Bacteria-algae composite adsorption module wetland substrate filler as well as preparation method and application thereof

Abstract

The invention relates to a bacteria-algae composite adsorption module wetland substrate filler as well as a preparation method and application thereof, and belongs to the technical field of biology. The bacteria-algae composite adsorption module wetland substrate filler is prepared by the following steps: preparing an adsorption module, fungicide microspheres and a diatom biological membrane layer, placing the diatom biological membrane layer on the upper layer of the fungicide microspheres to form a diatom fungicide composite layer, and placing the diatom fungicide composite layer on the upper layer of the adsorption module. The bacteria-algae composite adsorption module wetland substrate filler disclosed by the invention can effectively remove pollutants such as nitrogen, phosphorus, lead, cadmium and the like in sewage by independently using the bacteria-algae composite adsorption module wetland substrate filler, effectively reduces the chemical oxygen demand (COD) of the sewage, and simplifies the hierarchical design of an artificial wetland; and the regeneration capacity is high, the replacement period is prolonged, and the operation and maintenance cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of biological detection technology, and in particular relates to a wetland matrix filler for a bacteria-algae composite adsorption module and a preparation method and application thereof. Background Art

[0002] Constructed wetlands are engineered systems that use natural vegetation, soil and organisms to treat wastewater. The functional components of artificial wetlands include three major parts: matrix, plants and microorganisms. Among them, the matrix plays the role of purifying water, providing a growth carrier and nutrients for plants, providing an attachment surface for microorganisms, and providing good hydraulic conductivity for water flow. Studies have shown that most of the pollutant removal process occurs in the matrix filler layer, and the matrix filler of artificial wetlands plays a key role in the removal of pollutants.

[0003] Existing artificial wetlands generally use natural minerals such as gravel and zeolite as fillers, whose porosity is generally less than 40% and whose specific surface area is limited, resulting in low pollutant adsorption capacity. For example, the specific surface area of ​​gravel is less than 1m 2 / g, the adsorption capacity for phosphorus is only 15mg / g; although zeolite has a better adsorption effect on ammonia nitrogen (NH4 + -N adsorption capacity is about 10 to 15 mg / g), but the adsorption capacity for phosphorus is less than 5 mg / g, making it difficult to achieve simultaneous removal of nitrogen and phosphorus. At the same time, traditional fillers rely on a single physical adsorption or ion exchange mechanism, lack biological synergy, and are prone to desorption after adsorption saturation, leading to the risk of secondary release of ammonia nitrogen. At the same time, the biofilm formed on the surface of the filler has poor stability, and the loss rate of denitrifying bacteria and polyphosphate bacteria due to water scouring exceeds 30%. The system denitrification efficiency is generally less than 70%, and there is no carbon sink function. In addition, the particle size distribution of natural fillers is uneven. For example, the gravel particle size ranges from 5 to 50 mm, which can easily cause hydraulic short circuits inside the wetland and compaction of the filler layer. The pore blockage rate increases by 15% to 20% annually, and the filler needs to be replaced frequently (cycle ≤ 2 years), and the operation and maintenance cost is high. Therefore, it is very necessary to develop matrix fillers that have high removal efficiency for multiple pollutants, can cooperate with microorganisms, and have low operation and maintenance costs. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing a bacterial-algal composite adsorption module wetland matrix filler, the prepared filler can synergistically treat multiple pollutants, simplify the hierarchical design of artificial wetlands, have strong regeneration capabilities, and reduce operation and maintenance costs.

[0005] The present invention provides a method for preparing a wetland matrix filler of a bacteria-algae composite adsorption module, comprising the following steps:

[0006] Preparation of adsorption module: The biochar matrix was immersed in a solution containing Fe 3+ With Mn 2+The mixed aqueous solution was placed under ultrasonic vibration and then allowed to stand to obtain the loaded Fe 3+ With Mn 2+ The biochar matrix will be loaded with Fe 3+ With Mn 2+ The biochar matrix is ​​calcined to obtain an adsorption module; the biochar matrix is ​​a honeycomb biochar material prepared from biochar powder, polymer and binder;

[0007] Preparation of microbial agent microspheres: mixing denitrifying bacteria liquid and polyphosphate bacteria liquid to obtain a mixed bacterial liquid; mixing sodium alginate, diatomaceous earth and water to obtain a composite gel solution; mixing the mixed bacterial liquid and the composite gel solution and then dropping them into a CaCl2 solution to obtain microbial agent microspheres;

[0008] The adsorption module was placed in a 5 ~1.2×10 5 cells / mL diatom culture medium to obtain a diatom biofilm attached to the surface of the adsorption module, the diatom biofilm is peeled off and placed on the upper layer of the bacterial agent microspheres to form a diatom bacterial agent composite layer, and the diatom bacterial agent composite layer is placed on the upper layer of the adsorption module to form a bacterial-algae composite adsorption module wetland matrix filler.

[0009] Preferably, the porosity of the honeycomb biochar material is ≥85%, and the pore size is 2 to 3 mm.

[0010] Preferably, the Fe 3+ With Mn 2+ In the mixed aqueous solution, the molar ratio of Fe to Mn is (0.8-1.2):(0.8-1.2), the total metal ion concentration of Fe and Mn is 0.4-0.6 mol / L, and the pH value is 1.8-2.2.

[0011] Preferably, the ultrasonic oscillation is an ultrasonic oscillation with a power of 280 to 320 W and a frequency of 35 to 45 kHz for 28 to 32 minutes;

[0012] Preferably, the standing is 0.8 to 1.2 hours;

[0013] Preferably, the calcination is performed by heating the temperature to 490-510° C. at a rate of 4-6° C. / min and then calcining for 1.8-2.2 h.

[0014] Preferably, the volume ratio of the denitrifying bacteria solution to the polyphosphate bacteria solution is 1:(1.2-1.5), and the concentration of the denitrifying bacteria solution is 0.8×10 8 CFU / mL~1.2×10 8 CFU / mL, the concentration of the polyphosphate bacteria solution is 0.8×10 8 CFU / mL~1.2×10 8CFU / mL;

[0015] Preferably, the mass ratio of sodium alginate to diatomaceous earth is 1:(1.8-2.2);

[0016] Preferably, the total mass percentage of sodium alginate and diatomaceous earth in the composite gel solution is 4% to 6%;

[0017] Preferably, the mass ratio of the mixed bacterial solution to the composite gel solution is 1:(1.8-2.2).

[0018] Preferably, the concentration of the CaCl2 solution is 1.8-2.2 g / 100 mL.

[0019] Preferably, the culture medium further contains sodium silicate, and the concentration of the sodium silicate is 8-12 mg / L;

[0020] Preferably, the thickness of the diatom biofilm is 0.1 to 0.5 mm.

[0021] Preferably, the coverage rate of the bacterial agent microspheres on the adsorption module is ≥80%.

[0022] The present invention also provides a wetland matrix filler for a bacteria-algae composite adsorption module prepared by the method.

[0023] The present invention also provides the use of the method or the wetland matrix filler of the bacteria-algae composite adsorption module in treating sewage.

[0024] Beneficial effects of the present invention:

[0025] The wetland matrix filler of the bacteria-algae composite adsorption module provided by the present invention has the following beneficial effects:

[0026] The biochar matrix of the adsorption module of the present invention has a three-dimensional network structure with a porosity of ≥85%, and the specific surface area is increased to 3 times that of traditional fillers, providing sufficient active sites for phosphorus adsorption; after loading Fe-Mn oxide nanoparticles, the phosphorus adsorption capacity reaches 45 mg / g, and adsorption regeneration can be achieved through ion exchange.

[0027] Diatom agent composite layer: Denitrifying bacteria and polyphosphate bacteria are co-fixed in the diatom biofilm to form a biological barrier, the total nitrogen removal rate is increased to 92%, and carbon is fixed simultaneously (CO2 fixed amount ≥ 0.5g / (m 2 ·d)).

[0028] Anti-scouring effect: The bacterial embedding rate reaches 95%, and the bacterial survival period is extended to more than 6 months, reducing the need for frequent maintenance.

[0029] Comprehensive application advantages: The bacteria-algae composite adsorption module wetland matrix filler provided by the present invention is suitable for high-phosphorus (≤20mg / L) and high-nitrogen (≤50mg / L) wastewater, and is resistant to pH fluctuations (5.0-9.0). It can achieve phosphorus adsorption, nitrogen degradation and carbon fixation when used alone, and can synergistically treat multiple pollutants and simplify the hierarchical design of wetland systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the application of the bacteria-algae composite adsorption module wetland matrix filler of the present invention in the preparation of artificial wetlands.

[0031] Figure 2 This is a flow diagram of sewage when the wetland matrix filler of the bacteria-algae composite adsorption module of the present invention is used to treat sewage. DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing a wetland matrix filler of a bacteria-algae composite adsorption module, comprising the following steps:

[0033] Preparation of adsorption module: The biochar matrix was immersed in a solution containing Fe 3+ With Mn 2+ The mixed aqueous solution was placed under ultrasonic vibration and then allowed to stand to obtain the loaded Fe 3+ With Mn 2+ The biochar matrix will be loaded with Fe 3+ With Mn 2+ The biochar matrix is ​​calcined to obtain an adsorption module; the biochar matrix is ​​a honeycomb biochar material prepared from biochar powder, polymer and binder;

[0034] Preparation of microbial agent microspheres: mixing denitrifying bacteria liquid and polyphosphate bacteria liquid to obtain a mixed bacterial liquid; mixing sodium alginate, diatomaceous earth and water to obtain a composite gel solution; mixing the mixed bacterial liquid and the composite gel solution and then dropping them into a CaCl2 solution to obtain microbial agent microspheres;

[0035] The adsorption module was placed in a 5 ~1.2×10 5 cells / mL diatom culture medium to obtain a diatom biofilm attached to the surface of the adsorption module, the diatom biofilm is peeled off and placed on the upper layer of the bacterial agent microspheres to form a diatom bacterial agent composite layer, and the diatom bacterial agent composite layer is placed on the upper layer of the adsorption module to form a bacterial-algae composite adsorption module wetland matrix filler.

[0036] In the present invention, when preparing the adsorption module, a biochar matrix is ​​first prepared, and the biochar matrix is ​​a honeycomb biochar material prepared from biochar powder, polymer and binder; the present invention has no special limitation on the source of the biochar powder, and conventional commercial products in the field or homemade products can be used. The homemade method preferably comprises the following steps: rice husk and corn stalk are mixed, soaked, rinsed and impurities removed, crushed 1, dried, carbonized, and crushed 2 to obtain biochar powder; the mass ratio of the rice husk and corn stalk mixture is preferably 1: (0.8-1.2), more preferably 1: 0.8, 1: 0.9, 1: 1.0, 1: 1.1 or 1: 1.2; the soaking is preferably soaked for 4-8 hours, more preferably soaked for 4 hours, 5 hours, 6 hours, 7 hours or 8 hours; the rinsing is preferably rinsed with deionized water until the conductivity of the last rinse solution is ≤200μS / cm; the present invention has no special limitation on the impurity removal method, and the conventional impurity removal method in the field can be used. In one embodiment, a vibrating screen with an aperture of 1mm can be selected for filtration and impurity removal; the crushing 1 is preferably crushed to a particle size of ≤4mm to ensure that more than 90% of the particles can pass through a 4mm sieve. The present invention has no special limitation on the impurity removal method, and the conventional impurity removal method in the field can be used. In one embodiment, a vibrating screen with an aperture of 1mm can be selected for filtration and impurity removal; the crushing 1 is preferably crushed to a particle size of ≤4mm to ensure that more than 90% of the particles can pass through a 4mm sieve. The method is not particularly limited, and the conventional pulverization method in the field can be used; the drying is preferably dried to a moisture content of ≤2%. The present invention has no special limitation on the drying method, and the conventional drying method in the field can be used. Preferably, it can be dried at 80°C; the carbonization is preferably carried out in a nitrogen environment, at a temperature of 9-11°C / min (such as 9°C / min, 10°C / min or 11°C / min) to 590-610°C (such as 590°C, 600°C or 610°C), and the temperature is kept for 1.8-2.2h (such as 1.8h, 1.9h, 2.0h, 2.1h or 2.2h); the pulverization 2 is preferably pulverized to a powder of 95-115 mesh (such as 95 mesh, 100 mesh, 110 mesh or 115 mesh). The present invention has no special limitation on the method of pulverization 2, and the conventional pulverization method in the field can be used. In one embodiment, a grinding pulverization method can be selected.

[0037] In the present invention, the polymer is preferably polylactic acid (PLA), the binder is preferably polyvinyl alcohol, the mass ratio of the biochar powder to the polylactic acid is preferably 7: (2-4), more preferably 7: 2, 7: 3 or 7: 4, and the mass of the binder is preferably 4% to 6% of the total mass of the biochar powder and the polylactic acid, more preferably 4%, 5% or 6%. The biochar powder, polylactic acid and polyvinyl alcohol are mixed to obtain a mixed material for preparing a biochar matrix. The mixed material is used to prepare a honeycomb biochar material (biochar matrix), the porosity of the honeycomb biochar material is preferably ≥ 85%, and the pore size is preferably 2-3 mm. The present invention does not specifically limit the shape of the biochar matrix, and can be prepared into a corresponding shape according to actual needs. The present invention does not specifically limit the process of preparing a honeycomb biochar matrix from the mixed material, and the conventional method for preparing a biochar matrix in the art can be used. In one embodiment, the mixed material can be selected to be printed using 3D printing technology to obtain a biochar matrix. The present invention does not specifically limit the 3D printing process, and the conventional 3D printing process in the art can be used.

[0038] In the present invention, after obtaining the biochar matrix, the biochar matrix is ​​immersed in a solution containing Fe 3+ With Mn 2+ The mixed aqueous solution containing Fe 3+ With Mn 2+ The mixed aqueous solution (mixed metal ion solution) is preferably obtained by dissolving Fe(NO3)3·9H2O and MnSO4·H2O in deionized water, and the molar ratio of Fe to Mn in the solution is preferably (0.8-1.2):(0.8-1.2), more preferably 0.8:1.2, 0.9:1.1, 1:1, 1.1:0.9 or 1.2:0.8; the total metal ion concentration of Fe and Mn is preferably 0.4-0.6 mol / L, more preferably 0.4 mol / L, 0.5 mol / L or 0.6 mol / L; the pH value is preferably 1.8-2.2, more preferably 1.8, 1.9, 2.0, 2.1 or 2.2, and the pH value is preferably adjusted by 0.1 mol / L nitric acid to prevent hydrolysis and precipitation of metal ions. The ultrasonic oscillation is preferably carried out with a power of 280-320 W and a frequency of 35-45 kHz for 28-32 min. In one embodiment, the ultrasonic oscillation may be carried out with a power of 280 W, 290 W, 300 W, 310 W or 320 W and a frequency of 35 kHz, 38 kHz, 40 kHz, 43 kHz or 45 kHz for 28 min, 29 min, 30 min, 31 min or 32 min. After the ultrasonic oscillation, the Fe 3+ With Mn 2+The Fe-loaded 3+ With Mn 2+ The biochar matrix will be loaded with Fe 3+ With Mn 2+ The biochar matrix is ​​calcined, and the calcination preferably includes a drying process to remove free moisture. The present invention does not specifically limit the drying method. In one embodiment, forced air drying can be selected. The calcination is preferably carried out in an air atmosphere at 4 to 6 ° C / min to 490 to 510 ° C, and then calcined for 1.8 to 2.2 hours. In one embodiment, the temperature can be increased to 490 ° C, 495 ° C, 500 ° C, 505 ° C or 510 ° C at 4 ° C / min, 5 ° C / min or 6 ° C / min for 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours or 2.2 hours to crystallize Fe-Mn oxide nanoparticles (Fe2O3-MnO2 complex) with a particle size of 20 to 50 nm to obtain an adsorption module.

[0039] In the present invention, when preparing the microspheres, the denitrifying bacteria solution is mixed with the polyphosphate bacteria solution, and the concentration of the denitrifying bacteria in the denitrifying bacteria solution is preferably 0.8×10 8 CFU / mL~1.2×10 8 CFU / mL, more preferably 0.8×10 8 CFU / mL, 0.9×10 8 CFU / mL, 1.0×10 8 CFU / mL, 1.1×10 8 CFU / mL or 1.2×10 8 CFU / mL, the concentration of polyphosphate bacteria in the polyphosphate bacteria solution is preferably 0.8×10 8 CFU / mL~1.2×10 8 CFU / mL, more preferably 0.8×10 8 CFU / mL, 0.9×10 8 CFU / mL, 1.0×10 8 CFU / mL, 1.1×10 8 CFU / mL or 1.2×10 8 CFU / mL; the volume ratio of the denitrifying bacteria solution and the polyphosphate bacteria solution is preferably 1: (1.2-1.5), more preferably 1: 1.2, 1: 1.3, 1: 1.4 or 1: 1.5, to obtain a mixed bacterial solution. The present invention has no special restrictions on the sources of the denitrifying bacteria solution and the polyphosphate bacteria solution, and conventional commercial products or self-made products can be used. The present invention has no special restrictions on the method for self-making the bacterial solution, and conventional preparation methods in the art can be used.

[0040] Sodium alginate, diatomaceous earth and water are mixed to obtain a composite gel solution; the mass ratio of the sodium alginate to the diatomaceous earth is preferably 1:(1.8-2.2), more preferably 1:1.8, 1:1.9, 1:2.0, 1:2.1 or 1:2.2; the total mass percentage of sodium alginate and diatomaceous earth in the composite gel solution is preferably 4%-6%, more preferably 4%, 5% or 6%; the viscosity of the composite gel solution is preferably ≥200mPa·s; the present invention has no special limitation on the sources of sodium alginate and diatomaceous earth, and conventional commercial products in the field can be used.

[0041] The mixed bacterial solution and the composite gel solution are mixed and then dripped into the CaCl2 solution. The mass ratio of the mixed bacterial solution to the composite gel solution is preferably 1: (1.8-2.2), more preferably 1: 1.8, 1: 1.9, 1: 2.0, 1: 2.1 or 1: 2.2; the concentration of the CaCl2 solution is preferably 1.8-2.2 g / 100 mL, more preferably 1.8 g / 100 mL, 1.9 g / 100 mL, 2.0 g / 100 mL, 2.1 g / 100 mL or 2.2 g / 100 mL. After dripping into the CaCl2 solution, the cross-linking and curing is preferably carried out for 14-16 minutes, more preferably 14 minutes, 15 minutes or 16 minutes. After cross-linking and curing, it is preferred to further include a step of rinsing with physiological saline to remove residual Ca 2+ , and obtain bacterial agent microspheres, wherein the diameter of the bacterial agent microspheres is 3 to 5 mm and the mechanical strength is ≥0.5 MPa.

[0042] In the present invention, the diatom biofilm is preferably prepared using an adsorption module as a carrier. Before the preparation of the diatom biofilm, the adsorption module is preferably pretreated, and the pretreatment preferably includes acid activation and sterilization and drying; the acid activation preferably includes immersing the adsorption module in a 0.1M HNO3 solution for 2 hours to remove surface impurities and increase roughness; the present invention does not specifically limit the sterilization and drying method, and conventional sterilization and drying steps in the art may be used.

[0043] After the adsorption module was pretreated, the adsorption module was placed in a 5 ~1.2×10 5 cells / mL diatom culture medium, the diatom concentration is preferably 0.8×10 5 cells / mL、0.9×10 5 cells / mL, 1.0×10 5 cells / mL, 1.1×10 5 cells / mL or 1.2×10 5cells / mL; the present invention has no special restrictions on the source of diatoms and the composition of the culture medium. The conventional diatom sources and diatom culture medium compositions in the art can be used. In one embodiment, the culture medium can be selected from BG-11 culture medium with added sodium silicate. The concentration of sodium silicate in the culture medium is preferably 8-12 mg / L, more preferably 8 mg / L, 9 mg / L, 10 mg / L, 11 mg / L or 12 mg / L. The present invention has no special restrictions on the order of placing diatom inoculation and adsorption modules in the culture medium. The time when both are in the culture medium at the same time is the starting point of diatom biofilm culture. Diatom biofilm culture is preferably carried out in two stages. The first stage is preferably 0-48h static culture without stirring, and the initial attachment is completed by using the phototaxis and passive sedimentation of diatoms; the second stage is preferably dynamic culture and biofilm formation. During the dynamic culture and biofilm formation, environmental parameters suitable for diatom biofilm formation are preferably used for culture, preferably: Light: LED white light 60μmol / (m 2 ·s), light-dark cycle 14:10, simulating natural circadian rhythm; temperature: 20±1℃, avoiding high temperature to inhibit extracellular polymer (EPS) secretion; ventilation: sterile air 0.1vvm (volume ratio), maintaining dissolved oxygen <8mg / L. During dynamic culture and biofilm formation, low-speed stirring of 50rpm was used for 48h to 7 days to promote EPS secretion, and 50% fresh culture medium was added every 48h to supplement silicon source; after 7 days, low-speed stirring was used at 20-30rpm to reduce the damage of shear force to mature biofilm; at the same time, sodium silicate (maintaining its final concentration at 8-12mg / L, such as 8mg / L, 10mg / L or 12mg / L) and compound fertilizer (plant cell culture compound fertilizer, purchased from Sigma-Aldrich, product number P8483, containing nitrogen, phosphorus, potassium and trace elements) were continuously added to the culture medium to maintain a total nitrogen concentration of 5-10mg / L and a total phosphorus of 1-2mg / L to ensure the formation of diatom membrane shells. A diatom biofilm attached to the surface of the adsorption module is obtained, and the culture is stopped when the thickness of the diatom biofilm is 0.1 to 0.5 mm (such as 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm) detected by microscope.

[0044] The diatom biofilm attached to the surface of the adsorption module is peeled off. The present invention does not specifically limit the peeling method, and the conventional peeling method in the art can be used. After the diatom biofilm is peeled off, it is placed on the upper layer of the bacterial agent microspheres to form a diatom bacterial agent composite layer. Before the diatom biofilm is placed, the bacterial agent microspheres are preferably arranged in advance according to the shape of the peeled diatom film into a single-layer receptor surface, and deionized water is sprayed on the receptor surface to form a deionized water film with a humidity of >90% on the receptor surface to provide an adhesion buffer. After the diatom biofilm is placed on the receptor surface, it is placed in an environment of 28 to 32°C (such as 28°C, 29°C, 30°C, 31°C or 32°C) for 1.8 to 2.2h (such as 1.8h, 1.9h, 2.0h, 2.1h or 2.2h) to allow the bacterial agent microspheres to release Ca 2+ , forming an ion cross-linked network with the carboxyl group (-COOH) of the diatom biofilm, improving the interface bonding strength, and the shear adhesion is detected to be ≥0.4MPa, to obtain a diatom agent composite layer. The diatom agent composite layer is then placed on the upper layer of the adsorption module, preferably first spraying a binder on the surface of the adsorption module, the binder is preferably polyvinyl alcohol, and the thickness of the polyvinyl alcohol is preferably 48 to 52μm (such as 48μm, 49μm, 50μm, 51μm or 52μm), and then the diatom agent composite layer is placed on the upper layer of the adsorption module, so that the coverage rate of the microspheres on the adsorption module is ≥80%, forming a wetland matrix filler for the bacterial-algae composite adsorption module.

[0045] The present invention also provides a wetland matrix filler for a bacteria-algae composite adsorption module prepared by the method.

[0046] The present invention also provides the use of the method or the wetland matrix filler of the bacteria-algae composite adsorption module in treating sewage.

[0047] The bacteria-algae composite adsorption module wetland matrix filler provided by the present invention can achieve phosphorus adsorption, nitrogen degradation and carbon fixation when used alone to remove sewage, can synergistically treat multiple pollutants, simplify the hierarchical design of the wetland system, has strong renewability, and reduces operation and maintenance costs.

[0048] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0049] In the following embodiments, unless otherwise specified, all of them are conventional methods.

[0050] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0051] Example 1

[0052] A method for preparing a wetland matrix filler of a bacteria-algae composite adsorption module comprises the following steps:

[0053] 1. Preparation of biochar matrix

[0054] 1. Raw material pretreatment

[0055] (1) Cleaning and removal of impurities

[0056] Rice husks and corn stalks were soaked in deionized water at a mass ratio of 1:1 for 6 h, stirred and rinsed three times, and the conductivity of the last rinse solution was made ≤200 μS / cm to remove sediment and soluble salts.

[0057] The washed raw materials are filtered through a vibrating screen with a pore size of 1 mm to separate and remove residual impurities.

[0058] (2) Crushing and drying

[0059] Use a hammer mill to crush the raw materials into particles ≤4mm, so that more than 90% of the particles pass through a 4mm sieve to ensure uniform particle size.

[0060] The crushed and sieved materials are placed in a blast drying oven and dried at 80°C until the moisture content is ≤2% to obtain dry particles, thereby preventing pore collapse caused by water vaporization during the subsequent pyrolysis process.

[0061] (3) Pyrolysis carbonization

[0062] The dried particles were placed in a tubular furnace, nitrogen was introduced at 50 mL / min to expel the air, the temperature was raised to 600°C at 10°C / min, and the temperature was kept for 2 h to complete carbonization, thereby obtaining carbonized biochar;

[0063] The carbonized biochar was ground into 100-mesh powder using a ball mill to obtain biochar powder, which was sealed and stored for later use.

[0064] 2. 3D printing slurry preparation

[0065] (1) Material Proportion and Mixing

[0066] Take the biochar powder obtained in step "1." of this embodiment, weigh the biochar powder and polylactic acid (PLA) at a mass ratio of 7:3, add polyvinyl alcohol (PVA) accounting for 5% of the total mass of the biochar powder and the polylactic acid as a binder, and dry mix them in a high-speed mixer at a speed of 300 rpm for 10 minutes to ensure uniform dispersion to obtain a mixed material.

[0067] (2) Melt granulation

[0068] The mixed material was melt-blended at a temperature of 190° C. in a twin-screw extruder, and the screw speed was adjusted to 60 rpm to extrude strip-shaped particles.

[0069] The strip particles are cooled to room temperature, sieved to make the particle size ≤3 mm, and the raw materials for honeycomb printing are obtained, which are stored in a dry environment to prevent moisture absorption.

[0070] 3. Honeycomb structure forming

[0071] (1) Model design and slicing

[0072] Three-dimensional modeling: Use CAD software to design the honeycomb structure model and export it as an STL format file (surface accuracy ≤ 0.1 mm).

[0073] Slicing processing: The slicing software sets a path planning strategy to give priority to filling the thick honeycomb wall area (wall thickness 0.5mm) to avoid pore blockage.

[0074] Generate G-code in layers and mark support structure areas simultaneously.

[0075] (2) 3D printing equipment modification and parameter setting

[0076] Adopt fused deposition modeling (FDM) equipment, modify the feeding mechanism of FDM equipment, adopt a special feeding throat (inner diameter 3mm) for particles, and cooperate with a twin-screw extruder module to achieve continuous and stable feeding of particles. Temperature control: nozzle temperature 200℃ (to ensure that PLA is completely melted and biochar is evenly dispersed), printing platform temperature 60℃ (to reduce interlayer warping and improve interlayer bonding); motion parameters: layer thickness is set to 0.2mm (balance printing efficiency and structural accuracy), printing speed: 40mm / s (low speed to ensure sufficient deposition of molten material); structural parameters: filling rate is adjusted to 85%, honeycomb unit aperture is designed to be 2-3mm, ensuring porosity ≥85%; support structure: water-soluble PVA support material is used (nozzle temperature 180℃) to reduce post-processing damage.

[0077] (3) Molding and post-processing

[0078] The honeycomb printing raw material obtained in steps "1, 2" of this embodiment was dried in a vacuum drying oven at 60° C. for 4 hours to ensure that the water content was less than 0.1% to avoid pore defects caused by water volatilization during the printing process, thereby obtaining a dried honeycomb printing raw material.

[0079] The G code obtained in step "1.3.(1)" of this embodiment is transmitted to the printer, and then the dried honeycomb printing raw materials are stacked layer by layer to print the honeycomb structure using a device with set 3D printing parameters. After the molten particles formed by the honeycomb printing raw materials are extruded through the nozzle, they are precisely moved and deposited along the X / Y axis. The cooling time of each layer is ≤5 seconds to avoid thermal stress accumulation; the nozzle pressure (≤5MPa) is monitored in real time to prevent the biochar particles from clogging the nozzle; after printing every 5 layers, a pause of 10 seconds is made, and residual debris in the pores is removed using an air gun to ensure pore connectivity.

[0080] After printing, annealing was performed at 60°C for 2 hours to eliminate internal stress and improve structural stability, so that the compressive strength of the structure was ≥15Mpa.

[0081] After annealing, the substrate was immersed in deionized water at 40° C. for 4 hours to dissolve the PVA support material.

[0082] A scanning electron microscope (SEM) was used to detect the pore connectivity, and defective products with pore blockage, pore size deviation > 0.5 mm, structural deformation, and pore wall fracture were eliminated to obtain the biochar matrix.

[0083] Porosity detection: The actual porosity is determined by the Archimedes drainage method, and the deviation from the predetermined porosity "≥85%" is ≤3%.

[0084] 2. Preparation of adsorption module

[0085] 1. Solution Preparation

[0086] According to the Fe:Mn molar ratio of 1:1, Fe(NO3)3·9H2O and MnSO4·H2O were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of Fe and Mn of 0.5 mol / L, and the pH of the solution was ≈2.5. 0.1 mol / L nitric acid solution was added to adjust the solution to pH=2 to prevent hydrolysis and precipitation of metal ions, thereby obtaining a mixed metal ion solution.

[0087] 2. Maceration and Ultrasonication

[0088] The biochar matrix (pore size 2-3 mm, porosity ≥ 85%) obtained in "Step 1" of this embodiment is completely immersed in the mixed metal ion solution, placed in an ultrasonic cleaner, and oscillated at a power of 300 W and a frequency of 40 kHz for 30 min to ensure that the solution fully penetrates the pores.

[0089] After ultrasound, let it stand for 1 hour to allow Fe 3+ and Mn 2+ Uniformly adsorbed on the surface and pores of biochar to obtain loaded Fe 3+ and Mn 2+ of biochar matrix.

[0090] 3. Drying and calcination

[0091] Remove the load Fe 3+ and Mn 2+ The biochar matrix was dried at 80℃ for 12h to remove free moisture. It was placed in a muffle furnace and heated to 500℃ at 5℃ / min in air atmosphere, and then calcined for 2h to crystallize Fe-Mn oxide nanoparticles (Fe2O3-MnO2 complex) on the surface of the biochar matrix with a crystal particle size of 20-50nm to obtain an adsorption module.

[0092] 3. Preparation of microspheres

[0093] 1. Expansion of bacterial strains

[0094] Denitrifying bacteria (Pseudomonas denitrificans): Use LB liquid culture medium (tryptone 10 g / L, yeast extract 5 g / L, NaCl 10 g / L) and adjust the pH to 7.2-7.4.

[0095] Acinetobacter: Use modified LB medium containing sodium acetate (1 g / L) to enhance the metabolic activity of Acinetobacter.

[0096] Denitrifying bacteria and polyphosphate bacteria were inoculated into their respective culture media and placed in a constant temperature shaker (30°C, 120 rpm) for 24 h to make the concentrations of both bacterial solutions reach 10 8 CFU / mL, and denitrifying bacteria solution and polyphosphate bacteria solution were obtained.

[0097] 2. Carrier Embedding

[0098] Sodium alginate and diatomaceous earth are mixed in a mass ratio of 1:2 and dissolved in deionized water to form a 5% (the total mass of sodium alginate and diatomaceous earth per 100g of the composite gel solution is 5g) composite gel solution (viscosity ≥ 200mPa·s).

[0099] Denitrifying bacteria solution and polyphosphate bacteria solution were mixed at a volume ratio of 1:1.2 to obtain a mixed solution; the mixed solution was evenly mixed with the composite gel solution at a mass ratio of 1:2 and then dropped into a 2g / 100mL CaCl2 solution with a syringe, cross-linked and cured for 15 minutes to form microspheres with a diameter of 3-5mm. After curing, the microspheres were rinsed 3 times with physiological saline to remove residual Ca 2+ The mechanical strength of the microspheres was tested by a universal material testing machine and was ≥0.5MPa.

[0100] 4. Preparation of Diatom Biofilm

[0101] 1. Preparation of diatom-specific culture medium

[0102] Prepare the culture medium according to the BG-11 formula (per 1 L): dissolve 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4·7H2O, 0.036 g CaCl2·2H2O, and 0.02 g Na2CO3; then add a silicon source to supplement the final concentration to 10 mg / L Na2SiO3·9H2O, and adjust the pH to 7.8±0.1; sterilize at 121°C under high pressure for 20 minutes, cool, and pass sterile air for 10 minutes to re-dissolve CO2 to obtain a special culture medium for diatoms.

[0103] 2. Algae collection and pretreatment

[0104] Source of algae: Natural collection, by scraping the fine sand on the surface of the intertidal zone (yellow-brown area), washing and filtering to obtain concentrated algae liquid; the concentrated algae liquid was cultured in the laboratory, using diatoms (Cyclotella) in the logarithmic growth period, and centrifuged and concentrated to 1×10 6 cells / mL for future use.

[0105] Activation of algae: Use diatom-specific culture medium (obtained in step 4, 1. of this example) for pre-cultivation for 36 hours to restore metabolic activity.

[0106] 3. Biofilm Attachment Induction

[0107] Carrier pretreatment: The adsorption module obtained in step 2 of this embodiment was immersed in 0.1M HNO3 solution for 2 hours to remove surface impurities and increase roughness; then irradiated with 254nm ultraviolet light for 30 minutes, dried at 80°C, and placed in a diatom-specific culture medium (obtained in step 4, 1. of this embodiment); then the algae solution was inoculated in the culture medium to a final concentration of 1×10 5 cells / mL;

[0108] Static culture: No stirring within 48 hours, using diatom phototaxis and passive sedimentation to complete initial attachment.

[0109] Dynamic culture and biofilm formation: 48h-7 days: The culture medium was stirred at a low speed (50rpm) to promote the secretion of extracellular polymers (EPS), and 50% of the culture medium was replaced with fresh medium every 48h to supplement the silicon source. At the same time, the chlorophyll a content was monitored (monitoring results, ≥50μg / cm 2 ) and biofilm thickness (monitoring results, 80-120μm). After 7 days: stir at a low speed of 25rpm, and continuously supplement the culture medium with sodium silicate (add sodium silicate directly to the culture medium to maintain its concentration in the culture medium at 10mg / L) and compound fertilizer (plant cell culture compound fertilizer, purchased from Sigma-Aldrich, product number P8483, containing nitrogen, phosphorus, potassium and trace elements) to maintain a total nitrogen concentration of 8mg / L and a total phosphorus concentration of 1.5mg / L. Monitor the thickness of the diatom biofilm. When the thickness of the diatom biofilm detected at multiple points is within the range of 0.1 to 0.5mm, terminate the culture.

[0110] Environmental parameter control during dynamic culture and biofilm formation: Light: LED white light 60μmol / (m 2 ·s), light-dark cycle 14:10, simulating natural circadian rhythm. Temperature: 20±1℃, to avoid high temperature inhibiting EPS secretion. Ventilation: sterile air 0.1vvm (volume ratio), maintaining dissolved oxygen <8mg / L.

[0111] 5. Preparation of wetland matrix filler for bacterial-algal composite adsorption module

[0112] The 355nm wavelength ultraviolet laser penetrates the surface of the diatom biofilm and acts on the interface of the adsorption module to avoid damaging the diatom cells. It scans with a short pulse of 10ns and a single action area of ​​50×50μm 2 , until the diatom membrane is peeled off point by point.

[0113] The bacterial agent microspheres obtained in step 3 of this embodiment were pre-arranged into a single-layer bacterial agent microsphere layer according to the shape of the peeled diatom film as the receptor surface, and deionized water was sprayed to form a deionized water film with a humidity of more than 90% on the surface of the bacterial agent microsphere layer to provide adhesion buffer. The peeled diatom film was directionally ejected to the receptor surface at a speed of 25m / s through the gas explosion shock wave and placed in a constant temperature environment of 30℃ for 2h. The bacterial agent microspheres released Ca 2+ , forming an ion cross-linking network with the carboxyl group (-COOH) of the diatom biofilm, improving the interface bonding strength, and the shear adhesion was tested to be ≥0.4MPa, obtaining a diatom biofilm layer and a bacterial agent microsphere layer composite diatom bacterial agent composite layer.

[0114] After the surface of the adsorption module after the diatom biofilm is peeled off, a polyvinyl alcohol (PVA) adhesive layer with a thickness of 50 μm is sprayed on it, and then a diatom bacterial agent composite layer is placed on the surface of the adsorption module. The coverage rate of the bacterial agent microspheres on the adsorption module is ≥80%, thereby obtaining a bacterial-algae composite adsorption module wetland matrix filler.

[0115] The schematic diagram of the bacterial-algae composite adsorption module wetland matrix filler of the present invention for preparing artificial wetlands is as follows Figure 1 As shown (the immobilized bacterial agent microspheres are a bacterial agent microsphere layer).

[0116] Embodiment 2-3

[0117] The difference between Examples 2 and 3 and Example 1 is only in the following parameters (see Table 1), and the rest are the same as Example 1.

[0118] Table 1 Parameter values ​​of Examples 2 to 3

[0119]

[0120]

[0121] Test Example 1

[0122] Test on the purification effect of adsorption module on phosphorus-containing wastewater

[0123] 1. Material to be tested:

[0124] Experimental group filler: the adsorption module prepared in Example 1, wherein the biochar matrix has a porosity of 87% ± 2% and a specific surface area of ​​820 m 2 / g, loaded with Fe-Mn oxide nanoparticles (Fe:Mn molar ratio = 1:1, particle size 20-50 nm);

[0125] Control group filler: traditional wetland matrix filler (natural gravel, particle size 5-10mm, specific surface area 0.5-1.2m 2 / g).

[0126] Simulated sewage: prepare phosphate (PO4 3- -P) synthetic sewage, initial phosphorus concentration = 20 mg / L, pH = 7.0 ± 0.2, water temperature = 25 °C.

[0127] 2. Experimental Methods

[0128] Adsorption experiment: The fillers of the experimental group and the control group were placed in a static adsorption device (filler dosage = 10 g / L), injected with simulated sewage, and reacted at a constant temperature oscillation (150 rpm) for 24 h until adsorption equilibrium.

[0129] 3. Phosphorus concentration detection:

[0130] Take the supernatant of the treated sewage and determine PO4 by referring to the ammonium molybdate spectrophotometric method (HJ 670-2013) in the "Water and Wastewater Monitoring and Analysis Methods" (4th edition). 3- -P concentration, calculate the adsorption capacity (unit: mg / g).

[0131] The results showed that the equilibrium adsorption capacity of the experimental group was 45±1.8 mg / g, the supernatant phosphorus content was 0.3 mg / L, and the phosphorus removal rate was 98.5%; while the equilibrium adsorption capacity of the control group was only 14.3±0.9 mg / g, the supernatant phosphorus content was 5.7 mg / L, and the phosphorus removal rate was 71.5%.

[0132] 4. Regeneration performance verification:

[0133] The fillers of the experimental group and control group that were saturated with adsorption in step 2 of this test example were immersed in 0.1M NaOH solution (pH=12) and shaken for 2 hours. After centrifugal washing until neutral, the adsorption experiment was repeated for 5 cycles. The adsorption capacity retention rate after regeneration was measured. The results showed that the adsorption capacity of the experimental group after the 5th cycle was still above 92%, while the adsorption capacity of the gravel in the control group was close to 0 and could not be regenerated.

[0134] Test Example 2

[0135] Test on the denitrification and carbon fixation performance of diatom bacteria composite layer

[0136] 1. Test materials and wastewater parameters

[0137] Experimental group: diatomaceous inoculant composite layer prepared in Example 1, inoculant loading amount = 15% (w / w); Control group 1: free inoculant (the same amount of denitrifying bacteria and polyphosphate bacteria as the experimental group were directly added without immobilization);

[0138] Control group 2: traditional activated sludge (taken from the secondary sedimentation tank of a sewage treatment plant, MLSS = 3000 mg / L); simulated sewage: artificial water (NH4 + -N=50mg / L,NO3 - -N=30mg / L,PO4 3- -P=15mg / L, COD=150mg / L, pH=7.0±0.2).

[0139] 2. Experimental methods and results

[0140] Reactor operation: The experimental group and the control group were respectively loaded into sequencing batch reactors (SBR, effective volume 5L) to treat the simulated sewage, with hydraulic retention time = 12h, and operated continuously for 30 days.

[0141] Light conditions: The diatom biofilm in the experimental group received light (light intensity 80 μmol / (m 2 ·s), light-dark ratio 12h:12h), and the control group was protected from light.

[0142] Detection indicators and methods: Total nitrogen (TN): potassium persulfate oxidation-ultraviolet spectrophotometry (HJ 636-2012);

[0143] CO2 fixation: The LI-6800 photosynthesis meter was used to monitor the carbon fixation rate of diatom biofilm in real time. Bacterial activity: live bacteria count (plate method) and fluorescence microscopy observation (SYBR Green / PI double staining).

[0144] The results are shown in Table 2 below. The results show that the denitrification and carbon fixation performance of the diatomaceous earth agent composite layer of the present invention is significantly better than that of the unfixed bacteria agent or sludge. At the same time, the bacteria agent has a long survival period and high treatment efficiency, which can reduce operation and maintenance costs.

[0145] Table 2 Sewage treatment effect of diatomaceous earth composite layer

[0146]

[0147]

[0148] Test Example 3

[0149] Wastewater treatment effect of bacterial-algal composite adsorption module wetland matrix filler

[0150] The same industrial wastewater tail water was deeply treated by using the bacteria-algae composite adsorption module wetland matrix filler (hereinafter referred to as filler) and activated carbon prepared in Example 1 of the present invention. When the filler of the present invention is used for treatment, the filler of the present invention is placed at the outlet of the wastewater, so that the outlet water of the water flow passes through the adsorption module layer of the filler, the bacteria-algae synergistic layer (i.e., the diatom bacteria agent composite layer formed by the bacterial agent microsphere layer and the diatom biofilm layer) in sequence. Figure 2 As shown, the treated wastewater flowing out of the diatom biofilm layer was collected. TP, COD, NH3-N, lead (Pb 2+ ), cadmium (Cd 2+ )content.

[0151] The detection methods used are: TP determination method: ammonium molybdate spectrophotometry, COD determination method: dichromate reflux method; NH3-N: Nessler reagent spectrophotometry; lead (Pb 2+ ), cadmium (Cd 2+ ): Graphite furnace atomic absorption spectrophotometry.

[0152] The test results are shown in Table 3. The results show that the filler of the present invention can simultaneously and efficiently remove multiple pollutants such as TP, COD, NH3-N, lead (Pb 2+ ), cadmium (Cd 2+ ), the effect is significantly better than activated carbon.

[0153] Table 3 Results of sewage treatment by wetland matrix fillers with bacterial-algal composite adsorption modules

[0154]

[0155] Note: The measurement results of each pollutant are the results of measurement at multiple sampling points and are therefore range values.

[0156] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a wetland matrix filler of a bacteria-algae composite adsorption module, characterized in that: The following steps are involved: Preparation of adsorption module: The biochar matrix was immersed in a solution containing Fe 3+ With Mn 2+ The mixed aqueous solution was placed in a vacuum chamber and then ultrasonically shaken and allowed to stand to obtain Fe 3+ With Mn 2+ The biochar matrix will be loaded with Fe 3+ With Mn 2+ The biochar matrix is ​​calcined to obtain an adsorption module; the biochar matrix is ​​a honeycomb biochar material prepared from biochar powder, polymer and binder; Preparation of microbial agent microspheres: mixing denitrifying bacteria liquid and polyphosphate bacteria liquid to obtain a mixed bacterial liquid; mixing sodium alginate, diatomaceous earth and water to obtain a composite gel solution; mixing the mixed bacterial liquid and the composite gel solution and then dropping them into a CaCl2 solution to obtain microbial agent microspheres; The adsorption module was placed in a 5 ~1.2×10 5 cells / mL diatom culture medium to obtain a diatom biofilm attached to the surface of the adsorption module, the diatom biofilm is peeled off and placed on the upper layer of the bacterial agent microspheres to form a diatom bacterial agent composite layer, and the diatom bacterial agent composite layer is placed on the upper layer of the adsorption module to form a bacterial-algae composite adsorption module wetland matrix filler.

2. The method according to claim 1, characterized in that The porosity of the honeycomb biochar material is ≥85%, and the pore size is 2-3 mm.

3. The method according to claim 1, characterized in that: The Fe 3+ With Mn 2+ In the mixed aqueous solution, the molar ratio of Fe to Mn is (0.8-1.2):(0.8-1.2), the total metal ion concentration of Fe and Mn is 0.4-0.6 mol / L, and the pH value is 1.8-2.

2.

4. The method according to claim 1, characterized in that The ultrasonic oscillation is performed with a power of 280-320W and a frequency of 35-45kHz for 28-32 minutes; the standing is performed for 0.8-1.2 hours; and the calcination is performed by heating the temperature to 490-510°C at a rate of 4-6°C / min and then calcining for 1.8-2.2 hours.

5. The method according to claim 1, characterized in that The volume ratio of the denitrifying bacteria solution to the polyphosphate bacteria solution is 1:(1.2-1.5), and the concentration of the denitrifying bacteria solution is 0.8×10 8 CFU / mL~1.2×10 8 CFU / mL, the concentration of the polyphosphate bacteria solution is 0.8×10 8 CFU / mL~1.2×10 8 CFU / mL; the mass ratio of sodium alginate to diatomaceous earth is 1:(1.8-2.2); the total mass percentage of sodium alginate and diatomaceous earth in the composite gel solution is 4%-6%; the mass ratio of the mixed bacterial solution to the composite gel solution is 1:(1.8-2.2).

6. The method according to claim 1, characterized in that The concentration of the CaCl2 solution is 1.8-2.2 g / 100 mL.

7. The method according to claim 1, characterized in that The culture medium also contains sodium silicate, and the concentration of the sodium silicate is 8-12 mg / L; the thickness of the diatom biofilm is 0.1-0.5 mm.

8. The method according to claim 1, characterized in that The coverage rate of the bacterial agent microspheres on the adsorption module is ≥80%.

9. A wetland matrix filler for a bacteria-algae composite adsorption module prepared by the method described in any one of claims 1 to 8.

10. Use of the method according to any one of claims 1 to 8 or the wetland matrix filler of the bacteria-algae composite adsorption module according to claim 9 in treating sewage.

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