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Effects of ammonia on propionate degradation and microbial community in digesters using propionate as a sole carbon source

Li, Ying, Zhang, Yue, Kong, Xiaoying, Li, Lianhua, Yuan, Zhenhong, Dong, Renjie, Sun, Yongming
Journal of chemical technology and biotechnology 2017 v.92 no.10 pp. 2538-2545
Clostridiaceae, Syntrophobacter, ammonia, ammonium nitrogen, carbon, digesters, methane, methane production, methanogens, microbial communities, propionic acid
BACKGROUND: Propionate accumulation may lead to digester failure. This study aimed to investigate the effect of ammonia, a metabolic product of protein, on propionate degradation. The shift of microbial community was also investigated. RESULTS: Propionate accumulated over the experimental period in the reactor with a total ammonia nitrogen (TAN) concentration of 2.5 g N L⁻¹, as a result the digester failed after 4 hydraulic retention times (HRT) at an organic load rate (OLR) of 0.8 g propionic acid (HPr) L⁻¹ d⁻¹. The average HPr degradation rate was below 54% during the fourth HRT, while >97% of the degraded HPr was converted to methane. The reactor without ammonia stress did not experience HPr accumulation and OLR was increased stepwise to 1.2 g L⁻¹ d⁻¹ at the 8th HRT. The average HPr degradation rate and methane recovery rate of this reactor in the last HRT was 99% and 74%, respectively. According to the shifts of microbial community, acetoclastic methanogen was more vulnerable to ammonia than hydrogenotrophic methanogen CONCLUSION: TAN concentration of 2.5 g N L⁻¹ inhibited propionate degradation more severely than methanogenesis. The loss of abundance of Clostridiaceae and Syntrophobacter might be the main reason for the poor performance under ammonia stress. © 2017 Society of Chemical Industry