A high-hardness strontium-containing natural mineral water purification system

Abstract

A purification system for high-hardness strontium-containing natural mineral water relates to the field of water treatment technology. The invention comprises a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, a blending and adjustment unit, and an ozone ultraviolet disinfection unit connected sequentially along the water flow direction. The pretreatment unit removes suspended solids and colloidal particles from the raw water; the ultrafiltration unit retains beneficial minerals such as strontium; the nanofiltration unit efficiently retains calcium and magnesium ions to reduce hardness; the blending and adjustment unit automatically adjusts the ratio of ultrafiltration to nanofiltration permeate through an online strontium content detector and a flow control valve, precisely controlling the strontium content in the finished product water; and the ozone ultraviolet disinfection unit ensures microbial safety. This invention effectively reduces the hardness of raw water, prevents sedimentation, and stably controls the strontium content within the standard range, maintaining the mineral balance and good taste of the finished water. It is suitable for the large-scale, stable production of high-hardness strontium-containing natural mineral water.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a high-hardness strontium-containing natural mineral water purification system. Background Technology

[0002] Natural mineral water is favored by consumers for its beneficial mineral content. Strontium-containing mineral water, in particular, is gaining increasing demand in the mother and baby water market due to the beneficial effects of strontium on bone development and cardiovascular health. However, natural mineral water sources generally suffer from high hardness, primarily manifested in excessive calcium and magnesium ion content. This leads to the formation of white sediment during bottling, storage, and transportation, severely impacting product appearance and consumer acceptance. Traditional treatment methods, such as reverse osmosis and nanofiltration, effectively remove hardness, but also retain over 90% of beneficial elements like strontium, making it difficult to meet the national food safety standard for drinking natural mineral water (GB 8537-2018) requirement of ≥0.20 mg / L.

[0003] Existing technologies also employ simple nanofiltration treatment, but these systems mostly use a single membrane treatment unit, such as CN104843898A, a high-strontium natural mineral water purification system. This system cannot flexibly adjust the mineral ratio in the product water according to fluctuations in the raw water quality, resulting in poor product quality stability. The product may have a "soft" taste lacking natural mineral flavor, or a "hard" taste that is too bitter and salty, failing to meet the requirements for a balanced hardness and taste in the finished water. Therefore, developing a mineral water purification system that can effectively reduce the hardness of raw water and prevent sedimentation, accurately control the strontium content in the finished water, maintain a good mineral balance, and possess reliable microbial viability has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] This invention addresses the problem that existing technologies struggle to simultaneously and effectively reduce the hardness of raw water and prevent sedimentation while precisely controlling the strontium content and maintaining a good mineral balance in the finished product when processing strontium-containing natural mineral water. Therefore, this invention proposes a high-hardness strontium-containing natural mineral water purification system.

[0005] The technical solution adopted by the present invention to solve the above problems is as follows: This invention provides a high-hardness strontium-containing natural mineral water purification system, comprising a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, a blending and regulating unit, and a disinfection unit connected sequentially along the water flow direction. The pretreatment unit includes a quartz sand filter and an activated carbon filter. The inlet of the quartz sand filter is connected to the raw water pipeline, and the outlet is connected to the inlet of the activated carbon filter. The activated carbon filter outputs water in two paths: the first path is connected to the inlet of the ultrafiltration unit, and the second path is connected to the inlet of the nanofiltration unit. The outlet of the ultrafiltration unit is connected to the first inlet of the blending and regulating unit. The outlet of the nanofiltration unit is connected to the second inlet of the blending and regulating unit. The inlet of the disinfection unit is connected to the outlet of the blending and regulating unit.

[0006] Furthermore, the mixing and regulating unit includes a mixer, a first flow regulating valve, a second flow regulating valve, and an online strontium content detector. The inlet of the mixer is connected to the outlets of the ultrafiltration unit and the nanofiltration unit, respectively; its outlet is connected to the inlet of the disinfection unit; the first flow regulating valve is installed on the outlet pipeline of the ultrafiltration unit; the second flow regulating valve is installed on the outlet pipeline of the nanofiltration unit; and the online strontium content detector is installed on the outlet pipeline of the mixer.

[0007] Furthermore, the ultrafiltration unit adopts a hollow fiber ultrafiltration membrane module with a membrane pore size of 0.01-0.1 micrometers; the nanofiltration unit adopts a nanofiltration membrane module with a divalent ion rejection rate of ≥85% and an operating pressure of 0.8-1.0 MPa.

[0008] Furthermore, the disinfection unit includes an ultraviolet disinfection unit and an ozone disinfection unit. The ultraviolet disinfection unit includes at least one set of ultraviolet sterilizers, the ultraviolet lamps emit wavelengths of 254 nm, and the ultraviolet dose is not less than 40 mJ / cm². The ozone disinfection unit includes an ozone generator and a gas-liquid mixing device, the ozone dosage is 0.3-0.5 mg / L, and the contact time is not less than 5 minutes.

[0009] Furthermore, the system also includes a PLC automatic control system, which is electrically connected to the first flow regulating valve, the second flow regulating valve, and the online strontium content detector. When the online strontium content detector detects that the strontium concentration in the finished water is below 0.25 mg / L, the PLC automatic control system controls the opening of the first flow regulating valve to increase; when the strontium concentration in the finished water is above 0.60 mg / L, it controls the opening of the first flow regulating valve to decrease; when the strontium concentration in the finished water is detected to be below 0.25 mg / L and the opening of the first flow regulating valve is at its maximum, it controls the opening of the second flow regulating valve to decrease.

[0010] Furthermore, an intermediate water tank and a booster pump are provided between the ultrafiltration unit and the nanofiltration unit.

[0011] Furthermore, both the ultrafiltration unit and the nanofiltration unit are equipped with an online cleaning device, which includes a cleaning water tank, a cleaning pump, and a set of control valves.

[0012] Furthermore, a static mixer is provided between the ozone disinfection unit and the ultraviolet disinfection unit.

[0013] Furthermore, an online ozone detector is installed on the outlet pipe of the disinfection unit to monitor the residual ozone concentration in the finished water in real time, ensuring that the residual ozone concentration is below 0.01 mg / L.

[0014] Furthermore, the system also includes a finished water tank, the inlet of which is connected to the outlet of the disinfection unit, and a breathing filter is installed on the top of the finished water tank.

[0015] The beneficial effects of this invention are: 1. This invention retains more than 90% of the strontium element in the raw water through an ultrafiltration unit, while effectively reducing the total hardness of the water by using a nanofiltration membrane with a rejection rate of more than 80% for calcium and magnesium ions. Then, the two types of product water are mixed in proportion through a blending and adjustment unit, so that the strontium content of the finished water is stably controlled within a suitable range of 0.20-0.50 mg / L, and the total hardness is reduced to below 50 mg / L. This not only meets the national standard for strontium-type mineral water, but also completely solves the problem of precipitation caused by long-term storage of the product.

[0016] 2. This invention establishes a closed-loop automatic control circuit between an online strontium content detector and a flow regulating valve. When the raw water quality fluctuates, the mixing ratio of ultrafiltration permeate and nanofiltration permeate is adjusted to ensure that the strontium content of the finished water remains within the set range, thus overcoming the poor adaptability of traditional fixed-ratio mixing processes.

[0017] 3. The finished water of this invention has a reasonable ratio of divalent ions such as calcium, magnesium, and strontium. At the same time, the effective retention of sulfate ions by the nanofiltration unit further eliminates the astringent taste that may exist in the raw water, giving the water a natural "fullness" and a slightly sweet taste. This avoids the problem of the monotonous and bland taste of reverse osmosis pure water, and is especially suitable for consumers' demand for "soft and natural" drinking water.

[0018] 4. By coupling an ultrafiltration system and a nanofiltration system, this invention overcomes the problems of low water production by nanofiltration membranes and high water hardness by ultrafiltration membranes in the traditional production of strontium-containing mineral water, resulting in higher overall economic efficiency. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the natural mineral water purification system described in this invention; Figure 2 This is a pipeline layout diagram of the natural mineral water purification system described in this invention.

[0020] In the diagram: 1-Pretreatment unit; 2-Ultrafiltration unit; 3-Nanofiltration unit; 4-Blending and regulating unit; 5-Disinfection unit; 6-Intermediate water tank; 7-Booster pump; 8-Cleaning water tank; 9-Cleaning pump; 10-Finished water tank; 11-Quartz sand filter; 12-Activated carbon filter; 41-Mixer; 42-First flow regulating valve; 43-Second flow regulating valve; 44-Online strontium content detector; 51-Ultraviolet sterilizer; 52-Ozone generator; 53-Gas-liquid mixing device. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0023] This embodiment provides a high-hardness strontium-containing natural mineral water purification system, including a pretreatment unit 1, an ultrafiltration unit 2, a nanofiltration unit 3, a blending and adjustment unit 4, and a disinfection unit 5 connected sequentially along the water flow direction.

[0024] The pretreatment unit includes a quartz sand filter 11 and an activated carbon filter 12. The inlet of the quartz sand filter 11 is connected to the raw water pipeline, and the outlet is connected to the inlet of the activated carbon filter 12. It is used to remove suspended solids, colloidal particles, and other pollutants from the raw water and protect the subsequent membrane modules. Its product water is output in two paths: the first path is directly connected to the inlet of the ultrafiltration unit 2, and the second path is connected to the inlet of the nanofiltration unit 3.

[0025] The inlet of the ultrafiltration unit is connected to the first outlet of the activated carbon filter 12. The ultrafiltration unit 2 adopts a hollow fiber ultrafiltration membrane module with a membrane pore size of 0.01-0.1 micrometers. It is used to intercept bacteria, viruses and macromolecular organic matter in the water, while allowing dissolved ions to pass through. Its product water outlet is connected to the first inlet of the mixing and adjustment unit.

[0026] The inlet of the nanofiltration unit 3 is connected to the second outlet of the activated carbon filter 12. The nanofiltration unit 3 uses a nanofiltration membrane module with a divalent ion rejection rate of ≥85%. The nanofiltration membrane is a polyamide composite nanofiltration membrane with an operating pressure of 0.8-1.0 MPa. It is used to selectively reject calcium, magnesium and sulfate ions in the water to reduce the total hardness of the water. Its product water outlet is connected to the second inlet of the mixing and regulating unit 4.

[0027] The mixing and adjustment unit 4 includes a mixer 41, a first flow regulating valve 42 installed on the outlet water pipeline of the ultrafiltration unit, a second flow regulating valve 43 installed on the outlet water pipeline of the nanofiltration unit, and an online strontium content detector 44 installed on the outlet pipeline of the mixer. The first flow regulating valve 42 and the second flow regulating valve 43 are respectively signal-interlocked with the online strontium content detector 44 to automatically adjust the mixing ratio of ultrafiltration permeate and nanofiltration permeate according to the online detected strontium content of the finished water.

[0028] The inlet of the disinfection unit 5 is connected to the outlet of the mixing and regulating unit 4. The disinfection unit 5 includes an ultraviolet disinfection unit and an ozone disinfection unit. The ultraviolet disinfection unit includes at least one set of ultraviolet sterilizers 51, with ultraviolet lamps emitting a wavelength of 254 nm and an ultraviolet dose of not less than 40 mJ / cm², used to further inactivate residual microorganisms in the water and decompose residual ozone, ensuring the microbial safety of the finished water. The ozone disinfection unit includes an ozone generator 52 and a gas-liquid mixing device 53, used to add ozone to the water for primary disinfection, with an ozone dosage of 0.3-0.5 mg / L and a contact time of not less than 5 minutes.

[0029] Preferably, the system further includes a PLC automatic control system, which is electrically connected to the first flow regulating valve 42, the second flow regulating valve 43, and the online strontium content detector 44. When the online strontium content detector 44 detects that the strontium concentration in the finished water is below 0.25 mg / L, the PLC automatic control system controls the opening of the first flow regulating valve 42 to increase; when the strontium concentration in the finished water is above 0.60 mg / L, it controls the opening of the first flow regulating valve 42 to decrease; when the strontium concentration in the finished water is detected to be below 0.25 mg / L and the opening of the first flow regulating valve 42 is at its maximum, it controls the opening of the second flow regulating valve 43 to decrease.

[0030] Preferably, an intermediate water tank 6 and a booster pump 7 are provided between the ultrafiltration unit 2 and the nanofiltration unit 3 to stabilize the inlet water pressure of the ultrafiltration and nanofiltration units.

[0031] Preferably, the concentrate outlet of the nanofiltration unit 3 is connected to the raw water recovery pipeline. The nanofiltration concentrate is returned to the front end of the quartz sand filter, mixed with the raw water, and then re-enters the system for treatment. The total system recovery rate is ≥85%.

[0032] Preferably, both the ultrafiltration unit 2 and the nanofiltration unit 3 are equipped with an online cleaning device, which includes a cleaning water tank 8, a cleaning pump 9 and a set of control valves for periodic chemical cleaning of the membrane modules.

[0033] Preferably, the disinfection unit 5 is further provided with a static mixer to enhance the mixing effect of ozone and water.

[0034] Preferably, the system further includes a finished water tank 10, the inlet of which is connected to the outlet of the disinfection unit 5, and a breathing filter is provided on the top of the finished water tank to prevent external microbial contamination.

[0035] Example: This embodiment uses natural mineral water sourced from the Northeast King Mineral Water Plant in Shuangyashan City, Heilongjiang Province. The raw water quality was tested as follows: pH 7.6, turbidity 15.4 NTU, calcium content 33.79 mg / L, magnesium content 15.94 mg / L, strontium content 0.95 mg / L, total conductivity 590 μS / cm, and total dissolved solids (TDS) 295 mg / L. While the strontium content meets the requirements for strontium-type mineral water, the total hardness and turbidity are too high, necessitating purification treatment.

[0036] The raw water was sequentially fed into pretreatment unit 1. Pretreatment unit 1 includes a quartz sand filter 11 and an activated carbon filter 12. The filtration rate of the quartz sand filter 11 was controlled at 8-10 m / h, and the activated carbon filter 12 used coconut shell activated carbon with an iodine value of not less than 900 mg / g, with an empty bed contact time of not less than 10 minutes. The effluent quality after pretreatment was as follows: pH value 7.44, turbidity reduced to 0.736 NTU, removal rate 95.22%; calcium content reduced to 27.71 mg / L, removal rate 17.99%; magnesium content reduced to 15.13 mg / L, removal rate 5.08%; strontium content reduced to 0.794 mg / L, removal rate 16.42%; TDS reduced to 193.5 mg / L, removal rate 34.40%. Pretreatment unit 1 effectively removed suspended solids and some non-dissolved minerals from the raw water, providing good influent conditions for subsequent membrane treatment.

[0037] The pretreated effluent is output in two streams: the first stream enters ultrafiltration unit 2 at a flow rate of 200 L / h; the second stream enters nanofiltration unit 3 at a flow rate of 800 L / h (total treated water volume 1000 L / h, with ultrafiltration permeate accounting for 20% and nanofiltration permeate accounting for 80%). The ultrafiltration unit uses hollow fiber ultrafiltration membrane modules with a molecular weight cutoff of 150 kDa, operating at a pressure of 0.1-0.2 MPa, and membrane flux controlled at 50-80 L / (m²·h). After ultrafiltration treatment, the effluent turbidity is further reduced to 0.49 NTU, with a removal rate of 33.42%; calcium content is 22.1 mg / L, with a removal rate of 20.24%; magnesium content is 12.26 mg / L, with a removal rate of 18.96%; strontium content is 0.783 mg / L, with a removal rate of only 1.38% and a retention rate as high as 98.62%; TDS is reduced to 189.7 mg / L, with a removal rate of 1.96%. The results showed that ultrafiltration unit 2 effectively retained microorganisms and fine colloids while almost completely retaining dissolved beneficial minerals such as strontium, calcium, and magnesium.

[0038] Nanofiltration unit 3 uses a polyamide composite nanofiltration membrane module, operating at a pressure of 0.85 MPa, with a system recovery rate of 85%. The effluent quality after nanofiltration treatment is as follows: pH 7.66, turbidity 0.171 NTU (removal rate 76.77%), calcium content 5.347 mg / L (removal rate 80.70%), magnesium content 2.157 mg / L (removal rate 85.74%), strontium content 0.127 mg / L (removal rate 84.01%), and TDS reduced to 40.7 mg / L (removal rate 78.97%). The nanofiltration unit exhibits a high retention capacity of over 80% for divalent ions such as calcium, magnesium, and strontium, resulting in a significant reduction in effluent hardness.

[0039] Ultrafiltration permeate (125 L / h, Strontium 0.783 mg / L) and nanofiltration permeate (500 L / h, Strontium 0.127 mg / L) are fed into the mixer 41 of the blending and conditioning unit 4 and mixed uniformly at a ratio of ultrafiltration permeate:nanofiltration permeate = 1:4 (volume ratio). The permeate from the blending and conditioning unit 4 then enters the finished water tank 10 via the disinfection unit 5.

[0040] The finished water was tested with an online strontium content analyzer and found to have a strontium content of 0.258 mg / L, which meets the requirement of ≥0.20 mg / L for strontium in GB 8537-2018. At the same time, the finished water had a calcium content of 8.70 mg / L, a magnesium content of 4.18 mg / L, and a total hardness of approximately 39 mg / L (calculated as CaCO3). It had a mellow and slightly sweet taste, and after a 60-day storage test, no white precipitate or turbidity was observed.

[0041] When fluctuations in raw water quality cause the strontium content in the finished water to drop to 0.25 mg / L, the online strontium content detector feeds the signal back to the PLC automatic control system. The system automatically adjusts the opening of the first flow regulating valve 42 from 20% to 25%, increasing the proportion of ultrafiltration permeate flow to 25% and reducing the proportion of nanofiltration permeate flow to 75%. At this point, the strontium content in the finished water recovers to 0.273 mg / L, still meeting the standard. Meanwhile, the calcium and magnesium ion contents are 9.12 mg / L and 4.54 mg / L, respectively, and the total hardness is approximately 41.5 mg / L (calculated as CaCO3).

[0042] The above embodiments demonstrate that the purification system provided by the present invention can effectively reduce the hardness of raw water and prevent sedimentation, while accurately controlling the strontium content in the finished product water and maintaining excellent mineral balance and taste quality. It is particularly suitable for the large-scale and stable production of high-hardness strontium-containing natural mineral water.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A high-hardness strontium-containing natural mineral water purification system, characterized in that: The system includes a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, a mixing and adjustment unit, and a disinfection unit connected sequentially along the water flow direction; The pretreatment unit includes a quartz sand filter and an activated carbon filter. The inlet of the quartz sand filter is connected to the raw water pipeline, and the outlet is connected to the inlet of the activated carbon filter. The water produced by the activated carbon filter is output in two ways: the first way is connected to the inlet of the ultrafiltration unit, and the second way is connected to the inlet of the nanofiltration unit. The product water outlet of the ultrafiltration unit is connected to the first inlet of the mixing and regulating unit; The product water outlet of the nanofiltration unit is connected to the second inlet of the blending and regulating unit; The inlet of the disinfection unit is connected to the outlet of the mixing and regulating unit.

2. The high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The blending and regulating unit includes a mixer, a first flow regulating valve, a second flow regulating valve, and an online strontium content detector. The inlet of the mixer is connected to the outlet of the ultrafiltration unit and the nanofiltration unit respectively; its outlet is connected to the inlet of the disinfection unit. The first flow regulating valve is installed on the outlet pipe of the ultrafiltration unit; The second flow regulating valve is installed on the outlet pipe of the nanofiltration unit; The online strontium content detector is installed on the mixer outlet pipeline.

3. The high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The ultrafiltration unit uses a hollow fiber ultrafiltration membrane module with a membrane pore size of 0.01-0.1 micrometers; the nanofiltration unit uses a nanofiltration membrane module with a divalent ion rejection rate of ≥85% and an operating pressure of 0.8-1.0 MPa.

4. The high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The disinfection unit includes an ultraviolet disinfection unit and an ozone disinfection unit. The ultraviolet disinfection unit includes at least one set of ultraviolet sterilizers, the ultraviolet lamps emit wavelengths of 254 nm, and the ultraviolet dose is not less than 40 mJ / cm². The ozone disinfection unit includes an ozone generator and a gas-liquid mixing device, the ozone dosage is 0.3-0.5 mg / L, and the contact time is not less than 5 minutes.

5. A high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The system also includes a PLC automatic control system, which is electrically connected to the first flow regulating valve, the second flow regulating valve, and the online strontium content detector. When the online strontium content detector detects that the strontium concentration in the finished water is below 0.25 mg / L, the PLC automatic control system controls the opening of the first flow regulating valve to increase; when the strontium concentration in the finished water is above 0.60 mg / L, it controls the opening of the first flow regulating valve to decrease; when the strontium concentration in the finished water is detected to be below 0.25 mg / L and the opening of the first flow regulating valve is at its maximum, it controls the opening of the second flow regulating valve to decrease.

6. The high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: An intermediate water tank and a booster pump are also provided between the ultrafiltration unit and the nanofiltration unit.

7. The high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: Both the ultrafiltration unit and the nanofiltration unit are equipped with an online cleaning device, which includes a cleaning water tank, a cleaning pump, and a set of control valves.

8. A high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: A static mixer is also provided between the ozone disinfection unit and the ultraviolet disinfection unit.

9. A high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The disinfection unit is also equipped with an online ozone detector on its outlet pipe, which is used to monitor the residual ozone concentration in the finished water in real time and keep the residual ozone concentration below 0.01 mg / L.

10. A high-hardness strontium-containing natural mineral water purification system according to claim 1, characterized in that: The system also includes a finished water tank, the inlet of which is connected to the outlet of the disinfection unit, and a breathing filter is installed on the top of the finished water tank.

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