Study On The Effect Of Ultrasonic-ozone Synergistic Reduction Of Excess Sludge And Lysate On A~2/O Process

The treatment of activated sludge could destroy the sludge structure and the microbial cell membrane through ozone and ultrasonic,in which the materials of sludge cell transfer into liquid phase to achieve the sludge reduction.Moreover,the utilization of ozone and ultrasonic and the efficiency of cracking the sludge are varied with the addition method.This paper was investigated the effect of ozone,ultrasonic and ozone coupling with ultrasonic on the efficiency of sludge breakage,compared their dissolved cell mechanism,and evaluated the effect of above-mentioned treatment methods on wastewater quality of AAO process,sludge property and reduction efficiency.The effect of ozone,ultrasonic and ultrasonic-ozone on the efficiency of sludge re duction were studied,and the jet aeration applied in the process of ozone were compa red with the normal aeration in terms of sludge reduction.The conclusions could be d rew as following:the efficiency of sludge reduction was increased with energy density of sound,the sludge reduction rate reached 39.77%within 30min at 3.0W/mL,which was 13.99%higher than that at 1.0W/mL.During the process of jet aeration,the effi ciency of sludge reduction was increased with flow,the reduction rate achieved 47.89%at the dosage of 0.186gO3/gSS when the gas flow was 1200L/h,while the rate was43.15%through normal aeration at the dosage of 0.20gO3/gSS.According to the result s of response surface method in ultrasonic-ozone process,when the dosage was 0.18g O3/gSS at 1.37W/mL,the optimal sludge reduction reached 67.17%,which was 5.17%higher than the sum of ultrasonic and ozone alone,the synergistic effect could apply to explain the phenomenon.Based on the study of dissolution mechanisms,the results showed that the process of dissolved cell via ultrasonic-ozone was more effective than other treatment method,the protein solubility rate were 32.14mg/gSS,56.58mg/gSS and 59.8mg/gSS for ultrasonic,ozone and ultrasonic-ozone,respectively.Besides,the synergistic effect of ultrasonic-o zone was in favor of the death of microbial cell,the dehydrogenase activity was rapid decrease and completely inactivation until 0.064gO3/gSS.During the process of ultras onic-ozone,the sludge floc size was decreased,the amount of large particle was reduc ed,and the average particle size of sludge was reduced from 48.32?m to 32.64?m.S ome of dissolved organic matters were oxidized by ozone,and the loss of C,N and P were 16.6%,5.7%and 3.17%,respectively.Combined the analysis of microscope wi th fluorescein staining technique,the cavitation effect of ultrasonic was mainly to destr oy the sludge structure,while was poor to dissolve the sludge cell.Furthermore,ozon e was effective to dissolve cell and sludge was oxidized to the debris,then the intrac ellular nucleic acid was flowed up.The coupling of ultrasonic and ozone could enhan ce the mass transfer rate and oxidation,there was strong destructive effect on EPS,fil aments and other microbial membranes.After the sludge disintegration,the green fluor escence and flocs could not been found in the sludge.The influence of operational methods,such as on AAO process were investigated at the reflux ratio of 60%,the results showed that three types of reflux had no obvious effect on the COD removal and ammonia nitrogen in AAO system within a continuous run of 20 days,while the TN removal were 84.42%,82.55%and 81.79%,respectively.TP removal were 80.95%,83.77%and 85.26%.Compared with the control system,the recirculation of lysis fluid could enhance the nitrogen removal,while the removal efficiency of phosphorus was decreased.Accordingly,the value of MLVSS/MLSS increased and the sedimentation of the sludge was improved,while the value of SVI was decreased.What's more,the AAO system reached optimal sludge reduction when the dissolved cell liquid returned to the anaerobic zone,at this moment the sludge yield coefficient and the amount of sludge discharge were decreased by 39.84%and 51.3%,respectively.Combined the wastewater quality and sludge reduction efficiency,the optimal reflux was to anaerobic zone.