DEWATS technology for GWM in Bharasar village

In a shining example of public private partnership towards achieving ODF Plus status under Swachh Bharat Mission Grameen (SBM-G) Phase II, Bharasar village in Kutch district of Gujarat is managing greywater sustainably using DEWATS technology.

Background:  Having provided all 624 households with tap water connections and a minimum supply of 55 litres per capita per day under Jal Jeevan Mission, Bharasar village in Kutch district of Gujarat that comprises of a population of 4026 encountered a new challenge.  A whopping 70 per cent of the water supplied to households was converted into greywater that either flowed into the open or into water bodies, contaminating them.  It also led to vector borne diseases and posed other environmental and health risks.

The absence of a system for greywater treatment at the village level was greatly felt.  Although, wastewater from 150 households was connected to a drainage line, the greywater was discharged into the open.  Moreover, the remaining 474 households were connected to another drainage line which discharged the greywater into a stream outside the village, polluting the water body.

Issue:  The issue was identified by the Sarpanch and PRI members while preparing the Village Sanitation Plan (VSP) for implementation of SBM-G Phase II in order to manage solid and liquid waste at village level. Bharasar Gram Panchayat made sincere efforts to repair and construct the drainage system for managing the greywater. However, it was not a permanent solution.   In search of a solution and appropriate technology to manage the village’s greywater, the Sarpanch requested for technical assistance from the Swachh Bharat Mission (Grameen) of Kutch District. 

Strategy:  Around that time, UNICEF and PriMove initiated handholding, capacity building support to the PRIs and community leaders on the key components of solid and liquid waste management (SLWM) as per SBM-G Phase II guidelines to bring about visual cleanliness to villages.

With a focus on managing greywater sustainably, the development partners assisted Bharasar GP to revise their Village Sanitation Plan (VSP) based on a comprehensive assessment of the liquid waste management situation in the village. The process revealed that about 200 Kilo Litres per day (KLD) of wastewater consisting of both black and grey water was being generated.

Further technical assistance in the form of preparation of a Detailed Project Report (DPR) combined with capacity building, community mobilization activities and resource mobilization activities were held.  This was followed by discussions and strategic meetings amongst the PRI, SBM-G district team at district and block level and UNICEF to identify a strong Liquid Waste Management (LWM) system for the village.  Among the multiple options available to address the wastewater management needs of Bharasar, the DEWATS (Decentralised Wastewater Treatment System) technology was finalized by the PRI members and approved by the District Rural Development Agency (DRDA) – Kutch District.

Donor funding towards liquid waste management:  Additionally, the project received a donation of Rs. 86,22,361 from an NRI resident of the village. The funds acted as a catalyst to fast-track the construction of the wastewater treatment plant.  Thereafter, the PRI members were oriented on the working of the technology and O&M of the system. A handover meeting was conducted on June 6, 2022 with PRI members, the Sarpanch and community members and the plant was handed over to the Gram Panchayat for connecting all the households to the treatment plant.  In all this, the GP played a major role in allocation of land and generating revenue for construction and installation of the treatment plant.

DEWATS wastewater treatment technology:  Easy to integrate aesthetically into built environments, DEWATS technology is adaptable to a variety of organic wastewater characteristics. The system includes primary, secondary and tertiary treatment processes. What combinations would work best in a given situation can be decided depending on the required treatment efficiency, costs, land availability, etc. Thus, the technology is effective, efficient and affordable as a wastewater treatment solution for a small and medium-sized enterprises.

To treat the wastewater, natural bacteria and plants are used and gravity is also taken into account during the planning process. The decentralized system should be used in cases of high organic loading, particularly when treating the waste from small bore sewer systems or wastewater mixed with the supernatant from septic tanks.

Components of a DEWATS system

Settler: This is a two-chambered sedimentation tank that retains contaminants using floatation and sedimentation processes, which happens over a specific time frame.

Anaerobic Baffled Reactor (ABR):  In this segment of the process, anaerobic degradation of the suspended and dissolved solids occurs through the mixing of fresh wastewater with an active sludge blanket. The reactor is an RCC/masonry tank with a number of compartments separated by baffles. Wastewater enters the chamber from an elevated pipeline.  As the height of the water column increases, water flows to the next compartment. Thus, water travels through a series of chambers with a certain up-flow velocity that helps the organic content in the wastewater to settle at the bottom of each chamber while the wastewater moves forward for further treatment. It should be noted that greywater is low in solid content and so the provision of ABR should be adopted only where there is a high organic load.

Anaerobic Filter: This is a filter bed that ensures fixed digestion of suspended solids. It consists of an RCC/masonry chamber with a perforated slab where filter media are placed above it and settled wastewater is allowed to pass through the filter material. Filter media (cinder, corrugated pipes, gravel) which have a relatively large surface area are used. The microbial slime layer is allowed to grow on the surface of these filter media, which further treats the wastewater and removes the organic content in the wastewater.

Planted Gravel Filter: This tertiary treatment unit helps in discolouration of the wastewater and removes odour. In this treatment module, plants and gravel media capable of up-taking and treating organic matter and nutrients are used. The nutrients in the influent are consumed by the plants in the filter bed while the organics are decomposed primarily under anaerobic conditions. Plant roots allow the transport of oxygen from the air to a certain level, creating limited aerobic conditions near the root zone.

Polishing Ponds:  Following the planted gravel filter, a polishing pond is provided, which is an open shallow water body. Treated water is allowed to stay in this pond with a designated retention time. The main purpose of this pond is oxygen enrichment and elimination of pathogen germs through natural solar radiation.

Outcome:  UNICEF, PriMove, District Rural Development Agency (DRDA) and Bharasar Gram Panchayat had envisaged making Bharasar village a model village in June 2021. The village has now become one of the best examples of Public Private Partnership (PPP) through the involvement of a donor who provided financial aid for development of the village. With this, Bharasar has become self-reliant, capable of treating around 200 KLD of wastewater at village level. The Gram Panchayat plans to reuse the treated water for irrigation. Bharasar Gram Panchayat’s efforts for prioritizing wastewater treatment with community ownership and focusing on operating the treatment plant is a way forward in achieving ODF Plus status and sustaining the same in the long run.

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