A supportless soft flat membrane module for a membrane bioreactor

Abstract

The present invention provides a supported soft flat membrane module for a membrane bioreactor. The module contains a number of membrane sheet elements. The composite bio-membrane sheet includes a first filter membrane and a second filter membrane. The first filter membrane is sleeved outside the second filter membrane. The first filter membrane and the second filter membrane are prepared from different materials. The supported soft flat membrane module of the present invention is applied in a membrane bioreactor, has a good effect on sewage treatment, has a high permeation flux, a high BSA rejection rate, and at the same time has a high adsorption amount of BSA and HA in sewage and a short membrane formation time.

Description

Technical Field

[0001] The present invention relates to the field of membrane biotechnology, and particularly to a supported soft flat membrane module for a membrane bioreactor. Background Art

[0002] A membrane bioreactor (MBR) is a biochemical / solid-liquid separation system that integrates membrane separation technology and traditional activated sludge biological treatment technology. It is widely used in sewage treatment due to its advantages such as small floor area and stable effluent quality. Ultrafiltration or microfiltration membrane modules are used to replace the secondary sedimentation tank in the traditional activated sludge method to achieve efficient solid-liquid separation. In a membrane bioreactor, the flat membrane module needs to be immersed in the activated sludge, and there is no need to separately set up a dedicated secondary sedimentation tank or a special filtration system. Currently, the MER membrane module uses hollow fiber or flat membrane as the filtration core element. During use, activated sludge adheres to the surface of the hollow fiber membrane, reducing the membrane filtration flux and even causing flat membrane pollution, affecting the working efficiency and the stability of system operation. The existing solution is to add aeration shear and liquid turbulence to clean the pollutants on the flat membrane, so that activated sludge particles are not easily aggregated on the surface of the flat membrane, thereby maintaining a stable membrane flux. However, the surface pollutants of the flat membrane are the filter cake layer formed by negative pressure suction, resulting in a large force between the pollutants and the flat membrane, leading to membrane pollution. Membrane pollution will inevitably cause a decrease in the permeation flux, poor adsorption capacity for BSA, HA, etc. in sewage, and an increase in the sludge load. Summary of the Invention

[0003] In view of this, the present invention proposes a supported soft flat membrane module for a membrane bioreactor to solve the above problems.

[0004] The technical solution of the present invention is realized as follows: A supported soft flat membrane module for a membrane bioreactor, the module contains a number of membrane elements, the number of membrane elements are stacked, and the membrane element is a composite biological membrane.

[0005] Further, the composite biological membrane includes a first filter membrane and a second filter membrane, and the second filter membrane is rich in biological bacteria coating, covering 0.3 - 0.5 mm.

[0006] Further, the material of the second filter membrane includes the following raw materials in parts by weight: 3 - 13 parts of cellulose acetate, 1.2 - 3.5 parts of glass fiber, 0.3 - 1.5 parts of bismaleimide resin, 0.5 - 1.5 parts of hyperbranched polymer.

[0007] Further, the material of the first filter membrane includes the following raw materials in parts by weight: 5 - 15 parts of modified polyvinylidene fluoride, 1 - 5 parts of polyacrylonitrile, 2 - 4 parts of polyethersulfone, 0.8 - 2.5 parts of N-methylpyrrolidone.

[0008] Furthermore, the modified polyvinylidene fluoride is obtained by immersing polyvinylidene fluoride in a hydrophilic modification treatment solution for 15 - 20 min, stirring at 40 - 70 °C for 5 - 7 h, standing at room temperature for 4 - 12 h, and then distilling off the mixed solvent under reduced pressure to obtain a membrane solution, that is, the modified polyvinylidene fluoride. The mass - to - volume ratio (g / mL) of polyvinylidene fluoride to the hydrophilic modification treatment solution is 3 - 8:25.

[0009] Furthermore, the hydrophilic modification treatment solution is an aqueous solution of 25 - 55 wt% polyethyleneimine - epichlorohydrin with a molecular weight of 10 - 20 kDa.

[0010] Furthermore, the biological bacteria strains are Saccharomyces cerevisiae strain, Lactobacillus casei strain, and Bacillus licheniformis strain with a mass ratio of 1 - 3:2 - 4:0.5 - 1.6, and their viable cell counts are 3 - 6×10 7 cfu / g, 2 - 8×10 7 cfu / g, 1.3 - 5×10 7 cfu / g.

[0011] Furthermore, the flat - plate membrane module is applied to a sewage treatment system, which includes an oxygen - deoxidizing tank, an aeration tank, a sedimentation tank, a grille tank, a regulating tank, an anoxic tank, a flat - plate membrane bioreactor, and a storage tank connected in sequence through pipelines. The water inlet of the oxygen - deoxidizing tank is connected to a raw water inlet pipe. The sedimentation tank is provided with a sludge return pipe and a sewage discharge pipe. One end of the sludge return pipe is connected to the raw water inlet pipe, and the other end of the sewage discharge pipe is connected to a sludge recovery tank.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] The unsupported soft flat - plate membrane module of the present invention has super hydrophilic performance, high anti - fouling ability, and rapid flux recovery. The first filter membrane has a uniform pore size distribution and high filtration flux. The second filter membrane is made of modified polyvinylidene fluoride material, which has better chemical stability, anti - fouling property, and mechanical strength, and at the same time has rapid chemical cleaning efficiency and effect, ensuring that the membrane surface flux is quickly restored; the microstructure and pore size distribution of the filter membrane are effectively and precisely controlled, the membrane filtration performance is significantly improved, achieving the effects of low resistance, short process, and pollution resistance.

[0014] The unsupported soft flat - plate membrane module of the present invention is applied in a membrane bioreactor, has a good effect on sewage treatment, has a high permeation flux, a high BSA interception rate, and at the same time has a high adsorption amount of BSA and HA in sewage, a short membrane - hanging time, maintains a high activated sludge concentration in the bioreactor, improves the biological treatment organic load, uses the membrane bioreactor to intercept the activated sludge and macromolecular organic matter in water, and reduces the amount of excess sludge by maintaining a low sludge load. Description of the Drawings

[0015] Figure 1 is a sewage treatment flow chart;

[0016] Figure 2 is a composite biofilm sheet. Detailed Embodiments

[0017] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0018] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0019] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can all be obtained from commercial channels.

[0020] Example 1

[0021] A unsupported soft flat membrane module for a membrane bioreactor, the module contains a number of membrane elements, the number of membrane elements are stacked, the membrane element is a composite biofilm sheet, the composite biofilm sheet includes a first filter membrane 1 and a second filter membrane 2, the first filter membrane 1 is sleeved outside the second filter membrane 2, the pore size of the first filter membrane 1 is smaller than the pore size of the second filter membrane, the outer wall of the second filter membrane 2 is rich in a bio-strain coating, covering 0.3 - 0.5 mm, the material of the second filter membrane includes the following raw materials in parts by weight: 3 parts of cellulose acetate, 1.2 parts of glass fiber, 0.3 part of bismaleimide resin, 0.5 part of hyperbranched polymer, the material of the first filter membrane includes the following raw materials in parts by weight: 5 parts of modified polyvinylidene fluoride, 1 part of polyacrylonitrile, 2 parts of polyethersulfone, 0.8 part of N-methylpyrrolidone; the modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment solution for 15 min, stirring at 40 °C for 5 h, standing at room temperature for 4 h, and distilling off the mixed solvent by a vacuum distillation method to obtain a membrane solution, thus obtaining the modified polyvinylidene fluoride, the mass volume g / mL of polyvinylidene fluoride and the hydrophilic modification treatment solution is 3:25; the hydrophilic modification treatment solution is an aqueous solution of 25 wt% of polyethyleneimine-chloromethyloxirane, with a molecular weight of 10 kDa; the bio-strains are beer yeast strains, Lactobacillus casei strains, and Bacillus licheniformis strains with a mass ratio of 1:2:0.5, and their viable counts are 3×10 7 cfu / g, 2×10 7 cfu / g, 1.3×10 7 cfu / g.

[0022] Example 2

[0023] A unsupported soft flat membrane module for a membrane bioreactor, the module contains a number of membrane elements, the number of membrane elements are stacked, the membrane element is a composite biological membrane, the composite biological membrane includes a first filter membrane 1 and a second filter membrane 2, the first filter membrane 1 is sleeved outside the second filter membrane 2, the pore size of the first filter membrane 1 is smaller than the pore size of the second filter membrane 2, the outer wall of the second filter membrane 2 is rich in a biological bacterial strain coating, covering 0.3 - 0.5 mm, the material of the second filter membrane 2 includes the following raw materials in parts by weight: 13 parts of cellulose acetate, 3.5 parts of glass fiber, 1.5 parts of bismaleimide resin, 1.5 parts of hyperbranched polymer, the material of the first filter membrane 1 includes the following raw materials in parts by weight: 15 parts of modified polyvinylidene fluoride, 5 parts of polyacrylonitrile, 4 parts of polyethersulfone, 2.5 parts of N-methylpyrrolidone; the modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment solution for 20 min, stirring at 70 °C for 7 h, standing at room temperature for 12 h, and distilling off the mixed solvent by a reduced pressure distillation method to obtain a membrane liquid, thus obtaining modified polyvinylidene fluoride, the mass volume g / mL of polyvinylidene fluoride and the hydrophilic modification treatment solution is 8:25; the hydrophilic modification treatment solution is an aqueous solution of 55 wt% of polyethyleneimine-chloromethyloxirane, with a molecular weight of 20 kDa; the biological bacterial strains are brewer's yeast bacterial strain, Lactobacillus casei bacterial strain, Bacillus licheniformis bacterial strain with a mass ratio of 3:4:1.6, and their viable counts are 6×10 7 cfu / g, 8×10 7 cfu / g, 5×10 7 cfu / g.

[0024] Example 3

[0025] A unsupported soft flat membrane module for a membrane bioreactor, the module contains a number of membrane elements, the number of membrane elements are stacked, the membrane element is a composite bio-membrane, the composite bio-membrane includes a first filter membrane 1 and a second filter membrane 2, the first filter membrane 1 is sleeved outside the second filter membrane 2, the pore size of the first filter membrane 1 is smaller than the pore size of the second filter membrane 2, the outer wall of the second filter membrane 2 is rich in a bio-strain coating, covering 0.3 - 0.5 mm, the material of the second filter membrane 2 includes the following raw materials in parts by weight: 3 - 13 parts of cellulose acetate, 2.3 parts of glass fiber, 1.2 parts of bismaleimide resin, 1 part of hyperbranched polymer, the material of the first filter membrane 1 includes the following raw materials in parts by weight: 10 parts of modified polyvinylidene fluoride, 3 parts of polypropylene, 3 parts of polyethersulfone, 1.5 parts of N-methylpyrrolidone; the modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment solution for 18 min, stirring at 60 °C for 6 h, standing at room temperature for 8 h, and distilling off the mixed solvent by a vacuum distillation method to obtain a membrane liquid, thus obtaining the modified polyvinylidene fluoride, the mass-volume ratio g / mL of polyvinylidene fluoride and the hydrophilic modification treatment solution is 5:25; the hydrophilic modification treatment solution is an aqueous solution of 35 wt% of polyethyleneimine-chloromethyloxirane, with a molecular weight of 15 kDa; the bio-strains are brewer's yeast strains, Lactobacillus casei strains, and Bacillus licheniformis strains with a mass ratio of 2:3:1.1, and their viable counts are 5×10 7 cfu / g, 6×10 7 cfu / g, 2.3×10 7 cfu / g.

[0026] Example 4

[0027] A supportless soft flat membrane module for a membrane bioreactor, the module containing a number of membrane sheet elements, the number of membrane sheet elements being stacked, the membrane sheet elements being composite biological membrane sheets, the composite biological membrane sheets including a first filter membrane 1 and a second filter membrane 2, the first filter membrane sleeve 1 being provided outside the second filter membrane 2, the pore diameter of the first filter membrane 1 being smaller than the pore diameter of the second filter membrane 2, the outer wall of the second filter membrane 2 being rich in a biological bacteria strain coating, covering 0.3 - 0.5 mm, the material of the second filter membrane 2 including the following raw materials in parts by weight: 3 parts of cellulose acetate, 1.2 parts of glass fiber, 0.3 part of bismaleimide resin, 0.5 part of hyperbranched polymer, the material of the first filter membrane 1 including the following raw materials in parts by weight: 5 parts of modified polyvinylidene fluoride, 1 part of polyacrylonitrile, 2 parts of polyethersulfone, 0.8 part of N-methylpyrrolidone; the modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment liquid for 18 min, stirring at 60 °C for 6 h, standing at room temperature for 8 h, and distilling off the mixed solvent by a reduced pressure distillation method to obtain a membrane liquid, thereby obtaining modified polyvinylidene fluoride, the mass-volume ratio g / mL of polyvinylidene fluoride and the hydrophilic modification treatment liquid being 5:25; the hydrophilic modification treatment liquid is an aqueous solution of 35 wt% of polyethyleneimine-chloromethyloxirane, with a molecular weight of 15 kDa; the biological bacteria strains are beer yeast strains, lactic acid bacteria strains, and bacillus licheniformis strains with a mass ratio of 2:3:1.1, and their viable counts are respectively 5×10 7 cfu / g, 6×10 7 cfu / g, 2.3×10 7 cfu / g.

[0028] Example 5

[0029] A unsupported soft flat membrane module for a membrane bioreactor, the module contains several membrane elements, the several membrane elements are stacked, the membrane element is a composite biological membrane, the composite biological membrane includes a first filter membrane 1 and a second filter membrane 2, the first filter membrane sleeve 1 is arranged outside the second filter membrane 2, the pore diameter of the first filter membrane 1 is smaller than the pore diameter of the second filter membrane 2, the outer wall of the second filter membrane 2 is rich in a biological bacterial strain coating, covering 0.3 - 0.5 mm, the material of the second filter membrane 2 includes the following raw materials in parts by weight: 13 parts of cellulose acetate, 3.5 parts of glass fiber, 1.5 parts of bismaleimide resin, 1.5 parts of hyperbranched polymer, the material of the first filter membrane 1 includes the following raw materials in parts by weight: 15 parts of modified polyvinylidene fluoride, 5 parts of polyacrylonitrile, 4 parts of polyethersulfone, 2.5 parts of N-methylpyrrolidone; the modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment solution for 18 min, stirring at 60 °C for 6 h, standing at room temperature for 8 h, and distilling off the mixed solvent by a reduced pressure distillation method to obtain a membrane solution, thus obtaining modified polyvinylidene fluoride, the mass-volume ratio g / mL of polyvinylidene fluoride and the hydrophilic modification treatment solution is 5:25; the hydrophilic modification treatment solution is an aqueous solution of 35 wt% polyethyleneimine-chloromethyloxirane with a molecular weight of 15 kDa; the biological bacterial strains are brewer's yeast bacterial strain, Lactobacillus casei bacterial strain, and Bacillus licheniformis bacterial strain with a mass ratio of 2:3:1.1, and their viable counts are 5×10 7 cfu / g, 6×10 7 cfu / g, 2.3×10 7 cfu / g.

[0030] Apply the unsupported soft flat membrane module prepared in the above Examples 1 - 5 to a sewage treatment system, including a deoxidation tank, an aeration tank, a sedimentation tank, a grille tank, an adjustment tank, an anoxic tank, a flat membrane bioreactor tank, and a storage tank connected in sequence through pipelines, the water inlet of the deoxidation tank is connected to a raw water inlet pipe, the sedimentation tank is provided with a sludge return pipe and a sewage discharge pipe, one end of the sludge return pipe is connected to the raw water inlet pipe, the other end of the sewage discharge pipe is connected to a sludge recovery tank, detect the treated sewage, set a pressure of 0.01 Mpa and a temperature of 25 °C in the flat membrane bioreactor MER tank, and the effective membrane area is 4×5 cm 2 Measure its treatment effect;

[0031] Permeate flux In the formula, Vp - the volume of the permeate, m 3 ; Am - the effective membrane area, m 2 ; t - the permeation time, h;

[0032] BSA rejection rate R = (1 - C P / C f )×100%, in the formula R is the rejection rate, C P is the concentration of the BSA filtrate, Cf is the concentration of the BSA stock solution;

[0033] The adsorption capacity q = V(C0 - C) / m.

[0034] The test results are as follows:

[0035]

[0036] From the above results, it can be seen that the unsupported soft flat membrane module of the present invention is applied in a membrane bioreactor, has a good effect on sewage treatment, has a high permeation flux, a high BSA rejection rate, and at the same time has a high adsorption capacity for BSA and HA in sewage, and a short membrane hanging time. Among them, Example 3 achieves a better effect.

[0037] The following comparative examples are set for Example 3:

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 3 is that the material of the first filter membrane includes the following raw materials in parts by weight: 3 parts of modified polyvinylidene fluoride, 8 parts of polyacrylonitrile, 6 parts of polyethersulfone, and 0.2 part of N-methylpyrrolidone

[0040] Comparative Example 2

[0041] The difference between this comparative example and Example 3 is that the modified polyvinylidene fluoride in the material of the first filter membrane is replaced with an equal amount of polyvinylidene fluoride.

[0042] Comparative Example 3

[0043] The difference between this comparative example and Example 3 is that the material of the second filter membrane includes the following raw materials in parts by weight: 1 part of cellulose acetate, 5 parts of glass fiber, 0.2 part of bismaleimide resin, and 0.2 part of hyperbranched polymer.

[0044] Comparative Example 4

[0045] The difference between this comparative example and Example 3 is that the material of the second filter membrane includes the following raw materials in parts by weight: 2 parts of cellulose acetate, 5 parts of glass fiber, 0.1 part of bismaleimide resin, and 2.8 parts of hyperbranched polymer.

[0046] The comparative examples 1-4 are measured according to the above test method, and the measurement results are as follows:

[0047]

[0048] The above results show that by configuring the materials of the first filter membrane and the second filter membrane, the present invention has super hydrophilic properties, high anti-pollution ability, and rapid flux recovery. After modifying polyvinylidene fluoride, while having better chemical stability, anti-pollution property, and mechanical strength, it has rapid chemical cleaning efficiency and effect, ensuring that the membrane surface flux is quickly restored. Inside the membrane substrate layer of the second filter membrane, there is a flowing water transfer channel, and the outer wall is covered with a biological bacterial strain film, effectively removing most harmful bacteria, facilitating the disinfection of the effluent, and the second filter membrane achieves the effects of low resistance, short process, and pollution resistance.

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A supported soft flat membrane module for a membrane bioreactor, characterized in that: The component contains a number of diaphragm elements, and the number of diaphragm elements are stacked. The diaphragm elements are composite biological diaphragm; the composite biological diaphragm includes a first filter membrane and a second filter membrane. The first filter membrane is sleeved outside the second filter membrane, and the pore size of the first filter membrane is smaller than that of the second filter membrane. The outer wall of the second filter membrane is covered with a biological bacterial strain film, covering 0.3 - 0.5 mm; the biological bacterial strains are brewer's yeast strains, Lactobacillus plantarum strains, and Bacillus licheniformis strains with a mass ratio of 1 - 3:2 - 4:0.5 - 1.6, and their viable counts are 3 - 6×10 7 cfu / g, 2 - 8×10 7 cfu / g, 1.3 - 5×10 7 cfu / g; the material of the second filter membrane includes the following raw materials in parts by weight: 3 - 13 parts of cellulose acetate, 1.2 - 3.5 parts of glass fiber, 0.3 - 1.5 parts of bismaleimide resin, 0.5 - 1.5 parts of hyperbranched polymer; the material of the first filter membrane includes the following raw materials in parts by weight: 5 - 15 parts of modified polyvinylidene fluoride, 1 - 5 parts of polyacrylonitrile, 2 - 4 parts of polyethersulfone, 0.8 - 2.5 parts of N-methylpyrrolidone; The modified polyvinylidene fluoride is obtained by impregnating polyvinylidene fluoride in a hydrophilic modification treatment liquid for 15 - 20 min, stirring at 40 - 70 °C for 5 - 7 h, standing at room temperature for 4 - 12 h, and distilling off the mixed solvent by a vacuum distillation method to obtain a membrane liquid, thus obtaining the modified polyvinylidene fluoride. The mass - volume ratio (g / mL) of polyvinylidene fluoride to the hydrophilic modification treatment liquid is 3 - 8:25; the hydrophilic modification treatment liquid is an aqueous solution of 25 - 55 wt% of polyethyleneimine - epichlorohydrin with a molecular weight of 10 - 20 kDa.

2. The unsupported soft flat membrane module for a membrane bioreactor according to claim 1, characterized in that: The flat - plate membrane module is applied to a sewage treatment system, which includes a deoxidation tank, an aeration tank, a sedimentation tank, a grille tank, an adjustment tank, an anoxic tank, a flat - plate membrane bioreactor, and a storage tank connected in sequence through pipelines. The water inlet of the deoxidation tank is connected to a raw water inlet pipe. The sedimentation tank is provided with a sludge return pipe and a sewage discharge pipe. One end of the sludge return pipe is connected to the raw water inlet pipe, and the other end of the sewage discharge pipe is connected to a sludge recovery tank.

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