Application of PAC (polyaluminum chloride) in modern wastewater treatment PAC (polyaluminum chloride) application in modern wastewater treatment. PAC (polyaluminum chloride) in the application of modern wastewater treatment methods are divided into physical treatment, chemical treatment and biological treatment of the three categories. 1. Physical treatment: the separation and recovery of waste water by the physical role of undissolved wastewater was suspended in the form of pollutants (including oil film and oil droplets) wastewater treatment. Usually precipitation, filtration, centrifugal separation, air flotation, evaporation crystallization, reverse osmosis and other methods. Sewage, suspended solids, colloids and oils and other pollutants separated, so that the wastewater was initially purified. 2. Chemical treatment: Separation by chemical reaction and mass transfer to remove dissolved or colloidal pollutants in waste water or convert them into harmless substances. Commonly used methods are: neutralization, coagulation, redox, extraction, stripping, stripping, adsorption, ion exchange and electrodialysis and other methods. 3. Biological treatment: microorganisms through the metabolism, the wastewater solution, colloids and finely suspended organic matter, toxic substances and other pollutants into stable and harmless substances in wastewater treatment methods. Biological treatment is divided into aerobic treatment and anaerobic treatment of two methods. Aerobic treatment method currently used in activated sludge, biological filters and oxidation ponds. Anaerobic treatment, also known as biological reduction treatment, mainly for the treatment of high concentrations of organic wastewater and sludge, the use of processing equipment, mainly digesters and so on. Compared with the physical and chemical methods, the biological method has the advantages of low running cost and good treatment effect. However, there are biological methods exist for a relatively long processing time, waste water contains toxic substances difficult to use and other defects. Biologists and engineers are constantly working to improve the effectiveness of biological processes by improving microbial strains and improving treatment processes. Efforts are under way to reduce the pollution by treating the waste water by various means. However, the method of eliminating pollution completely is to produce no pollutants, on the one hand to find more effective wastewater treatment methods and to eliminate the pollutants; on the other hand, to develop the design A new clean production technology to reduce the generation of pollutants We hope that our best efforts to make our contribution to the cause of water treatment.