An anaerobic fermentation stable regulation method suitable for north high-salt kitchen waste

Abstract

The application discloses an anaerobic fermentation stable regulation method suitable for northern high-salt kitchen waste, and first, multi-stage synergistic conditioning and salt reduction pretreatment is carried out; then, the northern high-salt kitchen waste is crushed to 58 mm, hard sundries are removed, and two-stage countercurrent washing is carried out by using warm water in winter, short-time stirring and coarse washing are carried out by using 22 DEG C warm water, and high-salt soup and floating oil are removed by filtration. The anaerobic fermentation stable regulation method suitable for northern high-salt kitchen waste can reach more than 40% of overall water-saving rate compared with a conventional pure water washing process through a revolutionary improvement and innovation in a source pretreatment link, the water consumption of a front-end salt washing process and the generation amount of high-salt washing wastewater are greatly reduced, and the high-protein component of kitchen waste is balanced by relying on straw organic matter, so that the risk of free ammonia inhibition caused by high-protein decomposition is relieved from the source of the substrate, and the industry problems of large water consumption in traditional water washing and frequent ammonia inhibition explosion in subsequent fermentation are solved.

Description

Technical Field

[0001] This invention belongs to the field of food waste resource utilization and anaerobic fermentation technology of organic solid waste, and particularly relates to a stable control method for anaerobic fermentation of food waste with high salinity in northern regions. Background Technology

[0002] Food waste in northern regions is characterized by high salt, high oil, and high protein content. Influenced by regional dietary habits, the native sodium ion concentration in food waste generally reaches 6 to 15 grams per liter, far exceeding the tolerance threshold of conventional anaerobic fermentation. At the same time, the long and cold winters in the north, with outdoor temperatures reaching as low as -10 degrees Celsius to 0 degrees Celsius, make anaerobic fermentation tanks prone to temperature drops and large temperature fluctuations. This creates a double stress of high salt and low temperature, coupled with the synergistic inhibition of oil and free ammonia, resulting in many defects in traditional anaerobic fermentation processes.

[0003] The anaerobic fermentation of high-salt kitchen waste from northern China currently available on the market has the following problems when applied: 1. In practice, the traditional anaerobic fermentation of high-salt kitchen waste in northern China usually adopts a mode of single water washing for salt reduction, single sludge acclimatization, strong alkali adjustment of pH, and fixed organic load operation. This mode has obvious shortcomings, resulting in high water consumption and low resource utilization rate of simple water washing. It is also impossible to adjust the carbon-nitrogen ratio at the same time, which can easily lead to ammonia inhibition. 2. When anaerobic fermentation of most high-salt kitchen waste in northern China is applied, the conventional municipal sludge itself has weak salt tolerance of microorganisms, resulting in poor salt adaptability. When using low-temperature environment for microbial acclimatization, the overall acclimatization period is relatively long, the stability of functional microbial communities in the system is insufficient, and problems such as activity decline and large-scale inactivation are very likely to occur. The upper limit of salt concentration that the entire biological treatment system can withstand is relatively low, only reaching seven to nine grams per liter. 3. When anaerobic fermentation of most high-salt kitchen waste in northern China is applied, if only a single strong alkaline reagent is used to adjust the pH value of the system, a large amount of sodium ions will be continuously introduced into the water during the adjustment process, further increasing the total salt concentration of the system and aggravating the salt toxicity stress pressure on microorganisms; at the same time, this adjustment method has a high proportion of reagent consumption for acid-base neutralization reaction, resulting in a large overall amount of reagent added and high operating material costs. 4. In most cases, the existing equipment and processes for anaerobic fermentation of high-salt kitchen waste in northern China have not been adapted to the characteristics of the low-temperature environment in northern winters, and have not been equipped with customized temperature control structures and dynamic matching control mechanisms for organic load. Due to the inhibitory effect of low temperature, the biogas production of anaerobic fermentation devices can decrease by up to 35% in winter, and the stability of the fermentation system will drop significantly. This makes it very easy for chain reactions such as excessive accumulation of volatile fatty acids, imbalance of substrate acidification, and sudden drop in the activity of fermentation bacteria to occur. In severe cases, it can directly lead to acidification collapse and shutdown of the entire treatment system. 5. When applying anaerobic fermentation of most high-salt kitchen waste in northern China, a steady-state operation mode with constant organic load is adopted. This mode cannot adapt to the real-time fluctuations and dynamic changes in salinity and ambient temperature within the system. When faced with shock loads caused by fluctuations in water quality and temperature, the buffer adjustment space is small, the overall process has extremely poor shock resistance, and the metabolic balance of the microbial community is easily disrupted. In summary, the industry currently lacks a modified anaerobic fermentation control process that can accurately adapt to the harsh conditions of low temperature and high salinity in northern regions. This makes it difficult to simultaneously achieve multiple performance advantages such as water conservation and consumption reduction, rapid and efficient domestication of microbial communities, long-term stable operation, and strong resistance to load shocks. This technological shortcoming greatly restricts the large-scale implementation and continuous stable operation of high-salt kitchen waste resource utilization in northern regions. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions, thereby solving the technical problems mentioned in the prior art.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows: a method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions. The usage methods are as follows: S1, Screening: A multi-stage synergistic conditioning and salt reduction pretreatment process is adopted to crush the high-salt kitchen waste from the north to a particle size of 5 to 8 mm, screen out hard debris such as bones and plastics, and implement a two-stage countercurrent washing process using preheated warm water in winter. The first stage uses 22-degree Celsius warm water for short-term stirring and coarse washing to filter out high-salt soup and surface oil. The second stage selects corn stalks or fruit and vegetable waste as adsorbents and mixes them with kitchen waste at a volatile solids mass ratio of 4:6. The porous structure of the straw adsorbs free sodium ions in the material. The mixture is then subjected to screw extrusion to complete solid-liquid phase conditioning and separation. The sodium ion concentration of the solid filtrate after extrusion is controlled to be less than 7 grams per liter. The fermentation slurry conditioning medium is reflux biogas slurry, and the biogas slurry reflux volume ratio is set to 0.6:1. S2, Salt-Tolerant Composite Microbial Community Stepped Low-Temperature Acclimation: The salt-tolerant composite microbial community stepped low-temperature acclimation process is implemented: 85% municipal mature anaerobic digested sludge by volume is mixed with 15% saline-alkali wetland bottom mud to form a composite inoculated sludge. The total volatile solids of the inoculated sludge account for 35% of the total volatile solids in the fermenter. At the same time, 0.8% salt-tolerant methanogenic composite microbial agent is added to enhance the functional microbial community. The salt increase rate is divided according to the temperature inside the tank. Under the standard medium temperature operation condition of 35 degrees Celsius, the sodium ion concentration of the system is increased by 1 gram per liter every seven days. Under the low temperature operation condition of 28 to 32 degrees Celsius in winter, the acclimation rate is slowed down, and the sodium ion concentration is increased by only 0.6 grams per liter every twelve days. The gradient acclimation continues until the fermentation system can stably bear 10 to 12 grams per liter. S3, modified biochar composite buffering and toxicity control, is produced by mixing sawdust and iron mud and then pyrolyzing them at 900 degrees Celsius to obtain iron-containing biochar. It is then saturated and modified by impregnation with calcium hydroxide solution. The initial addition of modified biochar is 6% of the total volatile solids mass of the fermenter. Subsequently, fresh modified biochar is added monthly at a ratio of 1.5% of the total volatile solids in the tank. The acid-base buffering system uses a compound alkali agent with calcium hydroxide as the main component and sodium bicarbonate as the auxiliary component. The exogenous sodium ions introduced by the process are strictly controlled. The total alkalinity of the fermentation system is maintained at no less than 2,200 mg / L of calcium carbonate throughout the process, and the pH is controlled in the stable range of 6.9 to 7.4. S4 is a waste heat closed-loop low-temperature constant temperature control system. The tank body is covered with a 130 mm thick polyurethane insulation layer, and all material pipelines are fully covered with an electric heat tracing insulation structure. It uses a biogas waste heat boiler with coil circulation heating to keep the core temperature of the fermentation tank constant at 35 ± 0.5 degrees Celsius. The heating power is pre-adjusted four minutes before the feeding operation starts to offset the impact of the temperature drop in the tank caused by the low temperature of the incoming material. The temperature fluctuation of the tank is strictly controlled to be no more than ± 1 degree Celsius during the day and night. The stirring system implements an intermittent low-speed operation system, stirring at low speed for 15 minutes every two hours to reduce the heat loss of the tank. In the event of extremely cold weather, it switches to a 24-hour continuous micro-flow stable feeding mode to avoid drastic temperature fluctuations caused by a large batch of cold material entering the tank. S5 features three-dimensional adaptive regulation of temperature and salinity load. It dynamically matches and adapts organic load parameters based on real-time tank temperature, sodium ion concentration, and on-site operating conditions. When the sodium ion concentration is less than 7 g / L and the tank temperature is not lower than 34 degrees Celsius, the organic load rate is set to 2.0 to 2.4 kg volatile solids per cubic meter per day, with a hydraulic retention time of 22 days. When the sodium ion concentration is between 7 and 10 g / L and the tank temperature is maintained between 30 and 34 degrees Celsius, the organic load rate is adjusted to 1.3 to 1.7 kg volatile solids per cubic meter per day, with a hydraulic retention time of 28 days. Under the harsh conditions of sodium ion concentration reaching 10 to 12 g / L and tank temperature below 30 degrees Celsius, the organic load rate is strictly controlled at 0.9 kg volatile solids. S6, high-salt two-phase diversion and synergistic fermentation regulation: if the original sodium ion concentration of the incoming kitchen waste is higher than 12 grams per liter, the acidification and methanogenesis two-phase fermentation operation mode is switched. The acidification hydrolysis tank can withstand a high salt environment of 12 to 15 grams per liter and stably complete the hydrolysis of organic macromolecules and acid production reaction at a low temperature of 30 degrees Celsius. The high-salt solid residue is retained in the acidification unit, and only the acidified clear liquid with a large number of inhibitory components removed is transported to the methanogenesis main tank, thereby ensuring that the sodium ion concentration in the methanogenesis main tank is stably controlled within 10 grams per liter for long-term stable operation.

[0006] As a further preferred embodiment of the present invention, in step S1, corn stalks or vegetable waste are mixed with kitchen waste according to the volatile solids ratio to adjust the anaerobic fermentation substrate carbon-nitrogen ratio to the optimal range of 22 to 26:1. On the one hand, this dilutes and reduces the salt load of the system, and on the other hand, it balances the high-protein matrix structure of kitchen waste. This weakens the synergistic inhibitory effect formed by the superposition of high-salt environment and high-protein decomposition to generate free ammonia from the substrate source, creating a suitable substrate environment for the stable proliferation and metabolism of subsequent functional microorganisms.

[0007] As a further preferred embodiment of the present invention, in step S2, a clear acclimatization qualification judgment index system is set. Acclimatization can be judged to be completed only when the system simultaneously meets three continuous monitoring conditions. First, the fluctuation range of biogas production is stable at less than 8% within three consecutive hydraulic retention time cycles, reflecting the stable metabolic state of the methanogenic bacteria. Second, the ratio of propionic acid to acetic acid concentration in the system is less than 0.28, indicating that the volatile organic acid components are balanced and there is no risk of acidification imbalance. Third, the total alkalinity of the fermentation system is consistently higher than 2,200 mg / L of calcium carbonate, which has sufficient acid-base buffering capacity and can resist the shock stress caused by the accumulation of salt and organic acids. The three indicators work together to verify that the bacteria have adapted to the current salinity environment, the microbial community structure is stable, the anti-interference ability meets the standard, and it can be transferred to the normal load operation stage.

[0008] As a further preferred embodiment of the present invention, in step S3, the iron-containing biochar modified with calcium hydroxide saturation has multiple synergistic effects. The iron-containing biochar modified with calcium hydroxide saturation has multiple synergistic effects. Relying on its own well-developed porous structure, it efficiently adsorbs free sodium ions and toxic long-chain fatty acids in the fermentation liquid phase, directly reducing the effective concentration of toxic substances in the system. The calcium ions loaded on the carbon body can be slowly and continuously released to replace the excess sodium ions adsorbed on the surface of microbial cells, repair the osmotic pressure balance of cell membranes, alleviate the damage to cell metabolism caused by high salt stress, and the iron component in the carbon matrix can be stably dissolved to supply iron-based trace elements for the synthesis of key methanogenic enzymes, enhance the physiological activity of methanogenic bacteria and the efficiency of organic matter degradation and conversion, and stabilize the operation of the anaerobic fermentation system through multiple pathways.

[0009] As a further preferred embodiment of the present invention, in step S4, when the outdoor ambient temperature drops to minus five degrees Celsius or below, it is strictly prohibited to open the tank for maintenance and feeding operations without necessity or routine procedures. This is to minimize the loss of heat stored in the tank and prevent the sudden drop in temperature from disturbing the metabolic activity of methanogenic bacteria. In conjunction with the 130 mm thick polyurethane insulation layer of the tank, the electric heating of the entire pipeline, and the biogas waste heat circulation heating system, multiple insulation barriers are formed to lock in a constant temperature environment inside the tank and ensure that the temperature of the fermentation system is stable and controllable under extremely cold and low temperature conditions.

[0010] As a further preferred embodiment of the present invention, in step S5, when the concentration of volatile fatty acids in the system is in the range of 800 to 1400 mg / L with slight excess, the organic load is immediately reduced by 50%, and the amount of biogas slurry returned to dilute the acidic substances. Modified biochar is added to adsorb organic acids and free sodium ions. The acid-base balance is gradually restored by relying on the carbon-based buffer system. If a severe inhibition phenomenon of a sharp drop in gas production occurs, the feeding operation is completely suspended immediately. About one-third of the high-acid and high-salt fermentation waste liquid in the tank is extracted, and preheated and conditioned fresh substrate slurry and mature salt-tolerant anaerobic sludge are added to the tank. The value of volatile fatty acids in the liquid phase is continuously monitored until the concentration of volatile fatty acids drops below 500 mg / L and the buffer performance of the system is restored to stability. Then, the feeding is slowly restored with a very small amount of feed to prevent secondary acidification shock.

[0011] The anaerobic fermentation stabilization control method of the present invention adapted to high-salt kitchen waste in northern regions has the following advantages: 1. This method for stabilizing and controlling anaerobic fermentation of high-salt kitchen waste in northern China involves a revolutionary improvement and innovation in the pretreatment stage. It completely abandons the traditional, crude salt reduction model of simply soaking and washing with clean water. Instead, it innovatively constructs a synergistic composite salt reduction process system of two-stage countercurrent washing with preheated warm water and porous solid-phase adsorption with straw. Through the synergistic effects of graded washing, solid-phase adsorption to retain salt, and biogas slurry reflux conditioning, a single process simultaneously achieves three core effects: salt reduction, reduced clean water consumption, and precise control of the carbon-nitrogen ratio of the fermentation substrate. Compared with conventional pure water washing processes, the overall water saving rate can reach more than 40%. It not only significantly reduces the clean water consumption and high-salt washing wastewater generation in the front-end washing process, but also relies on the organic matter of straw to balance the high-protein components of kitchen waste, alleviating the risk of free ammonia inhibition caused by high protein decomposition from the source of the substrate. This fundamentally solves the industry problems of high water consumption and frequent outbreaks of ammonia inhibition in the subsequent fermentation process caused by traditional washing processes. 2. This method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern China innovates the cultivation of low-temperature salt-tolerant microbial communities in its inoculation and acclimatization system. It abandons the conventional method of simply adding municipal digested sludge, instead constructing a composite seed mud substrate of mature municipal anaerobic digested sludge and saline-alkali wetland sediment. An additional halophilic methanogenic compound microbial agent is added to enhance the functional microbial community base. Taking into full account the regional characteristics of large temperature differences between winter and summer in northern China and the decreased metabolic activity of microorganisms in low-temperature environments, a seasonally differentiated, stepped salt-increasing acclimatization rate control strategy is formulated. The rate of salt increase is slowed down in the low-temperature winter and moderately accelerated in the mid-temperature summer. This precisely matches the proliferation and growth patterns of salt-tolerant archaea and fermentation microorganisms under different temperature conditions. Compared with the traditional single-sludge uniform-rate salt-increasing acclimatization mode, the overall microbial acclimatization cycle is shortened by 20%, the upper limit of the system's steady-state tolerance to sodium ion concentration is significantly increased, the overall salt-bearing capacity is greatly improved, and the stability of the microbial community against salt shock under low-temperature conditions is significantly enhanced. 3. This method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern China is a pioneering system that uses calcium-modified iron-containing biochar coupled with a low-sodium composite alkali for synergistic regulation. This system completely replaces the traditional anaerobic process that relies solely on strong alkalis such as sodium hydroxide to neutralize acidity, thus eliminating the problem of cumulative salt toxicity caused by the continuous input of exogenous sodium ions during conventional alkali adjustment. This improved system relies on the synergistic effect of multifunctional modified biochar and composite alkaline agents to construct a multi-level, multi-dimensional salt toxicity mitigation system. It utilizes the porous structure of modified biochar to efficiently adsorb free sodium ions and toxic long-chain fatty acids within the fermentation system, reducing the effective toxic concentration in the liquid phase. Calcium ions loaded on biochar continuously and slowly replace excess sodium ions adsorbed on the surface of microorganisms, restoring the osmotic pressure balance of cell membranes. Iron elements immobilized on biochar, along with a supporting micronutrient system, replenish the metal ions required for key coenzymes in methanogenesis, repairing the metabolic activity of damaged microbial communities under high salt stress. Through multiple mechanisms, it weakens high salt toxicity in a stratified and stepwise manner, stabilizing the system's acid-base buffering capacity. While ensuring the long-term stability and high efficiency of the anaerobic system against salt shocks, it significantly reduces the dosage of strong alkaline agents, lowering the overall agent consumption by 35% compared to traditional single-alkali adjustment processes, effectively reducing engineering operating costs. Simultaneously, it significantly improves the survival and methanogenesis performance of anaerobic communities under high salt conditions. 4. This invention presents a stable anaerobic fermentation control method adapted to high-salt kitchen waste in northern regions. It features an innovative temperature control and load linkage mechanism specifically designed for northern areas. Addressing the shortcomings of northern regions with low winter temperatures, large diurnal temperature variations, rapid tank temperature drops, and strong salinity-temperature coupling inhibition, this invention innovatively constructs a closed-loop constant-temperature insulation system for biogas waste heat and a three-dimensional dynamic matching and control model for temperature, salinity, and organic load. This completely abandons the traditional extensive operation mode of fixed temperature and fixed load. Through thickened tank insulation, full-process pipeline heating, feedforward preheating, and intermittent low-heat dissipation stirring, this invention constructs an ultra-low-loss waste heat closed-loop temperature control system, achieving near-zero temperature fluctuation inside the tank under low-temperature winter conditions. The system achieves stable operation by eliminating the inhibitory impact of low-temperature disturbances on methanogenic bacteria metabolism. Simultaneously, it dynamically matches organic load and HRT based on real-time monitoring of tank temperature, sodium ion concentration, and organic acid accumulation. It intelligently and adaptively adjusts the feed load according to the intensity of salt toxicity stress and temperature levels, precisely avoiding core risks such as volatile fatty acid accumulation and system acidification collapse caused by overloading under low-temperature, high-salt coupling conditions. This effectively weakens the unique salt-temperature synergistic inhibitory effect in northern winters, greatly improving the operational stability and continuous gas production stability of the anaerobic system during cold seasons. It solves the technical problems of traditional processes, such as sharp drops in gas production, large operational fluctuations, and easy system instability in winter. 5. This method for stabilizing and controlling anaerobic fermentation of high-salt food waste in northern regions is an innovative approach adapted to ultra-high salinity conditions. Addressing the extreme treatment conditions in some northern catering clusters where the primary sodium ion concentration of food waste exceeds standards and the single-tank system's tolerance is insufficient, it adds an additional backup control mode of acidification hydrolysis and methanogenesis-based two-phase synergistic fermentation. This breaks away from the traditional framework of a single-tank integrated fermentation process. High-salt food waste is first fed into an acidification hydrolysis tank with higher toxicity tolerance for macromolecular hydrolysis and acidification reactions. The acidification tank can withstand ultra-high salinity environments of 12-15 grams per liter at low temperatures. Stable operation ensures that high-salt solid residue is retained in the acidification unit, while only the acidified liquid with significantly reduced toxicity is transported to the methanogenic main tank for fermentation. This achieves segmented diversion and isolation of inhibitory toxins such as salt, long-chain fatty acids, and ammonia nitrogen. By relying on the functional division of units and the zoned handling of toxins, it breaks through the salt tolerance limit of traditional single-tank anaerobic fermentation, significantly reducing the salt stress pressure on the main fermentation tank. It perfectly adapts to the actual engineering needs of large-scale stable treatment of ultra-high salinity kitchen waste in northern regions, broadens the range of applicable raw materials for the entire process, and significantly enhances the fault tolerance to the impact of extremely high salinity feed. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0014] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0015] In the description of the embodiments of the present invention, it should be understood that the terms "length", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0017] In the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0018] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0019] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, provides a method for stabilizing and controlling anaerobic fermentation of high-salt kitchen waste in northern regions.

[0020] like Figure 1 As shown, the present invention provides a method for stabilizing anaerobic fermentation of high-salt kitchen waste in northern regions, comprising: The usage methods are as follows: S1, Screening: A multi-stage synergistic conditioning and salt reduction pretreatment process is adopted to crush the high-salt kitchen waste from the north to a particle size of 5 to 8 mm, screen out hard debris such as bones and plastics, and implement a two-stage countercurrent washing process using preheated warm water in winter. The first stage uses 22-degree Celsius warm water for short-term stirring and coarse washing to filter out high-salt soup and surface oil. The second stage selects corn stalks or fruit and vegetable waste as adsorbents and mixes them with kitchen waste at a volatile solids mass ratio of 4:6. The porous structure of the straw adsorbs free sodium ions in the material. The mixture is then subjected to screw extrusion to complete solid-liquid phase conditioning and separation. The sodium ion concentration of the solid filtrate after extrusion is controlled to be less than 7 grams per liter. The fermentation slurry conditioning medium is reflux biogas slurry, and the biogas slurry reflux volume ratio is set to 0.6:1. S2, Salt-Tolerant Composite Microbial Community Stepped Low-Temperature Acclimation: The salt-tolerant composite microbial community stepped low-temperature acclimation process is implemented: 85% municipal mature anaerobic digested sludge by volume is mixed with 15% saline-alkali wetland bottom mud to form a composite inoculated sludge. The total volatile solids of the inoculated sludge account for 35% of the total volatile solids in the fermenter. At the same time, 0.8% salt-tolerant methanogenic composite microbial agent is added to enhance the functional microbial community. The salt increase rate is divided according to the temperature inside the tank. Under the standard medium temperature operation condition of 35 degrees Celsius, the sodium ion concentration of the system is increased by 1 gram per liter every seven days. Under the low temperature operation condition of 28 to 32 degrees Celsius in winter, the acclimation rate is slowed down, and the sodium ion concentration is increased by only 0.6 grams per liter every twelve days. The gradient acclimation continues until the fermentation system can stably bear 10 to 12 grams per liter. S3, modified biochar composite buffering and toxicity control, is produced by mixing sawdust and iron mud and then pyrolyzing them at 900 degrees Celsius to obtain iron-containing biochar. It is then saturated and modified by impregnation with calcium hydroxide solution. The initial addition of modified biochar is 6% of the total volatile solids mass of the fermenter. Subsequently, fresh modified biochar is added monthly at a ratio of 1.5% of the total volatile solids in the tank. The acid-base buffering system uses a compound alkali agent with calcium hydroxide as the main component and sodium bicarbonate as the auxiliary component. The exogenous sodium ions introduced by the process are strictly controlled. The total alkalinity of the fermentation system is maintained at no less than 2,200 mg / L of calcium carbonate throughout the process, and the pH is controlled in the stable range of 6.9 to 7.4. S4 is a waste heat closed-loop low-temperature constant temperature control system. The tank body is covered with a 130 mm thick polyurethane insulation layer, and all material pipelines are fully covered with an electric heat tracing insulation structure. It uses a biogas waste heat boiler with coil circulation heating to keep the core temperature of the fermentation tank constant at 35 ± 0.5 degrees Celsius. The heating power is pre-adjusted four minutes before the feeding operation starts to offset the impact of the temperature drop in the tank caused by the low temperature of the incoming material. The temperature fluctuation of the tank is strictly controlled to be no more than ± 1 degree Celsius during the day and night. The stirring system implements an intermittent low-speed operation system, stirring at low speed for 15 minutes every two hours to reduce the heat loss of the tank. In the event of extremely cold weather, it switches to a 24-hour continuous micro-flow stable feeding mode to avoid drastic temperature fluctuations caused by a large batch of cold material entering the tank. S5 features three-dimensional adaptive regulation of temperature and salinity load. It dynamically matches and adapts organic load parameters based on real-time tank temperature, sodium ion concentration, and on-site operating conditions. When the sodium ion concentration is less than 7 g / L and the tank temperature is not lower than 34 degrees Celsius, the organic load rate is set to 2.0 to 2.4 kg volatile solids per cubic meter per day, with a hydraulic retention time of 22 days. When the sodium ion concentration is between 7 and 10 g / L and the tank temperature is maintained between 30 and 34 degrees Celsius, the organic load rate is adjusted to 1.3 to 1.7 kg volatile solids per cubic meter per day, with a hydraulic retention time of 28 days. Under the harsh conditions of sodium ion concentration reaching 10 to 12 g / L and tank temperature below 30 degrees Celsius, the organic load rate is strictly controlled at 0.9 kg volatile solids. S6, high-salt two-phase diversion and synergistic fermentation regulation: if the original sodium ion concentration of the incoming kitchen waste is higher than 12 grams per liter, the acidification and methanogenesis two-phase fermentation operation mode is switched. The acidification hydrolysis tank can withstand a high salt environment of 12 to 15 grams per liter and stably complete the hydrolysis of organic macromolecules and acid production reaction at a low temperature of 30 degrees Celsius. The high-salt solid residue is retained in the acidification unit, and only the acidified clear liquid with a large number of inhibitory components removed is transported to the methanogenesis main tank, thereby ensuring that the sodium ion concentration in the methanogenesis main tank is stably controlled within 10 grams per liter for long-term stable operation.

[0021] In step S1, corn stalks or vegetable scraps are mixed with kitchen waste according to the volatile solids ratio to adjust the anaerobic fermentation substrate carbon-nitrogen ratio to the optimal range of 22 to 26:1. This dilutes and reduces the salt load of the system and balances the high-protein matrix structure of kitchen waste. It weakens the synergistic inhibitory effect of the high-salt environment and the free ammonia generated by the decomposition of high protein from the substrate source, creating a suitable substrate environment for the stable proliferation and metabolism of functional microorganisms.

[0022] In step S2, a clear acclimatization qualification assessment index system is established. Acclimatization can be determined to be complete only when the system simultaneously meets three continuous monitoring conditions. First, the biogas production fluctuation range is stable at less than 8% within three consecutive hydraulic retention time cycles, reflecting a stable metabolic state of the methanogenic bacteria. Second, the ratio of propionic acid to acetic acid concentration in the system is lower than 0.28, indicating a balanced volatile organic acid composition and no potential acidification imbalance. Third, the total alkalinity of the fermentation system is consistently higher than 2,200 mg / L of calcium carbonate, possessing sufficient acid-base buffering capacity to resist the shock stress caused by the accumulation of salt and organic acids. The three indicators work together to verify that the bacteria have adapted to the current salinity environment, the microbial community structure is stable, and the anti-interference ability meets the standards, allowing it to enter the normalized load operation stage.

[0023] In step S3, the iron-containing biochar modified with calcium hydroxide saturation has multiple synergistic effects. Relying on its well-developed porous structure, the iron-containing biochar can efficiently adsorb free sodium ions and toxic long-chain fatty acids in the fermentation liquid phase, directly reducing the effective concentration of toxic substances in the system. The calcium ions loaded on the char can be slowly and continuously released to replace the excess sodium ions adsorbed on the surface of microbial cells, repair the osmotic pressure balance of cell membranes, and alleviate the damage to cell metabolism caused by high salt stress. The iron component in the char matrix can be stably dissolved, providing iron-based trace elements for the synthesis of key methanogenic enzymes, enhancing the physiological activity of methanogenic bacteria and the efficiency of organic matter degradation and conversion, and stabilizing the operation of the anaerobic fermentation system through multiple pathways.

[0024] In step S4, when the outdoor ambient temperature drops to minus five degrees Celsius or below, it is strictly forbidden to open the tank for maintenance or feeding operations without due necessity or routine procedures. This is to minimize the loss of heat stored inside the tank and prevent the sudden drop in temperature from disturbing the metabolic activity of methanogenic bacteria. The tank is reinforced with a 130 mm thick polyurethane insulation layer, electric heating along the entire pipeline, and a biogas waste heat circulation heating system to form multiple insulation barriers. This comprehensively locks in a constant temperature environment inside the tank, ensuring that the fermentation system temperature is stable and controllable under extremely cold and low-temperature conditions.

[0025] In step S5, when the concentration of volatile fatty acids in the system is slightly above the standard range of 800 to 1400 mg / L, the organic load is immediately reduced by 50%, and the amount of biogas slurry returned is increased to dilute the acidic substances. Modified biochar is added to adsorb organic acids and free sodium ions. The acid-base balance is gradually restored by relying on the carbon-based buffer system. If a severe inhibition phenomenon of a sharp drop in gas production occurs, the feeding operation is completely stopped immediately. About one-third of the high-acid and high-salt fermentation waste liquid in the tank is extracted, and preheated and conditioned fresh substrate slurry and mature salt-tolerant anaerobic sludge are added to the tank. The value of volatile fatty acids in the liquid phase is continuously monitored until the concentration of volatile fatty acids drops below 500 mg / L and the buffer performance of the system is restored to stability. Then, the feeding is slowly restored in a very small gradient to prevent secondary acidification shock.

[0026] The working principle of this anaerobic fermentation stabilization control method adapted to high-salt kitchen waste in northern China is as follows: First, targeting typical high-salt kitchen waste in North China, this invention utilizes a multi-level synergistic stabilization control system. Through a complete improvement mechanism including source salt reduction and conditioning, gradient domestication of compound salt-tolerant bacteria, functional biochar buffering and detoxification, and precise matching of temperature and salt load, the long-term stable operation of anaerobic fermentation of high-salt kitchen waste is achieved. In the pretreatment stage, through precise material crushing and low-temperature preheating, two-stage countercurrent washing with warm water coupled with straw solid-phase adsorption technology, free salt and soluble high-salt broth components in the material are effectively removed without consuming a large amount of clean water. The porous adsorption characteristics of straw are used to fix residual free sodium ions. At the same time, the fermentation substrate is controlled to the optimal level through quantitative mixing of kitchen waste and straw. In the optimal anaerobic zone, the risk of ammonia inhibition caused by high salt stress and high-protein substrate is mitigated from the source, stabilizing the salt load of the incoming material to a safe fermentation range. Secondly, during the microbial acclimatization stage, salt-tolerant composite seed mud is inoculated with a gradient slow salt increase strategy. Under suitable mesophilic conditions, the system's salinity and pressure are gradually increased, inducing the targeted enrichment of functional methanogenic bacteria and completing osmotic pressure adaptation acclimatization. This significantly improves the bacteria's tolerance and metabolic stability to conventional high-salt kitchen substrates in northern regions. Subsequently, calcium-modified iron-containing biochar coupled with a low-sodium composite alkali system is added. Utilizing multiple mechanisms such as material adsorption, ion exchange, and trace element supplementation, the system continuously buffers salt toxicity, stabilizes the acid-base buffer system, ensures methanogenic enzyme activity, and effectively inhibits the accumulation of volatile fatty acids. Finally, biogas residues are used to... The thermal closed-loop constant temperature control and three-dimensional dynamic load matching mechanism maintain the fermenter temperature at extremely low fluctuations. It also matches appropriate organic load and hydraulic retention time according to the system salinity level, avoiding acidification imbalance caused by overload metabolism under high salinity conditions. After regulation by the entire improved method of this invention, the system can operate continuously and stably for more than 90 days, with gas production fluctuations controlled within 7% throughout the process. Propionic acid or acetic acid remains at an extremely low risk level of imbalance, and methane production is maintained at a high level. There are no acidification inhibition, sludge instability, or gas production collapse phenomena throughout the process. It is fully adaptable to the continuous, large-scale, and stable anaerobic fermentation treatment of conventional high-salt kitchen waste under normal temperature and low winter conditions in northern regions. However, it is suitable for the harsh conditions of extreme low temperatures and ultra-high salinity kitchen waste in Northeast China, where the original concentration is 12 to 10%. At a temperature of 4 grams per liter and as low as -8 degrees Celsius, this invention utilizes a two-phase synergistic fermentation coupled with a winter-specific low-temperature control system. This system overcomes the salt tolerance limits and low-temperature operation bottlenecks of traditional single-tank anaerobic fermentation, achieving stable operation of anaerobic fermentation under extreme high-salt and low-temperature coupled stress. This embodiment addresses the operating conditions characterized by feed salt content far exceeding conventional tolerance thresholds, significantly reduced microbial metabolic activity in winter, and extremely strong salt-temperature synergistic inhibition. It employs a modified pretreatment synergistic two-phase synergistic fermentation control mechanism. First, preheated warm water washing coupled with solid-phase adsorption of waste vegetables reduces the instantaneous high-salt shock load, lowering the fluctuation range of feed salt content. Further, a functional zoning fermentation strategy is adopted, preferentially introducing high-salt, high-impurity kitchen materials into an acidification hydrolysis tank with stronger high-salt and low-temperature tolerance.The process of hydrolysis and acidification of organic macromolecules is completed at a low temperature of 30 degrees Celsius. The acidification unit is highly tolerant to ultra-high salt toxic components while retaining high-salt solid residues. This achieves targeted diversion and isolation of inhibitory substances, allowing only the acidified liquid with significantly reduced toxicity and stable water quality to be transported to the methanogenic main tank for methanogenesis. This significantly reduces the salt stress pressure on the main fermentation system from a process perspective. In addition, a low-temperature operation and maintenance strategy specifically designed for northern winters is implemented, including full pipeline electric heating and insulation, closed-loop constant temperature control of tank waste heat, 24-hour micro-flow continuous feeding, and low-heat intermittent stirring, to completely eliminate the impact of cold materials in winter and heat loss from the tank. This invention addresses operational risks such as localized salt concentration enrichment and strictly adheres to differentiated, slow-rate salt acclimatization rules for winter low temperatures. It matches the growth and metabolic patterns of low-temperature microbial communities to ensure stable functional microbial structure. Through the modified phase-separated synergistic low-temperature regulation system of this invention, the system can operate continuously and stably under extreme low temperatures and ultra-high salt conditions in northern winters. Winter gas production decline can be controlled to within 8%. The system exhibits no abnormal accumulation of volatile fatty acids, pH fluctuations, or microbial instability. Methane production remains high and stable. This significantly broadens the adaptability of this process to extremely high-salt, low-temperature food waste in northern regions, and significantly improves the system's resistance to extreme operating conditions and its engineering versatility. The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0027] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions, characterized in that, Including control methods: S1, Screening: A multi-stage synergistic conditioning and salt reduction pretreatment process is adopted to crush the high-salt kitchen waste from the north to a particle size of 5 to 8 mm, screen out hard debris such as bones and plastics, and implement a two-stage countercurrent washing process using preheated warm water in winter. The first stage uses 22-degree Celsius warm water for short-term stirring and coarse washing to filter out high-salt soup and surface oil. The second stage selects corn stalks or fruit and vegetable waste as adsorbents and mixes them with kitchen waste at a volatile solids mass ratio of 4:

6. The porous structure of the straw adsorbs free sodium ions in the material. The mixture is then subjected to screw extrusion to complete solid-liquid phase conditioning and separation. The sodium ion concentration of the solid filtrate after extrusion is controlled to be less than 7 grams per liter. The fermentation slurry conditioning medium is reflux biogas slurry, and the biogas slurry reflux volume ratio is set to 0.6:

1. S2, Salt-Tolerant Composite Microbial Community Stepped Low-Temperature Acclimation: The salt-tolerant composite microbial community stepped low-temperature acclimation process is implemented: 85% municipal mature anaerobic digested sludge by volume is mixed with 15% saline-alkali wetland bottom mud to form a composite inoculated sludge. The total volatile solids of the inoculated sludge account for 35% of the total volatile solids in the fermenter. At the same time, 0.8% salt-tolerant methanogenic composite microbial agent is added to enhance the functional microbial community. The salt increase rate is divided according to the temperature inside the tank. Under the standard medium temperature operation condition of 35 degrees Celsius, the sodium ion concentration of the system is increased by 1 gram per liter every seven days. Under the low temperature operation condition of 28 to 32 degrees Celsius in winter, the acclimation rate is slowed down, and the sodium ion concentration is increased by only 0.6 grams per liter every twelve days. The gradient acclimation continues until the fermentation system can stably bear 10 to 12 grams per liter. S3, modified biochar composite buffering and toxicity control, is produced by mixing sawdust and iron mud and then pyrolyzing them at 900 degrees Celsius to obtain iron-containing biochar. It is then saturated and modified by impregnation with calcium hydroxide solution. The initial addition of modified biochar is 6% of the total volatile solids mass of the fermenter. Subsequently, fresh modified biochar is added monthly at a ratio of 1.5% of the total volatile solids in the tank. The acid-base buffering system uses a compound alkali agent with calcium hydroxide as the main component and sodium bicarbonate as the auxiliary component. The exogenous sodium ions introduced by the process are strictly controlled. The total alkalinity of the fermentation system is maintained at no less than 2,200 mg / L of calcium carbonate throughout the process, and the pH is controlled in the stable range of 6.9 to 7.

4. S4 is a waste heat closed-loop low-temperature constant temperature control system. The tank body is covered with a 130 mm thick polyurethane insulation layer, and all material pipelines are fully covered with an electric heat tracing insulation structure. It uses a biogas waste heat boiler with coil circulation heating to keep the core temperature of the fermentation tank constant at 35 ± 0.5 degrees Celsius. The heating power is pre-adjusted four minutes before the feeding operation starts to offset the impact of the temperature drop in the tank caused by the low temperature of the incoming material. The temperature fluctuation of the tank is strictly controlled to be no more than ± 1 degree Celsius during the day and night. The stirring system implements an intermittent low-speed operation system, stirring at low speed for 15 minutes every two hours to reduce the heat loss of the tank. In the event of extremely cold weather, it switches to a 24-hour continuous micro-flow stable feeding mode to avoid drastic temperature fluctuations caused by a large batch of cold material entering the tank. S5 features three-dimensional adaptive regulation of temperature and salinity load. It dynamically matches and adapts organic load parameters based on real-time tank temperature, sodium ion concentration, and on-site operating conditions. When the sodium ion concentration is less than 7 g / L and the tank temperature is not lower than 34 degrees Celsius, the organic load rate is set to 2.0 to 2.4 kg volatile solids per cubic meter per day, with a hydraulic retention time of 22 days. When the sodium ion concentration is between 7 and 10 g / L and the tank temperature is maintained between 30 and 34 degrees Celsius, the organic load rate is adjusted to 1.3 to 1.7 kg volatile solids per cubic meter per day, with a hydraulic retention time of 28 days. Under the harsh conditions of sodium ion concentration reaching 10 to 12 g / L and tank temperature below 30 degrees Celsius, the organic load rate is strictly controlled at 0.9 kg volatile solids. S6, high-salt two-phase diversion and synergistic fermentation regulation: if the original sodium ion concentration of the incoming kitchen waste is higher than 12 grams per liter, the acidification and methanogenesis two-phase fermentation operation mode is switched. The acidification hydrolysis tank can withstand a high salt environment of 12 to 15 grams per liter and stably complete the hydrolysis of organic macromolecules and acid production reaction at a low temperature of 30 degrees Celsius. The high-salt solid residue is retained in the acidification unit, and only the acidified clear liquid with a large number of inhibitory components removed is transported to the methanogenesis main tank, thereby ensuring that the sodium ion concentration in the methanogenesis main tank is stably controlled within 10 grams per liter for long-term stable operation.

2. The method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions according to claim 1, characterized in that, The operation steps include the following: In step S1, the multi-stage synergistic conditioning and salt reduction pretreatment process involves mixing corn stalks or vegetable waste with kitchen waste according to the volatile solids ratio to precisely control the carbon-nitrogen ratio of the fermentation substrate to the optimal range of 22 to 26:1 for anaerobic fermentation. This process dilutes and reduces the salt load of the system while balancing the high-protein matrix structure of the kitchen waste. It weakens the synergistic inhibitory effect of the high-salt environment and the free ammonia generated by the decomposition of high protein from the substrate source, creating a suitable substrate environment for the stable proliferation and metabolism of subsequent functional microorganisms.

3. The method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions according to claim 1, characterized in that, In step S2, a clear acclimatization qualification assessment index system is established. Acclimatization can be determined to be complete only when the system simultaneously meets three continuous monitoring conditions. First, the biogas production fluctuation range is stable at less than 8% within three consecutive hydraulic retention time cycles, reflecting a stable metabolic state of the methanogenic bacteria. Second, the ratio of propionic acid to acetic acid concentration in the system is lower than 0.28, indicating a balanced volatile organic acid composition and no potential acidification imbalance. Third, the total alkalinity of the fermentation system is consistently higher than 2,200 mg / L of calcium carbonate, possessing sufficient acid-base buffering capacity to resist the shock stress caused by the accumulation of salt and organic acids. The three indicators work together to verify that the bacteria have adapted to the current salinity environment, the microbial community structure is stable, and the anti-interference ability meets the standards, allowing it to enter the normalized load operation stage.

4. The method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions according to claim 1, characterized in that, In step S3, the iron-containing biochar modified with calcium hydroxide saturation has multiple synergistic effects. Relying on its well-developed porous structure, it efficiently adsorbs free sodium ions and toxic long-chain fatty acids in the fermentation liquid, directly reducing the effective concentration of toxic substances in the system. The calcium ions loaded on the char can be slowly and continuously released to replace the excess sodium ions adsorbed on the surface of microbial cells, repair the osmotic pressure balance of cell membranes, and alleviate the damage to cell metabolism caused by high salt stress. The iron component in the char matrix can be stably dissolved, providing iron-based trace elements for the synthesis of key methanogenic enzymes, enhancing the physiological activity of methanogenic bacteria and the efficiency of organic matter degradation and conversion, and stabilizing the operation of the anaerobic fermentation system through multiple pathways.

5. The method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions according to claim 1, characterized in that, In step S4, when the outdoor ambient temperature drops to minus five degrees Celsius or below, it is strictly forbidden to open the tank for maintenance or feeding operations without due necessity or routine procedures. This is to minimize the loss of heat stored inside the tank and prevent the sudden drop in temperature from disturbing the metabolic activity of methanogenic bacteria. The tank is reinforced with a 130 mm thick polyurethane insulation layer, electric heating along the entire pipeline, and a biogas waste heat circulation heating system to form multiple insulation barriers. This comprehensively locks in a constant temperature environment inside the tank, ensuring that the fermentation system temperature is stable and controllable under extremely cold and low-temperature conditions.

6. The method for stabilizing and regulating anaerobic fermentation of high-salt kitchen waste in northern regions according to claim 1, characterized in that, In step S5, when the concentration of volatile fatty acids in the system is slightly above the standard range of 800 to 1400 mg / L, the organic load is immediately reduced by 50%, and the amount of biogas slurry returned is increased to dilute the acidic substances. Modified biochar is added to adsorb organic acids and free sodium ions. The acid-base balance is gradually restored by relying on the carbon-based buffer system. If a severe inhibition phenomenon of a sharp drop in gas production occurs, the feeding operation is completely stopped immediately. About one-third of the high-acid and high-salt fermentation waste liquid in the tank is extracted, and preheated and conditioned fresh substrate slurry and mature salt-tolerant anaerobic sludge are added to the tank. The value of volatile fatty acids in the liquid phase is continuously monitored until the concentration of volatile fatty acids drops below 500 mg / L and the buffer performance of the system is restored to stability. Then, the feeding is slowly restored in a very small gradient to prevent secondary acidification shock.

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