How to clean hollow fiber ultrafiltration membrane?

How to clean hollow fiber ultrafiltration membrane? 1.First, rinse the entire hollow fiber ultrafiltration membrane system with clean water, and the water temperature should be a higher temperature that the ultrafiltration membrane can withstand.

2.Select the appropriate cleaning agent for circulating cleaning hollow fiber ultrafiltration membrane equipment.

3.Rinse with clean water to remove the detergent.

4.Check the permeable energy of the nuclear membrane under the specified conditions, and repeat the second and third steps of cleaning if the expected value is not reached.

5.Soak and disinfect with aqueous formaldehyde solution and store it.

Correct cleaning method for hollow fiber ultrafiltration membranes:

1. Rinse the entire hollow fiber ultrafiltration membrane (macromolecular substances and proteins that can intercept microns) system with clean water, and the water temperature is best to use ultrafiltration (with the help of semi-permeable membrane membrane membrane separation technology) The membrane module can withstand a higher temperature.

2. Select the appropriate cleaning agent for circulating cleaning hollow fiber ultrafiltration membrane equipment: drinking water list, the cleaning agent can contain complexing agents such as EDTA or sodium hexametaphosphate.

3. Rinse with water to remove the cleaning agent.

4. Check the permeable energy of the membrane under the specified conditions, and repeat the second and third steps of the cleaning process if it fails to reach the expected value.

5. Soak and disinfect with formaldehyde aqueous solution (refers to the method of killing pathogenic microorganisms, but not necessarily killing bacterial spores) and store.

There are several ways to clean ultrafiltration membranes:

When the pollution reaches a certain level, it is necessary to clean the ultrafiltration membrane, and the ultrafiltration membrane can restore the original water yield to the greatest extent after cleaning, so how many cleaning methods are there for the ultrafiltration membrane? The cleaning methods of ultrafiltration membranes can be divided into two types: physical cleaning methods and chemical cleaning methods.

Physical cleaning methods can also be divided into three types: reverse washing, backwashing, and positive washing. These cleanings have different actions and characteristics, and the following is a detailed introduction for you.

What are the cleaning methods of ultrafiltration membranes, detailed answers:

1. Physical cleaning method: The physical method is actually to rinse the ultrafiltration membrane with water under a certain pressure, which is also the most commonly used method. Because the direction of this water flushing is different, it can be divided into reverse flushing, backwashing and positive flushing.

1.Reverse flushing: Rinse impurities in the membrane and at the end of the inlet with raw water.

2.Backwashing: Use ultrafiltration water to flush loose and peel off the pollutants on the surface of the membrane, and discharge them from the water inlet and concentration port respectively (acid, alkali or sodium hypochlorite and other chemicals can be added to enhance the cleaning effect).

2. Chemical cleaning method:

The chemical reaction between chemicals and impurities on the membrane surface is used to achieve the purpose of cleaning the membrane.

Acid solution cleaning: commonly used solutions are hydrochloric acid, citric acid, oxalic acid, etc., the pH = 2 3 of the prepared solution, the use of cycle cleaning or soaking after cycle cleaning, the removal effect of inorganic impurities is better.

Alkali solution cleaning: the commonly used alkali is mainly NaOH, the pH = 10 12 of the prepared solution, the use of water circulation operation cleaning or soaking after circulation cleaning, can effectively remove impurities and grease.

Oxidant cleaning agent: Cleaning the ultrafiltration membrane with 1% 3% H2O2, 500 1000mg L Naclo and other aqueous solutions can remove dirt and kill bacteria. H2O2 and Naclo are commonly used fungicides.

Enzyme detergents: such as pepsin, trypsin, etc., which are effective in removing protein, polysaccharides, and oil pollutants.

The method is the same as the normal ultrafiltration process, the cleaning solution enters from the inlet of the stock solution, and the concentrate and ultrafiltrate are all returned to the cleaning solution container, discharged after circulation, and washed with clean water.

Ultrafiltration membrane cleaning steps:

1. Prepare cleaning solution.

2. Low flow input cleaning solution.

First, use a cleaning pump to mix the cleaning solution once to preheat the cleaning solution at a low flow rate. The raw water is then replaced with the lowest possible purge fluid pressure, which only needs to be sufficient to compensate for the pressure loss from the influent to the concentrated water, i.e. the pressure must be low enough to produce a significant permeate water production. The low-pressure displacement operation minimizes fouling and re-settles to the surface of the membrane (as appropriate), draining a portion of the concentrated water to prevent dilution of the cleaning solution.

3. Circulation. When the raw water is replaced, the cleaning solution should appear in the concentrated water pipe, so that the cleaning solution should be returned to the cleaning tank, and the temperature of the cleaning solution should be constant.

4. Soaking. Stop the operation of the cleaning pump and allow the membrane element to be completely immersed in the cleaning solution. Sometimes an hour or so of soaking is sufficient, but for stubborn contaminants, an extended soaking time is required, such as 10 to 15 hours or overnight. In order to maintain the temperature of the immersion process, a very low circulating flow rate can be used.

5. High flow pump circulation.

The high flow rate washes away contaminants washed out by the cleaning fluid. If the contamination is severe, the flow rate listed in Table 1 will be more than 50% for cleaning, while in the case of high flow rates, the problem of high pressure drop will occur. The maximum allowable pressure drop for a single element is 1 bar (15 psi) and the maximum allowable pressure drop for a multi-pressure vessel is.

6. Rinse. Unless there is a corrosion problem (e.g., static seawater can corrode stainless steel pipes), a pre-treated and qualified water flush system can be used to flush the cleaning fluid. To prevent precipitation, the minimum wash temperature is 20. Note:

During the pickling process, the change in the pH value of the cleaning solution should be checked at any time. When the acid is consumed by the dissolved inorganic salt precipitate, and when the pH rises exceeded, the acid should be added to the cleaning chamber. The total cycle time of the pickling solution should not exceed 20 minutes.

After this, the cleaning solution may be saturated with rinsed out inorganic salts, and contaminants can be deposited on the surface of the membrane. At this point, the qualified pre-treated water is used to drain the first cleaning solution from the membrane system and the cleaning system, and the cleaning solution is reconfigured for the first acid cleaning operation. If the system must be shut down for more than 24 hours, components should be stored in 1% (by weight) sodium bisulfite in aqueous solution.

Before cleaning the system, it is recommended that the membrane elements be removed from the system to be cleaned and that the cleaning effect of the individual elements be evaluated.

7. Clean the multi-stage system.

In the flushing and immersion steps of a multi-stage system, all parts of the entire system can be carried out simultaneously, but the high flow cycle must be carried out in stages to ensure that the circulation flow of the first stage is not too low and the circulation flow of the last stage is not too high. This can be achieved by cleaning each section separately or by setting up a different purge pump for each flow requirement.

Chemical cleaning method of ultrafiltration membrane:

1. Microbial contamination.

When the contaminant is bacteria or viruses, it can be cleaned with hydrogen peroxide with a concentration of 1 percent, and ultrafiltration membranes can also be chemically cleaned with a 50ppm sodium hypochlorite solution.

2. Inorganic pollution.

When the contaminant is inorganic colloid, iron salt or calcium carbonate, hydrochloric acid, citric acid or oxalic acid solution can be used for cleaning, and the pH value should be controlled at about 2. When the contaminant is some insoluble inorganic salts such as calcium sulfate or barium sulfate, EDTA solution with a concentration of 1% can be used for cleaning.

3. Organic pollution.

When the contaminants are oil, starch, protein or polysaccharides, they can be cleaned with amylase, protease, etc. at a concentration. When the ultrafiltration membrane contaminants are organic colloids, fats, or humic acids, they can be cleaned with a sodium hydroxide solution with a pH of 12. When the contaminants are grease substances or some organic substances that are difficult to clean, sodium dodecyl sulfate can be used for cleaning, and the concentration should be controlled at about that.

1. Prepare cleaning solution.

2. The low-flow input cleaning liquid should first be mixed with a cleaning water pump, and the cleaning liquid should be preheated with a low flow rate. The raw water in the element is then replaced with the lowest possible purge fluid pressure to a pressure loss sufficient to compensate the incoming water to the bristle, i.e. the pressure must be so low that it does not produce significant permeate permeate. The low-pressure displacement operation minimizes the re-settling of fouling onto the membrane surface and, depending on the situation, drains a portion of the concentrated water to prevent dilution of the cleaning solution.

3. CirculationWhen the raw water is replaced, the cleaning liquid should appear in the concentrated water pipeline, so that the cleaning liquid can be circulated back to the cleaning water tank and the temperature of the cleaning liquid should be kept constant.

4. Immersion stops the operation of the cleaning pump, and the membrane element is completely immersed in the cleaning solution. Sometimes soaking the elements for about 1 hour is sufficient, but for stubborn contaminants, an extended soaking time is required, such as soaking for 10-15 hours or soaking overnight. In order to maintain the temperature of the immersion process, a very low circulating flow rate can be used.

5. The high flow rate of the water pump can wash off the pollutants cleaned by the cleaning liquid, if the pollution is serious, please use 50% of the flow rate higher than the provisions of Table 1 will help to clean, under the condition of high flow, there will be the problem of excessive pressure drop, the maximum allowable pressure drop of a single element is 1 bar (15psi), and the maximum allowable pressure drop of the multi-element pressure vessel is limited to the first exceedance.

6. The qualified permeate of the flushing pretreatment can be used to flush the cleaning fluid in the system, unless there is a corrosion problem (for example, still seawater will corrode the stainless steel pipe).

7. Cleaning multi-stage system In the flushing and soaking steps of the multi-stage system, all sections of the whole system can be carried out at the same time, but the circulation of high flow must be carried out in sections to ensure that the circulation flow rate is not too low for the first section and not too high for the last section, which can be achieved by cleaning each section separately by a pump each time or setting different cleaning pumps for each section of flow requirements.

Here are a few ways to clean your ultrafiltration membranes:

Physical methods: 1. Reverse flushing. Use raw water to flush impurities in the ultrafiltration membrane and at the inlet end.

2. Backwashing. Use ultrafiltration water to loosen and peel off the pollutants on the surface of the membrane, and discharge them from the water inlet and concentration port respectively (acid, alkali or sodium hypochlorite and other chemicals can be added to enhance the cleaning effect).

3. Flushing. Rinse the impurities in the ultrafiltration membrane and the end face with raw water, and clean the ultrafiltration membrane according to the operating state.

Chemical methods: 1. Rinse with acid.

2. Use a mixed wash of sodium bifluoride and alkali, a mixed wash of sodium bifluoride and acid, or a mixed wash of sodium bifluoride and sodium fluoride for cleaning.

3. Clean with oxidant.

4. Use membrane cleaning additives for cleaning.

5. Use surfactant or organic solvent cleaning agent for cleaning.

Hope it helps.

OK. The ultrafiltration membrane is in operation for a long period of time, under the influence of concentration polarization, the gel layer and the pollutant deposit layer are gradually formed, and under the action of the pressure difference, the fluid resistance is significantly increased, the permeable flux decreases sharply, and when the flux cannot be restored by physical methods, it must be cleaned with chemical cleaning agents.

When cleaning membranes, it should be noted that the composition and nature of the contaminants must be clarified in advance. In this way, an effective cleaning method can be adopted. If you can rinse with clean water, you should try to rinse with clean water as much as possible. Chemical cleaning methods should only be considered when rinsing with water does not achieve the desired effect.

Depending on what the fouling is, organic matter can be cleaned with sodium hypochlorite plus sodium hydroxide, and inorganic scale and oxide can be cleaned with hydrochloric acid or citric acid.

The cleaning of ultrafiltration membranes is mainly carried out by backwashing, acid and alkali immersion chemical cleaning according to the length of use and the degree of pollution!

In order to restore the flux of the membrane, the membrane module needs to be chemically cleaned regularly, and the appropriate chemicals should be selected according to the impurities in the raw water.

Alkaline cleaning solution: sodium hydroxide (Naoh) + 200 ppm sodium hypochlorite (Nacio3) or 50 ppm chlorine (Cl2), pH: 10

Pickling cleaning solution: 2% citric acid or hydrochloric acid (.

Chemical Cleaning Method:

Water inlet of each component: Q cleaning = Q feeding.

Close the permeable valve and cycle for 45 minutes.

Open the permeable valve and cycle for 45 minutes.

Determining when a system should be chemically cleaned is determined by the operating state of the system, and when the system's transmembrane pressure difference is greater than that, the system should be chemically cleaned. After cleaning, within the cross-membrane pressure range of the system design, the produced water of the system should meet the original design requirements, otherwise the cleaning and chemical cleaning should be continued or the interval between chemical cleaning should be shortened, and the frequency and operation time of backflushing and backwashing should be adjusted.

Chemical cleaning: With the long-term use of ultrafiltration membrane modules, when the water yield of the ultrafiltration membrane decreases by more than 20% or is used for 1-4 months, the ultrafiltration membrane needs to be chemically cleaned in order to remove the pollutants on the ultrafiltration membrane in time and prevent the formation of stubborn scaling on the ultrafiltration membrane. In general, chemical cleaning is divided into pickling and alkaline washing.

A. Pickling: Use citric acid to adjust the pH value of RO reverse osmosis water (or ultrafiltration water) in the liquid medicine tank to pH=2, start the liquid medicine pump, adjust the throttle valve to make the pressure gauge display pressure P=, and use ultrafiltration water to rinse the ultrafiltration membrane after circulating pickling for 30 minutes.

b. Alkali washing: use sodium hydroxide and sodium hypochlorite to adjust the RO reverse osmosis water (or ultrafiltration water) in the liquid medicine tank to pH = 12, start the liquid medicine pump, adjust the regulating valve to make the pressure gauge display pressure p = , and use ultrafiltration water to rinse the ultrafiltration membrane after circulating alkali washing for 30 minutes.