What is membrane flux? What is membrane recovery? Membrane flux, also known as membrane water permeability, refers to the water flow through the unit membrane area under normal operating conditions, the unit is m3 / (m2?) Or m3 / (m2.d). The recovery of membrane separation method is the conversion of water supply through the membrane separation, that is, the percentage of permeated water as a percentage of water supply. Membrane flux and recovery and the thickness of the film, porosity and other physical characteristics, but also with the film's working environment such as water temperature, membrane pressure difference (or potential difference) on both sides, the concentration of raw water and so on. After selecting a certain kind of membrane, the physical properties of the membrane remain unchanged, the membrane flux and the recovery rate are only related to the working environment of the membrane. Within a certain range, increasing the water temperature and increasing the pressure difference can increase the membrane flux and recovery rate, and the increase of the influent concentration will reduce the membrane flux and recovery rate. With the extension of the use of time, the membrane pores will be clogged with debris by the Zhejiang, under the same pressure and the same water quality membrane flux and recovery will decline. In this case, the membrane needs to be cleaned to restore its original membrane flux value and recovery rate. If the membrane flux and recovery rate still have a large gap with the ideal value after cleaning, the membrane element must be replaced. What is microfiltration, ultrafiltration and nanofiltration? Microfiltration is a precision filtration technology, the use of pore size of 0.1 ~ 1.5μm filter for water filtration, the English is Micro-porousFilration, referred to as MF. Microfiltration is a low-pressure membrane filtration, water pressure is generally less than 0.2MPa, filtration accuracy between conventional filtration and ultrafiltration, the separation of water in the diameter of 0.03 ~ 15μm components, to remove water particles, turbidity, Bacteria, viruses, algae and so on. Ultrafiltration is a pressure-driven, the use of a pore size of 0.01-0.1μm filter on the water filtration method, the English is Ultra-Filtration, referred to as UF. The operating pressure is below 0.5MPa, the filtration precision lies between nanofiltration and ultrafiltration, the separation of macromolecular compounds and colloids with the diameter of 0.005 ~ 10μm in water and the molecular weight of more than 500 can effectively remove suspended solids, colloids and bacteria in water, Viruses and some organic matter. Nanofiltration English Nanometer-Filtration, referred to as NF, the filtration accuracy between reverse osmosis and ultrafiltration, also known as loose early reverse osmosis (LooseRO), the operating pressure of 3MPa or less. The early nanofiltration membrane, also known as softening film, has a high removal rate of calcium and magnesium ions, and can effectively remove soluble components with a molecular weight above 200 in water and a molecular size of about 1 nm. What are the filter cleaning methods? Membrane separation device in operation, the most common and most serious problem is due to membrane contamination or blockage and make the problem of water permeability decreased, so the membrane cleaning and cleaning process is an important part of the membrane separation method, cleaning the extension of the membrane Of the service life and restore the membrane water flux and other separation performance is directly related to the membrane when the water through the water or water quality dropped significantly or membrane device inlet and outlet pressure difference over 0.05MPa, the membrane segment must be cleaned. Membrane cleaning methods are mainly physical and chemical methods of two categories. The specific operation should be based on the configuration of the components, membrane material, the type of pollutants and the degree of pollution selected cleaning method. Physical cleaning method is the use of mechanical force to peel the membrane surface contaminants, in the cleaning process does not occur any chemical reaction. Specific methods are hydraulic flushing, gas and water mixed flushing, countercurrent cleaning, hot water flushing. Hydraulic cleaning is the use of membrane-side water after the formation of high-pressure flow-rate film on the loose accumulation of soft impurities. Gas-water mixed cleaning is the same time by the compressed water side of the membrane water and water flow, with the help of gas, water and membrane surface shear effect and membrane surface impurities will be washed down. Countercurrent cleaning is primarily used for the cleaning of hollow fiber membranes by applying reverse pressure to the support layer, causing the membrane to permeate backwards to loosen and remove contaminants from the feed side of the membrane. Chemical cleaning method is to use a chemical agent and the membrane surface of the harmful impurities to produce chemical reaction to achieve the purpose of cleaning the membrane. Different chemicals should be used according to different pollutants. The choice of chemical agents must take into account two points. First, the cleaning agent must have good ability to dissolve and decompose pollutants. Second, the cleaning agent can not pollute and damage the membrane surface. Therefore, according to different pollutants to determine the cleaning process, while the working temperature and the membrane of the cleaning agent to consider the membrane allows the use of pH range, the body's chemical stability. Cleaning filter membrane commonly used chemical cleaning method which? (1) pickling method. Pickling method to remove calcium deposits, metal hydroxides and inorganic glide deposits and other inorganic impurities best. The specific approach is to use acid circulation cleaning or soaking 0.5 ~ 1h, commonly used acid hydrochloric acid, oxalic acid, citric acid, acid solution pH value according to the membrane material may be. For example, cleaning cellulose acetate membrane, acid pH value of 3 to 4, while cleaning the other membrane, the acid pH value of 1 to 2. (2) alkaline washing method. Alkali washing method to remove grease and other organic impurities better effect, the specific practice is to use alkaline solution cleaning or soaking 0.5 ~ 1h, commonly used base with sodium hydroxide and potassium hydroxide, alkaline solution pH value should also be based on the membrane material And set. Such as cleaning cellulose acetate membrane, lye pH value of about 8, while cleaning other corrosion-resistant Liao, lye pH value can be about 12. (3) oxidation method. Oxidation method to remove grease and other organic impurities better, and can also play a bactericidal effect, the specific approach is to use oxidant solution cleaning or soaking 0.5 ~ 1h, commonly used oxidant is 1% to 2% of the peroxide Hydrogen solution or 500-1000 mg / L sodium hypochlorite solution or chlorine dioxide solution. (4) detergent method. Detergent method to remove grease, protein, polysaccharides and other organic impurities better. The specific method is to use 0.5% ~ 1.5% of the detergent or protein surfactant or anionic surfactant circulating cleaning or soaking 0.5 ~ 1h.