Hardware spraying refers to various appearance treatments of zinc, aluminum, die-casting and stamping hardware parts, such as powder and oil spraying on the surface of cabinets and chassis, powder and oil spraying on hardware appliances, powder and oil spraying on hardware equipment, powder and oil spraying on medical equipment, powder and oil spraying on hardware lighting fixtures, etc. During processing and production, the main pollutants are degreasing wastewater, spray painting wastewater, phosphating and passivation wastewater. These types of wastewater contain petroleum, phosphate ions, metal ions, low molecular weight, organic compounds, pigments, surfactants, COD, SS, pH and other pollutants. The concentration is high and the composition of the wastewater is complex, resulting in poor biodegradability and relatively high treatment difficulty.

　　Metal spraying wastewaterBy adopting process technologies such as coagulation sedimentation, anaerobic, aerobic, sedimentation, MBR membrane, etc., the discharge of Class A effluent meets the standard.

The wastewater from hardware spraying and cleaning flows automatically into the original regulating tank, where the water volume is regulated to achieve uniform water quality and reduce the impact load on the air flotation tank treatment caused by uneven water quality. The original regulating tank was equipped with a lift pump to lift the sewage into the air flotation unit for oil removal pretreatment, then into the reaction tank for flocculation reaction, and finally into the sedimentation tank for mud water separation, removing some COD from the water BOD、 Chromaticity, acidity, alkalinity, and SS, etc.

The sedimentation effluent enters the callback tank to regulate the water quality and then enters the anaerobic tank. Through the acidification and hydrolysis of anaerobic bacteria, the high molecular weight organic pollutants in the wastewater are converted into small molecule substances through the oxidation and decomposition of microorganisms, and then enter the aerobic tank. The oxygen is supplied through fan aeration, and under the action of aerobic microorganisms, the organic pollutants in the wastewater are degraded. The effluent from the aerobic tank flows into the secondary sedimentation tank. The main function of anaerobic tank is to further degrade large molecular organic matter, making the removal efficiency of aerobic tank higher. The packing material in the anaerobic tank increases the biomass in the tank, allowing microorganisms to come into contact with pollutants more thoroughly, resulting in more complete degradation of pollutants, especially with strong adaptability to high concentration wastewater. The function of an aerobic tank is to thoroughly degrade pollutants, further degrade small molecule organic matter, fully utilize pollutants in sewage, absorb, transform, store, and utilize pollutants, and degrade pollutants to an acceptable risk level in the water body, thereby achieving high-quality water quality.

After biochemical treatment, the wastewater from hardware product cleaning contains flocculants and needs to be subjected to solid-liquid separation treatment. MBR membrane has efficient solid-liquid separation effect, which is much better than traditional sedimentation tanks. The effluent quality is good, and the suspended solids and turbidity in the effluent are close to zero. It can be directly utilized to achieve complete separation of hydraulic retention time (HRT) and sludge age (SRT), and the operation control is flexible and stable. Finally, the MBR effluent is further filtered through sand and charcoal filtration, ultrafiltration, and reverse osmosis to ensure that the effluent meets the standard and is stable.

By adopting the above sewage treatment process and combination process design, the water quality can reach the first level standard of Guangdong Province's local standard "Water Pollutant Discharge Limits" (DB44/26-2001).