Method for inhibiting foam generation in anaerobic digestion process of organic wastewater

Abstract

The invention provides a method for inhibiting foam generation in the anaerobic digestion process of organic wastewater, which comprises the step of adding ascorbic acid into an anaerobic digestion system, and the inhibition of surface foam generation in the anaerobic digestion process of sludge is realized by using the anti-oxidation characteristic of the ascorbic acid. The method can be applied to white spirit wastewater treatment. When the white spirit wastewater is treated, the activity of methane-producing bacteria can be improved by adding ascorbic acid, so that the methane yield in the anaerobic digestion process is increased; by adding ascorbic acid, oxidative stress can be reduced, microbial metabolism can be adjusted, surface tension can be reduced, formation and expansion of foam can be effectively inhibited, and the stability of the anaerobic digestion process can be kept.

Description

Technical Field

[0001] The invention belongs to the technical field of wine wastewater treatment and relates to a method for inhibiting foam generation during anaerobic digestion of organic wastewater. Background Art

[0002] Anaerobic digestion, a key process for treating high-concentration organic wastewater, primarily involves the decomposition of organic matter in the water by anaerobic microorganisms, converting it into gases such as methane and carbon dioxide. UASB, EGSB, and CSTR are common reactor types used in anaerobic wastewater digestion projects. In actual anaerobic digestion projects, the continuous production of methane strips the wastewater of surface-active substances, leading to persistent foaming on the wastewater surface. This not only affects the stability of the digestion process, but the overflowing foam also significantly impacts the wastewater treatment plant's operations.

[0003] Currently, researchers have proposed a variety of foam control technologies to address the foaming problem during the anaerobic digestion of high-concentration organic wastewater, such as the use of chemical additives and physical methods. However, these technologies generally have some limitations: 1. Negative effects of chemical additives: Some chemicals (such as surfactants and defoamers) can effectively suppress foaming, but they may be toxic to the microbial population in the digestion process, interfere with the anaerobic digestion reaction, reduce the treatment effect, and even affect the final sludge stabilization.

[0004] 2. High energy consumption and high cost: Although certain physical methods (such as air blowing and mechanical stirring) can slow down foam generation, they often lead to higher energy consumption, increase operating costs, and may require frequent maintenance.

[0005] 3. Inconvenient operation: Existing control methods usually require intervention after the foam is generated, which results in a long operation cycle and difficult to control process. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for inhibiting the generation of foam during the anaerobic digestion of organic wastewater in order to achieve the effect of inhibiting the generation of foam during the anaerobic digestion of organic wastewater in order to address the defects of the prior art.

[0007] A first aspect of the present invention provides a method for inhibiting foam generation during anaerobic digestion of organic wastewater, comprising the step of adding ascorbic acid to the anaerobic digestion system, and utilizing the antioxidant properties of ascorbic acid to inhibit surface foam generation during anaerobic digestion of sludge.

[0008] A second aspect of the present invention provides a wastewater treatment test method based on ascorbic acid, comprising the following steps: Treatment object and system construction: Select high-concentration organic wastewater as the treatment object, configure the anaerobic reactor, and set the initial sludge concentration, anaerobic digestion temperature, working water level depth and treatment load; System startup: Start the anaerobic reactor and run it until the effluent COD concentration becomes stable. Record the foam height on the reactor surface at this time. Ascorbic acid dosing and grouping experiments: Set up at least four experimental groups, add different concentrations of ascorbic acid to each reactor, and set up a control group without ascorbic acid. Run for a certain period of time, and observe and record the changes in foam height on the surface of each reactor. Monitoring and effect evaluation: During the treatment process, the intensity of reactive oxygen species (ROS) in microbial cells, the content of viscous polysaccharides in sludge extracellular polymers (EPS), and the methane gas generation rate parameters during anaerobic digestion are monitored; based on the monitoring results, the effect of ascorbic acid on inhibiting foam formation and maintaining the stability of the anaerobic digestion system is evaluated.

[0009] Preferably, the initial sludge concentration is set in the range of 15000-25000 mg / L, the anaerobic digestion temperature is set at 35-39°C, the working water level is set at 0.6-0.8m, and the treatment load is set at 3-5kgCOD / m³.

[0010] Preferably, in the system startup step, the anaerobic reactor is operated until the effluent COD concentration fluctuation range does not exceed ±500 mg / L, that is, the effluent COD concentration tends to be stable.

[0011] Preferably, in the ascorbic acid addition and grouping experimental steps, the ascorbic acid concentration gradient added to the experimental group at least includes 0 mg / L, 10 mg / L, 50 mg / L, and 100 mg / L.

[0012] Preferably, the ascorbic acid addition and grouping experimental steps are run for 30-60 days, and the foam height on the surface of each reactor is observed and recorded every day.

[0013] Preferably, in the monitoring and effect evaluation step, a fluorescent probe method is used to monitor the intensity of reactive oxygen species (ROS) in microbial cells.

[0014] Preferably, in the monitoring and effect evaluation step, the inhibitory effect of ascorbic acid on foam generation is evaluated by measuring the viscous polysaccharide content of sludge extracellular polymeric substances (EPS); and the stability of the anaerobic digestion system is evaluated by the methane gas generation rate parameter.

[0015] Preferably, the method further comprises adjusting the concentration of ascorbic acid added according to the monitoring and effect evaluation results.

[0016] The third aspect of the present invention provides an application of the method for inhibiting foam generation during anaerobic digestion of organic wastewater in the treatment of liquor wastewater, comprising the step of adding ascorbic acid to the anaerobic digestion system.

[0017] Compared with the prior art, the present invention has the following beneficial effects: When the present invention is used to treat organic wastewater, the following beneficial effects can be achieved: (1) Increase methane production: By adding ascorbic acid, the activity of methane-producing bacteria can be increased, thereby increasing the methane production during anaerobic digestion. This is of great significance in terms of energy recovery and economic benefits.

[0018] (2) Improve sludge stability: Ascorbic acid can help reduce organic pollutants in sludge by promoting the anaerobic digestion process and convert them into more stable substances, thereby reducing sludge corruption and odor problems.

[0019] (3) Promote sludge reduction: The addition of ascorbic acid may increase the degradation rate of organic matter, thereby accelerating the reduction of sludge volume, which is conducive to sludge reduction and resource utilization. (4) Effectively inhibiting the formation and expansion of foam: The foam control effect of ascorbic acid in anaerobic digestion is mainly reflected in its antioxidant properties, intervention on surfactants, and promotion of microbial activity. By reducing oxidative stress, regulating microbial metabolism, and lowering surface tension, ascorbic acid can effectively inhibit the formation and expansion of foam, maintaining the stability of the anaerobic digestion process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a statistical diagram of methane yield during the reaction process in one embodiment of the present invention.

[0021] Figure 2 This is a statistical diagram of bubble height during the reaction process in one embodiment of the present invention.

[0022] Figure 3 This is a statistical chart of the production of viscous polysaccharides in one embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific embodiments. However, it should be understood that the drawings are only for illustrative purposes and cannot be understood as limiting this patent; in order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted; the positional relationships described in the drawings are only for illustrative purposes and cannot be understood as limiting this patent.

[0024] Our research has found that foam production during anaerobic digestion is closely related to the state of the microorganisms. When microorganisms face adverse conditions such as sudden temperature changes, exposure to toxic and hazardous substances, and oxygen ingress, they actively adjust their metabolism, producing large amounts of surface-active, sticky polysaccharides and proteins. This significantly increases the potential for bubble formation on the surface of the anaerobic reactor. This is because, when anaerobic microorganisms encounter adverse external environments, their internal electron respiratory chains suffer a degree of damage, leading to the production of intracellular ROS. This ROS production, in turn, drives the microorganisms to secrete sticky polysaccharides extracellularly to protect themselves. Sticky polysaccharides are a typical natural surfactant, which leads to the large-scale production of bubbles on the surface of anaerobic digesters.

[0025] Based on this, we propose a method for inhibiting the generation of foam during the anaerobic digestion of organic wastewater, including the step of adding ascorbic acid to the anaerobic digestion system, and utilizing the antioxidant properties of ascorbic acid to inhibit the generation of surface foam during the anaerobic digestion of sludge.

[0026] In addition, based on this, we also proposed a wastewater treatment test method based on ascorbic acid, which includes the following steps: Treatment object and system construction: Select high-concentration organic wastewater as the treatment object, configure the anaerobic reactor, and set the initial sludge concentration, anaerobic digestion temperature, working water level depth and treatment load; System startup: Start the anaerobic reactor and run it until the effluent COD concentration becomes stable. Record the foam height on the reactor surface at this time. Ascorbic acid dosing and grouping experiments: Set up at least four experimental groups, add different concentrations of ascorbic acid to each reactor, and set up a control group without ascorbic acid. Run for a certain period of time, and observe and record the changes in foam height on the surface of each reactor. Monitoring and effect evaluation: During the treatment process, the intensity of reactive oxygen species (ROS) in microbial cells, the content of viscous polysaccharides in sludge extracellular polymers (EPS), and the methane gas generation rate parameters during anaerobic digestion are monitored; based on the monitoring results, the effect of ascorbic acid on inhibiting foam formation and maintaining the stability of the anaerobic digestion system is evaluated.

[0027] Specifically, the initial sludge concentration is set in the range of 15,000-25,000 mg / L, the anaerobic digestion temperature is set at 35-39°C, the working water level depth is set at 0.6-0.8m, and the treatment load is set at 3-5kgCOD / m³.

[0028] It should be noted that in the system startup step, the anaerobic reactor is operated until the fluctuation range of the effluent COD concentration does not exceed ±500 mg / L, that is, the effluent COD concentration tends to be stable.

[0029] In some preferred embodiments, in the ascorbic acid addition and grouping experimental steps, the ascorbic acid concentration gradient added to the experimental group at least includes 0 mg / L, 10 mg / L, 50 mg / L, and 100 mg / L.

[0030] As a first preferred embodiment of the present invention, the ascorbic acid addition and grouping experimental steps are run for 30-60 days, with the foam height on the surface of each reactor regularly observed and recorded daily. The experiment can be terminated when the monitoring and analysis determine that the effluent COD concentration has stabilized and the optimal ascorbic acid addition concentration has been determined through adjustment.

[0031] Specifically, in the monitoring and effect evaluation step, a fluorescent probe method is used to monitor the intensity of reactive oxygen species (ROS) in microbial cells.

[0032] In the specific evaluation method, in the monitoring and effect evaluation step, the inhibitory effect of ascorbic acid on foam generation is evaluated by measuring the viscous polysaccharide content of sludge extracellular polymers (EPS); and the stability of the anaerobic digestion system is evaluated by the methane gas generation rate parameter.

[0033] Finally, the process involves adjusting the ascorbic acid concentration based on monitoring and effect evaluation results. These tests can determine the optimal ascorbic acid concentration for optimal foam suppression in specific organic wastewaters. This is related to the concentration and composition of organic components in the wastewater, so experimental analysis is required to determine the optimal ascorbic acid concentration for each wastewater source. By adjusting the ascorbic acid concentration and dosing method, foam generation can be precisely controlled, achieving the desired foam suppression effect.

[0034] In a specific test case, the high-concentration yellow liquor produced during the liquor brewing process was used as the treatment object. The COD of the yellow liquor was 317,000 mg / L, the ammonia nitrogen was 1,721 mg / L, the initial sludge concentration of the anaerobic reactor was 20,000 mg / L, the anaerobic digestion temperature was 37 degrees, the reactor structure type was CSTR, the working water level depth was 0.7m, and the treatment load was controlled to 4kgCOD / m3.

[0035] There are 4 experimental groups in total, Figure 1 As shown, Figure 1The methane yields of the four experimental groups were recorded during the reaction process. All four experimental groups were started simultaneously. After approximately 40 days of startup, the effluent COD concentration reached approximately 5000 mg / L, with surface bubble heights of approximately 10 cm. Following startup, ascorbic acid was added to the reactors at concentrations of 0 mg / L, 10 mg / L, 50 mg / L, and 100 mg / L, respectively. The reactor performance was observed, along with the surface foam heights of the different reactors.

[0036] like Figure 2 As shown, Figure 2 The changes in foam height during the reaction process of the four experimental groups were recorded. After 60 days of operation, it was found that the anaerobic digestion system with 0 mg / L of ascorbic acid added produced a large amount of foam, and the foam height eventually reached 40 cm; while the foam in the experimental groups with 10 mg / L, 50 mg / L, and 100 mg / L of ascorbic acid added was significantly lower than that in the control group, among which 50 mg / L was the most obvious, and the bubble height after the end of the experiment was only 8 cm.

[0037] During the experiment, the ROS intensity in the microbial cells was monitored and it was found that ascorbic acid had a significant effect on slowing down ROS, which resulted in the viscous polysaccharides in the sludge EPS being significantly lower than that in the control group. Figure 3 As shown, Figure 3 The production of viscous polysaccharides in the four experimental groups was recorded, and the stability of the reaction process was ensured by monitoring the methane gas generation rate parameters throughout the anaerobic digestion process. The results showed that ascorbic acid can maintain the stability of the anaerobic digestion system while reducing foam.

[0038] This invention combines the biological principles of ascorbic acid with the practical needs of anaerobic sludge digestion to design an effective foam suppression solution. It was found that adding ascorbic acid to anaerobic digestion can effectively reduce surface foam formation during anaerobic sludge digestion, thereby improving the efficiency and stability of the digestion process. This innovative technology has high application value and market prospects.

[0039] The core concept of this invention is to use ascorbic acid as a scavenger of intracellular ROS in microorganisms, reducing the production of intracellular ROS by anaerobic microorganisms when faced with adverse conditions. This prevents the accumulation of intracellular ROS from regulating the secretion of viscous polysaccharides and proteins by microbial cells, thereby effectively inhibiting the formation of foam during sludge digestion. Ascorbic acid not only has a strong antioxidant effect but also does not negatively affect the growth and metabolism of anaerobic microorganisms, making it highly compatible with the sludge digestion process.

[0040] In addition, as an environmentally friendly substance, ascorbic acid not only reduces pollution to the environment, but also reduces the interference of chemical defoaming agents in the sludge digestion process, which can improve digestion efficiency while reducing operating costs.

[0041] Ascorbic acid can neutralize free radicals and hydrogen peroxide within anaerobic bioreactors and anaerobic microbial cells. These substances cause oxidative stress in anaerobic microorganisms, prompting them to actively adjust their metabolic expression and release large amounts of EPS containing sticky polysaccharides to protect themselves. The content of sticky polysaccharides is closely related to the stability of the foam.

[0042] The accumulation of peroxides and free radicals in anaerobic reactors and microbial cells will lead to excessive production of surfactants and increase foam stability. The antioxidant properties of ascorbic acid can reduce these harmful substances, thereby effectively controlling the generation of foam.

[0043] Secondly, during anaerobic digestion, microbial metabolic products often affect foam production. As an electron donor, ascorbic acid plays a crucial role in microbial metabolism, helping to stabilize microbial communities, particularly the metabolic activity of methanogens, and preventing foam formation caused by the activation of certain metabolic pathways. Ascorbic acid can also help mitigate these effects by regulating microbial populations and metabolic processes, reducing the likelihood of foam formation.

[0044] In addition, ascorbic acid can also react with surfactants or interact with these substances to change their surface tension and reduce the stability of foam.

[0045] Therefore, reducing the generation of surface foam during anaerobic digestion of sludge based on ascorbic acid not only solves the shortcomings of the existing technology, but also provides a safe, environmentally friendly and efficient solution.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for inhibiting foam generation during anaerobic digestion of organic wastewater, characterized in that: The method comprises the steps of adding ascorbic acid into the anaerobic digestion system, and utilizing the antioxidant property of ascorbic acid to suppress the generation of surface foam during the anaerobic digestion of sludge.

2. A sewage treatment test method based on ascorbic acid, characterized in that: The following steps are involved: Treatment object and system construction: Select high-concentration organic wastewater as the treatment object, configure the anaerobic reactor, set the initial sludge concentration, anaerobic digestion temperature, working water level depth and treatment load; System startup: Start the anaerobic reactor and run it until the effluent COD concentration becomes stable. Record the foam height on the reactor surface at this time. Ascorbic acid dosing and grouping experiments: Set up at least four experimental groups, add different concentrations of ascorbic acid to each reactor, and set up a control group without ascorbic acid. Run for a certain period of time, and observe and record the changes in foam height on the surface of each reactor. Monitoring and effect evaluation: During the treatment process, the intensity of reactive oxygen species (ROS) in microbial cells, the content of viscous polysaccharides in sludge extracellular polymers (EPS), and the methane gas generation rate parameters during anaerobic digestion are monitored.

3. The sewage treatment test method according to claim 2, characterized in that: The initial sludge concentration is set in the range of 15,000-25,000 mg / L, the anaerobic digestion temperature is set at 35-39°C, the working water level depth is set at 0.6-0.8m, and the treatment load is set at 3-5kgCOD / m³.

4. The sewage treatment test method according to claim 2, characterized in that: In the system startup step, the anaerobic reactor is operated until the fluctuation range of the effluent COD concentration does not exceed ±500 mg / L, that is, the effluent COD concentration tends to be stable.

5. The sewage treatment test method according to claim 2, characterized in that: In the ascorbic acid addition and grouping experimental steps, the ascorbic acid concentration gradient added to the experimental group at least includes 0 mg / L, 10 mg / L, 50 mg / L, and 100 mg / L.

6. The sewage treatment test method according to claim 2, characterized in that: The ascorbic acid addition and grouping experimental steps were run for 30-60 days, and the foam height on the surface of each reactor was observed and recorded daily.

7. The sewage treatment test method according to claim 2, characterized in that: In the monitoring and effect evaluation steps, a fluorescent probe method is used to monitor the intensity of reactive oxygen species (ROS) in microbial cells.

8. The sewage treatment test method according to claim 2, characterized in that: In the monitoring and effect evaluation step, the inhibitory effect of ascorbic acid on foam generation is evaluated by measuring the viscous polysaccharide content of sludge extracellular polymeric substances (EPS); and the stability of the anaerobic digestion system is evaluated by the methane gas generation rate parameter.

9. The sewage treatment test method according to any one of claims 2 to 7, characterized in that: The method also includes the step of adjusting the concentration of ascorbic acid added according to the monitoring and effect evaluation results.

10. Application of the method according to claim 1 in the treatment of liquor wastewater.

Images