Industrial wastewater refers to the wastewater, sewage and waste liquid produced in the industrial production process, which contains industrial production materials, intermediate products, by-products and pollutants generated during the production process that are lost with the water. It causes environmental pollution, especially water pollution Important reason.
With the rapid development of industry, the types and quantities of industrial wastewater have increased rapidly. Although the treatment of industrial wastewater has been started as early as the end of the 19th century, there are still some technical problems that have not been completely solved due to the complex composition and variable nature. This article summarizes and summarizes ten common industrial wastewater treatment methods.
Treatment of heavy metal wastewater
Heavy metal wastewater is mainly from wastewater discharged by mining, smelting, electrolysis, electroplating, pesticide, pharmaceutical, paint, pigment and other enterprises. Among them, the heavy metals cannot be decomposed and destroyed by various common methods, but can only transfer their existence and change their physical and chemical forms.
The treatment of heavy metal wastewater can generally be divided into two categories: one is to convert the heavy metals in the wastewater in a dissolved state into insoluble metal compounds or elements, which can be removed from the wastewater by precipitation and floating, which can be neutralized by precipitation and sulfide precipitation Method, floating separation method, electrolytic precipitation method, membrane electrolytic method, etc .; Second, the heavy metals in the wastewater can be concentrated and separated without changing its chemical form. Reverse osmosis, electrodialysis, evaporation, and ion exchange can be used. Law, etc.
Treatment of cyanide-containing wastewater
The cyanide-containing wastewater mainly comes from electroplating, coal gas, coking, metallurgy, metal processing, chemical fiber, plastic, pesticide, chemical and other departments. It is a relatively toxic industrial wastewater. Cyanide is unstable in water and is relatively easy to decompose. The pollution of the electroplating wastewater containing cyanide to the environment and the harm to the human body are very serious.
The treatment methods of cyanide-containing wastewater include alkaline chlorination method, electrolytic method, pressurized hydrolysis method, biochemical method, biological iron method, ozone treatment method, and air stripping method. Among them, the alkaline chlorination method is widely used. It is a method to destroy cyanide by using chlorine-based oxidants such as sodium hypochlorite, bleaching powder, and liquid chlorine under alkaline conditions.
Treatment of phenolic wastewater
The phenol-containing wastewater mainly comes from the production processes of petroleum cracking to produce ethylene, synthetic phenol, polyamide fibers, synthetic dyes, organic pesticides and phenolic resins. The main pollutant in phenol-containing wastewater is a phenol-based compound, which is a protoplasmic toxicant that solidifies proteins.
Generally, phenol-containing wastewater with a mass concentration higher than 1000 mg / L is referred to as high-concentration phenol-containing wastewater, and phenol must be recovered before treatment; phenol-containing wastewater with a mass concentration lower than 1000 mg / L is referred to as low-concentration phenol-containing wastewater. Phenol is recycled after concentration and recovery. The methods for recovering phenol include solvent extraction method, steam stripping method, adsorption method and closed cycle method. Wastewater with a phenol mass concentration below 300mg / L can be treated or discharged by biological oxidation, chemical oxidation, physical chemical oxidation and other methods.
Treatment of paper industry wastewater
Papermaking wastewater mainly comes from the two processes of pulping and papermaking in the paper industry. Both processes discharge a large amount of wastewater. Papermaking wastewater has complex components and poor biochemical properties, and is a difficult industrial wastewater to treat.
Papermaking industry wastewater usually uses flotation to recover fibrous solid matter in white water, combustion method to recover sodium salt in black water, neutralization method to adjust the pH value of wastewater, coagulation sedimentation to remove suspended solids in wastewater, and chemical precipitation method to Decoloration, aerobic activated sludge treatment, and fungal treatment generally also give better results. In addition, treatment methods such as reverse osmosis, ultrafiltration, and electrodialysis are also applied.
Treatment of printing and dyeing industry wastewater
Printing and dyeing wastewater has the characteristics of large amount of water, high content of organic pollutants, large alkalinity, and large changes in water quality. It contains dyes, pastes, additives, oil agents, acids and alkalis, fiber impurities, sand substances, inorganic salts, etc. A more difficult type of industrial wastewater to treat.
Printing and dyeing wastewater can be recycled according to water quality characteristics, such as the diversion of bleaching and cooking wastewater and dyeing and printing wastewater to reduce emissions. Harmless treatment can be divided into physical treatment, chemical treatment and biological treatment. Physical treatment methods include precipitation method and adsorption method, chemical treatment methods include neutralization method, coagulation method and oxidation method, and biological treatment methods include activated sludge, biological disk, biological drum and biological contact oxidation method.
Chemical industry wastewater treatment
Chemical industry wastewater mainly comes from the production wastewater discharged from petrochemical industry, coal chemical industry, acid and alkali industry, chemical fertilizer industry, plastic industry, pharmaceutical industry, dye industry, rubber industry and so on.
Chemical industry wastewater is generally divided into three levels of treatment. The primary treatment mainly separates suspended solids, colloids, oil slicks, or heavy oils in water, and can use natural precipitation and floating methods. The secondary treatment is mainly to remove biodegradable organic dissolved matter and some colloids, usually biological Tertiary treatment is mainly to remove organic pollutants and soluble inorganic pollutants that are difficult to biodegrade in wastewater. Common methods include activated carbon adsorption method and ozone oxidation method.
Treatment of food industry wastewater
Food industry wastewater is characterized by high organic matter and suspended matter content, easy to spoil, and generally has no major toxicity. Its harm is mainly to make the water body eutrophic, which will cause the death of aquatic animals and fish, promote the odor of organic matter deposited on the bottom of the water, deteriorate the water quality and pollute the environment.
Food industry wastewater is generally suitable for biological treatment. If the effluent water quality is high or the organic matter content in the wastewater is high, a two-stage aeration tank or a two-stage biological filter, or a multi-stage biological turntable, or a combination of two This kind of biological treatment device can also adopt anaerobic-aerobic biological treatment system.
Treatment of metallurgical wastewater
There are many products in the metallurgical industry, and the production processes are in series. The main characteristics of metallurgical wastewater are large amounts of water, many types, and complex and variable water quality. It is one of the main wastewater polluting the environment. According to the sources and characteristics of wastewater, there are mainly cooling water, pickling wastewater, washing wastewater, slag washing wastewater, coking wastewater, and wastewater condensed, separated or overflowed during production.
Generally, the metallurgical wastewater is treated by the redox method, that is, the toxic and harmful substances dissolved in the wastewater are converted into non-toxic and harmless new substances through the redox reaction. In the redox reaction, when toxic and harmful substances are used as reducing agents, oxidants such as air, ozone, chlorine, and sodium hypochlorite need to be added; when toxic and harmful substances are used as oxidants, reduction by adding ferrous sulfate, ferrous chloride, zinc powder, etc Agent.
Treatment of beneficiation wastewater
The ore dressing wastewater includes ore dressing process drainage, tailing pond overflow water and mine drainage, and contains many types of harmful substances. The pollutants in beneficiation wastewater mainly include suspended solids, acids and alkalis, heavy metals, beneficiation agents, chemical oxygen-consuming substances and other pollutants.
For the pollutants in the wastewater, different treatment methods can be adopted separately. Suspended matter mainly adopts pre-precipitation, coagulation / precipitation method; acid and alkaline wastewater adopts mutual neutralization method; heavy metal ions can use co-precipitation technology, adsorption technology, ion exchange method, etc .; Biodegradation, advanced oxidation, adsorption methods, etc.
Treatment of acid and alkali wastewater
Acid wastewater mainly comes from steel plants, chemical plants, dye plants, electroplating plants and mines, etc .; alkaline wastewater mainly comes from printing and dyeing plants, leather mills, paper mills, oil refineries, etc. In addition to acid and alkali, acid and alkali wastewater often contains acid salts, basic salts, and other inorganic and organic substances, which is highly corrosive.
High-concentration acid and alkali wastewater should be prioritized for recycling. According to water quality, water volume and different process requirements, factory or regional scheduling should be carried out to reuse as much as possible; low-concentration acid and alkali wastewater should be neutralized, such as acid and alkali wastewater mutually Neutralize or use waste alkali (slag) to neutralize acidic wastewater, and use waste acid to neutralize alkaline wastewater.