Gas-lift anaerobic dynamic membrane bioreactors for high strength synthetic wastewater treatment: Effect of biogas sparging velocity and HRT on treatment performance

A laboratory scale external anaerobic dynamic membrane bioreactor (AnDMBR) treating high strength wastewater (influent COD ≈ 20 g/L) was operated to assess the effect of biogas sparging velocity (GSV) and hydraulic retention time (HRT) on removal efficiency and dynamic membrane (DM) filtration characteristics. An increase in GSV resulted in a decrease in DM filtration resistance. DM or cake layer was identified as the main contributor to the total filtration resistance. The external AnDMBR achieved over 99% COD removal efficiency irrespective of the GSV. The results showed that the DM formation process proceeded until a stable cake layer was reached. Reducing of HRT resulted in an increase in protein/carbohydrate ratio in soluble microbial products (SMP) and an increase in biomass concentration in the bioreactor. Therefore, HRT affected TMP and total filtration resistance in the AnDMBR. A high permeate quality was obtained by an effective DM layer at organic loading rates (OLRs) between 2 and 3.6 kg COD/m3 d. Based on the fluxes observed in this research, the filter cloth costs would be in the range of 0.17 €/m3 of treated wastewater. The investment and operational costs of the AnDMBRs are expected to be substantially lower than that of conventional membrane filtration.