Ammonia direct oxidation denitrification system and method for nitrate-containing sewage

Abstract

The invention belongs to the technical field of water pollution control, and particularly relates to an ammonia direct oxidation denitrification system and method for nitrate-containing sewage, the method comprises the following steps: S1, in an anoxic AMAO denitrification reactor, acetone is added into the ammonia nitrogen and nitrate-containing sewage, AMAO functional microorganisms take acetone as a mediator and take nitrate as an electron acceptor, and the ammonia nitrogen and nitrate-containing sewage is subjected to denitrification treatment; ammonia nitrogen is oxidized, nitrate is reduced, and nitrogen is generated synchronously; s2, the effluent in the step S1 enters an aerobic AMAO deep denitrification reactor, residual acetone is utilized to further oxidize residual ammonia nitrogen through an AMAO reaction under the aerobic condition, and deep denitrification is achieved. According to the method, the same core metabolic pathway is utilized, the nitrate and ammonia nitrogen removal problem is sequentially solved through environmental regulation and control, the process is compact, operation is easy and convenient, the treatment efficiency of the compound nitrogen polluted wastewater is remarkably improved, the total nitrogen removal rate can reach 95% or above, the total nitrogen of effluent is stably lower than 2 mg / L, the deep nitrogen removal effect is remarkable, and the method is suitable for industrial production. And the risk of nitrate residue or secondary pollution in the traditional process is thoroughly avoided.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a direct ammonia oxidation denitrification system and method for nitrate-containing wastewater. Background Technology

[0002] In many industrial processes (such as fertilizer production, explosives manufacturing, and metal processing) and contaminated sites (such as landfills and groundwater from farmland where excessive fertilizer has been applied), wastewater containing both ammonia nitrogen and nitrate is often generated. The treatment of this type of complex nitrogen-polluted wastewater is a current challenge in the water treatment field. Traditional biological treatment requires a process that separates "nitrification (ammonia → nitrate)" and "denitrification (nitrate → nitrogen)," resulting in a lengthy process that necessitates the construction of multiple reaction tanks and the addition of large amounts of exogenous carbon sources (such as methanol) in the denitrification stage. This not only leads to high construction and operating costs but also carries the risk of excessive carbon source addition causing COD exceeding standards in the effluent or insufficient addition resulting in incomplete nitrate removal. Anaerobic ammonia oxidation technology can oxidize ammonia nitrogen using nitrite as an electron acceptor, but it cannot directly treat nitrate. It requires a pre-treatment short-cut nitrification unit to convert some ammonia nitrogen into nitrite, and this combined process has extremely stringent control requirements and weak shock resistance. Currently, there is a lack of simple and efficient biological processes that can simultaneously and efficiently remove ammonia nitrogen and nitrate when nitrate concentrations are high.

[0003] In recent years, we have made significant progress in exploring novel microbial ammonia oxidation processes, discovering a process called acetone-mediated ammonium oxidation (AMAO, acetone + ammonia → acetone oxime → acetone + nitrogen). This process breaks through the traditional understanding of ammonia oxidation processes, and its electron acceptors are diverse, including O2 and NO2. - NO3 - Fe 3+ In an oxygen-deficient environment with nitrates, AMAO functional bacteria can adjust their electron transport chain, transferring electrons that were originally transferred to oxygen to nitrates, thereby catalyzing a new synergistic reaction: ammonia nitrogen is oxidized as an electron donor, and nitrates are reduced as electron acceptors. The two are directly converted into nitrogen gas under the mediation of acetone, which has the potential to remove ammonia nitrogen and nitrate nitrogen simultaneously. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to overcome the above-mentioned shortcomings and provide an ammonia direct oxidation denitrification system and method for nitrate-containing wastewater, so as to simultaneously remove ammonia nitrogen and nitrate, overcome the drawbacks of traditional segmented treatment technology, and achieve higher denitrification efficiency, lower carbon source consumption and simpler operation and management.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for simultaneous nitrogen removal via direct ammonia oxidation in nitrate-containing wastewater includes the following steps: S1. In the anoxic AMAO denitrification reactor, acetone is added to the wastewater containing ammonia nitrogen and nitrate. The AMAO functional microorganisms use acetone as a mediator and nitrate as an electron acceptor to oxidize ammonia nitrogen and reduce nitrate, and simultaneously generate nitrogen gas. S2. The effluent from step S1 enters the aerobic AMAO deep denitrification reactor, where residual ammonia nitrogen is further oxidized by the AMAO reaction using residual acetone under aerobic conditions, thus achieving deep denitrification.

[0006] Furthermore, the AMAO functional microorganisms in the anoxic AMAO denitrification reactor catalyze the following reaction: NH4 + + 0.6NO3 - + C3H3O → 0.8N2+ 0.4H + + C3H3O + 1.8H2O, ΔG 0 = -280.7 kJ mol -1 ; The C3H3O mentioned above is regenerated in a cycle.

[0007] Furthermore, the anoxic reactor is kept in a state of no dissolved oxygen (DO < 0.2 mg / L), and the sludge is kept in suspension by mechanical stirring.

[0008] Furthermore, the dissolved oxygen concentration in the aerobic reactor is controlled at 0.5-2.0 mg / L.

[0009] Further, in step S1, the amount of acetone added is in a molar ratio of 0.01 to 0.1 with ammonia nitrogen.

[0010] On the other hand, the present invention also provides a direct ammonia oxidation simultaneous denitrification system for nitrate-containing wastewater, comprising an anoxic AMAO denitrification reactor and an aerobic AMAO deep denitrification reactor connected in sequence, as well as an acetone dosing device; The anoxic AMAO denitrification reactor is used to enable AMAO functional microorganisms to simultaneously oxidize ammonia nitrogen and reduce nitrate to generate nitrogen gas under anoxic conditions, using added acetone as a mediator and nitrate as an electron acceptor. The aerobic AMAO deep denitrification reactor is used to further oxidize residual ammonia nitrogen with residual acetone under micro-aerobic conditions to achieve deep denitrification.

[0011] Furthermore, the anoxic AMAO denitrification reactor is equipped with a mechanical stirring device and the DO is controlled to be <0.2 mg / L; the aerobic AMAO deep denitrification reactor controls the DO to be between 0.5 and 2.0 mg / L.

[0012] Based on a profound understanding and innovative application of AMAO microbial metabolic flexibility, this invention designs a two-stage process: (1) Main co-processing denitrification section (anoxic AMAO denitrification reactor): This is the core innovative unit of the present invention. Wastewater rich in acetone, ammonia nitrogen and nitrate enters the anoxic AMAO denitrification reactor. In this environment, AMAO functional microorganisms use acetone as a medium and nitrate as an electron acceptor. Ammonia nitrogen and nitrate react to convert into nitrogen gas. In this process, acetone is not consumed by microorganisms and will flow into the next reaction unit to continue to play the role of medium.

[0013] (2) Deep purification protection section (aerobic AMAO deep denitrification reactor): After the anoxic section, nitrates are usually completely removed, but a small amount of ammonia nitrogen may remain (the concentration of ammonia nitrogen in general wastewater is much higher than that of nitrates); by setting up an aerobic AMAO section with a micro-aerobic environment in the aerobic AMAO deep denitrification reactor, the residual acetone in the water can be used to finally oxidize these residual ammonia nitrogen, ensuring that the ammonia nitrogen and total nitrogen in the effluent meet the standards.

[0014] The beneficial effects of this invention are as follows: This invention innovatively designs a two-stage anoxic-aerobic process using a novel metabolic pathway of AMAO functional microorganisms with nitrate as an electron acceptor under anoxic conditions. In the anoxic stage, AMAO microorganisms use acetone as a circulating mediator to drive the simultaneous oxidation of ammonia nitrogen and reduction of nitrate, directly generating nitrogen gas and achieving highly efficient co-removal of ammonia nitrogen and nitrate. In the aerobic stage, residual acetone is used to deeply oxidize residual ammonia nitrogen. This process utilizes the same core metabolic pathway and addresses the removal of nitrate and ammonia nitrogen sequentially through environmental control. The process is compact, easy to operate, and significantly improves the treatment efficiency of complex nitrogen-polluted wastewater.

[0015] First, it achieves simultaneous removal of ammonia nitrogen and nitrate. This technology breaks through the traditional segmented nitrification-denitrification model, completing the conversion of dual nitrogen pollutants in a single core reaction. The total nitrogen removal rate can reach over 95%, and the total nitrogen in the effluent is consistently below 2 mg / L. The deep denitrification effect is significant, completely avoiding the risk of nitrate residue or secondary pollution in traditional processes.

[0016] Secondly, carbon source utilization efficiency is significantly improved. As a recycling mediator, acetone only needs to be added at a low amount of 0.01-0.1 ammonia-nitrogen molar ratio. It is not consumed by microorganisms, and the residual acetone in the effluent of the anoxic stage can directly support deep denitrification in the aerobic stage. This is far lower than the amount of exogenous carbon source (such as methanol) required for traditional denitrification, avoiding the problem of excessive COD caused by excessive carbon source or incomplete denitrification caused by insufficient carbon source, thus achieving low-carbon and high-efficiency operation.

[0017] Third, aeration energy consumption is significantly reduced. In the anoxic stage, nitrates replace some oxygen as electron acceptors; in the aerobic stage, ammonia oxidation directly produces nitrogen gas instead of nitrates, and the theoretical oxygen demand is only 37.5% of that of the traditional nitrification process. The overall aeration energy consumption is reduced by more than 60% compared with the traditional process, with outstanding energy-saving effect, which is in line with the low-carbon development trend of wastewater treatment.

[0018] Fourth, it has a wide range of applications. This technology provides a simple and efficient biological treatment solution for complex polluted wastewater containing both ammonia nitrogen and nitrate, such as landfill leachate, chemical wastewater, and eutrophic groundwater. It has strong process stability and good shock resistance, providing a new path for achieving energy conservation, consumption reduction, and resource utilization in wastewater treatment, and has significant economic and environmental benefits.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of a direct ammonia oxidation denitrification system for nitrate-containing wastewater according to the present invention. Figure 2 The graphs show the variation curves of ammonia nitrogen and nitrate nitrogen along the process in the anoxic AMAO denitrification reactor and the aerobic AMAO deep denitrification reactor in the examples. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0023] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0024] like Figure 1 The image shows a method for simultaneous nitrogen removal via direct ammonia oxidation in nitrate-containing wastewater, comprising the following steps: S1. In the anoxic AMAO denitrification reactor, acetone is added to the wastewater containing ammonia nitrogen and nitrate. The AMAO functional microorganisms use acetone as a mediator and nitrate as an electron acceptor to oxidize ammonia nitrogen and reduce nitrate, and simultaneously generate nitrogen gas. S2. The effluent from step S1 enters the aerobic AMAO deep denitrification reactor, where residual ammonia nitrogen is further oxidized by the AMAO reaction using residual acetone under aerobic conditions, thus achieving deep denitrification.

[0025] Furthermore, the AMAO functional microorganisms in the anoxic AMAO denitrification reactor catalyze the following reaction: NH4 + + 0.6NO3 - + C3H3O → 0.8N2+ 0.4H ++ C3H3O + 1.8H2O, ΔG 0 = -280.7 kJ mol -1 ; The C3H3O mentioned above is regenerated in a cycle.

[0026] Furthermore, the anoxic reactor is kept in a state of no dissolved oxygen (DO < 0.2 mg / L), and the sludge is kept in suspension by mechanical stirring.

[0027] Furthermore, the dissolved oxygen concentration in the aerobic reactor is controlled at 0.5-2.0 mg / L.

[0028] Further, in step S1, the amount of acetone added is in a molar ratio of 0.01 to 0.1 with ammonia nitrogen.

[0029] On the other hand, the present invention also provides a direct ammonia oxidation simultaneous denitrification system for nitrate-containing wastewater, comprising an anoxic AMAO denitrification reactor and an aerobic AMAO deep denitrification reactor connected in sequence, as well as an acetone dosing device; The anoxic AMAO denitrification reactor is used to enable AMAO functional microorganisms to simultaneously oxidize ammonia nitrogen and reduce nitrate to generate nitrogen gas under anoxic conditions, using added acetone as a mediator and nitrate as an electron acceptor. The aerobic AMAO deep denitrification reactor is used to further oxidize residual ammonia nitrogen with residual acetone under micro-aerobic conditions to achieve deep denitrification.

[0030] Furthermore, the anoxic AMAO denitrification reactor is equipped with a mechanical stirring device and controls DO < 0.2 mg / L; the aerobic AMAO deep denitrification reactor controls DO between 0.5 and 2.0 mg / L; the aerobic AMAO deep denitrification reactor may be equipped with an aeration device to control the DO range.

[0031] Example 1 according to Figure 1A continuous flow pilot-scale system was constructed to treat groundwater contaminated by agricultural non-point source pollution. The system has a total effective volume of 40 L and consists of two reactors connected in series. The anoxic AMAO denitrification reactor has an effective volume of 30 L, and the aerobic AMAO deep denitrification reactor has an effective volume of 10 L. The wastewater treatment process is as follows: The contaminated groundwater first enters the anoxic AMAO denitrification reactor (DO < 0.2 mg / L). Acetone is added at a molar ratio of 0.05 (acetone to ammonia nitrogen), and the hydraulic retention time is set to 8 hours. Under anoxic conditions, AMAO functional microorganisms utilize acetone as a mediator and nitrate as an electron acceptor to simultaneously catalyze the oxidation of ammonia nitrogen and the reduction of nitrate. Finally, the effluent enters the aerobic AMAO deep denitrification reactor, where residual ammonia nitrogen is further purified under a hydraulic retention time of 3.3 hours and microaerobic conditions (DO = 0.5-1.0 mg / L). The influent water quality is: NH4+. + -N 45 ±5 mg / L, NO3 - -N 10 ± 2 mg / L, pH 6.5 - 7.5. After a 15-day acclimatization period, the system operated stably for 30 days.

[0032] like Figure 2 As shown in the figure, the operating results demonstrate that the anoxic AMAO denitrification reactor achieved highly efficient simultaneous denitrification. Ammonia nitrogen and nitrate in the influent were removed simultaneously at a ratio of approximately 1:0.6, with the average effluent ammonia nitrogen level reduced to 27.5 mg / L and nitrate nitrogen completely removed. This confirms the anoxic reaction pathway of AMAO. The subsequent aerobic AMAO deep denitrification reactor ensured the final effluent water quality, and the system's effluent NH4... + -N was below 1 mg / L, TN was below 2 mg / L, and the total nitrogen removal rate exceeded 96%. Experimental results confirm that this technology is a promising, efficient, and low-carbon solution for treating wastewater containing both ammonia nitrogen and nitrate, providing a new technological path for achieving energy conservation, emission reduction, and resource utilization goals in wastewater treatment.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for simultaneous nitrogen removal via direct ammonia oxidation in nitrate-containing wastewater, characterized in that, Includes the following steps: S1. In the anoxic AMAO denitrification reactor, acetone is added to the wastewater containing ammonia nitrogen and nitrate. The AMAO functional microorganisms use acetone as a mediator and nitrate as an electron acceptor to oxidize ammonia nitrogen and reduce nitrate, and simultaneously generate nitrogen gas. S2. The effluent from step S1 enters the aerobic AMAO deep denitrification reactor, where residual ammonia nitrogen is further oxidized by the AMAO reaction using residual acetone under aerobic conditions, thus achieving deep denitrification.

2. The method according to claim 1, characterized in that, The AMAO functional microorganisms in the anoxic AMAO denitrification reactor catalyze the following reaction: NH4 + + 0.6NO3 - + C3H3O → 0.8N2+ 0.4H + + C3H3O + 1.8H2O,ΔG 0 = -280.7 kJ mol -1 ; The C3H3O mentioned above is regenerated in a cycle.

3. The method according to claim 1, characterized in that, The anoxic reactor is kept in a state of no dissolved oxygen (DO < 0.2 mg / L), and the sludge is kept in suspension by mechanical stirring.

4. The method according to any one of claims 1-3, characterized in that, The dissolved oxygen concentration in the aerobic reactor is controlled at 0.5-2.0 mg / L.

5. The method according to claim 4, characterized in that, In step S1, the acetone is added at a molar ratio of 0.01 to 0.1 with ammonia nitrogen.

6. A simultaneous ammonia direct oxidation and denitrification system for nitrate-containing wastewater, characterized in that, It includes an anoxic AMAO denitrification reactor and an aerobic AMAO deep denitrification reactor connected in sequence, as well as an acetone dosing device; The anoxic AMAO denitrification reactor is used to enable AMAO functional microorganisms to simultaneously oxidize ammonia nitrogen and reduce nitrate to generate nitrogen gas under anoxic conditions, using added acetone as a mediator and nitrate as an electron acceptor. The aerobic AMAO deep denitrification reactor is used to further oxidize residual ammonia nitrogen with residual acetone under micro-aerobic conditions to achieve deep denitrification.

7. The system according to claim 6, characterized in that, The anoxic AMAO denitrification reactor is equipped with a mechanical stirring device and controls DO < 0.2 mg / L; the aerobic AMAO deep denitrification reactor controls DO between 0.5 and 2.0 mg / L.

Images