Ultrasonic-algae film bioreactor system and its construction method and application

Abstract

The present invention belongs to the field of sewage treatment technology and specifically relates to an ultrasonic-algae film bioreactor system, its construction method, and application. The ultrasonic-algae film bioreactor system comprises a membrane bioreactor and an ultrasonic system. The membrane bioreactor comprises a transparent reactor shell with an internal accommodating cavity and a membrane assembly disposed within the accommodating cavity. The ultrasonic system comprises an ultrasonic device disposed within the accommodating cavity. The accommodating cavity is also used to accommodate an algae-bacteria suspension, and the algae-bacteria suspension immerses the membrane assembly and the ultrasonic device. The ultrasonic device provides ultrasonic waves to promote the absorption and utilization of wastewater nutrients by the algae-bacteria symbiotic system and to clean the membrane assembly in situ. The ultrasonic-algae film bioreactor system provided by the present invention can effectively remove traditional pollutants from wastewater and effectively reduce membrane fouling.

Description

Technical Field

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

[0002] Water shortages caused by water pollution have severely impacted human life and sustainable development, making addressing this issue a major global challenge. In recent years, combined algae and bacteria biological treatment processes have garnered widespread attention due to their ability to efficiently remove large amounts of nutrients from wastewater under low aeration conditions. In algal-bacterial symbiosis (ABS) systems, algae provide oxygen to heterotrophic aerobic bacteria, promoting the mineralization of organic pollutants while also utilizing carbon dioxide produced by bacterial respiration to purify wastewater. However, algae are susceptible to unstable factors such as light, temperature, and nutrient concentration during system operation, leading to loss of algal colonies or decreased activity, thereby compromising wastewater treatment efficiency and limiting the long-term stability of the system. Therefore, improving algae survival and recovery rates has become a key challenge in the application of ABS systems.

[0003] Membrane bioreactors (MBRs), which combine bioreactors with membrane filtration devices, are widely used in wastewater treatment due to their advantages, including efficient water treatment, reduced floor space, and low sludge production. However, membrane fouling remains a major problem for MBR systems. Membrane fouling reduces permeate flux or increases the required transmembrane pressure, thereby increasing operating costs and limiting their widespread application in wastewater treatment. In algal membrane bioreactors, in particular, extracellular polymeric substances (EPS) secreted by bacteria and algae can lead to more severe membrane fouling during the membrane treatment process. This is particularly true of their polysaccharide (PS) and protein (PN) components, which further exacerbate membrane fouling. Furthermore, the high aeration requirement of the membrane to maintain an oxygen supply for the microorganisms can also alleviate membrane fouling to a certain extent.

[0004] In recent years, environmentally friendly ultrasonic treatment technology has garnered increasing attention for controlling membrane fouling in MBRs. Ultrasonic irradiation generates microjets, microflows, and shock waves through cavitation, effectively cleaning membrane surface fouling. Reactive hydroxyl radicals in the liquid phase can attach to fouling and degrade it, further alleviating membrane fouling. However, chemical reactions triggered by ultrasound can cause some damage to the membrane, so the effectiveness of ultrasound combined with MBR treatment still requires further exploration and improvement. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultrasound-algae film bioreactor system and its construction method and application. The ultrasound-algae film bioreactor system provided by the present invention can not only efficiently remove traditional pollutants in sewage, but also effectively reduce membrane pollution.

[0006] The first aspect of the present invention provides an ultrasonic-algae-bacteria membrane bioreactor system, which includes a membrane bioreactor and an ultrasonic system. The membrane bioreactor includes a transparent reactor shell with a accommodating cavity inside and a membrane assembly arranged in the accommodating cavity. The ultrasonic system includes an ultrasonic device arranged in the accommodating cavity. The accommodating cavity is also used to accommodate an algae-bacteria suspension, and the algae-bacteria suspension immerses the membrane assembly and the ultrasonic device; the ultrasonic device provides ultrasonic waves for promoting the absorption and utilization of sewage nutrients by the algae-bacteria symbiotic system and for in-situ cleaning of the membrane assembly.

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

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

[0009] In some embodiments of the present invention, the ultrasonic-algae membrane bioreactor system also includes: an aeration system connected to the internal holding chamber of the membrane bioreactor, the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algae suspension; and a lighting system, the lighting system is used to provide light for the algae suspension inside the membrane bioreactor.

[0010] In some embodiments of the present invention, the ultrasound-algae film bioreactor system further includes a water inlet system and a water outlet system, wherein the water inlet system is connected to the containing cavity of the membrane bioreactor, and the water outlet system is connected to the membrane assembly.

[0011] The second aspect of the present invention also provides a method for constructing the ultrasonic-algae film bioreactor system described in the first aspect, and the method for constructing the ultrasonic-algae film bioreactor system includes: constructing a membrane bioreactor with a transparent internal holding cavity, wherein a membrane assembly and an ultrasonic device are arranged in the holding cavity of the membrane bioreactor; the algae suspension obtained after mixing the cultured microalgae with the activated sludge is put into the holding cavity of the membrane bioreactor, and the membrane assembly and the ultrasonic device are immersed.

[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 ultrasound device is configured to perform ultrasound for 60 s to 240 s each time, and perform ultrasound every 12 h to 36 h.

[0015] In some embodiments of the present invention, the method for constructing the ultrasonic-algae film 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, the aeration system is used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algae suspension; the lighting system is used to provide light for the algae 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~10000 Lux.

[0018] The third aspect of the present invention also provides an application of the ultrasonic-algae film bioreactor system described in the first aspect or the ultrasonic-algae film bioreactor system constructed by the construction method of the ultrasonic-algae film bioreactor system described in the second aspect in sewage treatment. The ultrasonic-algae film bioreactor system regularly monitors the nitrogen and phosphorus nutrient concentrations and COD changes in the sewage, records the transmembrane pressure difference of the system every day, and simultaneously measures the algae biomass, lipid accumulation, and organic matter content 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 fouling 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, the effective retention based on the membrane can also alleviate the problem of algae cell loss to a certain extent, thereby improving the stability of the algae-bacteria system. The combination of the above two aspects makes the operation process of the ultrasonic-algae-bacteria membrane bioreactor system highly adaptable; it can be used for the efficient retention of pollutants in urban wastewater, resulting in nitrogen, phosphorus, and COD removal rates that are better than those of existing conventional membrane bioreactors, such as nitrogen, phosphorus, and COD removal rates of 57.40%, 46.38%, and 88.15%, respectively; it effectively removes most organic matter, reduces the pollutant load entering the membrane filtration unit, and thus slows down the rate of membrane fouling.

[0020] The present invention can promote the stability of the algae-bacteria symbiotic system suspension by introducing ultrasound, enhance the algae-bacteria biomass yield (increased by 1.1 to 1.2 times) and lipid accumulation (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 cell's storage capacity and stress resistance.

[0021] The present invention can significantly reduce the content of organic matter on the membrane surface, including loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS), and soluble microbial products (SMP), by introducing ultrasound, thereby inhibiting the clogging of membrane pores by PN and PS. It can also clean membrane fouling in the algae membrane bioreactor in situ, extending the membrane cleaning cycle and service life. While further improving the treated water quality, it effectively avoids frequent equipment cleaning due to membrane fouling, thereby reducing application costs.

[0022] The present invention adopts an ultrasonic-algae film bioreactor system to treat sewage, without chemical addition and causing secondary pollution.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. 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 briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of the ultrasound-algae film bioreactor system in an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the structure of the internal membrane components of the ultrasound-algae film bioreactor system in an embodiment of the present invention.

[0027] Figure 3 The results are a comparison of the nutrient content and removal efficiency of wastewater in the membrane bioreactor between the experimental group and the blank control group of the present invention; Figure 3 (a) shows the TN concentration and removal efficiency; Figure 3 (b) shows the TP concentration and removal efficiency; Figure 3 (c) in the figure shows the COD concentration and removal efficiency.

[0028] Figure 4 The MLSS changes of algae flocs inside the membrane bioreactor in the experimental group of the present invention and the blank control group.

[0029] Figure 5 The lipid content changes of algal flocs inside the membrane bioreactor in the experimental group of the present invention and the blank control group.

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

[0031] Figure 7 The graph shows the changes in the composition and content of organic matter on the membrane surface between the experimental group and the blank control group in the present invention.

[0032] Figure 8 Schematic diagram of the membrane surface morphology of the experimental group and the blank control group in the present invention; wherein, Figure 8 (a1) shows the membrane surface morphology in the experimental group; Figure 8 (a2) shows the morphology of algae and bacterial flocs on the membrane surface in the experimental group; Figure 8 (a3) shows the surface morphology of the membrane after cleaning in the experimental group; Figure 8 (b1) in the figure shows the surface morphology of the membrane in the blank control group; Figure 8 (b2) shows the morphology of algae and bacterial flocs on the membrane surface in the blank control group; Figure 8 (b3) in the figure shows the surface morphology of the membrane after cleaning in the blank control group.

[0033] Description of reference numerals:

[0034] 100-ultrasound-algae film bioreactor system;

[0035] 10-membrane bioreactor; 11-transparent reactor shell; 12-membrane assembly; 121-support plate; 122-gasket; 123-membrane cloth; 124-suction port;

[0036] 20- aeration system; 21- aeration stone; 22- gas flow meter; 23- aeration pump;

[0037] 30- Lighting system;

[0038] 40-water inlet system; 41-water inlet pipe; 42-first peristaltic pump;

[0039] 50-water outlet system; 51-water outlet pipe; 52-pressure controller; 53-second peristaltic pump;

[0040] 60-Ultrasound system; 61-Ultrasound device; 62-Power supply.

[0041] 70-Algae-bacteria suspension. DETAILED DESCRIPTION

[0042] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0043] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, 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 specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0044] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are used solely to distinguish between different objects and should not be understood to indicate or imply relative importance or to implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0045] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0046] In the description of the embodiments of the present invention, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exists simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0047] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0048] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0049] Some terms used in the present invention are explained below to facilitate understanding by those skilled in the art.

[0050] Algae-bacteria suspension: Algae-bacteria suspension is obtained by mixing microalgae with activated sludge. During the growth process, microalgae and sludge attach together to form large-particle algae-bacteria flocs with bacteria as the core and microalgae as the skeleton.

[0051] The term "MLSS" refers to the concentration of suspended solids in an algae-bacterial suspension, a key parameter for measuring biomass concentration in wastewater treatment systems. MLSS reflects the total amount of suspended solids in the sludge, including microbial biomass (bacteria, protozoa, micrometazoa, etc.), undegraded organic matter, inorganic particles, and other suspended matter. In this context, MLSS represents the concentration of algae-bacterial floc biomass in the algae-bacterial suspension.

[0052] The first aspect of the present invention provides an ultrasound-algae film bioreactor system, which is 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 shell 11 with an internal accommodating cavity and a membrane assembly 12 arranged in the accommodating cavity. The ultrasonic system 60 includes an ultrasonic device 61 arranged in the accommodating cavity. The accommodating cavity is also used to accommodate an algae-bacteria suspension 70, and the algae-bacteria suspension 70 immerses the membrane assembly 12 and the ultrasonic device 61; the ultrasonic device 61 is used to provide ultrasonic waves to promote the algae-bacteria symbiotic system to absorb and utilize nutrients in wastewater and to clean the membrane assembly in situ.

[0053] In an embodiment of the present invention, an ultrasonic-algae-bacteria membrane bioreactor system for urban wastewater treatment and membrane pollution control is constructed by combining an ultrasonic system, an algae-bacteria symbiotic system and a membrane bioreactor. 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, the effective retention based on the membrane can also alleviate the problem of algae cell loss to a certain extent and improve the stability of the algae-bacteria system. The combination of the above two aspects makes the operation process of the ultrasonic-algae-bacteria membrane bioreactor system highly adaptable and can be used for the efficient retention of pollutants in urban wastewater, so that the nitrogen, phosphorus and COD removal rates are slightly better than those of existing conventional membrane bioreactors; it effectively removes most organic matter, reduces the pollutant load entering the membrane component, and thus slows down the rate of membrane pollution.

[0054] In some embodiments of the present invention, the transparent reactor shell 11 of the membrane bioreactor 10 may be an open transparent reaction pool, and its shape may be a rectangular parallelepiped or a cube, etc., without specific limitation.

[0055] In some embodiments of the present invention, the effective volume of the internal accommodating chamber 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 that meets the above range.

[0056] As some embodiments of the present invention, the transparent reactor housing 11 may be composed of five transparent acrylic plates.

[0057] In the embodiment of the present invention, the membrane assembly 12 is vertically disposed in the containing chamber of the membrane bioreactor 10 and immersed in the algae-bacteria suspension 70 .

[0058] In some embodiments of the present invention, the membrane cloth material in the membrane assembly 12 includes polyvinylidene fluoride.

[0059] In some embodiments of the present invention, the membrane cloth type in the membrane assembly 12 adopts an ultrafiltration membrane to improve the solid-liquid separation effect and reduce membrane pollution.

[0060] In some embodiments of the present invention, the membrane pore size in the membrane assembly is 0.1 μm to 0.2 μm to improve solid-liquid separation and reduce membrane fouling. For example, the membrane pore size in the membrane assembly 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 within the above range.

[0061] As an embodiment of the present invention, a laboratory-scale submerged membrane bioreactor 10 is assembled. The effective volume of the internal holding chamber of the submerged membrane bioreactor 10 is 3 L to 8 L, and can be composed of five transparent acrylic flat plates. Then, a polyvinylidene fluoride (PVDF) ultrafiltration flat membrane assembly 12 is vertically arranged in the holding chamber of the submerged membrane bioreactor 10, and an ultrasonic device 61 is arranged in the holding chamber of the submerged membrane bioreactor 10.

[0062] In some embodiments of the present invention, the ultrasonic device 61 can be set at the top of the membrane component 12. Of course, the ultrasonic device 61 is not limited to being set at the top of the membrane component 12, but can also be set at any other position, such as being set at the bottom of the membrane component 12, or being set at a position close to or adjacent to the membrane component 12.

[0063] In some embodiments of the present invention, the ultrasound system 60 further includes a power supply 62 connected to the ultrasound device 61 , and the ultrasound device 61 is externally connected to the power supply 62 to provide power for its operation.

[0064] In an embodiment of the present invention, the algae-bacteria suspension 70 is added into the containing chamber of the submerged membrane bioreactor 10 , and the membrane assembly 12 and the ultrasonic device 61 are both immersed in the algae-bacteria suspension 70 .

[0065] In some embodiments of the present invention, microalgae are mixed with activated sludge to obtain an algae-bacteria suspension 70 , wherein the microalgae and sludge are attached together to form large algae-bacteria flocs during the growth process.

[0066] As some embodiments of the present invention, the algae-bacterial suspension 70 selects Chlorella sp. in the logarithmic growth phase as the algae seed source, which is inoculated into aerobic activated sludge sampled from the aeration tank of a sewage treatment plant, and the total biomass concentration of the initial mixed liquor is controlled to be 1.0 g / L~4.0 g / L. For example, the total biomass concentration of the initial mixed liquor can be one of 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 that meets the above range.

[0067] Continue to see Figure 1As shown, the ultrasound-algae film bioreactor system 100 of the present invention further includes an aeration system 20 , which is connected to the internal accommodating cavity of the membrane bioreactor 10 and is used to provide additional CO 2 and O 2 for the growth of microalgae and bacteria in the algae suspension.

[0068] In an embodiment of the present invention, the aeration system 20 includes an aeration stone 21 arranged at the bottom of the housing chamber of the membrane bioreactor 10. For example, the aeration stone 21 can be arranged directly below the membrane assembly 12 to better provide additional CO2 and O2 for the growth of microalgae and bacteria in the algae-bacteria suspension.

[0069] In some embodiments of the present invention, there is a certain space at the bottom of the accommodating chamber of the membrane assembly 12 and the membrane bioreactor 10 for placing the aeration stone 21 .

[0070] 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 .

[0071] In some embodiments of the present invention, the aeration system 20 provides additional CO2 and O2 for the growth of microalgae and bacteria at an airflow rate of 1.5 L / min to 3 L / min. For example, the airflow 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 within the aforementioned range.

[0072] In an embodiment of the present invention, the ultrasound-algae membrane bioreactor system 100 of the present invention further includes a lighting system 30 for providing light for the algae suspension inside the membrane bioreactor 10 .

[0073] In some embodiments of the present invention, the lighting system 30 provides a light intensity of 5000 Lux to 10000 Lux.

[0074] In some embodiments of the present invention, the lighting system 30 may be arranged above the exterior of the membrane bioreactor 10 .

[0075] As some embodiments of the present invention, the lighting system 30 may be an LED lamp.

[0076] In some embodiments of the present invention, the lighting system 30 continuously provides light during the operation of the ultrasound-algae film bioreactor system.

[0077] In an embodiment of the present invention, the ultrasonic-algae film bioreactor system 100 of the present invention also includes an inlet system 40 and an outlet system 50, wherein the inlet system 40 is connected to the containing cavity of the membrane bioreactor 10, and the outlet system 50 is connected to the membrane assembly 12.

[0078] In some embodiments of the present invention, the water inlet system 40 inputs the wastewater to be treated into the internal accommodation chamber of the membrane bioreactor 10 through the water inlet pipe 41.

[0079] 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 water inlet pipe 41 to maintain a constant liquid level in the containing chamber of the membrane bioreactor 10.

[0080] In some embodiments of the present invention, the water outlet system 50 uses a second peristaltic pump 53 to output the water filtered by the membrane assembly 12 through the water outlet pipe 51 , and measures the outlet water pressure through a pressure controller 52 .

[0081] In some embodiments of the present invention, the pressure controller 52 may be a pressure gauge.

[0082] The second aspect of the present invention provides a method for constructing the ultrasonic-algae-bacteria membrane bioreactor system described in the first aspect. The key to this construction method is that it includes constructing a membrane bioreactor with a transparent internal holding cavity, and a membrane component and an ultrasonic device are arranged in the holding cavity of the membrane bioreactor; the algae-bacteria suspension obtained after mixing the cultured microalgae with the activated sludge is put into the holding cavity of the membrane bioreactor, and the membrane component and the ultrasonic device are immersed.

[0083] In an embodiment of the present invention, when mixing microalgae with activated sludge, the total biomass concentration of the initial mixed liquor is controlled to be between 1.0 g / L and 4.0 g / L. For example, if the total biomass concentration of the initial mixed liquor is controlled to be 2.4 g / L, the inoculum ratio of microalgae to activated sludge is 1:5, the concentration of microalgae is 0.4 g / L, and the concentration of activated sludge is 2 g / L.

[0084] As some embodiments of the present invention, the algae-bacterial suspension selects Chlorella sp. in the logarithmic growth phase as the algae seed source, and is inoculated into aerobic activated sludge sampled from the aeration tank of a sewage treatment plant, and the total biomass concentration of the initial mixed liquor is controlled to be 1.0 g / L~4.0 g / L.

[0085] 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, 54kHz, 55 kHz, 56 kHz, 58 kHz, and 60 kHz, or any value within the above range.

[0086] In some embodiments of the present invention, the ultrasonic intensity is 40 W to 100 W. For example, 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 within the above range.

[0087] In some embodiments of the present invention, the ultrasound device is configured to perform ultrasound for 60 s to 240 s each time and perform ultrasound every 12 h to 36 h.

[0088] Illustratively, the ultrasonic wave lasts for one of 60 s, 80 s, 90 s, 100 s, 120 s, 150 s, 160 s, 180 s, 190 s, 200 s, 210 s, 220 s, and 240 s, or any value satisfying the above range, and the ultrasonic wave is performed once every one of 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, and 36 h, or any value satisfying the above range.

[0089] In some embodiments of the present invention, the method for constructing the ultrasonic-algae membrane bioreactor system of the present invention also 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 algae suspension; and the lighting system is used to provide light for the algae suspension inside the membrane bioreactor.

[0090] In an embodiment of the present invention, the gas flow rate of the aeration system is 1.5 L / min~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 that meets the above range.

[0091] In some embodiments of the present invention, the method for constructing the ultrasonic-algae film bioreactor system in the present invention also includes introducing an inlet system and an outlet system into the membrane bioreactor. Specifically, the inlet system is connected to the internal holding cavity of the membrane bioreactor, and the outlet system is connected to the membrane assembly.

[0092] The third aspect of the present invention provides an application of the ultrasound-algae film bioreactor system described in the first aspect or the ultrasound-algae film bioreactor system constructed using the construction method of the ultrasound-algae film bioreactor system described in the second aspect in sewage treatment.

[0093] In some embodiments of the present invention, the ultrasonic-algae film bioreactor system can be set with a hydraulic retention time (HRT) of 24 h to 48 h and a sludge retention time (SRT) of 20 days. For example, 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, and 48 h, or any value within the above ranges.

[0094] In an embodiment of the present invention, the first peristaltic pump and the second peristaltic pump of the ultrasonic-algae film bioreactor system are operated 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 minutes and pausing for 1 minute is adopted to pump the sewage to be treated into the containing cavity of the algae film bioreactor; an operation mode of turning on for 4 minutes and pausing for 1 minute is adopted to discharge the effluent from the membrane assembly.

[0095] In an embodiment of the present invention, changes in nitrogen and phosphorus nutrient concentrations and chemical oxygen demand (COD) in wastewater are regularly monitored; the transmembrane pressure (TMP) of the ultrasound-algae film bioreactor system is recorded daily; and algae biomass, lipid accumulation, organic matter content and composition, etc. are simultaneously measured.

[0096] In some embodiments of the present invention, an ultrasound-algae film bioreactor system is used to treat wastewater to be treated, maintaining a biomass concentration of 1 g / L to 4 g / L.

[0097] When the ultrasonic-algae film bioreactor system is used for sewage treatment and membrane pollution control, the present invention can effectively alleviate the loss of algae cells while promoting the production of algae biomass and lipid accumulation inside the system, and effectively remove organic pollutants; furthermore, the ultrasonic-algae film bioreactor system can effectively reduce the occurrence of membrane pollution during sewage treatment, can effectively remove most organic matter, reduce the pollutant load entering the membrane filtration unit, thereby slowing down the rate of membrane pollution and extending the cleaning cycle and service life of the membrane.

[0098] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following examples are all commercially available or can be obtained through existing methods; the amounts of the experimental reagents used, unless otherwise specified, are the amounts used in conventional experimental procedures; and the experimental methods, unless otherwise specified, are all conventional methods.

[0099] In the examples and comparative examples of the present invention, synthetic wastewater was used as the wastewater to be treated, and glucose was used as the carbon source to provide easily degradable organic matter and optimize the metabolic activity of the algae-bacteria symbiotic system. The synthetic wastewater composition 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, and 0.3 mg / L NaCl.

[0100] COD was determined using the potassium dichromate digestion method, total nitrogen using alkaline potassium persulfate digestion-UV spectrophotometry, and total phosphorus using ammonium molybdate spectrophotometry. EPS was extracted using a thermal extraction method: a 50 mL centrifuge tube containing the algae suspension was centrifuged at 4000 g for 10 minutes, and the supernatant was removed. The remaining pellet was resuspended in 0.05% NaCl (w / v) at 50°C and mixed using a simulated vortex mixer for 1 minute. The pellet was then centrifuged at 4000 g for 10 minutes, and the supernatant was designated as LB-EPS. Subsequently, the ABS system pellet was resuspended in 0.05% NaCl (w / v) and heated in a 60°C water bath for 30 minutes. Finally, the pellet was centrifuged at 4000 g for 15 minutes, and the supernatant was designated as TB-EPS. All EPS samples were filtered through a 0.45 μm filter before analysis. The protein (PN) content in EPS was calculated using the Folin colorimetric method with bovine serum albumin (BSA) as a standard substance, and the polysaccharide (PS) content was measured using the anthrone / sulfuric acid method with glucose as a standard substance.

[0101] Membrane fouling determination: The monitoring results obtained in the examples of the present invention and the comparative examples were all obtained by reading the data of the pressure controller.

[0102] Example 1

[0103] Construct an ultrasound-algae film bioreactor system 100, such as Figures 1 to 2 As shown, the ultrasonic-algae film bioreactor system 100 includes an inlet system 40, a membrane bioreactor 10, an aeration system 20, a lighting system 30, an outlet system 50 and an ultrasonic system 60, wherein the inlet system 40 introduces the sewage to be treated into the internal accommodating cavity of the membrane bioreactor 10 through an inlet pipe 41 and uses a first peristaltic pump 42; the outlet system 50 is connected to the membrane assembly 12 through an outlet pipe 51, and uses a second peristaltic pump 53 to discharge the filtered clean water, and uses a pressure controller 52 to monitor the outlet pressure in real time.

[0104] The membrane bioreactor 10 comprises an open, rectangular, transparent reactor housing 11 with an internal accommodating chamber, and a membrane assembly 12 disposed within the accommodating chamber. The ultrasonic system 60 includes an ultrasonic device 61 disposed within the accommodating chamber. The transparent reactor housing has an effective volume of 6 L. The accommodating chamber also contains an algae-bacteria suspension 70 with a biomass concentration controlled at 2.4 g / L (0.4 g / L microalgae and 2 g / L activated sludge). The algae-bacteria suspension 70 immerses the membrane assembly 12 and the ultrasonic device 61. The ultrasonic device 61 provides ultrasonic waves to promote biomass production in the algae-bacteria symbiotic system, absorb and utilize wastewater nutrients, and clean the membrane assembly in situ. The ultrasonic device 61 is connected to an external power supply 62 to ensure power supply.

[0105] The membrane assembly 12 is composed of two sets of support plates 121, two sets of gaskets 122, and a membrane cloth 123. A suction port 124 is provided on the top of the support plates, which is connected to the membrane cloth and connected to the water outlet pipe 51 to connect to the water outlet system 50. The membrane cloth 123 is made of polyvinylidene fluoride ultrafiltration membrane.

[0106] The aeration system 20 includes an aeration stone 21, a gas flow meter 22, and an aeration pump 23. The aeration stone 21 extends into the accommodating cavity and is arranged below the membrane assembly 12. The gas flow rate of the aeration system is 1.8 L / min.

[0107] The lighting system 30 uses LED lamps to provide lighting at an intensity of about 7000 Lux, and the entire sewage treatment process can operate for a long time at room temperature.

[0108] Comparative Example 1

[0109] The existing conventional algae film bioreactor is used.

[0110] Wastewater treatment performance experiment

[0111] The sewage treatment performance of the ultrasound-algae film bioreactor system of the present invention was investigated by using the ultrasound-algae film bioreactor system constructed in Example 1 as the experimental group and the conventional algae film bioreactor in Comparative Example 1 as the blank control group.

[0112] The experimental conditions are as follows:

[0113] Experimental group: Ultrasound was performed for 180 s every day and every 24 h, with the ultrasound frequency set at 25 kHz and the ultrasound intensity set at 60 W.

[0114] Blank control group: no ultrasound was added, and other operations were the same as those of the experimental group.

[0115] The reactor was operated in continuous flow mode and the effluent conditions of the experimental group and the blank control group were tested every three days. The experimental results are as follows: Figure 3 shown.

[0116] from Figure 3 As can be seen, the nutrient removal efficiency in the experimental groups was slightly higher than that in the control group. Under appropriate ultrasonic parameters, the target functional bacteria were strengthened and acclimated, and their activity and proportion were increased. To achieve rapid startup, stable operation, and rapid recovery from collapse (collapse recovery means that the reaction system returns to at least its original treatment efficiency after experiencing adverse conditions), as well as to improve the reaction system's resistance to shock loads, pollutant and organic matter removal must be achieved under optimal conditions.

[0117] Bioretention effect experiment

[0118] The ultrasonic-algae film bioreactor system constructed in Example 1 was used as the experimental group, and the conventional algae film bioreactor in Comparative Example 1 was used as the blank control group to treat simulated domestic sewage, and the algae biomass accumulation and lipid production effects of the membrane components of the ultrasonic-algae film bioreactor system in the filtration mode of the present invention were investigated.

[0119] The experimental conditions are as follows:

[0120] Experimental group: MLSS 1.6 g / L, lipid content 40.3%.

[0121] Blank control group: MLSS 1.4 g / L, lipid content 29.4%.

[0122] The reaction system was operated in continuous flow mode and the algae growth status inside was checked every three days. The experimental results are as follows: Figure 4 The lipid accumulation in the experimental and control groups was monitored regularly. Figure 5 shown.

[0123] from Figure 4 Ultrasound stimulation can enhance the permeability of microbial cell membranes in the experimental group, affecting nutrient transport and leading to changes in cell activity and intracellular compound synthesis. Microbial substrate utilization also increases biomass accumulation in the experimental group. In the algae-bacteria symbiotic system, ultrasound may further optimize bacterial metabolites (such as B vitamins and organic acids), indirectly promoting the activity of algal lipid metabolism pathways and activating the expression and activity of key enzymes involved in lipid synthesis (such as fatty acid synthase and acetyl-CoA carboxylase), further improving lipid production efficiency.

[0124] from Figure 5As can be seen, the lipid content in the experimental group was significantly higher than that in the control group. Ultrasonic treatment of liquids produces cavitation bubbles, whose implosion and collapse can induce localized high temperatures and high pressures. This environmental pressure can induce microalgae cells to synthesize lipids or other energy storage substances, thereby increasing lipid production. Furthermore, appropriate ultrasound treatment enhances cell membrane permeability, promoting the transfer and utilization of precursors involved in lipid synthesis.

[0125] Membrane fouling effect experiment

[0126] The ultrasonic-algae film bioreactor system constructed in Example 1 was used as the experimental group, and the conventional algae film 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 assembly in the ultrasonic-algae film bioreactor system of the present invention under the filtration mode was investigated.

[0127] The experimental conditions are as follows:

[0128] Experimental group: The membrane fouling threshold (30 kPa) was reached four times.

[0129] Blank control group: reached the membrane fouling threshold (30 kPa) five times.

[0130] The reactor was operated in continuous flow mode and the transmembrane pressure was recorded every day. The experimental results are as follows: Figure 6 shown.

[0131] from Figure 6 It can be seen that the experimental group introducing ultrasound mitigated membrane fouling to a certain extent. The oscillation of bubble size and the expansion and contraction of the generated bubbles cause rapid changes in the direction and size of the liquid flow. The contraction of the bubbles generated during the compression cycle pulls liquid molecules from the membrane surface. Furthermore, the expansion of the cavitation bubbles during the expansion cycle pushes liquid molecules toward the membrane surface. These rapid changes in the direction and size of the liquid flow near the membrane surface induce shear forces and drag on the membrane surface, leading to the release of fouling particles.

[0132] The mechanical force caused by ultrasound produces a shearing effect on the membrane surface, which can effectively disperse and remove particles and organic matter attached to the membrane surface. As a result, the organic matter content in the mud cake layer on the membrane surface is significantly reduced. Figure 7 Compared with the blank control group, ultrasound destroyed the long-chain molecular structure of these polysaccharides, reducing their deposition on the membrane surface; by regulating the microbial metabolism in the system, it produced less protein components, thereby reducing the impact on membrane fouling.

[0133] Ultrasonic treatment can effectively alleviate the blockage of membrane pores, thereby reducing 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 destruction mechanisms of membrane surface fouling under ultrasonic irradiation. At the end of the reaction system operation, the membrane surface was cleaned with pure water, and the membrane surface after cleaning showed that the membrane pores of the experimental group were clearly visible, see Figure 8 shown.

[0134] Despite cleaning, the blank control group still had some dirt clinging to the membrane surface or clogging the membrane pores. This suggests that the blank control group requires more frequent cleaning, which increases application costs. In contrast, the ultrasound-algae membrane bioreactor system of the present invention is more economical and feasible.

[0135] This invention combines green, clean, and secondary-pollution-free ultrasound with an algae-bacteria membrane bioreactor (MBR) for municipal wastewater treatment. The synergistic effect of the algae-bacteria symbiotic system can alleviate the high aeration requirements required for MBR operation. Furthermore, the effective retention of algae by the membrane can alleviate algal cell loss and improve the stability of the algae-bacteria system. Ultrasonic treatment can clean the MBR membrane in situ (online). Furthermore, proper ultrasonic treatment not only does not damage the biological cell structure but also enhances microbial enzyme activity and metabolic rate, promotes cell wall penetration, and increases interspecies transfer efficiency, thereby promoting the absorption and utilization of wastewater nutrients in the MBR by the algae-bacteria symbiotic system.

[0136] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing an ultrasound-algae film bioreactor system, characterized in that: The ultrasonic-algae-bacteria membrane bioreactor system includes a membrane bioreactor and an ultrasonic system. The membrane bioreactor includes a transparent reactor shell having an internal accommodating cavity and a membrane assembly disposed in the accommodating cavity. The ultrasonic system includes an ultrasonic device disposed in the accommodating cavity. The accommodating cavity is also used to accommodate an algae-bacteria suspension obtained by mixing microalgae with activated sludge, and the algae-bacteria suspension is immersed in the membrane assembly and the ultrasonic device. The membrane cloth type in the membrane assembly is an ultrafiltration membrane, and the ultrasonic device provides ultrasonic waves to promote the absorption and utilization of wastewater nutrients by the algae-bacteria symbiotic system and in-situ cleaning of the membrane assembly. The construction method of the ultrasound-algae film bioreactor system includes: Constructing a membrane bioreactor with a transparent internal accommodating chamber, wherein a membrane assembly and an ultrasonic device are arranged in the accommodating chamber of the membrane bioreactor; The algae-bacterial suspension obtained after the cultured microalgae and activated sludge are mixed is added to the containing chamber of the membrane bioreactor, and the membrane assembly and the ultrasonic device are immersed; when the microalgae and the activated sludge are mixed, the total biomass concentration of the initial mixed liquid is controlled to be 2.4 g / L, the inoculation ratio of the microalgae to the activated sludge is 1:5, the concentration of the microalgae is 0.4 g / L, and the concentration of the activated sludge is 2 g / L; the microalgae is Chlorella vulgaris in the logarithmic growth phase, and the activated sludge is aerobic activated sludge sampled from the aeration tank of a sewage treatment plant; The ultrasonic frequency of the ultrasonic device is 25 kHz, and the ultrasonic intensity is 60 W; the ultrasonic device is configured to perform ultrasound for 180 s each time, and ultrasound is performed once every 24 hours.

2. The method for constructing an ultrasound-algae film bioreactor system according to claim 1, wherein: The ultrasound-algae film bioreactor system also includes: an aeration system in communication with the internal accommodating chamber of the membrane bioreactor, the aeration system being used to provide additional CO2 and O2 for the growth of microalgae and bacteria in the algae-bacteria suspension; A lighting system is used to provide light for the algae-bacteria suspension inside the membrane bioreactor.

3. The method for constructing an ultrasound-algae film bioreactor system according to claim 1, wherein: The ultrasonic-algae membrane bioreactor system further includes a water inlet system and a water outlet system. The water inlet system is connected to the accommodating cavity of the membrane bioreactor, and the water outlet system is connected to the membrane assembly.

4. The method for constructing an ultrasound-algae film bioreactor system according to claim 1, wherein: The method for constructing the ultrasound-algae 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.

5. The method for constructing an ultrasound-algae film bioreactor system according to claim 4, 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~10000 Lux.

6. Application of an ultrasound-algae film bioreactor system constructed by the construction method of an ultrasound-algae film bioreactor system according to any one of claims 1 to 5 in sewage treatment, characterized in that: The ultrasound-algae film bioreactor system regularly monitors the concentration of nitrogen and phosphorus nutrients and COD changes in the sewage, records the transmembrane pressure difference of the system every day, and simultaneously measures the algae biomass, lipid accumulation, and organic matter content in the suspension.

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