DEWATS | Decentralized Wastewater Treatment Systems
"Decentralized Wastewater Treatment Systems and Sanitation in Developing Countries – A practical guide"
This new guidebook, published by BORDA, addresses wastewater-related issues faced by Urban Service Providers or national and local governments, and is also relevant for academic institutions, international NGOs and local community-based organizations.
DEWATS stands for “Decentralized Wastewater Treatment Systems”. DEWATS represents a technical approach rather than merely a technology package.
DEWATS applications are designed to be low-maintenance: most important parts of the system work without technical energy inputs and cannot be switched off intentionally.
DEWATS applications provide state-of-the-art technology at affordable prices because all of the materials used for construction are locally available.
Without considering facilities for necessary chemical pre-treatment of wastewater from industries, DEWATS applications are designed with four basic technical treatment modules which are combined and configured to provide a custom solution for a given sanitation/wastewater challenge:
DEWATS applications are designed and dimensioned in such a way that treated water meets requirements stipulated in environmental laws and regulations.
Advantages of DEWATS technology:
DEWATS technology is an effective, efficient and affordable wastewater treatment solution for small and medium sized enterprises (SME).
For many small and medium enterprises and housing estates, conventional wastewater treatment systems are too technically sophisticated and costly. These conventional systems often require high energy inputs for operation and rely on extensive maintenance services to ensure continuous operation.
For these potential clients, BORDA and its network of partner organisations started in 1994 to develop reliable and cost-efficient wastewater treatment systems which efficiently treat non-toxic organic wastewater according to environmental standards. Efforts to standardize main components of the DEWATS approach, such as a multi-stakeholder approach, modular design of systems, project planning, implementation and quality control have resulted in a significant increase of implementation capacity and dissemination of technical know-how.
Today, more than 1000 stakeholders from the private sector, governments and NGOs have been trained by the BORDA-Network to facilitate the dissemination, implementation and maintenance of DEWATS systems. This has resulted in the sustainable operation of more than 250 DEWATS plants. The success of DEWATS has fostered partnerships with numerous government ministries, municipalities and international donor agencies to improve capacities and increase technical implementations.
• 250 beds with outpatient department
• untreated wastewater discharge into nearby stream
• complaints of neighbouring communities
• limited funds
• limited technical skills of staff
• sufficient space
• Treatment system for 150 m3 wastewater/day
• Sedimentation + anaerobic filter + horizontal sandfilter + purification pond
• Pumping chamber after anaerobic filter
• Total construction cost: $ 50.0000
• Training of maintenance staff and 1 year guarantee
• More than 100 cattle slaughtered per day
• Extreme fluctuation of wastewater composition
• extremely high organic load
• limited space for construction near stream
• unreliable responsibility and maintenance
Separation of wastewater components:
• De-watering, sedimentation & floatation
Treatment system components:
• fully-mixed digestion in biogas reactor
• Anaerobic filter
• Open waste water lagoon within community
• 6 public toilets/6 bathrooms for 500 people
• Unwillingness of landlords to upgrade sanitation infrastructure
• Willingness to provide lagoon space
• Willingness of people to pay for use of proper sanitation infrastructure
• People willing to manage sanitation infrastructure
• Fully mixed digester (fixed dome biogas plant)
• Baffled reactor
• rehabilitation of WW ditches
• MOU between NGO and CBO regarding maintenance of Sanitation/DEWATS infrastructure
• Establishment of multi-stakeholder networks to combat water pollution
• Increases implementation capacity on various levels
• Provides treatment for both, domestic and industrial wastewater at affordable price
• Fulfillment of discharge standards and compliance with environmental laws
• Wastewater pollution reduction by up to 90% from pre-DEWATS levels.
• Provides treatment for wastewater flows up to 1000 m3 / day
• Reliable and long lasting applications
• Tolerant towards inflow and load fluctuation
• Materials/ inputs used for construction are locally available
• Minimal maintenance and long de-sludging intervals
• Low operation and maintenance costs
• Resource efficiency and non-dependence on energy
• Resource recovery through wastewater re-use and biogas generation