There are many electroplating production processes. Due to the different electroplating processes, the wastewater produced is also different. The wastewater discharged by general electroplating companies includes pre-treatment wastewater such as acid and alkali, cyanide-containing wastewater from cyanide copper plating, and copper-containing wastewater. , Nickel-containing wastewater, chromium-containing wastewater and other heavy metal wastewater. In addition, a variety of electroplating waste liquids are generated.
There are different treatment methods for electroplating wastewater containing different types of pollutants, which are introduced as follows:
1. Ultraviolet sterilization of cyanide-containing wastewater (i.e. the use process of ultraviolet sterilizer or ultraviolet sterilizer) disinfection process
At present, the more mature technology for treating cyanide-containing wastewater is the alkaline chlorination method. Care must be taken to strictly separate cyanide-containing wastewater from other wastewater to avoid mixing with metal ions such as nickel and iron, otherwise the treatment will be difficult. The principle of this method is to destroy and remove cyanide by using chlorine-based oxidants in the wastewater under alkaline conditions. The treatment process is divided into two stages. The first stage is to oxidize cyanide into cyanate, which is not completely destroyed. It is called the incomplete oxidation stage. The second stage is to further oxidize and decompose the cyanate into carbon dioxide and water, which is called the complete oxidation stage.
Cyanide-containing wastewater → conditioning tank → primary cyanide breaking tank → secondary cyanide breaking tank → inclined sedimentation tank → filter tank → callback tank → ultraviolet disinfection equipment (ultraviolet sterilizer or ultraviolet disinfector) → discharge
The treated cyanide-containing wastewater is mixed into the electroplating comprehensive wastewater for treatment together.
2. Ultraviolet sterilization of chromium-containing wastewater
Wastewater containing hexavalent chromium is generally treated by the chromium reduction method. The principle of this method is to add reducing agents ferrous sulfate, sodium sulfite, sodium bisulfite, sulfur dioxide, etc., to reduce hexavalent chromium to trivalent chromium under acidic conditions. Then, sodium hydroxide, calcium hydroxide, lime, etc. are added to adjust the pH value, so that trivalent chromium hydroxide is precipitated and separated from the wastewater. The treatment process is as follows:
Wastewater containing Cr6+→adjustment tank→reduction reaction tank→coagulation reaction tank→sedimentation tank→filter→pH callback tank→discharge
3. Comprehensive ultraviolet sterilization of heavy metal wastewater (i.e., the use process of ultraviolet sterilizer or ultraviolet sterilizer) disinfection process
Comprehensive heavy metal wastewater is composed of non-complex heavy metal wastewater containing copper, nickel, zinc and other non-complex compounds, as well as acid and alkali pretreatment wastewater. This type of wastewater treatment method is relatively simple, and generally adopts the process of generating hydroxide precipitation under alkaline conditions for treatment.
The treatment process is as follows:
Comprehensive heavy metal wastewater → regulating tank → fast mixing tank → slow mixing tank → inclined tube sedimentation tank → filtration → pH callback tank → ultraviolet sterilization equipment (ultraviolet sterilizer or ultraviolet sterilizer) → discharge
4. Comprehensive treatment of a variety of electroplating wastewater UV sterilization (i.e. UV sterilizer or UV sterilizer use process) disinfection process
When an electroplating plant contains a variety of electroplating wastewater, such as cyanide-containing wastewater, hexavalent chromium-containing wastewater, acid-base, heavy metal copper, nickel, zinc and other comprehensive wastewater, the wastewater is generally treated by diversion. First, cyanide-containing wastewater and chromium-containing wastewater Wastewater should be collected separately from the production line, and the cyanide-containing and chromium-containing wastewater should be treated in accordance with the corresponding methods mentioned above. The treated wastewater should be mixed into the comprehensive wastewater together with the coagulation sedimentation method for subsequent treatment.
The treatment process is as follows:
Cyanide-containing wastewater → regulating tank → primary cyanide breaking tank → secondary cyanide breaking tank → comprehensive wastewater tank
Chromium-containing wastewater → conditioning tank → chromium reduction tank → comprehensive wastewater tank
Comprehensive wastewater → comprehensive wastewater tank → fast mixing tank → slow mixing tank → inclined tube sedimentation tank → intermediate tank → filter → pH callback tank → ultraviolet disinfection equipment (UV sterilizer or ultraviolet disinfector) → discharge