Denitrification slow-release composite carbon source as well as preparation method and application thereof

Abstract

The invention relates to the technical field of water treatment, in particular to a denitrification slow-release composite carbon source as well as a preparation method and application thereof. Comprising the following components in percentage by weight: 2-10% of hydroxy acrylic acid, 2-10% of saccharides, 5-15% of straw waste liquid, 5-15% of kitchen waste liquid, 2-10% of saccharides, 3-15% of porous volcanic ash, 5-15% of polyvinyl alcohol, 0.2-1% of inorganic salt, 1-2% of polypeptide, 0.5-1% of growth factors, 0.2-1.5% of MFC agar, 0.1-0.5% of cellulase, 0.1-0.5% of protease, 0.1-0.5% of denitrifying bacteria and the balance of water. The sum of the percentages of the raw materials is 100%. The invention has the advantages that: each nutrient component is balanced, the nutrition is comprehensive, the activity of denitrifying bacteria is improved, the number of species and community layers of a biological system of a sewage treatment plant are increased, the growth of various microorganisms is facilitated, nutrient substances can be fully utilized, and the denitrification effect is far higher than that of related carbon sources such as single methanol, glucose and the like.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a denitrification slow-release composite carbon source and a preparation method and application thereof. Background Art

[0002] At present, more than 80% of my country's sewage treatment plants use nitrification and denitrification to remove total nitrogen. The main principle is that denitrifying bacteria use organic matter as electron donors to reduce nitrate nitrogen ions to nitrogen gas. Therefore, in order to maintain the smooth progress of the denitrification reaction, a certain amount of organic matter needs to be maintained in the sewage mixture, that is, sufficient COD. However, the carbon-nitrogen ratio has been in an unbalanced state in my country's sewage treatment for a long time, and the carbon-nitrogen ratio of most sewage treatment plants is less than 2.5. Under such conditions, it is difficult to meet the treatment standards for total nitrogen. Therefore, adding external carbon sources has become the primary way to remove total nitrogen in my country's sewage treatment.

[0003] At present, commonly used carbon sources mainly include sugars, alcohols, organic acids and organic acid salts (sodium acetate), solid fiber carbon sources, and common natural cellulose carbon sources include corn cobs, cotton, rice husks, wheat straw and rotten wood. Among them, alcohols have high COD, high denitrification efficiency and low price, but alcohols are flammable and explosive, and have certain toxic effects on the human body, so there are certain limitations in practical applications; such as glucose and sodium acetate, there are problems such as being easily consumed quickly, frequent addition, high cost, and may cause large fluctuations in carbon source concentration in water, thereby affecting microbial activity. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art, provide a denitrification slow-release composite carbon source and a preparation method and application thereof, solve the problems of poor stability and impact resistance of the biological treatment system, large carbon source addition amount, high operating cost, high transportation cost, large sludge output, and potential safety hazards caused by the addition of a single carbon source in a sewage treatment plant; realize the repeated reuse of garbage kitchen waste liquid and straw waste liquid, achieve harmlessness, reduction and resource utilization, so as to obtain greater economic benefits.

[0005] The present invention is achieved through the following technical scheme: on the one hand, a denitrification slow-release composite carbon source is provided, wherein the raw materials of the composite carbon source include, by mass percentage, 2-10% hydroxyacrylic acid, 2-10% sugar, 5%-15% straw waste liquid, 5%-15% kitchen waste liquid, 3-15% porous volcanic ash, 5-15% polyvinyl alcohol, 0.2-1% inorganic salt, 1-2% polypeptide, 0.5-1% growth factor, 0.2-1.5% MFC agar, 0.1-0.5% cellulase, 0.1-0.5% protease and 0.1-0.5% denitrifying bacteria agent, and the balance is water; the sum of the percentages of the raw materials is 100%.

[0006] Through the above technical scheme, organic acid provides a stable carbon source in the system, which can significantly promote the activity of denitrifying bacteria; its weakly acidic environment helps to balance the pH value of the system and enhance the metabolic efficiency of microorganisms. As a natural porous material, porous volcanic ash has good adsorption and slow release properties, provides a stable living environment for denitrifying bacteria, and can slowly release carbon sources and nutrients to prolong the duration of the denitrification effect. The introduction of polyvinyl alcohol enhances the viscoelasticity and water stability of the composite carbon source, and forms a stable three-dimensional network structure with other components through the action of intermolecular hydrogen bonds. In addition, inorganic salts provide the necessary ions required for microbial metabolism and improve the activity of the flora, while peptides and growth factors promote the rapid growth and reproduction of microorganisms through synergistic effects. MFC agar forms a colloid-like support structure in the system, which not only improves the morphological stability of the composite carbon source, but also enhances the attachment and fixation ability of denitrifying bacteria. The addition of cellulase and protease effectively decomposes organic matter, provides additional carbon sources and improves the flora environment. Denitrifying bacteria directly improve the denitrification capacity of the system and achieve efficient denitrification effect. Under this ratio, the raw materials form a composite system with optimized microstructure through various physical and chemical effects, such as the formation of a porous network, the uniform distribution of carbon sources and the slow release mechanism of nutrients. At the molecular level, the stable combination of ingredients is achieved through hydrogen bonding, electrostatic adsorption and enzymatic action.

[0007] A method for preparing the above-mentioned denitrification slow-release composite carbon source is also provided, comprising the following steps:

[0008] Step 1) pretreatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0009] Step 2) Thermal hydrolysis of kitchen waste filtrate: The obtained kitchen waste filtrate is hydrothermally heated at 170℃-205℃ for 50 minutes to obtain hydrolyzed kitchen waste filtrate; under high temperature hydrothermal conditions, the polarization effect of high temperature and high pressure water and the catalytic effect of ion products (such as H+ and OH-) are used to achieve the breaking and reorganization of chemical bonds. The β-1,4 glycosidic bonds of polysaccharides such as cellulose and hemicellulose in the kitchen waste filtrate are broken and hydrolyzed into oligosaccharides, monosaccharides, aldehydes and other compounds under high temperature conditions; proteins are degraded into short peptides and free amino acids. Lipid substances generate fatty acids and glycerol through hydrolysis and oxidation reactions;

[0010] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at a temperature of 35° C.-45° C. for 120 hours to obtain a kitchen waste carbon source;

[0011] Step 4) Preparation of straw carbon source: After pretreatment of straw waste liquid with acidic solvent, centrifugation and filtration, straw solution is obtained; and protease and cellulase are added to the straw solution to obtain straw carbon source; the acidic solvent releases cellulose chains by destroying the lignin and hemicellulose structures in the straw, thereby improving the efficiency of subsequent enzymatic hydrolysis reactions. The physicochemical changes increase the specific surface area of ​​contact between the enzyme and the substrate, laying the foundation for subsequent hydrolysis reactions. After protease and cellulase are added to the straw solution, the hydrolysis reaction begins. Cellulase mainly catalyzes the decomposition of cellulose into oligosaccharides and glucose, while protease can further degrade possible protein impurities and reduce interference in the reaction system. During the hydrolysis process, cellulose decomposition is achieved through the synergistic action of cellulose endonucleases, exonucleases and β-glucosidases, which break the β-1,4-glycosidic bonds of the cellulose chains through continuous action to achieve complete hydrolysis. Further hydrothermal reaction can provide the possibility for deep conversion of straw solution. The hydrothermal reaction accelerates the reaction rate under high temperature and high pressure conditions, thereby enhancing the decomposition capacity of cellulose and hemicellulose. During the hydrothermal treatment process, the dissociation of water molecules to generate H+ and OH- can effectively promote the hydrolysis reaction.

[0012] Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) and the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 25-30° C. for 3-5 min, and control the pH to 7-8.5 to obtain a composite carbon source solution;

[0013] Step 6) Preparation of modified volcanic ash: weigh a certain amount of volcanic ash, modify the volcanic ash with ferric chloride solution and sodium hydroxide solution, and dry it for later use;

[0014] Specifically, a certain amount of volcanic ash is weighed and placed in a reaction container. A certain concentration of ferric chloride solution is controlled at room temperature or appropriately heated to 50°C-80°C, and stirred continuously for 30-60 minutes to gradually generate iron hydroxide precipitation and adhere to the surface of the volcanic ash. During the modification process, the surface chemical properties and microstructure of the volcanic ash change significantly. The iron ions provided by the ferric chloride solution generate iron hydroxide precipitation under alkaline conditions, which undergo physical adsorption and chemical bonding with the surface of the volcanic ash to enhance its adsorption capacity and surface activity. At the same time, the pH control process may also improve the specific surface area and pore structure of the volcanic ash. After filtering and washing the modified volcanic ash to remove unreacted substances and excess solution, it is dried at 105°C to constant weight for standby use. The modified volcanic ash is usually verified for structure and performance by electron microscopy (SEM) and specific surface area analysis (BET). The results show that the surface metal ion content increases, the specific surface area and porosity increase, and the adsorption performance is significantly enhanced, which is suitable for application fields such as sewage treatment.

[0015] Step 7) polyvinyl alcohol, modified volcanic ash, composite carbon source solution, water, and denitrifying agent are sequentially added to the reactor and stirred for 10-15min to obtain a denitrifying slow-release composite carbon source. Specifically, polyvinyl alcohol, modified volcanic ash, composite carbon source solution, water, and denitrifying agent are sequentially added to the reactor. Polyvinyl alcohol is added, which is viscous in water and provides initial adhesion; then, modified volcanic ash is added, and its particles are quickly dispersed in the solution and preliminarily mixed with polyvinyl alcohol to form a certain suspension state. Next, the composite carbon source solution is added to provide the main organic carbon source, and the fluidity of the solution is combined with the first two and gradually becomes uniform. Then add an appropriate amount of water to adjust the overall viscosity so that it is suitable for subsequent reaction conditions. Finally, a denitrifying agent is added to participate in the biochemical reaction and further stabilize the system. During the 10-15 minute stirring process, the material gradually changes from the initial stratified or granular state to a uniform mixed state with moderate viscosity and good fluidity and formability. The composite carbon source after stirring has high uniformity and stability. The obtained slow-release composite carbon source is characterized by a uniform microporous structure and good mechanical strength, and can achieve long-term and stable carbon source release in water. The technical advantages include: ① excellent slow-release performance, extending the service life; ② strong stability, not easy to decompose and fail due to changes in the external environment; ③ economic and environmental protection, reducing the frequency of artificial release; ④ synergistic with denitrifying bacteria, improving denitrification efficiency, and significantly optimizing the water purification effect.

[0016] Pretreatment of kitchen waste liquid: Remove solid impurities and grease through stirring, degreasing, crushing and filtering. Based on the principles of physical separation and mechanical crushing, the kitchen waste liquid is purified, the interference of impurities on subsequent reactions is reduced, and the reaction efficiency is improved. Compared with traditional treatment methods, this step separates organic matter more efficiently and improves the utilization rate of raw materials.

[0017] Thermal hydrolysis of kitchen waste filtrate: Using high temperature and high pressure conditions (170℃-205℃), complex organic matter is decomposed into small molecular organic acids, sugars, etc. through hydrolysis reaction, which significantly improves the biodegradability of kitchen waste liquid. Thermal hydrolysis technology shortens the decomposition time of organic matter and enhances the carbon source potential of kitchen waste filtrate, which is better than conventional low-temperature hydrolysis.

[0018] Preparation of kitchen waste carbon source: Through anaerobic fermentation, the hydrolyzate is further converted into high-quality carbon sources such as volatile fatty acids with the help of microbial metabolism to ensure efficient release of carbon sources. Controlling temperature and pH optimizes microbial activity and achieves stable and efficient production of carbon sources, which is more stable than traditional processes.

[0019] Preparation of straw carbon source: Through acid solvent pretreatment and enzymatic hydrolysis technology, the cellulose and hemicellulose in the straw are degraded into soluble carbon sources, significantly improving the utilization rate of straw waste liquid. The enzymatic hydrolysis process is gentle and controllable, avoiding the damage of high temperature and high pressure to the straw structure, and ensuring the diversity and quality of the carbon source.

[0020] Preparation of composite carbon source: Mix kitchen waste and straw carbon source, adjust pH and add sodium bicarbonate, and use carbonate neutralization properties to optimize stability. Composite carbon source has both rapid effect and slow release, providing a lasting carbon source for denitrification reaction, solving the problem of insufficient single carbon source.

[0021] Preparation of modified volcanic ash: by modifying it with ferric chloride and sodium hydroxide, the specific surface area and adsorption capacity of volcanic ash are increased, and its loading effect on carbon sources and microorganisms is enhanced. This step significantly improves the denitrification slow-release effect and improves the reaction efficiency compared to ordinary fillers.

[0022] Preparation of slow-release composite carbon source for denitrification: Using polyvinyl alcohol as a matrix, combined with modified volcanic ash and composite carbon source to form a slow-release system, ensuring the stable release of carbon source during use; comprehensively improving denitrification performance, extending service life, and solving the problem of excessively fast release rate of traditional denitrification carbon source. The above scheme optimizes the carbon source preparation and release process in many aspects, and is highly efficient, stable and environmentally friendly.

[0023] Furthermore, in step 2), the kitchen waste filtrate is subjected to pyrolysis reaction, hydration reaction and free radical reaction to degrade organic matter.

[0024] Specifically, under high temperature and high pressure conditions of 170°C-205°C, the complex organic matter in the kitchen waste filtrate (such as macromolecular substances such as proteins, polysaccharides and fats) is decomposed and converted into easily degradable components such as small molecular organic acids, sugars and amino acids. During the reaction, the molecular chains are broken, the solubility is increased and the active groups are released, so that the filtrate is gradually converted from a complex mixed liquid to a uniform and stable hydrolyzate state. The depth of the hydrolysis depends on the reaction temperature and time. Controlling it within 50 minutes can avoid excessive decomposition or the generation of adverse by-products.

[0025] Pyrolysis: High temperature causes the CC, CN and CO bonds of organic matter to break, proteins are decomposed into amino acids through deamidation, polysaccharides are hydrolyzed into monosaccharides or oligosaccharides through chain scission, and fats are hydrolyzed into glycerol and fatty acids. These small molecules provide high-quality carbon sources for subsequent biochemical reactions.

[0026] Hydration: High-temperature water is used as a reaction medium to form superheated water with a higher ion product (Kw), which enhances the acid catalytic ability. The hydration between molecules accelerates the depolymerization reaction of organic matter and increases the reaction rate.

[0027] Free radical reaction: Under hydrothermal conditions, some reactions may involve free radical mechanisms, which further decompose refractory organic matter through the attack of hydroxyl radicals and improve conversion efficiency.

[0028] Further, in step 3), the preparation of the kitchen waste carbon source: the obtained hydrolyzed kitchen waste filtrate is cooled to room temperature, the protease, sugar, hydroxyacrylic acid, inorganic salt, and agar are added, and then poured into an anaerobic reaction tank, the pH is controlled to be 6, and the temperature is 35° C. and 45° C., and the reaction is carried out for 120 hours to obtain a reaction solution;

[0029] 7. Further, in step 6), the modified volcanic ash is prepared by any of the following methods: The modified volcanic ash is prepared by any of the following methods:

[0030] The first method is to incinerate the volcanic ash in a 400°C roasting furnace for 2 hours for modification, let it stand and cool to room temperature, place the volcanic ash in a reaction container, and place the ferric chloride solution at a temperature of 50°C-80°C and under continuous stirring for 30-60 minutes for 12 hours to allow the ferric hydroxide precipitation to gradually form and adhere to the surface of the volcanic ash to obtain modified volcanic ash 1; the modified volcanic ash 1 has a specific surface area of ​​15.5㎡ / g, a porosity of 75%, and a bulk density of 850kg / m 3 ;

[0031] The second method is to burn the volcanic ash in a calciner at 800℃-1000℃ for 2h for modification, let it stand and cool to room temperature, put the volcanic ash in a reaction container, add ferric chloride solution at a temperature of 80℃-110℃, stir continuously for 120-150min, let it stand for 24h, so that solid-liquid diffusion occurs between the ferric chloride solution and the volcanic ash. Modified volcanic ash II is obtained; the specific surface area of ​​the modified volcanic ash II is 20㎡ / g, the porosity is 80%, and the bulk density is 750kg / m 3 .

[0032] Specifically, a certain amount of volcanic ash is weighed and placed in a reaction container. A certain concentration of ferric chloride solution is controlled at room temperature or appropriately heated to 50°C-80°C, and stirred continuously for 30-60 minutes to gradually generate iron hydroxide precipitation and adhere to the surface of the volcanic ash. During the modification process, the surface chemical properties and microstructure of the volcanic ash change significantly. The iron ions provided by the ferric chloride solution generate iron hydroxide precipitation under alkaline conditions, which undergo physical adsorption and chemical bonding with the surface of the volcanic ash to enhance its adsorption capacity and surface activity. At the same time, the pH control process may also improve the specific surface area and pore structure of the volcanic ash. After filtering and washing the modified volcanic ash to remove unreacted substances and excess solution, it is dried at 105°C to constant weight for standby use. The modified volcanic ash is usually verified for structure and performance by electron microscopy (SEM) and specific surface area analysis (BET). The results show that the surface metal ion content increases, the specific surface area and porosity increase, and the adsorption performance is significantly enhanced, which is suitable for application fields such as sewage treatment.

[0033] Finally, an application of the above-mentioned denitrification slow-release composite carbon source in water treatment is provided, and the denitrification rate is positively correlated with the COD value.

[0034] Beneficial Effects

[0035] The present invention has balanced nutritional components, comprehensive nutrition, improved activity of denitrifying bacteria, increased species number and community level of biological system of sewage treatment plant, which is beneficial to the growth of various microorganisms, and nutrients can be fully utilized. The denitrification effect is much higher than that of single methanol, glucose and other related carbon sources.

[0036] After pretreatment and hydrolysis, kitchen waste liquid produces a large amount of humus organic matter, and then after adding inorganic salts, polypeptides, agar and other substances for catalytic fermentation, it has been tested that large molecules such as starch and fat in the kitchen waste liquid are converted into volatile fatty acids and lactic acid that are most easily absorbed by denitrifying bacteria, thereby improving the conversion rate and utilization rate of kitchen waste liquid.

[0037] After pretreatment, macromolecular substances such as straw waste liquid are added with auxiliary materials, protease and cellulase catalysts, and hydrolysis reactions occur to generate small molecular acids and alcohols, which enhance the absorption capacity of denitrifying bacteria and significantly improve the denitrification rate.

[0038] The liquid composite carbon source shows good denitrification performance after solidification, improvement and addition of additives. Its denitrification capacity reaches more than 80%. In some deep denitrification processes, it can replace the traditional liquid carbon source as the carbon source material for sewage treatment.

[0039] The present invention solves the problems of poor stability and impact resistance of the biological treatment system, large carbon source addition amount, high operation cost, high transportation cost, large sludge output, potential safety hazards, etc. caused by the addition of a single carbon source in a sewage treatment plant; it realizes the repeated reuse of garbage kitchen waste liquid and straw waste liquid, realizes harmlessness, reduction and resource utilization, and can also obtain greater economic benefits. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The experimental methods without specific conditions in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages, ratios, proportions or parts are by weight.

[0042] Unless otherwise specified, the reagents and raw materials used in the examples and comparative examples of the present invention can be obtained through commercial channels.

[0043] Example 1

[0044] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source, measured by mass percentage, include 10% hydroxyacrylic acid, 10% sugar, 15% straw waste liquid, 15% kitchen waste liquid, 15% modified volcanic ash II, 15% polyvinyl alcohol, 1% inorganic salt, 2% polypeptide, 1% growth factor, 1.5% MFC agar, 0.5% cellulase, 0.5% protease and 0.5% denitrifying bacteria agent, and the balance is water.

[0045] The method comprises the following steps:

[0046] Step 1) pre-treatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0047] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 205° C. for 50 min to obtain a hydrolyzed kitchen waste filtrate;

[0048] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 45° C. for 120 hours to obtain a kitchen waste carbon source;

[0049] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0050] Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) with the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 30° C. for 5 min, and control the pH to 8.5 to obtain a composite carbon source solution;

[0051] Step 6) Preparation of modified volcanic ash II: Weigh a certain amount of volcanic ash, which is modified by burning the volcanic ash in a calciner at 800°C for 2 hours, standing and cooling to room temperature, placing the volcanic ash in a reaction container, adding ferric chloride solution at a temperature of 80°C, continuously stirring for 120 minutes, standing for 24 hours, allowing solid-liquid diffusion to occur between the ferric chloride solution and the volcanic ash, to obtain modified volcanic ash II, and drying for standby use; the concentration of the ferric chloride solution is 2 mol / L;

[0052] Step 7) polyvinyl alcohol, modified volcanic ash II, composite carbon source solution, water, and denitrifying agent are sequentially added into the reactor and stirred for 15 minutes to obtain a denitrifying slow-release composite carbon source.

[0053] Example 2

[0054] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source, measured by mass percentage, include 10% hydroxyacrylic acid, 10% sugar, 9% straw waste liquid, 9% kitchen waste liquid, 15% modified volcanic ash, 15% polyvinyl alcohol, 1% inorganic salt, 2% polypeptide, 1% growth factor, 1.5% MFC agar, 0.5% cellulase, 0.5% protease and 0.5% denitrifying bacteria agent, and the balance is water.

[0055] The method comprises the following steps:

[0056] Step 1) pretreatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0057] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 205° C. for 50 min to obtain a hydrolyzed kitchen waste filtrate;

[0058] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 45° C. for 120 hours to obtain a kitchen waste carbon source;

[0059] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0060] Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) with the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 30° C. for 5 min, and control the pH to 8.5 to obtain a composite carbon source solution;

[0061] Step 6) Preparation of modified volcanic ash 1: Weigh a certain amount of volcanic ash, which is modified by burning the volcanic ash in a calciner at 400° C. for 2 hours, standing and cooling to room temperature, placing the volcanic ash in a reaction container, and placing a ferric chloride solution at a temperature of 80° C. and stirring for 30 minutes, standing for 12 hours to allow iron hydroxide precipitation to gradually form and adhere to the surface of the volcanic ash, to obtain modified volcanic ash 1, and drying for standby use; the concentration of the ferric chloride solution is 2 mol / L;

[0062] Step 7) polyvinyl alcohol, modified volcanic ash 1, composite carbon source solution, water, and denitrifying agent are sequentially added into the reactor and stirred for 15 minutes to obtain a denitrifying slow-release composite carbon source.

[0063] Example 3

[0064] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source, measured by mass percentage, include 2% hydroxyacrylic acid, 2% sugar, 5% straw waste liquid, 5% kitchen waste liquid, 5% modified volcanic ash II, 5% polyvinyl alcohol, 0.2% inorganic salt, 1% polypeptide, 0.75% growth factor, 0.2% MFC agar, 0.1% cellulase, 0.1% protease and 0.1% denitrifying bacteria agent, and the balance is water.

[0065] The method comprises the following steps:

[0066] Step 1) pre-treatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0067] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 190° C. for 30 minutes to obtain a hydrolyzed kitchen waste filtrate;

[0068] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 40° C. for 120 hours to obtain a kitchen waste carbon source;

[0069] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0070] Step 5) Preparation of a composite carbon source: After mixing the kitchen waste carbon source obtained in step 3) and the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 27° C. for 4 min, and control the pH to 7.5 to obtain a composite carbon source solution;

[0071] Step 6) Preparation of modified volcanic ash II: Weigh a certain amount of volcanic ash, which is modified by burning the volcanic ash in a 1000° C. calciner for 1 hour, standing and cooling to room temperature, placing the volcanic ash in a reaction vessel, stirring the ferric chloride solution at a temperature of 60° C. for 100 minutes, standing for 24 hours to allow solid-liquid diffusion between the ferric chloride solution and the volcanic ash, to obtain modified volcanic ash II, and drying for standby use; the concentration of the ferric chloride solution is 1.5 mol / L;

[0072] Step 7) polyvinyl alcohol, modified volcanic ash II, composite carbon source solution, water, and denitrifying agent are sequentially added into the reactor and stirred for 12 minutes to obtain a denitrifying slow-release composite carbon source.

[0073] Example 4

[0074] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source, measured by mass percentage, include 6% hydroxyacrylic acid, 6% sugar, 7% straw waste liquid, 7% kitchen waste liquid, 6% modified volcanic ash II, 10% polyvinyl alcohol, 0.6% inorganic salt, 1.5% polypeptide, 0.5% growth factor, 0.8% MFC agar, 0.3% cellulase, 0.3% protease and 0.3% denitrifying bacteria agent, and the balance is water.

[0075] The method comprises the following steps:

[0076] Step 1) pre-treatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0077] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 170° C. for 35 minutes to obtain a hydrolyzed kitchen waste filtrate;

[0078] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 35° C. for 120 hours to obtain a kitchen waste carbon source;

[0079] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0080] Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) with the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 25° C. for 3 min, and control the pH to 7 to obtain a composite carbon source solution;

[0081] Step 6) Preparation of modified volcanic ash II: Weigh a certain amount of volcanic ash, which is modified by burning the volcanic ash in a 900°C roasting furnace for 2 hours, standing and cooling to room temperature, placing the volcanic ash in a reaction container, adding ferric chloride solution at a temperature of 60°C, stirring continuously for 100 minutes, standing for 24 hours, allowing solid-liquid diffusion to occur between the ferric chloride solution and the volcanic ash, to obtain modified volcanic ash II, and drying for standby use; the concentration of the ferric chloride solution is 1.2 mol / L;

[0082] Step 7) polyvinyl alcohol, modified volcanic ash II, composite carbon source solution, water, and denitrifying agent are sequentially added into a reactor and stirred for 10 minutes to obtain a denitrifying slow-release composite carbon source.

[0083] Example 5

[0084] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source, measured by mass percentage, include 2% hydroxyacrylic acid, 2% sugar, 5% straw waste liquid, 5% kitchen waste liquid, 15% modified volcanic ash, 15% polyvinyl alcohol, 0.2% inorganic salt, 1% polypeptide, 0.65% growth factor, 0.2% MFC agar, 0.1% cellulase, 0.1% protease and 0.1% denitrifying bacteria agent, and the balance is water.

[0085] The method comprises the following steps:

[0086] Step 1) pretreatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0087] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 180° C. for 30-50 min to obtain a hydrolyzed kitchen waste filtrate;

[0088] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 38° C. for 120 hours to obtain a kitchen waste carbon source;

[0089] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0090] Step 5) Preparation of a composite carbon source: After mixing the kitchen waste carbon source obtained in step 3) and the straw carbon source obtained in step 4), adding a sodium bicarbonate solution and stirring at a temperature of 27° C. for 3.55 min, the pH value was controlled to be 7.5 to obtain a composite carbon source solution;

[0091] Step 6) Preparation of modified volcanic ash 1: Weigh a certain amount of volcanic ash, which is modified by burning the volcanic ash in a calciner at 400° C. for 2 hours, standing and cooling to room temperature, placing the volcanic ash in a reaction container, and placing a ferric chloride solution at a temperature of 50° C. and stirring for 60 minutes, standing for 12 hours to allow iron hydroxide precipitation to gradually form and adhere to the surface of the volcanic ash, to obtain modified volcanic ash 1, and drying for standby use; the concentration of the ferric chloride solution is 2 mol / L;

[0092] Step 7) polyvinyl alcohol, modified volcanic ash 1, composite carbon source solution, water, and denitrifying agent are sequentially added into the reactor and stirred for 12 minutes to obtain a denitrifying slow-release composite carbon source.

[0093] Example 6

[0094] A method for preparing a denitrifying slow-release composite carbon source. The raw materials of the composite carbon source include, by mass percentage, 10% hydroxyacrylic acid, 10% sugar, 15% straw waste liquid, 15% kitchen waste liquid, 5% porous volcanic ash, 5% polyvinyl alcohol, 1% inorganic salt, 2% polypeptide, 0.5% growth factor, 1.5% MFC agar, 0.5% cellulase, 0.5% protease and 0.1% denitrifying bacteria agent, and the balance is water.

[0095] The method comprises the following steps:

[0096] Step 1) pretreatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate;

[0097] Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 170° C. for 30 minutes to obtain a hydrolyzed kitchen waste filtrate;

[0098] Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at 35° C. for 120 hours to obtain a kitchen waste carbon source;

[0099] Step 4) Preparation of straw carbon source: pre-treating straw waste liquid with an acidic solvent, centrifuging, filtering, and obtaining a straw solution; and adding protease and cellulase to the straw solution to obtain a straw carbon source;

[0100] Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) with the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 25° C. for 3 min, and control the pH to 7-8.5 to obtain a composite carbon source solution;

[0101] Step 6) polyvinyl alcohol, porous volcanic ash, composite carbon source solution, water, and denitrifying agent are sequentially added into a reactor and stirred for 10 minutes to obtain a denitrifying slow-release composite carbon source.

[0102] Effect Example

[0103] In order to verify the denitrification ability of the new denitrification slow-release composite carbon source, it was compared with methanol, glucose and composite carbon sources of Examples 1-6 on the market:

[0104] ① Prepare 6 1000ml beakers, place them on a magnetic stirrer, take 1000ml of the anoxic section mixed solution from the Zhengzhou Wastewater Treatment Plant, the sludge concentration is about 4500mg / L, take 5ml of sodium nitrate solution with a concentration of 5000mg / L with a pipette, and drop it into the beakers;

[0105] ② Add the composite carbon source prepared in Examples 1, 2, 3, 4, and 5 to the sewage mixture and drip into the beaker at a carbon-nitrogen ratio of 5:1;

[0106] ③ Start stirring and control the temperature to 30℃;

[0107] ④ Starting from 0h, sampling every 2h, measuring the nitrate nitrogen concentration in the mixed solution, until the reaction is completed for 6 hours, calculating the nitrate nitrogen removal rate, subtracting the nitrate nitrogen content at the end of the reaction from the nitrate nitrogen content at the beginning of the reaction, and then dividing by time to obtain the nitrate nitrogen removal rate;

[0108]

[0109]

[0110] It can be seen from the above table that Example 1 has the highest nitrate nitrogen removal rate, indicating that its denitrification ability is stronger; the proportion of each raw material in Example 1 is higher than that in Example 3, especially straw waste liquid, kitchen waste liquid, modified volcanic ash II and polyvinyl alcohol; the nitrate nitrogen removal rate of Example 1 is significantly higher than that of Example 3, and the proportion of raw materials in Example 4 is adjusted compared with Example 1, especially the content of hydroxyacrylic acid, sugars, straw waste liquid, kitchen waste liquid and polyvinyl alcohol is lower, and the nitrate nitrogen removal rate of Example 1 is higher than that of Example 4; the nitrate nitrogen removal rate of Example 1 is significantly higher than that of Example 5, and the nitrate nitrogen removal rate of Example 1 is much higher than that of Example 6.

[0111] It can be seen from the data in the above table that, under the condition of consistent dosage, the nitrate nitrogen removal rate of the new semi-solid composite slow-release carbon source formed by modified volcanic ash, polyvinyl alcohol bonding, kitchen waste liquid, and straw waste liquid under different conditions is significantly higher than that of single carbon sources such as glucose and methanol. The present invention achieves a balance between rapid effect and slow release by optimizing the ratio of carbon source components (kitchen waste liquid, straw waste liquid); the combination of modified volcanic ash and polyvinyl alcohol significantly improves the slow release performance of the carbon source and the attachment effect of denitrifying bacteria; the synergistic effect of carbon source diversity and appropriate amount of inorganic salts enhances microbial activity and system stability, and the denitrification efficiency is better than that of traditional single carbon source technology. The comprehensive use of kitchen waste and straw waste liquid also realizes resource utilization, which is environmentally friendly and economically feasible.

[0112] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A denitrification slow-release composite carbon source, characterized in that: The raw materials of the composite carbon source include, by mass percentage, 2-10% hydroxyacrylic acid, 2-10% sugar, 5-15% straw waste liquid, 5-15% kitchen waste liquid, 2-10% sugar, 3-15% porous volcanic ash, 5-15% polyvinyl alcohol, 0.2-1% inorganic salt, 1-2% polypeptide, 0.5-1% growth factor, 0.2-1.5% MFC agar, 0.1-0.5% cellulase, 0.1-0.5% protease and 0.1-0.5% denitrifying bacteria agent, and the balance is water; the sum of the percentages of the raw materials is 100%.

2. A method for preparing the denitrification slow-release composite carbon source according to claim 1, characterized in that: The following steps are involved: Step 1) pretreatment of kitchen waste liquid: stirring, degreasing, crushing and filtering the kitchen waste liquid to obtain kitchen waste filtrate; Step 2) thermal hydrolysis of the kitchen waste filtrate: hydrolyzing the obtained kitchen waste filtrate at 170° C.-205° C. for 30-50 min to obtain a hydrolyzed kitchen waste filtrate; Step 3) Preparation of kitchen waste carbon source: Cool the obtained hydrolyzed kitchen waste filtrate to room temperature, pour it into an anaerobic reaction tank, control the pH to 6, and react at a temperature of 35° C.-45° C. for 120 hours to obtain a kitchen waste carbon source; Step 4) Preparation of straw carbon source: pre-treating the straw waste liquid with an acidic solvent, centrifuging, and filtering to obtain a straw solution; After adding protease and cellulase into the straw solution, the straw carbon source is obtained; Step 5) Preparation of a composite carbon source: Mix the kitchen waste carbon source obtained in step 3) and the straw carbon source obtained in step 4), add a sodium bicarbonate solution and stir at a temperature of 25-30° C. for 3-5 min, and control the pH to 7-8.5 to obtain a composite carbon source solution; Step 6) Preparation of modified volcanic ash: weigh a certain amount of volcanic ash, modify the volcanic ash with ferric chloride solution and sodium hydroxide solution, and dry it for later use; Step 7) polyvinyl alcohol, modified volcanic ash, composite carbon source solution, water, and denitrifying agent are sequentially added into a reactor and stirred for 10-15 minutes to obtain a denitrifying slow-release composite carbon source.

3. The method for preparing a denitrification slow-release composite carbon source according to claim 2, characterized in that: In step 2), the kitchen waste filtrate is subjected to pyrolysis reaction, hydration reaction and free radical reaction to degrade organic matter.

4. The method for preparing a denitrification slow-release composite carbon source according to claim 2, characterized in that: In step 3), the preparation of the kitchen waste carbon source: the obtained hydrolyzed kitchen waste filtrate is cooled to room temperature, the protease, sugar, hydroxyacrylic acid, inorganic salt and agar are added, and then poured into an anaerobic reaction tank, the pH is controlled to be 6, and the temperature is 35° C. and 45° C., and the reaction is carried out for 120 hours to obtain a reaction solution.

5. The method for preparing a denitrification slow-release composite carbon source according to claim 2, characterized in that: In step 6), the modified pozzolan is prepared by any of the following methods: The first method is to incinerate the volcanic ash in a 400°C roasting furnace for 2 hours for modification, let it stand and cool to room temperature, place the volcanic ash in a reaction container, and place the ferric chloride solution at a temperature of 50°C-80°C and under continuous stirring for 30-60 minutes for 12 hours to allow the ferric hydroxide precipitation to gradually form and adhere to the surface of the volcanic ash to obtain modified volcanic ash 1; the modified volcanic ash 1 has a specific surface area of ​​15.5㎡ / g, a porosity of 75%, and a bulk density of 850kg / m 3 ; The second method is to incinerate the volcanic ash in a calcining furnace at 800℃-1000℃ for 2h for modification, let it stand and cool to room temperature, place the volcanic ash in a reaction container, add ferric chloride solution at a temperature of 80℃-110℃, stir continuously for 120-150min, let it stand for 24h, so that solid-liquid diffusion occurs between the ferric chloride solution and the volcanic ash, and obtain modified volcanic ash II; the modified volcanic ash II has a specific surface area of ​​20㎡ / g, a porosity of 80%, and a bulk density of 750kg / m 3 .

6. Use of the denitrification slow-release composite carbon source according to any one of claim 1 in water treatment, characterized in that: The denitrification rate is positively correlated with the COD value.

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