The Delhi government on Sunday said that temporary weirs built on major drains flowing into the Yamuna have substantially helped to clean the drains by improving their biochemical oxygen demand (BOD) level and decreasing the amount of other pollutants as well.
In its approach to clean the Yamuna, the government said that it first plans to treat the water in the major drains that flow into the river. Water Minister Satyendar Jain said: “Cleaning the contributing drains of the Yamuna will directly lead us towards cleaning the river. Construction of temporary weirs is proving to be an impactful approach to reduce the amount of pollutants contaminating the contributing drains of the Yamuna”
What is a weir?
A weir is a small barrier built across a stream or river that helps to raise the water level slightly on the upstream side so that water is allowed to pool behind them and allowing water to flow steadily over top of the weir. Weirs are erected in the mid-flow of the drain to increase the retention of flowing water.
The government said that under this project, construction of 11 weirs has been completed on the supplementary drain and three weirs have been completed on the Najafgarh drain, while work on 10 weirs is in progress. It added that the Irrigation and Flood Control Department submitted a test report about the impact of these initiatives with water collected near Rithala STP, Rohini Sector 11 weir, Rohini Sector 16 weir, and Rohini Sector 15 weir.
“The report shows that there is a drastic reduction in suspended solids after the construction of the temporary weirs. Total suspended solids went down from 166 mg/l in Rithala to just 49 mg/l in Rohini Sector 15. There is a substantial reduction in ammonia content in the waste water as tests found ammonia to be 26 mg/l in Rithala and 18 mg/l in Rohini Sector 15,” the government said.
It added that the biochemical oxygen demand, which represents the organic material contamination, is found to be reduced after each weir as well.
