[Dry goods] common ultrafiltration membrane cleaning methods do you know several?

Ultrafiltration membrane, as the main equipment for wastewater treatment, gradually formed gel layer and pollutant sediment layer under the influence of concentration polarization after being operated for a long period of time, and was slowly compacted under the pressure difference , A significant increase in fluid resistance, a sharp decline in permeate flux, the use of physical methods can not make flux recovery, you must use chemical cleaning agents for cleaning.

However, when cleaning the membrane, two points should be noted: First, the composition of the pollutants and the nature of the pollution must be clarified in advance. In order to take effective cleaning methods. Second, if rinse with water, should try to rinse with water. Only when the water flushing less than the desired effect, only consider the use of chemical cleaning methods. To this ultrafiltration membrane cleaning, can be divided into physical cleaning and chemical cleaning two.

Physical cleaning method:

The most common and most used method in this regard is the hydraulic flush method. It can be due to the different direction of hydraulic flushing, divided into reverse flushing, backwashing and positive flushing.

Reverse flushing:

Rinse the membrane with the raw water and impurities in the inlet end.

Backwashing:

With ultrafiltration water from the membrane surface of the pollutants washed loose, spalling, respectively, from the inlet and concentrate discharge (can add acid, alkali or sodium hypochlorite and other drugs to enhance the cleaning effect).

Washing is washing:

With raw water rinse the membrane and the end of the impurities, according to the state of the ultrafiltration membrane to clean.

Chemical cleaning method:

According to the type of membrane surface contaminants, select the appropriate chemicals to be dissolved, oxidized or other chemical reactions to achieve the purpose of removal. The selection of commonly used chemicals must be based on the nature of the membrane material selection, such as acids, bases, oxidants, fungicides, surfactants and enzymes plus detergent. The process is the same as that of the normal ultrafiltration. The cleaning liquid enters from the inlet of the stock solution, and the concentrate and the ultrafiltrate are all returned to the cleaning solution container, discharged after the circulation, and washed with water.

Acid detergent commonly used 0.1N hydrochloric acid solution, 0.1M oxalic acid solution, 1 ~ 3% citric acid, citric acid amine, EDTA and so on. Such cleaning agent in the removal of calcium ions, magnesium ions, fluoride ions and other metal ions and their hydroxides, inorganic salt gel layer is more effective.

Alkaline cleaning agent is mainly 0.1 to 0.5% NaOH solution. It has a good effect on the removal of protein and oil pollution.

Oxidizing detergents such as 1 to 1.5% hydrogen peroxide, 0.5 to 1% NaOCl, 0.05 to 0.1% sodium azide and the like have a significant effect on the removal of organic substances.

Oxidizing detergents such as 1 to 1.5% hydrogen peroxide, 0.5 to 1% NaOCl, 0.05 to 0.1% sodium azide and the like have a significant effect on the removal of organic substances.

Bio-enzyme preparations such as 1% pepsin, trypsin and the like are effective in removing the contamination of proteins, polysaccharides and lipids. To remove organic pollution also have some effect. When using enzyme cleaning agent, such as cleaning at 55 ~ 60 ℃ better. The length of cleaning time is related to the level of enzyme concentration.

Although it is necessary to adopt the chemical cleaning method under the specific conditions, the ultrafiltration membrane must be used with caution. To avoid the chemical cleaning agent to damage the membrane separation performance; can not deform the pollutants, increase the membrane pollution; should not destroy the colloidal nature of pollutants, making it rigidified. In the food industry, pharmaceutical industry production, can not let the residues of cleaning agents affect product quality and so on.

UF membrane equipment is best to check once a month, while checking the body for leaks. UF ultrafiltration device according to the general requirements of water quality inspection. At the same time detection of UF system water flow and operating pressure.

Reverse osmosis membranes should have the following characteristics