Dynamic evaluation regulation and control method for stability of high-ammonia-nitrogen anaerobic fermentation system

Abstract

The invention discloses a dynamic evaluation regulation and control method for the stability of a high-ammonia-nitrogen anaerobic fermentation system, which eliminates the interference of ammonia nitrogen on total alkalinity through an effective alkalinity (EA) correction model, constructs a comprehensive stability index (CSI) by combining free ammonia (FA) inhibition compensation, and solves the problem of misjudgment of a traditional VFA / TA ratio method. By adopting the method provided by the invention, the CSI can early warn the system instability 12-24 hours in advance, and the methane production activity is maintained through a priority regulation strategy. The method is suitable for the anaerobic fermentation process of high-ammonia-nitrogen organic waste such as livestock and poultry manure and kitchen waste.

Description

TECHNICAL FIELD

[0001] The present application relates to an organic waste anaerobic fermentation technology, and in particular to a dynamic evaluation and regulation method for stability of a high-ammonia-nitrogen anaerobic fermentation system. BACKGROUND

[0002] At present, the organic solid waste in China mainly includes three types of sources, i.e., life sources such as municipal sludge, household garbage, and garden garbage, agricultural sources such as agricultural straw, mulching film, and livestock and poultry manure, and industrial sources such as oil sludge, drug residue, and fungus residue, with an annual output of more than 6 billion tons, accounting for more than 60% of the total solid waste production. However, a scientific and reasonable management and safe treatment technology system has not yet been formed. The organic solid waste has typical pollution properties, is complex in composition and contains many harmful substances, and if not properly handled and disposed, will have a negative impact on the ecological environment and human health. Reasonable and scientific treatment of the organic solid waste is a necessary measure to realize its harmless disposal.

[0003] The patent document with the application number "CN202110002289.0" discloses an organic solid waste anaerobic fermentation method, specifically adding a zirconium metal organic framework material as a catalyst in the organic solid waste anaerobic fermentation process. The present application improves the anaerobic fermentation efficiency and the methane production by introducing a zirconium metal organic framework material in the anaerobic fermentation process, which is beneficial to the reduction of the organic solid waste after anaerobic fermentation. The biogas residue after fermentation contains a large amount of nitrogen, phosphorus elements and other trace elements, and can be used for resource recovery or as a fertilizer applied in the agricultural production process.

[0004] The patent document with the application number "CN202022996575.7" discloses a movable anaerobic fermentation online monitoring integrated device, mainly focusing on the development of an index monitoring device, including a filtration system, a dilution mixing system, a detection tank, a distilled water heater, a data acquisition system, and a temperature control device. The filtration system is connected to the dilution mixing system and the detection tank in sequence through an anaerobic digestion liquid transmission pipeline. The top side of the detection tank is respectively provided with a data acquisition system and a temperature control device. The anaerobic digestion liquid transmission pipeline between the filtration system and the dilution mixing system is in communication with a distilled water transmission pipeline, and the distilled water transmission pipeline is connected with the distilled water heater.

[0005] The patent document with the application number "CN201710934587.7" discloses an anaerobic fermentation full-automatic online early warning diagnosis and treatment device. The anaerobic fermentation full-automatic online early warning diagnosis and treatment device provided by the present application comprises an anaerobic fermentation treatment module, a total control module, a data processing / sending module connected with the total control module, an I / O control module, a data acquisition module, a man-machine interaction module and a driving transmission module. The anaerobic fermentation treatment module comprises a sample feeding module, a cleaning module and a liquid adding / titration module connected in sequence. The sample feeding module and the cleaning module are connected with the I / O control module respectively. The liquid adding / titration module is connected with the driving transmission module, so as to realize full-automatic processing. The total control module detects the running state of anaerobic fermentation through the data acquisition module and sends the running state to a user end through the data processing / sending module. The user can remotely monitor and operate the whole device through the user end, so as to realize remote online early warning, monitoring and running state diagnosis, so as to ensure the stability of the anaerobic fermentation process.

[0006] The patent document with the application number "CN201310364454.2" discloses a high-temperature anaerobic fermentation monitoring system. The present application solves the problems of wiring difficulty, unstable signal and poor system anti-interference performance of the existing monitoring system. The present application realizes the monitoring of the high-temperature anaerobic fermentation operating parameters by using a high-temperature anaerobic fermentation operating parameter wireless real-time monitoring system. The PLC control system of the present application controls the temperature sensor, the flow sensor, the pressure sensor and the pH value sensor through the wireless transceiver circuit to collect the temperature, the pressure, the pH value and the flow of the fermentation liquid in the high-temperature anaerobic fermentation tank. The PLC control system receives the temperature, the pressure, the pH value and the flow information of the fermentation liquid in the high-temperature anaerobic fermentation tank through the wireless transceiver circuit.

[0007] The patent document with the application number "CN201710833822.1" discloses a method for quickly relieving organic acid inhibition of an anaerobic fermentation system. When a large amount of organic acid accumulates in the anaerobic fermentation system due to load fluctuation or other reasons, and the methanogenic bacteria are severely inhibited, stopping feeding and adding biochar can quickly relieve the organic acid inhibition. The recovery degree of the anaerobic fermentation system is comprehensively evaluated by monitoring the pH, volatile fatty acid (VFA) and gas production of the fermentation liquid. When the pH, VFA and gas production gradually recover to the state before acidification, low-load feeding can be started. After the fermentation system is stable, the load is gradually increased to recover the anaerobic fermentation system.

[0008] The above patent documents combined with the prior art disclose that the existing dynamic evaluation and control method for the stability of the high-ammonia nitrogen anaerobic fermentation system has the following defects:

[0009] (1) The traditional anaerobic fermentation system uses the VFA / TA ratio, i.e. the volatile fatty acid / total alkalinity, as a stability index. However, in a high-ammonia nitrogen system, the alkalinity (TA) contributed by ammonia nitrogen is not included in the VFA / TA ratio, so the VFA / TA ratio cannot accurately reflect the stability of the high-ammonia nitrogen anaerobic fermentation system.NH3 ) cause total alkalinity (TA) to be artificially high, making the VFA / TA ratio underestimate the actual risk.

[0010] (2) The inhibitory effect of free ammonia (FA) on methanogens is not quantified and included in the evaluation system, and the FA concentration is affected by the dynamics of pH and temperature, so traditional static indicators cannot reflect the system state in real time.

[0011] (3) Existing patents mainly focus on the development of index monitoring devices, such as CN202022996575.7 a mobile anaerobic fermentation online monitoring integrated device, online early warning diagnosis device development CN201710934587.7 an anaerobic fermentation full-automatic online early warning diagnosis and treatment device, which generally monitors temperature, pH, flow, NH4-N, VFA and gas production, etc. Conventional indicators such as CN201310364454.2 a method for real-time monitoring of high-temperature anaerobic fermentation operating parameters, CN201710833822.1 a method for relieving organic acid inhibition in anaerobic fermentation system and promoting VFA degradation, which does not consider composite diagnosis and early warning indicators and does not solve the problem of ammonia nitrogen interfering with alkalinity, resulting in one-sidedness of the control strategy. SUMMARY

[0012] In order to overcome the shortcomings of the prior art, the present application provides a dynamic evaluation and control method for the stability of a high-ammonia anaerobic fermentation system, which solves the problem of one-sidedness of the control strategy.

[0013] The first aspect of the present application is to provide a dynamic evaluation and control method for the stability of a high-ammonia anaerobic fermentation system, comprising the following steps:

[0014] S10 step: monitoring the real-time index data of the high-ammonia anaerobic fermentation system and recording;

[0015] S20 step: based on the dynamic monitoring of real-time index data, calculate the free ammonia (FA) concentration;

[0016] S30 step: calculate the free ammonia contribution alkalinity (TA NH3 ), and deduct TA NH3 from the total alkalinity (TA) to obtain the effective alkalinity (EA);

[0017] S40 step: construct a comprehensive stability index CSI, calculate according to the formula CSI=VFA / EA*I FA , wherein VFA is the mass concentration of volatile fatty acids, I FA is the ammonia inhibition factor, I FA =1+0.5Sigmoid[(FA-FA t ) / 100], FA t is the free ammonia inhibition threshold, and Sigmoid(x)=1 / (1+e-x

[0018] If yes, triggering high-risk early warning regulation instruction; if no, detecting whether 0.8≥CSI≥0.6, if yes, triggering low-risk regulation instruction.

[0019] In the first aspect of the present application, as a preferred embodiment, in the step S10, when "monitoring real-time index data of the high-ammonia anaerobic fermentation system and recording", the real-time index data includes monitoring total alkalinity (TA), total ammonia nitrogen (TAN), temperature, pH value, and volatile fatty acid (VFA) mass concentration.

[0020] In the first aspect of the present application, as a preferred embodiment, in the step S20, when "calculating free ammonia (FA) concentration based on the monitoring dynamics of the real-time index data", the formula for calculating the free ammonia (FA) concentration is:

[0021] FA=[TAN] / 14{1+10 [pKa(T)-pH]}(mol / L)=17[TAN] / 14{1+10 [pKa(T)-pH]}(mg / L)

[0022] Wherein, pKa(T)=0.09018+2729.92 / (T+273.15), T is temperature (℃).

[0023] In the first aspect of the present application, as a preferred embodiment, in the step S30, when "calculating free ammonia contribution alkalinity (TA NH3 ) and deducting TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA)", the formula for calculating the effective alkalinity (EA) is:

[0024] EA=TA-TA NH3 (mg / L).

[0025] In the first aspect of the present application, as a preferred embodiment, in the step S30, when "calculating free ammonia contribution alkalinity (TA NH3 ) and deducting TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA)", the formula for calculating the free ammonia contribution alkalinity (TA NH3 ) is:

[0026] TA NH3 =50FA / 17(mg / L).

[0027] In the first aspect of the present application, as a preferred embodiment, in the step S40, when "constructing a comprehensive stability index CSI according to the formula CSI=VFA / EA*I​FA When calculating, the FA t is set to 600 mg / L.

[0028] In the first aspect of the application, as a preferred embodiment, in the S40 step, if CSI < 0.6, it is determined that the system stability is good.

[0029] In the first aspect of the application, as a preferred embodiment, it further includes an S50 step, if a high-risk early warning regulation instruction is triggered, immediately stop feeding, start emergency sludge discharge or exogenous microbial addition, and preferentially reduce the concentrations of FA and VFA.

[0030] In the first aspect of the application, as a preferred embodiment, it further includes an S60 step, if a low-risk regulation instruction is triggered, increase the monitoring frequency, and if FA > FA t , add weak acid to adjust the pH to reduce the free ammonia concentration in the system.

[0031] In the first aspect of the application, as a preferred embodiment, in the S60 step, if FA ≤ FA t , preferentially supplement alkalinity.

[0032] Compared with the prior art, the application has the beneficial effects that:

[0033] 1. In a high ammonia-nitrogen system, the superimposed effect of high TA and FA inhibition often leads to the risk of misjudgment by traditional methods. By using the method of the application, ammonia-nitrogen contributes to alkalinity correction, FA dynamic compensation, and multi-parameter collaborative analysis, the system can be stably evaluated.

[0034] 2. The application is suitable for the anaerobic fermentation process of high ammonia-nitrogen organic waste such as livestock and poultry manure and kitchen waste. CSI can early warn system instability for 12-24 hours, and maintain the methanogenic activity through priority regulation strategy. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a flowchart of the application;

[0036] Figure 2 is a curve diagram of the synergistic inhibition effect of FA concentration and VFA / EA. DETAILED DESCRIPTION

[0037] Hereinafter, the application will be further described in conjunction with the drawings and specific embodiments, it should be noted that the following described embodiments or technical features can be combined arbitrarily to form new embodiments without conflict. Unless otherwise specified, the materials and equipment used in the embodiments can be purchased from the market. The examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the application and cannot be understood as a limitation on the application.

[0038] In the description of the application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise specified and limited.

[0039] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "connected", "communicated", "connected" should be understood in a broad sense, for example, it can be fixedly connected, or connected through an intermediate medium, or the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0040] The terms "first", "second", and the like in the specification and claims of the application and the above drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those clearly listed steps or units, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0041] As shown in Figure 1 A dynamic evaluation and regulation method for stability of a high-ammonia anaerobic fermentation system, comprising the following steps:

[0042] S10 step: monitoring the real-time index data of the high-ammonia anaerobic fermentation system and recording;

[0043] In the first aspect of the present application, as a preferred embodiment, in the step S10, when "monitoring real-time index data of the high-ammonia anaerobic fermentation system and recording", the real-time index data includes monitoring total alkalinity (TA), total ammonia nitrogen (TAN), temperature, pH value, volatile fatty acid (VFA) mass concentration.

[0044] Step S20: calculating free ammonia (FA) concentration based on the monitoring dynamics of real-time index data;

[0045] In the first aspect of the present application, as a preferred embodiment, in the step S20, when "calculating free ammonia (FA) concentration based on the monitoring dynamics of real-time index data", the formula for calculating free ammonia (FA) concentration is:

[0046] FA=[TAN] / 14{1+10 [pKa(T)-pH]}(mol / L)=17[TAN] / 14{1+10 [pKa(T)-pH]}(mg / L)

[0047] Wherein, pKa(T)=0.09018+2729.92 / (T+273.15), T is temperature (℃).

[0048] Step S30: calculating free ammonia contribution alkalinity (TA NH3 ) and deducting TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA);

[0049] In the first aspect of the present application, as a preferred embodiment, in the step S30, when "calculating free ammonia contribution alkalinity (TA NH3 ) and deducting TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA)", the formula for calculating effective alkalinity (EA) is:

[0050] EA=TA-TA NH3 (mg / L).

[0051] In the first aspect of the present application, as a preferred embodiment, in the step S30, when "calculating free ammonia contribution alkalinity (TA NH3 ) and deducting TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA)", the formula for calculating free ammonia contribution alkalinity (TA NH3 ) is:

[0052] TA NH3 =50FA / 17(mg / L).

[0053] S40 step: constructing a comprehensive stability index CSI, according to the formula CSI = VFA / EA*I FA , wherein VFA is the mass concentration of volatile fatty acids, I FA is the ammonia inhibition factor, I FA = 1 + 0.5Sigmoid[(FA-FA t ) / 100], FA t is the free ammonia inhibition threshold, and Sigmoid(x) = 1 / (1+e -x ).

[0054] Detect whether CSI>0.8, if yes, trigger a high-risk early warning control instruction; if no, detect whether 0.8>CSI>0.6, if yes, trigger a low-risk control instruction. Please refer to Figure 2 , in a high ammonia nitrogen system, the superimposed effect of TA virtual high and FA inhibition often leads to the risk of misjudgment by traditional methods, and the method of the present application integrates ammonia nitrogen contribution alkalinity correction, FA dynamic compensation and multi-parameter collaborative analysis, and then stable evaluation. The present application is suitable for the anaerobic fermentation process of high ammonia nitrogen organic waste such as livestock and poultry manure, kitchen waste, etc. CSI can early warning system instability for 12-24 hours, and maintain the methanogenic activity through priority control strategy.

[0055] It should be noted that the CSI set value of the present application is set according to repeated tests and comprehensive consideration. When CSI<0.6, it indicates that the system stability is good;

[0056] 0.6≤CSI≤0.8, low risk warning, indicating that the system has a certain stability risk, and the monitoring frequency needs to be increased. If FA>FA t , adjust pH first (such as adding weak acid), reduce the concentration of free ammonia in the system; if FA≤FA t , preferentially supplement alkalinity. Using the method of the present application, the problem of VFA / TA misjudgment caused by TA virtual high in high ammonia nitrogen system is solved, and the early warning sensitivity is improved.

[0057] CSI>0.8, high risk warning, need to stop feeding immediately, start emergency sludge discharge or exogenous microorganism addition, preferentially reduce FA and VFA concentration.

[0058] In the first aspect of the present application, as a preferred embodiment, in the S40 step, when calculating "constructing a comprehensive stability index CSI, according to the formula CSI = VFA / EA*I FA ", FA t is set to 600 mg / L.

[0059] In the first aspect of the present application, as a preferred embodiment, in the step S40, if CSI < 0.6, it is determined that the system is stable. Meanwhile, if other instructions are triggered, after the method of the present application is used, the interference of ammonia nitrogen on total alkalinity is eliminated by an effective alkalinity (EA) correction model, a comprehensive stability index (CSI) is constructed by combining free ammonia (FA) inhibition compensation, and the misjudgment problem of the traditional VFA / TA ratio method is solved.

[0060] In the first aspect of the present application, as a preferred embodiment, the step S50 is further included, if a high-risk early warning control instruction is triggered, immediately stop feeding, start emergency sludge discharge or exogenous microbial addition, and preferentially reduce the concentrations of FA and VFA.

[0061] In the first aspect of the present application, as a preferred embodiment, the step S60 is further included, if a low-risk control instruction is triggered, increase the monitoring frequency, if FA > FA t , add weak acid to adjust pH to reduce the concentration of free ammonia in the system.

[0062] In the first aspect of the present application, as a preferred embodiment, in the step S60, if FA ≤ FA t , preferentially supplement alkalinity.

[0063] I. Embodiment 1 (effective alkalinity correction and early warning sensitivity verification):

[0064] 1. Main status:

[0065] (1) Experimental conditions: anaerobic fermentation of pig manure;

[0066] (2) Monitoring data: TA = 12500 mg CaCO3 / L, VFA = 4900 mg / L, TAN = 4500 mg / L, reactor temperature = 35℃, pH = 8.2;

[0067] 2. Calculation process:

[0068] (1) Calculate FA:

[0069] pKa(35℃) = 0.09018 + 2729.92 / (35 + 273.15) = 9.03

[0070] FA = 4500 / 14[1 + 10 (9.03-8.2) ] = 41.4 (mol) = 704 (mg / L)

[0071] (2) Calculate FA contribution alkalinity

[0072] TA NH3 = 50 * 704 / 17 = 2071 (mg / L)

[0073] EA = 12500 - 2071 = 10429 mg CaCO3 / L

[0074] (3) Comparative illustration:

[0075] Traditional VFA / TA = 4900 / 12500 = 0.39, <0.4, in the safe range, and VFA / EA = 4900 / 10429 = 0.47;

[0076] (4) Calculate ammonia inhibition factor I FA

[0077] I FA = 1 + 0.5 Sigmoid [(704 - 600) / 100] = 1.369

[0078] CSI = 0.47 x 1.369 = 0.64, the system has triggered a low-risk warning, combined with FA calculation (FA = 704 mg / L > 600 mg / L), the ammonia nitrogen concentration in the system should be reduced in priority, which can be reduced by adjusting the pH method.

[0079] (5) Conclusion

[0080] The traditional method determines safety, while the CSI gives an early warning 12 hours in advance, verifying the necessity of EA correction.

[0081] II. Specific embodiment 2 (FA inhibition compensation and protection of methanogenic activity)

[0082] 1. Experimental group: dynamic control by CSI (pH is adjusted to 7.9, and FA is reduced to 377 mg / L);

[0083] 2. Control group: only VFA / TA method is used without intervention;

[0084] 3. Results: the VFA of the control group increased to 8000 mg / L after 24 hours, and the methane production rate decreased by 50%; the VFA of the experimental group was stable at 4900-5200 mg / L, and the methane production rate was not affected.

[0085] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-substantial changes and substitutions made by those skilled in the art based on the present application are within the scope of the present application.

Claims

1. A dynamic evaluation and regulation method for stability of a high-ammonia anaerobic fermentation system, characterized in that, The method comprises the following steps: S10: monitoring real-time index data of the high-ammonia anaerobic fermentation system and recording; S20: calculating free ammonia (FA) concentration based on the monitoring dynamics of the real-time index data; S30 Step: Calculate free ammonia contribution alkalinity (TA NH3 ) and subtract TA NH3 from total alkalinity (TA) to obtain effective alkalinity (EA); S40 step: constructing a comprehensive stability index (CSI) according to the formula CSI = VFA / EA*I FA , where VFA is the mass concentration of volatile fatty acids, I FA is the ammonia inhibition factor, I FA = 1 + 0.5 Sigmoid[(FA-FA t ) / 100], FA t is the free ammonia inhibition threshold, and Sigmoid(x) = 1 / (1+e -x ); If CSI>0.8, triggering a high-risk early warning control instruction; if not, detecting whether 0.8≥CSI≥0.6, if yes, triggering a low-risk control instruction.

2. The method of claim 1, wherein the ammonia nitrogen content is 1,000 mg / L or more. In the S10 step, when monitoring real-time index data of the high-ammonia anaerobic fermentation system and recording, the real-time index data includes monitoring total alkalinity (TA), total ammonia nitrogen (TAN), temperature, pH value, and volatile fatty acid (VFA) mass concentration.

3. The method for dynamic evaluation and control of the stability of a high ammonia nitrogen anaerobic fermentation system as described in claim 1, characterized in that: In the S20 step, when calculating free ammonia (FA) concentration based on the monitoring dynamics of the real-time index data, the formula for calculating free ammonia (FA) concentration is: FA = [TAN] / 14{1+10 [pKa(T)-pH]}(mol / L) = 17[TAN] / 14{1+10 [pKa(T)-pH]}(mg / L) Wherein, pKa(T)=0.09018+2729.92 / (T+273.15), T is temperature (℃).

4. The method of claim 1, wherein the ammonia nitrogen content is 1,000 mg / L or more. In the step S30, the free ammonia contribution alkalinity (TA NH3 ) is calculated and the TA NH3 is deducted from the total alkalinity (TA) to obtain the effective alkalinity (EA). The formula for calculating the effective alkalinity (EA) is: EA = TA - TA NH3 (mg / L).

5. The method of claim 1, wherein the method further comprises: determining the ammonia nitrogen concentration of the anaerobic fermentation system; and adjusting the pH of the anaerobic fermentation system to maintain the ammonia nitrogen concentration of the anaerobic fermentation system at a predetermined level. In the step S30, the free ammonia contributed alkalinity (TA NH3 ) is calculated, and the TA NH3 is deducted from the total alkalinity (TA) to obtain the effective alkalinity (EA). The formula for calculating the free ammonia contributed alkalinity (TA NH3 ) is: TA NH3 = 50 FA / 17 (mg / L).

6. The method of claim 1, wherein the method further comprises: determining the ammonia nitrogen concentration of the anaerobic fermentation system; and adjusting the pH of the anaerobic fermentation system to maintain the ammonia nitrogen concentration of the anaerobic fermentation system at a predetermined level. In step S40, "Constructing the Comprehensive Stability Index (CSI) according to the formula CSI = VFA / EA*I" FA When performing calculations, FA t Set to 600 mg / L.

7. The method of claim 1, wherein the ammonia nitrogen content is 1,000 mg / L or more. In the S40 step, if CSI<0.6, it is determined that the system stability is good.

8. The method of claim 1, wherein the ammonia nitrogen concentration is 1,000 mg / L or more. The method further comprises a S50 step, if the high-risk early warning control instruction is triggered, immediately stopping feeding, starting emergency sludge discharge or exogenous microbial addition, and preferentially reducing FA and VFA concentrations.

9. The method of claim 1, wherein the method further comprises: determining the ammonia nitrogen concentration of the anaerobic fermentation system; and adjusting the pH of the anaerobic fermentation system to maintain the ammonia nitrogen concentration of the anaerobic fermentation system at a predetermined level. Also included is a step S60 of increasing the monitoring frequency if a low-risk control instruction is triggered, and of decreasing the monitoring frequency if FA> FA t , adding a weak acid to adjust the pH to reduce the free ammonia concentration in the system.

10. The method of claim 1, wherein the method further comprises: determining the ammonia nitrogen concentration of the anaerobic fermentation system; and adjusting the pH of the anaerobic fermentation system to maintain the ammonia nitrogen concentration of the anaerobic fermentation system at a predetermined level. In the step S60, if FA≤FA t , alkalinity is preferentially supplemented.

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