CN-118005204-B - Treatment method of coating wastewater

Abstract

The invention discloses a method for treating coating wastewater, which is characterized in that high-concentration degreasing wastewater, low-concentration electrophoresis wastewater, surface-conditioning wastewater and washing wastewater are collected separately, the coating degreasing wastewater is treated by an acid washing precipitation method, the degreasing wastewater after acidification demulsification treatment is mixed with the rest of other wastewater and then treated by a Fenton oxidation and neutralization flocculation precipitation method, so that the treatment difficulty of the wastewater is reduced to a certain extent, the running cost of the coating wastewater is reduced, and a new thought is provided for preventing and treating water pollution in the vehicle coating industry.

Inventors

• JIANG YANG
• ZHANG YU
• DAI JIANJUN
• YANG FENG

Assignees

• 江苏南大华兴环保科技股份公司

Dates

Publication Date

20260512

Application Date

20221028

Claims (8)

1. 1. A method for treating coating wastewater, characterized in that the method for treating coating wastewater comprises the following steps: s1, performing acidification demulsification treatment on wastewater, wherein the wastewater is degreasing wastewater generated in the coating process; The degreasing wastewater contains 900-1200 mg/L of emulsified oil, 300-400 mg/L of surfactant, 2000-2500 mg/L of COD, 80-100 mg/L of phosphorus and not more than 20mg/L of zinc; then, introducing low-concentration wastewater into the effluent of the acidification demulsification treatment; wherein the input amount of the low-concentration wastewater is 3-4 times of that of the wastewater in the S1; the low-concentration wastewater comprises any one or more than two of electrophoresis wastewater, surface conditioning wastewater and washing wastewater generated in the coating process; s2, fenton oxidation treatment is carried out on the effluent after acidification demulsification treatment; S3, flocculating and settling the effluent after Fenton oxidation treatment; In the step S1, the pH value of the wastewater is regulated to be less than or equal to 2 by using acid liquor to form a solid-liquid blend, and solid-liquid separation is carried out to obtain the effluent of the acidification demulsification treatment.
2. 2. A method for treating coating wastewater according to claim 1, wherein, In the step S1, aeration treatment is performed.
3. 3. A method for treating coating wastewater according to claim 1, wherein, In the step S2, ferrous ions and hydrogen peroxide are added for Fenton oxidation treatment; the addition amount of the ferrous ions is 0.04-0.1 times of the COD amount; The mass ratio of the hydrogen peroxide to the ferrous ions is (5-8) to 1.
4. 4. A method for treating coating wastewater according to claim 3, wherein, In S2, the addition amount of the ferrous ions is 0.1-0.2 g/L.
5. 5. A method for treating coating wastewater according to claim 1, wherein, In the step S3, lime and flocculant are added for flocculation treatment, wherein, The addition amount of the lime is 8-10 g/L; The addition amount of the flocculant is 0.2-0.5 g/L.
6. 6. The method for treating coating wastewater according to any one of claims 1 to 5, characterized in that, In the step S1, solid-liquid separation is carried out to obtain effluent water and sludge of acidification demulsification treatment; carrying out filter pressing treatment on the sludge to obtain filtrate; And refluxing the filtrate to the effluent of the acidification demulsification treatment.
7. 7. A method for treating coating wastewater according to claim 6, wherein, The electrophoresis wastewater contains 200-250 mg/L of COD and 8-10 mg/L of phosphorus; The surface-modified wastewater contains 10-20 mg/L of surfactant, 20-50 mg/L of COD, 100-150 mg/L of phosphorus and not more than 2mg/L of zinc; The water washing wastewater contains 30-50 mg/L of surfactant, 90-100 mg/L of COD, 30-50 mg/L of phosphorus and nickel, manganese and zinc which are not more than 12mg/L in total.
8. 8. The method for treating coating wastewater according to any one of claims 1 to 5, characterized in that, The method also comprises the steps of: S4, filtering the effluent after flocculation and precipitation treatment.

Description

Treatment method of coating wastewater Technical Field The invention relates to the technical field of industrial wastewater treatment, in particular to a treatment method of coating wastewater. Background In recent years, the industrial development of China is rapid, the development of the coating industry is correspondingly driven, and a large amount of wastewater, such as electrophoresis wastewater, degreasing wastewater, surface-conditioning wastewater, washing wastewater and the like, is generated in the process of machining and manufacturing mechanical equipment by a coating process. Typically, in the production process of automobile parts, in order to ensure attractive appearance, performance and corrosion resistance of steel, automobile coating is a main measure for protecting and decorating automobiles, and is also an important link in the production process of automobiles, the assembled and exposed steel plate automobile body is subjected to a series of chemical corrosion protection treatments, and finally a plurality of layers of chemical coatings and related protection media are formed on the surface of the whole automobile steel plate substrate, including inner cavities, and the main functions of the coating are to prevent the corrosion of the steel plate of the automobile body and beautify the appearance of the automobile body. The automobile coating process flow comprises pretreatment, electrophoretic coating, electrophoretic polishing, PVC material sealing, middle coating polishing, color paint coating, varnish coating, baking, finishing and delivery, spot repair process, threshold black paint, cavity wax injection, final assembly repair and the like. The coating wastewater mainly comes from the pretreatment process (pre-degreasing, surface conditioning, phosphating, passivation and the like), the cathode electrophoresis process and the intermediate coating and finish spraying process of the automobile body. Degreasing agents, phosphating agents, surface conditioning agents, phosphoric acid and the like are main pollutants of automobile coating wastewater. Based on the method, the coating wastewater has the characteristics of multiple wastewater types, complex components, uneven water quality, high pollutant concentration, poor biodegradability and the like, and if the coating wastewater is not properly treated, serious pollution to the environment can be caused. The conventional treatment process of the coating wastewater mainly adopts a physical treatment method, a chemical treatment method, a biological treatment method, a physicochemical method and the like, wherein the physical treatment method comprises a separation method, a filtration method, a centrifugal separation method and the like, the chemical treatment method mainly comprises a neutralization method, a coagulation method, a redox method and the like, namely, corresponding acid-base, flocculating agent, oxidant, reducing agent and the like are added into the wastewater, the biological treatment method is also called a biochemical method, and is a metabolism process of utilizing microorganism groups to oxidatively decompose complex organic matters in the wastewater into carbon dioxide, methane, water and the like, and the physicochemical method mainly comprises the methods of ion exchange, electrodialysis, reverse osmosis and the like. However, any of the above methods has the problems of long treatment period, large occupied area, high treatment cost, unstable treatment effect, and the like. Based on this, most of the existing coating wastewater treatment processes adopt a mixed treatment method, such as first performing lime coagulation precipitation, then performing anaerobic reaction and aerobic oxidation treatment. Because degreasing agents and surface agents used in the automobile coating process all contain phosphate, and the coating additive also contains heavy metals such as zinc, nickel, manganese and the like. The total phosphorus and heavy metals in the wastewater generated by coating hardly reach the emission standard through primary precipitation, and the surfactant in the wastewater can have strong inhibition effect on acidogenic bacteria and methanogenic bacteria in the anaerobic reaction process, and lipid substances in the wastewater hardly reach the standard by virtue of an aerobic oxidation system. In addition, the anaerobic and aerobic treatments have certain requirements on indexes such as pH value, temperature, salinity and the like of the wastewater, so that the treatment method has certain limitations and also has unsatisfactory effects. In another typical coating wastewater treatment process, lime milk clarified liquid is firstly added, the pH value is adjusted to be 10-11, most of phosphate in the wastewater is removed by precipitation, the lime milk has a neutralization effect while dephosphorizing, and then the subsequent treatment sequence of operations such as Fenton oxidation, coagulation precipi