The source and treatment of coated wastewater.

In recent years, China's rapid economic development, which to a certain extent benefit from the development of the manufacturing industry, but the resulting negative effects also bring threats to our production and life, such as environmental pollution. As we all know, in the machining process coating process is very widely used, almost in most of the production process has a large number of wastewater discharge, and coating wastewater treatment has long been a hot topic about sewage treatment. This paper will start from the coating process, the coating wastewater treatment technology is mainly introduced

.I. The characteristics of coating process wastewater
1.1 source of coating wastewater
automotive coating as an important link in the automobile production process, is the assembly of the finished exposed steel body after a series of chemical anti-corrosion treatment, and finally in the vehicle steel substrate surface including the inner cavity to form a number of layers of chemical coating and related protective media, its main role is to prevent body steel plate corrosion and beautify the appearance of the body. Automotive coating process includes pre-treatment, electrophoresis coating, electrophoresis polishing, PVC material sealing, medium coating, medium coating polishing, color paint coating, varnish coating, baking, finishing delivery, dot repair process, threshold black paint, cavity waxing, assembly repair and so on.
coating wastewater mainly comes from the pre-car treatment process (pre-skimming, degreasing, table tone, phosphation, passivation, etc.), cathode electrophoresis process and medium coating, painting process. Degreasers, phosphates, surface regulators and phosphoric acid are the main pollutants of automotive coating wastewater.
1.2 Coating wastewater composition and characteristics
Wastewater contains the main toxic and harmful substances as follows: pre-coating treatment: nitrites, phosphates, emulsified oils, surfactants, Ni2 plus, Zn2 plus; Electrophoretic paint film, pigment, powder, epoxy resin, butanol, ethylene glycol monobutyl ether, isopropyl alcohol, dimethyl ethanolamine, polybutylene resin, dimethyl ethanol, paint, etc.;
automotive coating wastewater has the following characteristics: there are many types of wastewater, complex components of automotive coating line discharge of many types of wastewater, each wastewater quality (component concentration) varies according to the material used; In addition to the continuous overflow discharge of some wash water, most of the coated wastewater is intermittent concentrated discharge; Due to various wastewater composition, concentration, and irregular discharge, resulting in car coating line drainage water, water quality changes greatly, and irregular to follow.II, coating wastewater process research
2.1 basic principle
microelectrulation is a low-level Fe and high-power C in the wastewater composed of a large number of primary batteries, iron as an anode corrosion, carbon as cathode. These tiny primary batteries form a difference in the likee, producing electrode reactions and a series of resulting reactions that allow organic matter and inorganic contaminants in wastewater to be treated from the wastewater. The main roles are electric field action, Fe's reduction effect, the oxidation effect of the new ecology, filtration, adsorption, combined coagulation and so on.
chemical oxidation is mainly under the influence of chemical oxidants, so that the organic matter in wastewater further degraded to a stable impact on the natural environment of small inorganic salts. For wastewater treated by microelectrolytic reactor, the wastewater contains a certain amount of Fe2, Fe3, can catalytic oxidant H2O2, the release of redoxion level is relatively high OH free fundamentals. Under the combination of OH free agent and H2O2 oxidants, the organic matter in wastewater is degraded., coating wastewater treatment process
1. Chemical method in addition to zinc
chemical method in addition to zinc has sulphides and alkali method coagulation precipitation. The process uses alkali coagulation precipitation to remove zinc, because Zn(OH) 2 solubility constant Ksp is 7.1 x 10-18, according to the precipitation-dissolving balance of hydroxide M(OH)n The ion product of water, Kw, oh-, can calculate the pH that precipitates the hydroxide, i.e. the pH value is 14-1/n x (log (log(Mn)-logKsp). By adjusting the pH value of NaOH and controlling the optimal pH of coagulation precipitation is 8.5 to 9.0, under these conditions, Zn2 plus NaOH reacts to generate Zn(OH)2 precipitation, which is completely removed.
2. Lime chemical precipitation in addition to phosphorus
cast lime emulsion liquid, adjust the pH in 10 to 11, the vast majority of phosphates in wastewater can be precipitated to remove, lime milk in the removal of phosphorus at the same time also played a role in the mesification.
3. Coagulation gas floating phosphorus, de-oiling
plus human flocculants make the residual phosphorus and other polluting substances in the wastewater coagulation reaction, the resulting flocs and the air floating method produce a large number of fine bubbles attached together, using bubble buoyant force to bring it out of the water. In addition to phosphorus at the same time, can also adsorption to remove oil droplets, bubble floating speed, safe and reliable operation, is a cost-effective de-oiling technology.
4. Activated carbon adsorption of phosphorus
activated carbon is the most commonly used adsorbent in water treatment, with good adsorption properties and chemical stability, not easy to break, air flow resistance is small, commonly used powder and granular, the process uses the large surface area of activated carbon, fully adsorption of wastewater trace residual phosphorus and other contaminated components.
5. Mixing mixing device
first- and second-level reactors are equipped with stirring devices, the use of pistes or reducers is the groove stirring speed in turn decreased to meet the whole reaction process of different stages of mixing and mixing needs, so that the reaction is more thorough, more in the later precipitation process. The pipe mixer in the process makes the medium reaction easier when the H2SO4 is added, and the pH of the water discharge can be fully met.
6. Gravity or water pressure action discharge mud
system, the first- and second-stage reactors and gas floating pool produced sludge or slag are by gravity or water pressure action regularly discharge human sludge concentration pool concentration, and then after natural drying out of landfill, the upper liquid of the concentration pool back to the regulatory pool for materialization treatment.
7. The silicon sand filter and activated carbon adsorbent in the
system require regular backflushing to prevent clogging and the resulting wastewater is returned to the regulatory pool. In addition, in order to regenerate activated activated activated by high temperature heating and regeneration, water vapor is used to desorpt the particulate carbon in the activated carbon filter to ensure the normal adsorption effect.4. The application of wastewater treatment technology and conclusions
In summary, coating technology is widely used in many fields in China, coating makes the appearance of the product more beautiful, at the same time can play a role in protecting the appearance of the product, but the waste water generated during the coating process is a need for eager attention The problem, wastewater will not only pollute limited water resources, but also pollute the environment to people's lives and health threats, so the waste water generated in the coating process must be treated well, this paper mainly on the automobile coating waste water treatment technology analysis, hope that Hangzhou Near Source Environmental Protection Technology Co., Ltd. can provide reference for coating wastewater treatment..