Ultrapure water preparation system

Abstract

The utility model discloses a kind of ultrapure water preparation systems, it includes total organic carbon on-line analyzer, controller, multi-medium filter, activated carbon filter, filtered water tank, positive bed, decarbonization tower, negative bed, reverse osmosis device, first ultraviolet lamp, primary mixed bed, second ultraviolet lamp, polishing mixed bed and terminal ultrafilter, total organic carbon on-line analyzer is connected with the water outlet of terminal ultrafilter, to detect the total organic carbon in the water production of terminal ultrafilter, controller is connected with total organic carbon on-line analyzer and backwash pump, total organic carbon on-line analyzer can detect the total organic carbon content in the water production of terminal ultrafilter, and backwash activated carbon filter by controller control backwash pump with first backwash period or second backwash period, to make activated carbon filter in bacterial breeding consume small molecule organic matter in water.The ultrapure water preparation system of the utility model embodiment is high in work efficiency, and good in economy.

Description

Technical Field

[0001] This utility model belongs to the field of water treatment technology, and specifically relates to an ultrapure water preparation system. Background Technology

[0002] Ultrapure water preparation systems typically include a multi-media filter (MMF) for filtering suspended impurities such as leaves from the water, an activated carbon filter (ACF) for adsorbing residual chlorine, a UV lamp, and a mixed bed (MBX). The UV lamp breaks down the molecular chains of large organic molecules using UV light, while the mixed bed adsorbs and filters the broken organic matter to remove TOC (total organic carbon) from the water. However, existing ultrapure water preparation systems still suffer from TOC exceeding the standard. Utility Model Content

[0003] This utility model is based on the inventor's discovery and understanding of the following facts and problems:

[0004] In related technologies, ultrapure water preparation using UV lamps and mixed beds for TOC removal primarily targets large-molecule organic TOCs, but its effectiveness in removing small-molecule organic TOCs (such as urea) is poor. Related technologies have proposed using advanced oxidation processes (AOPs) for TOC removal; however, AOPs require a very complex system and are primarily used for COD removal from wastewater, with their effectiveness and efficiency in removing small-molecule organic TOCs remaining unverified. Another related technology proposes using biological activated carbon filters for TOC removal, but this method not only requires the addition of a biological activated carbon filter, leading to system complexity and high cost, but the effectiveness and efficiency of biological activated carbon filters in removing small-molecule organic TOCs have also not been practically verified.

[0005] The inventors of this utility model have discovered that excessive levels of small molecule organic matter (TOC) in water are a seasonal and occasional event. For example, due to seasonal and occasional events, the excessive levels of small molecule organic matter (TOC) in water sources make the investment in the system less economical and limit its application.

[0006] The inventors of this invention have realized that in related technologies, activated carbon filters in ultrapure water preparation systems typically require backwashing every 24 hours, meaning the backwashing cycle is usually no longer than 24 hours. This is to remove impurities and oxidizing substances adsorbed on the activated carbon surface to restore its activity and protect downstream process equipment (such as RO). If the backwashing cycle of the activated carbon filter is too long, bacteria will grow on the surface of the activated carbon particles, affecting the performance of the activated carbon filter.

[0007] Based on the above understanding and discovery, the inventors of this utility model propose an ultrapure water preparation technology that can avoid excessive levels of total organic carbon (TOC) in water. This technology effectively removes TOC from water simply by adjusting the operation of the activated carbon filter in the existing ultrapure water preparation system, thus solving the problem of excessive TOC levels, especially those caused by seasonal or sporadic events. It requires no major modifications to existing processes and systems, and no additional specialized equipment for TOC removal, thereby reducing costs and improving economic efficiency.

[0008] Specifically, the inventors of this invention recognized that bacteria require organic matter as nutrients to survive. By cultivating bacteria on the surface of an activated carbon filter, small-molecule organic matter (TOC) in the water (such as urea) can be consumed. Thus, contrary to the concept in related technologies, this invention intentionally promotes and cultivates bacteria on the surface of activated carbon particles by extending the backwashing cycle of the activated carbon filter, thereby consuming and removing small-molecule organic matter (TOC) in the water, preventing excessive levels of small-molecule organic matter in the water. It is simple to operate, low in cost, and economical, and is particularly suitable for situations where seasonal or occasional events cause excessive levels of small-molecule organic matter (TOC) in the water, further improving its economic efficiency.

[0009] The ultrapure water preparation system of this utility model embodiment includes an online total organic carbon analyzer, a controller, and a multi-media filter, an activated carbon filter, a filter water tank, a cation exchange bed, a decarbonization tower, an anion exchange bed, a reverse osmosis unit, a first ultraviolet lamp, a primary mixed bed, a second ultraviolet lamp, a polishing mixed bed, and a terminal ultrafiltration unit connected in sequence. The online total organic carbon analyzer is connected to the outlet of the terminal ultrafiltration unit to detect the total organic carbon in the product water of the terminal ultrafiltration unit. The activated carbon filter has an inlet connected to the multi-media filter, an outlet connected to the filter water tank, a backwash inlet, and a backwash outlet. The backwash inlet is connected to the filter water tank via a backwash pump. The controller is connected to the online total organic carbon analyzer and the backwash pump.

[0010] When the total organic carbon online analyzer detects that the total organic carbon content in the permeate of the terminal ultrafiltration unit is less than a preset threshold, the controller controls the backwash pump to backwash the activated carbon filter for a first backwash cycle.

[0011] When the total organic carbon online analyzer detects that the total organic carbon content in the permeate of the terminal ultrafiltration unit is greater than or equal to the preset threshold, the controller controls the backwash pump to backwash the activated carbon filter in a second backwash cycle, thereby extending the operating time of the activated carbon filter so that bacteria that consume total organic carbon can grow in the activated carbon filter, reducing the total organic carbon content in the permeate of the terminal ultrafiltration unit to less than the preset threshold. The second backwash cycle is longer than the first backwash cycle.

[0012] The ultrapure water preparation system of this utility model uses an online total organic carbon analyzer to monitor the total organic carbon content in the product water of the terminal ultrafiltration unit in real time. The controller controls the backwashing cycle of the activated carbon filter in the filter tank in real time based on the monitoring results, ensuring the growth of bacteria that consume small molecule organic matter in the activated carbon filter. This allows the bacteria to consume the small molecule organic matter (TOC) in the water, preventing the small molecule organic matter in the water from exceeding the standard. The system is simple to operate, highly efficient, and does not require additional special equipment to remove small molecule organic matter (TOC), thus reducing costs and improving economic efficiency.

[0013] In some embodiments, the first backwashing cycle is no more than 24 hours.

[0014] In some embodiments, the second backwash cycle is proportional to the total organic carbon content in the permeate of the terminal ultrafiltration unit as detected by the online total organic carbon analyzer.

[0015] In some embodiments, after the controller controls the backwash pump to backwash the activated carbon filter for the second backwash cycle, and the total organic carbon online analyzer detects that the total organic carbon content is less than the preset threshold, the controller controls the backwash pump to continue backwashing the activated carbon filter for at least one second backwash cycle, and then backwashes the activated carbon filter for the first backwash cycle.

[0016] In some embodiments, the inlet and backwash outlet of the activated carbon filter are the same, the inlet is connected to an inlet branch and a backwash drain branch, the inlet branch is connected to the multi-media filter and is equipped with an inlet valve, and the backwash drain branch is equipped with a backwash drain valve.

[0017] The activated carbon filter has the same outlet and backwash inlet. The outlet is connected to an outlet branch and a backwash inlet branch. The outlet branch is connected to the inlet of the filter tank and is equipped with an outlet valve. The backwash inlet branch is connected to the filter tank and is equipped with a backwash inlet valve and a backwash pump.

[0018] In some embodiments, the outlet of the activated carbon filter is further connected to a forward wash drainage branch, which is equipped with a forward wash drainage valve.

[0019] After the controller controls the backwash pump to backwash the activated carbon filter, it immediately performs a forward wash on the activated carbon filter using water discharged from the multi-media filter and discharges the forward wash water through the forward wash drain valve.

[0020] In some embodiments, the activated carbon filter is further provided with an exhaust valve.

[0021] In some embodiments, the total organic carbon includes urea.

[0022] In some embodiments, the raw water supplied to the multi-media filter is municipal tap water or water from a lake, river or reservoir. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an ultrapure water preparation system according to an embodiment of the present invention.

[0024] Figure reference numerals: 1. Raw water tank; 2. Raw water pump; 3. Multi-media filter; 4. Activated carbon filter; 401. Inlet; 402. Backwash outlet; 403. Outlet; 404. Backwash inlet; 5. Filter water tank; 6. Filter water pump; 7. Backwash pump; 8. Cation bed; 9. Decarbonization tower; 10. Intermediate water tank; 11. Intermediate water pump; 12. Anion bed; 13. Deionized water tank; 14. Deionized water pump; 15. Reverse osmosis unit; 16. Reverse osmosis water tank; 17. Reverse osmosis water pump; 18. First ultraviolet lamp; 19. Primary mixing... 20. Membrane bed; 21. First membrane degassing unit; 22. Ultrapure water tank; 23. Ultrapure water pump; 24. Second ultraviolet lamp; 25. Polishing mixed bed; 26. Second membrane degassing unit; 27. Terminal ultrafiltration unit; 28. Point of use; 29. ​​Total organic carbon online analyzer; 20. Inlet water branch; 291. Inlet water valve; 30. Backwash drain branch; 301. Backwash drain valve; 31. Outlet water branch; 311. Outlet water valve; 32. Backwash inlet water branch; 321. Backwash inlet water valve; 33. Forward wash drain branch; 331. Forward wash drain valve; 34. Exhaust valve. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] like Figure 1As shown, the ultrapure water preparation system of this utility model embodiment includes an online total organic carbon analyzer 28, a controller, and a multi-media filter 3, an activated carbon filter 4, a filter water tank 5, a cation exchange bed 8, a decarbonization tower 9, an anion exchange bed 12, a reverse osmosis device 15, a first ultraviolet lamp 18, a primary mixed bed 19, a second ultraviolet lamp 23, a polishing mixed bed 24, and a terminal ultrafiltration unit 26 connected in sequence. The online total organic carbon analyzer 28 is connected to the outlet of the terminal ultrafiltration unit 26 to detect the total organic carbon in the product water of the terminal ultrafiltration unit 26. The activated carbon filter 4 has an inlet 401 connected to the multi-media filter 3, an outlet 403 connected to the filter water tank 5, a backwash inlet 404, and a backwash outlet 403. The backwash inlet 404 is connected to the filter water tank 5 through a backwash pump 7. The controller is connected to the online total organic carbon analyzer 28 and the backwash pump 7.

[0027] When the total organic carbon online analyzer 28 detects that the total organic carbon content in the permeate of the terminal ultrafilter 26 is less than a preset threshold, the controller controls the backwash pump 7 to backwash the activated carbon filter 4 in the first backwash cycle.

[0028] When the total organic carbon online analyzer 28 detects that the total organic carbon content in the permeate of the terminal ultrafilter 26 is greater than or equal to a preset threshold, the controller controls the backwash pump 7 to backwash the activated carbon filter 4 with a second backwash cycle that is longer than the first backwash cycle, thereby extending the operating time of the activated carbon filter so that bacteria that consume total organic carbon can grow in the activated carbon filter 4, reducing the total organic carbon content in the permeate of the terminal ultrafilter 26 to less than the preset threshold. The second backwash cycle is longer than the first backwash cycle.

[0029] The ultrapure water preparation system of this utility model embodiment features an online total organic carbon analyzer 28 that can monitor the total organic carbon content in the product water of the terminal ultrafiltration unit 26 in real time. The controller controls the backwashing cycle of the activated carbon filter 4 in the filter tank 5 in real time based on the monitoring results, ensuring the growth of bacteria that consume small molecule organic matter in the activated carbon filter 4. This allows the bacteria to consume the small molecule organic matter (TOC) in the water, preventing the small molecule organic matter in the water from exceeding the standard. The system is simple to operate, highly efficient, and does not require additional special equipment to remove small molecule organic matter (TOC), thus reducing costs and improving economic efficiency.

[0030] Specifically, the ultrapure water preparation system of this utility model embodiment also includes a raw water tank 1, a raw water pump 2, a filter water pump 6, an intermediate water tower, an intermediate water pump 11, a deionized water tank 13, a deionized water pump 14, a reverse osmosis water tank 16, a reverse osmosis water pump 17, a first membrane degassing device 20, an ultrapure water tank 21, an ultrapure water pump 22, and a second membrane degassing device 25.

[0031] Raw water tank 1, raw water pump 2, multi-media filter 3, activated carbon filter 4, filtered water tank 5, filtered water pump 6, cation exchange bed 8, decarbonization tower 9, intermediate water tank 10, intermediate water pump 11, anion exchange bed 12, deionized water tank 13, deionized water pump 14, reverse osmosis unit 15, reverse osmosis water tank 16, reverse osmosis water pump 17, first ultraviolet lamp 18, primary mixed bed 19, first membrane degassing unit 20, ultrapure water tank 21, ultrapure water pump 22, second ultraviolet lamp 23, polishing mixed bed 24, second membrane degassing unit 25, and terminal ultrafiltration unit 26 are connected in sequence. Terminal ultrafiltration unit 26 is connected to water point 27 to deliver pure water to water point 27.

[0032] Raw water in raw water tank 1 is pumped by raw water pump 2 into multi-media filter 3 to filter suspended impurities. Then, it enters activated carbon filter 4 to remove chlorine. Backwash pump 7 pumps water from filter tank 5 into activated carbon filter 4 to backwash it, removing impurities adsorbed on the activated carbon surface and restoring its performance. Water from activated carbon filter 4 enters filter tank 5, which is then pumped by filter pump 6 into cation exchange bed 8 to remove cations such as calcium, magnesium, and sodium ions. Water from cation exchange bed 8 enters decarbonization tower 9 to remove carbon dioxide. Finally, the water passes through intermediate water tank 10 and is pumped by intermediate pump 11 into anion exchange bed 12 to remove anions such as sulfate, nitrate, bicarbonate, and chloride ions.

[0033] The water in the anion bed 12 then enters the deion water tank 13 to further remove cations and anions from the water. After that, the water passes through the reverse osmosis device 15, the reverse osmosis water tank 16, the first ultraviolet lamp 18, the primary mixed bed 19, the first membrane degassing device 20, the ultrapure water tank 21, the second ultraviolet lamp 23, the polishing mixed bed 24, and the second membrane degassing device 25 in sequence before entering the terminal ultrafiltration unit 26. The first ultraviolet lamp 18 breaks down the molecular chains of large organic molecules in the water, forming smaller organic molecules. Then, the primary mixed bed 19 removes cations and anions from the water, and adsorbs and filters the broken small organic molecules and bacterial remains. The first membrane degassing device 20 removes dissolved oxygen from the water. The second ultraviolet lamp 23 further breaks down the molecular chains of large organic molecules. The polishing mixed bed 24 further removes cations and anions, and adsorbs and filters the broken bacterial remains and small organic molecules. The second membrane degassing device 25 further removes dissolved oxygen from the water. Terminal ultrafiltration removes microparticles from the water, finally forming ultrapure water.

[0034] Specifically, the system's controller uses SCADA software for automatic operation. Key steps are manually verified to ensure safe and stable operation.

[0035] In some embodiments, the first backwash cycle is no more than 24 hours.

[0036] Specifically, when the total organic carbon online analyzer 28 detects that the total organic carbon content in the product water of the terminal ultrafiltration unit 26 is less than the preset threshold, it indicates that the amount of bacteria consuming small molecule organic matter in the activated carbon filter 4 is sufficient. Therefore, the first backwash cycle should not exceed 24 hours. This not only ensures that the amount of bacteria in the activated carbon filter 4 is moderate enough to consume the small molecule organic matter in the water and avoids the small molecule organic matter in the water from exceeding the standard, but also avoids the large amount of bacteria affecting the performance of the activated carbon filter 4, so that the oxidizing substances can be restored to activity in time and ensure the normal operation of subsequent process equipment.

[0037] In some embodiments, the second backwash cycle is proportional to the total organic carbon content in the permeate of the terminal ultrafilter 26 as detected by the online total organic carbon analyzer 28.

[0038] Specifically, when the total organic carbon online analyzer 28 detects that the total organic carbon content in the product water of the terminal ultrafiltration unit 26 is greater than or equal to the preset threshold, it indicates that the number of bacteria consuming small molecule organic matter in the activated carbon filter 4 is relatively small, resulting in a relatively high content of small molecule organic matter in the water. Therefore, it is necessary to extend the backwashing time in the activated carbon filter to increase the number of bacteria in the activated carbon filter, so as to consume more small molecule organic matter in the water, improve efficiency, and avoid exceeding the standard for small molecule organic matter in the water.

[0039] When the content of small molecule organic matter in the ultrapure water preparation circuit is low, the second backwash cycle is shorter, so that the amount of bacteria growing in the activated carbon filter 4 is reduced and sufficient to consume the small molecule organic matter TOC in the water. The operation is simple and economical, and it can also avoid the impact of a large amount of bacteria on the performance of the activated carbon filter 4.

[0040] In some embodiments, after the controller controls the backwash pump 7 to backwash the activated carbon filter 4 for a second backwash cycle, and the total organic carbon online analyzer 28 detects that the total organic carbon content is less than a preset threshold, the controller controls the backwash pump 7 to continue to backwash the activated carbon filter 4 for at least one second backwash cycle, and then backwashes the activated carbon filter 4 for a first backwash cycle.

[0041] Specifically, through the above operations, it can be ensured that the amount of bacteria growing inside the activated carbon filter 4 is sufficient to consume (remove) the amount of small molecule organic matter (TOC) in the water, ensuring that the bacteria can efficiently consume the small molecule organic matter (TOC) in the water, thereby improving the efficiency of pure water preparation. The activated carbon filter 4 is backwashed in the second backwash cycle, followed by the first backwash cycle, to remove impurities adsorbed on the surface of the activated carbon, restore the activity of oxidizing substances, and further ensure the efficiency of pure water preparation.

[0042] In some embodiments, the inlet 401 and the backwash outlet 403 of the activated carbon filter 4 are the same. The inlet 401 is connected to an inlet branch 29 and a backwash drain branch 30. The inlet branch 29 is connected to the multi-media filter 3 and is provided with an inlet valve 291. The backwash drain branch 30 is provided with a backwash drain valve 301.

[0043] The outlet 403 and backwash inlet 404 of the activated carbon filter 4 are the same. The outlet 403 is connected to the outlet branch 31 and the backwash inlet branch 32. The outlet branch 31 is connected to the inlet of the filter water tank 5 and is equipped with an outlet valve 311. The backwash inlet branch 32 is connected to the filter water tank 5 and is equipped with a backwash inlet valve 321 and a backwash pump 7.

[0044] Specifically, during normal ultrapure water treatment and purification, the controller controls the inlet valve 291 and the outlet valve 311 to open. The water in the multi-media filter 3 enters the activated carbon filter 4 through the inlet branch 29, and the water in the activated carbon filter 4 enters the filter water tank 5 through the outlet branch 31.

[0045] Specifically, when the controller controls the backwash pump 7 to backwash the activated carbon filter 4, the backwash inlet valve 321 and the backwash outlet valve 301 are opened. The backwash pump 7 pumps the water in the filter water tank 5 into the activated carbon filter 4 through the backwash inlet valve 321. After backwashing, the water is discharged through the backwash outlet branch 30.

[0046] In some embodiments, the outlet 403 of the activated carbon filter 4 is also connected to a forward wash drainage branch 33, which is equipped with a forward wash drainage valve 331. After the controller controls the backwash pump 7 to backwash the activated carbon filter 4, it opens the forward wash drainage valve 331, and immediately forward washes the activated carbon filter 4 with water discharged from the multi-media filter 3, and discharges the forward wash water through the forward wash drainage valve 331.

[0047] In some embodiments, the activated carbon filter 4 is further provided with an exhaust valve 34 to discharge the gas inside the activated carbon filter 4, ensuring the normal operation of the activated carbon filter 4.

[0048] In some embodiments, total organic carbon includes urea.

[0049] In some embodiments, the raw water supplied to the multi-media filter 3 is municipal tap water or water from a lake, river or reservoir.

[0050] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0052] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0053] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0054] In this utility model, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An ultrapure water preparation system, characterized in that, The system includes an online total organic carbon analyzer (28), a controller, and a multi-media filter (3), an activated carbon filter (4), a filter tank (5), a cation exchange bed (8), a decarbonization tower (9), an anion exchange bed (12), a reverse osmosis unit (15), a first ultraviolet lamp (18), a primary mixed bed (19), a second ultraviolet lamp (23), a polishing mixed bed (24), and a terminal ultrafiltration unit (26), connected in sequence. The online total organic carbon analyzer (28) is connected to the outlet of the terminal ultrafiltration unit (26) for detecting... The total organic carbon in the product water of the terminal ultrafiltration unit (26) is measured. The activated carbon filter (4) has an inlet (401) connected to the multi-media filter (3), an outlet (403) connected to the filter tank (5), a backwash inlet (404), and a backwash outlet (402). The backwash inlet (404) is connected to the filter tank (5) via a backwash pump (7). The controller is connected to the online total organic carbon analyzer (28) and the backwash pump (7). When the total organic carbon online analyzer (28) detects that the total organic carbon content in the permeate of the terminal ultrafiltration unit (26) is less than a preset threshold, the controller controls the backwash pump (7) to backwash the activated carbon filter (4) in a first backwash cycle. When the total organic carbon online analyzer (28) detects that the total organic carbon content in the permeate of the terminal ultrafilter (26) is greater than or equal to the preset threshold, the controller controls the backwash pump (7) to backwash the activated carbon filter (4) in a second backwash cycle, thereby extending the operating time of the activated carbon filter so that bacteria that consume total organic carbon can grow in the activated carbon filter (4), reducing the total organic carbon content in the permeate of the terminal ultrafilter (26) to less than the preset threshold. The second backwash cycle is longer than the first backwash cycle.

2. The ultrapure water preparation system according to claim 1, characterized in that, The first backwash cycle shall not exceed 24 hours.

3. The ultrapure water preparation system according to claim 1, characterized in that, The second backwash cycle is proportional to the total organic carbon content in the permeate of the terminal ultrafilter (26) detected by the total organic carbon online analyzer (28).

4. The ultrapure water preparation system according to claim 1, characterized in that, After the controller controls the backwash pump (7) to backwash the activated carbon filter (4) in the second backwash cycle, and the total organic carbon online analyzer (28) detects that the total organic carbon content is less than the preset threshold, the controller controls the backwash pump (7) to continue to backwash the activated carbon filter (4) in at least one second backwash cycle, and then backwash the activated carbon filter (4) in the first backwash cycle.

5. The ultrapure water preparation system according to claim 1, characterized in that, The activated carbon filter (4) has the same inlet (401) and backwash outlet (402). The inlet (401) is connected to an inlet branch (29) and a backwash outlet branch (30). The inlet branch (29) is connected to the multi-media filter (3) and is equipped with an inlet valve (291). The backwash outlet branch (30) is equipped with a backwash outlet valve (301). The outlet (403) and backwash inlet (404) of the activated carbon filter (4) are the same. The outlet (403) is connected to an outlet branch (31) and a backwash inlet branch (32). The outlet branch (31) is connected to the inlet of the filter tank (5) and is equipped with an outlet valve (311). The backwash inlet branch (32) is connected to the filter tank (5) and is equipped with a backwash inlet valve (321) and the backwash pump (7).

6. The ultrapure water preparation system according to claim 5, characterized in that, The outlet (403) of the activated carbon filter (4) is also connected to a forward wash drainage branch (33), which is equipped with a forward wash drainage valve (331). After the controller controls the backwash pump (7) to backwash the activated carbon filter (4), it immediately performs a forward wash on the activated carbon filter (4) with water discharged from the multi-media filter (3) and discharges the forward wash water through the forward wash drain valve (331).

7. The ultrapure water preparation system according to claim 6, characterized in that, The activated carbon filter (4) is also equipped with an exhaust valve (34).

8. The ultrapure water preparation system according to claim 1, characterized in that, The total organic carbon includes urea.

9. The ultrapure water preparation system according to claim 1, characterized in that, The raw water supplied to the multi-media filter (3) is municipal tap water or water from lakes, rivers or reservoirs.

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