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Floating Plant Pond

Application level

City

Household

Neighborhood

Management level

Household

Public

Shared

Inputs

Effluent

Outputs

Biomass
Author/Compiled by
Eawag (Swiss Federal Institute of Aquatic Science and Technology)
Niels Sacher (Xavier University)
Robert Gensch (Xavier University)
Dorothee Spuhler (seecon international gmbh)
Executive Summary

A floating plant pond is a modified maturation pond with floating (macrophyte) plants. Plants such as water hyacinths or duckweed float on the surface while the roots hang down into the water to uptake nutrients and filter the water that flows by.

Advantages
Water hyacinth grows rapidly and is attractive
Potential for local job creation and income generation
Relatively low capital costs; operating costs can be offset by revenue
High reduction of BOD and solids; low reduction of pathogens
Can be built and maintained with locally available materials
Disadvantages
Requires large land (pond) area
Some plants can become invasive species if released into natural environments
In Out

Freshwater, Blackwater, Greywater, Brownwater, Fertigation Water

Treated Water, Food Products

Water hyacinths are perennial, freshwater, aquatic macrophytes that grow especially fast in wastewater. The plants can grow large: between 0.5 to 1.2 m from top to bottom. The long roots provide a fixed medium for bacteria which in turn degrade the organics in the water passing by.

Duckweed is a fast growing, high protein plant that can be used fresh or dried as a food for fish or poultry. It is tolerant of a variety of conditions and can significantly remove quantities of nutrients from wastewater.

 

Design Considerations 

Locally appropriate plants can be selected depending on their availability and the characteristics of the wastewater.

To provide extra oxygen to a floating plant technology, the water can be mechanically aerated but at the cost of increased power and machinery. Aerated ponds can withstand higher loads and can be built with smaller footprints (see also aerated ponds). Non-aerated ponds should not be too deep otherwise there will be insufficient contact between the bacteria-harbouring roots and the wastewater.

Appropriateness

A floating plant pond is only appropriate when there is a sufficient amount of land (or pre-existing pond). It is appropriate for warm or tropical climates with no freezing temperatures, and preferably with high rainfall and minimal evaporation. The technology can achieve high removal rates of both BOD and suspended solids, although pathogen removal is not substantial.

Harvested hyacinths can be used as a source of fibre for rope, textiles, baskets, etc. Depending on the income generated, the technology can be cost neutral. Duckweed can be used as the sole food source for some herbivorous.

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Health Aspects/Acceptance

Water hyacinth has attractive, lavender flowers. A well designed and maintained system can add value and interest to otherwise barren land.

Adequate signage and fencing should be used to prevent people and animals from coming in contact with the water. Workers should wear appropriate protective clothing. WHO guidelines on wastewater and excreta use in aquaculture should be consulted for detailed information and specific guidance.

Operation & Maintenance

Floating plants require constant harvesting. The harvested biomass can be used for small artisanal businesses, or it can be composted. Mosquito problems can develop when the plants are not regularly harvested. Depending on the amount of solids that enter the pond, it must be periodically desludged. Trained staff is required to constantly operate and maintain it.

 

Applicability

A floating plant pond is only appropriate when there is a sufficient amount of land (or pre-existing pond). It is appropriate for warm or tropical climates with no freezing temperatures, and preferably with high rainfall and minimal evaporation. The technology can achieve high removal rates of both BOD and suspended solids, although pathogen removal is not substantial.

Harvested hyacinths can be used as a source of fibre for rope, textiles, baskets, etc. Depending on the income generated, the technology can be cost neutral. Duckweed can be used as the sole food source for some herbivorous.

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Library references

Small and Decentralized Wastewater Management Systems

Decentralised wastewater management presents a comprehensive approach to the design of both conventional and innovative systems for the treatment and disposal of wastewater or the reuse of treaded effluent. Smaller treatment plants, which are the concern of most new engineers, are the primary focus of this book.

CRITES, R. ; TCHOBANOGLOUS, G. ; (1998): New York: The McGraw-Hill Companies Inc

Duckweed Aquaculture

This literature review provides a first overview of the possibilities, potentials and limits of duckweed aquaculture and its combined use in wastewater treatment and animal feed production in low and middle-income countries. It is somewhat limited as critical literature on duckweed field use is scarce and difficult to obtain (e.g. unpublished internal documents).

IQBAL, S. ; (1999): Potentials, Possibilities and Limitations for Combined Wastewater Treatment and Animal Feed Production in Developing Countries. Duebendorf: Swiss Federal Institute of Aquatic Science and Technology (Eawag) URL [Accessed: 15.04.2014]

Community-Based Technologies for Domestic Wastewater Treatment and Reuse- options for urban agriculture

The report suggests that emerging trends in low-cost, decentralised naturally-based infrastructure and urban wastewater management which promote the recovery and reuse of wastewater resources are increasingly relevant. Technologies for these sanitation options are presented. The concept of managing urban wastewater flows at a decentralised or "intermediate" level, based on micro watersheds, is explored. Effluent treatment standards that are currently accepted in order to protect public health and safety are reviewed.

ROSE, D.G. ; (1999): (= Cities Feeding People (CFP) Report Series. , 27 ). Ottawa: International Development Research Center Canada (IDRC)

Guidelines for the safe use of wastewater excreta and greywater. Volume III. Wastewater and Excreta Use in Aquaculture

Volume III of the Guidelines for the Safe Use of Wastewater, Excreta and Greywater deals with wastewater and excreta use in aquaculture and describes the present state of knowledge regarding the impact of wastewater-fed aquaculture on the health of producers, product consumers and local communities. It assesses the associated health risks and provides an integrated preventive management framework.

WHO (2006): Geneva: World Health Organisation URL [Accessed: 26.02.2010]
Further Readings

Compendium of Sanitation Systems and Technologies (Arabic)

This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

TILLEY, E. ; ULRICH, L. ; LUETHI, C. ; REYMOND, P. ; SCHERTENLEIB, R. ; ZURBRUEGG, C. ; (2014): 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) PDF

Harvesting and Handling of Biomass

BAGNALL, L. O. ; SCHERTZ, C. E. ; DUBBE, D. R. ; (1987): REDDY, K.R. ; SMITH, W.H. (1987): Aquatic Plants for Water Treatment and Resource Recovery. Orlando: .

Chapter 4: Water Hyacinth Ponds

Comprehensive design manual. POLPRASERT, C. ; VEENSTRA, S. ; VAN DER STEEN, P. ; (2001): Wastewater Treatment II. Natural Systems for Wastewater Management. Delft: .

Aquaponics – Integration of Hydroponics with Aquaculture

Aquaponics is a bio-integrated system that links recirculating aquaculture with hydroponic vegetable, flower, and/or herb production. Recent advances by researchers and growers alike have turned aquaponics into a working model of sustainable food production. This publication provides an introduction to aquaponics with brief profiles of working units around the country. An extensive list of resources point the reader to print and Web-based educational materials for further technical assistance.

DIVER, S. ; (2006): Arkansas, USA: ATTRA - National Sustainable Agriculture Information Service URL [Accessed: 22.05.2012]

A Prototype Recirculating Aquaculture-Hydroponic System

This document introduces a recirculating aquaculture-hydroponic system. The system provides an artificial, controlled environment that optimises the growth of aquatic species and soil-less plants, while conserving water resources. In this system, fish and plants are grown in a mutually beneficial, symbiotic relationship.

JOHNSON, M. D. ; WARDLOW, G. W. ; (1997): Arkansas, USA: University of Arkansas, Department of Agricultural & Extension Education URL [Accessed: 21.04.2011]

Aquatic plants in Aquaculture

The article informs the reader about the biological role of aquatic plants in the waters with specific information on the anatomy of aquatic plants and descriptions of different types of plants.

PONGCHAWEE, K. ; (n.y): India: Aquatic Plants and Ornamental Fish Research Institute URL [Accessed: 21.04.2011]

Water plants

This factsheet informs the reader about the most common water plants used for floating plant ponds. There are further information on growing and harvesting the plants. It is illustrated with many pictures.

SHARP, D. ; (n.y): South Africa: Water Affairs, Agriculture Forestry and Fisheries, Environmental Affairs URL [Accessed: 21.04.2011]

Compendium of Sanitation Systems and Technologies. 2nd Revised Edition

This compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

TILLEY, E. ; ULRICH, L. ; LUETHI, C. ; REYMOND, P. ; ZURBRUEGG, C. ; (2014): Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) URL [Accessed: 28.07.2014] PDF

Design Manual Onsite Wastewater Treatment and Disposal Systems

Rather old design manual for onsite wastewater treatment options. However, valuable information on established systems such as septic tanks, sand filters, aerobic treatment units (suspended growth and fixed film), disinfection, nutrient removal as well as wastewater segregation and recycling are given. Additional information is given on disposal methods and appurtenances.

U.S.EPA (1980): (= EPA 625/1-80-012 ). United States Environmental Protection Agency, Office of Water Office of Research and Development (U.S.EPA) URL [Accessed: 18.03.2010]
Training Material

Volume III: Wastewater and excreta use in aquaculture.

This presentation gives a detailed overview on the 3. volume of the WHO guidelines on the safe use of wastewater and excreta in aquaculture including many pictures of existing wastewater-fed aquaculture and fish pond technologies all over the world. Apart from the health risk and appropriate health protection measures, a lot of information on socio-cultural, environmental and economic aspects is given as well as supporting information on planning and implementation of sewage-fed fish ponds.

EDWARDS, P. ; (2008): (pdf presentation). Bangkok, Thailand: Asian Institute of Technology

Key Issues in the Safe Use of Wastewater and Excreta in Aquaculture

This document is a guidance note for program managers and engineers that summarises the key issues of the 3. Volume of the WHO Guidelines that focuses on the safe use of wastewater and excreta in aquaculture.

EDWARDS, P. Asian Institute of Technology (2008): (pdf presentation). (= Guidelines for the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture , 3 ). Bangkok, Thailand: World Toilet Organisation URL [Accessed: 19.02.2010]

This is the compact version of the factsheet.

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