Performance of moving bed biofilm reactor using effective microorganisms

Abstract

Abstract This work shows the feasibility of using effective microorganisms (EM) to improve the performance of a moving bed biofilm reactor (MBBR) in treating primary settled wastewater. Two MBBR systems were compared, one inoculated with activated sludge only, and the other inoculated with a mixture of activated sludge and EM, under steady-state conditions, and under organic and hydraulic shock loadings. Results after a startup period showed that carriers in MBBR inoculated with activated sludge had only a thicker biofilm compared to MBBR inoculated with a mixture of activated sludge and EM. When compared to MBBR inoculated with activated sludge only, adding EM to the activated sludge was found to improve slightly the removal of particulate chemical oxygen demand (pCOD) and total ammonia nitrogen (TAN), while no improvement in the removal of soluble chemical oxygen demand (sCOD) was achieved. The average removal efficiencies for chemical oxygen demand (COD), sCOD, pCOD, and TAN were found to be 76.71%, 81.87%, 68.13%, and 45.92%, respectively in MBBR inoculated with activated sludge only for a period of 30 days; while those for MBBR inoculated with a mixture of activated sludge and EM were found to be 67.79%, 61.12%, 76.26%, and 56.97%, respectively, during the same period. Both MBBR systems were affected by shock loadings. Performance of MBBR inoculated with activated sludge only was much better than that for MBBR inoculated with a mixture of activated sludge and EM under both organic and hydraulic shock loadings with respect to removal of COD and TAN. MBBR inoculated with activated sludge only took much less time to reach steady-state conditions after the removal of both organic and hydraulic shock loadings when compared to MBBR inoculated with a mixture of activated sludge and EM. MBBR inoculated with a mixture of activated sludge and EM was able to reach steady-state conditions 5 h from removal of organic shock loading, while it was not able to reach original conditions after removal of hydraulic shock loading.