Logs wound with coir, mud balls, dyes, and certain plant species may soon be used as tools to clean sections of heavily polluted drains that flow into the river Ganga. The National Mission for Clean Ganga (NMCG) has approved eight projects that will use bioremediation techniques to clean specific drains in Patna, Hardwar, Allahabad, Bulandshahr and Varanasi.
The total flow across all these drains adds up to 377 million litres per day (MLD). The total cost for the projects is Rs 23.77 crore. “The project proponents have been given a month to show if their methods are working before funds are released,” NMCG director general Rajiv Ranjan Mishra told The Indian Express.
Bioremediation is a technique that uses bacteria, fungi or other biological agents that work towards reducing toxins in the environment, in this case a polluted water body. “After assessing the pollution load of a particular drain, a consortium of bacteria is designed that eats away a lot of the pollutants in the drain,” Mishra said. “Due to this, the water from the drain that eventually reaches the river has much lower pollution levels. But this technique has to be applied over and over, say every 15 days.”
For instance, in Varanasi’s Assi drain, which has a flow of 70 MLD, the microbial consortium will be embedded into logs wound with coir and placed at specific points in the drain. “The logs will be placed across the drain and some part of the logs will also be above the water. This has two functions. One, to increase retention time for the microbes to treat the water, and secondly, to trap solid waste in the drain, which can then be removed manually every day,” said a senior NMCG official. Municipal workers will collect the solid waste that floats in the water and take it to the dumping yards.
In Allahabad’s Nehru Drain, with a flow of 26 MLD, mud balls will be lowered into the drain. “The mud ball is divided into one part mud, one part bacteria. If the pollution is very heavy, the mud ball will sit on the sludge and continue to ferment. It will remain there for a fortnight,” said the official in charge.
Mishra said such in-situ bioremediation technologies have been taken up as a pilot project and once their efficacy is established, they will be scaled up. The Expression Of Interest call by NMCG drew over 200 proposals. “It is not feasible to set up a sewage treatment plant or a sewage network in all cities and towns in Ganga basin. These are some innovative ways to manage waste water and if these work then we have enough data to scale up the projects,” he said.
NMCG officials say that a monitoring committee decides the points in the drain, termed ‘control areas,’ between which the in-situ bio-remediation technologies are to be employed; a third party inspection committee is entrusted to monitor the water quality at both ends of the stretch picked up for treatment.
In Rajpura, Digha and Danapur drains in Patna, a simple consortium of microbes will inoculate particular sections of each drain. In Hardwar’s Laksar drain, which has a flow of 193 MLD, a specific dye will be used to increase dissolved oxygen levels and break down organic matter into water and carbon dioxide.
Galaothi drain in Bulandshahr will see a phytoremediation, which will be the use of certain plant species, that will help to reduce pollution levels. Ramnagar drain will see a method of aeration — simply allowing more air to enter so it can sustain the existing micro-organism.