Floating Plant Pond

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.

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.

References

Further Readings

  • Cover image of a reference book or miscellany.

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

    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.

  • Cover image of a reference chapter of a book/miscellany.

    ABBASI, S. A. (1987): Aquatic Plant Based Water Treatment Systems in Asia. In: REDDY, K.R. (Editor); SMITH, W.H. (Editor) (1987): Aquatic Plants for Water Treatment and Resource Recovery. Orlando.

  • Cover image of a reference chapter of a book/miscellany.

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

  • Cover image of a reference chapter of a book/miscellany.

    (n.y.): Chapter 4: Water Hyacinth Ponds. Comprehensive design manual. In: POLPRASERT, C.; VEENSTRA, S. ; VAN DER STEEN, P. (2001): Wastewater Treatment II. Natural Systems for Wastewater Management. Delft.

  • Cover image of a reference book or miscellany.

    DIVER, S. (2006): Aquaponics – Integration of Hydroponics with Aquaculture. Arkansas, USA: ATTRA - National Sustainable Agriculture Information Service. URL [Accessed: 22.05.2012]. PDF

    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.

  • Cover image of a reference journal article.

    GERBA, C. P.; STRAUB, T. M.; ROSE, J. B.; KARPISCAK, M. M.; FOSTER, K. E. ; BRITTAIN, R. G. (1995): Water Quality Study of Graywater Treatment Systems. In: Water Resources Bulletin 31, 109.

  • Cover image of a reference book or miscellany.

    JOHNSON, M. D.; WARDLOW, G. W. (1997): A Prototype Recirculating Aquaculture-Hydroponic System. Arkansas, USA: University of Arkansas, Department of Agricultural & Extension Education. URL [Accessed: 21.04.2011]. PDF

    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.

  • Cover image of a reference journal article.

    KANABKAEW, T.; PUETPAIBOON, U. (2004): Aquatic plants for domestic wastewater treatment: Lotus (Nelumbo nucifera) and Hydrilla (Hydrilla verticillata) systems. In: Songklanakarin J. Sci. Technology 26, 749.URL [Accessed: 21.04.2011]. PDF

    The study focussed on the overall performances of lotus and hydrilla systems for post treatment of domestic wastewater. Removal of water quality parameters such as pH, biochemical oxygen demand, suspended substances, nitrogen, phosphorus and total coliform bacteria showed the differences between various plants and control unitas.

  • Cover image of a reference book or miscellany.

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

    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.

  • Cover image of a reference book or miscellany.

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

    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.

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). URL [Accessed: 28.07.2014]. PDF

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

  • Cover image of a reference book or miscellany.

    U.S.EPA (Editor) (1980): Design Manual Onsite Wastewater Treatment and Disposal Systems. United States Environmental Protection Agency, Office of Water Office of Research and Development (U.S.EPA). URL [Accessed: 18.03.2010]. PDF

    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.

Training Material

  • Cover image of a reference book or miscellany.

    EDWARDS, P. (2008): Volume III: Wastewater and excreta use in aquaculture.. (pdf presentation). Bangkok, Thailand: Asian Institute of Technology. PDF

    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.

  • Cover image of a reference book or miscellany.

    EDWARDS, P. ; Asian Institute of Technology (Editor) (2008): Key Issues in the Safe Use of Wastewater and Excreta in Aquaculture. (pdf presentation). Bangkok, Thailand: World Toilet Organisation. URL [Accessed: 19.02.2010]. PDF

    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.

Important Weblinks

  • http://www.fishfarming.com/ [Accessed: 04.08.2011]

    This webpage describes the sustainable technology of growing plants (duckweed) and fish (Tilapia) in a symbiotic way. The text is illustrated with various pictures (English).