Remediation Of Phreatic Water Pollution In Coal Mining Area By Immobilized Sulfate Reducing Bacteria

SO₄^2-in most mine water and coal gangue leachate obviously exceeds the standard,and it may also be accompanied by different degrees of（heavy）metals exceeding the standard.If it leaks on the surface,the groundwater quality will deteriorate.In this thesis,the immobilized sulfate reducing bacteria（SRB）beads were used as the filling medium of permeable reaction barrier（PRB）to provide reference for groundwater pollution remediation in coal mining areas.The main achievements of this thesis are as follows:（1）A strain SRB-Citrobacter amalonicus strain S1 was isolated from mine water sediment.The optimum concentration of SO₄^2-for growth and metabolism was about1000 mg/L,the optimum growth temperature was about 30℃,and it belonged to mesophilic bacteria,and the optimum p H was between 7 and 8.High concentration of SO₄^2-（>2000 mg/L）can inhibit the growth of SRB,and S1 has stronger adaptability to low temperature than high temperature.（2）Chlorella pyrenoidosa is the best carbon source of SRB dominant bacteria solution,and the removal rate of SO₄^2-is about 44.3%within 10 days.Through 16orthogonal experiments with 5 factors and 4 levels,it was determined that the optimal ratio of immobilized SRB beads was PVA 4%,SA 4%,CaCl₂2%,bacterial suspension 30 mL and Chlorella pyrenoidosa 2 g,in which SA concentration was the primary factor affecting the removal rate of SO₄^2-,mechanical strength and mass transfer performance of immobilized SRB beads,and PVA concentration was the secondary factor.（3）The adsorption of SO₄^2-by immobilized blank beads is mainly controlled by chemical action,and the fitting degree is the best with Lagergren pseudo-second-order kinetic model.Freundlich adsorption isotherm model shows that the surface of the immobilized blank beads is heterogeneous,and it is easy to adsorb SO₄^2-.Using the concept of"black box model"and Michaelis-Menten equation for reference,the kinetic parameters V_maxand K_mof the immobilized SRB beads were obtained,which were 0.4679 mmol/（h·L）and 62.79 mmol/L respectively.（4）The process of SO₄^2-removal by immobilized SRB beads was preliminarily clarified.During the adaptation period of 0～15 h,SO₄^2-removal by beads was mainly based on liquid-solid mass transfer and internal diffusion.After 15 h,the SO₄^2-reduction of SRB on the surface and inside of the beads was enhanced.In the process of SO₄^2-reduction,the original adsorption site of SO₄^2-is vacant again,and the product S^2-is transferred to the outside.The concentration difference between internal and external SO₄^2-drives a new round of liquid-solid mass transfer and internal diffusion.（5）A small-scale PRB system with immobilized SRB beads and zeolite-activated carbon in series was constructed.The combined maximum removal rate of SO₄^2-was54.15%,and the order of removal effects of five heavy metals was Cd²⁺>Pb²⁺>Cu²⁺>Mn²⁺>Zn²⁺,and the removal rates were all greater than 80%.The results of EDS and XRD showed that multiple metal sulfides were formed in the immobilized SRB column,which confirmed that SO₄^2-reduction occurred inside it.In addition,a PRB structure consisting of grouting curtain,immobilized SRB beads filling well and zeolite-activated carbon continuous wall is designed.There are 43 figures,16 tables and 95 references in this thesis.