Method for preparing carbon source from kitchen waste anaerobic pretreatment slurry

Abstract

The invention discloses a method for preparing a carbon source from kitchen waste anaerobic pretreatment slurry, belongs to the field of organic waste treatment and resource recycling, and can realize resource recycling and high-value utilization of slurry generated in the kitchen waste anaerobic pretreatment process. The method specifically comprises the following steps: 1, carrying out thermochemical hydrolysis on slurry generated in the anaerobic pretreatment process of the kitchen waste as a raw material to obtain hydrolysate; 2, carrying out preliminary centrifugal filtration on the material after the thermochemical hydrolysis reaction to obtain a primary carbon source product; 3, carrying out secondary membrane filtration separation on the centrifugally filtered material to obtain a secondary carbon source product; 4, performing low-temperature evaporation and concentration on the carbon source product subjected to membrane filtration to obtain a final carbon source product; and 5, carrying out heat drying on the residues subjected to membrane filtration to obtain dried residues. The method provided by the invention can realize high-value utilization of the kitchen waste slurry, and the obtained carbon source product can be used for nitrogen removal by denitrification of leachate and municipal sewage.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and resource utilization, and in particular relates to a method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry. Background Art

[0002] The anaerobic digestion process of food waste is the main embodiment of the centralized resource utilization of wet waste in Shanghai. The three-phase separation slurry produced during the pretreatment of food waste mainly contains carbohydrates (30%-60%), proteins (5%-20%), fats (15%-40%) and other components, which have the characteristics of high nutritional value and high value utilization. At the same time, during the chemical oxidation process, carbohydrates such as starch and cellulose in food waste can be induced to oxidize and break bonds through the reaction of active oxygen free radicals and active nitrogen free radicals to generate small molecular weight organic acids such as acetate, propionate, and amino acid salts. This composite substance can be effectively utilized and degraded by microorganisms as a supplementary nutrition for microorganisms.

[0003] Most sewage (such as old leachate, etc.) cannot provide sufficient carbon sources due to its poor biodegradability. At this time, additional carbon sources need to be added artificially to assist denitrification. Single easily degradable organic substances such as glucose, ethanol, and sodium acetate have the advantage of fast denitrification rate and have always been the main choice of carbon source. However, the high cost of glucose, ethanol, sodium acetate, etc. and the harsh transportation conditions have also hindered their large-scale application. The development and application of high-efficiency carbon source technology for converting kitchen waste slurry into leachate or sewage treatment can maximize resource utilization and minimize treatment costs.

[0004] Although restaurant kitchen waste slurry can be directly used as a supplementary carbon source in conjunction with sewage treatment, it is difficult to use it as a carbon source for a long time or sell it as a commercial carbon source due to its high suspended matter and oil content. The present invention develops a method for producing a commercial carbon source from restaurant kitchen waste slurry, and then applies denitrification to sewage treatment. This technical method has not been reported. Summary of the invention

[0005] In view of the current situation that excess slurry from anaerobic fermentation of restaurant waste is directly discharged for treatment and wastes nutrient resources, the present invention provides a method for preparing a carbon source by anaerobic pretreatment of restaurant waste slurry. The method has simple process and low cost, can efficiently utilize the organic carbon nutrients in the restaurant waste slurry, and does not require artificial input of additional carbon source, so that the COD value of the carbon source can meet the requirements, and has high economic and social environmental benefits.

[0006] The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry of the present invention is implemented by the following steps: (1) using the slurry produced in the anaerobic pretreatment process of food waste as raw material, and subjecting it to thermochemical hydrolysis to obtain a hydrolyzate; (2) Preliminary centrifugal filtration of the material after the thermochemical hydrolysis reaction to obtain a primary carbon source product; (3) subjecting the centrifugally filtered material to secondary membrane filtration separation to obtain a secondary carbon source product; (4) The carbon source product after membrane filtration is evaporated and concentrated at low temperature to obtain the final carbon source product; (5) The residue after membrane filtration is thermally dried to obtain a dried residue.

[0007] Preferably, the anaerobic pretreatment slurry of food waste comes from a food waste anaerobic fermentation plant, and is obtained after primary screening, impurity removal, slurrying and three-phase separation and oil extraction.

[0008] That is, the oil phase (grease) is removed from the slurry.

[0009] Preferably, the anaerobic pretreatment slurry of the kitchen waste has a TCOD concentration of 120000-160000 mg / L, a TN concentration of 3000-4000 mg / L, a TP concentration of 150-250 mg / L, a pH of 4.5-5.5, and a SS concentration of 8000-10000 mg / L.

[0010] Among them, TCOD concentration is COD concentration; TN concentration is the total nitrogen concentration; TP concentration is the total phosphorus concentration; SS concentration is the total suspended solids concentration.

[0011] Preferably, in the thermochemical hydrolysis, the oxidant quickly converts particulate organic matter into dissolved organic matter. By adding the oxidant, organic components such as starch, cellulose, protein, etc. in wet garbage are decomposed into small molecular weight and high value-added organic acid salts (especially acetic acid, formic acid and its sodium salt) under specific conditions. The oxidant participates in the reaction and generates more easily soluble compounds by oxidizing certain parts of the solid organic matter. At the same time, the presence of the oxidant can increase the activity of the reaction system and promote the principle of converting large molecules of solid organic matter into small molecules. The oxidant significantly affects the COD value of the carbon source thermochemical hydrolysis product by accelerating the decomposition of organic matter, changing the oxidation state, affecting the stability of the product and coordinating with the reaction conditions.

[0012] Preferably, the reaction process does not adjust the pH, the temperature is controlled at 70-85°C, and the thermochemical hydrolysis reaction time is 1-3 hours. Experiments show that when the temperature is greater than 70°C, the COD concentration no longer decreases or the decrease phenomenon weakens after 30 minutes, and the dissolution effect is best at 85°C. The pH after the reaction is weakly acidic, which meets the environmental conditions of high carbon source conversion efficiency. Different temperatures have a significant effect on the conversion of kitchen waste slurry into carbon sources. As the temperature increases, the COD concentration increases and the time to stabilize is shortened.

[0013] Preferably, the oxidant composition is persulfate and ferrous sulfate, and the addition amount is 0.3-0.5% of the TCOD concentration. Different oxidant addition amounts significantly affect the effect of converting kitchen waste slurry into carbon source. The addition amount is 0.3-0.5% of the TCOD concentration, which can promote the dissolution of TCOD and glucose and increase the proportion of VFAs in the liquid carbon source. However, excessive addition leads to the generation of sulfate free radicals, a decrease in pH, and affects the glucose yield and the biodegradability of the carbon source.

[0014] Preferably, the filter cloth used for the centrifugal filtration has a mesh size of 300-400 meshes.

[0015] Preferably, the primary carbon source product obtained after filtration has a TCOD concentration of 80,000-100,000 mg / L and a TN concentration of 2,000-3,000 mg / L.

[0016] Preferably, the pore size of the secondary membrane filtration is 0.01-0.02 μm, providing the relevant centrifugal range and pore size range requirements to achieve COD 150,000-180,000.

[0017] Preferably, after the secondary membrane filtration, the secondary carbon source product obtained has a TCOD concentration of 50,000-70,000 mg / L and a TN concentration of 400-600 mg / L.

[0018] Preferably, the low-temperature evaporation concentration temperature is 50-70° C., and the TCOD of the final carbon source product is 150,000-180,000 mg / L.

[0019] Preferably, the residue is thermally dried to obtain a dried residue with a mass of 2-3% of the mass of the original slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the method for preparing a carbon source by anaerobic pretreatment of slurry from kitchen waste as shown in the example. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the embodiments shown in the accompanying drawings.

[0022] Specific implementation method: The method for preparing carbon source by anaerobic pretreatment of kitchen waste slurry in this implementation method is implemented according to the following steps: The slurry produced during the anaerobic pretreatment of food waste was used as raw material, with a TCOD concentration of 153000 mg / L, a TN concentration of 33210 mg / L, a TP concentration of 1505 mg / L, a pH of 4.5, and a SS concentration of 8200 mg / L.

[0023] Take 200 L and inject it into the thermochemical hydrolysis reaction system. The temperature of the reaction system is maintained at 75°C. Then, 0.5% sodium persulfate is added first, and then 0.5% ferrous sulfate is added after 5 minutes. The entire thermochemical hydrolysis reaction time is 2 hours.

[0024] After the thermochemical hydrolysis reaction is completed, the slurry is centrifuged and filtered, and the pore size of the centrifuge filter cloth is 400 meshes to obtain a primary carbon source product; The filtered slurry then enters the membrane filtration system with a membrane pore size of 0.01 μm. After membrane filtration, a clarified secondary carbon source product is obtained. At this time, the product TCOD concentration is 56,000 mg / L and the TN concentration is 475 mg / L.

[0025] Finally, the secondary carbon source product after membrane filtration was evaporated and concentrated at low temperature to obtain the final carbon source product. At this time, the TCOD concentration of the product was 150,000 mg / L and the TN concentration was 1120 mg / L.

[0026] In actual application, a 3 ton / day organic waste slurry thermochemical conversion carbon source demonstration project was built and operated. The reactor temperature was set to a low temperature range of 50~70 ℃, and the COD of the carbon source initially produced was 120000-150000 mg / L. The COD value of the carbon source obtained at this time is high enough to meet the requirements when these carbon sources are needed to treat sewage and wastewater.

[0027] The residues after centrifugal filtration and membrane filtration were thermally dried to obtain a dried residue mass of 2% of the original slurry mass.

[0028] The invention discloses a method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry, which belongs to the field of organic waste treatment and resource recycling, and can realize resource recycling and high-value utilization of slurry generated during anaerobic pretreatment of kitchen waste. The process is simple, the cost is low, and it has high economic and social environmental benefits.

[0029] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these implementations and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry, characterized in that: The following steps are involved: (1) using anaerobic pretreatment slurry of food waste as raw material, performing thermochemical hydrolysis on it to obtain a hydrolyzate; The anaerobic pretreatment slurry of the kitchen waste is obtained from the anaerobic fermentation plant of the kitchen waste after primary screening, impurity removal, slurrying and three-phase separation and oil extraction; The anaerobic pretreatment slurry of the kitchen waste has a TCOD concentration of 120,000-160,000 mg / L, a TN concentration of 3,000-4,000 mg / L, a TP concentration of 150-250 mg / L, a pH of 4.5-5.5, and a SS concentration of 8,000-10,000 mg / L; (2) Preliminary centrifugal filtration of the material after the thermochemical hydrolysis reaction to obtain a primary carbon source product; In the thermochemical hydrolysis, the oxidant rapidly converts the particulate organic matter into dissolved organic matter; (3) subjecting the centrifugally filtered material to secondary membrane filtration separation to obtain a secondary carbon source product; (4) The carbon source product after membrane filtration is evaporated and concentrated at low temperature to obtain the final carbon source product; (5) The residue after membrane filtration is thermally dried to obtain a dried residue.

2. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 1, characterized in that: The thermochemical hydrolysis does not adjust pH, the temperature is controlled at 70-85° C., and the thermochemical hydrolysis reaction time is 1-3 hours.

3. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 1, characterized in that: The oxidants included persulfate and ferrous sulfate, and the added amount was 0.3~0.5% of the TCOD concentration.

4. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 1, characterized in that: The mesh number of the filter cloth used in the centrifugal filtration is 300-400 meshes.

5. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 4, characterized in that: The primary carbon source product obtained after the filtration has a TCOD concentration of 80,000-100,000 mg / L and a TN concentration of 2,000-3,000 mg / L.

6. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 1, characterized in that: The pore size of the secondary membrane filtration is 0.01-0.02 μm.

7. The method for preparing a carbon source by anaerobic pretreatment of kitchen waste slurry according to claim 1, characterized in that: The low-temperature evaporation and concentration temperature is 50-70° C., and the TCOD of the final carbon source product is 150,000-180,000 mg / L.

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