Analysis Of Community Structure Of Sludge From Ultrasonic-aerobic/Anoxic Digestion

With the increase of sewage load, a larger number of municipal sewage sludge was produced inevitably. Treatment and disposal of sewage sludge becomes a difficult problem to wastewater treatment plants. Previous research has confirmed ultrasonic promotion for sludge aerobic/anaerobic was feasible. The paper had focused on the analysis in the process of sludge digestion microbial community structure, hydrolysis enzyme activity (amylase, glycosidase enzymes, protease, phosphatase) change trend, investigate the mechanisms of ultrasonic promotion for sludge aerobic/anoxicdigestibility will provide theoretical foundation of popularization and application.In this paper, the microbial community structure of sludge aerobic/anoxic digestion after ultrasonic pretreatment was firstly studied by PCR amplification and DGGE. The results indicated that the shift of microbial diversity was in correspondence to the different period. Compared with Od, the diversities microorganisms were61.2%,48.2%,46.4%,42.6%,41.7%respectively after5d,10d,15d,20d,25d. Shannon density index of bacteria experienced a process from a gradual reduction to stable state. This suggested that ultrasonic pretreatment had a significant impact on bacterial community structures. Cluster analysis of DGGE by UPGMA(unweighted air group method, arthmetic mean) divided all lanes into three clusters, which corresponded to different periods during the whole experiment. The sequencing indicated that5of predominant species in DGGE profiles of microbial communities are belonged to Bacillus,2is belonged to Firmicute、1is belonged to a-Proteobacteria、3is belonged to β-Proteobacteria, which playing an important role in sludge digestion and improving the efficiency of nitrogen removal. Nitrification and denitrification were improved by ultrasonic pretreatment, resulting in VSS removal efficiency of ultrasonic-aerobic/anoxic digestion was higher.Then the influences of ultrasonic pretreatment (28kHz,0.15kW-L-1,10min) on aerobic/anoxic digestion process were investigated with SS,VSS and hydrolytic enzyme activities(amylase, glucosidase, protease, phosphatase). Compared with the control treatment sludge the optimal sludge retention time is12d; the results showed that stability time of sludge was shortened greatly and digestion efficiency was improved by ultrasonic pretreatment. VSS went to44.3%, better than7.8%of traditional aerobic/anoxic digestion. The variational trend of sludge hydrolytic enzyme activities increased firstly and then fell off during13d digestion, the maximum of amylase activity and glucosidase activity in ultrasonic sludge, appeared in the5d, amylase activity was0.104μmol·g-1and glucosidase activity was0.637μmol·g-1. The maximum of intracellular protease activity and extracellular proteases activity in ultrasonic sludge, appeared in the7d, intracellular protease activity was23.68μmol·g-1, higher than extracellular proteases activity, it was playing a leading role in sludge digestion. The acid phosphatase activity of ultrasonic sludge was more than the control sludge, the alkaline phosphatase was sensitive to environment. So the alkaline phosphatase activity reduced when the internal properties of sludge was changed.Finally, through the electron microscopy scaned the changed of microbial population structure on sludge, the results showed that all kinds of lever bacteria and ball was survive in the sludge, the main was coli bacterium group. So Nitrification and denitrification were improved by ultrasonic pretreatment when the internal properties of sludge was changed.This research provided theoretical and practical basis for the popularization and application of the ultrasonic-aerobic/anoxic digestion technology.