Conventional drinking water treatment methods (coagulation, sedimentation, filtration, disinfection, etc.) are mainly to remove suspended solids and bacteria in the water, but the removal rate of various soluble chemical substances is low, and the harm caused by water pollution cannot be completely eliminated. It can’t meet people’s high standards for drinking water. In addition, long-distance pipeline transportation and secondary pollution of high-rise water tanks make drinking water no longer safe or sanitary. Therefore, advanced technology should be adopted as soon as possible for a more comprehensive treatment of drinking water. At present, with the intensification of water source pollution and the improvement of drinking water standards in various countries, the “drinking water advanced treatment” technology that can remove various organic and harmful chemical substances has attracted increasing attention. The need to adopt more effective water treatment methods and seek a process that occupies less land, is convenient for maintenance and management, and treats water with stable water quality has become a topic of general concern.
This method can remove odors, natural and synthetic organics, micro-pollutants, etc. in water through activated carbon adsorption.Although the quality of the effluent is good, it is good for toxic heavy metals, general salts, carcinogenic nitrites and radioactive substances, bacteria, viruses The removal effect will not be received. Some substances (such as bacteria) will even increase slightly when the treatment time is long. Moreover, the price of activated carbon is also high, which limits its use.
Ozone has strong disinfection ability, can oxidize organic matter, remove color, taste, soluble iron, manganese and phenol in water. However, it is unstable in water, easy to fail, and its sterilization effect cannot be sustained in the pipe network. Moreover, the equipment is complicated, the investment is large, and the energy consumption is large. It is currently less used in my country. In addition, the water oxidized by ozone creates small molecular organic compounds, which makes the biological stability of the water worse. Currently, the combined application of ozone and activated carbon is usually better.
Membrane separation technology is an emerging high-efficiency separation, concentration, purification, and purification technology. Its main characteristics are energy saving (because the membrane separation process does not change phase), and a wide range of separation objects (organic and inorganic matter, viruses, bacteria, particles), The device is simple, easy to operate, easy to control, easy to maintain (because pressure is only used as the driving force for membrane separation), and is especially suitable for the separation, classification, concentration and enrichment of heat sensitive substances (because the separation process only needs to be carried out at room temperature ). At present, the organic membranes that have been developed worldwide mainly include microfiltration membranes (MF), ultrafiltration membranes (UF), nanofiltration membranes (NF) and reverse osmosis membranes (RO). Among them, microfiltration (MF) and ultrafiltration (UF) cannot remove various low-molecular substances, so they cannot be called advanced treatment when used alone. Reverse osmosis (RO) and nanofiltration (NF), as one of the separation membranes for water and other liquids, occupy an important position in the field of separation membrane applications. In today’s world, the capacity of reverse osmosis and nanofiltration membrane water treatment devices has reached millions of tons per day. The largest reverse osmosis brackish water desalination device is the Canal Water Treatment Plant with a daily water output of 280,000 tons in Arizona, USA. The largest reverse osmosis desalination device is located in Saudi Arabia, with a daily water output of 128,000 tons. The largest nanofiltration desalination and softening unit is located in Florida, USA, with a daily water output of 38,000 tons.