CN113663537A - Bacterial biofilm for sewage treatment and preparation method thereof - Google Patents
Bacterial biofilm for sewage treatment and preparation method thereof Download PDFInfo
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- 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
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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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 preparing a porous carrier by grafting N- (2-ethylene oxide methyl) carbamate with cellulose, modified pseudo-boehmite powder and aminoethyl ethanolamine, embedding the porous carrier by sodium alginate and polyethylene glycol, has rich microporous structures and high specific surface area, provides a proper growth environment for microbial adsorption, is beneficial to the rapid biofilm formation of microorganisms, and has 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, the life of people is changed greatly, the living standard is improved continuously, more and more domestic sewage is generated, excessive ammonia nitrogen is brought in along with the discharge of the domestic sewage into a water body, the environment capacity of the water body is exceeded, the self-purification capacity of the water body is seriously influenced, the water quality is deteriorated, the ecological environment structure is damaged, the eutrophication of the water body is caused, the oxygen in the water is rapidly consumed, the fish and plankton die due to oxygen deficiency, the safety of a drinking water source and the normal life quality are seriously influenced, and therefore, the control of the nitrogen content in the water body is the root for treating the eutrophic sewage.
In the face of environmental problems caused by excessive nitrogen emission and pollution thereof, the national environmental protection plan increases the restrictive control index of total ammonia nitrogen emission on the basis of the total emission index, meanwhile, the pollutant emission standard of urban sewage treatment plants makes clear regulations on ammonia nitrogen and total nitrogen, the task of ammonia nitrogen emission reduction and the emission standard are increasingly strict, but the current sewage treatment technology has the defects of large floor area, high capital construction investment, low operation load, unsatisfactory removal effect, insufficient carbon source in the denitrification process and the need of additional carbon source, and can not meet the requirements of the current sewage treatment, so that the development of the sewage treatment method with enhanced denitrification is very necessary.
The biological aerated filter is a novel and efficient biological membrane sewage treatment technology, is a technology for degrading pollutants in wastewater by forming a biological membrane by attaching microorganisms to a carrier, and is very important for improving the wastewater treatment effect by reasonably selecting the carrier. The porous particle suspension carrier is a novel high-efficiency carrier filler in the wastewater treatment by the biofilm method at present, has the advantages of large microorganism attachment 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 mainly comprise inorganic materials such as activated 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 high cost, complex processing technology, difficult treatment after the fillers are discarded, poor degradability of the organic polymer fillers, and easy generation of secondary pollution. Therefore, 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 biomembrane for sewage treatment and a preparation method thereof, and the obtained bacterial biomembrane has the advantages of large specific surface area, high membrane hanging speed, high microorganism load, good impact resistance, difficult shedding of the biomembrane, high adsorption and degradation efficiency and long service life, and can be used in a biodegradation tank independently or operated in combination with an MBR (membrane bioreactor).
To achieve the above object, the present invention adopts a technical means including 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-ethylene oxide methyl) carbamate grafted cellulose prepared by grafting and modifying cellulose by N- (2-ethylene oxide methyl) carbamate.
The grafting ratio of the N- (2-ethylene oxide methyl) carbamate grafted cellulose is 14-20%.
The preparation method of the N- (2-ethylene oxide methyl) carbamate grafted cellulose comprises the following steps:
1) adding cellulose into 8-10 times by weight of a sodium hydroxide/urea mixed solution, introducing nitrogen, and stirring at 30-35 ℃ for 1-2 hours to obtain an alkalized cellulose solution;
2) adding N- (2-ethylene oxide methyl) carbamate into the alkalized cellulose solution, stirring for 15-30 min at the temperature of 30-35 ℃, then heating to 60-65 ℃, and stirring for reaction for 1-2.5 h;
3) and after the reaction is finished, cooling to room temperature, adjusting 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-ethylene oxide methyl) carbamate modified cellulose.
Further, in the step 1), the mass fraction of the sodium hydroxide in the sodium hydroxide/urea mixed solution is 5-10%, and the mass fraction of the urea is 8-10%.
Further, in the step 1), the stirring speed is 800-1000 r/min.
Further, in the step 2), the amount of N- (2-oxiranylmethyl) carbamate added is 24.5 to 30.8% by mass of the cellulose.
Further, in the step 2), the temperature rise 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 h.
The invention adopts the scheme, the N- (2-ethylene oxide methyl) carbamate is used for grafting modification of the cellulose, the internal structure of the cellulose can be improved, the introduction of active groups can improve the processing performance of the cellulose, the degradation rate is accelerated, the strength is improved, the N- (2-ethylene oxide methyl) carbamate modified cellulose is used as a raw material to prepare the bacterial biofilm, the bacterial biofilm has higher porosity, larger specific surface area and higher surface roughness, is favorable for absorbing and maintaining moisture, is favorable for microorganisms to enter the bacterial biofilm to grow and reproduce, cellulose shows that more active groups can play a role in protecting attached microorganisms, accelerates the attachment, fixation and reproduction of the microorganisms on a carrier, promotes the rapid formation of the biofilm, and can reduce the shearing action of water conservancy shearing action on the bacteria, good impact resistance and difficult shedding of the biological film.
[2] A bacterial biofilm for wastewater treatment comprising:
a functional microorganism;
a porous carrier comprising the N- (2-oxiranylmethyl) carbamate-grafted cellulose described in item [1], a modified pseudo-boehmite powder, and aminoethylethanolamine; and
film forming agent including sodium alginate and polyethylene glycol.
The functional microorganism is a synchronous nitrification and denitrification bacterium.
In the porous carrier, the porous carrier is provided with a porous carrier,
the grafting rate of the N- (2-ethylene oxide methyl) carbamate grafted cellulose is 14-20%;
the weight ratio of the N- (2-oxiranylmethyl) carbamate grafted cellulose to the modified pseudo-boehmite to the aminoethyl ethanolamine is 10: 2-3: 4-5;
the adding weight ratio of the modified pseudo-boehmite powder to the aminoethyl ethanolamine is 1: 1.5-2.
In the film-forming agent,
the weight average molecular weight of the sodium alginate is 50-100 ten thousand;
the molecular weight of the 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-ethylene oxide methyl) carbamate grafted cellulose as a main raw material, prepares a porous carrier by combining modified pseudo-boehmite powder and aminoethyl ethanolamine, and embeds functional microorganisms with sodium alginate and polyethylene glycol to prepare a biomembrane carrier, has rich microporous structure and high specific surface area, provides a proper growth environment for microorganism adsorption, is beneficial to the rapid biofilm formation of microorganisms, and has good mechanical property; the sodium alginate is utilized for embedding treatment, so that the stability of the biomembrane carrier is improved, the loss of microorganisms is prevented, the film-forming agent plays a role in protection and buffering, the stability is high, meanwhile, the strength of the biomembrane 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, and is specifically prepared by mixing and stirring pseudo-boehmite powder and a titanate coupling agent solution with the mass fraction of 4-8% for 15-30 min at the stirring speed of 300-500 r/min, filtering, and drying at 60-80 ℃.
Still further, the titanate coupling agent is any one of isopropyl tris (isostearoyl) titanate, isopropyl tris (dioctylphosphato) titanate, isopropyl tris (dodecylbenzenesulfonyl) titanate.
The modified pseudo-boehmite powder is added into the porous carrier, and has a synergistic effect with the compound addition of the aminoethyl ethanolamine, the microporous structure of the biological carrier can be regulated and controlled, the specific surface area is increased, the microbial load 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], which comprises:
1) adding modified pseudo-boehmite powder and aminoethyl ethanolamine into a sufficient amount of 1-3% by mass of potassium hydroxide solution, stirring at a high speed for 0.5-1 h, adding N- (2-oxiranylmethyl) carbamate grafted cellulose, heating to 60-70 ℃, soaking for 1-2 h, introducing nitrogen, heating to 200-230 ℃, 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 the mass fraction of 40-60%;
2) culturing synchronous nitrifying and denitrifying bacteria, centrifugally collecting thallus, and preparing to obtain thallus with concentration higher than 4X 109Uniformly mixing a porous carrier solution and a bacterial suspension of cfu/mL, concentrating the mixture in vacuum at the temperature of 35-40 ℃ until the solid content is more than or equal to 75%, and naturally drying the mixture to obtain an immobilized precursor substance;
3) mixing and dispersing sodium alginate and polyethylene glycol in 10-12 times by weight of deionized water to prepare a mixed solution, and obtaining an embedding agent;
4) uniformly mixing an embedding agent and an immobilized precursor substance, dripping the embedding agent into a calcium chloride solution by using an injector to crosslink for 16-24 hours when the surface of the immobilized precursor substance is in a semi-solidified state, forming spherical particles, and then washing by using deionized water to obtain the bacterial biofilm for sewage treatment.
Further, in the step 1), the high-speed stirring speed is not lower than 1000 r/min.
Further, in the step 1), the temperature rise rate is 5-10 ℃/min.
Further, in the step 1), drying refers to drying in a vacuum drying oven at 50-70 ℃ 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 the step 4), the weight ratio of the embedding medium to the immobilized precursor substance is 2-4: 1.
Further, in the step 4), the dropping speed is 5-10 g/min.
Further, in the step 4), the mass fraction of the calcium chloride solution is 2.5-5%.
According to the invention, the bacterial biofilm prepared by adopting the technical scheme is simple in preparation method, has a rich microporous structure, is high in specific surface area and surface roughness, provides a proper growth environment for microbial adsorption, is high in biofilm formation rate, is high in stability, is not easy to fall off, and is good in mechanical property and long in service life.
[4] The application of the bacterial biomembrane for sewage treatment in any one of the items [2] and [3] in the treatment of domestic sewage comprises the step of placing the bacterial biomembrane for sewage treatment in any one of the items [2] and [3] in a biodegradation tank and/or operating in combination with MBR.
Further, in the application of the bacterial biofilm for sewage treatment in domestic sewage treatment, the filling rate of the bacterial biofilm for sewage treatment is 10-30%.
The invention has the beneficial effects that:
1) the invention takes N- (2-ethylene oxide methyl) carbamate grafted cellulose as a main raw material, prepares a porous carrier by combining modified pseudo-boehmite powder and aminoethyl ethanolamine, and prepares a biomembrane carrier by embedding sodium alginate and polyethylene glycol, has rich microporous structure and high specific surface area, provides a proper growth environment for microorganism adsorption, is beneficial to the rapid biofilm formation of microorganisms, and has strong adsorption and degradation capability and good mechanical property; the sodium alginate is used for embedding, so that the stability of the biomembrane carrier is improved, the loss of microorganisms is prevented, the film-forming agent plays a role in protection and buffering, the phenomena of massive death and inactivation caused by direct contact of the microorganisms and waste water are avoided, meanwhile, the strength of the biomembrane carrier can be further improved, and the service life is greatly prolonged;
2) according to the invention, the modified pseudo-boehmite powder and the aminoethyl ethanolamine have a synergistic effect, have a good reinforcing effect, can obviously improve the mechanical property of the material, enhance the stability of the material, and also can increase the loading capacity of microorganisms, thereby improving the adsorption degradation performance;
3) according to the invention, the N- (2-ethylene oxide methyl) carbamate is used for modifying the cellulose, the processing performance of the modified cellulose is improved, the degradation rate is accelerated, and the strength of the cellulose is improved.
Drawings
In order to make the aforementioned and other objects, features, and advantages of the invention, as well as others which will become apparent, reference is made to the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a FTIR plot of 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 the compressive strength test of the bacterial biofilm for sewage treatment according to the present invention;
FIG. 3 is a diagram showing the results of the biofilm formation rate test of the bacterial biofilm for sewage treatment according to the present invention.
Detailed Description
To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. 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, and in case of conflict, the definitions in this specification shall control.
In the present invention, nitrifying bacteria and denitrifying bacteria were purchased from Anjian Ring engineering consultations, Inc., Guangzhou.
The following describes the technical solution of the present invention in further detail with reference to the detailed description and the accompanying drawings.
Example 1: a 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 9 weight times of sodium hydroxide/urea mixed solution (in the mixed solution, the mass fraction of sodium hydroxide is 10 percent, and the mass fraction of urea is 10 percent), introducing nitrogen, and stirring at 30 ℃ and 1000r/min for 2h to obtain an alkalized cellulose solution; adding N- (2-ethylene oxide methyl) carbamate (the addition amount is 28 percent of the mass of the cellulose) into the alkalized cellulose solution, stirring for 30min at the temperature of 30 ℃ and at the speed of 400r/min, heating to 60 ℃ at the speed of 3 ℃/min, stirring and reacting for 2 h; after the reaction is finished, cooling to room temperature, adjusting 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 the N- (2-ethylene oxide methyl) carbamate modified cellulose, wherein an FTIR (infrared ray diffraction) diagram of the N- (2-ethylene oxide methyl) carbamate modified cellulose is shown in the attached figure 1, and the modified cellulose (curve b) has characteristic peaks of-C ═ O and-NH by observing the attached figure 1, which indicates that the modified cellulose is formed;
2) preparing modified pseudo-boehmite powder: mixing and stirring pseudo-boehmite powder and 6 mass percent isopropyl tri (isostearyl) titanate solution for 20min at the stirring speed 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 aminoethyl ethanolamine into a sufficient amount of 3% potassium hydroxide solution, stirring for 1h at the rotating speed of 1000r/min, adding N- (2-ethylene oxide methyl) carbamate grafted cellulose, modified pseudo-boehmite powder and aminoethyl ethanolamine according to the adding weight ratio of 10:2.5:4.5, soaking for 2h at 60 ℃, introducing nitrogen, heating to 220 ℃ for activation for 4h, then 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 the mass fraction of 50%;
4) preparation of immobilized precursor material: culturing synchronous nitrification and denitrification strains, centrifugally collecting thalli, preparing 20 wt% of bacterial suspension, uniformly mixing the porous carrier solution and the bacterial suspension according to the weight ratio of 1:2.5, concentrating under vacuum at 35 ℃ until the solid content is more than or equal to 75%, and naturally drying to obtain an immobilized precursor substance;
5) preparing an embedding agent: mixing sodium alginate (with a weight-average molecular weight of 80 ten thousand) and polyethylene glycol (with a molecular weight of 1000) according to a ratio of 1:9, dispersing in 10 times of deionized water to prepare a mixed solution, and cooling to 45 ℃ to obtain an embedding agent;
6) preparing a bacterial biofilm: uniformly mixing an embedding agent and an immobilized precursor material according to the weight ratio of 3:1, adding the embedding agent into a calcium chloride solution with the mass fraction of 4% by using an injector to perform crosslinking for 24 hours when the embedding agent is in a semi-solidified state on the surface of the immobilized precursor material, and then washing 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 was prepared in substantially the same manner as in example 1, except that in this example, N- (2-oxiranylmethyl) carbamate was added in an amount of 20% by mass based on the mass of cellulose in the preparation of N- (2-oxiranylmethyl) carbamate-modified cellulose.
Example 3: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for wastewater treatment, which was prepared in substantially the same manner as in example 1, except that in this example, N- (2-oxiranylmethyl) carbamate was added in an amount of 24.5% by mass based on the mass of cellulose in the preparation of N- (2-oxiranylmethyl) carbamate-modified cellulose.
Example 4: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which was prepared in substantially the same manner as in example 1, except that in this example, N- (2-oxiranylmethyl) carbamate was added in an amount of 30.8% by mass based on the mass of cellulose in the preparation of N- (2-oxiranylmethyl) carbamate-modified cellulose.
Example 5: another bacterial biofilm for sewage treatment:
this example provides another bacterial biofilm carrier for sewage treatment, which was prepared in substantially the same manner as in example 1, except that in this example, N- (2-oxiranylmethyl) carbamate was added in an amount of 40% by mass based on the mass of cellulose in the preparation of N- (2-oxiranylmethyl) carbamate-modified 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 was the same as in step 3) of example 1, except that cellulose was used in place of the N- (2-oxiranylmethyl) carbamate-modified cellulose;
3) preparation of immobilized precursor material: 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) preparing a bacterial biofilm: the procedure was 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 wastewater treatment, which was prepared in substantially the same manner as in example 1, except that in this example, aminoethylethanolamine was not added to the porous carrier.
Example 8: 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 1, except that in this example, the modified pseudo-boehmite powder and aminoethyl ethanolamine are added in a weight ratio of 1: 1.5.
Example 9: 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 1, except that in this example, the modified pseudo-boehmite powder and aminoethyl ethanolamine are added in a weight ratio of 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 1) of example 1;
2) preparing a porous carrier: the steps are basically the same as the step 3) of the embodiment 1, except that pseudo-boehmite powder is used for replacing modified pseudo-boehmite powder;
3) preparation of immobilized precursor material: 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) preparing a bacterial biofilm: the procedure was 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 was prepared substantially as in example 10, except that pseudo-boehmite powder was not added in this example.
Experimental example 1:
the test of the graft ratio was carried out using the cellulose grafted with N- (2-oxiranylmethyl) carbamate provided in examples 1 to 5 as an experimental subject, and the graft ratio (GD/%) was calculated by the following formula (1),
in the formula (1), m1Mass of N- (2-oxiranylmethyl) carbamate-grafted cellulose, m0The mass of cellulose not grafted with N- (2-oxiranylmethyl) carbamate.
Tests show that the grafting ratios of the N- (2-ethylene oxide methyl) carbamate grafted cellulose provided in examples 1 to 5 are 18.6%, 13.2%, 14%, 20% and 23.7%, respectively, wherein the grafting ratios of the N- (2-ethylene oxide methyl) 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 by using the N- (2-ethylene oxide methyl) carbamate grafted cellulose as a raw material has excellent performance.
Experimental example 2:
taking the porous carrier provided in the embodiments 1-11 as an experimental object, and carrying out pore diameter, porosity and specific surface area tests;
pore size was determined using an XTS30 type optical microscope;
porosity the porosity (epsilon) of the finished cellulose carrier was measured by a weighing method and calculated according to the formula (2):
in the formula (2), m1Wet weight of carrier, m0-carrier dry weight, ρ -density of water, n-mass of water absorbed per gram of carrier, V-wetted volume of carrier;
measuring the specific surface area by adopting a BET method, and calculating according to formulas (3) and (4) to obtain the specific surface area (Sg);
in the formula (3), Wm-the mass of adsorbed gas required for the monolayer to be spread on all surfaces of the sample; wmol-the molar mass of the adsorbed gas;
in the formula (4), Vcal-a correction volume; a-sample integrator reading; a. thecal-correcting the integrator readings; pa-atmospheric pressure; m-molar mass of adsorbent; t-temperature; r-gas molar constant 8210m3·Pa·mol-1·K-1。
The test results are shown in table 1.
TABLE 1 pore diameter, porosity, specific surface area of porous support
| Examples | Pore size (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 average pore diameter of the porous carrier provided by the present invention is about 200. mu.m, and the porous carrier of the preferred embodiment 1 has 69.2% and a specific surface area of 8.57m2The porous membrane has high porosity and large specific surface area, can provide a proper growth environment for microbial adsorption, is beneficial to the formation of a biological membrane, and thus achieves higher denitrification efficiency; comparing examples 1 and 6, it can be seen that the graft modification of the N- (2-ethylene oxide methyl) carbamate to the cellulose is beneficial to improving the porosity and the specific surface area of the porous carrier, thereby improving the denitrification efficiency; compared with examples 1 and 7-11, the modified pseudo-boehmite powder and the aminoethyl ethanolamine have a synergistic effect, and can regulate the microporous 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 experimental subjects, and the compressive strength of the carrier was measured using a micro broadband pull-twist fatigue tester. The test results are shown in fig. 2.
As shown in FIG. 2, the highest strength of the bacterial biofilm can reach 6.87MPa, and the compressive strength is high, which shows that the biofilm carrier provided by the invention has good water impact resistance and long service life; as can be seen from comparative examples 1 to 6, the compressive strength of the carrier can be obviously improved by the graft modification of the N- (2-oxiranylmethyl) carbamate on the cellulose, and as can be seen from comparative examples 1 and 7 to 11, the modified pseudo-boehmite powder and the aminoethyl ethanolamine have a synergistic effect, and the compressive strength of the modified pseudo-boehmite powder and the aminoethyl ethanolamine can be obviously improved by adding the modified pseudo-boehmite powder and the aminoethyl ethanolamine in a certain proportion, so that the service life is prolonged.
Experimental example 4:
the bacterial biofilm for sewage treatment provided in examples 1 to 11 was used as an experimental subject to test the amount of the biofilm adhered thereto, and the test method was as follows:
in the experiment, artificially synthesized organic wastewater is adopted, glucose is used as a carbon source, and NH is used4Cl and KH2PO4Providing N and P (C: N: P ═ 100:5:1), respectively; inoculation in biofilm culturing experimentsThe sludge is taken from a certain sewage treatment plant (MLSS is 5000mg/L) in Hangzhou city in Zhejiang province, the biofilm carrier is placed in a beaker with the volume of 2L, the sludge is taken out after continuous aeration for 48h, the sludge is dried to constant weight at 105 ℃, and the biofilm formation rate (G) is calculated by using a formula (5):
in the formula (5), M1-raw biofilm carrier quality; m2And (3) the quality of the biomembrane carrier after the membrane is hung.
The test results are shown in fig. 3.
As shown in FIG. 3, the biofilm formation rate of the bacterial biofilm provided by the invention reaches 247.5% after 48 hours, which indicates that the biofilm carrier prepared by the method of the invention 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 modification with N- (2-oxiranylmethyl) carbamate has a high growth rate and a high biofilm amount, and compared with examples 1 and 7-11, the pseudoboehmite powder and the aminoethylethanolamine have a synergistic effect, so that the biofilm formation speed can be obviously increased, and the load of microorganisms can be increased.
Experimental example 5:
the bacterial biofilm for sewage treatment provided in examples 1 to 11 was used as an experimental object, and applied to a biological aerated filter to inoculate sludge MLSS: 4000mg/L, artificial synthetic simulated domestic sewage is used as raw water, and the simulated raw water is composed of glucose and NH4Cl、KH2PO4、NaHCO3Prepared by the raw water with the COD content of 400mg/L and NH4 +-N: 65 mg/L; reaction conditions (microporous aeration) DO 1.2mg/L, pH 6.8, HRT 6h, temperature T25 ℃; the reactor volume was 150L, bacterial biofilm addition rate (30% bulk volume); after the mixed liquid stays in the reaction tank for 6 hours in the operation mode, the mixed liquid flows out to a sedimentation tank, and the sludge after sedimentation flows back (the reflux ratio is 100%); COD content is determined by referring to HJ828-2017, and ammonia nitrogen and total nitrogen content are determined by referring to HJ535-2009 nH reagent spectrophotometry.
The test results of COD content, ammonia nitrogen and total nitrogen removal are shown in Table 2.
TABLE 2 COD removal, Ammonia Nitrogen removal, Total Nitrogen removal of bacterial biofilm for wastewater treatment
| Examples | COD removal Rate (%) | Ammonia nitrogen removal (%) | 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 present invention is as high as 94.1%, the ammonia nitrogen removal rate is as high as 94.2%, and the total nitrogen removal rate is as high as 90.3%, which indicates that the adsorption degradation efficiency of the biofilm provided by the present invention is high, and it can be seen that the degradation efficiency of the biofilm can be greatly improved by modifying the cellulose with N- (2-oxiranylmethyl) carbamate, mainly because a large amount of amide groups, ester groups, etc. are introduced on the surface of the modified cellulose, the initial attachment and fixation of microorganisms on the carrier can be effectively accelerated, so that the formation of the biofilm on the surface of the carrier can be promoted, and the degradation efficiency of the biofilm can be improved; in addition, the modified pseudo-boehmite powder and the aminoethyl ethanolamine have certain influence on the adsorption and degradation efficiency of the material, which shows that the modified pseudo-boehmite powder and the aminoethyl ethanolamine have a synergistic effect between the modified pseudo-boehmite powder and the aminoethyl ethanolamine, so that the film forming speed can be increased, the load of microorganisms can be increased, and the adsorption and degradation efficiency can be improved.
Conventional techniques in the above embodiments are known to those skilled in the art, and therefore, will not be 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. Accordingly, the invention is not intended to be limited by the specific disclosure of preferred embodiments herein.
Claims (9)
1. The application of the modified cellulose in preparation of bacterial biofilms for sewage treatment is characterized in that the modified cellulose is N- (2-ethylene oxide methyl) carbamate grafted cellulose prepared by grafting modification of cellulose by N- (2-ethylene oxide methyl) carbamate, and the grafting rate of the N- (2-ethylene oxide methyl) carbamate grafted cellulose is 14-20%.
2. The process for producing a modified cellulose according to claim 1, which comprises:
1) adding cellulose into 8-10 times by weight of a sodium hydroxide/urea mixed solution, introducing nitrogen, and stirring at 30-35 ℃ for 1-2 hours to obtain an alkalized cellulose solution;
2) adding N- (2-ethylene oxide methyl) carbamate into the alkalized cellulose solution, stirring for 15-30 min at the temperature of 30-35 ℃, then heating to 60-65 ℃, and stirring for reaction for 1-2.5 h;
3) and after the reaction is finished, cooling to room temperature, adjusting 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-ethylene oxide methyl) carbamate modified cellulose.
3. A bacterial biofilm for wastewater treatment, comprising:
a functional microorganism;
a porous support comprising the modified cellulose of claim 1, modified pseudoboehmite powder, aminoethylethanolamine; and
film forming agent including sodium alginate and polyethylene glycol.
4. The bacterial biofilm for sewage treatment as defined in claim 3, wherein the ratio of the N- (2-oxiranylmethyl) carbamate grafted cellulose to the modified pseudo-boehmite powder to the aminoethyl ethanolamine is 10:2 to 3:4 to 5.
5. The bacterial biofilm for sewage treatment as defined in claim 4, wherein the weight ratio of the modified pseudo-boehmite powder to the aminoethyl ethanolamine is 1: 1.5-2.
6. The bacterial biofilm for sewage treatment as defined in claim 3, wherein the modified pseudo-boehmite powder is a titanate coupling agent modified pseudo-boehmite, and specifically is a modified pseudo-boehmite powder obtained by mixing and stirring pseudo-boehmite powder and a titanate coupling agent solution with a mass fraction of 4-8% for 15-30 min, and then filtering and drying the mixture.
7. The method for producing a bacterial biofilm for sewage treatment according to any one of claims 3 to 6, comprising:
1) adding modified pseudo-boehmite powder and aminoethyl ethanolamine into a sufficient amount of 1-3% by mass of potassium hydroxide solution, stirring at a high speed for 0.5-1 h, adding N- (2-oxiranylmethyl) carbamate grafted cellulose, heating to 60-70 ℃, soaking for 1-2 h, introducing nitrogen, heating to 200-230 ℃, 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 the mass fraction of 40-60%;
2) culturing synchronous nitrifying and denitrifying bacteria, centrifugally collecting thallus, and preparing to obtain thallus with concentration higher than 4X 109cfu/mL of bacterial suspension, uniformly mixing the porous carrier solution and the bacterial suspension, concentrating the mixture in vacuum at the temperature of 35-40 ℃ until the solid content is more than or equal to 75%, and naturally drying the mixture to obtain an immobilized precursor substance;
3) mixing and dispersing sodium alginate and polyvinyl alcohol in 10-12 times by weight of deionized water to prepare a mixed solution, and obtaining an embedding agent;
4) uniformly mixing an embedding agent and an immobilized precursor substance, dripping the embedding agent into a calcium chloride solution by using an injector to crosslink for 16-24 hours when the surface of the immobilized precursor substance is in a semi-solidified state, forming spherical particles, and then washing by using deionized water to obtain the bacterial biofilm for sewage treatment.
8. Use of a bacterial biofilm for wastewater treatment according to any of claims 3 to 6 in domestic wastewater treatment, comprising placing a bacterial biofilm for wastewater treatment according to any of claims 3 to 6 in a biodegradation tank and/or operating in combination with an MBR.
9. The use according to claim 8, wherein the filling rate of the bacterial biofilm for sewage treatment is 10 to 30%.
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