Treatment Technology of Coating Wastewater in Automobile Industry

The coating of automobiles and related parts has always been an important link in automobile production, and it is also a link with a large amount of wastewater discharge. In recent years, with the continuous development of domestic automobile manufacturing technology and level, the production volume of the painting process has continued to increase, which has indirectly increased the discharge of wastewater. to this. The discussion of coating wastewater treatment technology is of great significance to environmental protection.

Characteristics of automobile coating wastewater

The wastewater formed during painting in the automobile production process is mainly degreasing and degreasing wastewater, battery wastewater, paint spraying wastewater and surface-adjusted phosphating wastewater. The above-mentioned various wastewaters are mainly COD, SS, PH, petroleum, metal ions. , phosphate, organic compounds, low molecular volume, pigments, surfactants and other pollutants, because many pollutants have high concentrations and complex wastewater costs.

Therefore, the biochemical properties are relatively poor, and the processing difficulty is relatively high.

Coating wastewater treatment technology

The specific process flow is as follows: the wastewater discharged from the automobile painting site is firstly pretreated with some substances with larger particles by cyclone sedimentation equipment, and then the wastewater after preliminary treatment is input into the wastewater tank, and the paint is sprayed. The generated waste water is filtered with a filter screen. Thereby, impurities such as paint lumps contained in it are removed.

Then, the treated wastewater is injected into the storage tank: after the wastewater is degreasing, it is filtered with paper tape, so that the particulate impurities in it are further removed, and then injected into the ultrafiltration device, and then flows to the wastewater storage tank. The waste water after ultrafiltration treatment is injected into the concentrated oil tank.

These waste liquids are handed over to professional waste water treatment institutions for treatment. In each waste water storage tank, two stirring devices are installed to keep the waste water flowing and avoid unnecessary precipitation. At this time, most of the metal ions contained in the wastewater have become flocculent and precipitated, and then the precipitate is discharged from the bottom to the concentration tank. Dehydration.

Preprocessing

Pretreatment technology is one of the most important processes in the treatment process of coating wastewater. At the same time, for some wastewater that is difficult to treat or affects subsequent treatment, the corresponding pretreatment can be realized according to the specific nature of the water quality, and then mixed into other wastewater. Carry out centralized processing. This method not only has better stable processing effect, but also is more reasonable in terms of economic cost.

In this study, the sewage treatment station mainly diverts the coating wastewater, and implements and treats it according to various types of wastewater. Set up four kinds of waste water pools for painting, battery, degreasing, and surface phosphating. At the same time, each waste water is stored separately, and by adding lime, PAC (coagulant), PAM (coagulant), and by means of sedimentation, stirring, separation, etc., metal ions are promoted to form hydroxides and precipitate.

Phosphate forms hydroxyapatite for precipitation, solid-liquid separation is achieved in the precipitator, PH is added from the supernatant to achieve reverse adjustment, and sulfuric acid is added to adjust the pH value and then added to the mixing tank to enter the next process for treatment.

Mixing adjustment tank

The pretreated wastewater is mixed and flowed into the conditioning tank. At the same time, because the coating wastewater lacks the nutrients required by microorganisms, it is necessary to appropriately add nutrients to the wastewater. In order to better improve the biochemical performance of wastewater, domestic sewage is appropriately added to the adjustment tank. The addition of domestic sewage needs to be added after the large suspended solids are dried out through the septic tank and grille.

Permanent solution acidification

The water in the mixing tank is lifted to the hydrolysis and acidification tank by a pump. With the help of the hydrolysis and acidification bacteria, part of the long-chain polymer substances are broken off and gradually become low-molecular-weight organic substances. And improve the biochemical performance of the water body, and provide effective water quality for the subsequent biological treatment technology.

Biological contact oxidation tank

Contact oxidation tank is a very important link in wastewater treatment, and it is also the key to ensure the quality of effluent. The biological contact oxidation tank is mainly based on aerators and fillers.

With the help of the aeration effect of the blower. To achieve biochemical treatment effect on microorganisms attached to the filler. Fill the tank with material. At the same time, the waste water is immersed in the filler, and at the same time, a sufficient content of oxygen is provided to the waste water for online detection.

When the wastewater passes through the filler that is not filled with the biofilm at a corresponding flow rate, the wastewater and the biofilm can be fully contacted, and the organic pollutants in the wastewater can be removed under the microbial metabolism of the biofilm.

Wastewater can flow through the biological filler up and down, and achieve extensive contact with the biofilm. Under the action of aerobic microorganisms, it can be partially synthesized into microbial cells, and the other part of the cells can be decomposed mainly with H2O. , CO2-based, and get a thorough explanation. Part of the excess microorganisms and organic matter can be discharged by means of the sludge discharge system.

Precipitation and air flotation

PAC and PAM were added to the reaction tank after the biological contact oxidation tank treatment. And carry out precipitation, complete solid-liquid separation during precipitation, remove tiny suspended substances, and then effluent to air flotation tank. During the sedimentation process, the sludge can be effectively discharged into the sludge tank.

The air flotation tank is mainly based on PAC and PAM. The coagulation reaction produces flocs, which are rapidly depressurized in the flotation tank with the help of contact chambers, releasers, etc., so that the solution gas and water meet. Allow the microbubbles to absorb the flocs. So as to achieve the treatment effect of clarified water.

Conclusion

In summary. Environmental issues in automobile production have gradually become a focus of attention.

The coating process of automobiles is the most likely part of the entire automobile design and production process to generate wastewater. Only by scientifically treating coating wastewater so that the environment is not damaged, can the social responsibility of automobile enterprises be fulfilled and their core competitiveness be built. . Based on the author’s practical experience in wastewater treatment, this paper expounds the method of reducing pollution through reasonable treatment, which has good theoretical value and practical significance.

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