Short-process drinking water flat sheet membrane filtration system and method

Abstract

The invention discloses a short-process drinking water flat sheet membrane filtration system and method, and aims to solve the problems that the traditional process flow is long and a hollow fiber membrane is easy to block, and adopts a collaborative design of a flat sheet membrane and a double-state friction cleaning material. The system comprises flat membranes arranged in parallel in a membrane box, and chambers for accommodating light friction cleaning materials (the specific gravity is less than 1) and heavy friction cleaning materials (the specific gravity is greater than 1) are respectively arranged at the upper part and the lower part. During operation, the cleaning material is separated and stored through buoyancy / gravity, and raw water is purified through a flat sheet membrane during filtration; during cleaning, light and heavy cleaning materials are driven to be fluidized in two directions through aeration, and the two sides of the membrane are physically abraded and cleaned, so that the problem of suspended matter blockage is effectively solved. The design has the advantages of flow simplification and turbidity impact resistance, is particularly suitable for small water supply scenes such as mountainous areas, and remarkably reduces the occupied area and the maintenance cost while ensuring the water quality.

Description

Technical Field

[0001] The present invention relates to the field of drinking water filtration, and in particular to a short-process flat membrane filtration system and method for drinking water. Background Art

[0002] Traditional drinking water treatment processes usually adopt a long-process system including grille, flocculation, sedimentation, sand filtration, ultrafiltration and disinfection. Although it can stably treat complex raw water, it has significant defects in small-scale water supply scenarios such as mountainous areas: the long process leads to a large floor area, difficult transportation of large equipment, and high operation and maintenance costs. For this reason, in recent years, rural water supply systems have generally simplified the process and adopted a treatment process with hollow fiber ultrafiltration as the core, omitting the sand filtration and some flocculation and sedimentation units. However, it is found in practice that it has a fatal defect - when the turbidity of the raw water suddenly changes (such as a sharp increase in suspended solids after rain), fine particles are likely to block the hollow membrane filaments, resulting in a sudden drop in flux or even the scrapping of the membrane module. In particular, the system without a sedimentation tank is more likely to be frequently paralyzed due to the direct impact of suspended solids on the membrane surface, seriously affecting the water supply stability. This contradiction highlights the bottleneck that it is difficult to balance the anti-pollution performance of the existing short-process technology and the demand for system simplification. Summary of the Invention

[0003] In view of the above defects of the prior art, the present invention first provides a short-process flat membrane filtration system for drinking water, including: a membrane box, inside which there are multiple flat membrane sheets arranged in parallel at intervals, and the distance between the flat membrane sheets is 1-20 millimeters; a plurality of upper accommodation chambers arranged on the upper part of the membrane box, the bottom of each upper accommodation chamber is connected to an air pipe, and inside it contains a light friction cleaning material with a specific gravity less than 1; a plurality of lower accommodation chambers arranged on the lower part of the membrane box, the bottom of each lower accommodation chamber is connected to an air pipe, and inside it contains a heavy friction cleaning material with a specific gravity greater than 1; the system has two working states: in the filtration state, the light friction cleaning material floats in the upper accommodation chamber, and the heavy friction cleaning material sinks in the lower accommodation chamber; in the cleaning state, the light and heavy friction cleaning materials are injected into the inside of the membrane box through the air pipe to form a two-way fluidized scrubbing interface.

[0004] Further, the light friction cleaning material is made of plastic or rubber, and the specific gravity is 0.85-0.95; the heavy friction cleaning material is made of glass or ceramic, and the specific gravity is 1.05-1.25.

[0005] Further, the particle size of the light friction cleaning material and the heavy friction cleaning material is 0.2-2 millimeters; the total volume of the friction cleaning material accounts for 3%-20% of the volume of the membrane box.

[0006] The present invention also provides a short - process drinking water flat - membrane filtration method. Using the system described above, it includes: raw water directly enters the membrane box for flat - membrane filtration; when membrane fouling is detected, switch to the cleaning mode: inject cleaning agents and start aeration to form an up - and - down two - way scouring flow with light and heavy abrasive materials; remove pollutants through the physical friction between the abrasive materials and the membrane surface; after cleaning is completed, automatically resume the filtration operation, and the abrasive materials are recovered by buoyancy / gravity separation.

[0007] By arranging upper and lower accommodation chambers to separate light and heavy abrasive cleaning materials, a two - way dynamic scouring interface is formed during aeration cleaning, enabling the front and back surfaces of the flat membrane to simultaneously bear the shearing force of the up - and - down abrasive materials, significantly improving the pollutant stripping efficiency; at the same time, through the automatic sorting and recycling mechanism of the cleaning materials, physical isolation between the abrasive materials and the working area of the membrane is achieved under the filtration condition, which not only avoids the risk of blockage caused by direct impact of suspended solids on the membrane surface during sudden turbidity changes but also breaks through the problem of redundant processes caused by the traditional hollow - fiber membrane's reliance on sedimentation tanks, effectively reducing the floor area of the system and extending the service life of the membrane module. On the premise of ensuring stable compliance of the effluent water quality, the construction cost and operation and maintenance energy consumption of small - scale mountain water supply systems are significantly reduced.

[0008] The following will further illustrate the concept, specific structure, and technical effects of the present invention in conjunction with the attached drawings to fully understand the purpose, features, and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of the short - process drinking water flat - membrane filtration system of the present invention;

[0010] Figure 2 is Figure 1 a side cross - sectional view of the short - process drinking water flat - membrane filtration system in the working state;

[0011] Figure 3 is Figure 1 a side cross - sectional view of the short - process drinking water flat - membrane filtration system in the aeration state. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The following introduces multiple preferred embodiments of the present invention with reference to the accompanying drawings of the specification to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0013] In the drawings, components with the same structure are denoted by the same numerical labels, and components with similar structures or functions are denoted by similar numerical labels. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. To make the drawings clearer, the thickness of some components is appropriately exaggerated in the drawings.

[0014] As Figures 1-3 shown, the short - process drinking water flat - membrane filtration system of the present invention includes a membrane box 1, and a plurality of parallel and spaced - apart flat - membrane sheets 2 are arranged in the membrane box 1. The spacing between the membrane sheets 2 is between 1 - 20 mm, preferably 4 - 10 mm. Too small a spacing is not conducive to the flow of abrasive particles between the membrane sheets and is prone to jamming; too large a spacing results in too small an overall packing density of the flat - membrane, increasing the investment cost of the membrane tank. The membrane sheet 2 can be an organic membrane, a ceramic membrane or a metal membrane.

[0015] At the upper part of the membrane box 1, there are a plurality of upper accommodation chambers 30 corresponding to the cavities between the flat - membrane sheets 2 and the membrane box 1 and between the flat - membrane sheets 2, and the bottom of each upper accommodation chamber 30 communicates with an air - blowing pipe 5. Light - weight abrasive cleaning materials 3 are accommodated in each upper accommodation chamber 30. Preferably, the materials are plastics or rubbers such as PP, PE, PS, TPU, silicone rubber, etc., and their specific gravity is less than 1, preferably between 0.85 - 0.95, because if the density differs too much from that of water, it will lead to poor fluidity of the abrasive. Thus, in the working state as Figure 2 shown, the light - weight abrasive cleaning materials 3 will float to each upper accommodation chamber 30 in the water of the membrane box 1. The size of the light - weight abrasive cleaning materials 3 is between 0.1 - 10 mm, preferably between 0.2 - 2 mm.

[0016] At the lower part of the membrane box 1, there are also a plurality of lower accommodation chambers 40 corresponding to the cavities between the flat - membrane sheets 2 and the membrane box 1 and between the flat - membrane sheets 2, and the bottom of each lower accommodation chamber 40 communicates with the air - blowing pipe 5. Heavy - weight abrasive cleaning materials 4 are accommodated in each lower accommodation chamber 40. Preferably, the materials are glass - like or ceramic - like, and their specific gravity is greater than 1, preferably between 1.05 - 1.25, because if the density differs too much from that of water, it will lead to poor fluidity of the abrasive. Thus, in the working state as Figure 2 shown, the heavy - weight abrasive cleaning materials 4 will sink to each lower accommodation chamber 40 in the water of the membrane box 1. The size of the heavy - weight abrasive cleaning materials 4 is between 0.1 - 10 mm, preferably between 0.2 - 2 mm.

[0017] The total volume of the light - weight abrasive cleaning materials 3 and the heavy - weight abrasive cleaning materials 4 is between 0.5% - 110% of the volume of the membrane box, preferably between 3 - 20%. Too little abrasive cleaning material requires a longer cleaning time to effectively clean the membrane sheets, and too much abrasive cleaning material will increase the system investment.

[0018] As Figure 1 、 2As shown in the figure, during operation, raw water enters the membrane box 1 through valve 7. After being filtered by multiple flat membrane sheets 2, the purified water flows out of the membrane box 1 through valve 8. At this time, the light friction cleaning material 3 accumulates in each upper accommodation chamber 30 between the flat membrane sheet 2 and the membrane box 1 and between the flat membrane sheets 2 under the action of buoyancy; while the heavy friction cleaning material 4 accumulates in each lower accommodation chamber 40 under the action of gravity, without affecting the water flow through the flat membrane sheet 2.

[0019] As Figure 1 , 3 shown, when surface abrasion cleaning of the flat membrane sheet 2 is required, the inlet valve 7 and the outlet valve 8 are closed, and valve 9 is opened to allow the chemical agent in the chemical agent water tank to enter the membrane box 1. At the same time, the aeration blower is operated, and the light friction cleaning material 3 in each upper accommodation chamber 30 and the heavy friction cleaning material 4 in each lower accommodation chamber 40 are sent into the interior of the membrane box 1 through the aeration pipe 5. The light friction cleaning material 3 and the heavy friction cleaning material 4 are fluidized by the power of aeration to abrade and clean the flat membrane sheet 2. Since the light friction cleaning material 3 and the heavy friction cleaning material 4 can be injected from both the upper and lower sides of the flat membrane sheet 2 to abrade and clean the flat membrane sheet 2, the problem that the far part on the other side of the membrane sheet cannot be sufficiently abraded and cleaned if the friction cleaning material is injected from one side can be avoided. When the abrasion cleaning is completed, the sewage is filtered and emptied through valve 10. When the inlet valve 7 is opened and the membrane box 1 is transferred to the working state again, the light friction cleaning material 3 and the heavy friction cleaning material 4 are automatically separated in water by buoyancy and gravity and restored to the state as Figure 2 shown. Specific embodiments:

[0021] The raw water is the natural river water in Zhejiang. The treatment process is: raw water ==> micro-flocculation ==> ultrafiltration ==> produced water. Among them, hollow fiber ultrafiltration is used for ultrafiltration, and the operating flux is operated at 30 LMH. After 2 days of operation, the flux drops to less than 10 LMH, and the pressure difference rises to 0.9 kg, and it can hardly continue to work. Then the inventor of the present invention replaces the ultrafiltration with the flat ultrafiltration system in the present invention. Due to the presence of the membrane friction material, the ultrafiltration membrane sheet is well abraded and cleaned. After 30 days of operation of the system, the pressure difference still remains below 0.3 kg, and the flow rate is stable at 30 LMH. Among them, there are 2 moderate rains, and the turbidity of the river water increases from 10 NTU in normal times to 120 NTU. It shows the strong anti-water quality change ability of the flat ultrafiltration system.

[0022] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the existing technology should be within the protection scope determined by the claims.

Claims

1. A short-process drinking water flat membrane filtration system, characterized in that Comprising: An aneroid box, inside which there are multiple flat diaphragms arranged in parallel at intervals, and the distance between the flat diaphragms is 1 - 20 millimeters; A number of upper accommodating chambers arranged at the upper part of the aneroid box, the bottom of each upper accommodating chamber is connected to an air diffuser pipe, and inside there is a light friction cleaning material with a specific gravity less than 1; A number of lower accommodating chambers arranged at the lower part of the aneroid box, the bottom of each lower accommodating chamber is connected to an air diffuser pipe, and inside there is a heavy friction cleaning material with a specific gravity greater than 1; The system has two working states: In the filtration state, the light friction cleaning material floats in the upper accommodating chamber, and the heavy friction cleaning material sinks in the lower accommodating chamber; In the cleaning state, the light and heavy friction cleaning materials are injected into the inside of the aneroid box through the air diffuser pipe to form a two-way fluidized abrasive washing interface.

2. The filtration system according to claim 1, wherein: The light friction cleaning material is made of plastic or rubber, and the specific gravity is 0.85 - 0.95; the heavy friction cleaning material is made of glass or ceramic, and the specific gravity is 1.05 - 1.

25.

3. The filtration system according to claim 1, wherein: The particle size of the light friction cleaning material and the heavy friction cleaning material is 0.2 - 2 millimeters; the total volume of the friction cleaning material accounts for 3% - 20% of the volume of the aneroid box.

4. A short-process drinking water flat membrane filtration method, characterized in that, Adopting the system according to any one of claims 1 - 4, comprising: raw water directly enters the aneroid box for flat diaphragm filtration; when membrane fouling is detected, switch to the cleaning mode: inject a cleaning agent and start aeration to make the light and heavy friction materials form an up-and-down two-way scouring flow; remove pollutants through the physical friction between the friction materials and the surface of the diaphragm; after cleaning is completed, automatically resume the filtration operation, and the friction materials are separated and recovered by buoyancy / gravity.

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