Membrane pollution control method

Abstract

The invention relates to a membrane pollution control method, which comprises the following steps: carrying out ultrafiltration on simulated raw water by using an ultrafiltration membrane along with a stirring process; the stirring process at least comprises a stirring stage; the total time of the stirring process accounts for 20-100% of the total time of the stirring stage by taking the total time of the stirring process as 100%. According to the membrane pollution control method provided by the invention, the stirring process in the ultrafiltration process is designed, and the flow state of the fluid in the ultrafiltration process is regulated and controlled through the disturbance effect of stirring on the simulated raw water, so that the sedimentation rate difference of different types of pollutants in the simulated raw water can be broken through; the probability that pollutants are adsorbed and blocked on the surface of the ultrafiltration membrane and in membrane holes is reduced, so that the pollution degree of the ultrafiltration membrane is effectively relieved, the membrane flux of the ultrafiltration membrane in the running process is improved, and the running life of the ultrafiltration membrane is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a membrane pollution control method. Background Art

[0002] With the development of material technology and the deepening of the concept of green water purification, water purification technologies with no or low drug consumption based on low-pressure membrane filtration technology have been widely used. However, the inevitable membrane pollution problem (membrane pore adsorption, membrane pore blockage and filter cake layer) during operation has become a bottleneck for the further development of low-pressure membrane filtration water purification technology. Based on this, coagulation, adsorption, oxidation and their combined use pretreatment processes have been developed successively, all of which can slow down membrane pollution to varying degrees. However, due to the wide distribution of pollutant particle sizes in water bodies, no matter which of the above pretreatment methods is used, small particle size pollutants will still be adsorbed in the ultrafiltration membrane pores during ultrafiltration, causing serious irreversible pollution after long-term operation. On the one hand, in the traditional membrane filtration process, the membrane pores are mostly laminar, which not only makes pollutants easy to adsorb and block the membrane pores, but also makes it difficult for pollutants to fall off after adsorption and blockage due to the small disturbance during operation. On the other hand, during the periodic gas-water backwashing process, although the backwash water flow rate is higher than the normal filtration flow rate, the backwashing time is short and the flow state of the fluid in the membrane pores is still laminar, so the pollutants adsorbed in the membrane pores cannot be effectively removed. In addition, the bubble size is large during conventional aeration, and its purpose is only to effectively remove the loose filter cake layer on the membrane surface. The bubbles cannot enter the membrane pores, and thus cannot change the flow state of the fluid in the membrane pores. Therefore, how to regulate the flow state of the fluid in the membrane pores becomes the key to effectively reduce the adsorption and clogging of pollutants in the membrane pores.

[0003] Prior art CN111533322A discloses a membrane pollution control method for ultrafiltration treatment of microbial contaminated wastewater. The method pre-treats the microbial contaminated wastewater by adding coagulants and coagulants, and then combines the ultrafiltration process to effectively remove pollutants such as microorganisms in the water. However, the method has the following problems: (1) The effect of adding coagulants and coagulants is limited, and the removal of small molecular pollutants in the wastewater is limited, and the membrane pores will eventually be blocked; (2) The addition of coagulants and coagulants will increase the treatment cost of wastewater; (3) The quality of wastewater will affect the coagulation process. When the coagulation effect is not good, coagulant residues will exist in the wastewater.

[0004] Prior art CN117427497A discloses a method for cleaning an ultrafiltration membrane, which uses six steps of "clean water rinsing - alkaline solution cleaning - clean water rinsing - alkaline / chlorine cleaning - clean water rinsing - acid solution cleaning" to restore the membrane flux of a severely contaminated ultrafiltration membrane. However, the complicated processing steps of this method will lead to a long membrane cleaning cycle, and the added cleaning agents such as liquid chlorine may affect the structure and performance of the membrane.

[0005] Therefore, how to regulate the fluid flow state in the ultrafiltration process to reduce the probability of adsorption of pollutants on the membrane surface and in the membrane pores, and thus effectively mitigate membrane fouling, has become a problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a membrane pollution control method. The membrane pollution control method provided by the present invention regulates the flow state of the fluid in the ultrafiltration process by stirring the disturbance effect of the simulated raw water in the ultrafiltration process, breaks the sedimentation rate difference of different types of pollutants in the simulated raw water, and can reduce the probability of adsorption and clogging of pollutants on the surface of the ultrafiltration membrane and in the membrane pores, thereby effectively alleviating the degree of pollution of the ultrafiltration membrane, thereby improving the membrane flux of the ultrafiltration membrane during operation and extending the operating life of the ultrafiltration membrane.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a membrane fouling control method, the membrane fouling control method comprising the following steps:

[0009] Ultrafiltration is performed on the simulated raw water using an ultrafiltration membrane, and the ultrafiltration process is accompanied by a stirring process;

[0010] The stirring process at least includes a stirring stage; taking the total time of the ultrafiltration process as 100%, the total time of the stirring stage accounts for 20-100%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, etc.

[0011] The membrane pollution control method provided by the present invention breaks the sedimentation rate difference of pollutants of different sizes by adding a stirring process in the ultrafiltration process, and effectively alleviates the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during operation. At the same time, for the already polluted ultrafiltration membrane, the water body is disturbed by stirring, and the water flow changes from laminar flow to turbulent flow at the initial moment of stirring, which can effectively remove the pollutants adsorbed on the surface of the ultrafiltration membrane or even inside the membrane pores, and effectively improve the membrane flux. Furthermore, in the method provided by the present invention, the stirring stage time in the stirring process is controlled, which can reduce the energy consumption of the membrane pollution control method while improving the membrane flux of the ultrafiltration membrane. Through the cooperation of the stirring stage and the non-stirring stage, the sedimentation rate difference of pollutants of different sizes is broken. Under the condition of low energy consumption, it can still effectively alleviate the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during the ultrafiltration process. Compared with pre-membrane pretreatment such as coagulation and physical and chemical cleaning measures for contaminated membranes, the stirring process design based on the ultrafiltration process effectively reduces the degree of contamination of the ultrafiltration membrane during operation and extends the service life of the ultrafiltration membrane to a certain extent, which is in line with the new environmentally friendly water purification concept of green, less medicine and low consumption.

[0012] Preferably, the stirring speed in the stirring stage is 50-200 rpm, for example, 50 rpm, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm, etc.

[0013] In the present invention, by regulating the stirring speed, the ultrafiltration membrane pollution can be effectively alleviated and the recovery of the ultrafiltration membrane flux can be improved. If the stirring speed is too low, the interference effect of the simulated raw water ultrafiltration process will be small, and the ultrafiltration membrane pollution cannot be effectively alleviated; if the stirring speed is too high, the energy consumption during the operation will increase, and the overall process operation cost will increase.

[0014] Preferably, the stirring process includes an interval stirring process repeated at least twice, and a single interval stirring process includes first a standing stage and then a stirring stage.

[0015] In the present invention, the "stirring stage" and the "stationary stage" both refer to the state of the stirring device in the ultrafiltration device. When the rotation speed of the stirring device is not 0 rpm, it is the stirring stage, and when the rotation speed of the stirring device is equal to 0 rpm, it is the stationary stage.

[0016] Preferably, in a single interval stirring process, taking the total time of the single interval stirring process as 100%, the time of the standing stage accounts for 20-80%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, etc.

[0017] Preferably, in a single interval stirring process, taking the total time of the single interval stirring process as 100%, the time proportion of the stirring stage is 20-80%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, etc.

[0018] The present invention controls the time proportion of the stirring stage and the standing stage in the repeated interval stirring process, thereby ensuring the improvement of the ultrafiltration membrane flux during the ultrafiltration process, thereby alleviating the contamination of the ultrafiltration membrane, and at the same time can effectively reduce the operating energy consumption and reduce the process cost.

[0019] Preferably, in a single interval stirring process, the standing time is the same as the stirring time.

[0020] Optionally, during the ultrafiltration process, the interval stirring process is repeated three times or more.

[0021] Preferably, the specific process of the ultrafiltration includes: the ultrafiltration process of the simulated raw water is sequentially performed in a first standing stage, a first stirring stage, a second standing stage, a second stirring stage, a third standing stage and a third stirring stage until the simulated raw water is completely ultrafiltered.

[0022] In the present invention, appropriately shortening the time of the single-stage stirring stage and the single-stage standing stage and increasing the number of standing and stirring stages during the ultrafiltration process can effectively improve the membrane specific flux, especially under conditions of high concentrations of pollutants, the membrane specific flux of the ultrafiltration membrane in the ultrafiltration process can be more effectively improved.

[0023] Preferably, the simulated raw water comprises humic acid, kaolin and water.

[0024] Preferably, in the simulated raw water, the concentration of humic acid is 5-30 mg / L, for example, 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L or 30 mg / L.

[0025] Preferably, in the simulated raw water, the concentration of kaolin is 3-7 mg / L, for example, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L or 7 mg / L.

[0026] Preferably, the turbidity of the simulated raw water is 2-4NTU, such as 2NTU, 2.5NTU, 3NTU, 3.5NTU or 4NTU.

[0027] Preferably, the ultrafiltration of the simulated raw water is carried out in an ultrafiltration device.

[0028] Preferably, the ultrafiltration device comprises an ultrafiltration container and a stirring device located inside the ultrafiltration container.

[0029] Preferably, the ultrafiltration container comprises an ultrafiltration cup.

[0030] Preferably, the stirring device comprises a stirring paddle or a stirring rod.

[0031] In the present invention, the rotation speed in the stirring stage is controlled by the stirring device in the ultrafiltration device.

[0032] Preferably, the ultrafiltration membrane comprises a polyvinylidene fluoride (PVDF) ultrafiltration membrane and / or a polyethersulfone (PES) ultrafiltration membrane.

[0033] Preferably, the ultrafiltration membrane has a molecular weight cutoff of 50-100 kDa, such as 50 kDa, 60 kDa, 70 kDa, 80 kDa, 90 kDa or 100 kDa.

[0034] Preferably, the ultrafiltration is performed under nitrogen and / or inert atmosphere.

[0035] Preferably, the pressure of the system during the ultrafiltration process is 0.05-0.14 MPa, for example, 0.05 MPa, 0.06 MPa, 0.08 MPa, 0.10 MPa, 0.12 MPa or 0.14 MPa.

[0036] In the membrane pollution control method provided by the present invention, by regulating the operating pressure of the ultrafiltration system, the membrane specific flux of the ultrafiltration membrane in the ultrafiltration process can be increased and the energy consumption can be reduced.

[0037] Preferably, before ultrafiltration of the simulated raw water, the ultrafiltration membrane needs to be pretreated.

[0038] Preferably, the pretreatment method of the ultrafiltration membrane includes: soaking the ultrafiltration membrane in ultrapure water to obtain a pretreated ultrafiltration membrane.

[0039] The present invention pre-treats the ultrafiltration membrane used in the ultrafiltration process of simulating raw water by soaking it in ultrapure water, aiming to remove impurities and preservatives on the surface of the ultrafiltration membrane, and at the same time, prevent the ultrafiltration membrane from being damaged due to drying and affecting the ultrafiltration effect.

[0040] Preferably, the soaking time is 10-20 hours, for example, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours.

[0041] Preferably, before ultrafiltration of the simulated raw water, ultrapure water is ultrafiltered using the pretreated ultrafiltration membrane to ensure the stability of the initial flux of the ultrafiltration membrane.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] The membrane pollution control method provided by the present invention breaks the sedimentation rate difference of pollutants of different sizes by adding a stirring process in the ultrafiltration process, and effectively alleviates the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during operation. At the same time, for the already polluted ultrafiltration membrane, the water body is disturbed by stirring, and the water flow changes from laminar flow to turbulent flow at the initial moment of stirring, which can effectively remove the pollutants adsorbed on the surface of the ultrafiltration membrane or even inside the membrane pores, and can effectively restore the membrane flux. Furthermore, in the method provided by the present invention, the stirring stage time in the stirring process is controlled, which can reduce the energy consumption of the membrane pollution control method while improving the membrane flux of the ultrafiltration membrane. Through the cooperation of the stirring stage and the non-stirring stage, the sedimentation rate difference of pollutants of different sizes is broken. Under the condition of low energy consumption, it can still effectively alleviate the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during the ultrafiltration process. Compared with traditional pre-membrane pretreatment such as coagulation and physical and chemical cleaning measures for contaminated membranes, the design of the stirring process based on the ultrafiltration process effectively reduces the degree of contamination of the ultrafiltration membrane during operation and extends the service life of the ultrafiltration membrane to a certain extent, which is in line with the new environmentally friendly water purification concept of green, less medicine and low consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a curve showing the change of membrane specific flux of the ultrafiltration membrane as a function of ultrafiltration time in the membrane pollution control method provided in Example 1-2.

[0045] Figure 2 It is a curve showing the change of membrane specific flux of the ultrafiltration membrane in the membrane pollution control method provided in Example 1 and Examples 3-5 as a function of ultrafiltration time.

[0046] Figure 3 It is a curve showing the change of membrane specific flux of the ultrafiltration membrane in the membrane pollution control method provided in Example 1 and Example 6 as a function of ultrafiltration time.

[0047] Figure 4 It is a curve showing the change of membrane specific flux of the ultrafiltration membrane in the membrane pollution control method provided in Example 1 and Example 7 as a function of ultrafiltration time.

[0048] Figure 5 It is a curve showing the change of membrane specific flux of the ultrafiltration membrane in the membrane pollution control method provided in Example 1 and Example 8 as a function of ultrafiltration time.

[0049] Figure 6 It is a curve showing the change of membrane specific flux of the ultrafiltration membrane in the membrane pollution control method provided in Example 1 and Comparative Example 1 as a function of ultrafiltration time. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0051] The simulated raw water used in the following examples is used as a simulated water sample and is prepared in the following manner:

[0052] A certain volume of 2g / L humic acid stock solution and 50g / L kaolin stock solution were added to the corresponding volume of ultrapure water to prepare four simulated raw water samples with humic acid concentrations of 5mg / L, 10mg / L, 20mg / L and 30mg / L, respectively, and turbidity of 3NTU. The kaolin concentration was 5mg / L, representing different types of natural water bodies.

[0053] The ultrafiltration membrane used in the following examples is also pretreated, and the pretreatment process of the ultrafiltration membrane includes the following steps:

[0054] Soak a brand new ultrafiltration membrane in ultrapure water for 12 hours. During this period, change the ultrapure water every 3 hours to remove impurities on the membrane surface. Then use the ultrafiltration membrane to ultrafilter 300 mL of ultrapure water. No stirring is performed during the ultrafiltration process. Nitrogen is used to maintain a constant system pressure of 0.1 MPa during the ultrafiltration process to ensure the stability of the initial flux of the ultrafiltration membrane.

[0055] Example 1

[0056] This embodiment provides a membrane pollution control method, which specifically includes the following steps:

[0057] A PVDF ultrafiltration membrane with a molecular weight cutoff of 100 kDa was selected, and 300 mL of a simulated water sample with a humic acid concentration of 30 mg / L, a kaolin concentration of 5 mg / L and a turbidity of 3 NTU was placed in an ultrafiltration cup containing a pretreated ultrafiltration membrane, and a stirring rod matching the ultrafiltration cup was placed. Nitrogen was used to maintain the system pressure at a constant 0.1 MPa, and the simulated water sample was repeatedly stirred at intervals, specifically: a 1-min standing stage (i.e., the speed of the stirring rod was 0 rpm), stirring at 200 rpm for 1 min, a 1-min standing stage, stirring at 200 rpm for 1 min, a 1-min standing stage, stirring at 200 rpm for 1 min, until the ultrafiltration of the simulated water sample was completed to obtain a water sample after ultrafiltration.

[0058] Example 2

[0059] The membrane fouling control method provided in Example 2 is the same as that in Example 1 except that the total time proportion of the stirring stage in the ultrafiltration process of the simulated water sample in Table 1 is changed.

[0060] Embodiment 3-5

[0061] The membrane fouling control methods provided in Examples 3-5 are the same as those in Example 1 except for the change in the humic acid concentration of the simulated water sample in Table 2.

[0062] Example 6

[0063] The membrane fouling control method provided in this embodiment is the same as that in Embodiment 1 except for the changes in the type of ultrafiltration membrane and the molecular weight cutoff of the ultrafiltration membrane in Table 3.

[0064] Example 7

[0065] The membrane pollution control method provided in this embodiment is the same as that in Embodiment 1 except for the pressure change of the ultrafiltration system in Table 4.

[0066] Example 8

[0067] The membrane fouling control method provided in this embodiment is the same as that in Embodiment 1 except for the change in the stirring speed in Table 5.

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 is that: in the membrane fouling control method provided in this comparative example, stirring is not performed during the ultrafiltration process, and only a static stage is performed. The rest of the contents are the same as in Example 1.

[0070] The ultrafiltration process of Example 1-8 and Comparative Example 1 is recorded as follows, specifically in the following manner: ultrafiltration membrane flux detection, using an electronic balance to record the membrane flux (J) change of the first 6 minutes of the ultrafiltration process, and by analyzing the decay of the membrane specific flux (J / J0) with the ultrafiltration time to evaluate the change of membrane pollution, record the minimum membrane specific flux when ultrafiltration is running, the membrane specific flux of the ultrafiltration membrane at 6 minutes of ultrafiltration, and calculate the maximum recovery of the membrane specific flux in the stirring stage. Wherein, J0 is the initial membrane flux of the ultrafiltration membrane, i.e., the membrane flux when ultrafiltration 300mL ultrapure water is applied, and the maximum recovery of the membrane specific flux in the stirring stage refers to the maximum value in the membrane specific flux difference before and after each stirring stage of the entire ultrafiltration process. Its test results are shown in Table 1-6.

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075] Table 3

[0076]

[0077]

[0078] Table 4

[0079]

[0080] Table 5

[0081]

[0082] Table 6

[0083]

[0084] The test results show that:

[0085] (1) It can be seen from Examples 1 to 5 that the membrane contamination control method provided by the present invention regulates the flow state of the fluid in the ultrafiltration process by stirring the disturbing effect of the simulated raw water in the ultrafiltration process, breaks the difference in sedimentation rates of different types of pollutants in the simulated raw water, and can reduce the probability of pollutants being adsorbed and blocked on the surface of the ultrafiltration membrane and in the membrane pores, thereby effectively alleviating the degree of contamination of the ultrafiltration membrane, thereby improving the membrane flux of the ultrafiltration membrane during operation.

[0086] Further, Example 1 is compared with Example 2. Figure 1 As shown (for the convenience of comparison, Figure 1-Figure 6 Only the variation curve of membrane specific flux of ultrafiltration membrane with ultrafiltration time in the membrane pollution control method within 6 minutes is given. It should be noted that the total time of the ultrafiltration process in each embodiment exceeds 6 minutes). Compared with Example 2 in which the stirring time accounts for 100% of the overall ultrafiltration process, that is, the entire ultrafiltration process is stirred throughout the entire process, the stirring time in Example 1 accounts for only 55%. While the stirring energy consumption is greatly reduced, the minimum value of the membrane specific flux and the membrane specific flux when the ultrafiltration is completed are still maintained at a high level. In addition, Example 1 adopts an interval stirring process in the stirring stage to effectively restore the decrease in membrane specific flux caused by the static stage, so that even if the stirring stage is shortened, the membrane pollution phenomenon can be effectively avoided.

[0087] Combined with Table 2 Figure 2 It can be seen that through the design of the ultrafiltration process, the added stirring stage can alleviate and restore the decline in membrane specific flux of the ultrafiltration membrane when ultrafiltration simulated water samples with different concentrations of humic acid, thereby slowing down membrane fouling. As the concentration of humic acid increases, the amount of recovery of membrane specific flux during the ultrafiltration process during the stirring stage gradually increases, effectively slowing down membrane fouling.

[0088] (2) By comparing Example 1 with Example 6, it can be seen that in the membrane pollution control method provided by the present invention, the selection of the type of ultrafiltration membrane and the regulation of the molecular weight cutoff of the ultrafiltration membrane can improve the membrane specific flux of the ultrafiltration membrane and the membrane specific flux recovery amount in the stirring stage during the ultrafiltration process. Figure 3 It can be seen that when the PVDF ultrafiltration membrane with a molecular weight cutoff of 100kDa is replaced by a PES ultrafiltration membrane with a molecular weight cutoff of 50kDa, due to the smaller minimum molecular weight cutoff of PES, the membrane fouling phenomenon under the same simulated water sample conditions will be aggravated, that is, the minimum membrane flux is lower, but the membrane flux can still be effectively restored through the stirring process, and the effect is more significant.

[0089] (3) By comparing Example 1 with Example 7, it can be seen that in the membrane pollution control method provided by the present invention, controlling the pressure of the ultrafiltration system can improve the recovery rate of the membrane flux. Figure 4 It can be seen that when using a higher pressure, although increasing the stirring stage can improve the decline in the ultrafiltration membrane specific flux, the higher pressure will cause the ultrafiltration membrane specific flux to drop rapidly in a short period of time, causing more serious pollution of the ultrafiltration membrane.

[0090] (4) By comparing Example 1 with Example 8, it can be seen that the membrane pollution control method provided by the present invention can effectively alleviate ultrafiltration membrane pollution and restore ultrafiltration membrane flux by adjusting the stirring speed. Figure 5 It can be seen that using a lower stirring speed will result in less disturbance to the simulated raw water and limited recovery of membrane flux, thus failing to effectively slow down ultrafiltration membrane fouling.

[0091] (5) By comparing Example 1 with Comparative Example 1, it can be seen that the present invention uses repeated interval stirring process in the ultrafiltration process to disturb the simulated raw water in the ultrafiltration process, regulate the flow state of the fluid in the ultrafiltration process, and thus effectively alleviate the degree of membrane contamination. Figure 6 It can be seen that compared with the stirring stage introduced in Example 1 and the design of the stirring process, when the stirring stage is missing and only the standing stage is performed during the ultrafiltration process, the membrane specific flux of the ultrafiltration membrane will be significantly reduced, and the recovery of the membrane specific flux of the ultrafiltration membrane cannot be achieved. At the same time, the pollutants in the water sample will clog the membrane pores of the ultrafiltration membrane, causing the water flux to decrease and thus leading to an extension of the ultrafiltration operation time.

[0092] In summary, the membrane pollution control method provided by the present invention breaks the sedimentation rate difference of pollutants of different sizes by adding a stirring process in the ultrafiltration process, and effectively alleviates the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during operation. At the same time, for the already polluted ultrafiltration membrane, the water body is disturbed by stirring, and the water flow changes from laminar flow to turbulent flow at the initial moment of stirring, which can effectively remove the pollutants adsorbed on the surface of the ultrafiltration membrane or even inside the membrane pores, and effectively improve the membrane flux. Furthermore, in the method provided by the present invention, the stirring stage time in the stirring process is controlled, which can reduce the energy consumption of the membrane pollution control method while improving the membrane flux of the ultrafiltration membrane. Through the cooperation of the stirring stage and the non-stirring stage, the sedimentation rate difference of pollutants of different sizes is broken. Under the condition of low energy consumption, it can still effectively alleviate the situation that the membrane flux of the ultrafiltration membrane decreases with the increase of ultrafiltration time during the ultrafiltration process. Compared with pre-membrane pretreatment such as coagulation and physical and chemical cleaning measures for contaminated membranes, the stirring process design based on the ultrafiltration process effectively reduces the degree of contamination of the ultrafiltration membrane during operation and extends the service life of the ultrafiltration membrane to a certain extent, which is in line with the new environmentally friendly water purification concept of green, less medicine and low consumption.

[0093] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A membrane fouling control method, characterized in that: The membrane fouling control method comprises the following steps: The simulated raw water is ultrafiltered by using an ultrafiltration membrane, and the ultrafiltration process is accompanied by a stirring process; The stirring process at least includes a stirring stage; taking the total time of the stirring process as 100%, the total time of the stirring stage accounts for 20-100%.

2. The membrane fouling control method according to claim 1, characterized in that: The stirring speed in the stirring stage is 50-200 rpm.

3. The membrane fouling control method according to claim 1 or 2, characterized in that: The stirring process includes an interval stirring process repeated at least twice, wherein a single interval stirring process includes first a static stage and then a stirring stage; Preferably, in a single interval stirring process, the total time of the single interval stirring process is 100%, and the time of the static stage accounts for 20-80%; Preferably, in a single interval stirring process, taking the total time of the single interval stirring process as 100%, the time of the stirring stage accounts for 20-80%.

4. The membrane fouling control method according to claim 3, characterized in that: In the single interval stirring process, the standing time is the same as the stirring time.

5. The membrane fouling control method according to claim 3 or 4, characterized in that: The specific process of the ultrafiltration includes: the ultrafiltration process of the simulated raw water is sequentially performed in a first static stage, a first stirring stage, a second static stage, a second stirring stage, a third static stage and a third stirring stage until the simulated raw water is completely ultrafiltered.

6. The membrane fouling control method according to any one of claims 1 to 5, characterized in that: The simulated raw water comprises humic acid, kaolin and water; Preferably, in the simulated raw water, the concentration of humic acid is 5-30 mg / L; Preferably, in the simulated raw water, the concentration of kaolin is 3-7 mg / L; Preferably, the turbidity of the simulated raw water is 2-4 NTU.

7. The membrane fouling control method according to any one of claims 1 to 6, characterized in that: The ultrafiltration of the simulated raw water is carried out in an ultrafiltration device; Preferably, the ultrafiltration device comprises an ultrafiltration container and a stirring device located inside the ultrafiltration container.

8. The membrane fouling control method according to any one of claims 1 to 7, characterized in that: The ultrafiltration membrane comprises a polyvinylidene fluoride ultrafiltration membrane and / or a polyethersulfone ultrafiltration membrane; Preferably, the ultrafiltration membrane has a molecular weight cut-off of 50-100 kDa.

9. The membrane fouling control method according to any one of claims 1 to 8, characterized in that: The ultrafiltration is carried out under nitrogen and / or inert atmosphere; Preferably, the pressure of the system during the ultrafiltration process is 0.05-0.14 MPa.

10. The membrane fouling control method according to any one of claims 1 to 9, characterized in that: Before ultrafiltration of the simulated raw water, the ultrafiltration membrane needs to be pretreated; Preferably, the pretreatment method of the ultrafiltration membrane comprises: soaking the ultrafiltration membrane in ultrapure water to obtain a pretreated ultrafiltration membrane; Preferably, the soaking time is 10-20 hours; Preferably, before ultrafiltration of the simulated raw water, ultrapure water is ultrafiltered using the pretreated ultrafiltration membrane to ensure the stability of the initial flux of the ultrafiltration membrane.

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