Study On The Efficiency Of Bioleaching Process For Treatment Of Residual Sludge

With the increasing demand for water quality,the increasing number of wastewater treatment plants and the improvement of sewage treatment technology are the general trend.As a kind of traditional and efficient wastewater biochemical treatment methods,activated sludge process is applied by the vast majority of sewage treatment plants,and using the activated sludge method to treat urban sewage,the production of a large amount residual sludge is inevitable.Due to the residual sludge is in the composition with heavy metals,pathogenic microorganisms,and the toxic organic compounds,if not properly handle and wanton waste will cause secondary pollution to the soil and water around,and a serious threat to human health.Therefore,the disposal of residual sludge is very important.Bioleaching technology as an economical and environmentally friendly sludge bio-conditioning technology has been applied to the disposal of residual sludge.This method not only can remove the heavy metals and pathogenic microorganism in the sludge,also can improve sludge dewaterability,realize sludge reduction,provide convenience for the follow-up sludge treatment and disposal,save transportation cost.How to improve the efficiency of bioleaching reaction and how to improve the dewatering performance of the residual sludge under optimal operating conditions are urgent problems.This study started from the cultivation of bioleaching functional strains and focused on several factors that affect the bioleaching to improve the process of dewaterability of residual sludge and the treatment effectiveness of bioleaching on residual sludge was studied;The bioleaching reaction parameters were optimized by response surface method in order to obtain the best operating conditions of bioleaching reaction;The biological community structure of bioleaching functional strains and bioleaching sludge was analyzed,the mechanism of bioleaching is clarified.In this paper,bioleaching functional strains were enriched in a specific culture medium,and the growth law of bacteria was studied in the enrichment process,and the growth curve was drawn.The results show that bioleaching functional strains to beenriched in the modified 9k medium creature,30?and 180r/min under the conditions of constant temperature oscillation training after 72 h can obtain high active and high density functional strains fermented liquid,the bacteria concentration is about2.5g/L.The fermented liquid was used to study bioleaching effect on the properties of residual sludge dewaterability,explored the influence of sludge concentration,nutritional agent dosing quantity and the adding ratio of bioleaching functional bacteria fermented liquid on treatment effect.The results show that for treatment of different concentration sludge has a corresponding nutrients dosing quantity which makes the best effect under the condition of the sludge dewatering.It was found that the concentration of sludge was positively correlated with the nutrient dosage through correlation analysis.Bioleaching functional strains fermented liquid was added at10% and nutrients were added at appropriate concentration.Bioleaching reaction can achieve better processing effect under this condition and processing cost is lower than the treatment without addition of nutrients.The effects of bioleaching on residual sludge were studied and the mechanism of biological leaching was analyzed.The results showed that the bioleaching processing due to functional strains have biological acidification,caused sludge microbial cells break,as the bioleaching reaction continues:(1)The nitrogen and phosphorus content in the supernatant on macroscopic showing a rising trend;(2)The content of heavy metals in the solid phase of sludge decreased gradually;(3)The content of EPS in the sludge mixture decreased significantly;(4)The total number of heterotrophic microorganisms in the sludge mixture decreased significantly.Based on the results of above-mentioned experiment,it is of great significance to use the scientific method to optimize the reaction parameters,so as to obtain the optimum parameters of bioleaching reaction.This study uesd the response surface design method of optimal design of Box-Behnken optimize the bioleaching reaction parameters,the three factors:sludge concentration,nutritional agent dosing quantity and reaction time are independent variables,specific resistance of sludge decrease rate is the response value.Through the establishment of the second order polynomial function model and the variance analysis and significance test of the data obtained from this model were carried out,finally get an optimum reaction parameter ratio andvalidate it.The results show that the second order polynomial function model obtained by the response surface optimization design is of high reliability,and the optimized parameters are: The sludge concentration is about 20000mg/L,the nutrient dosage is about 2g/L,that is the ratio of sludge concentration,nutrient dosage and bioleaching bacteria concentration is 80:8:1,and the reaction time is 1d.The parameters of this group are validated and the relative error of the actual value and predicted value is2.16%.In this paper,the six samples were obtained in bioleaching functional strains fermented liquid and different time periods of bioleaching,and the community structure of each sample was analyzed.First,the collected data is statistically analyzed and optimized to ensure the reliability of the analysis data.Then,OTU analysis,Alpha diversity analysis,dilution curve analysis,Venn diagram analysis and community composition analysis were conducted for each sample,and the relationship between samples and species was explored.The species richness of bioleaching functional strains fermented liquid is low,mainly composed of two species: Acidithillius and Acidiphillum.The richness of bioleaching functional strains in the sludge system increased significantly with the continuous process of bioleaching and the community structure of the residual sludge was changed obviously after bioleaching.The bioleaching mechanism was analyzed.It mainly includes the mechanism of biological damage,charge neutralization and adsorption bridging,the reduction of extracellular polymer substances,the transformation of microbial community structure and the generation of secondary iron minerals.