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How polluting are thermal power plants?

How polluting are thermal power plants? THOUGH Singrauli's thermal power plants have affected the availability of potable water in the area, studies show they have contributed only marginally to the high levels of dust and gaseous effluents there.

None of the wells in the area supply potable water that meets official Indian standards. Water from wells and hand pumps near the ash dumps shows traces of mercury and cadmium sulphate. The Rihand reservoir, the area's largest drinking water source, contains traces of toxic cadmium, arsenic, selenium and nickel, because excess water from ash ponds is released into the reservoir. Studies show, however, the water can be made potable with simple primary treatment.

An Electricite de France study found high concentrations of sulphate and boron in the groundwater near the ash ponds in Singrauli, Renusagar and Anpara "although they have not yet reached critical levels". Such contamination takes place, the study added, because of insufficient maintenance and careless operation of the ash disposal systems.

Suspended particulate matter (SPM) in the Singrauli area is lower than the permissible limit of 150 microgrammes per cubic metre (mg/cum). Gaseous pollutants emitted from coal combustion are mainly sulphur dioxide and oxides of nitrogen whose concentrations should not exceed 120 mg/cum. The thermal power plants average sulphur dioxide concentrations of 60-75 mg/cum, while that of nitrogen oxides are 80-100 mg/cum.

"To reduce even these emissions, we could install expensive desulphurisation and denoxification systems," says S L Kapoor, additional general manager at NTPC. "But as the ambient air quality is within the set norms, there is no need. Moreover, these measures would increase the cost of power generation to more than Rs 4 per MW, from about Rs 2 per MW now."

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