Effect of carriers on the performance of anaerobic sequencing batch biofilm reactor treating synthetic municipal wastewater

• Effects of GAC and zeolite in ASBBR treating synthetic wastewater was investigated.
• Lower effluent COD concentrations were observed in ASBBRs with GAC and zeolite.
• Higher gas productions were observed in ASBBRs with GAC and zeolite.
• The maximum gas production was observed in ASBBR containing both GAC and zeolite.

In this study, effects of granular activated carbon (GAC) and natural zeolite as attached carriers for microbes on anaerobic treatment of synthetic municipal wastewater were evaluated in laboratory scale anaerobic sequencing batch biofilm reactors (ASBBRs). An anaerobic sequencing batch reactor (ASBR) and three ASBBRs, individually named ASBR-1 without any carrier (control), ASBBR-2 with GAC, ASBBR-3 with zeolite, ASBBR-4 with both GAC and zeolite, were operated at 2.5 d HRT with non-fat dry milk to mimic municipal wastewater. The four reactors were successfully started up and attained steady state within two weeks of operation. Total COD and soluble COD removal efficiencies of more than 93% and 98%, respectively, were observed in the four reactors during steady-state. The average biogas productions for ASBR-1, ASBBR-2, ASBBR-3 and ASBBR-4 were 229, 246, 238 and 278 ml/d, respectively. Addition of carriers improved both the COD removal efficiency and biogas production. Apparently GAC improved COD removal efficiency and zeolite improved gas production. SEM results suggested higher number of biomass attached to GAC than zeolite.