Environment

Cleaning a River in Two Months, and on a Budget

An INTACH project at the Assi river in Varanasi, using bioremediation to remove pollutants from the water, has yielded considerable results in a short period of time.

Water from the Assi river before (L) and after treatment. Courtesy: INTACH

Water from the Assi river before (L) and after treatment. Courtesy: INTACH

New Delhi: An INTACH pilot project to clean the Assi river at Varanasi has yielded considerable results within two months, using low-cost unconventional methods. According to an article published on the South Asia Network on Dams, Rivers and People blog, the non-profit organisation managed to clean the wastewater flow in the Assi river (which flows into the Ganga at the Assi Ghat in Varanasi) using the process of bacterial bioremediation – or removing pollutants from water using biological products.

The Assi river is 3.5 km long, running through densely-populated areas that discharge their waste directly into the water. According to a report in Firstpost, INTACH’s decision to use these methods was based on their success in other areas. “We had cut our teeth in cleaning up the Palam nallah in Dwarka in 2012. Prior to that, we had cleaned up the Kushak nallah in Chankyapuri in 2010 and the east Taj drain which crosses the eastern entrance of the Taj Mahal. This was such a foul smelling drain that tourists would cover their nose to enter from this side. This clean up was undertaken last year,” Manu Bhatnagar from INTACH told the website.

According to Bhatnagar’s blog article, the organisation was faced with several challenges when they first began their Assi river project. There was large amounts of floating garbage; the water moves quickly making treatment difficult, there were structures very close to the water, leading to public protest against interventions that could increase the water levels; and several inflows in the river even towards the end of the river, which are hard to treat over a short stretch.

This meant that INTACH had to come up with ways to get around these challenges. According to the South Asia Network on Dams, Rivers and People article, the team introduced bacteria concentrates into the water (100 litres of concentrate a day) at six river locations. The bacteria degrades organic pollutants, enhances dissolved oxygen levels and removes odours, the article says. To get around the fast flow and increase retention time, the team installed soil bag weirs (to create lagoons and increase retention time) and coir log bundles (as a medium for bacteria to reside, grow and treat the pollutants, and also to reduce water velocity). Floating waste was removed manually.

Coir log arrangements on the Assi river. Courtesy: INTACH

Coir log arrangements on the Assi river. Courtesy: INTACH

Installing these interventions finished at the end of December 2016. Within four weeks, residents near the Assi river were saying the bad smell had reduced, Bhatnagar’s article says. When the water was tested two months after the treatment began, a significant improvement was visible. Biochemical oxygen demand levels had reduced by 83.7%, chemical oxygen demand levels by 50%.

The cost of this project, according to Bhatnagar, is Rs 4.34 crore in the first year and Rs 3.75 crore in subsequent years (at constant prices). Conventional methods including sewage treatment plants would require Rs 75 crore in capital equipment cost, with land costs, maintenance costs etc. on top of that. It was also be a long-term affair. In the interim, Bhatnagar has argued, the kind of treatment used at the Assi river is good for both the environment and local populations.