Method for preparing composite carbon source from kitchen waste

Abstract

The invention discloses a method for preparing a composite carbon source from kitchen waste. The method comprises the following steps: S1, pretreating to obtain kitchen slurry; s2, hydrolytic acidification: pumping the mixed slurry subjected to mixing and tempering into an anaerobic acid-producing tank to perform hydrolytic acidification reaction, and hydrolyzing insoluble organic matters into soluble organic matters by utilizing the reaction of hydrolytic bacteria and acid-producing bacteria; and S3, filtration and concentration: introducing the acidified liquid into a separation and purification device for pretreatment, sequentially performing coarse filtration, fine filtration, ultrafiltration membrane treatment and nanofiltration membrane concentration treatment, and removing filter residues to obtain a concentrated composite carbon source product. According to the method, the quality of the organic carbon source prepared from the kitchen waste can be improved, recycling of resources is achieved to the maximum extent, and the utilization value of kitchen waste recycling products is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of restaurant and kitchen waste treatment, and in particular to a method for preparing a composite carbon source by utilizing restaurant and kitchen waste. Background Art

[0002] In recent years, with the implementation of garbage classification policies and the continuous improvement of the food waste collection, transportation and treatment system, the promotion of garbage classification is of great significance. The current garbage classification standard adopts a four-part method, namely recyclables, hazardous waste, food waste and other garbage. With the continuous advancement of garbage classification, the amount of food waste collected and treated is increasing. Food waste refers to garbage generated in residents' daily life and food processing, catering services, unit meal supply and other activities, including discarded vegetable leaves, leftovers, leftover rice, fruit peels, eggshells, tea dregs, bones, etc. Its main sources are family kitchens, restaurants, hotels, canteens, markets and other industries related to food processing. Compared with ordinary garbage, food waste has the following characteristics: 1. The water content is as high as about 70-85%; 2. Organic matter accounts for about 90-95% of the dry matter, and it contains a large amount of biomass energy; 3. The oil content is high, the components are quite different, and the components change with seasonal changes. There are many interfering solid phases, and the composition is complex and changeable. It has the dual characteristics of "garbage" and "resources". The requirements for food wastewater treatment are: 1. Maximize the resource recovery of oil and fat from food waste; 2. Effectively separate and recycle organic matter from food waste; and 3. Minimize the disposal of inert solids. The reduction, resource utilization, and harmless treatment of food waste are increasingly becoming research hotspots in the environmental field.

[0003] Traditional food waste treatment processes include anaerobic fermentation, fertilizer production, and feed production. The primary product of anaerobic fermentation is biogas. However, the current low domestic natural gas price significantly reduces the economic viability of biogas. However, grid-connected power generation requires high economies of scale, and the scale of most food waste projects in small and medium-sized cities makes grid-connected power generation uneconomical, resulting in poor overall economic viability for anaerobic fermentation. Fertilizer production technology faces a serious challenge: limited fertilizer sales. Farmers' concerns about toxic and hazardous substances in compost and its effectiveness hinder the sales of compost products. Feed production offers better economic benefits, but concerns about feed homology make it difficult to obtain approval and promotion from relevant regulatory authorities. Consequently, anaerobic food waste methane production, fertilizer production, and feed production technologies face challenges such as high parameter control requirements and difficulties in exporting products, hindering their integration with other environmental protection facilities, such as sewage treatment plants and landfills.

[0004] Some of my country's urban sewage, landfill leachate, and anaerobic food waste treatment projects face challenges such as an imbalanced carbon-nitrogen ratio in biochemical treatment, insufficient carbon sources for denitrification, poor denitrification performance, and substandard effluent quality. These challenges necessitate the addition of large amounts of external carbon sources to meet process requirements. Most sewage treatment plants utilize methanol, sodium acetate, glucose, and other carbon sources for denitrification to adjust the carbon-nitrogen ratio and increase the system's denitrification rate. However, these sources present high costs, inconvenient storage and transportation, and potential risks. In recent years, research on the carbonization of food waste has emerged as a new research direction in its resource utilization. After proper treatment, food waste slurry is expected to become an economical, environmentally friendly, and efficient carbon source alternative in wastewater treatment and other fields, providing strong support for waste resource utilization and sustainable development.

[0005] Using food waste leachate to produce a carbon source for wastewater treatment is a green treatment approach that aligns with the concept of treating waste with waste. However, the long carbon source preparation cycle, high total salt content, and substandard COD concentrations in the prepared carbon source urgently require effective solutions. Food waste leachate has a complex composition and is high in oil and salt. Oil forms an oil film, which hinders oxygen and nutrient transport, affecting microbial activity; high salt content inhibits microbial growth and metabolism, reducing fermentation efficiency. The composition of food waste leachate fluctuates between batches, and fermentation microorganisms are sensitive to environmental conditions, which can affect fermentation stability and organic acid production. Organic acids require extremely high purity and quality in wastewater treatment, but the current lack of efficient purification technologies makes timely product isolation difficult and expensive. Existing treatment processes are ineffective in removing impurities such as suspended particulate matter, phosphates, and ammonia nitrogen from the leachate, resulting in a low-quality carbon source. This increases the load on wastewater treatment systems and affects effluent quality.

[0006] Chinese invention patent application publication number CN114315076A discloses a method for anaerobic co-fermentation of municipal sludge and food waste to produce acid. The product can be used as a supplemental carbon source for sewage treatment plants. The process involves the following steps: first, the wastewater treatment plant's excess sludge (moisture content 96%-98%) is uniformly mixed with food waste slurry (solid content 10%-15%). The mixture is then subjected to anaerobic bio-acidification at 35-37°C with a pH controlled between 8-10 for 2-3 days. The acidified liquid then enters a sedimentation tank for precipitation. The supernatant from the sedimentation tank enters a struvite recovery unit to recover nutrients such as nitrogen and phosphorus. The sludge residue at the bottom of the acidification tank and sedimentation tank is collected in a sludge storage tank. The sludge is dehydrated and transported as a mud cake. The effluent from the struvite recovery unit is sent to the biochemical process section of the sewage treatment plant as a supplemental carbon source. This invention not only treats food waste slurry but also recycles the sludge, reducing environmental pollution and producing high-value volatile fatty acids for use as a supplemental carbon source for sewage treatment plants. However, the application only describes the collection and integration of various types of residual sludge and food waste. The carbon source output rate is not high and there is no mention of improving the quality of the carbon source.

[0007] In light of this, this application utilizes a novel technology to prepare a carbon source: hydrolysis and acidification for targeted acid production, followed by acidified liquid purification. This technology allows traditional anaerobic fermentation to remain at the hydrolysis and acidification stage, converting food waste into a highly concentrated, biodegradable organic acidified liquid at low cost. This acidified liquid exhibits excellent biodegradability and can effectively replace expensive commercial carbon sources, thereby integrating food waste treatment plants, sewage treatment plants, and landfills to achieve a complete circular economy industry chain. Summary of the Invention

[0008] The present invention aims to address the widespread carbon source shortage faced by my country's food waste and sludge industries. Existing externally purchased carbon sources primarily include glucose, sodium acetate, methanol, and composite carbon sources, significantly increasing operating costs. Some qualified companies have opted to use leachate as an alternative to external carbon sources, but this approach is not environmentally friendly. Furthermore, leachate quality fluctuates significantly due to seasonal variations. Furthermore, pretreated slurry from food waste has not yet been used as a carbon source supplement for water treatment.

[0009] In order to solve the above technical problems, the present invention provides a method for producing a composite carbon source from food waste, comprising the following steps: S1: pre-treatment to obtain food waste slurry: the food waste is received in the form of a receiving silo, a bottom spiral is installed at the bottom of the silo, and the spiral is provided with a drainage separation mechanism to physically separate the solid and liquid of the food waste. The liquid phase is temporarily stored in the drainage separation mechanism and heated in a heating tank, and then pumped into a three-phase separator to extract crude oil. The remaining liquid residue flows into a homogenization tank for storage; the solid phase of the food waste is coarsely crushed by a crusher, and then subjected to secondary crushing, pulping and sorting by a pulping machine. The slurry is desanded by a desander and then pumped. to a homogenization tank; the liquid phase after the crude oil is extracted and the crushed slurry are mixed and tempered in the same homogenization tank; S2: hydrolysis and acidification: the mixed and tempered mixed slurry is pumped into an anaerobic acid production tank for hydrolysis and acidification reaction, and the insoluble organic matter is hydrolyzed into soluble organic matter by the reaction of hydrolytic bacteria and acid-producing bacteria, thereby increasing the organic matter concentration and soluble organic matter concentration in the liquid phase of the mixed slurry; S3: filtration and concentration: the acidified liquid is introduced into a separation and purification device for pretreatment, and sequentially undergoes coarse filtration, fine filtration, ultrafiltration membrane treatment and nanofiltration membrane concentration treatment to remove the filter residue and obtain a concentrated composite carbon source product.

[0010] According to the embodiment of the present application, the optimized conditions of the hydrolysis and acidification process in step S2 are: heating the mixed slurry to 34-40°C under stirring, adding Liboyuan hydrolysis and acidification anaerobic bacteria, cellulase, protein enzyme and oil-removing bacteria to the anaerobic acid production tank, adjusting the pH to 3.0-4.0, continuing to stir, and letting it stand after the specified hydrolysis time.

[0011] According to an embodiment of the present application, the stirring speed during the hydrolysis and acidification reaction is 100 r / min.

[0012] According to an embodiment of the present application, in step S2, the amount of bacterial agent added is: per 2000 ml of mixed slurry, the amount of Liboyuan hydrolytic acidifying anaerobic bacteria added is 16 g, the amount of Haicheng oil removal bacteria added is 50 g, the amount of protease added is 0.8 g, and the amount of cellulase added is 1 g.

[0013] According to the embodiments of the present application, during the hydrolysis and acidification process, the pH is manually adjusted by using dilute acid and alkaline additives to adjust the pH value in the anaerobic acid production tank every 12 hours, and samples are taken and centrifuged every 12 hours to measure relevant indicators.

[0014] According to an embodiment of the present application, in step S3, a bag filter is used in the coarse filtration step to intercept large particles larger than 800 microns.

[0015] According to an embodiment of the present application, in step S3, a bag filter is used in the fine filtration step to intercept large particulate matter larger than 500 microns.

[0016] According to an embodiment of the present application, in step S3, the ultrafiltration membrane treatment step uses a tubular ultrafiltration membrane with a pore size of 0.002 to 0.1 μm. Under the influence of the pressure difference, the solvent and small solute particles in the hydrolyzed acidified liquid pass through the membrane from the high-pressure feed liquid side to the low-pressure side.

[0017] According to an embodiment of the present application, in step S3, the nanofiltration membrane concentration treatment step uses a nanofiltration membrane, the pore size of the nanofiltration membrane is 1-2 nm, and the molecular weight cut-off range is between 500 and 100,000 Da.

[0018] According to the embodiment of the present application, the solid phase of the kitchen solid part needs to be removed and pulped again after the first-level coarse crushing by the crusher. Under the hammer-type cutting and stirring action of the pulper at 1000r / min, the material is further crushed into a slurry material. At the same time, it removes impurities mixed in the material to make the particle size less than 10mm.

[0019] The beneficial effects of the technical solution of the present invention compared with the prior art are:

[0020] 1. The present invention conducts a hydrolysis and acidification reaction on pretreated food waste slurry, and it is found that the addition of appropriate bacterial agents and promoters can increase the COD and SCOD contents of the food waste slurry to over 100,000 mg / L, meeting the COD content requirement for the composite carbon source. The method of the present invention can improve the quality of organic carbon sources made from food waste, maximize resource recycling, and increase the value of the recycled food waste products.

[0021] 2. The present invention obtains a carbon source preparation stock solution by hydrolyzing and acidifying the liquid phase of food waste, filling the gap in the use of food waste pretreatment slurry as a carbon source supplement for water treatment. At the same time, this process can not only improve the food waste treatment capacity, but also improve the level of resource utilization of food waste. At the same time, the commercial carbon source produced can also obtain certain economic benefits, while realizing the treatment of food waste and reducing pollution to the environment.

[0022] 3. The present invention has the characteristics of simple method, short time, low cost, and high carbon source quality. It can not only effectively improve the efficiency of sewage treatment, but also significantly reduce the operating cost of sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of a method for preparing a composite carbon source from kitchen waste according to the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] See Figure 1 As shown, a method for preparing a composite carbon source from kitchen waste is shown, comprising the following steps:

[0026] S1: Pre-processing to obtain food waste slurry: Food waste is received in a receiving silo. A spiral is installed at the bottom of the silo, each spiral being equipped with a drainage separation mechanism to physically separate the solid and liquid parts of the food waste. The liquid phase is temporarily stored in the drainage separation mechanism, heated in a heating tank, and then pumped into a three-phase separator to extract crude oil. The remaining liquid residue flows into a homogenization tank for storage. The solid phase of the food waste is coarsely crushed in a crusher, then subjected to secondary crushing and pulping in a pulper, and sorted. The slurry is desanded in a desander and then pumped into a homogenization tank. The liquid phase after the crude oil is extracted and the crushed slurry are mixed and tempered in the same homogenization tank.

[0027] Specifically, the solid phase of the kitchenware needs to be pulped again after the first-level coarse crushing by the crusher. Under the hammer-type cutting and stirring action of the pulper at 1000r / min, the material is further crushed into a pulpy material. At the same time, it can remove impurities mixed in the material and make the particle size less than 10mm.

[0028] S2: Hydrolysis and acidification: The mixed slurry after mixing and conditioning is pumped into the anaerobic acid production tank for hydrolysis and acidification reaction. The insoluble organic matter is hydrolyzed into soluble organic matter by the reaction between hydrolytic bacteria and acid-producing bacteria, thereby increasing the organic matter concentration and soluble organic matter concentration in the liquid phase of the mixed slurry;

[0029] Specifically, hydrolysis and acidification bypasses the methane fermentation stage of the anaerobic reaction. Instead, they utilize the reaction between hydrolytic and acidogenic bacteria to hydrolyze insoluble organic matter into soluble organic matter, treating both sludge and wastewater simultaneously. Throughout the hydrolysis and acidification process, over 80% of suspended matter is hydrolyzed into soluble matter, breaking down large molecules into smaller ones, and improving the BOD5 / COD ratio. Hydrolysis and acidification are highly adaptable to variations in water quality and temperature, offering high efficiency, low energy consumption, minimal investment, low operating costs, and ease of implementation. By controlling the anaerobic digestion process within the hydrolysis and acidification stages, efficient recovery of available carbon sources is achieved.

[0030] Specifically, the optimized conditions for the hydrolysis and acidification process in step S2 are as follows: heating the mixed slurry to 34-40°C under stirring, adding Liboyuan hydrolysis and acidification anaerobic bacteria, cellulase, protein enzyme and oil-removing bacteria to the anaerobic acid production tank, adjusting the pH to 3.0-4.0, continuing stirring, and letting it stand after the specified hydrolysis time.

[0031] Specifically, in step S2, the addition amount of the bacterial agent and the hydrolyzing agent is preferably: per 2000 ml of the mixed slurry, the addition amount of Liboyuan hydrolytic acidifying anaerobic bacteria is 16 g, the addition amount of Haicheng oil removal bacteria is 50 g, the addition amount of protease is 0.8 g, and the addition amount of cellulase is 1 g.

[0032] Specifically, during the hydrolysis and acidification process, the pH is manually adjusted every 12 hours using dilute acid and an alkaline additive. Samples are then taken and centrifuged every 12 hours to measure relevant indicators. pH adjustment can be achieved using a dilute hydrochloric acid solution and an alkaline additive. The alkaline additive is a substance with a certain alkalinity that can neutralize organic acids and increase the pH of the fermentation broth. It is specifically selected from one or more of anaerobic digestion slurry, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, and ammonia.

[0033] Specifically, experiments have shown that the COD value can be significantly increased after 24 hours of hydrolysis and acidification; the SCOD value is also significantly increased after 72 hours of hydrolysis and acidification, and the optimal hydrolysis time is 72 hours.

[0034] Specifically, the stirring speed during the entire hydrolysis and acidification reaction is preferably 100 r / min.

[0035] S3: Filtration and concentration: The acidified liquid is introduced into a separation and purification device for pretreatment, and sequentially subjected to coarse filtration, fine filtration, ultrafiltration membrane treatment and nanofiltration membrane concentration treatment to remove the filter residue to obtain a concentrated composite carbon source product.

[0036] Specifically, in step S3, the coarse filtration step uses a bag filter to intercept large particles larger than 800 microns. Bag filters are a versatile filtration device characterized by a novel structure, compact size, simple and flexible operation, energy-saving, high efficiency, airtight operation, and strong adaptability. Bag filters are a novel filtration system. A metal mesh basket supports the filter bag. Liquid flows in through the inlet, passes through the filter bag, and exits through the outlet after being filtered. Impurities are trapped in the filter bag, allowing continued use after the filter bag is replaced.

[0037] Specifically, in step S3, a bag filter is used in the fine filtration step to intercept large particles larger than 500 microns.

[0038] Specifically, in step S3, the ultrafiltration membrane treatment step utilizes a tubular ultrafiltration membrane with a pore size of 0.002 to 0.1 μm. Driven by a pressure differential, the solvent and small solute particles in the hydrolyzed acidified solution pass through the membrane from the high-pressure feed liquid side to the low-pressure side. The tubular ultrafiltration membrane is an organic membrane with a molecular weight cutoff of approximately 500 to 500,000. Organic tubular ultrafiltration membranes have the characteristic of precisely cutting off the molecular weight of organic membranes, and a complete set of membrane models with different molecular weight cutoffs are available. The material used for ultrafiltration is a semipermeable (selectively permeable) membrane. Under a certain pressure, the solvent (usually water), inorganic salts, and low-molecular-weight organic substances in the solution pass through the membrane, while other macromolecular substances are retained, resulting in an effluent ss of less than 1 mg.

[0039] Specifically, in step S3, the nanofiltration membrane concentration treatment step utilizes a nanofiltration membrane with a pore size of 1-2 nm and a molecular weight cutoff range of 500 to 100,000 Da. Nanofiltration membranes, with pore sizes greater than 1 nm, typically 1-2 nm, are functional semipermeable membranes that allow the permeation of solvent molecules, certain low-molecular-weight solutes, or low-valent ions. They are a unique and promising type of separation membrane, named for their ability to retain substances approximately nanometer in size. They are used to remove organic matter and color from surface water, remove hardness from groundwater, partially remove soluble salts, concentrate fruit juices, and separate useful substances from pharmaceuticals. The operating range of nanofiltration membranes lies between ultrafiltration and reverse osmosis, with a capacity to retain dissolved salts between 20% and 98%. The removal rate for soluble monovalent ions is lower than that for high-valent ions. Nanofiltration membranes can remove most COD and BOD, achieving carbon source concentration.

[0040] The working principle of this embodiment is as follows: After pre-treatment in a three-phase separator, the food waste slurry undergoes oil removal and then enters anaerobic fermentation. During the anaerobic fermentation phase, by adding suitable hydrolytic and acidifying anaerobic bacteria and controlling the reaction parameters, the anaerobic process is terminated at the hydrolysis and acidification stage, effectively shortening the anaerobic fermentation reaction cycle. The proteins, polysaccharides, starch, cellulose, and fats in the food waste slurry are all good acid-producing raw materials. Proteins are converted into amino acids by proteases, polysaccharides, starch, and cellulose are converted into monosaccharides by amylase and cellulase, and fats are converted into long-chain fatty acids and glycerol by lipase. These substances, under the action of acid-producing bacteria, generate organic acids such as volatile fatty acids (VFAs) and small molecules such as ethanol, effectively increasing the COD content and soluble organic matter (SCOD) in the water. Through this reaction process, the COD content in the food waste slurry can reach 100,000 mg / l, providing an appropriate COD content for carbon source production.

[0041] The present invention is described in detail below by way of examples. Unless otherwise specified, the raw materials used are all common commercially available commodities: ferrous sulfate, Tianjin Tianli Chemical Reagent Co., Ltd.; ammonium ferrous sulfate, Tianjin Yili Chemical Reagent Co., Ltd.; potassium aluminum sulfate, Tianjin Bohuatong Chemical Products Sales Center; anhydrous magnesium sulfate, Tianjin Yili Chemical Reagent Co., Ltd.; ammonium aluminum sulfate, Shanghai Shanpu Chemical Co., Ltd.; sodium thiosulfate, Tianjin Tianli Chemical Reagent Co., Ltd.; zinc oxide, Sichuan Xilong Science Co., Ltd.; potassium hydrogen phthalate, Tianjin Bohuatong Chemical Products Sales Center; potassium chromate, Tianjin Bohuatong Chemical Products Sales Center; phthalic acid, Fuchen (Tianjin) Chemical Reagent Co., Ltd.; hydrazine sulfate, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; Hydroxylamine chloride (Hydroxylamine hydrochloride), Tianjin Bohuatong Chemical Products Sales Center; Ammonium acetate, Tianjin Bohuatong Chemical Products Sales Center; Sodium tetraborate (Borax), Tianjin Kaitong Chemical Reagent Co., Ltd.; White vaseline, Hengshui Yiren Pharmaceutical Co., Ltd.; 1,4-phenanthroline, Tianjin Kaitong Chemical Reagent Co., Ltd.; Bromocresol green, Tianjin Kaitong Chemical Reagent Co., Ltd.; Disodium ethylenediaminetetraacetic acid, Tianjin Kaitong Chemical Reagent Co., Ltd.; Methyl red, Tianjin Bohuatong Chemical Products Sales Center; Methyl blue, Tianjin Komiou Chemical Reagent Co., Ltd.; Phenolphthalein, Tianjin Kaitong Chemical Reagent Co., Ltd.; Methyl orange, Shenyang Reagent Factory No. 3; Eriochrome black T, Tianjin Bohuatong Chemical Reagent Co., Ltd. Huatong Chemical Products Sales Center; Alkali Blue 6B, Tianjin Aopusheng Chemical Co., Ltd.; Disodium Magnesium Ethylenediaminetetraacetate, Tianjin Kaitong Chemical Reagent Co., Ltd.; Potassium Permanganate, Luoyang Haohua Chemical Reagent Co., Ltd.; Potassium Dichromate, Chengdu Jinshan Chemical Reagent Co., Ltd.; Hexamethylenetetramine, Chengdu Jinshan Chemical Reagent Co., Ltd.; Phosphoric Acid, Chengdu Jinshan Chemical Reagent Co., Ltd.; Potassium Persulfate, Tianjin Yili Chemical Reagent Co., Ltd.; Anhydrous Ethanol, Tianjin Bohuatong Chemical Products Sales Center; Calcium Carbonate, Tianjin Kaitong Chemical Reagent Co., Ltd.; Ammonium Chloride, Chengdu Jinshan Chemical Reagent Co., Ltd.; Sodium Chloride, Chengdu Jinshan Chemical Reagent Co., Ltd.; Anhydrous Sodium Carbonate, Tianjin Bohuatong Chemical Products Sales Center; Ethylenediamine Disodium tetraacetate, Tianjin Shengao Chemical Reagent Co., Ltd.; sodium bromide, Tianjin Tianli Chemical Reagent Co., Ltd.; soluble starch, Tianjin Beilian Fine Chemicals Development Co., Ltd.; potassium chloride, Chengdu Jinshan Chemical Reagent Co., Ltd.; sodium oxalate, Tianjin Damao Chemical Reagent Factory; sodium hydroxide (granules), Tianjin Bohuatong Chemical Products Sales Center; potassium hydroxide, Chengdu Jinshan Chemical Reagent Co., Ltd.; hydrochloric acid, Xi'an Sanpu Chemical Reagent Co., Ltd.; silver nitrate, Tianjin Yingda Rare and Precious Chemical Reagent Factory; nitric acid, Chengdu Jinshan Chemical Reagent Co., Ltd.; perchloric acid, Chengdu Kelong Chemicals Co., Ltd.; silver sulfate, Tianjin Dongjulong Chemical Technology Development Co., Ltd.; ammonia water, Tianjin Kaitong Chemical Reagent Co., Ltd.

[0042] Kitchen slurry: The slurry after kitchen waste is received and pre-treated (including the above-mentioned drainage separation, three-phase separation, crushing and sorting process). The physical and chemical parameters are: pH 3.88, SS 78110 mg / L, COD 740 million mg / L, VFAs (volatile fatty acids) 6533.1 mmol / L, NH4 + -N (ammonium nitrogen) is 364.1 mg / L, the total nitrogen content is 37733.3 mg / L, and the total phosphorus content is mg / L.

[0043] Example 1

[0044] This example is used to illustrate a method for preparing a composite carbon source from kitchen waste provided by the present invention. Figure 1 The process shown in the figure and follow the steps below:

[0045] (1) The pretreated food slurry is introduced into the anaerobic acid production tank and heated to 34-40°C under stirring at 100 r / min;

[0046] (2) In an anaerobic acid production tank, the pH of the kitchen slurry was adjusted to 3.0-4.0, and then Liboyuan hydrolytic acidifying anaerobic bacteria, Haicheng oil removal bacteria, protein enzyme and cellulase were added. The amount of bacterial agents added was: per 2000 ml of the mixed slurry, the amount of Liboyuan hydrolytic acidifying anaerobic bacteria added was 16 g, the amount of Haicheng oil removal bacteria added was 50 g, the amount of protease added was 0.8 g, and the amount of cellulase added was 1 g. The mixture was stirred at a stirring speed of 100 r / min.

[0047] (3) Continue stirring for 24 hours and let it stand;

[0048] (4) The acidified liquid is filtered through a filter and then introduced into an ultrafiltration membrane assembly to obtain a raw liquid for preparing a carbon source.

[0049] The results showed that the process was stable. The physicochemical parameters of the obtained stock solution are shown in Table 1.

[0050]

[0051] Table 1

[0052] Example 2

[0053] This example is carried out using a method similar to that of Example 1, except that the hydrolysis and acidification time in step (3) is 72 hours.

[0054] The results showed that the process was stable. The physicochemical parameters of the obtained stock solution are shown in Table 2.

[0055]

[0056] Table 2

[0057] Among them, the blank group (CK) was a group in which no preparation was added to the food waste slurry, and the experimental group (SY) was a group in which bacterial agents and promoters were added to the food waste slurry.

[0058] Comparative Example 1

[0059] This comparative example was carried out using a method similar to that of Example 1, except that step (2) was not performed. Instead, the mixture was stirred at a consistent intensity for 24 hours and then allowed to stand.

[0060] The results showed that the system operated stably. The specific physical and chemical parameters of the effluent liquid are shown in Table 1.

[0061] Comparative Example 2

[0062] This comparative example was carried out using a method similar to that of Example 1, except that step (2) was not performed. Instead, the mixture was stirred at a consistent intensity for 72 hours and then allowed to stand.

[0063] The results showed that the system operated stably. The specific physical and chemical parameters of the effluent liquid are shown in Table 2.

[0064] The results in Tables 1 and 2 show that by comparing the initial values ​​of the food waste slurry indicators and the indicators of different hydrolysis and acidification reaction times, it can be concluded that after 24 hours of hydrolysis and acidification, the addition of Liboyuan hydrolysis and acidification bacteria, Haicheng oil removal bacteria, protease and cellulase can significantly increase the COD value, which can reach 185,000 mg / L. After 72 hours of hydrolysis and acidification, the SCOD is also significantly improved, which can reach 109,000 mg / L. Example 2 can achieve the expected SCOD value of more than 100,000 mg / L, which is 533.7% higher than the SCOD of the blank control example 2. At the same time, in Example 1, VFAs also showed a significant increase trend after 24 hours of hydrolysis and acidification, which increased by 680% compared with the blank control example 1. After 72 hours of hydrolysis and acidification, the pH, SS, total nitrogen, total phosphorus and VFAs of Example 2 all showed a downward trend compared with the initial values. After 72 hours of hydrolysis and acidification, the NH4 + -N showed an increasing trend.

[0065] From the above, we can see that by adding Liboyuan hydrolytic acidifying bacteria, Haicheng oil removal bacteria, protease and cellulase for control experiments, it can be concluded that adding appropriate bacterial agents and promoters can make the COD and SCOD contents of food waste slurry exceed 100,000 mg / L, meeting the COD content requirements of the composite carbon source, and at the same time, the SS downward trend is obvious.

[0066] Example 3 Optimization of the hydrolysis and acidification conditions of kitchen slurry

[0067] First strain screening

[0068] Multiple control experiments were conducted using a single strain of hydrolytic acidifying bacteria, a combination of strains, and enzymes in varying proportions. Samples were taken at different times from these experiments and measured according to the indicators in Table 2. A complete first phase of the experiment has been completed. The methods for adding strains and accelerators are shown in Table 3.

[0069]

[0070] Table 3: Addition of bacterial agents and promoters in water samples. The specific determination results are shown in Table 5 according to Table 4.

[0071]

[0072]

[0073] Table 4 Experimental index determination method

[0074]

[0075]

[0076] Table 5 Test results of bacterial strain screening index

[0077] As shown in Tables 3 and 5, through the above-mentioned strain screening experiments of different groups, it can be seen that the COD range of the initial solution is in the range of 71000-76000 mg / l. After 24 hours of hydrolysis and acidification after adding the bacterial agent, the COD in the solution has exceeded 100000 mg / l in 7 treatments, and the highest can reach 192000 mg / l, which is 203% higher than the blank control COD. After 24 hours, the sample was filtered and the SCOD was measured. After 72 hours of reaction, SCOD of 2 treatments finally exceeded 100000 mg / l, namely, 40g of Qinggang high-efficiency anaerobic bacteria was added and 16g of Liboyuan hydrolysis and acidification bacteria was added. Among them, the SCOD of the treatment group with 16g of Liboyuan hydrolysis and acidification bacteria reached 109000 mg / l, which is the preferred group of the 10 bacterial agent-added groups.

[0078] During the experiment, indicators such as pH, SS, VFAs, NH4+-N, total nitrogen, and total phosphorus were also monitored.

[0079] It can be seen that the pH changes slightly during the reaction, with the main range of change being 3.47-3.88. SS shows an increasing trend. Since VFAs are measured after filtration in the later stage, the VFAs content decreases significantly compared with the initial stage. Total nitrogen shows a decreasing trend, and total phosphorus shows an increasing trend.

[0080] 2. Determination of the optimal hydrolysis and acidification time

[0081] After sampling and measuring various indicators at different times as mentioned above, referring to the hydrolysis and acidification time for the effluent SCOD to exceed 100,000 mg / l, the treatment time for the two groups of treatment with 40g of Qinggang high-efficiency anaerobic bacteria and 16g of Liboyuan hydrolysis and acidification bacteria was 72h, which was determined to be the optimal reaction time.

[0082] Optimization of stirring conditions for trihydrolysis acidification

[0083] The samples were stirred (100 rpm) and a non-stirred blank control was used. SCOD and VFA content were measured within the optimal hydrolysis and acidification time to determine the extent to which stirring conditions promoted hydrolysis and acidification. The detailed experimental design is shown in Table 6. The specific experimental index test results are also shown in Table 6.

[0084]

[0085] Table 6 Hydrolysis and acidification stirring experiment design

[0086]

[0087]

[0088] Note: The initial values ​​of YD0, YD2, and YH2 are the same as the initial values ​​of D0, D2, and H2. Table 7 Test results of the influence of stirring on hydrolysis and acidification

[0089] By setting up three groups of stirring control experiments, it can be seen that the SCOD values ​​of the YD0 and YD2 treatments are higher under stirring conditions, which shows that the hydrolysis and acidification are more thorough under stirring conditions.

[0090] In summary, through the control experiments on the addition of various hydrolysis and acidifying agents, it can be seen that in the hydrolysis and acidification test of the project of preparing composite carbon source from food waste slurry, after 24 hours of hydrolysis and acidification after adding bacterial agents, the COD in the solution has exceeded 100,000 mg / l in 7 treatments, and the highest can reach 192,000 mg / l, which is a maximum increase of 203% compared with the blank control COD. After 24 hours, the sample was filtered and the SCOD was measured. After 72 hours of hydrolysis and acidification, the SCOD of the slurry was greater than 100,000 mg / l. The optimal added bacterial agent was 16g of Liboyuan hydrolysis and acidification bacteria, and stirring adjustment can promote hydrolysis and acidification.

[0091] In summary, the technical solution of this application has the following beneficial effects:

[0092] 1. The present invention conducts a hydrolysis and acidification reaction on pretreated food waste slurry, and it is found that the addition of appropriate bacterial agents and promoters can increase the COD and SCOD contents of the food waste slurry to over 100,000 mg / L, meeting the COD content requirement for the composite carbon source. The method of the present invention can improve the quality of organic carbon sources made from food waste, maximize resource recycling, and increase the value of the recycled food waste products.

[0093] 2. The present invention obtains a carbon source preparation stock solution by hydrolyzing and acidifying the liquid phase of food waste, filling the gap in the use of food waste pretreatment slurry as a carbon source supplement for water treatment. At the same time, this process can not only improve the food waste treatment capacity, but also improve the level of resource utilization of food waste. At the same time, the commercial carbon source produced can also obtain certain economic benefits, while realizing the treatment of food waste and reducing pollution to the environment.

[0094] 3. The present invention has the characteristics of simple method, short time, low cost, and high carbon source quality. It can not only effectively improve the efficiency of sewage treatment, but also significantly reduce the operating cost of sewage treatment.

[0095] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite carbon source from kitchen waste, characterized in that: The following steps are involved: S1: Pre-processing to obtain food waste slurry: Food waste is received in a receiving silo. A spiral is installed at the bottom of the silo, each spiral being equipped with a drainage separation mechanism to physically separate the solid and liquid parts of the food waste. The liquid phase is temporarily stored in the drainage separation mechanism, heated in a heating tank, and then pumped into a three-phase separator to extract crude oil. The remaining liquid residue flows into a homogenization tank for storage. The solid phase of the food waste is coarsely crushed in a crusher, then subjected to secondary crushing and pulping in a pulper, and sorted. The slurry is desanded in a desander and then pumped into a homogenization tank. The liquid phase after the crude oil is extracted and the crushed slurry are mixed and tempered in the same homogenization tank. S2: Hydrolysis and acidification: The mixed slurry after mixing and conditioning is pumped into the anaerobic acid production tank for hydrolysis and acidification reaction. The insoluble organic matter is hydrolyzed into soluble organic matter by the reaction between hydrolytic bacteria and acid-producing bacteria, thereby increasing the organic matter concentration and soluble organic matter concentration in the liquid phase of the mixed slurry; S3: Filtration and concentration: The acidified liquid is introduced into a separation and purification device for pretreatment, and sequentially subjected to coarse filtration, fine filtration, ultrafiltration membrane treatment and nanofiltration membrane concentration treatment to remove the filter residue to obtain a concentrated composite carbon source product.

2. The method for preparing a composite carbon source from kitchen waste according to claim 1, characterized in that: The optimized conditions of the hydrolysis and acidification process in step S2 are as follows: heating the mixed slurry to 34-40° C. under stirring, adding Liboyuan hydrolysis and acidification anaerobic bacteria, cellulase, protein enzyme and oil-removing bacteria to the anaerobic acid production tank, adjusting the pH to 3.0-4.0, continuously stirring, and allowing to stand after the specified hydrolysis time.

3. The method for preparing a composite carbon source from kitchen waste according to claim 2, wherein: The stirring speed during the hydrolysis and acidification reaction is 100 r / min.

4. The method for preparing a composite carbon source from kitchen waste according to claim 2, wherein: In step S2, the amount of bacterial agent added is: per 2000 ml of mixed slurry, the amount of Liboyuan hydrolytic acidifying anaerobic bacteria added is 16 g, the amount of Haicheng oil removal bacteria added is 50 g, the amount of protease added is 0.8 g, and the amount of cellulase added is 1 g.

5. The method for preparing a composite carbon source from kitchen waste according to claim 2, wherein: During the hydrolysis and acidification process, the pH value in the anaerobic acid production tank is adjusted manually by using dilute acid and alkaline additives every 12 hours. At the same time, samples are taken and centrifuged every 12 hours to measure relevant indicators.

6. The method for preparing a composite carbon source from kitchen waste according to claim 1, characterized in that: In step S3, a bag filter is used in the coarse filtration step to intercept large particles larger than 800 microns.

7. The method for preparing a composite carbon source from kitchen waste according to claim 1, characterized in that: In step S3, a bag filter is used in the fine filtration step to intercept large particles larger than 500 microns.

8. The method for preparing a composite carbon source from kitchen waste according to claim 1, wherein: In step S3, the ultrafiltration membrane treatment step uses a tubular ultrafiltration membrane with a pore size of 0.002-0.1 μm. Under the pressure difference, the solvent and small solute particles in the hydrolyzed acidified liquid pass through the membrane from the high-pressure liquid side to the low-pressure side.

9. The method for preparing a composite carbon source from kitchen waste according to claim 1, wherein: In step S3, the nanofiltration membrane concentration treatment step uses a nanofiltration membrane, the nanofiltration membrane has a pore size of 1-2 nm, and a molecular weight cut-off range of 500 to 100,000 Da.

10. The method for preparing a composite carbon source from kitchen waste according to claim 1, wherein: The solid part of the kitchen kitchen solids needs to be removed and pulped again after the first-level coarse crushing by the crusher. Under the hammer-type cutting and stirring action of 1000r / min, the pulper further crushes the material into a pulpy material. At the same time, it removes impurities mixed in the material to make the particle size less than 10mm.

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