Method and system for adsorbing perfluorinated compounds by using microbubble reinforced modified activated carbon

Abstract

The application discloses a method and system for strengthening and modifying activated carbon adsorption of perfluorinated compounds by micro-bubbles, belonging to the technical field of water treatment. The application is to immerse activated carbon in a polydiallyldimethylammonium chloride aqueous solution, treat the immersed activated carbon to be neutral and dry to obtain modified activated carbon; raw water containing PFAS is treated by micro-bubbles, and then the modified activated carbon is added to the raw water for reaction, and the treated water is discharged from the upper layer. The application compensates for the insufficient adsorption of short-chain PFAS by traditional activated carbon through PDADMAC electrostatic adsorption, improves the removal effect by combining the enrichment effect of micro-bubbles; the mass transfer is strengthened by slight disturbance, the adsorption kinetics is accelerated, and the interference of natural organic matter can be resisted to protect the adsorption sites; the process condition is mild and safe, there is no secondary pollution, and the engineering popularization is convenient.

Description

Technical Field

[0001] This application belongs to the field of water treatment technology, specifically relating to a method and system for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are widely used, environmentally unfriendly, persistent, bioaccumulative, and toxic, polluting water bodies and threatening ecosystems and human health. Therefore, the removal and treatment of PFAS from water bodies is urgently needed. Conventional water treatment technologies are insufficient for efficiently removing PFAS pollutants from water bodies, necessitating large-scale water treatment solutions that are highly adaptable and provide stable treatment results to ensure water safety.

[0003] Currently, the main methods for removing PFAS from water bodies include activated carbon adsorption, ion exchange resins, and reverse osmosis. Among these, activated carbon adsorption has become the most widely used mainstream technology in drinking water and groundwater treatment due to its mature technology and low operating cost. However, ordinary activated carbon relies solely on physical adsorption, which is insufficient for adsorbing anionic PFAS and has extremely poor adsorption effect on short-chain PFAS with weak hydrophobicity, easily leading to adsorption breakthrough. Furthermore, adsorption equilibrium takes a long time and has low treatment efficiency. At the same time, natural organic matter (NOM) in actual water bodies competes with PFAS for adsorption channels, causing pore blockage and rapid deactivation of activated carbon. As a result, the overall treatment effect and service life are difficult to meet the actual water treatment needs. Summary of the Invention

[0004] This application addresses the technical problems of poor PFAS adsorption, susceptibility to interference, and slow adsorption of activated carbon by providing a method and system for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon.

[0005] To achieve the above objectives, this application adopts the following technical solution: The first aspect of this application provides a method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon, comprising: Activated carbon was impregnated in an aqueous solution of polydiallyldimethylammonium chloride, and the impregnated activated carbon was then treated to neutrality and dried to obtain modified activated carbon. Raw water containing PFAS is treated with microbubbles, then modified activated carbon is added to react with it, and the treated water is discharged from the top layer.

[0006] Furthermore, the mass concentration of the polydiallyldimethylammonium chloride aqueous solution is 0.05%~0.2%.

[0007] Furthermore, the drying temperature is 60~70℃.

[0008] Furthermore, the mass ratio of the activated carbon to the aqueous solution of polydiallyldimethylammonium chloride is 1:(10~15).

[0009] Furthermore, when the raw water containing PFAS is subjected to microbubble treatment, air is used as the air source, and the air intake rate is 20~60mL / min.

[0010] Furthermore, the average diameter of the bubble is 50 nm to 50 μm.

[0011] Furthermore, based on the volume of raw water, the dosage of modified activated carbon is 0.1~0.5g / L.

[0012] The second aspect of this application provides a system for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon, which is used to achieve the above-mentioned method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon. The system includes a microbubble generating tank, which is equipped with a stirrer for stirring raw water to generate microbubbles. The liquid circulation unit, together with the microbubble generator, can form a raw water circulation loop; The gas supply unit, connected to the liquid circulation unit, is used to provide gas for microbubble processing; The reaction column is connected to the microbubble generator at its bottom. Modified activated carbon is placed inside the reaction column. Raw water treated with microbubbles is sent into the reaction column for adsorption treatment, and the treated water is discharged from the top of the reaction column.

[0013] Furthermore, the liquid circulation unit includes a check valve and a self-priming pump, a pressure gauge and a pressure regulating valve; each component is connected in series through pipes and can form a raw water circulation loop with the microbubble generator. The gas supply unit includes a granular activated carbon adsorption box and a gas flow meter, which are connected in series and then connected to the pipeline between the check valve and the self-priming pump to provide a gas source for the raw water microbubble treatment.

[0014] The third aspect of this application provides the application of the above-mentioned method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon in the field of water treatment.

[0015] Compared with the prior art, this application has the following beneficial effects: This application introduces PDADMAC to provide electrostatic adsorption, effectively compensating for the weak physical adsorption capacity of traditional activated carbon for short-chain PFAS (such as PFBA). Simultaneously, combined with the enrichment effect of PFAS at the microbubble interface, it significantly increases the contact probability between PFAS and activated carbon, thereby greatly improving PFAS removal efficiency. The micro-perturbation generated by microbubbles significantly thins the liquid film boundary layer on the activated carbon surface, and the bubbles act as carriers to enhance the mass transfer process of pollutants to the adsorbent surface, achieving rapid adsorption kinetics. Utilizing the preferential adsorption of surface-active substances PFAS by microbubbles, its local concentration on the activated carbon surface is increased, giving it an advantage in competitive adsorption. This effectively resists interference from natural organic matter, protects the adsorption sites on the activated carbon, and significantly enhances the device's anti-interference capability and operational stability. Furthermore, this method does not require high-temperature, high-pressure conditions or strong oxidants and other chemical agents; the operating conditions are mild and safe, with a low risk of secondary pollution, making it easy to promote and apply to practical water treatment projects. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the system for removing perfluorinated compounds from water using microbubble-enhanced modified activated carbon, as described in this application. Figure 2 This is a comparison chart of the adsorption results of PFAS in the embodiments and comparative examples of this application; In the diagram: 1. Microbubble generator; 2. Agitator; 3-1. First metering pump; 3-2. Second metering pump; 4. Reaction column; 5. Check valve; 6. Granular activated carbon adsorption box; 7. Gas flow meter; 8. Self-priming pump; 9. Pressure gauge; 10. Pressure regulating valve; 11. Support layer; 12. Modified activated carbon; 13. Filter screen. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0020] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0021] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0022] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0024] Unless otherwise stated, all percentages are by mass; temperature is in °C; dimensions are in mm and thickness is in μm; rotational speed is in rpm. First, let's introduce the relevant terminology used in this application: GAC: Granular Active Carbon PFAS: Per- and polyfluoroalkyl substances.

[0025] PDADMAC: Poly(diallyldimethylammonium chloride).

[0026] Fine bubbles (FBs) refer to bubbles with diameters ranging from tens of micrometers to hundreds of nanometers, characterized by long residence time, large specific surface area, and high internal pressure.

[0027] Conventional activated carbon primarily relies on physical adsorption, and its adsorption capacity for anionic PFAS is limited. Especially for short-chain PFAS (such as PFBA and PFBS), due to their weak hydrophobicity, activated carbon adsorption is very poor, and breakthrough easily occurs. Furthermore, activated carbon adsorption typically requires a long contact time (several hours) to reach equilibrium, which limits treatment efficiency. In addition, actual wastewater contains a large amount of natural organic matter (NOM), which competes with PFAS for the pores of activated carbon, leading to rapid activated carbon deactivation (the "pore blockage" effect). To address these issues, cationic polymer-modified activated carbon is proposed to improve the removal efficiency of activated carbon for PFAS.

[0028] Polydiallyl dimethylammonium chloride (PDADMAC) is a common cationic polymer. When used to modify activated carbon, it adheres to the surface of the activated carbon, improving its electrostatic adsorption capacity. However, it easily clogs the pores of the activated carbon, leading to material agglomeration and reducing the specific surface area of ​​the activated carbon. Furthermore, although PDADMAC-modified activated carbon exhibits improved electrostatic adsorption capacity, its mass transfer process remains limited.

[0029] Based on this, this application provides a method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon, characterized by comprising: Activated carbon was impregnated in an aqueous solution of polydiallyldimethylammonium chloride, and the impregnated activated carbon was then treated to neutrality and dried to obtain modified activated carbon. The raw water containing PFAS is treated with microbubbles, and then modified activated carbon is added to react with it. The treated water is then discharged from the top layer.

[0030] In the method provided in this application, PDADMAC is a strong cationic polymer that can adhere to the surface of activated carbon, providing a large amount of positive charge. PFAS are usually in anionic (negatively charged) state in water, therefore the modified activated carbon can rapidly capture PFAS in the raw water through strong electrostatic attraction. Because PFAS molecules are surface-active (one end hydrophilic, the other hydrophobic); microbubbles rise slowly in water and have a large specific surface area, the hydrophobic end of PFAS is easily adsorbed at the gas-liquid interface of the microbubbles, thereby collecting and concentrating the dispersed PFAS at the interface. When microbubbles carrying a high concentration of PFAS come into contact with the modified activated carbon, due to the hydrophobic affinity between the activated carbon surface and the bubble surface, and the positive charge attraction of PDADMAC, a tight contact interface is formed, significantly reducing the mass transfer resistance of PFAS from the bubble surface to the activated carbon pores. Thus, through the synergistic mechanism of bubble enrichment and activated carbon locking, highly efficient removal of PFAS is achieved.

[0031] In some specific embodiments, the mass concentration of the polydiallyldimethylammonium chloride aqueous solution is 0.05% to 0.2%. For example, the mass concentration of the polydiallyldimethylammonium chloride aqueous solution can be 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, etc. At this concentration, polydiallyldimethylammonium chloride can form sufficient electrostatic adsorption sites with activated carbon, ensuring the effectiveness of subsequent adsorption treatment.

[0032] In some specific embodiments, the drying temperature is 60-70°C. For example, the drying temperature can be 60°C, 62°C, 65°C, 68°C, 70°C, etc. A suitable drying temperature balances drying efficiency with the stability of the modified activated carbon structure, quickly drying residual moisture on the activated carbon surface, ensuring a stable bond between polydiallyldimethylammonium chloride and the activated carbon surface, and preventing residual moisture from affecting subsequent adsorption effects.

[0033] In some specific embodiments, the mass ratio of activated carbon to the aqueous solution of polydiallyldimethylammonium chloride is 1:(10~15). As an example, the mass ratio of activated carbon to the aqueous solution of polydiallyldimethylammonium chloride can be 1:10, 1:12, 1:15, etc.

[0034] In some specific embodiments, when the raw water containing PFAS is subjected to microbubble treatment, air is used as the gas source, and the air intake rate is 20~60 mL / min. For example, the air intake rate can be 20 mL / min, 30 mL / min, 50 mL / min, 60 mL / min, etc. A stable air intake rate can generate a sufficient quantity of uniformly distributed microbubbles.

[0035] In some specific embodiments, the average diameter of the bubbles is 50 nm to 50 μm. Bubbles of this size rise slowly and remain in the water for a long time, allowing for sufficient contact with PFAS in the water. Simultaneously, it does not cause excessive emulsification of the water, thus enhancing the synergistic adsorption effect of the three phases.

[0036] In some specific embodiments, the dosage of modified activated carbon is 0.1~0.5 g / L based on the volume of raw water. Examples of modified activated carbon dosages include 0.1 g / L, 0.2 g / L, 0.3 g / L, and 0.5 g / L. At this dosage, the system has sufficient adsorption sites to completely adsorb the enriched PFAS substances without increasing water resistance or affecting microbubble diffusion, thus ensuring overall removal efficiency.

[0037] like Figure 1 As shown, this application also provides a system for adsorbing perfluorinated compounds with microbubble-enhanced modified activated carbon, which is used to realize the above-mentioned method for adsorbing perfluorinated compounds with microbubble-enhanced modified activated carbon. The system includes a microbubble generating tank 1, which is equipped with a stirrer 2. The stirrer 2 is used to stir the raw water to generate microbubbles and to fully mix the bubbles with the raw water. The liquid circulation unit, together with the microbubble generator tank 1, can form a raw water circulation loop; The gas supply unit, connected to the liquid circulation unit, is used to provide gas for microbubble processing; The bottom of the reaction column 4 is connected to the microbubble generator 1. Modified activated carbon (12) is installed in the reaction column 4. The raw water after microbubble treatment is sent into the reaction column 4 for adsorption treatment to achieve efficient removal of PFAS. The treated water is discharged from the top of the reaction column (4).

[0038] Specifically, the bottom of the reaction column 4 is connected to the bottom of the microbubble generator 1 through a pipe. A first metering pump 3-1 is installed on the raw water inlet pipe of the reaction column 4, and a second metering pump 3-2 is installed on the water outlet pipe of the reaction column 4. The first metering pump 3-1 is mainly used to control and measure the flow rate of the bubble mixture flowing between the reaction column 4 and the microbubble generator 1; the second metering pump 3-2 is used to control the water outlet flow rate.

[0039] The liquid circulation unit includes a check valve 5, a self-priming pump 8, a pressure gauge 9, and a pressure regulating valve 10. These components are connected in series via pipes and form a raw water circulation loop with the microbubble generator 1. The gas supply unit includes a granular activated carbon adsorption box 6 and a gas flow meter 7, connected in series and linked to the pipe between the check valve 5 and the self-priming pump 8. This provides the gas source for the microbubble treatment of the raw water. The self-priming pump 8 circulates the raw water solution within the microbubble generator 1. The check valve 5 is located at the beginning of the inlet pipe of the self-priming pump 8 to prevent backflow. The gas flow meter 7 regulates the inlet flow rate. The pressure regulating valve 10 and the pressure gauge 9 regulate and monitor the pressure on the liquid circulation pipeline, respectively. The granular activated carbon adsorption box 6 filters the air entering the reaction system.

[0040] Specifically, in the reaction column 4, the modified activated carbon 12 is placed in the middle of the column. The two ends of the modified activated carbon 12 are the support layer 11 and the filter screen 13, respectively. The support layer 11 can support the activated carbon packing, prevent loss and ensure uniform water flow distribution.

[0041] This application also provides the application of the above-mentioned method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon in the field of water treatment. This method is most widely used in drinking water and groundwater treatment, effectively removing PFAS from raw water while reducing operating costs.

[0042] This application constructs a stable gas-liquid-solid three-phase synergistic removal system by synergistically designing a microbubble system and a cationic modified activated carbon adsorption system. This changes the traditional liquid-solid two-phase adsorption mode and achieves a leap from single adsorption enhancement to multi-mechanism synergistic enhancement. At the same time, by utilizing the gas-liquid interface enrichment mechanism of the high specific surface area of ​​microbubbles, the migration path of PFAS is actively regulated, effectively improving mass transfer efficiency, shortening the pollutant diffusion distance, and accelerating the migration of pollutants to the adsorbent. In addition, this application can operate stably and efficiently under normal temperature and pressure conditions without the need to add strong oxidants. It can be directly embedded into existing activated carbon filter systems and has good potential for engineering scale-up and practical application.

[0043] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0045] Example 1 Step 1: Preparation of Modified Activated Carbon Pretreatment: Commercial granular activated carbon (GAC) is washed with deionized water to remove floating dust and dried at 105°C for later use.

[0046] Modifier preparation: Prepare a 0.05% (w / w) PDADMAC aqueous solution.

[0047] Impregnation loading: The pretreated activated carbon was immersed in the above PDADMAC aqueous solution at a mass ratio of 1:10, and the mixture was stirred at 400 rpm for 4 hours. This process utilizes the pore adsorption of activated carbon to anchor PDADMAC molecules on the carbon surface and within the macropores.

[0048] Post-treatment: The impregnated activated carbon was repeatedly rinsed with deionized water until the pH of the filtrate was neutral, and then dried in a vacuum oven at 65°C to obtain PDADMAC modified activated carbon for later use.

[0049] Step 2: Microbubble Synergistic Process Raw water containing PFAS is introduced into microbubble generator 1.

[0050] The air flow rate is adjusted by regulating the gas flow meter 7, the agitator stirs the raw water, and the pressure of the pipeline system is adjusted by the pressure regulating valve 10, which enables the self-priming pump 8 to generate microbubbles that meet the requirements during the circulation of raw water; the gas source is air; the average diameter of the bubbles is controlled at 50nm-50μm; the air intake is controlled at about 20mL / min, and the air intake time is about 10min.

[0051] The PDADMAC modified activated carbon prepared in step one is added to the reaction column 4 at a dosage of 0.5 g / L. Modified activated carbon 12 is filled between the support layer 11 and the filter screen 13. The mixture of raw water and microbubbles enters the reaction column 4 filled with PDADMAC modified activated carbon through the first metering pump 3-1. The empty bed time (EBCT) of the adsorption reaction is controlled by adjusting the flow rate of the first metering pump 3-1. The water flows through the reaction column 4 in an upward flow manner and is finally discharged from the top of the reaction column 4.

[0052] Comparative Example 1: Treatment using unmodified activated carbon Raw water containing PFAS is introduced into microbubble generator 1.

[0053] The air flow rate is adjusted by regulating the gas flow meter 7, the agitator stirs the raw water, and the pressure of the pipeline system is adjusted by the pressure regulating valve 10, which enables the self-priming pump 8 to generate microbubbles that meet the requirements during the circulation of raw water; the gas source is air; the average diameter of the bubbles is controlled at 50nm-50μm; the air intake is controlled at about 20mL / min, and the air intake time is about 10min.

[0054] Unmodified activated carbon was added to reaction column 4 at a dosage of 0.5 g / L; subsequent treatment was the same as in Example 1.

[0055] Comparative Example 2: No microbubbling treatment was applied to the raw water. The activated carbon was treated in the same way as in Example 1 to obtain modified activated carbon. The modified activated carbon was added to the reaction column 4, and the raw water containing PFAS was directly introduced into the reaction column 4. The subsequent treatment was the same as in Example 1.

[0056] like Figure 2 As shown, PDADMAC-modified GAC can accelerate the adsorption of PFAS in terms of adsorption kinetics. After introducing FBs, the adsorption rate is further improved. Since PDADMAC modification and the introduction of microbubbles do not change the active sites of GAC, the total adsorption amount of the three GAC adsorption systems remains the same after adsorption equilibrium.

[0057] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon, characterized in that, include: Activated carbon was impregnated in an aqueous solution of polydiallyldimethylammonium chloride, and the impregnated activated carbon was then treated to neutrality and dried to obtain modified activated carbon. Raw water containing PFAS is treated with microbubbles, then modified activated carbon is added to react with it, and the treated water is discharged from the top layer.

2. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, The mass concentration of the aqueous solution of polydiallyldimethylammonium chloride is 0.05%~0.2%.

3. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, The drying temperature is 60~70℃.

4. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, The mass ratio of activated carbon to aqueous solution of polydiallyldimethylammonium chloride is 1:(10~15).

5. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, When the raw water containing PFAS is treated with microbubbles, air is used as the air source, and the air intake rate is 20~60mL / min.

6. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, The average diameter of the bubbles is 50 nm to 50 μm.

7. The method for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 1, characterized in that, Based on the volume of raw water, the dosage of modified activated carbon is 0.1~0.5g / L.

8. A system for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon, characterized in that, The method for implementing the microbubble-enhanced modified activated carbon adsorption of perfluorinated compounds according to any one of claims 1-7, the system includes a microbubble generating tank (1), which is equipped with a stirrer (2) for stirring raw water to generate microbubbles. The liquid circulation unit, together with the microbubble generator (1), can form a raw water circulation loop; The gas supply unit, connected to the liquid circulation unit, is used to provide gas for microbubble processing; The bottom of the reaction column (4) is connected to the microbubble generating tank (1). Modified activated carbon is installed in the reaction column (4). The raw water after microbubble treatment is sent into the reaction column (4) for adsorption treatment. The treated water is discharged from the top of the reaction column (4).

9. The system for adsorbing perfluorinated compounds using microbubble-enhanced modified activated carbon according to claim 8, characterized in that, The liquid circulation unit includes a check valve (5), a self-priming pump (8), a pressure gauge (9), and a pressure regulating valve (10); each component is connected in series through pipes and can form a raw water circulation loop with the microbubble generator (1); The gas supply unit includes a granular activated carbon adsorption box (6) and a gas flow meter (7), which are connected in series to a pipeline between a check valve (5) and a self-priming pump (8) to provide a gas source for the microbubble treatment of raw water.

10. The method for adsorbing perfluorinated compounds by microbubble-enhanced modified activated carbon according to any one of claims 1-7 is applied in the field of water treatment.

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