A seawater desalination post-treatment system and method for producing high salinity potable water

Abstract

This invention provides a seawater desalination post-treatment system and method for producing high-mineralization drinking water. The system includes: a desalination water subsystem, a desalination subsystem, and a mixing device. The desalination water subsystem converts seawater into freshwater, and the desalination subsystem converts deep seawater containing minerals and rare elements into desalinated water. The inlet of the mixing device is connected to the outlets of both the desalination water subsystem and the desalination subsystem, and the mixing device is used to mix the freshwater and desalinated water to obtain high-mineralization drinking water. The desalination water subsystem includes, in sequence, a seawater pretreatment device, a seawater desalination device, a first freshwater pump, a first chlorine dosing device, and a first sodium hydroxide dosing device. The desalination subsystem includes, in sequence, a deep seawater pretreatment device, an electrodialysis seawater desalination device, a second freshwater pump, a second chlorine dosing device, and a second sodium hydroxide dosing device. This solution achieves safe, effective, and low-cost production of high-mineralization drinking water using seawater.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination post-treatment technology, and in particular to a seawater desalination post-treatment system and method for producing high-mineralization drinking water. Background Technology

[0002] With the increasing severity of global freshwater shortages, desalinated seawater is gaining more attention as a new type of freshwater resource. Its use as a supplementary municipal water supply and backup emergency water source will be a crucial technological measure to ensure water security in coastal areas and islands in the future. When desalinated seawater enters the pipeline network as drinking water, it requires accompanying mineralization post-treatment technology to reduce the impact on the network. Mineralization, as an important indicator of total dissolved solids content in water, has a decisive impact on drinking water quality. Mineralization mainly reflects the content of minerals and inorganic salts in water and is a key parameter for evaluating drinking water quality. High-mineralized drinking water has a good supplementary effect for people with weak constitutions, spleen and stomach deficiencies, and calcium deficiencies, and can also be used to treat specific diseases.

[0003] Currently, the commonly used post-treatment processes for desalinated water both domestically and internationally are mainly quicklime mineralization, limestone mineralization, and blending. Quicklime mineralization increases water hardness but does not increase carbonate alkalinity; it also requires pre-introduction of carbon dioxide or addition of sodium carbonate (or sodium bicarbonate) to increase carbonate concentration. Limestone mineralization involves introducing desalinated water into a limestone-filled reactor, where the limestone dissolves and releases calcium and carbonate ions into the water. To promote calcium carbonate dissolution, the desalinated water needs to be acidified with carbon dioxide. Currently, this is mainly achieved by vaporizing liquid CO2 and then acidifying the desalinated water, which is costly. Neither of these methods is suitable for producing high-mineralized drinking water; therefore, there is an urgent need to develop a safe, effective, and low-cost post-treatment system and method for producing high-mineralized drinking water from seawater desalination. Summary of the Invention

[0004] This invention provides a seawater desalination post-treatment system and method for producing high-mineralized drinking water. By mixing desalinated water with desalinated water, the hardness of the desalinated water can be adjusted and the desalinated water can be enriched with minerals, while simplifying the post-treatment steps of the desalinated water.

[0005] In a first aspect, a seawater desalination post-treatment system for producing high-mineralized drinking water includes: a desalination water subsystem, a desalination water subsystem, and a mixing device; the desalination water subsystem is used to convert seawater into freshwater, and the desalination water subsystem is used to convert deep seawater containing minerals and rare elements into desalinated water; the inlet of the mixing device is connected to the outlets of the desalination water subsystem and the desalination water subsystem, respectively, and the mixing device is used to mix the freshwater and desalinated water to obtain high-mineralized drinking water;

[0006] The desalination subsystem includes a seawater pretreatment device, a seawater desalination device, a first freshwater pump, a first chlorine dosing device, and a first sodium hydroxide dosing device connected in sequence; the desalination subsystem includes a deep seawater pretreatment device, an electrodialysis seawater desalination device, a second freshwater pump, a second chlorine dosing device, and a second sodium hydroxide dosing device connected in sequence.

[0007] Secondly, the present invention provides a method for post-desalination treatment of seawater to produce high-mineralized drinking water, comprising:

[0008] Based on the measured seawater quality, determine the seawater pretreatment device and the seawater desalination device;

[0009] Based on the water quality of the deep seawater obtained from the test, the deep seawater pretreatment device and the electrodialysis seawater desalination device are determined.

[0010] The amount of chlorine dioxide added to the first chlorine dosing device and the amount of sodium hydroxide added to the first sodium hydroxide dosing device are determined based on the desalinated water produced by the seawater desalination device.

[0011] The amount of chlorine dioxide added to the second chlorine dosing device and the amount of sodium hydroxide added to the second sodium hydroxide dosing device are determined based on the desalinated water produced by the electrodialysis seawater desalination device.

[0012] The ratio of the fresh water to the desalinated water is determined based on the target salinity of the high-mineralized drinking water, the salinity of the fresh water produced by the desalination subsystem, and the salinity of the desalinated water produced by the desalination subsystem, in order to obtain the high-mineralized drinking water.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] This invention mixes desalinated water produced by an electrodialysis unit with desalinated water produced by a seawater desalination unit. This mixture can be used to adjust the hardness of the desalinated water and simplify the post-treatment steps. Simultaneously, by employing a blending process to mix freshwater from two different seawater desalination processes with high-mineralization desalinated water, the safety and hygiene of the produced water can be ensured. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a seawater desalination post-treatment system for producing high-mineralization drinking water according to an embodiment of the present invention;

[0017] Figure reference numerals: 10-Desalinated water subsystem, 20-Desalinated water subsystem, 30-Mixing device, 101-Seawater pretreatment device, 102-Seawater desalination device, 103-First freshwater pump, 104-First chlorine dosing device, 105-First sodium hydroxide dosing device, 201-Deep seawater pretreatment device, 202-Electrodialysis seawater desalination device, 203-Second freshwater pump, 204-Second chlorine dosing device, 205-Second sodium hydroxide dosing device. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] The following describes the specific implementation of the concept in this application.

[0020] Please refer to Figure 1 This invention provides a seawater desalination post-treatment system for producing high-mineralized drinking water, the system comprising:

[0021] The system includes a desalination subsystem 10, a desalination subsystem 20, and a mixing device 30. The desalination subsystem 10 is used to convert seawater into freshwater, and the desalination subsystem 20 is used to convert deep seawater containing minerals and rare elements into desalinated water. The inlet of the mixing device 30 is connected to the outlets of the desalination subsystem 10 and the desalination subsystem 20, respectively. The mixing device 30 is used to mix the freshwater and desalinated water to obtain highly mineralized drinking water.

[0022] The desalination subsystem 10 includes a seawater pretreatment device 101, a seawater desalination device 102, a first freshwater pump 103, a first chlorine dosing device 104, and a first sodium hydroxide dosing device 105 connected in sequence; the desalination subsystem 20 includes a deep seawater pretreatment device 201, an electrodialysis seawater desalination device 202, a second freshwater pump 203, a second chlorine dosing device 204, and a second sodium hydroxide dosing device 205 connected in sequence.

[0023] In this embodiment of the invention, since the deep seawater treated by the desalination subsystem contains minerals and rare elements, the properly treated desalinated water also contains minerals and rare elements. Thus, when the freshwater produced by the desalination subsystem is mixed with the desalinated water, drinking water with high mineralization containing minerals and rare elements can be obtained. Obviously, the seawater desalination post-treatment system provided by the present invention uses seawater as the water source, does not require acidification treatment, can adjust the water hardness, and simplifies the post-treatment steps of desalinated water, thereby reducing costs and improving efficiency.

[0024] It should be noted that deep seawater refers to seawater at a depth of 200 meters or more below sea level, and is rich in minerals and rare elements. The mixing equipment includes, but is not limited to, a product water mixing tank.

[0025] In a preferred embodiment, the seawater pretreatment device includes a seawater intake pump, a coagulation sedimentation tank or flotation tank, a media filter, and a security filter.

[0026] In this embodiment of the invention, the specific combination of the seawater pretreatment device is determined according to the raw water quality and the requirements of the seawater desalination device inlet water.

[0027] In a preferred embodiment, the seawater desalination device is one of a multi-effect distillation seawater desalination device, a multi-stage flash distillation seawater desalination device, or a reverse osmosis seawater desalination device.

[0028] In a preferred embodiment, the deep seawater pretreatment device includes a water intake pump, a media filter, and a security filter.

[0029] In a preferred embodiment, the electrodialysis seawater desalination device uses a monovalent cation-selective permeable membrane for seawater concentration and salt production, and an anion-exchange membrane.

[0030] In a more preferred embodiment, in the electrodialysis seawater desalination device, all anions in the deep seawater can pass through the anion membrane, and monovalent cations can pass through the cation membrane.

[0031] In a preferred embodiment, the desalinated water produced by the electrodialysis desalination unit contains the same polyvalent cations as deep seawater.

[0032] In a preferred embodiment, seawater enters the seawater pretreatment device through the inlet of the seawater pretreatment device, the outlet of the seawater pretreatment device is connected to the inlet of the seawater desalination device, the outlet of the seawater desalination device is connected to the inlet of the first freshwater pump, the outlet of the first freshwater pump is connected to the inlet of the mixing device, and a first chlorine dosing device and a first sodium hydroxide dosing device are sequentially installed on the pipeline between the first freshwater pump and the mixing device.

[0033] Deep seawater enters the deep seawater pretreatment device through its inlet. The outlet of the deep seawater pretreatment device is connected to the inlet of the electrodialysis seawater desalination device. The outlet of the electrodialysis seawater desalination device is connected to the inlet of the second freshwater pump. The outlet of the second freshwater pump is connected to the inlet of the mixing device. A second chlorine dosing device and a second sodium hydroxide dosing device are sequentially installed on the pipeline between the second freshwater pump and the mixing device.

[0034] The present invention also provides a seawater desalination post-treatment method for producing high-mineralization drinking water based on the above system, comprising:

[0035] S1: Determine the seawater pretreatment device and seawater desalination device based on the detected seawater quality.

[0036] S2: Based on the water quality of the deep seawater obtained from the test, determine the deep seawater pretreatment device and the electrodialysis seawater desalination device;

[0037] S3: Determine the chlorine dioxide dosage of the first chlorine dosing device and the sodium hydroxide dosage of the first sodium hydroxide dosing device based on the desalinated water produced by the seawater desalination unit;

[0038] S4: Determine the chlorine dioxide dosage of the second chlorine dosing device and the sodium hydroxide dosage of the second sodium hydroxide dosing device based on the desalinated water produced by the electrodialysis seawater desalination unit;

[0039] S5: Determine the ratio of fresh water to desalinated water based on the target salinity of the high-mineralized drinking water, the salinity of the fresh water produced by the desalination subsystem, and the salinity of the desalinated water produced by the desalination subsystem, so as to obtain high-mineralized drinking water.

[0040] In a more preferred embodiment, step S3, based on the desalinated water produced by the seawater desalination unit, determines the chlorine dioxide dosage of the first chlorine dosing unit and the sodium hydroxide dosage of the first sodium hydroxide dosing unit, including:

[0041] Based on the detected initial flow rate of the desalinated water and the total amount of organic matter / colony count, determine at least one chlorination point and the chlorine dioxide dosage at each chlorination point, and at least one residual chlorine test point; wherein, the chlorination point and the residual chlorine test point are set at intervals;

[0042] Collect the residual chlorine amount at each residual chlorine test point and determine whether the residual chlorine amount at the end of the residual chlorine test point does not exceed the preset residual chlorine threshold within a preset time period.

[0043] If the judgment result is yes, the desalinated water produced by the first chlorine dosing unit will flow into the first sodium hydroxide dosing unit through the outlet; otherwise, return to adjust the chlorine dioxide dosage at each chlorination point until the judgment result is yes.

[0044] Based on the pH value of the desalinated water produced by the first chlorine dosing device, the amount of sodium hydroxide to be added in the first sodium hydroxide dosing device is determined in order to obtain desalinated water with the target pH value.

[0045] It should be noted that a residual chlorine test point is set after each chlorination point; and for at least two chlorination points, the residual chlorine test point is located between adjacent chlorination points. More specifically, for example, between the pipeline of the first freshwater pump and the first sodium hydroxide dosing device, chlorination point 1-residual chlorine test point 1-chlorination point 2-residual chlorine test point 2 are set in sequence.

[0046] More specifically, the initial dosage C at the initial chlorination point. cl,0 (mg / L) is determined by the following formula:

[0047]

[0048] Wherein, TOC is the total organic carbon of the desalinated water (mg / L); N0 is the initial total bacterial count (CFU / mL); N t The target total number of colonies (CFU / mL) to meet sterilization requirements; Y is the available chlorine utilization rate; k is the disinfection rate constant L / (mg·min); t is the unit time (min);

[0049] The real-time dosing acceleration rate v at the i-th chlorination point Cl,i (g / h) is determined by the following formula:

[0050]

[0051] Among them, C target The preset residual chlorine threshold (mg / L); C measured,i-1 is the measured residual chlorine value (mg / L) at the (i-1)th residual chlorine test point; F is the initial flow rate of the desalinated water (m³ / h). 3 / h); η is the pipeline attenuation coefficient, <1; α is the safety factor (0.05~0.1, to prevent sudden load increase); ρ is the effective chlorine coefficient, dimensionless; it should be noted that when adding chlorine as ClO2, ρ=1; when adding chlorine as NaClO, ρ=the density of NaClO solution (g / L) / the effective chlorine content in NaClO solution (g / L);

[0052] If the residual chlorine at the end of the test point exceeds the standard (i.e., the result is negative), the dosage at each chlorination point is reduced proportionally; if the residual chlorine at the end of the test point is insufficient, the dosage at the initial chlorination point is increased first to ensure initial sterilization.

[0053] It should be noted that, similarly, the determination of the chlorine dioxide dosage in the second chlorine dosing device and the sodium hydroxide dosage in the second sodium hydroxide dosing device is also made using the same method, and will not be repeated here.

[0054] In this embodiment of the invention, the real-time dosing rate of the chlorination point is dynamically adjusted by feedback of flow rate and residual chlorine, which can both meet the sterilization requirements and control the residual chlorine, thereby improving the chlorination control in the water treatment process.

[0055] In a more preferred embodiment, step S5 determines the ratio of fresh water to desalinated water, including:

[0056] Based on the target salinity of the high-mineralization drinking water, the salinity of the freshwater produced by the desalination subsystem, and the salinity of the desalinated water produced by the desalination subsystem, the initial ratio of freshwater to desalinated water is determined; the initial ratio is determined by the following formula:

[0057]

[0058] Where R0 is the initial ratio of fresh water to desalinated water; C 脱盐水 C represents the salt content of the desalinated water. 目标 For target salinity; C 淡水 This refers to the salinity of fresh water.

[0059] Fresh water and desalinated water are mixed in a mixing device according to the initial ratio to obtain initial drinking water; and the initial salt content of the initial drinking water is detected in real time.

[0060] Calculate the difference between the target salinity and the first salinity, and dynamically adjust the initial ratio based on the difference until the difference does not exceed a preset error threshold, then determine the current ratio; the current ratio is determined by the following formula:

[0061]

[0062] e t1 =C 目标 -C1

[0063] Among them, R 实际 This represents the current ratio; K p K i K d These are proportional gain, integral gain, and derivative gain, respectively; e t1 For the target salinity C 目标 The difference between the first salinity C1 and the first salinity C1; t is the current time;

[0064] Detect the current mineral content of the drinking water in the current mixing unit;

[0065] The mineral compensation amount is determined based on the current mineral content and the target mineral content; the mineral compensation amount is determined using the following formula:

[0066]

[0067] Among them, Q 补 Mineral compensation (L / h); F 总 For flow rate (m 3 / h); M 目标 The target mineral content (mg / L); M 当前 Current mineral content (mg / L); C 矿化剂 The concentration of the effective component of the mineralizer (g / L);

[0068] After compensating the mixing device with minerals according to the mineral compensation amount, the second salinity C2 of the drinking water in the mixing device is measured.

[0069] Based on the current mineral content, target mineral content, second salinity, and target salinity, determine the final ratio of fresh water to desalinated water:

[0070]

[0071] e t2 =C 目标 -(M 目标 -M 当前 )-C2

[0072] Among them, R 最终 For the final ratio; K p K i K d These represent proportional gain, integral gain, and differential gain, respectively; C2 is the second salt content; and t is the current time.

[0073] It should be noted that the salinity can be obtained using an online conductivity meter or a TDS analyzer. In step S5, the units for salinity and mineral content are both mg / L.

[0074] In this invention, PID mixing control of salinity is first achieved through staged control, followed by the addition of a mineralizing agent to further compensate for mineral content, ensuring the health and taste of high-mineralized drinking water. Since compensating for mineral content further affects the salinity of the drinking water, the final salinity of the drinking water needs to be dynamically adjusted to ultimately decouple salinity control and mineral supplementation, ensuring stable system operation.

[0075] To more clearly illustrate the technical solution and advantages of the present invention, the following describes in detail the application method of a seawater desalination post-treatment system for producing high-mineralized drinking water through several embodiments.

[0076] In the following embodiments, a product water mixing tank is used as the mixing device.

[0077] Example 1

[0078] 1) Pass the raw seawater (salt content of 33000mg / L) into the seawater pretreatment device 101 for raw seawater pretreatment (including raw seawater intake, coagulation sedimentation / air flotation, media filtration and security filtration steps);

[0079] 2) The pretreated raw seawater from step 1 is fed into the seawater desalination device 102 for desalination. The resulting desalinated water (with a salt content of less than 50 mg / L) is fed into the product water mixing tank 30 via the first freshwater pump 103. The desalinated water transport pipeline from the first freshwater pump to the product water mixing tank contains a first chlorine dosing device 104 (adding 1.5 mg / L ClO2 to the desalinated water) and a first sodium hydroxide dosing device 105 (adding 98% mass concentration NaOH).

[0080] 3) Deep seawater (salt content of 35000mg / L) is introduced into deep seawater pretreatment device 201 for deep seawater pretreatment (including water intake, media filtration and security filtration steps);

[0081] 4) The pretreated deep seawater from step 3 is passed into the electrodialysis seawater desalination unit 202 for electrodialysis seawater desalination, producing desalinated water (wherein, Na+...). + The concentration was 10 mg / L, K + The concentration was 2 mg / L, Ca 2+ The concentration was 212 mg / L, Mg 2+ The concentration was 1100 mg / L, Cl - The concentration was 2940 mg / L, SO4 2- The concentration was 4013 mg / L, PO4 3- The concentration of the deionized water is 0.185 mg / L, the concentration of TDS (total dissolved solids) is 8356 mg / L, and the total hardness is 5056 mg / L. The deionized water is pumped into the product water mixing tank 30 through the second fresh water pump 203. The electrodialysis deionized water transport pipeline from the second fresh water pump to the product water mixing tank contains a second chlorine dosing device 204 (adding 1.5 mg / L ClO2 to the deionized water) and a second sodium hydroxide dosing device 205 (adding 98% mass concentration NaOH).

[0082] 5) The fresh water produced in step 2 and the desalinated water produced in step 4 are fed into the product water mixing tank 30 at a ratio of 10:1 to output high-mineralized drinking water.

[0083] Example 2

[0084] 1) Pass the raw seawater (salt content of 33000mg / L) into the seawater pretreatment device 101 for raw seawater pretreatment (including raw seawater intake, media filtration and security filtration steps);

[0085] 2) The pretreated raw seawater from step 1 is fed into the seawater desalination device 102 for desalination. The resulting desalinated water (salt content 100 mg / L) is fed into the product water mixing tank 30 via the first freshwater pump 103. The desalinated water transport pipeline from the first freshwater pump to the product water mixing tank contains a first chlorine dosing device 104 (adding 1.5 mg / L NaClO to the desalinated water) and a first sodium hydroxide dosing device 105 (adding 98% mass concentration NaOH).

[0086] 3) Deep seawater (salt content of 35000mg / L) is introduced into deep seawater pretreatment device 201 for deep seawater pretreatment (including water intake, media filtration and security filtration steps);

[0087] 4) The pretreated deep seawater from step 3 is passed into the electrodialysis seawater desalination unit 202 for electrodialysis seawater desalination, producing desalinated water (wherein, Na+...). + The concentration was 138 mg / L, K + The concentration was 10 mg / L, Ca 2+ The concentration was 312 mg / L, Mg 2+ The concentration was 1300 mg / L, Cl - The concentration was 3140 mg / L, SO4 2- The concentration was 3913 mg / L, PO4 3- The concentration of NaClO (0.185 mg / L), the concentration of TDS (total dissolved solids) (9428 mg / L), and the total hardness (5891 mg / L) are introduced into the product water mixing tank 30 through the second fresh water pump 203. The electrodialysis demineralized water transport pipeline from the second fresh water pump to the product water mixing tank contains a second chlorine dosing device 204 (adding 1.5 mg / L NaClO to the demineralized water) and a second sodium hydroxide dosing device 205 (adding 98% NaOH by mass).

[0088] 5) The fresh water produced in step 2 and the desalinated water produced in step 4 are fed into the product water mixing tank 30 at a ratio of 12:1 to output high-mineralized drinking water.

[0089] Example 3

[0090] 1) Pass the raw seawater (salt content of 33000mg / L) into the seawater pretreatment device 101 for raw seawater pretreatment (including raw seawater intake, media filtration and security filtration steps);

[0091] 2) The pretreated raw seawater from step 1 is fed into the seawater desalination device 102 for desalination. The resulting desalinated water (salt content 80 mg / L) is fed into the product water mixing tank 30 via the first freshwater pump 103. The desalinated water transport pipeline from the first freshwater pump to the product water mixing tank contains a first chlorine dosing device 104 (adding 1.5 mg / L NaClO to the desalinated water) and a first sodium hydroxide dosing device 105 (adding 98% mass concentration NaOH).

[0092] 3) Deep seawater (salt content of 35000mg / L) is introduced into deep seawater pretreatment device 201 for deep seawater pretreatment (including water intake, media filtration and security filtration steps);

[0093] 4) The pretreated deep seawater from step 3 is passed into the electrodialysis seawater desalination unit 202 for electrodialysis seawater desalination, producing desalinated water (wherein, Na+...). + The concentration was 183 mg / L, K + The concentration was 12 mg / L, Ca 2+ The concentration was 309 mg / L, Mg 2+ The concentration was 1311 mg / L, Cl - The concentration was 3231 mg / L, SO4 2- The concentration was 4013 mg / L, PO4 3- The concentration of NaClO (0.185 mg / L), the concentration of TDS (total dissolved solids) (9981 mg / L), and the total hardness (6619 mg / L) are introduced into the product water mixing tank 30 through the second fresh water pump 203. The electrodialysis demineralized water transport pipeline from the second fresh water pump to the product water mixing tank contains a second chlorine dosing device 204 (adding 1.5 mg / L NaClO to the demineralized water) and a second sodium hydroxide dosing device 205 (adding 98% NaOH by mass).

[0094] 5) The fresh water produced in step 2 and the desalinated water produced in step 4 are fed into the product water mixing tank 30 at a ratio of 12:1 to output high-mineralized drinking water.

[0095] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on a seawater desalination post-treatment system for producing high-mineralized drinking water. In other embodiments of the present invention, a seawater desalination post-treatment system for producing high-mineralized drinking water may include more or fewer components than illustrated, or combine some components, or split some components, or have different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0096] The information interaction and execution process between the devices in the above system are based on the same concept as the method embodiments of the present invention, and the specific details can be found in the descriptions in the method embodiments of the present invention, and will not be repeated here.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for post-desalination treatment of seawater to produce high-mineralized drinking water, characterized in that, A seawater desalination post-treatment system is adopted, which includes a desalination water subsystem, a desalination water subsystem, and a mixing device. The desalination water subsystem is used to convert seawater into freshwater, and the desalination water subsystem is used to convert deep seawater containing minerals and rare elements into desalinated water. The inlet of the mixing device is connected to the outlets of the desalination water subsystem and the desalination water subsystem, respectively, and the mixing device is used to mix the freshwater and desalinated water to obtain high-mineralized drinking water. The desalination subsystem includes a seawater pretreatment device, a seawater desalination device, a first freshwater pump, a first chlorine dosing device, and a first sodium hydroxide dosing device connected in sequence; the desalination subsystem includes a deep seawater pretreatment device, an electrodialysis seawater desalination device, a second freshwater pump, a second chlorine dosing device, and a second sodium hydroxide dosing device connected in sequence; the electrodialysis seawater desalination device uses a monovalent cation-selective permeable membrane for seawater concentration and salt production, and an ion exchange membrane for the anion membrane; All anions in the deep seawater can pass through the anion membrane, and monovalent cations can pass through the cation membrane. The method includes: Based on the measured seawater quality, determine the seawater pretreatment device and the seawater desalination device; Based on the water quality of the deep seawater obtained from the test, the deep seawater pretreatment device and the electrodialysis seawater desalination device were determined. The dosage of chlorine dioxide in the first chlorine dosing device and the dosage of sodium hydroxide in the first sodium hydroxide dosing device are determined based on the fresh water produced by the seawater desalination device. The amount of chlorine dioxide added to the second chlorine dosing device and the amount of sodium hydroxide added to the second sodium hydroxide dosing device are determined based on the desalinated water produced by the electrodialysis seawater desalination device. The initial ratio of fresh water to desalinated water is determined based on the target salinity of the high-mineralization drinking water, the salinity of the fresh water produced by the desalination subsystem, and the salinity of the desalinated water produced by the desalination subsystem. Fresh water and desalinated water are mixed in a mixing device according to the initial ratio to obtain initial drinking water; and the initial salt content of the initial drinking water is detected in real time. Calculate the difference between the target salinity and the first salinity, and dynamically adjust the initial ratio according to the difference until the difference does not exceed the preset error threshold, then determine the current ratio; Detect the current mineral content of the drinking water in the current mixing unit; The amount of mineral compensation is determined based on the current mineral content and the target mineral content; After compensating the mixing device with minerals according to the mineral compensation amount, the second salinity of the drinking water in the mixing device is measured. The final ratio of fresh water to desalinated water is determined based on the current mineral content, target mineral content, second salinity, and target salinity.

2. The method according to claim 1, characterized in that, The seawater pretreatment device includes a seawater intake pump, a coagulation sedimentation tank or flotation tank, a media filter, and a security filter.

3. The method according to claim 1, characterized in that, The seawater desalination device is one of the following: a multi-effect distillation seawater desalination device, a multi-stage flash distillation seawater desalination device, or a reverse osmosis seawater desalination device.

4. The method according to claim 1, characterized in that, The deep seawater pretreatment device includes a water intake pump, a media filter, and a security filter.

5. The method according to claim 1, characterized in that, The desalinated water produced by the electrodialysis seawater desalination device contains the same polyvalent cations as the deep seawater.

6. The method according to any one of claims 1 to 5, characterized in that, Seawater enters the seawater pretreatment device through the inlet of the seawater pretreatment device. The outlet of the seawater pretreatment device is connected to the inlet of the seawater desalination device. The outlet of the seawater desalination device is connected to the inlet of the first freshwater pump. The outlet of the first freshwater pump is connected to the inlet of the mixing device. The first chlorine dosing device and the first sodium hydroxide dosing device are sequentially installed on the pipeline between the first freshwater pump and the mixing device. The deep seawater enters the deep seawater pretreatment device through its inlet. The outlet of the deep seawater pretreatment device is connected to the inlet of the electrodialysis seawater desalination device. The outlet of the electrodialysis seawater desalination device is connected to the inlet of the second freshwater pump. The outlet of the second freshwater pump is connected to the inlet of the mixing device. A second chlorine dosing device and a second sodium hydroxide dosing device are sequentially installed on the pipeline between the second freshwater pump and the mixing device.

7. The method according to claim 1, characterized in that, The determination of the chlorine dioxide dosage of the first chlorine dosing device and the sodium hydroxide dosage of the first sodium hydroxide dosing device based on the fresh water produced by the seawater desalination device includes: Based on the detected initial flow rate of the freshwater and the total organic matter / bacterial count, at least one chlorination point and the chlorine dioxide dosage at each chlorination point, and at least one residual chlorine test point are determined; wherein, the chlorination point and the residual chlorine test point are set at intervals. Collect the residual chlorine amount at each residual chlorine test point and determine whether the residual chlorine amount at the end of the residual chlorine test point does not exceed the preset residual chlorine threshold within a preset time period. If the judgment result is yes, then the fresh water produced by the first chlorine dosing device flows into the first sodium hydroxide dosing device through the outlet; otherwise, return to adjust the chlorine dioxide dosage at each chlorination point until the judgment result is yes. Based on the detected pH value of the fresh water produced by the first chlorine dosing device, the amount of sodium hydroxide added by the first sodium hydroxide dosing device is determined to obtain the fresh water with the target pH value.

Images