Ammonia direct oxidation denitrification and carbon recovery system and method for livestock and poultry breeding sewage

Abstract

The invention belongs to the technical field of environmental protection and resource recycling, and particularly relates to an ammonia direct oxidation denitrification and carbon recovery system and method for livestock and poultry breeding wastewater, and the method comprises the following steps: introducing pretreated livestock and poultry breeding wastewater into a first reaction unit under an anoxic condition; the method comprises the following steps: directionally converting part of organic matters in livestock and poultry breeding sewage into acetone through enriched functional microorganisms capable of producing acetone to obtain intermediate effluent containing acetone and residual ammonia nitrogen; introducing the intermediate effluent into a second reaction unit under a micro-aerobic condition, and directly oxidizing ammonia nitrogen into nitrogen through enriched AMAO functional microorganisms by taking acetone as an electron shuttle and a carbon source to obtain denitrified effluent containing residual acetone; and introducing the denitrified effluent into an acetone recovery unit to recover residual acetone. The three-in-one process of anoxic acetone production, micro-aerobic AMAO direct denitrification and efficient acetone recycling is creatively integrated, and efficient denitrification and carbon recycling of livestock and poultry breeding sewage are achieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and resource recycling technology, specifically relating to a direct ammonia oxidation denitrification and carbon recovery system and method for livestock and poultry breeding wastewater. Background Technology

[0002] Livestock and poultry farming wastewater is characterized by high organic matter concentration (COD often reaches thousands to tens of thousands of mg / L) and high ammonia nitrogen content (NH4). + Characterized by high concentrations of nitrogen (up to hundreds of mg / L), this type of wastewater is classified as high-concentration, difficult-to-treat organic wastewater. Currently, the mainstream treatment process for this type of wastewater generally adopts a combined model of "anaerobic digestion (biogas production) - aerobic treatment (nitrification for phosphorus removal) - anoxic denitrification." However, this model still faces several technical bottlenecks in practical engineering applications: First, the anaerobic process converts a large amount of organic carbon into methane and carbon dioxide, failing to effectively retain the carbon source needed for subsequent denitrification. This often necessitates the addition of exogenous carbon sources such as methanol during the anoxic denitrification stage, increasing operating costs and introducing new environmental risks. Second, the traditional nitrification-denitrification pathway is long, energy-intensive, and produces large amounts of sludge, with treatment efficiency significantly affected by fluctuations in influent water quality. Furthermore, the entire process ultimately converts carbon in the wastewater into greenhouse gases (CO2 / CH4) and excess sludge, resulting in low resource utilization and failing to meet the requirements of a circular economy and sustainable development.

[0003] However, with the development of technology, we have made important progress in the study of novel microbial ammonia oxidation processes. We have discovered a process called acetone-mediated ammonium oxidation (AMAO, specifically acetone + ammonia → acetone oxime → acetone + nitrogen). Microorganisms use acetone as a medium to directly oxidize ammonia into nitrogen. This process uses acetone as the key medium to achieve efficient conversion of ammonia into nitrogen. This discovery breaks through the traditional understanding of the nitrogen cycle.

[0004] Therefore, there is an urgent need to develop a new method for treating livestock and poultry wastewater that can use acetone-mediated ammonia oxidation process to break through traditional approaches and simultaneously achieve efficient removal of pollutants and high-value recovery of organic carbon. Summary of the Invention

[0005] In view of this, the purpose of this invention is to overcome the above-mentioned shortcomings and provide a direct ammonia oxidation denitrification and carbon recovery system and method for livestock and poultry breeding wastewater, so as to solve the problems of carbon source utilization contradiction, high operating cost and lack of resource recovery pathway in existing breeding wastewater treatment technologies, and achieve the unity of environmental benefits and economic benefits.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for direct ammonia oxidation denitrification and carbon recovery in livestock and poultry breeding wastewater includes the following steps: The pretreated livestock and poultry breeding wastewater is introduced into the first reaction unit under anoxic conditions. Through the enriched acetone-producing functional microbial community, some of the organic matter in the livestock and poultry breeding wastewater is directionally converted into acetone, resulting in intermediate effluent containing acetone and residual ammonia nitrogen. The intermediate effluent is introduced into the second reaction unit under microaerobic conditions. Through the enriched AMAO functional microbial community, acetone is used as a medium to directly oxidize ammonia nitrogen into nitrogen gas, thereby achieving denitrification and obtaining denitrified effluent rich in acetone. The denitrified effluent is introduced into an acetone recovery unit to recover residual acetone, resulting in recovered acetone and purified effluent.

[0007] Furthermore, a portion of the recovered acetone from the acetone recovery unit can be returned to the inlet of the second reaction unit to maintain a stable acetone concentration within the second reaction unit, while the remaining recovered acetone is output as a product.

[0008] Furthermore, the first reaction unit is an anoxic acetone production reactor, with operating conditions including: anoxic conditions, hydraulic retention time of 8-24 hours, and pH of 8.0-8.5, thereby converting 10%-30% of the organic matter in livestock and poultry breeding wastewater into acetone and controlling the effluent acetone concentration to reach 200-3000 mg / L.

[0009] Furthermore, the second reaction unit is a microaerobic AMAO denitrification reactor, with operating conditions including: dissolved oxygen concentration of 0.5-3.0 mg / L and hydraulic retention time of 6-30 hours. The AMAO functional microbial community uses acetone as a medium to achieve direct oxidation of ammonia nitrogen into nitrogen gas, with a total nitrogen removal rate of ≥90%.

[0010] Furthermore, the acetone recovery unit employs an adsorption-desorption-condensation combined process, including: Residual acetone in the denitrification effluent was adsorbed using a non-polar macroporous adsorption resin. Saturated resin was subjected to thermal vacuum desorption to obtain high-concentration acetone vapor; High-concentration acetone vapor is condensed into liquid acetone, with an acetone recovery rate of ≥90% and a recovered acetone purity of ≥85%.

[0011] Furthermore, the refluxed portion of the recovered acetone is precisely controlled by a metering device to compensate for the changes in acetone concentration within the second reaction unit caused by fluctuations in the influent load, thereby ensuring stable denitrification efficiency.

[0012] The core concept of this invention lies in the innovative integration of AMAO, a novel biological denitrification process, with the large-scale biosynthesis of acetone and efficient physicochemical recovery technology in a three-in-one manner.

[0013] Specifically, this invention divides the processing flow into three functionally distinct and synergistically efficient units: (1) Targeted Bioconversion Unit (Anoxic Acetone Reactor, i.e., First Reaction Unit): The core task of this unit is "carbon orientation." By inoculating and acclimating AMAO acetone-producing bacteria (AMAO bacteria can produce acetone themselves) to livestock and poultry wastewater, and utilizing conditions suitable for AMAO bacteria to produce acetone while inhibiting methanogens, such as anoxic environment, pH>8.0, high ammonia nitrogen, and high accumulation of volatile fatty acids, the complex organic matter in the wastewater (the main substrate is volatile fatty acids) is guided to flow to the acetone synthesis pathway (volatile fatty acids → acetyl-CoA → acetoacetyl-CoA → acetoacetic acid → acetone), rather than the traditional methanation pathway. This provides a stable and sufficient source of acetone for subsequent processes.

[0014] (2) High-efficiency biological denitrification unit (aerobic AMAO denitrification reactor, i.e., the second reaction unit): The core task of this unit is "nitrogen removal." The intermediate effluent rich in acetone and ammonia nitrogen from the front end enters this unit. Through the enriched AMAO functional microbial community, under micro-aerobic conditions, acetone directly mediates the oxidation of ammonia to nitrogen gas. This process avoids the accumulation of nitrate nitrogen, has an extremely short path, and therefore has low sludge production and low aeration requirements. The key to its stable operation lies in the stability of the acetone concentration in the reactor, which can be ensured by the subsequent acetone recovery unit for acetone recirculation.

[0015] (3) Carbon Resource Capture and Regulation Unit (Acetone Recovery Unit): This unit is the "control center" connecting bioconversion and denitrification, and realizing product output. It first captures acetone (usually 200-3000 mg / L) in the effluent of the aerobic AMAO denitrification reactor with a high recovery rate through an efficient adsorption-condensation process, obtaining relatively pure liquid acetone (purity greater than 85%). After the recovered acetone is stored in the storage tank, a portion can be accurately measured and returned to the inlet of the aerobic AMAO denitrification reactor to form an "internal circulation" to offset the changes in acetone concentration caused by fluctuations in the influent load, ensuring the absolute stability of denitrification efficiency; the other portion is output as surplus product. This design gives the entire system strong resistance to shock loads and operational flexibility.

[0016] On the other hand, the present invention also provides a direct ammonia oxidation denitrification and carbon recovery system for livestock and poultry breeding wastewater, comprising the following components in sequential fluid communication: The anaerobic acetone production reaction unit is used to convert organic matter in wastewater into acetone under anaerobic conditions. The aerobic AMAO denitrification reaction unit is used for the direct oxidation of ammonia nitrogen to nitrogen gas mediated by acetone. An acetone recovery unit is used to separate and recover acetone from denitrification effluent. The acetone reflux pipeline partially returns the recovered acetone to the inlet of the aerobic AMAO denitrification reaction unit, while the remaining recovered acetone is used as the product output pipeline.

[0017] Furthermore, the acetone recovery unit includes an adsorption concentration device, a thermal vacuum desorption device, and a condensation collection device connected in sequence, wherein the adsorption concentration device is filled with a non-polar macroporous adsorption resin. The adsorption concentration device includes two parallel acetone adsorption concentration columns to alternately adsorb and desorb acetone for recovery.

[0018] The beneficial effects of this invention are as follows: 1. This invention innovatively integrates anoxic acetone production, microaerobic AMAO direct nitrogen removal, and efficient acetone recovery and reuse into a three-in-one process, achieving efficient nitrogen removal and carbon resource utilization in livestock and poultry wastewater. The core innovation of this solution lies in utilizing a novel acetone-mediated ammonia oxidation (AMAO) process to directly convert ammonia nitrogen into nitrogen gas, avoiding the accumulation of intermediate products in the traditional nitrification-denitrification pathway, and achieving a total nitrogen removal rate consistently exceeding 90%. The acetone recovery and precise reflux mechanism effectively buffers fluctuations in influent water quality, ensuring strong system resistance to shocks, and stable compliance of effluent ammonia nitrogen and total nitrogen levels, significantly improving the stability and reliability of the treatment process, and possessing significant engineering application value.

[0019] 2. Compared with traditional processes, this invention completely solves the problem of dependence on external carbon sources, eliminating the need for any external carbon source and significantly reducing operating costs. Simultaneously, the micro-aerobic operating conditions reduce aeration energy consumption by more than 50% compared to traditional nitrification processes. The short AMAO pathway and low sludge yield further reduce sludge disposal costs. The practicality of this solution lies in its low-energy consumption and low-maintenance design, simple operation, and economic efficiency, making it suitable for large-scale livestock and poultry wastewater treatment projects, achieving a balance between environmental benefits and operational economy.

[0020] 3. This invention innovatively converts organic carbon (COD) in wastewater into high-value chemical raw material acetone, turning waste into treasure and opening up a new path for carbon resource utilization from aquaculture wastewater. Taking wastewater with a COD concentration of 10,000 mg / L as an example, based on a conservative conversion rate of 10%, treating 1,000 tons of wastewater daily can recover at least 1 ton of industrial-grade acetone (purity >85%), generating significant economic benefits. This innovation not only breaks through the bottlenecks of carbon source loss and greenhouse gas emissions in traditional processes but also provides a replicable technological model for the circular economy, with broad market prospects.

[0021] 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

[0022] 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 livestock and poultry breeding wastewater according to the present invention. Figure 2 This is a graph showing the changes in COD, ammonia nitrogen, and total nitrogen concentrations of the influent and effluent during the stable operation of the pig farm wastewater treatment process in this invention. In the graph, COD of the influent is ■, COD of the effluent is □, ammonia nitrogen of the influent is ▲, ammonia nitrogen of the effluent is △, total nitrogen of the influent is ●, and total nitrogen of the effluent is ○. Figure 3 This is a graph showing the changes in acetone concentration in the effluent of each unit during the stable operation of the pig farm wastewater treatment process in this invention. Detailed Implementation

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Example 1 This embodiment describes the construction of a continuous flow pilot-scale system for treating effluent from a real pig farm after solid-liquid separation. The main body of the system consists of four core units connected in series, with a total effective volume of 120L. The process flow is as follows: Figure 1 As shown, it includes an anoxic acetone production reactor, an aerobic AMAO denitrification reactor, a sedimentation tank, and an acetone recovery system connected in sequence. Anoxic acetone production reactor: effective volume 60L, with mechanical stirring and equipped with automatic pH control system; Aerobic AMAO denitrification reactor: effective volume 40L, using a microporous aeration and DO-aeration linkage control system; Sedimentation tank: used as a transition between the aerobic AMAO denitrification reactor and the acetone recovery system, used to separate the denitrified effluent and sludge discharged from the aerobic AMAO denitrification reactor, and to introduce the denitrified effluent into the acetone recovery system; The acetone recovery system includes an adsorption concentration device, a thermal vacuum desorption device, and a condensation collection device. The adsorption concentration device includes two parallel acetone adsorption concentration columns, each containing 20L of XDA-1 type non-polar macroporous adsorption resin. After one acetone adsorption concentration column becomes saturated, the system switches to the other acetone adsorption concentration column to ensure continuous system operation. At the same time, the saturated acetone adsorption concentration column is used for acetone desorption and recovery.

[0027] The thermal vacuum desorption device includes a vacuum pump and a heating jacket; the condensation collection device includes a condenser tube and a product receiving tank for receiving condensed acetone, used to collect acetone; the product receiving tank is connected to the inlet of the aerobic AMAO denitrification reactor via a precision metering pump to return a portion of the acetone to the aerobic AMAO denitrification reactor. The process for acetone recovery using the above-mentioned acetone recovery system is conventional technology, and therefore will not be described in detail here.

[0028] The process flow is as follows: the actual wastewater from the pig farm (after solid-liquid separation pretreatment) flows into the anoxic acetone-producing reactor (HRT=18h) to obtain intermediate effluent containing acetone and residual ammonia nitrogen. The effluent then flows into the aerobic AMAO denitrification reactor (HRT=24h) to obtain denitrified effluent containing residual acetone and sludge. After the sludge is separated in the sedimentation tank, the denitrified effluent flows into the acetone adsorption and recovery system for further treatment and effluent discharge.

[0029] Acetone recycling / product path in the acetone adsorption recovery system: After the acetone adsorption concentration column is saturated, vacuum thermal desorption (70°C, -0.095MPa) is initiated. The desorbed high-concentration acetone vapor is condensed and enters the product receiving tank. A portion of the acetone in the product receiving tank can be precisely returned to the inlet of the aerobic AMAO denitrification reactor via a metering pump (in this case, acetone levels did not fluctuate significantly and therefore did not require return), while the remainder is stored as surplus product.

[0030] Specifically, the anoxic acetone-producing reactor is inoculated with pre-acclimated acetone-producing bacteria sludge. The aerobic AMAO denitrification reactor is inoculated with an enriched culture of AMAO functional bacteria; the influent water quality is COD 8500±1200 mg / L, NH4+... + -N 650±80 mg / L, TN 720±90 mg / L, pH 7.5-8.5. Operating parameters were controlled as follows: The anoxic acetone-producing reactor operated under strictly anoxic conditions (dissolved oxygen below 0.2 mg / L) and a slightly acidic environment (pH 8.0-8.2), with a hydraulic retention time of 18 hours to efficiently guide the directional conversion of organic matter into acetone. The aerobic AMAO denitrification reactor operated under slightly aerobic conditions (dissolved oxygen 0.8-2.0 mg / L) and a pH of 7.2-8.5, with a hydraulic retention time of 24 hours to ensure the efficient and stable direct oxidation of ammonia mediated by acetone. In the subsequent acetone recovery system, the empty bed contact time of the adsorption and concentration unit was 30 minutes, and the non-polar macroporous adsorption resin in the acetone adsorption and concentration column was regenerated using vacuum thermal desorption conditions at 70°C and -0.095 MPa. After a 20-day acclimatization start-up, the entire system entered a stable operating period of 30 days.

[0031] like Figures 2-3 As shown in the test results, the effluent acetone concentration of the anoxic acetone-producing reactor remained stable between 600-850 mg / L, with an average of 715 mg / L. This translates to a COD of approximately 1572 mg / L, meaning that 18.5% of the influent COD (mainly organic matter) was directionally converted to acetone, confirming the feasibility of targeted acetone production from livestock and poultry wastewater. The effluent NH4 from the aerobic AMAO reactor... +The average concentrations of nitrogen (N) and nitrite (TN) in the effluent were 28 mg / L and 65 mg / L, respectively, with an average TN removal rate of 91.0%. The average residual acetone concentration was 633 mg / L. The concentrations of nitrite and nitrate in the effluent remained consistently below the detection limits, strongly demonstrating that the main ammonia nitrogen was directly converted to nitrogen gas via the AMAO main pathway, significantly inhibiting traditional nitrification. After treatment by the acetone recovery system, the effluent acetone concentration ranged from 23 to 58 mg / L, with an overall acetone recovery rate (from influent adsorption to the product receiving tank) exceeding 90%. Gas chromatography analysis of the condensed and recovered liquid acetone showed a purity greater than 87%. The final effluent COD was reduced to below 450 mg / L, and TN < 70 mg / L, achieving highly efficient pollutant removal. This indicates that the present invention is a wastewater treatment technology for aquaculture that combines pollution removal and resource recovery.

[0032] 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 direct ammonia oxidation denitrification and carbon recovery in livestock and poultry breeding wastewater, characterized in that, Includes the following steps: The pretreated livestock and poultry breeding wastewater is introduced into the first reaction unit under anaerobic conditions. Through the enriched acetone-producing functional microbial community, some of the organic matter in the livestock and poultry breeding wastewater is directionally converted into acetone, resulting in intermediate effluent containing acetone and residual ammonia nitrogen. The intermediate effluent is introduced into the second reaction unit under micro-aerobic conditions. Through the enriched AMAO functional microbial community, acetone is used as an electron shuttle and carbon source to directly oxidize ammonia nitrogen into nitrogen gas, thereby achieving denitrification and obtaining denitrified effluent containing residual acetone. The denitrified effluent is introduced into an acetone recovery unit to recover residual acetone, resulting in recovered acetone and purified effluent.

2. The method according to claim 1, characterized in that, A portion of the recovered acetone from the acetone recovery unit is returned to the inlet of the second reaction unit to maintain a stable acetone concentration within the second reaction unit, while the remaining recovered acetone is output as a product.

3. The method according to claim 1, characterized in that, The first reaction unit is an anoxic acetone production reactor, with operating conditions including: anoxic conditions, hydraulic retention time of 8-24 hours, and pH of 8.0-8.5, thereby converting 10%-30% of the organic matter in livestock and poultry breeding wastewater into acetone and controlling the effluent acetone concentration to reach 200-3000 mg / L.

4. The method according to claim 1, characterized in that, The second reaction unit is a microaerobic AMAO denitrification reactor. The operating conditions include: dissolved oxygen concentration of 0.5-3.0 mg / L and hydraulic retention time of 6-30 hours. The AMAO functional microbial community uses acetone as a carbon source and electron shuttle to achieve direct oxidation of ammonia nitrogen into nitrogen gas, with a total nitrogen removal rate of ≥90%.

5. The method according to claim 1, characterized in that, The acetone recovery unit employs an adsorption-desorption-condensation combined process, including: Residual acetone in the denitrification effluent was adsorbed using a non-polar macroporous adsorption resin. Saturated resin was subjected to thermal vacuum desorption to obtain high-concentration acetone vapor; High-concentration acetone vapor is condensed into liquid acetone, with an acetone recovery rate of ≥90% and a recovered acetone purity of ≥85%.

6. The method according to claim 2, characterized in that, The refluxed portion of the recovered acetone is precisely controlled by a metering device to compensate for the changes in acetone concentration within the second reaction unit caused by fluctuations in the influent load, thus ensuring stable denitrification efficiency.

7. A direct ammonia oxidation denitrification and carbon recovery system for livestock and poultry breeding wastewater, characterized in that, Including those that are fluidly connected in sequence: The anaerobic acetone production reaction unit is used to convert organic matter in wastewater into acetone under anaerobic conditions. The aerobic AMAO denitrification reaction unit is used for the direct oxidation of ammonia nitrogen to nitrogen gas mediated by acetone. An acetone recovery unit is used to separate and recover acetone from denitrification effluent. The acetone reflux pipeline partially returns the recovered acetone to the inlet of the aerobic AMAO denitrification reaction unit, while the remaining recovered acetone is used as the product output pipeline.

8. The system according to claim 7, characterized in that, The acetone recovery unit includes an adsorption concentration device, a thermal vacuum desorption device, and a condensation collection device connected in sequence. The adsorption concentration device is filled with a non-polar macroporous adsorption resin. The adsorption concentration device includes two parallel acetone adsorption concentration columns to alternately adsorb and desorb acetone for recovery.

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