Direct ammoxidation coupled autotrophic denitrification sewage treatment method and bioreactor

Abstract

The invention provides a direct ammoxidation coupled autotrophic denitrification sewage treatment method and a bioreactor. The sewage treatment method by coupling direct ammonia oxidation with autotrophic denitrification comprises the following steps: sewage enters a continuous flow bioreactor, the bioreactor comprises a first-stage aerobic section, a second-stage anoxic section and a third-stage aerobic section which are arranged in sequence, a direct ammonia oxidation microbial agent is put into the first-stage aerobic section, and the third-stage aerobic section is put into the second-stage anoxic section; a ferrous sulfide autotrophic-heterotrophic denitrification filler is put into the second-stage anoxic section; the sewage comprises high-ammonia-nitrogen low-carbon-nitrogen-ratio wastewater; sewage staying in the third-stage aerobic section enters a secondary sedimentation tank and then is discharged. According to the method, no additional carbon source is needed, the sludge yield is low, and green, low-carbon and efficient treatment of the high-ammonia-nitrogen and low-carbon-nitrogen-ratio wastewater is realized.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to a sewage treatment method and a bioreactor for direct ammonia oxidation coupled with autotrophic denitrification. Background Art

[0002] High ammonia nitrogen and low carbon nitrogen ratio wastewater is widely derived from a variety of industrial production processes, including fertilizer production, monosodium glutamate manufacturing, coking industry, landfill leachate, coal gas production, and livestock and poultry farming. The ammonia nitrogen concentration of high ammonia nitrogen and low carbon nitrogen ratio wastewater is usually high while the content of biodegradable organic matter is relatively low. Traditional biochemical treatment methods such as nitrification-denitrification process usually require a high carbon nitrogen ratio and a large amount of aeration. In addition, high concentrations of ammonia nitrogen have an inhibitory effect on microbial activity, and it is necessary to improve the treatment efficiency by dilution or additional addition of carbon sources, resulting in increased operating costs.

[0003] In order to overcome the limitations of traditional biological treatment methods in treating wastewater with high ammonia nitrogen and low carbon nitrogen ratio, some new biological denitrification technologies have been proposed. Direct ammonia oxidation (Dirammox) technology is an emerging wastewater treatment technology that uses microorganisms to remove ammonia nitrogen (NH4 + -N) is directly converted into nitrogen (N2), without the need to convert NH4 + First converted into nitrite (NO2 - ) and nitrate (NO3 - ), and then reduced to nitrogen gas. Dirammox technology mainly relies on certain heterotrophic bacteria. For example, patent number CN 117903994 A discloses a strain of direct ammonia oxidizing water-producing alkaline bacillus DN-1, which has excellent treatment performance for high carbon-nitrogen ratio and high ammonia nitrogen simulated wastewater. In recent years, research on Dirammox microorganisms has mainly focused on the treatment of high carbon-nitrogen ratio wastewater on a laboratory scale. There are no reports on how to achieve Dirammox microbial enrichment and application in continuous flow reactors. In addition, when direct ammonia oxidizing bacteria are inoculated into continuous sewage with high ammonia nitrogen and low carbon-nitrogen ratio, the lack of carbon source in the wastewater causes the direct ammonia oxidizing bacteria to be at a competitive disadvantage, making it difficult for them to stably reside in the sewage.

[0004] Sulfur iron autotrophic denitrification technology is a technology that uses pyrite as an electron donor to convert NO3 - The biological denitrification technology that is reduced to nitrogen gas N2 has the advantages of no need for an external carbon source, simultaneous nitrogen and phosphorus removal, and a wide range of raw materials and low prices. Sulfur-iron autotrophic denitrification technology can effectively solve the problem of residual nitrate nitrogen in high-ammonia-nitrogen and low-carbon ratio wastewater after treatment with Dirammox technology.

[0005] Based on the above, it is urgent to study a method for treating high ammonia nitrogen and low carbon nitrogen ratio wastewater to solve the above problems. Summary of the invention

[0006] The main purpose of the present invention is to provide a sewage treatment method and a bioreactor for direct ammonia oxidation coupled with autotrophic denitrification, so as to solve the technical problem that direct ammonia oxidizing bacteria in the above-mentioned common technologies have low abundance and are difficult to reside in sewage.

[0007] To achieve the above object, the present invention provides a sewage treatment method by direct ammonia oxidation coupled with autotrophic denitrification, comprising the following steps:

[0008] The sewage enters a continuous flow bioreactor, which includes a primary aerobic section, a secondary anoxic section and a tertiary aerobic section arranged in sequence, a direct ammonia oxidizing bacteria agent is added to the primary aerobic section, and a sulfide-iron autotrophic-heterotrophic denitrification filler is added to the secondary anoxic section; the sewage includes high ammonia nitrogen and low carbon-nitrogen ratio wastewater;

[0009] The filling ratio of the direct ammonia oxidizing bacteria agent in the primary aerobic section is 5% to 50%, and the filling volume ratio of the sulfide-iron autotrophic-heterotrophic denitrification filler in the secondary anoxic section is 10% to 30%; the composition of the direct ammonia oxidizing bacteria agent includes a slow-release carbon source, zeolite and a direct ammonia oxidizing bacteria mixture; the mass ratio of the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source is 10% to 20%: 30% to 50%: 40% to 50%;

[0010] The hydraulic retention time of the primary aerobic section is controlled to be 18 to 36 hours, the hydraulic retention time of the secondary anoxic section is controlled to be 6 to 12 hours, and the hydraulic retention time of the tertiary aerobic section is 1 to 2 hours. The sewage that has stayed in the tertiary aerobic section enters the secondary sedimentation tank and then is discharged.

[0011] Furthermore, the ammonia nitrogen content in the high ammonia nitrogen and low carbon nitrogen ratio wastewater is between 300 and 2000 mg / L, and the carbon nitrogen ratio is less than 2.86.

[0012] Furthermore, the preparation method of the pyrite autotrophic-heterotrophic denitrification filler comprises: adding pyrite powder to a molten degradable plastic, extruding and granulating, to obtain the pyrite autotrophic-heterotrophic denitrification filler;

[0013] The particle size of the pyrite powder is not greater than 100 μm, the mass proportion of the pyrite in the pyrite autotrophic-heterotrophic denitrification filler is 60% to 80%, and the mass proportion of the degradable plastic is 20% to 40%.

[0014] Furthermore, the slow-release carbon source includes one or more of peat, rice husk, straw, and degradable plastics, the direct ammonia oxidizing bacteria mixture includes direct ammonia oxidizing bacteria, and the direct ammonia oxidizing bacteria include one or more of Alcaligenes, Bacillus, Acinetobacter, Klebsiella, Pseudomonas, and Rhodococcus with direct ammonia oxidation ability.

[0015] Furthermore, the acquisition of the direct ammonia oxidizing bacteria mixture comprises the steps of:

[0016] Inoculating activated sludge containing the direct ammonia oxidizing bacteria into a reaction tank, and introducing the sewage containing 0.005% to 1% by mass of hydroxylamine into the reaction tank; controlling the residence time of the sewage in the reaction tank to 12 to 48 hours, and controlling the dissolved oxygen in the reaction tank to 2 to 5 mg / L;

[0017] When the total nitrogen removal rate of the effluent water is higher than 80%, the effluent mud-water mixture of the reaction tank is centrifuged at a speed of 6000-8000 r / min to obtain the centrifugal product, which is the direct ammonia oxidizing bacteria mixture.

[0018] Furthermore, the preparation of the direct ammonia oxidizing bacteria agent includes the steps of: mixing and granulating the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source to obtain the direct ammonia oxidizing bacteria agent, and the particle size of the direct ammonia oxidizing bacteria agent is 0.5 to 3 mm.

[0019] Furthermore, before adding the direct ammonia oxidizing bacteria agent into the primary aerobic section, the activated sludge concentration of the primary aerobic section is controlled to be 3000-5000 mg / L.

[0020] Furthermore, the dissolved oxygen in the primary aerobic section is 1-2 mg / L, the dissolved oxygen in the secondary anoxic section is no more than 0.5 mg / L, and the dissolved oxygen in the tertiary aerobic section is 2-4 mg / L.

[0021] Furthermore, the direct ammonia oxidizing bacteria agent and the sulfide-iron autotrophic-heterotrophic denitrification filler are respectively suspended in the primary aerobic section and the secondary anoxic section through cage filling.

[0022] The present invention provides a bioreactor, which is applied to the direct ammonia oxidation coupled autotrophic denitrification sewage treatment method as described in any one of the above, and the rear end is connected to the secondary sedimentation tank, comprising a primary aerobic section, a secondary anoxic section and a tertiary aerobic section connected in sequence;

[0023] The first aerobic section is suspended with a cage-filled direct ammonia oxidizing bacteria agent, and the second anoxic section is suspended with a cage-filled ferrosulphide autotrophic-heterotrophic denitrification filler; the filling ratio of the direct ammonia oxidizing bacteria agent in the first aerobic section is 5% to 50%, and the filling ratio of the ferrosulphide autotrophic-heterotrophic denitrification filler in the second anoxic section is 10% to 30%; the direct ammonia oxidizing bacteria agent is composed of a slow-release carbon source, zeolite and direct ammonia oxidizing bacteria;

[0024] When the direct ammonia oxidizing bacteria agent is added to the primary aerobic section, the concentration of activated sludge in the primary aerobic section is 4000-8000 mg / L;

[0025] The dissolved oxygen in the first-stage aerobic section is controlled at 1-2 mg / L, the dissolved oxygen in the second-stage anoxic section is controlled at less than 0.5 mg / L, and the dissolved oxygen in the third-stage aerobic section is controlled at 2-4 mg / L.

[0026] The beneficial effects of the present invention are as follows:

[0027] The present invention provides a sewage treatment method, which couples the direct ammonia oxidation section and the autotrophic denitrification section, solving the technical problem that when the organic carbon source is insufficient, the denitrification effect of direct ammonia oxidizing bacteria is limited, and part of the ammonia nitrogen is converted into nitrate nitrogen, resulting in an increase in the total nitrogen in the effluent. Among them, the pyrite autotrophic denitrification technology is a method of using pyrite as an electron donor to convert NO3 - The biological denitrification technology that is reduced to nitrogen gas N2 has the advantages of no need for an external carbon source, simultaneous nitrogen and phosphorus removal, and a wide range of raw materials and low prices. Sulfur-iron autotrophic denitrification technology can effectively solve the problem of residual nitrate nitrogen in high-ammonia-nitrogen and low-carbon-nitrogen ratio wastewater after direct ammonia oxidation technology treatment.

[0028] In addition, the iron ions released during the autotrophic denitrification process of ferrosulfur can further enhance the removal of total phosphorus in the system.

[0029] The present invention uses a method of preparing an immobilized bacterial agent to compound a slow-release carbon source, zeolite and direct ammonia oxidizing bacteria into a direct ammonia oxidizing bacterial agent, thereby achieving high abundance and long-term residence of direct ammonia oxidizing bacteria in continuous flow sewage. Direct ammonia oxidizing bacteria can directly utilize the limited carbon source in the influent under hypoxic conditions to directly convert ammonia nitrogen into nitrogen gas for removal; the incorporation of a slow-release carbon source effectively improves the activity of direct ammonia oxidizing bacteria in low-carbon wastewater with a high ammonia nitrogen ratio, and direct ammonia oxidizing bacteria are in a dominant position in the competition with nitrifying bacteria, and the released carbon source can be directly utilized by direct ammonia oxidizing bacteria for denitrification; zeolite has selective adsorption for ammonia nitrogen in sewage, and can specifically accelerate the enrichment of ammonia nitrogen on the surface of microbial preparations, increase the contact between ammonia nitrogen and direct ammonia oxidizing bacteria, and greatly improve the treatment efficiency.

[0030] The present invention does not require an external carbon source, has a low sludge yield, and does not release greenhouse gas N2O in the direct ammonia oxidation process and the sulfide-iron autotrophic denitrification process, thereby achieving green, low-carbon and efficient treatment of wastewater with high ammonia nitrogen and low carbon-nitrogen ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0032] Figure 1 Schematic diagram of the structure of a bioreactor in one embodiment of the present invention.

[0033] Figure 2 This is a diagram showing the effect of ammonia nitrogen removal in Example 3 of the present invention.

[0034] Figure 3 This is a diagram showing the total nitrogen removal effect in Example 3 of the present invention.

[0035] Figure 4 This is a diagram showing the total nitrogen removal effect along the process in Example 3 of the present invention.

[0036] Figure 5 This is a diagram of the microbial diversity analysis in Examples 4 to 6 of the present invention.

[0037] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0041] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] The direct ammonia oxidizing bacteria in the commonly used technology are directly inoculated into high ammonia nitrogen and low carbon nitrogen ratio wastewater, but the treatment effect is not good. The reasons are as follows: In the conventional activated sludge system, the abundance of Dirammox bacteria is extremely low (a few ten thousandths), and it is difficult to achieve stable enhanced denitrification. At present, introducing exogenous bacteria into the activated sludge system to enhance nitrogen removal is an effective way, but when exogenous bacteria are added to the sludge, they are prone to niche overlap with indigenous microorganisms, and their adaptability and competitiveness are not as good as those of indigenous microorganisms; in addition, Dirammox bacteria are heterotrophic bacteria, which show good performance at high C / N ratios (>10), but are at a competitive disadvantage in low C / N systems, which limits their application in low C / N ratio wastewater.

[0043] The present invention provides a sewage treatment method by direct ammonia oxidation coupled with autotrophic denitrification, comprising the following steps:

[0044] S1. The sewage enters a continuous flow bioreactor, wherein the bioreactor comprises a primary aerobic section and a secondary anoxic section arranged in sequence, a direct ammonia oxidizing bacteria agent is added to the primary aerobic section, and a sulfide-iron autotrophic-heterotrophic denitrification filler is added to the secondary anoxic section; the sewage comprises high ammonia nitrogen and low carbon-nitrogen ratio wastewater;

[0045] Wherein, the filling ratio of the direct ammonia oxidizing bacteria agent in the primary aerobic section is 5% to 50%, and the filling ratio of the sulfide-iron autotrophic-heterotrophic denitrification filler in the secondary anoxic section is 10% to 30%.

[0046] In some embodiments, the direct ammonia oxidizing bacteria and the sulfide-iron autotrophic-heterotrophic denitrification filler can be fixed in the primary aerobic section and the secondary aerobic section respectively by physical fixation.

[0047] S2. Control the hydraulic retention time of the primary aerobic section to 18 to 36 hours, and control the hydraulic retention time of the secondary anoxic section to 6 to 12 hours. The sewage that has stayed in the secondary anoxic section enters the secondary sedimentation tank and then is discharged to achieve sewage purification.

[0048] The rear end of the continuous flow bioreactor is connected to the secondary sedimentation tank, including a primary aerobic section, a secondary anoxic section and a tertiary aerobic section connected in sequence; wherein the primary aerobic section is suspended with a cage-filled direct ammonia oxidizing bacteria agent, and the secondary anoxic section is suspended with a cage-filled ferrosulphide autotrophic-heterotrophic denitrification filler; the filling ratio of the direct ammonia oxidizing bacteria agent in the primary aerobic section is 5% to 50%, and the filling ratio of the ferrosulphide autotrophic-heterotrophic denitrification filler in the secondary anoxic section is 10% to 30%; the composition of the direct ammonia oxidizing bacteria agent includes a slow-release carbon source, zeolite and a direct ammonia oxidizing bacteria mixture; the mass ratio of the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source is 10% to 20%: 30% to 50%: 40% to 50%;

[0049] The dissolved oxygen in the primary aerobic section is controlled at 1-2 mg / L, the dissolved oxygen in the secondary anoxic section is controlled at less than 0.5 mg / L, and the dissolved oxygen in the tertiary aerobic section is controlled at 2-4 mg / L. In some embodiments, the ammonia nitrogen content in the high ammonia nitrogen and low carbon nitrogen ratio wastewater is 300-2000 mg / L, and the carbon nitrogen ratio is less than 2.86.

[0050] In some embodiments, the direct ammonia oxidizing bacteria and the sulfide-iron autotrophic-heterotrophic denitrification filler can be directly put into a traditional sewage reactor, and the above parameters can be controlled.

[0051] By cage-loading direct ammonia oxidizing bacteria and ferrosulphide autotrophic-heterotrophic denitrification fillers, the filler cage materials can be frequently replaced. When replacement is required, the filler cage can be directly removed by a crane or a crane, and reset after replacement to ensure the use status of the direct ammonia oxidizing bacteria and ferrosulphide autotrophic-heterotrophic denitrification fillers. The replacement cycle of the direct ammonia oxidizing bacteria can be one year.

[0052] Exemplarily, the "sewage entering a continuous flow bioreactor" may mean that the sewage enters a bioreactor whose aerobic section and anoxic section are respectively equipped with direct ammonia oxidizing bacteria and sulfide-iron autotrophic-heterotrophic denitrification filler, or that direct ammonia oxidizing bacteria and sulfide-iron autotrophic-heterotrophic denitrification filler are respectively added into the aerobic section and anoxic section of the bioreactor containing sewage.

[0053] In some embodiments, before adding the direct ammonia oxidizing bacteria agent into the primary aerobic stage, the activated sludge concentration of the primary aerobic stage is controlled to be 3000-5000 mg / L.

[0054] High concentrations of ammonia nitrogen have an inhibitory effect on the activity of nitrifying bacteria, while direct ammonia oxidizing bacteria have a high tolerance to ammonia. Combined with the use of slow-release carbon sources, the competitiveness of direct ammonia oxidizing bacteria in the aerobic stage is guaranteed, and direct ammonia oxidizing bacteria can achieve exclusive growth in high-ammonia nitrogen wastewater. In common technologies, the combination of anaerobic ammonium oxidation and aerobic / anaerobic digestion is considered to be an effective method for simultaneously removing organic matter and ammonia from high-ammonia nitrogen wastewater and recovering resources. However, too much organic matter entering the anaerobic ammonium oxidation system will cause overgrowth of denitrifying bacteria, resulting in inhibition of the anaerobic ammonium oxidation process, leading to denitrification failure. Direct ammonia oxidation technology provides an alternative to the complex coupling process in the treatment of high-ammonia nitrogen wastewater, replacing it with a one-step aerobic process.

[0055] The direct ammonia oxidizing bacteria agent is composed of a slow-release carbon source, zeolite and direct ammonia oxidizing bacteria.

[0056] Exemplarily, the preparation of the direct ammonia oxidizing bacteria agent may include the steps of: mixing and granulating the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source to obtain the direct ammonia oxidizing bacteria agent, and the particle size of the direct ammonia oxidizing bacteria agent may be 0.5 to 3 mm.

[0057] In some embodiments, the slow-release carbon source includes one or more of peat, rice husks, straw, and degradable plastics, and the direct ammonia oxidizing bacteria include one or more of Alcaligenes, Bacillus, Acinetobacter, Klebsiella, Pseudomonas, and Rhodococcus with direct ammonia oxidation ability.

[0058] The degradable plastic may be powder of discarded degradable plastic.

[0059] The addition of slow-release carbon sources can effectively enhance the activity of direct ammonia oxidizing bacteria in low carbon-nitrogen ratio wastewater. The released carbon sources can be directly utilized by direct ammonia oxidizing bacteria for denitrification. Among them, the application of waste degradable plastic powder can realize the resource utilization of solid waste.

[0060] Zeolite has selective adsorption for ammonia nitrogen in sewage, which can accelerate the enrichment of ammonia nitrogen on the surface of direct ammonia oxidizing bacteria, increase the contact between ammonia nitrogen and direct ammonia oxidizing bacteria, and greatly improve the treatment efficiency.

[0061] Direct ammonia oxidizing bacteria directly oxidize ammonia to dinitrile gas under aerobic conditions and have strong tolerance to high ammonia nitrogen and high pH values. Direct ammonia oxidizing bacteria can directly convert ammonia nitrogen into hydroxylamine as a growth substrate, and directly convert hydroxylamine into dinitrile gas or nitrogen. Alcaligenes is a dominant species among direct ammonia oxidizing bacteria and has good adaptability to pH ranges from 8 to 10.

[0062] In some embodiments, obtaining direct ammonia oxidizing bacteria comprises the steps of:

[0063] S11. Inoculate the activated sludge containing the direct ammonia oxidizing bacteria into a reaction tank, introduce the sewage containing 0.005% to 1% by mass of hydroxylamine into the reaction tank, and adjust the COD / ammonia nitrogen of the sewage to 10 to 20 by adding a carbon source before entering the reaction tank; control the residence time of the sewage in the reaction tank to 12 to 48 hours, and control the dissolved oxygen in the reaction tank to 2 to 5 mg / L.

[0064] In some embodiments, the mass fraction of hydroxylamine in the sewage may be 0.05% to 0.5%.

[0065] S12. When the total nitrogen removal rate of the effluent is higher than 80%, the treated sewage is centrifuged at a speed of 6000 to 8000 r / min to obtain the centrifugal product, which is the direct ammonia oxidizing bacteria mixture.

[0066] The present invention adopts an in-situ enrichment method to prepare a direct ammonia oxidizing bacteria group with strong stability.

[0067] The sewage is the high-ammonia-nitrogen and low-carbon-nitrogen ratio wastewater in step S1.

[0068] In some embodiments, the preparation method of the pyrite autotrophic-heterotrophic denitrification filler includes: adding pyrite to a molten degradable plastic, extruding and granulating to obtain the pyrite autotrophic-heterotrophic denitrification filler, wherein the particle size of the pyrite is not greater than 100um, the mass proportion of the pyrite in the pyrite autotrophic-heterotrophic denitrification filler is 60% to 80%, and the mass proportion of the degradable plastic is 20% to 40%.

[0069] In some specific embodiments, after the high-ammonia-nitrogen and low-carbon-nitrogen ratio wastewater enters the primary aerobic section, due to the inhibitory effect of high ammonia-nitrogen on nitrifying bacteria and the nutrient supply of the slow-release carbon source, the direct ammonia oxidizing bacteria show a significant growth advantage in the primary aerobic section. The growing zeolite selectively adsorbs ammonia-nitrogen and enriches it on the surface of the direct ammonia oxidizing bacteria agent, and the direct ammonia oxidizing bacteria rapidly converts the ammonia-nitrogen into nitrogen gas.

[0070] As the high concentration of ammonia nitrogen in the sewage is reduced by the action of direct ammonia oxidizing bacteria, its inhibitory effect on nitrifying bacteria in the activated sludge is weakened, and part of the ammonia nitrogen is converted into nitric nitrogen by nitrifying bacteria. It should be noted that as the direct ammonia oxidizing bacteria multiply in large quantities, some of the direct ammonia oxidizing bacteria are desorbed from the zeolite and scattered in the sewage system, making the activated sludge a functional sludge with a combination of direct ammonia oxidation and nitrification, ensuring the biochemical reactor's ability to treat continuous flow sewage.

[0071] When the sewage enters the secondary anoxic section, the pyrite autotrophic-heterotrophic denitrifying bacteria and heterotrophic denitrifying bacteria show a growth trend that is evenly matched, as the pyrite autotrophic-heterotrophic denitrifying filler supplies pyrite and carbon source in the sewage system at the same time. A pyrite autotrophic-heterotrophic denitrification composite system is constructed, which can effectively and synergistically achieve efficient removal of nitrate nitrogen under low-carbon conditions. The iron ions released during the pyrite autotrophic denitrification process can complex phosphorus and enhance the removal of total phosphorus in the system. In addition, the introduction of degradable plastics as a slow-release carbon source can compensate for the consumption of alkalinity by pyrite autotrophic denitrification through heterotrophic nitrification, maintain the pH balance of the system, and use the flocculation ability of hydroxyl iron to enhance the sedimentation effect of sludge.

[0072] In the above process, no external carbon source is required, the sludge yield is low, and the direct ammonia oxidation process and the sulfide-iron autotrophic denitrification process do not release the greenhouse gas N2O, thus achieving green, low-carbon and efficient treatment of wastewater with a high ammonia-nitrogen carbon-nitrogen ratio.

[0073] For example, the dissolved oxygen in the primary aerobic section is 1-2 mg / L, the dissolved oxygen in the secondary anoxic section is no more than 0.5 mg / L, and the dissolved oxygen in the tertiary aerobic section is 2-4 mg / L. Direct ammonia oxidizing bacteria have a high utilization rate of dissolved oxygen, and the removal of ammonia nitrogen can be ensured by controlling the concentration at a lower level in the primary aerobic section, effectively reducing the aeration energy consumption in the sewage treatment process; the DO in the anoxic section is controlled to be less than 0.5 mg / L in order to eliminate the inhibitory effect of high dissolved oxygen on denitrification and achieve sufficient removal of nitrate nitrogen.

[0074] In some embodiments, the bioreactor further comprises a tertiary aerobic section connected to the secondary anoxic section, the tertiary aerobic section receives the secondary anoxic section and the secondary sedimentation tank, and the hydraulic retention time of the tertiary aerobic section is 1 to 2 hours.

[0075] Short-term aeration in the tertiary aerobic section can further remove organic matter and total phosphorus from the sewage.

[0076] The step of discharging the sewage after the sewage has stayed in the secondary anoxic section after entering the secondary sedimentation tank comprises: the sewage after the sewage has stayed in the secondary anoxic section passes through the tertiary aerobic section and then enters the secondary sedimentation tank, and the hydraulic retention time of the tertiary aerobic section is 1 to 2 hours.

[0077] In some embodiments, the sewage that has stayed in the secondary anoxic section enters the secondary sedimentation tank after passing through the tertiary aerobic section, including: when the nitrate-nitrogen content in the sewage treated in the tertiary aerobic section is higher than 10 mg / L, the sewage is returned to the anoxic zone for further treatment to ensure complete removal of nitrate-nitrogen;

[0078] When the nitrate-nitrogen content in the sewage after treatment in the tertiary aerobic stage is lower than 10 mg / L, the sewage enters the secondary sedimentation tank and is discharged.

[0079] For further understanding of the present invention, examples are given below:

[0080] Example 1 Preparation of direct ammonia oxidizing bacteria agent

[0081] Inoculate activated sludge containing direct ammonia oxidizing bacteria into a reaction tank, introduce sewage containing 0.1% by mass of hydroxylamine into the reaction tank, and adjust the COD / ammonia nitrogen of the sewage to 10-15 by adding a carbon source before entering the reaction tank; control the residence time of the sewage in the reaction tank to 24 hours, and control the dissolved oxygen in the reaction tank to 2-5 mg / L;

[0082] When the total nitrogen removal rate of the effluent is higher than 80%, the treated mud-water mixture is centrifuged at a speed of 6000 r / min to obtain the centrifugal product, which is the direct ammonia oxidizing bacteria mixture.

[0083] The direct ammonia oxidizing bacteria mixture, zeolite and waste biodegradable plastic powder are mixed in a weight proportion of 10%, 40% and 50% respectively, and granulated by gluing to obtain a direct ammonia oxidizing bacteria agent with a particle size controlled at 2 to 3 mm.

[0084] Example 2 Preparation of Sulfur-Iron Autotrophic-Heterotrophic Denitrification Filler

[0085] The pyrite is screened out through wet ball milling to obtain powder with a particle size of less than 100um, and the powder is added to the molten biodegradable plastic, wherein the mass proportions of the pyrite powder and the biodegradable plastic are 60% and 40% respectively. After extrusion granulation, the particle size is controlled at 2-3mm to obtain pyrite autotrophic-heterotrophic denitrification filler.

[0086] Example 3 Continuous Flow Test

[0087] The gasification effluent from a coal chemical plant was taken as the treatment object. The inlet water quality parameters were as follows: the inlet ammonia nitrogen concentration was 390.4-559 mg / L, the inlet COD was 400-941.9 mg / L, and the COD / ammonia nitrogen was 1.87, which is a typical inlet water with high ammonia nitrogen and low carbon nitrogen ratio.

[0088] First, a set of direct ammonia oxidation coupled autotrophic denitrification bioreactor was built, including the first aerobic section, the second anoxic section, the third aerobic section and the tail secondary sedimentation tank connected in sequence. Among them, the first aerobic section is suspended with cage-filled direct ammonia oxidizing bacteria, with a filling ratio of 40%; the second anoxic section is suspended with cage-filled sulfide iron autotrophic-heterotrophic denitrification filler, with a filling ratio of 20%. 。

[0089] The sludge concentration is controlled at 4000-5000 mg / L, the hydraulic retention time of the primary aerobic section is controlled at 24h, the hydraulic retention time of the secondary anoxic section is controlled at 8h, and the hydraulic retention time of the tertiary aerobic section is controlled at 1h; the dissolved oxygen in the primary aerobic section is controlled at 1-2 mg / L, the dissolved oxygen in the secondary anoxic section is controlled at less than 0.5 mg / L, and the dissolved oxygen in the tertiary aerobic section is controlled at 2-3 mg / L. The sewage that has stayed in the tertiary aerobic section enters the secondary sedimentation tank and then effluent. After the operation is stable, continuous sampling is carried out for 42 days for inlet and outlet water testing ( Figure 2 , Figure 3 ), and at the same time, samples were taken from the primary aerobic section, the secondary anoxic section, the tertiary aerobic section and the effluent from the secondary sedimentation tank for testing ( Figure 4 ) to evaluate the contribution of each segment to nitrogen removal.

[0090] Depend on Figure 2 It can be seen that the effluent ammonia nitrogen is between 1.3 and 6.7 mg / L, with an average of 3.98 mg / L; the effluent total nitrogen is between 5.2 and 9.8 mg / L, with an average of 7.59 mg / L, achieving efficient purification of high ammonia nitrogen and low carbon nitrogen ratio coal chemical wastewater. Figure 4It can be seen that the total nitrogen shows a gradual downward trend along the process. In the primary aerobic section, 84.5% of the effective removal is achieved through direct ammonia oxidation by direct ammonia oxidizing bacteria. The nitrate nitrogen converted by nitrifying bacteria in the activated sludge enters the secondary anoxic section, and 13.7% of the nitrogen is removed through the synergistic effect of ferrosulfur autotrophic-anomalous denitrification.

[0091] Example 4: Dosage of Hydroxylamine Compounds

[0092] In this embodiment, the inoculated sludge is taken to the aerobic end of a biochemical reaction tank of a sewage plant, and the inoculated sludge concentration of the SBR reactor is 500 mg / L, and the MLVSS / MLSS of the sludge is 0.49. The SBR reactor completes the basic processes of water intake, aeration, sedimentation, drainage and standby in a single reaction tank in chronological order to achieve biochemical treatment of wastewater. The operation cycle of the SBR process includes water intake process, aeration process, sedimentation process, drainage process and standby time.

[0093] In order to systematically evaluate the enrichment effect of hydroxylamine compounds on direct ammonia oxidizing bacteria, 4 sets of SBR reactors were set up to simulate enrichment tanks for testing, of which A0 was the blank group without hydroxylamine; the control group A1 had a hydroxylamine dosage of 0.002%; the experimental group A2 had a hydroxylamine dosage of 0.1%; and the control group A3 had a hydroxylamine dosage of 5%. The influent of this experiment was simulated wastewater. The water quality index range is approximately: NH4 + -N: 50~70mg / L, COD: 400~600mg / L.

[0094] The initial operating parameter settings of the reactor are shown in Table 1, where a peristaltic pump is used for water inlet during the water inlet stage, and the water inlet time is 10 minutes. In the aerobic stage, a stirrer is used to drive the stirring paddle for stirring, and the stirring speed is 120rpm. The dissolved oxygen in the process is controlled to 2-5mg / L. In the sedimentation stage, this stage is a static stage, and the stirrer and aeration pump do not work during the process. In the decanting stage, a peristaltic pump is used to discharge water, and the decanter is lowered to the set height of the reactor to pump the clear liquid out of the reactor through the pump tube to complete the water discharge. After 7 cycles of stable operation, samples were sent to detect the microbial diversity in the effluent NH4+-N, TN and mixed liquid.

[0095] Table 1 Reactor initial operating parameters

[0096]

[0097] As shown in Table 2, the removal rate of NH4+-N in the experimental group A2 was 99.45%, which was higher than 96.08%, 13.08% and 95.82% in the control group A1, A3 and blank group A0; the removal rate of TN in the experimental group A2 was 92.83%, the removal rate of TN in the control group A1 was 10.67%, and there was basically no TN removal in the control group A3 and blank group A0. TN usually needs to be removed by denitrification under anoxic conditions, while A2 can achieve efficient removal of TN under aerobic conditions, which indirectly indicates that microbial flora with direct ammonia oxidation function are enriched in the system; A1 did not inhibit other types of microorganisms due to too low hydroxylamine concentration; A3 caused the death of microorganisms in the system due to too high hydroxylamine concentration.

[0098] Microbial diversity analysis was performed on samples from each group. Figure 5 , the circled mark is the abundance value of direct ammonia nitrogen bacteria Alcaligenes. Figure 5 It can be seen that the abundance of direct ammonia oxidizing bacteria Alcaligenes in the experimental group A2 increased from 0.023% in the blank group A0 to 60.307%, which was much higher than 0.191% in the control groups A1 and 0.076% in A3.

[0099] Table 2 NH4+-N and TN in effluent under different dosages of hydroxylamine compounds

[0100] A0 A1 A2 A3 Outlet NH4+-N (mg / L) 2.51 2.35 0.45 39.68 Outlet TN (mg / L) 58.8 53.6 4.6 59.13

[0101] Example 5: Hydroxylamine compound types

[0102] In order to systematically evaluate the enrichment effect of hydroxylamine compound types on direct ammonia oxidizing bacteria, two sets of SBR reactors were set up to simulate enrichment tanks for testing, in which hydroxylamine sulfate was added to B1 and diethylhydroxylamine was added to B2. Except for the type of hydroxylamine compound, the operating parameters in this example were consistent with those of the test group A2 in Example 1.

[0103] Microbial diversity analysis was performed on samples from each group. Figure 5 .Depend on Figure 5 It can be seen that the abundance of direct ammonia oxidizing bacteria Alcaligenes in the B1 and B2 reactors increased from 0.023% of the blank group A0 to 53.819% and 78.963%, respectively, both achieving efficient enrichment of direct ammonia oxidizing bacteria.

[0104] Example 6: Influent COD / NH4 + -N

[0105] Evaluate influent COD / NH4 for the system +-N enrichment effect on direct ammonia oxidizing bacteria, two sets of SBR reactors were set up to simulate enrichment tanks for testing, and different ratios of COD / NH4 were configured by adjusting the COD content in the simulated wastewater. + -N influent, COD / NH4 of C1 influent + -N is 5; COD / NH4 of C2 influent + -N is 20. In this embodiment, the operating parameters are COD / NH4 + -N is inconsistent, and the other operating parameters are consistent with those of test group A2 in Example 1.

[0106] Microbial diversity analysis was performed on samples from each group. Figure 5 .Depend on Figure 5 It can be seen that the abundance of direct ammonia oxidizing bacteria Alcaligenes in the C1 reactor increased from 0.023% in the blank group A0 to 9.75%, which is much lower than 83.493% in C2. + -N can quickly increase the enrichment of direct ammonia oxidizing bacteria in the enrichment tank, thereby achieving stable supplementation of mainstream bacteria and realizing stable aerobic ammonia oxidation denitrification of the mainstream system.

[0107] In order to further verify the technical advantages of this application, the design comparison test is set as follows:

[0108] The other parameters of Comparative Example 1 are consistent with those of Example 3, except that the zeolite in the direct ammonia oxidizer is replaced by diatomaceous earth.

[0109] The other parameters of Comparative Example 2 are consistent with those of Example 3, except that the pyrite autotrophic-heterotrophic denitrification filler is replaced by a pyrite block filler.

[0110] The other parameters of Comparative Example 3 are consistent with those of Example 3, except that the direct ammonia oxidizing bacteria agent is not suspended, and the direct ammonia oxidizing bacteria mixture is directly added.

[0111] The average removal rates of ammonia nitrogen and total nitrogen and the results of anoxic terminal pH are shown in Table 3:

[0112] Table 3 Nitrogen and total nitrogen average removal rates and pH at the end of anoxic conditions in Example 3 and Comparative Examples 1 to 3

[0113] Ammonia nitrogen removal rate (%) Total nitrogen removal rate (%) Anoxic terminal pH Example 3 99.08％ 98.34％ 7.5～8.6 Comparative Example 1 91.32％ 89.23％ 7.6～8.5 Comparative Example 2 98.15％ 91.2％ 6.5～7.2 Comparative Example 3 77.66％ 71.23％ 7.2～8.5

[0114] According to the test results in Table 3, the direct ammonia oxidizing bacteria agent prepared by enriching the direct ammonia oxidizing bacteria mixture in the activated sludge of the plant area with hydroxylamine and combining it with the slow-release carbon source and zeolite can directly oxidize ammonia into dinitro gas or nitrogen in the primary aerobic stage. Among them, the selective adsorption of ammonia nitrogen by zeolite has a better ammonia nitrogen removal efficiency than the direct ammonia oxidizing bacteria agent prepared by diatomaceous earth; and the slow-release carbon source compound provides a growth substrate for direct ammonia oxidizing bacteria while realizing resource utilization.

[0115] In Comparative Example 2, the pH at the end of anoxic period decreased due to the influence of sulfur autotrophic denitrification, and external alkalinity supplementation was required to stabilize the system; while in Comparative Example 3, direct ammonia oxidation mixture was directly added, and the direct ammonia oxidizing bacteria were at a competitive disadvantage in the system, and the effluent quality was far worse than that in the embodiment.

[0116] In summary, the wastewater treatment method and bioreactor of direct ammonia oxidation coupled with autotrophic denitrification provided in the present application provide a new solution for the removal of high ammonia nitrogen and low carbon-nitrogen ratio wastewater.

[0117] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A sewage treatment method by direct ammonia oxidation coupled with autotrophic denitrification, characterized in that: The following steps are involved: The sewage enters a continuous flow bioreactor, which includes a primary aerobic section, a secondary anoxic section and a tertiary aerobic section arranged in sequence, a direct ammonia oxidizing bacteria agent is added to the primary aerobic section, and a sulfide-iron autotrophic-heterotrophic denitrification filler is added to the secondary anoxic section; the sewage includes high ammonia nitrogen and low carbon-nitrogen ratio wastewater; The filling ratio of the direct ammonia oxidizing bacteria agent in the primary aerobic section is 5% to 50%, and the filling volume ratio of the sulfide-iron autotrophic-heterotrophic denitrification filler in the secondary anoxic section is 10% to 30%; the composition of the direct ammonia oxidizing bacteria agent includes a slow-release carbon source, zeolite and a direct ammonia oxidizing bacteria mixture; the mass ratio of the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source is 10% to 20%: 30% to 50%: 40% to 50%; The hydraulic retention time of the primary aerobic section is controlled to be 18 to 36 hours, the hydraulic retention time of the secondary anoxic section is controlled to be 6 to 12 hours, and the hydraulic retention time of the tertiary aerobic section is 1 to 2 hours. The sewage that has stayed in the tertiary aerobic section enters the secondary sedimentation tank and then is discharged.

2. The sewage treatment method according to claim 1, characterized in that: The ammonia nitrogen content in the high-ammonia nitrogen and low-carbon-nitrogen ratio wastewater is 300-2000 mg / L, and the carbon-nitrogen ratio is less than 2.

86.

3. The sewage treatment method according to claim 2, characterized in that: The preparation method of the pyrite autotrophic-heterotrophic denitrification filler comprises: adding pyrite powder to a molten degradable plastic, extruding and granulating, and obtaining the pyrite autotrophic-heterotrophic denitrification filler; The particle size of the pyrite powder is not greater than 100 μm, the mass proportion of the pyrite in the pyrite autotrophic-heterotrophic denitrification filler is 60% to 80%, and the mass proportion of the degradable plastic is 20% to 40%.

4. The sewage treatment method according to claim 3, characterized in that: The slow-release carbon source includes one or more of peat, rice husk, straw, and degradable plastics; the direct ammonia oxidizing bacteria mixture includes direct ammonia oxidizing bacteria; and the direct ammonia oxidizing bacteria include one or more of Alcaligenes, Bacillus, Acinetobacter, Klebsiella, Pseudomonas, and Rhodococcus with direct ammonia oxidation ability.

5. The sewage treatment method according to claim 4, characterized in that: The acquisition of the direct ammonia oxidizing bacteria mixture comprises the steps of: Inoculating activated sludge containing the direct ammonia oxidizing bacteria into a reaction tank, and introducing the sewage containing 0.005% to 1% by mass of hydroxylamine into the reaction tank; controlling the residence time of the sewage in the reaction tank to 12 to 48 hours, and controlling the dissolved oxygen in the reaction tank to 2 to 5 mg / L; When the total nitrogen removal rate of the effluent water is higher than 80%, the effluent mud-water mixture of the reaction tank is centrifuged at a speed of 6000-8000 r / min to obtain the centrifugal product, which is the direct ammonia oxidizing bacteria mixture.

6. The sewage treatment method according to claim 5, characterized in that: The preparation of the direct ammonia oxidizing bacteria agent comprises the steps of: mixing and granulating the direct ammonia oxidizing bacteria mixture, the zeolite and the slow-release carbon source to obtain the direct ammonia oxidizing bacteria agent, wherein the particle size of the direct ammonia oxidizing bacteria agent is 0.5 to 3 mm.

7. The sewage treatment method according to claim 1, characterized in that: Before adding the direct ammonia oxidizing bacteria agent into the primary aerobic section, the activated sludge concentration of the primary aerobic section is controlled to be 3000-5000 mg / L.

8. The sewage treatment method according to claim 1, characterized in that: The dissolved oxygen in the primary aerobic section is 1-2 mg / L, the dissolved oxygen in the secondary anoxic section is no more than 0.5 mg / L, and the dissolved oxygen in the tertiary aerobic section is 2-4 mg / L.

9. The sewage treatment method according to claim 1, characterized in that: The direct ammonia oxidizing bacteria agent and the sulfide-iron autotrophic-heterotrophic denitrification filler are respectively suspended in the primary aerobic section and the secondary anoxic section through cage filling.

10. A bioreactor, applied to the wastewater treatment method of direct ammonia oxidation coupled with autotrophic denitrification according to any one of claims 1 to 9, characterized in that: The rear end is connected to the secondary sedimentation tank, including the primary aerobic section, the secondary anoxic section and the tertiary aerobic section connected in sequence; The first aerobic section is suspended with a cage-filled direct ammonia oxidizing bacteria agent, and the second anoxic section is suspended with a cage-filled ferrosulphide autotrophic-heterotrophic denitrification filler; the filling ratio of the direct ammonia oxidizing bacteria agent in the first aerobic section is 5% to 50%, and the filling ratio of the ferrosulphide autotrophic-heterotrophic denitrification filler in the second anoxic section is 10% to 30%; the direct ammonia oxidizing bacteria agent is composed of a slow-release carbon source, zeolite and direct ammonia oxidizing bacteria; When the direct ammonia oxidizing bacteria agent is added to the primary aerobic section, the concentration of activated sludge in the primary aerobic section is 4000-8000 mg / L; The dissolved oxygen in the first-stage aerobic section is controlled at 1-2 mg / L, the dissolved oxygen in the second-stage anoxic section is controlled at less than 0.5 mg / L, and the dissolved oxygen in the third-stage aerobic section is controlled at 2-4 mg / L.

Images