a,
4300991020
PROCEEDINGS OF
THE U.S. ENVIRONMENTAL
I PROTECTION AGENCY
MUNICIPAL WASTEWATER TREATMENT
9 TECHNOLOGY FORUM
1991
June 5-7, 1991
Portland, Oregon
September 1991
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ACKNOWLEDGEMENTS
This document was prepared by Eastern Research Group, Inc., Arlington, Massachusetts,
under EPA Contract 68-C1-0018. Denise Short was the Project Manager. Technical direction
was provided by Wendy Bell of EPA's Office of Wastewater Enforcement and Compliance. The
text was based on attendance at the Municipal Wastewater Treatment Technology Forum,
transcriptions of the presentations, and submissions made by the speakers. The time and
contributions of all the Forum speakers are gratefully acknowledged.
NOTICE
Mention of trade names or commercial products does not constitute endorsement or
recommendation for use by EPA.
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PREFACE
The 1991 Municipal Wastewater Technology Forum, sponsored by EPA's Office of
Wastewater Enforcement and Compliance (OWEC); provided the opportunity for wastewater
treatment professionals from the Federal and State governments to discuss foremost wastewater
treatment technology development and transfer issues. Presentations were made on land
treatment, sand and gravel filters, operation and maintenance (O&M), biological nutrient
removal, sludge, stormwater, disinfection, constructed wetlands, and municipal water use
efficiency. There were also two field trips that allowed participants to visit wastewater
treatment plants that employ some of the discussed technologies.
The Forum represents a part of OWEC's National Technology Support Program. One
of the main elements of this program is the Wastewater Technology Transfer Network (WTTN),
which supports and enhances the network of Regional and State wastewater technology transfer
coordinators. This yearly meeting provides these coordinators with the opportunity to exchange
information and learn from each other about promising and problem technologies.
There are several changes upcoming on the Federal level that affect all of those involved
in wastewater technology development and transfer. These include the impending sludge and
stormwater regulations, the reauthorization of the Clean Water Act, and the continued close-out
of the construction grants program. This year's Forum was coordinated with the National
Operator Training Conference in order to increase communication between the audiences and
help all the participants deal with the increased challenges that they face.
In addition to providing summaries of the speakers' presentations, this document
contains several appendices that can be useful to those involved in the WTTN:
• Appendix A contains the Forum Agenda
• Appendix B is a list of the speakers' addresses that can be used to obtain more
information about the presentations
• Appendix C is a list of addresses for Regional and State wastewater technology,
sludge, and outreach coordinators
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Appendix D is a summary of the innovative and alternative (I/A) technology
projects by State
Appendix E lists the current status of EPA's modification/replacement (M/R)
grant candidates by State
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TABLE OF CONTENTS
Page
INTRODUCTION
Update on EPA's Sludge Policy and New
Sewage Sludge Regulations 1
LAND TREATMENT
Best Available Technology for Design and Siting for Land
Application of Wastewater on the Rathdrum Prairie-Kootenai
County, Idaho 5
SAND AND GRAVEL FILTERS
Sand Filters: State of the Art 11
The Tennessee Experience with the Recirculating Sand Filter
Wastewater Treatment Systems for Small Flows 16
Recirculating Gravel Filters in Oregon 23
OPERATIONS AND MAINTENANCE
Assessment of O&M Requirements for
Ultraviolet Disinfection Systems 34
Trickling Filter Operation and Maintenance Issues 50
Update on the Microbial Rock Plant Filter 55
BIOLOGICAL NUTRIENT REMOVAL
Biological Nutrient Removal Systems 69
Operation of Anoxic Selector Activated Sludge
Systems for Nitrogen Removal at Rock Creek and
Tri-City 76
Summary of Patented and Public Biological
Phosphorous Removal Systems 83
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TABLE OF CONTENTS (cont.)
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SLUDGE
Case Study Evaluation of Alkaline Stabilization
Processes 89
Controlling Sludge Composting Odors 95
Total Recycling 98
STORMWATER
Washington State's Approach to Combined Sewer Overflow
Control 101
National Cost for Combined Sewer Overflow Control 108
Stormwater Control for Puget Sound 117
DISINFECTION
Total Residual Chlorine: Toricological Effects and Fate in
Freshwater Streams in New York State 121
EPA Disinfection Policy and Guidance Update 128
CONSTRUCTED WETLANDS
Use of Constructed Wetlands to Treat Domestic
Wastewater, City of Arcata, California 133
Constructed Wetlands Experience in the Southeast 154
MUNICIPAL WATER USE EFFICIENCY
How Efficient Water Use Can Help
Communities Meet Environmental Objectives 165
Impact of Indoor Water conservation on Wastewater
Characteristics and Treatment Process 169
VI
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TABLE OF CONTENTS (cont.)
Page
Fixed Film/Suspended Growth Secondary Treatment
Systems 185
Chemical Phosphorous Removal in Lagoons 198
APPENDIX A AGENDA A-l
APPENDIX B LIST OF SPEAKERS B-l
APPENDIX C LIST OF ADDRESSES FOR REGIONAL AND STATE
WASTEWATER TECHNOLOGY, SLUDGE, AND
OUTREACH COORDINATORS C-l
APPENDIX D SUMMARY OF INNOVATIVE AND ALTERNATIVE
TECHNOLOGY PROJECTS BY STATE D-l
APPENDIX E CURRENT STATUS OF MODIFICATION/
REPLACEMENT (M/R) GRANT CANDIDATES
BY STATE E-l
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TABLES
Page
Table 1. Recirculating Gravel Filters in Oregon—May 1991 27
Table 2. Performance Data from Four Oregon RGFs 31
Table 3. Summary of Design Sizing/Performance Characteristics
for Selected Plants 36
Table 4. Summary of Cleaning Practices for the
20 Selected Plants 48
Table 5. Summary of Selected Currently Licensed BPR Systems 85
Table 6. Summary of Selected Currently Used BPR Systems in
Public Domain 85
Table 7. Comparison of Alkaline Stabilization Processes 91
Table 8. Comparison of Pilot Project and Full-Scale Results
for NPDES Parameters 141
Table 9. Comparison of FWS and VSB Systems 155
Table 10. Denham Springs System 159
Table 11. Phillips High School VSB 160
Table 12. Toilet Fixtures 172
Table 13. Flows 176
Table 14. Suspended Solids 176
Table 15. Biological Oxygen Demand (BOD) 176
Table 16. Summary Characteristics of POTWs in Study 178
Table 17. Percent of Population Using Technology—Slow-Rate
Implementation Scenario 178
Table 18. Percent of Population Using Technology—Medium-Rate
Implementation Scenario 179
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TABLES (cont.)
Page
Table 19. Percent of Population Using Technology—High-Rate
Implementation Scenario 179
Table 20. Conventional Upgrading Requirements 192
Table 21. Observed Inert Support Media Biomass Values 193
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FIGURES
Page
Figure 1. Recirculating Filter System 12
Figure 2. Recirculating Effluent Pump System 13
Figure 3. Recirculating Sand Filter 14
Figure 4. Small Package Activated-Sludge Plant versus 18
RSF—Economic Analysis
Figure 5. Whitwell Hospital Recirculating Sand Filter 20
Figure 6. Facilities Inventory 21
Figure 7. Schematic of a Recirculating Gravel Filter 24
Figure 8. Cross-Section of an RGF 25
Figure 9. UV System Sizing for Selected Plants as a
Function of Peak Design Row 37
Figure 10. Labor Requirements for Replacement of
Lamps/Ballasts/Quartz 41
Figure 11. Estimate of O&M Labor 42
Figure 12. Schematic of UV Channel System Showing
Cleaning Tank 46
Figure 13. MRPF—Longitudinal Section 56
Figure 14. MRPF—Cross-Sectional area 56
Figure 15. MRPF—Plant/Root Functions 58
Figure 16. MRPF—Non-Maintenance Results 60
Figure 17. Root Control to Prevent Filter Clogging 62
Figure 18. Planting Pattern for Filter 62
Figure 19. Location and Status of MRPF in Region 6 67
Figure 20. Schematic Representation of Ecology's
CSO Treatment Requirements 102
Figure 21. Suspended Solids Removal as a Function
of Organic Loading over a 55 Week Period 137
Figure 22. Regression Curve of BOD Removal versus
BOD Loading to Arcata Pilot Project 137
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FIGURES (cont.)
Page
Figure 23. BOD Removal through Pilot Project Cell Showing the First
Order Removal of BOD through a Compartment Cell 139
Figure 24. Suspended Solids Removal through Pilot
Marsh 8 ..' 139
Figure 25. Ammonia Nitrogen Levels in Arcata Pilot Project
Influent and in the Effluent from Cell 3 143
Figure 26. Ammonia Nitrogen Levels in Arcata Influent
and in Effluent for Cells 5 and 11 143
Figure 27. Phosphorus Removal from Cell 3 (0.5 gpd/ft2)
and Cell 5 (2.94 gpd/ft2) 145
Figure 28. Fecal Coliform Removal in Pilot Project Cell 8,
1985-1986 145
Figure 29. CW Sewage Treatment System—Gravel and Surface
Flow Marshes 156
Figure 30. Fort Deposit, AL—FWS Constructed Wetland Cells 162
Figure 31. Influent Flow (mgd) Over Time for Goleta POTW 175
Figure 32. Influent Flow (mgd) Over Time for Santa Barbara's
El Estero POTW 175
Figure 33. Predicted BOD, Suspended Solids, and Per Capita
Wastewater Flow for High Rate Water Conservation
Scenario 181
Figure 34. BOD and Suspended Solids vs. Influent Flow at
Goleta POTW 181
Figure 35. Percent Removal of Suspended Solids vs. Influent
Suspended Solids for Central Contra Costa POTW 182
Figure 36. Percent Removal vs. Influent Suspended Solids
Mass Loading (Ibs/day) for Point Loma POTW 182
Figure 37. Plan and Section Views of a Bio-2-Sludge System 186
Figure 38. Plan and Section Views of a Ring Lace System 187
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INTRODUCTION
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UPDATE ON EPA'S SLUDGE POLICY AND NEW SEWAGE SLUDGE REGULATIONS
Robert Bastian
U.S. Environmental Protection Agency
Washington, DC
The initial round of comprehensive sewage sludge technical regulations required by
Section 405 of the Clean Water Act (CWA) were published on February 6, 1989, in the Federal
Register (Vol. 54, No. 23: 5746-5902) as "Proposed Standards for the Disposal of Sewage
Sludge" for public comment. The new proposed technical regulations (to be issued as 40 CFR
Part 503) cover the final use and disposal of sewage sludge when incinerated, applied to the
land, distributed and marketed, placed in sludge-only landfills (monofills), or on surface disposal
sites. Co-landfilling of sewage sludge with municipal solid waste will be covered under the new
40 CFR Part 258 Municipal Solid Waste Landfill regulations (proposed on August 30, 1988 [53
FR 3314] and expected to be issued in final form early in 1991). Ocean dumping is to be
phased out by the end of 1991 under the provisions of the Ocean Dumping Ban Act of 1988
(PL 100-68) signed into law on November 18,1988.
The proposed Part 503 rule contains standards for each end use and disposal method
consisting of limits for 28 pollutants in the form of sludge concentration limits or pollutant
loading limits, as well as management practices and other requirements such as treatment works
management controls over users and contractors, and monitoring, record keeping, and reporting
requirements. As proposed, the requirements would apply to the final use and disposal of
sludges produced by both publicly owned treatment works (POTWs), and privately owned
treatment works that treat domestic wastewater and septage, but would not apply to sludges
produced by privately owned industrial facilities that treat domestic sewage along with industrial
waste.
Over-650 parties submitted more than 5,500 comments identifying some 250 issues in
response to the Proposed Part 503 regulations. Formal comments on the proposed regulations
were received from 30 states and four environmental groups, as well as many POTWs,
consultants, equipment vendors, etc. During the 180-day comment period provided on the
proposal (which ended August 7,1989), experts from both inside and outside EPA were
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involved in thoroughly reviewing the technical basis of the proposal. The review involved
experts from the Agency's Science Advisory Board, environmental groups, academia, and
various scientific bodies with expertise in areas covered by the proposed rule. The majority of
commenters indicated that the proposed rules were overly stringent, used unrealistic
conservative assumptions, and at a minimum, will discourage beneficial use of sludge. Others
raised questions about how to better define the sludge use and disposal categories, terms such
as de minimus and "clean" sludge, and which models, risk assessment methodologies, and data to
use for determining the proposed numeric limitations.
The Agency also conducted a National Sewage Sludge Survey (NSSS) to obtain better
information on current sludge quality, use, and disposal practices. The survey collected
information from 479 POTWs on sludge use and disposal practices and costs, and analyzed
sludges from 181 POTWs for 419 analytes—all the metals and inorganics (including pesticides,
dibenzofurans, dioxins, and PCBs) for which gas chromatography/mass spectroscopy (GC/MS)
standards exist. These data are being used in developing regulatory impact analysis and
aggregate risk analysis of human health, environmental, and economic impacts and benefits of
sludge use and disposal practices to help refine the Part 503 regulations, and to help identify
which additional pollutants in sewage sludge should be regulated in the future. As a result of
settlement of litigation in Oregon concerning the failure of EPA to issue the new regulations by
the dates specified in the Water Quality Act Amendments of 1987, EPA will identify additional
pollutants and a schedule for a second round of sewage sludge rulemaking in June 1992.
The Agency published its analysis of the new NSSS data in the November 9, 1990,
Federal Register Notice (55 FR 47210) for public comment. In addition, the Notice requests
comments on alternative approaches that EPA is considering for various sections of the Part 503
regulations. These approaches are based on comments received on the proposed Part 503
regulations and information received since the proposal. These include:
Revised approaches for regulating 1) land application of septage, 2) organic
pollutants in emissions from sewage sludge incinerators, 3) the application of
sewage sludge to non-agricultural land, and 4) the disposal of sewage sludge on a
surface disposal site
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• Potential changes to the input parameters for the models used to develop
pollutant limits for sewage sludge applied to agricultural land or distributed and
marketed
• Alternative pollutant limits (i.e., "clean sludge concept" for sewage sludge applied
to the land or distributed and marketed)
• The eligibility of a pollutant for a removal credit with respect to the use and
disposal of sewage sludge
The public comment period on the notice closed on January 8,1991. EPA is utilizing
the comments received on the notice, the February 6,1989, proposal and the recommendations
of the peer review panels to craft the final rule. A number of the external scientists involved in
the peer review effort continue to be involved in assisting the Agency in developing scientifically
defendable pollutant limits and in addressing key technical issues raised in public comments. It
is anticipated that the proposed pollutant limits and management practices included in the
proposed regulations, and even some of the basic approaches for regulating sewage sludge taken
in the proposal, will change significantly. Current plans calls for promulgation of the final Part
503 regulations in January 1992, as a result of the Oregon court-imposed schedule.
Meanwhile, the Part 122-124 and 501 regulations, which will require the new Part 503
technical regulations (once issued in final form) to be imposed through an NPDES or state
permit (issued under an approved state program), were issued on May 2, 1989, in the Federal
Register (Vol. 54, No. 83: 18716-18796) as "NPDES Sewage Sludge Permit Regulations; State
Sludge Management Program Requirements." A "Sewage Sludge Interim Permitting Strategy"
was issued in September 1989, describing the Agency's strategy for carrying out the new Section
405 CWA requirements to impose controls on sewage sludge use and disposal practices in
NPDES permits issued to POTWs until the new Part 503 technical regulations become effective.
Pursuant to the "Interim Strategy," EPA or the states may issue sludge permits as agreed to by
the state/EPA agreements. POTWs should consult their NPDES authorities as to the
appropriate procedures and requirements. The final version of the "POTW Sludge Sampling
and Analysis Guidance Document" was issued in August 1989 to provide technical guidance on
the sampling and analysis of municipal sewage sludge. "Guidance for Writing Case-by-Case
Permit Requirements for Municipal Sewage Sludge" was issued in final form in December 1989.
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Copies of these documents are available from the Permits Division in EPA's Office of
Wastewater Enforcement and Compliance.
Finally, a number of issues concerning some programmatic and technical considerations
needed to implement sewage sludge beneficial use programs on federal lands have arisen among
federal agencies. To remedy this, EPA is working closely with the Office of Management and
Budget, the Bureau of Land Management, the U.S. Forest Service, the U.S. Fish and Wildlife
Service, the Department of Defense, the Department of Energy, TVA, FDA, and other federal
agencies that generate or use/dispose of sewage sludge on federal lands to establish a unified
federal policy on beneficial use of sludge and to prepare guidelines that federal agency land
managers can use in determining the appropriateness of land application of sewage sludge for
their facilities. A Federal Register notice containing the new "Interagency Sludge Policy on
Beneficial Use of Municipal Sewage Sludge on Federal Land" that has been designed to
supplement the existing 1984 EPA policy promoting beneficial use of sludge and the 1981
EPA/USDA/FDA policy and guidance document should be issued by early summer 1991.
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LAND TREATMENT
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BEST AVAILABLE TECHNOLOGY FOR DESIGN AND SITING
FOR LAND APPLICATION OF WASTEWATER ON THE
RATHDRUM PRAIRIE - KOOTENAI COUNTY, IDAHO
John Sutherland
IDHW-Division of Environmental Quality
Coeur d'Alene, Idaho
Introduction. Sewage was first applied to land to dispose of it or to fertilize vegetables. The
practice dates back at least to 1559. These forms of disposal increased in popularity through the
middle of the 19th century. In the last half of the 19th century land disposal was largely
abandoned in favor of centralized treatment and discharge to surface water. These plants are
designed to reduce the amounts of suspended material and oxygen demanding substances;
however, contaminants such as the nutrients nitrogen and phosphorous are not well treated and
may cause problems with accelerated plant growth resulting in degraded water quality. Various
types of advanced wastewater treatment can be used to substantially increase removal
efficiencies.
With population growth occurring in many areas, increasing wastewater flows are nearing
or exceeding the assimilative capacity of the receiving waters resulting in the need for increased
treatment or alternative methods of wastewater disposal. Modern wastewater land application
systems, designed and operated to protect surface water quality, are in operation throughout the
United States. The extent to which the protection of ground-water quality was incorporated
into the design and siting is largely unknown.
Land application of municipal wastewater offers some distinct advantages to other
wastewater treatment methods. Nutrients such as nitrogen (N) and phosphorous (P) can be
utilized by plants, tied up in the soil, and volatilized. Heavy metals often can be adsorbed onto
soil particles, and brganics can be volatilized and degraded. However, if improperly sited,
designed, and operated, ground-water contamination can result. When this ground water is the
only source of drinking water for 400,000 people, as in the case of the Rathdrum Prairie
Aquifer, informed decisions are imperative.
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The Idaho Division of Environmental Quality is currently engaged in a study, using
funds provided by the U. S. Environmental Protection Agency (EPA), to determine the
feasibility of applying secondary treated municipal wastewater to the Rathdrum Prairie of
northern Idaho. This area lies over a portion of a sole source aquifer, which the State of Idaho
Department of Health & Welfare, Division of Environmental Quality (IDHW-DEQ) has
determined to be susceptible to surface land use activities.
Background. The Spokane Valley/Rathdrum Prairie Aquifer, located primarily in Kootenai
County, Idaho, and Spokane County, Washington, lies in a valley filled with glacial outwash
deposits created when ice dams on glacial Lake Missoula breached and in catastrophic events
flooded the entire area. In Idaho the Rathdrum Prairie Aquifer covers 283 mi2 of the total 409
mi2 basin. It is bordered by mountainous terrain and numerous lakes which provide the
majority of the recharge to the aquifer. Ground-water flow is generally from the northeast from
Spirit Lake and Lake Pend Oreille to the southwest where it discharges to the Spokane and
Little Spokane rivers near Spokane, Washington.
The glacial outwash soils located over the aquifer are generally excessively drained, and
due to the general absence of confining layers in the soil profile little protection exists for the
ground water from surface land use activities.
In 1978 the Rathdrum Prairie was designated a "sole source aquifer" by EPA and in 1980
as a "special resource water" by the IDHW-DEQ.
These designations attest to the significance of this resource to the 400,000 users on both
sides of the state line. The majority of residents living on the Rathdrum Prairie and Spokane
Valley utilize this resource including the cities of Coeur d'Alene, Rathdrum, Bayview, Dalton
Gardens, Hauser, Post Falls, Hayden, Hayden Lake, and Athol, Idaho, as well as Spokane,
Washington.
Prevention of contamination is viewed as the best possible method of managing the
water quality of the Rathdrum Prairie Aquifer. This area is presently experiencing rapid
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population growth. Combined with the climate, hydrogeologic setting, and soil characteristics,
this presents some unusual challenges.
Best Available Technology. It is important to understand several concepts that are required to
protect the ground water from contamination. A distinction needs to be made between the
disposal of wastewater and its treatment. In using land application as a disposal method, the
wastewater is applied at rates too high for hydraulic uptake and often is not treated before
leaving the root zone where further treatment is unlikely to occur naturally. In a departure
from standard practice, which is to load the system at the agronomic uptake of nitrogen with
little or no consideration given to hydraulic overloads, Idaho DEQ feels the best available
technology is to load the system at the plant's consumptive use of water. In theory this will
generate little or no leachate to contaminate ground water. Application at rates in excess of the
hydraulic consumptive rate may result in contaminants such as nitrate being flushed below the
root zone, making them unavailable for crop uptake, and increasing the potential for aquifer
contamination. An important operational parameter of this approach is that it only allows for
seasonal land application during the months when plant growth is occurring and
evapotranspiration rates are in excess of precipitation.
The following criteria are important considerations in siting and designing a land
application system.
Hydrogeology. An understanding of the hydrogeology of a site is essential to the design of a
land application system. An understanding of the aquifer characteristics and the unsaturated
zone are important in determining the pollution potential of underlying ground water. Ground-
water flow direction and velocities are important for determining monitoring locations. Areas
of special vulnerabilities should be identified.
The Rathdrum Prairie Aquifer is recognized as one of the most productive aquifers in
the country. This aquifer has high porosities, permeabilities, and transmissivities. Ground-water
velocities have been calculated in some areas in excess of 50 ft/day. Recently, a well pump test
for a production well discharging 6,000 gpm was pumped with a 5 ft drawdown for 8 hours near
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the area of a proposed pilot study. Vulnerable areas include recharge sumps where the terminal
ends of streams flow out and disappear into the prairie.
Climate. Climate is important for several reasons. The growing season must be determined to
effectively design for application rates and seasons. Precipitation is important in determining
application rates. It is also important to know when evapotranspiration rates exceed
precipitation. Important to the Rathdrum Prairie are the approximately 24 inches of annual
precipitation, dry summers where evapotranspiration exceeds precipitation, and growing season
dates.
Soils. Soils have the ability to store some of the water from precipitation and land application
for plant growth, reducing infiltration to ground water. Soils can also retain nutrients and
potential contaminants allowing for biological or chemical degradation or utilization in plant
tissues. Important soil characteristics include soil depth, slope, texture, drainage, permeability,
cation exchange capacity (CEC), and organic matter content.
Due to the coarseness of the glacial outwash subsoils (Missoula Flood Deposits)
overlying the Rathdrum Prairie Aquifer and their rapid permeability, the surface soil layer is
extremely important. The soils tend to be excessively well drained. This, combined with the
nearly level (0 to 2 percent) to moderately sloping (2 to 7 percent) topography, promotes
infiltration as opposed to overland flow. The surface soil horizons are formed from a
combination of loess and volcanic ash in a gravelly silt loam with moderately rapid permeability.
Due to the finer texture of the silty surface soil and the presence of volcanic ash and allophone
ash weathering product, the surface soil has high water holding capacity and adsorption capacity
for selected nutrients and contaminants if present.
The soil pH and CEC are important in that they affect the soil's ability to store nutrients
and potential contaminants. Soil pH ranges from 5.6 to 7.4. The surface soils tend to have a
high CEC due to a high organic matter content which allows the soil to store positively charged
ions. These characteristics provide some capabilities for retaining certain chemicals (cationic
and polar); however, because of the lack of confining layers, negatively charged ions (anions)
such as nitrate can move with the soil water and potentially reach the ground water.
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Wastewater Characterization. A complete wastewater characterization is a necessary
component of a properly designed land application system. Although many of the potentially
toxic elements will receive some degree of treatment (volatilization or biodegradation of
organics) or are retained in the soils (heavy metals), some may have a detrimental effect on the
crops, livestock, or the ground water.
Cadmium is an example of an element that is toxic to both plants and animals and if
present can cause problems. Other heavy metals such as copper, zinc, and nickel are of concern
for plant toxicity. It is important to prevent phytotoxicity and food chain contamination.
Testing to identify potential toxics is mandatory. In areas that have industrial discharges to the
treatment plant an aggressive pretreatment program is imperative. An analysis and
characterization of the wastewater from two treatment plants near the Rathdrum Prairie
indicated acceptable levels for land application for the Idaho DEQ pilot study.
Crop. Crop selection is extremely important to a properly designed land application system.
The crop must have the ability to consume sufficient quantities of water as well as nutrients.
"Down time" from irrigating due to cropping practices must be considered in design.
Different crops have different rooting depths, as well as hydraulic and nutrient needs.
IDHW-DEQ feels that for the Rathdrum Prairie a split application to alfalfa-orchard grass hay,
and bluegrass for seed production is most appropriate, in that differing cropping requirements
will allow for continual application of wastewater during the growing season.
Pilot Project. Initial results from a literature review and office analysis are cautiously optimistic
that land application is a feasible form of wastewater treatment on the Rathdrum Prairie. A
pilot land application system is currently under design for the Hayden Lake area. The system
will be installed instead of a community drainfield. This system will be extensively monitored by
IDHW-DEQ for the next few years. Information collected should help to determine the
feasibility of using land application over the aquifer as a permanent solution to wastewater
disposal in Kootenai County.
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Conclusion. This study has determined that for the Rathdrum Prairie Aquifer the Best
Available Technology for land application is at the hydraulic consumptive use rate of the
selected crop. The design and siting of the system is determined by the climate, hydrogeology,
soils, wastewater characterization, and the crop.
This technology can likely be applied to many similar situations where the application of
wastewater is proposed over a vulnerable aquifer.
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SAND AND GRAVEL FILTERS
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SAND FILTERS: STATE OF THE ART
Harold L. Ball
Orenco Systems, Inc.
Roseburg, Oregon
Approximately 50 recirculating sand filters have been constructed on the West Coast
since 1980. Serving facilities such as apartment complexes, recreational vehicle parks, and other
small communities, they range in capacity from 5,000 gal/day to 120,000 gal/day. In most cases,
wastewater from dwellings is transported to the sand filter by pressure sewer (S.T.E.P.) systems
or by variable-grade small-diameter gravity systems.
Effluent discharged from a recirculating sand filter should have BOD5 and TSS
consistently less than 10 mg/L. The ammonia level should always be less than 1 mg/L and
nitrate nitrogen should run between 20 and 40 mg/L.
Figure 1 is a schematic of a typical recirculating filter system. The component parts are
the recirculation tank with its pumps, the sand filter followed by a splitter basin, and a dosing
tank. The recirculation tank (Figure 2) receives effluent from the septic tanks in the collection
system. Effluent is pumped from the recirculation tank to the filter, where it is applied to the
surface by means of PVC pipes with small, closely spaced orifices. Having passed through the
filter media, the effluent drains into a splitter basin (or Mickey Mouse ball valve) which returns
about 80 percent of the flow to the recirculation tank and diverts the other 20 percent to the
dosing chamber for final discharge. The electrical controls to operate the pumps will fit easily
into an enclosure (it should be NEMA 4X) the size of a suitcase; therefore, the extra expense of
a building to house the controls is unnecessary.
The volume of the recirculation tank needs to equal about one half the maximum
expected daily flow. The filter is sized to have at least one square foot of surface area for each
10 gal of incoming wastewater expected daily. Figure 3 is the side view of a filter.
Operation and maintenance of recirculating sand filters is inexpensive and easy. For
example, an average 50,000 gal/day recirculating sand filter should require fewer than two
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manhours per week. If disinfection is not required, the only other operating cost is powering
and maintaining the recirculation pumps. They should be small—typically 1/2 HP—so their
maintenance is relatively simple. Since all parts of the system are aerobic, odor is not a
problem.
The total cost of construction of a recirculating sand filter treatment and disposal system
ranges from $2 to $5 per treated gallon. Variables affecting cost are:
• Experience and skill of the designer
• Degree of cooperation from regulatory agencies
• Availability of site that is compatible with neighbors
• Topography and soil type
• Cost of sand and gravel
• Types of final disposal, e.g., drainfield, lagoon followed by irrigation, or
disinfection and discharge to river or bay
• Intervention by environmental activists
Of these variables, the most critical is the experience and skill of the designer. Since a
comprehensive design manual is not currently available and since the state of the art is changing
rapidly, anyone contemplating the construction of a recirculating sand filter is well advised to
get an experienced designer involved in the project.
University research as well as OSI's ongoing R&D program are already yielding
promising results. Optimum media sizes and dosing techniques are being determined and
specially designed equipment is being developed to bring down capital construction costs and
make the operation and maintenance of recirculating sand filters even easier than they are now.
-15-
-------
THE TENNESSEE EXPERIENCE WITH THE RECIRCULATING
SAND FILTER WASTEWATER TREATMENT SYSTEM
FOR SMALL FLOWS
Steve Fishel
Division of Water Pollution Control
Nashville, Tennessee
In 1987 the Tennessee Division of Water Pollution Control wrote a small flows design
criteria chapter that basically required the construction of recirculating sand filters (RSF) as a
primary alternative to package activated-sludge wastewater treatment facilities. At the advice of
our staff of lawyers, this initiative was also written into our rules, prohibiting the construction of
activated sludge plants for flows below 30,000 gpd.
We feel the benefits of the RSF alternative in performance, operability, reliability, and
low O&M cost are irrefutable. The recent interest in the RSF alternative has confirmed our
action. We feel one of our roles as a regulatory agency is to show leadership in promoting
these benefits.
Historical Small Flow (Package Plant) Problem. There are 350 small (less than 75,000 qpd)
domestic treatment plants in Tennessee, as compared to 250 municipal plants. These make up
about 1 percent of the state's total treated sewage discharge. Because of the high number of
operational complaints, and both the potential environmental and health related impacts of
these discharges located in populated or high-use areas, our field offices are driven to spend a
disproportionate amount of time at these facilities. The nature of these complaints involves real
or potential health problems from fecal coliform flushed over the discharge weir as a result of
bad operations.
The average small domestic wastewater plant in Tennessee is about 22,000 gpd. Most
were built in the 1970s. Package activated-sludge plants were utilized at the vast majority of
sites. Intermittent sand filters and lagoons were built in about 20 percent of the sites.
-16-
-------
There were many compliance problems with package plants that were hard to correct.
In 1986 we conducted a special O&M survey on our package plants that concluded that there
was 50 percent noncompliance. Several other states confirmed similar bad performance.
Advocates for package plants argued that the lack of compliance at plants was due to lack of
enforcement and operator training. Limited state resources have prevented adequate
enforcement and, to some degree, will always limit enforcement of these serious compliance
problems.
A clear conclusion of the compliance problems of package activated-sludge plants was
made only after similar experiences of visiting larger plants and making technical assistance
diagnoses of municipal plant problems. The small municipal systems demonstrate a similar
array of O&M problems.
In 1986 we also performed an economic analysis of the small package activated-sludge
plant versus the RSF. The attached graph (Figure 4) from this analysis shows that the package
plant has a hidden high O&M cost compared to the RSF. It also shows that the RSF's overall
cost was much cheaper than that of the package plants! Because of the irrefutable compliance
problems of the package plants, their adverse economics, and the limited enforcement resources,
a decision was made to force the consideration of a more operable alternative which also had
lower O&M cost—the recirculating sand filter.
Evolution of the Recirculating Sand Filter. In 1980, our state agency received a visit
from Mike Hines of the Illinois Health Department, who originally helped invent the RSF
concept. The RSF was presented as an optimized alteration of the intermittent sand filter
which demonstrated better economics and performance. Mr. Hines was an advocate of
reliability, operability, and economic design for small flows.
In early 1983, the consultant for Whitwell Hospital expressed an interest in a package
plant alternative for their proposed wastewater discharge. Their discharge would be going into
a high-use river adjacent to commercial canoeing. We suggested the RSF because an
intermittent sand filter alternative was too large for the site. We visited with Murl Teske in
Illinois to verify the capabilities of the RSF. The Illinois compliance data looked exemplary.
-17-
-------
30
ao-
10
CAP11AU
I 00 20OOO
GOOOO
Figure 4.
Small Package Activated-Sludge Plant versus
RSF—Economic Analysis
-18-
-------
The next year the Whitwell Hospital RSF was completed with the help of Mr. Hines and
Mr. Teske. It was also one of the first RSFs utilizing an efficient North Carolina-style above-
ground, low pressure pipe distribution system. While it was an exemplary design, it was also
economically built at $6/design gallon.
The subsequent performance of Whitwell Hospital has been spectacular (see Figure 5).
During close monitoring by a reputable operator, our agency, and many visitors, the discharge
has been described by most as "looking like drinking water!" Nevertheless, despite the high
compliance, performance, reliability, and relatively low cost, there were few advocates of this
alternative in Tennessee (outside of our agency and one consulting firm). This all changed with
our implementation of Tennessee's package plant alternative regulations. The attached
inventory of facilities (Figure 6) illustrates the recent trend toward RSF construction. At this
time, the RSF is the leading small flow alternative in Tennessee.
Other Agency Actions to Improve Package Plant Alternative Designs. In addition to the
aforementioned items of economic analysis, small flow design criteria, and design rules, the
following actions were taken:
Our design criteria procedures were changed to emphasize the engineering report
and design selection. The alternative selection was to be discussed earlier in the
process. This was intended to prevent the premature submittal of undesirable
alternatives as final plans.
A new Monthly Operating Report (MOR) was designed, which closed many
loopholes in reporting. This MOR requests the use of a sludge judge (a clear
plastic sludge core sampler) at package plants as well as sludge disposal
documentation.
Our Division has recently encouraged the use of Oregon's RSF design concepts.
Contact has mainly been via the Oregon RSF Design Criteria and Orenco
Systems, Inc. The interest in Oregon designs is driven by their ability to meet
ammonia standards and their use of a larger, more available gravel, as well as by
their demonstrated overall performance and economy.
The operator certification rules were changed so that sand filter operators are
now designated Biological Natural System operators rather than being grouped
-19-
-------
WHITWELL HOSPITAL RECIRCULATING SAND FILTER
1984
JAN 84
FEE 84
MAR 84
APR 84
MAY 84
JUNE 84
JULY 84
AUG 84
SEPT 84
OCT 84
NOV 84
DEC 84
1985
JAN 85
FEE 85
MAR 85
APR 85
MAY 85
JUNE 85
JULY 85
AUG 85
SEPT 85
OCT 85
NOV 85
DEC 85
1988
JAN 88
FEE 88
MAR 88
APR 88
MAY 88
JUNE 88
EFFLUENT
FLOW
gpm
2.9
4.3
4.2
3.1
4.2
3.7
3.3
3.8
5.9
4.3
3.9
3.7
3.6
3.6
4.4
3.7
3.2
2.8
3.3
11.4
5.6
4.7
4.9
5.1
7.5
BOD
mg/1
7.5
5.5
4.0
2.4
1.0
3.5
1.8
3.6
6.9
4.2
4.8
8.5
23.1
14.1
14.8
12.3
17.0
9.8
4.8
0.7
0.4
0.2
2.0
_
2.7
3.0
3.8
2.7
2.4
3.4
SUSP.
SOLIDS
mg/1
-
1.2
4.1
3.6
8.5
7.2
4.6
3.4
7.3
7.3
5.5
10.9
3.7
9.2
6.0
3.3
4.8
5.4
2.1
2.0
1.9
3.2
—
11.6
7.5
3.3
6.3
4.5
5.2
1986
JAN 86
FEB 86
MAR 86
APR 86
MAY 86
JUNE 86
JULY 86
AUG 86
SEPT 86
OCT 86
NOV 86
DEC 86
1987
JAN 87
FEB 87
MAR 87
APR 87
MAY 87
JUNE 87
JULY 87
AUG 87
SEPT 87
OCT 87
NOV 87
DEC 87
1988
JULY 88
AUG 88
SEPT 88
OCT 88
NOV 88
DEC 88
EFFLUENT
FLOW
gpm
3.0
7.0
3.9
3.6
3.4
3.0
3.6
3.6
4.9
5.8
6.8
10.2
6.1
11.3
8.3
5.8
2.5
3.1
3.4
3.4
4.1
4.1
4.9
5.0
10.1
9.2
12.4
7.7
10.8
10.9
BOD
mg/1
4.0
4.0
5.O
5.0
3.0
1.0
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
1.0
2.5
4.1
3.8
3.4
1.7
4.3
3.4
2.2
3.2
2.6
2.4
3.5
4.3
SUSP.
SOLIDS
mg/1
4.0
3.0
7.0
5.0
6.0
5.0
1.0
2.0
2.0
1.0
2.0
2.0
4.0
4.0
4.0
6.O
5.0
6.7
7.8
5.5
5.5
3.8
9.6
7.8
6.2
3.0
3.3
5.8
5.0
2.7
Most samples average from twice/month grabs. The flow data was
totalized average measured continuously at effluent pump station.
monthly
Jan. '85 - May '85 upset due to operational problems that were resolved. At
that time the grease trap was finalized, the septic tank disposed of in May
and recycle correctly adjusted.
Figure 5.
Whitwell Hospital Recirculating Sand Filter
-20-
-------
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-21-
-------
with package plant operators. This benefits operators who do not have to learn
all the activated sludge concepts.
A program to track gravel and sand sources has been implemented. We hope to
promote the use of cheaper sand such as sized bottom ash from area steam
plants.
The Division has continued to improve its information on RSF and Natural
Systems design even with minimal personnel and budget commitments. This has
been possible due to contributions of information from those Oregon and Illinois
sources already mentioned, as well as the Small Flows Clearinghouse in West
Virginia, EPA-Cincinnati, and others.
Conclusions. Small flows designs require special consideration compared to large flow
alternatives. They have different economic factors and operational considerations. A
comparison of reliability, operability, performance level, and overall economy between the RSF
and package activated-sludge has encouraged Tennessee to promote RSF and other natural
systems.
The Tennessee Division of Water Pollution Control's advocacy of natural systems by way
of Division Rules and staff education has stimulated a change to a healthy diversity of
alternatives such as RSF, constructed wetlands, lagoons, and spray irrigation. These alternatives
are cheaper overall and are performing better and more reliably than the mechanical plants they
are replacing.
-22-
-------
RECIRCULATING GRAVEL FILTERS IN OREGON
Jim Van Domelen
Oregon Department of Environmental Quality
Portland, Oregon
Introduction. This presentation focuses on presenting the results of studies of the performance of
recirculating gravel filters (RGFs) from four plants operating in Oregon. Figure 7 is a schematic
of an RGF, and Figure 8 shows a cross section of an RGF. There are many variables to consider
in the design and operation of RGFs:
• Media size and gradation
• Media depth
• Recirculation ratio
• Dosing method
• Loading rate: hydraulic and organic
• Expected final effluent
There is some research that is still needed to optimize design parameters versus performance. Each
of these variables must be considered to determine limits, safety factors, and the performance
results with a change in any one or all of the variables.
Monitoring Requirements. There are variable monitoring requirements in permits that are issued
in Oregon. Some requirements include:
• System flow
• Influent BOD5, at least quarterly during the first year
• Effluent nitrogen, NH3-N and NO3 (maybe TKN)
• Effluent BOD5 and TSS
-23-
-------
Final 4__
effluent
(optional)
Fin-il /
effluent
Recirc-
dilution
tank
Splitter Device (optional)
Septic tank /
effluent / Gravel Filter
@_
\
1%
20% ~~( 1
rjn
• 1
1 1
80% , |
float
valve
\
^ Underdrain System
Pump(s)
Dose line
Figure 7.
Schematic of a Recirculating Gravel Filter
-24-
-------
Pressure dosing line
1/2" - 3/4" Gravel
3 - 5 mm fine gravel
o o
o o
'1/2"-3/4" gravel
_Q
Underdrain
Figure 8. Cross-Section of an RGF
-25-
-------
Design Criteria. Design criteria that should be considered include hydraulic loading (5 gallons per
square foot), organics (150 mg/L, septic tank effluent), and depth of fine gravel (3 feet). Here is
an example of a design criteria taken from Oregon's requirements:
• The gravel filter treatment media shall pass a 3/8-in. sieve. Less than 1 percent shall
pass a No. 10 sieve. The effective size shall be between 3 and 5 millimeters. The
uniformity coefficient shall be equal to or less than two (2). The material shall be
a very well washed river gravel. This gravel filter treatment media must have DEQ
concurrence prior to shipment to the site. The engineer shall provide us a 5 pound
sample together with a gradation analysis and a particle distribution curve plotted
from this data on semi-log paper. Sieves to be included in this analysis shall be 3/8
in., 1/4 in., and Nos. 4, 6, 8,10, 50, and 100. There must be a quality assurance plan
during construction for this material.
Other design criteria to consider include the recirculation ratio, the doses per day, the orifice
pattern for dosing piping, the minimal burying of dosing piping, and the recirculation tank volume
in gallons relative to the gpd design flow.
Operation and Maintenance. Operation and maintenance of recirculating gravel filters is an
important part of achieving high performance levels. Some particular methods that have been
successful include:
• Keep all equipment operating as originally installed
• Remove vegetation on filter three times per year
• Flush dosing piping and orifices two times per year
• Pump the dregs (sludge) from the recirculation tank each second year
Examples from Oregon. Table 1 presents the numbers and kinds of systems in Oregon. Table 2
presents the performance experience from four plants that are currently operating in Oregon.
Conclusion. There are many common pitfalls and traps that can be avoided by attention to the
details of systematic operation and maintenance of the recirculating filters. The following list
presents common traps that, if avoided, will keep the recirculating filters operating at a consistently
high level of performance:
-26-
-------
Table 1. Recirculating Gravel Filters in Oregon—May 1991
Oregon Coast:
Tillamook County
Hebo Service District of Tillamook County - 1986
21,800 gpd / 4356 sq ft
Community / discharge to creek
Oregon Dept. of Corrections, South Fork Work Camp
12,500 gpd / 2500 sq ft
Forest Camp for Honor Inmates / on-site
Wi-Ne-Ma Church Camp - 1987
14,365 gpd / 2873 sq ft
Group retreat and summer camp / seepage beds
Lincoln
Oregon Parks, Beachside State Park - 1981
4500 gpd / 900 sq ft
Campground / irrigation
Whaler's Rest at Lost Creek (South of Newport) - 1984
9000 gpd / 2800 sq ft
Traveler and tourist (RV Park) / on-site
Benton County
Alsea County Service District of Benton County - 1986
30,000 gpd / 6340 sq ft
community / on-site
Coos County
Hauser Trailer Village - 1987
6800 gpd / 1296 sq ft
Mobile home park / on-site
Hilltop Restaurant (Doug Fennell) - 1985
1100 gpd / 975 sq ft (600 mg/1)
Restaurant / on-site
-27-
-------
Table 1. (cont)
Curry County
Roque Landing (Virginia Himar) - 1986
5250 gpd / 1846 sq ft
Rest., lounge, Motel, Apts., RV spaces / seepage pit
Sandpiper Subdivision - 1985
12,000 gpd / 2500 sq ft
43 lot subdivision / on-site
Whaleshead Beach Campground (Robert L. McNeely) - 1987
8,000 gpd / 1800 sq ft
Traveler and tourist (RV Park) / irrigation
Willamette Valley
Clackamas County
Athney Creek Middle School of West Linn School Dist. # 3 - 1991
6500 gpd / 1600 sq ft
elem school / on-site
Scouter Mtn, Boy Scouts (SE 147 th & Sunnyside Rd.) - 1991
9000 gpd / 1800 sq ft
Restrooms, showers, dining facility / on-site
Damascus Dairy Queen (Jim McDonald) - 1985
1600 gpd / 726 sq ft (450 mg/1)
fast food / on-site
Fischer's Forest Park (Clackamas Sunty Service District) - 1984
10,400 gpd / 3000 sq ft
26 lot rural subdivision / on-site
Forest Park Mobile Home Park (Jim Lawrence) - 1983
5000 gpd AIRR system
Rental spaces for mobile homes / discharge to Willamette River
Orchard Crest Care Center (near Sandy) - 1989
3725 gpd / 1225 sq ft
Nursing Home / on-site
Riverside RV Resort and Spa (David A. Van Doozer) - 1987
4870 gpd / 1078 (102 Spaces)
Traveler and tourist / on-site
Salvation Army, Camp Kuratli at Trestle Glen (Barton) - 1984
8575 gpd / 2450 sq ft
Church camp / on-site
-28-
-------
Table 1. (cent)
Lane County
Dexter Sanitary District - 1983
62,000 gpd / 12,483 sq ft
Community / on-site
Emporium, Eugene - 1988
12,200 gpd / 3025 sq ft
Warehouse and Office / on-site
Mapleton Commercial Area Owner Association - 1989
24,000 gpd / 4900 Sq Ft
Business Core of Community / Discharge to Siuslaw River
Oregon Dept. of Transportation, Oak Grove SRA - 1990
(North of Springfield)
20,000 gpd / 4032 sq ft
Traveler and tourist / on-site
Linn County
City of Mill City - 1991-92
92,500 gpd / 36,864 sq ft
Community / on-site
Polk County
City of Falls City - '1985
38,720 gpd / 7744 sq ft
Community / on-site
Yamhill County
Cove Orchard Service District of Yamhill County - 1986
11,300 gpd / 2280 sq ft
Community / on-site
Ewing Young Elementary School - 1980
3750 gpd
on-site
Mulkey RV Park (Wally A. Brosamle, Jr.) - 1990
6300 gpd / 1680 sq ft
Traveler and tourist / on-site
-29-
-------
Table 1. (cont)
f?ni Ti-mhja River
Clatsop County
Logger Restaurant (Richard J. Oja) - 1987
2000 gpd / 1200 sq ft (600 mg/1)
Restaurant / on-site
Riverwood Mobile Home Park (Magar E. Magar) - 1983
13,000 gpd / 4333 sq ft
Rental spaces for mobile homes / discharge to Columbia River
Westport Service District of Clatsop County - 1987
50,000 gpd / 10,000 sq ft
Community / discharge to Columbia river
Eastern and Central Oregon
Deschutes County
Redmond School District, Terrebonne School - 1989
6750 gpd / 1408 sq ft
Elem School (450 students) / on/site
Shaniko Restaurant & Hotel (Jean Farrell) - 1988
4000 gpd / 1575 sq ft
Traveler and tourist / on-site
Southern Oregon
Douglas County
City of Elkton - 1990
28,600 gpd / 6400 sq ft
Community / on-site
Oregon Dept. of Transportation, South Umpqua SRA - 1988
(North of Myrtle Creek)
2089 gpd / 520 sq ft
Traveler and Tourist / on-site
-30-
-------
Table 2. Performance Data from Four Oregon RGFs
Dexter - 0.062 mgd (design)
Date
Tno~rtf*^VE
01-25-90
02-19-90
03-12-90
04-27-90
05-16-90
06-28-90
07-30-90
08-16-90
09-21-90
10-29-90
11-28-90
12-12-90
01-18-91
02-20-91
03-07-91
BEjd
ave. mo.
.058
.052
.034
.030
.040
.039
.036
.037
.040
.041
.060
.074
.055
.056
.066
BOD
in/oat
10
5
5
11
13
12
10
9
5
5
7
5
16
7
5
Falls City
Date
mo— da— vr
03-15-90
04-11-90
05-17-90
06-14-90
07-12-90
08-14-90
09-11-90
10-18-90
11-13-90
12-11-90
01-16-91
02-14-91
03-14-91
ngd
ave. no.
.17 to
.22 mgd
BOD
in/out
165/2
183/18
164/8
108/3
76/5
155/32
80/13
48/36
95/20
36/8
40/4
135/2
195/5
TSS
in/out
-ill off
3
1
4
19
34
37
11
4
15
10
17
11
17
4
7
- 0.039 ngd
TSS
in/out
36/18
60/8
52/14
36/7
3/3
134/18
44/10
31/25
80/13
34/13
5/10
32/3
51/5
NH3-N
in/out
Luent only
9.5
5.4
4.6
5.6
4.5
6.8
6.4
3
2.9
10
7.3
9.2
5.6
1.8
.7
(design)
NH3^f
in/out
19/5
26/5
8/9
16/5
36/7
27/20
28/22
21/23
29/13
2807/6
17/3
46/2
24/2
ND3-N
in/out
H -,•(—.
16
12
3.9
24
24
25
26
27
17
14
15
6.6
18.4
16.9
15.9
N03-N
in/out
1/16
1/22
1/11
1/29
1/30
1/4
1/5
1/12
1/10
1/12
1/12
3/16
1/16
TKN
iij/out
12
6.6
6.8
6.7
7.1
7.0
6.8
3.1
3.8
12
10
10.7
8
2.55
1.3
TKN
in/out
22/17
37/7
20/12
21/7
42/9
27/21
33/23
25/25
35/15
31/6
21/5
51/2
26/3
-31-
-------
Table 2. (cont)
Westport - 0.050 mgd (design)
Date mgd
mo-da— yr ave. mo.
01-02-90
02-05-90
03-05-90
04-02-90
05-01-90
06-04-90
07-02-90
09-05-90
10-01-90
11-01-90
12-10-90
01-02-91
03-01-91
****>!*!** * fc****.fc.fc*-H
BOO
in/aat
100/5
170/5
225/3
230/2
235/5
145/18
135/6
45/3
80/3
30/2
20/8
85/2
120/2
i * *•* *•* * * **
TSS
in/aat
24/5
25/4
37/5
36/6
22/7
42/9
20/11
22/10
68/4
68/6
13/6
16/3
48/5
'* it 1*1* !*!»***
NH3-N
in/out
43/9
23/-
5V"
-/10.6
35/-
18/11.28
44/1
39.3/5.7
38/6.9
5/0.15
35/8.4
36/9
35/-
*.*.*** **.* * * *
ND3-N
in/out
-/16
V-
^ /^
/
-/4.5
V-
-/17.75
-/4
-/10.3
-/4.3
-/12.8
-/3.8
-/5.3
-/-
!***.» ****-
•ON
in/out
fc**.fci>.fci*
Hebo - 0.022 mgd (design)
Date mgd
mp-da-yr awe, mo.
03-06-90
03-21-90
04-04-90
04-19-90
05-02-90
05-17-90
06-06-90
06-25-90
07-10-90
08-09-90
08-21-90
09-11-90
09-25-90
10-17-90
10-31-90
11-14-90
11-29-90
12-27-90
01-02-91
01-15-91
02-05-91
02-19-91
03-06-91
03-20-91
BOD
in/out
TSS
in/out
NH3-N
in/cut
012 to 330/8
017 mgd 228/15
130/3
174/17
156/14
162/4
384/6
291/38
273/11
-/-
130/4
85/26
60/5
94/8
276/3
102/3
99/3
22/1
141/10
65/1
384/11
117/10
204/48
150/9
23/11
46/4
24/1
58/8
60/11
42/4
260/6
28/5
70/5
56/3
40/20
45/3
49/2
50/1
205/1
52/1
41/1
8/1
24/8
20/2
100/5
10/4
12/6
41/4
ND3-N
in/out
TKN
in/aat
-32-
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Ignoring the collection system and disposal system when designing the treatment
system
Incomplete explanations of RGF design criteria to designers and engineers and
owners
Not collecting influent data before design
Underestimating BOD5
Not collecting effluent (monitoring) data after years of operation
Excessive flow to the system, collection system defects
Failing to install the standard media
Placing any filter fabric within the media: Don't do it!
No operation and maintenance (O&M) manual
No operator
Failing to remove weeds and plant growth
Failing to keep dosing piping free of debris
Irretrievably (excessively) burying of dosing piping so flushing orifices is not practical
Tinkering with pumps and controls like timers, splitter boxes, alarms, floats, etc.
-33-
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OPERATIONS AND MAINTENANCE
-------
ASSESSMENT OF O&M REQUIREMENTS FOR UV DISINFECTION
O. Karl Scheible
HydroQual, Inc.
Mahwah, New Jersey
Ultraviolet (UV) disinfection systems are being widely considered for application to
treated wastewaters, for both new plants and retrofitting existing plants in lieu of conventional
chlorination facilities. The technology is relatively new, with most plants installed over the past
three to four years. It has generally been successful, although there had been many
problems with the systems installed in the early to mid-1980s. Subsequent "second generation"
designs have resolved many of the earlier issues, resulting in a higher degree of reliability and a
more rapid acceptance of the technology. These use modular, open-channel configurations in
place of the fixed, closed shell arrangements typical of the earlier designs.
An assessment of the UV process has been made, focusing on the newer designs that
utilize open-channel, modular configurations. It is a part of the Office of Wastewater
Enforcement and Compliance Control's (OWEC) program to provide technical assistance to
local governments in the area of municipal wastewater treatment by evaluating specific
technologies and reporting on their capabilities and limitations. Information was compiled from
the EPA, Regional, and state offices, literature, equipment manufacturers, and wastewater
treatment plant personnel. The report presents an assessment of the status of the technology
relative to the type and size of UV facilities that are currently operating, and discusses the
trends in system design, configuration, and operations. The design and operation of selected
plants are then reviewed; this information and current practices are then summarized to give a
perspective of key considerations that should be incorporated into the design of UV facilities.
This presentation addresses the portion of this study that focused on an evaluation of several
plants.
A total of 30 plants utilizing UV disinfection were selected for a detailed assessment of
their UV process design, operation, and maintenance. Only those with open-channel
configurations were chosen, in keeping with the focus of this evaluation. A random selection
was made, constrained by the desire to have plants of varying size, alternate system designs, and
-34-
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representation by several manufacturers. The information was compiled through the summer of
1990 on the basis of supplier data and direct contact with the plant owner, operator,
and/or engineer. The 30 plants are identified in Table 3.
Overall, of the 30 plants selected for evaluation, all are designed to treat to nitrification
levels at minimum, and several have tertiary filtration. These conditions suggest that, in general,
the facilities using UV have advanced secondary or tertiary processes, yielding effluents that are
especially conducive to the application of UV. Eight of the plants use the vertical lamp
configuration, somewhat higher in proportion to the horizontal configuration than is apparent in
the overall census. Eight of the 30 are facilities that have retrofitted their UV systems into
existing chlorine contact chambers, a procedure that is becoming popular, particularly as plants
are being upgraded and with larger facilities. Generally, the plants vary in their capacity relative
to design. About a third each are at approximately 25 percent, 50 percent, or 100 percent of
their design capacity.
Description of the UV Systems at the Selected Plants. The selected plants show a certain
consistency in their configurations. One to three channels are used, with a single channel in the
smaller plants and the multiple channels found with the larger plants. Most of the larger
systems have some flexibility in operating banks of lamps within the channel, although this is not
always the case. Redundancy to any degree is not typical; only 5 of the 30 plants have
redundant systems, and 4 of these are with the smaller plants. Flexibility appears to be limited,
with little ability to isolate a portion of the system for repair or replacement. Bypasses
were not evident with most plants, suggesting a difficulty with repairing/shutting down channels
when only one channel exists.
Sizing of the units appears to be relatively consistent, falling between 0.5 and 1.7
mgd/kW, with an average essentially equivalent to 1.0 mgd/kW. This is demonstrated in Figure
9, which presents the peak design flow of the plant as a function of the total UV power (kW at
253.7 nm) of the UV system. There is some scatter, but the slope of the relationship closely
approximates 1.0. Thus, a rough sizing estimate can be made for a given plant by assuming 1
kW of UV output for each mgd of peak design flow. This would be for advanced secondary
plants at minimum and peak to average flow ratios less than 2.5. The 1.0 kW is the nominal
UV output, equivalent to approximately 37 long lamps (1.47 m or 58 in. arc length) or 74 short
-35-
-------
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-36-
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(
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0.2 04 06 1.0 2-0 40 &0 KXO 20 90 44
RATED PEAK DESIGN FLOW (mgd)
Figure 9.
UV System Sizing for Selected Plants as a
Function of Peak Design Flow
-37-
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lamps (0.75 m or 30 in. arc length). Such an approximation should only be used in screening
type assessments and should not serve as a final design sizing parameter. Note also
that redundancy or standby capabilities would be added to this estimate.
Design Sizing and Performance Summary for the Selected Plants. Table 3 is presented as a
summary of the design sizing and performance record for each of the selected plants. Each of
the plants is generating a quality effluent and is in compliance with its permit. Those that are
accomplishing a high degree of nitrification are also discharging minimal levels of coliform. In
cases where the BOD and TSS levels tend to be at levels greater than 10 mg/L, the effluent
coliform levels also tend to be more pronounced, with measurable densities between 10 and 200
FC/100 mL.
UV disinfection efficiency is very dependent upon the quality of the effluent generated
by the upstream processes. As higher levels of treatment are accomplished, the UV process is
more efficient, resulting in the need for less hardware, or providing for a greater factor of
safety. Thus nitrification, denitrification, filtration and other tertiary processes that are added
to conventional secondary treatment operations are particularly conducive to assuring the
success of the UV process. The impact on water quality is generally represented by lower
coliform densities, increased sensitivity of the bacteria to UV, and increased UV transmissibility
at 253.7 nm by the wastewater. An interesting observation made from this assessment was
the lack of data regarding the incoming coliform densities and the transmissibility of the
effluent. The plants did not measure these parameters, even in cases where there may have
been difficulties and the data could be used for troubleshooting.
Summary of O & M Practices at Selected Plants. The replacement cycle could be estimated
fairly well for the lamps. It is based on the operators criteria for replacement and accounts for
seasonal/year-round use of the system, and the probable system utilization rate. Thus if the
system is operated on the basis of flow, the utilization would be approximately 50 percent; this
would increase up to 75 to 100 percent if the system was operated manually and was basically
kept in full operation as a matter of convenience or to assure compliance.
The criterion for failure is generally lamp failure and or increasing coliform densities
(except at those plants with fixed operating cycles, as discussed earlier). Generally, it appears
-38-
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that the latter condition would be the final trigger. The high operating life cycles that are being
obtained suggest that the lamps will not fail (i.e., electrode failure, shutoff); rather, their output
will deteriorate to such a degree that there is insufficient germicidal energy for effective
disinfection. The lamps are replaced at this point to restore the system efficiency. For design
purposes, a reasonable estimate of operating life would be 14,000 hours; thus the replacement
rate in a system with year-round disinfection, and an average 50 percent utilization,
would be approximately 30 percent per year:
((8,760 hours/year)/(14,000 hours/lamp)) x 50 percent = 31.2 percent
With the smaller systems, and to a lesser extent the larger plants, it appears that the
tendency is to operate the full system (75 to 100 percent utilization) at all times instead of
controlling it on the basis of flow. This would increase the replacement rate for the above
example to 50 to 60 percent per year. If disinfection is required on a seasonal basis the
replacement rate is reduced to 25 to 30 percent per year.
Regarding the quartz sleeves and the ballasts, it is not possible to make a direct
assessment of their expected life cycle. The experience with full scale systems, particularly with
respect to the open channel submerged units, is limited, covering a period of approximately five
years. This is not sufficient to evaluate in-field experience for long-term replacement rates of
the quartz and ballasts. Many of the replacements currently reported by operators have been
due to breakage and electrical wiring failures, reasons that do not speak to the degradation or
failure of the components themselves.
The quartz will degrade due to solarization of the quartz structure, resulting in a
cloudiness of the quartz and a loss of transmissibility. Abrasion of the surface due to long-term
exposure to the wastewater is also a contributing factor to their deterioration. There is no
current feedback of replacement of the quartz for these reasons. At this point, an estimate that
may be appropriate is a replacement rate of 10 years, to account for minimal breakage and for
deterioration of the quartz.
Similarly, there is little experience with ballast failures and replacement rates. Earlier
failures have been attributed to improper electrical design and the lack of proper ventilation in
-39-
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the ballast cabinets. These difficulties appear to have been corrected, although there are still
reports of electrical problems with a few installations upon startup. For purposes of life cycle
assessments with UV disinfection systems a 10-year replacement period is suggested.
The effort required for replacement of these key components (largely the lamps
themselves) is relatively low. This is also shown in Figure 10, which presents the hours spent
per year against the number of lamps that would replaced per lamp. The mean is 0.4 hours per
lamp, or 24 minutes per year. There is significant variability, with the rate ranging from
approximately 10 minutes to 50 minutes per lamp. Note that this is total labor, even if two
people are engaged in the activity (which tends to be typical).
This analysis can be used in screening the labor and parts replacement costs for UV
systems. One should be careful to acknowledge how the system will likely be operated in terms
of utilization; recall that the tendency is to have much of the system on at a given time,
regardless of the flow. Also account for the year-round versus seasonal disinfection
requirements. Note also that these charges could be incurred in discrete intervals, rather than
be spread out somewhat evenly over a period of time. This results from the likelihood
that the operators will change out the lamps in total, triggered by the overall operating time and
a decrease in disinfection efficiency, as discussed earlier.
A second labor factor is the time required, on a yearly basis, for activities other than
replacement of the lamps/quartz/ballasts and cleaning. These would include system monitoring
and sampling, area maintenance, component repair/replacement, etc. This tends to be a factor
of two to six times the amount of time estimated for the replacement of key components.
When added to the parts replacement activities, the total time required outside of routine
cleaning needs (discussed later) is estimated. These data are plotted on Figure 11, which
presents the total hours per year as a function of the system size. There is some scatter,
particularly with the smaller plants. For the 14 plants with less than 150 lamps, the mean labor
requirement was 120 hours per 100 lamps. The equivalent mean for plants with more than 150
lamps was 55 hours/100 lamps.
Upstream devices such as screens are used to protect the lamp battery from debris that
may reach the UV system and cause damage to the quartz/lamp assemblies. Other problems
-40-
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8
ffi
rf
te
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a ^
CO
160
140
120
100
80
<0
C. 60
UJ
u
a
a
tu
40
20
Lamps/Quartz/Ballast
Mean 0.4 hrs/lamp/year
SO 100 ISO 800 250 300
REPLACEMENT RATE (LAMPS/YEAR)
950
400 450
Figure 10.
Labor Requirements for Replacement of
Lamps/Ballasts/Quartz
-41-
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^
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fc
£
4000
2000
1000
600
400
200
too
40
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T/
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-
)tal O&M (w/o Cleaning)
50 120 hrs/100 lamp/yr
150 55 hrs/100 lamp/yr
•«• 4
4
^ ^
20 40 60 KX) 200 400 600 1000 2000 4000 6000
NO. OF LAMPS M W SYSTEM
Figure 11.
Estimate of O&M Labor
-42-
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occur from algae sloughing off the clarifiers and leaves falling into the channels; these catch on
the lamp modules and accumulate, creating additional head loss problems and maintenance
tasks.
Overall it appears that the installation of an upstream screening device is an option that
most plants do not choose. From this assessment, however, it also appears that it is most
appropriate to have one in place. These can be simple, large-mesh (0.5-in.) screens (stainless
steel), that can be slipped in and out of the channel manually for cleaning on a frequent basis.
This will save considerable labor if the alternative is to clean the debris attached to the
individual modules. An alternative device that may be more convenient to the operator would
be a bar screen that can be raked (a moving mesh or bar screen that is self-cleaning would not
be cost-effective); this would still have to be removed periodically for a thorough cleaning. Note
that it is important to remember that these devices, particularly as they accumulate material, will
impose a headless; this must be accounted for when considering the hydraulic design of the
facility.
A critical operating requirement is that the water level in the channel must be kept fairly
constant. If it fluctuates widely (greater than plus or minus one inch from the control level),
several problems can occur. In horizontal systems the top row of lamps can either be exposed
or the depth of water above this row can become so great that disinfecting effectiveness of the
unit is compromised. In vertical units this same problem occurs, except that
the top portion of each lamp is affected.
Most plants use a mechanical level control gate to maintain the desired level. These rely
on field setting and adjustment of the counter- weights to assure the proper level control over a
range of flow rates. They have generally been very successful and comprise the dominant
method for level control in open-channel systems. Problems are noted, however, at low flows
and at plants that have no flow at times. The gates will oscillate and cause wide fluctuations in
level. They are not designed to be watertight and will allow the channel to drain during periods
of very low or no flow.
The method of level control should be carefully considered in the design of a facility.
The mechanical gates would be the preferred device in most cases, particularly larger systems in
-43-
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which multichannels are used and the channel velocities can be maintained within a reasonable
operating range. If there are low flow (or no flow) periods, fixed weirs may be more
appropriate. Sufficient weir length must be provided, however, to avoid excessive level
fluctuation. This can be accomplished by using serpentine weirs and weir launders. An
alternative is to use a motorized adjustable weir slaved to a level sensor.
System control has generally been kept simple with the newer open channel UV units.
This has been limited to pacing the operation of multiple channels and banks to the flow rate.
The manner in which the UV system is controlled should be a function of the type and size of
plant. Above all, it should be kept simple; the objective is to conserve the operating life of the
lamps (and the associated power utilization). This becomes increasingly important with the
larger plants (greater than 150 to 200 lamp systems), and more practical. With the small plants,
it may be best to have the full system in operation, exclusive of the redundant units
incorporated into the design. Manual control and flexibility should be available as the system
increases in size, enabling the operator to bring portions of the system (i.e., channels and banks)
into and out of operation as a function of flow and performance. Automating this activity
becomes advantageous as the system becomes larger, using multiple channels.
Safety is important in the operation of UV systems, centering primarily on protection
from exposure to UV radiation. This affects the eyes with a temporary condition known as
conjunctivitus, or "welder's flash," that can last for several days, causing a painful burning
sensation. Bare skin also will be burned upon exposure to UV at these wavelengths. Exposure
risk is generally minimal, as long as the operating lamps are submerged and the lamp batteries
are shielded. The danger arises if the lamps are operated in air; this should never be necessary
except under extraordinary circumstances. Systems should be equipped with safety interlocks
that shut off operating modules if they are removed from the channel. Electrical hazards are
minimized by the inclusion of ground fault interruption circuitry with each operating module.
This feature is typically standard with current systems and should be a requirement with all
specified systems.
The precautions against exposure to UV radiation are straightforward. UV blocking
glasses, with side shields, should be worn at all times in the general area. One plant reported
that the shields were ineffective and switched to goggles for full protection. Exposure of skin
-44-
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should be minimized, using long sleeved shirts and buttoned necks, as examples. Signs should
also be posted near the equipment and in the general area that warn of the hazard and instruct
the use of glasses, at minimum. Of the selected plants, most all required and actively used eye
protection, generally preferring goggles. One plant imposed stricter rules after an eye injury
had occurred. Signs are also posted in several of the plants. Specific training is not typical,
except that which is given by the equipment manufacturer during startup, and this is not always
the case. At best, safety issues and training relating to the UV system should be incorporated
into the'plant's normal safety program.
Summary of UV Cleaning Practices at Selected Plants. Maintaining the quartz surfaces is a
critical element in the successful operation and performance of the UV process. This is a
simple task, entailing routine cleaning of the quartz sleeves with a standard agent. It is one that
has at times been overlooked, however, resulting in apparent failure of the UV process because
the quartz surfaces have become fouled and have lost their transmissibility. The fouling is most
often due to the deposition of inorganics such as calcium or magnesium carbonates and iron.
Greases or biological films can also adhere to the surface. The key task is to anticipate this and
to have a fixed protocol for maintenance of the quartz surfaces.
The assessment showed considerable variability amongst the plants, making each case
somewhat unique. Essentially all are successful, using methods that are relatively simple, easily
applied, and which fit specifically to the conditions of the facility. This is a marked
improvement from the earlier system configurations using closed shell, fixed in-channel, and
teflon pipe designs. These systems suffered serious problems relating to the ability to keep the
quartz or teflon surfaces clean and the access to the quartz for such maintenance tasks.
Note that the use of dip tanks is gaining favor and is generally supplied with most new
systems, including those using horizontal lamp configurations. These can be in a fixed location
or rolled on wheels to each bank of modules. An example is shown in Figure 12, which is a
sketch of a typical unit used for horizontal lamp modules. Modules are removed individually
from the channel and placed in the recirculating bath. It is then hung on the rack above the
tank to drain, where it can be physically wiped and/or rinsed with clean water. In certain cases,
a cage system is being devised to enable removal of banks of lamps from the channel (via a
moving overhead hoist) and placement in a large dip tank. This is especially useful at larger
-45-
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a
-------
plants. At present this is planned for the Nuese River plant in Raleigh-Durham, North
Carolina, and the LOTT plant in Olympia, Washington.
Cleaning practices are highly variable. The principal points are summarized on Table 4,
addressing the equipment and methods used for cleaning, the cleaning agents, the criteria used
for cleaning, and the resultant frequency and labor use.
The dominant practice is to remove the modules from the channel, with or without
provision of a rack to hang the module. In-place recirculation or dip tanks are more typically
used for the vertical lamp module systems. The standard practice for manually cleaning the
units is to simply apply the cleaner onto the quartz and then rinse the module with clean water.
Citric acid and Lime-Away are typically used as cleaning agents, although several others
are used including detergents and other dilute acids. There is no hard criterion that sets the
type of cleaner; the manufacturer will generally recommend one or more. It becomes a matter
of trial and error specific to the plant site. This is also the case with frequency; as noted, this
varies widely and depends on the specific site requirements.
The criterion for cleaning is typically based on fecal coliform densities. This was the
case for two thirds of the selected plants. The remaining third was split between using the
intensity meter reading, or simply setting a proscribed frequency.
In summary, the following observations are made:
Removal of the modules is appropriate and probably best for most plants. Cages
are suggested for larger plants for removing bundles of lamp modules.
Moving hoists/cranes will facilitate removal of the module bundles or vertical
lamp modules.
Dip tanks provide a convenience and assist in cleaning modules removed from
the channel.
In-place recirculation is effective, particularly for vertical lamp modules.
Agitation should be provided during the recirculation cycle. Plant should still
plan to remove the modules once per year for a rigorous cleaning.
-47-
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Table 4. Summary of Cleaning Practices for the 20 Selected Plants
A. Equipment Used for Cleaning
In-place recirculation
Mechanical wiper
Dip tanks
Remove modules onto a rack
Remove modules
B. Cleaning Agents
Citric acid
Lime-Away
Dilute HCI acid
Detergent
Phosphoric acid
Sulfuric acid
Tile/Bowl cleaner
C. Frequency (cycles)
Weekly (52/year)
Monthly to biweekly (12 to 26/year)
Six weeks to yearly (1 to 9/year)
D. Labor per cycle/per 100 lamps
ItolO
greater than 10
£. Criteria for Cleaning
Fecal coliform
Intensity meter
Routine
NUMBER
OF
PLANTS
4
1
2
5*
19*
9
10
4
3
2
1
1
2
14
14
24
6
20
5
5
COMMENTS
All vertical lamp modules; remove
once/year
One of four "in-place" units
No special equipment to hold the
module
2 dip tanks, 4 in-place, 3 external
modules
Commercial product
Dishwashing detergent; Windex; a
plant also uses Brillo pads
Commercial product
mean, 4.3 hours/cycle/100 lamps
mean, 17.4 hours/cycle/100 lamps
* Method is to rinse, apply cleaning agent, rinse, and return to channel.
-48-
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The cleaning agent(s) that suits the facility is dependent upon the nature of
fouling. A trial and error series of tests should be conducted, using readily
available, off-the-shelf commercial products, frequency of cleaning will be
dependent on the specific site requirements.
Small-scale piloting would be very effective in establishing the cleaning agents
and frequency most suitable to a specific plant.
Monitoring fecal coliforms is a effective tool for determining the need for
cleaning lamps. Note that this is also used for triggering lamp replacement.
Frequency and Labor Requirements for Cleaning. The frequency of cleaning is highly variable,
ranging from once per week to once per year. Table 4 presents the estimated time spent per
year for cleaning the quartz, based on input from the operators. It is not appropriate to simply
include this in the O&M labor requirement summarized in Figure 11. Rather, the time required
per 100 lamps is normalized to the cycles per year.
There is no clear trend in this value relative to plant type or size. The labor
requirement ranges from 0.7 to 26 hours/cycle/100 lamps. Eighty percent (24 of the 30 plants)
are less than or equal to 8.3 hours/cycle/100 lamps, with a mean value of 4.3 hours/cycle/100
lamps. The remaining 6 plants range between 10.4 and 26 hours/cycle 100 lamps, with an
average of 17.4 hours/cycle per 100 lamps. The overall 30 plants is 6.9 hours/cycle/100 lamps.
Overall, a value to 5 to 10 hours/cycle/100 lamps would appear to be appropriate for use
in screening a facility labor requirement for cleaning. Actual yearly requirements will than
depend on the frequency. Of the 30 plants, the median frequency was approximately one per
month or 12 times per year. Using a median estimate of 5 hours/cycle/100 hours and 12 cycles
per year, the yearly requirement would be 60 hours/100 lamps. When compared to the labor
requirements on Figure 11, this is equivalent to one-half that of the larger plants and one-half
that of the smaller plants. Thus, the cleaning activities can comprise one-third to one-half the
total labor requirement of O&M.
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TRICKLING FILTER
OPERATION AND MAINTENANCE ISSUES
Russell J. Martin
U.S. Environmental Protection Agency
Region 5
Chicago, Illinois
Within the Water Division of Region 5 is a team of engineers that maintains one of the
most active and aggressive federal municipal onsite assistance programs in the nation, providing
training, technical support, and consultation services for some of the 4,281 municipal wastewater
treatment facilities in Region 5. Region 5 staff have learned a great deal in the last five years in
this program, including successfully addressing measures that limit the wastewater treatment
plant performance at trickling filter facilities. This paper will discuss our experiences at four of
these facilities.
Fredericktown. Ohio.
Hardware—0.2 MGD rock media trickling filter wastewater treatment facility.
Initial evaluation—The wastewater treatment had difficulty in achieving CBODS limits of
25 mg/L for 6 out of 12 months preceding our assistance. The clarifiers were dark and had
previously been identified as anaerobic by the state agency. One trickling filter was down due to
freezing problems (plant evaluated in December). A great deal of leakage was evident around
the central shaft of the operating trickling filter. The WWTP recycle levels were all operating at
close to maximum levels 24 hours per day. Much pump wear was evident as three pumps were
down for repair.
Problem Identification—Dark color in clarifiers, pump, and trickling filter shaft was due
not to low dissolved oxygen (DO), as evidenced by a multitude of positive DO readings, but to a
combination of excessive recycle rates, grit, and ineffective grit removal.
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The trickling filter was not operating in an effective manner due to central shaft leakage,
freezing problems which halved use of trickling filters, and an inadvertent bypass in the
distribution box.
Maintenance could be more effective if it wasn't spent entirely on pumps repair/
replacement.
Remedies:
1. Recycle flows reduced through the use of timers
2. Wind barriers built around the trickling filters
3. Trickling filter central shafts were retooled and new seals were installed
4. Distribution box inadvertent bypass eliminated
5. Grit removal system being installed
6. Maintenance program revised
Preliminary Results—In 1990 25 percent improvement in CBOD5 effluent values was
demonstrated.
Dupo. Illinois.
Hardware—0.6 mgd plastic media trickling filter wastewater treatment facility.
Initial Evaluation—The wastewater treatment plant had difficulty in achieving CBOD5
limits 4 out of 12 months preceding our assistance, and suspended solids excursions also
periodically occurred. Much corrosion was evident at the facility. The valves were rusted
closed, steel covers in some cases were almost completely rusted through, and the structural
integrity of the trickling filter was also of concern. The trickling filter and primary clarifiers
were both performing poorly. One of the primary clarifiers would periodically completely
surcharge the effluent weirs.
-51-
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Problem Identification—Poor maintenance was the result of delayed maintenance
activity. This was due to contractor problems which delayed turnover of the plant to the Village
and a low Village priority for WWTP staffing. The trickling filter performance was being hurt
by inadequate and inconsistent wetting. Modifications to and maintenance of nozzles was
complicated by the walkways and handrails and other unnecessary hardware. The primary
clarifier performance was being impacted by uneven hydraulic loading in the primary diversion
box. Also, sludge was not being removed in sufficient quantities or in a consistent manner from
the primary clarifiers.
Remedies:
1. Emphasized importance of proper maintenance and protection of investment
with the Village fathers resulting in a greater investment of time at WWTP. A
50 percent increase in manhours at plant was obtained.
2. Installed flow restricter at one primary clarifier to equalize flows.
3. Opened the trickling filter recycle pipe.
4. Improved the solids control program by maintaining a regular schedule for solids
removal.
Preliminary Results—Eighteen percent reduction in CBOD5.
Linton, Indiana.
Hardware—0.9 mgd rock media trickling filters.
Initial Evaluation—The wastewater treatment plant was out of compliance 90 percent of
the time with frequent bypassing of overloaded primary system.
Problem Identification—This plant is home to a very unusual pipe which carries
wastewater in both directions, switching flow directions several times on some days. During dry
weather, the pipe carries 0.5 mgd of trickling filter recycled back to the head of the plant.
-52-
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During wet weather, the flow goes in the other direction through a bypass pipe where excess
flows are bypassed. This recycle flow was recommended during a previous WWTP evaluation.
Remedy—Reduce the amount of trickling filter recycle.
Results—The wastewater treatment plant is now in compliance 90 percent of the time.
Bypassing has been reduced by 37 percent.
Johnstown. Ohio.
Hardware—0.75 random dump plastic media two-stage trickling filter with a Dynasand
final filter.
Initial Evaluation—The wastewater treatment plant was out of compliance
11 out of 12 months for CBODS and 6 out of 12 months for NH,. The village had replaced
superintendents on three occasions in the previous 2 years.
Problem Identification—Comprehensive in-plant CBOD5 tests identified that the first-
stage trickling filter was not performing as expected. The failure of this first stage restricted the
second-stage nitrifying ability. An examination of actual operating conditions and design
parameters identified an extremely low wetting rate. Also, long in-plant holding time resulted in
an increased NH3-N value through an intermediate clarifier between the first- and second-stage
trickling filters.
Remedies:
1. Repiped an existing 950 gpm intermediate clarifier pump to provide more recycle
2. Installed bigger value to increase second-stage trickling filter recycle
3. Discontinued use of intermediate clarifier for dry weather flow and used basin to
capture stormwater
-53-
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Results—Fifty-four percent reduction in CBOD5 levels. Fifty-two percent reduction in
NHj-N levels.
Summary.
1. Take the time to evaluate carefully all trickling filter wastewater treatment plants.
2. Review trickling filter operation as an element of a wastewater treatment facility.
This technology is not as much of a "stand alone" process as activated sludge.
3. Proper and consistent wetting rates are very important where plastic media is
utilized.
4. The importance of proper maintenance cannot be overemphasized.
5. Recycle flows frequently are a critical element in poor performance at
trickling filter facilities.
6. Proper municipal onsite assistance can result in a significant increase in
trickling filter performance.
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UPDATE ON THE MICROBIAL ROCK PLANT FILTER (MRPF)
Ancil J. Jones
United States Environmental Protection Agency
Region 6
Dallas, Texas
This emerging and promising technology utilizing natural processes for municipal
wastewater treatment is the result of research conducted by the National Aeronautics and Space
Administration (NASA) at the Stennis Space Center (SSC) in Southern Mississippi over the
past 20 years (1). This technology utilizes aquatic and semi-aquatic plants, microorganisms, and
high surface area support media such as rocks or crushed stone. Communities, consulting
engineers, state agencies, and EPA Region 6 have continued the development.
The technology was developed to treat and reclaim wastewater for reuse in space
stations. On Earth, it is a low-cost, cost-effective technology for small communities, on-site
treatment, individual systems, and industrial wastewater. Haughton, Benton, and Denham
Springs, Louisiana, are the first applications of this technology in Region 6. Long shallow rock
filters are heated by solar energy maintaining biological activity rate during cold months.
Scientific Basis. The scientific basis for municipal wastewater treatment in a vascular aquatic
plant system combined with a microbial rock filter (MRF) is the cooperative growth of both the
plants and microorganisms associated with the plants and rocks. A major part of the treatment
process for degradation of organics is attributed to the microorganisms living on and around the
plant root systems and the rock filter. Organics are held in place by the rocks and plant roots
where microorganisms are given time for assimilation (see Figures 13 and 14).
This technology grows only selected plants in wastewater. The rock filters the
wastewater in conjunction with the plant roots. Hydroponics is defined as "the growing of plants
in a nutrient solution and without soil."
-55-
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MICROBIAL ROCK PLANT FILTER
LONGITUDINAL SECTION
12'
r-e-
TOP OF SMALL ROCK
\
EFFLUENT PIPE
TOP OF LARGE ROCK
DIRECTION OF FLOW OF WW • '
INLET (PERFORATED PIPE - 2' HOLES)
ROCKS AND ROOTS FILTER SOLIDS FROM WW AND
HOLD FOR MICROBIAL DIGESTION AND ASSIMILATION
Figure 13.
MRPF—Longitudinal Section
MICROBIAL ROCK PLANT FILTER
CROSS-SECTIONAL AREA
BULLRUSH
CANA LILLY
CALLA LILLY
MICROORGANISMS ON ROCKS
PLANT ROOTS ARE OPPOSITE CHARGES TO SS & HOLD THE SS TO ROOT
SS ARE HELD ON ROCKS BY FLOW OF WW AND GRAVITY
ROCKS AND ROOTS FILTERS SOLIDS FROM WW
AND HOLD FOR MICROBIAL DIGESTION AND ASSIMILATION
Figure 14.
MRPF—Cross-Sectional area
-56-
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Definition. This technology combines the application of hydroponics and the MRF
technologies. The rocks (inert) support the plants and roots in a nutrient solution (wastewater).
Thus the technology is appropriately defined as a microbial rock plant filter (MRPF).
It is defined by some as a subsurface flow constructed wetland. But this technology is
not a derivation of the wetland technology. It is a combination of two technologies: the MRF
+ hydroponics = MRPF. The MRPF uses different size filter media and design philosophy
than the surface and subsurface flow systems described in the EPA Design Manual "Constructed
Wetlands and Aquatic Plant Systems for Municipal Wastewater Treatment" (EPA/625/1-88/022).
The MRPF is a different design concept and requires a different operation and maintenance
and plant management program than constructed wetlands.
Plant Functions; Aquatic Plants Translocate Oxygen. Aquatic plants have the ability to
translocate oxygen from the upper leaf areas into the roots producing an aerobic zone around
the roots where aerobic conditions can be maintained. Bulrush (Scirpus Califomicus) roots in
Region 6 have been measured up to 20 inches in length. Canna Lily (Canna Flacdda) roots
have been measured up to 12 inches in length. Less oxygen is measured near the bottom of the
filter. Aquatic plant roots are also capable of absorbing, concentrating, and in some cases,
translocating toxic heavy metals and certain radioactive elements resulting in removal from the
wastewater (See Figure 15) (2,3,4,5). Caution is to be taken to ensure proper disposition of
hazardous harvested material.
Aquatic Plants Absorb Organic Molecules. In addition, aquatic plants have the ability to absorb
certain organic molecules intact where these molecules are translocated and eventually
metabolized by plant enzymes as demonstrated with systemic insecticides (6).
Biological reactions that take place between environmental pollutants, plants, and
microorganisms are numerous and very complex, and to date, are not fully understood. But
there is enough information available to demonstrate that aquatic and semi-aquatic plants serve
more of a function than simply supplying a large surface area for microorganisms as some have
suggested.
-57-
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MICROBIAL ROCK-PLANT FILTER
PLANT/ROOT FUNCTIONS
TRANSLOCATE OXYGEN
FROM LEAF THROUGH
STEM TO ROOTS
CROSS-SECTION OF
A ROOT FROM PLANTS
IN ROCK-PLANT FILTER
PRODUCTS OF MICROBIAL DEGRADATION OF
ORGANICS ARE ABSORBED BY PLANTS.
MICROORGANISMS USE SOME OR ALL
METABOLITES RELEASED THRU PLANT ROOTS
OPPOSITE CHARGES OF COLLOIDAL
PARTICLES (SS) AND PLANT ROOTS CAUSE
SS TO ADHERE 'TO ROOTS. SOLIDS FROM
WASTEWATER ARE REMOVED, DIGESTED, AND
ASSIMILATED BY MICROORGANISMS AND
ROOTS.
DO
6 INCH LAYER
SMALL ROCK
LARGE ROCK
WASTEWATER WITH
ABUNDANCE OF NUTRIENTS
TO SATISFY PLANTS
SHALLOW ROOT SYSTEM SATISFIES
PLANT LEAF STRUCTURE ABOVE
WAT
NATURAL WETLANDS WITH
FLUXUATING WATER LEVEL OR
IN RIVERS WITH LITTLE
NUTRIENTS
LONG ROOTS TO REACH
STREAM BOTTOM AND
SMALLER SURFACE
STRUCTURE
WASTEWATER WITH AN
ADEQUATE SOURCE OF
NUTRIENTS
LARGE PATTERN OF
SHORTER ROOTS WITH
LARGER LEAF AND
STEM ABOVE WATER
Figure 15.
MRPF—Plant/Root Functions
-58-
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Natural Regenerative Habitat. Each existing ecological system, using the other's waste products,
provides for a natural regenerative habitat and sustains accelerated removal of organics from
wastewater.
Removal of Suspended Solids. The vertical and horizontal flow of the wastewater holds the
solids on the rocks and roots. Charges associated with plant root hairs attract the colloidal
particles (suspended solids) with opposite charge. The solids are held in place for microbial
digestion (see Figure 15).
Growing Plants. By definition, to benefit from this technology, plants must be grown in a
nutrient solution only under conditions that maximize inter-process capability and symbiotic
relationships with microorganisms and rocks. Only plants selected are to be grown in the filter.
All other growth should be removed. This is not the case with the constructed wetlands
philosophy.
Plant Management. Unlike the constructed wetlands, plants in the MRPF must be managed.
Roots must be controlled and maintained as to depth and area to sustain the void ratio required
to maintain subsurface plug flow through the filter. The plant root system grows to satisfy plant
super structure (see Figure 15).
If the roots are not controlled, the filter void ratio will be reduced and cause surface
flow and ponding. Roots have been measured up to 20 inches in a 30 inch filter, drastically
reducing the void ratio and causing severe ponding and short circuiting. The planting density
also affects the void ratio (see Figure 16).
To control root depth and area, control the plant height and umbrella. Horizontal
growth varies with the umbrella of plant above the water line. Length of roots (depth below
water line) varies with the height of the plant above the water line. It is suggested that the
plants should be restricted to an 18-inch height above the water and the root's length and area
below be measured every 6 months. The umbrella of the plant above the water should also be
measured. Since terrestrial plants are utilized, this control relationship must be established (see
Figure 17).
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MICROBIAL ROCK PLANT FILTER
NON-MAINTENANCE RESULTS
GROWTH PATTERN
AFTER 2 YEARS
WITH NO PLANT
MANAGEMENT
o oooo
oo0oo
oOooo
ooooo
ROOT GROWTH AFTER
2 YEARS WITH NO
PLANT MAINTENANCE
BULRUSH
CANNA LILY
REDUCTION OF VOID SPACE
BULRUSH CANNA LILY
20/24 X 100% - 83% REDUCTION 10/24 X 100% • 17% REDUCTION
40%(100%-83%) • 17% REMAINING 40%(100%-17%) - 83% REMAINING
Figure 16.
MRPF—Non-Maintenance Results
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Assign Volume of Filter to Roots. Assign a volume of filter for plant roots and monitor every 6
months. Selective removal of plants may be necessary to maintain the void ratio for subsurface
flow and proper function of plants and microorganisms. The planting density must also be
maintained to control the proper density (see Figure 18).
Design. A major emphasis inherent in the design of the MRPF is the greater attention placed
on multi-objective planning, inter-media impact considerations, and total systems design.
Satisfaction of these objectives requires a higher level of multi-discipline in the systematic
screening and evaluation of alternatives than has been generally employed in the past. More
important, however, is the much greater effort needed in concept development and the
formation of management alternatives. Where performance data are lacking, a pilot scale might
be necessary to define operational parameters.
Design Considerations. A major factor in design is that there are 59 different elements of
design to be considered in this complex system, of which failure to consider one or more may
alter the symbiotic relationship of the natural processes which may change the results of the
synergistic effect, and which may result in a risk with unacceptable consequences.
Design elements to consider are not limited to the ones in the following list, but the list
will provide a general guide to achieve the design objective(s). It is vital that the designer
realize the complexity of this technology, and that the many elements of design have symbiotic
relationships that influence the synergistic effect affecting the quality of the effluent.
1. Wind directions and pond orientation.
2. Influent structure to pond.
3. Effluent structure from pond.
4. Hydraulic retention time in pond.
5. Depth of pond.
6. Wastewater characteristics to pond (influent).
7. Wastewater characteristics to filter (effluent from pond).
8. Wastewater characteristics of influent and effluent from other treatment units.
9. Wastewater characteristics of effluent from filter.
10. Anticipated algae from pond.
11. Organic loading on pond.
12. Operating conditions in pond-additional treatment in ponds, (aeration)
13. Anticipated effluent from filter.
14. Length x Width of filter. (Length is direction of flow)
15. L to W ratio of filter.
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SPATIAL CONTROL OF PLANTS IN A MRPF
ROOT CONTROL TO PREVENT FILTER CLOGGING
HEIGHT
TO BE CONFIRMED
IN THE FIELD
EVERY 6 MONTHS
ROOT LENGTH & WIDTH
TO BE CONFIRMED
IN THE FIELD EVERY
6 MONTHS
SMALL ROCK
NO WATER ZONE
T PLANT VOLUME APPEARS
TO HAVE A DIRECT
EFFECT ON ROOT VOLUME
ROOT SYSTEM DIAMETER
FIGURE
ROOT DEPTH
ROOT VOLUME SHOULD
BE CONTROLLED TO
MAINTAIN VOID RATIO
IN FILTER
Figure 17.
Root Control to Prevent Filter Clogging
SPATIAL CONTROL OF PLANTS IN A MRPF
PLANTING PATTERN FOR FILTER
INFLUENT
\
PLAN VIEW
— . o o
-_ ° °
0 0
FLOW o o
T O O
10 o o
.10' 0 C,
0 0
0 0
0 0
o o
0 0
0 0
o o
0 0
0 O
NOTE: PLANT DENSITY SHOULD
BE MAINTAINED AS SHOWN.
ADDITIONAL PLANTS THAT
MIGHT DEVELOP AND REDUCE
THE ORIGINAL P.ANT SPACING
SHOULD BE REMOVED
Figure 18.
Planting Pattern for Filter
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16. Influent structure to filter.
17. Effluent structure from filter.
18. Depth of filter.
19. Hydraulic retention time in filter.
20. Type of plants.
21. Number of plants.
22. Density of plants. (Super structure and root mass)
23. Planting pattern of plants.
24. Hydraulic gradient in filter.
25. Operating conditions in filter.
26. Rock gradation.
27. Rock sizes.
28. Depth of small rock, (no water zone)
29. Depth of large rock in filter.
30. Slope to bottom of filter.
31. Slope of filter surface.
32. Control of ponding in filter.
33. Temperature.
34. Allowance for evapotranspiration losses in filter.
35. Allowance for evaporation losses in pond.
36. Allowance for low flows.
37. Allowance for stormwater flows, infiltration/inflow analysis.
38. Provision for recirculation.
39. Provision to drain system. (Completely)
40. Removal procedures for undesirable plants.
41. Harvesting procedures for filter plants.
42. Removal procedures for excess filter plants.
43. Location of monitoring stations.
44. Design of monitoring station to ensure representative sample.
45. Protection against bank erosion.
46. Protection against leakage.
47. Allowance for insect and rodent control.
48. Acres required.
49. Design Flow. (Minimum, Average, Maximum)
50. Control of algae in ponds.
51. Control of algae in filter.
52. Control of root mass to maintain void ratio to ensure design detention time and
subsurface flow in filter.
53. Control height of plants to achieve design objectives.
54. Establish criteria for selection of plants.
55. Conduct pan evaporation test at each site to determine evaporation and
transpiration losses.
56. Determine plant transpiration rate.
57. Procedures to conform in-place void ratio.
58. Consideration of the use of calcium to enhance plant capability to uptake
ammonia nitrogen.
59. Establish procedure to confirm actual detention time.
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Design Obiective(s). Before field investigation and review of existing records, objectives should
be clearly understood. Objectives may be, but are not limited to: 1) achieve water quality
standards, 2) reduce quantity of water, 3) reuse, and 4) conservation of energy and water.
Plant Criteria. Depending upon design objectives, different plants have different capabilities to
satisfy design objectives to function at different sites in a specific wastewater. The filter void
ratio and rock size will require a specific design adjustment. The void ratio of the filter rock
will require adjustment to satisfy specific plant root substructures (volume) in order to maintain
design flow at the design detention time.
Evaporation/Transpiration. Pan evaporation tests should be conducted at each site. From the
pan evaporation test, compute the plant transpiration loss and the pond evaporation loss.
Recirculation Provision. Recirculation is vital during periods of low flow, high pond
evaporation, and plant transpiration. It is also important when backflushing is necessary.
Recirculation can increase detention time for additional treatment. Recirculation enables
alternate modes of operation and provides operation flexibility.
Drainage Provision. Complete drainage is required for satisfactory backflushing. It is necessary
for repairs to filter media and distribution system. Drainage is vital for measuring flow, water
volume of filter, detention time in filter and provides data to measure the in-place void ratio.
Measure the In-place Void Ratio. Measure the in-place void ratio by filling the filter before
planting. This will establish the in-place void ratio after construction is complete and before
planting.
Measure Detention Time. After measuring the in-place void ratio, measure the detention time
before planting. Measure detention time every 6 months until detention time remains constant.
In-place Void Ratio Adjustment. After confirming the void ratio of the rock media in place,
plant the plants at a spacing that is to be maintained. Monitor height of plant and spacing and
volume of root space. Predetermined volume must be assigned for root space for a specified
spacing of the plants. For each operating spacing and assigned volume for roots, the filter will
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have an operating void ratio that must be monitored and measured every 6 months until the
void ratio is a constant. Some plants may require removal to maintain required operating void
ratio.
Measure Dissolved Oxygen. Measure the dissolved oxygen (DO) at the same frequency as other
NPDES parameters, at the top, mid-depth, and bottom of filter. The DO should be measured
at the influent, mid-point, and effluent.
Design Criteria from Developed Technology May Be Suitable for Technology Transfer under
Certain Conditions. Design criteria should not be transferred from one site to another without
first determining that site conditions are similar enough for such a transfer. Changing design
criteria without performance data to substantiate the predicted result from the change is a risk
that is not recommended. Without performance data, upon which to base a prediction, the
anticipated effluent quality is in question. It follows, then, that the results of the technology
transfer would be in doubt.
How to Determine Acceptability for Design Criteria Transfer.
• The size of the principal unit processes and operations must be such that
physical, chemical, or biological processes will be accurately duplicated.
• All recycle streams have been considered.
• Process variables experienced will be the same as evidenced by accurate
measurement.
• The time of testing has been adequate to ensure process equilibrium.
• Variations in influent characteristics substantially affecting performance have
been accurately measured.
• Type and amount of all required process additives have been determined.
• The service life of high maintenance or replacement items has been accurately
estimated from past performance.
• Full control of all major process variables has been substantiated by performance.
• Basic process safety, environmental, and health risks have been considered and
found to be within local, state, and federal regulatory limits.
• All operational and management practices have been determined.
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Risk versus Potential State-of-the-Art Advancement. Implicit in this objective is a willingness to
accept a greater degree of risk in order to achieve a greater potential for a significant
advancement in state-of-the-art as evidenced by lower cost, greater reliability, or other similar
design objectives.
Construction Cost. The average construction cost for 22 facilities is $1.72/gal ranging from
$0.62 to $3.62 per gallon. Cost includes site preparation and construction of pond and filter.
The facilities varied in size from 0.26 mgd to 3.3 mgd. For locations and status see Figure 19.
Operation and Maintenance. For three facilities for 1989, the O&M costs were $.08, $.07, and
$.10 per thousand gallons. Reported cost for 1990 at Benton is $0.16/1000 gallons.
Performance. Effluents for BOD, TSS, and NH3-N ranged from 0-27, 5-30, and 1-10 mg/1,
respectively, for six operating facilities in Louisiana.
Technology Assessment. We are still on the learning curve. The technology is still in the
development stage. This is a success story. It is a viable technology especially for small
communities, individual, and onsite systems. We do not have all the answers, but we do
have sufficient design criteria based upon performance data to continue design, construction,
and development.
Problems In Design. Some problems in design that remain include:
• How to control plant density to maintain detention time
• How to control growth of plant roots to maintain void ratio
• How to maintain plug flow and aerobic conditions
• Criteria for selection of plants
Sustainable Development. This is a sustainable development. Sustainable development is
development that meets the needs of the present without compromising the ability of future
generations to meet their own needs (7). A similar definition is "growth based on forms and
processes of development that do not undermine the integrity of the environment on which they
depend (8)."
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LOCATION AND STATUS OF
THE MRPF IN REGION 6 (01-31-91)
RQURE 16
UNDER CONSIDERATION
PLANNING
DESIGN
UNDER CONSTRUCTION
OPERATING
AR
0
5
8
1
0
LA
10
8
2
5
25
NM
0
2
0
0
2
QK
1
1
0
5
0
IX
3
0
4
0
2
REGION
14
16
14
11
29
TOTAL
14 50
84
Figure 19.
Location and Status of MRPF in Region 6
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A Challenge to Central and Regional Systems. There are times when Regional facilities are the
most cost effective, but this technology is a real competitor and will challenge your imagination
and ingenuity in solving our environmental problems. It will treat and reclaim air and
wastewater to a quality for reuse at the point of waste generation. The environmental need
must become a fundamental component rather than a constraint to economic development.
Innovation via Imagination. Have a desire and do not be afraid to develop alternative and
innovative technologies beyond those found in textbooks, and do not be afraid to be imaginative
and creative.
REFERENCES
1. Wolverton, B.C., and R.C. McDonald. 1975. "Water Hyacinths and Alligator Weeds for
Removal of Lead and Mercury from Polluted Waters." NASA Technical Memorandum,
TM-X-72723.
2. McDonald, R.C. 1981. "Vascular Plants For Decontaminating Radioactive Water and
Soils." NASA Technical Memorandum, TM-X-72740.
3. Wolverton, B.C. 1975. "Water Hyacinths for Removal of Cadmium and Nickel From
Polluted Waters"." NASA Technical Memorandum, TM-X-72721.
4. Wolverton, B.C., and R.C. McDonald. 1975. "Water Hyacinths and Alligator Weeds for
Removal of Lead and Mercury from Polluted Waters." NASA Technical Memorandum;
TM-X-72723.
5. Wolverton, B.C., and R.C. McDonald. 1977. "Wastewater Treatment Utilizing Water
Hyacinths (Eichhornia Crassipes)." (Mary) Solms. pp. 205-208. "In Treatment and
Disposal of Industrial Wastewaters and Residues." Proceedings of the national
conference on treatment and disposal of industrial wastewaters and residues, Houston,
Texas.
6. Wolverton, B.C., and D.D. Harrison. 1973. "Aquatic Plants for Removal of Mevinphos
From the Aquatic Environment." J. Ms Acad. Sci., 19:84.
7. "World Commission on Environment and Development. 1987. Our Future. New York:
Oxford University Press, 43.
8. MacNeil, P. "Strategies for Sustainable Economic Development," Scientific American,
2613:155-165 (September).
-68-
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BIOLOGICAL NUTRIENT REMOVAL
-------
BIOLOGICAL NUTRIENT REMOVAL SYSTEMS
Glen Daigger
CH2M Hill
Denver, Colorado
Overview. This presentation covers the biological nutrient removal process options that are
currently available and applied by the sanitary engineering profession. Systems for the removal of
nitrogen or phosphorus and both nitrogen and phosphorus will be reviewed and compared. The
operating characteristics of each system will be discussed and situations where each process might
be used will be identified.
The presentation is structured to focus on the following concepts:
• An understanding of the mechanisms used in biological wastewater treatment
systems to remove nitrogen and phosphorus
• The ability to apply the mechanistic understanding described above to analyze the
capabilities of systems to remove nitrogen and phosphorus
• An understanding of the differences among the various biological nutrient removal
process options that are currently available
• The ability to use the knowledge obtained from the understanding of the biological
nutrient removal process options to select the process option most appropriate for
a particular application
A BNR System is:
A Conventional Suspended Growth
(Activated Sludge) Biological
Treatment Process;
Designed to Nitrify;
With an Anoxic Zone Added for
Nitrogen Removal;
And an Anaerobic Zone Added for
Phosphorus Removal.
-69-
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BNR System Reactors Are Segmented
Into Anaerobic, Anoxic, and Aerobic
Zones
NRCY
Anaerobic Anoxic Aerobic
RAS
WAS
The Aerobic Zone Provides Nitrification
and Final Effluent Polishing
NRCY
WAS
-70-
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The Anoxic Zone and Nitrified Recycle
(NRCY) Provide Denitrification
Capability
NRCY
Anaerobic AnOXiC
RAS
Aerobic
WAS
The Anaerobic Zone Provides
Phosphorus Removal
NRCY
Anaerobic Anoxic Aerobic
RAS
WAS
-71-
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A BNR System will:
Provide Nitrogen Removal
Provide Phosphorus Removal
Improve Sludge Setteability
Reduce Process Energy Requirements
Reduce Process Alkalinity Consumption
Nitrogen Removal Occurs Through
Nitrification/Denitrification
Nitrate Recycle
Denitrification:'
NO3-N -*N 2 f
WAS
Nitrification: NH3-N -*NO3-N
-72-
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The Anaerobic Zone Selects for High
Phosphorus Content Microorganisms
NRCY
BOD Update by
Poly-P Bugs
Uptake of
Phosphorus as
BOD is Oxidized
WAS
Increase Mass
of Phosphorous
Sludge Settleability is Improved Because
Filament Growth is Discouraged
NRCY
BOD
Oxidation
Less "Food" for
the Filaments
-73-
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Complimentary Reactions Reduce
Process Oxygen and Alkalinity
Requirements
Nitrification
- 4.6 Ib. O2 Consumed/to. NO3 -N Generated
- 7.2 Ib. Alkalinity as CaCO3 Consumed/lb. NO 3-N
Generated
Denitrification
- 2.86 Ib. Oxygen Demand Satisfied/lb. N03 -N Removed
- 3.6 Ib. Alkalinity as CaC03 Produced/lb. NO 3-N
Removed
VIP Project Objectives Emphasized
Cost-Effective Level of Nutrient
Removal
• Existing Plant Upgrade
• Total Process HRT of 6.5 Hours
• Remove Two-Thirds of Influent Phosphorus
• Remove 70% of Total Nitrogen Seasonally
• Obtain Associated Process Benefits
- Oxygen
- Alkalinity
-74-
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VIP Process Uses Anoxic Recycle (ARCY),
Staged Configuration and High-Rate
Operation to Optimize Phosphorus
Removal
Note: A staged reactor
configuration Is
provided by using at
least two complete
mixed cells In series for
each zone of the
biological reactor.
1to2QfTYP)_ __
" Anoxic RecyclelARCY) ~™ " 1
_1 to2Q(TYP)
NitrifiedIRecycfe i
(NRCY)
Return Activated Sludge (RAS)
Sludge (WAS)
The 40-mgd VIP Project Began in 1985
and is Nearing Completion
Facilities Plan Ammendment
15 Months of Pilot Testing Verified That
Project Objectives Achievable
18 Months of Successful Full-Scale
Operation at York River
Several Other Pilot Plants Completed
40-mgd VIP Plant Start-Up in May, 1991
-75-
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OPERATION OF ANOXIC SELECTOR ACTIVATED SLUDGE SYSTEMS FOR
NITROGEN REMOVAL AT ROCK CREEK AND
TRI-CITY WASTEWATER TREATMENT PLANTS
Gordon A. Nicholson
CH2M Hill
Portland, Oregon
Overview. The Rock Creek and Tri-City treatment plants were the first facilities in the Pacific
Northwest to have anoxic zones incorporated into the designs of the aeration basins. Anoxic zones
aid in controlling filamentous growth and the removal of nitrogen. Mixed liquor is recycled to the
head of the aeration basin where under anoxic conditions nitrate is used as the electron acceptor
for the uptake of soluble BOD. Metabolization of the BOD occurs in subsequent aerobic zones
of the aeration basin. Besides removing nitrogen and controlling filamentous organisms, the anoxic
selectors aid in the control of pH and reduce aeration demands. The Tri-City plant has been
operating for 5 years, consistently producing a high-quality effluent and maintaining SVIs less than
100. The Rock Creek plant has produced similar results with 2 years of operational history. Design
criteria, operational performance, and differing control strategies are included in this presentation.
The Objectives Of This Presentation Are.
1. To Update Anoxic Selector Performance
at Tri-City
2. To Describe Anoxic Selector Performance
at Rock Creek
3. To Compare Performance of the Two Systems
-76-
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Anoxic Selector Systems Possess
Several Documented Advantages
D Control of Filamentous Organisms
D Nitrogen Removal
D Reduced Alkalinity Consumption
D They are also Non Proprietary
Anoxic Selectors Are Provided At Both
Tri-City And Rock Creek
'Primary
Effluent ^
Return ^
Sludge
Submerged^1
Mixer
ML Recycle .
1 jS*™'~ N^
1
IOOO - OOO . *°0 . »*0 - OOO .. OOo .
-oe0° -o00° -oe0° -o00° -0»o to°°
>* • * ~* | o a * Oo* Oo° Oo* Oo° Oo°
00|0 0 0 0 0 0
— *•
Secondary
aartfiers
ANOXIC
SELECTOR
-77-
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At Current Loadings One Half The
Facilities Are Operated At Tri-Cfty
Ave
Max
Min
Aeration Basin
HRT (hr.)
5.3
8.3
3.5
Overflow
Rate
(gpd/ft2)
508
891
326
Effectiveness Of Anoxic Selector In
Controlling SVI Demonstrated At Tri-City
300
250
200
SVI
(mlVg)
150
100
50
Plug Flow Step Plug Flow Step Plug Flow Step Plug Flow PAnoS°W Step
AnUxJCL Feed ,i,Anoxic , Feed , Anoxic .Feed, Anoxic . Modified .Feed
JAODFAJAODFAJAODFAJAODFAJAODFA
1986 1987 1988 1989 1990 1991
-78-
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Effluent Quality Is Reliable Below
20/20 At Tri-City
30 Day Average (mg/L)
BOD TSS
Ave 7 8
Max 19 20
Min 2 2
Nitrogen Removal Is Maintained Year
Round At Tri-City
30 Day Average (mg-N/L)
NH3 NOx TN
Ave 2.0 7.0 9.0
Max 8.1 11.1 13.1
Min 0.3 4.1 4.8
-79-
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Process Loadings Are Similar
At Rock Creek
Ave
Max
Min
Aeration
Basin
HRT(hr)
5.7
8.5
4.7
Overflow
Rate
(gpd/ft2)
513
580
349
Primary Effluent Characteristics Vary
Seasonally At Rock Creek
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar.Apr
1989 1990 199l"
-80-
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Nitrogen Removal Varied Seasonally
At Rock Creek
Sep Oct Nov Dec Jan Feb Mar Apr May Jun lul Aug Sep Oct Nov Dec Jan Feb Mar Apr
1989 1990 1991
SW Also Varied Seasonally
At Rock Creek
Sep Oct Nov Dec Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
1989 1990 1991
-81-
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Secondary Effluent Quality Has Been
Excellent At Rock Creek
12
10
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
1989 1990 1991
Experience At Tri-City And Rock Creek
Demonstrates That:
1. Anoxic Selectors Effectively Control
Filamentous Bulking
2. Nitrogen Removal and Alkalinity Recovery
are Functions of BOD Loading
3. Design Details Facilitate Scum Handling
4. Effluent Quality is Good
5. Effluent BOD/TSS Varies between Facilities
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SUMMARY OF PATENTED AND PUBLIC
BIOLOGICAL PHOSPHORUS REMOVAL SYSTEMS
William C. Boyle
University of Wisconsin
Madison, Wisconsin
The removal of phosphorus from municipal wastewaters to control receiving water
eutrophication has been receiving high priority in many states and may become a significant
constraint in the NPDES discharge permit of many municipalities. Technologies exist for
removing phosphorus by physical, chemical, and/or biological means. Biological phosphorus
removal (BPR) has rapidly emerged as a desirable alternative process because of its relative
ease of implementation at existing plants using conventional activated sludge treatment.
There are a number of BPR system flowsheets in use today that are claimed to be
patented, although in certain cases the validity of the claim is in question. EPA needs to
establish which BPR processes lie in the public domain, which technical and/or other approaches
to BPR are currently valid processes, and the judicial rulings/findings associated with selected
BPR patent claims. The objective of this work was to summarize the status of patented and
public BPR systems in the United States so that the technology will be better understood by the
technical and regulatory communities.
This project consisted of two basic tasks:
1. Establish which patents issued since 1960 in the United States appear to cover
BPR processes and identify claims and holder of each.
2. Contact federal and state agencies, design engineers, and others knowledgeable in
BPR processes and identify municipal facilities where no license fees have been
paid, no allegations of patent infringement have been made, and/or no lawsuits
have been filed. These facilities are to be described, current or future NPDES
permit requirements identified, and plant operation/performance data
summarized for the past 12 months.
Patent Search — 1960-1990. A patent search on BPR processes was conducted by Christie,
Parker, and Hale. They identified 50 patents since 1960 that involve biological treatment
processes that in some way resulted in the removal of phosphorus. An additional 100 patents
-83-
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were also identified that had aerobic and anaerobic treatment steps that inherently may result in
some phosphorous removal, even though not specifically mentioned. A review of the 50 primary
patents revealed several important patented flowsheets currently used by municipalities in the
United States and a number of concepts that do not appear to be directly applicable to or
practical for municipal processes. Table 5 lists some of the currently licensed patents, assignee,
and number of facilities in operation or design/construction.
A search for litigation involving the 50 patents disclosed only one lawsuit by Air
Products & Chemicals vs. Orange Water and Sewer Authority in the Middle District of North
Carolina, filed January 6,1988. It appears that this suit has now been withdrawn, but further
details are still unavailable. One other point of interest on these patented processes is the
period of patent coverage: 17 years. Any reissue or "improvement" on the process reverts back
to the date of original patent issue, although specific improvements are extended 17 years from
their disclosure.
BPR Processes in Public Domain. A telephone survey of all states in the United States
attempted to identify municipal BPR processes currently operating or under design/construction
that are in the public domain. Needless to say, this is an enormous task and the likelihood of
omissions is high, especially for small facilities. Table 6 presents the tentative results of this
survey whereby generic system names are used to identify processes. Again, the numbers cited
for each system are tentative, at best.
A tentative review of the performance of public systems now in the ground suggests
substantial variability in process results. Most SBR and oxidation ditch systems employ
chemical additions to "polish" final effluent phosphorus levels. Most have been in service less
than 2 years and manufacturers/engineers are continuing to experiment and refine process
operation. The VIP and UCT flowsheets, which are very similar, have received significant
attention in the United States, and the process reliability appears to be very good based on pilot
and demonstration experience. Primary sludge fermentation (PSF), which may be a side-stream
or main-stream process, has been successfully applied at Kelowna, BC, and Orange Water and
Sewer Authority (Chapel Hill, NC). It is currently being applied at two Bardenpho installations
to upgrade performance. Licensing issues related to this process are yet to be resolved. Finally,
operationally modified activated sludge systems are probably grossly underestimated in Table 6
-84-
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Table 5. Summary of Selected Currently Licensed BPR Systems
Assignee
Trade Name
Facilities in
Operation
Facilities under
Design/Construction
Air Products
EIMCO
Biospherics, Inc
Orange Water/Sewer
Hampton Rds. San. Dist.
Transenviro, Inc.
AO, A2O
Bardenpho-5 Stage
Phostrip
OWASA
VIP
CASS
18
22
7
1
3*
10
19
17
9
9
4
9
*Pilot and demonstration system
Table 6. Summary of Selected Currently Used BPR Systems in Public Domain
Generic System
Facilities in
Operation
Facilities under
Design/Construction
SBR 8
Oxidation 11
Operationally Modified A.S. 4
VIP 3*
VCT/Modifications ?
Primary Sludge Fermentation 2
Aquatic Systems 1
1
4
9
4
3
1
9
*Pilot and demonstration systems
-85-
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owing to litigation concerns. Two factors may result in significant increases in the successful
application of this process: phosphate detergent bans and the reissue of the AO patent (1987),
which now specified "absence of supplied oxygen-containing gas" in the anaerobic zone.
Future Outlook. Results to date indicate that most mainstream BPR systems in operation can
meet a 1.0 mg/L P requirement most of the time. Factors that dictate good performance
include high soluble BOD to soluble P ratio (volatile fatty acids generated in mainstream or
sidestream reaction); low DO and nitrate concentrations in anaerobic zone; high sludge yields;
and effective P control in sludge processing. Sidestream processes such as Phostrip are
generally able to achieve lower effluent P values because of their operational flexibility and
insensitivity to influent wastewater BOD.
Selection of future BPR processes for greenfield or retrofit applications will be
dependent on NPDES discharge permits and influent wastewater characteristics that may be
greatly influenced by detergent phosphate bans. The currently licensed BPR processes will
likely continue to be used in many instances because of the years of experience with these
flowsheets. Several patents will lapse within a few years, a fact that is significantly influencing
some engineers in process selection.
PSF processes provide significant flexibility to plants with weak wastewaters, those with
fixed film processes and those having difficulty with high anaerobic zone nitrates. The concept
provides the engineer with an opportunity to provide greater operational stability and reliability
to mainstream BPR systems. One lingering question however relates to how the OWASA
patent may affect new PSF designs. Early interpretations of the OWASA patent suggest that it
applies to fixed film or chemical pretreatment processes where BOD/TP ratios are significantly
reduced prior to the BNR system. A broader interpretation of this patent may occur as future
designs are developed.
As discussed earlier, operationally modified activated sludge designs and retrofits may be
pervasive in the future as BOD/TP ratios increase. Combined with VIP/UCT flowsheets, it is
likely that engineers will select maximum flexibility with internal mixed liquor recirculation,
multiple sludge recycle feed points, tank baffling, and even PSF sidestream applications.
-86-
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Use of oxidation ditches and SBR configurations will likely continue for small facilities.
More experience with system operation and process modifications is in order and currently
underway. In many system designs, especially where NPDES permits may become more
stringent in the near future, standby chemical feed is an intelligent choice to ensure that the
municipality meets its permit under adverse situations. Effluent requirements below 0.5 mg/L
may dictate filtration polishing for most currently used BPR systems.
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SLUDGE
-------
CASE STUDY EVALUATION OF ALKALINE STABILIZATION PROCESSES
Lori A. Stone
Engineering-Science, Inc.
Fairfax, Virginia
The management of sewage sludge continues to be a major problem for municipalities.
Municipal sewage sludge management programs are being influenced by a number of factors,
including: increasing sludge volumes resulting from better wastewater treatment; the U.S.
Environmental Protection Agency's (EPA's) "Beneficial Use Policy," which actively promotes the
beneficial use of sludge while maintaining or improving environmental quality and protecting
public health; current and proposed federal and state regulations; conversion of the
Construction Grants program to a state revolving fund program; public acceptability; and a
desire by municipalities to select a cost-effective sludge management option. As environmental
issues continue to influence sludge management programs, municipalities are becoming aware of
alternative sludge use practices.
New forms of chemical stabilization other than lime treatment have been developed by
vendors and are being used by municipalities. Tiese technologies add alkaline materials such as
cement kiln dust, lime kiln dust, Portland cement, or fly ash for the stabilization of sludge.
Most of these technologies are modifications of traditional lime stabilization. The most
common modifications include the addition of other chemicals, a higher chemical dose
(depending on the chemical type), and supplemental drying. These processes alter the
characteristics of the sludge and, depending on the process, increase the stability and physical
strength, decrease the odor potential, and/or reduce pathogens.
As more municipalities become aware of these newer, alkaline stabilization technologies,
there was a need to compile information from operating, full-scale projects. An evaluation was
conducted to determine:
• How the major alkaline stabilization process have been and are being used
• The problems that have been encountered
-89-
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• The solutions that have been implemented to improve the processes
Site visits to four alkaline stabilization facilities were conducted in addition to follow-up
meetings with vendor representatives, plant managers, and regulatory officials. The four
facilities visited were: New Haven, Connecticut; Salem, Massachusetts; Toledo, Ohio; and
Greenville, South Carolina. The New Haven and Salem operations use the Chemfix process;
while the Toledo and Greenville facilities use the N-Viro process. Although the Chemfix and
N-Viro processes were the focus of this study, similar technologies have emerged which also use
alkaline additives to stabilize municipal sewage sludge, such as the BioFix IV process of BioGro
Systems and the En Vessel Pasteurization process of RDP, Inc. This document is not intended
to single out one design or technology as superior to another.
Case study evaluations were prepared to summarize the information gathered and the
observations made during the site visit. It should be emphasized that each case study represents
a "snapshot" of the process and operations at the time of the visit. The factual data presented,
such as the loading rates, operating practices, and odor production and control, are accurate
only for the time of the site visit and may have subsequently changed because the systems are
still rapidly developing.
The information collected from these visits and conferences is intended to assist
municipalities that are considering these processes in their own site-specific assessments.
Specifically, this document focuses on important issues that should be considered when
evaluating alkaline stabilization as a sludge management option. These issues include project
planning and implementation considerations, associated costs, procurement options, process
operations, monitoring and regulatory requirements, and product quality and use.
The study found that the N-Viro and Chemfix processes can be implemented in a very
short period of time. In many cases, these alkaline stabilization processes have been used to
solve an immediate problem (e.g., the shut down of another system or an odor problem) and
then for various reasons have been replaced by the repaired or other system. In addition,
several full-scale systems using alkaline processes have and are being implemented as long-term
solutions. Available information about these systems is summarized in Table 7.
-90-
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-91-
-------
The planning and implementation of a sludge management option depends on several
factors. Depending on the proposed end-use for the final product, alkaline stabilization can be
an effective management option for sludges with varying degrees of sludge quality. The addition
of alkaline, pozzolonic material serves to dilute concentrations of heavy metals and organic
chemicals on a dry weight basis and tends to immobilize these constituents. Although the
Chemfix and N-Viro processes could be modified to treat hazardous sludges, both vendors
require that the sludge be non-hazardous so the final product can be used in landfill or
agricultural applications.
From the study, it is apparent that the feed sludge and alkaline material should be
monitored frequently so that adjustments could be made to the process to maintain a consistent
product. Because the quality of the alkaline additives may have a direct effect on the quality of
the final product, it is extremely important that adequate monitoring be performed to ensure
consistent quality supply. More importantly, pilot or bench-scale testing should be performed to
determine how variations in the alkaline additives will affect the final product quality and how
the process and chemical dosages should be adjusted to account for these variations.
Parameters to be monitored include total solids, pH, and temperature of both the sludge and
final product. Quality control data were required for regulatory approval at each of the
facilities visited. The method and frequency at which these parameters were monitored
depended on the regulatory requirements. In some cases, odor characterization and emission
monitoring was required.
The product end-use has particular quality requirements and standards associated with it.
Depending on the end-use, it may be necessary to satisfy either Process to Significantly Reduce
Pathogens (PSRP) or Process to Further Reduce Pathogens (PFRP) requirements. Potential
markets for an alkaline stabilized product include agricultural, slope stabilization, structural fill,
or municipal landfill cover operations. As shown in Table 7, the majority of the N-Viro
facilities are PFRP; all of the Chemfix operations have been PSRP. Accordingly, the
predominant end-use for the N-Viro product is as an agricultural liming agent or soil
conditioner, which typically requires PFRP treatment; whereas, the Chemfix product is used
mainly as cover material for landfills, requiring only PSRP treatment. Research studies have
been performed investigating the use of the Chemfix material as a soil conditioner and as fill
-92-
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material. However, to date, the Chemfix product has been used only in landfill operations for
grading purposes and as daily, intermediate, and final cover.
Although these technologies use similar materials handling equipment as traditional lime
stabilization, the precise chemical formulas of the stabilization additives or processing steps are
generally proprietary. Consequently, many of these technologies are only available to
municipalities only as procurements from private firms. The type of procurement and
associated economics are important issues to consider when selecting a sludge management
option. The costs of an alkaline stabilization process should be evaluated with respect to the
total costs of the option over its useful life using present worth, equivalent annual cost, or
similar method. In addition, the costs of a privatized option, if that is the preferred
procurement method, should be compared to alternative management options that are to be
owned and operated by the municipality. The privatized facility is designed, operated,
constructed, furnished with all the necessary equipment, and eventually operated as a
commercial enterprise by a private firm. As shown in Table 7, the Chemfix facilities are
privatized procurements. Chemfix will allow municipalities to operate the process using their
own personnel and facilities; however, a licensing fee for the use of the process may be charged.
Although the majority of the N-Viro facilities are owned and operated by the municipality, a
royalty fee is charged for the use of the patented technology. Several of the N-Viro facilities
are owned by the municipality and operated by a third-party through a licensing agreement. A
technical service fee may also be applicable for the initial licensing of a facility. This fee
includes items such as process design, pilot testing, review of drawings and specifications, facility
startup services, and initial PFRP compliance testing.
Flexibility (adaptability) of the alkaline stabilization process and the use of existing
facilities should be considered when evaluating potential sludge management options. Although
it may be not always be possible to use or retrofit existing equipment, cost savings can be
achieved by the municipality if existing equipment is used as part of the alkaline stabilization
process train. Existing equipment was used to minimize capital expenditures at several of the
facilities visited. Depending on the site constraints, the type of process utilized, and the amount
of sludge to be processed, site preparation for both the Chemfix and N-Viro processes is
generally minimal. The process equipment can usually be arranged to accommodate various site
constraints. Because these processes are relatively simple to operate and do not require
-93-
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extensive, complex processing equipment, they can usually be implemented in a short time frame
and require relatively minimal space. Additionally, both Chemfix and N-Viro have mobile,
skid-mounted equipment that can be used for back-up or emergency situations and
demonstration programs to encourage interest in the final product.
Since the processes are not manpower or equipment intensive, alkaline stabilization can
be a cost-effective option depending on the product market and end-use program. In addition,
an advantage of these processes is the ability to start-up operations in a relatively short time
period. Because of their flexibility and ease in start-up, alkaline stabilization can be an effective
sludge management option, especially as an interim alternative.
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CONTROLLING SLUDGE COMPOSTING ODORS
William G. Horst,
City of Lancaster
Lancaster, Pennsylvania
and
Bert deVries
Connert, Inc.
Lancaster, Pennsylvania
In the early 1980s Lancaster began planning and designing new wastewater treatment
facilities. The City had a long history of odor complaints from the neighbors. Since the Zimpro
process for sludge handling was the cause of most of the bad odors, it was decided to look for
an alternate sludge handling process. To fully understand the odor problems, it should be
pointed out that the topography and location of the plant put neighbors in proximity with these
undesirable smells. This presented us with a major difficulty in arriving at a solution. The plant
is located in the lowest area of the city and the neighbors above are looking down onto the
sewer plant and the malodorous fumes are rising directly toward them with little chance of
dispersion.
The Authority therefore searched for a method to contain odors. What better way to
achieve this objective but to use "in-vessel" composting. This appeared to be the answer.
However, it was immediately apparent that "fugitive" emissions were a major problem.
Open conveyors on top of the Taulman Weiss composting vessels allowed unobstructed odor
release during many hours of each day. Also, the open top feed apertures of the vessels allowed
odors to escape all day long.
The City decided to tackle the fugitive emissions first. All conveyors were enclosed and
the air within the conveyors ducted to a Quad mist scrubber. This effectively controlled these
sources.
The second major construction job was to greatly increase the suction out of all four
reaction vessels. Three to four times more air was taken out of the vessels than aeration air was
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blown into the vessels. That created a suction inside the vessels. In fact, vacuum breakers were
installed to prevent a collapse of the tops of the vessels. This excess exhaust air prevents air
from escaping and becoming "fugitive" odors.
As part of the process instructions by Taulman Weiss, the City also turned off all
aeration blowers while loading or unloading vessels and while transferring material from one
vessel to another. Up to 8 hours each day, therefore, the biological process received no
aeration. Upon resumption of the aeration blowers, a large "spike" of odorous air, often at very
high temperature, would be blown into the odor control system. There was really no way to
control this variable "odor load."
Because of the higher airflow, and to somewhat "dampen" the odor fluctuations, the
Authority placed two scrubbers in sequence to scrub the odors.
The Pennsylvania Department of Environmental Resources last year accepted
recommendations to allow the City to work out a system to chemically treat the odors rather
than use a very costly incinerator. To that end Bert deVries, formerly with Quad, but now an
independent consultant, was hired to coordinate and expedite the work in progress.
The first scrubber is a "water wash" scrubber, with the multiple purpose to:
1. Cool the hot odorous gases.
2. Neutralize ammonia by acidifying the water.
3. Dampen the "shocks" which occur after the aeration blowers are put back on.
The second scrubber is a Quad mist scrubber which removes carbon sulfides and the
many other persistent odors.
Both scrubbers are pH controlled since both ammonia reduction and the oxidation of
the odors in the second scrubber take place under carefully controlled acidic conditions.
Readily available "process water" is used in the cooling-stripping scrubber and only a \Vz
gallon per minute mixture of chemicals and potable water is used in the second scrubber.
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Contrary to the Taulman-Weiss recommendation, we presently continue to aerate 24
hours a day. The excess air taken off at the top of the composting vessels creates a sufficient
vacuum, so that it is now possible to continue operation of at least 1,150 cfm by the aeration
blowers to supply air into the bottom of the vessels. The benefits of this procedure become
immediately obvious. The temperature of vapors into the "cooling" scrubber no longer rises 20
to 30°F. The "spike" of sudden odor levels to be treated also disappears. The more gradual
increases and decreases of temperature and odor levels can now be tracked automatically to a
better degree.
All the above improvements to solve the technical problems will still require attention
and care by the staff. It has become obvious once again, that good technology still depends on
good operators and that constant vigilance will be required to keep our neighbors "happy"
neighbors.
The Authority also is grateful for the patience and encouragement of the PADER who
stood by us throughout these difficult years. We understand the pressure they were subjected to
by neighbors who wanted a "quick-fix."
The City feels confident that after all the seemingly insurmountable problems, a practical
and innovative system was developed on-site. The City believes that others may benefit from
our experiences and persistence so that composting as an alternative sludge disposal technique
may shed some of its unfavorable image acquired over the last few years. This is new
technology, and the City feels it contributed by the lessons learned.
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TOTAL RECYCLING
Dale Cap
Southwest Suburban Sewer District
Seattle, Washington
Background. Southwest Suburban Sewer District's first wastewater treatment plant became
operational in 1956 providing primary treatment and chlorine disinfection. The Salmon Creek
plant was followed by construction of the Miller Creek plant in 1965 which provided the same
degree of treatment. Sludge was anaerobically digested, dewatered by a vacuum belt filter and
then later by a centrifuge, and made available to the public. All sludge produced at that time
(up to 750 yd3 in 1986) was stored originally at the Salmon Creek plant and then later on at the
Miller Creek plant and utilized by the public. The dewatered sludge had a solids content of
30 percent, was of a fairly loose texture that made it easy to handle, and the odor was not too
strong.
Construction took place in 1986 through 1989 to upgrade both treatment plants to
secondary treatment. Rotating biological contactors, a fixed film process, coupled with solids
contact was selected as the biological treatment process, and digester capacity was expanded to
handle the additional sludge. The biological solids changed the nature of the sludge throughout
the process. It doesn't compact as well nor dewater as easily after digestion, and it has a strong,
predominantly ammonia odor. This material, though providing the same or even greater benefits
for soil improvement, wasn't desirable for the average homeowner to work with. Furthermore,
the volume of dewatered sludge increased four- or five-fold.
Sludge Quantity. Each treatment facility treats a wastewater flow of about 3.5 mgd and pumps
11,000-13,000 gallons of 4 percent total solids raw sludge to the anaerobic digestion process
daily. Volatile solids reduction averages 50 percent to 65 percent. Each plant produces about
28 yd3 per week of 18 percent total solids dewatered digested sludge for a total of about 3,000
yd3 per year. The majority of the sludge is composted on-site for distribution and marketing,
and a small amount is applied to land.
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Composting. The District considered building a compost facility to produce a marketable
product that could increase the demand to equal the supply. Composting meets the EPA criteria
for a Process to Further Reduce Pathogens (PFRP) because of the high temperatures reached
in the process (above 55°C). After much investigation, including visits to installations across the
country, the idea of an in-vessel composter appeared to be too costly and risky as far as proven
reliability. The District decided to build a large odor-controlled enclosure that provided
flexibility for static pile composting. The composting project is working very well. The
composted-product we are now producing is a rich-looking humus that is loose and very
workable with virtually no odor. With the increasing interest being shown, we are selling
everything we can produce. For our static pile composting operation we use a front loader with
a 2 yd3 bucket for all the materials handling. The sludge is mixed by volume, one part
dewatered digested sludge to one part sawdust (or other amendment, such as yard waste) to one
part recycled compost. The mixture is organized into piles or rows in the compost building, and
numbered temperature probes are inserted into the pile to track the temperatures. Once the
temperature has remained above 55°C for at least three days, the pile is remixed and aerated.
We do this at least three times with the temperatures getting above 55°C to assure a safe
reduction of possibly harmful bacteria. Once a batch has substantially composted so that there
is no odor, it is moved out of the enclosed odor-scrubbed compost building into an open-sided
curing building where it is available for sale to the public. People bring their own containers or
pick-up trucks to purchase the compost at $10/yd3 with a $2 minimum. We deliver 4 yd3
minimum loads within a reasonable distance at no extra cost. We advertised our compost in the
District's newsletter, which is sent to District customers periodically. In a relatively short period
of time all the compost was sold and there was a waiting list for the next available batch.
We are fortunate that our treatment plants serve a "bedroom community" with little or
no industrial waste so that we have a high quality sludge that can be beneficially and safely
recycled into the environment. We started a program in cooperation with the City of Normandy
Park for recycling yard waste into our compost. At present we are accepting only grass
clippings, leaves, and other materials that don't require grinding. This has had a number of
benefits. It has given us more free amendment, it has increased the public visibility and
awareness of our program in a positive light, and it has put these valuable resources, sludge and
yard waste, to work for us.
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STORMWATER
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WASHINGTON STATE'S APPROACH
TO COMBINED SEWER OVERFLOW CONTROL
Ed O'Brien
Washington State Department of Ecology
Olympia, Washington
Introduction. Washington State has embarked upon a combined sewer overflow (CSO) control
program whose goals are:
To reduce the incidence of untreated overflows to an average of once per year
per overflow site
To comply with sediment quality standards and water quality standards during
and after overflow events
To not preclude unrestricted use of the receiving waters for their characteristic
uses
The program is both technology- and water quality-based. The pace of its
implementation is decided on a case-by-case basis by applying economic criteria to each
municipality's situation. Figure 20 presents a schematic of Washington's CSO treatment
requirements.
Overview of the Statute and Regulation. In 1987, Washington amended its Water Pollution
Control Act to include provisions specific to the reduction of combined sewer overflows. Those
provisions require the Department of Ecology, the state's pollution control regulatory agency,
and local governments "to develop reasonable plans and compliance schedules for the greatest
reasonable reduction of combined sewer overflows ... at the earliest possible date" (RCW
90.48.480). The initial reduction plans and schedules were due by January 1, 1988.
To implement this legislation, the Department of Ecology adopted a new regulation,
"Submission of Plans and Reports for Construction and Operation of Combined Sewer Overflow
Reduction Facilities." This regulation defined "the greatest reasonable reduction" as control of
each CSO such that an average of one untreated discharge may occur per year. Dischargers must
achieve and maintain at least this level of control. In addition, treated and untreated overflows
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must cause neither violations of applicable water quality standards nor restrictions to the
characteristic uses of the receiving water, nor accumulation of deposits that exceed sediment
quality standards. Therefore the regulation is both technology- and water quality-based.
The first required step is the submission of a CSO Reduction Plan. The plan must
include the following:
Documentation of CSO Activity. This includes a field assessment and mathematical modeling
study to establish each CSO's location, "baseline annual frequency and volume"; to characterize
each discharge; and to estimate historical impact. Flow monitoring is almost always required.
CSOs serving industrial/commercial basins require conventional, heavy metal, and organics
analysis. The extent of sludge deposits must be confirmed with chemical analyses required for
commercial/industrial areas.
A model must establish the rainfall stormwater runoff/CSO quantity relationship. A
CSO baseline condition is set by using the model, the historical rainfall record, and the existing
sewer system to estimate annual historical CSO volumes that would have occurred had the
sewer system existed as it does today. A graph of annual estimated CSO volumes versus annual
precipitation is developed. The baseline is taken as the 95 percent confidence limit line. It is
that annual overflow volume that should not be exceeded 95 percent of the time given the
corresponding annual rainfall amount.
Evaluation of Control/Treatment Alternatives. Municipalities must evaluate use of the following
alternatives for controlling their CSOs:
Delayed (storage) or direct transportation to the secondary treatment plant
serving the sewer system. All flow reaching the secondary plant must receive at
least primary treatment and disinfection with one bypass allowed per year. The
plant must not violate its pollutant concentration effluent requirements. Storage
and transport capabilities must be adequate to allow an average of only one
untreated discharge per year at each CSO site.
Onsite treatment equal to at least primary treatment, and offshore submerged
discharge. Disinfection may be required for sites that are near or impact water
supply intakes, shellfish beds, and primary contact recreation areas. The onsite
system must be sized such that an average of one untreated discharge may occur
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per year. Primary treatment is defined as removal of at least 50 percent of total
suspended solids and discharge of less than 0.3ml/l/hr of settleable solids.
Separation of the combined system, creating distinct sanitary and stormwater
systems.
As interim measures to reduce pollutant loading, municipalities can explore use
of best management practices, more restrictive sewer use ordinances, and
pretreatment programs. Sewer maintenance programs to reduce infiltration and
inflow are also acceptable control approaches.
Analysis of Proposed Alternatives. Proposed control alternatives must be analyzed for their
water quality and sediment impacts. This includes the impact of discharges from new storm
sewers. Construction and operation and maintenance costs must be estimated based on
preliminary designs. Phased construction of control alternatives also should be considered.
Ranking and Scheduling of Projects. Proposed projects shall be given priority rankings using
health, environmental (documented probable, and potential), and cost-effectiveness (e.g., cost
per annual mass pollutant, volume, or frequency reduction) criteria. Municipalities shall
propose compliance schedules based on these criteria:
• Total cost of compliance
• Economic capability of the community
• Other recent and concurrent expenditures for improving water quality
• Severity of existing and potential environmental and beneficial use impacts
Schedule Updates; Monitoring and Reporting. Annual reports must document frequency and
volumes from each CSO location based upon field monitoring. If any CSO increases over its
baseline condition, the municipality shall propose a project and schedule to reduce the CSO to
or below the baseline condition. Annual reports must also explain the year's CSO reduction
accomplishments.
Onsite treatment facilities shall have NPDES permits that limit effluent quality and
quantity, and include reporting requirements.
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CSO Reduction Plan amendments are due every 5 years in conjunction with the
application for renewal of all applicable NPDES permits. The amendments shall assess the
effectiveness of CSO reduction activities to date, reevaluate priorities, and propose new
schedules based on current economic conditions and environmental knowledge.
Those activities and accomplishments scheduled to occur during the 5-year life of the
municipality's NPDES permit shall be requirements of the permit or a companion administrative
order.
Rationale for Selection of One Untreated Discharge per Year per Site, and Minimum of
Primary Treatment.
Interpretation of new CSO statute had to be consistent with historical
interpretation of long-standing state water pollution control laws for technology-
based treatment.
The state's water pollution control statues include a long-standing requirement that all
wastes must receive "all known, available, and reasonable methods of treatment" prior to
discharge to the state's waters, regardless of the quality of the receiving water, in order to
prevent and control pollution. This is a technology-based law, somewhat equivalent to the
federal Best Available Technology (BAT) economically achievable requirement. For each
situation the state must decide what is technically possible and reasonable.
The historical interpretation of this requirement is that the term "reasonable" includes an
economic consideration. In the context of municipal sewage treatment, the state used economic
impact as a criterion for determining when secondary treatment was reasonable.
When the Water Pollution Control Statute was amended to include the requirement for
the "greatest reasonable reduction of combined sewer overflows ... at the earliest possible
date," the Department of Ecology had to interpret that requirement in a manner consistent with
the "all known, available, and reasonable" requirement.
Interpretation of new CSO statute could not conflict with state water quality
standards, nor the legislative record.
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In addition, state law and regulation prohibit discharges that cause "pollution" or violate
water quality standards. In reviewing the CSO discharge situations in the state, we determined
that in almost every instance, an untreated CSO discharge was causing a water quality standard
violation. This seems to require elimination or treatment of every CSO. However, the
legislative record behind the new CSO statute seemed to indicate that the legislature
intentionally stopped short of that requirement.
So, the Department of Ecology was faced with developing a technology-based CSO
treatment/control standard that satisfied both the technology-based and water quality-based
requirements of the law.
Minimum Treatment and Control Methods Identified. First, we reviewed the available CSO
treatment technologies. Sewer separation and storage were long-standing, available control
methods. Primary treatment of CSO had been applied in a number of states, including
Washington. It was considered a minimum treatment level necessary to prevent violation of
water quality standards outside a reasonable dilution zone. Technologies such as swirl
concentrators would still result in the discharge and accumulation of sediments at the discharge
locations. More advanced physical/chemical methods may be necessary to prevent violation of
water quality standards in some situations, and should be required in those instances.
With minimum treatment and control methods identified, we still had two issues to
resolve. Because CSOs are intermittent, and the list of reasonable technologies includes options
for continuing untreated discharge, there had to be a determination of an allowable frequency
for such untreated discharges. Secondly, the concept of economic reasonableness had to be
factored in.
Maximum Allowable Frequency of Untreated Discharge Selected. All of the CSOs in
Washington discharge to waters designated as Class A or AA. The characteristic uses of these
waters include primary contact recreation, and in the case of marine waters, shellfishing. A
review of past CSO control efforts within Washington and in other states led to the conclusion
that one untreated overflow per year was the minimum necessary to protect all these receiving
waters for their beneficial uses. In particular, CSO control planning efforts in the late 1970s
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and early 1980s by the Municipality of Metropolitan Seattle (METRO) and by the City of
Seattle had concluded that this control level was necessary for the CSO receiving waters in the
Seattle area in order to protect shellfishing and primary contact recreation.
The one untreated overflow per year level also seemed to satisfy the technology-based,
"available" requirement. It had been achieved in a number of areas in the Seattle area. In
addition, it was the strictest control level chosen in the San Francisco CSO control program.
That program used a cost/benefit analysis to pick control levels ranging from one to 10
overflows per site per year. A control level of four overflows per year had been selected by the
City of Sacramento.
One untreated overflow per year should also prevent significant recurring long-term
water quality degradation. The one untreated overflow may still cause a temporary water
quality standard violation. If monitoring confirmed such a situation, the state could require
additional control.
"Reasonable" Economics Accommodated through Compliance Schedules. The final factor to
consider was "reasonableness." Two years prior to the time of this decision, the Department of
Ecology had decided to deny a number of municipal applications for a waiver from the
requirement for secondary treatment. Such waivers were allowed under Section 301(h) of the
Clean Water Act. The State Pollution Control Hearings Board and the Department of Ecology
used economic impact as a criterion only for determining when such treatment would be
required to be on-line.
In the context of CSO control, economic criteria were used to establish reasonable
schedules for compliance with technology- and water quality-based treatment and control
requirements.
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NATIONAL COST FOR COMBINED SEWER OVERLFOW CONTROL
Atal Eralp, Norbert Huang, Michael Denicola,
Robert Smith, and Tim Dwyer
Office of Wastewater Enforcement and Compliance
EPA Headquarters
Washington, DC
Background. There are approximately 1,050 communities nationwide with combined sewer
systems with an estimated 10,770 combined sewer overflow (CSO) discharge points. These
communities are primarily located in New England, the Middle Atlantic region, and the upper
Midwest. Eleven states have 878 communities with combined sewer systems having
approximately 8,700 CSO discharge points.
CSO Wastewater Characteristics. The primary components of CSO discharges are raw sanitary
wastewater, industrial wastewater, and stormwater runoff. Characteristics of CSO discharge are
dependent on the ratio of the three primary components. CSO discharges are characterized by
the presence of fecal coliforms; total suspended solids; BOD; heavy metals (copper, lead, zinc,
chromium); toxic organics (benzene, phenols, and other organic solvents); fertilizers; and
pesticides. Other pollutants may be present in CSO discharges depending on the residential,
commercial, and industrial profile of the system's service area.
CSO Wastewater Impacts. During heavy rains, as much as 90 percent of the total wastes that
enter a combined sewer system never reach the POTW and are discharged untreated through
CSO points into receiving waters. Some of the immediate effects of CSO discharges are:
• CSO discharges are wholly or partly responsible for the designation of 175 river
miles and 4,400 lake acres in Kentucky and Tennessee as unsafe for recreation or
fishing (Region 5 OIG Report, March 1990).
• Although only four Boston area communities have CSOs, they are responsible for
the annual discharge of 9 billion gallons into Boston Harbor.
• CSO discharges resulted in the closing of beaches in the New York-New Jersey-
Connecticut area (NY Times, September 5, 1989) and led to beach closings and
shellfishing bans in Puget Sound (1987 Puget Sound WQM Plan, 1987), and the
permanent closing of 25 percent and temporary closure of 10 percent of the
Narragansett Bay's shellfishing beds.
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Existing CSO Control Authorities* There are several existing nationwide CSO control
authorities, including the Clean Water Act, the National Pollutant Discharge Elimination
System (NPDES) permits, and EPA's August 1989 National Combined Sewer Overflow Control
Strategy. The EPA strategy requires that states develop CSO permitting strategies that address
the following elements:
• Inventory of communities with CSOs and the permitting status of their CSO
discharges
• Prioritization of the unpermitted and inadequately permitted CSO discharges
• Issuance of single, system-wide permits
• Compliance schedules for technology-based permit limitations and applicable
water quality standards
• Minimum technology-based limitations in permits and additional CSO control
measures to meet the technology-based limits and water quality standards
• Monitoring of CSO discharges
• Adjusting water quality standards in limited cases to better address impacts in
wet weather
• Funding and permit application forms
There are also several individual state CSO permitting strategies. To date, 30 states
have submitted CSO permitting strategies. Twenty-one states have stated that they do not
require CSO permitting strategies either because they have no communities with combined
sewer systems or, if they have communities with combined systems, these communities have no
CSO discharges. Of the 30 strategies that have been submitted, EPA Regions have
unconditionally approved 19 and conditionally approved 3. Eight strategies are presently
unapproved.
Key CSO Issues. Some of the key CSO issues that must be considered are technology-
based standards, water quality standards, deadlines, and financing. Questions that relate to
these issues include:
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• Technology-Based Standards -
What minimum technology-based controls should be required of all
communities with CSO discharges?
• Water Quality Standards -
Should CSO systems be required to immediately comply with applicable
water quality standards regardless of costs?
Should EPA, as a matter of policy be encouraging states to downgrade
current water quality standards to existing uses to reflect financial
impacts?
• Deadlines -
Should statutory deadlines be extended for CSOs?
Should compliance with water quality standards be phased in over time?
• Financing -
What is the cost of CSO controls?
• Current estimates: $50 - $200 billion
How should CSO programs be financed?
• Current funding mechanisms: State Revolving Fund (SRF)
Program, local funding sources
Should there be a federal role in future financing of CSO control
programs beyond current Clean Water Act authorizations?
• Maintain current approach (funding through SRFs)
• Combination of SRFs and targeted grant funds to disadvantaged
communities
Alternative CSO Control Options. There are several alternative options to control discharges
from combined sewer overflows. The following section presents four options and their
relationship to the key CSO issues.
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Option 1: Implementation of EPA 1989 CSO Control Strategy.
Relationship to Key Issues
» Technology-based standards. Require six technology-based controls as minimum
BCT/BAT, and consider other control measures where appropriate.
• Water quality standards. Require compliance with water quality standards.
Evaluate whether appropriate to adjust water quality standards (downgrade,
temporary variance, seasonal limits) to reflect economic impacts.
• Deadlines. Require cmpliance with existing CWA deadlines for both technology-
based and water quality-based requirements. Since both these deadlines have
passed, compliance schedules in administrative or enforcement orders must be
used.
• Financing. References construction grants (which are no longer available) and
SRF as available ways to obtain funding for CSO control program
implementation.
Option 2: Legislative Action. Baucus/Mitchell S. 1081 requires states to inventory CSO
discharges within 1 year, and cities to develop CSO Elimination Plans within 3 years of
enactment. CSO Elimination is defined as no discharge during or following a l-year/6-hour
storm event. EPA must approve the municipal program within 3 months of submission only if
1) the statutory requirements for a "CSO Elimination Program11 are met and 2) the municipality
has adequate authority and financial resources are available. Cities must comply with these plans
within 5 years for discharges to section 305(b)(2)(B) waters and 7 years for other discharges
(2 year "good faith" compliance extensions are available).
Relationship to Key Issues
• Technology-based standards. Require the elimination of all CSO discharges
during or following a l-year/6-hour storm event. This in effect requires that any
CSO discharge resulting from such a storm receive secondary treatment before
discharge.
• Water quality standards. Require compliance with water quality standards.
• Deadlines. Require development of "CSO Elimination Programs" within 3 years
and implementation of those programs within 7 to 9 years after EPA approval.
(Note: Language provides that EPA cannot approve CSO Elimination Programs
unless it finds a municipality has "adequate financial resources.")
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• Financing. Provide grant funding authorization for states and municipalities up
to a total funding level of $10,000,000 in FY92, FY93, and FY94. Extend
eligibilities of other grants to include CSO controls. Extend eligibility of SRFs to
include CSOs.
Option 3: Combined Sewer Overflow Control Act. This act was developed by the CSO
Partnership. The proposal requires that:
• EPA must issue CSO permits in two phases.
• Phase 1 would require the elimination of dry weather overflows, proper operation
and maintenance of the system to minimize wet weather overflows, maximize use
of existing system, and implement the CSO study and plan requirement.
• Phase 2 must incorporate the technology-based and water quality-based controls.
• Requires compliance with water quality standards as soon as possible but
specifies no firm deadline.
• Provides for the establishment of wet weather water quality standards and a
variance from these standards when it is demonstrated that there is no
reasonable relationship between the costs and the benefits of complying with
these standards.
• Establishes a CSO Control Grant program ($500,000,000 in FY92 and in FY93).
Grants can be used to fund control program costs beyond the limit of the city's
financial capability to pay for the program with other funds which may be
available.
Relationship to Key Issues
Technology-based standards. Phase I permits require: 1) prohibition on dry
weather overflows, 2) implementation of sewer system O&M practices to
minimize CSOs, 3) maximum use of existing facilities to minimize CSOs, and 4)
development of site-specific CSO study and control plans
Water quality standards. Phase II permits require compliance with water quality
standards "as expeditiously as practicable" taking into account the city's ability to
pay and the availability of federal/state funding. Cost/benefit variances from water
quality standards available where no reasonable relationship between the costs
(economic and social) and the benefits of compliance.
Deadlines. No specific date or schedule for compliance with permit conditions or
achieving technology- or water quality-based requirements in the CWA. Phase II
permit compliance is linked to financing and ability to pay.
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Financing. Establishes a CSO Control Grant program ($500,000,000 in FY92 and
in FY93) for cities to use in implementing CSO control plans. Grants to be used
to fund control program costs beyond the limit of the city's financial capability to
pay.
Option 4: A policy paper was prepared by Gordon R. Garner, Executive Director, Louisville
and Jefferson County Metropolitan Sewer District. It would require:
• Permittees must have a state/EPA approved I&M program within 1 year.
• Systems with significant water quality impacts from CSOs must within 5 years
implement minimum requirements to eliminate floatables, eliminate excessive
fecal coliform impacts, eliminate through pretreatment any IU discharge that
causes toxicity violation of water quality standards, eliminate all CSO dry weather
overflows as quickly as possible.
• CSO Abatement Plan must be developed when there are significant impacts from
CSOs. Approvable CSO Abatement Plans include measures to reduce the CSO
event frequency; the pollutant loading and volume of untreated discharges by 85
percent; the maximization of capture, storage, and secondary treatment of first
flush flows at POTW if pollutant loadings in first flush are significantly higher
than in later flows.
• States/EPA may require additional CSO control measures for CSOs discharging
to selected receiving waters.
• Compliance deadline will be based on the cost of the abatement plan as a
function of CSO population served or the percentage increase in wastewater rates
needed to the finance abatement plan, whichever is longer.
• Abatement plans that cost more than 2,500 per equivalent customer or 1,000 per
capita financed over 20 years are considered not to be cost-effective and can be
scaled back. Permittees must still meet minimum requirements.
Relationship to Key Issues
• Technology-based standards. Systems with "significant water quality impacts"
from CSOs must meet implementation requirements within 5 years.
• Water quality standards. Requires controls to avoid "significant violations" of
water quality standards due to CSO discharges. Requires reduction in CSO
impacts "at least" to the point that other impacts are more significant (point
sources, nonpoint sources, naturally occurring background levels, etc.) and further
improvements in water quality can be better achieved by using available resources
to abate non-CSO impacts."
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Deadlines. Requires that minimum CSO control requirements be implemented
within 5 years. Cities requiring a more stringent plan must include in the plan a
schedule with appropriate interim target dates which become part of an
enforceable compliance schedule. Generally, longer deadlines (up to 20 years)
are established on a sliding scale linked to 1) size of city, 2) total costs, or 3)
percentage increase in wastewater rates.
Financing. Does not address the financing of CSO control program
implementation. Allows approved CSO Abatement Plans to be scaled back when
they cost more than 2,500 per equivalent residential customer or 1,000/per capita
financed over 20 years.
CSO Control Technologies. There are three types of control technologies to consider for
combined sewer overflow systems. The following list presents typical examples of these CSO
control technologies.
• Nonstructural controls
- Street cleaning
- Sewer flushing
- Litter control
- Industrial pretreatment programs
• Minimal structure controls
- Proper operation and maintenance of regulators and overflow control
devices
- Screening of CSO outfall
- Maximization of system's existing storage capacity
• Structurally intensive controls
- Off-system collection and storage
- Sewer separation
- Elimination of infiltration and inflow
- Swirl concentrators
Cost Estimates. As the experience with CSO control measures is very limited, to estimate the
total cost for all CSO control measures is very difficult. Many assumptions are made in any
attempt. Three approaches are presented here:
• Estimates based on needs surveys
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• Estimates based on design storms
• Estimates based on experience with major cities
Estimates Based on Needs Surveys. Needs surveys basically estimate the needs based on
four water quality goals: 1) aesthetics, 2) public health, 3) fish and wildlife, and 4) recreation.
The following list shows CSO needs survey estimates for the last 12 years:
Dollar Amount (1991 dollars)
Year (in billion dollars)
1978 46
1980 57
1982 46
1984 15
1986 17
1988 20
The latest needs surveys include only 328 communities. The following is an attempt to
extrapolate the needs survey total CSO cost to about 1,100 communities and allow some
adjustments for recent up-to-date estimates:
328 communities $20 billion
1,100 communities $32 billion
Adjustment for up-to-date estimates $50 - $70 billion
Estimates Based on Capture and Treatment of a Design Storm. Total inches of rainfall
varies greatly with frequency of storm. The following list of actual data for a location in New
York demonstrates this variation:
Storage and Treatment (6 hour duration)
Design Storm Total Inches
1 month 0.42
3 month 0.72
6 month 1.14
1 year 1.68
2 year 2.28
5 year 3.12
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If a one year 6-hour storm is considered as the design standard, the total national cost can be
estimated to be in the order of $150 to $200 billion. The assumptions for this estimate are as
follows:
National Cost for 1-Year 6-Hour Storm Event
2.5 million acres of CSO area
55 billion gallons collected
$2.00 to $2.50/gallon storage
Add 40 percent for secondary treatment
$150 to $250 billion
The cost for different storms can also be estimated as the cost that will be approximately
proportional to the inches of rainfall presented above. As can be seen, any change in the design
storm will change the cost substantially.
Storage and Treatment Cost (6-hour duration)
Design Storm Normalized Cost
1 month 0.25
3 month 0.43
6 month 0.68
1 year 1.00
2 year 1.36
5 year 1.86
Other Estimates. Several estimates were presented to the U.S. House of
Representatives Subcommittee on water resources hearing on April 1991. These were based on
the experience of the experts and varied from $56 to $322 billion.
Conclusions. Current plans for CSO control were briefly described. Several cost estimates
based on these plans and other available data are presented. As the abatement programs are
just starting and documented information is scarce, the estimates are based on many
assumptions and estimators' own experience, and thus may vary greatly. Although the estimates
vary from $30 to $300 billion, a range of from $50 to $150 billion appears most likely.
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STORMWATER CONTROL FOR PUGET SOUND
Peter B. Birch
Washington Department of Ecology
Water Quality Program
Olympia, WA
The Puget Sound Water Quality Management Plan. The 1991 Puget Sound Water Quality
Management Plan requirements form the foundation of the stormwater program being
developed by the Department of Ecology. The Plan was first adopted in 1987, updated in 1989,
and again in 1990. The Plan and the Department of Ecology's stormwater programs apply to
the cities and counties in the Puget Sound Basin.
Local Stormwater Program.
1) Basic Stormwater Program for ALL Counties and Cities
The Department of Ecology and the Puget Sound Water Quality Authority
(PSWQA) will adopt rules to implement the local stormwater program.
PSWQA's rule will emphasize procedures and processes while the Department of
Ecology's rule will concentrate on standards and criteria. In addition,
supplemental guidelines, including model ordinances, and a technical manual (see
below) are being prepared to describe how local governments can implement
their stormwater programs and meet the requirements of the rules.
The rules will set minimum standards for the following:
• Operation and maintenance programs are required for new and existing publicly
owned stormwater systems.
• Runoff control ordinances will address drainage, clearing, and grading, erosion
and sediment control, and protection of surface and ground water. They will
apply to all new development and redevelopment.
• Local governments will be required to adopt ordinances to ensure maintenance
and operation of privately owned stormwater facilities.
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• Local governments will be required to keep records of new drainage systems and
facilities.
Proposed schedule:
All cities and counties will be required to adopt ordinances and meet operation and
maintenance requirements 18 months from the effective date of adoption of the rules.
2) Comprehensive Stormwater Programs for Urban Areas
Rules and guidelines will be prepared for comprehensive stormwater programs
that will be implemented by all urbanized areas. This program is in addition to
the requirements of the basic stormwater programs described above. Urbanized
areas will be identified by the U.S. Bureau of Census definition.
These programs will address runoff from new and existing industrial, commercial, public
facilities and residential areas, including streets and roads.
At a minimum, each urban stormwater program shall include:
Identification of potentially significant pollutant sources and their relationship to
the drainage system and water bodies.
Investigations of problem storm drains, including sampling.
A water quality response program, to investigate sources of pollutants, spills, fish
kills, illegal hookups, dumping, and other water quality problems. These
investigations should be used to support compliance/enforcement efforts.
Assurance of adequate local funding for the stormwater program through surface
water utilities, sewer charges, fees, or other revenue-generating sources.
Local coordination arrangements such as interlocal agreements, joint programs,
consistent standards, or regional boards or committees.
A stormwater public education program aimed at residents, businesses, and
industries in the urban area.
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• Inspection, compliance, and enforcement measures.
• An implementation schedule.
• If, after implementation of the control measures listed above, there are still
discharges that cause significant environmental problems, retrofitting of existing
development and/or treatment of discharges from new and existing development
may be required.
Proposed Schedule:
Six of the larger cities (Seattle, Tacoma, Everett, Bellevue, Bellingham, and Bremerton)
and four early action areas will begin developing programs at date of adoption of the rules.
All urbanized areas will begin implementing programs by the year 2000.
Rule schedule:
The 1991 Puget Sound Water Quality Plan's target date to adopt the two rules is
November 1991.
Technical Manual. The Department of Ecology will develop and update a technical manual for
stormwater control practices. This manual will address:
• Erosion and sedimentation control at construction sites
• Detention/retention basins, infiltration, and conveyance systems
• Hydrologjc analysis
• Control of pollution in runoff from urban land uses
The manual will serve as the minimum technical standards for local jurisdictions. Those
that do not have their own manual may use the Department of Ecology manual; jurisdictions
with their own manual must meet or exceed Department of Ecology standards.
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Separate Technical Advisory Groups worked with the Department of Ecology to produce
a draft of the manual that was released July 1990. This draft was reviewed and presently is
being rewritten.
Proposed Schedule:
Another draft is being prepared for public review for July 1991.
Puget Sound Highway Runoff. The Department of Ecology has worked with the Washington
State Department of Transportation (WSDOT) to adopt a rule and develop a program to
control the quality of runoff from state highways in the Puget Sound basin. WSDOT will:
Adopt a Highway Runoff Manual equivalent to the Department of Ecology's
technical manual to enhance the quality of highway runoff
Adopt a vegetation management program
Include water quality best management practices (BMPs) as part of new
construction projects
Inventory and retrofit existing state highways with water quality BMPs where
practicable
Monitor where applicable
Submit biennial reports
Public workshops were held on the draft rule in January 1990, at Pt. Townsend, Everett,
and Tacoma, and meetings were held with the tribes. Public hearings were held in Bremerton
on March 13, in Everett on March 14, and in Tacoma on March 15, 1991.
Proposed Schedule:
The highway program is scheduled to be adopted in May and be effective in June.
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DISINFECTION
-------
TOTAL RESIDUAL CHLORINE
TOXICOLOGICAL EFFECTS AND FATE IN
FRESHWATER STREAMS IN NEW YORK STATE
Gary N. Neuderfer
New York State Department of Environmental Conservation
Avon, New York
Wastewater discharges frequently contain chlorine because it is used to disinfect potable
water and wastewater effluents, to control biofouling in cooling water systems, and in industrial
processes. The toxicity of chlorine to aquatic life has been the focus of extensive laboratory
research, but few field studies have documented the effects of chlorinated discharges on
freshwater aquatic life.
The fate of chlorine discharges to freshwater aquatic habitats has been the focus of
considerable research. These studies have shown that dilution, phototransformation, chemical
reaction demand and volatilization are the principle routes of chlorine dissipation in the aquatic
environment. The importance of each fate route is variable due to chlorine species present in
the effluent, physical characteristics of the receiving stream, and pH, temperature, turbidity and
chlorine demand of the receiving water.
National Pollutant Discharge Elimination System (NPDES) and State Pollutant
Discharge Elimination System (SPDES) permits for publicly owned sewage treatment plants
(POTW's) often require chlorination of the effluent to control human pathogens, thus reducing
the threat of waterborne infectious diseases. The U.S. Environmental Protection Agency (EPA)
and New York State Department of Environmental Conservation (NYSDEC) have established
ambient water quality standards (AWQS) for TRC to protect freshwater aquatic life. The EPA
AWQS is 11 ug/L as a four-day average and 19 ug/L as a one-hour average. The NYSDEC
standard is 5 ug/L for waters classified AA, A, B and C, and 19 ug/L for class D waters. These
AWQSs were derived from toxicity data obtained from single-species laboratory toxicity tests
with freshwater invertebrates and fish.
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Project Objectives. The project scope was limited to the effects of TRC from POTWs that
practice chlorine disinfection four or more months per year and discharge to lotic freshwater
streams.
The study objectives were:
To determine which POTWs were causing significant adverse effects to aquatic
life
To estimate the total stream distance in New York State that is affected by TRC
from these discharges
To use the study data to improve programs and polices on chlorine disinfection
to minimize adverse effects on aquatic life
Study Methods. The dilution of effluents in receiving streams is easy to predict with reasonable
accuracy. Plant design flows and receiving stream minimum average 7 consecutive day stream
flow expected to occur every 10 years (MA7CD10) are determined as a routine part of the
SPDES permit process. The factors affecting chlorine's fate in the aquatic
environment have wide temporal and spatial variability. This study combined these factors by
only looking at chlorinated effluent dilution and in-stream TRC concentrations. Effluent
dilution rates at MA7CD10 flows were then correlated with in-stream TRC concentrations to
predict which plants are likely to cause significant adverse aquatic ecosystem impact in
the receiving stream.
Twenty-seven sites were studied during 1988 and 1989. The site-study techniques were
designed:
» To identify significant TRC-caused impacts on aquatic organisms in the receiving
stream
• To locate the TRC impact zone under varying physical conditions
• To predict the dilution rates where in-stream TRC would be < 5 ug/L
A battery of physical, chemical, and toxicological tests were used to evaluate each study site.
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Tracer dye studies were used to determine in-stream time of travel, delineate the
effluent zone of mixing, measure discharge and stream flows, and determine chlorine dissipation
rate by comparing dye and TRC concentrations. Rhodamine WT dye was metered into the
effluent near the outlet from the chlorine contact chamber. Fluorescence was determined with
a portable fluorometer.
Chemical analyses included TRC, free chlorine, pH, ammonia, hardness, alkalinity,
conductivity, dissolved oxygen, and temperature. Chlorine concentrations were measured using
a modification of the amperometric titration method within 30 minutes of sample collection.
The quantitation limit for this method was 5 ug/L chlorine.
Acute 48-hour aquatic toxicity tests were conducted on unchlorinated composite effluent
samples and in situ (in receiving stream) upstream and downstream from the chlorinated
discharge. Daphnia magna neonates (24 to 48 hours old) and fathead minnow larvae (4 to 10
days old) were used in both tests. The unchlorinated effluent tests defined non-chlorination
induced effluent toxicity and helped isolate the TRC component of in situ toxicity.
All sites were studied during the low stream flow and warm water temperature period
from June to September. Physical and chemical tests were done during daylight hours only,
except at two sites where data were collected around the clock to determine diurnal trends.
Seven sites with year-around disinfection requirements were studied during the winter of
1988/89. These winter studies consisted of monitoring only the effluent and receiving stream
TRC concentrations, without the other chemical, physical, or toxicologjcal testing. The objective
was to determine the relative extent of winter versus summer receiving stream plumes.
In-stream TRC Versus Dilution. Initial work with several analysis of variance and multiple
regression statistical methods indicated that there was too much variability in the database to
produce meaningful statistical results. That variability was not surprising, since dilution is only
one of several factors that result in TRC dissipation in the receiving stream.
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An empirical interpretation of the data base can be gained by looking at in-stream TRC
based on the average concentration after mixing and at individual samples collected after
mixing. The average TRC site concentration data indicate that the break-point for in-stream
TRC concentrations exceeding the 5 ug/L AWQS lies somewhere between 32.9:1 and
39.5:1 dilution. At dilution ratios greater than this break-point, the receiving water is able to
assimilate the effluent TRC. The individual water sample TRC data collected at the first
downstream'station where mixing was complete supports a similar conclusion. At dilutions
greater than 40:1, only two samples had chlorine concentrations > 5 ug/L when the
effluent TRC concentration did not exceed 2,000 ug/L. Both incidents were at a site where the
stream temperature was less than 17°C or a chlorine slug may have occurred.
These empirical data interpretations were used to formulate a potential approach to
SPDES permit criteria to assure compliance with the 5 ug/L AWQS. Plants with MA7CD10
dilution of greater than 40:1 were in the no-effect category and would receive a 2,000 ug/L
permit limit. Plants with greater than 30:1 and less than or equal to 40:1 dilution would receive
a permit limit of 1,000 ug/L. Those with greater than 15:1 and less than or equal to 30:1
dilution would receive a permit limit of 500 ug/L. All plants with MA7CD10 dilutions less than
or equal to 15:1 would be required to use alternative disinfection, dechlorination or no
disinfection.
This project was not designed to measure the relative importance of each major TRC
dissipation route. But the data show that there was a significant and rapid initial loss of TRC
other than dilution between the discharge and the point of complete mixing with the receiving
stream. The rapid initial dissipation of TRC suggests that chemical demand was responsible for
the major portion of this chlorine loss in the receiving stream. Other studies have documented
this initial chlorine loss as well. In this study, the mean initial loss was 70.2 percent (SD = 19.2
percent). The majority of the study sites were located on small, heavily shaded, and
low-gradient streams where mixing was complete within a few minutes. Most of the effluent
TRC was combined chloramine species. Because chloramines have been shown to be less
subject to photodegradation than free chlorine, it is unlikely that photodegradation played a
major role in chlorine dissipation. The non-turbulent nature of the study streams was likely to
minimize volatilization losses as well.
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Kilometers of Stream Affected. An estimated total of 158.4 kilometers of stream have mean
TRC concentrations that would exceed the 5 ug/L AWQS at MA7CD10 flow during the
summer. Compared to a total of 129,710 kilometers of freshwater streams in New York State,
those potentially adversely affected by TRC from POTW's comprise 0.12 percent of the total.
Had winter data and more nighttime data been included in the estimate, this would have
increased significantly.
Diel In-Stream TRC Concentrations. Effluent and in-stream TRC concentrations were analyzed
on a 24-hour-a-day basis at two sites. Effluent and in-stream TRC concentrations were
significantly higher (p=0.05) during nighttime than during daylight hours.
Photodegradation of TRC has been documented in receiving streams. An EPA study
found that when chlorine alone was added to artificial streams (assumed TRC mostly present as
free chlorine), there was a strong diurnal trend in in-stream TRC concentrations due to
photodegradation during daylight hours. When chlorine and ammonia were added to closely
simulate a wastewater treatment plant discharge (assumed TRC mostly present as combined
chlorine), no in-stream diurnal trend was observed. The TRC at the two sites in this study was
present as combined chlorine, yet there were strong diurnal trends in in-stream TRC
concentrations.
The diurnal TRC trends were due to increased mass loading of TRC from the effluent
to the receiving stream at night. Effluent mass loading is defined as effluent TRC concentration
times effluent flow. Mass effluent TRC loading was proportional to in-stream TRC
concentrations.
In situ TRC Toxicitv to D. maena and Fathead Minnow. This project was not designed to
produce an LC50 for D. magna neonates and fathead minnow larvae under field exposure
conditions to TRC. The in situ toxicity test data from various sites was composited to get an
acute dose-response curve. There were indications in the data base that the toxicity of free and
combined chlorine toxicities might be different. Only data from sites where the majority of
effluent TRC were combined chlorine were used in the LC50 calculations. Data from sites with
upstream toxicity were also eliminated. Depending on which data points were used and the
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LC50 calculation method, the 48-hour LC50s ranged from 4.1 to 6.1 ug/L TRC for D. magna
neonates and 30 to 70 ug/L for fathead minnow larvae. The laboratory-derived species mean
acute values for these two species are 28 and 106 ug/L TRC, respectively. These field data
LCSOs indicate that in-stream TRC toxicity is higher than in the laboratory.
There are several factors that might affect the field LCSOs. These factors include:
• In-stream TRC concentrations were higher at night, but most of the data used in
the LC50 calculation were from the daytime
• Considerable variation in the exposure concentration
• May be difference in chlorine species tested between laboratory and field studies
• Toxicants in effluent and receiving stream
• Physical stresses of in situ exposure
Catfish (Ictalurus punctatus) have shown a similar response under field exposure conditions.
The catfish species mean acute value is 90 ug/L. When channel catfish were exposed in streams
where only chlorine was added, so the majority of TRC was presumed to be present as free
chlorine, there was no significant mortality at TRC concentrations as high as 183 ug/L. When
chlorine and ammonia were added, so it was assumed that most of the TRC was present as
combined chlorine, there was complete channel catfish mortality at 25 ug/1 and reduced growth
at less than 1 ug/L TRC. There is a clear indication that under field exposure conditions
combined TRC is significantly more toxic than expected and more toxic than free TRC.
. Fate of Free Versus Combined Chlorine. It is generally accepted that combined chlorine
degrades slower than free chlorine. An EPA study found that in-stream TRC was more
persistent when only chlorine was added to a study stream. The data from this study indicated
that after initial chemical demand by the receiving water, free chlorine is more persistent than
combined chlorine. It is possible that the free chlorine analysis method is measuring a more
persistent chlorinated organic chemical formed during the chlorination process. This unknown
chlorinated organic compound reads as free chlorine in the test, but it is more persistent and
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less toxic to aquatic life than combined chlorine species. This solution is only speculative, and
there could be other explanations for these observations.
Summer Versus Winter TRC. The data indicate that the average effluent TRC concentrations
were higher and in-stream plumes extend farther downstream during the winter. This was likely
due to reduced rates of chemical demand reactions, photodegradation, and volatilization at
colder water temperatures.
The impact of larger in-stream TRC plumes on aquatic life are unknown. The literature
indicates that at colder water temperatures the toxicity or rate of toxicity to aquatic life is
reduced. Chlorine toxicity at cold stream temperatures has not been well characterized.
The data from this study indicate that toxicity or rate of toxicity decrease proportional to
stream temperature. The lack of mortality to in situ test organisms at some sites appeared to be
due to reduced stream temperatures.
Compliance with SPDES TRC Permit Limits. The data base identifies a serious problem of
inadequate control of effluent TRC concentrations to protect aquatic life in the receiving stream
while achieving adequate effluent disinfection. During the summer studies, 14 percent of the
effluent samples analyzed exceeded the SPDES permit limits for TRC. This increased to 44
percent of the samples during the winter sampling. Out of 27 sites, only 10 were always in
compliance with their SPDES TRC permit limits. Two of these plants had electro-chemical
feedback systems, one was flow-proportional, and the remainder had static chlorinators.
Sites with static chlorinators, with or without manual diel adjustment of the chlorine feed
rate, in general were not able to consistently meet their SPDES TRC permit limit. Sites with
electro-chemical feedback systems that analyze the effluent TRC concentration and
automatically adjust the chlorine feed rate did the best job of controlling effluent TRC
concentrations. This was especially true if the systems were maintained daily.
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EPA DISINFECTION POLICY AND GUIDANCE UPDATE
Robert Bastian
U.S. Environmental Protection Agency
Washington, DC
State/EPA Task Force. A joint state/EPA Task Force was formed in 1988 to review EPA's
position on municipal wastewater disinfection. This review of the Agency's disinfection policy
was initiated to address concerns about the potential adverse effects on aquatic life and human
health from wastewater chlorination. In part this issue was raised by an EPA study released in
1986 that suggested that up to two-thirds of the POTWs were likely to discharge wastewater that
exceeds the acute freshwater chlorine criteria, putting some 3,500 different water bodies at risk.
The Task Force reviewed information which became available since 1976 to determine if
changes were needed to the existing policy (issued in 1976), which calls for disinfection
requirements to be set on a case-by-case basis, consistent with applicable state water quality
standards for bacterial indicator organisms and for chlorine.
A 2-day workshop was held in November 1988 to help summarize the current status of
information associated with a variety of topics relevant to disinfection of municipal wastewater
discharges including: the status of alternative disinfection technologies; water quality criteria for
chlorine and indicator organisms; and case history studies, including infield studies of residual
chlorine toxicity and application of alternative indicator organisms. The workshop and other
sources of information served as the basis of a technical support document and proposed draft
language designed to strengthen the existing case-by-case policy.
Task Force Findings and Conclusions. In general, the Task Force found that while wastewater
disinfection is necessary to protect public health, as currently practiced it may present significant
risks to aquatic life. These risks can be lessened by reducing disinfection where unnecessary or
excessive and utilizing dechlorination or alternative technologies to chlorination. In addition,
the Task Force agreed that the risks to aquatic life due to disinfection, and alternatively, the
risks to public health from reducing disinfection, are not fully understood.
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Some of the specific conclusions reached by members of the Task Force based upon
their examination of disinfection policies, practices, and the existing scientific data included the
following:
Residual chlorine is toxic to aquatic life at the low levels produced in wastewater
treatment effluents, but more information is needed on the actual instream risks,
particularly chronic effects, in order to better understand the impacts that
chlorine and other disinfectants have on aquatic life.
Although chlorination produces organic chlorinated by-products in wastewater,
some of which are toxic and potentially carcinogenic, they are generally not
considered to be a significant human health concern in wastewater effluents
because they are produced at low levels. However, not enough is known about
the possible aquatic life effects of these compounds, such as bioaccumulation and
chronic toxicity.
Numeric chronic water quality standards developed by the states, based on EPA
criteria or site-specific criteria, generally protect aquatic life from adverse impacts
due to unacceptable levels of chlorine toxicity.
Reduction of wastewater disinfection with chlorine will protect aquatic life by
reducing the levels of chlorine to which aquatic organisms are exposed. This can
be accomplished through seasonal disinfection, lower levels of disinfection, use of
alternative disinfection practices, and elimination of disinfection where
appropriate. More information is needed on the relative public health risks and
aquatic life benefits of changing disinfection practices.
Improvements in the efficiency of chlorination can effectively reduce chlorine
discharges at many treatment plants. Where further reductions are needed,
technological modifications to the treatment process will be necessary.
Dechlorination is generally easily and economically retrofitted to chlorination
facilities. However, dechlorination may not remove all potential toxicity.
Concerns have been raised that even an infrequent failure of a dechlorination
system that allows chlorine to enter receiving waters could substantially impact
aquatic life. Alternative disinfection technologies such as ultraviolet radiation
and ozone are often less hazardous to aquatic life than chlorination and are
becoming viable both technologically and economically.
New indicator organisms such as enterococci and E. coli can more accurately
determine risks associated with contaminated water than can fecal coliform
measures. However, further research may be needed to determine the
appropriateness of these indicators in certain situations.
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Proposed Revised Policy Language. Proposed draft policy language, which was widely circulated
for comment, emphasized reducing or eliminating wastewater disinfection requirements where
possible to do so without adversely affecting public health. It also stressed that the protection
of aquatic life from the adverse impacts of chlorination residuals and by-products may require
operational modifications at wastewater treatment facilities to improve the efficiency of
chlorination practices, dechlorination following chlorination, or the use of alternative forms of
disinfection. Comments received from the Task Force members, state water resources agencies
and health departments, and other interested parties in response to the proposed draft language
were mixed, some supporting the stronger language and others strongly opposed to any
"weakening" of disinfection requirements for fear of increased public health impacts. Many
reviewers noted that the draft did not functionally change the existing case-by-case policy, and
noted the need for better guidance to assist states with evaluating the potential public health
and aquatic life impacts of reducing or eliminating disinfection requirements.
Results of Task Force Policy Review. The results of this policy review effort have lead to a
decision by EPA not to issue a new or revised policy statement, but to restate and emphasize
the existing case-by-case policy issued in 1976 and to provide updated technical guidance. The
outputs generated by the review of EPA's position on municipal wastewater disinfection include
the following:
• A foldout titled "Municipal Wastewater Disinfection: Protecting Aquatic Life
and Human Health from the Impacts of Chlorination" (dated February 1991) to
be widely circulated
• An updated version of the proceedings of the municipal wastewater policy review
Task Force workshop in the form of a book edited by and with an overview
prepared by Dr. Charles Noss to be published by Lewis Publishers in 1991
• A "Municipal Wastewater Disinfection State-of-the-Art Document" produced
from the policy update technical support document to be published by EPA
during 1991
• A brochure summarizing the State-of-the-Art document to be published by EPA
during 1991
In addition, as funding allows, a methodology with sample case studies is being developed to
help states with evaluating the potential public health and aquatic life impacts of reducing or
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eliminating disinfection requirements. Finally, consideration is being given to updating the
Agency's 1974 shellfish sanitation guidance document "Protection of Shellfish Waters" to better
reflect the current state-of-the-art and explore potential improvements to current techniques for
protecting shellfish sanitation.
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CONSTRUCTED WETLANDS
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USE OF CONSTRUCTED WETLANDS TO TREAT
DOMESTIC WASTEWATER, CITY OF ARCATA, CALIFORNIA
Robert A. Gearheart
Environmental Resources Engineering Department
Humboldt State University
Arcata, California
Introduction. In recent years, there has been an increasing need for the development of
improved cost effective methods for wastewater treatment, specifically for those communities
which could be categorized as small to medium in size. While the "progress" Of our industrial
society continues at a rapid rate, technological advances in treatment methods for the new
variety of toxic chemicals, exotic organics, and general domestic sewage seems stymied. Initial
construction cost and continuing operational costs of wastewater treatment plants are the most
significant factors affecting the technology selection process. Along with the consulting
engineer's lack of understanding of natural process, this has focused the need to consider
alternative and innovative wastewater treatment processes. The cost to small communities for
reaching the same level of wastewater treatment as large communities using standard technology
is disproportionately high. Although large sums of money have been made available by the
Federal and State governments for pollution control systems, relatively few funds are being
applied to advance research and development of improved treatment technology. Since present
wastewater treatment systems are primarily designed after "natural" mechanisms for pollution
abatement (trickling filters, activated sludge, oxidation ponds, etc.), it is ironic that reliable, cost-
effective, and efficient treatment of wastewater utilizing controlled nutrient uptake by
macrophytes and microbial communities in a marsh is not in wider use and encouraged by
regulatory and funding agencies.
Use of wetland wastewater treatment systems based on emergent plant species and their
associated microbial communities is more widespread than use of floating aquatic plant systems.
Most wetland processes involve the growth of rooted emergent plants such as reeds and
bulrushes in an artificial bed and the passage of wastewater either across the surface of the
wetland (surface-flow systems), or through the growing medium in which the wetland plants are
rooted (subsurface-flow or root zone systems).
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Surface-Flow Wetlands—General. The surface-flow wetland approach utilizes the stems of
wetland plants as the main site for effluent treatment. In this method, beds of emergent
wetland plants, such as reeds or bulrushes, are flooded with pretreated effluent which is retained
within the wetland system for a predetermined period prior to discharge.
Surface-flow wetland plant stems provide a substratum for the microorganisms which
achieve the desired effluent treatment. Wetland processes result in an accumulation of organic
material in the bottom of the system where microorganisms also occur in high densities and
further enhance effluent treatment, particularly in terms of nitrogen elimination (Bartlett et al.,
1979) and anaerobic decomposition of detrital material to carbon dioxide and organic acids.
Figure 21 depicts the processes involved as suspended solids are removed in the initial volumes
of a wetland treatment system. The City of Arcata, California, has been experimenting for 8
years with twelve 6 x 10 meter pilot project cells, two 2V2 acre wetland treatment cells, and 31
acres of effluent receiving surface flow wetlands (Gearheart, 1985).
Subsurface Flow Wetlands—General. The principle behind the subsurface-flow wetland
treatment system involves passage of wastewater through a specially prepared soil, sand, or
gravel medium in which reeds or other emergent plants are grown. Wastewater treatment
occurs in the growing medium, principally as a consequence of the growth of wetland plant
rhizomes, which are claimed to enhance the hydraulic conductivity of the growth medium and
introduce oxygen into adjacent areas of the growing medium.
Surface Flow Wetlands—Natural. Discharge of pretreated wastewater to natural wetlands has
been a widespread practice for many years in the United States, where a number of sites have
been identified as being the subject of ongoing discharge for more than 50 years (Hammer and
Kadlec, 1983). Discharge sites have been reported from Florida to Canada's Northwest
Territories (Nichols, 1983). In the United Kingdom, wetlands have been used for treatment of
wastewater for more than 100 years at some sites (Cooper and Boon, 1987).
In general, few water quality problems have been observed with discharges to natural
wetlands, but the assimilative capacity of natural wetlands has only been monitored in detail
since 1960 (Knight, 1985), and in the light of insufficient long-term data some workers advocate
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caution in the management of natural wetlands to which wastewater is discharged (Nelson and
Weller, 1985).
Constructed Wetlands—Specific. The methodology of constructed wetlands, based on
constructed basins planted with wetland species, was pioneered by Dr. K. Seidel in the 1950s
(Rossiter and Crawford, 1984).
This methodology is presently utilized in the Netherlands, where it is applied to
intermittent flows such as campsites, or sewage disposal from small communities (DeJong and
Koridon, 1985).
Use of constructed wetlands for surface-flow effluent treatment in the United States and
Canada is presently restricted to a series of pilot scale trials at Arcata in northern California
(Gearheart et al., 1982; 1983; 1985), Gustine in southern California (Crites and Mingee, 1987),
Orlando and Lakeland in Florida (Feeney et al., 1986), Listowel (Herskowitz et al., 1987), and
Port Perry in Ontario, Canada.
It is emphasized that wetland treatment results might be interpreted in relation to the
particular characteristics of the wetland system for which the results have been derived.
Accordingly, treatment data presented in this section should be interpreted in the light of
associated data on wetland characteristics. The following results generally represent the level of
treatment effectiveness reported for such systems and are not intended to comprise a definitive
compilation of wetland treatment capabilities.
BOD. BOD (biochemical oxygen demand) is a measure of the oxygen uptake in a given aquatic
system principally as a result of the biochemical processes of the microorganisms in that system.
High levels of BOD in wastewater can result in dissolved oxygen depletion of the receiving
waters to which wastewater is discharged. The City of Arcata's pilot project showed that lower
hydraulic loading rates produced higher BOD removals. Seasonal variations in effluent
concentration were affected by vegetation type, density, and distribution. The rate varied from
41 to 65 percent. Those cells loaded at lower rates consistently produced BODs of 20 mg/L or
less. Retention periods of 200-300 hours produced BODs of 10 mg/L or less.
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The lowest BOD treatment efficiency value was reported for a subsurface-flow wetland
which was reported as not being operated effectively (Lienard, 1986). For remaining sites which
were operating correctly, reported BOD reductions ranged from 97 percent reported for long-
term surface-flow wetlands in the Netherlands (Greiner and DeJong, 1982), to 56 percent
reduction reported as an overall average for a surface-flow system at Arcata (Gearheart et al.,
1983). At Arcata quarterly BOD reductions ranged from 25 percent to 88 percent for oxidation
pond effluent, and reduction was found to be significantly influenced by temperature and low
rate.
Constructed wetlands were able to process shock organic loads with little to no effect on
effluent quality. Figure 22 shows a range of organic loadings from 30 Ibs/acre/day to 300
Ibs/acre/day (Gearheart et al., 1985). The effluent BOD did not significantly increase until
organic loadings of 200 Ibs/acre/day or greater were observed. Suspended solids levels, on the
other hand, were minimally affected even at this higher loading. There are very few wastewater
treatment processes that can produce an acceptable effluent quality over an order of magnitude
increase in the BOD and suspended loading to the system. This ability to accept shock loads
and to recover without any external process control is an important characteristic of wetland
treatment systems. Figure 22 shows these relations as the effluent BOD remains low and stable
up to the 150 Ibs BOD/acre/day loading. At these higher loadings, though, the pounds of BOD
removed are a function of the loading. This suggests that a wetland system can serve both as a
roughing and a polishing system in a wastewater treatment train as it applies to BOD and
suspended solids removal.
The wetland system affords a complex microbial community which processes both
particulate and dissolved organic material as it moves through the various communities. The
effect these microbial communities have on BOD removal can be seen in Figure 23.
It is clear that properly established and operated wetland treatment systems have the
potential to significantly reduce BOD levels in wastewater, but that wastewater influent
characteristics and wetland design will have a major influence on the level of BOD reduction.
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1
en
•3
1
u
8-
3
00
20-
12345
Detention time (days)
Figure 21. Suspended Solids Removal as a Function of Organic Loading over a 55 Week
Period
CELL 10
8 30°
03
1
I
g
i
8
PQ
v>
200-
100 H
y= - 0.2859 + 0.8054x R » 0.97
Q EFFBOO
• LBS REMOVED
100 200
Lbs BOD/Acre/Day
300
Figure 22. Regression Curve of BOD Removal versus BOD Loading to Arcata Pilot Project
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Suspended Solids. The suspended solids (nonfilterable residue) content of wastewater is of
direct water quality significance in terms of turbidity in receiving waters, and indirectly in
relation to the associated transport of other waste constituents such as nitrogen, phosphorus,
and BOD.
Suspended solids were removed in the first sections of the Arcata pilot project wetlands.
This represents a theoretical retention time of about one day. This autoflocculation/
sedimentation process builds a significant detrital bank in the upstream section of the wetland.
This detrital bank is about 70 to 90 percent of the volume in this first section after 8 years of
continuous loading. The detrital bank extends in a tapered fashion 75 percent of the length of
the cell (Gearheart et al., 1985). Organic loadings of suspended solids are approximately zero
order kinetics over the range 0 to 200 kg/ha/day, reflecting this progressive accumulation
through the cell length (Figure 24).
The effectiveness of constructed wetlands to treat domestic effluent can best be seen, as
in Table 8, by comparing the 8 years of research and monitoring in Arcata (Gearheart et al.,
1982, 1985). Table 8 shows the removal efficiency and effluent quality of the two pilot projects
and full-scale AMWS. The variations in suspended solids can be attributed to the high fraction
of open water at the Arcata Marsh and Wildlife Sanctuary compared with the pilot project's
densely vegetated water volume. The effectiveness of wetland systems to consistently (8 years of
data to date) remove SS and BOD at a level significantly below secondary standards is
noteworthy.
The dissolved oxygen levels in the wetlands is a function of the organic loading and the
fraction of open water. In the first pilot project, the cells were totally vegetated by the end of
the 2-year study. The average dissolved oxygen level was lowest in this study at 1.1 mg/L.
Compare this with the full-scale project where the open water fraction is 75 to 90 percent and
where the average dissolved oxygen was 5.0 mg/L reflecting the oxygen input from
phytoplankton populations.
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Data from "BOD K VALUE"
60
50
40-
Q
o
CQ 20-
10-
0
y - 38.5703 * 10"(-0.1092X) R - 0.95
BOD (mg/l)
0 1 2 3 4 56
Days
Figure 23. BOD Removal through Pilot Project Cell Showing the First Order Removal of BOD
through a Compartment Cell
§
E
~wT
T3
-.3
o
CO
"8
•a
1
V)
3
co
25-
20 -
15 -
10-
5 -
0 -
a SS mg/l
Q
o n
a0 Qa a Q
0 100 20
Kg/Ha/Day
Figure 24. Suspended Solids Removal through Pilot Marsh 8 (Samples Taken at 7 Weirs
through the 200-ft length)
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Nitrogen and Phosphorus. The nitrogen component of wastewater is of water-quality
significance (along with phosphorus) in relation to the potential enrichment of receiving waters,
which can lead to excessive algal growth and eutrophication.
The rate of nitrification is dependent on temperature and the oxygen availability in the
wetland (Stowell et al., 1981), and the process is only possible where oxygen can readily diffuse
to the reaction site (Hammer and Kadlec, 1983). For this reason, anaerobic wetlands which
may have been subject to high BOD loadings and surface flow wetlands which for a number of
reasons may have low dissolved oxygen levels, will not be effective as nitrification systems—for
example, Arcata (Gearheart et al., 1983). Oxygen translocation by plant roots has been
reported as potentially useful in this regard, particularly if the wetland plants are grown
hydroponically (Stowell et al., 1981).
In general, it appears that surface-flow wetlands are not effective nitrifiers as a
consequence of low dissolved oxygen levels, but they are potentially effective denitrifying
systems in view of the presence of anaerobic areas. Surface-flow wetlands would therefore
potentially be very effective in nitrogen removal for highly nitrified effluents.
Subsurface flow systems have been found to be relatively poor at denitrification unless
supplemental carbon is added (Gersberg et al., 1984, 1986). However, in view of the potential
for oxygen translocation by the roots, subsurface flow systems are potentially valuable in
nitrification.
Reported nitrogen removal efficiencies for wetlands vary for surface flow wetlands from
around 26 percent as an average at Arcata (Gearheart et al., 1983), to 88 percent for a long-
term detention system in the Netherlands (Greiner and DeJong, 1982); and for subsurface-flow
systems 13 percent for an inefficient system at Kalo in Denmark (Brix and Schierup, 1987) to 95
percent for a carbon supplemented system at San Diego (Gersberg et al., 1984; 1986).
The ammonia nitrogen levels from the oxidation varies significantly as a function of the
algae and bacteria. As the phytoplankton population grows, ammonia is taken up by the plants.
As zooplankton reduce the population and excrete ammonia as a byproduct, the levels go back
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Table 8. Comparison of Pilot Project and Full-Scale Results for NPDES
Parameters (Percent Change Oxidation Pond Effluent through
Wetlands) 1980-1988
BOD
Mean
% Change
% Less 30 mg/L
% Less 20 mg/L
% Less 10 mg/L
SS
Mean
% Change
% Less 30 mg/L
% Less 20 mg/L
% Less 10 mg/L
Dissolved Oxygen
Mean
% Change
pH
Mean
% Change
Theoretical Retention Time/s (days)
1981 Average
1982 Average
First
Pilot
Project,
AH Cells
11.4
-56
100
84
37
5.3
-85
100
100
91
1.5
-73
6.5
29
1.5-30
3.7
9.0
Second
Pilot
Project,
All Cells
13.8
-73
100
72
33
10.8
-80
100
93
43
1.1
-76
6.1
-14
Full-
Scale
Operation
12
-55
100
81
18
14
-54
100
78
45
5.0
-27
7.1
-6
Open Water Fraction
0-10
0-25
75-90
-141-
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up again. Very little ammonia is oxidized to nitrates in the oxidation ponds. The nitrifying
bacteria need attachment sites which are not found in the open water volumes of an oxidation
pond. As can be seen in Figure 25 (Gearheart et al., 1985), the influent varies from 3-4 mg/L to
35 mg/L over the study period of March through July.
Figure 26 shows the same time period with two different loading rates. Cell 5 was at
2.94 gpd/ft2 and cell 11 was loaded at 1.47 gpd/ft2. A similar phenomenon can be seen in Figure
26 compared with Figure 25. The only difference is that the vegetative system became saturated
faster for the higher loading rates. Cell 5, for example, did not remove ammonia nitrogen to
the 1 mg/L level. Cell 11 which was loaded at 3 times the rate of cell 3 saturated at the 18th
week, while cell 1 saturated at the 25th week.
It is concluded that nitrogen removal by surface-flow or subsurface-flow wetlands is
presently relatively consistent as a function of temperature, plant density, and nitrogen loading.
However, wetlands have a number of important attributes which should lead to effective
nitrogen removal, including wetland soil-water characteristics and an inviting environment for
denitrifying bacteria. Work with carbon supplementation (Gersberg et al., 1984; 1986) indicates
that nitrogen removal mechanisms can be optimized and that the means of optimizing these
nitrogen removal mechanisms is clearly an area for active research (Howard-Williams, 1985).
The removal of phosphorus from wetland systems is intermittent, and little is understood
about the mechanisms involved in uptake. The principal phosphorus removal mechanisms are
precipitation and adsorption to sediments, with secondary mechanisms including plant uptake
and sedimentation (Tchobanoglous, 1987). Phosphorus is rapidly immobilized in organic soils,
and thus saturation is reached reactively rapidly with the process being partially reversible
(Hammer and Kadlec, 1983). Ultimate removal of phosphorus from wetland systems could be
achieved by harvesting of plants, dredging of sediments, or resolubilizing of phosphorus stored
in sediments and released to receiving waters when it would have the least environmental
impact (Stowell et al., 1981).
442-
-------
^
s
c
u
1
Z
cd
1
<
30-
20-
.
10-
Q Influent « Q
• Cell 3
0
" *^ n
^^j
a a « Q
Q » DQ
a Q *
Q • * ••_
Q Q ^ *
Q °Q Q ••
•a ncP
^••••j •••^^•••^••' . j
0 10 20 30 40
Twice Weekly Samples 3/15-7/19/86
Figure 25. Ammonia Nitrogen Levels in Arcata Pilot Project Influent and in the Effluent from
Cell3
40
30 -
'I 20 -I
o
10-
Influent
Cells
Cell 11
\ • %
a *•• •••
QQ
• •••
^'
0 10 20 30 40
Bi-weekly Samples March 11 through July 19
Figure 26. Ammonia Nitrogen Levels in Arcata Influent and in Effluent for Cells 5 and 11
-143-
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Phosphorus is commonly released during winter in wetland systems (Wile et al., 1981;
Stowell et al., 1981) and this would be consistent with release during time of minimal
environmental sensitivity.
Phosphorus uptake by the macrophytes can be seen from data collected at the Arcata
pilot project study (Figure 27, Gearheart et al., 1983). The removal of soluble phosphorus from
the water column, approximately 3 mg/L, is correlated with the growing season for a hydraulic
loading rate of 0.5 gpd/ft2. This represents about 30 acres per million gallons of secondary
effluent. Uptake occurred for only the four months of the growing season. Over the whole
year, the phosphorus removal was approximately 10 percent at the lower loading rates and 0
percent at the higher loading rates.
Reported wetland removal results indicate a variable wetland performance with net
phosphorus removal rates ranging from 0 percent in subsurface-flow systems (Phillips et al.,
1987) and surface-flow systems (Gearheart et al., 1983) to 79 percent for a long-term surface-
flow system in the Netherlands (Greiner and DeJong, 1982) and 83 percent in sand/soil based
subsurface-flow systems in Denmark (Brix and Schierup, 1987).
Metals. In wetlands, metals are removed from wastewater by plant uptake, chemical
precipitation, and ion exchange with and adsorption to settled clay and inorganic compounds.
However, it is likely that the potential capacity of wetlands to remove metals by plant uptake
and harvesting will be small, and ultimate removal of metals from wetlands systems will probably
be most effectively achieved by methods for the removal of phosphorus (Stowell et al., 1981).
Fecal Coliform Removal. Wetlands have been shown to effectively remove fecal coliform
organisms (Gearheart et al., 1985; Gersberg et al., 1984). The mechanisms for removal have
been suggested to be flocculation sedimentation, adsorption, temperature ingestion, and
denaturing (OR potential, UV light, etc.) (Ives, 1986). Data from the Arcata Marsh pilot
project show a significant removal of fecal coliform in an experimental cell (20 x 200 ft) with a
theoretical detention time of 6 days. The removal data fit a logarithmic removal model with an
R value of 0.99 (Figure 28). The experimental constructed wetlands removed approximately 99
-144-
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a
«
a
a.
I
13
I
GO
B -
7 -
6 -
5-
4 -
3 -
2-
1 -
n Influent PO-4
• Effluent Cell 5 \
u Effluent Cell 3 °
a *
• •" « ?
a * • •
a B •
"a n«»B
B a a a
a
i
B
a
i
10
Study months March July-1982
20
Figure 27. Phosphorus Removal from Cell 3 (0.5 gpd/ft2) and Cell 5 (2.94 gpd/ft2)
5
4
3
2
1 -
y - 4.1978 - 0.3044x ' R - 0.99
a LOG FECAL
0 1 234567891011121314
Time (days)
Figure 28. Fecal Coliform Removal in Pilot Project Cell 8, 1985-1986
-145-
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percent of the fecal coliform in 6 days of retention. Extrapolated data showed a 3 log removal
(99.9) after 10 days of retention.
Engineering Approach. Wherever possible, emphasis should be placed on a "low impact"
engineering approach. This not only avoids unnecessary expense but can enhance the natural
processes involved in the use of wetlands. The design concept should be to have the system fit
naturally into the landscape following the topography and minimizing straight dikes and 90°
corners. If wetland habitat is a value, then islands with nooks and crannies should be liberally
placed in the wetland surface.
Water Depth. Initial establishment of emergent plants in surface-flow wetlands may require
initial shallow water depths of 0.15 m (Gearheart et al., 1982), after which depth should be
increased to 0.3-0.6 m. The water depth should be raised as the emergent macrophytes put on
stem length and increase in numbers of new sprouts from the rhizomes. If Scopus is the main
desired species, initial water depths should be maintained as shallow as possible to prevent
Typha domination. Scirpus does well in -0.05 m to 3 m depth, whereas Typha dominates at
depths >0.15 m (Stephenson et al., 1982).
Cell Construction. Bottom contours should be smooth, and abrupt bathymetric discontinuities
should be avoided to minimize potential problems with short circuiting, and to avoid formation
of refuges for predators during periods of drawdown (Fog et al., 1982). The cells should be
designed with length to width ratios of 5:1 to 10:1 and constructed in the direction of the major
axis of flow. The height of embankments should be as small as practicable to maximize wind
fetch, thus augmenting aeration and restricting problems with duckweed.
Drainage Points Within Cells. It will be important to provide for some means of enabling
complete wetland drainage. This could involve pumps or internal drainage points. If drainage
points are used, it will be important to ensure that they are readily able to be located if required
in the future. It may be important to be able to take separate cells out of commission for
maintenance, if necessary. Therefore, wherever practicable in final design, attention should be
given to ensuring cells are self-contained, and that effluent bypasses will be able to be
implemented.
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Inlet Systems. Knight (1987) concluded that a point source discharge into a wetland would be
preferable to a wide-front discharge. Nevertheless, on the basis of an overall review of available
data, including discussions in the United Kingdom, it is concluded that the discharge into a
wetland should be made across a wide front to take advantage of initial BOD and SS reductions
in the first 10-15 m of a wetland. This should also avoid the rapid formation of a BOD or SS
front which is referred to by Knight (1987).
Outlet Systems. The outlet system should be designed to encourage a uniform collection of the
effluent across the outlet zone of the wetland. This usually would involve several outlet weirs
connected by means of a collective manifold. The velocity is extremely low in the marsh, except
in the outlet region. If too much flow is forced through one collection point, increased
velocities will cause short circuiting (Gearheart et al., 1984).
Rhizome Planting. Rhizomes of most wetland plants are suitable for use in propagation. It is
less resource intensive to spread rhizomes than to plant individual plants. However, rhizomes
are themselves sensitive to desiccation and should be carefully managed. When obtaining
wetland plant rhizomes, or individuals for planting, stocks should be obtained from the
immediate vicinity of the wetland site, if possible.
Planting clumps of emergent plants (1 to 2 ft2) in the late fall with their vegetative tops
cut off on a 1 m2 centering will give a constructed wetland a good start. These clumps will bring
with them sufficient soil and enough rhizome protection to endure a running start in the spring.
The advocated approach would be "plug planting" with emergent wetland plants in early-
to mid-autumn and allow approximately one year for suitable establishment of the plants.
However, it is possible to plant at any time of the year provided that rhizomes and plants are
kept constantly moist.
Soil Composition. The soils used for a wetland plant establishment should be well-tilled fertile
humus/clayey soils. These types of soils will allow for rapid germination of plants and for
optimum rhizome proliferation (Gearheart et al., 1986).
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At Listowel, the wetland soil was conditioned prior to planting (Herskowitz et al., 1987).
In that case, marsh basins were composed of compacted clay, filled to a depth of 0.15 m with a
combination of topsoil and peat (10 percent by volume). It might be advisable, for example, to
utilize dewatered sewage sludge as a soil conditioner. This would be disked into the soil prior
to planting. This soil conditioning will be required if soil is to be removed from the wetland
area for construction of embankments.
Temperature. Wetlands will operate at higher efficiencies in situations of higher temperatures
but will operate over a wide temperature range. This is related to plant physiology and the
amount of litter deposited by plants during seasonal winter dieback. This would account for the
apparent success of wetlands in Saskatchewan, Canada, where temperatures were well below
freezing during the winter months (Laksman, 1982).
Botanical Input. In designing wetlands, the engineering principles of cell construction, flow
direction, depth, inlet and outlet structures, and application rates are relatively straightforward.
However, the key to successfully establishing a wetland system lies in the installation and
maintenance of the wetland plants. It takes at least two full growing seasons for the plant
density to be great enough to have an effect. This assumes a relatively high initial planting
density and high plant survival.
Plant Species Suitability. In terms of species suitability Typha (cattail) is considered to be less
suitable than Scirpus (bulrush), for a number of reasons. Typha has greater capacity for oxygen
translocation to the root system, greater degree of litterfall, which can cause problems with
anaerobic conditions, and problems with windthrow if its roots are not adequately deep in the
soil.
Odors. Hydrogen sulfide generation and associated odors occur periodically at wetland outlets.
The incidence of this problem is increased by use of plants which lead to anaerobic conditions
(e.g., Typha), and in these cases odor problems are exacerbated when the effluent is discharged
in a cascade. Controlling the outlet can prevent hydrogen sulfide odor problems.
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The odors identified most commonly in aquatic wetland treatment systems are associated
with organic compounds containing sulphur, such as mercaptans and skatoles, and with
hydrogen sulfide. Hydrogen sulfide is produced by obligate anaerobic organisms capable of
reducing sulfate (Tchobanoglous et al., 1979). In the absence of oxygen and nitrate, sulfate will
serve as an electron acceptor and is reduced to hydrogen sulfide in the process. Thus the
presence of sulfate in the wastewater can lead to the formation of hydrogen sulfide in the
bottom sludge accumulations. The organic matter in the sludge accumulation serves as a carbon
source for the anaerobic process. The incomplete oxidation of other organic materials
containing sulphur will also lead to the development of odors.
Anaerobic conditions develop when the treatment process is overloaded organically.
Most commonly, anaerobic conditions develop near the effluent end of an aquatic treatment
system.
Strategies that can be used to control the development of odors include the following:
more effective pretreatment to reduce the total organic loading on the aquatic treatment system,
more effective effluent distribution, step feed of influent waste stream, and supplemental
aeration.
In constructing wetlands, it will be necessary from the outset to consider whether the
organic loading will be likely to cause odor problems. The most common approach is to
estimate BOD loading in terms of kg/ha/day and compare with published BOD loading rates
(e.g., as outlined in Knight, 1987). Organic loadings at 166 kg/ha/day or less proved to be most
effective in terms of not overloading the Arcata wetland system (Gearheart et al., 1983).
Interestingly, loadings at Listowel (Herskowitz et al., 1987) were in the range 0.27-0.92 kg/ha/day
and hydrogen sulfide generation was observed, two to three orders of magnitude less than
Arcata.
Final Segment Polishing. The final segment of the wetland is of major significance in terms of
final effluent polishing and retention of suspended solids. This final segment should be retained
in as undisturbed a state as possible. If harvesting is selected as a management option (note
that research has shown harvesting to be not necessary and even deleterious), then the final
-149-
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section of the wetland should be retained in this natural state at all times. Harvesting 10 to 20
percent of the wetland cell per year can be an effective way to manage vegetation without
affecting water quality in the effluent. Care should be taken to minimize the disruption of the
vegetation in the near vicinity of the effluent zone (Gearheart et al., 1985).
Summary. Wetland treatment effectiveness is a function of retention time and capacity of the
vegetation and sediments to retain and/or cycle certain constituents (Gearheart et al., 1985). In
using a wetland to polish domestic secondary treated effluent, the following general guidelines
are considered reliable. It has been shown that an effluent suspended solids level of 5 to 10
mg/L can be achieved with a retention period of about 1 to 2 days. A longer retention time is
required for effective BOD removal. An effluent BOD value of 10 to 15 mg/L can be achieved
with 4 to 8 days of retention of a secondary treated effluent. Total nitrogen levels of the order
of 4 to 6 mg/L can be achieved with 10 to 12 days of retention. Total phosphorus levels of 2 to
4 mg/L can be achieved with 15 to 20 days of retention. In the case of nitrogen and phosphorus
removal vegetation and detritus, harvesting and collection will be necessary prior to
decomposition to capture the nitrogen and phosphorus associated with the biomass. This
management interval will be a variable depending on the removal requirements, the growing
period, and the size of the wetland. In the long run, when steady state conditions are reached,
an annual harvesting schedule of a portion of the wetland will be required.
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Cooper, P.G. and A.G. Boon. 1987. "Use of Phragmites for Wastewater Treatment by the
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Crites, R.W. and TJ. Mingee. 1987. "Economics of Aquatic Wastewater Treatment Systems,"
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Gearheart, R.A., S. Wilbur, J. Williams, D. Hull, et al. 1982. City of Arcata Marsh Pilot
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Resources Control Board, August.
Gearheart, R.A., S. Wilbur, J. Williams, D. Hull, B. Finney et al.. 1983. Final Report City of
Arcata Marsh Pilot Project, City of Arcata Department of Public Works, Arcata, California,
(April).
Gearheart, R.A., J. Williams, H. Holbrook, and M. Ives. 1985. City of Arcata Marsh Pilot
Project Wetland Bacteria Speciation and Harvesting Effects on Effluent Quality. Environmental
Resources Engineering Department, Humboldt State University, Arcata, California.
Gersberg, R.M., B.V. Elkins, and C.R. Goldman. 1983. "Nitrogen Removal in Artificial
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Gersberg, R.M., S.R. Lyon, B.V. Elkins, and C.R. Goldman. 1984. The Removal of Heavy
Metals by Artificial Wetlands," pp. 639-648, In: Future of Water Reuse, Vol. 2, Proc. Water
Reuse Symp. Ill, Aug. 26-31, San Diego, California, AWWA Research Foundation.
Gersberg, R.M., B.V. Elkins, and C.R. Goldman. 1984. "Use of Artificial Wetlands to Remove
Nitrogen from Wastewater," Journal WPCF. 56 (2) February.
Gersberg, R.M., B.V. Elkins, and C.R. Goldman. 1984. "Wastewater Treatment by Artificial
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Gersberg, R.M., R. Brenner, S.R. Lyon and B.V. Elkins. 1987. "Survival of Bacteria and
Viruses in Municipal Wastewaters Applied to Artificial Wetlands," pp. 237-247. In: Aquatic
Plants for Water Treatment and Resource Recovery. K.R. Reddy and W.H. Smith (eds.),
Magnolia Publishing Inc.
Gersberg, R.M., V.G. Elkins, S.R. Lyon, and C.R. Goldman. 1986. "Role of Aquatic Plants in
Wastewater Treatment by Artificial Wetlands," Water Research. 20 (3):363-368.
Greiner, R.W. and J. DeJong. 1982. "The Use of Marsh Plants for the Treatment of
Wastewater in Areas Designated for Recreation and Tourism," Flevobericht No. 225,
Introductory paper presented at 35th International Symposium (Cebedeau) May 24-26, at Liege.
Hammer, D. and R.H. Kadlec. 1983. Design Principles for Wetland Treatment Systems, EPA
600/S2-83-026, May.
Herskowitz, J., S. Black, and W. Lewandowski. 1987. listowel Artificial Marsh Treatment
Project, pp. 237-246. In: Aquatic Plants for Water Treatment and Resource Recovery. K.R.
Reddy and W.H. Smith (eds.), Magnolia Publishing Inc.
Howard-Williams, C. 1985. Cycling and Retention of Nitrogen and Phosphorus in Wetlands:
A Theoretical and Applied Perspective, Freshwater Biology 15:391-431.
Ives, M.A. 1986. "The Fate of Natural Virus in an Artificial Marsh Wastewater Treatment
System Utilizing a Coliphage Model." Master's thesis. Humboldt State University, Arcata,
California, 85 pp.
Kadlec, R.H. 1979. "Wetland Tertiary Treatment at Houghton Lake Michigan," pp. 101-139.
In: Bastian, R.K. and S.C. Reed (eds.). Aquaculture Systems for Wastewater Treatment:
Seminar Proceedings and Engineering Assessment, EPA 430/9-80-006.
Kappel, W.M. 1979. "The Drummond Project - Applying Lagoon Effluent to a Bog: An
Experimental Trial," pp. 83-90. In: Bastian, R.K. and Reed, S.C. (eds.). Aquaculture Systems
for Wastewater Treatment; Seminar Proceedings and Engineering Assessment. EPA 430/9-80-
006.
Knight, R.L. 1985. "Wetlands: An Alternative for Effluent Disposal, Treatment, and Reuse,"
pp. 6-9, Florida Water Resources Journal. (Nov.-Dec.).
Knight, R.L. 1987. Effluent Distribution and Basin Design for Enhanced Pollutant
Assimilation by Freshwater Wetlands, pp. 913-921. In: Aquatic Plants for Water Treatment
and Resource Recovery. K.R. Reddy and W.H. Smith (eds.), Magnolia Publishing Inc.
Laksman, G. 1982. 'Natural and Artificial Ecosystems for the Treatment of Wastewaters,
Saskatchewan Research Council Publication No. E-820-7-E-82.
Lacy, J. 1983. "A Bathe Study of Copper, Lead, and Zinc in a Marsh System - City of Arcata,
California," Special Study Environmental Resources Engineering Department, Humboldt State
University, Arcata, California.
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Lienard, A. 1986. Study of the Sewage Purification Works Using Beds of Macrophytes at Logis
a St. Bonaire, French Ministry of Agriculture, Department of Water Quality, Fishing and Fish
Farming, Lyon, October.
Nelson, R.W. and E.G. Weller. 1985. A Better Rationale for Wetland Management,
Environmental Management. 8:295-308.
Nichols, D.S. 1983. Capacity of Natural Wetlands to Remove Nutrients from Wastewater,
Journal WPCF. 55 (5) (May).
Phillips, G.L., B. Ayling, C. Clarke, and C. Thomas. 1987.
Rossiter, J.A. and R.D. Crawford. 1984. Evaluation of Artificial Wetlands in North Dakota:
Recommendations for Future Design and Construction, Transportation Research Record 948.
Stephenson, M., G. Turner, P. Pope, J. Colt, A. Knight, and G. Tchobanoglous. 1982.
Publication No. 65. The Use and Potential of Aquatic Species for Wastewater Treatment
Appendix A: Environmental Requirements of Aquatic Plants, California State Water Resources
Control Board, Sacramento, California.
Stowell, R., R. Ludwig, J. Colt, and G. Tchobanoglous. 1981. Concepts in Aquatic Treatment
System Design, pp. 16555-16569, Journal of the Environmental Engineering Division.
Proceedings of the American Society of Civil Engineers. 107(EE5) October.
Tchobanoglous, G. 1987. "Aquatic Plant Systems for Wastewater Treatment: Engineering
Considerations, pp. 27-48. In: Aquatic Plants for Water Treatment and Resource Recovery.
K.R. Reddy and W.H. Smith (eds.), Magnolia Publishing Inc.
Tchobanoglous, G., R. Stowell, R. Ludwig, J. Colt, and A Knight. 1979. Aquaculture Systems
for Wastewater Treatment: Seminar Proceedings and Engineering Assessment, EPA 430/9-80-
006, pp. 35-55. In: Bastian, R.K. and Reed, S.C. (eds.).
Valiela, I., S. Vince, and J.M. Teal. 1976. "Assimilation of Sewage by Wetlands." In:
Estuarine Processes. Vol. I. M. Wiley (ed.), Academic Press, 234-253.
Wile, I., G. Palmateer, and G. Miller. 1981. Use of Artificial Wetlands for Wastewater
Treatment, pp. 255-271. In: Proceedings of the Midwest Conference on Wetland Values and
Management. B. Richardson (ed.), St. Paul, Minnesota, June.
Williams, T.C. and J.C. Sutherland. 1979. Engineering, Energy and Effectiveness. Features of
Michigan Wetland Tertiary Wastewater Treatment Systems, pp. 141-173. In: R.K. Bastian and
S.C. Reed (eds.) Aquaculture Systems for Wastewater Treatment: Seminar Proceedings and
Engineering Assessment, EPA 430/9-80-006.
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CONSTRUCTED WETLANDS EXPERIENCE IN THE SOUTHEAST
Robert J. Freeman Jr., PE
Cobb County Water System
Marietta, Georgia
Constructed wetlands (CW) used as wastewater treatment technology have seen a
dramatic increase in use throughout the United States in the last several years. In part due to
the warmer climate and availability of land for siting, CW systems have been utilized in the
"sun-belt" states more frequently than elsewhere. Of the 154 constructed wetlands systems
(operational, under construction, and planned) inventoried in the United States in March 1990,
by Sherwood Reed under contract to EPA, 97 were in EPA Regions 4 and 6, the southeast and
southwest. In spite of the number of these systems in use, the shortage of meaningful data and
the lack of understanding regarding the basic physical and biochemical processes taking place
has resulted in little progress towards a sound design approach. This problem has led to
unexpected difficulties with a number of the CW systems in operation. Both gravel substrate,
subsurface flow, and soil substrate, surface flow, systems have encountered serious problems, in
some cases jeopardizing the continued use of the CW technology at those locations. This paper
will discuss some of those issues and the measures being considered to attempt to avoid those
problems in the future.
Constructed wetlands have been generally grouped into two basic categories, the simplest
being the systems in which rooted aquatic plants are planted in a soil substrate within a
constructed earthen basin. The basin may be lined or not depending on natural soil
permeability and ground-water protection requirements. The systems are generally designed to
allow wastewater effluent following preliminary treatment to flow at a depth of 1 to 2 in. up to
12 to 18 in. through the basin in a plug flow pattern. The Water Pollution Control Federation
(WPCF) design manual titled "Natural Systems for Wastewater Treatment" designates these
systems as Free Water Surface (FWS) systems referring to the nature of the surface flow. The
second type of CW system is similar to the FWS systems except the basin is filled with aggregate
such as gravel or crushed stone to a depth of 12 to 24 in. in which the aquatic vegetation is
planted and through which the wastewater flows with no visible surface flow. These systems
have likewise been designated as Vegetated Submerged Bed (VSB) systems by the WPCF
design manual. A brief comparison of those of the two types of systems is shown in Table 9.
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Table 9. Comparison Of FWS And VSB Systems
FWS Systems
Lower installed cost/gal
Simpler hydraulics
More natural wetland values can be
incorporated into the system
VSB Systems
Greater assimilation rate — less
required
No visible flow — less nuisance,
problems, odors
land
vector
More cold tolerant
The division of the 97 CW systems in Regions 4 and 6 is 17 of the FWS type and 80 of
the VSB type. The prevalence of the VSB type system is due, at least in part, to the success Dr.
Bill Wolverton, formerly with NASA at their southwest Mississippi test facility, had in
researching and promoting the use of these systems. Of those 80 VSB systems identified, 49 are
located in Mississippi and Louisiana.
The original and on-going popularity of the CW technology derives primarily from its
two-fold promise of lower costs and little requirement for operation and maintenance compared
to conventional technology. The EPA construction grants program encouraged the use of the
technology due to the Innovative/Alternative (I/A) grant bonus received by grantees selecting
the CW systems of either type. The Tennessee Valley Authority (TVA) has also played a
significant role in encouraging these systems, especially in the Tennessee Valley area.
Benton, Kentucky, was assisted by TVA in construction of a CW system to treat the
wastewater from the approximately 4,600 residents. Their previous system was a 10.5 ha (26
acre) facultative two-cell lagoon with a flow as high as 4,500 m3/d (1.2 mgd) due to
infiltration/inflow. The original 4.0 ha (10 acre) second cell was converted to three equal sized
parallel cells, one filled to a depth of 0.6 m (2 ft) with crushed limestone and the other two left
as native soil, giving one VSB cell and two FWS cells (Figure 29). The VSB cell was planted
with softstem bulrush and the FWS cells were planted with woolgrass in one and arrowhead and
cattail in the other. The system was designed for an average flow of 4,160 m3/d (1.1 mgd) with
50 percent of the flow intended to go through the VSB and the remaining 50 percent to be
equally divided between the two FWS cells.
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The City's NPDES permit required the following limits to be met:
SUMMER
WINTER
BOD (mg/I)
25
25
TSS (mg/1)
30
30
NH3 (mg/I)
4
10
DO (mg/1)
7
7
During the construction of the wetland system all of the lagoon effluent was routed
through the VSB cell while the FWS cells were built. During the first year of full operation,
1988, the influent flows to the wetland cells averaged a BODS of 25 to 30 mg/L, TSS of 40 to 70
mg/L, NH3 of 6 to 9 mg/L and flows averaging 1,800 to 2,600 m3/d (0.5 to 0.7 mgd). The flows
were within the design expectations with the exception of rainfall related high flows and the
construction period diversion of all the flow through the VSB as mentioned.
The BOD5 removals experienced were quite good, averaging 50 percent to 60 percent in
the FWS cells and 80 percent in the VSB cell. The NH3 performance, however, was very
disappointing. All three cells experienced a significant increase in NH3 through the cells, on the
order of 30 percent to 50 percent, yielding effluent consistently in noncompliance with the
summer NH3 limits and occasionally exceeding the winter NH3 limit as well. The effluent
dissolved oxygen (DO) limits were also consistently violated, both summer and winter. This
pattern continued in 1989, and in 1990 two major changes were made to the Benton system to
attempt to remedy the lack of nitrification occurring. The first attempted solution was the
implementation of a recycle system in one of the FWS cells to attempt to increase the
availability of DO to provide an environment in which the nitrification reactions could occur.
This effort proved fruitless even at a 3 to 4Q recycle and using sprinklers to introduce DO. The
second change was to reduce the loading in the VSB and one of the FWS cells dramatically and
route the remaining flow through the remaining FWS cell. The original design of the FWS cells
called for a loading of 1.5 ha/1,000 m3/2d (14 ac/mgd). The reduced loading was set at 4.5
ha/1,000 m3/d (42 ac/mgd). This reduced loading corresponds to the area required for ammonia
conversion in an FWS cell as calculated using the formulations in the WPCF Natural Systems
Manual. Unfortunately, the nitrification in that cell still did not appear to increase since the
NH3 in the effluent still exceeded that in the influent by 25 percent for the two months of data
available.
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It is not clear why the nitrification reactions are not more effective in reducing ammonia
(some is being oxidized as the decrease in TN and TKN suggests that organic N is being
converted to NH3 at the same time that some nitrification is occurring). Possible deposition of
organic material from the lagoon during the higher loading period may have created a
"background" DO load that will take some time (months or years) to satisfy such that enough
DO remains for more complete nitrification to take place. The often-cited ability of plant roots
to "pump" oxygen down into the VSB bed also appears to be questionable. Several observation
pits dug in the VSB cell showed little root penetration below the 0.15 to 0.25 m (6 to 10 in.)
depth, contrary to the expected full depth root penetration. It also may be that short-circuiting
could be occurring in the FWS cell that effectively reduces the area and increases the net
loading such that nitrification is not encouraged. Remedying any of these possible problems
would at best be difficult.
The VSB cell also experienced surfacing of wastewater at the original design flow of
2,080 m3/d (0.55 mgd). A detailed investigation of the cause of the surface flow showed that the
crushed limestone bed had plugged significantly with an inorganic gel-like substance formed
from a reaction of the limestone and silicon and algae in the wastewater. A reduction in
loading to approximately 10 percent of design brought the water level back below the surface.
The resulting loading was 11.7 ha/1,000 m3/d (105 ac/mgd) compared to the original design of
0.7 ha/1,000 m3/d (6.5 ac/mgd). The VSB cell is now finally achieving satisfactory nitrification,
with effluent NH3 values of 3 mg/L obtained (within the permit limit of 4 mg/L). At this
loading rate, however, another 90 acres or so of VSB cells would be necessary to bring Benton
into reliable compliance with their ammonia limit; this would be clearly economically
prohibitive.
These results at Benton seem to be in line with the recommendations in the WPCF
Manual of 1.2 ha/1,000 m3/d (11.2 ac/mgd) of VSB cell and 3 ha/1,000 m3/d (28 ac/mgd) of FWS
cell for removal of BOD. For significant ammonia conversion the size of those cells would
increase to at least 4 ha/1,000 m3/d (40 ac/mgd). These results bring into serious question the
commonly used assumptions regarding oxygen transport into the root zone in VSB systems, the
loading rates used for those systems, and the effectiveness of CW systems for NH3 removal
except at very low loadings.
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Denham Springs, Louisiana, is an example of a VSB system designed and constructed
under commonly used design criteria that this author believes are in serious question. The
system was designed to treat 11,300 m3/d (3.0 mgd) average flow following a 32 ha (80 ac) two-
cell facultative lagoon to meet effluent limits of 10 mg/L BOD and 15 mg/L TSS monthly. The
CW system consists of 3 VSB cells of 2 ha (5 ac) each, 320 m (1,050 ft) long and 66 m (215 ft)
wide. The aggregate consists of 0.45 m (18 in.) of 0.5 to 1.8 cm (1 to 4 in.) limestone topped
with 0.15 m (6 in.) of 2.5 cm (1 in.) gravel. Bulrush and canna lilies are planted in the cells. In
1989, the flow to the system averaged 9,000 m3/d (2.4 mgd) with an influent BOD of 27 mg/L.
During that period the 10 mg/L BOD permit limit was exceeded about half the time and a
significant portion of the length of the cells have experienced surfacing of wastewater. The
design loading of this system is approximately 0.5 ha/1,000 m3/d (5.0 ac/mgd) at average flow,
about 20 percent heavier than Benton, Kentucky, and about twice as heavy as the WPCF
manual recommendation. It will be interesting to see how the performance of the Denham
Springs system fares as it reaches design flow.
Two other troubling concerns with VSB systems are the use of the larger size rock in the
apparent hope that plugging will not be a problem, and the large length/width ratios. Using the
design methodology in the WPCF manual, as the size of the aggregate goes up and the
corresponding porosity goes down, larger area cells are required to give adequate opportunity
for the biological processes to occur. In addition, the configuration of VSB cells should
generally be much wider and not as long, a result based loosely on Darcy's Law. A system like
Denham Springs, if designed along the lines of the WPCF Manual for BOD removal only,
would have the configuration shown in Table 10.
Table 10. Denham Springs System
Denham Springs, LA: Q average = 11,355 m3/d (3 mgd)
Loading rate
Area needed
Length x width
Existing Design
0.5 ha/1,000 m3/d
(5 ac/mgd)
6 ha (15 ac)
320 m x 197 m
(1,050 ft x 645 ft)
New Design
1.6 ha/1,000 m3/d
(15 ac/mgd)
18 ha (45 ac)
80 m x 2,270 m
(262 ft x 7,440 ft)
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It is obvious that a dramatically different design would result if the WPCF procedure
were used. The two-dollar question is—which one is correct? Since the WPCF approach would
require a 300 percent increase in land and in rock (the most expensive thing about the system),
its use would render the economics of the VSB as described above questionable as a viable
alternative. The use of smaller aggregates would reduce the land area significantly and might
bring the costs back to an acceptable level but would still result in much wider and shorter cells.
If the design were to provide for NH3 removal, however, the size required would increase
significantly. An FWS system, for comparison, would require approximately 25 ha (62 ac) for
11,355 m3/d (3 mgd) using the WPCF approach for BOD removal but would increase to 70 ha
(172 ac) for NHj removal.
The sobering implication of these large differences in the design of the Denham Springs
system and the WPCF approach is that Denham Springs is typical of the design approach at a
number of other operational or under construction systems in Louisiana as well as several in
nearby states. An EPA-funded research effort presently underway is intended to evaluate more
thoroughly some of these VSB systems and shed some new light on these systems.
A promising VSB system designed and constructed by TVA has been in operation since
late 1988 at Phillips High School in Bear Creek, Alabama. The system is designed to treat 76
m3/d (20,000 gpd) of package treatment plant effluent to limits of BOD=20 mg/L, TSS=30
mg/L, and NH3 = 8 mg/L. The VSB is sized at 0.2 ha (0.5 ac) resulting in a loading of 2.6
ha/1,000 m3/d (25 ac/mgd) with 0.3 m (12 in.) of pea gravel substrate. This loading rate is one-
fourth the original design of the Benton, Kentucky, VSB cell and less than one-fifth the loading
of the Denham Springs VSB, in spite of the fact that the influent wastewater is more highly
treated (influent BOD averaged 13 mg/L, NH, 10.7 mg/L). The performance of the Phillips
VSB is excellent, as shown in Table 11.
Table 11. Phillips High School VSB
INFLUENT
EFFLUENT
BOD mg/L
13
<1
nTSS mg/L
60
<3
NH3mg/L
10.7
1.8
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The high degree of nitrification is due, at least in part, to the low loading of the system.
The nature of operation of the Phillips VSB may also contribute to its high-level treatment since
the high school is not in session for most of the summer and, therefore, little or no loading is
contributed then. Low loading combined with corresponding low nutrient application and a
relatively shallow gravel depth could be responsible for the full bed root penetration that has
been observed there, unlike that observed at several other systems. This intermittent type of
operation may assist the system in staying aerobic so the nitrification reactions can take place,
as in an intermittent sand filter or the like.
In FWS systems, two beneficial modifications have been utilized in the design and
construction of the cells that may address the problems of short-circuiting and inadequate
oxygen transfer. The Fort Deposit, Alabama, FWS system has two parallel cells that are
subdivided by three deep zones that are approximately 1 m (3 ft) deeper than the rest of the cell
to prohibit plant growth and redistribute the flow across the cell, shown in Figure 30. The zones
are 5 to 8 m (15 to 24 ft) wide and may also serve as a recreation area to help keep the DO
elevated. Fort Deposit is designed to treat 900 m3/d (0.24 mgd) following a partially aerated
lagoon to meet monthly limits of BOD=10 mg/L, NH3=2 mg/L on a year round basis. The
system has a total FWS area of 6.1 ha (15 ac) for a loading of 6.8 ha/1,000 m3/d (60 ac/mgd).
This rate is in line with the WPCF approach, due to the fact that Dr. Robert Knight of CH2M-
Hill designed the Fort Deposit FWS system and is the author of the Wetlands Systems chapter
of the WPCF manual. The Fort Deposit system will begin a detailed performance evaluation
this summer (1991), and results of the modifications utilized there will be forthcoming. Another
FWS system designed by Dr. Knight for West Jackson County, Mississippi, incorporates the
deep zones and also uses a shallow inlet area to maximize oxygen transfer. The FWS system is
a 2,300 m3/d (0.6 mgd) two cell (series) basin using 8.9 ha (22 ac) for a loading of 3.9 ha/1,000
m3/d (27 ac/mgd). The inlet zone in each cell is very shallow, 5 cm (2 in.), gradually deepening
to a normal depth of 0.3 to 0.5 m (12 to 18 in.). This inlet area should increase the oxygen
transfer capability to enhance nitrification to meet the effluent limits of BOD=10 mg/L, NH3=2
mg/L monthly on a year round basis. Since the loading rate in this system is relatively high for
a nitrification system with limits this tight, the data collection effort, which will begin in earnest
this summer (1991), will be interesting.
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The story of CW systems in the southeastern part of the United States is obviously not
over yet. It is also too soon to tell whether or not it will have a happy ending for the cities and
towns that have built and are operating these systems. The evidence so far suggests that the
early optimism which produced the relatively heavily loaded VSB and FWS systems was not
warranted and a serious reevaluation of those systems may be required. Hopefully, the newer
developments in CW system design and construction will prove to be successful in remedying
some of the problems described.
Until more definitive information is available regarding design protocols and expected
performance, the people involved in the review, approval, design, and construction of these
systems must exercise caution in their use. While under the right circumstances a CW system
can be a very desirable treatment technology, care must be taken to ensure an appropriate
system for the situation is selected.
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MUNICIPAL WATER USE EFFICIENCY
-------
HOW EFFICIENT WATER USE CAN HELP COMMUNITIES
MEET ENVIRONMENTAL OBJECTIVES
Stephen Hogye
U.S. Environmental Protection Agency
Washington, DC
Problem. This research project addresses how reducing water demand through more efficient
water use can help communities deal with a number of environmental problems, ranging from
ground-water contamination to compliance with expensive drinking water treatment
requirements.
Background. Of the many important functions performed by local units of government, one of
the most fundamental is the development of water supplies and the collection and treatment of
wastewater. The economic vitality of any community is heavily dependent upon the availability
of water in acceptable quantity and quality to sustain a multitude of uses, ranging from
industrial manufacturing to drinking and dishwashing. Meeting this objective is becoming
increasingly difficult. Available water sources are commonly contaminated, and development of
new sources carries a growing penalty in terms of high financial and environmental cost.
As water resources are subjected to higher levels of stress, local governments are finding
efficient water use to be an attractive means of meeting legitimate needs without sacrificing
lifestyles or compromising community development objectives. Improvements in technology
have resulted in products such as efficient showerheads, toilets, and sprinkler systems that satisfy
consumer needs while using considerably less water. In addition to conservation measures,
water efficiency can be increased through recycling and wastewater reclamation and reuse.
Many communities have gained considerable experience in adopting water conservation
as a response to drought or as a means of deferring expansion of drinking water and wastewater
treatment facilities. However, the purpose of this research project is to explore the effectiveness
of efficient water use toward achieving a range of additional environmental objectives.
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Research Approach. This project employs analytical computer models as well as field data to
evaluate the benefits of efficient water use under several common community scenarios. These
four hypothetical communities help illustrate the usefulness of reduced water use for
communities ranging in size, type of water supply and wastewater system, rate of growth, and
the kinds of environmental problems they face. The scenarios also include the need to upgrade
drinking water and wastewater treatment levels.
For each community scenario, several water efficiency options are considered, and
average and peak volume reductions are estimated. This illustrates the range of use reduction
responses available, and ways to distinguish what techniques may be most promising in a
particular situation. The impacts of these efficiency options on water utility operations and
costs are assessed, including technical, economic, rate, and institutional considerations. From
this, more general conclusions can be drawn about the usefulness of particular water efficiency
programs for a variety of environmental compliance problems.
Water Efficiency Techniques and System Responses. A wide range of water efficiency
techniques is available to today's system manager. These techniques produce different results in
terms of peak and average volumes, with correspondingly different effects on system operation
and budget. Actual results also vary in response to many other factors specific to an individual
community. Of greatest interest in this context is how to match the environmental issue with
the program that will yield the most benefit.
Utility actions such as leak repair, metering, and pressure reduction, primarily affect
base load volumes. Increasing plumbing efficiency for new and existing buildings, through
regulation, installation or retrofit, also affects base load. Another whole group of conservation
efforts aims to reduce peak or seasonal volumes by affecting outdoor use. Utility rate structures
can be designed for a variety of effects. Commercial and industrial conservation efforts vary in
result, depending on the industry targeted.
Reduced water demand and wastewater flows are not the entire story. Local utility
managers, municipalities, and federal and state regulators are also concerned about how these
reduced volumes may affect system operations and budget. The biggest institutional concern
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may be how an individual community assesses the impact of a water efficiency program, and
how they implement it.
A utility's or community's economic concerns may include the impact of reduced water
demand on utility rates and revenues, as well as the price of water for customers (especially
larger users). The relative costs and benefits of water efficiency strategies may appear as system
capital savings, deferred costs, operation and maintenance expenses, or savings from downsizing.
Of particular concern for some smaller communities is how to account for possible lost revenue
from successful water demand reduction efforts, further impeding ability to finance
environmental improvements.
Study Findings. Preliminary results of this study suggest the following:
Actual results of a water efficiency program are very specific to the community's
particular water and wastewater needs, the type of efficiency measures employed,
and a host of other factors. While it may be possible to identify the general
situations where a community should consider water use efficiency, it is essential
that each community develop its own community-specific analysis of the potential
costs and benefits of alternative programs for its own particular system.
Reducing peak water demand can reduce the potential for an existing aquifer
contaminant plume to enter drinking water wells. A community might thus
target peak use through an aggressive outdoor water use reduction program.
The success of conservation in downsizing drinking water treatment equipment
depends on the particular treatment and technology employed. For example,
some drinking water treatment facilities for very small service populations cannot
be scaled back further.
For small drinking water systems facing rising treatment costs, conservation may
still be useful. This may be especially true for communities with a flat fee
system, a high summer peak, a relatively high growth rate, or potential ground-
water contamination. Communities with very small service populations and rates
based on actual use may need to carefully consider their rate structure and
expected conservation savings to avoid potential revenue shortfalls from reduced
volumes.
Even without expansion or new treatment costs, utility conservation measures
involving system repair and maintenance may pay for themselves in communities
with older infrastructures. This may be more likely for water supply than for
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wastewater distribution systems, due to the relative contributions of stormwater
and infiltration/inflow problems for some systems.
Wastewater collection systems may experience problems such as odor, septicity,
and clogging due to flow reduction. However, many wastewater facilities provide
better treatment under reduced hydraulic loadings, and also experience some
savings in overall operating costs.
EPA's Offices of Policy Analysis, Wastewater Enforcement and Compliance, and Ground Water
and Drinking Water are supporting this project. The author also acknowledges the substantial
contribution of the project workgroup and participating consultants.
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IMPACT OF INDOOR WATER CONSERVATION ON WASTEWATER
CHARACTERISTICS AND TREATMENT PROCESS
Phase I Study
Robert A. Gearheart
Environmental Resources Engineering Department
Humboldt State University
Arcata, California
Introduction. The objective of this phase of the study is to determine the change in influent
wastewater characteristics (BOD and suspended solids) as a result of water conservation
strategies in California. This is the first phase of a study which examines the impact of indoor
water conservation on wastewater collections and treatment systems. This study developed from
an analysis of the San Diego Point Loma's advance primary clarification process as it related to
change in removal efficiency as a result of indoor water conservation.
Not all of the facilities were able to supply all the necessary data for the purposes of
developing a profile of the treatment system. The following treatment plants were examined in
this phase of the study.
• San Diego's Point Loma Plant - Southern California
• Santa Barbara's El Estero Plant - Central California
• Los Angeles - L.A. County Sanitation District Joint Water Pollution Control
Plant - Southern California
• Goleta's Wastewater Reclamation Plant - Central California
• Contra Costa Sanitary District - Northern California
• Arcata - Northern California
These plants were selected based upon their size, location in the state, and type of
treatment process. The Point Loma treatment plant is an advanced primary treatment system
with anaerobic digestion of the solids. The Los Angeles plant is a primary plant with secondary
treatment (conventional activated sludge) of a portion of the primary effluent. The solids from
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both these facilities are anaerobically digested. The Contra Costa treatment plant is an
advanced secondary treatment plant.
Water conservation programs are being proposed and implemented on several levels and
in several regions in the United States. The need to conserve water and/or to serve a greater
population with a finite water resource has become a major issue in the water utility sector.
Nowhere has this demand been greater than in California. The last five years' successive
droughts have forced water wholesalers and retailers to reevaluate their policies and programs.
While the arguments for conserving water appear to be apparent to the public, there is
resistance to structural changes in plumbing, etc., in the utility business and in the engineering
profession.
The public for the most part recognizes the need to reduce water uses, especially if 1)
there is a savings in their water bill and 2) there is a savings in their energy bill. There are
some other possible savings in the wastewater collection and treatment systems. There have
been limited numbers of studies to identify these beneficial and adverse impacts which might
occur and any economic consequence, either capital cost and/or operation and maintenance
cost, that might be incurred. Examples of the potential impact of indoor water conservation on
wastewater treatment and collection include:
Treatment Plant Efficiency:
• Increased mass suspended solids removal in the primary treatment process
• Increased mass BOD removal in the primary treatment process
• Increased gas production in anaerobic digesters
• Decrease in mixing energy requirements in activated sludge process
• Reduction of hydraulic transient condition due to inflow/infiltration and
hourly/daily fluctuations in the influent flow
Collection:
• Increased hydraulic efficiency, especially during periods of high inflow/infiltration
• Increased solubilization of particulate BOD
• Increased solids separation
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• Increased anaerobic breakdown of organics
• Increased hydrogen sulfide production, causing odors and corrosion
Water Conservation Techniques. This paper is interested in the effects of water conservation
on wastewater treatment, and the most significant factor that can change the characteristics of a
wastewater flow is household water conservation.
Water Use. The average house has a consistent pattern of water use for a typical day. For each
member of the house, one shower, four flushes of the toilet, and any dish and laundry water
together account for almost all the water that travels through indoor plumbing to the sewer line.
Indoor domestic water use in the United States ranges from 40 to 150 gallons/capita/day, with
an average of 70 gal/capita/day (1).
Wastewater. Typical wastewater flows from residential areas in the United States range from 30
to 130 gal/capita/day with an average of 65 gal/capita/day (1). However, other countries have
different ranges for their typical flows. Typical concentrations for domestic raw sewage's BOD
and suspended solids range from 150 to 200 mg/L (2).
Indoor Plumbing Devices
Toilets. The principal water saving device is the ultra low flush toilet at 1.6 gal/flush. The state
of California enacted a law effective January 1, 1992, that changes the California plumbing
requirement on all new (residential and commercial) construction to 1.6 gal/flush tanks. The
state's law since 1983 required all new buildings to use up to a maximum of 3.5 gal/flush. Table
12 gives an accurate idea of how much water savings can be expected by improving the type of
toilet installed.
Showers. A typical, nonconserving shower head can deliver as much as 8 gallons per minute, far
more than is necessary. In comparison, a low-flow shower head, in order to meet standards,
cannot exceed 3 gallons per minute.
Water Conservation Effects on Wastewater Treatment/Collection. There have been a number of
studies done on the effects of conservation on sewerage processes. After the drought in
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Table 12. Toilet Fixtures
Type of Toilet Gallons/Flush Gallons/Toilet/Day %
Savings
Nonconserving 5.5 33.0 0
Low-Rush 3.5 21.0 36
Ultra-Low-Flush 1.5 9.0 73
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California during the mid-'70s, the EPA sponsored a study titled "The Effects of Water
Conservation Induced Wastewater Row Reduction - A Perspective." (4) A summary of the
conclusions follows:
Half of the wastewater treatment systems (17) surveyed had operational problems
during drought conditions. However, none of the encountered problems
significantly affected the operations of any of the systems.
All of the systems surveyed operated continuously throughout the survey period,
despite any problems encountered.
There was no correlation between low-flow induced wastewater quality changes
and the treatment plants' occasional BOD/TSS violations.
The BOD and SS concentrations of the wastewater entering the treatment plant
generally increased, while the concentration leaving the plant generally decreased
during years of flow reduction. The efficiency of treatment plant removal of
BOD and SS generally increased slightly.
The two most common treatment plant factors influenced by wastewater flow
reductions were energy and chemical uses.
The operation and maintenance costs for the collection systems generally
decreased slightly. At 50 percent flow reduction, there was a 3 percent cost
reduction, probably due to energy savings from lift pumps.
Chemical use differences varied from plant to plant, while energy use generally
decreased. In some cases, an increase in chemical costs caused an increase in
O&M costs, while in others, the energy savings outweighed the encountered
increases.
A literature review on water conservation revealed that this activity will result in
significant increases in an activated sludge process wastewater treatment plant's influent
substrate concentrations (5). The authors concluded that "changes in substrate removal
efficiencies resulting from increases in influent substrate concentrations (water conservation)
range from zero to a few percent." They found that effluent BOD and COD concentrations
change nearly proportionally with their corresponding influent values. It is noted that this
occurrence might make it difficult for a plant to meet concentration-based discharge standards,
but there is no evidence that mass loading discharges will be affected.
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Wastewater Characteristic Changes. The city of Goleta, located in southern California adjacent
to Santa Barbara, reflected the greatest impact of indoor water conservation on sewage flows.
An analysis was made of their influent characteristic monthly average flow, BOD, and
suspended solids for the period January 1988 through July 1990. The flows show that until
about January 1989 the average monthly daily flow was about 6.5 mgd. At that time severe
water conservation practices were initiated in the city. The reduction in indoor water use is
shown as the sewage flows drop about 1.5 mgd the first year with a continuing reduction
through the period of the data set resulting in about 3.0 mgd or 58 percent reduction in sewage
flows in a 20-month period (Figure 31). This reduction was achieved with an aggressive
implementation of low-flush toilets and to some unknown extent with the use of graywater for
horticulture purposes. The BOD and TSS concentration in the influent wastewater averaged
230 and 200 mg/L, respectively, during this nonconservation period. Santa Barbara wastewater
flows also showed a drop from 15 mgd to 12.5 mgd during the same period (Figure 32).
Table 13 shows the range of flows for the POTWs shown in this study. The variation in
the influent TSS and BOD can be seen in Table 14 and Table 15. This again reflects the
dilution effect of inflow/infiltration, exfiltration, and, in the case of Goleta, water conservation.
The average TSS values ranged from 140 mg/L for Contra Costa county to 460 mg/L for Los
Angeles. BOD influent concentrations for these cities ranged from lOOmg/L at Contra Costa to
360 mg/L in Los Angeles (Table 16). The ratio of the influent SS/DOD ranged from 0.84 to
2.00.
Model; Water Conservation Strategies/Wastewater Characteristics. In order to gain insight
into the possible effects of household water conservation on the characteristics of household
wastewater, a model was developed. The model based its analysis on user-supplied, volume-per-
use data for different contributing devices of various levels of conservation technology. For
example, volume-per-use data for contributors such as toilets, showers, and garbage disposal is
supplied for four levels of technology.
Application. This model was used to analyze one community as it underwent a conservation
project at three rates of implementation. The initial community size was chosen to be 100,000
people, and grew at an annual rate of 2 percent. A slow, medium, and fast implementation rate
was applied to the 20-year project. The difference between the rates lies in the level of installed
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6n _
,O "
6 -
5C
.0 ~
5_
"
4C _
.O "
4 —
~
1
c
PpQQ
=00^
o
,,_„„ f\
1
p
DO
.... (~\ __.
50
- o —
o
°^
do
!> -c
0
o
Y^
o
O_
°c
1
\ ^
>d'
10 15 20 25 30 35
MONTHS
0 5
Figure 31. Influent Flow (mgd) Over Time for Goleta POTW
Figure 32.
0 50 100 150 200 250
DAILY
Influent Flow (mgd) Over Time for Santa Barbara's El Estero POTW
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Table 13. Flows (mgd)
10%
50%
90%
Goleta
Arcata
Santa Barbara
Los Angeles
Point Loma
Contra Costa
4.4
1.7
12.0
157.0
180.0
17.1
6.0
2.2
13.0
178.0
190.0
18.2
6.7
2.4
17.0
185.0
200.0
19.1
Table 14. Suspended Solids (mg/L)
Goleta
Arcata
Santa Barbara (all)
Los Angeles
Point Loma
Contra Costa
10%
180
75
200
420
182
100
In
50%
210
180
400
460
198
140
90%
250
250
800
470
195
190
10%
47
5
56
54
70
Out
50%
66
8
66
65
90
90%
105
15
74
76
125
Table 15. BOD
10%
In
50%
90%
10%
Out
50%
90%
Goleta
Arcata
Santa Barbara (all)
Los Angeles
Point Loma
Contra Costa
220
140
340
125
250
200
360
160
420
260
380
215
5
105
125
10
108
140
154
115
170
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conserving technology at the end of the project. Data were calculated at 5-year intervals. Each
scenario starts the community at the same level of conservation.
Slow-Rate Implementation Scenario. This scenario could simulate a community that has a low
incentive to install conserving technology. By the end of the 20-year project period, 60 percent
of the community still uses nonconserving devices (LO), and only 10 percent has installed L3
technology (Table 17).
Medium-Rate Implementation Scenario. This scenario models a community that is a little faster
installing conservation technology.
High-Rate Implementation Scenario. This is a model of a community with strong incentive to
reduce its water consumption. By the end of the project, this community has retrofitted every
home that once had Level 0 (LO) technology (Table 18). Fifty percent of the people live in
homes that utilize L2 devices. This represents a best-case scenario (Table 19).
Findings. Probably the most interesting result is the amount of reduction in wastewater flow for
each plan. The plan that had a slow implementation rate showed an increase of about 0.3 mgd
of wastewater flow per year, while the fast-rate plan reduced its flow at the 5-year point in the
project, but the amount decreased was gained again by the year 10. From that point on, the
daily wastewater flow remained more or less the same for the duration of the project. The
medium-rate plan fell between the slow and the fast, in terms of wastewater flow. This implies
that for a 25-year project, a fast-rate plan could stabilize the wastewater flow for a community
of 100,000 persons who begin the project not conserving any water (see Figure 33).
The average monthly influent BOD and TSS of six communities in California varied
significantly from 160 to 360 mg/L and 140 to 460 mg/L, respectively. This variation in influent
concentration can account for significant differences in organic loadings and removal efficiencies
in primary clarification. The 90 percentile BOD and SS for these communities varied from 215
to 420 mg/L and 190 to 800 mg/L, respectively.
The reduction in indoor water use concentrates the BOD and TSS concentration. These
concentrating factors are not totally accounted for by the decrease of wastewater flows. It
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Table 16. Summary Characteristics of POTWs in Study
Flow,,, SS^ BOD,,,
(mgd) (mg/L) (mg/L)
Goleta
Arcata
Santa Barbara (all)
Los Angeles
Point Loma
Contra Costa
6.0
2.2
13.0
178.0
190.0
17.1
210
188
400
460
198
140
250
-
200
360
-
160
0.84
-
2.00
1.28
-
0.875
Table 17. Percent of Population Using Technology—
Slow-Rate Implementation Scenario
Year 0 Year 5 Year 10 Year 15 Year 20
Level 0
Level 1
Level 2
Level3
100%
0
0
0
90%
5
5
0
80%
10
10
0
70%
20
10
0
60%
20
10
10
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Table 18. Percent of Population Using Technology—Medium Rate
Implementation Scenario
Year 0 Year 5 Year 10 Year 15 Year 20
Level 0
Level 1
Level 2
Level 3
100%
0
0
0
80%
10
5
5
60%
20
10
10
45%
25
15
15
30%
30
20
20
Table 19. Percent of Population Using Technology—
High Rate Implementation Scenario
YearO Year 5 Year 10 Year 15 Year 20
Level 0
Level 1
Level 2
Level 3
100%
0
0
0
60%
20
10
10
40%
20
20
20
20%
15
10
25
0%
10
50
40
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appears that the TSS are solubilized to a greater extent in those communities where reduced
wastewater flows were observed (Figure 34). It is suggested that the increased time of
concentration allows for a greater solubilization of particulate and suspended BOD in domestic
wastewater. No attempt was made in this phase of the study to determine the impact of
solubilization of the TSS on the collection and treatment system. To some extent BOD could
be removed within the collection system as the wastewater is exposed to a greater anaerobic
contact period.
Significant increases in suspended solid removal occurs as the concentration of the
influent suspended solids increases. This can best be shown with data from Central Contra
Costa Sanitation District (Figure 35). The removal efficiency increases from 40 to 70 percent as
the suspended solids in the influent increases from 100 to 200 mg/L. The mass removal rates
increase also, as shown by the Point Loma data (Figure 36). At Point Loma the mass removal
rate increases from 3.5 x 10s Ibs/day to 4.2 x 105 Ibs/day as the removal efficiency increases from
76 to 79 percent.
This analysis of the change in raw wastewater constituent as a result of reduced indoor
water use represents a preliminary finding. The fact that drought conditions and water
conservation strategies were occurring simultaneously makes it impossible to separate their
distinct impacts. Obviously drought conditions force policies and programs of water
conservation, which in turn collectively reduce wastewater flow. Exactly how much elasticity
exists in indoor water use without structural changes is not known. The real test, though, for
analyzing the impact of reduced inflow flows on wastewater collection and treatment will have
to wait for normal rainfall conditions. Some general observations can be made under these sets
of conditions which will help in the design of future information collection activities.
Based on information developed in this first study, the second phase should be directed
at an in-depth study of selected wastewater collection and treatment system. The selected
systems should meet the following criteria: 1) the system has a significant structural water
conservation program, 2) plant process efficiency data is readily available, and 3) collection
system information is readily available. The second phase of the study should include an in-
depth analysis of operation and maintenance activities during the period of diminished flows
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Figure 33.
"O
§; 200 -
$ 190 -
o
C 180 ^
w
CO
LL
170 -
160 -
o
o 150 -
140 -
130
-5
5 10 15
PROJECT LIFE(years)
500
o a
450 S £
o o
400 w §>
350
2
O
3 3
300
20 25
Predicted BOD, Suspended Solids, and Per Capita Wastewater Flow for High
Rate Water Conservation Scenario
Figure 34.
500
c
" Q
—
I f
'a
^ D
TSS In ° \
i Ora
BOD in ^!D
t^-eEX^fe®
-------
Figure 35.
.11 + 90.867loa(x) R= 0.
100 150 200 250 300
Percent Removal of Suspended Solids vs. Influent Suspended Solids for
Central Contra Costa POTW
85
Figure 36.
80--
y = -200
.09 + 49.75
3.000 1053.500 1054.000 1054.500 1055.000 105
INFLUENT MASS LBS/OAY
Percent Removal vs. Influent Suspended Solids Mass Loading (Ibs/day) for
Point Loma POTW
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due to water conservation activity. These O&M requirements could then be compared with
historic O&M requirements for a given type and size of wastewater collection/treatment system.
Summary. This study has incorporated operational data from six California POTWs, into a
comparative analysis of influent wastewater characteristics. This study shows that indoor water
conservation practices can significantly decrease the wastewater flows, thus increasing the
influent BOD and suspended solids concentration, contrary to previous studies. This study shows
the influence of the increase in time of concentration in the collection system as the ratio to
BOD to suspended solids. It appears that the suspended material is solubilized, giving a greater
BOD contribution in those systems with reduced wastewater flows.
Using a predictive model, it was shown that various scenarios of indoor water
conservation could significantly alter wastewater flows over the planning period of wastewater
treatment facility planning. For example, under the most restrictive scenario the wastewater
flows would remain the same over a 20-year period. These scenarios combined levels of
technology, percent of population involved, and percent of implementation. The BOD and
suspended solids predicted from the model agree with operational data obtained from Goleta
and Santa Barbara's water conservation efforts last year.
The efficiency of primary clarification increases with increased concentration of
suspended solids. It appears, from preliminary analysis, that this is due to the combined effect
of increased flux of suspended solids and increased retention times in the primary clarifier. The
increase in primary clarifier solids can be considered a positive benefit if anaerobic
digestion/cogeneration processes are involved.
The decrease in wastewater flows obviously will increase the retention time in various
unit processes. This could be a significant factor in the case of Goleta, where average
wastewater flows are reduced by 58 percent, increasing retention times in grit chambers, primary
clarifiers, aeration units, secondary clarifiers, and chlorine contact basins.
The next phase of the study will look at in-plant impacts of indoor water conservation
and collection systems. This phase will look in-depth at five POTWs, specifically Central Contra
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Costa Sanitation District, East Bay Municipal Utility District, Goleta, and Los Angeles
Sanitation District Joint Water Pollution Control Plant.
REFERENCES
1. Tchobanoglous, G. and E. D. Schroeder. 1985. Water Quality. Addison-Wesley
Publishing Company.
2. Bailey, J. R., R. J. Benoit, J. L. Dodson, J. R. Robb, and H. Wallman. 1969. A Study of
Flow Reduction and Treatment of Wastewater from Households. In General Dynamics,
Electric Boat Division (ed.). Federal Water Quality Administration.
3. Consumers Union. 1990. How to Save Water. Consumer Reports. June (55):463-473.
4. Koyasako, J. S. 1980. The Effects of Water Conservation Induced Wastewater Flow
Reduction—A Perspective. EPA-600/2-80-137.
5. Bohae, C. E. and R. A. Sierka. 1978. Effect of Water Conservation on Activated
Sludge Kinetics. Journal of Water Pollution Control 30(10):2313-2326.
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FIXED FILM/SUSPENDED GROWTH
SECONDARY TREATMENT SYSTEMS
Arthur J. Condren
James A. Heldman
Bjorn Ruster
Introduction. The addition of inert media to support fixed film biomass growth in activated
sludge aeration tankage offers the potential for cost-effective upgrading of municipal wastewater
treatment systems. To gain a better perspective of the potential benefits of utilizing these high
biomass systems, EPA undertook an investigation of plant performance at full-scale facilities
employing several of these systems. Results and observations from a number of site visits to
various European installations in mid-1988 are summarized in this paper.
Use of inert support media to serve as the locus for fixed film biomass growth is a
relatively old concept. Many current approaches to high biomass systems employ a combination
of fixed film and freely suspended biomass in the process. The suspended growth component
concentration is controlled by adjusting the amount of MLSS wasted from the underflow of the
system's secondary clarifiers. Since the fixed film biomass is retained in the system's aeration
tankage, problems with solids-liquid separation in hydraulically overloaded secondary clarifiers
can be addressed more easily with high biomass systems.
High biomass systems have gained a certain popularity in Europe. During the past few
years, a number of investigations undertaken in the Federal Republic of Germany (FRG) have
been reported (7-15). Among the advantages attributed to such systems have been
improvements in nitrification performance, sludge settleability, and effluent quality (16,17).
Currently Available High Biomass Systems. At the present time, there appear to be at least six
commercially available high biomass systems that can be incorporated into conventional aeration
tanks. Linde AG of the FRG and Simon-Hartley of Great Britain (Ashbrook-Simon-Hartley in
the USA) both use small, highly reticulated sponge pads as their inert support media.
Bio-2-Sludge (FRG) and Smith & Loveless, Inc. (USA) use racks of synthetic trickling filter
media to effect fixed film growth (see Figure 37). Ring Lace (Japan) employs a looped string
material as the inert support media (Figure 38), and a Chinese firm uses tassels of a synthetic
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Effluent
iiiiiiiiii
iiiiiiiiii
i i
Influent
TF Media Rack
Figure 37. Plan and Section Views of a Bio-2-Sludge System
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Effluent
1
1
I
Influent
Ring Lace Rack
Figure 38. Plan and Section Views of a Ring Lace System
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material attached to a string for fixed biomass attachment and growth. The latter two media
are tied to racks which are placed in the plant's aeration tanks.
Site Visits. During mid-1988, a U.S. EPA evaluation team visited a number of full scale high
biomass systems in the FRG. The purpose of the site visits was to view the systems in
operation, collect operational and performance data, learn about system design details from the
system manufacturers, and discuss process operational and maintenance concerns with the
treatment plant staffs. Data and information on the various types of high biomass systems from
these facilities are summarized below.
Freising (Linde AG System). The Freising activated sludge plant was converted to a Linde AG
high biomass system in 1984 after a series of pilot plant studies. The conversion employed a
sponge volume equal to 20 percent of the aeration tank volume. It appears that there were
three primary reasons for the conversion: frequently occurring poor sludge settleability, limited
space at the plant site, and higher costs of alternative technologies.
Operational and performance data were collected for a short period of time before and
after plant conversion. Before conversion, the plant could only maintain a MLSS concentration
of about 2,600 mg/L. Following conversion, a much higher MLSS concentration could be
maintained, which dramatically lowered the F/M of the system and greatly improved secondary
sludge settleability.
As a follow-up to this historic information, data from 1987 were collected and analyzed.
In 1987, the Freising plant was operated at 78 percent of its hydraulic capacity and 80 percent of
its BOD5 capacity. Instantaneous influent pH, because of industrial discharges, ranged from 6.2
to 12.0; effluent pH ranged from 6.8 to 7.5. An average of 65 percent nitrification was achieved
over a wastewater temperature range of 10 to 17 C, even though the dissolved oxygen
concentration averaged only 1.7 mg/L.
Munich (Linde AG System). Munich's Grosslappen plant was retrofitted with the Linde AG
high biomass system to allow for additional treatment capacity while a parallel activated sludge
plant of equal capacity was being constructed. Sponge media were installed to allow for full
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scale evaluation of the process and for possible inclusion in the new treatment plant design.
The existing Munich plant has three banks of aeration tanks, and during the site visit, two of the
banks had varying quantities of sponges in place.
Points of interest from the Munich data are: 1) a lowering of the system's F/M by the
presence of the fixed film biomass, 2) an increase in aeration rate to address the demand of
additional biomass in the system, and 3) improved effluent quality.
Olching (Ring Lace System). During the spring of 1988, the Olching plant was operating at 85
percent of its design hydraulic capacity of 35,000 m3/day and 83 percent of its design organic
loading, which was based on a population equivalent of 240,000. In late 1987, conversion of the
plant to a high biomass system began by adding the installation of a new 4,000 m3 denitrification
basin and the addition of 252,000 m of Ring Lace material to each of four 2,070 m3 aeration
tanks. The lead denitrification basin, which contains no Ring Lace and had not yet been placed
in operation at the time of the site visit, is equipped with paddle mixers and also contains
aeration equipment for nitrification if necessary. A portion of the mixed liquor from the Ring
Lace basins will eventually be recycled to the lead denitrification basin. At the time of the site
visit, influent flow was sent directly to the aeration basins containing the Ring Lace material.
The Ring Lace material was strung on racks, with the individual strands being separated
by approximately 50 mm. Spacing between the racks, which occupied 31 percent of the aeration
tank volume, was about 60 mm. A tensioning system was built into the racks in case the Ring
Lace material elongates with time. In addition to the above, the equipment supplier had to
provide a 10-year process performance and equipment guarantee. Required process
performance was based on the plant's discharge requirements of 15 mg/L BOD5, 20 mg/L TSS
and 10 mg/L NH4-N, the latter equating to an approximate 75 percent level of nitrification.
Because the Olching Ring Lace plant had been in operation for less than one year and
the required performance test had not been completed, no operational or performance data
were released to the U.S. EPA evaluation team. However, the following general observations
on the Ring Lace system were communicated from the treatment plant staff.
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• Before conversion to the high biomass system, the maximum operational MLSS
concentration that could be achieved was about 1,500 mg/L, which resulted in the
plant operating at a F/M of 0.6 to 0.70 kg BOD^g MLSS-day. At this loading
rate the MLSS were gray in color and had very poor settling characteristics. In
addition, no substantial nitrification could be achieved.
• After conversion, the suspended biomass varied from 3,500 to 4,500 mg/L. Fixed
biomass on the Ring Lace material was estimated at 6.5 g/m, which is equivalent
to an additional 790 mg/L of MLSS. This increase resulted in a MLSS with a
rich brown color and greatly improved settling characteristics. Operating F/M of
the system decreased to about 0.2 kg/kg-day and desired levels of nitrification
were being achieved.
• Other high biomass systems were evaluated at the pilot plant level by the Olching
treatment plant staff and they all yielded effluent qualities equivalent to that
realized by the Ring Lace system. However, the Linde AG system was not
selected because the staff felt that this system might require additional electrical
power for proper operation, the sponge cubes would be subject to wear by
abrasion and, upon extended levels of mineralization, the sponge cubes might
have a tendency to settle in the aeration tanks. The Bio-2-Sludge process was
not selected because the plant staff felt that the synthetic trickling filter media
might be subject to plugging by biomass and/or large particulates, either of which
might lead to anaerobic zones in the media. Such zones, if they developed, were
felt to potentially limit the nitrification process.
Schomberg (Bio-2-Sludge System). The Schomberg wastewater treatment plant was recently
expanded in throughput capacity and simultaneously converted to a Bio-2-Sludge high biomass
system. Both aeration tank volume and final clarifier surface area were more than doubled, and
denitrificatiori tankage was also added. Tropac media at 120 m2/m3 was added to 25 percent of
the aeration tank volume. In the spring of 1988, the plant was operating at 20 percent of its
design hydraulic capacity and 57 percent of its design BOD5 capacity.
Prior to conversion, the plant was slightly overloaded, and could not meet discharge
permit requirements primarily because of very poor settling MLSS. The poor settling
characteristics would allow the maintenance of only 1,000 to 1,500 mg/L MLSS in the system's
aeration tanks in spite of the very high RAS pumping. After conversion, overall plant
performance greatly increased.
Installation of the Bio-2-Sludge system at Schomberg along with the other plant
modifications greatly enhanced MLSS settleability as evidenced by the SVI of 82 mg/L after
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conversion. Although the RAS rate at this plant could have been adjusted to about 50 percent, a
return rate of 100 percent was used. It appears that this is a common design/operational
practice at smaller treatment plants in certain areas of Germany. It is interesting to note that
this plant, in addition to achieving an effluent containing 5 mg/L BOD5, realized nearly
complete nitrification.
Calw-Hirsau (Bio-2-Sludge System). In 1986, the Calw-Hirsau facility was upgraded from a
population equivalent design capacity of 23,000 to 53,000. Major changes included discontinuing
operation as a LURGI plant (chemical addition to the secondary clarifers), addition of Tropac
media (167 m2/m3) to 26 percent of the existing 1,617 m3 aeration tank, and an increase in
secondary clarifier capacity from 230 m2 to 1,267 m2 of surface area. Prior to plant conversion,
there were reported problems with sludge bulking, but no data were available to quantify
severity of the situation. Currently, process stability is reported to be good and maintenance has
posed no problems.
System Economics. It is interesting to compare the costs of upgrading an activated sludge
facility by high biomass and conventional approaches. Consider the hypothetical situation
summarized in Table 20, in which a 18,930 m3/day (5 mgd) plant is operated at a F/M of 0.33 kg
BODs/kg MLVSS'day and a secondary clarifier solids loading rate of 3.83 kg/m2"hr. Because of
operational instability and effluent quality excursions, plant upgrading will be undertaken.
There are basically three upgrading options available:
• Increase the volume of the plant's aeration tanks and operate the facility at a
lesser MLVSS concentration.
• Increase the surface area of the plant's secondary clarifiers and operate the
facility at a higher MLVSS concentration.
• Use the plant's existing tankage, but convert the facility to one incorporating a
high biomass system.
Conventional upgrading requirements were determined to be a F/M of 0.20 kg BOD5/kg
MLVSS'd and a solids loading on the secondary clarifiers of 2.85 kg/m2"hr (14 lb/d"ft2). One
approach, summarized in Table 20, would be to add aeration tankage (Case A); while an
alternative approach would be to add secondary clarifiers (Case B).
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Table 20. Conventional Upgrading Requirements
Existing
Parameter
Secondary System Influent
Row, m3/day
BODS, mg/L
TSS in Aeration Tanks
Suspended, mg/L
MLVSS/MLSS, %
Aeration Tanks
Volume, m3
Det'n Time, hr
F/M, kg/kg-day
SVI, mL/g
Secondary Clarifiers
Area, m2
SOR, m/hr
SLR, kg/m2-hr
Return Activated Sludge
Concentration, mg/L
R/Q, %
Plant
18,930
154
2,500
75
4,733
6.0
033
133
774
1.02
3.83
7,500
50
Upgrading
A
18,930
154
2,044
75
9,508
12.1
0.20
133
774
1.02
2.85
7,500
37
Option
B
18,930
154
4,107
75
4,733
6.0
0.20
133
2,513
0.31
2.85
7,500
121
Option A - Increase aeration tank volume/decrease MLVSS concentration
Option B - Increase secondary clarifier area/increase MLVSS concentration
Estimated total installed cost (design through start-up services) for Option A is
approximately $1,820,000, while that for Option B is about $2355,000. Option A
facilitiesinclude the new aeration tanks and associated air headers and diffusers, and a new
splitter box for equal flow distribution to all of the plant's aeration tanks. Option B facilities
include the new secondary clarifiers and associated return and waste activated sludge pumps and
piping, and a new splitter box for equal flow distribution to all of the plant's secondary clarifiers.
The costs expressed per unit of original aeration tank volume are $385/m3 of original tank
volume for Option A and $498/m3 of original volume for Option B. In all cases, the unit
volume costs exceed the typical costs reported for the high biomass systems evaluated (e.g.,
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Linpor at $250 to $350/m* of aeration tank volume; Ring Lace at $300 to $350/m3 of aeration
tank volume; and Bio-2-Sludge at $300 to 350/m3 of media installed).
Unfortunately there is no general design approach for sizing high biomass systems so
that their expected performance would be equivalent to the conventional activated sludge
upgrading alternatives evaluated in this design example. Based on available information, pilot
scale studies are necessary to properly size any of the high biomass systems.
Data gathered during the site visits which summarize the amount of immobilized
biomass in the fixed media systems are shown in Table 21. For both Linpor and Bio-2-Sludge
there are three-fold variations in the amount of immobilized biomass per unit of media.
Furthermore, it is unknown how immobilized biomass concentrations would normally vary as a
function of loading (F/M) or of other system parameters such as aeration intensity. Mass
transfer considerations are important in the evaluation of fixed media systems, and there may be
considerable difference in the percentage of active attached biomass among the various fixed
media systems as well as unit substrate removal rates (kg BOD/kg attached VSS) in combined
fixed/suspended systems at the same overall volumetric and total mass loading.
Table 21. Observed Inert Support Media Biomass Values
System
Ring Lace
Linpor
Bio-2-Sludge
Location
Olching
Freising
Munich
Munich
Calw-Hirsau
Schomberg
Immobilized Biomass
6.5 g/m
18.7 g/L of pad*
12.0 g/L of pad"
6.1 g/L of pad"
5775 g/m3 of media
1770 g/m3 of media
Overall System F/M
0.17
0.19
0.57
0.46
0.15
0.08
'At a theoretical pad density of 100% by volume
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If the 5,775 g/m3 of biomass observed for the Bio-2-Sludge system at Calw-Hirsau were
achieved in the hypothetical upgrading problem (Table 20) by adding trickling filter media to
the aeration tank, only 1,691 m3 of media would be required to give an overall system F:M of
0.20 with 2,044 mg/L of suspended MLSS; this provides the desired solids loading on the
secondary clarifier. Based on the German data, the installed cost for such a system would only
be $390,000. An independent estimate undertaken by a U.S. manufacturer of wastewater
treatment systems for this trickling filter media system would be about $850,000. These costs
are 19 to 47 percent of the lowest cost conventional alternative evaluated.
A similar analysis can also undertaken for the Linpor and Ring Lace Systems. At 18.7 g/L
of pads, a Linpor system would require about 11% pads by volume to achieve a total system
biomass loading of 0.2 (suspended MLSS of 2,044 mg/L). This is at the low end of Linpor pad
densities, suggesting that an installed cost of $250/m3 may be applicable. This is equivalent to a
total cost of $1,182,000, or 65 percent of the lowest cost conventional alternative. The reader
must bear in mind that these values are based on FRG material, construction, and labor costs,
which are not equivalent to those in the United States. The low biomass density on the Ring
Lace system shown in Table 21 equates to an installed Ring Lace density of 317 m/m3 of
aeration tankage to achieve an equivalent immobilized biomass of 2,063 mg/L (suspended MLSS
of 2,044 mg/L). At $2.65/m of Ring Lace, this equals a total cost of nearly $4,000,000.
Given the significant differences in mass transfer characteristics and the percentage of
aerobic biomass likely to exist among the various inert media systems, comparison on the sole
basis of mass of immobilized biomass is tenuous at best. Nonetheless, this simple type of
analysis does suggest that at least some of the high biomass systems are potentially cost-effective
upgrading approaches at overloaded conventional activated sludge plants. In addition, the
inclusion of inert support media may allow for similar cost-effective achievement of nitrification
at facilities originally designed to accomplish only carbonaceous BOD5 removal.
Summary. A number of high biomass systems have been installed at wastewater treatment
plants throughout the Federal Republic of Germany. These installations were designed to effect
improved effluent quality, and it appears that this goal is being realized.
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Reasons for selecting high biomass systems over construction of additional aeration
tanks and clarifiers (or other secondary treatment processes) include reduced space
requirements, increased process stability, and capital/operating cost savings.
High biomass systems call for installation of supplemental equipment over that
contained in a conventional activated sludge plant. More installed equipment generally implies
more maintenance, and, to some extent, this is true for some of the systems. In addition, the
presence of both suspended and fixed biomass forms and higher biomass concentrations may
require a certain level of additional operator time to achieve optimum system performance.
The presence of inert support media and higher biomass concentrations in these systems
can increase overall power consumption. To achieve desired mixing patterns in retrofitted
aeration tanks, power input may have to be increased. Also, the presence of additional biomass
increases system oxygen requirements which, in turn, requires additional power input. In
addition, high biomass systems generally yield higher levels of nitrification, which also can affect
overall power consumption. Such factors should be addressed when analyzing operating costs.
Certain system design limitations have been identified in the past, but many of these
have been corrected by the system manufacturers and/or operators. For example, influent
hydraulic surges at Linde AG plants have caused partial blinding of the retention screens by the
sponge media. This has been partially corrected by increasing the pumping rate of the sponge
return system. Also, abrasion of the sponge media was stated to result in losses of less than 5
percent per year, but there does not appear to be a corrective action for this system limitation
beyond adding new sponges as required. In Ring Lace systems, a question on the extent of
media stretching over time persists. Construction of self-tensioning media racks may address
this potential limitation. Plugging of the synthetic trickling filter media in Bio-2-Sludge systems
has been a concern of certain individuals. It appears that periodic use of an additional air
blower induces additional sloughing of the fixed film biomass, thus preventing this potential
problem. There were other problems communicated to the EPA evaluation team, but these
were of minor importance because solutions had, for the most part, already been developed and
field tested.
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The capacity for increased throughput realized by conversion to a high biomass system
cannot be assessed from available data. However, it appears that conversion can result in at
least the doubling of the biomass concentration in a system and for the reduction by at least
one-third of the required RAS pumping rate, compared to a conventional activated sludge plant.
These two factors alone indicate the potential for increased throughput capacity. A preliminary
economic analysis suggests that high biomass systems may be more cost effective for plant
upgrading than conventional approaches.
The actual capacity increase that can be realized by conversion to a high biomass system
should be established from the conduct of pilot plant studies. Representatives for both Bio-2-
Sludge and linde AG stated that to obtain accurate design and operational information, a pilot
plant should have an aeration tank with a volume of at least 100 m3.
REFERENCES
1. Peters, P. W. and I.E. Alleman. 1982. "The History of Fixed-Film Wastewater Treatment
Systems," Proc. First Internat. Conf. on Fixed-Film Biological Processes. Vol. 1, p. 60.
2. Wilford, J. and T.P. Conlon. 1957. "Contact Aeration Sewage Treatment Plants in New
Jersey," Sewage and Industrial Wastes. 29: 845.
3. Huang, C.S. 1982. "The Air Force Experience in Fixed-Film Biological Processes," Proc.
First Internat. Conf. of Fixed-Film Biological Processes. Vol. 3, p. 1777.
4. Boyle, W. C. and A.T. Wallace. 1986. "Status of Porous Biomass Support Systems for
Wastewater Treatment: An I/A Technology Assessment," EPA/600/S2-86/019, EPA,
Cincinnati, OH.
5. Heidman, J.A., R.C. Brenner, and HJ. Shah. 1988. "Pilot-Plant Evaluation of Porous
Biomass Supports," Jour. Env. Eng. Div.. ASCE. 114: 1077.
6. Arora, M.L. and M.B. Umphres. 1987. "Evaluation of Activated Biofiltration and
Activated Biofiltration/Activated Sludge Technologies," Jour. Water Poll. Control Fed..
59: 183.
7. Hegemann, W. and A. Wildmoser. 1986. "Sanierung einer Belebungsanlage durch den
Einsatz von schwimmenden Aufwuchskorpern zur Biomassenanreichung," gwf-
wasser/abwasser. (9):415-421.
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8. Lassmann, E. and H. Reimann. 1987. "Der Einsatz von offenporigem Schaumstoff als
Tragermaterial bei der biologischen Abwasser-Reinigung," Chemie-Ingenieur-Tcchnik.
(59):2:132-134.
9. Lang, H. 1981. "Nitrifikation in biologischen Klarstufen mit Hilfe des 'Bio-2-Schlmann-
Verfahrens'," Wasserwirtschaft. 71(6):166-169.
10. Eberhardt, H., O. Klee, and W. Weber. 1984. "Leistungssteigerung einer uberelasteten
Belebungsanlage durch Einbau submerser Festkorper," Wasserwirtschaft. 74(2):47-53.
11. Schlegel, S. 1984. "Ergebnisse von Versuchen einer aus Tropfkorper mit nachgeschalteter
Belebung bestehenden Anlage im Vergleich zur einstufigen Belebungsanlage,"
Korrestx>ndenz Abwasser. 31(3):252-253.
12. Schlegel, S. 1987. "Uberden Einsatz von getauchten Festbettkorpern bei der biologischen
Abwasserreinigung," Chemie-Ingenieur-Technik. 59(3):252-253.
13. Schlegel, S. 1988. "Der Einsatz von getauchten Festbettkorpern zur Nitrifikation,"
Korresoondenz Abwasser. 35(2):120-126.
14. Schlegel, S. 1988. "The use of Submerged Biological Filters for Nitrification," Wat. Sci.
Techn.. 20(4/5):177-187.
15. Scherb, K. 1987. "Abwasserreinigung nach dem Ring-Lace-Verfahren (Bioringschnur-
Verfahren)," Muchener Beitrage zur Abwasser. Fischereiund Flussbiologie. Band 41:
Stand der Techm'k bei der Elimination umweltrelevanter Abwasserinhaltsstoffe. pp. 212-
229, R. Oldenbourg, Muchen.
16. Wanner, J., K. Kucman, and P. Grau. 1988. "Activated Sludge Process Combined with
Biofilm Cultivation," Wat. Res.. 22(2):207-215.
17. Rogalla, F. et al. 1988. "Fixed Biomass to Upgrade Activated Sludge," Presented 61st
Annual WPCF Conference, Dallas, Texas, October.
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CHEMICAL PHOSPHOROUS REMOVAL IN LAGOONS
Charles Pycha
U.S. Environmental Protection Agency
Chicago, Illinois
Introduction. Phosphorus has been a contaminant of concern to EPA's Region 5 for many
years primarily because of the Great Lakes as well as numerous other smaller lakes and
impoundments. The basic chemistry of biological and chemical removal of phosphorus is
covered quite adequately in the EPA design manuals on phosphorus removal. What these
manuals do not address is removal of phosphorus from lagoon or pond systems. The technology
of removing phosphorus from ponds, or P-Ponds, is not really new but has not been used to a
great extent. The EPA Design Manual on Municipal Wastewater Stabilization Ponds does
address this technology. The purpose of this report is to take a more detailed look at how P-
Ponds are utilized in Region 5, principally in Michigan and Minnesota.
Background. In the early 1970s, the Ontario Ministry of the Environment initiated several
research projects on nutrient control in sewage lagoons. These reports provide the baseline
information upon which most applications of this technology were designed around. These
research projects addressed continuous as well as seasonal discharge lagoons. They covered the
addition of ferric chloride, alum, and lime at various dosages. Based on these studies, Ontario
decided to design and operate full-scale municipal seasonal discharge spring and fall lagoons
using alum to precipitate the phosphorus. Provincial personnel provide the manpower for the
chemical addition and discharge for over 20 lagoon systems. Their methodology, which is akin
to a contract operation, varies somewhat from Region 5.
Region 5 Experience. Ontario uses a team of four or five people and several boats. Each boat
is equipped with a tank for alum with a pump to inject the alum into the propwash at the stern
of the boat. Their stabilization ponds are usually 10 acres or more. They will typically have a
tank wagon with alum driven directly to the lagoon site, along with 3 boats 14 to 16 ft in length
with 50 or 60 HP motors that they operate simultaneously. They can almost continuously load
alum to the boats and apply it to the total lagoon cell in a couple of hours. The pond will be
given a day to settle and then the level will be lowered 3 to 4 ft over the period of 5 to 10 days.
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Using these procedures, the operating team can service a large number of lagoons in one
geographic area simultaneously. Ontario's operating approach appears to generally stay well
above the stoichiometric dosage rate, which usually ensures low effluent total phosphorus
residual levels often staying consistently below 0.5 mg/L.
Minnesota, the legendary land of 10,000 lakes, with hundreds of municipal lagoon
systems, has about a dozen that practice chemical addition (alum) directly to the final cells via
motorboat to achieve reduction of total phosphorus to meet a 1.0 mg/L effluent standard.
These lagoon systems range from a design flow of 25,000 gallons per day with a polishing lagoon
as small as 1.5 acres to a design flow of 0.7 mg/L with a polishing pond size of up to 20 acres.
Alum is applied to the lagoon surface with boats ranging from a 12-ft aluminum boat with a 5
HP outboard motor to a 17-ft pontoon boat with a 500 gal onboard storage tank and twin 50
HP motors for power. At most facilities liquid alum is used; bags of powdered alum are used at
some of the smaller facilities because they are more convenient to store.
The majority of the facilities will inject the alum into the outboard motors propwash,
following the Ontario example. Several of the smaller facilities have outrigger arms to pump
the alum onto the lagoon surface several feet to either side of the boat. This method, though
ensuring full surface coverage, would not appear to as thoroughly mix the alum with the pond
water, as would adding it to the propwash. It is successful in meeting a 1.0 mg/L effluent limit
possibly because it appears that the initial mixing plus the added mixing from the distribution
boats' cross-hatching pattern adequately precipitates the phosphorus. Influent phosphorus
values ranged as low as 3.0 mg/L, which is significantly lower than historic published values,
possibly due to the widespread marketing of nonphosphate detergents.
Michigan has taken a slightly different approach to phosphorus removal from lagoon
systems. There are some 26 lagoon facilities with phosphorus limits that fall into 3 general
types: 1) seasonal discharge, 2) continuous discharge with chemicals being added to the
polishing pond, and 3) continuous discharge with clarifiers following the pond system. Sizes of
these facilities range from 0.25 to 7.5 mgd. There is a wide combination of chemicals that are
used including ferric chloride or alum at equal numbers of facilities. One facility uses both
ferric chloride and alum, while several facilities use a polymer in conjunction with either metal
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or salt. A few of these facilities have been operating for as long as 20 years. Most of these
facilities add the chemicals between lagoon cells, often using a mixing chamber between the cells
or between the lagoons and the final clarifier. The chemicals are added continuously or more
specifically whenever wastewater is being transferred into the polishing pond or clarifier.
Discharge procedures for these systems vary from spring and fall discharge periods of
several weeks, to 24 or 8 hours per day on a continuous basis throughout the year. Additionally,
permit effluent limits, based upon total phosphorus, which are typically written in the standard
1.0 mg/L based on a 30-day average with a resultant pounds per day calculated based upon
design flow, also may include pounds per day daily maximum value and pounds per day based
upon a 30-day average without a concentration limit.
Conclusion. This causes a problem when one tries to draw a general conclusion regarding
Region 5 experience with P-Ponds. The conclusion is that the technology of adding chemicals
to precipitate phosphorus in lagoons is effective but there are problems. Only two of the 30
facilities reviewed as part of this report were in significant noncompliance, but there were many
minor excursions in excess of the permitted phosphorus limits at other facilities. Problems
identified included those typical of lagoon systems, namely mixing of the lagoon contents by
wind and waves during discharge as well as the expected algal blooms. Other typical problems
with the storage, pumping, and mixing of the chemicals were to be expected. Only one facility
identified a problem with resolubilization of the phosphorus in the bottom sediment, and this
was related to a change in the pond pH due to algal blooms, which can affect the reaction with
the ferric chloride used at this facility. Several of the seasonally discharged P-Ponds based the
initial chemical dose on past experience rather than by calculating the required dose based upon
the initial phosphorus concentration in the ponds. This could be a result of a tendency to
minimize operating costs (purchasing of excessive chemicals) and may be the cause of some of
the minor permit excursions that were documented. This varies from the Ontario experiences
where they prefer to add a heavier dose of chemical to ensure permit compliance as well as
reaping a secondary benefit of discharges of less phosphorus (and BOD and SS that is also
precipitated) to the receiving waters.
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On the positive side of these experiences is the fact that the seasonal discharge lagoons
require a minimum of operator attention. Chemical addition on a batch basis is easily
calculated and easily applied through an influent structure or via motorboat. The systems can
and have regularly achieved effluent total phosphorus limits of 1 mg/L or less under a wide
variety of lagoon configurations, climatic conditions, and a wide range of design flow rates
(0.025 to 7.5 mgd). As with any treatment system, P-Ponds depend upon operator knowledge
and attention. Chemical precipitation on BOD and SS is also of benefit to pond systems
because of the wide seasonal variability of the organic life within the pond.
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APPENDICES
-------
APPENDIX A
AGENDA
-------
APPENDIX A
U.S. ENVIRONMENTAL PROTECTION AGENCY
1991 WASTEWATER TECHNOLOGY FORUM
June 5-7, 1991
Portland Hilton
Portland, Oregon
AGENDA
TUESDAY. JUNE 4. 1991
5:00 p.m. - 7:00 p.m. Poster Session (Parlors A, B & C)
6:00 p.m. - 9:00 p.m. Early Registration
WEDNESDAY. JUNE 5. 1991
7:30 a.m. Registration
8:30 a.m. Introduction
• Opening Remarks
Wendy Bell, U.S. EPA, Office of Wastewater Enforcement and
Compliance (OWEC), Washington, DC
• Welcome
Bob Burd, U.S. EPA, Region 10
• Keynote Address
Mike Cook, U.S. EPA, OWEC, Washington, DC
• Some Thoughts on Wastewater Technology in the 90s
Bob Lee, U.S. EPA, OWEC, Washington, DC
9:30 a.m. Update on EPA's Sludge Policy and New Sewage Sludge Regulations
Bob Bastian, U.S. EPA, Washington, DC
10:15 a.m. Break
A-l
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WEDNESDAY. JUNE 5. 1991
(continued)
10:30 a.m. Land Treatment
Moderator: Bryan Yirn, U.S. EPA, Region 10
• Considerations for Overland Flow Diagnostic Evaluations
Tom Wooters/Chris King, Crowder College, Neosho, MO
• Best Available Technology for Design and Siting for Land
Application of Wastewater on the Rathdrum Prairie—Kootenai
County, Idaho
John Sutherland, State of Idaho, Division of Environmental
Quality, Coeur D'Alene, ID
11:45 a.m. Lunch with Speaker
Speaker: Skeet Arasmith, Arasmith Consulting Resources,
Albany, OR
1:15 p.m. Sand and Gravel Filters
Moderator: Steve Hogye, U.S. EPA, Washington, DC
• Sand Filters: State of the Art
Harold Ball, Orenco Systems, Inc., Roseburg, OR
• Tennessee Experience with Recirculating Sand Filters:
Wastewater Treatment Systems for Small Flows
Steve Fishel, Tennessee Division of Water Pollution Control,
Nashville, TN
• Recirculating Gravel Filters in Oregon
Jim Van Domelen, Oregon Department of Environmental
Quality, Portland, OR
3:00 p.m. Break
3:15 p.m. Operations and Maintenance
Moderator Lam Lim, U.S. EPA, Washington, DC
• Assessment of O & M Requirements for Ultraviolet
Disinfection Systems
Karl Scheible, HydroQual, Inc., Mahwah, NJ
• Trickling Filter O&M Issues
Russell Martin, U.S. EPA, Region 5
• Update on the Microbial Rock Plant Filter
Ancil Jones, U.S. EPA, Region 6
A-2
-------
WEDNESDAY. JUNE 5. 1991
(continued)
5:15 p.m. Adjourn
5:15 p.m. - 7:00 p.m. Poster Session (Parlors A, B & C)
THURSDAY. JUNE 6. 1991
8:00 a.m. Biological Nutrient Removal
Moderator: Atal Eralp, U.S. EPA, Washington, DC
• Meeting More Stringent Standards Using BNR
Glen Daigger, CH2M Hill, Denver, CO
• Operation of BNR systems at two Oregon POTWs
Gordon Nicholson, CH2M Hill, Bellevue, WA
• Summary of Patented and Public Biological Phosphorous Removal
Systems
William Boyle, University of Wisconsin, Madison, WI
9:45 a.m. Break
10:00 a.m. Sludge
Moderator: John Walker, U.S. EPA, Washington, DC
• Case Study Evaluation of Alkaline Stabilization Processes
Lori Stone, Engineering-Science, Inc., Fairfax, VA
• Controlling Sludge Composting Odors
William Horst, City of Lancaster, PA
• Co-composting
Dale Cap, Southwest Suburban Sewer District, Seattle, WA
11:45 a.m. Lunch - On Your Own
1:00 p.m. Field Trip to two Portland Wastewater Treatment Plants:
1. Tri-City Water Pollution Control Plant
Highlighting the Anoxic Selector Activated Sludge System for
Nitrogen Removal
2. Columbia Boulevard Wastewater Treatment Plant
Highlighting the In-Vessel Composting System
A-3
-------
5:00 p.m. Arrive Back at Hotel
FRIDAY. JUNE 7.1991
8:00 a.ra. Stormwater
Moderator: Jim Kreissl, U.S. EPA, Center for Environmental
Research Information (CERI), Cincinnati, OH
• Development of CSO Regulations in Washington State
Ed O'Brien, Washington Department of Ecology, Olympia, WA
• Cost of CSO Controls
Atal Eralp
• Stormwater Control for Puget Sound
Peter Birch, Washington Department of Ecology, Olympia, WA
9:45 a.m. Disinfection
Moderator: Jim Kreissl
• Total Residual Chlorine: lexicological Effects and Fate in
Freshwater Streams in New York State
Gary Neuderfer, New York Department of Environmental
Conservation, Avon, NY
• EPA Disinfection Policy and Guidance Update
Bob Bastian
10:30 a.m. Break
10:45 a.m. Constructed Wetlands
Moderator: Bob Bastian
• Arcata, CA
Bob Gearheart, Humboldt State University, Arcata, CA
• Constructed Wetlands Experience in the Southeast
Bob Freeman, Cobb County Water System, Marietta, GA
12:00 p.m. Lunch - On Your Own
1:15 p.m. Municipal Water Use Efficiency
Moderator: Bob Bastian
• How Efficient Water Use Can Help Communities Meet
Environmental Objectives
Steve Hogye
A-4
-------
FRIDAY. JUNE 7. 1991
(continued)
• Effects on POTWs
Bob Gearheart
2:15 p.m. High Biomass in Europe
Art Condren, James Montgomery Consulting Engineers, Pasadena,
CA
3:00 p.m. Chemical Phosphorus Removal in Lagoons
Chuck Pycha, U.S. EPA, Region 5
3:45 p.m. End of Forum
A-5
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APPENDIX B
LIST OF SPEAKERS
-------
APPENDIX B
U.S. ENVIRONMENTAL PROTECTION AGENCY
1991 WASTEWATER TECHNOLOGY FORUM
June 5-7, 1991
The Portland Hilton
Portland, OR
SPEAKER LIST
Skeet Arasmith
Arasmith Consulting Resources
1298 Elm Street, SW
Albany, OR 97321
503-928-5211
Harold Ball
Orenco Systems, Inc.
2826 Colonial Road
Roseburg, OR 97470
503-673-0165
Robert Bastian
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-547)
Washington, DC 20460
202-382-7378
Wendy Bell
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-547)
Washington, DC 20460
202-382-7292
Peter Birch
Water Quality Program
Washington Department of Ecology
Olympia, WA 98504
206-438-7076
William Boyle
Department of Civil &
Environmental Engineering
University of Wisconsin
3230 Engineering Building
Madison, WI 53706
608-262-1777
Bob Burd
Water Division
U.S. Environmental Protection Agency
1200 Sixth Avenue
Seattle, WA 98101
206-553-1014
Dale Cap
Southwest Suburban Sewer District
1015 Southwest 174th Street
Seattle, WA 98166
206-242-7907
Arthur Condren
James Montgomery Consulting Engineers,
Inc.
250 North Madison Avenue - P.O. Box 7009
Pasadena, CA 91109-7009
818-568-6589
Mike Cook
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-546)
Washington, DC 20460
202-382-5850
B-l
-------
Glen Daigger
CH2M Hill
P.O. Box 22508
Denver, CO 80222
303-771-0900
Atal Eralp
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-547)
Washington, DC 20460
202-382-7369
Steve Fishel
Division of Water Pollution Control
150 Ninth Avenue North
Nashville, IN 37247
615-741-0633
Bob Freeman
Cobb County Water System
680 South Cobb Drive, SE
Marietta, GA 30060
404-423-1000
Bob Gearheart
Department of Engineering
Humboldt State University
Arcata, CA 95521
707-826-3619
Stephen Hogye
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-547)
Washington, DC 20460
202-382-5841
William Horst
City of Lancaster
120 North Duke Street
Lancaster, PA 17603
717-291-4825
Ancil Jones
Water Management Division
U.S. Environmental Protection Agency
1445 Ross Avenue (6W-MT)
Dallas, TX 75202
214-655-7130
Chris King
Water/Wastewater Division
Crowder College
Route 6
Neosho, MO 64850
417-451-3583
Robert Lee
Office of Wastewater
Enforcement & Compliance
U.S. Environmental Protection Agency
401 M Street, SW (WH-547)
Washington, DC 20460
202-382-7356
Russell Martin
Water Management Division
U.S. Environmental Protection Agency
230 South Dearborn Street
Chicago, IL 60604
312-886-0268
Gary Neuderfer
New York State Department
of Environmental Conservation
6274 East Avon-Lima Road
Avon, NY 14414
716-226-2466
Gordon Nicholson
CH2M Hill
P.O. Box 91500
Bellevue, WA 98009
206-453-5000
Ed O'Brien
Water Quality Program
Washington Department of Ecology
Olympia, WA 98504
206-438-7037
B-2
-------
Chuck Pycha
Water Management Division
U.S. Environmental Protection Agency
230 South Dearborn Street
Chicago, IL 60604
312-886-0259
O. Karl Scheible
HydroQual, Inc.
1 Lethbridge Plaza
Mahwah, NJ 07430
201-529-5151
Lori Stone
Engineering-Science, Inc.
10521 Rosehaven Street
Fairfax, VA 22030
703-591-7575
John Sutherland
Division of Environmental Quality
Idaho Department of Health & Welfare
2110 Ironwood Parkway
Coeur d'Alene, ID 83814
208-667-3524
Jim Van Domelen
Department of Environmental Quality
Water Quality - 5th floor
811 Southwest Sixth Street
Portland, OR 97204
503-229-5310
Tom Wooters
Water/Wastewater Division
Crowder College
Route 6
Neosho, MO 64850
417-451-3583
B-3
-------
APPENDIX C
LIST OF ADDRESSES FOR REGIONAL AND STATE WASTEWATER
TECHNOLOGY, SLUDGE, AND OUTREACH COORDINATORS
-------
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Protection
122 Washington Stre<
Hartford, CT 06106
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Department of Envip
State House (Station
Augusta, ME 04333
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W
Massachusetts
Division of Water Po
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One Winter Street
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Mississippi Department
Office of Pollution Coi
P.O. Box 10385
Jackson, MS 39289-03
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Special Projects Section
Water Management Division
Indiana Department of Environ
105 South Meridian Street, P.O
Indianapoh's, IN 46206-6015
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State Office Bldg., Skth Floor
350 Ottawa St., N.W.
Grand Rapids, MI 49503/
Box 30028
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P.O. Box 1049
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Iowa
Program Operations Division
Iowa Department of Natural Reso
Environmental Protection Division
Henry A. Wallace Building
900 East Grand
Des Moines, IA 50319
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Nebraska
Construction Grants Brand
Water Quality Section
Nebraska Department of Ei
P.O. Box 98922
Statehouse Station
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REGION Vin
U.S. EPA Water Management
999 - 18th Street, Suite 500
Denver, CO 80202-2405
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4210 E. llth Avenue
Denver, CO 80220
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California
State Water Resources Control
Division of Clean Water Progr
P.O. Box 944212
Sacramento, CA 94224-2120
Hawaii
11
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Hawaii State Department of H
5 Water Front Plaza, Suite 250
500 Ala Moana Blvd.
Honolulu, HI 96813
Nevada
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Protection - Construction Gran
Capitol Complex
123 W. Nye Lane
Carson City, NV 89710
C-18
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-------
APPENDIX D
SUMMARY OF INNOVATIVE AND ALTERNATIVE
TECHNOLOGY PROJECTS BY STATE
-------
SUMMARY OF INNOVATIVE TECHNOLOGY PROJECTS
EPA
REGION STATE
I Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
HI Delaware
Washington DC
Maryland
Pennsylvania
Virginia
West Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Louisiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Arizona
California
Guam
Trust Territories
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon
Washington
TOTAL
Aeration
Counter Current Aeranon
1
1
5
1
1
1
5
1
7
1
24
Draft Tube Aeration
1
1
3
1
2
1
2
4
2
1
1
1
20
Fine Bubble Diffusers
1
1
2
1
2
2
2
11
Aero-mod System
1
1
3
5
Intermittent Cycle
Extended Aeraoon
4
2
...!.,.
Other Aeration
1
1
1
1
1
1
i
1
2
2
J?
Clarification
Flocculating Glanders
2
1
1
4
Integral Ganders
2
1
1
4
m
8
5
o
«
c
c
ia
_C
1
1
2
3
4
7
1
1
2
2
1
1
3
1
4
1
2
1
1
4
2
1
46
til
2
a
1
1
1
1
1
3
1
8
Other Clandcatlon
1
1
1
1
1
1
1
2
1
10
Collection
Small Diameter Gravity
Sewers
1
1
1
4
1
8
Other Collection Systems
t
2
1
1
5
D-l
-------
SUMMARY OF INNOVATIVE TECHNOLOGY PROJECTS (cont'd)
EPA
REGION STATE
1 Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
III Delaware
Washington DC
Maryland
Pennsylvania
Virginia
West Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Lousiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Arizona
California
Guam
Trust Territories
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon .
Washington
TOTAL
Disinfection
Ultraviolet Disinfection
2
1
1
1
1
4
3
1
1
5
3
1
1
4
4
1
3
1
1
4
4
1
1
49
Other Disinfection
2
1
1
1
1
1
1
1
1
1
11
Dfcpcsa,
Effluent
Other Disposal of Effluent
2
1
1
1
5
Energy
Conservation
and Recovery
Solar Heating
1
1
1
1
1
1
1
1
1
1
10
Other Energy Conservation
and Recovery
1
1
4
1
3
1
1
1
1
3
1
1
1
20
Filtration
Biological Aerated Filters
1
1
1
3
Microscreens
1
1
1
1
1
1
6
Other Filtration
1
2
2
1
1
2
1
1
1
1
2
2
3
20
Lagoons
Aquaculture
1
2
1
2
6
Hydrograph Controlled
Release Lagoons
3
5
2
8
1
2
1
1
1
1
25
Single Cell Lagoon
with Sand Filter
10
10
Other Lagoons
1
2
1
2
1
1
1
1
1
1
1
1
14
D-2
-------
SUMMARY OF INNOVATIVE TECHNOLOGY PROJECTS (cont'd)
EPA
REGION STATE
1 Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
III Delaware
Washington DC
Maryland
Pennsylvania
Virginia
West Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Lousiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Arizona
California
Guam
Trust Terntones
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon
Washington
TOTAL
Land
Application
of Effluent
Overland Flow
2
1
1
3
1
1
3
12
Other Land Application
of Effluent
1
1
1
1
1
1
1
1
1
1
1
1
1
1
14
Nitrifi-
cation
Other Nitrification
2
1
1
1
1
2
1
9
Nutrient Removal
Anoxic/oxic system (A/O)
1
1
1
1
1
1
6
a
to
in
1
2
1
1
5
Sequencing Batch Reactor
(SBR)
1
3
2
1
6
3
3
1
1
1
22
Other Nutrient Removal
2
1
1
1
2
1
1
2
1
1
13
Oxidation
Ditch
Barrier Wall Oxidation Ditch
3
1
4
Other Oxidation Ditch
1
3
2
6
1
5
2
1
3
1
2
1
1
5
2
1
1
1
1
1
41
Fixed Growth
Ib
if
If
li
no
1
1
1
1
1
5
Trickling Filter/Solids Contact
1
2
1
1
1
1
1
2
1
1
12
c5
1
ii
1
1
D-3
-------
SUMMARY OF INNOVATIVE TECHNOLOGY PROJECTS (cont'd)
EPA
REGION STATE
1 Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
III Delaware
Washington DC
Maryland
Pennsylvania
Virginia
West Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Lousiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Arizona
California
Guam
Trust Territories
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon
Washinqton
TOTAL
Sludge Technologies
Carver-Greenfield
1
2
3
Composting
2
11
1
1
3
6
1
14
2
2
2
2
1
1
2
4
5
1
1
62
§
§
s
1
1
2
1
1
1
1
8
o
1
1
2
1
5
Vacuum Assisted Sludge
Drying Beds
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1$
Other Sludge Technologies
4
1
1
2
1
1
1
1
2
3
2
1
1
1
2
1
25
Onsite
Tech-
nologies
Other Onsite Technologies
1
1
1
3
Miscellaneous
Q.
I
5
i
i
o
u
c
LJJ
1
1
2
4
Other Miscellaneous
2
1
1
1
1
1
1
1
1
2
1
1 ,
4
1
2
1
1
1
24
Suspended
Growth
Powdered activated
Carbon/Regeneration
1
1
2
4
Other Suspended Growth
1
1
D-4
-------
SUMMARY OF ALTERNATIVE TECHNOLOGY PROJECTS
EPA
REGION STATE
1 Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
III Delaware
Washington DC
Maryland
Pennsylvania
Virginia
Wast Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Lousiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Anzona
California
Guam
Trust Territories
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon
Washington
TOTAL
ONSITE TREATMENT
Septic Tank/Soil Absorption
System (Single Family)
4
1
3
3
1
1
2
4
1
2
10
1
1
2
36
Mound System
2
2
1
1
2
9
1
3
1
4
1
1
28
Evapotranspiration Bed
2
2
<
1
1
1
3
Sand Filter
1
5
1
4
2
12
2
1
2
15
2
1
1
1
1
2
3
56
Other Onsite Treatment
1
1
1
1
1
1
1
1
8
SOLIDS TREATMENT
13
1
C
1
1
1
7
19
7
2
11
4
3
3
2
1
1
3
1
1
4
69
Land Spreading of POTW Sludge
1
12
1
2
2
4
6
9
2
4
13
3
4
5
5
44
20
16
24
35
13
2
1
10
29
24
20
34
5
2
9
11
1
2
1
1
1
6
4
1
389
Composting
1
6
5
1
1
5
2
1
2
1
5
3
3
1
2
1
2
4
1
1
1
2
1
1
1
1
55
Preapplicanon Treatment
3
1
1
1
17
3
3
3
g
1
2
8
2
3
1
2
3
1
64
90% Methane Recovery
from Anaerobic Digestion
4
2
16
2
3
5
2 J
3
3
4
2
6
1
13
5
4
6
6
3
1
1
7
6
5
1
3
1
. 2
4
1
1
3
5
3
1
3
5
2
145
Self-sustaining Incineration
(Heat Recovery and Utilization)
1
2
1
1
2
1
1
1
1
1
2
1
1
16
Other Sludge Treatment or Disposal
1
1
2
3
1
1
1
5
1
1
1
2
8
2
1
1
2
1
2
37
D-5
-------
SUMMARY OF ALTERNATIVE TECHNOLOGY PROJECTS (cont'd)
EPA
REGION STATE
1 Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
II New Jersey
New York
Puerto Rico
Virgin Islands
III Delaware
Washington DC
Maryland
Pennsylvania
Virginia
West Virginia
IV Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
V Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
VI Arkansas
Lousiana
New Mexico
Oklahoma
Texas
VII Iowa
Kansas
Missouri
Nebraska
VIII Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
IX Arizona
California
Guam
Trust Territories
Hawaii
Nevada
N. Marianas Islands
X Alaska
Idaho
Oregon
Washington
TOTAL
TREATMENT/DISCHARGE SYSTEMS
Overland Flow
1
2
2
3
1
2
1
11
2
4
4
6
1
14
1
2
57
Rapid Infiltration Land
Treatment Systems
1
2
1
3
1
1
1
1
2
1
1
1
4
1
17
1
1
2
3
8
2
1
14
1
5
4
1
81
Slow Rate
Treatment Systems
1
1
1
5
5
1
2
20
18
2
2
21
g
6
3
1
14
15
1
1
5
2
6
31
11
2
16
25
5
2
8
6
1
3
2
12
20
2
6
9
6
3
312
B>
£
C
«
1
_1
-------
APPENDIX E
CURRENT STATUS OF MODIFICATION/REPLACEMENT
(M/R) GRANT CANDIDATES BY STATE
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