A Hybrid Treatment System of the Coagulation/Flocculation/Settling Stage Followed by a Membrane Bioreactor (CFS-MBR) for Superior Removal of Cr and Nutrient Pollutants from Tannery Wastewater

Abstract

The effluent from the tannery industry contains high concentrations of organic pollutants, particularly chromium (Cr), which is a priority pollutant that harms human health, plants, animals, and affects compliance with environmental standards. This study significantly reduced tannery wastewater pollution and its toxic effects through the innovative use of an integrated treatment system with a coagulation/flocculation/settling process followed by a membrane bioreactor (MBR). Experiments were conducted to maximize the removal of pollutants by evaluating the effects of pH values, coagulant doses in the chemical treatment, and the biological treatment coupled with membrane separation within the MBR. The results indicated that optimizing the parameters achieved the highest reductions during the chemical treatment step: 97% for Cr, 63% for chemical oxygen demand (COD), and 90% for turbidity. The wastewater was then treated using the MBR system, which further improved removal efficiency to 99% for Cr, 96% for COD, and 99.8% for turbidity. These outcomes demonstrate the effectiveness of the hybrid treatment process in significantly lowering pollutant concentrations in tannery wastewater, ensuring compliance with Environmental Protection Agency (EPA) standards and the regulatory obligations under European Regulation (EU) 2020/741. This hybrid approach offers promising potential for broader industrial applications.