4.4. The effect of adding ratio on WAS acidification under thermophilic conditons
Based on the pH 9.0 and T 60ć, the influence of adding ratio of WAS on acidification during
thermophilic anaerobic digestion was investigated. For the adding ratios of 12.5%, 25% and 50%, the
release of Soluble protein and Soluble carbohydrate appeared two peaks at 12h and 48h, while appeared
one peak at 48h for the adding ratio of 75%. It was likely to conclude that the fraction of quickly
hydrolysed of WAS led to the first peak at 12h and the fraction of slowly hydrolysed led to the second
peak at 48h for adding ratios of 12.5%, 25% and 50% (Mottet et al., 2009), while for the adding ratio of
75%, the content of the quickly hydrolysed fraction was more than other adding ratios, requiring more
time to hydrolyse, so as to appear only one peak within 60 hours.