UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
January 28, 1992
EPA-SAB-EEC-LTR-92-006
Honorable William K. Reilly
Administrator
U.S. Environmental Protection Agency THE ADMINISTRATOR
401 M Street, S.W.
Washington, D.C. 20460
Subject: Science Advisory Board Letter Report on Research-in-Progress
Review of ORD's "Constructed Wetlands for Wastewater Treatment"
Dear Mr. Reilly:
The Constructed Wetlands Subcommittee (CWS) of the Environmental
Engineering Committee (EEC) of the Science Advisory Board (SAB) met at EPA's
Environmental Research Laboratory (ERL), in Corvallis, Oregon to conduct a
Research-in-Progress Review of the Constructed Wetlands for Wastewater
Treatment Programs of the Cincinnati Risk Reduction Engineering Laboratory
(RREL) and the Corvallis and Duluth Environmental Research Laboratories (ERL)
on July 17-18, 1991.
Constructed Wetland Subcommittee Charge
The Subcommittee was charged with the four following tasks:
1) Examine the overall research plan, review the current balance among
the program areas, review future priorities among these areas, and
identify additional areas of research;
2) Make recommendations concerning the scope of research including
whether free water surface system research should be investigated by
the RREL and whether these systems should be applied to uses in
addition to municipal wastewater treatment;
3) Review the technical, ecological, and system implementation research
posed by the RREL and the ERL, identify additional potential problem
areas, and make recommendations for prioritization of research in
these areas; and
4) Consider other Agency research efforts and make recommendations
concerning the need for interagency coordination in research and
technical development.
-------
General Observations
The Subcommittee was impressed by the quality and knowledge of the
presenting staff and their commitment to the research program. The Subcommittee
appreciated the RREL advance material. A Document provided by ERL at the July
17-18 meeting (prepared and published in September, 1990) consisted of a five-year
plan for a portion of the research program, but was not included in the staff
presentations and is not a subject of this review.
The Subcommittee endorses the Agency move toward development of
constructed wetlands, rather than continued utilization or taking over of natural
wetland systems for wastewater treatment. Reasons for the Subcommittee
endorsement are: 1) protection against degradation and further loss of natural
systems, and 2) increased efficiency and cost-effectiveness of wastewater treatment
that could result from constructed/managed systems as design, operation and
maintenance are refined.
The Subcommittee found that the Agency has an important role in the
constructed wetland field which stems from its fundamental responsibility for
National water quality protection. It is difficult to understand from this single
research review, however, how and where the Agency fits into the constructed
wetland research field and how the overall effort is organized within EPA.
The focus of the RREL research program is constructed subsurface wetlands for
municipal wastewater treatment, a vital and critical area for research and
development. This is a growth area; constructed wetlands are now serving
approximately 100 million gallons per day with many design and health questions
needing to be answered with research. In the future, smaller municipal systems
may come to rely more on constructed wetlands, in some circumstances, due to the
promise of cost effective treatment. These circumstances relate to the availability of
land and its cost relative to more conventioal (i.e., traditional) systems.
If constructed wetlands are to be in the front line of future activities in
municipal wastewater treatment, the design specifications to meet effluent
limitations must be refined. Municipal systems should be designed with adequate
over capacity to allow for growth in the anticipated volume of water for treatment,
and consist of parallel systems in order to operate consistently within permitted
limits. Parallel components are required because single unit systems cannot be
allowed to shut down for maintenance or system failure so that they routinely
bypass untreated or incompletely treated wastes, and must have sufficient capacity
to treat wide flow ranges and surges. The individual homeowner system would not
be expected to meet these capacity conditions for other than peak flow
requirements.
It was observed by the Subcommittee that the RREL research had focused on
subsurface flow constructed wetlands, due to funding limitations and the specific appli-
cation of these systems as secondary wastewater treatment after primary sedimentation.
-------
Constructed Wetland Research Coordination And Funding
During the review it was clear that there is little organization or coordination
between ERL and RREL, other than in the database project (which is one of the
most important projects of this research program). There must be identification of
Agency and program needs to focus on critical and important areas. In this regard,
RREL appeared focused on design criteria factors research and guidance manual
revision, while the ERL effort appeared fragmented, other than in database
development. The ERL-Duluth effort seemed unrelated to the stated research
objectives and the laboratory efforts might have been better directed, with funding
from the basic wetland research program, to address wetland and wildlife habitat
restoration in accordance with recent SAB comments to the Agency in its reducing
risk report.
The Subcommittee believes that there is a need for a coherent program and
organization within ORD to maximize the return on expenditures and to leverage
limited Agency funding, particularly when the level of funding is as low as it is in
this case. Additionally, the Subcommittee believes that coordination of other
Federal programs needs to occur with respect to pooling of other Federal funds.
Due to the promise of this technology and its increasing level of use, the
Agency should prioritize and allocate adequate funding and staff support for further
growth areas. These growth areas should include surface flow and open water
systems (lagoons) designed for water quality improvement and wildlife habitat value
enhancement; integrated systems (subsurface flow with open water systems, as well
as these systems in tandem with primary and secondary treatment); urban storm
water treatment; other aspects of non-point source, agriculture, mine drainage,
road/highway runoff treatment; and, constructed wetlands as polishing/protection of
natural wetlands or surface water bodies. Systems for these areas are now in
development in several Federal, State and sometimes local agencies, and EPA must
be involved because of its fundamental charge for water quality protection. The
Agency needs to organize and expand its efforts, develop clear Agency goals and
research plans, and implement recommended research with adequate funding. This
is particularly important, because there is a national need to develop efficient and
cost-effective constructed wetlands for wastewater treatment, particularly urban
storm water and other non-point source controls. This fits into the overall Agency
goals as identified and or proposed in its Risk Reduction Strategy. In addition, it is
possible that wastewater effluent may have a role in rehabilitating drained, mined,
or otherwise degraded natural wetlands, although such investigations should not be
part of the constructed wetland research plan.
-------
Need For National Workshop And Refocusing of Agency Priorities
The entire area of Federal constructed wetland research appears fragmented,
not just EPA's research program. Coordination is needed, and while there are
various mechanisms to achieve a refocusing of Agency priorities, the Subcommittee
recommends that EPA cosponsor a national workshop with other Federal and
possibly State and local agencies, as well as private organizations (e.g., ASTM and
the Water Environment Federation) having similar needs. The workshop should
focus on identifying the programs and staff of Federal agencies conducting
constructed wetland research and the types of constructed wetlands and their uses.
The workshop would provide a forum to standardize definitions and terminology
being used in this developing field, identify the types of wetlands being developed,
the state-of-the-art technology for each, areas needing further development, and
provide the basis for developing potential partnerships which have similar goals to
expand cost-effective research in an area with current limited funding. Issues
identified at the workshop could help the Agency refocus its priorities in the
constructed wetland research program and target where additional funding would
provide the greatest benefits.
Comments Concerning Specific Projects
There are numerous areas for further research within the RREL subsurface
flow systems studies which the Subcommittee believes should be considered by the
Agency for further funding and investigation. These areas include:
1) Basic hydrological research, including flow dynamics, media structure,
and the role of particulates in pore plugging;
2) Fundamental microbiological research including nutrient treatment
dynamics, toxic contaminant treatability, and pathogenic organism fate
and transport;
3) Treatment efficiency research of other basic water quality parameters
beyond BOD, TSS and N, to develop performance criteria (e.g., organic
carbon, herbicides, pesticides, pathogens);
4) Research into the fate and transport of metals, including basic research
in oxidation/reduction relationships and the potential for creating
hazardous wastes in sediments due to the sequestering characteristics
of constructed wetland systems;
-------
5) Determine limits and capabilities of treatability of complex waste
streams so that guidelines can be developed for application of
constructed wetlands only to appropriate waste streams, that is, ones
which will be successfully treated by the system; and,
6) Research into the functions and values of constructed wetlands in
other geographical localities, including the arid west, and into the full
range of potential target wastewater systems such as non-point, urban,
and agricultural systems.
Furthermore, in the Tennessee pilot studies:
1) The analytical parameters and their frequency of measurement should
be expanded in quantitative, statistically valid studies to focus on the
kinetics of system function to replace the observational nature of
historical data;
2) The monitoring study should help design bench-scale experiments on
control mechanism research into basic parameters, such as
temperature, hardness, and continual versus intermittent flow, which
cannot be satisfied by the one field location;
3) The monitoring study, with controlled bench-scale experiments, should
be integrated with results from the database project to develop
research models to further explore kinetics, hydraulic loading rates,
treatability, temperature, etc. and analyze design and performance
criteria in order to provide a basis for manual redevelopment in design
and performance criteria;
4) The design studies should be expanded to include aeration control and
the role of aerobic/anaerobic relationships in treatment efficiency; and,
5) Research should be conducted into the role of aquatic plants and their
importance in the system as periphyton substrate, and in particulate
removal and potential for providing oxygen to the treatment medium.
It should be noted that there is no similar monitoring of free water surface
flow type of constructed wetlands implemented in this research effort. Therefore,
most of the information needs for these systems has to be met by the literature
database development effort. Some of the preliminary results shown at the review
meeting indicate that large variability exists in the existing constructed wetlands
design, and that key variables and their importance in the design and performance
-------
for secondary treatment of municipal wastewaters may not be adequately quantified.
Again, analysis of variables and improvement in design criteria could be
accomplished through development and manipulation of specific system models.
The database effort was regarded by the Subcommittee as very valuable and
appears well organized. Additional emphasis should be placed on collection of
ecological and wildlife utilization information, which has been extensively studied,
especially for surface water systems. It was unclear to the Subcommittee, however,
how extensive the coordination between RREL and ERL would be, and how much
analysis of the data generated would be made available to RREL in its manual
design effort. The database project should be able to provide additional data for
progress in kinetics studies, design and performance criteria, and seasonal or other
geographic climate data for use in manual development as discussed above in
comments concerning the Tennessee studies. Stronger and more systematic
coordination between RREL and ERL is recommended. If significant additional
funding is not forthcoming, ERL should consider abandoning its low level support
for 'the dairy wastewater project and possibly the ERL-Duluth ecological survey, as
well as the acid mine drainage project. Additional comments on these three projects
are provided below.
The ERL-Duluth ecological study did not appear to relate to any of the
RREL or ERL-Corvallis programs, consisting of single snapshot observations at six
open water system wetlands. The project consists of a short-term ecological
assessment with limited value for long-term assessment of true system value in
wildlife utilization or enhancement. It has been suggested that this project was
conducted due to a lack of information on enhanced productivity and wildlife
carrying/utilization capacity at open water treatment systems relative to natural
wetlands. If this was indeed the project goal, the research should have been
focused on system dynamics and productivity investigations in time, rather than
snap-shot utilization observations, and could have been funded by the wetland
ecological research program instead of the constructed wetland program. Funding
for this project would have been better spent in the database project to expand its
review of ecological data available in the literature. At the least, this study should
have concentrated on evaluation of wildlife utilization of subsurface or onsite
household systems in order to be consistent with other areas of field research in
this research program. This could include research in problem areas such as pest
control (e.g., burrowing and vegetation consumption).
The limited funding of the Oregon State University dairy treatment system
did not appear well spent or well defined. The project did not involve research and
no product was projected for the expenditure, other than construction of a wetland
to aid in dairy wastewater treatment. The dairy already has state-of-the-art
treatment, and it was unclear what the ERL staff expected to learn from
construction of a wetland at this site. At a minimum, the research program
objectives need better focus prior to undertaking demonstration projects such as
this. Additional program funding is needed before the current research program
6
-------
diversifies into project areas such as this. The funding could have been better
spent supplementing the database effort or expanding the ecological study effort in
subsurface constructed wetland research.
Similarly, while acid mine drainage should be a significant area for research,
the limited funding and lack of product for the RREL support of the Soil
Conservation Service project appeared to contribute little to overall project goals.
The mining industry has numerous (approximately 400 sites) constructed wetlands
in operation, and this issue dwarfs the small community individual home system
problem with respect to direct effects upon receiving water bodies. The
Subcommittee strongly believes that this is an important area of research but
suggests that, if recommendations for expansion of research funding in this area
cannot be implemented, the Agency should suspend further efforts until adequate
funding can be allocated. In fact, the funding would have been better spent in
support of a workshop on interagency coordination, and database efforts more
central to the goals of the current research program. As noted above, the
Subcommittee identified this as an important area for additional research and
encourages ORD to consider funding it as a major research effort.
The onsite system monitoring program is a good start in an important
development area, although there is some concern that these systems are of limited
importance in a national research effort with limited funding. This area needs
quantitative research to develop the kinetic and performance data necessary to
replace the information currently available only in the unrefereed literature and to
determine the efficacy of these systems. The current research program should be
expanded to include public health considerations, such as health endangerment of
local populations and treatability of pathogenic organisms. In particular, some
monitoring should be done with known viruses, such as M3-2, or male-specific
coliphage. Future studies should expand investigations of these systems into other
geographical areas.
The RREL focus on revision of the design manual and its publication is a
sensible and tangible goal. Given the modest funding for the current program, this
will undoubtedly lead to only a modest improvement of the manual until the above
basic research and model development studies are conducted. Clearly, at current
levels of funding, significant advancement in system design cannot be expected.
Therefore, the expectations for precision and accuracy of the resulting manual
should not be too high, since the current goals are too modest. The expansion of
the monitoring program and integration with the database program results, in order
to study underlying kinetics and fundamentals suggested above, will ultimately lead
to substantial improvement in design and performance of constructed wetland
systems and a need for further revisions to the manual.
The goal of the manual should be comprehensive, telling the community that is
considering a constructed wetland for municipal wastewater treatment how to select
between free water and subsurface flow systems, how to design a system for
maximum water quality improvement, and how to take into account ecological
-------
consequences and benefits. Because the current research effort is fragmented, it did
not appear that even such a limited objective will be accomplished. For example,
the RREL has focused on subsurface flow wetlands while the ERL is only
investigating free surface wetlands. Research and its funding should not be
allocated this way. The allocation should be made along engineering and ecological
lines designed to achieve common objectives.
In summary, the EEC and it's Constructed Wetlands Subcommittee strongly
supports research in the constructed wetlands field and recommends increased
funding for expanded research in a number of critical areas. While some of this
review may appear negative in nature, the Subcommittee believes that the quality of
staff involved in this program is excellent and the overall effort is commendable.
The Subcommittee has identified areas for additional or expanded research,
recommends ORD to improve its overall research strategy and organization to guide
priority development and coordinate activities at the various laboratories, and
increase funding and staffing in this important research area.
We appreciate the opportunity to assist and provide suggestions in this
research-in-progress review. This letter report involves scientific issues of relevance
to a program of national significance and the Subcommittee raises issues which
need to be considered by the Agency. We look forward to the Agency response.
Raymond C. Loehr, Chairman
Executive Committee
Science Advisory Board
Richard A. Conway, Chairmar
Environmental Engineering Committee
Science Advisory Board
George F. Carpenter, Chairman
Constructed Wetlands Subcommittee
Science Advisory Board
8
-------
NOTICE
This report has been written as a part of the activities of the Science
Advisory Board, a public advisory group providing extramural scientific information
and advice to the Administrator and other officials of the Environmental Protection
Agency. The Board is structured to provide a balanced, expert assessment of
scientific matters related to problems facing the Agency. This report has not been
reviewed for approval by the Agency; hence, the comments of this report do not
necessarily represent the views and policies of the Environmental Protection Agency
or of other Federal agencies. Any mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
-------
SCIENCE ADVISORY BOARD
ENVIRONMENTAL ENGINEERING COMMITTEE
CONSTRUCTED WETLANDS SUBCOMMITTEE
Chairman
Dr. George F. Carpenter, Michigan Department of Natural Resources, Lansing,
Michigan
MEMBERS & CONSULTANTS
Dr. Corale L. Brierley, Newmont Exploration Ltd., Salt Lake City, Utah
Mr. David E. Chalk, USDA Soil Conservation Service, Portland, Oregon
Dr. Donald Hey, Hey and Associates, Chicago, Illinois
Dr. Allan Hirsch, Director, Washington Office, Midwest Research Corporation, Falls
Church, Virginia
Dr. Ishwar P. Murarka, Senior Program Manager, Electric Power Research
Institute, Palo Alto, California
Dr. Betty Haak Olson, University of California, Irvine, California
Dr. Harold H. Prince, Michigan State University, East Lansing, Michigan
Dr. Robert Stewart, Director, National Wetlands Research Center, Slidell, Louisiana
Mr. Russell Theriot, US Army Corps of Engineers, Wetlands Research Program,
Vicksburg, Mississippi
Dr. C. Herb Ward, Rice University, Houston, Texas
Science Advisory Board Staff
Dr. K Jack Kooyoomjian, Designated Federal Official
Mrs. Diana L. Pozun, Staff Secretary
Dr. Donald G. Barnes, Staff Director, Science Advisory Board
10
-------
DISTRIBUTION LIST
Administrator
Deputy Administrator
Assistant Administrators
EPA Regional Administrators
EPA Laboratory Directors
Deputy Assistant Administrator for Office of Research and Development:
Director, Office of Environmental Engineering and Technology
Demonstration (OEETD)
Deputy Director, OEETD
Deputy Assistant Administrator for Water:
Director, Office of Science and Technology
Director, Office of Watersheds, Oceans, and Wetlands
Director, Office of Wastewater Enforcement and Compliance
EPA Headquarters Library
EPA Regional Libraries
EPA Laboratory Libraries
11
------- |