IMPACT OF FLY-ASH FROM COAL-FIRED POWER-STATIONS IN DELHI, WITH PARTICULAR REFERENCE TO METAL CONTAMINATION

Indraprastha Power Station (IPP Stn) and Rajghat Power House (RPH), ow ned by Delhi Electric Supply Undertaking, are both coal-fired power st ations located on Ring Road in New Delhi. Ash content of the coal used ranges between 38-47%. The ash is collected in electrostatic precipit ators which have an efficiency of 99.3% (IPP station), and 99.7% (RPH) . There are instances of major dust pollution around the power station s from fly ash dispersal. The main method of disposal of fly ash from the power stations is by mixing with water, the resultant slurry is pu mped through pipes to ash disposal ponds. The supernatant from these p onds is discharged into River Yamuna. Field studies have revealed larg e quantities of fly ash being deposited into the river. Local populati ons of Eichhornia crassipes have reduced dramatically between 1987-199 5, with a marked reduction in the year 1994-1995. Field studies, condu cted in January, 1995 have investigated the impact of fly ash dispersa l in the Delhi region with particular reference to metal contamination . Elemental concentrations for a range of elements are determined by I CP-AES in fly ash and top soils along four transects from the power st ations up to a distance of 8 km. The effects of fly ash leachates from the ash settling ponds on the river are determined by analyzing river overbank soils and vegetation for their elemental contents. It is con cluded that fly ash dispersal from the stacks are a source of alkali, alkaline-earth and to some extent heavy metals in soils in the vicinit y of the power stations, and enrichment of elements in river overbank soils are a result of discharge of fly ash leachates from ash disposal ponds. However, the impact from both these sources of metal contamina tion is not large enough to give cause for concern. Marked reduction i n populations of Eichhornia crassipes downstream of the river where it receives leachates from the ash disposal ponds are attributed to turb idity of the ash pond leachates and metal toxicity. Elemental enrichme nt in the floodplain soils, as a result of fly ash particle deposition during monsoons, may enhance the horticultural value of these soils a s is shown,by a healthy cultivated crop of Brassica juncea.