A slow-release carbon source based on wet waste and its preparation method

Abstract

This invention discloses a slow-release carbon source based on wet waste and its preparation method, relating to the field of wastewater treatment technology. The preparation method of the slow-release carbon source includes the following steps: after removing impurities from the wet waste, it is added to deionized water for crushing and homogenization, hydrolyzed and acidified to separate the hydrolyzed acidified liquid, flocculated and slag removed to separate the liquid phase component, and sodium citrate and citric acid are added sequentially to obtain a liquid phase carbon source; polyvinyl alcohol and sodium alginate are placed in deionized water, dissolved, cooled, and the liquid phase carbon source is added and stirred, then dropped into a calcium chloride-saturated boric acid solution, centrifuged and washed to obtain embedded particles; polyvinyl alcohol and sodium alginate are placed in deionized water, dissolved, cooled, and water-based polymer and embedded particles are added, stirred evenly, poured into a copper column mold for bidirectional freezing, natural thawing after freezing, and then naturally thawing and demolding after freezing again to obtain the slow-release carbon source; this slow-release carbon source has excellent slow-release effect and denitrification ability.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a slow-release carbon source based on wet waste and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the improvement of living standards in my country, the pressure on urban wastewater treatment plants to remove nitrogen and phosphorus pollutants is becoming increasingly prominent. Biological nitrogen and phosphorus removal is a core process in wastewater treatment, and its efficiency directly depends on the sufficiency of carbon sources and functional microorganisms such as denitrifying bacteria and polyphosphate-accumulating bacteria within the system. These microorganisms require carbon sources as energy carriers to complete metabolic processes such as nitrate reduction. However, most urban wastewater in my country suffers from a "low carbon-to-nitrogen ratio," and insufficient natural carbon sources lead to incomplete denitrification, resulting in excessive total nitrogen (TN) concentrations in the effluent, which has become a key bottleneck restricting wastewater treatment plants from achieving emission standards.

[0003] To address these issues, the industry widely adopts the technical approach of adding external carbon sources. Existing external carbon sources are mainly divided into two categories: First, traditional liquid carbon sources, including methanol, sodium acetate, and glucose. While these sources can be rapidly utilized by microorganisms, they have significant drawbacks, such as easy loss with water flow after addition, requiring continuous adjustment of the dosage to maintain carbon source concentration. Excessive addition can easily cause secondary pollution and increase the chemical oxygen demand (COD) load of the effluent. Second, solid slow-release carbon sources, such as natural cellulose materials and synthetic polymers. While natural materials are inexpensive, the carbon source release rate is difficult to control, easily resulting in excessively rapid release in the early stages and insufficient release in the later stages. Their poor mechanical strength also makes them prone to disintegration and loss in water. Although synthetic polymers have stable slow-release performance, they often rely on fossil raw materials, resulting in high costs and poor biodegradability, potentially leading to secondary pollution with long-term use.

[0004] In recent years, although some studies have attempted to use wet waste hydrolysate directly as a carbon source for wastewater treatment, the core problem of uncontrolled carbon source release rate has not been solved. For example, the small molecule carbon source produced by wet waste hydrolysis is prone to rapid dissolution, resulting in low carbon source utilization. At the same time, impurities such as large particulate organic matter and metal ions contained in the hydrolysate can affect the metabolic activity of microorganisms and even clog wastewater treatment equipment. Problems such as low purity of effective carbon source, poor slow-release performance, and insufficient mechanical strength make it difficult to meet the needs of long-term stable operation of wastewater treatment plants.

[0005] Therefore, developing a highly efficient slow-release carbon source based on wet waste has become an urgent need in the field of wastewater treatment. Summary of the Invention

[0006] The purpose of this invention is to provide a slow-release carbon source based on wet waste and its preparation method, so as to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a slow-release carbon source based on wet waste includes the following steps:

[0009] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization, then add compound enzyme agent for hydrolysis and acidification, separate the hydrolysis and acidification liquid, add lime slurry to adjust the pH of the system to 10-10.5, then add flocculant, stir and let stand, separate the liquid phase component from the solid and liquid, add sodium citrate and citric acid in sequence to obtain the liquid phase carbon source;

[0010] Step 2: Place polyvinyl alcohol and sodium alginate in deionized water, heat and stir to dissolve, then cool to obtain polyvinyl alcohol sodium alginate solution. Add liquid carbon source and stir evenly, then dropwise into calcium chloride-saturated boric acid solution. Stir for 2-4 hours, then centrifuge and wash to obtain encapsulated particles.

[0011] Step 3: Place polyvinyl alcohol and sodium alginate in deionized water, heat and stir to dissolve, then cool. Add water-based polymer and encapsulated particles, stir evenly, pour into a copper column mold for bidirectional freezing, freeze naturally after freezing, then place in a -20℃ freezer and freeze again, then thaw naturally and demold to obtain a slow-release carbon source.

[0012] Preferably, in step 1, the mass ratio of wet waste, deionized water, and compound enzyme agent is 1:(2~5):(0.1~0.3).

[0013] More preferably, the compound enzyme agent comprises the following raw materials in parts by weight: 1.0-1.5 parts lactic acid bacteria, 1.5-3.0 parts Bacillus, 0.5-0.8 parts yeast, 1.0-1.2 parts cellulase, 0.6-1.5 parts lipase, 0.8-1.0 parts protease, and 1.5-2.0 parts amylase, which need to be prepared and used immediately;

[0014] Preferably, the lime slurry in step 1 is composed of lime and deionized water, with a lime mass concentration of 120~160 g / L; the flocculant is cationic polyacrylamide, and the concentration of the flocculant in the hydrolysis acidification solution is 200~500 mg / L.

[0015] Preferably, in step 1, the solid-liquid ratio of sodium citrate to the liquid phase component is (0.2~0.5):100; citric acid is added to adjust the pH of the liquid phase component to 7.0~7.5;

[0016] Preferably, the process parameters for hydrolysis and acidification in step 1 are: temperature 35~55℃, added ion concentration 800~1000mg / L, stirring rate 60~100r / min, system pH 5.5~6.0, and incubation for 20~24h; the added ion is Ca in a mass ratio of 1.5:(3~5):(2~3):(0.2~0.4). 2+ Na +Fe 2+ and Fe 3+ composition;

[0017] Preferably, in step 2, the polyvinyl alcohol sodium alginate solution contains 10-15% polyvinyl alcohol and 1.5-2.0% sodium alginate, with a volume ratio of liquid carbon source to polyvinyl alcohol sodium alginate solution of 1:(20-25); the concentration of calcium chloride-saturated boric acid solution is 2-3%.

[0018] Preferably, step 3 includes the following raw materials in parts by weight: 16-25 parts polyvinyl alcohol, 1.0-1.5 parts sodium alginate, 1.5-3 parts water-based polymer, 15-25 parts encapsulated particles, and 90-100 parts deionized water;

[0019] Preferably, the bidirectional freezing uses an ethanol bath at -80 to -90°C as the cooling source for 30 to 50 minutes;

[0020] More preferably, the waterborne polymer is composed of konjac glucomannan and waterborne polyurethane in a mass ratio of (0.5~2):1;

[0021] More preferably, the preparation steps of waterborne polyurethane are as follows: take polyester diol and isophorone diisocyanate, add stannous octoate and heat to 80~85℃, react under nitrogen atmosphere for 2h, add dimethylolpropionic acid and acetone and stir for 1~2h, cool to 45℃, add trimethylolpropane and continue stirring for 1h, add triethylamine and react for 30~40min, add a mixed solution of L-arginine and deionized water and stir at high speed for 20~30min, let stand to defoam, and obtain waterborne polyurethane;

[0022] Preferably, the waterborne polyurethane comprises the following raw materials in parts by weight: 1-1.6 parts polyester diol, 0.3-0.5 parts isophorone diisocyanate, 0.02-0.03 parts stannous octoate, 0.1-0.2 parts dimethylolpropionic acid, 0.01-0.02 parts trimethylolpropane, 0.07-0.12 parts triethylamine, 0.01-0.02 parts L-arginine, 3-5 parts deionized water, and 0.6-1.2 parts acetone;

[0023] A slow-release carbon source based on wet waste is prepared by the above-described preparation method.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention extracts liquid carbon sources from wet waste and uses a compound microbial enzyme agent to rapidly produce the required carbon source components, shortening the process time. The added ions further activate the hydrolytic enzymes, promoting VFA production. The concentration of the added ions is designed to be within an appropriate range, achieving high VFA production while avoiding impact on microbial activity. A multi-stage purification process is then performed, including lime + polyacrylamide flocculation for impurity removal, sodium citrate chelation, and citric acid adjustment of the liquid carbon source pH to ensure that subsequent liquid carbon sources avoid the aforementioned added ion Ca. 2+ Fe 3+ The residue caused by sodium alginate pre-crosslinking improves the encapsulation rate;

[0026] 2. Embedded particles loaded with liquid carbon source are inserted into polyvinyl alcohol / sodium alginate gel and subjected to bidirectional freezing to form oriented channels inside the gel. Compared with random pores generated without orientation, this effectively achieves controllable slow release of carbon source. In addition, water-soluble polymers, including konjac glucomannan and waterborne polyurethane, are introduced into the polyvinyl alcohol / sodium alginate hydrogel at a mass ratio of (0.5~2):1. Konjac glucomannan, as a natural polysaccharide, can provide additional sustained-release effect and has good biocompatibility, but it is highly hydrophilic and easily swells. Waterborne polyurethane, through the hydrophobic segments of polyester and the hydrophilic segments of L-arginine, effectively improves the swelling disadvantage of PVA / sodium alginate gel, achieving a moderately hydrophilic effect, thereby improving the durability of the material in wastewater treatment. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the experiment, the wet waste was selected from kitchen waste, which came from a canteen in a mining area;

[0029] The compound enzyme agent comprises the following raw materials by weight: 1 part lactic acid bacteria, 2 parts Bacillus subtilis, 0.5 parts yeast, 1 part cellulase, 1 part lipase, 1 part protease, and 1.5 parts amylase; the strains are sourced from the China Industrial Microbial Culture Collection Center, with the lactic acid bacteria being *Lactobacillus plantarum* (CICC 22703), the Bacillus subtilis (CICC 20683), and the yeast being *Saccharomyces cerevisiae* (CICC 1311); all enzymes have an activity of 100,000 U / g.

[0030] The lime slurry is composed of lime and deionized water, with a lime mass concentration of 120~160 g / L.

[0031] The molecular weight of the cationic polyacrylamide is 12 million; the national drug code for polyvinyl alcohol is 30153160; the polyester diol was purchased from Zhejiang Huafeng New Material Co., Ltd., and the model number is PE3030.

[0032] Example 1: This example provides a method for preparing a slow-release carbon source based on wet waste, including the following steps:

[0033] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Then add a compound enzyme agent and perform hydrolysis and acidification at 50℃ with a stirring rate of 80 r / min, maintaining the system pH at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid, add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system is 400 mg / L. Stir for 5 min and let stand for 3 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, then add citric acid to adjust the system pH to 7.0 to obtain the liquid phase carbon source. The mass ratio of wet waste, deionized water, and compound enzyme agent is 1:3:0.2. The added ion concentration in the hydrolysis and acidification is 800 mg / L, and the Ca2+ is added at a mass ratio of 1.5:4:2.5:0.2. 2+ Na + Fe 2+ and Fe 3+ composition;

[0034] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 12% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 3 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:22.

[0035] Step 3: By weight, take 1.5 parts of polyester diol and 0.3 parts of isophorone diisocyanate, add 0.02 parts of stannous octoate and heat to 85°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.2 parts of dimethylolpropionic acid and 1.0 parts of acetone and stir for 2 hours. Then, cool to 45°C, add 0.01 parts of trimethylolpropane and continue stirring for 1 hour. Add 0.10 parts of triethylamine and react for 40 minutes. Dissolve 0.02 parts of L-arginine in 5 parts of deionized water and place it in the above polyurethane solution. Stir at 1000 r / min for 30 minutes. Let stand to defoam and obtain waterborne polyurethane.

[0036] Step 4: By weight, place 20 parts polyvinyl alcohol and 1.5 parts sodium alginate in 100 parts deionized water, heat to 95℃ and stir for 2 hours, then cool. Add 2 parts water-based polymer and 20 parts embedded particles, stir evenly, pour into a copper column mold, and freeze in both directions using an -80℃ ethanol bath as a cooling source for 50 minutes. After freezing, allow it to thaw naturally, then place it in a -20℃ freezer for 12 hours. After thawing naturally, demold to obtain a slow-release carbon source. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 1:1.

[0037] Example 2: This example provides a method for preparing a slow-release carbon source based on wet waste, including the following steps:

[0038] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Then add a compound enzyme agent and perform hydrolysis and acidification at 40℃ with a stirring rate of 100 r / min, maintaining the system pH at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid, add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system is 300 mg / L. Stir for 5 min and let stand for 4 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, and then add citric acid to adjust the system pH to 7.0 to obtain the liquid phase carbon source. The mass ratio of wet waste, deionized water, and compound enzyme agent is 1:4:0.1. The added ion concentration in the hydrolysis and acidification is 800 mg / L, and the Ca is added in a mass ratio of 1.5:3:2:0.4. 2+ Na + Fe 2+ and Fe 3+ composition;

[0039] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 10% and the mass fraction of sodium alginate was 1.5%. A liquid carbon source was added and stirred for 4 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 4 hours, the solution was centrifuged and washed to obtain the encapsulated particles; wherein the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:25.

[0040] Step 3: By weight, take 1 part polyester diol and 0.3 parts isophorone diisocyanate, add 0.02 parts stannous octoate and heat to 80°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.1 parts dimethylolpropionic acid and 0.6 parts acetone and stir for 2 hours. Then, cool to 45°C, add 0.01 parts trimethylolpropane and continue stirring for 1 hour. Add 0.10 parts triethylamine and react for 30 minutes. Dissolve 0.01 parts L-arginine in 5 parts deionized water and place it in the above polyurethane solution. Stir at 1000 r / min for 30 minutes. Let stand to defoam and obtain waterborne polyurethane.

[0041] Step 4: By weight, 16 parts of polyvinyl alcohol and 1.0 part of sodium alginate are placed in 100 parts of deionized water. After heating to 95℃ and stirring for 2 hours, 3 parts of water-based polymer and 15 parts of encapsulated particles are added. After stirring evenly, the mixture is poured into a copper column mold and subjected to bidirectional freezing for 50 minutes using an ethanol bath at -80℃ as the cooling source. After freezing, the mixture is allowed to thaw naturally and then placed in a -20℃ freezer for 12 hours. After thawing naturally, the mixture is demolded to obtain a slow-release carbon source. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 2:1.

[0042] Example 3: This example provides a method for preparing a slow-release carbon source based on wet waste, including the following steps:

[0043] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Then add a compound enzyme agent and perform hydrolysis and acidification at 55℃ with a stirring rate of 100 r / min, maintaining the system pH at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid, add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system is 500 mg / L. Stir for 5 min and let stand for 3 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, then add citric acid to adjust the system pH to 7.0 to obtain the liquid phase carbon source. The mass ratio of wet waste, deionized water, and compound enzyme agent is 1:5:0.3; the added ion concentration in the hydrolysis and acidification is 1000 mg / L, and the Ca is added at a mass ratio of 1.5:5:3:0.4. 2+ Na + Fe 2+ and Fe 3+ composition;

[0044] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 15% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 4 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:20.

[0045] Step 3: By weight, take 1.6 parts of polyester diol and 0.5 parts of isophorone diisocyanate, add 0.03 parts of stannous octoate and heat to 85°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.2 parts of dimethylolpropionic acid and 1.2 parts of acetone and stir for 2 hours. Then, cool to 45°C, add 0.02 parts of trimethylolpropane and continue stirring for 1 hour. Add 0.12 parts of triethylamine and react for 40 minutes. Dissolve 0.02 parts of L-arginine in 5 parts of deionized water and add it to the above polyurethane solution. Stir at high speed for 30 minutes and let stand to defoam, to obtain waterborne polyurethane.

[0046] Step 4: By weight, 25 parts of polyvinyl alcohol and 1.5 parts of sodium alginate are placed in 100 parts of deionized water. After heating to 95℃ and stirring for 2 hours, 3 parts of water-based polymer and 25 parts of encapsulated particles are added. After stirring evenly, the mixture is poured into a copper column mold and subjected to bidirectional freezing for 50 minutes using an ethanol bath at -80℃ as the cooling source. After freezing, the mixture is allowed to thaw naturally and then placed in a -20℃ freezer for 12 hours. After thawing naturally, the mixture is demolded to obtain a slow-release carbon source. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 0.5:1.

[0047] Comparative Example 1: As a control experiment for Example 1, the difference is that no compound enzyme agent was added in step 1, and it includes the following steps:

[0048] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Hydrolyze and acidify at 50℃ with a stirring rate of 80 r / min, maintaining the system pH at 5.5-6.0. After culturing for 24 h, separate the hydrolyzed and acidified liquid. Add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system reaches 400 mg / L. Stir for 5 min, then let stand for 3 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, then add citric acid to adjust the system pH to 7.0 to obtain the liquid carbon source. The mass ratio of wet waste to deionized water is 1:3; the added ion concentration during hydrolysis and acidification is 800 mg / L, and the solution is Ca2+ with a mass ratio of 1.5:4:2.5:0.2. 2+ Na + Fe 2+ and Fe 3+composition;

[0049] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 12% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 3 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:22.

[0050] Step 3: By weight, take 1.5 parts of polyester diol and 0.3 parts of isophorone diisocyanate, add 0.02 parts of stannous octoate and heat to 85°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.2 parts of dimethylolpropionic acid and 1.0 parts of acetone and stir for 2 hours. Then, cool to 45°C, add 0.01 parts of trimethylolpropane and continue stirring for 1 hour. Add 0.10 parts of triethylamine and react for 40 minutes. Dissolve 0.02 parts of L-arginine in 5 parts of deionized water and place it in the above polyurethane solution. Stir at 1000 r / min for 30 minutes. Let stand to defoam and obtain waterborne polyurethane.

[0051] Step 4: By weight, place 20 parts polyvinyl alcohol and 1.5 parts sodium alginate in 100 parts deionized water, heat to 95℃ and stir for 2 hours, then cool. Add 2 parts water-based polymer and 20 parts embedded particles, stir evenly, pour into a copper column mold, and freeze in both directions using an -80℃ ethanol bath as a cooling source for 50 minutes. After freezing, allow it to thaw naturally, then place it in a -20℃ freezer for 12 hours. After thawing naturally, demold to obtain a slow-release carbon source. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 1:1.

[0052] Comparative Example 2: As a control experiment for Example 1, the difference is that it uses waterborne polyurethane (Impranil eco DLS, purchased from Covestro) and does not contain konjac glucomannan; it includes the following steps:

[0053] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Then add a compound enzyme agent and perform hydrolysis and acidification at 50℃ with a stirring rate of 80 r / min, maintaining the system pH at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid, add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system is 400 mg / L. Stir for 5 min and let stand for 3 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, then add citric acid to adjust the system pH to 7.0 to obtain the liquid phase carbon source. The mass ratio of wet waste, deionized water, and compound enzyme agent is 1:3:0.2. The added ion concentration in the hydrolysis and acidification is 800 mg / L, and the Ca2+ is added at a mass ratio of 1.5:4:2.5:0.2. 2+ Na + Fe 2+ and Fe 3+ composition;

[0054] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 12% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 3 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:22.

[0055] Step 3: By weight, place 20 parts polyvinyl alcohol and 1.5 parts sodium alginate in 100 parts deionized water, heat to 95℃ and stir for 2 hours, then cool. Add 2 parts waterborne polyurethane and 20 parts embedded particles, stir evenly, pour into a copper column mold, and freeze in both directions for 50 minutes using a -80℃ ethanol bath as a cooling source. After freezing, thaw naturally, then place in a -20℃ freezer for 12 hours, thaw naturally, and demold to obtain a slow-release carbon source.

[0056] Comparative Example 3: As a control experiment for Example 1, the difference is that the two-way freezing method was replaced with the ordinary freeze-thaw method, including the following steps:

[0057] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization. Then add a compound enzyme agent and perform hydrolysis and acidification at 50℃ with a stirring rate of 80 r / min, maintaining the system pH at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid, add lime slurry to adjust the system pH to 10, then add cationic polyacrylamide until the concentration of cationic polyacrylamide in the system is 400 mg / L. Stir for 5 min and let stand for 3 h. Separate the solid and liquid phases to obtain the liquid phase component. Add sodium citrate at a solid-liquid ratio of 0.3:100, then add citric acid to adjust the system pH to 7.0 to obtain the liquid phase carbon source. The mass ratio of wet waste, deionized water, and compound enzyme agent is 1:3:0.2. The added ion concentration in the hydrolysis and acidification is 800 mg / L, and the Ca2+ is added at a mass ratio of 1.5:4:2.5:0.2. 2+ Na + Fe 2+ and Fe 3+ composition;

[0058] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 12% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 3 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:22.

[0059] Step 3: By weight, take 1.5 parts of polyester diol and 0.3 parts of isophorone diisocyanate, add 0.02 parts of stannous octoate and heat to 85°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.2 parts of dimethylolpropionic acid and 1.0 parts of acetone and stir for 2 hours. Then, cool to 45°C, add 0.01 parts of trimethylolpropane and continue stirring for 1 hour. Add 0.10 parts of triethylamine and react for 40 minutes. Dissolve 0.02 parts of L-arginine in 5 parts of deionized water and place it in the above polyurethane solution. Stir at 1000 r / min for 30 minutes. Let stand to defoam and obtain waterborne polyurethane.

[0060] Step 4: By weight, place 20 parts of polyvinyl alcohol and 1.5 parts of sodium alginate in 100 parts of deionized water, heat to 95℃ and stir for 2 hours, then cool. Add 2 parts of water-based polymer and 20 parts of encapsulated particles, stir evenly, and place in a -20℃ freezer for 12 hours. After natural thawing and demolding, a slow-release carbon source is obtained. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 1:1.

[0061] Comparative Example 4: As a control experiment for Example 1, the difference is that no external ions were added, and no lime, flocculant, sodium citrate, or citric acid were added. The experiment included the following steps:

[0062] Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization, then add compound enzyme agent, and perform hydrolysis and acidification at 50℃ with a stirring rate of 80 r / min, maintaining the pH of the system at 5.5~6.0. After culturing for 24 h, separate the hydrolysis and acidification liquid to obtain a liquid carbon source; the mass ratio of wet waste, deionized water and compound enzyme agent is 1:3:0.2.

[0063] Step 2: Polyvinyl alcohol and sodium alginate were placed in deionized water, heated to 95°C and stirred for 2 hours, then cooled to obtain a polyvinyl alcohol-sodium alginate solution, wherein the mass fraction of polyvinyl alcohol was 12% and the mass fraction of sodium alginate was 2.0%. A liquid carbon source was added and stirred for 5 minutes, then added dropwise to a 2% calcium chloride-saturated boric acid solution. After stirring for 3 hours, the mixture was centrifuged and washed to obtain the encapsulated particles; the volume ratio of the liquid carbon source to the polyvinyl alcohol-sodium alginate solution was 1:22.

[0064] Step 3: By weight, take 1.5 parts of polyester diol and 0.3 parts of isophorone diisocyanate, add 0.02 parts of stannous octoate and heat to 85°C. After reacting for 2 hours under a nitrogen atmosphere, add 0.2 parts of dimethylolpropionic acid and 1.0 parts of acetone and stir for 2 hours. Then, cool to 45°C, add 0.01 parts of trimethylolpropane and continue stirring for 1 hour. Add 0.10 parts of triethylamine and react for 40 minutes. Dissolve 0.02 parts of L-arginine in 5 parts of deionized water and place it in the above polyurethane solution. Stir at 1000 r / min for 30 minutes. Let stand to defoam and obtain waterborne polyurethane.

[0065] Step 4: By weight, place 20 parts polyvinyl alcohol and 1.5 parts sodium alginate in 100 parts deionized water, heat to 95℃ and stir for 2 hours, then cool. Add 2 parts water-based polymer and 20 parts embedded particles, stir evenly, pour into a copper column mold, and freeze in both directions using an -80℃ ethanol bath as a cooling source for 50 minutes. After freezing, allow it to thaw naturally, then place it in a -20℃ freezer for 12 hours. After thawing naturally, demold to obtain a slow-release carbon source. The water-based polymer is composed of konjac glucomannan and water-based polyurethane in a mass ratio of 1:1.

[0066] Testing and Experiment

[0067] 1. Slow-release performance: Add 5g of the slow-release carbon source prepared in Examples 1-3 and Comparative Examples 1-4 to 100mL of pure water, place it in a shaker at 100rpm, and take 1mL samples at 1h, 3h, 6h, 12h and 24h respectively. Using the permanganate index as the test index, the time to release half of the carbon source is calculated by fitting the data, and the data are recorded in Table 1.

[0068] 2. Static denitrification test: 50 mL of acclimated sludge (acclimated using simulated water with C:N=3) was placed in 250 mL of simulated wastewater, and 5 g of the slow-release carbon source prepared in Examples 1-3 and Comparative Examples 1-4 was added. After shaking on a shaker for 36 h, samples were taken at a speed of 100 r / min to test NO3. - -N removal rate; wherein the simulated wastewater uses potassium nitrate as the nitrogen source, and the mass concentration of potassium nitrate in the influent is controlled at 35 mg / L.

[0069] Table 1

[0070]

[0071] Conclusions: The above experiments show that Example 1 achieved better sustained-release and denitrification performance than Examples 2 and 3. Comparative Example 1, as a control experiment of Example 1, did not add compound enzyme agent. Although the sustained-release time was longer due to the large number of macromolecules in its liquid carbon source, the low effective carbon source led to a decrease in the denitrification rate, resulting in a significant decrease in the removal rate. Comparative Example 2, as a control experiment of Example 1, replaced the waterborne polyurethane with commercial waterborne polyurethane and did not add konjac glucomannan. The sustained-release performance decreased, and the accelerated release led to a lower overall carbon source utilization rate and a decrease in the removal rate. Comparative Example 3, as a control experiment of Example 1, replaced the two-way freeze-thaw cycle with ordinary freeze-thaw, resulting in disordered pores, decreased sustained-release performance, and decreased denitrification performance. Comparative Example 4, as a control experiment of Example 1, did not add external ions during hydrolysis acidification, nor did it include subsequent lime and flocculation purification. This resulted in more impurities in the liquid carbon source, which greatly affected subsequent gelation and significantly reduced denitrification performance.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a slow-release carbon source based on wet waste, characterized in that, Includes the following steps: Step 1: After removing impurities from the wet waste, add deionized water for crushing and homogenization, then add compound enzyme agent for hydrolysis and acidification, separate the hydrolysis and acidification liquid, add lime slurry to adjust the pH of the system to 10-10.5, then add flocculant, stir and let stand, separate the liquid phase component from the solid and liquid, add sodium citrate and citric acid in sequence to obtain the liquid phase carbon source; Step 2: Place polyvinyl alcohol and sodium alginate in deionized water, heat and stir to dissolve, then cool to obtain polyvinyl alcohol sodium alginate solution. Add liquid carbon source and stir evenly, then dropwise into calcium chloride-saturated boric acid solution. Stir for 2-4 hours, then centrifuge and wash to obtain encapsulated particles. Step 3: Place polyvinyl alcohol and sodium alginate in deionized water, heat and stir to dissolve, then cool. Add water-based polymer and encapsulated particles, stir evenly, pour into a copper column mold for bidirectional freezing, freeze naturally after freezing, then place in a -20℃ freezer and freeze again, then thaw naturally and demold to obtain a slow-release carbon source. In step 1, the solid-liquid ratio of sodium citrate to the liquid phase component is (0.2~0.5):100; citric acid is added to adjust the pH of the liquid phase component to 7.0~7.5; The process parameters for hydrolysis and acidification in step 1 are as follows: temperature 35~55℃, added ion concentration 800~1000mg / L, stirring rate 60~100r / min, system pH 5.5~6.0, and incubation 20~24h; the added ions consist of Ca in a mass ratio of 1.5:(3~5):(2~3):(0.2~0.4). 2+ Na + Fe 2+ and Fe 3+ composition.

2. The method for preparing a slow-release carbon source based on wet waste according to claim 1, characterized in that, In step 1, the mass ratio of wet waste, deionized water, and compound enzyme agent is 1:(2~5):(0.1~0.3); the compound enzyme agent includes the following raw materials in parts by mass: 1.0~1.5 parts lactic acid bacteria, 1.5~3.0 parts Bacillus, 0.5~0.8 parts yeast, 1.0~1.2 parts cellulase, 0.6~1.5 parts lipase, 0.8~1.0 parts protease, and 1.5~2.0 parts amylase.

3. The method for preparing a slow-release carbon source based on wet waste according to claim 1, characterized in that, The lime slurry is composed of lime and deionized water, with a lime concentration of 120-160 g / L; the flocculant is cationic polyacrylamide, with a flocculant concentration of 200-500 mg / L in the hydrolysis acidification solution.

4. The method for preparing a slow-release carbon source based on wet waste according to claim 1, characterized in that, In step 2, the polyvinyl alcohol sodium alginate solution contains 10-15% polyvinyl alcohol and 1.5-2.0% sodium alginate, and the volume ratio of the liquid carbon source to the polyvinyl alcohol sodium alginate solution is 1:(20-25); the concentration of the calcium chloride-saturated boric acid solution is 2-3%.

5. The method for preparing a slow-release carbon source based on wet waste according to claim 1, characterized in that, Step 3 includes the following raw materials by weight: 16-25 parts polyvinyl alcohol, 1.0-1.5 parts sodium alginate, 1.5-3 parts water-based polymer, 15-25 parts encapsulated particles, and 90-100 parts deionized water; bidirectional freezing is performed using an ethanol bath at -80 to -90°C as the cooling source for 30-50 minutes.

6. The method for preparing a slow-release carbon source based on wet waste according to claim 1, characterized in that, The waterborne polymer is composed of konjac glucomannan and waterborne polyurethane in a mass ratio of (0.5~2):

1. The preparation steps of the waterborne polyurethane are as follows: polyester diol and isophorone diisocyanate are taken, stannous octoate is added and heated to 80~85℃, and reacted under nitrogen atmosphere for 2h. Then, dimethylolpropionic acid and acetone are added and stirred for 1~2h. The temperature is then lowered to 45℃, trimethylolpropane is added and stirred for 1h. Triethylamine is added and reacted for 30~40min. A mixed solution of L-arginine and deionized water is added and stirred at high speed for 20~30min. The mixture is allowed to stand to defoam, and waterborne polyurethane is obtained.

7. The method for preparing a slow-release carbon source based on wet waste according to claim 6, characterized in that, The waterborne polyurethane comprises the following raw materials in parts by weight: 1-1.6 parts polyester diol, 0.3-0.5 parts isophorone diisocyanate, 0.02-0.03 parts stannous octoate, 0.1-0.2 parts dimethylolpropionic acid, 0.01-0.02 parts trimethylolpropane, 0.07-0.12 parts triethylamine, 0.01-0.02 parts L-arginine, 3-5 parts deionized water, and 0.6-1.2 parts acetone.

8. A slow-release carbon source based on wet waste, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

Images