The IIT-Madras expert team studying the contamination of groundwater in Tondiarpet said it would have to lift samples from a larger area in the neighbourhood to ascertain the quantity of dissolved petroleum compounds in the water table.

The team lead by Indumathi Nambi, associate professor and head, environment and water resources division, department of civil engineering, had recently run tests on samples from borewells contaminated by oil seepage from underground pipelines.

Speaking to The Hindu, Ms. Nambi said petroleum had thousands of compounds that dissolved in water. Benzene, highly carcinogenic in nature, is one of those compounds.

“There are chances the dissolvable compounds may have spread across a larger area. Once if dissolves, you cannot smell or see oil. A larger study is necessary to find out how far it has spread,” she said.

Ms. Nambi said it was necessary to remove the floating oil first so that oil in the soil could be dealt with next. “Residents must stop digging new borewells and avoid pumping water from the existing ones. A high-pressure pump must be used to suck the oil out completely,” she said.

To clean groundwater entirely, bioremediation using micro-organisms, that use carbon as a food source, should be carried out, she said. “The good thing is the compounds in petroleum are biodegradable and the micro-organisms will help. If proper measures are taken, it will take five years for the water in the borewells to return to normal condition,” she said. 

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