Decentralized wastewater treatment system that treats used water locally using natural and low-energy processes.
Pond-based treatment systems that use sunlight and microbes to treat used water naturally.
Working Principle:
DEWATS systems are based on modular technical configuration concept. Modules chosen for used water treatment consist of Settling tank (ST) for primary treatment, Anaerobic baffle reactor (ABR) with integrated filter (AF) for secondary treatment and Horizontal flow planted filter (HFPF) for tertiary treatment, polishing pond (if required for post treatment). Used water is passed through all these modules in sequence for treatment.
Suitability:
DEWATS (Decentralized Wastewater Treatment Systems) are designed based on the principle of low maintenance and energy-efficient operation. The modular combination of DEWATS components is well-suited for treating used water generated from housing communities or collected from drain endpoints with high volumes of used water. The treated effluent typically meets quality standards for safe reuse, particularly for landscape irrigation and non-food crops.
Pros/Cons:
Pros: DEWATS modules can be built and repaired with locally available materials and do not require energy or skilled labour and low in operations and maintenance cost as compared to electro-mechanically operated technologies. The units can be designed and easily integrated to blend with the surrounding landscape and produce a good quality effluent that can be reused.
Cons: Area requirement and capital cost is moderate to high.
O&M requirement:
Regular emptying of sludge (once in 2 to 3 years) and scum (once in 6 months) from ST and AF, cleaning (or replacement) of filter media once in 3 to 5 years in the AF and HFPF, harvesting of plants in the HFPF.
|
Parameter |
Design Value |
Unit |
|---|---|---|
|
Influent Characteristics |
||
|
BOD |
250 |
mg/l |
|
COD |
500 |
mg/l |
|
Hydraulic retention time |
2 |
Hours |
|
Peak hours |
8 |
Hours |
|
SS/COD ratio |
0.45 |
- |
|
De-sludging interval |
18 |
Months |
|
Effluent Characteristics |
||
|
BOD (At PGF Outlet) |
< 30 |
mg/l |
|
COD (At PGF Outlet) |
< 250 |
mg/l |
Note: In DEWATS design, peak flow is typically based on an 8-hour inflow duration aligned with daily wastewater generation patterns. This can be extended to 14–16 hours using an equalization tank with a pump sump, which regulates flow through controlled pumping. This approach, ideal for flows above 500 KLD, helps to reduce treatment unit size, land footprint, and capital cost. However, it increases O&M needs due to continuous pump operation and is suitable where reliable pump performance can be ensured.
• It is assumed that the site is a fairly level site with minor variations in levels.
• The Safe Bearing Capacity for the foundation design of the civil structures is assumed as 10 Tons/Sqm at a depth of 1.5m below the existing ground level.
• The Design Water Table for the design of the civil units of the STP is assumed at 5.0m below the Natural Ground Level.
• There is vehicular access available to the site.
• The site is fairly level ground, free of any structures, large trees requiring cutting permission, any kind of underground or overhead utilities, etc. except for small shrub's, vegetation, etc.
• The soil profile of the site involves earth work excavation in soil only, excavation involving rock blasting is not necessary.
• The site is not a low-lying area or marshy land or sewage farm, etc.
• The site is with original soil profile, without deep filling or overburden.
India’s rural sanitation sector has witnessed significant progress under the Swachh Bharat Mission Grameen (SBM-G), with increasing emphasis on sustaining Open Defecation Free (ODF) outcomes and strengthening Solid and Liquid Waste Management (SLWM) systems across villages. As rural communities continue to evolve and generate higher volumes of greywater and wastewater, there is a growing need for decentralized, cost-effective, and sustainable rural used water management solutions that are technically sound and easy to implement.
Despite the availability of various treatment technologies and management approaches, Gram Panchayats, Rural Development Departments, and implementation agencies often face challenges in selecting appropriate technologies, preparing technical designs, estimating costs, and planning site-specific interventions. The lack of standardized technical resources and easy access to implementation-ready designs further slows down the execution of rural sanitation infrastructure.
To address these challenges and support the effective implementation of rural used water management systems, WASH Institute has developed this dedicated web-based Rural Used Water Management Portal. The portal is envisioned as a comprehensive technical decision-support platform to assist states, districts, blocks, Gram Panchayats, and practitioners in planning and implementing sustainable rural sanitation infrastructure.
The portal provides a curated repository of commonly adopted rural treatment technologies and management systems, including soak pits, leach pits, waste stabilization ponds, DEWATS, drain-end treatment systems, co-treatment models, FSTPs and other decentralized greywater management solutions suitable for rural contexts. Each technology package includes standard design drawings, technical specifications, implementation guidance, and quantity estimates (BoQs) that can be readily adapted for field implementation.
The technical resources available on the portal have been prepared by experienced sector experts in alignment with CPHEEO guidelines, SBM-G operational guidelines, and established field practices. The technologies featured on the portal have been successfully implemented across multiple villages and states, ensuring their practicality, scalability, and suitability for diverse rural conditions.
By making standardized designs and implementation resources easily accessible, the portal aims to strengthen planning capacities, reduce duplication of technical efforts, improve the quality of infrastructure implementation, and accelerate the adoption of safe and sustainable rural used water management systems across India.
Importantly, the portal is designed as a dynamic and evolving knowledge platform rather than a static repository. It will continue to expand through contributions from sector practitioners, government departments, and technical institutions. Future enhancements will include state-specific schedule of rates, GIS-based planning support, case studies, operation and maintenance guidance, and real-time cost estimation tools to further support rural sanitation planning and implementation.
Local governments follow staged planning for grey water management projects — planning and project formulation, DPR preparation, tendering, construction, and operation & maintenance. This portal supports the tendering stage by providing standardized technical drawings and cost estimates.
The designs, drawings, and bills of quantities (BoQs) provided on this portal are intended for reference purposes only and cannot be used directly for construction. Validate design assumptions, adopt locally applicable Schedule of Rates, and ensure compliance with applicable national or state-level standards.