Assessment of drinking water quality characteristics and quality index of Rajshahi city, Bangladesh

The present study on chemistry, environmetrics and quality index of 116 groundwater samples collected in pre- and post-monsoon periods in the years of 2014 and 2015 from the drought-prone Rajshahi City Corporation area, Bangladesh, is carried out for its drinking suitability from management perspective. According to the Bangladesh Drinking Water Standards (2005), parameters like pH, Ca 2+ , Mg 2+ , Cl − , Fe (total) and Mn 2+ exceed the desirable limit, but within permissible limit without adverse effect except Mg 2+ concentration, which accounts for 45% in pre-monsoon period and makes groundwater unsafe for drinking purposes. The groundwater belongs to alkaline earth elements (Ca 2+ +Mg 2+ ) and exceed alkali elements (Na + +K + ), and weak acids (HCO 3 − ) exceed the strong acids (SO 4 2− ) where Ca 2+ and HCO 3 − are dominant ions, and attribute to temporary hardness of groundwater. The groundwater of the aquifer is of Ca 2+ –Mg 2+ –HCO 3 − type. The source of different ions is associated with partial ion exchanges, weathering of calcareous nodules and clay minerals, flow of groundwater system through aquifer lithology, municipal sewerage, anthropogenic influence, etc. The drinking water quality index also reveals that groundwater mostly falls in ‘good’ category having suitability for drinking purposes round the year. But increasing population and water demand in the area may create threat of quality hazard in near future, and regular groundwater quality monitoring should be carried out periodically for supplying safe drinking water to city dwellers.