ARTICLE

 EcoEng Newsletter No. 13, September 2007

A brief look at some new constructed wetlands in tropical Asia

EcoEng-NL 13/2007

  Title page / Index
  Editorial
Quality criteria for EcoEng:
  View of W. Blum
  View of A. Dakers
  Student's view 1
  Student's view 2
  Student's view 3
Articles:
  Shanthini: Compost
  Schoenborn: Stensund
  Blum: New Masters in EE
  Schoenborn: Novaquatis
  Wootton: CAWT
  Turon: EDSS
  Dallas: Indonesia
  Play with water
EcoEng News:
  Newsbits
Satire:
  Joe Swamp
Various issues:
  IEES Writers' Fund
  Calendar
  Mailing list
  Credits

By Stewart Dallas, EcoEng-Correspondent
Research Officer DK CRC
Remote Area Developments Group (RADG)
UNEP-IETC Environmental Technology Centre
South Street, Murdoch
Murdoch University, Western Australia 6150


Stewart is presently Director of Murdoch University's Environmental Technology Centre in Perth, Western Australia.


 

Constructed wetlands have for some time now been considered an ideal technology for wastewater treatment in developing countries, and particularly for those in the tropics ([1],[2],[3]). And while uptake has been very slow there are some signs things may be changing.

Java is the most densely populated island and one of the most densely populated regions in the world with a population of over 125 million on a land area of 127,000 km2. Understandably its environment is significantly affected and water and sanitation are critical issues with severely polluted rivers and groundwater. Wastewater treatment systems of any kind are rare (excepting septic tanks) and as has been found in many developing countries conventional 'hi-tech' wastewater treatment schemes are likely to be abandoned within several years of commissioning.

Fig1: Map of Indonesia

Fig 2: Map of Eastern Java

 

Two constructed wetlands have been installed recently in and around Malang, East Java in Indonesia. One is the USAid-sponsored pilot system built last year in the village of Temas to treat a blend of wastewater and some polluted river water. The project is part of a larger USAid Environmental Services Program (ESP) in the larger catchment to tackle both diffuse and point sources of pollution.  It has been a concerted effort to engage with the local community and establish and trial an appropriate low-cost wastewater treatment system.

The construction of the wetland has not been without its share of problems including a difficult steep site and burrowing animals damaging the original clay lining system which resulted in it being replaced by concrete. The treatment system consists of a large septic tank followed by nine constructed wetlands all of similar dimensions in series (varying free water surface and subsurface flow) until discharging into a final containment tank and finally a nearby stream.

Fig. 3: View of one of the free water wetland sections at the Temas site
Photo: S. Dallas

 

A second constructed wetland - a reedbed (subsurface flow) system - was installed under the direction of the author on the outskirts of Malang in June of this year to treat septic effluent at a local seminary. The project was the result of a collaboration between Merdeka University's Institute for Environmental management (IEMT) and Murdoch University's Environmental Technology Centre (ETC). A range of interested local government, NGOs and health and wastewater practitioners were invited to the four day capacity building and training workshop held at a local hotel.

One full day of the workshop was dedicated to team-building with the hands-on installation of a functional reedbed system. While some of the plumbing and excavation had been carried out prior to participants arriving at the site, the bulk of the work including lining the reedbed, carting gravel and planting up were all done by the participants. In this fashion they were all exposed to the details and logistics necessary for constructing a successful reedbed.

While it is not expected that participants go away fully trained in the building of reedbeds it is a grassroots means by which to expose and educate people who are able to make change in their communities to alternatives to high tech wastewater treatment systems. The workshop received coverage by local tv and radio stations and was well received by all of the participants.

Fig. 4: Workshop participants helping build the reedbeds
Photo: S. Dallas

Fig. 5: The finished two stage reedbed system
Photo: S. Dallas

 

Both of the Indonesian wetlands described here are primarily proof of concept systems. That is they are endeavouring to receive validation from the local communities and authorities that wetlands are viable and effective low-cost wastewater treatment systems. It can be argued that both of the systems as installed are too expensive for local communities which is true as at this stage of the technology uptake cycle economies of scale are not achieved. A recent analysis of the construction costs of various sized subsurface flow wetlands in Nicaragua and Portugal by WERF [4] highlighted this fact.

Not until larger systems designed to treat all the wastewater from a village or villages for example are installed will the true cost of construction and operation and maintenance be accurately known. In rural Indonesia for example where villages are commonly surrounded by rice paddies belonging to members of that village, it would seem eminently feasible to transform a section of nearby rice paddi into the village's own wastewater treatment system. 

Many of the main issues that confront constructed wetlands in Indonesia are common ones such as availability of land, suitable lining materials, affordable gravel media, and the need for a satisfactory level of wastewater pre-treatment. If wastewater recycling can be achieved in conjunction with useful wetland crops that can be harvested then the wetland systems can start to head towards a level of economic self-sufficiency.

Conventional wastewater treatment systems have been shown to be unsustainable in developing countries due to a combination of high operating and maintenance costs, lack of suitably skilled personnel and spare parts ([5],[6],[7],[8]). Constructed wetlands can provide an alternative to this paradigm. They are proven low-cost, low-maintenance systems that hopefully will go a long way towards achieving sustainable sanitation outcomes in developing countries.

  References
  [1] Denny, P., 1997, Implementation of Constructed Wetlands in Developing Countries, Water Science and Technology 35(5), 27-34

[2] Haberl, P., 1999, Constructed Wetlands: A chance to solve wastewater problems in developing countries, Water Science and Technology 40(3), 11-17

[3] Kivaisi, A., 2001, The potential for constructed wetlands for wastewater treatment and reuse in developing countries: a review, Ecological Engineering 16(4), 545-560

[4] WERF (2006), Small-scale constructed wetland treatment systems. Report 01-CTS-5. Water Environment Research Foundation. USA

[5] Esrey, S.A., Gouch, J., Rapaport, D., Sawyer, R., Simpson-Hébert, M., Vargas, J., 1998, Ecological Sanitation, Swedish International Development Cooperation Agency SIDA, Stockholm, Sweden

[6] Ho, G., 2002, Options for a sustainable future, Water21, IWA, February, 48-49

[7] Otterpohl, R., 2001, New developments of ecosan in Germany and Europe, in: Ecosan - closing the loop in wastewater management and sanitation, Proceedings of the International Symposium, 30-31 October 2000, Eschborn, Germany, pp. 68-79

[8] WHO/UNICEF, 2000, Global Water Supply and Sanitation Assessment 2000 Report, WHO/UNICEF, New York, USA

© 2007, International Ecological Engineering Society, Wolhusen, Switzerland