| Anaerobic digestion of sludge is one of the important processes for the treatment and energy recovery of the remaining activated sludge in a sewage treatment plant.As the activated sludge microbial cell wall is difficult to crack,the efficiency of anaerobic digestion of the sludge is limited.In response to this problem,many researchers have conducted pretreatment techniques such as ultrasound and ozone oxidation on the excess sludge,but there are few studies on the ultrasonic/ozone oxidation technology.This dissertation mainly focuses on the residual activated sludge from the Jinan WWTP-1,and studies the effects of ultrasonic treatment,ozone treatment,and ultrasonic/ozone oxidation on sludge decomposing,sludge dehydration and resistance changes.Impacts: Microbial population analysis was conducted to study the effect of pretreatment methods on the abundance of anaerobic microorganisms.The optimum conditions for the application of different pretreatment techniques were determined through experiments,and the gas production and the solid phase in the sludge were examined through anaerobic digestion experiments.The law of material change in liquid phase;the effect of gas production by co-digestion of pretreatment and kitchen waste,and the detection method of siloxane in anaerobic digestion of biogas and its adsorption in sludge were compared.The separate pretreatment technique of ultrasonic treatment and ozone treatment played a role in cracking the cell walls of the remaining sludge,but the degree of cracking was different.The effect was different: the cracking effect of sludge pretreatment was expressed by the concentration of SCOD and dissolved phosphate,and the ultrasonic treatment of sludge was studied.The results showed that the longer the ultrasonic time and the greater the sound energy density had a better cracking effect on the sludge.Through the calculation of the reaction kinetic equation in this experiment,the effect of the ultrasonic time on the cracking effect of the sludge was higher.Sound energy density.The sludge was treated with ozone.The results showed that the sludge cracking effect was positively correlated with the amount of ozone added.The dewatering performance of the remaining sludge after ultrasonic treatment and ozone oxidation treatment decreased.Ultrasound/ozone oxidation technology is superior to ultrasound and ozone oxidation alone in the cracking of sludge cells.Ultrasonic/ozone coupled pretreatment mode using ultrasound and ozone oxidation simultaneously,ultrasound can enhance the mass transfer rate and decomposition rate of ozone in water,and the effect of cracking sludge cells is better than that of ultrasonic treatment after ozone oxidation/Ozone sequential combination method.The optimal operating parameters for the experiment were ultrasonic conditions of 0.75 W/m L,acoustic energy density for 20 minutes,and ozone dosage of 0.14 g O3/g TS.The SCOD concentration after pretreatment was 8.6 times that of the initial SCOD.The analysis of absolute abundance and relative abundance of the resistance genes tet G and tet X in the residual sludge after pretreatment showed that ozone oxidation has a reduction effect on the two resistance genes,and the absolute abundance of tet G and tet X after ozone oxidation The degrees dropped by 16.2% and 24.6% respectively.The absolute abundance of tet X decreased by 30.5% after combined treatment with ultrasound/ozone oxidation technology.Microbial community analysis of sludge before and after ultrasonic/ozone pretreatment showed that Bacteroidetes,Proteobacteria,Firmicutes and Chloroflexi were the main microbial communities,and the abundance of Bacteroidetes and Proteobacteria was not affected by pretreatment.Ultrasonic treatment was more effective than both ozone and oxidative oxidation on Firmicutes and Chloroflexi.Oxygen microbes play a stronger role in reduction.The total gas production of anaerobic digestion of sludge after pretreatment was higher than that of non-pretreated sludge.The amount of gas generated by the ultrasonic treatment increased by 36.7%,the amount of sludge produced by ozone oxidation increased by 41.5%,and the amount of sludge produced by the ultrasonic/ozone combined treatment increased by 56.9%,and the peak time for reaching gas production was earlier than without Pretreatment group.The gas production rate of sludge unit VS was increased from 107.71 m L/g VS without pretreatment to 147.26 m L/g VS,152.51 m L/g VS,and 175.03 m L/g VS,respectively.In the three groups of pretreatment group,the VS/TS in the solid phase reached about 40% on the 20 th day,which was in line with the requirement of sludge treatment stabilization and reduction.The adsorption experiments of four siloxanes(L3,D4,L4,D5)in anaerobic sludge were studied by static spike experiments.It was found that the mass transfer process at the mud-water interface is a limiting step in the volatilization process of siloxanes.As the adsorption time increases,the siloxane content in the mud and water phases tends to be positively correlated with the molecular weight.After fitting the experimental results to the isotherm adsorption line analysis,it is found that the adsorption law is more consistent with the Freundlich adsorption isotherm,and the possibility of monolayer adsorption is higher. |
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