Study On Remediation Of Black And Odorous Water By Modified Bentonite And Sulfur Autotrophic Denitrification Enhanced Microbial Agent

With the rapid development of China’s economy and industry,the treatment of black and smelly water has been highly valued by the national government and social enterprises.At present,the remediation of black and smelly water bodies in the built-up areas of prefecture level and above cities has achieved results,but the black and smelly phenomenon of water bodies in the built-up areas of county-level cities is still serious,affecting the safety of the surrounding environment and the healthy life of residents.This study takes the overlying water and sediment of a black and smelly water body in Wuhan as the treatment object.Firstly,the components of photosynthetic bacteria,Bacillus subtilis,zeolite and bentonite were optimized by orthogonal experiment.Then,the bentonite was modified to enhance the phosphorus removal effect of the composite microbial agent.Finally,sulfur autotrophic denitrifying bacteria were added to prepare SAD-La-BT based composite microbial agent to enhance the sulfur removal effect of the composite microbial agent.The simulated remediation experiment were carried out under laboratory conditions.By testing the relevant physical and chemical properties of overlying water and sediment,analyzing the changes of microbial community structure in sediment,the remediation effect of the final optimized component compound microbial agent on the sediment of small,micro,black and smelly water body was deeply explored,and the mechanism of simultaneous removal of carbon,nitrogen,phosphorus and sulfur was clarified.The main results are as follows:（1）In order to optimize the components of the initial compound bacterial agent,the effects of different formulations of compound bacterial agent on the related physical and chemical properties of overlying water and sediment were investigated by designing orthogonal experiments.The results show that adding high doses of photosynthetic bacteria and Bacillus subtilis to the compound microbial agent will lead to the deterioration of the overlying water and sediment environment,and the compound microbial agent has poor effect on the removal of TP from the overlying water.The effect of A2B1C2D2 and A3B1C3D3 in the experimental group on the remediation of black and odorous water body shows that the addition of compound bacterial agent can significantly reduce the contents of NH₄⁺-N,TN and COD in the overlying water body,and its removal rates can be more than 90%,60%and 80%respectively.Also they can effectively reduce the contents of organic matter,NH₄⁺-N and TN in the sediment.Finally,the optimal components of the initial compound agent except bentonite are 0.3 g/L photosynthetic bacteria,0.1 g/L Bacillus subtilis and 2 g/L zeolite.（2）Aiming at the problem of poor phosphorus removal effect of initial compound bacterial agent,La（OH）₃ modified bentonite（La-Bt）was prepared by impregnation precipitation method.SEM and EDS characterization analysis showed that the morphology of bentonite changed significantly before and after lanthanum loading.After lanthanum loading,the layered bentonite disappeared,some small particles appeared on the surface,and the surface roughness increased significantly The characteristic peak of La appeared in EDS spectrum,indicating that lanthanum is successfully loaded into the interlayer structure of bentonite.La-Bt phosphorus removal experiment shows that it can effectively remove phosphorus in water,which is through two ways:the adsorption of active sites on the surface of La-Bt and the combination of La and phosphate to produce insoluble lanthanum phosphate.（3）La-Bt based compound microbial agent can effectively remove pollutants in water and sediment.With the increase of the amount of La-Bt in the compound bacterial agent,the better the removal effect of pollutants in the overlying water;For the reduction of organic matter in sediment,La-Bt based compound bacteria has no obvious effect,and the reduction of organic matter in sediment mainly depends on the biological metabolism and degradation of microorganisms;In view of the reduction of NH₄⁺-N,TN and TP in the sediment,with the increase of La-Bt addition in the composite bacterial agent,La-Bt based composite bacterial agent gradually forms a covering layer on the surface of the sediment,inhibits the diffusion of pollutants in the sediment to the water body,and makes the contents of NH₄⁺-N,TN and TP in the sediment decrease first and then increase.The optimal amount of La-Bt in the compound bacterial agent was 1.5 g/L.At the end of the experiment,the removal rates of NH₄⁺-N,TN,TP and COD in the overlying water were 98.1%,81.4%,94.8%and92.9%respectively,the reduction rate of organic matter in the sediment was 9.24%,and the contents of NH₄⁺-N,TN and TP in the sediment were 1.80 mg/g,2.17 mg/g and0.478 mg/g respectively.（4）Aiming at the removal of sulfur pollutants in sediment,SAD was compounded with the optimal component La-Bt based composite microbial agent.SAD-La-Bt based composite microbial agent can effectively remove pollutants in sediment of black and smelly water body.With the increase of SAD in the modified compound bacterial agent,the better the removal effect of pollutants in the overlying water body,and the lower the contents of AVS,TN and TP in the sediment.Comprehensively considering the removal of pollutants in overlying water and sediment by SAD-La-Bt based composite microbial agent and its cost-economic benefits,the optimal dosage of SAD-La-Bt based composite microbial agent with an addition amount of 0.3 g/L is selected.At this time,the removal rates of NH₄⁺-N,TN and TP in overlying water are 87.4%,70.0%and 71.5%respectively;the reduction rate of AVS in sediment is 53.23%,and the contents of TN and TP are 1.55 mg/g and 0.40 mg/g respectively.Proteobacteria（26.41%）is the dominant bacteria in the sediment,and the relative abundance of Thiobacillus,which mainly removes sulfide in the sediment,is 1.97%.In this study,the final components of SAD-La-Bt based compound bacterial agent are 0.3 g/L photosynthetic bacteria,0.1 g/L Bacillus subtilis and 2 g/L zeolite,1.5 g/L La-Bt and0.3 g/L SAD.