Microalgae membrane bioreactor and application thereof in wastewater denitrification and phosphorus removal treatment

Abstract

The application discloses a kind of microalgae membrane bioreactor and its application in sewage denitrification and phosphorus removal processing, including reactor main body, the microfiltration membrane assembly and suspended biological filler are equipped in the reactor main body, and inoculated with microalgae;The bottom in the reactor main body is equipped with aeration device;The reactor main body is transparent material, and the reactor main body outside is equipped with light source;The top of the reactor main body is communicated with water inlet pipeline, and water inlet pump is equipped on water inlet pipeline;The top of the microfiltration membrane assembly is communicated with water outlet pipeline, and water outlet pump is equipped on water outlet pipeline;The suspended biological filler is loofah sponge loaded with crab shell powder.The application is suspended and fixed culture to microalgae in microalgae membrane bioreactor using the way that suspended biological filler and microfiltration membrane assembly are combined, reduces the accumulation and aggregation of microalgae, expands the contact area of microalgae and sewage, and can significantly accelerate the removal of nitrogen and phosphorus in sewage by microalgae.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a microalgae membrane bioreactor and its application in wastewater denitrification and phosphorus removal. Background Technology

[0002] Membrane bioreactors (MBRs) are wastewater treatment processes that combine membrane separation technology with bioreactors. Compared to the traditional activated sludge process, MBRs can reduce the operating costs of wastewater treatment plants while achieving better treatment results, significantly improving the treatment efficiency for chemical oxygen demand (COD) and ammonia nitrogen. However, due to the long hydraulic retention time in MBRs, nitrifying bacteria proliferate rapidly, enhancing nitrification and inhibiting denitrification, resulting in lower total nitrogen treatment efficiency.

[0003] Microalgae have a short life cycle and can carry out full photosynthesis under suitable light conditions. They also have a strong absorption effect on nitrogen, phosphorus, poorly soluble organic matter and metal elements in water. Inoculating microalgae into MBR can combine the advantages of microalgae and MBR. Microalgae can enhance the nitrogen and phosphorus removal effect of MBR and improve the quality of effluent. At the same time, the membrane can be used to retain the microalgae after the reaction and make them available for resource utilization.

[0004] In existing microalgae bioreactors, microalgae are generally attached to a mesh-like biofilm carrier. For example, the "Method for Preparing Algal Biofilm" disclosed in Chinese patent literature, publication number CN106011122A, includes four specific steps: carrier pretreatment, algae cultivation, algae domestication, and algal biofilm preparation.

[0005] However, when microalgae are attached to a biofilm carrier, their accumulation and aggregation hinder photosynthesis and reduce the contact area between the microalgae and wastewater, making it difficult for them to rapidly absorb nutrients such as nitrogen and phosphorus from the wastewater. Therefore, although existing microalgae membrane bioreactors offer some improvement in nitrogen and phosphorus removal efficiency compared to traditional MBRs, the improvement is limited, and it is difficult to obtain effluent quality that meets standards when using them to treat wastewater. Summary of the Invention

[0006] The present invention aims to overcome the aforementioned problems of existing microalgae membrane bioreactors and provides a microalgae membrane bioreactor and its application in wastewater denitrification and phosphorus removal. In the microalgae membrane bioreactor, a combination of suspended biological packing material and microfiltration membrane components is used to suspend and fix microalgae for cultivation, which reduces the accumulation and aggregation of microalgae, expands the contact area between microalgae and wastewater, and can significantly accelerate the removal of nitrogen and phosphorus from wastewater by microalgae.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A microalgae membrane bioreactor includes a reactor body, within which a microfiltration membrane assembly and suspended biological packing material are disposed and inoculated with microalgae; an aeration device is provided at the bottom of the reactor body; the reactor body is made of transparent material, and a light source is provided on the outside of the reactor body; the top of the reactor body is connected to an inlet pipe, and an inlet pump is provided on the inlet pipe; the top of the microfiltration membrane assembly is connected to an outlet pipe, and an outlet pump is provided on the outlet pipe; the suspended biological packing material is a loofah sponge loaded with crab shell powder.

[0009] This invention simultaneously incorporates a microfiltration membrane assembly and a suspended biological packing material within the reactor body. The suspended biological packing material, made from loofah sponges loaded with crab shell powder, possesses low density, a large specific surface area, and good biocompatibility. Under the airflow generated by the aeration device, it can suspend within the reactor, fully adsorbing suspended microalgae and fixing them to its surface to form a microalgal biofilm. This suspended and fixed cultivation of microalgae promotes photosynthesis, enhancing their growth capacity and wastewater purification ability, while reducing algal accumulation and aggregation. It also expands the contact area between microalgae and wastewater, facilitating the rapid uptake of nutrients such as nitrogen and phosphorus from the wastewater and accelerating their accumulation and transformation within the algae. This significantly accelerates the removal of nitrogen and phosphorus from wastewater by microalgae. During reactor operation, wastewater enters the reactor body from the top. Under the illumination of an external light source, the microalgal biofilm undergoes photosynthesis to purify the wastewater, removing pollutants such as nitrogen, phosphorus, and COD. The treated wastewater passes through the microfiltration membrane assembly and flows out of the reactor via the effluent pipe. Due to the metabolic processes of microalgal biofilms, aging microalgal biofilms will detach. The installation of microfiltration membrane components helps to enrich the detached microalgal biofilms and prevent aging and dead algal cells from remaining in the reactor and blocking light, thereby affecting the photosynthesis of microalgal biofilms.

[0010] Therefore, the microalgae bioreactor of this invention, which uses suspended and immobilized microalgae cultivation, significantly improves the removal efficiency of nitrogen and phosphorus from wastewater. Furthermore, the added microfiltration membrane component helps to enrich and remove microalgae biofilms detached during wastewater treatment, preventing aging and dead algal cells from weakening the reactor's treatment effect. This enhances the reactor's ability to effectively remove COD, total nitrogen (TN), and ammonia nitrogen (NH4) from wastewater. + Both nitrogen (N) and total phosphorus (TP) showed excellent removal efficiency.

[0011] Preferably, the microalgae is Chlorella proteoglycans; the inoculum amount of the microalgae is 5-15% of the effective volume of the reactor body.

[0012] Preferably, the microfiltration membrane module is a curtain-type polyvinylidene fluoride hollow fiber membrane module with a pore size of 0.01–0.1 μm and a membrane flux of 5–20 L / (m²).2 ·h).

[0013] Preferably, the method for preparing the suspended biological packing is as follows:

[0014] A) After washing, crushing, and sieving the crab shells, they are treated with sodium hydroxide solution and hydrogen peroxide respectively. After washing and drying, pretreated crab shell powder with a particle size of 100-500 mesh is obtained.

[0015] B) Cut the loofah sponge into small sections of 4-5 cm, soak them in deionized water and sodium hydroxide solution respectively, then wash and dry them to obtain pretreated loofah sponge;

[0016] C) Add the pretreated crab shell powder to deionized water, disperse it evenly, add dopamine to the dispersion, stir evenly, add Tris-HCl buffer to adjust the pH of the system to 8.0-8.5, stir evenly to obtain the reaction solution;

[0017] D) The pretreated loofah sponge was immersed in the reaction solution and shaken for 6-12 hours. The loofah sponge was then removed and dried to obtain loofah sponge loaded with crab shell powder.

[0018] In the preparation process of the suspended biological filler in this invention, firstly, in step A), proteins, fats, etc., in the crab shell are removed and decolorized, which gives the pretreated crab shell powder good adsorption properties, enabling the reuse of aquatic processing by-products. Then, in step B), the loofah sponge is pretreated with alkaline solution, which improves the hydrophilicity of the loofah sponge surface and increases its specific surface area. Finally, in steps C) and D), through the self-polymerization reaction of dopamine on the surface of the crab shell powder and loofah sponge, polydopamine is used to load the crab shell powder onto the surface of the loofah sponge. Polydopamine has excellent adhesion properties, which can firmly attach the crab shell powder to the surface of the loofah sponge. At the same time, polydopamine can also improve the hydrophilicity of the surface of the crab shell powder and loofah sponge, which is beneficial to improving the affinity between the suspended biological filler and microalgae, making it easier for microalgae biofilms to attach and grow on its surface. Loading with crab shell powder can further increase the specific surface area of ​​loofah sponge and improve its surface roughness, which is conducive to the adsorption and loading of microalgae, and the microalgae biofilm on the surface is not easy to fall off. At the same time, crab shell powder, loofah sponge and polydopamine all have good biocompatibility, which is conducive to the adsorption and growth of microalgae on the surface of suspended biological filler.

[0019] Preferably, in step A), the mass concentration of the sodium hydroxide solution is 5-10%, and the mass ratio of crab shell powder to sodium hydroxide solution is 1:5-10, the treatment temperature is 70-80℃, and the treatment time is 1-3 hours; the mass concentration of hydrogen peroxide is 25-30%, and the mass ratio of crab shell powder to hydrogen peroxide is 1:5-10, the treatment temperature is 40-60℃, and the treatment time is 1-3 hours.

[0020] Preferably, in step B), the soaking time in deionized water is 1–3 h; the mass concentration of the sodium hydroxide solution is 5–10%, and the soaking time in the sodium hydroxide solution is 1–3 h.

[0021] Preferably, the concentration of dopamine in the dispersion in step C) is 2–4 mg / mL.

[0022] Preferably, in step C), the mass ratio of the pretreated crab shell powder to dopamine is 4-5:1; and in step D), the mass ratio of the pretreated loofah sponge to the crab shell powder in the reaction solution is 2-3:1.

[0023] Preferably, the feeding volume of the suspended biological packing is 10-30% of the effective volume of the reactor body.

[0024] The present invention also provides an application of the above-mentioned microalgae membrane bioreactor in wastewater denitrification and phosphorus removal treatment, comprising the following steps:

[0025] (1) Preparation of microalgae seed solution: Microalgae were inoculated into a culture medium and cultured under light. The algal solution in the logarithmic growth phase was used as microalgae seed solution.

[0026] (2) Microalgae biofilm formation: Add culture medium to the microalgae bioreactor, inoculate the microalgae seed liquid into the microalgae bioreactor, add mixed nutrient solution, and culture under light and aeration for 8-12 days to form a biofilm.

[0027] (3) Acclimation of microalgae biofilm: After the biofilm is attached, the culture medium in the microalgae biofilm bioreactor is replaced with the sewage to be treated within 6 to 7 days, and the culture is continued to be carried out under light aeration. After all the culture is replaced, the culture is stabilized for 1 to 3 days to complete the acclimation.

[0028] (4) Wastewater denitrification and phosphorus removal treatment: The wastewater to be treated is added into the domesticated microalgae membrane bioreactor and denitrification and phosphorus removal treatment is carried out under light and aeration conditions.

[0029] Preferably, the culture medium used in steps (1) and (2) is BG-11 culture medium.

[0030] Preferably, the mixed culture medium used in step (2) includes glucose, urea, and potassium dihydrogen phosphate, with the concentrations of glucose, urea, and potassium dihydrogen phosphate in the culture medium being 7.0–9.0 g / L, 1.0–2.0 g / L, and 70–80 mg / L, respectively. In this invention, a mixed culture medium is added during the microalgae biofilm formation process, using glucose as a carbon source, urea as a nitrogen source, and potassium dihydrogen phosphate as a phosphorus source. Compared to photosynthetic autotrophy, immobilization under mixed nutrient conditions can increase the number of microalgae cells and improve their efficiency in removing nitrogen and phosphorus from wastewater.

[0031] As a preferred option, the light cultivation conditions in step (1) are: cultivation temperature 27-29℃, light intensity 2300-2500 Lux.

[0032] Preferably, the light intensity during light-aerated cultivation in steps (2) and (3) is 2000–2200 Lux; the light cycle is 10–14 hours of light followed by 14–10 hours of darkness; and the aeration rate is 1–3 L / m³. 3 The lighting and aeration conditions in step (4) are the same as those in steps (2) and (3).

[0033] Therefore, the present invention has the following beneficial effects:

[0034] (1) The microalgae membrane bioreactor in this invention uses suspended biological packing to suspend and fix microalgae, which reduces the accumulation and aggregation of microalgae, expands the contact area between microalgae and sewage, and significantly improves nitrogen and phosphorus removal efficiency.

[0035] (2) The microfiltration membrane component in the microalgae bioreactor of the present invention helps to enrich and clean up the microalgae biofilm that falls off during wastewater treatment, and avoids the weakening of the reactor treatment effect by aging and dead algae cells, which can further improve the removal effect of pollutants in wastewater.

[0036] (3) The suspended biological filler uses loofah sponge loaded with crab shell powder. Through the self-polymerization reaction of dopamine on the surface of crab shell powder and loofah sponge, the crab shell powder is loaded on the surface of loofah sponge by polydopamine, which is conducive to the adsorption and growth of microalgae on the surface of the suspended biological filler. The microalgae biofilm on the surface is not easy to fall off. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the microalgae membrane bioreactor of the present invention.

[0038] In the diagram: 1 Reactor body, 2 Microfiltration membrane module, 3 Suspended biological packing material, 4 Aeration disc, 5 Aeration pump, 6 Light source, 7 Inlet pump, 8 Liquid level control system, 9 Outlet pump, 10 Time relay, 11 Water storage tank. Detailed Implementation

[0039] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0040] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. The methods in the following embodiments are conventional methods in the field unless otherwise specified.

[0041] General Implementation Examples:

[0042] The structure of the microalgae membrane bioreactor used in the embodiments of the present invention is as follows: Figure 1As shown, the reactor includes a main body 1 made of 5mm thick plexiglass, with dimensions of length × width × height = 0.3m × 0.3m × 0.5m and an effective volume of 45L. The reactor body contains a microfiltration membrane module 2 and suspended biological packing material 3, inoculated with microalgae, specifically *Chlorella proteoglycans*, at an inoculation rate of 5-15% of the reactor's effective volume. The microfiltration membrane module is a curtain-type polyvinylidene fluoride hollow fiber membrane with a pore size of 0.03μm and a total membrane area of ​​0.1m². 2 Membrane flux 8 L / (m 2 •h); The suspended biological packing material is a loofah sponge loaded with crab shell powder, and the feeding volume of the suspended biological packing material is 10-30% of the effective volume of the reactor body. An aeration disc 4 connected to the aeration pump 5 is located at the bottom of the reactor body. A light source 6 is located outside the reactor body, consisting of six 25W fluorescent tubes, with two tubes arranged on each of the left and right sides of the reactor body, and one tube arranged at the same height on each of the front and rear sides. The top of the reactor body is connected to the inlet pipe, and the other side of the inlet pipe is connected to the water storage tank 11. An inlet pump 7 is installed on the inlet pipe, and the inlet pump is connected to the liquid level control system 8. The top of the microfiltration membrane module is connected to the outlet pipe, and an outlet pump 9 is installed on the outlet pipe, and the outlet pump is connected to the time relay 10.

[0043] The preparation method of the suspended biological packing material is as follows:

[0044] A) After washing, crushing, and sieving the crab shells, treat them with a 5-10% sodium hydroxide solution and a 25-30% hydrogen peroxide solution, respectively. After washing and drying, pretreated crab shell powder with a particle size of 100-500 mesh is obtained. When treating with sodium hydroxide solution, the mass ratio of crab shell powder to sodium hydroxide solution is 1:5-10, the treatment temperature is 70-80℃, and the treatment time is 1-3 hours. When treating with hydrogen peroxide, the mass ratio of crab shell powder to hydrogen peroxide is 1:5-10, the treatment temperature is 40-60℃, and the treatment time is 1-3 hours.

[0045] B) Cut the loofah sponge into small sections of 4-5 cm, soak them in deionized water and sodium hydroxide solution with a mass concentration of 5-10% for 1-3 hours respectively, then wash and dry to obtain pretreated loofah sponge;

[0046] C) Add the pretreated crab shell powder to deionized water, disperse it evenly, and then add dopamine to the dispersion. The concentration of dopamine in the dispersion is 2-4 mg / mL, and the mass ratio of pretreated crab shell powder to dopamine is 4-5:1. After stirring evenly, add Tris-HCl buffer to adjust the pH of the system to 8.0-8.5, and stir evenly to obtain the reaction solution.

[0047] D) The pretreated loofah sponge is immersed in the reaction solution, and the mass ratio of the pretreated loofah sponge to the crab shell powder in the reaction solution is 2-3:1; after shaking the reaction for 6-12 hours, the loofah sponge is taken out and dried to obtain the loofah sponge loaded with crab shell powder.

[0048] In the operation of the microalgae membrane bioreactor of this invention, wastewater in the storage tank is pumped in by the inlet pump and flows into the reactor body from the top through the inlet pipe. Under the illumination of a light source, microalgae undergo nitrogen and phosphorus removal. The microfiltration membrane module retains algal cells, and the treated effluent is extracted by the outlet pump, passing through the microfiltration membrane module and collected through the outlet pipe. The liquid level control system can control the start and stop of the inlet pump, thereby controlling the liquid level in the reactor; the time relay can control the start and stop of the outlet pump, thereby controlling the hydraulic residence time in the reactor.

[0049] Application Example 1:

[0050] The application of the above-mentioned microalgae membrane bioreactor in the denitrification and phosphorus removal treatment of wastewater from aquatic product processing includes the following steps:

[0051] (1) Preparation of microalgae seed culture: BG-11 medium was placed into a 250mL Erlenmeyer flask (100mL of liquid), and sterilized at 121℃ for 20min; Chlorella proteoglycans slant culture (provided by Arge Hebei Life Science Co., Ltd.) was inoculated into the Erlenmeyer flask for light culture at 28℃, light intensity of 2400Lux, and shaking speed of 140rpm; the algal solution in the logarithmic growth phase was used as microalgae seed culture.

[0052] (2) Microalgae biofilm formation: 40 L of BG-11 medium was added to the microalgae bioreactor. Microalgae seed culture was inoculated into the microalgae bioreactor at 10% of the medium volume, and mixed nutrient solution was added. The biofilm formation was carried out after 8 days of light-aerated culture. The light intensity during the light-aerated culture was 2000 Lux, and the light cycle was 12 hours of light followed by 12 hours of darkness. The aeration rate was 2 L / m³. 3 The mixed culture medium contains glucose, urea and potassium dihydrogen phosphate, and the concentrations of glucose, urea and potassium dihydrogen phosphate in the culture medium are 8.0 g / L, 1.5 g / L and 75 mg / L, respectively.

[0053] (3) Acclimation of microalgae biofilm: After the biofilm is attached, the culture medium in the microalgae biofilm bioreactor is replaced with simulated sewage prepared with turtle shell breeding wastewater as a reference within 7 days, and the culture is continued to be carried out under light aeration under the conditions of step (2). 6L is replaced every day for the first 6 days, and the culture medium is completely replaced with simulated sewage on the 7th day. After 2 days of stable culture, the acclimation is completed.

[0054] (4) Wastewater denitrification and phosphorus removal treatment: The simulated wastewater was added into the domesticated microalgae membrane bioreactor and denitrified and phosphorus removed under the light and aeration conditions in step (2). The hydraulic retention time was 10h and the system was run continuously for 20d. The pollutant concentration in the effluent was tested every 4d and the removal rate of each pollutant was calculated. The results are shown in Tables 1 to 4. The water quality was measured using the standard methods in the "Surface Water Environmental Quality Standard" (GB3838-2002).

[0055] The feeding volume of the suspended biological packing material in the microalgae membrane bioreactor is 20% of the effective volume of the reactor body. The preparation method of the suspended biological packing material is as follows:

[0056] A) After washing, crushing, and sieving the crab shells, the crab shells were treated with 8% sodium hydroxide solution and 30% hydrogen peroxide solution, respectively. After washing and drying, pretreated crab shell powder with a particle size of 200 mesh was obtained. When treating with sodium hydroxide solution, the mass ratio of crab shell powder to sodium hydroxide solution was 1:8, the treatment temperature was 75℃, and the treatment time was 2h. When treating with hydrogen peroxide, the mass ratio of crab shell powder to hydrogen peroxide was 1:8, the treatment temperature was 50℃, and the treatment time was 2h.

[0057] B) Cut the loofah sponge into 5cm segments, soak them in deionized water and 8% sodium hydroxide solution for 2 hours respectively, then wash and dry them to obtain the pretreated loofah sponge.

[0058] C) Add the pretreated crab shell powder to deionized water, disperse it evenly, and then add dopamine to the dispersion. The concentration of dopamine in the dispersion is 3 mg / mL, and the mass ratio of pretreated crab shell powder to dopamine is 4.5:1. After stirring evenly, add Tris-HCl buffer to adjust the pH of the system to 8.1, and stir evenly to obtain the reaction solution.

[0059] D) The pretreated loofah sponge was immersed in the reaction solution, and the mass ratio of the pretreated loofah sponge to the crab shell powder in the reaction solution was 2.5:1. After shaking and reacting for 8 hours, the loofah sponge was taken out and dried to obtain the loofah sponge loaded with crab shell powder.

[0060] The simulated wastewater, prepared using turtle shell farming wastewater as a reference, consisted of: ammonium sulfate ((NH4)2SO4), anhydrous glucose (C6H2SO4), and other components. 12 O6), urea (H2NCONH2), potassium dihydrogen phosphate (KH2PO4), dipotassium hydrogen phosphate (K2HPO4·3H2O), soybean peptone, sodium bicarbonate (NaHCO3), sodium alginate (C6H7NaO6)n, polyvinyl alcohol (CH2CHOH)n, agar powder (C 12 H 18O9)n, calcium chloride (CaCl2·2H2O), and boric acid (H3BO3) were all purchased from Sinopharm Chemical Reagent Co., Ltd.; the simulated wastewater after sterilization had a pH of 7.5, TN of 101.27 mg / L, TP of 13.46 mg / L, COD of 983.12 mg / L, and NH4+ of... + -N was 50.83 mg / L.

[0061] Application Example 2:

[0062] The difference between Application Example 2 and Application Example 1 is that in step (2), the concentrations of glucose, urea and potassium dihydrogen phosphate in the mixed culture medium added during microalgae biofilm formation are 7.0 g / L, 1.0 g / L and 70 mg / L, respectively; the rest are the same as in Application Example 1.

[0063] Application Example 3:

[0064] The difference between Application Example 3 and Application Example 1 is that in step (2), the concentrations of glucose, urea and potassium dihydrogen phosphate in the mixed culture medium added during microalgae biofilm formation are 9.0 g / L, 2.0 g / L and 80 mg / L, respectively; the rest are the same as in Application Example 1.

[0065] Application Example 4:

[0066] The difference between Application Example 4 and Application Example 1 is that in step (2), the concentrations of glucose, urea and potassium dihydrogen phosphate in the mixed culture medium added during microalgae biofilm formation are 10.0 g / L, 3.0 g / L and 90 mg / L, respectively; the rest are the same as in Application Example 1.

[0067] Comparative application example 1:

[0068] The difference between Application Example 1 and Application Example 2 is that no mixed culture medium is added when microalgae attach to the biofilm in step (2), while the rest is the same as in Application Example 1.

[0069] Compare with application example 2:

[0070] The difference between Application Example 2 and Application Example 1 is that the microalgae membrane bioreactor does not have a microfiltration membrane module and suspended biological packing inside the reactor body, while the rest is the same as in Application Example 1.

[0071] Compare with example 3:

[0072] The difference between Application Example 3 and Application Example 1 is that the main body of the microalgae membrane bioreactor is equipped with only suspended biological packing material and no microfiltration membrane module. Everything else is the same as in Application Example 1.

[0073] Compare with application example 4:

[0074] The difference between Application Example 4 and Application Example 1 is that pretreated loofah sponge is used as a suspended biological packing material in the microalgae membrane bioreactor. The preparation method is as follows: the loofah sponge is cut into 5cm segments, soaked in deionized water and 8% sodium hydroxide solution for 2 hours respectively, and then washed and dried to obtain pretreated loofah sponge; the rest is the same as in Application Example 1.

[0075] Compare with application example 5:

[0076] The difference between Application Example 5 and Application Example 1 lies in the preparation method of the suspended biological packing material used in the microalgae membrane bioreactor:

[0077] A) After washing, crushing, and sieving the crab shells, the crab shells were treated with 8% sodium hydroxide solution and 30% hydrogen peroxide solution, respectively. After washing and drying, pretreated crab shell powder with a particle size of 200 mesh was obtained. When treating with sodium hydroxide solution, the mass ratio of crab shell powder to sodium hydroxide solution was 1:8, the treatment temperature was 75℃, and the treatment time was 2h. When treating with hydrogen peroxide, the mass ratio of crab shell powder to hydrogen peroxide was 1:8, the treatment temperature was 50℃, and the treatment time was 2h.

[0078] B) Cut the loofah sponge into 5cm segments, soak them in deionized water and 8% sodium hydroxide solution for 2 hours respectively, then wash and dry to obtain the pretreated loofah sponge;

[0079] C) The pretreated crab shell powder was blown into the pretreated loofah sponge using a hair dryer. The mass ratio of the pretreated loofah sponge to the pretreated crab shell powder was 2.5:1, resulting in a loofah sponge loaded with crab shell powder.

[0080] Everything else is the same as in Application Example 1.

[0081] Comparative application example 6:

[0082] The difference between Application Example 6 and Application Example 1 lies in the preparation method of the suspended biological packing material used in the microalgae membrane bioreactor:

[0083] A) After washing, crushing, and sieving the crab shells, the crab shells were treated with 8% sodium hydroxide solution and 30% hydrogen peroxide solution, respectively. After washing and drying, pretreated crab shell powder with a particle size of 200 mesh was obtained. When treating with sodium hydroxide solution, the mass ratio of crab shell powder to sodium hydroxide solution was 1:8, the treatment temperature was 75℃, and the treatment time was 2h. When treating with hydrogen peroxide, the mass ratio of crab shell powder to hydrogen peroxide was 1:8, the treatment temperature was 50℃, and the treatment time was 2h.

[0084] B) Cut the loofah sponge into 5cm segments, soak them in deionized water and 8% sodium hydroxide solution for 2 hours respectively, then wash and dry to obtain the pretreated loofah sponge;

[0085] C) Add the pretreated crab shell powder to an aqueous polyurethane emulsion (Bayer, solid content 50wt%), stir and disperse evenly, then immerse the pretreated loofah sponge in the emulsion. The mass ratio of the pretreated loofah sponge to the crab shell powder is 2.5:1. After shaking and reacting for 8 hours, take out the loofah sponge and dry it to obtain the loofah sponge loaded with crab shell powder.

[0086] Everything else is the same as in Application Example 1.

[0087] Table 1: COD removal rate test results.

[0088]

[0089]

[0090] Table 2: TN removal rate test results.

[0091]

[0092] Table 3: NH4 + -N removal rate test results.

[0093]

[0094] Table 4: TP removal rate test results.

[0095]

[0096] As can be seen from Tables 1 to 4, when the microalgae membrane bioreactor of this invention is used in Application Examples 1 to 4 for continuous dynamic treatment of simulated aquaculture wastewater, the reactor effectively reduces COD, TN, and NH4 in the wastewater. + Both -N and TP showed excellent removal effects.

[0097] In contrast, in Application Example 1, no mixed culture medium was added during the microalgae biofilm formation process, and only photosynthetic autotrophy was carried out. This was not conducive to the growth of Chlorella, and the biomass of Chlorella in the reactor decreased, resulting in a decrease in its removal rates of COD, TN, and TP compared to Application Example 1.

[0098] In contrast to Application Example 2, which did not include a microfiltration membrane module or suspended biological packing material in the reactor, the reactor effectively controlled COD, TN, and NH4+. + The removal efficiency of -N and TP was significantly lower than in the application example.

[0099] In contrast to Application Example 3, which only used suspended biological packing material in the reactor without a microfiltration membrane module, the removal rates of COD and TP in the reactor were significantly lower than those in Application Example 1, while the removal rates of NH4+ were also lower. + The removal efficiency of -N was not significantly different, while the removal rate of TN was similar within 8 days, but decreased significantly after 8 days. This is because of the metabolic activity of microalgal biofilms; with prolonged operation, aged microalgal biofilms will shed. The presence of microfiltration membrane modules helps to enrich the shed algal biofilms. Without microfiltration membrane modules, these shed microalgal biofilms remain in the reactor, which may block light, leading to a decrease in microalgae content and a decrease in the removal efficiency of pollutants in wastewater. These shed biofilms are also prone to putrefaction and degradation, which may be another reason for the increase in TN content in the system.

[0100] In contrast, in the reactor of Application Example 4, loofah sponge was used directly as a suspended biological packing material without loading crab shell powder on it. The specific surface area and surface roughness of the suspended biological packing material decreased, which was not conducive to the attachment of microalgae. As a result, the removal rates of COD, TN and TP in the reactor were all lower than those in Application Example 1.

[0101] In contrast to Application Example 5, where crab shell powder was directly filled into the loofah sponge without using polydopamine to bind the two together, the crab shell powder easily detached from the loofah sponge under the action of water flow, failing to effectively modify the surface of the loofah sponge. The removal rates of COD, TN, and TP in the reactor were also lower than in Application Example 1. Furthermore, the detached crab shell powder would also affect the quality of the effluent, making it unsuitable for practical application.

[0102] In contrast to application example 6, where crab shell powder was fixed onto the surface of loofah sponge using a water-based polyurethane emulsion, the polyurethane emulsion exhibited poor hydrophilicity and biocompatibility compared to polydopamine. Consequently, the biofilm formation of microalgae on the suspended biological packing was also affected, resulting in a decrease in the reactor's pollutant removal efficiency compared to application example 1.

Claims

1. A microalgae membrane bioreactor, characterized in that, The reactor body is internally provided with a microfiltration membrane assembly and a suspended biological filler, and is inoculated with microalgae; the bottom of the reactor body is provided with an aeration device; The reactor body is made of transparent material, and the reactor body is externally provided with a light source; The top of the reactor body is connected with a water inlet pipeline, and a water inlet pump is arranged on the water inlet pipeline; the top of the microfiltration membrane assembly is connected with a water outlet pipeline, and a water outlet pump is arranged on the water outlet pipeline; The suspended biological filler is a luffa sponge loaded with crab shell powder; the pretreated luffa sponge is immersed in a reaction solution, shaken and reacted, and then taken out and dried to obtain the suspended biological filler; The reaction solution is prepared by adding dopamine into a water dispersion of pretreated crab shell powder, stirring uniformly, and then adding Tris-HCl buffer to adjust the pH of the system to 8.0-8.5, and stirring uniformly; The pretreated crab shell powder is prepared by washing, crushing and sieving the crab shell, and then treating the crab shell with NaOH solution and hydrogen peroxide solution respectively; The pretreated luffa sponge is prepared by soaking the cut luffa sponge in deionized water and NaOH solution respectively, and then washing and drying.

2. The microalgae membrane bioreactor according to claim 1, characterized in that, The microalgae is Chlorella pyrenoidosa; the inoculation amount of the microalgae is 5-15% of the effective volume of the reactor body.

3. The microalgae membrane bioreactor according to claim 1 or 2, characterized in that, The microfiltration membrane module is a curtain type polyvinylidene fluoride hollow fiber membrane module, the membrane pore size is 0.01-0.1 μm, the membrane flux is 5-20 L / (m 2 ·h).

4. The microalgae membrane bioreactor according to claim 1, characterized in that, The preparation method of the suspended biological filler is as follows: A) washing, crushing and sieving the crab shell, and then treating the crab shell with NaOH solution and hydrogen peroxide solution respectively, and then washing and drying to obtain pretreated crab shell powder with a particle size of 100-500 mesh; B) cutting the luffa sponge into small pieces of 4-5 cm, soaking the small pieces in deionized water and NaOH solution respectively, and then washing and drying to obtain pretreated luffa sponge; C) adding the pretreated crab shell powder into deionized water, dispersing uniformly, and then adding dopamine into the dispersion, stirring uniformly, and then adding Tris-HCl buffer to adjust the pH of the system to 8.0-8.5, and stirring uniformly to obtain a reaction solution; D) immersing the pretreated luffa sponge in the reaction solution, shaking and reacting for 6-12 hours, taking out the luffa sponge and drying to obtain the luffa sponge loaded with crab shell powder.

5. The microalgae membrane bioreactor according to claim 4, characterized in that, The mass ratio of the pretreated crab shell powder to dopamine in step C) is 4-5:1; the mass ratio of the pretreated luffa sponge to the crab shell powder in the reaction solution in step D) is 2-3:

1.

6. The microalgae membrane bioreactor according to claim 1 or 4 or 5, characterized in that, The feeding volume of the suspended biological filler is 10-30% of the effective volume of the reactor body.

7. The use of the microalgae membrane bioreactor according to any one of claims 1 to 6 in the treatment of wastewater for nitrogen and phosphorus removal, characterized in that, The method comprises the following steps: (1) preparation of microalgae seed solution: inoculating microalgae in a culture medium for light culture, and taking the algal liquid in the logarithmic growth phase as the microalgae seed solution; (2) microalgae membrane formation: adding a culture medium into the microalgae membrane bioreactor, inoculating the microalgae seed solution into the microalgae membrane bioreactor, and adding a mixed nutrient solution, and culturing for 8-12 days under light and aeration to form a membrane; (3) domestication of microalgae biofilm: replacing the culture medium in the microalgae membrane bioreactor with the wastewater to be treated within 6-7 days after the membrane formation, and continuing to culture under light and aeration, and stably culturing for 1-3 days after the replacement is completed, and completing the domestication; (4) treatment of wastewater for nitrogen and phosphorus removal: adding the wastewater to be treated into the domesticated microalgae membrane bioreactor, and treating the wastewater for nitrogen and phosphorus removal under light and aeration.

8. Use according to claim 7, characterized in that, The culture medium used in step (1) and step (2) is BG-11 culture medium; the mixed culture solution used in step (2) comprises glucose, urea and potassium dihydrogen phosphate, and the concentrations of the added glucose, urea and potassium dihydrogen phosphate in the culture medium are 7.0-9.0 g / L, 1.0-2.0 g / L and 70-80 mg / L respectively.

9. Use according to claim 7, characterized in that, The light culture condition in step (1) is as follows: culture temperature is 27-29 DEG C, and light intensity is 2300-2500 Lux.

10. Use according to claim 7, characterized in that, The light intensity in the light exposure and aeration culture in steps (2) and (3) is 2000-2200 Lux; the light cycle is 10-14 hours of light and 14-10 hours of darkness; the aeration amount is 1-3 L / m 3 ; the light and aeration conditions in step (4) are the same as those in steps (2) and (3).

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