A process for biofilm formation on an MBBR carrier

Abstract

The application belongs to the technical field of sewage treatment and specifically relates to a MBBR carrier biofilm formation process, which comprises the following steps: S1, using a low-temperature plasma reaction gas to treat a MBBR carrier to obtain a modified MBBR carrier; S2, inoculating aerobic nitrifying bacteria in a reactor loaded with sewage to make the aerobic nitrifying bacteria expand and culture, and obtaining a bacterial solution; S3, adding the modified MBBR carrier and N-acyl homoserine lactone into the bacterial solution to make the modified MBBR carrier surface preliminarily form a biofilm, and obtaining a first biofilm formation system; and S4, inoculating anaerobic denitrifying bacteria into the first biofilm formation system to make the modified MBBR carrier surface form a biofilm, and obtaining a second biofilm formation system. Through the process of low-temperature plasma modification, signal factor introduction, special biofilm formation sequence and the cooperation thereof, the multiple stages of microbial biofilm formation are considered, the connection strength between the biofilm and the surface of the MBBR carrier can be strengthened while the biofilm formation process is shortened, and the sewage ammonia nitrogen treatment effect is good.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a biofilm formation process for enabling microorganisms such as bacteria to form biofilms on the surface of MBBR carriers. BACKGROUND

[0002] Among numerous biological sewage treatment methods, the most recognized economical and effective method is the moving-bed biofilm reactor (MBBR) sewage treatment method. The sewage treatment principle is to fill the sewage treatment equipment with MBBR carriers having a high specific surface area to provide an attachment site for microorganisms, so that the microorganisms are enriched and reproduced on the surface of the MBBR carriers to form a biofilm with a high biomass, and finally rely on the self-metabolic degradation of various sewage treatment microorganisms in the biofilm to degrade pollutants and purify sewage.

[0003] The biofilm is the core part of the moving-bed biofilm reactor sewage treatment, and the speed of the formation process of the biofilm, i.e., the biofilm formation, will directly affect the starting process of the reactor. It is found through research that the biofilm formation of bacteria and other microorganisms on the surface of the MBBR carrier mainly includes the following stages: (1) reversible adhesion stage, i.e., the microorganisms adhere to the surface of the MBBR carrier by using extracellular organelles such as cilia, hyphae, and flagella; (2) irreversible adhesion stage, i.e., the microorganisms enhance the adhesion between the microorganisms and the MBBR carrier by secreting extracellular polymers (EPS); (3) formation stage of a water gel coating layer, i.e., a water gel coating layer is formed on the cell surface as the amount of the secreted EPS increases; and (4) mature biofilm formation stage, i.e., the cells, the MBBR carrier, and the cells are glued together by the EPS to form a three-dimensional skeleton.

[0004] In the field of microbial biofilm formation technology, considering that the biofilm formation process is relatively mature, the current research on MBBR carrier biofilm formation is replaced by carrier modification or ammonia nitrogen biological degradation bacteria agent research. Recently, a few biofilm researchers focus on the reversible adhesion stage of microbial biofilm formation, hoping to convert the negative charge on the surface of the carrier into a positive charge to strengthen the electrostatic interaction between the carrier and the microorganisms with negative charge, and ultimately achieve rapid biofilm formation of microorganisms on the surface of the carrier. For example, patent CN111100321B discloses a method for modifying the surface of a polyurethane carrier to promote biofilm formation, which comprises the following steps: (1) immersing the polyurethane carrier in a ferromanganese salt solution to obtain a polyurethane carrier with a positive charge on the surface; (2) treating the polyurethane carrier with a positive charge with plasma to produce active free radicals on the surface, and then contacting the active free radicals with a sodium alginate polyanion solution to initiate graft polymerization to form a covalent bond; (3) finally, immersing the grafted MBBR carrier in a chitosan polycation solution, and using the electrostatic interaction between sodium alginate and chitosan for layer-by-layer self-assembly to form a polyurethane carrier with good biocompatibility and high chemical stability.

[0005] This patent improves the biofilm formation efficiency of microorganisms in the reversible adhesion stage through immersion modification, and on this basis, it combines low-temperature plasma graft polymerization and layer-by-layer self-assembly to form a polyelectrolyte film driven by electrostatic force, increasing the stability of the carrier surface. Although this kind of polyurethane carrier can attract microorganisms through electrostatic attraction in the reversible adhesion stage, and achieve rapid biofilm formation, the electrostatic attraction is a weak interaction, and the gravitational force formed mainly by electrostatic interaction cannot firmly fix the microorganisms on the surface of the carrier, so the biofilm on the surface of the carrier is easy to fall off during actual use, and it is difficult to cope with the hydraulic shear in the wastewater treatment process. SUMMARY

[0006] The purpose of the present application is to provide a MBBR carrier biofilm formation process with fast biofilm formation speed and firm biofilm, which is realized by the following technical scheme:

[0007] A MBBR carrier biofilm formation process, comprising the following steps:

[0008] S1, treating the MBBR carrier with a low-temperature plasma reaction gas to obtain a modified MBBR carrier;

[0009] S2, inoculating aerobic nitrifying bacteria in a reactor loaded with wastewater and expanding the culture to obtain a bacterial solution;

[0010] S3, adding the modified MBBR carrier and N-acyl homoserine lactone to the bacterial solution to form a preliminary film on the surface of the modified MBBR carrier, and obtaining a first biofilm formation system;

[0011] S4, inoculating anaerobic denitrifying bacteria into the first biofilm system, so that the modified MBBR carrier surface forms a biofilm, and a second biofilm system is obtained.

[0012] In the process of treating wastewater by using the moving bed biofilm reactor, the MBBR carrier loaded with the biofilm needs to be fully fluidized in the wastewater by means of aeration and flow pushing system, so as to promote the full contact of the biofilm with the wastewater. This means that the aeration and flow pushing will exert a certain pushing force on the surface of the MBBR carrier. Research shows that improper pushing force is one of the main reasons for the biofilm to fall off. In addition, when the moving bed biofilm reactor treats high-pollution-load water, a large amount of toxic and harmful substances can have a toxic effect on microorganisms, inhibit their attachment and growth, and ultimately cause the biofilm on the surface of the MBBR carrier to be unable to be normally maintained, thereby being easily fallen off.

[0013] In order to firmly attach the biofilm on the surface of the MBBR carrier and cope with the above-mentioned hydraulic shear and high-pollution-load water impact, the present application first introduces a large number of functional groups by bonding ionized gas and MBBR carrier surface molecules through low-temperature plasma surface treatment method. Secondly, the content of EPS secreted by microorganisms is significantly increased by adding N-acyl homoserine lactone signal factor to the bacterial solution in the preliminary biofilm formation stage. Since EPS itself contains functional groups such as hydroxyl, carboxyl, and amino phosphoric groups, cross-linking reaction will occur between the MBBR carrier and EPS to form covalent bonds, and a mutually interwoven network structure is formed, so that the microorganisms are firmly fixed on the surface of the MBBR carrier. On this basis, a large amount of EPS can improve the resistance of the biofilm to environmental pressure to cope with the impact of high-pollution-load water. Specifically, EPS can block toxic substances from invading microorganisms, and on the other hand, can be used as a carbon source or energy source by microorganisms under the condition of nutrient shortage in wastewater.

[0014] In the biofilm formation process of the present application, aerobic nitrifying bacteria are first allowed to preliminarily form a biofilm on the surface of the MBBR carrier, so as to fully exert the advantage of rapid reproduction of aerobic bacteria, and the surface of the MBBR carrier is preliminarily formed with a biofilm. At this time, anaerobic denitrifying bacteria are inoculated into the first biofilm system, the anaerobic bacteria will move to the inside of the MBBR carrier with low oxygen content, and rapidly form a biofilm by using the N-acyl homoserine lactone in the first biofilm system, which solves the technical problem of difficult anaerobic bacteria biofilm formation.

[0015] In summary, the present application takes into account multiple stages of microbial biofilm formation by means of low-temperature plasma modification, signal factor introduction, and special biofilm formation sequence, so as to shorten the biofilm formation process and strengthen the connection strength between the biofilm and the surface of the MBBR carrier.

[0016] As a preferred embodiment, the reaction gas in S1 is oxygen.

[0017] The low-temperature plasma treatment of the surface of the MBBR carrier with oxygen can introduce a large number of oxygen-containing functional groups on the surface of the MBBR carrier, and on the other hand, the electrons and ions generated by the plasma discharge can etch the surface of the MBBR carrier, which can increase the specific surface area of the carrier and further provide a place for the attachment of microorganisms, thereby improving the sewage treatment effect.

[0018] Preferably, the preparation method of the MBBR carrier in S1 is as follows:

[0019] In S1, the preparation method of the MBBR carrier is as follows:

[0020] In S1, the preparation method of the MBBR carrier is as follows:

[0021] In S1, the preparation method of the MBBR carrier is as follows:

[0022] The applicant found that when the mechanical strength of the MBBR carrier is low, the breakage of the carrier will also cause the partial shedding of the biofilm. Therefore, in the present technical solution, the introduction of polylactic acid into the polyurethane prepolymer for blending modification increases the order and tightness of the soft and hard segments of the polyurethane, thereby effectively improving the mechanical strength of the polyurethane skeleton. On this basis, the immersion process is used to give the MBBR carrier a relatively stable coating layer to cope with the degradation and erosion of the MBBR carrier by microorganisms.

[0023] Further preferably, the MBBR carrier contains inorganic adsorption powder, which includes one or more of zeolite powder, activated carbon or tourmaline.

[0024] The cross-linking structure formed between the soft and hard segments in the polyurethane skeleton not only increases the mechanical strength of the polyurethane skeleton, but also makes the surface of the polyurethane skeleton more and more rough with the increase of the cross-linking density. Therefore, the introduction of inorganic adsorption powder into the MBBR carrier for inorganic modification at this time provides excellent bonding sites for the adhesion of inorganic adsorption powder, and the inorganic adsorption powder is not easy to dissolve out in the subsequent sewage treatment process. On the other hand, the rough surface of the polyurethane skeleton means that more inorganic adsorption powder can be loaded, which can strengthen the performance of the inorganic adsorption powder itself. Specifically, tourmaline can act as a microbial growth factor to promote the rapid reproduction of nitrifying bacteria to form a biofilm, and in addition, tourmaline and activated carbon powder can effectively absorb and degrade toxic substances in sewage, thereby improving the system stability of the moving bed biofilm reactor; zeolite powder can quickly enrich ammonia nitrogen in slightly polluted water bodies to form a high-ammonia-nitrogen enrichment zone, thereby improving the efficiency of sewage treatment.

[0025] As preferred, the N-acyl homoserine lactone in S3 comprises one or several of C6-HSL, 3-oxo-C6-HSL, C10-HSL and 3-oxo-C12-HSL.

[0026] As further preferred, the concentration of the N-acyl homoserine lactone in the first biofilm formation system in S3 is 1-2 μmol / L.

[0027] As preferred, the dosing volume ratio of the modified MBBR carrier in S3 in the reactor is 8-15%.

[0028] As preferred, S4 further comprises: inoculating the first biofilm formation system with photosynthetic bacteria.

[0029] Both the photosynthetic bacteria and the anaerobic denitrifying bacteria are anaerobes, thus when inoculating the photosynthetic bacteria and the anaerobic denitrifying bacteria in the first biofilm formation system, both of them will move to the inside of the MBBR carrier with low oxygen content, thus the photosynthetic bacteria can provide organic matter as carbon source and energy source for the growth and reproduction of the anaerobic denitrifying bacteria while the anaerobic denitrifying bacteria are forming biofilm.

[0030] As preferred, the dissolved oxygen concentration in the second biofilm formation system in S4 is 0.5-1.0 mg / L.

[0031] As preferred, the biofilm formation process of the MBBR carrier further comprises: S5, dynamic acclimation culture: discharging the sewage while introducing the sewage into the second biofilm formation system, and dynamically acclimating and culturing the biofilm, and the hydraulic retention time in the dynamic acclimation culture is 6-12 h.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The present application first introduces a large number of functional groups by bonding the ionized gas with the surface molecules of the MBBR carrier through low-temperature plasma surface treatment method; secondly, the content of the EPS secreted by the microorganism is significantly improved by adding the N-acyl homoserine lactone signal factor to the bacterial solution in the initial biofilm formation stage, and since the EPS itself contains functional groups such as hydroxyl, carboxyl, amino phosphoric groups, etc., the cross-linking reaction will occur between the MBBR carrier and the EPS to form covalent bonds, and a mutual interlaced network structure is formed, so that the microorganism is firmly fixed on the surface of the MBBR carrier.

[0034] (2) The present application is in the process of biofilm formation, by first aerobic nitrifying bacteria in the MBBR carrier surface preliminary film formation, give full play to the advantages of aerobic bacteria rapid reproduction, so that the MBBR carrier surface preliminary film formation; At this time, the first biofilm system inoculated with denitrifying bacteria, anaerobic bacteria will move to the low oxygen content of MBBR carrier inside, and use the N-acyl homoserine lactone in the first biofilm system for rapid biofilm formation, which solves the technical problem of anaerobic bacteria biofilm formation.

[0035] (3) The present application by introducing polylactic acid as a blending modifier and cooperate with the impregnation process, the prepared MBBR carrier has excellent mechanical properties, in the actual use process can good response to hydraulic shear, airflow impact and the friction between the carrier collision, solve the technical problem of MBBR carrier damage caused by the partial shedding of biofilm; Further by polylactic acid modified polyurethane skeleton as organic framework, using organic-inorganic hybrid technology, greatly improve the specific surface area of MBBR carrier, strengthen the function of inorganic adsorption powder, thus provides a good environment for the growth of nitrifying bacteria biofilm. DETAILED DESCRIPTION

[0036] The present application will be further described below in conjunction with specific examples. Those skilled in the art will be able to implement the present application based on these descriptions. In addition, the examples of the present application involved in the following description are generally only a part of the embodiments of the present application, not all the embodiments. Therefore, based on the examples in the present application, all other embodiments obtained by those skilled in the art without making creative efforts shall belong to the scope of protection of the present application.

[0037] The ammonia nitrogen concentration in the following examples and comparative examples is determined by distillation and titration method in GB7478-87.

[0038] Example 1

[0039] The biofilm formation process of the MBBR carrier of the present embodiment comprises the following steps:

[0040] S1, using low temperature plasma reaction gas treatment MBBR carrier, get modified MBBR carrier; The reaction gas is oxygen, and the treatment conditions are: the gas pressure of the plasma reaction gas is 50 Pa, the treatment time is 10 min, and the power of the treatment device is 50 W. By low temperature plasma reaction gas treatment MBBR carrier, the electrons and ions generated by plasma discharge will etch the surface of MBBR carrier, so as to increase the specific surface area of the carrier, further provide a place for the attachment of microorganisms, and improve the sewage treatment effect. On the other hand, a large number of oxygen-containing functional groups can be introduced on the surface of MBBR carrier.

[0041] S2, inoculate aerobic nitrifying bacteria in the reactor loaded with sewage, and expand the culture to obtain a bacterial solution; the expansion culture conditions are: pH value is 7.5, temperature is 28℃, and dissolved oxygen concentration is 2mg / L. The ammonia nitrogen concentration of the influent sewage is 12.94mg / L.

[0042] S3, add modified MBBR carrier and N-acyl homoserine lactone to the bacterial solution to make the surface of the modified MBBR carrier preliminarily form a film to obtain a first biofilm formation system; wherein the volume ratio of the modified MBBR carrier in the reactor is 8%, and the N-acyl homoserine lactone is 3-oxo-C6-HSL, and the concentration thereof in the first biofilm formation system is 2μmol / L. The biofilm formation culture conditions at this preliminary film formation are: pH value is 7.5, temperature is 28℃, and dissolved oxygen concentration is 2mg / L.

[0043] S4, inoculate anaerobic denitrifying bacteria in the first biofilm formation system, and perform biofilm formation culture to make the surface of the modified MBBR carrier form a biofilm to obtain a second biofilm formation system; the biofilm formation culture conditions in this step are: pH value is 8, temperature is 30℃, and dissolved oxygen concentration is 0.5mg / L. The inoculation concentration of the aerobic nitrifying bacteria and the anaerobic denitrifying bacteria in this embodiment is both 12×10 5 CFU / mL.

[0044] S5, dynamic acclimation culture: introduce sewage into the second biofilm formation system while discharging sewage to perform dynamic acclimation culture on the biofilm, the hydraulic retention time in the dynamic acclimation culture is 10h, and the ammonia nitrogen content of the effluent is detected; when the effluent ammonia nitrogen content is basically flat (the biofilm formation time in this embodiment is about 68h), it is considered that the biofilm formation is completed.

[0045] In addition, the preparation method of the MBBR carrier in S1 of this embodiment is:

[0046] S1, pre-polymerization: heat the mixture of 100 parts of polyether polyol HSH-204 (hydroxyl value 265-300mgKOH / g, molecular weight 2000), 50 parts of toluene diisocyanate, and 10 parts of polylactic acid PLA-N3 (molecular weight 5000, added in the form of polylactic acid acetone solution) to 90℃, and stir for 2.5h to obtain a polyurethane prepolymer.

[0047] S2, foaming: add 5 parts of methyl acetate, 0.3 parts of triethylenediamine n-propanol solution, 0.5 parts of organic bismuth, 3 parts of silicone oil, and 1 part of ethylene glycol to the polyurethane prepolymer to obtain a polyurethane skeleton.

[0048] S3, impregnation: impregnate the polyurethane skeleton in polyether polyol HSH-204 at 35℃ for 3h, the polyether polyol HSH-204 further contains inorganic adsorption powder with a concentration of 3g / L, and the inorganic powder includes zeolite powder, activated carbon powder, and tourmaline powder.

[0049] S4, curing: taking out the polyurethane skeleton, and curing to obtain the MBBR carrier.

[0050] Example 2

[0051] The biofilm formation process of the MBBR carrier of the present example comprises the following steps:

[0052] S1, treating the MBBR carrier with low-temperature plasma reaction gas to obtain a modified MBBR carrier; the reaction gas is oxygen, and the treatment conditions are as follows: the gas pressure of the plasma reaction gas is 70 Pa, the treatment time is 15 min, and the power of the treatment device is 100 W.

[0053] S2, inoculating aerobic nitrifying bacteria in the reactor loaded with sewage, and expanding the culture to obtain a bacterial solution; the expansion culture conditions are as follows: the pH value is 8.5, the temperature is 38℃, and the dissolved oxygen concentration is 1 mg / L. The influent ammonia nitrogen concentration of the sewage is 30.94 mg / L.

[0054] S3, adding the modified MBBR carrier and N-acyl homoserine lactone to the bacterial solution to preliminarily form a biofilm on the surface of the modified MBBR carrier, and obtaining a first biofilm formation system; wherein the volume ratio of the modified MBBR carrier to the reactor is 15%, and the N-acyl homoserine lactone is C10-HSL, and the concentration thereof in the first biofilm formation system is 1 μmol / L. The biofilm formation culture conditions at this preliminary biofilm formation are as follows: the pH value is 8, the temperature is 30℃, and the dissolved oxygen concentration is 2 mg / L.

[0055] S4, inoculating anaerobic denitrifying bacteria and photosynthetic bacteria in the first biofilm formation system, and performing biofilm formation culture to form a biofilm on the surface of the modified MBBR carrier, and obtaining a second biofilm formation system; the biofilm formation culture conditions in this step are as follows: the pH value is 8, the temperature is 30℃, and the dissolved oxygen concentration is 1 mg / L. In the present example, the inoculation concentration of the aerobic nitrifying bacteria is 12×10 5 CFU / mL, and the inoculation concentration of the anaerobic denitrifying bacteria and the photosynthetic bacteria is 11×10 5 CFU / mL.

[0056] S5, dynamic acclimation culture: introducing sewage into the second biofilm formation system while discharging sewage to dynamically acclimate and culture the biofilm. In the dynamic acclimation culture, the hydraulic retention time is 6 h, the ammonia nitrogen content of the effluent is detected, and when the ammonia nitrogen content of the effluent is basically flat (in the present example, the biofilm formation time is about 71 h), it is considered that the biofilm formation is completed.

[0057] In addition, the preparation method of the MBBR carrier in S1 of the present example is the same as that in Example 1.

[0058] Example 3

[0059] The MBBR carrier of the embodiment adopts a common MBBR carrier on the market, and the specific biofilm formation process comprises the following steps.

[0060] S1, treating the MBBR carrier with a low-temperature plasma reaction gas to obtain a modified MBBR carrier; the reaction gas is oxygen, and the treatment conditions are as follows: the gas pressure of the plasma reaction gas is 50 Pa, the treatment time is 10 min, and the power of the treatment device is 50 W.

[0061] S2, inoculating aerobic nitrifying bacteria in the reactor loaded with sewage to make it expand, and obtaining a bacterial solution; the expansion conditions are as follows: the pH value is 7.5, the temperature is 28℃, and the dissolved oxygen concentration is 2 mg / L. The influent ammonia nitrogen concentration of the sewage is 12.94 mg / L.

[0062] S3, adding the modified MBBR carrier and N-acyl homoserine lactone to the bacterial solution to make the surface of the modified MBBR carrier preliminarily form a biofilm, and obtaining a first biofilm formation system; wherein the volume ratio of the modified MBBR carrier in the reactor is 8%, and the N-acyl homoserine lactone is 3-oxo-C6-HSL, and the concentration thereof in the first biofilm formation system is 2 μmol / L. The biofilm formation culture conditions at this preliminary biofilm formation are as follows: the pH value is 7.5, the temperature is 28℃, and the dissolved oxygen concentration is 2 mg / L.

[0063] S4, inoculating anaerobic denitrifying bacteria in the first biofilm formation system to carry out biofilm formation culture, so that the surface of the modified MBBR carrier forms a biofilm, and obtaining a second biofilm formation system; the biofilm formation culture conditions in this step are as follows: the pH value is 8, the temperature is 30℃, and the dissolved oxygen concentration is 0.5 mg / L. The inoculation concentration of the aerobic nitrifying bacteria and the anaerobic denitrifying bacteria in the embodiment is both 12×10 5 CFU / mL.

[0064] S5, dynamic acclimation culture: introducing sewage into the second biofilm formation system while discharging sewage to dynamically acclimate and culture the biofilm. In the dynamic acclimation culture, the hydraulic retention time is 10 h, the ammonia nitrogen content of the effluent is detected, and when the effluent ammonia nitrogen content is basically flat (the biofilm formation time of the microorganism in the embodiment is about 75 h), it is considered that the biofilm formation is completed.

[0065] Comparative Example 1

[0066] The comparative example and the embodiment 1 only have the following differences, and the same parts are not described here.

[0067] In the comparative example, the MBBR carrier is not treated with a low-temperature plasma reaction gas.

[0068] Comparative Example 2

[0069] The comparative example and the embodiment 1 only have the following differences, and the same parts are not described here.

[0070] No N-acyl homoserine lactone was added in the comparative example S3.

[0071] Comparative example 3

[0072] The comparative example is only different from example 1 in the following aspects, and the same parts are not described here.

[0073] The comparative example does not contain S4, and the reactor of sewage is inoculated with aerobic nitrifying bacteria and anaerobic denitrifying bacteria at the same time in S2.

[0074] Comparative example 4

[0075] The comparative example is only different from example 1 in the following aspects, and the same parts are not described here.

[0076] The MBBR carrier is not treated by low-temperature plasma reaction gas, and no N-acyl homoserine lactone is added in S3.

[0077] Performance test 1

[0078] During the dynamic acclimation culture, the sewage is treated at a push flow rate of 0.25 m / s, and the ammonia nitrogen concentration in the effluent when the biofilm is formed in examples 1-3 and comparative examples 1-4 is determined, the ammonia nitrogen removal rate is calculated, and the table is as follows:

[0079] Table 1, sewage treatment effect when the push flow rate is 0.25 m / s

[0080] Group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Ammonia nitrogen removal rate 98.6％ 98.1％ 90.3％ 98.2％ 97.1％ 85.6％ 80.7％

[0081] As can be seen from Table 1, the mobile bed bio-membrane reactor adopting the biofilm formation method of the application has an ammonia-nitrogen treatment effect of more than 90% at a plug flow velocity of 0.25 m / s, especially in the case of using the polylactic acid modified MBBR carrier for biofilm formation, the ammonia-nitrogen removal rate is as high as more than 98%. It can be seen that the biofilm formation method of the application can cooperate with the polylactic acid modified MBBR carrier to effectively improve the biomass on the surface of the carrier, so that the sewage treatment effect is better and the ammonia-nitrogen removal rate is higher. In addition, although the polylactic acid modified MBBR carrier is used in Comparative Examples 1-4, there is a certain difference between the biofilm formation method and the biofilm formation method of Example 1, so the sewage treatment effect and Examples 1-2 also differ. Specifically, the MBBR carrier is not subjected to low-temperature plasma modification in Comparative Example 1, and the ammonia-nitrogen removal rate is only reduced by 0.4% compared with Example 1, which shows that at a plug flow velocity of 0.25 m / s, low-temperature plasma modification has little effect on the ammonia-nitrogen removal rate, that is, the difference in biofilm microbial amount is small. The ammonia-nitrogen removal rate in Comparative Example 2 is only reduced by 1.5% compared with Example 1, which shows that the introduction of the signal factor can increase the secretion of EPS, so that more microorganisms are fixed on the surface of the modified MBBR carrier, but overall, at a plug flow velocity of 0.25 m / s, the introduction of the signal factor in the biofilm formation system does not have a great effect on the ammonia-nitrogen removal rate. The ammonia-nitrogen removal rate in Comparative Example 3 is greatly reduced by 13% compared with Example 1, which shows that on the one hand, the culture conditions of aerobic bacteria and anaerobic bacteria are different, and it is difficult to promote the high-speed reproduction and growth of both under the same culture conditions; on the other hand, it also proves that by culturing aerobic bacteria first to generate a gel layer and then adding anaerobic bacteria for culture, the anaerobic bacteria will move to the low-oxygen content area inside the carrier along the low-oxygen concentration position and reproduce and grow faster by using the signal factor for biofilm formation. Although the polylactic acid modified MBBR carrier is used in Comparative Example 4 and the order of aerobic bacteria and anaerobic bacteria is adjusted for biofilm formation culture, the ammonia-nitrogen removal rate is reduced by 17.9% compared with Example 1, which shows that the biofilm formation method of the application, especially the cooperation between plasma modification and the addition of the signal factor, can effectively improve the biomass on the surface of the carrier, so that the ammonia-nitrogen treatment effect in the sewage is better.

[0082] Performance Test 2

[0083] In order to verify the fixing strength of the biofilm on the surface of the carrier obtained by the biofilm formation method of the application, the plug flow velocity is increased to 1 m / s on the basis of Performance Test 1, and the ammonia-nitrogen concentration in the effluent is measured when the biofilm formation of Examples 1-3 and Comparative Examples 1-4 is completed, the ammonia-nitrogen removal rate is calculated, and the table is as follows:

[0084] Table 2, sewage treatment effect at a plug flow velocity of 1 m / s

[0085] Group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Ammonia nitrogen removal rate 98.3％ 98.0％ 84.3％ 90.1％ 91.5％ 85.2％ 68.2％

[0086] From the above table, it can be found that with the increase of the push flow speed, the ammonia nitrogen removal rates in Examples 1-3 and Comparative Examples 1-4 all show a certain degree of decrease, which indicates that the biofilm is impacted and falls off to different degrees in the wastewater treatment process. Among them, the ammonia nitrogen removal rate of Example 1-2 decreases the least, which indicates that the biofilm has the best fixing effect on the surface of the carrier. The ammonia nitrogen removal rate of Example 3 decreases by 6%, which indicates that the MBBR carrier modified by polylactic acid can be well matched with the biofilm formation method of the application to firmly fix the biofilm on the surface of the MBBR carrier to cope with the push flow impact. The ammonia nitrogen removal rate of Comparative Example 1 decreases by 8.1%, and the ammonia nitrogen removal rate of Comparative Example 2 decreases by 5.6%, which shows that neither the plasma modification alone nor the introduction of the signal factor alone in the biofilm formation system can avoid the falling off of the biofilm under high push flow speed, but on the contrary, only the good match between the two can effectively avoid the falling off of the biofilm in the wastewater treatment process to cope with the wastewater with high flow speed impact or strong push flow. The ammonia nitrogen removal rate of Comparative Example 3 decreases by 0.4%, which shows that the simultaneous biofilm formation of aerobic bacteria and anaerobic bacteria has a greater impact on the ammonia nitrogen removal rate, but when the push flow speed is increased, the signal factor is introduced into the system and the carrier has been modified, so it has little impact on the ammonia nitrogen removal rate. Compared with Comparative Examples 1-3, the ammonia nitrogen removal rate of Comparative Example 4 decreases greatly under the condition of increasing the push flow speed, which decreases by 12.5%, which shows that the biofilm falls off a lot under the action of the push flow in the biofilm reactor, which seriously affects the removal effect of the microorganisms on the ammonia nitrogen in the wastewater.

[0087] Performance Test 3

[0088] In order to further verify the fixing strength of the biofilm on the surface of the carrier obtained by the biofilm formation method of the application, the ammonia nitrogen concentration in the effluent of Examples 1 and 3 and Comparative Examples 1-4 when the biofilm formation is completed is measured, the ammonia nitrogen removal rate is calculated, and the table is as follows:

[0089] Table 3, Wastewater Treatment Effect of High Ammonia Nitrogen

[0090] Group Example 1 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Ammonia nitrogen removal rate 97.9％ 88.3％ 96.0％ 80.3％ 82.0％ 60.5％

[0091] As can be seen from the above table, when the ammonia nitrogen concentration of the influent is increased, the ammonia nitrogen removal rates of Examples 1, 3 and Comparative Examples 1-4 all show a certain degree of downward trend. Specifically, the ammonia nitrogen removal rates of Examples 1, 3 are decreased by 0.7% and 2% respectively, and it can be seen that the biofilm obtained by using the biofilm formation method of the present application is still relatively firm in the process of treating high ammonia nitrogen wastewater, and there is little shedding. The ammonia nitrogen removal rate of Comparative Example 1 is decreased by 2.2%, which also reflects good wastewater treatment effect, and it can be seen that the introduction of signal factor can improve the ability of microorganisms to resist high pollution water, so the biofilm shedding is less. Compared with Comparative Example 1, Comparative Example 2 does not add signal factor, and when treating high ammonia nitrogen wastewater, the ammonia nitrogen removal rate is decreased by 16.8%, and it can be seen that the biofilm exists a serious shedding, which eventually leads to a large decrease in the ammonia nitrogen removal rate. The ammonia nitrogen removal rate of Comparative Example 3 is only decreased by 3.6%, and it can be seen that the sequence of aerobic bacteria and anaerobic bacteria biofilm formation has little effect on the treatment effect of high ammonia nitrogen wastewater. In Comparative Example 4, because the biofilm formation method of the present application is not used, the ammonia nitrogen removal rate is decreased by 20.2%, and it can be seen that in the biofilm reaction system, the biofilm on the surface of the MBBR carrier is largely shed, and the biofilm formation effect is poor.

[0092] In summary, by using the process of low temperature plasma modification, introduction of signal factor, special biofilm formation sequence and the like, and the combination thereof, the present application takes into account multiple stages of microbial biofilm formation, and can shorten the biofilm formation process while strengthening the connection strength between the biofilm and the surface of the MBBR carrier. Therefore, by using the biofilm formation method of the present application, the biofilm in the moving bed biofilm reactor can resist the shedding phenomenon caused by high pollution wastewater and high plug flow velocity during the wastewater treatment process, and the wastewater treatment effect is excellent.

Claims

1. A process for biofilm formation on MBBR carriers, characterized in that, The method comprises the following steps: S1, treating the MBBR carrier with low-temperature plasma reaction gas to obtain a modified MBBR carrier; the reaction gas is oxygen; S2, inoculating aerobic nitrifying bacteria in a reactor loaded with sewage to make the bacteria expand, and obtaining a bacterial solution; S3, adding the modified MBBR carrier and N-acyl homoserine lactone to the bacterial solution to make the modified MBBR carrier surface preliminarily form a film, and obtaining a first biofilm formation system; S4, inoculating anaerobic denitrifying bacteria into the first biofilm formation system to make the modified MBBR carrier surface form a biofilm, and obtaining a second biofilm formation system; S5, dynamic acclimation culture: discharging sewage while introducing sewage into the second biofilm formation system to dynamically acclimate and culture the biofilm, and the hydraulic retention time in the dynamic acclimation culture is 6-12h.

2. The MBBR carrier biofilm process according to claim 1, wherein, The preparation method of the MBBR carrier in S1 is as follows: S1, pre-polymerizing a mixture of polyol, isocyanate and polylactic acid to obtain a polyurethane prepolymer, and the isocyanate index in the mixture is greater than 1; S2, adding a foaming agent, a catalyst, a foam stabilizer and a chain extender to the polyurethane prepolymer to make it foam to obtain a polyurethane skeleton; S3, dipping the polyurethane skeleton in polyol to make it polymerize, taking out the polyurethane skeleton, and solidifying to obtain the MBBR carrier.

3. The MBBR carrier biofilm process according to claim 2, wherein, The polyol further comprises inorganic adsorption powder, and the inorganic adsorption powder comprises one or more of zeolite powder, activated carbon powder or tourmaline powder.

4. The MBBR carrier biofilm process of claim 1, wherein, The N-acyl homoserine lactone in S3 comprises one or more of C6-HSL, 3-oxo-C6-HSL, C10-HSL and 3-oxo-C12-HSL.

5. The MBBR carrier biofilm process according to claim 1 or 4, wherein, The concentration of the N-acyl homoserine lactone in the first biofilm formation system in S3 is 1-2μmol / L.

6. The MBBR carrier biofilm process of claim 1, wherein, The dosing volume ratio of the modified MBBR carrier in the reactor in S3 is 8-15%.

7. The MBBR carrier biofilm process of claim 1, wherein, S4 further comprises: inoculating photosynthetic bacteria into the first biofilm formation system.

8. The MBBR carrier biofilm process of claim 1, wherein, The dissolved oxygen concentration in the second biofilm formation system in S4 is 0.5-1.0mg / L.