Slow-release carbon source and application thereof in wastewater denitrification

Abstract

The invention provides a slow-release carbon source and application thereof in wastewater denitrification. The preparation method comprises the following steps: preparing micron-sized konjac glucomannan microspheres; preparing the nano-scale konjac glucomannan microspheres; the micron-sized konjac glucomannan microspheres are taken and poured into the mold to the 1 / 3 position, the nano-sized konjac glucomannan microspheres are continuously added to the 1 / 2-2 / 3 position, and finally the micron-sized konjac glucomannan microspheres are added till the mold is filled; preparing a mixed resin liquid; casting the mixed resin liquid into a mold, filling and curing at room temperature; and demolding after curing to obtain the slow-release carbon source. According to the invention, konjac glucomannan microspheres are orderly stacked in a mold to form an ordered through porous channel, the effective time of sucrose in the early stage of microorganism utilization is longer, glucose in nanopores is dissolved out in the later stage, the diameter of the microporous channel is large, so that the glucose is easier to dissolve out, the glucose is monosaccharide and is easier to use, and the effect of rapidly supplying nutrients is achieved; in the later period, intake of carbon sources can be effectively supplemented, and utilization rate of the carbon sources is improved.

Description

Technical Field

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

[0002] At present, biological methods are widely used in environmental pollution prevention and control, such as sewage denitrification and phosphorus removal and biological flue gas desulfurization and denitrification. When using biological methods for treatment, due to the lack of electron donors (carbon sources), it is usually necessary to add easily degradable supplementary carbon sources. However, such treatments generally have problems such as "poor timeliness, high cost, complex operation and management, and difficulty in meeting emission standards". Usually, the external carbon sources added by researchers are mostly liquid single-carbon organic compounds. As early as 1991, researchers studied the effects of four external carbon sources, methanol, acetic acid, glucose and brewer's yeast waste, on nitrification and denitrification. Some people have compared the role of methanol as an external carbon source in promoting the denitrification process, and studied the effects of methanol, ethanol and acetic acid on denitrification. The results show that the denitrification rates of acetic acid and ethanol are significantly higher than those of methanol. However, the operating costs of acetic acid and ethanol are high, which are 7 times and 2 times that of methanol, respectively. Liquid organic carbon sources have the advantages of easy elimination and fast reaction speed. The disadvantage is that they need to be frequently supplemented, which is not conducive to long-term pollution treatment of water bodies. In addition, incompletely reacted liquid carbon sources may cause secondary pollution of water bodies. Therefore, in actual sewage treatment, it is generally not recommended to use liquid organic carbon sources as additional supplementary carbon sources for denitrification and phosphorus removal. Solid carbon sources can be used as carriers of biofilms and as electron donors for biological denitrification and phosphorus removal. The entire treatment system is easy to control, avoiding the risk of difficult-to-control carbon source addition in liquid carbon source processes, which in turn affects the quality of effluent water and is conducive to the stable progress of the water treatment process. Natural cellulose materials have been used as solid carbon sources since the 1990s. For the first time, research on the use of straw cellulose as an additional carbon source to treat groundwater nitrates was carried out. The nitrate removal rate in the study reached 20%. Since cellulose materials have a loose structure and a large specific surface area, which is conducive to the attachment of microorganisms, using them as an additional carbon source can significantly improve the removal efficiency of nitrate nitrogen. However, natural cellulose materials cannot be used for a long time and need to be regularly supplemented to maintain a high denitrification rate; and compared with liquid carbon sources, the denitrification efficiency of natural solid carbon sources is low. Therefore, seeking materials that are beneficial to the removal efficiency of nitrate nitrogen while maintaining a stable carbon source supply is an urgent problem to be solved. Summary of the invention

[0003] Technical problems to be solved: In view of the above technical problems, the purpose of the present invention is to provide a slow-release carbon source and its application in wastewater denitrification, by orderly piling konjac glucomannan microspheres in a mold, and then bonding and loading with unsaturated polyester resin to form a slow-release carbon source, when placed in wastewater, the konjac glucomannan microspheres gradually dissolve to form an orderly interconnected porous channel, first of all, sucrose in the micropores is dissolved, sucrose is a disaccharide, and the effective time in the early stage of microbial utilization is longer, and glucose in the nanopores is dissolved in the later stage, and the microporous channel has a large diameter, which makes it easier to dissolve, and glucose is a monosaccharide, which is easier to be utilized, has the effect of quickly supplying nutrients, can effectively supplement the intake of carbon source in the later stage, and improve the utilization rate of carbon source.

[0004] Technical solution: A slow-release carbon source, which uses unsaturated polyester resin as a carrier and has built-in konjac gum microspheres that encapsulate an organic carbon source. Furthermore, the konjac gum microspheres are micrometer-sized and nanometer-sized, the micrometer-sized particle size is 50-100 μm, and the nanometer-sized particle size is 50-100 nm. Furthermore, the organic carbon source includes sucrose and glucose. The method for preparing the above-mentioned slow-release carbon source comprises the following steps: (1) Preparation of micron-sized konjac gum microspheres: 20-30 parts of konjac gum, 1-2 parts of gelatin and 100 parts of water are mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac gum mixed solution; 5-8 parts of sucrose are added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac gum mixed solution and the sucrose solution are mixed and stirred, added to a homogenizer for homogenization for 1-2 minutes, and spray-dried to obtain micron-sized konjac gum microspheres; (2) Preparation of nano-sized konjac gum microspheres: 15-20 parts of konjac gum, 1-2 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac gum mixed solution; 3-5 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac gum mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1-2 minutes, and spray-dried to obtain nano-sized konjac gum microspheres; (3) take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, then continue to add nano-sized konjac glucomannan microspheres to 1 / 2-2 / 3, and finally add micron-sized konjac glucomannan microspheres to fill the mold; (4) taking unsaturated polyester resin, nano zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline, mixing and stirring uniformly, placing in a vacuum dryer to remove bubbles, and obtaining a mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Furthermore, the homogenization pressure in step (1) is 40-50 MPa. Furthermore, the homogenization pressure in step (2) is 25-35 MPa. Furthermore, in step (4), the mass ratio of polyester resin, benzoyl peroxide and N,N-dimethylaniline is 100:2:0.2. Furthermore, in step (4), the content of nano zero-valent iron is 0.5-2wt.% of the mixed resin solution. Application of the above slow-release carbon source in wastewater denitrification. Beneficial effects: 1. The present invention deposits konjac glucomannan microspheres in a mold in an orderly manner, and then carries out bonding load with unsaturated polyester resin to form a slow-release carbon source. After being placed in waste water, the konjac glucomannan microspheres gradually dissolve to form an orderly interlinked porous channel. First, the sucrose in the micropores dissolves, and sucrose is a disaccharide. The effective time in the early stage of microorganism utilization is longer. The glucose in the nanopores in the later stage dissolves, and the microporous channel diameter is large, so that it is easier to dissolve, and glucose is a monosaccharide, which is easier to be utilized, and has the effect of fast supply of nutrients. The intake of the carbon source can be effectively supplemented in the later stage, and the utilization rate of the carbon source is improved. 2. The present invention uses konjac gum microspheres to coat the biological carbon source, so that the carbon source can achieve a sustained release effect, can be stably and effectively used by microorganisms, and improve the utilization rate of the carbon source. 3. Konjac gum in the present invention, as a high molecular weight polysaccharide, can also be used as a carbon source, and also has a sustained release effect, and can provide a carbon source over a long period. 4. Nano-zero-valent iron is added to the resin of the present invention. The nano-zero-valent iron has good magnetic responsiveness. After being processed, it can be quickly magnetically separated by a magnetic field, which is convenient for recycling and reuse. 5. The present invention is compounded with konjac glucomannan and gelatin in the preparation of micron-sized konjac glucomannan microspheres. After adding gelatin, the konjac glucomannan microspheres have a more stable structure, and the dissolution rate in water slows down. However, the addition amount of gelatin should not be too much, and the solubility reduction also affects the release of the carbon source. The proportioning in this application is the best proportioning range after multiple tests. The nano-sized konjac glucomannan microspheres are similar. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a graph showing the denitrification performance of the slow-release carbon source of some embodiments; Figure 2 The following is a graph showing the change in effluent COD of the slow-release carbon source in some embodiments. DETAILED DESCRIPTION The present invention proposes a slow-release carbon source and its application in wastewater denitrification. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention will be further described in detail with examples below. 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. Example 1 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 20 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 5 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 2 parts of locust bean gum and 80 parts of water were mixed, heated to 85°C and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Example 2 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 30 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 8 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 2 parts of locust bean gum and 80 parts of water were mixed, heated to 85°C and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Example 3 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Example 4 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (2) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (3) Preparation of nano-scale konjac glucomannan microspheres: 20 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85°C and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 5 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 2 min, the homogenization pressure was 30 MPa, and spray dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Example 5 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) taking micron-sized konjac glucomannan microspheres and pouring them into a mold to 1 / 3, continuing to add nano-sized konjac glucomannan microspheres to 2 / 3, and finally adding micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Example 6 A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) taking micron-sized konjac glucomannan microspheres and pouring them into a mold to 1 / 3, continuing to add nano-sized konjac glucomannan microspheres to 2 / 3, and finally adding micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 2 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Comparative Example 1 The difference between this embodiment and embodiment 3 is that gelatin is not added in the preparation of micron-sized konjac glucomannan microspheres, specifically: (1) Preparation of micron-sized konjac glucomannan microspheres: 26.5 parts of konjac glucomannan and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 18 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. Comparative Example 2 The difference between this embodiment and embodiment 3 is that locust bean gum is not added in the preparation of nano-scale konjac gum microspheres, specifically: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) Preparation of nano-scale konjac glucomannan microspheres: 19.5 parts of konjac glucomannan and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres; (3) Take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, continue to add nano-sized konjac glucomannan microspheres to 1 / 2, and finally add micron-sized konjac glucomannan microspheres to fill the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (4) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source. The encapsulation rates of sucrose and glucose in the micron-sized konjac gum microspheres and nano-sized konjac gum microspheres were measured respectively, wherein the encapsulation rate = the mass of sugar encapsulated in the microspheres / the total amount of sugar × 100%. Table 1 Encapsulation efficiency of micron-sized konjac gum microspheres (%) Nano-scale konjac gum microsphere encapsulation efficiency (%) Example 1 87.6 89.1 Example 2 87.3 - Example 3 - 88.9 Example 4 - 88.6 Comparative Example 1 84.9 - Comparative Example 2 - 85.7 Note: “-” means not tested Comparative Example 3 The difference between the present embodiment and embodiment 3 is that nano-scale konjac glucomannan microspheres are not used, specifically: A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) pouring micron-sized konjac glucomannan microspheres into a mold and filling the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (3) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (4) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (2), and solidifying at room temperature; (5) After curing, demolding is performed to obtain a slow-release carbon source. Comparative Example 4 The difference between the present embodiment and embodiment 3 is that micron-sized konjac gum microspheres are not used, specifically: A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of nano-sized konjac glucomannan microspheres: 18 parts of konjac glucomannan, 1.5 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; the konjac glucomannan mixed solution and the glucose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 30 MPa, and spray-dried to obtain nano-sized konjac glucomannan microspheres; (2) Take nano-sized konjac glucomannan microspheres and pour them into a mold to fill it up; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (3) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (4) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (2), and solidifying at room temperature; (5) After curing, demolding is performed to obtain a slow-release carbon source. Comparative Example 5 The difference between this embodiment and embodiment 5 is that, instead of using nano-sized konjac gum microspheres, sucrose and glucose are coated together in micron-sized konjac gum microspheres, specifically: A method for preparing a slow-release carbon source, characterized in that it comprises the following steps: (1) Preparation of micron-sized konjac glucomannan microspheres: 25 parts of konjac glucomannan, 1.5 parts of gelatin and 100 parts of water were mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac glucomannan mixed solution; 6 parts of sucrose and 4 parts of glucose were added to 35 parts of water and stirred to dissolve, to obtain a sucrose solution; the konjac glucomannan mixed solution and the sucrose solution were mixed and stirred, added to a homogenizer for homogenization for 1.5 min, the homogenization pressure was 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres; (2) pouring micron-sized konjac glucomannan microspheres into a mold and filling the mold; the mold is a cylinder with a diameter of 1.5 cm and a height of 2 cm; (3) unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum dryer to remove bubbles to obtain a mixed resin liquid; the mass ratio of polyester resin, benzoyl peroxide, and N,N-dimethylaniline was 100:2:0.2; the content of nano-zero-valent iron was 1.0 wt.% of the mixed resin liquid; (4) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (2), and solidifying at room temperature; (5) After curing, demolding is performed to obtain a slow-release carbon source. Application of the above slow-release carbon source in wastewater denitrification. Using tap water and potassium nitrate as nitrogen sources, simulated wastewater was prepared, and the nitrate nitrogen mass concentration of the simulated wastewater was controlled to be 30 mg / L. A certain amount of simulated wastewater, the slow-release carbon source of the present application (the comparative example 6 group was added with sucrose and glucose calculated to be equal to that of Example 3), and domesticated sludge were added to a container, C / N was 16, sealed, and anoxic environment was maintained, and placed in a constant temperature oscillating box for cultivation at 28°C and 100r / min, and samples were taken at regular intervals. After filtering through a 0.45% m filter membrane, COD, nitrate nitrogen concentration, and carbon source utilization were determined. Nitrate nitrogen was determined by ultraviolet spectrophotometry; COD was determined by rapid digestion spectrophotometry. Table 2 At the same time, the recovery rate of the slow-release carbon source carrier of each example was measured, and it was found that the recovery rate of Example 3 was 0.9% lower than that of Example 6. Considering economic practicality, 1.0wt.% of nano zero-valent iron can be selected. Depend on Figure 1It can be seen that when sucrose and glucose are directly added (Comparative Example 6), the initial (1-2 addition) denitrification effect is obvious, and the removal rate of nitrate nitrogen can reach 99.16% on the second day of the reaction. This is because the directly added sucrose and glucose are easily utilized by microorganisms to provide sufficient carbon source for denitrification. However, due to the sufficient carbon source, microorganisms multiply rapidly, resulting in reduced carbon source utilization efficiency, poor stability in the later period, decreased nitrate nitrogen removal rate, and insufficient carbon source utilization. The removal rate of nitrate nitrogen in Example 3 steadily increased and stabilized at more than 99%, mainly due to its slow-release effect, which can provide a long-term and stable carbon source.

Claims

1. A slow-release carbon source, It is characterized in that The slow-release carbon source uses unsaturated polyester resin as a carrier and contains konjac gum microspheres coated with an organic carbon source.

2. A slow-release carbon source according to claim 1, It is characterized in that The konjac gum microspheres are micron-sized and nano-sized, wherein the micron-sized particle size is 50-100 μm, and the nano-sized particle size is 50-100 nm.

3. A slow-release carbon source according to claim 1, It is characterized in that The organic carbon sources include sucrose and glucose.

4. A method for preparing a slow-release carbon source according to any one of claims 1 to 3, It is characterized in that The following steps are involved: (1) Preparation of micron-sized konjac gum microspheres: 20-30 parts of konjac gum, 1-2 parts of gelatin and 100 parts of water are mixed, heated to 70° C. and stirred to dissolve, to obtain a konjac gum mixed solution; 5-8 parts of sucrose are added to 20 parts of water and stirred to dissolve, to obtain a sucrose solution; The konjac gum mixed solution and the sucrose solution were mixed and stirred, added into a homogenizer for homogenization for 1-2 minutes, and spray-dried to obtain micron-sized konjac gum microspheres; (2) Preparation of nano-scale konjac gum microspheres: 15-20 parts of konjac gum, 1-2 parts of locust bean gum and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, to obtain a konjac gum mixed solution; 3-5 parts of glucose were added to 15 parts of water and stirred to dissolve, to obtain a glucose solution; The konjac gum mixed solution and the glucose solution were mixed and stirred, added into a homogenizer for homogenization for 1-2 minutes, and spray-dried to obtain nano-scale konjac gum microspheres; (3) take micron-sized konjac glucomannan microspheres and pour them into a mold to 1 / 3, then continue to add nano-sized konjac glucomannan microspheres to 1 / 2-2 / 3, and finally add micron-sized konjac glucomannan microspheres to fill the mold; (4) taking unsaturated polyester resin, nano zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline, mixing and stirring uniformly, placing in a vacuum dryer to remove bubbles, and obtaining a mixed resin liquid; (5) casting the mixed resin liquid into the mold filled with konjac glucomannan microspheres in step (3), and solidifying at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source.

5. The method for preparing a slow-release carbon source according to claim 4, It is characterized in that The homogenization pressure in step (1) is 40-50 MPa.

6. The method for preparing a slow-release carbon source according to claim 4, It is characterized in that The homogenization pressure in step (2) is 25-35 MPa.

7. The method for preparing a slow-release carbon source according to claim 4, It is characterized in that In the step (4), the mass ratio of the polyester resin, benzoyl peroxide and N,N-dimethylaniline is 100:2:0.

2.

8. The method for preparing a slow-release carbon source according to claim 4, It is characterized in that The content of nano zero-valent iron in step (4) is 0.5-2 wt.% of the mixed resin solution.

9. Use of a slow-release carbon source according to any one of claims 1 to 3 in wastewater denitrification.

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