Water pollution in coal mines can be roughly divided into mineral pollution, organic matter pollution and pollution caused by bacteria. Mineral pollution is divided into sand dust, soil, mineral impurities, dust, dissolved salts, acidic and alkaline pollution, etc. Organic matter pollution is divided into coal particles, oil pollution, metabolites of biological life, wood and others.

The products of oxidation of substances; bacterial pollution mainly comes from the pollution of rock powder, coal powder, etc. During development, mining and transportation, which makes the water appear gray and black, turbid, and oil stains suspended on the water surface, while emitting A trace of fishy odor and the smell of decaying living organisms.

Properties of coal washing wastewater

Coal washing wastewater is composed of primary coal slime, secondary coal slime and water. Coal washing wastewater contains slime particles (coarse slime particles 0.5~1mm, fine slime particles 0~0.5mm), minerals, clay particles, etc. Coal washing wastewater generally has the characteristics of high concentrations of SS, CODcr, and BOD5. Therefore, the coal slime water not only has the properties of a suspension, but also often has the properties of a colloid; fine coal slime particles, clay particles, etc. are very small in size and are not easy to settle. These properties determine that this type of wastewater is highly polluted and difficult to treat.

Coal washing wastewater treatment technology

When treating coal washing wastewater, a certain amount of coagulant must be added to the wastewater, which can reduce its potential, destroy the stability of the colloidal particles in the wastewater, and thereby separate mud and water. According to the nature of coal washing wastewater, you can choose to use inorganic agents, but the diameter of the particles formed is relatively small, the settling speed is also very slow, and its filtration performance is also poor, which adds a certain degree of difficulty to further dehydration treatment and requires flocculation. agent.

The chemical composition of lime and carbide slag is basically the same, both are calcium oxide, but carbide slag is an industrial waste, its cost is very low, and general coal mines have this kind of industrial waste, so carbide slag is the most suitable as a coagulant. Carbide slag can cause damage to the stability of coal washing wastewater and can cause coal slime particles to agglomerate and settle. However, because its settling speed is relatively slow, flocculants need to be added to increase the settling speed, which can change the settling performance.

Non-ionic PAM is more suitable as a flocculant. The addition amount of carbide slag and PAM, as well as the stirring time and speed have an impact on sedimentation. Using carbide slag combined with PAM to treat coal washing wastewater can not only separate about 40% of clean water, but also the COD concentration and SS concentration in the clean water are lower than the coal mine coal washing wastewater discharge standards and reuse standards. At the same time, the filtration performance of the flocs can also be greatly improved, thus creating favorable conditions for further dehydration of coal slime.

The separated clean water can be reused for coal washing, which not only saves water resources, but also saves water bills for enterprises. Moreover, enterprises can recycle coal slime every year and obtain considerable economic benefits. By treating coal washing wastewater, they can also avoid high fees. The economic benefits obtained through the sewage discharge fee can not only offset the operating costs of treating wastewater, but also obtain additional economic benefits.