Effect of Biogas Sparging Flow on Fouling Control in Anaerobic Membrane Bioreactors

Membrane fouling behaviors were investigated to different biogas sparging flows such as 0.5, 1.0, and 1.5 L biogas/min for anaerobic submerged membrane bioreactor (AnSMBR) treating synthetic wastewater in a laboratory-scale. For each different biogas flow rate, the membrane module of the same feature was used in the system and the effect of biogas sparging flow on fouling control was examined in the process. Surface area of the used membrane module was selected as 162.6 cm(2). The sprarging biogas was supplied from the gas formed in reactor system. Treatment parameters were analyzed in the process of reactor operation. Also, a series of analysis, including soluble microbial products (SMP), extracellular polymeric substances (EPSs), scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, and filtration resistances were performed by considering the membrane module. The AnSMBR accomplished COD removal efficiencies between 95 and 98%. Total organic carbon and sulfate concentration in permeate were found in the range of 25-56 and 90-200 mg/L, and 96-98 and 38-65% in removal percentage; respectively. TSS and VSS concentrations in permeate were less than 10 mg/L that means removal efficiencies of 98%. Methane production rate in the system was determined of 0.35 +/- 0.08 LCH4/g COD removed. The results showed that differences between COD and TOC removals were negligible at different biogas sparging flows. The priority of biogas sparging flows in terms of providing high permeate fluxes were found to be 1.5 L biogas/min > 1.0 L biogas/min > 0.5 L biogas/min. The same order was found with the fluxes in terms of both SMP and EPS within cake formed on the fibers in membrane module. Studying results showed that biogas sparging flow increasing was found to effective on membrane fouling controls. It has been determined that sparging gas at an optimum flow rate (1.0 L biogas/min) can be effective in controlling membrane fouling.