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Electroplating industry is an indispensable link in the national economy, involving defense, industry, life. From the general category is divided into pieces of metal plating, plastic plating, to corrosion of the workpiece, beautiful, prolong life, the appearance of decoration and other effects.

Electroplating waste water toxicity, the soil, animals and plants are harmful. Therefore, we must strictly handle the discharge of wastewater standards, water-deficient areas to promote wastewater recycling compliance, from the technical aspects of production, due to electroplating and wastewater treatment process must be added to a certain amount of a variety of chemicals. Electroplating wastewater treatment to achieve recycling, reuse water must be desalinated before reuse for the production line water, the total amount of environmental salt will not be cut, resin exchange, reverse osmosis process concentrate still return to the ground.

1. Electroplating wastewater treatment process

Wastewater treatment process design is based on the nature of wastewater, components and business conditions and discharge of water quality parameters after the request, after the comprehensive technical and economic comparison determined.

Electroplating wastewater treatment process many: the 1970s popular resin exchange, electrolysis of the 1980s, chemical + air flotation. According to our plant in the past 20 years in the electroplating wastewater treatment practice concluded that resin exchange on the treatment of your lean metal ion wastewater, recovery of your precious metals have its advantages.

Electrolysis: high energy consumption, power consumption and iron consumption are high, the high concentration of chromium-containing wastewater sludge too much, do not meet, at the same time cyanide wastewater treatment is not ideal, so cyanide wastewater also chemical method.

Chemical + air flotation: the use of chemical redox and neutralization, floating with flotation method for mud and water separation, electroplating sludge due to a large proportion, and the wastewater contains a variety of organic additives, the actual use of air flotation separation is not complete, and Operation and management inconvenience, to the late 90s, flotation less and less application.

Chemical + precipitation: The method is the earliest application of the method, after more than 30 years of different treatment processes after the actual use of more. Now back to the earliest, but also the most efficient process up, the majority of foreign electroplating process is also used in this method, but the actual solid-liquid separation after a long run, the sludge tank will be turned up, the water is difficult to ensure stable compliance.

In recent years, the development of biological treatment process: a single plating of small quantities of water running high efficiency, the use of many large projects is very unstable, because of water quality and quantity of water is difficult to constant, microorganisms on water temperature, variety, heavy metal ion concentration, pH value changes difficult to adapt to stable, there A large number of instantaneous microbial deaths, environmental pollution accidents, and bacteria is not easy.

The process is based on different properties of waste water by adding different drugs for redox and neutralization, the use of direct pressure filtration separation of sludge separation method, investment, operation and operation management is convenient, stable and reliable, low energy consumption.

Many current water shortage areas require electroplating wastewater recycling. In the first level of GB8978-1996 pretreatment water quality based on the depth of purification, the main water reuse salinity, accounting for 20% - 23%, must be desalted, the use of coarse filter → fine filter → ultrafiltration → reverse osmosis , Up to drinking water quality standards, which is of some significance for the reuse of water resources, but concentrated salt contaminants such as 20% - 23% are still returned to the environment.

I plant five years ago, in the Qianjiang Group demanding electroplating wastewater treatment (requires heavy metals <0.05mg / l, better than the national emission standards 10 times, but also the use of chemical + precipitation, filtration, ion exchange method from today's technology Reverse osmosis level evaluation is more appropriate.

According to my unit over the years in the wastewater treatment project in the practical experience in the dosage of the appropriate agent to respond well under the conditions, whether it is flotation method, or precipitation method, are played the role of solid-liquid separation, as long as the solid-liquid separation And separation completely, stable and reliable, and also to adapt to high concentrations of wastewater treatment can also be timely and effective separation, flotation and precipitation solid-liquid separation methods can not meet the above conditions, this conclusion has been done in our plant in the past have been Confirmed. For example: Wenzhou Longwan plating base 85 small electroplating factory wastewater concentration and neutralization, the amount of suspended solids accounted for about 50% of the total volume, when the use of sedimentation tank separation, the first hour of water clear, the second hour there Sludge up, so that the water can not meet the standard, in order to ensure continuous water clear, will have to row of mud, sludge volume of 50% of the inflow, so sludge treatment capacity is large, these sludge dehydration.

According to our factory engineering experience over the years, this high concentration of waste water directly by pressure filtration step in place, can reduce the investment in sedimentation tanks, but also to ensure that different concentrations of wastewater treatment standards. When the amount of influent sludge is small, the amount of filter press water is still very large, and the method is applied in a number of wastewater treatment projects. After more than two years of operation, users reflect better. Using direct pressure filter can save investment more than 10%, covers an area of ​​20% reduction.

2. Electroplating process and discharge of waste water brief

Most electroplating plants are multi-plating operations involving chromium, nickel, zinc, copper and other plating, from being plated types can be divided into metal plating and plastic plating, cyanide plating process although the majority of outdated , But there are still many electroplating factories are still in use.

General electroplating factory production process is as follows: Electroplating production process mainly mechanical polishing (polishing or rolling) → degreasing → acid etching → plating → drying → storage of qualified products

Unqualified products stripping

2.1, plating pretreatment mechanical polishing (polishing or rolling)

Mainly by means of special machinery using mechanical polishing wheel or belt (or abrasive to remove some of the plated parts with roller plus abrasive rust) to be plated on the removal of burrs, scratches, welding tumor, trachoma, etc., in order to improve Plating is to improve the quality of plating flatness. This section of the process without waste water discharge.

2.2, degreasing

Metal parts plating, due to various processing and handling, will inevitably adhere to a layer of oil, in order to ensure a solid coating with the substrate, you must remove the oil on the surface to be plated. There are many kinds of degreasing process, the main use of organic solvent degreasing, the process is as follows: polished parts → clean water → organic solvent degreasing tank → clear water tank rinse water in this process mainly from the process of washing water, water PH value Between 8.5-10.

2.3, erosion

Degreasing parts, the surface often have a lot of rust and relatively thick oxide film, in order to obtain bright coating, the coating and the substrate better combination, you must remove the rust and oxide film on the parts, after the acid Soaking can also activate the part surface. The process is as follows:

After degreasing parts → acid water

Tank → recovery tank → water tank → water rinse

The main section of the waste water from the process of washing water, wastewater contains large amounts of iron ions, PH value of 2 to 5 between.

2.4, electroplating process and the plating of the water quality

The production process is generally: parts after etching → plating bath → recovery tank → clear water tank → rinse.

The waste water from this section mainly comes from the process of fresh water rinse. The waste water contains the corresponding metal ions or cyanide. Cyanide and copper ions are contained in the rinse water of cyanide copper plating. The chrome rinse water contains hexavalent chromium. The rinse water contains nickel ions Wait. Flushing water according to the plating of different effluent diversion treatment, such as cyanide-containing wastewater after secondary flow of broken cyanide, adjust the PH value, solid-liquid separation can reach standard discharge; chromium wastewater diversion after reduction reaction, and then through the neutralization, Solid-liquid separation up to standard discharge.

2.5, drying storage

The process is mainly by means of mechanical and natural energy, heat will be electroplating rinsing parts of the surface of the water drying, rust and oxide film to prevent damage. This section of the process without waste water discharge.

2.6, stripping

Plating process There are chemical dipping and anodic electrolysis two methods, the process is:

Unqualified plating → back plating tank → recovery tank → water tank → water rinse.

The wastewater PH of the section is between 2 and 6, the wastewater mainly comes from the rinse water after the stripping. Rinse rinse water can enter their own waste water pool for treatment, but not directly into the waste water mixing tank, should be pre-treated separately discharged into the corresponding waste water treatment tributaries.