Insights into integration of polyhydroxyalkanoates (PHAs) production into wastewater treatment: Comparison of different electron acceptors on system function and PHA-producer enrichment

Mixed microbial culture polyhydroxyalkanoates (MMC PHA) process combined with mainstream wastewater treatment is a competitive resource recovery integrated process in which economical non-oxygen electron acceptors can be used to enrich PHA-producer and reduce operating costs. Oxygen and three non-oxygen electron acceptors (endogenous nitrate, exogenous nitrate, and nitrite) were used and comprehensively compared in terms of PHA production ability and microbial community ecophysiology in this study. The results showed that the PHA production ability with exogenous nitrate was comparable to that of oxygen, which had a maximum PHA content of 64.0 wt% (versus 62.3% of oxygen), q_PHA of 0.7 mg COD/mg Xa/h, as well as 99.1% denitrification efficiency. The non-oxygen acceptors delayed the time for Arcobacter to occupy the dominant niche in the community, and the environmental selection pressure produced was slightly lower than that of oxygen. The symbiotic community between denitrifying bacteria and PHA-producers ensured the high PHA production potential and denitrification efficiency of the non-oxygen system. An economic assessment showed that the integrated PHA production and nitrate removal process with the mainstream wastewater treatment process proposed in this study could reduce aeration energy by 64%, and PHA recovery yield was 0.1 kg COD_PHA/kg COD_WAS from waste activated sludge (WAS).