Delhi Jal Board reviews ongoing work to clean Yamuna

The Delhi Jal Board has completed construction of 24 weirs and check-dams on the Najafgarh drain even as the department is testing a series of technologies to reduce the pollutant load in the three major drains falling into Yamuna, the water utility stated on Monday

The Delhi Jal Board has completed construction of 24 weirs and check-dams on the Najafgarh drain even as the department is testing a series of technologies to reduce the pollutant load in the three major drains falling into Yamuna, the water utility stated on Monday.

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DJB held a review meeting on Yamuna cleaning projects on Monday. A senior DJB official overseeing the project said that in Najafgarh drain all the 24 weirs have been completed, and the in-situ treatment has been initiated with aeration, disc filters, UV disinfection, odour control and floating wetlands systems.

“We are also testing new technologies such as concrete blocks and geotubes to check their impact on reduction in the pollution levels in wastewater. The final target is to achieve the parameters of bio-chemcial oxygen demand and total suspended solids at 10 units through these techniques,” a DJB spokesperson said. A dozen weirs have also been set up over the Supplementary drain.

The Najafgarh drain enters Delhi at Dhansa border along Haryana and it runs about 57 km before falling into the Yamuna. Similarly, the second biggest drain in the city, the Supplementary drain, takes off from Kakrola regulator and finally outfalls into the Najafgarh drain. “The first step under this project is the construction of small dams along these drains and then, the construction of natural floating rafters over the drains. Due to the construction of small dams, solid suspended solids are trapped by the wall of the dams allowing the water to flow through. After this, the natural floating rafters help in increasing the amount of oxygen in the water so that the biological power of the water can be returned. This process has proved to be so effective that 80% of the pollutants in the supplementary drain are being cleared during this process itself,” DJB said in an official statement.

The Delhi government has announced its goal to clean Yamuna by 2025. The 22 km stretch of Yamuna in Delhi, from Wazirabad barrage to Okhla Barrage, which is less than 2% cent of Yamuna’s total length but it accounts for nearly 76% of the total pollution in the river, the NGT appointed erstwhile Yamuna monitoring committee had noted.

Under the review process, the board has stated that the project for laying of sewer network in unauthorized colonies has been completed in 725 colonies and in the rest the developmental work is in various stages. There are a total of 1,799 unauthorised colonies in the city.

DJB vice-chairperson Saurabh Bharadwaj of the drains which fall into the Yamuna, 16 have been trapped, three drains have been diverted to Sewage treatment plants and for the remaining Najafgarh, supplementary and Shahdara drains, interceptor sewer projects (ISPs) have been constructed to trap sub-drains that would otherwise merge with the main drains and ultimately outfall in Yamuna.

“108 sub-drains that used to outfall in Najafgarh drain have been trapped by DJB,” he added.

DJB has also identified 59 points where the sewage enters the stormwater drains. “Of 59 such points, works on 52 such points have been taken up and the sewers remaining at 7 locations will be completed by the end of August, 2022,” DJB official added. DJB has stated the progress of these projects will now be reviewed on weekly basis.