A Study on Re-designing the Existing Ash Storage Pond for Leachate Control of Thermal Power Station

Thermal stations use coal as combustion material for fuel and the chemical energy stored in coal, which is converted successively into thermal energy, mechanical energy and finally electrical energy for continuous use and distribution across a wide geographic area. A study was conducted on a particular thermal power station to identify the ash disposal & storage system and the alternate design of the existing ash storage system since thermal stations use pulverized coal as fuel to generate electrical energy and produce ash as by-product. As such, Ennore thermal power station draws coal from Indian mines like Mahanadhi coal fields, Orissa (IB Valley, Talchar), Eastern coal field, Ranikanj and also imported coal from Australia & Indonesia is used. Indian coal has a high ash content exceeding 40%, with low calorific value but economical. In comparison the imported coal has a low ash content of less than 13%, high calorific value but costlier. As the residual end product of ash is more in Indian coal the concern on the need for safe storage, disposal for effective utilisation of flyash, a strategic approach evolving potential remedial measures to mitigate leaching of toxic minerals from the ash storage pond is necessary and the same is carried out in this study since wet ash is stored in ash ponds apart from disposal of dry ash at the source. Ash storage pond is constructed with high mounds of earth with filter media. To avoid contamination of the adjoining lands, streams and aquifers a reinforced cement channel drain along the ash bund is designed to collect the seepage of chemicals with a sloped gradient for further treatment of the leachate. Also as a Phyto-remediation specific species of plants as hyper-accumulators are planted along the downstream side slope of the bund and this absorbs the toxic minerals as well as strengthens the bund from breaching.