Energy-saving and emission-reducing type biochemical nitrogen and phosphorus removal sewage treatment system

Abstract

The invention discloses an energy-saving and emission-reducing type biochemical nitrogen and phosphorus removal sewage treatment system, which is based on basic theories of an AB process and an AAO process, basic physiological characteristics that phosphorus-accumulating bacteria need an organic carbon source and anaerobic ammonium oxidation bacteria do not need the organic carbon source, and a mature level of anaerobic ammonium oxidation technology development. A municipal sewage treatment system is divided into two independent sections, namely a section I and a section II, the section I is an APO (anaerobic / aerobic) system, and the section II is an ANO (anoxic / aerobic) system. The section I is specially used for dephosphorization and carbon source recovery, and the section II is specially used for denitrification. The section I is designed according to high load, and all carbon sources are used for biochemical phosphorus removal, so that efficient phosphorus removal is realized, and the carbon sources can be recycled. And the section II is designed according to an anaerobic ammonia oxidation process, and is additionally provided with a microorganism expanding culture device, a microorganism screening device and a microorganism hatching device. According to the invention, the living environments of functional bacteria required by different sludge ages are separated, so that the functional bacteria in the system at each stage are enriched and reach a certain abundance, and energy conservation and consumption reduction are realized while the nitrogen and phosphorus removal effect is comprehensively improved.

Description

Technical Field

[0001] The invention relates to the technical field of denitrification and dephosphorization in sewage treatment, and in particular to an energy-saving and emission-reducing biochemical denitrification and dephosphorization sewage treatment system. Background Art

[0002] Eutrophication of water bodies is caused by excessive discharge of sewage containing nitrogen and phosphorus, which leads to excessive growth of algae in the receiving water body and deterioration of water quality. Nitrogen in sewage usually exists in the form of organic nitrogen, nitrate nitrogen, ammonia nitrogen, etc. Phosphorus in sewage usually exists in the form of organic phosphorus, phosphate, etc., and has the ability to circulate and transform between solid and dissolved forms.

[0003] Biological denitrification refers to the conversion of organic nitrogen compounds into ammonia nitrogen through oxidative decomposition by heterotrophic microorganisms, i.e., ammoniation reaction, and then into nitrate nitrogen through nitrification, and finally into nitrogen gas through denitrification and escape from the water body, thereby reducing the nitrogen content in sewage.

[0004] Biological phosphorus removal refers to the process in which phosphorus, as a nutrient element necessary for microbial growth, is consumed by the synthesis and reproduction of microbial cells and as an energy carrier required for microbial life activities, accumulates in the microbial cells in the form of energy storage and is discharged in the form of biological sludge, thereby reducing the phosphorus content in the water.

[0005] Against the backdrop of stricter environmental protection and increasing requirements for nitrogen and phosphorus indicators in sewage plant effluent, various nitrogen and phosphorus removal processes have emerged.

[0006] At present, the most commonly used biochemical denitrification and phosphorus removal process in municipal sewage treatment plants at home and abroad is the AAO (anaerobic / anoxic / aerobic or anoxic / anaerobic / aerobic) process. Based on this process, research on the optimization process to improve the denitrification and phosphorus removal effect has been carried out, resulting in a variety of systems.

[0007] In order to improve the effect of biochemical phosphorus removal, some have improved the anaerobic section in the AAO process, placed the anaerobic section at the forefront of the biochemical process, divided it into two stages, and increased the residence time. In order to improve the effect of biochemical denitrification, some have improved the anoxic section in the AAO process, placed the anoxic section at the forefront of the biochemical process, and increased the residence time, so that denitrifying bacteria can preferentially use high-quality carbon sources to strengthen biochemical denitrification, so that there is sufficient time for biochemical reaction. These optimized and improved treatment systems either provide carbon sources and environments for polyphosphate bacteria to the maximum extent, or provide carbon sources and environments for denitrifying bacteria to the maximum extent. Compared with ordinary activated sludge treatment processes, the phosphorus removal or nitrogen removal effect has been improved. However, due to the consumption of high-quality carbon sources in sewage by the bacterial community, the improvement of nitrogen and phosphorus removal effects has been neglected, and the two have not been taken into account.

[0008] The most outstanding research result is the anaerobic ammonium oxidation process, which is also internationally recognized as the most energy-saving and consumption-reducing sewage treatment process. Therefore, it has become the first process to be studied in depth in the environmental protection industry. Some of the anaerobic ammonium oxidation processes currently implemented are anaerobic ammonium oxidation processes based on the AAO process. The AAO anaerobic ammonium oxidation process is mainly a process optimized on the basis of the activated sludge process. The key to its debugging and operation is to adjust the ordinary activated sludge system to the anaerobic ammonium oxidation activated sludge system, that is, to enrich the anaerobic ammonium oxidizing bacteria in the biochemical system to reach and maintain a certain abundance. However, there are still many problems that need to be improved in the AAO anaerobic ammonium oxidation process, such as: the contribution rate of anaerobic ammonium oxidizing functional bacteria in total nitrogen removal is difficult to exceed 20%, and the efficiency is not high; the generation cycle of anaerobic ammonium oxidizing functional bacteria is long, requiring an extremely long sludge age, while the generation cycle of other functional bacteria is short, so the residual sludge must be screened so that the biochemical system can maintain a certain abundance of anaerobic ammonium oxidizing functional bacteria, but this screening will lose some anaerobic ammonium oxidizing functional bacteria, thereby limiting the abundance value of anaerobic ammonium oxidizing functional bacteria in the biochemical system; the residual sludge discharged in the AAO anaerobic ammonium oxidation process has low organic matter.

[0009] The most energy-saving process for sewage treatment in the environmental protection industry is the AB process. The AB process is the abbreviation of the adsorption biodegradation process, which is a process developed on the basis of the traditional two-stage activated sludge process and the high-load activated sludge process. The AB process is structurally equivalent to a two-stage aeration treatment in series, that is, the A section and the B section are respectively provided with sedimentation tanks, so that the two sections are strictly separated, and the two sections are returned separately to maintain their own suitable microorganisms. The operation mode of the AB process is: the sewage directly enters the A section aeration tank, operates and treats under high load and short sludge age conditions, and then enters the first sedimentation tank. After the mud and water are separated, the sludge flows back to the A section aeration tank. The sewage treated in the A section enters the B section aeration tank, and is further subjected to biochemical degradation treatment under low load, and then flows into the second sedimentation tank. The sludge separated from the second sedimentation tank flows back to the B section aeration tank. The sewage treated in the B section meets the discharge standards. The operating conditions of the AB process are: Section A is equivalent to rough treatment, and most of its microorganisms are highly active bacteria and microbial communities, with good flocculation and strong adhesion, which can give full play to the adsorption and treatment capacity of sludge on pollutants. Therefore, Section A operates at high load, with high sludge yield and high concentration of residual sludge organic matter. Section B is equivalent to fine treatment, which operates at low load, with low sludge yield, to ensure the water quality of biochemical treatment effluent. The key point of energy saving in the AB process is that most of the organic matter in the sewage is not mineralized into inorganic matter, thus reducing energy consumption. At the same time, most of the organic matter in the sewage is converted into microorganisms and their adsorbents and extracted in the form of sludge as an energy storage carrier for the biogas production process. However, the AB process is only suitable for municipal sewage with moderate pollutant concentration, high carbon, low nitrogen and phosphorus, or no high requirements for denitrification and phosphorus removal; its denitrification effect is not good, there is no denitrification process, the distribution of carbon-nitrogen ratio is unreasonable, and nitrate is difficult to remove; the phosphorus removal effect is not good, and it cannot provide an anaerobic / aerobic environment for the dominant growth of polyphosphate bacteria, and cannot give full play to the role of biochemical phosphorus removal.

[0010] Therefore, in order to ensure nitrogen and phosphorus indicators under stricter environmental protection, the environmental protection industry has a long way to go in updating and iterating wastewater treatment technology, and research on the potential of anaerobic ammonia oxidation technology will always be a new topic. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide an energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system. On the basis of the basic theories of the AB process and the AAO (anaerobic / anoxic / aerobic) process, based on the basic physiological characteristics of polyphosphate bacteria requiring an organic carbon source and anaerobic ammonia oxidizing bacteria not requiring an organic carbon source and the mature level of the development of anaerobic ammonia oxidation technology, the conventional municipal sewage treatment system is divided into two independent sections - Section I and Section II. Section I is A P O (anaerobic / aerobic) system, stage II is A NO (anoxic / aerobic) system. Section I is dedicated to phosphorus removal, and Section II is dedicated to nitrogen removal. The two-stage system is structurally equivalent to a two-stage AO process in series, that is, Section I and Section II are respectively provided with sedimentation tanks, so that the two sections are strictly separated, and refluxed separately to maintain their own suitable microorganisms. The key to the present invention is to separate the living environment of various functional bacteria with different sludge age requirements, so that the functional bacteria in the system at each stage are enriched and reach a certain abundance, and the denitrification and phosphorus removal effects are comprehensively improved while achieving energy saving and consumption reduction.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions: an energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system, comprising a first-stage anaerobic / aerobic system and a second-stage anoxic / aerobic system connected in sequence, the first-stage anaerobic / aerobic system comprises a first-stage anaerobic tank, a first-stage aerobic tank and a first-stage sedimentation tank connected in sequence, the first-stage anaerobic tank is provided with a biochemical system water inlet pipe, the first-stage sedimentation tank is provided with a first-stage I and II connecting pipes, a sludge return pipe is connected between the first-stage sedimentation tank and the first-stage anaerobic tank, and a sludge discharge pipe is provided on the first-stage sedimentation tank; the second-stage anoxic / aerobic system comprises a second-stage anoxic tank, a second-stage aerobic tank and a second-stage sedimentation tank connected in sequence, the second-stage anoxic tank is connected to the first-stage anaerobic tank through the first and second connecting pipes. The second stage sedimentation tank is connected with an oxygen / aerobic system, a biochemical system outlet pipe is arranged on the second stage sedimentation tank, a mixed liquor return pipe is connected between the second stage aerobic tank and the second stage anoxic tank, a sludge return pipe is connected between the second stage sedimentation tank and the second stage anoxic tank, a microorganism expansion device is connected between the second stage aerobic tank and the second stage anoxic tank through a pipeline, and a first lifting pump is arranged on the pipeline between the second stage aerobic tank and the microorganism expansion device; a microorganism screening device is connected between the second stage sedimentation tank and the second stage anoxic tank through a pipeline, a second lifting pump is arranged on the pipeline between the second stage sedimentation tank and the microorganism screening device, and a sludge discharge pipe is arranged on the microorganism screening device; a plurality of microorganism incubation devices are arranged in the second stage aerobic tank.

[0013] The I-stage anaerobic / aerobic system is designed for high load, wherein the design residence time of the I-stage anaerobic stage is 1 to 2 hours, and the design residence time of the I-stage aerobic stage is anaerobic: aerobic = 1:2.

[0014] The II-stage anoxic / aerobic system is designed according to the anaerobic ammonium oxidation process, wherein the design residence time of the II-stage anoxic stage is 3 to 4 hours, and the design residence time of the II-stage aerobic stage is anoxic: aerobic = 1:1 to 1:1.5.

[0015] The beneficial effects of the present invention are as follows: a two-stage system is used to separate the living environments of different functional bacteria; by optimizing the living environment of each functional bacteria in stage I, the organic carbon source in sewage is fully utilized for biochemical phosphorus removal; the high load condition of stage I is utilized to extract the organic carbon source in sewage and achieve sewage energy recovery; and by optimizing the living environment of each functional bacteria in stage II, the denitrification efficiency of the anaerobic ammonia oxidation process is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the schematic diagram. It should be understood that the schematic diagram described herein is only used to explain the present invention and is not used to limit the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0019] In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0020] Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0021] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0022] The electrical devices, controllers, etc. described in the present invention are all conventionally configured, and the electrical connection method is also conventionally connected.

[0023] like Figure 1 As shown, the energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system of the present invention comprises a first section A connected in sequence P O (Anaerobic / Aerobic) Process 1 and II Stage A N O (Anoxic / Aerobic) Process 2, (I) Stage I AP The O (anaerobic / aerobic) system 1 is connected in sequence to the I-stage anaerobic tank 3, the I-stage aerobic tank 4 and the I-stage sedimentation tank 5. The I-stage anaerobic tank 3 is provided with a biochemical system water inlet pipe 6, the I-stage sedimentation tank 5 is provided with an I-II connecting pipe 7, the I-stage sedimentation tank 5 is connected with the I-stage anaerobic tank 3 and a sludge return pipe 8 is connected between the I-stage sedimentation tank 5 and the I-stage anaerobic tank 3, and the I-stage sedimentation tank 5 is provided with a sludge discharge pipe 9; (ii) II-stage A N The O (anoxic / aerobic) system 2 is connected in sequence to the II-stage anoxic tank 10, the II-stage aerobic tank 11 and the II-stage sedimentation tank 12. The II-stage anoxic tank 10 is provided with an I and II connecting pipe 7, and the II-stage sedimentation tank 12 is provided with a biochemical system outlet pipe 13. A mixed liquor return pipe 14 is connected between the II-stage aerobic tank 11 and the II-stage anoxic tank 10, and a sludge return pipe 15 is connected between the II-stage aerobic tank 11 and the II-stage anoxic tank 10. A microbial expansion device 16 is connected through a pipeline, and a first lifting pump 17 is arranged on the pipeline between the II-stage aerobic tank 11 and the microbial expansion device 16; a microbial screening device 18 is connected between the II-stage sedimentation tank 12 and the II-stage anoxic tank 10 through a pipeline, and a second lifting pump 19 is arranged on the pipeline between the II-stage sedimentation tank 12 and the microbial screening device 18, and a sludge discharge pipe 20 is arranged on the microbial screening device 18; a plurality of microbial incubation devices 21 are arranged in the II-stage aerobic tank 11.

[0024] Section I A P The O (anaerobic / aerobic) system is designed for high load, where the design residence time of the anaerobic section I is 1 to 2 hours, and the design residence time of the aerobic section I is based on A P :O=1:2.

[0025] Section II A N The O (anoxic / aerobic) system is designed according to the anaerobic ammonium oxidation process, in which the design residence time of the anoxic section II is 3 to 4 hours, and the design residence time of the aerobic section II is based on A N :O=1:1~1:1.5.

[0026] Section II A N The O (anoxic / aerobic) system needs to be equipped with microbial expansion devices, microbial screening devices and microbial incubation devices to ensure the start-up and stable operation of the anaerobic ammonium oxidation process.

[0027] Section I A PThe main functions of the O (anaerobic / aerobic) system are carbon reduction and phosphorus removal. All high-quality carbon sources are used for biochemical phosphorus removal, converted into activated sludge mainly composed of polyphosphate bacteria, and efficient phosphorus removal is achieved by discharging excess sludge; all excess carbon sources are used for sludge cultivation, converted into activated sludge mainly composed of heterotrophic bacteria and their adsorbents, and energy recovery is achieved by discharging excess sludge. Because the discharged excess sludge has high organic matter, it can be used as an energy storage carrier for biogas production process.

[0028] Section II A N The main function of the O (anoxic / aerobic) system is denitrification. Compared with the traditional denitrification process, which requires an organic carbon source for denitrification, the anaerobic ammonium oxidation process does not require an organic carbon source for denitrification. The sludge age of this process can be designed to be very long to meet the proliferation needs of anaerobic ammonium oxidizing bacteria.

[0029] In order to better understand the content of the present invention, it is necessary to describe the advantageous functional bacteria in the two-stage process:

[0030] Section Ⅰ contains functional bacteria that metabolize organic carbon.

[0031] The functional bacteria that metabolize organic carbon belong to heterotrophic aerobic bacteria.

[0032] The organic carbon-metabolizing functional bacteria oxidize organic carbon into inorganic carbon in aerobic state.

[0033] The organic carbon-metabolizing functional bacteria require an organic carbon source for metabolism.

[0034] There are polyphosphate functional bacteria in section Ⅰ.

[0035] The polyphosphate functional bacteria are heterotrophic aerobic bacteria.

[0036] The polyphosphate functional bacteria release phosphate and absorb organic carbon sources in an anaerobic state.

[0037] The polyphosphate functional bacteria utilize oxygen to oxidize the organic carbon source in an aerobic state.

[0038] The polyphosphate functional bacteria absorb excessive amounts of phosphate in water under an aerobic state.

[0039] The metabolism of the polyphosphate functional bacteria requires an organic carbon source.

[0040] There are nitrifying functional bacteria in section II.

[0041] The nitrifying functional bacteria are autotrophic aerobic bacteria.

[0042] The nitrifying functional bacteria oxidize ammonia nitrogen into nitrite in an aerobic state.

[0043] The nitrifying functional bacteria oxidize nitrite into nitrate in an aerobic state.

[0044] The nitrifying functional bacteria do not require an organic carbon source.

[0045] The nitrifying functional bacteria require an inorganic carbon source.

[0046] There are denitrifying functional bacteria in section II.

[0047] The denitrifying functional bacteria belong to heterotrophic anaerobic bacteria.

[0048] The denitrifying functional bacteria reduce nitrate to nitrite in anoxic state.

[0049] The denitrifying functional bacteria reduce nitrite to nitrogen gas in anoxic conditions.

[0050] The denitrifying functional bacteria require an organic carbon source.

[0051] There are anaerobic ammonium oxidizing functional bacteria in section II.

[0052] The anaerobic ammonium oxidizing functional bacteria belong to autotrophic anaerobic bacteria.

[0053] The anaerobic ammonium oxidizing functional bacteria reduce nitrite to nitrogen gas without being affected by oxygen.

[0054] The anaerobic ammonium oxidizing functional bacteria oxidize ammonia nitrogen into nitrogen gas without being affected by oxygen.

[0055] The anaerobic ammonium oxidizing functional bacteria do not require an organic carbon source.

[0056] The anaerobic ammonium oxidizing functional bacteria require an inorganic carbon source.

[0057] In order to better understand the content of the present invention, it is necessary to describe the two-stage system biochemical treatment process conditions:

[0058] Phase I process conditions:

[0059] The sewage flows into the anaerobic tank of Section I from the water inlet pipe of the biochemical system.

[0060] Wastewater contains organic carbon sources, phosphates and ammonia nitrogen.

[0061] Functional bacteria that metabolize organic carbon enter the anaerobic tank of Section I through the external return pipe of Section I.

[0062] The polyphosphate functional bacteria enter the anaerobic tank of Section I through the external return pipe of Section I.

[0063] In the anaerobic tank of Section I, the sewage is fully mixed and reacted with various functional bacteria in Section I and then flows into the aerobic tank of Section I by gravity.

[0064] In the aerobic tank of Section I, the sewage is fully mixed and reacted with various functional bacteria in Section I and then flows into the sedimentation tank of Section I by gravity.

[0065] In the Section I sedimentation tank, after the sewage and various functional bacteria in Section I are separated into sludge and water, most of the precipitated functional bacteria are returned to the Section I anaerobic tank through the Section I external return pipe, and a small part is discharged from the biochemical system through the Section I residual sludge pipe as residual sludge; the supernatant flows by gravity into the Section II anoxic tank through the Section I and Section II connecting pipe.

[0066] Phase II process conditions:

[0067] The supernatant of stage I sedimentation tank contains a small amount of organic carbon source and a large amount of ammonia nitrogen.

[0068] Part of the denitrifying functional bacteria enters the Section II anoxic tank through the Section II external recirculation pipe.

[0069] Another part of the denitrifying functional bacteria enters the anoxic tank of Section II through the recirculation pipe in Section II.

[0070] Part of the anaerobic ammonium oxidizing functional bacteria enters the section II anoxic tank through the section II external reflux pipe.

[0071] Another part of the anaerobic ammonium oxidizing functional bacteria enters the anoxic tank of Section II through the reflux pipe in Section II.

[0072] Part of the nitrifying functional bacteria enters the Section II anoxic tank through the Section II external reflux pipe.

[0073] Another part of the nitrifying functional bacteria enters the anoxic tank of Section II through the reflux pipe in Section II.

[0074] Nitrate and nitrite enter the anoxic pool of Section II through reflow within Section II.

[0075] In the section II anoxic tank, the sewage is fully mixed and reacted with various functional bacteria in section II and then flows into the section II aerobic tank by gravity.

[0076] In the Section II aerobic tank, the sewage is fully mixed and reacted with various functional bacteria in Section II and then flows into the Section II sedimentation tank by gravity.

[0077] In the Section II sedimentation tank, after the sewage and various functional bacteria in Section II are separated into sludge and water, most of the precipitated functional bacteria are returned to the Section II anoxic tank through the Section II external reflux pipe, and a very small part is discharged from the biochemical system through the Section II residual sludge pipe as residual sludge; the supernatant is discharged from the biochemical system through the biochemical system outlet pipe.

[0078] In order to better understand the content of the present invention, it is necessary to describe the two-stage process of biochemical carbon reduction, phosphorus removal and nitrogen removal mechanism:

[0079] Stage I carbon reduction and phosphorus removal mechanism working conditions:

[0080] In the first stage anaerobic tank, polyphosphate functional bacteria release phosphate and absorb organic carbon sources.

[0081] In the aerobic tank of stage I, the functional bacteria that metabolize organic carbon metabolize the organic carbon that is not absorbed in the anaerobic tank of stage I. Some of it is oxidized into inorganic carbon through catabolism, and some of it is converted into new functional bacteria that metabolize organic carbon through anabolism, so the functional bacteria that metabolize organic carbon proliferate.

[0082] In the aerobic tank of stage I, the polyphosphate functional bacteria metabolize the organic carbon source absorbed in the anaerobic tank of stage I, partially oxidize it into inorganic carbon through catabolism, and partially convert it into new polyphosphate functional bacteria through anabolism, and absorb excessive phosphate in the water, so that the polyphosphate functional bacteria proliferate.

[0083] Stage II denitrification mechanism and operating conditions:

[0084] In the section II anoxic pool, denitrifying functional bacteria reduce nitrate to nitrite, oxidize part of the organic carbon source to inorganic carbon through catabolism, and convert part of the organic carbon source into new denitrifying functional bacteria through anabolism, thereby proliferating the denitrifying functional bacteria.

[0085] In the section II anoxic pool, denitrifying functional bacteria reduce nitrite to nitrogen gas, oxidize part of the organic carbon source to inorganic carbon through catabolism, and convert part of the organic carbon source into new denitrifying functional bacteria through anabolism, thereby proliferating the denitrifying functional bacteria.

[0086] In the section II anoxic tank, anaerobic ammonium oxidizing functional bacteria reduce nitrite to nitrogen gas and oxidize ammonia nitrogen to nitrogen gas, and convert inorganic carbon sources into new anaerobic ammonium oxidizing functional bacteria through anabolism, so that the anaerobic ammonium oxidizing functional bacteria proliferate.

[0087] In the aerobic pool of stage II, nitrifying functional bacteria oxidize ammonia nitrogen into nitrite, and convert inorganic carbon sources into new nitrifying functional bacteria through anabolism, so that the nitrifying functional bacteria proliferate.

[0088] In the aerobic pool of stage II, nitrifying functional bacteria oxidize nitrite into nitrate, and convert inorganic carbon sources into new nitrifying functional bacteria through anabolism, so that the nitrifying functional bacteria proliferate.

[0089] In the stage II aerobic pool, anaerobic ammonium oxidizing functional bacteria reduce nitrite to nitrogen gas, and oxidize ammonia nitrogen to nitrogen gas, and convert inorganic carbon sources into new anaerobic ammonium oxidizing functional bacteria through anabolism, so that the anaerobic ammonium oxidizing functional bacteria proliferate.

[0090] The present invention operates through a two-stage process. The heterotrophic functional bacteria with a short generation cycle and a short sludge age requirement are distributed in the first-stage biochemical treatment unit, and the heterotrophic functional bacteria with a long generation cycle and a long sludge age requirement are distributed in the second-stage biochemical treatment unit. In this way, the living environments of the functional bacteria with different sludge age requirements are separated, the sludge age contradiction in the traditional biochemical denitrification and phosphorus removal process is solved, and the advantages of the functional bacteria are fully brought into play.

[0091] Through the two-stage process operation, the stage I biochemical treatment unit optimizes the biochemical phosphorus removal environment. Without the denitrifying bacteria competing for organic carbon sources, the biochemical phosphorus removal effect is enhanced, solving the carbon source contradiction in the traditional biochemical denitrification and phosphorus removal process.

[0092] Through the two-stage process operation, the stage II biochemical treatment unit optimizes the biochemical denitrification environment and provides a more suitable living environment for anaerobic ammonia oxidizing bacteria, such as an ultra-long sludge age environment and a low organic carbon source environment. The abundance value of anaerobic ammonia oxidizing functional bacteria can be greatly improved, and the contribution rate of anaerobic ammonia oxidation in total nitrogen removal can reach 80%, with high denitrification efficiency.

[0093] Through the two-stage process operation, the organic carbon source in the biochemical system influent is degraded in the stage I biochemical treatment unit. Its mineralization degree is low and most of it is converted into activated sludge. A large amount of sludge is discharged from the biochemical system. The discharged residual sludge has a high organic matter content and is suitable for subsequent sludge nitrification and methane recovery processes, which can truly recover energy from sewage.

[0094] Through the two-stage process operation, the system is energy-saving. First, the anaerobic ammonium oxidation process itself is energy-saving. Compared with the traditional process, more than 40% of the ammonia nitrogen in the two-stage anaerobic ammonium oxidation process can be directly oxidized into nitrogen without nitrification, saving about half of the energy consumption of ammonia nitrogen nitrification; the remaining ammonia nitrogen can be mostly controlled in the short-range nitrification stage, that is, controlled in the stage of oxidation of ammonia nitrogen to nitrite, saving the energy consumption of oxidation of nitrite to nitrate; the low-oxygen operating environment of anaerobic ammonium oxidation saves the energy consumption of producing a high residual dissolved oxygen environment relative to the requirements of traditional processes. Second, the residual sludge has a low mineralization degree and a high organic matter content, which saves the energy consumption of residual sludge mineralization. Third, by recycling carbon sources, new energy is generated in subsequent processes, which can achieve energy self-sufficiency in municipal sewage treatment plants.

[0095] The present invention creatively divides the municipal sewage treatment process into two independent systems. P O (anaerobic / aerobic) system, stage II is A N O (anoxic / aerobic) system. Section I is dedicated to phosphorus removal and carbon source recovery, and Section II is dedicated to nitrogen removal. It is a new breakthrough based on the mature level of anaerobic ammonium oxidation technology development, ensuring nitrogen and phosphorus indicators under strict environmental protection, and is the first case in China.

[0096] In summary, the content of the present invention is not limited to the above-mentioned embodiments, and people with insight in the same field can easily propose other embodiments within the technical guiding ideology of the present invention, but such embodiments are all included in the scope of the present invention.

Claims

1. An energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system, characterized in that: The invention comprises a first-stage anaerobic / aerobic system (1) and a second-stage anoxic / aerobic system (2) connected in sequence, wherein the first-stage anaerobic / aerobic system (1) comprises a first-stage anaerobic tank (3), a first-stage aerobic tank (4) and a first-stage sedimentation tank (5) connected in sequence, the first-stage anaerobic tank (3) is provided with a biochemical system water inlet pipe (6), the first-stage sedimentation tank (5) is provided with a first-stage and a second-stage connecting pipe (7), and the first-stage sedimentation tank (5) is connected to the first-stage anaerobic tank (3). There is a sludge return pipe (8), and the first stage sedimentation tank (5) is provided with a sludge discharge pipe (9); the second stage anoxic / aerobic system (2) includes a second stage anoxic tank (10), a second stage aerobic tank (11) and a second stage sedimentation tank (12) which are connected in sequence, the second stage anoxic tank (10) is connected to the first stage anaerobic / aerobic system (1) through I and II connecting pipes (7), and the second stage sedimentation tank (12) is provided with a biochemical system outlet pipe (13) A mixed liquid return pipe (14) is connected between the II-stage aerobic tank (11) and the II-stage anoxic tank (10); a sludge return pipe (15) is connected between the II-stage sedimentation tank (12) and the II-stage anoxic tank (10); a microorganism expansion device (16) is connected between the II-stage aerobic tank (11) and the II-stage anoxic tank (10) via a pipeline; a first lift pump (17) is arranged on the pipeline between the II-stage aerobic tank (11) and the microorganism expansion device (16); a microorganism screening device (18) is connected between the II-stage sedimentation tank (12) and the II-stage anoxic tank (10) via a pipeline; a second lift pump (19) is arranged on the pipeline between the II-stage sedimentation tank (12) and the microorganism screening device (18); a sludge discharge pipe (20) is arranged on the microorganism screening device (18); and a plurality of microorganism incubation devices (21) are arranged in the II-stage aerobic tank (11).

2. The energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system according to claim 1 is characterized in that: The I-stage anaerobic / aerobic system (1) is designed for high load, wherein the design residence time of the I-stage anaerobic stage is 1 to 2 hours, and the design residence time of the I-stage aerobic stage is anaerobic: aerobic = 1:

2.

3. The energy-saving and emission-reducing biochemical denitrification and phosphorus removal sewage treatment system according to claim 1 is characterized in that: The II-stage anoxic / aerobic system (2) is designed according to the anaerobic ammonium oxidation process, wherein the designed residence time of the II-stage anoxic stage is 3 to 4 hours, and the designed residence time of the II-stage aerobic stage is anoxic: aerobic = 1:1 to 1:1.5.

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