at present, there are mainly the following treatment technologies for industrial wastewater.

1. Coagulation and sedimentation

Coagulation and sedimentation is a method of purifying industrial wastewater with coagulant. Coagulants usually include inorganic < P > polymer flocculants, organic polymer flocculants and biological polymer flocculants. At present, polyaluminium salts and composite polyaluminium salts in inorganic polymer flocculants are the most widely used in water treatment. Polyaluminum chloride (

PAC) and polyaluminum sulfate (PAS) are the two most widely used polyaluminum salts in industry. Their production processes are mature, and

their raw materials are widely available. Experiments show that PAC has high flocculation effect on petrochemical wastewater treatment, not only has high turbidity removal rate, but also has little influence on the pH value of raw water, and the treated water has good chromaticity, so it can be used as a flocculant for petrochemical wastewater recovery and treatment. The effect of turbidity removal and COD (chemical oxygen demand) removal is good (turbidity removal is less than 4 mg < P >/L and COD is less than 6 mg/L). The flocculation effect of PAS is much better than that of the traditional aluminum sulfate flocculant, and it is suitable for the flocculation treatment of drinking water, industrial water and most wastewater, and it can achieve good treatment effect in both turbidity removal and COD removal. In recent years, in order to improve the flocculation effect of single polyaluminum salt < P >, people have synthesized new polymer composite aluminum salt flocculants, such as polyaluminum ferric chloride (PAFC)

, polyaluminum ferric sulfate (PAFS), polyaluminum ferric sulfate (PAFCS), polyaluminum silicophosphate (iron < P >) and so on. These polymer composite aluminum salt flocculants are widely used to treat drinking water, industrial water, mine wastewater, oily wastewater from oil fields, domestic water, natural Yellow River water, Yangtze River raw water, printing and dyeing wastewater and so on.

second, adsorption method

adsorption method is to treat wastewater with adsorbent. At present, magnesium hydroxide, < P > activated cellulose carbon (ACF) and chitosan and its derivatives are widely used in industry. Magnesium hydroxide, as a waste water treatment agent in acid industry, has a wide range of applications, and can be used in papermaking and printing and dyeing wastewater, municipal domestic sewage, electroplating wastewater < P >, fluorine-containing wastewater, etc. It is safe and reliable, and its PH value will not exceed 9 even if it is neutralized excessively, and the neutralization process is gentle. < P > Precipitated grains are coarse and dense, and sludge is easy to filter and discharge. Because of its large specific surface area and strong adsorption capacity, it can adsorb and remove heavy metal ions such as Ni2+, Cd2+, Mn2+, Cr3+ and Cr6+which are harmful to the environment from different industrial wastewater. Magnesium hydroxide can also effectively remove ammonia and phosphorus from industrial wastewater and domestic sewage, reduce the eutrophication of rivers and other water systems, control the growth of algae, and be beneficial to ecological protection; Activated cellulose carbon (ACF

) is an efficient adsorption material, which is obtained by carbonization of natural fibers and man-made fibers. The micropore structure distribution is narrow and uniform, the volume of micropores accounts for about 91% of the total volume, the pore diameter is about 1nm, and it has a huge specific

surface area (2111m3/g), so it has strong adsorption capacity. It can make the water clear, remove the peculiar smell in the water, and adsorb the manganese and iron ions in the water with the best effect. The removal rate of CN-, Cl-, F- and phenol is above 98%, and it has a good filtering effect on bacteria. Compared with polymer flocculant, activated cellulose carbon has strong < P > regeneration ability, so it has a wide application prospect in water treatment industry. Chitosan is the main derivative of chitin, which contains active groups-amino group and hydroxyl group. It is a good flocculant and chelating agent, and has strong chelation to transition metal ions. It can remove precious metal ions such as copper, chromium, cadmium, mercury and zinc from industrial wastewater, and the removal rate of mercury ions is greater than 99. 8%, the removal rates of heavy metal ions Cr3+, Ni2+,

Cu2+ and Zn2+ in electroplating wastewater are all over 99%, and heavy metals can be recovered. Carboxymethylated derivatives of chitosan have remarkable decolorization effect on water-soluble dye wastewater, especially anionic dyes with good water solubility. The research shows that the treatment of printing and dyeing wastewater with carboxymethyl < P >-based chitosan not only has good decolorization effect, but also has fast flocculation speed, and the floc is not easy to break, which is superior to the synthesis of polymer organic flocculants, such as polyacrylamide (PAM) and alum. Using chitosan and its derivatives to treat food < P > wastewater or wastewater with high protein content can recover residues as feed without causing secondary pollution. The results show that the turbidity removal rate can reach 99.5% and the CODcr removal rate can reach 89.7% when it is used to treat the wastewater from monosodium glutamate plant. It can be used to treat the wastewater from soybean processing and food production, which can effectively flocculate and recover protein solids, and can also process the treated residue into feed or bait. In addition, it is also widely used in the treatment of organic substances (such as chlorophenol and biphenyl) in water, papermaking wastewater, municipal domestic sewage and seawater, and also used to treat red tide organisms and COD in seawater and algae substances in wastewater from fixed oxidation pond.

third, the biodegradation method.

At present, printing and dyeing wastewater and papermaking wastewater are two major factors that cause environmental pollution. At present, most of the dyes used are macromolecular aromatic compounds synthesized artificially, which are complex in structure and difficult to degrade. Dye industrial wastewater is dark in color. Although the chromaticity of dye wastewater treated by physical < P > method is greatly reduced, the removal rate of COD is poor, and the treatment cost is expensive < P >, and it is easy to cause secondary pollution. However, the organic matter synthesized by chemical method will poison the water body. Using biological degradation < P > method can not only overcome the above problems. ②

has the anti-inclusion effect on other microorganisms; (3) It can treat pollutants with heavy pollution and toxicity; ④ The degradation products have < P > broad spectrum. White rot fungi and Phanerochaete chrysosporium are two kinds of < P > strains that can degrade printing and papermaking wastewater containing essential elements.

iv. ion exchange resin method

ion exchange resin (IER) is a kind of synthetic functional polymer material containing active groups, which is formed by introducing ion exchange groups with different properties into cross-linked high

molecular polymers. Ion exchange resin has exchange. The functions of selecting, absorbing < P > and catalyzing are mainly used to recover heavy metals and precious and rare metals, purify toxic substances, and remove acidic or alkaline organic substances such as phenol, acid and amine in organic wastewater treatment. At present, ion exchange resins used in industrial wastewater treatment include anion exchange resin, cation exchange resin and zwitterion exchange resin. Using IER to treat industrial wastewater, not only the resin can be regenerated, but also the operation is simple, the process is mature and the process is short. At present, IER has been adopted by some large enterprises, and its application prospect is very good.

v. membrane separation technology

in industrial wastewater treatment, membrane separation technology can be used to treat all kinds of wastewater. Using ultrafiltration membrane to treat oily wastewater can make the oil removal rate reach 97%-111%. The gradient alumina membrane tube and inorganic membrane bioreactor < P > were used to treat domestic wastewater. The removal rate of BOD was 83%, the removal rates of COD, NH3-N and turbidity were over 96%, 95

and 98% respectively, and the removal rate of SS was 1.111%. Alkaline papermaking black liquor is treated by acid-alkali resistant inorganic membrane, and the p>PH value does not need to be adjusted. Useful components such as cellulose and lignin can be recovered by membranes with different pore sizes, and the treated water can be used for

cooking and pulping to realize closed-loop circulation of papermaking wastewater. The removal rates of CODCr

, S2- and Cr6+ in tannery wastewater were 86.14%, 88.39% and 54.5%, respectively. In addition, membrane technology can also be used to treat catering wastewater, pharmaceutical and chemical wastewater, dye wastewater and so on.