Fig. 5

FE-SEM micrographs of bloom algae under different pretreatment conditions and after biodegradation: (a) control; (b) control after biodegradation; (c) hydrothermal pretreatment; (d) hydrothermal pretreatment after biodegradation; (e) hydrothermal-alkaline pretreatment; (f) hydrothermal-alkaline pretreatment after biodegradation.