CHENNAI: Fishermen and beach-goers were in for a shock on Thursday morning. Almost the city's
entire coastline was littered with foam. Thick blankets of white foam were seen along the city coasts from Ennore to Tiruvanmiyur.
Questions are being raised whether it is a sign that the city's overburdened wastewater system could have, once again, been spurting raw sewage into the sea. Due to heavy rain in the last 48 hours and rough sea conditions, there is a sudden influx of highly-polluted water from Adyar estuary into the sea.
"Frothing does happen once in a while during the rainy season, but the scale in which it happened this year is unprecedented," said M Kesavan, a local fisherman. The frothing started around 10 am on Thursday and continued till late in the night. None of the fishing boats have sailed into the sea due to rough sea as well as unusual foam deposit in the coast and offshore, said P Kathiravan, another fisherman from Pattinapakkam.
Joe K Kizhakudan, a scientist with Central Marine Fisheries Research Institute, said frothing happens due to the presence of non-biodegradable, detergent-like substances coming from municipal wastes and industrial effluents. Research says with increasing urbanisation, the popularity of synthetic detergents has increased which, in the long run, is adding phosphate to the water bodies.
"Sudden flushing of the backwaters filled with phosphate will cause frothing due to windy action. If the bar mouth is kept open continuously and there is constant flushing, this problem will not arise. All these pollutants are accumulated over a period of time and when it rains all of it drains suddenly and the surf action will cause frothing," he said.
He said frothing will severely damage plankton and invertebrates in the intertidal areas. "Frothing indicates very high alkaline water. All surface organisms will suffocate to death due to a respiratory problem, although it is only a short-time phenomenon. As more sea water exchange takes place, the dilution takes place," he said.
Environmentalists say this is similar to the case of Bellandur lake in Bengaluru. The chemical analysis of froth samples from Bellandur and Varthur lake reveals the presence of compounds containing nutrients (Nitrogen, Phosphorus and Carbon) and cations (Sodium, Potassium, Calcium and Magnesium), which come from detergents.
"There are a lot of illegal outfalls along Adyar river which discharge untreated sewage and other effluents. The government has to address the issue, otherwise, the incidence of frothing will frequent," said Saravanan, water expert.
When contacted, D Sekar, member secretary, Tamil Nadu Pollution Control Board (TNPCB), told Express that the board will collect samples and send them for chemical analysis to ascertain the cause for frothing.
Another senior official of TNPCB said seawater contains dissolved salts, proteins, fats, dead algae, detergents and other pollutants. "If you shake this glass of ocean water vigorously, small bubbles will form on the surface of the liquid. The frothing will intensify when the ocean is rough with strong wind and waves. Most seafoam is not harmful to humans," the official said.