Brackish water membrane desalination and water quality regulation and control process and device

Abstract

The invention relates to the technical field of drinking water treatment, and provides a brackish water membrane desalination and water quality regulation and control process and device, and the process comprises the process steps of filtration, nanofiltration-reverse osmosis desalination, tempering and disinfection. The method comprises the following steps: firstly, carrying out filtration pretreatment on brackish water, and filtering, namely quartz sand filtration and precision filtration, so as to obtain pretreated effluent without suspended solids and particulate matters; carrying out nanofiltration-reverse osmosis desalination treatment on the pretreated effluent, preliminarily removing divalent ions through nanofiltration, and then carrying out deep desalination through reverse osmosis to obtain desalted water; continuously monitoring the water quality of the desalted water, and conditioning according to the water quality condition to obtain mineralized water; performing disinfection treatment on the mineralized water to obtain direct drinking water; the produced direct drinking water is appropriate in TDS and hardness, can meet the requirements of higher water quality chemical stability, health indexes and the like, can meet the emergency movable water treatment requirements, and provides healthy and safe drinking water for water-deficient areas.

Description

Technical Field

[0001] The invention relates to the technical field of drinking water treatment, and in particular to a brackish water membrane desalination and water quality control process and device. Background Art

[0002] Drinking water safety has received widespread attention around the world. Hundreds of millions of people around the world do not have direct access to clean and safe drinking water. In many areas, people's drinking water is provided by seawater or brackish water after treatment and regeneration. The health and safety of drinking water usually refers to the absence of pathogenic bacteria and pathogens in the water. However, the mineral content in the water is also an important factor in determining people's physical health and balance. With the reduction of freshwater resources and the development of water purification technology, the issue of water mineral content has become increasingly important. Brackish water is widely distributed and abundant in inland areas of my country, and its salt content is relatively low compared to seawater. The abundant brackish water resources can be desalinated through desalination, combined with post-treatment processes such as conditioning and disinfection of desalinated water, to provide high-quality drinking water and establish a sound drinking water safety guarantee mechanism, which can effectively solve the problems of shortage and uneven distribution of freshwater resources.

[0003] Reverse osmosis is a desalination technology based on semipermeable membranes. When two solutions with different solute concentrations are separated by a semipermeable membrane, the solvent will spontaneously flow from the more dilute solution to the more concentrated solution to balance the potential energy of the two solutions; when pressure is applied to the high-concentration solution side, the permeation rate gradually decreases. If the permeation trend is completely offset by the externally applied pressure, an osmotic equilibrium is reached. This pressure is called osmotic pressure. If the externally applied pressure is greater than the osmotic pressure, the solvent flow is reversed, so the solvent can be extracted from the high-concentration solution. Nanofiltration desalination technology is based on a pressure-driven membrane separation process between ultrafiltration and reverse osmosis. The nanofiltration membrane used has a pore size of about 1 nanometer, which can remove particles with a molecular weight of 100~1000Da. It has the characteristics of low operating pressure, high flux, high multivalent ion removal rate, and low operating and maintenance costs. The ion selectivity of the nanofiltration membrane makes it more suitable for water softening. In the past decade, pressure-driven reverse osmosis has been the dominant technology for membrane desalination of seawater and brackish water, accounting for 64% or more of the total desalination technology. Nanofiltration has also developed rapidly in the combined process of brackish water desalination and seawater desalination, while ultrafiltration and microfiltration are widely used in pretreatment processes.

[0004] The "Nanofiltration Reverse Osmosis Direct Drinking Water System" disclosed in a Chinese patent has a publication number of CN216377691U, which includes a primary filter box, an activated carbon filter box, a precision filter, a nanofiltration filter assembly, a reverse osmosis filter assembly and a direct drinking water tank. The primary filter box, the activated carbon filter box, the precision filter, the nanofiltration filter assembly and the reverse osmosis filter assembly are connected in sequence through connecting pipes. This solution avoids the clogging of the filter screen that affects the filtration efficiency of the water source, and there is no need to frequently disassemble and clean the filter screen, thereby improving the practicality of the direct drinking water system. However, this solution lacks deep treatment of drinking water, cannot fully guarantee that the water quality meets the standards, and has a high cleaning cost.

[0005] In summary, in the research on the desalination of brackish water, only the removal of single-component or double-component dissolved solids is considered. However, according to the quality of brackish water in water-scarce areas in my country, the brackish water in most areas has high hardness and complex ion composition, and belongs to medium-to-high salinity brackish water. The quality of raw water will have a huge impact on the desalination effect; water treated by desalination technologies such as reverse osmosis or distillation is generally called desalinated water or desalted water. The effluent water generally has the characteristics of acidic pH, low total alkalinity and total hardness, low buffering capacity, unstable water quality, and easy to cause corrosion. It cannot be directly used for drinking. It is usually necessary to improve the water quality and disinfect the treated desalinated water. Summary of the invention

[0006] To this end, the present invention proposes a novel brackish water membrane desalination and water quality control process and device that can solve at least part of the above-mentioned problems, and ensure the supply of healthy and safe drinking water for residents in freshwater-deficient areas in emergency situations. The brackish water is first pre-treated by filtration, and the filtration includes quartz sand filtration and precision filtration to obtain pre-treated effluent water with suspended matter and particulate matter removed; the pre-treated effluent is subjected to nanofiltration-reverse osmosis desalination treatment, and the nanofiltration initially removes divalent ions, and then reverse osmosis is used for deep desalination to obtain desalinated water; the desalinated water is disinfected to obtain produced water; the produced water continuously monitors the water quality of the desalinated water, and is conditioned according to the water quality to obtain direct drinking water, thereby ensuring the safety and health of the direct drinking water.

[0007] Preferably, the brackish water has a salt content of 6-10 g / L.

[0008] Preferably, the process operating pressure of the nanofiltration-reverse osmosis two-stage membrane assembly is 1.1 MPa to 1.2 MPa for nanofiltration and 1.2 MPa to 1.5 MPa for reverse osmosis.

[0009] Specifically, according to the pure water flux test and desalination test, the operating pressure, influent dissolved solid concentration, and temperature were changed to screen out the membrane with the best performance. Among them, the pure water flux test showed that when the inlet pressure was 1.2 MPa, the pure water flux of the imported nanofiltration membrane 2540NH was the largest, reaching 74.8 L / (m 2 ·h), the pure water flux of the domestic reverse osmosis membrane BW2540 at 1.5 MPa was greater than that of the imported reverse osmosis membrane 2540HR; the two-stage desalination test results showed that when the inlet TDS concentration was 6-10 g / L and the operating pressure was 1.5 MPa, the TDS retention rates of the nanofiltration membrane 2540NH and the reverse osmosis membrane BW2540 reached 99.77% and 99.57%, respectively, and the TDS concentration of the produced water after two-stage deep desalination was lower than 60 mg / L.

[0010] Specifically, the two-stage membrane assembly was designed based on the water production and the membrane performance test results. In the reference test, the nanofiltration membrane flux was between 59.2 and 76.7 L / (m 2 ·h), the reverse osmosis membrane flux is between 45.4 and 50.2 L / (m 2 h), the design uses 2540 specifications.

[0011] Number of membranes

[0012] In the formula, is the target water production flow rate, L / h; is the reference membrane flux, L / (m 2 h); is the effective membrane area of ​​a single branch, m 2 .

[0013] According to the reverse osmosis water production, the reverse osmosis membrane assembly n=50 / (45.36*2.6)=0.43, rounded to 1.

[0014] According to the influent concentration and the recovery rate under pressure is 13.05%, the nanofiltration membrane water production is the reverse osmosis membrane influent, that is, the nanofiltration membrane water production is 50 / 0.1305=383.1 L / h, and the nanofiltration membrane component n=383.1 / (76.7*2.8)=1.87 pieces, rounded to 2 pieces.

[0015] According to the process flow, the membrane components are arranged in such a way that the first-stage nanofiltration membranes are connected in parallel, and then the second-stage reverse osmosis membranes are connected in series.

[0016] Specifically, the water inlet flow rate is not less than 1.8 m 3 / h, precision filter pressure drop <0.1MPa. Select the maximum flow rate as 2 m 3 / h, 18 m head high pressure pump, power 0.25 kW; stop valve can adjust the water flow. According to the overall system pressure required to be less than 1.5 MPa, select a flow rate of 2 m 3 / h, 100 m head high-pressure pump 2, with a power of 1.5 kW, can effectively reduce energy consumption.

[0017] Preferably, the conditioning is performed by chemical conditioning, and the chemical and chemical dosage are as follows: the dosage of CaCl2 is 40-50 mg / L, the dosage of MgCl2 is 20 mg / L, the total dosage of NaHCO3 and KHCO3 is 60-80 mg / L, and the molar ratio of NaHCO3 to KHCO3 is 1:1.

[0018] Preferably, the desalinated water enters the water production tank through a UV sterilizer and is equipped with a dosing device. Under continuous monitoring of the water quality of the desalinated water, the water is automatically conditioned through a program set in the electrical control box to ensure that the direct drinking water produced after the brackish water is desalinated by the device has the advantages of safety and health.

[0019] A brackish water membrane desalination and water quality control device includes a water inlet, a water inlet valve, a quartz sand filter, a precision filter, a high-pressure pump 1, a nanofiltration membrane assembly, a high-pressure pump 2, a reverse osmosis membrane, a UV sterilizer, a dosing box, a water production tank and a water outlet in the order of water flow direction. A water inlet pump is provided between the water inlet and the quartz sand filter; a high-pressure pump 1 is provided between the precision filter and the nanofiltration membrane assembly to provide nanofiltration pressure; a high-pressure pump 2 is provided between the nanofiltration membrane assembly and the reverse osmosis membrane to provide the pressure required for reverse osmosis; a nanofiltration membrane is provided inside the nanofiltration membrane assembly for pre-desalination; a reverse osmosis membrane is provided inside the reverse osmosis membrane for deep desalination; a monitoring instrument is provided in the water production tank to detect the quality of the outlet water; the nanofiltration membrane and the reverse osmosis membrane are provided with a concentrated water pipeline to discharge unqualified water, and a portion of reflux water is provided to improve the processing efficiency of the device.

[0020] As a preferred option, the device is equipped with an electric control box system, which has functions such as monitoring, alarm, and automatic shutdown. The automatic control part can be converted to manual control. The electric control box system can realize functions such as pump start and stop, membrane component cleaning, and automatic dosing and conditioning of desalinated water. For the convenience of use and management, the electric control box system of the device is programmed with automatic control and management functions.

[0021] Preferably, the nanofiltration membrane assembly can effectively intercept divalent ions at low pressure to achieve pre-desalting effect, and then perform deep desalination through a two-stage reverse osmosis membrane assembly. The two-stage membrane assembly ensures the quality of desalinated water production to a high-quality level. If the salt content of brackish water is low, both the nanofiltration membrane assembly and the reverse osmosis membrane assembly can be adjusted by valves to reflux concentrated water to reduce emissions.

[0022] Preferably, the pretreatment system is equipped with quartz sand filtration and precision filter elements, which have the characteristics of large pollution holding capacity and high filtration accuracy, can prevent the membrane assembly from being blocked by particulate matter, and protect the normal operation of subsequent processes.

[0023] Preferably, the precision filter is made of stainless steel 10 inches 5 cores with a filtration accuracy of 5 μm.

[0024] The advantages and positive effects of the present invention are:

[0025] (1) The nanofiltration-reverse osmosis double membrane process is used to improve the treatment capacity of the device and its adaptability to raw water of different water qualities. The process can adapt to and treat influent water with high salt content, complex composition, high hardness ion content, and large fluctuations in water volume. It can achieve desalination treatment under low pressure conditions, reduce the pressure requirements of pumps and pipelines, and improve the problem of membrane scaling and pollution;

[0026] (2) On the basis of effectively utilizing hard-to-treat raw water such as high-hardness brackish water and deeply removing excess salt ions and harmful substances, it can also adjust and improve the important mineral content of the produced water according to the water quality health standards, which helps to ensure the supply of freshwater resources and the safety and health of drinking water. The produced drinking water can meet the relevant requirements of the "Sanitary Standard for Drinking Water for Domestic Use" (GB5749-2006) and the "Sanitary Standard for Mineralization of Low-Mineralized Drinking Water" (GJB1335-92), including pH greater than 7.0, TDS and hardness not exceeding the corresponding appropriate values ​​(1000 mg / L and 200 mg / L);

[0027] (3) The device can realize multiple functions such as water production, shutdown, cleaning, online monitoring, protection, automatic operation and manual switching. The electronic control system of the device is equipped with relevant programs designed according to the results of desalinated water conditioning test. It can analyze the actual desalinated water quality, add the type and dosage of conditioning agent, produce direct drinking water with excellent health and stability, and provide high-quality drinking water supply solutions for areas lacking fresh water.

[0028] The above description of the technical solution of the present application is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0030] Figure 1 This is a flow chart of the brackish water membrane desalination and water quality control process in the embodiment of this application;

[0031] Figure 2 This is a schematic diagram of the connection between the brackish water membrane desalination and water quality control device in the embodiment of the present application;

[0032] Figure 3 This is a graph showing the effect of operating pressure and influent concentration on the flux of a nanofiltration membrane in Example 1 of the present application;

[0033] Figure 4 This is a graph showing the effect of operating pressure and influent concentration on the TDS retention rate of the nanofiltration membrane in Example 1 of the present application;

[0034] Figure 5 This is a graph showing the effect of operating pressure and influent concentration on different ion rejection rates of nanofiltration membranes in Example 1 of the present application;

[0035] Figure 6 This is a graph showing the influence of operating pressure and inlet water concentration on the TDS rejection rate of the reverse osmosis membrane and the produced water TDS in Example 2 of the present application.

[0036] In the figure: 1-water inlet, 2-water inlet valve, 3-water inlet pump, 4-quartz sand filter, 5-precision filter, 6-high-pressure pump one, 71-nanofiltration membrane one, 72-nanofiltration membrane two, 8-high-pressure pump two, 9-reverse osmosis membrane, 10-UV sterilizer, 11-dosage box, 12-water production tank, 13-water outlet, 14-concentrated water outlet, 15-concentrated water valve, 16-concentrated water reflux valve. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0038] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0039] This embodiment provides a brackish water membrane desalination and water quality control process, such as Figure 1 and Figure 2As shown, the process includes filtration, nanofiltration-reverse osmosis desalination, conditioning, and disinfection. The brackish water is first pre-treated by filtration, and the filtration includes quartz sand filtration and precision filtration to obtain pre-treated effluent water with suspended matter and particulate matter removed. The pre-treated effluent is subjected to nanofiltration-reverse osmosis desalination treatment, and the nanofiltration preliminarily removes divalent ions, and then reverse osmosis is used for deep desalination to obtain desalinated water. The desalinated water is disinfected to obtain produced water. The produced water continuously monitors the water quality of the desalinated water, and according to the water quality conditions, it is conditioned to obtain direct drinking water, thereby ensuring the safety and health of the direct drinking water.

[0040] Preferably, the salt content of the brackish water is 6-10 g / L.

[0041] Preferably, the process operating pressure of the nanofiltration-reverse osmosis two-stage membrane assembly is 1.1 MPa to 1.2 MPa for nanofiltration and 1.2 MPa to 1.5 MPa for reverse osmosis.

[0042] Preferably, the conditioning is performed by using reagents, and the reagents and the dosage of the reagents are as follows: the dosage of CaCl2 is 40-50 mg / L, the dosage of MgCl2 is 20 mg / L, the total dosage of NaHCO3 and KHCO3 is 60-80 mg / L, and the molar ratio of NaHCO3 to KHCO3 is 1:1.

[0043] A brackish water membrane desalination and water quality control device, the device adopts the process described in claim 1, and includes a water inlet 1, a water inlet valve 2, a quartz sand filter 4, a precision filter 5, a high-pressure pump 1 6, a nanofiltration membrane assembly 1 71, a nanofiltration membrane assembly 2 72, a high-pressure pump 2 8, a reverse osmosis membrane 9, a UV sterilizer 10, a dosing box 11, a water production tank 12 and a water outlet 13. A water inlet pump 3 is provided between the water inlet 1 and the quartz sand filter 4; a high-pressure pump 6 is provided between the precision filter 5 and the nanofiltration membrane assembly 7 to provide nanofiltration pressure; a high-pressure pump 8 is provided between the nanofiltration membrane assembly 7 and the reverse osmosis membrane 9 to provide the pressure required for reverse osmosis; a nanofiltration membrane is provided inside the nanofiltration membrane assembly 7 for pre-desalination; the reverse osmosis membrane 9 desalinates deeply; the water production tank 12 is provided with a monitoring instrument to detect the quality of the effluent; the nanofiltration membrane 7 and the reverse osmosis membrane 9 are provided with a concentrated water pipeline to discharge unqualified water and provide a portion of reflux water.

[0044] Preferably, when the salt content of brackish water is lower than a set value, the nanofiltration membrane assembly and the reverse osmosis membrane assembly can both adjust valves to reflux concentrated water to reduce concentrated water discharge, thereby improving the water production recovery rate.

[0045] Preferably, the device is equipped with an electric control box system with functions such as monitoring, alarm, and automatic shutdown, which can realize functions such as pump start and stop, membrane component cleaning, and automatic dosing and conditioning of desalinated water. The automatic control part can be converted to manual control.

[0046] Preferably, the membrane assembly is designed as a two-stage membrane assembly based on the water production and the membrane performance test results. 2540 NH is selected as the first-stage nanofiltration membrane assembly of the process, and BW 2540 is selected as the second-stage reverse osmosis membrane assembly of the process. One reverse osmosis membrane and two nanofiltration membranes are calculated according to the reverse osmosis water production. According to the process flow, the membrane assembly is arranged in such a way that the first-stage nanofiltration membrane is connected in parallel and then the second-stage reverse osmosis membrane is connected in series.

[0047] Preferably, the high pressure pump has a maximum flow rate of 2 m 3 / h, head 18 m, power 0.25 kW, stop valve can adjust the water flow. According to the overall system pressure required to be less than 1.5 MPa, the flow rate is selected as 2 m 3 / h, 100 m head high-pressure pump 2, with a power of 1.5 kW, can effectively reduce energy consumption.

[0048] Specifically, according to the flow rate 2 m 3 / h precision filter is made of stainless steel 10 inches 5 cores, the filtration accuracy is 5 μm.

[0049] Specifically, based on the membrane performance test results and process selection calculations, the system can prepare direct drinking water through a complete process of desalination and conditioning of high-salinity brackish water at a low pressure of less than 1.5 MPa. When selecting the device, lower-power high-pressure pumps can be considered, as well as the installation of engineering plastic pipes to prevent corrosion while reducing material and installation costs.

[0050] Preferably, the structure of the brackish water membrane desalination and water quality control device reasonably utilizes the sizes of the quartz sand filter, precision filter, membrane assembly and water production tank, and reasonably arranges and installs the engineering plastic pipes, and utilizes the water inlet pump and high-pressure pump to increase the height of the water production tank, so that the drinking water produced by the device can be directly discharged through the pipe.

[0051] Specifically, the brackish water membrane desalination and water quality control device is equipped with a metal shell to protect internal components and isolate noise, while ensuring that there is enough space inside to solve the heat dissipation problem under long-term operation. An outward-opening door is installed on the side to facilitate debugging or maintenance and overhaul of the components.

[0052] Specifically, the panel of the shell of the brackish water membrane desalination and water quality control device is connected to the electrical control box system, which monitors the operation status of each component in the device and the water quality of direct drinking water online. The device can be switched to automatic or manual control operation state, and is equipped with corresponding emergency stop buttons, pumps and related component switch buttons to deal with emergencies.

[0053] Specifically, the brackish water membrane desalination and water quality control device is equipped with an electric control box system, which has functions such as monitoring, alarm, and automatic shutdown, and the automatic control part can be converted to manual control. The electric control box system can realize functions such as pump start and stop, membrane component cleaning, and automatic dosing and conditioning of desalinated water. For the convenience of use and management, the electric control box system of the device is programmed with automatic control and management functions. Embodiment 1

[0054] This example tests the effects of operating pressure and influent concentration on the flux, TDS retention rate, and retention rates of different ions of the nanofiltration membrane. Figure 3 , Figure 4 and Figure 5 As shown, nanofiltration membranes can achieve higher membrane flux under low pressure, can effectively intercept divalent ions, and can pass monovalent ions. Under different operating conditions, the three nanofiltration membranes can show large differences in desalination performance. The experiment uses circulating water inlet, and explores the desalination performance (membrane flux, TDS retention rate, characteristic ion retention rate) of nanofiltration membranes by changing the operating pressure, inlet TDS concentration, temperature, and membrane type.

[0055] Nanofiltration membrane desalination performance test, such as Figure 3 As shown in the figure, the membrane flux increases with the increase of inlet water pressure and the decrease of inlet water TDS concentration. Figure 4 As shown in the figure, the TDS retention rate increases with the increase of inlet pressure and the decrease of inlet TDS concentration. Figure 5 As shown, nanofiltration membrane has a great influence on SO4 2– The maximum interception rate, Mg 2+ , Ca 2+ Next, Cl – and Na +The retention rate of divalent ions is significantly lower than that of divalent ions. DK2540 has the best TDS retention rate and ion retention rate, with a retention rate of divalent ions as high as 98.7%, but the membrane flux is low and the cost is higher. The TDS retention rates of 2540NH and VNF1 reached 62.0% and 60.3%, and the divalent ion retention rates were 98.3% and 96.5%, respectively. When the influent TDS concentration increased to 10 g / L, the TDS retention rates of 2540NH and VNF1 decreased by 13.0% and 12.5%, but both maintained high membrane flux and divalent ion retention rates. Considering the membrane flux, TDS retention rate and divalent ion retention rate of the nanofiltration membrane, and the fact that too high operating pressure will cause increased costs, the nanofiltration was selected to operate at 1.1 MPa to 1.2 MPa. Embodiment 2

[0056] This example tests the effects of operating pressure and influent concentration on reverse osmosis membranes. Figure 6 As shown, at a water inlet flow rate of 1 m 3 / h, influent TDS concentration 2.3 ~ 5.1 g / L, room temperature test, adjust the operating pressure 1.0 ~ 1.5 MPa, BW2540 reverse osmosis membrane TDS retention rate and product water TDS content changes with the operating pressure as shown in the figure Figure 6 As shown. When the inlet concentration increased from 2.3 g / L to 5.1 g / L, the TDS retention rate decreased from 99.00%~99.39% to 98.56%~99.04% and 98.25%~98.93%, respectively. The TDS retention rate changed slightly with the inlet pressure and was generally high. When the inlet water was 2.3 g / L, the final water production concentration of the reverse osmosis membrane was always lower than 30 mg / L; as the inlet water concentration increased to 5.1 g / L, the optimal water production concentrations of BW2540 at an inlet pressure of 1.5 MPa were 34 mg / L and 55 mg / L, respectively, which were far lower than the TDS concentration index of GB 5749-2022. Taking all factors into consideration, the reverse osmosis was selected to operate under the conditions of 1.2 MPa to 1.5 MPa.

[0057] In summary, the technical solution of the present application achieves at least the following technical effects: the process can adapt to and process influent water quality with high salt content, complex composition, high hardness ion content, large fluctuation of water volume, etc., and the membrane components are not easy to scale under long-term operation; the produced direct drinking water can meet the relevant requirements of the "Sanitary Standard for Drinking Water" (GB5749-2006) and the "Sanitary Standard for Mineralization of Low-Mineralized Drinking Water" (GJB1335-92), including pH greater than 7.0, TDS and hardness not exceeding the corresponding appropriate values ​​(1000 mg / L and 200 mg / L); the device can realize multiple functions such as water production, shutdown, cleaning, online monitoring, protection, automatic operation and manual switching. The electronic control system of the device is equipped with relevant programs designed according to the results of the desalinated water conditioning test. It can analyze the actual desalinated water quality, add the type and dosage of conditioning agent, produce direct drinking water with excellent health and stability, and provide a high-quality drinking water supply solution for areas lacking fresh water.

Claims

1. A brackish water membrane desalination and water quality control process, characterized in that: Includes filtration, nanofiltration-reverse osmosis desalination, conditioning and disinfection process steps; The brackish water is first pre-treated by filtration, which includes quartz sand filtration and precision filtration to obtain pre-treated effluent water with suspended matter and particulate matter removed; The pre-treated water is subjected to nanofiltration-reverse osmosis desalination treatment, wherein the nanofiltration preliminarily removes divalent ions, and then reverse osmosis is used for deep desalination to obtain desalinated water; The desalinated water is subjected to conditioning treatment to obtain mineralized water; The mineralized water is disinfected to obtain direct drinking water, so that the direct drinking water is safe and healthy.

2. The brackish water membrane desalination and water quality control process according to claim 1, characterized in that: The salt content of the brackish water is 6-10 g / L.

3. The brackish water membrane desalination and water quality control process according to claim 1, characterized in that: The nanofiltration and reverse osmosis of the nanofiltration-reverse osmosis desalination are operated at a pressure not higher than 1.5 MPa, the nanofiltration is operated at a pressure of 1.1-1.2 MPa, and the reverse osmosis is operated at a pressure of 1.2-1.5 MPa.

4. The brackish water membrane desalination and water quality control process according to claim 1, characterized in that: The conditioning adopts reagent conditioning, and the reagent and the dosage of the reagent are: the dosage of CaCl2 is 40-50 mg / L, the dosage of MgCl2 is 20 mg / L, the total dosage of NaHCO3 and KHCO3 is 60-80 mg / L, and the molar ratio of the dosage of NaHCO3 and KHCO3 is 1:

1.

5. A brackish water membrane desalination and water quality control device, characterized in that: The invention comprises, in order of water flow direction, a water inlet (1), a water inlet valve (2), a quartz sand filter (4), a precision filter (5), a high-pressure pump (6), a nanofiltration membrane assembly (71), a nanofiltration membrane assembly (72), a high-pressure pump (8), a reverse osmosis membrane (9), a UV sterilizer (10), a dosing box (11), a water production box (12) and a water outlet (13); a water inlet pump (3) is provided between the water inlet (1) and the quartz sand filter (4); the precision filter (5) and A high-pressure pump 1 (6) is provided between the nanofiltration membrane components (7) to provide nanofiltration pressure; a high-pressure pump 2 (8) is provided between the nanofiltration membrane components (7) and the reverse osmosis membrane (9) to provide the pressure required for reverse osmosis; a nanofiltration membrane is provided inside the nanofiltration membrane components (7) for pre-desalination; the reverse osmosis membrane (9) performs deep desalination; the water production tank (12) is provided with a monitoring instrument to detect the quality of the effluent water; the nanofiltration membrane (7) and the reverse osmosis membrane (9) are provided with a concentrated water pipeline to discharge unqualified water and provide a portion of reflux water.

6. The brackish water membrane desalination and water quality control device according to claim 5, characterized in that: When the salt content of brackish water is lower than 6 g / L, the nanofiltration membrane assembly 1 (71), the nanofiltration membrane assembly 2 (72) and the reverse osmosis membrane (9) can all be adjusted by valves to reflux concentrated water and reduce concentrated water discharge, thereby improving the water production recovery rate.

7. The brackish water membrane desalination and water quality control device according to claim 5, characterized in that: The device is equipped with an electric control box system with monitoring, alarm and automatic shutdown functions, and can realize pump start and stop, membrane component cleaning, and automatic dosing and conditioning of desalinated water. The automatic control part can be converted to manual control.

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