Assessment of Physicochemical Properties and Comparative Pollution Status of the Dhaleshwari River in Bangladesh

The Dhaleshwari river which flows near Dhaka, the capital of Bangladesh, is currently under threat due to the recent relocation of the Hazaribagh tannery to the Savar area. This study investigated the physicochemical parameters of water quality along with the heavy metal levels in the Dhaleshwari river and performed a comparative analysis among the peripheral rivers around Dhaka City. Surface water quality parameters such as total dissolved solids (TDS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) obtained for the Dhaleshwari river deviated by as much as 90% from World Health Organization (WHO) standards in certain instances due to direct discharge from untreated point sources. Concentrations of toxic metals such as chromium (Cr), cadmium (Cd), and nickel (Ni) were above the Food and Agriculture Organization (FAO) standards for heavy metals in surface waters. Strong correlations among the heavy metals indicated significant linear dependences. Based on the physicochemical and toxicity-based characterization, the river system in Dhaka city can be termed as severely polluted with respect to organic and solids discharge, while ecological risk indices (ERI) indicated disastrously high risk in the Dhaleshwari and Buriganga rivers. The study outcomes emphasize the necessity of frequent investigation while controlling the point and nonpoint urban pollution sources discharging into the peripheral rivers of Dhaka city.