Introduction to Mine Wastewater Treatment Procedure
Currently, the neutralization precipitation procedure is the most extensively utilized method, involving the...
Introduction to Mine Wastewater Treatment Procedure
Currently, the neutralization precipitation procedure is the most extensively utilized method, involving the addition of alkaline neutralizing agents (such as alkali limestone, hydrated lime, limestone, blast furnace slag, NaOH, etc.) to wastewater to counteract the hydrogen ions within the wastewater. As the pH value of the wastewater ascends, soluble metal ions react with hydroxide ions to form hydroxide or carbonate precipitates with diminished solubility. Simultaneously, through physical adsorption and co precipitation, effective treatment of environmental concerns such as low pH value and excessive metal ions in coal mine acidic waste can be accomplished.
The sulfide precipitation methodology involves the introduction of sulfurizing agents to wastewater to form sulfide precipitates of metal ions in the wastewater. Commonly employed sulfurizing agents encompass sodium sulfide, sodium hydrosulfide, hydrogen sulfide, calcium sulfide, iron sulfide, etc. The sulfide precipitation method exhibits a high removal rate of heavy metal ions, robust adaptability to wastewater treatment, and is conducive to the recovery and utilization of heavy metals. However, the pH value is challenging to regulate, and the treatment cost is substantial. When the temperature is not adequately controlled, it is prone to generate hydrogen sulfide gas and contaminate the atmosphere.
The artificial wetland method is an innovative sewage treatment technique developed in recent years. Presently, it has been implemented in the treatment of acidic wastewater from coal mines. There are two primary methods for constructing wetlands: one is to categorize them into aerobic wetland method and anaerobic wetland method based on the distinct removal mechanisms of pollutants; Secondly, according to the diverse flow patterns of sewage, it can be divided into free surface flow constructed wetland method, horizontal subsurface flow constructed wetland method, and vertical subsurface flow constructed wetland method. The artificial wetland method for treating acidic coal mine wastewater primarily involves the oxidation and hydrolysis of metals, the reduction of sulfates by anaerobic bacteria, and the adsorption and exchange of metal ions by plants, algae, and organic matter.
There are two methodologies for grouting sealing: one is grouting filling layer grouting sealing, and the other is grouting sealing at the water inflow wellhead. Grouting filling layer grouting sealing is achieved by injecting grout into the grouting filling layer, forming a sealing surface layer post the grout solidifies, reducing the quantity of groundwater recharge from atmospheric precipitation to the abandoned underground goaf in the target area. Grouting and sealing of water inflow wellheads is executed in abandoned small coal mines with favorable maintenance conditions. Grouting materials are utilized to seal the wellheads or water inflow fissures, obstructing their water inflow into the external environment.
After comparing the construction investment, operating expenses, operational stability, broad application, and technological maturity of the four methods, the neutralization sedimentation method was ultimately selected for the treatment of coal mine wastewater in the city. To economize operating costs and eliminate sulfate ions from wastewater, lime method is predominantly used as the neutralizing agent. For coal mine wastewater with minimal pollution and low wastewater volume, limestone natural neutralization filtration method is employed for treatment. The facilities for solid-liquid separation in wastewater treatment primarily utilize two types: horizontal sedimentation tanks and inclined tube sedimentation tanks. The specific selection principles for each mine are: horizontal sedimentation tanks are favored for wastewater treatment stations with substantial sludge production to facilitate sludge discharge; If the site is relatively compact and the amount of sludge is not extensive, inclined tube sedimentation tanks are preferred.
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