Ultrafiltration system membrane Cleaning

UF system operation and ultrafiltration membrane cleaning

UF system is often used for reuse of reclaimed water and is easily contaminated by impurities such as organic matter, microorganisms, metal ions, and suspended solids.

1) Operation of UF system

During operation, the surface of the membrane will be covered by the various harmful impurities it traps to form a filter cake layer, and even the membrane pores will be blocked by even smaller impurities, which will increase the membrane pressure of the water; therefore, the quality of the raw water is relatively low. Good or bad, it will affect the speed and speed of membrane fouling.

Even if the pretreatment is thorough, the very few impurities in the water will gradually affect the performance of the membrane due to the accumulation of time. Therefore, when the ultrafiltration membrane is polluted to a certain degree, it should be cleaned in time.

2) Determination of ultrafiltration membrane pollutants

In the first few months of operation, if you find that the pressure difference rises relatively quickly, you need to open the end cover and remove the ultrafiltration membrane for inspection.

If it is found that there is a layer of yellow viscose on the end face and shell of the UF membrane, which cannot be completely dissolved in HCl or NaOH, but fades in acid, it can be judged that the pollutants are mainly inorganic salt scale and colloidal fouling.

If it is found to have rancid smell, sticky attachments, black, yellow, black and green, and can be slowly dissolved in high concentrations of NaClO and HCl, it can be judged that the pollutants are mainly bacterial microorganisms, organic matter and inorganic salt scale.

3) Chemical cleaning of UF system

When choosing chemicals for chemical cleaning, you should first pickling and then alkali cleaning, or sterilizing and then pickling and alkali cleaning, the effect is the best, the commonly used agents are as follows:

A) Backwash with hydrochloric acid: remove metal ion attachments on the membrane

B) Backwashing with sodium hypochlorite: sterilization and virus elimination

C) Backwash with sodium hydroxide: to clean impurities such as organic matter

4) Determination of ultrafiltration membrane cleaning solution

Because the pollutants of ultrafiltration system are mainly organic matter, microbial pollution, and inorganic salt scale, it is recommended to pickling and then alkaline cleaning; during chemical cleaning, it is necessary to ensure that there is no air in the equipment. It is recommended to operate equipment according to the pressure difference, every 1~ The intensive cleaning is carried out once every 2 months. The agent is twice the normal chemical cleaning. The soaking time depends on the condition of fouling. The general soaking time should not exceed six hours.

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