Qualitative assessment of coal bed methane produced water for developing safe disposal strategies

With growing thrust on extraction of coal bed methane (CBM) gas in many countries, the concurrent generation and discharge of poor quality coal bed water (CBW) is emerging as a major threat to the environment of the nearby soils. Under this context, relevant properties of CBW of a CBM extraction site located in Eastern India were studied and the values were assessed with regard to permissible quality of irrigation water. The study revealed the quality of CBW is largely dominated by salinity, alkalinity, electrical conductivity (EC), pH, sodium absorption ratio (SAR) and residual sodium carbonate. Classification of the CBW samples showed most of the waters (88.88%) fall under High SAR Saline group, while the rest were under High SAR Alkali category. It was also interesting to observe that under comparatively lower EC ranges of CBW, alkalinity was high while the influence of salinity became more visible under higher EC regimes. The key components of CBW influencing the salinity as well as sodicity problems of such water were also determined through Principal Component Analysis.