CHENNAI: The Tamil Nadu Pollution Control Board on Sunday told the NGT-appointed expert committee that post-Sterlite closure, the ambient air quality has considerably improved around the factory in Thoothukudi. For instance, sulphur dioxide (SO2) emissions have dropped four times from 20 micrograms per cubic metre to 5.
Material evidence, submitted by the board, showed that average sample data of SO2 emission on September 22, 2017 was 20 micrograms/ m3 while recording from top of the scaffolding at the office of the All India Radio, the data collected on October 12-13 was 5 micrograms/m3. Nitrogen dioxide levels have come down from 15 micrograms/m3 to 7 micrograms/ m3. However, the PM10 levels have increased from 56 micrograms/ m3 to 64.9 micrograms/m3.
“The industry’s contention was that there is no appreciable change in the ambient air quality even after the Sterlite industry is closed. However, based on the above comparisons, it clearly shows that the parameter SO2 has very much reduced in the ambient air. The increase in PM10 could be due to the dust emanating from the open dump such as gypsum, slag and secured landfill facility,” TNPCB said in the comparative statement on ambient air quality.
TNPCB chairman Shambhu Kallolikar told Express that there was a clear evidence that after Sterlite copper unit was shut down, air quality had improved in and around the factory.
“The board has collected air samples at eight locations.” The official also said the government raised the issue of green belt and stack height violations as well. Sterlite claimed its chimney stacks were of adequate height because the company operates at an SO2 emission factor of 1 kg/tonne of acid produced.
However, TNPCB contention is that stack height should be calculated using the combined capacity of all acid production plants in the location, and using an SO2 emission factor of 2 kg/tonne of acid produced. Dr T Swaminathan, a retired professor of Chemical Engineering from IIT Madras, has calculated the stack heights for the sulphuric acid plants and the smelter. According to his scientific opinion, the stack attached to the sulphuric acid plants should be of minimum 83.5 metre height.
‘Stack should be of minimum 83.5-metre height’
Dr T Swaminathan, a retired professor of from IIT Madras, has calculated the stack heights for the ulphuric acid plants and the smelter. According to his scientific opinion, the stack attached to the sulphuric acid plants should be of minimum83.5-metres height.