Sources and characteristics of wastewater generated in the coal chemical process
The coal chemical industry uses coal as raw material and adopts a series of chemical methods for processing. In the entire process of coal processing into liquid fuels, solid fuels, or chemical products, there are many chemical processes that will produce a large amount of wastewater, that is, chemically polluted wastewater. These wastewaters contain strong toxicity or corrosiveness. Tar, sulfide, and other substances have pollution. Chemically polluted wastewater has three characteristics. First, it will not be degraded. These substances have a stable structure and are difficult to degrade.
Second, the volume is large and the degree of turbidity is high, and wastewater will be generated in each process of production. When the wastewater is finally merged together, the volume of the wastewater is particularly large and the color is particularly dark. Third, the composition of wastewater is complex, and the composition of wastewater produced by each process is different, which makes it difficult to handle.
The importance of treating chemically polluted wastewater from the coal chemical industry
With the development of the chemical industry, the types and volumes of wastewater continue to increase, which will not only pollute water resources but also endanger human health and safety. Chemically polluted wastewater is more critical than the treatment of municipal sewage. The composition of chemically polluted wastewater is very complex, and the treatment is difficult and costly.
Toxic raw materials can be replaced with non-toxic ones, reducing the amount of toxic wastewater. Use scientific operating procedures and equipment to reduce the use of toxic raw materials. Heavy metal wastewater, radioactive wastewater, and organic toxic wastewater that are difficult to biodegrade should be treated separately from other wastewater, using a closed cycle system.
At the same time, the factory can properly treat it, and then discharge it into the sewer after it is qualified, and the less polluted wastewater can be filtered and recycled, which can save water resources.
Coal chemical pollution wastewater treatment technology
3.1 Pre-wastewater treatment technology
3.1.1 Bubble float
The bubble float method mainly removes and recovers oily substances, makes chemically polluted wastewater generate air bubbles, makes oily substances stick to small air bubbles, and then discharges all air bubbles through certain methods, thereby separating oily particles. The use of the bubble float method can effectively separate the suspended solids, and the remaining scum can be filtered and reused, but it should be noted that the bubble float method is not a panacea, it can only deal with oily substances, and other methods need to be used comprehensively.
3.1.2 Coagulation sedimentation method
This method is used to treat the organic matter in wastewater. The suspended solids in the wastewater are separated from the liquid by gravity, and coagulants such as iron salt, polytron, aluminum salt, and polyaluminum are added to the chemical wastewater to achieve the effect of organic matter precipitation. When choosing the coagulation sedimentation method, the composition of chemical wastewater should be analyzed, and the dosage and type of coagulant should be determined according to the index of pH. The coagulation sedimentation method is simple in operation, low in cost, and can be treated in a large area, but it has no effect on COD (chemical oxygen demand).
3.1.3 MPA chemical precipitation
This method can effectively remove nitrogen and ammonia from wastewater. The wastewater contains insoluble substances such as magnesium ammonium phosphate or zinc ammonium phosphate. It is necessary to add some substances that can precipitate nitrogen and ammonia, such as disodium hydrogen phosphate, magnesium chloride, and precipitation. The English abbreviation of substance is MAP, so this method is called the MAP precipitation method. The process flow of this method is relatively simple, and the effect is relatively obvious. It will not be disturbed by toxins and temperature and will be completely removed without subsequent pollution.
3.1.4 Extraction and dissolution method
The extraction and dissolution method is mainly to remove and recover the phenolic components in the wastewater by extraction and dissolution. The phenolic components are more difficult to dissolve in water than some solvents. This is the basis for the extraction and dissolution method. The extraction equipment performs distillation to separate the phenol component from the solvent so that the extractant can be recycled and the purpose of separating phenol can be achieved at the same time.
3.2 Biochemical treatment technology
3.2.1 Sequential batch activated sludge process (SBR process)
The SBR process mainly includes five operational processes: water injection, chemical reaction, precipitation, sewage discharge, idle, and so on. The process has functions such as biodegradation, sedimentation, chemical reaction, and final sedimentation. It is intelligently implemented using high-end equipment and does not need to build a sewage and sediment return system. The SBR process has a very good chemical reaction function and wastewater treatment function. shock.
3.2.2 Immobilized biological methods
This technology can effectively treat the refractory toxic substances in chemically polluted wastewater. It is a newly developed wastewater treatment technology, which is selective and targeted when fixing certain organisms. The immobilized biological method can improve the cell purity and cell concentration of microorganisms, promote the maintenance of vitality of dominant bacteria, and reduce sludge production.
3.2.3 Hypoxic and aerobic technology (A2O process)
Hypoxic and aerobic technology has obvious effects on the treatment of organic matter and ammonia nitrogen in coal chemical wastewater. It is an improved treatment method for the anaerobic-aerobic process (AO process), mainly by adding an anaerobic tank before the anoxic tank. pool.
3.3 Deep processing technology
3.3.1 Activated carbon treatment technology
Activated carbon is a porous black carbon with strong adsorption, which is often used as an adsorbent in coal chemical processing. This method is also called the activated carbon adsorption method. It makes full use of its adsorption properties to carry out in-depth treatment of chemically polluted wastewater. Lactone, hydroxyl, and other substances on the surface of activated carbon have a good removal effect. Put 1g in wastewater with a pH of 6. The activated carbon will have the effect of almost complete removal.
3.3.2 Humidity Catalytic Oxidation Technology
Humidity catalytic oxidation technology is mainly to oxidize chemically polluted wastewater, but it must be carried out in a high temperature and high-pressure environment to convert chemical industrial wastewater into non-toxic and harmless substances such as nitrogen, CO2, and H2O. Humidity catalytic oxidation technology is generally used for the treatment of insoluble, toxic, and high-concentration chemical wastewater. This technology is easy to operate, practical, efficient, and has many uses, but the cost of investment will be higher than other technologies, and the requirements are strict.
3.3.3 Ozone oxidation technology
The operation process of ozone oxidation technology is to separate the phenolic components of wastewater, then adjust the pH, and then oxidize ozone and wastewater together through an oxidizer. Ozone oxidation technology has the advantages of short time, fast reaction, and no residue. It should be noted that ozone is inconvenient to store and should be used in time. In addition, the amount of ozone is not easy to control, the adaptability to water properties is weak, and it is expensive and costly high.
This paper mainly expounds on the source and characteristics of wastewater produced in the coal chemical industry, expounds on the importance of treating chemically polluted wastewater from the coal chemical industry, and analyzes the treatment technology of chemically polluted wastewater. Pre-wastewater treatment technology, biochemical treatment technology, and advanced treatment technology are three representative treatment technologies, and they include many sub-treatment technologies. People should comprehensively use various sewage treatment technologies to treat chemically polluted wastewater, so as to protect the ecological environment and achieve the harmonious development of man and nature.