Application Of Drop-exposure Sedimentation-three-stage Filter In The Treatment Of Closed Coal Mines Drainage

After coal mines are closed,coal mine drainage will be produced.The discharge of coal mine drainage into rivers will cause a lot of environmental problems.With the increase in the number of closed coal mines across the country,the problem of water pollution from old coal mines has occurred in many places.In this study,combined with the advantages of the existing technology,according to the water quality of the actual coal mine drainage in a certain place,the application of the semi-passive treatment process of falling water aeration-high-efficiency sedimentation-three-stage filter in practical engineering was carried out,and have explored the iron removal mechanism of the process.The main conclusions are as follows:（1）The monitoring found that the effluent contains Ca²⁺,Mg²⁺,CO₃^2-plasma,higher p H value and lower total iron content when the amount of the drainage is small.When the amount of drainage is large during the flood season,the content of ferrous ions in the water increases significantly,and at the same time,the acidity increases,and the total iron content of the mine outlet water increases.The aeration and sedimentation treatment facility takes into account both the role of providing Fe（Ⅱ）oxidation reaction time and precipitating iron sludge,and the treatment effect is mainly affected by the amount of influent water and p H.The dissolution of carbonate particles in the sedimentation tank increases the p H value,which is beneficial to the oxidation of Fe（Ⅱ）by dissolved oxygen.（2）Limestone has a special lamellar structure,which can increase the p H to 10.21.The iron removal mechanism of the limestone filter includes:the filter can filter and remove the suspended solids of the influent iron sludge;Fe（Ⅱ）can be oxidized and hydrolyzed by dissolved oxygen to precipitate in the weakly acidic environment of the filter;the surface of the filter material can adsorb Fe（Ⅱ）and iron mud suspended matter.Loose iron active filter membrane can be formed on the surface of the filter material to adsorb and catalyze the oxidation of Fe（Ⅱ）.The limestone filter has a certain p H adjustment effect,which is conducive to the oxidation and removal of Fe（Ⅱ）.（3）The surface of dolomite has a relatively dense block-like cubic structure,and the main components include Ca,Mg,etc.,and the distribution of elements is relatively uniform,which can quickly adjust the p H of distilled water from neutral to above 10.Dolomite filter is less worn during daily operation.The iron removal mechanism of dolomite filter is similar to the limestone filter.（4）The surface of manganese sand has a special morphology with stacked rods and relatively loose.Manganese sand has little effect on p H.The removal of total iron by manganese sand filter mainly includes Fe（Ⅱ）and iron sludge suspended solids in the influent.The manganese-containing active filter formed by the manganese sand filter during operation has a special morphology,which is more conducive to removing Fe（Ⅱ）and iron sludge suspended matter from the influent.