Test of Adyar estuary water reveals high metal levels of Biochemical Oxygen Demand (BOD)
A month after thousands of dead fish were washed ashore on the Urur Kuppam beach, a lab test has confirmed what was suspected all along: sewage pollution in the Adyar estuary.
A month after thousands of dead fish were washed ashore on the Urur Kuppam beach, a lab test has confirmed what was suspected all along: sewage pollution in the Adyar estuary.
At 28 mg/litre, the BOD was nearly five times the safe limit for aquatic life to survive, a water sample tested at the Tamil Nadu Water Supply and Drainage Board has revealed.
A BOD reading above 6 mg/l is not suitable for the survival of fish, according to Central Pollution Control Board guidelines.
The higher the sewage pollution, the higher is the proliferation of microorganisms such as algae that deplete oxygen, raising the BOD. The water sample also contained heavy metals including chromium, zinc, copper and iron.
“It had rained quite heavily the previous two days, and it is quite likely that in addition to the regular load of sewage, an additional shock load was discharged when Metrowater let out excess sewage into the river.”
Ever since the fish kill, speculation had been rife about the cause, with suspicions ranging from toxic and biomedical waste to the insurgence of excessive saline water.
Eutrophication
Rajesh Ramesh, an activist with Trust for Environment Monitoring and Action Initiating, who got the water sample tested, said: “What we essentially have here is the eutrophication of the water, which is preventing any life from surviving.”