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Business News/ Mint-lounge / Features/  Consortium for Dewats Dissemination Society: After the flush
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Consortium for Dewats Dissemination Society: After the flush

An organization that gets down and dirty when we are done cleaning ourselves for the day

A teacher cooking on a stove fired by biogas in Kengeri slum, Karnataka. Photo: Aniruddha Chowdhury/MintPremium
A teacher cooking on a stove fired by biogas in Kengeri slum, Karnataka. Photo: Aniruddha Chowdhury/Mint

The Beedi Workers’ Colony in Kengeri, about 20km from Bangalore, is, to all outward appearances, one of those peculiarly undistinguished housing settlements that come up in India after a major development project or a natural disaster-forced relocation. Roads cut across each other at right angles, the houses—mostly single-storeyed, but some two-storeyed ones as well—share a wall for economy, a slip of a veranda makes for easy camaraderie among neighbours.

Of the 540 independent houses in the colony, 120 are special. Lying on either side of a reinforced cement-concrete road, they keep the fires burning at the anganwadi around the corner.

Every day, these 120 households produce about 36 cubic metres of wastewater, including human excreta and kitchen waste. Sewage pipes laid under the central road lead directly to a biogas digester, a sedimentation tank that decomposes the organic particles anaerobically and helps generate biogas as an effluent. This biogas is channelled to a single-burner stove in the tiny kitchen in the anganwadi, where 55-60 children in the 3-6 age group are entitled to a hot meal every day.

As showcases go, this is a somewhat incomplete demo of a decentralized wastewater treatment system (Dewats). But the impact, even of the abbreviated system, is unmistakable. In place since 2005, when the system was installed—the colony itself was overhauled in 2001 under an initiative of Rajiv Gandhi Rural Housing Corp. Ltd (a Karnataka government company that promotes housing for the poor)—the blue flame has been a constant, except when the biogas unit undergoes scheduled maintenance, says anganwadi worker Meenakshi (she uses only one name). This biogas also fuels the beedi workers’ office, as well as a couple of households in the colony.

According to the Central Pollution Control Board (CPCB), urban domestic sewage is the biggest source of water pollution in the country. “All Class I cities and Class II towns (893 in all) together generate an estimated 29,129 MLD (million litres of sewage per day). Against this, installed sewage treatment capacity is only 6,190 MLD... a gap of 78.7%," says a 2005 CPCB report, “Status of Sewage Treatment in India" (independent reports, however, put the gap at as much as 90%). A 2013 CPCB report adds that while some cities—Hyderabad, Vadodara, Chennai, Ludhiana and Ahmedabad—are capable of treating 100% of the sewage they produce, at least in theory, only Delhi, Mumbai and Pune can treat more than 50% of their sewage; other cities can take care of less than half.

“Basically, we are wallowing in our waste," says Susmita Sinha, director, knowledge management, R&D and training, Consortium for Dewats Dissemination Society (CDDS), the organization responsible for the sewage treatment in the Beedi Workers’ Colony. “More than 500 million people lack access to safe sanitation and more than 200 million tonnes of human waste goes uncollected and untreated every year. This leads to contaminated water sources and increased risk of diseases. Centralized systems (which direct everything collected in sewers to a central treatment plant, usually located far away from the city or town) cannot cope with the waste we generate. Dewats fills the gap between on-site sanitation systems (cesspools, absorption pits) and conventional centralized systems."

Broken up into modules, Dewats—a trademarked “technical approach, rather than merely a technology"—uses organic chemical and gravitational processes to treat wastewater. A grease trap, a settler and the biogas digester comprise the first module. In the second stage, a graded anaerobic baffled reactor uses a naturally occurring sludge basket to break down suspended and dissolved solids. An anaerobic filter (rocks or cinder) then brings active bacteria in contact with the dissolved matter for further treatment. The tertiary treatment involves a horizontal planted gravel filter—a shallow tank of gravel or pebbles planted with specific shrubs, such as cannas—and a polishing pond, which allows sunlight to complete the work of pathogen removal. The last two can be integrated into landscaping.

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The biggest advantage of Dewats is probably its flexibility: it adapts to individual houses as well as apartments, institutions, hotels and resorts, even public toilets. Two prefabricated Dewats modules, in fact, were put in place at the Mahatma Gandhi Road Metro station in Bangalore last year.

CDDS works with the municipalities on pilots for Dewats, simplified sewage systems, decentralized solid waste management, as well as empowerment and knowledge dissemination, all of which are part of CDDS’ basic needs service packages. “Over the past 11 years, we’ve set up 400-odd Dewats projects across India and Nepal," says Sinha. “This allows the treatment of 1,02,33,000 litres of wastewater per day, and positively influences the living conditions of around 226,000 people."

Perhaps the biggest achievement, though, is the adoption of decentralized ways of wastewater treatment at the governmental level: the Union ministry of urban development included Dewats in its guidelines in 2012. It is an acknowledgement that the solution to India’s massive waste problem could lie in simple, easy-to-apply techniques, rather than technologies.

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Updated: 21 Oct 2014, 10:21 AM IST
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