AOO internal carbon source nitrogen and phosphorus removal and sludge reduction sewage treatment process

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an AOO internal carbon source nitrogen and phosphorus removal and sludge reduction sewage treatment process which comprises an anoxic tank, an aerobic tank I, an aerobic tank II, a secondary sedimentation tank and a nitrification filter tank which are sequentially arranged, the anoxic tank is communicated with a water inlet pipe and the aerobic tank I, the aerobic tank I is communicated with the aerobic tank II, and the nitrification filter tank is communicated with the secondary sedimentation tank. The aerobic tank II is communicated with the secondary sedimentation tank, the secondary sedimentation tank is communicated with the nitrification filter tank, and the nitrification filter tank is connected with a water outlet pipe; the nitrification filter tank is respectively communicated with the anoxic tank and the aerobic tank II through nitrification liquid return pipes, the secondary sedimentation tank is communicated with the anoxic tank through a sludge return pipe, and the sewage treatment process disclosed by the invention has the advantages of high efficiency, low consumption, small sludge amount and wide application range.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a wastewater treatment process for removing nitrogen and phosphorus from carbon sources and reducing sludge volume within an AOO (Air-Oxygen Container). Background Technology

[0002] With the increasing environmental awareness and rapid urbanization in my country, the demand for wastewater treatment has also grown significantly. By 2020, the daily wastewater treatment volume in my country had reached 193 million m³, a very large amount. Meanwhile, in recent years, my country's wastewater discharge requirements have been continuously raised, with effluent standards increasing from the traditional Class A standard to the Surface Water Standard IV, and even the Surface Water Standard III. This undoubtedly poses new challenges to wastewater treatment processes. Researching and developing efficient and economical wastewater treatment processes has become a current hot topic. Among traditional wastewater denitrification processes, biological methods have become an important and widely used method for nitrogen and phosphorus removal in urban wastewater in recent years due to their simplicity, high treatment capacity, and flexible operation.

[0003] Traditional biological nitrogen removal theory posits that ammonia nitrogen is removed by converting ammonia in water into nitrogen gas, NH4+, through two different types of bacteria (nitrifying bacteria and denitrifying bacteria). 4+ It requires a typical nitrification and denitrification process to convert ammonia nitrogen into nitrogen gas. In the nitrification reaction, nitrite-oxidizing bacteria first convert ammonia nitrogen into nitrite (NO). 2- Then, nitrifying bacteria convert nitrite into nitrate (NO). 3- Nitrification requires aerobic conditions and uses oxygen as the electron acceptor. Denitrification is the process of converting nitrates or nitrites into N2. Denitrifying bacteria utilize various organic substrates as electron donors and nitrates or nitrites as electron acceptors, undergoing anaerobic respiration. However, traditional biological nitrogen removal processes suffer from drawbacks such as high energy consumption, low reaction efficiency, large sludge production, and poor COD removal. The effluent cannot meet the IV standard for surface water quality. They are typically only suitable for biological nitrogen removal from ammonia nitrogen wastewater with a low C / N ratio (i.e., low COD content) and containing small-molecule organic matter, thus exhibiting significant limitations in application.

[0004] In addition, phosphorus is one of the main causes of eutrophication in water bodies, and phosphorus removal from wastewater is an effective way to prevent eutrophication. Wastewater phosphorus removal technologies are mainly divided into two categories: chemical methods and biological methods. Among them, biological methods are widely used due to their economic efficiency and environmental friendliness, but they also face problems such as low reaction efficiency, long treatment processes, large equipment footprint, and difficulties in sludge treatment.

[0005] Therefore, it is of great significance to explore a nitrogen and phosphorus removal wastewater treatment process that can meet increasingly higher effluent standards, while also being highly efficient, low-consumption, and widely applicable. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned technical problems by providing an AOO-based wastewater treatment process for nitrogen and phosphorus removal and sludge reduction, thereby overcoming the current wastewater treatment processes' high energy consumption, low reaction efficiency, large sludge production, poor COD removal effect, and limited applicability.

[0007] In view of this, the present invention provides a wastewater treatment process for nitrogen and phosphorus removal and sludge reduction within an AOO (Air-to-Oxygen) system, comprising the following components arranged sequentially:

[0008] The system includes an anoxic tank, an aerobic I tank, an aerobic II tank, a secondary sedimentation tank, and a nitrifying filter. The anoxic tank is connected to the inlet pipe and the aerobic I tank. The aerobic I tank is connected to the aerobic II tank. The aerobic II tank is connected to the secondary sedimentation tank. The secondary sedimentation tank is connected to the nitrifying filter. The nitrifying filter is connected to the outlet pipe.

[0009] The nitrification filter is connected to the anoxic tank and the aerobic II tank respectively through a nitrification liquid return pipe, and the secondary sedimentation tank is connected to the anoxic tank through a sludge return pipe.

[0010] Furthermore, the nitrification liquid return pipe and the sludge return pipe are respectively connected to the middle of the anoxic tank, the anoxic tank is connected to the aerobic tank I through a hole set in its upper part, the bottom of the aerobic tank I is connected to the aerobic tank II, and the upper part of the aerobic tank II is connected to the secondary sedimentation tank.

[0011] Furthermore, the wastewater retention time in the aerobic I tank is controlled to be 1-2 hours, and the dissolved oxygen is controlled to be above 2 mg / L; the wastewater retention time in the aerobic II tank is controlled to be 3-5 hours, and the dissolved oxygen is controlled to be below 1 mg / L.

[0012] Furthermore, the sludge return ratio of the secondary sedimentation tank (4) is 80%-100%, the return ratio of nitrified liquid to the anoxic tank is 200%-300%, and the return ratio of nitrified liquid to the aerobic II tank is controlled so that the concentration ratio of nitrate nitrogen to phosphate in the aerobic II tank is 2:1.

[0013] Furthermore, the wastewater treatment process also includes:

[0014] The first oxidation treatment tank is located between the aerobic II tank and the secondary sedimentation tank, and is connected to both the aerobic II tank and the secondary sedimentation tank. The effluent from the aerobic II tank enters the first oxidation treatment tank for oxidation treatment, and then enters the secondary sedimentation tank for mud-water separation.

[0015] The second oxidation treatment tank is located after the nitrification filter. The effluent from the nitrification filter enters the second oxidation treatment tank for deep oxidation treatment, and then is treated by a flocculation sedimentation tank before being discharged in compliance with standards.

[0016] Furthermore, the wastewater treatment process also includes a sludge treatment tank, which is connected to the secondary sedimentation tank and the anoxic tank via the sludge return pipe. The sludge in the secondary sedimentation tank enters the sludge treatment tank through the sludge return pipe and is then treated by alkaline oxidation and Fenton-like oxidation before being discharged into the anoxic tank.

[0017] Furthermore, several cuprous oxide mesh plates are installed in the first oxidation treatment tank, and an appropriate amount of Fe is added. 2+ Ions, under visible light irradiation, oxidize pollutants in the wastewater in the first oxidation treatment tank.

[0018] Furthermore, the second oxidation treatment tank is equipped with several cuprous oxide mesh plates, and an appropriate amount of Fe is added. 2+ Ions and transition metals are used to perform deep oxidation treatment on wastewater in the second oxidation treatment tank under visible light irradiation.

[0019] Furthermore, the cuprous oxide mesh plates in the first and second oxidation treatment tanks are prepared according to the following method:

[0020] First, the copper wire mesh is placed in an oxidizing atmosphere and kept at 500-800°C for 0.5-1 hour to form a cuprous oxide film on the surface of the copper wire mesh.

[0021] Then, prepare a copper oxide dispersion: dissolve 15-50 parts by weight of ascorbic acid in water to prepare an ascorbic acid aqueous solution with a concentration of 0.01-0.20 mol / L, and then disperse 20-40 parts by weight of nano copper oxide powder in the ascorbic acid aqueous solution and stir to obtain a copper oxide dispersion.

[0022] The copper wire mesh was then immersed in a copper oxide dispersion and reacted at 20–50°C and a stirring speed of 100–200 rpm for 1–2 hours. The resulting cuprous oxide was deposited on the copper wire mesh.

[0023] Finally, the copper wire mesh deposited with cuprous oxide is placed in an inert atmosphere and kept at 500–1200℃ for 20–40 minutes to obtain the cuprous oxide mesh plate.

[0024] Furthermore, the method for treating sludge in the sludge treatment pond is as follows:

[0025] First, the sludge in the secondary sedimentation tank is discharged into the sludge treatment tank, and the sludge concentration is controlled at 2000-4000 mg / L;

[0026] Then, sodium hydroxide solution is added to the sludge treatment tank to adjust the pH of the sludge to 10-12. The reaction is carried out for 0.5-1 hours under stirring. After the reaction is completed, sedimentation and sludge-water separation are performed. After sludge-water separation, the supernatant is directly discharged into the anoxic tank, while the sludge remains in the sludge treatment tank. At this time, the sludge concentration is controlled at 5000-7000 mg / L.

[0027] Then, acid solution is added to the sludge treatment tank to adjust the pH of the sludge to 3-5. Hydrogen peroxide is then added to the sludge, with an addition amount of 0.01-0.05g of hydrogen peroxide per kilogram of sludge. The mixture is then stirred and reacted under visible light for 0.5-1h.

[0028] The wastewater treatment process for denitrification, phosphorus removal, and sludge reduction within the AOO (Air-Oxygen Source) as described in this invention has the advantages of high efficiency, low consumption, small sludge volume, and wide applicability. Attached Figure Description

[0029] Figure 1 This is a flowchart of the wastewater treatment process described in this invention;

[0030] Figure 2 This is a plan view of the wastewater treatment process described in this invention;

[0031] Figure 3 This is another flow chart of the wastewater treatment process described in this invention;

[0032] Figure 4 This is another flow chart of the wastewater treatment process described in this invention.

[0033] The markings in the diagram are as follows:

[0034] 1-Anoxic tank, 2-Aerobic I tank, 3-Aerobic II tank, 4-Secondary sedimentation tank, 5-Nitrification filter, 6-Inlet pipe, 7-Aeration equipment, 8-Nitrified liquid return pipe, 9-Outlet pipe, 10-Nitrified liquid return pump, 11-Sludge return pipe, 12-First oxidation tank, 13-Second oxidation tank, 14-Sludge treatment tank, 15-Flocculation sedimentation tank. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0036] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0037] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0038] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0039] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0040] like Figures 1-4 As shown, a wastewater treatment process for denitrification, phosphorus removal, and sludge reduction within an AOO (Air-to-Oxygen) system includes the following components arranged sequentially:

[0041] The system comprises an anoxic tank 1, an aerobic I tank 2, an aerobic II tank 3, a secondary sedimentation tank 4, and a nitrifying filter 5. The anoxic tank 1 is connected to the inlet pipe 6 and the aerobic I tank 2. The aerobic I tank 2 is connected to the aerobic II tank 3. The aerobic II tank 3 is connected to the secondary sedimentation tank 4. The secondary sedimentation tank 4 is connected to the nitrifying filter 5. The nitrifying filter 5 is connected to the outlet pipe 9.

[0042] In addition, the nitrification filter 5 is connected to the anoxic tank 1 and the aerobic II tank 3 respectively through the nitrification liquid return pipe 8, and the secondary sedimentation tank 4 is connected to the anoxic tank 1 through the sludge return pipe 11.

[0043] Furthermore, a nitrification liquid return pump 10 is installed on the nitrification filter 5, which can return the nitrification liquid in the nitrification filter 5 to the anoxic tank 1 and the aerobic II tank 3 through the nitrification liquid return pipe 8.

[0044] Furthermore, several aeration devices 7 are installed at the bottom of the aerobic I tank 2 and aerobic II tank 3, through which oxygen can be supplied to the aerobic I tank 2 and aerobic II tank 3.

[0045] Preferably, the aeration facilities 7 in the aerobic I tank 2 are more numerous than those in the aerobic II tank 3, in order to facilitate the control of dissolved oxygen in the later stage, while reducing energy consumption and achieving energy saving and consumption reduction.

[0046] Preferably, a stirring device (not shown in the figure) is installed in or at the front end of the anoxic tank 1. The stirring device can stir the material entering the anoxic tank 1, so that the sewage in the anoxic tank 1 and the return material from the nitrification liquid return pipe 8 and the sludge return pipe 11 can be mixed evenly.

[0047] Preferably, the nitrification liquid return pipe 8 and the sludge return pipe 11 are respectively connected to the middle of the anoxic tank 1. The anoxic tank 1 is connected to the aerobic I tank 2 through a hole in its upper part. The bottom of the aerobic I tank 2 is connected to the aerobic II tank 3, and the upper part of the aerobic II tank 3 is connected to the secondary sedimentation tank 4. The wastewater described in this application can flow into the anoxic tank 1, aerobic I tank 2, aerobic II tank 3, secondary sedimentation tank 4, and nitrification filter 5 sequentially by gravity, without the need for other power sources, thus saving energy.

[0048] Furthermore, the anoxic tank 1 mainly uses denitrifying bacteria to carry out denitrification reactions.

[0049] Furthermore, in the aerobic tank 2, the external carbon source is rapidly converted into PHB endogenous substances for storage by microorganisms in the wastewater under sufficient nutrient conditions.

[0050] Furthermore, in the aerobic II tank 3, simultaneous nitrogen and phosphorus removal is mainly achieved through denitrifying polyphosphate-accumulating bacteria. Specifically, in the aerobic II tank 3, by controlling the dissolved oxygen content, a molecular oxygen conflict exists among the microorganisms in the aerobic II tank 3, forcing some microorganisms to utilize molecular oxygen in nitrate nitrogen for synthesis and maintenance metabolism, thus achieving simultaneous nitrogen and phosphorus removal. For example, DPAOs can use NOx-N as an electron acceptor, utilize synthesized PHB to obtain ATP and reduced nicotinamide adenine dinucleotide (NADH), absorb inorganic phosphorus to synthesize Poly-P, and simultaneously reduce it to N2, achieving simultaneous nitrogen and phosphorus removal.

[0051] Furthermore, the nitrification filter 5 mainly uses nitrifying bacteria to carry out the nitrification reaction.

[0052] During wastewater treatment, wastewater sequentially enters the anoxic tank 1, aerobic tank I 2, and aerobic tank II 3 for nitrogen and phosphorus removal. The effluent from aerobic tank II 3 undergoes sedimentation and sludge-water separation in the secondary sedimentation tank 4. The sludge is then returned to the anoxic tank 1 through the sludge return pipe 11, and the supernatant enters the nitrification filter 5 for nitrification. Subsequently, the nitrified liquid in the nitrification filter 5 is returned to the anoxic tank 1 and aerobic tank II 3 through the nitrified liquid return pipe 8. Simultaneously, the effluent from the nitrification filter 5 meets discharge standards.

[0053] The following describes the specific process of the wastewater treatment process described in this application: In the wastewater treatment process of AOO in-situ carbon source denitrification and phosphorus removal and sludge reduction described in this application, the anoxic tank 1 constitutes the anoxic section, the aerobic tank I 2 and aerobic tank II 3 constitute two aerobic sections, and the nitrification filter 5 constitutes the nitrification section. Wastewater first enters the anoxic section, i.e., the anoxic tank 1, where it is stirred and mixed evenly with the sludge and nitrification liquid returned to the anoxic tank 1 through the sludge return pipe 11 and the nitrification liquid return pipe 8, and undergoes denitrification in the anoxic tank 1. Afterward, the wastewater enters the aerobic tank I 2, where microorganisms consume the carbon source and... The phosphate is converted into PHB and stored intracellularly. It then enters the aerobic tank 3 through the effluent from the bottom of the aerobic tank 1 2. In the aerobic tank 3, due to competition for molecular oxygen under dissolved oxygen control, some microorganisms utilize molecular oxygen in nitrate nitrogen for synthesis and maintenance, resulting in simultaneous denitrification and phosphorus accumulation, thus improving the denitrification and phosphorus removal efficiency. After sludge-water separation in the secondary sedimentation tank 4, the supernatant enters the nitrification filter 5 for nitrification. Part of the nitrified liquid is recycled, where denitrifying bacteria denitrify nitrate nitrogen, achieving total nitrogen removal and ensuring the effluent meets discharge standards. The sludge from the secondary sedimentation tank 4 is recycled to the anoxic tank 1. Therefore, the wastewater treatment process described in this application eliminates the traditional anaerobic phosphorus release and aerobic phosphorus uptake stages. Phosphate is removed in the aerobic tank 2 through simultaneous denitrification and phosphorus removal, simplifying the wastewater treatment process while ensuring phosphorus removal efficiency.

[0054] Furthermore, the wastewater retention time in the aerobic tank 1 2 is controlled to be 1-2 hours, and the dissolved oxygen is controlled to be above 2 mg / L. This ensures the dissolved oxygen required for microbial metabolism, shortens the metabolic time, and allows microorganisms to quickly convert external carbon sources into PHB for storage in the cells within the aerobic tank 1 2. This avoids excessively long retention time, excessive aerobic proliferation of microorganisms, and reduces sludge production.

[0055] Furthermore, the wastewater retention time in the aerobic II tank 3 is controlled to be 3-5 hours, and the dissolved oxygen is controlled to be below 1 mg / L. In this way, the molecular oxygen competition between microorganisms in the aerobic II tank 3 can be utilized to achieve simultaneous nitrogen and phosphorus removal.

[0056] Furthermore, the simultaneous nitrogen and phosphorus removal process described in this application employs the activated sludge method to avoid the conflict between the sludge ages of autotrophic and heterotrophic bacteria, while simultaneously reducing the aerobic proliferation yield of sludge.

[0057] Furthermore, the nitrification reaction is carried out in the nitrification filter 5 using a biofilm method. The biofilm method produces little or no residual sludge, which can reduce sludge production.

[0058] Furthermore, when the C / N ratio in the influent or the anoxic tank 1 is less than 4, an external carbon source needs to be added.

[0059] Furthermore, in the wastewater treatment process of carbon source denitrification, phosphorus removal, and sludge reduction in the AOO, the sludge return ratio of the secondary sedimentation tank (4) is 80%-100%, and the return ratio of nitrified liquid to anoxic tank 1 is 200%-300%. This can reduce the load on anoxic tank 1 and reduce the addition of external carbon sources. In addition, the purpose of returning nitrified liquid to aerobic tank II 3 is mainly to ensure that microorganisms utilize nitrate nitrogen in nitrified liquid for simultaneous denitrification and phosphorus removal, further improving the denitrification rate, while ensuring that the total phosphorus effluent meets the standards. Therefore, the return ratio of nitrified liquid to aerobic tank II 3 needs to be controlled in conjunction with the actual phosphate concentration in the influent, specifically so that the nitrate nitrogen to phosphate concentration ratio in aerobic tank II 3 is 2:1.

[0060] Compared with traditional denitrification and phosphorus removal processes, the wastewater treatment process for AOO internal carbon source denitrification, phosphorus removal, and sludge reduction described in this application has the following advantages:

[0061] First, there is no need to set up the traditional non-anaerobic phosphorus release and aerobic phosphorus uptake stages. Phosphate is removed by a simultaneous denitrification and phosphorus removal reaction in the aerobic II tank 3, which can avoid the consumption of a large amount of organic carbon source by polyphosphate-accumulating bacteria in the anaerobic section and reduce energy consumption.

[0062] Second, wastewater can be directly introduced into the anoxic zone to fully denitrify using external carbon sources, which can reduce the amount of external carbon sources added by about 50%.

[0063] Third, after denitrification, the wastewater enters aerobic tank 1, which has a high dissolved oxygen content and a short residence time. Under sufficient nutrient conditions, microorganisms can quickly convert external carbon sources into endogenous PHB substances for storage, avoiding prolonged direct aerobic metabolism and preventing the microorganisms from generating large amounts of energy for sludge proliferation. Thus, this application achieves the goal of utilizing heterotrophic microorganisms to convert energy into intracellular energy storage when nutrients are sufficient but the metabolic rate is insufficient, thereby reducing the direct utilization rate of organic matter by microorganisms and reducing the sludge synthesis and metabolism yield.

[0064] Fourth, the wastewater treatment process for denitrification and phosphorus removal and sludge reduction in the AOO internal carbon source described in this application separates the nitrification reaction from the activated sludge biological system. By postponing the nitrification reaction, the contradiction between polyphosphate-accumulating bacteria and nitrifying bacteria sludge age is avoided, the residence time of wastewater in aerobic tank 1 2 is shortened, the aerobic metabolic time of microorganisms is reduced, and the sludge proliferation rate is low.

[0065] Fifth, the wastewater treatment process described in this application mainly adopts the principle of simultaneous nitrogen and phosphorus removal. After the wastewater in aerobic tank I 2 enters aerobic tank II 3, the dissolved oxygen and residence time in aerobic tank II 3 are controlled to keep it in a low-oxygen state. Under the contradiction of molecular oxygen competition when dissolved oxygen is limited, microorganisms use the nitrification liquid returned from nitrification filter 5 to remove nitrogen and phosphorus. By using the combined oxygen in nitrate nitrogen to remove nitrogen and phosphorus, one carbon can be used for two purposes. At the same time, the aeration volume of aerobic tank II 3 is small and the sludge proliferation is small.

[0066] Overall, compared with traditional processes, the wastewater treatment process described in this application can achieve a sludge reduction of more than 40%, a nitrogen and phosphorus removal efficiency improvement of more than 30%, and a lower overall operating cost. Therefore, the wastewater treatment process for nitrogen and phosphorus removal and sludge reduction with internal carbon source in AOO described in this application can be used in biodegradable wastewater treatment projects to effectively improve nitrogen and phosphorus removal efficiency, reduce sludge production, and lower wastewater treatment costs, and has great promotional value.

[0067] Furthermore, the wastewater treatment process for denitrification, phosphorus removal, and sludge reduction within the AOO can be directly used to treat wastewater with low to medium concentrations of COD, ammonia nitrogen, and phosphorus.

[0068] Preferably, the wastewater treatment process for denitrification, phosphorus removal, and sludge reduction within the AOO can be directly used to treat wastewater with COD < 1000 mg / L, ammonia nitrogen concentration < 200 mg / L, and phosphorus content < 20 mg / L.

[0069] When the concentration of pollutants in the influent exceeds this range, especially when the wastewater contains large-molecule, recalcitrant pollutants, the wastewater treatment cycle will become longer and the performance will decline. In this case, the process composition of this application, which consists of an anoxic section composed of the anoxic tank 1, two aerobic sections composed of aerobic tank I 2 and aerobic tank II 3, and a nitrification section composed of the nitrification filter 5, can be coupled with a chemical oxidation process for wastewater treatment. Specifically, the wastewater treatment process described in this application also includes:

[0070] The first oxidation treatment tank 12 is located between the aerobic II tank 3 and the secondary sedimentation tank 4, and is connected to both the aerobic II tank 3 and the secondary sedimentation tank 4. The effluent from the aerobic II tank 3 enters the first oxidation treatment tank 12 for oxidation treatment, and then enters the secondary sedimentation tank 4 for mud-water separation.

[0071] The second oxidation treatment tank 13 is located after the nitrification filter 5. The effluent from the nitrification filter 5 enters the second oxidation treatment tank 13 for deep oxidation treatment, and then is treated by the flocculation sedimentation tank 15 before being discharged in compliance with standards.

[0072] Furthermore, the wastewater treatment process also includes a sludge treatment tank 14, which is connected to the secondary sedimentation tank 4 and the anoxic tank 1 via the sludge return pipe 11. The sludge in the secondary sedimentation tank 4 enters the sludge treatment tank 14 through the sludge return pipe 11 and is then treated by alkaline oxidation and Fenton-like oxidation before being discharged into the anoxic tank 1.

[0073] Furthermore, the flocculation sedimentation tank 15 can be connected to the sludge treatment tank 14 to return the sludge in the flocculation sedimentation tank 15 to the sludge treatment tank 14 for further treatment. The sludge return ratio in the flocculation sedimentation tank 15 is 80%-120%.

[0074] Preferably, the wastewater treatment process for denitrification, phosphorus removal, and sludge reduction within the AOO is suitable for wastewater with COD > 10000 mg / L, especially COD > 20000 mg / L and ammonia nitrogen concentration > 1000 mg / L.

[0075] Furthermore, several cuprous oxide mesh plates are installed in the first oxidation treatment tank 12, and an appropriate amount of Fe is added. 2+ Ions, under visible light irradiation, oxidize pollutants in the wastewater in the first oxidation treatment tank 12.

[0076] Preferably, before oxidation treatment, acid or alkali solution should be added to adjust the pH of the first oxidation treatment tank 12 to 8-9.

[0077] As some embodiments of this application, the visible light can be light emitted by sunlight, lighting tubes, light-emitting diodes, etc.

[0078] Preferably, the visible light is light with a wavelength of 380–600 nm.

[0079] Furthermore, in the first oxidation treatment tank 12, Fe 2+ The amount of ions added is 5–15 mmol / L.

[0080] Furthermore, the wastewater retention time in the first oxidation treatment tank 12 is controlled to be 2-3 hours.

[0081] Furthermore, 5-10 mmol / L of reducing agent, such as soluble sulfides and sulfites, is added to the first oxidation treatment tank 12.

[0082] Furthermore, the dissolved oxygen in the first oxidation treatment tank 12 is controlled at 1-2 mg / L.

[0083] In the first oxidation treatment tank 12, under visible light irradiation, cuprous oxide can catalyze the reaction of water and dissolved oxygen therein to produce hydrogen peroxide, which can further react with Fe...2+ The ionic interaction generates hydroxyl radicals, which are then used to oxidize and decompose recalcitrant pollutants such as macromolecular organic matter in the water. This improves the utilization rate of carbon sources and the decomposition and treatment capacity of pollutants in the subsequent nitrification process. Simultaneously, the iron ions generated during oxidation can improve the settling properties of the sludge.

[0084] Compared to the traditional method of directly adding hydrogen peroxide, the method used in the first oxidation treatment tank 12 has a high pH adaptability to wastewater and requires less pH adjustment. Typically, the pH of the denitrification effluent is around 7 and the pH of the nitrification influent is around 8. Only a small amount of acid or alkali solution needs to be added to the first oxidation treatment tank 12, which is more environmentally friendly and has a lower cost.

[0085] In addition, the first oxidation treatment tank 12 can significantly improve the utilization rate of hydrogen peroxide and the stability of the oxidation reaction, ensuring stable effluent quality and good oxidation effect.

[0086] Furthermore, the first oxidation treatment tank 12 is set up between the denitrification tank and the nitrification tank, and photocatalytic oxidation is carried out by visible light irradiation, which has a certain inhibitory effect on the activity of nitrite oxidizing bacteria, which is conducive to the oxidation of ammonia nitrogen into nitrite, which is then directly reduced into nitrogen by denitrifying bacteria, thus reducing energy consumption.

[0087] Furthermore, the second oxidation treatment tank 13 is equipped with several cuprous oxide mesh plates, and an appropriate amount of Fe is added. 2+ Ions and transition metals are used to perform deep oxidation treatment on the wastewater in the second oxidation treatment tank 13 under visible light irradiation. The transition metals act as reducing agents during the deep oxidation process, reducing ferric ions to ferrous ions, thereby increasing the oxidation reaction rate in the second oxidation treatment tank 13.

[0088] Preferably, before performing deep oxidation treatment, acid or alkali solution should be added to adjust the pH of the second oxidation treatment tank 13 to 9-10.

[0089] As some embodiments of this application, the visible light used in the second oxidation treatment tank 13 can be sunlight, lighting tubes, light-emitting diodes, etc. Preferably, the visible light is light with a wavelength of 380-600 nm.

[0090] Furthermore, in the second oxidation treatment tank 13, Fe 2+ The amount of ions added is 30–50 mmol / L.

[0091] Furthermore, the wastewater retention time in the second oxidation treatment tank 13 is controlled to be 1.5 to 2.5 hours.

[0092] Furthermore, the second oxidation treatment tank 13 also contains 30-70 mmol / L of reducing agent, such as soluble sulfides and sulfites.

[0093] Furthermore, the dissolved oxygen in the second oxidation treatment tank 13 is controlled at above 2 mg / L.

[0094] More preferably, the amount of transition metal added in the second oxidation treatment tank 13 is 10-20 mmol / L.

[0095] Furthermore, the cuprous oxide mesh plates in the first oxidation treatment tank 12 and the second oxidation treatment tank 13 are prepared according to the following method:

[0096] First, the copper wire mesh is placed in an oxidizing atmosphere and kept at 500-800°C for 0.5-1 hour to form a cuprous oxide film on the surface of the copper wire mesh.

[0097] Then, prepare a copper oxide dispersion: dissolve 15-50 parts by weight of ascorbic acid in water to prepare an ascorbic acid aqueous solution with a concentration of 0.01-0.20 mol / L, and then disperse 20-40 parts by weight of nano copper oxide powder in the ascorbic acid aqueous solution and stir to obtain a copper oxide dispersion.

[0098] The copper wire mesh was then immersed in a copper oxide dispersion and reacted at 20–50°C and a stirring speed of 100–200 rpm for 1–2 hours. The resulting cuprous oxide was deposited on the copper wire mesh.

[0099] Finally, the copper wire mesh deposited with cuprous oxide is placed in an inert atmosphere and kept at 500–1200℃ for 20–40 minutes to obtain the cuprous oxide mesh plate.

[0100] Preferably, the diameter of the copper wire in the copper wire mesh is 10-100 μm, and the mesh aperture is 2-5 mm.

[0101] Preferably, the oxidizing atmosphere is an oxidizing atmosphere containing oxygen, such as air.

[0102] Thus, an integral structure can be formed in the cuprous oxide mesh: a copper wire mesh as the basic framework, a copper oxide film layer on the surface of the copper wire mesh as the connecting medium, and dendritic cuprous oxide particles generated by hydrothermal method as the surface structure. This method of preparing the cuprous oxide mesh is simple and does not require expensive equipment. The surface cuprous oxide particles are connected to the copper wire mesh surface through the copper oxide film layer. The surface cuprous oxide particles and the copper oxide film layer on the copper wire mesh are of the same material, and the particles in the resulting ionic crystalline cuprous oxide can be arranged according to the lattice structure of the crystal, and are stably bonded to each other through ionic bonds, van der Waals forces, etc., allowing the surface cuprous oxide particles to stably adhere to the copper wire mesh surface. The bonding strength between the two is high and they are not easily detached. Simultaneously, the resulting cuprous oxide mesh has a large specific surface area, reaching 31–52 m². 2 / g can significantly improve reaction efficiency.

[0103] As some embodiments of this application, the cuprous oxide mesh can be arranged vertically around a visible light source; or it can be arranged horizontally with the visible light source placed in the interlayer gaps of the cuprous oxide mesh.

[0104] Furthermore, the method for treating sludge using the sludge treatment tank 14 is as follows:

[0105] First, the sludge in the secondary sedimentation tank 4 is discharged into the sludge treatment tank 14, and the sludge concentration is controlled at 2000-4000 mg / L;

[0106] Then, sodium hydroxide solution is added to the sludge treatment tank 14 to adjust the pH of the sludge to 10-12. The reaction is carried out for 0.5-1 hours under stirring. After the reaction is completed, sedimentation and sludge-water separation are performed. After sludge-water separation, the supernatant is directly discharged into the anoxic tank 1, while the sludge remains in the sludge treatment tank 14. At this time, the sludge concentration is controlled at 5000-7000 mg / L.

[0107] Then, acid solution is added to the sludge treatment tank 14 to adjust the pH of the sludge to 3-5. Hydrogen peroxide is then added to the sludge, with an addition amount of 0.01-0.05g of hydrogen peroxide per kilogram of sludge. The reaction is carried out under stirring and visible light for 0.5-1h.

[0108] In the sludge treatment tank 14, the pH of the sludge is adjusted to 10-12 by adding sodium hydroxide solution, which can perform alkaline oxidation on the sludge, causing cell wall disruption, extracellular polymer disintegration, and cytolysis of some cells. Most of the organic matter and bound water in the cells are released, and large organic molecules are decomposed into smaller molecules, achieving the purpose of sludge reduction. At the same time, in a high-alkaline environment, metals in the sludge can be converted from complexed and oxidized states into metal precipitates, providing a basis for subsequent hydrogen peroxide oxidation. Then, through a Fenton-like reaction between hydrogen peroxide and metals such as iron and copper in the sludge, some insoluble organic matter in the sludge is treated, and the hydroxyl radicals generated by hydrogen peroxide are used to convert them into small-molecule carbon sources that can be directly utilized by organisms, realizing the release and reuse of carbon sources.

[0109] The following specific embodiments illustrate the wastewater treatment process for in-AOO carbon source denitrification, phosphorus removal, and sludge reduction described in this application:

[0110] Example 1

[0111] Wastewater from a wastewater treatment plant in Shandong Province was treated according to... Figures 1-2 The process shown is used for wastewater treatment. The influent COD is 320 mg / L, the influent TP is 4.34 mg / L, and the influent TN is 52.4 mg / L. The wastewater first enters the anoxic tank, where the retention time is 7 hours, the nitrification liquor return ratio is 200%, and the sludge return ratio is 80%. The effluent from the anoxic tank enters the aerobic tank I, where the retention time is 1.5 hours and the dissolved oxygen is controlled at 3 mg / L. Then it enters the aerobic tank II, where the dissolved oxygen is 1 mg / L and the retention time is 5 hours, with a nitrification liquor return ratio of 25%. The effluent enters the secondary sedimentation tank for sludge-water separation and finally enters the nitrification filter for nitrification.

[0112] After one month of experimentation, the total nitrogen in the effluent was less than or equal to 10 mg / L, the total phosphorus was less than or equal to 0.2 mg / L, the amount of dry sludge produced was reduced by about 45.60% compared with the traditional process, the power consumption per ton of water was reduced by 16%, the amount of phosphorus removal agent added was reduced by 22%, and the amount of PAM added was reduced by 39.80%.

[0113] It should be noted that the traditional process mentioned is the NPR denitrification and phosphorus removal process originally used by the plant.

[0114] Example 2

[0115] Wastewater from a wastewater treatment plant in Shandong Province was collected according to... Figure 4The process shown is used for wastewater treatment. The influent COD is 22012 mg / L, influent TP is 28.31 mg / L, and influent TN is 1225.4 mg / L. The wastewater first enters an anoxic tank with a retention time of 7 hours, a nitrification liquor recirculation ratio of 300%, and a sludge recirculation ratio of 100%. The wastewater then enters aerobic tank I with a retention time of 1.5 hours and dissolved oxygen controlled at 3 mg / L. Subsequently, it enters aerobic tank II with a dissolved oxygen of 1 mg / L and a retention time of 5 hours, with a nitrification liquor recirculation ratio of 6.4%. The effluent enters the first oxidation tank for oxidation treatment, where dissolved oxygen is controlled at 1.5 mg / L and Fe... 2+ The ion concentration was 7 mmol / L, and the visible light source was a lighting lamp with an irradiance of 100 μW / cm². 2 The retention time is 2 hours. The effluent from the first oxidation treatment tank enters the second sedimentation tank for sludge-water separation. The supernatant enters the nitrification filter for nitrification, and then enters the second oxidation treatment tank for deep oxidation treatment. In the second oxidation treatment tank, dissolved oxygen is controlled at 3 mg / L, and Fe... 2+ The ion concentration was 40 mmol / L, and the visible light source was a lighting lamp with an irradiance of 200 μW / cm². 2 The retention time is 2 hours. The effluent from the second oxidation treatment tank is discharged after flocculation and sedimentation to meet the standards. The sludge from the second sedimentation tank is returned to the sludge treatment tank for treatment. The sludge concentration is controlled at 3000 mg / L. Sodium hydroxide solution is added to adjust the pH of the sludge to 11. After stirring and alkali treatment for 1 hour, sedimentation and sludge-water separation are carried out. The supernatant is directly discharged into the anoxic tank 1, while the sludge remains in the sludge treatment tank. At this time, the sludge concentration is controlled at 6000 mg / L. Then, acid solution is added to the sludge treatment tank to adjust the pH of the sludge to 4. Hydrogen peroxide is added to the sludge, with an addition amount of 0.02 g of hydrogen peroxide per kilogram of sludge. After stirring and reacting under sunlight for 0.5 hours, the sludge is returned to the anoxic tank.

[0116] After one month of testing, the effluent quality was stable, with COD ≤ 30 mg / L, total nitrogen ≤ 15 mg / L, and total phosphorus ≤ 0.3 mg / L.

[0117] Comparative Example

[0118] The oxidation treatment section of the first oxidation treatment tank, the deep oxidation treatment section of the second oxidation treatment tank, and the sludge treatment tank section in Example 2 were removed respectively. The remaining processes were carried out according to the process shown in Example 2. The influent water quality shown in Example 2 was purified to verify the wastewater treatment process described in this application. The results are shown in Table 1 below.

[0119] Table 1 Results of wastewater treatment using different processes

[0120]

[0121] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A wastewater treatment process for nitrogen and phosphorus removal and sludge reduction within an AOO (Air-to-Oxygen) system, characterized in that, Including the following settings in sequence: The anoxic tank (1), aerobic tank I (2), aerobic tank II (3), secondary sedimentation tank (4) and nitrification filter (5) are respectively connected to the inlet pipe (6) and aerobic tank I (2), aerobic tank I (2) is connected to aerobic tank II (3), aerobic tank II (3) is connected to secondary sedimentation tank (4), secondary sedimentation tank (4) is connected to nitrification filter (5), and nitrification filter (5) is connected to outlet pipe (9). The nitrification filter (5) is connected to the anoxic tank (1) and the aerobic II tank (3) respectively through the nitrification liquid return pipe (8), and the secondary sedimentation tank (4) is connected to the anoxic tank (1) through the sludge return pipe (11).

2. The wastewater treatment process according to claim 1, characterized in that, The nitrification liquid return pipe (8) and the sludge return pipe (11) are respectively connected to the middle of the anoxic tank (1). The anoxic tank (1) is connected to the aerobic I tank (2) through a hole set in its upper part. The bottom of the aerobic I tank (2) is connected to the aerobic II tank (3). The upper part of the aerobic II tank (3) is connected to the secondary sedimentation tank (4).

3. The wastewater treatment process according to claim 1, characterized in that, The wastewater retention time in the aerobic I tank (2) is controlled to be 1-2 hours, and the dissolved oxygen is controlled to be above 2 mg / L; the wastewater retention time in the aerobic II tank (3) is controlled to be 3-5 hours, and the dissolved oxygen is controlled to be below 1 mg / L.

4. The wastewater treatment process according to claim 1, characterized in that, The sludge return ratio of the secondary sedimentation tank (4) is 80%-100%, the return ratio of nitrified liquid to the anoxic tank (1) is 200%-300%, and the return ratio of nitrified liquid to the aerobic II tank (3) is controlled so that the concentration ratio of nitrate nitrogen to phosphate in the aerobic II tank (3) is 2:

1.

5. The wastewater treatment process according to claim 1, characterized in that, The wastewater treatment process also includes: The first oxidation treatment tank (12) is located between the aerobic II tank (3) and the secondary sedimentation tank (4), and is connected to the aerobic II tank (3) and the secondary sedimentation tank (4) respectively. The effluent from the aerobic II tank (3) enters the first oxidation treatment tank (12) for oxidation treatment, and then enters the secondary sedimentation tank (4) for mud-water separation. The second oxidation treatment tank (13) is located after the nitrification filter (5). The effluent from the nitrification filter (5) enters the second oxidation treatment tank (13) for deep oxidation treatment, and then is treated by the flocculation sedimentation tank (15) before being discharged in compliance with standards.

6. The wastewater treatment process according to claim 1 or 5, characterized in that, The wastewater treatment process further includes a sludge treatment tank (14), which is connected to the secondary sedimentation tank (4) and the anoxic tank (1) through the sludge return pipe (11). The sludge in the secondary sedimentation tank (4) enters the sludge treatment tank (14) through the sludge return pipe (11), and is discharged into the anoxic tank (1) after being treated by alkaline oxidation and Fenton-like oxidation.

7. The wastewater treatment process according to claim 5, characterized in that, The first oxidation treatment tank (12) is equipped with several cuprous oxide mesh plates, and an appropriate amount of Fe is added at the same time. 2+ Ions, under visible light irradiation, oxidize pollutants in the wastewater in the first oxidation treatment tank (12).

8. The wastewater treatment process according to claim 7, characterized in that, The second oxidation treatment tank (13) is equipped with several cuprous oxide mesh plates and an appropriate amount of Fe is added. 2+ Ions and transition metals are used to perform deep oxidation treatment on the wastewater in the second oxidation treatment tank (13) under visible light irradiation.

9. The wastewater treatment process according to claim 8, characterized in that, The cuprous oxide mesh plates in the first oxidation treatment tank (12) and the second oxidation treatment tank (13) are prepared according to the following method: First, the copper wire mesh is placed in an oxidizing atmosphere and kept at 500-800°C for 0.5-1 hour to form a cuprous oxide film on the surface of the copper wire mesh. Then, prepare a copper oxide dispersion: dissolve 15-50 parts by weight of ascorbic acid in water to prepare an ascorbic acid aqueous solution with a concentration of 0.01-0.20 mol / L, and then disperse 20-40 parts by weight of nano copper oxide powder in the ascorbic acid aqueous solution and stir to obtain a copper oxide dispersion. The copper wire mesh was then immersed in a copper oxide dispersion and reacted at 20–50°C and a stirring speed of 100–200 rpm for 1–2 hours. The resulting cuprous oxide was deposited on the copper wire mesh. Finally, the copper wire mesh deposited with cuprous oxide is placed in an inert atmosphere and kept at 500–1200℃ for 20–40 minutes to obtain the cuprous oxide mesh plate.

10. The wastewater treatment process according to claim 6, characterized in that, The sludge treatment tank (14) uses the following method to treat the sludge: First, the sludge in the secondary sedimentation tank (4) is discharged into the sludge treatment tank (14), and the sludge concentration is controlled at 2000-4000 mg / L; Then sodium hydroxide solution is added to the sludge treatment tank (14) to adjust the pH of the sludge to 10-12. After stirring, the reaction is carried out for 0.5-1h. After the reaction is completed, the sludge is precipitated and the sludge is separated from the water. After the sludge is separated from the water, the supernatant is directly discharged into the anoxic tank (1), and the sludge remains in the sludge treatment tank (14). At this time, the sludge concentration is controlled at 5000-7000mg / L. Then, acid solution is added to the sludge treatment tank (14) to adjust the pH of the sludge to 3-5. Hydrogen peroxide is then added to the sludge, wherein the amount of hydrogen peroxide added per kilogram of sludge is 0.01-0.05g. The mixture is stirred and reacted under visible light for 0.5-1h.

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