Talking about the treatment method of water-based paint coating sewage

0 Introduction
With the increasingly strict national environmental protection requirements, the state's environmental pollution control is also more and more attention, water-based coatings in the paint industry market share is also increasing year by year.
Water-based coatings in containers, automobiles and parts, construction machinery, furniture and many other products on the application, the resulting coating wastewater discharge is also gradually increasing, the corresponding water-based coating wastewater treatment has become a headache for many enterprises now.
1 Water-based coating classification
All resin coatings that use water as a dispersant can be called water-based coatings

.
types of water-based coatings commonly found on the market can be divided into:
polyurethane type, epoxy resin type, acrylic resin type and aliclicic resin type.
1.1 hydroelesterated coatings
water-based polyurethane coatings include water-soluble, water-emulsified and water-dispersed.
can be divided into line type and cross-link type according to molecular structure, and there are two systems of single and double parts.
, water-based polyurethane coatings have the advantages of high hardness, strong adhesion, non-corrosion resistance and solvent resistance, in addition to the good performance of solvent-based polyurethane coatings.
But at present, the development of domestic water-based polyurethane coatings is also limited by raw materials, curing agents, crosslinkers, etc., therefore, the development of corresponding raw materials, additives are also the key to the development of water-based polyurethane coatings.
1.2 epoxy-type water-based coatings
Epoxy-type water-based coatings are composed of two components:
one group is divided into hydrophobic epoxy dispersions
(emulsions);
1.3 Acrylic water-based coatings
acrylic-type water-based coatings can be broadly divided into:
single component type, high-performance type, high-curing type 3 types.
It is difficult to prepare solvent-resistant acrylic raw materials into solvent-resistant water-resistant acrylic coatings, the focus of the current research lies in the modified acrylic raw materials, this technology is called "living polymerization", can be well controlled acrylic molecular weight and its chemical structure (single order, etc.) and distribution.
1.4 Aolic acid resin-type water-based coatings
aolic acid resin-type water-based coating development has undergone two stages of external emulsification and internal emulsification, currently mainly using internal emulsification method synthetic hydroolic acid resin dispersion.
emulsification method is to use the polymer's carboxyl or amino in the appropriate alkali or acid, so that the polymer can be dispersed in water.
Although water-based alicic acid resin coating has good brushing and smoothness, but there are also the shortcomings of slow film drying, low hardness and poor corrosion resistance, need to be modified to meet these performance requirements.
people's water-based alicic acid resin change mainly includes physical and chemical modified, of which acrylic resin, silicone resin and styrene modified the effect is most significant.
2 Water-based paint coating sewage characteristics
water-based paint coating sewage volume is generally larger, and mostly to take a cycle mode, water-based paint dissolved in water if not timely separation from the water body, easy to lead to paint subsidion, circulating sink odor, sewage treatment operation site air pollution, but also affect the health of operators.
containers, host plant water-based coated sewage organic content is high, sewage COD value of up to 1000 to 30000mg/L, if not timely separation of organic matter in sewage and water bodies, such a high COD value of sewage sent to sewage treatment station one-time treatment costs are very high.
Because of the characteristics of the above coated sewage, in order to save sewage treatment costs and enable sewage to meet the environmental protection emission requirements of the corresponding areas, coated sewage needs to be treated in a timely manner so that the water-based coating components in the sewage separated from the water.
3 Water-based paint coating sewage treatment process
the market of authentic water-based paint coating sewage treatment technology is the key to destroy the emulsification system of water-based paint sewage or a stable water-soluble system, so that water-based coatings in the form of flower particles, and then add flocculants, water in the form of flower particles of water flocculation into groups, slag separation, water can be recycled.
the key to wastewater treatment of pseudo-water-based coatings on the market is to use de-adhesives to remove the viscosity of pseudo-water-based coatings before breaking the emulsion to destroy the emulsification system.
3.1 milk-breaking effect
the milk-breaking effect is also known as anti-emulsification effect, the stability system of emulsion is completely destroyed, the phenomenon of two phases of oil and water stratification occurs.
methods are generally divided into mechanical, physical and physical chemistry.
mechanical method is mainly the use of external forces to break the emulsion, such as ion separators.
Physics has electro-deposition method, filtration method, ultrasonic milk breaking method, whereo-depositing method is the use of high-voltage electrostation field to disperse phase aggregation, filtration method is through porous materials to achieve milk breaking, and in the use of ultrasonic milk-breaking process ultrasonic strength can not be too large, otherwise it will affect the milk-breaking effect.
physicochemistry is mainly by changing the type of emulsion or interface properties to reduce the stability of the emulsion, and thus achieve the effect of breaking the milk.
3.2 Common treatment techniques for coated sewage
physicochemistry and biological methods for common treatment techniques.
because of the high concentration of sewage pollutants, B/C value is less than 0.3, biochemicality is poor, in the actual treatment process, often using a combination of pre-treatment and biological treatment.
process flow of coating sewage is shown in Figure 1.
4 Water-based paint treatment agent selection
4.1 Water-based paint treatment agent composition
water-based paint treatment agents generally contain additives, water-based paint separators and flocculants.
additives are divided into inorganic hybrids and organics, which mainly play a coagulation role.
water-based coating separator is polymerized polymer resin, which separates the hard-to-separate components of resins, pigments, etc. in the coating.
The product belongs to cation-type polymer composite material, the molecular main chain with a large number of positive charge groups, with super milk-breaking capacity, it is with soluble molecules in hydroxyl, sulfonate and other anionic groups to produce electrical neutrality, forming easy to capture adsorption flocculation particles.the main components of
flocculants are polyacrylamides with different polymerization degrees and different ion degrees, which are divided into anion type, cation type and modified sex ion type, and the type of flocculant should be selected according to the actual situation of the water body to be treated in practice.
flocculant is mainly to flocculate water in the form of flower particles, so as to achieve the purpose of slag water separation.
Figure 1 Coating Sewage Treatment Process
4.2 Water-based coating treatment pharmaceutical use
first of all, a small sample test in the laboratory to determine the combination of water-based paint treatment pharmaceutical solutions.
is generally in the customer's production line to take waste water or paint samples, back to the laboratory, after simulation of the site environmental conditions analysis and then provide on-site wastewater (paint) treatment program.
laboratory sample simulation test results determination standards should be based on the actual treatment requirements of customers, such as the requirements of treatment of paint residue floating or sinking, two different requirements of its water-based paint treatment agent combination scheme will also be different.
second, according to the laboratory sample simulation test results, the water-based coating treatment agent in the sewage field treatment process to apply the proposed scheme.
such as sewage treatment site is mostly continuous treatment, pharmaceutical also need to use metering pump continuous addition.
some customers on-site using intermittent treatment methods, such as the use of box treatment, a box of sewage quantitative one-time treatment, this case of pharmaceutical add-on needs to use a one-time delivery.
need to be based on the customer on-site treatment equipment, timely and reasonable arrangements for pharmaceutical addition points.
the general site for the circulating tank-type treatment system, additives and water-based paint separators are added at the inflow and flocculants are added in the reflow area.
If the on-site sewage is to take the box batch treatment method, the added point of the potion is not required, but it is recommended to add stirring equipment in the box, so that the potion can be fully dispersed and function in the water body.
water-based coating treatment agent in the actual application process needs to go through a small sample test process, on-site pharmacy debugging process before the final drug use plan can be determined.
5 Water-based coating wastewater treatment case
Water-based paint wastewater treatment involves automobiles and their components, containers and other industries, the following container company water-based coating sewage treatment as an example to illustrate, its treatment process diagram 2.
water-based paint coating sewage volume of a container company is 20m3/
d;
Figure 2 A company's water-based coating sewage treatment process
Table 1 coating wastewater treatment before and after water quality parameters
the sewage after initial treatment COD still reached about 7000mg/L, can be used back to the cycle tank, cycle can reach 6 months to 1 year.
when the water quality cycle life reaches 6 months to 1 year, due to the water body COD and other indicators are still high, can not be directly discharged, so further treatment is needed to make the sewage index to GB838-2002IV.
specific emission standards are set out in Table 2.
2 Specific discharge standards
Follow-up treatment process is as follows:
production wastewater →flocculation precipitation→ wastewater regulatory pool →nachic pool→ and oxygen pool → contact oxidation pool →MBR membrane pool→ ozone oxidation pool→ discharge.
6 Auxiliary Equipment Overview
auxiliary equipment are mainly slag separation equipment and slag dehydration equipment.
water separation equipment for slag water separation scraping machine, divided into air floater and sedimentation separator.
waste dewatering equipment includes plate frame filter, stacking screw machine, centrifuge, drying equipment and so on.
the role of the water separation equipment is to separate the water-based paint residue from the water body, the water body can continue to use in the circulation tank, can also enter the sewage treatment stage, the indicators after the direct discharge.
the role of waste dewatering equipment is to reduce the water content of slag, and reduce the quality of slag, and thus reduce the cost of solid waste disposal.
Solvent-based paint coating waste residue in the 2016 version of the National Hazardous Waste List is a dangerous solid, must pay to deal with hazardous waste qualified professional companies to deal with;
Usually waste paint residue can be treated by high temperature incineration, waste paint slag is mostly burned clean at high temperature, decomposed into CO2 and other harmless gases with exhaust emissions, a small part of the residue can be used in cement production as clyceration of cement, become cement products, and ultimately achieve zero pollution.
7 Conclusion
Water-based paint coating sewage after the initial treatment of water treatment agents, and then with water treatment equipment, after bio-chemical and other processes, sewage can be treated to meet the standard discharge, waste residue generated in the process can also meet the standard treatment, and eventually reached the degree of zero pollution to the environment.
source: Steel barrel packaging network
.