qPCR reveals the succession of syntrophic propionate-degrading consortia with OLR increase

To reveal the effects of organic loading rate (OLR) on the performance of upflow anaerobic sludge bed (UASB) reactor and syntrophic propionate-degrading consortia, this study investigated the effects of OLR increase on the treatment efficiency of UASB containing sugar refinery wastewater as substrate. The succession of syntrophic propionate-degrading consortia as OLR increasing was analyzed by quantitative real-time fluorescence polymerase chain reaction (qPCR). The results showed that the COD removal reached above 92.0% in UASB at OLR of 6.0~54.0kgCOD/(m³·d) conditions. qPCR explored that at least three identified species of propionate-oxidizing bacteria (Pelotomaculum schinkii, P. propionicum, and Syntrophobacter sulfatireducens) existed in the UASB system. S. sulfatireducens was dominated in UASB and its quantity was 126~1.2×10³ 16S rDNA copies per ng DNA, accounting for 47.9%~58.6% of the total detectable propionate-oxidizing bacteria. OLR increase from 6.0 to 54.0kgCOD/(m³·d) resulted in all detected propionate-oxidizing bacteria significantly decreased. In addition, Methanospirillum hungatei and Methanosaeta concilii were the dominant hydrogenotrophic methanogens and acetotrophic methanogens. The number of methanogens was significantly increased with OLR increase and achieved a maximum at OLR of 54.0kgCOD/(m³·d) condition.