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.
– drinking water treatment and supply (surface water and groundwater/sand filtration and disinfection)