Study On The Improvement Of Anaerobic Performance Of Residual Sludge By Freeze-thaw-chemical Combined Pretreatment

Taking the resource utilization of residual sludge as the goal,this paper aims at the problems of long fermentation cycle,low efficiency and low gas production in the process of anaerobic fermentation of sludge,and uses freeze-thaw(DR),sulfite(SS)and potassium perferite(PF)to pretreat sludge,and then performs freeze-thaw-chemical pretreatment after the conditions are optimized,and the effect of freeze-thaw-chemical pretreatment on the dissolution characteristics and anaerobic fermentation performance of the remaining sludge is studied,and the mechanism of freeze-thaw-chemical method on anaerobic fermentation is explained from the direction of bacterial community structure.The main conclusions of this study are as follows:(1)The results of individual pretreatment experiments showed that SCOD of DR and SS pretreatment first increased and then decreased,and the maximum was in DR10h group(freezing time was 10 h)and SS1400 group(sulfite dosage was 1400 mg/L),the change trend of sludge protein substances and microbial metabolites was basically consistent with SCOD,and humic acid and fulvic acid substances were dissolved very little,which was conducive to subsequent anaerobic fermentation.In PF pretreatment,the SCOD concentration was proportional to the PF dosage when the PF dosage was<0.5 g/g TSS,and the SCOD remained basically unchanged when the PF dosage was≥0.5 g/g TSS,and humic acid and fulvic acid substances were dissolved in large quantities,which may inhibit subsequent anaerobic fermentation.After the optimized DR,SS and PF pretreatment for anaerobic fermentation experiments,the cumulative methane production of DR10h group and SS1400 group was the largest,which was 2.17 and 1.60 times that of the blank group.The cumulative methane production of the remaining sludge after PF pretreatment was inversely proportional to the PF dosage,and the cumulative methane production of PF0.1 group(potassium perferrate dosage was 0.1 g/g TSS)was the highest,which was 2.17 times that of the blank group,because excess potassium perferrate would generate OH~-,which made the p H much larger than the suitable range of methanogens,and inhibited the activity of methanogens.(2)The results of combined pretreatment experiments showed that freeze-thaw-sulfite(DR-SS)and freeze-thaw-potassium perferite(DR-PF)pretreatment had a synergistic effect on sludge cracking,resulting in better sludge cracking effect,shorter freezing time and lower dosage.The experimental groups with the highest concentrations of SCOD in DR-SS and DR-PF pretreatment were DR8h+SS1400 group and DR6h+PF0.5 group,respectively,DR-SS pretreatment had a synergistic effect on the biodegradability index,and a large number of humic acids were dissolved by DR-PF pretreatment,which would inhibit the effect of subsequent anaerobic fermentation.In the anaerobic fermentation process,the experimental groups with the highest cumulative methane production by DR-SS and dr-PF pretreatment were DR8h+SS1400 and DR10h+PF0.1,which were 2.63and 2.41 times the blank group,which were significantly improved compared with the single-factor experiment.(3)Pretreatment can improve the richness and diversity of sludge,but the richness of microbial communities decreases when the PF dosage is 0.5 g/g TSS.Different pretreatment conditions had significant differences in the microbial community structure of sludge.Under the condition of high PF dosage,Firmicutes and Proteobacteria were the main dominant bacterial phylums,which could improve the acid production capacity and hydrolysis effect of sludge,while the proportion of Pseudomonas decreased,and the methanogenesis process was inhibited.DR8h+SS1400 group and DR10h+PF0.1 group play a synergistic role in the acid and methane production process of sludge.Comprehensive analysis shows that freeze-thaw-chemical combined pretreatment has a synergistic effect on sludge resource utilization,and the group with the highest cumulative methane production is DR-SS pretreatment DR8h+SS1400 group,which is163%higher than the blank group and 21%～64%higher than the single factor experiment.Figure[71]Table[7]Parameters[84]...