Study On The Mechanism Of Improving Sludge Dewatering Efficiency By Bioleaching With Dissolved Oxygen

Nowadays,because of the steady growth of China’s GDP and people’s production and living standards,the output of domestic wastewater and industrial wastewater is also increasing,which leads to the increasing number of sewage treatment plants,sludge production continues to create a new peak.These sludge covers an area of large,foul smell,contains a lot of harmful and toxic substances,epidemic viruses and parasitic worm eggs,resulting in the follow-up treatment and disposal of complex and redundant,so it is necessary to strengthen management,actively respond,and put into a lot of artificial and economic investment,in order to prevent the secondary pollution of the ecosystem.In addition,the sludge also contains many beneficial microorganisms and fertilizers,which can be used as secondary resources for recycling.However,the high water content is the main resistance to sludge treatment and disposal.Only through ordinary mechanical dewatering,the moisture content of sludge is still above 80%.Effective pretreatment or conditioning of sludge can improve the sludge dewatering effect.Because of the advantages of low experimental cost,simple operation,stable reaction and so on,bioleaching has become a popular technology to improve the sludge dewatering performance.Bioleaching’s microorganisms are acidophilic and aerobic,so the content of DO（dissolved oxygen）in the sludge system affects the efficiency of improving sludge dewatering performance directly.A high dose of DO will cause an increase in experimental or engineering costs,while a low dose of DO will not allow the rapid growth of functional microorganisms to play a role.The purpose of this study was to determine the optimal concentration of DO in the process of bioleaching and to study its dewatering mechanism.The main research contents include:（1）In the process of bioleaching sludge treatment,three levels of DO were controlled:L（0.8～3.1mg/L）,M（3.1～5.5mg/L）and H（5.5～7.5mg/L）.The effects of different DO concentrations on sludge dewatering performance were studied by analyzing the physicochemical properties of sludge and the dewatering performance indexes which are sludge ratio resistance（SRF）and Cell signaling technology（CST）.（2）The sludge of bioleaching on different DO concentration were study the distribution of the sludge extracellular polymers（EPS）:in determining the DO content affect sludge dewatering performance,through the analysis of the 3D-EEM EPS distribution,explore the DO concentration on biological drain function damage the influence of EPS,and disintegration and floc EPS distribution affect the performance of sludge dewatering.（3）Preliminary study on the mechanism of bioleaching to improve sludge dewatering performance:the microbial population succession in the sludge system was studied through RDA analysis,and the mechanism of bioleaching to improve sludge dewatering performance was explored.The results showed that:（1）the SRF of M and H system was 4.38×10¹¹m/kg,which was lower than that of low DO level.When DO concentration>3mg/L,the dewatering performance of sludge was significantly improved.When DO concentration>6mg/L,not only the dewatering performance of sludge was improved,but also the bioleaching reaction time was shortened.Considering the effects of biological leaching treatment and the economic cost of the experiment,the optimal biological leaching condition is to control the DO concentration in the range of 3.1～5.5mg/L.（2）In the study of EPS distribution of bioleaching sludge in response to DO concentration:the conversion of TB-EPS and LB-EPS into S-EPS is beneficial to improve sludge dewatering performance.PN contributes more to the improvement of sludge dewatering performance than PS,and the decrease of TB-EPS is more conducive to the improvement of sludge dewatering performance.The conversion effect of EPS was the best when the concentration of DO was kept in the range of M（3.1～5.5mg/L）.In addition,DO concentration can change the distribution of DO matter,the decrease of tryptophan protein and soluble microbial metabolites and the increase of humic acid,which can degrade unstable organic matter into stable organic matter.（3）The mechanism of bioleaching to improve sludge dehydration performance was studied:in the process of bioleaching,the abundance of microorganisms decreased,but the diversity of microorganisms decreased,and acidophilic Thiobacillus was gradually isolated.The explanation of the reduction of SRF and CST by TB-PS and TB-PN is 85.7%and 83.8%,which has significant effect on improving sludge dewatering performance.