ASSESSMENT OF SURFACE AND GROUNDWATER CONTAMINATION AND SEASONAL VARIATION AT THE TANNERY AREA IN DHAKA, BANGLADESH

Abstract

Hazaribagh in Dhaka is home to about 150 footwear factories and is known as a contamination hub. Although some tanneries have relocated to new industrial parks, it has been seen that many are still running. In the present study, 42 water samples, including surface and groundwater, from six different sampling points of the Hazaribag tannery complex were examined for one year (December 2019– August 2020; dry and rainy seasons respectively). This research aimed to assess the surface and groundwater quality of the sampling area and the seasonal variation on different parameters. During sampling, a sequence was maintained, from the tannery source points to the downstream Buriganga River, the ultimate destination of tannery effluents. Chemical and physicochemical properties pH, DO, BOD, NO 3- , C 2+ , Mg 2+ , K + , Na + , Cl - , TDS, TSS, EC, Eh, and turbidity of wastewater were evaluated using the standard method. However, our primary attention was on heavy metal contamination. Trace metals were analyzed by atomic absorption spectrophotometer. The excessively higher concentration of heavy metals was observed in the first three sampling sites. It was also found that heavy metal concentrations decreased significantly from the source point to the downstream Buriganga River. Such variations in metal content with the location may have occurred due to increasing distance from the source point and percolation of wastewater to downward groundwater by soil. Comparatively lower concentrations of heavy metals were observed in the rainy season than dry season due to dilution with rainwater but still was above the maximum allowable concentration. Concentrations of all investigated heavy metals and some physicochemical parameters such as pH, DO, BOD, TDS, TSS, EC, Cl - , and Na + of all the surface and groundwater samples were found above the national (DoE) and international (WHO) standards . tannery effluents.