Sensitivity analysis of operational parameters on excess sludge reduction in moving bed biofilm reactor (MBBR) system...

This study investigated the modeling of sludge reduction and process optimization in a moving bed biofilm reactor treating sewage upgraded to an integrated fixed film activated sludge process using GPS-X8 simulation. The sensitivity analysis of dissolved oxygen concentration, recycle activated sludge, media portion, and biofilm thickness on sludge generation was simulated. The results revealed that an increase in dissolved oxygen concentration from 2.7 to 5 mg/L resulted in an 89% reduction in sludge. Likewise, increasing the recycle activated sludge ratio from 50% to 200% decreased the sludge production from 1000 to 90 g/L, leading to a 91% reduction in sludge. Moreover, it was observed that sludge was highly eliminated from 910 to 400 g/L, as the media volume increased from 45 to 55%. Furthermore, a sludge reduction from 1000 to 400 g/L was achieved when the biofilm thickness increased from 1 to 5 mm, respectively. Finally, the process was optimized with minimum sludge production of 400 g/day and preferable system performance attributed to TSS, BOD, COD, NO₃, PO₄ ^-3-P, and NH₄ effluent concentrations of 14, 5, 10, 21, 1.25, and 0.4 mg/L, respectively. This concludes that sludge reduction can be achieved by operating the moving bed biofilm reactor as an integrated fixed film activated sludge process. PRACTITIONER POINTS: The MBBR system was upgraded to IFAS system by return activated sludge (RAS) to the MBBR reactor. Excess sludge can be efficiently reduced by operating the system as IFAS process. The IFAS process was successfully modeled using GPS-X8 simulation. Sensitive operational parameters effects: DO concentration, RAS, media portion, and biofilm thickness on sludge production have been evaluated. Sludge reduction (56% to 91%) is achieved at 5 mg/L DO concentration, 200% RAS, 55% media portion, and 5 mm biofilm thickness.