Method for preparing carbon source by using waste grease regenerated by-product

Abstract

A method for preparing a carbon source by hydrolytic acidification of a liquid-phase UCO byproduct comprises the following steps: (1) performing three-phase separation on the liquid-phase UCO byproduct to obtain an oil-phase product, a liquid-phase product and a solid-phase product, and adding the obtained liquid-phase product into a hydrolytic acidification tank; (2) adding a concentration regulator into a hydrolytic acidification tank, fully mixing, and carrying out acidification hydrolysis; and (3) filtering to obtain supernate rich in organic acid. The carbon source prepared by the method is low in cost, wide in raw material source and capable of being produced nearby, and the transportation cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of waste resource utilization, and specifically relates to a method for preparing a carbon source by utilizing a byproduct generated by extracting and regenerating waste edible oils and fats. Technical Background

[0002] UCO (Used Cooking Oil), or recycled waste cooking oil, mainly comes from restaurant kitchen waste and is an important raw material for biomass diesel. my country is currently the main supplier of UCO in the international market, with a supply potential of 12 million tons / year. On the other hand, the global demand potential for biodiesel (including biojet fuel) exceeds 83 million tons / year, and the market size is nearly one trillion yuan at the current price. Using UCO to prepare biodiesel is one of the important ways to treat UCO, but the by-products produced by using UCO to prepare biodiesel have the characteristics of high water content, high organic matter content, rich nutrition, and easy corruption. The current mainstream technology cannot effectively develop its economic value, but is treated as wastewater. The cost of treating waste oil regeneration by-products is very high. If improperly handled, it will seriously affect people's health and cause a huge pollution load on the urban water environment.

[0003] Sewage treatment usually requires denitrification, that is, the use of biological denitrification to convert nitrates in water into nitrogen gas. The intermediate products of the reaction process are NO2, NO, and N2O. Hydrogen ions serve as electron donors in the denitrification reaction, and electron donors are organic matter in the sewage or external carbon sources. In the process of carbon source decomposition by microorganisms, that is, the energy for cell synthesis to maintain cell life activities and growth metabolism is provided by the carbon source. The carbon source can be considered as the energy supplier required for cell life activities and the framework formed by microbial flocs. In engineering applications, external carbon sources are usually divided into three categories: a. Glycogen: glucose, sucrose, fructose, etc.; b. Alcohols: methanol, ethanol, propanol, butanol, etc.; c. Acids: acetic acid, sodium acetate, sodium formate, potassium acetate, citric acid, etc. Most of these organic substances come from the chemical industry, and the cost is too high. Some carbon source products need to be pretreated to ensure the absorption effect of microorganisms. Therefore, it is necessary to develop cheaper and more friendly organic carbon sources.

[0004] There are also methods in the prior art that use waste kitchen waste as raw materials to prepare carbon sources, but most of the methods directly use non-oil solid components in kitchen waste as raw materials for preparing carbon sources, and there are no reports on producing carbon sources from waste oil regeneration by-products. In addition, if waste oil regeneration by-products are directly used as carbon sources, their COD indicators cannot meet the carbon source usage standards and have certain toxicity to microorganisms.

[0005] CN111333179A discloses a method for producing a carbon source for denitrification of wastewater by lactic acid fermentation of kitchen waste, wherein kitchen waste is used as raw material, and after impurities are removed, ground, and phase-separated to recover waste grease, the remaining waste slurry is injected into an anaerobic fermentation tank for batch lactic acid fermentation, and after the fermentation is completed, solid-liquid separation is performed, and the lactic acid-containing supernatant can be used as a liquid carbon source in the wastewater denitrification treatment stage, thereby achieving a good biological denitrification effect.

[0006] CN117757600A discloses a method for preparing a carbon source by fermenting kitchen waste, in which organic matter in the kitchen waste is hydrolyzed and acidified to form a fermentation liquid rich in volatile fatty acids, which is used as an additional carbon source for a sewage biological treatment unit and applied in the field of sewage treatment to achieve industrial application.

[0007] CN114798694A discloses a solid-state denitrification carbon source prepared from restaurant kitchen waste and a preparation method thereof. The restaurant kitchen waste is used as a matrix material, and impurities are removed by sorting, and solid-liquid separation is performed. After the oil is recovered from the liquid phase, the residue and the solid separated from the solid phase are combined and processed together, and the solid is pre-frozen. After the pre-freezing is completed, vacuum freeze-drying is performed. After freeze-drying is completed, the freeze-dried solid is crushed to obtain a solid-state denitrification carbon source, which can be directly used as a carbon source and carrier material for denitrification, thereby strengthening biological denitrification and realizing efficient resource utilization of restaurant waste. Summary of the invention

[0008] The present invention utilizes the by-product of preparing waste oil and fat from kitchen waste as raw material, which is mainly composed of glycerol and soluble sugars, fatty acids, low-carbon alcohols, oils and fats, etc., and is hydrolyzed and acidified by specific strains of bacteria, which not only effectively eliminates the biological toxicity of microorganisms therein and significantly improves its biocompatibility, but also the B / C value of the obtained carbon source product is significantly higher than that of common carbon sources, which can effectively improve the activity of microorganisms and improve the denitrification efficiency.

[0009] A method for preparing a carbon source by hydrolyzing and acidifying a liquid phase UCO byproduct, the steps comprising:

[0010] (1) The UCO stock solution subjected to multi-stage treatment is subjected to three-phase separation to obtain an oil phase product, a liquid phase product and a solid phase product, and the obtained liquid phase product is added to a hydrolysis acidification tank;

[0011] (2) Filter to obtain the supernatant rich in organic acids.

[0012] (3) adding a COD concentration regulating agent and an acidifying agent into a hydrolysis acidification tank and mixing them thoroughly to perform acid hydrolysis;

[0013] The three-phase separation in step (1) is carried out by one of static separation, centrifugal separation and filtration separation.

[0014] The filtration in step (2) adopts one of ceramic membrane filtration or organic membrane filtration.

[0015] The acidifying agent in step (3) is one or more of sodium acetate, ethylene glycol, and glycerol; the volume ratio of the acidifying agent to the liquid phase UCO byproduct is 10-30:100; the pH of the acidified hydrolysis in step (3) is 3-6, more preferably 4-5; the pH value is adjusted by adding sodium hydroxide or hydrochloric acid; the temperature of the acidified hydrolysis in step (3) is 15-35°C, more preferably 20-30°C.

[0016] The bacterial species used in step (3) include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is greater than 30%, more preferably 30-50%.

[0017] The filtration in step (3) is carried out by using a ceramic membrane, which is a type of microfiltration and ultrafiltration, and ceramic membrane filtration is more preferred.

[0018] Preferably, the method further comprises a step (4), treating the filtered residue together with the solid phase product obtained by the three-phase separation in step (1).

[0019] The treatment in step (4) includes one or more of biological fermentation, carbonization, dry distillation, pyrolysis, and incineration.

[0020] Since the organic matter content of UCO byproducts fluctuates greatly, in the present invention, according to the change of COD of each batch of UCO byproducts and referring to the change of water quality in the sewage treatment plant, the COD of the carbon source is 80,000-350,000 mg / L, preferably 80,000-100,000 mg / L, COD 200,000-250,000 mg / L, 300,000-350,000 mg / L.

[0021] In the present invention, after a reaction time of 24 hours, the B / C is 0.8, which is significantly higher than that of the traditional carbon source.

[0022] The present invention has the following beneficial effects: the carbon source produced by the present invention has a high concentration, and under a suitable ratio, COD can reach 350,000 mg / L, and the carbon source is efficient and non-toxic; the carbon source of the present invention uses natural organic matter as a raw material liquid, has biological affinity, is easily fully utilized by microorganisms, reduces sludge discharge, does not produce additional carbon emissions, and truly achieves efficient carbon fixation. The carbon source produced by the present invention has a low cost, and the raw material source is extensive, and can be produced on-site at the place where the carbon source is used, reducing transportation costs. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods below, and similar technologies and methods should be considered within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail in conjunction with specific embodiments.

[0024] The present invention is further described in detail below with specific implementation modes.

[0025] Embodiment 1:

[0026] The raw liquid phase UCO regeneration byproduct is pumped into the reaction tank to inoculate the hydrolysis acidified bacterial water, the operating conditions are temperature 20 ° C, pH 5.1, and the reaction is filtered after 24 hours. The COD concentration in the filtrate is more than 100,000 mg / L, and the B / C is 0.87. The bacterial species used include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is 35%.

[0027] Example 2

[0028] The raw liquid phase UCO regeneration byproduct is pumped into the reaction tank to inoculate the hydrolysis acidified bacterial water, and the ethylene glycol with a mass ratio of 12.5% ​​is compounded, stirred and dissolved, and the operating conditions are a temperature of 20°C and a pH of 5.0. After 24 hours of reaction, the filtrate is filtered, and the COD concentration in the filtrate is more than 220,000 mg / L, and the B / C is 0.83. The strains used include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is 45%.

[0029] Example 3

[0030] The raw liquid phase UCO regeneration byproduct is pumped into the reaction tank to inoculate the hydrolysis acidified bacterial water, and the ethylene glycol with a mass ratio of 23% is compounded, stirred and dissolved, and the operating conditions are a temperature of 20°C and a pH of 5.0. After 24 hours of reaction, the filtrate is filtered, and the COD concentration in the filtrate is more than 310,000 mg / L, and the B / C is 0.80. The strains used include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is 35%.

[0031] Comparative Example 1

[0032] The other conditions were the same as those in Example 2, and the pH value was 3.2. After 24 hours of reaction, the filtrate was filtered, and the COD concentration in the filtrate was more than 200,000 mg / L, and the B / C was 0.62.

[0033] Comparative Example 2

[0034] The other conditions were the same as those in Example 2, and the pH value was 6.6. After 24 hours of reaction, the filtrate was filtered, and the COD concentration in the filtrate was more than 200,000 mg / L, and the B / C was 0.65.

[0035] Comparative Example 3

[0036] Other conditions were the same as those in Example 2, and the operating temperature was 15° C. After 24 hours of reaction, the filtrate was filtered, and the COD concentration in the filtrate was more than 200,000 mg / L, and the B / C was 0.71.

[0037] Comparative Example 4

[0038] Other conditions are the same as those in Example 2, wherein the strains used include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is 25%. After 24 hours of reaction, the filtrate is filtered, and the COD concentration in the filtrate is more than 230,000 mg / L, and the B / C is 0.51.

[0039] The prepared Examples 1-3 and Comparative Examples 1-4 were tested for denitrification performance, and the same process conditions were used in the tests. The raw water used in the experiment was a water sample from a regulating tank and a SBR aeration terminal of a municipal sewage treatment plant. Table 1 shows the main pollutant content of the raw water.

[0040] Table 1

[0041] Index (mg / L) COD TN NH3-N NO3--N NO2--N Detection value 300 45 30 5 <1

[0042] Table 2 is the index of UCO composite carbon source, methanol and sodium acetate. The water quality index of the regulating pool is shown in Table 2. Methanol is industrial-grade methanol solution, and sodium acetate is industrial-grade sodium acetate solid. Its various indexes are shown in Table 2.

[0043] Table 2

[0044]

[0045]

[0046] The experiment was carried out in accordance with the SBR process of the sewage treatment plant's sewage biochemical system, and the four main stages of the SBR process were simulated simultaneously: water inlet period, aeration and oxygenation period, sedimentation period and drainage period.

[0047] The residence time of each stage The time ratio of each stage of the SBR process is roughly as follows:

[0048] Simulate the water inlet stage, with a retention time of 1h. Inject the water sample from step 1 into the experimental device, and add the composite carbon source, sodium acetate, and methanol solution from step 2) at a ratio of COD / TN = 5:1 at one time. After adding, turn on the stirring device for anoxic reaction. The reaction is carried out in anoxic environment at an ambient temperature of 20°C, and the sludge concentration in the pool is maintained at about 1200mg / L.

[0049] Simulated aeration phase: lasts 6 to 7.5 hours.

[0050] Simulated precipitation phase: lasts 1 hour

[0051] The implementation standard is the urban construction industry standard CJ / T 221-2005. The main experimental instruments include Tester WGL-1258 electric heating blast drying oven, Lu Xiangyi RD-60TZ high-speed centrifuge, Hach DRB 200 fast digester, and Hach DR-6000 spectrophotometer.

[0052] The test results are shown in Table 3.

[0053] Table 3

[0054] Denitrification rate Example 1 94.28％ Example 2 95.14％ Example 3 95.23％ Comparative Example 1 71.56％ Comparative Example 2 86.31％ Comparative Example 3 83.25％ Comparative Example 4 88.39％

[0055] The experimental results show that when using UCO composite carbon source, its own TN needs to be calculated when calculating the carbon source dosage by COD / TN. UCO composite carbon source can completely replace traditional carbon sources and has excellent biological activity and high denitrification efficiency.

Claims

1. A method for preparing a carbon source by hydrolyzing and acidifying a liquid phase UCO byproduct, comprising the following steps: (1) separating the liquid UCO by-product into three phases to obtain an oil phase product, a liquid phase product and a solid phase product, and adding the obtained liquid phase product to a hydrolysis acidification tank; (2) adding the concentration regulator into the hydrolysis and acidification tank and mixing thoroughly to perform acid hydrolysis; (3) Filter to obtain the supernatant rich in organic acids.

2. The method according to claim 1, characterized in that The three-phase separation in step (1) is carried out by one of static separation, centrifugal separation and filtration separation.

3. The method according to claim 1, characterized in that The concentration regulator in step (2) is one or more of sodium acetate, ethylene glycol and glycerol.

4. The method according to claim 1, characterized in that The volume ratio of the concentration regulator to the liquid phase UCO byproduct in step (2) is 10-30:

100.

5. The method according to claim 1, characterized in that The pH of the acidification hydrolysis in step (2) is 3-6, more preferably 4-5.

6. The method according to claim 1, characterized in that The pH value in step (2) is adjusted by adding sodium hydroxide or hydrochloric acid; the bacterial species used in step (2) include Bacillus, Brevibacillus, Lactobacillus, and Citrobacter; preferably, the colony percentage of Brevibacillus is greater than 30%, more preferably 30-50%.

7. The method according to claim 1, characterized in that The temperature of the acidification and hydrolysis in step (2) is 15-35°C, more preferably 20-30°C.

8. The method according to claim 1, characterized in that The filtration in step (3) adopts one of ceramic membrane, organic membrane filtration, microfiltration and ultrafiltration, and ceramic membrane filtration is more preferred.

9. The method according to claim 1, characterized in that The method further comprises a step (4), wherein the filtered residue is treated together with the solid phase product separated by three phases in step (1); the treatment in step (4) comprises one or more of biological fermentation, carbonization, dry distillation, pyrolysis and incineration.

10. A carbon source prepared by the method according to any one of claims 1 to 9, characterized in that The COD of the carbon source is 80,000-350,000 mg / L, preferably 80,000-100,000 mg / L, COD 200,000-250,000 mg / L, or 300,000-350,000 mg / L.

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