Impact of Tanneries on Groundwater Environment of Dhaka City

Dhaka is one of the most densely populated cities in the world. The increased inhabitants of the city with unplanned urbanization and industrialization have already affected the environmental components of the city area. Hazaribagh is such a populated residential and industrial area in the city where about 185 tanneries have been operating their activities and processing 220 metric tons of hide every day and 40 to 50 liters of liquid for each kilogram of hide. The industrial effluent at Hazaribagh is discharged in low lands and canals with high concentrations of Na, Mg, Ca, NH4, Cl, SO4 and heavy metals specially Cr, Fe, S, Mn, Zn associated with high organic matter. Excessively high accumulation of Cr is detected in top soil and decreases significantly below 3.0 m, whereas Al, Fe, Mn, Zn, Ni, Cu are found high till the investigated depth of 6 m. Though the contamination in deep groundwater is not noticed and Government has decided to shift tanneries out of the city, however, rehabilitation of the already contaminated top soil and the polluted river water and implementation of Environment Conservation Act and Rules is required to reduce the vulnerability of water contamination.