High levels of phosphates caused frothing: Tamil Nadu Pollution Control Board

CHENNAI :  A day after unusual frothing was witnessed on the city beaches, officials of the  Tamil Nadu Pollution Control Board (TNPCB) on Friday conducted a detailed chemical analysis of the water samples collected and found that high concentration of detergent phosphates was the cause for frothing. 

A team of officials have collected seawater samples from Srinivasapuram near Besant Nagar where the Adyar estuary backwaters drain into the sea. This happened after the TNIE published a report on foam deposits all along the city beaches, more so near the Adyar river bar mouth. Local residents said pollution board officials came and took samples after frothing stopped.

“Beaches were spewing froth all through the day on Thursday and the officials came a day late,” a fisherman said, expressing concern whether the phenomenon would repeat and wondered it would have any impact on fish catch. However, TNPCB officials told Express that the test analysis revealed there were detergent phosphates which might have got agitated by rough waves resulting in foam. “We will carry on the water sample collection and testing for next three days for the benefit of general public, who use these beaches for recreation,” a senior official said. 

Due to heavy rains in the past couple of days, the high tide must have flushed a large quantum of the ‘highly-polluted’ Adyar estuary backwaters into sea. These backwaters are mixed with untreated sewage, which contains high concentrate of detergent phosphates and nitrates which, when caught between the currents and rapids, cause frothing, the official said. An IIT Madras team has also visited Besant Nagar and collected water samples for testing. 

Officials say phosphate content in the Adyar estuary goes up from 1 mg/litre to 5 mg/litre. In foam it can be as high as 70 mg/litre. However, it gets diluted when seawater exchange takes place.