New Delhi: Construction of weirs (low checkdams) on drains flowing into the Yamuna have been shown to have substantially reducing levels of pollutants like ammonia and suspended solid wastes and bringing down biological oxygen demand, the Delhi government said on Sunday, revealing the results of recent tests.
The test report submitted by the Irrigation and Flood Control department found that total suspended solids went down from 166 mg/L in Rithala to just 49 mg/L in Rohini Sector 15. The water samples were collected near Rithala STP, Rohini Sector 11 Weir, Rohini Sector 16 Weir, and Rohini Sector 15 Weir.
There was also observed a substantial reduction in ammonia content in the wastewater as tests found ammonia to be 26 mg/L in Rithala and 18 mg/L in Rohini Sector 15. The biochemical oxygen demand (BOD), which represents the organic material contamination, was found to be reduced after each weir.
The BOD recorded in the tests was 83 mg/L near Rithala STP, which was reduced to 27 mg/L at Rohini Sector 15, the statement said.
A weir is a small barrier built across the width of a stream or river that helps raise the water level slightly on the upstream side. The water collects behind the weirs in a pool and flows over it. So far, construction of 11 weirs has been completed on the supplementary drain and three on the Najafgarh drain. Work on 10 weirs is in progress, the statement said.
Apart from this, the department has also employed desilting of the drains, installation of trash barriers, floating boom to trap solid materials, removal of municipal solid waste and construction and demolition waste from the drains, removal of hyacinth, garbage, and weeds, and installing of wire mesh coverings on bridges and inlet mouths, to improve water quality.
"Construction of temporary weirs is proving to be an impactful approach to reduce the amount of pollutants contaminating the contributing drains of Yamuna," Irrigation & Flood Control minister Satyendar Jain said in a statement.
The government has started work to improve the quality of Najafgarh drain water that enters Delhi at Dhansa and travels about 57 km before falling into the Yamuna, and its supplementary drain, which takes off from near Kakrola Regulator and falls into the Najafgarh drain.
The minister said the department is focusing on solving the problem of polluted drains flowing directly into the Yamuna river, which will lead to the cleaning of the river. The Arvind Kejriwal government has set a target to clean the river by March 2023, he said.
The Delhi government in November last year had constituted a Yamuna Cleaning Cell (YCC) to ensure better coordination and integrated approach to achieve the objective of Yamuna cleaning.