Alarmed at the discharge of industrial effluents, including acids, into sewer and stormwater drain networks, a special purpose vehicle (SPV) that maintains the Ambattur Industrial Estate has issued notices to units not treating their emissions.

In its notices to the members, the Chennai Auto Ancillary Industrial Infrastructure Upgradation Company (CAAIIUC), pointed out that industrial effluents were being let into the underground drainage network, small canals and stormwater drains.

These effluents were not just detrimental to the environment but also caused damage to the sewage treatment plants operated in the estate by the CAAIIUC.

The SPV has identified 21 industrial units and hotels in the estate so far that discharge untreated effluents and food waste.

“We lifted samples of sewage being let out into the pipelines and found that 21 units were releasing effluents into the sewer network,” said G. Krishnamoorthy, chairman of CAAIIUC.

At present, the estate has two STPs with a capacity for treating 5 million litres of sewage a day. However, the STP in the south phase with 3 mld capacity receives one mld of sewage as of now.

“Along with sewage, this plant receives effluents like coolant oil and acid from the plating industry. We have asked the units to stop releasing the effluents as the STP is designed to treat only sewage,” he says.

The SPV has sought the aid of Japan International Cooperation Agency (JICA) to upgrade the STP operated in the south phase and improve the quality of treated sewage. A common effluent treatment plant is under construction in the estate and is expected to be operational in three months. “Until then, the units could use their own mechanism to treat effluents as per the Tamil Nadu Pollution Control norms and not pollute the smaller waterways,” he said.

While the chemical oxygen level in the treated sewage is reduced up to 100 mg/l, the biochemical oxygen demand level is decreased to 40-60 mg/l. This needs to be halved after treatment according to the new TNPCB norms.

In an attempt to achieve better quality after treatment, the CAAIIUC plans to install an online monitoring system to check lapses and upgrade treatment processes with JICA’s assistance.

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