Domestic sewage treatment method and system based on shortcut nitrification and anaerobic ammonia oxidation of Anammox bacterium preposed alkali reduction

Abstract

The invention provides a domestic sewage treatment method and system based on shortcut nitrification and anaerobic ammonia oxidation of Anammox bacteria preposed alkali reduction, and relates to the technical field of sewage treatment. The method comprises the following steps: anaerobic treatment: converting an organic suspended solid into an easily degradable carbon source through hydrolytic acidification bacteria; the carbon source is absorbed by denitrifying phosphorus-accumulating bacteria and denitrifying glycogen-accumulating bacteria and is stored as an intracellular carbon source; primary anoxic treatment: reacting ammonia nitrogen with nitrite through Anammox bacteria, and synchronously reducing alkalinity; aerobic treatment: under the condition of low alkalinity, in combination with low dissolved oxygen control, Comamox bacteria oxidize ammonia nitrogen into nitrite and accumulate the nitrite; and secondary anoxic treatment: denitrifying residual oxidation nitrogen into nitrogen by using intracellular carbon through denitrifying glycogen-accumulating bacteria. Through the synergistic effect of the hydrolytic acidification bacteria, the denitrifying phosphorus-accumulating bacteria, the Anammox bacteria, the Commox bacteria and the denitrifying glycogen-accumulating bacteria, efficient nitrogen and phosphorus removal is realized.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method and system for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonium oxidation. Background Technology

[0002] Existing domestic wastewater treatment systems primarily rely on traditional biological nitrogen removal and chemical or biological phosphorus removal processes to address high concentrations of nitrogen, phosphorus, and organic pollution. However, these methods have revealed drawbacks in practical applications, including high aeration requirements, significant energy consumption, the generation of greenhouse gases (such as N2O), and difficulty in adapting to fluctuations in water quality and quantity.

[0003] Traditional nitrogen removal pathways involve nitrification and denitrification: nitrification oxidizes ammonia nitrogen to nitrate, requiring extensive aeration; denitrification reduces nitrate to nitrogen gas, demanding a sufficient supply of readily biodegradable carbon sources. However, due to the limited carbon sources in domestic wastewater, nitrogen removal efficiency is low, often necessitating the addition of commercial carbon sources such as methanol, increasing operating costs and carbon footprint. Simultaneously, biological phosphorus removal relies on aerobic polyphosphate-accumulating bacteria for phosphorus absorption, and the limited availability of carbon sources also affects its efficiency.

[0004] In recent years, the coupled short-cut nitrification and anaerobic ammonia oxidation process has attracted widespread attention as a highly efficient and energy-saving nitrogen removal technology. This pathway oxidizes ammonia nitrogen only to nitrite, which is then directly converted into nitrogen gas by anaerobic ammonia oxidizing bacteria. Compared with the traditional pathway, it can save approximately 60% of aeration energy consumption and 100% of carbon source consumption. To achieve stable short-cut nitrification, conditions need to be controlled to enrich ammonia oxidizing bacteria and inhibit nitrite oxidizing bacteria. However, due to the difficulty in efficiently and stably inhibiting nitrite oxidizing bacteria, the widespread application of this pathway remains limited.

[0005] Research has found that Commammox bacteria, capable of completing the entire nitrification process—continuously oxidizing ammonia nitrogen to nitrite and then further to nitrate—within the same cell, exhibit complete nitrification capabilities. Traditional methods struggle to precisely control the metabolic processes of Commammox bacteria, preventing them from ceasing the reaction after oxidizing ammonia nitrogen to nitrite. Therefore, overcoming existing technological bottlenecks and achieving targeted regulation of the metabolic pathways of Commammox bacteria is crucial to achieving their short-range nitrification goals.

[0006] Anammox bacteria can consume alkalinity. If placed before ammonia-oxidizing bacteria, they can reduce the alkalinity in wastewater in situ, thereby effectively inhibiting the nitrite oxidation step of Anammox bacteria and promoting short-cut nitrification. Compared to conventional inhibition strategies that rely on free ammonia or free nitrite, this method does not require the addition of additional chemical agents, frequent pH adjustments, and avoids the operational complexity and operating costs caused by residual free ammonia and free nitrite from structure cleaning. Summary of the Invention

[0007] One objective of this invention is to provide a short-cut nitrification and anaerobic ammonium oxidation method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkalinity reduction, thereby addressing at least one of the technical problems existing in the prior art. This invention achieves highly efficient nitrogen and phosphorus removal through the synergistic effect of hydrolytic acidifying bacteria, denitrifying phosphorus-accumulating bacteria, denitrifying polysaccharide-accumulating bacteria, Anammox bacteria, and Commammox bacteria. This process requires no external carbon source, no chemical agents to control low alkalinity, saves approximately 60% of aeration energy consumption, and produces effluent with total nitrogen <5 mg / L, COD <40 mg / L, and PO4 <5 mg / L. 3- -P < 0.2 mg / L, with advantages such as energy saving, low carbon, and high efficiency.

[0008] A second objective of this invention is to provide a short-cut nitrification and anaerobic ammonia oxidation domestic wastewater treatment system based on Anammox bacteria for pre-treatment alkali reduction. This system utilizes packing material to enhance the retention of Anammox and Commammox bacteria, thereby improving reaction efficiency.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction through short-cut nitrification and anaerobic ammonia oxidation, comprising the following steps: (a) Anaerobic treatment: domestic sewage is anaerobically treated, and inert organic suspended solids in it are converted into easily degradable carbon sources by hydrolytic acidifying bacteria. The converted easily degradable carbon sources are absorbed and stored as intracellular carbon sources by denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria. (b) Anoxic treatment: The effluent from step (a) is subjected to anoxic treatment. At the same time, nitrite is introduced into the aerobic reflux liquid. Anammox bacteria use ammonia nitrogen in domestic sewage and nitrite in reflux liquid as substrates to carry out anaerobic ammonia oxidation denitrification reaction. Denitrifying polyphosphate bacteria remove phosphorus in the water simultaneously. (c) Aerobic treatment: The water obtained in step (b) is subjected to aerobic treatment, in which the remaining ammonia nitrogen is oxidized to nitrite by Commammox bacteria; (d) Secondary anoxic treatment: Part of the water obtained in step (c) is recycled to step (b) to provide nitrite, and the remainder is subjected to secondary anoxic treatment. The residual oxidized nitrogen is denitrified into nitrogen gas by denitrifying polysaccharide bacteria using the intracellular carbon source.

[0010] Furthermore, the hydraulic retention time for anaerobic treatment in step (a) is 1.0-2.0 hours; the temperature for anaerobic treatment is 30-35°C. The sludge age for the anaerobic treatment is 12-18 days.

[0011] Furthermore, in step (b), the hydraulic retention time for a single anoxic treatment is 2.0-4.0 hours; the dissolved oxygen concentration is below 0.5 mg / L; and the temperature for the single anoxic treatment is 30-35°C. The sludge age for the first anoxic treatment is 10-15 days. The alkalinity of the influent is reduced to 30-40 mg CaCO3 / L through the anaerobic ammonia oxidation reaction in step (b).

[0012] Furthermore, in step (c), the hydraulic retention time for aerobic treatment is 1.5-2.5 hours; the dissolved oxygen concentration is 0.5-1.0 mg / L; and the temperature for aerobic treatment is 30-35℃. The sludge age for aerobic treatment is 10-15 days.

[0013] Furthermore, in step (d), the hydraulic retention time for the secondary anoxic treatment is 1.0-2.0 hours; the dissolved oxygen concentration is below 0.5 mg / L; and the temperature for the secondary anoxic treatment is 30-35℃.

[0014] Furthermore, prior to step (a), a mixed activated sludge containing hydrolytic acidifying bacteria, denitrifying polyphosphate bacteria, denitrifying polysaccharide bacteria, Anammox bacteria, and Commammox bacteria is inoculated and allowed to stand for 24-48 hours to achieve colonization of the microbial community.

[0015] Secondly, the present invention provides a system for treating domestic wastewater based on the aforementioned method of short-cut nitrification and anaerobic ammonia oxidation using Anammox bacteria for pre-treatment alkali reduction, comprising: a hydrolysis acidification reaction tank for anaerobic treatment, an anoxic reaction tank for primary anoxic treatment, an aerobic reaction tank for aerobic treatment, and a post-anoxic reaction tank for secondary anoxic treatment, all connected in sequence.

[0016] Furthermore, the anoxic reaction tank and the aerobic reaction tank are equipped with fixed packing material, and the volume ratio of the fixed packing material added is 20%-30% of the effective volume of the reaction tank. The system also includes a first reflux pump, the inlet of which is connected to the aerobic reaction tank and the outlet of which is connected to the anoxic reaction tank, for recirculating 30%-50% of the effluent from the aerobic reaction tank to the anoxic reaction tank.

[0017] Furthermore, the hydrolysis acidification reaction tank is equipped with a first stirrer with a rotation speed of 50-100 rpm; The anoxic reaction tank is equipped with a second stirrer with a rotation speed of 30-80 rpm.

[0018] Furthermore, the system also includes an inlet tank and a sedimentation tank; The inlet tank is connected to the hydrolysis acidification reaction tank, and the post-anoxic reaction tank is connected to the sedimentation tank.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a short-cut nitrification and anaerobic ammonium oxidation method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction. By constructing a multi-stage biological treatment process of "anaerobic-anoxic-aerobic-secondary anoxic," it utilizes the synergistic functions of hydrolytic acidifying bacteria, denitrifying polyphosphate-accumulating bacteria, denitrifying polysaccharide-accumulating bacteria, Anammox bacteria, and Commammox bacteria to achieve efficient and simultaneous removal of carbon, nitrogen, and phosphorus from domestic wastewater. In this invention, wastewater first enters the anaerobic stage, where hydrolytic acidifying bacteria convert macromolecular organic matter into easily degradable carbon sources, and denitrifying polyphosphate-accumulating bacteria and denitrifying polysaccharide-accumulating bacteria simultaneously absorb and store these as internal carbon sources. Subsequently, it enters the anoxic stage, where Anammox bacteria utilize the returned NO2... - -N and NH4 + -N undergoes anaerobic ammonia oxidation, consuming alkalinity in the process. In the aerobic stage, Commammox bacteria oxidize only ammonia nitrogen to nitrite under low alkalinity conditions and provide nitrite for the primary anoxic stage through reflux. Finally, in the post-anoxic stage, denitrifying polysaccharide bacteria utilize an internal carbon source to oxidize residual NO2. - -N and NO3 - -N is denitrified into nitrogen gas, achieving deep nitrogen removal. The entire process requires no external carbon source or chemical reagents, and the effluent quality is stable and meets standards. It has advantages such as energy saving, low carbon footprint, and high efficiency. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a domestic wastewater treatment system based on Anammox bacteria for pre-treatment alkali reduction, involving short-cut nitrification and anaerobic ammonia oxidation, provided in an embodiment of the present invention.

[0022] Icons: 1-Inlet tank; 2-Hydrolysis acidification reaction tank; 3-Anoxic reaction tank; 4-Aerobic reaction tank; 5-Post-anoxic reaction tank; 6-Sedimentation tank; 21-First inlet pump; 22-First agitator; 31-Second agitator; 32-First return pump; 33-Anoxic reaction section sludge discharge port; 41-Aeration pump; 51-Third agitator; 52-Post-anoxic section outlet; 61-Second return pump; 62-Sedimented sludge discharge port. Detailed Implementation

[0023] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The first aspect of this invention provides a method for treating domestic wastewater based on pre-treatment alkali reduction using Anammox bacteria, comprising the following steps: (a) Anaerobic treatment: domestic sewage is anaerobically treated, and the organic suspended solids in it are converted into easily degradable carbon sources by hydrolytic acidifying bacteria. The converted easily degradable carbon sources are absorbed and stored as intracellular carbon sources by denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria. (b) Primary anoxic treatment: The effluent from step (a) is subjected to anoxic treatment, while the aerobic reflux liquid is introduced into the anoxic treatment unit to provide nitrite. Anammox bacteria use ammonia nitrogen in domestic sewage and nitrite in reflux liquid as substrates to carry out anaerobic ammonia oxidation denitrification reaction, while denitrifying polyphosphate bacteria remove phosphorus from the water simultaneously. (c) Aerobic treatment: The water obtained in step (b) is subjected to aerobic treatment, in which the remaining ammonia nitrogen is oxidized to nitrite by Commammox bacteria; (d) Secondary anoxic treatment: Part of the water obtained in step (c) is recycled to step (b) to provide nitrite, and the remainder is subjected to secondary anoxic treatment. The residual oxidized nitrogen is denitrified into nitrogen gas by denitrifying polysaccharide bacteria using the intracellular carbon source.

[0026] This invention utilizes the highly efficient collaboration of Commammox bacteria (full-process ammonia oxidizers), Anammox bacteria (anaerobic ammonia oxidizers), denitrifying polyphosphate-accumulating bacteria, denitrifying polysaccharide bacteria, and hydrolytic acidifying bacteria to achieve energy-saving, low-carbon, and green biological wastewater treatment. In the anaerobic stage, hydrolytic acidifying bacteria convert organic suspended solids into easily degradable carbon sources, which are then absorbed and stored as intracellular carbon sources by denitrifying polyphosphate-accumulating bacteria and denitrifying polysaccharide bacteria. In the anoxic stage, Anammox bacteria utilize nitrite and residual ammonia nitrogen for denitrification while simultaneously reducing the alkalinity of the wastewater, while denitrifying polyphosphate-accumulating bacteria absorb phosphorus to remove phosphorus from the water. In the aerobic stage, under alkalinity-limited conditions, Commammox bacteria dominate short-cut nitrification, oxidizing ammonia nitrogen to nitrite, and the resulting nitrite is returned to the anoxic stage. In the post-anoxic stage, denitrifying polysaccharide bacteria utilize internal carbon sources to denitrify residual nitrate and nitrite, achieving deep denitrification. In addition, to enhance the retention of slow-growing Anammox and Commammox bacteria, packing materials were added to the anoxic and aerobic sections to promote the formation of biofilms by Anammox and Commammox bacteria.

[0027] Furthermore, Anammox bacteria can consume alkalinity. By pre-positioning Anammox bacteria before Commammox bacteria, the alkalinity in wastewater can be reduced in situ by Anammox bacteria, inhibiting the nitrite oxidation step of Commammox bacteria and thus achieving short-cut nitrification. Compared with commonly used free ammonia and free nitrite, it does not require the addition of additional chemical agents, pH adjustment, or additional cleaning of structures to remove residual free ammonia and free nitrite. Denitrifying polyphosphate bacteria can simultaneously denitrify while removing phosphorus, achieving dual carbon utilization. Compared with aerobic phosphorus removal bacteria, it can save 50% of carbon source requirements and increase nitrogen removal efficiency by 50%. In the anaerobic treatment stage of this invention, hydrolytic acidifying bacteria effectively convert large molecular organic matter in wastewater into easily degradable small molecular organic matter; denitrifying polyphosphate bacteria utilize these small molecular carbon sources for metabolic activities and simultaneously absorb phosphates from the environment, storing them in the cells in the form of polyphosphate, thereby achieving effective enrichment and removal of phosphorus. Furthermore, denitrifying polysaccharide bacteria can utilize intracellular carbon sources to achieve denitrification. They can remove residual nitrite and nitrate from the effluent, theoretically reducing the total nitrogen in the effluent to zero, thus achieving deep denitrification.

[0028] The advantages of the domestic sewage treatment method provided by this invention are as follows: (1) Achieve efficient and stable short-cut nitrification control. By utilizing the characteristic of Anammox bacteria to pre-consume alkalinity, the alkalinity of wastewater is reduced in situ to inhibit the nitrite oxidation step of Commammox bacteria, thus achieving stable short-cut nitrification. Compared with traditional methods that rely on free ammonia and free nitrite for inhibition, no additional chemical agents, pH adjustment, or additional structure cleaning is required. The operation is simple and environmentally friendly.

[0029] (2) Significantly reduced energy consumption and carbon emissions. Through the synergistic effect of short-cut nitrification dominated by Commammox bacteria and anaerobic ammonium oxidation by Anammox bacteria, approximately 60% of aeration energy consumption can be saved compared to traditional denitrification processes, and carbon source addition is completely avoided. At the same time, hydrolytic acidifying bacteria convert inert carbon sources in domestic sewage that are difficult to use directly into directly usable carbon sources, and denitrifying polyphosphate-accumulating bacteria achieve "one carbon, two uses", which significantly reduces the carbon footprint while reducing operating costs and exploring usable carbon sources in sewage.

[0030] (3) Simultaneous and efficient nitrogen and phosphorus removal with increased treatment load. Through the zonal cooperation of four functional bacteria and the enhancement of the packing biofilm, carbon source conversion, nitrogen removal and phosphorus removal are achieved simultaneously in the anaerobic-anoxic-aerobic-post-anoxic zone. Hydrolytic acidifying bacteria solve the problem of insufficient carbon source utilization, Anammox bacteria and denitrifying polyphosphate-accumulating bacteria respectively achieve efficient nitrogen and phosphorus removal in the anoxic zone, and Commammox bacteria stably provide nitrite in the aerobic zone. The overall system has a high treatment load and excellent effluent quality.

[0031] (4) Deep denitrification is achieved. The internal carbon source denitrification is achieved by using polysaccharide bacteria, which further removes the remaining nitrates and nitrites in the aerobic effluent, so that the total nitrogen in the effluent can theoretically be reduced to 0.

[0032] In some preferred embodiments, the hydraulic retention time of the anaerobic treatment in step (a) is 1.0-2.0 hours, for example, 1.0 hour, 1.5 hours, 2.0 hours, etc.; the temperature of the anaerobic treatment is 30-35℃, for example, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.; the sludge age of the anaerobic treatment is 12-18 days, for example, 12 days, 13 days, 14 days, 15 days, 16 days, 17 days, 18 days, etc.

[0033] In this invention, in the anaerobic treatment stage: domestic sewage is introduced into the hydrolysis acidification reaction tank 2 and hydrolyzed and acidified at 30-35℃ for 1.0-2.0 hours. The hydrolysis acidification bacteria convert inert organic matter into easily degradable carbon sources, and denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria simultaneously absorb and store them as intracellular carbon sources.

[0034] In some preferred embodiments, the hydraulic retention time of the first anoxic treatment in step (b) is 2.0-4.0 hours, for example, 2.0 hours, 3.0 hours, 4.0 hours, etc.; the dissolved oxygen concentration is below 0.5 mg / L to maintain the anoxic environment; the temperature of the first anoxic treatment is 30-35℃, for example, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.; the sludge age of the first anoxic treatment is 10-15 days, for example, 10 days, 11 days, 12 days, 13 days, 14 days, 15 days, etc.; through the anaerobic ammonium oxidation reaction in step (b), the alkalinity of the influent is reduced to 30-40 mg CaCO3 / L, thereby inhibiting the nitrite oxidation activity of Commammox bacteria and achieving stable short-cut nitrification.

[0035] In this invention, during the anoxic treatment phase: the effluent from the anaerobic phase is introduced into the anoxic reaction tank 3, with the temperature controlled at 30-35℃, the HRT at 2.0-4.0 hours, and DO < 0.5 mg / L. Anammox bacteria utilize the NO2 in the reflux liquid. - -N and NH4 + -N carries out anaerobic ammonia oxidation, simultaneously reducing influent alkalinity, while denitrifying polyphosphate-accumulating bacteria absorb PO4. 3- -P achieves phosphorus removal.

[0036] In some preferred embodiments, the hydraulic retention time of the aerobic treatment in step (c) is 1.5-2.5 hours, for example, 1.5 hours, 2.0 hours, 2.5 hours, etc.; the dissolved oxygen concentration is 0.5-1.0 mg / L; the temperature of the aerobic treatment is 30-35℃, for example, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.; and the sludge age of the aerobic treatment is 10-15 days, for example, 10 days, 11 days, 12 days, 13 days, 14 days, 15 days, etc.

[0037] In this invention, in the aerobic treatment section, the effluent from the anoxic section is introduced into the aerobic reaction tank 4, with DO controlled at 0.5-1.0 mg / L, temperature at 30-35℃, and HRT at 1.5-2.5 hours. Under low alkalinity conditions, Commammox bacteria oxidize ammonia to NO2. - -N and accumulate.

[0038] In some preferred embodiments, the hydraulic retention time of the secondary anoxic treatment in step (d) is 1.0-2.0 hours, for example, 1.0 hours, 1.5 hours, 2.0 hours, etc.; the dissolved oxygen concentration is less than 0.5 mg / L; and the temperature of the secondary anoxic treatment is 30-35℃, for example, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.

[0039] In this invention, in the post-anoxic treatment section, a portion of the effluent from the aerobic section is recirculated to the primary anoxic section, while the remainder enters the post-anoxic reaction tank 5. The temperature is controlled at 30-35℃, the HRT is 1.0-2.0 hours, and DO < 0.5 mg / L. Denitrifying polysaccharide bacteria utilize the internal carbon source to denitrify the residual NO2. - -N and NO3 - -N is denitrified into nitrogen gas, achieving deep denitrification.

[0040] In some preferred embodiments, prior to step (a), a mixed activated sludge comprising hydrolytic acidifying bacteria, denitrifying polyphosphate bacteria, denitrifying polysaccharide bacteria, Anammox bacteria and Commammox bacteria is inoculated and allowed to stand for 24-48 hours to achieve colonization of the microbial community.

[0041] like Figure 1 As shown, the second aspect of the present invention provides a system for a short-cut nitrification and anaerobic ammonia oxidation method for treating domestic wastewater based on Anammox bacteria for pre-alkali reduction, comprising: a hydrolysis acidification reaction tank 2 for anaerobic treatment, an anoxic reaction tank 3 for primary anoxic treatment, an aerobic reaction tank 4 for aerobic treatment, and a post-anoxic reaction tank 5 for secondary anoxic treatment, which are connected in sequence.

[0042] In some preferred embodiments, the system further includes an inlet tank 1 and a sedimentation tank 6; The inlet tank 1 is connected to the hydrolysis acidification reaction tank 2, and the post-anoxic reaction tank 5 is connected to the sedimentation tank 6.

[0043] The system provided by the present invention includes: an inlet tank 1, a hydrolysis acidification reaction tank 2, an anoxic reaction tank 3, an aerobic reaction tank 4, a post-anoxic reaction tank 5, and a sedimentation tank 6; the inlet tank 1 is connected to the hydrolysis acidification reaction tank 2 via a first inlet pump 21; the outlet of the hydrolysis acidification reaction tank 2 is connected to the anoxic reaction tank 3, the outlet of the anoxic reaction tank 3 is connected to the aerobic reaction tank 4, the outlet of the aerobic reaction tank 4 is connected to the post-anoxic reaction tank 5, and the post-anoxic reaction tank 5 is connected to the sedimentation tank 6 via the post-anoxic section outlet 52.

[0044] Optionally, the sedimentation tank 6 is equipped with a sludge return pump, which can return part of the sludge to the hydrolysis acidification reaction tank 2. The sedimentation tank 6 and the hydrolysis acidification reaction tank 2 are connected through a second return pump 61.

[0045] Optionally, the sedimentation tank 6 is provided with a sludge discharge port 62; the anoxic reaction tank 3 is provided with an anoxic reaction section sludge discharge port 33.

[0046] In some preferred embodiments, the anoxic reaction tank 3 and the aerobic reaction tank 4 are equipped with fixed packing material. The volume ratio of the fixed packing material is 20%-30% of the effective volume of the reaction tank, such as 20%, 25%, 30%, etc., to enhance the retention of Anammox and Commammox bacteria and promote biofilm formation. The biofilm thickness is controlled at 200-400 μm.

[0047] The system also includes a first reflux pump 32, the inlet of which is connected to the aerobic reaction tank 4, and the outlet of which is connected to the anoxic reaction tank 3. This pump is used to reflux 30%-50% of the effluent from the aerobic reaction tank 4 to the anoxic reaction tank 3, preferably with a reflux ratio of 40%, to provide the NO2 required for anaerobic ammonia oxidation. - -N.

[0048] In some preferred embodiments, the hydrolysis acidification reaction tank 2 is equipped with a first stirrer 22 with a rotation speed of 50-100 rpm, such as 50 rpm, 75 rpm, 100 rpm, etc., to achieve thorough mixing of sewage and sludge; the anoxic reaction tank 3 is equipped with a second stirrer 31 with a rotation speed of 30-80 rpm, such as 30 rpm, 55 rpm, 80 rpm, etc.; and the post-anoxic reaction tank 5 is equipped with a third stirrer 51.

[0049] Optionally, the aerobic reaction tank 4 is equipped with an aeration pump 41 to adjust the dissolved oxygen to 0.5-1.0 mg / L to support the short-cut nitrification reaction dominated by Commammox bacteria.

[0050] In a preferred embodiment of the present invention, the method for treating domestic sewage includes the following steps: (1) System construction and strain inoculation: (1-1) Construct a biochemical system including a hydrolysis acidification reaction tank 2, an anoxic reaction tank 3, an aerobic reaction tank 4, and a post-anoxic reaction tank 5; (1-2) Add fixed packing material to the anoxic reaction tank 3 and the aerobic reaction tank 4. The volume ratio of the packing material is 20%-30% of the effective volume of the reaction tank, preferably 25%. The packing material is submerged in the reaction tank mixture to enhance the retention of Anammox and Commammox bacteria and promote biofilm formation. (1-3) Inoculate with mixed activated sludge containing hydrolytic acidifying bacteria, denitrifying polyphosphate bacteria, denitrifying polysaccharide bacteria, Anammox bacteria and Commammox bacteria. After inoculation, allow to stand for 24-48 hours to achieve colonization of the microbial community, and maintain the temperature at 30-35℃ during this period.

[0051] (2) Anaerobic treatment: (2-1) Domestic sewage is introduced into hydrolysis acidification reaction tank 2. The hydrolysis acidification bacteria convert inert organic suspended solids into easily degradable carbon sources. Denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria simultaneously absorb the carbon source and store it as an intracellular carbon source.

[0052] (3) One hypoxia treatment: (3-1) The effluent from the anaerobic section is introduced into the anoxic reaction tank 3, where Anammox bacteria utilize the NO2 returned from the aerobic section. - -N and NH4 + -N undergoes anaerobic ammonia oxidation for nitrogen removal, significantly reducing influent alkalinity and facilitating subsequent short-cut nitrification in the aerobic stage. Furthermore, denitrifying polyphosphate-accumulating bacteria absorb PO4. 3- -P achieves phosphorus removal, and regular sludge discharge achieves biological phosphorus removal.

[0053] (4) Aerobic treatment: (4-1) The effluent from the anoxic zone is introduced into the aerobic reaction tank 4. Under the low alkalinity influent conditions of the anoxic zone, the Commammox bacteria only oxidize ammonia to NO2. - -N (accumulation rate > 85%), and achieve accumulation.

[0054] (4-2) The effluent from the aerobic section is returned to the primary anoxic section to support the anaerobic ammonia oxidation denitrification demand of the anoxic section.

[0055] (5) Secondary hypoxia treatment (i.e., post-hypoxia treatment section): (5-1) Introduce the effluent from the aerobic section into the post-anoxic reactor.

[0056] (5-2) Denitrifying polysaccharide bacteria utilize the internal carbon source stored in the anaerobic section to convert the remaining NO3- into nitrogen. - -N and NO2 - -N is denitrified into nitrogen gas, achieving a deep denitrification effect.

[0057] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0058] The influent water quality of the domestic sewage used in the following examples and comparative examples is as follows: Table 1. Water quality of domestic sewage

[0059] Example 1 This embodiment provides a method for treating domestic sewage, including the following steps: (1) System construction and strain inoculation: (1-1) The main biochemical device includes a hydrolysis acidification reaction tank 2, an anoxic reaction tank 3, an aerobic reaction tank 4 and a post-anoxic reaction tank 5, and the reaction tanks are connected in series; the tank body material is plexiglass with a volume ratio of 1:2:2:1.

[0060] (1-2) Add fixed packing material to the anoxic reaction tank 3 and the aerobic reaction tank 4. The addition volume ratio is 25% of the effective volume of the reaction tank. The packing material is submerged in the mixed liquid of the reaction tank. The biofilm thickness is controlled at 200-400 μm.

[0061] (1-3) Inoculate with mixed activated sludge containing hydrolytic acidifying bacteria, denitrifying polyphosphate bacteria, denitrifying polysaccharide bacteria, Anammox bacteria and Commammox bacteria. After inoculation, allow to stand for 36 hours to achieve colonization of the microbial community, and maintain the temperature at 30-35℃ during this period.

[0062] (2) Anaerobic reaction section: (2-1) The domestic sewage in the domestic sewage inlet tank 1 is introduced into the hydrolysis reaction tank through the first inlet pump 21. The temperature is controlled at 30~35℃ and the hydraulic retention time (HRT) is set to 1.5 hours to ensure that the sewage fully contacts the sludge in the reactor. The first agitator 22 is started and the speed is controlled at 75 rpm.

[0063] (2-2) Maintain the mixed MLSS (sludge concentration) in the hydrolysis acidification reaction tank 2 within the range of 3000-4000 mg / L, and adjust the concentration by sludge return or discharge; the sludge return ratio is controlled at 80% (the returned sludge comes from the sedimentation tank 6).

[0064] (2-5) Under anaerobic conditions, during the reaction process, hydrolytic acidifying bacteria convert organic suspended solids into easily degradable carbon sources, while denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria simultaneously absorb and store the easily degradable carbon sources as intracellular carbon sources; sludge age (SRT) is controlled at 15 days.

[0065] (3) Hypoxia reaction section: (3-1) The effluent from the hydrolysis acidification reaction tank 2 is introduced into the anoxic reaction tank 3. The temperature inside the reactor is controlled at 30-35℃ and the HRT is 3 hours to match the slow growth characteristics of Anammox bacteria. The second stirrer 31 is turned on at a speed of 50 rpm, the DO is less than 0.5 mg / L, and the MLSS is in the range of 3500~4500 mg / L. Combined with the contribution of the biofilm in the packing material (thickness 200-400 μm), the total concentration is not less than 4000 mg / L.

[0066] (3-2) Anammox bacteria utilize NO2 returned from aerobic reactor 4 - -N and remaining NH4 +-N undergoes anaerobic ammonia oxidation for nitrogen removal, reducing the influent alkalinity to 30-40 mg CaCO3 / L; in addition, denitrifying polyphosphate-accumulating bacteria absorb PO4. 3- -P achieves phosphorus removal, and the sludge age SRT is controlled at 10 days.

[0067] (4) Aerobic treatment section: (4-1) The effluent from the anoxic reaction tank 3 is introduced into the aerobic reaction tank 4, and the temperature is controlled at 30~35℃ with an HRT of 2 hours. The aeration rate is adjusted to control the DO at 0.5-1.0 mg / L, which is adjusted by aeration pump 41. The MLSS is monitored and maintained at 3500~4500 mg / L. Combined with the packing biofilm (thickness 250-450 μm), the total retention concentration is stabilized at 4000 mg / L. The stirring is completed by aeration pump 41.

[0068] (4-2) 40% of the effluent from the aerobic section is returned to the anoxic reaction tank 3 via the first return pump 32, with a return ratio of 40%.

[0069] (5) Post-anoxic treatment section: (5-1) Introduce the effluent from the aerobic section into the post-anoxic reaction tank 5, control the temperature at 30-35℃, HRT at 1.5 hours, turn on the third stirrer 51 at 40 rpm, keep the DO below 0.5 mg / L and the MLSS at 3000~4000 mg / L.

[0070] (5-2) Denitrifying polysaccharide bacteria utilize stored internal carbon sources to convert excess NO2 into nitrogen. - -N and NO3 - -N is denitrified into nitrogen gas; SRT is controlled at 10 days, and sludge is regularly discharged to maintain system balance; the effluent is discharged in compliance with standards through the sedimentation tank outlet.

[0071] Example 2 This embodiment provides a method for treating domestic sewage, which differs from Embodiment 1 in that: In the anaerobic reaction section, the HRT is 1 hour; During the hypoxic reaction phase, the HRT is 4 hours; In the aerobic treatment section, the HRT is 1.5 hours; The post-anoxic treatment section has an HRT of 2 hours.

[0072] Example 3 This embodiment provides a method for treating domestic sewage, which differs from Embodiment 1 in that: In the anaerobic reaction section, the HRT is 2 hours; During the hypoxic reaction phase, the HRT is 2 hours; In the aerobic treatment section, the HRT is 2.5 hours; The post-anoxic treatment section has a HRT of 1 hour.

[0073] Example 4 This embodiment provides a method for treating domestic sewage, which differs from Embodiment 1 in that no fixed packing material is installed in the anoxic reaction tank 3 and the aerobic reaction tank 4.

[0074] Comparative Example 1 This comparative example provides a method for treating domestic sewage, which differs from Example 1 in that it does not include a post-anoxic treatment stage.

[0075] Comparative Example 2 A comparative example provides a method for treating domestic sewage, which differs from Example 1 in that: no effective hydrolysis and acidification treatment is performed in the anaerobic reaction stage, i.e., no hydrolysis and acidification bacteria are added.

[0076] Comparative Example 3 The comparative example provides a method for treating domestic sewage, which differs from Example 1 in that Anammox bacteria are not added, i.e., the Anammox pre-alkali consumption mechanism is missing in the anoxic reaction stage.

[0077] Test case Test method: After each reaction cycle, the mixed sludge from each reaction tank was collected, filtered, and the supernatant was used to detect total nitrogen (HJ 636-2012 alkaline potassium persulfate digestion ultraviolet spectrophotometry), COD (HJ 828-2017 potassium dichromate method) and total phosphorus (GB 11893-89 ammonium molybdate spectrophotometry).

[0078] The test results are shown in Table 2.

[0079] Table 2

[0080] As shown in Table 2, after treating domestic sewage using the method and system of this invention, the effluent total nitrogen is <5 mg / L, COD is <40 mg / L, and PO4 is <5 mg / L. 3- -P < 0.2 mg / L. Specifically, Example 1 showed that total nitrogen (2.3 mg / L), COD (25 mg / L), and PO4 were... 3--P (0.01 mg / L) showed the best performance across all three indicators, reflecting the close connection and stable operation of the anaerobic hydrolysis, Anammox pre-treatment for alkalinity reduction, Commammox short-cut nitrification, and internal carbon source denitrification processes. Although Examples 2 and 3 adjusted the hydraulic retention times of each stage to the extremes of the range listed in this invention, the total nitrogen in the effluent remained at 3.1-3.2 mg / L, and COD and phosphorus were also at good levels, indicating that this parameter range is practically feasible. In Example 4, after removing the packing material, the total nitrogen rose to 4.3 mg / L, and COD and phosphorus increased simultaneously, indicating that the packing material has a substantial effect on the retention of Anammox and Commammox bacteria, and its absence directly affected the alkalinity control effect and the continuity of subsequent reactions. The comparative examples, from different perspectives, confirmed the functional necessity of each component in the process: the lack of a post-anoxic stage led to an increase in total nitrogen; the absence of hydrolysis acidification resulted in poorer COD and phosphorus removal; and without the introduction of Anammox bacteria, the total nitrogen rose to 12.3 mg / L. The mg / L concentration fully demonstrates its fundamental role in reducing influent alkalinity and ensuring stable operation of subsequent short-cut nitrification.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction, involving short-cut nitrification and anaerobic ammonium oxidation, characterized in that, Includes the following steps: (a) Anaerobic treatment: domestic sewage is anaerobically treated, and inert organic suspended solids in it are converted into easily degradable carbon sources by hydrolytic acidifying bacteria. The converted easily degradable carbon sources are absorbed and stored as intracellular carbon sources by denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria. (b) Anoxic treatment: The effluent from step (a) is subjected to anoxic treatment. At the same time, nitrite is introduced into the aerobic reflux liquid. Anammox bacteria use ammonia nitrogen in domestic sewage and nitrite in reflux liquid as substrates to carry out anaerobic ammonia oxidation denitrification reaction. Denitrifying polyphosphate bacteria remove phosphorus in the water simultaneously. (c) Aerobic treatment: The water obtained in step (b) is subjected to aerobic treatment, in which the remaining ammonia nitrogen is oxidized to nitrite by Commammox bacteria; (d) Secondary anoxic treatment: Part of the water obtained in step (c) is recycled to step (b) to provide nitrite, and the remainder is subjected to secondary anoxic treatment. The residual oxidized nitrogen is denitrified into nitrogen gas by denitrifying polysaccharide bacteria using the intracellular carbon source.

2. The method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonium oxidation, as described in claim 1, is characterized in that... The hydraulic retention time for anaerobic treatment in step (a) is 1.0-2.0 hours; the temperature for anaerobic treatment is 30-35℃. The sludge age for the anaerobic treatment is 12-18 days.

3. The method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonium oxidation, as described in claim 1, is characterized in that... In step (b), the hydraulic retention time for one anoxic treatment is 2.0-4.0 hours; the dissolved oxygen concentration is below 0.5 mg / L; and the temperature for the first anoxic treatment is 30-35℃. The sludge age for the first anoxic treatment is 10-15 days. The alkalinity of the influent is reduced to 30-40 mg CaCO3 / L through the anaerobic ammonia oxidation reaction in step (b).

4. The method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonia oxidation, as described in claim 1, is characterized in that... In step (c), the hydraulic retention time for aerobic treatment is 1.5-2.5 hours; the dissolved oxygen concentration is 0.5-1.0 mg / L; and the temperature for aerobic treatment is 30-35℃. The sludge age for aerobic treatment is 10-15 days.

5. The method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonia oxidation, as described in claim 1, is characterized in that... In step (d), the hydraulic retention time for the secondary anoxic treatment is 1.0-2.0 hours; the dissolved oxygen concentration is below 0.5 mg / L; and the temperature for the secondary anoxic treatment is 30-35℃.

6. The method for treating domestic wastewater based on Anammox bacteria for pre-treatment alkali reduction and short-cut nitrification and anaerobic ammonia oxidation, as described in claim 1, is characterized in that... Before step (a), a mixed activated sludge containing hydrolytic acidifying bacteria, denitrifying polyphosphate bacteria, denitrifying polysaccharide bacteria, Anammox bacteria and Commammox bacteria is inoculated and allowed to stand for 24-48 hours to achieve colonization of the microbial community.

7. A system for treating domestic wastewater based on the short-cut nitrification and anaerobic ammonia oxidation method using Anammox bacteria for pre-treatment alkali reduction as described in any one of claims 1-6, characterized in that, include: The reactor consists of a hydrolysis acidification reactor for anaerobic treatment, an anoxic reactor for primary anoxic treatment, an aerobic reactor for aerobic treatment, and a post-anoxic reactor for secondary anoxic treatment, all connected in sequence.

8. The system according to claim 7, characterized in that, The anoxic reaction tank and the aerobic reaction tank are equipped with fixed packing material, and the volume ratio of the fixed packing material added is 20%-30% of the effective volume of the reaction tank. The system also includes a first reflux pump, the inlet of which is connected to the aerobic reaction tank and the outlet of which is connected to the anoxic reaction tank, for recirculating 30%-50% of the effluent from the aerobic reaction tank to the anoxic reaction tank.

9. The system according to claim 7, characterized in that, The hydrolysis acidification reaction tank is equipped with a first stirrer with a rotation speed of 50-100 rpm; The anoxic reaction tank is equipped with a second stirrer with a rotation speed of 30-80 rpm.

10. The system according to claim 7, characterized in that, It also includes an inlet tank and a sedimentation tank; The inlet tank is connected to the hydrolysis acidification reaction tank, and the post-anoxic reaction tank is connected to the sedimentation tank.

Images