United States
Environmental Protection
Agency
Office of Environmental Engineering1^
and Technology
Washington DC 20460 '/ FI \s
Research and Development
EPA-600/S2-83-075 Nov. 1983
Project Summary
Water Hyacinth Wastewater
Treatment Systems:
Opportunities and Constraints in
Cooler Climates
Michele Leslie
Aquatic plant wastewater treatment
systems, mainly those involving water
hyacinths, have been demonstrated to
be cost-effective in warm areas of the
U.S., such as southern Texas and
Florida. However, no prior studies have
been undertaken to systematically
identify areas where cool temperatures
would limit the use of such aquatic
plant wastewater treatment systems. In
this report, three geographic zones in
the U.S. where various types of aquatic
plant systems would be likely to provide
reliable year-round treatment are identi-
fied. The coolest of these zones extends
northward to a latitude of about 35° N.
The costs of using greenhouse structures
to extend the geographic range of
effective treatment are evaluated. It is
concluded that greenhouse construction
and heating fuel costs would tend to
increase total costs substantially above
those for conventional treatment alterna-
tives. Several potential legal and
regulatory barriers to the use of aquatic
plant wastewater treatment systems
also are discussed. Finally, various
concepts that may lead to the wider
application of this innovative technology
are identified. These include: seasonal
facility operation, approaches for
reducing the costs of climate control,
selection of cold-tolerant plant species,
and concepts for overcoming legal and
regulatory barriers, such as safeguarding
against undesirable introductions of
exotic plant species into receiving
waterbodies.
This Project Summary was developed
by EPA's Office of Environmental
Engineering and Technology, Washing-
ton, D.C. to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The U.S. Environmental Protection
Agency (EPA) is responsible for evaluating
grant applications for the construction of
publicly owned treatment works under
Section 201 of the Clean Water Act of
1977 (33 U.S. Code 1251,etseq.).Aspart
of this mission, the EPA supports
research leading to the development and
operation of innovative and alternative
technologies for municipal wastewater
treatment. At a seminar sponsored by the
EPA in 1979, it was concluded that
certain aquaculture systems, particularly
those utilizing water hyacinths, are ready
for routine use in municipal wastewater
treatment. However, certain problem
areas were noted, including questions
regarding the usefulness of water
hyacinth systems in cooler climates,
where the plant would not grow naturally,
and the potential usefulness of other
plant species in such regions. In a recent
publication, Middlebrooks and Reed
(1981) concluded that based on the
limited data available, it appears that it
would be uneconomical to develop a
water hyacinth wastewater treatment
system in cold regions. In general, there
has been concern that a need for climate
control using a greenhouse would
increase the costs of aquatic plant
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systems to a point that they would be
impractical.
The broad purpose of this study was to
evaluate the potential for using selected
aquatic plant wastewater treatment
systems in temperate or cooler regions
of the U.S., based on the limited data
currently available. Emphasis was placed
on those selected species for which
temperature tolerance information was
available, principally, water hyacinth,
duckweed, bulrushes, reeds and cattails.
This study is intended as a preliminary
evaluation, helpful in guiding research
and development efforts. As current and
anticipated projects yield new insights,
the conclusions of this report may be
refined or substantially altered.
In general, this study was directed
toward examining the major factors that
could potentially limit the use of aquatic
plant wastewater treatment systems in
cooler climates. Specific objectives were:
• To identify the ecological limitations
of systems without climate control, as
represented by the temperature
requirements of key plant species.
• To identify legal and institutional
barriers to the increased use of
aquatic plant wastewater treatment
technology.
• To undertake a preliminary evaluation
of the economic feasibility of using
aquatic plant systems in cooler
climates.
• To identify concepts and approaches
that might be helpful in overcoming
any identified limitations.
Approach and Limitations
This study was initiated with a general
information search. Three computerized
bibliographic data bases were examined
for relevant titles:
• AGRICOLA (Agriculture Online Ac-
cess), produced by the National
Agricultural Library of the U.S.
Department of Agriculture, Washing-
ton, D.C.
• POLLUTION ABSTRACTS, produced
by Cambridge Scientific Abstracts,
Washington, D.C.
• WRA (Water Resources Abstracts),
produced by the Water Resources
Scientific Information Center of the
U.S. Department of the Interior,
Washington, D.C.
In addition to the computer-assisted
search, several recent documents were
reviewed for lists of references. Most
important among these was the proceed-
ings of a recent seminar sponsored by the
EPA (Bastian and Reed 1979). Key
investigators were contacted for informa-
tion on the present status of their
research.
Based upon the results of this first
phase, the scope of this study was refined
and specialized approaches were developed
to meet project objectives. Efforts were
focused on developing an approach for
systematically identifying areas in the
U.S. where aquatic plant wastewater
treatment systems would provide reliable
year-round treatment without climate
control. The relationship between air
temperature and plant growth was
selected as the key predictor of system
performance. Generalized temperature
data for the U.S. were used to map zones
where various plant species would be
expected to be effective in contaminant
removal year-round, nine months out of
the year, and six months out of the year.
The identification of legal and regulatory
barriers mainly involved interviewing
representatives of various Federal and
state agencies. A detailed listing of
personal communications is given at the
end of the report. The preliminary
evaluation of economic feasibility consisted
of estimating the costs of using a
greenhouse and evaluating the impact of
these additional costs when compared to
the costs of conventional treatment
alternatives.
The development and implementation
of an innovative wastewater treatment
technology is a complex and dynamic
process. This study addresses some of
the key issues relating to aquatic plant
treatment systems. However, it is subject
to some important limitations:
• The analyses undertaken were intended
to provide a broad overview. They
would not provide definitive guidance
for evaluating a specific proposal for
the construction of an aquatic plant
wastewater treatment facility.
• The technical information available
for this technology area is limited.
Sources included the available litera-
ture, contacts with researchers,
government administrators, and
some representatives of private firms
active in this area. One site visit was
made to the Disney World water
hyacinth facility in Lake Buena Vista,
Florida.
• This study is limited to municipal
wastewater treatment applications.
Potential industrial wastewater trea^
ment applications are not addressed.
• Species analyses are limited to five
types of higher aquatic plants common-
ly used in aquatic plant wastewater
treatment systems. As research
progresses in this technology area,
other types of plants may prove
equally or more suitable for cooler
climate facilities.
• The approach used to map aquatic
plant utility zones relies on the
relationship between average daily
air temperature and plant growth as a
meaningful indicator of contaminant
removal potential. As discussed in
detail in the report, there are some
important limitations associated with
this approach.
Conclusions
In general, the results of this study
indicate that there are several barriers to
the use of higher aquatic plants for
municipal wastewater treatment in
cooler climates. As detailed below, major
concerns are the temperature require-
ments of many of the species that are
presently used in aquatic plant systems,
certain legal and regulatory constraints,
and the high construction and operating
costs associated with climate control. It is
important to note that current and future
research and development activities may
substantially alter this outlook. A number
of concepts that could enhance opportuni-
ties for cooler climate applications of this
innovative technology are discussed in
the recommendations. Concepts, such
as land treatment, the use of winter
storage and the use of peat bogs were
beyond the scope of this study.
• Reliable year-round performance by
aquatic plant wastewater treatment
systems without climate control is
likely only in southern portions of the
continental U.S. (to a latitude of about
35°N) and in Hawaii, Puerto Rico and
the Virgin Islands.
- Water hyacinth systems probably
would be successful only in areas
where the average daily temperature
is at least 15°C (59°F), such as
southern Florida, the southern tip of
Texas and in Hawaii.
- Emergent or wetland species may be
effective at cooler temperatures (i.e.,
average daily air temperature at least
10°C (50°F). Recent studies indicate
that those species having extensive
rhizome systems may be particularly
well suited for cooler climate applica-
tions. However, most studies o
contaminant removal by wetlan
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species have involved the use of
associations of a number of species in
a natural or artificial wetland setting.
The complexity of such systems
makes it difficult to identify the
effectiveness and cold-temperature
tolerances of individual species.
- Some duckweed species may be
capable of removing contaminants at
temperatures as low as 7 to 10°C (45
to 50°F). This suggests thatduckweed
wastewater treatment systems may
have the highest potential for applica-
tions in cooler climates. The estimated
zone of utility extends northward in
the continental U.S. to a latitude of
35°N.
• The use of aquatic plant treatment
technology in cooler climates (north
of 35°N latitude) probably would
necessitate the use of a greenhouse.
The additional construction and
operating costs of greenhouse use
would increase total costs substantial-
ly above those for conventional
treatment alternatives.
- Construction costs for a 0.1-MGD
water hyacinth system designed to
meet advanced secondary treatment
standards would increase from about
$133,000 to $1,202,000, with the
addition of a standard, rigid structure
greenhouse. Construction costs of
conventional treatment alternatives
would be $170,000 to $732,000.
- Parts and supplies costs for a 0.1-
MGD water hyacinth system would
increase from about $3,500 per year
to $90,600 per year, with the addition
of greenhouse heating fuel require-
ments. Parts and supplies costs for
conventional treatment alternatives
range from $6,000 to $8,OOO per
year.
- Cost increases would be accentuated
at larger facility scales.
• A wide range of Federal and State
statutes and regulations apply to
municipal wastewater treatment.
While some recent developments in
this area may favor the use of aquatic
plant wastewater treatment technol-
ogy, a number of legal and regulatory
barriers to technology diffusion were
identified.
- Regulatory personnel from five tem-
perature climate states indicated that
wetland or marsh/pond overflow
systems may be suitable for cooler
climate areas. In general, they were
skeptical regarding the potential
usefulness of other types of aquatic
plant systems.
- Regulations governing municipal
wastewater discharges are being
reviewed and modified. Some trends,
including a movement toward season-
ally adjusting limitations based on the
assimilative capacity of receiving
waters, may favor the use of aquatic
plant treatment alternatives.
- Laws restricting the use, sale and
transport of exotic plants within the
U.S. may prevent the use of some
plants for wastewater treatment in
cooler climate states.
Recommendations for
Future Research and
Development Activities
In the course of this study, a number of
concepts that could accelerate the
development of aquatic plant wastewater
treatment systems were identified. These
ideas, grouped into five categories, are
identified and briefly described below.
Seasonal Facility Operation
This study indicates that during the
warmest six months of the year some
aquatic plant systems probably would be
effective in wastewater treatment through-
out most of the U.S. Accordingly, aquatic
plant systems may be well suited for use
by summer recreational communities.
This concept has been tested successfully.
A project involving the use of bulrushes in
a recreational community setting in the
Netherlands was reported to be cost-
effective. Successful projects in the U.S.
include a natural wetlands system
employed at Kutcher's Hotel, a summer
resort in New York State.
In addition to the summer community
application, aquatic plant systems could
be attached to existing conventional
treatment systems to meet the more
stringent effluent limitations that some
states are imposing during summer
months. In this case, a small greenhouse
facility could be constructed to overwinter
seed plant stock. Natural systems,
utilizing indigenous wetland plants and
storage of wastewater over the winter
months, could also extend aquatic
treatment systems to cooler climates.
Concepts Relating to Climate
Control
Several concepts relating to climate
control and aquatic plant wastewater
treatment have been developed by other
investigators. For example, it has been
suggested that spraying wastewater,
which is typically warmer than ambient
air temperature, over the leaves of
floating aquatic plants, could slightly
extend the use of these systems into
cooler areas.
With regard to greenhouses, there is
evidence that the high costs of heating an
enclosure could be reduced or mitigated.
As discussed by Ruttle (1978) advances
in passive solar greenhouse design can
substantially reduce (e.g., by 30 percent)
fuel costs. Middlebrooks and Reed (1981)
discuss the alternative of using methane
produced from harvested plants to heat a
greenhouse enclosure. Production of
methane from harvested water hyacinths
is a major element of research being
conducted at the Disney World facility in
Lake Buena Vista, Florida. Results of this
research should provide important insights
regarding the potential for reducing
greenhouse heating costs. Other concepts
that have been suggested include the use
of geothermal energy and waste heat
utilization (e.g., power plant discharges)
These concepts probably would be widely
applicable.
Species Selection
Although a number of plant species
have been identified as potential candi-
dates for wastewater treatment applica-
tions, very little is known about their
temperature requirements. Thus, it is
likely that additional investigation will
result in the identification of general,
species and even strains of plants that
would be effective in removing contami-
nants at lower temperatures. For example,
Hillman and Culley (1978) concluded that
a strain of duckweed that would grow
rapidly at 5 to 10°C could be identified
through an intensive selection program.
A more complete understanding of the
performance of various species over a
range of temperature could be helpful in
developing a program of species rotation
over the course of a year. For example, a
plant species with a high temperature
requirement, such as water hyacinth,
could be used during summer months,
while a cold-tolerant strain of duckweed
could be used during cooler months
Development of Related
Technologies
One aspect of an innovative technology
that is especially difficult to assess is its
ramifications over time. Several of the re-
searchers working with aquatic plant
treatment technology have demonstrated
a vision of the possible long-term benefits
that could accrue from use of this tech-
nology.
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One basic technical concept involves
the potential for linking an aquatic plant
treatment approach with other treatment
approaches. For example, the new NASA
Hybrid System combines anaerobicfilters
with a trough planted with Phragmites to
produce a synergistic treatment effect
(Wolverton 1981). Wolverton also is
investigating the potential for linking food
production facilities to treatment systems.
As noted previously, the Disney World
project includes an investigation of the
potential for linking methane production
to the treatment process. Considering
these opportunities, the cost-effectiveness
of aquatic plant wastewater treatment
technology may change dramatically over
the next few years.
Concepts Related to Legal and
Regulatory Barriers
As noted by Eichbaum (1976) regulatory
offices often lack personnel with the
kinds of training that would permit an
adequate evaluation of the concepts and
opportunities inherent in an innovative
wastewater treatment technology. In
addition, private engineering firms often
lack the kinds of expertise required to
develop a sound design for an aquatic
plant wastewater treatment facility.
Thus, one important step toward the
development of aquatic plant systems in
cooler climate states may be the consolid-
ation and dissemination of available
information on this innovative technology.
This could be accomplished by alerting
state regulatory authorities to the avail-
ability of recent studies on aquatic plant
wastewater treatment and by the conduct
of informative seminars. One important
topic would be the potential for aquatic
plant wastewater treatment in states
having seasonally adjusted discharge
limitations
The effects of laws governing the use,
sale and transport of exotic plants on the
development of aquatic plant wastewater
treatment systems may be an important
topic for detailed investigation. Many of
the plant species that are most commonly
used in wastewater treatment facilities
are not presently found in the cooler
climate states. The use of these species
would require a demonstration that their
introduction would not have adverse
environmental effects. Important areas of
investigation are the overwintering
potential of candidate plant species, and
the potential for confining the aquatic
plants within a facility.
References
1. Middlebrooks, E. J., and S. C. Reed,
1981. The Flowering of Wastewater
Treatment. Water Engineering and
Management 128(6): 51-54.
2. Bastian, R. K. and S. C. Reed, 1979.
Aquaculture Systems for Waste-
water Treatment: Seminar Proceed-
ings and Engineering Assessment.
U.S. Environmental Protection
Agency 430/9-80-006. Washington,
D.C. 489 pp.
3. Ruttle, J., 1978. The Freestandin
Greenhouse, pp. 121-174. In: J.
McCullagh (ed.). The Solar
Greenhousing Book, Rodale Press,
Emmaus, Pennsylvania.
4. Hillman, W. S. and D. D. Culley, Jr.,
1978. The Uses of Duckweed.
American Scientist 66:442-451.
5. Wolverton, B. C., 1981. New Hybrid
Wastewater Treatment Systems
Using Anaerobic Microorganisms
and Reeds. Paper presented at a
Seminar on Innovative Wastewater
Treatment Technology, April
15, 1981, Louisville, Kentucky, 16
PP.
6. Eichbaum, W. M. 1976. Legal and
Political Restraints to Implementa-
tion of Novel Systems, pp. 317-322,
J. Tourbier and R. W. Pierson, Sr.
(eds.). Biological Control of Water
Pollution, University, University of
Pennsylvania Press, Philadelphia,
Pennsylvania.
Michele Leslie is with The MITRE Corporation. McLean, VA 22JO2.
H. R. Jhacker is the EPA Project Officer (see below).
The complete report, entitled "Water Hyacinth Wastewater Treatment Systems:
Opportunities and Constraints in Cooler Climates," (Order No. PB 83-251 223;
Cost: $10.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Office of Environmental Engineering and Technology
U.S Environmental Protection Agency
Washington, DC 20460
*US GOVERNMENT PRINTING OFFICE 1983-659-017/7223
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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