Study On Sludge Solubilization Efficiency By Ozonation

The reduction of sludge is an environmental problem that need to be solved urgently in China.In this study,a bubble column contact reactor was used to study the effect of the main factors(sludge concentration,ozone concentration,ozone dosage,mixed liquor height)on the sludge ozonation efficiency,and the regular pattern of significant influencing factors,in order to find out the process of sludge ozonation.Based on the analysis of intracellular dissolved matter and the utilization efficiency of ozone,a high cell lysis rate was achieved in the bubble column,accompanied by an obvious mineralization of organism in the process of sludge ozonation,which resulted in the loss of both ozone and COD.Compared with the sludge concentration and ozone concentration,the height of mixed liquid column and the time of ozonation had a greater influence on the optimization of sludge cell lysis process.With the mixed liquid column height above 0.8 m and the ozone dosage of 0.015 gO3·(gMLSS)-1 or so,the ozone utilization rate remained above 90%,at the same time,a high quantity of organism which released from the sludge could be achieved.Response surface analysis was carried out to study the influencing factors of sludge cell lysis rate,organism release rate and ozone utilization efficiency,which found that there was an interaction effect among those factors,and ranked them according to their significant effect.For the sludge cell lysis rate: ozone concentration > sludge concentration > ozone dosage;for TCOD release rate of total organism: ozone concentration > ozone dosage > sludge concentration;and for the ozone utilization efficiency: mixed liquid column height > sludge concentration > ozone dosage ozone concentration.The multiple quadratic regression model for each response target were established,and the optimal operating conditions of the influencing factors were determined.Ozone concentration of 21 mg·L-1,sludge concentration of 10.49 g·L-1,and ozone dosage of 0.011 gO3·(gMLSS)-1,under these conditions,the sludge cell lysis rate and the organism release rate were 223 mgMLSS·(L·min)-1 and 15.22 mgTCOD·(L·min)-1,respectively;for the efficiency of ozone utilization: the predictive value could up to more than 98%,when the ozone concentration,sludge concentration,ozone dosage and mixed liquid height were found to be 17 mg·L-1,14 g·L-1,0.010 gO3·(gMLSS)-1 and 1.05 m,respectively.