SV Krishna Chaitanya By

Express News Service

CHENNAI: Chennai beaches spewing snow-like foam at an unprecedented level, has compelled the State government to ask for a report from Tamil Nadu Pollution Board (TNPCB), which, after detailed analysis of samples collected, has indicated that illegal letting out of untreated sewage into Adyar river has led to ‘toxic’ algal bloom. This, in turn, resulted in accumulation of phosphates which possess foaming properties under wave action.

The report, accessed by Express, shows that levels of dissolved phosphate, ammonia, nitrogen and total dissolved solids (TDS) are on the higher side. The TNPCB officials collected two seawater samples on November 29 evening, a day after foaming started. One sample was collected 500 metres away from the confluence point of Adyar river into sea and another sample 1 km away. The exercise was repeated again on October 3 as the foaming continued along the city beaches.

All four samples results indicate high phosphate levels at 0.672 mg/l. A senior TNPCB official told Express that sewage smell was observed in the samples. “The sewage with rich phosphates from detergents and oils is the cause for frothing.”

Joe K Kizhakudan of Central Marine Fisheries Research Institute (CMFRI) said the TNPCB report results prove there is unregulated discharge of domestic sewage and industrial effluent into the river.

“Liquid detergents, animal wastes, fertilizers and sewage are resulting in high phosphates. Heavy rains have brought in sediments and organic matter packed with phosphorus, which is readily available for plankton, leading to sudden algal bloom. When combined with nitrogen and ammonia, it emits the froth,” he said.

For long, scientists of Indian Institute of Sciences (IISc) are recommending a ban on phosphates in detergents. This follows scientific studies of water quality in lakes, which established that frothing was caused due to high concentration of phosphates.

‘Test for heavy metals needed as well’

Environmentalist Shweta Narayanan questioned TNPCB’s decision to not test for heavy metals. “There is a suspicion that fertilizers from agriculture fields are draining into waterways and sea, in which case the board should have tested for heavy metals, which are pose a serious health hazard and carcinogenic.”

TNPCB’s response

A TNPCB official said that heavy metals are not linked to foaming, but the board will test for heavy metals shortly, to profile the kind of effluent being released upstream