Process performance and microbial interaction in two-stage continuously stirred tank reactors for sludge anaerobic digestion operated at different temperatures

The two-stage continuously stirred tank reactor (CSTR) is widely used for anaerobic digestion, which shows many advantages over the conventional anaerobic digestion reactor. This work investigated the effects of temperature on the process performance and microbial community structure of two two-stage CSTRs. The volatile solids (VS) removal rate, solubilization percentage and methane (CH4) yield increased from 37.3 +/- 5.3 %, 6.2 +/- 3.9 % and 74.5 +/- 16.8 mL/g VS in the thermophilic-mesophilic anaerobic digestion process (CSTRHi-CSTRM) to 41.4 +/- 4.9 %, 19.6 +/- 4.2 % and 87.5 +/- 20.8 mL/g VS in the thermophilic-thermophilic anaerobic digestion process (CSTRHi-CSTRT), respectively. The effluent volatile fatty acids (VFAs) concentration of CSTRT was higher than that of CSTR M and the accumulation of propionate was observed in CSTRT . The heat of CSTRT to maintain the reactor temperature was 3 times that of CSTRM . The maximum CH4 production rate of CSTRM was 62 % higher than that of CSTRT , and CSTRM had a good methanogenesis potential. The analysis of microbial community structure showed that temperature affected the process performance by changing the species and relative abundance of fermentation bacteria and methanogens.