Fueling the rapid growth of duckweeds requires
amounts of nutrients. Thus duckweeds have evolved
the ability to
rapidly remove minerals necessary for their growth from
the water on
which they float. When present, duckweeds also can
organic nutrients. These mineral and organic
converted into the substance of the plants, that is, their
biomass. Research has shown that duckweeds are
at removal of phosphates and nitrogen, particularly
The treatment of sewage and wastewater from agricultural
operations requires the removal of great amounts of
phosphate. These wastes are a growing problem around
because of population growth and the trend of modern
to concentrate livestock in small areas.
The duckweed biomass that results from water treatment
operations must itself be removed from the water.
This can be
done by skimming it off. Duckweed grown on sewage or
wastes normally does not contain toxic pollutants and can
be fed to fish or to livestock,
or spread on farmland
as a fertilizer. If the duckweed is to be fed to
period in clean water will be necessary to ensure that the
of water-borne pathogens.
The links on this page illustrate both potential and
Above: swine in North Carolina, Below:
treatment lagoon inside a plastic greenhouse. Photos
of Paul Skillikorn.
- USDA Research:
Finding better processes to convert renewable materials into
value-added bioproducts. USDA Northern Regional
Center, Peoria, Illinois. CRIS
- "The purpose of this research is to improve the
technologies for the conversion of renewable agricultural
value-added products (e.g., fuel ethanol, lactate, and
conversions are currently possible but are cost prohibitive
plant biomass other than starch."
Report: Design Manual Constructed Wetlands and
Plant Systems for Municipal Wastewater Treatment, US EPA
Research and Development, Center for Environmental Research
Information, Cincinnati, OH 45268, September 1988, 1058 kB
and waste water treatment: importance of macrophyte, algae and
a slide show by Jan Vermaat & Sabine Koerner, Department of
Environmental Science and Water Resources, University of Delft,
domestic sewage, from the postdoctoral research project of Sabine Körner, now at
'The relative importance of duckweed, bacteria and microalgae
the treatment of domestic sewage in duckweed-covered systems'
scale experiments on duckweed-covered domestic sewage were
determine whether removal of organic material is faster in the
duckweed... ...Removal of COD was significantly
faster in the
of duckweed. ...approximately ¾ of the total
be attributed to the duckweed mat."
Publications on duckweed growth in wastewater from this
Vermaat, Jan & Hanif, Khalid (1998) Performance of
duckweed species (Lemnaceae) and the water fern (Azolla
on different types of waste water. Water Res.
Körner, S., Vermaat, J.E. & Lyatuu, G.B.
influence of Lemna gibba L. on the degradation of
in duckweed-covered domestic wastewater. Water
Körner, S. and Vermaat, J.E. (1998) The relative
importance of Lemna gibba L., bacteria and micro-algae
domestic sewage in duckweed-covered systems. Water
Körner, S.; Das, S.K.; Vermaat, J.E. and Veenstra, S.
(in prep.) Ammonia toxicity to the duckweed Lemna gibba
treatment of wastewater.
Wastewater Treatment Method for Swine Production: Students
Jay Cheng at North
Carolina State University have studied a reactor and harvesting
for growing and removing
duckweed, a small aquatic plant, from swine wastewater.
B.A. Bergmann, J. Cheng, J. Classen, A.-M. Stomp, In
vitro selection of duckweed geographical
isolates for potential use in swine lagoon effluent
renovation, (2000) Bioresource Technology 73 (1)
Cheng, J, Landesman, L, Bergmann, BA, Classen, JJ, Howard, WJ,
Yamamoto, YT (2002) Nutrient Removal from Swine Lagoon
by Lemna minor 8627. Trans. Amer. Soc. Agric. Eng.
45(4):1003-1010. [ link
download site ]
Lyerly, Courtney Neil, Swine Wastewater Treatment in an
Integrated System of Anaerobic Digestion and Duckweed Nutrient
Pilot Study, M.S. Thesis, North Carolina State University,
Biological and Agricultural Engineering, Raleigh, NC, 2004, 104
pp. [ link
download site ]
Smith, Ryan Andrew. Harvesting Duckweed By Skimming,
Thesis, North Carolina State University, Biological and
Engineering, Raleigh, NC, 2003, 153 pp. [ link
download site ]
"Duckweed may be the most promising plant for the
century for the following reasons:
Dr. Landesman has worked closely with Jay Cheng and his group (see
link) on using duckweed to recover nutrients from swine
- Duckweed produces more protein per square meter than
- Duckweed is easier to harvest than algae or other
- Duckweed can be used to feed fish, poultry and cattle
- Duckweed can purify and concentrate nutrients from
- Duckweed provides food for wildlife, especially
Landesman L, Parker N C, Fedler C B and
Konikoff M (2005) Modeling duckweed growth in wastewater
systems. Livestock Research for Rural Development. Vol.
#61. Retrieved October 30, 2005, from http://www.lrrd.org/lrrd17/6/land17061.htm
Study: Lemna Wastewater Treatment Process Ogema
District, Wisconsin. by Ernesto R. Lopez and Charles Pycha,
Environmental Engineers, Technical Support Section, Water
Branch, U.S. EPA, Chicago, IL 60604.
Using Duckweed Plants In Process Gets EPA Award
In this lagoon, Lemnaceae plants (duckweed) were introduced to
create a floating blanket of vegetation that prevents sunlight
reaching the water. Allen Atkins, supervisor of public works for
that this "helps with the control of algae in our lagoon, and
remove other nutrients from the wastewater."
Problems in Ashland Chemical Polishing Ponds
"One in five industrial plants uses lagoons for some part of
wastewater treatment process. These lagoons are often troubled
excessive algae growth
which can cause compliance problems. Lemna Systems, widely
solve this problem in municipal lagoons, can also be used for
in industrial polishing ponds. One such application was done for
Chemical's methanol production facility in Plaquemine,
is a Low-Cost Water Purifier, Anne E. Platt, Worldwatch Institute.
Ms Platt identified the following deficiencies for
Can these deficiencies be overcome by creative thinking
- Duckweed can't process heavy metals, pesticides, or toxic
substances; so if the duckweed is to be used as food, it must
- Duckweed purification ponds must be large, flat, and
they can't be used in mountains or cities.
- On a per person basis, duckweed purification takes up more
room that conventional plants; it takes two square meters of
per person to do the purifying.
research shows that duckweeds actively remove and
certain pesticides and industrial wastes.
- New designs for duckweed purification plants take up
less space. [ link
to patent ]
- Phytoremediation Web Page, Biological
of environmental problems using plants. Links
to: conferences, research sponsors, books,
of Heavy Metals.
Zayed, A. Phytoaccumulation of trace elements by wetland
I. Duckweed. (1998) Journal of Environmental Quality 27
"...under experimental conditions, duckweed [Lemna
L.] proved to be a good accumulator of Cd, Se,
a moderate accumulator of Cr, and a poor accumulator of
and Pb." "The toxicity effect of each trace
growth was, in descending order of damage, Cu > Se >
> Ni > Cr. We conclude that duckweed shows promise
of Cd, Se, and Cu from contaminated
it accumulates high concentrations of these elements. Further,
rates and harvest potential make duckweed a good species for
G.N.H. Rahmani, S.P.K. Sternberg, Bioremoval of lead from
water using Lemna minor, Bioresource
Technology 70 (3) (1999) pp. 225-230.
de Plantas Acuaticas para el Tratamiento de Aguas Residuales,
"Advantages of Aquatic Plants for the Processing of Aqueous
Eugenia Olguín, Elizabeth Hernández, Patricia
Coutiño y Rosalía González, from Tecnologías
para el desarrollo sustentable, ISBN 968-7213-63-9.
"Las macrofitas acuáticas han sido consideradas por varios
autores como una plaga debido a su rápido crecimiento,
que en ocasiones llegan a invadir lagunas y generan varios
(Arrivallaga y Arredondo, 1978). Sin embargo, si las plantas
acuáticas se manejan adecuadamente, su poder de
proliferación , su capacidad de absorción de
bioacumulación de otros compuestos del agua, las
una herramienta útil en el tratamiento de aguas residuale
This book describes an experimental program in Mirzapur,
where duckweed cultivation was established and fresh duckweed fed
carp and tilapia. "Duckweed-fed fish production does not
depend on mechanical aeration and appears to be significantly
productive and easier to manage than traditional pond fish
Evaluation, Bangladesh, (1993) Enterprise,
Accumulation and Income Generation in Bangladesh: A New Model
in Development, Rebecca Torres, University of
For other World Bank publications related to duckweed
applications in the developing world [ link
Fasakin, EA, Balogun, AM and Fasuru, BE. (1999) Use of
duckweed, Spirodela polyrrhiza L. Schleiden, as a protein
feedstuff in practical diets for tilapia, Oreochromis
L. Aquaculture Research 30(5): 313.
Fletcher, A., Warburton, K. (1997) Consumption of fresh and
decomposed duckweed Spirodela sp. by Redclaw crayfish, Cherax
quadricarinatus (von Martens) Aquaculture Research 28(5):
Space: Aquatic food production modules in
bioregenerative life support systems. The smallest
duckweed, Wolffia, is being
tested as part of an
aquatic food production system for spaceflight at
Bochum in Germany. Read about the design
this system. Also see research by NASA.
Aquaculture - Potentials, Possibilities and Limitations
Combined Wastewater Treatment and Animal Feed
countries, [pdf, 990 k] by Sascha Iqbal, SANDEC Report No.
Price: CHF 25.-
(scroll down to Agricultural and Aquacultural Aspects of
"SANDEC is the Department
Water and Sanitation in Developing Countries at the Swiss
Institute for Environmental Science and Technology (EAWAG) in
Duebendorf, Switzerland. ...Its mandate is to assist in
developing appropriate and sustainable water and sanitation
and technologies adapted to the different physical and
conditions prevailing in developing countries"
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Revised: October 6, 2012