Optimization of the quality of reverse osmosis-treated coal bed water in relation to its effect on soil health

Abstract

During the time of extraction of coal bed methane (CBM) gas, vast quantity of imbedded water is also simultaneously released to the surface. Quality of this water is generally very poor owing to high salt content, and discharge of such water to the land surface frequently results in serious deterioration of the soil health through expansion of salinity and alkalinity problems. Use of reverse osmosis (RO) technology has appeared to be an effective proposition for bringing down the ionic concentrations of coal bed water (CBW) and facilitating their safe release. However, reclaiming the large volume of CBW through RO is expensive and is difficult to be afforded by many CBM producers from developing countries. In this study, we assessed the possibility of releasing an intermediate-quality RO-treated CBW which will not affect the health of the flooded soils and also will involve lesser cost of RO operation. The study showed that the quality of RO-treated CBW below 2 mmho/cm did not affect the incubated soil very adversely with regard to the major soil health attributes. However, exchangeable sodium percentage of the RO water-treated soil exhibited sharp increments when the EC value of the RO water increased to 2.0 mmho/cm resulting in development of high alkalinity. It is, therefore, suggested that while treating CBW with RO technology for discharging the resultant water to adjacent areas, it is not necessary to produce highly purified reclaimed water. Instead of going for high level of reclamation, discharge of a moderate-quality treated water may be an effective proposition for improving the economy of CBW reclamation without affecting the health of the CBW-influenced soils.