CN108483644B

CN108483644B - Composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation and preparation method and application thereof

Info

Publication number: CN108483644B
Application number: CN201810404533.4A
Authority: CN
Inventors: 刘波; 盛世雄; 杜凌峰; 程绍举; 侯玉倩; 孙信伯; 梁子
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2018-04-28
Filing date: 2018-04-28
Publication date: 2020-06-26
Anticipated expiration: 2038-04-28
Also published as: CN108483644A

Abstract

The invention discloses a composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation, and a preparation method and application thereof, and belongs to the field of water treatment. The composite biological filler for promoting the rapid start and the stable operation of the anaerobic ammonia oxidation comprises polyurethane foam, activated carbon and iron powder which are connected through a cross-linking agent, and is prepared by a method of directly adding the activated carbon, the iron powder and the cross-linking agent in a foaming process during the preparation of the polyurethane foam. According to the filler disclosed by the invention, the activated carbon and the iron powder are firmly connected to the surface of the polyurethane foam, and the filler is applied to the UASB reactor, so that the starting efficiency of anaerobic ammonia oxidation can be effectively improved.

Description

Composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation and preparation method and application thereof

Technical Field

The invention belongs to the field of water treatment, and particularly relates to a composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation, and a preparation method and application thereof.

Background

Anammox (Anammox) has been gaining tremendous scientific interest since its discovery. It is prepared by anaerobic ammonium oxidation bacteria under anaerobic condition with ammonia nitrogen NH₄ ⁺-N as electron donor, nitrous nitrogen NO₂ ^--N is an electron acceptor to N₂The reaction of (1). Different from the traditional ammoxidation-denitrification process, the Anammox does not need an additional organic carbon source and does not need aeration, thereby greatly reducing the energy consumption and the cost in the treatment process.

The Anammox reaction, although having many advantages, still has many problems in practical use: the slow doubling rate of Anammox bacteria and the long bacterial enrichment time result in start-up times of the Anammox reactor often requiring more than a year. The reasons for the slow start of Anammox are mainly: (1) the Anammox bacteria are easily influenced by external interference factors, and the growth and proliferation of the Anammox bacteria can be inhibited by too low temperature, too high dissolved oxygen concentration, nitrite concentration and the like; (2) when a common UASB reactor is used as an Anammox reaction carrier, Anammox sludge particles in a starting stage are small and easy to float upwards, and the Anammox sludge particles are easy to flow out along with effluent to cause loss of Anammox bacteria; (3) without external stimuli and gains, Anammox bacteria are often at a disadvantage when they compete with other anaerobic bacteria in the reactor.

The traditional filler such as sponge, zeolite and the like can increase the internal surface area of the reactor, enlarge the growth space of sludge and have certain promotion effect on the starting of Anammox. However, the fillers have single and overlapped functions, can only be used as a film-forming carrier of sludge, and have no obvious effect on shortening the starting time of the Anammox. The polyurethane has the advantages of the traditional filler, and the surface of the polyurethane has certain cationic active groups, hydroxyl groups and other hydrophilic groups, so that the polyurethane can be combined with microbes with negative charges in sewage to generate valence and bond, so that the sludge can be more stably attached to the surface of the filler and is not easy to lose under the shearing of water and air. However, the function of polyurethane foam is still limited to the function of sludge retention, so that the use of polyurethane alone does not obviously help Anamox, and the application of polyurethane filler still has room for further improvement.

The prior art with the Chinese patent application number of CN201410137223.2 discloses preparation and application of an anaerobic ammonium oxidation bacteria immobilized fixed bioactive filler based on a reticular carrier, wherein the prepared reticular polyethylene and other materials are used as the carrier, an anaerobic ammonium oxidation bacteria suspension and a polyvinyl alcohol mixed solution are added, and the anaerobic ammonium oxidation bacteria are attached to the carrier under the soaking of a saturated boric acid solution, so that the efficiency of an anaerobic ammonium oxidation reactor is improved. The method can effectively improve the growth rate of the anammox bacteria and shorten the starting time, but the anammox bacteria liquid required by the raw materials is rare and expensive, the attachment mode is simple, and attachments are easy to fall off under the condition of large shearing force, so the treatment effect is influenced.

The prior art with the Chinese patent application number of CN201310382236.1 discloses a biological deodorization filler and a device, wherein the biological deodorization filler is formed by uniformly mixing biochar, mineralized garbage and polyurethane according to the mass ratio of (2-4): 3-5): 1-5, and a polyurethane filler layer formed by a layer of polyurethane material blocks is independently arranged. In the filler composition, biochar is used as a deodorant for removing the foul smell of the garbage sewage, and the improvement of the Anammox reaction efficiency by using activated carbon is not disclosed.

The prior art with Chinese patent application number of CN201520717744.5 discloses equipment for treating high-concentration ammonia nitrogen organic wastewater, wherein a first packing layer is a polyurethane biological sponge packing fixed with microorganisms and/or biological enzymes, a second packing layer is zeolite and granular activated carbon, and the working period of the zeolite is prolonged by adding the granular activated carbon.

The prior art of Chinese patent application No. CN201510697742.9 discloses a phosphorus removal filler, which is formed by bonding sponge iron and activated carbon by polyurethane foam, wherein the mass ratio of the sponge iron to the activated carbon is 1: 5-5: 1; the mass ratio of the total mass of the sponge iron and the activated carbon to the mass of the polyurethane foam is 1: 3-3: 1; the particle size of the phosphorus removal filler is 5-25 mm. This prior art relies on polyurethane foam's adhesive property self, combines sponge iron, active carbon, polyurethane foam together, has overcome the drawback that exists when sponge iron alone is as the carrier filler, can also exert electrochemistry and the easy advantage of attaching to of organic porous carrier microorganism, with the inseparabler contact of iron element, multiple effects such as make full use of microorganism effect, physical adsorption effect, chemical flocculation and precipitation, electrochemistry reach the purpose of dephosphorization. However, the sponge iron, the activated carbon and the polyurethane foam in the filler are combined by the viscosity of the polyurethane foam, so that the binding force is weak, and when the filler is impacted by water power, other filler substances in the polyurethane foam flow out along with effluent, the water quality is influenced, and the filler structure is damaged. Meanwhile, when the particles of the activated carbon and the sponge iron are large, the specific surface area is small, the efficiency is low, even if the activated carbon and the sponge iron are ground into small particles, the problem that the activated carbon and the iron powder flow out along with effluent due to weak binding force of the activated carbon and the sponge iron can also cause instability of a system, and certain limitations exist in practical application.

Disclosure of Invention

1. Problems to be solved

Aiming at the technical problem that the starting time of an Anammox reactor in the prior art is too long, the invention provides the composite biological filler for promoting rapid starting and stable operation of Anammox, and the preparation method and the application thereof, wherein the function of effectively attaching polyurethane foam to and intercepting sludge, the reduction function of iron powder and the function of promoting Anammox reaction by activated carbon are combined, the starting efficiency of Anammox is synergistically improved, and the composite biological filler has wide practical value and prospect.

2. Technical scheme

In order to solve the above problems, the present invention adopts the following technical solutions.

A composite biological filler for promoting the quick start and stable operation of anaerobic ammonia oxidation comprises a composite polyurethane filler formed by connecting activated carbon and iron powder on the surface of polyurethane foam through a cross-linking agent.

Preferably, the mass ratio of the polyurethane foam to the activated carbon to the iron powder is 150 (1-2) to 1.

Preferably, the cross-linking agent is a mixture of polyvinyl alcohol, glucomannan and calcium chloride added to distilled water.

Preferably, the mass ratio of the polyvinyl alcohol to the glucomannan to the calcium chloride is 6: (2-4): 1.

preferably, the mass ratio of the iron powder to the polyvinyl alcohol is 1: 6.

Preferably, the particle size of the activated carbon is 5-50 μm.

Preferably, the particle size of the iron powder is 0.1-0.25 mm.

The invention also provides a preparation method of the composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation, which comprises the following steps:

1) weighing polyvinyl alcohol, glucomannan and calcium chloride, adding distilled water, and mixing to form a cross-linking solution;

2) adding iron powder and activated carbon powder into the crosslinking solution obtained in the step 1) to obtain a crosslinking mixed solution;

3) adding raw materials for preparing polyurethane foam into a mould, and stirring at a high speed;

4) adding the cross-linking mixed solution in the step 2) into the reaction solution in the step 3), and continuously stirring and foaming to obtain composite polyurethane foam;

5) and (3) placing the composite polyurethane foam obtained in the step 4) in a refrigerator, and storing for 48 hours at the temperature of 0 ℃ to obtain the composite polyurethane filler.

Preferably, the raw materials for preparing the polyurethane foam are polyester polyol, polyisocyanate, water, a catalyst, a surfactant and a foaming agent, and the catalyst can be an organic amine catalyst, an organic amine catalyst or a polyamine catalyst.

Preferably, the mass ratio of the iron powder to the polyvinyl alcohol is 1: 6.

Preferably, the activated carbon powder in the step 2) is obtained by soaking in a 5% NaCl solution for 1 hour and then drying.

Preferably, the mass ratio of the polyvinyl alcohol, the glucomannan and the calcium chloride in the step 1) is 6: (2-4): 1.

Preferably, the mass ratio of the activated carbon powder to the polyvinyl alcohol in the step 2) is (1-2): 6.

preferably, the high-speed stirring time in the step 3) is 2-3 s.

The invention also provides an application of the composite biological filler for promoting rapid start and stable operation of anammox in a UASB reactor, wherein the anammox start process parameters are as follows: the starting sludge is the denitrification sludge of the sewage treatment plant and the inlet water NH₄ ⁺-N and NO₂ ^-N is 60mg/L, the hydraulic retention time HRT is 10h, and the filling volume of the composite filler accounts for 60 percent of the total volume of the reactor.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the main components of the filler of the invention are polyurethane and granular activated carbon, and the good elasticity and adsorbability of polyurethane foam are utilized as the framework of the composite filler, the polyurethane biological filler not only has the advantages of the traditional filler, but also has certain cationic active groups, hydroxyl groups and other hydrophilic groups on the surface, can be combined with microorganisms with negative charges in sewage to generate valence and bond combination, so that the sludge can be more stably attached to the surface of the filler and is not easy to lose under the shearing of water and air; the specific surface area of the activated carbon particles in the composite filler is large, so that a good growth environment can be provided for microorganisms, the electron transfer among Anammox reactions can be promoted, and the Anammox reaction efficiency is improved; the composite filler is obtained by crosslinking the active carbon in the polyurethane foaming process, so that the active carbon is directly crosslinked on the surface of polyurethane foam through a crosslinking agent, and the connection of the active carbon is more stable than that of the traditional method of directly mixing and adsorbing or bonding the active carbon on the prepared polyurethane foam, thereby not only retaining the advantages of the active carbon for film hanging and promoting the electron transfer between sludge, but also avoiding the problem that the active carbon is not firmly fixed and flows out along with effluent to block a water outlet;

(2) the addition of the iron powder in the technical scheme of the invention effectively prevents the oxidation of ferrous ions and further promotes the rapid growth of anaerobic ammonium oxidation bacteria; due to Fe²⁺Is an important component of the heme of Anammox bacteria, and sufficient Fe²⁺The concentration can promote the rapid growth of the anaerobic ammonium oxidation bacteria, so a certain amount of FeSO is often added into the inlet water of the Anammox reactor₄Etc., however, in general, ferrous ions are very easily oxidized and often become Fe in the reactor³⁺So that bacteria in a normal Anammox reactor are present against Fe²⁺The utilization rate of the Anammox reactor is low, and the addition of the iron powder in the technical scheme of the invention ensures that the added ferrous ions keep sufficient concentration, further promotes the rapid growth of anaerobic ammonium oxidation bacteria, improves the Anammox reaction efficiency and effectively shortens the starting time of the Anammox reactor; meanwhile, the iron powder is directly mixed in the crosslinking solution to be fixed on the surface of the polyurethane together with the active carbon, so that the iron powder can be uniformly distributed in the polyurethane, and the FeSO in the inlet water₄Keep higher concentration from being oxidized all the time, and the iron powder can not be oxidizedFlows out along with the effluent.

(3) According to the invention, a NaCl solution with the concentration of 5% is adopted to soak the activated carbon for 1h, and the aim of the method is to clean the surface of the activated carbon and remove dust on the surface of the activated carbon.

(4) The cross-linking agent is prepared by mixing polyvinyl alcohol, glucomannan and calcium chloride, has the advantages of capability of stably cross-linking iron powder and active carbon in polyurethane foam, low cost and easy obtainment.

(5) The particle size of the active carbon is 5-50 mu m, the active carbon can be prepared by a small-sized grinding machine, and the specific surface area of the active carbon is improved while the cost is kept low.

(6) The invention adopts the foaming process adding method to combine the polyurethane foam with the active carbon and the iron powder to form the composite polyurethane filler, and the attachment of attachments among foam gaps is more stable because of the mixed material added in the foaming process of the polyurethane foam;

(7) the composite polyurethane filler has good overall flexibility, and can be cut at will to adapt to reactors with different sizes and shapes; the whole composite polyurethane filler has stable and excellent treatment effect and strong shock load resistance, and plays a physical and chemical auxiliary role in starting anaerobic ammonia oxidation.

(8) Compared with the single polyurethane filler, the application of the composite polyurethane filler in the UASB reactor in the embodiments 1-3 of the invention shortens the starting time by 12-18 days; compared with the comparative example 1 in which polyurethane is directly bonded with activated carbon and iron powder on the prepared polyurethane foam, the perfectness of the filler is improved by about 25%.

(9) According to the invention, the activated carbon and the iron powder are directly and fixedly connected to the surface of the carrier polyurethane foam, so that the blockage caused by the outflow of the activated carbon and the iron powder along with effluent is avoided, and the problem of low water outflow speed caused by directly adopting a compact activated carbon layer is also avoided; different from the extrusion method for permeating substances such as activated carbon and the like into polyurethane foam, the method has the advantages that the adhesion of iron powder and activated carbon powder is more stable, the method can be more suitable for the impact of hydraulic load during the actual operation of the reactor, and the stability can be kept for a long time, so that the cost is saved, and the operation of frequently replacing the filler is simplified.

Drawings

FIG. 1 is a diagram showing the effect of the start-up effluent of a UASB anammox reactor equipped with the packing of example 1;

FIG. 2 is a diagram showing the effect of starting effluent of a UASB anaerobic ammonium oxidation reactor equipped with a filler formed by directly bonding polyurethane foam, iron powder and activated carbon in comparative example 1;

FIG. 3 is a diagram of the effect of starting effluent of a UASB anaerobic ammonia oxidation reactor with common polyurethane filler.

Detailed Description

The processing effect of the present invention will be further described with reference to the following specific examples, it should be noted that the parameters given in the examples are only for explaining the present invention, and have no substantial relation with the result, and the parameters, the proportions, etc. in the actual application should be selected according to the specific situation and the circumstances.

In the following examples and comparative examples, the starting and reaction conditions were the same except for the difference in the selection or preparation of the filler. The starting conditions are as follows: a UASB reactor having an effective volume of 600mL was selected as a start-up reactor for anammox. Starting sludge, namely denitrifying sludge of a sewage treatment plant and initial water inlet NH₄ ⁺-N and NO₂ ^-N is 60mg/L, and the hydraulic retention time HRT is 10 h. The total packing volume of the packing was 60% of the total volume of the reactor.

Example 1

The granulated activated carbon was weighed and the laboratory granulated activated carbon was ground to a powder of 5 μm with a small grinder. And adding the obtained powdered activated carbon into a NaCl solution with the mass concentration of 5%, soaking for 1h, washing and drying for later use. 60g of polyvinyl alcohol, 40g of glucomannan gum, 10g of calcium chloride and 10g of 0.1mm iron powder are weighed and added into 500mL of distilled water, 20g of prepared activated carbon powder is added into the solution, stirred and dissolved to form a cross-linked mixed solution, and the mixture is stirred uniformly.

Adding 50g of polyester polyol, 50g of polyisocyanate, 100g of water, 20g of tetramethylethylenediamine catalyst, 35g of surfactant and 15g of foaming agent into a container, stirring at a high speed for 2s, adding the prepared cross-linked mixed solution, continuing stirring for 2min, injecting into a mold for molding, and then placing into a refrigerator to store at 0 ℃ for 48h to obtain 200g of composite polyurethane filler.

Example 2

The granulated activated carbon was weighed and the laboratory granulated activated carbon was ground to a 20 μm powder with a small grinder. And adding the obtained powdered activated carbon into a NaCl solution with the mass concentration of 5%, soaking for 1h, washing and drying for later use. 60g of polyvinyl alcohol, 20g of glucomannan gum, 10g of calcium chloride and 10g of 0.25mm iron powder are weighed and added into 500mL of distilled water, 10g of prepared activated carbon powder is added into the solution, stirred and dissolved to form a cross-linked mixed solution, and the mixture is stirred uniformly.

Adding 50g of polyester polyol, 50g of polyisocyanate, 100g of water, 20g of tetramethylethylenediamine catalyst, 35g of surfactant and 15g of foaming agent into a container, stirring at a high speed for 3s, then adding the prepared cross-linked mixed solution, continuing stirring for 2min, injecting into a mold for molding, and then placing into a refrigerator for storage at 0 ℃ for 48h to obtain 179g of composite polyurethane filler.

Example 3

The granulated activated carbon was weighed and the laboratory granulated activated carbon was ground to a powder of 50 μm with a small grinder. And adding the obtained powdered activated carbon into a NaCl solution with the mass concentration of 5%, soaking for 1h, washing and drying for later use. 60g of polyvinyl alcohol, 30g of glucomannan gum, 10g of calcium chloride and 10g of 0.2mm iron powder are weighed and added into 500mL of distilled water, 15g of prepared activated carbon powder is added into the solution, stirred and dissolved to form a cross-linked mixed solution, and the mixture is stirred uniformly.

Adding 50g of polyester polyol, 50g of polyisocyanate, 100g of water, 20g of tetramethylethylenediamine catalyst, 35g of surfactant and 15g of foaming agent into a container, stirring at a high speed for 2.5s, then adding the prepared cross-linked mixed solution, continuously stirring for 2min, injecting into a mold for molding, and then placing into a refrigerator for storage at 0 ℃ for 48h to obtain 188g of composite polyurethane filler.

Comparative example 1

50g of polyester polyol, 50g of polyisocyanate, 100g of water, 20g of tetramethylethylenediamine catalyst, 35g of surfactant and 15g of foaming agent are added into a container, stirred at a high speed for 123 seconds and injected into a mold for molding, so as to obtain 150g of blank polyurethane foam filler.

The granulated activated carbon was weighed and the laboratory granulated activated carbon was ground to a powder of 5 μm with a small grinder.

40g of polyvinyl alcohol, 20g of glucomannan and 10g of iron powder are weighed and added into 500mL of distilled water, 10g of ground activated carbon is added, and the mixture is stirred to form a cross-linked mixed solution. And (3) putting the blank polyurethane foam into a cross-linking solution, repeatedly extruding the polyurethane foam to enable the activated carbon to be adsorbed into the foam, and then putting the foam into a refrigerator to be stored for 48 hours at the temperature of 0 ℃ to obtain the filler formed by directly bonding the polyurethane foam, the iron powder and the activated carbon.

Application of examples 1-3 and comparative example 1 in UASB anaerobic ammonia oxidation start-up reactor

The composite polyurethane fillers prepared in examples 1 to 3 and the fillers prepared in comparative example 1 by directly bonding the polyurethane foam, iron powder and activated carbon are respectively filled in four identical UASB anaerobic ammonia oxidation start-up reactors R1, R2, R3 and R4 (the effective volumes are all 600mL), and an anaerobic ammonia oxidation start-up reactor R0 of a common polyurethane filler is additionally arranged to test the start-up effect of anaerobic ammonia oxidation.

The anaerobic ammonium oxidation bacteria widely exist in denitrification sludge, anaerobic granular sludge and activated sludge of a sewage treatment plant, and the three kinds of sludge can be used as starting sludge of an anaerobic ammonium oxidation reactor; the literature indicates that the potential anammox bacteria in the denitrification sludge may be greater than the rest of the sludge, and therefore, the sludge is selected as the start-up sludge of the invention.

Starting sludge in five reactors and selecting initial influent NH of denitrifying sludge of sewage treatment plant₄ ⁺-N and NO₂ ^-N is 60mg/L, and the hydraulic retention time HRT is 10 h. The total filling volume of the composite packing accounts for 60 percent of the total volume of the reactor.

The effect of anaerobic ammoxidation reactors R1, R4 and R0 on water output over 92 days is shown in FIGS. 1, 2 and 3. Due to the bacterial autolysis phenomenon, the ammonia nitrogen in the initial effluent of the four reactors is higher than that in the water. It can be seen that the ammonia nitrogen effluent of the reactor with R1 and the composite packing prepared in example 1 is lower than the water inlet value faster and is lower than the water inlet value on the 30 th day, while the ammonia nitrogen effluent of R4 and R0 is lower than the water inlet value on the 50 th and 45 th days, namely, the anaerobic ammonia oxidation reaction in R1 filled with the composite packing prepared in example 1 is faster under the same conditions. In the whole process, the effluent ammonia nitrogen and nitrite nitrogen of R1 are slightly lower than those of R4 and R0, and the starting effect of the composite polyurethane filler prepared in the embodiment 1 of the invention on anaerobic ammonia oxidation is proved to be better than that of the filler prepared by a post-connection method in the comparative example 1.

TABLE 1

Technical effects	Common polyurethane filler	Example 1	Example 2	Example 3	Comparative example 1
						Starter	R0	R1	R2	R3	R4
Days of Start	84	66	63	72	80
						Ammonia nitrogen removal rate of 92 days	66.4％	77.1％	80.3％	72.5％	70.9％
Removal of nitrous oxide for 92 days	97.4％	99.9％	98.7％	99.1％	95.0％
						Running for 92 days	100％	97％	99％	95％	72％
92 days effluent ammonia nitrogen concentration (mg/L)	26.81	18.36	15.76	22.01	23.21
						The sub-nitrogen concentration (mg/L) of the effluent water after 92 days	2.08	0.04	1.03	0.75	4.03

As can be seen from table 1, the R1 starter of example 1 has a 18-day start-up time that is shorter than that of the R0 starter with a single polyurethane filler, and after 92 days of operation, the ammonia nitrogen removal rate of R1 is 77.1% higher than that of R0, 66.4% higher than that of R0, and the nitrite nitrogen in R1 is almost completely removed, achieving a better anaerobic ammonia oxidation level. Meanwhile, the mass and volume of the filler are hardly lost even after a long-term reaction, which shows that the composite polyurethane filler prepared in example 1 is stable in the reactor.

The R1 starter of example 1 was 14 days shorter than the R4 starter of comparative example 1, and both the ammonia nitrogen removal and the nitrous oxide removal from R1 were slightly higher than those from R4 at 92 days. In addition, after a period of operation, the filler loss in R4 was large, compared to the initial state integrity of only 72%, whereas the composite filler prepared by the method of this patent had an integrity of up to 97%, fully illustrating the stability and impact resistance of the composite polyurethane filler prepared in example 1.

Claims

1. A composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation is characterized by comprising a composite polyurethane filler formed by connecting activated carbon and iron powder on the surface of polyurethane foam through a cross-linking agent;

the cross-linking agent is a mixture of polyvinyl alcohol, glucomannan and calcium chloride added into distilled water;

the particle size of the iron powder is 0.1-0.25 mm;

the preparation method of the composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation comprises the following steps:

3) adding raw materials for preparing polyurethane foam into a mould, and stirring at a high speed to obtain a reaction solution;

5) and (3) storing the composite polyurethane foam obtained in the step 4) at 0 ℃ to obtain the composite polyurethane filler.

2. The composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation according to claim 1, wherein the mass ratio of the polyurethane foam to the activated carbon to the iron powder is 150 (1-2) to 1.

3. The composite biological filler for promoting rapid start-up and stable operation of anaerobic ammonia oxidation according to claim 1, wherein the mass ratio of the polyvinyl alcohol to the glucomannan to the calcium chloride is 6: (2-4): 1.

4. the composite biological filler for promoting rapid start-up and stable operation of anaerobic ammonia oxidation according to claim 3, wherein the mass ratio of the iron powder to the polyvinyl alcohol is 1: 6.

5. The composite biological filler for promoting the rapid start-up and stable operation of the anaerobic ammonia oxidation according to claim 1, wherein the composite polyurethane foam in the step 5) is placed in a refrigerator and is preserved for 48 hours at 0 ℃.

6. The composite biological filler for promoting the rapid start and stable operation of anaerobic ammonia oxidation according to claim 1, wherein raw materials for preparing polyurethane foam are polyester polyol, polyisocyanate, water, catalyst, surfactant and foaming agent.

7. The composite biological filler for promoting rapid start and stable operation of anaerobic ammonia oxidation according to claim 6, wherein the high-speed stirring time in the step 3) is 2-3 s.

8. The application of the composite biological filler for promoting the rapid start and the stable operation of the anaerobic ammonia oxidation in the UASB reactor according to any one of claims 1 to 4.