorganisms.
The intent of this portion  of  the study was  not  to  develop new  methods but  to
evaluate  existing procedures  and  techniques  to yield the  most  precise  and
accurate determination  of the  levels of microorganisms.  Table 1 shows the
selected microorganisms assayed and the  method employed.

CHEMICAL AND PHYSICAL MEASUREMENTS
      Total solids (TS)  was  performed at 103  C  according, to  Standard  Methods
(APHA 1985).   Total  fixed  solids (TFS)  were  determined at 550 C according  to
Standard Methods  fAPHA. 1985).   Total  volatile solids (TVS) were determined  by
subtraction (total solids-fixed solids).  Suspended  solids (SS)  was  performed
at 103 C with  Gooch crucibles  containing Whatman 934-AH  according  to  Standard
                                     427

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Methods (APHA,  1985).   Fixed  suspended  solids  (FSS) were  determined  at 550 C
according to Standard Methods (APHA, 1985).  Volatile suspended solids (VSS) were
determined  by  subtraction  (Suspended solids^fixed suspended  solids).   The  pH
was determined electrometrically according to Standard  Methods (APHA,  1985).

                                    RESULTS

LEVELS OF MICROORGANISMS
      The logarithmfc  mean level  per 100 ml for each of  the  microorganisms
assayed is shown in Table 2a,b  and c.  The density of microorganisms for the raw
sewage at the three treatment plants was remarkably similar.  Higher logarithmic
mean levels per 100 ml were found for the raw sewage and  undigested sludge, while
the  plant effluents and digested  sludges  were  lower.   Similar trends  were
observed for the data presented per unit solids except that the logarithmic mean
levels per  unit solids  for  the plant effluents  were  not  as reduced  as  that
observed for unit volume.  The  most numerous  indicators were the coliforms with
total coliforms higher than  fecal  which were higher than  E.  coli.   The fecal
streptococci were about 2 orders of magnitude lower than the total coliform with
fecal streptococci consistently higher than the enterococci.  The logarithmic mean
levels of Clostridium  and  Mvcobacteria were  about 3 and  4  orders of magnitude
lower  than  the  coliforms.    The  slow  growing  or   late  Mvcobacteria  were
consistently higher than the fast  growing Mvcobacteria.  The logarithmic mean
levels of coliphage Were generally 2 to 3 orders of magnitude  lower  than the
levels of coliforms.  The logarithmic mean levels observed  for phage counted on
. coli C were similar to  the  levels observed for male specific phage counted
with Havelaar's strain.
      The pathogenic microorganisms were all  observed at relatively low levels.
In many  of the samples,  particularly  the digested sludges,  and  effluents  no
pathogens were recovered.  The  logarithmic mean  levels  of Salmonella were about
5 orders of magnitude lower than the coliforms   but about 2 orders of magnitude
higher  than  the  human enterovirus  virus  and  parasites.    Salmonella  was
consistently isolated from raw wastewater and sludges and less frequently found
in digested  sludges.
      The level of human enteric viruses was  very low in all  samples.  The levels
of virus in the raw wastewater  was  particularly  low and suggests that the level
of virus  was low  in the populations  served  by  the three  plants.   Only a few
viruses were observed  per  100  ml of the" sludge samples.
      Parasites were recovered  from most of the samples  collected from the early
part of the  treatment  process.  The average levels observed in raw sewage were
less than 10/100 ml,   but  in  primary,  trickling  filter  sludge,  and activated
sludge,  the levels were 29-170,45-150,  14-66  /100 ml,  respectively.   After
anaerobic  digestion,   the  frequency of  the  isolation  of  parasites decreased
slightly.  When found,  the  average level  of parasites was 14-60/100 ml.  The cyst
concentrations  in  raw  sewage ranged between 0 and  30 cysts per 100 ml, whereas
the concentrations in  final effluents ranged from 0 to 1 cyst per 100 ml.
      Cysts  of Giardia were the most frequently  recovered parasite.   Helminths
were infrequently found and other human parasites were at  best occasionally
observed  in  the samples of wastewater and sludges.

CORRELATION  OF  LEVELS  OF MICROORGANISMS

      The   correlation  coefficients  for  the   level   of  selected  indicator

                                     428

-------
 microorganisms  and  the  level  of  selected  human  pathogens  for  all  samples
 collected at  the  three wastewater treatment plants are shown  in Table  3.   The
 levels of microorganisms are  presented  in 3 different  formats; #/100 ml,  #/gTS
 and #/g VSS.  The  second number presented below each correlation coefficient was
 the number of sample pairs used to  calculate the correlation coefficient.   The
 significance  was  evaluated by determining  the probability  that  there was  no
 correlation between the levels of  indicators and pathogens, the null  hypothesis.
 I significance was indicated at the 95 % level by an  asterisk (*)  and at the
 99% level by a double  asterisk {**).
       Significant correlations were observed at the 99% level for  the #/ 100 ml
 of total coliforms,  fecal  coliforms,  E. coll,  fecal streptococci, phage C and
 phage H and the #/100 ml Salmonella.  Similar significant correlations were found
 for  human   enteric   viruses,  except  that  the  phage  H  correlation  was   not
 significant.  Only  the correlations between the #/100  ml  of  total  coliforms,
 fecal  streptococci   and  phage C  and  the #/100  ml of total  parasites   were
 significant.   The correlation coefficients  in  each case were very low and  were
 between 0 17 and 0.34 for Salmonella,  0.14 and 0.46 for  human enteric virus and
 0.18 and 0.19 for  total,parasites.   No  significant correlations  were found
 between the #/100 ml Of enterococci,  Clostridium  and  Mvcobacteria.    It should
 be noted that the  sample number for  these  calculations was between 230 and  427
 Calculating the correlation coefficient with the microbial  densities per  gram
 of  various  solids  categories  yielded  poorer  correlations".    Significant
 correlations  at  the 99%  level  were  observed  only for  the  levels  of total
 thln#/[So'ml  SimnnlifrmSp * ^4> fecal  streptococci, phage C and  phage H and
 the #/ioo ml  Salmonella.  Few  significant correlations were found for virus and
 E?rSS^eS>   T-r fT1^0311* correlations were found for correlations calculated
 with the microbial levels  per  various solids criteria.

 LOG REDUCTION OF MICROORGANISMS  THROUGH ANAEROBIC  DIGESTION

 arP Jn Tna\]?oldUCtT?nS  for'V6 #/1 ml  of  the  selected microorganisms
 are shown ini  Table 4.   The mean  log reduction was  calculated from the  log
 reductions  observed  for  each  set of  samples  collected at  each of  the three
 wastewater treatment plants as shown below.  The  relative log digester  input
MEAN LOG REDUCTION = .S^.^OG_DIGESTER_INPUT:LOG_DIGESTER_OUTPUT)

WHERE.                             NUMBER OF SAMPLES

LOG DIGESTER INPUT-LOG DIGESTER OUTPUT
  FOR PLANT A=
                            lA3 x A3>+<#/ioomiA4 x QA4)-i.oG <#/ioo mi^ x OA5>
  FOR

  FOR
AND'
 Q=FLOW IN HGD

 Aa,A3,A4,A5,B2fB3,B4,B5,C2,C3, AND C5=SLUDGE SAMPLES AT PLANT A,   B. AND C.
thMi   JHSttehd bel-W the Tan  log  reduct1n are "the standard deviation for
this value and the maximum and minimum reductions  observed during the course of
                                     429

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the sampling  period.    It  should be noted  that considerable  variability  was
observed^ fof the  mean  log  reduction values with almost 2  orders  of magnitude
range for  the mean log reduction of the indicator bacteria,  {he ranges for the
log reduction values for the coliform indicators were 1.27 to 1.45, 2.82 to Z.9/
and 1.06 to 1.25 for "plants A,  B and C, respectively.  Lower  log reduction values
were  found for  the  streptococci  and  phage  indicators.   Relatively  little
reduction of Clostridium and Mvcobacterium were found with no reductions observed

3  P 3Human  pathogens  were  reduced by anaerobic  digestion.    The mean  log
reduction values for Salmonella were 1.92, 3.33  and 1.38 for plants A, B and C.
The mean log reduction for human enteric virus was lower with 1.12,  1.37 and0.4b
for plants  A, B  and C.   Total  parasites mean  log reduction was similar: 0.90,
1 27  and 0.55 for plants A,  B and C.    In  each case plant B  had the highest
reduction  in the  level of indicator and pathogenic microorganisms.

CORRELATION OF LOG REDUCTION
      The  correlation  coefficients for  the  linear regression  for the  log
reductions of selected  indicator and pathogenic microorganisms are shown in Table
5 for all samples. Significant correlations at the 99% level were  found between
the log reduction of the indicator  microorganisms  (except  for  the slow growing
Hvcobacteria  which was  significant at  the 95% level) and Salmonella.   The
correlation coefficients ranged  from  0.27 for  the  slow growing MYcobacteria
which was  significant at the 95% level  to 0.65 for  E.colj. which was  significant
at  the  99% level.   The  correlation  coefficients  for log reduction  of the
coliforms  and streptococci  indicators with log reduction of  Salmonella  were  0.58
to  0.65 and 0.47 to  0.62,  respectively.   Similar but  lower correlations  were
observed for all samples with  log  reductions  of human enteric virus.  Lesser
correlations were found for total  parasites..   However,  when the log  reductions
for each treatment plant were considered separately, only the  log  reduction for
 E.coli  at  plant  B was  significant at  the 95%  level  for the  log reduction  of
Salmonella.

 RELATIVE MICROBIAL BALANCE
        The relative  microbial mass balance through  the three  treatment plants
 is shown  in table 6.   The  relative  mean  microbial  mass  for  each selected
 indicator and pathogen was calculated from the product of the flow  in  MGD for
 the waste  stream and the level of microorganism, #/WQ ml.  The data was reported
 as the relative  microbial mass since no correction  was made for the volume  term.
 The units  are # million gallons/100 ml day.  The  overwhelming majority of the
 microbial  mass leaves the wastewater treatment plant after conventional secondary
 treatment  in the liquid effluent.  Without terminal  disinfection,  only 1  to 2
 orders of magnitude reduction are accomplished  by  secondary treatment.  The log
 reduction  in the microbial mass from the raw wastewater after anaerobic sludge
 digestion was 2 to 3 orders of magnitude.  The microbial mass leaving the  plant
 by the solids route after anaerobic sludge digestion was about  10 fold lower than
 by the liquid route without disinfection.
 LOG PROBABILITY                                                     .   ..
       An  alternative presentation  for the  levels  of microorganisms in  the raw
 sewage  (open points)  and the  digested sludge  (filled  points)  for plant A
 (circles), B (triangles) and C  (squares) is shown in figures 1,  2, 3 and 4 for
 fecal  coliform,  fecal streptococci, coliphage C and Salmonella,  respectively .
 For  each  indicator  and pathogenic microorganism  assayed,  the log probability

                                       430

-------
plot approximates  a  straight  line  and indicates that the distribution for the
levels of microorgantsms follows a log-normal distribution:  As seen in figure
1, 2, 3 and  4, the levels of each of the microorganism in raw wastewater at plant
A, B,  and C was similar.  The  differences found  in  the raw sewage was small.
However, the levels of microorganisms in the  digested sludge for each treatment
plant  varied.    A  visual  inspection  of each  figure  shows the approximate log
,#/gTS reduction from raw sewage thru  anaerobic  sludge digestion (open vs closed
points) for each of the  indicator and pathogenic microorganisms assayed.  This
visual log  reduction  differs  from  the mean log reduction calculation shown in
table  4 and 6.   Nevertheless, a 2 to 3  log  reduction  from raw sewage through
sludge  digestion is  shownt for  the  coliform (figure  1)  and a  1.5 to  2  log
reduction for fecal  streptococci  (figure 2).  The levels of coliphage (figure
3) also yielded a straight line for the  log probability  plot and follows a log-
normal distribution in raw sewage and digested sludge.  About 2 logs reduction
were observed for phage C (figure 3).  Similar log probability plots are shown
for Salmonella  in  figure 4.   Like the indicator bacteria,  the log of Salmonella
levels also approxomated  a straight line on the log probability plot and appeared
to follow a  log normal distribution.  The levels of Salmonella for the raw sewage
at each plant were a little more variable than the  indicators and reflected the
poorer precision of the multiple tube  culture method and the most probable number
calculation used for enumeration.    About 2 to 3 logs reduction were observed
from raw sewage through anaerobic digestion.

                                 CONCLUSIONS

      Considerable variation  was observed for  samples  collected at the  same
sample station at a given treatment  plant.  The levels  of  selected microorganisms
and human pathogens  in the  raw wastewater entering the  three treatment plants
were remarkably similar.   The variability between treatment plants appeared to
be no  more  than the variability between  type  of samples.  The levels  of  the
selected indicators and pathogens appeared to follow  the order of densities  for
the samples  of  wastewater  and wastewater sludge sampled  in this  study:  total
coliform >  fecal coliform > E.coli > fecal streptococci  > enterococci  > phage
C -  phage  H >  Clostridium  > Mvcobacterium  >  Salmonella > enteric  viruses  >
parasites.
     The levels of human pathogenic bacteria,  viruses  and parasites were  low
in all the samples compared to the levels of indicators.  Salmonella SDP. were
consistently found  in raw wastewater,  raw sludges, treated sludges and wastewater
effluents.  Parasites were found in most of the samples of raw wastewater,  raw
sludges, and digested sludges but rarely observed in  the wastewater effluents.
Enteric viruses were infrequently recovered from raw wastewater but found in many
of the raw sludge samples and  few of  the digested sludge samples.   Viruses were
not recovered from the wastewater effluent.  The  low frequency of  recovery in
the liquid flows at the  treatment plants  was probably due to a combination of
low virus densities and low volume (100 ml) assayed.
      The anaerobic digestion  process yielded  reductions in the densities  of
selected indicator and pathogenic microorganisms at each of the three treatment
plants.  The mean log reduction  varied  for the  three treatment plants  for  the
same microorganism, but followed  the  same relative order.   Plant B, Sod Run,  had
the highest  mean log reductions, followed by  plant A, Back River,  and plant C,
Blue Plains.   One  to three  log reductions were observed  for  the  coliform
indicators  thru  the  anaerobic  digestion process, while  only 0.2  to  2 logs

                                     431

-------
reduction for the streptococci were found at the three plants.   Salmonella were
reduced 1.3 to 3.3  orders  of magnitude.  While the  level's  of human virus and
parasites were  low and  the log  reductions difficult  to determine,  the log
reduction observed were less than those found  for  the bacteria.    Only 0.4 to
1.4 and 0.5 to  1.2  orders  of magnitude reduction  were  observed  for virus and
parasites, respectively.  Correlations significant  at the 95% and  99% level were
found  between  the log reduction  of indicator  and pathogenic microorganisms.*
Correlations were generally higher (as  high as  0.65)  than  that observed for the
levels of microorganisms.   Again  no particular indicator consistently yielded
higher correlations.

                               ACKNOWLEDGEMENTS

The authors wish to  acknowledge the cooperation of Nick francos and staff  at the
sludge  facility  at the  Back River  Wastewater Treatment Plant  in Baltimore,
Maryland, Wayne  Ludwig and staff  at the Sod Run Wastewater Treatment Plant in
Bel  Air,  Maryland,  and Russel  Thomas  and Sam  Alamine at  the  Blue  Plains
Wastewater Treatment  Plant in Washington,DC.  This  work  was  supported ,by the
USEPA  Project #:  CR B135 98.

                                  REFERENCES

Adams, M. 1959.   Bacteriophages.  Interscience  Publishers, New York, New York.

Berg,  G.  et  a]_.  1975.   Methods  for Recovering Viruses from Sludges (and other
solids).  In: U.S. EPA Manual of Methods for Virology, EPA - 600/4-84-013, U.S.
EPA, Cincinnati,  Ohio.

Bisson,  0.  and  V.  Cabelli.  1979.   Membrane  Filter Enumeration  Method for
Clostridiura perfrinoens.   Appl. Environ.  Microbiol.
37:55-66.

Dufour, A.P.  1984.  Bacterial  Indicators of Recreational Water Quality.   Can  J
of Public Health 75:49-56.

Engelbrecht,  R.N.  and  C.  Haas.   1977.    Acid-Fast' Bacteria  and Yeast  as
Disinfection  Indicators:   Enumeration Methodology.    In:    Proc.  AWWA  Water
Quality Technology  Conference, Kansas City,  Kansas.

Fox, 0.,  P.'Fitzgerald,  C. Lue-Hing. 1981.  Sewage Organisms:   A Color  Atlas.
The  Metropolitan Sanitary  District  of Greater  Chicago,  Chicago,  Illinois.

Geldreich, E.E.  1981. Membrane Filter Techniques for Total  Coliform and Fecal
Coliform  Populations  in  Water.    In:    Membrane  Filtration:    Applications,
techniques and problems, B.J. Dutka ed.,  Marcel Dekker,  Inc.,  New York.

Havelaar, A.H.,  W.M. Hogenboom and R. Pot.  1984.  F. specific RNA  bacteriophages
in sewage: methodology and occurrence.  Water  Sci. Technol.  17:645-655.

Skeat, W.O.  (1969)  Manual  of British Water Engineering. 4th ed.  Institution of
Water  Engineers, W. Heffer and Sons, Ltd.,  Cambridge, England.
                                      432

-------
Standard Methods  for the Examination  of Water and Wastewater.  16th edition.
1985.  American Public Health Association, New York, New York.

U.S. EPA. 1978. Microbiological  Methods  for Monitoring the Environment, Water,
and Waste.   Cincinnati, Ohio.
                                   433

-------
TABLE  1.   METHODS EMPLOYED  FOR  THE  RECOVERY OF MICROORGANISMS.
Microorganism
Total coliform

Fecal Coliform

E. sail

Fecal Streptococci
Enterococci
Clostridiun
Hvcobacteria
Salmonella
Phoge

Enteric Virus

Protozoan cysts

Helminth Ova
 Methods
ra-Endo Plate Count

m-FC Plate Count

 m-Tech Plate Count

 Plate Count
 Membrane Filter
 Membrane Filter
 Membrane Filter
 Multiple Tube Dilution
 Agar Overlay, E_. coli c
 S.typhimurium UG49  *
 Elution and organic
 flocculation
 Sedimentation with
 sucrose floatation*
 Sedimentation with
 zinc sulfate floatation
     References
Standard Methods (APHA 1985}
Geldreich <1981)
Standard Methods (APHA 1985)
Geldreich (1981)
  Dufour et al.(1984)

  Standard Methods        (APHA, 1985)
  Dufour et aI (1984)
  Bisson et al (1979)
  Engelbrecht & Haas (1977)
 Standard Methods (APHA, 1985)
 Adams  (1959)
 Havelaar (1984)
 USEPA  Manual of Methods
 for Virology (1984)
 Fox et al. (1981)

 Fox et al. (1981)
TABLE  2a.    LOGARITHMIC  MEAN  LEVELS  PER  100  ML  OF  BACTERIAL   INDICATORS  AND
PATHOGENS,  HUMAN  ENTERIC VIRUS AND  HUMAN  PARASITES  FOR SAMPLES' COLLECTED  AT
PLANT A

               TC   FC   EC   FS ENT   CP  MY  LTMY SAL  PHAGE C HEV  PHAGE H  TP
RAW
SEWAGE

LM
STD
H
PRIMARY LH
SLUDGE

TFS


AS


OS


HE


STD
H
LM
STD
H
LH
STD
N
LH
STD
H
LH
STD
H
7.99
0.04
24
8.20
0.15
24
8.62
0.15
21
8.59
0.11
23
8.15
0.08
24
7.00
0.15
24
7.34
0.08
24'
7.34
0.15
24
7.61
0.18
21
7.73
0.08
23
7.20
0.11
24
6.38
0.18
24
7.08
0.15
24
7.00
0.18
24
7.34
0.18
21
7.62
0.11
23
6.99
0.11
24
6.15
0.20
24
5.74 5.58 3.79 1.86
0.08 0.08 0.15 0.11
24 24 23 23
4.92 4.52 4.45 3.36
0.15 0.20 0.20 0.11
24 24 23 23
6.18 5.97 4.79 3.18
0.20 0.15 0.28 0.18
21 21 20 20
6.40 6.32 5.04 3.61
0.15 0.08 0.23 0.18
23 23 22 22
5.72 5.64 5.32 4.60
0.11 0.08 0.23 0.15
24 24 23 23
4.82 4.52 3.72 1.57
0.15 0.15 0.11 0.18
24 24 23 23
2.20
0.18
18
3.58
0.20
18
3.75
0.23
16
4.08
0.23
17
4.95
0.20
18
1.96
0.18
17
2.11
0.11
23
1.99
0.18
23
2.66
0.08
21
2.64
0.20
24
1.68
0.15
24
1.26
0.18
24
5.43
0.08
23
4.62
0.15
23
5.11
0.08
20
5.57
0.08
22
5.11
0.15
23
4.64
0.11
23
0.18
0.08
23
0.79
0.15
23
OJ34
0.11
20
1.04
0.15
22
0.40
0.11
23
0.18
0.08
23
5.78
0.23
13
4.54
0.23
13
5.36
0.26
10
5.62
0.23
12
5.26
0.18
13
4.63
0.32
13
0.48
0.08
23
1.32
0.11
22
0.82
0.18
21
0.71
0.18
23
1.34
0.18
24
-0.03
0.04
24
  NOTE:   LH = LOGARITHMIC MEAN.  STD = LOGARITHMIC STANDARD DEVIATION,  N
        TFS - TRICKLING FILTER SLUDGE, AS - ACTIVATED SLUDGE,
        DS - DIGESTED SLUDGE, ME - MIXED EFFLUENT
                                              NUMBER OF OBSERVATIONS.
                                                434

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TABLE  2b.   LOGARITHMIC MEAN LEVELS  PER 100 ML  OF BACTERIfll  TNnmmws  inn
PATHOGENS,  HUMAN  ENTERIC  VIRUS AND  HUMAN  WWBITB  K^^"cOLLECTH) AT.
            TC  FC   EC   FS  ENT  CP
                                   MY LTMY SAL  PHAGE C HEV  PHAGE H  TP
RAW LM
SEWAGE STD
N
PRIMARY LM
SLUDGE STD
N
TFS
AS
DS
DS
(STORED)
ME
SEPTAGE
'ABLE 2
LM
STD
N
LM
STD
N
LM
STD
N
LM
STD
N
LM
STD
N
LM
STD
N

8.04 7.00 6.93 5.90 5.53 3.83 2.08 2.40 1 60
0.08 0.11 0.11 0.08 0.04 0.15 0.15 0 20 
-------
             TC
                   FC
                         EC
                                FS
                                       correlation coefficient
                                            . number
                                     EHT     CP     MY    LTHY
PHAGE C  PHAGE H
JT/100 HL
*/9TS
*/gVSS
SAL
HEV
TP
SAL
HEV
TP
SAL
HEV
TP
0.32 **
427
0.28 *
412
0.20 **
423
0.10 *
427
0.01
412
0.04
423
0.09
425
0.03
410
0.04
422
0.28 **
427
0.15 **
412
0.09
423
0.19 **
427
0.06
412
0.06
423
0.27 *
425
0.07
410
0.05
422
0.17 **
427
0.18 **
412
0.05
423
0.16 **
427
0.03
412
0.05
423
0.06
425
0.53 **
410
0.01
422
0.34
427
0.14
412
0.19
423
0.24
-427
0.08
412
0.21
423
0.27
425
0.20
410
0.24
422
** 0.02
426
** 0.00
411
** 0.00
422
**-0.02
426
-0.01
411
**-0.02
422
** 0.00
424
**-0.01
409
**-0.02
421
-0.03
409
-0.01
412
0.08
405
0.01
409
0.00
412
0.04
405
0.07
407
0.00
410
-0.03
404
-0.06
409
-0.03
412
-0.01
405
-0.05
409
-0.02
412
-0.04
405
-0.02
407
-0.01
410
-0.03
404
0.06
319
-0.03
320
-0.01
313
0.08
319
-0.03
320
0.05
313
0.04
317
0.03
318
-0.07
312
0.33 **
410
0.46 **
395
0.18 **
406
0.38 **
410
0.15
395
0.04
406
0.36 **
408
0.15 **
393
0.03
405
0.26 **
234 "
0.07
235
-0.04
230
0.40 **
234
0.02
235
0.08
230
0.29 **
233
0.00
234
0.12
230
TABLE 4   MEAN  LOG REDUCTION OF THE 1/100 ML OF SELECTED MICROORGANISMS FROM RAW SEWAGE THRU
CONVENTIONALANAEROBIC DIGESTION AT THREE WASTEWATER TREATMENT PLANTS
                                       EHT
                                              CP
                                                     HY
                                                            LHY
                                                                   SAL
                                                                          PHC
                                                                                 PHH'
                                                                                        HEV
                                                                                               TP
PIAUT A
HEW) LOG
REDUCTION
SID
MX
HIM
M
HAHT_I
XEAH LOG
REDUCTION
STD
MAX
HIM
H
PtAHT C
KEAM LOG
REDUCTION
STD
HAX
HIM
H
1.25
0.41
2.06
0.13
24.00
2.97
1.12
5.69
1.15
24.00
1.25
0.73
2.85
0.07
23.00
1.39
0.64
3.08
-0.01
24.00
2.82
1.15
5.34
1.22
24.00
1.06
0.55
2.36
0.04
23.00
1.35
0.57
2.48
0.33
24.00
2.91
1.38
7.19
0.44
 24.00
1.18
0.79
3.03
-0.60
23.00
1.17
0.60
3.02
0.04
24.00
2.04
0.88
4.60
1.01
24.00
0.43
1.35
6.35
0.94
23.00
1.10
0.40
1.88
0.43
24.00
2.13
0.88
4.49
0.67
24.00
0.26
0.58
1.53
1.16
23.00
0.60
1.30
6.48
-0.37
24.00
0.81
0.65
1.95
-0.21
23.00
-0.34
0.74
1.02
-1.31
22.00
0.12
1.01
3.94
-1.46
24.00
0.20
0.46
1.26
-0.48
23.00
0^54
0.64
0.92
2.16
22.00
0.93
1.94
5.70
-1.43
23.00
0.65
0.57
1.34
-0.65
18.00
-0.30
0.83
1.57
-1.85
17.00
1.87
0.87
4.04
0.51
24.00
3.33
0.85
5.25
2.10
24.00
1.38
1.04
2.88
-1.32
23.00
1.16
1.14
6.13
0.07
24.00
1.81
0.79
4.42
0.77
23.00
0.40
0.40
1.27
1 -0.70
22.00
1.88
2.08
6.67
0.21
16.00
3.03
0.70
4.18
1.91
13.00
1.34
0.86
2.90
0.42
13.00
1.14
0.32
1.90
0.31
24.00
1.37
0.40
2.19
0.74
23.00
0.45
0.39
1.22
0.23
22.00
1.01
0.85
2.85
-0.10
24.00
1.22
1.07
3.43
1.31
24.00
0.55
0.80
2.03
0.51
22.00
                                                436

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 7n5Lnr,^ORRELATION COEFFICIENTS FOR THE LOG REDUCTION OF INDICATOR MICROORGANISMS AND THE
                F HUMAN PATHOGENS FOR  ALL SAMPLES COLLECTED AT' THREE  WASTEWATER1  TREATMENT
          TCR
                  FCR
                           ECR
                                    FSR
CORRELATION COEFFICIENT
 PROBABILITY  THAT H=0
       NUMBER
    ENTR     CPR
                                                             HYR
                                                                     LTHYR
                                                                             PHAGE CR   PHAGE HR
SALR

HEVR

TPR

0.62816
0.0001 **
69
0.46712
0.0001 **
66
0.29146
0.0159 *
68
0.58489
0.0001
69
0.48219
0. 0001
66
0.23363
0.0552
,68
0.64799
** 0.0001 **
69
0.48995
** 0.0001 **
66
0.33649
* 0.005 **
68
0.47003
0.0001 **
69
0.451
0.0001 **
66
0.26595
0.0284 *
68
0.6199
0.0001 **
69
0.64232
0.0001 **
66
0.30236
0.0122 *-
68
0.37327
- 0.002
66
0.49419
0.0001
66
0.02307
0.8553
.65
0.32343
** 0.0081 **
66
0.33542
** 0.0059 **
66
0.1196
0.3426
65
0.27615
0.0498 *
51
0.33927-
0.0149 *
51
0.13059
0.366
50
0.55113
0.0001 **
66
0. 61'254
0.0001 **
63
0.2197
0.0787
65
0.56131
0.0002 **
38
0.48638
0.002 **
38'
0.10912
0.5143
38
PLANTS6A  BRANDTCV* MICRBIAL BALANCE FROM RAW "ASTEWATER FOR  THE SELECTED  MICROORGANISMS  AT
           TC
                  FC
                         EC
                                FS
                                       ENT
                                              CP
                                                     MY
                                                            LHY
                                                                   SAL
                                                                          PHC
                                                                                 PHH
                                                                                        HEV
 CALCULATION BASED ON THE HICROBIAL LEVELS AS #/ 100 ML
                                                                                               TP
PLANT A

RAW 10.29
DIGESTER IN 9.15
DIGESTER OUT 7.90
EFFLUENT 9.27

DIGESTED 2.40
EFFLUENT 1.0Z
PLANT B











RELATIVE MEAN LOG HICROBIAL MASS
9.62
8.33
6.95
8.64

2.68
0.98

9.38
8.08
6.73
8.40

2.65
0.98

8.05
6.64
5.47
7.08

2.58
0.98

7.87
6.48
5.38
6.77
MEAN LOG
2.49
1.10

6.15
5.46
5.06
5.97
REDUCTION
1.08
0.18

RELATIVE HEAM LOG
RAW SEWAGE 8.8S
DIGESTER IN 8.46
DIGESTER, OUT 5.49
EFFLUENT 6.97
DIGESTED 3.40
EFFLUENT 1.92
PLANT C
RAW SEWAGE 10.37
DIGESTER IN 9.29
DIGESTER OUT 7.75
EFFLUENT 7.51
DIGESTED 2.62
EFFLUENT 2.87
7.83
7.33
4.51
5.84
3.32
1.99

9t39
8.33
6.98
6.78
2.40
2.60
7.77
7.16
4.25
5.92
3.52
1.84

9.50
8.26
6.83
6.54
2.66
2.95
6.73
6.05
4.01
4.93
2.72
1.81

8.36
6.59
5.89
5.68
2.47
2.68
6.36,
5.74
3.61
4.60
MEAN LOG
2.76
1.77

4.66
4.43
3.61
4.07
REDUCTION
t.05
0.59

RELATIVE MEAN LOG
8.07 6.25
6.48 5.63 ,
5.96 5.94
5.78 5.77
MEAN LOG
2.11
2.29
REDUCTION
0.31
0.48
4.22 4.43
4.27 4.61
4.34 4.46
3.82 4.24
FROM RAW SEWAGE
0.12 -0.02
0.39 0.20

MICROBIAL M/fsS
H.92 3.26
3.21 3.46
3.01 2.81
2.60 2.61
FROM RAU SEWAGE
-0.09 0.44
0.32 0.65

MICROBIAL MASS
4.31 5.09
4.29 4.90
4.80 5.20
3.97, 4.23
FROM RAW SEWAGE
-0.49 -0.10
0.34 0.86
4.37
3.30
1.42
3.52

2.95
0.85


2.44
2.10
-1.23
1.34
3.67
1.10

4.42
3.52
2.10
2.80
2.32
1.62
7.69
5.82
4.86
6.95

2.83
0.75


5.82
5.09
3.28
5.59
2.55
0.24

7.56
5.69
5.07
5.35
2.49
2.21
8.02
5.98
5.04
6.88

2.98
1.13


6.16
5.31
2.29
5.26
3.87
0.90

8.04
6.03
4.69
5.18
3.35
2.85
3.30
1.85
0.75
3.22

2.55
0.07


1.80
0.95
-0.42
1.81
2.23
-0.00

3.51
2.04
1.59
3.48
1.92
0.03
2.75
2.08
1.08
2.22

1.68
0.53


1.40
1.11
-0.11
0.81
1.51
0.59

3.00
2.10 
1.51
2.49
1.48
0.50
                                              437

-------
                           PROBABILITY
Figure 1.  Log # fecal coliform/gts vs probability for
samples raw sewage (open points) and digested sludge
(closed points) at plant A  (circles, plant B, (triangles)
and C, (squares) from August  1987  thru September  1988.
                            PROBABILITY
 Figure 2.   Log # fecal streptococci/gts vs probability
 for samples of raw sewage (open points) and digested
 sludge (close points) at plant A (circles),,plant B,
 (triangles) and C, (squares) from August 1987 thru
 September 1988.
                          438

-------
-2
                          PROBABILITY
Figure 3.  Log # coliphage C/gts vs probability for
samples of .raw sewage  (open points) and  digested sludge
(closed points) at plant A (circles), plant  B,  (triangles)
and C, (squares) from August  1987 thru September 1988.
 ie
                           PROBABILITY
Figure 4.  Log # Salmonella/gts vs probability for
samples of raw sewage (open points) and digested
sludge (closed, points) at plant A (circles), plant B,
(triangles) and C, (squares) from August 1987 thru
September 1988.
                        439

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             IN-VESSEL COMPOSTING OF MUNICIPAL
                     WASTEWATER SLUDGE
                            by

Donald Brown, USEPA, Risk Reduction Engineering Laboratory
    John Johnston, California State Univerisity-Fresno
         ,  Leslie Beyer, Eastern Research Group
     This paper has been reviewed in accordance with
     the U.S. Environmental Protection Agency's peer
     and administrative review policies and approved
            for presentation and publication.
              Prepared for Presentation at:

         Twelfth United States/Japan Conference
             on Sewage Treatment Technology
                    Cincinnati, Ohio

                   October 12-13,  1989
                           441

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                                 INTRODUCTION
                                                      *

      Since the late 1970s, composting has become a more frequently used
method for stabilizing and processing municipal sewage sludge in the United
States   The interest in this technology has been extremely rapid, from less
than 10 facilities operating in 1975 to nearly 200 under design or in
operation in 1989.  Today much of the compost produced is being used as for
soil improvement in accordance with the U.S. Environmental Protection Agency s
(EPA's) policy that encourages the beneficial use of  sewage sludge  (49 FR
24358, June 12, 1984).

      More recently, because of odor, labor, and materials-handling problems,
a greater number of composting systems are being designed and built which
contain the materials within a vessel.  Other reasons for choosing  an  in-
vesseltf system have been space limitations and adverse climates.  In-vessel
systems also  differ from other composting  systems  because they  use  mechanical
mixers to blend amendments with  the  sludge prior  to  composting,  and they
extensively use conveyors for materials handling.  The evolution of  these
in-vessel*systems  has been very  rapid,  and municipalities continue  to
encounter problems in  dealing with odors,  removing moisture,  and handling.
materials.

       To learn from the experiences-of  these mostly first-generation in-vessel
 sludge composting systems and their operators,  EPA decided  in early 1988  to
 gather information from 8 of the 13 full-scale facilities operating in the
 United States.                                                f      '

       This paper presents a brief discussion of the findings of this study.
 First, a description of the facilities surveyed and the reactor systems used
 will be presented.  Then the major problem areas discovered by this survey -
 materials handling, moisture removal, aeration of curing/storage piles,  and
 odor control - will be discussed.  Finally, capital and operation and
 maintenance costs will be presented.


                            DESCRIPTION OF FACILITIES

       The location of  the  facilities and the type of composting system used at
 each  facility are shown  in Figure 1.  The eight facilities studied included
 all six types of  in-vessel systems operating in early 1988.  Akron, Cape May
 County, Newberg,  Portland, Pittsburgh, and Schenectady were the first
 facilities of their kind to be built in this country.  Only Cape May County
 and Portland were operating prior  to 1986.

       A  survey team conducted a  1.5  to  2-day  long  site visit at  each facility.
 The  survey  team  interviewed plant  supervisors,  operators,  and   others familiar
 with  each  facility's procurement,  construction,  and operations.  Contract
 documents  and operating records  were also examined when  available.  The
  information  collected  represents a "snapshot"  of  each facility taken at  the
                                       442

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 time of the site visit.   The data presented are accurate only for the time of
 the site visit and may have subsequently changed.

       Figure 2 gives a summary of the configuration of each of the facilities.
 Composting is often defined as a two stage process, a high-rate stage followed
 by a curing stage.  The  first stage is characterized by high oxygen uptake
 rates,  high temperatures,  rapid degradation of biodegradable volatile solids,
 and high potential for odor production.  The second stage is characterized by
 lower temperatures, reduced oxygen uptake rates, and a lower,  but significant,
 potential for odor production.  No precise definition or distinction exists
 between these two stages,  however.  Moreover,  although the first stage of
 composting is performed  in reactors at all in-vessel facilities,  the second
 stage can be performed in  a reactor,  an exterior pile, or both.   Because of
 the lack of a clear definition,  the term "first-step reactor"  will be used to
 denote  the first vessel  that the compost enters.  "Second-step reactor" will
 be used to denote the second vessel the compost enters in series.   At several
 plants, there is no second reactor.  The reactors will be discussed in more
 detail  in a following section.

      All of the facilites haVe  exterior piles for curing or storage.  Because
 no consistent measure of compost stability was used at the facilities,  it was "
 not possible to define whether material in outside piles  was  "curing"  or just
 being "stored."  Therefore,  the  term  "exterior curing/storage  piles"  refers to
 any compost piles located  outside the reactors,  both aerated and  unaerated.

 AKRON,  OHIO

      Table  1  summarizes pertinent  information  for  the Akron, Ohio facility,
 which uses  four Paygro reactors.   Each'of  the 'reactors is  6  meters wide,  3
 meters  deep,  and 223  meters  long.   Akron,  at 66  dry metric  tons per day,  had
 the largest  design, capacity  of the  facilities  surveyed.  Akron was operating
 at  reduced  capacity because  of complaints  about  odors  by neighbors.
      Figure 3 is a schematic of a Paygro reactor.  Compost
in the reactors by a series of conveyors.  The operation of
similar to an extended aerated static pile facility in that
reactor bin are treated as individual batches.  The compost
periodically mixed in place as desired by a machine called
The extractoveyor also removes the compost from the reactor
to the bottom of the reactor through a plenum covered by a
is exhausted from the top of the compost into the building
reactors, and the building air is exhausted by roof fans.

CAPE MAY COUNTY, NEW JERSEY
 material is placed
 the facility is
 sections of each
 is then
an "extractoveyor".
   Air is supplied
steel grate.  Air
which -encloses the
      Table 2 summarizes pertinent information for the Cape May County,  New
Jersey facility, which uses two Purac reactors.  This facility was originally
designed with one first-step, and one second-step reactor.  However/to
increase the capacity of the facility, both reactors are now used as the
first-step, and aerated piles located outside the building are used for the
second-step.  At the time of the survey, Cape May County was operating at
reduced capacity because of complaints about odors by neighbors.  Since the
end of the summer of 1989,  the facility has been operating at full capacity.
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The reactors are rectangular in shape, 8 meters tall, and the walls slope
slightly outward from top to bottom.  One reactor has a volume of 850 cubic
meters and the other reactor is 1050 cubic meters.

      The reactors at Cape May County have had fires on several occasions,
caused by both spontaneous combustion and welding accidents.  Spontaneous
combustion fires occurred when the composting materials were held in the
reactor for too long because some other part of the  system slowed or had
topped proc ssing material.  Fires can start at surprisingly low temperatures
in dry compost.  Cape May found that when the solids content of  compost is
greater than 65 percent and tHe temperature exceeds  80'C, it is  possible  for  a
series of exothermic chemical reactions to elevate  the temperature  to a point
where true  ignition and smoldering  fires occur.

      Figure 4 is a schematic of a Purac reactor.   The compost mix  is spread
uniformly across  the top  of the reactor by a  series of conveyors.   The    _

                                    ^^
 manifold located about 2 meters below the top of- the compost mass.  -The
 exhaust airflow rate is higher than the supply airflow rate, so some  air is
 drawn from outside the reactor through the headspace and through the  top 2
 meters of the compost mass.

 CLAYTON COUNTY, GEORGIA

       Table 3 summarizes pertinent information for the Clayton County,  Georgia
 facility  which uses two Taulman reactors.  The facility has one first-step
 reactor!'and one second-step reactor.  Clayton County had the smallest design
 capacity of the facilities surveyed.  Clayton County was processing all of the
 sludge being produced by the wastewater treatment plant   Both reactors are
 f 8 meters tall and 7.6 meters in diameter.  Material Discharged from the
 reactors is stored in unaerated piles located in a  covered  shed.

       Figure 5 is a schematic view of a Taulman reactor.  The compost mix is
 uniformly  spread across the top of the reactor by a "slinger" which throws the
 material ou? from the  center.  The composting material  then moves by gravity
 to  the  bottom  of the  reactor,  where  it is  removed by a  horizontal auger that
 rotates  around a center pivot.  Air  is supplied  to  the  bottom of the reactor
 through a  series of  perforated pipes and  is  exhausted out the top of the
 reactor.

 NEWBERG, OREGON

       Table  4  summarizes pertinent information for  the  Newberg, Oregon
  facility,  which uses two Ashbrook-Simon-Hartley  (Ashbrook)  reactors    Each
  reactor is 5.5 meters wide,  2.7  meters high, and 19 meters  long.  This
  facility has had major structural failure of the concrete walls of one  of the
  reactors-  the walls buckled due to excessive pressure inside the reactor.
  Neither reactor at Newberg is being operating while the failed reactor  is
  being rebuilt.  Operation is scheduled to begin in October  1989.

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   ,     Figure  6  is  a  schematic of  an Ashbrook reactor.   Compost material 'is
  loaded into the reactor by a large hydraulically operated door or  "ram"   The

  atmtheSf^ Inl-T^1 thrUgh I6ngth f the reaCtr'  and a bori-ntal auglr
  forward ahn,?n^/eaCt0rvremOVeS th* CmpSt-   The comPst m^s is moved
  forward about 0.25 meters with each push by the ram.   Air is supplied to and
  exhausted from  the reactor through a series of perforated pipes embedded in
  the  floor of  the reactor.   Each set of three adjacent  pipes can be either air
  supply or air exhaust  as needed.                                    eitner air

  PLATTSBURGH,  NEW YORK

  *  .,.!ableu5 summarizes pertinent  information' for the Plattsburgh, New  York
  facility,  which uses two Fairfield  reactors.   The reactors  are 35.4 meters in
  diameter  and  3 meters  deep.   Plattsburgh  was  processing  all  of thVsludae
  being  produced by  the  wastewater  treatment  plant.  Pla'tsburgh has had
  numerous  odor complaints and  is modifying the  odor control  systems.

       Figure 7 is a schematic of a Fairfield reactor.  The compost mix is
 Placed around the perimeter of the  reactor  by  a traveling bridge   The comoost
 material  is mixed and move\| toward  the center  of the reactor bTa series  of 5$
 augers which hang from the traveling bridge.   Material is removed from the
 center of  the reactor.   Air is supplied to  the bottom of the  reactor by a
   ri8Per"ted Plpes/  Air is e^sted  from the top of  the compos? into
                                           and  ^ ""W air is            
 PORTLAND, OREGON
               summarizes  pertinent  information  for  the  Portland,  Oregon
 r*af,+n~-     r-  v    tW para*lel Process trains each using three  Taulman
 reactors     Each process  train has  two first-step reactors,  and one  larjer
 second-step reactor.   The first-step reactors are 8.8 meters tall and  13
 Tc.lal5  in diame*er-   The  second-step reactors are 8.8 meters tall and  16
 meters  in diameter.   Compost  material is processed  in either one  of  the first-
 step  reactors,  and then conveyed to the second-step reactor   -Material
 PnrM^r  fr?v thVeact?rs  "  stored in unaerated piles  located outside
 Portland  was^the only facility composting digested  sludge.   It  was also-
 processing the  largest  amount  of  sludge.   Portland  is operating at reduced
 excels1  ve weear SSSVl ""^'i --tenance  problems,  mosUy'rtlated to
 accident.        prtland has  also.had reactor  fires  caused  by  welding


 SARASOTA,  FLORIDA

 f   TlableJ summarizes pertinent information for the Sarasota, Florida
?*   '      uses two Purac reactors.  Sarasota was processing  all of the
sludge being produced by the wastewater treatment plant.  Sarasota has also

tls one'firs? st'en8 Y ^ mdified the dr Cntro1 s^stems-  ^is  facility
^*^^^^^
reactors is stored in unaerated piles located in a. covwed Sad!
                                     445

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SCHENECTADY, NEW YORK

      Table 8 summarizes pertinent information for the Schenectady, New York
facility, which uses four American Bio Tech (ABT) reactors.  There are two
first-step reactors and two second-step reactors contained inside a building.
All of the reactors are 7.5 meters tall, and have a volume of about 500 cubic
meters.  This facility has had several problems including compost fires caused
by spontaneous combustion and minor structural failures of the reactor s
exterior steel frame.  However, odor complaints are the reason that the
facility is not operating now.  It will not be operated until a new odor
treatment system, which is currently being constructed, is operational.
Operation is scheduled to begin in October 1989.

      'Figure 8 is a schematic of an ABT reactor.  The compost mix is spread
uniformly across  the  top of the reactor by a  series of  conveyors.  The
composting  material then moves by gravity to  the  bottom of the reactor, where
it is removed by  a horizontal auger that spans the  reactor width  and travels
back-and-forth along  the length of the  reactor.   The  reactors  are constructed
of corrugated fiberglass walls that hang from an  exterior  steel frame.  Air  is
supplied to and  exhausted  from the reactor through  a'series  of "air  lances
that  hang from headers  located at the  top of  the  reactor,  The operating  mode
of the  headers   alternates  between air  supply and exhaust, and the operating
mode  is reversed every  20  minutes.  That  is,  one  set  of air  lances supplies
air  for 20 minutes,  and then  exhausts  air  for 20  minutes,  while  the  next  set
of air  lances  exhausts  air  for 20 minutes,  and then supplies air  for 20
minutes, and so  on.
                                  PROBLEM  AREAS
 MATERIALS HANDLING

       Mixing appropriate proportions of sludge, amendment, and recycle is
 essential to create a desirable compost structure with respect to porosity,
 moisture content, and energy balance.  Proper porosity promotes easier
 materials handling and thorough aeration.  Proper moisture content and energy
 balance support the biological decomposition of the organic material.  Table 9
 shows the design and actual percent solids in the mix, and the design and
 actual volumetric mix ratios.  All of the facilities have had to use more
 amendment or recycle than expected, and most have had to use a drier mix than
 expected, for several reasons.  The reasons include:  sludge with a lower
 percent solids than expected, difficulty conveying the mix at the design mix
 ratio, and  difficulty with aeration of the mix  in the reactor.  These
 increases resulted in a  greater volume of material to be handled than
 expected.

       Mechanically and operationally, conveyance systems are the dominant
 physical  features of in-vessel facilities.  Conveyors were the second biggest
 cause of  system  problems at  the sites  (after odor production).   Although  a   .
 high degree of automation for conveyor systems  is not required, most in-vessel
 composting  facilities chose  automation to minimize labor  costs.          .
       The type of conveyors  used at these facilities have been used reliably
 in industry for  years;  none  are experimental.   Yet due  to differences in
                                       446

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  materials characteristics, conveyors at in-vessel plants have experienced
  problems with jamming, breakage, excessive wear, and spillage.

        Screw conveyors  and belt conveyors have been used with the most success
  The few reported problems with scre.w conveyors were related to excessive wear*
  and the accumulation of material on flights and housings.  Regular cleaning
  and lining the housings with ultra-high molecular weight plastic were
  effective for preventing problems.   Spillage has been the major problem with
  belt conveyors.  Wet materials adhere to the belts and do not transfer
  completely, resulting  in spills and labor intensive cleanup problems   These
  problems were minimized by using belt scrapers or by placing a layer of dry
  material,  such as sawdust, onto the belt before adding a wet material.

        Drag  chain  conveyors have not performed well,  suffering  from plugging
  and excessive wear.  Modifications  to these conveyors  have  .included increasing
  the distance between flights,  increasing the clearance between the flights and
  the conveyor housing,  and decreasing the area of the flights themselves
  These modifications  allow the  composting material to push backwards over or
.  around the  flight, so  it won't be compacted.   These  modifications,  however
  also reduce the capacity of the conveyor.                                  '

        Cleated belts have  had a  number of problems including  excessive  spillage
  of  both wet and dry  materials,  and  do not  appear to  be  suitable  for compostina
  facilities.   These belts,  because of their cleated design,  cannot  be
  effectively scraped.

        Reactor-discharge devices are  key conveyors in the materials-handling
  system;  if  they fail,  the  reactors  cannot -be  used.   If  compost becomes  too
  dry,  it  can form  into  hard  chunks;  if it becomes  too wet, it can form  a  glue-
  like mass.   Both  conditions make it  difficult to move the compost with a
  discharge device.                                         -          '

       A few structural  failures with discharge devices have  been noted  but
  excessive wear of auger flights has .been the major mechanical problem '
  observed.  Compost is  a surprisingly abrasive material, especially when it is
  compressed at the bottoms of vertical reactors.  Decreases of as great as 15
 percent of flight thickness in 6 months because of wear on the flight face
 were reported.  Discharge screws originally hard-surfaced with Triten steel on
 both the flight edge  and face have not suffered excessive wear.

 MOISTURE REMOVAL

       There  are three basic demands  on the aeration  system:   (1)  heat  removal
  (2)  moisture removal, and (3)  oxygen for biological  metabolism.  The aeration'
 systems at the sites  visited appeared to be adequately  sized'to meet the
 oxygen supply and  heat  removal  requirements; only Schenectady had problems
 with elevated temperatures.  Table 10 shows the total aeration  capacity of the
 facilities,  the unit  capacity per cubic  meter of empty  reactor  volume,  and the
 length of the path that air must take to pass through the  reactor.
       The major  problems  have been related  to  moisture removal:  condensation
 and  fog formation  above the reactors and formation of a  "hardpan" layer
 Inadequate  aeration for curing/storage piles was a third major  problem."

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Condensation and Fog Formation

      In-vessel composting systems must provide for adequate collection of air
after it has passed through the compost.  Air can hold four times as much
water at 60C than at 40C. Therefore, if the temperature drops before the air
leaves the reactor, it does not remove as much water, and condensation occurs
JiSil the reactor and composting mass.  If  the air collection piping extends
into the composting mass, exhaust holes  in the piping can become exposed due
to natural settling and uneven subsidence.   Such exposure can cause odors to
escape  saturated air to  cool, and  condensate to form within the reactor.

      Systems with open reactors discharge warm, moist air from the compost
bed into a building or work space  above  the  reactor.  In these cases,  the
introduction of  too much  cold outside air  into  these same areas results  in  the
condensation of  water vapor and  the formation of fog   The worst case  was
found  at Pittsburgh, where the  fog hampers  the stabilization of the product,
promotes corrosion  of equipment,  and is  so thick that operators cannot  see  to
work.

Hardpan Formation

       At least three of  the facilities have  noted  the formation of  a "hardpan"
 layer  at the bottom of  the reactor that  is nearly  impermeable  to  air.
 Formation of a hardpan layer  occurs when leachate  forms  because  of  "adequate
 moisture removal from the reactor.  The leachate extracts  solubles  as  it moves
 down through the compost and drains to the low points  in the reactor.   If
 these low areas are low in humidity, the leachate  dries,  cementing  material in
 the boUom of the reactor into an impermeable layer.  At Clayton" County
 leachate seeped into the one-centimeter unwashed river stone layer  on the
 bSttoi of the reactor, cemented the particles together and plugged the holes
 in the aeration piping.  The stone was replaced "t^^T"?*^" ;a!j!jer
 round river rock, and the aeration piping was remounted in the middle rather
 than at the bottom of the gravel layer, separating it from the pooling
 leachate.  At Cape May County a hardpan layer formed which was attributed to
 excessive leachate generation.  The mix ratio and amendment specifications
 were Ranged  to obtain a more porous  initial compost mix, which significantly
 reduced leachate generation.  Also,  the aeration system was j"* "> fve
 the operators better control of the  airflow.  The hardpan problem has not
 recurred since  these changes were  made.

 CURING/STORAGE  AERATION

       The curing/storage process  is  an  important step in the overall sludge
 composting  process.  The composting process does  not stop when material  js
 removed from the reactor(s); the  compost  continues  to have  an oxygen  demand.
 Ken  where  compost  is  processed in two  reactors  (at Clayton. County, Portland,
 slrasota!  and Lhenectady),  the unaerated curing/storage piles have reheated,
 indicating the continuation  of  biological activity.  Depending on  the
 lability of the compost,  oxygen demand may be elevated  to  the point  where the
  available oxygen is consumed and anaerobic conditions develop.  Movingthe
 piles then causes odors to be  emitted.   At Akron  and Cape  May County  the
  exteriofcuring/storage piles  are aerated or  will be  aerated  in  the  future
  because of odor problems.  At Plattsburgh,  the curing/storage piles  are
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 odorous, and an evaluation is underway to determine whether they should be
 aerated.

 ODOR CONTROL

       In the U.S.  effective odor control is a critical requirement for the -
 success of a composting facility.  Fear of potential odors can cause public
 opposition to proposed plant sites.  Qdor complaints can cause a regulatory
 agency to shut down or curtail the operations of an existing facility.  Plant
 odors can also hurt product sales.

       Odor control was the greatest problem found at the sites surveyed.   Of
 the eight composting facilities surveyed in this project, six had received
 odor complaints from the local community.  At five of these sites, the com-
 plaints were serious enough to cause the plant owners to retrofit the facili-
 ties with additional odor treatment equipment.  Two of the five plants ceased
 operations while the new equipment was being installed.   Two plants were
 operated at reduced capacity to limit odor production while the new treatment
 equipment was piloted, designed,  and installed.   The last plant continued to
 operate but at the same time was proceeding with the odor treatment system
 retrofits as quickly as possible.

       Odors found  at compost  facilities  are  caused  by  a  large  number  of
 compounds that originate in both the sludge  and  the amendment.   In-vessel
 systems may produce more amendment-related odors than  static pile or  windrow
 systems because the sawdust used  at most  in-vessel  facilities  has a greater
 surface area than  the wood chips  usually used in the other  systems.

       Odor-causing  compounds  fall  into a number  of  classes  that differ in-
 their  physical and chemical properties.   Some are acidic; some  are  basic.
 Some can be destroyed by oxidation;  others cannot.   These compounds are not
 equally soluble in water,  nor equally amenable to adsorption.   Moreover, the
 mix of compounds in the odorous gas  stream can change  over  time,  depending on
 the composting materials  and  the  reactor  operating  conditions.  For this
 reason,  treatment  systems  must employ a broad spectrum of removal mechanisms
 to  be  effective.   Treatment systems  that  rely on only  one or two  removal
 mechanisms  such as  single-stage wet  scrubbers  and ozone oxidation chambers
 have not  been  successful.

      Table 11  summarizes the odor treatment methods that were found at the
 eight  plants surveyed.  Of  all the methods shown in Table 11, bubbling air
 through  wastewater  appeared to be  the most successful.  Dilution alone was
 completely  ineffective  as a treatment method.  Biofilters appeared to remove a
 large  fraction  of odors based on measurements  taken at the site.  However, the
 facility using  the  biofilters "has still had numerous odor complaints and is
planning to install wet scrubbers to replace the  biofilters.  Ozonation was
 ineffective and replaced by wet scrubbers.  Activated carbon was tested at
pilot  scale at  one  location but also appeared  to be ineffective.

      At Portland,  Newberg, and Clayton County, odorous air  is  bubbled through
wastewater for  treatment.  Operators at Clayton County have received some  odor
complaints, but the odors are, generally not a problem,  partly because  of  the
rural setting of the plant.  The Portland and Newberg facilities have  not

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received any odor complaints, but both plants are located in outlying in-
dustrial areas and both compost relatively stable sludges.  These mitigating
factors make it difficult to determine the effectiveness of this technique.
The design parameters associated with this technique are not well established,
and a ground-level discharge is created.

      At the time of the.site visits, packed tower wet scrubbers were in use
at three of the eight facilities visited.  Table 12 lists the odor sources
treated and the chemicals used in these scrubbers.  Sarasota installed the
system shown in Table 12 after the site visit.  "DeAmine" is a proprietary
chemical.

      Single-stage wet scrubbers were ineffective for several reasons.. In
addition to not being able  to treat  a broad  spectrum of compounds, reasons
include overloading  the  scrubbers and using  inappropriate scrubbing  chemicals.

      Two stages appear  to  be the minimum number needed for effective odor
treatment.  Table  13 lists  the planned  odor  treatment facilities at  several  of
the plants.  Typically,  one stage uses  an acid, and the other stage  uses  an
oxidizing  agent.   Cape May  County is planning  to try corn syrup as a
surfactant  for aldehyde  compounds.   Packed,tower wet scrubbers were  the only
scrubbers  observed at the  eight  plants  studied.  Mist-type  scrubbers have been
used  successfully  at the Montgomery  County  Composting Facility, a large
enclosed static pile operation  in suburban  Washington, D.C.

      Although this  discussion of odors has  concentrated on treatment systems,
an effective  odor  control  system must  include  more  than  just  a  treatment
system.  A complete odor control plan,  including quantification and
qualification of all odor  sources,  and proper  control  of  the  composting
process, must be'implemented.   In  addition,  no treatment  system is 100 percent
effective;  some concentration of odorous  compounds  will  be  discharged after
treatment.   To avoid undesirable effects  on local  residents,  the odorous
emissions  must be diluted and/or dispersed so  that  ambient  air  concentrations
of the odorous gases fall below detection thresholds.
                                      COSTS

       Capital costs for the eight facilities are shown in Table 14.   The
 facilities are listed by design capacity, from smallest to largest.   Costs
 shown are the original construction, including change orders, in millions of
 dollars; additional expenditures made, since start-up, in thousands of dollars;
 and expeditures that the facilities anticipate in the near future, in
 thousands of dollars.  Note that the majority of additional and future capital
 costs are for odor control equipment, and that these costs range up to 40% of
 the original cost.

       Figure 9 shows annual operation and maintenance costs,  expressed as
 dollars per dry metric ton, as a function of current operating capacity.  This
 figure shows an economy of scale for these  facilities.  Clayton County, the
 smallest^facility, appears to have  low costs, but this facility obtains its
 amendment at no cost.  Akron, the largest facility, appears to have high

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costs, but the cost shown includes sludge dewatering costs which are not
included for the other facilities.
                                  CONCLUSION

      In-vessel composting is a total system that comprises a number of
integrally related components, including materials handling, reactors, an
aeration system, exterior curing/storage facilities, an odor control system,
and marketing of the compost product.  Inadequate or improper design,
management, operation, or maintenance of any of these components will
seriously impact the total system, and most likely adversely affect the
compost product.

      Most of these facilites failed to realize that JL sludge in-vessel
composting system includes much more than just the reactor(s).  The major
problems encountered at these facilities were not related  to the reactor
itself, but to the other components, including materials handling and odor
control.  Indeed, many of the difficulties encountered resulted from a failure
to recognize the totality of the system that must be managed.

      Finally,  it should be noted that because this study focused on problem
areas, in-vessel composting appears to be plagued with problems.  However, all
but two of the facilites discussed were producing and marketing a compost
product.  All of, the facilities were meeting EPA requirements for pathogen
reduction, and all were meeting State limits on heavy metals and organics.
                                ACKNOWLEDGEMENT

      The study described in this report has been funded wholly or in part by
the United States Environmental Protection Agency under contract 68-03-334S to
Camp, Dresser, and McKee, Inc. and contract 68-C8-0014 to Eastern Research
Group.  This study is fully documented in a report entitled "Technology
Transfer Summary Report: In-Vessel Composting of Municipal Wastewater Sludge",
EPA 625/8-89/016," available from the Center for Environmental Research
Information, U.S. Environmental Protection Agency, Cincinnati, Ohio, 45268.
                                      451

-------
          1988  In-Vessel  Study
                                PlattsburgjTjjfai^field)

                                           Tdy (ABT)

                                         May County
                                         Purac)
                               Sarasota^jfPurac)
FigDre 1.  In-Vessel Locations Studied
                         452

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          Plant Configurations
    Site
    AKR
   "CAP
    CLA
    NEW
    PLA
    POR
    SAR
    SCH
Horz, Reactor
            System
             Paygro
             Purac
             Taulman
                    
-------
o
0)
O
CO
CO
 J_
                                           454

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HEADSPACE
VENTILATION
   PIPING
(to odor control
   system) \
                                                       FEED CONVEYOR
   EXAUSTx
     AIR
   HEADER
                                                         TO ODOR CONTROL SYSTEM
                                                       AIRFLOW DIRECTION
                      7/ ff / /' // J/ / / / / ft /}?/?/ /i
    mm
                                                                     DISHARGE
                                                                     /SCREW
                                                                       DISHARGE
                                                                      CONVEYOR
 Figure 4.  Purac Reactor
                                       455

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   TO ODOR
   CONTROL
DISCHARGE
 SCREWS
                                                               INFEED
                                                             CONVEYOR
                                                             DISTRIBUTOR
                                                             AIRFLOW
                                                            DIRECTION
                              COMPOST TO
                          DISCHARGE CONVEYOR
                                               AERATION PIPING
 Figure 5.  Taulman Reactor
                                  456!

-------
   o
  +J
   o
   to
   o>
  <0

   I

  O
  O
 O
  s.
 -Q
 x:
  W)
 =C
VO
 
-------
                     si
                           o
                           
                           
458

-------
    AIR
  SUPPLY
 BLOWERS
DISCHARGE
  SCREW
              AIR-SUPPLY
              MANIFOLD
\\1A\\\\\\\\\\\\\\
                               FEED
                            CONVEYOR
                             EVACUATION
                              BLOWERS

                             TO ODOR
                             CONTROL

                               AIRFLOW
                              DIRECTION
                                                            AIR-LANCE
                           -DISCHARGE
                            CONVEYOR
 Figure 8.  American Bib Tech Reactor
                                 459

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            ANNUAL COSTS
Annual O&M Costs ($$/dmt)
$500
$400

$300

$200

$100

   $0
             CAP
SAR
 CLA
                PLA
                             POR
               10    15   20    25   30
             Current Capacity (dmt/d)
Figure 9. Annual Operation and Maintenance Costs
                    460

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          Akron. Ohio  (AKR)

System:            Paygro
Design Capacity:   66 dmt/d*
Start-Up Date:     12/86
Type of Sludge:  Primary + Waste Activated
                 20 - 26% Total Solids
                 > 70% Volatile Solids
Current Capacity:
Current Status:

* dry metric tons per day
19 dmt/d*
Operating at reduced
  capacity due to odors
Table 1.  Summary of Akron, Ohio Facility
                    461

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Cape Mav County. New Jersey  (CAP)
System:
Design Capacity:
Start-Up Date:
Type  of Sludge:
Current Capacity
Current Status:
  Purac
  18 dmt/d*
  5/85
Primary + Waste Activated
20 - 30% Total Solids
70 - 80% Volatile  Solids
FeCI3 added to primary
  6.6 dmt/d*
  Operating at reduced
     capacity  due  to odors
* dry metric tons per day
Table 2. Cape May County, New Jersey Facility
                    462

-------
  Clayton County. Georgia  (CLA)
System:
Design Capacity:
Start-Up Date:
Type of Sludge:
Current Capacity:
Current Status:

* dry metric tons per day
   Taulman
   2.6 dmt/d*
   8/8.6
Waste Activated
15 - 17% Total Solids
68 - 79% Volatile Solids
AI2(SO4)3 added
   1.2 dmt/d*
   Processing all sludge
     produced by WWTP
Table 3.  Summary of Clayton County, Georgia Facility
                     463

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      Newbera.  Oregon (NEW)

System:            Ashbrook-Simon-Hartley
                     (Ashbrook)
Design Capacity:    3.2 dmt/d*
Start-Up Date:      8/87
Type  of Sludge: Oxidation Ditch.
                12 - 20% Total Solids
                - - -  Volatile Solids
Current Capacity:    dmt/d*
Current Status:     Not operating due to
                      structural failure
* dry metric tons per day
Table 4.  Summary of Newburg,  Oregon Facility
                     464

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    Plattsburah.  New York  (PLA)
System:
Design Capacity:
Start-Up Date:
Type of Sludge:
Current Capacity:
Current Status:

* dry metric tons per day
   Fairfield
   31 dmt/d*
   3/86
Primary + Waste Activated
20 - 25% Total Solids
- - -  Volatile Solids
KMnO4 added to sludge
   18 dmt/d*
   Processing all sludge
     produced by WWTP
Table 5.  Summary of Pittsburgh, New York Facility
                    465

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      Portland.  Oregon (FOR)
System:
Design Capacity:
Start-Up Date:
Type of Sludge:
Current Capacity
Current Status:
  Taulman
  54 dmt/d*
  3/85
Digested Primary +
Digested Waste Activated
23 - 28% Total Solids
35 - 50% Volatile Solids
  27 dmt/d*
  Reduced capacity due
    to mechanical problems
* dry metric tons per day
                 i
Table 6. SUtomary of Portland, Oregon Facility
                    466

-------
       Sarasota.  Florida  (SA-R)
System:            Purac
Design Capacity:    5.7 dmt/d*
Start-Up Date:      8/87
Type of Sludge: t Waste Activated
                 14% Total Solids
                 76%  Volatile Solids
Current Capacity:
Current Status:

* dry metric tons per day
3.3 dmt/d*
Processing all sludge
   produced by WWTP
Table 7. Summary of Sarasota, Florida Facility
                   467

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  Schenectadv. New York (SCH)

System:            American Bio Tech
                       (ABT)
Design Capacity:    14 dmt/d*
Start-Up Date:      7/87  .
Type of Sludge:  Primary + Waste Activated
                20 - 28% Total Solids
                73% Volatile Solids
Current Capacity:    dmt/d*
Current Status:     Operating at reduced
                     capacity due  to odors
* dry metric tons per day
Table 8. Summary of Schenectady, New York Facility
                    468

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        Design  vs  Actual  Mix
AKR
CAP
CLA
NEW
PLA
POR
SAR
SCH
           Vol. Mix Ratio*
                          % Solids
   Design
1/0.66/1.33

   1/1/1
 1/0.35/5
1/0.67/1.67
 1/0.4/0.6
   1/1/2
   Actual
   1/1/2
 1/0.6/1
 1/1.4/1.4
 1/0.5/10
 1/1.4/3.3
 1/1.6/0.6
1/0.56/2.44
Design
   40
   40

   38
   40
   32
   35
   35
  Sludge/Amendment/Recycle
Table 9. Design and Actual Mix Ratios
Actual
 44
 37
 34
 38
 4.0
 37
 40
 37
                   469

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          Aeration Capacity




AKR
CAP
CLA
NEW
PLA
POR
SAR
SCH
Total

Capacity
(L/s)
110,000
7800
710
2400
15,000
3700
2500
4500
Unit ,

Airflow
(L/m3-s)
6.8
4.1
.0.88
3.0
3.5
0.43
1.2
2.3
Path
*
Length
(ml
2.4-3.0
6.4
7.9
0.6-9.1
2.4-3.0
7.9
7.0
1.8-2.1
Table 10.  Aeration Capacity of Reactors
                      470

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  Initial  Odor  Treatment Systems
AKR   Dilution (Process Air)
       Compost Biofilter (Non-process Air)
CAP   2-Stage  Scrubber (Process Air)
       1-Stage Scrubber (Non-process Air)
CLA   Bubbling  into  Wastewater Pond
NEW   Bubbling  into  Oxidation Ditch
PLA   Single-Stage  Wet Scrubber
POR   Bubbling  into  Channel at  Headworks
SAR   Ozone Contact Chamber
SCH   Single-Stage  Wet Scrubber
     *
                           /""
Table 11. Initial Odor Treatment Systems
                   471

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Wet Scrubber Installations
Stage Source
CAP
PLA
SAR
SCH
1
1
1
2
1
1
2
3
1
Chemicals
Sludge storage NaOCI+NaOH
Mixing
Reactors
All
All
All
NaOCI+NaOH
NaOCI+NaOH
H2S04
H2SO4+DeAmine
Cooling
H2S04
NaOCI+NaOH
H2SO4+DeAmine
Table 12.  Current Wet Scrubber Installations
                                  472

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       Planned Wet Scrubbers
              Stage
Chemicals
AKR
CAP
PLA
SCH
1
2
1
2
3
1
2
1
2
3
H2S04
NaOCI+NaOH
Cooling
H2SO4+Corn Syrup
H9(V
H2SO4+DeAmine
NaOCI+NaOH
Cooling
H2SO4+DeAmine
NaOCL+NaOH
Table 13. Planned Wet Scrubber Installations
                    473

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            Capital Costs
         Original     Additional    Future
      ($$ Millions) ($$ Thous) ($$ Thous)
^ *
CLA
NEW
SAR
SCH
CAP
PLA
POR
AKR
i*r ^r1 * ^^  B^
2.0
2.8
4.2
6.7
8.4
13
12
22
80
 -

	
* 3000*

205


??
200*
470*

5300*
??
7500*
 Odor Control
Table 14.  Capital Costs
                    474

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THE DEVELOPMENT OF RISK ASSESSMENT METHODOLOGIES
 FOR USE IN REGULATION OF SEWAGE SLUDGE DISPOSAL
                       by

               Randall J.F,  Bruins
                 Norman E.  Kowal
              Cynthia SpnVch-MullIn
              Steven D. Lutkenhoff

  Environmental Criteria and Assessment Office
      U.S. Environmental Protection Agency
                Cincinnati, Ohio
This paper has been reviewed In accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
          Prepared  for  Presentation at:

     Twelfth United States/Japan Conference
         on Sewage Treatment Technology
                Cincinnati,  Ohio

              October  12-13, 1989
                      475

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                                 INTRODUCTION
     Risk assessment 1s a structured procedure for making quantitative
estimates of the potential for harmful agents to cause adverse effects on
human health or the environment.  The use of risk assessment methods to
determine appropriate limits for chemicals In environmental media such as
air and water 1s well established.  This paper will describe their use for
estimating risk from chemicals 1n sewage sludge, and their potential use for
estimating pathogenic risks as well.

     The Environmental Criteria and Assessment Office of the U.S. EPA Office
of Research and Development In Cincinnati, Ohio, has recently developed risk
assessment methodologies which can be used to calculate criteria for
protecting human health and the environment from toxic pollutants In
municipal wastewater sludges (1-4).  Since municipal sludges are managed
utilizing a number of different reuse or disposal practices, separate
assessment methods were developed to address land application (Including
distribution and marketing [D&M]), Iandf1ll1ng, land-based Incineration, and
ocean disposal of sludges.  Assessment methods to address surface disposal
(I.e., surface Impoundment) of sludges are currently under development.
Each methodology provides procedures for estimating the fate and transport
of sludge-borne pollutants and for evaluating the potential for effects on
humans or other organisms.  The methods also describe data requirements for
using these procedures to calculate criteria.  Th^ criteria are not
necessarily numerical 1n all cases.  In some Instances, the risk assessment
calculations can be used to determine appropriate controls on the design or
operation of the management practice which achieve the same level of
environmental protection.  Such management controls are often preferred for
their practicality.  In many cases, however, the methodologies suggest that
numerical limits on pollutant levels 1n the sludge should be calculated.

     The risk assessment methodologies for each practice describe algorithms
that can be used to calculate whether or not adverse effects would  be
expected from a given sludge constituent under a given set of conditions.
Separate algorithms are presented for different pathways of potential
exposure.   For example, the methodology for sludge landfUUng develops
separate algorithms for contaminant movement to groundwater and  for
volatilization through  the soil cap.  The algorithms range from  simple to
complex.  For example,  1n order to  prevent phytotoxldty,  the land
application methodology states  that soil levels toxic to plants  should be
determined  from the literature  for  each chemical,, and that sludge
applications should be  limited  to prevent the occurrence of such  levels.
Minimal  calculation  Is  required.  On  the other  hand, the algorithm  for the
                                      476

-------
  groundwater  pathway  for  sludge  landflVMng requires the use of three
  computer models  In succession to determine the effects of unsaturated zone
              eChWlJa\equl11br1a- and saturated zone transput
              , on potential for  human exposure.

      Using these procedures, conditions can be established which would
         ffSe effecls*  As ^ntloned previously, these cond tlons
  of  h  n fr  .^ ?nSlSt of,a S6t Of ^commendations for design or operation
  of the Practice   For example, a maximum ground slope or minimum depth to
  groundwater  could be recommended for land application practices In Srder  to
  prevent surface or groundwater pollution, respectively   Often  however
  numerical criteria which limit the chemicals  themselve  are derlJed    '
  Depending on the algorithm, these numerical  criteria may take the form of
  nf d SI    The C!i ter1on 1s  the amount  Wh1ch  co"1d  be  reapplled annually
without ever  exceeding  a maximum cumulative amount.               dnnuany

                         huma!?S  r  3n1ma1s may consume the Slud9e
                                    477

-------
son and could be exposed to pure sludge.   For  these .types  of  exposures,  the
dry-weight pollutant concentration 1n the  sludge Is  more pertinent  than  the
pollutant application rate.

     Offslte movement of sludge-borne chemicals can  also occur through
transport 1n surface runoff or by percolation to groundwater.   These
movements are treated as a function of annual areal  pollutant  application
rate, rather than sludge concentration.  A1r concentrations resulting from
volatilization may be a function of sludge concentration (wet  weight)
Immediately upon application, but long-term average concentrations  would
again be a function of the annual areal application rate.
                                  LANDFILLING
     LandfUUng was estimated to account for 15 percent of municipal sludge
 disposal  1n 1980 (5) and was estimated at 42 percent 1n 1986 (6).  Host
 landfUled sludge  1s codlsposed with municipal solid waste, while a lesser
 amount  (1.3 percent of  total sludge disposal In 1986) Is disposed In
 sludge-only landfills,  or monofUls.  The risk assessment methodology for
 landfllUng (2) considers only the monofHUng practice; codlsposal will be
 dealt with 1n  a separate assessment effort.  It Is assumed that site design
 features  such  as runon/runoff controls are adequate to protect local surface
 waters  and that the dally application of cover material prevents any
 problems  of windblown  dust.  Numerical criteria are suggested to prevent
 hazard  from groundwater contamination:  design criteria are not recommended
 since  very few sludge  landfills  have  liners  and these liners may rupture.
 Numerical criteria are also  suggested  In order to  limit the vapor
 concentrations downwind from the site.

      Contaminant movement  to groundwater and subsequent movement to  a point
 of human use  are predicted  using a  succession  of  transport and geochemlcal-
 equlllbrlum models.   The  required Input  to  the first model  (unsaturated  zone
 transport)  Is a leachate  concentration.   In  addition  to  leachate
 concentration, the total  mass  1n the  landfill  of  each  pollutant must be
 estimated In  order to determine the maximum length of  time  over which a
 leachate of  a given concentration could  be  produced,  since  this  duration can
 affect the predicted maximum concentration  at the point  of  use.

      Downwind movement of vaporized contaminant  1s estimated  using  a
 Gaussian air dispersion model.   The vapor  concentration  Immediately above
 the source during dally (uncovered) operation, or post-closure,  Is  estimated
 from the leachate concentration using Henry's Law.  Thus  the  leachate
 concentration Is  required for both of these transport pathways.

      For organic  compounds, the leachate concentration can be estimated from
 the whole-sludge  concentration and the partition coefficient  of the
 contaminant.  Inorganic compounds are assumed to be present at the limits; or
 their  solubility, based on  the maximum effluent or leachate levels observed
 1n wastewater treatment plants.

                                      478

-------
  hu     ?f a       be  ana1yzed  1n  the  leachate or whole sludge, as determined
  by  preliminary  screening procedures,  could  Include various Setals. cyln"de

  e te?s  (7  55Sam1neS* chlorinated hydrocarbon pesticides, PCB and phthallte
                                SURFACE DISPOSAL
      Placement of sludge 1n surface Impoundments of some type 1s common-

         /J6 'f 
-------
                                OCEAN DISPOSAL
     Ocean disposal of municipal sludge by barging 1s currently permitted  In
only one location, the newly designated 106-Mile Ocean Waste Dump Site off
the New York/New Jersey coast (9).  Ocean disposal (at the previously
designated Hl2-H1le Site") accounted for about 4 percent of U.S. sludge
disposal 1n 1980 (5) and about 5.5 percent In 1986 (6).

     The risk assessment methodology for ocean disposal of sludge Is
concerned with both protection of marine life near the site and protection
of humans consuming seafood from that area.  Water-column concentrations to
which marine organisms are exposed are estimated from dispersion models.  To
calculate short-term concentrations within the dump site Itself, where toxic
effects on marine organisms are most likely, the sludge concentration (wet
weight), as well as speed, dumping rate and positioning of barges, Is the
required Input Information.  To estimate long-term, down-range concen-
trations, which are of more Importance for assessing human exposure, only
the total contaminant  Input to  the dump site on a dally basis  Is required.
Methods are not yet available to estimate  sedimentation rates  for sludge
particles and potential for seafloor accumulation at the 106-Mile site.

     Chemicals potentially requiring analysis  Include metals,  chlorinated
hydrocarbon pesticides, PCB, PAH, phthalate esters and aromatic amines
(7 8).  In addition to analysis of  Individual  constituents, whole-sludge
bloassay methods may  be used to determine  the  degree of dilution required  to
prevent aquatic toxldty.  While  not dealt with  1n these risk  assessment
methodologies, which  focus on evaluating  hazards  of  Individual  chemicals,
these  bloassay methods have  been  required  for  ocean-disposed wastes  under
other  authorities  (10), and  are also useful  for  sewage  sludge.


                                   PATHOGENS
      The U S  EPA Is currently Devaluating the existing,  technology-based
 pathogen regulations, which define Processes to Significantly Reduce
 Pathogens (PSRP) and Processes to Further Reduce Pathogens (PFRP)  (11).   A
 feasibility study for performing risk assessments for Pathogens  was
 completed 1n 1985 (12, 13).  Based on the feasibility study,  the U.S.  EPA Is
 developing a quantitative risk assessment methodology for  pathogens  (I.e.,
 bacteria, viruses, protozoa and helminths) 1n land-applied sludge.   The
 methodology examines human exposures to pathogens that could  result  from the
 following pathways:

           aerosols generated by sludge application or Incorporation
           wind-generated partlculates from soil surface
           runoff of precipitation or Irrigation
           direct contact with soil or crop

                                      480

-------
   movement through ground water to well
   use of contaminated ground water for Irrigation
   consumption of crops or animal products









                                                 i

                    CONCLUSION
               aswsa t: SWOT,, 


                    481

-------
                                 REFERENCES
(1)
Office of Water Regulations and Standards,
1986.
                                                          , O.C., April,
m  11 S  EPA   Development of Risk Assessment Methodology  for Municipal
{2)  SluVe Undflllln?   Prepared by the Office of  Hea 1th  and.  nv  roental
     Assessment  Environmental Criteria and Assessment Office, Cincinnati,
     Shlo! Tor the Of.f?ce of Water Regulations and Standards, Washington,
     D.C.', April, 1986.
m  US  EPA   Development of Risk Assessment Methodology  for Municipal
(3)  U.S. EPA.  ^ve.opm                   Qfnce Qf Health and
               ,taT^ssment? Environmental Criteria and Assessment Office,
            _!, Ohio! forthe Office of Water Regulations  and  Standards,
     Washington', D.C., April, 1986.
 (4)  U  S  EPA.  Development of Risk Assessment Methodology for  Ocean
 {*)  u.a. crn.     _P   , .,...   DronareH  hw the Office of Health
      Uiliwiiviiv*1*-*  _.---,      -    f\nf
      Washington,  D.C.,  April,  1986.

 151  S^ EPJ3SM JK.^ll  ^rSJtaVSI^arcH Laboratory.
      Cincinnati,  Ohio,  Oct.,  1983.  p.  1-2.
 (6)  U S  EPA   1989.  Standards for the Disposal  of  Sewage  Sludge; Proposed
      Rule.  Federal Register, 54 (23):  5754.
 m  U S  EPA.  Summary of Environmental Profiles  and Hazard Indlcles  for
 {?)  Constituents of Municipal Sludge:  Methods and Results,  Office of
      Water Regulations and Standards, Washington,  D.C.,  July, 1*03.

 (8)  LomnUz, E.. Bruins. R. and Fradkln, L.  Blocycle.  Vol. 26,  No. 7,
      Oct., 1985, pp. 52-54.
 (9)  U.S. Epa.   Ocean  Dumping:  Final Designation of Site.  Federal
      Register. 49 (88):   19005-19012, 1984.
  MO) rnrio nf  Federal Regulations Title  40,  Part 227, July 1, 1985,
      pp.  155-168.
  m) nnri* Of  Federal Regulations.  Title 40, Part  257, 3uly  1, 1985,
       pp.  341-342.
                                       482

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(12) Fradkln, L.  Lutkenhoff,. S.,  Stara, J.,. Lomnltz, E., and Cornaby  B
     J.  Water Poll.  Contr.  Fed.  55 (2):   1036-1039,  1985.      orndy.  >


(13) U.S.
        ,;  Pathogen Risk Assessment Feasibility Study.

              ?3^0ft1Ce Jfealth and Environmental Assessment.
 ff r  nCrlter a4!nd Assessment Office, Cincinnati, Ohio and
Office of Water Regulations.and Standards, Washington, D.C., Nov
                              483

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            UV DISINFECTION
                   by

            0.  Karl  Scheible
            HydroQual, Inc.
           1  Lethbridge Plaza
       Mahwah,  New Jersey  07430
This paper h.as been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
  ,   Prepared  for Presentation  at:

Twelfth United States/Japan Conference
    on Sewage Treatment Technology
           Cincinnati, Ohio

          October 12-13,  1989

                . 485

-------
INTRODUCTION

    The  use of  ultraviolet  (UV)  radiation  for  the  disinfection  of treated
wastewaters is  an  accepted practice  in  the  United  States.   There  is  an
increasing pace of installation at new plants and chlorine contact chambers at
a number of existing plants  are being retrofitted with UV equipment. This has
been spurred by  the acceptance of the technology  as  a viable and established
process,  and  by  the  negative aspects of  chlorination:    very  often
dechlorination is  required to meet  increasingly  stringent  limits on residual
chlorine levels; chlorination can result  in the formation of  toxic chlorinated
organics;  and  there are significant  concerns  over the safety of transporting
and storing chlorine and sulfur dioxide.   Conversely, UV has  no residual, does
not affect chemical reactivity, and  does  not  have safety concerns that would
affect the  surrounding community.

    The USEPA disinfection program initiated research and demonstration efforts
in the  mid-seventies to develop the  UV process as an  effective alternative to
chlorination.   This  support has continued,  particularly  in  the  construction
          at
grants funding under the EPA Innovative and Alternative Technology program.  By
1987  forty-two plants had  received  I/A  funding  for  UV facilities.   Research
efforts  were  directed to  assessing  the  efficiency  of the process,  and to
establishing and demonstrating  protocols  by which the process can be designed
and evaluated.   This design procedure will comprise the major portion of this
presentation.  Before this, 'however, .some discussion will be given  to how UV
works and  the  status of UV installations  in the United States today.
 UV DISINFECTION

     Ultraviolet  radiation  disinfection  is  a  physical process,  relying  on
 photochemical changes  brought  about when far-UV radiation emitted from a source
 is absorbed by the genetic material of a cell (deoxyribonucleic acid,  or DNA).
 The damage  to  the DNA results  in, the inability  of  the cell  to  replicate,  a
 lethal  effect.   The  most effective  spectral  region for  germicidal  activity
'corresponds to the  maximum absorption spectrum  of nucleic acids  (Figure  1) .
 This is between 250  and 265  nm.C1)
                                      486

-------
    Very conveniently,  low pressure mercury  arc  lamps are very  efficient in
generating UV light within this range:   approximately 85 percent of their light
output is monochromatic at  253.7 hm.   They are typically made of Vycor glass,
are  0.75 m or  1.5  m long,  and  0.75  cm in diameter.   Some  disinfection
applications exist  that use alternative lamps.   The  Lewisburg plant  in Ohio
uses medium pressure mercury lamps,  which have higher intensities and a broader
spectrum of  output.   A modified low pressure lamp that  is  capable  of higher
intensities  than  the  conventional  low pressure lamp is  being demonstrated at
the Baldwin, Florida  plant.  Overall, however, the  conventional  low pressure
lamps comprise the source of UV energy in  effectively  all disinfection systems
today.

PHOTOREACTIVATION

    Most organisms have an ability to repair and reverse the lethal effects of
UV,  a phenomenon broadly  termed  photoreactivation.    It  is  typically  a
photoenzymatic mechanism, and  requires  concurrent  or  post-treatment  with non-
ionizing  radiation in the  near  UV  or visible range.   The  repair is  of  a
constant fraction,  independent of  dose.   This is clearly exhibited  by data
shown on Figure  2,  developed from an  EPA  study conducted at a New  York City
treatment plant.(2)  The figure^ shows the  residual fecal coliform density as a
                                               f
function of  UV loading (Ipm/UV  Watt).   The data represent analyses of samples
held,in the dark after UV exposure,  and the same sample exposed to sunlight for
at least one hour.  Photorepair accounted for  approximately a 1 log increase in
fecal coliform density.                                                     .

    Most  organisms  have  the  ability  to repair,  although  there  are  some
pathogens that will not,  including  the  viruses.   The  total and fecal coliform
groups will exhibit photorepair, while the  enterococcus group does not/  In the
design  of  UV  systems,  it is important  to understand that environmental
conditions  at.  a  treatment  plant will  be  conducive to photoreactivation.   As
such, the phenomenon  must be considered in sizing the system;  generally this
suggests  that  the  system  must  be  sized to accomplish  an additional  log
reduction beyond the design effluent conditions.
                                     487

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STATUS OF UV SYSTEM APPLICATIONS IN THE UNITED STATES

    There are a number  of ways in which the UV reactors have been  designed  to
disinfect treated wastewaters.   Basically the intent  must be to minimize the
loss of UV  energy and to maintain a minimum exposure  time  for  the  wastewater.
This requires close contact of the wastewater with the  UV source,  and plug flow
conditions within the reactor itself.

    Closed  shell  quartz  reactors  have the lamps  (with quartz sleeves)  fixed
within stainless steel cylinders in full contact  with the wastewater.   The lamp
spacing is typically 8 to 12 cm (centerline),  with the  wastewater  flow directed
parallel  to the quartz.   The systems  are typically gravity flow,  with  piped
inlet  and  outlet.   These  systems,  because  of  the higher  velocities at the
entrance and exit  points,  tend  to  exhibit higher advective  dispersion,
affecting disinfection  performance.    The  design  also  provides poor  access  to
the lamps and quartz for maintenance and repair.   These  types  of units  tended
to dominate the  market through the mid-eighties, but  are  currently being used
less frequently.

    A  "non-contact"  configuration uses thin-walled Teflon pipes  to  carry the
liquid.   These are  surrounded  by unsheathed lamps,  placed  coaxially with the
Teflon tube.   The  hydraulics  of this  arrangement  are  very  good, with low
dispersion  plug  flow  through the  long   (typically  1.5  to 3 meters),  small
diameter  (9 cm) pipes.  Energy efficiency is generally  lower, however, than the
quartz  systems,  and the  systems have been difficult  to maintain.    These are
generally not considered  for new applications.

    Open-channel systems  rely  on the submergence  of the quartz  and  lamp  bundle
in  an open-channel.   The lamps  are either fixed in place,  with  flow directed
perpendicular  to  the. lamp, or  inserted as modules,  with  the flow  parallel  to
the  lamp.   The  fixed open-channel units  reflect the  earlier .designs and
suffered problems  with  accessibility and  maintenance;  these  are  no  longer
installed.
                                      488

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     The newer open-channel designs use a modular arrangement of quartz-sheathed
 lamps that can be easily inserted into and removed from the channel.   The  lamps
 are placed vertically into the channel,  or horizontally,  with the  flow parallel
 to the lamps.  Figure 3 shows an  open-channel, horizontally  placed, modular UV
 design.    These  systems  represent  the  state-of-the-art  in UV equipment,
 accounting  for  the major  fraction of  new installations  and retrofitting of
 chlorine contact basins.

     The open-channel modular design  is  best suited to  UV process design. The
 lamps are placed in the  liquid at  relatively close  spacing, affecting efficient
 use of  the UV energy.   Additionally,  the open-channel design itself  can be
 exploited to favor  lower  dispersion,  plug flow conditions,  by forcing a long
 liquid pathlength relative  to  its  cross-sectional  dimension-    The modular
 design also allows easy  removal  of the units for cleaning and repair,  the lack
 of which  hampered the efficient operation of the earlier designs.

     Figure 4 gives a perspective  on  how UV has progressed,  particularly  with
 the types of systems that  are being installed.   A surveyO) in 1984 identified
 53  operating plants.  Most were  small;  80 perdent  had design flows less than 1
 mgd (3,900 m3/d).   Nearly  a third were  the non-contact  Teflon units,  and  half
 were  closed shell reactors.   The  remainder were open-channel  designs,  but  only
 one of these used  the modular approach.

    In  1988 there were  close  to 300 plants  in operation.   Of 177 for which
 information was available, 59 percent had design flows less  than  1 mgd  (3,900
m3/d).  Larger  systems are being put on-line;  however, 38  percent have  design
flows between 1 and  10  mgd  (3,900 and 39,000 m3/d)  and several  plants  have
capacities  greater  than  10 mgd  (39,000 m3/d).   The largest operating plant  is
Madison, Wisconsin, with  a  design peak of approximately 100 mgd (390,000 m3/d).
Quebec  City,  Canada, has  commissioned two  plants  with a  combined design
capacity of 230 mgd (900,000  m3/d).
            r
    The distribution of the systems reflects the direction of  the  UV equipment
field.  Seventeen  percent are Teflon,,with only a few new  installations since
                                     489

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1984.  Only a  quarter '(26 percent)  of the plants use the closed shell design;
they are still being  installed, but the trend is away from  them for wastewater
applications.   There are no new fixed in-channel units.   The trend  is  obviously
to  the open-channel  modular  systems, which  after  four-years now  comprise'
greater  than half  the operating plants.   Of  these,  85 percent  utilize  the
horizontal configuration and 15 percent the vertical placement.

DESIGN OF UV PROCESS

     Through  the  mid-eighties,  reflecting experience with "first-generation"
systems,  problems  with UV  installations  related   to  severe component,
fabrication and  installation deficiencies  (ballast failures,  panel  heating,
electrical  failures,  and poor reliability).   This -has changed as  the field is
dominated more and  more by "second generation" systems.   There is a far greater
degree of standardization, and  the  modular  concept is  allowing for  a greater
degree of  flexibility and ability to  affect quick repair and maintenance.  More
attention  is  being directed to design protocols that will assure proper sizing
and can assist in the evaluation of  existing systems.

     A significant effort  for  the EPA Disinfection  Program  was  the development
 and demonstration  of a  design  protocol  for the UV process.   This  was first
 described from a large  scale  pilot study conducted at  the New York City Port
 Richmond plant(2), and  subsequently detailed in the EPA Design Manual^) and
 the Journal. WPCF.(4>  Several  in-field,studies were also  conducted  to  support
 specific  aspects  of the design  protocol,  and  are described in the  Manual.
 Since then, the design protocol has been used to develop the process  sizing and
 layout  of  several new plants.   Most  recently,  the USEPA has  funded a pilot
 Study  to  further evaluate UV process  design.   The field  effort,  conducted  in
 Rehoboth Beach,  Delaware, has  been  completed,  and the  project is  now in the
 analysis phase.
                                                            k-
 DESIGN EXPRESSION^

     The  inactivation of  bacteria  by UV  radiation ,can  be  approximated by  the
 first order expression (Figure  5):
           N - N0e -
490

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where:
    N  = density after exposure (organisms/100 ml)
    N0 = initial density (organisms/100 ml)
    k  - inactivation rate (cm2//iWatts-sec)
    I  = intensity at. 253.7nm (/iWatts/cm2)
    t  = exposure time (second)         .        

    This  is  ideal.    However,  under  actual  conditions there will  be  a
distribution of 'exposure times  about  the  mean,  the intensity cannot be defined
by  direct  measure,  and  particulates  will  set  a  base^ level for  the  effluent
density.  The modified model incorporates these design elements (Figure 6):
         N =
                     i -
                              u
N
where:
    x  = the  characteristic  length of  the  reactor,  defined  as the  average
         distance traveled under direct UV exposure (cm)

    u  = the liquid velocity (cm/sec).   This is calculated as

                                       x/(Vv/Q)

         where Vv is the void, or liquid volume in the reactor (L) and Q is the
         flow rate (Lps)

    E  = the dispersion coefficient  (cm^/sec), which  quantifies  the  breadth of
         the residence time distribution about the mean time

    K  = the inactivation rate (sec'l)

    Np = the bacterial density associated with the particulates  and  unaffected
         by exposure to UV (org/100 mL
                                      491

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RESIDENCE TIME DISTRIBUTION

    The  dispersion  coefficient is  a key  parameter  defining  the  hydraulic
behavior of  the  reactor,  providing a measure of  the  spread of time about  the
mean residence time.  It  is  estimated from a residence  time  distribution  (RTD)
analysis of  a reactor,  such  as  shown on part (a)  of Figure 6.  E  is estimated
by the expression:
             uxcr
         E -
              26'
where:
    a2 - the variance of the RTD (sec2)
    u   reactor velocity (cm/sec)
    x   characteristic length (cm)
                                                                          '.
    S   mean residence time (sec)

    This assumes  that the RTD determined  for  a reactor approximates a  normal
distribution.   Under ideal  plug  flow conditions,  E approaches  zero; with
increased mixing,  E will approach infinity,  which defines ideal complete mix.
Generally,  an  E  less  than 100  cm2/sec  would be  considered acceptable  for
effective design.

    Figure  7  gives an example of  a hydraulic  analysis of a-UV system in West
Virginia.   It is  an open-channel,  horizontal  lamp unit,  which originally  had
over and under baffles to break the velocity of the piped inlet to  the channel.
An RTD  analysis of this channel showed very high  dispersion,  with  E  estimated
at greater  than 2,000  cm2/sec.  The ratio  of tgg to  t]_Q,  which is  the time  for
90 and  10  percent of the tracer to  pass,  respectively, ranged between 2.2  and
6.4.    Known  as  the Merrill Dispersion  Index,  this  will also  indicate
significant dispersion at values greater than 2.0.  Mixing was occurring  in  the
reactor, preventing  the unit from achieving expected disinfection efficiencies.
                                      492

-------
     Removing the baffles provided  some  improvement,  but not sufficient.   The
 higher velocities  from  the  inlet pipe caused a significant degree of dispersion
 to  occur in the reactor.   The E  was  estimated to be  between 800  and  3,500
 cm2/sec, with a  Merrill Index of 1.7 to 2.7.

     A stilling  plate  was  installed  in  place  of  the baffles.    This  is  a
 uniformly perforated plate  that is  able to equalize the velocities entering the
 reactor  lamp battery,   encouraging  plug flow.   The E was reduced  to less  than
 100  cm2/sec  in this case, indicating good plug flow conditions.

     Thus,  it  is important  to  design a UV disinfection system for  plug  flow.
.This can be  quantified by the  dispersion coefficient, which has  also  been
 incorporated  into  the  design  expression.   RTD  analysis should be used  to
 determine E  (and other  hydraulic  indices),  both  from the design standpoint and
 to troubleshoot  performance problems.                           .  .        
                                                          *^,
 INACTIVATION RATE AND REACTOR INTENSITY

     Returning to  the  design .expression  (Figure  6),  the  inactivation  rate
 coefficient,  K,  is described as a  function of the average intensity in the  UV
 reactor:
         K
where  Iavg is
                     average  reactor intensity  (/iWatts/cm2) ,  and a  and b  are
 coefficients  developed from  a  Log-Log regression of  K and  Iavg.   These  are
 specific  to wastewater conditions,  reflecting  the  sensitivity of the organisms
 to UV.
     There  is  no  method  to directly  measure  the  actual  intensity within a
 complex,  multi-lamp  reactor.    Rather,  a  computational  scheme (point  source
 summation method)  is  employed,  based on the  number  of lamps in a reactor  (UV
 density)  and  the absorptive  properties  of  the  liquid  (UV  absorbance
 coefficient) .    Solutions have  been developed and  are presented in the  EPA
 Design Manual  for a number of system configurations.

                                     493

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    Figure 8 shows such an analysis for the symmetrical array of lamps  employed
by the modular, open-channel, horizontal lamp systems.   Thus  for units  having a
centerline spacing  of 6.35 cm  (typical),  the  UV density, D,  is  approximately
5,0 UV Watts/Liter; at an absorbance coefficient of 0.4 cm"!  (representative  of
a "secondary"  effluent), the nominal  average  intensity is approximately  15,000
    For  design purposes this nominal  intensity  should be adjusted to  reflect
deterioration  of lamp  output  with time  and fouling  of  the quartz  surfaces.
Both conditions will obviously attenuate the UV intensity.   Typically,  the lamp
UV output will be at 70 percent of the nominal rating during the latter half of
its  operating  life.    The quartz  surfaces  will get  dirty,  generally from
inorganic deposits such as iron, and calcium and magnesium carbonates.   Routine
maintenance of the quartz surfaces (which is a critical O&M task) can typically
keep  the transmissibility of the quartz  at- an average 8,0 percent  of  nominal.
Thus, the design intensity can be 50 to 60 percent (70 percent x 80 percent) of
the nominal reactor intensity.

    Developing  a  rate  coefficient  for  a  specific  application requires
influent/effluent bacterial sampling over a range of intensity levels.   This is
typically  done by operating  two UV pilot  units,  each with  differing  average
intensities.   Figure 9  shows an analysis conducted at the Port Richmond WPCP in
New York City. (2)  In this case,
          K
1.45 x 10-5 (Iavg)1.3
     This  procedure was demonstrated at four additional plants as a special EPA
 sponsored project  in 1985.   The  results  are summarized  in reduced  form  on
 Figure 10.   There  was  sufficient variability  to suggest  that this  type  of
 information may  best be  developed for  a  specific site  (particularly larger
 plants),  although using the combined expression may be adequate for estimating
 purposes.   The  combined data,  shown by  the heavy dark  line,  yielded  an
 expression
          K - 1.38 x 10-5 (Iayg)l-28
                                      494

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EFFECT OF WASTEWATER PARTIGULATES

    Bacteria  that  are  occluded  in particulates will  not be  effected by UV
radiation, and, as  such, will comprise the base  level of  effluent  density  that
can  be achieved  for  a specific application.   The  term Np  in  the design
expression quantifies  this effect  (Figure  6)  by relating  it to the  effluent
suspended solids:
         Np = c SSm
where SS  is  the suspended solids  (mg/L)  and c and m are1 coefficients  derived
from a Log-Ldg regression of effluent bacterial density and suspended solids.
 3                                     '

    These data  must be  generated  under very high  dose  levels,  such that  the
residual density can be attributed to those bacteria which were occluded  from
the radiation.  An  example is  shown  on Figure  11  for  data developed during the
Port Richmond project.(2)   The log effluent fecal  coliform density  is  plotted
against the log effluent suspended solids.  A linear regression analysis yields
the expression (when transformed):
         Np = 0.26 SSl-96
Studies conducted at  several plants  show considerable  variability,  although  it
appears that these coefficients provide a reasonable estimate of Np.

Calibrated Disinfection Model

    The  design  expression takes  on the  following  format,  incorporating the
coefficients required for model calibration (Figure 12):
          N = N exp
ux
2E
                                 4E(aI
I    )      -,
 avg       ,1
^ - > ' }\  +
c SS
                                                         m
    The  coefficients a,  b,  c and  m  are specific to  a  given wastewater
application.  These  can be  determined by pilot testing;  alternatively,  one  may
                                      495

-------
use approximations  determined  from e'arlier studies, recognizing that  they may
not be fully representative of actual conditions.   In  this  case, the  suggested
coefficients are:

    a  - 1.38 x ID'5
    b  - 1.28                                          ,
    c  - 0.26 (fecal coliform); 0.9 (total coliform)
    m  - 1.96

    To  confirm  the model  calibration,  measured  effluent densities can  be
compared to the residual predicted by the model.  An example is given on Figure
13, developed from  an evaluation of the Northfield, Minnesota plant(5), showing
the observed versus predicted fecal coliform densities,.   The  calibrated model
was  subsequently  used to  determine  equipment  requirements to  upgrade the
system.

SYSTEM SIZING USING THE DESIGN MODEL

    The  design model is  a  very effective tool  in the sizing of  a full-scale
facility and assessing alternative configurations.  This is especially the case
when the model has  been calibrated by direct testing.

    Figure  14  is an  example  of design  curves  developed from the  model  for a
wastewater  treatment plant.   The  figure gives  the log N'/No  as a function  of
the reactor loading,  which is defined as  the flow (Lpm)  per unit  UV watt (W).
The sizing  assumes  using  a horizontal lamp, open-channel system, with a 6.35  cm
centerline  spacing, and  1.5 m lamps.   The solutions are  for two banks of lamps
in series  and  a  dispersion coefficient (E)  of  100  cm2/sec.   The  curves
represent  different inactivation rates  that  are defined by varying  levels  of
the UV absorbance  coefficient in the wastewater (recall  that these affect the
UV intensity in  the reactor).

    Consider sizing for  the maximum six-hour design condition:
                                       496

-------
     Q
     TSS
     NO
     UV Absorbance Coefficient
     Design Effluent N
= 42 mgd (160,000 m3/d)
= 30 mg/L
=^600,000 FC/100 mL.'
= 0.55 cm-1
= 800 FC/100 mL
     The inactivation rate, K, at this  condition was  estimated to be 1.0 sec'l.
 The .performance requirement  (Log N'/N0)  is determined by  first  accounting for
 the particulate coliform density,- Np:

     Np = 0.26-(30 mg/L)L96 = 2Q4 FC/100 mL
     N' = N - Np = 800 - 204 - 596 FC/100BmL

         N                       '              .
     Log  = .3.03
          o

     From Figure 14,  the loading  is  estimated to be  2.0  Lpm/UV Watt.   The number
 of lamps is computed on  the  basis  of  the design flow and a  lamp  specification
 of 26.7 UV Watts/Lamp.   This  yields  2,070  lamps for the maximum six-hour design
 condition.                                    ~   .

     With two units in series,'the lamp  requirement is  1,035/unit.  At  8 lamps
 per  module, approximately  140 modules are  required  per  unit.   This would be
 divided to parallel  channels toprovide  flexibility  and  control  of  operations
 under  varying conditions.  A simplified layout is given on  Figure  15.  This
 shows  5 channels,  each  with  2 banks  in  series  and  26 eight-lamp modules  per,
bank.   A sixth channel is provided  as  standby.  Each channel is  hydraulically
 independent,  with  liquid  level control  gates at the  effluent  end of  the
channel.  The control panels and wireways are generally located near each bank.

SUMMARY
    In summary,  UV disinfection is  an- established technology that  is  rapidly
gaining  acceptance -and  is  being  put  into  operation  at a  growing number  of

                                     497

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plants.  The technology configuration that represents current state-of-the-art
is  the open-channel  system with  modular, horizontally% placed  lamp banks.
Design protocols  have  been  developed that  address key  process  elements,.
including  the dimensional  configuration of .the  unit,  UV  intensity,  reactor
dispersion  and RTD characteristics,  and key water  quality parameters.    The
modeling  approach  is  generic and  can be  used  to  characterize  most reactor
configurations and wastewater conditions.

REFERENCES

1.   Oda, A.  Ultraviolet Disinfection of Potable Water Supplies.   Ontario Water
     Resources  Commission, Division of Research, Paper 2012,  1969.

2.   Scheible,  O.K., M.C. Casey and  A.  Forndran.   Ultraviolet Disinfection of
     Wastewaters  from Secondary Effluent  and Combined Sewer  Overflows.   EPA-
     600/2-86/005, NTIS No. PB86-145182, USEPA, Cincinnati,  Ohio,  1986.

 3.   naatpn  Manual:  Municipal Wast--ewater Disinfection.    USEPA,  Office of
     Research and Development,  Water  Engineering  Research  Laboratory,
     EPA/625/1-86/021, Cincinnati, Ohio, October ,1986.

 4.   Scheible, O.K.   "Development of a Rationally  Based  Design Protocol for  the
     Ultraviolet Light Disinfection Process,"  Journal WPCF, Volume  59, No.  1,
     j>p 25-31, January 1987.

 5.  HydroQual, Inc.  Report to  the  City of Northfield,  Northfield,  Minnesota,
     "Evaluation of  the  UV  Disinfection  Process  at  the  Northfield  Water
     Pollution Control Plant," Mahwah, New Jersey,  December  1984.
                                      498

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       2
       -J


       *,




       X

       2
                             Z500

                     WAVELENGTH (ANGSTROMS - A )
FIGURE  1.   RELATIVE GERMICIDAL EFFECTIVENESS AS A  FUNCTION

            OF WAVELENGTH, (1) .
                         499

-------
 0
-1
-2
-3
-4
-5
-6
-7
                        	1	
                         Uo (Light)
                                  to
              Total Coliform  , -
                    Unitl
                                         o to
                                         t.o
                     _L
_L
                                   _L
JL
 Unit 2
_L	
                     ,1      2      3      4      5
                         Flow/UV Output (LPM/Wts)
                      12345
                         Flow/UV Output (LPM/Watti)
FIGURE 2.  PHOTOREACTIVATION  EFFECTS  FOR TOTAL AND FECAL
            COLIFORM AT PORT RICHMOND  (2).
                                500

-------
                                     System UV 2000
                                     UV Modules in
                                     effluent channel.
FIGURE 3.  SCHEMATIC OF OPEN-CHANNEL, MODULAR UV SYSTEM

           (COURTESY OF TROJAN ENVIRONMENT,  INC.,

           LONDON,  ONTARIO, CANADA),.'

                     .501

-------
                1984

OPERATING PLANTS

 80% WITH Q < 1.0 MGD
 35% TEFLON UNITS
 49% CLOSED SHELL REACTORS
                1988

ESTIMATE OF 250 TO 300 OPERATING PLANTS

OF 177 PLANTS SURVEYED

 59% < 1 MGD    "    
 38% 1 TO 10 MGD
.  3% > 10 MGD

TYPE OF SYSTEMS

    17% TEFLON
    26% CLOSED VESSEL
  4.5% OPEN CHANNEL  (FIXED)
 52.5% OPEN CHANNEL  (MODULAR)
FIGURE 4.  STATUS OF UV INSTALLATIONS
                 502

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               N
N  =
NO =
k  =
T  ss:
t  =
It =
effluent density  (organisms/100 mL)
initial density (organisms/100 mL)
inactivation rate  (cm2//iWatts-sec)
intensity at 253.7 nm  (/iWatts/cm2)
exposure time (sec)
Dose = /tWatt-sec/cm2
  FIGURE 5.  UV DISINFECTION EQUATION
                  503

-------
N= NQe
              dispersion
                           K
                                            K= a I
                                                  avg
                                   avg
   Eff.
 Coliform
Np=  CSS
                                 m
              Eff. SS
  FIGURE 6.  CONCEPTUALIZATION OF UV DESIGN MODEL
                        504

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      Baffle Plates
              Stilling Plate
              (156- 1" 2000
                 800-3500       20-90
WlO
2.2-6.4
1.7-2.7
1.5-2.2
        FIGURE 7.  WILLIAMSON, WEST VIRGINIA HYDRAULIC ANALYSIS
                             505

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  40,000
  36.OOO
  30,000
  23,000
   20,000 -
Jg 15,000
^i

I 10,
000
     5OOO
                 \
                                                         ABSORBANCE

                                                         COEFFICIENT
                                              UNIFORM LAMP ARRAY
                                      ASSUMES  1OO% LAMP OUTPUT

                                                10O% TRANSMITTANCE

                                                QUARTZ O.D = 2.3CM
                                      _L
                                                                      O
                                                                   6  *-

                                                                      O
                                                                      2

                                                                      O

                                                                   4  2
                                                                      CO

                                                                      Ul
                                                                      2

                                                                      3
                                                                   3  1C
                                                                      IU

                                                                      Z
                                                                      IU
                                                                      O
                             8        12        16        20

                         UV  DENSITY  (WATTS/LITER)
                                                            24
 FIGURE 8.  NOMINAL INTENSITY SOLUTIONS FOR SYMMETRICAL,  UNIFORM LAMP ARRAY.
                                      506

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            20.0,
            10.0
             8.0
             6.0
             5.0
             
             3.0
          S
          S.
          i  1.0
          tt  0.8
             0.6
             0.5
             0.4
             0.3
             0.2
 Unit 1
 Unit 2
               600 1000  2000  4000    10000  20000   60000
                        Average Intensity, l.,0 (fj W/cm2)
FIGURE 9.  AN  EXAMPLE  FOR DERIVING AN ESTIMATE  OF THE
            INACTIVATION RATE FOR FECAL  COLIFORMS AS A
            FUNCTION OF THE CALCULATED AVERAGE INTENSITY
            (2).                         '....
                                507

-------
          S
          5
          CC
6.0








4.0





3.0








2.0






1.5








1.0




0.8





0.6








0.4






0.3








0.2





0.15
                1500 2000   3000 4000    6000     10OOO


                       Average Intensity, !., (// W/cmz)
FIGURE 10.   COMPARISON OF INACTIVATION RATE ESTIMATES

              FROM SEVERAL WASTEWATER TREATMENT PLANTS.
                               508

-------
           I  7
           1  
           CO
           i  5
           e
             4
              3
           o  2
           CD
           I  0
           LLJ
           ? -1
             -2
               0.5  1    2  3 4  6 8 10   20304060 100200300
                        Effluent Suspended Solids (mg/I)
FIGURE  11.   EXAMPLE OF DERIVING AN ESTIMATE OF THE RESIDUAL
             FECAL COLIFORM DENSITY ASSOCIATED WITH PARTIC-
             ULATES AS A FUNCTION OF SUSPENDED SOLIDS  (2).
                              509

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N = NQexp|^:
  4E(aIaVS } ,1/2\1  . r __m
+ 	-jj     )   |J + c SS
              FIRST APPROXIMATION:







     a =  1.38 x  ID'5






     b -  1.28






     c =  0.26  (fecal  coliform)



      =0.9  (total  coliform)







     m -  1.96
  FIGURE 12.'  DESIGN EXPRESSION INCORPORATING THE



       COEFFICIENTS REQUIRED FOR CALIBRATION
                        510

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4.
         Mean Observed   = 140
         Mean Calculated - 140
0.00
                           1-20         1.80        3.HJ        3.00         3.60

                        LOG  L  CflLC  (F.  COLI)
 FIGURE  13.  EXAMPLE OF COMPARISON OF.OBSERVED DENSITIES WITH DENSITIES
            PREDICTED BY MODEL  (NORTHFIELD,  MN).
                                 511

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(ON/.N)
        512

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                               Overflow weir with
                               automatic slide gate-
     Influent Channel
o
o
          /-Stilling
          v  plate
             I   I
          J   I
                Lamp
                banks
O
                         4=4
o
                                           Control
                                           panels?
                                  J   I
                                      ^-\A/i
                                  Wireways
                                  I   I
                                     /Level control
                                        gates
     Effluent Channel
                                        I
                                        I
      EIGURE 15.   SIMPLIFIED LAYOUT FOR DESIGN EXAMPLE
                             513

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           A PRELIMINARY ASSESSMENT OF
               HIGH BIOMASS SYSTEMS
                        by

             Arthur J.  Condren,  Ph.D.
 James M. Montgomery, Consulting Engineers, Inc.
            Pasadena, California, USA

               Bjorn Rusten, Ph.D.
  Aquateam Norwegian Water Technology Centre AS
                   Oslo,  Norway

             James A. Heidman,  Ph.D.
      Risk Reduction Engineering.Laboratory
       U.S.  Environmental Protection Agenc
                Cincinnati, Ohio
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
         Prepared  for  Presentation  at:

     Twelfth United States/Japan Conference
         on Sewage Treatment Technology
                Cincinnati,  Ohio

              October  12-13, 1989
                      515

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INTRODUCTION

The  Federal grants  program  for the  construction of  municipal
wastewater treatment plants  will end on 30 September 1989.  With
its termination, municipalities will be seeking plant modifications
which  will  allow  for  increased  capacity  of  their  existing
facilities with minimal capital outlay.  To assist municipalities
in  their  search  for  cost-effective  solutions  to  their  plant
capacity dilemma,  the  U.S.  Environmental Protection Agency (U.S.
EPA) has undertaken a  search for new technologies which may allow
for  the  realization  of this goal.  One  such technology thus far
identified is what has been termed high biomass systems.

High biomass systems allow  for the growth of both fixed film and
suspended  biomass  in  the  aeration  tanks  of  activated  sludge
systems.   The  suspended growth  concentration  is  controlled by
adjusting  the  amount of MLSS  recycled  in the underflow from the
secondary clarifier. Inert  support media is placed in the aeration
tanks and serves as the locus for fixed biomass growth.  This_fixed
film growth increases the concentration of biomass in an activated
sludge plant's  aeration  tanks  which,  in turn, lowers the food to
mass ratio  (F/M) and increases the solids  residence time (SRT) of
the  system.   It also  lowers  the  concentration of biomass being
conveyed to  secondary  clarifiers since the fixed film biomass is
retained in the system's aeration tanks.  Such retention allows for
enhanced  levels  of  solids-liquid  separation,  especially  in
hydraulically overloaded clarifiers.  In addition to the above, the
presence of the fixed film biomass has  been shown  to allow for
enhanced wastewater nitrification  as well as  to yield a better
settling secondary sludge.

CURRENTLY  AVAILABLE  HIGH BIOMASS SYSTEMS  ,

At the present  time,  there appear  to be at least  six (6)  high
biomass  systems commercially  available which can be incorporated
into conventional aeration tanks.  Linde AG of the Federal Republic
of'Germany  (FRG)  and  Simon-Hartley  of Great  Britain  (Ashbrook-
Simon-Hartley  in the USA) both use  small, highly reticulated sponge
pads as  their inert support media.   Bio-2-Sludge (FRG) and  Smith
& Loveless, Inc.  (USA)  use racks of synthetic  trickling  filter
media  to -effect fixed film growth.   Ring Lace  (Japan) employs  a
looped string material as  the inert support media and a  Chinese
firm uses  tassels  of a synthetic material attached to a string for
fixed  biomass  attachment and growth.  The latter two inert  support
media  are tied to racks which are placed in the  plant's aeration
tanks.
                               516

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SYSTEM DESCRIPTIONS                                          

Linde AG/Ashbrook-Simon-Hartley

The basic concept of systems offered by these two manufacturers is
to use highly reticulated  sponges  as the inert support media for
the fixed film biomass growth.   The systems are marketed as Linpor
(Linde AG)  and  as  Captor  (Simon-Hartley).   Linpor  sponges are
approximately cubical with  sides  of about 10  to 12  mm whereas
Captor sponges are about 12x25x25 mm.  The Linpor system includes
solids recycle from the secondary clarifier whereas a Captor system
normally does not include secondary  solids return to the aeration
basin.  Volume of sponge in  Linpor secondary systems approximates
10-30 percent of the aeration  tank volume.   Biomass accumulation
in the sponges may range from 9-37 g/L (of sponge) , thus accounting
for 25-60 percent of  the total biomass in Linpor secondary system
aeration tanks.  Measurements of the fixed film biomass in Linpor
systems have  indicated equivalent mixed liquor suspended solids
(MLSS-)  concentrations  of  1,200-3,800   mg/L.    Linde AG's  cost
estimate for the conversion  of an  existing conventional activated
sludge  plant  to  a  high biomass  system  is  in the range  of
$250-350/m  of aeration tank volume.

The  inert support  media  in the Linpor  system are kept  in the
aeration tanks by means of retention screens located approximately
0.3  m upstream  of the effluent launder as  shown in  Figure 1.
Openings  in  the retention screen  are 8-mm holes placed on  12-mm
centers.  Forward flow of wastewater through the aeration tank can
cause  a  maldistribution   of sponges  in the  tank,  .with  higher
concentrations  occurring  at the  retention  screen  than  at the
influent  end  of the tank.   To normalize the concentration,  Linde
AG  has  installed  air lift pumps  to   convey  sponges  from the
discharge to  the influent end of aeration tanks at installations
where concentration maldistributions have occurred.

Ashbrook-Simon-Hartley has  developed a  process to  squeeze  fixed
biomass from sponges  in their systems. An air-lift pump lifts the
pads  to  a  conveyor  system where  they  are  transported through
pressure  rollers.   This  has been viewed as a means  of removing
excess  biomass  from the  pads  and  producing  concentrated  waste
secondary sludge solids.   The iinde  AG system  relies on naturally
occurring sloughing of fixed biomass from the  sponges and wasting
excess biomass  from the return  activated sludge (RAS) system.

Ring Lace

The basic concept of a Ring Lace system is the installation of a
poiyvinyl chloridene  (PVCE)  string on racks  in  an aeration tank as
shown  in Figure 2.    Clear spaces above  and ' below  the  racks
approximate 0.5 m each to allow for normal side roll mixing in the
aeration tanks.   Each string has numerous attached loops of  the
                                517

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Effluent



































































,,,,."77! 	 	 v_ '

-------
Effluent *
(

c

c

c

L

L

(

<

(
r
o

c

c

(

<
H
c
-N






























 Influent
                            \B) Ring Lace Rack
     "Figure 2.  Basic  Layout of a Ring Lace System.




                       519

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same material, thus greatly increasing the surface area available
for fixed  film  growth.   The European  distributor indicated  that
typically  25-50 percent of  an aeration  tank's total volume  is
occupied by the Ring Lace racks, and the racks are spaced to yield
a  density  in this volume  of  120-300 m  of Ring Lace/m .    One
distributor  in  the US  indicated  that the racks  would typically
occupy from 50 to 80 percent of the basin volume with a density of
about  120   linear meters  per mj  of  the  entire basin  volume.
Retrofitting  a  conventional  activated sludge  plant  in  Olching
Germany to  a Ring Lace system was  at  a cost of about $2.65/m of
Ring Lace material installed.

Fixed film  growth on the inert media has  been  reported to be 6-7
g/m and thus  the  equivalent MLSS  of fixed biomass in a Ring Lace
system could vary from roughly  200-1,100 mg/1 of total tank volume.
As the  fixed film  biomass continues  to.  grow,  natural sloughing
occurs.  The  sloughed material then becomes a part of the MLSS in
the system  and  is removed  by conventional wasting practices.   The
level  of  suspended  MLSS is controlled by the amount  of solids
recycled from the secondary clarifiers.

Bio-2-Sludge/Smith  & Loveless, Inc.

The basic  concept of these systems is the inclusion of synthetic
trickling  filter  media  to  provide the  surface on which fixed film
biomass growth  can occur  as shown in  Figure 3.   Volume of media
used  in  Bio-2-Sludge  systems approximates  25  percent of  the
aeration tank volume while in Smith & Loveless systems, it is close
to 75 percent., In contrast to the Bio-2-Sludge systems, the Smith
and  Loveless  system does  not recycle  settled  sludge  from the
secondary  clarifier back to the aeration  tank.

Bio-2-Sludge systems use just  about any synthetic media as long as
the  openings in  the media are at least  2x2 cm.  Typical surface
area  of the media is in the range of 90-120 itr/m    Racks to hold
the media  are constructed to provide approximately  0.5 m  of clear
space above  the  air diffusion system as well  as about 0.5 m of
clear space between the top of the racks and the liquid surface in
the  aeration tanks.  This arrangement allows for  normal  side roll-
mixing in  the tank.   If the media begins to plug from excess fixed
film growth, a common practice is to turn on an additional blower
to  induce   surplus  biomass  sloughing.    Retrofit  costs  for
Bio-2-Sludge systems have been" reported to be  in the vicinity of
 $300-350/m3 of media installed.

 Chinese system

 As mentioned above the Chinese system uses tassels of a synthetic
material which are tied to strings and then mounted in the aeration
 tanks.   At the present time,  there is no  additional information
 available on this system.
                                520

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    Effluent

5

     Influent
                                 TF Media Rack
       Figure 3.  Basic Layout of a  Bio-2-Sludge System.
                       521

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SITE VISITS

During the late spring of 1988,  a U.S. EPA evaluation team visited
a number of full scale high biomass systems in the Federal Republic
of Sany.  The purpose of the site visits was to view the systems
in opS-ation,  collect operational and performance data,  learn of
system design  details from the system manufacturers  and discuss
process  operational and maintenance  concerns with the treatment
plant staffs.

Facility locations  and types visited included, among others, those
presented  in Table  1.

                  Table  1. Site Visit  Basic Information.
                    Type of System

                     Linde AG


                     Ring Lace

                     Bio-2-Sludge
Location .

Freising
Munich

Olching

Schomberg
Calw/Hirsau
 Summarized below are data and information on the various  types  of
 high biomass systems from certain of the above facilities.

 Freising (Linde AG System)

 The  Freising  activated sludge  wastewater  treatment  plant was
 converted to a Linde AG high biomass system in 1984 after a series
 of pilot plant studies.  It appears that there were three primary.
 reasons  for  the conversion:  frequently  occurring  poor  sludge
 settleability, limited space at the plant site and higher costs  of
 alternative technologies.   Operational  and performance data were
 collected for a  short period of time before and after conversion
 and these are summarized  in Table  2.

 Before  conversion to the  high biomass  system,  which  employed a
 sponge volume equal to 20 percent of the aeration tank volume, the
 plant could only maintain a MLSS concentration of about  2,600 mg/L.
 Following  conversion, a much  higher MLSS concentration  could  be
 maintained  which dramatically lowered the F/M  of  the system and
 greatly  improved the secondary sludge settleability.

 As a follow-up to this historic information, data for calendar year
 1987 were  collected and analyzed.   A summary of this  information
 is presented  in  Table 3.
                                 522

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                  Table  2.  Historic Freising  Data.

Parameter
Solids, g/L
Suspended
Fixed
Total
F/M,
kg/kg-d
SVI ,
ml/g
Effluent BOD5,
mg/L
Conversi
Before

2.6

2.6

0.47

485

48
.on
Afte>r
^ l> v? 4.
,5.1
1.7
6.8

0.17

85

4
                Table 3. Freising Data Averages for 1987.
                            Parameter
                     .Secondary Influent
                         Flow, m3/d
                        .BOD5, mg/L
                     Secondary Effluent
                         BOD5, mg/L
                     Biomass, g/L
                         Suspended
                         Fixed
                         Total
                     Aeration Tank
                         Det'n Time,  hr
                         F/M, kg/kg-d
                         SVI/Aml/g
                         D.O. ,  mg/L       1.7
                     Aeration Rate
                        m3/kg BODS Removed
                     Secondary Clarification
                        SOR   ,  m/hr
                        R/Q    ;  %
                                               Value
10,100 
   273
  2.59
  3.75
  6.34

   5.5
  0.19
   114
   64

   0.34
     41
                              Oxygen
                             Overflow Rate
                      Ratio of return/influent flow
          thS Frisin9  Plant was  operated  at. 78 percent  of its
r          capacity   and  80  percent  of   its   BOD5  capacity?
Instantaneous influent pH, because of industrial discharges to th4

                               523

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system, ranged  from 6.2- 12.0; effluent pH  ranged from 6.8-7.5.
An average  of 65 percent nitrification was  also  achieved  over a
wastewater  temperature range  of  10-17 C,  even though  the  D.O.
concentration averaged only  1.7 mg/L.

Munich  (Linde AG System)

The Munich Grosslappen plant was retrofitted with the Linde  AG high
biomass system  to allow  for  additional treatment whale a parallel
activated  sludge plant  of  equal capacity  is being constructed.
Sponge media were also installed to allow for full  scale evaluation
of the process  for  possible  inclusion in the new treatment plant.
The  existing Munich plant has  three banks of aeration tanks and
during the  site visit, two of the banks had  varying  quantities of
sponges in  place.   Data  from the  plant are summarized in Table 4.

                      Table  4. Munich Data  for 1987.
                Parameter
   Sponge Volume  in Tanks. %
    0          10       .30
         Secondary Influent
              Flow,  mj/d
              BODS,  mg/L
         Secondary Effluent
              BOD5,  mg/L
              TSS, mg/L
         Biomass,  g/L
              Suspended
              Fixed
              Total
         Aeration Tank
              Det'n Time, hr
              F/M, kg/kg-d
              kg BOD5/nr-d
              Sludge Age, days
              SVI, ml/g
              D.O., mg/L
         Aeration Rate
              m^ Air/itr WW
              m /kg BODS Removed
         Secondary Clarification
              SOR, m/hr
              SLR , kg/nr-hr
              R/Q, %
              RAS, g/L
         Waste Activated Sludge
              kg/kg BOD5 Removed
165,100
    186

     21
     20

   2.81

   2.81

   1.91
   0.84
   2.39
    1.3
    145
    2.1

    5.4
     33

   1.08
    3.05
     76
   6.24

   1.08
165,060
    183

     18
     16

   2.90
   1.20
   4.10

   1.90
   0.57
   2.34
    2.0
     95
    2.2

    6.1
     37

   1.08
    3.15
     73
   6.86

   1.02
145,800
    183

     14
     13

   2.77
   1.84
   4.60

   2.15
   0.46
   2.11
    2.3
     90
    2.2

    8.5
     50

   0.95
    2.82
     49
   6.94

   1.03
          'Surface Loading  Rate
                                524

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Of  interest  to note with the Munich data are: 1) the lowering of
the system's F/M by the presence of the fixed film biomass, and 2)
the required increase in aeration  rate  to address  the demand of
additional biomass  in the system.

Olching  (Ring  Lace  System)

During the spring of 1988,  the Olching plant was operating at 85
percent  of its design hydraulic capacity of 35,000 m /day and 83
percent  of  its  design  organic  loading  which  was  based  on  a
population equivalent of 240,000.  In late 1987,  conversion of the
plant  to a high  biomass system began by adding a  new 4,000 rir
denitrification basin and also by  adding 252,000 m of Ring Lace
material  to each of  four  2,070  m3  aeration  tanks.    The  lead
denitrification basin, which contains no Ring Lace and had not yet
been placed in operation at  the time of the site visit, is equipped
with  paddle  mixers  and also contains  aeration  equipment for
nitrification  if necessary.   A portion  of the mixed liquor from the
Ring  Lace  basins  will  eventually  be   recycled  to  the  lead
denitrification basin.  At the time of  the site visit, influent
flow was sent  directly to the  aeration basins containing the Ring
Lace.                                                    .        '

The Ring Lace material was strung  on  racks, with the  individual
strands  being  separated  by  approximately 50 mm.   Spacing between
the racks, which  occupied 31 percent of the  aeration tank volume,
was about 60 mm.  A tensioning system  was  built  into the racks in
case the Ring  Lace material elongates  with time.  In addition to
the above, the equipment supplier had to provide  a 10-year process
performance-and equipment guarantee. Required process performance
was based on  the  plant's discharge requirements of 15 mg/L BOD5,
20  mg/L  TSS  .and  10 mg/L NH4-N,  the  latter  equating  to  an
approximate 75 percent level of nitrification.

Because the Olching Ring Lace plant had been in operation for less
.than  one year  and the  required performance  test  had  not  been
completed, no  operation  or  performance data were released to the
U.S.  EPA . evaluation team.    However,  the.  following  general
observations on the Ring Lace  system  were communicated from the
treatment plant staff.

     o  Before conversion to the High  biomass system, the maximum
        operational MLSS concentration that could be achieved was
        about 1,500 mg/L, which resulted  in the plant operating at
        a F/M of 0.6-0.70 kg BOD5/kg MLSS-day.  At this loading
        rate the MLSS were gray in color and had very poor settling
        characteristics.  In addition, no substantial nitrification
        could be achieved.

     o  After conversion, the suspended biomass varied from 3,500
        to 4,500 mg/1. The fixed biomass on the Ring Lace material
        was estimated at 6.5 g/m which is equivalent to an
        .additional 790 mg/1 of equivalent basin MLSS.  This

                               525

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        increase resulted in a MLSS with a rich browi? color
        that had greatly improved settling characteristics.
        Operating  F/M of the  system decreased to about-0.2 kg/kg-
        day and desire'd levels of nitrification were being
        achieved.

     o  Other high biomass systems were evaluated at the pilot
        plant level by the Olching treatment plant staff and  they
        all yielded effluent qualities equivalent to that realized
        by the Ring Lace system.  However, the Linde AG  system was
        not selected because the  staff felt that this  system might
        require additional electrical power for proper  operation,
        the sponge cubes would be subject to wear by abrasion  and,
        upon extended levels of mineralization, the sponge cubes
        might have a tendency  to settle in the aeration tanks.  The
        Bio-2-Sludge process was not selected because the plant
        staff felt that the synthetic trickling .filter media might
        be subject to plugging by biomass and/or large
        particulates, either of which might lead to anaerobic zones
        in the media.  Such zones,  if they developed,  were felt  to
        potentially limit the nitrification process.

Schomberg  (Bio-2-Sludge' System)

The Schomberg wastewater treatment plant was recently expanded  in
throughput capacity and simultaneously converted  to a Bio-2-Sludge
high biomass system.  Both aeration /tank volume and final clarifier
surface area were more  than doubled and a denitrification section
was  added to the aeration  tankage.   In the spring of  1988, 'the
plant was operating at 20 percent of its design hydraulic capacity
and 57 percent of its design  BOD5 capacity.

Prior  to  conversion, ,  the  plant was  neither hydraulically nor
organically  overloaded,  but  could  not meet  discharge  permit
requirements  primarily because of very poor settling  MLSS.   The
poor settling characteristics would allow the maintenance of only
1,000-1,500  mg/L in the system's aeration  tanks in  spite  of the
very  high RAS pumping  rate employed.   After conversion,  overall
plant performance greatly  increased as  indicated in Table 5.

Installation of the Bio-2-Sludge  system at Schomberg along with the
other plant  modifications greatly enhanced MLSS settleability as
evidenced by the SVI of 82 ml/g after conversion. Although the RAS
rate  at  this plant could have been adjusted' to about 50 percent,
a return  rate of 100  percent  was used.  It  appears that this is a
common design/operational  practice  at smaller  treatment plants in
certain areas of Germany.  Of interest to note is that this plant,
in  addition  to  achieving  an effluent  containing 5  mg/L  BODS,
realized  nearly  complete nitrification.
                              .  526

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               Table 5. Schomberg Data Averages for 1987
                       Parameter
                 Secondary Influent
                      Flow, m /day
                      BODS, mg/L
                      NH4-N, mg/L (Approximate)
                 Secondary Effluent
                      BOD5, mg/L
                      NH4-N, mg/L
                 Biomass,  g/L
                      Suspended
                      Fixed (Estimated)
                      Total
                 Aeration  Tank
                      Detention Time,  hr
                      F/M,  kg/kg-d
                      Kg BOD5/m3-d
                      SVI,  ml/g
                      D.'O.,  mg/L
                 Secondary Clarification
                      SOR,  m/hr
                      SLR,  kg/m -hr
                      R/Q,  %
Value
3,161
  120
   40

    5
  0.4

 3.96
 1.74
 5.70

  6.7
 0.08
 0.45
   82,-
  3.2

 0.18
 1.42
  100
SUMMARY AND CONCLUSIONS

A number of high biomass systems have been installed at wastewater
treatment plants throughout the Federal Republic of. Germany.  These
installations were designed to effect improved effluent quality and
it appears that-this goal  is  being  realized.
               *

Reasons for  selecting high biomass systems over construction of
additional  aeration  tanks and clarifiers  (or  other  secondary
treatment processes) include reduced space requirements, increased
process stability and capital/operating cost savings.

High  biomass   systems  call   for   installation  of  supplemental
equipment over  that contained 'in a conventional activated sludge
plant. More .installed equipment generally implies more maintenance
and, to a .certain  extent, this occurs with some of the high biomass
systems;  In  addition,  the presence of both  suspended  and fixed
biomass forms  and  higher  biomass  concentrations  may require  a
certain level of additional operator time to achieve optimum system
performance.
                               527

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The  presence   of  inert   support  media  and  higher   biomass
concentrations  in  these  systems  can  increase  overall  power
consumption.  To achieve desired mixing patterns and velocities in
retrofitted aeration tanks,  power input  may have to be increased
to overcome additional headless brought about by the installation
of the  inert  support media.   Due to  endogenous  respiration rate
alone   the presence of  additional biomass will  increase system
oxygen requirements which, in  turn, will require .additional power
input    In addition,  high biomass systems generally yield lower
effluent BODS concentrations and/or higher levels of nitrification
which also can effect  overall power  consumption.   Such factors
should be  addressed when analyzing high biomass system operating
costs.

Certain system design limitations have been identified in the past,
but many of these have been  corrected by the system manufacturers
and/or operators.  For example, influent hydraulic  surges  at Linde
AG plants  have caused  blinding of the  retention  screens by the
sponge media.  This has been partially corrected  by increasing the
pumping  rate" of the sponge return system. , Also, abrasion of the
sponge media was stated to result in losses of  less than 5 percent
per year,  but there does not appear to be  a corrective -action for
this system limitation  beyond adding  new sponges as  required.  In
Rincr  Lace  systems,  a question on the extent of media stretching
over time  persists.  Construction of  self-tensioning media racks
may address this potential limitation.  Plugging of the synthetic
trickling  filter media  in  Bio-2-Sludge systems has been a concern
of certain individuals.  It appears that turning on an additional
air  blower periodically for a short  period of  time will  induce
additional sloughing of the  fixed film biomass, thus negating this
potential  problem.   There  were  other  potential  problems areas
communicated  to the U.S. EPA  evaluation team, but their  relative
importance was deemed  minor because  solutions had, for  the most
part,  already been developed and field tested.

Cost of retrofitting a 3,785 m3/day  activated  sludge plant with
high biomass   system  equipment  appears  to  be  $77,000-260,000,
depending on the process selected.  These estimated costs.are_based
 on an activated sludge  plant with six hours of contact time in the -
 system's aeration tanks.

 Additional throughput  capacity realized by conversion< to  a  high
 biomass system cannot be ascertained  from the data and information
 thus far amassed.   However,  it appears conversion  can allow for at
 least the doubling of the biomass concentration in a system and for
 reducing  by  at  least  one-third the required  HAS pumping  rate
 compared  to  a  conventional activated  sludge  plant.   These  two
 factors  alone indicate  the  potential  for increased  throughput
 capacity.
                                 528

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Actual  capacity increase which can be realized by  conversion to a
high biomass system should be established from the conduct of pilot
plant  studies.    Representatives  for both Bio-2-Sludge  and Linde
AG  stated  that  to  obtain  accurate   design  and  operational
information,  a pilot  plant  should have  an  aeration  tank with a
volume  of  at least  100 m .
                                                         .*

ACKNOWLEDGEMENTS

This article was prepared by Arthur J. Condren, PhD of James M
Montgomery, Consulting Engineers, Inc., Pasadena, California  USA-
Bjorn Rusten, PhD of Aquateam Norwegian'Water Technology Centre As'
Oslo, Norway; and James  A. Heidman, PhD  of the U.S. Environmental
Protection Agency, Cincinnati, Ohio, USA.  The authors wish to
acknowledge the assistance of  the  system developers and  facility
operators in providing the data  and information contained in this
.article.  Efforts undertaken on this project  were funded  wholly or
in part by the U.S.  Environmental Protection  Agency under Contract
No. 68-03-3429 to James  M. Montgomery, Consulting Engineers, Inc
                              529

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       EXPERIENCE WITH INTRACHANNEL CLARIFIERS

                    IN THE U.S.A.
                          by

                   James  F. Kreissl
Water and Hazardous Waste Treatment Research Division
        Risk Reduction Engineering Laboratory
         U.S.  Environmental Protection  Agency '
               Cincinnati, Qhio  45268

                  Dr. A.  T.  Wallace
               College of Engineering
                 University of Idaho
               Moscow,  Idaho   83843
        U.S
       Jon  H.  Bender
Technical Support Division
 Office of Drinking Water
Environmental Protection Agency
  Cincinnati,  Ohio  45268
   This -paper has been reviewed in accordance with
   the U.S.  Environmental Protection Agency's peer
   and administrative review policies and approved
         for presentation and publication..
            Prepared for Presentation at:

       Twelfth United States/Japan Conference
           on Sewage Treatment Technology
                  Cincinnati, Ohio

                 October 12-13,  1989

                         531

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INTRODUCTION

     The modern oxidation ditch (OD) which is depicted in
Figure 1, is a high-sludge-age variation of activated sludge or
suspended growth biological treatment system which emanates from
the work of Dr. Pasveer of The Netherlands in 1954.  Since the
time of its introduction in 1973 more than 9200 such plants have
been constructed in the U.S., and are widely perceived as the
state-of-the-art treatment in small-to medium- sized communities
(populations/capacities of 5,000 -to 50,000 (0.5 to 5.0 million
gallons per day (MGD)).  This status has been attained owing to
the OD's simplicity of operation, reliability of performance and
overall cost-effectiveness.

     Intrachannel clarifiers (ICCs) as depicted in Figure 2, were
introduced during the 1980's to replace the conventional external
clarifiers which have been commonly employed for OD facilities in
the U.S.  These systems are marketed by a variety of commercial
entities and are of a variety of configurations (1,2), but in
general are physically placed in the ditch and do not employ,
return sludge thickening and pumping.  Consequently, T0
purveyors have claimed:
ICC
     1.   Lower capital costs owing to elimination of return
          activated sludge  (RAS) pumping and piping facilities

     2.   Lower operation and maintenance.(O&M) costs owing to
         - the elimination of 'RAS facilities and external
          clarifier control problems

 '    3.   Reduced land area requirements by elimination of
          separate aeration and sedimentation structures.

     These claimed advantages served the purveyors well during
the early 1980's as an EPA-sponsored study  (2) in 1987 revealed
approximately 54 systems in design, construction or operation-, of
which  26 were in the  last category.  The majority of these
systems  were approved under the innovative technology provisions
of the USEPA Construction Grants Program whereby they received an
increased Federal grant with potential guarantees of performance.
In fact, the ICC systems were the  second most popular technology
approved under the innovative technology provisions, second only
to ultraviolet light  disinfection.
                                532

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     The most widely employed version of  an ICC  is  known as  a
 BMTS'" system.  Descriptions of this ICC  can be  found in
 references  1 and 2.   For the purpose of  this discussion,  it is
 sufficient  to describe  the  BMTS  system as  one which  has generally
 been field  constructed  integral  with the ditch  structure, as
 shown in Figure 3.   The second and  almost  equally  popular .ICC
 system is the BOAT clarifier.  It  is described in more detail
 in  references 1 and 2.   The BOAT, as opposed to the  BMTS, is
 factory fabricated  and  delivered to the  site for installation in
 a more conventional OD  geometry, and is  schematically displayed
 in  Figure 4.   Since these two types of ICC clarifiers constitute
 46  of the 54 systems noted  in 1987,  much of the remainder of this
 discussion  deals with these two  systems  as subcategories  of ICC
 technology.

      With any degree of popularity  a proportionate degree of
 attention is naturally  drawn,  in this case in the  form  of
 investigative studies and reports.   Early  literature citations
 were generally from the commercial  purveyors and already
 committed clients and were  quite positive  in their nature
 regarding the costs  and perceived benefits of the  technology.
 Several  articles appeared (3,4,5,6)  which  provided some
 performance  and comparative cost data, but the  circumstances and
 assumptions  for the  data presented  were  generally  undefined.  For
 example,  Parsons (5)  described a Florida BOAT system which  was
 estimated to provide 20 percent  capital  cost savings over an
 external  clarifier.   Some articles  (3,4)  published by BMTS
 advocates addressed  the results  of  short-term studies which were
 subsequently adopted as full-scale  design  criteria and  the  basis
 for  cost  savings and other  claims which  provided the stimulus for
 system adoption.

 USEPA STUDIES

      The  USEPA had participated  in  some  of  the conceptual and
 development studies  which led  to the widespread adoption of  the
 ICC  concept  in its role of  assisting new technological  ideas.
 However,  the nature  of  these developmental.projects merely
 identified a  few crucial  areas of concern,   but failed to quantify
 the  extent of  potential  problems in  full-scale application.
 Likewise  an early attempt to generically assess the ICC
 technology was  abandoned  owing to difficulties encountered  in
providing an unbiased assessment without full-scale information
 on systems which approached the ICC concept  from significantly
different directions.   In a 1984 USEPA Seminar Series an attempt
was^made to assess the  status of development of the commercially
available ICC options and to restate generic advantages and
disadvantages of the generic technology  (7).  The advantages were
cited to be:
                               533

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     1.    Elimination of separate clarifiers
     2.    Elimination of sludge return pumps
     3.    Reduced O&M associated with #1 and #2
     4.    Elimination of sludge septicity problems
     5.    Reduced capital and O/M costs.

Disadvantages were listed as:

     1.    Minimal control over sludge blanket depths and return
          sludge flows
     2.    Less operational flexibility.
     3.    Difficulty in adding flocculant aids
     4.    Generally unthickened MLSS wastage
     5.    Unknown response to high peak flows
     6.    Unknown control of bulking sludges
     7.    Unknown scum control effectiveness.

     In a 1986 USEPA Seminar Series on ICC technology, an
assessment based 'several short-term site visits was
presented (8).  Since most installations had been operational for
only a short period, the findings were presented in a manner
designed to identify potential problems which designers and
operators might minimize through awareness.  The most serious
problem identified was the inadequate mixing and aeration
resulting in below critical  (1.0 foot/sec.) horizontal velocities
and inadequate dissolved oxygen in the mixed liquor.  The latter
problem was correctable, since the -total aeration capacity should
be the same for an ICC systems as it is for a conventional OD.
The other common problem identified was the general undersizing
of sludge handling facilities, e.g., thickeners and drying beds.
Other manufacturer-specific problems noted were a need for better
scum removal for ICCs which completely baffle the ditch water
surface, e.g., BMTS, and the need to improve the design
understanding of propeller mixers which impart horizontal
velocity in systems which separate this function from aeration.

     With the advent of significant population of operating ICC
systems a more thorough technology evaluation was initiated in
1987.  This evaluation involved the development of a master list
of available information from the operating  facilities.  From
this list eleven systems were selected  for one-day site visits to
collect more extensive information and  to assess O&M and
laboratory procedures, competence, etc.  The purpose of this
evaluation was to evaluate the true comparative costs of ICC
systems, the design tradeoffs identified by  Bender  (1), and the
relationships between these  factors.
                                534

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 RESULTS

 Costs

      The initial effort on cost comparison dealt with the cost-
 effective analyses supplied by the designers/municipalities  to
 justify their choice of an ICC system over an OD design.   In the
 Construction Grants regulations a 15  percent  cost savings based
 on life cycle costs or a 20 percent net  energy savings is
 generally required to justify designation  as  a innovative
 technology.   For a list of eleven projects, comprised of
 facilities employing only ICC equipment  from  the two  major ICC
 purveyors,  capital cost savings of from  4  to  45 percent were
 claimed by the engineers.   Interpretation  of  these data was
 impossible because of the unequal components.   For example,  ift
 some  cases a 10- to 20-hour ICC aeration time was compared to a
 24-hour aeration time in the OD,  in others no additional  cost for
 the handling of MLSS vs thickened sludge from a conventional
 clarifier was provided,  several others used lower aeration/mixing
 costs for the ICC than the op despite the  fact that the ICC
 creates additional headloss in the channel, and one even  omitted
 preliminary treatment in the ICC.

      Even with bid tabulations from 26 projects indexed to a
 common date the widespread practice of package bidding and
 lumping together of individual contractual  subdivisions made
 quantitative comparisons impossible.   Generally,  bid  prices
 (indexed to the second quarter of 1987)  indicated that small
 (<0.5 MGD)  ICC-based total treatment  systems varied between  $2.00
 and $5.00/gallon of daily  capacity, while  larger  (>2.0  MGD)
 systems varied from $1.00  to'$1.SO/gallon.  Between 0.5 and  2.0
 MGD the scatter reflects the entire spectrum  from $1.00 to
 $5.00/gallon.

      In order to attempt to  compare the  real capital  costs of the
 two technologies it was  decided to  perform quantity takeoffs and
 detailed cost estimates  from some  ICC  system designs  and replace
 those components with  conventional  OD  components using  accepted
 construction  guides supplemented by vendor-installed prices.
 This  technique was  applied to  three BMTS plants with  capacities
 from  0.8  to  1:9  MGD and  resulted  in the  construction costs of
 conventional  OD  being  consistently  less  expensive by  5 to 17
 percent.  A similar analysis  for two BOAT systems  (0.25 and
 0.88 MGD) reveals an even  greater ICC plant cost.  However,
 comparison of bid tabulations  on two recent projects with nominal
plant capacities  from  2.0  and  2.4 MGD showed the capital costs of
BOAT systems to be  less than a conventional OD by only 3 to 5
percent.  Although, there  is inconsistency in these data,  they do
 indicate that the capital  cost of properly designed ICC systems
can be,expected to be  similar to a conventional OD system.
                               535

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Performance

     Performance of operating ICC facilities was compared to
previously analyzed OD facilities to roughly assess whether
significant differences in BOD5 and TSS  were apparent.   The ICC
data were based on the 17 plants which were apparently operating
at a steady state.  The OD data were based on the performance of
29 facilities (8).  The'data shown on figures 5 and 6 indicate
that performance is generally comparable, with slightly higher
effluent concentrations likely attributable to the newness of the
ICC technology in terms of developing operational staff
understanding and problems owing to first-generation design
shortcomings in sludge thickening and aeration/mixing systems.
Subsequent analyses of components provide insight into the latter
problems.  Although clarifier loadings for both sets of data are
comparable, e.g., actual/design clarifier overflow rates  (gal/sq
ft-day) are 357/485 for the OD plants and 357/500 for the ICC
plants, influent wastewater characteristics are not documented.
Therefore, the above comparisons are only qualitative, but lead
one to the conclusion that design overflow rates should be made
at least equal to those of external clarifiers.

Design Tradeoffs

     Bender  (1) has previously  identified the key design
tradeoffs which should be quantified to  fully evaluate the ICC
technology against the conventional OD  alternative.  These key
tradeoffs were identified as:

     O    Waste sludge concentration -  Must the ICC system
          provide external thickening to compensate for the
          internal thickening 'provided  in an external clarifier
          to be fully comparable?

     O    Restriction in aeration  channel flow - How much
          additional mixing power  must  bevemployed to compensate
          for the increased headless of the  ICC placed  in the
          channel?

     O    Aeration channel and clarified maintenance -  Owing to
          the interdependence  of the ICC and the aeration
          channel, will  increased  redundancy in design  (and cost)
          be required to satisfy effluent permit requirements
          while performing major O/M tasks?

     0    Operational flexibility  - Without sludge return
          facilities, how.can  the  O&M  staff monitor control and
          chemically treat  (as necessary) return sludges  to
          control the activated sludge system?
                                536

-------
     The present study was initiated to provide some field
experience for the purpose of quantifying these issues in
addition to analyzing costs and performance information.

Waste Sludge - -                '  "

     Early promotional literature (3,4) dismissed this'issue by
asserting that the required surface area of a thickener is
determined only by the mass of solids entering the unit, and was
therefore identical for the MLSS from an ICC system and the
partially thickened (1 to 1.5 percent solids) underflow from an
external clarifier.  Although other references (9,10,11)
generally confirm this analysis for determining surface area of
the thickener, they also note limitations on hydraulic loading
and on thickener volume which would indeed equate to additional
construction costs for treatment of significantly more dilute
suspensions.  Also, in cases where sludge is removed from the.
plant directly without thickening, additional costs will be
associated with ICC systems owing to increased sludge volume.

     This problem, i.e., inadequate sludge thickening capacity,
was noted as a significant performance limitation at 3 of 11
facilities visited and was reported as a significant problem at
several of the other plants contacted by telephone with
subsequent information submission.  At one ICC facility visited,
the engineer increased thickener capacity such that with the
added capital cost of thickening the ICC was 67 percent more
costly than for the external clarifier alternative.  At the time
of the visit the enlarged thickener was receiving 2,000 to 4,000
mg/L MLSS and yielding an underflow of 2 percent solids.
                               %
     The above information, when combined with the fact that the
average ICC plant-was being loaded at 53 percent of design
organic loading, provides qualitative support for Bender's
concern over the relative thickening requirements for thin MLSS
wasted directly from the ditch or from the ICC with minimal
thickening.  Additional analysis of this design issue is
underway.

Channel Headloss -

     Of all the issues investigated in the present study, this
one appears to be the most serious due both to the fact that
manufacturers tend to dispute that there is a problem and the
general uncertainties on how to properly address the issue.
Actual channel headlosses have not been adequately characterized.
In systems which employ propeller mixers and diffused air
aeration the wall of rising bubbles also represents an additional
                               537

-------
headless on which there is little quantitative data.  Aeration
energy required for an ICC or conventional OD should be the same
for the same detention time and operating conditions, but the
horizontal-shaft mechanical aeration systems commonly employed,
i.e., surface rotors and disks/ provide both mixing and aeration
in a single mechanical function, making total power requirements
to reach the required operating conditions the only means of
comparison between the two applications.  The newer propeller
mixer/diffused aeration designs theoretically permit direct
analysis of each of the two functions.

     Six of the ICC plants investigated in this study which
employed horizontal-shaft mechanical aeration had aerator energy
data.  The total power required in these six plants varied from
6.2 to 91.6 W/m3 of channel volume.   Only one plant was in
steady-state operation with reasonable  (75% of design loading)
organic loading, and it required 12.2 W/m3.   Ettlich (8)  suggests
that 10 to 25 W/m3 is required for ODs to maintain a proper D.O.
(1.0-2.0 mg/L) and V min (1.0 ft/sec), while Hartley (12)
estimates 5 to 10 W/m3 with full baffling.   Measurement of total
energy use by 30 O.D. systems in the field yielded a range of 4
to 78 W/m ' which reduced to a range of  6 to 30 W/m3 in the 11
plants which had reasonable organic and hydraulic loading (13).
Koot and Zeper (14) performed a theoretical hydraulic analysis of
OD systems using the Chezy formula and estimated that 5.0 to 7.5
W/m  are required to provide 1.0 ft/sec velocity  and adequate
aeration.  In comparing the above operating ICC facility with
these ranges, no- quantitative determination is possible,
especially since the average channel velocity in this plant has
been measured to be as low as 0.7 to 0.8 ft/sec and the larger
power-use system operated at 82 hours of detention time.

     However, the placement of an ICC in the ditch/channel will
undoubtedly increase headless -and, therefore, the power required
to maintain any specified velocity.  One promotional report for
the BOAT unit describes studies showing a 15-30% velocity
reduction (15) by their own measurement based on average
velocities in the channel with and without the ICC.  Using the
manufacturer's figures and the horizontal-shaft aerator
relationship (12) between power input and average velocity, i.e.,
average velocity varies as the 0.55 power of the power per unit
volume, the increase in power required to overcome a 15 to 30%
average velocity loss is about 25 to 50% of the effective power.
Therefore, to restore average channel velocity to the original
level, approximately 25 to 50% more power must be applied to the
horizontal shaft aeration/mixing system.  Since the effects of
these constrictions on oxygen transfer are unknown, this increase
is ascribed only to maintaining required channel velocity..
                               538

-------
     The theoretical analysis of Root and Zeper indicated that
mixing, i.e., maintaining a velocity of 1.0 ft/sec, was
approximately 10 percent (0.3-0.4 W/m )  of the total energy
required for shallow OD systems and about 1 percent  (0.1 W/m3)
for deep, short submerged turbine systems, e.g., the Carrousel
system.  Analysis of the operating ICC facilities employing
propeller/mixer these systems yielded only five facilities
operating at reasonable organic loadings  (0.3-1.3 of design
loading) with channel detention times between 17 and 29 hours,
i.e, reasonably conventional OD systems.  The mixing power demand
for these five facilities varied from 4.6 to 29.6 W/m ,  or about
10 to almost 100 times the theoretical mixing requirement
computed by Koot and Zeper.  The ratio of mixing power to total
power demand varied from 23 to 71 percent, and total power/unit
volume varied from 18 to 54 W/m3.

     Even in the early promotional literature-on ICC .systems
inadequate concern over minimum velocities in the presence of
large channel headlosses was apparent.  Average channel
velocities were shown to meet the 1.0 ft/sec standard and the
presence of 0.5 ft/sec velocities at a certain point in the
channel was acknowledged and dismissed (4*).  Attainment of 1.0
ft/sec velocity in the ditch prior to insertion of an ICC has
also been promoted as a proper test of adequate mixing  (6,15).
Field experience at some ICC installations has shown the value of
adjustable mixing systems not only in adapting to different
operating conditions, but also in providing periodic, e.g., once
per week, scouring velocities of at least 1.3 ft/sec to clear
settled s'olids from the bottom of the ditches in ICC systems
which have locations where local velocities are significantly
less than 1.0 ft/sec.  Numerous problems  from poor distribution
of velocities within the channel have been reported by the
operating ICC facilities.

     Clearly, the increased headless in the OD channel due to the
presence of the ICC has substantially"increased the power
requirement for maintaining adequate channel velocities to
prevent biological solids deposition.  However, more data will be
needed to fully quantify this effect.' Since the original claim
of energy savings was based on RAS pumping elimination, the above
power increase must be compared against the power saved by
elimination of RAS pumping.  Middlebrooks, et al,  (16)  indicate
that the power required for return and waste activated  sludge
pumping and conventional clarifier sludge collection are about 3,
percent of aeration requirements for 1-MGD extended aeration
systems.  Also, Wesner, et al  (17) indicate that RAS pumping
and extended clarifier mechanisms require approximately 6 percent
of aeration energy requirements.  Therefore, energy savings
claimed for ICC systems are apparently non-existent or extremely
minor in nature.
                               539

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Additional O&M Problems

     Although several unanticipated O&M problems were discovered
with ICC systems, many were due to design deficiencies.  In
addition to those items described above, preliminary treatment
deficiencies were abundantly apparent in most facilities
employing propeller mixers.  Early systems employed a        
conventional propeller design which became fouled with rags and
debris and resulted in power demand increases, vibrational
imbalances and frequent removal and cleaning efforts by the O&M
staff.  Although replacement with "weedless" blade designs has
reduced this problem, the use of conventional OD preliminary
treatment, e.g., coarse screens and comminutors, has resulted in
scum removal and orifice/baffle opening plugging problems with
certain ICC designs.  Improved preliminary treatment with fine
screens with approximately 0.5-inch openings would be beneficial
in reducing high O&M staff requirements for existing systems and
preventing these problems in new facilities.  Also, the need to
provide good flow distribution across the channel crossection has
become increasingly apparent.  Although problems due to this
inadequacy have been proven soluble, systematic prevention in the
form of design criteria are still forthcoming.

     Other design deficiencies in ICC systems which have resulted
in excessive O&M demands include:

     1.   ICC bottom baffle spacing in BMTS systems - The value
          of wider spacing is under investigation at the largest
          BMTS system.  A frequent problem found at these
          facilities has been the buildup of solids on top of the
          bottom baffles.  This buildup apparently results in an
          inordinate percentage of the MLSS being accumulated in
          the ICC instead of freely returning to the channel.
          These conditions cause an apparent reduction in
          effective solids retention time (SRT)  in the channel.
          and result in deteriorating system performance until
          corrected.

     2.   Effluent orifice pipe design in BMTS - The outlet
          orifices of the BMTS system are submerged and can .
          result in significant water level changes, e.g., a 9-
          inch difference was recorded at one small BMTS plant.
          This water level swing can make slotted scum trough
          removal systems ineffective and increase O&M labor
          requirements.   This problem can be solved by designing
          auxiliary weirs in the effluent collection box or by
          modifying scum collection troughs for a varying water
          level.
                               540

-------
     3.   Placement and design of propeller mixers and diffusers
          - The performance of propeller mixing systems in ICC
          systems has been a learning experience for both mixer
          suppliers and design engineers.  The headlosses
          represented by the ICC systems and the banks of
          diffusers must be accounted for in determining power
          requirements to attain a 1.0 ft/sec minimum ditch
          velocity.  For systems which vary ditch dimensions such
          that velocities vary over a wide range, the deposition
          of solids has been controlled through periodic higher
          ditch scour velocities.

SUMMARY AND CONCLUSIONS                                          -

     ICC^systems appear to be a viable alternative to a
conventional oxidation ditch.  Technologically, the ICC concept
can provide secondary treatment if the same overflow rates are
employed as are used in the design of external darifiers.  Early
problems with ICC systems appear to be amenable to improved
design procedures which provide better preliminary treatment to
minimize rags and debris, proper mixing to insure a maintenance  >
of at least a 1.0 ft/sec minimum velocity, and adequate sludge
handling and thickening capacities.  Cost savings are not
inherent with ICC designs, so the relative advantages and
disadvantages of this technology must be thoroughly analyzed for
each potential application.
                               541

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REFERENCES

      1.
      8,
      10,
      11.
      12,
Bender, J.H. "Assessment of Design Tradeoffs When
                   Using Intrachannel Clarifiers."
Jour. WPCF, 59, 871-6    (Oct. 1987).

Zirschky, J.H. "Intrachannel Clarification State of the
Art."  USEP Technology Transfer Seminar, Field
Evaluation of I/A Technologies. Handout No. CERI-86-22
(Aug. 1986).

Novak, J.T., and Christopher, S.A. "The Use of
Intrachannel Clarification in the Design of Oxidation
Ditches." in Civil Engineering for Practicing and
Design Engineers. 2_, 45-55 (1982) .

Christopher, S.A., and Titus, R.L. "New Design Combines
Concepts to Cut Costs."  Pollution Engineering, 16>, 40-
2 (Mar. 1984).
          Parsons, W.C.  "A New  Concept  in  Clarifiers."
          Works Jour.,  118.  61-2  (Oct.  1987).
                                              Public
Stensel, H.D. "Oxidation Ditch Modification Shows
Promise."  Water/Engineering and Management, 134, 10,
40-2  (May 1987).

Bowker, R.P.G.  "In-Channel Clarification." USEPA
Technology Transfer Seminar, New Municipal Wastewater
Treatment Technology, Handout No. CERI-84-16 (April
1984).

Ettlich, W.F. "Performance Capabilities and Design of
Oxidation Ditch Processes" in Proceeding of Operation
and Maintenance of POTW's. USEPA Publication No.
600/9-83-021  (Dec. 1983) .

USEPA.  Process Design Manual for Sludge Treatment and
Disposal.  USEPA Publication No. 625/1-79-011  (Sept.
1979).                                      ,

Fitch, B. "Batch Tests Predict Thickener Performance."
Chemical Engineering, 78. 83-8  (Aug. 1971).

Scott, K.J. "Continuous Thickening of Flocculated
Suspensions.11   Ind. Eng. Chem. Fundamentals, 9., 422-7
(Mar. 1970).                    '                    

Hartley, K.J. "Hydraulics of Horizontal Shaft  Oxidation
Ditches.1^  Jour. WPCF, 59, 686-94 (July 1987).
                                542

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13.
14.
15.
16.
17.
Weston, R.F., Inc.  "Evaluation of the  Energy
Requirements  for Oxidation Ditches" USEPA-OWPO  Report
No. 18, Contract No.  68-01-6737.    

Koot, A.C.J.  and Zeper, J. "Carrousel, A New Type  of
Aeration-System with  Low Organic Load."  Water
Research,              -  
.6, 401-6  (Apr.-May  1972).

Smalley, Wellford and Nalven, Inc. Report to Central
County Utilities. Inc. on Selection of Clarifier System
for CCUI Wastewater Treatment Plant (March 1984).

Middlebrooks, E.J. and Middlebrooks, C.H. Energy
Requirements  for Small Flow Wastewater Treatment
Systems.  U.S. Army Corps of Engineers Cold Regions
Research and Engineering Laboratory Special Report 79-7
(April 1979).

Wesner, G.M., Gulp, G.L., Lineck, T.S.  and Hinrichs,
D.J.  Energy Conservation in Municipal Wastewater
Treatment.  U.S.  EPA Report No.  430/9-77-011 (March
1978) .
                         543

-------
                                        WAS
                     SLUDGE RETURN SYSTEM
                 f
    INFLUENT
            OXIDATION DITCH
                                    SECONDARY
                                    CLARIFIER
                                              EFFLUENT
Figure 1.
CONVENTIONAL OXIDATION DITCH SYSTEM
     INFLUENT
                                    WAS
                                  THICKENER
             OXIDATION DITCH
                                    INTRACHANNEL
                                     CLARIFIER
                                              EFFLUENT
                 OXIDATION DITCH WITH
               2. INTRACHANNEL CLARIFIER
                          544

-------
                   AERATION ZONE

CLARIFIER
}
' \

t
                      EFFLUENT
    UPSTREAM END WALL
                        SUBMERGED ORIFICE
                        DISCHARGE PIPES
   CLARIFIER
BOTTOM BAFFLES
                                    DOWNSTREAM
                                    END WALL
                                            AERATION
                                            CHANNEL
         Figure 3.
BMTS SYSTEM
(2)
                        545

-------
                   AERATION ZONE
                   	A
                 BOAT CLARIFIER }
                   	^X^,
    AERATION CHANNEL
                                BOAT CLARIFIER
   SLUDGE HOPPERS

         ==
                               WEIR
        INLET
                        SLUDGE RETURN PORTS
Figure 4.
UNITED INDUSTRIES BOAT CLARIFIER (21
                       546

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           EFFLUENT BOD5  PERFORMANCE
        5O
        40
     O
     O
     CO
     l-
     -3L
     UJ
     1U
       30
       20
       10
                             -iii	1	1
DATA FROM 17
INTRACHANNEL
CLARIFIER PLANTS
(EPA, 1988)
                     _L
                                  DATA FROM 12
                                  CONVENTIONAL
                                  OXIDATION DITCH
                                  PLANTS
                                 (ETTUCH,1978)
                              -JI	1    II
         1     5  10  2O 304050607080  90 95    99

Figure 5.   PERCENT OF TIME VALUE WAS LESS THAN OR EQUAL TO
                         547

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      10
             EFFLUENT SUSPENDED

             SOLIDS PERFORMANCE
DATA FROM 17
INTRACHANNEL
CLARIFIER PLANTS
(EPA, 1988)
                   DATA FROM 12
                   CONVENTIONAL
                   OXIDATION
                   DITCH PLANTS
                   (ETTLICH.1978)
             5  1O  2O 3O4O506070 80  90  95
                                 99
Figure 6. PERCENT OF TIME VALUE WAS LESS THAN OR EQUAL TO
                4U.S. GOVERNMENT PRINTING OFFICE:  1990-718-159/20162
                          548

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