A moving bed biofilm reactor and a wastewater treatment method

Abstract

The present application belongs to the technical field of sewage treatment, and particularly relates to a moving bed biofilm reactor and a sewage treatment method. Compared with the technical scheme of improving the effect of microbial sewage treatment by increasing the equipment structure of the moving bed biofilm reactor in the past, the present application takes the MBBR carrier, which is the specific place where the microorganisms are actually enriched and sewage treatment is carried out, as the research and development focus, provides an MBBR carrier with super-high specific surface area and high mechanical performance by modifying the MBBR carrier. On this basis, the present application also performs high adaptability design on the moving bed biofilm reactor equipment, and matches with a targeted sewage treatment method, so that the sewage, especially the agricultural source light pollution water body, can be efficiently treated. The present application provides a new type of sewage treatment equipment and method with high cost performance for the treatment of agricultural source pollution water body, and to some extent, solves the problems of high dispersion of agricultural source pollution, difficulty in centralized treatment and high cost of sewage treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a moving bed biofilm reactor for treating sewage by using microorganisms. BACKGROUND

[0002] Water resource is the most scarce basic natural resource, strategic economic resource and public social resource in the 21st century. At present, with the acceleration of industrial development and urbanization, water resource crisis and water environment pollution increasingly become the hot spot in the field of environmental protection at home and abroad. With the implementation and deepening of the ecological civilization construction in China, the state has put forward more and more strict requirements for sewage discharge standards, and therefore, how to more economically and efficiently treat sewage has become a problem to be solved in the field of environmental protection.

[0003] At present, in the technical field of sewage treatment, the sewage treatment methods mainly include physical method, chemical method, physical-chemical method and biological method. The biological method is a sewage treatment technology that appeared in the late 19th century, and has become the main means for treating sewage in the world and occupies an important position in the field of sewage treatment. Specifically, the biological method of sewage treatment is a sewage treatment method that uses various organic pollutants existing in sewage as nutrients, cultivates mixed microorganisms, and uses microorganisms to remove organic pollutants. It can be further divided into activated sludge method, biological fluidized bed, biological aerated filter, anaerobic biological treatment method, biological contact oxidation method, moving bed biofilm reactor (MBBR) and the like.

[0004] Among the numerous biological sewage treatment methods, the most recognized economical and effective method is the moving bed biofilm reactor. The reactor was developed by the cooperation of KMT Company of Norway and Norwegian Science and Technology Industry Research Institute in the late 1980s, which absorbs the advantages of traditional biological fluidized bed and biological contact oxidation method. Without increasing the equipment area, by adding a certain amount of MBBR carrier to the sewage treatment equipment, the moving bed biofilm reactor provides an excellent attachment place for sewage degradation microorganisms, ensures that the biomass in the aeration tank is at a high level, and greatly improves the sewage treatment efficiency. The principle of sewage treatment is that the fluidized MBBR carrier fully contacts with the nutrients and microorganisms in the sewage. After a period of operation, the surface of the MBBR carrier is gradually covered with microorganisms to form mature biofilm. Finally, the pollutants are degraded and the sewage is purified by relying on the metabolism of various sewage treatment microorganisms in the biofilm.

[0005] Specifically, the microorganism in the moving bed biofilm reactor for wastewater treatment mainly includes the following two steps: (1) nitrification step of nitrifying bacteria, which is completed in two steps. First, ammonia nitrogen in wastewater is oxidized to nitrite by nitrite bacteria under aerobic conditions, and then nitrite is oxidized to nitrate by nitrate bacteria under aerobic conditions. (2) Denitrification step of denitrifying bacteria, i.e. the process of reducing nitrate or nitrite to nitrogen by denitrifying bacteria using organic matter as electron donor under anaerobic conditions. It can be seen that various bacteria need to cooperate with each other in the process of wastewater degradation by microorganisms, and because the wastewater treatment conditions required by different bacteria are different, in order to fully stimulate the wastewater treatment potential of each wastewater treatment bacteria and improve the wastewater treatment effect, most of the existing moving bed biofilm reactors are provided with multiple wastewater treatment reaction tanks.

[0006] For example, patent CN 104445830 B discloses a moving bed biofilm reactor, which includes pre-denitrification tank, anaerobic tank, anoxic tank, aerobic tank, sedimentation tank and clean water tank which are sequentially connected, and nitration liquid reflux mechanism arranged between the aerobic tank and the anoxic tank, anoxic liquid reflux mechanism arranged between the anoxic tank and the anaerobic tank, anaerobic liquid reflux mechanism arranged between the anaerobic tank and the pre-denitrification tank, and sludge reflux mechanism arranged between the sedimentation tank and the anaerobic tank. The above-mentioned reflux mechanism, taking the nitration liquid reflux mechanism as an example (other reflux mechanisms can be similarly applied), includes a riser connected between the aerobic tank and the anoxic tank, and a fan for blowing the nitration liquid in the aerobic tank into the anaerobic tank along the riser. By arranging the reaction tanks in a special order and providing the reflux mechanism between the reaction tanks, the patent can avoid the technical problem that after the direct aerobic nitrification step of all wastewater, the oxygen content in the wastewater is too high to meet the oxygen content requirement of the wastewater treatment by anaerobic denitrifying bacteria, thereby causing difficulty in the denitrification step. In addition, the patent can effectively improve the removal rate of ammonia nitrogen in wastewater by providing the reflux mechanism for sufficient circulation treatment of wastewater.

[0007] However, the technical solution of arranging the reaction tanks in a special order and providing the reflux mechanism between the reaction tanks will greatly increase the wastewater treatment cost of the moving bed biofilm reactor. On the one hand, the arrangement of multiple reaction tanks and reflux mechanisms will directly increase the preparation cost of the wastewater treatment equipment; on the other hand, in order to achieve a high removal rate of ammonia nitrogen and other pollutants during wastewater treatment, the fan of the reflux mechanism needs to be continuously turned on to realize the sufficient reflux of wastewater, which will generate a large amount of wastewater treatment cost. In addition, during the wastewater treatment process using the moving bed biofilm reactor disclosed in the patent, the wastewater needs to flow through the pre-denitrification tank, the anaerobic tank, the anoxic tank, the aerobic tank, the sedimentation tank and the clean water tank in sequence, and will also be continuously refluxed back to the previous reaction tank under the driving of the reflux mechanism. Under high reflux ratio, the wastewater treatment efficiency is extremely low, which will further increase the wastewater treatment cost. SUMMARY

[0008] The purpose of the present application is to provide a mobile bed biofilm reactor and a sewage treatment method with high sewage treatment efficiency and low sewage treatment cost, and the purpose is achieved by the following technical solutions:

[0009] The mobile bed biofilm reactor comprises a reaction tank and a sedimentation tank which are sequentially connected in the direction of sewage flow, and the reaction tank is internally loaded with MBBR carriers, the MBBR carrier comprises a polyurethane skeleton modified by polylactic acid, and a coating layer is fixedly arranged on the polyurethane skeleton, and the coating layer also contains inorganic adsorption powder; the mobile bed biofilm reactor further comprises an oxygen dissolution control device for adjusting the dissolved oxygen content of sewage in the reaction tank.

[0010] Compared with the technical solutions of increasing the equipment structure of the mobile bed biofilm reactor to improve the effect of microbial sewage treatment in the past, the present application takes a different approach, taking the MBBR carrier as the research and development focus, which is the specific place where microorganisms are actually enriched and sewage treatment is carried out, and through high adaptability design of the mobile bed biofilm reactor equipment, a mobile bed biofilm reactor with high sewage treatment efficiency and low sewage treatment cost is provided. Specifically:

[0011] Firstly, the present application innovatively introduces polylactic acid as one of the raw materials in the preparation process of the MBBR carrier, which strengthens the crosslinking action between the soft segment and the hard segment in the polyurethane skeleton of the MBBR carrier, greatly improves the mechanical properties of the polyurethane skeleton, and therefore the MBBR carrier of the present application can better cope with the shear of water force, the impact of air flow and the friction and collision between MBBR carriers during sewage treatment. Compared with ordinary carriers on the market, its service life is longer, and it does not need to be frequently supplemented to maintain the sewage treatment effect, which reduces the long-term operation cost of the mobile bed biofilm reactor.

[0012] Secondly, the applicant found that the crosslinking structure formed between the soft segment and the hard segment in the polyurethane skeleton not only increases the mechanical strength of the polyurethane skeleton, but also the surface of the polyurethane skeleton becomes more and more rough with the increase of crosslinking density. Therefore, by introducing inorganic adsorption powder for inorganic modification on the surface of the polyurethane skeleton, the specific surface area of the MBBR carrier will be further improved. It is determined that the specific surface area of the MBBR carrier of the present application is more than 20000 m 2 / m 3 , which is 13 times the specific surface area of ordinary carriers on the market. This means that the same volume of MBBR carrier can enrich more sewage treatment microorganisms, so under the same effective volume of sewage treatment in the reaction tank, the carrier dosage of the present application is only 8%-15% compared with 30%-40% of the existing carrier, which reduces the engineering cost of the mobile bed biofilm reactor.

[0013] The present application is not only developed for the MBBR carrier, but also the mobile bed bio-membrane reactor equipment is designed. Specifically, the mobile bed bio-membrane reactor of the present application discards the complex structure of the prior art, and only a single reaction tank is provided. By providing the oxygen dissolving control device matched with the MBBR carrier in the reaction tank, the technical problem of difficult unification of the sewage treatment conditions of the two essential bacteria, i.e. the anaerobic denitrifying bacteria and the aerobic nitrifying bacteria, under the condition of the single reaction tank is ingeniously solved. Specifically, based on the different contact degrees between the inside and the outer surface of the MBBR carrier and the sewage, the oxygen gradient from high to low is formed from the outside to the inside of the MBBR carrier. Therefore, after the microorganism is attached to the membrane, the aerobic nitrifying bacteria are enriched on the surface of the MBBR carrier, and the anaerobic denitrifying bacteria move along the low oxygen gradient direction until they are attached in the inside of the MBBR carrier. However, the conventional attachment does not mean that the sewage treatment can be well performed. The oxygen dissolving control device is further provided to dynamically adjust the dissolved oxygen content in the sewage, so as to fully stimulate the nitrification of the aerobic nitrifying bacteria and the denitrification of the anaerobic denitrifying bacteria. In addition, the MBBR carrier with high specific surface area provided by the present application can be matched with the denitrification process of the anaerobic denitrifying bacteria, so as to promote the formation of the anaerobic layer in the inside of the MBBR carrier. Specifically, after the aerobic digestion bacteria on the outer surface of the MBBR carrier are oxidized, the ammonia nitrogen is converted into nitrate. The nitrate is reduced by the anaerobic denitrifying bacteria in the inside of the MBBR carrier to generate nitrogen. Since the MBBR carrier of the present application has a large specific surface area, compared with the prior art, more nitrogen is trapped in the inside of the MBBR carrier to form the anaerobic zone. This can provide the most suitable sewage anaerobic treatment environment for the further denitrification step of the anaerobic denitrifying bacteria. In summary, after the microorganism is attached to the membrane and the sewage is treated, the stable aerobic and anaerobic zones are formed from the outside to the inside of the MBBR carrier of the present application, so as to cooperate with the microorganism to treat the sewage. Therefore, the steps of the multiple treatment liquid reflux reaction in the prior art are omitted, and the sewage treatment efficiency is effectively improved.

[0014] As preferred, the preparation of the MBBR carrier comprises the following steps:

[0015] S1, pre-polymerization: a mixture of polyol, isocyanate and polylactic acid is pre-polymerized to obtain a polyurethane prepolymer, and the isocyanate index in the mixture is greater than 1;

[0016] S2, foaming: a foaming agent, a catalyst, a foam stabilizer and a chain extender are added to the polyurethane prepolymer to make it foam to obtain a polyurethane skeleton;

[0017] S3, impregnation: the polyurethane skeleton is impregnated in a polyol solvent containing inorganic adsorption powder to make it polymerize to obtain the MBBR carrier.

[0018] Polylactic acid is a polyester polymer formed by polymerization of lactic acid monomers, which contains abundant ester groups and is a recognized biodegradable material. It is currently widely used in fields such as degradable packaging materials and degradable medical materials. From the chemical nature, the degradation mechanism is that the ester group provides a binding site for microbial catalytic degradation, and after the action of the proteinase secreted by the microorganism, the ester bond is cleaved.

[0019] However, the operating environment of the MBBR carrier of the present application is extremely harsh. On the one hand, the MBBR carrier needs to be soaked in sewage for a long time. On the other hand, the treatment of sewage depends on the microorganisms loaded on the MBBR carrier, which is obviously an excellent environment for the degradation of polylactic acid materials. Therefore, it is difficult for those skilled in the art to imagine polylactic acid as one of the preparation materials of the MBBR carrier, and through searching, polylactic acid materials have not been found to be applied in sewage treatment equipment and carrier fillings in the field of sewage treatment technology.

[0020] However, the present applicant found that after introducing polylactic acid into the polyurethane prepolymer for blending modification, a polyurethane skeleton with excellent mechanical properties can be obtained. Based on experiments and theoretical analysis, it is found that: (1) polylactic acid reacts with polyols and isocyanate to form polyurethane soft segments and hard segments with high crystallinity, which increases the order and tightness of the soft segments and hard segments, thereby effectively improving the mechanical strength of the polyurethane skeleton. (2) Polylactic acid reacts with polyols and isocyanate to form polyurethane soft segments and hard segments containing a large number of functional groups, and a large number of hydrogen bonds are formed between the soft segments and the hard segments through mutual attraction, which enhances the crosslinking between the hard segments and the soft segments. At the same time, the crosslinking can further increase the crystallization behavior of the polyurethane skeleton, forming a more ordered and compact structure, so that the polyurethane skeleton has higher mechanical strength. In addition, the introduction of a large number of functional groups improves the hydrophilicity of the polyurethane skeleton. (3) Polylactic acid contains a large number of ester groups, and polymer cohesive energy research experiments show that the cohesive energy of ester groups is high. By blending modification of polylactic acid, the polyurethane skeleton is given excellent wear resistance.

[0021] On this basis, in order to avoid the technical problem that the polyurethane skeleton is rapidly degraded in the sewage treatment process due to the introduction of a large number of ester groups by polylactic acid, the present application forms a polyurethane coating layer on the surface of the polyurethane skeleton through the dipping process. The coating layer fixedly arranged on the polyurethane skeleton can isolate the polyurethane skeleton from the easily degradable environment such as sewage and microorganisms. Specifically, when the isocyanate index of the S1 mixture is greater than 1, the mixture is prepolymersized and foamed to obtain a polyurethane skeleton mainly containing terminal isocyanate prepolymers and isocyanate monomers, and then the polyurethane skeleton is dipped in S3 to form a coating layer. The terminal isocyanate prepolymers and isocyanate monomers on the surface of the polyurethane skeleton will again undergo polymerization reaction with the polyol solvent.

[0022] Furthermore, the applicant also found that the cross-linking structure formed between the soft segments and the hard segments in the polyurethane skeleton not only increases the mechanical strength of the polyurethane skeleton, but also the surface of the polyurethane skeleton becomes rougher and rougher with the increase of the cross-linking density. Therefore, the inorganic adsorbing powder is introduced into the MBBR carrier for inorganic modification during the impregnation. On the one hand, the rough surface of the polyurethane skeleton provides excellent bonding sites for the adhesion of the inorganic adsorbing powder, and the inorganic adsorbing powder is not easy to be dissolved out in the subsequent sewage treatment; on the other hand, the rough surface of the polyurethane skeleton means that more content of inorganic adsorbing powder can be loaded, which can strengthen the performance of the inorganic adsorbing powder itself. Specifically, the tourmaline and activated carbon inorganic adsorbing powder can effectively absorb and degrade toxic substances in the sewage, and improve the system stability of the moving bed biofilm reactor; the zeolite powder can quickly enrich ammonia nitrogen in the micro-polluted water body to form a high ammonia nitrogen enrichment area, so that the sewage treatment efficiency is higher. Secondly, the loading of more content of inorganic adsorbing powder also means that the adjustable range of the carrier density is expanded, which is helpful to realize the good self-suspension and self-fluidization of the carrier in the sewage, and reduce the energy consumption of the fluidization auxiliary equipment.

[0023] In summary, the poly-lactic acid is innovatively introduced as a blending modification material in the preparation process of the MBBR carrier and is matched with the impregnation process, so that the mechanical strength of the polyurethane skeleton is improved. Therefore, compared with the existing MBBR carrier, the MBBR carrier has a longer service life, and it is not necessary to frequently supplement to maintain the removal rate of ammonia nitrogen and other pollutants in the sewage. In addition, the specific surface area of the MBBR carrier is greatly improved through the organic-inorganic hybrid technology. On the one hand, more microorganisms can be enriched to treat the sewage, so that the sewage treatment efficiency is higher; on the other hand, compared with the existing MBBR carrier, fewer MBBR carriers can be assembled in a moving bed biofilm reactor of the same size, which will greatly reduce the input cost of the MBBR carrier.

[0024] Preferably, the temperature of the prepolymerization in S1 is 70-90℃, and the temperature of the impregnation in S3 is 10-35℃.

[0025] Preferably, the adding amount of each component in the mixture in S1 is 100-200 parts of polyol, 30-50 parts of isocyanate and 10-40 parts of poly-lactic acid in terms of mass fraction.

[0026] Preferably, the hydroxyl value of the polyol is 26-300, and the molecular weight is 2000-6000.

[0027] Preferably, the molecular weight of the poly-lactic acid is 5000-10000.

[0028] Preferably, the inorganic adsorbing powder in S3 comprises one or more of zeolite powder, activated carbon or tourmaline.

[0029] Preferably, the concentration of the inorganic adsorption powder in the polyol solvent in S3 is 2-5 g / L.

[0030] Preferably, the polyol solvent in S3 contains one or more of a catalyst and a chain extender.

[0031] Preferably, the polyol includes one or more of a polymeric polyol and a polyether polyol. The isocyanate includes one or more of toluene diisocyanate, diphenyl methane diisocyanate, and methylcyclohexyl diisocyanate. The blowing agent includes one or more of water, methyl acetate, dichloromethane, and liquid carbon dioxide. The catalyst includes one or more of a blowing agent catalyst which is a n-propyl alcohol solution of triethylene diamine, and a gel catalyst which includes one or more of organic bismuth, dibutyl tin dilaurate, stannous octoate, and triethylenediamine. The cell opener is silicone oil. The chain extender includes one or more of 1,4-butanediol, 1,4-cyclohexanediol, ethylene glycol, and propylene glycol.

[0032] Preferably, the reaction tank is further provided with a flow guide plate for dividing the reaction tank into an inflow area and a reflux area along the direction of the sewage flow when the sewage enters the reaction tank; the water inlet of the reaction tank is directly connected to the front end of the inflow area, the end of the inflow area is directly connected to the front end of the reflux area, the end of the reflux area is connected to the front end of the inflow area, the reaction tank is further provided with a guide plate for guiding the sewage at the end of the inflow area to the front end of the reflux area; the guide plate divides the reaction tank into two areas with and without MBBR carriers, and a water outlet of the reaction tank is arranged in the area without MBBR carriers and is connected to the sedimentation tank; the guide plate is provided with water passing holes.

[0033] As described above, the MBBR carrier of the present application forms stable aerobic and anaerobic zones from outside to inside during the sewage treatment process, and accordingly, based on the comprehensive consideration of factors such as equipment cost, the reaction tank, which is the main sewage treatment device of the moving bed biofilm reactor of the present application, is only provided as one. In order to solve the technical problem that the MBBR carrier with low dosage cannot fully contact with the sewage under the condition of a single reaction tank, the present application specially designs the inside of the reaction tank. Specifically, the present application can fully utilize the impact force of the inflow water flow to realize the self-circulation flow of the sewage in the reaction tank through the design of the flow guide plate and the guide plate, so that the MBBR carrier is fully fluidized in the sewage under the driving of the sewage, and then the microorganisms on the MBBR carrier treat the sewage. In addition, compared with the existing design of the reflux mechanism, the present application further saves the operation energy consumption of the sewage treatment equipment through the flow guide plate and the guide plate, and is more in line with the requirements of green development.

[0034] Preferably, a push-flow stirring device is arranged in any one of the inflow area and the backflow area along the sewage flow direction, and the push-flow stirring device comprises a stirrer and a slide rail for adjusting the depth of the stirrer in the sewage, and the push-flow stirring device further comprises a control motor for driving the stirrer to move along the slide rail and a working motor for driving the stirrer to work.

[0035] Although the impact force of the inflow water flow can be effectively utilized to realize sufficient contact between the MBBR carriers and the sewage by arranging the flow guide plate and the flow guide plate, the kinetic energy of the sewage is inevitably lost during the flow of the sewage in the reaction tank, so the flow rate of the sewage will gradually tend to be gentle, and the distribution of the sludge will be more concentrated, which is not conducive to the full treatment of the sewage by the microorganisms in the MBBR carriers or the sludge. Based on this, the push-flow stirring device is arranged in any one of the inflow area and the backflow area along the sewage flow direction, which can provide power for the flow of the sewage, and can also make the sewage treatment microorganisms and the sewage more effectively contact, thereby improving the overall treatment effect of the sewage in the reaction tank.

[0036] Preferably, the oxygen dissolution control device comprises an oxygen dissolution sensor for measuring the dissolved oxygen content in the sewage in the reaction tank, and a PLC controller for receiving the measurement information of the oxygen dissolution sensor, and the PLC controller is electrically connected with a blower for providing oxygen to the reaction tank; the oxygen dissolution control device further comprises an aeration device arranged in the reaction tank, and the aeration device comprises an aeration pipeline connected with the blower and a plurality of aeration heads connected with the aeration pipeline and dispersing gas, and the aeration heads are located at the bottom of the sewage.

[0037] During the sewage treatment process in the moving bed biofilm reactor, the dissolved oxygen content in the sewage in the reaction tank is a key factor for maintaining the metabolism of the microorganisms in the MBBR carriers and the sewage treatment. Therefore, by monitoring the dissolved oxygen content in the sewage in real time and dynamically adjusting the dissolved oxygen content in the sewage by opening or closing the blower through the PLC controller, a more suitable oxygen environment for the sewage treatment of the microorganisms can be provided.

[0038] Preferably, the water outlet of the reaction tank is communicated with the water inlet of the sedimentation tank; the sedimentation tank is provided with a clear water area and a sludge disposal area from top to bottom along the water depth direction with the water inlet of the sedimentation tank as a boundary line; the clear water area is provided with a clear water outlet; the sludge disposal area comprises a sludge pool for collecting the sludge in the water inlet of the sedimentation tank and a sludge backflow pump arranged in the sludge pool, and the sludge backflow pump is connected with a sludge backflow pipe for backflowing the sludge in the sludge pool to the reaction tank.

[0039] In the moving bed biofilm reactor, in addition to the MBBR carrier surface will be rich in sewage treatment microorganisms, sludge surface in the sewage will also be attached to some microorganisms. Therefore, in order to avoid the direct discharge of the water treated in the reaction tank to cause the loss of sewage treatment microorganisms, the technical scheme is provided with a sludge disposal area, which can return the sludge attached with microorganisms to the reaction tank in time, so as to ensure the corresponding biomass in the reaction tank; on the other hand, the sedimentation tank can also reduce the impurities in the water, and the water quality of the water flowing out of the clear water outlet is higher.

[0040] As a further preferred, the clear water zone and the sludge disposal area are further provided with a sludge screening zone for filtering the sludge in the water flowing into the clear water zone; the sludge screening zone comprises a screening filler arranged above the inlet of the sedimentation tank, and a screening filler fixing member for fixing the screening filler.

[0041] In principle, the clear water zone and the sludge disposal area are arranged in the sedimentation tank, so that the water and the sludge are layered up and down by the gravity of the sludge itself, but the technical scheme can further control the water quality of the clear water zone by arranging the sludge screening zone between the clear water zone and the sludge disposal area. Specifically, the treated water flowing into the inlet of the sedimentation tank will be screened by the screening filler, and the sludge and other large-particle materials will be gradually settled in the sludge disposal area under the action of gravity and then returned to the reaction tank through the sludge return pipe; however, the water except the large-particle materials will penetrate through the screening filler and flow into the clear water zone as the water level in the sedimentation tank rises, and finally flow out of the clear water outlet.

[0042] As a further preferred, the clear water zone comprises a water outlet groove for guiding the water to the clear water outlet, the water outlet groove comprises an overflow weir platform for controlling the water flow size in the water outlet groove, and the water outlet groove is surrounded by the overflow weir platform and the side surface of the sedimentation tank.

[0043] The technical scheme sets the overflow weir platform in the clear water zone, which can make the water in the clear water zone flow uniformly through the overflow weir platform and then flow along the water outlet groove to the clear water outlet; on the other hand, the overflow weir platform can also block the impurities in the sewage, which further improves the water quality of the outlet water.

[0044] The application also provides the moving bed biofilm reactor for use in sewage treatment.

[0045] As a preferred, the moving bed biofilm reactor is applied in agricultural source water pollution treatment.

[0046] The agricultural source water pollution refers to one or more of water pollution caused by agricultural activities, including water pollution caused by the use of pesticides, fertilizers and the like in the process of farmland planting, livestock and poultry breeding industry, aquaculture, and the like, and is mainly characterized by exceeding the standard of chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus. According to the Second National Pollution Source Census Bulletin, the agricultural source water pollutant discharge amount in 2017 was: chemical oxygen demand 1067.13 million tons, ammonia nitrogen 21.62 million tons, total nitrogen 141.49 million tons, and total phosphorus 21.20 million tons, accounting for 49.78%, 22.44%, 46.52% and 67.22% of the total amount of water pollutants discharged in China respectively, which shows that the agricultural source water pollution treatment is imperative.

[0047] The mobile bed biofilm reactor provided by the application greatly reduces the land occupation area, equipment engineering cost and long-term operation and maintenance cost of the equipment under the premise of ensuring that a specific sewage treatment effect is achieved, and the hydraulic retention time of the sewage in the reaction tank is reduced by more than half compared with the prior art, which means that the operation cost of the sewage treatment is further reduced, and high economic value is embodied. Therefore, the economic burden of the mobile bed biofilm reactor of the application is lower, which will accelerate the construction of the agricultural activity sewage treatment plant to a certain extent, and then solve the problem of high dispersion and difficult centralized treatment of the agricultural source water pollution. In addition, according to the performance test results, the removal rates of ammonia nitrogen, total phosphorus, total nitrogen and chemical oxygen demand in the sewage are all more than 90% under the hydraulic retention time of 4h, which shows that the reactor can efficiently treat large amounts of concentrated sewage, which is very suitable for the treatment demand of the agricultural source sewage, and has special significance for improving the surface water quality environment and assisting the construction of beautiful countryside.

[0048] A sewage treatment method using the mobile bed biofilm reactor according to any one of the above; the sewage treatment method comprises the following steps:

[0049] S1, biofilm formation: the MBBR carrier is added into the reaction tank loaded with the sewage, so that the bacteria in the sewage perform biofilm formation on the MBBR carrier to obtain a biofilm system; the bacteria include aerobic nitrifying bacteria and anaerobic denitrifying bacteria;

[0050] S2, sewage treatment: introducing the sewage into the biofilm system, and adjusting the dissolved oxygen content in the sewage by the oxygen dissolution control device, so that the MBBR carrier after biofilm formation treats the sewage to obtain treated water.

[0051] Preferably, the step S1 comprises:

[0052] S1.1, adding microbial nutrients into the sewage, the microbial nutrients including urea, dipotassium hydrogen phosphate and sucrose to obtain a nutrient solution;

[0053] S1.2, adding aerobic nitrifying bacteria to the nutrient solution to make it expand, and obtaining a bacterial solution;

[0054] S1.3, adding MBBR carriers to the bacterial solution to make the aerobic nitrifying bacteria form a biofilm on the surface of the MBBR carriers, and obtaining a biofilm formation system;

[0055] S1.4, inoculating anaerobic denitrifying bacteria into the biofilm formation system to form a biofilm on the surface of the MBBR carriers, and obtaining a biofilm formation system.

[0056] As preferred, in step S1.3, the dosage of the MBBR carriers is 8%-15% of the effective wastewater treatment volume of the reaction tank.

[0057] As preferred, in step S2, the introduction of wastewater includes the following steps:

[0058] S2.1, introducing wastewater into the front end of the inflow zone through the water inlet of the reaction tank, and then the wastewater flows to the end of the inflow zone along the guide plate;

[0059] S2.2, part of the wastewater at the end of the inflow zone flows into the reflux zone under the guidance of the guide plate, and the wastewater entering the reflux zone flows to the end of the reflux zone along the guide plate, and finally flows into the front end of the inflow zone; the remaining wastewater at the end of the inflow zone passes through the water holes of the guide plate, and finally flows out of the water outlet of the reaction tank.

[0060] As preferred, in step S2, the step of controlling the dissolved oxygen content in the wastewater by the oxygen dissolution control device includes:

[0061] S2.1, the dissolved oxygen sensor collects the dissolved oxygen content data in the wastewater in the reaction tank, and then uploads the dissolved oxygen content data to the PLC controller through the communication module of the dissolved oxygen sensor;

[0062] S2.2, the PLC controller analyzes the dissolved oxygen content data, and adjusts the dissolved oxygen content in the wastewater according to the analysis results by instructing the opening or closing of the air blower.

[0063] As further preferred, the step S2.2 further includes:

[0064] When the dissolved oxygen content in the wastewater is less than 1 mg / L, the PLC controller instructs the air blower to be turned on, so that oxygen flows to the bottom of the wastewater along the aeration pipeline and flows out through the aeration head to increase the dissolved oxygen content in the wastewater; when the dissolved oxygen content is higher than 4 mg / L, the PLC controller instructs the air blower to be turned off.

[0065] As preferred, step S2 further includes: adding calcium carbonate to the wastewater in the reaction tank to maintain the pH value of the wastewater at 7.0-8.5.

[0066] As preferred, the temperature of the sewage in step S2 is 15-30 DEG C.

[0067] As preferred, the hydraulic retention time of the sewage in the reaction tank in step S2 is 2-4h.

[0068] As preferred, the sewage treatment method further comprises:

[0069] S3, water purification: the treated water flowing out of the reaction tank outlet flows into the sedimentation tank along the sedimentation tank inlet, as the water level of the treated water in the sedimentation tank continues to rise, the water in the treated water will penetrate through the screened filler and flow into the clear water area, and finally flow out of the clear water outlet; and the sludge in the treated water flowing into the sedimentation tank sinks into the sludge disposal area under the action of gravity, and is returned to the reaction tank through the sludge return pipe.

[0070] Compared with the prior art, the present application has the following beneficial effects:

[0071] The present application improves the mechanical properties of the polyurethane skeleton by modifying the MBBR carrier of the moving bed biofilm reactor, so that the MBBR carrier of the present application can better cope with the shear of water force, the impact of air flow and the friction and collision between MBBR carriers during sewage treatment. Compared with the ordinary carrier on the market, the service life of the present application is longer, and it is not necessary to frequently supplement to maintain the sewage treatment effect, which reduces the long-term operation cost of the moving bed biofilm reactor.

[0072] The present application further improves the specific surface area of the MBBR carrier by introducing inorganic adsorption powder on the surface of the polyurethane skeleton. It is determined that the specific surface area of the MBBR carrier of the present application is more than 20000m 2 / m 3 , which is 13 times the specific surface area of the ordinary carrier on the market. This means that the same volume of MBBR carrier can enrich more sewage treatment microorganisms, so that the carrier dosage of the present application is only 8%-15% under the same effective sewage treatment volume of the reaction tank, compared with 30%-40% of the existing carrier, which reduces the engineering cost of the moving bed biofilm reactor.

[0073] The moving bed biofilm reactor provided by the present application cooperates the MBBR carrier, the reaction tank and the oxygen dissolution control device, on the one hand, under the premise of ensuring the specific sewage treatment effect, greatly reduces the land occupation area, equipment engineering cost and long-term operation and maintenance cost of the reactor, and embodies high economic value; on the other hand, compared with the prior art, the hydraulic retention time of the sewage in the reaction tank of the present application is shortened by more than half, which means that the present application greatly improves the sewage treatment efficiency and further reduces the operation cost of sewage treatment.

[0074] From the performance test results, the mobile bed bio-membrane reactor of the present application can remove more than 90% of ammonia nitrogen, total phosphorus, total nitrogen and chemical oxygen demand in agricultural source sewage under 4h hydraulic retention time, which can treat large amount of sewage in a centralized manner with high quality and high efficiency, and is very suitable for the treatment of agricultural source sewage, and has special significance for improving the surface water quality environment and assisting the construction of beautiful countryside. BRIEF DESCRIPTION OF DRAWINGS

[0075] In order to clearly describe the embodiments, the drawings will be briefly introduced as follows:

[0076] Figure 1 It is a schematic diagram of the overall structure of the mobile bed bio-membrane reactor of Example 1.

[0077] Figure 2 It is a schematic diagram of the partial structure of the reaction tank of the mobile bed bio-membrane reactor of Example 1.

[0078] Figure 3 It is a sectional view of the mobile bed bio-membrane reactor of Example 1.

[0079] Figure 4 It is a top view of the partial structure of the reaction tank of the mobile bed bio-membrane reactor of Example 1.

[0080] Figure 5 It is a sectional view of the sedimentation tank of the mobile bed bio-membrane reactor of Example 1.

[0081] Figure 6 It is a top view of the sludge disposal area of the mobile bed bio-membrane reactor of Example 1.

[0082] Figure 7 It is a top view of the clear water area of the mobile bed bio-membrane reactor of Example 1.

[0083] Reference signs: 1, reaction tank, 11, inflow area, 12, reflux area, 13, flow guide plate, 14, reaction tank water inlet, 15, guide plate, 16, reaction tank water outlet, 17, push-flow stirring device, 171, stirrer, 172, slide rail, 173, protective shell, 18, aeration device, 181, aeration pipeline, 182, aeration head, 19, flow guide plate, 2, sedimentation tank, 21, sedimentation tank water inlet, 22, clear water area, 221, clear water outlet, 222, water outlet tank, 223, overflow weir table, 23, sludge screening area, 231, screening filler, 232, screening filler fixing piece, 24, sludge disposal area, 241, sludge pool, 242, sludge reflux pump, 243, sludge reflux pipe, 244, sludge guide plate, 3, MBBR carrier. DETAILED DESCRIPTION

[0084] The application will be further described below in conjunction with the accompanying drawings and specific embodiments. Those skilled in the art can implement the application based on the description. In addition, the embodiments of the application described in the following description are generally only embodiments of a part of the application, not all embodiments. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments in the application without creative labor should be within the scope of protection of the application.

[0085] Embodiment 1

[0086] Please refer to Figures 1-7 The mobile bed biological membrane reactor of the embodiment comprises:

[0087] The reaction tank 1 loaded with the MBBR carrier 3 is provided with a flow guide plate 13 for dividing the reaction tank 1 into an inflow area 11 and a reflux area 12 along the direction of the sewage flow when the water enters the reaction tank 1. The water inlet 14 of the reaction tank directly communicates with the front end of the inflow area 11, the end of the inflow area 11 directly communicates with the front end of the reflux area 12, and the end of the reflux area 12 communicates with the front end of the inflow area 11. The reaction tank 1 is also provided with a guide plate 15 for guiding the sewage at the end of the inflow area 11 to the front end of the reflux area 12. In the embodiment, the guide plate 15 is an arc-shaped plate provided outwardly convex along the direction of the water flow when the water enters. The guide plate 15 divides the reaction tank 1 into two areas with and without the MBBR carrier, and the reaction tank water outlet 16 is arranged in the area without the MBBR carrier. The guide plate 15 has water passing holes for water passing. The reaction tank 1 of the embodiment can make full use of the impact force of the water flow to realize the self-circulation of the sewage in the reaction tank 1 by arranging the flow guide plate 13 and the guide plate 15, which greatly saves the operation energy consumption of the sewage treatment equipment compared with the design of the existing reflux mechanism, and is more in line with the requirements of green development. In addition, the reaction tank 1 of the embodiment is also provided with two flow assisting plates 19 on the side close to the water inlet 14 of the reaction tank. The flow assisting plates 19 form a triangular prism structure by surrounding the side wall of the reaction tank 1, which can avoid the formation of a water flow dead angle in the reaction tank 1 and promote the full flow of the sewage in the reaction tank 1.

[0088] The backflow area 12 of the embodiment is provided with a push-flow stirring device 17 along the sewage flow direction, the push-flow stirring device 17 comprises a stirrer 171 and a slide rail 172 for adjusting the depth of the stirrer 171 in the sewage, the push-flow stirring device 17 further comprises a control motor for driving the stirrer 171 to move along the slide rail 172 and a working motor for driving the stirrer 171 to work. When the water inlet of the reaction tank 1 flows into the backflow area 12 from the inflow area 11 along the guide plate 15, the sewage flow in the backflow area 12 is relatively gentle compared with the inflow area 11, and it is inevitable that the problem of insufficient sewage circulation power occurs, therefore, the embodiment can push the sewage flow back to the front end of the inflow area 11 by setting the stirrer 171 in the backflow area 12 to realize circulation. At the same time, the stirrer 171 can also mix the sewage and sludge in the backflow area 12 uniformly by moving up and down, promote the full contact between the microorganisms in the sludge and the sewage, and thus improve the overall treatment effect of the sewage. In addition, in order to avoid the paddle of the stirrer 171 shearing the MBBR carrier 3 in the sewage while stirring the sewage, the push-flow stirring device 17 of the embodiment further comprises a protective shell 173 arranged outside the stirrer 171.

[0089] The reaction tank 1 of the embodiment is also provided with an oxygen dissolution control device for adjusting the dissolved oxygen degree of the sewage in the reaction tank 1, the oxygen dissolution control device comprises an oxygen dissolution sensor for measuring the dissolved oxygen amount in the sewage in the reaction tank, and a PLC controller for receiving the measurement information of the oxygen dissolution sensor, the PLC controller is electrically connected with a blower for providing oxygen to the reaction tank 1; the oxygen dissolution control device further comprises an aeration device 18, the aeration device 18 comprises an aeration pipeline 181 connected with the blower, and a plurality of aeration heads 182 connected with the aeration pipeline 181 and dispersing gas, the aeration heads 182 are arranged at the bottom of the reaction tank 1. In the sewage treatment process, the size of the dissolved oxygen amount in the sewage directly affects the effect of the microorganisms on the sewage treatment, therefore, the embodiment can accurately dynamically adjust the oxygen concentration of the inflow area 11 and the backflow area 12 by setting two groups of oxygen dissolution control devices in the inflow area 11 and the backflow area 12, to provide a suitable sewage treatment environment for the microorganisms.

[0090] A sedimentation tank 2 is provided with a sedimentation tank water inlet 21 which is communicated with the reaction tank water outlet 16. In this embodiment, the sedimentation tank 2 is provided with a clear water area 22, a sludge screening area 23 and a sludge disposal area 24 from top to bottom along the water depth direction. The clear water area 22 is provided with a clear water area water outlet 221 and a water outlet groove 222 for guiding water to the clear water area water outlet 221, the water outlet groove 222 is enclosed by the overflow weir 223 and the side surface of the sedimentation tank 2. Specifically, the water in the clear water area 22 will flow along the water outlet groove 222 to the clear water area water outlet 221 after overflowing the overflow weir 223. The sludge screening area 23 includes a screening filler 231 arranged above the sedimentation tank water inlet 21 and a screening filler fixing member 232 for fixing the screening filler 231. The sludge disposal area 24 includes a sludge pool 241 for collecting sludge in the water inlet of the sedimentation tank 2 and a sludge backflow pump 242 arranged in the sludge pool 241, the sludge backflow pump 242 is connected with a sludge backflow pipe 243 for backflowing sludge in the sludge pool 241 to the reaction tank 1. In order to make the sludge backflowed by the sludge backflow pipe 243 flow sufficiently in the reaction tank 1, the other end of the sludge backflow pipe 243 connected with the sludge backflow pump 242 is arranged at the upper part of the reaction tank water inlet 14. In addition, the sludge pool 241 of this embodiment is enclosed by a sludge guide plate 244 and the bottom surface of the sedimentation tank 2, and the sludge backflow pump 242 is arranged on the bottom surface of the sedimentation tank 2. Therefore, the sludge flowing into the sedimentation tank 2 through the sedimentation tank water inlet 21 will flow to the bottom surface of the sedimentation tank 2 under the guidance of the sludge guide plate 244, and finally backflow to the reaction tank 1 along the sludge backflow pipe 243 under the action of the sludge backflow pump 242, thereby reducing the loss of sewage treatment microorganisms in the reaction tank 1.

[0091] In addition, the preparation method of the MBBR carrier 3 in this embodiment includes the following steps:

[0092] S1, pre-polymerization: a mixture of 100 parts of polyether polyol HSH-204 (hydroxyl value 265-300 mgKOH / g, molecular weight 2000), 50 parts of toluene diisocyanate, 10 parts of polylactic acid PLA-N3 (molecular weight 5000, added in the form of polylactic acid acetone solution) is heated to 90℃, and stirred for 2.5h to obtain a polyurethane prepolymer;

[0093] S2, foaming: adding 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;

[0094] S3, Immersion: immerse the polyurethane skeleton in polyether polyol HSH-204 containing inorganic adsorption powder (particle size less than 15 μm, the ratio of activated carbon to zeolite powder is 1:1) with a concentration of 3 g / L at 35°C for 3 h;

[0095] S4, Curing: take out the polyurethane skeleton and cure to obtain the MBBR carrier.

[0096] Example 2

[0097] In this example, the mobile bed bio-membrane reactor of Example 1 is used to treat sewage, and the treatment steps are as follows:

[0098] S1, Microbial biofilm formation: introduce agricultural source sewage into the inside of the reaction tank 1 through the water inlet 14 of the reaction tank, and then add microbial nutrients to the sewage, the microbial nutrients including urea, dipotassium hydrogen phosphate and sucrose (n(C):n(N):n(P) in the microbial nutrients is 100:6:1), to obtain a nutrient solution; add 400 g / m 3 (of the sewage added in the reaction tank 1) of aerobic nitrifying bacteria to the nutrient solution, start the plug flow stirring device 17, so that the aerobic nitrifying bacteria can be evenly distributed in the sewage for cultivation, to obtain a bacterial solution; add 8% of the MBBR carrier 3 to the bacterial solution (calculated based on the effective sewage treatment volume of the reaction tank 1), so that the aerobic nitrifying bacteria form a biofilm on the surface of the MBBR carrier 3, to obtain a biofilm formation system; inoculate 450 g / m 3 (of the sewage added in the reaction tank 1) of anaerobic denitrifying bacteria to the biofilm formation system, so that a biological membrane is formed on the surface of the MBBR carrier 3, to obtain a membrane formation system.

[0099] In this example, the technical problem of difficult biofilm formation of anaerobic denitrifying bacteria is solved by adjusting the sequence of biofilm formation. Specifically, in the process of biofilm formation in this example, aerobic nitrifying bacteria are added first. On the one hand, the reproduction and metabolism of aerobic nitrifying bacteria will gradually reduce the dissolved oxygen content in the sewage, which will provide a good dissolved oxygen environment for the addition of anaerobic denitrifying bacteria; on the other hand, the nitrification step of aerobic nitrifying bacteria will provide sufficient substrate for the denitrification process of denitrifying bacteria. In addition, the preliminary biofilm formation of aerobic nitrifying bacteria will make the inside of the MBBR carrier 3 have a lower oxygen content, so that after the preliminary biofilm formation of aerobic nitrifying bacteria, the addition of anaerobic denitrifying bacteria can provide the best sewage environment for the reproduction and biofilm formation of anaerobic denitrifying bacteria.

[0100] S2, sewage treatment: introduce sewage into the film forming system, open the reaction tank water outlet 16 at the same time, adjust the hydraulic retention time to 4h, the sewage flows into the inflow pipe, and then flows along the guide plate 13 to the end of the inflow area 11; part of the sewage at the end of the inflow area 11 flows into the reflux area 12 under the guidance of the guide plate 15, and the sewage entering the reflux area 12 flows along the guide plate 13 to the end of the reflux area 12, and finally flows into the reaction tank 1 in front of the inflow area 11; the remaining sewage at the end of the inflow area 11 passes through the water hole of the guide plate 15, and finally flows out of the reaction tank water outlet 16.

[0101] In addition, in order to fully exert the potential of microorganisms in sewage treatment, the pH, temperature and dissolved oxygen content of the sewage in the reaction tank 1 are also controlled. First, the temperature of the sewage in the reaction tank 1 of the present embodiment is 15-30℃. Second, in order to avoid the increase of nitrite and nitrate content leading to too low pH of the sewage, which is difficult to meet the sewage degradation needs of microorganisms, calcium carbonate is added to the sewage to adjust the pH value of the sewage in the reaction tank 1, so that it is maintained at 7.0-8.5. Finally, the oxygen dissolution control device needs to be opened during the sewage treatment process. The dissolved oxygen sensor of the oxygen dissolution control device collects the dissolved oxygen content data of the sewage in the reaction tank 1, and then uploads the dissolved oxygen content data to the PLC controller through the communication module. The PLC controller analyzes the dissolved oxygen content data, and according to the analysis result, adjusts the dissolved oxygen content in the sewage by instructing the opening or closing of the air blower. Specifically, when the dissolved oxygen content in the sewage is less than 1mg / L, the PLC controller instructs the air blower to open, so that oxygen flows to the bottom of the sewage along the aeration pipe 181 and flows out through the aeration head 182, so as to increase the dissolved oxygen content in the sewage and promote the aerobic step of aerobic nitrifying bacteria. When the dissolved oxygen content is higher than 4mg / L, the PLC controller instructs the air blower to close. At this time, with the progress of the nitrification step of aerobic nitrifying bacteria, the dissolved oxygen content in the sewage will be gradually consumed, and at the same time, the decrease of the dissolved oxygen content will promote the progress of the denitrification process of anaerobic denitrifying bacteria, and further accelerate the reduction of nitrite produced in the nitrification process. The oxygen dissolution control device dynamically adjusts the dissolved oxygen content in the sewage, which can further provide a better denitrification environment for anaerobic denitrifying bacteria, promote the progress of the reduction reaction, and solve the technical problem of difficult denitrification under the condition of only setting a single reaction tank 1.

[0102] S3, water purification: the treated water flowing into the sedimentation tank 2 through the water inlet 21 of the sedimentation tank is screened by the screening filler 231, and the sludge and other large-particle substances cannot pass through the screening filler 231 and flow to the sludge disposal area 24 under the action of gravity. Under the driving of the sludge backflow pump 242, the sludge and other large-particle substances flow back to the reaction tank 1 through the sludge backflow pipe 243. However, the water other than the large-particle substances penetrates through the screening filler 231 and flows into the clear water area 22 as the water level in the sedimentation tank 2 continuously rises. The clear water in the clear water area 22 higher than the overflow weir table 223 uniformly overflows the overflow weir table 223, and then flows along the water outlet groove 222, and finally flows out through the clear water area water outlet 221 to obtain clear water.

[0103] Example 3

[0104] The mobile bed bio-membrane reactor of the present example is only different from the mobile bed bio-membrane reactor of example 1 in the following aspects, and the same parts are not described here again.

[0105] In the present example, the flow guide plate 15 and the flow guide plate 19 arranged on the side of the reaction tank 1 close to the water inlet 14 of the reaction tank are mirror-symmetrically arranged, and both are arc-shaped plates.

[0106] The preparation method of the MBBR carrier 3 in the present example includes the following steps:

[0107] S1, pre-polymerization: a mixture of 200 parts of polyether polyol HSH-210 (hydroxyl value 105-119 mgKOH / g, molecular weight 2000), 45 parts of methylcyclohexyl diisocyanate, and 40 parts of polylactic acid PLA-NHS (molecular weight 10000, added in the form of polylactic acid acetone solution) is heated to 70°C, and stirred for 3h to obtain a polyurethane prepolymer;

[0108] S2, foaming: 4 parts of water, 0.5 parts of triethylenediamine n-propanol solution, 0.5 parts of dibutyl tin dilaurate, 3 parts of silicone oil, and 1 part of propylene glycol are added to the polyurethane prepolymer to obtain a polyurethane skeleton by foaming;

[0109] S3, impregnation: the polyurethane skeleton is impregnated in the polyether polyol HSH-210 at 35°C for 5h, and the polyether polyol HSH-210 further contains inorganic adsorption powder (particle size less than 50μm, the ratio of activated carbon, tourmaline and zeolite powder is 1:1:1) with a concentration of 2g / L, 0.6g / L of triethylenediamine n-propanol solution, 0.1g / L of organic bismuth, and 0.2g / L of 1,4-butanediol;

[0110] S4, curing: the polyurethane skeleton is taken out and cured to obtain the MBBR carrier.

[0111] Example 4

[0112] The mobile bed bio-membrane reactor of Example 3 is used to treat sewage, and the treatment steps are only different from those of Example 2. The same parts are not described here.

[0113] In step S1 of the present example, 10% of the MBBR carrier 3 is added to the reaction tank 1, which is calculated based on the effective sewage treatment volume of the reaction tank 1.

[0114] Example 5

[0115] The mobile bed bio-membrane reactor of the present example is only different from that of Example 1. The same parts are not described here.

[0116] The preparation method of the MBBR carrier 3 in the present example includes the following steps:

[0117] S1, pre-polymerization: a mixture of 190 parts of polyether polyol Poly Qs-26 (hydroxyl value 26 mgKOH / g, molecular weight 6000), 30 parts of diphenyl methane diisocyanate, and 40 parts of polylactic acid PLA-NHS (molecular weight 10000, added in the form of polylactic acid acetone solution) is heated to 80℃, and stirred for 2h to obtain a polyurethane prepolymer;

[0118] S2, foaming: 5 parts of dichloromethane, 0.6 parts of triethylene diamine n-propanol solution, 0.5 parts of stannous octoate, 3 parts of silicone oil, and 1 part of triethanolamine are added to the polyurethane prepolymer to obtain a polyurethane skeleton by foaming;

[0119] S3, impregnation: the polyurethane skeleton is impregnated in polyether polyol Poly Qs-26 containing inorganic adsorption powder (particle size less than 15μm, the ratio of activated carbon to tourmaline is 1:1) with a concentration of 5g / L at 10℃ for 3h;

[0120] S4, curing: the polyurethane skeleton is taken out and cured to obtain the MBBR carrier.

[0121] Example 6

[0122] The mobile bed bio-membrane reactor of Example 5 is used to treat sewage, and the treatment steps are only different from those of Example 2. The same parts are not described here.

[0123] In step S1 of the present example, 10% of the MBBR carrier 3 is added to the reaction tank 1, which is calculated based on the effective sewage treatment volume of the reaction tank 1. In addition, the hydraulic retention time of the sewage in the reaction tank 1 in the present example is 2h.

[0124] Comparative Example 1

[0125] The present comparative example and Example 2 only have the following differences, and the same parts are not described here.

[0126] The MBBR carrier 3 in the present comparative example is a common commercially available carrier.

[0127] Comparative Example 2

[0128] The present comparative example and Comparative Example 1 only have the following differences, and the same parts are not described here.

[0129] The addition amount of MBBR carrier 3 in the present comparative example is 40% of the effective sewage treatment volume in the reaction tank 1.

[0130] Comparative Example 3

[0131] The present comparative example and Comparative Example 2 only have the following differences, and the same parts are not described here.

[0132] The hydraulic retention time of the sewage in the reaction tank 1 in the present comparative example is extended to 8h.

[0133] Performance test

[0134] The sewage treatment and performance parameters of the MBBR carrier of Example 2 and Comparative Examples 1-3 were determined. Specifically, in the present performance test, the determination of ammonia nitrogen adopts the Nash reagent spectrophotometric method of HJ535-2009; the determination of chemical oxygen demand adopts the dichromate method FJ828-2017; the determination of total phosphorus adopts the ammonium molybdate spectrophotometric method of GB / T11893-1989; the determination of total nitrogen adopts the alkaline potassium persulfate digestion ultraviolet spectrophotometric method of HJ636-2012. The specific surface area of the MBBR carrier is determined according to GB / T19587; in the hardness test, the MBBR carrier needs to be cut into 2cm*2cm*2cm cubes, and then tested with a Shore hardness tester according to the standard of GB / T531-2008. After testing, the table is as follows:

[0135] Table 1, sewage treatment and performance parameters of MBBR carrier

[0136]

[0137] From the observation of the above table, the performance parameters of the MBBR carrier involved in the present application are far superior to ordinary carriers. In terms of specific surface area, it reaches 13 times that of commercially available carriers, which means that in the same sewage treatment volume of the reaction tank, the dosage of the MBBR carrier of the present application will be lower under the premise of ensuring the sewage treatment effect, which can reduce the investment cost of the moving bed biofilm reactor. In terms of hardness, the hardness of the MBBR carrier modified by polylactic acid in the present application is more than one time that of commercially available carriers, which shows that the MBBR carrier of the present application can better cope with the push flow and stirring of the push flow stirring device and the friction between the MBBR carriers during the sewage treatment process, and therefore has a longer service life compared with ordinary carriers, and does not need to be frequently supplemented during long-term sewage treatment, so the long-term cost of sewage treatment is lower.

[0138] By comparing Example 2 and Comparative Example 1, it can be found that under the same sewage treatment conditions (8% MBBR carrier dosage, 4h hydraulic retention time), the sewage is treated by using MBBR carriers with different specific surface areas, and the treatment effect shows a huge difference. Specifically, the removal rates of ammonia nitrogen, total phosphorus, total nitrogen and chemical oxygen demand in Example 2 are as high as about 96.3%, 96.4%, 95.6% and 92% respectively; however, the sewage treatment rates of ammonia nitrogen, total phosphorus and total nitrogen in Comparative Example 1 are only 29.1%, 34.7%, 24.9% and 25.5%. Preliminary analysis shows that under the same dosage, the MBBR carrier of the present application can attach more sewage treatment microorganisms due to its higher specific surface area, so under the conditions of 4h water flow retention time and low dosage, the sewage can still be treated to meet the Class IV water standard in the "Surface Water Environmental Quality Standard" (GB3838-2002). The MBBR carrier in Comparative Example 1 has a smaller specific surface area, so after the same amount of bacteria is added, the actual biofilm amount of the MBBR carrier is low, and most of the microorganisms are lost because they are not attached to enough carriers (MBBR carriers or sludge), so the sewage treatment effect is poor.

[0139] On this basis, the dosage of commercially available MBBR carriers is increased in Comparative Example 2. From the indicators after sewage treatment, the content of ammonia nitrogen is greatly reduced, and the removal rate of ammonia nitrogen reaches about 95.3%, reaching the emission limit value of the pollutant ammonia nitrogen; however, in terms of total nitrogen content, the removal rate of total nitrogen is still low, only about 49.5%, which shows that by increasing the dosage of the carrier, the content of aerobic nitrifying bacteria attached to the MBBR carrier can be effectively increased, however, since the commercially available MBBR carriers cannot provide a good anaerobic environment for denitrifying bacteria, the reduction step of nitrate to nitrogen gas is limited in the moving bed biofilm reactor device of the present application, which ultimately leads to that under the condition of 4h hydraulic retention time, the total nitrogen content of the effluent is still difficult to meet the emission standard.

[0140] Based on this, the comparative example 3 increases the hydraulic retention time of the sewage inside the reaction tank, and from the indicators after sewage treatment, the removal rates of ammonia nitrogen, total phosphorus, total nitrogen and chemical oxygen demand of the comparative example 3 are 96.5%, 93.3%, 65% and 58.1% respectively. It can be seen that by increasing the hydraulic retention time, sufficient denitrification time can be given to anaerobic denitrifying bacteria, thereby improving the removal rates of total nitrogen and chemical oxygen demand of the sewage. However, compared with the example 1, the sewage treatment time is doubled, and from the removal rates of total nitrogen and chemical oxygen demand, the removal rates of total nitrogen and chemical oxygen demand of the comparative example 3 still have a large difference with those of the example 1.

[0141] In summary, by modifying the MBBR carrier, the present application provides an MBBR carrier with super-high specific surface area and high mechanical properties. On this basis, the present application also designs a mobile bed biological membrane reactor device with high adaptability and matches with a reasonable sewage treatment method, so that the sewage, especially the agricultural source light pollution water body, can be treated efficiently. The present application provides a high-efficiency sewage treatment device and method with high cost performance for the treatment of agricultural source pollution water body, and to a certain extent, solves the problems of high dispersion of agricultural source pollution, difficulty in centralized treatment, high cost and low efficiency of sewage treatment, and has high economic value and social value.

Claims

1. A moving bed biofilm reactor, comprising a reaction tank and a sedimentation tank sequentially connected in the direction of wastewater flow, characterized in that, The reaction tank is loaded with an MBBR carrier, which includes a polylactic acid-modified polyurethane skeleton and a coating layer fixed on the polyurethane skeleton. The coating layer also contains inorganic adsorption powder. The moving bed biofilm reactor also includes an oxygen control device for adjusting the dissolved oxygen content of the wastewater in the reaction tank. The preparation of the MBBR vector includes the following steps: S1. Prepolymerization: A mixture of polyol, isocyanate, and polylactic acid is prepolymerized to obtain a polyurethane prepolymer, wherein the isocyanate index in the mixture is greater than 1; S2. Foaming: A foaming agent, catalyst, foam leveling agent, and chain extender are added to the polyurethane prepolymer to foam it and obtain a polyurethane skeleton; S3. Impregnation: The polyurethane skeleton is impregnated in a polyol solvent containing inorganic adsorption powder to polymerize it and obtain an MBBR carrier; the polyol solvent in S3 also contains one or more of a catalyst and a chain extender, and the inorganic adsorption powder includes one or more of zeolite powder, activated carbon, or tourmaline.

2. A moving bed biofilm reactor according to claim 1, characterized in that, The reaction tank is also equipped with a flow guide plate that divides the reaction tank into an inlet zone and a return zone along the direction of sewage flow when water enters the reaction tank. Furthermore, the inlet of the reaction tank is directly connected to the front end of the inlet zone, the end of the inlet zone is directly connected to the front end of the return zone, and the end of the return zone is connected to the front end of the inlet zone. The reaction tank is also equipped with a guide plate that directs sewage from the end of the inlet zone to the front end of the return zone. The guide plate divides the reaction tank into two areas: one with an MBBR carrier and one without. An outlet for the reaction tank, connected to the sedimentation tank, is located in the area without the MBBR carrier. The guide plate has water passage holes for water supply.

3. A moving bed biofilm reactor according to claim 2, characterized in that, The inflow zone and the return zone are each provided with a flow-pushing and stirring device along the sewage flow direction to push the sewage and / or sludge containing the MBBR carrier to flow. The flow-pushing and stirring device includes a stirrer and a slide rail for adjusting the depth of the stirrer in the sewage. The flow-pushing and stirring device also includes a control motor that moves the stirrer along the slide rail and a working motor that drives the stirrer to work.

4. A moving bed biofilm reactor according to claim 1, characterized in that, The dissolved oxygen control device includes a dissolved oxygen sensor for measuring the dissolved oxygen content in the wastewater of the reaction tank, and a PLC controller for receiving the dissolved oxygen sensor measurement information. The PLC controller is electrically connected to a blower for supplying oxygen to the reaction tank. The dissolved oxygen control device also includes an aeration device, which is wholly or partially installed inside the reaction tank. The aeration device includes an aeration pipe connected to the blower, and multiple aeration heads connected to the aeration pipe and dispersing the gas. The aeration heads are located at the bottom of the wastewater.

5. A moving bed biofilm reactor according to claim 1, characterized in that, The outlet of the reaction tank is connected to the inlet of the sedimentation tank. Taking the inlet direction of the sedimentation tank as the dividing line, the sedimentation tank is provided with a clear water zone and a sludge treatment zone from top to bottom along the water depth direction. The clear water zone is provided with a clear water outlet. The sludge treatment zone includes a sludge tank for collecting sludge from the inlet water of the sedimentation tank, and a sludge return pump installed inside the sludge tank. The sludge return pump is connected to a sludge return pipe for returning the sludge in the sludge tank to the reaction tank.

6. A moving bed biofilm reactor according to claim 5, characterized in that, A sludge screening section is also provided between the clear water zone and the sludge treatment zone to filter the water flowing into the clear water zone; the sludge screening section includes screening packing material installed above the inlet of the sedimentation tank, and screening packing material fixing components for fixing the screening packing material.

7. A moving bed biofilm reactor according to claim 5 or 6, characterized in that, The clear water zone includes a water outlet trough for diverting water to the clear water outlet. The water outlet trough includes an overflow weir for controlling the water flow rate inside the trough. The water outlet trough is enclosed by the overflow weir and the side surface of the sedimentation tank.

8. The moving bed biofilm reactor according to any one of claims 1-7 is used in wastewater treatment.

9. The application according to claim 8, characterized in that, The moving bed biofilm reactor is used in the treatment of agricultural water pollution.

10. A wastewater treatment method, characterized in that, The wastewater treatment method uses the moving bed biofilm reactor according to any one of claims 1-7, and includes the following steps: S1. Biofilm formation: The MBBR carrier is added to the reaction tank containing wastewater, so that the bacteria in the wastewater can form a biofilm on the MBBR carrier to obtain a biofilm system; the bacteria include aerobic nitrifying bacteria and anaerobic denitrifying bacteria; S2. Wastewater treatment: Wastewater is introduced into the membrane-forming system, and the dissolved oxygen content in the wastewater is regulated by an oxygen dissolution control device, so that the MBBR carrier after membrane attachment can treat the wastewater to obtain treated water.

11. A wastewater treatment method according to claim 10, characterized in that, Step S1 includes: S1.1 Add microbial nutrients to the wastewater, the microbial nutrients including urea, dipotassium hydrogen phosphate and sucrose, to obtain a nutrient solution; S1.2 Add aerobic nitrifying bacteria to the nutrient solution to allow it to expand and obtain a bacterial solution; S1.3 Add MBBR carrier to the bacterial solution to allow aerobic nitrifying bacteria to attach to the surface of the MBBR carrier, thus obtaining a biofilm system; S1.4 Inoculate anaerobic denitrifying bacteria into the biofilm system to form a biofilm on the surface of the MBBR carrier, thus obtaining the biofilm system.

12. A wastewater treatment method according to claim 11, characterized in that, In step S1.3, the dosage of the MBBR carrier is 8%-15% based on the effective wastewater treatment volume of the reaction tank.

13. A wastewater treatment method according to claim 10, characterized in that, In step S2, the introduction of wastewater includes the following steps: S2.

1. Wastewater is introduced into the front end of the inlet zone through the inlet of the reaction tank, and then the wastewater flows along the diversion plate to the end of the inlet zone; S2.

2. Some of the sewage at the end of the inlet zone flows into the return zone under the guidance of the guide plate. The sewage entering the return zone flows along the guide plate to the end of the return zone and finally merges into the front end of the inlet zone. The remaining sewage at the end of the inlet zone flows out through the water passage of the guide plate and finally flows out at the outlet of the reaction tank.

14. A wastewater treatment method according to claim 10, characterized in that, In step S2, the steps of the oxygen control device regulating the dissolved oxygen content in wastewater include: S2.1 The dissolved oxygen sensor's monitoring probe collects dissolved oxygen data in the wastewater of the reaction tank, and then uploads the dissolved oxygen data to the PLC controller through the dissolved oxygen sensor's communication module. S2.2 The PLC controller analyzes the dissolved oxygen data and, based on the analysis results, regulates the dissolved oxygen in the wastewater by instructing the blower to turn on or off.

15. A wastewater treatment method according to claim 14, characterized in that, Step S2.2 also includes: When the dissolved oxygen level in the wastewater is below 1 mg / L, the PLC controller will instruct the blower to turn on, so that oxygen flows along the aeration pipe to the bottom of the wastewater and flows out through the aeration head to increase the dissolved oxygen level in the wastewater; when the dissolved oxygen level is above 4 mg / L, the PLC controller will instruct the blower to turn off.

16. A wastewater treatment method according to claim 10, characterized in that, Step S2 also includes adding calcium carbonate to the wastewater in the reaction tank to maintain the pH value of the wastewater at 7.0-8.

5.

17. A wastewater treatment method according to claim 10, characterized in that, The temperature of the wastewater in step S2 is 15-30℃.

18. A wastewater treatment method according to claim 10, characterized in that, The hydraulic retention time of the wastewater in the reaction tank in step S2 is 2-4 hours.

19. A wastewater treatment method according to claim 10, characterized in that, Also includes: S3. Water purification: The treated water flowing out of the reaction tank outlet flows into the sedimentation tank through the sedimentation tank inlet. As the water level in the sedimentation tank continues to rise, the water in the treated water will permeate through the screening packing and flow into the clear water zone, and finally flow out at the clear water outlet. Meanwhile, the sludge in the treated water flowing into the sedimentation tank settles into the sludge disposal zone under gravity and flows back to the reaction tank through the sludge return pipe.

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