Effect of cow dung on anaerobic digestion characteristics of poplar fuel ethanol wastewater

Direct disposal of poplar fuel ethanol wastewater (PFEW) and incineration of cow dung caused serious harm to the environment. To investigate the effect of cow dung on the mesophilic digestion of PFEW, the anaerobic mono-digestion (PFEW) and co-digestion (PFEW + cow dung) were performed, respectively. The maximum cumulative methane production of mono-digestion was 254.7 mL/gVS when the substrate concentration of PFEW was 2.58 g/LVS, which was 22.16% higher than that of co-digestion. The volatile fatty acids (VFAs) testing results indicated that the degradation of propionic acid by acetogen was inhibited and the methane process was weakened in anaerobic co-digestion. The analysis of the microbial community showed that norank f Bacteroidetes vadinHA17, Clostridium sensu stricto and Leptolinea were acid-producing bacteria, Anaerolineaceae was acetogen, Methanosarcina and Methanobacterium were methanogens, of which appeared in both co-digestion and mono-digestion. Psychrobacillus which was only found in the co-digestion inhibited the growth of acetogen and affected the methane production, which revealed the exogenous inhibitory effect of cow dung on the anaerobic digestion of PFEW.