Domestic sewage treatment method and system based on carbon capture and autotrophic nitrogen removal

Abstract

The invention discloses a domestic sewage treatment system and method based on carbon capture and autotrophic nitrogen removal. The domestic sewage treatment system mainly comprises a carbon capture reactor, a nitrification reactor and a sulfur autotrophic denitrification coupling anaerobic ammonia oxidation reactor. Carbon and phosphorus in the sewage are removed in the carbon capture reactor through flocculent precipitation and are used for energy and resource recovery; nitrogen in effluent of the carbon capture reactor is removed through an autotrophic nitrogen removal technology; a part of sewage enters a nitration reactor for complete nitration; nitration effluent containing nitrate nitrogen and carbon capture reactor effluent containing ammonia nitrogen are mixed and then pumped into a sulfur autotrophic denitrification coupling anaerobic ammonia oxidation reactor; in the sulfur autotrophic denitrification coupling anaerobic ammonia oxidation unit, nitrate nitrogen is converted into nitrite nitrogen by sulfur autotrophic denitrification, and anaerobic ammonia oxidation realizes autotrophic nitrogen removal by using ammonia nitrogen and nitrite nitrogen. According to the invention, carbon and nitrogen in sewage are separated, carbon in wastewater is effectively captured and utilized, and nitrogen in sewage is effectively removed through a low-energy-consumption autotrophic nitrogen removal system.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method, system and device for treating domestic sewage based on carbon capture and autotrophic denitrification. Background Art

[0002] Sewage treatment plants play a key role in addressing the "water-energy-sanitation" challenge and are currently facing a dual contradiction: the existing process dominated by the traditional activated sludge method is energy-intensive, and the chemical energy contained in the sewage is far from being recycled. At present, the "anaerobic-anoxic-aerobic" (A2O) process and its modified process are mainly used to treat domestic sewage, mainly to achieve the removal of carbon, nitrogen and phosphorus. However, the carbon-nitrogen ratio in domestic sewage is often low, and sewage treatment plants have to add a large amount of carbon source to ensure the denitrification efficiency, which will greatly increase the operating cost. In addition, the denitrification process of microorganisms using an external carbon source will produce a large amount of residual sludge, and the cost of treating the residual sludge can reach 25% to 40% of the entire sewage treatment plant. Therefore, there is an urgent need to seek a sewage treatment system with low energy consumption and recyclable energy.

[0003] Anaerobic ammonium oxidation is an autotrophic denitrification process that does not consume organic carbon, making it possible to separate carbon and nitrogen in sewage treatment. If the carbon in sewage is captured to achieve energy recovery, and anaerobic ammonium oxidation technology is used to achieve low-energy nitrogen removal, this will enable sewage treatment plants to achieve energy self-sufficiency and even become "energy plants." Currently, carbon capture technology is relatively mature, including chemically enhanced primary treatment technology (CEPT), anaerobic biofilm technology (MBR) and high-rate activated sludge process (HRAS), all of which have been verified on a large scale.

[0004] However, the application and promotion of mainstream anaerobic ammonium oxidation remains a major challenge. The process usually relies on partial nitrification or partial denitrification to provide the required nitrite-nitrogen. The mainstream application of partial nitrification-anaerobic ammonium oxidation is difficult to achieve, mainly because stable short-term nitrification is difficult to achieve, so the supply of nitrite-nitrogen required for the anaerobic ammonium oxidation process is unstable. Short-term denitrification is more controllable than short-term nitrification and has received widespread attention in recent years. However, in the short-term denitrification-anaerobic ammonium oxidation system with organic matter as electron donor, there is a competitive relationship between heterotrophic denitrifying bacteria and anaerobic ammonium oxidizing bacteria. The excessive proliferation of heterotrophic denitrifying bacteria will suppress the activity of anaerobic ammonium oxidizing bacteria, resulting in the difficulty of stable operation of the denitrification system.

[0005] Based on this, a new solution is needed. Summary of the invention

[0006] The main purpose of the present invention is to provide a method and system for treating domestic sewage based on carbon capture and autotrophic denitrification.

[0007] To achieve the above-mentioned object, the present invention provides a domestic sewage treatment system based on carbon capture and autotrophic denitrification, comprising a carbon capture reactor, a first sedimentation tank, a nitrification reactor, a second sedimentation tank and a sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, wherein the carbon capture reactor is connected to the first sedimentation tank, the first sedimentation tank is connected to the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor through a first water pump pipeline and a second water pump pipeline respectively, the nitrification reactor is connected to the second sedimentation tank, the second sedimentation tank is connected to the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor through a third water pump pipeline, the carbon capture reactor is used to capture organic matter and phosphorus in sewage through a flocculant; the first sedimentation tank is used to The wastewater treated by the carbon capture reactor is precipitated, and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor in proportion; the nitrification reactor is used to nitrify the supernatant from the first sedimentation tank, and oxidize the ammonia nitrogen in the supernatant into nitrate nitrogen; the second sedimentation tank is used to separate the effluent from the nitrification reactor into mud and water; the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is used to use reducing sulfur as an electron donor to reduce the nitrate nitrogen in the effluent from the second sedimentation tank to nitrite nitrogen through sulfur autotrophic short-range denitrification, and then convert the nitrite nitrogen and the ammonia nitrogen in the supernatant from the first sedimentation tank into nitrogen gas through anaerobic ammonium oxidation.

[0008] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the flocculant consists of ferric chloride and anionic polymer, and the usage of the flocculant is determined by a coagulation experiment.

[0009] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the ratio of the supernatant pumped from the first sedimentation tank into the nitrification reactor to the supernatant of the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is not less than 3:2.

[0010] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the hydraulic retention time in the nitrification reactor is 2h to 4h; the concentration of dissolved oxygen should be sufficient, usually >2.0mg / L.

[0011] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the hydraulic retention time in the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is 2h to 6h.

[0012] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the reducing sulfur used in the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is selected from one or more of elemental sulfur, thiosulfate, sulfide, ferrous sulfide, and sodium sulfite.

[0013] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the carbon capture reactor is selected from one of a CEPT reactor, a high-speed activated sludge device or an anaerobic membrane bioreactor.

[0014] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the nitrification reactor is selected from one of a moving bed biofilm reactor, a continuous stirred tank reactor, a sequencing batch reactor and a membrane bioreactor.

[0015] In the domestic sewage treatment method based on carbon capture and autotrophic denitrification provided by the present invention, the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is selected from one of an upflow anaerobic sludge blanket reactor, a membrane bioreactor, and a sequencing batch reactor.

[0016] In addition, to achieve the above-mentioned purpose, the present invention also provides a method for treating domestic sewage based on carbon capture and autotrophic denitrification, comprising:

[0017] Step S1, carbon capture reactor startup phase: determine the amount of flocculant through flocculation experiments, add the flocculant into the carbon capture reactor according to the determined amount, monitor the removal efficiency of carbon and phosphorus in the sewage, and determine that the carbon capture reactor is successfully started when the removal rates of suspended solids, biochemical oxygen demand, and total phosphorus reach preset values ​​respectively;

[0018] Step S2, nitrification reactor startup phase: adding secondary sedimentation tank sludge as seed sludge to the nitrification reactor, using sewage from the carbon capture reactor as a culture matrix to provide dissolved oxygen, and operating in sequencing batch mode and continuous flow mode in sequence. When the ammonia nitrogen removal rate reaches more than 90%, the nitrification reactor is successfully started;

[0019] Step S3, the startup phase of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor: inoculating laboratory-cultured anaerobic ammonium oxidation sludge in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, using simulated wastewater, first starting at a first nitrogen concentration, a first hydraulic retention time and a first operating temperature, after the reactor is stable, successively reducing the influent nitrogen concentration, reducing the operating temperature to the ambient temperature and gradually reducing the hydraulic retention time, continuously regulating the operation until the reactor is stable, and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is considered to be successfully started when the total nitrogen removal rate reaches more than 80%;

[0020] Step S4, system operation stage: the sewage passes through the carbon capture reactor to capture organic matter and phosphorus in the sewage through the flocculant, and then passes through the first sedimentation tank to precipitate the sewage treated by the carbon capture reactor, and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor in proportion; the supernatant from the first sedimentation tank is nitrified by the nitrification reactor, and the ammonia nitrogen in the supernatant is oxidized into nitrate nitrogen; the second sedimentation tank is used to separate the effluent of the nitrification reactor from mud and water; the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is used to use reduced sulfur as an electron donor to reduce the nitrate nitrogen in the effluent from the second sedimentation tank to nitrite nitrogen through sulfur autotrophic short-range denitrification, and then the nitrite nitrogen and the ammonia nitrogen in the supernatant from the first sedimentation tank are converted into nitrogen gas through anaerobic ammonia oxidation.

[0021] The domestic sewage treatment system and method based on carbon capture and autotrophic denitrification provided by the present invention have the following beneficial effects: the present invention can capture carbon and phosphorus in sewage as much as possible for energy and resource recovery, reduce the amount of organic matter oxidized to carbon dioxide by oxygen / nitrate nitrogen, thereby maximizing energy recovery; the production mode of nitrite nitrogen is changed, and no large number of sensors and precise control systems are required, and the nitrite nitrogen production process is simple and stable; sulfur autotrophic denitrification is used to provide nitrite nitrogen for anaerobic ammonia oxidation, solving the problem that the excessive proliferation of heterotrophic denitrifying bacteria makes it difficult for anaerobic ammonia oxidizing bacteria to remain stably; the denitrification technology of nitrification-sulfur autotrophic denitrification coupled with anaerobic ammonia oxidation is adopted, which greatly reduces the sludge production and aeration energy consumption, and does not require the addition of expensive organic carbon, thereby achieving low-cost denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative work:

[0023] Figure 1 Shown is a schematic diagram of a domestic sewage treatment system based on carbon capture and autotrophic denitrification provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Typical embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] Figure 1 The schematic diagram of the domestic sewage treatment system based on carbon capture and autotrophic denitrification provided by the present invention is shown. Figure 1 As shown, the domestic sewage treatment system based on carbon capture and autotrophic denitrification provided by the present invention includes a carbon capture reactor 1, a first sedimentation tank 2, a nitrification reactor 3, a second sedimentation tank 4, and a sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor 5. The carbon capture reactor 1 is connected to the first sedimentation tank 2, the first sedimentation tank 2 is connected to the nitrification reactor 3 and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor 5 through a first water pump pipeline 61 and a second water pump pipeline 62, respectively, the nitrification reactor 3 is connected to the second sedimentation tank 4, and the second sedimentation tank 4 is connected to the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor 5 through a third water pump pipeline 63.

[0027] Specifically, in one embodiment of the present invention, the carbon capture reactor 1 is used to capture organic matter and phosphorus in sewage by flocculants. A stirring device 11 is provided in the carbon capture reactor 1 for fully mixing sewage and flocculants to ensure that the flocculants can fully react with organic matter and phosphorus in the water. By stirring, the flocculants can be more evenly distributed in the sewage, thereby improving the flocculation effect. The first sedimentation tank 2 is used to precipitate the sewage treated by the carbon capture reactor, and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor in proportion, and the sludge generated in the first sedimentation tank is collected through the mud discharge port at the bottom. The sewage treated by the carbon capture reactor enters the first sedimentation tank, and the main function of this stage is separation and precipitation. The carbon capture reactor captures the organic matter and phosphorus in the sewage into floccules by flocculation. After precipitation, these substances will be deposited at the bottom of the sedimentation tank to form precipitation. At this stage, most of the organic matter and phosphorus in the sewage will be removed, and the remaining water (supernatant) will enter the subsequent treatment unit through diversion.

[0028] In this embodiment, sewage is introduced into a carbon capture reactor, and flocculants are added to cause some of the organic matter (carbon) and phosphorus in the sewage to flocculate and settle, thereby achieving effective capture of carbon and phosphorus through precipitation separation, and obtaining sewage with a low carbon-nitrogen ratio, thereby creating suitable conditions for the subsequent autotrophic denitrification process. By removing some organic matter in the carbon capture reactor, the chance of them being converted into carbon dioxide in the subsequent biological treatment stage is reduced. Therefore, the system can minimize greenhouse gas emissions and achieve environmental protection purposes. The captured carbon and phosphorus can be used for subsequent energy recovery and resource utilization. For example, the captured phosphorus can be used to produce fertilizers, and the carbon can be converted into biomass energy or other chemical energy. This resource recovery process provides additional economic value for sewage treatment.

[0029] Further, in one embodiment of the present invention, the carbon capture reactor is selected from one of a CEPT reactor, a high-speed activated sludge reactor or an anaerobic membrane bioreactor. In an embodiment of the present invention, a suitable carbon capture reactor can be selected from a CEPT reactor, a high-speed activated sludge reactor or an anaerobic membrane bioreactor according to the specific sewage treatment requirements and environmental conditions to provide the best treatment effect for sewage with different characteristics. If there are more suspended solids in the sewage and phosphorus and organic matter need to be removed quickly, a CEPT reactor can be selected, which has a faster treatment speed and a stable treatment effect. If the concentration of dissolved organic matter in the sewage is high and it needs to be efficiently removed by biodegradation, a high-speed activated sludge reactor can be selected, which can efficiently remove dissolved organic matter in sewage. If it is necessary to achieve direct energy recovery and reduce suspended particulate matter in sewage as much as possible during the treatment process, an anaerobic membrane bioreactor can be selected, which can efficiently remove organic matter and recover energy, while greatly reducing suspended particulate matter in the effluent. By selecting a suitable carbon capture reactor according to sewage characteristics and treatment requirements, the sewage treatment efficiency can be maximized, energy consumption can be reduced, and resource recovery can be achieved.

[0030] Furthermore, in one embodiment of the present invention, the flocculant is composed of ferric chloride and anionic polymer, and the amount of the flocculant used is determined by a coagulation experiment. Ferric chloride is a common flocculant that can effectively combine with phosphorus and organic matter in sewage to form a precipitate. Anionic polymers help to enhance the stability and efficiency of the flocculation process. Through coagulation experiments, the optimal amount of flocculant used can be determined to ensure the sewage treatment effect while avoiding excessive use and waste of resources.

[0031] Specifically, in one embodiment of the present invention, the nitrification reactor is used to nitrify a portion of the supernatant from the first sedimentation tank, oxidize the ammonia nitrogen in the supernatant into nitrate nitrogen, and provide the necessary nitrate nitrogen for the subsequent sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reaction. A second agitator 31, a K5 filler 32, an air compressor 33, an aeration disk 34, a pH meter 35 and a dissolved oxygen electrode 36 are provided in the nitrification reactor 3. The second agitator 31 helps to mix the sewage in the reactor to ensure the uniformity during the reaction and improve the reaction efficiency of the microorganisms. The K5 filler provides a large amount of surface area for microorganisms to attach and grow, increasing the concentration of microorganisms in the reactor. The air compressor provides oxygen supply to support the oxidation reaction of ammonia nitrogen. The aeration disk is used to distribute oxygen to the reactor to ensure uniform oxygenation of the water body in the reactor. The pH meter 35 and the dissolved oxygen electrode 36 are used to monitor the pH value and dissolved oxygen concentration in the reactor to ensure that the reaction conditions remain in a range that is conducive to the growth of nitrifying microorganisms. The concentration of dissolved oxygen should be sufficient, usually >2.0 mg / L. By carrying out sufficient nitrification in the nitrification reactor, the ammonia nitrogen in the sewage is completely converted into nitrate nitrogen. In particular, it does not require a precise and complex control system, and the operation is simple and stable.

[0032] Specifically, in one embodiment of the present invention, the nitrification reactor is connected to the second sedimentation tank 4, and the second sedimentation tank is used to separate the effluent of the nitrification reactor from mud and water. Most of the excess sludge is removed through this process, reducing its impact on subsequent treatment steps (such as sulfur autotrophic denitrification and anaerobic ammonia oxidation reaction).

[0033] In this embodiment, a portion of the above-mentioned low carbon-nitrogen ratio sewage that has undergone carbon-phosphorus capture treatment is pumped into a nitrification reactor for complete nitrification; in the nitrification reactor, the small amount of residual organic matter is further oxidized and removed, and the ammonia nitrogen is completely oxidized into nitrate nitrogen. By changing the traditional post-nitrification effluent return mode, the energy consumption in the aeration process is reduced. The traditional nitrification effluent return mode will cause repeated aeration of sewage, consuming a lot of energy. In this embodiment, by completely nitrifying only part of the sewage, unnecessary backflow and repeated aeration are avoided, reducing the demand for energy.

[0034] Furthermore, in one embodiment of the present invention, the hydraulic retention time in the nitrification reactor is 2 h to 4 h.

[0035] Furthermore, in one embodiment of the present invention, the nitrification reactor is selected from one of a moving bed biofilm reactor, a continuous stirred tank reactor, a sequencing batch reactor and a membrane bioreactor.

[0036] Specifically, in one embodiment of the present invention, the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is used to reduce nitrate nitrogen in the effluent from the second sedimentation tank to nitrite nitrogen through sulfur autotrophic short-range denitrification using reduced sulfur as an electron donor, and then convert nitrite nitrogen and ammonia nitrogen in the supernatant from the first sedimentation tank into nitrogen gas through anaerobic ammonium oxidation. In this embodiment, the effluent of the nitrification reactor is mixed with another part of the sewage treated by carbon and phosphorus capture and then pumped into the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation system for denitrification; the effluent of the nitrification reactor contains nitrate nitrogen, and the sewage treated by carbon and phosphorus capture contains ammonia nitrogen; in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation system, nitrate nitrogen is reduced to nitrite nitrogen through sulfur autotrophic short-range denitrification using reduced sulfur as an electron donor, providing a nitrite nitrogen substrate for anaerobic ammonium oxidation; anaerobic ammonium oxidation converts nitrite nitrogen and ammonia nitrogen into nitrogen gas to achieve the denitrification process.

[0037] Further, the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor 5 is an upflow anaerobic sludge blanket reactor, equipped with a three-phase separator 51 on the top, a pH electrode 52 inside, and a gas circulation pump 53. The three-phase separator is used to separate the gas, liquid and solid phases in the reactor, and is mainly used to separate gas (such as carbon dioxide, nitrogen, etc.), liquid (wastewater) and solid (sludge). The installation of the pH electrode allows the pH value in the reactor to be monitored in real time. During the denitrification and ammonia oxidation processes, the pH value has an important influence on the activity of microorganisms and the progress of the reaction. By monitoring the pH value, the reaction conditions can be adjusted in time to ensure that the reaction process is always carried out within the optimal pH range. The gas circulation pump generates gas through the circulation reactor, strengthens the mixing inside the reactor, promotes the contact of various substances in the reactor, and optimizes the anaerobic ammonia oxidation and sulfur autotrophic denitrification reactions.

[0038] In this embodiment, the production mode of nitrite nitrogen is changed, and a large number of sensors and precise control systems are not required, and the nitrite nitrogen production process is simple and stable; the present invention uses sulfur autotrophic denitrification to provide nitrite nitrogen for anaerobic ammonia oxidation, which solves the problem that the excessive proliferation of heterotrophic denitrifying bacteria makes it difficult for anaerobic ammonia oxidizing bacteria to remain stably; the denitrification technology of nitrification-sulfur autotrophic denitrification coupled with anaerobic ammonia oxidation adopted by the present invention greatly reduces the output of sludge, reduces aeration energy consumption, and does not require the addition of expensive organic carbon, thereby achieving low-cost denitrification. During the startup process of the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor, the startup can be completed quickly and stably by directly using anaerobic ammonia oxidation sludge, and there is no need to prepare sulfur autotrophic denitrification sludge in advance; the reactor hardly produces sludge, and a very small amount of sludge will be discharged with the effluent, so there is no need to discharge sludge regularly.

[0039] Furthermore, in one embodiment of the present invention, the ratio of the supernatant pumped into the nitrification reactor from the first sedimentation tank to the supernatant pumped into the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is not less than 3:2. The nitrification reactor is mainly used to oxidize ammonia nitrogen into nitrate nitrogen, providing a source of nitrate nitrogen for the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor. The sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor utilizes the nitrate nitrogen in the effluent of the nitrification reactor and the ammonia nitrogen in the supernatant of the first sedimentation tank to realize the denitrification process of sulfur autotrophic short-range denitrification coupled anaerobic ammonia oxidation. To ensure the reaction effect, the nitrate nitrogen concentration in the sewage pumped into the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor must be higher than the ammonia nitrogen concentration. Under the above ratio, it can be ensured that the nitrate nitrogen concentration in the sewage pumped into the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is higher than the ammonia nitrogen concentration, and the synergistic effect between denitrifying bacteria and anaerobic ammonia oxidizing bacteria is also optimized. In addition, according to actual needs and changes in influent water quality, the ratio of nitrate nitrogen to ammonia nitrogen in the influent of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor can be flexibly adjusted by adjusting the inflow ratio of the supernatant of the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor to ensure stable operation and efficient treatment of the system.

[0040] Furthermore, in one embodiment of the present invention, the residence time in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is 2 h to 6 h.

[0041] Further, in one embodiment of the present invention, the reducing sulfur used in the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is selected from one or more of elemental sulfur, thiosulfate, sulfide, ferrous sulfide, and sodium sulfite. The amount of reducing sulfur added needs to be adjusted according to the nitrogen concentration in the sewage and the type of sulfur source selected, so as to realize that nitrate nitrogen is converted into nitrite nitrogen by sulfur autotrophic denitrifying bacteria, supply anaerobic ammonia oxidizing bacteria for utilization, and minimize the further utilization of nitrite nitrogen by sulfur autotrophic denitrifying bacteria. Too little sulfur source may lead to incomplete short-range denitrification process, while too much sulfur source may cause fierce competition between denitrifying bacteria and anaerobic ammonia oxidizing bacteria in the system for nitrite nitrogen. Therefore, the amount of sulfur source added needs to be reasonably configured according to the nitrogen concentration in the sewage and the reducing equivalent of sulfur. Especially for insoluble sulfur sources (such as elemental sulfur and ferrous sulfide), a small amount and multiple additions should be adopted.

[0042] Furthermore, in one embodiment of the present invention, the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is selected from one of an upflow anaerobic sludge blanket reactor, a membrane bioreactor, and a sequencing batch reactor. In the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, the gas generated by the reactor is used to improve the mixing efficiency inside the reactor, and the ratio of the gas circulation volume to the reactor inlet flow rate is 1.3. In this embodiment, the selection of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor needs to be determined according to the actual sewage characteristics and treatment requirements. The design of gas circulation can effectively improve the mixing efficiency inside the reactor, thereby promoting the smooth progress of the sulfur autotrophic denitrification reaction and the anaerobic ammonium oxidation process, and ensuring the efficiency and stability of sewage treatment.

[0043] The present invention also provides a method for treating domestic sewage based on carbon capture and autotrophic denitrification. The domestic sewage treatment system based on carbon capture and autotrophic denitrification as described above is used. During the startup and operation process, each reactor should be independently started and optimized. After the reactor runs stably, it is operated in series. Therefore, the following steps are included:

[0044] Step S1, carbon capture reactor startup phase: determine the amount of flocculant through flocculation experiments, add the flocculant into the carbon capture reactor according to the determined amount, monitor the removal efficiency of carbon and phosphorus in the sewage, and determine that the carbon capture reactor is successfully started when the removal rates of suspended solids, biochemical oxygen demand, and total phosphorus reach preset values ​​respectively;

[0045] Specifically, in one embodiment of the present invention, the type of CEPT reactor used is a continuous stirred tank reactor; first, the optimal dosage of the flocculant is determined by flocculation experiment, and then the final dosage is determined to be 30 mg / L ferric chloride and 0.5 g / L anionic flocculant based on the cost and large-scale application cases; the above flocculant is added to the CEPT reactor, and after sufficient stirring and mixing, the mixed liquid flows into the first sedimentation tank for solid-liquid separation; the removal efficiency of carbon and phosphorus in the sewage is monitored, and when the removal rates of suspended solids, biochemical oxygen demand, and total phosphorus are greater than 70%, 55%, and 60%, respectively, the reactor can be considered to be operating successfully. The hydraulic retention time of the CEPT reactor and the first sedimentation tank are 15 minutes and 30 minutes, respectively.

[0046] Step S2, nitrification reactor startup phase: adding secondary sedimentation tank sludge as seed sludge to the nitrification reactor, using sewage from the carbon capture reactor as a culture matrix to provide dissolved oxygen, and operating in sequencing batch mode and continuous flow mode in sequence. When the ammonia nitrogen removal rate reaches more than 90%, the nitrification reactor is successfully started;

[0047] Specifically, in one embodiment of the present invention, the type of nitrification reactor is a moving bed biofilm reactor, the filler type is K5, the filling ratio is 20% to 30%, the dissolved oxygen concentration is controlled at more than 2.0 mg / L, and the above-mentioned CEPT effluent is used as a culture matrix. The secondary sedimentation tank sludge is inoculated, and the initial inoculation amount of SS is 3.0 g / L. In the first 7 days, the reactor adopts a sequencing batch operation mode, with water intake for 10 minutes, aeration and stirring for 5 hours, sedimentation for 40 minutes, and drainage for 10 minutes. Each inlet and outlet water is half of the reactor volume, and the hydraulic retention time is set to 12 hours. Afterwards, it is operated in a continuous flow mode, and the hydraulic retention time is set to 4 hours. When the removal rate of ammonia nitrogen reaches more than 90%, the reactor is considered to be successfully started.

[0048] Step S3, the startup phase of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor: inoculating laboratory-cultured anaerobic ammonium oxidation sludge in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, using simulated wastewater, first starting at a first nitrogen concentration, a first hydraulic retention time and a first operating temperature, after the reactor is stable, successively reducing the influent nitrogen concentration, reducing the operating temperature to the ambient temperature and gradually reducing the hydraulic retention time, continuously regulating the operation until the reactor is stable, and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is considered to be successfully started when the total nitrogen removal rate reaches more than 80%;

[0049] Specifically, in one embodiment of the present invention, the type of sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is an upflow anaerobic sludge blanket reactor, which is provided with a gas reflux stirring system. The gas generated by the reactor is injected into the bottom of the reactor through a gas circulation pump to improve the effective mixing of the substrate and the microorganisms. The inoculated sludge is anaerobic ammonia oxidation sludge cultured in the laboratory, and the initial inoculation concentration is 7.0g SS / L. In the startup phase of the reactor, simulated wastewater is used, and its composition is 50mg / L nitrate nitrogen, 50mg / L ammonia nitrogen, 1.0g / L sodium bicarbonate, and a small amount of trace elements such as calcium chloride, magnesium chloride, and phosphorus; sulfur powder is used as the electron donor (sulfur source), the reactor HRT is set to 6 hours, and the temperature is set to 30 degrees Celsius. When the total nitrogen removal rate of the reactor reaches more than 80%, the startup is considered successful; then the inlet nitrogen concentration is reduced to the mainstream conditions (25 mg / L nitrate nitrogen and 25 mg / L ammonia nitrogen), and the operation continues. After the reactor is stable, the temperature is reduced to room temperature; then, the HRT is reduced from 6 hours to 4 hours, and finally to 2 hours, and the operation is continuously adjusted until the reactor is stable and the total nitrogen removal rate reaches more than 80%.

[0050] Step S4, system operation stage: the sewage passes through the carbon capture reactor to capture organic matter and phosphorus in the sewage through the flocculant, and then passes through the first sedimentation tank to precipitate the sewage treated by the carbon capture reactor, and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor in proportion; the supernatant from the first sedimentation tank is nitrified by the nitrification reactor, and the ammonia nitrogen in the supernatant is oxidized into nitrate nitrogen; the second sedimentation tank is used to separate the effluent of the nitrification reactor from mud and water; the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is used to use reduced sulfur as an electron donor to reduce the nitrate nitrogen in the effluent from the second sedimentation tank to nitrite nitrogen through sulfur autotrophic short-range denitrification, and then the nitrite nitrogen and the ammonia nitrogen in the supernatant from the first sedimentation tank are converted into nitrogen gas through anaerobic ammonia oxidation.

[0051] Specifically, in one embodiment of the present invention, after the sewage is treated with CEPT and passed through a sedimentation tank to remove suspended particles, 60% of the CEPT effluent enters the nitrification system for complete nitrification; the effluent of the nitrification reactor is treated with sedimentation, and the supernatant is mixed with 40% of the CEPT effluent and enters the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor. After more than one year of actual operation, the system has shown excellent performance, with total chemical oxygen demand, total phosphorus and total nitrogen removal rates all reaching more than 80%; the contribution rate of anaerobic ammonium oxidation to total nitrogen is also higher than 80%, truly realizing autotrophic mainstream denitrification based on anaerobic ammonium oxidation.

[0052] Compared with the prior art, the method and system based on carbon capture and autotrophic denitrification of the present invention have significant advantages, which are specifically manifested in the following aspects:

[0053] 1. Effective capture and utilization of carbon and phosphorus in wastewater

[0054] Traditional sewage treatment processes usually use carbon for nitrogen and phosphorus removal, but the present invention captures carbon and phosphorus in wastewater and recovers energy through fermentation to produce methane, while purifying phosphorus to achieve resource recovery. This design makes the system more environmentally friendly and sustainable, and provides a new way for energy recovery.

[0055] 2. Achieved high denitrification contribution rate of mainstream anaerobic ammonium oxidation

[0056] Mainstream anaerobic ammonium oxidation is a low-energy nitrogen removal technology. The present invention significantly improves the contribution of anaerobic ammonium oxidation to denitrification by optimizing process conditions. Compared with the traditional nitrification-denitrification method, the present invention significantly reduces the energy consumption in the denitrification process.

[0057] 3. Solved the problem of stable supply of nitrite nitrogen

[0058] Nitrite nitrogen is a necessary substrate for anaerobic ammonium oxidation. Short-range nitrification, as a traditional nitrite nitrogen supply process, is often difficult to achieve stable operation, resulting in unsatisfactory treatment effects. The present invention changes the way nitrite nitrogen is produced through innovative autotrophic denitrification technology. It does not require a large number of sensors and precise control systems, and the nitrite nitrogen production process is simple and stable. In this way, the system can remove nitrogen pollutants more efficiently and further improve the quality of treated water.

[0059] 4. Changed the traditional post-nitrification effluent reflux mode

[0060] Traditional sewage treatment technology often adopts a post-nitrification effluent return mode, which not only increases the complexity of the system, but also increases energy consumption. Relatively speaking, the present invention avoids this traditional return mode by improving the reactor design and process, thereby greatly reducing the energy consumption during the aeration process and further improving the economy and energy efficiency of the system.

[0061] 5. Low-cost elemental sulfur helps achieve efficient mainstream anaerobic ammonium oxidation

[0062] The use of sulfur as an inorganic carbon source plays a key role in the present invention. Sulfur can not only effectively promote the short-range denitrification coupled anaerobic ammonia oxidation reaction, but also greatly reduce the operating cost of the system. Compared with other expensive chemical reagents / organic carbon sources, the low cost of sulfur makes this technology more economical and practical.

[0063] 6. Fully autotrophic denitrification system reduces energy consumption

[0064] The present invention adopts fully autotrophic denitrification technology, which means that no expensive organic carbon source needs to be added. The system achieves efficient and low-cost nitrogen removal through the action of autotrophic microorganisms, while reducing the generation of sludge and greatly reducing the energy consumption required by traditional sewage treatment systems.

[0065] The present invention fully recovers energy resources in wastewater by rationally designing the reactor and process flow, thus reducing the demand for external energy. The overall design of the system can significantly reduce operating costs and energy consumption while meeting treatment requirements, providing a new solution for achieving sustainability and economy in wastewater treatment.

[0066] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc., does not indicate any order. These words may be interpreted as names.

Claims

1. A domestic sewage treatment system based on carbon capture and autotrophic denitrification, characterized in that: The invention comprises a carbon capture reactor, a first sedimentation tank, a nitrification reactor, a second sedimentation tank and a sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, wherein the carbon capture reactor is connected to the first sedimentation tank, the first sedimentation tank is connected to the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor through a first water pump pipeline and a second water pump pipeline respectively, the nitrification reactor is connected to the second sedimentation tank, the second sedimentation tank is connected to the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor through a third water pump pipeline, the carbon capture reactor is used to capture organic matter and phosphorus in sewage through a flocculant; the first sedimentation tank is used to precipitate the sewage treated by the carbon capture reactor and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor respectively in proportion; the nitrification reactor is used to nitrify the supernatant from the first sedimentation tank, and oxidize the ammonia nitrogen in the supernatant into nitrate nitrogen; the second sedimentation tank is used to separate the effluent from the nitrification reactor into mud and water; the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is used to reduce the nitrate nitrogen in the effluent from the second sedimentation tank into nitrite nitrogen through sulfur autotrophic short-range denitrification using reduced sulfur as an electron donor, and then convert the nitrite nitrogen and the ammonia nitrogen in the supernatant from the first sedimentation tank into nitrogen gas through anaerobic ammonium oxidation.

2. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The flocculant consists of ferric chloride and anionic polymer, and the usage of the flocculant is determined through a coagulation experiment.

3. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The ratio of the supernatant pumped from the first sedimentation tank into the nitrification reactor to the supernatant of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is not less than 3:

2.

4. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The hydraulic retention time in the nitrification reactor is 2h to 4h.

5. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The hydraulic retention time in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is 2h to 6h.

6. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The reducing sulfur used in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is selected from one or more of elemental sulfur, thiosulfate, sulfide, ferrous sulfide, and sodium sulfite.

7. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The carbon capture reactor is selected from one of a chemically enhanced primary treatment (CEPT) reactor, a high-rate activated sludge reactor or an anaerobic membrane bioreactor.

8. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The nitrification reactor is selected from one of a moving bed biofilm reactor, a continuous stirred tank reactor, a sequencing batch reactor and a membrane bioreactor.

9. The method for treating domestic sewage based on carbon capture and autotrophic denitrification according to claim 1, characterized in that: The sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is selected from one of an upflow anaerobic sludge blanket reactor, a membrane bioreactor, and a sequencing batch reactor.

10. A method for treating domestic sewage based on carbon capture and autotrophic denitrification, using the domestic sewage treatment system based on carbon capture and autotrophic denitrification according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1, carbon capture reactor startup phase: determine the amount of flocculant through flocculation experiments, add the flocculant into the carbon capture reactor according to the determined amount, monitor the removal efficiency of carbon and phosphorus in the sewage, and determine that the carbon capture reactor is successfully started when the removal rates of suspended solids, biochemical oxygen demand, and total phosphorus reach preset values ​​respectively; Step S2, nitrification reactor startup phase: adding the secondary sedimentation tank sludge as seed sludge to the nitrification reactor, using the sewage from the carbon capture reactor as the culture matrix, and providing sufficient dissolved oxygen, and operating in sequencing batch mode and continuous flow mode in sequence. When the ammonia nitrogen removal rate reaches more than 90%, the nitrification reactor is considered to be successfully started; Step S3, the startup phase of the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor: inoculating laboratory-cultured anaerobic ammonium oxidation sludge in the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor, using simulated wastewater, first starting at a first nitrogen concentration, a first hydraulic retention time and a first operating temperature, after the reactor is stable, successively reducing the influent nitrogen concentration, reducing the operating temperature to the ambient temperature and gradually reducing the hydraulic retention time, continuously regulating the operation until the reactor is stable, and the sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reactor is considered to be successfully started when the total nitrogen removal rate reaches more than 80%; Step S4, system operation stage: the sewage passes through the carbon capture reactor to capture organic matter and phosphorus in the sewage through the flocculant, and then passes through the first sedimentation tank to precipitate the sewage treated by the carbon capture reactor, and the obtained supernatant is pumped into the nitrification reactor and the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor in proportion; the supernatant from the first sedimentation tank is nitrified by the nitrification reactor, and the ammonia nitrogen in the supernatant is oxidized into nitrate nitrogen; the second sedimentation tank is used to separate the effluent of the nitrification reactor from mud and water; the sulfur autotrophic denitrification coupled anaerobic ammonia oxidation reactor is used to use reduced sulfur as an electron donor to reduce the nitrate nitrogen in the effluent from the second sedimentation tank to nitrite nitrogen through sulfur autotrophic short-range denitrification, and then the nitrite nitrogen and the ammonia nitrogen in the supernatant from the first sedimentation tank are converted into nitrogen gas through anaerobic ammonia oxidation.

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