Upgrading Of Anaerobic Digestion Of Waste Activated Sludge By Ultrasonic Pretreatment

Anaerobic digestion is the most commonly applied technique for stabilization ofwaste activated sludge. However, the waste activated sludge is difficult to degrade,which results in the slow degradation, long residence time and large fermenter volume.If some methods are applied as pretreatment to disintegrate the sludge flocs anddisrupt bacterial cells'wall, the hydrolysis can be improved a lot, so that the residencetime can be shortened, fermenter volume be reduced, methane production besignificantly increased. Ultrasonic disintegration is an effective method in variouspretreatmental techniques. The aim of this experiment is to study the upgrading ofanaerobic digestion of ultrasonic pretreatment.The ultrasonic densities in the experiment are 2W/mL and 1.36W/mLrespectively , and the disintegration times are 5min,10min and 15min,respectively.The digestion time is controlled by the dilution rate. The effects of the ultrasonicdensity and disintegration time on the biogas production and the removal efficiency oforganic matters are studied.It has been found that the biogas production is increased with the argument ofdisintegration time and the dilution rate in the anaerobic digestion after ultrasonicpretreatment at two ultrasonic densities. Compared to the fermenter operated with thenon-pretreated sludge, the removal efficiency of organic matters can be improved andnot be decreased with the increasement of the dilution rate in the anaerobic digestionof disintegrated sludge. When the dilution rate is 12.5%, at 2W/mL, the removalefficiencies of TCOD and VS at disintegration time 5min,10min and 15min are 38.3%～42.47%,31.14%～34.13%, respectively;At 1.36W/mL, the TCOD and VSremovals at disintegration time 5min,10min and 15min are 31.15%～38.37%,38.5%～40.14%, respectively. The sludge mass expressed in VSS can be reduced in theanaerobic digestion of pretreated sludge. At 2W/mL, when the dilution rate is 12.5%the removal efficiency of VSS at disintegration time 5min,10min and 15min is34.13%～ 38.66%. At 1.36W/mL, when the dilution rate is 12.5% and thedsintegration time is 5min,the average removal efficiency of VSS is 35.46%. Finally,after a comprehensive analysis based on the upgrading of anaerobic digestion ofdisintegrated sludge, the specific methane production and the removal efficiency ofVSS at 2W/mL are higher than that at 1.36W/mL. The removal efficiency of VS at1.36W/mL is higher than that at 2W/mL, but the biogas production produced per unitvolume of degradede sludge at 1.36W/mL is lower than that at 2W/mL.