Decentralized Wastewater Treatment Systems (DEWATS)
DEWATS are decentralized, community-level wastewater treatment technology.
DEWATS is a technical approach to decentralized wastewater treatment in developing communities. The passive design uses physical and biological treatment mechanisms such as sedimentation, floatation, aerobic and anaerobic treatment to treat both domestic and industrial wastewater sources. DEWATS is designed to be affordable, low maintenance, use local materials, and meet environmental laws and regulations. DEWATS has service packages available for the sanitation needs of small and medium sized enterprises including communities, schools, municipalities, agro-industry, emergency settlements, hospitals, hotels, and prisons.
Afghanistan, Bangladesh, Bhutan, Cambodia, Cuba, Ecuador, Haiti, India, Indonesia, Iraq, Lao People’s Democratic Republic, Lesotho, Mali, Mexico, Myanmar, Nepal, Nicaragua, Philippines, South Africa, Tanzania, Viet Nam, Zambia
Bremen Overseas Research & Development Association (BORDA)
Goal 6: Clean water and sanitation
Users seeking improved waste disposal, users with no sewer network or municipal treatment plant, users seeking passive wastewater treatment made from local materials
All materials used for construction are locally available.
Users can contact BORDA for information on service packages offered.
More than 750 DEWATS plants are currently operating.
Continuous, Recharging only (V, time required, battery life), Other
1. Primary treatment: sedimentation and flotation
2. Secondary anaerobic treatment in fixed-bed reactors: baffled upstream reactors or anaerobic filters
3. Tertiary aerobic treatment in sub-surface flow filters
4. Tertiary aerobic treatment in polishing ponds
5. Systems can be designed to handle organic wastewater flows from 1-1000 m3 per day
6. Systems are built to be tolerant towards fluctuations in loads
Experienced DEWATS experts facilitate comprehensive training programs for qualified staff of partner organizations and take on a supervisory role during the first technical implementations.
Advantages of DEWATS technology
1. Providing treatment for domestic and industrial wastewater
2. Low primary investment costs as no imports are needed
3. Efficient treatment or daily wastewater flows up to 1000m3
4. Modular design of all components
5. Tolerant towards inflow fluctuations
6. Reliable and long-lasting construction design
7. Expensive and sophisticated maintenance not required
8. Low maintenance costs
Average removal efficiencies for a DEWATS facility in Nepal consisting of an Anaerobic Baffled Reactor and Constructed Wetland: 96% TSS, 90% BOD, 90% COD, 70% NH4-N, 26% Total P, and 98% FC.
Nepal Environmental and Public Health Organization (ENPHO)
Sludge must be handled, treated and disposed of in accordance with hygiene and environmental standards.
DEWATS technical layouts can be optimized to provide a renewable energy source in the form of biogas.
Bright-Davies, L. et al (2015); DEWATS for Urban Nepal: a comparative assessment for community wastewater management”
Cardona, J. et al (2010); “DEWATS Capacity Building for Primary Schools in Jordan and Palestine”
Kerstens, K.M. et al (2012); “Evaluation of DEWATS in Java, Indonesia”
Regulations vary by project location. A case study in Indonesia revealed over 90% of systems tested complied with Indonesian environmental regulations of BOD effluent less than 100 mg/L.
The current status and future outlook for BORDA’s DEWATS global programs can be viewed in the 2014-15 Annual Report.
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