Change of sludge dewaterability during alkaline fermentation was investigated by controlling temperature at 25℃ and 35℃ and using Ca(OH)2 and NaOH to adjust the pH of reactor.The factors influencing dewaterability of alkline fermentation sludge were analyzed.Alkaline fermentation sludge with pH adjusted by NaOH had poorer dewaterability than that with pH adjusted by Ca(OH)2.Dewaterability of the sludge fermented at 35℃ was worse than the sludge fermented at 25℃ using the same alkaline fermentation.The CST(capillary suction time)correlated with the soluble proteins concentration in alkaline fermentation sludge within a certain range and the change of soluble carbohydrates concentration had a more remarkable influence on the CST than proteins.The analysis combining Zeta potential

particle size with soluble carbohydrates and proteins indicated that temperature and concentration of Ca2+ may be the cause for dewaterability difference of the sludge using different alkaline reagents.Ca2+ could neutralize more negative charge and act as a better bridging agent between flocs

which may inhibit sludge hydrolysis and dissolution of organics

but improve dewaterability of the sludge.From the angle of dewatering cost and SCFAs(short chain fatty acids)products

Ca(OH)2 is a better alkaline reagent than NaOH to adjust the pH of sludge during alkaline fermentation.