Assessing the Efficiency of Wastewater Treatment in Steel-galvanizing Industries: A Case Study of Industrial ETPs in Chattogram, Bangladesh

Abstract

This study aims to investigate the wastewater treatment process and assess the industrial wastewater quality before and after being treated by effluent treatment plants (ETPs) of steel-galvanizing industries located in Mirsharai, Sitakunda, Karnaphuli, and Kalurghat industrial areas of Chattogram, Bangladesh. Wastewater samples were collected from six steel-galvanizing industries during the dry season and monsoon season. The water quality was evaluated based on five physiсochemical parameters, namely pH, dissolved oxygen (DO), biological oxygen demand (BOD₅), chemical oxygen demand (COD), total dissolved solids (TDS), as well as the concentration of heavy metals including Fe, Cu, Cr, Ni, and Cd. The measured data were compared with the national and international standards established for ensuring water safety. It was observed that steel plants generate complex wastewater rich in highly dissolved solids and heavy metal ions. Although pH, BOD₅, and COD values were within acceptable ranges in these industries, high TDS values were observed. The Fe concentration of discharged stream areas ranged from 0.992 to 16.89 mg/L, exceeding the guideline limits. Additionally, the Cr concentration in both the inlet and outlet exhibited high concentrations, surpassing the standard limits, particularly those set by the United States Environmental Protection Agency (US EPA). Thus, steel-galvanizing industries are likely contributing to water pollution through the discharge of wastewater, particularly in terms of Fe and Cr. The efficiency of ETPs varied for different metals. Furthermore, this study highlighted the importance of the effective design of ETPs to mitigate potential pollution and promote sustainable practices.