Assessing membrane biofilm predevelopment strategies to improve anaerobic membrane bioreactor effluent quality

Abstract

Recycling and reuse of treated wastewater has been addressed as an alternative water resource to a great extent lately because of major water scarcity faced worldwide. Among wastewater treatment technologies envisaged, anaerobic membrane bioreactors (AnMBRs) have demonstrated considerable benefits for high quality effluent and energy recovery. Specifically, recent developments in the understanding of membrane biofilms in AnMBRs indicate additional advantages to their known benefits as an emerging technology. In addition to high COD removal, increased biogas production and lower energy costs, AnMBRs are found to play a key role for the degradation of emerging contaminants of concern. The present work aimed to determine the effect of combining different membrane biofilm development conditions in an AnMBR on effluent quality, trimethoprim removal, antibiotic resistance genes (ARGs) proliferation, and effluent methane concentrations. The experiment consisted of two phases during which membrane biofilms were initially developed at different transmembrane pressures (TMPs) by varying the membrane flux rates and subsequently operated at the same flux rate for performance comparison. The first phase consisted of membrane biofilm development at low flux rate while the second phase was devised to allow membrane biofilm development at high flux rate. Improved performance was observed for a membrane on which the biofilm was initially developed at high TMP. After reduction of flux, lower TMP was sustained for the same membrane, on which higher COD and trimethoprim removals were observed. Analysis of membrane biofilm communities revealed presence of specific groups, notably methanogens and their associated syntrophic groups that confer benefits to effluent quality. Moreover, a remarkable difference between the microbial groups of the membrane biofilm layers developed at high TMP was observed. This study highlights a new approach for controlled membrane biofilm operation that can potentially promote water quality and micropollutant removal.