Method and system for controlling membrane pollution in wastewater membrane separation process

Abstract

The invention provides a control method and a control system for membrane pollution in a wastewater membrane separation process, the control method is suitable for membrane separation treatment of wastewater so as to reduce the rate of membrane pollution caused by wastewater, and the control method comprises the following steps: introducing a water sample after biological treatment into an irradiation treatment unit, and carrying out ionization irradiation treatment; enabling the water sample subjected to ionization irradiation treatment to pass through a carbon column treatment unit to obtain a pretreated water sample; introducing the pretreated water sample into a membrane separation unit containing a membrane, and filtering pollutants; the membrane is selected from a reverse osmosis membrane or a nanofiltration membrane; according to the method, the organic pollutants, the microorganisms and the colloidal particles in the wastewater are subjected to cooperative treatment by regulating and controlling the ionization irradiation conditions, so that regulation and control of the properties of the organic pollutants, efficient inactivation of the microorganisms and modulation of charges on the surface of the colloid are realized; the change of organic matter structures and the optimization of colloid charge properties enhance the adsorption and interception capabilities of subsequent carbon column treatment units, inhibit the formation of biological membranes, and significantly slow down membrane pollution.

Description

Technical Field

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

[0002] Membrane separation technology, a key means of advanced wastewater treatment and reuse, offers advantages such as high effluent quality, minimal footprint, and a high degree of automation. However, membrane fouling is a common problem during long-term operation, particularly when treating wastewater containing organic matter, microbial residues, or colloids. Membrane fouling not only reduces membrane flux and increases operating energy consumption, but also requires frequent chemical cleaning, shortening membrane life and increasing operating costs.

[0003] Currently, common methods for controlling membrane fouling include optimizing the pretreatment process, adding chemical reagents, and regular cleaning. However, these methods have certain limitations, such as unstable effects, complex operations, or the possibility of introducing secondary pollution.

[0004] In recent years, the introduction of advanced oxidation processes in the front section of membrane systems has been considered an effective strategy to reduce membrane fouling. However, existing advanced oxidation processes generally rely on the addition of oxidants or catalysts, and these chemicals may have adverse effects on subsequent membrane systems. For example, although Fenton oxidation can effectively reduce the organic load in wastewater, the residual Fe 2+ and H2O2 will aggravate membrane fouling.

[0005] Therefore, it is of great significance to develop a new pretreatment technology that is efficient, green and well compatible with existing membrane systems. Summary of the Invention

[0006] In response to the above-mentioned problems existing in the prior art, the present invention provides a method and control system for controlling membrane pollution for wastewater treatment, which can significantly slow down the membrane pollution rate, extend the membrane cleaning cycle and reduce operating energy consumption, and has good practical value and promotion prospects.

[0007] The specific content of the invention is as follows: In a first aspect, the present invention provides a method for controlling membrane fouling in a wastewater membrane separation process. The method is applicable to membrane separation and purification treatment of a pretreated water sample obtained through a carbon column treatment unit to reduce the fouling rate of the wastewater on the membrane. The method comprises: The biologically treated water sample is passed into an irradiation treatment unit for ionizing irradiation treatment; The water sample after ionizing radiation treatment is passed through a carbon column treatment unit to obtain a pretreated water sample; The pretreated water sample is passed into a membrane separation unit to filter out pollutants; The membrane used in the membrane separation unit is selected from a reverse osmosis membrane or a nanofiltration membrane.

[0008] Optionally, the radiation source of the ionizing radiation treatment is selected from electron accelerator, 60 Co or 137 Cs.

[0009] Optionally, the dose of the ionizing radiation treatment is 1 kGy to 20 kGy.

[0010] Optionally, the carbon used for carbon adsorption treatment is selected from activated carbon, coconut shell carbon or activated coke.

[0011] Optionally, the wastewater includes coal chemical wastewater, pharmaceutical wastewater, printing and dyeing wastewater or landfill leachate.

[0012] Optionally, in the water sample after biological treatment, the chemical oxygen demand is 150 mg / L to 350 mg / L, and the conductivity is not higher than 50,000 μs / cm.

[0013] Optionally, before the ionizing radiation treatment, the control method further comprises: adding an appropriate amount of an auxiliary agent to the water sample after the biological treatment, or exposing it to air, and then passing it into the radiation treatment unit for ionizing radiation treatment; The auxiliary agent includes hydrogen peroxide or sulfite.

[0014] Optionally, the dosage of the hydrogen peroxide is 0.1 mM to 0.3 mM.

[0015] Optionally, the dosage of the sulfite is 0.3 mM to 6.0 mM.

[0016] In a second aspect, the present invention provides a membrane fouling control system in a wastewater membrane separation process, wherein the control system is applicable to the control method described in the first aspect to reduce the fouling rate of the wastewater on the membrane, and the system comprises: A biological treatment unit, used to perform biological treatment on the wastewater to obtain a water sample after biological treatment; an irradiation treatment unit, configured to perform ionizing irradiation treatment on the biologically treated water sample to obtain an ionizing irradiation treated water sample; a carbon column treatment unit, for removing impurities including particles and colloids, and irradiation products including hydrogen peroxide from the water sample after the ionizing irradiation treatment by adsorption, to obtain a pretreated water sample; The membrane separation unit is used to filter out pollutants from the pretreated water sample to obtain a water sample that meets the discharge standard.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention provides a method for controlling membrane fouling in a wastewater membrane separation process. The control method is applicable to membrane separation and purification treatment of wastewater to reduce the fouling rate of the wastewater on the membrane. The method comprises: passing a water sample after biological treatment into an irradiation treatment unit for ionizing irradiation treatment; passing the water sample after ionizing irradiation treatment into a carbon column treatment unit for carbon adsorption treatment to obtain a pretreated water sample; passing the pretreated water sample into a membrane separation unit for pollutant filtration; the membrane used in the membrane separation unit is selected from a reverse osmosis membrane or a nanofiltration membrane; the present invention coordinates the treatment of organic pollutants, microorganisms and colloidal particles in the wastewater by regulating ionizing irradiation conditions, thereby achieving regulation of the properties of organic pollutants, efficient inactivation of microorganisms, modulation and optimization of the surface charge of the colloids, and changes in the structure of organic matter, thereby helping to enhance the interception capacity of subsequent membrane processes, reduce wastewater load and inhibit biofilm formation, significantly slow down membrane fouling, and improve membrane flux and system operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 shows a flow chart of a control method provided by an embodiment of the present invention; Figure 2 The image of the membrane surface under an atomic force microscope after the control method provided in Example 1 of the present invention is continuously used for one month to treat wastewater; Figure 3 The image of the membrane surface under an atomic force microscope after the wastewater treatment is continuously performed for one week using the control method provided in Comparative Example 1 of the present invention is shown; Figure 4 The image of the membrane surface under an atomic force microscope after the control method provided in Example 2 of the present invention is continuously used for one month to treat wastewater is shown; Figure 5 The image of the membrane surface under an atomic force microscope after the wastewater treatment is continuously performed for one week using the control method provided in Comparative Example 2 of the present invention is shown; Figure 6 The image of the membrane surface under an atomic force microscope after the control method provided in Example 3 of the present invention is continuously used for one month to treat wastewater is shown; Figure 7 The membrane surface image under atomic force microscope is shown after the wastewater treatment is continuously performed for one week using the control method provided in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product that is identical or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work fall within the scope of protection of the present invention.

[0021] Ionizing radiation is a novel advanced oxidation technology. It effectively degrades organic pollutants, kills microorganisms, and disrupts biomacromolecules through the direct action of high-energy radiation or the indirect action of reactive species generated by water molecules. Currently, ionizing radiation has been successfully applied to the treatment of a variety of industrial wastewaters, demonstrating promising results, stability, and cost-effectiveness. However, research and engineering applications of ionizing radiation for membrane fouling control remain limited.

[0022] Based on this, the present invention provides a technical solution that applies ionizing radiation to the membrane pretreatment process, combined with carbon column filtration and membrane separation technology, which significantly reduces membrane fouling, extends the membrane cleaning cycle and reduces operating energy consumption. It has good practical value and promotion prospects. The specific implementation method is as follows: In a first aspect, the present invention provides a method for controlling membrane fouling in a wastewater membrane separation process, wherein the control method is applicable to membrane separation treatment of wastewater to reduce the fouling rate of the wastewater on the membrane. Figure 1 FIG. 1 shows a flow chart of a control method according to an embodiment of the present invention. Figure 1 As shown, the method includes: S1. Passing the biologically treated water sample into an irradiation treatment unit for ionizing irradiation treatment; S2. Passing the water sample after ionizing radiation treatment through a carbon column treatment unit to obtain a pretreated water sample; S3, the pretreated water sample is passed into a membrane separation unit to filter out pollutants; The membrane used in the membrane separation unit is selected from a reverse osmosis membrane or a nanofiltration membrane.

[0023] In practice, biologically treated wastewater is introduced into an irradiation treatment unit, where irradiation conditions are controlled for irradiation treatment. High-energy radiation (e.g., gamma rays, electron beams) is used to manipulate the physical and chemical properties of organic pollutants, such as hydrophilicity and surface charge, promote the aggregation of colloidal particles, and kill microorganisms. The irradiated wastewater then passes through a carbon column treatment unit to further remove irradiation products, particulate impurities, and any residual H2O2. Irradiation products refer to H2O2 generated during the irradiation process, as well as organic transition state substances. After passing through the carbon column unit, oxygen-containing functional groups (e.g., carboxyl groups) on the carbon column surface activate and decompose these irradiation products, preventing their impact on subsequent membrane processes. The carbon column's secondary function is to adsorb a small amount of low-molecular-weight organic matter produced after irradiation and colloidal substances generated during the irradiation process. Finally, the pretreated wastewater enters the membrane separation unit for deep purification. The properties of pollutants in the wastewater, such as colloidal substances and soluble microbial products, change after irradiation. For example, the charge of the colloidal substances changes, making it difficult for them to bind to the membrane and effectively retained by the membrane separation unit. The inactivation of soluble microorganisms reduces the secretion of extracellular polymers, thereby reducing the risk of membrane clogging, while achieving efficient removal of pollutants and ensuring that water quality meets discharge or reuse standards.

[0024] It should be noted that biological treatment relies on the metabolic activity of microorganisms (bacteria, fungi, etc.) to decompose organic pollutants and some inorganic pollutants (such as ammonia nitrogen) in wastewater into harmless or low-toxic substances (such as CO2, H2O, N2) or the microbial cells themselves. Biological treatment is accomplished using biological treatment units, which can be divided into aerobic, anaerobic, or facultative biological treatment units based on the type of microorganism. After biological treatment, the chemical oxygen demand (COD) in the wastewater is 150 mg / L to 350 mg / L, and the conductivity is no higher than 50,000 μs / cm. Most biodegradable organic matter has been removed, leaving some refractory organic matter. Ionizing radiation is then used to control the properties of refractory organic pollutants, effectively inactivate microorganisms, and modulate and optimize the surface charge of the colloids.

[0025] In some embodiments, the ionizing radiation treatment is carried out using an irradiation source selected from an electron accelerator, 60 Co or 137 Cs; the dose of ionizing radiation treatment is sufficient to kill microorganisms and regulate the physical and chemical properties of organic pollutants, and can be specifically controlled within the range of 1 kGy to 20 kGy.

[0026] In some embodiments, the carbon used in the carbon column treatment unit is selected from activated carbon, coconut shell carbon or activated coke.

[0027] In some embodiments, the wastewater includes coal chemical wastewater, pharmaceutical wastewater, printing and dyeing wastewater or landfill leachate.

[0028] In some embodiments, prior to ionizing radiation treatment, the control method further includes: adding an appropriate amount of an additive to the biologically treated wastewater, or exposing it to air before passing it through an irradiation treatment unit for ionizing radiation treatment. The additive includes hydrogen peroxide (oxidizing agent) or sulfite (reducing agent). Different additives can be added for different types of pollutants to leverage the synergistic effect between ionizing radiation and the additive. For example, when an appropriate amount of hydrogen peroxide is added, ionizing radiation itself generates free radicals, which also break down under irradiation to produce hydroxyl radicals, thereby increasing the free radical concentration. Furthermore, the addition of hydrogen peroxide can accelerate certain reactions during irradiation, such as disrupting the cell structure of microorganisms, thereby enhancing the inactivation effect. The addition of hydrogen peroxide can also affect the surface charge of colloidal particles, promoting their aggregation.

[0029] In some embodiments, the type and concentration of pollutants present in the wastewater are the main factors affecting the demand for auxiliary agents. The present invention is directed to the treatment of different types of wastewater (coal chemical wastewater, pharmaceutical wastewater, printing and dyeing wastewater or landfill leachate), and the dosage of hydrogen peroxide is selected to be 0.1 mM to 0.3 mM; the dosage of sulfite is selected to be 0.3 mM to 6.0 mM.

[0030] The present invention coordinates the treatment of organic pollutants, microorganisms and colloidal particles in wastewater by regulating the ionizing radiation conditions, thereby achieving the regulation of the properties of organic pollutants, the efficient inactivation of microorganisms, the modulation and optimization of the surface charge of colloids, and the change of the structure of organic matter, significantly reducing membrane fouling, and improving membrane flux and the stability of system operation. Compared with traditional membrane separation processes, the control method provided by the present invention has a simple structure, a controllable process flow, and good engineering feasibility and economy; it can significantly reduce the membrane fouling rate and extend the membrane cleaning cycle to 3 to 4 times the original; improve membrane flux and system stability, reduce energy consumption per unit water volume by about 20%; and enhance the removal capacity of difficult-to-degrade organic pollutants. In addition, the ionizing radiation control method for alleviating membrane fouling proposed by the present invention also has the characteristics of high efficiency, environmental protection and sustainability, providing a new and effective solution for alleviating membrane fouling of membrane separation units in wastewater treatment process units, and has broad industrial application prospects.

[0031] In a second aspect, the present invention provides a membrane fouling control system in a wastewater membrane separation process, wherein the control system is applicable to the control method described in the first aspect to reduce the fouling rate of the wastewater on the membrane, and the system comprises: A biological treatment unit, used to perform biological treatment on the wastewater to obtain a water sample after biological treatment; an irradiation treatment unit, configured to perform ionizing irradiation treatment on the biologically treated water sample to obtain an ionizing irradiation treated water sample; Used to adsorb and remove impurities including particles and colloids, and irradiation products including hydrogen peroxide in the water sample after ionizing radiation treatment to obtain a pretreated water sample; The membrane separation unit is used to filter out pollutants from the pretreated water sample to obtain a water sample that meets the discharge standard.

[0032] In order to enable those skilled in the art to more clearly understand the present invention, the method and control system for controlling membrane fouling for wastewater treatment according to the present invention are now described in detail through the following examples.

[0033] Example 1 After biological treatment, the effluent from the coking plant has a chemical oxygen demand (COD) of 126 mg / L and a conductivity of 2247 μS / cm. The effluent first enters an irradiation treatment unit, where 0.135 mM H₂O₂ is dosed and irradiated with a dose of 2 kGy. The irradiated water sample then passes through a coconut shell activated carbon column treatment unit and an RO membrane separation unit, where the effluent meets quality standards before being discharged.

[0034] Comparative Example 1 As a control for Example 1, the coking wastewater was treated biologically without ionizing radiation pretreatment and directly entered the carbon column treatment unit and then the RO membrane separation unit.

[0035] Figure 2 The surface image of the membrane under an atomic force microscope after the wastewater treatment method provided by Example 1 of the present invention is continuously carried out for one month is shown. Figure 2 As shown in Figure 2, the surface roughness of the RO membrane was measured by atomic force microscopy (AFM) and was 53.37 nm. Figure 3 The surface image of the membrane under atomic force microscope after the wastewater treatment is continuously carried out for one week by the control method provided in Comparative Example 1 of the present invention is shown. Figure 3 As shown in Figure 3, after one week of operation, the surface roughness of the RO membrane was 53.28 nm.

[0036] Through comparative analysis, it can be seen that the surface roughness of the RO membrane after one month of operation when ionizing irradiation is used as pretreatment is similar to the surface roughness of the RO membrane after one week of operation when ionizing irradiation is not used as pretreatment, indicating that ionizing irradiation pretreatment can significantly reduce the pollution rate of coking wastewater on RO membrane.

[0037] Example 2 After biological treatment, the coking wastewater has a chemical oxygen demand (COD) of 126 mg / L and a conductivity of 2247 μS / cm. This effluent first enters an irradiation treatment unit, where it is irradiated with a dose of 1 kGy. The irradiated water sample then passes through a coconut shell activated carbon column unit and a NF membrane separation unit, meeting the effluent quality standards before being discharged.

[0038] Comparative Example 2 As a control for Example 2, the coking wastewater was treated biologically without ionizing radiation pretreatment and directly entered the carbon column treatment unit and then the NF membrane separation unit.

[0039] Figure 4 The surface image of the membrane under an atomic force microscope after the wastewater treatment is continuously performed for one month using the control method provided in Example 2 of the present invention is shown. Figure 4 As shown in Figure 3, the surface roughness of the NF membrane was measured by atomic force microscopy (AFM) and was 63.44 nm. Figure 5 The surface image of the membrane under atomic force microscope after the wastewater treatment is continuously carried out for one week by the control method provided in Comparative Example 2 of the present invention is shown. Figure 5 As shown in Figure 3, the surface roughness of the NF membrane is 65.47 nm after one week of operation.

[0040] Through comparative analysis, it can be seen that the surface roughness of the NF membrane after one month of operation when ionizing irradiation is used as pretreatment is similar to the surface roughness of the NF membrane after one week of operation when ionizing irradiation is not used as pretreatment, indicating that ionizing irradiation pretreatment can significantly reduce the pollution rate of coking wastewater on NF membrane.

[0041] Example 3 After biological treatment, the effluent from the printing and dyeing plant has a chemical oxygen demand (COD) of 215 mg / L and a conductivity of 3724 μS / cm. This effluent first enters an irradiation unit, where 0.27 mM sodium sulfite is added and irradiated with a dose of 2 kGy. The irradiated water sample then passes through a coconut shell activated carbon column unit and a NF membrane separation unit, meeting effluent quality standards before being discharged.

[0042] Comparative Example 3 As a control for Example 3, the printing and dyeing wastewater was treated biologically without ionizing radiation pretreatment and directly entered the carbon column treatment unit and then the NF membrane separation unit.

[0043] Figure 6 The surface image of the membrane under an atomic force microscope after the control method provided in Example 3 of the present invention has been continuously used for one month to treat wastewater is shown. Figure 6 As shown in Figure 3, the surface roughness of the NF membrane was measured by atomic force microscopy (AFM) and was 52.82 nm. Figure 7 The surface image of the membrane under atomic force microscope after the wastewater treatment is continuously carried out for one week by the control method provided in Comparative Example 3 of the present invention is shown. Figure 7 As shown in Figure 3, the surface roughness of the NF membrane is 55.01 nm after one week of operation.

[0044] Through comparative analysis, it can be seen that the surface roughness of the NF membrane after one month of operation when ionizing radiation is used as pretreatment is similar to the surface roughness of the NF membrane after one week of operation when ionizing radiation is not used as pretreatment, indicating that ionizing radiation pretreatment can significantly reduce the pollution rate of NF membrane by printing and dyeing wastewater.

[0045] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0046] For the method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily necessary for the present invention. Specific experimental steps or conditions are not specified in the embodiments, and the operations or conditions of the conventional experimental steps described in the prior art in this area can be carried out. The reagents used and other instruments that do not specify the manufacturer are all conventional reagent products that can be purchased commercially.

[0047] The above is a detailed introduction to the membrane pollution control method and control system for wastewater treatment provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for controlling membrane fouling in a wastewater membrane separation process, characterized in that: The control method is applicable to membrane separation and purification treatment of wastewater to reduce the pollution rate of the wastewater on the membrane, and the method comprises: The biologically treated water sample is passed into an irradiation treatment unit for ionizing irradiation treatment; The water sample after ionizing radiation treatment is passed through a carbon column treatment unit to obtain a pretreated water sample; The pretreated water sample is passed into a membrane separation unit to filter out pollutants; The membrane used in the membrane separation unit is selected from a reverse osmosis membrane or a nanofiltration membrane.

2. The control method according to claim 1, characterized in that: The radiation source of the ionizing radiation treatment is selected from electron accelerator, 60 Co or 137 Cs.

3. The control method according to claim 1, wherein: The dosage of the ionizing radiation treatment is 1 kGy to 20 kGy.

4. The control method according to claim 1, wherein: The carbon used in the carbon column treatment unit is selected from activated carbon, coconut shell carbon or activated coke.

5. The control method according to claim 1, characterized in that: The wastewater includes coal chemical wastewater, pharmaceutical wastewater, printing and dyeing wastewater or garbage leachate.

6. The control method according to claim 1, characterized in that: In the wastewater after biological treatment, the chemical oxygen demand is 150 mg / L to 350 mg / L, and the conductivity is not higher than 50,000 μs / cm.

7. The control method according to claim 1, characterized in that: Before the ionizing radiation treatment is performed, the control method further comprises: adding an appropriate amount of an auxiliary agent to the water sample after the biological treatment, or exposing it to air, and then passing it into the radiation treatment unit for ionizing radiation treatment; The auxiliary agent includes hydrogen peroxide or sulfite.

8. The control method according to claim 7, characterized in that: The dosage of the hydrogen peroxide is 0.1 mM to 0.3 mM.

9. The control method according to claim 7, characterized in that: The dosage of the sulfite is 0.3 mM to 6.0 mM.

10. A membrane fouling control system in a wastewater membrane separation process, characterized in that: The control system is applicable to the control method according to any one of claims 1 to 9 above, so as to reduce the fouling rate of the wastewater on the membrane, and the system comprises: A biological treatment unit, used to perform biological treatment on the wastewater to obtain a water sample after biological treatment; an irradiation treatment unit, configured to perform ionizing irradiation treatment on the biologically treated water sample to obtain an ionizing irradiation treated water sample; a carbon column treatment unit, for adsorbing and removing impurities including particles and colloids, as well as irradiation products including hydrogen peroxide, from the water sample after the ionizing irradiation treatment to obtain a pretreated water sample; The membrane separation unit is used to filter out pollutants from the pretreated water sample to obtain a water sample that meets the discharge standard.

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