In contrast to Europe and North America where 95% of urban areas have conventional and centralised wastewater treatment systems, there are many countries where wastewater treatment systems are inadequate or do not even exist. Building a conventional sewerage system often proves difficult due to financial reasons and local conditions. As a result, more than 80% of the world’s wastewater is untreated when discharged to the environment. DEWATS are able to supply densely populated urban areas, as well as rural areas, with adequate wastewater treatment.
DEWATS offer good solutions, particularly to reduce the organic load from wastewater, which is the most significant problem for people and the environment.
The easy maintenance, low construction and operation coasts, and independence from urban infrastructure makes DEWATS suitable for poor urban and peri-urban areas, schools, hospitals, and small businesses with organic loads in their wastewater.
The DEWATS technology implemented by the BORDA network has proven itself for many years in Asia and Africa, and has become an integral part of various government sanitation programmes.
The DEWATS Technology
DEWATS do not have a standard design, but can adapted depending on the treatment requirements. For instance, municipal wastewater has different treatment needs than wastewater from hospitals. Another advantage lies in the simplicity of decentralised systems, which allows local people to be involved in construction and maintenance, as well as local construction materials to be used.
The heart of every DEWATS is the anaerobic baffled reactor (ABR), which unlike centralised wastewater treatment systems, treats the wastewater using anaerobic processes. This means that oxygen is not needed to break down the organic matter in wastewater. The resulting faecal sludge may be composted and used as a fertiliser. The treated wastewater itself, which is usually nutrient-rich, can also be used as irrigation water and fertiliser in agriculture. By reusing the products from wastewater treatment, it also becomes possible to close the water and nutrient cycles.
Typical DEWATS combine different wastewater treatment processes:
Primary treatment is done using sedimentation tanks, septic tanks or biogas plants. Secondary treatment uses the previously described anaerobic baffled reactors, while tertiary treatment uses an aerobic horizontal gravel filter. The final treatment step uses a purification tank.
The service package also includes a quality management system, monitoring and evaluation, so-called in-house-management, health and hygiene training, and an evaluation of the health impacts.
More information can be found in the Downloads.