Wastewater treatment method and bioreactor for direct ammonia oxidation coupled with autotrophic denitrification

Abstract

The present invention provides a sewage treatment method and bioreactor for direct ammonia oxidation coupled with autotrophic denitrification. The sewage treatment method for direct ammonia oxidation coupled with autotrophic denitrification comprises the following steps: sewage enters a continuous flow bioreactor, the bioreactor comprises a primary aerobic section, a secondary anoxic section, and a tertiary aerobic section arranged in sequence; a direct ammonia oxidizing bacterial 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; the sewage that has stayed in the tertiary aerobic section enters a secondary sedimentation tank and is discharged. The present invention does not require an external carbon source, the sludge yield is low, and green, low-carbon, and efficient treatment of high-ammonia nitrogen and low-carbon-nitrogen ratio wastewater is achieved.

Description

Technical Field

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

[0002] Wastewater with high ammonia nitrogen and low carbon-nitrogen ratios originates from a wide range of industrial processes, including fertilizer production, monosodium glutamate manufacturing, coking, landfill leachate, coal gas production, and livestock and poultry farming. Wastewater with high ammonia nitrogen and low carbon-nitrogen ratios typically has high ammonia nitrogen concentrations and relatively low biodegradable organic matter content. Traditional biochemical treatment methods, such as nitrification-denitrification, typically require high carbon-nitrogen ratios and extensive aeration. Furthermore, high ammonia nitrogen concentrations inhibit microbial activity, necessitating dilution or the addition of additional carbon sources to improve treatment efficiency, leading to 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 reduce 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 No. 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 the enrichment and application of Dirammox microorganisms 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 - Biological denitrification technology, which reduces nitrogen to N2, offers advantages such as requiring no external carbon source, simultaneous nitrogen and phosphorus removal, and a wide range of low-cost raw materials. Sulfur-iron autotrophic denitrification technology can effectively address residual nitrate and nitrogen in wastewater with high ammonia-nitrogen and low carbon ratios after treatment with Dirammox technology.

[0005] Based on the above, it is urgent to study a treatment method for 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 bioreactor for direct ammonia oxidation coupled with autotrophic denitrification, so as to solve the technical problems of low abundance and difficulty of direct ammonia oxidizing bacteria in sewage in the above-mentioned common technologies.

[0007] To achieve the above object, the present invention provides a wastewater 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 controlled to be 1 to 2 hours. The sewage that has stayed in the tertiary aerobic section enters the secondary sedimentation tank and 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 husks, 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, obtaining the direct ammonia oxidizing bacteria mixture includes 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 be 12 to 48 hours, and controlling the dissolved oxygen in the reaction tank to be 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 in 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 for use in any one of the above methods for treating wastewater by direct ammonia oxidation coupled with autotrophic denitrification, wherein the rear end is connected to a secondary sedimentation tank and comprises 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 sulfide-iron 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 sulfide-iron 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 activated sludge concentration in the primary aerobic section is 4000 to 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 below 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 a direct ammonia oxidation section and an autotrophic denitrification section, solving the technical problem that when the organic carbon source is insufficient in the conventional technology, 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 that uses pyrite as an electron donor to convert NO3 into nitrate nitrogen by autotrophic microorganisms under anoxic or anaerobic conditions. - Biological denitrification technology, which reduces nitrogen to N2, offers advantages such as requiring no external carbon source, simultaneous nitrogen and phosphorus removal, and a wide range of low-cost raw materials. Sulfur-iron autotrophic denitrification technology can effectively address residual nitrate and nitrogen in wastewater with high ammonia and low carbon-nitrogen ratios after direct ammonia oxidation 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 an immobilized bacterial agent preparation method to combine a slow-release carbon source, zeolite, and direct ammonia oxidizing bacteria into a direct ammonia oxidizing 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 low-oxygen conditions to directly convert ammonia nitrogen into nitrogen gas for removal; the incorporation of a slow-release carbon source effectively enhances the activity of direct ammonia oxidizing bacteria in low-carbon wastewater with a high ammonia-nitrogen ratio. 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, which can specifically accelerate the enrichment of ammonia nitrogen on the surface of the microbial agent, increase the contact between ammonia nitrogen and direct ammonia oxidizing bacteria, and greatly improve 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 during 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any 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 effect of total nitrogen removal along the process in Example 3 of the present invention.

[0036] Figure 5 Graphs showing the microbial diversity analysis in Examples 4 to 6 of the present invention.

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

[0038] The following will be combined with the accompanying 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 embodiments described 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 making creative efforts 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 various 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, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0041] Moreover, 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 ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] The commonly used technique of inoculating direct ammonia-oxidizing bacteria directly into wastewater with high ammonia nitrogen and low carbon-nitrogen ratios has poor treatment effects for the following reasons: In conventional activated sludge systems, the abundance of Dirammox bacteria is extremely low (a few parts per ten thousand), making it difficult to achieve stable enhanced denitrification. Currently, introducing exogenous bacteria into activated sludge systems to enhance nitrogen removal is an effective approach, but when exogenous bacteria are added to the sludge, they easily overlap with the native microorganisms in their ecological niche, making their adaptability and competitiveness inferior to those of the native microorganisms. In addition, Dirammox bacteria are heterotrophic bacteria and exhibit good performance at high C / N ratios (>10), but are at a competitive disadvantage in low C / N systems, limiting 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. Wastewater enters a continuous flow bioreactor comprising a primary aerobic section and a secondary anoxic section. A direct ammonia oxidizing bacterial agent is introduced into the primary aerobic section, and a sulfide-iron autotrophic-heterotrophic denitrifying filler is introduced into the secondary anoxic section. The wastewater contains high ammonia nitrogen and low carbon-nitrogen ratio wastewater.

[0045] 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 agent 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, and includes 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 sulfide-iron 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 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%;

[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, 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 agent and the sulfide-iron autotrophic-heterotrophic denitrification filler can be directly added to a traditional sewage reactor, and the above parameters can be controlled.

[0051] Cage-type packing of direct ammonia oxidizing bacteria and ferrosulphur autotrophic-heterotrophic denitrification fillers allows for frequent replacement of the filler cages. When replacement is needed, the cages can be removed using a crane or hoist and then repositioned to ensure the continued use of the direct ammonia oxidizing bacteria and ferrosulphur autotrophic-heterotrophic denitrification fillers. The direct ammonia oxidizing bacteria can be replaced annually.

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

[0053] In some embodiments, before adding the direct ammonia oxidizing bacteria agent into the primary aerobic section, the activated sludge concentration in the primary aerobic section 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 section is guaranteed, and direct ammonia oxidizing bacteria can achieve exclusive growth in high-ammonia nitrogen wastewater. Among commonly used 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, excessive organic matter entering the anaerobic ammonium oxidation system will cause excessive growth of denitrifying bacteria, resulting in the inhibition of the anaerobic ammonium oxidation process, which in turn leads to the failure of denitrification. 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 incorporation of slow-release carbon sources effectively enhances 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 (DAOs) directly oxidize ammonia to dinitrile gas under aerobic conditions and are highly tolerant to high ammonia nitrogen and high pH values. They can directly convert ammonia nitrogen into hydroxylamine, which in turn is converted directly into dinitrile gas or nitrogen. Alcaligenes is a dominant species among DAOs and exhibits excellent adaptability to pH values ​​between 8 and 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 ratio 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 direct ammonia oxidizing bacteria mixture as a centrifugal product.

[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 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%.

[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, 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 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 some of the ammonia nitrogen is converted into nitrate nitrogen by the nitrifying bacteria. It should be noted that as the direct ammonia-oxidizing bacteria multiply, some of the direct ammonia-oxidizing bacteria desorb from the zeolite and scatter in the sewage system, making the activated sludge a functional sludge that combines 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 ferrosulphide autotrophic-heterotrophic denitrifying filler simultaneously supplies pyrite and a carbon source to the sewage system. The ferrosulphide autotrophic and heterotrophic denitrifying bacteria exhibit a balanced growth pattern, forming a ferrosulphide autotrophic-heterotrophic denitrification composite system that efficiently and synergistically achieves efficient nitrate and nitrogen removal under low-carbon conditions. The iron ions released during the ferrosulphide autotrophic denitrification process can complex with phosphorus, enhancing the removal of total phosphorus within the system. Furthermore, the introduction of biodegradable plastics as a slow-release carbon source can compensate for the alkalinity consumed by ferrosulphide autotrophic denitrification through heterotrophic nitrification, maintain the system's pH balance, and utilize the flocculation ability of hydroxyl iron to enhance sludge settling.

[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 level in the primary aerobic zone is 1-2 mg / L, the dissolved oxygen level in the secondary anoxic zone is no greater than 0.5 mg / L, and the dissolved oxygen level in the tertiary aerobic zone is 2-4 mg / L. Direct ammonia oxidizing bacteria have a high dissolved oxygen utilization rate, and controlling the DO level in the primary aerobic zone at a relatively low concentration ensures ammonia nitrogen removal, effectively reducing aeration energy consumption during wastewater treatment. Controlling the DO level in the anoxic zone to less than 0.5 mg / L eliminates the inhibitory effect of high dissolved oxygen on denitrification, achieving sufficient nitrate nitrogen removal.

[0074] In some embodiments, the bioreactor further comprises a tertiary aerobic section connected to the secondary anoxic section, the tertiary aerobic section receiving 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 into 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 wastewater that has stayed in the secondary anoxic section passes through the tertiary aerobic section and then enters the secondary sedimentation tank, comprising: if the nitrate-nitrogen content of the wastewater after treatment in the tertiary aerobic section is higher than 10 mg / L, the wastewater is returned to the anoxic section for further treatment to ensure complete removal of the 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, now illustrate with examples:

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

[0081] Inoculating activated sludge containing direct ammonia oxidizing bacteria into a reaction tank, introducing sewage containing 0.1% by mass of hydroxylamine into the reaction tank, and adjusting the COD / ammonia nitrogen ratio of the sewage to 10-15 by adding a carbon source before entering the reaction tank; controlling the residence time of the sewage in the reaction tank to 24 hours, and controlling 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 with the mass proportions 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-Ferric Autotrophic-Heterotrophic Denitrification Filler

[0085] Pyrite is sieved through wet ball milling to obtain powder with a particle size of less than 100um, and then added to molten biodegradable plastic, wherein the mass proportions of pyrite powder and 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 influent water quality parameters are as follows: the influent ammonia nitrogen concentration is 390.4-559 mg / L, the influent COD is 400-941.9 mg / L, and the COD / ammonia nitrogen is 1.87, which is a typical influent with high ammonia nitrogen and low carbon nitrogen ratio.

[0088] First, a set of direct ammonia oxidation coupled autotrophic denitrification bioreactors was built, including the first aerobic section, the second anoxic section, the third aerobic section and the tail secondary sedimentation tank. Among them, the first aerobic section is hung with cage-filled direct ammonia oxidizing bacteria, with a filling ratio of 40%; the second anoxic section is hung 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 24 hours, the hydraulic retention time of the secondary anoxic section is controlled at 8 hours, and the hydraulic retention time of the tertiary aerobic section is controlled at 1 hour; 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 below 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 is discharged. After the operation stabilizes, 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 first aerobic section, the second anoxic section, the third aerobic section and the effluent of the secondary sedimentation tank for testing ( Figure 4 ), and evaluate the contribution of each section 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 showed a gradual downward trend along the process. In the primary aerobic section, 84.5% of the total nitrogen was effectively removed by direct ammonia oxidizing bacteria through direct ammonia oxidation. The nitrate nitrogen converted by nitrifying bacteria in the activated sludge entered the secondary anoxic section and achieved 13.7% of the nitrogen removal through the synergistic effect of sulfide-iron autotrophic-anomalous denitrification.

[0091] Example 4: Dosage of hydroxylamine compounds

[0092] In this example, inoculum sludge was taken from the aerobic terminal of a biochemical reactor at a sewage treatment plant. The SBR reactor was started with an inoculum sludge concentration of 500 mg / L and an MLVSS / MLSS ratio of 0.49. The SBR reactor achieves biochemical treatment of wastewater by completing the basic processes of water intake, aeration, sedimentation, drainage, and standby in a single reaction tank in a chronological order. The SBR process cycle includes water intake, aeration, sedimentation, drainage, and standby time.

[0093] To systematically evaluate the enrichment effect of hydroxylamine compounds on direct ammonia oxidizing bacteria, four SBR reactors were set up to simulate enrichment tanks for testing. A0 served as the blank group, with no hydroxylamine added; control group A1 was dosed with 0.002% hydroxylamine; experimental group A2 was dosed with 0.1% hydroxylamine; and control group A3 was dosed with 5% hydroxylamine. The influent for this experiment was simulated wastewater. Water quality indicators ranged from approximately: NH4 + -N: 50~70mg / L, COD: 400~600mg / L.

[0094] The initial operating parameter settings of the reactor are shown in Table 1. In the water inlet phase, a peristaltic pump is used for water inlet, and the water inlet time is 10 minutes. In the aerobic phase, a stirrer is used to drive the stirring paddle for stirring, and the stirring speed is 120 rpm. The dissolved oxygen during the process is controlled at 2-5 mg / L. The sedimentation phase is a static phase, during which neither the stirrer nor the aeration pump is working. In the decanting phase, a peristaltic pump is used for water discharge. 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 for testing of NH4+-N, TN, and microbial diversity in the mixed liquid.

[0095] Table 1 Reactor initial operating parameters

[0096]

[0097] As shown in Table 2, the NH₄⁺-N removal efficiency of experimental group A2 was 99.45%, significantly higher than the 96.08%, 13.08%, and 95.82% of control groups A1, A3, and blank group A0, respectively. The TN removal efficiency of experimental group A2 was 92.83%, compared to 10.67% for control group A1. Control groups A3 and A0 showed virtually no TN removal. TN is typically removed through denitrification under anoxic conditions, but A2 achieved efficient TN removal under aerobic conditions, indirectly indicating that microbial communities capable of direct ammonia oxidation were enriched within the system. However, due to the low hydroxylamine concentration in A1, other microbial species were not inhibited. Furthermore, due to the high hydroxylamine concentration in A3, microbial death occurred within the system.

[0098] The 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% of the blank group A0 to 60.307%, which was much higher than 0.191% of the control group A1 and 0.076% of A3.

[0099] Table 2 NH4+-N and TN in effluent at 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] To systematically evaluate the enrichment effect of hydroxylamine compound types on direct ammonia-oxidizing bacteria, two SBR reactors were set up to simulate enrichment tanks. Hydroxylamine sulfate was added to reactor B1, and diethylhydroxylamine was added to reactor B2. The operating parameters in this example remained consistent with those of experimental group A2 in Example 1, except for the type of hydroxylamine compound.

[0103] The 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 the enrichment tank 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] The 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 stable aerobic ammonia oxidation denitrification of the mainstream system.

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

[0108] The other parameters of Comparative Example 1 are consistent with those of Example 3, with the difference being 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, with the difference being that the pyrite autotrophic-heterotrophic denitrification filler is replaced by a pyrite block filler.

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

[0111] The average removal rates of ammonia nitrogen and total nitrogen and the pH results at the end of anoxic conditions 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] The test results in Table 3 show that the direct ammonia oxidizing bacteria agent prepared by enriching a mixture of direct ammonia-oxidizing bacteria in the activated sludge of the plant using hydroxylamine and combining it with a slow-release carbon source and zeolite directly oxidizes ammonia to dinitrogen or nitrogen in the primary aerobic stage. The zeolite's selective adsorption of ammonia nitrogen resulted in a higher ammonia-nitrogen removal efficiency than the direct ammonia oxidizing bacteria agent prepared with diatomaceous earth. The slow-release carbon source compound provides a growth substrate for the direct ammonia oxidizing bacteria while achieving 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 water quality was far worse than that of the embodiment.

[0116] In summary, the wastewater treatment method and bioreactor of direct ammonia oxidation coupled with autotrophic denitrification provided in this 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 do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description 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 direct ammonia oxidizing bacteria agent is filled in the primary aerobic section at a ratio of 5% to 50%, and the ferrosulphur autotrophic-heterotrophic denitrification filler is filled in the secondary anoxic section at a ratio of 10% to 30% by volume. The direct ammonia oxidizing bacteria agent comprises 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 controlled to be 1 to 2 hours. The wastewater that has been retained in the tertiary aerobic section enters the secondary sedimentation tank and then is discharged; The preparation method of the pyrite autotrophic-heterotrophic denitrification filler comprises: adding pyrite powder to molten degradable plastic, extruding and granulating to obtain the pyrite autotrophic-heterotrophic denitrification filler; 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.

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 particle size of the pyrite powder is not greater than 100 μm, the mass proportion of the pyrite powder 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 plastic.

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, introducing sewage containing 0.005% to 1% by mass of hydroxylamine into the reaction tank, controlling the residence time in the reaction tank to be 12 to 48 hours, and controlling the dissolved oxygen in the reaction tank to be 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 0.5-3 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 in 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 below 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 for 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 of the 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; 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 sulfide-iron 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 sulfide-iron 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 a mixture of direct ammonia oxidizing bacteria; When the direct ammonia oxidizing bacteria agent is added to the primary aerobic section, the activated sludge concentration 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 below 0.5 mg / L, and the dissolved oxygen in the third-stage aerobic section is controlled at 2-4 mg / L.

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