Membrane filtration-type water treatment apparatus and water treatment method applying pulsating backwash air to increase recovery rate

Abstract

The objective of the present invention is to provide a membrane filtration-type water treatment apparatus applying pulsating backwash air, the apparatus meeting consumer demand for quality of purified water in the face of increasing water volume via membrane filtration-type water treatment using a separation membrane, and raising the recovery rate of raw water, which accounts for a large proportion of water purification costs, to increase cost-effectiveness by using pulsating backwash air, and, by means of more effective air backwashing, improving filtration efficiency and extending filtration duration, as well as extending the service life of a separation membrane module. Another objective of the present invention is to provide a water treatment method capable of increasing the recovery rate of raw water by utilizing the membrane filtration-type water treatment apparatus applying pulsating backwash air, and by means of more effective air backwashing, improving filtration efficiency and extending filtration duration, as well as extending the service life of a separation membrane module.

Description

Water purification device and water purification method using membrane filtration with pulsating backwash air applied to increase recovery rate

[0001] The present invention relates to water purification treatment using a membrane filtration method with a hollow fiber membrane, and more specifically, to a water purification treatment device and a water purification treatment method using a membrane filtration method that applies pulsating backwash air to increase the recovery rate of raw water while using a hollow fiber membrane used in water purification filters or water treatment membrane modules.

[0002] A membrane is a membrane having fine pores of a size of several μm or less, and can be classified in order of pore size as microfiltration membrane > ultrafiltration membrane > nanofiltration membrane > reverse osmosis membrane.

[0003] The membrane removes contaminants by utilizing the sieve effect, which allows substances smaller than the pores on the membrane surface to pass through while preventing substances larger than them from passing through. This enables the almost perfect removal of harmful organic and inorganic contaminants, crypto parasites, bacteria, microplastics, general bacteria, E. coli, etc. contained in water, making it possible to produce safe water. Furthermore, since it uses less chemicals compared to conventional water treatment processes, it can be considered an environmentally friendly treatment process.

[0004] Currently, microfiltration and ultrafiltration membranes are generally used to produce drinking water through water purification or to treat domestic sewage and industrial wastewater, while nanofiltration and reverse osmosis membranes are applied in fields requiring pure water containing almost no contaminants.

[0005] Here, ultrafiltration membranes are desirable for use in water purification systems due to their excellent ability to remove microorganisms and undissolved impurities; however, they have the disadvantage of requiring a small amount of filtered water, which leads to larger equipment and higher costs as the number of membrane modules used increases. Additionally, microfiltration membranes have lower filtration performance compared to other membranes, so they are currently mainly used for pretreatment.

[0006] The primary reason for using membranes is that they facilitate the securing of consistent treated water quality. In particular, in Korea, the variation in raw water quality across the four seasons is very large, including algal blooms in spring and autumn, high turbidity in summer, and low water temperatures in winter; therefore, it is almost impossible to secure consistent treated water quality using conventional sand filtration methods. Other advanced treatment processes, such as UV and ozone, also have their own problems.

[0007] However, when using membranes, these problems are largely resolved, allowing for the securing of consistent treated water quality without being significantly affected by variations in raw water quality or the presence of protozoa. Furthermore, using membranes for water treatment offers the advantage of high ease of management. Since membrane filtration allows for the automation of the entire process, and all processes, from water purification to backwashing, can be largely automated, it can be applied even in situations where specialized management personnel are insufficient.

[0008] However, in filtration processes using membranes, there is a problem where filtration efficiency decreases as contaminants accumulate on the membrane as filtration progresses, so there is a limitation that the membrane must be effectively backwashed at an appropriate time. Accordingly, various studies and efforts have been made to effectively backwash the membrane.

[0009] Hollow fiber membranes refer to threads that have a hole in the middle and fine pores on the surface, similar to a straw, and are used to filter and remove contaminants in water purification systems.

[0010] In water purification systems using hollow fiber membranes, increasing the raw water recovery rate {amount of purified water from raw water, (purified water / raw water) × 100} to improve purification efficiency according to treatment capacity, and extending the lifespan of the hollow fiber membranes used are important factors in determining the water purification system.

[0011] Conventional water purification methods utilizing hollow fiber membranes are known, and membrane filtration operation methods include pressurized prefiltration, cross-flow filtration, and suction prefiltration.

[0012] In the case of the pressurized dead-end filtration system, artificial pressure is applied to the raw water flowing into the hollow fiber membrane to force it to pass through and filter out contaminants, whereas the suction dead-end filtration system uses a pump to create a near-vacuum at the downstream end of the hollow fiber membrane, causing the entire volume of raw water flowing into the tank where the membrane is immersed to be drawn into the membrane due to the pressure difference, thereby filtering out contaminants.

[0013] The cross-flow filtration system, also known as the cross-type filtration system, aims to prevent the accumulation of contaminants on hollow fiber membranes by continuously circulating water. While the cross-flow filtration system has the effect of extending the lifespan of membranes by reducing the rate of contaminant accumulation on hollow fiber membranes when the flow rate of the circulating water is increased, it has the disadvantage of consuming a large amount of energy because a large amount of water must be circulated by a water purification device to maintain the flow rate of the circulating water.

[0014] The pressurized pre-filtration method is a process in which raw water is passed through a hollow fiber membrane module in an outside-in flow, and contaminants contained in the raw water are trapped by the hollow fiber membrane.

[0015] Unlike the cross-flow filtration method, the pressurized pre-filtration method has the advantage of high treatment efficiency due to the absence of unnecessary water flow, and the outside-in flow direction is ideal for treating water with high turbidity.

[0016] In the pressurized pre-filtration method, contaminants contained in the raw water accumulate entirely on the surface of the hollow fiber membrane, causing contamination to occur on the surface of the hollow fiber membrane in a relatively short period of time, resulting in a very high daily differential pressure rise rate; therefore, backwashing of the membrane must be performed at short intervals.

[0017] As a prior art, Korean registered patent No. 10-0954426 (published on April 26, 2010, hereinafter referred to as 'Patent Document 1'), titled 'Pressurized membrane filtration water treatment device for reducing membrane fouling and method of operation thereof,' discloses a pressurized membrane filtration water treatment device for reducing membrane fouling and a method of operation thereof in which air injected only in the membrane cleaning process is also injected into the membrane filtration process to prevent membrane fouling that occurs during the filtration process.

[0018] In addition, the 'Membrane Filtration Device with Forward Fluid Flow and Backwash Air Equal Distribution', which is Korean Patent No. 10-1687386 (published on December 16, 2016, hereinafter referred to as 'Patent Document 2') filed and registered by the present applicant, presents a method to increase the recovery rate by applying backwash water and backwash air to the backwashing of the membrane filtration device. However, there was a problem in that there were limitations in increasing the recovery rate and extending the lifespan of the hollow fiber separation membrane used according to the prior art and Patent Documents 1 and 2.

[0019] Therefore, since the cost of purchasing raw water accounts for the largest share of water purification plant production costs (excluding equipment depreciation) and high energy consumption leads to lower overall production costs, making it more economical, there is an urgent need for research on efficient water purification devices and methods that utilize improved backwashing air to increase the recovery rate and extend the lifespan of membrane modules.

[0020] [Prior Art Literature]

[0021] [Patent Literature]

[0022] (Patent Document 1) Korean Registered Patent No. 10-0954426 (Published April 26, 2010), 'Pressurized membrane filtration water treatment device for reducing membrane fouling and method of operating the same'

[0023] (Patent Document 2) Korean Registered Patent No. 10-1687386 (Published Dec. 16, 2016), 'Membrane Filtration Device for Forward Fluid Flow and Backwash Air Equal Distribution'

[0024] To solve the aforementioned problems, the objective of the present invention is to provide a water purification device using a membrane filtration method that utilizes a separation membrane, capable of satisfying consumer demands for water quality in increasingly large water volumes through membrane filtration, increasing economic efficiency by raising the recovery rate of raw water—which accounts for a large portion of water purification production costs—by applying pulsating backwash air, and extending the lifespan of the separation membrane module by improving filtration efficiency and increasing the duration of filtration through more effective air backwashing.

[0025] In addition, another objective of the present invention is to provide a water purification method that utilizes a membrane filtration type water purification device applying the above-described pulsating backwash air to increase the recovery rate of raw water, perform more effective air backwashing to increase filtration efficiency and extend the filtration duration, and extend the lifespan of the separation membrane module.

[0026] In order to achieve the objective of providing a membrane filtration water treatment device that applies pulsating backwash air to increase the recovery rate of raw water as described above, thereby increasing economic efficiency, and to perform more effective backwashing to increase filtration efficiency and extend the filtration duration, and to extend the lifespan of the membrane module, the membrane filtration water treatment device that applies pulsating backwash air to increase the recovery rate in the present invention comprises:

[0027] 1) A water purification device of the membrane filtration type that backwashes a separation membrane containing contaminants in raw water with air, comprising: a membrane filtration section in which a membrane filtration unit is formed by arranging a plurality of separation membrane modules in two rows; a fluid discharge section in which a fluid inlet pipe through which raw water flows into the membrane filtration unit, a production water discharge pipe through which production water that has passed through the separation membrane modules is discharged, a backwash discharge water discharge pipe through which backwash discharge water containing turbidity is discharged during air backwashing, and a backwash drain pipe through which backwash wastewater containing turbidity is discharged during air scrubbing are installed to correspond to the membrane filtration unit of the membrane filtration section, wherein the fluid inlet pipe and the fluid discharge pipe are respectively arranged at the front and rear ends of the membrane filtration unit, so as to have a straight flow in which the flow direction of the incoming fluid passing through the membrane filtration section coincides with the longitudinal direction of the membrane filtration unit; Between the above-mentioned two-row arranged membrane modules, a backwash air piping system comprising: an air supply pipe installed along the longitudinal direction of the membrane filtration unit to perform backwashing after the discharge of the production water that has passed through the membrane modules is finished; backwash air injection pipes branching off from both sides of the air supply pipe and respectively connected to the upper portions of the two-row arranged membrane modules to inject backwash air into the lumen side, which is the inside of the hollow fiber membrane of the membrane module; and an air scrubbing air piping system comprising a pair of air scrubbing air injection pipes connected facing each other to the lower portions of the two-row arranged membrane modules to perform air scrubbing after backwash air is injected through the backwash air piping system, and a vortex union branched from the air supply pipe and connected to the pair of air scrubbing air injection pipes.

[0028] 2) The membrane filtration type water purification device according to the present invention is further characterized in that the production water discharge pipe and the backwash discharge water discharge pipe further include an exhaust valve for discharging air.

[0029] 3) The membrane filtration type water purification device according to the present invention also injects backwash air into the lumen side, which is inside the hollow fiber membrane of the membrane module, through the backwash air piping, and simultaneously closes the valve of the backwash discharge water discharge pipe; and injects backwash air into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure pushed by the lumen side into which backwash air has been injected, so that turbidity attached to the pores, etc., on the surface of the membrane is removed or made possible, thereby allowing some of the production water remaining in the lumen to be discharged to the shell side, and after the pressure inside the membrane housing is 80 to 150 kPa at the top and 100 to 170 kPa at the bottom due to hydrostatic pressure, the valve of the backwash discharge water discharge pipe is instantaneously opened so that the backwash discharge water of the membrane module is discharged and drops to natural pressure It is characterized by operating to cause a surging phenomenon in which the membrane inside the membrane housing shakes, and then additionally introducing backwash air to the lumen side to push the remaining production water inside the lumen and discharge it to the shell side.

[0030] 4) The membrane filtration type water purification device according to the present invention is also characterized by operating to effectively remove turbidity on the surface of the membrane by injecting air scrubbing air in a vortex form at an air pressure of 30 to 50 kPa and shaking the membrane surface for an air scrubbing time of 20 to 60 seconds through a vortex union branched from an air supply pipe and connected to the pair of air scrubbing air injection pipes, after which backwash air is injected and then air scrubbing air is injected into the shell side inside the membrane housing.

[0031] 5) The water purification device of the membrane filtration method according to the present invention is further characterized in that the air scrubbing air injection pipe is mounted by a shell-side connection part inside the membrane housing at the bottom of each separation membrane module composed of several parts, and includes a vortex union that allows the cleaning air (Air Scrubbing) to be distributed and injected into the membrane housing in a vortex form after a constant air pressure is formed inside the pipe for each separation membrane module during air scrubbing, and a through hole is formed in the orifice of the vortex union through which the cleaning air (Air Scrubbing) can pass, and the diameter of the through hole on the upper surface of the orifice is expanded to be larger than the diameter of the through hole on the lower surface of the orifice so as to generate a vortex of air.

[0032] 6) The membrane filtration water treatment device according to the present invention is also characterized by a vortex union that enables the injection of cleaning air (Air Scrubbing) at a constant air pressure into each separation membrane module composed of multiple units in the air scrubbing air injection pipe, wherein the diameter of the through hole on the lower surface of the orifice is 8 mm and the diameter of the through hole on the upper surface of the orifice is expanded to 15 mm, thereby creating an air passage inside the vortex union to vortex the air flow and increase the backwashing efficiency of the membrane to extend the filtration duration.

[0033] 7) The membrane filtration type water purification device according to the present invention is further characterized in that the backwash drain pipe rapidly discharges turbidity on the surface of the backwashed membrane after air scrubbing is performed on the shell side inside the membrane housing, and a backwash drain pit with a size of at least four times the inner diameter of the backwash drain pipe is installed at the downstream end of the valve of the backwash drain pipe so that turbidity on the surface of the backwashed membrane can be discharged quickly, and then, in order to prevent high turbidity from remaining inside the backwash drain pipe, the raw water pump is operated for 1 to 2 seconds while the valve of the backwash drain pipe is open by a sequence to remove turbidity on the surface of the backwashed membrane, and then raw water filtration begins.

[0034] In another aspect of the present invention, a membrane filtration water treatment method that applies pulsating backwash air to increase the recovery rate by utilizing the membrane filtration water treatment device described above is,

[0035] 8) A water purification method using a membrane filtration type water purification device that applies pulsating backwash air to increase the recovery rate, wherein raw water is introduced from a raw water tank through a fluid inlet pipe by a raw water pump into membrane modules in a membrane filtration unit, and after being filtered through a membrane, the produced water is discharged; When the filtration of the raw water is completed in the above filtration process, the valve of the production water discharge pipe is closed. Simultaneously, backwash air is injected into the lumen side, which is inside the hollow fiber membrane of the membrane module, through the backwash air piping, and the valve of the backwash effluent discharge pipe is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure exerted by the lumen side into which the backwash air has been injected. This allows some of the production water remaining in the lumen to be discharged toward the shell side to remove, or enable, turbidity attached to the pores on the membrane surface. As pressure is applied to the raw water on the shell side in the form of compression by the backwash air, the pressure inside the membrane housing is transmitted to the water, with the upper part at 80 to 150 kPa and the lower part at 100 to 170 kPa due to hydrostatic head pressure, after which the backwash effluent An air backwash process that operates by momentarily opening the valve of the discharge pipe to discharge the compressed backwash discharge water from the membrane module and causing a pulsating phenomenon in which the membrane inside the membrane housing shakes as it drops to natural pressure, and then additionally injects backwash air into the lumen to push the remaining production water inside the lumen toward the shell side;After the above air backwashing process, the method comprises: a pair of air scrubbing air injection pipes connected facing each other at the bottom of the membrane module to inject air scrubbing into the shell side inside the membrane housing; and an air scrubbing process that operates to effectively remove turbidity from the membrane surface by injecting air scrubbing in a vortex form at an air pressure of 30 to 50 kPa for an air scrubbing time of 20 to 60 seconds through a vortex union branched from an air supply pipe and connected to the pair of air scrubbing air injection pipes, thereby shaking the membrane surface to effectively remove turbidity; and a discharge process that discharges the removed turbidity from the membrane surface through a backwash drain pipe after performing air scrubbing on the shell side inside the membrane housing.

[0036] 9) The water purification method of membrane filtration according to the present invention is also characterized by including a vortex union that is installed by a shell-side connection portion inside the membrane housing at the bottom of each membrane module, wherein a pair of air scrubbing air injection pipes are configured in multiple numbers, and during air scrubbing, a constant air pressure is formed inside the pipe by the vortex union for each membrane module, and then the air scrubbing is distributed and injected into the membrane housing in a vortex form, and a through hole is formed in the orifice of the vortex union through which the air scrubbing can pass, and the diameter of the through hole on the upper surface of the orifice is expanded to be larger than the diameter of the through hole on the lower surface of the orifice so as to create a vortex of air.

[0037] 10) The water purification method of membrane filtration according to the present invention is also characterized in that, in a vortex union connected to a pair of air scrubbing air injection pipes to inject air scrubbing at a constant air pressure into each separation membrane module composed of several units, the diameter of the lower surface of the orifice through hole is 8 mm and the diameter of the upper surface of the orifice through hole is 15 mm, which expands to change the flow of fluid within the orifice by acting as a vortex, and is formed to create a flow path inside the vortex union to create a vortex of air flow.

[0038] 11) The water purification method of membrane filtration according to the present invention is also characterized by installing a backwash drainage pit at least four times the inner diameter of the backwash drainage pipe at the downstream end of the valve of the backwash drainage pipe in the discharge process so that turbidity on the surface of the backwashed membrane can be quickly discharged, and then, in order to prevent high turbidity from remaining inside the backwash drainage pipe, operating a raw water pump for 1 to 2 seconds while the valve of the backwash drainage pipe is open by a sequence to remove turbidity on the surface of the backwashed membrane, and then starting raw water filtration.

[0039] Accordingly, the present invention provides a water purification device and method using a membrane filtration method that utilizes pulsating backwash air, which can increase filtration efficiency and extend the filtration duration by performing more effective backwashing with a pulsating air through a membrane filtration method using a separation membrane, and extend the lifespan of the separation membrane module.

[0040] According to the present invention, through water purification treatment using a membrane filtration method utilizing a separation membrane, it is possible to satisfy the demand of consumers for the quality of purified water in gradually increasing quantities, while increasing economic efficiency by increasing the recovery rate of raw water, which accounts for a large proportion of water production costs and energy reduction. Furthermore, by introducing an improved backwashing method in which a valve of the backwash discharge water discharge pipe is closed and then momentarily opened to cause a pulsation phenomenon during air backwashing, and by applying a pair of air scrubbing air injection pipes connected facing each other at the bottom of the separation membrane module and an improved type of vortex union to create an air flow path inside the vortex union and inject it in a vortex form, it is possible to perform more effective air backwashing, thereby increasing filtration efficiency and extending the filtration duration, and extending the lifespan of the separation membrane module.

[0041] Furthermore, the present invention has an excellent effect of completely removing high-turbidity backwash wastewater in a short period of time from multiple membrane modules by improving the shape of the backwash drain pipe and the backwash drainage method to prevent the vicious cycle in which raw water and residual backwash wastewater enter the membrane housing together and are filtered again when raw water filtration begins before high-turbidity backwash wastewater has been completely discharged during the air scrubbing process, thereby shortening the filtration duration and accelerating membrane fouling.

[0042] FIG. 1 is a side view of a membrane filtration type water purification device according to an embodiment of the present invention.

[0043] FIGS. 2 and FIGS. 3 are a plan view and a side view schematically illustrating a membrane filtration type water purification device according to an embodiment of the present invention.

[0044] FIG. 4 is a drawing illustrating an air pipe and a vortex union according to an embodiment of the present invention.

[0045] FIG. 5 is a side view of a vortex-shaped flow path of a vortex union according to an embodiment of the present invention.

[0046] Figure 6 is a diagram showing the airflow with an enlarged view of the orifice in the vortex union of Figure 4.

[0047] FIG. 7 is a drawing illustrating the installation of a pair of air injection pipes and a vortex union for air scrubbing according to an embodiment of the present invention to perform air scrubbing.

[0048] FIGS. 8 and 9 are schematic diagrams illustrating a backwashing process and an air scrubbing process according to an embodiment of the present invention.

[0049] FIG. 10 is a schematic diagram illustrating the change in air distribution of a membrane module when a vortex union is installed and when it is not installed in an air scrubbing process according to an embodiment of the present invention.

[0050] FIG. 11 is a schematic diagram illustrating an improved air scrubbing process according to an embodiment of the present invention.

[0051] FIG. 12 is a drawing specifically showing the shape of the membrane module used in the present invention.

[0052] Figure 13 is a graph showing the change in turbidity and pressure over time during pulsating air backwashing.

[0053] Figure 14 is a graph showing the change in turbidity and pressure over time during conventional air backwashing.

[0054] Terms and words used in the description and claims of the present invention shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0055] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail with reference to the drawings. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the technical spirit and scope of the present invention.

[0056] In describing the present invention, if it is determined that a detailed description of known technologies or configurations related to the present invention may obscure the essence of the present invention, such detailed description is omitted, and the present invention is defined only by the scope of the claims.

[0057] In the present invention, terms such as "includes" or "consists of" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0058]

[0059] In this invention, the fluid flowing into the membrane filtration unit is referred to as raw water, the fluid filtered and discharged while passing through the membrane module in the membrane filtration unit is referred to as production water, the fluid used during the backwashing process is referred to as backwash air, and the fluid used for air washing in the air scrubbing process added after the backwash air is injected is referred to as washing air. Furthermore, contaminants formed on the surface of the membrane due to membrane filtration are referred to as turbidity, and in particular, the fluid flowing through the membrane filtration unit during the filtration process, backwashing process, and air scrubbing process is collectively referred to as the inflow fluid.

[0060] Referring to the drawing in Fig. 12, which specifically illustrates the form of the membrane module used in the present invention, in the membrane module of the present invention, the module case is called a housing, a plurality of hollow fibers are used inside the housing, the inside of the membrane of the hollow fibers is called a lumen, and the outside of the membrane of the hollow fibers is called a shell.

[0061] The greatest advantage of hollow fiber membranes is that they allow for back flushing, and periodic back flushing restores performance and extends the membrane's lifespan.

[0062] The separation membrane used in the present invention is an ultrafiltration (UF) membrane or a microfiltration (MF) membrane, which uses a pressure difference as a driving force to separate particles in a larger area than a reverse osmosis filtration membrane.

[0063] Although ultrafiltration shares the same basic principle as microfiltration, microfiltration membranes have a symmetric pore structure in which the pore cross-sectional structure along the membrane thickness direction has a uniform shape. In contrast, ultrafiltration membranes have a dense layer structure with an asymmetric design, consisting of a thin, dense layer on the membrane surface that performs separation and a porous support layer on the back. This allows for the separation of smaller particles than microfiltration, enabling the efficient production of high-quality purified water by preventing the entry of microplastics, midge larvae, E. coli, and bacteria—which have recently become major concerns—into drinking water.

[0064] The membrane filtration method of the present invention is a pressurized dead-end filtration system that filters contaminants by applying artificial pressure to raw water flowing into a hollow fiber membrane to force the raw water to pass through the membrane. The membrane module is formed by installing a certain number of hollow fiber membranes inside a housing, which is a module case of a certain shape, and filtration occurs as the raw water passes through the membrane module. The method involves passing the raw water through the membrane module in an outside-in flow manner, thereby allowing contaminants contained in the raw water to be filtered by the hollow fiber membrane.

[0065] Unlike the cross-flow filtration method, the pressurized pre-filtration method has the advantage of high treatment efficiency due to the absence of unnecessary water flow, and the outside-in flow direction is ideal for treating water with high turbidity.

[0066] The present invention is installed in an advanced water purification plant, etc., and during the filtration process, raw water pumped from a raw water tank flows into a membrane filtration unit and passes through a membrane module to perform filtration. During the backwashing process, backwashing air pushes out the production water remaining in the lumen inside the hollow fiber membrane to remove turbidity in the pores on the surface of the membrane or to remove it in a swollen state. Subsequently, during the air scrubbing process, for backwashing, cleaning air passes through the shell side outside the membrane and shakes the membrane to further remove turbidity on the surface of the membrane, thereby thoroughly cleaning the membrane and then filtering the raw water again to discharge clean production water. This increases filtration efficiency and extends the filtration duration, while also extending the lifespan of the membrane module.

[0067] "Vortex Union" is a device for forming a vortex inside a membrane housing during air scrubbing, and is an improved version of the orifice union of Patent Document 2, which was filed and patented by the applicant as described in the background art, and is also called a "vortex-type orifice union" to indicate that the flow path acts in a vortex form.

[0068] In the present invention, an air scrubbing air piping system may be used in which an improved type of vortex union is installed, which is connected to a pair of air scrubbing air injection pipes that are respectively connected facing each other at the bottom of the membrane module to inject air scrubbing air into the shell side inside the membrane housing in order to effectively form a vortex inside the membrane housing during air scrubbing.

[0069] Hereinafter, a water purification device and a water purification method using a membrane filtration method that apply pulsating backwash air to increase the recovery rate according to the present invention will be described with reference to the attached drawings.

[0070]

[0071] Water purification device using membrane filtration with backwash air to increase recovery rate

[0072] FIG. 1 is a side view of a water purification device using a membrane filtration method according to an embodiment of the present invention, FIG. 2 and FIG. 3 are a plan view and a side view schematically illustrating a water purification device using a membrane filtration method according to an embodiment of the present invention, FIG. 4 is a drawing illustrating an air pipe and a vortex union according to an embodiment of the present invention, FIG. 5 is a side view showing a vortex-shaped flow path of a vortex union according to an embodiment of the present invention, FIG. 6 is a drawing showing an enlarged view of the orifice in the vortex union of FIG. 4 and the air flow, FIG. 7 is a drawing illustrating the installation of a pair of air injection pipes for air scrubbing and a vortex union according to an embodiment of the present invention to explain air scrubbing.

[0073] The present invention relates to a water purification device of the membrane filtration type that backwashes a separation membrane containing contaminants in raw water with air, as shown in FIGS. 1 to 7,

[0074] A membrane filtration unit (110) formed by arranging multiple membrane modules (120) in two rows;

[0075] In order for raw water from the raw water tank to flow into the membrane filtration unit (110) and for the production water that has passed through the separation membrane modules (120) to be discharged, the fluid transport unit (200) is installed such that the fluid discharge pipe, which consists of a fluid inlet pipe (210), a production water discharge pipe (220) through which the production water that has passed through the separation membrane modules (120) is discharged, a backwash discharge water discharge pipe (230) through which backwash discharge water containing turbidity is discharged during air backwashing, and a backwash drain pipe (240) through which backwash discharge water containing turbidity is discharged during air scrubbing, corresponds to the membrane filtration unit (110) of the membrane filtration unit (100). The fluid inlet pipe (210) and the fluid discharge pipe are respectively positioned at the front and rear ends of the membrane filtration unit (110), so that the flow direction of the incoming fluid passing through the membrane filtration unit (100) has a straight flow that coincides with the longitudinal direction of the membrane filtration unit (110). The basic configuration is the transmission unit (200).

[0076] In the above membrane filtration unit (100), the separation membrane module (120) is formed by installing a certain number of hollow fiber separation membranes inside a housing, which is a case of a certain shape, and the raw water from the raw water tank flows into the membrane filtration unit (110) and passes through the separation membrane module (120) in an outside-in flow according to the pressurized dead-end filtration system, thereby performing filtration.

[0077] The above membrane filtration unit (100) has a plurality of separation membrane modules (120) arranged in two rows to form one membrane filtration unit (110), and two membrane filtration units (110) are arranged in two rows to form one series and operate simultaneously.

[0078] These membrane filtration units (100) are connected to each row of membrane modules (120) by a single pump, with a fluid inlet pipe (210) connected by a fluid inlet branch pipe (211) that corresponds to each membrane filtration unit (110).

[0079] The fluid inlet pipe (210) and the fluid outlet pipe of the above fluid transport unit (200) are installed to correspond to the membrane filtration unit (110), so that raw water pumped from the raw water tank is filtered as it passes through the membrane filtration unit (110), and as shown in FIGS. 1 and 2, the produced water is discharged through the produced water outlet pipe (220).

[0080] That is, a fluid discharge pipe comprising a fluid inlet pipe (210), a production water discharge pipe (220) through which the raw water passes through the separation membrane modules (120) and the production water is discharged, a backwash discharge water discharge pipe (230) that discharges backwash discharge water containing turbidity during air backwashing, and a backwash drain pipe (240) that discharges backwash drainage containing turbidity during air scrubbing, is each disposed at the front and rear ends of the membrane filtration unit (110), so that the flow direction of the incoming fluid passing through the membrane filtration unit (100) has a straight flow that coincides with the longitudinal direction of the membrane filtration unit (110).

[0081] The above fluid inlet pipe (210) is connected to a raw water tank (not shown) to allow raw water to flow in, and is branched into two fluid inlet branch pipes (211) to pass through the lower part between two rows of membrane filtration units (110), and the production water filtered and discharged from the separation membrane module (120) is transferred to a production water tank (not shown) through a production water discharge pipe (220).

[0082] In addition, as shown in FIG. 1, the fluid discharge pipe of the fluid transport unit (200) is connected to the backwash discharge water branch pipe (231) of the membrane module (120) to transfer the backwash discharge water discharged from the air backwash process to the backwash drainage tank (not shown) through the backwash discharge water discharge pipe (230).

[0083] And the fluid discharge pipe of the fluid transport unit (200) is connected to the backwash drainage branch pipe (241) of the membrane filtration unit (110) to transport the backwash drainage discharged from the air scrubbing process to a backwash drainage tank (not shown) through the backwash drainage pipe (240).

[0084] In the present invention, particularly in the backwash discharge pipe (230) that discharges backwash discharge water containing turbidity during air backwashing, an exhaust valve (232) is installed so that the cleaning air (Air Scrubbing) used during air scrubbing is exhausted.

[0085] In addition, since the bubble point at which air does not come out from the lumen to the shell side even when backwash air is injected into the lumen inside the hollow fiber membrane of the ultrafiltration (UF) membrane or microfiltration (MF) membrane used in the present invention is designed to be around 200 kPa, the backwash air used at a pressure of 80 to 150 kPa during the backwashing process in the present invention remains in the lumen even after the backwashing process is completed.

[0086] Here, in the present invention, using backwash air at a pressure of 80 to 150 kPa is set to 150 kPa, which is an appropriate pressure sufficiently lower than the Bubble Point of 200 kPa, where the minimum pressure at which pulsation may occur during air backwashing is 80 kPa and air does not come out from the Lumen to the Shell side even when backwash air is injected into the Lumen, and is the optimal range for pulsating air backwashing.

[0087] Accordingly, an exhaust valve (222) is installed in the production water discharge pipe (220), so that when the filtration process restarts and the production water is discharged, the backwash air remaining in the lumen of the separation membrane module is discharged through the exhaust valve (222).

[0088]

[0089] Here, the exhaust valve (222) and the exhaust valve (232) may be air vent valves that automatically discharge air when it fills the pipe.

[0090] In order to increase the recovery rate, the present invention applies pulsating backwash air in the backwash process, and as shown in FIGS. 1 and 4, includes an air supply pipe (310) and a backwash air injection pipe (320) branched from the air supply pipe (310) and connected to each of the plurality of membrane modules (120).

[0091] The air supply pipe (310) is connected to a separate compressor (not shown) to supply backwash air with controlled air pressure.

[0092] In the present invention, by a sequence, backwash air is injected into the lumen side of the membrane module (120) through the backwash air injection pipe (320) and simultaneously the valve of the backwash discharge water discharge pipe (230) is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure pushed by the lumen side into which the backwash air has been injected, so that turbidity attached to the pores, etc., on the surface of the membrane is removed or made possible, and the production water remaining in the lumen is partially discharged to the shell side. After the pressure inside the membrane housing is compressed and transmitted to the water at 80 to 150 kPa in the upper part and 100 to 170 kPa in the lower part due to hydrostatic pressure, the valve of the backwash discharge water discharge pipe (230) is opened instantaneously to the membrane module It can be operated so that as the backwash discharge water is discharged and falls under natural pressure, a surging phenomenon occurs in which the membrane inside the membrane housing is shaken.

[0093] In addition, the valve of the backwash discharge pipe (230) is opened momentarily to discharge the compressed backwash discharge water of the membrane module (120), causing a pulsating phenomenon in which the membrane inside the membrane housing shakes, and then additional backwash air is introduced into the lumen side to push the remaining production water inside the lumen and discharge it to the shell side.

[0094] Figure 13 is a graph showing the change in turbidity and pressure over time during pulsating air backwashing, and Figure 14 is a graph showing the change in turbidity and pressure over time during conventional air backwashing.

[0095] In the present invention, the time required for the air backwashing process is approximately 22 to 25 seconds, and as shown in FIG. 13, the holding time during which the pressure on the shell side inside the membrane housing becomes equal to the pressure pushed by the lumen side into which backwash air is injected is typically about 5 seconds, and after the surging phenomenon in which the membrane inside the membrane housing shakes occurs, the remaining time may be the time required to additionally inject backwash air into the lumen side to push the remaining production water inside the lumen and discharge it to the shell side.

[0096] At this time, the instantaneous maximum turbidity (195 NTU) of the backwash effluent discharged by the pulsating air backwashing process with an air backwashing pressure of 110 kPa in Fig. 13 is much higher than the instantaneous maximum turbidity (115 NTU) of the backwash effluent discharged by the air backwashing pressure of 70 kPa in the conventional air backwashing process in Fig. 14, as the turbidity removal effect is very high.

[0097] Meanwhile, typically, when backwash water is introduced into the membrane housing during conventional water backwashing, the head pressure at the top of the membrane housing is about 0 kPa, but the head pressure at the bottom of the membrane housing is 20 kPa due to the membrane height of 2,160 mm. Therefore, even if backwash water is introduced into the lumen during water backwashing, the head pressure acts on the bottom of the membrane housing, resulting in a low distribution of turbidity removal and a somewhat lower efficiency of turbidity removal. Consequently, a significant amount of production water is consumed as backwash water to remove turbidity, which leads to a disadvantage and a problem where the recovery rate is lowered as much as the production water is used as backwash water.

[0098] In addition, there was a problem where the unit cost of water purification production increased because conventional backwashing required facilities such as backwash pumps, backwash tanks, backwash piping, and other equipment, consuming facility and energy costs.

[0099] In order to improve the various problems associated with conventional water backwashing, the present invention allows turbidity attached to the pores, etc., on the surface of the membrane to be effectively removed by the pulsating phenomenon of the membrane shaking during the backwashing process with air, or at least allows the turbidity attached to the pores, etc., on the surface of the membrane to be easily removed as some of the production water remaining in the lumen of the membrane module (120) is discharged by the backwashing air.

[0100] Meanwhile, as shown in FIGS. 1 and 3, the chemical piping consisting of a chemical injection pipe (260) and a chemical discharge pipe (270) is configured so that, when chemical backwashing is specifically required, the chemical passes through the membrane module (120) together with the raw water, allowing the turbidity remaining in the membrane module (120) to be removed by the chemical. The chemical injection pipe (260) is connected to a chemical circulation pipe installed in the membrane filtration room, and the chemical discharge pipe (270) is connected to a chemical wastewater tank (not shown) so that the chemical is injected and the chemical wastewater is discharged.

[0101] The above chemical injection tube (260) can pass a chemical through the membrane filter (100) to perform cleaning when the differential pressure rises rapidly due to severe contamination of the membrane filter (100).

[0102] As shown in FIGS. 1 and 3, the present invention, which has such a structure, is formed in a forward direction that coincides with the longitudinal direction of the membrane filtration unit (110), such as the flow direction of the incoming fluid and chemical passing through the membrane filtration unit (100), that is, the flow direction of the raw water and the production water being discharged during the filtration process, the flow direction of the backwash air and the backwash air being discharged during the backwash process, and the flow direction of the chemical being introduced together with the backwash water and the chemical being discharged together with the backwash water during the chemical backwash. By preventing stagnation of the incoming fluid or residual occurrence of the chemical, it is possible to prevent contamination of the separation membrane module (120) and the production water due to turbidity or chemical accumulation.

[0103] Each of these pipes is individually equipped with a valve to open and close the respective flow path and a pump to guide the fluid flow.

[0104] As an embodiment of the present invention, in the membrane filtration unit (110), when the membrane module (120) is composed of several (about 20) membrane modules (120) to show the change in air distribution of the membrane module when a vortex union is installed and when it is not installed in the air scrubbing process according to an embodiment of the present invention, the cleaning air (Air Scrubbing) must be supplied at a constant pressure into each housing through the air scrubbing air injection pipe (330), but the air is first delivered to the housing (No. 1, No. 20) furthest from the inlet.

[0105] Here, if the air line flows toward the 10th membrane module (housing), such as when the vortex union is not installed and the air pressure is low, air flows into the 1st and 20th modules first, so the air pressure distribution is such that the 1st and 20th modules have a large amount of air inflow and air scrubbing is effective, while the area around the 10th module has a small amount of air inflow and is pushed out by the hydrostatic pressure, preventing air from entering, which results in an extremely low backwashing effect.

[0106] Therefore, if a vortex union (340), which is a device for forming a vortex inside a membrane housing such as the right drawing of FIG. 4 and FIG. 5 and 6, is installed so that a constant pressure is formed from number 1 to number 20, such as the air pressure installed by the vortex union, and the amount of air entering is constant, it acts as an orifice, and after an air pressure distribution is evenly formed inside the pipe to overcome the hydrostatic pressure acting on the bottom of the housing, such as the air pressure installed by the vortex union shown in FIG. 10, cleaning air (Air Scrubbing) can be injected into the housing at the same pressure.

[0107] The connection portion of the above air scrubbing air injection pipe (330) is connected to the nipple (343) of the vortex union (340) to form an air passage, and a narrow through hole (342) is formed with a diameter smaller than the passage of the nipple (343) so that a constant pressure is formed in the orifice (341) and a constant amount of air is introduced, through which the cleaning air (Air Scrubbing) can pass during air scrubbing.

[0108] However, since the diameter of the membrane housing is typically quite wide at about 21.6 cm, a drift phenomenon occurs where the cleaning air (Air Scrubbing) passing through the narrow through hole (342) is driven toward the side with less resistance to hydrostatic pressure. Therefore, as shown in FIGS. 5 and 6, the diameter of the upper through hole (342) is expanded to be larger than the diameter of the lower through hole (342) of the orifice (341) to form a vortex-like fluid flow on the inner shell side of the membrane housing, thereby ensuring that the cleaning air (Air Scrubbing) is evenly distributed on the inner shell side of the membrane housing.

[0109] In one embodiment of the present invention, preferably, in order to inject a constant pressure equally into each module composed of multiple modules, the diameter of the through hole (342) on the lower surface of the orifice (341) in the vortex union (340) installed in a conventional air scrubbing air injection pipe (330) with an inner diameter of 25 mm is set to 8 mm and the through hole (342) on the upper surface of the orifice (341) is expanded to 15 mm so that the air pressure is evenly distributed to each module, and when the pressure becomes equal, the air from the vortex union (340) flows in in a vortex form and shakes the surface of the separation membrane to remove turbidity.

[0110] By forming a flow path in the form of a vortex on the shell side inside the membrane housing, the cleaning air (Air Scrubbing) is evenly delivered to the shell side inside the membrane housing, thereby maximizing the backwashing effect of the membrane.

[0111] In the present invention, the air piping (300) is formed by branching into two pipes so that the air supply pipe (310) is vertically connected to the front end of the membrane filtration unit (100) and corresponds to each membrane filtration unit (110). As shown in the schematic diagram illustrating the backwashing process and air scrubbing process according to an embodiment of the present invention in FIGS. 8 and 9, in order to perform the air scrubbing process following the backwashing process, a pair of air scrubbing air injection pipes (330) are branched left and right from the two pipes and connected to face each other at the bottom of the two-row arranged membrane modules as shown in FIG. 7, and an air scrubbing air piping is installed to inject cleaning air (Air Scrubbing) into the bottom cell (Shell) of the membrane housing through a vortex union (340) that branches from the air supply pipe (310) and is connected to the pair of air scrubbing air injection pipes (330).

[0112] Here, the valve of the backwash discharge water discharge pipe (230) is opened momentarily to effectively remove turbidity attached to the pores, etc., on the surface of the membrane by the pulsating phenomenon of the membrane shaking, and the compressed backwash discharge water of the membrane module (120) is partially discharged. Then, backwash air is additionally injected into the lumen side to push the remaining production water inside the lumen and discharge it toward the shell side. Subsequently, a pair of air scrubbing air injection pipes (330) are connected facing each other at the bottom of the membrane module (120) to inject air scrubbing into the shell side inside the membrane housing, and through a vortex union (340) branched from the air supply pipe (310) and connected to the pair of air scrubbing air injection pipes (330), air scrubbing is performed on the shell side inside the membrane housing at an air pressure of 30 to 50 kPa for an air scrubbing time of 20 to It can be operated to more effectively backwash and remove turbidity from the membrane surface by introducing air scrubbing in a vortex form for 60 seconds and shaking the membrane surface.

[0113] In one embodiment of the present invention, as shown in FIG. 7, a pair of air scrubbing air injection pipes (330) are connected facing each other at the bottom of a membrane module (120) to inject air scrubbing into the shell side inside the membrane housing, and by injecting air scrubbing through a vortex union (340) that branches off from an air supply pipe (310) and is connected to the pair of air scrubbing air injection pipes (330), as shown in FIG. 5 and FIG. 6, a vortex-shaped flow path of the vortex union (340) is formed, and mutual synergy is created so that the air scrubbing can be injected more effectively in a vortex shape.

[0114] That is, the “Vortex Union” is a device for forming a vortex inside the membrane housing during air scrubbing after ensuring that the same pressure is formed before the air scrubbing is introduced into each membrane module (120). It is an improved version of the orifice union of Patent Document 2, which was filed and patented by the applicant as described in the background art, but rather than forming a flow path of eccentric flow by installing only one air scrubbing air injection pipe (330) connected to the lower part of the membrane module (120), it is installed in pairs facing each other in different directions to create a mutual synergy and more easily act in the form of a vortex.

[0115] Here, if the air pressure is lower than 30 kPa, the force shaking the membrane surface is weak, and if the air pressure is higher than 50 kPa, the membrane may be damaged, so it is desirable to maintain the optimal range of air pressure between 30 and 50 kPa.

[0116] In addition, if the air scrubbing time is lower than 20 seconds, backwashing does not occur sufficiently properly during air scrubbing, and if it is higher than 60 seconds, the air scrubbing takes too long, so the separator module (120) may dry out, be damaged, and break, so it is desirable to maintain the optimal range of the air scrubbing time between 20 and 60 seconds.

[0117] At this time, the air scrubbing air pipe (300) is installed at the connection point of the lower part of the air scrubbing air injection pipe (330) and each membrane module (120) as shown in FIG. 4, and includes a vortex union (340) connected to act as an orifice, which forms a constant air pressure of the cleaning air (Air Scrubbing) injected into each membrane module (120) and then distributes and injects it into the membrane housing in a vortex form.

[0118] As illustrated in FIGS. 1, 8, and 11 of the present invention, the backwash drain pipe (240) discharges turbidity on the surface of the backwashed membrane after air scrubbing is performed on the shell side inside the membrane housing. A particularly important part of the membrane separation method is that when backwashing is performed after air scrubbing and the membrane is composed of multiple membrane modules (120), the backwashing drainage of high turbidity must be completely removed within a short period of time. However, when raw water filtration begins before it can be completely drained, the raw water and residual backwashing drainage enter the membrane housing together and are filtered again, resulting in a vicious cycle. This causes the filtration duration to be shortened and accelerates membrane fouling.

[0119] Accordingly, in one embodiment of the present invention, a backwash drainage pit (250) with a size of at least four times the inner diameter of the backwash drainage pipe (240) is installed at the downstream end of the valve of the backwash drainage pipe (240) so that backwash drainage containing high turbidity turbidity on the surface of the backwashed membrane can be quickly discharged, and then, as shown in the schematic drawing illustrating the improved air scrubbing process according to one embodiment of the present invention in FIG. 11 to remove high turbidity remaining in the backwash drainage pipe (240), the raw water pump is operated for 1 to 2 seconds while the valve of the backwash drainage pipe (240) is open by a sequence to remove the backwash drainage containing high turbidity turbidity on the surface of the backwashed membrane, and then raw water filtration can be controlled to start.

[0120]

[0121] Water purification method using membrane filtration with backwash air to increase recovery rate

[0122] In the present invention, a water purification method using a membrane filtration method that applies pulsating backwash air to increase the recovery rate is a water purification method using a membrane filtration water purification device described above,

[0123] A filtration process in which raw water is introduced from a raw water tank into a membrane module in a membrane filtration unit by a raw water pump, filtered through a membrane, and then the produced water is discharged;

[0124] When the filtration of the raw water is completed in the above filtration process, the valve of the production water discharge pipe is closed. Simultaneously, backwash air is injected into the lumen side, which is inside the hollow fiber membrane of the membrane module, through the backwash air piping, and the valve of the backwash effluent discharge pipe is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure exerted by the lumen side into which the backwash air has been injected. This is done to remove turbidity attached to the pores on the membrane surface, or to enable removal, while allowing a portion of the production water remaining in the lumen to be discharged to the shell side. As pressure is applied to the raw water on the shell side in the form of compression by the backwash air, the pressure inside the membrane housing is transmitted to the water, with the upper part at 80 to 150 kPa and the lower part at 100 to 170 kPa due to hydrostatic head pressure, after which the backwash effluent An air backwash process that operates by momentarily opening the valve of the discharge pipe to discharge the compressed backwash discharge water from the membrane module and causing a surging phenomenon in which the membrane inside the membrane housing shakes as it drops to natural pressure, and then additionally injects backwash air into the lumen to push the remaining production water inside the lumen and discharge it to the shell side; After the above air backwashing process, an air scrubbing process is operated to effectively remove turbidity from the surface of a membrane by injecting air scrubbing air in a vortex form into the shell side inside the membrane housing through a vortex union branched from an air supply pipe and connected to the pair of air scrubbing air injection pipes for an air scrubbing time of 20 to 60 seconds at an air pressure of 30 to 50 kPa, thereby shaking the membrane surface to vibrate it.The basic configuration includes a discharge process in which turbidity on the surface of the membrane is discharged through a backwash drain pipe after air scrubbing is performed on the cell (shell) side inside the membrane housing.

[0125] Hereinafter, the membrane filtration water treatment method of the present invention will be explained with reference to FIGS. 8 to 11.

[0126] FIGS. 8 and 9 are schematic diagrams illustrating a backwashing process and an air scrubbing process according to an embodiment of the present invention, FIG. 10 is a schematic diagram illustrating the change in air distribution of a membrane module when a vortex-type orifice union is installed and when it is not installed in the air scrubbing process according to an embodiment of the present invention, and FIG. 11 is a schematic diagram illustrating an improved air scrubbing process according to an embodiment of the present invention.

[0127] As illustrated in FIGS. 8 to 11,

[0128] (1) Filtration process

[0129] In the filtration process, with only the valve (①) of the fluid inlet pipe (210) and the valve (⑤) of the production water discharge pipe (220) open, raw water is introduced from a raw water tank (not shown) through the fluid inlet pipe (210) by a raw water pump into a separation membrane module (120) in the membrane filtration unit (110), and after being filtered through the separation membrane, the production water is discharged.

[0130] (2) Air backwashing process

[0131] In the air backwashing process, after the filtration of raw water in the filtration process is completed, the valve (⑤) of the production water discharge pipe (220) is closed, and while only the valve (④) of the backwash air injection pipe (320) is left open in the previous step, backwash air is injected into the lumen side, which is inside the hollow fiber membrane of the membrane module (120), through the backwash air injection pipe (320), and at the same time, the valve (③) of the backwash discharge water discharge pipe (230) is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure pushed by the lumen side into which the backwash air has been injected, so as to remove or enable the removal of turbidity attached to the pores, etc. on the surface of the membrane, and to partially discharge the production water remaining in the lumen to the shell side, pressure is applied to the raw water on the shell side in the form of compression by the backwash air. When applied, the pressure inside the membrane housing is 80 to 150 kPa in the upper part and 100 to 170 kPa in the lower part due to hydrostatic pressure, and then the valve (③) of the backwash discharge water discharge pipe (230) is opened instantaneously so that the compressed backwash discharge water of the membrane module (120) is discharged and drops to natural pressure, causing a surging phenomenon in which the membrane inside the membrane housing shakes.

[0132] In the air backwash of the present invention, turbidity attached to the pores, etc., on the surface of the membrane can be effectively removed by the pulsating phenomenon in which the membrane is shaken, or the production water remaining in the lumen of the membrane module (120) is partially discharged by being pushed by the backwash air, so that at least the turbidity attached to the pores, etc., on the surface of the membrane can be disturbed and swollen in water so that it can be removed.

[0133] That is, as some of the production water inside the lumen is discharged and flows into the shell side, and the water compression phenomenon occurs while the valve (③) of the backwash discharge pipe (230) is closed along with the raw water on the shell side, if the valve (③) of the backwash discharge pipe (230) is opened at a moment, the membrane shakes like a pulsating phenomenon.

[0134] After that, additional backwash air is injected into the Lumen side to push the remaining production water inside the Lumen and discharge it to the Shell side.

[0135] In the present invention, the time required for the backwashing process is approximately 22 to 25 seconds, and the holding time during which the pressure on the shell side inside the membrane housing becomes equal to the pressure pushed by the lumen side into which backwash air is injected is typically about 5 seconds, and the remaining time may be the time required to push the remaining production water inside the lumen side to the shell side by additionally injecting backwash air after a surging phenomenon occurs in which the membrane inside the membrane housing is shaken.

[0136] In addition, since the bubble point at which air does not come out from the lumen to the shell side even when backwash air is injected into the lumen inside the hollow fiber membrane of the ultrafiltration (UF) membrane or microfiltration (MF) membrane used in the present invention is designed to be around 200 kPa, the backwash air used at a pressure of 80 to 150 kPa during the backwashing process in the present invention remains in the lumen even after the backwashing process is completed.

[0137] Here, in the present invention, using backwash air at a pressure of 80 to 150 kPa is set to 150 kPa, which is an appropriate pressure sufficiently lower than the Bubble Point of 200 kPa, where the minimum pressure at which pulsation may occur during air backwashing is 80 kPa and air does not come out from the Lumen to the Shell side even when backwash air is injected into the Lumen, and is the optimal range for pulsating air backwashing.

[0138] Here, an exhaust valve (222) is installed in the production water discharge pipe (220), so that backwash air remains in the lumen and when the filtration process starts again, it passes through the production water discharge pipe (220) together with the production water, and the backwash air remaining in the lumen of the membrane module (120) is discharged through the exhaust valve (222).

[0139] (3) Air scrubbing process

[0140] The air scrubbing process is carried out by closing the valve (④) of the backwash air injection pipe (320) that was opened in the air backwash process, and opening the valve (③) of the backwash discharge water discharge pipe (230) and the valve (②) of the air scrubbing air injection pipe (330). It can be operated to effectively remove turbidity from the surface of the membrane by introducing air scrubbing air in a vortex form at an air pressure of 30 to 50 kPa for a backwashing time of 20 to 60 seconds through a pair of air scrubbing air injection pipes (330) connected facing each other at the bottom of the membrane module (120) and a vortex union (340) branched from the air supply pipe (310) and connected to the pair of air scrubbing air injection pipes (330).

[0141] In one embodiment of the present invention, as shown in FIG. 7, a pair of air scrubbing air injection pipes (330) are connected facing each other at the bottom of a membrane module (120) to inject air scrubbing into the shell side inside the membrane housing, and by injecting air scrubbing through a vortex union (340) that branches off from an air supply pipe and is connected to the pair of air scrubbing air injection pipes (330), as shown in FIG. 5 and FIG. 6, a vortex-shaped flow path of the vortex union (340) is formed, and mutual synergy is created so that the air scrubbing can be injected more effectively in a vortex shape.

[0142] That is, the “Vortex Union” is a device for forming a vortex inside the membrane housing during air scrubbing, and is an improved version of the orifice union of Patent Document 2, which was filed and patented by the applicant as described in the background art. However, rather than forming a flow path of eccentric flow by installing only one air scrubbing air injection pipe (330) connected to the lower part of the membrane module (120), a pair of air scrubbing air injection pipes (330) are installed facing each other from different directions and connected to the vortex union (340) to create a mutual synergy and more easily act in the form of a vortex.

[0143] The above air scrubbing air injection pipe (330) is mounted at the bottom of each membrane module (120) by a connection on the shell side inside the membrane housing, and includes a vortex union (340) that allows the cleaning air (Air Scrubbing) to be distributed and injected into the membrane housing in a vortex form after a constant air pressure is formed inside the pipe for each membrane module (120) during air scrubbing, and a through hole (342) through which the cleaning air (Air Scrubbing) can pass is formed in the orifice (341) of the vortex union (340).

[0144] However, since the diameter of the membrane housing is typically quite wide at about 21.6 cm, a drift phenomenon occurs in which the cleaning air (Air Scrubbing) passing through the narrow through hole (342) is driven toward the side with less resistance to hydrostatic pressure. Therefore, the orifice union of Patent Document 2, which was filed and patented by the applicant as described in the background art, is improved so that the diameter of the through hole (342) on the upper surface of the orifice (341) is larger than the diameter of the through hole (342) on the lower surface, thereby forming a vortex-shaped fluid flow on the inner shell side of the membrane housing, so that the cleaning air (Air Scrubbing) is evenly delivered to the inner shell side of the membrane housing.

[0145] In one embodiment of the present invention, as shown in FIG. 6, the diameter of the through hole (342) on the lower surface of the orifice (341) is set to 8 mm and the through hole (342) on the upper surface of the orifice (341) is expanded to 15 mm so that air pressure is evenly distributed to each membrane module (120), and when the pressure becomes equal, the cleaning air (Air Scrubbing) flows into the inner shell of the membrane housing through the vortex union (340) in a vortex form, thereby effectively shaking the membrane surface to remove turbidity.

[0146] By forming a flow path in the form of a vortex on the shell side inside the membrane housing, the cleaning air (Air Scrubbing) is evenly delivered to the shell side inside the membrane housing, thereby maximizing the backwashing effect of the membrane.

[0147] (4) Discharge process

[0148] After performing air scrubbing on the cell (shell) side inside the membrane housing in the above air scrubbing process, the valve (②) of the air scrubbing air injection pipe (330) is closed, and the valve (③) of the backwash discharge pipe (230) and the valve (⑥) of the backwash drain pipe (240) are opened, and the backwash discharge containing turbidity on the surface of the removed membrane is discharged through the backwash drain pipe (240).

[0149] In addition, in the present invention, an exhaust valve (232) is installed in the backwash discharge pipe (230) that discharges backwash discharge water containing turbidity, particularly during air backwashing, so that the cleaning air (Air Scrubbing) used during air scrubbing passes through the backwash discharge pipe (230) and is discharged through the exhaust valve (232).

[0150] As illustrated in FIGS. 1, 8, and 11 of the present invention, the backwash drain pipe (240) discharges high-turbidity turbidity from the surface of the backwashed membrane after air scrubbing is performed on the shell side inside the membrane housing. A particularly important part of the membrane separation method is that when backwashing is performed after air scrubbing and the membrane is composed of multiple membrane modules (120), the backwashing drainage of high-turbidity turbidity must be completely removed within a short period of time. However, when raw water filtration begins before it can be completely removed, the raw water and residual backwashing drainage enter the membrane housing together and are filtered again, resulting in a vicious cycle. This causes the filtration duration to be shortened and accelerates membrane fouling.

[0151] In one embodiment of the present invention, a backwash drainage pit (250) with a size of at least four times the inner diameter of the backwash drainage pipe (240) is installed at the downstream end of the valve (⑥) of the backwash drainage pipe (240) in the discharge process so that turbidity on the surface of the backwashed membrane can be discharged quickly.

[0152] In addition, to remove backwash wastewater containing high turbidity remaining in the backwash drain pipe (240), the valve (③) of the backwash discharge pipe (230) and the valve (⑤) of the production water discharge pipe (220) are closed as shown in FIGS. 9 and 11, and the raw water pump is operated for 1 to 2 seconds while the valve (⑥) of the backwash drain pipe (240) is open by a sequence, so that raw water filtration can begin only after the backwash wastewater containing high turbidity is completely removed when the concentration of turbidity on the backwashed membrane surface is high and has not been completely removed by the drain pipe.

[0153] The above raw water filtration begins after closing the valve (⑥) of the backwash drain pipe (240) and then introducing raw water into the membrane module (120) through the fluid inlet pipe (210).

[0154]

[0155] Foregoing, specific parts of the present invention have been described in detail. It will be apparent to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the invention. Accordingly, the actual scope of the invention is defined by the claims of the appended claims and their equivalents.

Claims

1. In a water purification device of the membrane filtration type that backwashes a separation membrane containing contaminants in raw water with air, A membrane filtration section in which a membrane filtration unit is formed by arranging multiple membrane modules in two rows; A fluid discharge pipe comprising a fluid inlet pipe through which raw water flows into the membrane filtration unit, a production water discharge pipe through which production water that has passed through the separation membrane modules is discharged, a backwash discharge water discharge pipe through which backwash discharge water containing turbidity is discharged during air backwashing, and a backwash drain pipe through which backwash wastewater containing turbidity is discharged during air scrubbing, is installed to correspond to the membrane filtration unit of the membrane filtration section, and the fluid inlet pipe and the fluid discharge pipe are respectively positioned at the front and rear ends of the membrane filtration unit, so that the flow direction of the incoming fluid passing through the membrane filtration section has a straight flow that coincides with the longitudinal direction of the membrane filtration unit; Between the above-mentioned two-row arranged membrane modules, a backwash air piping comprising an air supply pipe installed along the longitudinal direction of the membrane filtration unit to perform backwashing after the discharge of the production water that has passed through the membrane modules is finished, and backwash air injection pipes branching from both sides of the air supply pipe and respectively connected to the upper portions of the two-row arranged membrane modules to inject backwash air into the lumen side, which is the interior of the hollow fiber membrane of the membrane module; and The air scrubbing air piping comprises: a pair of air scrubbing air injection pipes connected facing each other to the lower portions of membrane modules arranged in two rows to inject air scrubbing into the shell side inside the membrane housing after backwash air is injected through the above backwash air piping, and a vortex union branched from an air supply pipe and connected to the pair of air scrubbing air injection pipes. Simultaneously with injecting backwash air into the lumen side, which is inside the hollow fiber membrane of the membrane module, through the aforementioned backwash air piping, the valve of the backwash effluent discharge pipe is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure exerted by the lumen side into which the backwash air has been injected. This is done to remove turbidity attached to the pores on the membrane surface, or to enable removal, by allowing a portion of the production water remaining in the lumen to be discharged to the shell side. Since the backwash air applies pressure to the raw water on the shell side in the form of compression, the pressure inside the membrane housing is transmitted to the water, with the upper part at 80 to 150 kPa and the lower part at 100 to 170 kPa due to hydrostatic head pressure; subsequently, the valve of the backwash effluent discharge pipe is instantaneously opened to discharge the backwash effluent from the membrane module. After operating to cause a pulsating phenomenon in which the membrane inside the membrane housing is shaken as it drops due to natural pressure, additional backwash air is injected into the lumen side to push the remaining production water inside the lumen and discharge it to the shell side, and The above air scrubbing air injection pipe is mounted at the bottom of each membrane module by a connection on the shell side inside the membrane housing, and includes a vortex union that allows the air scrubbing air to be distributed and injected into the membrane housing in a vortex form after a constant air pressure is formed inside the pipe for each membrane module during air scrubbing, and the orifice of the vortex union has a through hole formed through it to allow the air scrubbing air to pass through, and is characterized by expanding the diameter of the through hole on the upper surface of the orifice to be larger than the diameter of the through hole on the lower surface of the orifice. This is a water purification device using a membrane filtration method that applies pulsating backwash air to increase the recovery rate.

2. In Paragraph 1, A membrane filtration type water purification device that applies pulsating backwash air to increase recovery rate, characterized in that the above-mentioned production water discharge pipe and backwash discharge water discharge pipe further include an exhaust valve for discharging air.

3. In Paragraph 1, A water purification device of the membrane filtration type applying pulsating backwash air to increase recovery rate, characterized by operating to effectively remove turbidity from the surface of a membrane by injecting backwash air through the backwash air pipe, followed by injecting air scrubbing air into the shell side inside the membrane housing through a pair of air scrubbing air injection pipes connected facing each other at the bottom of the membrane module, and injecting air scrubbing air into the shell side inside the membrane housing in a vortex form at an air pressure of 30 to 50 kPa for an air scrubbing time of 20 to 60 seconds, thereby shaking the membrane surface.

4. In Paragraph 1, A water purification device of a membrane filtration type that applies pulsating backwash air to increase recovery rate, characterized in that a vortex union capable of injecting air scrubbing air at a constant air pressure into each membrane module composed of multiple units in the air scrubbing air injection pipe has an air passage at the lower surface of the orifice with a diameter of 8 mm and an air passage at the upper surface of the orifice with a diameter of 15 mm, thereby creating an air passage inside the vortex union to vortex the air flow and increase the backwashing efficiency of the membrane to extend the filtration duration.

5. In Paragraph 1, The above-mentioned backwash drain pipe discharges turbidity from the surface of the backwashed membrane after air scrubbing is performed on the shell side inside the membrane housing, and is characterized by installing a backwash drain pit at the downstream end of the backwash drain pipe that is at least four times the inner diameter of the backwash drain pipe to allow the turbidity on the surface of the backwashed membrane to be discharged quickly, and then, in order to prevent high-turbidity turbidity from remaining inside the backwash drain pipe, operating a raw water pump for 1 to 2 seconds while the valve of the backwash drain pipe is open by a sequence to remove the turbidity from the surface of the backwashed membrane, after which raw water filtration begins. This describes a water purification device using a membrane filtration method that applies pulsating backwash air to increase the recovery rate.

6. A water purification method using a membrane filtration type water purification device that applies pulsating backwash air to increase the recovery rate of Paragraph 1, A filtration process in which raw water is introduced from a raw water tank through a fluid inlet pipe by a raw water pump into a membrane module in a membrane filtration unit, filtered through a membrane, and then discharged as produced water; When the filtration of the raw water is completed in the above filtration process, the valve of the production water discharge pipe is closed. Simultaneously, backwash air is injected into the lumen side, which is inside the hollow fiber membrane of the membrane module, through the backwash air piping, and the valve of the backwash effluent discharge pipe is closed. Backwash air is then injected into the lumen side at an air pressure of 80 to 150 kPa until the pressure on the shell side inside the membrane housing becomes equal to the pressure exerted by the lumen side into which the backwash air has been injected. This allows some of the production water remaining in the lumen to be discharged toward the shell side to remove, or enable, turbidity attached to the pores on the membrane surface. As pressure is applied to the raw water on the shell side in the form of compression by the backwash air, the pressure inside the membrane housing is transmitted to the water, with the upper part at 80 to 150 kPa and the lower part at 100 to 170 kPa due to hydrostatic head pressure, after which the backwash effluent An air backwash process that operates by momentarily opening the valve of the discharge pipe to discharge the compressed backwash discharge water from the membrane module and causing a surging phenomenon in which the membrane inside the membrane housing shakes as it drops to natural pressure, and then additionally injects backwash air into the lumen to push the remaining production water inside the lumen and discharge it to the shell side; After the above air backwashing process, an air scrubbing process is operated to effectively remove turbidity from the surface of a membrane by injecting air scrubbing air in a vortex form into the shell side inside the membrane housing through a vortex union branched from an air supply pipe and connected to the pair of air scrubbing air injection pipes for an air scrubbing time of 20 to 60 seconds at an air pressure of 30 to 50 kPa, thereby shaking the membrane surface to vibrate it. The method comprises a discharge process in which turbidity on the surface of the membrane is removed after air scrubbing is performed on the shell side inside the membrane housing, and then discharged through a backwash drain pipe. A water purification method using a membrane filtration method that applies pulsating backwash air to increase recovery rate, characterized in that a pair of air scrubbing air injection pipes are installed at the bottom of each membrane module by a connection on the shell side inside the membrane housing, and during air scrubbing, a vortex union is included such that a constant air pressure is formed inside the pipe by the vortex union for each membrane module, and then the air scrubbing air is distributed and injected into the membrane housing in a vortex form; a through hole is formed in the orifice of the vortex union through which the air scrubbing air can pass, and the diameter of the through hole on the upper surface of the orifice is expanded to be larger than the diameter of the through hole on the lower surface of the orifice to generate a vortex of air.

7. In Paragraph 6, A water purification method using a membrane filtration method that applies pulsating backwash air to increase recovery rate, characterized in that in a vortex union configured to inject air scrubbing at a constant air pressure into each of the multiple separation membrane modules connected to the above-mentioned pair of air scrubbing air injection pipes, the diameter of the lower surface of the orifice through hole is 8 mm and the diameter of the upper surface of the orifice through hole is 15 mm, which expands to change the fluid flow within the orifice by acting as a vortex, and forms a flow path inside the vortex union to create a vortex of air flow.

8. In Paragraph 7, A water purification method using a membrane filtration method applying pulsating backwash air to increase recovery rate, characterized by installing a backwash drain pit at least four times the inner diameter of the backwash drain pipe at the downstream end of the valve of the backwash drain pipe in the above discharge process so that turbidity on the surface of the backwashed membrane can be quickly discharged, and then, in order to prevent high-turbidity turbidity from remaining inside the backwash drain pipe, operating a raw water pump for 1 to 2 seconds while the valve of the backwash drain pipe is open by a sequence to remove turbidity on the surface of the backwashed membrane, and then starting raw water filtration.

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