Method for preparing carbon source from kitchen garbage

Abstract

The invention provides a method for preparing a carbon source from kitchen garbage, and belongs to the technical field of kitchen garbage treatment. According to the method, firstly, the kitchen garbage and the fermentation tail water are mixed for fermentation pretreatment, then hydrolytic acidification is performed, and alkali-adding pretreatment can improve the proportion of a denitrification component VFAs in SCOD of fermentation liquor; the total amount of SCOD and C / N can be increased through heating pretreatment; the total amount of VFAs can be increased by enzyme pretreatment, so that the quality of the prepared carbon source is improved. The result of the embodiment shows that the VFAs / SCOD value of the carbon source prepared by the method is between 0.24 and 0.4, the proportion of VFAs is high, and the carbon source belongs to a high-performance carbon source product.

Description

Technical Field

[0001] The invention belongs to the technical field of kitchen waste treatment, and particularly relates to a method for preparing a carbon source from kitchen waste. Background Art

[0002] Kitchen waste includes food waste, leftovers, flowers and plants generated by households, catering waste generated in the production process of catering operators, unit canteens, and other kitchen waste such as melon peels and fruit cores generated in the market. Kitchen waste is characterized by easy decay, high organic matter and high water content. It is easy to cause secondary pollution to the environment during the process of mobile phone, transportation and storage, and emits odor and greenhouse gases, which is harmful to human health. In recent years, the state has supported and encouraged the high-value utilization of kitchen waste, and anaerobic fermentation to prepare volatile fatty acids (VFAs) is one of the paths for high-value utilization. VFAs are highly biodegradable and can be used as a carbon source for microorganisms to increase the removal rate of nitrogen and phosphorus in sewage. In the existing technology, kitchen waste is directly used for anaerobic fermentation, but there are problems such as slow hydrolysis rate and low VFAs conversion rate, resulting in poor quality of the prepared carbon source.

[0003] Therefore, there is an urgent need for a method for preparing carbon sources from kitchen waste with better carbon source quality. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a carbon source from kitchen waste. The carbon source prepared by the preparation method of the present invention has better quality.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing a carbon source from kitchen waste, comprising the following steps: (1) mixing kitchen waste with fermentation tail water, performing fermentation pretreatment, and obtaining pretreated fermentation liquid; the fermentation pretreatment is performed under the conditions of adding alkali, heating or adding enzyme; the mass ratio of the kitchen waste to the fermentation tail water is 1: (0.5-2); When the fermentation pretreatment is carried out under alkaline conditions, the pH value of the fermentation pretreatment is 6 to 9; When the fermentation pretreatment is carried out under heating conditions, the temperature of the fermentation pretreatment is 50-70°C and the time of the fermentation pretreatment is 1-4 hours; When the fermentation pretreatment is carried out under enzyme addition conditions, each kilogram of kitchen waste contains 40,000 to 100,000 U of enzyme activity; (2) The pretreated fermentation liquid obtained in step (1) is hydrolyzed and acidified to obtain a carbon source.

[0006] Preferably, microbial agents or solid enzyme mediator materials are also added during the hydrolysis and acidification in step (2).

[0007] Preferably, in step (2), the temperature of the hydrolysis and acidification is 30-50° C., the pH value of the hydrolysis and acidification is 5-7, the initial solid content of the hydrolysis and acidification is 10-20%, the ORP value of the hydrolysis and acidification is -300-100 mV, and the headspace volume ratio of the hydrolysis and acidification is 10-30%.

[0008] Preferably, the hydrolysis and acidification in step (2) is carried out by indirect stirring.

[0009] Preferably, the indirect stirring is stirring for 12 to 16 hours and standing for 4 to 8 hours.

[0010] Preferably, in step (2), the soluble chemical oxygen demand of the carbon source is 6000-10000 mg / L, the volatile fatty acid concentration is 8000-25000 mg / L, BOD / COD>0.6, NH4-N / TN>0.75, volatile fatty acid / soluble chemical oxygen demand>0.2, and C / N>20.

[0011] The present invention provides a method for preparing a carbon source from kitchen waste, comprising the following steps: (1) mixing kitchen waste with fermentation tail water, performing fermentation pretreatment, and obtaining a pretreated fermentation liquid; the fermentation pretreatment is performed under alkali addition, heating or enzyme addition conditions; the mass ratio of the kitchen waste to the fermentation tail water is 1:(0.5-2); when the fermentation pretreatment is performed under alkali addition conditions, the pH value of the fermentation pretreatment is 6-9; when the fermentation pretreatment is performed under heating conditions, the temperature of the fermentation pretreatment is 50-70°C, and the fermentation pretreatment time is 1-4 hours; when the fermentation pretreatment is performed under enzyme addition conditions, each kilogram of kitchen waste contains 40,000-100,000 U of enzyme activity; (2) hydrolyzing and acidifying the pretreated fermentation liquid obtained in the step (1) to obtain a carbon source. The present invention first mixes kitchen waste and fermentation tail water for fermentation pretreatment, and then performs hydrolysis and acidification. Alkali pretreatment can increase the proportion of VFAs, a denitrification component of the fermentation liquid, in SCOD; heating pretreatment can increase the total amount of SCOD and C / N; enzyme pretreatment can increase the total amount of VFAs, thereby improving the quality of the prepared carbon source. The results of the embodiment show that the VFAs / SCOD value of the carbon source prepared by the present invention is between 0.24 and 0.4, and the proportion of VFAs is high, which belongs to a high-performance carbon source product. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart of the method for preparing carbon source from kitchen waste provided by the present invention; Figure 2 SCOD concentration variation diagram of the hydrolysis acidified solution in Examples 1 to 3 and Comparative Example 7; Figure 3Graph showing changes in VFAs concentration in the hydrolyzed acidified liquid in Examples 1 to 3 and Comparative Example 7. DETAILED DESCRIPTION

[0013] The present invention provides a method for preparing a carbon source from kitchen waste, comprising the following steps: (1) mixing kitchen waste with fermentation tail water, performing fermentation pretreatment, and obtaining pretreated fermentation liquid; the fermentation pretreatment is performed under the conditions of adding alkali, heating or adding enzyme; the mass ratio of the kitchen waste to the fermentation tail water is 1: (0.5-2); When the fermentation pretreatment is carried out under alkaline conditions, the pH value of the fermentation pretreatment is 6 to 9; When the fermentation pretreatment is carried out under heating conditions, the temperature of the fermentation pretreatment is 50-70°C and the time of the fermentation pretreatment is 1-4 hours; When the fermentation pretreatment is carried out under enzyme addition conditions, each kilogram of kitchen waste contains 40,000 to 100,000 U of enzyme activity; (2) The pretreated fermentation liquid obtained in step (1) is hydrolyzed and acidified to obtain a carbon source.

[0014] The invention mixes kitchen waste with fermentation tail water, performs fermentation pretreatment, and obtains pretreated fermentation liquid; the fermentation pretreatment is performed under the conditions of adding alkali, heating or adding enzymes.

[0015] In the present invention, the kitchen waste refers to a type of household waste specified in the national standard "Classification Marking of Household Waste" (GB / T 19095-2019), including food waste, leftovers, flowers and plants, etc. generated by households, catering waste generated in the production process of catering operators, unit canteens, etc., and other kitchen waste such as melon peels and fruit cores generated in the market. The present invention does not specifically limit the specific source of the kitchen waste, and any kitchen waste from a source familiar to those skilled in the art can be used.

[0016] In the present invention, the kitchen waste is preferably pretreated before being mixed with the fermentation tail water.

[0017] In the present invention, the pretreatment preferably includes impurity removal, sorting and oil removal performed sequentially.

[0018] In the present invention, the impurity removal and sorting are preferably: using a bag breaking device to break the bag of the kitchen waste, then using a coarse crushing device to perform coarse crushing, and then sequentially sorting through a wind selection system, a magnetic sorting system and a gravity screening system, and finally finely crushing through a fine crushing device.

[0019] The present invention has no special limitation on the operation of using the bag breaking device to break the bag of kitchen waste, and a technical solution well known to those skilled in the art can be used. The present invention has no special limitation on the model of the bag breaking device, and a bag breaking device well known to those skilled in the art can be used.

[0020] The present invention has no special limitation on the operation of using a coarse crushing device for coarse crushing, and a technical solution well known to those skilled in the art can be used. The present invention has no special limitation on the model of the coarse crushing device, and a coarse crushing device well known to those skilled in the art can be used.

[0021] The present invention does not specifically limit the operation of sequentially sorting through the air sorting system, the magnetic sorting system and the gravity screening system, and a technical solution familiar to those skilled in the art can be used. The present invention does not specifically limit the models of the air sorting system, the magnetic sorting system and the gravity screening system, and equipment familiar to those skilled in the art can be used. The present invention removes light impurities such as plastic bags, metal impurities and non-degradable heavy objects such as stone particles through sorting.

[0022] The present invention has no special limitation on the operation of fine crushing by fine crushing equipment, and a technical solution familiar to those skilled in the art can be used. The present invention has no special limitation on the model of the fine crushing equipment, and a fine crushing equipment familiar to those skilled in the art can be used. In the present invention, the particle size of the kitchen waste after fine crushing is preferably less than 0.5 cm.

[0023] The present invention has no special limitation on the oil removal operation, and the oil removal technical solution well known to those skilled in the art can be used. In the embodiment of the present invention, a three-phase centrifuge is used to remove floating oil.

[0024] In the present invention, the kitchen waste is in a muddy state after pretreatment.

[0025] The present invention preferably hydrolyzes and acidifies the kitchen waste to obtain fermentation tail water.

[0026] In the present invention, the temperature of the hydrolysis and acidification is preferably 30-50° C. In an embodiment of the present invention, the temperature of the hydrolysis and acidification may specifically be 30° C., 35° C., 40° C., 45° C. or 50° C.

[0027] In the present invention, the pH value of the hydrolysis acidification is preferably 5-7.

[0028] In the present invention, the initial solid content of the hydrolysis and acidification is preferably 10-20%. In an embodiment of the present invention, the initial solid content of the hydrolysis and acidification may specifically be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0029] In the present invention, the ORP value of the hydrolysis acidification is preferably -300 to -100 mV. In an embodiment of the present invention, the ORP value of the hydrolysis acidification may be specifically -300 mV, -250 mV, -200 mV, -150 mV or -100 mV.

[0030] In the present invention, the hydrolysis-acidified headspace volume ratio is preferably 10-30%. In an embodiment of the present invention, the hydrolysis-acidified headspace volume ratio may specifically be 10%, 15%, 20%, 25% or 30%.

[0031] In the present invention, the headspace pressure of the hydrolysis and acidification is preferably positive pressure, negative pressure or normal pressure.

[0032] The present invention preferably closes the exhaust valve of the hydrolysis acidification tank, and the produced gas remains in the tank body to form a positive pressure.

[0033] In the present invention, the negative pressure is preferably -90 to -70 kPa, more preferably -80 kPa.

[0034] In the present invention, the hydrolysis and acidification preferably adopts indirect stirring. In the present invention, the indirect stirring is preferably stirring for 12 to 16 hours and standing for 4 to 8 hours.

[0035] In the present invention, the hydrolysis and acidification time is preferably 1 to 15 days.

[0036] After the hydrolysis and acidification is completed, the present invention preferably allows the hydrolysis and acidification product to stand and then separate to obtain fermentation liquid and fermentation residue.

[0037] In the present invention, the standing time is preferably 6 to 24 hours. The present invention has no special limitation on the separation operation, and the fermentation liquid and fermentation residue can be obtained by using separation technical solutions well known to those skilled in the art.

[0038] In the present invention, the fermentation residue is preferably returned to the fermentation pretreatment process.

[0039] In the present invention, the fermentation broth is preferably filtered through a ceramic membrane to obtain a membrane-passing liquid and a membrane-posting liquid.

[0040] In the present invention, the material of the ceramic membrane is preferably alumina, the pore size is preferably 0.5 μm, and the thickness is preferably 150 μm. The present invention removes suspended matter by filtering through the ceramic membrane.

[0041] In the present invention, the post-membrane liquid is fermentation tail water.

[0042] In the present invention, the mass ratio of the kitchen waste to the fermentation tail water is 1:(0.5~2). In an embodiment of the present invention, the mass ratio of the kitchen waste to the fermentation tail water may be specifically 1:0.5, 1:1, 1:1.5 or 1:2. The present invention controls the mass ratio of the kitchen waste to the fermentation tail water within the above range, which can further improve the quality of the carbon source.

[0043] As an embodiment, the fermentation pretreatment is carried out under alkaline conditions.

[0044] In the present invention, the base preferably includes sodium hydroxide or sodium carbonate.

[0045] In the present invention, after the kitchen waste, fermentation tail water and alkali are mixed, the pH value of the obtained mixed solution is 6 to 9, that is, the pH value of the fermentation pretreatment is 6 to 9. In an embodiment of the present invention, the pH value of the fermentation pretreatment can be specifically 6, 7, 8 or 9.

[0046] In the present invention, the temperature of the fermentation pretreatment is preferably 20-40°C; the time of the fermentation pretreatment is preferably 0.5-2h. In an embodiment of the present invention, the temperature of the fermentation pretreatment may be specifically 20°C, 25°C, 30°C, 35°C or 40°C; the time of the fermentation pretreatment may be specifically 0.5h, 1h, 1.5h or 2h. The present invention controls the pH value, temperature and time of the fermentation pretreatment within the above range, which can further improve the quality of the carbon source.

[0047] As an embodiment, the fermentation pretreatment is carried out under heating conditions.

[0048] In the present invention, the temperature of the fermentation pretreatment is 50-70°C; the time of the fermentation pretreatment is 1-4h. In an embodiment of the present invention, the temperature of the fermentation pretreatment may be specifically 50°C, 55°C, 60°C, 65°C or 70°C; the time of the fermentation pretreatment may be specifically 1h, 2h, 3h or 4h. The present invention controls the temperature and time of the fermentation pretreatment within the above range, which can further improve the quality of the carbon source.

[0049] As an embodiment, the fermentation pretreatment is carried out under enzyme addition conditions.

[0050] In the present invention, the enzyme is preferably an enzyme having a cellulose hydrolyzing function, and more preferably a cellulose hydrolyzing enzyme.

[0051] In the present invention, each kilogram of kitchen waste contains 40000-100000U of enzyme activity. In an embodiment of the present invention, each kilogram of kitchen waste may specifically contain 40000U, 50000U, 60000U, 70000U, 80000U, 90000U or 100000U of enzyme activity. The present invention controls the enzyme activity contained in each kilogram of kitchen waste within the above range, which can further improve the quality of the carbon source.

[0052] In the present invention, the temperature of the fermentation pretreatment is preferably 35-55°C; the time of the fermentation pretreatment is preferably 0.5-2h. In an embodiment of the present invention, the temperature of the fermentation pretreatment may be specifically 35°C, 40°C, 45°C, 50°C or 55°C; the time of the fermentation pretreatment may be specifically 0.5h, 1h, 1.5h or 2h. The present invention controls the temperature and time of the fermentation pretreatment within the above range, which can further improve the quality of the carbon source.

[0053] In the present invention, the fermentation pretreatment is preferably carried out under stirring conditions; the stirring rate is preferably 250-300 rpm.

[0054] After obtaining the pretreated fermentation liquid, the present invention hydrolyzes and acidifies the pretreated fermentation liquid to obtain a carbon source.

[0055] In the present invention, the temperature of the hydrolysis and acidification is preferably 30-50° C. In an embodiment of the present invention, the temperature of the hydrolysis and acidification may specifically be 30° C., 35° C., 40° C., 45° C. or 50° C.

[0056] In the present invention, the pH value of the hydrolysis acidification is preferably 5-7.

[0057] In the present invention, the initial solid content of the hydrolysis and acidification is preferably 10-20%. In an embodiment of the present invention, the initial solid content of the hydrolysis and acidification may specifically be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0058] In the present invention, the ORP value of the hydrolysis acidification is preferably -300 to -100 mV. In an embodiment of the present invention, the ORP value of the hydrolysis acidification may be specifically -300 mV, -250 mV, -200 mV, -150 mV or -100 mV.

[0059] In the present invention, the hydrolysis-acidified headspace volume ratio is preferably 10-30%. In an embodiment of the present invention, the hydrolysis-acidified headspace volume ratio may specifically be 10%, 15%, 20%, 25% or 30%.

[0060] In the present invention, the headspace pressure of the hydrolysis and acidification is preferably positive pressure, negative pressure or normal pressure.

[0061] The present invention preferably closes the exhaust valve of the hydrolysis acidification tank, and the produced gas remains in the tank body to form a positive pressure.

[0062] In the present invention, the negative pressure is preferably -90 to -70 kPa, more preferably -80 kPa.

[0063] In the present invention, the hydrolysis and acidification preferably adopts indirect stirring. In the present invention, the indirect stirring is preferably stirring for 12 to 16 hours and standing for 4 to 8 hours.

[0064] In the present invention, the hydrolysis and acidification process preferably uses a fully automatic sampling and detection system to detect the physicochemical indicators such as the pH value, solid content, COD and VFAs of the fermentation liquid; the pH value and solid content are preferably sampled under stirring; the COD and VFAs are preferably sampled by taking the static supernatant after the stirring stops for 1 hour. In the present invention, the detection frequency of each indicator is preferably once every 12 to 36 hours. The present invention determines the material flow direction by the change of each indicator.

[0065] In the present invention, when the COD concentration of the supernatant is greater than 6000 mg / L or the VFAs concentration is greater than 8000 mg / L, the present invention preferably transfers 1 / 4 to 1 / 2 of the volume of the supernatant to a storage tank, and simultaneously supplements the same volume of fermentation tail water to continue hydrolysis and acidification.

[0066] In the present invention, when the solid content reduction rate in the hydrolysis acidification reactor is greater than 25%, the present invention preferably transfers the product in the hydrolysis acidification reactor to a storage tank, and at the same time supplements the pretreated fermentation liquid to continue hydrolysis acidification.

[0067] In the present invention, microbial agents or solid enzyme mediator materials are preferably added during the hydrolysis and acidification.

[0068] In the present invention, the solid enzyme mediator material is preferably an immobilized enzyme formed by loading the cellulose hydrolyzing functional enzyme on a carrier material. In the present invention, the carrier material preferably includes an iron-based material, a carbon-based material or a gel-state material, more preferably ferroferric oxide, zero-valent iron, biochar, graphene, sodium alginate or chitosan. In the present invention, the loading amount of the cellulose hydrolyzing functional enzyme in the solid enzyme mediator material is preferably 100-200 mg / g, more preferably 150 mg / g.

[0069] In the present invention, the mass ratio of the solid enzyme mediator material to the pretreated fermentation broth is preferably (0.5-2):100, more preferably (1-2):100.

[0070] In the present invention, the microbial agent is preferably composed of strains or bacterial communities derived from anaerobic organic matter environments and having efficient hydrolysis and acid production functions, more preferably Clostridium microorganisms screened from leachate of domestic waste landfills, anaerobic biogas production systems of kitchen waste, or animal intestinal system environments, or mixed bacterial communities enriched from the environments with Clostridium, Bifidobacterium, or Enterococcus as dominant species.

[0071] In the present invention, the Clostridium microorganism preferably includes Sporogenes and / or Clostridium acetogenicum.

[0072] In the present invention, the microbial agent is preferably Clostridium sporogenes and Clostridium acetogenes; the number ratio of Clostridium sporogenes to Clostridium acetogenes is preferably 1:(0.5-1.5), more preferably 1:1.

[0073] In the present invention, the microbial agent is preferably inoculated into the anaerobic culture solution to obtain a microbial agent solution, and then the microbial agent solution is added to the pre-treated fermentation solution.

[0074] In the present invention, the mass ratio of the microbial agent to the anaerobic culture solution is preferably (1-3):100, more preferably 2:100.

[0075] In the present invention, the volume ratio of the microbial agent solution to the pretreated fermentation broth is preferably (1-3):100, more preferably 2:100.

[0076] In the present invention, the microbial agent is preferably subjected to salt tolerance acclimation before use. The present invention preferably continuously cultures the microbial agent in an LB culture solution having a sodium chloride content of 20 to 50 g / L, and then centrifuges to obtain a microbial solution. The present invention performs salt tolerance acclimation on the microbial agent to improve the tolerance of the microbial agent to high-salt kitchen waste.

[0077] The present invention does not specifically limit the screening and preparation process of the microbial agent, and a technical solution familiar to those skilled in the art can be used. In an embodiment of the present invention, the preparation process of the microbial agent is as follows: (1) 1.5 kg of kitchen waste fermentation slurry (water content 98%) and 300 g of kitchen waste (water content 85%) are mixed and placed in a fermentation tank, 3 g of SBES is added as a methanogenic inhibitor, and the mixture is run for 4 days at a stirring rate of 900 r / min, a temperature of 37°C, and an initial pH value of 7-8 to start the anaerobic fermentation reaction, and then 300 mL of fermentation liquid is discharged every day, 300 g of kitchen waste is added, and the material is continuously fed and discharged for 2 weeks to enrich acid-producing microorganisms. After the fermentation tank is run until the VFAs content of the fermentation liquid is higher than 8000 mg / L, the fermentation liquid is taken as an inoculum to start the strain screening step. (2) The fermented liquid of kitchen waste was used as inoculum, and was spread on anaerobic screening plates in gradient dilutions. The single colonies were repeatedly streaked and separated until single colonies appeared. The single colonies were transferred to anaerobic culture medium and cultured for 3 days. The growth curve was determined. The bacterial liquid in the logarithmic growth phase was inoculated into cellulose culture medium at a 2% inoculation rate. The cellulose hydrolysis rate was analyzed by measuring the reducing sugar yield; at the same time, it was inoculated into kitchen waste leachate (COD was 4500 mg / L) and the VFAs yield was determined. Two single colonies with higher cellulose hydrolysis rate and VFAs yield were selected for the preparation of mixed bacterial agents. The components of the anaerobic screening plates included (g / L): cellulose powder 10, tryptone 10, soluble starch 1.0, glucose 1.0, cysteine ​​hydrochloride 0.5, chloramine 0.6, sodium hyaluronate 0.1, sodium pyruvate 0.2, sodium pyruvate 0.3, sodium pyruvate 0.4, sodium pyruvate 0.6 The ingredients of anaerobic culture medium include (g / L): 0.293 g of dipotassium hydrogen phosphate, 0.176 g of potassium dihydrogen phosphate, 0.5 g of sodium chloride, 0.45 g of ammonium sulfate, 0.045 g of calcium chloride, 0.094 g of magnesium sulfate, 0.001 g of resazurin, 0.5 g of L-cysteine, 0.5 g of L-ascorbic acid, 4 g of sodium carbonate, 1 g of beef powder, 1 g of peptone, 1 g of agar, and the pH value is 7.5-8.0. The ingredients of cellulose culture medium include (g / L): 5 g of sodium carboxymethyl cellulose, 0.293 g of dipotassium hydrogen phosphate, 0.176 g of potassium dihydrogen phosphate, 0.5 g of sodium chloride, 0.45 g of ammonium sulfate, 0.001 g of resazurin, and 0.5 g of L-cysteine, and the pH value is 7.5-8.0. (3) The selected single colonies were cultured in anaerobic culture medium in shake flasks for 3 days and counted using the CFU method. The bacterial suspensions of each single bacterium were mixed and then transferred to fresh anaerobic culture medium at an inoculation rate of 2% for expansion culture. The bacterial suspension after expansion culture was used as the mixed bacterial agent.

[0078] The invention adds microbial agents or solid enzyme mediator materials to increase the hydrolysis and acidification rate of kitchen waste and strengthen the fermentation acid production effect. The invention controls the amount of microbial agents or solid enzyme mediator materials within the above range, which can further improve the quality of the carbon source.

[0079] After the hydrolysis and acidification is completed, the present invention preferably allows the hydrolysis and acidification product to stand and then separate to obtain fermentation liquid and fermentation residue.

[0080] In the present invention, the standing time is preferably 6 to 24 hours. The present invention has no special limitation on the separation operation, and the fermentation liquid and fermentation residue can be obtained by using separation technical solutions well known to those skilled in the art.

[0081] In the present invention, the fermentation residue is preferably returned to the fermentation pretreatment process.

[0082] In the present invention, the fermentation broth is preferably filtered through a ceramic membrane to obtain a membrane-passing liquid and a membrane-posting liquid.

[0083] In the present invention, the material of the ceramic membrane is preferably alumina, the pore size is preferably 0.5 μm, and the thickness is preferably 150 μm. The present invention removes suspended matter by filtering through the ceramic membrane.

[0084] In the present invention, the post-membrane liquid is used as fermentation tail water in the subsequent fermentation pretreatment process.

[0085] The present invention preferably detects the suspended solids content (SS), total nitrogen content (TN) and COD content in the membrane liquid, and when COD / TN>20 and SS<0.2g / L, a carbon source is obtained.

[0086] When the membrane liquid does not meet the above requirements, the present invention preferably treats the membrane liquid through a membrane to reduce the nitrogen content and the suspended matter content so that it meets the requirements and obtains a carbon source. The present invention has no special limitation on the operation of treating the membrane to reduce the nitrogen content and the suspended matter content, and a technical solution familiar to those skilled in the art can be used.

[0087] In the present invention, the soluble chemical oxygen demand of the carbon source is preferably 6000-10000 mg / L, the volatile fatty acid concentration is preferably 8000-25000 mg / L, BOD / COD is preferably >0.6, NH4-N / TN is preferably >0.75, volatile fatty acid / soluble chemical oxygen demand is preferably >0.2, and C / N is preferably >20.

[0088] The present invention first mixes kitchen waste and fermentation tail water for fermentation pretreatment, and then performs hydrolysis and acidification. Alkali pretreatment can increase the proportion of VFAs, a denitrification component of the fermentation liquid, in SCOD; heating pretreatment can increase the total amount of SCOD and C / N; enzyme pretreatment can increase the total amount of VFAs; thereby improving the quality of the prepared carbon source, and microbial agents or solid enzyme mediator materials are added during the hydrolysis and acidification process to increase the hydrolysis and acidification rate, strengthen the fermentation acid production effect, and further improve the quality of the carbon source.

[0089] The method for preparing carbon source from kitchen waste provided by the present invention solves the problem of urban solid waste and sewage treatment in a coordinated manner, and is suitable for the high-value utilization of high-oil and high-salt kitchen waste. The carbon source prepared from kitchen waste is a composite carbon source, and the main active ingredients include VFAs such as acetic acid, propionic acid, and butyric acid, which has a better denitrification effect than a single carbon source. Compared with traditional commercial carbon sources (sodium acetate, etc.), the production process of kitchen waste carbon source does not rely on fossil raw materials, and the cost and carbon emissions are lower, which belongs to green low-carbon products and pollution reduction and carbon reduction technology. The present invention effectively strengthens the hydrolysis and acidification process of kitchen waste through technical means such as heating pretreatment, solid enzyme, top air conditioning, etc., and the soluble COD after fermentation can be as high as 80,000~90,000 mg / L or more, the concentration of effective denitrification component VFA is as high as 20,000 mg / L or more, VFAs / SCOD is higher than 0.24, and the C / N ratio is higher than 20, between 26 and 62. Compared with the prior art, the concentration of VFAs, an active denitrification ingredient, in the kitchen waste hydrolysis acidified liquid of the present invention is relatively high, and the effective COD equivalent is relatively high, thereby effectively improving the quality of the carbon source product.

[0090] The present invention has no special limitation on the equipment used in the method for preparing carbon source from kitchen waste, and the equipment can be selected according to actual needs.

[0091] The process and equipment diagram of the method for preparing carbon source from kitchen waste provided by the present invention are as follows Figure 1 shown.

[0092] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0093] The kitchen waste used in each embodiment comes from the kitchen waste treatment plant in Chengdu, Sichuan Province. After sorting, impurity removal and coarse crushing, the particle size is greater than 0.5 cm, and strip fibers and pepper skins can be seen with the naked eye. The physical and chemical analysis of the kitchen waste nutritional components includes 328.88 g / kg of mineral oil, 65.50 g / kg of cellulose, 60.23 g / kg of protein, 54.09 g / kg of fat, 24.81 g / kg of total sugar, and 3.92 g / kg of salt; the nutrient content is carbon (C) 13.99%, hydrogen (H) 15.645%, oxygen (O) 45.580%, nitrogen (N) 4.35%, and sulfur (S) 0.124%; it is a typical high-oil, high-fiber, and high-salt kitchen waste, and the simulated molecular formula is C7H8O 23 N2S 0.05 .

[0094] The fermentation tail water in each embodiment and comparative example is: kitchen waste is finely crushed to obtain muddy kitchen waste with a particle size of less than 0.5 cm, and the floating oil is removed by centrifugation at 3000rpm for 10min. The pH value of the kitchen waste after the floating oil is removed is adjusted to 6.5, and the hydrolysis and acidification reaction is started. The temperature of hydrolysis and acidification is 35°C, the initial solid content is 15%, the ORP value of hydrolysis and acidification is -150mV, the headspace volume of hydrolysis and acidification accounts for 20%, and the headspace pressure is normal pressure. Indirect stirring is adopted, stirring for 12h, standing for 8h, hydrolysis and acidification for 4 days, and the product after hydrolysis and acidification is separated after standing for 12h to obtain fermentation liquid, and the fermentation liquid is filtered through a ceramic membrane (the material of the ceramic membrane is alumina, the pore size is 0.5μm, and the thickness is 150μm) to obtain the post-membrane liquid, i.e., fermentation tail water.

[0095] Comparative Example 1 The kitchen waste was finely crushed to obtain muddy kitchen waste with a particle size of less than 0.5 cm, and the floating oil was removed by centrifugation at 3000 rpm for 10 minutes. The kitchen waste after the floating oil was removed and the fermentation tail water were mixed in a mass ratio of 1:2, and transferred to a hydrolysis acidification tank for fermentation. The effective volume of the hydrolysis acidification tank was 5L, the headspace space accounted for 10%, the hydrolysis acidification temperature was 35°C, the hydrolysis acidification pH value was 6.5, the initial solid content was 15%, the hydrolysis acidification ORP value was -150mV, the headspace pressure was normal pressure, indirect stirring was adopted, the stirring rate was 150rpm, the stirring was 12h, and the mixture was allowed to stand for 8h. The hydrolysis acidification reaction lasted for 4 days. The tested pH value was 5.5, and the solid content reduction rate was 39.73%, and the fermentation liquid was obtained.

[0096] Comparative Example 2 The kitchen waste was finely crushed to obtain muddy kitchen waste with a particle size of less than 0.5 cm, and the floating oil was removed by centrifugation at 3000 rpm for 10 minutes. The kitchen waste after the floating oil was removed and the fermentation tail water were mixed in a mass ratio of 1:1, and transferred to a hydrolysis acidification tank for fermentation. The effective volume of the hydrolysis acidification tank was 5L, the headspace space accounted for 10%, the hydrolysis acidification temperature was 35°C, the hydrolysis acidification pH value was 6.5, the initial solid content was 11.5%, the hydrolysis acidification ORP value was -150mV, the headspace pressure was normal pressure, indirect stirring was adopted, the stirring rate was 150rpm, the stirring was 12h, and the mixture was allowed to stand for 8h. The hydrolysis acidification reaction lasted for 4 days. The tested pH value was 5.5, and the solid content reduction rate was 18.17%, and the fermentation liquid was obtained.

[0097] Comparative Example 3 The kitchen waste was finely crushed to obtain muddy kitchen waste with a particle size of less than 0.5 cm, and the floating oil was removed by centrifugation at 3000 rpm for 10 minutes. The kitchen waste after the floating oil was removed and the fermentation tail water were mixed in a mass ratio of 1:0.5, and transferred to a hydrolysis acidification tank for fermentation. The effective volume of the hydrolysis acidification tank was 5L, the headspace space accounted for 10%, the hydrolysis acidification temperature was 35°C, the hydrolysis acidification pH value was 6.5, the initial solid content was 7.6%, the hydrolysis acidification ORP value was -150mV, the headspace pressure was normal pressure, indirect stirring was adopted, the stirring rate was 150rpm, the stirring was 12h, and the mixture was allowed to stand for 8h. The hydrolysis acidification reaction lasted for 4 days. The tested pH value was 5.5, and the solid content reduction rate was 18.82%, thereby obtaining a fermentation liquid.

[0098] The fermentation broths in Comparative Examples 1 to 3 were allowed to stand for 10 hours, and the supernatants were taken to analyze the physicochemical properties. The results are shown in Table 1.

[0099] Table 1 Physical and chemical properties of the supernatant after the fermentation liquid in Comparative Examples 1 to 3 was left to stand for 10 hours

[0100] As can be seen from Table 1, under the condition of 1:2 mixing of kitchen waste and fermentation tail water, the highest VFAs concentration of the fermentation liquid is 21419.67 mg / L, which is 2.6 times the standard requirement of carbon source products (8000 mg / L); the C / N ratio is 42.46, which is 2.1 times the C / N standard of carbon source products (>20), which provides a higher effective COD equivalent for wastewater treatment and denitrification.

[0101] Comparative Example 4 The kitchen waste was finely crushed to obtain muddy kitchen waste with a particle size of less than 0.5 cm, and the floating oil was removed by centrifugation at 3000 rpm for 10 minutes. The kitchen waste after the floating oil was removed and the fermentation tail water were mixed in a mass ratio of 1:2, and transferred to a hydrolysis acidification tank for fermentation. The effective volume of the hydrolysis acidification tank was 5L, the headspace space accounted for 30%, the hydrolysis acidification temperature was 35°C, the hydrolysis acidification pH value was 6.5, the initial solid content was 15%, the hydrolysis acidification ORP value was -150mV, the headspace pressure was normal pressure, indirect stirring was adopted, the stirring rate was 150rpm, the stirring was 12h, the standing was 8h, the hydrolysis acidification reaction was 7 days, and the fermentation liquid was obtained.

[0102] Comparative Example 5 The headspace air pressure in Comparative Example 4 was replaced with positive pressure, the exhaust valve of the hydrolysis acidification tank was closed, and the produced gas was retained in the tank body to form a positive pressure. The other parameters were the same as those in Comparative Example 4.

[0103] Comparative Example 6 The headspace air pressure in Comparative Example 4 was replaced with negative pressure, and a suction pump was used to extract the gas in the hydrolysis acidification tank at any time to form a negative pressure of -80 kPa. Other parameters were the same as those in Comparative Example 4.

[0104] The fermentation broths in Comparative Examples 4 to 6 were allowed to stand for 10 hours, and the supernatants were taken to analyze the physicochemical properties. The results are shown in Table 2.

[0105] Table 2 Physical and chemical properties of the supernatant after the fermentation liquid in Comparative Examples 4 to 6 was left to stand for 10 hours

[0106] It can be seen from Table 2 that the SCOD concentration is higher in the normal pressure mode, the C / N meets the carbon source product standard of greater than 20, and the solid content is the lowest, that is, the hydrolysis liquefaction effect in the normal pressure mode is better than that in the positive pressure and negative pressure modes.

[0107] Example 1 (1) Finely crushing the kitchen waste to obtain muddy kitchen waste with a particle size of less than 0.5 cm, centrifuging at 3000 rpm for 10 min to remove the floating oil, mixing the kitchen waste after the floating oil removal with the fermentation tail water in a mass ratio of 1:2, then adding sodium hydroxide to a system pH value of 8.5, and pre-fermenting in a water bath at 35°C for 1 h to obtain a pre-treated fermentation liquid; (2) The pH value of the pretreated fermentation liquid obtained in step (1) was adjusted to 6.5, and the hydrolysis and acidification reaction was started. The hydrolysis and acidification temperature was 35°C, the initial solid content was 15%, the ORP value of the hydrolysis and acidification was -150 mV, the headspace volume ratio of the hydrolysis and acidification was 20%, the headspace pressure was normal pressure, indirect stirring was adopted, stirring was carried out for 12 h, standing for 8 h, and hydrolysis and acidification was carried out for 14 days, and the changes in the SCOD and VFAs composition of the fermentation liquid were dynamically monitored.

[0108] Example 2 (1) Finely crushing kitchen waste to obtain muddy kitchen waste with a particle size of less than 0.5 cm, centrifuging at 3000 rpm for 10 min to remove floating oil, mixing the kitchen waste after the floating oil removal with fermentation tail water in a mass ratio of 1:2, and then pre-fermenting in a 60° C. water bath for 1 h to obtain a pre-treated fermentation liquid; (2) The pH value of the pretreated fermentation liquid obtained in step (1) was adjusted to 6.5, and the hydrolysis and acidification reaction was started. The hydrolysis and acidification temperature was 35°C, the initial solid content was 15%, the ORP value of the hydrolysis and acidification was -150 mV, the headspace volume ratio of the hydrolysis and acidification was 20%, the headspace pressure was normal pressure, indirect stirring was adopted, stirring was carried out for 12 h, standing for 8 h, and hydrolysis and acidification was carried out for 14 days, and the changes in the SCOD and VFAs composition of the fermentation liquid were dynamically monitored.

[0109] Example 3 (1) Finely crushing kitchen waste to obtain muddy kitchen waste with a particle size of less than 0.5 cm, centrifuging at 3000 rpm for 10 min to remove floating oil, mixing the kitchen waste after the floating oil removal with fermentation tail water in a mass ratio of 1:2, and then adding 1wt% cellulose hydrolase powder (10000U / g), with 100000U enzyme activity per kilogram of kitchen waste, and pre-fermenting in a 40°C water bath for 1 h to obtain a pre-treated fermentation liquid; (2) The pH value of the pretreated fermentation liquid obtained in step (1) was adjusted to 6.5, and the hydrolysis and acidification reaction was started. The hydrolysis and acidification temperature was 35°C, the initial solid content was 15%, the ORP value of the hydrolysis and acidification was -150 mV, the headspace volume ratio of the hydrolysis and acidification was 20%, the headspace pressure was normal pressure, indirect stirring was adopted, stirring was carried out for 12 h, standing for 8 h, and hydrolysis and acidification was carried out for 14 days, and the changes in the SCOD and VFAs composition of the fermentation liquid were dynamically monitored.

[0110] Comparative Example 7 The fermentation pretreatment in Example 1 was omitted, and the hydrolysis and acidification process was the same as in Example 1.

[0111] The changes in SCOD and VFAs concentrations of the hydrolyzed acidified liquids in Examples 1 to 3 and Comparative Example 7 are as follows: Figure 2~3 As shown. Figure 2~3 It can be seen that under the alkali, heating and enzyme pretreatment schemes, the maximum SCOD of the hydrolysis acidified liquid was 64800 mg / L, 93150 mg / L and 79425 mg / L, respectively, the maximum VFAs were 19594.15 mg / L, 22178.88 mg / L and 22590.00 mg / L, respectively, VFAs / SCOD were 0.30, 0.24 and 0.28, and the C / N ratio was 44.4, 61.6 and 56.2, respectively. It can be seen that alkali pretreatment can increase the proportion of VFAs in the denitrification component of the fermentation liquid in SCOD; heating pretreatment can increase the total amount of SCOD, and the C / N is as high as 61.6, with the highest effective COD equivalent; enzyme pretreatment can increase the total amount of VFAs. Therefore, pretreatment of kitchen waste by alkali, heat, enzymes and other means before hydrolysis and acidification can effectively improve the quality of carbon sources.

[0112] Example 4 (1) Finely crushing kitchen waste to obtain muddy kitchen waste with a particle size of less than 0.5 cm, centrifuging at 3000 rpm for 10 min to remove floating oil, mixing the kitchen waste after the floating oil removal with fermentation tail water in a mass ratio of 1:2, and then pre-fermenting in a 60° C. water bath for 1 h to obtain a pre-treated fermentation liquid; (2) Inoculating the microbial agent into the anaerobic culture solution to obtain a microbial agent solution, wherein the microbial agents are Clostridium sporogenes and Clostridium acetogenes, the number ratio of Clostridium sporogenes to Clostridium acetogenes is 1:1, and the mass ratio of the microbial agent to the anaerobic culture solution is 2:100; the components of the anaerobic culture solution are (g / L): 0.293 dipotassium hydrogen phosphate, 0.176 potassium dihydrogen phosphate, 0.5 sodium chloride, 0.45 ammonium sulfate, 0.045 calcium chloride, 0.094 magnesium sulfate, 0.001 resazurin, 0.5 L-cysteine, 0.5 L-ascorbic acid, 4.0 sodium carbonate, 1.0 beef powder, 1.0 peptone, 1.0 agar and ultrapure water, with a pH value of 7.5; (3) The pH value of the pretreated fermentation liquid obtained in step (1) was adjusted to 6.5, and then the microbial agent solution in step (2) was added, the volume ratio of the microbial agent solution to the pretreated fermentation liquid was 2:100, and the hydrolysis and acidification reaction was started. The hydrolysis and acidification temperature was 35°C, the initial solid content was 15%, the ORP value of the hydrolysis and acidification was -150mV, the headspace volume ratio of the hydrolysis and acidification was 20%, the headspace pressure was normal pressure, indirect stirring was adopted, stirring was carried out for 12 hours, standing for 8 hours, and hydrolysis and acidification was carried out for 6 days.

[0113] In Test Example 4, VFAs in the hydrolysis acidified fermentation broth reached the highest value, with a total concentration of 27039.89 mg / L, which was 34% higher than the total concentration of 20217.57 mg / L in Comparative Example 7 without inoculation of bacterial agent and pretreatment, and the time was shortened by 8 days.

[0114] In summary, the carbon source prepared by the present invention has better quality.

[0115] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a carbon source from kitchen waste, comprising the following steps: (1) mixing kitchen waste with fermentation tail water, performing fermentation pretreatment, and obtaining a pretreated fermentation liquid; The fermentation pretreatment is carried out under the conditions of adding alkali, heating or adding enzymes; the mass ratio of the kitchen waste to the fermentation tail water is 1: (0.5~2); When the fermentation pretreatment is carried out under alkaline conditions, the pH value of the fermentation pretreatment is 6 to 9; When the fermentation pretreatment is carried out under heating conditions, the temperature of the fermentation pretreatment is 50-70°C and the time of the fermentation pretreatment is 1-4 hours; When the fermentation pretreatment is carried out under enzyme addition conditions, each kilogram of kitchen waste contains 40,000 to 100,000 U of enzyme activity; (2) The pretreated fermentation liquid obtained in step (1) is hydrolyzed and acidified to obtain a carbon source.

2. The method according to claim 1, characterized in that In the step (2), microbial agents or solid enzyme mediator materials are also added during the hydrolysis and acidification.

3. The method according to claim 1, characterized in that In the step (2), the temperature of the hydrolysis and acidification is 30-50° C., the pH value of the hydrolysis and acidification is 5-7, the initial solid content of the hydrolysis and acidification is 10-20%, the ORP value of the hydrolysis and acidification is -300-100 mV, and the headspace volume of the hydrolysis and acidification accounts for 10-30%.

4. The method according to claim 1, characterized in that: The hydrolysis and acidification in step (2) is carried out by indirect stirring.

5. The method according to claim 4, characterized in that The indirect stirring is stirring for 12 to 16 hours and standing for 4 to 8 hours.

6. The method according to claim 1, characterized in that In the step (2), the soluble chemical oxygen demand of the carbon source is 6000-10000 mg / L, the volatile fatty acid concentration is 8000-25000 mg / L, BOD / COD>0.6, NH4-N / TN>0.75, volatile fatty acid / soluble chemical oxygen demand>0.2, and C / N>20.

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