Study On Sludge Hydrolysis And Acidification Of Pretreatment By Ultrasonic Waves And Ultrasonic/alkali

At present, the wastewater treatment plant sludge production is large, in order tomake the environmental problems which are caused by sludge treatment and disposalprocess be alleviated, how to reduce the excess sludge, its moisture content and takinginto account the sludge recycling are also our problems to be solved. The sludge ispretreated by ultrasonic, alkali and ultrasonic/alkali, then it is hydrolyzed and acidified.The product of volatile acids can be used as a carbon source.The study included, excess sludge was pretreated by ultrasonic, alkali,ultrasonic/alkali respectively, then the sludge was determined the optimum conditionsof pretreatment conditions; excess sludge which had been pretreated by ultrasonic,alkali, ultrasonic/alkali respectively was hydrolyzed and acidified and the effect ofdifferent conditions were compared.The results indicated that,(1) excess sludge pretreated by ultrasonicwaves/alkaline was better than that pretreated by ultrasonic waves and alkaline alone.The concentration of SCOD rose with ultrasonic waves operating time; SCODincreased when ultrasonic energy density increased from0.063W/mL to0.188W/mL;the pH was adjusted from8to10and the concentration of SCOD increased withresidence time; the pH was adjusted from8to10, then the sludge was treated byultrasonic waves and the concentration of SCOD increased; the concentration ofSCOD was more than3000mg/L when the ultrasonic energy density, pH, treatmenttime were0.188W/mL,10,30min respectively.(2) The concentration of SCODreached1164.4mg/L when ultrasonic energy density, treatment time, hydrolysis andacidification time were0.188W/mL,30min,7days respectively. During this process,the concentration of TN, NH4-N increased; SCOD decreased; at first, TP rose then itdropped; VFA maximum concentration was326.4mg/L at4days.(3) Theconcentration of SCOD, TN, NH4-N, TP, VFA were3614.4mg/L,451.8mg/L,233mg/L,82.5mg/L,128.6mg/L respectively when sludge was pretreated by ultrasonic waves atpH11. The VFA was higher than the others. During the process of hydrolysis andacidification, these indicators changed clearly, but it still was higher than that in pH9and pH10. The concentration of VFA reached500mg/L at3days.The studies have shown that, sludge was pretreated by ultrasonic waves/alkaline which was bettere than that pretreated by other pretreatment methods.