Two-stage anaerobic digestion of food waste coupled with in situ ammonia recovery using gas membrane absorption: Performance and microbial community

A two-stage GAs Membrane Absorption anaerobic Reactor (GAMAR) was developed by combining the gas membrane absorption (GMA) system with two-stage anaerobic digestion. The two-stage configuration consisted of an acidogenic reactor (AR) and a methanogenic reactor (MR) with GMA. With the application of GMA, the ammonia concentration of MR was maintained at 2200 mgN L-1 to alleviate potential ammonia inhibition. The setup of AR enhanced hydrolysis and acidogenesis of FW and alleviated volatile fatty acids (VFA) accumulation in MR. Two-stage GAMAR could be operated stably at 6.1 kg VS m(-3) d(-1) and the volumetric biogas production rate was 3.21 m(3) m(-3 )d(-1). The different environmental conditions caused a significant shift in the microbial community. Lactobacillus and Aeriscardovia became predominant in AR under low pH, while Syntrophomonas was dominant in MR when the reactor was stable. The dominant archaea genus in MR was Methanothrix and it greatly decreased when MR was acidified.