CN113663537B - Bacterial biological membrane for sewage treatment and preparation method thereof - Google Patents
Bacterial biological membrane for sewage treatment and preparation method thereof Download PDFInfo
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- CN113663537B CN113663537B CN202110359796.XA CN202110359796A CN113663537B CN 113663537 B CN113663537 B CN 113663537B CN 202110359796 A CN202110359796 A CN 202110359796A CN 113663537 B CN113663537 B CN 113663537B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
- B01D71/78—Graft polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
- B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
- C02F3/1236—Particular type of activated sludge installations
- C02F3/1268—Membrane bioreactor systems
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/38—Graft polymerization
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
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Abstract
The invention belongs to the technical field of sewage treatment, and particularly relates to a bacterial biofilm for sewage treatment and a preparation method thereof. The invention provides a bacterial biomembrane for sewage treatment, which is prepared by grafting N- (2-oxiranylmethyl) carbamate with cellulose, modified pseudo-boehmite powder and aminoethylethanolamine to prepare a porous carrier, and embedding sodium alginate and polyethylene glycol to prepare the biomembrane, has a rich micropore structure and high specific surface area, provides a proper growth environment for microorganism adsorption, is favorable for quick film formation of microorganisms, and has the advantages of strong adsorption degradation capability, good mechanical property and long service life.
Description
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a bacterial biofilm for sewage treatment and a preparation method thereof.
Background
With the development of economy and the progress of society, people's life has changed greatly, and the living standard is constantly promoted, and domestic sewage is more and more, along with domestic sewage is discharged into the water, has brought excessive ammonia nitrogen, has exceeded the environmental capacity of water, has seriously influenced the self-cleaning ability of water, leads to quality of water to worsen and ecological environment structure's destruction, causes the eutrophication of water, consumes the oxygen in the water fast, makes fish, plankton die because of the hypoxia, seriously influences drinking water source safety and normal quality of life, therefore control the nitrogen content in the water is the radical of administering eutrophication sewage.
In the face of the environmental problems caused by excessive emission of nitrogen and pollution thereof, the national environmental protection planning increases the constraint control index of the total emission of ammonia nitrogen on the basis of the index of the total emission, meanwhile, the pollutant emission standard of urban sewage treatment plants clearly prescribes the emission reduction of ammonia nitrogen and total nitrogen, the emission standard of ammonia nitrogen is increasingly strict, the existing sewage treatment technology has the defects of large occupied area, high capital investment, low operation load and unsatisfactory removal effect, and the defects of insufficient carbon source and additional carbon source in the denitrification process, and cannot meet the requirements of the existing sewage treatment, so that the development of the sewage treatment method with enhanced denitrification is very necessary.
The aeration biological filter is a novel efficient biological film sewage treatment technology, and is a technology that microorganisms adhere to a carrier to form a biological film so as to degrade pollutants in the wastewater, and the reasonable selection of the carrier is very important to improve the effect of wastewater treatment. The porous particle suspension carrier is a novel high-efficiency carrier filler in the wastewater treatment by the current biomembrane method, has the advantages of large microorganism adhesion amount, low fluidization energy consumption, high treatment efficiency and the like, and is one of the main directions of the development of the wastewater treatment carrier in the future. The materials of the porous carrier used at present are mainly inorganic materials such as active carbon, zeolite, ceramic balls and the like, and organic polymer fillers such as polyvinyl chloride, polystyrene, polypropylene, plastics and the like, but the inorganic materials have higher cost, complex processing technology, difficult treatment after the waste of the fillers, poor degradability of the organic polymer fillers and easy secondary pollution generation, and researchers are finding a material which has low price, wide sources, easy treatment after use, less environmental pollution and can ensure the sewage treatment effect. Thus, there is a need for a porous support that can solve the above problems.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a bacterial biological membrane for sewage treatment and a preparation method thereof, wherein the obtained bacterial biological membrane has the advantages of large specific surface area, high membrane hanging speed, high microorganism load, good impact resistance, difficult falling-off of the biological membrane, capability of being independently used in a biodegradation tank or combined with MBR (membrane bioreactor) for operation, high adsorption and degradation efficiency and long service life.
In order to achieve the above object, the present invention adopts a technical scheme comprising the following items [1] to [4].
[1] An application of modified cellulose in preparing bacterial biomembrane for sewage treatment.
The modified cellulose is N- (2-oxiranylmethyl) carbamate grafted cellulose prepared by grafting and modifying cellulose by N- (2-oxiranylmethyl) carbamate.
The grafting rate of the N- (2-oxiranylmethyl) carbamate grafted cellulose is 14-20%.
The preparation method of the N- (2-oxiranylmethyl) carbamate grafted cellulose comprises the following steps:
1) Adding cellulose into a sodium hydroxide/urea mixed solution with the weight being 8-10 times that of the cellulose, introducing nitrogen, and stirring for 1-2 hours at the temperature of 30-35 ℃ to obtain an alkalized cellulose solution;
2) Adding N- (2-oxiranylmethyl) carbamate into the alkalized cellulose solution, stirring for 15-30 min at 30-35 ℃, then heating to 60-65 ℃ and stirring for reacting for 1-2.5 h;
3) Cooling to room temperature after the reaction is finished, regulating the pH to be neutral by using 1-2 mol/L hydrochloric acid solution, precipitating by using 85-90% ethanol solution, filtering, washing and drying to obtain the N- (2-oxiranylmethyl) carbamate modified cellulose.
Further, in the step 1), the mass fraction of sodium hydroxide in the sodium hydroxide/urea mixed solution is 5-10%, and the mass fraction of urea is 8-10%.
Further, in the step 1), the stirring speed is 800-1000 r/min.
Further, in the step 2), the addition amount of N- (2-oxiranylmethyl) carbamate is 24.5 to 30.8% by mass of cellulose.
Further, in the step 2), the temperature rising rate is 1-3 ℃/min.
Further, in the step 2), the stirring speed is 200-400 r/min.
Further, in the step 3), the drying temperature is 50-70 ℃ and the drying time is at least 6 hours.
According to the scheme, the N- (2-oxiranylmethyl) carbamate is used for grafting modification of cellulose, so that the internal structure of the cellulose can be improved, the introduction of active groups improves the processability of the cellulose, the degradation rate is accelerated, the strength is improved, the N- (2-oxiranylmethyl) carbamate modified cellulose is used as a raw material for preparing the bacterial biomembrane, the bacterial biomembrane has higher porosity, larger specific surface area and higher surface roughness, the absorption and the maintenance of moisture are facilitated, the growth and the propagation of microorganisms are facilitated, the cellulose shows that more active groups can also play a role in protecting attached microorganisms, the attachment, the fixation and the propagation of microorganisms on a carrier are accelerated, the rapid formation of the biomembrane is promoted, the shearing action of water conservancy shearing action on bacteria can be reduced, the impact resistance is good, and the biomembrane is not easy to fall off.
[2] A bacterial biofilm for sewage treatment, comprising:
a functional microorganism;
a porous carrier comprising the N- (2-oxiranylmethyl) carbamate grafted cellulose, modified pseudo-boehmite powder, and aminoethylethanolamine of item [1 ]; and
the film forming agent comprises sodium alginate and polyethylene glycol.
The functional microorganism is a synchronous nitrifying and denitrifying bacterium.
In the porous support, the porous support may be a porous support,
the grafting rate of the N- (2-oxiranylmethyl) carbamate grafted cellulose is 14-20 percent;
the weight ratio of the N- (2-oxiranylmethyl) carbamate grafted cellulose to the modified pseudo-boehmite to the aminoethylethanolamine is 10:2-3:4-5;
the addition weight ratio of the modified pseudo-boehmite powder to the aminoethylethanolamine is 1:1.5-2.
In the film-forming agent, the water-soluble polymer,
the weight average molecular weight of the sodium alginate is 50-100 ten thousand;
the molecular weight of polyethylene glycol is 800-2000;
the mass ratio of the sodium alginate to the polyethylene glycol is 1:8-10.
The invention takes N- (2-oxiranylmethyl) carbamate grafted cellulose as a main raw material, combines modified pseudo-boehmite powder and aminoethylethanolamine to prepare a porous carrier, and uses sodium alginate and polyethylene glycol to embed functional microorganisms to prepare a biomembrane carrier, thus having abundant micropore structures and high specific surface area, providing a proper growth environment for microorganism adsorption, being beneficial to rapid film hanging of microorganisms and having good mechanical property; the sodium alginate is used for embedding treatment, so that the stability of the biological film carrier is improved, the loss of microorganisms is prevented, the film forming agent also plays roles in protection and buffering, the stability is high, meanwhile, the strength of the biological film carrier can be further improved, and the service life is greatly prolonged.
Further, the modified pseudo-boehmite powder is a titanate coupling agent modified pseudo-boehmite, specifically, the pseudo-boehmite powder and a titanate coupling agent solution with the mass fraction of 4-8% are mixed and stirred for 15-30 min, the stirring rate is 300-500 r/min, and then the modified pseudo-boehmite powder is obtained after filtration and drying at 60-80 ℃.
Still further, the titanate coupling agent is any one of isopropyl tris (isostearyl) titanate, isopropyl tris (dioctyl pyrophosphoryl) titanate, isopropyl tris (dodecylbenzenesulfonyl) titanate.
The modified pseudo-boehmite powder is added into the porous carrier, and the modified pseudo-boehmite powder and the aminoethylethanolamine are added in a compounding way to have a synergistic effect, so that the micropore structure of the biological carrier can be regulated and controlled, the specific surface area is increased, the microorganism load capacity is improved, the adsorption degradation performance is improved, the reinforcing effect is good, the mechanical property of the material can be obviously improved, and the stability of the material is enhanced.
[3] The method for producing a bacterial biofilm for sewage treatment according to item [2], comprising:
1) Adding modified pseudo-boehmite powder and aminoethylethanolamine into a sufficient amount of potassium hydroxide solution with mass fraction of 1-3%, stirring at a high speed for 0.5-1 h, adding N- (2-oxiranylmethyl) carbamate grafted cellulose, heating to 60-70 ℃ for soaking for 1-2 h, introducing nitrogen, heating to 200-230 ℃ for activating for 3-5 h, cooling to room temperature, washing with water, drying to obtain a porous carrier, and dispersing the porous carrier in water to obtain a porous carrier solution with mass fraction of 40-60%;
2) Culturing synchronous nitrifying and denitrifying bacteria, centrifuging to collect thallus, and preparing into thallus with concentration higher than 4×10 9 Uniformly mixing a porous carrier solution and a bacterial suspension in cfu/mL, concentrating in vacuum at 35-40 ℃ until the solid content is more than or equal to 75%, and naturally air-drying to obtain an immobilized precursor substance;
3) Mixing and dispersing sodium alginate and polyethylene glycol in deionized water with the weight of 10-12 times to prepare a mixed solution, so as to obtain an embedding agent;
4) After uniformly mixing the embedding agent and the immobilized precursor, dripping the embedding agent into a calcium chloride solution by using a syringe to crosslink for 16-24 hours when the surface of the immobilized precursor is in a semi-solidification state, forming spherical particles, and then flushing with deionized water to obtain the bacterial biofilm for sewage treatment.
Further, in the step 1), the high-speed stirring rate is not lower than 1000r/min.
Further, in the step 1), the temperature rising rate is 5-10 ℃/min.
Further, in step 1), drying means drying in a vacuum drying oven at 50 to 70 ℃ for at least 6 hours.
Further, in the step 2), the weight ratio of the porous carrier solution to the bacterial suspension is 1:2-3.
Further, in step 4), the weight ratio of embedding agent to immobilized precursor is 2-4:1.
Further, in the step 4), the dropping rate is 5 to 10g/min.
Further, in the step 4), the mass fraction of the calcium chloride solution is 2.5-5%.
The bacterial biofilm prepared by adopting the technical scheme has the advantages of simple preparation method, rich micropore structure, high specific surface area, high surface roughness, high biofilm forming speed, high biofilm stability, difficult falling off, good mechanical property of the bacterial biofilm and long service life, and provides a proper growth environment for microorganism adsorption.
[4] The use of the bacterial biofilm for sewage treatment according to any of the items [2] and [3] in the treatment of domestic sewage, comprising placing the bacterial biofilm for sewage treatment according to any of the items [2] and [3] in a biodegradation tank and/or operating in combination with an MBR.
Further, in the application of the bacterial biofilm for sewage treatment in the treatment of domestic sewage, the filling rate of the bacterial biofilm for sewage treatment is 10-30%.
The beneficial effects of the invention are as follows:
1) The invention takes N- (2-oxiranylmethyl) carbamate grafted cellulose as a main raw material, combines modified pseudo-boehmite powder and aminoethylethanolamine to prepare a porous carrier, and prepares the biomembrane carrier by embedding sodium alginate and polyethylene glycol, thus having abundant micropore structures and high specific surface area, providing a proper growth environment for microorganism adsorption, being beneficial to quick film formation of microorganisms, having strong adsorption and degradation capability and good mechanical property; the sodium alginate is used for embedding treatment, so that the stability of the biological film carrier is improved, the loss of microorganisms is prevented, the film forming agent also plays a role in protection and buffering, the phenomenon that the microorganisms are directly contacted with wastewater and die and deactivate in a large amount is avoided, meanwhile, the strength of the biological film carrier can be further improved, and the service life is greatly prolonged;
2) In the invention, the addition of the modified pseudo-boehmite powder and the aminoethylethanolamine has a synergistic effect, has a good reinforcing effect, can obviously improve the mechanical property of the material, enhance the stability of the material, and can also increase the load capacity of microorganisms, thereby improving the adsorption and degradation properties;
3) According to the invention, the N- (2-oxiranylmethyl) carbamate is used for modifying cellulose, the processability of the modified cellulose is improved, the degradation rate is accelerated, the strength of the cellulose is improved, the N- (2-oxiranylmethyl) carbamate modified cellulose is used as a raw material for preparing the bacterial biomembrane, the gap is large, the specific surface area is large, the surface roughness is high, the absorption and the retention of moisture are facilitated, the direct shielding protection effect on attached microorganisms can be realized, the initial attachment and the fixation of microorganisms on a carrier are effectively accelerated, the formation of the initial biomembrane on the surface of the carrier can be promoted, the shearing effect of the water conservancy shearing effect on bacteria can be reduced, and the bacterial biomembrane has good impact resistance and is not easy to fall off.
Drawings
The foregoing and other objects, features, advantages and embodiments of the invention will be apparent from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a FTIR view of an N- (2-oxiranylmethyl) carbamate grafted cellulose of example 1 of the present invention; a represents cellulose, b represents N- (2-oxiranylmethyl) carbamate grafted cellulose;
FIG. 2 is a graph showing the results of a compressive strength test of a bacterial biofilm for sewage treatment according to the present invention;
FIG. 3 is a graph showing the results of film formation rate test of the bacterial biofilm for sewage treatment of the present invention.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, in the event of a conflict, the definitions of this specification shall control.
In the present invention, nitrifying bacteria and denitrifying bacteria were purchased from Guangzhou city An Jian ring engineering consultation Co.
The technical scheme of the invention is further described in detail below with reference to the detailed description and the accompanying drawings.
Example 1: bacterial biofilm for sewage treatment:
the embodiment provides a bacterial biofilm for sewage treatment, which is prepared by the following steps:
1) Preparation of N- (2-oxiranylmethyl) carbamate modified cellulose: adding cellulose into a mixed solution of sodium hydroxide and urea (the mass fraction of the sodium hydroxide is 10% and the mass fraction of the urea is 10%) with the weight being 9 times that of the cellulose, introducing nitrogen, and stirring at 30 ℃ and 1000r/min for 2 hours to obtain an alkalized cellulose solution; adding N- (2-oxiranylmethyl) carbamate (the addition amount is 28% of the mass of cellulose) into an alkalized cellulose solution, stirring for 30min at 30 ℃ and 400r/min, heating to 60 ℃ at a speed of 3 ℃/min, and stirring for reaction for 2h; cooling to room temperature after the reaction is finished, regulating the pH to be neutral by using 1mol/L HCl solution, precipitating by using 90% ethanol solution, filtering, washing, and drying at 60 ℃ to obtain N- (2-oxiranylmethyl) carbamate modified cellulose, wherein an FTIR chart is shown in figure 1, and as can be seen from the figure 1, characteristic peaks of-C=O and-NH appear in the modified cellulose (curve b), which indicates that the modified cellulose is generated;
2) Preparing modified pseudo-boehmite powder: mixing and stirring pseudo-boehmite powder and 6% isopropyl tri (isostearyl) titanate solution for 20min at a stirring rate of 400r/min, filtering, and drying at 70 ℃ to obtain modified pseudo-boehmite powder;
3) Preparing a porous carrier: adding modified pseudo-boehmite powder and aminoethylethanolamine into a sufficient amount of potassium hydroxide solution with mass fraction of 3%, stirring for 1h at a rotating speed of 1000r/min, adding N- (2-oxiranylmethyl) carbamate grafted cellulose, the modified pseudo-boehmite powder and the aminoethylethanolamine with the weight ratio of 10:2.5:4.5, soaking for 2h at 60 ℃, introducing nitrogen, heating to 220 ℃ for activation for 4h, cooling, washing with water, and drying to obtain a porous carrier, and dispersing the porous carrier in water to obtain a porous carrier solution with mass fraction of 50%;
4) Preparing an immobilized precursor substance: culturing synchronous nitrification and denitrification strains, centrifugally collecting thalli, preparing 20wt% of bacterial suspension, uniformly mixing a porous carrier solution and the bacterial suspension according to the weight ratio of 1:2.5, concentrating in vacuum at 35 ℃ until the solid content is more than or equal to 75%, and naturally air-drying to obtain an immobilized precursor substance;
5) Preparing an embedding agent: mixing sodium alginate (weight average molecular weight 80 ten thousand) and polyethylene glycol (molecular weight 1000) according to a ratio of 1:9, dispersing in deionized water with a weight of 10 times to prepare a mixed solution, and cooling to 45 ℃ to obtain an embedding agent;
6) Preparation of bacterial biofilms: uniformly mixing an embedding agent and an immobilized precursor according to a weight ratio of 3:1, adding the embedding agent into a solution of calcium chloride with a mass fraction of 4% by using a syringe to crosslink for 24 hours when the surface of the immobilized precursor is in a semi-solidified state, and then flushing with deionized water to obtain the bacterial biofilm for sewage treatment.
Example 2: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in the same manner as in example 1, except that in this example, the addition amount of N- (2-oxiranylmethyl) carbamate is 20% of the mass of cellulose in the process of preparing N- (2-oxiranylmethyl) carbamate modified cellulose.
Example 3: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in the same manner as in example 1, except that in this example, the addition amount of N- (2-oxiranylmethyl) carbamate in the process of preparing N- (2-oxiranylmethyl) carbamate modified cellulose is 24.5% of the mass of cellulose.
Example 4: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in the same manner as in example 1, except that in this example, the addition amount of N- (2-oxiranylmethyl) carbamate in the process of preparing N- (2-oxiranylmethyl) carbamate modified cellulose is 30.8% of the mass of cellulose.
Example 5: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in the same manner as in example 1, except that in this example, the addition amount of N- (2-oxiranylmethyl) carbamate in the process of preparing N- (2-oxiranylmethyl) carbamate modified cellulose is 40% of the mass of cellulose.
Example 6: another bacterial biofilm for sewage treatment:
the embodiment provides another bacterial biofilm carrier for sewage treatment, which is prepared by the following steps:
1) Preparing modified pseudo-boehmite powder: the procedure is the same as in step 2) of example 1;
2) Preparing a porous carrier: the procedure is the same as in step 3) of example 1, except that cellulose is used instead of N- (2-oxiranylmethyl) carbamate modified cellulose;
3) Preparing an immobilized precursor substance: the procedure is the same as in step 4) of example 1;
4) Preparing an embedding agent: the procedure is the same as in step 5) of example 1;
5) Preparation of bacterial biofilms: the procedure is the same as in step 6) of example 1.
Example 7: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in the same manner as in example 1, except that in this example, aminoethylethanolamine is not added to the porous carrier.
Example 8: another bacterial biofilm for sewage treatment:
the present example provides another bacterial biofilm carrier for sewage treatment, which is basically the same as that of example 1, except that in this example, the weight ratio of modified pseudo-boehmite powder to aminoethylethanolamine is 1:1.5.
Example 9: another bacterial biofilm for sewage treatment:
the present example provides another bacterial biofilm carrier for sewage treatment, which is basically the same as that of example 1, except that in this example, the weight ratio of modified pseudo-boehmite powder to aminoethylethanolamine is 1:2.
Example 10: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment,
1) Preparation of N- (2-oxiranylmethyl) carbamate modified cellulose: the procedure is the same as in step 1) of example 1;
2) Preparing a porous carrier: the procedure is substantially the same as in step 3) of example 1, except that pseudo-boehmite powder is used instead of modified pseudo-boehmite powder;
3) Preparing an immobilized precursor substance: the procedure is the same as in step 4) of example 1;
4) Preparing an embedding agent: the procedure is the same as in step 5) of example 1;
5) Preparation of bacterial biofilms: the procedure is the same as in step 6) of example 1.
Example 11: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which is prepared in substantially the same manner as in example 10, except that in this example, pseudo-boehmite powder is not added.
Experimental example 1:
the graft ratio test was carried out using the cellulose grafted with N- (2-oxiranylmethyl) carbamate provided in examples 1 to 5 as an experimental object, and the graft ratio (GD/%) was calculated by the following formula (1),
in the formula (1), m 1 Quality, m of the cellulose after grafting of N- (2-oxiranylmethyl) carbamate 0 The quality of the cellulose not grafted with N- (2-oxiranylmethyl) carbamate.
According to tests, the grafting rates of the N- (2-oxiranylmethyl) carbamate grafted cellulose provided in examples 1-5 are 18.6%, 13.2%, 14%, 20% and 23.7%, respectively, wherein the grafting rates of the N- (2-oxiranylmethyl) carbamate grafted cellulose provided in examples 1, 3 and 4 meet the requirements of the invention, and the bacterial biofilm carrier for sewage treatment prepared from the N- (2-oxiranylmethyl) carbamate grafted cellulose as a raw material has excellent performance.
Experimental example 2:
taking the porous carriers provided in examples 1 to 11 as experimental objects, and testing the pore diameter, the porosity and the specific surface area;
the pore size was determined using XTS30 optical microscope;
the porosity (epsilon) of the finished product cellulose carrier is measured by adopting a weighing method, and is calculated according to a formula (2):
in the formula (2), m 1 Carrier wet weight, m 0 -dry weight of support, ρ -density of water, n-mass of water absorbed per gram of support, V-wet volume of support;
the specific surface area is measured by adopting a BET method, and the specific surface area (Sg) is obtained by calculation according to formulas (3) and (4);
in the formula (3), W m The mass of adsorbed gas required when all surfaces of the sample are fully coated with a monolayer; w (W) mol -the molar mass of the adsorbed gas;
in the formula (4), V cal -correcting the volume; a-reading of a sample integrator; a is that cal -correcting the integrator readings; pa-atmospheric pressure; m-adsorbent molar mass; t-temperature; r-molar constant of gas 8210m 3 ·Pa·mol -1 ·K -1 。
The test results are shown in Table 1.
TABLE 1 pore size, porosity, specific surface area of porous support
| Examples | Aperture (mum) | Porosity (%) | Specific surface area (m) 2 /g) |
| 1 | 216 | 67.5 | 8.57 |
| 2 | 206 | 52.1 | 6.05 |
| 3 | 212 | 65.7 | 8.03 |
| 4 | 217 | 67.2 | 8.36 |
| 5 | 198 | 63.5 | 7.43 |
| 6 | 208 | 46.8 | 4.41 |
| 7 | 212 | 51.1 | 5.12 |
| 8 | 214 | 65.4 | 7.61 |
| 9 | 210 | 64.7 | 8.01 |
| 10 | 208 | 56.7 | 6.23 |
| 11 | 206 | 52.3 | 5.37 |
As shown in Table 1, the porous carrier provided by the invention has an average pore diameter of about 200 μm, and the porous carrier of preferred embodiment 1 has a specific surface area of 8.57m up to 69.2% 2 The porous rate is high, the specific surface area is large, a proper growth environment can be provided for microorganism adsorption, and the formation of a biological film is facilitated, so that higher denitrification efficiency is achieved; as can be seen from comparative examples 1 and 6, the graft modification of cellulose by N- (2-oxiranylmethyl) carbamate is advantageous for increasing the porosity and specific surface area of the porous support, thereby increasing the denitrification efficiency; the comparative examples 1 and 7-11 show that the modified pseudo-boehmite powder and the aminoethylethanolamine have a synergistic effect, and can regulate and control the micropore structure of the biological carrier and increase the specific surface area.
Experimental example 3:
the bacterial biofilms for sewage treatment provided in examples 1 to 11 were used as test subjects, and the compressive strength of the carriers was measured using a mini-type broadband tension-torsion fatigue tester. The test results are shown in fig. 2.
As shown in figure 2, the strength of the bacterial biomembrane of the invention is up to 6.87MPa, and the compressive strength is high, which indicates that the biomembrane carrier provided by the invention has good water impact resistance and long service life; comparative examples 1 to 6 show that the compressive strength of the carrier can be obviously improved by grafting modification of the N- (2-oxiranylmethyl) carbamate on the cellulose, and comparative examples 1 and 7 to 11 show that the modified pseudo-boehmite powder and the aminoethylethanolamine have a synergistic effect, and the compressive strength of the modified pseudo-boehmite powder and the aminoethylethanolamine can be obviously improved by adding the modified pseudo-boehmite powder and the aminoethylethanolamine in a certain proportion, so that the service life of the carrier is prolonged.
Experimental example 4:
the bacterial biofilms for sewage treatment provided in examples 1 to 11 were used as test subjects, and the amounts of attached biofilms were measured as follows:
in the experiment, artificial synthetic organic wastewater is adopted, glucose is used as a carbon source, and NH is used 4 Cl and KH 2 PO 4 Providing N and P (C: N: p=100:5:1), respectively; the inoculated sludge in the film hanging experiment is obtained from a sewage treatment plant (mlss=5000 mg/L) in Hangzhou city of Zhejiang province, a biological film carrier is placed in a 2L beaker, continuously aerated for 48 hours, taken out, dried to constant weight at 105 ℃, and the film hanging rate (G) is calculated by a formula (5):
in the formula (5), M 1 -the biofilm carrier mass; m is M 2 Biofilm carrier quality after film formation.
The test results are shown in FIG. 3.
As shown in FIG. 3, the bacterial biofilm provided by the invention has a biofilm formation rate of 247.5% after 48 hours, which indicates that the biofilm carrier prepared by the method has high biofilm formation speed and large biofilm amount; it can also be seen that compared with unmodified cellulose (example 6), the biofilm carrier prepared by modifying N- (2-oxiranylmethyl) carbamate has the advantages of fast biofilm growth rate, high biofilm amount, and synergistic effect between the pseudo-boehmite powder and aminoethylethanolamine in comparative examples 1, 7-11, and can obviously improve the film forming speed and increase the load of microorganisms.
Experimental example 5:
the bacterial biofilms for sewage treatment provided in examples 1 to 11 were used as experimental subjects in a biological aerated filter, and sludge MLSS was inoculated: 4000mg/L, artificial synthetic simulated domestic sewage is used as raw water, and the simulated raw water is prepared from glucose and NH 4 Cl、KH 2 PO 4 、NaHCO 3 Is prepared into raw water with COD content of 400mg/L and NH 4 + -N:65mg/L; reaction conditions (microporous aeration) do=1.2 mg/L, ph=6.8, hrt=6 h, temperature t=25 ℃; reactor volume 150L, bacterial biofilm addition rate (30% of bulk); after the mixed liquor in the operation mode stays in the reaction tank for 6 hours, the mixed liquor flows out to a sedimentation tank, and the sludge after sedimentation flows back (the reflux ratio is 100%); and (3) measuring the COD content by referring to HJ828-2017, and measuring the ammonia nitrogen content and the total nitrogen content by referring to a HJ535-2009 Nardostat spectrophotometry method.
The test results of COD content, ammonia nitrogen and total nitrogen removal rate are shown in Table 2.
TABLE 2 COD removal Rate, ammonia nitrogen and Total Nitrogen removal Rate of bacterial biofilm for wastewater treatment
| Examples | COD removal Rate (%) | Ammonia nitrogen removal rate (%) | Total nitrogen removal (%) |
| 1 | 93.7 | 94.2 | 90.3 |
| 2 | 86.3 | 84.7 | 80.4 |
| 3 | 90.5 | 91.4 | 86.2 |
| 4 | 94.1 | 93.4 | 88.4 |
| 5 | 90.2 | 90.8 | 83.8 |
| 6 | 80.4 | 78.9 | 65.7 |
| 7 | 85.7 | 84.4 | 81.8 |
| 8 | 90.6 | 91.1 | 88.0 |
| 9 | 91.7 | 92.3 | 89.5 |
| 10 | 89.2 | 87.2 | 84.9 |
| 11 | 87.1 | 84.8 | 82.7 |
As shown in Table 2, through continuous 10-day experiments, the COD removal rate of the bacterial biofilm provided by the invention is up to 94.1%, the ammonia nitrogen removal rate is up to 94.2%, and the total nitrogen removal rate is up to 90.3%, which shows that the adsorption degradation efficiency of the biofilm provided by the scheme of the invention is high, and it can be seen that the degradation efficiency of the N- (2-oxiranylmethyl) carbamate on cellulose is greatly improved due to the fact that a large number of groups such as amido groups, ester groups and the like are introduced into the surface of the cellulose after the cellulose is modified, so that the initial attachment and fixation of microorganisms on a carrier can be effectively accelerated, the formation of the biofilm on the surface of the carrier can be promoted, and the degradation efficiency of the cellulose can be improved; in addition, the modified pseudo-boehmite powder and the aminoethylethanolamine have a certain influence on the adsorption and degradation efficiency of the material, which shows that the modified pseudo-boehmite powder and the aminoethylethanolamine have a synergistic effect, so that the film forming speed can be increased, the load of microorganisms can be increased, and the adsorption and degradation efficiency is improved.
The conventional technology in the above embodiments is known to those skilled in the art, and thus is not described in detail herein. While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or method illustrated may be made without departing from the spirit of the disclosure. In addition, the various features and methods described above may be used independently of one another, or may be combined in various ways. Many of the embodiments described above include similar components, and thus, these similar components are interchangeable in different embodiments. While the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Therefore, the present invention is not intended to be limited by the specific disclosure of the preferred embodiments herein.
Claims (7)
1. The application of modified cellulose in preparing a bacterial biomembrane for sewage treatment is characterized in that the modified cellulose is N- (2-oxiranylmethyl) carbamate grafted cellulose prepared by grafting and modifying cellulose with N- (2-oxiranylmethyl) carbamate, and the preparation method of the modified cellulose comprises the following steps:
1) Adding cellulose into a sodium hydroxide/urea mixed solution with the weight being 8-10 times that of the cellulose, introducing nitrogen, and stirring for 1-2 hours at the temperature of 30-35 ℃ to obtain an alkalized cellulose solution;
2) Adding N- (2-oxiranylmethyl) carbamate into the alkalized cellulose solution, stirring for 15-30 min at 30-35 ℃, then heating to 60-65 ℃ and stirring for reacting for 1-2.5 h;
3) Cooling to room temperature after the reaction is finished, regulating the pH to be neutral by using 1-2 mol/L hydrochloric acid solution, precipitating by using 85-90% ethanol solution, filtering, washing and drying to obtain N- (2-oxiranylmethyl) carbamate modified cellulose; the porous carrier prepared by taking the N- (2-oxiranylmethyl) carbamate modified cellulose as a raw material has rich micropore structure and high specific surface area, provides a proper growth environment for microorganism adsorption, is beneficial to quick film formation of microorganisms, and has the grafting rate of 14-20 percent of the N- (2-oxiranylmethyl) carbamate grafted cellulose.
2. A bacterial biofilm for sewage treatment, comprising:
a functional microorganism;
a porous carrier comprising the modified cellulose, modified pseudo-boehmite powder, aminoethylethanolamine according to claim 1; and
film forming agent including sodium alginate and polyethylene glycol;
the modified pseudo-boehmite powder is a titanate coupling agent modified pseudo-boehmite, specifically, the pseudo-boehmite powder and a titanate coupling agent solution with the mass fraction of 4-8% are mixed and stirred for 15-30 min, and then the modified pseudo-boehmite powder is obtained after filtration and drying.
3. The bacterial biofilm for sewage treatment according to claim 2, wherein the weight ratio of the N- (2-oxiranylmethyl) carbamate grafted cellulose, the modified pseudo-boehmite powder and the aminoethylethanolamine is 10:2-3:4-5.
4. The bacterial biofilm for sewage treatment according to claim 3, wherein the addition weight ratio of the modified pseudo-boehmite powder to the aminoethylethanolamine is 1:1.5-2.
5. The method for producing a bacterial biofilm for sewage treatment according to any one of claims 2 to 4, comprising:
1) Adding modified pseudo-boehmite powder and aminoethylethanolamine into a sufficient amount of potassium hydroxide solution with mass fraction of 1-3%, stirring at a high speed for 0.5-1 h, adding N- (2-oxiranylmethyl) carbamate grafted cellulose, heating to 60-70 ℃ for soaking for 1-2 h, introducing nitrogen, heating to 200-230 ℃ for activating for 3-5 h, cooling to room temperature, washing with water, drying to obtain a porous carrier, and dispersing the porous carrier in water to obtain a porous carrier solution with mass fraction of 40-60%;
2) Culturing synchronous nitrifying and denitrifying bacteria, centrifuging to collect thallus, and preparing into thallus with concentration higher than 4×10 9 Uniformly mixing the porous carrier solution and the bacterial suspension with cfu/mL, concentrating in vacuum at 35-40 ℃ until the solid content is more than or equal to 75%, and naturally air-drying to obtain an immobilized precursor substance;
3) Mixing and dispersing sodium alginate and polyvinyl alcohol in deionized water with the weight being 10 times that of the sodium alginate and polyvinyl alcohol to prepare a mixed solution, so as to obtain an embedding agent;
4) After uniformly mixing the embedding agent and the immobilized precursor, dripping the embedding agent into a calcium chloride solution by using a syringe to crosslink for 16-24 hours when the surface of the immobilized precursor is in a semi-solidification state, forming spherical particles, and then flushing with deionized water to obtain the bacterial biofilm for sewage treatment.
6. Use of the bacterial biofilm for sewage treatment according to any of claims 2 to 4 in the treatment of domestic sewage, comprising placing the bacterial biofilm for sewage treatment according to any of claims 2 to 4 in a biodegradation tank and/or operating in combination with an MBR.
7. The use according to claim 6, wherein the filling rate of the bacterial biofilm for sewage treatment is 10-30%.
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