The Research On The Mechanism Of Bioleaching Affects The Sludge Dewaterability

With the rapid development of the sewage treatment industry,the rate of disposing municipal sewage has been increasingly improved,and thereby leading to production of a huge quantity of sludge.The method,safely and economically disposing the municipal sludge,has become a heated topic in this field.While the water content of sludge decreased to 80%,the traditional mechanical dewatering is difficult to reduce it.Therefore,to solve this problem,it has a significant impact on industrial application that developing a pretreatment technology,which enhances the sludge dewaterability.Bioleaching is regarded as an economical technology to remove heavy metals from sewage sludge with high efficiency,and improve sludge dewatering property,which has been increasingly concerned.Whereas,a significant controversy exists in researching on the mechanism of sludge dewaterability during bioleaching.Therefore,this research focus on improving municipal sewage by bioleaching,optimizing the bioleaching conditions and investigating the changes of extracellular polymeric substances during the process,in order to find out the significant factors that affecting the sludge dewaterability.The main contents and results in this research were as follows:?1?All the low-molecular organics listed above had negative effects on sulfur-oxidation of Acidithiobacillus thiooxidans.Furthermore,the effect intensities of different treatments were ranked as follows:acetic acid>propionic acid>humic acid>oxalic acid>citric acid.The R.mucilaginosa could eliminate the inhibition effect of organic matter on A.thiooxidans.Moreover,the smaller of the molecular weight of organic matter,the ability of eliminating of inhibition effect by R.mucilaginosa was more obvious.?2?Comprehensively considering the results and operation cost of sludge dewatering by bioleaching,the optimum conditions of bioleaching were:the best acidification sludge dosage,aeration,sludge concentration and leaching time was 5%,0.5 m³·min^-1·m^-3-L,20 g·L^-11 and 48h,respectively.Through investigating the relationship between pH and sludge dewaterability under the optimized conditions,the results showed that sludge dewaterability could be improved only when sludge pH was 2³,corresponding CST decreased by 52%.?3?Researching on the mechanism of bioleaching affects the sludge dewaterability indicated that the improvement dewaterability of sludge by bioleaching has no direct relationship with total EPS content,but has a positive correlation with TB-EPS content.The less content of protein in TB-EPS,the lower CST and more benefit to dewatering,conversely,the S-EPS has a negative correlation with improvement dewaterability of sludge.