The claim by the Narla Tatarao Thermal Power Station (NTTPS) authorities that the mercury levels in groundwater and ash pond effluent samples were well within the standard limits of the Andhra Pradesh Pollution Control Board (APPCB) is itself an admission that the water was contaminated with heavy metals leached from coal ash, said adviser to the National Alliance of People’s Movement and former Institute of Chemical Technology (IICT) scientist K Babu Rao.
In a note to The Hindu, Mr. Babu Rao said that the claim by the NTTPS Chief Engineer (Operations and Maintenance) that the mercury contamination was “within limits” needed to be verified by a third independent organisation as the “credibility” of the Environment Training, Protection and Research Institute (EPTRI) and the APPCB was “questionable”.
Mr. Babu Rao said that it was an established fact that the coal contained a large number of chemical elements including halogens. According to a study made by the U.S. Geological Survey, there were 78 trace elements in coal and in Indian coal the number was 35. Some of them leach out from the ash and some were emitted through the stack gas. The NTTPS had no measures to prevent leaching of heavy metals from fly ash in the ash pond and percolating into the groundwater.
Mr. Babu Rao said there was enough scientific evidence of soil and water body contamination around coal-fired power plants in India.
According to the online monitoring of stack gas data available for all seven units of the NTTPS taken from website http://pcbsite.nic.in/stack_industries.aspx the Solid Particle Matter (SPM) emission by units 2-6 exceeded (290 mg/N metre cube) against the prescribed limit of 115 mg/Nm3 on October 2. The stack gas data collected under the RTI, before the online monitoring system was in place, also showed that the SPM always exceeded the permitted limit. Neither the APPCB took any action nor the NTTPS initiated steps to bring down the levels, he alleged.
This showed that the Chief Engineer’s statement that the Electro Static Precipitators (ESPs) were provided for all the units to control dust emission was “hollow”, Mr.Babu Rao said .
The claims of the Chief Engineer with regard to mercury were also dubious, he alleged. Quoting the technical guidance manual for thermal power plants prepared by the IL&FS for the Ministry of Environment and Forests in 2010, Mr. Babu Rao said, “Upon combustion, coal ash tends to have a higher concentration of mercury. Estimates indicate that Indian coal has an average mercury concentration of 0.53 mg/kg. Annexure-I of the manual put the average concentration of mercury in Indian coal at 0.35 mg/kg.
Calculating at the minimum concentration, the existing 1,760 MW plant at NTTPS was releasing 2.448 tonnes of mercury per annum, Mr. Babu Rao opined.
