Effect of ultrasound on particle surface charge and filterability during sludge anaerobic digestion

摘要

The goal of this study was to follow and compare dewaterability parameters of untreated andn“pre-sonicated” sludge during semicontinuous anaerobic digestion by particle charge density andnsludge filterability measurements. Floc disintegration due to sonication resulted in a significantnincrease of soluble COD and colloidal charge density. It is interesting to note that in all the testsndespite the higher specific charge density and soluble COD values of the sonicated feed, thendigested sludge at steady state present in both reactors statistically comparable values,nindependently on the pretreatment. The biological hydrolysis of the untreated sludge causesna large release of dispersed charged fines whereas the digestion of the sonicated sludge isncharacterized by a significant removal of fines and colloids already present in the pretreated feed.nThe amelioration of the filterability during the digestion of the sonicated sludge in test #2 suggestnthat anaerobic digestion may be very effective for degrading fine dispersed particles producednby mechanical pre-hydrolysis. Nevertheless, ultrasound pre-treatment does not improve thendewaterability of the digested sludge with respect to the untreated one. Optimisation of bothndisintegration degree and hydraulic residence time is necessary to improve the dewaterabilitynof the digested sonicated sludge.