Upgrading Of Hydrolysis Rate Of Waste Activated Sludge By Ultrasonic Pretreatment

If ultrasonic are applied as pretreatment to disintegrate the sludge flocs and disrupt bacterial cells'wall, the hydrolysis can be improved a lot, so that the residence time can be shortened and the efficiency of anaerobic digestion be significantly increased. This study covers the following: the effect on the anaerobic hydrolysis rate using ultrasonic disintegration; the establishment of the dynamics model based on the gained data.It has been found that volatile fatty acids (VFA) concentration in the non-pretreated sludge supernatant doesn't change for the initial 4 hours and then a slowly increase is observed, so that the initial 4 hours belong to hydrolysis stage for the sludge. A considerable increase in VFA concentration in disintegrated sludge supernatant is observed from beginning of the anaerobic hydrolysis and VFA concentration is enhanced lineally with the extending of time. That is to say, during the initial time of the experiment, the anaerobic hydrolysis of disintegrated sludge is a zero-order reaction. The hydrolysis rate of the sludge increases with the increase in ultrasonic pretreatment time and intake energy.The degradation rate of protein and carbohydrate concentration in disintegrated sludge supernatant accords with the Monod equation for the initial 24 hours during anaerobic hydrolysis and the degradation rate increase with the increase in ultrasonic pretreatment time and intake energy.VFA production rate of disintegrated sludge increases with the augment of dilution rate in the anaerobic hydrolysis but the degradation rate of protein and carbohydrate decreases. VFA production rate and the degradation rate of protein and carbohydrate are different with different ultrasonic disruption methods when the ultrasonic intake energy is the same and the experiment result is better when the"weak"ultrasonic pretreatment time is longer.