Experimental Study On The Treatment Of Acid Mine Water With Dispersed Alkaline Substrate

In order to gradually promote the concept of"clean,green and low carbon"in the energy revolution,in recent years,Kaili in Guizhou has closed coal mines in which the resources of the Yudong River Basin are depleted and mining risks are high.As a result,a large amount of acid mine water was discharged,which caused serious water environment pollution problems and caused serious harm to the social economy and residents’lives.Based on the conditions and water quality characteristics of the closed coal mine site in the Yudong River Basin,a disperse alkaline substrate system was selected to treat acid mine water.The thesis has monitored the acid wastewater of Qiaotou Coal Mine by sampling,clarified the water quality characteristics,studied the effects of material ratio,combination method,residence time on the treatment effect,and analyzed the pollutant fate and reaction mechanism.The main conclusions are as follows:（1）The acid mine water in Qiaotou mining area has strong acidity,high SO₄^2-content,rich in metal elements such as Fe and Al,and its water chemistry type is Fe-SO₄.The suspended matter in water is mainly composed of schwertmannite,goethite,etc.The results of precipitation experiments of trace harmful elements,Pearson correlation and saturation calculation results show that the concentrations of Ga,Sr and Se in water are mainly affected by Fe and Al,and the concentrations of Co,Ni,Cu,Ba,Pb and As are affected by Mn and Zn.（2）Increasing the ratio of magnesium oxide in the dispersed alkaline substrate system is beneficial to the treatment effect of divalent metal ions Fe²⁺,total Fe,Mn,Zn,and Cd,and increasing the ratio of limestone in the dispersed alkaline substrate system to the stable increase in pH and Al³⁺,Fe³⁺removal is more effective.When the ratio of limestone and magnesium oxide is 6:4⁵:5,the pH effluent is stable above 6,and the removal rates of Al,Fe²⁺,total Fe,Mn,Zn and Cd are relatively high.The longer residence time and the material combination of CaCO₃→MgO are used to remove each pollutant better.（3）The main type of bacteria in the dispersed alkaline substrate system is Proteobacteria,accounting for 55.12%,of which the dominant bacteria are Methylovirgula,Acidibacter,Dechloromonas.In addition,an acid heterotrophic iron oxidizing bacterium Acidibacillus ferrooxidans also exists in the system.（4）In the surface layer of the CaCO₃-DAS system,Fe（Ⅱ）is converted to Fe（Ⅲ）through the oxidation of air or Acidibacillus ferrooxidans bacteria,and then combined with free OH-in water to form Fe（OH）₃,which is dehydrated or complexed to form ferrihydrite,goethite,lepidocrocite and metahohmannite.Acidibacter,Acidiphilium are involved in the trace reduction of Fe（Ⅲ）in the surface layer system.In the deep layer of the CaCO₃-DAS system,Fe²⁺precipitates to produce FeCO₃,and complexes with Fe³⁺to produce green rust.（5）The surface layer of the MgO-DAS system contains all processes of the surface layer of the CaCO₃-DAS system except for the creation of green rust.The deep reaction system of the MgO-DAS system involves two paths.Path one is the formation of Fe（OH）₂,and it continues to be oxidized to Fe₃（OH）₈ with the participation of Dechloromonas.Path two is the production of water-soluble ferrous minerals such as zincmelanterite,szomolnokite,iron sulfite hydrate and the production of FeS through the action of sulfate-reducing bacteria.During this period,Fe³⁺complexed with dissolved Mg²⁺,OH^-,SO₄^2-and H₂O to form pyroaurite.The precipitation and complexation of Al occurs in the surface layer of CaCO₃-DAS and MgO-DAS,in which jurbanite will dissolve deep in the MgO-DAS system,and rhodochrosite will form deep in the MgO-DAS system.There were 51figures,11 tables and 182 references in this dissertation.