1. 1. Cleaning water for parts; 2. 2. Waste plating solution; Other waste water, including washing the floor of the workshop, washing electrode plates, condensate from ventilation equipment, as well as various run-offs and discharges of "run, run, drip, leak" caused by leakage or improper operation and management of the plating tank. 4． Equipment cooling water, in addition to temperature rise, the cooling water is not polluted during use.
Composition of electroplating wastewater
Except for cyanide (CN-)-containing wastewater and acid-base wastewater, heavy metal wastewater is a potentially hazardous wastewater category in the electroplating industry. According to the classification of heavy metal elements in heavy metal wastewater, it can be generally divided into chromium (Cr) wastewater, nickel (Ni) wastewater, cadmium (Cd) wastewater, copper (Cu) wastewater, zinc (Zn) wastewater, and Gold (Au) wastewater and silver (Ag) wastewater.
Three, electroplating sewage treatment method
Chemical oxidation method: the use of certain toxic and hazardous substances dissolved in wastewater can be oxidized or reduced in the redox reaction, by adding oxidants or reducing agents to convert them into non-toxic and harmless new substances, or into It is easy to separate the excluded gas or solid form from the water, so as to achieve the purpose of processing these toxic and harmful substances. This method is the redox method.
1. Chromium-containing wastewater: Under the condition of acidic pH value of 2￣3, hexavalent chromium is reduced to trivalent chromium by sulfite, and then the pH value is adjusted to 8￣10.5, so as to generate hydroxide precipitation.
2. Cyanide-containing wastewater: Under alkaline conditions, the oxidative decomposition of hypochlorite cyanide into non-toxic substances. The reaction principle is that under alkaline conditions, sodium chlorate is used as an oxidant to oxidize cyanide to nitrogen and hydrogen. And carbonate.
3． Copper pyrophosphate-containing wastewater: Using the principle that the solubility product of heavy metal sulfides is very small, Na2S is added to the reaction sedimentation tank to break the network, and then the lime is automatically added through the pH control system to adjust the pH value of 10.5. Phosphoric acid in the wastewater Root ions and calcium ions generate base phosphates. After the reaction is complete, after standing, the supernatant flows into the integrated wastewater conditioning tank, and the sediment is discharged into the sludge transition tank by gravity.
4． Copper, nickel-acid-base comprehensive wastewater: The wastewater containing nickel, acid-alkali integrated wastewater flowing into its regulation tank after chrome-breaking is combined, and then lifted to the mixing tank. The mixed tank and the cyanide-containing wastewater are combined, and hydroxide is added. Sodium adjusts the pH value to about 10.5, and then flows into the reaction tank. At this time, nickel and chromium ions form a precipitate with a small solubility. By adding lime and flocculant, the particles in the water are added under the action of the flocculant. Large, then the sedimentation tank uses the principle of shallow sedimentation to accelerate sedimentation and separation to achieve the purpose of removing heavy metals.
Fourth, wastewater reuse process wastewater after physical and chemical treatment is pumped to the reuse water system. After the chromium-containing wastewater is treated and meets the standard, it is directly recycled to the water used in the pre-treatment process. The acid-alkali wastewater and zinc-containing wastewater that have passed the standard are treated by multi-stage precipitation. After filtering, it enters the reuse system. In the pre-treatment device of the reuse system, the wastewater that has passed the treatment standard is pumped into a multi-media filter to retain and remove the angular particle size suspended matter, insoluble organic matter, colloidal particles, microorganisms and other impurities in the water. The carbon filter can adsorb the water Heavy metal ions and dissolved organic matter can adsorb the residual chlorine that cannot be removed in the previous stage filtration to prevent the subsequent stage membrane module from being decomposed by the oxidation of residual chlorine into the membrane module. The residual chlorine requirement is greater than 0.1 mg / L.
Even if the impurities in the wastewater after carbon filtration and microfiltration are greatly reduced, the water cannot be recovered directly by reverse osmosis. Microfiltration can only retain particles between 0.1 and 1um, which allows macromolecular organic matter and dissolved solids to pass. In order to reduce the number of cleaning of the reverse osmosis membrane and extend the service life of the reverse osmosis membrane, ultrafiltration is particularly important as a reliable reverse osmosis treatment system. The ultrafiltration membrane can trap particles with large particle diameter and large membrane solutes and molecular solutes with a molecular weight of 30,000 to 10,000, while inorganic ions and solutes with a molecular weight of less than 5000 can pass through the membrane.
Reverse osmosis membranes can trap various metal ions, non-metal ions, colloids, and small molecules of organic matter in the reverse osmosis membrane. In general, the separation rate of divalent and high valence for inorganic ions, especially for wastewater can reach more than 95.
The box-type filter press realizes the effect of solid-liquid separation through the barrier of the medium (generally filter cloth) in the equipment. The device makes a pressure difference between the two sides of the medium, so that the liquid is discharged through the filter cloth through the pipe, and the solid is left on the filter cloth, which slowly accumulates and forms.
The advantages of the box filter press are as follows:
1. The box-type filter press is more durable than the plate and frame filter press.
2. High filtration efficiency. With the same number and size of filter plates, the effective filter area of a box filter is twice that of a plate and frame filter.
3. The box type is more widely used and can be used in many industries such as pharmaceuticals, food processing, metallurgical smelting, and mining.
4. The box-type filter press is generally used at a higher temperature than the plate and frame filter press, so its application range is wider.
5. The box-type filter press better integrates the current technology and can be well designed for automation. Many automated filter presses now use the same filtration mode as box filter presses.