In order to maximize the accumulation of VFAs for providing more carbon, the optimal operating
conditions for WAS thermophilic anaerobic digestion observed in this study. Firstly, compared to the
conditions of pH uncontrolled, the VFAs accumulation was enhanced obviously at pH 9.0, but was
retarded at acidic, neutral or strong alkaline pHs. The hydrolysate was greater at alkaline pHs than that at
acidic pHs or neutral pH. Secondly, the influence of temperature during thermophilic anaerobic digestion
process was little analysised by researchers, while, the conclusion of this study indicated that 60ć was
the best one, and low (50ć) or excessive (70ć) temperatures would influence the final quality of the
VFAs products. At last, each adding ratio had its own optimal HRT to producing maximum VFAs,
however, the excess adding ratio of WAS cannot improve VFAs products. The results showed that adding
ratio of 12.5% and its optimal HRT 8d were the best choice for VFAs accumulation.