ACC IS searching for foreign collaboration to install pollution controls at its new manufacturing unit with one million tonne per annurn capacity. It has assigned a separate unit to look after pollution control and made a substantial increase in pollution control investment. The firm has also planted 602,800 saplings in a bid to improve its green image.

Officials at the ACC plant contend that existing electrostatic precipitators (ESPs) - devices that trap particulate matter in the effluent gas - have been modified extensively and an additional ESP has been installed. Dust bag collectors and cyclones - devices that suck in dust - have been placed at strategic spots and modified for better efficiency.

However, technological solutions to pollution from small cement plants will not be easy. Recently, the Ventury scrubber - a modified version of the conventional wet scrubber - was installed in one of the small plants and the results have been encouraging.

"Ananta cements, which became operational in August this year, has tried out this technology for its chimney emissions," says state pollution control board secretary S S Juneja.

Vijayandra Mahajan, Ananta's proprietor, says the Ventury scrubber may spive the problem of replacing conventional wet scrubhers in mini-plants. Wet scrubbers spray water at high velocity at dust just below the chimney outlet. This method is unpopular because it affects the heat inside the kiln and increases coal consumption by 7 per cent.

The Ventury scrubber, on the other hand, is*an improvement because the emission is diverted initially through an, inclined pipeline and then jet-sprayed. If the point at which spraying takes place is connected to a cyclone, "the emission level 'will come down from the present 100 Mg SPM to 70 ing SPM per cubic metre," says Mahajan. The Ventury scrubber is also said to be more efficient at trapping dust, which can be recycled.

However, K P Nyati of the Confederation of Indian Industries discounts such claims of the recycling efficiency of the Ventury scrubber. "It is not very clear to what extent the wet cement particles can be recycled profitably," he noted.

The capital cost of the Ventury device is much higher than the conventional wet scrubber and this would make it unpopular with mini-plant owners. Mahajan disclosed that of the total capital investment of Rs 1.75 crore in his plant, Rs 7 lakh was spent on pollution control devices, including one Ventury scrubber and two cyclones. The wet scrubber costs about Rs70,000.

Ashok Gupta, proprietor of Renuka Cements, says_ he opted for the wet scrubber because "the authorities are not yet clear about the right mix of the pollution control devices. First we were told that we must install cyclones along with our wet scrubber, but later they said that it was not necessary."