Wetland Purification Of Coal Mine Wastewater

The pollution of mine wastewater is one of main environmental problems in mine. Coal exploitation quantity and mine drainage as the main mine wastewater are increasing, as economy is developing continuously. Containing a lot of pollutants, such as heavy metal, suspended matter and fiuorin, the mine wastewater is usually high salinity and acidity. Lots of mine drainage without treated is perennially draining, which leads to not only tremendous cost, damage of the farming and water environment but a great waste of water resource. The other mine drain is treated by wastewater treatment plant, which has many problems, such as high cost, huge land-occupying, secondary pollution and inharmony with natural environment. Henan Province, as the main coal exploitation province in our country, annually produces huge amounts of mine wastewater. But recent treatment effect and program cannot meet requests of environment-friendly and resource-saving society. Hence it has important significance to the researching ideas and methods of treating mine wastewater and wastewater resource recovery.Pollution is that human action disturbs the distribution of elements according to eco-geological theories. Based on the essence of mine wastewater pollution, the thought of mine wastewater treatment should be that the structure of geo-environment system in coal mine is changed, to speed up the natural sediment rate of elements, such that the originally underground elements go back to be mineralized and imbedded as quickly as possible. But actual methods are almost conventional, that is to say, human set up all kinds of reactors in which reagents react to pollutants for changing the existing form of harmful compositions and reducing or avoiding pollution harm. However, the methods may bring a series of negative effects, for example, the new resultants may become the new pollutants which lead to secondary pollution, and even bring more complicated ecological negative effect because composition ratios change in eco-system. So the natural methods, such as wetlands-using, are tried to treat wastewater, to avoid the above disadvantages.Whereas there are many difficulties in wetlands-using for waste water, especially for coal mine drainage. The present evaluation method of wetland purification depends on long-term data, can not forecast the purification capability of conceptive wetland; in the design phase of wetlands the parameters about hydraulics and chemistry are usually received considerable attentions, but the researches on the key factors of purification, such as plants and sediment, are insufficient, the studies on sulfur are much less. Furthermore the known researches and methods do not be synthesized. Radically, the reason of the problems is that the eco-geology study about the structure of wetland eco-system is lacking.On the basis of considering the above problems, the dissertation puts forward the thought of waste treatment in the guidance of system-thinking and eco-geology theories. The pollution of mine wastewater is considered as the result that artificial geological agents disturb natural distribution of elements. Constructed wetlands can speed up the sediment of pollutants to purify wastewater, through combining and cooperating physical, chemical and biological functions. The research area is located in Dayugou Mine, Henan Province. After field investigation and laboratory analysis, the factors and structure of wetland eco-system are analyzed. The absorption and containing capability of wetland plants and sediment, especially about sulfur, is comparatively particularly researched for the first time. The paper synthesizes several subjects, brings forward the new evaluated method of the wetland purification. Then according to the characteristics of the main pollutant in wetlands, the suggestions of reconstructing wetland are made. The purification capability of the wetland in future is forecasted. The research contents and conclusions are as follows:A. Eco-geology essence of mine waste is discussed. When mines are exploited, all kinds of underground elements are quickly taken to the ground and then go into the cycle system of matter and energy on the surface. 'Old matter' on the ground strongly disturbs the modern natural-matter movement and bio-activity. The new distribution of elements affects people's normal work and life.B. According to the analysis of pollution essence, the thought of waste treatment based on geology theory is put forward. Wastewater takes underground matter to surface by disturbing natural cycle. Therefore the thought of mine wastewater treatment should be that ground matter is imbedded as quickly as possible through natural cycle that human speed up. First, wastewater with pollutants must be insulated as much as possible and be limited in the bottomland near the outfall and be far away from densely populated area, namely, local sink areas, to avoid diffusion. Second, wastewater is treated in wetland by the compositive means including physics, chemistry and biology.C. After the eco-geology investigations of flow, sediment and plants are finished in Dayugou Wetland, the containing gross of every element in the plants and sediment is obtained. The new evaluation method of the wetland purification is created. Then by the method purification capability of each element in present wetland is counted.D. The main pollutant is SO₄^2-. On the basis of mechanism of desulfurization in wetland, the paper makes the suggestions of reconstructing wetland. In the end, the purification capability of the wetland in future is forecasted. The results show that after restructuring the desullwization capability of the whole wetland will increase by 22.818-30.212t/a; removing gross of SO₄^2- will be up to 307.495-477.165t/a. By then, the past mine wastewater will become fresh water from light saline water, which achieves wastewater resource recovery.