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2.1.06 Vietnam – clean water for the Mekong Delta

Although Vietnam gets plenty of rain, many regions lack both clean drinking water and water for farming. The Mekong Delta is one such region: a German- Vietnamese project is developing water supply and disposal solutions to suit the conditions found there. This not only involves securing drinking water for the population, but also recovering recyclable products from wastewater treatment for use in agriculture, e.g. compost and biogas.

The Mekong Delta in southern Vietnam is home to around 17 million people, about a fifth of the country’s population. Most of them work in agriculture or fish farming. Around half those living in the cities have access to a regulated water supply and disposal facility, as opposed to just 10% in rural areas. As there are only a few sewage plants, most of the wastewater ends up getting into the rivers without being treated, and often fish ponds too in the rural regions.

Increasing water consumption in the Mekong Delta is causing the groundwater level to drop. Seawater is frequently getting into the groundwater in coastal areas, resulting in rising salt concentrations. Farming is the region’s greatest consumer of water: farmers use around 90% of the water for growing rice because although the precipitation is plentiful, rice fields still need intensive irrigation.

Obtaining organic fertiliser from sewage water

Farmers use large amounts of expensive mineral fertiliser in order to increase the crops from their rice fields. But there could be cheaper and more environmentally friendly ways to add nutrients to the soil: human excrement, which currently contaminates the water. The German- Vietnamese SANSED project investigated how this could be achieved (full name “Closing Nutrient Cycles in Decentralised Water Treatment Systems in the Mekong-Delta”). The universities of Bonn and Bochum, Can Tho university in Vietnam and numerous German companies were involved in the project.

Decentralised systems aim to process drinking water as cost-effectively as possible while simultaneously treating wastewater so that local farmers can make use of the sludge and compost. In an ideal scenario, the 120,000 or so tonnes of nitrate and 19,000 tonnes of phosphorous produced in the Mekong Delta every year could be returned to the nutrient cycles through an environmentally friendly process.

Biogas plant used for agriculture

Biogas plant used for agriculture
Biogas plant used for agriculture

Seven aspects

Decentralised wastewater disposal and water supply systems that are adapted to local structures and also factor in the low income of the population are especially useful. The second phase set up demonstration systems and operated them together with Vietnamese partners: SANSED wants to demonstrate that the cost of constructing and operating the systems can be refunded through the sale of the products produced (biogas, fertiliser, compost). There were seven sub-projects within SANSED.

Biogas: The country’s typical biogas plants, which use bacteria to break down waste, either do not produce enough gas or allow excess amounts to escape unused. The approach followed by SANSED uses fungi to break down degradation-resistant polymers in sugar; this triggers increased activity in the bacteria and thus increases the gas yield. Excess gas can be converted into power or stored in bottles.

Partial wastewater flow treatment: The project team installed toilets that separate the wastewater from the faeces in two university halls of residence to serve as models for wastewater cleaning. The urine and solids were used to obtain fertiliser for farming and biogas. Pathogens and organic contaminants from the urine water were either removed or at least considerably reduced through sundrying. The earthworms added to the solids converted the substrate into compost (cold rotting).

Drinking water supply system

Drinking water supply system
Drinking water supply system

Wastewater sieving/soil filtration: At one of the halls of residence, fine sieves filter out solids from the wastewater. The water is then cleaned further through soil filters, and the solids are composted.

Drinking water from surface water: One system treated surface water polluted with organic substances and micro-organisms – using slow sand filters and sunlight (UV disinfection) among other things – to supply water to one of the halls of residence.

Drinking water from groundwater: The scientists optimised the drinking water supply for around 100 households: quick sand filters treated the heavily ferrous groundwater.

Natural fertilisation used in farming

Natural fertilisation used in farming
Natural fertilisation used in farming

Further training: Many districts in Can Tho have a central supply of drinking water that could be described as process water at best. There is also a system that involves filling containers with drinking water. The project team devised a special information and training programme for the staff at the Can Tho Water Supply and Sewerage Company.

Handling recommendations: The team collaborated with the local supply company to create a sample feasibility study using a district of Can Tho that previously had no regulated water supply or disposal: the study shows where it would be useful to implement (de)centralised systems.

Verifying transferability

The SANSED project is to be used as a basis to verify whether decentralised wastewater treatment and water supply systems could be used in other regions with poor infrastructure.

The SANSED final report appeared in volume 31 of the “Bonner Agrikulturchemische Reihe” (Bonn agriculturechemical series, ordered and purchased via www.ipe.uni-bonn.de/publikationen).

Further information can be found on the project website.
Project website www.sansed.uni-bonn.de

University of Bonn

Dr. Ute Arnold
Karlrobert Kreiten Straße 13
53115 Bonn, Germany
Tel.: +49(0)2 28/73 36 39
Fax.: +49(0)2 28/73 24 89
Internet: www.ipe.uni-bonn.de
Funding reference: 02WD0620
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