Enhanced nutrient removal and bioenergy production in microalgal photobioreactor following anaerobic membrane bioreactor for decarbonized wastewater treatment

Abstract

This study investigated the nutrient removal, decarbonization potentials, and bioenergy production (i.e., algal biomass and biogas) between a membrane photobioreactor (MPBR) and a sequencing photobioreactor (SPBR) as the post-treatment process of an anaerobic membrane bioreactor (AnMBR) for municipal wastewater treatment. All photobioreactors without aeration showed favourable performance on AnMBR effluent polishing and bioenergy production. In comparison, MPBRs achieved higher removal efficiencies with 98.4 %−99.1 % NH4-N and 74.8 %−88.4 % PO4-P removal compared to the SPBRs with 41.1 %−82.0 % NH4-N and 39.6 %−72.9 % PO4-P removal. MPBRs enhanced more nutrient utilization (24.9–49.3 g(N)/(m3·d) and 3.4–8.1 g(P)/(m3·d)) and CO2 assimilation (22.9–43.4 g(C)/(m3·d)), and concentrated more microalgae with 1.58–1.98 g/L higher than the SPBRs. Moreover, the MPBR effectively upgraded the biogas from AnMBR with superior methane percentage of 89.4 %−93.4 % due to its better CO2 biofixation. The MPBR, with better carbon, nitrogen and phosphorous removal and bioenergy production, following AnMBR is an attractive decarbonized technology for future sustainable wastewater treatment.