A microbial gel culture medium, its preparation method and application

Abstract

The present application belongs to the kitchen garbage treatment technical field, and particularly relates to a microbial gel culture medium and a preparation method and application thereof. The preparation method of the microbial gel culture medium comprises the following steps: (1) sorting, crushing, homogenizing and hydrolyzing the resident kitchen garbage to obtain a base solution; (2) adding agar powder in the base solution according to a proportion of 1.5-2 wt%, heating to 90-100 DEG C until the agar is completely dissolved; adjusting the pH value of the solution to 7.2-7.4, then cooling, shaping, sterilizing to obtain the microbial gel culture medium; wherein the step of hydrolysis is: adding water in the homogenized solution, stirring for 10-20 min to obtain the base solution; the water content of the base solution is 70-80%. The treatment process of the present application does not cause fermentation, and does not cause secondary pollution problems of the environment; the treatment process has low cost. Compared with the current anaerobic digestion and aerobic composting resource technology, the present application has more environmental protection advantages.

Description

Technical Field

[0001] This invention belongs to the field of kitchen waste treatment technology, specifically relating to a microbial gel culture medium, its preparation method, and its application. Background Technology

[0002] The study by Yang Na et al., "Comparative Analysis of the Physicochemical Properties of Household Kitchen Waste and Food Waste in my country—The Impact of Source Classification," points out that kitchen waste can be divided into food waste and household kitchen waste according to their location of generation. The former, originating from restaurants, canteens, and other commercial establishments, is mainly "post-meal waste" generated during meals, with a higher content of "cooked food." Years of exploration have led to a mature management model. The latter, originating from residential households, is mainly "pre-meal waste" generated during food preparation, with a higher content of "raw food." It consists of leftover food, fruit peels, eggshells, tea dregs, animal offal, Chinese medicine residue, bones (chicken bones, fish bones, etc.), etc. Its main components are starch, protein, cellulose, lipids, inorganic salts, and a small amount of minerals. It is a new type of organic waste that emerged after the implementation of the mandatory household waste classification system in 2019. Due to differences in their location and generation methods, the two types of kitchen waste exhibit significant differences in their physicochemical properties, including density, salt content, fat content, and heavy metal content. Figure 1 As shown.

[0003] Since the pilot program for the resource utilization and harmless treatment of kitchen waste was launched in 2010, in order to prevent "swill oil" from returning to the dining table and the occurrence of "swine fever," the state has successively issued the "Opinions on Strengthening the Management of Swill Oil and Kitchen Waste" (State Council Document No. 36

[2010] ) and the "Notice on Organizing and Carrying Out Pilot Work on the Resource Utilization and Harmless Treatment of Urban Kitchen Waste" (National Development and Reform Commission Document No. 1020

[2010] ). The government has supervised and strictly enforced the entire process of kitchen waste classification, collection, and treatment. All of the above indicate that kitchen waste and food waste differ in terms of source, physicochemical properties, composition, treatment technology, and management policies. They belong to different categories, and the relevant experience in the treatment technology and management path of kitchen waste is not applicable to the treatment of household food waste.

[0004] Household kitchen waste is a major component of household waste, accounting for as much as 40-60%. It has both resource value and pollution value, and whether it can be effectively treated is the key to the effectiveness of reducing household waste at the source and utilizing resources.

[0005] Existing technology CN 119432932 A provides a method for preparing a carbon source from kitchen waste. First, kitchen waste and fermentation wastewater are mixed for fermentation pretreatment, followed by hydrolysis and acidification. Alkali pretreatment increases the proportion of volatile organic compounds (VFAs) in the total dissolved oxygen (SCOD) of the fermentation broth. Heating pretreatment increases the total SCOD and C / N ratio. Enzyme pretreatment increases the total VFAs, thereby improving the quality of the prepared carbon source. Results show that the carbon source prepared by this invention has a VFAs / SCOD value between 0.24 and 0.4, with a high VFAs content, classifying it as a high-performance liquid carbon source product.

[0006] Existing technology CN 119932120 A provides a method for preparing a composite carbon source through two-phase fermentation of kitchen waste, comprising: crushing and screening the kitchen waste to select target waste; performing a primary fermentation on the target waste to obtain a first fermentation product; performing solid-liquid separation on the first fermentation product to obtain a fermentation broth; performing a secondary fermentation on the fermentation broth to obtain a second fermentation product; and performing ultrafiltration separation on the second fermentation product to obtain a filtrate and a concentrate, wherein the filtrate is the prepared composite liquid carbon source. The above-mentioned method for preparing a composite carbon source through two-phase fermentation of kitchen waste reduces the cost and energy consumption of carbon source preparation; it also improves mass and heat transfer efficiency and reaction efficiency, thereby increasing the yield of the composite carbon source.

[0007] However, both of the aforementioned existing technologies involve fermentation processes in the treatment of kitchen waste. Regardless of whether it is anaerobic or aerobic fermentation, the fermentation process and the non-fermentation process are two main metabolic modes in microbial culture. They differ significantly in metabolic mechanisms, culture conditions, and ATP production. The differences between the two are as follows: Summary of the Invention

[0008] The purpose of this invention is to provide a microbial gel culture medium using residential kitchen waste as raw material, its preparation method, and its application in wastewater treatment.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a microbial gel culture medium includes the following steps:

[0011] (1) Sorting, crushing, homogenizing and hydrolyzing residential kitchen waste to obtain a base liquid;

[0012] (2) Add agar powder to the base solution at a ratio of 1.5-2wt%, heat to 90-100℃ until the agar is completely dissolved; adjust the pH of the solution to 7.2-7.4, then cool, set, and sterilize to obtain microbial gel culture medium;

[0013] The hydrolysis step is as follows: water is added to the homogenized solution and stirred for 10-20 minutes to obtain the base solution;

[0014] The base fluid has a water content of 70-80%;

[0015] By weight, residential kitchen waste consists of 60-70 parts water, 20-30 parts organic matter, and 10-15 parts impurities.

[0016] In one preferred embodiment, on a dry basis, by weight, residential kitchen waste includes 76.2-87.4 parts organic matter, 40-45 parts carbohydrates, 6-12.3 parts fat, and 12-19.3 parts protein.

[0017] The pH of the solution is 7.2-7.4, which provides an optimal growth environment for microorganisms in the solution.

[0018] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0019] In one preferred embodiment, sorting is performed using equipment to remove non-organic matter and plastics from kitchen waste, and manual intervention may be necessary to ensure that the purity of biological organic matter in kitchen waste is >98%.

[0020] In one preferred embodiment, the device is a magnetic separator or a vibrating screen to remove metals and impurities.

[0021] In one preferred embodiment, the particle size of the crushed particles is ≤10mm.

[0022] If the particle size is too large, the specific surface area will be reduced, which will prevent microorganisms or enzymes from fully contacting the interior of the organic matter and reduce the reaction rate.

[0023] In one preferred embodiment, the crushing equipment used is a twin-shaft crusher.

[0024] In one preferred embodiment, the crushed particles are ground, and the particle size of the ground particles is ≤1mm.

[0025] In one preferred embodiment, the homogenization step is as follows: homogenize in a homogenization container at 25-30 rpm for 10-30 min.

[0026] In one preferred embodiment, the homogenizing container is a twin-shaft crusher.

[0027] In one preferred embodiment, the hydrolysis temperature is 10-40°C and the pH value is 5.8-8.5.

[0028] In one preferred embodiment, the stirring speed during hydrolysis is 100-300 rpm.

[0029] During hydrolysis, if the water content of the system is lower than 70-80%, water needs to be added to ensure that the water content of the base solution meets the requirements.

[0030] In one preferred embodiment, shaping is achieved by extruding the microbial gel culture medium into spherical shapes of a specific size using an extrusion method.

[0031] In one preferred embodiment, the diameter of the sphere is one or more of the following: SΦ2mm, SΦ4mm, SΦ6mm, SΦ8mm, and SΦ10mm.

[0032] Based on the unified inventive concept, the present invention also claims protection for the microbial gel culture medium prepared by the said preparation method.

[0033] In one preferred embodiment, the microbial gel culture medium contains, by weight, 1-1.5 parts sugars; 0.5-1 parts nitrogen and vitamins; 0.5 parts inorganic salts; and 96-98 parts water.

[0034] Based on the unified inventive concept, the present invention also claims protection for the application of the microbial gel culture medium in wastewater treatment.

[0035] In one preferred embodiment, wastewater treatment is carried out in a wastewater treatment system.

[0036] In one preferred embodiment, the wastewater treatment system includes an inlet tank, an anaerobic tank, an anoxic tank, an aerobic tank, and a secondary sedimentation tank connected in sequence; the aerobic tank has two outlets, the first outlet being connected to the secondary sedimentation tank and the second outlet being connected to the anoxic tank; the secondary sedimentation tank has a return outlet, which is connected to the inlet tank.

[0037] The recyclable sludge from the secondary sedimentation tank is returned to the inlet tank for reuse through the return outlet.

[0038] The mixed liquor from the aerobic tank is transported to the anoxic tank for reuse through the second outlet.

[0039] In one preferred embodiment, the secondary sedimentation tank is provided with an outlet for water and an outlet for sludge. The treated water is discharged through the outlet for water and the sludge is discharged through the outlet for sludge.

[0040] In one preferred embodiment, the microbial gel culture medium is placed in the anoxic tank of the wastewater treatment system.

[0041] Therefore, the following attempts to further explain the present invention:

[0042] The wastewater treatment microbial culture medium (gel) of this invention is prepared using household kitchen waste as raw material. Its innovation lies in:

[0043] 1. Provides nutrient sources, increasing the nutrient content of microorganisms in traditional wastewater treatment.

[0044] ① Carbon and nitrogen sources: Kitchen waste contains abundant fermentable sugars (such as glucose and xylose) and amino acids, which can serve as carbon and nitrogen sources for microorganisms.

[0045] ②Inorganic salts and trace elements: Kitchen waste contains minerals such as potassium, phosphorus, and magnesium, which provide essential inorganic nutrients for microorganisms.

[0046] ③ Growth factors: Kitchen waste contains natural vitamins, hormones, etc., which can promote the proliferation and differentiation of microbial cells.

[0047] 2. Optimize the physical structure of the culture medium to promote microbial growth.

[0048] ① Air permeability and anti-caking: The specific gravity of the microbial culture medium (gel) is slightly greater than 1, and it generally suspends and settles at the bottom of the sewage treatment tank. This improves the air permeability of the culture medium and avoids the substrate caking problem in traditional solid-state fermentation, thereby promoting the formation of microbial spores (such as *Cladosporium javanica*) and increasing the spore production to 5.98 × 10⁻⁶. 10 Spores / g.

[0049] ② Humidity and pH buffering: The wastewater treatment microbial culture medium (gel) prepared from kitchen waste has good water retention and pH buffering capacity, which helps to maintain a stable culture environment for wastewater treatment microorganisms.

[0050] 3. Achieve resource recycling and reduce costs.

[0051] Alternative to non-renewable resources: Kitchen waste can replace non-renewable substrates such as peat and perlite, reducing the cost of cultivating microorganisms for wastewater treatment, achieving resource recycling and reducing the pressure on municipal solid waste disposal.

[0052] Kitchen waste can be used to prepare microbial culture medium (gel) for wastewater treatment without the need for chemical pretreatment, which is in line with the trend of green production.

[0053] 4. Supports the microbial reproduction process in wastewater treatment scenarios.

[0054] Wastewater treatment microbial culture medium (gel) uses kitchen waste as raw material to provide physical support and nutrition, promoting the development and reproduction of microorganisms.

[0055] 5. Environmental Protection and Sustainable Development

[0056] ① Reduce carbon emissions: The use of kitchen waste as raw material reduces reliance on waste incineration, while reducing greenhouse gas emissions through microbial carbon sequestration.

[0057] ② Biodegradability: The biodegradability of natural carriers such as kitchen waste avoids the environmental pollution problems of traditional inert carriers (such as polyurethane).

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] 1. Using household kitchen waste to prepare sewage treatment microbial culture medium (gel) is an on-site source reduction treatment, which reduces various links in the centralized transportation of kitchen waste, greatly reduces the cost of domestic waste treatment, and is in line with the concept of green and sustainable development.

[0060] 2. During anaerobic fermentation, microorganisms decompose some organic matter into biogas (mainly composed of CH4 and CO2), which is then lost. Therefore, the fermentation process leads to a decrease in the absolute amount of total carbon.

[0061] 3. The processing of this invention does not involve fermentation, thus avoiding secondary environmental pollution; there is no wastewater discharge during the processing; the processing does not involve drying, saving energy and reducing processing costs.

[0062] 4. The wastewater treatment microbial culture medium (gel) of the present invention has application scenarios covering multiple fields such as wastewater treatment, bioenergy, agriculture, and environmental protection. Compared with the current resource utilization technologies of anaerobic digestion and aerobic composting, it has more environmental protection advantages.

[0063] 5. Liquid and powdered carbon sources have high storage requirements, are expensive, require special transportation, and are difficult to control in terms of dosage. The dosage must prevent microorganisms from over-exploding and also avoid carbon source waste due to wastewater runoff. In contrast, the gel-type wastewater treatment microbial culture medium of this application is prepared into spherical shapes of a certain size, with a fixed volume and weight. The dosage is easy to control during wastewater treatment, making it convenient to use. Furthermore, the gel-type wastewater treatment microbial culture medium releases slowly, preventing microorganisms from over-exploding and avoiding carbon source loss due to short residence time.

[0064] 6. The microbial culture medium prepared in this application is a gel, which has advantages such as high compatibility for wastewater treatment at atypical domestic sewage treatment plants, strong economic practicality, and simple management. The microbial culture medium is a gel, with a specific gravity slightly greater than 1. In water, the gel-state microbial culture medium is suspended and deposited in block, filament, and flocculent forms. Furthermore, the slow-release effect of the gel-state microbial culture medium prevents excessive microbial proliferation and avoids loss due to short retention time. This high compatibility for wastewater treatment at atypical domestic sewage treatment plants, strong economic practicality, and simple management solves the difficulties and pain points of wastewater treatment in this industry. Attached Figure Description

[0065] Figure 1 This is the basic situation of household kitchen waste in my country.

[0066] Figure 2 This is a flowchart of the process of preparing a microbial culture medium (gel) for wastewater treatment using kitchen waste.

[0067] Figure 3 This is a structural diagram of a wastewater treatment system.

[0068] Figure 4 This is a comparative diagram showing the effects of the concentration and release time of the microbial culture medium (gel) of Example 1 and Comparative Examples 1-3 on liquid sodium acetate, powdered flour carbon source, and fermentation carbon source. Detailed Implementation

[0069] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0070] The abbreviations involved in this invention are:

[0071] pH value: an indicator of the acidity or alkalinity of a solution;

[0072] VFAs: Volatile fatty acids;

[0073] ATP: Molecules that convert chemical energy from food into energy that cells can directly use;

[0074] HRT: Hydraulic Retention Time;

[0075] COD: Chemical Oxygen Demand;

[0076] BOD: Biochemical Oxygen Demand;

[0077] Eh: Oxidation-Reduction Potential;

[0078] TN: Total Nitrogen;

[0079] TP: Total Phosphorus;

[0080] MLSS: Mixed Liquor Suspended Solids.

[0081] By weight, residential kitchen waste includes 60-70 parts water, 20-30 parts organic matter, and 10-15 parts impurities; on a dry basis, it contains 76.2-87.4 parts organic matter, 40-45 parts carbohydrates, 6-12.3 parts fat, 12-19.3 parts protein, and heavy metals below the detection limit.

[0082] The main microorganisms contained in residential kitchen waste:

[0083] The main enzymes contained in household kitchen waste:

[0084] These enzymes mainly come from microorganisms (such as bacteria and fungi) and animal and plant cells in kitchen waste.

[0085] Example 1

[0086] The process of preparing wastewater treatment microbial culture medium (gel) using kitchen waste is as follows: Figure 2 As shown.

[0087] I. Collection and treatment of household kitchen waste

[0088] 1. Collection of kitchen waste: Kitchen waste such as vegetables, fruit peels, food scraps, bone fragments, eggshells, shellfish, fruit shells and pits, tea dregs, etc. are collected through a waste sorting and recycling system.

[0089] 2. Pre-treatment of kitchen waste:

[0090] ① Sorting: Use equipment such as magnetic separators and vibrating screens to remove non-organic materials such as mud, labels, and metals, as well as various plastics from kitchen waste. Manual intervention may be necessary when required to ensure that the purity of biological organic matter in kitchen waste reaches >98%.

[0091] ② Crushing: A twin-shaft crusher suitable for crushing high-moisture kitchen waste is used, which utilizes low-speed, high-torque shearing to produce small particles with a discharge size of ≤10mm.

[0092] ③ Grinding: A grinding and pulping machine is used to grind the crushed kitchen waste into a pulp of ≤1mm.

[0093] ④ Homogenization: Place the ground slurry into a homogenization container and homogenize at 25-30 rpm for 10-30 minutes. ⑤ Hydrolysis:

[0094] Add water to the homogenized solution until the water content reaches 70-80%, and stir at 100-300 rpm for 15 minutes to obtain the base solution. The hydrolysis temperature is 10-40℃, and the pH value is 5.8-8.5.

[0095] 1. pH value

[0096] If the pH value is >8.5, a large amount of acid is needed for subsequent neutralization, which not only increases the cost but also reduces the reactivity and causes the hydrolysis reaction to stop.

[0097] If the pH value is <5.8, a large amount of alkali needs to be used for neutralization, which not only increases the cost, but also inhibits the growth of microorganisms, reduces enzyme activity, and may even cause the hydrolysis reaction to stop.

[0098] Enzyme activity, microbial growth, and stability are best when the pH value is in the range of 5.8-8.5.

[0099] pH control must consider not only the optimal pH for the enzyme, but also its long-term pH stability during operation.

[0100] 2. Moisture content

[0101] When the moisture content is >80%, the reaction rate decreases, leading to microbial contamination and non-enzymatic decomposition of the substrate or product.

[0102] With a moisture content of 70-80%, the reaction rate is moderate, and post-processing is easy.

[0103] When the water content is less than 70%, the reaction rate decreases or even stops, and the diffusion of substrate and product becomes difficult.

[0104] 3. Temperature

[0105] Temperatures above 40℃ will cause the enzyme protein to denature and become inactive, and the hydrolysis reaction will slow down or even stop drastically.

[0106] At temperatures below 10℃, molecular kinetic energy decreases, reducing the frequency of enzyme-substrate collisions and binding efficiency, resulting in a very slow hydrolysis rate.

[0107] Within the temperature range of 10-40℃, the spatial conformation of the enzyme protein is most favorable for binding to the substrate, and the catalytic reaction rate reaches its peak. Within this range, the chemical reaction rate increases by approximately 1-2 times for every 10°C increase in temperature.

[0108] 4. Stirring speed

[0109] Stirring speeds >300 rpm lead to decreased stability, disruption of metabolic pathways, and damage to microbial structures.

[0110] Stirring speed <100rpm, resulting in stratification, slow reaction, and low hydrolysis efficiency;

[0111] With a stirring speed of 100-300 rpm, the material is uniform, the temperature / concentration / pH is consistent, the hydrolysis rate is stable, the efficiency is high, and the microbial activity is high.

[0112] The stirring speed needs to be balanced with the characteristics of the material to achieve a balance between efficient mass transfer and maintaining a healthy microbial ecosystem.

[0113] Stirring time >20min will damage shear-sensitive components, introduce more air into the liquid, and generate a large amount of stable foam, which will cause trouble for subsequent sterilization and foam control.

[0114] Stirring time <10min can easily lead to localized excessively high or low concentrations, low mass transfer efficiency, slow hydrolysis rate, and incomplete hydrolysis.

[0115] Stirring time should be within the range of 10-20 minutes to ensure system homogeneity, sufficient contact between enzyme and substrate, and stable mass transfer efficiency and hydrolysis rate.

[0116] Analysis of various factors in the hydrolysis process of microbial culture medium preparation, and the results of synergistic optimization of various parameters, show that the optimal conditions for hydrolysis are: a water content of 70-80%, a temperature of 10-40℃, a pH of 5.8-8.5, and a stirring speed of 100-300 rpm for 10-20 minutes. Under these conditions, a high-quality and relatively stable culture medium hydrolysis effect can be achieved, and its reactivity reaches its maximum.

[0117] II. Adjusting the nutritional ratio

[0118] 1. Many factors affect the nutrition of the culture medium. In addition to carbon source, nitrogen source, and inorganic salts, trace elements, carbon-nitrogen ratio (C / N ratio), pH, etc. also have a significant impact on the nutrient ratio of the culture medium. Moreover, there are strong interactions between these factors, and they are not independent of each other.

[0119] The optimal nutrient ratio, verified through experiments, is as follows in this application: carbohydrates = 1%; nitrogen + vitamins = 0.5%; inorganic salts = 0.5%; water = 98%.

[0120] 2. Physicochemical data control

[0121] The growth of wastewater treatment microorganisms is closely related to physicochemical factors such as pH, redox potential, and osmotic pressure of the culture medium. The methods for controlling these factors are as follows:

[0122] ① Methods for controlling pH: First, adjusting the concentration ratio of K2HPO4 and KH2PO4 can obtain a series of stable pH values ​​between pH 6.4 and 7.2; second, adding CaCO3 to the liquid can adjust the pH of the culture medium by dissolving CaCO3; third, adjusting the pH of the culture medium by using acid or alkali solutions from the outside.

[0123] ② Redox potential (Eh) control: Add appropriate amounts of reducing agents (thioglycolic acid, cysteine, iron filings, etc.) to reduce the redox potential.

[0124] ③ Osmotic pressure control: Add an appropriate amount of inorganic salt to the culture medium to adjust the osmotic pressure to about 290 mosm / L.

[0125] III. Preparation of Microbial Culture Media for Wastewater Treatment

[0126] ① Add agar powder slowly and evenly to the prepared wastewater treatment microbial culture medium solution at a ratio of 1.5-2%; use direct heating method to heat to 90-100℃ until the agar is completely dissolved and the solution is transparent and free of particles;

[0127] ② Adjust the pH of the wastewater treatment microbial culture medium solution to 7.2-7.4;

[0128] ③ After the solution has cooled to about 50°C, prevent it from cooling suddenly and dispense it into 400×400×30 containers;

[0129] ④ After standing at room temperature for 30 minutes, the wastewater treatment microbial culture medium completely solidifies into a gel with a smooth surface and no cracks.

[0130] 2. Formation and sterilization of gel-based microbial culture media for wastewater treatment

[0131] To facilitate the use of gel-based microbial culture media for wastewater treatment, and to ensure its slow absorption, encapsulation, and phagocytosis by microorganisms during a 1-8 hour residence time in wastewater, the gel-based microbial culture media needs to be shaped. This invention uses an extrusion method to compress the gel-based microbial culture media into spherical shapes of different sizes (SΦ2mm, SΦ4mm, SΦ6mm, SΦ8mm, SΦ10mm). Radiation sterilization is employed (due to the strong penetrating power of radiation, the sterilization effect is excellent, leaving no chemical residues, preserving its nutritional value and physicochemical properties without heat damage).

[0132] IV. Wastewater Treatment

[0133] like Figure 3 As shown, the wastewater treatment system includes an inlet tank, an anaerobic tank, an anoxic tank, an aerobic tank, and a secondary sedimentation tank connected in sequence. The aerobic tank has two outlets, the first outlet connecting to the secondary sedimentation tank and the second outlet connecting to the anoxic tank. The secondary sedimentation tank has a return outlet, which is connected to the inlet tank.

[0134] The recyclable sludge from the secondary sedimentation tank is returned to the inlet tank for reuse through the return outlet.

[0135] The mixed liquor from the aerobic tank is transported to the anoxic tank for reuse through the second outlet.

[0136] In one preferred embodiment, the secondary sedimentation tank is provided with an outlet for water and an outlet for sludge. The treated water is discharged through the outlet for water and the sludge is discharged through the outlet for sludge.

[0137] The volume of the anoxic tank in a certain wastewater treatment plant is V=100m³. 3 The influent concentrations are COD=180mg / L and TN=72mg / L. Based on the influent C / N ratio, this is an atypical domestic wastewater treatment plant (such as those located in highway service areas, tourist attractions, stations, docks, and airports). These atypical plants primarily serve transient populations, who mainly rely on wastewater for urination and defecation. These plants are located far from urban areas, lack professional on-site wastewater treatment management, and have a severely imbalanced C / N ratio. Using conventional management methods, it is difficult for the effluent to meet discharge standards, which has always been a challenge and pain point in the industry's wastewater treatment.

[0138] The AAO wastewater treatment process requires an optimized carbon-to-nitrogen ratio (C / N) of approximately 7 and a hydraulic retention time (HRT) of approximately 3 hours in the anoxic tank. The current station's anoxic tank has a C / N ratio of 180 / 72 = 2.5. To achieve the required C / N ratio of 7, an external carbon source needs to be added, bringing the carbon content to C = 7 × 72 = 504 mg / L.

[0139] The core task of the anoxic tank is biological denitrification (i.e., denitrification), which gradually reduces nitrate nitrogen to nitrogen gas (N2) and allows it to escape from the water. A high C / N ratio leads to excessive carbon source, causing sludge bulking. When easily degradable organic matter enters the anoxic tank, it is utilized by polyphosphate-accumulating bacteria, releasing phosphorus and causing the effluent to exceed total phosphorus standards. A low C / N ratio results in insufficient carbon source, reducing the activity of denitrifying bacteria and preventing them from completely converting the returned nitrate nitrogen (NO3⁻) into nitrogen gas, leading to excessive total nitrogen (TN) in the effluent. Incomplete denitrification reduces the compensation for the alkalinity consumed in the nitrification process, causing the overall system pH to drop, inhibiting nitrifying bacteria activity, and creating a vicious cycle.

[0140] To provide sufficient carbon source for denitrification, additional carbon source needs to be added. Wastewater treatment microbial culture medium (gel) prepared from SΦ4mm kitchen waste was used. After the carbon source was added to the anoxic tank, the release rate of the microbial culture medium (gel) was slow, and the increase in chemical oxygen demand (COD) was also slow. The increase in COD in the tank became significant after 20 minutes, peaking at 60 minutes. Afterward, the COD in the anoxic tank slowly decreased. Experimental data are shown below. Figure 4 (Blue line in the image).

[0141] The carbon source provided by the microbial culture medium (gel) is released slowly and steadily, which will not cause excessive proliferation of microorganisms due to rapid dissolution, resulting in an increase in sludge volume. It will also not cause impact on the sewage treatment equipment due to improper dosage. Therefore, the bioavailability and sewage treatment efficiency are high.

[0142] Experiments were conducted on gel wastewater treatment microbial culture media of different sized spheres under static purified water conditions at room temperature. At 25℃, 50g of gel wastewater treatment microbial culture media of different sized spheres (SΦ2mm, SΦ4mm, SΦ6mm, SΦ8mm, SΦ10mm) were respectively added to five different culture containers, and 250ml of purified water was added. The changes of the gel wastewater treatment microbial culture media of different sized spheres in the water were observed under static conditions. The results are shown in Table 5.

[0143] The results showed that the gel-like wastewater treatment microbial culture medium absorbs water and swells at room temperature, becoming larger and softer, but does not dissolve; instead, it disperses into lumps, filaments, and flocs. The dispersion of the gel-like wastewater treatment microbial culture medium at room temperature is related to its volume; the smaller the volume, the easier it is to disperse and suspend and settle.

[0144] This is because the gel-like microbial culture medium for wastewater treatment prepared in this invention does not dissolve in water but merely disperses and settles, i.e., it settles but does not disperse. This is determined by the inherent nature of the gel-like microbial culture medium for wastewater treatment. Agar powder can dissolve in hot water at around 90°C. The high temperature breaks down some of the bonds between agar molecules, causing them to disperse and combine with water molecules. When the solution cools, the agar molecules rearrange to form a three-dimensional network structure, "locking" the water molecules within and preventing them from flowing freely.

[0145] When gel-like wastewater treatment microbial culture medium is placed in water, it absorbs water, swells, and softens, causing the edges of the medium to become indistinct and irregular. When the water provides sufficient energy, the weak bonds (mainly hydrogen bonds) maintaining the three-dimensional network structure of the gel are broken, releasing the "locked" water. Some agar molecules redisperse into the water, forming lumps, filaments, and flocs that suspend and deposit in the lower layer of the wastewater, but they do not dissolve. The specific gravity of the gel-like wastewater treatment microbial culture medium is slightly greater than 1, and it exists as a lumpy, filamentous, or flocculent suspension in water.

[0146] The dispersion of wastewater treatment microbial culture medium (gel) at room temperature is related to its volume; smaller volumes are easier to disperse, suspend, and settle. Therefore, the specifications of wastewater treatment microbial culture medium (gel) are determined based on the hydraulic retention time of different wastewater treatment tanks, ensuring that the hydraulic retention time is close to the dispersion time of the wastewater treatment microbial culture medium (gel). This ensures a slow and stable release rate of the wastewater treatment microbial culture medium (gel) in the wastewater tank, preventing rapid dissolution that could lead to microbial overgrowth or excessive sludge production, and avoiding the impact on wastewater treatment equipment due to improper dosage. This also reduces the amount of gel wastewater treatment microbial culture medium needed, resulting in high bioavailability and wastewater treatment efficiency.

[0147] Similarly, at different temperatures (10℃, 15℃, 20℃, 25℃, 30℃, 35℃), equal amounts of 50g of gel wastewater treatment microbial culture medium containing spheres of different sizes (SΦ2mm, SΦ4mm, SΦ6mm, SΦ8mm, SΦ10mm) were added to purified water (150mL, 200mL, 250mL, 300mL, 350mL), and the changes of the gel wastewater treatment microbial culture medium in the water were observed.

[0148] The results show:

[0149] 1. For the same spherical gel microbial culture medium for wastewater treatment, the higher the temperature, the faster the spherical gel microbial culture medium absorbs water, expands, becomes larger, and softens, and the faster it presents a blocky, filamentous, or flocculent state in water.

[0150] 2. At the same temperature, the same spherical gel wastewater treatment microbial culture medium absorbs water and expands, grows larger and softens at different rates in pure water of different masses, and exhibits different states in the water, such as blocky, filamentous and flocculent.

[0151] According to GB50014-2016, the total hydraulic retention time (HRT) of the AAO process should be ≥7 hours, and the retention time of each tank can be referred to Table 6. However, the actual hydraulic retention time (HRT) should be adjusted appropriately based on factors such as influent water quality (COD / BOD, TN, TP), water temperature, return system, and sludge concentration.

[0152] The volume of the microbial culture medium (gel) can be adjusted to correspond to a residence time of 1-7 hours based on the residence time in the tank. The closer the designed residence time of each tank in the AAO process is to the residence time of the microbial culture medium (gel) spheres in the tank, the more sustainably and slowly the external carbon source can be provided for the decomposition of organic matter. This will not cause carbon enrichment or waste; nor will it increase the burden on the metabolic system of microorganisms and affect their normal metabolism and growth.

[0153] Comparative Example 1

[0154] Different carbon sources were introduced into anoxic ponds to compare their release effects.

[0155] When the carbon source used is liquid sodium acetate (the dosage is calculated based on a carbon content of C=7×72=504mg / L), the chemical oxygen demand (COD) in the anoxic tank increases rapidly after the addition of liquid sodium acetate. However, over time, the COD concentration in the wastewater also decreases rapidly. Experimental data indicate that: firstly, the reaction rate of the liquid sodium acetate carbon source is extremely fast; secondly, even slight errors in the dosage of the liquid carbon source can easily lead to the death of microorganisms or its loss with the wastewater. (Experimental data can be found in...) Figure 4 (Orange line in the image).

[0156] Comparative Example 2

[0157] When the carbon source was powdered flour (the dosage was calculated based on a carbon content of C=7×72=504mg / L), the chemical oxygen demand (COD) in the tank initially increased slowly. This is because large sugar molecules need to be hydrolyzed into smaller sugar molecules for efficient utilization. However, the rate of increase in carbon source was stable, reaching a peak after 45 minutes, after which the COD concentration rapidly decreased over time. The experiment indicates that: firstly, the reaction rate of powdered flour carbon source is slower than that of liquid carbon source; and secondly, careless dosage of powdered flour carbon source can easily lead to microbial overgrowth or loss with the wastewater. Experimental data can be found in [link to experimental data]. Figure 4 (Red line in the picture).

[0158] Comparative Example 3

[0159] When the carbon source used is a commercially available anaerobic fermentation liquid carbon source (the dosage is calculated based on a carbon content of C=7×72=504mg / L), the chemical oxygen demand (COD) in the anoxic tank increases rapidly. However, over time, the COD concentration in the wastewater also decreases quickly. Experimental data indicates that: firstly, the reaction rate of the liquid anaerobic fermentation carbon source is fast; secondly, even slight errors in the dosage of the anaerobic fermentation liquid carbon source can easily lead to microbial overgrowth or loss with the wastewater. (Experimental data can be found in...) Figure 4 (Green line in the image).

[0160] The four different external carbon sources were compared in terms of various performance aspects, including cost, reaction rate, transportation and storage safety, bioavailability, impact on the treatment system, impact on dosage, and residence time in the pool. The results are shown in Table 7.

[0161] By conducting comparative experiments under the same environmental conditions, the characteristics of the wastewater treatment microbial culture medium (gel) prepared from kitchen waste are further illustrated: it slowly releases carbon source, maintains a stable carbon source supply, reduces the frequency of addition, and avoids the problems of microorganisms dying from overeating or being lost with the flow of wastewater.

[0162] Wastewater treatment culture medium made from kitchen waste is in a gel state, making it easy to control the dosage during use. It also has a strong slow-release effect and can remain in the wastewater tank for 1-7 hours, making it less prone to activated sludge bulking and foaming.

[0163] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing a microbial gel culture medium, characterized in that, Includes the following steps: (1) Sorting, crushing, homogenizing and hydrolyzing residential kitchen waste to obtain a base liquid; (2) Add agar powder to the base solution at a ratio of 1.5-2wt%, heat to 90-100℃ until the agar is completely dissolved; adjust the pH of the solution to 7.2-7.4, then cool, set, and sterilize to obtain microbial gel culture medium; The hydrolysis step is as follows: water is added to the homogenized solution and stirred for 10-20 minutes to obtain the base solution; The base fluid has a water content of 70-80%; By weight, residential kitchen waste consists of 60-70 parts water, 20-30 parts organic matter, and 10-15 parts impurities.

2. The preparation method according to claim 1, characterized in that, The particle size of the crushed particles is ≤10mm; the crushed particles are then ground, and the particle size of the ground particles is ≤1mm.

3. The preparation method according to claim 1, characterized in that, The homogenization process is as follows: homogenize in a homogenization container at 25-30 rpm for 10-30 min.

4. The preparation method according to claim 1, characterized in that, The hydrolysis temperature is 10-40℃, the pH value is 5.8-8.5, and the stirring speed is 100-300rpm.

5. The preparation method according to claim 1, characterized in that, The shaping process involves extruding the microbial gel culture medium into spherical shapes of a specific size using an extrusion method.

6. The preparation method according to claim 5, characterized in that, The diameter of the sphere is one or more of the following: SΦ2mm, SΦ4mm, SΦ6mm, SΦ8mm, and SΦ10mm.

7. The microbial gel culture medium prepared by the preparation method according to any one of claims 1-6.

8. The microbial gel culture medium according to claim 7, characterized in that, Microbial gel culture medium contains 1-5 parts sugars; 0.5-2 parts nitrogen and vitamins; 0.5-3 parts inorganic salts; and 90-98 parts water.

9. The application of the microbial gel culture medium according to claim 7 in wastewater treatment.

10. The application according to claim 9, characterized in that, The microbial gel culture medium was placed in the anoxic tank of the wastewater treatment system.

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