The Research Of Excess Sludge Treatment By Hydrodynamical Cavitation

In the case of excess active sludge digestion, the biological hydraulic has been identified as the rate-limiting step. If some methods are applied as pretreatment to disintegrate the sludge flocs and disrupt bacterial cells'wall, the hydrodynamic can be improved a lot, so that the residence time can be shortened, fermenter volume be reduced, methane production be significantly increased. In this paper, the pretreatment of excess active sludge by cavitatation disintegration on a laboratory-scale is studied.The sludge disintegrated in the research is cultivated using MBR process excess active sludge. This study covers the following:the effect of changing input and output press, sludge concentration and disintegration time on the disintegration result; the mechanism of cavitation disintegration by adding NaHC03 to eliminate the contribution of hydroxyl; the improvement of disintegration by combining cavitation and alkaline.It has been found that applying cavitation as pretreatment to disintegrate sludge is an effective method which can break up sludge flocs and disrupt bacterial cells'wall and lead to the release of intracellular material into the sludge supernatant.After being disintegrated,the DOC,SCOD in the sludge supernatant is increased greatly.The increment of DOC,SCOD is enhanced with the augment of input and output press, sludge concentration and disintegration time.But the increment of DOC, SCOD is stopped after two hours (24times). However, under low sludge concentration, the increment of DOC, SCOD is very slowly, could also balance too.Combining cavitation and alkaline can improve the effect of disintegration a lot. By adding NaHC03 to eliminate the hydroxy contribution to the cavitation sludge disintegration, the mechanism of disintegration is investigated. Nometer what input press is, the contribution of hydroxyl becomes less and less, the main contribution to the disintegration is hydraulic shear force.