Ultrafiltration plant and method for the automatic operation of such an ultrafiltration plant

Abstract

Ultrafiltration system for drinking water treatment in a domestic installation with - at least two filter modules (1, 2) connected in parallel and operable in filtration and backwashing modes, - Valves (11, 12, 21, 22, 31, 32, 41, 42) which are arranged on the filter modules (1, 2) and in the lines (10, 20) connecting the filter modules (1, 2), - a disinfectant addition device (40) which is connected to at least one supply line (10) of the raw water to the at least two filter modules (1, 2), - a control unit (50) to which sensors (15, 16, 25, 26) are assigned and which is assigned to the valves (11, 12, 21, 22, 31, 32, 41, 42) and via which the valves (11, 12, 21, 22, 31, 32, 41, 42) are opened and closed depending on sensor, flow rate and / or time values, and - a chlorine dioxide generation plant (60) for producing an aqueous chlorine dioxide solution, which is connected to the disinfectant addition device (40).

Description

[0001] The invention relates to an ultrafiltration system for drinking water treatment in domestic installations, in which raw water is passed through at least two parallel connected filter modules, and a method for automatically operating such an ultrafiltration system.

[0002] In municipal and industrial water treatment, ultrafiltration systems are used to separate solids, turbidity, and microorganisms. An ultrafiltration system removes solid particles, bacteria, and other germs almost completely from the water. Raw water, such as surface water, is forced under pressure through tubular filter elements arranged in filter modules. These elements typically have an inner diameter of approximately 0.5 to 2 mm. The actual filtration process takes place within the fine-pored walls of the filter elements, which have a pore size of approximately 0.01 to 0.05 µm and thus retain solids larger than approximately 0.05 µm. Germs, such as bacteria, viruses, or fungi, are significantly larger than 0.05 µm and therefore cannot pass through an ultrafiltration membrane and are thus removed from the water.During the operation of an ultrafiltration plant, the solid particles and germs contained in the raw water are retained as filter residues. This results in the accumulation of a coating of organic and inorganic solids, known as "fouling," on the wall surfaces of the filter elements. These deposits on the filter elements increase the filtration resistance and reduce the raw water flow rate, thus also reducing the efficiency of the ultrafiltration plant. Therefore, the deposits must be removed regularly to prevent clogging and subsequent blockage of the filter elements. This removal is achieved through a process called "backwashing."

[0003] Backwashing involves switching between filtration and backwashing modes. This is achieved by abruptly switching mechanically and electromagnetically operated valves located in the lines to and from the filter modules. This allows for a rapid changeover between operating modes. A disadvantage of this process is the occurrence of pressure surges, which can stress or damage the membranes of the ultrafiltration systems.

[0004] The backwashing of ultrafiltration membranes is often supported by the addition of chemicals. To aid the backwashing process, biocides and cleaning agents are used discontinuously in high concentrations, which then have to be laboriously rinsed out of the filter elements.

[0005] DE 10 2005 055 146 A1 relates to a closed-loop process for treating pool water, in which the pool water is filtration based on hydraulic and hygienic requirements and then returned to the pool. The filtration process includes membrane filtration, with a portion of the circulating water flowing through a bypass. The membrane system consists of parallel membrane filters, the filtrate from which is returned to the pool after chlorination. Sludge water generated during backwashing of the membrane system is either disposed of in the sewer system or returned to the surge tank as treated process water.

[0006] The object of the present invention is to provide a method for operating an ultrafiltration system and an ultrafiltration system as such, which enable an improvement in the drinking water quality in the domestic installation and a longer period of time for the use of the filter elements, thereby improving health care and energy efficiency in hot water preparation.

[0007] According to the invention, this problem is solved by an ultrafiltration system with the features of the main claim and a method with the features of the dependent claim. Advantageous embodiments and further developments are described in the dependent claims, the description, and the figure.

[0008] The ultrafiltration system for drinking water according to the invention, for the treatment of drinking water in a domestic installation, provides at least two filter modules connected in parallel. Valves are arranged on the filter modules, in the lines connecting the filter modules, and on a disinfectant dosing device. The valves are connected to a control unit with associated sensors, which open or close the valves depending on sensor values, flow rates, and / or time values. The disinfectant dosing device is connected to at least one supply line of the raw water to the at least two filter modules.By installing a control unit that automatically opens and closes the valves based on sensor readings, such as pressure and flow rates, and / or a time interval, fully automated chemical disinfection of the ultrafiltration system can be performed during operation. The ultrafiltration system can continue operating in parallel with the automatic backwashing of the filter modules being cleaned. It is also possible to fully automate the start-up and backwashing processes using chlorine dioxide as a chemical disinfectant. The system also includes a chlorine dioxide generation unit coupled with the disinfectant dosing system, such as a dosing pump. This allows the aqueous chlorine dioxide solution to be generated within the system without requiring the operator to handle chemicals.

[0009] The valves are preferably electrically driven and can be designed as motor-operated valves, e.g., ball valves or motorized butterfly valves. Pressure sensors for detecting the differential pressure at a filter module can be provided; likewise, a timer or timer and / or a water meter for recording the water flow rate can be assigned to the control unit in order to carry out automatic maintenance and cleaning of the respective filter modules after a defined period.

[0010] All components of the system – the filter modules, control unit, valves, chlorine dioxide generator, disinfectant dispenser, and, if applicable, pipes, sensors, or timers – can be integrated into a single module with connections to the building's water supply network, simplifying installation, commissioning, and operation. The module simply needs to be connected to the building's drinking water supply and power supply.

[0011] The inventive method for operating an ultrafiltration system for drinking water treatment in domestic installations, in which raw water is passed through at least two filter modules connected in parallel, wherein valves are arranged on the filter modules and in the lines connecting the filter modules, with a disinfectant addition device connected to a supply line, and with a control device to which sensors are assigned and which is assigned to the valves and by which the valves are opened and closed depending on sensor, flow rate and / or time values, wherein a chlorine dioxide generation system for producing an aqueous chlorine dioxide solution is connected to the disinfectant addition device connected to a raw water supply line, provides thatChlorine dioxide is added as a chemical disinfectant in a proportionally dosed manner, and a backwash cycle with chlorine dioxide addition is automatically initiated based on sensor readings, flow rate measurement, and / or a timer. This proportional dosing of the chemical disinfectant allows for precise dosing of the disinfectant to the raw water or backwash water via a dosing pump. This ensures compliance with the applicable drinking water regulations, extends the service life of the filter elements, and ensures that the drinking water meets the requirements of the respective drinking water regulations after backwashing, preventing disinfectant residues in the filter modules from impairing drinking water quality.

[0012] The backwash cycle is designed to be initiated automatically based on sensor readings, flow rate measurements, and / or a timer. Fouling increases the differential pressure between the filter inlet and outlet. If a predefined limit is exceeded, the backwash cycle can be initiated automatically. For this, the respective filter module is disconnected from filtration by closing the corresponding valves. The chemical disinfectant is then added and can optionally remain in the filter module for a specified period to kill existing germs and loosen deposits. After the predetermined residence time within the filter module, an outlet valve can be opened, and the backwash water is removed from the filter element. The backwash water flushes the deposits out of the filter module.

[0013] In addition to pressure-based initiation of the backwash cycle, it is possible to implement a timer and / or a flow-rate-based activation, so that cleaning and backwashing are performed after a defined operating period and / or a defined water flow rate, regardless of the state of the deposits in the filter module. Sensor- or time-based initiation of the backwash cycle ensures fully automatic operation of the ultrafiltration system over extended periods without manual intervention from the user. With time-based initiation of the backwash cycle, the automatic, volume-proportional addition of the disinfectant chlorine dioxide during each timed backwash prevents bacterial growth in the filter elements, even during extended periods without water withdrawal by the operator.

[0014] In one embodiment of the invention, the disinfectant is added to the backwash water at a higher concentration than during filtration operation. It is provided that only the maximum permissible amount of disinfectant for drinking water is added to the backwash water in order to avoid exceeding the limit value when the system is restarted for filtration operation.

[0015] Alternatively or additionally, it is planned that the disinfectant will be continuously added to the raw water during filtration in order to achieve an effective improvement in the quality of the drinking water.

[0016] Advantageously, chlorine dioxide is added as a disinfectant, with a maximum concentration of 0.4 mg / l added to the backwash water during the backwashing process. The chlorine dioxide is produced as an aqueous solution under controlled conditions in a chlorine dioxide generation plant using the hydrochloric acid-chlorite process and then added to the backwash water. The addition of chlorine dioxide to the backwash water kills existing germs and improves the removal and flushing of deposits from the system. This extends the intervals between backwashes and increases the service life of the respective filtration membranes. Furthermore, less backwash water is required overall due to the extended intervals and the longer service life of the ultrafiltration membranes.

[0017] During filtration, a maximum of 0.2 mg / l of disinfectant is added to the raw water, ensuring that the maximum permissible concentration for continuous chemical disinfection is not exceeded. The use of chlorine dioxide does not produce chloramines or trihalomethanes that could pollute the wastewater.

[0018] A further development of the invention provides that the changeover between filtration and backwashing operation is achieved by a successive opening and closing of valves, thus avoiding abrupt opening and closing of the respective valves. The valves are therefore opened and closed slowly, resulting in a continuous, steady pressure drop and rise within the filter module. Pressure peaks are not generated, so the fine-pored membranes of the ultrafiltration system are not subjected to high pressure differentials. This slow rise and fall in pressure significantly extends the service life of the filter modules.To achieve slow or gradual opening and closing of the valves, they are advantageously driven by a motor, particularly an electric motor, for example as motor-driven ball valves, which allow for a slow, complete opening or closing of the respective line, for example over a period of 20 to 30 seconds. This enables a smooth transition or change of operating states without pressure surges.

[0019] After being added during backwashing, the disinfectant can remain in the filter module for a specified period and is only removed from the filter module after the specified period has elapsed.

[0020] Advantageously, several filter modules are arranged in parallel to each other, so that the backwashing operation can be carried out in one filter module while the filtration operation can continue in the other filter module or in the other filter modules.

[0021] An embodiment of the invention is explained in more detail using the single figure, which shows a simplified circuit diagram of an ultrafiltration plant.

[0022] The ultrafiltration system shown in the figure comprises two filter modules 1 and 2, which are connected to each other via pipelines. A supply line 10 for raw water is provided. The filter modules 1 and 2 are connected in parallel to each other, and inlet valves 11 and 12 are arranged upstream of the filter modules 1 and 2. Bypass lines 20 are provided parallel to the filter modules 1 and 2 and are also equipped with shut-off valves designated as bypass valves 41 and 42. A connecting line with shut-off valves 31 and 32 located therein leads to a discharge line 30, through which the filtered and optionally also disinfected water is discharged.

[0023] Furthermore, outlet valves 21, 22 are arranged on the filter modules 1, 2, which drain the backwash water through rinse water lines 23, 24.

[0024] The disinfectant is produced fully automatically in a chlorine dioxide generation plant 60 and dosed proportionally to the quantity into the raw water line 10 using the disinfectant addition device 40, which can be designed as a dosing pump.

[0025] All valves 11, 12, 21, 22, 31, 32, 41, 42 are coupled to a control unit 50, which can adjust the motor-driven valves 11, 12, 21, 22, 31, 32, 41, 42. In the factory setting, all valves 11, 12, 21, 22, 31, 32, 41, 42 are closed. During the break-in period, the outlet valves 21, 22 on the filter modules 1, 2 are first opened for a specific period. Subsequently, the inlet valves 11, 12 for the filter modules 1, 2 are opened for a defined period to flood and flush the filters 1, 2. Subsequently, the outlet valves 21, 22 are closed and the shut-off valves 31, 32 for the connecting line are opened, so that the filtered water can flow out of the extraction line 30.

[0026] The position with the inlet valves 11, 12 open and the shut-off valves 31, 32 open is also the one that is adopted during extraction or in filtration operation.

[0027] To backwash filter module 1, 2 while water is still being drawn off, a shut-off valve 31, 32 is first closed. If the first filter module 1 is to be backwashed first, the left shut-off valve 31 is closed. Then the left outlet valve 21 is opened, followed by the inlet valve 11 being closed. Finally, the bypass valve 41 is opened for a specific period, allowing backwash water to be supplied to filter module 1 via the bypass line 20. The inlet valve 11 is then opened, and the shut-off valve 31 is also opened again for water withdrawal. The valve positions for valves 12, 22, 32, 42 of the second filter module 2 remain unchanged.

[0028] For the subsequent backwashing in the second filter module 2, the open shut-off valve 32 is first closed, then the outlet valve 22 is opened, the inlet valve 12 is closed, and finally the bypass valve 42 is opened for backwashing. After backwashing in the second filter module 2, the inlet valve 12 is opened, and the remaining valves 22, 32, and 42 are either closed or remain closed. For the next extraction in parallel operation, the outlet valve 22 and the bypass valve 42 are closed, and the inlet valve 12 and the shut-off valve 32 are opened.

[0029] The disinfectant dosing unit 40 doses a pre-defined, volume-proportional amount of chlorine dioxide into the backwash water or the raw water. If a higher dose of disinfectant is required, a line can also be run from the disinfectant dosing unit 40 to the bypass lines 20 downstream of the bypass valves 41 and 42, allowing for a separate dose of disinfectant for backwashing.

[0030] Valves 11, 12, 21, 22, 31, 32, 41, 42 are opened or closed slowly, for example within a period of approximately 30 seconds, to avoid pressure surges.

Claims

[1] Ultrafiltration system for drinking water treatment in a domestic installation with - at least two filter modules (1, 2) connected in parallel and operable in filtration and backwashing modes, - Valves (11, 12, 21, 22, 31, 32, 41, 42) which are arranged on the filter modules (1, 2) and in the lines (10, 20) connecting the filter modules (1, 2), - a disinfectant addition device (40) which is connected to at least one supply line (10) of the raw water to the at least two filter modules (1, 2), - a control unit (50) to which sensors (15, 16, 25, 26) are assigned and which is assigned to the valves (11, 12, 21, 22, 31, 32, 41, 42) and via which the valves (11, 12, 21, 22, 31, 32, 41, 42) are opened and closed depending on sensor, flow rate and / or time values, and - a chlorine dioxide generation plant (60) for producing an aqueous chlorine dioxide solution, which is connected to the disinfectant addition device (40). [2] Ultrafiltration system according to claim 1, characterized by , that the valves (11, 12, 21, 22, 31, 32, 41, 42) are designed as motor-driven valves. [3] Ultrafiltration system according to claim 1 or 2, characterized by , that pressure sensors (15, 16, 25, 26) are provided for detecting the differential pressure on a filter module (1, 2). [4] Ultrafiltration plant according to any one of the preceding claims, characterized by , that the filter modules (1, 2), the control unit (50), the valves (11, 12, 21, 22, 31, 32, 41, 42), the chlorine dioxide generation unit (60) and the disinfectant addition unit (40) are combined as one module with connections to a house supply network. [5] Method for the automatic operation of an ultrafiltration plant for drinking water treatment in a domestic installation, in which raw water is passed through at least two filter modules (1, 2) connected in parallel, wherein valves (11, 12, 21, 22, 31, 32, 41, 42) are arranged on the filter modules (1, 2) and in the lines (20) connecting the filter modules (1, 2) as well as a disinfectant addition device (40) and a control device (50) is assigned to the valves (11, 12, 21, 22, 31, 32, 41, 42) by means of which the valves (11, 12, 21, 22, 31, 32, 41, 42) are opened and closed depending on sensor, flow rate and / or time values, wherein a chlorine dioxide generation plant (60) is used to generate a aqueous chlorine dioxide solution with the disinfectant addition device (40), which is connected to a supply line (10) of the raw water to the at least two filter modules (1, 2), characterized by, that chlorine dioxide is added as a disinfectant in a quantity-proportional dose and that a backwashing operation with chlorine dioxide addition is automatically initiated based on sensor values, a flow rate measurement and / or a time switch. [6] Method according to claim 5, characterized by , that during backwashing, a higher amount of chlorine dioxide is added to the backwash water compared to filtration. [7] Method according to claim 5 or 6, characterized by that the disinfectant is continuously added to the raw water during the filtration process. [8] Method according to any one of claims 5 to 7, characterized by , that a maximum of 0.4 mg / l of disinfectant is added to the backwash water during backwashing operation. [9] Method according to any one of claims 5 to 8, characterized by , that a maximum of 0.2 mg / l of disinfectant is added to the raw water during filtration. [10] Method according to any one of claims 5 to 9, characterized by , that the changeover between filtration operation and backwash operation is carried out by successively opening and closing valves (11, 12, 21, 22, 31, 32, 41, 42). [11] Method according to claim 10, characterized by , that the valves (11, 12, 21, 22, 31, 32, 41, 42) are opened and closed by motor, in particular by electric motor. [12] Method according to any one of claims 5 to 11, characterized by , that the disinfectant remains in the filter module (1, 2) for a specified period after being added during backwashing and is then removed from the filter module (1, 2). [13] Method according to any one of claims 5 to 12, characterized by that the backwashing operation is carried out in parallel with the filtration operation.

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