United States
Environmental Protection
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
  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).
  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

systems to a point that they would be
  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
   To undertake a preliminary evaluation
    of the economic feasibility of  using
    aquatic plant  systems  in cooler
   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.

    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
  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
  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,
  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.

  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
   35N) 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  15C (59F),  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
    10C (50F). 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

  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 10C (45
  to 50F). 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

 The use of aquatic plant treatment
  technology in cooler climates (north
  of  35N  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

 - 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

 - 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
  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

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 10C  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
  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-

     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
     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.

          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
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,
          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
Center for Environmental Research
Cincinnati OH 45268
Official Business
Penalty for Private Use $300