The West Bengal Pollution Control Board (WBPCB) is developing an online system to monitor industrial units polluting the Ganga and plans to encourage industries to adopt a mechanism ensuring zero liquid discharge, an official said Friday.

WBPCB chairman Kalyan Rudra, a known river expert, also expressed concern over the alarming rate of ground water depletion and said he was apprehensive that Kolkata may one day cave in if the depletion was not arrested.

"In pursuance of the Supreme Court order, we have identified 800 odd industrial units that have the potential to pollute the Ganga. These units are being monitored and those found guilty of flouting the norms are being ordered closure," Rudra said.

Of the 800 units spread across the Ganga catchment area, the Board has already ordered the closure of 79 dying bleach units and 16 slaughter houses for flouting pollution norms.

Participating in a MCCA Chamber of Commerce and Industry organised interaction, Rudra said a system was being developed for online monitoring of industries that come under the ‘red category’ or the heavily polluting industries.

"We are in the process of developing a system whereby heavy polluting industries are required to set up facilities for online monitoring of their discharge and maintain a record of its effluents. Industries like steel plants, sponge iron units, thermal power plants come under this mandate," said Rudra, claiming that the system will become fully operational by March 2016.

He said the Board would soon convene a meeting of all industries in the state for adopting zero liquid discharge (ZLD) system.

"Under ZLD, the entire waste water of an industrial unit is recycled and made fit for reuse. We are hopeful that the industry here will be eager to adopt this mechanism."

Rudra also expressed apprehension that Kolkata may cave in some day if the depletion of ground water was not arrested.

"Kolkata is a city which is hydrologically subsidised, thanks to the Ganga, but the people dependence of ground water is ever increasing. The way high rises are coming up and the ground water is being depleted, I have this apprehension that the city may cave in someday.

"It’s not Kolkata alone. In fact, 174 blocks across the state have been identified where the annual rate of ground water depletion is around 20 cm which is alarming," he added.