Ultrasonic-phycomycete membrane bioreactor system as well as construction method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an ultrasonic-phycomycete membrane bioreactor system and a construction method and application thereof, and the ultrasonic-phycomycete membrane bioreactor system comprises a membrane bioreactor and an ultrasonic system, the membrane bioreactor comprises a transparent reactor shell internally provided with a containing cavity and a membrane assembly arranged in the containing cavity, the ultrasonic system comprises an ultrasonic device arranged in the containing cavity, the containing cavity is further used for containing phycomycete suspension liquid, and the membrane assembly and the ultrasonic device are immersed in the phycomycete suspension liquid; the ultrasonic device is used for providing ultrasonic waves for promoting absorption and utilization of the phycomycete symbiotic system on sewage nutrient substances and in-situ cleaning of the membrane assembly. The ultrasonic-phycomycete membrane bioreactor system provided by the invention not only can effectively remove traditional pollutants in sewage, but also can effectively reduce membrane pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to an ultrasonic-algal-bacterial membrane bioreactor system, a construction method thereof, and an application thereof. Background Art

[0002] The problem of water resource shortage caused by water environmental pollution has seriously affected human life and sustainable development. Solving the water pollution problem has become a major challenge faced globally. In recent years, the biological treatment process combining algae and bacteria has received extensive attention because it can efficiently remove a large amount of nutrients in wastewater under low aeration conditions. In the algal-bacterial symbiosis (ABS) system, algae provide oxygen for heterotrophic aerobic bacteria to promote the mineralization of organic pollutants, and at the same time utilize the carbon dioxide produced by bacterial respiration to help purify wastewater. However, during the operation of the system, algae are easily affected by unstable factors such as light, temperature, and nutrient concentration, resulting in the loss of algal populations or a decrease in activity, thus affecting the wastewater treatment efficiency and limiting the long-term stability of the system. Therefore, improving the survival rate and recovery rate of algae has become a key challenge in the application of the algal-bacterial symbiosis system.

[0003] Membrane bioreactors (MBRs) combine a biological reactor and a membrane filtration device and are widely used in wastewater treatment due to their advantages such as high-efficiency water quality treatment, land area savings, and low sludge production. However, membrane fouling remains the main problem faced by MBR systems. Membrane scaling reduces the permeate flux or increases the required transmembrane pressure, thereby increasing the operating cost and thus limiting its wide application in wastewater treatment. Especially in algal-bacterial membrane bioreactors, extracellular polymeric substances (EPS) secreted by bacteria and algae cause more serious membrane fouling during the membrane treatment process, especially the polysaccharide (PS) and protein (PN) components, which further exacerbate the membrane fouling. In addition, the membrane has a high aeration requirement to maintain the oxygen supply of microorganisms, which can also alleviate membrane fouling to a certain extent.

[0004] In recent years, the green and environmentally friendly ultrasonic treatment technology has received increasing attention in controlling MBR membrane fouling. Ultrasonic irradiation generates microjets, microflows, and shock waves through cavitation, effectively cleaning the dirt on the membrane surface. The active hydroxyl radicals in the liquid phase can attach to the dirt and degrade the dirt molecules, further improving the membrane fouling problem. However, the chemical reactions induced by ultrasound can cause certain damage to the membrane, so the treatment effect of ultrasonic combined with MBR still needs to be further explored and improved. Summary of the Invention

[0005] The object of the present invention is to provide an ultrasonic-algal-bacterial membrane bioreactor system, a construction method thereof and an application. The ultrasonic-algal-bacterial membrane bioreactor system provided by the present invention can not only efficiently remove traditional pollutants in sewage, but also effectively reduce membrane fouling.

[0006] In the first aspect of the present invention, there is provided an ultrasonic-algal-bacterial membrane bioreactor system, which includes a membrane bioreactor and an ultrasonic system. The membrane bioreactor includes a transparent reactor housing with an accommodation cavity inside and a membrane module disposed in the accommodation cavity. The ultrasonic system includes an ultrasonic device arranged in the accommodation cavity. The accommodation cavity is also used to accommodate an algal-bacterial suspension, and the algal-bacterial suspension submerges the membrane module and the ultrasonic device; the ultrasonic device provides ultrasonic waves for promoting the absorption and utilization of sewage nutrients by the algal-bacterial symbiotic system and in-situ cleaning of the membrane module.

[0007] In some embodiments of the present invention, the membrane cloth material in the membrane module includes polyvinylidene fluoride.

[0008] In some embodiments of the present invention, the membrane cloth type in the membrane module is an ultrafiltration membrane.

[0009] In some embodiments of the present invention, the ultrasonic-algal-bacterial membrane bioreactor system further includes: an aeration system communicated with the internal accommodation cavity of the membrane bioreactor, and the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal-bacterial suspension; a lighting system, and the lighting system is used to provide light for the algal-bacterial suspension inside the membrane bioreactor.

[0010] In some embodiments of the present invention, the ultrasonic-algal-bacterial membrane bioreactor system further includes an inlet water system and an outlet water system. The inlet water system is communicated with the accommodation cavity of the membrane bioreactor, and the outlet water system is communicated with the membrane module.

[0011] In the second aspect of the present invention, there is also provided a construction method of the ultrasonic-algal-bacterial membrane bioreactor system described in the first aspect. The construction method of the ultrasonic-algal-bacterial membrane bioreactor system includes: constructing a membrane bioreactor with a transparent internal accommodation cavity, and a membrane module and an ultrasonic device are arranged in the accommodation cavity of the membrane bioreactor; putting the algal-bacterial suspension obtained after mixing the cultured microalgae with the activated sludge into the accommodation cavity of the membrane bioreactor, and submerging the membrane module and the ultrasonic device.

[0012] In some embodiments of the present invention, when the microalgae are mixed with the activated sludge, the total biomass concentration of the initial mixed solution is controlled to be 1.0 g / L to 4.0 g / L.

[0013] In some embodiments of the present invention, the ultrasonic frequency of the ultrasonic device is 20 kHz to 60 kHz, and the ultrasonic intensity is 40 W to 100 W.

[0014] In some embodiments of the present invention, the ultrasonic device is configured to continuously perform ultrasonic treatment for 60 s to 240 s each time, and perform ultrasonic treatment once every 12 h to 36 h.

[0015] In some embodiments of the present invention, the method for constructing the ultrasonic-algae-bacteria membrane bioreactor system further includes: introducing an aeration system, a lighting system, a water inlet system, and a water outlet system into the system and cooperating with the membrane bioreactor. The aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algae-bacteria suspension; the lighting system is used to provide light for the algae-bacteria suspension inside the membrane bioreactor.

[0016] In some embodiments of the present invention, the gas flow rate of the aeration system is 1.5 L / min to 3 L / min.

[0017] In some embodiments of the present invention, the light intensity provided by the lighting system is 5000 Lux to 10000 Lux.

[0018] The third aspect of the present invention also provides an application of the ultrasonic-algae-bacteria membrane bioreactor system described in the first aspect or the ultrasonic-algae-bacteria membrane bioreactor system constructed by using the construction method of the ultrasonic-algae-bacteria membrane bioreactor system described in the second aspect in sewage treatment. The ultrasonic-algae-bacteria membrane bioreactor system regularly monitors the concentrations of nitrogen, phosphorus nutrients and COD changes in the sewage, records the transmembrane pressure difference of the system every day, and simultaneously measures the algae-bacteria biomass, lipid accumulation, and the content of organic matter in the suspension.

[0019] The present invention combines an ultrasonic system, an algae-bacteria symbiotic system, and a membrane bioreactor to construct an ultrasonic-algae-bacteria membrane bioreactor system for urban wastewater treatment and membrane pollution control. On the one hand, the synergistic effect of the algae-bacteria symbiotic system can alleviate the high aeration conditions required for the operation of the membrane bioreactor to a certain extent. On the other hand, based on the effective retention of the membrane, the problem of algae cell loss can be alleviated to a certain extent, and the stability of the algae-bacteria system can be improved. The combination of the above two aspects makes the operation process of the ultrasonic-algae-bacteria membrane bioreactor system have strong adaptability; it can be applied to the efficient retention of pollutants in urban wastewater, and the removal rates of nitrogen, phosphorus, and COD are better than those of existing conventional membrane bioreactors. For example, the removal rates of nitrogen, phosphorus, and COD reach 57.40%, 46.38%, and 88.15% respectively; most of the organic matter can be effectively removed, reducing the pollutant load entering the membrane filtration unit, thereby slowing down the speed of membrane pollution.

[0020] The present invention can promote the stability of the suspension in the algal-bacterial symbiotic system by introducing ultrasound, enhance the algal-bacterial biomass production (increase by 1.1 - 1.2 times) and lipid accumulation (increase from 28.6% to 40.4%); it can also enhance the enzyme activity and metabolic rate of microorganisms, thereby promoting the progress of cell anabolism, and improving the storage capacity and stress resistance of cells.

[0021] The present invention can greatly reduce the organic matter content on the membrane surface by introducing ultrasonic waves, including loosely bound extracellular polymers (LB-EPS), tightly bound extracellular polymers (TB-EPS), and soluble microbial products (SMP), and inhibit the blockage of membrane pores by PN and PS; it can clean the membrane pollution in the algal-bacterial membrane bioreactor in situ, extend the membrane cleaning cycle and service life; while further improving the treated water quality, it effectively avoids the frequent equipment cleaning caused by membrane pollution and reduces the application cost.

[0022] The present invention uses an ultrasonic-algal-bacterial membrane bioreactor system to treat sewage without chemical addition and will not cause secondary pollution.

[0023] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following specifically illustrates the specific embodiments of the present invention. Brief Description of the Drawings

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of the ultrasonic-algal-bacterial membrane bioreactor system in the embodiment of the present invention.

[0026] Figure 2 It is a schematic structural diagram of the internal membrane module of the ultrasonic-algal-bacterial membrane bioreactor system in the embodiment of the present invention.

[0027] Figure 3 It is a comparison of the content and removal efficiency of wastewater nutrients inside the membrane bioreactor between the experimental group and the blank control group of the present invention; among them, Figure 3 (a) in it shows the TN concentration and removal efficiency.Figure 3 Among them, (b) shows the TP concentration and removal efficiency; Figure 3 Among them, (c) shows the COD concentration and removal efficiency.

[0028] Figure 4 This is the change of MLSS of the algal-bacterial flocs inside the membrane bioreactor in the experimental group and the blank control group of the present invention.

[0029] Figure 5 This is the change of lipid content of the algal-bacterial flocs inside the membrane bioreactor in the experimental group and the blank control group of the present invention.

[0030] Figure 6 This is the change of TMP during the membrane filtration process in the experimental group and the blank control group of the present invention.

[0031] Figure 7 This is the change of the composition and content of organic substances on the membrane surface in the experimental group and the blank control group of the present invention.

[0032] Figure 8 This is a schematic diagram of the membrane surface morphology in the experimental group and the blank control group of the present invention; among them, Figure 8 Among them, (a1) shows the membrane surface morphology in the experimental group; Figure 8 Among them, (a2) shows the morphology of the algal-bacterial flocs on the membrane surface in the experimental group; Figure 8 Among them, (a3) shows the membrane surface morphology after cleaning in the experimental group; Figure 8 Among them, (b1) shows the membrane surface morphology in the blank control group; Figure 8 Among them, (b2) shows the morphology of the algal-bacterial flocs on the membrane surface in the blank control group; Figure 8 Among them, (b3) shows the membrane surface morphology after cleaning in the blank control group.

[0033] Explanation of reference numerals: 100 - Ultrasonic-algal-bacterial membrane bioreactor system; 10 - Membrane bioreactor; 11 - Transparent reactor housing; 12 - Membrane module; 121 - Support plate; 122 - Gasket; 123 - Membrane cloth; 124 - Suction port; 20 - Aeration system; 21 - Aeration stone; 22 - Gas flow meter; 23 - Aeration pump; 30 - Lighting system; 40 - Inlet water system; 41 - Inlet water pipe; 42 - First peristaltic pump; 50 - Outlet water system; 51 - Outlet water pipe; 52 - Pressure controller; 53 - Second peristaltic pump; 60 - Ultrasonic system; 61 - Ultrasonic device; 62 - Power supply.

[0034] 70 - Algal-bacterial suspension. Detailed implementation manners

[0035] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0036] It should be understood that the terms used herein are for the purpose of describing specific exemplary embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless the order of performance is explicitly stated. It should also be understood that additional or alternative steps may be used.

[0037] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "a plurality" is more than two, unless otherwise explicitly and specifically defined.

[0038] Reference to "an embodiment" in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The phrase does not necessarily refer to the same embodiment at every occurrence in the specification, nor is it an independent or alternative embodiment mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0040] In the description of the embodiments of the present invention, the term "a plurality" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0041] In the description of the embodiments of the present invention, unless otherwise clearly defined and limited, technical terms such as "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0042] The following explains some terms in the present invention to facilitate the understanding of those skilled in the art.

[0043] Algae-bacteria suspension: Mix microalgae with activated sludge to obtain an algae-bacteria suspension. During the growth process, the microalgae and the sludge attach together to form large particle algae-bacteria flocs with bacteria as the core and microalgae as the skeleton.

[0044] The term "MLSS": refers to the concentration of suspended solids in the algae-bacteria suspension, which is an important parameter for measuring the biomass concentration in a sewage treatment system. MLSS reflects the total amount of suspended solids in the sludge, including microbial biomass (bacteria, protozoa, metazoa, etc.), undegraded organic matter, inorganic particles, and other suspended substances. In the present invention, MLSS represents the biomass concentration of algae-bacteria flocs in the algae-bacteria suspension.

[0045] The first aspect of the present invention provides an ultrasonic-algae-bacteria membrane bioreactor system, combined with Figure 1 and Figure 2 introduction, the ultrasonic-algae-bacteria membrane bioreactor system 100 includes a membrane bioreactor 10 and an ultrasonic system 60. The membrane bioreactor 10 specifically includes a transparent reactor housing 11 with an accommodation cavity inside and a membrane module 12 arranged in the accommodation cavity. The ultrasonic system 60 includes an ultrasonic device 61 arranged in the accommodation cavity. The accommodation cavity is also used to accommodate the algae-bacteria suspension 70, and the algae-bacteria suspension 70 submerges the membrane module 12 and the ultrasonic device 61; the ultrasonic device 61 is used to provide ultrasonic waves to promote the absorption and utilization of wastewater nutrients by the algae-bacteria symbiotic system and in-situ clean the membrane module.

[0046] In an embodiment of the present invention, an ultrasonic-algal-bacterial membrane bioreactor system for urban wastewater treatment and membrane fouling control is constructed by combining an ultrasonic system, an algal-bacterial symbiotic system, and a membrane bioreactor. On the one hand, the synergistic effect of the algal-bacterial symbiotic system can alleviate the high aeration conditions required for the operation of the membrane bioreactor to a certain extent. On the other hand, based on the effective retention of the membrane, the problem of algal cell loss can be alleviated to a certain extent, improving the stability of the algal-bacterial system. The combination of the above two aspects makes the operation process of the ultrasonic-algal-bacterial membrane bioreactor system have strong adaptability, and it can be applied to the efficient retention of pollutants in urban wastewater, making the removal rates of nitrogen, phosphorus, and COD slightly better than those of existing conventional membrane bioreactors; effectively removing most of the organic matter, reducing the pollutant load entering the membrane module, and thus slowing down the rate of membrane fouling.

[0047] In some embodiments of the present invention, the transparent reactor housing 11 of the membrane bioreactor 10 can be an open transparent reaction tank, and its shape can be a cuboid shape, a cube shape, or other structures, without specific limitation.

[0048] In some embodiments of the present invention, the effective volume of the internal accommodation cavity of the membrane bioreactor 10 is 3 L to 8 L, for example, it can be one of 3 L, 4 L, 5 L, 6 L, 7 L, 8 L or any value satisfying the above range.

[0049] As some embodiments of the present invention, the transparent reactor housing 11 can be composed of five transparent acrylic plates.

[0050] In an embodiment of the present invention, the membrane module 12 is vertically arranged in the accommodation cavity of the membrane bioreactor 10 and immersed in the algal-bacterial suspension 70.

[0051] In some embodiments of the present invention, the membrane cloth material in the membrane module 12 includes polyvinylidene fluoride.

[0052] In some embodiments of the present invention, the membrane cloth type in the membrane module 12 adopts an ultrafiltration membrane to improve the solid-liquid separation effect and reduce membrane fouling.

[0053] In some embodiments of the present invention, the membrane pore size in the membrane module is 0.1 μm to 0.2 μm to improve the solid-liquid separation effect and reduce membrane fouling. Exemplarily, the membrane pore size in the membrane module can be one of 0.1 μm, 0.12 μm, 0.15 μm, 0.16 μm, 0.18 μm, 0.2 μm or any value satisfying the above range.

[0054] As an embodiment of the present invention, a laboratory-scale submerged membrane bioreactor 10 is assembled. The effective volume of the internal accommodation cavity of the submerged membrane bioreactor 10 is 3 L to 8 L, and it can be composed of five transparent acrylic plates. Then, a polyvinylidene fluoride (PVDF) ultrafiltration flat membrane module 12 is vertically arranged in the accommodation cavity of the submerged membrane bioreactor 10, and an ultrasonic device 61 is arranged in the accommodation cavity of the submerged membrane bioreactor 10.

[0055] In some embodiments of the present invention, the ultrasonic device 61 can be arranged on the top of the membrane module 12. Of course, the ultrasonic device 61 is not limited to being arranged on the top of the membrane module 12, and it can also be at any other position, such as being arranged at the bottom of the membrane module 12, or being arranged at a position close to or adjacent to the membrane module 12.

[0056] In some embodiments of the present invention, the ultrasonic system 60 further includes a power supply 62 connected to the ultrasonic device 61. The ultrasonic device 61 is externally connected to the power supply 62 to supply power for its operation.

[0057] In an embodiment of the present invention, an algal-bacterial suspension 70 is added to the accommodation cavity of the submerged membrane bioreactor 10, and both the membrane module 12 and the ultrasonic device 61 are immersed in the algal-bacterial suspension 70.

[0058] In some embodiments of the present invention, microalgae and activated sludge are mixed to obtain an algal-bacterial suspension 70, in which large granular algal-bacterial flocs are formed by the co-attachment of microalgae and sludge during the growth process.

[0059] As some embodiments of the present invention, the algal-bacterial suspension 70 selects Chlorella sp. in the logarithmic growth phase as the algal seed source, inoculates it into the aerobic activated sludge sampled from the aeration tank of a sewage treatment plant, and controls the total biomass concentration of the initial mixed solution to be 1.0 g / L to 4.0 g / L. For example, the total biomass concentration of the initial mixed solution can be 1.0 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, 2.0 g / L, 2.1 g / L, 2.2 g / L, 2.3 g / L, 2.4 g / L, 2.5 g / L, 2.6 g / L, 2.7 g / L, 2.8 g / L, 2.9 g / L, 3.0 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L, 4.0 g / L or any value satisfying the above range.

[0060] Continue to refer to Figure 1As shown, the ultrasonic-algal and bacterial membrane bioreactor system 100 in the present invention further includes an aeration system 20, which is connected to the internal accommodation cavity of the membrane bioreactor 10 and is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal and bacterial suspension.

[0061] In an embodiment of the present invention, the aeration system 20 includes an aeration stone 21 disposed at the bottom of the accommodation cavity of the membrane bioreactor 10. For example, the aeration stone 21 can be arranged directly below the membrane module 12 to better provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal and bacterial suspension.

[0062] In some embodiments of the present invention, there is a certain space between the membrane module 12 and the bottom of the accommodation cavity of the membrane bioreactor 10 for placing the aeration stone 21.

[0063] In some embodiments of the present invention, the aeration system 20 further includes a gas flow meter 22 and an aeration pump 23 to cooperate with the aeration stone 21.

[0064] As some embodiments of the present invention, the aeration system 20 provides additional CO2 and O2 for the growth of microalgae and bacteria at an air flow rate of 1.5 L / min to 3 L / min. Exemplarily, the air flow rate of the aeration system 20 can be one of 1.5 L / min, 1.6 L / min, 1.8 L / min, 2 L / min, 2.2 L / min, 2.5 L / min, 2.6 L / min, 2.8 L / min, 3 L / min or any value satisfying the above range.

[0065] In an embodiment of the present invention, the ultrasonic-algal and bacterial membrane bioreactor system 100 in the present invention further includes a lighting system 30 for providing light to the algal and bacterial suspension inside the membrane bioreactor 10.

[0066] In some embodiments of the present invention, the lighting system 30 provides a light intensity of 5000 Lux to 10000 Lux.

[0067] In some embodiments of the present invention, the lighting system 30 can be arranged above the outside of the membrane bioreactor 10.

[0068] As some embodiments of the present invention, the lighting system 30 can be an LED lamp.

[0069] In some embodiments of the present invention, the lighting system 30 continuously provides light during the operation of the ultrasonic-algal and bacterial membrane bioreactor system.

[0070] In an embodiment of the present invention, the ultrasonic-algae and bacteria membrane bioreactor system 100 of the present invention further includes an influent system 40 and an effluent system 50, wherein the influent system 40 is communicatively connected to the accommodation cavity of the membrane bioreactor 10, and the effluent system 50 is communicatively connected to the membrane module 12.

[0071] In some embodiments of the present invention, the influent system 40 inputs the wastewater to be treated into the internal accommodation cavity of the membrane bioreactor 10 through an influent pipeline 41.

[0072] In some embodiments of the present invention, a liquid level sensor can be used to control the first peristaltic pump 42 to pump the wastewater to be treated into the membrane bioreactor 10 through the influent pipeline 41 to maintain a constant liquid level in the accommodation cavity of the membrane bioreactor 10.

[0073] In some embodiments of the present invention, the effluent system 50 uses a second peristaltic pump 53 and outputs the water filtered by the membrane module 12 through an effluent pipeline 51, and measures the effluent pressure through a pressure controller 52.

[0074] In some embodiments of the present invention, the pressure controller 52 can be a pressure gauge.

[0075] The second aspect of the present invention provides a construction method of the ultrasonic-algae and bacteria membrane bioreactor system described in the first aspect. The key to this construction method is to include constructing a membrane bioreactor with a transparent internal accommodation cavity, where a membrane module and an ultrasonic device are arranged in the accommodation cavity of the membrane bioreactor; putting the algae and bacteria suspension obtained after mixing the cultured microalgae and activated sludge into the accommodation cavity of the membrane bioreactor, and submerging the membrane module and the ultrasonic device.

[0076] In an embodiment of the present invention, when mixing the microalgae and the activated sludge, it is necessary to control the total biomass concentration of the initial mixture to be 1.0 g / L to 4.0 g / L. For example, control the total biomass concentration of the initial mixture to be 2.4 g / L, the inoculation ratio of microalgae to activated sludge to be 1:5, the concentration of microalgae to be 0.4 g / L, and the concentration of activated sludge to be 2 g / L.

[0077] As some implementation manners of the present invention, the algae and bacteria suspension selects Chlorella sp. in the logarithmic growth phase as the algae seed source, inoculates it into the aerobic activated sludge sampled from the aeration tank of the sewage treatment plant, and controls the total biomass concentration of the initial mixture to be 1.0 g / L to 4.0 g / L.

[0078] In some embodiments of the present invention, the ultrasonic frequency of the ultrasonic device is set to 20 kHz to 60 kHz. For example, the ultrasonic frequency can be one of 20 kHz, 22 kHz, 24 kHz, 25 kHz, 26 kHz, 28 kHz, 30 kHz, 32 kHz, 34 kHz, 35 kHz, 36 kHz, 38 kHz, 40 kHz, 42 kHz, 44 kHz, 45 kHz, 46 kHz, 48 kHz, 50 kHz, 52 kHz, 54 kHz, 55 kHz, 56 kHz, 58 kHz, 60 kHz or any value that satisfies the above range.

[0079] In some embodiments of the present invention, the ultrasonic intensity is 40 W to 100 W. Exemplarily, the ultrasonic intensity can be one of 40 W, 45 W, 50 W, 55 W, 60 W, 65 W, 70 W, 75 W, 80 W, 85 W, 90 W, 95 W, 100 W or any value that satisfies the above range.

[0080] In some embodiments of the present invention, the ultrasonic device is configured to perform ultrasonic waves continuously for 60 s to 240 s each time, and perform ultrasonic waves once every 12 h to 36 h.

[0081] Exemplarily, the ultrasonic waves are continuously performed for 60 s, 80 s, 90 s, 100 s, 120 s, 150 s, 160 s, 180 s, 190 s, 200 s, 210 s, 220 s, 240 s each time, or any value that satisfies the above range, and perform ultrasonic waves once every 12 h, 14 h, 15 h, 16 h, 18 h, 20 h, 22 h, 24 h, 25 h, 26 h, 28 h, 30 h, 32 h, 34 h, 35 h, 36 h, or any value that satisfies the above range.

[0082] In some embodiments of the present invention, the method for constructing the ultrasonic-algal-bacterial membrane bioreactor system of the present invention further includes introducing an aeration system and a lighting system into the system and cooperating with the membrane bioreactor. Specifically, the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal-bacterial suspension; the lighting system is used to provide light for the algal-bacterial suspension inside the membrane bioreactor.

[0083] In an embodiment of the present invention, the gas flow rate of the aeration system is 1.5 L / min to 3 L / min. Exemplarily, the gas flow rate of the aeration system 20 can be one of 1.5 L / min, 1.6 L / min, 1.8 L / min, 2 L / min, 2.2 L / min, 2.5 L / min, 2.6 L / min, 2.8 L / min, 3 L / min or any value satisfying the above range.

[0084] In some embodiments of the present invention, the method for constructing the ultrasonic-algal-bacterial membrane bioreactor system of the present invention further includes introducing an influent system and an effluent system into the membrane bioreactor. Specifically, the influent system is communicatively connected to the internal accommodation cavity of the membrane bioreactor, and the effluent system is communicatively connected to the membrane module.

[0085] The third aspect of the present invention provides an application of the ultrasonic-algal-bacterial membrane bioreactor system described in the first aspect or the ultrasonic-algal-bacterial membrane bioreactor system constructed by using the construction method of the ultrasonic-algal-bacterial membrane bioreactor system described in the second aspect in sewage treatment.

[0086] In some embodiments of the present invention, the ultrasonic-algal-bacterial membrane bioreactor system can be set with a hydraulic retention time (Hydraulic retention·times, HRT) of 24 h to 48 h and a sludge retention time (Sludge-retentiontimes, SRT) of 20 days. Exemplarily, the HRT can be one of 24 h, 25 h, 26 h, 27 h, 28 h, 29 h, 30 h, 31 h, 32 h, 33 h, 34 h, 35 h, 36 h, 37 h, 38 h, 39 h, 40 h, 41 h, 42 h, 43 h, 44 h, 45 h, 46 h, 47 h, 48 h or any value satisfying the above range.

[0087] In an embodiment of the present invention, the first peristaltic pump and the second peristaltic pump of the ultrasonic-algal-bacterial membrane bioreactor system operate intermittently. For example, a liquid level sensor is used to control the intermittent operation of the first peristaltic pump and the second peristaltic pump. Exemplarily, an operation mode of turning on for 4 min and pausing for 1 min is adopted to pump the sewage to be treated into the accommodation cavity of the algal-bacterial membrane bioreactor; an operation mode of turning on for 4 min and pausing for 1 min is adopted to discharge the effluent from the membrane module.

[0088] In an embodiment of the present invention, the concentrations of nitrogen and phosphorus nutrients and the change of chemical oxygen demand (COD) in sewage are monitored regularly; the transmembrane pressure (TMP) of the ultrasonic-algal-bacterial membrane bioreactor system is recorded every day; meanwhile, the algal-bacterial biomass, lipid accumulation, organic matter content and components are measured.

[0089] In some embodiments of the present invention, the ultrasonic-algal-bacterial membrane bioreactor system is used to treat the sewage to be treated, and the biomass concentration is maintained at 1 g / L to 4 g / L.

[0090] When the ultrasonic-algal-bacterial membrane bioreactor system of the present invention is applied to sewage treatment and membrane fouling control, it can effectively alleviate the loss of algal cells while promoting the production of algal-bacterial biomass and lipid accumulation inside the system, and effectively remove organic pollutants; further, the ultrasonic-algal-bacterial membrane bioreactor system can effectively reduce the generation of membrane fouling during sewage treatment, can effectively remove most of the organic matter, reduce the pollutant load entering the membrane filtration unit, thereby slowing down the speed of membrane fouling and extending the cleaning cycle and service life of the membrane.

[0091] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments and equipment used in the following embodiments can all be obtained through market purchase or by existing methods; the dosages of the experimental reagents are the dosages of the reagents in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0092] In the embodiments and comparative examples of the present invention, synthetic wastewater is used as the sewage to be treated, and glucose is used as the carbon source to provide easily degradable organic matter and optimize the metabolic activity of the algal-bacterial symbiotic system. The specific composition of the synthetic wastewater is as follows: 40 mg / L MgSO4·7H2O, 21.9 mg / L KH2PO4, 1.3 mg / L Na2MoO4, 0.3 mg / L CuSO4·5H2O, 0.22 mg / L MnCl2•4H2O, 0.5 mg / L ZnSO4•7H2O, 0.4 mg / L CoCl2•6H2O, 300 mg / L NaHCO3, 242 mg / L NaNO3, 0.3 mg / L NaCl.

[0093] Among them, the COD determination method refers to the potassium dichromate digestion method, the total nitrogen determination method refers to the alkaline potassium persulfate digestion-ultraviolet spectrophotometry, and the total phosphorus determination method refers to the ammonium molybdate spectrophotometry. The EPS extraction adopts the thermal extraction method, that is, a 50 mL centrifuge tube containing the algal-bacterial suspension is centrifuged at 4000 g for 10 min to remove the supernatant. The remaining particles are resuspended in a 0.05% NaCl (w / v) solution at 50 °C and mixed for 1 min using a simulated vortex mixer. Then it is centrifuged at 4000 g for 10 min, and the collected supernatant is regarded as LB-EPS. Subsequently, the ABS system particles are resuspended again in a 0.05% NaCl (w / v) solution and heated in a water bath at 60 °C for 30 min. Finally, it is centrifuged at 4000 g for 15 min, and the collected supernatant is called TB-EPS. Before analyzing the content, all EPS samples are filtered through a 0.45 μm filter membrane. Using bovine serum albumin (BSA) as the standard substance, the Folin colorimetric method is used to calculate the protein (Protein, PN) content in EPS. Using glucose as the standard substance, the anthrone / sulfuric acid method is used to measure the polysaccharide (Polysaccharide, PS) content.

[0094] Membrane fouling determination: The monitoring results obtained in the examples and comparative examples of the present invention can be obtained by reading the data of the pressure controller.

[0095] Example 1 Construct an ultrasonic-algal-bacterial membrane bioreactor system 100, as Figures 1 to 2 shown. The ultrasonic-algal-bacterial membrane bioreactor system 100 includes a water inlet system 40, a membrane bioreactor 10, an aeration system 20, a lighting system 30, a water outlet system 50, and an ultrasonic system 60. Among them, the water inlet system 40 passes through a water inlet pipe 41 and uses a first peristaltic pump 42 to introduce the sewage to be treated into the internal accommodation cavity of the membrane bioreactor 10; the water outlet system 50 is connected to the membrane module 12 through a water outlet pipe 51, and uses a second peristaltic pump 53 to discharge the filtered clear water, and at the same time uses a pressure controller 52 to monitor the water outlet pressure in real time.

[0096] The membrane bioreactor 10 includes an open cuboid transparent reactor housing 11 with an accommodation cavity inside, and a membrane module 12 arranged in the accommodation cavity. The ultrasonic system 60 includes an ultrasonic device 61 arranged in the accommodation cavity. The effective volume of the transparent reactor housing is 6 L. The accommodation cavity also contains an algal-bacterial suspension 70, and the biomass concentration is controlled at 2.4 g / L (the microalgae concentration is 0.4 g / L, and the activated sludge concentration is 2 g / L). And the algal-bacterial suspension 70 submerges the membrane module 12 and the ultrasonic device 61; the ultrasonic device 61 provides ultrasonic waves to promote the biomass production of the algal-bacterial symbiotic system, the absorption and utilization of sewage nutrients, and the in-situ cleaning of the membrane module. The ultrasonic device 61 is externally connected to a power supply 62 to ensure the working power supply.

[0097] The membrane module 12 is jointly composed of two groups of support plates 121, two groups of gaskets 122, and a membrane cloth 123. Among them, the top of the support plate is provided with a suction port 124 communicating with the membrane cloth, and it is connected to the water outlet pipe 51 to connect to the water outlet system 50. The membrane cloth 123 uses a polyvinylidene fluoride ultrafiltration membrane.

[0098] The aeration system 20 includes an aeration stone 21, a gas flowmeter 22, and an aeration pump 23. The aeration stone 21 extends into the interior of the accommodation cavity and is arranged below the membrane module 12. Among them, the gas flow rate of the aeration system is 1.8 L / min.

[0099] The lighting system 30 uses LED lights to provide light at an intensity of about 7000 Lux, and the entire sewage treatment process can operate continuously at room temperature.

[0100] Comparative Example 1 An existing conventional algal-bacterial membrane bioreactor is used.

[0101] Wastewater treatment performance experiment Using the ultrasonic-algal-bacterial membrane bioreactor system constructed in Example 1 as the experimental group, and the conventional algal-bacterial membrane bioreactor in Comparative Example 1 as the blank control group, the sewage treatment performance of the ultrasonic-algal-bacterial membrane bioreactor system of the present invention is investigated.

[0102] The experimental conditions are as follows: Experimental group: Continuously ultrasonic for 180 s every day, ultrasonic once every 24 h, set the ultrasonic frequency to 25 kHz, and the ultrasonic intensity to 60 W.

[0103] Blank control group: Without ultrasonic, and the rest of the operations are the same as those in the experimental group.

[0104] Operate and run in a continuous flow mode, and set to detect the effluent situation of the reactors in the experimental group and the blank control group every three days. The experimental results are as Figure 3 shown.

[0105] From Figure 3It can be seen that the removal effect of nutrients in the experimental group is slightly higher than that in the control group. Under appropriate ultrasonic parameters, the target functional bacteria are strengthened and domesticated, and the activity and proportion of functional bacteria are increased. In order to achieve rapid start-up, stable operation, rapid recovery from collapse (collapse recovery means that the reaction system can recover to no less than the original treatment efficiency after experiencing adverse conditions), and improve the resistance of the reaction system to shock loads, it is necessary to remove pollutants and organic matter under optimal conditions.

[0106] Biointerception effect experiment Using the ultrasonic-algal-bacterial membrane bioreactor system constructed in Example 1 as the experimental group, and the conventional algal-bacterial membrane bioreactor in Comparative Example 1 as the blank control group to treat simulated domestic sewage, the accumulation of algal-bacterial biomass and lipid production effect of the membrane module in the ultrasonic-algal-bacterial membrane bioreactor system of the present invention in the filtration mode were investigated.

[0107] The experimental conditions are as follows: Experimental group: MLSS 1.6 g / L, lipid content 40.3%.

[0108] Blank control group: MLSS 1.4 g / L, lipid content 29.4%.

[0109] Operating in the continuous flow mode, the growth status of algae and bacteria inside the reaction system was inspected every three days, and the experimental results are as Figure 4 shown. The lipid accumulation in the reactors of the experimental group and the control group was monitored regularly, and the results are as Figure 5 shown.

[0110] From Figure 4 it can be seen that the ultrasonic stimulation in the experimental group can improve the permeability of the microbial cell membrane, which will affect the transport of nutrients, resulting in changes in cell activity and the synthesis of intracellular compounds; the utilization rate of substrates by microorganisms increases the accumulation of biomass in the experimental group. In the algal-bacterial symbiotic system, the metabolites secreted by bacteria (such as vitamin B group and organic acids) may be further optimized under ultrasonic action, indirectly promoting the activity of the algal lipid metabolic pathway and activating the expression and activity of key enzymes related to lipid synthesis (such as fatty acid synthase and acetyl-CoA carboxylase), further improving the lipid production efficiency.

[0111] From Figure 5 it can be seen that the lipid content in the experimental group is significantly higher than that in the control group. Cavitation bubbles will be generated after the liquid is ultrasonically treated, and the implosion collapse of the bubbles can trigger local high temperature and high pressure. This environmental pressure can induce microalgae cells to synthesize lipids or other energy storage substances, thus increasing the lipid yield. In addition, appropriate ultrasound enhances the cell membrane permeability and promotes the transfer and utilization of lipid synthesis-related precursor substances.

[0112] Membrane fouling effect experiment The ultrasonic-algal-bacterial membrane bioreactor system constructed in Example 1 was used as the experimental group, and the conventional algal-bacterial membrane bioreactor in Comparative Example 1 was used as the blank control group to treat simulated domestic sewage, and the membrane fouling effect of the membrane module in the filtration mode in the ultrasonic-algal-bacterial membrane bioreactor system of the present invention was investigated.

[0113] The experimental conditions are as follows: Experimental group: Reached the membrane fouling threshold (30 kPa) four times.

[0114] Blank control group: Reached the membrane fouling threshold (30 kPa) five times.

[0115] Operating in the continuous flow mode, the transmembrane pressure value of the reactor was recorded every day, and the experimental results are as Figure 6 shown.

[0116] From Figure 6 it can be seen that the experimental group with the introduction of ultrasonic waves slowed down the membrane fouling phenomenon to a certain extent. The oscillation of the bubble size and the expansion and contraction of the generated bubbles will cause the direction and magnitude of the liquid flow to change rapidly. The contraction of the bubbles generated during the compression cycle causes the liquid molecules to be pulled out from the membrane surface. In addition, the expansion of the cavitation bubbles during the expansion cycle causes the liquid molecules to be pushed towards the membrane surface. The rapid change of the direction and magnitude of the liquid flow near the membrane surface will cause shear force and resistance on the membrane surface, resulting in the release of fouling particles.

[0117] The mechanical force caused by ultrasonic waves has a shearing effect on the membrane surface, which can effectively disperse and remove the particles and organic substances attached to the membrane surface. Therefore, the content of organic substances in the cake layer on the membrane surface is significantly reduced, see Figure 7 shown. Compared with the blank control group, ultrasonic waves destroy the long-chain molecular structure of these polysaccharides and reduce their deposition on the membrane surface; by adjusting the microbial metabolism in the system, less protein components are produced to reduce the impact on membrane fouling.

[0118] Ultrasonic treatment can effectively relieve the blockage of membrane pores and thus reduce membrane fouling. The chemical reaction between the membrane and the generated hydroxyl radicals and the collision of particles with the membrane surface are also considered to be the main fouling destruction mechanisms on the membrane surface under ultrasonic irradiation. At the end of the operation of the reaction system, the membrane surface was cleaned with pure water, and it can be seen from the cleaned membrane surface that the membrane pores on the surface of the experimental group are clearly visible, see Figure 8 shown.

[0119] Although the blank control group was cleaned, some dirt still remained adhered to the membrane surface or blocked the membrane pores. This shows that the blank control group requires more frequent cleaning, which will lead to an increase in cost during the application process. In contrast, the ultrasonic-algal-bacterial membrane bioreactor system of the present invention is more economically feasible.

[0120] The present invention combines ultrasonic waves, which are green, clean and will not cause secondary pollution, with an algal-bacterial membrane bioreactor to treat urban wastewater. On the one hand, the synergistic effect of the algal-bacterial symbiotic system can, to a certain extent, alleviate the high aeration conditions required for the operation of the membrane bioreactor. On the other hand, based on the effective retention of the membrane, the problem of algal cell loss can also be alleviated to a certain extent, improving the stability of the algal-bacterial system. By applying an ultrasonic system, ultrasonic waves can clean the MBR membrane in situ (online); at the same time, appropriate ultrasonic treatment will not only not damage the biological cell structure, but can also be used to enhance the enzyme activity and metabolic rate of microorganisms, promote the penetration of the microbial cell wall and enhance the transfer efficiency between species, thereby promoting the absorption and utilization of wastewater nutrients in the membrane bioreactor by the algal-bacterial symbiotic system.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrasonic-algal and fungal membrane bioreactor system, characterized in that, It includes a membrane bioreactor and an ultrasonic system, wherein the membrane bioreactor includes a transparent reactor housing with an accommodation chamber inside and a membrane module disposed in the accommodation chamber, the ultrasonic system includes an ultrasonic device arranged in the accommodation chamber, the accommodation chamber is also used to accommodate an algal-bacterial suspension, and the algal-bacterial suspension submerges the membrane module and the ultrasonic device; the ultrasonic device provides ultrasonic waves for promoting the absorption and utilization of sewage nutrients by the algal-bacterial symbiotic system and in-situ cleaning of the membrane module.

2. The ultrasonic-algal and bacterial membrane bioreactor system according to claim 1, characterized in that, The type of membrane cloth in the membrane module is an ultrafiltration membrane.

3. The ultrasonic-algal and bacterial membrane bioreactor system according to claim 1, characterized in that, It also includes: An aeration system communicated with the internal accommodation chamber of the membrane bioreactor, and the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal-bacterial suspension; A lighting system, and the lighting system is used to provide light for the algal-bacterial suspension inside the membrane bioreactor.

4. The ultrasonic-algal and fungal membrane bioreactor system according to claim 1, wherein It also includes a water inlet system and a water outlet system, the water inlet system is communicated with the accommodation chamber of the membrane bioreactor, and the water outlet system is communicated with the membrane module.

5. A method for constructing the ultrasonic-algal and bacterial membrane bioreactor system according to any one of claims 1 to 4, characterized in that, The construction method of the ultrasonic-algal-bacterial membrane bioreactor system includes: Constructing a membrane bioreactor with a transparent internal accommodation chamber, and a membrane module and an ultrasonic device are arranged in the accommodation chamber of the membrane bioreactor; Putting the algal-bacterial suspension obtained after mixing the cultured microalgae and activated sludge into the accommodation chamber of the membrane bioreactor, and submerging the membrane module and the ultrasonic device.

6. The construction method of the ultrasonic-algal and fungal membrane bioreactor system according to claim 5, characterized in that, When mixing the microalgae and the activated sludge, the total biomass concentration of the initial mixture is controlled to be 1.0 g / L to 4.0 g / L.

7. The construction method of the ultrasonic-algal and bacterial membrane bioreactor system according to claim 5, characterized in that, The ultrasonic frequency of the ultrasonic device is 20 kHz to 60 kHz, and the ultrasonic intensity is 40 W to 100 W; and / or, The ultrasonic device is configured to continuously ultrasonic for 60 s to 240 s each time, and ultrasonic once every 12 h to 36 h.

8. The construction method of the ultrasonic-algal-bacterial membrane bioreactor system according to claim 5, characterized in that, The construction method of the ultrasonic-algal-bacterial membrane bioreactor system also includes: introducing an aeration system, a lighting system, a water inlet system and a water outlet system into the system and cooperating with the membrane bioreactor to work, wherein the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algal-bacterial suspension; The lighting system is used to provide light for the algal-bacterial suspension inside the membrane bioreactor.

9. The construction method of the ultrasonic-algal and fungal membrane bioreactor system according to claim 8, wherein The gas flow rate of the aeration system is 1.5 L / min to 3 L / min; and / or, The light intensity provided by the lighting system is 5000 Lux to 10000 Lux.

10. The application of the ultrasonic-algal-bacterial membrane bioreactor system according to any one of claims 1 to 4 or the ultrasonic-algal-bacterial membrane bioreactor system constructed by using the construction method of the ultrasonic-algal-bacterial membrane bioreactor system according to any one of claims 5 to 9 in sewage treatment, characterized in that the ultrasonic-algal-bacterial membrane bioreactor system regularly monitors the changes in the concentrations of nitrogen, phosphorus nutrients and COD in the sewage, records the transmembrane pressure difference of the system every day, and simultaneously measures the algal-bacterial biomass, lipid accumulation and the content of organic matter in the suspension.

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