Types of coal wastewater

Coal wastewater mainly comes from coal processing and production processes, with a wide variety of types, and the composition and characteristics of each type of wastewater are also different. The following are some main types of coal wastewater:

1. Coal selection wastewater: This type of wastewater mainly comes from the coal washing process, characterized by being neutral, with high suspended solids in the water, mainly containing dust, coal rocks, rock layers, etc. The mineralization degree of coal preparation wastewater is relatively low, but the content of suspended solids (SS) is high. Coagulation sedimentation, separation filtration and other methods are mostly used for treatment.

2. Acidic mine water: This type of wastewater mainly comes from the oxidation of pyrite coexisting with coal during the coal mining process, which produces sulfuric acid, leading to a decrease in its pH value. If discharged directly without treatment, it will lead to acidic surface water and affect the survival of aquatic animals and plants. During treatment, methods such as acid-base neutralization or wetland microbial ecological management are usually used.

3. Mineralized wastewater: Mineralized wastewater generally has high hardness, high inorganic salt content, and mostly tends to be neutral or alkaline. Direct emissions can lead to soil salinization and affect planting. In addition, this type of wastewater is prone to scaling in equipment, so desalination treatment is generally required. Common methods include ion exchange, electrodialysis, reverse osmosis, etc.

4. Coal chemical wastewater: According to the coal chemical production process, coal chemical wastewater mainly includes liquefaction wastewater, gasification wastewater, and coking wastewater. These wastewater contain complex chemical components such as sulfides, ammonia nitrogen, phenolic compounds, cyanide, etc., making treatment difficult. Among them, gasification wastewater generally contains organic pollutants such as ammonia nitrogen, phenols, and oils; The characteristic pollutants of coking wastewater are cyanide and phenolic compounds, which are toxic and difficult to degrade.

In addition to the main types of coal wastewater mentioned above, there are also coal to methanol wastewater, which also needs to be treated before discharge to avoid damage to the environment and ecology.

Overall, there are various types of coal wastewater and its treatment is quite complex. In order to protect the environment and ecological balance, it is necessary to choose appropriate treatment processes and technologies to effectively treat and utilize these wastewater.

Treatment methods for coal wastewater

The treatment of coal wastewater is a complex and important process, as different types of wastewater have different components and characteristics, requiring different treatment methods. The following are some common methods for treating coal wastewater:

1. Physical processing method:

Sedimentation method: To remove suspended solids and heavy metals from wastewater through physical means, including natural sedimentation and coagulation sedimentation.

Filtering method: using specific materials or devices to intercept suspended solids, particles, etc. in wastewater, achieving the goal of purifying water quality.

Adsorption method: Using the adsorption effect of adsorbents to remove harmful substances from wastewater, commonly used adsorbents include activated carbon, zeolite, etc.

Membrane separation technology: including microfiltration, ultrafiltration, reverse osmosis, etc., separates suspended solids, microorganisms, and dissolved substances in wastewater through the pore size and selectivity of the membrane, achieving deep purification and recycling of wastewater.

2. Chemical treatment method:

Chemical oxidation method: By adding oxidants (such as advanced peroxides, ozone, etc.), the reducing substances in wastewater are oxidized into harmless or low toxic substances.

Neutralization method: For acidic or alkaline wastewater, an appropriate amount of acid or alkali can be added to adjust its pH value to neutral or near neutral, in order to reduce the harm to the environment.

3. Biological treatment methods:

Activated sludge method: By cultivating and domesticating activated sludge, it has the ability to degrade organic matter, thereby achieving the goal of purifying wastewater.

Biofilm method: By cultivating and domesticating microorganisms in wastewater, a layer of biofilm is formed on the surface of the filler, and the microorganisms on the biofilm can degrade organic matter in the wastewater.

Anaerobic digestion method: Under anaerobic or low oxygen conditions, anaerobic microorganisms are used to convert organic matter in wastewater into gases such as methane, achieving wastewater treatment and energy recovery.

Advanced oxidation technology: using strong oxidants (such as ozone, hydrogen peroxide) or ultraviolet radiation to oxidize and degrade organic matter in wastewater, effectively removing difficult to degrade organic pollutants and toxic substances.

Electrochemical technology: Using the principle of electrolysis to convert harmful substances in wastewater into harmless or low toxicity substances, it is an emerging wastewater treatment technology.

In summary, various coal wastewater treatment methods can be used alone or in combination to achieve better treatment results. In practical applications, it is necessary to choose the most suitable treatment method or combination method based on factors such as the specific composition of wastewater, treatment requirements, and economic conditions. At the same time, with the continuous progress of technology, new methods and technologies for wastewater treatment are also constantly developing, providing more choices and possibilities for the treatment of coal wastewater.

The process flow of coal wastewater treatment

The process flow of coal wastewater treatment usually includes three stages: pretreatment, main treatment, and post-treatment. The specific content of each stage is as follows:

Pre processing stage:

1. Wastewater collection: Firstly, collect the wastewater generated during the coal mine production process in a centralized manner to ensure that the wastewater can fully enter the treatment system.

Coarse screen filtration: Preliminary filtration of large particle impurities, coal slag and other solid substances in wastewater through coarse screen or coarse grid to reduce the load in subsequent treatment processes.

2. Sedimentation tank: Utilizing equipment such as sedimentation tanks to remove sand particles and sediments from wastewater through gravity settling, avoiding blockage and wear on subsequent treatment equipment.

3. Oil water separation: If there is grease in the wastewater, it can be separated and removed through an oil-water separator using the difference in oil-water specific gravity.

Regulating tank: Adjusting the inflow to maintain stable inflow flow and concentration, which helps to ensure stable operation of subsequent treatment steps.

Main processing stage:

1. Coagulation sedimentation: Adding coagulants to coagulate suspended solids and colloidal substances in wastewater into larger particles, which are separated and removed through gravity sedimentation or flotation.

2. Aeration tank and activated sludge method: The pre treated wastewater is sent to the aeration tank, and sufficient oxygen is provided by the aeration equipment to promote the degradation of organic matter in the wastewater by microorganisms. At the same time, the activated sludge method is used to mix with the wastewater in the aeration tank for full contact and degradation, allowing for further removal of organic matter.

3. Sedimentation tank: Utilizing the principle of gravity sedimentation, activated sludge and other suspended solids settle at the bottom of the tank to form sludge. Clear water flows out from the top of the pool for further purification.

4. Filter tank: The settled clean water is sent into the filter tank, and through the filtering effect of the filter material layer, weak suspended solids and colloidal substances in the wastewater are removed to further improve the water quality.

Post processing stage:

1. Activated carbon adsorption: The water treated by the filter is sent to the activated carbon adsorption tank, and the organic matter in the water is adsorbed by activated carbon to improve the purification effect of water quality.

2. Disinfection treatment: The water adsorbed by activated carbon enters the disinfection tank and is disinfected by adding disinfectants (such as sodium hypochlorite) to kill bacteria, viruses, etc. in the water, ensuring that the water quality meets the discharge standards.

It should be noted that the specific process flow may vary depending on factors such as wastewater type, treatment objectives, and economic conditions. In practical applications, adjustments and optimizations need to be made according to specific circumstances to achieve the best processing effect.

Emission standards for coal wastewater

The discharge standards for coal wastewater usually follow national or regional laws and regulations to ensure that the impact of wastewater on the environment is minimized. The following are some common coal wastewater discharge standards and their main indicators:

1. Chemical Oxygen Demand (COD): This is the chemical oxygen required for the oxidation of organic compounds in wastewater. The discharge standards for coal mine wastewater generally require COD concentration to be below a certain limit value to ensure that the impact of wastewater on water bodies is minimal. The specific limit values may vary depending on the region and policy.

Suspended solids: The concentration of suspended solids in wastewater should comply with national or regional regulations, usually requiring discharge within a certain concentration limit range. Suspended solids include solid particles, coal dust, etc.

2. Total petroleum index (TPH): This is the total concentration of petroleum substances in wastewater, including crude oil, fuel oil, lubricating oil, etc. Wastewater discharge standards usually require TPH concentration to be below a certain limit value.

Sulfide: The concentration of sulfide in wastewater is generally limited to prevent adverse effects on the environment.

3. PH value: The pH value of wastewater must also meet certain requirements, usually requiring stability within a certain range.

In addition, according to the laws and regulations of different countries or regions, other parameters may also be restricted, such as ammonia nitrogen, heavy metals, nitrogen oxides, etc. It should be noted that the specific standards for coal wastewater discharge may vary depending on the specific situation of the country, region, and coal mine discharge.

In China, the discharge standard for coal industry wastewater adopts national standards, such as the Coal Industry Pollutant Discharge Standard (GB 20426-2006). These standards specify the requirements that wastewater discharge should meet, including the limiting values of the main indicators. To ensure that wastewater meets discharge standards, coal mining enterprises need to take corresponding wastewater treatment measures, such as physical treatment, chemical treatment, etc., to remove pollutants from wastewater and meet discharge standards.

Therefore, it is recommended that coal mining enterprises closely monitor the relevant laws, regulations, and standard requirements in their respective regions to ensure that wastewater discharge complies with regulations, in order to protect the environment and human health.