r
             United States
             Environmental Protection
             Agency
Office Of Water
(WH-595)
EPA 430/09-91-022
September 1991
 v>EPA      Municipal Wastewater Reuse

             Selected Readings On
             Water Reuse

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                                           EPA 430/09-91-022
                                             September 1991
    MUNICIPAL WASTEWATER REUSE:
SELECTED READINGS ON WATER REUSE
                 Reprinted Articles From The
              Water Pollution Control Federation's

           Water Environment & Technology Journal
                 Reprinted with Permission by
               U.S. Environmental Protection Agency
                     Office of Water
            Office of Waste water Enforcement & Compliance
                   Washington, D.C. 20460
                                    Selected Readings on Water Reuse — i

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                                  TABLE OF CONTENTS
This document contains reprints of the following articles from the Water Pollution Control Federation's Water Environment
& Technology Journal:

WPCF's Committment to Water Reuse - Completing the Cycle	2
   by Ron Young (Chairman, WPCF Water Reuse Committee) (October, 1990)
Guidelines for Developing a Project	3
   by Ramond R. Longoria, David C. Lewis & Dwayne Hargesheimer (October, 1990)
Keys to Better Water Quality	9
   by Kenneth J. Miller (November, 1990)
CONSERV'90 brings together experts on water reuse	10
   by Alan B. Nichols (November, 1990)
Water Reuse in Riyadh, Saudi Arabia	11
   by James M. Chansler (November, 1990)
Realizing the Benefits of Water Reuse in Developing Countries	13
   by Daniel A. Okun (November, 1990)
U.S. Water Reuse:  Current Status and Future Trends	18
   by Kenneth J. Miller (November, 1990)
On-site Wastewater Reclamation and Recycling	25
   byJohnlrwin (November, 1990)
Wastewater Reuse Gains Public Acceptance	27
   by J. Gordon Milliken (December, 1990)
Obstacles to Implementing Reuse Projects	28
   by Scott B. Ahlstrom (December, 1990)
Irvine Ranch's Approach to Water Reclamation	30
   by John Parsons (December, 1990)
Florida's Reuse Program Paves the Way	34
   by David W. York & James Crook (December, 1990)
Economic Tool for Reuse Planning	39
   by J. Gordon Milliken (December, 1990)
Water Reuse: Potable or Nonpotable? There is a Difference!	43
   by Daniel A. Okun (January, 1991)
Report Sets New Water Reuse Guidelines	44
   by Christopher Powicki  (January, 1991)
Clarification and Filtration to Meet Low Turbidity Reclaimed Water Standards	46
   by Joel A. Faller & Robert A. Ryder (January, 1991)
Potable Water Reuse	53
   by Carl L. Hamann & Brock McEwen  (January, 1991)
Potable Water via Land Treatment and AWT	59
   by Sherwood Reed & Robert Bastian (August, 1991)
Groundwater Recharge with Reclaimed Water in California	67
   by James Crook, Takashi Asano & Margret Nellor (August,  1990)

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             PRELUDE
         WPCF's Committment to Water

         Reuse—Completing the Cycle

             This month marks the twenty-fifth anniversary of the
             establishment of WPCF's Water Reuse Committee. During the
             last 25 years WPCF, through this committee, has committed
             programs that promote and aid in the development of water
         reuse technology. In this anniversary year, coincidentally, WPCF
         received an EPA grant to publish information on water reuse as
         section in four issues of Water Environment & Technology,
         beginning with this October issue.
           EPA representatives, speaking at the WPCF Annual Conference
         held in San Francisco, 1989, affirmed WPCF's position on water
         reuse, "Effluent reuse is a resource management option whose time
         has come. EPA encour-
         ages the reuse of treated
         wastewater effluents
         because  of  the great
         potential  for resource
         recovery and for pollution
         minimization." In the
         presentation, EPA repre-
         sentatives affirmed, also,
         that reuse projects can be
         difficult to  implement.
         Thus, in these  WE&T
         sections, experts in the
         field describe successful
         projects and  provide
         guidance to those who
         may be considering or are
         involved in managing
         water reuse and recla-
On the Cover and In this Issue:
  Officials and engineers are becoming
increasingly concerned over the clean water
supply. Thus, wastewater reclamation plants
have been designed and more are being
planned in areas where the water supply is
diminishing or where demand is greater than
supply. The Upper Occoquan Reclamation
Plant, Centreville, Va., is one such plant that
discharges treated wastewater, that meets
stringent discharge permit limits, into a
drinking water source; it's design and
operation was the model for the Abilene, Tex.,
Reclamation Project Plan, whose story is told in
this WE&T inset. The Abilene,  Tex.,
Reclamation Plant, when completed, will
discharge its effluent to the Lake Fort Phantom
Hill reservoir.
  One acceptable reuse of wastewater is
irrigation. (The picutre of the spicket spraying
water was taken by Carl Morrison). A recent
poll of 1102 residents of California showed that
a vast majority—89% of the polled residents—
felt that reclaimed water would be safe for
outdoor uses. Public attitudes and issues on
wastewater reuse will be covered in a future
inset.
         mation projects.
           Many  of the contrib-
         utors to  this EPA-funded
         project are WPCF Water
         Reuse Committee mem-
         bers.  Along  with the
         committee's long range
         plan, their contributions
         demonstrate  that the
         Water Reuse Committee
         is more active than ever. For example, as part of its
         long range plan, the committee is focusing on the need for
         national water reuse standards or guidelines. As chairman and
         member  of this committee, I share my colleague's enthusiasm
         for a project of such scope.
           With this project, WPCF hopes to focus attention of its members
         on what  can be accomplished, today, in recovering wastewater and
         what is needed to meet the growing public expectation for
         renewable resources in the future.
                                                           Ron Young
                               Chairman, WPCF Water Reuse Committee
2 - Selected Readings on Water Reuse

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                                                      WATER  RECLAMATION/REUSE
                       GUIDELINES  FOR
             DEVELOPING  A  PROJECT
                       Raymond R. Longoria, David C. Lewis,
                              and Dwayne Hargesheimer
       Today's technology provides
       a variety of water reclama-
       tion/reuse techniques to
       help meet the  growing
       demand for high-quality,
       treated water. An organized
       management  strategy  is
       necessary to completely
evaluate available options and select
the proper approach. A four-phase
planning effort was used in the
development of a water reclamation/
reuse project initiated in  1988 to
indirectly augment potable water
supplies  for Abilene, Tex.,  by
increasing the flows into the surface
water supply reservoir. The four
work phases focused on project defi-
nition and formation, creation of
baseline data, treatment process eval-
uation and selection, and implemen-
tation.
  Under this management approach,
each phase is nearly independent,
with distinct orientation meetings
and schedules. The information gen-
erated from the  major tasks in each
phase is assembled in separate techni-
cal memoranda (TM) that deal with
specific   issues,   focusing  the
approach.
  Each phase ends in an intensive 1-
to 2-day project team meeting fol-
lowed by a coordination meeting
with the owner (in this case, officials
from the city of Abilene) and a pub-
lic advisory committee. Thus, each
TM can be drafted, reviewed by the
project team, reviewed  with the
owner, modified, and then prepared
in final form before the next phase
begins.
  Together, the TMs form a com-
prehensive report. During the final
phase, they are condensed, providing
the basis for the summary report.
This report, a  concise, 40-  to 60-
page account  of the key project
issues, is intended for a broad and
often non-technical audience. All of
the elements  of the project are
assembled  into two volumes: the
summary report and an appendix con-
taining TMs (Table 1).

PHASE 1: PROJECT DEFINITION AND
FORMATION
  Phase 1 involves formation of the
project team, including a public advi-
sory committee (PAC), and requires
the project team to develop, in
detail, the specific goals  and objec-
tives of the project.
  Establishing a team. In addition

Table 1—Titles of Technical
Memoranda lor the Abilene Project

Research Project Objective, Goals
  and Approach
Public Advisory Committee Activities
  and Meetings
Baseline Data Development
Water-Quality Assessment
Lake Fort Phantom Hill - Water
  Quality Studies
Water-Quality Criteria and Goals
Process Selections, Conceptual
  Designs and
  Preliminary Cost Options
Process Selection, Sizing and
  Location
Bench-Scale Study - High  Lime and
  Alum Coagulation
Bench-Scale Study -
  Nitrification/Denitrification
Recommended Plan
Evaluation of Financing Options
Non-potable Water System
to the owner, engineers, and a PAC,
the project team might include envi-
ronmental scientists, virologists, epi-
demiologists, the owner's financial
consultant, a water rights attorney, a
public relations consultant, agron-
omists, economists, and other spe-
cialists.
  Despite all the technological and
economic elements that comprise a
water-reclamation research project, it
is foremost a public involvement
project requiring unwavering public
support to be successful. Therefore,
the PAC, as  an advisory group  of
local citizens with scientific and non-
scientific backgrounds, is vital  to
project success. PAC candidates
should have good communication
skills and a history of sound judg-
ment, open-mindedness, and public
activity. It is likely—and possibly
preferable—that the PAC members
will not be familiar with wastewater
treatment technologies. They should
be introduced to current technology
through visits to successful full-scale
reuse/reclamation projects.
  The PAC's charter is to provide
guidance to the  project team and  to
express the community's interests  in
the project. It should also choose the
appropriate level of public participa-
tion. For example, the Abilene PAC
recommended that the project team
provide it with regular project
updates, hold informal meetings with
it frequently, and hold only one for-
mal  public  meeting. This  was
designed to  allow the PAC to dis-
seminate accurate information to the
public and channel citizens' concerns
back to the project team.
  Raising issues and  forming
goals.  The  PAC should identify,
                                                                      Selected Readings on Water Reuse-3

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                                                  PROPOSED
                                    IMPLEMENTATION  SEQUENCE
                                      WATER SUPPLY vs WATER DEMAND
                           TRIBUTARY
                            FACILITY
                                            IMPLEMENTATION
                                                RANGE
                                             WATER SUPPLY
                                             INCREASE FROM
                                              RECLAMATION
                  STACY RESERVOIR
                    15,000 AC-FT
        HAMBY
        FACILITY
                          PROJECTED
                        WATER SUPPLY
                                                        - WATER REDUCTION
                                                    BY USE OF NON POTABLE WATER
                                                        YEARS
              1. SUPPLY AND DEMAND FIGURE ARE FOR WEST
                CENTRAL TEXAS (ABILENE REPRESENTS 75-80X OF TOTAL)
                      2. PROJECTED WATER DEMAND IS FOR "DRY" YEAR USE
                        APPROXIMATELY 10X ABOVE NORMAL USE.
          with the project team, the project
          goals, objectives, and key issues and
          approve of the technical experts
          selected to address those issues.
          Once the basic project structure is in
          place, the project team assembles for
          a 2-day meeting.
            The meeting begins with a clear
          restatement of the goals, which are
          usually established well before the
          first project team meeting (see Box).
          Part of the first day is set aside for
          "brainstorming," while the remain-
          der of the meeting is focused to
          refine the issues and statement of
          objectives, to  establish relative  levels
          of importance, and prepare the draft
          TMs.
            The project team should plan to
          address  key issues identified by the
          PAC promptly, to the satisfaction of
          the PAC. Timely issue resolution will
          improve the chances  of public  accep-
          tance. The Abilene  PAC narrowed
          the key  issues to two questions: "Is
          water reclamation needed?  Is water
          reclamation safe?"

          CREATION OF BASELINE DATA
            In Phase 2, the project team com-
          piles fact sheets of relevant baseline
          information on a specific  subject.
          The fact sheets, no more than 3
          pages long, are incorporated in a sin-
          gle document—the baseline data
          TM. For the Abilene project, fact
                   Goals  and Objectives
      Plan, test, and verily the feasibility of reclaiming water
      from wastewater
      Provide a meaningful increase in water supply
      Prevent adverse effects on water quality in Lake Fort
      Phantom Hill that would limit its potential uses
      Comply with state and federal water-quality regulations on
      wastewater effluent discharges
      Provide a source of drinking water of equal or higher quality
      than that currently produced
      Maintain or enhance the aesthetic conditions of waters in Lake
      Fort Phantom Hill
      Reduce or prevent increases in public-health risks associated with
      the potable water supply and the wastewater treatment and dis-
      posal method
      Recommend implementation of water reclamation only if it is
      shown to  be economically favorable
      Select treatment technology consistent with the city's
      operations and maintenance capabilities
      Investigate non-potable water reuse options to  reduce demands
      on the potable water supply
      Secure  public  involvement and participation in the
      development and execution of the project
sheets summarized data on existing
and projected population, reservoir
models, historical water quality,
potable water production and use,
wastewater flows  and quality,
wastewater treatment plant capacity,
water treatment plant capacity, water
rights, climatological data, and water
conservation measures. These data
are used to evaluate the need for
water reclamation and the adequacy
of potential treatment processes and
to provide  a context within which
alternatives are considered.
  Sources of historical water-quality
data and water quality model calibra-
4 - Selected Readings on Water Reuse

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                                                           WATER  RECLAMATION/REUSE
Table 2—Phase 2 Monitoring Progam:
Water Quality Parameters	
Algal identification
Alkalinity
Aluminum
Ammonia
Arsenic
Barium
Biochemical oxygen demand
Boron
Bromide
Cadmium
Calcium
Chloride
Chlorophyll a
Chromium
Cobalt
Color
Copper
Cyanide
Dissolved oxygen
Fecal coliform
Fecal streptococcus
Fluoride
Iodide
Iron
Lead
Magnesium
Manganese
Mercury
Methylene blue active substances (MBAS)
Nitrate-N
Nitrite-N
Nitrogen, total Kjeldahl
Pesticide scan
Phosphorus
Potassium
Selenium
Silica
Silver
Sodium
Standard plate count
Strontium
Sulfate
Temperature
Threshold odor
Total dissolved solids (TDS)
Total hardness
Total organic carbon
Total organic halogens
Total suspended solids (TSS)
Total trihalomethanes (THM)
Total THM forming potential
Turbidity
Virus
Volatile organic carbon
Zinc
tion information include the owner,
state regulatory agencies, the U.S.
Geological Survey, and other users of
water bodies, such as power plants or
park and wildlife departments.
  Because available data may be
incomplete or of questionable validi-
ty, supplemental data should be
acquired. An intensive water-quality
monitoring program, specifically
designed for the project, should be
established early on in the project or,
if possible, before the project is start-
ed. Monitoring for a  full year,
including hot, cold, dry, and wet sea-
sons, should be conducted. Several
parameters should be monitored
(Table 2) and samples should be
taken from at least two points in the
reservoir and  at least one spot in
each major tributary feeding the
reservoir. A sample should also be
drawn from the existing wastewater
treatment plant effluent.
  Because unexpected areas of con-
cern may arise, the monitoring bud-
get should  contain contingency
funds. Special testing was required
on the Abilene project after the pro-
ject team determined that Giardia
lamblia and Cryptosporidium sp.
could be present.

PROCESS EVALUATION AND SELECTION
  In Phase 3, fundamental technical
information is developed. Water-
Lake Fort Phantom Hill will received reclaimed effluent from the Abilene, Tx., wastewafer treatment plant when the project is completed.

                                                                              Selected Readings on Water Reuse - 5

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          quality standards are identified, com-
          puter modeling  is conducted to
          determine the impact of the stan-
          dards on the receiving water, and
          treatment alternatives are developed
          and evaluated.
            The establishment  of appropriate
          water-quality standards for treated
          effluents and receiving streams is
          crucial. Numerous federal and state
          regulations must be considered, and
          other regional and local water-quali-
          ty regulations may be applicable.
            Water-quality modeling for the
          receiving water begins with these
          standards. The project team uses the
          computer model to evaluate the
          discharge effects on the reservoir at
          various flows and degrees of treat-
          ment. For modeling,  the recom-
          mended minimum flow is a flow that
          would increase the lake's volume by
          approximately 5 to 10%. This water
          supply increase should produce  a
          measurable positive or negative
          impact on the lake water quality. The
          maximum flow should be based on a
          projection of the practical limit  of
          wastewater that would be available for
          reclamation during the study period.
            For treatment  levels, one set  of
          model parameters should be  set
          equal to the normal effluent dis-
          charge permit requirements of the
          receiving stream.  One or two other
          sets  that meet more  and less strin-
          gent water-quality requirements also
          should be selected.
            In the Abilene  project (Table 3),
          one effluent set represented the rea-
          sonable best practical treatment level
          obtainable by current treatment pro-
          cesses (Row A in the table) and
          another set represented the treat-
          ment to maintain the state's water-
          quality standards  (Row C). Row B
          represented the highest treatment
          level obtainable without  chemical
          coagulation. The  project team used
          the U.S. Army Corps of Engineers
          River and Reservoir  Water Quality
          Model with  flow values that ranged
          from 3 to 17 mgd under conditions
          of a 2-year critical  drought period.
            The water-quality standards review
          and the water-quality modeling
          results reveal the appropriate effluent
          quality criteria and allow selection of
          appropriate treatment processes.
          Specific effluent criteria will be
          required for the different reclaimed
          water uses proposed in the water
          reclamation plan.  This could include
          reclaimed water used for irrigation,
          discharged to a tributary stream of
       CITY OF ABILENE
 TEXAS WATER DFVELOPMfc'it BOARD
       PROPOSED
VATER RECLAMATION PROCESS
       SCHEMATIC
                             BIOLOGICAL
                           PHYSICAL
                          CHEMICAL
                 LAKE FORT PHANTOM HU.
 the reservoir, and discharged directly
 to the reservoir (Tables 4 and 5).
   Demonstrating effectiveness. In
 selecting alternative treatment pro-
 cess configurations, the project team
 should give preference to ones  cur-
 rently in use elsewhere. The PAC can
 be more confident in support of the
 project if members have visited a suc-
 cessful  project that uses the same
 process scheme.
   Regardless of other treatment  pro-
 cess  successes, bench-scale tests
 should be conducted for key process
 parameters to demonstrate  to the
 public that a process successful in
 other areas of the country is equally
 successful under  local conditions.
 For  example, the water-quality
 model for the  Abilene project indi-
cated sensitivity to phosphorous and
nitrates. High lime coagulation
bench-scale tests demonstrated that
phosphorous could be removed ade-
quately within  a range of dosages,
while nitrification/denitrification
rate tests determined the appropriate
design criteria.
  The project team  reviews the pro-
cess alternatives (Tables 6, 7, and 8),
prepares a  detailed analysis of the
advantages and disadvantages of
each, selects a process, and then pre-
pares a detailed description of the
selected process.
  During this phase, the  project
team should meet twice, once to
address the water-quality standards
and  once to evaluate the process
alternatives.
6 - Selected Readings on Water Reuse

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                                                          WATER   RECLAMATION/REUSE
Table 3—Sample of Water-Quality Modeling Values

                            Degree of Treatment
Effluent
Set
A
B
C
BOD5
3.0
5.0
10.0
TSS
1.0
5.0
15.0
ortho-
Phosphate
0.2
2.0
10.0
Ammonia
2.0
3.0
3.0
Nitrate
10.0
25.0
25.0
Table 4—Recommended Reclamation Levels for Irrigationa
Contaminant
Levels for
controlled access
Levels for limited
control access areas
Biochemical oxygen
demand (BOD), mg/L  20
Total suspended
solids (TSS), mg/L

Chlorine residual

Fecal coliform, per
lOOmL

Total coliform, per
lOOmL

Turbidity, NTU
20

1.0


100


not specified

not specified
20


20

not specified


not specified


2.2

 2
 Levels at the time when the Abilene project was being planned.
Table 5—Recommended Reclamation Level for Supply Augmentation

Contaminant or Quality            Quantity        Flow, mgd
BOD, mg/L
Turbidity, NTU
Ammonia nitrogen, mg/L
Nitrate/nitrite nitrogen, mg/L
Total phosphorus
Dissolved oxygen
5
2
2
20
10
2.0
0.2
>5.0



<3
>3
<3
>3

IMPLEMENTATION
  By the onset of the fourth phase,
the major TMs are completed, and
the project team should be ready to
draft the summary report. In this
final phase, the recommended treat-
ment plan and other infrastructure
requirements are combined in a
comprehensive  water reclamation
plan. Non-potable water system or
water conservation plans should also
be incorporated into the reclamation
plan during this phase.
  The implementation phase should
delineate  the  needed  system
improvements, establish an imple-
mentation schedule, develop a water
supply vs. demand curve, enumerate
costs, and identify any non-structural
requirements. In addition to  the
treatment units,  implementation
plans should include the required
wastewater   collection  system
improvements and the pumping and
non-potable  water distribution sys-
tem requirements.
  The implementation schedule and
the supply vs. demand curve should
complement  one another. The exist-
ing supply vs. demand conditions are
used to determine when improve-
ments will be needed and to develop
an implementation schedule. The
changes in the  supply  vs. demand
curve caused by system  improve-
ments are then observable in a modi-
fied supply  vs. demand curve (see
Figure).
  At this stage,  estimated costs
should be considered in planning
budget estimates, which  will be used
to establish project financing needs,
and should provide adequately for
contingencies. In addition to overall
capital  costs and annualized costs,
the project dollars  should   be
expressed in  terms of cost per vol-
ume (dollars/1000 gal)  and cost for
developing a  water supply in terms of
volume  per year (dollars/ac-ft.yr).
These figures would be compared to
conventional surface water supply
project costs.
  Non-structural (management and
operations)  needs,  which   are
addressed in this phase, include
water rights,  water-quality monitor-
ing, financing, and public informa-
tion.  Because  water rights  to
reclaimed wastewater have become
complex,  a  water rights attorney
should be retained to prepare a posi-
tion paper on the owner's legal
authority for reuse of wastewater to
supplement surface water sources.
                                                                            Selected Readings on Water Reuse - 7

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            Monitoring for ongoing evalua-
          tion.  The water-quality monitoring
          program should  be  continued
          through Phase  4 to provide data
          needed to evaluate the impact of the
          reuse  improvements.  The program,
          however, could be scaled back. Loca-
          tions, both within the reservoir and
          on its tributaries, should continue to
          be sampled. While sampling and test-
          ing of the more  sensitive parameters
          should be stepped up, many parame-
          ters repeatedly shown to be  below
          detection limits or well within crite-
          ria can be tested less frequently or
          eliminated from the monitoring pro-
          gram.
            Testing should involve a local uni-
          versity or some  other independent
          agency to increase the likelihood of
          public acceptance. A technical com-
          mittee could be  appointed to  review
          the water-quality data.
            Financing     and    public
          acceptance. Financing options for  a
          reclamation project  are similar to
          those for conventional wastewater
          treatment systems. Reclamation pro-
          jects  also may qualify for funding
          from  programs geared toward water
          supply development. Additionally,
          most  non-potable water supply sys-
          tem improvements will benefit spe-
          cific entities that should be asked to
          assist in  financing the non-potable
          system improvements.
            In  general,  the public perception
          of water  reuse is positive as long as  a
          project is presented using the  proper
          approach. Because the connection
          between  wastewater and water is not
          one that the public desires to make,
          asking the public to accept wastewa-
          ter as a water source is a "difficult
          sell."
            It normally requires a public infor-
          mation and relations campaign to
          convince the public to accept this
          concept.  The development of a public
          information and acceptance program
          should begin with the study and con-
          tinue  throughout the implementation
          phase. There are several approaches
          and the  owner's  public information
          staff should develop  and  direct the
          public acceptance program.         •

            Raymond R. Longoria is an engi-
          neer with Freese and Nichols, Inc., in
          Fort  Worth, Tex.; David C. Lewis  is
          an engineer  with CH2M Hill in
          Austin,    Tex.;   and   Dwayne
          Hargesheimer is the  director of the
          water utility department of the city of
          Abilene,  Tex.
Table 6—Four Treatment Process Alternatives: System Train
High-Lime
Activated sludge
Nitrification
Denitrification
Clarification
High-lime
Recarbonation
Filtration
Chlorination
Post aeration

Alum
Activated sludge
Nitrification
Denitrification
Coagulation
Chemical phosphorus removal
Clarification
Filtration
Break-point chlorination
Post aeration

Table 7—Treatment Alternative Design (and Average) Operating Conditions

                                     Treatment Type
                   Alum and biophosphorus removal
                   Activated sludge
                   Nitrification
                   Biological phosphorus removal
                   Coagulation
                   Filtration
                   Clarification
                   Filtration
                   Break-point chlorination
                   Post aeration

                   Nitrification
                   Activated sludge
                   Nitrification
                   Biological phosphorus removal
                   Clarification
                   Filtration
                   Chlorination
                   Post aeration and force main
Effluent quality,
mg/L
High-Lime Alum
Alum and
biological
phosphorus
removal
Nitrification
BOD
TSS
TKN
Nitrate
Phosphorus
Dissolved oxygen
Coliform, per
lOOmL
Turbidity, NTU
5.0 (2.0)
5.0(1.0)
2.0(1.0)
10.0(5-7)
0.2(0.1)
5.0 (6.0)
2.2 (2.0)
2.0(1.0)
5.0 (2.0)
5.0 (2.0)
2.0(0.1)
10.0(5-7)
0.2(0.15)
6.0 (6.0)
2.2 (ND)a
5.0 (2.0)
5.0(1.0)
2.0(0.1)
15-20(15-20)
0.2(0.15)
5.0 (6.0)
2.2 (ND)
5.0 (3.0)
5.0 (5.0)
2.0(1.5)
15-20(15-20)
2.0 (2.0)
5.0 (6.0)
200.0(100)
                                2.0(1.0)      2.0(1.0)    NAb (4-10)

 P Not detected.
 " Not applicable.
Table 8—Preliminary Cost Data for Abilene, Tex., Reuse Project	

                                    Treatment Type
Cost, million
dollars
Capital
Operations and
High-Lime
13.41
0.70
Alum
11.26
0.56
Alum and
biological
phosphorus
removal
10.12
0.46
Nitrification0
11.58
0.35
maintenance

Equivalent
annuaP
2.09
1.73
1.51
1.55
a Includes construction of pump station and force main to pump beyond
reservoir during droughts.
b Based on 20 years at 8% interest.
8 - Selected Readings on Water Reuse

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PRELUDE
  Keys to  Better Water Quality

     Larger populations and a higher standard of living require more
     water—from all available resources—to satisfy domestic and
     industrial needs. Unfortunately, growth and population increas-
     es have generally been associated with water-quality deteriora-
  tion. The quality of many of Earth's surface supplies will continue
  to show deterioration until, at some point, planned reuse and its
  associated treatment process will offer a higher-quality product
  than conventional treatment. Thus, the key to dealing with water-
  resource problems will lie in our ability to extend and augment
  existing supplies through various reclamation processes. Success in
  water-reuse technology
  will probably depend
  on our ability  to com-
  municate and apply the
  technological advances
  that are achieved.
    The government's
  role should be to coor-
  dinate  research and
  demonstration projects
  and promulgate  con-
  trolling rules and regu-
  lations.  Over ten  gov-
  ernment agencies  have
  some interest in water
  reuse and  recycling.
  For the  sake  of effi-
  ciency and sound man-
About this section
  This is the second installment in a series
devoted to the subject of water reuse.
Installments were scheduled, for publica-
tion in four issues of Water Environment
& Technology.  The publication of these
insets was made possible by a grant from
the Environmental Protection Agency.
  Last month WE&T published an arti-
cle on planning a reclamation project.
This month WE&T focuses on the world-
wide status of wastewater reclamation.
The trends in reuse in developing coun-
tries, in the arid Middle East, and in  the
U.S. are described. Papers on reclamation
and reuse of wastewater that were fea-
tured in several sessions of the recent Con-
serv 90 are also summarized in an article.
  agement, one agency
  should coordinate and
  manage  all reuse re-
  search and demonstration projects.
    Public participation is necessary during each step of reuse
  programs: the public should not be expected to automatically
  understand and support reuse projects and, although increasingly
  recognized as a significant natural resource, reuse or disposal of
  wastewater will continue to receive greater scrutiny. The public's
  role can be one of a supporting partner or major antagonist. The
  difference seems to be involvement by the public—local and
  national—in all parts of the reuse effort.
    Water reuse began out of necessity brought about by expanding
  industries, ever-increasing populations, and the need for larger vol-
  umes of water to support growing agricultural needs. As mankind
  approaches the 21st century with a world population projected to
  nearly double by the year 2000, it is realistic to project that, with-
  out significant change, existing water resources will be taxed
  beyond our current abilities to satisfy demand. The role of water
  reuse must therefore, be expanded.
                                               Kenneth J. Miller
                                      Vice President and Director
                                     Water Supply and Treatment
                                                    CH2M Hill
                                                  Denver, Colo.
                                                   MJifcMkh.if.4Mr
     Irrigated with wastewater
reclaimed by the Riyadh Wastewoter Treat-
  ment Plant, soil and plant samples are
      collected in Dirab, Snutli Arabia,
                                                                                      11  If

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                                                                             WATER RECLAMATION/REUSE
          Conserv  90  brings  together experts
          on water  reuse
             Conserv 90 was conceived in the
             wake of the 1988 drought that
             devastated the country and raised
          concerns about water supply and use.
          Conserv 90  is a joint effort of the
          American Society of Civil Engineers,
          American Water Resources Associa-
          tion, American Water Works Associa-
          tion, and the National  Water Well
          Association. The theme of Conserv 90,
          which was held in Phoenix, Ariz., in
          August, was  "Offering Water Supply
          Solutions for the 1990s."  This summa-
          rizes the session Effluent Reuse.

          EFFLUENT REUSE
            Water  reclamation and reuse  is
          taking on added significance in a cli-
          mate in which increased community
          development is putting a lot of pres-
          sure on water resources and sewer
          services.
            To minimize subsurface discharge
          of wastewater in an arid rural area of
          poor drainage not served by public
          sewer services, a  new 800-student
          high school  in a rural Texas school
          district included an on-site advanced
          treatment system  that included the
          use of reclaimed water  for flushing
          toilets. This system reduced wastew-
          ater discharge by 85%.
            In Houston, Tex., a  sewer mora-
          torium imposed on a high-growth
          area meant that all new  construction
          projects  could discharge no more
          than 1600 gpd/ac of property. High
          property values could  not be sup-
          ported by the level of development
          which the discharge limit imposed.
          As  a solution, a construction project
          of the Alliance Bank and Trust Com-
          pany included an on-site wastewater
          treatment and recycling system with
          water conservation plumbing fix-
          tures. When fully completed, the
          200,000-sq-ft building will discharge
          only 1000 gpd.
            Similarly, on-site treatment and
          use of reclaimed water greatly
          reduced the wastewater  discharges  of
          the Squibb Corp.  building in Mont-
          gomery Township, N.J., near Prince-
          ton, that does not have  public sewer
          services. The system has enabled the
          township to control growth and
          avoid unwanted sewer infrastructure
          expenses  while maintaining environ-
          mental goals.
  In conservation-conscious Santa
Monica, Calif, a 1.3-mil sq-ft com-
plex consisting of four buildings for
office and retail space is, when com-
pleted, expected to  produce only
40,000  gpd  as opposed  to an
expected 70,000 gpd. The reason:
low flush toilets and other water
conserving fixtures,  on-site treat-
ment and reclamation for landscape
irrigation.
  A successful on-site wastewater
treatment system  like those described
above typically consists of on-line
flow equalization  and emergency
storage tanks, biological nitrification
and denitrification,  membrane filtra-
tion, activated  carbon, and disinfec-
tion. Membrane  filtration is used to
clarify biological process solids down
to a particle size of  about .005 (J,.
Granular activated carbon is used for
color removal and is a backup for
organic  carbon removal. Typical
removal rates are: biochemical  oxy-
gen demand (BOD)  and total sus-
pended solids (TSS) < 5 mg/L, tur-
bidity < 0.5 NTU, total coliform <
2.2/100 mL.
  Factors inhibiting the wider prac-
tice of on-site  reclamation and recy-
cling include  lack of state regula-
tions, lack of standards for reclaimed
water  quality,  and ambiguous
plumbing codes.
  In another paper, a  project in
Beaufort County near Hilton Head
Island, S.C., which is experiencing
rapid   population   growth,  is
described. To accommodate this
growth,  the Beaufort-Jaspar Water
and Sewer Authority is planning
two wastewater treatment plants
which would  be designed to  pro-
duce effluent that could be applied
to  area  golf courses.  Also,  the
authority has been investigating the
development of a wet-weather dis-
charge system that would combine
the flows of both plants and dis-
tribute the treated effluent  to  a
forested floodplain  wetland.  The
wetland  would  provide additional
treatment while protecting the adja-
cent tidal freshwater river.
  In  the rural  areas of Brevard
County, Fla., reclamation is a neces-
sity in light of  the growth of the
county  along  the coast. Just com-
pleted is the South Central Regional
Wastewater System which will serve a
25-sq mile area of the mainland and
will provide total reuse of effluent. It
consists of four pumping stations,
several miles of force  main, a 3-mgd
plant, and effluent reuse for irriga-
tion of sod farms. The  county has
also decided to provide filtration and
high-level disinfection because the
effluent will eventually be extended
to irrigation of public  contact areas.
  Venice, Fla., which has a critical
water supply problem and a high
growth rate, is constructing a new
plant, the East Side WWTP, which
will provide advanced  secondary
treatment to produce  reclaimed
water suitable for urban irrigation.
The reclaimed effluent  must meet
state standards for public access irri-
gation: 20  mg/L BOD, 5 mg/L
TSS and no detectable fecal col-
iforms. Nutrients  are not regulated
because their presence in irrigation
water is beneficial  as a fertilizer. The
reclaimed water will  greatly reduce
pressure on local aquifers which have
been the source of golf course irri-
gated water.-
   One of the  most water conserva-
tion-conscious states is Arizona,
where Tucson and  Phoenix have
developed elaborate reclamation sys-
tems for golf course and  other forms
of irrigation. Reclamation takes great
pressure off of the groundwater sup-
plies in a state that is  heavily agricul-
tural.
   Meanwhile, in  Southern Califor-
nia, where  the water supplies are
under great stress, the Irvine Ranch
Water District has expanded its  15-
year-old  reclamation  system  to
include nonpubhc-contact use of
reclaimed water for office and other
highrise buildings. Feasibility studies
began in  1987 for a dual-distribution
system that delivers  potable water
and reclaimed wastewater to these
sites. Pipes and fixtures are color-
coded to allow  easy distinction.
Almost all of the  hurdles, from test-
ing to design approval,  have been
surmounted and  officials announce
that the system  will be in actual
operation in a building soon.
   Also in  Southern California, a
blend of groundwater  and highly
treated wastewater is being injected
underground to stem saltwater intru-
sion that has resulted from ground-
water overdrafting.
   -Alan B. Nichols, senior staff writer
for Water Environment & Technology.
10 - Selected Readings on Water Reuse

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Above: In Doriyoh, Saudi Arabia, palm trees and fodder crops grow where land was irrigated with reclaimed wastewater. Below Right: Plants in this Dirab, Saudi
Arabia, greenhouse are watered with wastewater reclaimed by the Riyadh Wastewater Treatment Plant.
Water Reuse in
Riyadh, Saudi Arabia
   Riyadh, the capital of Saudi Arabia,
   is nestled in the central part of
   the arid Najd highlands. Its loca-
tion, combined with a population
that has nearly tripled to almost 2
million people over the last 10 years,
guarantees water  shortages  and
necessitates water reclamation. In the
city, there are approximately 30 pro-
jects involving water reuse. Industrial
and agricultural programs rely on
effluent from the Riyadh Wastewater
Treatment Plant (RWWTP).
  The  first stage of the RWWTP
began operations in 1976 with a
capacity  of 40,000  m3/day (10.6
mgd) to  serve a  population  of
160,000 persons. Because of the
city's rapid growth, the plant was
almost immediately overloaded, and
plans were quickly made to expand
the facility. By 1980 the plant's
capacity was  expanded to  80,000
ma/d (21.2 mgd), and, in 1983, the
second stage of development was
completed giving the
site an  average daily
capacity of 200,000
m3/d (52.8 mgd). The
collection system uses
1980  km (1228 miles)
of lines and no lift sta-
tions. Greater collec-
tion-line depths are
tolerated in order to
avoid lift-station oper-
ation  and maintenance
costs.
  The plant, which
provides preliminary,
primary, secondary,
and chlorination treat-
ment, is a high-rate
trickling filter system
with random-fill plastic
media, followed by
two aerated lagoons,
and finally chlorina-
tion.
  Sludge treatment is
achieved by anaerobic
digestion, followed by sand drying
beds. The dried sludge is hauled
away by farmers who use the material
as a  soil conditioner or additive.
Plans have been completed to pro-
vide  tertiary  treatment  of the
wastewater; this will be gravity sand
filtration of the final effluent.
                                                                              Selected Readings on Water Reuse -11

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                                                                               WATER RECLAMATION/REUSE
             Riyadh WWTP Influent and Effluent Composition
             Constituent
    Concentration, mg/L
                                                 Influent
                   Effluent
Total dissolved solids
Suspended solids
Settleable solids (ml/L)
BOD5/ 20°
Chemical oxygen demand (COD)
Ammonia-nitrogen
Nitrate-nitrogen
Phosphates
Chlorides
Alkalinity
Grease
Temperature, °C
Free available chlorine
Total chlorine residual
PH
Dissolved oxygen
Total coliform
1300
250
3
250
450
25
-
10
180
240
100
29
0.0
0.0
7.3
0
< 1 06/mL
1200
40
ND
45
100
25
< 1
7
160
200
10
27
0.8
4.0
7.4
5
50 to 100/1 00 mL
             A center pivot irrigation system sprays reclaimed wastewater on crops in Dirab, Saudi Arabia.
             REUSE PRACTICES
               The  Petromin Oil Refinery uses
             some 20,000 m'/d  (5.3 mgd) of
             RWWTP's effluent. About 75% is
             treated to produce high-quality boil-
             er feed water, while  the balance is
             treated and used for crude oil desalt-
             ing and cooling water and is also
             available for fire  fighting should that
             prove necessary.
               About 3600  m3/d (0.9mgd) of
             effluent is  used  for landscape irriga-
             tion at the RWWTP. The grassed
             areas are aerial-spray irrigated while
             the shrubs and flowers are flood irri-
             gated. Areas adjacent to the housing
             and main offices at the plant are
             watered with potable water to pre-
             vent any unwarranted use of the
             effluent.
  The largest portion of the plant's
effluent is pumped to Dirab and
Dariyah for agricultural irrigation.
The pumping station at Riyadh has a
capacity of 120,000  m3/d (31.7
mgd) with an on-line storage of
300,000 m3/d (79.3 mgd). The
transmission line to Dariyah, which
has a capacity of 200,000 m3/d
(52.8 mgd), is 50 km (31 miles)
long and  800  mm (41.5 in.) in
diameter. The transmission line to
the Dirab irrigation site is 55 km (34
miles) long and 1000 mm (39.4 in.)
in diameter.

MEETING STANDARDS AND DEMANDS
  In 1985, 92,000 m3/d (24  mgd)
of RWWTP effluent was pumped to
Dirab and spread generally over
2000 ha (5,000 acre) The farms at
Dirab average around 65 ha (106
ac.) in size and the main crops  are
wheat, fodder, and vegetables. In
1985,  70,400 m3/d (19 mgd) of
RWWTP effluent was pumped to
Dariyah. The farms at Dariyah aver-
age about 15 ha (37 acre) and  the
main crops are  date palms, fruit
trees, vegetables, and fodder.
  The  irrigation  water has made it
possible to  more than double  the
land under cultivation at Dirab; as in
the past, the wells at Dirab used for
irrigation would  be dry  during  the
summer months.  Also, the nutrients
in the effluent (see Table), especially
nitrogen and phosphorus, reduce the
need for fertilizers, thus, reducing
costs,  and substantial savings  are
being  realized.  Farmers are also
using treated sludge from the plant
as a soil conditioner.
  The  tentative  Saudi Arabian
Water  Quality Standards for unre-
stricted agricultural irrigation are 10
mg/L for 5-day biochemical oxygen
demand (BOD5) and 10 mg/L for
suspended solids.  The effluent does
not  meet the tentative standards,
but, as soon as the tertiary plant is
completed, there should be little
difficulty in producing  an effluent
that meets these  requirements.
However, overloading,  also, pre-
sents problems.
  Wastewater flows to the RWWTP
have been increasing dramatically,
and at present the flows are over
330,000 m-yd (87 mgd). Plans have
been completed and construction is
presently  underway  on a new,
200,000 m3/d (52.8 mgd) plant
located just to the north of the exist-
ing plant.
   The new  plant will also provide
preliminary,  primary, secondary,  and
tertiary treatment. The  secondary
treatment process, however,  will be
an activated sludge system incorpo-
rating  a nitrification-denitrification
process, and tertiary treatment  will
consist of sand filtration and chlori-
nation.
   -James M. Chansler,  Wastewater
Management Division, Broward
County Office of Environmental  Ser-
vices, Pompano Beach, Fla.; Donald
R. Rowe, Larox Research Corpora-
tion, Bowling Green, Ky.; Khaled Al-
Dhowalia, Civil Engineering Depart-
ment, King Saud University, Riyadh,
Saudi Arabia; and Alan  Whitehead,
Riyadh Water and Sewerage Authori-
ty, Riyadh, Saudi Arabia.
12 - Selected Readings on Water Reuse

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                                         Daniel A.  Okun
        The  proportion   of the
        world's population living in
        urban  areas  is  rapidly
        increasing, especially  in
        developing countries  in
        Asia, Africa, and  Latin
        America. In  1950, only
        New York and London had
populations exceeding 10 million;  by
1975,  the number of "megacities"
had grown to seven, including three
in developing countries. By the year
2000,  forecasts indicate that there
will be some 25 of these huge popu-
lation centers, with 20  in developing
countries.
  Inevitably,  the water-supply
demands of growing urban regions
will   outstrip  available  water
resources, especially in developing
countries. As a result, large industri-
al, commercial, and residential devel-
opments often develop their own
supplies— frequently by tapping
local groundwater—without ade-
quate  planning or government
supervision. This causes  problems
such as land subsidence and saltwater
intrusion.
  Also, because of water shortages,
water service in most urban areas  of
developing countries is intermittent,
allowing the distribution system to
be contaminated by infiltration of
contaminated groundwater, posing a
serious threat to public health. Water
reclamation,   by  reducing   the
demand on the potable supply, may
help maintain water pressure.
  The location of burgeoning urban
centers creates other  problems.
About half of all megacities and most
secondary cities are inland,  in areas
where there is insufficient water for
the disposal and dilution of their
increasing wastewater flows.
  In industrialized countries,  the
practice of water reclamation  for
nonpotable  purposes  has been
increasingly relied on to provide a
new source of water to meet urban
needs. For cities in developing areas,
water reclamation has the potential
to  reduce  the  magnitude   of
inevitable problems by providing
additional water while at the same
time  reducing  the  amount   of
wastewater that must be discharged.
  As in  recent water and wastewater
planning efforts for municipalities in
Florida, California, and  the south-
west U.S., engineers formulating
plans for cities in developing coun-
tries should assess  the potential  for
integrating water-supply and sewer-
age-system planning to maximize the
benefits that water reclamation can
provide.

PLANNING CONSIDERATIONS
  The costs of developing new water
resources for urban areas are high—
much higher in constant dollars than
the costs of developing existing
sources  because the latter were the
lowest-cost options when they were
selected. Thus, water reclamation, by
substituting nonpotable for potable
water where feasible, may be a more
attractive alternative. Also, for inland
cities where wastewater  treatment
costs are high because of the need to
protect  downstream water quality,
water reclamation for reuse may well
be economically attractive.
  Direct potable reuse should not be
considered because it is not yet
proven or acceptable, nor is it likely
to be in  the current planning hori-
zon. Moreover, because of the fre-
quent occurrence of water-borne
infectious  diseases in the developing
world, the  risks of transmitting
cholera, typhoid,  and dysentery
through reclaimed water are far
greater  than in the industrialized
                                                                              Selected Readings on Water Reuse -13

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                                                                              WATER  RECLAMATION/REUSE
                                      Parameter
world, where these diseases have vir-
tually been eliminated.
  Groundwater recharge, a form of
indirect potable reuse, is also con-
strained by public-health uncertain-
ties. Agricultural reuse,  which is
widely practiced throughout the
world, should not be a prime consid-
eration for urban planners because
the water is  far more valuable in
urban use.  In the  early stages of a
water-reclamation project, providing
reclaimed water to nearby agricultur-
al lands may be attractive. However,
as the metropolitan area
expands, displacing agricul-
ture, the reclaimed  water
would be shifted to  urban
uses. Also, irrigation is a
consumptive use, whereas
many  other nonpotable
uses, such as industrial pro-
cessing and toilet flushing,
permit another cycle of
reuse.
  For a water-reclamation
program to be instituted,
urban  areas must  be sew-
ered. In developing  coun-
tries, while 50% to 80% of
urban  areas are provided
with water service, only 10%
to 50% are provided with
sewerage.  Programs  to
increase urban sewerage ser-
vice now have a high priori-
ty, but systems intended for
water reclamation should be
planned differently  than
conventional    systems
               discharge
                                              doses of either coagulant, polymer, or
                                              both; direct conventional sand filtra-
                                              tion; and chlorine disinfection can
                                              easily and continuously provide a sat-
                                              isfactory product. The design, opera-
                                              tional, and quality parameters that
                                              have been adopted in California are
                                              shown in Table 1. These criteria,
                                              which may be  modified  for cities in
                                              developing countries, are best deter-
                                              mined by pilot studies.
                                                Reclamation plants differ from
                                              typical wastewater treatment plants,
                                              which are built to treat and discharge
                                      Table 1—California Criteria for Urban Nonpotable
                                               Reuse
                 remainder of the wastewater may
                 travel to another plant for disposal.
                 Finally, and perhaps most impor-
                 tantly, the effluent is a  marketable
                 product and should be treated as
                 such:  quantity and quality  are
                 important if customers are to be sat-
                 isfied.
                   Therefore, reclamation plants are
                 designed for reliability, with duplicate
                 units, standby power sources,  and
                 continuous on-line monitoring of
                 effluent  turbidity and chlorine
                 residual, as well as monitoring for
                          chlorine residual on the
                      —   distribution system.
Criteria
           designed   to
           wastewater to  a receiving
           body of water.
                                      Coagulant (alum, polymer)
                                      Rapid mix

                                      Filter media

                                      Effective media size
                                        Anthracite
                                        Sand

                                      Filter bed depth

                                      Filter loading rate

                                      Chlorine residual
                                      Chlorine contact time
                            Chlorine chamber
           WATER QUALITY FOR REUSE
             In urban settings, be-
           cause significant numbers of
           people could potentially be
           exposed  to  nonpotable
           reclaimed water used for
           landscape irrigation, indus-
           trial purposes, toilet flushing, and
           many other uses, there must be no
           hazard. The most important water-
           quality objective is that the water
           must be adequately disinfected, and
           a chlorine residual should  always be
           present. Also, the water must be
           clear, colorless, and odorless; other-
           wise, it would be aesthetically unac-
           ceptable.
             Research by the  Los Angeles
           County Sanitation Districts' has
           demonstrated that a high-quality sec-
           ondary effluent, treated with small
                            Coliform bacteria, MPN
                              7-day median
                              maximum
                            Filter effluent turbidity,
                            24-hour average
Required unless effluent
turbidity <5 NIL)

High energy

Anthracite and sand


1.0 to 1.2 mm
0.55 to 0.6 mm

0.92 m  (3 ft)

12 m/h (5 gpm/sq ft)

Minimum of 5 mg/L
after 2 hours

2 hours

40:1 (lenglh:width or depth)
2.2/100 ml
23/100 mL
2NTU
                                    effluent to receiving waters, in sever-
                                    al ways. The location of the plant is
                                    primarily influenced by potential
                                    markets  for the reclaimed  water,
                                    rather than the service area's  topog-
                                    raphy or the location of the receiving
                                    water. The sludge that is produced is
                                    not necessarily treated at the recla-
                                    mation plant because it may be
                                    returned  to the sewer for treatment
                                    and disposal at another plant. The
                                    amount of wastewater treated at the
                                    reclamation plant  depends on the
                                    demand  for reclaimed water; the
          NONPOTABLE REUSE
          PROGRAMS
           Water-reuse programs
          in the industrialized world
          are instructive in gauging
          the chances for success in
          the  developing world.
          The widest experience
          with water reclamation
          and nonpotable reuse is in
          the U.S., not only  in the
          arid Southwest but also in
          humid Florida; in Singa-
          pore,  where,   despite
          extraordinarily high pre-
          cipitation, water resources
          are  limited; in Israel,
          where innovative  reuse
          practices have a long his-
          tory; in the oil-rich  coun-
          tries of the Middle East,
          where 1 L of fresh water
          may cost more than 1 L
          of petrol,  and  costly
          desalination practices are
          common along with high-
          tech systems of reclama-
          tion; and in the resort
          islands of the West  Indies
          where the value  of fresh
          water for tourism also jus-
          tifies the high  cost  of
          reclamation.
           A  typical  approach
involves the reclamation of wastewa-
ter for a single large  user, such as a
program initiated in Baltimore, Md.,
in 1942. About 4.5 nr'/s (100 mgd)
of effluent from the city's Back River
activated-sludge plant was chlorinat-
ed and conveyed 7.2  km (4.5  miles)
through a 2.44-m (96-in.) pipeline
to the Sparrows Point plant operated
by Bethlehem Steel Co. This is gen-
erally the way reuse begins  in many
urban centers.
  Power plants with evaporative
cooling towers are  large users of
14 - Selected Readings on Water Reuse

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reclaimed water. A 58-km (36-mile)
transmission main was installed in
1982 to carry secondary effluent
from Phoenix, Ariz., to a 3.9-m3/s
(90-mgd) reclamation plant at the
Palo Verde nuclear power station. At
the plant, biological nitrification (on
trickling filters), lime-soda softening,
coagulation, dual-media  filtration,
and chlorination are  provided to
meet the  special water-quality
requirements of cooling towers. A
large Phoenix developer who needed
the water for a housing  and commer-
cial development sued the  city for
making this agreement, illustrating
the value of reclaimed water.
  A growing practice  involves the
use of dual-distribution systems—
one for potable water and the other
for nonpotable purposes. The first
system was installed in 1926 in
Grand Canyon Village, Ariz., where
scarce drinking water is pumped
from a spring near the bottom of the
canyon  about   1   km   below.
Reclaimed wastewater is used in the
village for most nonpotable  purpos-
es, including extensive landscape irri-
gation and toilet flushing.
  The Irvine Ranch Water District in
southern California initiated waste-
water reclamation using a dual sys-
tem, mainly for urban irrigation as an
alternative to ocean disposal of efflu-
ent.  However,  even when  the
requirement for secondary treatment
for ocean discharge  was waived, it
was determined that reclaimed water
service was  about 33% less expensive
than drawing additional potable
water from the local  water supplier.
Consequently, all new  development
in the district is provided with a dual
system, and this is being extended to
high-rise office buildings for toilet
flushing.  Currently, about 25% of all
the water  used in Irvine is non-
potable water produced by its recla-
mation plant. The district hopes to
provide about 0.6 m3/s (13 mgd) of
reclaimed water to its customers by
the year 2000.2
  An important  feature of reclama-
tion programs, as illustrated by those
of the Los  Angeles County Sanita-
tion Districts, is that the reclamation
plants are located far up on the sew-
erage network, near the markets for
reclaimed water. The plants do not
treat the sludge produced;  it goes
back into the sewerage  system to be
treated at a plant near  the point of
wastewater  disposal. This is also the
practice in Irvine and other reclama-
tion plants in Orange County, Calif.
  The largest dual system in opera-
tion began  to be retrofitted in St.
Petersburg, Fla., in 1977. One major
reason for installing the dual system
was because  the cost of treatment for
reclamation was considerably less
than   the   cost  to  provide  the
advanced wastewater treatment that
is required  for discharge to Tampa
Bay and the  Gulf of Mexico. Another
major benefit evolved from the city's
reliance on a groundwater source for
potable water that is limited and
located a considerable distance away.
  The city provides an annual aver-
age total water supply of about 2.7
m3/s (60 mgd). About 0.9 m3/s (20
mgd) of this  is reclaimed water, which
goes to some 6000 customers, includ-
ing about 5650 residential users and
250 commercial, industrial, and other
users.  This  represents only a small
fraction of the  potential market,
which  is being serviced as rapidly as
facilities can  be provided. The city has
experienced  about 10% growth since
1976, without any increase in potable
water demand, because of its success-
ful water-reclamation program.
  The Japanese  have confronted
problems similar to those facing the
developing world. In Japan, a rela-
tively  small portion of urban areas—
about 40%—is sewered while the
entire country has serious water-sup-
ply shortages because of its very high
population density.3
  Water reclamation was first prac-
ticed  in Japan through recycling.
Reclamation plants were built "on-
site,"  primarily for toilet flushing  in
large  buildings.  Emphasis is now
shifting to reclamation at municipal
publicly owned  treatment works
(POTWs).  The  country currently
uses about  3.2 nr'/s (72 mgd) of
reclaimed water from POTWs (Table
2). Up to  now, the reclamation
plants installed at POTWs have been
small—generally about 0.05 nr'/s
(1.0 mgd)—and less than 1% of all
wastewater  is reclaimed, but plans
are underway to  extensively increase
such reuse.
  About 1.3 mVs (30 mgd) is used
in buildings  (Table 3). In Tokyo, the
use of reclaimed water for toilet
flushing is mandated  in buildings
larger than  10,000 m2 (100,000 sq
ft). The  many  diverse  uses of
reclaimed water in urban dual sys-
tems in Japan are shown in Table 4.
Because of the heavily urban setting,
landscape irrigation is far less impor-
tant than in the U.S.
  In Singapore, secondary wastewa-
ter is discharged  to the  ocean
through outfalls. At one location,
effluent is intercepted, filtered, and
chlorinated at a 0.5-m3/s (10-mgd)
plant to provide water to an industri-
al park. This program has been
extended to provide  water  for flush
toilets for some 25,000 residents in
12-story apartment buildings.
  Throughout the world, dual distri-
bution systems are proliferating,
speeded up by policies adopted by
states in the  U.S. and governments
elsewhere. An  important feature of
all these reclamation systems  is that
customers pay for  the  reclaimed
water, but generally at a price  signifi-
cantly less than for fresh water.

REUSE PLANNING
  Cities in the industrialized world
have a major advantage in initiating
reclamation programs: they already
have the necessary sewerage systems
and secondary treatment plants.
However, this is not  always positive,
as treatment plants are typically situ-
ated to minimize treatment and dis-
posal  costs. Consequently, plants are
generally at a low elevation, located a
great distance  from  reuse markets.
Also, the costs to retrofit streets and
buildings in  developed urban areas
to add a new service  may be pro-
hibitive.
  In developing countries, on the
other hand, the investment  in urban
infrastructure is so far short  of the
need that the costs of conventional
and dual systems may not be  so dif-
ferent; with a dual system, the sav-
ings incurred in avoiding the need to
exploit an additional water supply
may, in fact, offset the cost  differen-
tial. If the initial  cost for needed
facilities is too great to be borne,
which  is generally the case in devel-
oping countries, at least the planning
might  be done to facilitate  reclama-
tion and reuse in the  future. Further,
an important feature of reclamation
is that it  can be  staged,  with
reclaimed water being introduced
into the system in small, affordable
increments.
  In any event, it is clear that the tra-
ditional practice of considering sewer-
age separately from water supply is
inappropriate. With  the  difficulties
inherent in financing systems in devel-
oping  countries, planners can lower
costs by considering  water  reclama-
tion in initial planning stages and by
                                                                               Selected Readings on Water Reuse -15

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                                                                             WATER  RECLAMATION/REUSE
          Toble 2—Uses of Reclaimed Water in Japan
Category Percent of total
Nonpotable in dual systems 40
Industrial 29
Agricultural 15
Stream flow augmentation 1 2
Snow removal 4
Total 100
Amount, mYs
1.3 (29)
0.9 (21)
0.5 (11)
0.4 (8)
0.1 (3)
3.2 (72)
(mgd)






          Table 3—Buildings Using Reclaimed Water in Japan

          Type
                Percent
Schools
Office buildings
Public halls
Factories
Hotels
Others (residences, shopping centers, etc.)
Total
18
17
9
8
4
44
100
          Table 4—Uses of Reclaimed Water in Dual Systems in Japan
          Use
                Percent
          Toilet flushing
          Cooling water
          Landscape irrigation
          Car washing
          Washing and cleansing
          Flow augmentation
          Other
          Total
                   37
                    9
                   15
                    7
                   16
                    6
                   10
                  100
          situating plants in appropriate areas.
          In developing countries, where the
          impetus for reuse comes from water
          resource needs, the plants should be
          located upstream on the sewerage sys-
          tem, nearer the potential markets.
          This has a further advantage in that
          reclaimed water that is not sold can
          help sustain the flow in urban streams
          that would otherwise run dry.
            Another characteristic of cities in
          developing countries  is that  storm
          drainage is inadequate, and stormwa-
          ter  management programs might be
          somewhat different if reclamation is
          being considered. Depending on
          Local circumstances, stormwater may
          be stored and then fed into the recla-
          mation system.

          EXPERIENCES IN DEVELOPING COUNTRIES
            Water reuse  in urban areas in
          developing countries  has generally
          been  unplanned and indirect. In
          Bogota, Colombia, for example, the
          city installed a good  sewerage  sys-
          tem,  but  the  sewers  discharge
          untreated wastewater to the Rio
          Bogota. Water is taken from  the
          heavily polluted river to irrigate mar-
ket crops, with inevitable negative
health consequences, particularly to
unwary visitors.
  The city of Sao Paulo in Brazil is
illustrative of large, rapidly growing
urban  areas that confront water
shortages while planning extensions
to  their sewerage  systems  and
wastewater treatment plants. A 3.5-
m3/s (80-mgd) module of a sec-
ondary treatment plant went into
operation in 1988 in the western
part of the city in the vicinity of
rapidly growing urban and industrial
areas. The quality of the effluent was
so high that pilot-plant  studies were
initiated to determine whether coag-
ulation, sedimentation, and sand fil-
tration would produce an effluent
that would meet quality require-
ments for urban reuse.
  The  research results were so
encouraging that Sao Paulo is now
surveying industry requirements for
nonpotable water. Paper and chemi-
cal plants are the largest water users.
Other uses,  such as  seasonal  land-
scape and local market crop irriga-
tion and toilet flushing in the large
office and residential buildings that
characterize Sao Paulo, are also
being evaluated. Further pilot-plant
studies are being undertaken to
develop design criteria for reclama-
tion, with the aim of eliminating the
sedimentation step, which sharply
reduces coagulant dosages.
  The Beijing-Tianjin region of
China, with a total  area of 28,000
km2 (11,000 sq miles)  and a popula-
tion of about 18 million, 60% of
which is urban, provides another
example of the potential for reuse. In
1984, water allocations totaled about
200 m3/s (4500 mgd)—about 65%
for agriculture and 35% for industrial
and domestic use.4 Studies showed
that the most economical source  of
additional water for the region
would be through  reclamation of
wastewater  for agricultural, industri-
al, and domestic uses with the recog-
nition that, over time, the reclaimed
water for  agriculture would be
switched to urban and  industrial use.
  The major problem is that much
of the region's population is not yet
served by sewerage, and that only
about 10% and 20% of the municipal
wastewater in Beijing and Tianjin,
respectively, receives treatment. Pro-
jects for urban sewerage, wastewater
treatment, and water reclamation
and reuse are underway. It is expect-
ed that a total of about 25 m3/s
(600 mgd) will be available for non-
potable reuse in 2000.
  The practice of nonpotable reuse
will also be valuable in the arid Mid-
dle East and North Africa. Other
than in oil-rich  countries, the focus
has been on reclamation  of urban
wastewater for agriculture.  Reclama-
tion in the region has followed the
pattern elsewhere, where farmers
take water from polluted drains and
rivers that would be dry  most of the
year except for the wastewater. This
focus is understandable, as the tradi-
tional priority use for  fresh water in
arid areas has  been agriculture. How-
ever, it is now being recognized that
in many countries  in this region,
urban and industrial demands for
water may constitute  30 to 45%  of
the total demand,  representing  a
substantial need, but also providing a
potential source of reclaimed water.
  Plans for Jordan exemplify the new
approach  to water  reclamation.
About  70%  of the population is
urban, and this percentage is  grow-
ing. The portion of total  water
demand for urban and industrial use
is expected to increase from  about
16 - Selected Readings on Water Reuse

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   Figure 1: Typical Flow Diagram for Los Angeles County Sanitation Districts Reclamation Plant.
                                                               Chlorine and
                                                               coagulant    Chlorine
                                                        Final settling |—|_Mixer    [—|      Pump
                       Wastewater Trunk Sewer
                                                                   To Wastewater Treatment Plant
                                                                          and Disposal
25% today to about 45% in 25 years,
with a commensurate drop in agri-
cultural allocations. Because sewer-
age in urban areas is expected to
increase over the next 10 years from
about 45% to 85%, the strategy is to
use the increased volume of urban
effluent to provide reclaimed water
for agriculture, releasing fresh water
now going to agriculture  for use in
the cities and in industry.
  Unfortunately, in Jordan and else-
where in the region, there are many
issues that are not yet being examined.
The potential exists for better use of
very limited freshwater supplies by
using reclaimed water for nonpotable
purposes in urban areas, stretching the
existing freshwater resources to serve a
much greater population. Otherwise,
the only additional sources of water
would  be new dams and  reservoirs
that would be extremely costly and of
questionable political feasibility. Most
of the reclaimed water, after being
used to meet industrial, toilet flushing,
and other nonconsumptive demands,
could be reclaimed for agricultural
use.
  Because the value of water in
urban and industrial uses is much
greater than in agriculture, the cost-
recovery potential  to  municipalities
providing the reclamation  service
gives better assurance that the system
will be properly managed than if the
reclaimed water were used solely for
agriculture, where cost recovery is far
less likely. Furthermore, providing a
nonpotable water distribution system
in urban areas in Jordan is more fea-
sible than in many  countries because
more than a third of the urban popu-
lation is not yet served with piped
water—a service that does have a
high priority for the future.

MEETING MANY NEEDS
  For the protection of the public
health and the conservation of water
resources in the developing world,
sewerage and wastewater treatment
must be provided, reclaimed water
quality must be monitored and, most
importantly, the use of the water
must be metered,  charged for, and
regulated. If reclaimed water is con-
sidered a resource  rather than a
waste,  a potential  for cost  recovery
exists. Only with cost recovery will a
reclamation program  be sustainable.
  Urban areas throughout  the
world,  and especially  in the develop-
ing countries of Asia, Africa, and
Latin America, are growing rapidly,
and  many cities are facing water
shortages. The reuse of wastewater
for agriculture is widely practiced in
the developing world, but it is often
unplanned and unregulated, posing
major threats to the public health of
farmers and those using the crops.
Even if agricultural practices can be
improved—and they  should  be—the
advantages of reclaiming water for
urban and industrial uses are many.
  The principal impetus is the short-
age of water. Those  responsible for
planning or engineering water-
resource, sewerage, or pollution-con-
trol projects in urban areas of devel-
oping countries should  assess the
potential for water reclamation for
nonpotable urban and  industrial
reuse as well as agricultural reuse. If
capital investments  for  additional
water-resource development are
imminent, the option of water recla-
mation should be evaluated. If recla-
mation for reuse is feasible, either
immediately or in the future, the
design of the sewerage system and
the situating of water reclamation
plants should be undertaken to mini-
mize costs.

  Daniel A. Okun is Kenan professor
emeritus of environmental engineer-
ing at the University of North Caroli-
na in Chapel Hill and is a consultant
with Camp, Dresser and McKee, Inc.
  This paper was presented at the
1989 WPCF Annual  Conference in
San Francisco, Calif., and a version of
it was published in Water & Waste-
water International, 5 (1) 1990.

REFERENCES

  1. "Pomona Virus Study,  Final
Report." Los Angeles County Sani-
tation Districts, California Water
Resources Control Board, Sacramen-
to, Calif. (1977).
  2. Young, R. E., et al., "Wastewa-
ter  Reclamation—Is it Cost Effec-
tive? Irvine Ranch Water District—A
Case Study." Proc. Water Reuse
Symposium IV, AWWA Research
Foundation, Denver, Colo.,  55
(1987).
  3. Murakami, K.,  "Wastewater
Reclamation and Reuse  in Japan."
Pro.  26th Annual Tech.  Conf.,
International Session,  Japan  Sewage
Works Assn., Tokyo, 43 (1989).
  4. "Water Resources Policy and
Management for the Beijing-Tianjin
Region." State Science and Technol-
ogy Commission, Beijing, and  Envi-
ronment and Policy Inst., East-West
Center, Honolulu (1988).
                                                                                Selected Readings on Water Reuse -17

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                                                             WATER RECLAMATION/REUSE
                        U.S.  WATER   REUSE:
                          CURRENT  STATUS
                     AND  FUTURE  TRENDS
                                        Kenneth J. Miller
              The hydrologic cycle repre-
              sents the ultimate water-
              reuse process: the finite
              amount of water on the
              planet undergoes continu-
              ous use and regeneration
              while travelling through the
              various stages of the hydro-
        logic continuum. Today, the world's
        rising population and its concurrent
        increase in industrialization have out-
        paced the slow-moving natural cycle.
        Many areas already face severe water
        shortages, and things are
        only going to get worse.
        To meet the  growing
        demand for water, the
        pace of regeneration and
        subsequent reuse must be
        accelerated.
          Planned, unplanned,
        direct, and indirect water
        reuse have been practiced
        for  over  2000 years.
        Unfortunately, water-
        reuse technology has been
        negatively affected by the
        public's  reticence  to
        accept historical and exist-
        ing reclamation practices.
        The best example that
        supports this claim is the
        water-supply industry in
        the U.S. There are very
        few surface-water bodies
        in the U.S. that do not
        receive wastewater dis-
        charges from the upstream munici-
        palities and industries. In fact, by the
        early 1950s, nearly all surface-water
        and some groundwater supplies
        showed evidence of man's industrial
        and municipal wastes. The public
        does not want to hear this, however,
        and when a water reuse project is
        proposed, the initial public reaction
        is generally negative.
         Notwithstanding the sentiment of
        the consuming public, indirect and
        direct reuse has been contributing to
Agricultural irrigation in Santa Rosa, Calif., reclaims 16 mil. gal
of wastewater a day.
our recreational and agricultural
water, aquifer recharge, and potable
water supply for more years than we
care to acknowledge.

BENEFITS OF WASTEWATER RECLAMATION
  Benefits attributable to wastewater
reclamation generally  fall into two
categories:  supplementing available
resources and pollution abatement.
Water reclamation and reuse supple-
ment or enlarge what may otherwise
be a fixed quantity of water available
          for use in a given area.
           The quality of water
          required for various
          uses often dictates  the
          most desirable form of
          reclamation and reuse.
          For example, water for
          most agricultural uses
          and many industrial
          uses need not be of as
          high a quality as that
          used for  human con-
          sumption. In such cases,
          water    reclamation
          through crop irrigation
          and use of treated efflu-
          ents for industrial pur-
          poses may relieve  the
          burden of supplying
          these needs with high-
          quality potable water.
          Artificial recharge of
          groundwater, either by
          injection  or spreading
18 - Selected Readings on Water Reuse

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of reclaimed water is often possible
in areas that depend  largely on
groundwater sources.  This also
results in augmenting the available
source by essentially  "banking"
reclaimed water in the subsurface
against the time when withdrawal of
groundwater   exceeds   natural
recharge.
  Finally, in  areas where sufficient
potable water is not available, highly
purified reclaimed water can be recy-
cled into the potable water  system.
This should  not be implemented
without considerable research cover-
ing all possible effects. It is not, how-
ever, an action without precedent;
direct or semi-direct domestic recy-
cling is now being practiced in some
areas of the world and will undoubt-
edly become more widespread.
  The  other major pollution abate-
ment benefit of water reuse and recla-
mation involves the removal of more
pollutants than conventional sec-
ondary waste treatment processes can
accomplish. Generally,  the  quality
standards for water reuse are such
that some additional waste treatment
is necessary  to reduce  oxygen
demand; nutrient content; avoid
undesirable algal growths; remove
suspended solids, color,  taste, odor,
and refractory materials;  and  remove
or inactivate potential disease-causing
organisms.
  In the U.S.  today, water reuse
practices can  be broken down into
the following categories: indirect
potable reuse, agricultural reuse,
urban landscape irrigation, industrial
reuse,  groundwater recharge, and
potable reuse demonstration.

INDIRECT POTABLE REUSE
  Indirect potable reuse  is practiced
by nearly all communities dependent
on  surface water. The difference
from city  to city can, in several
instances, be quantified by the dilu-
tion factor. The classic  case in the
U.S. is the Upper Occoquan  Sewage
Authority (UOSA)  that provides
potable water to the suburbs of
Washington, B.C.
  The  9.8-bil.-gal Occoquan Reser-
voir—the principal water supply in
Northern Virginia—serves more than
660,000  people. In the  1960s,
before  the formation of UOSA in
1971, discharges of conventionally
treated wastewater deteriorated the
reservoir's water quality. To  reverse
this trend, the Virginia State Water
Control Board adopted a compre-
Table 1—Agricultural Reuse Statistics
Agricultural Reuse Statistics

Leesburg, Fla.
maximum reuse volume:
irrigation area:
reservoir capacity:
pumping station capacity:
irrigation pipeline:
irrigation guns/gun spray rate:

Maui, Hawaii
maximum reuse volume:
irrigation area:
distribution system type:
distribution distance:

Sonora, Calif.
reservoir capacity:
distribution system:
number of release points:
irrigation area:
flow rate, per release point:
     3 mgd (3400 ac-ft/yr)
     330 ac of total 915-ac site
     10 mil. gal
     6400 gpm
     44,000 ft
     83/620 gpm
     4 mgd (4500ac-ft/yr)
     400 ac
     3 side-wheel roll systems
     960ft
      1800 ac-ft
      9 miles
      19
      1300 ac
      100 to 1300 gpm
hensive policy that required con-
struction of a highly sophisticated,
regional, advanced wastewater recla-
mation plant to replace the  11
largest existing secondary treatment
plants, and to reclaim the wastewater
as a water resource.
  Criteria accompanying the  policy
specified  treatment standards for
UOSA that are  among the most
stringent in the U.S. Additional cri-
teria established treatment processes
deemed necessary  to achieve the pre-
scribed level of treatment. A 15-mgd
treatment plant designed to meet
these criteria began operation in
June  1978 (see Box).  The facility
has performed  so  well  that the
plant's capacity has been expanded
to treat 27 mgd and planning con-
tinues for further expansion  to  54
mgd.  Operating  costs  for conven-
tional and advanced  wastewater
treatment are $0.83/1000 gal to
$1.37/1000 gal.

AGRICULTURAL REUSE
  To  provide for  its inevitable
growth  and to minimize impact  on
its natural environment, in 1970,
Leesburg, Fla., began exploring ways
to improve its wastewater treatment
plant and to discontinue the practice
of discharging  effluent to Lake Grif-
fin.  Efforts  culminated  in  an
improved 3-mgd (3400 ac-ft/yr)
secondary treatment plant and new
wastewater reuse  irrigation system,
which began operation in January
1981. Effluent was diverted away
from Lake Griffin by pumping 8
miles west of the  plant. At this site,
approximately 330 ac are irrigated
with reclaimed wastewater.
  This wastewater reuse irrigation
system is currently the largest solid-
set  (fixed-gun) system in the state
(Table 1). Because of the seasonally
high water table, approximately 100
ac of the irrigated areas are planted
with Coastal Bermuda grass, which is
harvested  using city-owned agricul-
tural field machines and tractors.
  Reclaiming wastewater for irriga-
tion not only makes Maui Hawaii's
first large-scale wastewater reclama-
tion facility and new collection sys-
tem a zero-discharge plant, but also
converts the reclaimed wastewater
into a valuable resource for the arid
Kihei region. The Kihei  secondary
treatment plant serves Maui's south-
west coast and has an average design
capacity of 4 mgd (Table 1).
  Designed to eventually serve a
4400-ac area, the collection system
includes eight pump stations that
deliver collected wastewater to the
main-9-mgd pump station that deliv-
ers wastewater to the Kihei plant.
  Most of the reclaimed water  is
used for irrigating ranch land and
newly landscaped roadways. About
250,000 gpd are treated  further  by
mixed-media filtration and chlorina-
tion to produce higher quality water
for park irrigation.
  A standby injection well is used
                                                                              Selected Readings on Water Reuse -19

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                                                                              WATER  RECLAMATION/REUSE
          Table 2—Urban Landscape Irrigation Statistics
          St. Petersburg, Fla.
          delivery volume:
          distribution network:
          residential user fees:
          industrial user fees:
          Tucson, Ariz.
          annual delivery volume
          demonstration delivery volume:
          spreading basin area:
          extraction well:
          monitoring wells:
          suction lysimeters:
          access wells:

          Colorado Springs, Colo.
          annual delivery volume
           flow design:
          daily flow design:
          user fees:

          Aurora, Colo.
          golf course irrigation area:
          golf course reservoir:
          plant effluent reservoir:
          annual average volume reused:
          distribution pipeline:
          user fees:
68.4 mgd
92 miles
$6/mo
$6/mo for the first ac-ft and
$1.20 for each 0.5 ac-ft increment or
$0.25/1000 gal ($81/ac-ft)
35,000 ac-ft/yr
1000 ac-ft
3 ac
1 on-site
10
6
20
1000-1250 ac-ft/yr
7 mgd
$0.60/1000 gal ($196/ac-ft)
120ac
6 mil. gal
0.5 mifgal
100 mil. gal
4 miles
$0.78/1000 gal
          during the infrequent, but heavy,
          rainy periods.  The well takes the
          reclaimed water through solid rock
          layers into a cinder layer more than
          100 ft below sea level.
            The unique  Tuolumne County
          Water District in Sonora, Calif.,
          reuse plan called for an irrigation
          system rather than a wastewater dis-
          posal system.  Reclaimed water is
          delivered to individual ranchers
          based on a predetermined irrigation
          schedule, adjusted  each year for
          cropping patterns, rainfall, and other
          factors. Over 30 ranchers, with a
          combined 1300 ac, will use the
          reclaimed water for  irrigation.
          Acceptable uses  of the reclaimed sec-
          ondary effluent,  according to the Cal-
          ifornia State Department of Health,
          include irrigation of pasture, fodder,
          fiber,  or seed crops, plus stock-water-
          ing and aesthetic uses where public
          contact is prohibited.
            Each rancher  signs a contract with
          the district to take a specified quanti-
          ty of  water—depending on irrigated
          acreage—during the April through
          October irrigation season. The water
          is free, but the rancher agrees to take
          the water for 20, 30, or 40 years.
  The contract is also binding on suc-
  cessive property owners. If a rancher
  does not take the water, the district
  may enter the land and apply the
  water as contracted. To provide sys-
  tem flexibility, each rancher agrees to
  take all water made available up  to
  125% of the contracted amount.  At
  the  same time, the district is obligat-
  ed to make every  effort to temporari-
  ly reduce the  water delivered in any
  given year if there are cropping pat-
  tern changes.
    A unique feature of the irrigation
  system is the automated operation of
  the  irrigation turnouts (Table 1).
  Solenoid-actuated,  hydraulically
  operated globe valves  on each pipe
  turnout are remotely operated  by
  command from  a control panel at
  the  Sonora  Treatment Plant. Com-
  mands are transmitted by radio sig-
  nals initiated on a keyboard at the
  treatment  plant. Flow rates and
  totalized flows at each turnout can
  be displayed on  a cathode ray tube
  (CRT) screen or line printed on
  command at the treatment  plant
  control panel. The  remote station
  transmits actual flow  data to the
  CRT for visual confirmation.
URBAN LANDSCAPE IRRIGATION
  The use of reclaimed wastewater
for urban irrigation of landscaped
areas is  one of the  fastest growing
reuse types in the U.S. Many munici-
palities find this the easiest and least
costly method of reuse. The benefits
can also be great because exterior
residential and commercial watering
on a yearly basis can average more
than 40% of a residential customer's
total water  consumption in arid and
semiarid areas.
  In St. Petersburg, Fla., which is
located in a water-short region,
potable  water must be piped in from
limited  well fields located  30 to 50
miles from St. Petersburg.
   In the mid-1970s, the city decided
to embark on a water-reuse program
to help solve its wastewater and
water supply problems by construct-
ing a limited dual distribution system
(Table 2) that would provide non-
potable  water for irrigation of public
and private properties, including golf
courses, parks, school grounds, com-
mercial and residential sites, and
street medians.
   Secondary wastewater treatment,
including grit removal,  aeration, and
clarification, results in a greater than
90% reduction of biochemical oxygen
demand (BOD) and total suspended
solids (TSS). The wastewater is then
filtered, chlorinated, and placed in a
12-hour retention area. When neces-
sary, treated wastewater is rechlori-
nated. An auxiliary deep-well injec-
tion system ensures zero-discharge or
reduces  use during rainy periods.
   The dual water system has had a
profound effect upon the city's water
system, reducing potable  water
demands by 10% to 15% of the water
use in 1982 and 1983.  The potable
water savings in 1983 was  nearly
14,700  ac-ft, saving the city thou-
sands of dollars. Reclaimed water is
sold to other city departments and to
private and public entities at $6/mo.
   In 1982, Tucson, Ariz., initiated a
metropolitan wastewater reuse pro-
gram mandating that reclaimed
wastewater be used to irrigate all
municipal and private  golf courses,
school  grounds, cemeteries, and
parks, as well as for other identified
uses.  By 1984, the Tucson  Water
Department was operating the first
elements of a wastewater reuse treat-
ment plant, reservoir, and transmission
system.  To date, $23 million has been
spent on the system, and  a 10-year
capital development program calls for
20 - Selected Readings on Water Reuse

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an additional $40 million to complete
the system. The completed system will
provide approximately 35,000 ac-ft/yr
of reclaimed wastewater.
  Because irrigation water demands
vary as much as 400% from winter to
summer, subsurface  storage  of
reclaimed wastewater in an aquifer
storage-and-recovery system was
installed. A demonstration recharge
project showed that effluent could
be safely recharged and later recov-
ered.  The recharge system has been
expanded for  large-scale controlled
recharge and recovery.
  Colorado Springs, Colo., is locat-
ed at the  eastern  base of the Rocky
Mountains in a water-short area. To
reduce dependence on water from
the western slopes  of the mountains,
in the early 1960s the city imple-
mented a limited  dual-distribution
system in  which reclaimed wastewa-
ter  and surface water from a nearby
stream was used to meet major irri-
gation demands. This is one of the
oldest operating systems in the U.S.
in which  reclaimed wastewater  is
used for urban landscape irrigation.
  Reclaimed  water, which comes
from  the city's secondary wastewater
treatment  facility, is recycled through
two major distribution systems that
parallel the city on the east and west
sides (Table 2). Current users include
parks, golf courses, cemeteries, and
commercial properties. Each site must
provide its own pumping to meet
individual pressure requirements.
  Since 1970, Aurora, Colo., has
used  reclaimed domestic wastewater
to irrigate the Aurora Hills Golf
Course (Table 2). Aurora uses  an
average  of  100  mil. gal/yr  of
reclaimed  wastewater pumped from
the Sand Creek Wastewater Reclama-
tion Facility to an onsite nonpotable
water reservoir. In 1982, four city
parks were added  to the reclaimed
water system, and their irrigation
requires an additional 50 mil. gal/yr.
  The plant uses conventional
screening and  grit  removal followed
by aeration and final clarification. A
chlorine solution is added to the final
clarifier  effluent  immediately
upstream  from the contact  basin.
From an onsite 0.5-mil.-gal reser-
voir, the effluent is either reused or
discharged into a nearby stream. The
reuse  system pumps the water from
the reservoir through  multi-media
pressure filters and a 14-in.-diameter
pipeline.
  In  1982, when  irrigation of city
Table 3—Inverness Reclaimed Wastewater Characteristics
 Characteristics
      Concentration
 5-day BOD
 Total suspended solids
 Total dissolved solids
 Ammonia nitrogen
 Sodium
 Sulfur oxide
 pH
 Fecal coliform
      20 mg/L
      20 mg/L
      460 mg/L
      14 mg/L
      20 mg/L
      30 mg/L
      6.9 to 7.3
      20 organisms/100 mL
Table 4—Water Factory 21 Performance and Requirements
Secondary
Constituent effluent
COD, mg/L
Methylene blue active
substances, mg/L
Ammonia nitrogen, mg/L
Cadmium, mg/L
Chromium, mg/L
Mercury, mg/L
E-coli, MPN/lOOmL
Turbidity, NTU
130
2.7
45
29
154
9
41 x 106
36
Blended
injection
water
10
0.08
0.9
0.6
8.8
2.4
>2
0.4
Requirements
for blended
injection
water
30
0.05
1.0
10
50
5
>2
1.0
parks began, the reuse  facility's
capacity was doubled, and the plant's
effluent standards were tightened.
When reclaimed water was  used
exclusively for golf course  irrigation,
the standards required a  discharge
limit of 30 mg/L each of BOD and
TSS and 200 fecal coliform organ-
isms/100 mL. However, because
football and soccer are  played at the
parks—sports that promote frequent
human contact with irrigated grass—
the mean total coliform standard was
made more stringent at 23 col-
iform/100 mL.
  Process modifications were made
to meet the proposed standards,
including the addition of a flow-
paced jet disinfection system to
replace the old chlorine solution sys-
tem. The reuse water for the park is
taken directly from the  line that
feeds the onsite reservoir, rather than
from the reservoir itself, thus maxi-
mizing the  available chlorine residu-
al. In the filter complex, a polymer-
feed system was added to improve
solids recovery in the pressure filters.
An  additional chlorine-feed system
allows for post-chlorination of all
reclaimed water. The 4-mile pipeline
allows for an additional 80-minute
contact time at peak pumping rates.
  Three operational problems are
currently being addressed. To allevi-
ate problems with algal growths,
which contribute to unsightly condi-
tions and some sprinkler nozzle-
clogging, algacides are  used on a
continuous basis. To  prevent reser-
voir debris from causing nozzle-clog-
ging, a self-cleaning  drum strainer
was installed on the pump discharge.
Salt buildup in low-lying areas where
ponding of surface runoff occurs is
being mitigated by eliminating
ponding or by seeding those low-
lying areas with more salt-resistant
strains of grasses.
  The economics of the Sand Creek
reuse program have been quite favor-
able for the city. In the past, an aver-
age of 100 mil. gal/yr were used for
irrigation. The 1980, costs of the
reuse system, including debt service
of the original filtration complex and
transmission line, but  excluding irri-
gation  pumping  costs, averaged
$0.43/1000 gal.
  Since 1975, the Inverness Water
and Sanitation  District, Colo., has
reclaimed wastewater from the com-
mercial office park it  services to irri-
gate the park's  18-hole,  140-ac golf
course.  The park,  located south of
Denver, will ultimately  have over
                                                                               Selected Readings on Water Reuse -21

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                                                                             WATER RECLAMATION/REUSE
          Toble 5—Denver Demonstration Plant Quality Goals
          Characteristic, unit of measure
            Average,
             potable
              water
          Turbidity
          Carbon alcohol extract, mg/L
          Alkalinity, mg/L as CaCO3
          Harmful organics
          Suspended solids, mg/L
          Total coliform, no./100 mL
          Total dissolved solids, mg/L
          Fecal coliform, no./100 mL
          Nitrate nitrogen, mg/L
          Fecal strep, no./100 mL
          Ammonia nitrogen, mg/L
          Virus
          Total phosphate, mg/L as P
          Gross metals
          Hardness, mg/L as CaCO3
          Taste
          BOD, mg/L
          Odor
          COD, mg/L
          Total organic carbon, mg/L
          Carbon chloroform extract, mg/L
               0.6
               0.09
              60.0
          None present
               0.0
               0.1
             157.0
               0.0
               0.3
               0.0
               0.0
          None present
               0.07
          None harmful
              88.0
         Unobjectionable
              <1.0
         Unobjectionable
              <5.0
              5 to 8
               0.06
            The purification process used at
            UOSA  includes activated-sludge
            secondary treatment,  phosphorus
            removal  by lime coagulation,
            two-stage recarbonation, nitrogen
            removal by ion exchange, mixed-
            media filtration, activated-carbon
            adsorption, and breakpoint chlo-
            rination.  Resource recovery and
            reuse are achieved using ion-
            exchange media,  carbon regen-
            eration, and organic-solids com-
            posting. The plant uses a closed-
            cycle ammonia stripping and
            adsorption process for regenera-
            tion of the ion-exchange system
            regenerate solution.  The ammo-
            nia removal and  recovery pro-
            cess recovers 40%  ammonium
            sulfate  solution  for resale as an
            agricultural fertilizer.  A compost-
            ing system converts waste organ-
            ic  solids to a stable organic soil
            conditioner suitable for  recre-
            ational land rehabilitation or agri-
            cultural use.
           1000 developed acres with a projected
           average daily wastewater flow of 0.9
           mgd. In 1984, the development aver-
           aged flows  of 250,000 gpd. All
           wastewater flows are  collected and
           treated onsite. The golf course uses an
           average of 100 mil. gal/yr; almost half
           this amount is reclaimed wastewater.
  The park's treatment  facility
includes a flow equalization basin,
aeration basins, secondary clarifiers,
and a chlorine contact basin. Disin-
fection is accomplished using chlo-
rine gas that is put into solution and
mixed with the secondary effluent.
At a flow rate of 250,000 gpd, a the-
oretical contact time of 45 minutes is
provided.
  The treatment facility's chlorinat-
ed effluent is pumped  through  a
4200-ft-long, 8- and 10-in.-diameter
pipeline to a storage reservoir, allow-
ing an additional contact time of 20
minutes.  The storage  reservoir,
which is not part of the golf course,
has a capacity of approximately 55
mil. gal. The reservoir is designed for
an annual fill and draw; water fluctu-
ation is approximately 20 ft.  Because
the reservoir receives  all  water from
the wastewater treatment plant, it is
sized to store water throughout the
year, with irrigation occurring from
April  through October. The typical
water quality of the irrigation water
discharged to the reservoir is pre-
sented in Table 3.
  At  the  pump  station drawing
water from the  storage reservoir,
chlorine may be added to the irriga-
tion  water before it is pumped to
the distribution system.  However,
in general, the addition  of  chlorine
is not required to meet the dis-
charge standard of 23 fecal coliform
organisms/100 mL.
  Water quality  at the sprinklers will
generally be equal to that shown in
Table 3, with the exception of TSS
and fecal coliform; these values may be
markedly higher because of the  pres-
ence of algal blooms and wastes pro-
duced by waterfowl on the reservoir.
  The average application of water
to the golf course is equivalent to
0.55 mgd, with peaks of 1.4 mgd.
Of the 100 mil.  gal required to oper-
ate the irrigation system, the current
wastewater flow provides approxi-
mately 65%, with the remaining 35%
provided by the district's well.  By
1987,  100%  of the  irrigation
demands were  met with reclaimed
wastewater.
  The 1980 costs  of the reuse sys-
tem,  excluding debt service, but
including all operation and mainte-
nance costs of the reuse pumping
systems, averaged $0.64/1000 gal.
Because of the high cost of obtaining
additional water for irrigation, which
is estimated at over $1.00/1000 gal,
the district saved  over $0.36/1000
gal of water used. As the district
grows, and a greater percentage of
the irrigation water demand is met
with reclaimed  wastewater, the dis-
trict  will realize greater savings.
Future plans for the district include
irrigation of lawns and other  open
spaces. Plans are  already underway
for a  complete dual distribution sys-
tem. Use of the reclaimed wastewa-
ter for lawn irrigation will require
additional treatment to meet the
stringent water-quality standards
proposed by the Colorado Depart-
ment of Health.

INDUSTRIAL REUSE
   There are many  uses of reclaimed
wastewater for  industrial purposes;
each use may require specific levels of
treatment. In 1979, industrial  reuse
process  flows  averaged  66  mgd
(73,000 ac-ft/yr), and reclaimed  water
for industrial cooling accounted  for
nearly 142 mgd (159,000 ac-ft/yr).
   In  the city  of Tampa, Fla., a
remodeled incinerator facility burns
1000 ton/day of refuse  and uses
approximately  1 mgd of reclaimed
wastewater for  cooling-water make-
up. The water  is  pumped from the
Hookers Point  advanced wastewater
treatment facility,  1.5 miles from the
McKay Refuse-to-Energy Facility.
Although the remodeling cost was
$60  million,  the  system  saves
Tampa's water department  over
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1000 ac-ft/yr of potable water.
  Water was an important raw mate-
rial for the initial 200-MW stage of
the R.D. Nixon Power Plant, a coal-
fired, steam/electric plant near Col-
orado Springs,  Colo. Although
brackish, the well-water supply was
selected to provide water to the facil-
ity. As  the  power plant expands,
however, reclaimed water will  be
relied on because the well-water sup-
ply is limited. With conventional
blow-down practices for cooling-
water systems relying on well water,
effluents from the power plant would
exceed state water-quality limits for
dissolved salts and metals in the small
receiving stream. Thus, it was neces-
sary to develop an effluent recovery
and recycle system that would allow
these supplies  to be reused.  The
selected process recovers and recycles
power plant cooling-water effluent,
attaining zero  discharge. Well water
is softened by ion exchange; effluent
is treated and recovered by floccula-
tion, clarification, filtration, reverse
osmosis, and vapor-recompression
evaporation. Brine concentrates are
disposed in evaporation ponds.
Within  the  recovery system, flows
range up to 1  mgd with salinities
ranging from one-fifth to over five
times that of seawater.
  The system produces water and
treats effluents for less than alterna-
tive systems using municipal waste -
water or purchased water.

GROUNDWATER RECHARGE
  In 1975, the Orange County
Water District (OCWD) began oper-
ating a water reclamation facility—
Water  Factory  21—capable  of
reclaiming  15 mgd of secondary
effluent  and injecting it into the
coastal aquifer  to prevent seawater
intrusion and to recharge the exist-
ing potable groundwater basin.
  Processes similar to those used at
South Lake Tahoe, Calif, along with
breakpoint chlorination and reverse
osmosis, were selected. This combi-
nation was chosen to help ensure a
product water able to meet drinking-
water  standards.  Blending  of
reclaimed wastewater with at least
50% desalinated seawater or deep
well water was provided as further
insurance.
  Specific unit processes include lime
clarification with sludge recalcining,
ammonia stripping, recarbonation,
breakpoint  chlorination,  mixed-
media filtration, activated-carbon
adsorption with carbon regeneration,
post-chlorination, and reverse-osmo-
sis demineralization.
  The 5-mgd, high-pressure, reverse
osmosis system  was designed to
operate in parallel with the 15-mgd
activated carbon facility. Today, the
activated carbon system operates in
standby mode largely  because of
high-quality secondary effluent and
because of reduced groundwater
recharge needs.
  Performance  and   treatment
requirements for Water Factory 21
are shown in Table 4. Total capital
and operating costs, based on 1983
dollars, were  estimated  to be
$1510/mil.  gal  (491/ac-ft). The
lime/reverse-osmosis process tested
at Water Factory 21 offers significant
potential for meeting treatment
needs. The process would eliminate
ammonia stripping, sand filtration,
and activated-carbon adsorption and
regeneration.  Costs for the new low-
pressure system are estimated to be
$1346/mil.  gal ($438/ac-ft), as
compared  to  $1510/mil.  gal
($492/ac-ft)  for  the Water Factory
21 treatment trains.

POTABLE REUSE DEMONSTRATION
  Chanute, a relatively  small com-
munity in southeast Kansas, relies
entirely on the Neosho River for its
water supply. Chanute  maintained
and operated a conventional rapid-
sand-filtration plant to treat Neosho
River water  before it entered the
city's  potable water distribution sys-
tem. During the years 1953 through
1957, a record drought struck the
Neosho drainage  basin.  Flow
decreased and, in early 1956, it prac-
tically ceased. Although all possible
water conservation measures were
instituted and flow-augmentation
procedures were attempted,  the
water supply  continued  to dwindle.
On October  14, 1956, without any
fanfare, city officials opened a valve
that permitted mixing  of effluent
that had received conventional sec-
ondary treatment with water stored
in the Neosho River channel behind
the water treatment plant impound-
ment dam.
  The recycling process was used for
a total of 5 months during the fall
and winter of 1956 and  1957. Dur-
ing this period, treatment removed,
on the average, 86% of the BOD and
76% of the chemical oxygen demand
(COD)  contents of the  wastewater.
It substantially reduced both total
nitrogen and ammonia-nitrogen
concentrations; detergent concentra-
tions decreased an average of 25%. It
was estimated  that  one complete
cycle through the waste treatment
and back through the water treat-
ment required about  20 days. Thus,
during the total period of time dur-
ing which water recycling was prac-
ticed, the same water  passed through
the treatment plant  approximately
seven times.
  The  Denver Water Department is
operating a 1-mgd demonstration
plant that produces  potable water
from secondary  treatment plant
effluent. The need for the project
grew out of the  recognition that
additional conventional sources, if
available, might cost $5000/ac-ft to
develop by the year 2000; and indus-
trial reuse of wastewater would not
substantially reduce water demands.
The construction  of the demonstra-
tion plant is part of a $35-million, 7-
year project by the department to
demonstrate that high-quality water,
equal to or better than Denver's cur-
rent drinking water, can be produced
safely  and reliably  from  treated
wastewater treatment plant  effluent.
EPA is also participating in this
demonstration project by contribut-
ing approximately $7 million  of the
total cost.
  The demonstration plant cost
approximately $16.2  million to
build. Its capacity is  1  mgd for the
initial  processes through the first
stage of carbon adsorption, and 0.1-
mgd for the remaining processes.
Water  treated  by this facility has
undergone 5 years of extensive test-
ing for more than 200 potential con-
taminants, and an exhaustive pro-
gram of health-effects testing is
underway.
  None of the reuse water produced
from this demonstration plant will be
added to drinking-water supplies. It
will be allocated strictly for industrial
use at the Metropolitan  Denver
Sewage  Disposal District No. 1
(MDSDD) Treatment Plant and for
the extensive testing program. If the
absolute  dependability of this reuse
facility is established, reuse may be
instituted on a full-scale basis.
  The  treatment process was  devel-
oped from information obtained
from 10 years of operation of a 5-
gpm pilot plant by the Denver Water
Department  and University of Col-
orado and from information gained
by CH2M Hill from the design, con-
                                                                              Selected Readings on Water Reuse -23

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                                                                              WATER RECLAMATION/REUSE
          struction, and  review of the Lake
          Tahoe Advanced Wastewater Treat-
          ment Plant,  Occoquan Advanced
          Wastewater Treatment Plant, and
          several other projects.
            The MDSDD Treatment Plant is
          adjacent  to the Denver  Water
          Department's reuse demonstration
          plant. Unchlorinated secondary
          effluent is pumped from the treat-
          ment plant to the reuse plant. Sec-
          ondary effluent enters the reuse plant
          at the rapid-mix basins, where lime is
          added and mixed with the water.
          Lime facilitates the removal of sus-
          pended  particles, phosphorous, and
          some heavy metals, and aids in the
          destruction of viruses  and most
          microbiological organisms. Water
          then flows  to flocculation basins. If
          necessary, aluminum sulfate and
          polymer are added to enhance floc-
          culation and settling characteristics.
            Following  flocculation, the water
          enters the chemical clarifiers, which
          remove  settleable solids and reduce
          solids loading into the filters. The
          water then passes into  the recarbona-
          tion basin, where carbon dioxide is
          added to reduce the pH to between 7
          and 8, and through ballast ponds to
          equalize the flow to downstream pro-
          cesses. Pressure filters remove most of
          the remaining suspended particles,
          improving the subsequent treatment
          steps. The  treated water then flows
          into the selective ion-exchange pro-
          cess, which removes nitrogen in the
          form  of ammonium (NH4) from the
          process flow by passing the water
          through a naturally occurring zeolite
          media (clinoptilolite). Sodium chlo-
          ride is added to regenerate the zeo-
          lite media. The ammonia recovery
          and removal system them removes
          the ammonium ions from the regen-
          erate  solution. Ammonium sulfate, a
          commercial-grade fertilizer produced
          as a byproduct of the system, is
          stored  onsite and sold to reduce
          treatment expenses. The water then
          passes through first-stage carbon
          adsorption process.  This process
          removes remaining dissolved organic
          compounds. The product water then
          passes through the ozonation pro-
          cess.  Ozone oxidizes organic sub-
          stances  that remain after first-stage
          carbon adsorption and also acts as a
          primary disinfectant. The water then
          passes on to second-stage granular
          activated carbon treatment where the
          remaining  organics that have been
          rendered more  absorbable by ozone
          oxidation are removed. In addition,
biological activity on the carbon fil-
ter is used to remove organics by
biodegradation.
  The demonstration plant can
regenerate and store spent granular
activated carbon. A fluidized bed
regeneration furnace that can operate
at a maximum temperature of 2000°
F regenerates the carbon that has
adsorbed the organics. The water
then flows to the reverse-osmosis
system where dissolved salts are
removed back to  the range of Den-
ver's present supply. Reverse osmosis
also serves as the final physical barrier
to the  passage of a variety of poten-
tial contaminants.
  Following reverse osmosis, the
water passes through an air-stripping
tower  that  removes carbon dioxide
and volatile organic compounds. The
final product water is treated with
either chlorine dioxide or chlorine to
destroy any disease-causing organ-
isms and provide  a residual disinfec-
tant for transmission and storage.
   Recognizing that true  standards
for potable wastewater reuse fail to
exist, the Denver  Water Board elect-
ed to meet  the same water quality as
the potable water currently being
consumed  by the Denver citizens.
Table 5 contains  a partial  list of the
water-quality goals for this demon-
stration facility.

WATER REUSE PRACTICES IN THE FUTURE
   In 1983, Tampa began a study to
determine  reuse  alternatives for an
extremely high-quality  effluent from
the  Hooker's  Point Advanced
Wastewater  Treatment Plant. To
evaluate the  effects of additional
treatment  on the effluent, a  pilot
plant  has  been constructed  with
capabilities  that include pre-aeration,
high-lime treatment, multi-media fil-
tration, reverse osmosis, ultrafiltra-
tion, granular activated carbon, and
disinfection.
   A  research program has been
designed to determine the health
risks  associated with  reuse of the
pilot-plant  product water  as a com-
ponent blended into a raw potable
water supply.
   The ultimate goal of the Tampa
Water Resources Recovery Project is
to treat an  advanced wastewater
treated effluent to potable quality.
The  final product will be placed into
the Tampa bypass canal to recharge
an adjacent aquifer and then flow
into the Hillsboro River upstream of
a raw water intake. To date, water-
quality parameters of the treated
water exceed those of the river water.
  Surface supplies, while improving,
may never be swimmable and fishable,
if indeed they ever were, and ground-
waters are showing evidence of man's
encroachment and of his  industrial
renaissance. The quality of many sur-
face supplies, like that of  the Hills-
boro River, will continue to deterio-
rate until planned reuse and its associ-
ated treatment process will offer a
higher-quality product than conven-
tional treatment. The need for ever-
improving advanced wastewater treat-
ment processes and recycling technol-
ogy will continue to grow worldwide
as the  population increases and the
standard of living of the third-world
developing nations begins to improve.
The key to our success in dealing with
the water-resource problems will lie in
our ability to extend and augment
existing supplies through various
reclamation processes.
  The task of applying current state-
of-the-art in water reuse will tax the
ingenuity of all sectors of our soci-
ety, not just  the water-supply com-
munity. Research and demonstration
projects will be required. Moreover,
water reuse will not be limited by
the ability to successfully treat
wastewater, but by the costs  associ-
ated with the construction and oper-
ation of the treatment. Water  quality
standards will be required  to process
or recycle water to qualities that will
be  desired; conceivably,  five or six
water quality standards for agricul-
tural use, alone, could be developed.
In  addition  to effluent discharge
standards, standards which relate
directly to industrial needs are likely
to be promulgated.
  Water reuse in  both the U.S. and
worldwide will inevitably increase as
existing water supplies are incapable
of meeting future demand brought
about  by increasing world popula-
tions and  industrialization. The
municipal, industrial, and agricultur-
al demands will, thus, have to  be met
and, this prospect, thereby,  clearly
reveals the need for expanded water
reuse research in the 21st century.
   Kenneth J. Miller is vice president
 and director of water engineering with
 CH2M HILL Consulting Engineers
 in Denver, Colo. This updated report
 was reprinted for 1987 Annual Con-
ference Proceedings, American Water
 Works Association, Denver Colo.
24 - Selected Readings on Water Reuse

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     JJEYNOTES
On-Site Wastewater
Reclamation and Recycling
 i John Irwin
      ith the onset of the
      1990s, many com-
      munities and town-
ships  have been strug-
gling with the problem of
providing for increasing
residential and commer-
cial growth  at a time
when water resources are
more scarce  and envi-
ronmental capacity to
adequately   manage
wastes is severely limited.
This is evidenced by the
movement   in   many
towns and states to adopt
new standards for water
conservation in plumbing fixtures. It is also
evidenced by the significant number of
communities that have imposed sewer
moratoriums or sewer-capacity restrictions.
Finding additional water supplies and ex-
panding wastewater treatment plant ca-
pacity is expensive, sometimes impractical,
and, at best, involves long-range planning
when an immediate solution to the prob-
lem is needed.
  On-site water reclamation  and reuse
systems have been successfully used to solve
these problems. A rural school district in
central Texas experienced significant
growth, making it necessary to build a new
800-student high  school. Numerous po-
tential sites were evaluated. None of the
acceptable and available locations were
served with public sewers, and poor soil
conditions in the area made conventional
septic and drainfield  wastewater manage-
ment very difficult. Some means had to be
found to reduce the wastewater volume so
the site could be served with only a small
subsurface discharge. On-site, advanced
wastewater treatment and use of reclaimed
water for flushing toilets within the school
reduced the wastewater discharge by about
85%. This solution to a difficult wastewa-
ter management problem also had a major
impact on water conservation for the en-
tire school district.
  In southwest Houston, Tex., the Alli-
ance Bank and Trust Company owned
several acres of prime commercial property.
This site was served by the municipal sewer
district, but years of growth and the inabil-
ity to increase the capacity of the existing
municipal wastewater facility resulted in a
sewer moratorium. Under the moratorium,
a new project could discharge no more than
1600 gpd of wastewater/ac, meaning new
office  construction could not exceed
                 16,000 sq  ft/ac  of
                 property. This pro-
                 perty's very high value
                 could not support the
                 small amount of devel-
                 opment, which the
                 sewers would permit.
                 But using an on-site
                 wastewater treatment
                 and recycling system
                 and water-conserving
                 fixtures  permitted
                 construction  of  a
                 200,000-sq-ft facility
                 on the site. The waste-
                 water system is in the
                 building's basement
                 and provides  reclaimed
                 water for toilet flushing
                 throughout the 12-
story structure. The sewer discharge is less
than 1000 gpd when the building is fully
occupied.
  Montgomery Township, N.J., a rural
area adjacent to Princeton,  is undergoing
tremendous development  pressure as a
result of hi-tech growth near Princeton
University. The township is without sew-
ers and residents have no desire  to build a
wastewater facility that would encourage
commercial and industrial  development.
But  development  in the township seems
inevitable, and office and research facilities
are therefore not discouraged. Local resi-
dents are concerned about  the impact of
this development on the local water supply
resources and on groundwater quality.
  In 1985, the Squibb Corporation began
developing a 366,000-sq-ft office and R&D
complex in Montgomery Township. Initial
construction involved a 60,000-sq-ft office
which would use a conventional septic and
subsurface drainfield wastewater system.
During initial construction, the New Jersey
Department of Transportation established
a new  highway alignment that crossed
through a major portion of the Squibb
property. The only way to  proceed with
the project was to substantially reduce the
wastewater volume and the corresponding
size of the subsurface disposal system. On-
site wastewater treatment and recycling of
reclaimed water for toilet flushing was
evaluated and found to satisfy project re-
quirements. In addition, the on-site recla-
mation system was found to be less costly
than alternatives.
  The  success of this project, which has
been on-line for 3 years, has convinced the
Montgomery Township officials of the
environmental benefits of recycling, water
conservation, and a much lower pollution
impact, and now other projects within the
township are on-line or are in the design
phase. With on-site treatment and  recy-
cling, Montgomery Township has  been
able to control growth, avoid a major sewer
infrastructure expense, and achieve  envi-
ronmental goals.
  The city of Santa Monica, Calif, is also
evaluating  the impact of growth under
severe resource restrictions. The city has a
controlled but healthy development climate
which has added many new facilities over
the past few years. This continuing devel-
opment however, is viewed with mixed
emotions. In California, water supplies are
limited. For years citizens have been in-
censed by periodic sewage overflows into
Santa Monica Bay. Last year, Los Angeles
County, from which Santa Monica con-
tracts for wastewater disposal, issued a sewer
moratorium which could severely restrict
new development. These conflicts between
growth and environmental resources have
led Santa Monica to become an outspoken
advocate of water conservation and  envi-
ronmental protection. The city has been a
forerunner  in adopting strict water con-
servation regulations. In addition, on sev-
eral major development projects, it has re-
quired use of on-site wastewater treatment
and water reclamation.
  The first  example of this aggressive ap-
proach to resource conservation is a project
called Water Garden, a  1,300,000-sq-ft
complex consisting of four buildings con-
taining office and retail uses.  The typical
wastewater  volume from a facility of this
size is approximately 70,000 gpd. Using
ultra-low flush toilets and other water
conserving fixtures required under city or-
dinance, the projected flow can be reduced
to 40,000 gpd. Using a creative mix of
landscaping (which includes a small orna-
mental pond system), on-site wastewater
treatment, and reclamation for landscape
watering and pond evaporative loss make-
up  will virtually eliminate any sewer dis-
charge during the project's first phase which
includes two buildings comprising 650,000
sq ft. The need for potable water for land-
scape purposes is also eliminated. Phase two
of the project is intended to incorporate a
second on-site wastewater treatment system,
which will recycle the reclaimed water for toilet
flushing in the phase-two buildings. Total
water use can be reduced by about 75% and
wastewater discharge can be reduced by almost
95% in this project, which is currently under
construction.
                                                                                 Selected Readings on Water Reuse -25

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          WASTEWATER TREATMENT
             A critical component in establishing a
          successful on-site wastewater reclamation
          facility is providing a reliable treatment
          process that can produce reclaimed water
          on a consistent basis. The figure shows a
          system that has been used very effectively.
          The process includes on-line flow equal-
          ization and emergency storage tanks, bio-
          logical nitrification and denitrification,
          membrane filtration, activated
          carbon, and disinfection.  The
          emergency storage tank provides
          several days' flow accumulation
          in the event of any mechanical
          malfunction.  Membrane filtra-
          tion is used to provide fail-safe
          clarification of biological process
          solids down to a particle size of
          approximately .005 (J,. Granular
          activated carbon is used for color
          removal  and provides a backup
          for organic carbon removal.
          Disinfection with ultraviolet light
          or ozone provides an essentially
          pathogen-free effluent.  Post-
          chlorination can also be added
          to provide a distribution system
          residual.  Typical water quality
          achieved is BOD and TSS < 5
          mg/L,  turbidity  < 0.5 NTU,
          and total coliform <_2.2/1 OOmL.
             Just as critical and perhaps
          more important is the operation
          and management  of the recla-
          mation  facility. There is no
          greater assurance of success than
          providing single responsibility for
          process equipment and system
          operation and management.
          Several years of providing systems
          under a wastewater management
          service contract have  demon-
          strated that process performance
          is more  reliable when routine
          preventive maintenance and in-
          spection is provided rather than
          periodic  emergency response.
          Long-term  operating costs are
          most effectively controlled when
          the equipment manager is made
          responsible for parts and equipment re-
          placement under a fixed management fee
          arrangement.

          REGULATORY OBSTACLES
             The use of on-site water reclamation and
          recycling, although a successful and grow-
          ing practice, is relatively new and is not yet
          widely used. In many states, lack of expe-
          rience with water reclamation and lack of
          specific standards and regulations have se-
          verely restricted its use. Four areas are of-
          ten obstacles to reclamation.
             Regulatory codes. Some codes impose
          guidelines for wastewater treatment but
          don't recognize water conservation and
          water-reclamation  activities.  Many states
use a "cookbook" code approach involving a
lengthy variance procedure for applications
which aren't part of the listed recipes.
  Lack of a standard for reclaimed wa-
ter quality. In many states projects can be
rejected or significantly delayed in the ab-
sence of an approved standard.
  Ambiguous plumbing codes. Most
standards include language stating that each
plumbing fixture (including toilets and
luctant  to consider using non-potable
water in a building because  of a lack of
experience  with procedures used to
control  dual plumbing systems.
  More than 10 years of experience in the
U.S. with on-site wastewater treatment and
recycling in commercial facilities has dem-
onstrated that it is a safe, environmentally
superior, and economically viable practice.
There have been no public health prob-
urinals) shall be provided with potable wa-
ter except where not deemed necessary by
the administrative authority . The caveat
"except where not deemed necessary by
the administrative authority" was specifi-
cally added to the codes to encourage the
use of safe applications for non-potable
water, such as recycling.  Many local ad-
ministrators are not aware of the purpose
of the enabling language and are unwilling
to consider such proposals.
   Lack of confidence in standard
practices for controlling cross con-
nections.  Although all the experience
with  using reclaimed water for toilet
flushing has been successful, many
building and safety departments are re-
lems and use  of recycled water has not
caused any adverse reaction from building
owners or occupants. The systems are reli-
able, efficient in producing a high-quality
water for toilet flushing or landscape irri-
gation, and have a positive impact on the
environment by conserving water and re-
turning a highly treated effluent back to
the environment.                    •
  John Irtvin is vice president of Thetford
 Systems, Inc., in Ann Arbor, Mich. The above
 presentation was given at the Conserv 90
 Conference in August 1990.
26 - Selected Readings on Water Reuse

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Wastewater  Reuse

Gains Public  Acceptance
    Twelve years ago, Orange County, Calif., Water District's
    Water Factory 21 was completed. The widespread and
    growing attention given to wastewater reuse over the past
    dozen years is gratifying, if somewhat astonishing, to those
of us who have been concerned with reuse during this period. It
is clear that water resource planners now consider reuse as an
acceptable alternative method of meeting increasing water
demands, not only for agriculture, but also for municipal and
industrial uses.
  The technological and engineering concepts underlying
wastewater reuse projects
are becoming increasingly
well understood. This is
true even with our knowl-
                           On the Cover and In this Issue:
                             In this section, Water Environment &
                           Technology publishes the third installment of
  ,    c i   i i    cc     c    n series on wastewater reuse and reclamation
edge or health effects or       ,    ....,_.       , _
  0                        made possible by me bnvironmmtal rrotection
                           Agency. Economics and case studies in Irvine,
                           Calif., and in Florida are the selected topics.
potable reuse, which has
been  the  most difficult
area in which to achieve
general acceptance. Indirect potable reuse, as from groundwa-
ter injection, appears to be fully accepted. Direct potable reuse
is just a few years away from implementation in Denver, Colo.,
and its public acceptance is expected to be fairly uneventful.
  Planners, engineers, and the public have accepted waste-
water reuse; the spotlight next turns to the economists. These
economists playfully ask, "Well, it works in practice, but I
wonder if it will work in theory?"
                                —Introduction to the paper,
                           "Economics of Potable and Non-
                       potable Wastewater Reuse," presented
                         at the 1987 American Water Works
                            Association Annual Conference
                         by]. Gordon Milliken of the Milliken
                           Research Group in Littleton, Colo.

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                                                                   NEWS
          Obstacles  to  Implementing
          Reuse  Projects
           In 1988 the American Water Works
           Association (AWWA)  Research
           Foundation  commissioned a study
          to determine what obstacles exist in
          water reuse implementation  and to
          identify activities that could help
          remove these  obstacles. Information
          about reuse projects, regulations,
          practices, and experience was collect-
          ed through a questionnaire and  fol-
          low-up telephone survey.  The study
          included 188 participants, most of
          whom were selected because of their
          expressed  interest in or experience
          with water reuse. The broad nature
          and  experience  of the individuals
          who provided input  to  the study
          served to significantly strengthen the
          recommendations and emphasized
          the need for action.
            Based on  the experience of the
          study participants, there are three
          obstacles of primary concern when
          implementing a  reuse project: cost
          effectiveness, information  dissemina-
          tion  and education, and water-quali-
          ty and health issues.
            The degree to which these issues
          become obstacles depends on  the
          type of reuse anticipated and  the
          environmental appeal of the project.
          For example, if the reuse application
          conserves  a valuable water resource
          or benefits the  environment, it is
          more likely to be acceptable to the
          community.
            In a few states, special issues  like
          water ownership are major deterrents
          to reuse. For example, in New Mexi-
          co, credits  against groundwater
          pumping  are given to those cities
          that  return their treated effluent to
          the  river system. Reuse would entail
          returning  less effluent to the river
          system,  thus constraining the utility
          to pump less groundwater.  There-
          fore, while conservation  is encour-
          aged, reuse is not.

          QUANTIFYING THE OBSTACLES
            The cost effectiveness of reclaim-
          ing water varies significantly with
          current practices and raw  water sup-
          ply.  Unusual circumstances would
          need to exist in order to proceed
          with a reuse project that  is not  cost
          effective. Most reuse projects have
          resulted from a need to identify new
water sources. A number of reuse
applications have also grown out of a
need to find an alternative to more
stringent discharge standards.
  Survey results demonstrate that
urban irrigation of public use  areas
such as golf courses and parks, indus-
trial reuse, and agricultural reuse
projects are easiest to accomplish.
When  project implementation is
economically appropriate, few seri-
ous obstacles exist.  This is demon-
strated in California and Florida
where irrigation projects number in
the hundreds. The general public's
attitude about health and water qual-
ity is an occasional implementation
obstacle, but it is  seldom the major
issue. However, if education, water
quality, and  health issues are not
properly dealt with, even these  easily
implemented reuse projects will  be
halted.
  The principal obstacle limiting
either direct or indirect potable reuse
is public attitude. Cost effectiveness
is  also a  significant obstacle  to
potable reuse projects. However, the
results of the survey showed that,
unless careful attention is paid to in-
formation dissemination and water-
quality and health issues, a cost effec-
tive  potable  reuse project—either
direct or indirect—will be difficult to
implement.
  Ten  specific activities were recom-
mended in the study. However,
action is most urgently needed in
information dissemination to all par-
ties involved in potential reuse pro-
jects, including engineers, regulators
and other technical staff, community
officials, and the general public; and
water-quality and health-effects guid-
ance for the implementation of dif-
ferent types of reuse projects.

INFORMATION DISSEMINATION
  Many of the barriers to reuse stem
from a lack of information. Fortu-
nately, much of the information
needed already exists. One of the
most pressing needs is to compile the
body of knowledge into a format
that those who are responsible for
implementing reuse can use. Equally
pressing is  the need to assemble
information into a format that can be
presented and understood by the
public that is trying to make an
informed decision about a proposed
reuse project in its community.
  An information dissemination pro-
gram covering the following subjects
can be key to  the success of a reuse
program:  the need for, availability
and cost of, additional water supplies
and the environmental impact of
reuse  versus developing additional
raw water supplies; and the effective-
ness of the water-reuse  technology
applicable to the type of reuse antici-
pated  and the  safeguards incorporat-
ed in the water reclamation  and
reuse  processes. Utilities practicing
indirect potable reuse found public
awareness  of a water shortage to be
the best way to overcome a negative
public attitude.

WATER QUALITY AND HEALTH EFFECTS
  There is a universal call for consis-
tency and  informed decision making
in the area of guidelines and regula-
tions for reuse. A clearer definition
of requirements for both potable and
non-potable  reuse projects is urgent-
ly needed.
  A significant effort associated with
current reuse  projects involves the
definition of treatment and water-
quality standards. Even  where state
regulations exist, significant effort is
often  expended to define  necessary
treatment  requirements  or to
demonstrate the efficacy of alterna-
tive treatment methods.
  Assurances that  the proposed
method of water reuse  is safe  may
not be adequate to allay public fears.
Regulatory agencies and the general
public  want to know that the reuse
system will consistently perform at
levels that provide that safety.
  Reuse projects that are the first of
their kind for  a state or  that involve
potable reuse generally require a
demonstration  project.  A well-
thought-out and staged reuse  plan
that includes  a demonstration  pro-
gram will serve to generate confi-
dence and foster success.

CONCLUDING OBSERVATIONS
  Attitudes will not change by them-
selves. A more concerted effort to
make  water  reuse a universally
understood and accepted water sup-
ply practice is needed.

   —Scott B.  Ahlstrom is division
manager for -water and waste-water at
CH2MHILL in Denver, Colo.
28 - Selected Readings on Water Reuse

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Selected Readings on Water Reuse -29

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                   The ever-increasing demands
                   for water have thrust water
                   reclamation practices to the
                   forefront  of water and
                   wastewater system planning
                   efforts  throughout  the
                   world. Because of skyrock-
                   eting populations and limit-
          ed water resources, water and
          wastewater districts in Southern Cali-
          fornia received early  lessons on the
          importance of a careful, organized,
          and comprehensive approach to the
          successful design  and implementa-
          tion of water reuse  systems. Main-
          taining control, from planning stages
          all the way to operational monitor-
          ing, is key to a system that operates
          effectively, economically, and,  most
          importantly, safely.
             The Irvine Ranch  Water District
          (IRWD) serves  an area of about
          72,000 ac and an existing population
          of 100,000 people. The service pop-
          ulation is expected to grow to over
          300,000 after the year 2000. The
          district,  located in Orange County
          about midway between Los Angeles
          and San Diego, provides potable
          water service, treats  and disposes of
          wastewater, and also  distributes irri-
          gation water for landscape and agri-
          cultural uses.
             The area  is a semi-arid region
          receiving only about 12 to 14 in. of
          rain annually. The  rainfall occurs
          during the winter months, not dur-
          ing the  traditional growing season
          when demand is highest. Even with
          an extensive reservoir system built to
          capture natural runoff, the  water
          does not provide a year-round source
          for irrigation for either landscape or
          agricultural crops. Additional water
          supply then must  be either diverted
          from the Colorado River to the east
          and piped 240 miles to the district or
          imported from Northern California
          through a 450-mile system of canals,
          reservoirs, and large pumping sta-
          tions. Natural groundwater provides
          an additional source.
             To reduce the area's reliance on
          these limited supplies, IRWD  began
          the installation of a dual distribution
          system in the 1960s.
             Dual  distribution system. The
          heart of the district's dual distribu-
          tion system is the irrigation system
          which  contains  the network of
          pipelines that distributes reclaimed
          water to its users. When the system
          was designed, IRWD prepared an
          Irrigation Master Plan outlining
          future pipe  sizes  and locations so
   To reduce reliance on limited water
   supplies, the Irvine Ranch Water District in
   Irvine, Calif., developed a dual-distribution
that adequate pressure  and flow
could be maintained for all the
future uses. This was done  to prevent
growth and retrofitting problems.
  The irrigation system provides
water for three different  uses. The
first system is for the landscape users
including parks, schools, street medi-
an strips, and homeowner associa-
tions that water open-space areas
within the district.  There  are about
850 individual meters  for these
areas. Water is reclaimed mainly for
agricultural purposes such as or-
chard crops—oranges and avoca-
dos—but it is also used in  row crops
such as  asparagus, corn, pole toma-
toes, peppers, and  cabbage. There
are 12 individual meters  for differ-
ent fields within the district.
  The landscape irrigation and agri-
cultural systems serve a network of
about 107 miles of pipe varying from
2 to 54 in. in diameter. About 2050
ac are irrigated for landscape  uses,
while the agricultural land comprises
about 1000 ac. The  sizes of these
two areas will vary as agricultural
land is taken out  of service and dis-
placed by residential development in
the growing city area.
  The third system, which provides
reclaimed water to high-rise build-
ings, is now  in  the  development
stages. It will be used for toilets, uri-
nals, and trap drains, as up to 80% of
the water used in a high-rise may be
for toilet flushing.
30 - Selected Readings on Water Reuse

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ENCOURAGING USE
  Landscape irrigation is the main
end use of reclaimed water from the
dual system. Between 8000 and
9000 ac-ft/yr are used for landscape
irrigation, while  the agricultural sys-
tem uses 3000 to 4000 ac-ft/yr. It is
projected that ultimately the 15-mgd
Michelson Water Reclamation Plant
will be able to supply almost double
the current amount  for landscape
users as the agricultural demand
declines  because of development in
the district.
  The district requires new develop-
ments to be designed with dual dis-
tribution systems so that  all appro-
priate areas can be irrigated with
reclaimed water  rather than potable
water. In fact, IRWD has a set of
rules and regulations similar to city
ordinances that require developers to
use reclaimed water as  a water con-
servation measure in extending the
supply of potable water throughout
the district.
  IRWD has established the authori-
ty and a procedure for expanding the
dual system into the developing areas
by working closely with developers,
designers, and contractors as the sys-
tems are constructed. It has a set of
standard specifications that outline
the basic materials required for this
type of system. These materials
include the pipe, meters, strainers,
and various fixtures that are required
for irrigation.
  The process of expanding the dual
system is atypical of many govern-
mental reviews, as it includes early
contact with the developing compa-
ny when it applies for  a will-serve
notice. The will-serve certifies that
the district has reclaimed water avail-
able  so the developer can proceed
through  the  city planning process
during  which the tract map  is
reviewed and approved.  For the
development to receive approval, the
developer's  engineer must put
together plans showing the distribu-
tion system to be built by the devel-
oper.  This system is reviewed by the
IRWD reclaimed water  section staff
that  works with the engineer to
finalize plans and specifications. Once
                                                                                Selected Readings on Water Reuse -31

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          the review is complete and the devel-
          oper's plans are approved, the devel-
          oper  engages a contractor to con-
          struct facilities for the development.

          CONFORMING TO THE SYSTEM
             During construction, IRWD staff
          provides on-site inspection as all the
          facilities are built to ensure that they
          meet the standard specifications of
          the district.
             Once the developer has completed
          a  tentative tract map outlining the
          scope  of his development  and
          requested  a will-serve, a  service
          agreement is entered into with the
          district for  water, sewer, and land-
          scape irrigation service. As part of the
          agreement, the district collects funds
          to cover the plan check  and inspec-
          tion fees incurred during the process
          of designing and installing the system.
             Most of the equipment and pipe
          used  in the on-site facilities—those
          on the property owners' side of the
          meter—are  typical for the irrigation
          industry.  Special  specifications
          required by the district  are  used to
          distinguish between  the use of
          reclaimed water and potable water
          for irrigation. The health and safety
          reasons for  this provide  added pro-
          tection to the customer.
             One of the most important princi-
          ples  of irrigating with  reclaimed
          water is that all facilities must be
          clearly marked  so that  there is  no
          possibility of future cross connec-
          tions to the potable system with
          reclaimed water or vice versa. This is
          carefully checked during the design
          phase when IRWD  staff work with
          the design engineer to ensure compli-
          ance with the standard specifications.
             Specifications  include the prohibi-
          tion of hose-bib  connections to the
          reclaimed water system. This pre-
          vents incidental use and possible
          drinking of the water by users.
          Quick-coupling  valves used in the
          reclaimed water system are operated
          by a  key with an Acme thread. This
          thread is not used  in the potable
          water  system.  The   covers   on
          reclaimed water quick-couplers are
          required to be  green and made of
          rubber or vinyl.  The potable system,
          on the  other hand,  is distinguished
          by having either brass or yellow cov-
          ers. All pressure piping used for the
          reclaimed  water system must be
          labeled as reclaimed water by using
          labeled purple pipe, marking the pipe
          with  a colored tape, or  by  actually
          stenciling on the pipe  "reclaimed
          water." If potable water pipe is also on
the same site, it must also be labeled so
that the difference is obvious.
  When IRWD evaluates the devel-
opment's plans, the acreage irrigated
must be  provided. This is used to
predetermine watering rates using
evapotranspiration data and to check
meter readings for over-watering once
the system is on-line. It's also impor-
tant not to overlook basic items such
as the point of connection where the
landscape architect connects irriga-
tion hose  to the IRWD system.
Often the  architect will choose a
location without checking the  best
available district facility, let alone
whether  or  not there is an IRWD
pipe  on that particular street.
   Pipe classes are required to ensure
that they match district specifica-
tions, and water pressures and sprin-
kler  patterns are set to cover areas
properly without overwatering. If a
project has several reclaimed water
meters, they are checked to ensure
that  there are no cross connections.
Reclaimed water meters cannot be
cross-connected because of difficulty
in isolating  problems if several
meters must be shut off. The word-
ing  in plan notes  is checked to
ensure  that  the  district is  not
exposed to undue liability.
   IRWD staff ensure that a master
pressure regulator or pressure-regu-
lating valves are used and require the
strainer screen to be 30  mesh or
greater to protect the sprinkler sys-
tem and the pressure  regulator.
Another item is  the inclusion of the
plan notes regarding the installation
of an on-site reclaimed water system.
This is a must, as it points out to the
landscape contractor what is required
by the district inspection team and
surveyor.
   Last and not least, the IRWD
looks for incorrect items such as a
backflow device on the reclaimed
water system. Backflow devices are
not used in reclaimed water systems;
if they are installed in a reclaimed
water system they could cause confu-
sion  because  of the similarity to the
domestic water system.
   During this plan check procedure,
as each plan set is received it is given
a permanent  file number. File books
containing  all communication or
comments made on a project from
start of construction to operation are
kept as a record for the future. The
architect provides  a  set of mylar
drawings of approved plans, which
are kept on file, thus completing the
file on each project.
  Some of this information is input
to a computer, allowing IRWD staff,
by typing in the meter number or
account number, to bring forward
information on any irrigation project
built in Irvine  on the Reclaimed
Water System.

FIELD REVIEW
  Once the plans are approved,
IRWD monitors the actual construc-
tion  of the project to ensure  proper
installation and hook up. During the
field review,  which is accomplished
by the same  staff that did the plan
review, various important points are
stressed to again ensure compliance
with the rules and regulations of the
water  district. The inspectors will
look at meter and strainer devices to
ensure that they are properly labeled
and installed. The strainers are a safe-
ty precaution to ensure maintenance-
free  use of the system. Either Y-
strainers or basket strainers provide a
backup for maintaining an easy dis-
tribution  of  the water through the
irrigation system. When improper
water  construction  has taken  place,
the work must be corrected.
  There   are   several  common
improper  construction techniques.
Domestic  and reclaimed water lines
may be too  close together. There
must be a vertical  separation of at
least 6 in. and a horizontal separa-
tion of 10 ft from either domestic
water or sewer lines, and the
reclaimed  water line must be sleeved
to 5  ft on  either side of  a per-
pendicular crossing of a domestic
water line.
  Improper labeling sometimes
occurs. A  contractor once put in 1.5
miles  of reclaimed water line and
taped  the pipe with domestic tape
instead of reclaimed water tape. The
quick-connect  coupling whick is
checked; if the wrong type is used,
reclaimed  water could be used incor-
rectly. Pipe depths are checked,  as
building codes  are not always fol-
lowed.
  Other important points include
the application of the label tape so
that  future construction will be able
to determine the type of water that is
used in the pipeline. On some appli-
cations, the pressure in the distribu-
tion  system may need to be reduced
in order to best fit the design pres-
sure used in the irrigation design.
Pressure-reducing valves have been
successfully used for extensive peri-
ods without any excessive mainte-
nance  or problems  that might have
32 - Selected Readings on Water Reuse

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               Irvine's Irrigation Guidelines

     Irrigate between the hours of 9:00 p.m. and 6:00  a.m. only.
   Watering  outside this time frame must be  done manually with quali-
   fied supervisory personnel on-site. No system shall at any  time be left
   unattended during use outside the normal schedule.
     Irrigate  in a manner that will minimize runoff pooling and ponding.
   The application rate  shall not exceed  the  infiltration rate  of the soil.
   Timers must be adjusted so as to be compatible with the lowest soil
   infiltration rate present. This procedure may be facilitated by the effi-
   cient  scheduling of the automatic  control clocks by employing the
   repeat function to break up the total irrigation time into cycles that will
   promote maximum soil absorption.
     Adjust spray heads to eliminate overspray onto areas  not under the
   control of  the customer such as pool decks,  private patios,  streets, and
   sidewalks.
     Monitor and maintain the system to minimize equipment  and  materi-
   al failure.  Broken sprinkler leads, leaks, and unreliable valves should
   be repaired as soon as they become apparent.
     Educate all maintenance  personnel, on a continuous  basis, of the
   presence of reclaimed water and the fact  that it is not approved for
   drinking purposes.  Given the high  turnover rate of employees in the
   landscape industry, it is important that this  information be disseminat-
   ed frequently. It is the landscape contractor  who is responsible for
   educating each and every one of these employees.
     Obtain  prior approvals for all proposed changes and  modifications
   to any on-site facilities. Such changes must be  submitted to, and
   approved by, the IRWD engineering  office and designed in accor-
   dance with district standards.
been caused by the quality of the
water. The pressure regulator is used
to minimize fogging and misting of
sprinklers.
  The final step in the field inspec-
tion is cross-connection  control. A
cross-connection control  test is per-
formed on all reclaimed water  sys-
tems to be absolutely sure that there
are no  connections  between  the
domestic and reclaimed water lines.
The system is then tested to check the
spray  patterns of the sprinkler devices.
Normally, typical irrigation products
are  used. These are  important parts of
the  irrigation system.
  Spray patterns are tested; one of
the requirements is that overspraying
not be allowed  to  prevent  the
reclaimed water from running into
the storm drain system. Besides wast-
ing water, this is important in Irvine
because the water drains into a sensi-
tive area that includes an ecological
preserve and wetlands.
  During the overspray test, the sys-
tem is operated at  full pressure with
reclaimed water and, where improper
spray patterns occur, the contractor
is required to replumb the system or
use different spray devices to control
the overspray. There are also over-
spray aesthetic concerns,  such as
watering the concrete and asphalt
and interfering with the appearance
of a newly washed and waxed car,
creating potential ill-will within the
community.

MONITORING AND GUIDELINES
  The IRWD uses guidelines that
were developed in a joint effort
between the local health depart-
ments. The guidelines (see Box) are
posted in the system's control center
in both Spanish and English. Com-
pliance with these guidelines is fre-
quently monitored.
  The monitoring is designed to
police the system to ensure that the
facilities are maintained and operated
properly so that new problems are
not created. Monitoring includes
working with the contract operators
and irrigation users to make sure that
timers are set so that water is used
between the restricted hours  of 9:00
p.m. and 6:00 a.m., when  contact
with the public is minimized. The
automatic timer systems include
Rainbird, Griswold, and Toro, and
are the modern electronic timers
used because, as the price of water
continues to increase, it is  easy to
justify the use of sophisticated timers
to control the application of water so
that proper irrigation takes place.
  The monitoring work also includes
detection of main breaks and other
malfunctions in the system. This is
done by selecting random  evenings
and actually patrolling the district
during the evening hours  between
9:00 p.m. and 6:00 a.m. to look for
broken sprinkler heads, main breaks,
and overwatering situations—espe-
cially when they cause gutter rivers,
which are used to locate the  prob-
lem. Monitoring also includes check-
ing the water quality throughout the
distribution system.  Several stations
or  sampling points are  located
throughout the system and random
samples are taken during the normal
use times to ensure that the bacterial
quality of the water is similar to the
water's quality when it leaves the
treatment plant.
  Another important aspect  of the
monitoring program is the visual
assessment of new construction
areas. This is  important  because
there  is always someone  trying to
save time or money by building with
no  inspections or plan checks. This
avoids many headaches by catching
the contractor early before the trans-
gressions endanger  the public and
become expensive to fix.
  The previously mentioned  1.5
miles of pipe that were laid with the
wrong pipe identification had to be
dug up and re-labeled—an  unneces-
sary expense that could easily have
been  avoided.  Another example
involved a  sprinkler system that was
installed without IRWD's knowl-
edge.  It was discovered around a
new office building on a weekend
inspection. The  developer applied
for a  meter, but did not receive
one because the plans were not
approved by the  district. To top it
off, the installed system did not fol-
low the reclaimed water rules and
regulations, requiring costly field
modifications.
  IRWD is trying to avoid similar
complications by  getting involved in
the initial planning stages for a devel-
opment and then following through
for the direction of the project. The
district's goal is to maximize  water
reuse and limit the unnecessary use
of potable water in the safest and
most effective manner. Control from
planning and permitting  through
operational monitoring is  essential
for this goal to be met.           •

  John Parsons is irrigation services
supervisor/engineering technician III
for the Irvine Ranch  Water District
in Irvine, Calif.
                                                                              Selected Readings on Water Reuse -33

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                             Because conditions in Florida necessitate wuler
                              reuse, spray irrigation systems using reclaimed
                              water, such as this one in Tallahassee, are being
                                   encouraged by the state.
FLORIDA'S REUSE
PROGRAM PAVES
THE WAY
David \\. York, Jnnics ('rook

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                                                            WATER   RECLAMATION/REUSE
       Florida is different than the
       major  reuse states in the
       semi-arid southwest U.S. In
       Florida, it rams an average of
       54 in./yr and the state seem-
       ingly has  abundant water
       resources — particularly
       groundwater,  which ac-
counts for about 90%  of all water
used for domestic purposes. Howev-
er, there  are increasing  demands on
the state's water resources.
  Florida continues to face rapid
population growth.  Its population,
which nearly doubled from 1960 to
1980, continues to increase by more
than 6000 persons each week.
Between  1980  and 1990 the popula-
tion rose 33%, and  from  1990 to
2000 the population is expected to
grow an additional 19%.
  Almost 79% of Florida's 13 million
people lives near the coast, and
about 82% of the anticipated popula-
tion growth will occur in coastal
counties.  These coastal growth areas
are served  primarily  by  shallow
aquifers that are most vulnerable to
overdraft  and saltwater intrusion.
  These conditions necessitate water
reclamation and reuse. The state has
developed programs that encourage
the  reuse of reclaimed
water and comprehensive
regulations that govern
reuse projects. The  rules
provide detailed require-
ments for development of
reuse projects that involve
irrigation in public  access
areas such as parks,  play-
grounds,  and golf courses,
as well as irrigation of resi-
dential property and  edible
crops and must address the
use of reclaimed water for
fire protection, toilet flush-
ing, and aesthetic purposes
such as decorative ponds
and  fountains. The reuse
rules provide requirements
for preapplication  treat-
ment, reliability, operation
control, buffer  zones, stor-
age,  cross-connection con-
trol,  and  other design and
operational features.  These
rules also  provide a mecha-
nism for  limited discharge
of excess reclaimed  water
during wet-weather, high-
stream-flow conditions
when  demand  for  re-
claimed water  is lowered.
Such limited wet-weather
discharge  provisions should
         encourage development of reuse pro-
         jects by reducing storage require-
         ments.

         DEVELOPMENT OF REUSE
           During  the last 20 years, the pri-
         mary driving force behind implemen-
         tation of reuse projects in Florida has
         been  effluent disposal. While the
         state has many streams, they typically
         have low flows, are shallow, have low
         gradients, flow slowly, are  warm all
         year, and flow into lakes or estuaries.
         Most surface waters in Florida simply
         will not assimilate large quantities of
         effluent. As a result, many communi-
         ties have turned  to land application
         to dispose of unwanted effluent.
           Regulations developed in the early
         1980s for reuse and land application
         are in the manual, Land Application
         of Domestic Wastewater Effluent in
         Florida1, that contains  detailed
         design and operation  requirements
         for slow-rate land application sys-
         tems,  rapid-rate land application sys-
         tems, absorption fields, overland
         flow systems, and other land applica-
         tion systems.  Irrigation of public
         access areas or  edible crops was
         allowed, but requirements for such
         activities were incomplete.
Table 1 - Disinfection Levels Defined by Florida Rules
Disinfection
level
Fecal coliform limit    Application
High-level     No detectable
Intermediate
Basic
200/100 ml
Low-level      2400/100 ml
              maximum
Public access maxi-
mum fecal coliform
TSS 5 mg/L. Irriga-
tion and irrigation
of edible crops, for
discharge  to Class I
surface waters
(potable water  sup-
plies).

14/100 ml. For
discharge  to waters
tributary to Class II
surface waters
(shellfish propaga-
tion or harvesting).

For most land appli-
cation systems, for
most discharges to
surface waters.

For overland flow
systems and some
underdrained irriga-
tion systems.
  The land application manual was
designed to be used in conjunction
with Chapter 17-6, Florida Adminis-
trative Code (FAC), titled "Waste-
water Facilities." As shown in Table
1, four  levels of disinfection were
defined in the rule.
  The   high-level   disinfection
requirements were developed in the
early 1980s based largely on the tes-
timony of epidemiologists and virol-
ogists before the  Florida Environ-
mental Regulation Commission. The
criteria  were designed to provide
treated  water  that was essentially
pathogen free. Where chlorine was
used for disinfection, maintenance of
a 1.0-mg/L total chlorine residual
after a 15-minute contact  time at
maximum daily flow or after a 30-
minute contact time at average daily
flow was to be accepted as evidence
that the  fecal coliform criteria would
be met.
  Secondary treatment was estab-
lished in Chapter 17-6, FAC, as the
minimum pretreatment level for
most land application and reuse sys-
tems. Florida's definition of sec-
ondary treatment requires that the
wastewater treatment facility be
designed to produce an effluent  con-
          taining not more than 20
          mg/L of biochemical
          oxygen demand (BOD)
          and total  suspended
          solids  (TSS)  or  90%
          removal of BOD  and
          TSS, whichever is more
          stringent. The  annual
          average BOD and  TSS
          concentrations may not
          exceed 20 mg/L and the
          monthly average may not
          exceed  30  mg/L.  A
          lower level of secondary
          treatment—40  to  60
          mg/L  for BOD  and
          TSS—was allowed for
          overland flow systems
          and for some  under-
          drained irrigation  sys-
          tems.
            In September 1989,
          Chapter 17-6, FAC, was
          rewritten  into a  new
          series of rules. Regula-
          tions governing domestic
          wastewater  treatment
          and disinfection are  now
          found in Chapter 17-600,
          FAC, titled "Domestic
          Wastewater Facilities."
            During the 1970s and
          1980s, the number of
          projects involving reuse
                                                                             Selected Readings on Water Reuse -35

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          or land application increased sub-
          stantially.  By 1985, more than 100
          individual projects involved some
          form of reuse, including several
          excellent reuse projects such  as the
          St.  Petersburg dual water distribu-
          tion system, the Tallahassee spray
          irrigation system, and the CONSERV
          II citrus irrigation project serving
          Orlando and Orange Counties.
            The 1990 Reuse Inventory1 identi-
          fied about 200 reuse projects in
          Florida. These  projects use  about
          320 mgd of reclaimed water for a
          wide range of beneficial uses.
            With the growing popularity and
          acceptance of water reuse projects,
          the state has  begun  to promote
          water reclamation. Statewide  com-
          prehensive planning has been  imple-
          mented to ensure that adequate
          infrastructure is provided. Increased
          attention is being placed on protec-
          tion of water resources  and provision
          of adequate water supply. Reuse of
          reclaimed water is receiving greater
          attention as a means  to reduce
          demands on potable water resources
          and recharge groundwater.

          THE STATE'S REUSE PROGRAM
            Beginning in 1987, the Florida
          Department of Environmental Regu-
          lation embarked on  an ambitious
          program of rule making designed to
          facilitate  and  encourage reuse of
          reclaimed water. Three rules were
          effected:  Chapter   17-6,  FAC,
          "Wastewater  Facilities", Chapter 17-
          40, FAC,  "Water Policy", and Chap-
          ter  17-610,  FAC,  "Reuse  of
          Reclaimed Water and Land Applica-
          tion."
            In addition,  1989 state legislation
          and other related rule making also
          affected reuse in Florida.
            Updated reuse rules were  devel-
          oped with significant assistance from
          a technical advisory committee con-
          sisting of representatives of the Flori-
          da  Pollution  Control Association,
          Florida Engineering Society, Ameri-
          can Water Works Association Florida
          Section, American Water Resources
          Association, a representative of a pri-
          vate utility, and the former head of
          California's reuse program. Commit-
          tee members offered a wealth of
          experience and expertise covering a
          wide range of reuse activities.
            Consistent definitions for reuse
          and reclaimed water were included in
          all  three  rules.  Reclaimed water is
          water that has received at least sec-
          ondary treatment and is reused after
          flowing out  of a wastewater treat-
Wastewater restoration, occurring in this Orlando, Fla., wetland, is identified as a reuse
application for surface-water enhancement.
ment facility. Reuse is the deliberate
application of reclaimed water in
compliance with applicable rules for
a beneficial purpose.
  The rules identify landscape irriga-
tion, agricultural irrigation, aesthetic
uses, groundwater recharge, industri-
al uses, and fire protection as legiti-
mate beneficial purposes. Environ-
mental enhancement of surface
waters resulting from discharge of
reclaimed  water that  has received at
least advanced wastewater treatment
or from discharge of reclaimed water
for  wetlands  restoration also are
identified as reuse applications.
  Chapter 17-40, FAC The  "Water
Policy" rule outlines the state's poli-
cy for the use and  regulation of
water. It provides general guidance
to the state's five water-management
districts that are responsible for
water-quantity management, includ-
ing  the consumptive-use permitting
program.
  An October 1988  amendment to
Chapter 17-40, FAC, created a pro-
gram  for  mandatory  reuse  of
reclaimed  water. The water-manage-
ment districts were required to assess
the  water resources within their juris-
dictions—including  an estimate of
water needs and sources for the next
20 years—and to publish a compre-
hensive district water-management
plan. As part of this planning activi-
ty, the water-management districts
were  required to identify critical
water-supply problem areas. Reuse
will be required within critical water-
supply problem areas  that exist
today, and in areas that are projected
to develop over a 20-year  planning
horizon. The program will be in full
operation by November 1991.
  The rule also allows the water-
management districts to require
reuse  outside of critical water-supply
problem areas if reclaimed water is
readily available to the applicant for a
consumptive-use permit. This mea-
sure was designed to facilitate imple-
mentation of reuse at  the local level.
The primary responsibility for imple-
mentation of this program rests with
the water-management districts
through the consumptive-use per-
mitting process.
  Chapter 17-6, FAC Amendments
to the rule focused on  two areas.
First,  the  high-level disinfection
requirements were  modified to
reflect existing technology and expe-
rience. Revised high-level  disinfec-
tion criteria include  requirements
that 75% of all fecal coliform obser-
vations be less than  the detection
limit and  that no sample exceed
25/100 mL for fecal coliform. Daily
sampling  for fecal coliform was
36 - Selected Readings on Water Reuse

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Toble 2 • Requirements for Reuse
Parameter
Requirements
Minimum treatment level


Disinfection

Minimum system size




Reliability


Staffing



Continuous monitoring

Operating protocol




Storage requirements




Reject storage



Limits on reuse
Cross-connection control
Setback distances
Other O&M requirements
Secondary with filtration and chemical feed,
maximum TSS of 5 mg/L.

High-level.

378.5 m3/d (0.1  mgd) for any public
access irrigation system, 1 893 m3/d (0.5
mgd) for residential lawn irrigation or edible
crop irrigation.

Class I—requires multiple units or backup
units and a second power source.

24 hr/day, 7 days/wk; may be reduced to
6 hr/day, 7 days/wk, if additional reliabili-
ty measures are included.

Required for turbidity and disinfectant residual.

Required—a formal statement of how the
treatment facility will be operated to ensure
compliance with treatment and disinfection
requirements.

System storage  (minimum 3 days, may be
unlined) or back-up system required;  golf
course lakes may be used for system  stor-
age.

Minimum 1 day, lined,  to hold unacceptable
quality product water for return for addition-
al treatment.

Only product water meeting the criteria of
the operating protocol shall be released to
the reuse system; reclaimed water shall not
be used to fill swimming pools, hot tubs, or
wading pools.

Prohibit cross-connections to potable  water
systems; reclaimed water shall not enter a
dwelling unit; minimum standards for sepa-
ration of reclaimed water lines from water
lines and sewers; color coding or marking
required; back-flow prevention devices
required on potable water sources entering
property served by reclaimed water systems;
dual check valves are acceptable.

22.9 m (75 ft) to potable water-supply wells;
otherwise, none.

Approved operating protocol; approved
cross-connection control program; documen-
tation of controls on individual users (agree-
ments or ordinance); assess need for  indus-
trial pretreatment program.
included as a requirement for reuse
systems. The TSS limitation remains
at a maximum of 5 mg/L before
application of the disinfectant. Tur-
bidity is not incorporated in the
rule as a permitting parameter.
However, for public access irrigation
and for irrigation of edible crops,
continuous on-line turbidity moni-
toring is required as part of the oper-
ational control provision in Chapter
17-610, FAC Disinfection require-
ments are now found in Chapter
17-600, FAC.
  Provisions for limited wet-weather
discharge were  added  to  the
"Wastewater Facilities" rule. This
section is designed to  facilitate dis-
charge of reclaimed water during
wet-weather, high-flow periods when
demand for reclaimed water normal-
ly is reduced. When the  applicant
demonstrates  sufficient  dilution dur-
ing periods of high stream flow, the
state will permit a discharge with
minimal  water  quality  review.
Required dilution ratios are based on
the quality of the reclaimed water
and the anticipated frequency of dis-
charge:
   SDF= J^O.085 CBODS+ 0.272
         TKN- 0.484)
   Where
   SDF = minimum required stream
dilution factor, dimensionless;
   P =  percent of the  days of the year
that limited wet-weather discharge
will occur during an average rainfall
year;
   CBOD5 = the treatment facility's
design monthly maximum limitation
for carbonaceous BOD5 in mg/L;
and
   TKN = the  treatment facility's
design monthly maximum limitation
for total Kjeldahl nitrogen  expressed
in mg/L of nitrogen.
  The  dilution ratio is increased if
travel time to sensitive downstream
environments such as lakes, estuaries,
and water supplies is  less than  24
hours. Limited wet-weather dis-
charge provisions were  subsequently
relocated to Chapter 17-610, FAC.
  Chapter 17-610, FAC The "Reuse
of Reclaimed Water and Land Appli-
cation" rule was adopted in 1989. It
supersedes and expands upon the old
land application manual.1 The focus
of this rule making was to provide
detailed requirements for the design
and operation of reuse projects in
public  access areas, including irriga-
tion of residential lawns, parks, golf
courses, landscape areas, as well as
for the irrigation of  edible food
                                                                              Selected Readings on Water Reuse -37

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          crops. These requirements are con-
          tained in Part III of the rule.
            Table 2 presents a summary of the
          key provisions of this part for public-
          access irrigation systems, irrigation of
          residential lawns,  and irrigation of
          edible crops.  Reclaimed  water that
          has received high-level disinfection,
          secondary treatment,  and filtration,
          and that meets the full requirements
          of Part III may also be used for toilet
          flushing in commercial and industrial
          facilities that do not contain dwelling
          units, for fire protection, for con-
          struction dust control, for aesthetic
          purposes, and for other uses.
            Any reuse system regulated by Part
          III must provide a minimum of sec-
          ondary treatment, filtration, and
          high-level disinfection. Class I relia-
          bility and full-time operator atten-
          dance are required; some reduction
          in operator attendance is allowed if
          additional reliability measures are
          provided. Each facility must develop
          an operating protocol; a  clear state-
          ment of how the facility will be oper-
          ated to ensure  that only acceptable
          reclaimed water is discharged into
          the reuse system. While turbidity and
          disinfectant residual must be  contin-
          uously monitored for operational
          control, these are not permit  limita-
          tions. The facility  must be operated
          such that the high-level disinfection
          criteria (TSS and fecal coliform lim-
          its) will be met. Unacceptable prod-
          uct water must be diverted to a
          lined, reject storage system for addi-
          tional treatment before   being
          released to the reuse system.
            As shown in the Table, minimum
          system sizes were established for
          treatment  facilities that  make
          reclaimed water available for irriga-
          tion in public access areas or  for irri-
          gation of edible food crops. These
          minimum size limits reflect reduced
          confidence in a small facility's ability
          to continuously produce high-quality
          reclaimed water. Both the technical
          advisory committee and the  Florida
          Department of Health and Rehabili-
          tative Services  recommended mini-
          mum size limits.
             Rules  that existed before 1989
          allowed the irrigation  of edible food
          crops if high-level disinfection was
          provided and the permit applicant
          demonstrated that processing of the
          food crop  would  inactivate or
          remove pathogens. Few edible crop
          irrigation systems were proposed.
            The original provisions of the rule
          allowed  irrigation of edible food
          crops without restriction beyond
Part III requirements. This position
represented a consensus  from the
technical advisory committee, which
noted that the potential for disease
transmission from  an edible food
crop irrigation system is not signifi-
cantly different from that  of a resi-
dential lawn irrigation system, as
long as the full requirements of Part
III  are met. However, in response to
concerns raised by the Florida
Department of Health and Rehabili-
tative Services, the issue was revisited
in July 1989. It was amended to pro-
hibit direct contact of reclaimed
water on edible food crops that
will not be peeled, skinned, cooked,
or thermally processed before hu-
man consumption. Indirect applica-
tion methods  such  as ridge and
furrow, drip irrigation, or subsur-
face distribution systems are still
allowed for these crops. No restric-
tions were placed on the  irrigation
of citrus, tobacco, or other crops
that are peeled, skinned, cooked,
or thermally processed before con-
sumption.
  Other Legislation and Rule
making. The Department of Envi-
ronmental Regulation pursued state
legislation in  1989 to allow the
department to  require that waste-
water treatment facilities located
within designated critical water-sup-
ply problem areas make  reclaimed
water available for  reuse.  Unfortu-
nately, the resulting legislation3
stopped short of vesting such author-
ity. The law does require that, begin-
ning in 1992, applicants for wastew-
ater-management permits located
within critical water-supply problem
areas complete reuse feasibility stud-
ies. The law clearly establishes that
reuse of reclaimed water and conser-
vation of water are formal state
objectives.
  In 1989, the  Department of Envi-
ronmental Regulation also revised
Rule 17-302, FAC, "Surface Water
Quality Standards,"  and Rule 17-4,
FAC,  "Permits,"  to include  an
antidegradation policy. This policy
requires that any new or  expanded
surface-water discharges be clearly in
the public interest.  The  applicants
for surface-water discharges must
demonstrate that reuse of domestic
reclaimed water is not economically
or technologically reasonable.
  Rule clean-up. Chapter 17-610,
FAC, was revised in 1990. Setback
distance (buffer zone) requirements
were updated throughout the rules.
Streamlined permitting requirements
and  associated forms were added.
The  use of reclaimed water for toilet
flushing and fire protection was
extended to  motels, hotels, apart-
ments, and other units where the
resident does not have ready access
to the plumbing system for repairs or
modifications.

THE FUTURE
  Reuse of reclaimed water will
increase significantly during the next
decade. Recent droughts in southern
Florida emphasized the need for
conservation of valuable potable
water supplies and for reuse of
reclaimed water. As the water-man-
agement  districts identify critical
water-supply  problem areas and
implement mandatory reuse provi-
sions, additional pressures will be
placed on communities to move
toward reuse. Requirements for
applicants for wastewater-manage-
ment permits to conduct reuse feasi-
bility studies also will focus the com-
munity's attention on the need for
reuse.   Continued  population
growth, most of which will occur in
coastal areas, will increase the pres-
sure on cities, counties, and utilities
to protect valuable and fragile water
resources by conserving water and
reusing  reclaimed water for non-
potable purposes.
   The Florida Department of Envi-
ronmental Regulations strongly sup-
ports reuse of reclaimed water. The
goal is to increase the amount  of
reuse in Florida by 40% above 1987
levels by 1992. Recently adopted
technical reuse rules, the mandatory
reuse program, 1989  state legisla-
tion, and the antidegradation policy
will  contribute to the promotion  of
   David W. York is reuse coordinator
for the Florida Department of Envi-
ronmental Regulation m Tallahassee,
Flu.; James Crook is principal engi-
neer with Camp Dresser & McKee,
Inc., in Clearwater, Fla.

REFERENCES
   1. Land Application of Domestic
Waste-water Effluent  in  Florida.
Florida  Department of Environ-
mental Regulation, Tallahassee, Fl.
(1983).
   2. 1990 Reuse Inventory. Florida
Department of Environmental Regu-
lation, Tallahassee, Fla. (1990).
   3. Section  403.064,  Florida
Statutes. State of Florida,  Tallahas-
see, Fl. (1989).
38 - Selected Readings on Water Reuse

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                                                     WATER  RECLAMATION/REUSE
                ECONOMIC TOOL  FOR
                      REUSE  PLANNING
                                   /. Gordon Milliken
      Economics provides several
      useful tools to guide plan-
      ners contemplating a poten-
      tial wastewater reuse project,
      but the tools and their appli-
      cations to water-resource
      development are not univer-
      sally well understood by
engineers and managers.  If cost-
effectiveness, cost/benefit, and
financial feasibility analyses and a
market research pricing study are
conducted, many of the key ques-
tions faced in water-resource plan-
ning can be answered.

MAKING DECISIONS
  Planners in all areas have a com-
mon goal: meeting future water
demands in the best possible man-
ner. Local conditions complicate this
common  goal, throwing a variety of
alternatives that must be considered
into the ring. The simplest  example
involves the choice of either con-
structing a water reclamation plant
or developing a new water supply
and expanding the existing  conven-
tional wastewater treatment plant.
It's never that easy in the real world,
but the first  question that must be
answered is, among the alternatives,
which is the best?
  Cost/benefit calculations have
been used for decades to compare
the returns offered by different pro-
posed investments. The costs of the
resources required are related to the
market value of the flow of benefits
expected, using discounted cash-flow
techniques.
  When comparing alternatives that
cause complex social and environ-
mental effects, such as changes in the
quality of life or permanent changes
in rivers and forests, this technique is
hard to use. The investments and
expenditures really do not fit  the
cost/benefit framework because the
outcomes  often cannot be measured
in dollars. In such cases, cost-effec-
tiveness comparisons are more use-
ful. This technique uses an effective-
ness scale as a measurement concept.
  The alternative methods  for
achieving  water-resource (supply or
quality) goals differ in many ways: in
amount and timing of the capital
investment required; in amount of
operating  and maintenance cost; in
useful life of capital investment in
facilities; in effectiveness, both as to
magnitude of effect and certainty of
effect; and in impact on the rest of
the economy, the environment, pub-
lic health, and other factors.
  Cost-effectiveness. To establish a
clear basis to compare  the alterna-
tives, this methodology requires a
single, uniform measure of effective-
ness such as the volume of water of a
specified quality produced annually,
either in added supply or in reduced
demand, at a selected confidence
level. All other measures of differ-
ences among alternatives are treated
as costs or ranked according to their
degree of effect. By this means, all of
the  alternatives can be equated on
the basis of their ability to produce a
unit quantity of water of a specified
quality. Their relative types and
degrees of cost, such as direct cost,
quality  of life effect, environmental
effect, and others, can then be com-
pared. The  various costs and effects
can be arrayed together to help plan-
ners choose among the competing
alternatives.
  Cost benefit and feasibility anal-
yses. Once  an alternative is selected,
a true cost/benefit analysis should be
conducted.  The analysis should ask
and answer two basic questions: Is
this  reuse project economically desir-
able—does society receive a net ben-
efit if resources are used to build it?
Are  the total benefits greater than
the total costs?
  The analysis, if properly conduct-
ed, will  identify the various beneficia-
ries of the project, estimate the
amount of their benefits, and deter-
mine when these benefits will be
received.
  U.S. federal law specifies that fed-
eral  agencies involved in water plan-
ning use the economic and environ-
                                                                     Selected Readings on Water Reuse -39

-------
          mental principles and guidelines
          developed by the U.S. Water Re-
          sources Council.1 The framework
          provides the means  to identify  all
          costs and parties on whom the direct
          or indirect costs fall and to identify
          beneficiaries and the amount of ben-
          efit they will receive. To the extent
          possible, the framework provides the
          means  to allocate costs  appropriately
          to beneficiaries.
            A financial feasibility analysis
          determines whether the plans for the
          proposed  reuse plant are financially
          sound—if the costs of capital invest-
          ment plus the costs of operation and
          maintenance can be covered by user
          charges and rev-
          enues  from sales
          of reuse water.
            Studies of fi-
          nancial feasibility
          require that reuse
          project costs be
          estimated  with
          substantial accura-
          cy, although some
          estimating uncer-
          tainty  is inevita-
          ble. Capital costs
          may be paid from
          an  existing capital
          construction fund
          (typical   of  an
          industrial  firm) or
          by bonded debt
          (typical of a gov-
          ernmental utility).
          Bonded debt requires  a forecast of
          the bond interest rate, which varies
          with the credit rating of the issuing
          organization, and the degree of risk
          of  the  bonds, whether backed  by
          future  revenues or  by taxes. Op-
          eration and maintenance  (O&M)
          costs will vary because of inflation of
          energy and labor costs and possible
          technological improvements  in
          future  operating efficiency.
            In the financial feasibility analysis,
          the future stream of costs, including
          bond  payments, is projected and
          compared with a future stream of
          revenues  that will come from user
          fees and charges, contracts to sell
          reuse water, and perhaps from gov-
          ernment grants. Although it violates
          sound  economic principles, some
          revenue may be planned from tax
          subsidies if the user fees are con-
          sidered so high  as to be politically
          unacceptable.
            In any  case, the future revenues
          must equal the future  costs for the
          plan to be financially sound.  In
            industrial projects, it is customary to
            plan a reserve fund for ultimate
            replacement of the facility after its
            useful life ends or it becomes obso-
            lete. This forward  planning is less
            common in government because
            officials customarily do not consider
            that accruing reserves from taxes or
            excess user fees is good public policy.
              Market pricing research. The
            financial  feasibility analysis relies
            largely on market research pricing
            studies. Setting the price of reuse
            water may or may not be a com-
            plex problem,  depending on several
            factors.
              For example, if the reuse water is
  Significant Economic  Factors  Impacting

          Future Wastewater Reuse

The rapidly rising costs of alternative sources  of water in a great
many metropolitan areas,  not only the traditionally water-poor,
semi-arid cities;

The stabilization of wastewater reuse production costs and their
increasing competitiveness with other water supply sources;

The very serious limitations on water supply and  the reduction in
volume of traditional water supplies faced by certain cities; and

The growing  impact of water-quality regulations that place  bur-
densome costs on wastewater discharges and thus  narrow the
cost differential between discharge and reuse.
             used by the governmental entity that
             produces it, such as by a municipality
             that operates both a water supply
             and a wastewater  treatment utility,
             the question of pricing may never be
             raised. The price will be  set as is cus-
             tomary on a cost-of-service basis—
             uniformly—for the blend of reuse
             water and the water from traditional
             sources.
               A more complex problem arises
             when the reuse water is offered as a
             nonpotable supply to customers—
             usually industrial firms that have the
             option of buying it, buying potable
             water, or obtaining water  from an-
             other source,  such as a  self-supplied
             groundwater or an in-plant reuse sys-
             tem. In such a case, a thorough mar-
             ket-research  study is necessary to
             determine whether potential  cus-
             tomers are willing to pay  for reuse
             water and how this compares to the
             actual cost of producing suitable
             reclaimed water. The most compre-
             hensive study  to date was conducted
             in 1981 and  involved  250 on-site
interviews of industrial water users in
Orange and Los Angeles Counties.

ECONOMICS OF WASTEWATER RECYCLING
  Simple economic models of a con-
ventional water system and a waste-
water recycling project exist.2  The
conventional water supply/wastewa-
ter treatment system  costs compo-
nent includes operating and mainte-
nance costs and amortization of capi-
tal expenditures (Equation 1). The
costs of an equivalent water reuse
system   are somewhat different
(Equation 2).
  An equivalent water supply system
using recycled water would incur vir-
                tually  identical
                costs for raw water
                treatment, distri-
                bution, and waste-
                water treatment.
                Some costs differ
                where  recycling
                provides a portion
                of the water sup-
                ply:  the cost of
                water collection
                (raw supplies ver-
                sus effluent); and
                the additional cost
                necessary to bring
                wastewater  from
                the  quality neces-
                sary for its dis-
                charge  or disposal
                under  applicable
                regulations to a
useful and marketable quality as recy-
cled water.
  Some  additional  distribution costs
also  may be incurred as the recycled
water must be  transferred from the
wastewater treatment location to a
point where it can be reused or inte-
grated into a supply system.
  Primarily, however, the cost of
renovated water is a direct function
of the relative  levels  of wastewater
treatment required for effluent dis-
posal and the particular  reuse con-
templated. The higher the quality of
treated wastewater, the lower the
additional cost  necessary  to produce
recycled water. The true cost of recy-
cled water is only its net cost above
the cost  associated with all elements
of a conventional water system. This
additional cost is the appropriate one
to use when comparing the cost of
recycled  water with that of new sup-
plies from conventional sources.
  The economic feasibility of a
municipal or industrial wastewater
reuse system, therefore, is a function
40 - Selected Readings on Water Reuse

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                                                           WATER  RECLAMATION/REUSE
of added costs less cost savings and
revenues (see Box).
  Transport costs may be substantial
if they involve a dual distribution sys-
tem. They will at least include the
costs of transport from the reuse
plant to the place of use or of inte-
gration into the supply system. For
example, if the  system is potable
reuse, costs for transport into supply
reservoirs or  onto the spreading
ground for groundwater recharge
must be considered.
  The interaction  of these factors in
individual cases will determine the
cost of recycling as compared to the
cost of once-through water use, and
thus the advisabili-
ty of reuse.
                                   building a large reservoir and diver-
                                   sions of water from the Colorado
                                   River drainage basin through the
                                   Continental Divide will  have a
                                   capital cost of about S8.ll/m3
                                   ($10,000/ac-ft) of safe annual yield.
                                   The  marginal long-term capital  cost
                                   of new supplies is estimated at
                                   $ll,000/household  in addition to a
                                   share of the amortized cost of the
                                   existing water system.
                                     Although the quantity of water
                                   available for reuse is strictly limited
                                   by state law to  water imported
                                   from other basins, the relative  cost
                                   of reuse is low. Nonpotable reuse,
                                   providing an annual safe yield of
                     Equation 1
                     Total $ Water Service <
                     Equation 2
                     Total $ Water Service =
ECONOMIC FACTORS
  Some economic
factors that affect
the  decision  to
build a reuse facili-
ty are  reasonably
constant and pre-
dictable regardless
of geographic loca-
tion.  Some vary
widely depending
on location, site
conditions, and the
use to be made of the reuse water.
  Local supply and demand. If the
local water  supply is ample or inex-
haustible, or if municipal demand is
steady, reflecting no population
growth, there is little incentive to
create new  water supplies  through
reuse.  Reuse may still be chosen,
however, for reasons related to
wastewater quality regulations.
  It is far more important to consid-
er reuse when  a municipality has
exhausted all other supply alterna-
tives and still faces growing  demand,
or when part of the existing supply is
threatened with elimination. El Paso,
Texas, and the Los  Angeles/San
Diego  Region are examples.  Both
metropolitan areas have strong pro-
grams for water conservation and
reuse because their historical supply
sources  are  threatened with decline
and no  economical alternatives are
available.
  Costs of •water from alternative
sources. As cities grow and exhaust
their  traditional water  supply
sources, they must seek alternative
supplies, usually by diversion from
ever more distant streams or by buy-
ing agricultural water for municipal
use.  One scenario that  includes
                                    System Cost Equations
$ Collection + $ Treatment •
$ Distribution +
$ Wastewater treatment
$ Conventional wastewater treatment +
$ Effluent collection +
$ Additional treatment for reuse +
$ Additional transportation to supply system +
$ Distribution
                                   12.1 X 106 m3 (9830 ac-ft), would cost
                                   about $0.45/m3 • a ($560/ac-ft/y)-
                                     Potable reuse water from Denver's
                                   pioneering 3.79 X 106 L/d (1 mgd)
                                   Potable Water Reuse Project is  cur-
                                   rently produced at  an operational
                                   cost,  including facility O & M, of
                                   $0.52/1000 L ($1.97/1000 gal) or
                                   $640/ac-ft.  Based on 1989 experi-
                                   ence, Denver expects a full-scale
                                   reuse  plant to convert sewage efflu-
                                   ent to potable water at a cost of
                                   $0.45 to $0.59/1000 L ($1.72 to
                                   $2.25/1000 gal), or from $560 to
                                   $733/ac ft, including amortized cap-
                                   ital cost.  This is substantially less
                                   than the cost of raw water obtained
                                   from  structural diversion from the
                                   Colorado River Basin.
                                     Quality standards for direct
                                   addition to potable supplies. Water-
                                   quality regulations can significantly
                                   affect the cost of reuse water pro-
                                   duced for potable  purposes.  For
                                   example,  in Southern California,
                                   Regional Water Quality  Control
                                   Board regulations require that water
                                   injected in the groundwater aquifers
                                   which serve as seawater intrusion
                                   barriers have a maximum salinity
                                   level of 540 mg/L  total dissolved
                                   solids (TDS). However, the wastew-
ater effluent flowing into Water Fac-
tory 21 from the Santa Ana River
and local wastewater  treatment
plants is at 700 mg/L TDS.  Thus
the water must be demineralized by
reverse osmosis (RO) as well as treat-
ed for  normal wastewater contami-
nants  before recharge into the
groundwater. The current RO cost
at Water Factory 21  is $0.34/m3
($415/ac-ft), but the cost is expect-
ed  to  be reduced to $0.30/m3
($375/ac-ft) after investment in new
pumps.
  Currently, some 246 X 106  m3
(200,000 ac-ft) of water are being
discharged to  the  ocean  from
                Orange County.
                As population and
                demand  grow,
                there  will  be a
                growing incentive
                to increase reuse.
                  Regulatory
                constraints  on
                wastewater dis-
                charge. Another
                economic incen-
                tive  to  re-use
                wastewater is the
                likelihood    of
                increasing  con-
                straints  on  the
quality  of treated wastewater dis-
charge  that may degrade groundwa-
ter supplies.  For example, the  Santa
Ana Regional Water Quality Control
Board requires that water or waste-
water used for groundwater replen-
ishment, or discharged into the
Santa Ana River or  another  open
channel, cannot exceed the salinity of
present  groundwater  or 600 mg/L
TDS, whichever is less. If it does,
more fresh water must be provided
for dilution, the discharge must be
treated  to remove  salt, or the dis-
charge must be sent directly to an
ocean outfall via a  brine line.  Thus
far, capital costs for  the brine line
from the upper reaches of Riverside
County are  $50 million. Another
$30 million in capital investment is
being planned to extend the line into
San Bernardino  County.  Current
yearly O & M costs for the brine line
are $6.1 million, and these costs will
rise to  $10.8 million before the
year 2010.
  In some areas, such high disposal
costs may be spent instead on facili-
ties that desalt and  reuse the waste-
water. Within the Santa Ana water-
shed, desalting  plants are being
planned or projected for future con-
                                                                             Selected Readings on Water Reuse -41

-------
          struction in three areas, with a
          potential capital cost of $58 million
          and annual O & M of up to $21 mil-
          lion. Two of these plants will be
          necessary for water supply purposes
          and one is necessary to successfully
          implement  planned  water reuse
          programs.
            Under Arizona's new groundwater
          protection law, similar constraints on
          salinity levels of treated wastewater
          used for groundwater  recharge may
          come into play in Tucson, once it
          receives deliveries of Central Arizona
          Project (CAP) water which is sub-
          stantially   more
          saline than Tuc-
          son's present sup-
          ply. As CAP water
          is  intended  for
          direct use, to con-
          serve groundwater
          supplies, the ground-
          water protection
          law may  result in
          a requirement for
          demineralization
          of effluent.
            Quality  stan-
          dards for  non-
          potable    uses.
          Nonpotable reuse
          water used  for
          landscape irriga-
          tion, or even some
              decrease as plant size increases.
                Significant economies of scale can
              be realized by large reuse plants but
              these economics can be achieved
              only as long as the plants operate at
              near capacity. Given the seasonal
              variation in urban water use  and the
              variability of return flow, however, a
              plant designed to recycle the maxi-
              mum amount of effluent will neces-
              sarily run at less than capacity  for
              part of the year.
                A  more  modest-sized plant,
              though it continually operates  at
              capacity, not only will have the high-
                  Economic  Feasibility
Added costs of a reuse system
• Added capital facility costs.
• Added operating costs to collect wastewater effluent.
• Added operating costs to treat wastewater to quality standards.
• Added transport costs.

Savings of a reuse system
• Avoidance of part of the costs  of treating wastewater  to the
  extent necessary to meet pollution control  requirements before
  discharge.
• Curtailment of water supply acquisition costs through extension
  of the use available from existing supplies, that is, reduction or
  postponement of water supply development costs.
          crop irrigation, is
          normally accept-
          able for  use after
          secondary treatment. Restrictions
          apply to contact uses, such as swim-
          ming, and to irrigation of food chain
          crops. Nonpotable water also is
          acceptable for industrial  cooling,
          although it may require cold lime
          softening to protect from scale, and
          the addition of biocides  and biodis-
          persants to water in cooling towers.
          For other industrial processes, a vari-
          ety of treatment is used,  and quality
          standards for reuse water prior to
          treatment are not usually  severe. The
          primary  criterion from  industry's
          viewpoint is that the water supply be
          of consistent quality  so that pretreat-
          ment can be maintained routinely.
            Economies of scale.  Some costs
          associated with reuse treatment are
          expected to remain  nearly constant
          per unit volume of water treated,
          such as membranes, energy, chemi-
          cals, and other materials. Other
          costs related to facility construction,
          laboratory analysis, and labor for
          supervision  and  operation  will
Revenues for a reuse system
• Sale of water.
• Use by the municipality itself, following a first use.
District that is tertiary-treated and
chlorinated. The water is used with-
out further treatment for landscape
irrigation on parks, golf courses, and
schools. The reuse water is available
for sale to industrial users  for
$0.029/1000 L ($0.083/100 cu ft) com-
pared with potable water selling for
$0.25/1000 L ($0.71/100 cu ft).
  Long Beach petroleum producers
who are on an interruptible supply of
potable water  had considered using
recycled water for reinjection and
secondary recovery from oil wells,
but have since opted to use the more
                expensive potable
                water instead. Evi-
                dently the reuse
                water must  be
                treated  with  a
                chemical agent to
                avoid a slime con-
                dition that blocks
                the aquifer. Even
                though the cost of
                chemical  treat-
                ment adds little
                to  the  cost  of
                reuse water,  the
                use  of  potable
                water avoids  the
                inconvenience of
                treatment.
              er unit costs of a smaller plant but
              will also be unable to process all  of
              the effluent. The overflow that can-
              not be recycled back into the system
              still must be treated to  meet dis-
              charge standards, but it then is dis-
              charged  and lost. In areas where
              water is scarce and expensive, this
              may be a costly loss.
                The choice of plant capacity is
              therefore  a complex one. It is worth
              noting, however, that the larger the
              metropolitan area and the greater the
              amount of effluent,  the simpler the
              decision about plant size becomes,
              since even a large, efficient plant may
              have a capacity significantly lower
              than the total amount of effluent
              available for reuse.
                Market behavior.  Market behav-
              ior exhibits anomalies despite price
              differentials between conventional
              and recycled water. For example,
              Long Beach,  Calif,  obtains a high-
              quality nonpotable reuse water from
              the Los Angeles  County  Sanitation
                CONCLUSION
                  The most signi-
                ficant economic
                factors impacting
future potable and non-potable
water reuse (see Box)  show trends
that favor  the  future expansion
of both  potable and  nonpotable
  J. Gordon Milliken is senior research
economist with Milliken  Research
Group, Inc., in Littleton, Colo. This
paper was reprinted with permission
from "1987 Annual Conference Pro-
ceedings," American Water  Works
Association.

REFERENCES
   l.U.S. Water Resources Council,
Economic and Environmental Princi-
ples and Guidelines for Water and
Related Land Resources Implementa-
tion Studies,  Government Printing
Office, Washington, D.C. (1983).

  2.Milliken,  J.  Gordon, and
Trumbly, Anthony S.,  "Municipal
Recycling of Wastewater," Journal
AWWA, 71, 10, 548 (1979).
42 - Selected Readings on Water Reuse

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Water reuse: potable  or

nonpotable? There is a  difference!

        ater reclamation and reuse offers an increasingly attractive option
        for meeting the growing water shortages facing urban, industrial,
        and agricultural consumers throughout the world. However, the
        failure to identify clearly whether a project,a principle or practice,
or a table of water-quality parameters refers to potable or nonpotable reuse
may easily confuse the reader. Both potable and nonpotable reuse have the
potential for adding to the water resource and reducing water pollution,
but in every other aspect the two practices are very different.
  • Water-quality monitoring and
treatment for potable reuse needs
                                     This last segment in a series on reuse
                                   was made possible by a grant from
                                   EPA. WE&T hopes that the four seg-
                                   ments in  the series, which began in
                                   October, have provided readers with a
                                   better sense of the reuse potential of
                                   wastewater.
to address all parameters embod-
ied in primary drinking-water reg-
ulations with due attention to the
many contaminants soon to be in-
cluded in the regulations. For
nonpotable reuse, the concerns
are only with microbiological con-
taminants and some parameters in secondary drinking-water regulations.
  • A potable water reuse project requires extensive preliminary study
including less conventional treatment processes and more intensive
monitoring, often of organic compounds difficult to analyze. A nonpotable
reuse project uses fewer and  only conventional treatment processes and
simple  monitoring of only a  handful of contaminants.
  • There are hundreds of pipe-to-pipe nonpotable reuse systems in the
U.S., Japan, and elsewhere, some of which incorporate full dual-
distribution systems. On the other hand, there are no pipe-to-pipe potable
reuse systems in service anywhere in the world. The discharge of reclaimed
wastewater  to a reservoir that formerly had only fresh water to supplement
a potable supply may  be more acceptable than pipe-to-pipe reuse, but it
introduces new health concerns that those cities that now draw on run-of-
river supplies already face.
  • An obstacle that faces potable water reuse projects is public acceptance,
and public education  programs are vital. On the other hand, nonpotable
reuse for  urban, industrial, and agricultural purposes is widely accepted and
engenders public enthusiasm as being environmentally appropriate.
  EPA regulations state that "...priority should be given to selection of the
purest source.  Polluted sources should not be used unless other sources are
economically unavailable..."  Should we really be trying to persuade the
public that we should draw our drinking water from sewers? To claim that
it is better than some  presently used waters does not inspire confidence.
The distrust of public supplies is  already widespread, with increased use
of costly bottled water and point-of-use treatment devices.
  Accordingly, while nonpotable reuse continues  to be seen as having the
potential  to be immediately feasible, it should not have to carry this
baggage of uncertainties and public resistance that constrain potable reuse.
More precise labelling in the literature would be helpful.

                                                     Daniel A. Okun
                  Kenan Professor of Environmental Engineering, Emeritus
                              University of North Carolina at Chapel Hill
                                                                 Selected Read

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                                                                  NEWS
          Report Sets  New Water
          Reuse  Guidelines
          Christopher Powicki
            For nearly 20 years, the U.S. World
            Health organization (WHO) has
            been considering the implications
          of reclaiming wastewater treatment
          plant effluent and has been evaluat-
          ing the safeguards needed to protect
          human health. Most recently, in 1987,
          WHO sponsored a meeting of inter-
          national experts in the  wastewater
          treatment and public-health fields
          that resulted in the 1989 publication
          of a report, "Health Guidelines for
          the Use of Wastewater in Agriculture
          and Aquaculture."
            The report discusses historical and
          current reuse practices from a public-
          health perspective,  recommends
          guidelines and alternative mea-
          sures for the  control of infectious
          diseases,  and identifies areas of
          uncertainty that require future re-
          search. It affirms that wastewater
          is a viable and valuable resource
          needed  to meet "perhaps the
          greatest challenge of the next cen-
          tury: appropriate management of
          the  limited water resources avail-
          able."

          NEW GUIDELINES
            Conventional primary and sec-
          ondary treatment practices empha-
          size the reduction or removal of bio-
          chemical oxygen demand and sus-
          pended solids—the  traditional para-
          meters of water quality. Treatment
          for reuse requires  the  removal of
          pathogenic organisms for which con-
          ventional treatment  practices are not
          very effective. Engineers designing
          reuse plants are further challenged by
          the variation  in the maximum per-
          missible  concentrations  of specified
          pathogenic organisms for the differ-
          ent end uses of reclaimed water. This
          variation is based on the potential
          levels of human exposure to the re-
          claimed water for each reuse scheme.
            To  achieve the highest level of
          health protection,  engineers must
          have clearly defined  quality standards
          for each end use, and they must con-
          sider economic and operational fac-
          tors. According to the report, "waste-
          water of the  required quality should
          be produced at all times...without the
need for continuous monitoring.
Emphasis must therefore be placed
on careful selection  and design of
treatment plants  rather than on a
high degree of care in operation."
The report states that this is most
important in developing countries,
where money and adequate infras-
tructure are lacking and there is lim-
ited experience in operating treat-
ment plants.  In these areas,  "the sim-
plest and cheapest technology will
have the greatest chance of success."
  Unfortunately, in many poor coun-
tries, organized water reuse programs
have made little headway,  primarily
 Reuse is the greatest
    challenge of the
      next century.
because many wealthy countries
committed to reuse have relied on
advanced and expensive technology,
according to the report.  Wealthy
countries often rely on tertiary treat-
ment, including rapid sand filtration
and chlorination, to meet strict micro-
biological standards for effluents ap-
plied to agricultural lands.
  The  report states that recent epi-
demiological research indicates that
the risks from irrigation  with re-
claimed water have been  overesti-
mated  and that these standards are
"unjustifiably restrictive, particularly
with respect of bacterial pathogens."
The report recommends new guide-
lines containing less stringent stan-
dards for fecal coliform.
  The guidelines contain stricter stan-
dards for the concentration of hel-
minth  eggs (Ascaris sp., Trichuris
sp., and hookworms), which are the
main public-health risks associated
with wastewater irrigation in areas
where  helminthic diseases are  en-
demic, such as developing countries.
According to the report, stabilization
ponds with a retention time of 8 to
10 days are particularly effective in
achieving helminth concentrations
less than or equal to 1 egg/L.
  The guidelines do not cover all
helminths and protozoa that poten-
tially threaten humans exposed to re-
claimed water. For example, Giardia
sp.  are not cited. According to the
report, the helminths that are cov-
ered should serve as indicator organ-
isms for  all large, settleable patho-
gens. Other pathogens of interest ap-
parently become non-viable  in long-
retention-time pond  systems. "It is
thus implied  by the guidelines that
all  helminth eggs and protozoan
cysts will be removed to the same ex-
tent," states the report.
  The previous high standards and
the need for costly, sophisticated
treatment technologies to meet them
have caused poor countries to fail  to
incorporate wastewater reuse into
new sewerage schemes, resulting  in
the uncontrolled use of raw sewage
or treated effluent by farmers for irri-
    gation purposes. The  new guide-
    lines, which are in line with the
    quality of river water used for the
    unrestricted irrigation of all crops
    in  many  countries  without
    known ill effects, were designed
    to eliminate these problems. The
    idea  was to "increase public-
    health protection for a  greater
    number of people, while at the
same time set targets that were both
technologically and economically
feasible."
  The report states that the guide-
lines must be carefully interpreted and
that they may need to be modified in
light of local epidemiological, socio-
cultural, and environmental factors.

OTHER ISSUES
  The report describes the treatment
technologies that can be  used  to
meet the revised guidelines in the
most economical  manner.  It also
outlines application methods and
other measures that can reduce the
risks associated with ingesting crops
irrigated with wastewater. It suggests
an  institutional framework  for the
implementation of health safeguards
including the development of appro-
priate regulations.
  Research needs are outlined in sev-
eral areas: water-quality assessment
methods, treatment technologies,  ir-
rigation technologies, epidemiology,
sociology, and economics.
  —The report is available from the
WHO Publications  Centre, 49 Sheri-
dan Ave., Albany, NT 12210.
44 - Selected Readings on Water Reuse

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Selected Readings on Water Reuse -45

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      The  use  of treated wastewater
      for field  and crop irrigation
      has a long history in the state
      of California but, in the last
      25  years,  wastewater reclama-
      tion has  become even more
prevalent  in the state. This change
was largely driven  by the need for
restrictions on wastewater  effluent
discharges to watercourses and by
increased urbanization and ground-
water depletion. Primary uses for
reclaimed  wastewater include irriga-
tion of parks, green belts, and golf
courses; impoundment of seasonal
waste discharges; and percolation to
recharge groundwater basins.
  California water and wastewater
management districts have been chal-
lenged to incorporate reclaimed water
into existing treatment and convey-
ance systems while meeting tighten-
ing state  water-quality standards.
Wastewater treatment plants (WWTPs)
using trickling filters in their  secon-
dary treatment train have a unique
problem: trickling filter effluent meets
secondary  treatment standards, but
has higher  turbidity levels than efflu-
ent from the activated-sludge process.
Therefore,  for trickling-filter effluent,
the standard reclamation approach—
rapid sand filtration followed by chlo-
rination—does not meet California's
turbidity standard.
  At a reclamation plant operated by
the Marin Municipal Water District
(MMWD), an in-depth evaluation of
clarification and filtration options was
undertaken to identify the most eco-
nomical and effective process to treat
trickling-filter effluent to meet tur-
bidity standards for reclaimed water.

TIGHTER STANDARDS
  In 1978, the MMWD constructed
a water reclamation plant at Las Galli-
nas Valley Sanitary District's WWTP
north of San Rafael, Calif. The  1 -mgd
reclamation plant used direct sand fil-
tration and chlorination  processes to
treat effluent from the final clarifier of
the adjacent two-stage trickling filter,
secondary treatment plant. Reclaimed

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                                                                     WATER RECLAMATION/REUSE
wastewater has been used to irrigate
nearby Mclnnis Park and freeway
landscaping, and for utility services at
theWWTP.
  Before the  reclamation facility was
completed, the clarity requirements
for reclaimed wastewater used for irri-
gation of unrestricted public-access
landscaped facilities and recreational
impoundments were modified. The
California State Department of Health
(DOHS) proposed reclamation criteria
based on operation of several operat-
ing WWTPs. The  DOHS required
that reclaimed water for use on these
areas have an  average turbidity of less
than 2 nephelometric  turbidity units
(NTUs), with a maximum not-to-ex-
                  I/'
ceed value of 5 NTU; and an average
coliform count of less than 2.2/100
mL, with a maximum not-to-exceed
value of 23/100 mL. Turbidity mea-
surement was  established as a  surro-
gate for effective removal of patho-
genic organisms, including viruses,
following extensive testing of re-
claimed water processes in California.
  The reclamation plant was able to
meet the bacterial requirement,  but
there was considerable difficulty meet-
ing the clarity  standard. This was de-
spite the maintenance of good opera-
tions and the installation of several
improvements, including chemical
feed and prefiltration of the waste-
water effluent.
  Direct filtration processes, with the
aid of chemical coagulants, have suc-
cessfully operated when the secon-
dary effluent turbidity is 10 NTU or
less, as is typical for many activated-
sludge secondary effluents. However,
trickling-filter effluent typically  has
higher turbidity levels, and direct fil-
tration as a single treatment process
will not produce reclaimed water that
meets the turbidity standard.
  After extensive testing by MMWD
staff, it was decided in 1987 that the
criteria for unrestricted landscape  irri-
gation could be met by the plant if
the water was coagulated, settled,
and filtered through improved media.
Process improvements evaluated by
on-site pilot-plant testing were rec-
ommended to determine the type of
treatment necessary to achieve state
reclamation standards. The pilot-
plant tests would also identify  the
cost of modifications and attendant
operational costs.
  The  MMWD authorized a study in
winter  1987 to evaluate and test pro-
cesses for improving wastewater treat-
ment. The study would also suggest
the apparent best process for provid-
ing a present capacity of 2 mgd, ex-
pandable to 4 mgd, that would  use
the current and projected dry-weath-
er wastewater flows of Las Gallinas.

WASTEWATER TREATMENT
  The  processes  and operations of
Las Gallinas have major impacts on
the operation and performance of the
reclamation plant. The WWTP uses a
two-stage, high-rate rock trickling-fil-
ter process that has a dry-weather
capacity of 2.9 mgd and wet-weather
peaks of up  to 8  mgd. The WWTP
was upgraded in 1984 to provide  ad-
vanced secondary treatment through
a nitrification fixed-film reactor tower
and effluent polishing through  deep-
bed filters. Disposal to storage ponds
for dry-season irrigation of pastures
and hay fields, and  to a marsh pond
for effluent enhancement before wet-
season discharge to  Miller Creek was
improved.
  The MMWD reclamation  plant
was an in-line filtration facility that
has alum and polymer coagulant
addition and storage, a static rapid
mixer, deep course-media silica-sand
filtration, chlorination, and storage in
a combination chlorine-contact and
distribution reservoir.
  The quality of influent delivered to
the reclamation plant depends on
whether the influent is pumped di-
rectly from the WWTP's final clarifier
Figure
Turbid
60
50
_l
^ 40
1

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           Figure 2—High-Rate Solids-Contact Clarification
                        Winter Discharge
                         to Miller Creek
            Las Gallinas Valley
             Sanitary District
           Wastewater Treatment
           related in terms of biochemical oxy-
           gen demand  (BOD) and suspended
           solids (SS). EPA requires secondary
           treatment to  reduce wastewater con-
           centrations of both to 30 mg/L. Las
           Gallinas' permit  has seasonal  and
           temporal SS limits (Table 1).
             To achieve the treatment levels,
           discharge from the secondary clari-
           fiers is the final effluent from June to
           August, when discharge to San Fran-
           cisco Bay is prohibited and the efflu-
           ent is stored in holding ponds for irri-
           gation.  The  nitrification fixed-film
           reactor and effluent filter are in use
           for the remainder of the year when
           the final effluent is discharged to San
           Francisco Bay via nearby Miller
           Creek. Reclaimed water is used for
           irrigation between April and Novem-
           ber; thus, water-quality standards and
           effluent quality differ periodically.
             For trickling-filter effluent, the SS
           concentration usually exceeds the tur-
           bidity value. A plot of the relationship
           of turbidity and SS for Las Gallinas
           effluent shows that the summer ratio
           was about 1.75:1, during the winter
           it was only 0.75:1, with an overall
           average of 1.25:1 and considerable
           scattering of data (Figure 1).

           FILTRATION OF TRICKLING-
           FILTER EFFLUENT
             The literature reports that the
           average  removal of SS by rapid sand
               Direct  and Tertiary  Filtration
     Trickling-filter effluent achieved a poorer degree of biological floccula-
   tion tfian activated sludge. The strength of the biological floe is also great-
   er than chemical coagulation, as it is more difficult to achieve low turbidi-
   ty by direct filtration of trickling filter effluent.
     A review of tertiary filtration of wastewater found that the greatest fac-
   tor affecting SS removal efficiency is the size  of the particles in the influent
   wastewater, and that about  30% of trickling filter effluents contain very
   small particles that are  not easily filtered.  It  was also found that trickling
   filter effluent contains large quantities of submicron colloidal material, and
   because of the  stoichiometric effect for chemical destabilization, large
   coagulant  doses can  be required. Other tests conducted in Seattle found
   that over 95% of the number of particles in trickling filter effluent were in
   the 0.5 to 2 micron range and that they contributed the greatest portion of
   the turbidity. Also,  only 30% of the  particles in this size range were
   removed by filtration.
     There are specific  recommendations  for treatment processes to produce
   a highly treated effluent; however, for reclaiming trickling filter effluent,
   full rfocculation  sedimentation before  filtration is highly recommended,
   and for activated-sludge effluent, only direct filtration is recommended.
filters is two-thirds to three-fourths
of the settled water concentration. In
the nearby Ignacio WWTP that uses
a shallow-bed rapid sand filter, SS is
reduced by about 50%.
  In fact,  data on available technolo-
gy was for direct filtration used
mostly in  activated-sludge treatment
processes, while clarification and fil-
tration were required for most trick-
ling- filter effluents  to achieve  the
standard of an average of less than 2
NTU (see Box). There are many ref-
erences to support what  has practi-
cally been found in the years of oper-
ation of Las Gallinas WWTP—that
direct filtration alone is not sufficient
to produce  reclaimed water with an
average turbidity of less than 2 NTU.
  The DOHS recognized that, for
wastewater  reclamation plants with
direct  filtration,  secondary effluent
should have  a turbidity of less than 10
NTU.  This  was not usually achieved
48 - Selected Readings on Water Reuse

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                                                                     WATER  RECLAMATION/REUSE
Table 1—Las Callings Effluent limits for Suspended Solids, mg/L

                                  Measurement Period
Period
Monthly average    Weekly maximum   Daily maximum
November to
March
April to May
September
to October
June to August
30
15
15
not required
45
18
18
not required
60
20
20
not required
Upflow adsorption clarification is a new development that combines flocculotion and solids capture in
a granular-media bed before filtration.
at Las Gallinas for the WWTP's sec-
ondary clarifier or polishing filter pro-
cesses.
  There are effective means of up-
grading trickling-filter effluent, usual-
ly by  the installation of a coupled or
short-detention aeration of activated
sludge to achieve effective biological
oxidation.  In view of the district's
existing plant layout and need for
                    biological nitrification reaction, it was
                    not a viable consideration.

                    CLARIFICATION PROCESSES
                      Several clarification processes were
                    considered for Las Gallinas WWTP.
                      Conventional coagulation and
                    settling. Conventional  coagulation
                    and settling have been used success-
                    fully  to  clarify wastewater before  fil-
tration to provide flexibility for coag-
ulant chemical doses, flocculation
energy,  and sludge recirculation.
Coagulation times range  from 15 to
30  minutes, settling overflow rates
range from 0.5 and 0.75  gpm/sq ft,
and detention times are 1 to 2 hours.
To provide effective conventional
clarification of wastewater, it is nor-
mal that alum doses range from 75 to
250 mg/L and polymer  doses range
from 2 to 10 mg/L.
  The tests conducted in  this investi-
gation found that conventional clari-
fication used the  normal amount of
coagulant, flocculation energy,  and
time. The tests also showed that set-
tling overflow rates that  produced a
settled-water turbidity of less than 3
NTU could then be filtered to pro-
duce a finished-water turbidity of 1.2
to 1.8 NTU. This requires a dose of
70  to 100 mg/L of alum,  2  to 5
mg/L of polymer, 10 to  15 minutes
of flocculation, and an overflow  rate
of 0.75 gpm/sq ft.
  High-rate  inclined-plate tube
settlers.  Inclined-plate  and tube set-
tlers have been used in  several clarifi-
cation applications following floccu-
lation.
  In all instances, there is an accumu-
lation of sludge near the top of the
inclined tubes that is most effectively
removed by periodically shutting off
the plant and  dropping the water
level below the tubes. The floe slides
off and plates  or tubes are cleaned.
This tube cleaning is necessary every
5 to 7 days and takes several hours.
Water-jet cleaning of the surface of
the tubes can also be used, but is
more time consuming and less satis-
factory than the draining practice.
  Solids-contact clarification.
Solids-contact clarification has been
used in several wastewater clarifica-
tion processes. It usually combines
high-rate flocculation with a turbine
mixer and upflow clarification. Usual
overflow rates are 1 to 1.5 gpm/sq ft.
  A recently developed high-rate
solids clarifier has been  successfully
used in  Germany  to clarify wastewa-
ter  effluents with an overflow rate of
5 gpm/sq ft without tubes, and 10
gpm/sq  ft with tubes. One advan-
tage of this clarifier is that the blow-
down  sludge  concentration  can
approach 10%, as compared to  the
usual 1% or less of conventional or
upflow clarifiers. This new process
was selected for the pilot-plant test at
Las Gallinas.
  Adsorption  clarification. The ad-
sorption clarification process is a new
                                                                                Selected Readings on Water Reuse -49

-------
          development that combines the
          functions of flocculation and solids
          capture in a granular-media  bed
          before filtration. The process is  akin
          to two stages of filtration in that the
          initial adsorption clarifier uses a high
          flow rate of 5 to 10 gprn/sq ft and
          large media of 3 to 5 mm. Coagulant
          chemicals are introduced before the
          adsorption clarifier and are flocculat-
          ed within the  granular  bed by the
          high-flow  energy and turbulence
          passing through the bed. This causes
          an enlargement of floe size  and
          retention within the granular bed.
            There are two basic types of ad-
          sorption clarifiers: the  downflow
          mode and  the  upflow mode.  The
          downflow mode, developed in the
          early 1970s, is used extensively in
          Europe  and South America. Down-
          flow adsorption clarifiers have had
          limited  use in wastewater clarifica-
          tion. Both  types of clarifiers use an
          air-wash-aided  backwash, silica-sand,
          and  4 to 6 ft  of anthracite media.
          The  clarified-water turbidity is moni-
          tored to aid in the adjustment of
          coagulant dose, and a polyelectrolyte
          filter aid is used to enhance the filter-
          ability of the clarified water.
            Pilot-plant trials of upflow adsorp-
          tion clarification were conducted by
          the Desert Water Agency at the Palm
          Springs WWTP on trickling-filter
          effluent in 1984 and 1985. The clari-
          fier used a  4-ft bed on polyethylene
          beads retained by a stainless-steel
          screen. The clarifier was back-washed
          by an air-water backwash cycle  when
          the head loss was 4 ft through the bed.
            The pilot-plant tests were success-
          ful in producing a reclaimed water
          with turbidity of less than 2 NTU at
          influent turbidity concentrations as
          high as 19 NTU when operating at a
          flow rate of 10 gpm/sq ft, using a
          minimal alum  and an anionic  poly-
          electrolyte dose controlled by a
          microprocessor that  monitors fil-
          tered-water turbidity. Water produc-
          tion was 94.4% in summer when
          influent turbidity was less than 10
          NTU, and 92.4% in winter when
          turbidity was between 10 and 19
          NTU. Thus, a relatively high propor-
          tion of water is used in  backwash—
          5.5% to 7.5%.
            Based on these tests,  the Desert
          Water Agency constructed a 5-mgd
          treatment facility using upflow
          adsorption  clarification, and Las Gal-
          linas pilot  tested the same option.
          Dissolved-air flotation.
            Dissolved-air flotation (DAF)
          has been used for clarification of
Table 2-Capital Cost of Clarifier
                                                 Treatment capacity
 Alternatives
Process
1 mgd
2 mgd
Rank
1
2
3
4
5
6
7
8
9
CRFS
CCSF
SCUC
FIPS
DAF
DEF
HRSFS
UAC
DAV
$581 000
556 000
360 000
230 000
324 000
61 8 000
337 000
262 000
265 000
$1 025000
810000
540 000
345 000
396 000
975 000
411 000
446 000
450 000
9
7
6
4
2
8
3
4
5
'Capital costs for construction of process units exclusive of any piping, electrical,
sludge handling, site, or ancillary facilities at February 1988 costs.
2Based on 2 mgd capacity.
wastewater effluents at several Euro-
pean installations with typical over-
flow rates of 1  to  2  gpm/sq ft.
Bench-scale tests were conducted at
Las Gallinas and it was found  that
direct flotation was not too success-
ful, but recycle pressure flotation
could provide a clarified water with a
turbidity of less  than 4 NTU at an
overflow  rate of 0.25 gpm/sq ft.
This is not nearly as  good as the  1-
gpm/sq ft for a settling process.
DAF did not seem to be a promising
clarification process  for wastewater
reclamation at Las Gallinas.
  Diatomaceous-earth filtration.
Diatomaceous-earth filtration (DEF)
can, with  adequate precoat, produce
a highly clarified  effluent with only a
trace of suspended solids—but at a
high cost.  Frequently there is a prob-
lem in handling variations in suspend-
ed-solids loading, and automation of
body feed and backwash are required
for the process to be reliable.
  Bench-scale tests of DEF on the
direct filtered effluent of Las Gallinas
achieved  a reduction in turbidity
from 2.2  to 1.7 NTU. Because  of
this relatively low turbidity reduction
(30%), it  was  concluded that DEF
would not provide sufficient polish-
ing clarification when filtered-water
turbidities were above 5 NTU.  This
process was,  however, tested  for a
limited  period at Las Gallinas and
found to  require excessive doses of
diatomaceous  earth to produce the
desired low-turbidity  effluent.
  Ozonation microflocculation
clarification. Ozonation, which has
been used at several WWTPs for dis-
infection,  may provide microfloccula-
tion of organic color compounds, de-
crease coagulant dose, and improve
effectiveness. Usually, ozone doses
                   for disinfection are high—from 10 to
                   25 mg/L. Doses of about 10 mg/L
                   in wastewater effluent can provide
                   microflocculation benefits with 5 to
                   10 minutes of contact time and re-
                   duce coagulant dose requirements by
                   50% before clarification and filtration.
                   Chlorination is still required after fil-
                   tration to produce a coliform concen-
                   tration of less than 2.2/100 mL.
                     Clarification costs. Preliminary
                   capital and operations and mainte-
                   nance (O &  M) costs were devel-
                   oped for each clarification alternative
                   to  relate  probable cost-effectiveness
                   (Tables 2  and 3). In  addition,  non-
                   cost factors including  reliability, flex-
                   ibility, implementation, and aesthet-
                   ics were compared for each alterna-
                   tive  (Table 4). This information
                   determined the rationale for why cer-
                   tain processes were selected for pilot-
                   plant testing. The  information also
                   provided  a reference of the more
                   detailed clarification process analyses
                   that were used to  formulate  an
                   apparent-best-process for upgrading
                   Las Gallinas.

                   BENCH- AND PILOT-SCALE TESTING
                     Bench-scale studies were conduct-
                   ed to evaluate conventional coagula-
                   tion, flocculation, and clarification
                   processes. DAF and DEF  processes
                   were also  screened. The bench-scale
                   tests indicated that conventional
                   flocculation and clarification  were
                   the best  processes; however,  high
                   concentrations of alum—70 to 100
                   mg/L—were required to produce
                   good settling.
                     The objective of the pilot-plant
                   testing was to identify and demon-
                   strate the effectiveness of various
                   treatment processes in removing tur-
                   bidity and suspended solids in the
50 - Selected Readings on Water Reuse

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Table 3—Operation and Maintenance Costs of Clarifier
Alternatives Process
1
2
3
4
5
6
7
8
9
CRFS
CCFS
SCUC
FIPS
DAF
DBF
HRSFS
UAC
DAC
Energy
hp $/yr
15
14
17
6
27
150
14.5
3
6
5,250
4,900
5,950
2,100
9,450
52,500
5,100
1,050
2,100
Chemical
Ib/day $/yr
1,280
1,280
1,200
1,280
1,680
5,000
1,030
600
600
24,600
24,600
23,400
24,600
30,400
121,800
20,000
20,000
20,000
Operation Maintenance
hr/day $/yr $/yr
0.5
0.5
0.5
1
1
2
1
1
1
2,100
2,100
2,100
4,200
4,200
8,400
4,200
4,200
4,200
10,200
8,200
8,400
6,900
7,300
9,800
8,250
13,400
1 3,600
Total
$/yr
42,150
39,800
39,850
37,800
51,350
192500
37,550
38,650
39,900
Table 4—Comparison of Clarifier Alternatives for Cost and Non-Cost Factors
              Process  Capital O&M                      Implement- Permit-  Expand-             Total
Alternative     Type    cost1   costs  Reliability2 Flexibility   ability   ability   ability  Aesthetics valuation Rank
Proportionate
evaluation%             25     25      15       10        5        5        5        10       100     -
1
2
3
4
5
6
7
8
9
CRFS
CCFS
SCUC
FIPS
DAF
DEF
HRSFS
UAC
DAC
0
8
18
25
23
2
23
21
21
25
25
25
25
23
0
25
25
25
15
13
12
5
10
2
12
8
8
10
9
8
5
2
3
8
7
7
1
1
1
3
3
5
4
5
5
5
5
3
3
3
2
2
2
2
1
1
1
2
3
4
4
5
5
10
10
8
6
8
8
6
4
4
52
59
76
74
75
24
84
77
77
7
8
4
6
5
9
1
2
3
'Capital and annual O&M valuations are on the basis of full 25% for the lowest cost alternative and 0% for the most costly, with every
other alternative as a cost proportion of this scale.
2Non-cost factors amount to 50% of worth and are based on estimate of process performance reliability; relative ease to implement at
the site; and appearance, noise, and odor aesthetics
wastewatcr  effluent to meet the
reclamation requirements. The pilot
processes were evaluated on chemical
coagulant requirements, loading
rates, impact of source water-quality
variables, waste volumes and concen-
trations, and O&M considerations.
  Three pilot processes were tested:
high-rate  solids-contact and upflow
clarification processes for treatment
upstream of the existing direct filtra-
tion reclamation plant, and a  DEF
process for polishing treatment down-
stream of the existing sand filters.
  All three of the pilot plants tested
were successful m removing turbidity
in the wastewater  to less than 2
NTU. The upflow adsorption clarifi-
er used the least amount  of chemical
coagulant but produced the most
backwash water.  This resulted in a
low 90% net production  of filtered
water. The high-rate solids-contact
clarifier required about twice the
dose of chemical  coagulant but pro-
duced little blowdown waste, result-
ing in a  99.7% net production of
clarified water. The high-rate clarifier
met  the 2-NTU turbidity require-
ment without filtration; however, fil-
tration was required to meet DOH's
virus removal requirements. Because
of filter backwash requirements, the
net production of the combined high-
rate solids contact clarification  and
filtration process exceeds 97%.
  The DEF polishing was  successful
in producing a final effluent with tur-
bidity less than 2 NTU,  with the
existing filters producing an effluent
with a turbidity of 3.4 to 4.5  NTU.
However, higher turbidities from the
filters required greater body feed of
diatomaceous earth and further
reduced the short 9- to 10-hour fil-
tration cycle.  For this system to be
effective, the existing filters would
need to produce a constant effluent
turbidity of less than 4.5 NTU.

CLARIFIER COMPARISONS
  Results of the pilot-plant  tests were
evaluated  to develop alternative plant
process and operating configurations
to meet requirements  for  virus-free
water. Particular emphasis was given
to pilot-plant testing of alternative
clarification processes, effluent flow
and water quality produced by Las
Gallinas,  operating experience and
planning objectives of the current
MMWD reclamation plant, and cur-
rent and future requirements for
reclaimed wastewater in California.
  Alternative  plant improvement
facilities were compared on the basis
on capital costs, O&M costs, annual
cost effectiveness, and non-monetary
factors including reliability, flexibility,
ease in construction, ease in imple-
mentation, institutional  and mtera-
gency  requirements, aesthetics, and
environmental factors. Proportionate
ranking of these factors  favored the
high-rate solids-contact  clarification
process as the best project to design
and construct (Figure 2).
  The  suggested improvement facili-
ties included more than the  clarifica-
tion process. Other features of the pro-
ject include a new inlet pump station
and pipeline from Las Gallinas' stor-
age and marsh  ponds, improved and
expanded filtration facilities, and wash-
water and sludge-handling facilities. •

  Joel A. fatter and Robert A. Ryder
are  environmental engineers for
Kennedy/ Jenks/ Chilton in San
Francisco, Calif.
                                                                                 Selected Readings on Water Reuse - 51

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                      Water reuse is becoming
                      an increasingly common
                      component of water re-
                      source planning as op-
                      portunities for conven-
                      tional water-supply de-
           velopment dwindle and  costs for
           wastewater disposal climb. Both non-
           potable and potable reuses of re-
           claimed wastewater offer  means to
           extend and maximize the utility of
           limited water resources.
             Factors that contribute  to the
           consideration of potable reuse  as an
           alternative water supply include fu-
           ture water  demand exceeding sup-
           ply, limited locally available conven-
           tional surface-water and groundwa-
           ter supplies; polluted local conven-
           tional supplies; lack of politically vi-
           able, demand-reduction measures;
           lack of economically viable nonpot-
           able reuse opportunities;  high cost
           of wastewater disposal; water rights
           favoring reuse rather than disposal;
           and high cost and environmental im-
           pacts of developing remote conven-
           tional water supplies.
             Successful implementation of a
           potable reuse project hinges on satis-
           factory response to common concerns
           often raised regarding both planned
           indirect and direct potable reuse.

           WATER-QUALITY STANDARDS
           AND PUBLIC HEALTH
             For indirect, potable reuse, the re-
           covered water must be of equal or
           better quality than the  receiving
           water source.  For instance, if the  re-
           ceiving water source is a potable
           water aquifer requiring only disinfec-
tion before distribution, then the re-
covered water recharged  to the
aquifer needs to be of drinking-water
quality. Similarly,  if the receiving
water source is a  river requiring full
conventional water  treatment before
distribution, then the recovered water
augmenting the river flow need only
be of a quality equal to the  natural
quality of the river water.  In either
case, the recovered water should  be
of a quality to prevent deleterious ef-
fects in the receiving water source
      Public Education

           Program

   A public  education program
   should consider the following
   subjects:
   •  The need for additional
   water supplies.
   • The availability of additional
   water supplies.
   • The cost of additional water
   supplies.
   • The environmental impact of
   developing additional water
   supplies.
   •  The status of potable water
   recovery technology.
   • The safeguards incorporated
   in potable water recovery and
   reuse processes such as multi-
   ple barriers, extensive  moni-
   toring, and possible blending
   of the recovered water with
   another water source.
such as dissolved oxygen depletion,
eutrophication, increased total dis-
solved solids, or accumulation of
trace organics or inorganics.
  For direct, potable reuse, the re-
covered water must be of equal or
better quality than the finished water
produced from the  highest quality
source water locally available.
  At this  stage in the development
of potable reuse projects, a demon-
stration-scale  plant is required to sat-
isfy regulatory agencies that the re-
covered water quality is suitable for
reuse. The recovered water should
be produced for at least 1 year to
document the reliability of the quali-
ty during seasonal variations. The re-
covered water should be subjected to
extensive  physical, chemical,  micro-
biological, and toxicological  testing
for direct comparison to either the
receiving water source  (indirect
potable reuse) or the highest quality
finished  water available (direct
potable reuse). In addition, the re-
covered water quality should be
compared with existing and pro-
posed drinking-water standards  and
public health  advisories.
  The U.S. Environmental Protect-
ion Agency (EPA) does not explicitly
regulate the practice of potable reuse.
However, the Clean Water Act and
the Safe Drinking Water Act (SDWA)
establish laws that govern the opera-
tion of facilities that  treat wastewater
and drinking  water. Outside of these
constraints, EPA delegates permitting
of specific wastewater reuse opera-
tions to the states. Currently, individ-
ual states  prohibit potable  reuse, do
                           Reuse Terms
             Unplanned, indirect,  potable reuse occurs when a
          water supply is withdrawn for potable purposes from a
          natural surface or underground water source that is fed in
          part by the discharge of a wastewater effluent.   The
          wastewater effluent is discharged to the water source as a
          means of disposal and subsequent reuse of the effluent is
          a byproduct of the disposal plan. This type  of potable
          reuse commonly occurs whenever an upstream water  user
          discharges wastewater effluent into a water course  that
          serves as a water supply for a downstream user.
             Planned, indirect potable reuse is similar to  unplanned,
          indirect potable reuse; however, the wastewater effluent is
          discharged to the water source with the intent of reusing
          the water instead of as a  means of disposal.  This type or
          potable reuse is becoming more common as water re-
          sources become less plentiful and the luxury of wastewater
          disposal declines.
             Direct potable reuse is the piped connection of water
          recovered from wastewater to a potable water-supply dis-
                  tribution system or a water treatment plant.  Currently,
                  there are no examples of direct potable reuse in practice
                  in the U.S.; however, demonstration of direct potable
                  reuse is occurring in Denver, Colo., and San Diego, Calif.
                     Conventional-plant water recovery involves linking the ex-
                  isting wastewater treatment plant with a new water resource
                  recovery treatment facility designed to reclaim wastewater
                  to a quality suitable for either indirect or direct potable
                  reuse. The conventional-plant approach to water  recovery
                  has  been the method of choice to date for most existing
                  planned, indirect, potable reuse facilities.
                     Single-plant water recovery is the reclamation of previ-
                  ously untreated municipal wastewater to a quality suitable
                  for either indirect or direct potable reuse in a single treat-
                  ment facility. The single-plant approach may have advan-
                  tages over the conventional-plant approach under some cir-
                  cumstances for the following  reasons.
                     •  A single plant can be  located near both a source of
                  untreated wastewater and a desired point of introduction
                  to either a water source  or a finished water distribution
                  system.  In contrast, a conventional  plant is linked to an ex-
                  isting treatment plant that is often far removed from the
52 - Selected Readings on Water Reuse

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                                                             WATER RECLAMATION/REUSE
POTABLE
WATER  REUSE
 Carl L. Hamann, Brock McEwen
desired point of recovered water distribution. Therefore, a
single plant has increased siting flexibility that could re-
duce the cost of pumping associated with distribution of
the recovered potable water.
  • The siting flexibility of the single plant relative to the
conventional plant could allow location near a wastewa-
ter  interceptor conveying predominantly domestic
wastewater as opposed to a conventional plant possibly
downstream of industrial and commercial dischargers.
Domestic wastewater is generally lower in contaminants,
which eases the burden on the potable water recovery
treatment process.
  • Water recovery in a single plant may be more oper-
ationally convenient than water  recovery  in individual
plant modules. A single plant would have a single treat-
ment objective—to recover water for indirect or direct
potable reuse from untreated wastewater—while  the
treatment plant link of the conventional plant may have
two treatment objectives—to meet National Pollutant
Discharge Elimination System requirements for disposal
and to meet performance standards for contribution to a
potable reuse treatment.
  Multiple contaminant barriers refers to the provision of
more than one unit process capable of treating the physi-
cal, chemical, and microbiological contaminants or con-
cern. Multiple contaminant barriers provide treatment reli-
ability because failure of one unit process to effectively re-
move a contaminant of concern does not preclude effective
overall treatment, because additional contaminant barriers
are available. For instance, provision  of biological treat-
ment, GAC adsorption, and reverse osmosis in a potable
water recovery treatment train establishes  multiple barri-
ers to the passage of total organic carbon  into the recov-
ered water. Similarly, unit process combinations can be
configured to deal with  other contaminanf categories such
as heavy metals, nutrients, and pathogens. Fortunately,
many unit processes act as barriers to move more than
one contaminant category, so the number of unit processes
required  for potable water recovery does not become ex-
cessive.
  Process redundancy refers to the provision of duplicate
unit processes to provide treatment reliability in the event
that equipment failure or maintenance requirements ren-
der a particular unit process inoperable.
                                                                       Selected Readings on Water Reuse - 53

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          not  have  regulations regarding
          potable reuse,  or evaluate potable
          reuse projects on a case-by-case basis.
          Therefore,  it is essential to identify
          and involve concerned state agencies
          early in a potable reuse assessment.
          Similarly, it is important to involve
          local agencies.  Agencies should be
          identified that have specific responsi-
          bility to  public  health,  water-quality
          standards, development of reclama-
          tion  policies or requirements, water
          ownership issues, permit require-
          ments, and potential funding sources.
            Close involvement with such agen-
          cies  is paramount to the develop-
          ment of a potable reuse implementa-
          tion  program that encourages a vari-
          ance from  regulation  prohibition,
          serves  as a  catalyst for  the develop-
          ment of potable reuse regulations,
          and  persuades responsible agencies
          of the benefits and safety of the
          potable reuse project.
            Public acceptance is  generally the
          most crucial element in determining
          the success or  failure  of a potable
          reuse project, particularly because
          regulatory agencies often have politi-
          cal roots that react to  public senti-
          ment. A  potable reuse project can be
          technically viable, the recovered
          water proven safe by the best scientif-
          ic procedures available,  and regulato-
          ry agencies poised for acceptance; yet,
          a project can still fail because of a lack
          of public acceptance. A  public educa-
          tion  program is  vital to  the success of
          a potable reuse program (see Box).
            Several technical issues and con-
          cerns are often raised during the de-
          velopment of a potable  reuse pro-
          ject, all  of which can  be addressed
by the operation of a demonstration
plant, thoughtful engineering de-
sign, and sound operations manage-
ment  (see Box).

POTABLE REUSE TREATMENT PROCESSES
AND PERFORMANCE
  Unit processes and their relative ca-
pabilities to remove specific contami-
nants are  shown in  the Figure.
Contaminant removal is considered to
be a relative measure of unit-process
ability to act as a barrier to that con-
taminant. Unit processes identified as
contaminant barriers are expected to
remove at least 50% of the contami-
nant.  Potable water recovery systems
contain more contaminant barriers
than a conventional water treatment
plant, because wastewater is typically
of poorer quality than  a conventional
surface-water or groundwater supply.
Unit processes often included in a
potable reuse  facility are biological
treatment with or without nitrogen
removal, high-lime treatment with
two-stage recarbonation, granular-
media  filtration, granular activated
carbon (GAC), demineralization
(membrane treatment), air stripping,
rapid infiltration and recovery, and
disinfection (see Box).

POTABLE REUSE CONCEPTUAL LAYOUT
AND TREATMENT SELECTION
  Selection of a potable reuse  treat-
ment and its  planned integration
into a  water-supply system is  site-
specific. The geographic layout of a
city's water resource system should
be evaluated to determine factors
that may inhibit or favor develop-
    Potable Reuse Technical Issues  and  Concerns

   The following are common issues of concern:
   • The ability to recover potable water from wastewater, safe for either in-
   direct or direct human consumption.
   • The process redundancy or operational procedures necessary to assure
   product safety in the event of mechanical and operational malfunction.
   • The flexibility to modify water recovery treatment processes in response
   to changes in raw water quality and new regulatory requirements.
   • The method of reuse or disposal of potable water waste residuals.
   • The distribution  of  recovered potable  water so that the benefits are
   shared equitably.
   • The  chemistry and benefits of blending recovered potable water with
   other finished waters.
   • The  cost and  reduced environmental impact of potable water recovery
   in comparison to other alternative water supplies.
                     Potable Reuse History

             Unplanned, indirect, potable reuse has been in practice
           since humans first began disposing wastewater into wa-
           tersheds that are hydrologically connected to raw water
           supplies. As population has increased, so has the quantity
           of wastewater and the technology to manage the in-
           creased volumes of wastewater. Potable reuse  is  one of
           the developing strategies to manage wastewater and re-
           cover and reuse water resources.
             The following is a summary of some of the  historical
           milestones marking the development of planned potable
           reuse as a viable component of a water  resource man-
           agement plan.
             In 1931, Los Angeles, Calif., demonstrated that  prima-
           ry sedimentation, secondary biological treatment, and
           sand filtration treatment of wastewater created a recov-
           ered water suitable for spreading on  soil, thereby  con-
           tributing significantly to the groundwater  supply without
           impairing its quality.
                     In  1956 and  1957, severe drought conditions forced
                   the city of Chanute,  Kans., to practice direct potable
                   reuse. Secondary treated water was impounded and re-
                   cycled back through the city's  water treatment plant
                   where it received super chlorination to inactivate the
                   greater pathogen concentrations  associated with the re-
                   cycled effluent.  No adverse health effects were noted;
                   however, after several cycles, the  water became pale yel-
                   low in color and  was aesthetically unappealing.
                     In  1960, tfie Advanced Waste Treatment Research Pro-
                   gram of the United States Public Health Service was direct"
                   ed to develop new treatment technology for renovating
                   wastewater to allow more direct and deliberate water reuse.
                     In 1962, at Whittier Narrows, near Los Angeles, Calif.,
                   disinfected secondary effluent from a 10-mgd water re-
                   clamation plant was spread on the ground for infiltration
                   to an underground potable water supply. This operation
                   continues  and the amount of reclaimed water recharged
                   annually averages 16% of the total inflow to the ground-
                   water basin.  Depending on the physical characteristics,
54 - Selected Readings on Water Reuse

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                                                                     WATER RECLAMATION/REUSE
ment of indirect versus direct  pot-
able reuse and single-plant versus
conventional-plant water recovery.
The treatment selected should  pro-
vide multiple contaminant  barriers
and process  redundancy to assure
product reliability. The conceptual
layout and specific treatment select-
ed  should satisfactorily address
health, regulatory, social, and techni-
cal issues and concerns.
  Conceptual layout.  The selection
of indirect versus direct potable re-
use and single-plant versus conven-
tional-plant  water recovery starts
with a review of the geographic lay-
out of the overall water and waste-
water system. Important factors to
review and evaluate include  location
and character of existing and future
water supplies and transmission  sys-
tems, location and character  of exist-
ing and future water treatment facili-
ties and distribution systems, cus-
tomer service area existing  and fu-
ture  demographics and zoning,  and
location and character  of  existing
and future wastewater collection  and
treatment facilities.
  Treatment selection. Based on the
conceptual layout of the potable reuse
facility, a water recovery treatment
 Unit Process Containment Barriers
     Gross
  Containment
    Category
system must be selected to reclaim
the wastewater influent to a suitable
quality for reuse. Usually, alternative
systems are conceptually developed,
evaluated, and screened to arrive at a
selected alternative for further devel-
opment.  Generally, a  qualitative and
quantitative analysis of evaluation cri-
teria is used to arrive at a selected
treatment system (see Box).
  Based  on existing  planned,  indi-
rect, potable reuse projects in opera-
tion and on  existing or planned,
demonstration-scale  direct  potable
reuse projects, there are several likely
treatment scenarios for the defined
potable reuse systems. These  treat-
ments vary on a case-by-case basis.
  Planned, indirect potable reuse
with single plant water recovery and
recycle to a groundwater of "irface-
water supply. Likely  treatment in-
cludes primary treatment, secondary
treatment, biological nitrogen re-
moval, high-pH lime  treatment with
recarbonation, filtration, activated
carbon adsorption, slip-stream re-
verse osmosis with decarbonation,
ozonation, and storage.
  Planned, indirect potable reuse with
conventional plant water recovery and
recycle to a ground-water or surface-
water supply. Likely treatment is the
same as  the previous single-plant
water recovery except the primary
treatment, secondary  treatment, and
possibly  the biological nitrogen re-
moval would be offset to an existing
treatment plant with such capabilities.
  Direct potable reuse with single-
plant water recovery and recycle to a
finished  water distribution system.
Likely treatment includes primary
location, and pumping history of a given well, the popu-
lation drawing potable water from the groundwater basin
is estimated to be exposed  to a reclaimed wastewater
percentage ranging from 0%  to 23%. After extensive data
acquisition, evaluation, and  statistical analysis, no mea-
surable adverse health effects have been correlated to the
use of the groundwater replenished with recovered water.
  In  1965, the South Lake  Tahoe Water Reclamation
Plant was the first large-scale facility to  use advance
wastewater treatment processes to remove  nutrients and
organics from wastewater.
  In 1968, the Windhoek, South Africa, experimental di-
rect potable reuse plant was commissioned;  and in 1970,
the  experimental  1.2-mgd Strander Water Reclamation
plant in Pretoria, South Africa, was commissioned. Since
1968, finished water from the Windhoek plant has occa-
sionally been used to directly  augment potable water sup-
plies. No identifiable diseases have been associated with
this water recovery and reuse  practice.
  In 1972, the Federal Water Pollution Control Act stated
                  that discharge of pollutants into all navigable waters will be
                  eliminated, thereby encouraging water recovery and reuse.
                     In  1976,  the Orange County, Calif., Water District's
                  Water Factory 21  began operation. The 15-mgd facility re-
                  claims unchlorinated secondary effluent to drinking-water
                  quality and  recharges it into a heavily used groundwater
                  supply to prevent salt water intrusion.  The water recovery
                  treatment includes lime clarification,  air stripping, recarbon-
                  ation, filtration, carbon adsorption, slip-stream reverse os-
                  mosis, and disinfection. Estimates project that no more than
                  5% of the recovered water actually  comprises the domestic
                  supply. The Orange County Water District has found no evi-
                  dence that indicates  that this indirect potable reuse practice
                  poses a significant risk to users of the groundwater.
                     In  1978, the  15-mgd Upper Occoquan  Sewage
                  Authority (UOSA) Water  Reclamation plant in Fairfax
                  County, Va., began reclaiming wastewater for subsequent
                  discharge to the Occoquan Reservoir.  The Occoquan
                  Reservoir serves more than 1 million people and is the prin-
                  ciple water-supply reservoir in Northern Virginia.  During
                                                    (continued on page 78)

                                            Selected Readings on Water Reuse -55

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          treatment, secondary treatment, bio-
          logical nitrogen removal,  high-pH
          lime treatment with recarbonation,
          filtration, GAC adsorption, full-
          stream reverse osmosis,  ozonation,
          residual disinfection, and storage.
            Direct potable reuse with conven-
          tional plant water recovery  and recy-
          cle to a finished water distribution sys-
          tem. Likely treatment is the same as
          the previous single-plant water recov-
          ery except the primary treatment, sec-
          ondary treatment, and possibly the
          biological nitrogen removal  would be
          offset to an existing treatment plant
          with such capabilities.
            Based on these  scenarios,  the in-
          direct and direct potable  reuse water
          recovery plants are very similar, except
          that the  direct potable reuse treat-
          ment includes residual disinfection
          and full-stream rather than slip-stream
          reverse osmosis. The difference seems
          marginal, but the cost for full-stream
          versus slip-stream reverse osmosis is
          substantial because of the difficulty in
          handling increased volumes of brine
          concentrate from the higher-capacity
          reverse osmosis process.
            One method to reduce the direct
          potable reuse reverse osmosis re-
          quirement is to evaluate  the  includ-
          ing of a rapid  infiltration and recov-
          ery process in the treatment train.
          This option, however, is highly site
          specific, as land requirements and soil
          and aquifer characteristics are crucial
          to its feasibility.
            The treatment scenarios focused
          on the liquid  side of the treatment;
          however, waste residuals  such as pri-
          mary and biological sludges, lime
          sludges, filter  backwash wastewater,
and spent activated carbon must also
be handled.
  Beyond liquid and waste treat-
ment, there are often considerable
costs associated with pumping and
conveyance  of the recovered water
to the point of distribution. These
requirements and costs are site spe-
cific and must be evaluated on a case-
by-case basis.

POTABLE REUSE COSTS
  The factors  that have the greatest
influence on the capital and operat-
ing costs  associated with a potable
reuse  project include the capacity of
the proposed potable reuse project;
the level and type of treatment select-
ed to recover the potable water; the
volume and type of wastes  requiring
disposal;  proximity of the potable
reuse  project to a wastewater source
and recovered water point  of distri-
bution; and the provision of ade-
quate storage capacity in the potable
recycle stream to monitor potable
quality before reuse.  This storage
may be natural (aquifers,  lakes) or
manmade (tanks, impoundments).
  The economic feasibility of potable
reuse should be based on a cost com-
parison of developing other raw water
supplies. Those cost components that
are the same, regardless of the source
of the raw water supply, should be
deleted to simplify the analysis. The
cost benefits of potable reuse need to
be accounted for; potable reuse
deletes some wastewater disposal
costs that would otherwise increase if
water supplies were increased and
reuse was not practiced.
  The economics of potable reuse
should  be evaluated against other
water supplies at the margin or in-
crement of additional water supply.
The financial feasibility of potable
reuse, however, should be evaluated
from a system-wide perspective. The
financial feasibility of implementing
a potable  reuse project comes down
to cash flow that depends on system-
wide revenues and debt service.

POTABLE REUSE IMPLEMENTATION
  The steps necessary to implement a
potable  reuse project address the is-
sues and concerns regarding water-
quality standards and public  health;
legal, regulatory, and political influ-
ences; public acceptance; and  techni-
cal process engineering. First and
foremost,  early inclusion of all state,
county,  and local regulatory agencies
in the development of a potable reuse
project is  paramount to project suc-
cess and helps to clarify agency per-
spectives and identify potential flaws.
  Second, a demonstration facility is
required  at this stage  of potable
reuse  development  in the U.S.
Although  demonstration projects are
underway in Denver, Colo., San
Diego, Calif., and Tampa, Fla., site-
specific demonstration is necessary
to address unique regulatory, public,
and technical concerns.
  Third, a regulatory approval pro-
gram is required  to promulgate
potable reuse standards of perfor-
mance and operation and to define
procedures to gain acceptance.
  Fourth, a public involvement pro-
gram is  required to  educate and gain
public acceptance of potable reuse.
  Therefore, a potable  reuse imple-
           extended droughts, the plant discharge has accounted for
           as much as 80% of the flow into the reservoir. The recla-
           mation treatment includes primary treatment, secondary
           treatment, biological nitrification and  denitrification, lime
           clarification and recarbonation, filtration, activated-carbon
           adsorption,  and disinfection. The plant is currently being
           expanded to a  38-mgd average capacity to handle  in-
           creased wastewater volumes.  No  negative health effects
           attributable to the plant or effluent discharges have been
           reported since the plant has been in operation.
             Also, in 1978, the 4.83-mgd Tahoe-Truckee Sanitation
           Agency Water Reclamation Plant in  Reno, Nev., began
           operation. This plant also uses advanced wastewater recla-
           mation processes to recover water suitable for release to
           the Truclcee River that is used as a water supply by Reno.
             From 1981 to  1983, the 1-mgd Potomac Estuary
           Experimental Water Treatment Plant was operated with a
           plant influent blend of Potomac estuary water and nitrified
           secondary effluent to simulate the influent water quality ex-
           pected during drought conditions when as much as 50% of
                   the estuary flow would be comprised of treated wastewa-
                   ter. Treatment included aeration, coagulation, clarification,
                   predisinfection, filtration, carbon adsorption, and post dis-
                   infection. An independent National Academy of Science
                   and National Academy of Engineering panel reviewed the
                   extensive testing performed by the Army Corps of Engi-
                   neers. The  panel concluded that the advanced treatment
                   could recover water from a highly contaminated source
                   that is similar in quality to three major water supplies for
                   the Washington, D.C., metropolitan area.
                      In 1983, the  1 -mgd Potable Reuse Demonstration Plant
                   in Denver, Colo., began operation. This plant was de-
                   signed to evaluate the feasibility of direct potable reuse of
                   secondary-treated municipal wastewater. After several
                   years of testing and evaluating alternative treatments, a
                   conventional-plant  potable water recovery system has
                   been selected for comprehensive health-effects testing. The
                   results of this health-effects resting will  be integrated with
                   chemical,  physical,  and  microbiological examinations to
                   provide a basis to determine the suitability of  recoversd
56 - Selected Readings on Water Reuse

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                                                                    WATER RECLAMATION/REUSE
        Unit Processes

     Biological treatment removes
  gross levels  of organic matter from
  water, thus preparing  the water for
  further processing. Although biologi-
  cal treatment removes substantial
  amounts of suspended matter, its
  principal function  is to reduce the
  dissolved organic matter to relatively
  low levels. Well-operated biological
  treatment plants produce effluent
  with soluble  5-day  biochemical  oxy-
  gen demand values of 1 to 2 mg/L.
  Additional  benefits of biological
  treatment include reduction of path-
  ogen content; removal  of heavy  met-
  als and radionuclides depending on
  the food to  microorganism ratio in
  the system, the sludge age, and the
  concentration  of  metals and  ra-
  dionuclides  in the  raw water; strip-
  ping 80% to 90% of volatile organic
  chemicals; and stripping radon if it
  is present in the wastewater.
     Biological nitrogen removal by ni-
  trification and  denitrification  pro-
  duces water from secondary effluent
  with a total nitrogen  content of 5
  mg/L. It also results removes  sus-
  pended solids, volatile organic
  chemicals,  heavy  metals,  and
  pathogens.
     High-lime treatment with two-
  stage recarbonation provides a
  number of  barriers:  coagulation
  and precipitation of suspended mat-
  ter, where an average filtered water
  turbidity less than  0.5  NTU is  rou-
  tinely achievable;  coagulation  and
  precipitation of pathogen concen-
  trations and a high pH at a level at
which  pathogens are destroyed;
and precipitation of heavy metals,
radionuclides, and phosphorus.
High-lime treatment is  the usual
method of reducing the concentra-
tions of nearly all neavy metals to
less than SDWA limits.
  Granular-media filtration re-
moves the majority of suspended
matter remaining after biological
treatment or coagulation and pre-
cipitation. Following biological treat-
ment, filtration produces turbidity
levels of 1  to 2 NTU. Following co-
agulation,  filtration reduces the tur-
bidity to less than 0.5 NTU. The re-
moval  of suspended matter auto-
matically results in a reduction of
the  microbial contamination of the
water (approximately 1 to 2 logs).
  The  benefit of  GAC  is the re-
moval of organic chemicals—
whether biodegradable, synthetic,
or volatile—by adsorption. Because
the  degree of  adsorption depends
on the  nature of the compound, for
example its molecular weight and
polarity, and  a number of other
factors, exact  removals cannot be
predicted. However, the fact that
GAC  is used in all treatment sys-
tems concerned with producing
high-quality water in  compliance
with SDWA requirements for or-
ganic compounds is an  indication
of its effectiveness.
  Demineralization, specifically
membrane treatment, is the one
method that bars all contaminants,
including  pathogenic organisms,
organic chemicals,  heavy metals
and radionuclides, nutrients, and
dissolved  solids. Reverse osmosis
and ultrafiltration are the most
widely used membrane processes.
Although ultrafiltration is less costly
to operate, reverse osmosis remains
the  favored process because of its
greater removal efficiency.
  Air stripping following mem-
brane  treatment removes  excess
carbon dioxide from the water. It
also provides a barrier to volatile
organic compounds.
  Rapid infiltration and recovery
bars the passing through of sus-
pended matter and microbial or-
ganisms. Infiltration is also an effec-
tive barrier to heavy metals and ra-
dionuclides, depending on the ion
exchange capacity of the soil.
Suspended solids can be removed
by infiltration, phosphorus by ad-
sorption, and nitrogen by nitrifica-
tion and denitrification in the soil.
Nitrogen removal is dependent  on
the  organic carbon content of the
wastewater and  is  reduced as the
biodegradable organic content of
the water is reduced.
  Chemical oxidation with ozone
and hydroxyl radical promoters
breaks down and conditions organ-
ics to a state more amenable to re-
moval in subsequent unit processes.
Breakpoint chlorination provides a
means to remove nitrogen.
  Disinfection is  normally the final
barrier to  microbial organisms. It is
most effective  at the end  of the
treatment  process where very little
suspended matter  remains in  the
water, and oxidant demand has
been greatly reduced.
water as a drinking-water supply.
  The final report, including the health-effects study results,
will be completed  in 1992.  Based on analytical testing
data to date, the water produced by this system will be the
highest purity ever proposed for a municipal potable water
supply. The treatment includes high-pH lime clarification,
recarbonation, filtration, ultraviolet disinfection, activated-
carbon adsorption, reverse osmosis, air stripping, ozona-
tion, and chlorination as a residual disinfectant.
  In 1983, the San  Diego, Calif., 1-mgd single-plant
potable water recovery demonstration facility was commis-
sioned as part of a total resource recovery program estab-
lished in San Diego. The treatment system  includes primary
treatment,  a water  hyacinth aquaculture system, coagula-
tion, clarification, filtration, ultraviolet disinfection, reverse
osmosis, aeration, carbon adsorption, and disinfection. The
program still in progress includes an extensive health-effects
study designed to determine the potential  health effects re-
sulting from reuse of the recovered water  and to compare
the recovered water to current supplies used by San Diego.
                  Results of the health-effects study are pending. A change
                  in California state law would be required to allow reuse of
                  the recovered water for potable purposes.
                    In 1985, the 10-mgd Fred Hervey Water Reclamation
                  Plant began operation in El Paso, Tex. Recovered water is
                  recharged to a drinking-water aquifer where, over a 2-
                  year period, the water travels to one of El Peso's potable
                  water wells to become part of the potable water supply.
                  The treatment of  raw wastewater  to recharge quality
                  water includes primary treatment,  activated-sludge and
                  powdered activated-carbon treatment, lime treatment, re-
                  carbonation, filtration, ozonation, and GAC adsorption.
                    In 1986, the Tampa, Fla., Water Resource Recovery
                  Pilot Plant began  operation. The pilot project was de-
                  signed to evaluate the feasibility of reclaiming denitrified
                  secondary effluent to a quality suitable for blending with
                  existing surface-water and groundwater sources for indi-
                  rect potable reuse. Several alternative treatments were
                  evaluated and one was selected  for health-effects testing
                  after 2 years of evaluation. The treatment selected includ-
                                                   (continued on page 80)

                                          Selected Readings on Water Reuse - 57

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          mentation plan should include three
          primary parallel programs with com-
          plementary objectives.
            Technical Demonstration Pro-
          gram. A technical demonstration
          program should include elements
          and  activities such as defining goals
          and  objectives; the design and con-
          struction of the demonstration facili-
          ty; the development of a demonstra-
          tion-plant operation and mainte-
          nance manual, performance criteria,
          and  reporting requirements; require-
          ments for start-up, operation, shut-
          down, and process control; the de-
          sign and implementation of water-
          quality monitoring and health-effects
          testing; and the formation of a tech-
          nical awareness committee.
            Public Involvement Program.
          The technical demonstration program
          should be developed with public in-
          volvement in mind. Emphasis should
          be placed on attractive architecture
          and  beneficial uses of demonstration-
          plant product water. A public involve-
          ment program may include a commu-
          nity awareness committee to help dis-
          seminate information and media re-
          leases, and organize tours, educational
          programs, and research opportunities.
            Regulatory Approval Program.
          The regulatory approval program is
          best developed by the appropriate reg-
          ulatory agencies. Documentation, re-
          ports, meetings, or other supporting
          information should be identified early
          so these programs can be designed to
          satisfy regulatory requirements.
            Successful completion  of the dem-
          onstration phase of the potable reuse
          implementation plan would then al-
          low progress toward design and con-
          struction of a full-scale  facility.

          CONCLUSION
            Prudent use of our water resources
                      Evaluation  Criteria

  • Water-quality results refer to the ability of an alternative water recovery
  treatment to meet physical, chemical, microbiological, and lexicological
  standards of performance and to meet or exceed the quality of the exist-
  ing receiving water source (indirect reuse) or finished water (direct reuse).
  • System reliability refers to the ability of the system to consistently pro-
  duce the required water quality through the use of multiple contaminant
  barriers, process equipment redundancy, and provision of adequate stor-
  age to allow monitoring and assessment of water quality before reuse.
  • System operability refers to the ease of operation of the system  that
  can be based on the labor expertise and man-hours  required to operate
  and maintain the system.
  • System flexibility refers to the ability of the treatment system to  respond
  to variations in  source wastewater quality and quantity  and to future
  variables that may affect performance  requirements such  as  stricter re-
  covered water standards and change over from indirect to direct reuse.
  • Waste residuals refer to the quantity, character, and handling require-
  ments  to properly dispose  of waste residuals. Disposal of  brine concen-
  trate from  a reverse osmosis process is always a major consideration
  with potable reuse projects.
  • Physical  requirements refer to the land and housing  requirements to
  support the water recovery system.
  • System costs refer to the capital and operation and maintenance costs
  associated with the liquid processing and  waste-residuals handling.
  Most important to this analysis is organizing these costs on a basis  that
  provides fair comparison to other new water-supply  alternatives. For in-
  stance, importing a  remote groundwater source would entail costs for
  pumping and transmission, out also may include additional costs for
  necessary water and wastewater treatment,  distribution, and collection
  systems to  handle the increased water flow. However, development  of a
  water  recovery  plant for  potable  reuse may preclude construction of
  water  and wastewater treatment facilities.
  • Regulatory and public acceptance refers to the site-specific concerns
  or  biases that may  inhibit development of  a  particular  potable reuse
  system alternative.
assures that water in all its states of   other undeveloped water sources. I
both natural beauty and manmade
utility is available for future genera-
tions to enjoy.  Potable reuse is one
of many methods available to extend
the utility of  our existing water
sources and reduce the pressure on
  Carl L. Hamann is director of in-
novative technology  and  Brock
McEwen  is assistant director of wa,ter
reuse at CH2M Hill in Denver, Colo.
          ed aeration, high-pH lime clarification, two-stage recar-
          bonation, filtration, GAC adsorption, and ozonation.  Final
          results of the study should be available in 1990. If imple-
          mented,  the recovered water would comprise as much as
          30% of the Hillsboro River raw water supply during low
          flow conditions.
             In 1988, the city of Phoenix, Ariz.,  conducted a potable
          reuse feasibility study to evaluate the cost-effectiveness, in-
          stitutional constraints, and social constraints associated with
          direct potable reuse.  The feasibility study results suggested
          that potable reuse is cost competitive with other alternative
          water-supply development projects for this desert-based
          city. The city is currently evaluating the pursuit of a 0.1 -
          mgd demonstration plant to document technical feasibility
          and to gain public and regulatory acceptance.
             In summary, planned, indirect potable reuse is currently
          practiced at the following locations in  the U.S.:
                    • Whittier Narrows, Calif.,
                    • Orange County, Calif. Water District's Water Factory
                    21,
                    • UOSA Water Reclamation Plant in Fairfax County, Va.,
                    • Tahoe-Truckee Sanitation Agency Water Reclamation
                    Plant in Nevada County, Calif., ana
                    • Fred Hervey Water Reclamation Plant in El Paso, Tex.
                    Direct potable reuse is still in the demonstration phase of
                  development in the U.S. Results from the Denver and San
                  Diego demonstration projects will contribute  to the ad-
                  vancement of direct potable reuse as a technically feasible
                  water-supply alternative. The major impediments to full-
                  scale  implementation of direct potable reuse will likely con-
                  tinue to be  regulatory  and  social acceptance.
                  Nevertheless, the  existing evidence to date does not indi-
                  cate that existing  potable water recovery projects present
                  an unusual or unacceptable risk to public health.
58 - Selected Readings on Water Reuse

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                                       WATER R
                 EUSE
     Potable  Water Via  Land
          Treatment  and   AWT
                                 Sherwood Reed, Robert Bastion
                  hat would have
                  been the result
                  if the land treat-
                  ment planners,
                  designers, and
                  community had
opted for advanced wastewater treat-
ment (AWT)?" Finding the answer to
this question was, in part, the purpose
of a study conducted for the U.S. En-
vironmental Protection Agency (EPA).
The study determined if land treatment
systems constructed in the 1970s were
       Wastewater

   Treatment History,

     Clayton County

    In the early 1970s, the county
  had several secondary treatment
  plants discharging to surface wa-
  ters.  Two  of these, the Casey
  plant and the Jackson plant, dis-
  charged to the Flint River. The
  mean annual flow in this river is
  only  0.34 m3/s (12 ftVs) and
  wastewater effluent discharges
  averaged 0.14 m3/s (5 ftVs) in
  1974. During summer  months,
  the wastewater effluent exceeded
  natural streamflow. The state of
  Georgia imposed new discharge
  standards and a limited flow al-
  location for these existing systems.
  Because the projected wastewa-
  ter flows were significantly higher
  that the discharge allocation, it
  was necessary to limit growth in
  the county, provide very high lev-
  els of treatment to satisfy the dis-
  charge limits, or develop a new
  treatment method discharging to
  another watershed.
meeting  their original expectations
with respect to performance and costs.
The study included comparisons of
land treatment systems and AWT sys-
tems operating in the same regions and
having similar performance require-
ments. One of these comparisons in-
volved water reuse: effluent from each
system entered the potable water sup-
ply for its respective community.
  As part of the study, two wastewa-
ter treatment systems were  evaluated:
a land treatment system in Clayton
County,  Ga. (see  Box on Clayton
County History), and an AWT system
in Centerville, Va. (see Box on UOSA
History). The Clayton County system
is a municipally operated, forest-cov-
ered, slow-rate land treatment system;
the Upper Occoquan Sewage Author-
ity (UOSA) system, in Centerville, Va.,
uses AWT in a mechanical-plant.
  Although it was not the purpose of
the study to critique the planning, de-
sign, and selection decisions made at
the communities where the AWT pro-
cesses actually exist, the study allowed
a side-by-side comparison of a land
treatment system and a realistic AWT
alternative. In all cases, selecting AWT
was appropriate.

SYSTEM DESCRIPTIONS
  Clayton County,  which is immedi-
ately south of Atlanta, Ga., is a subur-
ban area with some light industrial and
commercial establishments. The county
government provides water supply,
wastewater treatment and disposal, and
power distribution. The population
served by the land treatment system was
about 85,000 in 1988.
  The area has a relatively mild climate,
with a mean annual temperature of
17°C. Typically one or two light snow-
falls occur during the winter, and daily
average minimum temperatures never
fall below 0°C. Because of the mild cli-
mate, year-round operation is possible
using suitable vegetation.
  Major system components in the se-
lected process  (see Box on Choosing
Land Treatment) included upgrades of
the two existing treatment plants, the
0.1-m3/s (2.3-mgd) Casey plant and
the 0.5-m3/s (11.8-mgd) Jackson plant,
and a land application facility (Table 1).
  The land  treatment system  re-
charges, via soil percolation, to Pates
Creek, which is the major source for
the Clayton County municipal water
supply. The surface soils at the land
treatment site are sandy clay loams with
moderate permeabilities, the deeper
soils and those underlying the surface
drainage network are sandy clays and
clays. The groundwater table varies
from 2 to 24 m (10 to 80 ft) below
the ground's surface depending on el-
       Wastewater
                  »
   Treatment History,
           UOSA
    In 1971, the state of Virginia
  determined that the 11 existing
  wastewater treatment plants dis-
  charging into the Occoquan wa-
  tershed were accelerating eu-
  trophication  in the Occoquan
  Reservoir and increasing the po-
  tential risks to the potable water
  supply. As a result, the 11  sys-
  tems were taken off-line, and the
  flow was combined and given
  state-of-the-art treatment in a re-
  gional AWT plant. UOSA  was
  established as an independent
  regional authority to  construct
  and operate the new facility.
                                                                    Selected Readings on Water Reuse - 59

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               Choosing Land Treatment in Clayton County

                The major alternatives considered were providing high levels of AWT at
             the two existing activated sludge plants, or using land treatment at another
             location for wastewater management. Five potential land treatment sites
             were evaluated, all within 12 Km (7.5 mi) of the two existing treatment
             systems, and all were forested to ensure that year-round operation would
             be possible. An extensive screening and evaluation process led to the  se-
             lection of the largest contiguous site. It was 80% forested, had well-defined
             drainage networks, and would require displacing the fewest  number of
             property owners. Detailed site investigations on this site confirmed the suit-
             ability for land treatment. The cost comparisons for developing this site
             versus AWT indicated that land treatment was the most cost effective alter-
             native for Clayton County. It was also more cost-effective to upgrade  the
             two existing plants to secondary treatment as compared to their abandon-
             ment and the construction of a new multiple-cell aerated lagoon.
                A very positive public acceptance of the land treatment concept was
             obtained by an extensive education and information program. This involved
             meetings with  local and state officials and environmental groups, tours  for
             journalists and local officials to successful land treatment systems, special
             programs for affected property owners, and hearings for the general pub-
             lic. Public acceptance has continued and land adjacent to the operational
             forested site is in demand for  residential developments. In many cases  the
             house abuts the land treatment system and operating sprinklers are visible
             in the adjacent forest. The majority of homeowners see the system as a
             benefit because further development is unlikely. However, these residential
             developments  around the perimeter of the site may limit the capability to
             expand the site if that proves necessary.

           evation and location on the site.
             The UOSA AWT system serves the
           cities of Manassas and Manassas Park,
           Va., which are in Fairfax and  Prince
           William counties in Northern Virginia.
           The area served is residential with at-
           tendant commercial establishments.
           The 1987 population served by this
           system was approximately 90,000.
             The area has a moderate climate with
           a mean annual temperature of 13°C.
           The low temperatures that occur in the
           winter include an average temperature
           in January of 3°C. There are about 20
           days/yr with persistent snow  cover.
           These conditions would have required
           some winter effluent storage for a slow-
           rate land treatment system.
             The  UOSA system  discharges to a
           reservoir and then to a stream that flows
           to the Occoquan Reservoir, which is the
           municipal water supply source. The im-
           portance of this source is recognized in
           the UOSA  discharge  requirements,
           which call for very stringent nitrogen
           removals during low- flow stream con-
           ditions when the impact of the discharge
           has the potential to be the most detri-
• ,  '«'• f,
           Whole-tree harvest at the Clayton County lond
           treatment system. The growing trees remove nutrients,
           metals, and other wastewater constituents. The whole
           tree is then harvested and removed as wood chips on a
           20-year rotational cycle.
60 - Selected Readings on Water Reuse

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Table 1—Clayton County System Components
Primary & activated sludge secondary treatment
   Jackson plant and Casey plant
   Transmission lines from the two treatment plants to a 20-mgd pumping
   station carrying undisinfected effluent.
   Transmission line to the land application facility

Land application facility0
   Effluent storage pond: 12 days detention, 66 ac
   Distribution pumps: 3 each, 1500 hp; 2 each, 28,000 gpm.
   Distribution pipes: 270 mi of buried pipe, 1.5 to 40 in.
   Risers and sprinkler nozzles: 17,500
   Land treatment area, 2650 ac
   Buffer zones: 440 ac
   Buildings and roads: 81 ac
   Flood plains and inaccessible areas: 363 ac
   Total site area: 3600 ac

"metric conversions are mgd X 0.04383 = m3/s; ac X 0.404 = ha;
hp X 0.745 = kW; mi X 1.609 = km; and in. X 25.4 = mm.
mental to the receiving water.
  The  major  components  in  the
UOSA system are listed in Table 2. All
of the components listed have at least
one backup redundant unit.

DESIGN AND OPERATING CONDITIONS
  Determining the  land area needed
for the treatment system was a critical
step  in the design and was based on
the limiting design  parameter (LDP)
approach (see Box on LDP).
  At Clayton County, the hydraulic ca-
pacity of the surface  soils limits the de-
sign wastewater application rate to 6.4
cm/wk (2.5 in./wk). Thus, the design
wastewater application would be 3.3 m/
yr (10.8 ft/yr), and the average design
daily hydraulic loading would be about
8 L/m2»d (0.2 gal/ft'.d). At this load-
ing rate, the design projections indicated
that nitrate-nitrogen  in percolate enter-
ing Pates Creek or  the groundwater
would be well below the 10-mg/L limit
required for drinking water. Moreover,
this rate is equivalent to the lower rates
typically used for household leach-field
systems and illustrates that the hydrau-
lic loading on most slow-rate land treat-
ment systems is quite conservative.
  Land treatment operation. The
wastewater is sprinkled, in rotation, on
the forested units in the land treatment
site.  Some of the applied wastewater
percolates vertically and reaches the
native groundwater table, but most of
the applied wastewater infiltrates to a
relatively shallow depth, percolates lat-
erally through the soil, and emerges as
surface or  subflow in the site's drain-
age network, which eventually flows
into  Pates Creek. Operating the land
treatment system has significantly in-
creased flow in Pates Creek. During
very dry summers a major portion of
the flow in this creek is probably per-
colate from the land treatment site.
  The site was divided into 42 blocks,
each averaging about 24 ha (60 ac).
The dominant tree species on the site
is loblolly pine, and there are also sig-
nificant stands of mixed pine and hard-
wood trees. Open land was also planted
with loblolly pine. Distribution piping
was buried and wide access lanes were
cleared at each sprinkler distribution
row. Five blocks are irrigated every day.
Seven blocks on the site are reserved
for contingency use when other areas
need maintenance or timber is  being
harvested. Currently, all of the sprinklers
in a given section are replaced on a regu-
lar schedule, and the removed units are
taken to the shop for repair and reha-
bilitation and then used as replacement
units elsewhere. This is more  efficient
than trying to find and repair individual
malfunctioning sprinklers.
  The original management plan called
for clear-cut harvesting for pulpwood
of several blocks per year by a contrac-
tor on a 20-year rotation. The cleared
areas  would  then be replanted with
pine. This procedure was used for the
first year of operations and then aban-
doned because of excessive erosion and
Table 2— UOSA AWT System, Major System Components"
Wastewater Management
Emergency storage pond, 45 X
Screening, grit removal, and conventional primary treatment
Conventional activated sludge secondary treatment
Chemical clarification (lime + polymer)
Two-stage recarbonation, with settling
Flow equalization
Multi-media filtration
Granular activated carbon (GAC) adsorption
Nitrogen treatment
   normal weather: nitrification only, total Kjeldahl nitrogen(TKN), 1 mg/L
   drought conditions: ammonia removal with ion exchange
   to 4 mg/L, breakpoint chlorination to 1 mg/L
Final filtration:  ion-exchange columns
Chlorine disinfection and dechlorination
Final effluent reservoir, 180  X TO6 gal
Final discharge to tributary of water supply reservoir

Solids Management
Biological solids: anaerobic digestion, filter press, composting
Chemical solids: thickeners, filter press, landfill
Spent GAC: on-site regeneration by carbon furnace

Ion Exchange Regeneration _
Purge columns  with sodium chloride, volatilize ammonia with sodium hydrox-
ide, and strip the ammonia with sulfuric acid in adsorption tower. Final product
is ammonium sulfate, which could be sold as a fertilizer
"metric conversion for gallons is 1 06 gal X 3785 = m3.
                                                                                    Selected Readings on Water Reuse - 61

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                Limiting Design

                   Parameter

               The LDP is the parameter or
             wastewater constituent that re-
             quires the largest land area for
             acceptable  performance. The
             LDP might be based on the abil-
             ity of the soil to pass the design
             volume of water or  on some
             wastewater constituent such  as
             nitrogen, phosphorus, organics,
             or metals. Experience witn typi-
             cal municipal effluents has shown
             that the LDP for this type  of
             project is usually the hydraulic
             capacity of the soil or the ability
             to remove nitrogen and thereby
             maintain drinking-water levels
             for nitrate in the groundwater at
             the project boundary.
                                              Table 3—UOSA Discharge Limits
          related problems caused by the con-
          tractor's equipment.
            In-house staffhas since harvested the
          trees to produce wood chips in  the
          field. The wood chips are then trucked
          to the county's secondary treatment
          plants and either used as fuel for sludge
          drying and pelletizing or as a bulking
          agent for in-vessel composting.
            AWT system. The design capacity
          of the UOSA system was 0.66 m3/s (15
          mgd) in 1987, and the actual flow that
          year averaged 0.53  m3/s (12.2 mgd).
          Future expansions  to 1.18 m3/s  (27
          mgd) and then to 2.37 m3/s (54 mgd)
          were planned. Stringent discharge lim-
          its were established for the UOSA de-
          sign (Table 3). Nitrogen limits for nor-
          mal  weather  and  drought were
          established. In normal weather condi-
          tions,  base flow from  other  surface
          streams that feed the Occaquan Res-
          ervoir would dilute the effluent nitrate
          to acceptable levels, and the concen-
          tration of the  unoxidized nitrogen
          forms  represented by total Kjeldahl
          nitrogen(TKN) was a suitable limit. In
          extreme  droughts, water in  surface
          streams is not adequate and the limit
          changes to 1 mg/L total nitrogen.
          Under extreme drought  conditions,
          the AWT effluent  is the  major flow
          component of the reservoir.
            The variable nitrogen limits require
          two different modes of operation for the
          activated sludge system component.
          Under normal weather conditions when
          the TKN limits prevail, the activated
          sludge component is operated in an ex-
          tended aeration mode. This  typically
          results in a final effluent having a TKN
          of 0.5 mg/L or less and a nitrate con-
Chemical oxygen demand (COD), 10 mg/L
Total suspended solids (TSS), 1.0 mg/L
Phosphorus, 0.1 mg/L
Surfactants, 0.1  mg/L
Turbidity, 0.5 JTU
Total Kjeldahl nitrogen (TKN), 1.0 mg/L in normal weather
Total nitrogen, 1.0 mg/L during drought


Table 4—Clayton County System Annual Loadings
Parameter
Design
assumption, lb/ac*yr
1987
actual load, lb/ac*yr
BOD5
TSS
Total nitrogen
Total phosphorus
896
896
404
224
226
178
139
76
lb/ac»yrX 1.121 = kg/ha»yr
                                              Table 5—Clayton County System Groundwoter Quality
                                                                                     Parameter, mg/L
Year
1979
1980
1981
1982
1983
1984
1985
1986
1987
Nitrogen
0.69
0.54
0.63
0.34
0.44
0.43
0.15
0.65
0.18
Phosphorus
0.03
0.03
0.04
0.03
0.02
0.09
0.01
0.01
0.04
Chloride
1.0
1.6
2.3
3.6
10.8
12.6
15.4
21.0
21.5

Table

Year
1978
1984
1985
1986
1987
6— Pates Creek Water Quality

Nitrogen
0.65
0.96
1.15
2.02
1.04

Parameter, mg/L
Phosphorus
0.05
0.05
0.26
0.32
0.17


Chloride
1.0
7.5
13.3
18.3
18.9
centration of 19 mg/L or more, so that
the total nitrogen concentration in the
effluent approaches 20 mg/L. Under
drought conditions, when the total ni-
trogen limit of 1 mg/L controls, the
activated sludge process is operated with
a short detention time to provide only
carbon oxidation so that  most of the
ammonia remains unoxidized.  Ion ex-
change and break-point chlorination will
be used to remove remaining nitrogen.
  The activated sludge  component,
when operated in the nitrification mode,
requires more aeration energy, but pro-
duces less  sludge. The effluent is  more
                stable and easier to treat in the remain-
                ing AWT units. The ion exchange col-
                umns are also part of the process in the
                nitrification mode  (see Box on Nitro-
                gen Removal), but in this case serve as
                final filters to remove the carbon fines
                and other particulates in the granulated
                activated carbon (GAC) effluent. The
                680 X 109-m3 (180 X  106-gal) storage
                pond provides 12 days effluent storage
                at the 0.66-m3/s (15-mgd) design flow.
                  The land area requirements for the
                Occoquan system were 24 ha (60 ac)
                for the treatment plant, 22 ha (55 ac)
                for the final effluent reservoir, and 20
62 - Selected Readings on Water Reuse

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Table 7— UOSA System Water Quality Concentration Data
Influent,
Parameter mg/L
Permit Limit,
mg/L
BOD5 200 —
COD 400 10.0
TSS 170 1.0
Nitrogen
normal weather 34.2 (total N) 1 .0 (TKN)°
drought periods 34.2 (total N) 1 .0 (total N)
Phosphorus 9.0 0. 1
Surfactants 5.3 0.1
Turbidity — 0.5 JTU
Effluent,
mg/L
8.0
0.1
0.5 (TKN)°
19.3(NO3)°
0.05
0.04
0.1 JTU
"As nitrogen
Table 8— Clayton County System
Upgrade Casey Plant
Upgrade Jackson Plant
Pump station and transmission line
Land treatment facility
Storage ponds
Pump and distribution system
Structures, roads, and the like
Land costs (3000 ac)a
Future salvage value of the land
Capital Costs, $ x 106
Sub total
Sub total
Total
Total, with salvage

6.95
1.42
8.37
1.70
0.46
5.30
0.60
10.30
16.66
26.73
-(10.30)
16.43
aac x 0.404 = ha
Table 9 — Clayton County System
1976 Estimate,
Item 1987$
Secondary 1,251,000
treatment
Land 837,000
treatment
Annual 0 & M Costs
1987 Actual,
1987$
2,084,000
1,015,000

1987,
$/1000gal°
0.40
0.20
°$/3.785x  1000 = $/L

ha (50 ac) for the sludge landfill. This
total of 67 ha (165 ac) is much less
than the 1477 ha  (3650 ac) required
for the Clayton County system.

SYSTEM PERFORMANCE
  It was clear from the data that the
existing  activated  sludge plants in
Clayton County were producing bet-
ter than secondary effluent with respect
to 5-day biochemical oxygen demand
(BOD.) and TSS and it was likely that
the short detention time in the  stor-
age pond contributed to further treat-
ment. The total flow in 1987 was only
0.62m3/s(14.1 mgd), which was 0.14
m3/s  (3.4 mgd) lower than that as-
sumed for design. Thus, the actual an-
nual loadings on die 1072-ha (2650-ac)
treatment area were lower than the as-
sumed annual loadings (Table 4).
  The data suggest that the design as-
sumptions were conservative  and that
the land treatment site was not stressed
and was underused during the first 10
years of operation. This then  suggests
that Clayton County might gain eco-
nomically by reducing the performance
efficiency at the activated sludge plants,
thereby allowing removal of higher
concentration of soluble BOD and the
related nutrients on the land treatment
site. System performance is evaluated
using  monitoring wells on the  appli-
cation sites and  in Pates Creek as it
flows away from the site. Nitrogen was
                                                                             Nitrogen  Removal
                                                                              The UOSA system has never
                                                                            been required to operate in the
                                                                            nitrogen removal mode since the
                                                                            plant was constructed, so the
                                                                            more liberal TKN limits have pre-
                                                                            vailed. However,  during  a 4-
                                                                            month trial period in 1982, the
                                                                            ion-exchange system was oper-
                                                                            ated for ammonia removal. This
                                                                            long-term test concluded that it
                                                                            was not practical to reach the 1 -
                                                                            mg/L  ammonia standard with
                                                                            just ion exchange. The current
                                                                            plans  are to use the  ion-ex-
                                                                            change columns to reach 3 to 4
                                                                            mg/L ammonia and then break-
                                                                            point chlorination will be used to
                                                                            achieve the required  1  mg/L.
the greatest concern, because nitrogen
was the LDP for the Clayton County
secondary treatment design. Nitrate
contamination   of  drinking-water
sources had to  be  avoided. Total ni-
trogen concentration in the groundwa-
ter and in Pates Creek at the project
boundary were monitored because
wastewater was applied beginning in
1979 (Tables 5 and 6). Phosphorus
was monitored because of its eutrophi-
cation potential. Chlorides were moni-
tored because they served as a  tracer,
confirming that wastewater percolate
reached the sampling point.
   The data indicate that chlorides in-
creased significantly from start-up un-
til 1986 and  then leveled off. The fi-
nal concentration of chlorides is about
one-half of that present in the applied
wastewater, indicating that there is sig-
nificant mixing  and dilution with the
surface water and groundwater.
   The nitrogen and phosphorus data
indicate excellent removal efficiency and,
although the pattern for nitrogen is
somewhat erratic, the concentration has
always remained below  the  10-mg/L
target value.  At the present nitrogen
loading rates, this performance can be
expected to continue indefinitely. Even
if the chloride values in the ground-
water  and  surface  water were  to
double, a phenomenon that would in-
dicate the presence of wastewater per-
colate without any dilution, the nitro-
gen concentration should only increase
proportionally and still  not exceed 5
mg/L. If the nitrogen  loadings ever
reach the design values, the percolate
nitrogen reaching the groundwater and
Pates Creek may approach, but still not
exceed, the 10-mg/L target value.
  AWT  system.   In   comparison,
                                                                               Selected Readings on Water Reuse - 63

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          Use of wood chips at the Clayton County land
          treatment system as the fuel source for a sludge
          pelletizing operation. Chips ore also used as a bulking
          agent for composting
          Sherwood C Reed
          UOSA's performance is demonstrated
          by its effluent charaeteristics. Table 7
          compares typical influent and effluent
          values to the permit requirements for
          the UOSA system.

          MANPOWER AND COSTS
            The 1987 Clayton County staffing
          requirements, including the secondary
          treatment and sludge pelletizing opera-
          tions and the land treatment compo-
          nent, totalled 61.  The staff at the land
          treatment facility increased from 13
          people when land treatment operations
          began in 1978  to 24 people in 1987.
          Staff was needed  to harvest trees and
          to maintain and repair the sprinklers
          and appurtenant equipment.
            At the present flow rate of 0.62 ms/s
          (14.1 mgd)  of capacity the manpower
          requirements would be 9.8  people/
          m3»s (4.3 people/mgd) of capacity.
            The actual capital costs of the  total
          project were within 2% of the estimate
          (Table 8). About  30% of the total was
          used to upgrade the existing activated
          sludge plants. If Clayton County had
          been required to build entirely new ac-
          tivated sludge systems, the cost for these
          components might have been about
          $10.2 million and the total would have
          been about $37 million, rather than the
          $26.73  million shown in the table. If
                                               the county had constructed aerated la-
                                               goons for preliminary treatment, the
                                               total costs might have been about $32
                                               million (all 1976 dollars).
                                                 The salvage value of the land should
                                               be much higher at the end of the 20-
                                               year design period; the cost for land
                                               adjacent to the treatment site was ap-
                                               proaching $27,750/ha ($10,000/ac)
                                               in 1988. The costs for just  the land
                                               treatment facility  would be  about
                                               $13,600/ha ($5500/ac), not includ-
                                               ing the salvage value.
                                                 The actual annual operations and
                                               maintenance (O & M) costs for sec-
                                               ondary treatment are about 67% higher
                                               than the original estimate because la-
                                     bor costs for the skill levels required
                                     to operate the system were higher than
                                     planned (Table 9). The land treatment
                                     costs are about 20% higher that the
                                     original estimate. In-house tree har-
                                     vesting accounts for most of the in-
                                     crease. With respect to the distribution
                                     of these O & M costs for the second-
                                     ary  treatment  system and the  land
                                     treatment component, the labor costs
                                     for secondary treatment are two times
                                     that for the land treatment component,
                                     and costs  reflect the skill levels in-
                                     volved—the number of people for each
                                     component is about the same (Table
                                     10). The power costs for land treat-
                                     ment are slightly higher than for sec-
                                               Toble 10—Clayton County System Distribution of Direct 1987 0 & M Costs
                                                                                    Costs, $/1000 gal
Item Secondary treatment
Labor
Chemicals
Power
Other
0.14
0.03
0.09
0.14
Land treatment
0.07
0.00
0.10
0.03
°$/3.785x 1000 gal = $/L
Table 11—Clayton County System Total Annual Costs (1987, $)"
Total direct costs                                       3,088,000
Depreciation/debt service                              2,004,000
Indirect and administrative                              1,595,000
Sale of sludge pellets                                  -(199,000)
                                             Total    6,488,000
Secondary treatment, $/l 000 gal
Land treatment facility, $/1000 gal

Total
0.85
0.41
1.26
"Total gallons treated = 5,146,500,000
Table 12—UOSA System Capital Costs, 1982 $ x 10"
Treatment system
Land acquisition
Engineering and administration
52.04
 1.69
10.87
                                            Total
64.60
"Unit cost =$4.31 million/mgd($89.23 X 10Vm3«s;
Table 13—UOSA 1987 Total 0 & M Costs
Activity
Secondary treatment
Phosphorus removal
Filtration
Carbon adsorption
Final filters
Totals
Unit O & M with ion exchange
Total Costs,
1987$
2,229,333
1,319,023
363,508
472,598
270,851
4,655,313
Unit Costs,
$/1000gah
0.50
0.29
0.08
0.11
0.06
1.04
$1.72
"metric conversion for unit cost is $/3.785 X 1000 = $/L
64 - Selected Readings on Water Reuse

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Table 14—UOSA 1987 Total Annual Costs, 1987 $
Operation maintenance and management, $
Depreciation/debt service, $
"Nitrification mode, $/gal
Ion-exchange mode, $/gal
Ion-exchange plus breakpoint chlorination, $/gal
                                             Total
                        4,655,313
                        2,077,280
                        6,732,593

                              1.50
                              2.18
                              2.46
"Total gallons treated = 4,474,706,000 (16,936.76 m3)

Table 15—Distribution of 0 & M Costs, UOSA and Clayton County
                                	Costs ($/1000 gal)
Item
UOSA, Va
Clayton Co., Ga
Labor
Chemicals
Power
Other
                        Total
   0.52
   0.11
   0.25
   0.16
 $1.04°
      0.21
      0.03
      0.19
      0.17
      0.60
"with ion exchange, costs are $1.72/1000 gal and with ion exchange and
break-point chlorination costs are $2.00/1000 gal.
ondary treatment because of the need
for transmission pumping to the site
and then distribution pumping on the
site. Using the wood chips as fuel how-
ever significantly reduces the cost of the
pelletizing operation as compared to
using natural gas or oil as a fuel source.
  The total annual cost for secondary
treatment was $225/L ($0.85 /1000
gal), and S108/L  ($0.41/1000 gal)
for the land treatment component, for
a total of $333/L  ($1.26/1000 gal)
(Table 11).
  If a completely new activated sludge
planrhad been built, the  total annual
cost might approach $373/L ($1.41/
1000 gal) because of the  higher capi-
tal costs and related debt service. If a
new aerated lagoon had been  con-
structed, the total annual  costs would
have been close to $356/L ($1.35/
1000 gal).
  The state of Georgia requires treat-
ing wastewater to secondary  treatment
levels before applying the wastewater.
Experience elsewhere with  slow-rate
land treatment indicates excellent results
with influent treated  to primary stan-
dards. A partial relaxation of the second-
ary requirement might allow a signifi-
cant expansion of future plant capacity
without additional capital expense.
  AWT system. UOSA 1987 staff re-
quirements, including all on-site person-
nel, totalled 81. At this flow rate, UOSA
uses 15 people/m3»s (6.6 people/
mgd).
  Capital costs for construction—at
the plant site only—were about $64
million (Table 12). The total cost of
     the entire AWT system in 1982 dol-
     lars was $82 million. These costs in-
     clude the provision of 100% redun-
     dancy in all components to protect the
     water supply system, but do not in-
     clude the costs of the new break-point
     chlorination facilities. The unit cost at
     design  capacity is  $98 million/m3»s
     ($4.31  million/mgd).
       O & M costs for the UOSA system
     were  compared in terms of the  total
     annual  expenditure and the unit costs
     per 3.8 m3 (1000  gal) treated (Table
     13). During this period, the system was
     in the nitrification mode and did not
     use ion  exchange and break-point chlo-
     rination for ammonia removal, so these
     costs are not included. The unit costs
     with ion exchange for ammonia re-
     moval would be $454/L ($1.72/1000
     gal) treated. The break-point chlorina-
     tion facilities costs  are not included in
     the analysis.
       The total 1987 costs for the UOSA
     system are given in Table 14. The unit
     cost per 3.8 m3 (1000 gal) is based on
     actual expenditures. The values for the
     unit costs with ion exchange and with
     ion exchange plus  break-point chlori-
     nation are estimates.

     COST COMPARISON
       Because   construction costs  are
     higher in Northern Virginia as  com-
     pared to Clayton County, a direct com-
     parison is not possible. Adjusting the
     unit costs for location produces an es-
     timate  of $88  million/m3»s ($3.84
     million/mgd) if the system had been
     constructed in Georgia in 1982. Up-
dating the previously cited Clayton
County capital costs to  1982 dollars
produces an estimate of $52 million/
m3»s  ($2.27 million/mgd) for com-
parison with the AWT value.
  The Clayton County system paid
$8500/hs ($3433/ac)  for 1212 ha
(3000 ac) of land; in Virginia, the unit
cost was $25,350/ha ($10,242/ac) for
67 ha (165 ac). At that rate, the land
costs in Northern Virginia would have
been  over  $30 million  for 1212 ha
(3000 ac). This amount of land would
not have been available in  a single block
or a few large parcels in Northern Vir-
ginia, so construction costs for the
other  land treatment  components
would have been much higher than at
Clayton County. In addition, the soil
characteristics  in the vicinity of the
UOSA plant are  not well suited for a
slow-rate  land treatment  system. It
seems clear that land treatment would
not have been  an economical alterna-
tive for UOSA. However, the purpose
of the analysis was to determine what
the costs would be had the Clayton
County authorities selected a similar
AWT system instead of land treatment.
  The UOSA O & M costs for oper-
ating  in the nitrification mode for the
gallons actually treated in 1987 are dis-
tributed to the major cost factors and
are  compared  to  the  values  from
Clayton County (Table 15).
  The addition of break-point chlori-
nation might increase UOSA's  total
O&M costs to about $528/L ($2.00/
1000 gal). The comparable cost for the
Clayton County system, which achieves
<1  mg/L total nitrogen, is $159/L
($0.60/1000 gal).
  The labor costs for UOSA are sig-
nificantly higher partly because of the
location and because the skill levels re-
quired are much higher for the AWT
process. The unit costs for the labor at
the  land treatment facility are signifi-
cantly less than at the secondary treat-
ment systems because less skilled labor
is required.
  The difference in chemical costs re-
flects the fact that Clayton County uses
few chemicals. The difference in power
costs are significant but are closer than
many would expect.  Land treatment
systems such as Clayton County, where
extensive transmission and distribution
pumping are required, are not neces-
sarily low-energy systems.

PROCESS COMPARISONS
  Both systems  are  satisfying  their
project goals and producing a  final
product that is acceptable for reuse in
their water supply systems. This capa-
bility, it seems, will not diminish over
the  long term.
                                                                               Selected Readings on Water Reuse - 65

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             UOSA's unit cost values can be com-
           pared to the $333/L ($1.26/1000 gal)
           for Clayton County's land treatment
           system as constructed, with upgrading
           of the  existing secondary treatment
           units. However, such a comparison is
           biased in favor of land treatment be-
           cause Occoquan had to build a com-
           pletely new system including the sec-
           ondary treatment components. It is
           estimated that if a new secondary treat-
           ment plant had been built at Clayton
           County,  the  total annual unit cost
           might be $373/L ($1.41/1000 gal).
           At this level, the cost advantage for land
           treatment is smaller, but still significant.
             The cost comparison is also biased in
           favor of the AWT process because the
           $396/L ($1.50/1000 gal) represents
           the nitrification mode when the system
           is discharging close to 20 mg/L nitrate.
           The  land treatment system discharges
           about 1 mg/L (average 1980 to 1987
           0.7 mg/L) total nitrogen to ground-
           A typical sprinkler used for wastewatet application
           at the Clayton County, Go., land treatment system.
water and surface water. Therefore, on
a water-quality basis, it is necessary to
compare the land treatment process to
the AWT ammonia removal process ef-
fluent to have equivalent water qual-
ity. On this basis, the total annual costs
for land treatment with a new second-
ary treatment plant would be $373/L
($1.41/1000 gal) compared to $528/L
($2.00/1000 gal) for the AWT pro-
cess. At the present flow, Clayton
County would produce a cost savings
of over $3 million/yr.

CONCLUSIONS
  It can be concluded from the com-
parisons that the goals and projections
for the  Clayton  County system were
valid and that the land treatment con-
cept was the proper choice. The land
treatment system was, and remains, the
most cost effective  alternative for the
situation in Clayton County, when com-
pared to the costs for an AWT process
capable  of producing the same-quality
final effluent. The Clayton County sys-
tem  continues, after 10 years, to pro-
duce a high-quality effluent that can be
directly  introduced  into  the drinking-
water sources for the community. That
capability is expected to continue indefi-
nitely. Similarly, selection of the AWT
process  at Occoquan was the proper
choice for the circumstances prevailing
at that location.
  The availability of a sufficient area of
suitable land at a reasonable cost is
probably the major factor for imple-
menting a cost-effective land treatment
system.  The cost of all other compo-
nents and the O & M requirements
should be less for land treatment than
for alternative processes.
  The  comparison indicated that the
land treatment system could reliably
produce an equivalent effluent at a sig-
nificantly lower cost than the  AWT
process. This suggests that in locations
where a sufficient area of suitable land
is available at a reasonable cost, land
treatment will be the more cost effec-
tive alternative.                   •

  Sherwood  Reed is an environmental
engineering consultant in Norwich, Vt.;
Robert Bastian is a scientist at the  U.S.
Environmental Protection Agency in
Washington, D.C.
66 - Selected Readings on Water Reuse

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                                       WATER REUSE
     Groundwater  Recharge
      with  Reclaimed  Water
                       in  California
                             James Crook, Tokashi Asano, Margaret Nellor
      n  California, increasing de-
   **  mands for water have given rise
   "  to surface water development
  i I  and large-scale projects for wa-
•*^  *  ter importation. Economic and
, • ,•**'.  environmental concerns associ-
ated with these projects have expanded
interest in reclaiming municipal waste-
water to supplement  existing water
supplies. Groundwater recharge repre-
sents a large potential use of reclaimed
water in the state. For example, several
projects have been identified in the Los
Angeles area that could use up to 150 x
106  m3/a  (120,000 ac-ft/yr) of re-
claimed water for  groundwater re-
charge. Recharging groundwater with
reclaimed wastewater has several pur-
poses: to prevent saltwater intrusion
into freshwater aquifers, to store the
reclaimed water for future use, to con-
trol or prevent ground subsidence, and
to augment nonpotable or potable
groundwater aquifers.1 Recharge can
be accomplished by surface spreading
or direct injection.
  With surface spreading,  reclaimed
water percolates from spreading basins
through an unsaturated zone to the
groundwater. Direct injection entails
pumping reclaimed water directly into
the groundwater, usually into a con-
fined aquifer. In coastal areas, direct
injection effectively creates barriers that
prevent saltwater intrusion. In other
areas, direct injection may be preferred
where groundwater is deep or where
the topography or  existing land use
makes surface spreading impractical or
too expensive. While only  two large-
scale, planned operations for ground-
water recharge are using reclaimed water
in California, incidental or  unplanned
recharge is widespread.
  The constraints of groundwater re-
charge with reclaimed water include
water quality, the potential for health
hazards, economic feasibility, physical
limitations, legal restrictions, and the
availability of reclaimed water. Of these
constraints, the health concerns are by
far the most important, as they pervade
all potential  recharge projects. Health
authorities emphasize that indirect po-
table reuse  of reclaimed wastewater
through groundwater recharge en-
compasses a much broader range of
potential risks to the public's health
than nonpotable  uses of reclaimed
water. Because the reclaimed  water
eventually becomes drinking water and
is consumed, health effects associated
with prolonged exposure to low levels
of contaminants and acute health ef-
fects from pathogens or toxic substances
must be considered. Particular atten-
tion must be given to organic and in-
organic substances that may  elicit
adverse  health responses in  humans
after many years of exposure.

HISTORICAL DEVELOPMENT
  In the early 1970s  several water-
quality control plans (Basin Plans) were
developed under the direction of the
State Water Resources Control Board
(SWRCB). The Basin Plans identified
as many as 36 potential projects for
groundwater recharge in the  state.
Regulatory  agencies  involved in
wastewater reclamation and reuse play
a key role  in the management of
California's water  resources  and any
projects involving the recharge of
groundwater with reclaimed water (see
Box). In 1973, the Department of
Health Services (DOHS) prepared a
position statement in response to pro-
posals in the Basin Plans for augmenta-
tion of domestic water sources with
reclaimed water. Three uses of reclaimed
water were considered in the state-
ment: groundwater recharge by surface
spreading, direct injection into an aqui-
fer suitable for use as a domestic water
source, and direct discharge of reclaimed
water into a domestic water supply.
  Position statement. The DOHS
position statement recommended
against direct discharge into a domestic
water-supply system and direct injec-
tion into aquifers used as a source of a
domestic water supply stating that some
organic constituents of wastewater are
not well enough understood to permit
setting limits and creating treatment-
control systems. In  particular, the in-
gestion of water  reclaimed from
wastewater may produce long-term
health effects associated with the stable
organic materials that remain after
treatment. It also stated that injection
to prevent saline water intrusion could
be considered  in the future. With re-
gard to surface spreading, the position
statement contained  the following:
surface spreading appears to have great
potential; information relative to health
effects is uncertain; if new information
indicates adverse effects are created with
recharge, closure of basins may be nec-
essary; specification of allowable per-
centages  of  reclaimed water in
groundwater is inappropriate at this
time because of a lack of information
on health effects; proposals for the re-
charge of small basins with large quan-
tities of reclaimed water will  not be
Groundwater recharge, occurring at the Rio
Spreading Grounds in Los Angeles, represents a large
potential use of reclaimed water in California.
                                                                    Selected Readings on Water Reuse - 67

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     "vS* Cs»
68 - Selected Readings on Water Reuse

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            Milestones in Historical Development
                    of Groundwater Recharge
   1962 The first large-scale planned operation for groundwater recharge was imple-
mented when secondary effluent from the Whittier Narrows Water Reclamation Plant in
Los Angeles County  was spread in the Montebello Forebay  area  of the Central
Groundwater Basin.
   1973 The California  Department  of Health  Services (DOHS) developed a position
statement on the uses of reclaimed water involving ingestion, essentially placing a
moratorium on new projects for groundwater recharge.
   1975 The State of California convened a Consulting Panel on the Health Aspects of
Wastewater Reclamation for Groundwater Recharge to provide recommendations  for
research thatwould assist DOHS in the establishment of statewide criteria for groundwater
recharge.
   1976 DOHS developed draft regulations for groundwater recharge that were subse-
quently used as guidelines.
   1976 Groundwater recharge by direct injection was initiated by the Orange County
Water District to prevent saltwater intrusion.
   1978 The Sanitation Districts of Los Angeles County (LACSD) initiated a 5-year Health
Effects Study to investigate the health significance of using reclaimed water for ground-
water replenishment.
   1986 The state of California appointed a Scientific Advisory Panel on Groundwater
Recharge with Reclaimed Wastewater to provide information needed for the establish-
ment or statewide criteria for groundwater recharge.
   1987 State regulatory agencies approved a 50% increase in the amount of reclaimed
water that could oe spreaa in the Montebello Forebay area.
                      Research Tasks
  Water-quality characterizations of groundwater, reclaimed water, and
  other recharge sources in terms of their microbiological and inorganic
  chemical content.
  Toxicological and chemical studies of groundwater, reclaimed water, and
  other recharge sources to isolate ana identify health-significant organic
  constituents.
  Percolation studies to evaluate the efficacy of soil in attenuating inorganic
  and organic chemicals in reclaimed water.
  Hydrogeological studies to determine the movement of reclaimed water
  through aroundwater and the relative contribution of reclaimed water to
  municipal water supplies.
  Epidemiological studies of populations ingesting groundwater containing
  reclaimed water to determine if their health characteristics differ signifi-
  cantly from a demographically similar control population.
            recommended; proposals
            for recharge of large basins
            with small amounts of
            reclaimed water may be
            possible depending  on
            community well locations
            and other conditions; and
            surface spreading as a fu-
            ture  option may  be a
            possibility.
              Consulting panel. In
            1975, a Consulting Panel
            on the Health Aspects of
            Wastewater Reclamation
            for  Groundwater  Re-
            charge was established by
            three state  agencies—
            DOHS, SWRCB, and the
            Department  of Water
            Resources (DWR).  Its
            purpose was to recom-
            mend a program of re-
            search thatwould provide
            information  to  assist
            DOHS  in  establishing
            reclamation criteria for
            groundwater recharge
            and to assist DWR and
            SWRCB in planning and
            implementing programs
            to encourage  use of re-
            claimed water consistent
            with those criteria. A state-
of-the-art report on the health aspects
of wastewater reclamation for ground-
water recharge was prepared as a back-
ground document.
  The  Consulting Panel confined its
discussions to groundwater recharge
by surface spreading and reached sev-
eral conclusions. The panel concurred
with DOHS that there were uncertain-
ties regarding potential health effects
associated with groundwater recharge
using reclaimed wastewater. The panel
suggested that comprehensive studies
directed at the health aspects associated
with groundwater recharge be initiated
at existing projects, and that new dem-
onstration projects would be needed to
gain field information under selected
and controlled conditions. The panel
stated that to provide a database  for
estimating health  risk, contaminant
characterization,  toxicology, and epi-
demiological studies of exposed popu-
lations  were needed.
  Health Effects Study. In the after-
math  of the 1976-77  California
drought,  there was considerable  pres-
sure to use supplies of reclaimed water
in southern California, particularly for
groundwater recharge. However, an
unofficial moratorium suspended new
projects and the expansion of existing
operations  until  some  health-related
issues associated with groundwater re-
charge were answered and the Consult-
                                                                     Selected Readings on Water Reuse - 69

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                    ing Panel's  recommendations  were
                    implemented. In 1978, the Sanitation
                    Districts of Los  Angeles  County
                    (LACSD) initiated a 5-year, $1.4 mil-
                    lion study of the Montcbello Forebay
                    Groundwater Recharge Project that had
                    been replenishing groundwater with
                    reclaimed water since 1962. By 1978,
                    the amount of reclaimed water spread
                    averaged 33 x 106 m'/a (26,500 ac-ft/
                    yr) or 16% of the total inflow to the
                    groundwater basin with no more than
                    40 x 106 m3 (32,700 ac-ft) of reclaimed
                    water spread in any year.  The percent-
                    age of reclaimed water contained in the
                    potable water supply ranged from 0 to
                    23% on an annual basis, and 0 to 11%
                    on a long-term (1962-1977)  basis.
                      Historical  impacts on  groundwater
                    quality and human health and the rela-
                    tive impacts of the different replenish-
                    ment sources—reclaimed  water,
                    stormwater runoff,  and imported sur-
                    face water—on groundwater quality
                    were assessed after conducting a wide
                    range of research tasks (see Box).
                      The study's results indicated that the
                    risks associated with the  three sources
                    of recharged water  were not signifi-
                    cantly different and that  the historical
                    proportion of reclaimed water used for
                    replenishment had no  measurable im-
                    pact on  either groundwater quality or
                    human  health.2 The  Health Effects
                    Study did not demonstrate any measur-
                    able  adverse effects  on  the area's
groundwater or the health of the popu-
lation ingesting the water. The cancer-
related epidemiological study findings
were  weakened by the minimal ob-
served latency period (about 15 years)
between first exposure and disease for
human  cancers. Because of the rela-
tively short time that groundwater con-
taining reclaimed  water  had  been
consumed, it is unlikely that examina-
tion of cancer incidence and mortality
rates would have detected an effect of
exposure to reclaimed water resulting
from this groundwater recharge opera-
tion.
  Groundwater recharge  regula-
tions. In 1976, DOHS developed draft
regulations for groundwater  recharge
of reclaimed  water by surface spread-
ing. The proposed criteria were princi-
pally directed at the control  of stable
organics. The level of treatment speci-
fied in the draft regulations was con-
ventional secondary treatment followed
by carbon adsorption and percolation
through at least 3 m (10 ft) of unsatur-
ated soil. Reclaimed water-quality re-
quirements were specified for inorganic
chemicals, pesticides, radioactivity,
chemical oxygen demand (COD), and
total organic carbon (TOC).  Require-
ments for  groundwater quality were
specified for  inorganic chemicals and
pesticides. An effluent monitoring pro-
gram was proposed for 20  specific or-
ganic compounds. The draft regulations
Water Factory 21 is on advanced wastewater
treatment facility whose effluent is used to prevent
saltwater intrusion into potable water-supply aquifers.
70 - Selected Readings on Water Reuse

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Table 1— Analyses of Reclaimed Water— Montebello Forebay,
Constituent
Arsenic
Aluminum
Barium
Cadmium
Chromium
Lead
Manganese
Mercury
Selenium
Silver
Lindane
Endrin
Toxaphene
Methoxychlor
2,4-D
2,4,5-TP
Suspended
solids
BOD
Turbidity
Total
coliform
Total
dissolved solids
Nitrate and
nitrite
Chloride
Sulfate
Fluoride
Units San Jose Whittier
Creek Narrows
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
n0A
^g/L
(jtg/L
n-gA
wA
(xg/L

mg/L
mg/L
TU

No./lOOmL

mg/L

mg/L
mg/L
mg/L
mg/L
0.005
<0.06
0.06
ND
<0.02
ND
<0.02
<0.0003
<0.001
<0.005
0.05
ND
ND
ND
ND
<0.11

<3
7
1.6

<1

598

1.55
123
108
0.57
0.004
<0.10
0.04
ND
<0.03
ND
<0.01
ND
0.007
ND
0.07
ND
ND
ND
ND
ND

<2
4
1.6

<1

523

2.19
83
105
0.74
1988-1989
Pomona Discharge
limits
<0.004
<0.08
0.04
ND
<0.03
<0.05
<0.01
<0.0001
<0.004
<0.005
<0.03
ND
ND
ND
ND
ND

<1
4
1.0

<1

552

0.69
121
82
0.50
0.05
1.0
1.0
0.01
0.05
0.05
0.05
0.002
0.01
0.05
4
0.2
5
100
100
10

15
20
2

2.2

700

10
250
250
1.6
ND means not detected.
restricted the maximum application of
reclaimed water to not more than 50%
of the total water spread during a 12-
month period. A minimum residence
time of 1  year  in the underground
before  groundwater  withdrawal was
specified. Other proposed requirements
included   detailed   reports   on
hydrogeology  and spreading opera-
tions, establishment of a program to
control industrial sources, development
of contingency plans, and implementa-
tion of a program to monitor the health
of the population receiving reclaimed
water. Because the proposed regula-
tions were based on  the worst-case
situation and it would have been virtu-
ally impossible for any individual project
to comply with all of the requirements,
the  proposed  regulations were not
adopted as statewide criteria but were
used as guidelines for new projects on
groundwater recharge.
  The DOHS revised the Wastewater
Reclamation Criteria in 1978 to  re-
quire that  reclaimed water used  for
groundwater recharge of aquifers car-
rying domestic water supplies by sur-
face spreading be of a quality that fully
protects public health and that recharge
recommendations be based on all rel-
evant aspects of each project. Factors to
be considered included treatment pro-
vided,  effluent  quality and quantity,
spreading-area operations, soil charac-
teristics, hydrogeology, residence time,
and distance to  withdrawal. The
amendments  required that the State
Department of Heath Services (DOHS)
hold public hearings  before projects
were approved.
  Scientific Advisory Panel. In 1986,
California commissioned a Scientific
Advisory Panel  on Groundwater Re-
charge with Reclaimed Wastewater that
offered several  recommendations  for
statewide  water-reuse activities. The
Scientific Advisory Panel concurred with
the Health Effects Study's findings.
The panel advised that the best avail-
able water in an area should be reserved
for drinking water, the Whittier Nar-
rows  Groundwater Replenishment
Project should continue, recharge  via
spreading is preferable to injection, re-
claimed water should be  disinfected
before injection or spreading, and dis-
infection should not produce harmful
by-products.  The  panel  stated that
available  treatment processes can ad-
equately remove organic constituents
of concern, all proposed groundwater
recharge projects should include pro-
spective health surveillance of popula-
tions, biochemical tests of concentrates
are necessary to determine whether
likely harmful substances are present at
low levels, state-of-the-art toxicology
studies with animals are needed for risk
evaluation, and there should be contin-
ued analytical chemistry investigation
and monitoring to  identify and quan-
tify chemical constituents.

MAJOR GROUNDWATER-
RECHARGE PROJECTS
  Two significant projects for ground-
water recharge have been implemented
in California: one in Montebello Fore-
bay and another in Orange County.
Replenishing groundwater basins is ac-
complished by artificial recharge  of
aquifers in the Montebello Forebay
area of south-central Los Angeles
County. Waters used for recharge by
surface  spreading  include local
stormwater runoff, imported surface
water from the Colorado  River and
state project, and reclaimed municipal
wastewater. The latter has been used as
a source of replenishment since 1962,
when approximately  15 x  106 nr?/a
(12,000 ac-ft/yr) of disinfected  acti-
vated sludge from the LACSD Whittier
Narrows  Water Reclamation Plant's
(WRP) secondary effluent was spread
in the Montebello Forebay that has an
estimated  usable storage capacity  of
960 x 106m' (780,000 ac-ft). In 1973,
the San Jose Creek  WRP was placed in
service  and supplied secondary effluent
for recharge. In addition, effluent from
the Pomona WRP that is not reused for
other purposes is discharged into San
Jose Creek, a tributary of the San Gabriel
River, and ultimately becomes a source
for recharge in the Montebello Fore-
bay.  The  use of  effluent  from the
Pomona WRP is expected to decrease
as the reclaimed water is used more for
irrigation and industrial applications in
the Pomona area.
  In 1978, all three reclamation plants
were upgraded  to provide  tertiary
treatment with dual-media filtration or
filtration  with activated carbon  and
chlorination/dcchlorination.3  The
groundwater  replenishment program
is operated by the Los Angeles County
Department of Public Works (DPW),
while  overall management of the
groundwater  basin is administered by
the Central and West Basin Water Re-
plenishment District.  The  DPW has
constructed special spreading areas de-
signed  to increase the indigenous per-
colation  capacity. Specifically,  this
activity has consisted of modifications
to the San Gabriel  River channel and
construction  of off-stream  spreading
basins adjacent to the Rio Hondo and
San  Gabriel rivers. The Rio Hondo
                                                                                 Selected Readings on Water Reuse - 71

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             spreading basins have 173 ha (427 ac)
             available  for  spreading and the San
             Gabriel River spreading grounds have
             91 ha(224ac).
               Under normal operating conditions,
             batteries of basins arc rotated through
             a 21-day cycle. The cycle consists of
             three  7-day periods during which  the
             basins are filled to maintain a constant
             depth, the flow to the basins is termi-
             nated, and the basins are allowed to
             dram  and dry  out thoroughly. This
             wetting and  drying operation serves
             several purposes, including maintenance
             of aerobic conditions in the upperstrata
             of the soil and vector   control in  the
             basins.
               The reclaimed  water produced by
             each treatment facility complies with
             primary drinking-water standards and
             meets total  cohform and turbidity
             requirements of less than 2.2 MPN/
             100 mL and 2  NTU, respectively.
             Analysis  of samples  taken  at  three
             WRPs from  October 1988 through
             September 1989 provides examples of
             reclaimed water quality (Tables  1 and
             2).  The WRPs tested for some con-
             stituents  in  samples  taken  daily and
             others in samples taken bimonthly to
             provide these yearly averages.
               In  1987, conceptual authorization
             was given to increase the amount of
             reclaimed water used to replenish  the
             Montebello Forebay by approximately
             50% over 3 years to allow incremental
             evaluation, contingent on data gener-
             ated by an expanded monitoring pro-
             gram. The other general requirements
             limited the total quantity of reclaimed
             water spread in any year to 50% of the
             total inflow to the basin. These require-
             ments, based on an annual running
             average, stipulated that the
             reclaimed water must meet
             all California drinking-wa-
             ter standards and action
             levels— concentrations of
             contaminants in  drinking
             water at which adverse
             health effects would not be
             anticipated to  occur. Ap-
             proval was also contingent
             upon demonstrating  that
             there was  no  measurable
             increase  in organic  con-
             taminants in the ground-
             water caused by the surface
             spreading of reclaimed wa
             ter. Since the initial autho-
             rization,  three incremental
             increases totaling 21.3 x 106
             m3/a (17,300 ac-ft/yr)
             have  been  approved, in
             creasing the quantity of re-
             claimed  water used  for
             groundwater recharge to 62
             x 106 m3/a (50,000 ac-ft/
       Table 2—Organic Analyses of Reclaimed Water—Montebello Forebay,
       1988-1989
Average Concentrations, ug/L
Constituent San Jose
Creek
Atrazine
Simazine
Methylene chloride
Chloroform0
1,1,1 -Trichloroethane
Carbon tetrachloride
1,1-Dichloroethane
Trichloroethylene
Tetrachloroethylene
Bromodichloromethane
Dibromochloromethane
Bromoform
Chlorobenzene
Vinyl chloride
o-Dichlorobenzene
m-Dichlorobenzene
p-Dichlorobenzene
1,1-Dichloroethane
1 ,1 ,2-Trichloroethane
1 ,2-Dichloroethane
Benzene
Toluene
Ethyl benzene
o-Xylene
p-Xylene
Trans- 1 ,2-dichloroethylene
1 ,2-Dichloropropane
2 Cis-1 ,3-Dichloropropenec
Trans- 1 ,3-dichloropropenec
1,1 ,2,2-Tetrachloroethane
Freon 1 1
Pentachlorophenol
ND°
ND
<2.1
5.0
<1.0
<0.2
<0.2
<0.2
<0.8
0.7
<04
<0.3
ND
ND
<0.7
ND
<1.8
ND
ND
<0.2
<0.2
ND
<0.2
<0.4
<0.4
ND
ND
ND
ND
ND
ND
ND
Whittier
Narrows
ND
ND
8.6
4.6
<1.6
<0.3
ND
ND
<0.5
<0.6
<0.3
ND
ND
ND
<0.5
ND
<1.8
<0.2
ND
<0.3
<0.2
<0.5
<0.4
<0.4
<0.7
ND
ND
ND
ND
ND
ND
ND
Ponoma
ND
ND
<4.7
5.5
<0.5
ND
ND
<0.3
4.1
<0.9
<0.5
ND
<0.3
ND
ND
ND
ND
ND
ND
ND
ND
ND
<0.3
<0.4
<0.3
ND
ND
ND
ND
ND
ND
ND
Discharge
limits, ug/L
3
10
40
d
200
0.5
6
5
5
10
10
10
30
0.5
130
130
5
5
32
0.5
1
100
680
1750
1750
10
5
0.5
0.5
1
150
30
       0 ND means not detected.
        Limit for total trihalomethanes is 100 ug/L.
       c Limit for total of both isomers is 0.5 ug/L.
                       Regulatory Authority
  The principal agencies involved in wastewater reclamation and reuse in California
are the California Department of Health Services (DOHS), local health agencies, the
State Water Resources Control Board (SWRCB), and the nine California Regional Water
Quality Control Boards (RWQCBs).
  The SWRCB and RWQCBs have  the primary responsibility for controlling and
protecting the  water quality in California, and the SWRCB is also responsible for
administering water rights. The DOHS has the authority and responsibility to establish
health-related standards for wastewater reclamation, including groundwater recharge,
and reviews project proposals and individual requirements for wastewater reclamation.
If it is determined that contamination exists because of using reclaimed water, DOHS and
local health agencies have the authority to order abatement of contamination and issue
peremptory orders. Local health agencies can impose requirements more stringent than
those specified by DOHS.
  The Porter-Cologne Water Quality Control Act gives authority to the nine RWQCBs
to establish water-quality standards, to prescribe and enforce requirements for waste
discharge to protect surface water and groundwater quality, and, in consultation with
DOHS, to prescribe and enforce reclamation requirements. Thus, DOHS's criteria for
wastewater reclamation are enforced by the regional boards, and each project must
have a permit from the appropriate RWQCB conforming to the DOHS criteria.
72 - Selected Readings on Water Reuse

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Table 3—Water Factory 21 Injection-Water Quality
Constituent
Discharge limits
Injection water

Sodium
Sulfate
Chloride
Total dissolved solids
Hardness
pH
Ammonia nitrogen
Nitrate nitrogen
Total nitrogen
Boron
Cyanide
Fluoride
MBAS
Concentration
115
125
120
500
180
6.5-8.5
—
—
10
0.5
0.2
1.0
0.5
in mg/L
82
56
84
306
60
7.0
4.7
0.4
5.8
0.4
<0.01
0.5
0.5
                                    Concentration in ng/L
Arsenic
Barium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Mercury
Selenium
Silver
50
1000
10
50
200
1000
300
50
50
2
10
50
<5.0
18
0.6
<1.0
<1.0
4.7
33
<1.0
4.3
<0.5
<5.0
3.3
yr), or approximately 30% of the total
inflow to the MontebelloForebay. This
level of reuse represents  a significant
effort  in  water conservation corre-
sponding to the replacement of potable
water that would otherwise be used by
about 50,000 households.
  Additional  research since the
completion of the Health Effects Study
conducted by  LACSD included an
evaluation of the efficiency of LACSD's
full-scale carbon filters for  removing
mutagenicity as determined by  the
Salmonella microsome assay.4 Results
from this  work indicate that average
mutagenicity removals of 80% could be
achieved based on a 10-minute, empty-
bed contact time, and that the effects of
chlorine disinfection on mutagenic ac-
tivity vary significantly. These later re-
sults suggest that chlorine can oxidize
and thus deactivate some types of mu-
tagens, but also can react with available
organic matter  to create  more muta-
gens in a given sample.
  Ongoing research has focused on the
development of a groundwater  tracer
suitable for characterizing the move-
ment of reclaimed water in groundwa-
ter  basins. The study has  thus  far
evaluated a series of alkyl pyridone sul-
fonate (APS)  compounds and several
fluorocarbon compounds in the labo-
ratory to measure the degree of adsorp-
tion of these compounds  on soils and
           their ability to withstand photodecom-
           position and biodegradation under
           aerobic  and anaerobic  conditions.
           Volatility studies and biological assays
           have been conducted to determine the
           potential of the tracer  compounds to
           elicit  acute  toxicity or mutagenicity.
           The laboratory phase of study has been
           completed and the second phase of
           study will consist of investigations to
           verify the laboratory results under ac-
           tual field conditions.
             Additional research  has been  pro-
           posed to provide comparative, supple-
           mental  data for  the  Health Effects
           Study's findings. Plans call for similar
           toxicological and chemical procedures
           to be  used to characterize any changes
           in reclaimed water  or groundwater
           quality that might have occurred since
           the study's samples were originally col-
           lected for evaluation. Additionally, the
           proposed work would  attempt to use
           current techniques to learn more about
           the characteristics of compounds in
           mutagenic fractions, thereby providing
           a better understanding of the origins
           and health significance of these com-
           pounds and the  alternatives  available
           for their removal.
             Water Factory 21 direct injection
           project. A project involving ground-
           water recharge by the injection of re-
           claimed water is operated by the Orange
           County Water District (OCWD). The
OCWD first began pilot studies in 1965
to determine the feasibility of using
effluent from an advanced wastewater
treatment (AWT) facility in a hydraulic
barrier to prevent the encroachment of
saltwater into aquifers carrying potable
water  supplies.  Construction  of an
AWT facility known as Water Factory
21 was started in 1972  in Fountain
Valley, and injection operations began
in 1976.
  Water Factory 21 has a design capac-
ity of 0.7 m3/s (15 mgd) and can treat
the secondary effluent's activated sludge
from the adjacent  Orange  County
Sanitation District's  (OCSD) Sewage
Treatment Plant by  the following unit
operations: lime clarification for removal
of suspended solids, heavy metals,  and
dissolved minerals;  air stripping (not
currently  in service) for  removal of
ammonia  and volatile  organic com-
pounds; carbonation for pH  control,
mixed-media filtration for removal of
suspended solids, adsorption with acti-
vated carbon for removal of dissolved
organics;  reverse osmosis (RO)  for
demineralization; and chlorination for
biological control  and  disinfection.
Because of a required 500-mg/L limi-
tation of total dissolved solids before
injection,  RO is used to demineralize
up to 0.2 m3/s (5 mgd) of the waste-
water used for injection.
  The feed water to the RO plant is
effluent from the mixed-media filters.
Effluent from carbon columns is disin-
fected  and blended with  RO-treated
water. Activated carbon is regenerated
on site. Solids from  the settling basins
are incinerated in a multiple-hearth  fur-
nace from which lime is recovered  and
reused in the chemical clarifier. Brine
from the RO  plant is  pumped to
OCSD's facilities for ocean disposal.
   Reclaimed water produced at Water
Factory 21 is injected into a series of 23
multi-casing wells providing 81 indi-
vidual injection points into four aqui-
fers to form a seawater-mtrusion barrier
known as the Talbert Injection Barrier.
The   injection  wells are located  ap-
proximately 5.6 km  (3.5 miles) inland
from the Pacific Ocean. There are seven
extraction wells not currently  being
used located between the injection wells
and coast. Before injection, the prod-
uct water is blended 2:1 with deep-well
water from an aquifer not subject to
contamination.  Depending on basin
conditions, the  injected  water flows
toward the ocean forming a seawater
barrier, flows inland to  augment  the
potable groundwater supply, or both.
  The AWT processes at Water Factory
21 reliably produce high-quality water.
No coliform organisms were detected
in any of the  179 samples of Water
                                                                                    Selected Readings on Water Reuse - 73

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          Factory 21 effluent tested during 1988.
          Although the discharge permit requires
          OCWD to institute a virus monitoring
          program that is acceptable to DOHS,
          virus sampling is not being conducted
          at present. A virus monitoring program
          conducted from 1975 to 1982 demon-
          strated to the satisfaction of the state
          and county health agencies that Water
          Factory 21 produces effluent that  is
          essentially free of measurable levels of
          viruses. The average turbidity of filter
          effluent was 0.22 FTU  and did not
          exceed 1.0 FTU during 1988. The
          average COD and  TOC concentra-
          tions for the year were 8 mg/L and 2.6
          mg/L, respectively. The effectiveness
          of Water Factory 21's treatment pro-
          cesses for the removal of inorganic and
          organic constituents is shown in the
          present  water-quality data for the
          blended injection water (Tables 3 and
          4). Fifty-three specific volatile organic
          compounds were not detected in injec-
          tion water samples, which were blended
          in a 2:1 ratio  with  deep-well water
          before analysis.
            The OCWD has developed a plan for
          groundwater management in response
          to potential water shortages and local
          water-quality problems. The plan
          documents several potential projects to
          reuse wastewater by groundwater re-
          charge. Included is the possible expan-
          sion of Water Factory 21 to provide
          injection water for seawater-intrusion
          barriers at  Sunset and Bolsa Gaps in
          Orange County, and for injecting re-
          claimed water directly into the ground-
          water basin in central Orange County.
          Another project under consideration is
          the construction of an AWT facility,
          similar to Water Factory 21, that would
          provide reclaimed water for a seawater-
          intrusion barrier at Alamitos Gap. Based
          on current growth projections, waste-
          water treatment capacity in the service
          area of OCSD will be exceeded by the
          year 2000. A possible project involves
          construction of a wastewater reclama-
          tion plant in the Anaheim area, where
          as much as 1.1 m3/s (25 mgd) of re-
          claimed water could be used for various
          types of reuse, including groundwater
          recharge by direct injection.

          GUIDELINES FOR GROUNDWATER
          RECHARGE
             Groundwater recharge  with re-
          claimed water represents a large poten-
          tial use of reclaimed water in California;
          yet there are few planned  recharge
          projects in  the state, partly because of
          economic considerations and continu-
          ing health concerns.  This  situation,
          coupled with  the  knowledge that
          unplanned or incidental recharge with
          wastewater is widespread and relatively
Table 4—Volatile Organic Compounds in Injection Water—Water Factory 21
Constituent	Injection water |ag/L
Methylene chloride
Chloroform
Dibromochloromethane
Chlorobenzene
Bromodichloromethane
Bromoform
1,1,1 -Trichloroethane
                     1.0
                     5.4
                     1.1
                Trace amount
                     3.7
                     0.8
                Trace amount
     The Goals and Objectives  of the Guidelines
             for Groundwater  Recharge with
            Reclaimed Municipal Wastewater
     To plan and encourage efficient use of the state's water resources and
     increase the reliability of the water supply by implementing the safe use
     of treated municipal wastewater for groundwater recharge
     To guide the RWQCBs in establishing objectives for groundwater quality
     and requirements for wastewater reclamation that will adequately protect
     health and environment while encouraging optimum use of the region's
     water resources
     To ensure that groundwater recharge with reclaimed wastewater, whether
     planned or incidental, is regulatea in a consistent manner
     To assist planning for groundwater recharge with reclaimed wastewater
     by providing the criteria and guidelines that detail the required informa-
     tion for review by regulatory agencies
uncontrolled, suggested that it  was
essential to undertake a comprehensive
review of existing regulations  and
establish statewide policies and guide-
lines for planning and implementing
new projects for groundwater recharge.
In a coordinated effort to address these
needs, DOHS, SWRCB, and DWRare
developing a document titled "Guide-
lines for Groundwater Recharge with
Reclaimed Municipal Wastewater." It
is anticipated that the guidelines will be
adopted by the DOHS in 1991  (see
Box).
  The proposed  guidelines include
principles, permitting procedures, and
criteria for groundwater recharge. The
criteria for surface spreading and injec-
tion of reclaimed water will address
treatment processes, treatment reliabil-
ity, water quality, monitoring,  dilu-
tion,  time underground,  distance to
withdrawal, and operational procedures.
It  is  anticipated that criteria for
groundwater  recharge  will be some-
what  flexible  and take  into consider-
ation  site-specific conditions such as
percolation rate and depth to ground-
water. The criteria are currently under
development  by DOHS, with input
from  other state and local regulatory
agencies, and operating agencies. The
guidelines will  also include a back-
ground document to provide a detailed
rationale for the criteria.           •
  James Crook is a principal engineer
with Camp Dresser & McKee  Inc. m
Clearwater, Fla.; Takashi Asa-no is the
water reclamation specialist with the
California State Water Resources Con-
trol Board in Sacramento, Calif., and is
also an adjunct professor in the Depart-
ment of Civil Engineering at the Uni-
versity of California at Davis, Calif.;
Margaret Nellor is head of the Indus-
trial Wastes Section  of the Sanitation
Districts of Los Angeles County, Whittier,
Calif.

REFERENCES
  1. Asano, T.,  (ed.) "Artificial  Re-
charge of Groundwater." Butterworth
Publishers, Stoneham, Mass. (1985).
  2. Nellor, M.H., et al. "Health Ef-
fects Study Final Report." County
Sanitation Districts of Los Angeles
County, Whittier, Calif. (1984).
  3. Crook, J., "Water Reclamation."
In Encyclopedia of Physical Science and
Technology,  1990 Yearbook. Academic
Press, Inc., San Diego, Calif. (1990).
  4. Baird, R.B., etui., "GC - Negative
Ion CIMS and Ames Mutagenicity As-
says of Resins in Advanced Wastewater
Treatment Facilities." In Advances in
Sampling and Analysis of Organic Pol-
lutants from Water. I.H. Suffet and M.
Malaiyandi  (Eds.), Vol.  2, ASC Ad-
vances in Chemistry, Washington, D.C.
(1987).
74 - Selected Readings on Water Reuse

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