How to treat electroplating wastewater?
Electroplating wastewater is one of the industrial wastewater with wide sources and great pollution.
There are two ways for electroplating wastewater to pollute the environment:
– Discharge of electroplating waste liquid with small quantity but high concentration.
– Discharge of electroplating wastewater with relatively low concentration.
Due to the dispersion of electroplating plants, compared with other industrial sites, although the amount of waste water is relatively small, the pollution diffusion area is relatively large.
The pollutants in electroplating wastewater mainly include cyanide, chromium, acid, alkali, salts and heavy metals.
This problem also exists in our metal screen filter industry. For example, galvanized wire, galvanized perforated tube(support of the filter element), etc.
Johnson screen does not need galvanizing treatment, but the final surface treatment is usually carried out by pickling. It also causes pollution.
Since 2017, our factory no longer uses the pickling surface treatment process. We use a more environmentally friendly physical surface treatment method.
Through this kind of environmental protection surface treatment process, the corrosion resistance of our wedge wire screen products will be improved, and the service life of the products will be improved.
Treatment of cyanide containing wastewater
The cyanide containing wastewater shall be designed as a separate treatment system, and shall not be mixed with other electroplating wastewater.
In particular, mixing with iron ions will cause great difficulties in treatment.
There are many methods to treat cyanide containing wastewater, such as alkaline chlorination, electrolytic oxidation, activated carbon adsorption, ion exchange (resin trap screen filter for ion exchange), ozone and ferrous sulfate.
The cyanide containing wastewater flows into the cyanide containing wastewater regulating tank automatically from the workshop, and is pumped into the primary cyanide breaking tank with the lift pump, with the adjusted pH value of 8.5 ~ 11.5.
In the alkaline condition, chlorine dioxide oxidizes cyanogen to non-toxic substances.
After passing through the primary cyanogen breaking tank, the waste water flows to the secondary cyanogen breaking tank automatically, and the pH is reduced to 7.5-8.5 under the control of pH meter.
Under the action of chlorine dioxide, the nacno produced by the primary cyanogen breaking tank generates N2 and CO2, and the waste water after the secondary cyanogen breaking is collected into the integrated regulating tank and treated together with the integrated waste water.
Treatment of chromium containing wastewater
There are two basic routes for the treatment of hexavalent chromium wastewater:
– The hexavalent chromium is reduced to trivalent chromium with low toxicity, and then removed by chemical precipitation, including chemical reduction, electrolytic reduction and agglomeration, etc.
– Resource recovery routes, such as ion exchange, activated carbon adsorption, reverse osmosis and other processes.
The chromium containing waste water flows into the chromium containing waste water regulating pool automatically from the workshop, adjusts the pH value to a certain value with dilute acid, and then pumps it into the waste water treatment unit. The wastewater flows from top to bottom in the treatment unit, reacts with iron filings, and the treated water flows to the integrated wastewater regulating tank.
Comprehensive wastewater treatment method
The comprehensive waste water, cyanogen containing waste water and chromium containing waste water flow into the waste water regulating tank together.
After rapid and uniform mixing of reagent before pump, it will enter into the coagulation reaction tank, and pH meter will be set to automatically control reagent addition, generally pH value is controlled 8-10, and then it will enter into the sedimentation tank.
The clarified supernatant flows into the water storage tank, pumps into the filter, flows into the pH regulating tank, and then flows out of the outlet weir after adjusting the pH.
The sludge from the sedimentation tank flows into the sludge concentration tank through the pipeline, the supernatant from the concentration tank flows back to the comprehensive wastewater regulation tank, the sludge is pumped to the filter press for dehydration, and the desuperheated water flows back to the comprehensive wastewater regulation tank, and the sludge cake is transported outside.
The water of pH regulating tank is used for backwashing filter and wastewater treatment machine, which can save water consumption.