An innovative approach to minimize excess sludge production in sewage treatment using integrated bioreactors

The present investigation deals with an application of integrated sequential oxic and anoxic bioreactor (SOABR) and fluidized immobilized cell carbon oxidation (FICCO) reactor for the treatment of domestic wastewater with minimum sludge generation. The performance of integrated SOABR-FICCO system was evaluated on treating the domestic wastewater at hydraulic retention time (HRT) of 3 hr and 6 hr for 120 days at organic loading rate (OLR) of 191 ± 31 mg/(L·hr). The influent wastewater was characterized by chemical oxygen demand (COD) 573 ± 93 mg/L; biochemical oxygen demand (BOD₅) 197 ± 35 mg/L and total suspended solids (TSS) 450 ± 136 mg/L. The integrated SOABR-FICCO reactors have established a significant removal of COD by 94% ± 1%, BOD₅ by 95% ± 0.6% and TSS by 95% ± 4% with treated domestic wastewater characteristics COD 33 ± 5 mg/L; BOD₅ 9 ± 0.8 mg/L and TSS 17 ± 9 mg/L under continuous mode of operation for 120 days. The mass of dry sludge generated from SOABR-FICCO system was 22.9 g/m³. The sludge volume index of sludge formed in the SOABR reactor was 32 mL/g and in FICCO reactor it was 46 mL/g. The sludge formed in SOABR and FICCO reactor was characterized by TGA, DSC and SEM analysis. Overall, the results demonstrated that the integrated SOABR-FICCO reactors substantially removed the pollution parameters from domestic wastewater with minimum sludge production.