Assessing the effect of green tuff as a novel natural inorganic carrier on methane-producing activity of an anaerobic sludge microbiome

The upflow anaerobic sludge blanket (UASB) process is an anaerobic biological system that is widely used for the treatment of a variety of wastewater owing to its benefits such as low energy requirements and energy recovery as methane gas; however, unstable reactor performance is often observed. To solve this problem, several inert inorganic carriers and polymer materials have been studied for stabilization of the sludge microbial community and promotion of methane production. In this study, we demonstrate the effects of green tuff (GT) as a novel natural inorganic carrier on methane-producing activity (MPA) in combination with syntroph/methanogen-utilizable substrates and on the microbial community assembly of methanogenic batch cultures fed with granular sludge collected from UASB reactors treating milk-(MMW) or soy sauce-(SSW) manufacturing wastewater. The MPAs of MMW cultures with GT were 4.56-(propionate), 2.01-(n-butyrate), 1.37-(n-valerate), and 1.22-(benzoate) fold higher than those without GT. Likewise, SSW cultures with GT showed 1.34-(acetate) and 1.42-(propionate) fold higher MPA than those without GT. These results indicate that GT has potential to enhance MPAs during methanogenic degradation of these substrates. According to 16S rRNA transcripts-based community profiling, populations of syntrophic bacteria (Syntrophobacter and Smithella) and hydrogenotrophic methanogens (Methanobacterium and Methanolinea) in the cultures with GT were higher than in those without GT. Therefore, GT can be a potential solution for the activation of syntrophic partnerships and improvement/stabilization of reactor performance. (C) 2021 Elsevier B.V. All rights reserved.