Evaluation Of Goaf Water Quality In Datong Kouquangou-Yunganggou Coal Mine

Datong City is located in the Loess Plateau of northern Shanxi Province which is drought,little rain and fragile ecology.It is one of the cities with sierious water shortage in China.Datong Coalfield is an important base for coal energy in China.With the large-scale development of coal mines and the increase of water in the goaf,the safety of coal mine production is seriously threatened.Therefore,the utilization of water resources in the goaf can alleviate the water supply tension in the city and the mining area,and also reduce the safety threat to the adjacent or similar mining face in the goaf.In this paper,the goaf water in Kouquangou-Yunganggou mining area of Datong coalfield is taken as the research object.The geological and hydrogeological conditions in the study area were analyzed.Combined with the results of the water sample test,the water chemistry characteristics and the water quality evaluation were carried out.Based on this,the coagulation and iron removal experiments were carried out,and the treatment process of the separated water supply was proposed.This paper draws the following conclusions:（1）Through the analysis of the conventional components of the water in the goaf,it can be known that the water in the goaf of the coal mine is mainly slightly alkaline salt water.The main cation content changes to Na⁺>Ca²⁺>Mg²⁺>K⁺.The main anion content changes to SO₄^2->HCO₃^->Cl^->NO₃^-.Na-Ca-Mg-SO₄ and Ca-Mg-Na-SO₄ are the main water chemistry types in the goaf.（2）Using Gibbs graph analysis,it is concluded that rock weathering and dissolution is an important controlling factor for the chemical composition of water in the goaf.Analysis of the ion scale coefficient map shows that rock salt dissolution is not the only factor controlling the Na⁺content,and there may be other mechanisms increase the Na⁺content in the goaf water.The dissolution of gypsum,dolomite and calcite is the main source of Ca²⁺and Mg²⁺in the goaf.（3）Using the single factor evaluation method,it is shown that the indicators exceeding the standard in the water body under different evaluation criteria are mainly chromaticity,suspended matter,iron and so on.Using the Nemero evaluation method,it is known that 80%of the water in the goaf is used for landscape entertainment and is in good grade and above.When goaf water is used in industry,it is 78%in good grade or above.Goaf water is in good grade or above when used for farmland irrigation.According to the results of the fuzzy comprehensive evaluation method,12%of the water in the goaf is Grade I water,36%is Grade III water,12%is Grade IV water,and40%is Grade V water.（4）According to the water quality evaluation results of water supply in goaf,the removal experiments of suspended solids and iron were carried out,and the coagulant dosage,mixing time and mixing speed at the best removal rate were obtained respectively.On this basis,the process flow of water treatment in goaf was put forward,and the main structures were selected.Figure 16 table 18 reference 78...