Effects of spent wash of ethanol industry on groundwater: A case study of Rahimyar Khan district, Pakistan

3/day spent wash highly loaded with salts, oxygen demanding wastes and nutrients into evaporation ponds, which percolate into ground water and affects its quality. The groundwater around the evaporation ponds is used as drinking water and irrigation. Thirty-five representative water samples (3 spent wash, 2 drainage water and 30 groundwater) were collected and analyzed for 15 different parameters; pH, electrical conductivity, total dissolved solids (TDS), total hardness, chlorides, phosphates, alkalinity, nitrates, sulphates, chemical oxygen demand (COD), Na, K, Ca and Mg. The spent wash indicates a high concentration which is above the permissible limits of National Environmental Quality standard (NEQS) for industrial effluents. Groundwater samples collected near the evaporation ponds indicate high concentrations of nitrate and COD indicating contamination of groundwater. Coefficient of correlation among the parameters, contamination index and sodium absorption ratios were calculated to correlate the sources of contamination and suitability of water for drinking and irrigation purposes. Fourteen groundwater samples indicate the contamination index of more than 3 and are considered as highly contaminated.