A seawater desalination pretreatment filtration system

Abstract

This utility model discloses a seawater desalination pretreatment filtration system, belonging to the field of seawater desalination. It includes a chemical dosing mixer, a modified fiber filter, a coarse sand filter, a fine sand filter, and a product water tank. The outlet of the chemical dosing mixer is connected to the inlet of the modified fiber filter, the outlet of the modified fiber filter is connected to the inlets of the coarse and fine sand filters, and the outlet of the coarse sand filter is connected to the inlet of the fine sand filter. By setting up a filtration system consisting of a chemical dosing mixer, a modified fiber filter, a coarse sand filter, and a fine sand filter, and utilizing the characteristics of modified polypropylene and quartz sand filter media of different particle sizes, combined with the flexible two- or three-stage filtration based on water quality indicators such as seawater turbidity, SDI15, and TOC, and the addition of coagulants when necessary, this system solves the problems of poor treatment effect, high energy consumption, and high investment and operating costs of traditional seawater desalination pretreatment processes, achieving stable effluent quality and reduced costs.

Description

Technical Field

[0001] This utility model belongs to the field of seawater desalination technology, specifically relating to a seawater desalination pretreatment filtration system. Background Technology

[0002] Membrane-based seawater desalination is an energy-intensive process, and reducing energy consumption has always been a key research focus for seawater desalination systems. Pretreatment not only reduces impurities and dissolved substances in seawater, but also, by selecting appropriate pretreatment processes, can specifically remove harmful substances, protect desalination equipment and reverse osmosis membrane materials, reduce system energy consumption, and extend system lifespan, which is of great significance.

[0003] The quality of seawater in my country's coastal waters varies due to geographical location. The turbidity of seawater differs significantly in different sea areas, influenced by surface currents flowing into the sea, tides, and algae, or both. The water quality varies considerably between different locations and at different times within the same location, placing high demands on the pretreatment facilities for seawater desalination. To adapt to this situation and ensure the stability of the water supply quality, complex treatment processes are often implemented, requiring high energy consumption to achieve this goal.

[0004] Currently, the pretreatment processes for seawater desalination projects in China mainly consist of three combined processes: coagulation sedimentation, dissolved air flotation (DAF), and ultrafiltration (microfiltration). While coagulation sedimentation is simple and requires little space, its treatment effect is relatively poor. Dissolved air flotation has high separation efficiency but high energy consumption and construction costs. Ultrafiltration produces good water quality but suffers from high investment, high operating costs, and the need for regular membrane replacement. Moreover, the equipment in these three combined processes cannot be substituted for each other, resulting in a technical bottleneck that prevents dynamic process adjustments based on seawater turbidity (e.g., different ranges such as 5-50 NTU, >50 NTU, etc.). This leads to excessive energy waste in low-turbidity sea areas and the risk of insufficient pollutant retention in medium- and high-turbidity sea areas, making it difficult to adapt to the complex and variable seawater quality conditions in my country's coastal waters, and significantly limiting the applicability of these processes. Utility Model Content

[0005] The purpose of this invention is to provide a seawater desalination pretreatment filtration system to solve the problems of poor treatment effect, high energy consumption or cost, and inability to dynamically adjust according to the turbidity of seawater in different sea areas (5-50 NTU, >50 NTU) in existing domestic seawater desalination project pretreatment processes (coagulation sedimentation, dissolved air flotation, ultrafiltration).

[0006] To achieve the above objectives, this utility model provides the following technical solution: a seawater desalination pretreatment filtration system, comprising a chemical dosing mixer, a modified fiber filter, a coarse sand filter, a fine sand filter, and a product water tank;

[0007] The outlet of the dosing mixer is connected to the inlet of the modified fiber filter, the outlet of the modified fiber filter is connected to the inlet of the coarse sand filter and the fine sand filter, the outlet of the coarse sand filter is connected to the inlet of the fine sand filter, and the outlet of the fine sand filter is connected to the inlet of the product water tank.

[0008] The seawater desalination pretreatment filtration system has two operating modes.

[0009] Furthermore, the outlet of the water production tank is connected to the bottom of the modified filter, the bottom of the coarse sand filter, and the bottom of the fine sand filter via a backwash water pump.

[0010] Furthermore, a Roots blower is provided on one side of the modified fiber filter.

[0011] Furthermore, the modified fiber filter uses modified polypropylene as the filter media.

[0012] Furthermore, the coarse sand filter uses 1-2mm quartz sand as the filter media.

[0013] Furthermore, the fine sand filter uses 0.4-0.6mm quartz sand as the filter media.

[0014] Furthermore, the seawater desalination pretreatment filtration system operates in two-stage or three-stage filtration modes.

[0015] Furthermore, the secondary filtration employs a modified fiber filter and a fine sand filter in sequence.

[0016] Furthermore, the three-stage filtration process employs a modified fiber filter, a coarse sand filter, and a fine sand filter in sequence.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] This seawater desalination pretreatment filtration system consists of a chemical mixing unit, a modified fiber filter, a coarse sand filter, and a fine sand filter. Utilizing the characteristics of modified polypropylene and quartz sand filter media of different particle sizes, and combining this with the ability to flexibly switch between two or three stages of filtration based on water quality indicators such as seawater turbidity, SDI15, and TOC, and to add coagulants when necessary, it solves the problems of poor treatment effect, high energy consumption, and high investment and operating costs of traditional seawater desalination pretreatment processes. It achieves stable effluent quality and reduced costs. Attached Figure Description

[0019] Figure 1 Schematic diagram of a seawater desalination pretreatment filtration system;

[0020] Figure 2 This is a schematic diagram of a two-stage filtration system consisting of a modified filter and a fine sand filter.

[0021] Figure 3 This is a schematic diagram of a three-stage filtration system.

[0022] In the diagram: 1. Chemical dosing mixer; 2. Modified filter; 3. Coarse sand filter; 4. Fine sand filter; 5. Product water tank; 6. Backwash water pump; 7. Roots blower. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments.

[0024] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0025] Please see Figure 1-3 This utility model provides a seawater desalination pretreatment filtration system, including a chemical mixing unit 1, a modified filter 2, a coarse sand filter 3, a fine sand filter 4, and a product water tank 5.

[0026] The outlet of the dosing mixer 1 is connected to the inlet of the modified filter 2 through a pipe and a valve. The outlet of the modified filter 2 is connected to the inlet of the coarse sand filter 3 and the fine sand filter 4. The outlet of the coarse sand filter 3 is connected to the inlet of the fine sand filter 4 through a pipe and a valve. The outlet of the fine sand filter 4 is connected to the inlet of the product water tank 5 through a pipe and a valve.

[0027] The outlet of the water production tank 5 is connected to the bottom of the modified filter 2, the bottom of the coarse sand filter 3, and the bottom of the fine sand filter 4 via the backwash water pump 6.

[0028] A Roots blower 7 is installed on one side of the modified filter 2.

[0029] Dosing mixer 1: Add sodium hypochlorite bactericide at the inlet end. Utilize the chemical properties of the bactericide to remove organic matter in the water, creating more favorable conditions for subsequent filtration treatment and reducing the risk of organic matter contamination to subsequent filtration equipment and reverse osmosis membranes.

[0030] Modified fiber filter 2: Utilizing modified polypropylene as the filter media, this material features low density, high strength, good hydrophobicity, and strong resistance to biofouling. It also exhibits excellent resistance to seawater corrosion, hydrolysis, and long-term stability. Its extremely large specific surface area and porosity effectively adsorb and trap suspended particles in seawater, fully leveraging the deep-layer interception capacity of the filter media. When the filter surface is covered by particle accumulation to form a filter cake layer, the interception efficiency for fine particles can be further improved, typically achieving a filtration accuracy of 1-2 μm.

[0031] Coarse sand filter 3: Uses 1-2mm quartz sand as filter media, mainly for further filtration of seawater after preliminary filtration by modified fiber filters. The larger particle size of the quartz sand filter media can intercept and remove larger suspended solids and impurities in seawater, further reducing the turbidity of seawater and providing better influent for subsequent fine sand filtration.

[0032] Fine sand filter 4: Uses 0.4-0.6mm quartz sand as filter media for finer filtration of seawater. The smaller particle size of the quartz sand filter media can trap even smaller suspended solids and fine impurities in seawater, further purifying the seawater and ensuring that the effluent turbidity is less than 1 NTU, meeting the water quality requirements for direct entry into the RO membrane.

[0033] Backwash water pump 6: When the amount of suspended solids trapped in the filter increases, the amount of treated water decreases, and the pressure reaches the set value, the backwash water pump 6 starts and uses the treated water in the product water tank 5 to backwash each filter, discharge the pollutants trapped in the filter through the discharge pipe, restore the filter's filtration performance, and ensure the continuous and stable operation of the system.

[0034] Roots blower 7: Located on one side of the modified filter, Roots blower 7 provides compressed air during backwashing, which, together with the backwash water, performs air-water backwashing on the modified fiber filter. The introduction of compressed air enhances the backwashing effect, more effectively removes contaminants adhering to the modified fiber filter media, improves the backwashing efficiency of the filter, and ensures the filtration effect of the modified fiber filter 2.

[0035] In the pretreatment process of seawater desalination, different combinations of the three-stage filtration process can be flexibly switched according to the seawater quality to further save process costs.

[0036] When seawater is subjected to the combined effects of surface currents and tidal forces, the water quality exhibits a high suspended solids and low turbidity state (turbidity less than 50 NTU). In this case, seawater pretreatment primarily focuses on removing suspended solids and turbidity. The pretreatment process can employ a two-stage filtration system using modified fiber filters and fine sand filters. A coagulant (such as...) needs to be added before the filters. Figure 2 As shown), by adding coagulants, pollutants are coagulated and flocculated, forming larger floc particles. These floc particles are more easily intercepted by the filter, thereby improving the pretreatment effect and ensuring the normal operation of subsequent filtration processes and the stability of effluent quality. When seawater is combined with other unfavorable factors, resulting in a high suspended solids and high turbidity state (turbidity greater than 50 NTU), the SDI15 is likely to be greater than 5, and the annual TOC is greater than 4 mg / L, which may lead to severe algal blooms or oil pollution. Sodium hypochlorite bactericide is added to the dosing mixer 1 to remove organic matter in the water, and then the water is filtered in three stages: modified fiber filter 2, coarse sand filter 3, and fine sand filter 4 (e.g., Figure 3As shown in the figure, this is used to ensure stable effluent water quality.

[0037] When the amount of suspended solids (impurities) trapped in the filter increases, the treated water volume decreases, and the pressure reaches the set value, the backwashing process is automatically initiated. Compressed air and treated water are used for backwashing, and the contaminants are discharged through the discharge pipe. The filtered water then automatically re-enters the filtration process, thus achieving the purpose of removing contaminants and retaining clean water.

[0038] Compared with the traditional membrane-based seawater desalination pretreatment process, this invention significantly reduces investment and operating costs. The investment for the traditional process is approximately 700 yuan / ton, while the investment for the three-stage filtration process is approximately 150 yuan / ton, which is only about 25% of the traditional process. The operating cost of the traditional process is approximately 0.4~0.6 yuan / ton, while the operating cost of the three-stage filtration process of this invention is approximately 0.1 yuan / ton, which is only 25%~15% of the traditional process.

[0039] This combined process fully considers the water quality characteristics of various nearshore waters, optimizes the treatment process, and flexibly switches between secondary and tertiary filtration according to the turbidity and suspended solids concentration of the incoming water, so as to achieve stable effluent water quality, reduce system energy consumption, extend equipment service life, reduce equipment maintenance work, and achieve the goal of energy saving and consumption reduction.

[0040] Example 1: A pretreatment experiment on seawater samples taken from the east bank of Yueqing Bay in southeastern Zhejiang Province showed that the raw seawater quality was: pH=8.0, suspended solids 105mg / L, and turbidity approximately 450NTU. After three-stage filtration pretreatment, the suspended solids in the effluent were 1.8mg / L and the turbidity was 0.9NTU.

[0041] Example 2: A pretreatment experiment on seawater samples taken from the east bank of Yueqing Bay in southeastern Zhejiang Province showed that the raw seawater quality was: pH=8.0, suspended solids 12.6 mg / L, and turbidity approximately 19.8 NTU. After two-stage filtration using coarse sand and fine sand, the suspended solids in the effluent were 1.5 mg / L and the turbidity was 0.8 NTU.

[0042] The above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. For those skilled in the art, other variations or modifications can be made based on the above description, and these obvious variations or modifications derived from the spirit of this utility model are still within the protection scope of this utility model.

Claims

1. A seawater desalination pretreatment filtration system, characterized in that: Includes a dosing mixer, modified fiber filter, coarse sand filter, fine sand filter, and product water tank; The outlet of the dosing mixer is connected to the inlet of the modified fiber filter. The outlet of the modified fiber filter is connected to the inlet of the coarse sand filter and the fine sand filter. The outlet of the coarse sand filter is connected to the inlet of the fine sand filter. The outlet of the fine sand filter is connected to the inlet of the product water tank.

2. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: The outlet of the water production tank is connected to the bottom of the modified filter, the bottom of the coarse sand filter, and the bottom of the fine sand filter via a backwash water pump.

3. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: A Roots blower is installed on one side of the modified fiber filter.

4. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: The modified fiber filter uses modified polypropylene as the filter media.

5. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: The coarse sand filter uses 1-2mm quartz sand as the filter media.

6. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: The fine sand filter uses 0.4-0.6mm quartz sand as the filter media.

7. The seawater desalination pretreatment filtration system according to claim 1, characterized in that: The seawater desalination pretreatment filtration system operates in either a two-stage or three-stage filtration mode.

8. A seawater desalination pretreatment filtration system according to claim 7, characterized in that: The secondary filtration process employs a modified fiber filter and a fine sand filter sequentially.

9. A seawater desalination pretreatment filtration system according to claim 7, characterized in that: The three-stage filtration system uses a modified fiber filter, a coarse sand filter, and a fine sand filter in sequence.

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