A method for enzymatic pretreatment of wet hot water hydrolysate of kitchen waste

Abstract

This invention discloses a method for enzymatic pretreatment of wet hydrolysate from kitchen waste. The method involves wet hydrolyzing the kitchen waste slurry and separating the three phases, with the liquid phase product being the wet hydrolysate. A portion of the wet hydrolysate is fed into a liquid fermentation tank, where an enzyme preparation is added for liquid fermentation to obtain a composite enzyme solution. The composite enzyme solution is then mixed with another portion of the wet hydrolysate for enzymatic hydrolysis, completing the pretreatment. This invention also discloses a method for treating kitchen waste, first using the aforementioned enzymatic pretreatment method for the wet hydrolysate, and then feeding the enzymatically hydrolysate into a high-efficiency anaerobic reactor for anaerobic treatment. This invention can reduce the investment cost of enzymatic pretreatment and even kitchen waste treatment without affecting the treatment efficiency.

Description

Technical Field

[0001] This invention belongs to the field of food waste treatment technology, and specifically relates to a method for enzymatic pretreatment of wet hot water hydrolysate of food waste. Background Technology

[0002] Biological treatment of wastewater mainly includes aerobic biological treatment and anaerobic biological treatment. Anaerobic biological treatment is widely used due to its advantages such as low energy consumption, high load capacity, low operating costs, and the potential to generate bioenergy, with high-efficiency anaerobic reactors being the primary technology. Typical examples of high-efficiency anaerobic reactors include upflow anaerobic sludge blanket (UASB) reactors and expanded granular sludge blanket (EGSB) reactors, both of which can achieve an organic load of 3 kg COD / m³. 3 •d, It is simple to operate, has a short residence time, and high treatment efficiency, and is widely used in the treatment of industrial wastewater and municipal sewage.

[0003] The wet hydrolysate of food waste is the liquid product resulting from the three-phase separation of food waste slurry after wet hydrolysis. It accounts for 70-80% of the total liquid and is rich in various organic matter such as starch, protein, lipids, and inorganic salts. It has a high suspended solids content and strong biochemical properties. If a high-efficiency anaerobic reactor is directly used to treat the wet hydrolysate of food waste, the high suspended solids content will increase the reactor's processing load, reduce the sludge content and activity within the reactor, ultimately leading to a decrease in reactor efficiency and a reduction in methane production.

[0004] To address the aforementioned issues, ensure the processing efficiency of high-efficiency anaerobic reactors, and increase methane production, various pretreatment methods are required in practical applications to reduce the suspended solids content in the wet hydrolysate of kitchen waste, thereby enabling resource recovery and utilization through anaerobic digestion technology. Enzyme pretreatment is widely used due to its strong environmental friendliness and high processing efficiency; however, because biological enzymes are relatively expensive, using enzymes produced from the fermentation of various organic wastes for pretreatment can effectively improve the economic benefits of enzyme pretreatment.

[0005] Currently, the main method for preparing biological enzymes is microbial fermentation. As an important industrial enzyme preparation strain, Aspergillus niger can produce amylase, cellulase, acidic protease, pectinase, etc. Therefore, in existing technologies, Aspergillus niger is often fermented in liquid / solid culture media to obtain various biological enzymes.

[0006] Given the characteristics of wet hydrolysate from kitchen waste, if traditional microbial fermentation is used for enzymatic pretreatment, the overall cost is high due to the limited production capacity of biological enzymes at the fermentation site and the input of culture medium materials, and it is not conducive to large-scale industrial production. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for enzymatic pretreatment of wet hot water hydrolysate of kitchen waste, so as to reduce the investment cost of enzymatic pretreatment and even kitchen waste treatment without affecting the treatment efficiency.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a method for enzymatic pretreatment of wet hot water hydrolysate of kitchen waste, comprising the following steps:

[0010] Step 1: After wet hydrolysis of the kitchen waste slurry, the three phases are separated, and the liquid phase product is the wet hydrolysis liquid;

[0011] Step 2: A portion of the wet hydrolysate is sent into a liquid fermentation tank, and enzyme preparation bacterial solution is added for liquid fermentation to obtain a compound enzyme solution;

[0012] Step 3: Mix the composite enzyme solution with another part of the wet hot hydrolysate to carry out the enzymatic hydrolysis reaction, thus completing the pretreatment.

[0013] In one embodiment, step 2 involves feeding 5-10% by volume of the wet hydrolysate into a liquid fermentation tank for liquid fermentation.

[0014] In one embodiment, the solid product obtained from the three-phase separation is subjected to dry anaerobic digestion, and the resulting digestate is sterilized at high temperature and then enters a liquid fermenter. The TCOD of the wet hydrolysate is adjusted to 20-30 g / L, the TN content to 3-6 g / L, and the TP content to 0.1-0.25 g / L.

[0015] In one embodiment, the enzyme preparation bacterial solution is Aspergillus niger solution, Aspergillus oryzae solution, or Aspergillus oryzae solution, and the bacterial solution concentration is 10. 8 -10 9 CFU / mL, by volume, the dosage is 3-5% of the total liquid volume in the fermenter.

[0016] In one embodiment, in step 2, the liquid fermentation temperature is 28-32℃, the tank pressure is 0.02-0.03MPa, the aeration rate is 160-180L / h, and the fermentation time is 5-7 days.

[0017] In one embodiment, in step 3, the temperature of the enzymatic hydrolysis reaction is 28-32°C, and the hydrolysis time is 12-36 hours.

[0018] In one embodiment, in step 3, the weight ratio of the complex enzyme solution to the wet hydrolysate is 1:18-19.

[0019] In a second aspect, the present invention also provides a method for treating kitchen waste, wherein the pretreatment is first performed by enzymatic hydrolysis of the wet hot hydrolysate of the kitchen waste, and then the wet hot hydrolysate after the enzymatic hydrolysis reaction is sent to a high-efficiency anaerobic reactor for anaerobic treatment.

[0020] In one embodiment, the anaerobic digestate from the high-efficiency anaerobic reactor is partially refluxed, sterilized at high temperature, and then enters the liquid fermenter. The TCOD content of the wet hydrolysate in the liquid fermenter is adjusted to 20-30 g / L, TN content to 3-6 g / L, and TP content to 0.1-0.25 g / L, either alone or together with the digestate produced by dry anaerobic digestion.

[0021] In one embodiment, the total amount of wet hydrolysate, dry anaerobic digestate, and anaerobic digest reflux from the high-efficiency anaerobic reactor in the liquid fermenter is 50-80% of the total volume of the liquid fermenter.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) This invention provides a method for enzymatic pretreatment of wet hydrolysate of kitchen waste. The method uses enzyme preparations such as Aspergillus niger liquid to carry out liquid fermentation of part of the wet hydrolysate of kitchen waste to produce a complex enzyme, and uses the complex enzyme to carry out enzymatic pretreatment of the remaining wet hydrolysate. While ensuring high treatment efficiency, it effectively reduces the investment cost of enzymatic pretreatment and is more conducive to industrial production.

[0024] (2) This invention uses dry anaerobic digestion liquid and / or anaerobic digestion reflux liquid from a high-efficiency anaerobic reactor to adjust the TCOD, TN and TP content of wet hot hydrolysate in a liquid fermenter. Since the total amount of both is relatively small, it effectively reduces the energy consumption of wet hot hydrolysate pretreatment, saves land area, and greatly improves the efficiency of resource recycling. It is of great significance for the efficient treatment and utilization of kitchen waste.

[0025] (3) The wet hydrolysate of the present invention has a reduced suspended solids content after enzymatic pretreatment, and can be used for efficient anaerobic treatment, with significant environmental and social benefits. Attached Figure Description

[0026] Figure 1 This is a flowchart of the enzymatic pretreatment method for wet hot water hydrolysate of kitchen waste provided by the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the purpose, technical solution, and beneficial effects of this invention, the invention will be further described in detail below with reference to specific examples. The specific examples described are merely illustrative and are not intended to limit the invention. This invention can be embodied through various different embodiments, and the scope of protection is not limited to the embodiments described herein.

[0028] Unless otherwise specified, all test methods used in this embodiment are conventional methods. Reagents and instruments used without a manufacturer's name are all standard products that can be purchased from legitimate channels.

[0029] This invention relates to a method for enzymatic pretreatment of wet hydrolysate from kitchen waste. After wet hydrolysate of the kitchen waste slurry, a portion of the liquid phase product from the three-phase separation is introduced into a liquid fermentation tank for liquid fermentation, while the other portion participates in the enzymatic hydrolysis reaction. Specifically, as follows... Figure 1 As shown, the main steps include the following:

[0030] Step 1: Take the kitchen waste slurry and perform wet hydrolysis, then perform three-phase separation to obtain liquid phase product, solid phase product and oil phase product, wherein the liquid phase product is the wet hydrolysis liquid.

[0031] Step 2: A portion of the wet hydrolysate obtained in Step 1 is transferred to a liquid fermenter, and enzyme preparation bacterial solution is added to the fermenter. The fermenter parameters are adjusted, and liquid fermentation is carried out to obtain a composite enzyme solution. This composite enzyme solution contains a large number of biological enzymes and fungi, among which the biological enzymes mainly include acidic protease and α-amylase.

[0032] Step 3: Mix the compound enzyme solution obtained in Step 2 with another part of the wet hot hydrolysate for enzymatic hydrolysis. Under the action of the compound enzyme produced by the fermentation of the enzyme preparation bacterial solution, a large amount of suspended particulate matter in the wet hot hydrolysate of kitchen waste is decomposed, thus completing the pretreatment.

[0033] This invention utilizes an enzyme-based bacterial solution to perform liquid fermentation on a portion of the wet hydrolysate to produce a composite enzyme, which is then used to enzymatically hydrolyze the remaining wet hydrolysate. In this invention, the wet hydrolysate of kitchen waste participates in both liquid fermentation and enzymatic hydrolysis as a reactant, avoiding the drawback of existing technologies that require additional liquid / solid culture media for enzyme production. This effectively reduces the investment cost of enzymatic pretreatment and improves subsequent anaerobic treatment efficiency and methane production, resulting in significant environmental and social benefits.

[0034] In an embodiment of the present invention, a portion of the wet hydrolysate is fed into a liquid fermentation tank. Specifically, 5-10% of the wet hydrolysate obtained from the three-phase separation is fed into the liquid fermentation tank by volume, and the enzyme preparation bacterial solution is used for liquid fermentation to produce a complex enzyme. The remaining portion undergoes enzymatic hydrolysis under the action of the complex enzyme.

[0035] In embodiments of the present invention, to further reduce energy consumption and improve resource recycling efficiency, the solid-phase product obtained from the three-phase separation can be subjected to dry anaerobic digestion. The digestate produced by dry anaerobic digestion is sterilized at high temperature and then enters a liquid fermentation tank to adjust the TCOD, TN, and TP content in the wet hydrolysate, ensuring the liquid fermentation effect and producing a highly active complex enzyme. For example, the adjustment targets are: TCOD to 20-30 g / L, TN content to 3-6 g / L, and TP content to 0.1-0.25 g / L. For example, the high-temperature sterilization temperature is 121°C, and the sterilization time is 20-30 minutes.

[0036] In embodiments of the present invention, the enzyme preparation bacterial solution can be Aspergillus niger solution, Aspergillus awamori solution, Aspergillus oryzae solution, etc., and the bacterial solution concentration is recommended to be 10. 8 -10 9 CFU / mL. The dosage, by volume, is 3-5% of the total liquid volume in the fermenter.

[0037] In an embodiment of the present invention, in step 2, the wet hydrolysate is mixed with the enzyme preparation bacterial solution to form a fermentation mixture. The fermentation tank parameters are adjusted so that the wet hydrolysate undergoes liquid fermentation for 5-7 days under these conditions. For example, the temperature of the liquid fermentation tank is adjusted to 28-32°C, the tank pressure to 0.02-0.03 MPa, and the aeration rate to 160-180 L / h. Under these conditions, the wet hydrolysate undergoes liquid fermentation for 5-7 days, and the fermentation tank rotation speed can be adjusted to 250 r / min.

[0038] In an embodiment of the present invention, in step 3, the temperature of the enzymatic hydrolysis reaction is 28-32°C, and the enzymatic hydrolysis time is 12-36 hours.

[0039] In an embodiment of the present invention, in step 3, the weight ratio of the compound enzyme solution to the wet hydrolysate is 1:18-19.

[0040] It is worth noting that in this invention, the amount and source of the wet hydrolysate participating in the enzymatic hydrolysis reaction can be adjusted according to actual conditions. For example, a composite enzyme can be produced by liquid fermentation using the wet hydrolysate of the previous food waste, and the resulting composite enzyme can be used to carry out an enzymatic hydrolysis reaction with the wet hydrolysate of the subsequent food waste. Alternatively, the total amount of wet hydrolysate participating in liquid fermentation and enzymatic hydrolysis is not equal to the total amount of wet hydrolysate from the same food waste. This allows for a continuous operating mechanism, where both liquid fermentation and enzymatic hydrolysis are continuously running.

[0041] This invention also provides a method for treating food waste. First, pretreatment is performed using an enzymatic pretreatment method with the wet hydrolysate of the food waste. Then, the wet hydrolysate after the enzymatic reaction is fed into a high-efficiency anaerobic reactor for anaerobic treatment. After enzymatic pretreatment, the suspended solids content of the wet hydrolysate is reduced, facilitating efficient anaerobic treatment. For example, the high-efficiency anaerobic reactor is typically represented by an upflow anaerobic sludge blanket (UASB) reactor and an expanded granular sludge blanket (EGSB) reactor.

[0042] In embodiments of the present invention, to further reduce energy consumption and improve resource recycling efficiency, a portion of the anaerobic digestate from a high-efficiency anaerobic reactor can be refluxed, sterilized at high temperature, and then introduced into a liquid fermenter. This reflux, either alone or in combination with the digestate from dry anaerobic digestion, adjusts the TCOD, TN, and TP content of the wet hydrolysate in the liquid fermenter to ensure effective liquid fermentation and produce highly active complex enzymes. For example, the adjustment targets are: TCOD to 20-30 g / L, TN to 3-6 g / L, and TP to 0.1-0.25 g / L. For example, the high-temperature sterilization temperature is 121°C, and the sterilization time is 20-30 minutes.

[0043] In an embodiment of the present invention, the total amount of wet hydrolysate, dry anaerobic digestion liquid and anaerobic digestion reflux liquid from the high-efficiency anaerobic reactor in the liquid fermenter is 50-80% of the total volume of the liquid fermenter.

[0044] To verify the effectiveness of the present invention, a specific embodiment is provided as follows:

[0045] Step 1: Take 1L of wet hydrolysis liquid from kitchen waste (TCOD content is 25.4g / L, TN content is 0.9g / L, TP content is 0.15g / L, SS content is 12.84g / L). After adjustment with dry anaerobic digestion liquid and high-efficiency anaerobic digestion reflux liquid, the TCOD content is 25.7g / L, the TN content is 4.5g / L, and the TP content is 0.2g / L.

[0046] Step 2: Sterilize the dry anaerobic digestion liquid and the high-efficiency anaerobic digestion reflux liquid in a vertical high-temperature sterilizer for 20 minutes. After sterilization, add the mixture to the liquid fermentation tank. The temperature of the vertical high-temperature sterilizer is 121℃.

[0047] Step 3: Add Aspergillus niger liquid to the liquid fermenter at a dosage of 3%. Mix the wet hydrolysate with the Aspergillus niger liquid to form a fermentation mixture. Set the liquid fermenter temperature to 30℃, tank pressure to 0.02MPa, rotation speed to 250r / min, and aeration rate to 170L / h. The wet hydrolysate is fermented in liquid for 7 days under these conditions. The volume of the liquid fermenter is 1.5L.

[0048] Step 4: After the wet hydrolysate was fermented in liquid state for 7 days, the activity of biological enzymes in the compound enzyme solution was measured. The activity of acidic protease was 113.4 U / mL and the activity of α-amylase was 88.9 U / mL.

[0049] Step 5: Mix the compound enzyme solution with the wet hydrolysate of kitchen waste (20L) and hydrolyze at 28°C for 24 hours.

[0050] Step 6: The suspended solids content in the enzymatically hydrolyzed mixture was measured to be 1.94 g / L, and the suspended solids removal rate reached 84.89%.

[0051] The specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and improvements based on the concept of the present invention. Therefore, any technical solutions obtained by those skilled in the art based on the concept of the present invention through analysis, reasoning, or experimentation on the basis of existing technology should be considered within the scope of protection of the present invention.

Claims

1. A method for treating kitchen waste, characterized in that, Includes the following steps: Step 1: The kitchen waste slurry is hydrolyzed in wet water and then separated into three phases. The liquid phase product is the hydrolysate; the solid phase product is subjected to dry anaerobic digestion, and the resulting digestate is sterilized at high temperature. Step 2: A portion of the wet hydrolysate is transferred to a liquid fermentation tank, and an enzyme preparation solution is added for liquid fermentation to obtain a compound enzyme solution; the enzyme preparation solution is Aspergillus niger solution, Aspergillus oryzae solution, or Aspergillus oryzae solution, with a concentration of 10. 8 -10 9 The dosage is CFU / mL, by volume, and is 3-5% of the total liquid volume in the fermenter; the liquid fermentation temperature is 28-32℃, the tank pressure is 0.02-0.03 MPa, the aeration rate is 160-180 L / h, and the fermentation time is 5-7 days. Step 3: Mix the composite enzyme solution with another part of the wet hot hydrolysate to carry out the enzymatic hydrolysis reaction, and complete the pretreatment; Step 4: The wet hydrolysate after enzymatic hydrolysis is sent to a high-efficiency anaerobic reactor for anaerobic treatment. Part of the anaerobic digestion liquid from the high-efficiency anaerobic reactor is refluxed and sterilized at high temperature before entering the liquid fermentation tank. Together with the digestion liquid produced by dry anaerobic digestion, the TCOD of the wet hydrolysate in the liquid fermentation tank is adjusted to 20-30 g / L, the TN content to 3-6 g / L, and the TP content to 0.1-0.25 g / L. The total volume of the wet hydrolysate, dry anaerobic digestate, and anaerobic digest reflux from the high-efficiency anaerobic reactor in the liquid fermenter is 50-80% of the total volume of the liquid fermenter.

2. The method for treating kitchen waste according to claim 1, characterized in that, In step 2, 5-10% of the total volume of the wet hydrolysate is fed into a liquid fermentation tank to participate in liquid fermentation.

3. The method for treating kitchen waste according to claim 1, characterized in that, In step 3, the enzymatic hydrolysis reaction is carried out at a temperature of 28-32℃ for 12-36 hours.

4. The method for treating kitchen waste according to claim 1, characterized in that, In step 3, the weight ratio of the compound enzyme solution to the wet hydrolysate is 1:18-19.

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