Overview of Industrial Wastewater 　　Industrial wastewater refers to the wastewater, sewage, and waste liquid generated during the industrial production process, which contains industrial production materials, intermediate products, and products that are lost with water, as well as pollutants generated during the production process. Industrial wastewater is usually divided into the following three types:
　　The first type is classified according to the chemical properties of the main pollutants contained in industrial wastewater. Inorganic wastewater mainly contains inorganic pollutants, while organic wastewater mainly contains organic pollutants. For example, electroplating wastewater and mineral processing wastewater are inorganic wastewater; Wastewater from food or petroleum processing is organic wastewater.
　　The second type is classified according to the products and processing objects of industrial enterprises, such as metallurgical wastewater, papermaking wastewater, coking gas wastewater, metal pickling wastewater, chemical fertilizer wastewater, textile printing and dyeing wastewater, dye wastewater, leather wastewater, pesticide wastewater, power plant wastewater, etc.
　　The third type is classified according to the main components of pollutants in wastewater, such as acidic wastewater, alkaline wastewater, cyanide containing wastewater, chromium containing wastewater, cadmium containing wastewater, mercury containing wastewater, phenol containing wastewater, aldehyde containing wastewater, oily wastewater, sulfur-containing wastewater, organic phosphorus containing wastewater, and radioactive wastewater. Classification of wastewater treatment According to the principle of wastewater treatment:
　　·Physical method: Using physical effects to separate suspended pollutants from wastewater, without changing the properties of the pollutants during the treatment process.
　　·Chemical method, physical chemical method: a method of removing pollutants from wastewater by using a certain chemical reaction to change their properties or forms.
　　·Biochemical method (biological method): a method of using microorganisms to remove colloids and dissolved organic matter from wastewater.
According to the degree of wastewater treatment:
　　·First level processing (including pre-processing)
　　·Secondary treatment (biological treatment)
　　·Third level processing (deep processing)

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wastewater treatment process

　　The treatment of industrial wastewater can currently be divided into the following methods:
　　oneMembrane separation method
　　In industrial wastewater treatment, membrane separation technology can be used to treat various types of wastewater. Using ultrafiltration membranes to treat oily wastewater can achieve a removal rate of 97% -100% for oil. Using acid and alkali resistant inorganic membranes to treat alkaline papermaking black liquor does not require adjusting the pH value. By utilizing membranes with different pore sizes, useful components such as cellulose and lignin can be recovered. The treated water quality can be used for steaming, pulping, and achieving closed-loop circulation of papermaking wastewater; The mud film mixing process was used to treat tannery wastewater, with removal rates of 86.14%, 88.39%, and 54.5% for CODCr, S2-, and Cr6+, respectively. In addition, membrane technology can also be used to treat wastewater from catering, pharmaceutical and chemical industries, dye wastewater, etc.

　　IIIon exchange resin method
　　Ion exchange resin has the ability to exchange. The functions of selection, adsorption, and catalysis are mainly used in industrial wastewater treatment to recover heavy metals and precious rare metals, purify toxic substances, and remove acidic or alkaline organic substances such as phenols, acids, and amines from organic wastewater. The application of IER for industrial wastewater treatment not only allows for resin regeneration, but also has simple operation, mature process conditions, and short flow. It has been adopted by some large enterprises and has a promising application prospect. 　　IIIBiodegradation method
　　At present, printing and dyeing and papermaking wastewater are the two main factors causing environmental pollution. The dye industry wastewater has a deep color. Although the color reduction of dye wastewater treated by physical methods is significant, the removal rate of COD is poor, and the treatment cost is expensive, which can easily cause secondary pollution. Organic compounds synthesized by chemistry can cause poisoning of the water body. Using biodegradation method not only overcomes the above problems, but also has the following advantages: ① No pre-treatment of pollutants is required; ② Has anti microbial properties against other microorganisms; ③ Can handle pollutants with heavy pollution and high toxicity; ④ Degradation products have broad-spectrum properties. White rot fungi and Aspergillus flavus are two excellent bacterial strains that can degrade wastewater containing essential elements from printing and dyeing papermaking. 　　4coagulant sedimentation
　　Coagulation precipitation method is a method of purifying industrial wastewater using coagulants. There are usually three categories of coagulants: inorganic polymer coagulants, organic polymer coagulants, and biopolymer coagulants. At present, the most widely used inorganic polymer flocculants in water treatment are polyaluminum salts and composite polyaluminum salts. Polyaluminum chloride (PAC) and polyaluminum sulfate (PAS) are the two most widely used polyaluminum salts in industry. Experimental results have shown that PAC has an efficient flocculation effect on the treatment of petrochemical wastewater. It not only has a high turbidity removal rate, but also has a small impact on the pH value of the raw water. The color of the treated water is good, and it can be used as a flocculant for the recovery and treatment of petrochemical wastewater. The treatment of river water with it has good results in removing turbidity and COD (chemical oxygen demand) (turbidity less than 4mg/L, COD less than 6mg/L). The flocculation effect of PAS is significantly better than that of traditional aluminum sulfate flocculants. It has a wide temperature range and is suitable for flocculation treatment of drinking water, industrial water, and the vast majority of wastewater. Using PAS to treat river water can achieve good treatment results in both turbidity removal and COD removal. In recent years, in order to improve the flocculation effect of single polyaluminum salts, new types of polymer composite aluminum salt flocculants have been synthesized, such as polyaluminum ferric chloride (PAFC), polyaluminum ferric sulfate (PAFS), polyaluminum ferric chloride sulfate (PAFCS), polyaluminum silicate (phosphate) (iron), etc. These polymer composite aluminum salt flocculants are widely used to treat drinking water, industrial water, mine wastewater, oilfield oily wastewater, domestic water, natural Yellow River water, Yangtze River raw water, printing and dyeing wastewater, etc.