Denitrification performance and microbial community of bioreactor packed with PHBV/PLA/rice hulls composite

In this study, a novel biodegradable PHBV/PLA/rice hulls (PPRH) composite was applied and tested as biofilm attachment carrier and carbon source in two bioreactors for biological denitrification process. The denitrification performance, effect of operational conditions and microbial community structure of PPRH biofilm were evaluated. The batch experiment results showed that PPRH-packed bioreactor could completely remove 50 mg L^-1 of NO₃^--N at natural pH (ca. 7.5) and room temperature. The continuous flow experiments indicated that high NO₃^--N removal efficiency (77%-99%) was achieved with low nitrite (<0.48 mg L^-1) and ammonia (<0.81 mg L^-1) accumulation, when influent NO₃^--N concentration was 30 mg L^-1 and hydraulic retention time was 2-6 h. Furthermore, the microbial community analysis indicated that bacteria belonging to genus Diaphorobacter in phylum Proteobacteria were the most dominant and major denitrifiers in denitrification. In summary, PPRH composite was a promising carbon source for biological nitrate removal from water and wastewater.