Assessment of physico-chemical characteristics of river water emphasizing tannery industrial park: a case study of Dhaleshwari River, Bangladesh.

Pollution of industry-adjacent surface water bodies become a major environmental concern in Bangladesh recently. Therefore, this study aimed to elaborate assessment of physico-chemical characteristics of the Dhaleshwari River (the adjacent river of newly shifted tannery industrial park) and also the discharged effluent from the central effluent treatment plant (CETP) considering both seasonal and spatial variations. Among the examined 30 water quality parameters (including 11 heavy metals), only TDS, Cl-, NO3-N, EC, Cu, Zn, Cd, and Ni met the standards for discharged wastewater from industrial units into inland surface water set by Bangladesh government. This indicated that the CETP is not fully and/or effectively functioning. Out of 19 parameters (excluding heavy metal), 14 parameters exceeded the Bangladesh standard for drinking water quality either spatially or seasonally. The river water quality indicated slowly biodegradable capacity with algal bloom risk. The concentrations of the studied heavy metals in the river water followed a decreasing order of Ca > K > Mg > Na > Fe > Cr > Pb > Ni > Cu > Zn > Cd, and Cr concentration in the winter season exceeded the standard values. The concentrations of other heavy metals met the quality standard that indicated still the river is capable to self-purify. Furthermore, strong (p < 0.01) and significant (p < 0.05) correlation were observed among the quality parameters in river water. This study suggested that the efficiency of the existing CETP needs to be enhanced, and the proper operation and maintenance are required to meet the desired discharge standard quality. Also, all the unauthorized wastewater outfalls from tanneries must be closed to save the Dhaleshwari River.