Industrial coating wastewater treatment
The coating of steel drums has always been an important link in the production of steel drums, and it is also a link with a large amount of wastewater discharge. In recent years, with the continuous development of the domestic steel drum manufacturing process and level, the production volume of the coating process has continued to increase, which has also indirectly increased the discharge of wastewater. To this. It is of great significance to explore the treatment technology of coating wastewater for environmental protection.
1. Characteristics of coating wastewater
The wastewater formed during painting in the steel drum production process is mainly degreasing and degreasing wastewater, cleaning wastewater, painting wastewater and surface adjustment phosphating wastewater. The above-mentioned kinds of wastewater are mainly COD, SS, PH, petroleum, and metal Pollutants such as ions, phosphates, organic compounds, low molecular volume, pigments, surfactants, etc., because many pollutants have high concentrations and complex wastewater costs. Therefore, the biochemical properties are relatively poor, and the processing difficulty is relatively high.
2. Coating wastewater treatment technology
The specific technological process is as follows: the wastewater discharged from the steel drum coating site is firstly pretreated with the cyclone settling equipment to some substances with larger particles contained in it, and then the wastewater after the preliminary treatment is input into the wastewater tank, and The wastewater produced by painting is filtered with a filter. So that impurities such as paint blocks contained in it are removed. Then the treated wastewater is injected into the storage tank: after degreasing, the wastewater is filtered with a paper tape to further remove the particulate impurities, then injected into the ultrafiltration device, and then flows to the wastewater storage tank. The wastewater after ultrafiltration treatment is injected into the thick oil tank. These waste liquids are handed over to professional wastewater treatment institutions for treatment. In each wastewater storage tank, two stirring devices are installed to keep the wastewater flowing and avoid unnecessary sedimentation. At this time, most of the metal ions contained in the wastewater have become flocs and precipitated, and then the precipitates are discharged from the bottom to the concentration tank. Dehydrate.
1. Pretreatment
Pretreatment technology is one of the very 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 first according to the specific nature of the water quality and then mixed into other wastewater. Centralized processing. This method can not only have a better stability 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 wastewater pools for painting, cleaning, degreasing, and surface adjustment and phosphating respectively. At the same time, each kind of wastewater is stored separately, and by adding lime, PAC (coagulant), and PAM (coagulant aid), by means of sedimentation, stirring, separation, etc., metal ions are promoted to form hydroxides and precipitate. Phosphate forms hydroxyapatite for precipitation, realizes solid-liquid separation in the precipitator, adds pH from the supernatant to achieve reverse adjustment, adds sulfuric acid to adjust the pH value, and then adds it to the mixing tank to enter the next process for processing.
2. Mixing adjustment pool
The various wastewater after pretreatment are mixed and flowed into the regulating tank. At the same time, because the coating wastewater lacks the nutrients needed by microorganisms, it is necessary to add nutrients to the wastewater appropriately. In order to better improve the biochemical performance of wastewater, domestic sewage is properly added to the regulating tank. The addition of domestic sewage needs to be added after drying out large suspended matter through septic tanks and grilles.
3. Permanent solution acidification
The water in the mixing tank is pumped into the hydrolytic acidification tank, and part of the long-chain macromolecular substances are gradually broken into low-molecular organic substances by hydrolytic acidification bacteria. And improve the biochemical performance of the water body, and provide effective water quality for the subsequent biological treatment technology.
4. Biological contact oxidation pool
The contact oxidation tank is a vital link in wastewater treatment, and it is also the key to ensuring the quality of effluent. The biological contact oxidation tank is mainly based on aerators and fillers. Aeration with the help of a blower. The biochemical treatment effect is achieved on the microorganisms attached to the filler. Fill the tank with the material. At the same time, the wastewater is immersed in the filler, and at the same time, online detection of sufficient oxygen is provided for the wastewater. When the wastewater passes through the filler that is not full of biofilm at a corresponding flow rate, the wastewater and the biofilm can fully contact, and under the microbial metabolism of the biofilm, the organic pollutants in the wastewater can be removed. Wastewater can pass through the biofilter up and down and flow, and achieve extensive contact with the biofilm. Under the action of aerobic microorganisms, it can be partially synthesized into microbial cells, while the other part of the cell decomposition is mainly based on H2O, CO2-based, and get a thorough explanation. Part of the excess microorganisms and organic matter can be discharged through the sludge discharge system.
5. Sedimentation and air flotation
Add PAC and PAM to the reaction tank after the treatment in the biological contact oxidation tank. And carry out precipitation, complete solid-liquid separation in the precipitation, remove the tiny suspended matter, and then discharge the water to the air flotation tank. During the sedimentation process, the sludge can be effectively released into the sludge tank. The air flotation tank is mainly based on PAC and PAM. The coagulation reaction generates flocs, and in the air flotation tank, the pressure of the contact chamber, releaser, etc. is quickly reduced to realize the solution gas-water encounter. Let the microbubbles absorb the flocs. So as to achieve the treatment effect of clarified water.
3. Conclusion
In summary. Environmental protection issues in the production of steel drums have gradually become a focus of attention. The painting process of steel drums is the most likely to generate wastewater in the whole production process. Only by scientifically treating the painting wastewater so as not to damage the environment can we fulfill the social responsibility of the barrel-making enterprises and build their own core competitiveness. This paper combines the author's practical experience in wastewater treatment to expound the method of reducing pollution through reasonable treatment, which has relatively good theoretical value and practical significance.
