The Delhi Government on Friday set up an 11-member committee to probe the incident of mass fish deaths in Delhi's Najafgarh jheel  and one of the areas it is focusing on is fertiliser pollution.

According to a senior member of the committee, the committee includes members from the Delhi Pollution Control Committee (DPCC), Central Pollution Control Board (CPCB), Revenue Department, Forest and Wildlife Department and Animal Husbandry Department.

The Delhi Government team has collected biological oxygen demand (BOD) and the chemical oxygen demand (COD) levels of the drain, which connects the Najafgarh Jheel to river Yamuna.

"We have collected water samples from several spots and these are being tested to ascertain the concentration of dissolved oxygen, heavy metals, ammonia, nitrates and phosphates...  “There is a possibility of fertiliser runoff from the agricultural fields (in nearby villages)," a panel member said on condition of anonymity. COD is the total measure of chemicals (organics and inorganic) in the water/waste water, while BOD is a measure of the amount of oxygen required for bacteria to decompose organic components present in water.

"Some fish have been collected for dissection. The report will be available in three-four days," the member said.

Another panel member explained that nitrogen and phosphorus pollution can run off from agricultural fields into drains, lakes and rivers and can cause algal blooms.

"As algae blooms, it depletes the water of oxygen and creates a dead zone, killing aquatic plants and animals," he said.

A senior DPCC official said the test results of the water samples collected from the drain on Sunday morning have arrived. The report has been handed over to the committee which will correlate it with their findings.

According to officials, a huge number of fish have mysteriously died in the upstream stretch of the Najafgarh drain along the Delhi-Haryana border.Residents in the nearby Jhuljhuli village said fish in a pond in their village, around 200 meters from the drain, have also died. 

The fish have died only in a five-kilometre upstream stretch of the drain between Rawta village in Delhi and Dhansa dam in Haryana.

No such incident has been reported at Najafgarh Jheel, the second largest water body in Delhi-NCR after the Yamuna.  Local residents said they have never seen something of this sort in the past.

The Najafgarh drain enters Delhi near Dhansa village and flows into the Yamuna. It is the largest drain in Delhi and accounts for around 60 per cent of the wastewater discharged from the capital into the river.

The standard for BOD in drains is 30 mg/l. But as per the DPCC's latest monthly report on Delhi drains, compiled on June 1, 2022, the Najafgarh drain has a BOD reading of 70 mg/l and a COD reading of 346 mg/l, as opposed to a prescribed limit of 250 mg/l, DPCC officials said.