DEWATS | Decentralized Wastewater Treatment Systems


    About DEWATS

    Main DEWATS modules for physical and biological wastewater treatment:
    1. Settler 2. Anaerobic Baffled Reactor 3. Anaerobic Filter 4. Planted Gravel Filter

    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.

    • DEWATS applications provide treatment for both domestic and industrial sources
    • Systems can be designed to handle organic wastewater flows from 1-1000 m3 per day
    • Systems are built to be reliable, long lasting and tolerant towards fluctuations in loads
    • DEWATS applications do not require sophisticated maintenance

    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:

    • Primary treatment: sedimentation and floatation
    • Secondary anaerobic treatment in fixed-bed reactors: baffled upstream reactors or anaerobic filters
    • Tertiary aerobic treatment in sub-surface flow filters
    • Tertiary aerobic treatment in polishing ponds

    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:

    • Provides treatment for domestic and industrial wastewater
    • Low initial investment costs as no imported materials or components are needed
    • Efficient treatment for daily wastewater flows of up to 1000m3
    • Modular design of all components
    • Tolerant towards inflow fluctuations
    • Reliable and long-lasting construction design
    • Low maintenance costs     


    DEWATS technology is an effective, efficient and affordable wastewater treatment solution for small and medium sized enterprises (SME).

    The Challenge

    The demand for reliable, efficient and low-cost wastewater treatment systems is increasing around the world, especially in densely populated urban regions. In these areas, adequate wastewater treatment systems often do not exist and uncontrolled discharge of wastewater endangers health and pollutes local water resources.

    Many governments have passed new environmental regulations stipulating that dischargers of wastewater, such as small and medium enterprises and housing estates, will be held responsible for wastewater pollution. Therefore these entities should treat wastewater adequately on-site before it is discharged or released into the environment.

    Many SME are not able to pay high investment and maintenance costs required for sophisticated wastewater treatment systems.
    Maintenance of sophisticated wastewater treatment systems requires high-skilled personnel.
    Due to lack of investment capital and technical knowledge SME often adapt non-effective low-cost "solutions".
    Wastewater discharged by SME often does not meet environmental standards.

    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.


    A narrow technical approach is insufficient to assure sustainable growth of appropriate wastewater treatment infrastructure in the long term. Therefore, BORDA’s approach for implementation of DEWATS projects includes, in addition to the construction of “hardware”, a comprehensive set of integrated measures, such as:

    Information seminars and workshops to introduce DEWATS to key stakeholders
    Early information to key-stakeholders is vital to ensure continuous support for the programme on a macro-level.

    Co-financing of demonstration projects
    Financial support during the startup phase of a demonstration project improves the probability of desired results and impacts.

    Sector-specific information seminars
    An early focus on specific priority sectors supports an exchange of ideas between experts and potential clients that have similar professional experiences.

    Technical training
    Experienced DEWATS experts facilitate comprehensive training programmes for qualified staff of partner organisations and take on a supervisory role during the first technical implementations.

    Project planning
    Project planning includes technical feasibility studies, detailed engineering designs and cost-estimates.

    Project implementation
    Service provision depends on preferences of clients and network partners and may include supervision of construction, contractor services or turn-key operation. To ensure high quality standards, major tasks are always carried out by qualified experts.

    Technical support and monitoring
    Staff responsible for operation and maintenance of new DEWATS plants are thoroughly trained by technical experts during the first year of operation.

    Quality Control
    All DEWATS systems constructed are designed and guaranteed to fulfill specified discharge standards. Effluent tests are conducted at regular intervals.

    Research & Development
    Continuous efforts are made by members of the DEWATS partner network to improve efficiency and effectiveness of treatment systems.

    Dome shaped anaerobic baffled reactor for biogas recovery.
    Good Practice
    DEWATS for Hospitals

    • 250 beds with outpatient department
    • untreated wastewater discharge into nearby stream
    • complaints of neighbouring communities
    • limited funds
    • limited technical skills of staff
    • sufficient space

    Technical Solution:
    • 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

    DEWATS for Agroindustries

    • 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

    Technical Solution:
    Separation of wastewater components:
    • De-watering, sedimentation & floatation
    Treatment system components:
    • Screening
    • Sedimentation
    • Composting
    • fully-mixed digestion in biogas reactor
    • Anaerobic filter

    DEWATS for Communities

    • 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

    Technical Solution:
    • Fully mixed digester (fixed dome biogas plant)
    • Baffled reactor
    • Landscaping
    • rehabilitation of WW ditches
    • MOU between NGO and CBO regarding maintenance of Sanitation/DEWATS infrastructure

    Laboratory Test Results
    Effluent Quality during first month of DEWATS operation
    Benefits of DEWATS

    • 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