3. Results and discussion
3.1. Biodegradability improvement by hydrothermal pretreatment
Table 1 shows the composition characteristics of the tested raw CPCAR after press filtration at 1.2 Mpa and the results of proximate and ultimate analyses for its dried samples. For the raw CPCAR, its water content was still high as 85.4 wt.% even after press filtration, thus showing its refractoriness to mechanical dewatering. The total content (12.2 g L−1) of saccharide and protein in EPS accounts for only 24.8% that (49.1 g L−1) in the raw CPCAR, indicating that a certain amount of “supra-colloids” were present but and fermentative substrates took up a bigger proportion. The residue ha not fixed carbon and contains a large amount of volatiles (91.6 wt.%) and less ash (8.4 wt.%). The residue is also rich in H and O, with their contents (dry basis) being 6.7 wt.% and 43.7 wt.%, respectively.