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                                             EPA/600/9-36/015C
                                             July 1986
                    PROCEEDINGS



        TENTH UNITED STATES/JAPAN  CONFERENCE
           ON SEWAGE TREATMENT TECHNOLOGY

                OCTOBER 17-18, 1985


                        AND


NORTH ATLANTIC TREATY ORGANIZATION/COMMITTEE  ON  THE
CHALLENGES OF MODERN SOCIETY  (NATO/CCMS) CONFERENCE
           ON SEWAGE TREATMENT TECHNOLOGY

                OCTOBER 15-16, 1985

                 CINCINNATI,  OHIO
                     VOLUME  II.

NORTH ATLANTIC TREATY ORGANIZATION/COMMITTEE  ON  THE
  CHALLENGES OF MODERN SOCIETY  (NATO/CCMS)  PAPERS
        U.S. ENVIRONMENTAL PROTECTION AGENCY
         OFFICE OF RESEARCH AND DEVELOPMENT
               CINCINNATI, OHIO 45268

            n S Environmental Protection Agency
            Region 5, Library (PL-12J)
            77 West Jackson Boulevarjd, 12th Floor
            Chicago, tl 60604-3590

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                     NOTICE

This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication.  Mention of trade names
or commercial products does not constitute endorse-
ment 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 Japan-United States-North
Atlantic Treaty Organization/Committee on the Challenges
of Modern Society (NATO/CCMS) Conferences on Sewage Treat-
ment Technology completed their conferences in  Cincinnati,
Ohio, in October 1985.  Scientists and engineers of the
participating countries were given the opportunity to study
and compare the latest practices and developments in Canada,
Italy, Japan, The Netherlands, Norway, the United Kingdom and
the United States.  The proceedings of the conferences comprise
a useful body of knowledge on sewage treatment  which will be
available not only to Japan and the NATO/CCMS countries  but
also to all nations of the world who desire it.
                        Lee M. Thomas
                        Administrator
Washington, D.C.
                             fii

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                              CONTENTS


Foreword	iii

Japanese Delegation  	  vi

United States Delegation 	 vii

North Atlantic Treatment Organization/Committee on the
   Challenges of Modern Society (NATO/CCMS) Delegation 	viii

Volume I.
   Part A.  Japanese Papers	   3

Volume I.
   Part B.  United States Papers	367

Volume II.
   North Atlantic Treaty Organization/Committee on the
   Challenges of Modern Society (NATO/CCMS) Papers 	 633

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                           JAPANESE DELEGATION
DR. TAKESHI KUBO
  Head of Japanese Delegation,
  Counselor, Japan Sewage Works Agency

TOKUJI ANNAKA
  Chief, Water Quality Section
  Water Quality Control Division
  Public Works Research Institute
  Ministry of Construction

DR. KEN MURAKAMI
  Deputy Director, Research and
  Technology Development Division
  Japan Sewage Works Agency

DR. KAZUHIRO TANAKA
  Chief Researcher, Research and
  Technology Development Division
  Japan Sewage Works Agency

KENICHI OSAKO
  Chief, Eastern Management Office
  Sewage Works Bureau
  Tokyo Metropolitan Government

SAKUJI YOSHIDA
  Chief, Facility Section
  Construction Division
  Sewage Works Bureau
  City of Yokohama

YUKIO HIRAYAMA
  Director, Planning Division
  Sewage Works Bureau
  City of Fukuoka

MASAHIRO TAKAHASHI
  Extraordinary Participant,
  Researcher, Sewerage Section
  Water Quality Control Division
  Public Works Research Institute
  Ministry of Construction

TAKASHI KIMATA
  Extraordinary Participant,
  Researcher, Research and Technology
  Section, Research and Technology Division
  Japan Sewage Works Agency

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                           UNITED STATES DELEGATION
JOHN J. CONVERY
 General Chairman of Conference and
 Head of Cincinnati U.S. Delegation
 Director, Wastewater Research Division
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnai, OH 45268

DOLLOFF F. BISHOP
 Co-Chairman of Conference
 Chief, Technology Assessment Branch
 Wastewater Research Division
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268

FRANCIS T. MAYO
 Director,
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268

LOUIS W. LEFKE
 Deputy Director,
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268

DR. JAMES A. HEIDMAN
 Environmental Engineer
 Innovative & Alternative Technology Staff
 Systems & Engineering Evaluation Br., WRD
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268

HENRY H. TABAK
 Research Chemist,
 Toxic Research & Analytical  Support Staff
 Technology Assessment Branch, WRD
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268

DR. ALBERT D.  VENOSA
 Microbiologist,  Ultimate Disposal Staff
 Systems & Engineering Evaluation Br., WRD
 Water Engineering Research Laboratory
 U.S. Environmental Protection Agency
 Cincinnati, OH 45268
ARTHUR H. BENEDICT, Ph.D.
 Brown & Caldwell Consulting Engrs
 P.O. Box 8045
 Walnut Creek, CA 94546-1220

DR. WILLIAM C. BOYLE
 Dept. of Civil Engineering
 & Environmental Engineering
 University of Wisconsin
 3230 Engineering Building
 Madison, Wisconsin 55706

DR. MICHAEL CARSIOTIS
 Dept. of Microbiology
 & Molecular Genetics
 University of Cincinnati
 College of Medicine
 231 Bethesda Avenue
 Cincinnati, OH 45267

DR. CLEMENT FURLONG
 Dept. of Medical Genetics, SK50
 University of Washington
 Seattle, WA 98195
GILBERT B. MORRILL,  P.E.
 McCall, Elingson, Morrill,
 Consulting Engineers
 1721 High Street
 Denver, CO 80218
Inc.
DR. GEORGE PIERCE
 Battelle-Columbus Laboratories
 505 King Avenue
 Columbus, OH 43201

DR. JOHN N. REEVE
 The Ohio State University
 Dept.  of Microbiology
 484 West 12th Avenue
 Columbus, OH 43210-1292

DR. H.  DAVID STENSEL
 Dept.  of Civil Engrg, FX-10
 University of Washington
 Seattle, WA 98195
                                    vn

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       NORTH  ATLANTIC  TREATY ORGANIZATION/COMMITTEE ON THE CHALLENGES
                  OF MODERN SOCIETY  (NATO/CCMS) DELEGATION


DR. J. DUANE  SALLOUM
 Chairman of  NATO/CCMS Committee
 Director, Technical  Services  Branch
 Environmental  Protection Service
 Ottawa, Canada K1A 1C8

DR. B. E. JANK
  A/Director,
  Wastewater  Technology Centre
  Canada Centre for Inland Waters
  P.O. Box 5050,
  Burlington, Ontario  L7R 4A6
  Canada

DR. ROLF C. CLAYTON
  Director,
  Process Engineering
  Water Research Laboratory
  Elder Way,  Stevenage, Herts, SGI  1HT,
  England

DR. IR. WILHELMUS H.  RULKENS
  Department  of Environmental  Technology
  Division of Technology for  Society
  MT/TNO
  P.O. Box 342, 7300  AH Apeldoorn
  The Netherlands

DR.ING. BJ0RN RUSTEN
  Aquateam, Norwegian  Water Technology Centre A/S
  P.O. Box 6593
  Rodelrfkka,  N-0501 Oslo 5,
  Norway

DR. MARIO SANTORI
  Institute di  Ricerca sulle  Acque
  Consiglio Nazionale delle Ricerche
  Rome, Italy 00198
                                   vm

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  DELEGATES TO THE NATO/CCMS CONFERENCE AND THE TENTH UNITED STATES/
           JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
ANDREW W.  BREIDENRACH ENVIRONMENTAL RESEARCH CENTER,  CINCINNATI,  OHIO

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DR. JOHN H.  SKINNER,  DIRECTOR,  OFFICE  OF  ENVIRONMENTAL  ENGINEERING
 AND TECHNOLOGY,  MR.  FRANCIS  T.  MAYO,  DIRECTOR,  WATER ENGINEERING
   RESEARCH  LABORATORY,  U.S.  EPA AND DR.  TAKESHI  KUBO,  HEAD  OF
  JAPANESE DELEGATION AND COUNSELOR, JAPAN  SEWAGE WORKS AGENCY
   MR. DOLLOFF F. BISHOP, U.S. DELEGATE AND DR. ROLF C. CLAYTON,
             NATO/CCMS DELEGATE FROM THE UNITED KINGDOM

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  VIEW OF CAPTOR WASTEWATER TREATMENT PROCESS
 TEST AND EVALUATION FACILITY, CINCINNATI,  OHIO
   VISIT TO THE MULTIPLE DIGESTION PROJECT,
TEST AND EVALUATION FACILITY, CINCINNATI, OHIO

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            NORTH ATLANTIC TREATY ORGANIZATION/COMMITTEE ON THE
              CHALLENGES OF MODERN SOCIETY (NATO/CCMS) PAPERS


CANADIAN ADVANCES IN SLUDGE MANAGEMENT TECHNOLOGY	    635
   H.W. Campbell, T.R. Bridle, P.O. Crescuolo, and B.E. Jank,
   Environment Canada, Environmental Protection Service,
   Wastewater Technology Centre, Burlington, Ontario, Canada

ITALIAN ADVANCES IN WASTEWATER TECHNOLOGY	    661
   Mario Santori, Institute di Recerca sulle Acque, Consiglio
   Nazionale delle Ricerche, Rome, Italy

JAPANESE ADVANCES IN WASTEWATER TREATMENT	    719
   Takeshi Kubo, Dr. Eng., Counselor, Japan Sewage Works
   Agency

DEVELOPMENTS IN THE FIELD OF WASTE WATER TECHNOLOGY IN THE
NETHERLANDS	    793
   A.B. van Luin and W. van Starkenburg, Governmental Institute for
   Sewage and Waste Water Treatment, Inland Waters Department,
   Lelystad, The Netherlands; and W.H. Rulkens and F. van Voorneburg,
   Netherlands Organization for Applied Scientific Research, Division
   of Technology for Society, Apeldoorn, The Netherlands

NORWEGIAN ADVANCES IN WASTEWATER TREATMENT 	    827
   Dr. ing. Bjtfrn Rusten, Aquateam, Norwegian Water Technology
   Centre A/S, Oslo, Norway

RESEARCH AND DEVELOPMENT IN DOMESTIC WASTEWATER TREATMENT IN THE UK.  .    851
   Staff of WRC Processes, Water Research Centre, Elder Way,
   Stevenage Herts, United Kingdom

ADVANCES IN WASTEWATER TREATMENT AND SLUDGE MANAGEMENT PRACTICES
RELATED TO PATHOGEN AND TOXICITY CONTROL 	    879
   J.J.  Convery,  D.F. Bishop, and A.D. Venosa, Wastewater
   Research Division, Water Engineering Research Laboratory,
   U.S. Environmental Protection Agency, Cincinnati, Ohio, USA
                                     633

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                  NORTH ATLANTIC TREATY ORGANIZATION/
             COMMITTEE ON THE CHALLENGES OF MODERN SOCIETY
               CONFERENCE  ON SEWAGE TREATMENT TECHNOLOGY

                            CINCINNATI, OHIO
                          OCTOBER 15-16, 1985


       A Committee on Advanced Wastewater Treatment of the North
Atlantic Treaty Organization/Committee on the Challenges of Modern
Society (NATO/CCMS) held a conference on sewage treatment technology
in Cincinnati, Ohio, on October 15-16, 1985.  The NATO/CCMS Committee
on Advanced Wastewater Treatment, chaired by Dr. J. Duane Salloum of
Canada, included delegates from six NATO countries: Canada, Italy,
the Netherlands, Norway, the United Kingdom and the United States.

       The conference on sewage treatment technology featured National
papers on advances in wastewater treatment and sludge management technology
in the participating NATO countries.  Highlights of the conference included:


          A Canadian report on improved control of sludge dewater-
          ing and on conversion of sludge to oil;
          Italian advances on control  of toxic  metals and innovative
          anaerobic treatment of wastewaters;
          Dutch studies on toxics removal  and disposal  of sludges;
          Norwegian advances in sludge management,  nutrient control
          and septage handling;
          British advances in sludge digestion and improved manage-
          ment of wastewater treatment plants; and
          American advances in wastewater treatment and sludge
          management related to control  of pathogens and toxics.
                                   634

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CANADIAN ADVANCES IN SLUDGE MANAGEMENT TECHNOLOGY
                        by
       W. Campbell,  T.  R.  Bridle,  P.  J.  Crescuolo
          and B. E.  Jank
       Environment Canada
       Environmental Protection Service
       Wastewater Technology Centre
       P. 0. Box 5050
       Burlington, Ontario,  L7R 4A6
       Canada
        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.
 North Atlantic Treaty Organization/Committee on the
 Challenges of Modern Society (NATO/CCMS) Conference
            on Sewage Treatment Technology
           j
                October 15-16, 1985
                  Cincinnati, Ohio
                         635

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                CANADIAN ADVANCES IN SLUDGE MANAGEMENT TECHNOLOGY

                by:  H.W. Campbell, T.R. Bridle, P. J. Crescuolo
                       and B.E. Jank
                     Environment Canada
                     Environmental Protection Service
                     Wastewater Technology Centre
                     P.O. Box 5050
                     Burlington, Ontario, L7R 4A6
                     Canada
                                  ABSTRACT
     Two new approaches to sludge management in the sewage treatment industry
have been developed over the past few years.  A new concept in automated
control of the conditioning and dewatering of sludge using rheology as the
control approach optimized the dewaterability of sludge while minimizing the
cost of polymer addition.  The control strategy used a computer algorithm
which correlates the Theological properties of the sludge measured by a
viscometer with polymer demand.  The viscometer and polymer feed pump,
interfaced to the computer, were successfully used by the control algorithm
to automatically adjust the polymer flow rate.  In a second approach, the
conversion to sludge to oil has been developed at batch and continuous pilot
scale as an attractive alternative to the sludge disposal options currently
in operation.  The conversion process, at 300 to 500C heating dried sludge
in a nitrogen atmosphere, successfully produced oil and char from sludge.
The process was stable with typical oil yields of 25.4 percent, char yields
of 61.1 percent and non-condensable gas of 11.1 percent.  The oil viscosity
under optimum operating conditions was 33.7 centistokes.
                                     636

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                                  INTRODUCTION
    Sewage  sludge  is  an unavoidable  by-product of  wastewater treatment  and
roughly  one tonne  of  sludge is generated  per  4>540 nr  (1.0  million gallons)
of wastewater  treated  (1).    Disposal  of sewage sludge is an expensive process
and normally  constitutes up to 50% of  the  total annual costs   for wastewater
treatment.   It   is estimated  that over 500,000 tonnes  of  dry  sewage sludge
are produced annually  in Canada and disposed of at a total  cost of about $104
million   (2).     Major   sludge  disposal  options  used  in   Canada  include
agricultural   utilization,   landfilling  and  incineration,   with  estimated
disposal  costs ranging  from about $126/tonne  for  agricultural utilization to
over  $300/tonne  for incineration (3).

    The  problems of sludge  disposal  are expected  to  intensify in  the future
due to a number  of factors.  The total  cost of  sludge disposal will increase
as the quantity  of  sludge to be disposed of,  increases. The  fraction of sludge
disposed  of by  agricultural utilization will probably  decrease  due  to  the
problem  of  finding  suitable  land within  a   reasonable distance  of  large
population  centres.  Potential  restrictions  on the loading rates  for sludges
with  high levels of  heavy  metals may  also  contribute to  a  decline  in this
practice.    The feasibility of landfilling will decrease as public opposition
to the licensing of new disposal sites continues to grow.

    It would  appear that  the  immediate  future in sludge disposal technology
will  feature  a trend  towards more complex systems, which also implies higher
costs. This will  be especially  true for the large urban areas  where the impact
of  the above  factors  will  be  most  keenly felt.   In order to control costs,
alternative resource recovery oriented solutions based on either the upgrading
of current  technology  or the implementation of  new technology, are needed.

                              TECHNOLOGY REVIEW
    Upgrading   current   technology   has   been   primarily   concerned   with
improvements  in  dewatering and  incineration.   The  trend  has  been  towards
considering  sludge  treatment from  an  overall systems   design approach.   The
incentive  for  upgrading has    been provided by the large  increases in energy
costs over the  last ten years, and  the  realization of how  energy  inefficient
most  incinerator  installations  were.    In  1973  when  natural  gas cost  3.6
cents/m ,  it was economically  justifiable  to incinerate sludge  cakes  of only
15  to  18% total  solids.   Today,  natural  gas costs  are in  the order  of  18
cents/m3,  and  more  cost-effective methods  of accomplishing  moisture  removal
must be implemented.
                                      637

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    Modifications which have  been designed to either  increase  cake solids  or
improve the amount of energy recovered from an  incinerator system  include  the
following:
     1.Upgrading from vacuum filters to belt or membrane presses.
     2.The  use  of  incinerator  off-gases  to  dry  a  portion  of  the   sludge
       stream.
     3.Modification of incinerator burners to use digester gas  as fuel.
     4.Modifications  to  multiple-hearth  incinerators  to  allow  very   dry
       cakes to be introduced on an intermediate hearth.
     5.Waste  heat  recovery to  generate  steam, which  can in turn  be used  to
       drive other processes such as thermal conditioning.
In Canada, the improvements described above are either  still  in the  design  and
construction  phase  or  have only  been  in  operation  for  a  relatively  short
period of time.  Consequently,  reliable information is not yet available with
respect to the cost of the modifications  or their effect on the energy balance
of the system.

     Another  approach to  offset costs is  the  introduction of  process  control
to make treatment systems more  efficient.   This  is being investigated for  the
treatment of  the liquid  train in  areas  such  as dissolved  oxygen  control  in
aeration  basins,  control  of  sludge  inventories  and  the control  of pumps  in
lift stations,  and  shows  promise of  realizing  substantial savings.  With  the
large expenditures being committed to sludge processing it seems reasonable to
assume  that comparable  savings  could  be  achieved  by  the  implementation  of
process control.   One of  the major  drawbacks  to this has  been  the lack  of
sensors  capable  of  measuring  sludge  characteristics and  consequently most
attempts  have  had  to rely on  indirect  measurements.   Knudsen  and  Mathes  (4)
evaluated a strategy to control  chemical conditioning, vacuum filtration  and
multiple-hearth  incineration.   Indirect  measurements  had to  be used  because
sensors  for the on-line  measurement of  sludge  dewaterability,  cake  moisture
and  sludge  calorific value  were not  available.    Under these  circumstances,
they  were  still able  to  show  a  saving  of approximately 26%  in  chemical
conditioning costs.

    Alternative  technologies  also  offer  the  potential  for  improved  energy
recovery  and  decreased cost.One  of the  most  advanced is the  Hyperion  Energy
Recovery  System currently  being installed  in Los  Angeles  (5).  This  system
comprises digestion, dewatering,  Carver-Greenfield  dehydration and starved air
fluid  bed  incineration of  the  sludge   derived  fuel.  It is   estimated  that
processing  366  tonnes  of  raw sludge per  day will  generate a total of 25 MW of
electricity,  with 10 MW  available  for  sale back  to  the  local utility.  The
complete  plant  is expected  to be  in operation  by  late 1985.

     Sludge  liquefaction  has  been reported  as  a  viable method   for  energy
production  from sewage sludge,  but the  technology is  still  in  its  infancy.
Researchers   from  Battelle   Northwest  Laboratories   have   reported   on  a
sophisticated  process  consisting   of   sludge   alkaline   pretreatment   and
subsequent  autoclaving at  320C  for one  hour  at   10,000 kPa under  an Argon
atmosphere  (6).  This process  produces  oil, asphalt and  char,  with oil yields
ranging  up  to  15%  (on a  total  sludge  solids  basis).   The technology  is
currently being  evaluated  at  pilot  scale.
                                      638

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     The basic concept of low temperature pyrolysis of  sewage  sludge  to  produce
 fuel products has been known for many years  (7).  Recently, German researchers
 have made significant advances in understanding the mechanisms by which sludge
 is converted  to oil  (8).  They  heated dried sludge to 300-350C in an oxygen
 free  environment for about  30  minutes.    The  researchers  postulated  that
 catalysed vapour phase  reactions converted  the organics  to  straight  chain
 hydrocarbons, much  like  those  present in  crude  oil.   Analysis of the  product
 confirmed that aliphatic hydrocarbons were produced,  in contrast to all  other
 processes which produce  aromatic  and  cyclic  compounds,  whether   utilizing
 sludge,  cellulose or  refuse as  the substrate.   The  German  researchers  have
 demonstrated oil yields  ranging  from  18-27% and char yields  from 50-60%.  The
 oil had a heating value of approximately 39 MJ/kg and  the char about 15 MJ/kg.

      Environment Canada's Wastewater Technology Centre is currently developing
 two processes  which  involve  both  approaches  to upgrading  sludge management
 practices.    The  first  process  which  will be  discussed  is  an example of
 upgrading existing  technology  and  consists of  developing  a method  for the
 automatic control of  polymer addition for sludge conditioning.   This work is
 based on  the  concept that  measured rheological  properties  can be  used to
 predict  the  dewaterability of a  sludge.  The second  process is the conversion
 of sludge to solid and  liquid  fuels,  and  is  an  example  of alternative new
 technology.   The conversion process  under evaluation  is  carried out  at low
 temperature  and atmospheric pressure.
                          AUTOMATIC POLYMER CONTROL
BACKGROUND

     Rheology can  be  defined as the study  of  the properties and  behaviour of
matter  in  the  fluid  state.    Most  single-phase  fluids  exhibit  Newtonian
behaviour  in that  the  rate of  viscous  flow is  proportional to the  shear
stress.  The addition of  solid  particles  to the  fluid  interferes with the free
flow of  the  dispersion medium  to a degree that is dependent  on  the  rate of
shear.   Dispersed  systems such as  these can exhibit  a variety of rheological
behaviours  including  plastic,  pseudoplastic  and  altered  Newtonian.    Most
sewage   sludges  have   been  interpreted   as  exhibiting  either   plastic  or
pseudoplastic  flow (9). They may or may  not possess  an initial characteristic
yield  stress  depending on the  shape of the flow curve  and the definition of
yield  stress.

     The  rheology  of  sewage sludge  is further  complicated by the  fact that
most sludges  are also thixotropic, meaning they possess  an  internal structure
which  breaks down  as  a  function of  time  and  shear  rate.   A flow  curve or
                                     639

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rheogram  (Figure  1)  of  a typical  sludge,  showing  the curves  produced by  a
rotating viscometer during the increasing and  decreasing rate of shear cycles,
indicates that the rheology  of the  sludge has been altered during  the initial
(increasing)  phase  of  the  test.    The displacement   of  the  two curves  is
referred to as a hysteresis  loop  and  is a measure of the degree of thixotropy
exhibited by the sludge.
               250
               200-

            LLJ
            CC.
            55
            QC
            CO
                        100     200    300     400     500

                                   SHEAR RATE (s~1)
                                                          600
                                                                700
             Figure 1. Typical rheogram illustrating thixotropy.

     The concept of using  rheology  as a control measure arose  out  of a sludge
characterization  study conducted  at  the  Wastewater  Technology Centre  (WTC)
(10).  The  general relationship between sludge rheology and  polymer addition
shown  in  Figure 2 was consistent for  all  sludges tested and  resulted in two
important observations.  Firstly, the initial  shear stress  or yield stress was
observed to  increase  as the polymer  dosage increased.  Secondly,  the polymer
dosage (6 kg/t)  which resulted in  an initial peak  or point of  inflection in
the  rheogram compared favourably  with that  dosage which  produced efficient
performance during concurrent  pilot-scale dewatering  trials.   The  fundamental
assumption  which prompted  evaluation of  rheology  as  a means  of  control was
that optimum conditioning  of  the  sludge would be achieved when  a  peak became
evident in the rheogram.

     The  use  of  rheology  as  a  basic  parameter  required that  a standardized
laboratory methodology be  developed  (11).   This  included  both  the  method of
adding the  polymer and  the method  of operating  the  viscometer.   The method
selected  for  adding  chemicals  (polymers)  to  the  sludge,  consisted  of adding
the  required volume   of  polymer  over a  10-second period,  while  mixing  the
sludge at  1000  rpm  by  a   standard  stirrer developed by  the  Water Research
                                     640

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Centre  (12).   A Haake  Rotovisco RV3 rotational  viscometer with a MVTI sensor
system  (gap width = 2.5  mm)  was used  for  all  rheological  measurements.   The
acceleration  rate was  standardized at 75  rpm/min and the damping option was
not utilized.
               300
                        POLYMER DOSE
                        (kg/tonne)
                       100    200    300    400    500    600    700
                                  SHEAR RATE (s"1)
                                                                800
              Figure 2. Rheograms  of  polymer conditioned sludge.

     The  second  phase of  the  study  (13)  demonstrated  the   sensitivity  of
rheograms  to  changes  in  sludge  dewaterability  and  solids  concentration.
During this  phase the  viscometer equipment  was  upgraded to a Haake RV-100 and
was  interfaced to  a  real-time  computer.   Experiments  were  conducted using
sludge  conditioned  in batch  samples  and  analyzed  in  the  batch mode  on the
viscometer.    The   results  indicated  that  rheological   measurements  were
sufficiently sensitive to quantitatively identify differences between sludges,
the  effect  of  polymer  addition,  the  effect  of changes   in  sludge  solids
concentration  and  the  effects   of   changes  in  dewaterability  induced  by
detergent addition.

PILOT-SCALE CONDITIONING SYSTEM

     The  most recent  stage  of the  program  involved  the  development of  a
continuous-flow,  pilot-scale sludge  conditioning system, the  modification of
the  viscometer to  function  on-line  and  the  development  of  a  preliminary
control strategy.

     A schematic  drawing of  the  pilot-scale  conditioning  set-up is  shown in
Figure 3.  The sludge  storage  tank  was  capable of holding approximately 1200 L
                                      641

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of  sludge   and   was  equipped  with   a  variable  speed   mixer  to  prevent
sedimentation.   The  sludge  pump was  a variable  speed positive displacement
Moyno pump with  a range of 0.05 to 0.37 L/s.   Solids  concentration was varied
by the  addition  of  dilution water  to the  suction side of the  sludge  pump.
Cationic  polymer was injected into  the sludge line just prior to the in-line
mixer.   The  in-line mixer  was housed in  a  clear PVC pipe  section  (47  mm
internal  diameter,  470  mm long) and  consisted of  a  series of  six stainless
steel, helical elements  welded together.   Each element was  approximately 75 mm
long  and  rotated the  flow through  180,  with adjacent elements being offset
by 90.   The  sludge flowed  into the  flocculator  through  the  bottom of the
tank and drained through an overflow.   Although a mixer was provided to ensure
good mixing of the conditioned sludge,  the final methodology involved shutting
off the  mixer during the viscometer run  in order to reduce turbulence.   The
viscometer  sensor system was attached to  a  bracket  such that it  could  be
lowered  into the  conditioned sludge   in  the  flocculator.   Experiments  were
conducted at a sludge flow rate of 0.08 L/s with a nominal retention time in
the in-line mixer of  9  seconds.  The concentration of  the  polymer solution was
adjusted  such  that  the  polymer  dosing  rate never  exceeded  10%  of  the sludge
flow rate.
                                                   VISCOMETER SENSOR
                                                      SYSTEM
                                                       FLOCCULATOR
     Figure 3. Pilot-scale,  continuous-flow,  sludge conditioning system.

     The  viscometer  sensor system had to be  modified to allow measurements  to
be taken  in an open  vessel.   The sensor  system selected was comparable to that
used  in  the  batch  experiments,  in that  it was  an  integral  cup  and rotor
system.   The differences  were that  the gap was marginally wider  (2.6  mm  as
compared  to  2.5  mm),  the  geometry  was  slightly  different  (length  and
diameter),  and  the  cup  had  four slots  in  the wall  and several  holes  in the
bottom.   The batch  sensor was operated by putting the sample  in the cup and
then inserting the rotor.   In the pilot-scale sensor system the cup and rotor
                                       642

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were  assembled as a unit  attached to the motor  drive.   The cup/rotor portion
was immersed  in an open  container of sludge  where the  sludge  flowed through
the slots  and holes in  the cup, and filled the  annular space between the  cup
and the  rotor.   Additional modifications  included enlarging  the  holes in  the
bottom  of  the  sensor  cup and  placing  an inverted plastic  container over  the
cup/rotor  assembly  such that the bottom was  completely  open  and  there was an
annular  ring  around  the  sensor  approximately  30  mm  wide.   These changes
facilitated the flow of  sludge into the area between the cup  and  the rotor,
particularly  when the  sludge  was highly flocculated.

     The  rheograms  shown  in  figures  4,  5  and  6  were  generated  with  the
pilot-scale  sludge  conditioning system  and  represent   typical  curves.     The
general  relationships  were valid  for  all sludges  tested.      Although some
noise was  apparent  in  the curves  these  rheograms have  been drawn  as smooth
curves  to  facilitate   interpretation when  there  are several  curves on  one
figure.  Capillary   suction  time   (CST)   was   also  used   to  measure   the
dewaterability  of the  conditioned  sludge and is  shown in the figures.

     Figure 4 shows the  effect of  polymer dosage  on rheology when the sludge
is  conditioned on  a  continuous basis.   Since  all   of  the  experiments  were
conducted  with  the  intent of eventually applying the results to the operation
of  a  belt  filter  press,  it  was accepted  that  the  sludge  would  have  to  be
highly  flocculated.   This condition is normally  satisfied  with  a CST  < 20
seconds.  Reference to  Figure 4 shows that  the shear  stress at low shear  rates
10s  ) increases  as  the polymer dosage  increases.  The  limiting condition
of  CST  =  20  seconds   is  achieved  at   a  polymer  dosage of 3.5  kg/t  and a
           0>
           a
           c
           1/5
           en
           ac.
           i
           en
           a:
           LU
           i
           CO
             200
              160 -
              120
                                30    40    50    60
                                 SHEAR RATE (s'1 )
               Figure 4. Effect  of polymer  dosage on rheology.
                                     643

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significant peak is  evident  in the rheogram.  The trends  shown are similar to
those observed with  the batch  system but the curves have  a  slightly different
shape.   The  continuous-scale curves  rise  very  rapidly  to a  peak and  then
decay, resulting in  curves which  are more definitely skewed to  the right  than
those  generated on  the  batch  system.   This  effect  is  attributed  to  the
differences between  the geometries of the  batch and  continuous  systems.

     Another difference is also evident.   With the batch system it was  assumed
that a peak  in  the rheogram, i.e., a point  of inflection with  zero slope,  was
sufficient to ensure optimum conditioning.  This is no  longer  completely  true
with the  continuous  system.   Curve  C in Figure 4 very  definitely has  an  area
of  zero  slope  at   approximately  10  s~1  but  the  corresponding  CST  of  118
seconds indicates that the sludge  is  not optimally conditioned.   The situation
is  such  that  while  the  existence  of  a peak  in  the  rheogram  is  still  a
necessary  condition  for optimal  conditioning,  it does  not  represent adequate
flocculation as measured by  the CST  test.

     Figure 5  shows  the effect of varying  the  solids concentration when  the
polymer  flow rate   is  not  adjusted  accordingly.   In  this  test  the  solids
concentration was  altered  by adding dilution water  but the total sludge  flow
rate (including dilution water) and  the polymer volumetric flow rate were kept
constant.  Under these  conditions, as the solids concentration decreases,  the
polymer  dosage on   a  unit  basis  (kg/t)  increases.   At  the   highest  solids
concentration (4.4%) the effective polymer dosage is 3.2 kg/t and results in a
CST of 37  seconds.   At this  CST the  sludge would  not be considered to be super
flocculated,  and  while  a  peak  is  present  in  the  rheogram,  it  is  not
substantial.   As  the solids  concentration  decreases  to 3.1%  the effective
             140 -
                     10    20    30    40   50    60    70   80
                                 SHEAR RATE (s'1 )
90
Figure  5.   Interaction between solids  concentration and  polymer dosage  with
             respect to rheology.
                                      644

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polymer dosage  increases  to 4.4  kg/t,  the CST decreases to 17 seconds, and the
rheogram  peak  becomes quite pronounced.   The  situation has changed  from one
where the polymer  dosage is less than optimum to one where polymer overdosing
may be occurring.

     The  results in Figure 6 show the effect of detergent  addition  on sludge
conditioning and the  resulting rheograms.  Detergent, a deflocculant, was used
to  artifically alter the  dewatering characteristics  and polymer demand  of a
sludge without  changing  the solids  concentration.  Curve A, with a significant
peak and  a CST of  16 seconds represents  a well conditioned  sludge.   Curve B,
at  the  same  polymer dosage  but  with   the  addition of  0.2%  by  volume  of
detergent  has   the  appearance of  an  unconditioned  sludge  in  terms  of  both
rheogram  peak  and  CST.    As polymer addition  increases,  under a  constant
detergent  addition,  the  polymer  (Curves  C through E) overcomes  the  effect of
the detergent  until  at Curve E,  the  situation is very similar to that of Curve
A.  The notable exception  is that  4.4  kg/t of polymer is  required for Curve E
as  compared to 3.8  kg/t for Curve  A.    This is analagous  to  what  happens in
actual  operation.    As  the  dewaterability of  a sludge  changes, usually for
unknown reasons, the  polymer dosage  must  vary accordingly in order to maintain
the same  level  of performance.
                               30    40    50   60
                                 SHEAR RATE 
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          3.  respond  to  changes  in  sludge  properties  by  altering  polymer
             dosage.
The control  strategy  developed at the Wastewater Technology  Centre utilized a
HP87/HP1000 computer  combination and the  pilot-scale conditioning system shown
in  Figure 3.    A preliminary algorithm  was  developed  which correlated  the
rheological  properties  measured by the viscometer,  with polymer demand.   The
viscometer and polymer  feed  pump were interfaced  to the computer,  such that
data  from   the   viscometer  run  was  used  by  the  control   algorithm  to
automatically  adjust  the polymer  flow  rate.    A  tentative optimum  polymer
dosage  was  identified  on the  basis  of  CST   (i.e.,  <20   seconds)  and  the
particular  rheogram  corresponding  to  that  polymer  dosage  selected  as  a
reference rheogram.   Specific characteristics  of the reference  rheogram were
stored in the  computer  memory and  used  as the  control setpoints.

     Figure  7  shows one  of the  preliminary attempts to  automatically control
polymer  dosage.   It had  been determined  that  the  optimum polymer  dosage for
the sludge was approximately  4 kg/t.   The test  run  was  initiated  at a dosage
of  0.5  kg/t  and  the  control  system  allowed  to  determine  the  optimum.
Viscometer tests  were conducted at 8 minute intervals.   Based on this input to
the control  algorithm,  polymer dosage was  increased  from the initial 0.5 kg/t
to  4.0  kg/t over a period of  70  minutes.  Although the control  is somewhat
crude due  to the necessity of manual  sampling,  it  is  obvious that  the basic
concept  is valid.
           N
           CD
           JC
           a
           a
           a
           o_
                    10
                         20
                              30
                                   40
                                        50
                                            60
                                                 70
                                                      80
                                                           90
                                                               100
                                   TIME (minutes)
            Figure 7.  Effect of automatic control on polymer dosage.
DEMONSTRATION

      The final  stage  of the  study,  which  is  currently  underway,  involves
demonstration of  the  control package  at full-scale.   The  general layout  is
                                      646

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 shown  schematically  in  Figure 8 and  utilizes a 0.5  m Komline-Sanderson belt
 filter  press.    Both  the  dilution  water/detergent  and  polymer  pumps  are
 interfaced   with   the  computer.     Temporal   variations  in   feed  sludge
 characteristics  are  generated by programming the  operation  of  the  dilution
 water/detergent  pumps.  Samples of  the conditioned sludge are withdrawn to the
 sample  vessel   at  discrete  intervals.    Viscometer  tests   are  initiated
 automatically  by the  computer and  data  input to the  control  algorithm.   The
 computer will then initiate the appropriate control action with respect to the
 polymer pump.
                                                               Sludge
                                                               Cake
                             Dilution Water
                               or
                             Detergent
  Figure 8. Control  strategy for full-scale sludge conditioning/dewatering.

     The results  in  Figure 9 illustrate the response of  the  control system to
changes  in the   concentration  of  the feed  sludge.   During  the  initial 60
minutes  the  dewatering   system  was  coming  to  equilibrium.    During  the
steady-state  period  (as defined by consistent belt  press performance)  from 60
to 200  minutes,  the average  polymer  flow rate was  4.54  L/min.  The  break in
the  data from  200  to  270  minutes resulted  from  some  pluggage in  the  feed
lines,   but when  this  had been  rectified  and the solids  concentration of the
sludge decreased  from  4.6 to 4.2  %,   the  resulting average polymer dosage had
also decreased.   The  decrease  in  polymer flow rate from 4.54 to  3.69  L/min
represents  a  polymer  saving of approximately  20  % whereas the  decrease in
solids was only about  10%.

     In Figure 10 the effect  of  altering  the  dewaterability of a sludge by the
addition  of  detergent  is  shown.    The   polymer dose  during  the  first
steady-state  period  was  4.45 L/min.   At  approximately  105  minutes  a  small
percentage  (0.15% by volume)  of detergent was  added to  the incoming sludge.
The  control  system  sensed  that  the polymer  requirement  had  changed  and
proceeded  to  adjust the  polymer  pump accordingly.   The  average  flow  rate
required  during  the period of  detergent  addition was 5.51  L/min,  or an
increase    of  approximately 24%.     When  the  addition  of  detergent  was
terminated, the polymer flow rate returned to the  same  general level as before
the addition.
                                       647

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                 0   30  60  90 120 150  180 210  240 270 300  330 360 390  420


                                       TIME (mm)
Figure  9.  Response  of  control  strategy  to  fluctuations  in  sludge  solids

            concentration.
            o
            Q-
                 0  30  60  90  120  150  180  210  240  270 300 330 360 390


                                       TIME  (mm)



Figure   10.   Response   of   control   strategy  to   fluctuations  in   sludge

               dewaterability.
                                        648

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     The preliminary  results from the demonstration phase have  shown that the
control system is sensitive  to  gross  changes  in  sludge dewaterability, whether
these  are  the  result  of changing  solids concentration or  the presence  of
materials which act as deflocculants.  The  net impact  on cost  will depend upon
what  degree  of  fluctuation  in  sludge  dewaterability  is  observed when  the
system is field tested.   The  projected benefits  of  an  automatic  control system
include  reduced  polymer  cost,  decreased  product  variability  and  reduced
process costs downstream.

                CONVERSION OF SLUDGE  TO  LIQUID AND  SOLID FUELS
     The  Wastewater  Technology  Centre's   evaluation  of   low  temperature
conversion  of  sewage  sludge  to fuel,  an  example  of  an  alternative  new
technology, was  designed as  a  three  phase  program.  The  first  phase involved
testing  a  number  of  sludges  using  a  batch  apparatus.    The  second  phase
consisted  of  designing,  constructing  and testing a  1  kg/h  continuous-flow
reactor.   The primary purpose  of  the second  phase was  to generate  process
design  information  and  cost data,  in order to assess the potential  of  the
technology  at   full  scale.     The   final  phase  of  the  program  will  be
demonstration  of the technology at full scale.

BENCH-SCALE STUDIES

Methodology

    Raw  sludges  containing  a mixture of  primary  and  waste activated  sludge
(WAS) from  three different sewage treatment  plants in Ontario  were evaluated
during  this  study.    All  sludges  were  oven  dried  (70C)  to about  90-95%
solids.  Analyses  of these sludges indicated they  were  similar  in composition
with volatile  solids  of  55-64%, calorific values  of  15-18 MJ/kg  and  carbon
contents of 24-36%.

    The  bench-scale  studies  were  carried out using  a batch  reactor  and  a
continuous flow  system.   The  batch  reactor,  a pyrex tube  70mm in diameter and
720 mm in length, was  heated  in a three-zone  Lindberg  furnace  under a nitrogen
atmosphere  (Figure  11).   Off-gases were condensed  in a trapping system using
ice as the  coolant.   Non-condensable gases (NCG) were  vented  from the system.
A run was  conducted by  charging 550 g of  dried sludge  into  the  reactor  and
deaerating  with  nitrogen.   Once operating temperature  had been  reached,  the
nitrogen purge rate was reduced.  When  all  visible  signs of reaction  (i.e.,
gas/oil  flow)  ceased, the  heat was  switched off  and the nitrogen purge rate
was increased  for approximately 30 minutes.   The system was  dismantled and the
char, oil  and reaction  water  collected  and stored  for analysis.   Oil/water
separation was achieved using a separatory funnel.

    A photograph of  the  continuous  reactor system  is  shown  in Figure 12.   it
comprises a stainless steel  shell,  50 mm internal diameter by  1000  mm long,
fitted  with a sludge/char  conveying system and  is   heated  using the  same
furnace  as  for  the batch  reactor  system.   The  reactor is  subdivided by  a
helical gas seal, into a volatilization zone  and a  char/gas  contact zone.  The
                                      649

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NZLINE
                                1. GAS CYLINDER
                                2. ROTAMETER
                                3. FURNACE
                                  FURNACE CONTROLLER
                                  REACTOR TUBE
                                  TRAP
                                  MULTIPLE THERMOCOUPLE SWITCH & DIGITAL READOUT
                                  FURNACE THERMOCOUPLES
                                  SLUDGE THERMOCOUPLES
                                    POWDER DRY SLUDGE
                                    GLASS WOOL PLUG
                                                              FUME
                                                              HOOD
                                    ICE BATH"
              Figure 11.  Batch experimental equipment.
               Figure 12.  Continuous reactor system.
                               650

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reactor  system is  designed  for dry sludge feed rates of up to 1  kg/h.  Solids
retention  time in the  reactor  is controlled by  varying both the  sludge feed
rate  and  reactor  inventory.   Sludge is  fed  to the  reactor by  a calibrated
screw  conveyor  and  travels through the  reactor  by  means  of  the  reactor
conveyor.   Volatilized material  is  withdrawn in  the  first  zone and  can  be
contacted  with the char  in  both co-current and  counter-cur rent modes  in the
second  stage.   Product  vapours  are condensed  externally as  per the batch
reactor  system.   Inert gas  is used  to  purge the  system of  oxygen and the
operating  pressure is generally less  than 2 000  pascals.   Prior to collection
of  experimental data  the system  was allowed  to reach  thermal  and  chemical
equilibrium by operating  for at least three  solid retention times (SRT).

Results

    The  results achieved  with  both  the  batch  and continuous reactor systems
are presented in detail in other publications  (14,15).   A summary  of typical
results  are  presented  in  Table 1.   All the data is expressed on  a dry  solids
basis  (corrected for  the  normal 4-7%  moisture  present in the sludge) and the
calorific  values  are  expressed  on  a total solids  basis (not corrected for
volatiles).
               TABLE  1. TYPICAL  OPERATING  CONDITIONS AND RESULTS

            	Batch	Continuous

            Feed Rate  (g/h)                  NA                 750
            Temperature  (C)                450                 450

            OIL
              Yield  (%)                    22.3                25.4
              Viscosity  (cstks)            >214                33.7
              Calorific Value  (MJ/kg)      38.9                36.7
           CHAR
              Yield  (%)                    54.6                61.1
              Calorific Value  (MJ/kg)       9.4                 6.2
           NCG
              Yield  (%)                    12.1                 11.1
              Calorific Value  (MJ/kg)        NM                 5.8
           REACTION WATER
              Yield  (%)                    11.0                 5.0
           NA=Not Applicable
           NM=Not Measured
    In general,  the  results from  the batch and  continuous systems are  quite
comparable.   The oil  and  char yields  are  slightly higher from  the  continous
unit  but  it  is  difficult to  say  whether the  difference  is  statistically
significant.    The  lower  calorific  value  of  the  char  from  the  continuous
reactor  is  the  result of  the  lower  carbon  content.    The  most  obvious

                                      651

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difference between the products from the  two  systems  is  the  oil  viscosity.  The
oil  from  the batch  runs was  solid at  room temperature  O214  centistokes),
while  the  oil  from  the continuous  runs  was fluid  at  room temperature  (33.7
centistokes).   The batch system  generated approximately  twice  the  amount  of
reaction water  as did the continuous one.

    Although  most  observations  are  valid  for  either  batch  or  continuous
results,  the following  discussion  will  be  limited to only  the  continuous
system due to the fact that the experimental  data base is  much  larger.

    The  yield  of  individual  products and the split  between  products  is  a
function of  operating temperature.    At  low temperatures,  the  product  split
tends  towards  the  formation  of  char.   As the temperature  increases to  the
optimum, the oil yield increases  (8 to 25%) while the char yield decreases  (75
to  61%).   Above the  optimum  temperature the oil  yield  begins  to  decrease as
conditions favour  the formation  of increasing  quantities of non-condensable
gas. Oil yield  appears  to be  related  to  solids residence  time  but since  it is
impossible to completely separate the effects  of  SRT and char  inventory,  the
trends  are not  clear.    The  yield  of reaction water  does not appear  to be
directly related  to the  operating  parameters of  the system.    The  yields  of
both oil and  char  are very much a  function of  the  specific  sludge used as the
feed material.

    The  calorific  value  of  the  oil  appears to  be  related to both  SRT  and
temperature but their effects are relatively small.  A  range  of SRT's from 10
to  24   minutes  resulted in  calorific values   from 36  to  37  MJ/kg,  while
temperature  variations  from  300  to 500C  resulted in a  range  of  only  36 to
39  MJ/kg.   The calorific value  of  the char tends  to decrease  with increasing
temperature but is relatively insensitive  to changes in  SRT.    The magnitude
of  change in the  energy of  the  char   (i.e.,  from  10.4 to  5.5  MJ/kg),  is
substantially  greater than  that of  the oil.    The  calorific  value of  the
non-condensable gas  increases in direct  proportion to the temperature.   This
is  due to the  increase  in  the percentages  of hydrogen, methane  and ethane
produced at higher temperatures.

    The  viscosity  of the  oil  is  a  function of  both  SRT and  temperature.
Viscosity  decreases as  either SRT or temperature increases.  The viscosity of
the oil  produced  under  a given  set of operating  conditions will be dependent
on  the source sludge  used.   For  example, under optimum  operating conditions,
two different  sludges  produced   oils   with  viscosities  of   33.7  and  52.3
centistokes.

    The  elemental  characteristics  (C,H,N,0,S)  of  the oil appear  to be  quite
stable with  respect to  processing conditions.  Some fluctuations in the carbon
content  are  evident,  but the magnitude of  change  is  relatively  small.  In
general,  40   to 50%  of  the  carbon  from  the sludge  is  recovered  in the oil.
Oxygen is  difficult to  measure  because  an unrealistically  high oxygen result
will  be obtained  if  water  is present in the oil  sample.   Although oxygen is
generally  in  the range  of 6-9%,  levels as low as 2.7% have been obtained.  The
elemental  characteristics of  the char tend to be  affected  more by  processing
conditions than do  those  of the  oil.    As  the  temperature  increases,  the
carbon,  hydrogen and  nitrogen in the char tend to decrease.

                                      652

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    The reaction water  has  a  total Kjeldahl  nitrogen content (TKN)  of 4-6% and
a total organic carbon   content  (TOC)  of 10-18%.  Based on  the  data currently
available,  there  does  not  appear to be  any relationship between  TKN/TOC and
operating parameters.

    In general, the process has  proven  to be very  stable,  at least  at  bench
scale.   As  the  process variables  change,   the split  between  products  also
changes gradually.    Similarly,  the quality of  the products is   affected  by
process modifications but the magnitude  of the  change is small.  The result of
this is that over the practical  range of  operating  conditions, the  performance
of  the  system can  be described  as a relatively flat plateau as opposed  to a
peak.   In  practical  terms this  means  that if  the temperature unexpectedly
changes  by  50c   in   full-scale operation,   one   can  expect  to  see  this
reflected  in relative  yields,   but  the  process will  not fail.   It  is  also
unlikely that the  product  qualities  will change  sufficiently  in short periods
of time to  affect end uses  or specifications.

IMPACT OF SLUDGE TREATMENT  PRACTICES

    The  selection  of  the most  appropriate  sludge management   scheme  must
consider many factors including  capital cost, operation and maintenance  cost,
cost   stability   in   the    future,   energy   recovery/usage,  environmental
acceptability  and  the  difference between new  construction versus  upgrading
existing facilities.  Other less  tangibles include  the desirability of capital
versus 0  and M expenditures,  the public  perception of acceptable technology
and the flexibility to  respond to changing needs in the future.  The impact of
sludge handling  and  disposal  practices  can be  illustrated  by  examining the
four  sludge management alternatives shown  in  Figure 13.  They  range from a
relatively  low  level  of technology with many years  of  documented  experience,
to  a very   sophisticated   system which,  to date,   has  only been proven  at
bench-scale.  In  Table  2 the four alternatives  are  compared  on the  basis  of
their energy recovery potential.  The analysis uses  a raw sludge  input, for all
alternatives, of 25 dry tonnes  of sludge solids  per  day.   It is assumed  that
sludge, char,  NCG  and  reaction  water  are  combusted at  75%  efficiency.    In
order to be consistent, the methane  from digestion  is  only allocated 75%  of
its gross energy,  since it still has to be  burned  in a furnace  of  some nature
before the energy becomes usable.

    Alternative A,  the   application   of digested   sludge   on agricultural
land, has  traditionally been the preferred method  of  sludge management for
many  municipalities.    For  smaller  communities which  have  a  sludge  with
acceptable  levels  of   heavy  metals,  this is  still the  most cost  effective
method of disposal.  As communities  become  larger,  drawbacks to  this system
become evident.   It is difficult for  large municipalities  to find sufficient
land within  a reasonable distance of the plant  on  which to apply  the sludge.
Even  if  the  required  land  is  available,   the number of  trucks needed  to
transport liquid sludge may create a local traffic  problem which can adversely
affect public  relations.   As municipalities become more industrialized, the
potential that  the sludge  may  not  satisfy  heavy  metal  guidelines  for  land
application also increases.  In  terms of energy recovery the system is quite
efficient showing a net energy of 4.06 MJ/kg of  raw sludge.    The  reason  for
                                      653

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           TABLE 2. ENERGY BALANCE FOR SLUDGE DISPOSAL ALTERNATIVES

   ALTERNATIVE (See Figure 13)     A           B           C
   Total Energy Available
    in Raw Sludge (MJ/h)         17072       17072       17072        17072

   ENERGY OF PRODUCTS
    Methane (MJ/h)                4230        4230        4230            0
    Oil (MJ/h)                       000         8327
    Char+NCG+H20 (MJ/h)              0           0           0         5111
    Digested Sludge (MJ/h)           0        5414        5414            0

   ENERGY REQUIREMENTS
    Reactor/Dryer
    Incinerator/Combustor (MJ/h)     0       12797        7580         1739

   NET ENERGY
      (MJ/h)                      4230       -3063        2064        11699
      (MJ/kg raw sludge)          4.06       -2.94        1.98        11.23

   ENERGY RECOVERY
      (%)                         24.8           0        12.1         68.5
   NOTE * Net Energy = Total Energy of Products - Total Energy Requirements
        * Energy Recovery = (Net Energy / Raw Sludge Energy)x(100)

this level  of  efficiency is that there  are no large  energy requirements  for
this alternative, although  the  energy required to transport the  sludge  to the
farmland has not been  accounted for.   One of the  major  problems with methane
as an energy source is that because it is difficult to store and  transport,  it
must be utilized on-site continuously.  Many sewage treatment plants  find that
this is not possible in summer, and consequently,  flare a  significant fraction
of their gas. Thus,  while a digester may be generating potential  energy  at the
rate  of 4230  MJ/h,  the rate  of  utilization over  the  entire  year  may  be
considerably less.

    Alternative B  has been  a  common  practice for  many  installations.    The
sludge   is   digested,  dewatered   to  20   to  22%   and   incinerated   in   a
multiple-hearth   or  fluidized   bed   incinerator.     This   alternative   is
significantly  more  expensive  than  Alternative  A  and  is  much  less  energy
efficient.   Reference  to Table  2  shows that there is  a  net energy deficit  of
2.94 MJ/kg  of  raw sludge,  assuming that  the incinerator has been  modified  to
burn methane  as auxiliary  fuel.  This  inefficiency is  primarily  due to  the
energy  requirements  to evaporate the water (78%) in  the incinerator.  If the
energy  deficit were  satisfied  by  natural gas,  this would translate  to  an
auxiliary  fuel  cost   of  approximately  $150  000  per  year.     The  positive
features are that there  is  a minimum quantity  of  material (ash) for ultimate
disposal,   and the majority  of heavy metals will be  immobilized  in the ash.
Due to  the  high energy  requirements, this  system is generally  being  phased
out.
                                      654

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   A. RAW
METHANE
*
DIGESTION


4% I
LAND DISPOSAL
1
               METHANE
   B. RAW
                                               22%
                                                HEAT RECOVERY
               METHANE
   C. RAW
                                                                    STACK


30%
DEWATERING
30%
DRY I NG



90%
45%



INCINERATION
                                                                     ASH
                                                                    STACK
                                             HEAT RECOVERY
   D. RAW
                                   40%


DRYING

95%

CONVERSION
*
OIL



COMBUSTION
ASH
     NOTE: (%)  numbers refer to sludge solids concentrations at various points  in
           the  process.
                    Figure 13. Sludge disposal alternatives.

    Alternative C  is  one  approach to  maintaining  the  same basic  system  as
outlined  above,  but upgrading  it in  order  to  improve  energy  efficiency  and
subsequently  reduce operation and maintenance costs.   The  sludge dewatering
equipment  is  upgraded  in order to achieve 27 to  30% solids  in  the cake on a
consistent  basis.   A  portion of  the  cake  is then dried  to  85  to 90%  solids
using  waste heat from  the incinerator.   This portion is  backmixed with  the
rest of the dewatered cake  (30% solids)  such that the  combined sludge  feed  to
the  incinerator  is  in  the order  of  40   to 50%  solids.   Depending on  the
volatile  fraction of the sludge,  the  cake may or  may not  be autogenous.   The
                                      655

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capital cost will  be higher than for Alternative B  due  to the addition of the
dryer  but  the energy balance is  much more  positive.    In this  case, a  net
energy  surplus  of  1.98  MJ/kg  of  raw  sludge  is produced but  it should  be
stressed that any  net energy  not utilized in the process  is only  available as
either  methane  gas  or  hot  flue gas.    Both of these  represent  a  difficult
problem in  terms of either storage  or transportation.   Another  problem  with
either  Alternative  B or  C is  that, in  many cases, the public  views sludge
incineration as  an undesirable practice.

    Either  system  could  also  be used without digestion.  This would  probably
increase  the  level of  cake   solids   acheivable   in   dewatering  and  would
significantly  increase  the  available  energy  in   the   sludge  going  to  the
incinerator.   The  potential of  using  methane as auxiliary fuel would be  lost
and the elimination of  digestion would  mean that a backup method for sludge
disposal during  incinerator down-time would also be  lost.   When all factors
are considered,  it is not clear whether it  is  more economical to incinerate
raw or digested  sludge.

    Alternative  D  has   currently only   been evaluated  at  bench-scale,  but
appears to  have a number of  novel  aspects  which  could make  it a  publicly
acceptable  and economical method of  sludge disposal.  As mentioned above,  the
fact  that  raw sludge is being  dewatered indicates that cake  solids in  the
order  of  40%  can  be  achieved  using  technology such   as  a  diaphragm filter
press.  The energy  balance in Table 2  shows the impact on recovered energy.
The  net  energy   (11.23  MJ/kg  of   raw   sludge)  is 2.75  times  higher  than
Alternative A,  and  almost  six  times higher  than Alternative  C.   All  process
energy  requirements  for  Alternative D could  be  supplied  by 34% of the energy
in the  char,  NCG   and  reaction water.  This  would  leave 3372 MJ/h of energy
available for  other uses in  the form of recovered  heat, and 100% of  the  oil
(8327  MJ/h)  would  be   available   for   sale.   The   primary   reason   for   the
differences  in  the  energy  balances  between Alternatives  C  and  D is in  the
manner  of  energy  conversion.    In C the  conversion is  either  by biological
means  (i.e., digestion),  or by heat  recovery.  Neither of these  methods are as
efficient  as  the  process  in  D which   consists  of  catalysed  vapour  phase
reactions converting the lipids and proteins in the sludge to  straight  chain
hydrocarbons.

    The  fact  that  a large  percentage   of  the  energy   in  Alternative  D  is
available  as oil  has a  significant  impact  on the entire sludge management
philosophy.   Instead of  having to  use  recovered   energy  in-house,  which  is
usually the case with methane,  steam, hot flue  gas,  and even  electricity,  the
energy  is   now  in  a storable,   transportable and potentially saleable  form.
Currently,  the  least  valuable  end-use  for  the   oil   appears   to  be  as  a
substitute  for No. 6 fuel oil.   If  the  oil  can be  sold  for  $30/barrel,  then
the  net  revenue  from  a 25  tonne   of   dry  sludge  per  day  plant  would  be
approximately  $365 000 per  year.  However,  the   potential exists to  increase
end-use value, and upgrading  to  a transportation fuel is a possibility.

    The use of  a  char  combustor as opposed  to  a sludge  incinerator  may  also
have a  distinct  advantage with  respect  to  public acceptance.  The combustion
of  char may  be  seen  to  be more  analagous  to burning coal,   rather  than
incinerating sewage  sludge  with  all  of the perceived associated  environmental

                                     656

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 concerns.  The char  combustor will be  similar to an  incinerator  in that they
 will  produce the same amount of  material for ultimate disposal  and the heavy
 metals  will, to a large extent,  be  immobilized  in the resulting ash. A   char
 combustor  should  also be  considerably  smaller  than an  incinerator  to burn
 sludge  from an  equivalent  sized plant  because  the capacity  to  evaporate the
 large amounts  of water which are normally present in sludge, is not required.

    Sludge  management  by  conversion  to oil  will  be  most advantageous when
 considering  the  construction of new plants.   Since the major source of the raw
 material for oil is  the biomass from the biological treatment plant, the ideal
 feed  stock  for  the  process is raw sludge.   This eliminates  the  need for the
 construction  of  digesters  and  can  be  translated  into  savings   in  capital
 investment  for  new  plant  construction.  The process is  also compatible with
 high-rate  biological processes.  One  of the drawbacks of  high-rate processes
 has   always  been the  additional  quantities  of   sludge  generated  and  the
 corresponding  increases in  sludge  disposal  costs.   By converting  the excess
 sludge  to  oil,   any additional  cost  resulting  from  the  increased  quantity
 requiring treatment, should be  offset by the increased volume of  oil produced.

                                 CURRENT STATUS
    The  approach to  sludge management  in the  sewage treatment  industry has
changed  over the  past  few years  and will continue to change in the foreseeable
future.   Considerations of energy, cost  and  availability have shown that many
sludge  handling  options,  which  were  considered state-of-the-art  only  a few
years ago,  are no longer economically justifiable.   Sludge management schemes
must be  designed  with  an overall systems approach to  both  the solids flow and
energy efficiency.

    The  automatic control  of  polymer  in the conditioning/dewatering phase of
sludge treatment  represents an  opportunity  to  save money  and improve process
performance.    The  basic  concepts of  the  control  logic developed at  the
Wastewater Technology  Centre  have  been shown to be valid.   A  Canadian company
is  currently  working  on a government  sponsored  contract  to  develop  a
commercial  prototype  of  the control  system  which  should  be  commercially
available in 1987.

     The  conversion  of  sludge  to  oil  offers  an  attractive alternative  to
sludge options currently in operation.   The  conversion technology is estimated
to be at  least comparable to  incineration in terms  of capital  cost and minimal
negative  impact on the environment.  The most important  advantage  is that the
recovered energy  is in  the form  of oil which is storable, transportable and
potentially saleable.

    It is estimated that in   1985,  350  000  tonnes  of  sewage sludge will  be
incinerated  in Canada.   Thermal conversion  of  this  sludge could  produce 700
000 barrels of oil, with a  market  value  of at least  $21  million.

    Environment Canada's long  term plans are  to  demonstrate this  technology by
construction of  a 25  tonne  per day  facility.   The  first component of this
demonstration study has  been completed,under  contract, with the development of

                                      657

-------
 the pre-engineering data, identification of suitable sites and a thorough
 assessment of the process economics.  Current activities are centred around
 the selection of a company to act as the licencee for the technology.  The
 25 tonne per day demonstration facility is scheduled to be operational in
 1986.
                                   REFERENCES
1.  Black, S.A. and  Schmidtke,  N.W.  Practises and Trends in  Sewage  Sludge
    Utilization and Disposal, presented  at  1st  Workshop on  Canadian-German
    Cooperation, Burlington, Ontario 1979.

2.  Bridle, T.R.   Sludge  Derived Oil:  Wastewater Treatment  Implications
    Env. Tech. Letters vol. 3, pp 151-156,  1982.

3.  Simcoe  Engineering,   Sludge   Management  Study   for   the   Regional
    Municipality of Halton, Pickering,  Ontario,  1980.

4.  Knudsen,  D.I.,  and   Mathes,   G.A.     Automatic  Control  of  Sludge
    Conditioning and  Vacuum Filtration.   Wat.  Sci.  & Tech.,  13,  Munich,
    611-617, 1981.

5.  Haug, R.T.  and   Sizemore,  H.M.  Energy Recovery and  Optimization:   The
    Hyperion  Energy  Recovery   System,  presented  at  the  International
    Conference  on Thermal  Conversion of  Municipal Sludge,  Hartford,  Conn.
    1983.

6.  Molton,  P.M.    Batelle-Northwest   Sewage  to  Fuel Oil  Conversion,
    presented  at  the  International Conference  on Thermal Conversion  of
    Municipal Sludge, Hartford, Conn, 1983.

7.  Shibata,  S., Precede  de Fabrication d'une Huille  Combustible a Partir
    de Boue Digeree.   French Patent 838,063,  1939.

8.  Bayer, E.  and  Kutubbudin,  M. Low Temperature Conversion  of Sludge and
    Waste  to  Oil.    Proceedings  of  the International  Recycling  Congress,
    Berlin, West Germany,  1982.
                                     658

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9.  Dick, R.I.   Physical  Properties of  Activated Sludge.   Presented  at
    the  NATO   Advanced  Study   Institute,   Sludge   Characteristics   and
    Behaviour,  University of Delaware, 1979.

10.  Campbell,  H.W.,  Rush,  R.J.   and Tew,  R.    Sludge  Dewatering  Design
    Manual.   Canada-Ontario Agreement Research Report No. 72, 1978.

11.  Campbell,  H.W.,  and Crescuolo,  P.J.   The  Use of Rheology  for Sludge
    Characterization.   Wat. Sci. & Tech., 14, Capetown,  475-489, 1982.

12.  Cost-Project 68.  Sewage Sludge  Processing,  Commission  of  the European
    Communities Report No.  EUCO/SP/48/75, 1975.

 13.  Campbell,   H.W.,   and   Crescuolo,   P.J.     Assessment   of  Sludge
     Conditionability Using Rheological Properties.   Proceedings of an  EEC
     Workshop  on  Methods  of  Characterization  of Sewage  Sludge,  Dublin,
     Ireland, 1983.

 14.  Bridle,  T.R.   and  Campbell,   H.W.  Liquid  Fuel Production  from Sewage
     Sludge,  presented  at  the ENFOR  Third   Canadian Biomass Liquefaction
     Experts  Meeting, Sherbrooke,  Quebec,  1983.

 15.  Bridle,  T.R.  and Campbell, H.W.  Conversion of Sewage Sludge  to Liquid
     Fuel,  presented at  the 7th  Annual  AQTE  Conference, Montreal,  Quebec,
     1984.
                                      659

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  ITALIAN  ADVANCES  IN  WASTEWATER  TECHNOLOGY
                      by
                Mario  Santori
       Institute di Ricerca sulle Acque
      Consiglio Nazionale  delle  Ricerche
              Rome,  Italy   00198
       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.
North Atlantic Treaty Organization/Committee on tke
Challenges of Modern Society (NATO/CCMS)  Conference
           on Sewage Treatment Technology

               October 15-16, 1985
                 Cincinnati, Ohio
                        661

-------
                    ITALIAN ADVANCES IN WASTEWATER TREATMENT

                by:   Mario SANTORI
                     Institute di Ricerca sulle Acque
                     Consiglio Nazionale  delle Ricerche
                     Rome, Italy  00198
                                   ABSTRACT

     Italian legislation on wastewaters control establishes fixed quality
limits not dependent on the characteristics of receiving water bodies.  In
order to protect low receiving capacity water bodies, the limits are very
restrictive, especially with regard to heavy metals and nutrients.  Further-
more, typical products of the Mediterranean area, and particularly of Italy,
such as olive oil, originate seasonal discharges with high BOD concentration
(up to 100,000 ppm) which are poor in nutrients.  These discharges are not
easily treatable by means of traditional aerobic biological processes, as
they require a long start-up time and very high degrees of dilution, in order
to eliminate toxicity phenomena.

     This situation created the necessity for the research reported herein:
- heavy metals removal by advanced precipitation processes; - nutrients
removal with a single sludge system without addition of external reactives;
- anaerobic treatment of highly concentrated soluble wastes either in UASB
reactors or mixed with domestic sludges in traditional 3ludge digesters.
                                     662

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              TOXIC METAL REMOVAL AND RECOVERY FROM WASTEWATERS

     Two main research projects have been devoted by the  Institute di Ricerca
sulle Acque (I.R.S.A.) to this problem:

- metal precipitation using the water soluble starch xanthate, a derivative of
  an inexpensive natural product;
- synthesis and characterization of new Ionic Exchange (IE) materials high
  with  high affinity  for metal  ions


METAL PRECIPITATION WITH STARCH XANTHATE
     Starch xanthate  (SX) is a water soluble polymeric reagent  which is
easily synthetizable  starting from starch, CS2 and NaOH aqueous solution.   It
shows high metal removal efficiency for Cd (II), Cr (III), Cu (II),  Pb  (II),
Hg (II), Ag(I) and Ni(ll), either separately or in combination, over a  large
pH range.  The parameter xanthate/metal ratio is most significant both  for
metal removal efficiency and for solid/liquid separation  efficiency, and  can
be controlled by a potentiometric system.


     Figure 1 report  the residue concentration of Ag(l), Hg(II), Cu(ll),
Zn(ll) as a function  of the SX/metal molar ratio, after 0.4S/  filtration
at constant pH = 5 (7-5 for Ag) and ionic strength  0.1 M NaNO^, obtained
during batch tests.
     The data indicate that very low concentrations are reached for Ag, Hg
and Cu (0.01; 0.005 and 0.09 mg Metal/1, respectively).  On the contrary, the
removal of Zn is not complete, and the final concentration is in order  of
20 mg/1.
     As far as the stoichiometry and thermodynamics of uetal-xanthate systems
are concerned, literature data are available only for the metal-ethylxanthate
reaction.  Preliminary numerical simulation with these data showed that neither
stoichiometric nor equilibrium parameters of metal-ethylxanthate systems could
be used to successfully  model the behaviour of metal-starch xanthate systems,
as shown in Figure 1.  According to the stoichiometry of the reaction between
metals and ethylxanthates, the theoretical SX/M  molar ratios in the precipi-
tated compounds should be 1 : 1 for mono-valent metals and 2 :  1 for divalent
ones. For example the following reaction can be assumed for a divalent metal:
                                          /   s
                 + 2 R-O-C/'    	*  R-0-C7/      ,C-0-R
                           C             ^Q M Q
                                     663

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                 io-3
                            0.5
                                      SX/M
                                            15
    Figure  1.  Effect  of  SX/M molar  ratio on the residual metal ion  concen-
              tration in solution after 0.45 #m filtration
              pH  =  5-0 1 0.5 Stat (   7-5 i 0.5 for Ag)
              Ionic  strength =  0.1  M  NaNOo.

      As  Figure 1 indicates *he best  experimental SX/M  ratios for a complete
 removal  of metals  are not  consistent with the theoretical ones, for Ag(l)
 and Hg(ll).   In  these cases the quantitative removal of the metals from  the
 solution ( >  99.9%) is  reached when  the SX/M ratios are 0.5 and 0.8, respec-
 tively.

      Experimental  work  was carried out in order to determine metal binding
 capacities of the starch xanthate  and conditional formation constants  of the
 metal-starch xanthate insoluble complexes.

     Figure 2  shows an example  of the the Scatchard pilot extrapolation method
 applied  to the results  of the  potentiometric filtration of starch  xanthate
solutions with metal  ions.  The Scatchard extrapolation method evidenced two
metal binding mechanisms, the  first  related to chemical precipitation  of the
metal ions with xanthate groups and, the second, to the adsorption of  metal
 ions on  the precipitate.

      The determined  stability  constants and complexing capacities  of starch
 xanthates  with heavy metals were then incorporated in  a computer program, in

                                     664

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                    1.25-
                    1.00
                 T, 0.75
                    0.50
                    0.25
                                    --*-*
                                  05
                                                        1.5
     Figure 2. Scatchard  plot  for  the  binding  of  Cd(ll)  by ethylxanthate
               at pH 7-5  and 0.1 M NaNO  .
                                       O
order to simulate the fate  of  a metallic ion in wastewater after treatment
with SX.

     As an example, Figure  3 compares  theoretical and  experimental trends of
the residual silver concentration  after treatment of uncomplexed Ag ions
(from AgNO^ salts) of initial  concentration 10~4  M, corresponding to 10.7
mg/1 as Ag. The curve represents the theoretical  behaviour,  assuming K =10  j
n =2; K =6.9xlo3; n =2.5. The  experimental points, determined  either by po-
tentiometric ISE measurements  or by AA analysis after  0.45 /um  filtration,
are in good agreement with  the predicted behaviour.

     Further experiments  are being run in order to compare the results of the
theoretical simulation of the process  with the experimental  ones,  particular-
ly in the case of the presence of  metal complexing agents  in wastewaters.
                                    665

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                  0.01
                                      4        6
                                        I05(mol/l)
     Figure 3. Silver (from AgNO  salt) removal with starch xanthate.
               Starting solution: AgNO  1.0_x 1CT4 M5 0.1 M NaN03;
               pH = 7.5; / SX_/ = 1.18 x 10~3M.
                  from potentiometric data
               A   AA determinations
               The continuous line represents the calculated curve.

     The behaviour of the system is completely different when complexed
metal ions are to be precipitated.  For the  sake  of  example, Figures 4 and 5
report the distribution diagram ot the hydrolysis products and chlorocom-
plex species of Hg(II) in ionic strength 0.1 M NaNO  and 0.1 M NaCl, respec-
tively.  Working at pH = 5, the prevailing species in  solution is Hg(OH)2 in
the first case, while the sum of HgCl"  and HgCl^~ accounts for about 60% of
the total Hg in the second case.Figure 6 shows ttte difference in the kinetics
of precipitation of the mercury at pH = 5 starting from the hydroxocomplexes
(curve a) and from the chloro-complex (curve b). The removal of 99-9% of Hg
is obtained after 5 minutes and 35 h,  respectively. The slow kinetics is
probably to be ascribed to the repulsive electrostatic forces between the
negative xanthic groups and the anionic chlorocomplex  species of  mercury.
                                   666

-------
100
80-

:? so
"i
o
"CT
20
0
\H9 /'
\ /
\ ,'
\ 1
\ /
i i
\'l
I
1\
// V. H9(OH)3
2 i 6 8 10 12




s
n
Q
     Figure 4. Theoretical distribution  of  hydrolysis products of
               Hg(ll) in NaNO^ 0.1 M  test  solutions.
            100
            80
            60-
          (J
          =? 40
           Ol
             20
                                          /Hg(OH)j

                    YV\
________ _ ' A \
                      '
                                         Hg(OH)CI
 I   I
 2
                                    r  <
                              6      8
                                pH
                                          10
                                                12
Figure 5- Theoretical  distribution of hydrolysis products and
          chlorocomplexes  of Hg(ll) in 0.1 M NaCl test solutions
                               667

-------
                  101
       Figure 6. Kinetics of precipitation of Hg(ll) at pH = 5 Stat.
                 a) hydroxide-complex in 0.1 M
                 b) chloro-complex in 0.1 M NaCl
     It is interesting to note that, while metal speciation greatly affects
the kinetics of precipitation, it does not influence the solubility of the
mercury xanthate: the quantitative precipitation of the metal from 0.1 M
NaNO-i or 0.1 M NaCl solutions is obtained at
the same ratio SX/Hg =0.8.
     Table 1 summarizes the experimental results obtained in batch tests
when the viscous SX(0.7 mmol S/g) was added to 1 dn>3 of solutions containing
dissolved metals In, Cu, Cd, Hg, and Ag  (one at time) at pH stat = 5- The
final concentrations of the metals are still found to be below the limits of
current Italian Legislation.  Also the optimum polycation dosage is report-
 ed in Table 1 at the ionic strength indicated. The operative removal capa-
city in batch tests for Zn, Cu, Cd, Hg and Ag was found to be 19-1; 22.2$
39; 143; 154 g of metal/kg of SX (viscose), respectively.

     The small amounts of sludge obtained after precipitation with SX are
                                   668

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    TABLE  1.  EXPERIMENTAL RESULTS  OBTAINED IN BATCH TESTS  WITR METAL ION
              SOLUTIONS  (SEPARATE EXPERIMENTS) AT pH = 5  STAT.  (INITIAL
              STARTING VOLUME  =  1 dm3.  SX VISCOSE = 0.7 tnmol/g  AS SULFUR
              TOTAL  REACTIVE).

Feed cone, (mg/1)
SX/M ratio (mol/mol)
Residual cone, after filtration
(0.45/un) (mg/1)
Optimum polyelectrolyte dosage
(mg/dm3 PC-7)
Operative removal capacity
(g/Kg SX Viscose)
Zn
500
2.4
10
100-;;-
19.1
Cu
50
2.0
0.01
10-"---
22.2
Cd
53
2.0
0.02
7+
39
Hg
100
1.0
0.001
30++
143
Ag
11
0.5
0.01
12+
154
*: Ionic strength = 0.3 M NaCl; **: 0.04 M NaN03$ +: 0.1 M NaN03?
++: 0.005 M NaN03.
 easily dewaterable by traditional techniques (filtration, mechanical dehydra-
 tion) . Preliminary tests carried  out with acid solutions to recover metals
 in solution gave unsatisfactory results. An oxidant treatment with NaCIO
 solution  and  iodine  to  lower  the  pH below 3 gave  quantitative recovery, as
 reported  on Figure 7, in  the  case of mercury sludge.   In this case,  the
 reaction  proceeded the  formation  of insoluble  starch  xanthide,  a non-toxic
 residue disposable without  difficulty.


      The SX process is now being tested in a pilot plant (1.5 m3/h),  Figure
 8,on a real chlor-alkali wastewater in order to verify its applicability
 from the technical and economic point of view.

 NEW I.E. MATERIALS FOR METAL ION UPTAKE

      Two main types of materials are being investigated: the water insoluble
 cellulose xanthate and the copolymer Poly /(N-Dithiocarboxylato)-iminoethen-
 hydrogenoiminoethene_/(PIED).  The water insoluble cellulose xanthate (ICX)
 can be used as a chelating ion-exchange resin, characterized by relatively
 low costs of synthesis.  The ICX can be synthetized slightly modifying the
 viscose synthesis procedure in the rayon process.

      The research was initially aimed at finding the best operating condi-
tions for the synthesis in order to obtain an insoluble material with high
                                     669

-------
          100-
          80- 
      60
      t-l
      0)
      o
      0)
                            6     8    10
                              eq Ox/eq Hg
Figure 7. Recovery of mercury from  sludge  by chemical oxidation at
          pH = 3-5.
          a) NaCIO; b) I-
Figure 8. Lay-out  of  the  plant.
          VA = Storage  tank;  SI  = Precipitation reactor? S2 = Settling
          tank5 a) =  Acid;  b) =  Base;  c)  = Starch xanthate; d) = Poly-
          electrolyte.
                               670

-------
 ion-exchange  capacity.  Under  optimal  conditions  the final compound had a metal
 extraction capacity in the range of 1 to 2.5 meq/q.  The ICX was obtained
 both  in Ma  and  in  Mg-form.  The Mg-ICX  (dried, in powder form) proved to be
 stable  for  1  year  at  ambient  temperature.

      Table  2  reports  the  results obtained with column operations with a bed


    TABLE 2.  EXPERIMENTAL RESULTS OBTAINED WITH CELLULOSE XANTHATE PROCESS
              IN COLUMNS
              ICX-Mg  (Total capacity =1.2 mmol/g).
              Flow velocity = 10 BV/h; Separate  experiments for each metal.

Feed concentration (mg/1)
Initial pH
ICX-Mg used (g)
Volume of ICX-Mg (cm )
Concentration limits in Italy
(mg/D
Water treated (V/BV )--"-
Operative removal capacity
(mg of metal/g ICX-Mg)
(mmol metal/g ICX-Mg)
-"-: USA Regulation (1982)
Cu
30
6.5
8.4
40
0.1

65
9.28

0.15
Ag
30
6.6
7.6
30
0 . 2-"-

168
19-9

0.18
Cd
30
7.0
7.0
30
0.02

130
16.7

0.15
Hg
30
7.2
7.3
30
0.005

45
5.55

0.028

-;H;": to obtain a leakage corresponding to the maximum metal concentration
permitted by law.
of Mg-ICX as chelating resin. Working with feed solutions of 30 mg/1 of each
metal and at a flow rate of 10 BV/h, a leakage corresponding to the units
imposed by law for Cu, Ag, Cd and Hg was reached UD to 65? 168; 130 and 45
V/VR, respectively.
     The corresponding operative removal capacities
5-5 mg of metal/g of ICX.
are 9.285  19.95  16.7 and
     It is interesting to note that columns of CX can be used to "polish"
very low concentrations of metals in solution.  By way  of example, Figure  9
                                     671

-------
             0.05
                                                       50
     Figure 9- Removal of trace concentrations of Cadmium by treatment with
               ICX-Mg in column operation.
               Initial Cd = 0.054 mg/dm3; Flow rate = 10 BV/h5 1: Limit by
               law.
 reports  the  effluent  concentration  of  Cadmium,  fed  at  a  velocity of  10 BV/h
 and  at initial  concentration  of  0.054  mg/1,  as  a  function  of  the treated bed
 volumes.

      The data show that  the Cd concentration in the product water is below
 the  0.02 mg/1 limit set  by Italian  Legislation.   Furthermore,  the removal
 efficiency of the  ICX-Mg is unchanged  after  a 69-day interruption of the run.
 This is  a confirmation of the good  stability of this material  with time, as
 reported previously.

      The exhausted ICX materials were  then treated  for metal  recovery, with
 either chemical or thermal treatment.
     Table 3 shows the metal yields obtained by treating different ICX sludge
exhausted with Cu,  Ag and Cd:  70-90% metal recovery was achieved.

     Finally, the synthetic copolymer  PIED was investigated, in cooperation
with the Chemical Department of Reading University (U.K.), for selective
metal extraction from wastewaters.
                                     672

-------
     TABLE 3.   RECOVERY OF METALS FROM SLUDGE IN THE CX-Mg TREATMENT BY
               BURNING AND CHEMICAL OXIDATION

Metal in sludge (mg)
Amount of sludge (g)
Metal recovery (mg)
a) by burning (mg)
(%}
b) by oxidation with NaCIO (mg)
(%}
Cu
121.5
8.4

108
89
87
72
Ag
246
7.6

219
89


Cd
152.5
7-0

118
77
136
89
    The studied material is a copolymer which is prepared from poly(imino-
ethene) and carbon disulphide. An idealised formulation of the repeating unit
of PIED is given below:
     The N-dithiocarboxy]ate groups are thought  to be mainly on the primary
amine groups. In addition to the -NHCS" groups,  there are the remaining pri-
mary amine groups and the other nitrogen-containing groups which can bonded
to the metal ion.

     Figure 10 show that PIED rapidly extracts cadmium from aqueous solutions.
The addition of PIED (**, Ig) to a solution (100 ml) containing cadmium (10.2
mg/1) reduce the concentration to 0.001 mg/1 in ten minutes. Moreover in accor-
dance with the fact that N-dithiocarboxylates had a greater affinity for cad-
mium than zinc, it was found that PIED can perform a useful separation of the
two metal ions. The results in Figure 11 refer to the extraction from solu-
tions containing cadmium (11.2 mg/1) and zinc (13-Omg/l) at pH 2 (H SO ) as
commonly experienced in waste waters containing both metal ions.  The salt Zn-
PIED was used with different loadings of cadmium. The lower the loading of
cadmium the faster the kinetics, but the presence of zinc does not influence
the kinetics of cadmium uptake on PIED.
                                     673

-------
          1.0
                                 25   30
                                   t(min)
Figure 10. Uptake of Cd(ll)  by  PIED at pH 5-5 as a function of time,
           Ionic medium 0.1  M NaNO-,
           a) 0.09   mmol Cd added/g PIED
           b) 0.392    "  "      "       "
           c) 0.72     "  "      "       "
                                674

-------
         0.01
Figure 11. Residual cadmium concentration in solution after treatment
           with Zn-PIED (0.100 g) as a function of time.
           Ionic medium 0.1 M NaN03 5  pH = 2 (H SO )

           : Initial (Cd) = 11.2 mg/dm3
           H: Initial (Cd) = 11.2 mg/dm3 and (Zn)  = 13-0 mg/dm3

           a) Cd Loaded =0.10 mmol Cd/g Zn-PIED
           b) Cd Loaded =0.50 mmol Cd/g Zn-PIED
                                 675

-------
                    INNOVATIVE AND ALTERNATIVE ENGINEERING
ANAEROBIC PROCESS DEVELOPMENT

     In recent years considerable interest has  been focused   on anaerobic
treatment of a wide range of waste waters, ranging from high strength ef-
fluents to very diluted ones, as an interesting alternative  to high energy
consuming aerobic processes.

     The main advantages of anaerobic digestion are well known: low high-grade
   energy requirements for process operation and in many cases, a net overall
energy balance*, low production of well stabilized excess sludge; low capital
cost.

     The main draw-backs consist of start-up and process control problems,
mainly due to the slow growth rates of some anaerobic bacteria and to the
still inadequate understanding of the complex interactions between biological
and the physicochemical factors.

    Several Italian Research Institutes are developing innovative anaerobic
research processes.

Istituto di Ricerca sulle Acque

     Most of the experimental activity carrieu out or currently in progress
at this Institute on anaerobic digestion is related to the treatment of olive
   oil mill waste waters, which considerably increase the polluting load dur-
 ing the milling season in the Mediterranean area and in the Apulia region,
where the Bari IRSA laboratories are located.

     With reference to the anaerobic treatment of olive oil mill wastewaters,
IRSA has developed high rate UASB  (Upflow Anaerobic  Sludge  Bed)  reactors  for
digesting these concentrated effluents (COD in the range 50-200 kg/m^).

     UASB reactors are expanded bottom-fed sludge vessels? there is no mechan-
 ical stirring in the system and this fact, as well as the relatively high
upflow velocity, promotes the formation of well settling sludges.

     Treatment of olive oil mill waste waters in UASB digesters was made
possible by dilution with well water. For full scale applications, dilution
by sewage will be used as it also eliminates nitrogen deficiency in the waste.

      Experiments have been performed both on laboratory and pilot-scale
 reactors (volume 15 1 and 5 m-*, respectively) maintained under mesophilic
 conditions (35C).

                                     676

-------
      Most start-up problems have been solved by starting with a very diluted
 waste (about 5 kg COD/m3) and then increasing the concentration by steps  of
 2, 5 kg COD/m^ to a final concentration of about 15 kg COD/m^, while also
 adding suitable amounts of nitrogen  (available nitrogen in the waste is
 deficient) and alkalinity (sodium bicarbonate, soda and calcium hydroxide)
 to the feed.
      The hydraulic residence time (HRT)  was kept  constant at  1 d during the
 tests. The volumetric loading rate was increased  from 5 kgCOD/(m3.d) to 16
 and 21 kgCOD/(m3.d) for the pilot and the  laboratory reactor, respectively.

      Removal efficiencies in the range of  70 - 75% on the COD were obtained,
as well as specific gas production rates of the order of 4 to 6 m^/m^r'd.

      These results can be justified by the high concentration of active bio-
 mass which built up in the reactor and by  the beneficial effect which the
 added chemicals seem to have on the net  microbial growth rates.

      Sludge granulation as achieved in Dutch UASB digesters,  fed on carbohy-
 drate wastes,  was not obtained but,  even so,  the  settleability of the sludge
 proved very good.

     Experimental results related to a start-up of a 5 m3 pilot reactor  are
 reported in Figure 1, where loading rates  are given as  kg TOC/(m3'd).  Load-
 ing rates as COD can be obtained by multiplying TOC values by 2.5 - 3.  From
 the diagram it can be seen that after about 30 days the system has been
 overloaded with  a  consequent  increase of  volatile  organic acids (TVA).

      Present research is aimed at defining a start-up procedure to minimize
 chemical consumption and energy (heating)  requirements  during the transient
 operation until full load conditions are reached.

      The experiments are currently being carried  in laboratory and pilot
 scale plants at the IRSA laboratory,  and will be subsequently replicated on
 a test bed plant (two 750 m-* digesters) the  construction of  which will be
 funded by the Apulia Regional Authorities within 1986 in the municipality of
 Pallo del Colle.

      The design of this demonstration plant has been made by IRSA and  by re-
 gional technical engineers  (as far as the sizing of the reactors  and the
 concrete structures, respectively, are concerned).
                                     677

-------
     g*j
         0


         ft 
    TVA
  /kgHAcN
  \   m3 ,'
         0
        80-
    (%)  40-

        20
    Figure 12.
                                        -YV'
                     20
                40
                                           60
                                      80
100
                                                               (d)
Pgas = Specific Biological gas production)  L = Specific
load; TVA = Volatile  organic acids$ TOC = Removal efficiency,
     Experiments  are  also being performed on the direct anaerobic treatment
at ambient temperature  of raw sewage in sludge blanket reactors.  The  most
interesting feature of  this process is a much lower production of sludge than
aerobic   systems ( e.g.: activated sludge and trickling filters). Direct  an-
 aerobic treatment of raw sewage is being investigated on laboratory UASB
reactors and in the  near future  the  tests will  be  extended to a  5 m^ pilot
plant.

     Results obtained on the laboratory reactor are promising, as 50-60%  of
the polluting load can  be removed by this process.

Agip  Giza S.p.A..

      This Company, in  cooperation with the ENI Research Laboratories
(ENI  RICERCHE), has  developed fixed film anaerobic digesters (anaerobic
filters)  for wastewaters with a prevalently soluble pollution load.

      The  main advantantages of fixed film reactors are related  to the high
sludge retention times, the high sludge concentrations that  can be  attained
                                   678

-------
 and  maintained  to  their  capacity  to  withstand  very  high  temporary
 hydraulic and organic overloadings.   Two full scale plants have been built.
 The first one, made of two 1500 m3 anaerobic filters using quartz rock as
 filling media, has been successfully operating on a sugar factory for
 several years.  The second one, treating vegetable canning industry
 effluents, is a 300 m3 anaerobic filter and was started up in Spring 1985.

      The anaerobic filters  in  the  sugar  factory  treat the  regeneration
 streams from ion exchange  resin columns  that  purify  the  sugar juice from non
 crystallizable organic (mainly proteinaceous)  compounds.
      The  operating  conditions  are  as  follows: loading rate 9 kg
 hydraulic retention time:  2  days,  specific  gas production 2.3
 with 70%  methane, removal  efficiency  60%  on the COD. All these data refer
 to  the  full  volume  of  the  filters ,  which  have a void fraction of approxi -
 mately  50%.

 ENI Ricerche

      Eni  ricerche has  carried  out  the R.  & D. for  the above mentioned anaero-
 bic filters  on sugar wastewaters up to the pilot plant  scale . A trucked pi-
 lot plant has  been  designed  and built for the purpose of carrying out treat-
  ability  experiments in the  factories producing the effluents to be tested.

     Eni ricerche is presently developing anaerobic fluidized beds using
sand particles as supporting media.

      Very interesting  results  have been obtained using  laboratory scale reac-
 tors. At  loading rates of  the  order of 150 kg COD/(m3-d) and retention
 time of 0.11 days,  specific gas  production rates of 26.5 m3/(m3.d) and COD
 efficiencies of the order  of 45% have been achieved.
                                     679

-------
                    PROCESS UPGRADING AND PLANT MANAGEMENT
BIOLOGICAL NITROGEN REMOVAL FROM INDUSTRIAL WASTEWATERS

     Within  the framework  of biological nitrogen removal, the aim of this
 work was  to  verify the applicability of single sludge systems (see Figure  13)
 for treatment of high strength ammonia industrial wastewaters.
                                                                      in
                                                                      c/1
       Figure  13.   Flow-sheet of single sludge anoxic-aerobic process.
                    i: influent; e: effluent; a: nitrified mixed liquor
                    recycle? b: sludge recycle? W: waste sludge; Rj: an
                    oxic reactor; R2-. aerobic reactor; S: settling tank.

     Effective application of such a system is dependent on the value assumed
by denitrification kinetics when internal carbon is used as electron donor sub-
stance; this means that the rate of this process must be high enough to be of
industrial interest.

     Furthermore, in the case of industrial wastewater in which inhibitors
for nitrifying bacteria are present, the nitrification stage is the critical
phase of the whole process and ammonia oxidation  is possible only if the
wastewaters are  diluted.  As inhibition problems  are  independent  of  the
chosen process scheme, the single sludge system is  in any case  preferable
to separate systems, and affords considerable  saving  of  primary and
secondary energy.
      The wastewaters examined (see Table 4 for typical composition) are  rep-
 resentative of two quite distinct categories: slaughter-house discharge is
characterized by high biodegradability and the absence of inhibitory com-
pounds; coke oven liquid wastes contain typical lowly biodegradable substances
                                    680

-------
                TABLE 4.  TYPICAL COMPOSITION OF WASTEWATERS
Slaughter-house
Parameter
(mg/1)
COD
~Q(~\T\
D\JiJ C
TOC
TKN
NH4-N
SS
Non filtered
sample
3,070
2,050
-
260
-
610

Filtered sample
2,080
1,350
670
240
225
-
1
//
1
1
!
^
!
'i
''I
Coke plant
Parameter
(mg/1)
TOC
Phenols (Total)
NH4-N
ci-
SS

Non filtered
sample
3,300
2,500
3,800
3,000
0

and inhibitory compounds.  The findings can therefore be extrapolated to
wastewater that have intermediate characteristics with respect to the two
effluents studied, thereby extending the applicability of the results
obtained.

Results
     The experimental work, which takes in various sets of tests run in both
bench and pilot scale, is summarized in the data reported in Tables 5 and 6.
These data clearly show the applicability of single sludge anoxic-aerobic
systems for the biological treatment of both wastewaters studied.


     As can be seen, satisfactory results have been also obtained with
coke-oven liquor.  After suitable dilution, good removal efficiencies for
carbonaceous substances (phenols and thiocyanates) have been achieved, as
well as for nitrification.  As far as denitrification efficiency is con-
cerned, the results show that the N03~N removal is the maximum that can be
obtained with a wastewater with such a phenol/nitrogen ratio*.

     The process parameters obtained from the continuous tests of Tables 5
and 6 and, when necessary, confirmed by supplementary batch tests^, allowed
*This ratio (~ 0.7) is considerably lower than the specific phenol consump-
 tion ratio found in anoxic reactor (1.7).
^Since in completely mixed biological reactors, the substrate concentration
 in the effluent is practically the same as in the reactor, the rate of the
 process could be kinetically limited by one or more substrates.
                                    681

-------
                   TABLE 5.   MEAN WORKING CONDITIONS AND RESULTS WITH SLAUGHTER-HOUSE WASTEWATER
Anoxic reactor




Analytical
data





Working
conditions





Process
parameter
Process
performance
Parameter

COD
BOD-
TOC
TKN
NH4-N
N03-N
Volume
Hydraulic retention time
Sludge age
Biomass concentration
PH
Temperature
Dissolved oxygen
Biomass nitrogen content
vss/ss
Nitrif. mixed liquor rec. rat.
Sludge recycle ratio
Denitrification rate
Net growth yield coefficient
COD removal efficiency
Nitrification efficiency
Nitrogen removal efficiency
Feed
A.
mg/1 2,080
mg/1 1,350
mg/1 670
mg/1 240
mg/1 225
mg/1 0
1
h
d
mg MLSS/1

C
mg/1
% ss



kg N03-N/kg VSS-d
kg VSS/kg COD solub
% 88
% 100
% 74
or
reactor outlet
510
-
163
87
66
0
670
4-5
1.1
4,920
8.1
20
0.2
6.9
0.79


0.19
. 0.34

Aerobic reactor
or
A. reactor outlet
256
19
76
15
0
58
2,670
17.8
4.6
4,870
7-6
20
3-0
7-3
0.69
1.2
1



CD
00

-------
                  TABLE 6.  MEAN WORKING CONDITIONS AND RESULTS WITH SLAUGHTER-HOUSE WASTEWATER



Analytical
data






Working
conditions





Process
parameters

Process
performance
Parameter

Phenols (total)
CNS-
NH4-N
N02-N
N03-N
Volume
Hydraulic retention time
Sludge age
Biomass concentration
pH
Temperature
Dissolved oxygen
Biomass nitrogen content
vss/ss
Sludge recycle ratio
Denitrification rate
Nitrification rate
Specific phenol consuption ratio
Net growth yield coefficient
Phenol removal efficiency
Nitrification efficiency
Nitrogen removal efficiency
Anoxi
Feed
A. rea
mg/1 400
mg/1 40
mg/1 600
mg/1 0
mg/1 0
1
h
d
mg MLSS/1 2

C
mg/1
% ss


kg NO^-N/kg VSS-
kg NH4-N.kg VSS-
kg C6H5OH/kg N03
kg VSS/kg C6H5OH
% 95-0
% 98.3
% 35-8
c reactor
or
ctor outlet
28
1
300
3
78
5
20
40
,720
7.5
25
0
8.5
0.86

d 0.11
d 0.25
-N 1.7
0.13


Aerobic reactor
or
A. reactor outlet
20
0.5
10
3
374
7
28
47
2,310
7.5
25
2.5
8.5
0.86
1






Ol
oo
CO

-------
 the plants  to  be  designed  and  the  costs  estimated  once  the  flowrate  and  the
 concentration  of  pollutants  were known.

 Biological  reactor design

      Table  7 shows the  flow-rates  and  concentration  figures assumed  for  the
 dimensioning of full-scale plant for both  the wastewaters studied.
                             TABLE 7.  DESIGN DATA
                       Wastewater
   Parameter
                                        Slaughter-house
               Coke plant
    Flow rate  (m3/d)

    Ammonia  concentration  (mg  NH^-N/1)

    Ammonia  load  (kg  NH^-N/d)
4,000

  300

1,200
  250

3,800

  950
      More  specifically,  for  the  slaughter-house  wastewaters,  the  economic
 analysis refers  to  plants  catering for  10^  equivalent  inhabitants (referred
 to  nitrogen).  Assuming 12  g  N/dinhabitant,  the  total  nitrogen  that  must be
 removed is :  12-10   '10^ = 1,200  kg N/d and the  related  flow  rate :  1,200
 kg  N/d : 0.3  kg  N/m3 = 4,000 m3/d.

      As far as the  coke  oven wastewater is  concerned,  reference is made to  a
discharge treatment plant that produces  1,000 t  of coke  a day.  The  discharge
    produced is assumed to  be 0.25 m3 of discharge for  every t of  coke  and so
 the flow rate will  be :  1,000-0.25 = 250 m3/d.

      Hydraulic residence times,  sludge  ages and  recycle  ratios  can then be
 calculated (see  Table 8) using the model reported by Ramadori (1).
                                     684

-------
                TABLE 8.  DIMENSIONING OF BIOLOGICAL REACTORS
Wastewater
Parameter
Hydraulic retention time in the anoxic reactor
Hydraulic retention time in the aerobic reactor
Sludge age (total)
Nitrified mixed liquor recycle ratio
Sludge recycle ratio
Slaughter-
house
6.7 h
14-4 h
5.9 d
13-3
1.0
Coke plant
38 h
21 h
87 d
0
2.0
Technical and economic evaluations of a full-scale plant

     With regard to the schemes in Figure 14, which also include the sludge
treatment section, Table 9 and 10 summarizing the values of the design pa-
rameters for the various units considered.  These values result from the
experimental work summarized in 3.1 and from the literature (2), (3).

Plant costs

     Plant costs for each operating unit have been obtained from the func-
tions reported in Table 11.  Plant costs are expressed as a functions of
parameters chosen as variables.  For the sake of example, the costs of civil
works for biological reactors (both anoxic and aerobic) are expressed as a
                                                                 vn
                                                                 g
                                                                 in
Figure 14.  Process flow-sheet of full scale plant, a: influent; b: dilution
            water (coke plant wastewater only); e: effluent; W: waste sludge;
            r: sludge recycle; r': nitrified mixed liquor sludge (slaughter-
            house wastewater only); 1: anoxic reactor; 2: aerobic reactor;
            3: settling tank; 4: pre-thickner; 5: anaerobic digester
            (slaughter-house wastewater) or aerobic digester (coke plant
            wastewater); 6: post-thickner.
                                     685

-------
TABLE 9.  DIMENSIONING PARAMETERS FOR COMPONENT UNITS RELATED TO
          SLAUGHTER-HOUSE WASTEWATER TREATMENT
Unit
Anoxic
reactor
Aerobic
reactor
Settling
tank
Pumping
station
Pre-
thick-
ner
Anaer .
dig.
Post-
thick-
ner
Belt-
press
Parameter
Biomass concentration^
Denitrification rate
Specific BOD consumption ratio
NOo-N in the effluent
Specifing stirring power installed
Net growth yield coefficient
Biomass concentration
Minimum sludge age
Dissolved oxygen
Oxygen required for nitrification
Mechanical efficiency:
oxygenation
BODr removal
TKN in the effluent
COD in the effluent
Hydraulic retention time
3verflow rate
Sludge recycle ratio
Recycle ratio
Pump pressure head
Pump efficiency
Residence time
Solids load
Concentration of sludge before thickening
Concentration of sludge after thickening
Residence time
Volatile solids reduction
Residence time
Solid load
Concentration of sludge before thickening
Concentration of sludge after thickening
Operating time
4,000 mg MLSS/1
0.2 kg N-N03/kg VSS-d
2.5 kg BOD5/kg N-N03
0 mg/1
15 W/m3
0.4 kg VSS/kg COD soluble
4,000 mg MLVSS/1
4 d
2 mg/1
4.6 kg 02/kg N-NH4
1.55 kg 02/kWinst-h
1.26 kg BOD5/kWinst-h
15 mg/1
256 mg/1
4 h
0.4 m/h
1
13-3
0.2 bar
0.70
38 h (1.58 d)
30 kg SS/m2-d
1% (' ' 10 kg SS/m3)
3% (~30 kg SS/m3)
480 h (20 d)
50$
38 h (1.58 d)
63.6 kg SS/m2-d
1.8% ("V18 kg SS/m3)
4% (AX 40 kg SS/m3)
8 h/d
 Biomass characteristics: VSS/SS = 0.80; Nitrogen ponderal fraction = 0.075
                               686

-------
TABLE 10.  DIMENSIONING PARAMETERS FOR ALL COMPONENT UNITS RELATED TO COKE
           PLANT WASTEWATER TREATMENT
Unit '
Equalization
tank
Pumping
station
Anoxic reactor
Aerobic reactor
Settling tank
Pumping station
Pre-thickner
Aerobic-
digester
Drying bed
Parameter
Hydraulic retention time
Specific stirred power installed
Pump pressure head
Pump efficiency
Biomass concentration
Denitrification rate
Specific phenol consumption ratio
Specific stirring power installed
Net growth yield
Biomass concentration^
Nitrification rate
Oxygen required for nitrification
Efficiency of oxygenation
Overflow rate
Hydraulic retention time
Recycling ratio
Pump pressure head
Pump efficiency
Residence time
Solid load
Concentration of thickned sludges
4 h
15 W/m3
0.6 bar
0.7
3,000 mg SS/1
0.05 kg N03-N/kg VSS-d
1 . 7 kg phenols/kg NO^-N
15 W/m3
0.2 kg VSS/kg phenols
3,000 mg SS/1
0.25 kg NH4-N/kg VSS-d
4.6 kg 02/kg NH4-N
1.6 kg 02/kW'h
0.5 m/h
7 h
2
0.3 bar
0.70
20 h
30 kg SS/m2-d
20 kg SS/m3
Residence time 12 d
Specific oxygen consumption ratio 2.3 kg 02/kg VSS
Mechanical efficiency of oxygenation 1.6 kg 02/kW'h
Volatile solids reduction 50%
Specific area
Equivalent inhabitants
 Biomass characteristics: VSS/SS = 0.85; Nitrogen
200 m2/l,000 inhab.
0.08 kg SS/inhab.
ponderal fraction = 0.085
                                    687

-------
TABLE 11.  COST FUNCTIONS FOR CIVIL WORKS AND ELECTROMECHANICAL EQUIPMENT
Operating units
Equalization tank
Pumping station
Anoxic reactor
Aerobic reactor
Settling tank
Recycling pumping station
Thickner
Aerobic digester
Anaerobic digester
Drying bed
Beltpress
Electr. equip, and hydr. network
Accessory works
Cost functions
Civil works Eleotromech .
C

C
C
C

C
C
C
C
C

C
= 0


= 0
= 0
= 0


= 1
= 0
= 0
n

= 2


n

.308 v


.308 v
.308 v
.882 V


.162 v
.37 V
.204 V
.165 s
 97 Q +


.11 Cg
.86

.86
.86
.74

 71
.84
.916
.85
64.8


C
C
C
C
C
C
C
C
C

C
C

= 3-
o

= 3.
= 3-
= 2.
o

= 3.
= 2.
= 0.


= 13
o



332
566
332
332
702
566
668
5
370


.47
23


equipment
W
Q
wo
W
A
QU
Au
W
VU

Q
Ct

.82

.82
.82
.88
.62
.86
.88
.853

+ 114-5


A: transversal area; C: cost (10^ Italian liras);  Cg:  total plant cost (10"
Italian liras); Ct: total cost plant without the accessory works (10" Italian
liras); Q: flow rate (m3-h~M; S: drying surface (m2).  V:  volume (m3);
W:  power installed  (CV).
function of the relative volumes while for electromechanical equipment, the
costs are expressed as a function of installed power.  The functions in
Table 11 have been obtained from correlations with a statistical processing
of cost data from 35 treatment plants throughout Italy and from design esti-
mates (3).


     Costs are referred to October, 1982.

     Table 12, which summarizes total plant costs, shows the figures of
3,434-lo6 and 1,638-106 Italian liras for slaughter-house and coke-oven
wastewaters, respectively.
                                     688

-------
                TABLE 12.   CAPITAL COSTS (106 ITALIAN LIRAS)


Operating units

Equalization tank
Pumping station
Anoxic reactor
Aerobic reactor
Settling tank
Recycling pumping station
Pre-thickner
Aerobic digester
Anaerobic digester
Post-thickners
Beltpress
Drying beds

Electr. equip, and hydr. network
Accessory works
Total plant cost


Slaughter-house
wastewater
Civil
works
-
-
129
249
108
-
92
-
216
42
82
-
918
-
378
1,296

Electron).
equipment
-
-
43
620
65
67
128
-
242
80
190
-
1,435
703-
-
2,138

3,434 ( 1.7-106 $)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
1 ,
1
I
1
I
I
1
Coke plant
wastewater
Civil
works
40
-
280
168
89
-
10
13
-
-
-
20
620
-
180"
800

Electrom .
equipment
H
8
91
254
82
13
31
10
-
-
-
-
503
335+

838

1,638 ( 0.8-106 $)
* 0.23(918+1,435+703) = 703? + 0.23-(620+503+335) = 335?   0.11-(9l8+l,435+
+703+378) = 378; " O.ll-(620+503+335+180) = 180.
 Running costs

      Running costs  have  been  broken  up  as  follows:  staffing, electric power,
 operation and maintenance and chemicals (Table  13).   In  further  detail:
 -  Electric power  has  been  calculated consistently with the value  chosen for
   the dimensioning  parameters for  each  component units, considering also the
   data reported in  specialized literature  (4),  (5). The specific  cost of
 electric power has been assumed equal  to  80  Italian liras/kWh.

- Operation  and maintenance costs have been assumed  equal  to  3% of the
  electromechanical equipment.
                                     689

-------
   The  alkali  consumption  to  neutralize  the  acidity  released  during  nitrifica
   tion,  and the  phosphorus need  for  bacteria metabolism  resulted  equal  to  5
   NaOH   /m3  of  wastewater and 63  g  P 2 /m3 of wastewater, respectively. The
   polyelectrolyte  consumption for  chemical  conditioning  of sludge has been
   taken  equal to 3 kg /t  of  SS.
              TABLE  13.   RUNNING COSTS  (106  TTATJA.N LTRA/YR)
Item
Staffing
Power
Operation and Maintenance
Chemicals
Total
Slaughter-house
wastewater
258
280
64
14
615
(~0.3-106 $/yr)
/
/
/
'/
',
i
Coke plant
wastewater
168
113
25
134
440
("0.2 $/yr)
Overall Costs

     The overall costs for treatment plants as outlined above  (including
amortization and running costs) are reported in Table  14.

     Amortization costs were determined on the basis of 15 years for the
electromechanical equipment and 30 years for the civil works and on an annual
interest on capital of 10%.
                              o
     The specific costs, per mj of wastewater and per kg of incoming pollutant
are reported in Table 15.
  250  Italian  liras/kg
 23,400  Italian liras/kg, as H-
 37,000  Italian liras/kg
                                     690

-------
                TABLE 14.  OVERALL COSTS (106 ITALIAN LIRAS/YR)
Item
Amortization costs:
civil works
electromechanical equipment
total
, Running
Overall costs
Slaughter-house
wastewater

137
281
418
615
1, 033(^0. 5 'I06$^r
Coke plant
wastewater

85
100
195
440
635(^0. 3 -lo6$/yr)
                       TABLE 15.   SPECIFIC COSTS
                                       Slaughter- house
                      Coke plant
 Flow rate

 Equivalent inhabitants
            with respect to COD
            with respect to NH^-N

 Total cost (10^ Italian liras/yr)

 Specific costs
          Italian liras/m^
          Italian liras/kg COD
          Italian liras/kg
     4,000


    120,000
    100,000

     1,033
            $/yr)
  708 (  0.3'$)
  240 (  0.1-$)
2,360 (  1.2-$)
      250

     14,000
     80,000
     635
 ( 0.3-106 $/yr)
 6,960  ( 3-5-$)
 1,200  ( 0.6-$)
1,831* (  0.9-$)
-- With reference to nitrogen removal equal to 36%
                                     691

-------
     In the case of slaughter-house wastewaters, Table  15 shows how these
costs are comparable to the costs related to urban sewage of the same  strength
and with both BOD and nitrogen removal.

     The specific cost referred to coke-oven wastewater is  apparently  very
high but it must be pointed out that conservative figures have been assumed
for design calculation, and consequently costs are  also over-estimated.
Furthermore, treatment costs may be reduced by ammonia  stripping before bio-
logical treatment; this would be facilitated by high temperature (~25C),
high pH (~9.5) and by favourable free ammonia/combined  ammonia ratio  ( 40%)
of the raw discharge.

     Lastly, it is worth observing that the specific cost of about 7,000
Italian liras per m^ for wastewater drops to less than  2,000 Italian  liras
per t of coke produced.  Furthermore, if we consider that in steel proces-
sing the most highly polluting stage is coke production, the cost is  seen to
be greatly reduced if it is referred to each unit of steel produced,

UPGRADING CONVENTIONAL DIGESTERS BY FEEDING COMBINED SLUDGE AND CONCENTRATED
SOLUBLE WASTEWATERS

     In most European countries many conventional digesters  for  sludge stabili-
zation operate under  underloaded conditions. One of the probable reasons for
this situation is the overestimation of polluting  load for the water  works
or/and overestimation  of sludge production at the design stage.

     On the other hand many of the (agro)  industrial wastes  to be treated  are
concentrated  in  organics,  poor in nutrients and hence unfit for direct biolog-
  ical  treatment.

     Mathematical modeling  and experiments have shown that  the addition of con
centrated  wastewaters  to underloaded  once-through concentrational sludge diges-
  ters  is beneficial  because existing  works are upgraded by a  "free of charge"
treatment  of  the concentrated  wastes  which could otherwise be treated and/or
disposed of  in new wastewater  plants.

     Using mathematical models, I.R.S.A. researchers have investigated the
 operation of anaerobic digesters as a function of the wastewater composition,
 namely the ratio between suspended solids and soluble COD.

     Although well known in practice, it has been further verified,  that the
loading  rate  of  a digester fed on suspended  solids  is  relatively low  because
of limitations on: a)  the  cell residence  times  (at  low feed  suspended solids
concentrations)  which lead to  wash-out of the microorganisms  or b) maximum
                                     692

-------
sludge concentration in the  reactor.  On the other hand, loading rates for di-
gesters fed on prevalently soluble wastewaters can be increased to much
higher values

    One unforeseen aspect of the modeling  study  was  that it is possible to
increase the loading rates of  digesters fed on suspended solids if the extra
loading is provided as soluble substrate, because the increase of biomass  con-
centration due to the latter substrate does not appreciably alter the total
sludge concentration in the  reactor.

    This  functional relationship can easily be seen  in  figure  15, where the
sludge concentrtion in the reactor is plotted vs the sludge residence time
for a given voltatile suspended solids loading rate Lsa and for different
values of the soluble COD loading rate Lsb.
       50
       m
        \
         en
        00
        00
                                Lsa = 1 Kg VSS/m3d
                         20
40           60
    SRT(d)
80
      Figure 15.  Relationship between solids  concentration and solids
                  retention time of fixed loading  rates.
                                    693

-------
    Taking  into account  these considerations and the fact that in Southern
Italy there are several oversized sludge digesters, as well as the urgent
need to treat or dispose of olive oil mill wastewaters, an experimental re-
search on the combined digestion of sewage sludge and of these highly pol-
luting agroindustrial effluents has been started by I.R.S.A.

    Two 25  liter digesters are being tested.  The  first one is fed on  sewage
sludge only while the second one is fed on both sewage sludge and olive oil
wastewaters.  A mixture of primary and secondary sludges from the Bari water-
   works is used as suspended solids substrate.

    Preliminary results  are reported in Table 16.

    It is worth noting that specific gas production in reactor II fed  on
sludge and  olive oil  effluents  increased  by  about  75% with  respect  to
reactor I without  any appreciable  negative influence  on the anaerobic
decomposition  of the  sludge.

    The experiments will be continued on different loading conditions  for the
two substrates on order to optimize the overall treatment process that will
then be tested on real scale plants to verify its application potential.

                              SLUDGE MANAGEMENT

SLUDGE MECHANICAL  DEWATERING

Introduction

     In municipal wastewater treatment processes residual sludges amount to
approximately \% by volume of the treated  sewage,  but  in big plants  their
treatment  and handling account for up to 50%  of  the total operating  costs.  It
is then evident the importance of analysing the  different technological alter-
natives appropriate for transforming a liquid matter  (2-3% in concentration)
into a material to be disposed of without  causing  any damage to  the  receiving
body and eventually reused.

     Among the sludge treatment processes, mechanical dewatering is considered
to be the  most delicate and expensive one  and is utilized in the majority of
the cases. The mechanical dewatering process  can take  place by filtration or
centrifugation; the various technologies available have well marked features
that render them capable to meet different requirements and suitable for dif-
ferent utilizations.
     Characteristics  and problems of sludge mechanical dewatering processes
are reviewed in this  paper.
                                    694

-------
C31
to
in
                    TABLE 16.   ANAEROBIC DIGESTION OF SEWAGE SLUDGE AND OLIVE OIL WASTEWATERS.
                               CHARACTERISTICS OF THE FEED REACTOR I (SEWAGE SLUDGE ONLY):
                               COD = 56 kg/m3; COD FILT.  =3.6 kg/m3;  SS = 32.5 kg/m3;
                               VSS = 25.3 kg/m3.
                               REACTOR II (SLUDGE + OLIVE OIL WW): COD = 66.9 kg/m3;
                               COD FILT. = 27.6 kg/m3; SS = 33.5 kg/m3; VSS = 26 kg/m3.

Reactor I
Reactorll
Mean working
conditions of
reactors
kgCOD
2,6
4,2
kgVSS
1,2
1,2
i c
d
21
16
Gas
production
J^TTd
0,51
0,89
CH4$
62
58
Reactor outlet
pH
7,6
7,3
COD
inifil.
kg 02
23
30
COD
filt.
kg 02
0,6
6,5
SS
kg
21,5
22,8
VSS
kg
14,5
15,6
TVA
kg AC
m3
0,2
1,45
alkali
nity-
kg
m3
i\
2,95
3,5
Efficiency
COD
unfil
tered
%
59
55
-
34
32
-<
43
40

-------
Characterization and conditioning
      One  of  the  essential  conditions  to tackle the problem  is  the knowing  of
 the  sludge characteristics.

      Many laboratory  tests are available for  sludge technological characteri-
 zation; the  most often  utilized parameters are the solid  content (total,  sus-
  pended,  volatile), the density of the dry solids (1.3-2.1  g/cm3),  the  pH,
 the  alkalinity  (up  to 6,000  g/m3), the SVI (Sludge Volume Index), the speci-
 fic  resistance  to filtration (values  of 1.1012 m/kg at  4-9  N/cm2 are general-
 ly required  for  good  filtration), the compressibility coefficient and the  CST
 (Capillary Suction  Time; values of about 10s  with  10  reservoir generally
 mean good dewaterability).

      These parameters,  easy  to determine, are indirect  measurements of  funda-
 mental properties (e.g. particle  size distribution, Zeta  potential, rheologi-
 cal  properties)  which would  be necessary to measure in  order to promote a
 real technical  innovation. The influence of these properties on the condi-
 tioning and dewatering operation was studied by Campbell et al. (6) and Karr
 and Keinath (7).
     Dewatering is generally preceded by chemical or physical conditioning in
order to improve the sludge dewaterability.

     In chemical conditioning a destabilization as well as a flocculation can
be distinguished.  Reagents can be either organic or inorganic,  the latter in-
cluding iron and aluminum salts,  lime and a combination of these.  Lime,  in
particular, may be used either as a pre-conditioner (to reduce the  alkalinity
and thus the reagent consumption), or as a filter aid with an important mass-
effect in those cases where cake of a certain thickness are required (as in
the case of vacuum-filters).  According to Christensen ind Style (8) iron
salts give better results when used as ferric chloride combined with lime;
this treatment, moreover, is suitable (pH>12) for sludges to dispose on land-
fill.  Aluminium chlorohydrate, instead, does not require the use of lime
 since it does not interact with the alkalinity.

     Organic reagents consist of polymeric macromolecular compounds  which are
characterized by monomer type, molecular  weight, ionic charge and hydrolysis
degree.
                                     696

-------
     The conditioner type and dosage can be assessed in laboratory by general
tests  (jar-test, specific resistance to filtration, CST, etc.) and specific
tests  for each type of dewatering technology (filter-leaf, drainability, floe-
strength, ecc.) which are in many cases useful to predict full-scale equip-
ment performances.  In the following the main specific tests are briefly out-
lined .

     Filter-leaf allows  to  simulate in laboratory the phases  of a vacuum-
filter cycle.  Methods for  predicting  beltpress  performance have been
proposed by  Baskerville  et  al.  (9)  and Heide  et  al.  (10); the first one
consist in a series of drainage tests  and  one pressure test with a piston
press, the second, uses  a Modified  Filtration Test (MFT)  to give an impres-
sion of the  final dry solid content and of the rate  of dewatering.   CST
measurements at  1,000 rpm stirring  with standardized stirrer  may be
employed to  obtain information  about the optimal conditioner  dosage for
centrifugation (Mininni  et  al.  (11); measures of the Theological properties
utilizing a  modified rheometer  (12, 13) give  indications  similar to that
obtainable from the above mentioned tests, while measures of  sludge con-
sistency (penetrability) and centrate  concentration  (14)  have not provided
satisfactory results with activated sludges.   When sludge flocculation is
necessary, it is suggested  (15) stirring at about 100 rpm for 10-15 minutes
followed by  stirring at  30  rpm  only to avoid  sedimentation.


     Physical methods  include thermal conditioning, freezing and the use of
inorganic  admixture.

      Thermal conditioning  involves  heating of sludges at  a temperature of
 180-220 C for 30-90 minutes. With  a mixed sludge it is possible to obtain a
high  reduction of the specific  resistance  to  filtration operating at  210 C
 for 30 minutes  (16).   After such a process the supernatants or  filtrates
 recycled  back to the  plant cause a supplementary load of  15-20%; odour
problems could also arise.  This process has been applied  in Europe  in big
plants equipped with filter-presses or vacuum-filters  where it  is  possible  to
reach  cake concentration up to  50 and  40%  respectively.

     Conditioning by freezing generally results  in a  sludge that dewaters  ex-
tremely well by gravity on  subsequent  thawing, in this case also the  effluent
would  exert  a considerable  supplementary load  if  recycled  back  to the  treat-
ment plant.  Energy requirements  seem to  iustify  this process only if accom-
plished by natural means.  The use  of  inorganic  substances  (ash,  diatomaceous
earth,  etc.)  allows to obtain a mixture with  improved  filtering  character-
istics  and usually less compressible than  the  sludge  alone, but the calorific
value  is reduced. Ratios  of admixtures to  sludge  solids  typically range
from 0.5:1.0  to 2:1.
                                    697

-------
Machine  operation

      A survey  concerning  conditioning and dewatering  practice  in EEC Coun-
tries (17)  showed  that  centrifuge  (as of now  indicated with  CF)  and filter-
presses  (FP) are the machines mostly used; belt-presses  (BP) are utilized on
the  average of 20%, while scarse interest is  shown  for vacuum-filters (VF),
except for  France.

      For the future everything seems  to indicate a  growing interest towards
 BP and FP,  while the percentage of CF can be  expected to keep  constant.  Si-
 milar trends are to be found in N. America  where, at  present,  VF are widely
 utilized (about 30$).

      As far as conditioning is concerned, polyelectrolytes and iron salts,
 with or without lime,  are widely used,  while  an increasing preference is
 shown toward the first ones.

 Filter-press
                                            2
      Filtration under pressure (50-140 N/cm ) is the  dewatering operation
 which allows to obtain the highest final solid concentrations. The schematic
 section of a traditional fixed-plate  filter is shown  in  Figure  16.

     The operating variables affecting the  process are: pressure, filtration
time, thickness of chambers and type of cloth. Ferric chloride, with or with-
out lime, and aluminium chlorohydrate  are used for conditioning; the use of
organic polyelectrolytes has been considered (18) also in view of the savings
brought about by the elimination of the flocculation tank, but care must be
taken since an overdose would cause cloth blinding.   Typical results of
filter-pressing are reported in Table  17.
      Plate  FP  operation requires a great deal  of  labour  for filter  opening
and  cleaning;  moreover  the  filter  yield is low compared  to BP  and VF. Experi-
 mental tests (15) showed an average yield  of   1.5 kg/m^.h at 147 N/cm^ and  1.0
 at 69 N/crn^ with an average pressing  time  of   2-3 h, beyond which filtrate
 flow rate gets down to very low values (~ 4 1/m^h).

      Different systems  have been introduced in order  to  overcome these incon-
veniences;  the automation of plate movement and  cloth washing  have  made  pos-
 sible a  reduction  of the  costs  due to labour,  while it has been  possible  to
 increase filter yield by  the membrane FP (see  Figure  16). Parallel  tests con-
 ducted on chemical sludge conditioned with lime  ( 23 )    indicated that
membrane FP dewater satisfactorily at lower lime  dosage  and with a  greater
yield (2.0-3-5 kg/m2h). Other  tests  (15)  indicated  that  mixed
 sludges conditioned at 19.6%  of  lime  and 6.5% of ferric chloride reach
                                      698

-------
Figure 16. Schematic view of a fixed-plate filter-press (oi) and a membrane
              press (ft): I filtration phase, II compression phase.
           A: feed sludge; B: filtrate; C: pressurized air or water;
           1: cloth; 2: soft rubber membrane; 3= cake under compression;
           4: moulded rubber body.
                                    699

-------
                                    TABLE  18.  FILTER-PRESS OPERATING DATA
Input
Sludge type (sludge cone.



volume
T)
X
H
fe


volume
H
Variat
Raw Primary. U.S. EPA (19)
Digested Prim. Parkhurst
et al. (20)
Raw Prim. + Activ. U.S.
EPA (20)
Raw Prim. + Activ. White
and Baskerville (21)
Dig. Prim. + Activ. U.S.
EPA (19)
Dig. Activ. Spinosa and
Mininni (22)
Raw. Prim. + Activ. U.S.
EPA (19)
Dig. Prim. + Activ. (U.S.
EPA (19)
5-0-10.0

3.8- 4-0
1.0- 6.0
4.6- 7.6

3.5- 5.0

4-4- 5.6

4.0
2.5-6.4
Cake
cone .
45

23-37
45
27-41

42

37-42

40
36-50
Time of
filtration
(min. )
90-120

60-180
150
290-390

-

240-360
Yield
(kg/m2h)

4-4
3.0-9.8
Conditioner dosags
FeCl3
40-60

40-60
50-60
-

27



50
40-90
CaO
100-140

200
100-120
-

170



150
110-290
Alum ,-Chlor
(kgA!203/t)












o
o

-------
a final cake concentration of 38.7%? a  yield of 2.4 kg/m h with 17 minutes
of pumping at 69 N/cm2 and 18 minutes of pressing at 147 N/cm2 was obtained.
The most accepted method of generating design information is to operate a pi-
lot scale plant; being this not always possible, it should be useful to have
methods to predict the industrial FP performance. The prediction of pressing
time on the basis of the well known equation developed  by Jones provides
values equal to about 40% of the actual ones.   Tests carried out  with pilot
scale FP have made it possible to develop a new model which allows  to corre-
late the coefficients a and b of the equation expressing  the filtrate flux
vs time (4 = a  . t^) with pressure,  specific resistance and input sludge
concentration.  Once a, b, the chamber volume,  the  filtration surface and the
dry solids density are known, it is  possible to estimate  the values of the
yield and cake  concentration.
     A new theory of filter pressing has been developed by Hoyland et al.
 (24).-  A small micro-processor programmed with the theory, which is an exten-
sion of the classical one of parabolic filtration, can monitor the progress
of any filter pressing and, in its later stages, predict the residual press-
ing time required to produce a cake of a given quality.

Belt-press

     BP have been recently introduced into the specific field of sludge dewa-
tering.Dewatering takes place through drainage and compression; moreover, in
the final zone, sludge undergoes also a shearing action due to the relative
movement of the two belts. A schematic section is reported in Figure 17.
                                                     //tv
      Figure 17. Schematic view of a belt-press.
                A: feed sludge; B: dewatered sludge? C: filtrate.
                                     701

-------
      The operating variables affecting the machine performance  are:  belt
 speed, the pressure exercised on the belts in the compression zone and the
 specific sludge flow rate (m^/h-m);  this last variable is limited due to the
 need of avoiding lateral leakage of  the sludge.  High speed of belts  allows to
 operate at higher capacity values, but a lower final concentration is
 obtained.   In practice, the belts operate at speed ranging between 50 and 100
 m/h with a sludge flow rate of 2-5 m^/h'm.  For good machine operation, it is
 advisable  to feed the sludge at a concentration not lower than 3-4%.  Special
 care must  be taken in belt washing:   rinsing  water flow rates of 50-200% of
 that of the sludge at a pressure of  40-60 N/cm^ are reported by Eckenfeder
 and Santhaman (25) but higher values (up to 10 nrVh'm) are not uncommon.

      Conditioning is carried out by  polyelectrolytes with mixing immediately
 before the drainage zone. Typical results are reported in Table 18 .
     TABLE 18.  BELTPRESS OPERATING DATA, U.S. EPA (19); IMHOFF,  (26)
Sludge type

Raw Primary
Raw Activated
Raw Primary + Activated
Aerobic Digested
Anaerobically Digested
Thermal Conditioned
Input Sludge
concentr .
(0?\
\/o)
3 -10
0.5 - 4
3 - 6
1 - 8
3-9
4 - 8
Cake concentr .
(%}
25 - 44
12 - 32
20 - 35
12 - 30
18 - 34
38 - 50
Polyelectrol.
dosage
(kg/t)
0.5 - 4.5
1.0 - 6.0
0.6 - 5.0
0.8 - 5.0
1.5 - 4-5

     Tests    carried   out   (27)  with  pilot  machine   (belt   width
0.5 m)  on sludges from slaughter house wastewater enabled to correlate dewa
tered sludge concentration C^ (%) with belt speed  (m/h), input sludge flow
rate Q (m^/h) and initial concentration CQ (kg/m^) with the equation:
                       Ck = 76.54 -

having a correlation coefficient  of 0.92. The input specific flow rate ranged
from 1.2 to 3.4 m^/hm.
                                     702

-------
Centrifuge

     The type of machine mostly utilized for sludge centrifugation consist of
a cylindrical-conical bowl shell with an internal Archimedean screw  (the
scroll) which revolves at a slightly lower speed.  The solid liquid separa-
tion takes place like sedimentation, but at g values up to 3000. A centrifuge
schematic section and some typical  results  are  reported  in Figure 18  and
Table  19, respectively.
               A	
               Figure 18.   Schematic view of a bowl centrifuge.
                           A - feed sludge;  B - dewatered sludge;
                           C - centrate
     The operating variables which the performance of the machine depends on
are: bowl speed, liquid ring height, bowl/conveyor differential speed and in-
put sludge flow rate. Widely accepted indications on the effects of such va-
riables are not found in literature and it is commonly known that for some of
them opposite results may also ensue due to values of other variables. For ex.
an increase of the differential speed generally causes an increase in solid
recovery, but under certain conditions (low liquid ring volume, sludge with
a low floe strength) the results might be the opposite due to the high turbu-
lence induced by the scroll which determines the breaking off of the floes
and their resuspension.
                                     703

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    TABLE 19.  CENTRIFUGE OPERATING DATA, U.S. EPA (19) AND EXPERIMENTAL
               STATISTICAL CORRELATIONS, MININNI ET AL. (27)
Sludge type
Raw Primary

Raw Activated
Raw Primary + Activated
Digested Primary +
Activated
Thermal Cond. Prim. +
Activated
Feed
cone .
(%)
5- 8

0.5- 3
4- 5
2- 4
4- 7
9-14
13-15
Cake
cone.
(%}
25-36
28-36
8-12
18-25
15-18
17-21
35-40
29-35
Cond.
dosage
(kg/t)
0.5-2.5
0
5-0-7.5
1-5-3-5
3-5-5.0
2.0-4.0
0
0.5-2.0
Solid
rec.
(50
90-95
70-90
85-90
90-95
90-95
90-95
75-85
90-95
                       bl  b2
 Type equations:  Y = axj  X2
bn
y
W)
"d
^watered sli
concent.
n

T* b
O O
CO O
^
Slude
type
1
2
3
4
5
6
4
5
6
Coeff .
a
73.75
81.79
61.25
1.22
11.97
0.0122
93-95
397.30
96.78
Exponents of x^ = ....
xi = tb
(s)
0.215
0.203
0.244
0.123
0.092
0.230
	
	
	
hlr
(mm)
0.273
0.093
0.263
-0.056
- 0.272
0.399
	
	
	
GSU

0.717
0.084
1.745



CO
(rpm)

	
	
	
0.313
0.399
0.311
0s
(kg/In)

	
	
	
-0.946
- 1 . 594
-0.493
t^: sludge resid. time on the beach; h^r:  liquid ring height;  Csu:  cone, after
2 h settling in 11 cylinder; CO  :  differential speed; 0S:  solids input flow
rate/liquid ring volume (solids flux); 1:  4>8% Aerob. Dig.  Activated; 2: 3-2%
Aerob. Dig. Activated with dephospation by A^SO^K; 3:  4-5% Aerob. Dig.
Activated with dephospatation by FeSO^ 4: 0.7% Aerob. Dig. Activated using
pure 02; 5: 1.5% Aerob. Dig. Activated using pure Q; 6: 2.1% Aerob. Dig.
Activated using air.
                                    704

-------
     To clear up the aspects linked to the solid/liquid separation mechanisms
 in a centrifuge, pilot  scale tests have been carried out with different kinds
of sludges(19). From the statistical correlation of the results obtained it was
 evidenced that the most significant variables influencing the dewatered
 sludge  concentration are  the  sludge  residence  time on the beach (which is
 correlated  to the  differential speed through the  beach length and the scroll
 pitch)  and  the liquid  ring height.   As  far as  solid recovery is concerned,
 similar relationships  have been looked  for,  but only with liquid ring heights
 higher  than 11 mm  (bowl diameter 151 mm)  good  correlations were obtained; the
 differential speed and the flux of solids (referred to liquid ring volume)
 fed  in  the  centrifuge  resulted the most  significant variables.   Coefficients
 and  exponents experimentally  obtained are reported in Table 19.   Lower bowl
 speed values corresponding to  500-800 g  bring  about advantages  in lowering
 power consumptions, noise, maintenance  needs,  floes mechanical  stress and,
 then, conditioner  consumption.
     It must be kept in mind that, in order to guarantee a good performance
and a long life of the machine, coarse or abrasive materials should be
avoided, while skilled labour must be employed for maintenance.   The  advan-
tage of this technology consists  above all in the fact  that  the  solid/liquid
separation occurs in a place completely  isolated from the  outside and that
the equipment size is limited.

Selection criteria

     In treatment plants great care has to be taken in the proper selection
of the dewatering machine from which depends the good performance of the sub-
sequent treatments (incineration, composting, etc.) and the easyness and
cheapness of disposal.

     The most important items to be considered in selecting the dewatering
machine are the following:
concentration of the dewatered sludge;
volume of sludge to dewater;
characteristics of the sludge;
investment costs;
operational costs;
treatment of liquids separated during the dewatering operation.

     As far as the first point is concerned,  the field of application of dif-
ferent technologies is well known: CF allows to obtain a final solid concen-
tration of less than 20% with activated sludges,  BP up to 30% and FP of 40%
                                     705

-------
 and even greater if sludge is thermal conditioned. The advantage of a higher
 solid concentration is easily quantified either if the sludge is subsequently
 carried to landfill or agricultural soil (volume to be disposed of is reduced)
 or if it is incinerated (saving of auxiliary fuel). The input sludge flow
rate does not prove, in general, to be discriminating toward  the various  tech-
nologies since the potentiality of the dewatering machines available  on the
market is very wide; in case, the plant has to be equipped with an  adequate
number of units in parallel with, at least, a spare unit.

      Sludge characteristics, either biological or technological, are instead
 an important factor in the choice of the most suitable equipment.  Parameters
 and tests which is possible to utilize for characterizing sludges  and asses-
 sing the optimal conditioner dosage have been already mentioned; the evalua-
 tion and application of the technological characterization parameters was
 discussed by Spinosa et al. (29). If the sludge is not well  stabilized (vola-
 tile solids concentration > 70% and 0  up-take>10 mg/gSSVh)  technologies apt
 to keep the sludge separated from the ambient are to be preferred  thus avoid-
 ing any trouble to the operators; CF has this requirement.

      Another aspect to be taken into account is the area occupied  by the  de-
 watering equipment because dimensions are very important in the costs of
                                                           i
 civil works.   In Figure 19, the area required for different machines as a
 function of the feed sludge flow rate is shown; the advantage of a more
 compact machine is then made up by a lower final concentration.

      Operational costs are heavily affected by labour ones; as already men-
 tioned, FP operation,  carried out with traditional machines,  requires
 considerable personnel being the working cycle intermittent,  while CF as well
 implies high personnel costs due to the fact that skilled one is required
 for maintenance.  From this point of view, it is then evident the advantage
 of BP.

      Another important feature of dewatering machines is the  efficiency of
 the solid-liquid separation which is good for FP (> 95%), intermediate for BP
 (around 95%) while with CF lower values (<95%) are generally obtained. Since
 the liquid separated after dewatering is recycled back to the treatment plant,
 the additional load brought about by this, either in terms of solids or orga-
 nic matter, is not negligible and could causing the bad operation of the
 sewage treatment work; from this viewpoint FP has  to be preferred.

 Design criteria

      The designing of dewatering equipment is generally based on empirical
 criteria derived from experience, rather theoretical developments  of general
 applicability since modelling of filtration and centrifugation processes  is

                                     706

-------
                                                             1000   Q(m3/d)
     Figure 19.  Area occupied by dewatering machines vs wet sludge flow rate
                (a) centrifuge, (b) belt-press, (c) filter-press
                Design data:
                            m3/d        20   50   100   500   1000
                            h oper./d    88     8    12     24
                            n of units   1    1     2   (n + 1 spare)

very complex and it is not possible to reach functional relationship, solved
in finite terms, between the dependent variables  (cake  concentration,  solid
removal efficiency) and independent ones  (input sludge  characterization
parameters, operating variables of machines).
     For FP designing it is necessary to determine the chamber volume V for
treating a daily amount Q of sludge having a concentration C :
                               V =
                                      Q Cf
                                    707

-------
where:
n = number of daily
filtration cycles;
C = concentration required for the cake, weight fraction;
n = cake density.

     To calculate this volume it is essential to know the concentration C,
                                                                          K
obtainable after a certain time of filtration; it has therefore to carry  out
tests on pilot scale. As already mentioned, it is possible to estimate theo-
retically Ck as a function of time and  pressure  (20);  estimated cake concen-
trations and actual ones for several  cases  are compared in  Figure 20.
            50
         o
         u
            30
            20-
            to
                      10
20
                 30
50
    Figure 20.  Comparison of calculated cake concentrations and observed
               ones
               a) IRSA-CNR (l) tests; b) IRSA-CNR (I) tests; c) WRC (UK)
               tests; d) TNO (NL) tests.

     As far as BP is concerned one often refers to values taken from expe-
rience and that, in particular, are referred to the wet sludge flow rate
which can be treated per unit of belt width. Data available in literature
                                    708

-------
            -J2-
            E
            10-
             cr
               8-
                6-
               4-
                2-
                            A  A
                                   a
                                   a
o 1
D 2
* 3
v 4
A 5
 6
 7
                 0       2       4       6       8      10      12
                                                          C0(%)

      Figure  21.   Sludge specific  flow rate  in  belt-pressing  vs initial
                   concentration.
                   1)  Imhoff  (26);  2)  Baskerville et  al.  (31); 3)  Sibamat
                   belt-press  tests;  4) Zeper and Pepping (37);  5) Hansen
                   and Budgaard-Hansen (33);  6)  Sernagiotto (34);  7)
                   Ecomacchine (35).
(Figure 21) are very discordant thus making difficult to draw general conclu-
sions; it appears however to be appropriate to consider values not higher
 than 4 m^/h-m, but a value between  2  and  3  seems to be  on the safe side in a
 stage project.  Due to  the wide variation  in reported  results it would stress
 the  need to  conduct pilot-scale tests before  specifying the size of BP.

      Designing  of  a CF is generally made by utilizing  the theory of 2   (14)
 being:
                           Q,     Qa
                          2,     2,
 where Q  is  the flow rate and 2  a  peculiar characteristic of the equipment
 representing the area  which a gravity sedimentator  should have in order to
 obtain the same solid  recovery; subscript 1 is referred to a pilot machine
 and  subscript 2 to an  industrial  one.
                                    709

-------
     Tests are carried out to determine sludge flow rate Q , which can be
treated by the pilot CF having a known.2,  characteristic with a solid liquid
separation efficiency not lower than 80%;  the above equation gives then the
characteristic 2^  of the industrial CF for treating a flow rate Q2 . This
procedure, however, only accounts for liquid loading while the movement of
solids out of the machine is not considered; the 2  concept (14) allows to
estimate  the  solids handling  capacity.  The lowest  rate (liquid or solid) is
then to be considered  the limiting  factor  and must  be used for scale-up.
Consumptions and costs

     It has been dealt with the different aspects characterizing the various
dewatering technologies and which have to be taken into consideration in or
order  to  select  the  proper  dewatering equipment.

     In the absence of specific requirements the choice should fall upon the
cheapest alternative.

     Cost item to consider are the following:

Cost of installation
     electromechanical equipments
     civil works

Cost of operation
     amortization
     electric power
     labour
     maintenance
     chemicals
Costs due to the outputs
     dewatered sludge disposal
     biological treatment of the liquid (filtrate or centrate)
     separated during dewatering.

     Just  an example, Table 20 shows the costs for dewatering a 4% digested
mixed sludge produced in a sewage treatment plant for 100,000 inhabitants;
figures considered in the cost analysis are summarized in Table 21.  As for
calculation of plant costs,up-dated relationships by Beccari et al.  (36)
have been taken into consideration.
                                    710

-------
        TABLE 20.  COST COMPARISON OF DEWATERING SYSTEMS FOR A 100,000
                   INHAB. PLANT
Cost item

-* Civil work amortization
";H;" Electrom . eq. amort.
-:;-;:-;;- Maintenance
+ Electric power
++ Operation personnel
+++ Chemicals
 Cake disposal
 Biol. treat, of filtrates
Total
(Lit/cap, y)
Filterpress.
(MLit/y)
15.04
86.89 101.93
14.80
5.08
18.25
35-37 73-50
93.98
10.95 104.93
208.36
2.800
Beltpressing
(MLit/y)
9-36
117.14 126.50
21.59
7.05
13-69
44.71 87.04
101.51
27.37 128.88
342.42
3-400
Centrifuging
(MLit/y)
13.18
69.34 82.52
18.50
7.20
18.25
51.10 95-05
H4.36
54-75 199-11
376.68
3.800
  *: Interest rate 10%, 25 years; *#: Interest rate 10% 12 y for FP,  10 y for
  BP, 8 y for CF; **: 2.5% of electromech. eq. cost/y for FP, 3% for  BP, 5%
  for CF; +: 80 Lit/kWh; ++: 12.500Lit/h;  +++: FeCl3 340 Lit/kg, CaO  60 Lit/kg,
  Polyelectr. 7-000 Lit/kg; : 17-500 Lit/t wet sludge transported?  :  600
  Lit/kg BOD  treated
  -"- 1 $ = 1.400 Lit.
      The prevailing energy consumption for FP is due to sludge pumping; con-
 sumptions for filter opening and cloth cleaning  may be  considered  equal  to
 10$ of pumping ones. With a pressure  of 98  N/cm2 and a  2$% efficiency the
 energy required is  given by:

                             E = 437-6 Q(kWh/y)
 being Q  the  wet  conditioned sludge flow rate  (t/d).

      The  following  equation has  been  taken  into  consideration for  BP:

                          E = 23600 F'74 (kWh/y)
                            o
 where F is  the flow rate  (m /h)  and taking  into  account a  specific flow  rate
 of  3  m3/hm.
                                                        o
      CF consumptions are  generally between  1 and 2  kWh/m   of treated  sludge,
 being the lower values  referred  to units at low  speed.  In  calculations a
value of  1.7 has been considered as it  represents an  average value for
machines by Pennwalt operating at 3000-4000 rpm.
                                     711

-------
           TABLE 21.   ANALYSIS  OF DEWATERING EQUIPMENT OPERATION
                      (PLANT FOR 100,000 INHAB.)

Input dry solids* (kg/d)
Input sludge flow rate (m^/d)
Conditioners*"" (kg/d)
Conditioner solution (m /d)
Cake concentration (%)
Solid/liquid separation effic. (%)
Cake density (kg/m^)
Sludge to dispose (kg/d)
Filtrate to treat (kg.BOD^/d)
Machine design***
FP
5000
125
985
17-7
40
98
1129
14712
50
1 unit
BP
5000
125
17-5
17-5
30
95
1094
15892
125
3 units
CF
5000
125
20
20
20
90
1061
22600
250
1 unit
  *: 50 g/cap.d; **: FP: 27 kgFeCl3/t$S + 170 kgCaO/tSS, BP:  3,5 kgPolyel./
  /tSS, CF: 4,0 kgPoluel./tSS; ***: 8 h/d, 2 cycles/d for FP, FP chambers
  volume: 6,51 m3, BP belt width: 2 m, CF: 18,1 m^/h.
     To calculate costs for operation and maintenance the following values
were considered (37):
0.5 h/operational h/machine for FP and CF
0.125      "            "    "  BP

     From Table 20 it appears that filter pressing is the most  convenient
system if the additional costs due to outputs are considered.   Otherwise  the
three machines seem to be equivalent; the total  cost  of  only dewatering is
equal to 95-115 lit/kgSS. Dewatered sludge disposal and  filtrate biological
treatment involve additional costs of 60% for FP and  BP  and 112$ for CF.

Technological progress

     The operating problems the various dewatering equipments present forced
manufacturers to search for any kind of technical and economical solutions
apt to overcome them.

     Manufacturers have shown a great interest  toward FP and have  introduced
innovations to extenuate the inconveniences due  to non-continuous operation
and low yield.
                                    712

-------
      Improvements  for BP  concern  the  route  of  the cloths  (with presence of
many  rollers of different diameter),  the  drainage phase and  the belt  washing.

      Low speed CF allow,  above all, a reduction in power  and conditioner con-
 sumption. In Equicurrent CF the settled solids are not disturbed by the oppo-
 site movement of the liquid and solids are collected throughout the drum
 length thus bettering compaction and reducing conditioner demand.

 Conclusions

      What previously discussed can be so summarized:
 Filter-press,  belt-press and centrifuge are the machines  most widely used in
 sludge mechanical dewatering.

      With filter-press the highest cake concentrations are obtained,but opera-
 ration is discontinuous and yield low. Belt-press allows to.couple  advantages
 of good cake concentration and continuous operation,but problems can arise
 in belt washing.

      Centrifuge has a lower performance,  but the operation is simple and,
above all, the  liquid-solid separation takes place completely isolated from
 the out-side.

      Filter-pressing is the most convenient system if costs  for cake disposal
 and filtrate or centrate treatment are considered; otherwise the three machi
 nes seem to be equivalent.

      The main  general features of filter-presses, belt-presses and centrifu-
 ges are reported  In Table (22).

      From a general point of view efforts  in the future have  to be  addressed
in assessing simple and reliable  laboratory methods for selecting  conditioner
agent type  and optimal  dosage.  Moreover, it seems necessary to go deep into
the knowing of a  few sludge fundamental properties and of the theoretical
modelling of filtration and centrifugation  processes if a real technical
innovation  has to  be achieved.
                                     713

-------
TABLE 22.  DEWATERING EQUIPMENT FEATURES


Filter-press
Belt-press
Centrifuge
Flow rate
range per
unit
(m3/h)
0.1 - 35
1.0 - 25
0.5 - 80
Cake
concentrat .
(af\
\/o}
30
20 - 30
20
Solid/liquid
sep.effic .
(%)
95
about 95
95
Area
requirement

high
med - high
low
Energy
demand

low
medium
med - high
Typical
advantage

high solid/liquid
separ. efficiency
low personnel
requxrem.
dewatering oper.
separated from
ambient

-------
                                REFERENCES

 1.   Ramadori, R.  (1982):   State Dell1  Arte E.  Prospettive Delia  Rimozi-
     one Biologica Dell1  Azoto Dalle Acque Di  Scarico -  Acqua  E  Aria,  835.

 2.   Metcalf,  E.  Eddy (1979):   Wastewater  Engineering:   Collection,  Treat-
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 3.   Beccari,  M.  DiPinto,  A.C., Mauri,  A., Passino,  R.,  Santori,  M.,
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     Acque di  Scarico Urbane - Quaderno N. 46  I.R.S.A.   C.N.R.

 4.   U.S. Environmental  Protection  Agency  (1978):   Energy Conservation in
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 5.   Annesini, M.C., Beccari,  M., DiPinto, A.C., Giona,  A.R.,  Gironi,  F.,
     Mininni,  G.  (1982):   Consumi di Energia Negli  Impianti  di  Depurazione
     Delle Acque  di Scarico -  Quaderno  N.  58 I.R.S.A. C.N.R.

 6.   Campbell, H.W., Rush, R.J., Tew, R.   Sludge dewatering design manual.
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     Service Fisheries and Environmental,  Canada.  1978.

 7.   Karr, P.R.,  Keinath,  T.M. Influence  of particle size on  sludge de-
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     1978.

 8.   Christensen, G.L.,  Stule, D.A. Chemicals  reactions  affecting filter-
     ability in iron-lime sludge conditioning.   Journal  of Water  Poll.
     Control  Feder., 51,  (10), 2499. 1979.

 9.   Baskerville, R.C.,  Bruce, A.M., Day,  M.C.  Laboratory techniques for
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     Filtration & Separation,  15 (5), 1967.

10.   Heide, B.A., Kampf,  R., Van Veen,  H.J., Visser, M.A. Selection and
     use of polyelectrolytes in sludge  dewatering with belt-presses.
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11.   Mininni,  G., Spinosa, L., Scalici, E.  A study  on sludge centrifug-
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12.   Colin, F., Study of the shearing strength of flocculated sludges.
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13.   Colin, F., Characterisation des boues residuaires.   Techniques et
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14.   Vesiling, P.A., Treatment and disposal of wastewater sludges.  Ann
     Arbor Science publ.  1974.
                                     715

-------
15.  Cassel, A.F., Johnson, B.P. Evaluation of dewatering devices for pro-
     duction of high-solids sludge cake.  U.S. EPA 600/2-79-123.  1979.

16.  Everett, J.G. Dewatering of wastewater sludge by heat treatment.  Jour-
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17.  Spinosa, L., Erikum, A. Dewatering of municipal  sludges.   2nd European
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18.  Charlesworth, B.R., Knott,  T.A., Fox, R.A.  Polyelectrolytes in pressure
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19.  U.S. EPA. Process design manual  for  sludge  treatment and  disposal.
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20.  Parkhurst, J.D., Miele, R.P., Hayashi, S.T., Rodrigue, R.S. Dewatering
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21.  White, M.J.D., Baskerville, R.C.  Full-scale trials of polyelectrolytes
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22.  Spinosa, L., Minnini, G.  Experimental research on  activated sludge de-
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24.  Hoyland, G., Day, M., Baskerville, R.C.  Getting more out of a filter-
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25.  Eckenfelder, W.W. Jr., Santhanam,  C.J.,  Sludge treatment.   Marcel
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26.  Imhoff, K.R.,  Sludge dewatering tests with a belt-press.  Water Re-
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27.  Mininni, G., Santori, M., Spinosa, L.,  Disidratazione dei  fanghi:
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28.  Mininni, G., Santori, M., Spinosa, L.,  La  disidrazione dei fanghi.
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     ziario 27. 1981.
                                     716

-------
29.   Spinosa, L., Aveni,  A., Lamarca, V.   Valutazione ed applicazione dei
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     November,  1982.

30.   Mininni, G., Spinosa, L.,  Un nuovo  modello per la valutazione delle
     prestazioni  della filtropress.  Seminario  sul  tema  Disidratazione mec-
     canica dei fanghi.   I.R.S.A. - C.N.R., Bari, November,  1982.

31.   Baskerville, R.C.,  Komorek, J.A.,  Gale, R.S.,   Effect of operating vari-
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32.   Zeper, J., Pepping,  R.,  Handling  of aerobic mineralized sludges by
     centrifuges  and belt-press filters.   Water Research, 6, (4/5), 507.
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33.   Hansen, T.,  Bundgaard-Hansen, E.,   Comparison of centrifuge and filter-
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34.   Sernagiotto  S.p.A.   Prove di disidratazione su fanghi residui da im-
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35.   Ecomacchine  s.r.l.  Dati di prove su  impianti di depurazione.   Private
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36.   Beccari, M., Di  Pinto, A.C., Mauri,  A., Passino, R., Santori, M.,
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                                     717

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             JAPANESE ADVANCES

                        IN

           WASTEWATER TREATMENT
                    Takeshi Kubo,

                  Dr. Eng., Counselor

              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.
North Atlantic Treaty Organization/Committee on the
Challenges  of Modern Society (NATO/CCMS) Conference
           on Sewage Treatment Technology

              October 15-16, 1985
                Cincinnati, Ohio
                        719

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                              TABLE OF CONTENTS
                                                                          Page
1.   INTRODUCTION 	     721
2.   MICROPOLLUTANT (TOXICS)  CONTROL IN JAPAN 	     729
 2.1   Outline of Toxics Control System in Japan 	     729
 2.2   Toxics Control by Effluent Standards 	     729
 2.3   Other problems of pollution Related to Toxic Substances 	     735
 2.4   Measures Relating to Safety of Chemicals 	     740
3.   CURRENT STATUS OF SLUDGE TREATMENT AND DISPOSAL IN JAPAN 	     743
 3.1   Introduction 	     743
 3.2   Improvement in the Incinerating Process for
       Energy Conservation 	     745
 3.4   Development of a Technology Producing Construction Materials
       from Sewage Sludge	     751
 3.5   Regional plan for Treatment and Disposal of Sewage Sludge 	     755
4.  RECENT TECHNOLOGICAL DEVELOPMENT IN WASTEWATER TREATMENT 	     765
 4.1   Overview	     765
 4.2   Some Typical Examples of the Recent Technological Development .     770
5.   UPGRADING OF EXISTING WASTEWATER TREATMENT PLANTS 	     784
 5.1   Background	     784
 5.2   Necessity for Upgrading of Existing Wastewater
       Treatment Plants 	     784
 5.3   Tentative Guideline for Upgrading of Existing
       Treatment Plants 	     786
 5.4   Examples of Upgrading of Existing Plants 	     787
                                     720

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1.   INTRODUCTION

          The sewage works in Japan started in 1880 when a sewer  of  about
     2.5 km was constructed in the Kanda area in Tokyo after experiencing
     epidemics of infectious diseases/  such as cholera, several  times.   Later
     in 1900, the government enacted the Sewerage Law (old)  to provide
     sewerage systems systematically throughout the country.  However,  the
     investment for the sewage works was not big.  As of 1940, forty years
     after the enactment of the law, the sewered area was merely 26,393 ha,
     and the population served was 5.06 million or about 8 percent of the
     total population at that time.  Main purposes for the sewage works at
     that time, were to prevent from flooding in urban areas and to maintain
     the cleanliness in cities.  Due to the increase in population in cities,
     the amount of wastewater discharged increased, and therefore, it became
     necessary to construct wastewater  treatment plants in big cities from a
     viewpoint of public health.  In this connection, the secondary treatment
     of sewage in major cities started  rather early.  The first  wastewater
     treatment plant with tricklig filters was constructed in Tokyo City in
     1922.  In succession, two plants using the activated sludge process were
     constructed in Nagoya City in 1930.  In 1940, 12 plants with secondary
     treatment were in service.
          The economic growth, particularly the growth of heavy  industries,
     and the concentration of population in big cities in 1950's were quite
     marked posing the serious problem  of river and coastal water pollution
     especially around big cities.  Water pollution became more  serious
     during late 1950's and 1960's, which was typically represented by  two
     tragic events, namely "Minamata" disease (an organomercury  poisoning)
     and "Itai-Itai" disease (a cadmium poisoning).  To cope with these
     situations, the relevant laws for  the water pollution control were
     enacted late in 1960's.  The Basic Law for Environmental Pollution
     Control was established in 1967; through this enactment the
     environmental water quality standards relating to human health and
     living environment were set up as  shown in Tables 1.1 and 1.2,
     respectively.  In addition, such concrete steps as the preparation of. a
     public hazard prevention plan were established one after another.   Also,
     in 1970, the water pollution control law was revised to strengthen the
     effluent regulation.  Through this amendment, uniform effluent standards
     were established by the national government as a minimum requirement,
     and also, it was guaranteed that the prefectural governments could
     establish more stringent standards by their ordinances depending on the
     conditions of each water body.  The national uniform standards are given
     in Table 1.3.  At present, all of  the prefectural governments have
     established their own ordinances which enforce standards more stringent
     than the national uniform ones. As a typical example of the overlay
     standard, the effluent standards of Chiba prefecture are also shown in
     Table 1.3.  The prefectural governments are also authorized to set
     effluent standards relating to pollutants which are not regulated  by the
     national uniform standards.  The effluent standards for phosphorus and
     nitrogen were established by the Shiga Prefecture for the Lake Biwa
     basin in 1979, which is shown in Table 1.4 is an example of  the
     standards of this kind.
                                     721

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     Regarding to the pretreatment  standards  which are applied to the
industries discharging their wastewater  into  a public sewerage system, a
sewerage authority under the Sewerage  Law can establish the same
standards as those applied  to  the industries  discharging their
wastewater directly into the public bodies of water under the Water
pollution Control Law as far as  the toxic substances are concerned.


    Table  1.1   Environmental water quality standards relating  to
               human health (Dec. 28,  1971)
Item
Cadmium
Cyanide 2
Organic phosphorus
Lead
Chromium (sexivalent)
Arsenic
Total mercury
AlkyZ mercury
FCB
Standard values
0.01 ppm or less
Not detectable
Not detectable
0.1 ppm or less
0.05 ppm or less
0.05 ppm or less
0.0005 ppm or less
Not detectable
Not detectable
          Notes: 1. Maximum values.  But with regard to total mercury, standard
                 value is based on the yearly average value.
               2. Organic phosphorus includes parathion, methyl parathion, methyl
                 demeton and E.P.N.

           The sewage works actually  restarted from  the  enactment of the new
      Sewerage Law in 1958.   Since the role of sewage works in the field of
      water pollution control had been widely  recognized,  the clause, "to
      contribute to the preservation  of water  quality in public water bodies",
      was added to the purpose of the sewage works defined by the law through
      its amendment in 1970.  The construction of sewerage facilities has
      further been promoted by the amendment.  Figure 1.1  shows trends in the
      investment in the sewage works  in the past. Prom  this figure, it is
      seen that the investment in sewage works increased at a far higher rate
      when compared with that of the  GNP or the government fixed capital
      formation.   Although the investment after fiscal year 1982 declined a
      little reflecting the financial condition of the Japanese government,
      the investment in fiscal year 1983 remained 1.6 billion yen, which
      accounted for 0.57% of  the GNP.  As the  result this  rush investment in
      sewerage construction, population served has recently increased fairly
      rapidly in big cities for instances, 80% in Tokyo, 99% in Osaka, 87% in
      Nagoya, 72% in Kyoto, 56% in Yokohama and 46%  in Hiroshima in 1984,
      although its nationwide ratio still remains rather low at 33%.
      Therefore,  the situation of water pollution has improved considerably.
      The ratio of compliance to environmental water quality standards has
      become steadily better as shown in Fig.  1.2.   The  problem relating to
      toxic substances is discussed in Chapter 2.
           There still remains, however, a lot of problems  in the field of
      sewage works, such as sludge treatment and  disposal,  advanced wastewater
      treatment,  energy conservation  and proper wastewater  treatment process
      for smaller scale facilities.   For preventing  eutrophication of lakes,
      environmental water quality standards for phosphorous and nitrogen were
      set up in 1982 as shown in Table 1.5.  At present, the standards are
                                       722

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being  individually set  for  lakes throughout  the country.    Some
wastewater  treatment plants  which  discharge  effluent to this  kind of
lakes  have  already started  treatment  to  remove phosphorous and nitrogen
from  their  effluent.   In  this paper the  recent progress in wastewater
treatment technology in Japan will be summarized.
      Table  1.2   Water quality standards relating  to  the  living
                     environment  (rivers, lakes,  coastal  waters)

                                     Coastal waters
Cate-
gory
A

B
C
0s e
Fishery class le;
bathing; conservation
of natural environment,
and uses listed in B-C
Fishery class 2,
industrial water , and
uses listed in C
Conservation of
environment
Standard values
EH
7.8-8.3

7.8-8.3
7.0-8.3
Chemical
oxygen
demand
(COD"")
2 mg/
or less

3 mg/i
or less
8 rag/4
or less
Dissolv-
ed oxgen
(DO)
7.5 mg/
or more

5 mg/*
or more
2 mg/
or more
Number of
coliform
groups'*
1000 MPN/100
mi or less

-
-
N-hexane
extracts
Not
detectable

Not
detectable
-
              a  The standard values are based on the daily average values.   (The same
                applies to standard values for lakes and coastal waters.)
              b  At the inlet of agricultural water, pH shall be between 6.0  and 7.5
                and dissolved oxygen shall not be less than 5 rag/jt.  (The same applies
                to standard values for lakes.)
              c  With regard to fisheries,  classes 1, 2, and 3, the standard  values for
                suspended solids shall not be applicable for the time being.
              d  With regard to the quality of fisheries, class 1 for planting oysters,
                the number of coliform groups shall be less than 70 MPN/100  ml.
              e  Fishery class 1: Aquatic life such as red sea-bream, yellow  tail,
                seaweed.
              f  Fishery class 2: Aquatic life such as gray mullet, laver,  etc.

              Notes:  Conservation of natural environment: of scenic spots and other
                    natural resources.

                    Water supply class 1:
                    Water that requires simple cleaning treatment such as filtration.
                    Water supply class 2:
                    Water that requires normal cleaning treatment such as
                    sedimentation and filtration.
                    Water supply class 3:
                    Water that requires highly sophisticated cleaning treatment
                    including pretreatment.
                    Fishery class 1:
                    For fish such as trout  and bull trout in oligosaprobic waters, and
                    those of fisheries class 2 and class 3.
                    Fishery class 2:
                    For fish such as fish of the salmon family  and sweetfish in
                    oligosaprobic waters and those of fisheries class 3.
                    Fishery class 3:
                   For fish such as carp and silver carp in S-mesosaprobic water.
                    Industrial water class  1:
                   Water  should be given normal cleaning treatment such as
                    sedimentation.
                    Industrial water class  2:
                   Water  should be given sophisticated treatment  by chemicals.
                   Industrial water class  3:
                   Water  should be given special  cleaning treatment.
                   Conservation of environment:
                   Up  to  the  limits at which  no nuisance is caused to people in daily
                   life  (including walking by the riverside, shore, and so on).
                                         723

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Table 1.2  Water quality  standards relating to  the living

            environment  (rivers, lakes, coastal  waters)  (Cont'd)


           Lakes (Natural lakes, reservoirs, marshes, and artificial lakes or
               more than 1 x 16* n3 water)
Cate-
gory
AA




A



B




C






Use
Water supply class 1|
fishery class li
conservation of natural
environment, and uses
listed In A-C
Water supply classes 2
and 3t fishery class 2>
bathing, and UBBS
listed In B-C
Fishery class 3;
Industrial water
class 1; agricultural
water, and uses
listed In C
Industrial water
class 2; conservation
of environment




Standard values9
P"
6.5-0.5




6.5-8.5



6.5-8.5




6.0-8.5






Chemical
oxygen
demand
(COD"")
I mg/i
or less



3 rag/*
or less


5 ag/i
or less



8 mg/i
or less





Sus-
pended
solids
(SS)
1 mg/i
or less



5 mg/i
or less


15 mg/i
or less



Floating
matter
such as
garbage
should
not be
visible
Dissolved
oxygen
(DO)
7.5 mg/i
or more



7.5 mg/
or more


5 mg/i
or more



2 mg/i
or more





Number of
collform
groups
500 MPN/100 i
or less



1000 MPN/100
mt or less


-




-






                                  Rivers


Cate-
gory
AA



A



B


C



D




E








Use
Water supply class 1;
conservation of natural
environment, and uses
listed in A-E
Water supply class 2)
fishery, clasa 1;
bathing and uses listed
in B-E
Water supply class 3;
fishery class 2, and
uses listed In C-E
Fishery class 3|
industrial water
class 1, and uses
listed in D-E
Industrial water
class 2s agricultural
water, and uses '
listed in E
/
Industrial water
class 3; conservation
of environment






pH
6.5-8.5



6.5-8.5



6.5-8.5


6.5-0.5



6.0-8.5




6.0-8.5







Bio-
chemical
oxygen
demand
1 mg/
or less


2 mg/i
or less


3 mg/
or less

5 mg/i
or lees


8 mg/i
or less



10 mg/i
or less





Standard

Sus-
pended
solids
(SS)
25 mg/i
or less


25 mg/
or less


25 mg/i
or less

50 ag/i
or less


100 mg/i
or less



Floating
matter
such as
garbage
should
not be
visible.
values

Dissolved
oxygen
(DO)
7.5 mg/i
or more


7.5 mg/i
or more


5 mg/i
or more

5 mg/i
or more


2 mg/
or more



2 mg/
or more







Number of
coll form
groups
50 MPN/100 I
or less


1000 MPN/100
ml or less


5000 MPN/100
ml or less

-



_




-






                                724

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            Table  1.3   Effluent standards
               Substances related to human health
                                                          (Dnit mg/l)
Toxic substances
Cadmium and its compounds
Cyanide compounds
Organic phosphorus compounds
(parathion, methyl parathion, methyl
demeton and EPN only)
Lead and its compounds
Chromium (Vl) compounds
Arsenic and its compounds
Total mercury
Alkyl mercury compounds
PCS
National uniform
standards
0.1
1
1
1
0.5
0.5
0.005
Not detectable a
0.003
Overlay standards of
Chiba Pref.
0.01
Not detectable a
Not detectable a
0.1
0.05
0.05
0.0005
Not detectable a
Not detectable a
                Items  related to living environment
Item
PH
BOD, (DDM"
SS
N-hexane extracts
phenols
Copper
Zinc
Dissolved iron
Dissolved manganese
Chromium
Fluorine
No. of coliform groups
(per cc)
National uniform
standards
5.8-8.6 for effluent
discharged into public
water areas other than
coastal waters, and
5.0-9.0 for effluent
discharged into coastal
waters
160 mg/Jt (daily average
120 rag/*)
200 mg/ (daily average
150 rag/i)
5 mg/ (mineral oil)
30 mq/Z (animal and
vegetable fats)
5 mq/S.
3 mgj.
5 mg/je
10 mg/i
10 mg/
2 rag/jj
15 mg/Jj
3000 (daily average)
Overlay standards of
Chiba Pref.
5.8-8.6 for effluent
discharged into public
water areas other than
coastal waters, and
5.0-9.0 for effluent
discharged into coastal
waters
25 mg/je
50 rag/*
3 mg/ (mineral oil)
10 mg/ (animal and
vegi table fats)
0.5 mq/i
1 mq/i
3 mq/i
5 mq/i
5 mq/i
1 mg/i
10 mq/i
3000 (daily average)
a  By the term "not detectable" is meant that substance is  below  the
   level detectable by the method designated by the Law or  the ordinance.

Note: The effluent standards in this table are applicable to  effluents
      from industrial  plants or other business places whose volume of
      effluents per day is 50 m^ or more.  The effluent standards for
      BOD are applied  to public waters other than coastal waters  and
      lakes, whereas the standards for COD*1" are applied only to
      effluents discharged into coastal waters and lakes.
      Overlay standards shown in this Table as examples are those
      provided for by  the ordinance of Chiba Prefecture and are applied
      for food industry with a discharge of 500 m3/day or more.
                             725

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                    Table  1.4   Effluent  standards relating to  phosphorus  and nitrogen
                                  provided  for  by  the ordinance of Shiga  Prefecture for
                                  controlling eutrophication of Lake Biwa
                                                                                                               (Units mg/i)

parameter

Total
nitrogen






Total
phosphorus






New or
existing
facility

Existing




New


Existing



New



Discharge

m3/day
30 - 50
50 - 1,000
more than 1,001)

30 - 50
50 - 1,000
more than 1,000
m /day
30 - 50
50 - 1,000
more than 1,000
30 - 50
50 - 1,000
more than 1,000

Food
industry


25
20
15

20
12
10

4
3
2
2
1.5
1

Textile
industry


15
12
10

12
8
8

2
1.5
1
1.2
0.8
0.5
Chlmical
industry
(excluding
gelatin
industry)

12
10
8

10
8
8

2
1.5
1
1.2
0.8
0.5

Gelatin
manufacturing
industry


20
15
12

15
10
10

Z
1.5
1
1.2
0.8
0.5

Other
manufacturing
industries


15
12
8

12
8
8

1.5
1.2
0.8
1
0.6
0.5

Sewage
treatment
plant

Average
20
20
20
Provisional
20
20
20
Average
1
1
1
0.5
0.5
0.5

Collective
night soil
treatment

Average
20
20
20

10
10
10
Average
2
2
2
1
1
1

night soil
treatment
plant

Average
(20)
(20)
(20)

(20)
(20)
(20)
Average
(5)
(5)
(5)
(5)
(5)
(5)

Other
businesses


30
25
20

25
20
20

5
5
3
4
3
2
Remarkat 1. Values for sewage treatment plants, collective night soil treatment plants and night soil  treatment facilities are daily average.
          Others are maximum.
        2. Standards for night soil treatment facilities shall not be enforced for the time being.
        3. Nitrogen standard for sewage treatment plants shall be a provisional one.

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            ABC
          (Bill.  (%)   (%)
          Yen)
           2.0    1.0   10
           1.6   0.8   8
           1.2   0.6   6
           0.8   0.4   4
           0.4   0.2   2
Investment in Sewage Waters  USW)   (A) billion  yen
ISW/GNP                           (B) %
ISW/Gov. Inv.  Fixed Capital        (c) %
                             1960
                                       1965       1970
                                                          1975
                                                                     1980
               Fig.  1.1   Investment in  sewage  works  in  the past

ul
O
a
o

4J
tfl
0
a)
u
c
H
e1
0
o
o
o
H
4J
a

100

90

80

70

60


50
40


30

20

10
0
-

-
Coastal Waters (COD\,
	 x^ 	 	 ^ 	 "' '"

-""" Rivers (BOD)
0 	 ^"~-^ 	 o
	 0. 	 o/


o
Lakes (COD)
A^ . ^^' 	 A 	 A 	 &

^A--





, , i 	
                             1974 75  76  77  78  79 RO  81   82

              Remarks: 1.                    .,.,.,
                                         Number of water bodies where
                                 ,.      environmental standards  are met
                      Rate of compliance = Numbec of watec bodles whe[e	 " "0 (*)
                                         environmental standards  are set

                      2. For the  environmental water quality standards, 6  categories
                         are set  for rivers, 4 categories for lakes, and 3 categories
                         for coastal waters according to the water  uses.


Pig.  1.2   Ratio of compliance  to environmental water quality standards
                                           727

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Table 1.5   Environmental water quality  standards  for
               lakes  relating to phosphorous and nitrogen
\ Item
Category \
I
II
III
IV
V
Applicability to
water use
Conservation of natural
environment and for water
uses listed in Categories
II - V
Water supply classes 1, 2,
and 3 (excluding special
ones). Fishery class 1,
Bathing and water uses
listed in Categories
III - V
Water supply class 3
(special ones) and water
uses listed in Categories
IV and V
Fishery class 2 and water
uses listed in category
Fishery class 3,
Industrial water,
Agricultural water, and
Conservation of
environment
Standards
Total nitrogen
Less than 0.1 mg/i
Less than 0.2 rag/
Less than 0.4 mg/2
Less than 0.6 mg/2
Less than 1 mg/jj
Total phosphorous
Less than 0.005 mg/2
Less than 0.01 mg/
Less than 0.03 mg/je
Less than 0.05 mg/
Less than 0.1 rag/S.
Remarks: 1. standards are based on the annual average values.
2. The standard of total phosphorous is not applied to agricultural
water.
   Notes: 1. Conservation of natural environment: of scenic spots and other
             natural resources.
          2. Water supply class  1:
             Water that requires purifying operation such as filtration.
             Water supply class  2:
             Water that requires normal purifying operation such as
             sedimentation and filtration.
             Water supply class  3:
             Water that requires highly sophisticated purifying operation
             including pretreatment.
          3. Fishery class 1:
             Water for fish, such as salmon and sweetfish, etc., and those
             of fishery classes  2 and 3.
             Fishery class 2:
             Water for fish, such as pond smelt, etc., and those of fishery
             class 3.
             Fishery class 3:
             Water for fish, such as carp and crucian.
          4. Conservation of environmental conditions:
             Up to the limits at which no nuisance is caused to people in
             daily life (including walking by the shore and so on).
                                 728

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2.   MICROPOLLUTANT (TOXICS)  CONTROL IN JAPAN

2.1  Outline of Toxics Control System in Japan

          The fundamental law for environmental pollution control in Japan is
     the Basic Law for Environmental Pollution Control which was established
     in 1970.  The legal system for water quality management based on this
     law is shown in Fig. 2.1.
          In order to maintain better environmental quality, particularly
     relating to toxic substances, a comprehensive policy should be adopted
     taking local conditions into consideration.  The major countermeasures
     against toxic substances pollution would be classified as follows:

     (1)  effluent discharge regulation
     (2)  construction of wastewater treatment facility
     (3)  regulation on production and use of particular substances
     (4)  stream flow augmentation and removal of contaminated sediments, and
     (5)  others such as monitoring, development of treatment technology, tax
          or financial system, compensation for damage and so forth

          The effluent discharge regulation is done based on the water
     Pollution Control Law.   It is difficult, however, in most cases to
     control pollutant discharge from small scale industries or household
     individually.  Therefore, the construction of sewerage systems is quite
     important for protecting public water bodies.  It sometimes is effective
     to introduce dilution water or to dredge contaminated sediments,
     particularly for polluted rivers in urban areas.
          Some of chemical compounds might have properties affecting
     seriously on human health or on the environment.  In order to prevent
     potential hazards of this kind, new and existing chemical substances are
     being examined by the system provided by the Chemical Substances
     Screening and Control Law.

2.2  Toxics Control by Effluent Standards

2.2.1  Compliance of toxic substance with environmental water quality
       standards

          As described in Chapter 1, environmental water guality standards
     relating to toxic substances are set for nine items: cadmium, cyanide,
     organic phosphorous, lead, chromium (hexavalent), arsenic, total
     mercury, alkyl mercury,  and PCBs.  (Refer to Table 1.1)  Most of these
     values are identical to those for drinking water supply.  For mercury
     and PCB, however, their standard values were determined taking into
     consideration damage caused by their accumulation/concentration in fish
     and shellfish.
          According to measurement results for public water bodies throughout
     Japan in 1983 for these substances, of the total number of samples
     179,000 taken at 5,239 stations throughout the country, the percentage
     of samples exceeding the environmental standards was only 0.04% as shown
     in Table 2.1.  Mercury,  organic phosphorous, and PCB were not detected
     at any sampling stations.  No sampling stations recorded average annual


                                      729

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  concentrations  of  total mercury in  excess  of  the  environmental  quality
  standard.

Table 2.1  Ratio of toxic substances exceeding environmental standards
Item
Cadmium
Cyanide
Organic
phosphorus
Lead
Hexavalent
chromium
Arsenic
Total
mercury
Year
1971
1983
1971
1983
1971
1983
1971
1983
1971
1983
1971
1983
1971
\
1983
""\^
Alkyl
mercury
PCBs
Total
1971
1983
1975
1983
1971
1983
Number of samples
(A)
15,944
27,881
12,453
23,500
5,116
8,529
14,515
27,962
11,532
24,167
11,530
25,488
12,364
Number of samples
29,978
Number of samples
(A)
5,624
7,850
3,130
4,086
89,074
149,463
Number of samples
exceeding environmental
standards (B)
114
28
142
8
11
0
202
7
15
3
48
12
32
Number of samples
exceeding 0.0005 mg/
13
Number of samples
exceeding environmental
standards (B)
0
0
12
0
504
58
Ratio (%)
(B)/(A)
0.72
0.10
0.14
0.03
0.22
0
1.39
0.03
0.13
0.01
0.42
0.05
0.26
Number of points
exceeding
environmental
standard value
0
Ratio (%)
(B)/(A)
0
0
0.38
0
0.57
0.04
       Fig.  2.2  shows  trends  in  the  ratio  of  non-compliance with the
  environmental  standard for  each  toxic  substance.   As  shown in this
  figure,  the water  quality in public water bodies  has  been remarkably
  improved over  these  15 years as  the result  of  the efforts in  water
  pollution  control.
                                  730

-------
Basic Law for  Environmental
Pollution Control
                                 Environmental  Pollution Control
                                 Programs:
                                  Established by  the prefectural
                                  governments
      Water Quality Standards:   set by national government
 For the protection of
 human health: applied
 equally to  all public
 water areas in the
 country
For the conversation of the living
environment
                             Application of the categories
                             of standards to each water area

                             Inter-prefectural water areas:
                             by national government

                             Other water areasi by prefec-
                             tural governors
                                                                                                L
                                                                                                     Source Control Laws
                                                                                                     Water Pollution Control Law: effluent control
                                                                                                     Marine Pollution Prevention Lawi oil and
                                                                                                     wastes dumping and discharge control
                                                                                                     Sewerage Law: comprehensive programing for
                                                                                                     river-basin sewarage
Mine Safety Law
                                                                          Coal Washing  Law
                                                                                                      River  Law
                                                                          Port Regulation  Law
                                                                          Natural Parks Law
                                                                                                      Fishery Resource Protection Law I
                                                                                               	|  Waste Disposal and Public Cleaning Law I
                                                                                                      Poisonous and Deleterious Substances
                                                                                                      Control Law
                                                                                                      Agricultural Chemicals Regulation Law
                                                                                                      Chemical Substances  Screening and Control
                                                                                                      Law
                                  Fig.  2.1   Legal  system  for  water quality  management

-------
                  u
                  9
                                     'Total Mercury
                                      , Organic Phosphorus
                                             , PCBs
                       FY1971 72  73  74  75  76  77  78   V9  80  81
            Remarks: 1.  Standards for alkyl mercury,  organic phosphorus, and PCBs were
                      set at N.D. from 1971, 1972 and 1975, respectively.
                   2  For total mercury, annual average at each point was determined as
                    '  the base for evaluation since September, 1974. No locations was
                      found to exceed the standard value since then.
                   3.  The total was obtained for 8 substances excluding mercury.

 Fig. 2.2   Changes in  the rate  of  non-compliance with water quality standards
            (ratio of samples exceeding the  standards)


2.2.2   Sources of water pollution

           In the Water Pollution  Control  Law,  facilities which discharge toxic
     substances or facilities of  more than  certain scale, which.discharge
     non-toxic pollutants, are  defined as specified facilities, and the
     factories which have these specified facilities are made  a subject  for
     control.
           As shown in  Table 2.2,  the total  number  of specified factories as of
     31 March 1985 was 278,861  in Japan.  Out of  them, the number of factories
     where toxic substances were  discharged was 13,161,  constituting 4.7
     percent of the total number.
                                         732

-------
               Table 2.2  Number of specified factories
^^^
(A) Fiscal Year
1984
(B) Fiscal Year
1983
Rate of increase
(A)/(B)
Discharge more than
50 m3/day
30,006 (3,820)
29,913 (3,782)
1.01 (1. 01)
Discharge less than
50 n>3/day
248,855 (9,341)
247,227 (8,652)
1.01 (1.08)

278,861 (13,161)
277,140 (12,434)
1.03 (1.06)
           Note: Numbers in parenthesis are factories which discharge toxic
               substances.
      The major types of factories which discharge toxic substances are
 given in Table 2.3.
       Table 2.3  Types of facilities discharging majot toxic substances
                                                                (1983)
\
1

2
3

4
5

6
7

8
9
10

Kind of business or name of
facilities
Natural science institute
and laboratory
Electroplating facilities
Acid and alkali treatment
facilities of metal surface
Cement manufacturing
Ready mixed concrete
manuf actur i ng
Glass manufacturing
Metallic goods manufacturing
and machinery industry
Wastes treatment plant
photo developing
Automatical washing
facilities of car
Number of
facilities
2,832

2,226
1,554

776
672

633
600

508
459
328

Major toxic substances being
discharged
CN, Alkyl mercury, organic
phosphorus, Cd, Pb, Cr6+, As, Hg
CN, Cd, Pb, Cr6+
Cd, Pb, Cr6+, As




CN, C8, Pb, As
CN, Cd, Pb, Cr6+, As, Hg


CN, 03, Pb, Hg
Hg

2.2.3  Control of factories

          The responsible person for controlling and monitoring  factories is
     the governor of each prefecture.  When a factory  installs a specified
     facility or changes the structure of his specified facility,  he must
     notify it to the prefectural governor.  When  the  governor judges  that the
     effluent from the specified facility is unlikely  to be compliant  with the
     standards, he can order an alternation for the plan in installment or
     structure within 60 days from acceptance of the notice.  In 1983, the
     number of notice reporting an installment of  a specified facility was
     9,493 (cases) (including those discharging non-toxic pollutants).  While,
     the number of notice reporting an alternation in  the structure was 5,146
     (cases).  In neither of these cases was change in plan asked by  the
     governor.
          When a prefectural governor judges that  effluent from  an existing
     specified facility does not comply with the effluent standards,  he can
     order an improvement in the structure or operation of the specified
                                      733

-------
     facility, or the wastewater treatment method within a specified period;
     or he can order to temporarily discontinue the use of the specified
     facility or the discharge of effluent.  The number or factories ordered
     to improve their structure or operation of the specified facilities, or
     the wastewater treatment method totalled 304 (cases)  in 1983.  While, the
     number of specified facilities ordered to temporarily discontinue use of
     those specified facilities or the effluent discharge totalled 14 (cases)
     in the same year.  In addition, those subjected to the administrative
     guidance for improvement, although not ordered to improve, totalled
     17,000 (cases).
          The law provides that if dischargers violate the standards, they are
     sentenced to a prison term not exceeding 6 months, or punished with a
     fine not exceeding 300 thousands yen.  The number of cases violating the
     effluent standards totalled 201 in 1983.  Two cases resulted from regular
     inspection, 19 cases resulted from reports by local inhabitants, and 180
     cases resulted from police or Maritime Safely Agency action.  The
     parameters that were violated are shown in Table 2.4, and the types of
     industries which violated the standards are shown in Table 2.5.  Of those
     who were arrested until 1982 and sentenced within 1982, nobody was given
     a prison term, however, 114 persons were fined.
          The prefectural governor can send his personnel  to enter a specified
     factory for inspection of the structure, the wastewater treatment
     facilities, and relevant documents of the factory.  Inspections made in
     1983 were 88,155 cases during the day and 2,335 cases at night, totalling
     90,470 cases.

2.2.4  Measures taken at sources

          To prevent pollution from public water bodies, it is necessary for
     the relevant authorities to take proper measures to enforce the standards
     and to monitor the discharge from working places where use any toxic
     substances.  However, it is essential as well that each polluter makes
     his effort to curb the discharge of  pollutants  as far as possible.   It is
     the first step for a discharger  in reducing effluent  toxicity to change
     the manufacturing process if there is a better  process or to reduce or
     change chemicals and materials used,  or to recover wastes.   To treat the
     effuent is the second step to comply with the effluent standards.
          The treatment method varies according to the toxic substance to be
     treated.   Table 2.6 shows typical treatment methods for toxic substances
     used in Japan.
                                      734

-------
                 Table 2.4  Violation of effluent  standards
                                                  (1983)
\
1
2
3
4
5
6
7

8

9
10
parameters violated
Suspended solid
BOD
pH
COD
Hexavalent chromium
Cyanide
Number of coliform
groups
Normalhexame
extracts
Copper
Zinc
Number of violations
102
80
70
32
23
10
8

7

6
5
Table 2.5  Types of facilities violating  toxic substance discharge standards
                                                             (1983)
Item
Hexavalent chromium
Cyanide
Lead
Cadmium
Kind of violating facilities
1 Electroplating facility
2 Cement manufacturing
3 Acid and alkali treatment
facilities of metal surface
4 Metallic goods manufacturing and
machinery industry
5 Textile industry
1 Electroplating facility
2 Acid and alkali treatment
facilities of metal surface
3 Metallic goods manufacturing and
machinery industry
1 Electroplating facility
2 Raw pottery materials
manufacturing
3 Glass manufacturing
1 Industrial waste treatment plant
Number of violations
14
4
3
1
1
8
5
1
2
2
1
1
          Table 2.6  Typical treatment methods for toxic substances
Item
Cyanide
Heavy metals ^
(Cd, Pb, Cu, Zn, Pe, Mn, Cr )
Hexavalent chromium
Mercury
Arsenic
PCB
Organic phosphorus
Treatment method
Alkaline chlorination
Electrolytic oxidation
Complex ion method
Chemical precipitation
ion exchange
Reduction and neutralization
Ion exchange
Sulfide precipitation
Carbon absorption
Chelate resin adsorption
Hydroxide co-precipitation
precipitation carbon absorption
Carbon absorption
                                      735

-------
2.3  Other Problems  of Pollution Related  to  Toxic Substances

2.3.1  Bottom sediment contamination by mercury  and PCB

          Toxic  substances accumulated in bottom sediments affect the  human
     health through  fish and shellfish.   Now in  Japan, provisional removal
     standards for bottom sediments have  been set for mercury and PCB.
     Contaminated sediments are removed on the basis of these standards.  The
     standards for removing sediments are 25 mg/kg DS for mercury (this value
     varies according to conditions for sediments in the sea) and 10 mg/kg  DS
     for PCB.
          For mercury contaminated sediments, 42 water areas in Japan  have
     been specified  as areas where sediments must be removed according to
     surveys conducted since 1973.  Of these, contaminated sediments have
     already been removed from 38 areas and  sediments from the remaining water
     areas are now being removed.
          For sediments contaminated by PCB,  79  water areas have been
     specified as areas for sediment removal according to surveys conducted
     since 1972.  Of these, contaminated  sediments have already been removed
     from 70 water areas and sediments in other  two areas are now being
     removed.
          The most typical one of these sediment removal projects is the
     mercury contaminated sediments removal  project in the Minamata Bay,  shown
     in Fig. 2.3.
                                      Uroeda Portj'  (Chisso Corp.)

                                                   ,X
              Shiranui Sea


            Noncon tarn mated
            public waters
1	jDredging area

  Master monitoring stations

 O Auxiliary monitoring stations

 A Underground water monitoring
 	s-caticns
   Stationary fishing net
 G- purse for catching fish

   Pisciculture grounds
          Fig. 2.3  Dredged sediments disposal plan  for Minamata Bay
                                      736

-------
               The Minamata Plant of Chisso Corporation had used mercury as  a
          catalyzer  in the manufacturing process of acetaldehyde for about 40 years
          since 1932.   The amount of mercury discharged from the plant and
          accumulated  in the bay is estimated to have been approximately 70  to 250
          tons or  more.  The thickness of the bottom deposit containing mercury
          reached  4  meters in some places in the bay.  The project in this bay is
          to partly  reclaim or dredge about 1.5 million m3 of bottom sediments
          containing mercury of 25 mg/kg DS or more in concentration.   In carrying
          out this project, to maximize safety, a strict monitoring of water
          quality  as well as fish and shellfish has been done to prevent secondary
          contamination by the diffusion of bottom sediments.
               In  the  disposal of removed bottom sediments,  banks  are constructed
          to divide  the dump site and public water area, thus preventing toxic
          substances from flowing outside or exuding from "the reclaimed area.  The
          surface  layer is covered with good quality soil, and groundwater
          conditions in the surrounding area are strictly monitored.
2.3.2  Groundwater contamination by chemical substances

     (1)   Present state of groundwater contamination

               Groundwater use in Japan is about 14 billion m3 a year.   This
          accounts for 16 percent of the total amount water used.   When
          restricted to water for domestic use only, groundwater accounts for
          24%.
               Main environmental problems for groundwater have so far  been
          ground subsidence and salinity intrusion caused by excessive  pumping
          of groundwater.  For groundwater contamination problems, accidents
          caused by hexavalent chromium and cyanide have been reported  in a
          quite few cases.
               Recently, as a result of water supply surveys in some cities,
          there arose a suspicion of local groundwater contamination by
          chlorinated organic compounds.  In this connection, a nationwide
          survey of groundwater contamination was done in 15 representative
          cities shown in Pig. 2.4 in 1982.   The number and percentage  of
          samples in which each pollutant was detected, and the ranges  of
          detected concentration from this survey are shown in Table 2.7.
          Pollutants which were in high percentage of detection were
          @ nitrate and nitrite (approx. 87%),  (2) trichloroethylene  (28%),
          (3) tetrachloroethylene (27%), (?) chloroform (22%), (5) 1. 1.
          1-trichloroethane (14%), and (6) carbon tetrachloride (10%).
          According to the result of the survey in nearby rivers carried out
          for reference, those six pollutants were also detected highly in the
          river water.
               No water quality standards are set for groundwater  in Japan at
          present.  However, since groundwater is used for the drinking
          purpose in the majority of areas throughout Japan, it is necessary
          to maintain the quality of the groundwater suitable for  drinking
          water.   Table 2.8 shows a comparison between the results of the
          above survey and the water quality standards provided by the  Water
          Works Law in Japan,  or specified in the tentative guideline for


                                     737

-------
 drinking water  by the World Health Organization (WHO).  Of  the  water
 quality parameters compared, nitrates  and nitrites  in 9% of  the
 samples exceeded the water  quality standard of  the  Water Works  Law.
 Of the other  pollutants,  tetrachloroethylene and  trichloroethylene
 exceeded the  tentative  guideline  of WHO  in  4% and 3% of samples,
 respectively.
              Fig. 2.4  Map of surveyed area
Table 2.7  Detection of chemical substances in ghoundwater
Classification
Number of samples
~~~^-^samples, etc.
Name of sub8tance~~~-^^^
Nitrate and Nitrite
Methyl chloride
Dichloro methane
Chloroform
Carbon tetrachloride
1.1-dichl or oe thane
1.2-dichloroe thane
1.1. 1-trichloroethane
1.1-dichloroethylene
Cia-l.2-dlchl.oro-
ethylene
Trans-1. 2-dichloro-
ethylene
Trichloroethylene
Tetrachloroethylene
Benzene
Toluene
Xylene
Di-n-butyl ph thai ate
Di-ethylhexyl phthalate
Shallow well
1,083
Number and
percentage
oE detected
samples (%)
980 (90)
2 ( 0)
5 ( 0)
240 (22)
84 ( 8)
20 ( 2)
14 ( 1)
142 (13)
10 ( 1)

68 ( 8)

15 ( 1)
269 (27)
289 (27)
3 ( 0)
12 ( 1)
5 ( 0)
27 ( 2)
40 ( 4)
Detected
range

20 - 12,000
-
6
0.5 - 31
0.05 - 1.7
1-30
3-13
0.2 - 70
1-5

1 - 338

2-10
0.5 - 210
0.2 - 190
-
3-15
-
8
5-10
Total
1,360
Number and
percentage
oE detected
samples (%)
1,162 (87)
2 ( 0)
6 ( 0)
305 (22)
131 (10)
29 | 2)
16 ( 1)
186 (14)
13 ( 1)

119 ( 9)

20 ( 1)
379 (28)
372 (27)
3 ( 0)
20 ( 1)
5 ( 0)
26 ( 2)
45 ( 3)
Detected
range
(M9/O
20 - 80,000
2
2-6
0.5 - 31
0.05 - 2,200
1 - 175
1-33
0.2 - 1,600
1-7

1 - 537

1-15
0.5 - 4,800
0.2 - 23,000
4-11
2-42
3-17
2-46
4-16
River (Reference)
139
Number and
percentage
of detected
samples (1)
127 (91)
0 I 0)
9 ( 6)
40 (291
8 ( 6)
0 ( 0)
1 ( 1)
33 (24)
0 ( 0)

2 ( 1)

0 ( 0)
5< (39)
50 (36)
0 0)
2 1)
1 1)
1 1)
< 3)
Detected
range
lug/*)
20 - 25,000
-
1-5
0.5 - 13
0.05 - 0.20
-
7
0.2 - 93
-

1

-
0.5 - 16
0.2 - 3.0
-
14
3
9
5-21
       It was found by this survey that the contamination of
  groundwater was noticeable in a fairly wide area unexpectedly.
                            738

-------
    Therefore, a follow-up survey was made in 1983 on the same wells in
    13  cities  and  their  adjacent wells for trichloroethylene and
    tetrachloroethylene  which were detected in high concentration in
    many  samples in  1982.
          Prom  the  results of the follow-up survey, the groundwater
    contamination  by trichloroethylene and tetrachloroethylene was
    confirmed  to have been noticeable in most parts of those wells and
    in  even a  wider area in many cases.  Although some factories were
    checked to find  the  sources, no particular sources could not be
    identified.
Table 2.8  Comparision of detect concentration with water quality in
           Water Works Law or WHO'S guideline
^*. Classification
\.
\^
\v
\.
Name of substanceX^
Nitrate and Nitrite


Chloroform
Carbon tetra-
chloride
1.2-dichloroe thane
1. 1-dichloroethylene
Trichloroethylene
Tetrachloroethylene
Benzene
Number of samples exceeding water quality standard or WHO'S
guideline
Shallow well
Number of
surveyed wells:
1,083
116 (11%)


0(0)

2(0)
3(0)
10 ( 1 )
26 ( 2 )
41 ( 4 )
1(0)
deep well
Number of
surveyed wells:
277
3 ( 1%)


1(0)

0(0)
1(0)
3(1)
14 ( 5 )
12 ( 4 )
0(0)
Total
Number of
surveyed wells:
1,360
119 ( 9%)


1(0)

2(0)
4(0)
13 ( 1 )
40 ( 3 )
53 ( 4 )
1(0)
River (Reference)
Number of
surveyed rivers:
139
4 ( 3)


0(0)

0(0)
0(0)
0(0)
0(0)
0(0)
0(0)

Water quality
standard valuer
or WHO ' s
guideline

10 mq/Z


30 g/i

3 1/i
10 g/i
0.3 g/i
30 g/i
10 g/i.
10 g/i


Remarks



Water quality
standard in Water
Works Law
WHO'S guideline

WHO'S guideline
WHO'S guideline
WHO'S guideline
WHO'S guideline
WHO'S guideline
WHO'S guideline
(2)  Measures taken for contamination control

          As a result of the nationwide surveys made in 1982-1983,  the
     groundwater contamination was feared to be in progress in urbanized
     areas over a fairly wide area.  Since wide area contamination  of
     groundwater had not been revealed in the past in Japan, no primary
     legal control has been set for the groundwater quality.
          In view of the fact that such chemicals as trichloroethylene,
     which contaminate groundwater, are widely used in various forms in
     dry cleaning industry, metal processing industry, semiconductor
     manufacturing industry, and many other industries, and that it is
     very difficult to recover groundwater once contaminated; it has been
     considered necessary to put some regulation toward proper use  and
     management of these chemicals in the factories using them.
          As an urgent measure, for the time being, to prevent the
     contamination from these chemicals, "Provisional Guideline for
     Discharge of Trichloroethylene and other Compounds "was set in
     August 1984.  In this guideline, control targets are set for water
     quality when discharging the wastewater into goundwater or surface
     water.  The control targets were set for trichloroethylene,
     tetrachloroethylene, and 1.1.1 trichloroethane; the letter's use
     has recently increased since it is an alternate chemical for other
     two.  The same guideline is being applied to the discharge of
                                 739

-------
         wastewater  to  the public sewerage  system.
         these chemicals are shown in Table 2.9.
The cbntrol targets for
      Table  2.9  Control  targets for selected chlorinated hydrocarbons
^^^^^
Tr i chl or oe thyl en e
Tetrachloroethylene
1.1.1-trichloroe thane
Control targets to prevent
from penetration
Less than 0.03 mg/
Less than 0.01 mg/S.
Less than 0.3 mg/Jl
Control targets for discharge
into public water bodies
Less than 0.3 mg/
Less than 0.1 mg/
Less than 3 mg/
2.4  Measures Relating to Safety of  Chemicals

          Chemical substances are varied in their use and types.   Their number
     is said to reach several tens of  thousands even when confined to those
     used in industry.  Some of them are discharged into the environment
     during their manufacture or during various processes in their use, thus
     contaminating the enviroment.
          To cope with this problem, the Chemical Substances Screening and
     Control Law was established in  Japan in 1973.  According to this law, new
     chemicals are examined, before  manufacture or importation,  for their
     three properties, namely, degradability, accumulativity and effect on
     human health by continuous ingestion.   Any chemicals having properties of
     low degradability, high accumulativity and toxic effect on  human health
     are designated as "specified chemical  substances",  and its  manufacture,
     importation and use are regulated.  The control system under this law is
     shown in Fig. 2.5.
          Among new chemical substances, 2,482 were reported by  industries to
     the government as of 31 December  1984.  Of them, 1,985 chemicals were
     publicized by the government as not classified as the specified chemical
     substances and approved to be manufactured and imported.
          As to existing chemical substances, investigation and  checking is
     also under way for their biological degradability,  accumulation in fish,
     toxicity and distribution in the environment.  So far, 7 chemicals; PCB,
     HCB, PCN, aldrin, dieldrin, endrin, and DOT have been designated as
     specified chemical substances.   To check the safety of existing chemical
     substances efficiently, a test  for decomposition and accumulation is
     being done mainly on alternative substances those similar in structure to
     specified chemical substances,  as well as on chemicals with large
     production and large imports.  At the  end of 1984,  511 chemicals were
     determined to be high in decomposition and low in accumulation.
          To expedite checking of existing  chemical substances earlier and
     more effectively, efforts are being made to develop a decomposition
     testing method using anaerobic  bacteria, an evaluation method using
     physical and chemical properties of the substances, and a data reference
     system for information on the sefety of ofeemical substances.
          A special investigation on the distribution and the level of
     chemical substances in the environment has been under way since 1974.
     This investigation was strengthened in 1979 and named as "comprehensive
                                     740

-------
checking of chemicals  in the environment" to make it more effective  for
systematic assessment  of existing  chemicals.
      In this  assessment  system, the  checking is made in  three steps  as
shown in Fig.  2.6.  In the 1st step, a screening is made for chemical
substances presumed to readily remain in the environment (about 50
chemical substances/year).  In the 2nd step, residual chemicals are
selected (about 5 chemicals/year)  by the water  quality and bottom
sediment surveys some  ten areas throught the country, and a further
detailed environmental survery on  these residual chemicals is made for
the water quality, bottom sediments, and in fish and shellfish in 40
areas throughout Japan.   In the 3rd  step, certain chemicals which reguire
particular attention are screened  from residual chemicals (1 or 2
chemicals in  2 years).  A special  test to examine their  effects on  the
eco-system is performed  with respect to these  substances, and a long-term
biological monitoring  survey using fish, shellfish, and  birds is carried
out in 14 areas throughout the country.
      In 1983,  general  environmental  surveys were made on 45 chemicals.
In this test,  no chemical was detected from water samples, but 10
chemicals were detected  from sediment samples  as shown in Table 2.10.  It
was determined that a  more detailed environmental survey would be made on
6  of those chemicals picked up by  their residual results in 1984.
         , Free manufacture and use,-.
          etc. are permitted until
          designated or recommended
          as specified chemical   >
         ssubstances
                                  Application to manufacture or
                                  importation of chemicals
            _L
Reference to list of existing chemicals
substances declared "White" and
specified chemical substances	
Existing
chemicals




                                                       'Manufacture or impor-
                                                       tation prohibited
                                                       until results of
                                                       screening available
                             See if they are produced or imported below a
                             Certain volume and if they are likely to pol-
                             lute environment and to affect human health
                             judging from the knowledge already available.
                                _L
                             Application for recog-
                             nition as small-volume
                             chemical product
                                                     _L
                 Prior notification
                                                  Examination of
                                                  documents
                              /"Enforcement of\
                              V regulations  /
                  /Free manufacture,
                  \importation and use
Pig.  2.5  System  of controls under the Chemical  Substances  Control Law
                                     741

-------
                          Chemicals
                      (tens of thousands)



Im
de
an
me



Identification
chemical residu
in the environm
tl
alytical
thod
t__

__








of Priority list j *>fortion "
(about 2,000 ltOX!;C che^als
. i in Japan and
ent substances) *
(overseas
5-20 substances! (200 substances)



ng tests



(50 substances)


Development 1
of analyses  '
method  ,


General environmental
~" " surveys (of air, water",
bottom sediments)



([Detailed environmental
"Hpurveys (of-aJ.r, water,
(bottom sediments .'~ documented information
I   ] Laborat<
          .ory surveys
(I   JField
                                surveys
       Fig. 2.6  Scheme  of total  checks of  chemicals
Table 2.10  Result of  general environmental survey  (1983)

Name of substances


Tributyl tin compounds
Dibutyl tin compounds
Acenaph thyl enc
Acenaphthene
Fluorene
Diphenyl methane
2-Naph thyl ami ne
Benzothiazole
Dibenzothiophene
P-Bromophenol
Water
Incidence of
detection/
Number of
samples
0/75
0/75
0/33
0/33
0/33
0/33
0/48
0/30
0/45
0/33
Detected
range

nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Bottom sediments
Incidence of
detection/
Number of
samples
9/75
3/75
13/33
13/33
27/33
3/33
5/48
4/30
6/45
5/33
Detected range
(wg/g-dry)

0.05 - 0.70
0.02 - 0.03
0.008 - 0.053
0.008 - 0.13
0.003 - 0.091
0.059 - 0.16
0.0017 - 0.0079
0.0016 - 0.0033
0.001 - 0.005
0.02 - 0.03
   Remark:  "nd" indicates that the concentration is less than detectable
           limits.
                               742

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3.   CURRENT STATUS OP SLUDGE TREATMENT AND DISPOSAL IN JAPAN

3.1  Introduction

          As of the end of March 1985, municipalities operating public sewer
     systems totaled 496, and the number of cities started to implement
     sewage treatment operations has increased significantly within past
     several years.  Table 3.1 shows the increase in the number of
     municipalities that have started operation of sewage treatment.


      Table 3.1   The  number  of municipalities that have started sewage
                  treatment operations  (cumulative total)
^~-\^^ Fiscal year
Size of^~\^^
municipal i ty"^^.^
Population in
thousands persons
More than 1000
300 to 1000
100 to 300
Less than 100
Total
'71

6
15
63
64
148
'75

10
37
87
93
227
'76

10
37
95
109
251
'77

10
37
97
127
271
'78

10
37
101
143
291
'79

10
38
104
174
326
'80

10
38
107
198
353
'81

10
44
116
212
382
'82

10
44
120
236
410
'83

10
44
120
281
455
'84

10
45
123
318
496
          The total amount of  sewage  sludge  produced in these treatment
     plants from April  1983  to March  1984  was  about 2,200,000 m3/year.   As
     shown in Table 3.2, 67% of  the sludge was disposed of  by landfill, 9% by
     coastal reclamation 10% by  ocean disposal, and 14% was utilized as
     resources such as  agricultural use.
                 Table  3.2   Status  of  sewage sludge disposal

                          (From April 1, 1987 to March 31,  1984)
                                                            (in 1,000 mj)
\^ Method of
^\disposal
State of\^
sludge ^^^
Dewatered cake
Ash
Dried sludge
Digested,
thickened sludge
Total
j (%)

Landfill

1,241
229
10
2

1,482
(67)

Coastal
reclamation

127
75
0
0

202
(9)

Utilization as
resources

246
30
30
4

310
(14)

Others

44
0
0
168

212
(10)

Total r(%)

1,658 (75)
334 (15)
40 (2)
174 (8)

2,206
(100)1
                                      743

-------
     Thus, the greater part of sewage sludge is disposed by landfill.
As cities continue to expand, finding sites for landfill has become
increasingly difficult.  In large cities and their peripherals it has
become especially difficult for an individual municipality to
independently secure a potential disposal site.  To cope with these
problems, there has been an increasing need for sewerage authorities to
take an regional approach to prepare for proper disposal site or to seek
the possibility of using more sludge as resources.
     To achieve a stable and ever-lasting disposal of sludge, efforts
should be made to facilitate its reuse by recognizing sewage sludge as a
useful resource.  The status of sludge reuse were as shown in Table 3.3
according to the survey made in 1984.  The total amount of reuse
achieved was about 310,000 m3, almost all of it was for agricultural
use.  The greater part of agricultural use was done in a state of
dewatered cake.
      Table 3.3  Status of utilization of sludge as resources

                   (From April 1, 1983 to March 31, 1984)
\ State of sludge
Classification \
Agri-
cul-
tural
use
Executed by
local
municipalities
Delivered to
fertilizer
companies
Subtotal
Construction
materials
Total
Dewatered
cake
193
53
246
0
246
Ash
3
6
9
21
30
Dired sludge
5
0
5
0
5
Compost
18
7
25
0
25
Digested
sludge
4
0
4
0
4
Total
223
66
289
21
310
     As of the end of March 1985, public organizations that are
utilizing sludge as resources are 6 prefectures and 92 local
municipalities, including Tokyo.  The number of sewage treatment plants
is 118.  The greater part of farmland in Japan consists of paddy fields
for growing rice, where the use of sewage sludge is difficult and
therefore, sludge is used for farmland and green spaces other than paddy
fields.
     Even though the greater part of the reuse of sludge is in the form
of dewatered cake, a certain amount of sludge is used after being
composted for farmland application.  The advantages of composting are
easiness in handling and minimum odor.  These properties are quite
desirable because of the agricultural situation in Japan, wherein the
lifestyle of farmers has become urbanized, the farmers are getting old,
and the houses have come to be nearer the farmland. Besides these
points, when the reuse of sludge in farmland or in green spaces is
attempted, care should be taken in regard to the quality of sludge
products to keep the soil free from pollution by heavy metals.  Efforts
should be made to help people understand the usefulness of sludge
products by distributing information on its proper use.
                                744

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          The use of sewage sludge as a construction material could be a
     promising way because of sludge's good potentiality for this kind of
     use.  Research and investigations on this matter have been continued by
     the government, by municipalities, and by private companies. .  The
     Ministry of Construction has been continuing research on the use of
     sewage sludge as construction materials in the comprehensive technical
     development project.
          As a result, it has been shown that sewage sludge has bright
     prospects of being used as molten sludge, light weight aggregate, and
     ceramic materials.  Because feasibility studies have proved that these
     objects can be achieved technically and economically, the on-site use
     and the establishment of a distribution system will be the next subjects.

3.2  Improvement in the Incinerating Process for Energy Conservation

3.2.1  General

          As the sewer systems are expanded, the quantity of sewage sludge
     produced is continuously increasing.  There has been a necessity,
     therefore, to reduce the quantity of sludge to be disposed of  and to
     stabilize its quality because of the difficulty in securing sites for
     disposal and the environmental problems.  This has resulted in an
     increase in the quantity of sludge incinerated.  Table 3.4 shows the
     change in the total capacity of sewage incinerators during post several
     years.
           Table 3.4  Change in Total Capacities of Sewage Sludge
                      Incinerators in Japan

                                     Tons of Wet Cake/day
1978
7,917
1979
8,469
1980
9,091
1981
10,042
1982
10,557
          Inasmuch as a great deal  of auxiliary fuel was required to
     incinerate the dewatered cake,  with energy crises  on two occasions  in
     1973  and 1975 being the turning points,  technologies for achieving
     energy-saving,  resource-saving,  and incinerating systems with less  air
     pollution have considerably progressed.
          Generally speaking,  to maintain a stable  autogeneous combustion  in
     an incinerator,  a conventional  multiple-hearth furnace requires a cake
     with  a lower  heating value  of  about 600  Kcal/kg-cake,  and a  conventional
     fluidized bed reactor requires  about 800 Kcal/kg-cake.  From a  view
     point of heat balance,  measures to save  energy in  incineration  can  be
     classified into the following  three categories:
          (a)  increase in the  heating value of the  cake,  (b)  decrease in the
     amount of exhaust gas and lowering its temperature,  and (c)  effective
     use of the exhaust heat.
                                     745

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3.2.2  Example of improvement  in an existing multiple-hearth furnace

           Takaoka City improved their seven-hearth incinerators at the
     Yotsuya Sewage Treatment  Plant, and has been operating them without any
     auxiliary fuel for  the past several years.   The major improvements being
     made  were as follows:  (Fig. 3.1):
         Hopper
                                                    To exhaust gas
                                                    ventilator
                	' Cake mixer

         Cake cutter
                                                   Maximum tempera-
                                                   ture controlling
                                                   unit
                                               Heavy oil
                                               Burner
            Air for
            burners
     Secondary combus
     tion air port
     Primary combustioi
     air port
                                                                     Other ventilated
                                                                     air with offensive
                                                                     odor
                                                                 To funnel through exhaust
                                                                 gas treatment facilities
Air from
blower
                                   Blower for shaft
                                   cooling
      Fig. 3.1  Schematic diagram of  the multiple-hearth incinerator  of
                the Yotsuya STP, Takaoka City Improved for energy saving
      (a)   The primary combustion air was  taken by means  of  natural
           ventilation from the bottom  (7th)  furnace, and the secondary  air
           was supplied  at normal temperature at the 5th  hearth.

      (b)   Cake mixers were installed at the  1st and the  3rd hearths in
           addition to the normal teeth to assure complete mixing.

      (c)   Special teeth were used at the  4th and the 5th hearths to reduce
           short circuit.

      (d)   A controlling system was introduced, which could  maintain the
           optimum temperature in the incinerator at a  constant level  by
                                       746

-------
          manipulating the secondary combustion air supply.  This control was
          effective to reduce the air supply.

     (e)   Heating value of the cake was improved by changing the dewatering
          method.  High pressure belt presses were used with a polymer and
          ferric chloride addition.  Water content of the cake is normally
          about 70%.

          The limit of the lower heating value for autogeneous combustion
     with this improved multiple-hearth furnace is 350 to 370 Kcal/kg-cake.
     The range of loading with which autogeneous combustion is possible is
     from 32% to 135% of the design loading when the low heat value of the
     cake is more than 400 Kcal/kg-cake.
          Heat losses due to unburned sludge and radiation account for only
     3% of the total heat input to the incinerator.
          The combustion air supply system of this furnace, that is, to
     supply the primary air by natural ventilation from the bottom hearth and
     to control the secondary air supply so as to maintain the temperature at
     the combustion hearths at 800 to 900C, was found very effective against
     variation of sludge cake loading and fluctuation of heating value of the
     cake.

3.2.3  Example of improvement in a fluidized bed furnace

          The Arakawa Basin-wide Sewage Treatment Plant of Saitama Prefecture
     employed a fluidized bed furnace with a preliminary sludge drier using
     exhaust heat to decrease the auxiliary fuel requirement.
          The schematic diagram of the furnace is shown in Fig. 3.2.
          In this system, the heat of the exhaust gas is recovered at the
     heat exchanger, and the recovered heat is supplied to a sludge drier in
     the form of heated oil at temperature about 250eC.  The drier is an
     hollow screw type of indirect heating.  The evaporated vapour is
     returned to wastewater treatment process after condensation, and the
     exhaust gas with some offensive odor is supplied to the freeboard of the
     furnace for deodorization.
          The percentage of moisture evaporated at the drier is about 25% of
     the original water content.  The lower heating value becomes twice as
     much as that of the sludge cake before drying.  The reduction of the
     auxiliary fuel consumption is 60 to 100% as shown in Fig. 3.3

3.3  Development in Technology to Produce Compost from Sewage Sludge

3.3.1  General

          To facilitate the use of sewage sludge for farmland and green
     spaces, it is desirable to improve the characteristics of the dewatered
     cake for its safety, stability, and easiness in handling.  To counter
     these problems, technology has rapidly developed to produce sewage
     sludge compost capable of maintaining a stable quality through an
     aerobic fermenting process.
                                     747

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  Fig. 3.2   Schematic diagram of  the  fluidized Bed Furnace  of
             the Arakawa Basin-wid SCP Improved for Energy Saving
              100 r Direct incineration
                   (without drying)

               80
           rH X
           o) 
-------
      (4)   To meet  the standards relating to heavy metals as  a special
           fertilizer  regulated  by the Fertilizer Management  Law, which  is
           shown in Table 3.5.

           As to application of  sewage sludge to farmland, a  management
     guideline was stipulated  using Zinc as an index as shown in Table  3.6.
 Table 3.5  Standards concerning heavy metal contents in special fertilizers
             (Regulations by  the Fertilizer Management Law)
Item
Arsenic
Cadmium
Mercury
Standard
Less than 50 rag/kg DS
Less than 5 mg/kg DS
Less than 2 mg/kg DS
        Table  3.6  Management guideline to prevent the accumulation  of
                    heavy metals in  the soil of  farmland
                    (Notification of Water Quality Protection Bureau  of
                    the Environment Agency)
             1.  The Index for controlling accumulation of heavy metals In the soil of
                farmland shall be the zinc content.

             2.  The management guideline relating to controlling accumulation of heavy
                metals In the soil of farmland shall be 120 mg of zinc per 1 kg of dry
                soil.

             3.  The analytical method to measure the zinc content In the surface soil
                shall be the atomic absorption spectrophotometry following the
                digestion by mineral acids.
3.3.2  Methods of  composting

           The methods for producing compost using  sewage sludge can be
     classified depending on  the types  of fermentation tank.   Each type of
     method could  be further  classified depending  on with or  without addition
     of  bulking agent and with or without preliminary drying  of the dewatered
     cake prior to composting.
                  r- Vertical
                   type
      Type of
      compostors
                  Horizontal-
                   type


                   -Pile type
Multi-stage 
system

Single-stage 
system
-Flap-door type, Paddle type,
 Moving-floor type and Arm type

- Silo  type
               Scoop type, Paddle type, Auger
               type, Circular  auger type,
               Shovel type
                                         749

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3.3.3  Design  data for composting facilities

          The first sewage sludge composting facility in Japan started
     operation  in  1976 and composting  does not have a long history.
     Therefore, concrete design criteria  have not been established yet.
     Table 3.7  summarizes the range of design data of the  composting
     facilities based  on experiments and  actual facilities.
                    Table 3.7  Composting facility design  data

Pre-con-
ditioning
Primary
Fermenta-
tion and
Secondary
Fermenta-
tion
I ten
Water content of
feed mixture (%)
Feed mixture pH (-)
Bulking agent M
(% - WB)
Return ratio Re
(* - WB)
Apparent specific
gravity (t/m3)
Fermentation period
Pile height (m)
Frequency of mixing
(days)
Air supply
Data values
840 - 55
60 - 70
About 8 to 10
(2) 15-40
100 - 300
30 - 100
Remarks
The feed mixture means input
materials to the ferment tank
that is a mixture of raw
materials (cake and bulking
agent) and the return compost.
When pH of the dewatered cake ia
excessively high, an adjustment
is necessary.
Bulking agent's wet weight
 , (kg/day)
oewatered cake's wet weight
(kg/day)
Return compost's wet weight
nc _ (kg/day)
Dewatered cake's wet weight
(kg/day)
(Feed mixture) (Primary compost,
secondary compost)
0.65 - 0.75 0.60 - 0.80
0.50 - 0.65 0.65 - 0.75
Primary fermentation 10 to 14 days
Secondary fermentation (Forced ventilation)
7 to 14 days)
(Natural ventilation)
1 to 2 months
Primary fermentation
 { Silo type 3.0 - 5.0
(Other than silo type 0.6 - 1.4
 j Shovel type 2.5 - 3.0
1 Other than shovel type 1.0 - 1.5
! (Natural ventilation) 1.0 - 2.0
1 (Forced ventilation) about 2.5
The pile height for secondary fermentation is
about 1-1.3 times as high as that for primary
fermentation.
Primary Secondary
fermenta- fermenta-
tion tion
(3) 0.5 - 4 7 - 14
ft. I Shovel type 4-7 7-14
^ i Other than shovel type 1-3 7-14
ff. 1 (Natural ventilation) 0.3 - 0.5 7-14
'*' 1 (Forced ventilation) - 2-10
100 - 200 4/min-m3
                Note: @ Composting without bulking agent
                     (2) Composting with bulking agent
                        Vertical type
                        Horizontal type
                        Pile type
                                       750

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3.3.4  Composting facilities under operation

          As shown in Table 3.8, composing of sewage sludge is being done at
     15 cities as of the end of October 1984.  The capacities of the
     facilities are from 3 tons of wet cake a day to 206 tons of wet cake a
     day.  For promoting the agricultural use of sewage sludge compost, an
     efficient and stable distribution system needs to be structured with a
     consideration for competition with conventional fertilizers both
     chemical and organic and through the cooperation with farmers
     associations and private businesses, depending on the actual situation
     of the districts.

3.4  Development of a Technology Producing Construction Materials from Sewage
     Sludge

3.4.1  possibility of sludge utilization

          Composting is a technology to utilize organic subtances contained
     in sludge, whereas production of construction materials from sludge is a
     technology to utilize mineral contents of sludge such as Si02,
                   and CaO.
     (1)  Dewatered cake

               Direct use of dewatered cake for banking or filling materials
          is not practical because of problems such as insufficient strength,
          subsidence due to compaction and leachate.  However, after mixing
          with incinerated ash or cement, it has been used for that purpose
          to some extent.

     (2)  Incinerated ash

               When the ash is compacted under conditions near an optimum
          water content, the finished product has the sufficient
          ground-resistant force required for the construction machine
          operation, and exhibits a consistency near that of sandy soil.
          Therefore, it is suitable for use in a wide range of construction
          materials, such as road foundation, banking, and landfill.
               The possibility of its indirect use has been explored
          extensively for various purposes including production of light
          weight aggregates, clay pipes, bricks, earthenwares concrete
          products  such as Hume pipe, or additives for cement.  Some of them,
          such as production of light weight aggregates, which is explained
          more in detail below, are very promising.  For producing clay
          pipes, it was found that ash can be added up to about 25% without
          problems.
                                     751

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Table 3.8  Sewage sludge composting facilities under operation
Installation site
Name of city

Tendo city
Yamagata city
Akita city
Hitachi city
Tokyo
Kasugai city
Okayama city
Koriyama city
Ibaragi pref.
Tokorozawa
city
Kayano city
Nozawa
hotspring
village
Sapporo city
Kagoshima
city
Kofu city
Mobara city
Fukuoka city
Name of plant
(Date of completion)

Tendo sewage
treatment plant
(April 1979)
MaeaJcashi cake
treatment plant
(April 1980)
Akita city compost
center (April 1982)
Namekawa sewage
treatment plant
(Oct. 1982)
Hinamitama sewage
treatment plant
(Hay 1980)
Kozoji sewage
treatment center
(April 1984)
Takashima sewage
treatment center
(April 1981)
Koriyama city sewage
treatment center
(April 1983)
Kasumigaura sewage
treatment center
(April 1984)
Tokorozawa sewage
treatment center
(Sept. 1983)
Lake Shirakaba
sewage treatment
center (Sept. 1983)
Nozawa hotspring
village sewage
treatment center
(April 1983)
Atsubetsu sludge
compost plant
(April 1984)
Kagoshima city
sewage sludge
compost plant
(april 1981)
Otsu sewage
treatment plant
(April 1984)
Kawanakajima sewage
treatment plant
(Aug. 1984)
Fukuoka sewage
sludge control
center (Jan. 1982)
Composting facilities
Addition of
bulking agents

With addition
Without
addition
With addition
Ditto
Without
addition
Ditto
With addition
Without
addition
Ditto
Ditto
Ditto
Ditto
Ditto
Ditto
With addition
Ditto
Without
addition
Primary fermentation
Type

Vertical
silo type
Horizontal
shovel type
vertical
multi-stage
paddle type
Vertical
multi-stage
flap- door
type
Horizontal
scoop type
Horizontal
scoop type
Vertical
two-stage
paddle type
Horizontal
scoop type
Horizontal
scoop type
Vertical
multi-stage
paddle type
Horizontal
scoop type
Vertical
multi-stage
type
Horizontal
paddle type
Vertical
silo type
Vertical
silo type
Vertical
multi-stage
flap- door
type
Horizontal
shovel type
Capacity and
number of units
ton/day x number
5 x 1
15 x 1
(8- tanks)
30 x 1
IS x 1
(2- tanks)
7x1
(4- tanks)
13 x 1
0.72 x 1
12.2 x 1
(3- tanks)
3x1
10 x 1
3x1
(2- tanks)
4x1
(2- tanks)
50 x 1
(4- tanks)
53.6 x 1
(8- tanks)
17.5 x 1
8.8 x 1
206 x 1
(13- tanks)
Fermenting
period
days
14
12
12
35
10
14
14
14
16
10
10
10
12 - 13
8
14
21
30
Secondary fermentation
Method

Indoor
piling
Included in
primary
fermentation
Indoor
piling
Included in
primary
fermentation
"

Open-air
piling
Included in
primary
fermentation
Ditto
"*
"

Indoor
piling
(Forced
ventilation)
Horizontal
shovel type
Indoor
piling
(Forced
ventilation)
Horizontal
shovel type
(Forced
ventilation)
(Entrusted
with private
businesses)
Fermenting
period
days
40 - 60

15

"
"
About 60
14
14
"



30
60
30

                               752

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     (3)  Smelted slug

               The smelted slug satisfies almost all of the conditions
          required for the materials sustitute for sands or gravels.   In
          addition, it has an advantage of no resolubilization of heavy
          metals.  The only problem is the cost, and efforts are being made
          to reduce the production cost, as well as to find the other  uses
          which justify the higher cost.

3.4.2  production of light weight aggregate from incinerated ash

          This technology was developed by paying attention to the similarity
     of the constituents of incinerated ash to shale, which is the light
     weight aggregate raw material.  The Metropolitan Tokyo Government
     constructed a multi-stage jet-flow furnace with a capacity of 3  tons a
     day, which is shown in Fig. 3.4, and has been producing light weight
     aggregates as a routine practice.
          Aggregates are produced in such a way that a bonding agent  (waste
     alcohol liquor)  is added to ash to give it viscosity,  and the mixture is
     subsequently granulated and dried.  It is then burned in an air  current
     heated to a temperature of from 1,100C to 1,150C and cooled.  During
     burning, a portion of the constituent is gasified, causing the granules
     to inflate.  While cooling, the granules maintain their inflated volume,
     and the finished products have cavities inside and a hard shell
     outside.  The specific gravity of the product is 1.3 to 1.65, which is
     only half that of gravel or sand.  It is easy to produce completely
     spherical aggregates with a diameter of from 0.3 mm to 3.5 mm.  The
     strength of the aggregates is considerably high.  The destruction
     strength is about several kilograms per granule.  It lends itself to
     many uses.  Direct uses are for backfill materials for shield
     tunnelling, aggregates for permeable pavement, block wall material, and
     precast outer wall material.  Indirect uses include backfill material
     for sewer construction, tennis court floor materials,  and supporting
     materials for potted growth of plants.
          The Metropolitan Tokyo Government  has entrusted with certain
     experienced private companies the distribution of the  lightweight
     aggregates on an experimental basis to  investigate the types of  suitable
     and potential markets, the estimated future demand, the required
     quality, and the appropriate prices.  The percentages  of the product
     classified by use in fiscal 1983 are shown in Table 3.9.
          Although selling prices differ depending on the types of packing,
     the amount of sale,  and the types of shipping work,  the product is being
     marketed at a price of from about 9,500 yen/ton to 20,000 yen/ton.
     Problems still  to be solved include restructuring of shipping facilities
     and warehouses,  arranging bagging facilities, integrating production and
     shipments,  and optimizing the amounts of  production and sales.
                                     753

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                   Green pellet
                                    Exhaust
                 Heating by
                 a burner
                 Heating gas
                                                Sedimentation
                                                layer
                                                Dense flowing
                                                layer
                                                Thin flowing
                                                layer
Finished
product
  Fig.  3.4  Schematic diagram of  a multi-stage jet  flow furnace
Table 3.9  Ose of  light-weight  aggregate made from sewage sludge

                        (FY 1983, Metropolitan Tokyo)
Use
Filling materials
for underground
storage of liquid
combustibles
Aggregate for GRC
products
Aggregate for
resin concrete
and other resin
Cement concrete,
and other
construction
materials
Gardening, filter
media, and others
Total
Reason of use
Absolute dryness
Light-weight
Absolute dryness.
Light-weight
Light-weight,
Absolute dryness.
Fire-resistant,
Sound proof
High void ratio,
water absorption
characteristics,
light-weight
-
Amount of use
Quantity
163 t
41 t
25 t
3 t
4 t
242 t
Percentage
67%
10%
10%
1.5%
2.5%
100%
                                   754

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3.5  Regional Plan for Treatment and Disposal of Sewage Sludge

3.5.1  Current status of sludge treatment and disposal in the Tokyo Bay and
       Osaka Bay basins

          Both Tokyo Bay and Osaka Bay are symbolic water bodies from the
     viewpoint of maintaining proper water quality of Japan's coastal sea.
     The statistics in 1983 show that the Tokyo Bay basin (Metropolitan
     Tokyo, Chiba prefecture, and Kanagawa Prefecture) has a total areas of
     8,591 km2, a population of 25.1 million and total of 169 local
     municipalities including cities, towns, and villages.  The Osaka Bay
     basin has a total area of 7,441 km2, a population of 16.1 million, and
     total of 123 local municipalities.   Both are densily populated developed
     areas (Table 3.10)
          Table 3.10  Outline of the Tokyo Bay and Osaka Bay basins

                                                             (1983)
Basin
Area (km2)
Prefecture
Number of
municipalities
Population
(person)
Tokyo Bay
8,591
Metropolitan Tokyo, Chiba,
Saitaraa and Kanagawa
Prefectures
169
(23 wards, 97 cities,
44 towns, and 15 villages)
25,093,236
Osaka Bay
7.441
Osaka, Kyoto, Byogo,
prefectures
123
(66 cities, 53 towns,
4 villages)
and Nara
and
16,137,972
          Japan's total area is 377,765 km2,  and total population is
     119 million, of  which the Tokyo Bay basin accounts for  2.5%  in area and
     21% in population.  The Osaka Bay basin  accounts for 2.0% in area and
     14% in population.  Both districts also  have prominent  industrial areas,
     with a great number of sources of pollution.
          In order to comply with the environmental standards set for  Tokyo
     Bay and Osaka Bay it was considered that the enforcement of  the effluent
     quality regulation was not sufficient in strength.  This has resulted in
     an implementation of the loading regulation system for  Tokyo Bay in 1979
     and for Osaka Bay in 1980.  The water quality parameter regulated by
     this system is COD^ at present, but a guide line was also issued to
     control the total loading of phosphorus.   To comply with the regulation
     and to improve the water quality of the  bays, the construction of
     sewerage systems is one of the most effective measures.  The current
     status of sewerage systems in Tokyo Bay  and Osaka Bay Basins in 1983 is
     shown in Table 3.11.
                                     755

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          Table  3.11  Current  status of sewerage systems in
                       the Tokyo Bay and Osaka Bay basins
Basin
Population
Population served
Percentage
Tokyo Bay
25,093,236
11,726,506
46.7
Osaka Bay
16,137,972
7,760,513
48.1
      The  total volume of  sewage sludge produced during one  year in 1980
 was 1,120,000 m3 in Tokyo Bay and 830,000 m3  in Osaka Bay,
 respectively,  expressed in  terms of dewatered cake.  As shown in
 Fig. 3.5,  the greater part  of dewatered cake  produced was disposed of by
 landfill;  a  very small amount was applied to  form land and  green spaces.
                            Tokyo Bay basin
      Others *
      9,000 ton/year
      1.5%
                  (Expressed in term*, of
                  disposed sludge weight)
          (Expressed in terms of
 ,         dewatered cake weight)
22,500 ton/year
2.0%
                                               Landfill
                                             240,900 ton/year
                                               21.6%
 * "Others"  means sludge  utilized for farmland and green  spaces.

Fig. 3.5   The amount of sludge classified by disposal methods in 1980
                                  756

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                            Osaka Bay basin
                 (Expressed in terms of
                 disposed sludyu weight)
               (Expressed in terms of
               dewatered cake weight)
  "Others
   6,775 ton/year
   1.6%
* Others
 37,942 ton/year
*  "Others" means  sludge handed to fertilizer

        Fig. 3.5   The amount of sludge classified by disposal
                   methods in 1980 (Cont'd)
     Because of  the difficulty in obtaining proper site  for sludge
disposal due to  an increased  density of population in  these areas,  local
municipalities are anxious to secure potential sites for the disposal of
sludge.   Most of the minicipalities have  disposal sites  of capacities
only less than five years.  Some local municipalities  have been seeking
sites  to dispose of sludge, where are more than 100 km apart from their
home teritories,  because no proper site in their districts are available
(Table 3.12).
       Table 3.12   Distance from the sewage  treatment plant to
                    the landfill  site (1980)
^\, Classifi-
^\. cation
District ^^^^
Tokyo metropolitan
district
Kinki district
Total
Transportation distance and the number of
sewage treatment plants
Less than
10 km
8
17
25
10 - 20 km
13
14
27
20 - 50 km
5
4
9
50 - 100 km
2
0
2
More than
100 km
9
6
15
       Note: In the Tokyo metropolitan district,  sewage treatment plants
            operating in Tokyo, Chiba, Saitama,  and Kanagawa prefectures are
            taken for investigation,  in the Kinki district, those in Osaka,
            Kyoto, Hyogo, and Nara prefectures are taken for investigation.
                                   757

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3.5.2  The necessity for a regional sludge  treatment and disposal plan

          Because of  progress and expansion in  sewerage systems and the
     necessity to advance the level of treatment,  it will become more  and
     more difficult  to  depend on only landfill  to  dispose of sludge.
     Therefore, the  possibilities of converting sludge into resources, such
     as construction materials and fertilizers  for cultivation of farmland
     and green spaces must be explored as a method for sewage sludge disposal.
          There are,  however, social, economical and technical problems  to be
     solved before the  majority of sludge can be effectively used as
     resources.  Therefore, the most practical  way will be to continue the
     disposal by means  of landfills while simultaneously expanding the
     effective uses  of  sludge as resources.
          In 1981, the  government asked the opinions of municipalities within
     the area of the Tokyo Bay and Osaka Bay basins, about the measures  to
     reduce the volume  of sludge to be disposed of, the problems associated
     with, and the planned disposal methods.  As a result, it was made clear
     that every municipality considers that it  will be more difficult  in the
     future to dispose  of sludge in its own jurisdiction independently.
     Figure 3.6 shows the estimated amount of sludge disposed classified by
     disposal methods in 1995.
                                Tokyo Bay basin
                        (Expressed in terms of
                         disposed sludge weight)
                                  (Expressed in terms of
                                   dewatered cake weight)
      Landfill
      15,300 ton/year
      0.8%
Others
30,400 ton/year
1.6%
             Disposal depending on
             the regional treatment
             and disposal plan
             1,880,000 ton/year
                  97.6%
Landfill
24,500 ton/year
0.4%
Others
128,600 ton/year
2.2%
            Fig.  3.6  The estimated amount of sludge classified  by
                      sludge disposal methods in 1995
                                       758

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                            Osaka Bay basin
             (Expressed in terms of
             disposed sludge weight)
    Landfill
    52,500 ton/year
    4.3%
                   Others
                   6,000 ton/year
                     0.5%
Landfill
276,000 ton/year
8.4%
               (Expressed in terms of
               dewatered cake weight)
                     Others
                     32,300 ton/year
                     1.0%
                                            Disposal depending on the
                                            regional treatment and
                                            disposal plan 2,988,000
                                            ton/year
                                                    90.6%
       Fig. 3.6  The  estimated amount of  sludge classified  by
                 sludge disposal methods  in 1995  (Cont'd)
     The  ratio of the sludge disposed of by means of landfill is
expected  to be just 0.8%  in the Tokyo Bay basin and 4.3% in the Osaka
Bay basin,  respectively.  The ratio of the sludge utilized for farmlands
or other  resources is estimated to be only 1.6% in the Tokyo Bay  basin
and 0.5%  in the Osaka Bay basin, respectively.   The amount of sludge
that are  expected to be disposed of by means  of the regional plan
accounts  for 98% in the Tokyo Bay basin and 95% in the Osaka Bay  basin,
respectively.
     To carry  out regional  treatment and disposal of sludge, it is
necessary to collect sludges by some means.   As the result of a study on
the sludge  collection system from both technical and economical
viewpoints, it was found  that collecting raw  sludge to a central  sludge
treatment plant by a pipeline followed by dewatering and incineration is
more advantageous than the  dewatering and incineration at each treatment
plant when  the transportation distance is within 20 to 30 km (Fig.  3.7).
                                  759

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                      500
                   ;o  400
                   tn
                   mB

                   >2  300
                      200
                      100
                         0.8
.. u
X
                             10
                                 20
                                          40
                                               50
                                                    60
                                                        70
                                                             80
                                                                  90
                          Distance from the
                          disposal site

                Notes: 1. The numerals in the diagram are

                         The case of raw sludge transportation
                       The case of incinerated ash transportation

                       representing the ratios of costs to each other. The diagram
                       indicates that the raw sludge transportation is possible at
                       less than 1.0.

                     2. The cost for raw sludge transportation includes the
                       construction expenses of transportation facilities, joint
                       sludge disposal facilities (thickening  *  dewatering *
                       incineration), and their maintenance expenses.  The cost for
                       the incineration ash transportation includes the construction
                       and maintenance expenses of the sludge disposal facility
                       (thickening   dewatering  *  incineration) in the individual
                       treatment plant and also the expense for transporting the
                       incinerated ash to the disposal site.


          Fig.  3.7  Review on the characteristics  of sludge collected
                     and the total cost of sludge disposal
           In  consideration  of the  current  status  of sludge disposal  in both
      Tokyo Bay and Osaka Bay basins and of the opinions  of local
      municipalities,  a regional sludge treatment  and disposal  plan including
      the effective use of sludge,  needs to be materialized.

3.5.3  A conception of a regional  sewage sludge treatment and  disposal plan

           On  the basic assumption  that landfill will be  continued for  the
      time being but that there will be a gradual  shift  to other  effective
      ways such as utilization as resources,  the following business concept is
      under review.

      (1)   A centralized sludge treatment plant including incineration  is
           constructed on the landfill site,  and sludge  within  an area  of 20
           to  30 km range from this centralized plant is collected by means of
           a   pipeline.  In  the future, the disposal of  the greater part of
           the sludge  will be shifted from  landfill to such effective uses as
           construction materials.
                                           760

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     (2)   As to treatment plants outside 20 to 30 km range from the
          centralized plant,  such effective uses as the agricultural use of
          composted sludge should be considered as a first choice.

     (3)   When the agricultural use is not possible, and when reduction of
          the sludge volume is needed, a joint incineration will be taken.

     (4)   As for the site for landfill of incinerated ash or dewatered cake
          the coastal reclamation site for regional is to be jointly used,
          and simultaneously landfill sites in the inland area are to be
          seeked for.

3.5.4  A detailed plan in the Osaka Bay basin

          Of the two districts of Tokyo Bay and Osaka Bay basins, the
     necessity for the regional treatment and disposal plan is much higher
     for the Osaka Bay basin being highly desirable and advantageous from an
     economical viewpoint.

     (1)   Disposal districts

               The project area needs to be divided into disposal districts
          for actual planning, paying attention that the collection,
          transportation, and treatment of sludge will be performed in an
          efficient and economical manner from a long term view point, even
          when an effective use of sludge becomes possible in the future.
               In the Osaka Bay basin, three disposal districts were
          formulated as shown in Fig. 3.8 considering the following
          conditions:

          (a)  The time when each sewage treatment plant wants to join the
               regional sludge treatment and disposal plan

          (b)  The economy of sludge collection, including the basic
               assumption of pipeline collection within 20 km range from the
               central sludge treatment plant.

          (c)  Long rivers, such as Yodo River, as a boundary.

     (2)   Planning the pipeline transportation of liquid sludge

               The liquid sludge  (with a water content of 90%) within 20 km
          range is to be pumped from the sludge storage tank at each sewage
          treatment plant to the central sludge treatment plant through a
          pipeline.  All pipeline system will be constructed as a dual-line
          structure for easiness in repair and in coping with increase in the
          amount of sludge as time goes.  A relay pumping station will be
          installed where the length of the pipe becomes about 10 km or more.
                                     761

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          Prefectural boundary
          Sewage treatment plant to be
          included in the sludge disposal district
                                         .
                                       ' * I Osaka nort
                                    Osaka City  /  block
                                        -  X I
 Fig. 3.8  Map of the Regional Sludge  Treatment and Disposal  Plan
(3)   The central sludge  treatment plant

          The basic policy on sludge treatment  and disposal is to reduce
     the volume of sludge  as much as possible for  conserving the
     disposal site for  the time being, and to shift gradually from
     landfill to utilization and of sludge other effective purposes.  To
     meet these requirements, thickning  -> dewatering -  incineration
     (melting) system will be employed.  Returning wastewater treatment
     facility, a control building and an electrical room will also  be
     installed at the site.
          The block diagram of sludge collection,  treatment and disposal
     system is shown in  Fig. 3.9, and an example of the layout of a
     central sludge treatment plant is shown in Fig.  3.10.
                                762

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                                                       (Facility for effective
                                                        uses in the future)
Fig. 3.9  Block diagram of sludge collection,  treatment and disposal system


    (4)  Economical analysis

              The regional sludge treatment  and disposal plan was formulated
         as a long-term plan  extending  about 24 years,  from 1986 to 2010.
         The construction of  this facility was planned  on the assumption
         that national grant  would  be provided, as in the case of the public
         sewerage system.  The results  of trial computation on the revenue
         and expenditure of the projects relating to each disposal district
         shows that in order  to make the cumulative account positive 10 and
         20 years after the project starts,  the treatment and disposal cost
         per unit volume of liquid  sludge should be 575 - 730 yen/ra^ and
         570 - 695 yen/m-3, respectively.  These costs are cheaper than
         those when sludge is treated and disposed at each existing
         treatment plant, which is  680  - 2,770 yen/m^.
              The construction case of  the facilities at each disposal
         district is estimated to be from 63.3 billion  yen to 81.4 billion
         yen.
                                    763

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                                       320.0
  Designed sludge disposal amount = 35,500 mVday



Fig. 3.10  An example of the layout of a central sludge  treatment plant
                                  764

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4.   RECENT TECHNOLOGICAL DEVELOFMENT IN WASTEWATER TREATMENT

4.1  Overview

          In the recent technical advances of wastewater treatment in Japan,
     large cities,  the Ministry of Construction,  and the Japan Sewage Works
     Agency have had leading roles.  Technical development has especially
     been made in such large cities as Tokyo, Osaka, and Yokohama, where the
     sewage works have been carried out since the 1920s,  progress in
     technology has been particularly notable in  such fields as the
     development of equipments,  the vertical  utilization of wastewater
     treatment plant sites, the improvement of dewatering machines and
     incinerators to reduce the volume of sludge, and the development of
     automation and instrumentation.   All these technologies were essential
     to the construction of wastewater treatement plants in Japanese  large
     cities where the population density is extremely high.
          The Ministry of Construction is responsible for the administration
     of the sewage works in Japan.  It has been planning and funding  the
     research and development programs relating to common and urgent  problems
     in conducting sewage works.  Most of the actual research works are
     carried out by three institutions, namely, the Water Quality Control
     Division of the Public Works Research institute of  the Ministry  of
     Construction,  the Research and Technical Development Division of the
     Japan Sewage Works Agency,  and the Japan Sewage Works Association.
          The research projects, including those  performed by the Ministry  of
     Construction itself, in fiscal 1984 were as  follows.  The greater part
     of them are being continued for  FY 1985.

     (1)   Researches on rational design methods for wastewater treatment
          facilities

            Comprehensive planning for offensive  odor control
            Evaluation of the effect of the nutrient load reduction on lake
            eutrophication control
            Treatment methods for storm sewage
            Investigations on the fate of micropollutants within  the
            wastewater treatment processes

     (2)   Researches on treatment and disposal  of sludge

            Guidelines on the use of  sludge for green spaces and  agricultural
            land
            Testing  methods for  converting sludge into construction materials
            Investigations on ocean disposal  and  land reclamation of  sludge.
            Investigations on improving the management techniques of  sludge
            dewatering processes

     (3)   Researches on advanced wastewater treatment processes and the  reuse
          of the effluent

            Research on the reuse of  treated effluent
            Research on removal  of nutrients  in wastewater
                                    765

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      Research on removal of dissolved organics in wastewater
      Soil treatment of secondary effluent for nutrient removal

 (4)  Research on development of automatic water quality monitoring
     devices for controlling industrial discharge

 (5)  Research on resource and energy conservation in sewerage facilities

      Guidelines for coincineration of sewage sludge and municipal refuse
      Research on the recovery of energy through sludge digestion

 (6)  Research on the small wastewater treatment system

      Research on the treatment characteristics of small wastewater
       treatment plants
      Research on development of facilities suitable for a small
       wastewater treatment plant

     Private industries have also played preeminent roles in developing
 new technologies in Japan.  Many of their research and development have
 attained highly advanced technical levels.  Therefore, it is necessary
 to promote technical cooperation with these private industries for
 carrying out sewage works effectively and properly.
     There has been, however, a tendency for a sewerage authority to
 take a cautious attitude toward employing new technology developed by a
 particular private company for sewerage construction projects, which are
 inherently public-oriented projects.
     This has been attributable to the followings:

 (1)  The source of funds for construction are completely the public
     expenses, such as those originating from taxes.
 (2)  The economical benefit induced by the use of new technology may not
     be evaluated readily, and
 (3)  Any failure resulting from the use of a new technology cannot be
     tolerated easily.

     Therefore, to utilize the fruitful results of new technologies
 developed by private industries, there was a necessity to formulate a
 proper system for evaluating these new technologies.
     The Ministry of Construction has established a new technology
 assessment system in 1978.  This system is intended to evaluate properly
 the functions and performances of new technologies developed by private
 industries and to promote actual use of these new technologies
 extensively by disclosing publicly the results of the evaluation.  The
Minister of Construction announces the particular technology to be
 assessed in an official publication and invites private industries to
 submit applications for assessment.  An assessment certificate is issued
 to each applicant after the assessment is completed.
     Table 4.1 summarizes the subjects on which the assessment has been
made.
                                766

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Table 4.1  Themes of technology assessment by Ministry of Construction
Fiscal year
of invitation
1978


























1979



















1980



















Subjects
Development of microwave
furnace for sewage
sludge to melt

























Development of large-
diameter egg-shaped hard
vinyl chloride pipe with
high rigidity

















Development of ultra-
deep aeration system for
sewage treatment

















Objects of development
To develop microwave
melting furnace capable
using microwaves to melt
and solidify sewage
sludge , turning it into
chemically stable glassy
material without however
generating harmful
exhaust gas but
permitting, the melted
and solidified
substances to be used as
construction materials.















To develop hard vinyl
chloride pipe having an
egg-shaped section with
excellent hydraulic
properties, large
diameter, sufficient
strength and endurance.














To develop activated
sludge process using
ultra-deep aeration tank
requiring only a small
area.















Goals of development
) Maximum treating
capacity of furnace of
about 5 tons/day.
) Exhaust gas generated
from the process, being
capable of meeting the
requirements set forth
in Air Pollution
prevention Law
(Law No. 97 in 1968) .
) Melted and solidified
glassy materials being
capable of meeting the
Order of Prime
Minister's Office (Order
Ho. 5 in 1973)
determining the criteria
for industrial wastes.
4) Melted and solidified
glassy substances being
capable of providing the
strength required for
aggregates.
5) Comparatively low costs
of manufacturing.
operating and
maintaining the melting
furnace.
1) strength determined by
the flat test (in
accordance with test
method established by
Standard K-l of Japan
Sewage Works
Association) being
capable of meeting the
strength of class 1
centrifugal reinforced
concrete pipe (external
pressure strength
against cracking load of
JIS A 5303).
2) Nominal diameter of
about 500 mm.
3) Endurance almost equal
to or higher than that
of class 1 centrifugal
reinforced concrete
pipe.
1) Required processing
capacity greater than
1,000 m3/day.
2) process providing values
of biochemical oxygen
demand (BOD) and
suspended solids (SS) of
final effluent capable
of meeting the technical
requirements set forth
in para. 1 of Article 6
of the Enforcement
Ordinance of Sewarage
Law (Cabinet Order
No. 147 in 1959) .
3) simple operation.
4) Low maintenance and
management costs.
5) Simple environmental
measures.
ssuance date of the
evaluation certificate
September 1979


























July 1980



















July 1981



















                                   767

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     Table 4.1  Themes of technology assessment by Ministry of
                Construction  (Cont'd)
Fiscal year
of invitation
1981





















1982










1983








1984







Subjects
Development of energy-
saving type aerator by
diffused air.



















Development of
mechanical aerator for
oxidation ditch process








Development of sewage
solid-liquid separation
method by screen process






Development of highly
efficient belt-press
for sewage sludge
dewatering




Objects of development
To develop energy-saving
type aerator to be used
for diffused air type
activated sludge process
at the sewage treatment
plant.
















To develop efficient
mechanical aerator using
oxidation ditch process
as one of sewage
treatment methods.






TO develop solid-liquid
separation process using
screens for economically
separation of sewage
solids from liquids,
conventionally performed
with settling basin.


To develop a belt-preas
capable of efficiently
dewatering sludge to
obtain a cake with low
moisture content.



Goals of development
1) power consumption is to
be reduced by more than
20% compared to
conventional air
diffusing equipment.
2) For ordinary sewage, the
aerator is to be able to
provide the values of
biochemical exygen
demand (BOD) and
suspended solids (S3) of
final effluent meeting
the technical
requirements set forth
in Para. 1 of Article 6
of the Enforcement
Ordinance of Sewerage
Law.
3) Connection to existing
aeration tank is to be
easily made.
4) Simple operation.
1) Required current speed
is to be obtained.
2) Oxygen is to be
efficiently supplied.
3) Sufficient mixing and
agitating ability.
4) Easy equipment
maintenance and
operation.
5) Simple environmental
measures.
1) Quality of treated water
almost equal to that of
settling basin is to be
obtained.
2) Eeasiness in operation
and maintenance.
3) Sufficient durability.
4) Economical operation and
maintenance.
1} The system must have a
highly efficient
dewatering capability.
2) Easiness in operation
and maintenance.
3) Sufficient durability.
4) Economical operation and
maintenance.
Issuance date of the
evaluation certificate
July 1982





















July 1983










July 1984








Expected to be
July 1985






     As seen in the Table 4.1, four subjects are related to wastewater
treatment, two are related to sludge handling, and one is related to
sewers.
     The period required for assessment under this system is about one
year from the time of inviting applications until completion of
assessment, thus making a quick evaluation possible.  This is a very
convenient system for assessing equipments or machinery within short
period of time, but is not suitable system for evaluating treatment
processes which requires usually a relatively long time to evaluate.
     The Japan Sewage Works Agency has a technology evaluation committee
which was established in 1974, to evaluate new technologies, particularly
treatment processes.  This committee consists of representatives from the
                                768

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Ministry of Construction and Local municipalities as well as from the
academic circle.
     The president of the Japan Sewage Works Agency asks the committee to
evaluate a particular technology, and the committee discusses the
features and the functions of the technology, the scope of its
applicability and the design parameters based on the data obtained from
actual plants employing the technology.  The committee prepares a
evaluation report which is incorporated into the design criteria of the
Japan Sewage Works Agency to be reflected in the Agency's daily
operations.  The official report is published openly, and those published
so far have contributed greately not only to the Japan Sewage Works
Agency but also to the Ministry of Construction, local municipalities and
private industries for proper utilization of the new technologies.
     Table 4.2 shows the technologies that have been evaluated by the
committee so far.
 Table 4.2  Technologies evaluated by the JSWA evaluation committee
Items submitted for deliberation
@ Automatic control of sewage
treatment plant
(|) Oxygen-activated sludge
process
@ Existing sludge incinerating
facilities
(?) Single hearth cyclonic furnace
(?) Evaporation-dewatering-
incinerating process
(C-G process)
(D RBC for small flow wastewater
treatment plant
(7) Sewage sludge composting
facilities for agricultural
use of sludge
(8) Oxidation-ditch process
Date of
inquiry
July 1974
July 1974
July 1975
Aug. 1977
Aug. 1977
Aug. 1977
June 1981
Dec. 1982
1st report
Oct. 1975
Oct. 1975
June 1980
Oct. 1980
Aug. 1979
Nov. 1978
"
Dec. 1983
2nd report
June 1980
Nov. 1978
-
-
"
Dec. 1982
"
-
3rd report
Aug. 1983
June 1981
-
-
"
-

-
     Technologies evaluated by the Japan Sewage Works Agency's system are
in principle those being developed competitively by several companies,
and those being already used at some actual treatment plants.  The field
data for evaluation are collected by the personnel of the Agency over a
necessary period of time, and are submitted to the evaluation committee
after analysis.
     Design and 0 & M manuals for the new technology are usually prepared
after the report of the evaluation committee is published.
     The Public Works Research institute of the Ministry of Construction
is reviewing the existing rules so that joint research with private
companies can be positively under-taken.  The joint research projects on
development and utilization of biotechnology in wastewater treatment will
be the first case of joint research with private companies.  The Japan
Sewage Works Agency has a provision on the joint research with private
companies since 1984.  The projects being carried out now include the
                                769

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     sequencing batch activated sludge process,  a simplified sludge collector
     for a small flow sewage treatment facility, and a technique to reduce
     phosphorus returned from the sludge treatment process dealing with excess
     sludge from biological phosphorus removal process.
          To carry out this joint research project, the  expenses generally are
     shared evenly between the Agency and the private company,  and the fruits
     of the project such as patents are also shared equally.
          In the following, some typical instances of the recent technological
     development in Japan are outlined.

4.2  Some Typical Examples of the Recent Technological Development

4.2.1  Multiple deck sedimentation tank and deep aeration tank

          In Japan, the area of a wastewater treatment plant site is generally
     determined to be roughly 4.5 times as large as the  area required for the
     major treatment facilities and service passages. In such  large cities as
     Tokyo, Osaka, and Kyoto, however, it is often difficult to obtain a land
     enough as prescribed in the guidelines mentioned above,  for reasons of
     cost and availability of land.  Also, room  must sometimes  be left for the
     future expansion or for constructing advanced wastewater treatment
     facilities.
          In addition, special considerations often become necessary in
     heavily urbanized area to take coordination between wastewater treatment
     plant and its surrounding environment or residents  by means of
     multipurpose use of the site.  Under these  circumstances,  the concept of
     the high degree and vertical uses of a treatment plant site was
     introduced around 1960, and the design method for a multiple deck
     sedimentation tank and a deep aeration tank have been established.   In
     most cases, these facilities are designed to have covers,  and the top of
     the cover are utilized as a park, tennis courts or  similar facilities.
          In Fig. 4.1, the comparison of site areas for  wastewater treatment
     plants with multiple deck sedimentation tanks and/or deep  aeration tanks
     and for those with conventional design is shown. The average site area
     of a wastewater treatment plant per unit capacity of the plant is about
     0.5 m^/WVday in Japan.  The site area in Metropolitan Tokyo,
     however, is just 0.3 nr/m /day on the average.
                                     770

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            40
            30
          a 20

          a
          a>
          \4
          s
          d>
          3 10
e
e
go-
                 o'e0
           o
           o
                                   o
                ..o
                   o o  o
                            o.s
                                                          1.5
                              Capacity of STP (million m /day)
o STP with multiple deck  settler  and/or deep aeration tank
 STP with conventional design
e STP that part of its facility is multiple deck structure

 Fig.  4.1  Comparison of site areas for  sewage  treatment plants with
          multiple deck settlers  and/or deep aeration tanks and
          for those with  conventional  design
          Gear box
                                     Section
                                              Overflow weir
         Fig. 4.2  Double deck  secondary sedimentation tank
(1)   Sedimentation tank

          The concept of surface loading proposed by T.R.  Camp indicates
     that the removal by sedimentation  can  be  determined only by the
     surface loading to the sedimentation tank.   Experience suggests that
     the suitable ranges of surface loadings for  primary and secondary
     sedimentation tanks are 20 to 50 m?/m*/3ay and 20 to
     30 mVm2/day, respectively.  However,  when the sedimentation
     tank is structured into two stories or more  by placing one on the
                                 771

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     top of  another,  it  is possible  to acquire  the  treatment capacity
     multiplied  by the number  of  stories  with the same  site area.   The
     first double  deck sedimentation tank (Fig.  4.2) was constructed in
     1964 at the Ochiai  Sewage Treatment  Plant  in Tokyo.  Later  in  Osaka,
     a three deck  sedimentation tank was  constructed for more effective
     use of  the  site.  As the  experience  of  construction and maintenance
     of these facilities is accumulated,  the important  points in the
     design  have become  clear,  which are  as  follows:

     (a)  The flows in the upper  and lower decks should be made  equal as
         much as  possible by  the proper  installation of valves  and
         overflow weirs.

     (b)  The sedimentation tank  should also be  structured so that  no
         scum accumulates on  the bottom  of  the partitioning slab between
         the upper and  lower  decks;  this can be accomplished through the
         utilization of a lower  deck rake as a scum collector.

     (c)  Smooth collection and withdrawal of sludge should be guaranteed
         by proper equipments and maintenance,  which include the use of
         a  durable link belt,  careful consideration about the shape and
         capacity of the sludge  hopper,  and a  device to prevent the
         sludge withdrawal pipe  from clogging.

(2)   Deep aeration tank

         In 1970,  the Metropolitan  Tokyo Government decided to  employ
     aeration tanks with a depth  of  10 meters for constructing the
     Shingashi and Morigasaki Higashi sewage treatment  plants in order to
     utilize the site effectively.   The cross section of the tank is
     shown in Fig.  4.3.   This  plan was beyond the experience of  the
     conventional  design with  5 m depth.  The problems  which might
     associate with such a deep aeration  tank were  thought to be the
     adaptability  of  microorganisms  to high  hydraulic pressure and  the
     energy  efficiency.   The tests made before  design had proved the
     following facts:

     (a)  The microorganism activities did not  decline  even when the
         cyclic hydraulic pressure  of 0  to  20  m was repeatedly  applied.

     (b)  As shown in Fig. 4.4  the theoretical  energy required to supply
         unit volume of air increased as the depth of  the diffuser
         increased.  When this relationship was expressed by an
         exponential function of the depth  H as anB, the exponent  3 was
         roughly  0.7.   On the other hand, the  oxgen transfer capacity
         was also found to increase proportionally to  the 0.7th power  to
         the depth H as shown in Fig. 4.5.  Therefore, it was found that
         the energy  efficiency was  not dependent on the depth of  the
         tank.
                               772

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                                  Cross section

                                           Air supply pipe
                  Diffuser
                 Baffle wall -_   	j
                          Fig. 4.3  Deep aeration tank
,*
X
0)
o
3
o<
OS
M
0)
H
m
 H
4J
OJ
0
OJ
H
2
1
1
1
1
1

0
o

0
0

.0
.8
.6
.4
.2
.0

.8
.6

.4
.2
0
X
X
/
/'
/
/
*
/
/
/
/
/
I 	
           2  4  6  8 10 12 14 16 18

             Depth of Diffuser(m)
Fig. 4.4  Relationship between
          Theoretical Energy
          Requirement and the Depth
          of Diffuser
                                                   2,000


                                                   1,000



                                                    500



                                                  ,  200



                                                    100


                                                     50



                                                     0
               4 6 8 10  20
                   M (M)
Fig. 4.5  Relationship between Overall
          Oxygen Transfer Rate Kj^'V
          and  the Depth of Diffuser H
           (c)  When  the depth of the diffuser was more than 5 meters, it
               became difficult to continue stable  treatment because of poor
               settlability of sludge due to gassification of the
               supper-saturated air.

               From  these experiences, it was concluded that the following
          consideration should be taken for the  design of the facility:

           (a)  TO prevent activated sludge from  floating, the diffuser is
               placed at about a depth of 5 meters,  not near the bottom of
               the tank.
                                      773

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          (b)  To assure good mixing even with  an  increased cross sectional
               area, it is necessary to use  the baffle walls effectively.

               The design concept noted above has  been employed in the
          "Design Criteria for Sewerage Facilities"  issued by the Japan
          Sewage Works Association.
               In fact, 7 wastewater treatment  plants  out of 10 plants in
          service in Tokyo, or 55% of  the total capacity of
          5,880,000 mV<3ay, are those  employing multiple deck sedimentation
          tanks and/or deep aeration tanks.  In Osaka  City, among 12
          wastewater treatment plants, 8 plants employ multiple deck primary
          sedimentation tanks, 4 plants have deep  aeration tanks, and 10
          plants have multiple deck secondary sedimentation tanks.  Another
          fomous example is the kisshoin wastewater  treatment plant in
          Kyoto.  This treatment plant employs  the oxygen activated sludge
          process, and the aeration tank is  installed  above the final
          sedimentation tank.  (Fig. 4.6.)   Coupled  with the effective use of
          space created on the top of  the cover of the treatment facilities,
          the greater part of the facilities to be constructed in big cities
          in the future will employ this kind of technique.
                                                                       Effuent
                                                Mixers
                                                Aeration tank
                                                Final sedimentation tank
                                                Return sludge pump
                                                Electricity room
                                                Oxygen generators
                                                Compressors
                                                Ventilators
       Fig. 4.6
Perspective view of secondary  treatment facilities of
the Kisshoin STP in Kyoto
4.2.2  Phosphorous and nitrogen removal  technology

          In 1972, the public Works Research  Institute of the Ministry of
     Construction established a pilot plant with a treatment capacity of
     250 m3/<3ay at the Shimomachi Sewage Treatment Plant in Yokosuka City,
     and started the research on removal of phosphorous from secondary
     effluent by means of chemical coagulation.   This was the start of the
     research on advanced wastewater treatment technology in Japan.  Since
     then, research and development for  advanced treatment technology has
                                      774

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come  to be carried out extensively by major research institutions
including Research Division of the Japan Sewage Works Agency Tokyo and
other large cities.
     Research at the beginning focused on physical-chemical treatment.
However, after the energy crisis in autumn in 1973, the saving or
conserving of resources and energy has become a demand of society, and
therefore, the emphasis on research and development for advanced
treatment technology shifted to the biological removal of phosphorous
and nitrogen.
     During these periods, phosphorous removal by addition of a
coagulant to the aeration tank has been put to practical use.  This
method has been employed by the wastewater treatment plants at Lake
Kasumigaura and Lake Biwa.  In addition to minimize the amount of sludge
being generated, the crystalization method has been developed.  This
method is to crystallize orthophosphate ions on the surface of the
contact media as calcium hydroxyapatite.  In 1983, a full-scale plant
with a capacity of 12,000 m^/day was built by Metropolitan Tokyo.
     As for the biological nitrogen removal process the single stage
nitrification and denitrification process with nitrified liquor recycle
has been put to practice as a means of removing nitrogen.  The Konan
Chubu Sewage Treatment Center in the Lake Biwa area began to operate in
April 1982 as a full scale facility employing this method.
     At a small sewage treatment plant in Hamamatsu City, biological
denitrification by the Wuhrmann process, which utilizes endogeneous
respiration, has been successfully carried out using the facility which
originally designed as an extended aeration process.  An anaerobic
section is installed in the latter half of the aeration tank.
     The first full-scale evaluation project of the biological
phosphorus removal process in Japan was performed by the Japan Sewage
Works Agency at the Arakawa Sewage Treatment Center in 1982.  Since
then, researches for practical application have started at many
treatment plants in various cities such as Hamamatsu, Kawasaki, Kyoto,
Tokyo, Fukuoka and so forth.
     One of the major targets of research on biological phosphorus
removal in Japan is to find the method to stabilize the treatment even
during the rainy season and the typhoon season in the summer time;
another target might be to pursue measures to reduce the return load of
phosphorous from the sludge treatment processes.
     Another research field of interest is to reduce the capacity of a
nitrification tank by increasing the efficiency of nitrification.  The
effect of installing rotating disks or other media in the aeration tank
has been studied at various institutions by pilot scale experiments.
Application of biotechnology for improving the efficiency of
nitrification has also been persued at many research institutions.
Also, as an advanced wastewater treatment process for a small flow
treatment plant, nitrogen and phosphorous removal by sequencing batch
activated sludge process has been studied.
     Table 4.3 shows a list of wastewater treatment plants that have
been performing phosphorous and nitrogen removal as a routine practice.
Besides these plants, many demonstration projects for biological
phosphorus and nitrogen removal have been carried out at many places,
including Tokyo, Kyoto, and Osaka cities.


                                775

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           Table  4.3   List of  wastewater  treatment plants  employing
                      advanced wastewater  treatment  technology for
                      phosphorous and  nitrogen  removal
Receiving water
body
Lake Kasumigaura
Lake Hamana
Lake Biwa
Name of
wastewater
treatment plant
Kasumigaura
Wastewater
Treatment Center
Itako Wastewater
Treatment Center
Hitomigaoka
Hastewater
Treatment Center
Koto Wastewater
Treatment Center
Konan Chubu
Wastewater
Treatment Center
Okinoshima
Wastewater
Treatment Center
Kosei Wastewater
Treatment Center
Design
capacity
(m /day)
55,400
4,200
1,620
1,980
14,000
210
5,000
Treatment method
Nitrified Liquor recycle method
with coagulant addition to the
aeration tank
The same as above, and the
modified Phoredox process
Biological phosphorus removal,
and biological nitrification and
denitrif ication by the Wuhrmann
process
Same as above
Nitrified Liquor recycle method
with coagulant addition to the
aeration tank, and the modified
Phoredox process
Batch operated oxidation ditch
with coagulant addition
Bardenpho process with coagulant
addition
4.2.3  Instrumentation

          One of the most advanced instrumentation technologies  applied to
     wastewater treatment systems in Japan is the centralized supervision and
     distributed control system.   In this system, process computers,
     microcontrollers (CTR),  and sequence controllers (SQC)  are  rationally
     arranged so that the surveillance,  data processing and  supervision are
     executed at the control  center, and the actual control  is executed
     locally at the site.
          This system has been realized  as the result of advances in  digital
     control technology applied to instrumentation, including quantitative and
     qualitative measuring devices, various control units, data  transmission
     units, and data processing units.  The use of this system has resulted in
     stable automated control, and efficient and labor-saving wastewater
     treatment.
          Taking an example of the Kanagawa Wastewater Treatment Plant of
     Yokohama City, which employs this system, detailed explanation of the
     system will be made.  The Kanagawa  Treatment Plant is a relatively new
     treatment plant with a design capacity of 540, 000 m3/day.   The plan of
     the treatment plant is shown in Fig. 4.7.

     (1)  Configuration of the supervision and control system

               The control center of this system consists of central computers
          installed at the control room, and microcomputers and sequence
          controllers distributed to each electric room.
                                      776

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         Pig. 4.7  Plan of Kanagawa Sewage Treatment Plant
          The complicated controls for automation are performed by the
     microcontrollers and sequence controllers at the local stations
     according to the instructions given by the central  computer.   The
     contents and results of these controls are transmitted to the
     central  computer from remote stations  for CRT display in  characters
     and diagrams by means of the high-speed data transmission system
     using optical-fiber cables.
          This centralized supervision and  distributed control system can
     process  an enormous amount of informations required for automated
     process  control.
          Because the supervision function  and the control function are
     separated and work independently of each other,  continuous control
     is possible for stable wastewater treatment operations even while
     the central computer is down.
          Fig. 4.8 shows the system configuration.

(2)   Function of the central computer system

          To  ensure reliability and maintainability,  the central computer
     system employs a dual system; one is for operation  and the other is
     a standby.
          These  two computers are operated  by means of the load-sharing
     and duplex  system.
          The standby computer is used for  off-line processing,  such as
     preparation for the equipment management ledger  and other off-line
     batch processing.
                               777

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CTR: Mlcorcontroller




dH^)
1 Disk 1



System
rypewn ter



snt roller
jller









computer










l
Data way
controller
System
Console


|d>
1 I Disk)
1 l^-^l

^ 	 **^ Data link

Graphical monitoring
panel controller

x 3

t
Peripheral equipment








Standby
computer










i
Data way

                                                       o-


7
CTR



1
J
SfiC

Data way (optical fiber
transmission)



Same as
left
1 	 	 1



Same as
left
1 	 	



Same as
left
I 	



Same as
left
1 	
1
^
1
1
1
' Same as
1 left
I
1
1
(
L



Same as
left
L_

1


Trans-
mission
control-
ler

MODEM


1 1
1 	 1
1 	 1
Trans-
mission
control-
ler

MODEM
1
-^
. -. - J
Receiving and
power station
block
Main pump and Blower
grit chamber  facility
block      block
Primary     Secondary   Disinfection  Sludge
sedimentation sedimentation and filtration treatment
tank block   tank block   block       block
Transmission Pumping stations
to and from  (remote supervision
other treat- and control)
ment plants
       Fig.  4.8  Schematic diagram of  the centralized supervision
                  distributed control system
            The major  functions of the central computer system are  as
       follows:

       (a)  Supervision and operation
                  The system processes  such  information as the status of the
            equipments, control modes, and measured  values  transmitted from
            each local station to be displayed at a  CRT and/or a graphical
            monitoring panel for man-machine  interface.
                  Operators can operate the  equipments, and  alter the
            automatic  control  modes or predetermined values by looking at
            the CRT.
                                       778

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     (b)   Slips and books generating function
               This system can store various process values into the
          files sequentially and, using these data/ it can produce
          automatically an output on the typewriter to generate various
          slips and books.

(3)   Functions of local stations

          A local station consists of a microcontroller,  a sequence
     controller,  and a high-speed data transmission system.
          Normally, these controllers perform various complex automatic
     controls and arithmetic controls.
          The system is provided with a backup unit capable of
     performing the minimum required controls to ensure trouble-free
     operations of the wastewater treatment system even when these
     original controllers have failed.
          Table 4.4 shows the principal control parameters.   Note that
     those in the table to which the * mark are attached are the
     controls that are not regularly executed.

(4)   Measuring instruments

          Besides such data as water levels,  flow,  pressure, and air
     supply which are necessary to control  operations, a need for
     collecting water quality data has increased.   In this treatment
     plant, a PH meter is installed in the  grit chamber;  a
     sludge-density meter in the primary sedimentation tank; DO, MLSS,
     PH,  and temperature meters in the aeration tank; and sludge
     density, turbidity, PH, and UV absorption meters in the secondary
     sedimentation tank.  The readings of these meters are used as
     inputs for automatic control, and are  stored in the computer as
     well as being displayed on the central CRT.

(5)   Effect of the automatic controls

          As mentioned, the Kanagawa wastewater treatment plant in
     Yokohama is a relatively large treatment plant with a design
     capacity of  540,000 m3/day.  By employing an automatic control
     system it has been possible to reduce  the number of  plant operators
     significantly.  This has been especially noticeable  in the number
     of operators in service at night and on holidays; only two
     operators are required to operate the  whole plant including two
     relay pumping stations during these times.
          In addition, DO control of the aeration tank makes some
     contribution to the reduction in operation cost.  It has been found
     that air supply, particularly during storm period when  the strength
     of sewage is weak, can be reduced from 20 to 30% compared with that
     with the flow proportional air supply  strategy.
                                 779

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                      Table 4.4  List of control modes
Local station
Extra-high
tension receiving
and transforming
power block
power station block
Grit chamber and
Main pump block
Blower facility
block
Primary
sedimentation tank
block
Aeration tank and
secondary
sedimentation tank
block
Disinfection and
filtration block
Control device
1. Power-receiving
equipments
2. Power-distributing
equipment
3. Generating station
4. Main pump and
blower
1. Main pump
1 . Blower
1. Primary sludge
pump
1. Aeration
2. Return sludge
pump
3. Excess sludge pump
1. Disinfection
2. Filtration
Control mode
1. Power failure control
2. Recovery control
3. Automatic receiving line switching
control
1. Manual pattern shifting control
2. Power factor control
1. Peak load cut control
2. Automatic starting control
3. Automatic synchronized control
4. Number of units control
5. Load transition control
6. Automatic frequency control
7. Automatic voltage control
B. Load sharing of active and
reactive power control
9. Dummy load control
1. Load limit control
2. Load lock control
1. Constant water level control*
2. Constant flow control*
3. Level and flow control
4. Revolutions control
1. Constant pressure control*
2. Constant air flow control*
1. Constant sludge density control*
2. Intermittent withdrawal control*
3. Continuous withdrawal control
(preset control)
1. Constant DO control
2. Constant air flow control*
1. Constant MLSS control*
2. Constant flow control
3. Constant return rate control
1. SRT control*
2. Intermittent withdrawal control*
3. Continuous with drawal control
(preset control)
1. Constant injection volume control*
2. Constant injection rate control
1. Inflow control
2. Number of units control
              Note: Those with * mark are the control systems available as an option.
4.2.4  Control of offensive odor from wastewater treatment plants

          The offensive odor prevention law was enacted in 1966.  As shown  in
     Table 4.5, eight substances generating offensive odors are presently
     regulated.  The governers of prefectures shall determine the actual
     standards within the ranges of  concentration listed in the Table 4.5
     considering the actual situations of the local districts.  These
     standards are applied to the concentration at a site boundary.
                                      780

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Table 4.5  Regulated substances under the offensive odor prevention law
Restricted
materials
Ammonia
Methyl mercaptane
Hydrogen sulfide
Methyl sulfide
Tr line thyl ami ne
Methyl disulfide
Ace tal deny de
Styrene
Range of
standard (ppm)
1 - S
0.002 - 0.1
0.02 - 0.2
0.01 - 0.2
0.005 - 0.07
0.009 - 0.1
0.05 - 0.5
0.03 - 20
                   Note: Standards are applied to the concentrations
                        at the boundary of the site.
       Wastewater treatment plants in Japan must often be built  adjacent
  to residential areas; therefore, attention has to be paid usually  to
  prevent offensive odors.  For this reason, measures to control offensive
  odors have attained significant advances.  The operating wastewater
  treatment plant have never failed to meet the legal standards, and only
  a few complaints about odors have been made to wastewater treatment
  plants.
       As shown in Table 4.6, most of the wastewater treatment plants
  install a cover on their main source of offensive odors, such  as
  thickners, and the percentage of treatment plants without such a cover
  is only about 30%.
       As shown in Table 4.7, 43% of treatment plants have odor  control
  facilities for sludge thickners, and 57% of treatment plants have
  control facilities for sludge dewatering machines.  Even 41% of the
  total treatment plants have control facilities for grit chambers which
  are known to generate little offensive odor.  The deodorizing  method
  most widely used is chemical scrubbing with sodium hydroxide and sodium
  hypochlorate, and it accounts for about half the total deodorizing
  facilities in use.  The absorption method using activated carbon or ion
  exchange resin and the ozone oxidization method each accounts  for  only
  12% of the total deodorizing facilities.  The rest of the facilities
  almost employ highly advanced means of deodorization by combining  these
  methods.
       A representative method of this category is activated carbon
  absorption following acid and alkali scrubbing, or a method that
  combines ozone oxidation and activated carbon absorption.  In  some
  treatment plants, soil deodorizing method is used, which passes
  offensive odor through a soil layer.  A method that induces the air with
  offensive odor into the aeration tank is also being applied.   This
  method is less-costly in both construction and maintenance costs.
                                  781

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CXI
                          Table  4.6   status of  covers for wastewater treatment facilities

Secondary
sedimentation tank
Sludge thickening tank
Dewatering machine
Indoor
(T) Covered
67
38
198
(2) uncovered
128
46
150
Outdoor
(5) Covered
26
168
-
(T) Uncovered
78
97
-
percentage of
uncovered facility
0/+
-------
     About 12% percent of the total wastewater treatment plants in Japan
have spaces which are open to the public within their premises as a
park, an athletic field, or a district public meeting facility, all of
which has contributed to better relations with residents living near
wastewater treatment plants.  Progress in odor control technology has
contributed significantly to this kind of practice.  In addition, when
the construction of a wastewater treatment plant is undertaken, it is
sometimes difficult to obtain the consent of residents near the
prospective construction site.  Complete control of odor, in some cases,
is a key factor to get consent from nearby residents.  In this sense,
odor control technology has become one of the indispensable technologies
relating to wastewater treatment in Japan.
                                 783

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5.   UPGRADING OP EXISTING WASTEWATER TREATMENT PLANTS

5.1  Background

          During the 100 year history of Japan's sewage works, there have
     been considerable changes in the socioeconomic situation that have
     brought more variety in the concept of planning and designing the
     sewarage systems.  In the past, sewerage systems were only constructed
     at large cities where the population desity was high, and most of the
     wastewater treatment plants had large capacities.  At present, however,
     the demand for wastewater treatment has increased in small and medium
     sized cities,  and many small and medium-sized plants are being built.
     As to the collection system in the past, the combined sewer system was
     employed for the construction of sewers in large cities, but now, new
     sewer systems  are being constructed by the separate system.
          The changes in socioeconomic situation, such as people's lifestyle,
     concentration  of population in cities, and development of industries,
     were very fast and large.  In some cases, they were more than expected
     at the time of planning of the facilities.  These changes have directly
     affected treatment plant operation, often resulting in deterioration of
     effluent quality.

5.2  Necessity for  Upgrading of Existing Wastewater Treatment Plants

          There has been a variety of causes which made upgrading of existing
     treatment plants necessary.   Typical ones are as follows:

     (T)  Upgrading the effluent standards

               Legal system concerning environmental protection was
          restructured and subsequently enacted around 1970, and the
          environmental standards on the major water bodies in Japan were
          then established.   The importance of sewage works in controlling
          pollution of public water  bodies was legally defined by the
          amendment of the Sewerage Law at that time.   For almost all of the
          river basins, the effluent standards requiring secondary theatment
          were established.   In some areas, more stringent standards which
          require better treatment than the conventional secondary treatment
          have been enforced based on local necessity.

     (g)   Rapid concentration of  population and industrial development

               Some treatment plants became overloaded because of the
          unexpectedly rapid concentration of population and industrial
          development.   Especially industrial wastewater discharge often
          affects greatly on the  operation of a treatment plant.   Large
          variation of flow and load,  and discharge of  non-biodegradable
          organics  are another problems associated with industrial
          wastewater.   At present almost all of the municipalities have
          pretreatment standards,  and can order industries to improve their
          pretreatment facilities according to its necessity.  They also have
          surveillance systems to enforce the pretreatment standards.


                                     784

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Increase in load

     The improvement of the standard of living and the change in
food consumption have caused a considerable increase in pollutant
load per person.  Per capita BOD load used to be 35 - 40 g/cap/day
in 1950's.  However, it increased rapidly since then and is now
about 50 - 60 g/cap/day in large cities as shown in Fig. 5-1.
            1973
                   1975
                         1977
                                1979
                                       1981
                                             : Hei}0 STP

                                             : Arino STP
                                             : Tamon STP

                                           O: Nishiyama STP

                                           A: Sayama STP
         Fig. 5.1  Change in per capita BOD Load
     Recent increase in organic content in sludge, which  is mainly
due to increase in fats and oil in sewage, has  created  difficult
problems in sludge handling.  Poor thickenability and
dewaterability often required upgrading the sludge treatment
facilities.

Revision of design criteria

     The conventional design criteria were determined in  reference
to data obtained from large sewage treatment plants connected with
combined sewer system.  At a medium or small sized treatment  plant
of the separate sewer system based on these criteria  troubles
sometimes occurred even under normal loading conditions.  For
example, at a small treatment plant treating sewage from  a housing
complex, due to extremely large flow variation, sludge  washout
ocurrs at the time of peak flow, or sludge bulking may  easily occur
due to high organic loading.
     The conversion of a collection system from combined  to
separate sewer adversely affects the sludge's settlability,
compressibility, and dewaterbility, and some treatment  plants have
troubles in sludge handling.  The treatment plant employing a
separate sewer system can easily be upset by inflow and
infiltration of storm water and ground water.   Thus, a  measure to
reduce inflow and infiltration needs to be taken  throughout the
collection system.
                            785

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     (5J   Direct discharge of  collected night soil  into the wastewater
          treatment plant

               There have been cases  in which night soil collected  from
          non-sewered area was directly discharged  into the wastewater
          treatment plants at  large amount,  or partially treated  effluent or
          sludge produced from the night soil treatment plants  was   disposed
          into the sewer  systems.  These activities often caused  treatment
          plants to malfunction because of  overloading and excessive nitrogen.

     (&)   improper operation and maintenance

               A wastewater treatment plant cannot  produce good quality
          effluent unless it is properly operated and maintained.   It is
          desirable that  plant-operators are well-trained, employing such an
          operator, however, may sometimes  be difficult.  In  a  medium or
          small-sized treatment plant,  personnel expenses may tend  to account
          for  the greater part of its total  operating cost, resulting in
          reduced personnel expenses.  A treatment  plant without  well-trained
          operators often fails to discover  the early symptom of  malfunction
          and  cannot take any  remedial  measures to  prevent deterioration of
          effluent quality.

     (?)   Others

               To attain  a reduction  of operational costs and efficient
          energy conservation  the  improvement of existing facilities and
          adequate operation and management are required.

5.3  Tentative Guideline  for Upgrading of Existing  Treatment  Plants

          The  existing sewerage facilities  in the greater part  of sewer
     districts in Japan are under  continuous construction and expansion.
     Therefore, the wastewater flows  at treatment plants are  continuously
     increasing.  Consequently, almost all  of treatment plants  in Japan  have
     experienced the both conditions  that their treatment capabilities were
     temporarily too small or  too  large, and the personnels of  these
     treatment plants have experienced troubles caused by these conditions.
     These experiences have become valuable references to the future
     operation & maintenance,  and  they have been reflected in the design of  a
     facility in the case of expansion projects.
          Although some common problems to  be solved have been  made clear,
     and the case studies and  experiences for upgrading in these  matters have
     been utilized for operations  or  design of other treatment  facilities,
     seldom are the cases in which the detail of  the experience and process
     of upgrading from identification of the cause  of malfunction to the
     improvements achieved have often been  disclosed to the public.
          The  Japan Sewage Works Agency collected  information on  cases
     concerning the causes of  malfunction and improvements applied  throughout
     the country during a six-year  period from 1975 to 1981.  In  some cases,
     on-sight identifications  of the  causes were made and corrective steps
     were taken in close cooperation  between the Agency and the persons  in


                                     786

-------
     charge of the plants.   The Agency also investigated to verify the
     effectiveness of some measures to counter the problems by using pilot
     and full-scale plants.  A report was subsequently made by summarizing
     these results.
          The Japan Sewage Works Association organized a committee consisting
     of competent engineers with an expert knowledge on the plant's
     management to prepare a guideline based on this report.  The results
     were disclosed to the public as "Tentative Guideline for Upgrading of
     Existing Treatment Plants".
          The guideline describes the causes and symptoms of troubles
     encountered in operation and maintenance of the activated sludge
     process, and explains the precautions to be taken and the methods to be
     employed being classified by causes.

5.4  Examples of Upgrading of Existing Plants

          Among many cases in which existing treatment plants were upgraded,
     some representative cases are introduced in the followings.

5.4.1  Improvement in effluent quality by means of separate treatment of
       supernatant from the sludge treatment processes

          There have been many cases in which treatment plants are suffering
     from loading by supernatant from the sludge treatment facilities.
          The examples described below are the Toyohiragawa Treatment Plant
     in Sapporo City and the Senboku Sewage Treatment Plant in Sakai City,
     each of which has a heat treatment process for sludge treatment.  Both
     treatment plants experienced deterioration in performance caused by high
     supernatant loading from sludge heat treatment process, and  have been
     successfully improved by separate treatment of supernatant.

     (1)   Conditions before improvement

               The strength of the supernatant generated by the heat
          treatment process is very high, and the following troubles occurred
          in the wastewater treatment facilities.

               The aeration tank became overloaded.
               The loading  to the aeration tank varied largely depending on
               the on-off operation of the heat treatment facility.
               The secondary effluent was colored,  and an offensive  odor was
               generated.

               Besides the  common problems mentioned above,  the following
          troubles were added to the Senboku Sewage Treatment Plant.

          (T)   The treated  water  could not easily conform with the effluent
               standard (Relating to COD^).
          (2)   The function of sludge thickening was extremely deteriorated,
               and solids twice as much as those in raw sewage were
               recirculating from sludge treatment  processes.
                                     787

-------
          Because  of  these  troubles,  both plants were unable  to obtain
     the  stable  effluent quality.

(2)   Corrective  measures

          As  the results of detailed  investigations, separate treatment
     process  on  the supernatant  from  sludge  treatment process was  taken
     to be the basic  policy for  both  treatment plants.

     (a)   Improvement applied  to the  Toyohiragawa Treatment Plant

              The supernatant is diluted with an equal amount of  the
          secondary effluent,  and is  treated by means of  the  extended
          aeration process.  The effluent from this  separate  treatment
          process  is  returned  to the  primary sedimentation tank.
              In  order to prevent wash-out  of sludge at  the  secondary
          sedimentation tank,  the weir  loading was reduced and the
          arrangement of the weir was redesigned.

     (b)   Improvement applied  to the  Senboku Sewage  Treatment Plant

              The facility for  treating supernatant separately has been
          constructed.  The process was the  aerobic/anaerobic biological
          process  including biological  denitrification, and the effluent
          is  returned to the primary  sedimentation tank.

(3)   Plant performance after improvement

          BOD, COD, and SS  removals have been considerably improved
     after improvements at both  plants, and  effluent quality  has come to
     conform  with  the effluent standards.  Offensive odor was completely
     removed  from  the effluent.
          The effect  of upgrading by  means of separate treatment process
     is summarized in Fig.  5.2.
          Table  5.1 shows a comparison  of the effluent qualities of the
     Senboku  Sewage Treatment  before  and after the improvement.
     Fig.  5.3 shows a comparison of stability of the effluent qualities;
     and  Fig. 5.4  shows a comparison  of solid mass balances before and
     after the improvement.
 Table 5.1  Comparison of  effluent qualities  of  the Senboku Sewage
            Treatment Plant
                                788

-------
L	i
                                                   Stabill zed settling
                                                   efficiency in primary
                                                   sedimentation  tank
                                                   Refreshing of sludge
                                                   (eliminated putre-
                                                   faction)
                                             Secured optimum
                                             solids concentration
                                             to gravity thickener
                                             (primary sedimenta-
                                             tion tank) and to
                                             centrifugal thickener
                                                                                            Improved and stabilized
                                                                                            effluent qualtiy
                                                                                       Improved removal rate
                                                                                            Promoted nitrogen removal
                                                                                            in wastewater treatment
                                                                                            Simplified operation
                                                                                            control
                                                                                       Improved and stabilized
                                                                                       gravity thickening and
                                                                                       centrifugal thickening
                                                                                       functions
                                                                                            Early removal of sludge
                                                                                            generated in wastewater
                                                                                            treatment system
                                                                                            Simplified operation
                                                                                            control
                                                                                            Allowance in facility
                                                                                            capacity particularly in
                                                                                            sludge treatment system
        Fig.  5.2   Effects  by introduction  of supernatant  separate  treatment

- 100
dP
o1 80
c
(U
g- 60
>H
n 40
.u
J3 20

0
Jan. to Sept. 1982
(n=273)
.




. r







_.










 i

~ 100
dP
requency
en CD
a, 40
H

0
Oct. to Jan. 1982
(n=124)



 , r







i, ,
                          10    20   30   40   50
                                COD  (mg/JU
                           Before  improvement

Fig.  5.3   Comparison of  the effluent
              improvement
                                                                  10  20   30   40   SO
                                                                     COD  (mg/Ji.)

                                                                  After  improvement
                                                                    histograms before and after
                                                      789

-------
        Raw sewage
                     394 kg/day
                    (290 kg/day)
Upper figure: Before improvement

(Lower figure: After improvement)
                                                   4,028 kg/day
                                                  (4,098 kg/day)
                                8,533 kg/day
                                (1,460 kg/day)

        Fig.  5.4  Comparison of Solid Mass Balances before and after
                  the Improvement in the Senboku STP
5.4.2  Improvement in Treatment Capabilities  by Chemical Dosing to Primary
       Sedimentation Tank and by Injecting  Pure Oxygen to Return Sludge at the
       Tobu Sewage Treatment Plant  in Mitaka  City

     (1)   Condition before improvement

               This plant is of combined flow type with a design capacity of
          21,000 mV<3ay  Due to the increase of population in the drainage
          area, the volume of influent  increased annually to 40% in excess of
          the design capacity about 30,000  mV^ay as of 1975.  As a
          solution to this overloading  condition, expansion of the treatment
          facility was the first consideration, however, it was practically
          impossible due to restrictions from location and site space.  As
          such being the situation, this plant was taking great pains in
          finding effective measures for oxygen supply to the aeration tank.

     (2)   Corrective measures

               Additional installation  or rebuilding of blowers could not be
          chosen due to the limited budget.   After studying a method to
          supply dissolved oxygen to the aeration tank, injection of pure
          oxygen into the return sludge was decided and applied after the
          repeated experiments on pure  oxygen injection on site started in
          January, 1975.
               The newly installed  equipment  for pure oxygen injection
          consisted of an oxygen supply unit  and an oxygen dissolving unit.
          In the oxygen supply unit, liquid oxygen was gasified and regulated
          to 1.5 to 2.5 kg/cnr by the final pressure control valve, and
          then supplied to the line mixer,  which was installed just after the
          return sludge pump.
               As the second corrective measure to mitigate the load of the
          aeration tank, a coagulant was dosed into the sewage at the primary
          sedimentation tank, and thus  upgraded the efficiency of primary
          sedimentation tank.
                                      790

-------
               For this purpose, a coagulant dissolving tank and a dosing
          tank were provided, and a diffuser pipe was installed in the
          conduit to the primary sedimentation tank for mixing.  Because the
          raw sludge production increased as a result of coagulant addition,
          beltpress filters were installed instead of vacum filters for
          sludge dewatering.

     (3)  Plant performance after improvement

               The injection of pure oxygen has been made at a rate of
          40 /min. for the amount of 5.3 m3/min. of the return sludge.  As
          a result, even the sewage to be treated increased from
          24,000 m3/<3ay to 30,000 m3/<3ay, the effluent quality after
          improvement was equivalent or better than that before the
          improvement.  Because dissolved oxygen in the aeration tank was
          maintained at a desirable level by increasing the oxygen supply, a
          stabilized effluent quality could be obtained.  These results are
          shown in Table 5.2.
   Table 5.2  Comparison effluent qualities before and after improvement,
              Tobu Sewage Treatment  Plant, Mitaka City
Item
Before
improvement
1975/1 - 2
After
improvement
1975/3 - 4
Flow
23,703 m3/day
29,563 m3/day
DO of aeration
tank effluent
1.65 mg/je
2.31 rng/H
Effluent
Trans-
parency
43 cm
68 cm
COD
9.8 mg/i
11 mq/H
BOD
-
17 mg/i
SS
-
25 mg/Z
5.4.3  Other Proposed Methods for Upgrading

          The followings are the list of other methods recommended in the
     tentative guideline for upgrading.

     (1)   Corrective measures for overloading

          (T)   improving the efficiency of the primary sedimentation tank by
               addition of a coagulant
          (g)   Reducing the supernatant loading by improving the performance
               of sludge treatment processes
          (5)   Increase in oxygen supply by employing the improved aerator
          (4)   Conversion from the conventional activated sludge process to
               the step-aeration process
          ()   Employment of the pure oxygen-activated sludge process

     (2)   Corrective measures for large flow variation

          (T)   To install more capacity of the equalization tank
                                      791

-------
        Utilization of the capacity of trunk sewers
     (T)   Conversion of the primary sedimentation tank to an
          equalization tank

(3)   Corrective measures for bulking

          Modification of the operating condition of the aeration tank
          Addition of inorganic SS to the aeration tank
          Addition of chemical coagulant to the aeration tank
          Employment of the anaerobic/aerobic activated sludge process
          Employment of the pure oxygen-activated sludge process

(4)   Improvement of the aeration tank operation

     (1)   Use of efficient aeration devices
          Automatic DO control
          Effective use of baffle boards to prevent from short-circuit
          of flow
     (4)   Reaeration of return sludge

(5)   Improvement in secondary sedimentation tank to prevent wash-out of
     sludge
                                792

-------
DEVELOPMENTS IN THE FIELD OF WASTE WATER TECHNOLOGY
                 IN THE NETHERLANDS
                          by

       A. B. van Luin and W. van Starkenburg
       Governmental Institute for Sewage and
         Waste Water Treatment
         Inland Waters Department
         DBW/RIZA
         P.O. Box 17
         8200 AA Lelystad
         The Netherlands

      W. H. Rulkens and F. van Voorneburg
      Netherlands Organization for Applied
         Scientific Research
         Division of Technology for Society
         MT/TNO
         P.O. Box 342
         7300 AH Apeldoorn
         The Netherlands
        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.
North Atlantic Treaty Organization/Committee on the
Challenges of Modern Society (NATO/CCMS) Conference
           on Sewage Treatment Technology

               October 15-16, 1985
                 Cincinnati, Ohio

                         793

-------
               DEVELOPMENTS IN THE FIELD OF WASTE WATER TREATMENT
                               IN THE NETHERLANDS

               by:  A. B. van Luin and W. van Starkenburg
                    Governmental Institute for Sewage and
                      Waste Water Treatment
                    Inland Waters Department
                    DBW/RIZA
                    P.O. Box 17
                    8200 AA Lelystad
                    The Netherlands

                    W. H. Rulkens and F. van Voorneburg
                    Netherlands Organization for Applied
                      Scientific Research
                    Division of Technology for Society
                    MT/TNO
                    P.O. Box 342
                    7300 AH Apeldoorn
                    The Netherlands
                                  ABSTRACT

     Recent advances in waste water treatment in the Netherlands are summa-
rized in this paper for three major research areas of micro-pollutants,
sewage sludge and innovation and upgrading of waste water purification
systems.

     In micro-pollutant research, the sources and amounts of organic and
inorganic micro-pollutants in domestic waste water, municipal waste water
with industrial contributions and direct industrial waste waters are
characterized.  A surprisingly large dispersion of dichloromethane was
observed in the domestic wastewaters.  In addition to trace metals,
municipal waste waters with industrial contributions usually contain
volatile chlorinated hydrocarbons, chlorophenols, hexachlorocyclohexane,
polychlorinated biphenyls, and polycyclic aromatic hydrocarbons, generally
at low concentration levels.  Industrial wastewaters invariably contain
volatile chlorinated hydrocarbons such as tetrachloromethane and chloro-
phenols, especially pentachlorophenol.  Removals for the various
micro-pollutants are presented.

     In research on sewage sludge, substantive studies on autothermal
combustion, sludge thickening and dewatering, pathogenic content and disin-
fection, and disposal of sludge as agricultural soil conditioners and as a

                                   794

-------
 substrate for trees have been completed.  Raw sludge with an ash content of
 about 20% and dry matter content of about 25% may be burnt autothermically.
 Thickening can be improved by use of polyelectrolytes.  Laboratory studies
 on sludge conditioning have characterized sludges such that practical (full-
 scale) improvements in dewatering are likely.  The hygienic problems from the
 use of sewage sludge in agriculture are highly dependent on regional factors
 and a "safe" procedure for disposal on agricultural applications cannot be
 provided in general terms, each case must be assess separately.

      Research on innovation and upgrading of waste water purification
 systems has produced novel elements, especially in anaerobic treatment.  The
 research should stimulate potential applications of anaerobic treatment of
 municipal waste water using either the anaerobic sludge bed (USAB) reactors
 or fluidized bed technology.  Industrial uses of anaerobic treatment are
 extensive and successful in a variety of Dutch industries.  A novel approach
 to removing nitrite from ground water features ion exchange removal of the
 nitrate with biological denitrification to eliminate the nitrate and provide
 regenerant for the ion exchangers.


                                  INTRODUCTION

     In  this  report  a  review  is  given  of water  pollution  control  research
currently in progress  and  the application of waste water treatment processes in
the Netherlands.  The  accent  is  placed  on advanced waste  water treatment pro-
cesses.  Additional  attention  is  also  given  to  the possibilities  of reducing
waste  water  discharges  by  internal  measures  and the  application  of  "clean
technology".  The  research  described here  is mainly  related  to work  which is
still  in  progress or  has  just  finished at  universities,  research institutes,
engineering firms and  industries,  the results of  which are publicly available.
Much of  the  work  is carried out for  central or local government in the form of
contract  research.  The  work  is  partly  paid  by  industry and  partly  by the
research institutes themselves.

     This report comprises three major sections:
The first  section describes  the problems  of pollution by micro-pollutants.  A
great deal of research on monitoring micro-pollutants as well as research in the
field of curbing this pollution has been done.
     Sewage-sludge  is  the main-subject  of the second  section.  There are  great
problems with  the quality  and the  application  of  sewage  sludge.  In the  past,
most of  the sludge was applied  in agriculture.  Over the  past  few years alter-
native applications and treatment methods have been  investigated.
     The third  section describes  the innovation  and  upgrading of  waste  water
purification  systems.  This   section reviews  the  developments  concerning the
treatment of  municipal,  industrial and  agricultural waste waters,  and contami-
nated ground water.
                                     795

-------
Primary sources on which this paper is based are:
     The  (Dutch)  journal "HO", mainly  the volumes  for  the years  1982,  1983,
     1984 and 1985.
     Research reports from the Dutch Ministery of  Housing,  Physical Planning and
     Environment.
     Research reports from the Governmental Institute for  Sewage and Waste  Water
     Treatment (RIZA) and several research institutes and  industries.

     It has  to be  noticed  that the  information  in this  report does  not  fully
reflect the  state  of the art of water pollution control research in the Nether-
lands, but a serious attempt has been made to show principal developments.

                                MICRO-POLLUTANTS

 INTRODUCTION

      The  legal  framework  for the  fight  against  water pollution in the Nether-
 lands has been  laid down  in the Pollution of the Surface Water Act which  was
 passed on 1  December 1970.  It prohibits  the unlicensed discharge of  polluting or
 harmful substances  into surface water.  Although  considerable progress has been
 made in  recent  years,  surface water pollution continues  to be a serious  cause
 for concern, and its curbing remains  the  chief  objective of governmental policy.
 In  the  years after the Pollution of  the Surface  Water Act  had become law,
 emphasis  was  placed on  oxygen consuming substances. More recently, however,
 attention has primarily focused on non-oxygen consuming substances.
 To this category of substances belong:
      Nutrients (phosphate and nitrate);
      Inorganic micro-pollutants  (e.g. heavy metals);
      Organic micro-pollutants (e.g. persistent  pesticides and PCB's).

      The  name micro-pollutants is  used because  the  concentrations  at which these
 substances may  cause  harmful  effects are at  the  level  of micrograms and even
 nanograms per liter. In cases  of  oxygen consuming substances the  concentration
 levels amount to tens of milligrams per  liter.

 In this  chapter  the results are given of  a number of research projects  in  the
 field of  inorganic and  organic micro-pollutants.
 SOURCES OF ORGANIC MICRO-POLLUTANTS

 Organic micro-pollutants in domestic waste  water


      In 1984  the  Governmental Institute for Sewage and  Waste Water  Treatment
 carried out  an initial study on  the presence  of a number  of organic  micro-
 pollutants in  domestic  waste water.  Waste  water of five residential  areas  was
 sampled and analysed. The  waste  water streams contained neither rain-water  nor
 industrial waste water.  The results of the  study  are given in  Table 1.
      The enormous  dispersion in the  figures for  dichloromethane  is  especially
 striking and  its causes  are still unclear.  The study will  be continued.


                                     796

-------
TABLE 1.  ORGANIC MICROPOLLUTANTS IN DOMESTIC WASTE WATER7
                 (in mg/inhabitant/year)
Compound
d ichloromethane
tr ichloromethane
tetrachloromethane
trichloroethene
1 ,2-dichloropropene
tetrachloroethene
1,2 dichloroethane
1,1, 1-trichloroethane
monochlorobenzene
1 , 2-dichlorobenzene
1 ,4-d ichlorobenzene
hexachlorobenzene
\-hexachlorocyclohexane
y-hexachlorocyclohexane
2 , 4 , 5- tr ichlorophenol
2,4 , 6- tr ichlorophenol
2,3,4, 5-ttrachlorophenol
2,3,4 ,6-tetrachlorophenol
pen tach lorophenol
polychlorinated biphenyls
polycyclic aromatic
hydrocarbons^)
') number of samples: 10
2) number of samples: 5
3) average over 35 samples
4) sum of PCB 8,52,101,138
Amsterdam! )
min. max. mean
157 80000 9000
84
Q6)
0




0

212
0
0,8
5.5

2.1

4.4
10,2
0

13



204
296
394




299

1680
0,8
2*1
77

4.4

11
36
3.4

27



150
88
40

0
0

29
0
647
0,15
0.31
21
0
6,2
0
6,9
23
0,73

21



Steenwijk2) Enschede(I) 1 ) Enschede ( II ) 1 ) Maarssen2)
min. max. mean min. max. mean min. max. mean min. max. mean
400 390103 124103 0 110
146
146







84
0
0
6,2

3.7

3,7
12
0

6,9



285
402







281
0,8
0.4
26

4.7

4.7
33
2,2

1.6



,153 and 180
5) sum of fluoranthene, benzo(6) fluoranthene,
(benzo(k) fluoranthene,
perylene and indeno(1,2
benzol a) pyrene
, benzo(g ,h,i) ,
,3-c,d)pyrene
6) zero means concentration below
detection limit
190 48 139
157
0 0 139

0 0 2835
0

0
0 0 139
197 869 1830
0,32
0,07 0 0,91
15 1.4 3,5
0 0 28
4,0 2.3 14
0
4.0 8,4 32
20 18 51
0.9

11 18 68
40 0 92000
102 58
0 0
51

686 0
0 0

0
28 0
1190 0
0 0
0.4 0
2.0 1.0
8.4
6.2 2,7
0 0
14 0
35 12
0

20 6.2
7 ) 1 , 3-dichloropropane
1 , 1 ,2-trichloroethane
1 ,2,3-trichloropropane
1 ,2,3-trichlorobenzene
1 , 2 , 4- tr ichlorobenzene
1 ,3,5-trichlorobenzene
(\ -hexachlorocyclohexane
)

325
270


172
157


270
2770
0,51
1.1
4.0

16
7.7
27
439


18


in
15000 73 383
200 820 1570
80 0 606
0

29
15

0
120
836 1350 4590
0,04 Oi91 1,5
0.58 1,3 3.5
2,7 3,6 7,7
0
7.3 4,4 9.5
0.7
5,8 28 139
77
0

13 2,3 16


all samples below
256
1130
223
0

0
0

0
0
2960
1.1
2.1
5,5
0
7t7
0
53
0
0

1 1



MEAN3)
24600
303
102
1R

106
4.0

0,4
40
1040
0,26
0,91
12.8
1.1
6.6
0,2
14
36
0,32

16



detection limits

















-------
Organic micro-pollutants in municipal waste water treatment plants

     In 1983  the Governmental Institute  for Sewage  and  Waste Water  Treatment
(RIZA) studied  the  presence  of  organic micro-pollutants  in  influent,  effluent
and sewage sludge of six municipal waste water treatment plants.
     The  results of  the  study  were  published and  presented at  the  IAWPRC-
congress of Amsterdam in September 1984.  The conclusions  of the study are:
The conclusions of the study are:
     Volatile chlorinated hydrocarbons in sewage appear to originate mostly from
     industrial emissions. The amount  of the emissions may fluctuate considera-
     bly,  especially in the case  of dichloromethane and 1,2-dichloroethane.
     Chlorophenols,  hexachlorocyclohexane,  polychlorinated biphenyls  (PCB)  and
     polycyclic  aromatic  hydrocarbons  are  -  on a  low basic  level  -  invariably
     present  in  municipal  waste  water  and  in many industrial  waste  water
     streams.
     In addition to  point  sources  there  are also  diffuse sources  such  as
     deposit from the air and road traffic, which  are responsible for the extra
     sewage pollution.  In the  study this is demonstrated especially in the case
     of polycyclic aromatic hydrocarbons.
     PCB and fluoranthene are invariably detected in sewage sludge.  Occasionally
     hexachlorobenzene,  2,4,5-trichlorophenol, 2,3,4,6-tetrachlorophenol, penta-
     chlorophenol and benzo(b)fluoranthane were also present.
     In the study it has not been possible to give  a full assessment of the fate
     of these  substances  in  a treatment plant. More  intensive research will be
     initiated for that purpose.
     The overall removal in the municipal treatment plants amounts to:
         volatile chlorinated hydrocarbons        50-90%
         hexachlorobenzene                           95%
         hexachlorocyclohexanes                   40-65%
         chlorophenols                            20-40%
         PCB                                   about 90%
         polycyclic aromatic hydrocarbons         85-95%

Organic micro-pollutants  in industrial  waste water


     Since  1980  RIZA  has  been  researching  the   presence  of  organic  micro-
pollutants in  industrial  waste water (1).   In  1983  waste  water of 37 industries
was examined for the presence of:
     Heavy metals
     Drins (e.g. aldrin)
     Polychlorinated biphenyls
     Chlorophenols
     Benzene and chlorinated benzenes
     Tri-  and tetrachloromethane.

     The  overriding  conclusion was  that components  such as  pentachlorophenols
are  present  in  most  waste   waters.   Even  in  brewery  waste water.   In  this
particular case  the waste  water  became  "polluted"  because  of the glue on the
beer-bottle labels.
                                    798

-------
      Table 2 shows  that  a large number of components  are  present in the various
 waste water streams.  It  has  not  yet become clear  why  these  components  are
 present in most cases. Consequently, research  is  continuing.


           TABLE  2.  SURVEY OF THE PRESENCE OF HAZARDOUS SUBSTANCES IN
                INDUSTRIAL WASTE  WATER FROM DIFFERENT INDUSTRIES
substance
branch  of  industry
(number of  plants measured)

slaughtery  (2)
dairy products  (3)
fruit and vegetables  (1)
margarine and fats (2)
sugar (1)
soft drinks and
carbonated  waters (1)
brewery (1)
textile (2)
leather (2)
paper, pulp and
paperboard  (2)
wood-impregnation (2)
printing (1)
painting (2)
soap and cleaning (detergent)
preparations (1)
rubber (2)
dye (3)
electroplating  (4)
photographic laboratory  (1)
laundry (1)
motor-overhaul  (1)
hospital (1)
incineration of refuse (1)
                                      v
                                      d
                                      18
                                      41

                                      O
                                      u
                                      1-1
                                      0
                                      0
                                      0

                                      0
                                      0
                                      0
                                      0
0

0
                                             o
                                             d
                                             
                                             4-1
                                             O
                                             U
                                             o
                                            II
                                            .d
                                             u
                                             4-1
                                             0)
                                             4-)
              O
              u
              JS
              a
              o
              u
              o
              JO
              u
              H
              VI
              4-1
              0
              0
              0
              0
                                                    0
                                                    0
0

0

0
       o
       v
       JS
       a
       o
                     d
                     OJ
                     a,
d
v
N
d
v
.a
o
              J3
              U
              18
              X
              .
      xi  d
      U  (U
      >>  -C
      ft  04
      O  -H
      a,  f>
        0
        0
        0
                                                                         0
+  = present in waste water
   = undetected in waste water
0  = research has not finished,  no  positive results thus far
*) = (probably) one or more  of  the  isomers: PCB 28, 52, 101, 138, 153 and  180
                                     799

-------
REDUCTION IN THE EMISSION OP ORGANIC MICRO-POLLUTANTS
Polycyclic aromatic hydrocarbons

     In  1984  Hoogovens  IJmuiden installed two precoat-vacuumfliters - each with
a filter surface of 36 m2 - for the removal of polycyclic aromatic hydrocarbons
(PAH).  The amount of waste water to be processed is 120 m3/hr.  PAH-emission has
been reduced from 15 to less than 1 kg/day.  The costs of investment of the
filters were 1.7 million Dutch guilders.  Total investments,  constructional and
electrotechnical supply included, amounted to 3.1 million Dutch guilders.

     PAH are among other components caused by pyrolysis of organic material such
as occurs in the coke oven process. A coking-plant produces  coke by heating
coal, air-free, to a temperature of about 1300 C. The volatile substances
released in the process are called coke oven gas and are used in the production
plant.
     Before use the gas has to be cooled and purified. In this  process waste
water containing PAH and other substances is produced.

     Analyses show that PAH is generally present in - or on the surface of -
suspended solids in the waste water (Table 3).

                   TABLE 3. PAH IN WASTE WATER (IN pG/L)
                                     liquid
                             total
54
                   suspended solids
naphthalene
acenaphthene
dibenzfurane
f luorene
fenanthrene + anthracene
f luoranthene
pyrene
1,2-benzanthracene + chrysene
benz(b+j+k)f luoranthene
( 1 , 2+3 , 4)benzpyrene
1,12 benzperylene
coronene
n.d.
n.d.
n.d.
2
30
15
6
1
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
5
5
185
405
205
280
120
155
60
35
1470
n.d. = non-detectable (< 1

     For the removal of PAH a particular filtration method has been chosen. Pre-
coat filtration gives the best environmental and economical results (Table 4).
                                    800

-------
               TABLE 4. RESULTS PILOT-PRECOAT FILTER. (PAH IN
                                 infl.  effl.
                 infl.   effl.
                        infl.   effl.
naphthalene
acenaphthene
dibenzfurane
f luorene
fenanthrene + anthracene
fluoranthene
pyrene
1,2-dibenzanthracene + chrysene
benz (b+j +k) fluoranthene
1,2-3,4 benzpyrene
1 , 12-benzperylene
n.d.
n.d.
n.d.
n.d.
65
487
448
873
755
965
160
n.d.
n.d.
n.d.
n.d.
5
4
n.d.
15
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
7
225
1435
1093
2660
1315
1180
240
n.d.
n.d.
n.d.
n.d.
10
8
n.d.
4
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
10
370
356
1190
440
520
70
n.d.
n.d.
n.d.
n.d.
15
20
7
4
n.d.
n.d.
n.d.
                    total
3753
24
8155
22
2956
46
dissolved 13 24
adsorbed 3740 n.d.
removal percentage (%) 99,4
38 22
8117 n.d.
99,7
41 46
2915 n.d.
98,4
n.d. = non-detectable (< 1 pg/1)

     It  should be  noticed  that  a  biological  treatment  process has  been in-
plemented  - following  filtration -to  remove  other components.  The  biological
treatment  process  will effect  a  further reduction in  the  concentration of
PAH (2).

Volatile chlorinated hydrocarbons  and dioxines

     In the beginning of 1985 the pesticides factory Duphar (Amsterdam) realized
the second phase of its scheme for waste water purification.
     The  first phase uses  filtration and  a  steam-stripper for  the  removal of
suspended  solids  and  volatile chlorinated hydrocarbons  such as  tetrachloro-
methane,   trichloromethane   and   monochlorobenzene.   This  phase  has  been  in
operation  since  the spring  of  1984.  The application of  a  filtration step also
reduces the emission of dioxines and dibenzofuranes considerably to values below
the detection  limit (25 ng/1). This  emission amounted to 40 g a year.
     Filtration  consists  of four  steps:  coarse  filter,  gravel  filter  and two
close  grained  anthracite filters. Steam-stripping  reduces  the concentration of
volatile  solvents  from 210  to  less  than 10 mg/1; a  removal  efficiency of more
than 95%. The  emission of these substances amounted to 33,000 kg a year.

     The  second  phase,  activated carbon  adsorption,  is  meant  to  remove non-
volatile,  adsorbable  chlorinated  hydrocarbons.  Two columns in series are used.
The  activated  carbon  is  regenerated by  a  thermal method.  The  content  of ad-
sorbable  compounds  in  the  waste water is reduced from 160 to less than 10 mg/1.
The emission amounted to 25,000 kg/year. Total costs of investment are in excess
of  ten millions  of Dutch  guilders. The  annual exploitation  involves several
millions of Dutch guilders.
                                    801

-------
     Duphar  is also  taking  part in  research on  the  disintegration of organic
chlorinated  compounds through thermolysis with hydrogen. This "hydrodechlorina-
tion process"  is a discovery of the University of Leiden,  which University is
developing the process in  co-operation with Kinetics  Technology International
(KTI) of Zoetermeer.
     Thermal  hydrodechlorination may  be  an  effective  method   in  eliminating
dioxines. Duphar's initial research is scheduled to finish early in 1986 (3,4).

Volatile chlorinated hydrocarbons and hexachlorinated compounds

     AKZO Zout Chemie  (Delfzijl) is investing several millions of Dutch guilders
in the construction of a treatment plant for the removal of volatile chlorinated
hydrocarbons   such  as  tetrachloroethylene  and  tetrachloromethane  and  hexa-
chlorinated compounds.
     The  volatile  compounds  are  removed  from waste  water by the  use  of  a
stripper. The  current emission comes to at least 16,500 kg/year. The removal of
hexachlorinated compounds occurs through sedimentation, its costs of investment
will amount to two million Dutch guilders.
     Hexachlorobenzene, -butadiene and  -ethane  are byproducts of solvents. Most
of  the compounds  (99,9%)  are  separated,  collected  in  drums  and sent  to salt
mines  in W-Germany. The discharge of about 60 kg of hexachlorinated compounds a
year and the pollution of the sediment through this emission will soon belong to
the past (5).

Phenoxy acetic  acids and chlorinated  cresols

     AKZO Zout Chemie (Rotterdam)  intends to construct  a  waste  water treatment
plant  to  process waste water  from  the pesticides plant  and the vinylchloride
plant.  The  new  treatment process  consists  of an activated sludge  plant with
activated carbon  dosing (PACT-process). The treatment plant is due to come into
operation in January  1987 and will cost  15.5 million Dutch guilders.
     The pesticides  plant produces  phenoxy acetic acids  (MCPA  and  MCPP).  The
plant's  waste  water  contains  these  acids  as  well as  chlorinated cresols.  The
annual emission of these substances comes to 6600 kg.
     Using  the foregoingly mentioned treatment process the governmental  demand
for  a  concentration  of  less than  1 mg/1 of the  cited substances  in the waste
water may be met. This is comparable with a maximum emission of  1650 kg/year.
     In  cases  of peak loads of  chlorinated  aromates,  the  waste water is pre-
treated with hydrogen peroxide. Additional process-integrated measures have also
been taken.
     Instead  of  the  use  of  activated  carbon,  resin-adsorption with Amberlite
XAD-4  was  taken into   consideration  as  a pretreatment.  Its execution would prove
to be  successful.  Higher  costs  of investment have resulted in  the selection of
the  PACT-process.  The  waste water of  the  vinylchloride-plant  is pretreated by
steamstripping,  precipitation  and  sodiumsulphite dosing.  Ethylenedichloride,
copper and chlorine concentrations are  reduced below 1  ing/1.
     The treatment  plant  must  have  a capacity of  70 m3  of waste  water per hour.
The volume of  the aeration tank amounts  to 3800 m3 (6).
                                    802

-------
 INORGANIC MICRO-POLLUTANTS

 Sources  of  inorganic micro-pollutants
      In  1984 the  presence  of arsenic and  heavy  metals  in domestic waste  water
 was  studied.  Domestic waste water  -  unmixed with rainwater or  industrial  waste
 water - of seven residential  areas  was  sampled and analysed  four times.  The
 results  are  given  in  Tables 5 and  6. The  annual  sum of the average quantity of
 arsenic  and heavy metals is 16.5 grams per inhabitant.
     A study  of this  nature  has  never previously been executed  in the Nether-
 lands. Calculations on the basis of literature data have been used thus far (7).

            TABLE 5.  ARSENIC AND HEAVY METALS IN DOMESTIC WASTE WATER
                               (CONCENTRATIONS IN |JG/L)
Location
Zn
Cu
Pb
Ni
Cr
As
Cd
            TABLE 6. ARSENIC AND HEAVY METALS IN DOMESTIC WASTE WATER
                               (G/INHABITANT/YEAR)
Location
Zn
Cu
Pb
Ni
Cr
As
Cd
Hg
Amsterdam
- Meijehof
- Nieuwlandhof
Enschede
- Stokhorst
- Stro'inkslanden
Maarssen
Steenwijk
Vught

168
143

172
155
212
195
146

166
244

139
127
149
33
96

15
13

22
18
18
28
15

11
13

9
10
6
13
9

5
4

5
4
4
4
4

4
3

4
4
4
3
4

1.5
1.3

1.0
1.0
1.8
1.3
0.6

0.7
0.6

0.6
0.3
0.2
0.3
0.3
Hg
Amsterdam
- Meijehof
- Nieuwlandhof
Enschede
- Stokhorst
- Stro'inkslanden
Maarssen
Steenwijk
Vught
Median
Mean

7.2
6.5

7.6
8.9
10.1
8.7
7.5
7.5
8.1

7.1
11.1

6.2
7.3
7.1
1.5
4.9
7.1
6.5

0.6
0.6

1.0
1.0
0.9
1.2
0.8
0.9
0.9

0.5
0.6

0.4
0.6
0.3
0.6
0.5
0.5
0.5

0.2
0.2

0.2
0.2
0.2
0.2
0.2
0.2
0.2

0.2
0.1

0.2
0.2
0.2
0.1
0.2
0.2
0.2

0.05
0.06

0.04
0.05
0.09
0.06
0.03
0.05
0.05

0.03
0.03

0.03
0.02
0.01
0.01
0.02
0.02
0.02
     The  environmental  problems  of  heavy  metals  focus  especially  on  the
pollution  of subaquatic  soils,   the  consequences  for  organisms  in water  and
sediments and the  pollution of sewage sludge. Heavy metals in surface water are
for a considerable part (75% as an average) attached to suspended solids.
                                    803

-------
Reduction  in  the emission of inorganic pollutants
      The solution  to  the heavy metal problem has to be found in the fight
with the pollution source, aimed at reducing the pollution.  In principle,
two ways are  open:  process alteration and waste water purification.
      To  prevent polluting substances from originating by applying  less polluting
production processes  is of main interest where the fight against water pollution
by heavy metals is  concerned. Two, so-called clean technology processes are:  the
use of a new, blue passivating-bath and the substitution  of cadmium by galvano-
aluminium.
     The first  process -  developed by TNO  -  consists of  a  blue  passivating
technique without  nitric acid  or nitrate-ions, with substitution of chromic-acid
by  the less agressive potassium chromium sulfate.  When this process  is applied,
savings are especially made  in the  field of  reducing  costs  of waste water  treat-
ment. The  process  control at  varying  product supplies  remains a  restriction,
rendering it as yet only suitable  for the treatment of  one  constant product.
     The  second  clean-technology-process,   the   substitution   of  cadmium   by
aluminium,   has  been developed by  the  electroplating industry of  Hegin Galvano
Aluminium in  co-operation with the  German Siemens  Company. The  process  consists
of  the electrolytic precipitation of aluminium at  a  temperature of about  100 C
in  an organic  electrolyte, excluding water  and  air, and it precludes pollution
of water or air. The  process  has been  successfully tested  in a  so-called  "rack"
machine (parts placed  on racks), which  is already on  the market.

     When  choosing a purification  plant,  a  distinction  may   be  made between
systems for the treatment of  the  total waste  water flow and systems for partial
treatment.   Systems belonging  to  the   first  category  are  precipitation,  de-
toxification,  neutralization,  de-watering (ONO)  and  ion exchange.  These systems
are  extensively  applied  in  the  electroplating  industry.  By  applying process
integrated  techniques  or  provisions for  treatment of reaches  of  streams  which
contain  heavy metals, the metals  in question may be re-used  in principle.  A
couple of  process  integrated  systems which  are  being developed  appear  to offer
fair  prospects. They  concern the removal and the  recuperation of  heavy  metals
from  waste water  with the  aid  of membrane  filtration   and  the  electrolytic
recuperation  of heavy metals from  diluted  solutions. Hyperfiltration  (reverse
osmosis) can  be applied on  separate  rinsing water  streams  as  well as  on  the
total  waste water  flow.  With regard  to a  number of types  of rinsing  water,
especially  those   originating  from  nickel   baths, the  treatment  by  means  of
hyperfiltration offers economic advantages.

     An investigation into the applicability of electrolysis  for the removal  and
recuperation  of  nickel and  zinc  from  rinsing  tanks in  the  plating  industry
is carried  out by TAUW,  TNO  and  Magneto  Chemie.  Thus far,  application  of
electrolysis mostly takes  place when precious  metals  have  to be  removed.
     Finally,  in the  field of heavy metal removal, a  number of recent  develop-
ments may  be  mentioned, namely  the  recuperation of metal  by means of fluidized
bed  crystallization  and the  removal  of metal  (Cd)  with  the  aid  of bacterial
processes.

     Further  activities  in  the  field  of metal  removal will  give priority to
process  integrated provisions. The  further development of  the membrane  tech-
nology and the electrolysis  are also expected to  gain more  attention (8).


                                    804

-------
                                 SEWAGE SLUDGE

     When municipal sewage water (a combination of domestic and industrial waste
 water) is treated,  sludge containing heavy metals developes.   The  level  of  heavy
metals in sewage sludge has decreased considerably during the past few years due
to  reorganizations  in industry.  The decrease  for nickel,  cadmium  and  mercury
amounted  to  50% or  more in  the  period 1976-1980. The  copper  and lead  content
decreased by  30%,  while  the  chromium content decreased by 20%. At  present the
heavy metal contents are on average below the limits set for direct agricultural
use.  However,  it   does  not  mean  that  every quantity  of sludge  necessarily
satisfies the  limit.  From the sludge that  was  deposited in agriculture in 1981
only 42% satisfied the limit.

     Notwithstanding  the observed opposition against combustion, an increasing
interest  in  sludge combustion  as  a sludge processing method may  be  noticed in
the Netherlands. The  opposition against combustion is especially based upon the
supposed  environmental  objections  and the  heavy  costs.  The increasing interest
in  combustion  is  expressed  by  an  intensification   in   combustion  research.
However, the interest has not yet produced an expansion of  the  number  of
combustion plants.   The preference for the fluidized bed combustion system
is remarkable in this context.

     Within the scope of study and research much attention has been given to the
problem  of  energy,   because  this  item  is of  major   interest  with  regard  to
capacity and  costs  of combustion.  It is  important that the sludge may be burnt
autothermically  (energetic  equilibrium).  Important factors in  this  respect are
the dry  matter content  of the  sludge  and the  ash content of  the  dry  matter.
Based  upon energetic  equilibrium,  the mutual relation between these factors has
been worked out in Figure 1.

     From the above  it  appears  that - roughly speaking - raw sludge with an ash
content  of  20%  and  a  dry matter  content  of 25%  (heat  of combustion  equals
23 MJ/kg of organic material) may  be burnt autothermically. This  type of rela-
tion,  based upon the thermal balance, may be a useful expedient when application
of  sludge  combustion  is considered.  It  is  possible  to   check  the  degree  of
de-watering necessary for  autothermal  combustion and/or  to  check whether the
required degree  of de-watering  is  feasible in  technical  terras.  Combustion  of
sludge becomes  expensive when additional  fuel  has to be added. In  these cases
the capacity  of the  combustion  plant decreases,  while extra energy  has  to  be
added.   It can  be   stated  in general that new  developments  in  the field  of
de-watering,   resulting  in  higher  dry  matter  contents   and  improvement  of
energy-efficiency of  the combustion  process  may  take  combustion  closer within
the range of sludge processing methods (9,10).
     Within the scope of an investigation into sludge combustion, carried out in
a fluidized bed  incinerator  (inner diameter 0.5 m, total height 5  m), attention
has been given  to  the energy balance as well as to the environmental aspects of
the combustion  process.  In this investigation  long-term experiments  (52 hours)
were  carried   out  with  de-watered  sewage  sludge (14% dry matter)  under  the
following conditions:  sludge output  100  kg/hr,  temperature of  the  bed  825 C,
                                     805

-------
                   5C
                                                           kg V3/ton cat
                              JS      X       36     10
                                 Degree of dewatering % TS
                 Figure 1.   Autothermal combustion.   Thermal
                            efficiency of incinerator 70%.
excess  air  20%  and static  height of  the  bed 0.55 m.  The composition  of the
flue-gases was as  follows:  0  3.5% by volume, C02  11.4%,  CO 78 mg/Nm3, N0x 348
mg/Nm3, C H   14 mg/Nm3  and  SO- 923 mg/Nm3.  By applying a  cyclone  and  a cloth
filter^heavy'metals remained    (about 98%)in the solid residue. In other words,
about  2%  of  the  heavy  metals disappears  into  the atmosphere.  Fluidized bed
combustion may  be an  attractive  treatment  method for  sewage  sludge.  Test runs
are  required  to realize  a  well-made design  for a  full  scale combustion plant
plant (11,12).

     Within  the  scope  of  sludge  thickening  and de-watering  the  following
developments can be mentioned.
                                     806

-------
      From research it has appeared that the thickening of digested sludge may be
 improved upon the  addition  of a polyelectrolyte. The mixing  of  polyelectrolyte
 and sludge appears  to  be of vital importance in this process. A relatively low
 amount  of polyelectrolyte  is  applied  to  improve  the  thickening.  The  poly-
 electrolyte present in the water phase must be dispersed uniformly over  the  the
 sludge particles. However,  excessive  mixing must not occur,  to avoid destroying
 the formed sludge  flocks.  By  means of experiments at a sewage treatment plant a
 correct mixing  between polyelectrolyte  and sludge has  been  obtained.   Using  a
 polyelectrolyte  dosing  (Praestol  423  K)  of  2.5 g/kg  of  dry matter,   the  dry
 matter content  - after  thickening -  was  increased  from 3% to  almost  6%.  This
 signifies a reduction in the sludge volume that has to be disposed of(13).
      An investigation has been carried out into optimization of the conditioning
 of sewage  sludge with  inorganic  chemicals  in relation  to sludge handling with
 filter presses.  In  1982 twelve municipal sewage treatment plants in the Nether-
 lands were  equipped with  filter  presses, with  a total processing  capacity of
 4.2 million  population  equivalents  (p.e.).  The  sludge  of  about  3.3 million
 p.e.'s is conditioned with inorganic chemicals.  This  involves  an  amount  of money
 for chemicals  of about  3.5 million  Dutch guilders.  Even  a minor  reduction in
 chemical consumption will result in considerable savings on running costs.
      An investigation  has been carried  out into simple tests for conditioning
 on a  laboratory  scale,  a  method  which  can  also be  used to characterize  the
 sludge.   A standard mixer  in  an  experimental  set-up  of  1 liter  appears  to
 work well. After adding Fed  , 15 seconds  of mixing at a speed  of  1000 rpm is
 required;  after  adding Ca(OH} , 60  seconds  at 500 rpm  is required. With this
 set-up and method of conditioning, characterization of  sludge becomes possible.
 For that  purpose, conditioning tests at 2.5, 5,  7.5 and  10% Fed  by weight and
 10,  20,  40  and  60% Ca(OH)   by weight,  based on  dry matter are carried out,
 whereupon pH-value,  suction Time and MFTx-dry matter are  determined. After these
 tests  combinations  of  FeCl3   and  Ca(OH)   are  selected,  which   simultaneously
 satisfy  the  following  conditions:  pH  > 12,  suction  time  ^ 100  seconds  and
 MFT-dry matter ^  21% of  dry matter. Close agreement appears to exist between the
 results  of the  laboratory experiments  and  the  practical (full-scale) results.
 The developed test  method is  also  suitable for  checking  whether other condi-
 tioning  chemicals e.g.  A1C13  instead  of Fed ,  or waste lime are suitable for
 the chemical conditioning  of a specific type ol sludge (14).

     An  other aspect  of  sewage  sludge  permanently  drawing  attention   is  the
 further processing  and  disposal of the sludge.  For the  benefit  of the applica-
 tion of  sludge  in agriculture, attention has been given to the hygienic  aspects
 of  this   particular  application.   Pathogenic  bacteria  such  as  Salmonella,
Clostridium botulinum,  Taenia  saginata,  Ascaris Itonbricoides,  Escherichia coli,
Campylobacter jejuni,  Toxoplasraa gondi'i,  Sarcocystis  spp  and viruses have the
potential to  spread  by sewage  sludge. With  regard  to  pathogenic  bacteria three
ways of restriction may be recognized:
     Restriction of the application of sewage sludge (in the production of crops
     for human consumption);
     Restriction  of  the  use  of land following application  of  sewage sludge (to
     institute waiting times);
     Disinfection of sewage sludge.

1MFT = Modified Filtration Test.
                                     807

-------
Disinfection processes may be divided into a group which has disinfection as its
primary  target  (pasteurization,  irradiation)  and a group in which stabilization
is  the  primary  aim,  but in which proper  dimensioning can also realize adequate
disinfection  (aerobic  thermophilic stabilization,  composting and stabilization
with  lime).  The hygienic problems of the  application of sewage sludge in agri-
culture  are  complex  and highly dependent on regional factors. This leads to the
conclusion  that a "safe"  procedure  cannot be  indicated in  general  terms, and
each  case has to be assessed separately (15) .
      It  has been  verified to  which  extend  the  forests,  which  take  up eight
percent  of Dutch  soil  area,  can contribute  to the  disposal of sewage sludge.
Some  aspects have  been investigated,  such as sewage  sludge in existing forests,
sewage  sludge  as  soil  conditioner  and sewage sludge as  a  substrate  for trees.
Research has  led to  the conclusions that  sewage  sludge is a material of widely
varying composition and qualities, which may alter considerably in the course of
time  (flushing  of lime,  degradation  of organic  substances)  and that therefore
planting  advice for  dumping  sites  for  sewage sludge  can  only  be  given con-
ditionally.  The necessity  for  planting  research  on sewage  sludge  of various
origins  remains.  Dutch  forests offer  hardly  any  potential  at all  for the
disposal of sewage sludge (16).

          INNOVATION  AND UPGRADING OF  WASTE WATER PURIFICATION SYSTEMS

MUNICIPAL WASTE  WATER

     In  the  past  few  years the  technology for  the  purification of  municipal
waste water is  strongly  developing  in the Netherlands.  Novel techniques are in-
creasingly being used.
     Biological   dephosphating   constitutes an  important  development  in  this
field.  Its  has  been proven that  biological  dephosphating  is also a  suitable
method for removing phosphate  at moderate  temperatures.  An important  fact - when
using this technique -is  that  it makes the removal of the phosphate possible in
such a way that  the removed phosphate  is  regained in a very pure form.

     In  the  past  five years  a great  deal of  research has  been done  on  the
potential use of Nitrilotriaceticacid  (NTA)  in  detergents.  The biodegradability
of  NTA  and also the  influence of NTA on the  binding of heavy metals  to  the
sewage sludge have been researched.
     The research  has  been  done on laboratory-scale  (batch)  and  on pilot-plant
scale  (continuous-system).  The  content of  NTA  in  the  waste  water amounted to
20-40 g/m3 (as  free  acid  H-NTA).  This content is  expected whenever  NTA is used
on a large scale.
     It has been proven that NTA has  no adverse  effects on the metal "household"
of the activated sludge system  when it has become completely degraded.  When this
is  not  the case, the introduction of NTA  is  thought to give  a  higher effluent
load, especially  of  the metals  nickel,  zinc and lead in the activated sludge
process (17).
     Two cases have been investigated:  an activated sludge plant with low sludge
load and an activated sludge plant with high sludge load.
                                     808

-------
     The investigation  of the plant with  the low sludge load  (0.13  kg  BOD/kg.
dry mater per day) resulted in the following conclusions:
-    The adaptation  to  10 g of  NTA/m3 takes  three  days.  From  literature  it
     appeared that many researchers experienced adaptation times of two weeks.
-    After adaptation NTA  degradates very  well. Even a strong changing influent
     flow does not have adverse effects on  the degradation of NTA.
     The degradation of  NTA  decreases  greatly when the temperature falls.  Below
     7 C  the  degradation  becomes very poor,  a  fact confirmed  by  literature
     references.
     The bio-degradation of  NTA  is especially sensitive to interruptions in the
     degradation process of the total amount of organic materials.  A disturbance
     of the process, for instance a decrease in the COD-degradation from 95% to
     80%, will result in a decrease in degradation of the NTA of up to 60%. When
     the COD-degradation drops to 60%,  the degradation of NTA stops completely.
     Recovery  of  the  COD-degradation  is   much  faster  than  recovery  of  the
     NTA-degradation (18).

     The investigation  of the plant  with   the  high sludge  loading  (0.4-0.8 kg
BOD/kg dry matter per day) resulted in the  following conclusions:
-    The degradation of  NTA  takes more time when  the  sludge load  is higher and
     the sludge age is  lower.
     The degradation of  NTA  is  poor when the plant  is overloaded  or when there
     is a disturbance in the COD-degradation.
     At temperatures below 7 C,  the NTA-degradation decreases greatly.
     NTA  is  degrading very  well  during periods  of non-disturbance  (at  sludge
     loadings  of 0.13-0.41 kg BOD/kg dry matter per day). This  is even the case
     when  the NTA-content  of  the  waste water  is varying widely.
     When  the  NTA content remains constant adequate degradation occurs, also at
     sludge  loads  of 0.83 kg BOD/kg dry solids per day. There are problems with
     the NTA-degradation when the  NTA-content varies.

The  overall  conclusion must be  that  adequate  degradation will  occur  in  an
activated  sludge system  when:
     The sludge  load is  beyond 0.4 kg BOD/kg dry solids per day;
     There is no strong  change in NTA-contents;
     There are no  disturbances during the purification proces;
     The temperature is  not  lower  than 7C (19).

     Similar  research  has  been done on three types of purification plants. They
were an oxidation ditch, an  activated sludge system and a trickling filter. The
research  concludes  that a  content of  20 mg  of  NTA/1  degrades  completely in
an oxidation  ditch  and  in  an  activated sludge  system.  In cases  of trickling
filters  the  degradation will not be  above 75%.  None of  the  plants produced
increased  transportation of heavy metals.  When the NTA content is 40 mg/1,great
differences  in  degradation will  occur because of  the  type of plant and the time
of  year.   When  the  degradation   of  NTA is  poor,  chances  of  increased  metal-
transport  activities are  higher  and sensitivity  to  peak loads  is higher. The
presence of  NTA in the  influent  does not interfere with  the biological activity
of above mentioned plants (20).
                                      809

-------
     Novel elements  in the  field  of waste  water  treatment in  the  Netherlands
mainly deal  with anaerobic  treatment.  Scientists  have  succeeded  in getting  a
high sludge  content  inside  the  reactor.  This high sludge  content  in the Upflow
Anaerobic Sludge Blanket (UASB)  reactor is caused by the development  of granular
sludge in the  reactor.  This particular sludge has a  high  settling velocity.  In
filter- and fluidized bed reactors  the sludge is fixed to supporting  media.
     In the  past  few years  a great deal  of  research  has been done to stimulate
the application  of anaerobic treatment  of municipal waste water. A full-scale
plant is expected  to be built in 1986.  In this plant  municipal waste water will
be treated before it is sent to  an  aerobic plant.

     Haskoning,  a  Dutch engineering  consultancy has  done research  -  together
with the Agricultural  University of Wageningen - on  the  treatment of municipal
waste water  in Colombia. Thus far  results have been outstanding. The opinion is
that the  success of  this  research will stimulate the  application of anaerobic
treatment in moderate temperature regions  too (21).

     At  the  Technological  University of  Delft a process-model of  a  methane-
reactor has  been  constructed. This model will improve the control of the system
(22)-
     Another perspective constitutes  the  use  of the  fluidized-bed  technology.
This  type  of  anaerobic treatment  is  already operating  on full-scale  for the
treatment of industrial waste water (23).

     The major problem  of  the future will constitute  the  application of sewage
sludge. This  problem has both  quantitative and qualitative  aspects. Currently
the greater  part  of  the sludge  is  put to agricultural use. Because an excess of
fertilizer is  already available,  this  application becomes more and more  of a
problem and  the quality requirements  become increasingly demanding.  The major
demands are  in the  field of the heavy metal content of the sludge. It has to be
expected that  in  the future demands will  also be  introduced  with regard to the
content of organic pollutants.  To  reduce  its quantity,  research is  in progress
on thermophilic digestion.

     It is expected  that within 15-30 years a great  deal  of  waste water treat-
ment plants will have to be partially or totally renewed.  On that moment invest-
ments will have to be made  to fulfil future environmental demands.  Noise, odour,
effluent  quality  come  to  mind.   The  financial  aspects are  naturally  very
important (exploitation, costs of investment).
     At TNO  and  the  engineering consultancy of Witteveen en Bos, a feasibility-
study  is  in  progress  aimed  at coming  up  with an  answer to the  question  of
renovation.   The  study  is   required  to give the correct  answer to  the above-
mentioned question, and will be  completed in 1985 (24).

INDUSTRIAL WASTE WATER

Abattoirs and slaughter-houses

     The Dutch engineering  consultancy Technisch Adviesbureau voor  de  Unie van
Waterschappen  (TAUW)  has developed a  complete waste  water purification system
for the waste water from slaughter-houses.
                                     810

-------
The  system (Figure 2)  consists  of an  anaerobic  treatment step  (UASB-reactor)
followed  by an  aerobic treatment  step (biorotor).  Thus far many problems have
occurred.    The major  problem was  the passage  of  sludge  - from the  biorotors
used  -by suspended materials. Owing  to the presence  of suspended materials no
granular  sludge  developed.  The  COD-load  remains  limited  to  about  4 kg  of
COD/m3.day  (27).

Sugarwork factories

     The  engineering consultancy Grontmij has developed an anaerobic  treatment
plant to  treat the waste  water from  sugarwork  factories. The  waste  water has a
high content of  starch  and invert-sugars.  The plant  has  already been  started up.
The  load by volume  is  9  kg of  COD/m3.day and the  conversion is 90%  (based on
COD) (28).
                                  TREATMENT PLANT
                                  BUILDTNG CONTAINING
                                  PUMPS. HEATING EQUIFHEKT
                                  AND SLUOGK OEWATERING
                                  EQUIPMENT
   Figure 2.  Waste water  purification of slaughter-house waste water.
                                     811

-------
Dairy industry

     The production of  dairy products results in large  amounts  of waste water.
Normally the waste  water is treated aerobically. In  1984  the Dutch consultancy
Grontmij applied  the  so-called  AB-process  for the purification  of  dairy waste
water.  The AB-process  consists  of  a  high-loaded aerobic  first step  (A)  with
sludge  recycling  and  a  sedimentation tank.  The second  step  (B)  is a low-loaded
aerobic one with sedimentation and separate  sludge recycling.

     There  has  been  an  investigation  on  a  pilot-plant scale  with a  flow of
240 1/h. The waste water (dairy/cheese factory) had the following features:
     COD                 3000 mg/1
     Kjeldahl-N           110 mg/1
     pH                  5.0-13.0
     Temperature           24 C
     COD/BOD                1.6

     The following results have been obtained:
     A step    COD-load       35    kg/m3.day
               BOD-reduction  45%
     B step    COD-load        1.7 kg/m3.day
               BOD-reduction  97%
               Sludge load     0.3 kg BOD/kg volatile suspended solids per day

     The removal percentage of BOD for the whole plant were better than 99%. The
waste water did  not  have   to be neutralized. The settling characteristics and
the digestion  of the  sludge proved  to  be  excellent.  At  this  moment  the con-
struction of a full-scale plant is being taken into consideration (29) .

Maize starch industry

     The engineering consultancy Heidemij has developed an anaerobic waste water
treatment  plant  for  the  purification  of  waste  water  from  a  maize  starch
industry. It concerns a  reactor of the UASB-type with a volume of 800 m3. Before
the water enters  the methane reactor, it is  held in a buffer basin of
1000 m^.  The basin is necessary to smooth the hydraulic peaks in the flow.
Some acidification also  takes place in this basin.  Because of the peaks in
the flow, the load varies from 5-30 kg (COD/m^.day.  The conversion of the
organic materials remains nevertheless highly constant.  The removal,
on the  basis of BOD, varies between 91-94%.   The presence of granular
sludge  in the plant is taken to be responsible for this positive result
(26,30,32,32).
                                     812

-------
Potato starch industry

     The potato  starch industry is  a  very important branch of  industry  in the
Netherlands. The  winning of  starch  from potatoes  results in large  amounts  of
waste water. For  the  purification  of this water an anaerobic reactor of 5500 m3
was built in De Krim.  After 4 years the following results have been obtained:
     Sludge-activity     0.65 kg COD/kg volatile suspended solids.day
     biogas production   1000-1200  m3/h
     COD conversion      16.5 kg COD/m3.day
     COD reduction       80%. (31,33)-

Yeast- and alcohol industry

     Gist-Brocades  of Delft  is a  yeast- and  alcohol producing  factory.  With
governmental   financial   support  Gist-Brocades  has   developed  an  anaerobic
fluidized bed plant.
     In  the beginning  of  1984 the full scale  reactors were  started  up.  It
concerns a  two-phase  process.  The  acidification-reactor has a volume of 80 m3.
The methane-reactor has a volume of 300 m3.
     The following results have been obtained:
     Acidification
     COD-load            60 kg/m3.day
     COD-conversion      13 kg/m3.day
     Sludge activity      0.8 kg COD/kg. volatile suspended solids day
     COD-reduction       about 20%

     Methanization
     COD-load            47 kg/m3.day
     COD-conversion      30-35 kg/m3.day
     Sludge-activity     2-2.5 kg COD/kg volatile suspended solids day
     COD-reduction       about 70%

     The third step of the plant consists of a nitrogen removal reactor. In this
reactor nitrification  and  sulfide-oxidation  take place. The micro-organisms are
also fixed  to  inert materials in this  reactor.  The laboratory-  and pilot-plant
experiments have already been completed. In the reactor a nitrogen-conversion of
1.5-2.0 kg  Nitrate-N/m3.day at a  retention  time of  1.5 hours  is  obtained.  On
account of  the positive  results  a  full-scale  reactor with a volume of 300 m3
will be built in 1986 (26,32,34).

     Gist-Brocades  has also  put a  full-scale plant  into operation  to regain
ammonia from  waste water.  In this  case  it  concerns  waste  water  with a large
amount  of  solvents.   The  purification  method  is based on   cold  extractive
distillation (35).

Breweries

     In 1984 the  construction firm Paques BV carried out a pilot-plant investi-
gation  on   anaerobic  treatment of  brewery-waste  water.  The  waste water  had a
very low COD  (1000-1500  mg/1) content and a  low  temperature (20-24 C). Never-
theless, results were  positive enough  to merit the construction of a full-scale
plant.


                                    813

-------
                                 A  r dosingpwiip
                                                     9I
                                         imam,
                                              REAKTOR
                                                              _o
                                                              J
                                                                   GASHOLDER
        GASFLARE
                                                                  MMMO'Mm
                                                           aOWOIAGRAM
         influwt   SETU1NG TANK
                                                     AlUIROaiC Ct>.
                                                      BBtWWY
                                          ^"W
                                                    MK&i
<*fcij^
*^7t
             Figure 3.   Anaerobic treatment of brewery waste water.


     The full-scale plant  (see Figure 3) ,  was  put into  operation  in November
1984 and is charactarized by the following features:
     Flow               6000 m3/day
     COD-influent        1000-1500 mg/1
     Temperature         20-24 C
     Volume buffer       1500 m3
     Volume UASB-reactor 1400 m3

     Because the  plant was  started  up  with  sludge  of another  waste  water
treatment plant it  reached design capacity within  two  weeks.
     The results  of the  full  scale  plant  are  very  similar  to those  of  the
pilot-plant:
     COD-load           4.5-7 kg COD/m3.day
     COD-reduction       80%
     Biogas-production   0.25 m3/kg COD (removed).
     Because of  the construction  of  the anaerobic  plant  the  quality  of  the
sludge  of   the  aerobic plant  (second  step)  of  the  waste  water purification
improved. The effluent  quality is less than 5  mg BOD/1 (36,37,38) .

Paper industry

     The waste  water of paper factories  contains  among other things cellulose.
Waste  and  waste  water  containing  cellulose  are very hard to  treat,  because
cellulose is difficult  to degrade.
                                   814

-------
      The department  of  microbiology of  the  University of Nijmegen studies  the
 destruction of high  concentrations  of  cellulose  containing wastes  such  as  verge
 grass,  and primary and secondary sewage sludge  from waste  water  treatment plants
 applied in the paper- and cardboard-industry. The experiments  are carried out by
 way of  a  two-phase-system  consisting of  a  mixed  reactor on laboratory  scale
 (30 1)  connected  in series with a UASB-reactor.
      In the first phase  cellulose fibers  are  partly converted  by micro-organisms
 by hydrolysis  into fatty acids,  carbonic  acid and hydrogen.  Methane is formed
 out of hydrogen and  carbon  dioxide. The aqueous phase with the dissolved  fatty
 acids   is  pumped  into  the   UASB-reactor  where  the  acids  are  converted   into
 methane.
      On laboratory scale positive  results  have been obtained. Some results  are
 presented in Table 7.

                         TABLE 7.  RESULTS  LABORATORY STUDY


 Waste                     Load          Retention-time    COD-reduction
                     (kg  COD/m3.day)        (days)               (%)
Paperpulp
Grass
Potato-waste
30-40
30-30
20
2
2
2
60-70
70-80
60-70
      Potential  sources  for  application may  be  waste- and  waste water  streams
 from  the  paper  industry,  waste-  and waste  water  streams from  the  canning
 industry,  the processing  of verge  grass,  wastes  from parks, the processing  of
 waste from vegetable  markets etc.
 The   system  will be  further developed  through  the  testing of  a  reactor on  a
 pilot-plant  scale  at an  industrial  firm.  This phase will  be  started in  1985
 (39)-

      Large amounts  of water  are  used in paper making. The  waste water contains
 high concentrations  of  dissolved organic  substances  and  must be treated via  a
 biological process.  In  1981 Biihrmann-Tetterode,  a  Dutch paper  industry  group,
 started  a  study  on  the application of anaerobic  waste water  treatment.
      After a short  testing period on laboratory  scale a pilot-plant  was put  into
 operation.  The  results were  satisfactory enough that at  this moment three full-
scale plants (Figure 4) for paper industries have been realized in co-operation
with Paques BV (Balk) and a fourth plant is  currently under construction
(Industrie-water Eerbeek).
      By  using  anaerobic  (pre)treatment, short  pay-back  times  may be  realized
 (about  1.5  years). Moreover, the present overloaded aerobic treatment  plants
 will come down  in  costs  after  they  have  been  expanded  with an anaerobic  pre-
 treatment  system.
      Table 8 gives  a survey of  the anaerobic  treatment  plants  in  the paper
 industry.
                                     815

-------
             A (before upgrading)
(after upgrading)
                     darifier
  Recycled
   sludge
//////
f 	 '
1
Aeration
basin
1.400 m'
1
i


I
\
 r
i
Aeration
basin
1.400 m'
//////


Aeration
basin
1.400m"
-





1
r



I
i



f
\
r
1
Aeration /
basin/
n.OOOm*

" r IT
&-
Buffer
basin
^ -
400m"
Ik
L - > -
J
Nutrients ^
                                                                 UASB
                                                                reactor
                                                                (14.5 m)


                                                                Gasholder
                                                                Steam-
                                                                 boiler
                                                               capacity
                                                              2.5 tons/hr
                                                        Steam (10 bar)
                                                         to paper mill
                            Wastewater
                            from paper mid
                Wastewater
                from paper mtU
Figure 4.   Schematic diagram of the waste water treatment  plant
             at Papierfabriek  Roermond.
                                  816

-------
    TABLE 8. ANAEROBIC WASTE WATER TREATMENT PLANTS IN THE PAPER INDUSTRY (40)
                                (SEPTEMBER 1985)
Factory    Product      Date of   Reactor  Temp.   Load      Inf1.      COD-
                       operation  volume   (C)   (kg COD/  COD     reduction
                                   (m3)           m3.day)  (g/m3)       %
Ceres
Cardboard
April
1983
70
35
5000     70
Papier-
fabriek
Roermond

Celtona

Others




Testliner
cora-
medium
Schrenz
Hygienic
paper
Testliner
cora-
medium
cardboard
envelopes
October 1000 30-40
1983


November 700 20-25
1984
September 2200 25
1985



10 3500 75



5 1200 60

* ca.1300 *




Fertilizer-industry
           The production of phosphoric acid, a raw material for phosphate fertiliz-
ers, results in the formation of about two million tons of waste gypsum a year.
Until now this gypsum has been discharged into surface water. Since gypsum from
phosphoric acid production is contaminated with heavy metals, among which are
cadmium and mercury, governmental policy has been directed at stopping these
gypsum discharges. However, it has so far proved impossible to find suitable
processing- or marketing potentials for phosphate-gypsum. Government, industry
and research institutes, cooperating in the "Phosphate-gypsum working group",
are making enquiries into the potential of phosphate-gypsum, by supporting
research projects among other things.

           The Dutch firms UKF, DSM and the Technological University of Delft are
carrying out research on the development of a new phosphoric-acid process. This
process distinguishes itself from the conventional hemihydrate processes by
dividing the disclosure of the phosphate ore and the crystallization of the
hemihydrate -which normally occur simultaneously - into two separate stages.  In
the first stage, the so-called predisclosure stage, the ore is totally converted
into a monocalcium phosphate (MCP) solution by a recycle stream of phosphoric
acid, whereupon hemihydrate is precipitated (Figures). Impurities such as
heavy metals - present in the ore - are removed during, or directly after the
predisclosure. This process makes it possible to produce a relatively clean
gypsum and phosphoric acid. The study is still in a laboratory phase. At the end
of 1986 the technical, economical and environmental consequences of this
promising process will have become more clear (41) 
                                    817

-------
     phosphate ore
            Figure 5.   Process  scheme  of  new phosphoric  acid  process.
Oil-containing waste water  streams

     The  treatment of oil-containing waste  water streams from garages,  bunker-
stations  and  waste-oil  refiners  can  be  improved using  membrane  filtration,
flocculation/flotation  or flocculation/filtration.  The use  of  conventional  oil-
separators  results into  an oil  concentration  in  the  effluent of about 200 mg
oil/1  or  more.  By using  the  above  mentioned techniques, concentrations  of  less
than  some scores of mg of  oil/1  may be  reached.  However, the average costs  will
increase  by  a factor 2  to  5.
     These are the results  of a study done by Tebodin Engineering  Consultancy by
order  of  the Governmental Institute for  Waste Water Treatment.
Electrochemical  detoxification of aqueous waste  solutions

     TNO  has  studied  a  method  which  uses  cathodic   dehalogenation of  penta-
chlorophenol (PCP)  in  aqueous  solution as  a  model  reaction.  PCP  has  been
chosen because  it is a representative pollutant of the type of waste waters in
question,  and because  it  has  strong  carbon-chlorine  bonds   and a  relatively
high solubility  in (alkaline) aqueous solutions.

     After 30 minutes of electrolysis  the PCP concentration  (Figure 6) had
fallen below the  detection limit of  0.5 ppm.   Simultaneously, the chloride con-
tent of the solution showed that five  chlorine atoms per molecule of  PCP were
removed.  The current efficiency for complete dehalogenation is  1%.  The adding
of  small quantities of  certain surface active agents, improves the  efficiency.
     During  electrolysis  the toxicity   of  the  solution  fell  from  an  initial
EC 50 = 2% to a final 40%, indicating  almost complete detoxification.
                                       818

-------
                       IPfPI/ppm
nunotr ef Cl'ioni
ptr PCP mottcult
       S
                                        JO      45
                                 hmt of Htctratysii limn I
   Figure 6.  Decay  of  PCP and yield of Cl ions per  PCP molecule during
              electrolysis of 1 litre of solution  containing 50 ppm PCP.
     An  experiment  with two  litres  of the  test solution was  conducted for  the
purpose  of determining  the intermediates  and product(s)  formed.  Figure 7  shows
the  formation  and  decay  of  tetra-,  tri-,  di-  and monochlorophenols, finally
resulting  in  the  formation  of  phenol  and, possibly,  monochlorophenols.  The
experiment  shows  that  the total  molar  concentration  of  the phenols remains
constant in time.
     Experiments  with other organohalogens  and  industrial waste waters are in
progress.

                                    fraction
                                    IV.)
                                         60   90    W   ISO
                                        ' hat of tltctrolysis (mini
        Figure 7.  Mole  fraction of the phenols during electrolysis of
                   2 liters  of  solution containing 50 ppm  PCP.
                      1.   PCP
                      3.   Trichlorophenols
                      5.   monochlorophenols
       2.  tetrachlorophenols
       4.  dichlorophenols
       6.  phenols
                                      819

-------
     The  advantage   of   electrolysis   over  alternative  methods  of  chemical
treatment is that additional  chemicals  are not generally required.  Electrolysis
with  electrodes  of  a large specific area,  such as those composed  of  very thin
fibres, may reduce the concentration of toxic compounds to a very low level.

Agricultural industry

     Seed-potatoes  are  treated  with   a   mercury  containing  disinfectant  for
protection against diseases.  The  disinfection takes  place in plunging tanks.  In
the Netherlands  it is obligatory  to treat  the  used  mercury containing plunging
liquids at specified  central places.
     In the past the  treating was  done  decentralized, with activated carbon.  The
use  of activated carbon  filters  rendered  unsatisfactory results,  because  the
saturated filters were not  replaced in time. This  resulted in soil- and surface
water pollution.

     In  1984  a central treatment plant was put into operation  in  Dronten.  The
treatment plant consists  of the following  process steps:
- Pre-sedimentation
- Coagulation/flocculation
- Sedimentation
- Filtration
- Activated carbon adsorption

The effluent figures  are  mostly below 10 (Jg/1 mercury.

AGRICULTURAL WASTE WATER  (MANURE PROCESSING)

     Owing to  the great  increase  and  the  concentration of  the so-called bio-
industry during the  last  decades  in the Netherlands, a  large surplus of manure
(mainly  pig-  and cattle  manure)  has  formed.  Roughly estimated,  this  surplus
amounts  to  about 17  million  tons a year.  This surplus  constitutes a  menace  to
the fertility of the  soil (too much phosphate) and  the environment.  The emission
of ammonia, the  formation of  nitrate in ground water,  eutrophication of surface
water  and  pollution  of   surface  water  by  salts present in  the manure may  be
mentioned.  The problem of manure surplusses is mainly a problem of minerals.

     In  principle the  problem of the  manure surplusses  may be  solved.  A
possibility  is  the   large-scale  processing  of manure   surplusses  in  central
processing plants where the manure  is  converted into products,  which no longer
constitute a  menace   to the fertility  of  the soil and the  environment.  Central
processing of  manure may  take  place in  various ways.  Each  way consists  of a
series of  a  number  of  known processes or unit operations.  The more important
processes  are:  anaerobic  digestion,   separation,  dewatering,  NH -stripping,
desalination,  concentration,  drying, combustion and aerobic  biological  treat-
ment.  In Figure 8 one of  the potential ways  of processing is outlined. Most of
these  unit-operations are  frequently  applied  in  the  processing industry.  The
various ways of  processing  are distinguished by differences  in endproducts  and
running costs. Dependent  on  the market for endproducts,  a selection may be made
for the best possible way of processing.
                                     820

-------
      The costs  for central  manure processing  are estimated  at 30 to  60  Dutch
 guilders per m3  of manure to be  treated,  for a plant  capacity  of  some  hundreds
of thousands of m^  a year, not including  the  costs  for transportation of the
manure to the central processing plant.   The  profit of potential  products,
which can be obtained at  the  central manure processing plant, are not taken
into account.  This expected  profit, however, will  not cover the  total costs
of manure processing.
     On  short-term, central  manure processing  might solve  the  problem of the
manure  surplusses.  Perhaps long-term  solutions  are also possible  by way of the
cattle  feed. The paramount  thought  is  of a pre-treatment  of  the  feed,  aimed
at the  improvement  of  the  nitrogen  digestibility  and  the increase   in the
availability of  phosphorus,  or,  of an  alteration of the composition of the  feed,
aimed  at  a reduction  in  the  nitrogen  and  phosphorus content and  any  other
minerals  such as, e.g.  potassium.
                                 Animal Slurry
                  Main Route
                                 Centralised
                                 Processing
                  Effluent
Cake
                                     NH
Oven


                     Ash
                                   solution
A  Brine
 Dried
  Cake
   Dried
   Brine
                           Figure 8.   Manure processing.
                                    821

-------
GROUNDWATER

     Owing to  the  production of manure surplusses and  connected over-manuring,
at  some  locations  the nitrate  content  in  groundwater  has  greatly  increased
during the last  years.  A high concentration of nitrogen in ground water creates
a problem  for the  preparation  of drinking  water.  The problem  has  become even
more pressing  since on  1  July  1984  the standard for nitrate in drinking water
was brought down from 100 mg/1 to 50 mg/1.

     Recently  the   Landbouwhogeschool  Wageningen   (Agricultural   University)
developed  a  method  to remove  nitrate from groundwater.  The  method  consists
of a combination of two  techniques,   namely,  ion exchange and  microbiological
denitrification.  Nitrate  ions  are adsorbed in the ion-exchanger.  After satura-
tion regeneration  takes place,  releasing the nitrate. The regenerate,  high on
nitrate  content  is then biologically  denitrified,  by which process  nitrate is
converted  by micro  organisms  into elementary  nitrogen  under  the  addition of
methanol.  The  regenerate,  from which the nitrate  has  been removed,  contains
hydrogen  carbonate,  a  product  of the  microbiological  conversion.  Hydrogen
carbonate may be used  to regenerate the ion-exchanger, so that  the regeneration
liquor may be used again. By using two  ion-exchange  columns and  one denitrifica-
tion column,  one exchanger  may adsorb nitrate  from groundwater, while at the
same  time the   other  exchanger  -which  is   saturated  with  nitrate  -  may be
regenerated again.
     The process is shown in Figure 9.
L
denitrification
reactor M
NOj  N2
org
H
NaCl
HCl
~" E^-3 ^on exchanger for
// "regeneration
^ cr+ NO; -CT+NO;
\
NOj 1
1
. C-source
            Figure 9.  Biological regeneration of an ion exchanger
                       by means of a denitrification column.
                                     822

-------
      The major benefits of this process are:
      The groundwater  that is to be  treated  does  not come into contact with the
      denitrifying organisms and the  carbon source (e.g. methanol);
      The  regeneration of the ion-exchangers  takes place in  a closed  loop.  A
      bulky waste brine, such as is the case in the usual way of regenerating, is
      therefore avoided. Regeneration of the ion-exchanger may of course also be
      carried out with chloride, e.g. as NaCl or HC1.

      The  chloride  content  in the  recirculation  loop must  be maintained  at
 a constant  level,  so that  salt  consumption  for   the  regeneration will  also
 decrease. Aspects, which  will come forward in the investigation are:
      The adaptation of denitrifiers  to a high chloride content;
      The prevention of a  pollution of the ion-exchanger in the regeneration loop
      with organic material;
      The effect  of an  increasing sulphur content  on  the regeneration.  Sulphur
      will  accumulate  in  the  regeneration loop, because  it  is  fixed during the
      removal  of  nitrate  and  is  released  again  during  regeneration.  However,
      contrary to nitrate, sulphate is not converted  (42,43,44).
                                  REFERENCES


1.  Van Luin, A.B., Van Starkenburg, W. Hazardous substances in waste water,
    Wat. Sci. Tech. Vol 17, 843-853, 1984.

2.  Welraadt C. Van afvalstoffen naar grondstoffen in de staalindustrie.
    H20 (16) 1983, no. 16, 364-368, 375.

3.  Anonymus, Chemisch Weekblad 26 juli 1984, pag. 238.

4.  Anonymus, Chemisch Weekblad 2 mei 1985, pag. 169.

5.  Anonymus, Nederlandse Chemische Industrie (NCI), 31 oktober 1985. pag. 25.

6.  Anonymus, AZC Interlocaal, 29 maart 1985, also communication.

7.  STORA-rapport maart 1985. Het inwonerequivalent getoetst.

8.  Allessie, M.M.J., van Luin, A.B. en Visscher, K. Bestrijding water-
    verontreiniging door zware metalen. H?0 (17), 1984, nr. 24, 569-574.
                                    823

-------
 9.  Eggink, H.J. Verbrandingswaarde van zuiveringsslib en de vereiste
     ovencapaciteit. H2
-------
24.   Communication RIZA.  Problematiek huishoudelijk afvalwater  Lelystad.
     20 juni 1985.

25.   Lettinga, G., Heijnen,  J.J.  en Houwink,  E.H.  Verslag European Anaerobic
     Waste Water Symposium.  Nederland koploper in  de anaerobe technologie.
     PT/Procestechniek 39.  1984,  nr. 3,  59-61.

26.   Rulkens, W.H., Van Voorneburg, F.,  Van Luin,  A.B.  en Van Starkenburg,  W.
     Ontwikkeling op het gebied van de afvalwaterzuivering in Nederland.
     NATO/CCMS, Bari, 1982.

27.   Communication TAUW-Infra Consult, Deventer, 22 mei 1985. Zuivering van
     slachthuisafvalwater.

28.   Communication Grontmij, Zeist, 23 november 1984. Anaerobe  behandeling van
     het afvalwater van een dropfabriek.

29.   Communication Grontmij, Zeist, 23 november 1984. Behandeling van zuivel-
     afvalwater met de AB-technologie.

30.   Van Luin, A.B., Van Starkenburg, W.,  Rulkens, W.H. en Van  Voorneburg,  F.
     Ontwikkeling op het gebied van de afvalwaterzuivering in Nederland.
     NATO/CCMS. Apeldoorn,  1983.

31.   Maaskant, W. Operational aspects of anaerobic waste water  treatment plants,
     especially for starch industries. Heidemij Arnhem, mei 1985.

32.   Euroconsult. Energy saving by anaerobic waste water treatment.
     3rd Mediterranean Congress on Chemical Engineering, Barcelona.
     November 1985.

33.   Communication AVEBE, Veendam, 20 juni 1985. Afvalwaterbehandeling aard-
     appelzetmeelindustrie.

 34.   Communication Gist-Brocades,  Delft,  15  mei 1985.  Volledige  zuivering  van
      het  afvalwater  van  de  gist-  en alcoholfabricage.

 35.   Communication Gist-Brocades,  Delft,  15  mei 1985.  Ammoniak terugwinning uit
      afvalwater door koude  extractieve  destillatie.

 36.   Paques B.V.,  Balk,  1984.  Anaerobe  zuivering  van het afvalwater  van  Bavaria
      met  een U.A.S.B.-pilot plant.

 37.   Hack,  P.J.F.M.  (Paques B.V.).  Application of the  U.A.S.B.-reactor for
      anaerobic treatment of brewery effluent. Poster at I.A.W.P.R.C.-symposium
      1984.  Amsterdam,  September  1984.

 38    Swinkels,  K.Th.M,  Vereijken,  T.L.F.M.,  Hack  en P.J.F.M. Anaerobic treatment
      of waste-water from a  combined brewery, malting and soft-drink-plant.
      20th Congress of the European Brewery Convention, Helsinki,  1985.
                                     825

-------
39.  Communication Haskoning,  Nijmegen,  20 december 1984.  De  anaerobe verwerking
     van cellulosehoudend afval of afvalwater.

41.  Habets, L.H.A. en Knelissen,  J.H.  Application of the  U.A.S.B.-reactor for
     anaerobic treatment of paper  and board mill effluent.  Water Science and
     Technology, 1985. vol 17, no. 1.

41.  Weterings, K. en Van Rosmalen Cr.  Een schoon fosforzuurproces.  Chemisch
     magazine, September 1984, 473-474,  493.

42.  Anonymus. L.H. Wageningen ontwikkelt methode om nitraat  uit grondwater te
     verwijderen. H20 (18), nr. 2, 1985, N7.

43.  Van der Hoek, J.P. en Klapwijk,  A.  Nitraatverwijdering uit grondwater.
     H20 (18), nr. 3, 1985, 57-62.

44.  Van der Hoek, J.P. en Klapwijk,  A.  Biologisch/fysisch-chemische methoden
     Nitraatverwijdering grondwater.  PT/Procestechniek 40  (1985) nr. 5,  22-25.
                                    826

-------
   NORWEGIAN ADVANCES IN WASTEWATER TREATMENT


                       by
              Dr.ing. Bjeirn Rusten
Aquateam, Norwegian Water Technology Centre A/S
            P.O. Box 6593 Rodeldkka
                 N-0501  Oslo 5
                     Norway
        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.
 North Atlantic Treaty Organization/Committee on the
 Challenges of Modern Society  (NATO/CCMS) Conference
           on Sewage Treatment Technology

               October 15-16, 1985
                 Cincinnati,  Ohio
                         827

-------
                NORWEGIAN  ADVANCES  IN WASTEWATER TREATMENT

                by:  Dr.ing. Bj0rn Rusten
                    Aquateam,  Norwegian Water Technology Centre A/S
                    P.O.Box 6593 Rodelokka
                    N-0501   OSLO 5
                    Norway
                                 ABSTRACT

     This paper gives a short summary of some recent advances in wastewater
treatment and sludge handling in Norway.

     Projects briefly summarized are:

          Aerobic,  thermophilic digestion of pre-thickened sludge using air.
          Septage handling.
          Phosphorus removal from wastewater by the use of granular activa-
          ted alumina.
          Treatment plants for single houses.
          Wastewater treatment with aerated submerged biological filters.
          Separate treatment of septage liquor.
                                    828

-------
                                INTRODUCTION

     In Norway today  research  concerning  industrial  and municipal  wastewater
treatment and sludge  treatment is  mainly  carried  out by Aquateam,  Norwegian
Water Technology Centre A/S  and by The  Water Treatment Group,  Norwegian
Hydrotechnical Laboratory, The University of Trondheim.

     This paper will  give  a  short  summary of some of the recent projects
relevant to advanced  wastewater treatment and sludge handling.

                             SLUDGE MANAGEMENT

AEROBIC THERMOPHILIC  DIGESTION OF  PRE-THICKENED SLUDGE USING AIR

     Several methods  for hygienization  of sewage  sludge have been  evaluated
in Norway: lime treatment, composting,  long-term  storage and aerobic,
thermophilic digestion using pure  oxygen.  In 1983 the Danish company JANCA
introduced on the Norwegian  market a new  version  of  the aerobic, thermophi-
lic digestion process using  a  special device (vibrating sieve)  for thicken-
ing the raw sludge  up to 8-10% DS  before  digestion.  With this concentrated
sludge, a closed and  insulated reactor  and oxygen supply from a surface
aerator, it was claimed that the sludge would be  hygienized with a retention
time of about 1 day (batch operation).

     Aquateam has performed  a  pilot plant study of the JANCA-process at the
HIAS sewage treatment plant  (1). A flow diagram of the OANCA pilot plant is
shown in Figure 1.
   Polymer
                                            Aerobic digester
 Sludge from
 plant thickener
                                                      r? ={g)	> Hygienized sludge
                        Sludge liquor
              Figure 1.  Flow diagram of the JANCA pilot plant.

     The digester was operated on  a  draw  and  fill  basis  (batch operation).
Mixed primary-activated-chemical (Al)  sludge  was  pumped  from one of the
treatment plant thickeners  to the  vibrating sieve.
                                      829

-------
     The hygienic quality of the sludge was monitored  by  microbiological
examinations of faecal coliforms, faecal  streptococci,  spores  of Clostridium
perfringens, Salmonella bacteria and  bacteriophages  (coliphage MS 2).  The
bacteriophages were added to the feed  sludge.

     Due to variations in solids concentration of the  pre-thickened sludge
and operational problems with the thickening device, both organic and
volumetric loadings on the digester varied considerable during the study.
Table 1 gives data on retention time  and  organic loading  for the test
periods.
                   TABLE  1.  LOADING  DATA FOR THE DIGESTER
  Phase
                         Retention time   >
                              (days)
Organic loading
 (kg VS/m3 . d)

Start-up
Test period 1
Test period 2
Range
2.1-3.6
1.5-2.2
2.4-4.0
Mean
2.8
1.9
3.1
Mean
16
27
11
*) Retention time is calculated as  the  sludge  volume  in  digester after
   feeding (m^) divided by the sludge feed  rate  (m-Vd).

     During test period 1 and 2 the digester temperature normally followed
the curves shown in Figure 2.
                        12       18       24       30       36
                       Time after start of feeding sludge to the reactor (hours)
            42
48
Figure 2. Typical temperature  curves  in  digester  after start of feeding
          sludge.

                                      830

-------
     Based on the  results  from  the  pilot  plant  study  the  following con-
clusions were drawn:

          The JANCA-process  with  sludge draw  and  fill  every morning  (average
          retention  time  1.9 days)  could  raise  the  sludge temperature to
          above 60C and  maintain this level  for  8-12  hours. This caused a
          limited  improvement in  the  sludge hygienic  quality.

          With sludge draw and  fill every second  morning  (average retention
          time 3.1 days)  temperatures above 60C  could  be maintained for 27-
          34 hours,  and the  sludge  was satisfactorily  hygienized.

          The data on organic matter  reduction  during  the process is
          uncertain,  but  figures  of 20-25% is indicated.  This means  the
          treated  sludge  is  not stable and can  create  odor problems  during
          subsequent handling and disposal.

          The original pre-thickening unit (vibrating  sieve) did not
          function properly  with  the  mixed primary-activated-chemical
          sludge. Mean dry solids concentrations  after  sieving was 7.1% and
          5,5%, respectively,for  test period  1  and  2. Another device
          (dewatering container)  seemed to be capable of  concentrating the
          sludge up  to about 10%  dry  solids.

          Total power consumption for the pilot plant was 30 and 42  kWh per
          m3 sludge  from  plant  thickener  with sludge  feeding every day and
          every second day,  respectively.  These figures are higher than
          expected for a  full scale plant with  automatic  process control.

          Capital cost for a 2100 tonnes  DS/year  plant  is about NOK  2
          million (1984).  The operating costs (energy and polymer) will be
          about NOK  150/tonne DS.

SEPTAGE HANDLING

     Treatment and handling  of  septage is  a major problem in Norway. A
project concerning separate  treatment of  septage  liquor will be presented
later in this paper.  Here, a short  summary of two other projects will be
given,

Septage Discharge to  Sewer System

     The VEAS treatment plant outside Oslo is a primary precipitation plant
designed to handle wastewater from  565,000 population equivalents.  Septage
from the Oslo area can be  discharged to the sewer system.

     During a test period Aquateam evaluated the effects  of septage dis-
charge  on the operation and  performance of the treatment  plant and the
sewer system (2).  The sludge  quantities used were the same as those expected
to be discharged from the Oslo area in the future. The septage was added to
the sewer about 25 km upstream from the treatment plant.
                                     831

-------
     The results from the one month test period led to the following
conclusions:

          It is possible to maintain the previous treatment efficiency
          at the treatment plant, even after addition of about 200 m-Vd
          of septage to the sewer system. This does, however,  require a
          10-15% increase in the consumption of chemicals (ferric chloride),
          in order to keep phosphorus concentration in plant effluent below
          0.5 mg P/l.  The sludge production will increase approximately 10%.

          The composition of the septage during the test period was such
          that installation of bar screens and a grit removal  unit at the
          discharge facility was found unnecessary.

          Only a slight increase in odor level can be expected at the
          treatment plant. At some ventilation points along the sewer
          quite high odor levels were found.  At these points the use of
          simple odor reduction methods should be considered.

Mobile Septage Dewatering

     As an alternative to septage treatment at a wastewater treatment plant.
mobile dewatering units have recently been introduced in Scandinavia.  Mobile
dewatering has several potential advantages:

          Reduced overall septage volume for treatment and ultimate dispo-
          sal.

          Lower costs for transportation.

          Higher capacity. On-the-road dewatering increases the number of
          septic tanks that can be visited before disposal.

          Filtrate is returned to the septic tanks. This reduces the
          problems caused by adding untreated septage liquor directly
          to the treatment plant influent.

     A Swedish system, called "Hamstern" was evaluated by NIVA (Norwegian
Institute for Water Research) in 1980. This system is based on lime condi-
tioning and dewatering in a special type of vacuum filter.

     Recently Aquateam tested a Danish mobile dewatering system,  called MOOS
KSA (3).  Figure 3  shows  the  sequential  steps  in  septage  collection  and
on-the-road dewatering using the MOOS KSA-system.

     First the septage is sucked into a tank.  Then filtrate from the
previous dewatering is returned from the filtrate collection tank to the
empty septic tank.  Polymer is added when the septage is pumped from the
vacuum tank to the dewatering tank. The sludge settles while the filtrate
drains through a filter cloth to the filtrate collection tank. The dewater-
                                     832

-------
ing  sequence goes  on all the  time, while  the truck  goes from septic tank to
septic  tank. After a day of work the sludge is left in the dewatering tank
overnight,  in order to achieve higher  dry solids concentrations.
                                                              Suction of septage
                                                              into the vacuum tank
                                                              Septic tank
                                                              Filtrate from the previous
                                                              dewatering operation is
                                                              returned to the empty
                                                              septic tank
                                                              Septage from vacuum tank
                                                              pumped into dewatering
                                                              tank with simultaneous
                                                              addition of polymer
                                                              All day through there is
                                                              continuous dewatering
                                                              of the sludge cake.
                                                              Filtrate goes to the
                                                              filtrate collection tank
Figure  3.  Sequential  steps  in  septage collection and  on-the-road  dewatering
           using the  MOOS KSA-system.

     The following conclusions were drawn  from the tests of this  mobile
dewatering unit:

           Actual capacity will depend on the distance between septic
           tanks, type and size of septic tanks,  septage composition,
           standard of roads, maximum allowable weight etc.  Until  we get
                                        833

-------
performance in relation  to the adsorption capacity and kinetics. Such  an
understanding is required  in order to optimize the process design  and
operation. The scope  of  this work has been to contribute to such an  under-
standing, in interpreting  the results from isotherm and column experiments
with the help of a mathematical  model based on generally accepted  mass
transfer theory.

     The Homogeneous  Surface Diffusion Model (HSDM) was used to describe  the
process. More information  about this model can be found in (4) and (5). The
input data for the model was found in equilibrium experiments on alumina
powder, and in lab-scale tests of fixed-bed adsorption of a synthetic
secondary wastewater  using granular alumina. The lab-scale column  system  is
shown in Figure 4.
           1.50m


           1.15m


           0.85m


           0.55m


           0.20m

           0.00m
                    head-columns -
                       columns
                       /    \
                T   "7

]
I/
0

\.



/
rs

\

L M HC1 1 H NaOH
                                                      CFG Prominent
                                                      Dulcometer
                             Underdrain
                                            Influent
                                            water
                                            tank
Figure 4.  Lab-scale  column system for phosphorus adsorption  on  granular
           activated  alumina.

     The  adsorption  capacity is very pH-dependent, as  shown  by  the adsorp-
tion isotherms  in  Figure 5.  The capacity is at its maximum at pH = 4.5.
                                      834

-------
        3.0
      O
      81
        2.0
        1.0
           -4.0
                        -3.0
            pH
            pH
            PH
            pH
5
6
7
8
K
K
K
K

F
F
F
T*
a
%
3
as
7
7
5
3
36
1
3
1
4
1
7
.2
.5
.7
. 1
n
n
n
n
at
_
3,
3
0
0
0
0
.12
.20
.20
.25
7
7
8
3
                           Q(mmoleP/kg
                                 C(mmoleP/l)
Figure 5. Adsorption isotherms for Compalox AN/V at different pH values,
          T = 20C, t = 7 days.

     The HSDM model was found to give a fairly good description of the
process. The  process is well suited for designing a beds-in-series system.
Figure 6 shows the recommended design criteria for a semi-continuous
countercurrent system of three bed units with a total bed length of 6.0 m.
The design criteria was calculated by the model for a pH of 6.0 and a
required effluent quality of 0.5 mg P/l.

     Figure 6 demonstrates that the influent phosphorus concentration and
the alumina particle size are important factors regarding the design liquid
flow velocity. A sensitivity analysis of the model stated that the three
most important parameters determining the column performance were the pH,
the alumina particle size, and the column length. The rate of adsorption is
limited by intraparticle diffusion. Therefore the use of a coarse-grained
type alumina will necessitate a low hydraulic loading and a long contact
time within the bed.

Treatment of Real Wastewater

     One possible application of this adsorption process is selective
removal of phosphorus from small scale/on-site treatment plant effluents.

     The effluent from a small RBC package plant was treated in two pilot-
                                     835

-------
scale columns for a period of about 10 months (6). Coarse-grained type
alumina (1.9 mm diameter) was used in order to reduce the potential for
clogging of the beds. The influent concentration was close to 10 mg PCty-P/l
and the pH was close to 7.0 throughout the experiment. Both columns had
variable flowrates that simulated the daily fluctuations in a real treatment
plant. However, the mean liquid flow velocity was low (0.2 m/h) in order to
provide sufficient contact time for intraparticle diffusion of phosphate.
The bed-heights were 1.0 m and the column diameters were 0.2 m.
        10.0
    o
    g
    UJ
    O
    Q

    O
        5.0
          0
         0.050
0.075                        0.100

          PARTICLE  RADIUS R(cm)
Figure 6. Recommended design criteria for a 6.0 m long in-series system of 3
          bed units, for phosphorus adsorption on activated alumina (Compa-
          lox AN/V). Valid for pH = 6.0 and an effluent concentration of 0.5
          mg P/l.

     The breakthrough curves at different column lengths are shown in Figure
7. The dashed lines show the expected breakthrough curves for a simple
phosphate adsorption process, as predicted by the mathematical model
mentioned earlier.

     From these results it is evident that a significant amount of phospho-
rus has been removed by mechanisms other than simple adsorption. Such
mechanisms could be complexation, chemical precipitation by Ca^+ and Mg2+
present in the wastewater, and biological consumption of phosphate. Conse-
quently, use of the mathematical model presented earlier on, will give
conservative design criteria. It is, of course,  an advantage that these
mechanisms increase the column's capacity for phosphorus removal.

     Phosphorus removal from wastewater using granular activated alumina
seems to be an efficient and reliable treatment process, with a minimum of
operation and maintenance requirements. However, important questions are
still to be answered. The most urgent ones are pretreatment requirements and
                                     836

-------
the influence of organic matter and more condensed type phosphates when
treating a real wastewater, and in particular how regeneration of spent
alumina should be optimized.
            0
Figure 7. Breakthrough of PC^-P at different column heights, treating real
          secondary wastewater. Columns filled with activated alumina
          (1.9 mm diameter Compalox AN/V). Solid lines show actual break-
          through curves, based on the mean value from the two columns.
          Dashed lines show expected breakthrough curves, predicted by a
          mathematical model.

TREATMENT PLANTS FOR SINGLE HOUSES

      In  a lot of countries there  is a big demand for simple and reliable
plants that can treat wastewater  from a single house. These plants have to
meet  the regulatory effluent criteria under highly variable loads and over a
long  period of time.

      Biovac A/S of Norway has developed and produces a unit for year-round
treatment of wastewater  from single houses. Over the last couple of years
10-15 such units has been monitored. Three units for removal of organic
matter were closely monitored and evaluated over a 6-month period (7). Later
two more units designed  for removal of both organic matter and phosphorus
were  thoroughly tested by Aquateam from July 1984 to January 1985 (8).

      Flow diagram of a BIOVAC treatment plant with co-precipitation of
phosphorus is shown in Figure 8.  In the two process tanks the wastewater  is
biologically treated in  an aerated suspended growth system. A vacuum fan
sucks air into the process tanks, keeps the sludge in suspension and
recycles the sludge from the clarifier. The sludge return is intermittent
                                     837

-------
and Is controlled by a timer. Once a week, at night, the  clarifier  is
stirred for a few seconds, in order to prevent accumulation  of  floating
sludge.
                                    Sodium aluminate
                                  Air in
   Influent-
                                                        Effluent
                                                                      Air out
                                                             o
                                                           Vacuum fan
                                                         I	
                                                                    Sludge drier
                               Sludge return
                                                      Filtrate to
                                                    process tank 1
Figure 8. Flow diagram of a BIOVAC treatment plant.

     The process tanks have a total effective volume  of  1.08
clarifier has an effective area of 0.35 m^.
                                                                  while the
      Liquid sodium aluminate  (Na^l^)  is used as  precipitant.   It is  added
to process tank 2 intermittently, either once every hour or once  a  day.

      Excess sludge is pumped  to  the  sludge drier  by an airlift pump once a
day.  The sludge liquor  is  returned to  process tank  1.  The  biological-
chemical sludge dewaters quite well, and excess heat  from  the vacuum fan is
used  to dry the sludge  further.

      The plants are supposed  to  be routinely serviced every 4 months. The
service people then dispose of the accumulated sludge and  fill the sodium
aluminate tank.

      So far the BIOVAC  treatment plants  have been very reliable and have
performed very wel 1 .

      Oxygen concentrations between 2.5 and 6.3 mg/1 have been observed in
process tank 1, while the  concentrations  in  process tank 2 have been
slightly higher, 4.5 to 6.8 mg/1.
                                     838

-------
      The organic loading has been low,  with F/M-ratios from 0.02 to 0.07 kg
 BOD7/kg MLSS .  d.  Hence, BOD-removal has been excellent,  with effluent
 concentrations  c10 mg BODy/l.

      Co-precipitation with  sodium aluminate has given residual total phospho-
 rus concentrations of 0.1-0.6 mg P/l.  An addition  of chemicals equivalent to
 2.0 mol Al/mol  P is recommended. For a home with 4 people this will be
 equivalent to 11.7 1  of  sodium aluminate solution over a 4-month period.

      Daily fluctuations in wastewater flow has no  negative  influence on the
 performance,  provided that the total daily flow is less  than 700 I/day.

 WASTEWATER TREATMENT  WITH AERATED SUBMERGED BIOLOGICAL FILTERS

      Almost all the wastewater treatment plants in Norway are inside
 buildings.  This is because of the strict rules governing  working conditions
 and the cold winter climate. To reduce the plant construction costs,  it is
 essential to use a compact treatment process.  Many biodisc  plants have been
 built in Norway during the last few  years.  They have,  however,  had some
 mechanical  problems.  An aerated submerged  biofilter has  no  moving parts,  and
 with a high density filter medium it should be possible  to  get a high
 organic removal rate  per unit volume.

      Figure 9 shows the principle for a two-stage  aerated submerged bio-
 filter.
      Influent
*x



  1

                    \
                      Aeration
                      system
                                                   t
Effluent
                                                      Filter
                                                      medium
 Figure  9.  Principle  lay-out  of  a  two-stage  aerated  submerged  biofilter.

      In  1982  the Water  Treatment  Group  at The  University  of Trondheim
 started  pilot-scale  research on aerated submerged biofilters.   Filter media
with specific surfaces of 140 m2/m3 and 230  m2/m^, respectively, were used
to treat municipal wastewater (9).  The removal rates were the same in both
filters, as organic matter removed per unit  surface  area.   Thus, the filter
                                     839

-------
               2   3
with the  230 m /m  medium gave the highest volumetric removal rate.  The
air bubbles stripped off excess biofilm and the strong turbulence also
ensured that the  substrate was evenly distributed  to  all  parts of the
filter.   Tracer response curves showed both filters to behave as complete
mix reactors.

     Figure 10 shows removal rate versus organic load when the filters were
run as single-stage reactors. Figure 11 shows  the  same with the filters
operating as a two-stage reactor.
              D
              O
                80 -
                60 -
              $
              a
              n 40
              o

              I
                20 -
                     tilter A (MO m /m ) : O
Total COD influent.

Soluble COD effluent.
>^x 	
>'0
X
-n . VCOD .
'A, COD -" Bft|COD * 360

                         20
                               40
                                     60
                                            80
                                                  100
                                                        120
                                     Organic load, g COD/m -d
Figure 10. Total  organic removal rate versus  total  organic load. Filter
           A  and  Filter B operated as single-stage  reactors,  treating
           municipal  wastewater. r^coo =  organic removal rate, B^CQD
           =  organic  load.
                            Two-stage process

                            Total COD influent
                            Soluble COD effluent

r - ,. BA,COD
A, COD BA>COD+ 120

                                   10   15   20  25  302 35
                                   Organic load, g COD/m -d
Figure  11.  Total  organic removal rate  versus  total organic load.  Filter
            A  and  Filter B operated as  a  two-stage reactor without
            intermediate clarification, treating municipal wastewater.
            r/\ coo = organic removal  rate,  B^CQD = organic load.
     Volumetric  removal rates in excess  of 10 kg COD/m^ . d were  observed in
both filters,  treating municipal wastewater with low COD-concentration.
                                      840

-------
     With the filters operating as single-stage reactors, specific sludge
production was between 0.35 and 0.55 g TS/g COD removed. With the two-stage
process the sludge production  increased from virtually  zero at an organic
removal rate of 3 g COD/m? . d, up to 0.40 g TS/g COD removed at a rate of
25 g COD/m2 . d.

     Oxygen transfer was good  in both filters. In a full-scale plant, with a
depth of aeration of 3 m, an air supply of about 10 to  15 m^ per kg COD
applied should be sufficient with the tested filter media.

     A different study compared high-rate treatment of  food-industry
effluents in an activated sludge unit and in a submerged aerated biological
filter (10). The filter had a  medium with a specific surface area of 230
m2/m3.

     Removal rate versus organic load is shown in Figure 12, for the
submerged biofilter. The maximum volumetric removal rate was in excess of 15
kg COD/m^ . d. This was about  four times higher than the maximum achievable
rate in the activated sludge unit.

o
00
          4)
          P
          a
          j-i
va
          D
         K
   80-|
             60-
                 QAir= 25.0 m3/m3h :  o

                 Q.. = 12.5 m3/m3.h :  
                  Air
                          Organic load, g COD/m d
Figure 12. Total organic load versus total organic removal rate  in the
           aerated submerged biological filter treating food-industry
           wastewater. Air supplies of 12.5 and 25.0 m^ per m^ filter
           volume and hour have been used, r^ QQQ = organic removal rate,
           fy\ COD = organic load.

     On an average basis, an effluent concentration of 1000 mg COD/1
corresponds to a removal efficiency of about 70% using the wastewater in
this study. The activated sludge unit and the biofilter could be  loaded at
2.8 kg COD/m3 . d and 12.7 kg COD/m^ . d, respectively, in order  to obtain
                                     841

-------
an effluent concentration of 1000 mg/1.  This shows that the aerated sub-
merged biological filter was superior to the activated sludge process in
terms of required tank volumes.

     It can be seen from Figure 13 that the aerated submerged biological
filter can be operated at a lower specific air supply than the activated
sludge unit.  With the same specific air supplies,  the biological  filter
always showed the highest dissolved oxygen concentrations. The filter medium
increases the contact time between the air and the liquid. Thus more oxygen
can be transferred.
\
e
 c
jxygen
a. c
i
w t
0)
M 
o ^
en
w
H
Q
^
1



/
O
0
t
/

/
0 '
2
.


*
0
S
^
,
o
3
^

0X

0 <
^" \

^

0 6
*^
\
^


0




1

o- 


00 1!
                                                   Biological Filter:
                                                   Activated Sludge:
              Specific  air supply, ra /kg COD

Figure 13. Specific air supply versus dissolved oxygen concentration for
           the two pilot-plants,  treating food-industry wastewater.
           Data recalculated to a submerged depth of 3 m.

     The first full-scale aerated submerged biological filter in Norway was
put into operation in 1984.  Two more plants were started in the spring of
1985 and several plants are on the planning stage.

     Two of the plants in operation treat municipal  wastewater. The third
plant treats mainly dairy wastes, and some municipal wastewater.

     As of yet there are no performance data available from these full-scale
installations. However, aerated submerged biological filters seem to be a
good alternative to other biological treatment processes.  The microorganisms
grow on the media, eliminating sludge recycle and any disturbance resulting
from sludge bulking.  Trickling filters need a certain minimum hydraulic load
to work efficiently.  In aerated submerged biological filters the air bubbles
are believed to erode the biofilm and prevent clogging of the filter media.
The strong turbulence also ensures good contact between substrate and
microorganisms.  An aerated submerged biological filter with a high surface
area filter media should be a simple and compact treatment process.
                                     842

-------
 PROCESS UPGRADING AND IMPROVED MANAGEMENT OF WASTEWATER TREATMENT SYSTEMS

SEPARATE TREATMENT OF SEPTAGE LIQUOR

     Treatment of septage is a major problem in many European countries. In
Scandinavia septage is quite often discharged directly to the sludge
treatment units at a municipal sewage treatment plant. Small primary or
secondary chemical precipitation plants are very common in Norway. The
operational problems due to septage discharge have been severe at these
plants. In addition, the return of untreated septage liquor to the treatment
plant influent frequently leads to unacceptable effluent qualities.

     One way to reduce the problems caused by septage discharge is to treat
the septage liquor separately in a biological unit. No data about separate
treatment of septage liquor have been found in the literature, except for a
brief experiment made by the Norwegian Institute for Water Research.

     In order to gain more knowledge, pilot-scale research using both the
RBC-process and the activated sludge process was initiated in 1983. This led
to a full scale demonstration project in 1984 and 1985. These projects were
carried out by research engineers presently employed by Aquateam.

Pilot-Scale Research

     This work had two main objectives: to study biological treatment of
septage liquor, and to study chemical precipitation of treated and untreated
septage liquor when mixed with primary treated municipal wastewater.

Treatment in RBCs (ID-

     Biological treatment of septage filtrate was studied in two pilot-scale
RBCs, one operating at 5.4C and the other at 14.5C. In addition, chemical
precipitation of untreated and RBC-treated septage liquor, mixed with
municipal sewage, was studied in order to find the effects of return flows
of septage liquor on alum treatment of wastewater. The septage filtrate used
in this study was less concentrated than typical septage liquor.

     Figure 14 shows total organic removal rates versus total organic loads
for the two RBCs. Most of the reduction of organic matter in the RBC systems
took place in the first stage. Removal rates as high as 80-90 g CODj/m^ . d
were observed at 14.5C. A maximum removal efficiency of about 85% total COD
was found at a temperature of 14.5C and an organic load of about 80 g
CODT/m2d.

     Based on the removal  rates  of total  COD at 5.4 C and 14.5 C respec-
tively,  a temperature coefficient (9) of  1.10-1.11  was found.

     The results indicated simultaneous nitrification and  denitrification in
the RBC unit operated at 14.5C.  The low  temperature RBC unit showed no  sign
of nitrification.
                                     843

-------
             T
             20
               ~t
               40
1	I	\	1	1	T
60   80   100  120  140   160   180

  Total  organic load, g COD /m d
                                                           RBC A (  5.4 C) :

                                                           Stage 1       : o

                                                           Stage 1+2    : *

                                                           Stage 1+2+3  : T

                                                           Stage 1+2+3+4: 



                                                           RBC B (14.5 C):

                                                           Stage 1       : O

                                                           Stage 1+2    : a

                                                           Stage 1+2+3  : v

                                                           Stage 1+2+3+4: o
Figure 14. Separate treatment of septage  filtrate  in  pilot-scale
           RBCs. Shows total organic removal  rates  versus  total  organic
           loads, based on data from all  4  stages.  r/\tcOD  = organic
           removal rate, B/\ QQQ = organic load.
to
 Jar-tests showed that nitrification of the  septage  liquor was required
reduce the consumption of chemicals for phosphorus removal.
     Low effluent phosphorus and SS concentrations  could  be obtained in the
jar-tests with both treated and untreated  septage  liquor.  With respect to
COD, previous RBC treatment was essential,  as  shown in Figure 15.  High rate
treatment in a RBC unit (<30% removal of CODy) was  sufficient to have a very
positive effect on the residual concentrations of  total  and filtrable COD
after blending with municipal sewage  and precipitation  with alum.
                                     844

-------
                    100-
                     80-
                  8  60-
                  i
                     40-
                     20-
        TnfL
        cone., mg/l
                 10% untr.
                 40 % untr.
                 10%AI
                 40%AI
                 10%BI
        271 a	o 40%BI
                       100
                    120-
                    100-
                     80-
o
O
o
O)
                     60-
                     40-
                     20-
                 200          300
                Alum addition, mg/l
400
         Infl.
         cone., mg/l
         126 - 10% untr.
         343 oo 40 % untr.
          98 T	v 10%AI
         169 w	 40%AI
          81  10%BI
         171 a	o40%BI
                                                      'V  '
                       100
                  200          300
                 Alum addition, mg/l
                                                            400
Figure  15.  Total and  filtrable COD  concentrations  after alum  precipitation
            in jar-tests,  for different fractions  of RBC treated and un-
            treated septic sludge  filtrate in primary treated  municipal
            wastewater.
                                        845

-------
Treatment With the Activated Sludge Process (12)

     The septage liquor used in this experiment was more concentrated
than the filtrate used in the RBC-experiments. Figure 16 shows removal
efficiency versus F/M-ratio. The pilot-plant operated at 8C and a F/M-ratio
of 0.41 kg BOD7/kg MLVSS . d was obviously overloaded. Otherwise the pilot-
plants performed excellent at the temperature levels indicated in Figure 16.
           f-
          Q
          O
          03
             90
   80-

o  70n
           | 60H
           tt>
          01 50H
          10C
           8C
             0.1      0.2      0.3      0.4      0.5

                F/M-ratio (kg BOD7/kg MLVSS  d)
                                                                0.6
Figure 16. Separate treatment of septage liquor in pilot-scale
           activated sludge units. Shows removal rates versus F/M-ratios.

     Chemical precipitation of treated and untreated septage liquor, mixed
with municipal wastewater, was studied in jar-tests. The alkalinity of the
septage liquor determined the required alum addition. Thus nitrification of
the septage liquor is necessary in order to reduce the consumption of
chemicals.

     An alum addition equivalent to 2-3 mol Al/mol P is required for
satisfactory removal of phosphorus. Consequently the phosphorus concentra-
tion will determine the necessary alum addition for nitrified septage
liquor.

     Similar to RBC-treatment, pretreatment of septage liquor with the
activated sludge process significantly reduced the residual concentrations
of organic matter after blending with municipal wastewater and precipitation
with alum.
                                     846

-------
Full-Scale Demonstration  Project (13)

     Sorumsand sewage  treatment plant  was chosen for the full-scale demon-
stration project. This is a  secondary  precipitation plant designed for
6 000  p.e., but with  an  actual load of about 1  500 p.e. Alum is used as
precipitant.

     Septic sludge  is  discharged to the sewer a  few yards upstream the
treatment plant. The volume  of  septage discharged at this plant is equiva-
lent to 5-10% of the total flow to the plant.

     The sludge going  from the  plant thickener to the dewatering centrifuge
is a mixture of septic-primary-chemical sludge.  This is a common situation
at many Norwegian treatment  plants.

     The full-scale test  was carried out over a  period of 6 months. The
sludge liquor from  the centrifuge was  treated in an activated sludge unit,
operated as a batch system.

     Figure 17 shows the  flow diagram  for this process. Sludge liquor from
the centrifuge flowed  to  a tank.  From  there it could either be returned to
the treatment plant influent, or be pumped to the activated sludge unit. The
activated sludge unit  had a  total volume of 30 m^r Every morning a maximum
of 17.5 m^ of treated  sludge liquor was pumped out of the tank, and replaced
with an equivalent  volume of untreated septage liquor. Air was supplied
through coarse bubble  aerators  at the  bottom of  the tank.
     Centrifuge
                          Untreated
Floating pump
  Treated
sludge liquor


r



i

r
 


_J
                                            Max.
         Return to
         treatment
        plant influent
                                            Min.
                                         Batch-operated
                                        activated sludge unit
                                                                   Excess sludge
Figure 17. Flow diagram of  a  full-scale,  batch-operated, activated sludge
           system for separate  treatment  of sludge liquor.
                                     847

-------
     Dewatering units at Norwegian treatment plants are normally in opera-
tion only during regular working hours, from Monday to Friday.  Thus,  we had
an ideal situation for batch operation of the activated sludge unit.  A
regular cycle was like this:

          Aeration was stopped early in the morning,  and the sludge was
          allowed to settle for 1-1.5 hours.

          Treated sludge liquor was pumped to the treatment plant influent.

          Aeration was resumed and the tank was filled with untreated sludge
          liquor.

          Aeration was continued until the following morning.

     On Saturdays and Sundays the activated sludge unit was aerated all day.
The process cycle was controlled by two simple timers.

     Results from a one month period with intensive monitoring are shown in
Table 2. During this period the aeration tank had a pH of 6.8-7.2 and a
temperature of 12-13 C. The organic loading (F/M-ratio) was between 0.049
and 0.137 kg BODy/kg MLSS . d, with a mean value of 0.094 kg BODy/kg MLSS.d.
A COD/BODy-ratio of 1.8 was found for untreated sludge liquor.  Treated
sludge liquor was not analysed for BOD.

    TABLE 2. SEPARATE TREATMENT OF SLUDGE LIQUOR IN A FULL-SCALE PLANT.
               RESULTS FROM PERIOD WITH INTENSIVE MONITORING
 Parameter          Influent            Effluent            Rem. Eff. %
                Range      Mean     Range      Mean     Range        Mean
COD, mg/1
SS, mg/1
Tot-N, mg/1
Tot-P, mg/1
P04-P, mg/1
Alkal inity,
meq/1
990-3050
688-1403
68-237
6.0-22.9
1.1-2.4

2.8-17.2
1539
1047
no
16.5
1.8

4.7
62-760
110-640
20-111
0.1-10.9
0.1-1.0

1.0-8.0
244
319
60
3.4
0.4

3.1
63-96
46-88
1-73
17-99
29-95

~~
86
70
45
76
78

33
     In general the removal of organic matter was very good. A fairly good
reduction of suspended solids was also obtained. At the low F/M-ratios used
in this study nitrification took place. The data are not consistent, but it
is assumed that some of the nitrogen was used for cell synthesis, and that
some was removed by nitrification/denitrification due to the batch operation
of the activated sludge process.
                                     848

-------
     The previous pilot-scale experiments have shown that the alkalinity and
the phosphorus concentration determines the required chemical addition for
phosphorus removal. Table 2 shows that the alkalinity was reduced, but only
with 33% on an average basis. However, the removal of phosphorus was
excellent. The removal of particulate phosphorus can be attributed to the
reduction in suspended solids. The extremely low concentration of soluble
phosphorus may have been caused by precipitation, due to the fraction of
chemical sludge in the sludge mixture.

                               ACKNOWLEDGEMENT

     The author wants to thank Mr. B. Paulsrud, Mr. R. Storhaug,
Dr. A.S. Eikum and Dr. H. Brattebo for their contributions, by permitting
the author to use their material in the preparation of this paper.
                                 REFERENCES

 1.   Paulsrud,  B.  and Langeland,  G.   Aerobic,  thermophilic digestion of pre-
     thickened  sludge using air.  Paper presented at COST 68-seminar, New
     Developments  in Processing of Sludges and Slurries, RIVM,  Bilthoven,
     April  21,  1985.

 2.   Paulsrud,  B.  et al.   Tilf0rsel  av septikslam til  VEAS-tunnelen. Project
     3684,  Aquateam,  Norwegian Water Technology Centre A/S,  1984.   48 pp.

 3.   Paulsrud,  B.   Mobilt avvanningsutstyr for septikslam  Utpreving av
     MOOS-KSA-system.  Project  4284,  Aquateam,  Norwegian Water Technology
     Centre A/S, 1985.  28 pp.                                         9*

 4.   Bratteb0,  H.   Phosphorus  removal  from wastewater  by fixed-bed  adsorp-
     tion on granular  activated alumina.   Ph.D.-thesis,  The  University of
     Trondheim, 1983.

 5.   Brattebo,  H.   Phosphorus  removal  from wastewater  by the use of granular
     activated  alumina. Paper  presented at Int.  Conf.  on Management Strate-
     gies for Phosphorus  in the Environment, Lisbon, July 1-4.

6.   Brattebo, H. et al.   Rensing  av av!0psvann  ved spredt bebyggelse.
     Fosforfjerning ved adsorpsjon pa  aktivert  alumina.   Report no.  STF  21
    A84080, SINTEF, Trondheim, 1984.  43 pp.

7.  Paulsrud,  B.   Driftsoppf01ging av BIOVAC renseanlegg  for helarsboliger.
     VA-report 16/84, Norwegian  Institute for Water Research, 1984.
                                    849

-------
 8.  Eikum, A. S. et al. BIOVAC husanlegg  Fjerning av fosfor og organisk
     stoff i avlep fra enkelthus. Project 1084, Aquateam, Norwegian Water
     Technology Centre A/S, 1985.  36 pp.

 9.  Rusten, B.  Wastewater treatment with aerated submerged biological
     filters. J.  Water Pollut. Control Fed.   56: 424, 1984.

10.  Rusten, B. and Thorvaldsen,  G.  Treatment of food-industry effluents 
     Activated sludge versus aerated submerged biological filters. Env.
     Techn. Letters,   4: 441,  1983.

11.  Rusten, B.  Treatment of septic sludge filtrate in rotating biological
     contactors.  In:  Proceedings of the Second Intern. Conf. on Fixed-Film
     Biological Processes,  Arlington, Virginia, July 10-12, 1984.

12.  Storhaug, R.  Separat behandling av slamvann fra avvanning av septik-
     slam  Biologisk rensing med aktivslam.  Prosjektraport 14/84, NTNF
     Program for VAR-teknikk,  1984.   54 pp.

13.  Paulsrud, B.  Full-scale demonstration of separate treatment of sludge
     liquor. In preparation.
                                     850

-------
RESEARCH AND DEVELOPMENT IN DOMESTIC WASTE WATER TREATMENT
                     IN THE UK, 1985

                            by
                  Staff of WRC Processes
                  Water Research Centre
                        Elder Way
                     Stevenage, Herts
                      United Kingdom
             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.
      North Atlantic Treaty Organization/Committee on the
      Challenges of Modern Society (NATO/CCMS) Conference
                 on Sewage Treatment Technology

                     October 15-16, 1985
                       Cincinnati, Ohio
                               851

-------
                          LOPMEM1 JN DOMESTIC WASTE WAI
                               IN THE UK. 1985
                by:  Staff of WRc Processes
                     Water Research Centre
                     Elder Way
                     Stevenage, Herts
                     SGI 1TH
                     United Kingdom


                                  ABSTRACT

     Research  in  the UK  Water  Research  Centre  in wastewater  treatment
include  studies  on  sewage  treatment,  biological  sludge  treatment  and
handling,  operational  aids  and  management  aids.    Research  in  sewage
treatment  features   studies  on   optimising  aeration   efficiency,   both
fine-bubble  and  mechanical  surface  aeration,  energy  saving  in  sewage
pumping, the CAPTOR   process, nitrification in a  biological  fluidised bed,
anaerobic  treatment   of  sewage, a modified  rotating biological  contactor
system, and biological filtration  of  finely screened sewage.   Highlights of
the research in biological  sludge  treatment and handling include studies of
aerobic  digestion of sludge,  submerged  combustion  of  digester gas  for
prepasteurization  of  sludge,  digester   gas   utilisation,   consolidation
thickening  filter  pressing  control,  oil  from  sludge  and  instrumental
analyses of biogas.   In operational aids,  the  research  includes studies on
desludging of  sedimentation  tanks, management  of  small  dispersed unmanned
plants and maintenance simulation  studies.   The research in management aids
include  studies on  per  capita sewage load  assessment,  cost  performance
indices and field evaluation of instruments.
                                     852

-------
                               1. INTRODUCriON

     This paper  provides a summary of  the current state of R  & D Projects
being undertaken at  the UK's Water Research Centre  Processes  Laboratory in
Stevenage  together  with  an  overview  of  relevant  research  in  British
Universities.

     1.  Brief introduction
     2.  Sewage treatment
     3.  Biological sludge treatment and handling
     4.  Operational aids
     5.  Management aids
     6.  Research in British Universities  (Appendix)


                            2. SEWAGE TREATMENT

2.1  OPTIMISATION OF FINE-BUBBLE AERATION

     Since the last NATO/CCMS meeting this project has been completed.  The
object of the project was to improve the efficiency of oxygen utilisation in
conventional fine-bubble diffused aeration sewage treatment plant (STP) and
to achieve  nitrification of the  treated waste.  The  project  was funded by
the Water Research  Centre,  the UK Department  of Energy,  the US EPA and the
Canadian Department of the Environment with assistance from the Thames Water
Authority.    The work  was  carried out  on  the  Thames Water  Authority's
full-scale STP at Rye Meads.

     Aeration tanks  have been modified by the installation of an optimised
diffuser  layout  and DO  control system  to  achieve  and maintain a 50%
improvement  in aeration efficiency compared to similar unmodified tanks.

     Results  have  indicated that the  production  of a high quality,   fully
nitrified  effluent  may  be  no  more  expensive  than  the  production  of
non-nitrified effluents if the costs of surplus sludge  disposal are  taken
into  account.   The optimisation of  the  aeration  tank layout  and the
installation  of  a  DO control  system  also  allows a  greater  flow  rate of
sewage per unit tank volume to be treated, thereby reducing the capital cost
of new plants.

     A general procedure for the design of efficient activated sludge plants
has  been established and published as  a replication guide.   Optimisation
projects are currently  in progress at about fifteen large activated sludge
plants in the UK.

     A cost-benefit study has been carried out by the Thames Water Authority
on the  "Net Present Value" of  the energy which can be saved by  introducing
this  system  into  all   fine-bubble  sewage   treatment  plants  of  >10,000
population: the NPV  (using a discount rate of  5% and plant life of 20 years)
was  16 million  (about $22.5  million)   (and roughly 35  million  or $50
million for  the UK).
                                      853

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     The  success  of this  project  has led  to the establishment  of  another
project, the Optimisation of Mechanical Aeration (see below).

2.2  OPTIMISATION OF MECHANICAL SURFACE AERATION

     A  survey  of  the  aeration efficiencies achieved  at  large activated
sludge  plants  in  the  UK  have  revealed  that  diffused-air  systems  are
potentially more  efficient than surface aeration systems  when installed in
processes designed  to produce fully  nitrified  effluents.    However,  it has
been found that mechanical surface aeration systems may be more efficient in
non-nitrifying processes.

     The  same  general  principles  of optimisation  of  aeration  efficiency
should apply to surface aeration systems as well as diffused-air systems and
there  is potential  for  considerable energy savings to  be made at large
installations.

     Accordingly  a  full-scale  project has recently been initiated  at the
Blackburn  Meadows   STP  of  the  Yorkshire  Water   Authority  to  develop
improvements in surface  aeration efficiency.  One of the primary objectives
of  the  project is to assess the performance  of several different dissolved
oxygen  control mechanisms  which may be used separately or in combination to
vary the oxygenation capacity of surface aerators.  These mechanisms include
on-off  switching of  individual  aerators,  controlling  aerator  speed and
adjusting the depth of immersion of aerators  in the aeration tank (1).

     Equipment for  this  project is  being ordered this month and the project
itself will be commencing  in early 1986.

2.3  ENERGY SAVING  IN SEWAGE PUMPING

     This project was reported in the UK paper at the NATO/CCMS Conference
in  1983.   Since  then  the work  has been  completed with  the satisfactory
demonstration  that  savings can be  made by modifications  in the design and
operation of  sewage pumping stations.   The  project examined two different
installations, one  small and one medium  sized.

     The first,  at  a small rural  pumping  station,  showed  that  80% of the
flow  could  be delivered  at pipe  velocities  of  0.4  metres/second, provided
the remainder  is  delivered  in  excess  of  0.9  m/s,  without problems of
deposition or  slime growth in  the pipeline.   The  recommended minimum pimping
velocity for  a  single  rate  pumping  system  is  0.76  m/s.   Savings due to
reduced friction head exceeded 25%  on a  bill  of 1,600  ($2,200) annually.

     At a larger urban pumping station,  a microprocessor was used to  control
the pumps according to a  flow-balancing algorithm,  this saved energy  equal
to  3,200 pa  ($4,500) and increased the use of night-time, off-peak energy
to  make  a  total  saving  of  5,000  pa  ($7,000)  on a bill  of  35,000 pa
 ($50,000 or  about 14%).   The experimental system is now being replaced by  a
permanent system  by the Wessex Water Authority.   The Water Research Centre
is  negotiating to  license the FLOBAL control  software for inclusion  in  a
commercial computerized  pump controller.  Work  is under way  to extend the

                                      854

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algorithm to optimise pimping against a tidally varying head (2).

     As an  additional  aid to  design  engineers a computer  program has been
developed to help  to  optimise  the selection of  pumps for  sewage pumping
stations.   The  program will perform all the  necessary calculations to size
the  pumps  for  a specified  duty,  and  it  then  selects the pump  with  the
optimum efficiency  from a  pump data-base.   The program  uses inter-active
graphics and produces  hard copy of  pump curves and the selected design data
for inclusion in procurement specifications.

2.4. THE "CAPTOR" PROCESS

     The  project  was  reported  in detail  in  the 1983  NATO/CCMS paper,  and
details of  the process  have been  given elsewhere  (3,  4).  It  is a joint
project with funding from the  Water Research  Centre, the Severn-Trent Water
Authority   (STWA),  Simon-Hartley Limited,  the  UK  Department  of  Trade  &
Industry and the US EPA.

     The  current   objective   of the   project  is  to  evaluate  a  CAPTOR
installation  at  the  Severn-Trent  Water  Authority's  full-scale  STP  at
Freehold.    The  CAPTOR installation   (Figure  1)   is  being  used  as  a
pre-treatment stage to reduce  a substantial  proportion of the BOD load so
that the  subsequent activated  sludge stage can be  operated with a greater
sludge age  and thus achieve nitrification.

     So  far about  50% removal  of  dissolved  BOD  has been  achieved in the
initial CAPTOR stage but it  has been found that a significant proportion of
the  biomass in the CAPTOR  sponge-particles disengages and passes  forwards
into  the   activated  sludge  stage  thus  reducing  sludge  age  and  the
concentration of nitrifiers.

     The  CAPTOR   process  enables  us  to  double   the  activated  sludge
concentration in  the  aeration stage  but laboratory evidence suggests that
the activity is only about 50%  of  non-captured sludge.  The nett effect is
therefore relatively little different from  conventional AS  systems.

     Pilot-scale  work  has  been started  since the last  report  with  the
objectives  of examining

(i)  the use of CAPTOR sponge  particles to enhance biomass  concentration in
     the secondary process; and

(ii) the  use   of  CAPTOR   sponge   particles  as   a  tertiary  stage  for
     nitrification which currently  looks premising.
                                     855

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                                                               EFFLUENT
                                 NITRIFICATION
                                                               EFFLUENT
                                                       	I
                                    RETURN SLUDGE
     Figure 1.  Diagram of the arrangements made at
                Freehold WRW to uprate  the activated
                sludge plant using CAPTOR and allow
                its evaluation.
2.5  NITRIFICATION OF A SECONDARY SEWAGE EFFLUENT IN A BIOLOGICAL
     FLUIDISED BED (BFB)

     The intention to establish a plant at  the Horley  Works of the Thames
Water  Authority  was  reported  in  the  1983  NATO/CCMS  paper  following
small-scale tests by the Authority at its Beckton STP.  This work indicated
that  it  was  possible to remove  about  30  mg NH3-N/1  in a  reactor  with a
retention time of 35 minutes.

     The process has  recently been tested on a much larger scale in a  joint
development project  with  the  Water Research Centre,  Thames Water Authority
and Dorr-Oliver Ltd  at the  Horley Sewage Treatment Works (South of London)
of the Thames Water Authority.   The pilot plant (1.83 m x  1.22  m x  5.4 m
high) had  previously been used in carbonaceous oxidation and  nitrification
tests at the Water  Research  Centre's  former  Coleshill Experimental  Site.
The pilot plant layout is shown in Figure 2.

     The plant  has been operated at three different  ammonia  loading  rates
for  extended periods  to determine  the optimum  performance.    During  the
latter part of 1985 the plant  will be operated  over a diurnal  flow pattern.

     The results  of  the plant performance  at the design flow  rate is  shown
in Table 1.   It has  not  been found necessary  to sand  clean when operating
under nitrifying conditions.
                                     856

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                                                  NITRIFIED EFFLUENT
                                                 	4f	
I
                                    EFFLUENT
                                         FEED-f-RECYCLE
                                              >-
       FEED
co

                                                                                                 NITRIFYING

                                                                                                    BFB
                                                                     ////////////^^^
                                                            ^ BELOW GROUND

                                                               OXYGENATOR
                  Figure 2.   Flow sheet for the nitrifying BFB at Horley  STW.

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           TABLE 1.   PERFORMANCE OF NITRIFYING BFB AT HORLEY SOW
                      (AVERAGE VALUES FOR THE PERIOD)
       Operational conditions

       Feed flow                         370 m3/d  (1700 pe)
       Bed volume                        9.8 m3
       Superficial HRT                   38 rain
       Biomass concentration             8.1 g BTS/1
       Temperature                       17.9QC
       Run length                        69 d

       Performance
                                                         Effluent
       BOD5      mg/l                    18                12
       NH3.N     mg/l                    27                 3
       SS        mg/l                    30                23
       pH value  mg/l                     6.8               6.1

       Loading and removal rates

       BOD loading rate                  0.084 kg BODAg BTS.d
       NH3-N removal rate                0.112 kg NH3~NAg BTS.d
       NH3-N removal rate                0.91 kg NHs-N/m3.d
     The work  has shown the process  is feasible on  a larger scale.   Cost
evaluations done during the project have shown that the BFB has a much lower
(60% less)  capital cost than a comparable activated sludge extension but the
operating cost  is higher because of the  cost  of  oxygen.   The BFB  is about
10% lower in total cost  using DCF  analysis,  but is sensitive to the cost of
oxygen (5).

2.6. ANAEROBIC TREATMENT OF SEWAGE

     Fermentation  using  anaerobic  (methane-forming)  bacteria  to  convert
oxygen demand  to methane  has  proved successful  for  the treatment  of food
processing and agricultural wastes.

     Following  pioneering  studies  in Holland  (6)  using enrichment cultures
of methane bacteria  at 12-20C and laboratory  trials  at  the Water Research
Centre  (7)  using digested sewage  sludges at 20OC, pilot-scale  trials were
initiated  to  determine  the  performance of   the  process  at  UK  ambient
temperatures.

     A  30  m3  capacity  UASB   reactor  was  constructed  at  the  Stevenage
Laboratory   by  converting  an  existing  sewage  storage   tank;   it  was
commissioned  in  Spring  1984  and  fed  continuously  with  settled  domestic
sewage.

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     We   had   operational   problems  with   the   design   of   the   gas
collection/sludge  settlement  system  (which  does  not allow free  passage of
settled solids back to the fermentation zone)  and with the low methanogenic
activities  of  the  digested  sewage  sludges  used  for  inoculation,  but
otherwise  the mechanical  and  hydraulic   performance  of  the plant  proved
satisfactory and entirely trouble-free.

     The  level  of BOD  reduction  was disappointing and appeared  to  be
severely limited by the  relatively  low temperatures of the incoming sewage.
During the  summer  and autumn of 1984  purification  efficiencies  were 27-46%
at  hydraulic  retention  times of  12-48  hours and  sewage temperatures  of
15-20OC.   During the winter  of  1984/85,   sewage  temperatures fell to lOoc,
fermentation ceased and purification efficiencies fell to zero.

     The  reactor  was reinoculated  with digested sludge  in  the  simmer and
trials will continue until December 1985.

2.7  MDDIFIED ROTATING BIOLOGICAL CONTACTOR  (RBC)  SYSTEM

     Problems  have been encountered in  RBC plants - especially  on small
flows -  as a  result  of  uneven growth  of biomass on  the  discs.   The Water
Research Centre  developed  a technique for overcoming  this problem which is
currently the subject of a patent application.

     A joint project has been established between the Water Research Centre,
the Wessex  Water Authority and Dewplan  (ET) Ltd to develop, construct and
evaluate  a  prototype WRc RBC  on  a  Wessex Water  Authority  site.    The
operation  of  the  prototype  commenced during  the  first  quarter  of  1985.
There were  initial mechanical problems to be  overcome and although soluble
BOD is satisfactorily removed the  unit's  mode of  operation tends to cause a
higher level  of solids  to appear  in the  treated effluent.   These problems
are being currently addressed.

2.8  BIOLOGICAL FILTRATION OF FINELY-SCREENED SEWAGE
     (THE "LOSLUJ"  PROCESS)

     The cost  of sludge  treatment  and disposal in the UK is  typically about
45% of  the total  cost  of  running a  sewage  treatment works.   One approach
towards  reducing  this  cost  is  to  thicken  sludge  prior  to treatment and
disposal.  An alternative approach is to modify sewage treatment in order to
produce  less sludge.   About two thirds  of  the total sludge production is
derived  from primary  sedimentation, and  if  this stage  could be eliminated
total sludge production could be reduced provided the  settleable solids were
biologically  oxidised  in the  secondary treatment stage.  This  approach is
not  economically  attractive  in  activated  sludge  plants  because of  the
increased energy consumption required to oxidise the additional solids load.
However,  in biological  filtration plants  the  oxygen consumed in destroying
the solids is provided by natural convection at no cost.

     The  operating costs  of  this biological  filtration  treatment  show a
reduction   of   approximately  45%  compared  with   traditional  biological
                                     859

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filtration.  In this method sewage is finely screened (about 1.5 ram aperture
size) to remove large particles before  being  treated in a filter containing
a specially developed high voidage plastic medium.   The screened sewage is
discharged to the filter via  a self-cleaning  distributor (also developed by
WRc).  Final clarification takes place in a conventional humus tank.

This  method has  been  successfully  demonstrated  on  a  large pilot  scale
installation which showed  that total sludge production was  reduced by 45%.
Estimates of costs for  a typical  works  of 5,000 population indicate savings
of about 30% for capital and 20% for operating costs.

     A  full-scale  installation is under  construction  for the Welsh  Water
Authority and two further plants are being designed.

2.9  THE SEWAGE TREATMENT OPTIMISATION MODEL (STOM)

     The UK water authorities spend  around 150M pa to construct and extend
sewage  treatment works, and  about 300M pa  on operating the works.   STOM
provides these water authorities with a means to:

a)   assess  the  performance  of   existing works,   to  allow  any  remedial
     measures to be  targetted more effectively  on  those works and processes
     which are in need of improvement,

b)   check  the  effectiveness  and  costs of proposed  extensions  or complete
     new  works,  so  that  satisfactory  performance  is  achieved  without
     over-design,

c)   predict the effects of long-term trends in operating conditions so that
     a  view can be  taken of  the plant's  future  capability and  any  plant
     changes can be planned well in advance.

     The Sewage  Treatment Optimisation  Model  (STOM) is  a complex computer
program developed  by the Water Research Centre following an  initiative by
the British Construction Industry Research & Information Association, and is
now   in routine   use   by  the  UK   water undertakings,  consultants  and
universities.  It offers a flexible means of modelling performance and costs
for  groups of  processes  at  sewage works. The model contains  modules for
individual  treatment   processes   such   as   activated  sludge,   biological
filtration, anaerobic digestion, and auxiliary processes  such as flow mixing
and  division.    Each module   relates performance  and  costs to  design and
operation; most  of the common processes are included.   The user links the
corresponding modules together to  represent a complete works.

     The model  is  under continuous  development  involving both the addition
of  modules  for further   processes  and  enhancement  of  existing modules.
Models  for  some processes  have yet to be included  (e.g.  rotating biological
contactors and tertiary treatment).   Currently  a module for the performance
of  tertiary rapid sand filtration,  prepared in co-operation with Imperial
College, London, is  being evaluated for eventual inclusion in the model.
                                     860

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     The standard capital and operating costs in STOM are updated from their
1976 base  by  government cost indices, although the  user  can substitute his
own costs.  The cost indices do  not  take into account changes in operating
and maintenance practices since 1976  (e.g. the replacement of resident staff
by  mobile  gangs).    A detailed manual  containing  all  the formulae  and
parameters used in the model has also been prepared.
               3.    BIOLOGICAL SLUDGE TREATMENT AND HANDLING

3.1  AEROBIC DIGESTION OF SLUDGE

     When  aerobic conditions  are maintained  in sewage  sludge,  exothermic
reactions  take  place  and the temperature of the sludge  can rise to 55OC or
higher  in a  well lagged  tank.   This  increase in  temperature offers  an
opportunity to  reduce  the  retention times required  to achieve stabilisation
and/or to achieve a disinfection.

     Successful  aerobic  digestion using pure  oxygen  and subsequently using
air was reported in the  1983  NATO/CCMS paper.   Costs when using oxygen were
unacceptably high, but further work showed that the  process was viable and
economically attractive  when air was used to maintain  aerobic conditions.
It has been established that the layer of foam which builds up on top of the
sludge  is critical in achieving very high oxygen  utilisation efficiencies
from air  and  recent  work has concentrated upon  more  detailed evaluation of
foam management  techniques.    Economic  comparisons  show that  the process
could  be   competitive  with alternative  methods  of pre-treatment  prior  to
anaerobic digestion for  producing a  disinfected  sludge should this prove to
be necessary.

     The next stage of this project  will consist of a joint evaluation of a
technique developed in Switzerland in which aerobic digestion is followed by
anaerobic  digestion.   This technique  appears  to produce a sludge  in which
all pathogens have been killed or deactivated and which readily consolidates
to thicknesses of 8-10%.

3.2  SUBMERGED COMBUSTION OF DIGESTER GAS FOR PRE-PASTEURISATION
     OF SLUDGE

     An alternative method to aerobic digestion of achieving a disinfected
and  stable sludge  is  to pre-heat  the  sludge  to about  65C by burning
digester  gas  in  a submerged  combustion device.   The  hot sludge  is then
cooled and anaerobically digested at about 35C.

     The  joint   project  reported  in the 1983 NATO/CCMS paper encountered
problems  with  the submerged combustion  equipment  and this  resulted  in
delays.   These  were eventually  overcome and sufficient  data were obtained
for  the  design  of  a  full-scale  system.     The  full-scale  (20,000  pop)
demonstration   plant   comprising   automatic    primary   tank   desludging,
consolidation  thickening,  submerged   combustion  pre-pasteurisation,  and
mesophilic anaerobic digestion has now been designed  and is currently being
installed in the north of England.

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     Commissioning will be completed in  the first quarter of 1986 when a 12
month   intensive   monitoring  programme   of  the  plant  performance  and
microbiological quality of the sludge will commence.

3.3  DIGESTER GAS UTILISATION

     A  survey  of  digester  gas utilisation in  the  UK  has recently been
completed which shows that of  the 1.4 million tonnes dry  solids of sewage
sludge produced each year in the UK, about 50% is anaerobically digested and
produces  about 250  x 106 m3  of  gas  with  an  energy value of  about IQlO
Joules.  This  is less than 0.1% of all UK energy needs,  but is about 30% of
the energy consumption of the UK water industry.

     About 30%  of digester gas  is  used for digester heating and 50% is used
to generate  electrical power for  use  in sewage  works, mainly  in dual-fuel
engines on  large  works.  Waste heat from  the  engines is  used  to heat the
digesters.

     Minor uses for digester gas  include use as a road  vehicle fuel 1%)
but  this is not  an economic  proposition.   Before  use  the  gas  must  be
scrubbed to  remove corrosive sulphides and then compressed.

     About 40 x 106 m3 of digester gas is unused each year, mostly on sewage
works  in the  size  range 10,000 - 100,000  population,  and there  has been
significant  interest recently  in  installing small packaged spark-ignition
engines for  combined heat and power generation in these works.  Case studies
at a small  works  (10,000 pop)  and  large works  (100,000 pop)  is currently
being  carried  out.    Results  to  date  show that the  economics  are very
doubtful on  works of  10,000  pop or lower, but that at larger sizes of works
considerable savings can be made.

3.4  CONSOLIDATION THICKENING

     Consolidation  under gravity  can  be a  very cheap  and cost-effective
method  of thickening sludges  in  order  to  reduce the   cost of treatment,
transport and disposal.  A study undertaken by the Water  Research Centre has
indicated that savings  in operating costs  of  15-20M pa  ($20-$30 million)
could be  achieved  in the UK by the planned use of consolidation thickening
of sewage sludges.

     Consolidation  thickening  of  sludges is an  apparently simple  process.
The  sludge  is held  in  a  tank  and  consolidation takes  place  under  the
influence  of  gravity as  the  sludge  is  compressed   under its  own weight
forcing the  interstitial water within the sludge  into the supernatant  liquid
above.   The performance of the  process depends upon a number of factors
including the sludge blanket height,  sludge retention time, the method of
operation  (i.e. batch  or  continuous),  and the design and  operation of
mechanical  aids including picket  fences.   The sludge height and  retention
time,  in  particular,  are  critically dependent upon  the  properties  and
characteristics of  the  particular sludge but  until  now there has been no
reliable method of  relating tank dimensions  and sludge characteristics to
                                     862

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plant performance.  Consequently,  many thickening tanks perform poorly, and
it is not uncommon to see sludge solids floating rather than consolidating.

     Theoretical  and  full-scale  plant studies  have  led  to an  improved
understanding  of  the  fundamental  mechanisms  involved  in  consolidation
thickening.    Consolidation can  be  predicted from  three  easily  measured
sludge  parameters,  the Compression  Coefficient,  Compression  Index and the
Resistance  to  Consolidation which can be  measured in  the laboratory using
specially developed procedures.

     A  mathematical  model  programmed  into a  computer  handles the data to
produce  performance curves showing  how sludge  blanket height  and sludge
retention  time affect  the solids  concentration in  the output  sludge.   A
family  of  curves  is produced  depending on  the mode  of operation  of the
thickener,  i.e.  batch or  continuous.   These  performance  curves  enable the
engineer to select with confidence an appropriate combination of the sludge
blanket height,  tank  diameter and method of  operation  to give the required
performance.

     Picket fences  and effective process control  are essential for optimum
performance and further  experimental work  has shown  how these components
should  be designed and operated.

     This design procedure has already been used to produce process designs
and plant  specifications  for  a wide range of  sludges, and in most  cases the
size and shape of thickener has been suitable  for prefabricated construction
methods using steel  tanks.   Several  full-scale demonstration  plants are
being installed and the first to come  on-line  was commissioned early in 1985
and produces a thickened  sludge  of about 12% solids from a primary sludge
feed of about 4% solids.

3.5  FILTER PRESSING CONTROL

     The  1983  NATO/CCMS paper described a  co-operative project between the:
Severn-Trent Water Authority  and the Water Research Centre which had as its
objective  the  automation and optimisation  of  sludge filter-pressing.  This;
project is  now  nearing  completion and a study  has  shown that  potential
savings in  the UK are in the region of 5M.

     About  30% of UK sludge is chemically conditioned and dewatered, mostly
in  filter  plate presses.   The  operating cost  is  about  25M pa and the
process is  expensive, the major elements of cost being  chemicals and labour,
which each  account for  nearly 50% of total  operating  costs.

     The   microprocessor-based  process  control   system  which  has  been
developed has achieved  a reduction in  the costs of both labour and  chemicals
of  about  50%  on  the  full-scale  installation at  the  Severn-Trent Water
Authority's Mansfield STP.
                                     863

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     The essential features of this system are:

     -  Accurate  and  efficient chemical dosing  over the wide  variation in
        sludge flow rate that occurs during the pressing cycle.

     -  Control  of  press  feed  pumps  to  achieve  and  maintain  optimum
        conditions throughout the press cycle.

     -  Continuous  monitoring  of  cake  quality  and  termination  of  the
        pressing cycle when adequate product quality has been achieved.

Chemical conditioning and filter  pressing  are thereby made very competitive
with  other  sludge treatment  and  disposal  routes.   The  process management
system  is  now commercially available  and  it is being  installed at several
other sites.

3.6  OIL FROM SLUDGE

     The  UK water  industry  currently operates a well  managed  system of
sludge  treatment  and  disposal   that  takes  due  account of  envirormental
protection.   However,  looking  to the long-term future it  is  essential to
consider alternative  sludge treatment  and  disposal routes that could either
be cheaper  than  current methods or  could meet new targets for environmental
constraints in the most cost effective manner.

     Against  this background the  Water  Research Centre  is  evaluating  a
number  of Long  Term  Options  for alternative sewage sludge treatment and
disposal routes.  Any  radical alternative  approach is likely to be economic
only  if  some  of  the  resource-value  of  sludge can  be  offset  against
processing  costs.  Any financial  value a  raw sludge may have is associated
mostly  with  its fat  and protein  content  and  there  are  many strategies
available for  tapping this resource.   A preliminary  desk study showed that
thermochemical  processing  of  sludges  to  produce  fuels  was potentially
attractive, and that slow pyrolysis was amongst the processes that warranted
further investigation.

     Professor Bayer  in Germany  has  already  shown that  it is technically
possible to convert by pyrolysis much of the organic matter  in  sewage sludge
to  oil  and char  with  both  products having potential value as  a fuel.
Comprehensive  process  design  and  economic  studies  have recently  been
completed  of  a pyrolysis route for both  raw  and  digested sludges using UK
cost data.

     The  process flow  sheet  is  potentially complex  (see Figure 3)  and a
process  model  has been  developed to  study the  interaction  between the
various  process  stages,  and to  evaluate  the  numerous  options for heat
recovery within the process route.

     These  studies indicate that  the  process could be very  competitive with
incineration  (see Figure 4) but it  is  important  to note that the capital and
operating costs  of the pyrolysis  stage are only a  small fraction  (less than
10%) of the total route costs, and therefore  the economical  viability of the


                                     864

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        AIBOPMTRE
       CONDFNSATE TO PRIMARY
        SEOIHENfAION TANKS
                                                                                                                                       MAIER-tFFLUENI
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              CHAR FOR STORAGE

            DISTRieuriON/OlSPOSAL
                                                                                                                                       SUPPLfnENIARY
                                                                                                                                      NATURAL GAS/IP6
Figure 3
                                Draft process flow  diagram  for the  pyrolytic  processing  of
                                anaerobically digested sewage  sludge.

-------
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process  lies  in  optimising the  total  route  and not  simply  concentrating
effort upon the  reactor design.   Route costs  are critically dependent upon
the following:

(i)   Process route energy demand.

      Critical areas  are the  energy required for  drying and  the measures
      taken for  heat  recovery between  the various process  stages.   The
      energy for drying depends upon the  performance of the pre-thickening,
      dewatering and drying stages.

(ii)  Anaerobic digestion.

      Whilst the quantity of oil  produced from  raw sludge is substantially
      greater than that produced from digested sludge a desk study has shown
      that this advantage is more than offset by the greater on-site costs
      of processing raw sludge.   This is due, in part,  to the reduction in
      quantity of sludge  solids passing forward  for processing, and hence a
      reduction in capital cost of downstream plant.  There are also savings
      in  fuel  costs   due   to the  reduced  load  on  the  drying  stage.
      Furthermore,  the  inclusion  of   anaerobic   digestion  considerably
      increases the scope  for cost-effective recovery  of low grade heat,
      which further reduces the need to burn primary fuel.

(iii) The value of the pyrolytic oil produced.

     The  studies  being  carried   out by the Water  Research Centre  are
complementary  to the  work  being undertaken  at the Wastewater Technology
Centre in Burlington  Ontario with whom there  has been regular contact.   It
is  hoped  that  these  contacts  will  be  strengthened  into  more  formal
arrangements for collaboration.

3.7  INSTRUMENTAL ANALYSIS OF BIOGAS

     Studies are being undertaken to develop new and improved strategies for
the  monitoring and control of the anaerobic digestion process,  based on
detailed analysis of the composition of the biogas produced.

     Theoretical  (mathematical modelling)  studies  of  the microbial ecology
of  the fermentation (8)  identified  hydrogen  (H2) as a  key intermediate in
the  conversion of organic matter  to methane and trials are now in progress
to  determine  whether  on-line monitoring of H2  in biogas  can be  used to
detect small  fluctuations  in the performance  of  the  anaerobic digestion
process.

     Typical  concentrations of hydrogen  in the biogas  from  sewage sludge
digesters are 36-220 vpm  (parts per million by volume (average 73 vrjn).

     At one particular  works,  a comparison was made between the start-up of
two   identical   new   digesters.      Late  modifications   and  last-minute
"teething-troubles"  during  the  commission  of  one  digester  caused  the
                                     867

-------
concentration of hydrogen in the biogas to  rise  to 240 vpm before settling
down  to  a  baseline  value  of  60  vpm.    In  the  other  digester,  the
modifications were  completed before commissioning  and  the concentration of
hydrogen in the biogas remained at 40 - 80 vpm throughout.

     The extreme sensitivity of the analysis can be seen from Figure 5 which
shows  the changes  in  hydrogen content  of  the  biogas  from  one  of these
digesters during its hourly feeding cycle (9).


                            4. OPERATIONAL AIDS

4.1  DESLUDGING OF SEDIMENTATION TANKS

     In  order to  reduce significantly  the  frequency  of visits  by mobile
gangs to unmanned sewage  treatment works, automatic control of sedimentation
tank desludging is  essential.   Following extensive field trials carried out
in  association with  the Thames and Anglian Water Authorities  it has been
established  that  simple timer-only control  is  rarely satisfactory since it
results in blockages or  in the production of very thin sludges.

     Using existing equipment a microprocessor based control system has been
developed which has been used satisfactorily over  many months.   Control is
achieved  by  a combination of timing and monitoring of sludge blanket level
in  the tanks.

     As a result  of this work, a  commercial unit has been developed and is
undergoing field trials.   This  unit offers a choice of desludging pumps and
a range of  sensing  devices to deal with most situations likely to be met on
small to medium sized works  (less than 10,000 population equivalent).

4.2 MANAGEMENT OF SMALL DISPERSED UNMANNED STP

     Following a  joint  study undertaken by  the Water  Research  Centre with
the Anglian  Water  Authority to develop  an ICA based operating strategy for
some  150  sewage  pumping  stations and 50 treatment works, it was decided to
implement  the proposed  scheme  on  a pilot scale  before proceeding with the
full scheme.

     The  pilot scheme has  now  been completed and  encompasses a biological
treatment  works,  an oxidation  ditch treatment works and a pumping  station
each   equipped with  micro-processor  based  outstations  and  appropriate
Instrumentation,  Control &  Automation  (ICA) equipment and connected via  a
telemetry network  (representative of that proposed  for  the  full scheme) to  a
master-station at  the Central Operations Room.   The master station  is based
upon  a DEC LSIll/23  computer but nevertheless has software which provides
full  management  information  facilities.    Data  and  operating experience
collected from the  pilot system is now being used  for  the  final designs for
the full-scale scheme.

     The  results obtained will  be used in a  Guideline for the  development of
a process management  system for dispersed works.

                                     868

-------
c
o-i
ID
                           mixing
feed
mixing
feed
                                               100             105

                                                  Hme (hours)
                                 110
                                    115
              Figure 5.   Variations  in the concentration of hydrogen  in  the headspace

                         gas  during  the feed cycle of an anaerobic  sludge digester.

-------
4.3  MAINTENANCE SIMULATION STUDIES

     The study described  in section 4.2 and the  resulting pilot evaluation
have provided valuable experience in the  selection of operating strategies
for groups of dispersed  works.   However,  the selection  of  an appropriate
maintenance  strategy  is  nearly  always left  to  chance.   Following some
success  using a  simulation  technique   (originally  developed  for  study of
production line queueing problems in the motor industry) in the study of the
consequences  of  alternative  operating  strategies  carried   out  with  the
Anglian  Water Authority,  the Water  Research  Centre  is  now  applying  the
technique to the study and optimisation of maintenance  strategies.


                             5. MANAGEMENT AIDS

5.1  PER CAPITA SEWAGE LOAD ASSESSMENT

     There  is  concern in the  UK water  industry about  the accuracy of
available  data on the strength of domestic  sewage and the volume of  sewage
produced per  person since  these  data are used in the calculation of trade
effluent charges.

     In  agreement  with  the  Confederation  of British Industry  (CBI)  the
Mogden formula is used as the basis for charging, viz.


                     C  =  R  +  V  +  S. .Svi  +  B. Q
                                          Ss        Os

  Where

  C  = total charge per cubic metre of trade effluent

  R  = reception and conveyance charge per cubic metre

  V  = volumetric and primary treatment cost per cubic  metre

  S  = treatment  and disposal costs  of  primary sludges per  cubic metre of
       sewage

  Sw = suspended solids content of trade effluent

  Ss = suspended solids content of crude sewage

  B  = biological oxidation cost per  cubic metre of settled sewage

  Ow = COD of trade effluent  after settlement

  Os = COD of settled  sewage
                                     870

-------
     In response to this concern, the Water Research Centre is undertaking a
project to  assess the contribution  per  head of population to  the flow and
strength  of  domestic sewage.    The  project  will provide  the  necessary
up-to-date  information to  enable the water authorities to  set  firmly based
and readily defensible trade effluent charges.

     The  data generated by  the project  will also be  useful  to  the water
authorities in connection with performance measurement.

     The  project,  which  is due to  start in  the third  quarter  of 1985,
consists of a scheduled programme  of sampling and analysis, over a 12 month
period, of  sewage frcm a  residential catchment which  is  entirely domestic
except  for  a small number of  retail shops.   The  sewer frcm the catchment
passes  under  the Water Research Centre's  Stevenage  site.    Flow measuring
facilities  have  been  installed to permit flow  related  analysis.   The study
will cover diurnal, hebdomadal and seasonal variations in flow and strength.
The  sewerage  system  is  a  separate  one  and will  permit  the  study  of the
effects of  storm flows and of infiltration.   The catchment is well defined
and  accurate  population  figures are  available.    Demographic  data  are
available frcm census returns and these will be used for data analysis.

     The  variables being  determined  include BOD,  COD,  suspended matter,
settleable  matter,   total  organic   carbon,   ammonia,   Kjeldahl  nitrogen,
nitrite, nitrate, orthophosphate and chloride.

     A  similar  study  was  carried out on the same sewer in 1956-57 and thus
it will be possible  to  see what  changes have occurred during the 29-year
intervening period.

5.2  COST PERFORMANCE INDICES STUDY

     A  useful management  tool  is the setting of  performance  targets.   In
wastewater  treatment  this can  take the  form of  setting  targets  for the
quality  of  the  treated  effluent  and for  the total  running  costs  of the
treatment plant.   The former  is set by  reference  to envirormental quality
objectives, or  - in some countries - by legislation or directive.  Quality
targets  are relatively easy  to set  and monitor since they  can be defined
numerically in  terms  of well established variables (e.g.  concentrations of
BOD, NH3 etc).

     However, operating-cost  targets are more  difficult  to  set.   There is
relatively  little  data available to guide  managers in assessing whether or
not a sewage  treatment plant is  operating as efficiently as it might.  There
are  many  factors which   affect the  operating  cost,  and  similar  plants
treating similar sewage may justifiably  have very different operating costs.
The problem becomes more difficult if the manager has a number of different
types   of   treatment   plant  under  his  control   (e.g.  activated  sludge,
biological  filters,   RBC  etc)  and cannot  therefore compare the  costs of
similar processes.
                                     871

-------
     In an  attempt  to improve efficiency  water  authorities in the  UK have
asked for guidance on target costs for  the operation of treatment plant.   A
co-operative project  has therefore been established by the Water  Research
Centre, involving all ten UK water authorities,  in which operating cost data
are being collected for  the majority of sewage  treatment  plants  in England
and Wales.  These data are  then  collated and analysed making it possible to
produce median costs for plants  of similar types and size.  These data then
allow managers to identify plants whose operating costs lie outside the
norm and then  to evaluate the reasons  for the performance.   Since the data
are held  in a  large  database with facilities for data manipulation  it  is
possible to make individual comparisons between  specified  plants,  groups of
plants,  different  regions,  different  processes  etc.    This  will  enable
managers to set more realistic cost-performance targets.

     A  further  objective of  the project  is to enable the Water  Research
Centre to identify areas of greatest cost and thus to develop R & D projects
with the best potential for savings.   It will also help to identify the most
efficient plants which  can  then be evaluated to provide guidelines for the
operators of other treatment plant.

5.3  FIELD EVALUATION OF INSTRUMENTS

     The 1983  NATO/CCMS paper reported on the development of  this project
which  is designed  to obtain "the cost  of  ownership" of instruments used in
the water  industry and  thus to enable management to ensure that  the best
instruments are  bought  for  any  specified  application.    An  important
criterion is  that  the test fluids and  test environment should be those for
which  the  instruments will normally  be bought  rather  than in a laboratory
environment with clean water as the test fluid.

     Two full-scale test facilities have now been established in the UK with
partial  funding  from  the Department  of Trade  &  Industry.    The  first
Evaluation  and Development Facility  (EOF)  was opened early  in 1985 at the
Witney  STP of  the  Thames Water  Authority.  The second EOF was opened in
early  June at  the Eccup Drinking  Water  Treatment Plant  of  the Yorkshire
Water  Authority.    The  former  EOF   provides  evaluation  facilities  for
instruments for sewage  treatment plant,  whilst the  latter  EOF  will take
instruments intended for use in Drinking Water Plant.

     A careful  testing  and  evaluation protocol has been developed which has
been discussed with a number of  organisations  including the IAWPRC so that
reports  on instruments  tested at  one of the  UK  EDF's may  have validity
internationally.  Already instruments from a number of countries, including
the UK,  have  been  submitted to the Water  Research Centre  for evaluation and
are  currently being  evaluated  under field conditions at the  EOF  for a 12
month  period,  relevant data  being  logged  automatically via  the on-site
computer  system for later off-line analysis  on  the Water Research Centre's
own computer facilities.
                                     872

-------
     A concise report is produced for  each instrument detailing the results
and findings of the evaluation and providing an indication of the total cost
of ownership, taking into account:-

                   accuracy
                   reliability
                   response times
                   maintenance needs
                   calibration
                   cleaning
                   construction
                   ease of use.

     These  reports are  made  available  to potential  users  in the  Water
Industry to  assist them  in equipment selection.   Benefits to manufacturers
include  reference to  reports in  publicity material and  the  feedback  of
valuable field test data to the design and marketability of the instruments.

     In the  first year  of tests, up to  ten instruments are being evaluated
in each of the following categories:

                   activated sludge flow measurement
                   crude sewage flow measurement
                   open channel flow measurement
                   ammonia measurement.

     Evaluation  of DO  measuring  instruments  will  commence shortly  with
further test programmes being  introduced at regular intervals over the next
few years.
                                     873

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T,;./''  v"' ''-'"  '' :;;'"-:   '   "   REFERENCES, .,.

1.   Thomas,  V.K.    Optimisation  of  Aeration  Efficiency  -  internal  WRc
     Report.    Proposals for   Automatic  Control   of  the  Simplex  Plants,
     Blackburn  Meadows S1W, Southern  Division,  Yorkshire Water Authority.
     April 1985.

2.   Hobson,  J.A.    "Energy  Saving:  Pumping  of  Sewage".   Dec, 1982.   WRc
     Report No 189-S.

3.   Atkinson,  B.,  Black,  G.M.  and Pinches,  A.   "The  characteristics of
     solid  supports and  bicmass  support  particles when  used  in fluidised
     beds".     From   "Biological  Fluidised   Bed  Treatment   of   Water  &
  ',  Wastewater", ed. Cooper & Atkinson, pub.  Ellis Horwood Ltd,, 1981, p.75.
!4.   Walker, I. and Austin,  E.   "The use of plastic, porous bicmass supports
  >:in a pseudo-fluidised bed for effluent treatment",  ibid, p.272.

5.   Williams,  S.C.,   Harrington,   D.W.,   Quinn,   J.J.   and  Cooper,   P.F.
     High-rate  nitrification in a biological fluidised bed at Horley  STW.
     Paper  presented  to  the  Metropolitan  and  Southern  Branch  of  the
     Institute  of  Water  Pollution Control,  High  Wycombe,  Bucks.,  21  May,
     1985.

6.   Grin, P.C., Roersma, R.E.  and Lettinga,  G.  "Anaerobic Treatment of Raw
     Sewage at Lower Temperatures".    Proc.  of European  Symp.  on Anaerobic
     Waste Water Treatment  (AWWT), Noordwijkerbout, 1983.

7.   Fernandes,  X.A.,   Cantwell,   A.D.C.  and  Mosey,   F.E.    "Anaerobic
     Biological Treatment of Sewage".   Wat. Pollut. Control, 1985, 84,  (1),
     pp 99-110.

8.   Mosey,  F.E.    "Mathematical  modelling  of  the  anaerobic  digestion
     process:   regulatory   mechanisms   for  the  formation  of  short-chain
     volatile  acids  from glucose".   Water Science and Technology, 1983, 15,
     pp 209-232.

9.   Collins,  L.J., Fernandes, X.A. and  Paskins, A.R.    "Hydrogen  in the
     headspace  gas during start-up of  anaerobic  digesters at Cotton Valley
     Sewage Treatment  Works, Milton  Keynes, 21/11/84 - 3/4/85".  WRc Report
     355-S. April 1985.
                                     874

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                                6. APPENDIX
A  SELECTION   OF  UNIVERSITY  DEPARTMENT   RESEARCH  PROJECTS  RELEVANT  TO
WASTEWATER TREATMENT
institution
University of
London Imperial
College of Science
and Technology
University of Leeds
University  of
Birmingham
Pro-iect description
Risk analysis in planning
and design of wastewater
treatment processes in both
the developed and developing
countries.  Modelling, fore-
casting and real-time control
of wastewater treatment
processes.

Dynamic modelling and design
of waste stabilisation ponds.

Analysis and removal of
herbicides and related
materials in wastewater treat-
ment processes.  Behaviour
of nitrilo triacetic acid in
sewage and sludge treatment
systems.

Design and performance of
rotating biological contactors.

Anaerobic treatment of
high-strength waste water in
a fixed film system.

Use of immobilised whole
cells in the treatment of
domestic and industrial waste-
waters.
Role of extra cellular
poly-saccharides in sludge
flocculation and sludge bulking.

Use of aerated lagoons for
industrial wastewater
treatment.

Stable foams in activated
sludge process.
Flocculation and attachment
in anaerobic systems.
Principal
Researcher

Jowitt, P W
                                                            Lumbers, J P


                                                            Perry,  R
Lumbers, J P


Stentiford, E I



Horan, N J
Tebbutt, THY
                                                             Forster,  C F
                                     875

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Trent Polytechnic
Paisley College
of Technology
University of
Newcastle upon Tyne
University of
Manchester Institute
of Science and
Technology
Loughborough
University of
Technology

University of Surrey
University of York
Degradation of stored
treated and untreated waste-
water prior to its use in
the flushing of household
toilets.

Sludge activity measure-
ments in biological
oxidation of wastewaters.

Mathematical modelling of
the scale-up of aerobic
reactors for wastewater
treatment.

Attachment of bacteria to
solid surfaces in anaerobic
wastewater filters.

Evaluation of performance
and mathematical modelling
of anaerobic rotating
biological contactors for
wastewater treatment.

Fluidised bed fermentation;
applications in aseptic
fermentation and wastewater
treatment.
Supported biomass in reactors;
hold-ups, substrate uptake,
product formation.

Design formula for aerated
lagoon wastewater treatment.
 Inhibiting  conditions  in
 biological  removal  of
 nitrogenous pollutants
 from wastewater.

 Development of  attached
 microbial film  process
 variants for wastewater
 treatment;  relationship
 between biochemical
 activity and population
 structure in activated
 sludge systems.
Ferris, S A
Clark, J H
Shaaban, M G B
                                                            Sanderson, J A
                                                            Echaroj, S
Black, G M
Ellis, K V



Winkler, M A




Davies, M
                                     876

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University of Oxford    Characterisation of                 Beckett, P H T
                        insoluble compounds of
                        toxic elements in sewage
                        sludge and sludge treated
                        soil.
                        Decomposition of sewage
                        sludge and character of
                        decomposition products.
                        Study on recovery from
                        sewage of phosphorus
                        usable as fertiliser.

University of           Control of nuisance flies           Dancer, B N
Wales Institute         in sewage filter beds by
of Science &            Bacillus thuringiensis.
Technology

University of           Stability of bubble induced         Davidson, J F
Cambridge               circulation of liquid in a
                        deep shaft u-tube sewage
                        treatment plant.

University of           Design of electro-separators        Wakeman, R J
Exeter                  for  the filtration and
                        thickening of slurries.
                                     877

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ADVANCES IN WASTEWATER TREATMENT AND SLUDGE MANAGEMENT PRACTICES
            RELATED TO PATHOGEN AND TOXICITY CONTROL
                                  by
               J. Convery, D. F. Bishop and A.  D.  Venosa
                  Wastewater Research Division
               Water Engineering Research Laboratory
               U.S. Environmental Protection Agency
                     Cincinnati, Ohio 45268
               This  paper has  been  reviewed  in  ac-
               cordance with  the U.S.  Environmental
               Protection Agency's  peer  and  adminis-
               trative review policies and  approved
               for presentation and publication.
         North Atlantic Treaty Organization/Committee on the
         Challenges of Modern Society (NATO/CCMS) Conference
                     on Sewage Treatment Technology

                        October 15-16, 1985
                          Cincinnati, Ohio
                                 879

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     ADVANCES IN WASTEWATER TREATMENT AND SLUDGE MANAGEMENT PRACTICES
                 RELATED TO PATHOGEN AND TOXICITY CONTROL

            by:  J. J. Convery, D. F. Bishop and A. D. Venosa
                 Wastewater Research Division
                 Water Engineering Research Laboratory
                 U.S. Environmental Protection Agency
                 26 West St. Clair Street
                 Cincinnati, Ohio 45268
                                 ABSTRACT

       Research to support municipal sludge regulations includes the deter-
mination of the kinds and concentrations of pathogens in sewage sludge from
various wastewater treatment systems and the characterization of the pathogen
reduction capabilities of alternative solids handling processes.  The extend-
ed aeration process produces greater reductions in bacterial densities of
waste sludge than conventional aeration and achieves in the waste sludge
a one-log reduction in Salmonella.  Sludge handling processes, producing
significant reduction in pathogens but not disinfecting the sludge, include
conventional aerobic digestion, anaerobic digestion, conventional composting
and lime stabilization.  Processes, producing further reduction in pathogens
and disinfecting the sludge, include composting for 3 days at 55C for with-
in vessel and static pile systems and 15 days at 55C for windrow systems,
heat drying, heat treatment and thermophilic digestion.  Autothermal
thermophilic aerobic digestion produces especially effective inactivation
of Salmonella and total plaque forming units (viruses) in the sludges.

       Ultraviolet light (UV) processes for disinfection of wastewater have
evolved from the development and demonstration stage to full-scale application
with 60 facilities now in operation.  UV processes are competitive, if not
less expensive, than chlorination.  Suitable design approaches and disinfec-
tion models have been developed.  Operation and maintenance experiences are
summarized.

       Toxics treatability and control research includes the characteri-
zation of removals and effluent concentrations of specific toxics in a range
of treatment systems, the determination of the fate of these toxics by the
three principal removal mechanisms of sorption, volatilization and biodegra
dation, and the evaluation of the toxicity reduction capability of treatment
systems for the removal of overall toxicity.  The toxics removal data indicate
that conventional primary-activated sludge treatment provides best overall
control of specific toxics.  The limited kinetic studies on the specific re-
moval mechanisms suggests that biodegradation in activated sludge systems is
                                     880

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the principal removal mechanism for the organics studied but that volatili-
zation of the moderately volatile compounds also is important.  Further
work is needed to appropriately characterize the three removal mechanisms
especially for highly volatile and sorbable toxics.  Conventional primary-
activated sludge treatment provides good toxicity reduction capabilities
for complex mixtures of toxics.  The use of biomonitoring methods for
toxicity appears to provide a practical method for managing complex
mixtures of toxics, especially in municipal wastewaters.
                               INTRODUCTION

       This paper presents recent information and control approaches for
pathogens and toxicity in municipal wastewater and sludge process streams.
The rationale behind the pathogen control technology standards for munici-
pal sludge application to the land are described together with relevant
performance and cost capabilities of the Autothermal Thermophilic Aerobic
Digestion Process.

       A rational procedure for designing Ultraviolet Radiation facilities
for disinfecting wastewaters is described.  Observed performance of a full
scale operating facility is compared to the performance predicted by the
model.

       Two approaches, described in this paper, are being used to evaluate
and control toxics in wastewater treatment.  The first approach using repre-
sentative specific toxics evaluates overall removals in pilot scale treatment
systems and specific removal mechanisms in laboratory studies.  The second
approach uses bioassay tools for characterizing toxicity control for complex
mixtures of unknown toxics.
                  MUNICIPAL SLUDGE DISPOSAL REGULATIONS

       The interim final regulations specifying the criteria for sludge use
on land pertaining to disease prevention and pathogen control as required by
The Resource Conservation and Recovery Act (RCRA) were published in September
1979 - Code of Federal Regulations (CFR, Title 40, "Criteria for Classifica-
tion of Solid Waste Disposal Facilities and Practices", Para. 257.3-6, Disease,
Interim Final Regulations, Effective October 15, 1979).  Farrell (1) described
the rationale behind these regulations as being either:


       0  eliminate the possibility of contact by eliminating the
          pathogens
                                    881

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       0  require a series of formalized barriers (including processing
          to reduce pathogen densities) that insure that the probability
          of human contact is low.   Figure 1 illustrates the management
          options provided by the regulations for use of sludge on the
          land.

       Two technology-based standards for control are included in the
regulations:

       0  processes to significantly reduce pathogens (PSRP)

       0  processes to further reduce pathogens (PFRP).

       Processes to significantly reduce pathogens are described in
Table 1 (1).  These technologies provide a one-log reduction of bacterial
and viral pathogens.  While a two-log reduction in indicator organisms,
such as fecal coliform and total coliform densities, is attainable with
anaerobic digestion under these operating conditions, the relative reduc-
tions in pathogens and indicator organisms varies with each technology.
          TABLE 1.  PROCESSES TO SIGNIFICANTLY REDUCE PATHOGENS
       Technology	Conditions	
       Aerobic Digestion             60 days @15C
                                     or 40 days @20C &
                                     38 % volatile solids (V.S.) reduction
       Anaerobic Digestion           60 days @20C to
                                     15 days @35C - 55C &
                                     38% V.S. reduction
       Composting                    5 days @40C &
                                     4 hours @>55C
       Lime Stabilization            pH 12 & 2 hours contact
       Other                         Equivalent reduction
                                     of pathogens and
                                     volatile solids
                                    882

-------
   Raw Sludge
   From POTW




NoPSRP |


i
1



Receives
PSRP
1
1
1
1
1

Receives
PFRP
                          NP
       No Use On Land               i
                                             Public Access To Site
                                                Is Restricted
                                               For 12 Months
                                             After Use Of Sludge
          Grazing
                                                              No Restrictions
                                                                 On Use

                               Grow Crops
  Animal
 Products
   Not
Consumed
By Humans
  Animal
 Products
Consumed
By Humans
                                             No Crop
                                            No Grazing
 Crops Not
 For Direct
  Human
Consumption
  Crops For
Direct Human
Consumption
               1 Month Waiting
                 Period Before
                   Grazing
                    T
                                   Crops That
                                     Do Not
                                   Touch The
                                     Sludge
                                                       T
                              Crops That
                              Touch The
                                Sludge
              P  Permitted
              NP  Not Permitted
                                                  Crops Not Grown
                                                  Until 18 Months
                                                  After Sludge Use
                                                                         T
          Figure  1.    RCRA criteria  for  use  of  sludge  on  land  (1).
                                             883

-------
       The inability of anaerobic digestion and most of the other PSRP
processes to reduce the density of helminth eggs is offset by the restric-
ted access and proper siting considerations identified in the regulations.

       In addition to pathogen reduction, PSRP's must eliminate the poten-
tial of. the sludge to cause a vector problem by either drying the sludge,
raising the pH or reducing the odor and organic content.

     Processes to further reduce pathogens (PFRP) which disinfect the
sludge (i.e., reduce pathogens to below their detectable limits, viruses
- 1 PFU/100 ml, Salmonella-3 CFU/100 ml and Ascaris - 1 viable EGG/100
ml) are described in TABLE 2 (1).
            TABLE 2.  PROCESSES WHICH FURTHER REDUCE PATHOGENS
       Technology
Conditions
       Composting
       Heat Drying
       Heat Treatment

       Thermophilic Aerobic
         Digestion

       Other
3 days @55C for
within vessel & static pile
15 days @55C & 5 turns
for windrow

Cake moisture <10% & 80C
wet bulb temperature of gas
stream in contact with sludge
or sludge particles reach 80 C

30 minutes @180C

10 days @55C & 38% V.S.S.
reduction

Equivalent pathogen & volatile
solids reduction
       PSRP PROCESSES PLUS

           Beta Ray Irradiation

           Gamma Ray Irradiation

           Pasteurization

           Other
1.0 Megarad @20C

1.0 Megarad @20C

30 minutes @70C

Equivalent pathogen reduction
                                     884

-------
       The U.S. EPA plans  to issue revised municipal sludge disposal
regulations in  1986 for  use  of  sludge on the land, as well as land-
filling, distribution  and  marketing,  incineration and ocean disposal.
This regulation development  activity  has stimulated a high level of
interest and effort in characterizing and improving the pathogen reduc-
tion capabilities of sludge  stabilization processes and practices as
well as identifying more cost-effective designs.

       Figure 2 from Farrell (2)  shows the log of the bacterial densities
(no/gram) in the influent  wastewater  solids from five treatment plants.
The bacterial densities  are  surprisingly consistent.  This study was
conducted to determine the bacterial  content of the waste activated
sludge from extended aeration-type facilities.  Figure 3 shows that this
type of facility is capable  of  achieving greater reductions in bacterial
densities than  conventional  treatment facilities and a one-log reduction
in Salmonella.  The current  sludge regulations, however, require a separate
sludge processing step which achieves an additional one-log reduction in
pathogens.                                  ta	^
                  Salmonella
                  Fecal
                  Streptococcus 7
                      10
                  Fecal
                  Collform
                                                            10
                  Total
                  Coliform
                     City

                  Williamsburg
                  Sardina
                  Frankfort
                  Jackson Center  0.25
                  Little Miami    38
  8         9
    Process
Extended Aeration
Extended Aeration
Brush Aerator
Brush Aerator

Conventional
Confidence Interval
                                                           (95%)
             Figure 2.  Log of  bacterial  densities (No./gram)
                          in  influent wastewater solids (2).
                                     885

-------
       A recent summary  of  the  available literature and research had identi-
fied the kinds and concentrations  of  pathogenic bacteria, viruses, helminths,
protozoans and fungi found  in sewage  sludges,  as well as their fate and trans-
port in the environment  and their  infectivity  to man (3).  Table 3 summarizes
the survival times for major pathogens  of interest.  The long survival times
(>1 year) for helminths  are usually for organisms underground where human
exposure and risk are very  low.  While  the Agency has affirmatively evaluated
the feasibility of conducting a pathogen risk  assessment there are important
data gaps to be filled.  Among  these  are control technology issues such as  the
performance of aerobic digesters.  Many of the 3,400 aerobic digesters in the
U.S.A. are incapable of  meeting the PSRP requirements;  particularly during  the
winter months in the northern States.   A research study is currently being  con-
ducted at Cornell University on how to  upgrade, at minimum cost, the PSRP per-
formance of aerobic digesters through the use  of submerged aeration, covers,
and insulation.
       A feed solids concentration of 2% will  be used.   A primary research
objective is to establish the minimum time requirements (5 to 20 days) to
reliably achieve a one-log  reduction  of pathogens while maintaining an
operating temperature of about  30C.  This work is a followup on activity
to our earlier research  at  Cornell on autothermal thermophilic aerobic
digestion (ATAD).
                     Salmonella
                     Fecal
                     Streptococcus 6"
                     Fecal
                     Coliform
                     Total
                     Coliform
                        City
                     Williamsburg
                     Sardina
                     Frankfort
                     Jackson Center
                     Little Miami

                             K	
   Extended Aeration
   Extended Aeration
   Brush Aerator
   Brush Aerator
   Conventional (Mixed SI)
              (Return SI)
-^1 Confidence Interval
                Figure 3. Reductions in log of bacterial densities
                               (No./gram) caused by  treatment (2).
                                      886

-------
       TABLE 3.   SURVIVAL TIMES OF PATHOGENS ON SOIL AND PLANTS (3)
PATHOGEN
BACTERIA
VIRUSES
PROTOZOA
HELMINTHS
SOIL PLANTS
Absolute Common Absolute Common
Maximum Maximum Maximum Maximum
1 year 2 months 6 months 1 month
6 months 3 months 2 months 1 month
10 days 2 days 5 days 2 days
7 years 2 years 5 months 1 month
                AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION

       The most extensive study of ATAD in the U.S. was conducted by Jewell
(4).  This full-scale study, using a 28.4 nH (1,000 cu. ft.) reactor, demon-
strated that a single-stage digester utilizing self-aspirating aerators
with ambient air, treating a continuous feed of primary and waste activated
sludge (3%-6% total solids), resulted in autoheated reactor temperatures
normally in the range of 50C to 60C.  Complete inactivation, that is
below the limits of detection, of Salmonella and total plaque forming
units (viruses) was observed except for one test date.  Parasites (viable
ova) were reduced significantly, but not completely.  Maximum temperature
development (55 C to 60 C) and a maximum organic removal rate of 6.5 kg
BCOD/m-'-day (.4 Ib/day/cu. ft.) occurred when the organic loading rate was
12 to 15 kg TS/m3-reactor-day (.75 to .94 Ib/day/cu. ft.) and the dissolved
oxygen concentrations were  <1 ppm.  Where BCOD is  the biodegradable chemi-
cal oxygen demand and TS  is total solids.  Oxygen  transfer efficiencies of
20% or more were reported with  recommended power input levels of  150 to 200
W/m^ of reactor.  Both  a  DeLaval Centri-rator aerator and a Midland-Frings
aerator were evaluated.   Hydraulic retention time  varied from 3 to 11 days
with 5 days being the most  typical value.  The dewaterability of  the
digested sludge deteriorated  significantly at all  HRT's evaluated.


       Even though Jewell's full-scale reactor was not completely mixed
as evidenced by stratification of the dissolved oxygen concentration, he
described the process performance as being approximately a first-order,
                                    887

-------
completely-mixed steady state system where K, the reaction rate coefficient
can be determined by the expression:
                          SE  =      1	                         (1)
                          SI      1 + K (HRT)
       where SE = biodegradable organics out [TVS, gm/1]

             SI = biodegradable organics in [TVS, gm/1]

            HRT = hydraulic retention time, day

              K = reaction rate coefficient,

                  gm biodegradable TVS removed per gm

                  of biodegradable TVS in the reactor per

                  day, day~l
       The biodegradable fraction (%) of the sludge constituents was found by
Jewell (4) to be as follows:
                     COMPONENT            BIODEGRADABLE FRACTION (3Q


               Chemical Oxygen Demand             47.4 - 76.5

               Total Solids                       22.9 - 62.0

               Total Volatile Solids              42.2 - 71.7

               Total Kjeldahl Nitrogen             57.0 - 85.0


       The reaction rate coefficient K (using COD as a measure of bio-
degradable organics) is shown in Figure 4 (5).  The temperature relationship
shown below, which was developed by Jewell (4), is in basic agreement with
that of other researchers in the temperature range of 45 to 55C.


                     K  = (0.022) 1.076TR-20                            (2)
               where
                     TR = temperature of the reactor, C
                                     888

-------
                               RetcttM Rite CotMclent Versus AeraMc
                                  Ngtsltr Liquid Ttmptratynt
               I
               
                         A
                                    Airimn ind KimMw 1970)
                                              )  ,
                                 Tinwefibn Of LH In *itk DlfMtif, *C
           Figure 4.   Reaction rate coefficient versus  aerobic
                          digester liquid temperatures  (5).
Figure  5  illustrates the sources and  losses  of heat for the aerobic  digester.
There are  three types of heat loss:

              0   loss through the discharge of exhaust gas

                 loss with the digested  sludge

                 loss to the surroundings.


The first  two are  the major losses (6).  They can be controlled by provid-
ing efficient aerators (e.g., 15% efficiency or better) to reduce the  flow
through the  reactor and thickening the  sludge fed to the reactor in  order
to reduce  the total  quantity of material to  be processed.  Thickening  of  sludge
to 3% solids  or greater has been recommended (5).  Convection losses from the
reactor can  be  controlled by covering of the digester and adding insulation.
                                     889

-------
Heat With
Sludge Input
Heat With
Gas Input
Mixing Heat

-------
oo
           C
           i
                600,000 
                 500,000
                 400,000 
300,000
                 200,000
                100,000 
                                       Comparative Digestion Capital Costs
                                                                                                               ATAD
                                  I
                                 250
                          I
                         500
 I
750
1000
  I
1250
                     I
                   1500
 1
1750
  I
2000
                                                2250
 I
2500
 I
2750
                                                                 Kg/Day of TS Throughput
                                  Figure  6.   Comparative  digestion capital  costs  (7).

-------
per day was required to operate and maintain the system.   Performance was
very acceptable including: 40% reduction of volatile solids, thermophilic
(>43C) temperature operation in the second stage reactor, apparent pathogen
reduction to the FRG limitation of 100 enterobacteria/ml and infrequent
incidence of odors.  The ATAD process has been shown by Strauch and Bohm
to be capable of destroying salmonella, parasite eggs and viruses provided
a temperature of 50C is maintained for 57 hours of aeration time (6).

       A summary of the design parameters for all three of the ATAD
manufacturers in FRG is shown in Table 4.  The Fuchs and Thieme systems
employ two insulated and covered reactors in series operation with batch
feeding cycles.  The Thieme system uses a rotary screen to prethicken the
sludge feed concentration to 10 to 12 percent solids which results in a
70% reduction in reactor volume requirements.  Fuchs also prethickens the
sludge to 3 to 5 percent solids.  Dissolved air flotation thickening of
primary and waste activated sludge is practiced.  The batch feeding cycle
is used to prevent contamination of the pasteurized sludge with incoming
raw sludge.  Mechanical components in a typical Fuchs reactor consists
of two rotary blade type foam cutters, two side mounted aspirator type
aerators and one center floating aerator depending upon reactor sizing.
Design oxygen transfer efficiency is 2.1 kg 02/kWh (3.5 Ib 02/hp-hr).
A 20-day storage period is recommended for the digested sludge to cool
(20C) to improve post thickening or dewatering.

       Figure 7 shows the schematics for all three systems.  The Babcock
ATAD system utilizes a single reactor with semi- or fully-continuous
sludge feeding.  A submerged turbine is used for aeration in this system.

       Actual operating conditions for five Fuchs systems is shown in
Table 5 (7).

       The ATAD batch operating strategy maximizes pathogen destruction
potential and minimizes the possibility of product contamination from
incoming sludge.  A specific volume is removed daily from the second stage
reactor.  A comparable volume is then transferred daily from the first
stage to the second stage which provides a minimum detention time of 24
hours at thermophilic temperatures.  Some researchers have been concerned
about possible temperature depression in the first stage with a batch
feeding operation .  Deeny et al, (7) observed that the first and second
stage temperatures were depressed by approximately 5 to 6C and 3 to 4C,
respectively.  Both reactors recovered at a rate of 1 per hour.  Volatile
solids destruction were reported as being >40 percent at detention times
in excess of 4 days.

       There are only limited data on sludge dewatering performance.
Experience at the Vilsbiburg ATAD facility using a belt press and decanter
centrifuges indicate acceptable performance with sludge cake total solids
of 30 to 35 percent with a feed solids content of 2.5 percent (7).  Polymer
dose was approximately 5 g/kg of sludge.  Feed temperature range was 48
to 63C.
                                     892

-------
   TABLE 4.  SUMMARY OF ATAD DESIGN PARAMETERS  (7).
DESIGN PARAMETER
Sludge Feed Concentration, percent (%)
Hydraulic Detention Time, Days
Number of Reactors
Sludge Storage Capacity, Days
Operating Strategy
Aeration Requirement,
KWH/M3 of sludge throughput
Mixing Requirements,
W/M3 reactor volume

FUCHS
3-5
5-6
2
20
Batch
12-14
86
MANUFACTURERS
THIEME
10-12
6-7
2
70
Batch
.
200-300

8ABCOCK
3-6
3-6
1
-
Semi-Continuous
12-17
-
TABLE 5.  SUMMARY OF ATAD ACTUAL OPERATING CONDITIONS
Parameter
No. of Reactors
Dimension, 0xH, M

Volume (Occupied by
Sludge) Total, m3
Sludge Influent Flow,
m3/day
Sludge Concentration,
TSS/TVSS, percent
Sludge Mass Loading,
TVSS, kg/day
Sludge Volumetric
Loading, kg/day/m3
Reactor(s) Detention
Time, days
Aeration Installed
Power, kw
Aeration Power
Consumption , kwh
Aeration Power/
Sludge Volume,
kwh/m3/day
Aeration Power/
Reactor Volume,
w/m3
Aeration Power/
Sludge Mass,
TVSS, kwh/kg/day

Facility
2
5x3


120

9
4/3.1


280

2.3
13
(6.6)

8.8

211

23.4
(12.0)


73


0.75

2
7.0x
3.5

120

20
4/3.4


680

5.7
12
(6)

9.5

228

22.8
(12.6)


79


0.74
893
2
7.5x4


360

70
5.5/
3.6

2,520

7.0
5.1


38

912

13.0



106


0.36

2
3.5x
2.5

48

8
5/3.0


240

5.0
6.0


4.4

106

13.3



92


0.44

2
6.5x
2.25

150

15
3.5/
2.8

420

2.8
10


11.8

284

18.9



79


0.68


-------
      Sludge
                       Thickener
            V
                                                  Ti
                                                                        To Land Application
ATAD Reactors
                 Sump   Sludge Storage
       Sludge
co
UD
       Sludge
                     n.,,
                          Mazorator
                  Holding Tank
                       Thickener
                                         Fuchs ATAD System
  *L1
                JUj^J

         Rotating Screen

Conditioning Tank


     Thieme ATAD System
                                5
                             ATAD Reactor

                                    ATAD Reactors
                                               Foam Breaker Scrubber
            Q
                                     Heat Exchanger               Sludge Storage


                                         Babock ATAD System

                          Figure 7.   Alternative flow schemes of ATAD systems.
L_L.
Sludge Storage
                                                                                            Land Application
                                            To Land Application

-------
        APPLICATION OF ULTRAVIOLET LIGHT FOR DISINFECTING WASTEWATER

     The use of Ultraviolet Radiation (UV) for the disinfection of treated
domestic wastewaters has evolved relatively quickly from the development and
demonstration stages to full scale application.  This has been spurred in
large part by the U.S. Environmental Protection Agency's (EPA) direct re-
search funding efforts and its encouragement to build UV plants through its
Construction Grants Innovative and Alternative (I/A) Program.  Over the last
10 years the technology has received considerable attention, with an increas-
ing number of full-scale plants coming on line, particularly over the last
three to five years.  UV disinfection is being considered at approximately
120 municipal wastewater facilities in the U.S.A.  Currently some 60 are in
operation with the remainder under design or construction.  Most of these
facilities are quite small.  The largest facility at, Madison, Wisconsin,
will have design flow of 2.4 m-Vs (55 MGD).  The process application is
viable, technically feasible, and cost-effective for most wastewater situ-
ations.

     A comparison of costs had been performed in 1979 as part of an evalua-
tion of UV disinfection at Northwest Bergen County, New Jersey.  This study
had assembled unit costs for a number of disinfection processes and compared
them to the estimated unit cost for UV disinfection.  These same unit costs
are presented on Figure 8, updated to 1984 (USEPA Index = 460).  Unit costs
developed from a recent study (8) of existing full-scale UV disinfection
facilities have also been included in Figure 8.  In certain cases, a wide
range in cost estimates was found for a specific process.  The values used
on Figure 8 represent an approximate average of the various estimates
to achieve an effluent quality objective of 200 FC/100 ml.  Additionally,
the costs presented in various sources may differ in their assumptions for
labor, power, etc.  Caution is, therefore, warranted in any direct cost
comparisons.

     The analysis presented on Figure 8 suggests that UV is considerably
less expensive than ozonation and is competitive, if not less expensive,
than the chlorination or chlorination/dechlorination processes.  It was
found that the costs estimated for UV in our recent study (8) were less
than the estimates from the 1979 report.  The reasons for this are primarily
the reduction in real costs for equipment and the more rational manner in
which UV systems can now be designed.  A noted shortcoming in the applica-
tion of UV, however, has been the lack of a generic, technically acceptable
design approach.  Most in-field designs, with a few notable exceptions, have
relied on equipment manufacturers for system sizing and hardware designs.
These have been based on limited experience with wastewater applications and
have often followed generalized rules of thumb.  The design assumptions and
the hardware configurations themselves often do not adequately account for
the basic variables that are key to effective UV design and performance.

     The most common configurations are the "submerged" quartz covered
lamp designs of Pure Water Systems, Inc. and Ultraviolet Purification
Systems,  Inc. and the teflon tube flow-through design of ENERCO.
                                    895

-------

          1.0 *-
            0.4  0.5
                   1.0
             Figure  8.
 Design Annual Average Daily Flow (m'/min)

Comparison of unit costs for a1,'-"T"laflve
     disinfection processes (9;.
     A systems analysis procedure has been developed as part of  a  recently
completed EPA study at the Port Richmond Water Pollution Control Plant  in
New York City, and reported by Scheible, et al. (9).  The procedure  incorpor-
ates the use of mathematical modeling techniques, which generically  describe
the hydraulic, kinetic, and water quality elements important to  UV disin-
fection.  The utility of the modeling approach, when properly  applied,  is
the efficient evaluation and optimization of an existing system, and the
optimization of a design for a new system.

     The following discussion presents the application of this procedure
to a full-scale system.  The tasks associated with this study  involved  col-
lecting the appropriate data to calibrate the disinfection model,  and then
using the model to evaluate the system design, particularly under  anticipated
design loading conditions.  The objectives were to assess the  utility of  the
procedure and to determine what modifications and/or refinements would  be
appropriate to strengthen it.  A brief discussion of the model is  first
presented; this is followed by a discussion of the key elements  of the
model and how these were determined for the study site.  The use of  the
calibrated model is then presented, with a discussion of observations and
conclusions derived from the study.
                                      896

-------
UV DISINFECTION MODEL

     The reader is referred to the Port Richmond study report (9) for a
detailed development of the disinfection model.  It incorporates an estimate
of the residence time distribution in the reactor, describes the inactiva-
tion rate as a function of the intensity, and empirically accounts for the
effect of particulates on UV performance efficiency.  The expression is
written:

           N = Nn exp rux {!-(!+ 4EK)1/2}] + N                     (3)
                       2E            U2
where:

     N  =  the bacterial density remaining after exposure to UV
           (organisms/100 ml)

     N0 =  the initial density, measured immediately before entry
           into the UV reactor (organisms/100 ml)

     x  =  the distance traveled by an element of water while
           under direct exposure to UV light (cm).  This is gener-
           ally taken as the reactor dimension in the direction of
           flow.

     u  =  the velocity of the wastewater as it travels through
           the UV reactor (cm/sec).  This is calculated as:

                u = x/Vv/Q)

           where Q is the flow rate in liters/second and Vv is the
           reactor liquid volume in liters.

     E  = the reactor dispersion coefficient in cm^/sec.

     K  = the inactivation rate coefficient  (second"^-).

     Np = the bacterial density associated with the particulates  in
          the wastewater.  These coliforms are affected minimally by
          the UV radiation,  effectively  becoming  the base  residual
          density determining the performance of  a given system.

     Thus, the information required by the model  includes  the dimensions  of
the reactor  (x,Vv), and the  system loading conditions (Q and No); E describes
the hydraulic characteristics of the unit.   The sensitivity of the coliforms
is described by the inactivation rate, K; this, in turn, is estimated as  a
function of  the calculated intensity.  The wastewater characteristics are
described by the K rate, the particulate coliform density, Np, and by the
UV absorbance coefficient.
                                    897

-------
DETERMINING THE MODEL PARAMETERS FOR EXISTING FULL-SCALE SYSTEMS

     The following discussion briefly describes the approach and data re-
quirements for properly calibrating the model.  From the above presentation,
this can be addressed by evaluating three basic elements:

     1.  hydraulic characteristics,
     2.  intensity of UV in the UV reactor, and
     3.  water quality conditions for the wastewater.

Hydraulic Characteristics

     The data requirement for determining the appropriate hydraulic char-
acteristic of the UV reactor lies principally in determining its residence
time distribution (RTD).  Hydraulically, the design objectives are to have
a reactor that behaves in a plug flow manner with minimal dispersion; that
the flow be turbulent radially from the direction of flow; and that the
reactor liquid volume be used effectively.

     Figure 9 from (10) presents a "typical" RTD curve, which can be devel-
oped by injecting a conservative tracer into the influent of a reactor and
measuring its concentration, c, as it exits the reactor with time.  Several
indices can be estimated from the RTD curve that are useful in describing
the hydraulic behavior of the reactor.  Referring to Figure 9, these are
defined as follows:

     tgo/tio = the ratio of the time for 90% of the tracer to pass to the
               time for 10 percent of the tracer to pass.  This is common-
               ly known as the Morrill Dispersion Index; it would be
               equal to 1.0 for ideal plug flow conditions, and 21.9 for
               complete mix.  Generally, it is best to have this index
               less than 2.

     tm/T    = the ratio of the actual mean residence time (first moment
               of the RTD curve) to the theoretical residence time.  T is
               computed as the  Liquid volume, Vv, divided by the flow
               rate, Q.

     tp/T    = the ratio of  the time at  which the peak concentration occurs
               to the theoretical residence time.

     tf/T    = the ratio of  the time when tracer first appears  to  the
               theoretical  residence time.

             = tne ratio of  the time for 50% of the  tracer to  pass  to the
               mean residence  time.   The deviation from a  value of  one  is
               a  measure of  skew from a  normal distribution.   As an
               example,  a value significantly less than one would  char-
               acterize an  RTD with a long tailing effect,  indicative of
               stagnant areas  within the reactor.
                                    898

-------
     o
     S
     s
     g
     CJ
     u
         Figure 9.   Typical residence time distribution curve (10).

     A very useful parameter, particularly in reactor design, is the dis-
persion number:

               Dispersion Number = E/ux

where E is the dispersion coefficient (cm^/second), u is the fluid velocity,
and x is the reactor dimension in the direction of the flow.  The dispersive
properties of a reactor are indicated by the relative spread of the RTD
curve.  The value of E will approach infinity in completely mixed systems,
while in ideal plug flow systems it will approach zero.  Levenspiel (11)
suggests values of the dispersion number for a plug flow reactor with
increasing degrees of dispersion:

               E/ux = 0; plug flow, no dispersion

                    = < 0.01; low dispersion

                    = 0.01 to 0.1, moderate dispersion

                    = > 0.1 high dispersion

In cases where the RTD is a normal (Gaussian) distribution, the dispersion
number can be estimated from the variance of the distribution:
                          ~ 2(E_)
                              ux
                                                                       (4)
                                    899

-------
where the variance, 002, normalized to the mean residence time, is dimension-
less.

Intensity

     Intensity is the rate at which energy is being delivered.  The unit
generally used for UV disinfection is microwatts/cm^; the energy is speci-
fically at the wavelength of 253.7 nm.  This is the maximum spectral line
for low pressure mercury arc lamps, which are almost universally used in
wastewater disinfection systems.  A serious shortcoming in the design of
UV systems has been the inability to estimate accurately the light intensity
in complex multi-lamp reactors.  Detectors are generally planar and will
account for only a portion of the light energy available within a system.
Several approaches have been proposed to estimate light intensity, includ-
ing chemical actinometry, biological assays (12), and calculation.  It is
suggested that the calculation approach offers the most versatile and
efficient means to determine the intensity within a reactor, and is the
method used in this study.

     The point source summation method is generally the technique used
to calculate intensity.  It was first applied to UV disinfection systems
by Johnson and Quails (12) and then applied by Scheible, et al (9).  It
presumes that the lamp  is a finite series of point sources, each of which
radiates its energy radially.  The energy attenuates by two mechanisms:
the first is by dissipation and is proportional to the inverse of the
radius squared; the second is by absorption by the medium through which
the energy is passing.

     A single receptor  in the reactor will be exposed to all point sources
that have an unobstructed straight line path to the receptor.  The inten-
sity, therefore is the  sum of the intensities from all point sources
affecting the receptor.  This calculation is then performed for a number
of receptors located in a defined cross-sectional grid pattern, allowing
one to eventually compute the average intensity in the reactor.  The
final product is generally a plot of  the average nominal intensity as
a function of the wastewater UV absorbance coefficient.

     The reader should  refer to the cited references for a more detailed
discussion of the  calculation technique.  The information required to
compute the intensity for a given system may be summarized as  follows:

-    reactor dimensions and the configuration of the lamps and lamp
     enclosures

     the output rating  of the  lamp.   The nominal rating  for low pressure
     mercury arc  lamps  is approximately 18.2 Watts/meter of arc (at
     253.7 nm).  This will degrade with use; thus  it is  also  important
     to understand the  lamp output with time.

     the absorbance  of  the  liquid  to  be treated.   This  is  the  absorbance
     coefficient  at  253.7 nm  (base e), with  the units  cm"1.


                                     900

-------
     the transmissibility of the enclosures; submerged lamp systems have
     quartz sheaths about each lamp.  Other systems utilize Teflon tubes
     to carry the liquid, with the lamps surrounding the tubes.  In
     either case, the energy must pass through the enclosure before it
     reaches the liquid.  Thus, it is important to account for the loss
     of energy through these enclosures.

     In the example that is to be provided, the intensity calculation is
made assuming that all the lamps are at their nominal output rating and
that the enclosures will transmit 100 percent of the energy.  This allows
general use of the calculation output; the resulting intensity need only be
adjusted (by direct ratio to nominal) for actual and/or projected conditions.


Wastewater Quality

     The four wastewater parameters that most affect the design or per-
formance of a UV system are the flow, initial bacterial density, suspend-
ed solids (or some measure of the particulates in the wastewater), and
the UV absorbance of the wastewater.  The flow rate is set by  the design
of the main plant and projected hydraulic loads from the facility collec-
tion system.  The initial density is a parameter that is not generally
monitored at a facility; in the case of disinfection by UV, however,  it
is a critical parameter.

     The occlusion of bacteria in particulates will have a significant
effect on the design of a system.  For model calibration and system
evaluations it is best to use the suspended solids analysis as the
primary indicator of particulates.  The level of suspended solids in
the effluent of a wastewater treatment plant is, in effect, set by the
design of the plant, limiting the range of  suspended solids concentrations
to be considered in the design of the UV process.

     The one parameter that is solely in the venue of UV disinfection is
the UV "demand" of the wastewater, in which components in the water will
absorb energy at the 253.7 nm wavelength.  The spectrophotometric UV  ab-
sorbance coefficient is a measure of the UV "demand" of the water and is
used in the context of the model expression (and intensity calculations),
with the units cm~l.

     The single beam spectrophotometric method for measuring absorbance
is the simplest procedure.  This "direct" method, however, does not
account for light which is scattered and still available; the  detector
does not receive this light and thus considers it to be absorbed.  Inte-
grating sphere accessories are available to correct the absorbance reading
for this effect and give a more representative measure of the  true absorb-
ance.  If such an instrument is not available, a direct measurement of
the sample filtrate would give a reasonable approximation of the true
absorbance.
                                     901

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Calibrating the Model

     Referring to Equation 3, for a fixed, existing system, we are given
the variables of flow, the dimension x, the velocity u; from the water
quality data we can estimate the initial density, No.  The task of
calibrating the model, for an existing system, then involves determining
the dispersion coefficient E, the inactivation rate K, and the density
associated with the particulates, Np.

     Dispersion Coefficients.  As discussed above, the dispersion coef-
ficient can be estimated from the RTD curve developed from direct tracer
analyses of the reactor.  If the distribution is approximately normal,
E can be estimated from Equation 4.  Alternatively, the E can be estimat-
ed from a series of trial and error solutions to the following equation:

               dc = 	W       exp r-(x - ut)2-i                      (5)
               dt    2A(irEt)1/z           4Et

 where:

      dc = observed change in concentration of tracer with time (gm/l/sec)
      dt
      W = rate of mass input (gm/sec)
      A = cross-sectional area of  the  tracer stream at x (cm2)
      x = distance from injection  to the observation point (cm)
      u = velocity (cm/sec)
      t = time (sec)
      E = dispersion  coefficient (cm2/sec)

 Estimate of  the  Coliform Density Associated with Particulates

      The data required to estimate these densities are collected from the
 UV  system at  very high apparent  dose levels.   This can be done by operating
 the full system  at low flow  rates.   The  premise  is that  the  remaining den-
 sities  measured  after such high  doses  are those  that  are associated  with
 the particulates  and  would not have been affected by  the UV  radiation.
 These data are then correlated with the  suspended solids of  the  sample
 (or some other measure of  particulates,  such as  turbidity).

      A  linear regression analysis  can  be performed of  the log  effluent fecal
 coliforms  as  a function  of the log effluent  suspended  solids.  When  trans-
 formed  this will  yield an expression in  the  form,

               Np  = cSSd                                              (6)

where Np  is the density  associated  with  the  suspended  solids (organisms/
 100 ml)  and SS is  the suspended  solids concentration  (mg/1).   The  co-
 efficients c  and  d are the intercept and  slope of  the  regression line,
 respectively.  The coefficients  c  and  d  at Port  Richmond  were  0.25 and
 2.0,  respectively.
                                    902

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     Estimate of the Fecal Coliform Inactivation Rate.  The required data
are those in which the operating conditions would allow a still significant
coliform density in the effluent.  This permits one to use the influent
and effluent coliform densities to estimate the rate of inactivation.
These data are generally collected under high hydraulic loading conditions.

     Once the data are collected, the rate can be estimated for each
sampling by manipulation of the model expression (Equation 3) to solve
for K.  The estimate of Np is first made (as discussed earlier) and sub-
tracted from the measured effluent density:

               N' = N - Np                                            (7)

Manipulation of Equation 3 yields:

               K = [U2(p2 - 1)]/4E                                    (8)

where:

                P =  1  -  [2E  In  (N'/Nn)l                                 (9)
                             ux

      The  log K can  be regressed against  the  log  intensity  for  the  corre-
sponding  sampling.  This would yield  the expression (when  transformed)  in
the  form:

                K =  a  Iavgb

where K is  the inactivation rate in seconds"1, and  Iavg  is  the average  in-
tensity (uWatts/cm2).   The  coefficients  a and  b  are the  intercept  and  the
slope of  the regression line,  respectively.

      In summary, the  final  calibrated model  will take on the form:
                                                   1/2
                N =  N0 exp  {ux  [1 -  (1 +  4E al    b)   ]} + cSSd         (10)
                            2E             U2

SITE EVALUATION AT  SUFFERN,  NEW YORK

      A  full-scale,  operating UV system was evaluated as  part of this  special
study project.   Recall  that the intent was to  collect the  appropriate  infor-
mation  about the system's hydraulics, performance,  and the  wastewater  char-
acteristics.   These would be used to  calibrate the  disinfection model,  which
in turn would  be used to evaluate the system design.   Secondarily,  an  ob-
jective was to evaluate the model analysis procedure itself, and to deter-
mine refinements and/or modifications necessary  to  enhance  its utility.
                                    903

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Methods

     Analytical methods for fecal coliforms, chemical oxygen demand (COD),
suspended solids (SS), and turbidity followed Standard Methods (13) and
USEPA (14) procedures.  The UV absorbance coefficient was measured at
253.7 nm with a Perkin-Elmer 552A-UV Visible Scanning Spectrophotometer.
The correction for scattering in the UV absorbance measurement (spherical
absorbance coefficient) was accomplished with a necessary Integrating Sphere
(Model No. B010-3751).  The materials and methods for measuring the resi-
dence time distribution of the UV reactors, and the output and transmit-
tance of the UV radiation were described elsewhere (8,9).

     Process Description. The UV process at Suffern consists of two parallel
units, designated as Units 1 and 2, both designed for 10,600 1pm (4.0 mgd)
maximum flow.  The average design flow is 5,000 1pm (1.9 mgd).  The units
are submerged quartz systems with the flow directed perpendicular to the
lamps.  Upon entering the influent chamber the water must pass through an
inlet stilling plate prior to contact with the UV light.  A similar plate
exists at the exit from the lamp pattern.  These were installed to ensure
uniform flow distribution through the unit.  Each unit has 260 lamps
arranged in a staggered pattern with the length having a total of 35 lamps
and the height alternating between 7 and 8 lamps.  The units can be operat-
ed with one to four banks of lamps on.
     Systems  Hydraulics.   Several tracer  measurements  were  made at  Suffern
to determine  the hydraulic characteristics  of  the units.

     From an  analysis  of  the mean and variance of the  distribution,  the
dispersion number is  estimated to be 0.037.   This suggested a low to
moderately dispersive  plug flow reactor.   The hydraulic indices can also
be calculated,  and are summarized on Table  6.   These suggest that there
is a degree of  axial  mixing occurring in  the reactor.   This is supported
by the low value of tf/T,  and the dispersion numbers.   The  lower value of
tp/T suggests that the total void volume  is not being  used  effectively.
These data and  those  from the other tracer  runs indicated that an
effective volume of 70 percent actual should be used in subsequent
analyses.

            TABLE 6.  SUMMARY OF HYDRAULICS  ANALYSIS, SUFFERN. N.Y
Parameter
Dispersion Coefficient, E, cm^/s
Dispersion Number, d
tf/T
tp/T
t90/t!0
tm/T
t- -^ /t-
Measured Value
150
0.037
0.35
0.83
2.2
0.88
1.04
          __ Lm
         Estimated Effective Volume
            (% of Actual)                                        70
                                     904

-------
     Intensity Calculation.  The cross-sectional dimensions of the lamps
and quartz sleeves are given on Figure 10, which also presents an example
of the intensity field calculated for an absorbance coefficient of 0.2 cm""*-.
The average intensity is reduced from this type of intensity field analysis.

     The final product of these calculations is presented on Figure 11.   As
already discussed, these estimates must then be adjusted for the actual  lamp
output and the estimated quartz transmissibility at the time of sampling.
Direct measurements were made at Suffern.   The lamp outputs were found to
average 95 percent of their nominal rating (the plant was in startup); the
quartz transmittance was determined to range from an average of 60 to 40
percent (relative to a clean quartz sleeve) during the term of the study.
These were applied to the intensity estimates for each sampling.   The data
are summarized on Table 7.

     Estimation of the coefficients c and  d.  Insufficient data were gen-
erated at Suffern to give an accurate estimate of the coefficients c and d.
It was presumed, therefore, that the values derived for the coefficients in
the Port Richmond project would give a reasonable approximation of the fecal
coliform density associated with the effluent suspended solids.
             QUARTZ SLEEVE
            EQUAL AREA  GRIDS
LAMP


CALCULATED INTENSITY
AT AN<*-0.2cm-1
   WATTS/cm2 x103)
D HO
A
21.1
18.9
22.1
'^
s
D At
/21.0
17.9
16.7
18.3
y 21.7
16.7
16.4
16.7
16.7
16.9
16.1
16.2
16.7
16.6
16.1
17.0
20.5
19.7

19.7

22. ( BULB 55
20.0
17.0
^
19.8
tfti
19.8
\
17.0
23.4
] 23.
20.0
16.9
16.1
16.9
16.7
16.6
16.1
1v3.7
16.4
15.7
16.6
16.9
21.0
17.3
16.6
18.3
21.8/
k
21.0
18.8
22.1
_^, 	
Rill I
' -x
y t
           Figure  10.   Cross  sectional  dimensions  of  lamps/quartz
                         in Suffern unit, with  an  example  of  a
                      calculated  intensity  profile in one  area  (9),
                                    905

-------
          20.000
                                            ASSUME NOMINAL LAMP OUTPUT
                                            AND
                                            100% QUARTZ TRANSMITTANCE
              0.00
                       0.20
                                0.40
                                         0.60
                                                  0.80
                                                           1.00
                                                                    1.20
                                                     ~1
                             ABSORBANCE COEFFICIENT (cm  )

  Fi'gure 11.   Calculated average intensity vs. UV absorbance coefficient
         	TABLE 7.  SUMMARY OF FIELD DATA  FROM SUFFERN,  N.Y.	
         Parameter	                   Measured Value
         No. of Samplings
         Flow Range, 1/s
         N0, fecal colif orms/100 mL
            (Geometric Mean)
            (Range)

         UV absorbance coefficient, cm"-'-  (base  e)
            (avg)
            (range)
         Nominal Intensity,
         Adjusted Intensity,
            (95% lamp output, 40-60% transmittance)
       64
    52 - 138

     95,500
20,000 - 274,000
      0.282
 0.235 - 0.350

     13,880

      6,600
     Estimation of the Inactivation Rate Coefficients.   The  samplings
selected at Suffern to estimate the inactivation  rate were  those ir> which
there was a single bank operating at a high flow.   A shortcoming in the
analysis of the data at Suffern is that the range of intensities over which
the rate data were collected was very narrow.  The system configuration at
Suffern did not allow for artificial adjustments  to the  unit intensity
                                     906

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(such as reducing the  line  voltage,  etc.);  the variation would only be
induced by the changes naturally occurring in the UV absorbance of the
wastewater.

     The estimates of  K were  regressed as a function of the estimated
average intensity.  The effective volume that was used to estimate the
velocity in Equation 10 was assumed  to be 70 percent of the actual liquid
volume; this was based on the hydraulics analysis discussed earlier.  The
transformed regression line from the log-log plot of the Suffern data is
written:
               K = 0.00059  I
                                0.922
                             avg

     Model Calibration.   The calibration of the Suffern wastewater to  the
model (Equation 10) uses  the following coefficient values:

               a = 0.00059
               b = 0.922
               c = 0.25
               d = 2.0

     The dispersion coefficient E was assumed to be 150 cm^/second.
Figure 12 presents a  comparison of the observed data to the predicted  data
for effluent fecal coliforms.   As can be seen, the model was very effective
in predicting the performance of the system and responding correctly to  the
          e.oo


          5.25


          4.50


       3  3.75
       O
       O
       u!  3.00
        in
       O
       O
          2.25
          1.50
          0.75
          0.00
 FECAL COLIFORM
 LOG Nobs= 0.944 LOG N ca,c + 0.1 91
 (r=0.91.)
REGRESSION
LINE
                             IDEAL LINE
             0.00      1.00       2.00      3.00      4.00      5.00
                                 LOG NCalc
-------
parameters that defined the process operations.  Ideally, the slope of the
regression line for the correlation of the observed and predicted data
should equal 1.0, with an intercept of zero.  Analysis indicated that in
either instance the regression line was not significantly different
(0.05 level) from the ideal line.

Analysis of the Suffern UV System

     Figure 13 presents solutions to the calibrated model expression in
situations where there are 1, 2, 3, and 4 banks of lamps in operation.
The Suffern plant is designed to handle an average flow of 5,000 1pm
(1.9 mgd) and a peak daily flow of 10,600 1pm (4.0 mgd).  The treatment
requirements at the plant call for seasonable nitrification and disinfec-
tion (April through October).  The two units at Suffern are each designed
to handle the total plant flow, even during peak conditions.

     Let us first consider the system under average loading conditions:

               Average UV absorbance Coefficient = 0.3 cm"-'-
               Average Suspended Solids = 15 mg/1

               Average daily flow = 5,000 1pm (1.9 mgd)

               Average Initial Fecal Coliform Density = 120,000/100 ml

     Assume that the average output of the lamps is approximately 80
percent nominal and that the quartz transmittance is maintained at a
level no less than 60 percent.  Referring to Figure 11, the calculated
intensity is 13,500 yWatts/cm^ at an absorbance coefficient of 0.3 cm"-'-.
This is then adjusted:

               Average Intensity = 13,500 x 0.8 x 0.6 = 6480 yWatts/cm^

     The density associated with the suspended solids i.s estimated:

               Np = 0.25(15)2 = 56 FC/100 mL

     Assuming a mean effluent density of 200 FC/100 mL is required, the N'
is equal to 200 - 56 = 144 FC/100 mL.  This yields,

               Log N'/N0 = Log (144/120000) = -2.92

     From Figure 13, the following Log N/N0 is predicted at average flow and
at an average intensity of approximately 6500 uWatts/cm^:

               1 Bank,   Log N/NO = -1.75
               2 Banks,  Log N/NO = -3.40
               3 Banks,  Log N/NO = -5.00
               4 Banks,  Log N/NO = -6.80
                                     908

-------

     0

    -1

    -2

    -3
    -6

    -7

    -8
t BANK
  2000
           AVG 0 (1.9 MOD)
                                   PEAK 0 (4
                                           0 MOD)
                    4       6       8      10     12
                    FLOW ( 
-------
     This analysis suggests that under average conditions, the system will
meet its performance requirements with 2 banks in operation.   This presumes
maintenance of the quartz transmissibility and lamp output at or above the
levels used in these calculations.  As an example, a similar simulation at a
quartz transmittance of 40 percent (the lower level determined during the
study period) indicates that three banks would be required to meet the re-
quired performance goal.  This points to the economic benefits (in addition
to the obvious performance benefit) derived from keeping a system clean.
OPERATION AND MAINTENANCE EXPERIENCE

     As part of its I/A technology assessment program, EPA funded a study
in 1984 to evaluate the performance of six UV disinfection systems currently
in operation in the U.S.  The following discussion briefly summarizes the
results of certain aspects of that field study as well as the performance
of the Port Richmond facility (9).

     The survey results indicate highly variable performance depending on
the water quality of the influent and the reactor design.  Some facilities
such as those at Togus, Maine, Suffern, New York and Pella, Iowa were capa-
ble of consistently producing effluent fecal coliform levels of <200/100 ml.
Start-up problems including overheating and failure of electrical components
such as lamps, ballasts and circuits were experienced at some facilities
necessitating redesign.  Operational availability of 75% were recorded for
experimental units at Port Richmond (9).  Twenty-five percent of the down-
time was process influent related (foaming) and seventy-five percent of the
downtime was related to equipment failure.

     Two major considerations in the proper and effective operation of a UV
system are: 1) the hydraulics of the unit, and 2) the cleaning methods
required for each of the different types of units.  The importance of plug
flow hydraulics has already been discussed earlier.  Suffice it to say
that every unit studied in the field suffered in some very fundamental way
from axial dispersion resulting in short-circuiting and non-ideal flow.
This, in turn, caused a certain degree of non-compliance with coliform
limitations.  The rest of this report will focus on the cleaning methods in
use and the general maintenance requirements of UV systems.
Cleaning of UV Units

     An overriding concern in the proper maintenance of a UV reactor is to
keep all surfaces through which the UV radiation must pass as clean as pos-
sible.  The effects of surface fouling on energy utilization efficiency can
be quite significant.  Maintaining clean UV radiation transmission surfaces
is a very important operation and maintenance parameter and fouled or dirty
Teflon or quartz tubes can very often be pointed to as the primary reason
for the poor disinfection performance of a particular system.
                                     910

-------
     Typically, fused quartz sleeves are rated at a UV transmittance of 90
to 95 percent when new.  The transmittance of Teflon tubes will vary with
the thickness of tube wall and, under typical designs, one should expect
a transmittance between 70 and 85 percent for a virgin Teflon.  Current
Teflon units are utilizing thinner wall tubes and the virgin UV trans-
mittance is close to 85%.  Fouling can occur on both the wetside and the
dryside surfaces of both quartz and Teflon tubes.  For quartz tubes, water-
side fouling on the outside of the tube typically causes the highest per-
centage of UV intensity loss.  Depending on the water quality of the
wastewater to be disinfected, fouling of the outside quartz surfaces can
be caused by relatively high oil and grease content or by a hardness
scaling phenomenon that occurs due to the higher temperature (from the
UV lamp) at the outside surface of the quartz tube.  The scale on the
quartz surfaces, and to a lesser extent on the Teflon surfaces, has been
found to be inorganic magnesium and calcium hydroxides and carbonates.
Organic fouling is usually caused by a high oil and grease content, but
biofilms can also grow on quartz or Teflon surfaces that are not fully
irradiated or irradiated non-continuously.

     The inner (dry) side of a quartz tube can become fouled due to the
passage of air and dirt particles in between the UV lamp and the quartz.
Reductions of 15 to 25 percent in the quartz UV transmittance have been
noted due to this inside fouling.  The outside surfaces of Teflon tubes
have been observed to become heavily coated with dust, thereby reducing
UV penetration.  This is thought to be caused by the highly charged
atmosphere between the UV lamp and the Teflon tube, creating an ideal
environment for electrostatic precipitation of dust onto the Teflon
tubes.

     There are basically two approaches to cleaning the quartz and Teflon
tube units, chemical and physical.  Most of the quartz units recently
constructed have been equipped with accessory equipment that attempts to
maintain clean outside surfaces on the quartz tubes.  The two most common
types of accessory equipment for the quartz units are mechanical wipers
and ultrasonics.  These devices are used on a frequent basis and are con-
sidered part of the normal operation of the unit.  Chemical cleaning is a
task that will typically be required for quartz units on a routine basis.
For example, the quartz tube units at Pella, Iowa were mechanically
wiped once every three hours and chemically cleaned once every two weeks.
The chemical cleaning required one hour per unit.

     Cleaning of UV units will be required in all cases to improve the UV
transmittance properties of the Teflon or quartz.  Teflon has been market-
ed as a non-fouling material, however, observations and measurements made
during this study and prior studies have demonstrated that it is capable
of being fouled by secondary wastewater, in some cases quite severely.
Frequent visual monitoring of the Teflon tubes in a unit is recommended
in order to determine the need for physically and chemically cleaning
the tubes.  A high pressure nozzle cleaning device is available for
scouring fouled surfaces.  Swabbing of the tubes, where possible, is
also recommended.
                                     911

-------
     The need for cleaning quartz tube UV units has been anticipated
since their first usage.  Quartz will foul biologically and/or chemically,
with the rate of fouling dependent on water quality and whether the UV
lamps are on or not.  Accessory cleaning equipment, usually ultrasonics
or mechanical wipers, are provided with most quartz units.   Wipers appear
to have a greater potential for keeping the quartz surfaces clean than
do ultrasonics, however, neither device will preclude the necessity for
chemical cleaning.  Designs incorporating quartz UV units should provide
for some form of chemical cleaning, preferably a recirculation system.

       A solution of the cleaning agent is prepared in the tank with
warm water, then recirculated for a period of time, usually overnight,
typically with the lamps on.  Food-grade citric acid and sodium hydro-
sulfite are the typical cleaning agents used.  Both of these chemicals
have been tested for their ability to clean fouled surfaces of quartz,
including biologically-fouled and inorganic chemically fouled.

     Sodium hydrosulfite is a highly reactive chemical and a strong
oxidant.  This material appears to be most effective in sealed systems
where the cleaning relies solely on contacting the surface under agitated
conditions.  It must be handled with great care, however, and special
requirements will be required to properly store and handle this material
and also to dispose of the spent recirculation waste.  At Suffern, after
an overnight cleaning period, the sodium hydrosulfite, at a concentration
of 0.15%, returned the UV transmissibilities of the quartz tubes to like-
new conditions, roughly 92% UV transmittance for all of the tubes measured.
Even though this chemical is relatively hazardous to handle, it should be
considered as one of the chemicals to be used in cleaning a quartz unit.

     Citric acid is also a commonly used agent to clean quartz surfaces.
A similar testing procedure was followed at Suffern as with sodium hydro-
sulfite, only using citric acid at a concentration of 0.15% as the recircu-
lation chemical cleaning agent.  Although the results of the citric acid
cleaning were not as impressive as with the sodium hydrosulfite, neverthe-
less, citric acid appeared to do an adequate job of cleaning the fouled
surfaces of quartz tubes.

     Other types of cleaning agents can be considered for use with quartz
systems.  Diluted mineral acids such as sulfuric or hydrochloric could be
used to dissolve inorganic scales and to remove biological films from quartz
surfaces.  In a couple of locations, it was noted that a chlorine solution
was being used in an attempt to clean the surface of the quartz.  Chlorine,
which is a disinfectant, will not provide the dissolving ability necessary
to remove the inorganic scales, although it can remove some types of bio-
logical films from the surface of the quartz.

       An effective technique for cleaning the teflon tubes was to spray
a detergent solution through a high pressure (2,800 kgf/cm^ - 400 psi)
circular spray nozzle on the end of a flexible hose which was snaked through
each tube.  The technique took an hour for each set of eight, three meter
tubes.
                                     912

-------
                        TOXICS  TREATABILITY  AND  CONTROL
      The U.S.  Environmental Protection  Agency  (EPA) has  established  a
 National "Policy for the Development  of Water-Quality-Based Permit Limita-
 tions for Toxic Pollutants."  The  EPA national policy was  developed
 because of data indicating  that, even with  efficient removal  of  conven-
 tional pollutants,  toxic substances in  amounts significant to water  quality
 are being discharged through the Nation's wastewater treatment systems.  An
 overall water-quality based toxics control  process  (15)  is available to
 support the policy  of water quality-based permit  limitations  on  toxic
 pollutants entering  treatment  plants.   The  toxics control  process includes
 procedures for evaluating toxics problems in receiving waters, for identi-
 fying bioaccumulative potential of the  toxics for locating and identifying
 the responsible point source discharges and for controlling the  toxic dis-
 charge to eliminate  the  water  quality problem.

      Research  on toxics  in  wastewaters  by the EPA has revealed that  water
 quality problems associated with point  source discharges of toxics exhibit
 extensive site-specific  factors including the amounts, types  and sources of
 toxics,  the control  effectiveness  of  existing treatment  plants and the char-
 acteristics and dilution capacity  of  the receiving water.  Unfortunately,
 solutions to such water  quality problems have complex site-specific  aspects.

      In the past, the study of toxic  discharges into receiving waters by
 treatment plants had focused chiefly  on specific chemicals (16,17).  The
 complexity of  many wastewaters, especially  municipal wastewaters involving
 multiple  industrial  components, however, has also forced the  use of  bio-
 logical measurements  for assessing (18,19)  ecosystem toxicity (overall
 ecosystem toxic effects)  and potential  health effects of these wastewaters.
 Thus  an integrated monitoring and  control approach using both specific
 chemical  and bioassay techniques is evolving for evaluating toxics water
 quality problems.  The monitoring, especially by bioassays on plant
 effluent,  provides sensitive screening  for  identifying potential toxic
 impacts from plant discharges.

 RESEARCH  APPROACHES

     As part of  the  overall  toxics control  process, two parallel approaches
 are being  employed to solve  the toxics  control problems in wastewater
 treatment.   The  first approach uses representative specific toxic compounds;
 the second uses bioassay  tools for characterizing toxic impacts of complex
mixtures  of  unknown toxics.

     In the  first approach,  the characterization of removals and effluent
concentrations of spiked  representative toxics  for a range of treatment and
management practices  involves three levels of research:

        Characterization of  specific toxics  removals for representative
        treatment systems and management practices.
                                     913

-------
     0  Deterministic assessments of the fate of specific toxics and the
        inter-relationships (treatability research) of various removal
        mechanisms in the treatment and management practices.

     0  Development of predictive correlations from the treatability
        research and the specific removal studies.

     A study of specific chemical removals of representative toxics has
recently been completed on conventional secondary treatment and on alter-
native treatments (20) for marine discharge.   Significant treatability
assessments(21,22,23) with a number of representative specific compounds have
also been completed.  One assessment includes predictive methods for fate and
removals of toxics in the activated sludge process using experimentally
determined kinetic rates for the principal removal mechanisms.  Additional
treatability assessments with representative  chemicals are also underway.  A
treatability protocol is being developed to permit municipalities and indus-
tries to evaluate, at bench scale, the fate and treatability of both specific
chemicals and unknown toxic mixtures during wastewater treatment.  Finally,
in the first research approach, a structure for modeling is beginning to
evolve for predicting, from molecular and structural properties of the
toxics, the removal and fate of toxics during treatment.

     In the second approach, characterization of the toxicity removal cap-
abilities of representative treatment and management practices involves
biological assessments (bioassay for ecosystem and health effects) and, to
reduce costs of water quality management, assessments with near real-time
chemical, bacteriological or enzymatic indicators potentially useful as
surrogate bioassays.  Studies are ongoing to  relate the biological
assessment/monitoring, especially of complex  toxic mixtures, to treatment
operations and management practices including treatment alternatives for
marine discharge.

     An important step in the overall toxics  control process is called a
Toxicity Reduction Evaluation (TRE) at individual municipal or industrial
wastewater treatment plants.  Initiated after confirmation of a toxics water
quality problem, the TRE, using an integrated monitoring approach at the
treatment plant, determines the toxics sources, the toxics fate during and
impact on treatment, the variability of pass-through of the overall toxicity
in the effluent wastewater and finally the probable solutions for controlling
the toxicity discharge.   Case histories of toxicity reduction evaluations are
being initiated at the Patapsco Treatment Plant in Baltimore and at other
sites for the purpose of developing TRE protocols for use by the wastewater
treatment industry.

                            TOXICS REMOVAL STUDIES

     The EPA's Office of Marine and Estuarine Protection is concerned about
toxics pass-through in alternative treatment  systems for marine discharge
cases where removal of conventional pollutants by full secondary treatment
is not necessary to meet conventional water quality objectives.  Primary
interest has been focused on a list of 129 organic and inorganic priority
                                     914

-------
pollutants developed from a Consent Decree between the National Resources
Defense Council and the Administrator of the U.S. Environmental Protection
Agency (24).  A specific toxics removal study (20) using a spiking mixture
of 21 volatile and semi-volatile organic priority pollutants and the
indigenous trace metals in the Cincinnati wastewater was completed for five
alternative systems with the conventional primary-activated sludge treatment
system used as a control.  The pilot-scale alternative treatment systems
included primary treatment plus commercial pulsed-bed filtration, chemical
clarification with alum, primary-high rate trickling'filter treatment, and
single stage aerated and facultative lagoon treatments.

       Removal efficiencies for total suspended solids (TSS), chemical
oxygen demand (COD), total Kjeldahl nitrogen (TKN), and total phosphorus
(TP) for each alternative system during the study averaged:

                                       TSS %     COD %     TKN %     TP %

     0    Primary plus filtration  -    86        40        15       44

          Chemical clarification   -    89        49        12       75

     0    High rate trickling
          filtration               -    76        47        14       39

     0    Aerated lagoon           -    85        60         2       19

          Facultative lagoon            84        65        11       31
o
          Activated sludge         -    93        82        80       58

     The removals of the volatile, semivolatile and the trace metal priority
pollutants for the alternative treatment systems and for primary and primary-
activated sludge treatment are shown for the three pollutant classes in
Tables 8, 9 and 10, respectively.  Paralleling the removals of conventional
pollutants, the primary-activated sludge control system produced the best
overall removals of organics, typically 80-90% removal of volatiles, 85-95%
removal of semivolatiles and 24 to 82 percent removal of the metals.  The
facultative lagoon with 26-day hydraulic retention was the best overall
alternative treatment system followed by the aerated lagoon (6-day hydraulic
retention) for overall control of toxics.  Metals removals, however, were
not established for chemical treatment and primary plus filtration.  Chemi-
cal treatment (25) is known to remove most metals very efficiently.

     While none of the alternative processes provided overall toxics removal
capabilities equal to the activated sludge system, the facultative lagoon
provided similar removals of volatile organics and the best observed
removal of lindane.  The chemical treatment system produced good removals
of those organics which partition strongly to the solids in the treatment
system.  The study revealed that alternative treatment systems, especially
those without biological treatment components, would permit significantly
increased toxics pass-through.
                                     915

-------
TABLE 8.  VOLATILE ORGANICS REMOVALS BY DIFFERENT PROCESSES (20)

Primary Primary Plus
Compound Inf Treatment Filtration
>ig/L jig/L ZRem jug/L ZRem
Carbon Tetra- 69 63 19 56 22
chlorJ.de
1,1, Dichloro-
ethane 144 144 - 98 32
1,1, Dichloro-
ethylene 212 188 5 138 22
Chloroform 135 143 -7 113 18
1,2 Dichloro-
ethane 153 135 7 96 34
Bromoform 90 83 18 119 2
Ethylbenzene 111 102 9 70 35
Average Removal
of Volatiles 7 24
Chemical
Clarifi- Trickling Aerated Facultative Activated
cation Filter Lagoon Lagoon Sludge
jug/L ZRem .ug/L %Rem jug/L ZRem jug/L ZRem *ig/L ZRem
101 -13 26 59 15 70 11 77 13 74

111 21 94 34 45 68 19 87 8 94
150 25 85 58 83 60 35 85 14 92
106 20 102 25 53 61 31 80 18 86
109 22 93 33 45 70 15 90 22 84
114 -6 41 57 15 80 22 84 29 65
73 31 31 71 27 70 12 96 6 93
14 48 68 86 84

-------
                                            TABLE 9.  REMOVAL OF SEMIVOLATILE ORGANICS BY DIFFERENT PROCESSES (20)
vo
Compound
Bis(2 ethylhexyl)-
phthalate
Dibutylphthalate
Naphthalene
Phenanthrene
Pyrene
Fluoranthene
Isophorone
Bis(2-chloroethyl)-
ether
p-Dichlorobenzene
Phenol
2,4 Dichlorophenol
Pentachlorophenol
Lindane
Heptachlor
Inf
pg/L
168
73
108
95
104
104
89
143
93
126
228
84
39
39
Primary
Treatment
Pg/L
90
68
92
76
84
80
77
122
75
112
133
78
40
26
ZRem
37
2
13
21
18
22
4
6
19
23
45
16
-4
32
Primary Plus
Filtration
Mg/L
47
56
86
48
39
39
74
120
66
131
300
90
-
-
ZRem
75
22
20
49
61 .
61
8
20
29
4
-
19
-
-
Chemical
Clarifi-
cation
/L
15
47
79
24
12
13
80
114
66
99
92
50
32
14
ZRem
89
31
23
74
88
87
5
17
28
21
60
50
17
64
Trickling
Filter
/ig/L
39
52
74
51
48
49
72
132
58
64
200
82
34
18
ZRem
75
26
28
45
54
53
17
-
36
50
31
4
13
53
Aerated
Lagoon
>ug/L
34
44
36
40
36
36
68
102
31
84
155
57
22
13
ZRem
77
40
64
55
63
64
22
23
65
30
48
37
42
66
Facultative
Lagoon
AL
30
14
13
16
25
23
62
78
12
18
65
20
7
13
ZRem
80
78
87
82
75
77
25
43
87
86
73
74
80
62
Activated
Sludge
/L
18
7
4
4
5
5
2
30
5
14
1
3
31
13
ZRem
87
88
97
95
95
95
98
80
94
86
99
96
18
65

-------
TABLE 10.  METALS REMOVALS BY DIFFERENT PROCESSES (20)
Metal Inf
yg/L
vo Cr 221
CO
Cu 345
Ni 141
Pb 165
Cd 25
Primary
Treatment
yg/L
206
279
136
115
22
%Rem
7
19
4
30
12
Trickling
Filter
yg/L
107
137
98
86
18
%Rem
52
60
30
48
28
Aerated
Lagoon
Ug/L
65
89
91
70
_
%Rem
71
74
35
50
_
Facultative
Lagoon
Ug/L
46
71
81
82
17
%Rem
79
79
43
50
32
Activated
Sludge
Pg/L
40
61
81
58
19
%Rem
82
82
43
65
24

-------
                            TREATABILITY  RESEARCH

      The  completed  studies  (21,22,23)  on treatability have evaluated  the
 relative  removals of  selected  toxics by  the  three  principal  removal mecha-
 nismsvolatilization,  biodegradation  and sorptionin  the activated  sludge
 process.   Two  of the  studies  (21,22) also evaluated the impact  of  the selected
 toxics on anaerobic digestion.   One study (23) assessed the  effect of powdered
 carbon adsorption on  toxic  removals in the activated sludge  system.   These
 studies have generated  experimental kinetic  data on the competitive removal
 rates of  the principal  removal mechanisms and have provided  insight into
 effects of operating  design factors such as  sludge retention time  (SRT) on
 the  toxic control capabilities.

      Data from the  Purdue studies  (21,22)  on 8 representative priority
 organics  in Table 11  reveal that efficient (often  more  than  99%) removal
 of the organics was achieved after treatment using acclimated biomass, even
 for  highly chlorinated  organics  such as  pentachlorophenol (PGP).  The data
 further reveal that biodegradation was the principal removal mechanism.
 The  sorption mechanism  contributed approximately 20% of the  removal of
 bis(2-ethylhexyl) phthalate (BEHP) for all operating SRT except 3 days.  At
 the  low 3-day  SRT,  sorption was  responsible  for 55% of  the removal.   The
 volatilization mechanism contributed from 20 to 80% of  the removals of
 toluene (TOL)  and naphthalene  (NAPTH) with the high volatilization
 contributions  occurring at  the high SRTs  of  7 and  11 days.   The modest
 removal contributions of the sorption mechanism in the  activated sludge
 process indicates that  biodegradation  by  acclimated biomass  will degrade
 even those organics with high octanol water  partition coefficients such as
 bis(2-ethylhexyl) phthalate.  The study  found that the  rates of volatiliza-
 tion for  moderately volatile organics  such as toluene and naphthalene were
 competitive with the  rates  of biodegradation.

     Data on acclimated anaerobic digestion  of the same 8 organics revealed
 that parachlorometacresol (PCMC) was partially refractory to the anaerobic
 process with 30 to  40%  remaining after digestion.  Four  organics, penta-
 chlorophenol,  dimethyl  phthalate (DMP), dinitro-orthocresol  (DNOC) and
 bis(2-ethylhexyl) phthalate were reduced  in  concentration by more than 99%;
 chlorobenzene  (MCB) and naphthalene were  reduced by more than 95% and
 toluene,  by 91%.  In  the anaerobic process,  variable amounts of these
 organics  were  removed by the sorption and  volatilization mechanisms.

     Data  from  the  University of Michigan  studies  (23)  on 8  priority  organics
 in Tables  12 and 13 confirm the importance of the  biodegradation mechanism
 in removing organics of moderate volatility.   For  the organics studied,
 sorption  contributed little to the removal process.  The relative importance
 of the biodegradation and volatilization mechanism shown in Table 12  revealed
 that volatile but non-biodegradable organics such  as 1,2,4-trichlorobenzene
are  removed effectively from the water by  the volatilization mechanism.
Non-biodegradable and poorly sorbable organics such as  lindane pass through
the  treatment process.  The relative importance of the volatilization and
biodegradation mechanisms in the removal of  the organics depended upon the
                                     919

-------
                                          TABLE 11.   FATE  OF  ORGANICS IN ACCLIMATED ACTIVATED SLUDGE (22)
PO
o
Compound
PCP



MCB



DMP



BEHP



TOL



NAPTH



PCMC



DNOC



SRT
Days
3
5
7
11
3
5
7
11
3
5
7
11
3
5
7
11
3
5
7
11
3
5
7
11
3
5
7
11
3
5
7
11
Compound
in
Feed
mg/L
20
20
20
20
16.3
16.3
16.3
16.3
20
20
20
20
2.64
2.64
2.64
2.64
26.1
26.1
26.1
26.1
4.24
4.24
4.24
4.24
20
20
20
20
20
20
20
20
Compound
Remaining
in Eff .
Ug/L
214
105
68
64
<5
<5
<5
<5
<5
<5
<5
<5
138
75
66
68
<5
<5
<5
<5
<5
<5
<5
<5
7.9
4.8
4.0
5.0
666
760
301
85
Affected
Other
COD
Removal?
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Fate of Compound: Percentage
Stable
Compound
Removal ?
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
In
Effluent
1.07
0.53
0.34
0.32
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
5.2
2.8
2.5
2.6
<0.02
<0.02
<0.02
<0.02
<0.12
<0.12
<0.12
<0.12
0.08
0.05
0.04
0.05
6.7
7.6
3.0
0.85
Sorbed
on Solids
0.31
0.15
0.10
0.08
2" x 10~4
2 x 10~4
2 x 10~4
2 x 10~4
<10~2
<10~2
<10~2
<10~2
55.4
15.5
13.3
18.7
<10~2
<10~2
<10~2
<10~2
0.23
0.19
0.19
0.20
3.04
0.95
0.83
1.26
0.11
0.17
0.02
<10~2
Vola-
tilized
0.03
0.03
0.03
0.04
<7
<11
<16
<21
<10~2
<10~1
<10~1
<10~1
<10"2
<10~2
<10~2
<10"2
<21
<32
<48
<60
<29
<32
<68
<84
<10"2
93
>89
>84
>79
>99.9
>99.9
>99.9
>99.9
39.4
81.7
84.2
78.7
>79
>68
>52
>40
>71
>68
>32
>16
96.9
99.0
99.1
98.7
92.7
91.7
96.7
99.0

-------
              TABLE 12.  FATE OF TOXIC ORGANICS IN ACCLIMATED
                         ACTIVATED SLUDGE BIOREACTORS (23)
                         	Percent of Influent	
   Compound              Effluent     Off-Gas     Biosorbed     Biodegraded
Benzene
Toluene
Ethylbenzene
o-Xylene
Chlorobenzene
1 , 2-Dichlorobenzene
1,2, 4-Trichlorobenzene
Nitrobenzene
Lindane

-------
relative kinetic rates of the two removal mechanisms (Table 13).  Dichloro-
benzene, a relatively slowly degradable organic, exhibited the highest
volatilization removal contributions.  Acclimation periods for the organics
ranged from 7 to 14 days.

     The addition of powdered activated carbon (PAC) provided enhanced
removals of 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, and lindane.
Powdered carbon addition effected reductions in both the effluent and off-
gas concentrations of volatile, non-biodegradable compounds.  PAC doses as
small as 25 to 50 mg/L produced significant improvements in non-biodegrad-
able toxics removal compared with control activated sludge systems.  Greater
than 90% removals occurred at influent carbon doses of 100 mg/L.  The
addition of PAC at influent doses less than 100 mg/L did not enhance the
removal of the biodegradable toxic organics.

     PAC bioreactor studies in the University of Michigan study, conducted
at solids retention times (SRT's) of 0.25 to 12 days and a 50-mg/L carbon
dose, showed that the removal of non-biodegradable toxics was the same over
the range of SRT's studied.  The most important operating parameter with
respect to removals of toxics was the influent PAC concentration.

     A major EPA inhouse research effort has recently been initiated to
expand the data on specific removal contributions of the principal removal
mechanisms in the activated sludge process.  Studies on biodegradation
using bench scale completely mixed reactors and electrolytic respirometry
techniques (Figure 13) are underway on selected organics to ultimately
permit prediction of the biodegradability from molecular properties and
structures.  The electrolytic respirometry techniques readily provide
acclimation data, toxics inhibition data, and biodegradation kinetics.
Parallel kinetic studies with appropriate organics on raw solids, accli-
mated and unacclimated biomass and digester solids are also being conducted
to provide the needed removal contributions from the sorption and volatili-
zation mechanisms.

     The inhouse research effort is also evaluating the fate and removal of
metals in the conventional primary-activated sludge process.  The sorption
of metals on raw solids, biomass and digestion solids is being evaluated in
equilibrium and kinetic studies.  Typical empirical adsorption isotherms
for metals on activated sludge biomass are shown in Figure 14.  The desorp-
tion of metals and organics from sludges, both in seawater and freshwater
is also being evaluated.
                                    922

-------
                                         Oxygen Consumption (mg/L)
                   500
10
ro
CO
                   400
                00
                6
                
-------
        100
        10
     r
         1.0
         0.1
                                                  F
                                                    j'
                                                            TTT
                                                            Cu
                                                            Cr
          0.001
0.01             0.1

        Residual Cone. (C,), mg/l
                                                       1.0
                                                                      10
      Figure 14.  Adsorption isotherms for metals on aerobic biomass.
                  THE TOXICITY REDUCTION EVALUATION  (TRE)

     The biomonitoring screening of point source discharges  and  the  follow-
on studies to evaluate the impact of the toxic discharge on  the  receiving
water establish the control requirements for the TRE at the  treatment
plant.  The control requirements usually are presented as  integrated
toxicity levels that must be achieved by the point source  discharge  to
eliminate the toxic water quality impact.  Such levels will  ultimately be
established using a statistical approach that will be based  upon desired
water quality and the historical variability of the  receiving water  flow or
dilution capacity.

     With the desired toxicity levels established for the  discharge, the
overall elements of a typical TRE at the treatment plant are presented in
Table 14.  The first step is the evaluation of the toxicity  reduction  occur-
ring across the treatment plant and the determination of the probable  cause
of the excessive toxicity in the discharge.  A key determination is  whether
operational deficiencies at the plant significantly  contribute to the
toxicity pass-through or whether the presence of toxicity  refractory to the
plant's treatment processes principally produces the excessive toxicity.
                                     924

-------
     The next step in the TRE involves two elements, occurring in parallel,
in which the toxicity is traced to its sources and the important toxicity
components, if possible, are identified and the ecosystem and the health
effect biomonitoring assays, in-plant toxicity monitoring assays, and
specific chemical analytical techniques are all employed to achieve the
goals of this step.

     Finally, an evaluation of the control alternatives to eliminate the
excessive pass-through is conducted.  The evaluation includes assessing
possible industrial process modifications to minimize release of the toxics,
the use of pretreatment approaches to control the toxics before discharge
to the central plant, and improvement of the central plant's operations to
control the toxicity.

     The research approach to developing appropriate protocols on TRE for
use in municipal wastewater treatment involves:

     0    Toxicity reduction studies on pilot and full-scale treatment
          systems to determine representative toxicity reduction capabili-
          ties of municipal wastewater treatment processes.

     0    Case histories of research TRE at selected full-scale treatment
          plants to assess the capabilities of the monitoring tools and the
          treatability and pretreatment approaches likely to be incorporated
          in the municipal protocols for TRE.

     0    Research on techniques to enhance the toxicity reduction capabili-
          ties of the central treatment plant.
           TABLE 14.  ELEMENTS OF A TOXICITY REDUCTION EVALUATION
          Treatment Plant Evaluation of Causes of Toxicity Pass-through.
               A.   Plant Operations Deficiency.
               B.   Presences of Refractory Toxicity.

          Tracing of Toxicity to Sources.
               A.   Bioassay Monitoring.
               B.   Alternative Monitoring Techniques.

          Identification of Toxicity Components.
               A.   Specific Chemical Identification.
               B.   Bioaccumulative Potential.

          Evaluation of Control Alternatives.
               A.   Industrial Process Modifications.
               B.   Pretreatment Alternatives.
               C.   Central Treatment Plant Control of Toxicity.
                                     925

-------
Parallel research is also ongoing on TRE protocols and case histories for
industrial wastewater treatment.  The parallel research will include the
assessment of approaches for industrial process modification to minimize
toxicity release.  These industrial techniques will be appropriately
referenced in the protocols on the municipal TRE.

TOXICITY REDUCTION CAPABILITIES

     Pilot-scale research using wastewater spiked with representative toxic
mixtures has revealed a good capability of the central treatment plant to
reduce toxicity, but toxicity penetration into the plant effluent does
occur.  As an example of the treatment plant capabilities, acute toxicity
reductions (18) of 100 percent based upon Fathead Minnow bioassays (26) were
achieved in a pilot-scale primary-activated sludge treatment plant for the
indigenous (metals and organics) toxicity in an industrialized raw Cincin-
nati wastewater.  The spiking at 50 yg/L levels of each compound in a
mixture of 22 of the Agency's priority organic pollutants into the same
wastewater, however, produced an increase in the toxicity of the raw waste-
water and substantial pass-through, even with acclimation, of residual
toxicity (Table 15).  Selected compounds, most importantly lindane in the
spike, were refractory to the treatment processes.  High conventional pollu-
tant removals (17) were always achieved during this study, independently of
the spiked toxics.

     Pilot and full-scale studies (19), using Ames (27) and mammalian
cell (28) assays have revealed the presence and pass-through of mutagenic
materials in municipal wastewaters.  The mutagenic materials were extracted
from several Cincinnati wastewaters with methylene chloride, first at pH 2,
then at pH 11.  The concentrated extracts were combined and solvent trans-
ferred into dimethyl sulfoxide (DMSO) to eliminate the effect of methylene
chloride on the subsequent mutagenicity assays.  The results of the Ames
assays (Table 16) revealed substantive but variable amounts of mutagenicity
in the influent wastewaters, ranging to approximately 20,000 revertants per
liter.

     The mutagenicity removals in these tests with efficient conventional
treatment, varied from substantive removal to essentially no removal of the
mutagenicity.  This study and others also revealed that wastewaters of
domestic origin have extractable mutagenicity levels, usually around 500
revertants per liter of effluent.

     The high number of not detectable (N.D.) responses in these studies on
the raw wastewaters or primary effluents are usually caused by cytotoxic
effects from the large amounts of extracted organics in the extract.  Unlike
the secondary effluent tests,  the cytotoxic effects prevented testing of the
extracted organics from the raw or primary wastewater over an appropriate
concentration range to properly evaluate the mutagenicity.  Additional tests
with mammalian cell assays (28) using Syrian hamster cells reveal qualita-
tively similar responses between the two assays.   The results from the
mammalian cell assays suggest  higher removals of  mutagenicity measured by
the mammalian cell compared with the results from the Ames test.
                                     926

-------
     Currently, the assay results from the Ames test or other health effects
screening assays have not been related to health effects risk.  Research,
currently ongoing, is attempting to establish a link between health risks
and the screening assay results.
             TABLE 15.  ACUTE TOXICITY* IN WASTEWATER TREATMENT
            Control System
Spiked System**
LC-50 percent % Toxicity
Inf. Eff. Reduction***
30
11
9.3
30
10.2
18.5
10.1
20.6
> 100
> 100
> 100
> 100
> 100
> 100
> 100
> 100
100
100
100
100
100
100
100
100
LC-50 Percent I
Inf. Eff.
4.6
2.7
9.5
4.5
4.3
5.8
6.5
1.9
13.1
16.1
35.5
6.6
9.4
30
30
8.0
I Toxicity
Reduction***
65
83
73
32
55
81
78
76
    *Fathead Minnow  acute toxicity.   (Data developed by the Environmental
     Monitoring and  Support Laboratory-Newtown Facility, Cincinnati, Ohio.)

   **Spiked with 22  priority organics.

                                 [(l/LC-50) inf -  (l/LC-50) eff]
  ***% Toxicity Reduction
                                                                 x 100
                                          (l/LC-50) inf
     At an LC-50 in the effluent of > 100; equation does not apply and
     the acute toxicity reduction is considered as 100%.
                                    927

-------
                         TABLE 16.  MUTAGENICITY IN THE AMES TEST OF MUNICIPAL WASTEWATER SAMPLES AT VARIOUS TREATMENT  STAGES
ro
00
TA98 Mutagenicity
Treatment Wastewater
Plant Type
Mill Creek Industrial/
T&E Facility Domestic





Mill Creek Industrial/
Plant Domestic

Muddy Creek Domestic
Plant
Sample
Designation
(Date)
Series Aj
09/02/81


Series A2
09/09/81


Series Bi
08/31/82
Series 82
06/20/83
Series C,
01/11/83
Total
Treatment Liters
Stage Extracted
Raw Wastewater
Primary Effluent
Secondary Effluent
Secondary + Cl2
Raw Wastewater
Primary Effluent
Secondary Effluent
Secondary + Cl2
Raw Wastewater
Secondary Effluent
Primary Effluent
Secondary Effluent
Raw Wastewater
Secondary Effluent
2
2
6
6
2
2
6
6
8C
50C
23
86
24C
92C
Conc.a
(mg/L)
48.8
41.8
4.9
4.6
66.5
46.0
4.6
4.0
91.0
7.7
70.4
8.7
36.8
2.2
net
revertants/
mg
-S9
173
1,057
169
196
N.D.
77
5,645
6.370
N.D.
417
N.D.
693
N.D.
161
+S9
381
524
1,376
1,768
182
392
4,074
4,318
89
353
129
761
N.D.
175
netb
rever-
tants/
liter
18,593
21,903
6,674
8,133
12,103
18,032
18,944
17,272
8,099
2,718
9,082
6,621
385
TA100 Mutagenicity
net
revertants/
mg
-S9
N.D.
N.D.
N.D.
N.D.
N.D.
N.D.
1,836
2,246
N.D.
N.D.
N.D.
928
N.D.
208
+S9
N.D.
N.D.
258
409
N.D.
N.D.
1,035
2,146
N.D.
244
N.D.
1,540
N.D.
284
ne^
rever-
tants/
liter
;
1,251
1,881

4,813
8,584
1,879
13,398
625
             N.D. - not detectable  (i.e. response at any sample dose  level was  less  than 2-fold  above  concurrent  solvent  control).
             aRefers to the concentration of extractable organlcs based on the  residue  weights of  the  extract*.
             bBased on the mutageniclty values from the assays with S9 activation.
             Extraction at pH  11.0 was omitted.

-------
TOXICITY REDUCTION SURVEY

     A toxicity reduction survey is now being completed at six municipal
wastewater treatment plants in the State of Ohio.  The plants were selected
for the survey to represent wastewaters of chiefly domestic origin, waste-
waters with modest industrial contributions, and wastewaters with substantial
industrial contributions.  The toxicity entering and leaving the treatment
plants were measured using static renewal seven-day acute-chronic Fathead
Minnow (29) and Geriodaphnia (30) assays for assessing ecosystem effects, the
Ames test and mammalian cell assays cells for mutagenicity screening, and the
Sister Chromatid Exchange assay (31) using Chinese hamster ovary cells for
genotoxicity.  Analyses for conventional pollutants and for specific toxic
trace metals and individual organics were also provided.  The State of
Ohio's Environmental Protection Agency also conducted fish diversity studies
using electroshock techniques on the receiving waters associated with some of
the treatment plants.

     Examples of representative toxicity reductions are shown in Tables 17
and 18 for the wastewater treatment plant at Akron, Ohio and the Little
Miami Plant in Cincinnati.  The Akron Plant, with substantive industrial
contributions to the wastewater, exhibited the highest influent toxicity of
all the surveyed plants with no effect concentrations (NOEC) ranging from
0.3 to 1 percent of the influent wastewater.  The Akron plant, which was
achieving nitrification and meeting its conventional pollutant removal
requirements during the survey, also achieved efficient toxicity removal
with the NOEC ranging from 10 percent of the effluent for acute (survival)
effects on Fathead Minnows to 100 percent effluent for acute (survival)
effects on both the Fathead Minnow and the Ceriodaphnia assays.  The NOEC
of 10 and 30 percent in the Akron effluent suggests only a modest toxicity
in the discharge to the receiving water ecosystem.

     The Little Miami Plant, with modest industrial contributions to its
wastewater, exhibited less toxicity in the influent wastewater but also
achieved little toxicity reduction across the treatment plant.  The Little
Miami effluent with NOEC of 1 to 10 percent effluent for the Ceriodaphnia
assay was the most toxic of the effluents evaluated in the survey, even
though the plant was meeting its conventional pollutant removal require-
ments.  Finally, the data presently available on plants in the survey with
wastewaters of chiefly domestic origin revealed modest toxicity in the
influent and essentially no aquatic toxicity in the effluent.

     To assess the probable effect of the effluent on the receiving stream,
however,  the stream dilution capacity must be considered.  For the Akron
Plant, the effluent contributes more than 50 percent of the stream flow
during summer low flow conditions.   In contrast, the Little Miami effluent
provides less than 1 percent of the flow to the Ohio River, even at summer
low flow conditions.   With substantive dilution, the Little Miami toxicity
discharge is unlikely to affect the Ohio ecosystem.  The effluent-dominated
Cuyahoga River at Akron, however,  could be affected by the modest toxicity
discharges from the Akron Plant.
                                    929

-------
     TABLE 17.  TOXICITY REDUCTION AT AKRON, AS NO OBSERVED EFFECT
                CONCENTRATIONS* (NOEC), IN PERCENT EFFLUENT
                   	Fathead Minnows	   	Ceriodaphnia	

  Sample             Survival	Growth      Survival    Reproduction
                   8/84   5/85   8/84   5/85   8/84   5/85   8/84   5/85
 Influent          <0.3   1.0    0.3     1.0    0.3    1.0    0.3    1.0

 Secondary
 Effluent            30    10    10a      30    >30     30     30     30

 Chlorinated
 Secondary           10    10  M00b    MOO     30   MOO     30     30

 Dechlorinated
 Secondary         MOO    10  M00b      30     30   MOO     30     30


a - CLo may have been present in sample.
  - Low control value, NOEC may be lower.
*A11 NOEC data are subject to final statistical review.  (Data developed
 by the Environmental Monitoring and Support Laboratory-Newtown Facility,
 Cincinnati, Ohio.)
 TABLE 18.   TOXICITY REDUCTION AT LITTLE MIAMI, AS NO OBSERVED EFFECT
             CONCENTRATIONS* (NOEC), PERCENT EFFLUENT
Sample
Influent
Secondary
Effluent
Fathead Minnows Ceriodaphnia
Survival Growth Survival Reproduction
12/84 5/85 12/84 5/85 12/84 5/85 12/84 5/85
10 10 10 10 3 10 0.3 3
MOO MOO 30 30 1 10 1 3
 Chlorinated          30    30      30    30      1    10
 Plant Effluent

 Dechlorinated        30    30      30    30      1    10
 Plant Effluent
*A11 NOEC data are subject to final statistical review.  (Data developed
 by the Environmental Monitoring and Support Laboratory-Newtown Facility,
 Cincinnati, Ohio.)


                                   930

-------
     The fish diversity studies (Figure 15) on the Cuyahoga River, indeed,
indicated a major toxic impact on the fish population beginning at the point
of discharge of the Akron Plant.  Upstream of the discharge, the fish popula-
tion was found to be good.  The fish populations in the River's tributaries
also, usually ranged from fair to good.  The fish diversity study, conducted
three times during the Summer of 1984 and spanning the time of the toxicity
survey, revealed a persistent loss of fish in the Cuyahoga for about 10 miles
down stream of the Akron discharge and a second toxics impact when the River
entered the Cleveland Ship Channel at Lake Erie.  No other significant waste-
water discharges enter the Cuyahoga immediately below Akron, as the River
passes through the Cuyahoga National Park Recreational Area.  In addition,
appropriate measurement of stream dissolved oxygen (D.O.) and ammonia concen-
trations revealed no D.O.  or ammonia toxic impacts on the River immediately
below Akron.  Overall, the stream fish diversity indicated major toxicity
impacts on the River, perhaps the most significant impacts in the State of
Ohio.
               o
               x
               O
               UJ
          o.
          t-
                    o
                    DC
       X
       HI
       Q
       CO
       cc
       Ul
       X
       CO
10-

 8.


 6-
Ul
UJ
CC
O
UJ
z
                      Q
                      Z
                      <
                      a.
                      m
in
UJ
cc
o
CO
cc
UJ
                                      J_
                                            0.
                                            H
           Ul _l X
           Ul CC UJrf
           CC UJ Wo
           |Egl
                                2 co mo
                                U	U_B
LU
Z
z
X
o

I  CLEVELAND HARBOR
co	
                               O - TRIBUTARY MEASUREMENT
                                                         EXCEPTIONAL
                                                               GOOD
                                                     POOR
            45   40  35   30  25   20  15   10

                           CUYAHOQA RIVER, miles
                                               -5  -10  -15
             Figure 15.   Toxicity impact on the Cuyahoga River.
                        (Data developed by the Ohio EPA.)
                                    931

-------
     Other data obtained during the survey revealed low metals concentra-
tions (Table 19) and very modest concentrations of specific extractable
organic residuals in the Akron plant's effluent (Table 20).  In addition, the
relatively complex GC chromatograms on the highly toxic plant influent, and
the relatively "clean" GC chromatograms of the effluent (Figures 16 and 17)
supported the observed efficient toxlcity reduction achieved by the treat-
ment plant.  Further, the Ames test screening for mutagenicity (Table 21)
also revealed only modest mutagenicity in the effluent, indeed not signifi-
cantly different from effluents from plants treating chiefly domestic
wastewater.  Unfortunately, because the plant's Influent is highly toxic
its mutagenicity could not be determined.
                      TABLE 19.   AKRON METALS REMOVAL*
                                    Concentration (mg/L)
Metal
Inf.
As BDL**
Ca 90.3
Cd 0.0012
Cr .088
Cu 0.19
Fe 0.28
Mg 22.7
Mn 0.204
Ni 0.34
Pb 0.057
Zn 0.447
1984
Eff.
0.0077
75.8
BDL
.016
.026
0.17
14.5
0.102
BDL
BDL
0.038

Inf.
BDL
95.6
0.028
BDL
.029
2.14
24.2
0.417
0.022
0.046
1.333

Eff.
BDL
72.1
0.0094
BDL
.011
0.913
16.5
0.313
0.013
BDL
BDL
1985
Up
Stream
BDL
65.1
0.0041
BDL
BDL
0.583
15.7
0.200
0.0062
BDL
BDL

Down
Stream
BDL
67.6
0.0097
BDL
BDL
0.633
16.5
0.165
0.010
BDL
BDL
 *Data developed by the Water Engineering Research Laboratory-Cincinnati,
  Ohio.
**BDL - Below detection limit.
                                    932

-------
cX
               TABLE 20.  EXTRACTABLE ORGANIC ANALYSIS OF AKRON CHLORINATED SECONDARY*
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Compound
d( 10) anthracene
n,n-dimethylf ormamide
tetrachloroethene
1 , 6-hexanediol
1 -cyclohexen- l-ol
2-cy clohexen- 1-one
benz aldehyde
unknown
unknown
hydrocarbon
hexane
unknown
5-hexen-2-ol
benzothiazole
unknown
unknown
unknown
unknown
unknown
hexanedioic acid, bis(2-ethylhexyl)
bis(ethylhexyl)phthalate
unknown
Pg/L
Internal. Std.
8
65
10
7
4
6
5
4
3
2
2
7
4
2
24
2
2
5
ester 50
7
2
               *Data developed by the Water Engineering Research Laboratory-Cincinnati,
                Ohio.
                                                 933

-------
                                         Detector Response
                                                                                         O
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5T O
fD ft
u>
rt H-
tt> O


Pi O

eg g"
(* o


0) rt
         Ol
         O
         O
         O
         o
         o
b
TO
        g.  Q-
fu  r^  Cr  ^^
r(  ftj  (0  O

s-*-H
c-1
pi  CO
o1 rf
o  n>
rt
o
O ^^
H- O
3  IB
O  rt
H. pj


3  O.
in  m
rt  <
   O
o-o
 -
      2
      2
      2.
       *
         IN)
         O.
         o
         o
         IN}
         en.
         o
         o
         CO
         o
         o-
         o
                                                                                               O
                                                                                               Z
c
m
z
H

-------
                                        AKRON CHLORINATED EFFLUENT
           16.7-x
UD
OO
tn
           
01
p
                000
               500
1  I  '

1000
1500
2000
1  I  '

2500
1  I  '
3000
3500
                                          scan number, seconds

                   Figure  17.  Total ion  chromatogram on plant effluent.   (Data developed by
                              the Water  Engineering Research Laboratory,  Cincinnati, Ohio.)

-------
'/I
                                TABLE  21.   AKRON MUTAGENICITY  STUDY*
                                           Concentration  of
                Sample                  Extractable  Organics      AMES      Mutagenicity
                (1984)                          mg/L           REV**/mg        Rev*/L
                Raw Wastewater                  45.09           N.D.***          	


                Secondary Effluent                3.66              140             512


                Chlorinated Secondary            3.02              130             393
              *Data developed by the Health Effects Research Laboratory-Cincinnati,  Ohio.
             **REV = revertants.
            ***N.D.** = Not  detectable  (i.e.,  response  at  any  sample  dose  level was  less
               than 2-fold above solvent  control).

                 The toxicity in the Akron effluent with the relatively  "clean" waste-
            water, as measured by residual metals  and specific extractable organics,
            raised questions about the  sources of  the toxics causing  the observed and
            persistent loss  of fish in  the Cuyahoga River  at Akron.   Thus, studies to
            measure variability of the  effluent toxicity,  to reconfirm the lack of fish
            in the River,  and to identify responsible specific toxics in the  effluent
            are being conducted this summer.

                 Finally,  a  preliminary review of  the plant's  operating  records has
            also revealed  intermittent  bypassing of combined sewer  flows at the treat-
            ment plant.  Indeed, the bypassing of  the highly toxic  plant influent could
            represent the  most important  contribution to Cuyahoga's toxicity  problem at
            Akron.  A full-scale TRE, as  a research case history, is  now under consid-
            eration for Akron.  The decision  to use Akron  as a detailed  case  history
            will follow the  review of the ongoing  confirmatory studies on  the toxicity
            impact.

            TRE CASE HISTORIES

                 Two case  history studies on  TRE's are  about to begin.  The first case
            history, to begin this fall,  is at the Patapsco Wastewater Treatment  Plant
            in Baltimore,  Maryland.  The  second case history will likely be at Akron,
            if the ongoing confirmatory studies confirm the need.

                 The Patapsco Wastewater  Treatment Plant,  completed in 1982,  is a 70 mgd
            pure oxygen activated sludge  plant, currently  treating  35 mgd  at  design
            conditions using one-half the plant's  treatment capacity. The industrial
            contribution to  the Patapsco  municipal wastewater, chiefly from the organic
            chemicals industries in Baltimore, currently totals about 30 percent  of  the


                                                936

-------
plant influent.  The case history TRE for Baltimore was selected not only
because of substantive influent toxicity at the treatment plant and a
history of intermittent pass-through of that toxicity (Tables 22 and 23)
but also because of a historical and ongoing in-plant toxicity monitoring
and control program.

     Two sources of wastewater, a chiefly industrial flow (IPI) and a flow
(SWD) from domestic-commercial sources are combined to form the plant
influent.  The in-plant monitoring MICROTOX procedure (32) on daily composite
samples at the plant uses a maximum of 45.5 percent wastewater in the test.
For low toxicity levels that require more than 45.5 percent wastewater to
produce a measurable EC5Q, the 50 of the sample was recorded as > 45.5
percent.  Thus, the low toxicity effluents and the domestic-commercial
influent flows (SWD) do not always have a defined 50-  To provide the
monthly average perspective given in Table 22, EC^Q values of > 45.5 percent
were included in the monthly averaging procedure as 45.5 and the monthly
average EC5Q in the table was presented as a greater than ( value.  The
number of days in the month that an EC5Q lower than > 45.5 occurred is also
included in Table 22.  The averaged monthly ^59 values for the effluent
are all less than > 45.5 and indicate a toxicity pass-through during each
month.  The number of days that measurable toxicity pass-through occurs
ranged from 7 days per month to 26 days per month.
                  TABLE 22.  MICROTOX TOXICITY AT PATAPSCO*
1985
Jan.
Feb.
Mar.
Apr.
May
Jun.
IPIa
Avg.
3.
2.
3.
3.
5.
8.
INF.
EC5QC
o . '
7 :
6 :
2 :
8 :
2 :
SWDb
Avg.
> 18.
> 34.
> 33.
> 33.
> 16.
> 13.
2
5
9
9
4
4
INF.
EC5Q
(27)**
(12)**
(18)**
(20)**
(27)**
(29)**
COMBINED INF.
Avg. EC50
16.
26.
18.
12.
9.
9.
5
6
2
8
4
4
EFFLUENT
Avg. EC50
> 41
> 35.3
> 25.8
> 34.7
> 36.0
> 40.7
(7)**
(17)**
(26)**
(18)**
(16)**
(12)**
  aIPI, plant influent chiefly from industrial sources.
        plant influent from chiefly domestic-commercial sources.
   "EC
     50
for a 5-minute exposure time is given as percent effluent.
  *Data developed by the Patapsco Wastewater Treatment Plant, Baltimore,
   Maryland.
 **Number of days, the EC50 was less than > 45.5 during each month.
                                     937

-------
     The limited ecosystem bioassay toxicity developed by the  EPA on
Patapsco plant effluents (Table 23) qualitatively confirmed the  variability
and pass-through of toxicity indicated by the routine MICROTOX measurements.
The results suggest that a desirable statistical link between  the pragmatic
in-plant monitoring and the expensive Agency ecosystem bioassay  may be
developed.

     Effective toxics control at treatment plants require monitoring tools
that can preferably respond in real-time and be used in monitoring approaches
to provide warnings of potential toxic impacts or pass-through before the
toxics reaches the treatment plant.  The specific chemical, (33,34) bioassay
toxicity (26,35) and health effects (15) screening tools, many available to
the Environmental Protection Agency for the water-quality-based  toxics
control process, require relatively long measurement times with  multi-step
procedures.  The practical functions of these tools in a TRE are as
monitors of the plant's discharge requirements and as linkage  to probable
receiving water effects and to waste load allocation procedures.

     Although limited by their costs, these bioassays could also be used in
the development of monitoring approaches for warning of potential toxic
plant impacts or pass-throughs and for tracing toxics to their source.
However, less expensive and simpler monitoring tools, are more desirable for
routine in-plant and in-sewer toxics monitoring.


  TABLE 23.  EPA BIOASSAY EVALUATION OF THE EFFLUENT AT THE PATAPSCO PLANT

                       Fathead Minnow*                  Ceriodaphnia**
Test Date
3/8 - 15/84***
Survival
100% Mortality
in 100%
Effluent
Growth
NOEC at 30%
Effluent
Survival
100% Mortality
in 3% Effluent
Repro-
duction
NOEC at
0.37%
Effluent
 6/23/84***
45% Mortality
in 100%
Effluent
100% Mortality
in 10% Effluent
7/13-20/84***
No Mortality
at 100%
None up to
6% effluent
100% Mortality None up
at 30% effluent to 6%
effluent
    *Seven-day Early Life Stage Growth Test using Fathead Minnow.
   **Ceriodaphnia Seven-day Life Cycle Toxicity Test.
  ***Data  developed by the Duluth Environmental Research Laboratory, Duluth,
    Minnesota.
 ****Data  developed by the Environmental Monitoring and Support Laboratory-
    Newtown Facility, Cincinnati, Ohio.
                                     938

-------
     In November 1980, the City of Baltimore in anticipation of potential
industrial toxics impacts during the start-up and operation of its new
activated sludge treatment process at the Patapsco Plant began monitoring
its wastewaters for toxicity using the 5-minute MICROTOX (32) analyses.
The City ultimately will expand its evaluation to three candidate in-plant
monitoring approaches for the TRE study at its Patapsco Wastewater Treat-
ment.  These in-plant monitoring tools for indicating the presence of
toxicity are the Beckman MICROTOX analyzer with a fluorescent bacterium,
respirometry (oxygen uptake) measurements (36,37) on the plant's biomass,
and Adenosine Triphosphate (ATP) measurements.  These inexpensive moni-
toring tools have near real-time responses ranging from actual real-time
for the TOXIGARD respirometry alternative to about a 1-hour response time
for the ATP measurement.

     The overall objectives of the planned case history TRE at the Patapsco
Plant are given in Table 24.  These objectives emphasize use of the prag-
matic in-plant monitoring methods and the development of a link between the
near real-time measures and the Agency's ecosystem bioassays used in the
toxics regulatory process.
             TABLE 24.  PATAPSCO TOXICITY REDUCTION EVALUATION
       Research Objectives:

          0     Evaluate toxicity reduction across plant using MICROTOX,
                Respirometry and ATP

          0     Summarize specific chemical inventory across plant
                (organics and metals)

          0     Assess techniques to identify and trace toxicity
                to sources

          0     Evaluate link between in-plant monitoring and ecosystem
                bioassays

          0     Assess treatability of wastewater for toxics control
                as related to plant design

          0     Develop techniques to minimize toxicity pass-through
                                     939

-------
SUMMARY

     The progress on the toxicity reduction research suggests that the TRE
concept, with protocols, has potential to support the wastewater treatment
industry's efforts to solve the site specific problems of toxicity dis-
charges by treatment plants.  Indeed, the TRE concept with the pragmatic
in-plant monitoring tools may be the only affordable approach for managing
complex mixtures of toxics, especially in municipal wastewaters.

     Key procedures for efficient tracing of the toxicity to its source,
identifying the principal components of the toxicity, and demonstrating
practical control responses to eliminate excessive toxicity discharges,
however, have not yet been sufficiently tested at full-scale treatment
plants to confirm the ultimate utility of the concept.  Research on
approaches to improve the operation of municipal plants for toxics control
also has not yet been initiated.  The EPA will diligently pursue these
remaining research needs to confirm the TRE concept and, thereby, improve
the Nation's ability to control toxicity water quality problems from point
source discharges.

                              ACKNOWLEDGEMENTS

     The use of data in this paper from the ongoing research effort in
Cincinnati, Ohio, is appreciated and acknowledged (38,39).

     The authors would like to acknowledge and thank their coworkers,
Dr. Farrell, Dr. Heidman, Dr. Smith, Mr. Neiheisel, Dr. Dobbs, Dr. Austern,
Mr. Reed, Mr. Tabak and Dr. Hannah, for generously sharing their research
information for this paper.

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2.   Farrell, J.B.  Reduction in bacterial densities of wastewater solids
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     Engineering Research Laboratory, U.S. Environmental Protection Agency,
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3.   Kowal, N.E.   Health effects of land application of municipal sludge.
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4.   Jewell, W.J., et al.   Autoheated aerobic thermophilic digestion with
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                                     940

-------
5.   Camp, Dresser, and McK.ee, Inc.  Engineering and economic assessment of
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     Ohio, September 1982.
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17.   Petrasek,  A.C.,  et al.   Fate  of  toxic  organic  compounds  in wastewater
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20.   Hannah, S.A., et al.   Comparative removal  of toxic pollutants by six
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22.   Kirsch, E.J. and Wukasch,  R.F.  Fate of  eight  organic priority pollu-
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23.   Weber, W.J.  and Jones,  B.E.   Toxic substances  in activated sludge  and
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     nati, Ohio,  1985.

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29.  Norberg, T.J., and Mount, D.I.   Seven-day early life stage growth test
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     fractions of liquid waste using freshwater and salt water  algae and
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35.  Horning, W.B. and Weber, C.I., eds.  Methods for measuring chronic
     toxicity of effluents  and receiving waters to freshwater organisms.
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36.  Arthur, R.M.  Toxicity-treatability testing using respirometry.  Arthur
     Technology, Fond du Lac, Wisconsin, September 15, 1981.

37.  TOXIGARD, Eu-Control,  Toxigard TG-10  Installation Operation, and
     Maintenance Manual, Preliminary M 218.60, Eu-Control USH,  Inc., Decatur,
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38.  Neiheisel, T.M., et al.  Toxicity reduction survey of six  Ohio cities.
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39.  Dobbs, R.A., et al.  Toxics treatability studies.  Water Engineering
     Research Laboratory, U.S. jEj^yi^qu^enkal.'Pr^teetfon Agency, Cincinnati,
     Ohio, 1985.  (Ongoing: research) '" ' l': {'^'J,  I '., ,\.'."
                               ' '   *'   ^-"' ''  ' '''
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