During the precision machining process of hardware, there are wastewater discharges such as coolant, organic cleaning solution, coating wastewater, and electrical discharge fluid. These wastewater have a small amount, but high organic matter concentration, among which the CODCr of the cooling liquid reaches 50000-30000mg/L. Direct discharge without treatment will cause serious pollution to the environment. At present, there is a bottleneck in the treatment of high concentration precision machining wastewater in China. Many combination treatment technologies can reduce CODCr to several thousand milligrams per liter, but it is difficult to further improve treatment efficiency.

At present, China's improper treatment of high concentration and severely emulsified oily wastewater discharged during mechanical processing. The main reason is that with the improvement of technology, the stability of emulsions is becoming increasingly high, and breaking emulsions is becoming more and more difficult. This type of wastewater has complex components, poor biochemistry, and toxicity. At present, the treatment of this waste liquid mainly adopts physical and chemical methods such as chemical oxidation decomposition, chemical electrolysis, activated carbon adsorption and reverse osmosis.

1. Chemical oxidation decomposition method is currently widely used and effective for the treatment of mechanical processing wastewater both domestically and internationally. This method is economically simple, with low requirements for raw water quality, simple treatment technology and equipment, easy operation, low equipment maintenance, low energy consumption, stable operation and treatment effect, good decolorization effect, organic matter decomposition, and is suitable for the treatment of waste emulsion in small and medium-sized enterprises. This project uses chemical oxidation decomposition method to treat waste emulsion (waste coolant and other wastewater).

2. The deep treatment of mechanical processing wastewater is mainly achieved through reverse osmosis or activated carbon adsorption. Reverse osmosis technology is an effective membrane separation technique. However, the RO process has high requirements for wastewater pretreatment, large investment, minimal impact on the color of waste liquid treatment, and low operational management level. The principle of activated carbon adsorption filtration is that when the raw water passes through the filtering medium (quartz sand, activated carbon, etc.) in the activated carbon filter, it undergoes contact flocculation, adsorption, and interception, causing impurities in the raw water to be adsorbed and intercepted. According to the different raw water and usage range, filter media include quartz sand, quartz sand, activated carbon, etc. This method has high efficiency, good stability, and is easy to operate and manage.

3. Biochemical treatment of oily wastewater. Through physical and chemical pretreatment, the oil content and chemical oxygen demand of oily wastewater are greatly reduced, but it still contains a large amount of polymers and has poor biodegradability. The biochemical treatment system for wastewater from precision machining of hardware adopts the A/O process, namely hydrolysis acidification aerobic treatment process, to reduce operating costs and improve biochemical efficiency.

After pretreatment, the wastewater needs to enter the hydrolysis and acidification tank (tank A). Under the action of aerobic bacteria in the tank, difficult to decompose large molecular organic pollutants are broken down into small molecular organic compounds, improving the biodegradability of the wastewater. In order to keep the wastewater in the hydrolysis stage and fully mix the sludge and wastewater, a stirring system is installed in the tank, which is filled with fillers. A large number of microorganisms attach to the tank, forming a biofilm and improving the treatment efficiency of the system. The effluent from the hydrolysis acidification tank flows into the aerobic tank for aerobic biological treatment.