Water Quality Assessment of Mirpur Thana of Dhaka City, Bangladesh

The research work was carried out to evaluate the quality and suitability of surface and groundwater of Mirpur thana of Dhaka city for drinking purpose. Water samples were collected during winter (January), pre-monsoon (May) and monsoon (June) periods of the year 2014. Groundwater samples were collected from Dhaka Water Supply and Sewerage Authority (DWASA) deep wells and some private wells whereas surface water samples were collected from Turag River which is situated beside the study area. Several physical parameters like pH, Eh, EC, temperature, hardness and TDS were measured for both surface water and groundwater. Concentration of some major cations (Na+, K+, Ca2+, Mg2+), major anions (HCO3-, Cl-, SO4-,NO3-) and some trace elements (Fe and Mn) were determined. Hydrochemical study reveals that the overall drinking water quality of the area is good. But Iron, Manganese and Nitrate concentration of some water samples exceed the drinking water standard limits of World Health Organization and Department of Environment, Bangladesh. Higher nitrate concentration was observed in the wells which are less than 360ft deep. The study shows that all the sampled groundwater of the study area are of Ca-Mg-HCO3 and Ca-Cl type. On the other hand, river water quality is poor and polluted as they are marked by high electrical conductance (EC) and all the waters except those collected during monsoon period are of Na-Cl type. During monsoon period, EC values decrease significantly mainly due to higher precipitation which change the water to Ca-Mg-HCO3 type. It is urgently required to undertake comprehensive measures and holistic approaches to save the surface water from pollution and to lessen the dependency on groundwater.