Improving Disintegration And Acidification Of Waste Activated Sludge By Combined Alkaline And Microwave Pretreatment

With the development of activated sludge treatment technology，the amount ofwaste activated sludge increased very rapidly. The effective and economical disposaltechnology of waste activated sludge had become one of the most urgent to deal with.Traditional anaerobic digestion technologies exist some shortcomings such as lowdigestion rate, long residence time and low producing gas rate, which limit theirwidespread application. So this study focuses on the influence of different factors onsludge disintegration and acidification and sludge dewatering performance, so as toeffectively improve the efficiency of anaerobic digestion of sludge treatment.The individual alkaline or microwave pretreatment has been proved to be effectivein disintegration and acidification of waste activated sludge. In this study, single factorexperiment is used to investigate the effect of microwave power of the alkali-microwave pretreatment on sludge treatment. With different microwave power as factors,SCOD, DNA, soluble protein and sugar as an indicator test, microwave power for thesludge disintegration has a certain impact, but it is not important impact, the bestmicrowave power is300W.In the optimization of alkali-microwave pretreatment of waste activated sludgeusing response surface methodology, the experimental factors are pH and specific energyinput (Es), the response value is disintegration degree (%). Selecting experiment factoron the basis of single factor experiment, then designing a two factors, five levels by CCDresponse surface design, establishing a quadratic multinomial mathematical model aboutthe alkali-microwave pretreatment on waste activated sludge disintegration degree. Theresults show that the effect on sludge disintegration degree of pH is higher than thespecific energy input, the best operating conditions is: Es of38400kJ/kg TS and pH of11.0.The effect of alkali-microwave pretreatment on the accumulation and compositionof the intermediate products volatile fatty acids (VFAs) in the anaerobic digestionprocess is investigated with single factor experiments. Anaerobic batch experimentresults show that the united pretreatment not only significantly improve the accumulationof VFAs and also shorten the highest accumulation time of VFAs. Maximum VFAsaccumulation occurred at28800kJ/kg TS (1500mg COD/L) and fermentation time for72h, is twice the accumulation of the without pretreatment (850mg COD/L). The mainly composition of VFAs is acetic acid and iso-valeric acid, accounting for57.3%to70.1%of total VFAs.The effect of individual alkali and microwave pretreatment on the specificresistance of sludge is compared. To a certain degree, the microwave pretreatmentimprove the specific resistance of sludge, but the high microwave power has a negativeimpact on sludge dewatering. Alkali treatment will make the sludge dewateringdeterioration.