Assessment of an Urban Contaminated Site from Tannery Industries in Dhaka City, Bangladesh

Abstract

Abstract The Hazaribagh tannery area of Bangladesh is considered an extremely polluted site owing to the disposal of untreated Cr-enriched tannery effluent. This study was undertaken from 2006–2008 to characterize the nature and extent of pollution in the area, the associated health risks, and to assess the feasibility and effectiveness of the selected cleanup strategies. A comprehensive soil, wastewater, and groundwater sampling and detailed laboratory analysis were done. The results of the study indicated that the site is extremely polluted by Cr (up to ), mineral oils, and extractable organohalogenic compounds (EOX), and the most severe soil pollution was confined up to a depth of 10–20 ft (3.048–6.096 m). The phenol index and chromium level in the tannery effluent were very high, and most of this Cr was found to adsorb onto suspended solids in the wastewater. Analysis of groundwater samples from tubewells in the Hazaribagh area indicated that groundwater is not contaminated by Cr or any other heavy metals. Soil leaching tests indicated a very low Cr mobility and thus a low risk of spreading with infiltrating rainwater. Most of the Cr in the subsoil exists as Cr(III) and was found to be very stable. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis of the Cr-containing soil structures showed that the Cr is predominantly present in association with clay mineral structures.