Method for treating municipal wastewater based on anaerobic ammonia oxidation reaction coupled with algal-bacterial symbiosis process

Abstract

The application provides a kind of urban domestic wastewater treatment method based on anaerobic ammonia oxidation reaction coupling algal fungus symbiosis process, and relates to wastewater treatment technical field.Processing method is carried out in the reactor provided with multiple biological streamers, multiple biological streamers are vertically arranged along the direction of water flow, and constitute soft isolation in the reactor;The method comprises: inoculating activated sludge into the reactor, while adding chlorella to the reaction pool;Simulated wastewater containing carbon source and nitrogen source is introduced into the reaction pool to cultivate the microorganism system containing anaerobic ammonia oxidation bacteria, and the simulated wastewater uses NH4Cl as the nitrogen source, NaHCO3 as the inorganic carbon source and glucose as the organic carbon source;Urban domestic wastewater is treated by using the reactor.The oxygen produced by the photosynthesis of chlorella replaces the aeration effect, which maximally reduces the energy consumption, and there is no need for additional carbon source, thereby reducing the denitrification cost and carbon emission.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a method for treating urban domestic wastewater based on an anaerobic ammonia oxidation reaction coupled with an algae-bacterial symbiosis process. Background Technology

[0002] Biological denitrification is a process in which organic nitrogen and ammonia nitrogen in wastewater are converted into nitrogen gas by microorganisms. It is economical, effective, easy to operate, and produces no secondary pollution. This process mainly consists of three stages: ammonification, nitrification, and denitrification.

[0003] Ammonification refers to the conversion of organic nitrogen in wastewater into ammonia nitrogen (NH3-N) through microbial action under anaerobic or anoxic conditions. Nitrification, on the other hand, refers to the conversion of ammonia nitrogen into nitrite nitrogen (NO2-N) and nitrate nitrogen (NO3-N) through nitrifying bacteria under aerobic conditions. This process consists of two stages: nitrification and nitrification, completed synergistically by nitrite-oxidizing bacteria and nitrifying bacteria. Denitrification refers to the reduction of nitrate nitrogen and nitrite nitrogen into nitrogen gas (N2) by denitrifying bacteria using carbon sources as electron donors under anoxic conditions, thereby achieving nitrogen removal.

[0004] Anaerobic ammonia oxidation (AAO) is a widely discussed process in recent years, showing promising application prospects in the treatment of urban domestic wastewater. AAO refers to the process where, under anaerobic conditions, anaerobic ammonia-oxidizing bacteria (AnAOB) use CO2 as an inorganic carbon source and NH4+ to generate nitrogen. + NO2 as an electron donor - It is directly oxidized to N2, thus completing the denitrification process. The theoretical reaction equation is as follows:

[0005] NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →0.26NO3-+1.02N2+0.066CH2O 0.5 N 0.15 +2.03H2O.

[0006] As can be seen from the above reaction equations, sufficient NH4+ is required to achieve anaerobic ammonium oxidation. + and NO2 - NH4 in urban sewage + High concentration of NO2 - Almost zero. Therefore, a stable and sufficient amount of NO2. - The source of nitrogen has become a limiting bottleneck in the application of anaerobic ammonia oxidation technology in the treatment of urban domestic sewage, resulting in a low nitrogen removal rate in urban domestic wastewater treated by anaerobic ammonia oxidation technology. Summary of the Invention

[0007] In order to improve the NO2 content in urban domestic sewage - The low nitrogen content in anaerobic ammonia oxidation technology leads to a low nitrogen removal rate in urban domestic wastewater. This application provides a method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with an algae-bacterial symbiotic process.

[0008] This application provides a method for treating urban domestic wastewater based on an anaerobic ammonia oxidation reaction coupled with an algae-bacterial symbiotic process, employing the following technical solution:

[0009] A method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algae-bacteria symbiosis, wherein the treatment method is carried out in a reactor equipped with multiple biological ribbons, which are arranged vertically along the water flow direction to form soft isolation within the reactor.

[0010] The method includes the following steps:

[0011] Step S1: Inoculate the reactor with activated sludge and simultaneously add Chlorella to the reactor;

[0012] Step S2: Introduce simulated wastewater containing carbon and nitrogen sources into the reactor to cultivate a microbial system containing anaerobic ammonia-oxidizing bacteria, wherein the simulated wastewater uses NH4Cl as the nitrogen source, NaHCO3 as the inorganic carbon source, and glucose as the organic carbon source.

[0013] Step S3: Use the reactor to treat urban domestic wastewater.

[0014] This application achieves low-energy and low-discharge treatment of low-C / N urban domestic wastewater by introducing an anaerobic ammonia oxidation-algae-bacteria symbiosis system into a bio-ribbon reactor. The reactor uses bio-ribbons as the loading material to simulate aquatic plants; its rich internal porous structure provides approximately 180-200 m² of space for the growth and reproduction of algae and other microorganisms. 2 The large surface area for biological attachment provides numerous attachment sites and favorable growth conditions, thereby improving the treatment effect of wastewater; the biological ribbon is made of fiber strips, which fundamentally determines the excellent performance and quality of the ecological substrate, and the ecological substrate is inexpensive and readily available, reducing treatment costs.

[0015] This application uses Chlorella as a photosynthetic bacterium. Chlorella not only provides oxygen to heterotrophic bacteria using the oxygen produced by photosynthesis, but also simultaneously absorbs nutrients such as nitrogen and phosphorus from wastewater, as well as organic byproducts of anaerobic ammonia oxidation, for its own growth and the removal of ammonia nitrogen (NH4). +Chlorella enhances the degradation capacity of anaerobic ammonia oxidation sludge by reducing pollutants such as nitrogen (N), total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD). In addition, Chlorella improves the settling performance of anaerobic ammonia oxidation sludge through mucus production, particle aggregation, surface charge, bio-adhesion, pH adjustment, oxygen supply, organic matter degradation, and microbial community structure.

[0016] The heterotrophic bacteria attached to the surface and inside the bio-belt, such as nitrifying and denitrifying bacteria, further degrade organic matter and utilize the oxygen produced by Chlorella photosynthesis to oxidize the remaining ammonia nitrogen. Under anaerobic conditions inside the bio-belt, anaerobic ammonia-oxidizing bacteria oxidize the ammonia nitrogen (NH4+) in the wastewater. + -N) and nitrite nitrogen (NO2) - The nitrogen gas (N2) is converted into nitrogen gas (N2), thus achieving a highly efficient denitrification effect.

[0017] This application utilizes oxygen produced by the photosynthesis of Chlorella to replace aeration, thereby minimizing energy consumption and eliminating the need for an external carbon source, thus reducing denitrification costs and carbon emissions. Therefore, it demonstrates significant advantages in treating low C / N urban domestic sewage. This method does not require COD removal pretreatment, improving the overall denitrification effect of the system.

[0018] Optionally, the activated sludge concentration MLVSS (volatile suspended solids in sludge mixed liquor) is 4.0–4.4 g / L, the activated sludge concentration MLSS (mixed liquor suspended solids) is 9.9–10.2 g / L, the Chlorella concentration is 4.3–4.4 g / L, and the mass ratio of Chlorella to activated sludge is 4.89–5.50:1.

[0019] Furthermore, the activated sludge concentration MLVSS is 4.2 g / L, and the addition ratio of Chlorella to activated sludge is 5:1.

[0020] This application helps to form a stable microbial community in the reactor by further limiting the concentration and addition ratio of activated sludge and Chlorella, thereby removing pollutants from wastewater more efficiently.

[0021] Optionally, step S2 includes three stages:

[0022] Step S21: Control the NH4 in the simulated wastewater + -N concentration is 50-100 mg / L, HCO3 - With NH4 + The mass ratio of NO2 to nitrogen is 1.0–1.5, the wastewater recirculation ratio is 100%, and the NO2 content in the effluent is... - / NH4 + When the value is 1, it is considered that partial nitrification has been successfully initiated, and the process proceeds to the next stage;

[0023] Step S22: Maintain the simulated influent from step S21, while simultaneously adding NaNO2 to the simulated wastewater to control the NH4+ content in the simulated wastewater. + -N concentration is 120-150 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0 to 1.5, and NO2 - The ratio of wastewater to NH4+-N is 1 to 1.32, the wastewater return ratio is 100%, and the hydraulic retention time is 18 hours.

[0024] Step S23: Maintain the simulated influent from step S21, while simultaneously adding 120-150 mg / L of glucose to the simulated wastewater to maintain a C / N ratio of 1 in the influent and control the NH4+ content in the simulated wastewater. + -N concentration is 120-140 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0 to 1.5, the wastewater recirculation ratio is 100%, and the hydraulic retention time is 12 hours.

[0025] The purpose of step S21 in this application is to initiate the nitrification process, that is, to produce ammonia nitrogen (NH4+). + Part of the -N) is converted into nitrite (NO2). - ), by controlling NH4 + -N concentration and HCO3- - With NH4 + The -N ratio can optimize the growth environment of nitrifying bacteria (AOB) and promote the nitrification process. Moreover, this stage also plays a role in screening and domesticating microorganisms, enabling microorganisms that can adapt to low C / N environments and specific growth conditions to survive and reproduce, thereby gradually establishing a stable microbial community.

[0026] The purpose of step S22 in this application is to cultivate and acclimatize anaerobic ammonia-oxidizing bacteria (AnAOB) and increase their abundance. By adding NaNO2 to the simulated wastewater, electron acceptors are provided for the anaerobic ammonia oxidation process, accelerating the anaerobic ammonia oxidation reaction. Moreover, by adding NaNO2, the growth environment of anaerobic ammonia-oxidizing bacteria can be optimized, making them more adaptable to the treatment conditions of low C / N wastewater.

[0027] The purpose of step S23 in this application is to achieve simultaneous nitrification and denitrification. By adding glucose to the simulated wastewater, the organic carbon source in the actual wastewater can be simulated, providing a sufficient carbon source for the denitrification process. The C / N ratio in the wastewater can be adjusted to make it more suitable for the simultaneous nitrification and denitrification process.

[0028] Therefore, this application uses a phased cultivation method to help microorganisms gradually adapt to the treatment conditions, thereby improving the removal rate of nitrogen and organic matter.

[0029] Optionally, in step S21, the dissolved oxygen concentration remains constant throughout the reactor along the water flow direction; in steps S22 and S23, the dissolved oxygen concentration decreases along the water flow direction within the reactor.

[0030] Optionally, the reactor is divided into a first reaction section, a second reaction section, and a third reaction section sequentially along the water flow direction.

[0031] In step S21, the dissolved oxygen concentration in each reaction section of the reactor is maintained at 0.5–0.8 mg / L.

[0032] In step S22, the dissolved oxygen concentration in the first reaction section is controlled at 0.75-0.85 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.55-0.65 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.35-0.45 mg / L.

[0033] In step S23, the dissolved oxygen concentration in the first reaction section is controlled at 0.55-0.65 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.35-0.45 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.15-0.25 mg / L.

[0034] Further, in step S21, the dissolved oxygen concentration in each reaction section of the reactor is maintained at 0.8 mg / L; in step S22, the dissolved oxygen concentration in the first reaction section is controlled at 0.8 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.6 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.4 mg / L.

[0035] In step S23, the dissolved oxygen concentration in the first reaction section is controlled at 0.6 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.4 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.2 mg / L.

[0036] In step S21, this application controls the concentration to be the same in each reaction section, which ensures that nitrifying bacteria maintain high activity, thereby accelerating the oxidation process of ammonia nitrogen. Moreover, under appropriate dissolved oxygen concentration, not only can the nitrification rate be optimized, but it also does not inhibit nitrifying bacteria or cause problems such as sludge bulking.

[0037] In step S22 of this application, the dissolved oxygen concentration in the reactor is controlled to show a decreasing trend. The high concentration of dissolved oxygen in the first reaction section can provide the necessary oxygen for the subsequent anaerobic ammonia oxidation process, while avoiding direct inhibition of anaerobic ammonia oxidizing bacteria. The dissolved oxygen concentration in the second reaction section is reduced to further reduce the interference of oxygen on the anaerobic ammonia oxidation process. The dissolved oxygen concentration in the third reaction section is further reduced to be closer to anaerobic conditions and promote the activity of anaerobic ammonia oxidizing bacteria.

[0038] In step S23, this application controls the dissolved oxygen concentration in the reactor to show a decreasing trend. The high dissolved oxygen concentration in the first reaction section can support the nitrification process while avoiding the inhibition of the denitrification process. The dissolved oxygen concentration in the second reaction section is reduced, creating more favorable conditions for the denitrification process. The dissolved oxygen concentration in the third reaction section is further reduced to more closely approximate anoxic conditions, promoting the denitrification process.

[0039] Furthermore, in step S22, the overall dissolved oxygen concentration in the reactor is higher than in step S23. Since step S22 primarily involves anaerobic ammonia oxidation, and anaerobic ammonia oxidizing bacteria are the main microbial species, they are highly sensitive to dissolved oxygen. Therefore, controlling the dissolved oxygen concentration is necessary to optimize their growth environment. Step S23 involves simultaneous digestion and denitrification. Because both nitrifying and denitrifying bacteria communities exist simultaneously, precise control of the dissolved oxygen concentration is required to balance the growth needs of both microorganisms, thereby achieving efficient simultaneous nitrification and denitrification processes.

[0040] Optionally, in step S2, the simulated wastewater undergoes pH adjustment treatment before entering the reactor, and the adjusted pH value is 7.2-8;

[0041] In step S3, the urban domestic wastewater undergoes pH adjustment treatment before entering the reactor, and the adjusted pH value is 7.2-8.

[0042] In step S2, this application adjusts the pH value of the simulated wastewater to a range more suitable for the growth of anaerobic ammonia-oxidizing bacteria.

[0043] Optionally, the simulated wastewater also contains a trace element reserve solution, with 5-5.5 mL of trace element reserve solution added per 15 L of simulated wastewater.

[0044] Optionally, the trace element stock solution contains the following components at the following concentrations: 3515 mg / L FeCl3·6H2O, 359 mg / L MnCl2·4H2O, 75 mg / L CuSO4·5H2O, 300 mg / L ZnSO4·7H2O, and 375 mg / L CoCl2·6H2O.

[0045] This application provides the necessary elements for microbial growth by adding a stock solution containing trace elements to simulated wastewater, thereby enhancing the metabolic activity of microorganisms.

[0046] Optionally, in step S3, a continuous water intake mode is adopted, and the hydraulic residence time is adjusted by controlling the water intake flow rate.

[0047] Optionally, in step S3, the interior of the reactor is illuminated and the temperature inside the reactor is controlled to be maintained within the range of 28-32°C.

[0048] This application promotes the photosynthesis of Chlorella and the growth of microorganisms by providing light to the inside of the reactor and controlling the temperature inside the reactor to maintain it within a suitable range.

[0049] In summary, this application includes at least one of the following beneficial effects:

[0050] 1. This application achieves low-energy and low-discharge treatment of low C / N urban domestic sewage by introducing an anaerobic ammonia oxidation-algae-bacteria symbiosis system into a biological ribbon reactor. The reactor uses biological ribbons as the loading material to simulate aquatic plants; these ribbons have a rich porous structure, providing approximately 180-200 m² of space for the growth and reproduction of algae and other microorganisms. 2 The large surface area for biological attachment provides numerous attachment sites and favorable growth conditions, thereby improving the treatment effect of wastewater.

[0051] 2. This application uses Chlorella as a photosynthetic bacterium. Chlorella not only provides oxygen to heterotrophic bacteria using the oxygen produced by photosynthesis, but also simultaneously absorbs nutrients such as nitrogen and phosphorus from wastewater, as well as organic products from anaerobic ammonia oxidation, for its own growth and to remove ammonia nitrogen (NH4). + Chlorella enhances the degradation capacity of anaerobic ammonia oxidation sludge by reducing pollutants such as nitrogen (N), total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD). In addition, Chlorella improves the settling performance of anaerobic ammonia oxidation sludge through mucus production, particle aggregation, surface charge, bio-adhesion, pH adjustment, oxygen supply, organic matter degradation, and microbial community structure.

[0052] 3. This application utilizes heterotrophic bacteria, such as nitrifying and denitrifying bacteria, attached to the surface and interior of the bio-belt to further degrade organic matter, and uses oxygen produced by the photosynthesis of Chlorella to oxidize the remaining ammonia nitrogen; under anaerobic conditions inside the bio-belt, anaerobic ammonia-oxidizing bacteria oxidize the ammonia nitrogen (NH4+) in the wastewater. + -N) and nitrite nitrogen (NO2) - The nitrogen gas (N2) is converted into nitrogen gas (N2), thus achieving a highly efficient denitrification effect.

[0053] 4. This application utilizes the oxygen produced by the photosynthesis of Chlorella to replace aeration, which minimizes energy consumption and eliminates the need for an external carbon source, thus reducing denitrification costs and carbon emissions. Therefore, it demonstrates significant advantages in treating low C / N urban domestic sewage. This method does not require COD removal pretreatment, thereby improving the overall denitrification effect of the system. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the connection relationship of an algae-bacteria symbiotic denitrification device based on anaerobic ammonia oxidation according to an embodiment of this application;

[0055] Figure 2 yes Figure 1 The diagram shows a process flow diagram of an algae-bacteria symbiotic denitrification device based on anaerobic ammonia oxidation.

[0056] Figure 3 yes Figure 2 The image shows a physical diagram of the reactor for an algae-bacteria symbiotic denitrification device based on anaerobic ammonia oxidation.

[0057] Figure 4 yes Figure 3 A photograph of the biological ribbons in the reactor shown.

[0058] Figure 5 This is a scanning electron microscope image of activated sludge samples taken after the operation of step S3 has stabilized.

[0059] In the diagram: 1. Water distribution tank; 2. Equalization tank; 3. Reactor; 4. LED energy-saving light strip; 5. Dissolved oxygen detector; 6. Sedimentation tank; 7. Biological ribbon; 8. Return pump; 9. Inlet pump. Detailed Implementation

[0060] In response to the technical problems raised in the background section, the applicant discovered that the oxygen produced by algae photosynthesis can promote nitrification, that is, the conversion of ammonia nitrogen into NO2-, thereby providing a stable and sufficient supply of NO2 for anaerobic ammonia-oxidizing bacteria. - Source. However, the presence of oxygen is not conducive to the denitrification reaction. Therefore, the applicant uses biological ribbons as the loading material, which have a rich porous structure that can provide anaerobic conditions for the denitrification reaction. This does not affect the conversion of ammonia nitrogen to NO2- / NO3-, nor does it affect the conversion of NO2- / NO3- to nitrogen gas, thus achieving efficient denitrification of wastewater.

[0061] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0062] First, a detailed description of the reaction apparatus used in this application is provided. See [link to application]. Figure 1-4The reaction device includes a reactor (3), which is made of plexiglass, is 40cm long, 15cm wide and high, has a reactor volume of 9L and an effective volume of 7.8L, and has a sealable top cover to facilitate the collection of water samples in different reaction sections and the replacement of packing material.

[0063] The reactor (3) is equipped with eight biological ribbons, which divide the interior of the reactor into nine reaction spaces. Each three reaction spaces are designated as a reaction section, and the sections from the inlet to the outlet are designated as the first reaction section, the second reaction section, and the third reaction section. The biological ribbons are made of fiber strips that are 15cm long and 13cm wide. They are used to simulate aquatic plants in the water and provide attachment points for microorganisms. Their advantages are that algae and microorganisms attach more easily, form biofilm quickly, and are inexpensive, resulting in excellent cost performance.

[0064] The outer layer of the reactor is equipped with heating, insulation and lighting facilities (to simulate sunlight) to ensure that algae and microorganisms grow under suitable conditions. At the same time, the outer layer of the reactor is wrapped with a heating plate to regulate the temperature inside the reactor and keep it at 30±2℃. Since light has a certain inhibitory effect on anaerobic ammonia oxidizing bacteria, the insulation layer can also play a role in shading light.

[0065] The reaction apparatus also includes an equalization tank located at the front end of the reactor and a sedimentation tank located at the rear end of the reactor. The equalization tank is connected to the reactor inlet via an inlet pump, and the sedimentation tank is connected to the equalization tank via a reflux pump.

[0066] The activated sludge used in the following examples was taken from the secondary sedimentation tank of Xiamen Xinglin Wastewater Treatment Plant, China, with an MLVSS (mixed liquor volatile suspended solids) of 4.2 g / L; the Chlorella used in the following examples was purchased from Hainan Yuanquan Biotechnology Co., Ltd.; the bio-ribbons used in the following examples were made of polymer fibers with a suitable internal pore structure and a high surface area for bio-attachment, and were purchased from Xiangtan Yunfan New Materials Co., Ltd.

[0067] The simulated wastewater used in the following examples includes conventional nutrients in addition to water. These conventional nutrients include carbon sources (glucose, sodium bicarbonate), nitrogen sources (ammonium chloride), etc., and the corresponding pollutants are chemical oxygen demand (COD) and nitrogen (NH4+). + -N, TN, etc. Simultaneously, to provide a favorable growth environment for microorganisms, a quantitative trace element solution needs to be added to the simulated wastewater, with 5.125 mL of trace element stock solution added per 15 L of simulated wastewater. The trace element stock solution contains the following components at the following concentrations: 3515 mg / L FeCl3·6H2O, 359 mg / L MnCl2·4H2O, 75 mg / L CuSO4·5H2O, 300 mg / L ZnSO4·7H2O, and 375 mg / L CoCl2·6H2O.

[0068] One embodiment of this application provides a method for treating urban domestic wastewater based on an anaerobic ammonia oxidation reaction coupled with an algae-bacterial symbiosis process, which includes the following steps:

[0069] Step S1: Inoculate the activated sludge into the reactor and simultaneously add Chlorella to the reactor. The mass ratio of Chlorella to activated sludge is 5:1. The effective volume of the reactor is 7.8L, the amount of activated sludge added is 7.8L, filling the effective volume of the reactor. The activated sludge concentration MLVSS is 4.2g / L, and the Chlorella concentration is 4.3-4.4g / L.

[0070] Step S2: The simulated wastewater is passed through an equalization tank to adjust the pH to 7.2-8 before being introduced into the reactor for microbial cultivation. This process is divided into three stages:

[0071] Step S21, Partial Nitrification Start-up and Acclimation Stage: The simulated wastewater uses NH4Cl as the nitrogen source and NaHCO3 as the carbon source, controlling the NH4 content in the simulated wastewater. + -N concentration is 50-100 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0–1.5. Other components include those providing alkalinity suitable for microbial growth: KH₂PO₄ 2.7 mg / L, MgSO₄·7H₂O 30 mg / L, and CaCl₂ 13.6 mg / L. During this stage, the dissolved oxygen concentration in the reactor is maintained at 0.5–0.8 mg / L, the hydraulic retention time is 24 h, and the wastewater recirculation ratio is 100%. When NO₂ in the effluent... - / NH4 + When the value is approximately 1, it is considered that partial nitrification has been successfully initiated, and the process proceeds to the next stage.

[0072] Step S22, Acclimation stage of anaerobic ammonia oxidizing bacteria: Maintain the simulated influent from step S21, control the NH4+-N concentration in the simulated wastewater to be 120-150 mg / L, and the mass ratio of HCO3- to NH4+-N to be 1.0-1.5. At the same time, add NaNO2 to the simulated wastewater to provide NO2-, so that the NO2- to NH4+-N ratio is 1-1.32. Other components in the simulated wastewater are the same as in the previous partial nitrification start-up acclimation stage. In this stage, control the dissolved oxygen concentration in the reactor to follow a gradient decreasing trend, with the first reaction section controlled at 0.8 mg / L, the second reaction section at 0.6 mg / L, and the third reaction section at 0.4 mg / L. The hydraulic retention time is 18 h, and the wastewater recirculation ratio is 100%.

[0073] Step S23, Simultaneous nitrification and denitrification stage: Maintain the simulated influent from step S21 and control the NH4 in the simulated wastewater. + -N concentration is 120-140 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0–1.5. Nitrite in step S22 is eliminated, and glucose is added to the simulated wastewater to provide COD, which is 120–150 mg / L. The C / N ratio of the influent is maintained at 1. Other components in the simulated wastewater are the same as in the previous partial nitrification start-up and acclimatization stage. In this stage, the dissolved oxygen concentration in the reactor is controlled to decrease gradually, with the first reaction stage controlled at 0.6 mg / L, the second reaction stage at 0.4 mg / L, and the third reaction stage at 0.2 mg / L. The hydraulic retention time is 12 h, and the wastewater recirculation ratio is 100%. In this stage, due to the presence of COD, the growth rate of denitrifying bacteria is higher than that of nitrifying bacteria and anaerobic ammonia oxidizing bacteria, so no additional inoculation of denitrifying bacteria is required in the reactor.

[0074] Step S3: The municipal wastewater is treated using a reactor. The wastewater to be treated enters the equalization tank via a distribution channel and mixes with some returned wastewater. The pH is adjusted to 7.2-8, and then the wastewater enters the reactor. Eight biological conduits within the reactor divide the interior into nine reaction sections. As water flows in, water from one reaction section overflows into the next, eliminating the need for an additional peristaltic pump. Finally, the treated wastewater enters a sedimentation tank, where part is returned to the equalization tank, and part is discharged after sedimentation. A sludge discharge port is located at the bottom of the sedimentation tank, and some sludge is returned to the reactor to replenish the lost microbial concentration.

[0075] In step S3 above, the hydraulic retention time of each reaction section can be controlled by adjusting the influent flow rate. Specifically, the influent flow rate is controlled at 10.83 mL / min, and the hydraulic retention time can be controlled at 12 h. Furthermore, the dissolved oxygen concentration in the reactor can be controlled by adjusting the amount of Chlorella inoculated and the lighting conditions to regulate the growth location of the Chlorella. In step S3, the dissolved oxygen concentration in each reaction section of the reactor is consistent with that in step S23, i.e., 0.6 mg / L for the first reaction section, 0.4 mg / L for the second reaction section, and 0.2 mg / L for the third reaction section.

[0076] In step S3 above, the microorganisms in the reactor are mainly divided into three categories: Chlorella, anaerobic ammonia-oxidizing bacteria, and other bacteria (nitrifying bacteria, denitrifying bacteria, etc.). Sufficient light is provided in the reactor to promote the photosynthesis of Chlorella. Chlorella uses sunlight, water, and carbon dioxide to produce organic matter and release oxygen through photosynthesis. Other bacteria can utilize the products produced by Chlorella, while anaerobic ammonia-oxidizing bacteria can utilize the metabolic products of other microorganisms for metabolic activities, such as ammonia nitrogen, nitrite nitrogen, and carbon dioxide. Simultaneously, anaerobic ammonia oxidation granular sludge can significantly improve the settling performance of the algae-bacteria symbiotic system, change the community structure of activated sludge, and increase microbial abundance. Furthermore, the suspended growth of Chlorella has a protective effect against photodamage to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).

[0077] After the operation in step S3 stabilizes, water samples are taken periodically for water quality testing, measuring the nitrogen concentration and COD in the water samples. Cr The analytical methods for nitrogen content in water samples are as follows: COD Cr The following standards were used for determination: GB / T 11914-1989 "Determination of Chemical Oxygen Demand in Water - Dichromate Method"; ammonia nitrogen was determined using HJ 535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method"; nitrate nitrogen was determined using HJ / T 346-2007 "Determination of Nitrate Nitrogen in Water - Ultraviolet Spectrophotometric Method"; and nitrite nitrogen was determined using GB / T 7493-1987 "Determination of Nitrite Nitrogen in Water - Spectrophotometric Method". Total nitrogen was calculated as the sum of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen. The results of the water samples from three days are shown in Table 1.

[0078] Table 1. Water sample test results

[0079]

[0080] As can be seen from the results in Table 1, the urban domestic wastewater treatment method of this application can remove COD from wastewater. Cr The content decreased from 124.2-172.8 mg / L to 16.27-21.84 mg / L, with a removal rate of at least 86.5%. The total nitrogen content in the wastewater decreased from 141.6-153.6 mg / L to 22.2-27.47 mg / L, with a removal rate of at least 80.6%.

[0081] Figure 5 These are scanning electron microscope (SEM) images of activated sludge samples taken after the process in step S3 had stabilized. Figure 5 It can be seen that both Chlorella and activated sludge have a large number of extracellular polymers (EPS) on their surfaces. Chlorella has a relatively smooth and plump morphology, and no bacteria are attached to its surface. The surface of anaerobic ammonia oxidation granular sludge has a multi-hollow structure, which can provide a large number of adsorption sites and an anaerobic environment.

[0082] Furthermore, metagenomic sequencing analysis was conducted to analyze the microbial characteristics and metabolic functions within the system at different stages, with the following results. In the initial sludge, the relative abundance, from highest to lowest, was Proteobacteria, Actinobacteria, Green Curvularia, Acidobacteria, Bacteroidetes, and Planktonicomycetes, with relative abundances of 32.48%, 18.17%, 13.28%, 9.02%, 8.61%, and 5.6%, respectively. In the final stage of process operation (i.e., the end of step S23), the top five phyla in terms of relative abundance included Planktonicomycetes, Proteobacteria, Green Curvularia, Bacteroidetes, and Actinobacteria, accounting for 33%, 12.3%, 10.1%, 9.8%, and 4.9%, respectively. *Candidatus Brocadia*, a typical genus of anaerobic ammonia oxidizing bacteria, had a relative abundance of 29.85%, making it a major contributor to nitrogen removal in the anaerobic ammonia oxidation reaction.

[0083] These results effectively demonstrate that co-culturing Chlorella with activated sludge significantly alters the bacterial community structure, forming a specific community structure dominated by functional microorganisms, increasing the abundance of microbial species, and effectively inhibiting sludge bulking.

[0084] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for treating urban domestic wastewater based on an anaerobic ammonia oxidation reaction coupled with an algal-bacterial symbiotic process, characterized in that, The treatment method is carried out in a reactor equipped with multiple biological ribbons made of polymer fibers. The multiple biological ribbons are arranged vertically along the water flow direction to form a soft barrier within the reactor. The processing method includes the following steps: Step S1: Inoculate the activated sludge into the reactor, and simultaneously add Chlorella to the reactor; Step S2: Introduce simulated wastewater containing carbon and nitrogen sources into the reactor to cultivate a microbial system containing anaerobic ammonia-oxidizing bacteria, wherein the simulated wastewater uses NH4Cl as the nitrogen source, NaHCO3 as the inorganic carbon source, and glucose as the organic carbon source. Step S3: Treat urban domestic wastewater using the reactor; Step S2 includes three stages: Step S21: Control the NH4 in the simulated wastewater + -N concentration is 50~100 mg / L, HCO3 - With NH4 + The mass ratio of NO2 to nitrogen is 1.0~1.5, the wastewater recirculation ratio is 100%, and the NO2 in the effluent... - / NH4 + When the value is 1, it is considered that partial nitrification has been successfully initiated, and the process proceeds to the next stage; Step S22: Maintain the simulated influent from step S21, while simultaneously adding NaNO2 to the simulated wastewater to control the NH4+ content in the simulated wastewater. + -N concentration is 120-150 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0~1.5, and NO2 - With NH4 + The -N ratio is 1~1.32, the wastewater return ratio is 100%, and the hydraulic retention time is 18h; Step S23: Maintain the simulated influent from step S21, while simultaneously adding 120-150 mg / L of glucose to the simulated wastewater to maintain a C / N ratio of 1 in the influent and control the NH4+ content in the simulated wastewater. + -N concentration is 120-140 mg / L, HCO3 - With NH4 + The mass ratio of -N is 1.0~1.5, the wastewater recirculation ratio is 100%, and the hydraulic retention time is 12h; In step S21, the dissolved oxygen concentration remains constant throughout the reactor along the water flow direction; in steps S22 and S23, the dissolved oxygen concentration decreases along the water flow direction within the reactor.

2. The method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algal-bacterial symbiosis as described in claim 1, characterized in that, The activated sludge concentration MLVSS is 4.0~4.4 g / L, the Chlorella concentration is 4.3-4.4 g / L, and the mass ratio of Chlorella to activated sludge is 4.89-5.50:

1.

3. The urban domestic wastewater treatment method based on anaerobic ammonia oxidation coupled with algae-bacteria symbiosis as described in claim 1, characterized in that, The reactor is divided into a first reaction section, a second reaction section, and a third reaction section in sequence along the water flow direction. In step S21, the dissolved oxygen concentration in each reaction section of the reactor is maintained at 0.5~0.8 mg / L. In step S22, the dissolved oxygen concentration in the first reaction section is controlled at 0.75-0.85 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.55-0.65 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.35-0.45 mg / L. In step S23, the dissolved oxygen concentration in the first reaction section is controlled at 0.55-0.65 mg / L, the dissolved oxygen concentration in the second reaction section is controlled at 0.35-0.45 mg / L, and the dissolved oxygen concentration in the third reaction section is controlled at 0.15-0.25 mg / L.

4. The method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algal-bacterial symbiosis as described in claim 1, characterized in that, In step S2, the simulated wastewater undergoes pH adjustment treatment before entering the reactor, and the adjusted pH value is 7.2-8. In step S3, the urban domestic wastewater undergoes pH adjustment treatment before entering the reactor, and the adjusted pH value is 7.2-8.

5. The method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algal-bacterial symbiosis as described in claim 1, characterized in that, The simulated wastewater also contains a trace element reserve solution, with 5-5.5 mL of trace element reserve solution added per 15 L of simulated wastewater.

6. The method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algal-bacterial symbiosis as described in claim 5, characterized in that, The trace element stock solution contains the following components at the following concentrations: 3515 mg / L FeCl3·6H2O, 359 mg / L MnCl2·4H2O, 75 mg / L CuSO4·5H2O, 300 mg / L ZnSO4·7H2O, and 375 mg / L CoCl2·6H2O.

7. The method for treating urban domestic wastewater based on anaerobic ammonia oxidation coupled with algal-bacterial symbiosis as described in claim 1, characterized in that, In step S3, a continuous water intake mode is adopted, and the hydraulic residence time is adjusted by controlling the water intake flow rate.

8. The method for treating urban domestic wastewater based on an anaerobic ammonia oxidation reaction coupled with an algal-bacterial symbiotic process according to any one of claims 1-7, characterized in that, In step S3, light is provided to the inside of the reactor and the temperature inside the reactor is controlled to be maintained at 28-32°C.

Images