Method for rapidly increasing the load of snad process by modified biochar

Abstract

The application discloses a method for rapidly increasing the SNAD process load by using modified biochar, and belongs to the technical field of resources and environment; the method comprises the following steps: pretreating biochar by using dilute sulfuric acid; configuring a pyrrole solution and adding a persulfate salt as an antioxidant to protect the pyrrole from being oxidized; adding the pyrrole solution into the pretreated biochar solution, and freeze-drying to obtain polypyrrole modified biochar; adding the polypyrrole modified biochar into a successfully started SNAD system, stopping water feeding under the original aeration condition, and forming a bacteria-polymer-biochar complex; and taking HRT, TN load and upflow velocity as core process parameters to rapidly increase the nitrogen load of the system; the application realizes rapid load increase after the SNAD process is started, reduces the risk of free ammonia inhibition, and improves the load increase rate.

Description

Technical Field

[0001] This invention belongs to the field of resources and environmental technology, and specifically relates to a method for rapidly increasing the load of the SNAD process using modified biochar. Background Technology

[0002] In recent years, SNAD (Simultaneous Partial Nitrification, Anammox, and Dennitrification) technology has gained widespread attention and some engineering applications in the treatment of wastewater with high ammonia nitrogen and low C / N ratio due to its ability to simultaneously achieve nitrification, anaerobic ammonium oxidation, and denitrification within a single reactor. This reduces power consumption for aeration while significantly lowering the amount of external carbon source required for denitrification. SNAD technology typically treats high ammonia nitrogen wastewater with influent total nitrogen concentrations ranging from 500 to 3000 mg / L. During the initial reactor startup phase, when the total nitrogen concentration is low, the system's load ramp-up cycle is relatively short. However, as the total nitrogen concentration gradually increases to above 800-1000 mg / L, the system becomes highly susceptible to changes in process conditions such as dissolved oxygen (DO) and pH, which can lead to an increase or decrease in the activity of certain functional bacterial communities. This imbalance in the abundance of functional bacteria can affect load ramp-up and even cause system collapse. Researchers and engineers often use the MBBR (Medium-Magnetic Batch Reactor) reaction method to allow anaerobic ammonia-oxidizing bacteria, which are susceptible to shock loads and loss, to grow on a carrier packing material. This increases the microbial biomass within the reaction system and ensures the abundance and stability of the core microbial community in the SNAD (Syndrome-Oriented Acid-Degradation) reaction. MBBR packing material is generally made of PE (polyethylene). Besides providing a carrier for microorganisms, it has weak biocompatibility and lacks bioactivity-promoting functions when unmodified, making it difficult to accelerate the increase of SNAD process load.

[0003] Biochar generally refers to porous carbon products formed by processing plant waste through hydrothermal conversion or pyrolysis carbonization. Due to its large specific surface area, abundant active functional groups on the surface, and good adsorption properties, it has received extensive research and attention in the field of wastewater treatment. Summary of the Invention

[0004] The purpose of this invention is to provide a polypyrrole-modified biochar that serves as both a biological carrier and a means of promoting electron transfer rates in SNAD microbial communities, thereby helping to rapidly increase the SNAD process load and improve start-up efficiency.

[0005] To achieve the above objectives, the technical solution of this application is: a method for rapidly increasing the load of the SNAD process using modified biochar, comprising:

[0006] S1. The modified material is pyrrole with good cell compatibility and conductivity. First, the biochar is pretreated with dilute sulfuric acid with a mass concentration of 5%-10%. The amount of biochar added is controlled below 10%. The pretreatment temperature is 45-60℃ and the time is 10-15min.

[0007] Prepare a 0.3-1 mol / L pyrrole solution with a pH range of 1-3, and add 0.5-3 mol / L persulfate as an antioxidant to protect the pyrrole from oxidation;

[0008] Pyrrole solution was added to the pretreated biochar solution at a rate of 0.1-0.5 mL / min. The reaction system was heated and protected with nitrogen gas. The reaction was carried out continuously for more than 12 hours. Polypyrrole modified biochar was obtained by freeze drying.

[0009] S2. Add polypyrrole-modified biochar to the successfully started SNAD system at 0.5%-2% of the sludge concentration, and stop the influent for 12-24 hours while maintaining the original aeration conditions to form a complex of bacterial flocs and modified biochar.

[0010] S3. Start the internal circulation of the SNAD system, control the upward flow velocity to 3-5 m / h, with an HRT of 20-24 h and a TN load of 0.2-0.3 kg N / (m³). 3 •d) Under conditions of continuous culture of bacterial flocs and modified biochar composites, if the average particle size of the system sludge is still less than 200 μm within 20 days, first maintain the TN load unchanged and shorten the retention time to 12-16 h. If the average particle size requirement still cannot be met, maintain the HRT unchanged and increase the total nitrogen load to 0.3-0.5 kg N / (m³). 3 ·d), until anaerobic SNAD granular sludge with an average particle size greater than 200 μm is formed in the system;

[0011] S4. After the initial granular sludge is formed, ensure that the SAA (specific anaerobic ammonium oxidation activity) is above 0.5 kg N / (kg VSS·d), and then adjust according to 0.5-1.0 kg N / (m³). 3 •d) The system load is rapidly increased in a cycle, and the upward flow velocity is increased to 5-8 m / h to control the sludge particle size to remain below 1 mm.

[0012] Furthermore, the reactor of the SNAD system has a height-to-diameter ratio of 6-8:1, is equipped with an aeration disc at the bottom, and has an average pore size of 100-150 μm for the aeration membrane.

[0013] Furthermore, the core of the anaerobic SNAD granular sludge is polypyrrole-modified biochar, the inner layer of the granular sludge is a mixture of anaerobic ammonia-oxidizing bacteria and denitrifying bacteria, and the outer layer is nitrite-oxidizing bacteria.

[0014] This invention utilizes dilute sulfuric acid to pretreat biochar, followed by reaction with pyrrole solution and freeze-drying to obtain polypyrrole-modified biochar material. The modified material is then added to a successfully started SNAD system, and parameters such as HRT, TN load, and upflow rate are limited to rapidly increase the system's nitrogen load.

[0015] Compared with the prior art, the present invention has the following advantages: a method for rapidly increasing the load of the SNAD process using polypyrrole-modified biochar, which can significantly increase the load increase rate of the SNAD process, reduce the cost of adding load materials, and improve the system stability of the load increase process. Specific implementation methods

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the application; that is, the described embodiments are only a portion of the embodiments of this application, and not all of them. The experimental methods used in these embodiments are all conventional methods, and the experimental equipment, materials, reagents, etc., used are all commercially available.

[0017] Example 1

[0018] Biochar was added to a 5% dilute sulfuric acid solution at a mass ratio of 5%. The pretreatment temperature was controlled at 50℃. After reacting for 10 min, a mixed solution with pH 1, persulfate concentration of 2 mol / L, and pyrrole concentration of 0.5 mol / L was added at a rate of 0.2 mL / min. The mixture was heated and protected with nitrogen gas. The reaction was continued for 16 h until the pyrrole reaction was complete. The polypyrrole-modified biochar material was obtained by freeze drying.

[0019] Polypyrrole-modified biochar was added to the successfully started-up SNAD reactor at a sludge mass concentration of 1%. The effective volume of the reactor was 0.15 m³. 3 The water surface height-to-diameter ratio is approximately 6:1, the average pore size of the aeration membrane is 100μm, and after 12 hours of simmering aeration, the load increase stage begins. The upward flow velocity is controlled at 3.5m / h, the HRT (heat recovery time) at 20 hours, and the TN (total nitrogen) load at 0.2 kg N / (m³). 3 •d) Begin continuous cultivation. Around day 15, when the average sludge particle size in the system reaches 220 μm, increase the upflow velocity to 6 m / h, control the sludge particle size to below 1 mm, and maintain SAA at 0.5 kg N / (kg VSS·d). 3 •d) Periodically increase load rapidly.

[0020] The specific details of the load increase process are shown in Table 1. The difference in Comparative Example 1 is that MBBR packing was used instead of modified biochar; the difference in Comparative Example 2 is that no packing was added.

[0021]

[0022]

[0023] aRaw material price basis: A total of about 12g of modified biochar was added, of which finished biochar cost about 3 yuan / kg, pyrrole about 100 yuan / kg, and potassium persulfate about 20 yuan / kg.

[0024] Example 2

[0025] Biochar was pretreated with 8% (w / w) dilute sulfuric acid at a temperature of 60°C for 15 min. A 1 mol / L pyrrole solution was prepared at pH 2.5, and 2.5 mol / L persulfate was added as an antioxidant to protect the pyrrole from oxidation. The pyrrole solution was added to the pretreated biochar solution at a rate of 0.4 mL / min. The reaction system was heated and protected with nitrogen atmosphere for 24 h. The resulting polypyrrole-modified biochar material was then freeze-dried.

[0026] Polypyrrole-modified biochar was added to the successfully started-up SNAD reactor, which had an effective volume of 1.3 m³. 3 The effective height-to-diameter ratio is 6.5:1, the average pore size of the aeration membrane is 150μm, the concentration of modified biochar added is 1.5% of the sludge mass concentration, and after 24 hours of simmering, it enters the load increase stage.

[0027] The upward flow velocity is controlled at 4.5 m / h, the HRT is 24 h, and the TN load is 0.3 kg N / (m³). 3 Under continuous cultivation conditions (d), after 20 days, the average particle size of the system sludge was approximately 160 μm, which did not meet the requirements for increasing the load. Therefore, the retention time was shortened to 16 hours, and after 6 days of reaction, the average particle size reached approximately 200 μm, at which point the load could be rapidly increased. During the increase process, ensuring that SAA levels were above 0.5 kg N / (kgVSS·d), the load was increased to 0.8 kg N / (m³). 3 •d) The system load is rapidly increased in a cycle, and the upward flow velocity is increased to 8 m / h to control the sludge particle size to remain below 1 mm.

[0028] The specific details of the load increase process are shown in Table 2. The difference in Comparative Example 3 is that MBBR packing was used instead of modified biochar.

[0029]

[0030] a Calculation basis: Approximately 120g of modified biochar was added.

[0031] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made to the invention. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for rapidly increasing the load of SNAD process using modified biochar, characterized in that, include: S1. Pretreatment of biochar with dilute sulfuric acid, with the amount of biochar added controlled below 10%; Prepare a 0.3-1 mol / L pyrrole solution and add persulfate as an antioxidant to protect the pyrrole from oxidation; add the pyrrole solution to the pretreated biochar solution, react continuously for more than 12 h, and freeze-dry to obtain polypyrrole modified biochar; S2. Add polypyrrole-modified biochar to the successfully started SNAD system, and stop the water intake while maintaining the original aeration conditions to form a complex of bacterial flocs and modified biochar. S3. Start the internal circulation of the SNAD system, control the upward flow velocity to 3-5 m / h, with an HRT of 20-24 h and a TN load of 0.2-0.3 kg N / (m³). 3 •d) Under conditions of continuous culture of bacterial flocs and modified biochar composites, if the average particle size of the system sludge is still less than 200 μm within 20 days, first maintain the TN load unchanged and shorten the retention time to 12-16 h. If the average particle size requirement still cannot be met, maintain the HRT unchanged and increase the total nitrogen load to 0.3-0.5 kg N / (m³). 3 ·d), until anaerobic SNAD granular sludge with an average particle size greater than 200 μm is formed in the system; S4. After the initial granular sludge is formed, ensure that the SAA is above 0.5 kg N / (kg VSS·d), and then adjust according to 0.5-1.0 kg N / (m³). 3 •d) The system load is rapidly increased in a cycle, and the upward flow velocity is increased to 5-8 m / h to control the sludge particle size to remain below 1 mm; The core of the anaerobic SNAD granular sludge is polypyrrole-modified biochar, the inner layer of the granular sludge is a mixture of anaerobic ammonia-oxidizing bacteria and denitrifying bacteria, and the outer layer is nitrite-oxidizing bacteria.

2. The method for rapidly increasing the load of the SNAD process using modified biochar according to claim 1, characterized in that, In step S1, biochar is pretreated with dilute sulfuric acid with a mass concentration of 5%-10%. The amount of biochar added is controlled below 10%, and the pretreatment temperature is 45-60℃ for 10-15 min.

3. The method for rapidly increasing the load of the SNAD process using modified biochar according to claim 1, characterized in that, In step S1, a 0.3-1 mol / L pyrrole solution is prepared with the pH range controlled between 1 and 3, and 0.5-3 mol / L persulfate is added as an antioxidant to protect the pyrrole from oxidation.

4. The method for rapidly increasing the load of the SNAD process using modified biochar according to claim 1, characterized in that, In step S1, pyrrole solution is added to the pretreated biochar solution at a rate of 0.1-0.5 mL / min. The reaction system is heated and protected with nitrogen gas. The reaction is carried out continuously for more than 12 h. Polypyrrole modified biochar is obtained by freeze drying.

5. The method for rapidly increasing the load of the SNAD process using modified biochar according to claim 1, characterized in that, In step S2, polypyrrole-modified biochar is added to the successfully started SNAD system at a concentration of 0.5%-2% of the sludge concentration. The influent is stopped for 12-24 hours while maintaining the original aeration conditions to form a complex of bacterial flocs and modified biochar.

6. The method for rapidly increasing the load of the SNAD process using modified biochar according to claim 1, characterized in that, The SNAD system has a reactor height-to-diameter ratio of 6-8:1, is equipped with an aeration disc at the bottom, and has an average pore size of 100-150 μm for the aeration membrane.

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