Chemical oxygen demand removal efficiency of biological treatment process treating tannery wastewater following seawater flocculation

Seawater-induced flocculation of alkaline tannery wastewater can increase the removal efficiency of organic compounds, such as particulate, colloids, colored compound, and other dissolved organic compounds. Evaluation of the potential biological treatment was performed by the activated sludge system of suspended micro-organisms using seawater flocculated tannery wastewater. The pH adjustment of the influent wastewater and PO4-P addition after seawater flocculation were the most important operational parameters to enhance the removal efficiency of chemical oxygen demand (COD) in the activated sludge process. Removal efficiency of COD was also increased as the sludge retention time (SRT) was increased. With the pH adjustment and PO4-P addition after seawater flocculation, 75% of COD was removed at the SRT of 15 days. Flocculation through the use of seawater was used as the primary treatment in the on-site tannery wastewater treatment plant. Experimental results demonstrated that seawater flocculation was more effective than the comparable ferric salt flocculation in enhancing the biological treatment during the 110 days of operation.