Research On Passive Treatment Of Acid Mine Drainage In Yudong River Basin

Due to the exhaustion of resources,complicated geological conditions and adjustment of industrial policies,a large number of coal mines in the Yudong river basin in Kaili were closed or abandoned,and the acid mine drainage discharged from the mine seriously polluted the Yudong River.In order to make full use of abandoned mine roadway to treat acid mine water,simulated abandoned mine roadway successive alkalinity producing systems?SAPS?was designed.According to the surrounding site conditions ofabandoned coal mine,dispersed alkaline substrate?DAS?-aeration-wetland combination system was designed.The main influencing factors of the system and the mechanism of pollutant removal were investigated,and the following conclusions were drawn:?1?The pH value of the abandoned mine acid mine drainage in the Yudong river basin is 2.78⁷.57,and the Fe concentration is 0.07¹092.00 mg/L,most of samples were seriously exceeded the limits of coal industry waste water and Guizhou local discharge standards.Affected by mine drainage,pH,the concentration of SO₄^2-,Fe,Mn and Cd of Yudong river water exceeds the surface water III class standard limit and water source area supplement standard limit,and was seriously polluted.?2?The results of the study on SAPS show that SAPS has obvious treatment effect on simulated acid mine drainage,the pH of effluent from SAPS is above 6.0,the removal rate of Fe is 79.6%.By setting two-stage SAPS,the removal rate of Fe by SAPS can be improved.Improvement of SAPS with inert materials increase the SO₄^2-removal effect of the system.?3?The main reaction mechanism of SAPS is to consume oxygen through the microbial action of the organic layer,reduce the oxidation of Fe²⁺to reduce the precipitation of Fe³⁺,and remove the sulfate by sulfate reduction,and the alkali-producing layer can raise the pH by neutralization reaction.?4?The results of the study on DAS show that the limestone to inert material weight ratio increase,the particle size of limestone decrease and the hydraulic retention time increase are all beneficial to improve the pollutants removal effect of the DAS.The decrease of vertical flux is beneficial to the decrease of Fe concentration and acidity in DAS effluent,but it has little effect on the daily unit area removal of Fe²⁺,under the experimental conditions,the unit area removal of Fe²⁺is 18¹9 g/?m²·d?.The unit area removal of Fe decreases as Fe²⁺concentration increase in the influent.However,when the influent Fe²⁺concentration reaches 100 mg/L,the increase of influent Fe²⁺concentration has little effect on the unit area removal of Fe.Based on the above research results,DAS-aeration-wetland combination system was constructed to treat simulated acid mine water.The effluent meet the standard of coal industry wastewater and Guizhou local discharge standards.?5?DAS uses fine-grained limestone to increase the reaction rate,and increases the porosity and permeability coefficient of the system by adding inert materials.The main reaction mechanism is raise the pH by dissolution of limestone and remove Fe by forming minerals such as schwertmannite,jarosite and goethite with the action of iron oxidizing bacteria..The Yudong River Basin can treat acid mine water with SAPS or DAS according to site conditions.SAPS can be constructed by using the original roadway,and the DAS-aeration-wetland combination system can be constructed outside the roadway to treat the acid mine drainage.