Nitrogen and residual organic matter removal from anaerobic reactor effluent <b>in a fixed‐bed reactor with biogas for denitrification</b>

Abstract

Abstract BACKGROUND This paper describes an evaluation of a fixed‐bed aerobic/anoxic reactor ( AAFBR ) for the post‐treatment of effluent from an up‐flow anaerobic sludge blanket ( UASB ) reactor treating domestic sewage. This is a new reactor configuration comprising an upper aerobic nitrification chamber fed with effluent from the UASB reactor. The nitrified effluent flows downwards to an anoxic chamber that is fed synthetic biogas ( CH 4 , CO 2 and H 2 S ) from the bottom for denitrification. RESULTS The AAFBR removed organic matter at efficiencies higher than 90% for hydraulic detention times ( HDT ) of 7.5 and 5.0 h. The average nitrogen removal efficiencies were higher than 70% under conditions of excess H 2 S in the synthetic biogas. At an HDT of 5.0 h and with synthetic biogas of a similar composition to that in UASB reactors treating domestic sewage, the average N removal was approximately 50%. Under these conditions, the reactor achieved hydrogen sulfide and methane removal efficiencies of 100% and 60%, respectively. CONCLUSIONS The results obtained for the denitrifying activity indicated the coexistence of both autotrophic and heterotrophic denitrification in the anoxic chamber. The AAFBR exhibited additional ability as a gas cleanup system. The results demonstrate the potential of AAFBR as an alternative for the tertiary treatment of domestic wastewater. © 2014 Society of Chemical Industry