Nutrient recycling by application of human excreta to maintain soil fertility has been practiced in Eastern Asia and the Western Pacific region for 4,000 years. In many countries the need for nutrient recycling increases due to the economic downturn, resulting in socio-economic constraints for the population, e.g. in rural areas of countries in transition.

The international project “Closing Nutrient Cycles by means of Hygienically Harmless Substrates in Decentralised Water Treatment Systems in the Mekong Delta, Vietnam” (SANSED) had an interdisciplinary approach to solve problems associated with wastewater in rural areas by recycling nutrients: Substrates from decentralized water management may supply nutrients to agro-ecosystems. To apply these substrates in a distinguished way they have to match site-specific demands depending on soil and plant production.

Within the SANSED project, site-adapted concepts for water supply and wastewater treatment are developed for the densely populated agricultural region of the Mekong Delta. The systems shall minimize nutrient losses and provide adequate substrates for agriculture, thus producing an additional benefit for the operators of water supply and wastewater treatment systems.

Important Results

Within SANSED project important experiences on operation and performance of decentralized water and wastewater treatment systems in the Mekong Delta and in tropical areas were gained:
– to develop decentralized water supply and wastewater treatment systems;
to test the most suitable options for water supply (e.g. rain, surface and groundwater) before its installation;
to ensure that all systems are socially accepted, reliable and affordable;
to recycle as many nutrients as possible. The wastewater systems are regarded as “fertilizer factories”. Thus, not the technical philosophy, but the agro-ecological demands define the wastewater treatment system.
– d
rinking water treatment and supply (surface water and groundwater/sand filtration and disinfection)

Closing nutrient cycles in decentralized water treatment systems


12/2002 - 07/2009

Project area(s)

Cần Thơ, Mekong Delta

Coordination (GER)

Dr. Joachim Clemens & Ute Arnold
University of Bonn
INRES – Plant Nutrition
Karlrobert-Kreiten-Strasse 13
53115 Bonn
+49 (0)228 732150

Coordination (VN)

Dr. Nguyen Hieu Trung
Can Tho University
College of Technology/
College of Environment and Natural Resources
Can Tho

Project partner (GER)

  • University of Bonn, Institute of Crop Science and Resource Conservation, INRES-Plant Nutrition; Institute for Hygiene and Public Health, Institute for Food and Resource Economics, ILR-Economic Sociology
  • Ruhr-University Bochum, Faculty of Civil and Environmental Engineering
  • Leibniz University Hannover, Institute of Soil Sciences
  • Martin-Luther-University of Halle-Wittenberg, Institute of Agricultural and Nutritional Sciences, Soil Sciences
  • B3 Biogas Beratung Bornim GmbH, Potsdam
  • Bioreact GmbH, Troisdorf
  • gewitra Ingenieurgesellschaft für Wissenstransfer mbH, Hannover
  • Gewitra GmbH, Bonn
  • Hans Huber AG, Berching
  • IBAU Innovatives Büro für Aquakultur und Umwelttechnik, Beelitz
  • GSan GmbH, Berlin
  • Ith Ingenieurbüro für Technische Hydrologie, Bayreuth
  • Sachsen Wasser GmbH, Leipzig

Project partner (VN)

  • Can Tho University (CTU)
  • College of Environment and Natural Resources (CENRes) – Department of Environmental Engineering
  • College of Environment and Natural Resources (CENRes) – Department of Environment Management and Natural Resources
  • College of Agriculture and Applied Biology – Department of Soil Science and Land Management
  • College of Agriculture and Applied Biology – Department of Animal Sciences
  • College of Agriculture and Applied Biology – Department of Plant Protection
  • College of Aquaculture and Fisheries – Department of Applied Biology
  • Hoa An Biodiversity Research Center