United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/625/R-92/010
September 1992
Technology Transfer
v>EPA Summary Report
Small Community
Water and Wastewater
Treatment
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EPA/625/R-92/010
September 1992
Summary Report
Small Community Water and Wastewater Treatment
Prepared for:
U.S. Environmental Protection Agency
Center for Environmental Research Information
26 West Martin Luther King Drive
Cincinnati, OH 45268
Prepared by:
Science Applications International Corporation
501 Office Center Drive
Fort Washington, PA 19034
Printed on Recycled Paper
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NOTICE
This material has been funded wholly or in part by the United States Environmental Protection Agency
(EPA) under Contract No. 68-C8-0062to Science Applications International Corporation (SAIC). It has
been subjected to the Agency's peer and administrative reviews and it has been approved for
publication as an EPA document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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ACKNOWLEDGMENTS
Appreciation is expressed to the following individuals who assisted by providing technical direction and
resource materials for the development and presentation of the pilot workshops and this publication:
James E. Smith, Jr.
James F. Kreissl
A.W. Marks
Marlene Regelski
Lorene Lindsay
Kathleen Stanley
Buss Donaghue
Karen Mancl
U.S. EPA, Center for Environmental Research Information
U.S. EPA, Center for Environmental Research Information
U.S. EPA, Office of Ground Water and Drinking Water
U.S. EPA, Office of Wastewater Enforcement and Compliance
Coalition of Environmental Training Centers
Rural Community Assistance Program
National Rural Water Association
Ohio Cooperative Extension Service
The following individuals are recognized for their assistance in the development of the case studies
presented in this publication:
Fred Testa
Elwin Fisher
Dick Elliot
Thomas F. Poage
Jerry Love
Peter Thurston
David Casey
Carl Meuer, Jr.
Jim Berry
Mary Baiza
Herbert L. Pratt
Jeff Tracy
New York Department of Environmental Conservation
Town of West Monroe
Stearns and Wheler Engineers and Scientists
Poage Engineering and Surveying, Inc.
Town of Westfir
Oregon Rural Community Assistance Program
Mockingbird Hill Water Association
Blaylock, Threet, Phillips and Associates, Inc.
Mockingbird Hill Water Association
Community Resource Group, Inc.
Community Resource Group, Inc.
Rural Community Assistance Corporation
Peer review was performed by the following individuals:
Randy Revetta U.S. EPA Center for Environmental Research Information
Walt Feige U.S. EPA Risk Reduction Engineering Laboratory
Jim Westrick U.S. EPA Office of Ground Water and Drinking Water
Technical oversight during the development of the pilot workshops and this publication was provided
by Daniel J. Murray, Jr., U.S. EPA Center for Environmental Research Information. Case study
preparation, technical writing, editorial work, production, and design was provided by Stephen Dowhan,
Jo-Ann Hockemeier, Mark Klingenstein, Yvonne Ciccone, William Hahn, Lynn Sadosky, and Lisa
Kulujian of Science Applications International Corporation.
in
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Table of Contents
Page
Introduction (
Technology Overviews
Wastewater Treatment 5
Pressure Sewers 7
Vacuum Sewers 10
Small Diameter Gravity Sewers 14
Package Treatment Plants .16
Trickling Filter Plants 19
Oxidation Ditches 21
Sequencing Batch Reactors 23
Lagoons 26
Intermittent Sand Filters 29
Land Treatment Methods 32
Submerged Bed Constructed Wetlands 36
Sludge Treatment and Reuse 38
Drinking Water Treatment.... 41
Coagulation/Flocculation 43
Sedimentation 45
Filtration 47
Disinfection 51
Activated Carbon 54
Case Studies
Wastewater 57
West Monroe, New York 59
Mapleton, Oregon 63
Portville, New York 67
Drinking Water 71
Los Ybanez, Texas 73
Westfir, Oregon 76
Mockingbird Hill, Arkansas 80
Resource Directory . 83
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INTRODUCTION
OVERVIEW
Small communities face a variety of environmental
infrastructure and public health issues. One of the largest
concerns of a small community is the provision of safe
drinking water and reliable wastewater collection and
treatment. Due to their size, small communities are often
limited in their ability to address this technically complex
and potentially costly issue.
Many organizations existto provide technical and financial
services to small communities as they struggle with their
drinking water and wastewater problems. These "service
providers", through a network of local, county, state, and
regional offices, are uniquely qualified to assist small
communities in identifying the most cost-effective solutions
to their problems. Four such organizations are: the
National Rural Water Association (NRWA); the Rural
Community Assistance Program (RCAP); the Coalition of
Environmental Training Centers (CETC); and the U.S.
Department of Agriculture, Cooperative Extension Service
(USDA-CES). Traditionally, these organizations work
with the U.S. Environmental Protection Agency (U.S.
EPA) to provide valuable technical assistance to small
communities dealing with many different environmental
and public health issues.
PROJECT DESCRIPTION
During the summer of 1991, two pilot workshops were
conducted to test a unique conceptf or providing assistance
to small communities. The U.S. EPA's Office of Water
(OW) and Office of Research and Development (ORD)
collaborated to develop a two-day workshop designed to
assist small communities dealing with the many new
drinking water and wastewater treatment requirements.
Different U.S. EPA perspectives on small-community
drinking water and wastewater problems were provided
by the Office of Ground Water and Drinking Water
(OGWDW); the Office of Wastewater Enforcement and
Compliance (OWEC); the Risk Reduction Engineering
Laboratory (RREL); and the Office of Technology Transfer
and Regulatory Support (OTTRS).
This cooperative effort produced a workshop that combined
technical presentations, open discussions, and group
exercises to achieve the following objectives:
To provide technical information on drinking water
and wastewater technologies suited for small-
community applications
To provide a forum for small-community decision
makers (mayors, council members, town
managers) and drinking water and wastewater
system operators to foster improved
communications at the local level
To use the talents of local, county, and state
service providers (NRWA, RCAP, CETC, USDA-
CES) to develop and present technical information
and to provide important local perspectives on
drinking water and wastewater issues
To improve communication among small
communities and the network of government
agencies and non-government organizations that
provide technical and financial assistance
To encourage communication and cooperation
among small communities to develop and
implement mutually beneficial solutions to drinking
water and wastewater problems
Pilot workshops were conducted in Lafayette, Louisiana
and Eugene, Oregon. In both locations, local, county,
state, and regional service providers were involved to
provide local insights into the problems faced by the
participating small communities. About 15 to 20 small
communities were represented at each workshop.
The following issues were addressed during the two-day
workshop:
Drinking water and wastewater regulations
Building a good management team
Importance of well trained operators
Drinking Water distribution and treatment systems
Wastewater collection and treatment systems
Funding and maintaining financial health
Small community self-assessment
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Four Utah Communities Work Together
to Reduce the Cost of Complying with
........................ ...... ^
[[[ Analyses ....... Rli^irements -ป"-?
The 1 986 amendments to the Safe Drinking Water
Act resulted in new sampling and analyses ,
requirements for small communities. Many small
communities have a limited understanding of the
technical aspects of the new requirements and
the costs for additional sampling and analyses
can be high.
Several communities in Washington County, Utah
have banded togetherto help each otherto comply
with newvofatiie organic compound (VOC) testing
requirements. Assisted by the Rural Community
Assistance Corporation (RCAC) and the Five
County Association of Governments (FCAG).the
communities Identified state-certified laboratories
and negotiated the best price for the VOC analyses.
The laboratories offered discount rates for the,
testing, provided the group submit samples as
one entity.
RCAC and FCAG provided technical assistance
on proper sampling procedures to the system
operators in these communities and also facilitated
several meetings for the system operators to
discuss other issues of mutual interest. The
communities have continued to meet on a quarterly
basis to discuss problems and have received
technical presentations from state and U.S. EPA
speakers.
PROJECT RESULTS
Comments supplied by the participants indicated they felt
the pilot workshops were successful. While many of the
participants valued the technical information presented,
many also valued the workshop's emphasis on the
Importance of teamwork and communication within and
among communities. Many participants also thought the
service providers supplied previously unknown information
on available technical and financial resources.
The workshop materials developed for use in these pilot
workshops have been distributed to the service providers,
who have been encouraged to incorporate all or part of the
workshop into their ongoing small-community outreach
efforts. This Summary Report, which documents the results
oftheworkshops.isanotherproductofthepilotworkshops.
To continue the momentum created by the workshops,
this report presents information on drinking water and
wastewater technologies suited to small-community
applications. Six case studies illustrate the use of effective
communication, available technical and financial services,
and cost-effective technologies for the solution of small-
community drinking water and wastewater problems. This
report also provides a directory of state and regional
locations of the U.S. EPA, NRWA, RCAP, CETC, and
USDA-CES.
SUMMARY REPORT DESCRIPTION
The Technology Overview section of this report presents
summaries of drinking waterandwastewatertechnologies
suited to small communities. These overviews do not
include every technology suitable for small-community
application. Rather, the overviews present technical and
cost information on those technologies most widely used.
As every small-community drinking waterand wastewater
problem is unique, the selection of the most appropriate
technology should be based on the site-specific
environmental, public health, and financial constraints
each small community faces.
The Technology Overviews - Wastewater Treatment
summaries present information on collection systems,
treatmenttechnologies, and sludge treatment and disposal
methods. The Technology Overviews - Drinking Water
Treatment summaries present information on the most
widely applied treatment technologies. Each technology
overview presents a process description and discussions
of operation and maintenance requirements, the limitations
of the technology, and financial considerations.
The Case Studies section of this report presents case
studies that show how six small communities addressed
their unique drinking water and wastewater problems.
Case studies were selected that best illustrate the use of
cost-effective technologies and available technical and
financial assistance.
Case Studies - Wastewater presents three case studies:
West Monroe, New York
This small community effectively used assistance
from the New York State Department of
Environmental Conservation's Self-Help Program
and the Oswego County Department of Health to
evaluate numerous wastewater collection and
treatment options. West Monroe selected low
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Mapleton, Oregon
This small community received valuable
assistance from the Oregon Department of
Environmental Quality, the Lane County Board of
Health, and the Oregon Rural Community
Assistance Program. Mapleton selected a two-
cell recirculatingfiltertotreatwastewater received
from a system of new sewers (service lines,
laterals, and mains) and new septic tanks.
Portville, New York
This village was willing to step back from the
process of selecting an appropriate treatment
system, evaluate its progress, and change
direction based on its knowledge of small
community problems. While this case study
presents a successful project and many positive
experiences, it also illustrates some of the pitfalls
that can be encountered by small communities.
Case Studies - Drinking Water presents three case studies:
Los Ybanez, Texas
This small community worked effectively with the
Community Resources Group, Inc., a private,
non-profit rural development organization, to
obtain funding and technical assistance. The
selection of a reverse osmosis system was largely
based on information provided by a neighboring
community.
Westfir, Oregon
This community obtained assistance from the
Rural Community Assistance Corporation and
the Lane County Housing Authority and
Community Services Agency. Westfir ultimately
selected slow sand filters to treat its drinking
water. The community also solved other related
problems by installing new intake pumps, a sodium
hypochlorite disinfection system, and new water
supply pumps.
Mockingbird Hill, Arkansas
This very small community received financial and
technical assistance from the Farmers Home
Administration and the Arkansas Rural Water
Association. The community eventually selected
an air stripping and package precipitation
treatment system to deal with ground water with
high levels of hydrogen sulfide and dissolved and
suspended solids.
The Resource Directory section of this report presents
listings of state and regional organizations that can pro-
vide a wide variety of technical and financial services to
small communities. These organizations can be con-
tacted as small communities address their drinking water
and wastewater problems and start to identify the techni-
cal and financial resources available to them.
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TECHNOLOGY OVERVIEWS - WASTEWATER TREATMENT
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PRESSURE SEWERS
TECHNOLOGY APPLICATIONS
Pressure sewer systems provide small communities with
an economical alternative to more expensive conven-
tional gravity sewer systems. Pressure sewers are most
cost-effective in areas where housing density is low and
the terrain is rolling. They can also be effective where the
terrain is extremely flat, significant bedrock is present, or
the groundwater table is high.
PROCESS DESCRIPTION
The components of pressure sewer systems may be
subdivided into the sewer main components and onsite
system components. These subsystems are briefly de-
scribed in the following paragraphs.
Sewer main components typically consist of the following:
Sewer mains are usually installed using PVC or poly-
ethylene pipe ranging in diameter from 2 to 8 inches.
The actual diameter selected depends on the number
of homes to be served and the need to maintain a
cleansing velocity of 2 feet per second. Pressure
mains are installed at a minimum depth of 30 inches.
Deeper installations are necessary in colder climates
or high traffic locations. Since the small diameter
plastic pipe used is somewhat flexible, the sewer
mains can be routed around obstacles.
Isolation valves may be installed almost anywhere in
the system. They are usually located at intersections
or terminal ends of mains; on long, steep grades; at
bridge or stream crossings; or as part of the design of
other facilities, such as cleanouts or flowmeters.
Cleanouts may be installed where pipe sizes change,
at the terminal ends of mains, or in service laterals.
Air release valves are usually installed at high points in
the sewer mains to vent excess air that may accumu-
late at these points. Valves designed for drinking water
systems have not worked well in these applications
and should not be used.
Two types of onsite systems may be installed: Septic
Tank Effluent Pump (STEP) units or Grinder Pumps
(GPs). These systems consist of the following:
STEP systems (see Figure 1) typically consist of a
septic tank and submersible pump at each service
connection. The septic tanks are usually 1,000- gallon
prefabricated concrete or fiberglass units with internal
baffles. The tanks must be watertight to prevent the
infiltration of groundwater. Grit, settleable solids, and
grease are removed from the raw wastewater in the
septic tanks. Centrifugal submersible pumps are used
to pump the septic tank effluent to the sewer main.
STEP pumps may be installed inside the septic tank
using an internal vault orinapump vault external to the
septic tank. The pumps may be 1/3 to 1/2 horsepower
(HP). The discharge line from the pump is equipped
with a check valve and gate valve. Electrical service is
required at each service connection. In most installa-
tions, three mercury float liquid level sensors are in-
stalled in the pump vaults: two to turn the pump on and
off and one to trigger a high water alarm.
GP installations (see Figure 2) do not include a septic
tank. Instead, the building sewer is connected to a
fiberglass pump vault, 3 feet in diameter with a liquid
capacity of 40 gallons. A centrifugal or progressing
cavity GP is suspended inside the pump vault. The
vault also contains liquid level sensors, as described
previously, to operate the pump. GPs shred or reduce
the size of wastewater solids, which results in a
pumpable slurry. The pumps are usually 1 to 2 HP and
require 220 V electrical service. Pump discharge lines
to the sewer main are generally plastic, 1.25 inches in
diameter, and contain a check valve and gate valve.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Small systems of approximately 300 homes or less do not
normally require a full-time staff. Service can be per-
formed by personnel from the municipal public works or
highway department who have received instruction in
system O&M requirements. The routine O&M require-
ments of both STEP and GP systems are minimal. The
majority of the system maintenance activities are in re-
sponse to homeowner service calls. Most of the service
calls are due to electrical control problems or pump
blockages. STEP systems also require periodic pumping
(once every 5 to 7 years) of the septic tank contents.
Due to the inherent septic nature of the wastewater
present in pressure sewers, the system personnel must
take appropriate safety precautions whenever they un-
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On-Site STEP Components: Alternative A
Separate Pump Well
Automatic Air
Release Valve
On-Site
llr
r,
House
Plumbing
STEP Components: Alternative B
Integrated Pump Well
Pump Well
"
Septic Tank 1
Scum s_
*1^_
Sludge
Gate
1 A ff
1 ^
1 -^ -
.
1 1/4" s
"/j Main
"\Check
Valve
^x. Effluent
Pump
. - I
Float Switches
Figure 1. Schematic of a STEP pressure sewer system.
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On-Site Grinder Pump Component
d
Pump Well
4"
House Plumbing
Float Switches x
X
7
Gate
Valve
Check \ _
Valve M>
> H
" ofi
* / \ 1
1 1/4"
O
., Grinder Purr
Main
Automatic Air
Release Valve
Main Sewer
ป Flow Direction
Figure 2. Schematic of a GP pressure sewer system.
dertake maintenance activities to minimize exposure to
toxic gases, such as hydrogen sulfide, which may be
present in the sewer lines, pump vaults, or septic tanks.
Occasionally, odor problems may develop in pressure
sewer systems. In many cases, improper house venting
has been the cause of odor problems. The addition of
chemicals such as chlorine or hydrogen peroxide which
are strong oxidizing agents may be necessary to control
odor in situations where venting is not the cause of the
odor problem.
Generally, it is in the best interests of the municipality and
the homeowners to have the municipality or sewer utility
responsible for the O&M of all system components. Gen-
eral easement agreements are needed to permit access
to onsite components, such as septic tanks, STEP units,
or GP units located on private property.
TECHNOLOGY LIMITATIONS
Pressure sewers are usually not as cost-effective as
conventional gravity sewers when the treatment plant is at
a lower elevation than the collection system and the
service area undulations are of low relief. Due to the
septic nature of the wastewater generated by these sys-
tems, corrosion-resistant materials, such as plastic pipe
and fittings, must be used throughout the system. Both
STEP and GP systems may experience problems due to
interruptions in the electrical power service, pump block-
ages, or float switch malfunction caused by excessive
grease accumulation in the pump vault. STEP systems
may also experience sewer main blockages due to the
failure to periodically remove sludge from the septic tanks.
Excessive infiltration or inflow problems may occur from
building sewers, leaking septic tanks or pump vault cov-
ers, and connections from building roof and basement
drains.
FINANCIAL CONSIDERATIONS
Cost estimates for construction vary widely depending on
site-specific conditions. The feasibility of using a
community's public works staff and equipment to install all
or parts of a pressure sewer system should be considered
to reduce installation costs. Accurate O&M costs for
pressure sewers have not been well documented. Gross
estimates for construction and O&M costs are presented
in Table 1. These estimates were prepared by updating
cost data presented in EPA's Innovative and Alternative
Technology Assessment Manual. Communities planning
to install pressure sewers should check with nearby com-
munities using these systems to obtain more reliable cost
information.
Table 1. Estimated Construction and O&M Costs
for Low Pressure Sewers (1992 $)
Component
Annual
Construction 6&M
Costs ($) Costs ($)
Sewer Mains (PVC)
1-3 Inch Diameter
4-6 Inch Diameter
STEP Units
Septic Tank, Pump,
Controls, Service
Line, etc.
GP Units
GP, Controls, Pump
Vault, Service Line, etc.
5.30/foot
6.20-8.20/foot
2,110-4,000
2,820-4,140
175-350/mile
90
130
Bibliography
Alternative Wastewater Collection Systems. EPA/625/1 -
91/024, U.S. Environmental Protection Agency, Cincin-
nati, Ohio, 1991.
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
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VACUUM SEWERS
TECHNOLOGY APPLICATIONS
Vacuum sewers can be a cost-effective alternative to
conventional gravity sewers under one or more of the
following conditions: flat terrain or rolling terrain with small
elevation changes, high water table, low population den-
sity, orthe presence of bedrock at shallow depths. Vacuum
sewer systems do not experience the odor and corrosion
problems inherent in small diameter and pressure sewer
systems.
PROCESS DESCRIPTION
A vacuum sewer system (see Figure 1) has three major
subsystems: the central collection station, the collection
network, and the onsite facilities. Vacuum is generated at
the central collection station and is transmitted by the
collection network throughout the area to be served.
Sewage from conventional plumbing fixtures flows by
gravity to an onsite holding tank. When about 10 gallons
of sewage has been collected, the vacuum interface valve
opens for a few seconds allowing the sewage and a
volume of air to be sucked through the service pipe and
into the main. The difference between the atmospheric
pressure behind the sewage and the vacuum ahead
provides the primary propulsive force. The fact that both
air and sewage flow simultaneously produces high veloci-
ties which prevent blockages. Following valve closure,
the system returns to equilibrium and the sewage comes
to rest at the low points of the collection network. After
several valve cycles, the sewage reaches the central
collection tank, which is under vacuum. When the sewage
reaches a certain level, a conventional non-clog sewage
pump discharges it through a force main to a treatment
plant or gravity interceptor.
The vacuum interface is a unique component of a vacuum
sewer system. These valves operate automatically using
pneumatic controls. The onsite facilities do not use any
electricity. The valve is placed in a valve pit (see Figure 2)
buried above the holding tank.
On-Site Components
y|nt Valve vacuum
pit - Valve
Holding Tank
Vacuum v|cuum
Reserve pu.mP
Tank" |"
*
Central
Collection
* Station
Valve
Figure 1. Vacuum sewers.
10
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L
TRAFFIC OR NON-TRAFFIC COVER AVAILABLE
MASS CONCRETE
//fS/HSfi
VALVE CONTROLLER
ANTI-FLOTATION COLLAR
L
GRAVITY SEWERS
FROM 1-4 HOMES
FIBERGLASS SUMP
Figure 2. Vacuum sewers.
Plastic pipe is used throughout vacuum sewer systems.
The gravity flow house sewer is usually 4-inch diameter
pipe. It contains an external vent to admit air when the
valve cycles, preventing the house plumbing traps from
being sucked dry. Typical service connections are 3-inch
pipe; mains range in size from 4 to 10 inches depending
on the flow and layout. Joints are either solvent-welded or
vacuum-certified rubber ring types.
The profile of the collection network makes use of the
limited ability of vacuum propulsion to flow upward in order
to avoid excessive excavation. Where the ground slopes
in the flow direction more than 0.2 %, the pipe parallels the
ground. Otherwise the pipe is laid with a downward slope
of about 0.2 % until the depth becomes excessive. When
this occurs, a lift formed by two 45-degree elbows and a
short length of pipe (see Figure 3) is inserted to gain
elevation. The typical lift raises the pipe by 2 feet or less,
but higher lifts have been used. Division valves are
usually placed at main junctions and at about 1,500-foot
intervals to facilitate troubleshooting and repairs. Service
lines or tributary mains always join the continuing main
from above through a Y-connection.
Several mains may be served by a single collection
station. Each main is connected directly to a collection
tank through a division valve. Air flows through the
collection tank through a vacuum reserve tank to the
vacuum pumps, which discharge to the atmosphere. Dual
vacuum pumps are provided to improve reliability. Both
liquid ring and sliding vane pumps have been used.
Automatic controls cycle the vacuum pumps alternately to
maintain the vacuum in the desired range, usually 18 to 23
feet of water. A backup diesel generator set is used to
maintain service during electrical outages. An autodialing
telephone alarm is provided to summon the operator in
case of malfunctions.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Operator training provided by the system manufacturer is
critical to proper O&M of vacuum sewer systems. The
training program should begin during the construction
phase of the project. This will permit the operator to
become familiar with all the system components, includ-
ing the locations of sewer mains, valve pits, division
valves, and other key components.
Typical operation of vacuum sewersystems includes daily
checks of the vacuum station to monitor sewage pump run
times, vacuum pump oil and block temperatures, and
vacuum gauge readings. The standby emergency gen-
erator should be checked and exercised weekly. At least
twice a year, the sewer main division valves should be
inspected and exercised. All service connection vacuum
valves should be inspected annually and manually cycled
11
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45' PVC SOLVENT-WELD
SCHEDULE 40 DWV FITTING
FLOWi
SCHEDULE 40 OR SDR 21 PVC PIPE
Figures. Vacuum sewers.
to verify proper operation. The vacuum valves should be
rebuilt once everyStolOyears. The seals and diaphragm
of the controller/sensor for the vacuum valves should be
replaced every 5 years.
TECHNOLOGY LIMITATIONS
Vacuum sewers are not recommended for hilly terrain or
areas with significant elevation changes; vacuum sewers
have a maximum lift capability of 15 to 20 feet. The
Installation and O&M requirements of vacuum sewers are
more rigorous than small diameter or pressure sewer
systems. Energy consumption may also be greater for
vacuum sewers than for pressure and small diameter
gravity sewer systems. Grease accumulation on control
probes located in the vacuum station sewage collection
tank may disrupt the vacuum pump and sewage pump
operating cycles.
FINANCIAL CONSIDERATIONS
Vacuum system costs are highly site-specific. The follow-
ing costs are estimates based on a 1989 telephone survey
of 32 of 42 U.S. vacuum systems, bid tabulations, and
information from manufacturers and design engineers
and are In December 1989 dollars (ENR Construction
Cost Index=4679). These costs were obtained from U.S.
Environmental Protection Agency Municipal Wastewater
Treatment Technology Fact Sheets (1990) for vacuum
sewers which updates the original material presented in
EPA's innovative and Alternative Technology Assess-
ment Manual.
Based on data from 17 systems, the total construction
costs of a vacuum system may range from $7,000 to
$18,000 per valve. Note that one valve may serve more
than one house. A more detailed estimate can be based
on the following typical installed unit costs, but wide
variations from these values are to be expected.
3-inch interface valve, pit, cover $2,000.00
4-inch house vent $60.00
4-inch gravity flow house sewer $5.00/foot
3-inch vacuum service pipe $7.00/foot
4-inch vacuum main $8.00/foot
6-inch vacuum main $11.00/foot
8-inch vacuum main $14.00/foot
10-inch vacuum main $19.00/foot
4-inch division valve $350.00
6-inch division valve $500.00
8-inch division valve $700.00
10-inch division valve $1,000.00
4-inch cleanout $150.00
6-inch cleanout $180.00
150-gpm prefabricated
central collection station,
including building, excluding land $116,000.00
12
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Accurate O&M costs for vacuum sewers have not been
well-documented. However, for planning purposes, the
following figures (in February 1992 dollars) may be used
to estimate annual O&M costs:
Annual O&M costs per valve pit
Annual O&M cost per
$5.32
central collection station
Power consumption
$2,540.00
250 kWh/yr/customer
Bibliography
Alternative Wastewater Collection Systems. EPA/625/1 -
91/024, U.S. Environmental Protection Agency, Cincin-
nati, Ohio, 1991.
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
The following formula may be used to compute total
estimated vacuum sewer system annual O&M costs:
C = 2540*NS + 205*LR*NS + 0.5*LR*NDV + 5.3*NIV +
1.2*LR*NIV + 250*NIV*ER
where:
o
NS =
LR =
NDV =
NIV =
ER =
Annual O&M costs (February 1992 dollars)
Number of central collection stations
Labor rate including fringe benefits and
overhead (February 1992 $/hour)
Number of division valves
Number of vacuum interface valves
Electric power rate (February 1992 $/kWh)
13
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SMALL DIAMETER GRAVITY SEWERS
TECHNOLOGY APPLICATIONS
Small Diameter Gravity Sewers (SDGS) are suitable for
low-density residential and commercial developments.
SDGS systems collect the effluent from septic tanks and
transport the wastewater to a community treatment plant
by gravity. Unlike conventional large diameter gravity
sewers, SDGS do not require straight alignment and deep
excavation and may be installed on a variable gradient
provided that there is enough elevation head to maintain
flow In the desired direction. SDGS can be installed where
the terrain is too flat for conventional gravity sewers.
PROCESS DESCRIPTION
Typical SDGS systems consist of the following compo-
nents: building sewer, septic (interceptor) tank, service
laterals, collector mains, cleanouts, manholes, and vents
(see Figure 1). Some systems may also include lift
stations when elevation differences do not permit gravity
flow in the collection mains. When the collector main
hydraulic gradient is greater than a service lateral, a
Septic Tank Effluent Pump (STEP) unit may be installed
In the individual service lateral to overcome the head
differential. A brief summary of SDGS system compo-
nents follows.
* Building sewers convey raw wastewaterf ram the build-
Ing to the septic or interceptor tank. To prevent
blockages, no smaller than 4-inch diameter pipe should
be used.
Septic tanks are critical components of SDGS sys-
tems. They permit the removal of a significant portion
of settleable solids and grease from the raw wastewa-
ter. Septic tanks also provide for flow equalization and
storage of the settled solids. The tanks are typically
1,000-galIon prefabricated watertight concrete or fi-
berglass units with internal baffles. Larger tank vol-
umes are necessary when multiple dwellings are con-
nected to a single tank.
Service laterals convey the septic tank effluent to the
collector mains. They are typically 3- or 4-inch plastic
pipe. The diameter of the lateral should not exceed the
diameter of the collector main. Service laterals in low-
lying areas may also contain check valves to prevent
backups during peak flow periods.
Collector mains convey the settled wastewater to ei-
ther a lift station, conventional gravity sewers, or com-
munity treatment plant. To resist corrosion from sul-
f ides present in the wastewater, plastic pipe is typically
used. It should be at least 3 to 4 inches in diameter.
Deep excavation is usually not required, because the
mains may be installed with variable or inflective gra-
dients. Where the pipe is not buried below pavement
or subject to traffic loadings, the minimum recom-
mended burial depth is 30 inches.
Cleanouts, or less frequently manholes, provide ac-
cess to the mains for periodic maintenance and inspec-
tion. Cleanouts are usually installed at intervals of 400
to 1,000 feet, at high points, and at upstream terminal
sections of the mains.
Air release valves and vents are required to maintain
free-flow conditions in the collector mains. Venting is
usually accomplished through the building plumbing
stack vent. Air release valves or ventilated cleanouts
are installed at high points in the mains.
Lift stations are installed in the collector main system
when elevation differences will not permit gravity flow.
STEP units can be installed in service laterals located
at lower elevations than the collector mains.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
O&M requirements for SDGS systems are usually mini-
mal, especially if there are no STEP units or lift stations
present in the system. Periodic flushing of low-velocity
segments of the collector mains may be required. The
septic tanks must be pumped periodically to prevent
solids from entering the collector mains. It is generally
recommended that pumping be performed once every 3 to
5 years. However, the actual operating experience of
SDGS systems indicates that once every 7 to 10 years is
adequate. Lift stations should be checked on a daily or
weekly basis. A daily log should be kept on all operating
checks, maintenance performed, and service calls. Regu-
lar flow monitoring is useful in evaluating whether inflow
and infiltration problems are developing.
The municipality or sewer utility should be responsible for
O&M of all of the SDGS system components to ensure a
14
-------
^FATS, GREASES, & OILS
INTERCEPTOR TANK T*
SOLUBLE BOD LATERAL
BUILDING SETTLEABLE SOLIDS
SEWER
INFLECTIVE
GRADIENT
EFFLUENT
Figure 1. SDGS system.
high degree of system reliability. General easement
agreements are needed to permit access to components,
such as septic tanks or STEP units located on private
property.
TECHNOLOGY LIMITATIONS
SDGS systems may be prone to frequent blockages if the
individual septic tanks are not pumped at regular intervals.
Connection of existing septic tanks to newly installed
SDGS systems is undesirable, since many of the older
tanks are not watertight and may also receive flow from
building roof and basement drains.
The septic wastewater conveyed by SDGS systems can
result in severe odor and corrosion problems. The injec-
tion of air or oxygen and chemical oxidizers, such as
chlorine, hydrogen peroxide, or potassium permangan-
ate, at various points in the collection system may be
necessary to control odor and corrosion. Corrosion-
resistant materials, such as plastic pipe, must also be
used throughout the system.
In general, SDGS systems are not cost-effective unless
the topography allows the sewer profile to stay close to the
ground surface without using a large number of lift sta-
tions.
FINANCIAL CONSIDERATIONS
Construction costs will vary widely, depending mostly on
topography, housing density, and subsurface conditions
in the service area. Construction cost figures per foot of
main installed have been reported in EPA's Manual on
Alternative Wastewater Collection Systems to range from
$25.51 to $94.70 (February 1992 dollars). The costs of
installing the collection mains and septic tanks usually
account for more than 50 percent of total construction
costs. Insufficient data exist to estimate O&M costs.
However, it has been reported that most systems charge
a flat rate of $10 to $20 per month for each connection to
pay for administrative, O&M, and financing expenses.
Alternatively, planning estimates of $50 per year per
septic tank and $430 per year per mile of piping may be
used to estimate annual O&M costs as per EPA's Waste-
waterTreatment Technology Fact Sheets (1990) forsmall
diameter gravity sewers.
Bibliography
Alternative Wastewater Collection Systems. EPA/625/1 -
91/024, U.S. Environmental Protection Agency, Cincin-
nati, Ohio, 1991.
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
15
-------
PACKAGE TREATMENT PLANTS
TECHNOLOGY APPLICATIONS
Prefabricated and pre-engineered treatment plants, known
as package plants, have been widely used in situations
where activated sludge treatment was desired and where
flows were generally less than 30,000 gallons per day
(gpd). These plants are capable of providing satisfactory
treatment of wastewaterflow from developments generat-
ing normal domestic wastewater with reasonably consis-
tent flow patterns. Skillfully operated package plants can
achieve high levels of Biochemical Oxygen Demand
(BOD5) and Total Suspended Solids (TSS) removal with
effluent concentrations ranging from 20 to 30 mg/L. These
systems require the presence of a qualified operator on a
daily basis.
PROCESS DESCRIPTION
Activated sludge package treatment plants typically in-
clude a bar screen, comminutor, aeration tank, aeration
system(diffusedairormechanical), clarifier, and disinfec-
tion and sludge handling/disposal components. Primary
clarification Is not usually employed in package plant
designs. Typically, the aeration tank and final clarifier are
prefabricated into a dual compartment, circular or rectan-
gular steel tank (see Figure 1).
Within the aeration tank, the wastewater and activated
sludge (usually referred to as Mixed Liquor Suspended
Solids or MLSS) are mixed and aerated together. Be-
cause primary settling is not provided, the aeration tank
should have sufficient agitation to keep the heavier solids
which are normally removed by primary settling in suspen-
sion. The bacteria present in the MLSS feed on the
organic content of the wastewater as it flows through the
tank. The bacteria use this organic material for food and
energy to live and to reproduce. A portion of the organic
material is converted to carbon dioxide; the remainder is
used to produce new bacteria cells. After the aeration
tank, the activated sludge is removed from the wastewater
by gravity settling in the final clarifier. The settled sludge
is returned to the aeration tank to maintain a sufficient
population of bacteria to treat the wastewater. As more
wastewater is treated, additional activated sludge is gen-
erated. Some sludge must be periodically wasted (re-
moved) from the system to prevent an overload of solids.
A solids overload typically results in excessive solids loss
from the final clarifier; this, in turn, results in excessive
TSS and BOD5 concentrations in the plant effluent.
Package plants are most commonly designed as an
extended aeration activated sludge process. The aera-
tion tanks are normally sized to provide an average
hydraulic detention time of 18 to 36 hours. As a result of
the long detention time, extended aeration systems gen-
erate a somewhat more stabilized sludge than other
variations of the activated sludge process.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
O&M requirements are the same as those for extended
aeration activated sludge systems. Package treatment
plants should be checked daily by a qualified operator
experienced in the operation of biological treatment sys-
tems. Depending upon the size of the facility, the operator
should be present from 2 to 4 hours per day. Adequate
time should be allocated for process control, sampling,
maintenance, and recordkeeping. To properly operate
the treatment facility, the following operating parameters
should be monitored daily:
MLSS concentrations (weekly)
Dissolved oxygen (DO) levels in the aeration tank
Final clarifier sludge blanket depth
Return activated sludge rate
Waste activated sludge rate
These parameters should be checked against predeter-
mined target values to evaluate the performance of the
system. Typical operational target ranges for package
treatment plants are as follows:
Solids Retention Time (SRT) 20 to 30 days
MLSS 3,000 to 6,000 mg/L
Food/Microorganism
Ratio (F/M)
DO
PH
0.05 to 0.15
1.5 to 2.5 mg/L
7.0 to 8.0
16
-------
EFFLUENT
WEIR-^
SCUM
rBAFFLE
r SLUDGE RETURN
/ TROUGH
EFFLUENT
INFLUENT
PLAN
EFFLUENT
WEIR
SCUM RETURN j if
BLOWER
EFFLUENT
AIRLIFT -V .
> 1
\"-"-"l_
u
TAN
/
AIR LINE -\
3
9
K/
/
ซ=
=3" ฃ=
1 IrtlNIX IINLCI y
I /
8=ฑ 1 | ^=n/
AERATION TANK
/- DIFFUSERS
II
INFLUEN
SECTIONAL ELEVATION
Figure 1. Extended aeration treatment plant with air diffusers.
Regular preventive maintenance (PM) is required to keep
the equipment in good operating condition. A formalized
PM program should be established based on equipment
manufacturer recommendations. This program should
include a listing of all equipment, required PM tasks, and
the frequency of each task to be performed. Equipment
which requires routine maintenance typically includes
pumps, air blowers, and diffusers. Most of the package
plant clarifiers are equipped with air lifts to pump the
settled activated sludge back to the aeration tanks or to
sludge handling and disposal equipment. These air lifts
tend to clog frequently due to the very dense sludge solids
and various debris; therefore, they must be checked daily.
A scheduling system for required tests and process obser-
vations should be established. A schedule showing all
regular and intermittent maintenance procedures along
with emergency procedures should be posted. Access to
a complete and relatively easy to understand O&M manual
should be provided. This manual should be reviewed by
all operating personnel. Adequate training of operators
and assistant operators should be provided.
17
-------
RESIDUES GENERATED
The characteristically long detention times and high sludge
age (about 20 to 30 days) of package treatment plants
generally result in a sludge low in volatile solids. Sludge
Is sometimes aerated in a digester or separate aerated
storage basin included in the prefabricated plant. Stabi-
lized solids are often dewatered on sand drying beds and
eventually disposed of at a landfill or by land application.
TECHNOLOGY LIMITATIONS
Properly operated package treatment plants offer an
added measure of performance over other biological
processes but are subject to some of the same limitations
that other activated sludge treatment processes face.
These limitations include hydraulic shock loads due to
large flow variations, denitrification in final clarifier caus-
ing solids carryover, difficult control of MLSS, upsets due
to cold weather, and sensitive operational control. The
characteristically long detention time in package plants
usually results in the effluent containing significant con-
centrations of fine suspended solids termed "pin-floe." A
filtration unit may be needed to remove the fine sus-
pended solids to meet the permit limitations for BOD5
and TSS.
FINANCIAL CONSIDERATIONS
The costs for package treatment plants are broken down
in Table 1 into construction and O&M costs. The construc-
tion costs include screening or comminution, extended
aeration package unit, disinfection facilities, and sludge
drying beds. They do not include costs of land, engineer-
ing, laboratory, legal services, and financing. O&M costs
include labor, utilities, chemicals, and maintenance mate-
rials.
Table 1. Package Treatment Plant
Construction and O&M Costs (1992 $)
Plant Capacity
(gpd)
Construction
Costs ($)
O&M Costs
($)
10,000
60,000 - 83,000 8,600 -13,000
Bibliography
WastewaterTreatment Facilities forSewered Small Com-
munities. EPA/625/1-77-009, U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio, 1977.
A Reference Handbook on Small-Scale WastewaterTech-
nology. U.S. Department of Housing and Urban Develop-
ment, Washington, D.C., 1985.
18
-------
TRICKLING FILTER PLANTS
TECHNOLOGY APPLICATIONS
Trickling filters can be used for the aerobic treatment of
domestic and industrial wastewater. Trickling filter plants
are capable of achieving a high level of Biochemical
Oxygen Demand (BOD5) and Total Suspended Solids
(TSS) removal, typically 85-percent removal. Additional
treatment may be required to meet stricter discharge
standards. When designed for nitrification, trickling filters
can achieve fu rther BOD5 and TSS removal (final concen-
tration less than 30 mg/L). Trickling filters have been
popular for use in small systems because they perform
well with a minimum of skilled technical supervision and
have lower operating costs than activated sludge sys-
tems.
PROCESS DESCRIPTION
Trickling filters accept wastewater that has been previ-
ously treated by primary sedimentation. The wastewater
is applied through a distribution system to a bed of rock or
plastic media. As the wastewater trickles down over the
media, a bacterial slime forms upon the media, which
removes organic matter from the wastewater. The grow-
ing slime layer is constantly scoured by the wastewater
applied. Once the slime layer has reached its critical
thickness, outer portions of the layer begin to slough off
and are discharged to the underdrain system. The waste-
water and solids collected in the underdrain system are
transported to a secondary settling tank where the solids
and wastewater are separated. In practice, a portion of
the treated wastewater is usually recycled back to the
trickling filter. Recirculation often aids in the dilution of
incoming wastewater and improves the quality of the final
effluent. More equalized hydraulic loads, better distribu-
tion over filter media, and less clogging contribute to
increased treatment efficiency when recirculation is used.
Trickling filter systems will typically include screens, grit
removal tank, primary clarifier, trickling filter, secondary
clarifier, disinfection system, and sludge treatment and
disposal components (see Figure 1). The trickling filters
themselves include a distribution system to apply waste-
water to the filter media; filter media to provide a surface
area forthe growth of microorganisms; and an underdrain
system to support the media, provide drainage, and per-
mit the circulation of air for aerobic conditions.
The distribution system usually consists of distributor
arms that evenly distribute the wastewater to the media.
Most distributors rotate by the reaction force of the waste-
water discharging from the distributor arm orifices.
Filter media vary in types and include river rock or granite
media varying in size from 3 to 5 inches diameter, red-
wood media, and plastic media. The depth of rock media
filters is usually limited to 5 -10 feet. Depths for plastic or
redwood media vary between 20 and 40 feet.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Trickling filter plants should be checked daily by personnel
experienced in the operation of biological attached growth
processes. Adequate time should be allocated for pro-
cess control, sampling and testing, maintenance, and
recordkeeping. Operating checks that should be per-
formed on a daily basis include the following:
Check distributor orifices, top of filter media, underdrain
system, and vent pipes for plugging.
Check biological growth layer on filter media.
Monitor recirculation rate.
Check quality of filter effluent prior to final clarifier
treatment.
Perform sampling and testing as required by discharge
permit.
Check sludge blanket in clarifier.
These parameters should be checked against predeter-
mined target values to evaluate the performance of the
system. Typical design and operation parameters for low-
rate and high-rate trickling filters are listed in Table 1.
Regular preventive maintenance (PM) is required to keep
all equipment in good operating condition. A PM program
should be developed based on the equipment manufac-
turer recommendations. This program should include a
list of all equipment, required PM tasks, and frequency of
tasks that should be performed. Typical equipment that
requires routine maintenance includes rotary distributor
bearings, distribution arms, orifices, and recirc-
ulation pumps.
19
-------
ROTARY
DISTRIBUTOR
FILTER
MEDIA
SCREENED RAW
WASTEWATER /PRIMARY
MCLARIFIER
EFFLUENT
Figure 1. Trickling filter treatment system.
Table 1. Operational Parameters
Parameter
Low-Rate
High-Rate
Hydraulic Loading
gpdVtt2
25-100
200-1000
Organic Loading
IbBOD/l ,000ft3
Depth, Feet
Filter Media
5-25
6-8
Rock
25-300
15-40
Plastic
Gallons par day
TECHNOLOGY LIMITATIONS
As with any biological treatment process, trickling filters
are adversely affected by hydraulic and organic over-
loads. Cold weather also significantly reduces the treat-
ment efficiency of trickling filters. Trickling filters alone are
generally unable to meet stringent effluent limitations
without the installation of additional treatment processes.
FINANCIAL CONSIDERATIONS
The estimated construction cost as obtained from a single
supplier for a trickling filter with a design capacity of
100,000 gpd and consisting of plastic media, steel (bolted)
tank, and rotary distributor is $100,000. Costs do not
include pumping, clarifiers, engineering, and legal
services.
RESIDUES GENERATED
Sludge produced by the trickling filter process originates
frorn the primary clarifiers and the biomass or solids that
are continually sloughed off from the filter media and
collected In the secondary clarifier. The sludge must be
digested either aerobteally or anaerobically before it is
disposed of, usually in a landfill or by land application.
Inadequate solids removal from the trickling filter process
will result in a poor effluent quality.
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
O&M of Trickling Filters, RBCs, and Related Processes,
Manual of Practice No. OM-10. Water Environment
Federation, Alexandria, Virginia, 1988.
20
-------
OXIDATION DITCHES
TECHNOLOGY APPLICATIONS
Oxidation ditch technology is applicable in any situation
where activated sludge treatment is appropriate and where
the flow is greater than 50,000 gallons per day (gpd).
These plants are capable of consistently achieving high
levels of Biochemical Oxygen Demand (BOD5) and Total
Suspended Solids (TSS) removal with effluent concentra-
tions as low as 10 to 15 mg/L, even in extremely cold
climates. High levels of nitrification (95 to 99%) are
possible with proper operation. Total nitrogen removals
up to 80 percent may be achieved by maintaining oxygen-
rich (aerobic) and oxygen-deficient (anoxic) zones around
the ditch. Nitrification will take place in the aerobic zones,
and denitrification will occur in the anoxic zones. In-
creased operator attention or automatic control packages
are required to produce high levels of nitrogen removal.
PROCESS DESCRIPTION
An oxidation ditch is a variation of the extended aeration
activated sludge process that uses a continuously recircu-
lating closed loop channel or channels as an aeration
basin. The aeration basin is normally sized to provide an
18- to 24-hour hydraulic detention time. The long deten-
tion time provides protection against shock loads and
results in high levels of treatment and reduced sludge
production.
The components of an oxidation ditch system will typically
include screening, grit removal, oxidation ditch, second-
ary clarification, and sludge handling (see Figure 1).
Sludge handling often consists only of a periodically
aerated tank, sometimes with a dewatering bed, and
rarely includes digestion. Primary clarification is not
usually included in the oxidation ditch plant design. The
typical oxidation ditch aeration basin is a single channel;
multiple interconnected concentric channels can be used
for larger systems. The oval configuration or "racetrack"
is the most common channel configuration. Other chan-
nel configurations which have been used include circular,
ell, or horseshoe patterns.
Mechanical aerators are commonly used for mixing, aera-
tion, and circulation of the activated sludge. Generally,
these are horizontal brush, cage, or disc-type aerators
designed specifically for oxidation ditches. Occasionally,
vertical turbine aerators will be used. The aerators must
supply the required oxygen to the channel and impart a
sufficient velocity in the channel (greater than 1.0 foot per
second) to keep the contents in suspension. .Oxygen
transfer capabilities of an aerator will vary depending
upon the particular design. The number of aerators
provided depends on the size, configuration, and oxygen
requirements of the plant. A minimum of two aerators
should be installed.
Screened Raw
Wastewater
Dividing Strip
Aeration Rotor
Return Sludge
> Effluent
Excess Sludge
T
Figure 1. Oxidation ditch flow diagram.
Sludge
Disposal
21
-------
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
O&M requirements are very similar to those for extended
aeration activated sludge systems. Oxidation ditch plants
should be checked daily by personnel who are experi-
enced in the operation of biological treatment systems.
Depending on the size of the facility, the operator should
be present from 2 to 8 hours per day. Adequate time
should be allocated for process control, sampling, main-
tenance, and recordkeeping. To properly operate the
treatment system, the following operating parameters
should be monitored at least weekly:
* 30-mlnute sludge settling volume
Mixed liquor suspended solids concentration in the
ditch
Dissolved oxygen levels in the ditch
Final clarifier sludge blanket depth
Return activated sludge rate
Waste activated sludge rate
These parameters should be checked against predeter-
mined target values to evaluate the performance of the
system. Typical operational target ranges for oxidation
ditches are as follows:
Solids Retention Time (SRT) 10 to 20 days
Mixed Liquor Suspended Solids
(MLSS) 2,000 to 5,000 mg/L
* Food/Microorganism Ratio 0.05 to 0.15
Dissolved Oxygen (Minimum level) 1.5 to 2.0 mg/L
PH 6.0 to 9.0
Regular preventative maintenance (PM) is required to
maintain the equipment in optimal condition. Aformalized
preventative maintenance program should be established
based upon the recommendations of the equipment manu-
facturers. This program should include a listing of all
equipment, the required PM tasks, the frequency the
tasks should be performed, and a record of their perfor-
mance. Typical equipment which requires routine preven-
tative maintenance includes pumps, aerators, motors,
and drives.
RESIDUES GENERATED
The characteristically long detention times and high sludge
ages of oxidation ditches generally result in slightly re-
duced waste sludge production and a sludge with a low
volatile content. If the volatile content of the waste sludge
is low enough (below 50 percent), the waste sludge may
be directly applied to drying beds for dewatering, prior to
final disposal.
TECHNOLOGY LIMITATIONS
Oxidation ditches offeran added measure of reliability and
performance over other biological processes but are sub-
ject to some of the same limitations that other activated
sludge treatment processes face. These limitations in-
clude plant upsets due to high organic loadings from
industries, high hydraulic loadings from excessive inflow
and infiltration, changes in the types of microorganisms
present, inadequate solids removal, and poor operational
control.
FINANCIAL CONSIDERATIONS
The costs for the oxidation ditches are broken down into
construction and O&M costs. The capacity of the plants
ranges from 50,000 to 500,000 gpd. The construction
cost includes the oxidation ditch, clarifier, pumps, build-
ing, laboratory, and sludge drying beds. It does not
include costs for land, engineering, legal services, or
financing. Operation and maintenance costs include la-
bor, utilities, chemicals, and maintenance materials. The
cost breakdown is shown in Table 1.
Table 1. Oxidation Ditch Construction and
Annual O&M Costs (1992$)
Plant Capacity
(gpd)
50,000
150,000
500,000
Construction
Costs ($)
342,000
418,000
722,000
Annual
O&M Costs ($)
38,000
53,200
79,800
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
22
-------
SEQUENCING BATCH REACTORS
TECHNOLOGY APPLICATIONS
Sequencing Batch Reactors (SBRs) are an excellent
alternative to conventional activated sludge treatment
plants. SBRs are capable of achieving high levels of
Biochemical Oxygen Demand (BOD5) and Total Sus-
pended Solids (TSS) removal (greater than 90 percent)
with effluent concentrations as low as 10 mg/L. In addition
to BOD5 and TSS removal, nitrification, denitrification,
and phosphorus removal are possible with modifications
to the plant operation. SBRs offer additional features
applicable to small communities. These features include
easy installation, simple operation, lower maintenance
than most activated sludge variations, and energy effi-
ciency.
PROCESS DESCRIPTION
SBRs are a variation of the conventional activated sludge
treatment system in which equalization, aeration, clarifi-
cation, and sludge wasting processes are carried out
sequentially in the same tank. SBRs consist of a single
tank equipped with an inlet for raw wastewater, air diff us-
ers with associated blowers and piping for aeration, a
sludge draw-off mechanism at the bottom to waste sludge,
a decant mechanism to remove supernatant after settling,
and a control mechanism to time and sequence pro-
cesses. SBRs operate in cycles of five periods carried out
in sequence as follows: FILL, REACT (aeration), SETTLE
(clarification), DRAW (decant), and IDLE (sludge wast-
ing). These processes are controlled by time to achieve
the objectives of operation. They are discussed further in
the following paragraphs. Figure 1 shows a typical single
cycle.
FILL
The purpose of the FILL operation is to add raw wastewa-
ter to the reactor. During the FILL phase, performance
standards may require alternating conditions of low and
high dissolved oxygen (DO) concentrations. Periods of
aeration during FILL are critical to the development of
organisms with good settling characteristics. Conversely,
periods of zero DO (anaerobic conditions) or low DO
(anoxic conditions) are necessary for biological nutrient
removal of nitrogen and phosphorus.
REACT
The purpose of the REACT phase is to complete the
reactions initiated during the FILL stage. Depending on
design type, influent flow may be diverted to another
reactor during this phase and aeration continues on a
constant basis or influent flow may continue during this
period separated by long distances, baffles, etc., in other
designs. Organic removal occurs during this stage. Nitri-
fication (ammonia removal) may also occur during this
phase if loading is low enough compared to Mixed Liquor
Suspended Solids (MLSS) (i.e., high Solids Retention
Time [SRT]).
SETTLE
The purpose of the SETTLE phase is to allow solids
separation to occur in the system while providing a clari-
fied supernatant to be discharged as effluent. In the
SETTLE mode, reactor contents are completely quies-
cent, eliminating the short-circuiting of continuous flow
clarifiers.
DRAW
The purpose of the DRAW phase is to remove the clarified
supernatant from the reactor as final effluent. Floating
and adjustable weirs are the most popular decanting
mechanisms for this phase of treatment, but submersible
pumps are also used.
IDLE
The purpose of the IDLE phase is to provide time for one
reactor to complete its fill cycle prior to switching to
another unit. IDLE is not a necessary phase and can be
eliminated. Depending upon the process and treatment
goals, aeration, mixing, or sludge wasting can occur
during the IDLE phase.
Continuous influent types of SBRs do not have an IDLE
phase.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
O&M requirements for SBRs are minimal compared to
other conventional activated sludge treatment systems.
However, SBR plants should be checked daily by person-
nel experienced in operating biological treatment sys-
tems. Depending on the size of the facility and the com-
23
-------
% Max Volume
25 to 100
100
100
100 to 35
35 to 25
% Cycle Time Influent
Purpose
25
35
20
15
FILL
REACT
SETTLE
DECANT
EFFLUENT
IDLE
Add
Substrate
Reaction
Time
Clarification
Withdraw
Effluent
Waste
Sludge
Operation
Aeration On
or Off
Aeration On
Aeration Off
Aeration
Off
Aeration On
or Off
Figure 1. Typical SBR operating sequence.
plexity of treatment processes (i.e., nitrogen and phos-
phorus removal), the operator should be present from 2 to
8 hours per day. Adequate time should be allocated for
process control, sampling, O&M, and daily recordkeeping.
Unless these plants receive at least some daily attention
and maintenance from a qualified operator, effluent qual-
ity will eventually become unsatisfactory. To operate the
treatment system properly, the following operating pa-
rameters should be monitored at least weekly:
30 to 60 minute sludge settling volume
* MLSS concentration
DO concentrations
Decant heights
These parameters should be checked against predeter-
mined target values to evaluate the performance of the
system. Typical operating target ranges for SBRs are as
follows:
SRT
MLSS
Food/Microorganism
Ratio (F/M)
PH
20 to 30 days
2,000 to 6,000 mg/L
0.08 to 0.16
7.0 to 8.0
Regular preventive maintenance (PM) is required to keep
the equipment in optimal condition. A formalized PM
program should be established based upon the recom-
mendations of the equipment manufacturers. This pro-
gram should include a listing of all equipment, required
PM tasks, and the frequency with which the tasks should
be performed. Typical equipment that requires routine
PM includes pumps, blowers, air diffusers, and automatic
controllers.
RESIDUES GENERATED
Generally, SBRs generate the same quantities of sludge
as extended aeration activated sludge facilities. Excess
or waste activated sludge may be typically aerobically
digested, dewatered on drying beds, and applied to the
land.
TECHNOLOGY LIMITATIONS
SBRs, especially systems designed to remove nitrogen
and phosphorus, require the presence of an experienced
operator. Performance depends heavily on the reliability
of automatic controllers for valves, pumps, aeration sys-
tems, and decanting systems. Cold weather will also
affect the performance of SBRs.
24
-------
FINANCIAL CONSIDERATIONS
Construction costs for SBRs treating flows less than
100,000 gallons per day (gpd) were obtained from a single
manufacturer. O&M costs were not available. However,
in general, SBRs are recognized as being economical to
operate and maintain. Estimated construction costs
(1992$) for systems having design capacities of 10,000
gpd, 50,000 gpd, and 75,000 gpd are $76,000, $136,000,
and $165,000, respectively. The cost of each system
includes two SBRs and an aerobic digester of steel tank
construction, piping, valves, controls, and a concrete
support pad. The estimated construction costs do not
include the cost of land, engineering, legal, or finan-
cial fees.
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
Sequencing Batch Reactors. EPA/625/8-86/011, U.S.
Environmental Protection Agency, Cincinnati, Ohio, 1986.
25
-------
LAGOONS
TECHNOLOGY APPLICATIONS
Lagoons are the most commonly employed wastewater
treatment technology, especially for small communities.
They provide a simple and economical means of treating
a community's wastewater. However, due to increasingly
stringent permit limitations, additional downstream treat-
ment processes, such as intermittent sand filters, may be
necessary to polish the lagoon effluent. Lagoon systems
are also used to pretreat and store wastewater in land
application or constructed wetlands systems.
PROCESS DESCRIPTION
Lagoon systems are natural treatment processes in which
bacteria and algae reduce the organic content of a
community's wastewater. During daylight hours, the
algae release oxygen into the lagoon, and the bacteria
use this oxygen for respiration. A healthy lagoon will
exhibit a green color due to the large algae population
that develops. Additional aeration may be provided by
wind action or in some cases by a mechanical or diffused
aeration system. Facultative lagoon systems operate at
very long detention times, ranging from 20 to 150 days
depending on design and climate conditions. Aerated
lagoons generally require shorter detention times.
Lagoons operated in cold climates require longer deten-
tion times. Asshown in Figure 1, alagoon system typically
includes screening, lagoon, and disinfection components.
Lagoon systems for domestic wastewater treatment are
typically categorized into two types: stabilization ponds or
aerated lagoons. In stabilization ponds, aerobic condi-
tions are maintained by algae and wind action. The ponds
must be kept shallow (3 to 5 feet deep) to permit the
adequate mixing needed to maintain aerobic conditions.
Stabilization ponds operate best with detention times in
excess of 30 days. As a result of their shallow depths and
long detention time requirements, stabilization ponds re-
quire large amounts of land, usually 1 acre for every 200
people served. To avoid organic overload, ponds should
be sized to treat a Biochemical Oxygen Demand (BOD5)
loading of 15 to 50 Ibs/acre/day, depending on climate.
Aerated lagoons can treat a much higher organic loading
than stabilization ponds. This is due primarily to the
supplemental aeration process. Air is introduced into the
lagoons via mechanical surface aerators or subsurface
diffusers. Aerated lagoons require one-tenth to one-third
of the land required for stabilization ponds and have
shorter detention periods (3 to10 days in warm climates).
The average depth of an aerated lagoon is between 6 and
10 feet. Shorter detention times and increased depths
reduce the land requirements. This is an attractive alter-
native where land costs are high or large amounts of land
are unavailable.
Lagoon systems are usually designed with a minimum of
three separate cells or basins connected in series. Some-
times, the first cell is larger than the other cells and
receives the bulk of the organic load. The remaining two
cells act as polishing ponds or settling basins for sus-
pended solids removal. Algae cells compose most of the
Bar Screen
I
Influent
Dike
Outlet Depth
Control
Transfer Lines'
Figure 1. Wastewater treatment lagoon system.
Effluent to
Disinfection
26
-------
suspended solids that must be removed from lagoons. In
aerated lagoon systems, the last cell in a series is usually
left unaerated to provide for suspended solids removal.
Additional downstream treatment, such as intermittent
sand filters, may be necessary to produce an effluent
containing less than 10 mg/L BOD5 or Total Suspended
Solids (TSS). Floating baffles may also be used to
updgrade an existing large single-cell lagoon into several
smaller cells to prevent short-circuiting.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
As a result of their simple design characteristics, lagoons
have few O&M requirements. The O&M of a lagoon
normally involves daily site inspections; routine site main-
tenance, such as grass cutting, and erosion and aquatic
weed control; and periodic sample collection and testing.
Typically, a full-time maintenance staff is not required.
Many small communities use their public works staff to
operate and maintain the lagoon system. This type of
arrangement can work, provided the community officials
permit the public works staff to be trained properly and to
spend sufficient time at the treatment facility. In addition
to routine monitoring activities, the lagoons should be
checked at least once each year for sludge accumulation.
Excessive sludge deposits in lagoons may result in re-
duced detention times and increased BOD5 and TSS
levels jn the effluent. Sludge may need to be removed
every 5 to 10 years depending on actual site conditions.
Operating parameters should be monitored weekly and
sometimes daily in order for proper treatment to occur.
Operating checks should include the following:
Check dikes for erosion, leaks, and signs of burrowing
.animals.
Keep inlet and outlet structures clear of obstructions.
Check pond surface and outlet structures for scum
build-up.
Monitor pond for temperature, color, pH, dissolved
oxygen (DO), and suspended solids.
Monitor screening devices.
Sample effluent and test as required by permit.
Monitor condition of mechanical equipment.
A Preventive Maintenance (PM) program should be initi-
ated for all equipment according to manufacturer
recommendations. Records should be kept for the influ-
ent and effluent BOD5, TSS, and pH. Generally, for
lagoons, the pH ranges from 6.5 to 10.5. Pond conditions
including DO, solids content, and sludge depths should
also be recorded. The lagoon DO should be greater than
1.0 mg/L, and it should be checked at several locations
within the lagoon.
RESIDUES GENERATED
During the normal course of treatment, algae and bacteria
cells eventually die and settle to the bottom of the lagoon
along with incoming setteable solids forming a sludge
layer. Since there is little or no oxygen at the bottom of the
lagoon, the sludge is partially stabilized by anaerobic
digestion. Eventually the sludge accumulation in the
lagoon becomes excessive and must be removed. De-
pending on state regulations, the sludge may be disposed
of at landfills or by land application. The sludge should be
tested for toxic pollutants, such as heavy metals, before it
can be applied to the land.
TECHNOLOGY LIMITATIONS
Lagoons are low-cost and simple biological treatment
systems suitable for domestic wastewatertreatment where
strict discharge limits are not imposed. Additional down-
stream treatment processes must be installed to provide
further reductions in TSS concentrations, especially dur-
ing the warmer months when algal activity increases.
Lagoon systems have far greater land requirements than
mechanical treatment systems. This may restrict their
application in communities where the cost of land is
prohibitive or where insufficient land is available. Like
most biological treatment systems, lagoons are adversely
affected by cold weather and organic and/or hydraulic
overloads.
FINANCIAL CONSIDERATIONS
The costs of lagoons are broken down into construction
and O&M costs in Table 1. The construction costs for a
lagoon usually depend on excavation prices. The con-
struction costs include excavation of the lagoon, associ-
ated aeration equipment, pumps, piping, and disinfection.
They do not include costs for land, legal and engineering
services, or financing. O&M costs will vary with location
as a function of labor and utilities required for treatment.
O&M costs include labor, utilities, and maintenance mate-
rials.
27
-------
Table 1. Aerated Lagoons Construction and Annual
Operational Costs (1992$)
Plant Capacity
(gpd)
10,000
100,000
Construction
Costs ($)
47,000-71,000
118,000-353,000
Annual O&M
Costs ($)
4,300 - 6,500
17,200-25,800
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
WastewaterTreatment Facilities for Sewered Small Com-
munities. EPA/625/1-77-009, U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio, 1977.
Rich, Linvil G. Low-Maintenance, Mechanically Simple
WastewaterTreatment Systems. McGraw Hill, Inc. 1980.
A Reference Handbook on Small-Scale WastewaterTech-
nology. U.S. Department of Housing and Urban Develop-
ment, Washington, D.C., 1985.
28
-------
INTERMITTENT SAND FILTERS
TECHNOLOGY APPLICATIONS
Intermittent sand filters are most often used to provide
further treatment of lagoon or septic tank effluent. These
filters are ideally suited for populations of less than 1,000
people and where flow is less than 100,000 gallons per
day (gpd). These facilities are capable of consistently
achieving high removals of Biochemical Oxygen Demand
(BOD5) and Total Suspended Solids (TSS) removal with
effluent concentrations normally in the range of 5 to 10
mg/L. High levels of nitrification (90 to 95%) can also be
realized with proper operation. Intermittent sand filters
are especially applicable to small communities due to low
cost and minimal operator requirements.
PROCESS DESCRIPTIONS
Intermittent sand filters (see Figure 1) are variations of
fixed film biological treatment systems. They consist of
two types of processes: single-pass (where wastewater
travels through the filter once) and recirculating (where
the wastewater travels through the filter several times).
Single-pass filters can be further divided into buried and
open types. Recirculating filters are similar in design to
the open types except a coarser media is used and a
portion of the filtered effluent is piped back to the dosing
tank and reapplied to the filter.
Basically, an open intermittent sand filter consists of a bed
of sand, usually 30 to 36 inches deep, resting upon a layer
of gravel containing an underdrainage system of open
joint/perforated pipe. The filter floor (usually earthen) is
graded and sloped to provide necessary drainage. Side
walls extend approximately 18 inches above the sand
filter surface. The total bed area is usually divided into two
or more smaller filters. Each individual filter is dosed on
an alternating cycle. This allows the filter to drain com-
pletely after each dose which is necessary to maintain
aerobic conditions.
The recirculating intermittent sand filter utilizes a recircu-
lation tank where most of the discharge from the sand filter
is diverted and mixed with pretreated wastewater to be
reapplied to the filter. This system dilutes the wastewater
stream being applied to the filter while improving filter
performance and decreasing clogging. A recirculating
filter normally operates in the range of 2.0 to 3.0 gpd/ft2.
Open single-pass filters are operated at rates as high as
10 gpd/ft2.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
This section pertains to open and recirculating sand filters
since buried filters are not readily accessible. The hydrau-
lic loading to the filters should be checked daily. To
maintain aerobic conditions, the filters should drain com-
pletely before the next dosing cycle begins. Hydraulically
overloaded filters will typically exhibit septic (anaerobic)
conditions and reduced effluent quality. For recirculating
filters, a recirculation ratio of 3:1 to 5:1 should be main-
tained for proper operation. The dosing interval should be
adjusted so that each dose results in about 2 to 4 inches
of wastewater uniformly distributed across the filter.
Maintenance of sand filters is primarily concerned with
keeping the filter inlet distribution channels clear of any
debris, cleaning or raking the upper layer of the filter bed,
and replenishing sand lost from the filter bed. The filter
surface should be cleaned wheneverthe top layerof sand
begins to show signs of clogging. Weeds and grasses
should not be allowed to grow in the filter. Sand should be
replaced periodically to maintain a sand depth in excess
of 24 inches.
RESIDUES GENERATED
Some sludge will be generated whenever the surface of
the filter is cleaned. The sludge and sand removed should
be properly disposed of in accordance with state regula-
tions.
TECHNOLOGY LIMITATIONS
Intermittent sand filters are easily upset by excessive
hydraulic loading. These filters are also unable to handle
excessive solids levels in the influent wastewater. Cold
weather may also adversely affect intermittent sand fil-
ters; sometimes, removable covers are installed to pre-
vent freezing. Intermittent sand filters have intermediate
land requirements, lower than land treatment systems but
much more than mechanical plants.
29
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TYPICAL RECIRCULATING INTERMITTENT SAND FILTER
Raw\
Pretreatmeni
Unit
-it
Boat Valve
1
i
X
1
L
\
Media
<*&-ฃ; " ^/>:Sln.
Graded Gravel 1/4" to 11/2"
Perforated or Open
Joint Pipe. Tarpaper
Over Open Joints
Figure 1. Schematic showing the three types of intermittent sand filters.
30
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FINANCIAL CONSIDERATIONS
The costs for intermittent sand filter systems are broken
down in Table 1 into construction and O&M costs. The
capacity of the plants ranges from 10,000 to 100,000 gpd.
The construction costs include the following components:
concrete, sand, gravel, distribution system, and pumps.
They do not include the cost of land, engineering, legal
and financing, pretreatment, and disinfection costs. O&M
costs include labor, utilities, maintenance materials, and
associated chemicals.
Table 1. Intermittent Sand Filters Construction
and O&M (1992 $)
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
O&M of Trickling Filters, RBCs, and Related Processes,
Manual of Practice No. OM-10. Water Envrionment
Federation, Alexandria, Virginia, 1988.
A Reference Handbook on Small-Scale WastewaterTech-
nology. U.S. Department of Housing and Urban Develop-
ment, Washington, D.C., 1985.
Capacity (gpd)
Construction
Costs ($)
Annual
O&M Costs ($)
10,000
50,000
100,000
42,000
200,000
450,000
3,500
10,000
12,500
31
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LAND ^TREATMENT METHODS
TECHNOLOGY APPLICATIONS
Land application systems can be utilized to provide further
treatment of secondary effluents and/or a means of ulti-
mate effluent disposal. Benefits of land treatment include
nutrient recovery, cash crop production, groundwater
recharge, and water conservation (if used for irrigation of
landscaped areas). These systems are highly desirable
In areas where surface water discharge requirements are
strict and land is relatively inexpensive. Soil characteris-
tics play a significant role in the siting of land treatment
systems.
PROCESS DESCRIPTIONS
In land treatment systems, pretreated wastewater is ap-
plied to the site by either overland flow (OF), rapid infiltra-
tion (RI), orslow rate irrigation (SRI) methods. Treatment
is provided by natural processes as the wastewater efflu-
ent flows through the soil and vegetation. Organic mate-
rial is removed within the top inch of soil. Nitrogen is
removed primarily by plant uptake in SRI and by nitrifica-
tion-denitrification in OF and RI systems. Phosphorus is
removed by adsorption in varying degrees by OF, SRI,
and RI systems. A portion of the wastewater is lost to
evaporation and evapotranspiration; the remainder re-
turns to the surface waters via overland flow or to the
groundwater via percolation during irrigation. The major
components of land application systems are summarized
In Table 1. Land treatment methods are discussed in the
following paragraphs.
In the overland flow method, wastewater is applied at the
top of a gently sloping (2 to 8%) hill and allowed to flow
over the surface of the ground to the bottom of the hill
where it is collected, disinfected, and discharged to the
receiving water (see Figure 1). The suspended solids in
the wastewater settle out and attach themselves to
surface vegetation where they are decomposed. Organic
matter is consumed by bacteria on grass and soil, while
nutrients are absorbed by the grasses, which are har-
vested periodically. The effluent produced generally
exceeds requirements of most secondary treatment
systems.
Overland flow systems have been effectively used to treat
preliminary or primary effluent, as well as secondary
effluent. Overland flow systems provide a high level of
treatment with minimal use of mechanical equipment.
Typical removal and treatment levels to be expected are
listed below:
Parameter
Percent Removal
Biochemical Oxygen Demand (BOD5) 85 to 92
Total Suspended Solids (TSS) 85 to 92
Nitrogen 60 to 80
Phosphorus 20 to 50
For spray irrigation, wastewater is pumped through a
network of pipes to the various fields. The effluent is
applied utilizing sprinklers or spray nozzles. The sprin-
klers are either fixed or mounted on a rotary distributor.
In spray irrigation systems, the rate at which the effluent
is applied depends on the weather, stage of plant growth,
and soil drainage characteristics. Since wastewater can-
Distribution
Pipe
Evapotranspiration
4
^ ^v?lfi
Figure 1. Overland flow method.
32
-------
Table 1. Components of Land Application Systems
Preliminary or secondary equivalent treatment
Transmission to the land application site
Wastewater storage for non-irrigation periods
Distribution network over the irrigated area
(SRI only)
System to recover the treated wastewater
(OF only)
Crop harvesting system
not be applied continuously, there must be a provision for
storing effluent for periods of as long as 90 days. Usually,
this is accomplished using lagoons or stabilization ponds.
Wastewater can be applied to cultivated croplands, or-
chards, pastures, meadowlands, and woodlands. Waste-
water is removed by percolation and evapotranspi ration
(see Figure 2). Typical removal levels from secondary
effluent by irrigation are provided below:
Parameter
BOD5
Chemical Oxygen Demand (COD)
TSS
Nitrogen
Total Phosphorus
Percent Removal
90 to 99
80 to 90
90 to 98
75 to 95
95
For rapid infiltration systems, pretreated wastewater is
applied to highly permeable soils by distributing in basins
(see Figure 3). Additional treatment occurs by filtration,
adsorption, and microbial action as the wastewater perco-
lates through the soil matrix. Wastewater is continuously
applied to the basins for periods lasting from several hours
to one week. During the resting period, wastewater
continues to drain through the soil matrix. Alternating
periods of flooding and drying maintain the infiltration
capacity of the soil matrix. Vegetation is usually not
planted in Rl systems. Depending on the system design,
treated wastewater either percolates to the groundwater
or collects in underdrains for reuse or surface discharge.
Of the three land treatment methods, Rl systems have the
lowest land requirements. Typical removal and treatment
levels to be expected are listed below:
Parameter
BOD5
TSS
Nitrogen
Phosphorus
Percent Removal
85 to 99
85 to 99
50
70 to 95
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
O&M requirements are nominal and typically consist of
the following elements: monitoring of wastewater applica-
tion rates, pump maintenance, pipeline maintenance, and
crop harvesting. Pump maintenance involves routine
lubrication and inspection and equipment repair as re-
quired. For permanently installed pipelines and spray
irrigation systems, pipeline maintenance is minimal and
involves the occasional flushing of lines or draining of the
system at the end of the irrigation season. Since spray
nozzles will become clogged with solids, they should be
checked and cleaned frequently.
In Rl basins, a biological mat forms on the surfaces of the
infiltration areas which reduces the infiltration rate. The
surfaces should be disked or harrowed to break up the
mat. This should be performed at regular intervals or
whenever it is observed that routine periods of drying do
not restore infiltration rates to acceptable levels.
Once an operating schedule is established (rate and
duration of wastewater application), operation becomes
routine. However, daily attention by the operator is
critical. Automatic timers can be placed on pumps to
eliminate the daily responsibility of turning the system on
EVAPOTRANSP1RATION
CROP
SPRAY OR
SURFACE
APPLICATION
ROOT ZONE
SUBSOIL.
SLOPE
VARIABLE
'DEEP
PERCOLATION
Figure 2. Schematic of spray irrigation.
33
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EVAPORATION
Figure 3. Rapid infiltration.
Table 2. Comparison of Design and
Operating Parameters, Land Treatment Systems
Parameter
Irrigation
Overland Flow
Estimated Land
Required for
100,000 gpd (acres)
Minimum
Preapplication
Treatment
Requirements
Climate Restrictions
Slope
Soil Permeability
20 to 25
Lagoons
Storage
Needed for
Cold and Wet
Climates
<20%
Slow to
Moderate
Rapid Infiltration
Weekly Application
Rate (inches)
Annual Application
Rate (feet)
0.5 to 4.0
2 to 18
2.4 to 6.0
8 to 40
4 to 96
20 to 410
5 to 10
Screening and
Grit Removal
Storage
Needed for
Cold and Wet
Climates
Smooth Slopes of
2-8%
Impermeable
(clays, silts, soils
with impermeable barriers)
1 to 7
Lagoons
Cold Weather May
Reduce Hydraulic
Loading Cycles
Not Critical
Rapid
34
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or off. Highly skilled operators are not usually required,
but these systems should be checked by personnel who
have experience in agricultural techniques. Adequate
time should be allocated for process control, sampling (if
required), maintenance, and recordkeeping.
Crop management may be one of the most important
operating requirements for OF and SRI systems. The
application rate of the wastewater must be regulated to
match not only crop requirements (especially for nitro-
gen), but soil drainage properties as well. Application
rates must also be regulated to suit changing weather
conditions. Excessive application rates can result in crop
failure, erosion, groundwater contamination (irrigation
systems), surface runoff (irrigation systems), and short-
circuiting (overland flow).
When evaluating the performance of the treatment sys-
tems, common design features for proper operation should
be observed. These are presented in Table 2.
RESIDUES GENERATED
Land treatment systems generate residuals (rags, grit)
and sludge from the associated preapplication treatment
processes. Periodically, grass crops must be mowed and
harvested from the application sites. The frequency of
harvesting will vary depending on climate conditions but
generally should be at least two to three times per year if
substantial nutrient removal is desired.
TECHNOLOGY LIMITATIONS
Land treatment systems are limited by soil type, topogra-
phy, climate (cold weather and annual precipitation), crop
selection, and land availability. In addition to the preced-
ing factors, spray irrigation systems may also be affected
by wind conditions, spray nozzle clogging, and reduced
infiltration rates caused by sealing of the soil. High
flotation tires are required for mowing and harvesting
equipment used in overland flow systems. These sys-
tems may also require preapplication disinfection de-
pending on state regulations.
Groundwater quality may be impacted by nitrate contami-
nation, especially for rapid infiltration systems. Rl sys-
tems may also be adversely impacted by inadequate TSS
removals by upstream treatment units.
FINANCIAL CONSIDERATIONS
The construction and O&M costs for spray irrigation and
overland flow land treatment system methods are pre-
sented in Tables 3 and 4, respectively. The capacity of the
plants ranges from 10,000 to 100,000 gpd. The construc-
tion costs for spray irrigation systems include expenses
for pumps, distribution piping, and fixed rotary sprinklers.
Costs for pretreatment facilities, storage lagoons, and
land are not included. The construction costs for overland
flow systems pertain to a complete system, including
disinfection and discharge facilities; land costs are not
included.
Table 3. Typical Construction and O&M Costs for
Spray Irrigation (1992$)
Plant Capacity
(gpd)
Construction Costs O&M Costs
($/gpd) ($/1,OOOgal)
10,000
100,000
5.50 to 10.95
1.83 to 5.50
0.92101.83
0.1 9 to 0.52
Table 4. Typical Construction and O&M Costs for
Overland Flow Systems (1992 $)
Plant Capacity
Construction Costs
($/gpd)
O&M Costs
($/1,OOOgal)
10,000
100,000
7.20 to 14.40
1.46 to 2.92
1.46 to 2.92
0.37 to 0.73
The estimated construction and annual O&M costs for a
100,000 gpd rapid infiltration system is reported in the
literature to be $79,200 and $8,000, respectively. The
construction costs do not include pretreatment or storage
facilities.
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
Rich, Linvil G. Low-Maintenance, Mechanically Simple
WastewaterTreatment Systems. McGraw-Hill, Inc. 1980.
Land Treatment of Municipal Wastewater. EPA/625/1-
81 -013, U.S. Environmental Protectional Agency, Cincin-
nati, Ohio, 1981.
A Reference Handbookon Small-Scale WastewaterTech-
nology. U.S. Department of Housing and Urban Develop-
ment, Washington, D.C., 1985.
35
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SUBMERGED BED CONSTRUCTED WETLANDS
TECHNOLOGY APPLICATIONS
Constructed wetlands (CW) treatment technology is ap-
plicable to situations where direct stream discharge is
either prohibited or restricted. Wetlands systems may
also be utilized as polishing or tertiary treatment units,
accepting effluent from prior treatment facilities (i.e., la-
goons). The capacities of these systems range from 500
gallons per day (gpd) to 1 million gallons per day (MGD)
with the great majority being less than 100,000 gpd.
Submerged bed systems can produce an effluent which
contains low concentrations of Biochemical Oxygen De-
mand (BOD5) and Total Suspended Solids (TSS), typi-
cally below 20 mg/L.
PROCESS DESCRIPTION
As shown In Figure 1, submerged bed constructed wet-
lands systems typically consist of single or multiple chan-
nels ortrenches with impermeable linings. The channels
permit plug-flow conditions. Wastewater is distributed to
the channels by perforated or grated pipe. The channels
contain a layerof gravel to support the growth of emergent
vegetation such as cattails, rushes, and reeds^
The majority of the wastewater BOD5 and suspended
solids are reduced by either sedimentation or filtration as
the wastewater passes through the beds. The treated
wastewater is typically discharged from the channel by an
outlet pipe which can be adjusted to vary the depth of the
water level in the channel. A general criterion of
5 m2/person is presently employed to establish the needed
bed area.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Operating requirementsforconstructed wetlands are mini-
mal. The water level in the channels may need to be
periodically adjusted to regulate the detention time in the
system. Excessive detention times can result in an
unnecessary capital expense. Shorter detention times
can result in inadequate treatment. It is important that the
wastewater is equally distributed to all of the channels. In
general, harvesting of the wetlands vegetation is not
practiced, but newer designs suggest better treatment
may result from such practice. The inlet sections of the
channels should be checked regularly for excessive sol-
ids buildup or the accumulation of debris.
SLOTTED PIPE FOR
WASTEWATER \
DISTRIBUTION \
INLET STONE
DISTRIBUTOR
SLOPE 1%
CATTAILS
PHRAGMITES
ADJUSTABLE
EFFLUENT OUTLET
RHIZOME
NETWORK
GRAVEL
WATERTIGHT
MEMBRANE
Figure 1. Submerged bed constructed wetland.
36
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The influent and effluent should be monitored for process
control and permit requirements. The BOD5 loading to the
system should be checked periodically to avoid an organic
overload. Generally, primary or septic tank treatment
should precede the submerged wetlands.
tion costs include the inlet and outlet structures, gravel
filterbed, pretreatment, and final disinfection. They do not
include the costs of land, engineering, laboratory, legal
services, or financing. O&M costs include labor, utilities,
chemicals, and equipment maintenance.
RESIDUES GENERATED
Constructed wetlands systems do not generate sludge as
do conventional biological treatment systems. However,
the aquatic vegetation may need to be periodically har-
vested. The ultimate service life on a CW system prior to
solids overloading is unknown.
TECHNOLOGY LIMITATIONS
Constructed wetlands should not be used to treat raw
wastewater. Most U.S. applications have been limited to
the treatment of secondary effluents. Pretreatment of raw
wastewater is necessary to prevent organic overload and
to prevent excessive accumulations of solids, especially
at the inlet ends of the channels.
FINANCIAL CONSIDERATIONS
Due to a wide variety of designs and existing site condi-
tions, the costs of constructing and operating wetlands
treatment systems vary greatly. Since land requirements
are significant, they are an important factor in site selec-
tion.
The costs for wetland treatment systems are broken down
in Table 1 into construction and O&M costs. The construc-
Table 1. Typical Costs For Wetlands
Treatment Systems (1992 $)
Artif ical Wetlands
System
Pretreatment
Disinfection
Construction
Costs
($/gpd)
0.58 - 2.36
1.18-3.53
0.88-1.18
O&M
Costs
($71000 gal.)
0.12-0.58
0.58-1.18
0.24 ^ 0.35
Bibliography
Constructed Wetlands and Aquatic Plant Systems for Mu-
nicipal Wastewater Treatment. EPA/625/1-88/022, U.S.
Environmental Protection Agency, Cincinnati, Ohio, 1988.
A Reference Handbook on Small-Scale WastewaterTech-
nology. U.S. Department of Housing and Urban Develop-
ment, Washington, D.C., 1985.
37
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SLUDGE TREATMENT AND REUSE
TECHNOLOGY APPUCATIONS
Several of the wastewater treatment processes previ-
ously described (e.g., oxidation ditches, trickling filter
plants, package treatment plants, SBRs and lagoons)
generate sludge that must receive proper treatment and
disposal. Before disposal, sludge must be stabilized to
remove pathogens and reduce the organic content. After
stabilization, some communities dewater the sludge to
reduce its total volume for disposal. Small communities
should dispose of their stabilized sludge by application to
the land wherever possible.
PROCESS DESCRIPTIONS
Stabilization processes, dewatering, and land applica-
tions practices are briefly described in the following para-
graphs.
Stabilization
For small communities, sludge stabilization is typically
accomplished by aerobic digestion or lime application. In
the aerobic digestion process, excess sludge from oxida-
tion ditches or package plants is pumped to an uncovered
and unheated aerobic digester. The sludge is retained in
the digesterfor20 to 30 days (three to fourtimes longerfor
cold climates) to reduce the Volatile Suspended Solids
(VSS) content and pathogens. The digester contents are
aerated and mixed during the digestion period. In the lime
application method of sludge stabilization, lime is added
to raw or digested sludges. Enough lime must be added
to the sludge to raise the pH to greater than 12 to reduce
pathogens. For raw sludge, the pH should be raised to
12.4 and then kept above 11 for 14 days to stabilize the
sludge, as well as to kill pathogens.
Dewaterlng
Uncovered sand drying beds are commonly used by small
communities to remove excess water from sludge priorto
disposal. Some beds consist of an impervious clay
bottom or liner upon which underdrain piping is placed.
The underdrain piping is covered by 6 to 12 inches of
graded gravel. The upper layer of the bed contains 12 to
18 Inches of sand. In normal use, approximately 8 to 12
Inches of sludge are applied to the entire bed surface.
Some of the liquid drains from the sludge, collects in the
underdrains, and is returned as influent to the wastewater
treatment plant while the rest evaporates. Alternative
designs, such as vacuum-assisted, chemically assisted,
asphalt bottoms, may also be applicable.
Land Application
Beneficial sludge constituents include nitrogen, phospho-
rus, potassium, and certain trace metals that act as
fertilizer nutrients, and organic material that serves as a
soil conditioner. Therefore, sludge can be an excellent
supplement to commercial fertilizers and soil amend-
ments. The method by which the sludge is applied to land
and the application rate depend on the characteristics of
the sludge and soil, as well as the type of crop. Three
categories of crops are usually grown: agronomic or row
crops, forage crops and grasses, and forested systems.
Liquid sludge can be applied to either the land surface (by
spreading or spraying) or to the land subsurface (by
injection, disking, or plowing). Dewatered sludge cannot
be pumped or sprayed and is typically spread over the
land surface and then plowed or disked into the soil.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
The following paragraphs discuss O&M requirements for
the various processes presented above.
Stabilization
Aerobic digesters are relatively simple to operate and
maintain. The process should be monitored at least
weekly for dissolved oxygen (DO), pH, and VSS reduc-
tion. The DO should be kept between 1.0 and 2.0 mg/L
The pH in the digester should be between 6.5 and 8.0. A
properly operated digester should achieve a VSS reduc-
tion of at least 40 percent after 15 to 20 days in warm
climates. Cold weatheroperation may require much more
time to achieve adequate VSS reduction. Periodically, the
air supply is turned off to allow the sludge to settle. The
supernatant is then decanted to the head of the plant. The
sludge may also be removed at this time if adequate VSS
reduction has been achieved.
Dewatering
O&M requirements for sand drying beds primarily involve
dried sludge removal from the bed and maintenance of the
38
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sand beds. In most small plants, dried sludge is removed
manually and represents a very large labor demand. A
small quantity of sand is lost each time sludge is removed
and must be replaced periodically. The surface of the bed
must be raked and kept level. Weeds and grasses must
also be removed from the beds.
Land Application
The land application of sludge requires good coordination
between the treatment plant management and farming
operations management. The scheduling of sludge appli-
cations should not interfere with farming operations (i.e.,
planting, tilling, harvesting) but should meet the removal
requirements of the treatment plant. The application rate
should be in accordance with any state permit limits to
prevent excessive accumulation of nutrients or heavy
metals in the soil. All site runoff should be contained. Gold
and wet weather will generally prevent land application
operations. The quality of the sludge must be tested
periodically for nutrients, minerals, heavy metals, and
pesticides.
TECHNOLOGY LIMITATIONS
The technology limitations for stabilization, dewatering,
and disposal are highlighted in the following paragraphs.
Stabilization
Aerobic digesters are energy-intensive operations. They
are adversely affected by excessive solids loading, cold
weather, and low pH (< 6.0).
Dewatering
The efficiency of sand drying beds is significantly affected
by wet weather, freezing temperatures, intense sunlight,
and poor maintenance practices. Holding tanks are
necessary to store sludge during periods of inclement
weather.
Land Application
Land application of sludge is subject to crop management
requirements and climate conditions. Holding tanks or
lagoons are necessary to store sludge. For dedicated
land disposal, land may have to be purchased or leased;
buildup of metals in the soil may limit future use of the land.
Odors and site runoff may limit land application opera-
tions. Prior to application, sludge must first be treated by
a stabilization process, such as digestion, sand drying
beds, composting, or lime stabilization.
Bibliography
Innovative and Alternative Technology Assessment
Manual. EPA/430/9-78-009, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1980.
Operation of Municipal Wastewater Treatment Plants,
Manual of Practice No. 11. Water Environment Federa-
tion, Alexandria, Virginia, 1990.
Sludge Treatment and Disposal. EPA/625/1 -79-011, U.S.
Environmental Protection Agency, Cincinnati, Ohio, 1979.
39
-------
-------
TECHNOLOGY OVERVIEWS - DRINKING WATER TREATMENT
-------
-------
CO A GULA TION/FLOCCULA TION
TECHNOLOGY APPLICATIONS
Coagulation and flocculation processes are used to pre-
pare non-settleable (colloidal) and dissolved solids for
removal from a drinking water supply. Colloidal and
dissolved solids may adversely affect the quality of the
drinking water supply and make it unsuitable for use due
to the presence of turbidity, color, taste, heavy metals, or
microbiological contamination. Coagulation and floccula-
tion processes are installed upstream of sedimentation or
filtration processes; colloidal and dissolved solids are not
removed by sedimentation or filtration processes alone.
PROCESS DESCRIPTION
During the coagulation step, chemicals referred to as
coagulants are added to the water in a rapid mix tank (see
Figure 1). Rapid mixing is important to ensure uniform
distribution of the coagulant throughout the water. The
coagulant neutralizes the electrical charge on colloidal
particles; this permits the small particles to begin to stick
together to form larger particles. Examples of coagulants
are aluminum sulfate (alum) and ferric sulfate. Polymers
are sometimes added to improve the coagulation process.
The rapid mix step generally takes place in 30 to 60
seconds within a small tank equipped with a mechanical
mixer. Hydraulic jumps or in-line static mixers have also
been used to mix the coagulating chemicals and water.
Immediately following the rapid mix tank is a flocculation
basin (see Figure 2). During flocculation, the coagulated
water is gently mixed in a basin for a period of 30 to 60
minutes. The gentle mixing allows the suspended par-
ticles to collide and form heavier particles called floe. The
floe particles can be ultimately removed from the water by
gravity settling and/or filtration.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
The proper operation of coagulation/flocculation processes
requires regular monitoring by the operating personnel.
The monitoring frequency will be determined by actual site
conditions, i.e., size of treatment system and variability of
raw water quality. Parameters to be monitored regularly
and recommended monitoring locations are presented in
MOTOR
OVERFLOW
RAW
WATER
Figure 1. Rapid mix tank.
Table 1. The operator should also visually check at least
daily the floe particle size and distribution in the floccula-
tion basin to maintain adequate mixing rates. Adequate
mixing is demonstrated by the presence of a well-formed
floe and uniform distribution of the floe throughout the
flocculation basin. Records of the treated water flowrate,
chemical feed pump settings, and chemical feed rates
should also be maintained.
The optimal coagulant feed rate depends on the type of
coagulant used and the raw water quality and tempera-
ture. Typical dosages for alum range from 15 to 100 mg/L;
ferric sulfate dosages range from 10 to 50 mg/L. Lower
water temperatures require higher coagulant dosages.
Operators should periodically perform jar tests to deter-
mine the optimal coagulant dosage.
43
-------
.Control Valve
JL
W.L.
Influent
Paddles
Pfflnont
3
Drive Ur
lit
:;:
II II II
, H H II
II II II
II II
II II II
1 n n n '
u u u
II II 1!
II II II
n n n
ii n n
,
' II II II ฃ
Figure 2. Flocculation basin with horizontal paddle wheel agitators.
Table 1. Recommended Process Monitoring for
Coagulation / Flocculation Processes
Parameter
Location
Turbidity Raw water
Temperature Raw water
pH Raw water, flocculator effluent
Alkalinity Raw water, flocculator effluent
Color Raw water
TECHNOLOGY LIMITATIONS
Coagulation/f locculation processes are adversely affected
by low water temperatures, insufficient alkalinity, inad-
equate mixing, and a highly variable raw water quality.
Continuous, uniform raw water flowrates are necessary
for good performance. Low-turbidity waters are difficult to
treat and may result in inadequate floe formation. Well-
trained operators are needed for reliable operation.
FINANCIAL CONSIDERATIONS
The costs forcoagulation/flocculation systems include the
baste chemical feed system (mix tank, mixer, metering
pump, valves, and piping), the rapid mix system, and the
flocculator. Construction cost estimates forchemical feed
systems range from $1,830 to $11,030. Annual O&M
costs will be dependent on the chemical used and the
application rate. Estimated annual O&M costs range from
$2,620 to $10,950. The costs presented above are for
systems with maximum chemical feed rates of 10 Ibs/day
upto1,000lbs/day.
For small community systems with flows less than 100,000
gallons perday (gpd), the estimated construction costs for
adding rapid mix facilities range from $23,000 to $31,800.
The O&M costs do not vary significantly for flows under
100,000 gpd and are estimated to be approximately
$5,000 per year.
Estimated construction costs for flocculators range from
$17,600 to $32,000 for systems treating flows under
100,000 gpd. O&M costs are estimated to be $2,000 per
year-
Costs presented in 1992$.
For most small communities, coagulation/f locculation sys-
tems are included as part of a package treatment system
also consisting of sedimentation and filtration. Costs of
package treatment systems are presented under the
filtration overview.
Bibliography
Estimation of Small System WaterTreatment Costs. EPA/
600/2-84/184a, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1984.
Introduction to Water Treatment. American Water Works
Association, Denver, Colorado, 1984.
Water Treatment Plant Operation. California State Uni-
versity, Sacramento, California, 1990.
Environmental Pollution Control Alternatives: Drinking
Water Treatment for Small Communities. EPA/625/5-90/
025, U.S. Environmental Protection Agency, Cincinnati,
Ohio, 1990.
Technologies for Upgrading Existing or Designing New
Drinking WaterTreatment Facilities. EPA/625/4-89/023,
U.S. Environmental Protection Agency. Cincinnati,
Ohio, 1990.
44
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SEDIMENTATION
TECHNOLOGY APPLICATIONS
In sedimentation basins or clarifiers, settleabie solids are
removed from raw water by gravity settling. Non-settle-
able (colloidal) solids can also be removed from water by
sedimentation with the aid of coagulants added to up-
stream coagulation/flocculation treatment units. The co-
agulants convert the colloidal solids to large, dense, and
settleabie floes which are removed by settling in sedimen-
tation basins. Sedimentation also helps to reduce the
solids loading to filtration systems which results in longer
filter runs.
PROCESS DESCRIPTION
Sedimentation may take place in rectangular, circular, or
square basins or tanks. The tanks are sized to provide
sufficient time for gravity settling to take place. Inlet
structures are provided to reduce the velocity of the water
and to distribute the water uniformly across the tank. The
outlet or effluent section of sedimentation tanks contain
weirs that control the exit velocity of the clarified water to
prevent short-circuiting. Sludge collection mechanisms
may also be provided to remove the settled solids from the
bottom of the basin.
Modifications to conventional sedimentation basins have
included the installation of tube or plate settlers and the
solids-contact process. The installation of tube settlers in
existing sedimentation basins results in improved settle-
able solids removal efficiencies. In many cases, the flow
capacity of existing basins has been increased by 100
percent following the installation of tube settlers. Tube or
plate settlers are made of plastic and placed in modules
which are 2 to 3 feet in length. The tubes or plates are
installed at an incline about 60 degrees from the horizon-
tal. As water flows upward through the modules, solids
settle out on the plates and eventually move downward
and into the basin from which they are removed.
Solids-contact basins or upflow clarifiers (see Figure 1)
combine coagulation, flocculation, and sedimentation into
a single basin. Coagulation and flocculation take place in
the reaction zone where the water and the coagulating
chemicals first enter the basin. The flocculated solids are
allowed to settle and accumulate around the reaction
zone. Water exiting the reaction zone passes through the
accumulated solids (or "sludge blanket") which act as a
filter trapping smaller floe particles. After passing through
the sludge blanket, the water flows up and over the weirs
located at the top of the clarifier. A portion of the settled
solids is removed from the clarifier for disposal while the
remainder is recycled back to the reaction zone. The
recycled sludge speeds up the coagulation/flocculation
process and reduces coagulant dosage requirements.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Sedimentation basins should be checked daily to ensure
adequate solids removal. Typically, the raw water and
individual basin effluent should be checked for turbidity.
The temperature of the raw water should also be moni-
tored since low water temperatures will reduce the settling
rate of particles. During cold-weatheroperation increased
dosages of coagulants may be needed orthe flowrate may
be reduced to increase the detention time in the basin.
The overflow weirs must be kept clean and level to prevent
short-circuiting and poor solids removal.
The sludge blanket level should also be checked daily in
all operating basins. Sludge should be withdrawn fre-
quently from conventional sedimentation basins to pre-
vent excessive accumulations of sludge. Excessive accu-
mulations result in significant solids loss from the basins
and blinding of downstream filtration processes. Solids-
contact clarifiers require careful monitoring of the sludge
blanket for the following reasons: (a) a sufficient blanket
level must be maintained to ensure that all water passes
through the blanket priorto exiting the clarifier; and (b) the
sludge removal and recirculation rates are adjusted based
on the level of the sludge blanket.
Sedimentation basins should be drained annually for
inspection. Inlet baffles should be cleaned of any algae
or solids accumulation. Effluent weirs must be level.
Basins equipped with tube or plate settlers may need to be
drained more frequently to flush out accumulations
of solids.
TECHNOLOGY LIMITATIONS
Depending on the design characteristics, some sedimen-
tation basins may be upset by sudden increases in flow
rates. Low water temperatures may result in reduced
solids removal due to a reduction in settling rates or the
production of density currents which cause short-circuit-
ing. Inadequate inlet baffles or uneven effluent weirs can
result in poor solids removal due to short-circuiting.
45
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Variable Speed
Recirculafon Pump
k Sludge Wasting Sump
Collector Drive
Flocculatoon and
Secondary Reaction Zone
IT \^L/
Sludge Slowdown
Sectional Elevation
Sludge Collector
Figure 1. Solids contact clarifier with tube settlers.
SLUDGE HANDLING AND DISPOSAL
Sludge removed from sedimentation basins can be dis-
posed of by landfilling or land application. The discharge
of water treatment plant sludge to receiving waters is not
considered an acceptable practice, unless approval has
been obtained from a state or federal environmental
regulatory agency and a National Pollutant Discharge
Permit (NPDES) has been issued to regulate the dis-
charge of pollutants.
The quantity of sludge generated will depend upon the
quality of the raw water supply and the quantity and type
of coagulants added to the raw water. For most small
communities, sludge is dewatered prior to disposal. De-
watering may be accomplished at relatively low operation
and maintenance (O&M) costs by pumping sludge into
lagoons or sand drying beds. More efficient dewatering
may also be accomplished by using belt filter presses,
pressure filters, or centrifuges; however, these units also
have higher O&M costs than the simpler drying beds or
lagoons.
FINANCIAL CONSIDERATIONS
Formost small community systems, sedimentation basins
are included as part of a package treatment system
consisting of coagulation/flocculation, sedimentation, and
filtration. Costs of package systems are presented under
the filtration overview.
Existing sedimentation basin performance and capacity
may be increased by the addition of tube or plate settling
modules. For basins treating flows under 100,00 gpd, the
estimated costs for installing the modules range from
$2,000 to $4,050.
Costs presented in 1992$.
Bibliography
Estimation of Small System Water Treatment Costs. EPA/
600/2-84/184a, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1984.
Introduction to Water Treatment. American Waterworks
Association, Denver, Colorado, 1984.
Water Treatment Plant Operation. California State Uni-
versity, Sacramento, California, 1990.
Environmental Pollution Control Alternatives: Drinking
Water Treatment for Small Communities. EPA/625/5-90/
025, U.S. Environmental Protection Agency, Cincinnati,
Ohio, 1990.
Technologies for Upgrading Existing or Designing New
Drinking Water Treatment Facilities. EPA/625/4-89/023,
U.S. Environmental Protection Agency. Cincinnati,
Ohio, 1990.
46
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FILTRATION
TECHNOLOGY APPLICATIONS
Filtration processes are utilized to reduce turbidity and
microorganism levels in a community's surface water
supply. Filtration can be very effective in removing patho-
genic microorganisms, including Giardia cysts and vi-
ruses. Conventional filtration processes are normally
preceded by coagulation, flocculation, and sedimenta-
tion. Direct filtration processes are preceded by coagula-
tion and flocculation only; the floe is removed directly by
the filters.
PROCESS DESCRIPTION
Numerous filtration technologies are available for drinking
water treatment. This section will limit discussion to four
technologies most appropriate to small-community sys-
tems.
Slow sand filters (see Figure 1) consist of a bed of fine
sand approximately 3 to 4 feet deep supported by a 1 foot
layer of gravel and an underdrain system. The effective
size of the sand ranges from 0.25 to 0.35 mm, with a
uniformity coefficient of 2 to 3. Slow sand filters are
designed to operate at very low application rates (0.03 to
0.10 gallons per minute/ft2 of filter bed area) and therefore
have relatively extensive land requirements. Slow sand
filters are operated under continuous, submerged condi-
tions maintained by adjusting a control valve located on
the discharge line from the underdrain system.
Biological processes, and chemical/physical processes
common to various types of filters occur at the surface of
the filter bed. A biological slime or mat referred to as
"schmutzdecke" forms on the surface of the bed which
traps small particles and degrades organic material present
in the raw water. Slow sand filters are limited to treating
surface waters with turbidity levels less than 20 nephelo-
metric turbidity units (NTU) due to the surface biological
mat which forms as well as the small void spaces in the
bed. Generally, water applied to slow sand filters is not
pretreated by coagulation/flocculation and sedimentation
processes.
Recent studies have demonstrated that certain modifica-
tions to slow sand filters can result in improved perfor-
mance and possibly extend the application range to more
turbid waters. Someof these modifications require further
full-scale investigations to support the results of these
studies and to develop more comprehensive design crite^
ria. Slow sand filter modifications investigated include
several pretreatment steps, such as roughing filters and
preozonation, to extend the application range to lower
quality waters; filter mats to increase filter runs and
simplify cleaning procedures; surface amendments to
remove organic precursors and control disinfection by-
product formation; and harrowing techniques to reduce
cleaning costs and filter "ripening" periods.
Slow Sand Filter
Effluent Flow
Control Structure
Clearwell
Raw
Water
To Sewer or Raw
Water Source
Sand Filter Bed
Support Gravel
Perforated Drain Pipe
Control Valve
Filtered Water for Backfilling
Backfill
Pump
Figure 1. Typical unhoused slow sand filter installation.
47
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Filter Tank
Graded Gravel
Perforated Laterals
Filter Floor
Cast-Iron Manifold
Figure 2. Cutaway view of typical rapid sand filter.
Rapid sand filters (see Figure 2) can treat raw water with
high orvariable turbidities at f lowrates up to 2 gpm/ft2. The
filter components (except for the control panel) are con-
tained in a watertight tank. The effective size of the sand
ranges from 0.4 to 0.6 mm; this results in larger void
spaces which do not fill and clog as quickly as in slow sand
filters. The filter bed is usually 24 to 36 inches deep and
rests on top of a layer of gravel 6 to 18 inches deep. The
sand and gravel bed is supported by an underdrain
system which collects the filtered water and also evenly
distributes the backwash water.
Rapid sand filters are highly automated and are usually
included in "package planf systems (see Figure 3). Pack-
age plants generally consist of coagulation/flocculation,
sedimentation, and filtration components. Occasionally,
the sedimentation step is omitted. The filters are
backwashed automatically at a predetermined head loss
or whenever the turbidity of the filtered water begins to
increase. On-line turbidimeters are used to continuously
monitorand record the turbidity of the filtered water. Head
loss indicators are provided to continuously measure the
filter head loss.
High rate filters operate at application rates ranging from
3 to 10 gpm/ft2. They are well-suited to treating raw water
supplies with high or variable turbidities. High rate filters
may be divided into dual-media and multi-media filters.
Dual-media filters consist of an upper layer of coarse coal
(anthracite) and a lower layer of sand; both layers are
supported by a gravel bed. Multi-media filters consist of
three types of media installed from top to bottom in the
following order: coarse coal, sand, garnet. High rate filters
are highly automated and contain components similar to
those found in rapid sand filters. High rate filters are also
included in package plant systems.
Diatomaceous earth (DE) filters have been used exten-
sively for filtering swimming pool water; they may also be
applicable for some small-community systems. DE filters
are compact, pressure filters capable of removing Giardia
cysts and algae from water supplies. However, they are
most suited for water supplies with low turbidities (less
than 10 NTU) and low bacteria counts.
48
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jj- liJJpolyelectrolyte
Alum
Chlorine
Raw Water
Influent
Connection
Effluent
Connection
Clear Water
and
Backwash
Storage
Backwash
Connection
Figure 3. Flow diagram of a package plant.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Slow sand filters are the simplest to operate. Daily
operation consists of checking the rawwatertemperature
and turbidity, filter effluent turbidity, and filter head loss.
The filter effluent control valve should be periodically
adjusted to maintain a constant discharge rate. Slow sand
filter runs may last from 20 to 90 days depending on raw
water quality before cleaning is necessary. Slow sand
filters are not backwashed. Instead, the top 1 to 2 inches
of sand are manually removed from the surface of the filter
bed. The removed sand may be either washed and then
stored for future use, or simply discarded. After cleaning,
a "ripening period" of one to two days is required to allow
the schmutzdecke or surface biological mat to redevelop.
The filtered water is typically wasted during this period due
to the poor water quality. New or washed sand should be
added to the filter when the bed depth reaches 24 inches.
Other filter types, such as rapid sand filters, high rate
filters, and package plants, can be highly automated.
However, these systems require the presence of a prop-
erly trained operator on a daily basis to ensure continu-
ous, reliable operation. The temperature and turbidity of
the raw water should be checked daily. In addition, the
filter flowrate, filter run time, filter head loss, backwash
cycles, and filtered water turbidity should also be moni-
tored on a daily basis. The duration of the typical filter run
will range from 12 to 36 hours depending on the filter
influent quality. The operator should periodically observe
the filter backwash cycles to verify adequate cleaning of
the filter and to check for excessive loss of filter media
during the backwash cycle.
The effluent turbidity from diatomaceous earth filters
should be checked periodically. The application of addi-
tional diatomaceous earth should be adjusted according
to the measured turbidity levels. When the filter headloss
reaches a predetermined level, the filter must be
backwashed. After backwashing, a new precoat layer of
diatomaceous earth must be formed on the filter elements
before filtration can resume.
TECHNOLOGY LIMITATIONS
Slow sand filters are not recommended for waters with
high or variable turbidities; water with high turbidity or
algae levels will result in short filter runs. Generally, the
raw water turbidity should be less than 20 NTU and the
color should be less than 30 units. Slow sand filters do not
remove synthetic organic compounds, disinfection by-
product precursors, or inorganic chemicals. These filters
also have relatively extensive land area requirements.
Filters installed in cold climates must be housed.
Other filter types, such as rapid sand filters, high rate
filters, and package plants, require daily attendance by
properly trained operators. Inadequate coagulant dos-
ages and/or poor sedimentation can result in filter blinding
and reduced filter runs. Excessive levels of turbidity and
color in the raw water may exceed package plant design
specifications; in these cases, the flow capacity of the
plant must be downrated to produce an acceptable water
quality.
Diatomaceous earth (DE) filters do not effectively remove
viruses unless the water is pretreated with coagulants and
filter aids. Also, DE filters do not remove dissolved
substances, such as color-causing materials.
49
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FINANCIAL CONSIDERATIONS
Slow Sand Filters
Estimated construction and annual O&M costs are pre-
sented in Table 1 for uncovered slow sand filters. Con-
struction costs include clay-liner, earthen berms, PVC
piping, steel tank reservoir, effluent flow control structure,
effluent flow meter, and pump for filter backfilling. The
filter loading rate is 70 gpd/sq. ft. The costs for two filter
sizes are as follows:
Table 1. Slow Sand Filter Construction and O&M
Costs (1992$)
Capacity
(gpd)
50,000
100,000
Construction
Costs ($)
207,900
271,100
Annual
O&M Costs ($)
6,800
8,100
Mixed Media Filters
Estimatedconstructioncostsfor prefabricated, steel pack-
age filter units designed for flows less than 100,000 gpd
and filtration rates between 2 to 5 gpm/sq. ft. range from
$55,000 to $95,000. O&M costs are dependent on the
filter size and the number of backwashes performed per
day. Annual O&M costs are estimated to range between
$4,200 to $9,500 for flows less than 100,000 gpd.
Complete Package Treatment Plants
Estimated construction costs for package plants consist-
ing of coagulation/fInoculation, sedimentation, and multi-
media gravity filtration range from $98,000 to $160,000 for
flows between 14,000 gpd and 144,000 gpd. The filtration
rate is assumed to be 5 gpm/sq. ft. Annual O&M costs are
projected to range from $10,100 to $14,400 for the same
range of flows.
Diatomaceous Earth Filters
Estimated construction costs for package pressure DE
filters with design capacities of 28,000 gpd and 86,000
gpd are $71,000 and $80,000, respectively. O&M costs
for both systems (exclusive of DE filter aid cost) are
estimated to be $10,000 per year. The annual DE filter aid
cost for each filter is estimated to range from $225
(28,000 gpd) to $700 (86,000 gpd) at an application rate
of 15 mg/L
Costs presented in 1992$.
Bibliography
Estimation of Small System WaterTreatment Costs. EPA/
600/2-84/184a, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1984.
Introduction to WaterTreatment. American Waterworks
Association, Denver, Colorado, 1984.
Water Treatment Plant Operation. California State Uni-
versity, Sacramento, California, 1990.
Environmental Pollution Control Alternatives: Drinking
Water Treatment for Small Communities. EPA/625/5-90/
025, U.S. Environmental Protection Agency, Cincinnati,
Ohio, 1990.
Technologies for Upgrading Existing or Designing New
Drinking Water Treatment Facilities. EPA/625/4-89/023,
U.S. Environmental Protection Agency. Cincinnati,
Ohio, 1990.
50
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DISINFECTION
TECHNOLOGY APPLICATIONS
The destruction or inactivation of disease-causing organ-
isms (pathogens) in a community's drinking water supply
is accomplished by disinfection processes. This is achieved
in most small-community systems by using chlorine, ozone
(O3), or ultraviolet (UV) light to disinfect the water supply
(sometimes referred to as primary disinfection) and by
maintaining a chlorine residual in the community's water
distribution system to prevent the regrowth of microorgan-
isms (sometimes referred to as secondary disinfection).
Community drinking water systems using a surface water
supply ora ground-water supply underthe direct influence
of surface watermust disinfect the watersupplyto comply
with the requirements of the Surface Water Treatment
Rule (SWTR).
PROCESS DESCRIPTION
The most commonly used disinfectant for small-commu-
nity systems is chlorine. Ozone and UV may also be used
as primary disinfectants; chlorine must still be added to
the water to prevent regrowth of microorganisms in the
distribution pipelines. A comparison of these three dis-
infectants is presented in Table 1; a brief description follows.
Chlorination may be accomplished by the application of
chlorine gas or hypochlorite to the drinking water supply.
Chlorine gas systems for small communities utilize 150
pound chlorine cylinders with cylinder mounted chlorina-
tors. The chlorinator is used to regulate the chlorine gas
feed rate. Chlorine gas is withdrawn from the cylinder by
a vacuum which is created by circulating some of the
water supply through an ejector. A small centrifugal pump
is used to Circulate waterthrough the ejector to create the
vacuum. The chlorine gas mixes with the water flowing
through the ejector. A chlorine solution is then ejected into
the water supply at the entrance to a contact tank or
directly into a water main leading to the distribution sys-
tem.
Chlorination may also be accomplished by using sodium
hypochlorite, a liquid, or calcium hypochlorite, a solid.
Sodium hypochlorite is available in concentrations rang-
ing from 5 to 15 percent chlorine. A dilute solution is
generally prepared and fed into the water by a chemical
feed pump which has a variable output. Calcium hypo-
chlorite is available in tablet, granular, or powdered form
and contains about 70 percent available chlorine. Chlo-
rine solutions are prepared by dissolving the calcium
hypochlorite in a 30 to 50 gallon solution tank. The
solution is applied to the water by a chemical feed pump
with a variable output. Hypochlorite systems are gener-
ally safer and simpler to use than gaseous chlorine sys-
tems.
The pathogen reduction efficiency of Chlorination systems
is affected by contact time, concentration of free available
chlorine, pH, temperature, and turbidity. Generally, the
efficiency of chlorine disinfection is reduced under the
following conditions: short contact times, insufficient dos-
ages of chlorine, water pH above 7.2, low water tempera-
ture, and high turbidity levels. The SWTR specifies
minimum chlorine concentrations (expressed as C) and
contact times (expressed as T) which must be achieved at
various pH concentrations and temperatures to provide
inactivation of Giardia and viruses. These values are
presented in the SWTR as CT values which are the
product of the chlorine concentration (C) and the contact
time (T). The contact time is defined as the time required
for the water to travel from the point of chlorine application
to the first customer during peak flow periods.
Ozone may be used as a primary disinfectant, especially
in communities where Chlorination may result in signifi-
cant levels of trihalomethanes (THMs) or other disinfec-
tion byproducts. Ozone cannot be stored and must
therefore be generated onsite. Efficient contact with the
water supply is critical, since ozone is not highly soluble in
water. A two-stage contactor is normally provided to
satisfy any ozone demand and to ensure adequate con-
tact. Chlorine must be added to the ozonated water prior
to entry into the distribution system.
Ultraviolet light may be used as a primary disinfectant for
small ground water supply systems. UV is not recom-
mended for surface water systems as it is unable to
inactivate Giardia cysts. UV systems consist of one or
more UV lamps enclosed by quartz tubes. Water flows
past the lamps and is exposed to the UV radiation; the UV
radiation penetrates the microorganisms it comes in con-
tact with and destroys the genetic material inside the
bacteria or virus cells. UV systems cannot be used on
turbid water supplies and are usually installed down-
stream of coagulation/flocculation, sedimentation, or fil-
tration processes. Chlorine must be added prior to the
distribution system entry point.
51
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Table 1. Comparison of Three Disinfectants for Small-Commmunity Drinking Water Systems
Disinfectant
Advantages
Disadvantages
Application Point
Chlorine
Effective for viruses,
bacteria, and Giardia cysts
Can be used as either a
primary or secondary
disinfectant
Chlorine residual can be
easily monitored
Available as a gas, liquid, or
solid
Minimal O&M requirements,
especially for liquid and solid
forms
May result in potentially
harmful byproducts (THMs)
Significant safety concerns,
especially for gas systems
May result In precipitation of
iron and manganese
Variety of application points
To minimize THM formation,
generally added at the end of
treatment steps
Ozone
Effective against viruses,
bacteria, and Giardia cysts
Enhances removal of
biodegradable organics in slow
sand filters
Must be generated onsite
Does not produce a stable,
long-lasting residual
May result in harmful
byproducts
Low solubility in water
Complex O&M requirements
Exhaust gas must be treated
to remove ozone
Difficult to measure residual
Prior to rapid mixing step
Should provide adequate
time for biodegradation of
oxidation products prior to
chlorination
Ultraviolet Light
Effective against viruses and
bacteria
Minimal O&M requirements
Very short contact times
Not effective against Giardia
cysts
Limited to groundwater
systems not directly influenced
by surface water supply
Not suitable for water
containing significant levels of
turbidity, color, or organic
compounds
Downstream of
sedimentation or filtration
processes
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
Chlorination systems must be monitored on a daily basis.
Gaseous chlorine systems are more labor intensive and
complex than hypochlorite systems. Regardless of the
form of chlorine used, all chlorination systems should be
checked daily for the following items:
Chlorine residual concentration at the well house or
treatment plant and at the farthest points of the distri-
bution system
Chlorine feed rate
Amount of chlorine remaining in the cylinder or amount
of solution remaining in mix tank; an adequate supply
is essential to provide continuous chlorination of the
water supply
All chlorine containers should be stored in a safe, secure
room. Petroleum-based products, such as paints, thinners,
and pesticides, should never be stored in the same room.
All chlorine gas cylinders should be stored upright and
52
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securely chained to a wall. Containers of calcium hy-
pochlorite should be kept sealed and stored in a dry
location. Sodium hypochlorite solutions must be stored in
cool, dark locations. These solutions lose their disinfect-
ing power rapidly when exposed to sunlight. A maximum
of about 1 month's supply of sodium hypochlorite should
be stored onsite.
Ozone and U V systems must also be monitored on a daily
basis. Most small systems consist of package units with*
built-in process monitors. Typical parameters monitored
forozonation systems include gas pressure, temperature,
flowrate, electric powerconsumption, and ozone residual.
For UV systems, when the light intensity decreases, the
surface of the quartz tubes should be cleaned. UV lamps
may require periodic replacement. In general, the lamps
should be replaced annually; the actual frequency should
be established based on site-specific experience. The
turbidity of the water feed to the UV unit should also be
monitored; excessive turbidity will impair UV disinfection.
TECHNOLOGY LIMITATIONS
The presence of organic compounds in a community's
water supply could limit the use of chlorine as a primary
disinfectant. Chlorine reacts with organic compounds and
forms THMs; several THMs are suspected carcinogens.
To prevent THM formation in systems using chlorine,
treatment processes to remove organic material are nec-
essary; these processes include coagulation, filtration,
and activated carbon. Gaseous chlorine is very toxic;
systems using chlorine gas require the following safety
features:
A separate room or building should be provided for
chlorination equipment and cylinder storage.
All chlorine handling areas should be well-ventilated
and heated. A chlorine gas leak detector should also
be installed.
Emergency repair kits to stop leaks and self-contained
breathing apparatus should also be provided.
Ozonation systems are complex to operate and have high
O&M costs. Ozonation may also result in the formation of
harmful byproducts. Ozone is highly unstable and has a
low solubility in water; it does not produce a long-lasting
residual. Chlorine must still be used as a secondary
disinfectant.
UV light does not inactivate Giardia cysts; therefore, UV
should not be used as a primary disinfectant for surface
water systems and for groundwatersystems directly influ-
enced by surface water. UV systems are not suitable for
water containing significant concentrations of turbidity,
color, or organic compounds.
FINANCIAL CONSIDERATIONS
Chlorine
Estimated construction costs for small community gas
chlorination systems do not vary significantly for capaci-
ties ranging from 10 to 80 Ibs/day. A typical gas chlorina-
tion system consists of the chlorinator, scale, booster
pump, and injector housed in a 10 ft. by 10 ft. building. The
estimated construction cost for such a system is $25,350.
The O&M cost is estimated to be approximately $3,500
per year. Hypochlorite systems (including housing) are
estimated to have construction costs of $20,700 and
annual O&M costs of $3,100. The actual equipment costs
for hypochlorite systems are usually half of that for gas
chlorination systems.
Ozone
Most small community ozonation systems have design
capacities ranging from 5 to 20 Ibs/day of ozone. Esti-
mated construction-costs (including housing) range from
$153,500 to $ 189,000. O&M costs are estimated to range
from $12,000 to $16,000 per year.
Ultraviolet Light
The costs reported in the literature for UV light systems
vary widely. Generally, for systems treating less than
100,000 gpd, the estimated construction cost is less than
$40,000. The annual O&M cost is estimated to be ap-
proximately $2,400.
Costs presented in 1992$.
Bibliography
Estimation of Small System Water Treatment Costs. EPA/
600/2-84/184a, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1984.
Introduction to Water Treatment. American Waterworks
Association, Denver, Colorado, 1984.
Water Treatment Plant Operation. California State Uni-
versity, Sacramento, California, 1990.
Environmental Pollution Control Alternatives: Drinking
Water Treatment for Small Communities. EPA/625/5-90/
025, U.S. Environmental Protection Agency, Cincinnati,
Ohio, 1990.
Technologies for Upgrading Existing or Designing New
Drinking Water Treatment Facilities. EPA/625/4-89/023,
U.S. Environmental Protection Agency. Cincinnati,
Ohio, 1990.
53
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ACTIVATED CARBON
TECHNOLOGY APPLICATION
Drinking water supplies, especially from surface water
sources, may contain significant concentrations of natu-
rally occurring organic materials. These dissolved organ-
ics may cause taste, odor, or color problems in a
community's drinking water and result in excessive con-
sumer complaints. Some small-community drinking water
supplies may become contaminated by synthetic organic
chemicals (SOCs) originating from leaking underground
storage tanks; agricultural runoff containing pesticides or
herbicides; solid waste or hazardous waste landfills; or
chemical wastes which have been disposed of improp-
erly. These SOCs are toxic substances and may threaten
the public health if significant concentrations develop in
the drinking water. Activated carbon has been success-
fully used to remove synthetic organic chemicals such as
benzene, carbon tetrachloride, trichloroethylene, and pes-
ticides like DDT. Activated carbon effectively removes
naturally occurring organic compounds which cause taste,
odor, and color problems.
PROCESS DESCRIPTION
Two types of activated carbon, granular and powdered,
have been used in drinking water treatment. Powdered
activated carbon (PAC) is added directly to the raw water
and removed by settling in sedimentation basins. PAC is
most often used for taste and odor control. Granular
activated carbon (GAC) units are more reliable for SOC
removal than PAC units and are also very effective in
controlling taste and odor.
Activated carbon processes remove dissolved contami-
nants by a process called adsorption. Particles of acti-
vated carbon contain an immense network of pores.
These pores provide a very large surface area to which
contaminants can adhere or stick. It has been estimated
that one gram of activated carbon has a surface area
equivalent to a football field. Significant bacterial popula-
tions may develop within the pores of the carbon particles.
This may result in a reduction of the adsorptive efficiency
of the carbon or an increase in the bacterial counts of the
treated water.
All organic contaminants are not adsorbed by activated
carbon at the same rate. The presence of dissolvedjsolids
orother competing contaminants may reduce the removal
efficiency of activated carbon for a particular organic
contaminant. It is therefore essential that adequate pilot
testing be conducted on a community's water supply
during the design phase. Typically, the addition of coagu-
lation/flocculation, sedimentation, or filtration processes
is necessary to pretreat surface water prior to GAC treat-
ment.
The typical GAC unit can be similar in design to either a
gravity or pressure filter. In some communities, the sand
in existing filters has been either partially or completely
replaced with GAC. A minimum GAC bed depth of 24
inches is recommended for taste and odor control. How-
ever, greater media depths (up to 10 feet) are needed to
ensure adequate removal of potentially harmful organic
contaminants and to extend the operating life of the unit.
Activated carbon filters can be designed to treat hydraulic
loadings of 2 to 10 gpm/ft2. Sufficient detention time in the
filter must be provided to achieve the desired level of
removal of the organic contaminants. The detention time
is determined by the volume of the GAC filter divided by
the flow rate. This is referred to as the empty bed contact
time (EBCT) since the volume of carbon in the bed is not
considered. For adequate removal of most organic con-
taminants to occur, the EBCT should be about 10 minutes.
EBCTs less than 7.5 minutes are generally ineffective.
OPERATION AND MAINTENANCE (O&M)
REQUIREMENTS
GAC filters have O&M requirements which are very simi-
lar to rapid sand or multimedia filters. The major process
control requirements include:
Frequent monitoring of the head loss across the filter to
determine backwashing requirements
Monitoring of the feed water turbidity or suspended
solids
Monitoringof thefiltereffluentturbidity, bacterial counts,
and organic contaminant concentrations
54
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Monitoring of the filter flowrate, backwash flowrate,
and carbon loss due to backwashing
Since the pores of the carbon particles will over time
eventually become saturated with the organic contami-
nant, the activated carbon must be periodically removed
and replaced. The GAG vendor will be able to provide
guidance concerning when to replace the GAG.
TECHNOLOGY LIMITATIONS
GAG filters require periodic testing of the finished waterto
determine the remaining bed life. The performance of
GAG systems is affected by the contaminants present in
the water, the variability of the raw water quality, rapid
fluctuations in the filter flowrate, the types and operation
of upstream treatment processes, and significant bacte-
rial growth within the carbon particle pores which may
result in filter plugging or a reduction in the surface area
available for adsorption.
FINANCIAL CONSIDERATIONS
Construction costs for skid-mounted, pressure activated
carbon filters having an empty bed contact time of 10
minutes and capable of treating flows ranging from 1,880
gpd to 67,900 gpd are estimated to range from $26,700 to
$112,000. Costs may vary significantly depending on
actual site specific pollutants and concentrations present.
Annual O&M costs without carbon replacement are esti-
mated to range from $2,750 to $5,000 for the flow ranges
noted above. The frequency of carbon replacement will
be dependent on site specific design criteria. For the flow
ranges noted above and an annual replacement fre-
quency, estimated annual carbon replacement costs range
from $100 to $2,400.
Costs presented in 1992$.
Bibliography
Estimationof Small System Water Treatment Costs. EPA/
600/2-84/184a, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1984.
Introduction to Water Treatment. American Waterworks
Association, Denver, Colorado, 1984.
Water Treatment Plant Operation. California State Uni-
versity, Sacramento, California, 1990.
Environmental Pollution Control Alternatives: Drinking
Water Treatment for Small Communities. EPA/625/5-90/
025, U.S. Environmental Protection Agency, Cincinnati,
Ohio, 1990.
Technologies for Upgrading Existing or Designing New
Drinking Water Treatment Facilities. EPA/625/4-89/023,
U.S. Environmental Protection Agency. Cincinnati,
Ohio, 1990.
55
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CASE STUDIES - WASTEWATER
-------
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WEST MONROE, NEW YORK
CASE STUDY #1
BACKGROUND
The Town of West Monroe is located in Oswego County
along the northern shores of Oneida Lake in upstate New
York. This small community has a population of approxi-
mately 5,000 people. Priorto 1989, the community had no
municipal wastewater collection or central treatment sys-
tem. Up until that time, all wastewater was treated
exclusively by individual onsite septic tank systems. The
majority of these systems had functioned properly, but
many of the septic systems in the Big Bay area of the Town
were unreliable. This case study discusses the problems
faced by the homeowners in the Big Bay area of West
Monroe and the wastewater collection and treatment
systems implemented to resolve these problems.
The Big Bay area consists of 220 homes on a small parcel
of land adjacent to Oneida Lake. These homes, originally
constructed as summer cottages, had gradually been
converted into year-round residences as the population
increased. The change in residency, combined with poorly
draining soils and a high water table, caused the majority
of the septic systems serving this area to fail. This
situation persisted for almost 20 years due to the limited
financial resources of the community and the perception
that this was an individual homeowner problem rather
than a community-wide problem. Eventually, the
homeowners in the community were faced with the need
to implement a solution to the failed septic systems or risk
condemnation proceedings.
COMMUNITY RESPONSE
In response to this problem, several residents volun-
teered to form a committee (the Sewer Committee) to
investigate alternative wastewater collection and treat-
ment systems and to initiate the process of securing
necessary government approvals and applying for avail-
able funds. The Sewer Committee received assistance
from several state and county agencies during the plan-
ning stages of the project.
One of the first agencies to be contacted by the committee
was the New York Department of Environmental Conser-
vation (NYDEC). The NYDEChasaSelf-Help Program to
assist small communities with environmental problems.
Personnel from the Self-Help Program helped the Town
form a sewer district (a prerequisite to obtaining approval
to construct municipal collection or treatment facilities in
New York) and prepare a Request for Proposals (RFP) to
hire a consulting engineering firm. Self-Help Program
personnel also helped process the paperwork through the
multilayered regulatory approval system, resulting in mini-
mal delays and lower costs. In addition, the Oswego
County Health Department assisted the Sewer Commit-
tee by helping prepare the RFP and by reviewing the
collection system plans and specifications.
As the project proceeded, the Sewer Committee con-
ducted several public information meetings which were
attended by homeowners, Town Board members, and the
Oswego County Health Department. Periodically, the
Sewer Committee distributed flyers to the homeowners to
keep them informed about the progress of the project.
EVALUATION OF ALTERNATIVES
A consulting engineering firm was selected to help the
Town evaluate various alternatives and select a reason-
able solution. The Sewer Committee had an active role in
this process, visiting several municipalities to evaluate the
performance of various systems. Several technologies
were evaluated for the collection and treatment systems.
A secondary treatment system was considered necessary
to meet the NYDEC permit limitations of 30 mg/L Bio-
chemical Oxygen Demand (BOD5), 30 mg/L Total Sus-
pended Solids (TSS), and 85-percent removal for both
BOD5 and TSS. In evaluating the various technologies,
system reliability and overall cost were considered equally
important. The alternative technologies evaluated and
their estimated costs are shown in Table 1. The "life-
cycle" costs presented include the initial construction
costs', operation and maintenance (O&M) costs, and de-
preciation or replacement costs.
As can be seen in Table 1, the gravity sewer system and
aerated lagoon alternatives had the lowest life-cycle costs.
However, other factors precluded the selection of these
technologies. The lagoon system was rejected because
of proximity to residences, odor potential, and reduced
performance under cold weather conditions. It was also
observed that, for each alternative considered, the initial
59
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construction cost accounted for most of the life-cycle cost.
Therefore, alternative construction methods using exist-
ing municipal resources were evaluated in orderto reduce
the initial construction costs, the annual user fee, and,
ultimately, the total life-cycle costs. The subsurface sand
filter was rejected due to its rigorous installation require-
ments. The gravity sewer system was also considered to
be inappropriate for Installation by municipal staff be-
cause of complex installation requirements.
SELECTION OF COLLECTION AND
TREATMENT SYSTEMS
As a result of this process of evaluating alternative con-
struction methods, the pressure sewer system and the
activated sludge package plant technologies were cho-
sen. By using municipal resources and having the
homeowner install the grinder pump, the initial construc-
tion cost estimate for the pressure system sewer was
reduced to $400,000. The revised construction cost
estimate f orthe package plant (using municipal resources)
was $250,000.
DESIGN CRITERIA
The design criteriaforthe collection system and treatment
plant are discussed below. The key features of the
pressure sewer system and package plant are summa-
rized in Table 2.
Collection System
A low pressure sewer system with grinder pumps was
Installed. The sewer mains consist of PVC pipe ranging
from 1.25 to 4.0 inches in diameter. The house service
laterals are all 1.25 inch diameter polyethylene water pipe.
The grinder pumps are progressing cavity pumps. The
pump motors are 1 horsepower and require a 240 volt
electrical service.
Treatment Plant
A prefabricated, steel package plant was installed. The
plant is a 50,000 gallon per day extended aeration acti-
vated sludge process with secondary clarification. The
plant also includes alum addition for phosphorus reduc-
tion in anticipation of future permit conditions containing
phosphorus limitations. Excess capacity was provided to
meet the demands of future growth in the community. The
treatment plant effluent is disinfected by the application of
sodium hypochlorite prior to discharge.
REDUCTION OF COSTS
The total project costs were significantly reduced by the
following steps taken by the Town.
Assumption of General Contractor Functions
The Town acted as the general contractor for the entire
project. The Town Highway Department Superintendent
was instrumental in this role, overseeing the subcontrac-
tors used in the project and communicating on a regular
basis with the consultant when problems arose during
construction.
Use of Municipal Resources for Construction
Highway Department employees and equipment were
used to build an access road to the treatment plant site
and to clear and excavate the site. Use of the highway
crew was limited from May 1 to October 15 so that highway
Table 1. Collection and Treatment System Alternatives and Costs for West Monroe, NY
Initial Construction
Costs ($)
Annual
O&M ($)
Life-Cycle
Costs ($)
Collection System
Conventional Gravity Sewers
Pressure Sewers
860,000
800,000
5,000
10,000
924,100
936,400
Treatment System
Subsurface Sand Filter
Aerated Lagoon
Activated Sludge Package Plant
450,000
350,000
400,000
5,000
10,000
15,000
530,200
471,300
580,800
60
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Table 2. Key Design Features of the
Selected Collection System and Treatment Plant
. ซ , ~ ,!*-,.
Collection System
... *-%l_ow Pressure Sew'iffs'r/- ~~,
" " '''" ~ ' *''
,:' * " \Grtoder,Purnps ;
^sj&Ajukj; tt^' v ., . . ">y'-s SA*
ซ-,- - *'>:^'PVefabricalea,"Steet Package Pl'aht\ ,, ^,/
personnel would be available for maintaining municipal
roads during the winter season. Therefore, adherence to
a strict schedule was essential to ensure completion of the
site work prior to the start of the winter season. An
unexpected pocket of "soft" or unconsolidated material at
the site prevented the construction of the thick concrete
slab needed to support the package plant and could have
resulted in a significant delay. The consultant proposed
the use of a timber pile foundation as a solution to the
problem. The Highway Department purchased and in-
stalled 65 used telephone poles, using a pile driver bor-
rowed from the Oswego County Road Department.
Direct Purchase of Materials and Equipment
Additional cost savings were achieved by direct purchase
of the majority of system components and equipment
specified by the consultant. West Monroe purchased all
pipe, fittings, and manholes required for the low-pressure
sewer system as well as the sand and gravel needed for
the pipe bedding and backfill. Bids on the prefabricated
steel package plant were requested from several manu-
facturers; the contract was awarded to the lowest respon-
sible bidder. Complete grinder pump (GP) packages
consisting of pump, fiberglass reinforced polyester tank,
and controls were also purchased directly by the Town.
Creative Allocation of Responsibilities
Additional project cost reductions were achieved by mak-
ing the GP installation and hook-up to the low-pressure
sewers the responsibility of the homeowners. The GP
packages were sized to accept wastewater from two
residences, which resulted in the purchase of fewer GP
packages and significantly reduced installation costs.
Minimum monthly service charges assessed by the elec-
tric power company were avoided by connecting the GP
package to the existing electrical service of one of the two
homes. (The home which incurs the additional electrical
fees receives a credit on its sewer use charge.) As
general contractor, West Monroe provided installation
guidelines and inspected each installation. This creative
arrangement was successfully achieved by having all
parties consent to a three-party agreement or easement
between the Town and the two homeowners sharing the
GP service. GP packages were not distributed until both
homeowners had signed the agreement. The arrange-
ment also provided that the Town be responsible for
maintenance of the GPs.
RESULTS AND SUMMARY
The collection and treatment systems have been in opera-
tion since spring 1989, and, according to the Highway
Department Superintendent, both systems have performed
well since startup. A summary of the treatment plant
performance is provided in Table 3.
Since the Town could not afford to hire a full-time treat-
ment plant operator, a member of the Highway Depart-
ment staff was assigned to operate the treatment plant.
This individual has attended State of New York Operator
Training courses to prepare forthe state-certified operator
licensing exams; his time is divided equally between the
treatment plant and the Highway Department.
Table 3. Performance Summary
West Monroe, NY, Wastewater Treatment Plant
January - December 1991
Parameter
Flow
(MGD)
BOD5
(mg/L)
TSS
(mg/L)
Permit Limit*
Influent**
Effluent*
% Removal
0.056
0.020
30
312
13
96
30
212
28
87
* Permit requires 85-percent removal for both BOD5 and TSS.
** Influent and effluent values shown are annual averages.
61
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Long-term financing for the entire project was obtained
through the New York State Revolving Loan Program.
A 20-year loan was secured at 5-percent interest.
Short-term fundingforinitial project costs was obtained by
the Issuance of bond anticipation notes (BANs).
Overall, project costs were reduced by more than $500,000;
the final project cost for 220 homes was $695,000 rather
than $1,200,000 as was initially estimated. Annual sewer
userfees are approximately $425 per home as compared
to initial estimates of $625 using conventional construc-
tion methods.
In summary, the Town of West Monroe solved a
longstanding public health problem at an affordable cost
by incorporating the elements and strategies summarized
in Table 4. This was achieved through the combined
efforts of community, county, and state personnel, and
careful cost reductions.
Table 4. Key Elements of West Monroe's Successful Project Resolution
Community volunteers
Assistance from the New York State Department of Environmental Conservation
Self-Help Program and Oswego County Department of Health
Employment of an engineering firm with small-community experience and knowledge of
alternative collection and treatment technology
Assumption of general contractor functions by the Town
Project labor requirements supplemented by highly motivated municipal employees
Direct purchase of materials and equipment
Multiple hook-ups to properly sized single GP installations
Use of existing municipal labor force to operate wastewater treatment plant
\
62
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MAPLETON, OREGON
CASESTUDY#2
BACKGROUND
Mapleton is located on the west bank of the Siuslaw River
in Lane County, approximately 10 miles inland from
Oregon's Pacific coast. This small community, which has
a population of approximately 800, is located in the Siuslaw
National Forest.
Mapleton is an unincorporated village in a region that has
been historically dependent on the timber and timber
products industry. The commercial area of Mapleton
encompasses approximately 30 acres and consists of
three residences and approximately 16 commercial/in-
dustrial establishments. Due to its location on the bank of
the Siuslaw River, local topography, and hydrogeology,
this area experiences seasonal, very high groundwater
tables. This condition has negatively affected the use of
onsite disposal systems by the properties in this area.
Mapleton had been aware of the wastewater disposal
problem in this area for decades; a combination of factors
in the early 1980s resulted in the active pursuit of a
solution to the problem.
Prior to the construction of the Mapleton Sewerage Facil-
ity, all commercial establishments and residences either
1) utilized onsite septic systems, 2) discharged sewage
untreated to the earth via cesspools, or 3) discharged
directly to the Siuslaw River. Septic systems in general
provided an acceptable means of handling wastewater in
all but the riverside commercial area. Several buildings in
this area had direct discharges to the river, and septic
systems in this area were subject to seasonal surface and
lateral leakage.
In the early 1980s, the severity of Mapleton's problem
became apparent to the County Board of Health and to the
Oregon Department of Environmental Quality (DEQ).
Sanitary surveys of Mapleton's commercial area con-
vinced DEQ and Lane County officials that the situation in
Mapleton's commercial area warranted serious attention.
To encourage action on Mapleton's part, a building permit
moratorium was imposed on the commercial area until
appropriate alternative sewage handling could be pro-
vided.
This case study examines the technical and financial
problems Mapleton encountered and discusses how a
joint effort by the state, local businesspersons, Lane
County, and Mapleton resulted in the construction of an
innovative and effective wastewater collection and treat-
ment system.
COMMUNITY RESPONSE
In an effort to find a solution to this problem, the owners of
the properties in the commercial area sought the assis-
tance of a number of agencies. These included the Rural
Communities Assistance Corporation (RCAC) , the Or-
egon DEQ, the Oregon Rural Communities Assistance
Program (ORCAP), and Lane County. ORCAP and DEQ
conducted sanitary surveys that indicated that onsite
treatment was not feasible in the commercial area and
that some form of centralized treatment and offsite dis-
posal would be necessary for Mapleton.
Because Mapleton was unincorporated, it was recog-
nized that a legal entity would need to be created to make
decisions, pursue funding, and ultimately build and oper-
ate a centralized wastewater treatment system. To this
end, the owners of the commercial properties formed the
Mapleton Commercial Area Owners' Association (Asso-
ciation). An agreement was established between Lane
County and the Association whereby the County would
sponsor a request for an Oregon Community Block Grant.
Once the treatment facility was built, all responsibility for
its operation and maintenance would be passed to the
Association.
Lane County and ORCAP remained actively involved in
the project throughout both the pursuit of funding and the
construction of the collection and treatment systems that
were ultimately selected. The Siuslaw Port District (which
is a state-established port management agency with au-
thority over a substantial part of the Siuslaw River) pro-
vided legal assistance in the formation of the Association
and ultimately acted as title holder to the property on
which the treatment plant was constructed to provide the
benefits of public rather than private ownership of the
property.
The Association was actively involved in all phases of this
project due to the willingness of both individuals and
businesses to support the project. For example, the local
63
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bank made both staff time and the bank's physical re-
sources available to the Association during the project.
Members of the Association perceived the successful
elimination of this problem as of major importance to the
economic health of Mapieton.
A first application for block grant funding submitted by
Lane County was not successful. With the continued
assistance of Lane County, a second application was
prepared; this ultimately resulted in the award of a grant in
the amount of $319,000.
EVALUATION OF ALTERNATIVES
A consulting firm was hired by Lane County to assess the
situation more completely and to recommend possible
solutions. The consulting engineer determined that cen-
tralized treatment and offsite disposal would only be
necessary for the commercial area, with the effluent to be
disposed of by land application.
Early in the evaluation process, several factors were
considered to be of great importance. First, the limited
number of connections made the selection of a treatment
system extremely sensitive to capital cost and the avail-
ability of state funds. Second, the isolated location of
Mapieton in conjunction with the financial limitations made
any system requiring the routine attention of experienced
operations personnel unattractive. Finally, very small
wastewaterflows are difficultto treat effectively in conven-
tional biological treatment systems.
As a result of these considerations, the engineer initially
recommended the use of a recirculating gravel filter with
filter effluent to be disposed of by application to public
land. (Oregon requires that all treatment facilities use
non-surface discharge options whenever possible.)
As the Association and the engineer further pursued the
Initial proposal, several major impediments to the use of
land application became apparent. These included diffi-
culties in obtaining right-of-way for installation of the
necessary pipeline to the potential application sites and
unacceptably high projected pumping costs due to the
significant difference in elevation between the commer-
cial area and the proposed application sites.
These considerations prompted the pursuit of a surface
discharge permit from DEQ. In addition to Oregon's
general bias against surface water discharges, DEQ had
apparently not approved surface water discharges for
many recirculating filter systems. As a result, Mapieton
was required to evaluate the potential impact that the
proposed system would likely have on the Siuslaw River.
The results of this study in conjunction with review of
NPDES monitoring data for other Oregon recirculating
filters ultimately prompted DEQ to grant a surface water
discharge permit to the Association.
SELECTION OF COLLECTION AND
TREATMENT SYSTEMS
As a result of the process previously described, Lane
County and the Association ultimately elected to construct
a recirculating gravel filter on a site in the middle of the
commercial area. In addition, due to the condition of the
existing septic systems in the commercial area, new
septic tanks and piping were installed for every connec-
tion served by the new system. The cost of the collection
and treatment systems together was approximately
$400,000.
DESIGN CRITERIA
The design criteria for the collection and treatment systems
are examined below. Key features of the septic/gravity
sewer collection system and filter are presented in Table 1.
Table 1. Key Design Features of the
Selected Collection System and Treatment System
Collection System
All New Services, Laterals, Mains; Laterals
and Mains of 6-lnchPVC * * ซ
'*,. .installation of N4w Septic Tanks With
Concrete Construction; Capacities From '
1,000 to 3,000 Gallons - v -.
; v?5 4 < f" *
'' ซ, Laterals'and Mains Gravity Drain f}
f^" to Plant , <.***-
Treatment Pliant "" <*> ,-"* '
Two Recircufatipn Tanks; Total Capacity
of 25,000 Gallons ^
25,000 gpd" Design Capacity f"'
'' ' '
64
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Collection System
As noted, new building services, laterals, septic tanks,
and mains were installed for the service area. PVC piping
was used for branches and mains. The topography of the
commercial area allowed the use of a gravity collection
system, with no lift stations required. Septic tanks in-
stalled were of prefabricated concrete construction and
ranged in size from 1,000 to 3,000 gallons.
Treatment System
A two-cell recirculating filter was constructed on a 1.5-
acre site located in the commercial area. Each cell
measures 35 by 70 feet and has a pea gravel media depth
of 3 feet. Cell construction is bermed earth with concrete
retaining walls and a PVC membrane liner. The distribu-
tion manifold is constructed of 2-inch perforated PVC
pipe; the underdrains are perforated 4-inch PVC pipe.
Two recirculation tanks are provided, each consisting of
60 feet of 72-inch diameter reinforced concrete pipe. Two
recirculation pump stations are provided; each station
consists of one 250 gpm (@ 22 ft. total dynamic head)
submersible pump. Effluent is chlorinated using sodium
hypochloriteand dechlorinated using sulfurdioxide. Efflu-
ent is pumped to the Siuslaw River by a discharge pump
station which consists of two 100 gpm (@ 15 ft. total
dynamic head) submersible pumps. A small chemical
feed/control/lab building was also constructed. A sche-
matic of the system is provided in Figure 1.
REDUCTION OF COSTS
The total project costs were reduced by the following
steps.
Adoption of a Low Capital/Operating Cost Treatment
System
The selection of a septic/recirculating filter treatment
system has provided Mapleton with a cost-effective solu-
tion to its problem. Installation costs of the gravity sewers
were somewhat higher than if Small Diameter Pressure
Sewers (SDPS) had been used; however, the elimination
of the grinder pumps associated with SDPS provided an
offset savings. In addition, maintenance costs of the
installed collection system are expected to be significantly
less than if a SDPS system had been used.
As in the case of the collection system, the major cost
savings associated with the treatment system are opera-
tions and maintenance (O&M) rather than capital. The
recirculating filters do not require regular solids disposal,
which eliminates a major conventional treatment operat-
ing cost. It should be noted that to a certain extent, this
cost has been picked up directly by the customers in the
form of septic tank cleanout costs. Another significant
savings is realized due to the limited need for operator
control. Mapleton has retained a local water distribution
system operator on a part-time basis, thereby eliminating
the need to hire an operator from outside the area.
Recirculation
Pump
Stations
North
Gravity
Main
Recirculation
Tanl
Splitter
Manhole
Influent
Manhole
Discharge
Pump
Station
South
Gravity
Main
Discharge
to River
Figure 1. Plant schematic for Mapleton, Oregon.
65
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Reliance on Lane County and Other Agencies
Mapleton made full use of the various types of assistance
available to it from the State, County, and various commu-
nity outreach programs. This reduced project costs in two
ways. The most obvious was that these agencies pro-
vided technical and organizational guidance and services
for which Mapleton might otherwise have obtained by
contract. Examples of this include both Lane County's
hiring of the consulting engineer and the provision of
county resources to carry out improvements on the treat-
ment plant access road.
Less obvious is the impact that the guidance had in
keeping Mapleton "on the right track." Had Mapleton's
citizens made decisions regarding this project with less
guidance, they might well have made inappropriate and
ultimately more costly choices.
Limitation of Funding Sources to Impacted Parties
in addition to the block grant, funding for this project was
obtained directly from the affected parties; total local
fundingwasapproximately$100,000. Asaresult, Mapleton
incurred no debt with this project.
The direct funding of this project was to a large extent
made possible by the local bank's decision to provide
loans at very attractive terms to businesses and residents
affected by the project. In addition, the bank elected
simply to pay the connection fees of one or more senior
citizens. Monthly sewer fees for businesses are $64 per
month; those for residences are $20 per month.
RESULTS AND SUMMARY
The collection and treatment systems have been in ser-
vice since 1989 and both have generally performed up to
or above expectations. A summary of recent plant perfor-
mance data is provided in Table 2.
As noted above, the Village has retained an operatorf rom
the local Water District on a part-time basis; this individual
has received the additional state training necessary to be
type-certified for the Mapleton plant.
Relatively minor problems have surfaced since the plant
went on line. Settlement of the plant site has required the
addition of media to eliminate a low area on the level upper
surface of the filter.
As a result of the successful start-up of the treatment
system, DEQ lifted the building moratorium. Several new
businesses have opened in the downtown area, and the
Florence Regional Library recently opened a branch in the
commercial area. Progress is also now being made to
restore several commercial area buildings of historical
significance.
In summary, Mapleton has overcome a number of techni-
cal and institutional barriers to solve a serious human
health and environmental problem. This success was
achieved in no small part through the cooperative effort of
the Village and a number of agencies and through thought-
ful consideration of Mapleton's resource limitations when
evaluating alternative solutions. Table 3 summarizes
these elements and strategies.
Table 2. Performance Summary
Mapleton, Oregon, Wastewater Treatment Plant
July 1991 to February 1992
Parameter
Permit Limits
June 1991
July 1991
August 1991
September 1991
October 1991
November 1991
December 1991
January 1992
February 1992
BOD5
(mg/L)
10
6
10
7
-
34*
3
4
8
14
TSS
(mg/L)
10
7
6
7
-
7
5
10
6
8
* This datapoint was considered to be the result of laboratory error.
Table 3. Key Elements in Mapleton's
Successful Project Resolution
Community involvement
Local businesses championed the project
Employment of an engineering firm
with experience in small-system design
Selection of a low O&M cost treatment
alternative
Successful pursuit of state funding
66
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PORTVILLE, NEW YORK
CASE STUDY #3
BACKGROUND
The Village of Portville is located in Cattaraugus County in
the southwestern portion of the State of New York, ap-
proximately 7 miles east of Olean on the north bank of the
Allegheny River. The population of this bedroom commu-
nity is approximately 1,100. Prior to 1988, the Village
operated a primary treatment system consisting of an
Imhoff tank and sand sludge drying beds.
As Portville's Imhoff tank provided only primary treatment,
the New York State Department of Environmental Con-
servation (NYDEC) had been applying increasing pres-
sure on Portville for more than a decade to upgrade the
Village's wastewater treatment capabilities. This pres-
sure ultimately took the form of a formal enforcement
action against the Village. Finally, on New Year's Day in
1988, the Imhoff tank suffered a major structural failure.
As a result, the Village was faced with the need to replace
the existing treatment system with one that would consis-
tently meet secondary treatment standards or it would
face further enforcement actions.
This case study examines the challenges encountered by
the Village of Portville in upgrading its treatment plant,
describes how the Village ultimately elected to construct
a type of treatment system rarely used in the Northeast,
and evaluates how well the Village has been served by
that decision.
COMMUNITY RESPONSE
The Village government consists of four trustees and the
Mayor. Together, these individuals made all the decisions
concerning selection of both consulting engineers and a
treatment system. Efforts to involve the general citizenry
were somewhat limited; notification of Village residents
was limited to those within 500 feet of the proposed plant
site (which was the site of the former treatment plant).
General community involvement was largely limited to the
resolution of a post-startup odor problem.
In response to the NYDEC enforcement action, the Village
retained a consulting engineer to design a new treatment
plant, to handle the completion and submission of applica-
tions for the necessary permits, and to complete various
grant and loan applications. As a result of the engineer's
success in pursuing available funding, the Village re-
ceived a grant of approximately $1.5 million, or 82.7% of
the estimated cost of the treatment system first proposed.
(Treatmenttechnology selection is discussed subsequently
in this case study.)
Following receipt of funding approval, the consulting en-
gineer revised the original cost estimates for the proposed
system; these revisions indicated higher than expected
capital and operating costs. In conjunction with evaluation
of the experiences of other area towns that had recently
upgraded their treatment systems, these higher cost es-
timates convinced the Mayor and the trustees that the
Village would not be financially capable of operating the
proposed treatment system. This was perceived by the
Village to be a "Catch-22" situation, in that failure to
upgrade the treatment plant would place the Village at risk
of further enforcement action by NYDEC, as would failure
to operate the proposed treatment plant properly.
In an effort to resolve this conflict, a second consulting
engineer was retained, who in turn retained a treatment
process design engineer with experience in alternative
small-scale treatment technologies. This individual's rec-
ommendation was ultimately accepted and constructed.
Coincidentally, the capital cost of this second recom-
mended technology was very close to that of the original
more conventional recommendation.
NYDEC originally had concerns regarding the Village's
revised proposal and did not immediately issue approval
forthe change. Following review of additional information
regarding this technology, NYDEC did allow the Village
and its engineers to proceed. The cost of the new facility
and attendant equipment was approximately the same as
originally estimated for the more conventional plant ($1.8
million). Funding forthe remaining 17.5% of capital costs
was provided by the Village through long-term loans.
SELECTION OF TREATMENT SYSTEM
In the early 1980s, the Village inspected portions of the
collection system to evaluate the feasibility of reducing
infiltration. At that time, rehabilitation was judged to be
economically infeasible. Based on this earlier evaluation,
67
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the possibility of rehabilitating the collection system was
not considered when the need to upgrade treatment
capability was addressed in the late 1980s.
The Village's first consulting engineer recommended a
Rotating Biological Contactor (RBC) treatment system.
As noted previously, operating cost estimates for this
original system convinced the Mayor and trustees that the
Village could not carry the debt service necessary to fund
the Village's share of the construction cost and at the
same time cover the expected annual operations and
maintenance (O&M) costs.
As a result of reaching this conclusion, the Mayor and
trustees decided that a reevaluation of treatment alterna-
tives was In order. The Village decided to consider a
substantial change in project direction, knowing that this
might entail the expenditure of more funds on system
redesign.
A second consulting engineering team retained by the
Village recommended a recirculating stone filter (RSF)
treatment system. This recommendation was made on
the basis of 1) this type of system's ability to handle wide
ranges of hydraulic loading (important due to the high rate
of infiltration and inflow experienced by Portville's collec-
tion system) and 2) its low O&M requirements and costs.
DESIGN CRITERIA
The design criteria for the Village of Portville's RSF
system are discussed in the following paragraph. Key
design features are presented in Table 1. A schematic of
the system is shown in Figure 1.
The RSF design was chosen for its low O&M costs and its
ability to treatwidelyfluctuatingflows and waste strengths.
The system ultimately constructed by the Village consists
of three major components: a 700,000 gallon capacity
"communal" septic tank, a 28,000 gallon recirculation
dosing tank (with associated recirculation pumps and
controls), and a 54,000 square foot pea gravel media
filter. In orderto handle septic tank solids, the Village also
purchased an all-terrain sludge hauling/application ve-
hicle, constructed a separate septage holding facility, and
secured the use of a 30-acre application site.
REDUCTION OF COSTS
Capital cost reduction was not significant in Portville's
wastewater treatment plant upgrade project. The con-
structed cost of $1.8 million was in fact somewhat high
compared to the expected cost for a similarly sized,
"package-type" extended aeration treatment system
(source of comparison - MEANS Cost Data). This is due
to several factors. First, RSF systems cannot effectively
treat raw wastewaters. The solids content of typical raw
Table 1. Key Design Features of the Selected
Portville, NY, Wastewater Treatment System
?* ' S J -_> '' V ';
f fffjfff '' '/ 'S ft fV V ' '
S*%>*ป*"> * '"'' '-'
Design capac
, .v ./? f,/^>,<(>- '^\Vt--,', ,~ ^^W^'ฃ<ซS
**wf:,' Septic Tank Vo'lume^^OOO Gallons ; "*
4^W^^"'^' "" ' ' """"; f;^f> :", 4^|^|!''-:'-;f^f;;-:
,^.*^Filter-AreaofS^OCtts^ft^W.' , ^^-/
sanitary wastewater will quickly plug the filter media and
significantly reduce the life of the filter. It is therefore
essential that the raw wastewater receive adequate pre-
treatment. This can be accomplished using gravity set-
tling in either septic tanks, Imhoff tanks, or primary clari-
fiers. For the Portville treatment system, a communal
septic tank was constructed to provide the necessary
pretreatment and equalization. This 700,000-gallon unit
increased capital costs substantially.
The Village also made a large investment in the septage
storage facility and transport/disposal truck. This capital
expenditure was motivated by both concern regarding
disposal of material from the "communal" septic system
and an interest in developing septage handling capability
as a revenue-generating operation.
The impetus for selecting the system ultimately con-
structed was its expected low operating costs. Actual
annual operating costs through late 1990 were averaging
about $1.93 per 1,000 gallons of sewage treated, includ-
*- River
Figure 1. RSF system schematic.
68
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ing debt service (which represents more than 50%). Labor
costs are somewhat higher than normal for this type of
system because the Village has provided a full-time
operator. Non-labor, non-debt service operating costs
have in fact been low, with pumping costs averaging about
$.10/1,000 gallons. As a result of the operating costs
mentioned earlier, the average resident pays approxi-
mately $12 per month, or $144 per year.
The effect of this was to render the filters effectively
inoperable. The pulp and paper mill was ordered to cease
its discharge to the plant. The mill has since achieved zero
discharge. Rehabilitation of the system was carried out by
the Village, which is currently attempting to recover the
costs from the mill. Table 3 provides an overview of both
positive and negative aspects of Portville's experience in
upgrading its treatment-system.
RESULTS AND SUMMARY
In general, the selected treatment system has provided a
high quality effluent which has easily met the require-
ments of the SPDES permit. Table 2 summarizes plant
performance from January 1989 through August 1990.
During that time period, plant effluent BOD5 averaged
about 7 mg/L and effluent TSS averaged about 2 mg/L.
The plant has also achieved complete nitrification, with
certain effluent samples showing ammonia concentra-
tions below 1 mg/L.
The plant has also experienced and had to overcome
operational difficulties related to high flow, odors, and
industrial discharges.
Higherthan expected flow rates initially caused difficulties
in meeting the filter bed's dosing and resting require-
ments. The pump supplier provided considerable assis-
tance (at no cost) in modifying the recirculation system to
allow it to function properly under the entire range of flows
being experienced.
Odor control was one of the major community and regula-
tory concerns with the system ultimately constructed.
Following startup, odor from the dosing tank became a
problem. The addition of an aeration system to this tank
did not provide the expected relief, and the Village was
forced to install an odor control system.
In June 1991, a local pulp and paper mill significantly
changed its production processes. This substantially
changed the characteristics of the suspended solids in its
discharge. This change in characteristics resulted in
significant amounts of solids passing through the septic
tank to the filter. This in turn resulted in the plugging of the
dosing pumps and clogging of the pea gravel filter media.
Table 2. Portville, NY, Performance Summary
January 1989 Through August 1990
Parameter
Influent
Effluent
% Removal
BOD5
(mg/L)
85
6.8
92
TSS
(mg/L)
85
1.7
98
Table 3. Key Elements of Portville's Experience
Positive Elements
/ Willingness to "step back" and change
direction
/" Selection of an engineering firm with small-
system experience
t/' Successful pursuit of funding assistance
^ Selection and construction of a treatment
technology which under most conditions
has easily met its permit
Negative Elements
/" Overpurchase of O&M staffing and
equipment
/ Failure to consider effects of industrial waste
source
69
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CASE STUDIES - DRINKING WATER
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LOS YBANEZ, TEXAS
CASE STUDY #4
BACKGROUND
The Town of Los Ybanez is located in Dawson County,
Texas. The dwellings that make up the Town were
originally constructed by the United States Department of
Agriculture (USDA) as a migrant labor camp known as
Dawson County Labor Camp. A total of 75 units were
constructed on an 85-acre site.
In 1980, the entire site was purchased by the Ybanez
family. The family began to renovate some of the 40-year-
old dwelling units, since the site had fallen into general
disrepair. Tenants began to move into units as they were
rehabilitated. Most residents of the community are on low
or moderate fixed incomes. Eighty percent of the units are
subsidized by the Department of Housing and Urban
Development.
In 1982, the 39 residents voted unanimously to incorpo-
rate the site into a town to be known as Los Ybanez. The
Town was formally incorporated on April 2,1983, and is
governed by four councilmen and a Mayor.
By 1988, 22 of the wood frame structures had been
rehabilitated, and were occupied by 40 households. Part
of one structure was used as the Town Hall. The Town
also had a church and general store. The total population
of the Town was 150 persons. Drinking water for the
residents was supplied by one well provided by the USDA
when the original labor camp was built. A 50,000 gallon
underground storage tank was provided, but the system
did not include pressurized storage. Water distribution
was accomplished through 4 inch and 6 inch asbestos
cement mains. Due to the high dissolved solids content of
the water, extensive mineral deposits had built up in the
mains through the years, severely reducing available
water pressure.
In 1988, the Texas Attorney General notified the Town of
his intent on behalf of the Texas Department of Health to
file suit against Los Ybanez. The suit would charge
violations of rules and standards established by the Texas
Department of Health governing the construction, opera-
tion, and maintenance of public drinking water systems.
The following specific violations were to be charged:
1. That Los Ybanez failed to provide two water samples
to the Department of Health for bacteriological analy-
sis;
2. That minimum pressurized storage tank capacity of
50 gallons per connection was not provided;
3. That two or more pumps having a combined capacity
of more than 2 gallons per minute per customer
connection were not provided; and
4. That maximum allowable concentration limitsforfluo-
ride, chloride, and sulfate were exceeded.
The suit would allege a direct potential hazard to public
health and sought civil penalities and injunctive relief to
close the system until compliance was achieved.
COMMUNITY RESPONSE
Los Ybanez responded to the Attorney General in March
1988, prior to the suit being filed. The Town indicated that
16 samples for bacteriological analysis were submitted in
1987 and attributed the failure to submit two samples in
1988 to an operator who had subsequently been dis-
missed. The Town acknowledged that 9 of the 16 samples
submitted in 1987 did not meet Health Department bacte-
riological standards.
Los Ybanez further advised the Attorney General of its
intent to upgrade the water system. To this end it had
contacted the Community Resources Group, Inc. (CRG)
located in Lubbock, Texas. CRG works with the Texas
Department of Agriculture to bring needed and affordable
water and wastewaterservices to small, low-income com-
munities in Texas.
CRG is a private, non-profit rural development organiza-
tion established in 1975 to seek long-term solutions to
problems faced by rural people and communities in the
southern states of Alabama, Arkansas, Louisiana, Missis-
sippi, Oklahoma, Tennessee, and Texas. CRG's work is
supported financially by both public and private sources.
In general, services are provided at no cost to rural
communities.
The Town hoped to obtain a low-interest loan from CRG
in order to meet the current Texas requirements and to
73
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provide sufficient capacity to allow the full occupancy of all
available housing units. CRG advised the Attorney Gen-
eral that it was offering assistance, and requested that the
suit be delayed for as long as the Town made good faith
efforts to correct the problems.
CRG then contacted a consulting engineering firm. CRG
requested that the firm investigate rapid means of provid-
ing safe water for Los Ybanez. The engineer responded
In April 1988 that the quickest means would be to buy
water from the neighboring City of Lamesa through an
existing but abandoned 4 inch asbestos cement line which
ended near the northwest part of Los Ybanez. Although
parts of the line had been damaged or destroyed, the firm
believed the line could be restored to service. The
estimated cost of rehabilitation and repair was $35,000.
In May 1988, it was learned that the owner of the property
on which the line was located objected to its repair and
contended that the easement for its installation had been
lost by non-use or abandonment.
With the assistance of CRG, Los Ybanez applied to the
State of Texas for a grant to use in solving its drinking
water problems. In December 1988, the Town was
notified that it had been awarded $352,650 by the Texas
Department of Commerce for water system improve-
ments. The Town continued to work with the engineering
firm to identify possible alternatives. In March 1991, the
firm wasappointed as the design engineerforthe drinking
water improvement project.
EVALUATION OF ALTERNATIVES
In order to improve the quality of water to comply with the
standards established by the Texas Department of Health,
four alternatives were evaluated:
1. Purchase water from the City of Lamesa;
2. Treat water from the existing well with activated alu-
mina;
3. Treat waterfrom the existing well with an electrodialy-
sis system; and
4. Treat water from the existing well with a reverse
osmosis system.
Purchase of water from the City of Lamesa was judged to
be the most attractive option because of its low implemen-
tation cost. In addition, it was the only option which did not
require Los Ybanez to operate a treatment system. This
option was not selected because resolution of the ease-
ment issue was unlikely to be accomplished until after a
protracted legal dispute.
The use of activated alumina would have been much less
effective than either electrodialysis or reverse osmosis.
Activated alumina has been shown to reduce fluoride
levels, but does not effectively remove chloride, sulfate, or
hardness. This option was therefore rejected.
Both electrodialysis and reverse osmosis are membrane
separation technologies. Low total dissolved solids (TDS)
water passes through the membrane, leaving a more
concentrated stream on the feed side of the membrane.
The low TDS side of the membrane is the product water
stream. The higher TDS concentration side of the mem-
brane produces a reject stream that must be disposed.
The two technologies differ in the force used to drive water
across the membrane. In electrodialysis, electrical en-
ergy is used directly. In reverse osmosis, hydrostatic
pressure produced by a pump is the driving force.
Reverse osmosis was the treatment alternative ultimately
selected by Los Ybanez because of its lower capital cost.
The reverse osmosis system was estimated to cost be-
tween $23,000-25,000, based on 15,000 gallons per day
(gpd) of product water. The electrodialysis system was
estimated to cost $54,000, based on production of 11,000
gpd.
Another factor considered in selecting the treatment sys-
tem was operating costs. Vendor estimates showed an
operating cost of $0.94/1,000 gallons product water for
electrodialysis compared to $2.00/1,000 gallons for re-
verse osmosis. However, the Town obtained operating
costs from Dell City, Texas which was already operating
an electrodialysis system. Operating costs for 1983 in
Dell City were $4.29/1,000 gallons.
PROJECT DESIGN
An approach for utilization of the reverse osmosis system
was developed which took advantage of the fact that
reverse osmosis would provide a product water quality
which would significantly exceed the Health Department
standards. In order to minimize capital investment, prod-
uct water would be blended with untreated well water prior
to disinfection. The resulting blend of 70 percent treated
water and 30 percent untreated water was projected to
meet the applicable standards.
In addition to the installation of the reverse osmosis
treatment system, a series of other improvements to the
system were accomplished. These included:
Installation of a seal on the existing well to meet state
requirements;
Construction of two evaporation ponds to dispose of
reject water from the reverse osmosis system;
Installation of home water meters;
74
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Installation of a pressure tank to meet Texas
requirements;
Installation of a new distribution system from the
pressure tank to each customer;
Construction of a new fire protection system including
lines, hydrants, and a 400 gallon per minute fire pump;
Cleaning of the existing storage tank;
Construction of a new pump station ; and
Construction of a new 20,000 gallon ground storage
tank.
The project was completed in late 1990. The total cost of
the project was $336,060. User rates in Los Ybanez
average $1.38/1,000 gallons for residential users.
RESULTS AND SUMMARY
The Town's drinking water was sampled by the Texas
Department of Health in January 1991. The results of this
sampling are shown in Table 1. Compliance with all
parameters except fluoride, sulfate, and selenium has
been achieved. Discussion with State personnel who
have inspected the new system indicates they believe that
by decreasing the percentage of raw water in the blend,
compliance with all Texas Health Department standards
can be achieved.
Los Ybanez is typical of small, rural communities which do
not have either the financial or technical resources to
comply with increasingly stringent drinking water require-
ments. By working with CRG, the Town was able both to
obtain the necessary funding and to develop a suitable
corrective action program. In addition to providing safe
water, fire protection for the community was enhanced.
This was achieved in less than two years, a short period
given the extensive upgrade to the system and the need
to obtain funding from outside the community. Prompt
action by the Town avoided.an enforcement action by the
State of Texas which could have delayed compliance.
Table 2 summarizes the key elements of Los Ybanez's
reponse to solve its drinking water problems.
Table 1. Drinking Water Quality Los Ybanez, TX
Parameter
Chloride
Flouride
Nitrate (as N)
Sulfate
pH
IDS
Arsenic
Barium
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Selenium
Silver
Zinc
Raw Well
Water
(mg/L)
300
4.8
7.41
540
8.1
1458
0.019
<0.05
<0.005
<0.02
<0.02
0.42
<0.02
<0.02
0.0005
0.029
<0.01
0.03
Jan. 1991
Sample
(mg/L)
165
2.7*
5.31
315*
6.9
823
0.011
<0.02
<0.005
<0.02
0.13
0.03
<0.02
<0.02
0.0002
0.016*
<0.01
0.08
SDWA
Standard
(mg/L)
250
2
10
250
6.5-8.5
1000
0.05
1
0.005
0.05
1.3
0.3
0.05
0.05
0.002
0.01
0.05
5
'Concentration In violation of SDWA standards.
Table 2. Key Elements of Los Ybanez's Successful
Project Resolution
y Assistance from CRG
/ Successful pursuit of state funding
S Selection of an engineering firm with small-system
experience
/" Selection of a low operating cost treatment
alternative by comparing vendor estimates with
actual costs experienced by neighboring
communities
75
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WESTFIR, OREGON
CASESTUDY#5
BACKGROUND
Westfir Is a small community located in Lane County about
40 miles southeast of Eugene, Oregon. The current
population is approximately 310. The community was
originally established to house workers from a nearby
lumbermlll. The City was incorporated in 1981 to improve
its ability to provide municipal services to the community's
residents.
In 1946, the lumbercompany constructed a drinking water
system for the community. The system used a surface
water supply and included chlorination, a storage reser-
voir, and a distribution system. Although the original water
system supplied the community with a sufficient quantity
of water, itbecame apparent during the late 1970s that the
existing treatment system could not consistently comply
with the turbidity maximum contaminant level (MCL) of the
Safe Drinking Water Act (SDWA).
Violation notices issued at first by the Oregon Drinking
WaterProgram (DWP) and later by the U.S. Environmen-
tal Protection Agency (EPA) culminated in the City agree-
ing to a compliance schedule to address the turbidity MCL
violations. This case study discusses the actions the
community of Westfir took to comply with the turbidity
MCL of the SDWA.
COMMUNITY RESPONSE
Like most small communities, Westfir did not have the
technical or financial resources to select an appropriate
treatment technology and to obtain adequate funding to
comply with the compliance schedule. Therefore, the
community turned to the Lane County Housing Authority
and Community Services Agency (HACSA) for help in
Identifying a treatment option and applying for financial
assistance. The Lane County HACSA is a quasi-munici-
pal agency that operates public housing at the local level
and provides technical assistance to help rural communi-
ties solve problems thatthey do not have the resources to
address on their own. The Rural Community Assistance
Corporation (RCAC) was also instrumental in assisting
Westfir. RCAC provided funding to Westfir through a
small project development grant that enabled the commu-
nity (with HACSA's assistance) to prepare an engineering
report and an application for a Community Development
Block Grant (CDBG). No local funds were available to
prepare the application for the CDBG.
The City was successful in obtaining a $294,000 CDBG to
upgrade the existing treatment system. Lane County
HACSA contracted with Westfir to provide assistance for
the duration of the project. These services included
preparation of the Request for Proposals (RFP) for engi-
neering services, development of bid documents and
specifications, construction oversight, and grant closeout
functions. The participation of the Lane County HACSA
from project inception to completion was a key element in
ensuring the successful completion of this project within
the available funding allotment.
EVALUATION OF ALTERNATIVES
The engineering report submitted with the CDBG applica-
tion had specified a package pressure filtration system to
reduce turbidity levels. However, this design was ulti-
mately rejected for the following reasons:
For small community systems, the Oregon DWP fa-
vored a treatment system that could be more readily
observable, in a physical sense, rather than the pro-
posed closed pressure filters.
The proposed filtration system would require regular
attendance by a properly trained operator. Experience
with similartypes of systems in Oregon's rural commu-
nities indicated that this was not readily achievable due
to limited financial resources and high rates of operator
turnover.
An alternative water supply source (i.e., groundwater)
was not feasible due to limited groundwater resources in
the area and the potential for natural arsenic contamina-
tion due to volcanic rock formations.
Unable to use a groundwater supply, the consulting engi-
neer retained by the City proposed a slow sand filter to
meet Westfir's requirements. The consultant had prior
experience with both small communities and slow sand
filter applications. Slow sand filters do not have complex
operation and maintenance requirements; similarly, they
do not have complicated design requirements. During the
76
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early 1980s, however, slow sand filters were still a rela-
tively unproven technology. Therefore, the State ap-
proved the project contingent on the results of a pilot filter
study. The compliance schedule was renegotiated with
the EPA to permit adequate time for the pilot study. The
Oregon DWP, which had decided in the early 1980s to
encourage the use of alternative and simpler treatment
technologies for small communities, assumed an active
role in the study. The DWP supplied a pilot apparatus
previously used in another study as well as technical
assistance and analytical support. The pilot study was
conducted during an 8-month period. The duration of the
study ensured that the pilot system was subjected to any
potential seasonal fluctuations in water quality, such as
temperature, turbidity, color, and suspended solids. The
pilot system was monitored daily for temperature, turbid-
ity, filter head loss, and flow. The weather and river
conditions were also monitored. Periodically, samples for
total and fecal coliform analyses were collected and
shipped to the state laboratory in Portland. The filter
media utilized in the pilot study was slightly "out-of-spec."
However, the engineer decided to use it because abun-
dant supplies were available locally and at a reasonable
cost. The results obtained at the end of the pilot study
indicated that the proposed system would consistently
achieve the turbidity MCL of 1 nephelometric turbidity unit
(NTU), and construction approval was granted by the
Oregon DWP.
DESIGN CRITERIA
Figures 1 and 2 present plan and cross-sectional dia-
grams of the installed treatment system. The total cost of
the treatment system and distribution system improve-
ments was $217,483 (1986 dollars), exclusive of engi-
neering and grant administration fees.
The main treatment system components, summarized in
Table 1, consist of the following:
The raw water intake consists of two, 2 horsepower
(HP), submersible, 100 gallons per minute (gpm) pumps
at a total dynamic head (TDH) of 50 feet. The pumps
were installed in an infiltration-type wet well located
immediately adjacent to the Willamette River.
Filtration is provided by two 45 square foot (ft2) slow
sand filters designed to operate at 70 gallons per day
per square foot (gpd/ft2). To control costs, the filters
were constructed with earth berms and elastomeric
membrane liners rather than with reinforced concrete
walls and bottoms. The filter underdrain system is
comprised of 4-inch PVC pipe. The filter bed consists
of a 30-inch graded gravel support layer and a 3-foot
layer of filter sand. The filter sand media has a
uniformity coefficient of 2.32, an effective size of 0.315
mm. A control manhole distributes filtered water either
to the chlorine contact tank or, during periods of low
North Fork of Middle Fork of Willamette River
Distribution
System
200,000 gal
Redwood Reservoir
Rltarto Waste-
Two Service
Pumps (100 gpm Each)
D - Drain
O - Overflow Weir Manhole
P - Pump
A -Filter Overflows
Filter Drains-
Chlorine
r
II
..kit
*M
M
u.
II
\a
Filter 1
45ftx45ft
Slow Sand Filter
70gpd/sq.ft
Filtered
Water
Control
Valve
Intake Pumps
Source: Leeland, D.E. and Damewood, M. (1990).
Figure 1. Westfir slow sand filtration plant schematic plan.
77
-------
-ฉ
\_T
ourco: LoelB
Overflow to Was
(El. 1,086.0)
El. 1,086.0 v
Baffled
Contact ^
Chamber .^^
<\
Chtorine-J >
wo 100 gpm Pumps
to Distribution
System
El. - Elevation
nd, D.E. and Damewood, M.
Overflow Weir (El. 1 .089.0)
^Filter Overflow (El. 1,091.5)
te. ~\ * .../ ,
1 \ 1 o +f
^ \ \\ /
*~\ \ \^'.. :'v.. Filter Sand -:-.:;'.:^
:\ rซป^ \0 9 o 0 Q/ Medlu
1 Valve / 1
To River Pea Gravel L 4in.pvc
Perforated
-ol Valve
(1990).
6 in. PVC
-^ Raw-Water
Line
Intake
Pumps
_ El. 1,065.0
*EL'l',055.o"
Figure 2. West!Ir slow sand filtration plant schematic profile.
demand, to the river. An overflow weir inside the
control manhole maintains a minimum water level just
above the surface of the sand. This prevents acciden-
tal dewatering of the filter, which could adversely affect
the microbiological population present at the surface of
the filter.
Filtered water is chlorinated by feeding sodium hy-
pochlorite solution prior to the chlorine contact tank.
* Two 100 gpm centrifugal pumps were installed to pump
treated water to the distribution system. Storage is
provided by an existing 200,000 gallon redwood reser-
voir.
In addition to the treatment system project, a portion of the
grant funds were used to replace some of the distribution
system steel water mains to reduce water loss from
leaking mains.
RESULTS AND SUMMARY
Operation of the treatment system commenced in Novem-
ber 1986. During the first year of operation, filtered water
turbidity levels were slightly higher than the raw water
levels due to the presence of excessive fine particles in
the sand media. This problem demonstrates the need to
thoroughly wash the sand media prior to installation.
As expected, operating requirements have been minimal.
Daily equipment and process control checks (turbidity,
chlorine residual) are performed by the operator in ap-
proximately 60 minutes. The turbidity of the river is also
monitored daily. If the river turbidity levels become
excessive, the raw water intake pumps are shutdown until
the turbidity levels subside or the reservoir level becomes
too low. The reservoir contains about a 3-day supply of
Table 1. Key Design Features of the Westf ir,
Oregon, Slow Sand Filtration Installation
ป , i ,, ,.', ' , .,,
Water Intake Pumps -.fwo^V HP, 100 ;
* Staw&ini _.
-'&-' Two 45 tt2 Filters
J, "tr^'Hydraulic Lc
B;J,^4-?Satfd^edt^UJ5itorm^ ^
''^, - 2,32'andeffectivek&&'JQf,'Q,3i'5mm) /*?/
, * , Sodium Hypochloritedhlprinationi System ^^
ป^Jlireated>Water^up3fyPumSps^Tw'o1^
ssxiKKl i ,t '.W"ป
-------
water for the community. Each filter is cleaned twice per
year. One filter remains in service while the other one is
cleaned. Experience has indicated that it takes about 36
hours to drain and dry out the filter. Two men use flat-
bladed shovels to manually scrape the filter in about 7
hours. Approximately 1 inch of sand is removed to clean
the filters. The removed sand is not cleaned for reuse; it
is disposed of onsite.
The raw water submersible intake pumps were replaced
by a single 200 gpm centrifugal pump. Apparently, the
intake screens to the submersible pumps required fre-
quent cleaning due to debris in the river. During periods
of high river water, it was not possible to raise the pumps
to remove the debris. Pump removal was also a problem
due to limited manpower resources.
The requirements of the EPA compliance schedule were
satisfied by the installation of a slow sand filter system.
Although the capital cost for slow sand filtration is about
the same as for package filtration plants, the operation
and maintenance requirements are significantly less for
slow sand filters. Westfir currently charges system users
$20.00 per month to cover operation and maintenance
expenses, utility charges, and water analyses. The rate
was recently increased from $12.50 per month due to
additional testing requirements recently implemented by
the State. A summary of the key elements that contributed
to the success of this project is presented in Table 2.
Table 2. Key Elements of Westfir's Successful
Project Resolution
V Assistance from Lane County Housing
Authority and Community Services Agency
during entire project
/ Funding provided by Rural Community Assis-
tance Corporation to prepare CDBG applica-
tion
S Project funded by CDBG
/ Engineer experienced with small-community
systems and alternative treatment technolo-
gies for small communities
S State regulatory agency supportive of alter-
native treatment technologies for small com-
munities
/ Performance of pilot study to adequately as-
sess treatment technology capabilities under
various water quality conditions
/ Selection of a treatment system with low
operation and maintenance requirements
Bibliography
Leeland, D.E. and DamewoOd, M. "Slow Sand Filtration in
Small Systems in,Oregon." Journal American Water
Works Association 82 (1990):50-59.
79
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MOCKINGBIRD HILL,
ARKANSAS
CASE STUDY #6
BACKGROUND
Mockingbird Hill is a very small, unincorporated commu-
nity in northwestern Arkansas. This group of residences
and businesses is located in Newton County within the
Ozark National Forest. Tourism is the dominant industry
In this region.
By the early 1970s, the Mockingbird Hill area had grown
to Include approximately 90 residences and businesses.
Historically, one of the impediments to development in the
area had been limited drinking water sources. To foster
further development, the residents of Mockingbird Hill
decided to establish a centralized water supply. To
accomplish this task, the Mockingbird Hill Water Associa-
tion (MHWA) was formed, and Farmers Home Administra-
tion (FmHA) grant funding and loans were secured. A
3,200 foot deep well was drilled and a distribution system
constructed. The deep well and rough terrain of the area
contributed to the substantial $1.6 million cost of the
project.
From the time service was established, there were prob-
temswiththequalityofwaterproducedbythe Association's
well. The water was high in hydrogen sulfide, dissolved
and suspended solids, and color. To maskthe unpleasant
odors In the water, high chlorine dosages were routinely
applied. Together, the raw water characteristics and the
high chlorine dosage resulted in undrinkable water.
The residents of Mockingbird Hill generally used bottled
water for drinking until the opportunity arose to tie into the
nearby Deer-Wayton Water Association supply. This
connection was made in 1982, and the MHWA was
absorbed into the Deer-Wayton Water Association.
Joining the Deer-Wayton Water Association did not solve
Mockingbird HilFswatersupply problems, however. Water
quality was substantially improved, but drought conditions
in 1983,1984, and 1985 resulted in water shortages for
the Deer-Wayton system.
This case study examines steps taken by the residents of
Mockingbird Hill to address their water supply problem
and evaluates the performance of the technical solutions
that were ultimately selected.
COMMUNITY RESPONSE
The drought-related shortages that occurred after the
connection to the Deer-Wayton Water Association supply
resulted from a series of shallow (less than 200 ft.) wells
that supplied Deer-Wayton's system. These shortages
caused a number of actual shutdowns of the supply from
Deer-Wayton to Mockingbird Hill, which convinced nu-
merous residents of Mockingbird Hill that Deer-Wayton
was not the solution to their problem. As a result, several
of the residents tookthe lead in re-establishing the MHWA.
The reborn Association retained a consulting engineer to
test the water in the original deep well to determine if it
could be economically treated to an acceptable quality.
The Association and it's engineer also evaluated the
condition of the well pumping system, which had been
abandoned in place when the connection to Deer-Wayton
occurred. The MHWA received significant assistance in
both these tasks from a circuit rider with the Arkansas
Rural Water Association (ARWA).
When the results of the engineering evaluation were
received, the MHWA held a series of meetings that in-
cluded the Association Board, the consulting engineer,
and the County Health Department. As a result of these
meetings, it was decided that the MHWA would rehabili-
tate the existing well and construct a treatment system to
address the raw water quality problems. The president of
MHWA, with the support of several local congressmen
and senators, lobbied successfully to secure $600,000 in
grant funding (FmHA). An additional $350,000 of long-
term, low-interest loans were arranged. In addition, the
MHWA Board, the consulting engineer, and the County
Board of Health held discussions to determine the appro-
priate level of treatment.
EVALUATION OF ALTERNATIVES
Mockingbird Hill's engineer did not formally evaluate
multiple alternative treatment systems. Instead, the engi-
neer made recommendations based on recent experi-
ences in dealing with low-quality drinking water sources.
Onsite testing at Mockingbird Hill revealed a hydrogen
sulfide concentration of approximately 20 mg/L. Based on
previous experience, the consulting engineer recom-
80
-------
mendedthatthe hydrogen sulfide be removed using an air
stripping tower.
In addition, excessive amounts of iron and manganese
were present. The engineer recommended alum precipi-
tation and filtration to remove these remaining contami-
nants. Given the very small flow to be treated and the
desire that the selected treatment system require limited
attention, the engineer recommended using a package-
type water treatment system. The engineer had recently
had a very positive experience with this proprietary water
treatment system.
SELECTION OF DISTRIBUTION AND
TREATMENT SYSTEMS
As noted above, Mockingbird Hill's engineer recommended
installing an air stripping system, degassed water stor-
age, and a package precipitation/filtration treatment sys-
tem.
DESIGN CRITERIA
The design criteria for the treatment system are discussed
below. Table 1 presents design characteristics of the
selected treatment system.
The air stripping system was specified to provide 85-
percent removal of hydrogen sulfide. The design capacity
was specified as 100 gpm, with a design air throughput of
1,300 cf m. The resulting tower, which is approximately 3
feet in diameter and 10 feet tall, is situated on top of a
stripped water storage tank.
Table 1. Key Design Features of the Selected
Treatment System
* s s ;'*$&& J^'s^- .. / ff$& " ~- Wฎ=Vs ^^" ">*<" - -, J^X^^'A'Jt'iwB
"'^41 ^Stripping TSfeh f dcj'gpm^'l iSOoffm, Air
S;-- ;?'-Throughput%" ' -*" " -^'*-'""
The proprietary skid mounted treatment system incorpo-
rates chemical feed and mixing, an upflow adsorption
clarifier, and gravity multi-media filtration. The nominal
capacity rating by the manufacturer is 100 gpm; however,
the State of Arkansas rates the unit at 60 gpm, based on
a filter loading criterion of 3 gpm/ft2.
Figure 1 illustrates the system installed to treat Mocking-
bird Hill's water supply.
COST REDUCTION
Cost-reduction efforts appear to have been limited in
Mockingbird Hill's attempt to address its water supply
problem. This can probably be attributed largely to the
severity of the water shortage problem and to the techni-
cal difficulties posed by treating Mockingbird Hill's water
supply.
Raw
Water
Degassified
Water
Storage
Air Stripping
Tower
Alum and
Polymer
Addition
I
Adsorption
Clarifier
Multimedia
Filter
Treated
Water
to
Distribution
System
Figure 1. Plant schematic for Mockingbird Hill Water Association.
81
-------
RESULTS AND SUMMARY
Table 2 summarizes the key elements of Mockingbird
Hill's response to solve its drinking water problem. Since
start-up, hydrogen sulfide removals have averaged 90
percent according to the system operator. The operator
noted that at the present time, alum and polymer are not
being added to the degassified water. Instead, chlorine is
Injected Into the degassified water as it is pumped from the
storage tank to the package treatment system. The
chlorine Is continuously applied at a dose of 4 mg/L This
dosage results in additional removal of hydrogen sulfide
and the oxidation of Iron and manganese. The insoluble
precipitate resulting from the oxidation of iron and manga-
nese Is removed by settling and filtration in the package
plant.
An online turbidimeter monitors the quality of the treated
effluent. The turbidimeter regulates the application rate of
coagulants when used. At preset turbidimeter levels, the
package system will either automatically initiate a back-
wash cycle or shut-down (after a preselected time delay)
if excessive turbidity levels are measured after the back-
wash cycle has been completed.
Since the installation of the treatment system, the service
area has been expanded to 165 customers. Nonetheless,
the debt service associated with the non-grant funded
portion of the capital cost of the treatment system has
been difficult for Mockingbird Hill to bear. The present
monthly user charge is $16.25 for the first 1,000 gallons
and $2.75 for each additional 1,000 gallons used. The
average water use per customer is 3,000 gallons/month.
In addition to the financial difficulties, radium was de-
tected in Mockingbird Hill's treated water after the treat-
ment system was started up. While ongoing testing
appears to indicate that concentrations of radium are
below threshold levels, this issue has provoked significant
concern on the part of the customers served.
Table 2. Key Elements of Mockingbird Hill's
Experience
Effort "championed" by a concerned citizen
Assistance provided by Arkansas Rural Water
Association
All available financial assistance options
successfully pursued
Engineer knowledgeable of local water
conditions
Effective treatment technologies and
equipment selected
82
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RESOURCE DIRECTORY
-------
-------
U.S. ENVIRONMENTAL PROTECTION AGENCY
HEADQUARTERS AND REGIONAL OFFICES
Headquarters
401 M Street, SW
Washington, DC 20460
202-260-2090
Region 1
JFK Federal Building
Boston, MA 02203
617-565-3420
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26 Federal Plaza
New York, NY 10278
212-264-2657
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215-597-9800
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Region 4
345 Courtland Street, NE
Atlanta, GA 30365
404-347*4727
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312-353-2000
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Region 6
1445 Ross Avenue
Dallas, TX 75202
214-655-6444
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Region 7
726 Minnesota Avenue
Kansas City, KS 66101
913-551-7000
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415-744-1305
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206-553-4973
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85
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COALITION OF ENVIRONMENTAL TRAINING CENTERS
Arkansas Environmental Academy
SAU-Tech Station
JOOCarrRoad
East Camden, AR 71701
Contact: Mr. James Bailey
(501)574-4550
Central Community College-
Hastings Campus
East Hwy 6, P.O. Box 1024
Hastings, NE 68902
Contact: Mr. Greg DuMonthier
(402)461-2481
Colorado Environmental Training
Center
13300 West 6th Avenue
Lakewood, CO 80401-5398
Contact: Mr. Thomas Feeley
(303)980-9165
Crowder College
Enviromental Resource Center
601 Laclede Ave.
Neosho, MO 64850
Contact: Ms. Lorene Lindsay
(417)451-3583
Fleming Training Center
2022 Blanton Drive
Murfreesboro, TN 37129
Contact: Mr. James Coe
(615)898-8090
Georgia Water & Wastewater
Institute
301 Old Hickory Trail North
Carroliton, GA 30117
Contact: Mr. John Henderson
(404) 836-6656
Kentucky Division of Waste Man-
agement
18ReillyRoad
Frankfort, KY 40601
Contact: Ms. Lisa Detherage
(502)564-6716
Kirkwood Community College
6301 Kirkwood Blvd. S.W.
P.O. Box 2068
Cedar Rapids, IA 52406-2068
Contact: Mr. Douglas Fell
(319)398-5678
Linn-Benton Community College
6500 S.W. Pacific Blvd.
Albany, OR 97321
Contact: Dr. John Carnegie
(503) 928-2361
Massachusetts DEP Training Center
Route 20
Milbury, MA 01527
Contact: Mr. Kimball Simpson
(508) 756-7281
New England Interstate ETC
2 Fort Road
South Portland, ME 04106
Contact: Mr. Kirk Laflin
(207) 767-2639
NREP Cabinet-Division of Water
18Reilly Road
Frankfort, KY 40601
Contact: Ms. Nancy Fouser
Operator Training Committee of
Ohio
3972 Indianola Ave.
Columbus, OH 43214-3158
Contact: Mr. John McCraight
(614)268-6826
Southern Illinois University
Environmental Training Center
Edwardsville, IL 62025
Contact: Mr. Donald Anderson
Sumter Area Technical College
Environmental Training Center
506 North Guignard Drive
Sumter, SC 29150
Contact: Dr. William Engel
(803)778-1961
TREEO Center, Univ. of Florida
3900 S.W. 63rd. Blvd.
Gainesville, FL 32608-4830
Contact: Dr. James Bryant
(904)392-9570
Utah Valley Community College
800 West 1200 South
Orem, UT 84058
Contact: Ms. Lasca Rose
(801)226-5000
Washington Environmental Training
Center
12401 S.E. 320th St.
Auburn, WA 98002
Contact: Mr. Fred Delvecchio
(206)833-9111
86
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RURAL COMMUNITY ASSISTANCE PROGRAM
NATIONAL OFFICE
Rural Community Assistance Program (RCAP)
602 South King Street, Suite 402
Leesburg, VA 22075
Phone:(703)771-8636
Fax: (703) 777-8753
NORTHEASTERN REGION
Rural Housing Improvement (RHI)
Earnest Beresh
218 Central Street
Winchendon, MA 01475
Phone:(508)297-1376
Fax: (508) 297-2606
SOUTHEASTERN REGION
Virginia Water Project (VWP)
Mary Terry ,
1314 Peter's Creek Road #210
Roanoke.VA 24017
Phone:(703)345-1184
Fax: (703) 342-2932
GREAT LAKES REGION
WSOS Community Action Commission (WSOS)
Orville Burch
109 S. Front Street
Fremont, OH 43420
Phone:(419)334-8911
Fax: (419) 334-5125
MIDWESTERN REGION
Midwest Assistance Program (MAP)
Ken Bruzelius
P.O. Box 81
New Prague, MN 56071
Phone:(612)758-4334
Fax: (612) 758-4336
SOUTHERN REGION
Community Resource Group (CRG)
Mark Rounsavail
2705 Chapman Road
Springdale, AR 72764
Phone:(501)756-2900
Fax:(501)756-2901
WESTERN REGION
Rural Community Assistance Corporation (RCAC)
Beth Ytell
2521 19th Street, #203
Sacramento, CA 95818
Phone:(916)447-2854
Fax:(916)447-2878
87
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U.S. DEPARTMENT OF AGRICULTURE
STATE EXTENSION SERVICE DIRECTORS
Alabama Cooperative Extension
Service
109 Duncan Hall
Auburn University, AL 36849-5612
205/844-4444
Dr. Ann Thompson
University of Alaska
103AHRB
Fairbanks, AK 99775-5200
907/474-7246
Dr. Irvin Skelton
College of Agriculture
University of Arizona
Forbes Bldg., Rm. 301
Tucson, AZ 85721
602/621-7209
Dr. James Christenson
University of Arkansas
P.O. Box 391
Little Rock, AR 72203
501/671-2001
Dr. David Foster
University of California
Office of the Vice President
Agric. & Nat. Resources
300 Lakeside Dr., 6th Fl.
Oakland, CA 94612-3560
510/987-0060
Dr. Kenneth Farrell
Colorado State University
1 Administration Bldg.
Fort Collins, CO 80523
303/491-6208
Mr. Milan Rewerts
College of Agriculture and
Natural Resources
University of Connecticut
Box U-66,1376 Storrs Road
Storrs, CT 06269-4066
203/486-4125
Dr. John Brand
University of Delaware
Townsend Hall, Rm 131
South College Avenue
Newark, DE 19717-1303
302/831-2504
Dr. Richard Fowler
University of the District of Columbia
901 Newton St., N.E.
Washington, DC 20017
202/576-6993
Mr. Reginald Taylor
University of Florida
1038 McCarthy Hall
Gainesville, FL 32611
904/392-1761
Dr. John Woeste
University of Georgia
Room 111, Conner Hall
Athens, GA 30602
404/542-3824
Dr. C. Wayne Jordan
University of Hawaii
3050 Maile Way
Gilmore 202
Honolulu, HI 96822
808/956-8234
Dr. Noel Kefford
University of Idaho
Agricultural Science Building
Moscow, ID 83843
208/885-6639
Dr. LeRoy Luft
University of Illinois
122MumfordHall
1301 West Gregory Drive
Urbana, IL 61801
217/333-2660
Dr. Donald Uchtmann
Purdue University
104 Agriculture Admin. Bldg.
West Lafayette, IN 47907
317/494-8489
Dr. Henry Wadsworth
Iowa State University
315BeardshearHall
Ames, IA 50011
515/294-6192
Dr. Robert M. Anderson
Kansas State University
Waters Hall, Room 113
Manhattan, KS 66506
913/532-7137
Dr. Walter Woods
University of Kentucky
Ag. Science Building N
Lexington, KY 40546-0091
606/257-4772
Dr. C. Oran Little
Louisiana State University
Knapp Hall
Baton Rouge, LA 70803-1900
504/388-6083
Dr. Denver Loupe
University of Maine
102LibbyHall
Orono, ME 04469
207/581-3186
Dr. Judith Bailey
University of Maryland
3300 Metzerott Road
Adelphi, MD 20783
301/853-4746
Dr. Craig S. Oliver
University of Massachusetts
Room 117, Stockbridge Hall
Amherst, MA 01003
413/545-2766
Dr. Robert G. Helgesen
88
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U.S. DEPARTMENT OF AGRICULTURE
STATE EXTENSION SERVICE DIRECTORS (Continued)
Michigan State University
106 Agriculture Hall
East Lansing, Ml 48824
517/355-2308
Dr. Gail L Imig
University of Minnesota
240 Coffey Hall
1420 Eckles Avenue
St. Paul, MN 55108
612/624-2703
Dr. Patrick J. Borich
Mississippi State University
Box 5446
201 Bost Extension Center
Mississippi St., MS 39762
601/325-3036
Dr. Hiram D. Palmertree
University of Missouri
309 University Hall
Columbia, MO 65211
314/882-7754
Dr. Ronald C. Powers
Montana State University
210 Montana Hall
Bozeman, MT 59717
406/994-4371
Dr. Andrea Pagenkopf
University of Nebraska
214 Agriculture Hall
Lincoln, NE 68583-0703
402/472-2966
Dr. Kenneth R. Bolen
University of Nevada-Reno
Mail Stop 222
Reno, NV 89557-0004
702/748-6611
Dr. Bernard M. Jones
University of New Hampshire
Taylor Hall, Room 103
Durham, NH 03824
603/862-1520
Dr. Peter J. Home
Cook College
Box 231
New Brunswick, NJ 08903
908/932-9306
Dr. John L. Gerwig
New Mexico State University
Box 3AE
Las Cruces, NM 88003
505/646-3015
Dr. Robert L. Gilliland
Cornell University
276 Roberts Hall
Ithaca, NY 14853-5901
607/255-2237
Dr. Lucinda A. Noble
North Carolina State University
Box 7602
Raleigh, NC 27695-7602
919/515-2811
Dr. Robert C. Wells
North Dakota State University
311 Morrill Hall
Fargo,.ND 58105
701/237-8944
Dr. William H. Pietsch
Ohio State University
2120FyffeRoad
Columbus, OH 43210
614/292-4067
Dr. Keith L. Smith
Oklahoma State University
139 Agriculture Hall
Stillwater, OK 74078-0500
405/744-5398
Dr. Charles B. Browning
Oregon State University
Corvallis, OR 97331
503/737-2713
Dr. O..E. Smith
Pennsylvania State University
201 Ag. Admin. Bldg.
University Park, PA 16802
814/865-2541
Dr. Lamartine F. Hood
University of Rhode Island
113 Woodward Hall
Kingston, Rl 02881
401/792-2474
Dr. Robert H. Miller
Clemson University
103BarreHall
Clemson, SC 29634
803/656-3382 ,
Dr. Byron K. Webb
South Dakota State University
P.O. Box 2207D, Ag. Hall 154
Brookings, SD 57007-9988
605/688-4792
Dr. Mylo A. Hellickson
University of Tennessee
Box1071
Knoxville.TN 37901-1071
615/974-7114
Dr. Billy G. Hicks
Texas A&M University
System Administration Bldg.
Room 106
College Station, TX 77843-7101
409/845-7967
Dr. Zerle L. Carpenter
Utah State University
Agric. Science Building
Logan, UT 84322-4900
801/750-2200
Dr. R. Paul Larsen
89
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U.S. DEPARTMENT OF AGRICULTURE
STATE EXTENSION SERVICE DIRECTORS (Continued)
University of Vermont
108 Merrill Hall
Burlington, VT 05405-0106
802/656-2980
Dr. Lawrence K. Forcier
College of Agriculture and Life
Sciences
104HutchesonHall
Virginia Polytechnic Institute and
State University
Blacksburg, VA 24061-0402
703/231-9892
Dr. James F. Johnson
Washington State University
411 HulbertHall
Pullman, WA 99164-6230
509/335-2933
Dr. Larry G. James
West Virginia University
817KnappHall
P.O. Box 6031
Morgantown, WV 26506
304/293-5691
Dr. Rachel B. Tompkins
University of Wisconsin Extension
432 N. Lake Street
Room 527, Extension Building
Madison, Wl 53706
608/262-3786
Dr. Patrick G. Boyle
College of Agriculture
University of Wyoming
P.O. Box 3354
Laramie, WY 82071
307/766-5124
Mr. Jim DeBree
National Association of State
Universities & Land Grant Colleges
One Dupont Circle, Suite 710
Washington, DC 20036
202/778-0829
Dr. Robert L. Crom
90
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NATIONAL RURAL WATER ASSOCIATION
STATE ASSOCIATIONS & STATE AFFILIATES
National Rural Water Association
P.O. Box 1428
Duncan, OK 73534
405/252-0629
Alabama Rural Water Assn.
4556 South Court St.
Montgomery, AL 36105
205/284-1489
Arizona Small Utilities Assn.
1955 W. Grant Road, Suite 125
Tucson, AZ 85745
602/620-0230
Arkansas Rural Water Assn.
P.O. Box192118
Little Rock, AR 72219
501/568-5252
California Rural Water Assn.
216 W. Perkins St., Suite 204
Ukiah, CA 95482
707/462-1730
Colorado Rural Water Assn.
2648 Santa Fe Drive, #10
Pueblo, CO 81006
719/545-6748
Connecticut & Rhode Island Rural
Water
11 Richmond Lane
Willimantic, CT 06226-3825
203/423-6737
Delaware Rural Water Assn.
P.O. Box 118
Harrington, DE 19952
302/398-9633
Florida Rural Water Assn.
1391 Timberlane Rd., Suite 104
Tallahasee, FL 32312
904/668-2746
Georgia Rural Water Assn.
P.O. Box 383
Barnesville, GA 30204
404/358-0221
Idaho Rural Water Assn.
P.O. Box 303
Lewiston, ID 83501
208/742-6142
Illinois Rural Water Assn.
401 South Vine
Mt. Pulaski, IL 62548
217/792-5011
Indiana Water Assn.
P.O. Box 103
Sellersburg, IN 47172
812/246-4148
Iowa Rural Water Assn.
1300 S.E. Cummins Rd., Suite 103
Des Moines, IA 50315
515/287-1765
Kansas Rural Water Assn.
P.O. Box 226
Seneca, KS 66538
913/336-3760
Kentucky Rural Water Assn.
P.O. Box 1424
Bowling Green, KY 42102-1424
502/843-2291
Louisiana Rural Water Assn.
P.O. Box 180
Kinder, LA 70648
318/738-2896
Maine Rural Water Assn.
14 Maine St., Suite 407
Brunswick, ME 04011
207/729-6569
Maryland Rural Water Assn.
P.O. Box 207
Delmar, MD 21875
301/749-9474
Michigan Rural Water Assn.
P.O. Box 17
Auburn, Ml 48611
517/662-2655
Minnesota Rural Water Assn.
RR 2, Box 29
Elbow Lake, MN 56531
218/685-5197
Mississippi Rural Water Assn.
P.O. Box1995
Hattiesburg, MS 39403-1995
601/544-2735
Missouri Rural Water Assn.
P.O. Box 309
Grandview, MO 64030
816/966-1522
Montana Rural Water Systems
Assn.
925 7th Avenue South
Great Falls, MT 59405
406/454-1151
Nebraska Rural Water Assn.
Routes, Box 115
Humboldt, NE 68376
402/862-3140
91
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NATIONAL RURAL WATER ASSOCIATION
STATE ASSOCIATIONS & STATE AFFILIATES (Continued)
Nevada Rural Water Assn.
P.O. Box 837
Overton, NV 89040
702/397-8985
New Jersey Assn. of Rural Water &
Wastewater Ut.
RD1 Route 72
Vincentown, NJ 08088
609/894-2750
New Mexico Rural Water Users
Assn.
3218 Silver, S.E.
Albuquerque, NM 87106
505/255-2242
New York State Rural Water Assn.
P.O. Box 487
Claverack, NY 12513
518/851-7644
North Carolina Rural Water Assn.
P.O. Box 540
Welcome, NC 27374
704/731-6963
North Dakota Rural Water Systems
Assn.
Route 1, Box 34C
Bismarck, ND 58501
701/258-9249
Northeast Rural Water Assn.
512 St. George Road
Williston, VT 05495
802/878-3276
Ohio Assn. of Rural Water Systems
P.O. Box 397
Grove City, OH 43123
614/871-2725
Oklahoma Rural Water Assn.
1410 S.E. 15th
Oklahoma City, OK 73129
405/672-8925
Oregon Assn. of Water Utilities
1290 Capitol Street NE
Salem, OR 97303
503/364-8269
Pennsylvania Rural Water Assn.
P.O. Box 90
Saltsburg, PA 15681-0090
412/639-3246
South Carolina Rural Water Assn.
P.O. Box 479
Clinton, SC 29325
803/833-5566
South Dakota Assn. of Rural Water
Systems
5009 W. 12th Street, Suite 5
Sioux Falls, SD 57106
605/336-7219
Tennessee Assn. of Utility Districts
P.O. Box 2529
Murfreesboro, TN 87133-2529
615/896-9022
Texas Rural Water Assn.
6300 Lacalma, Suite 120
Austin, TX 78752
512/458-8121
Rural Water Assn. of Utah
P.O. Box 661
Spanish Fork, Utah 84660
801/798-3518
Virginia Rural Water Assn.
133 West 21st Street
Buena Vista, VA 24416
703/261 r7178
Washington Rural Water Assn.
P.O. Box141588
Spokane, WA 99214-1588
509/924-5568
West Virginia Rural Water Assn.
P.O. Box 225
Teays, WV 25569
304/757-0985
Wisconsin Rural Water Assn.
2715 Post Road (Whiting)
Stevens Point, Wl 54481
715/344-7778
Wyoming Assn. of Rural Water
Systems
P.O. Box1750
Glenrock,WY 82637
307/436-8636
!ป U.S, GOVERNMENT PRINTING OFFICE:1993-750-002/60107
92
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