Used Water Management
India faces a significant issue with untreated wastewater, as over 40,000 million litres are generated daily.
This accounts for approximately 60 per cent of the total daily wastewater and is equivalent to the water needs of nearly 300 million individuals. India also struggles with water availability, posing a significant challenge for its residents.
One of the main reasons is the lack of treatment facilities in most areas of the country. The existing facilities, like centralized Sewage Treatment Plants (STPs), can only handle 44 per cent of the wastewater generated. These STPs also have high operational costs and maintenance problems, so the amount of wastewater meeting discharge standards may be even lower. This is a common issue for developing countries trying to ensure water security.
Treating wastewater can increase its potential for reuse, reducing the strain on freshwater sources and addressing public and environmental health concerns related to water pollution. Therefore, finding solutions to enhance wastewater treatment is necessary.
What is DEWATS™ ?
DEWATS™ is a modular, decentralized, and nature-based approach to wastewater treatment tailored for households, institutions, and communities. Using gravity flow, microorganisms, and plants, these systems eliminate the need for electricity, chemicals, or highly skilled labor. DEWATS™ makes water reuse possible at source—helping reduce freshwater consumption and convert treated sludge into useful soil conditioners
Key Features of DEWATS™
- Simple and robust design
- Uses local materials and unskilled labor
- Low life-cycle cost—up to 50% lower than conventional systems
- No odor or operational disruptions
- Can be contextualized to match landscape and community needs
- Reliable long-term performance
Recognitions and Accreditations
- Accredited by the Dr. Mashelkar Committee (Prime Minister’s Office)
- Featured in CPHEEO Manual on Sewerage & Sewage Treatment
- Empaneled by Kerala Suchitwa Mission
- Certified trademark under Government of India’s Trade Marks Act
- Accredited by Govt. of Kerala for wastewater and faecal sludge management
- Acknowledged by UNESCO (World Water Development Report 2019)
Treatment Process in DEWATS™
DEWATS is based on four treatment modules:
- Sedimentation and primary treatment in sedimentation ponds, Settler, or Imhoff tanks
- Secondary anaerobic treatment in Anaerobic baffled reactors or fixed bed filters
- Advance Secondary or Tertiary aerobic treatment in constructed treatment wetlands (subsurface flow filters)
- Post-treatment in polishing or aerobic ponds or conventional disinfection methods.
These four principal processes and systems are selected and designed as per the local context and considering the quantity and quality of influent wastewater, and the required effluent quality.
Components of a Typical DEWATS™ System
- Grease & Grit Chamber: Captures oils and grit, especially in kitchens and dairies
- Settler: Sedimentation tank with anaerobic sludge stabilization
- Biogas Digester: Anaerobic tank producing usable biogas
- Anaerobic Baffled Reactor (ABR): Multi-chamber reactor for primary organic load reduction
- Anaerobic Filter: Media-filled chambers that support biofilm growth for enhanced treatment
- Horizontal Gravel Filter: Subsurface flow wetlands for nutrient and solids removal
- Polishing Pond: Aerobic pond using sunlight to kill pathogens
Treatment Efficiency of DEWATS™
Modules | HRT (hrs) | BOD Removal (%) | BOD Output (mg/L) |
Settler | 2-3 | 30-40 | 180-200 |
ABR | 8-12 | 50-70 | 100-120 |
Anaerobic Filter | 12-20 | 70-75 | 50-60 |
Planted Gravel Filter | 24-36 | 85-90 | ~30 |
Polishing pond | 12-18 | ~95 | < 20 |
DEWATS™ Across Scales
Initially designed for rural and peri-urban settings, DEWATS™ has been adapted for apartment complexes, schools, public toilets, and institutions. CDD India has implemented over 400 systems across India and abroad, treating over 15,000 million liters of wastewater per year for more than 200,000 people.
Innovations such as prefabricated units and hybridization with conventional systems have allowed DEWATS™ to expand its reach. The system is now being explored for large-scale interventions like waterbody rejuvenation.
DEWATS™ in City-Wide Sanitation
CDD India has scaled DEWATS™ to the city level by implementing 10 Faecal Sludge Treatment Plants (FSTPs) and supporting lake rejuvenation efforts in Bengaluru. The system aligns with global urban development goals like Citywide Inclusive Sanitation (CWIS), water-sensitive urban design, and circular economy principles.
DEWATS™ Plus : Hybrid Innovations
To meet new CPCB norms (2017), DEWATS™ is now hybridized with additional modules:
- Vortex Units: Low-energy aeration with swirling oxygenation
- ECO2 Aerators: Cost-efficient aeration for small-scale use
- Sand & Carbon Filters: Final-stage polishing of suspended solids and micropollutants
- Vertical Flow Wetlands: Aerobic filtration in compact vertical beds
A Proven Solution
Today, DEWATS™ is recognized globally and implemented in over 17 countries. With its ability to treat wastewater sustainably and at scale, it serves as a cornerstone for water-secure and resilient communities across the global South.
ECO2 Aeration Tank: A second economic alternative to conventional aerators, the ECO unit is used to aerate, circulate, and de-gasify smaller volumes of water. It is placed submerged within the water body at a depth ranging from 0.5 to 1 meter (about 0.2 mts above the bottom surface clamped to a cement block).
Sand and Carbon Filter: This is used at the polishing stage for removal of suspended solids and pathogens that are left out.
The sand media traps all suspended matter while the activated carbon filter removes unwanted contaminants from wastewater including micropollutants such as chlorine, methane, organic compounds, and even any unpleasant taste and odor
Vertical flow constructed wetland: This is a planted filter bed that is drained at the bottom. Wastewater is poured or dosed onto the surface from above using a mechanical dosing system. The water flows vertically down through the filter matrix to the bottom of the basin where it is collected in a drainage pipe. The important difference between a vertical and horizontal wetland is not simply the direction of the flow path, but rather the aerobic conditions.
Today DEWATS™ is a proven technology, which has been implemented in over 17 countries. CDD Society, its trainees, and partner organizations have implemented over 400 DEWATS™ systems across India, which treat 15,000 million litres of wastewater, generated by 2 lakh people every day.
DEWATS™ Sector of Application
Schools
- Spartan School (Chennai)
- Silver Oak School (Bangalore)
- Harvest International School (Bangalore)
Factories
- Positive Labels (Bangalore)
- Gokuldas Images (Bangalore)
- Kamal Solar Factory (Bangalore)
Apartments
- Padma Sai Enclaves (Madurai, Tamil Nadu)
- Housing Apartments (Thilothu, Bihar)
- Pristine Temple Tree Apartments ( Bengaluru, Karnataka)
Colleges/Universities
- Colleges/Universities Indian Institute of Technology (Gandhinagar)
- MVJ College of Engineering (Bangalore) Kathmandu University (Nepal)
Communities
- Ullalu Bus stand (Bangalore)
- Sunga Cimmunity (Thimi, Nepal)
- Mahajan Nagar Community (Nagpur)
Food Processing Units
- Shyam Rice Mills (Palwal, Haryana)
- Saria Rice Mills (Haryana)
- Alternative (Bangalore, Karnataka)
Hospitals
- Seven Hills Hospital (Mumbai)
- Arvind Eye Hospital (Pondicherry)
- Dhulikhel Hospital (Nepal)
Housing Colonies
- VBHC (Chennai)
- Singanayakanahalli Housing Colony (Bangalore)
- Good Earth (Bangalore)
Institutions
- Friends of Camphill (Bangalore)
- Avatar Meher Baba Trust (Meherabad)
- Association of People with Disability
Disaster Relief
- Kadampadi (22 communities) and Kuttiyadiyur – post the 2004 Tsunami Rehabilitation of flood affected colonies – Madapura and Galibeedu – in Coorg
Water Body Rejuvenation
- Mahadevapura Lake (Bengaluru)
- Sadarmangala Lake (Bengaluru)