Comparative study between activated sludge process (ASP) and moving bed bioreactor (MBBR) for treating composite chrome tannery wastewater

Abstract

The comparative performance of a laboratory-scale MBBR and an ASP system has been studied in batch mode of operation for the removal of organic carbon from composite chrome tannery wastewater. The reactors were operated under initial MLSS concentration 2000-2500 mg/L for both the systems and 20g/L of PVC rings was introduced as moving bio-carrier in the MBBR. Corrugated PVC ring of diameter 12.5 and height 15 mm was used for providing attached surface in the present batch study. Total batch period was taken maximum 7.5 hrs and the influent chemical oxygen demand (COD) was provided in the range of 100 ± 50mg/L to 500 ± 50 mg/L. It was observed that 85-90% of COD removal could be obtained at the end of 7.5 hrs. in the MBBR system for initial COD concentration of 150-250 mg/L as compared to ASP reactor, which showed only 60-70% removal. However, in case of MBBR system COD removal efficiency marginally decreased with higher initial COD concentration like the ASP reactor. A sharp inhibition was also observed in the ASP reactor when initial concentration increased to the range of 300-500 mg/L. Apart from that a steady growth of attached biomass was noticed on the media surface of the MBBR system.