A slow-release carbon source and its application in wastewater denitrification

Abstract

The invention provides a kind of slow-release carbon source and its application in wastewater denitrification.Preparation method comprises the following steps:The preparation of micron-sized konjac glucomannan microspheres;The preparation of nano-sized konjac glucomannan microspheres;Take micron-sized konjac glucomannan microspheres and pour into mould to 1 / 3 place, continue to add nano-sized konjac glucomannan microspheres to 1 / 2 2 / 3 place, finally add micron-sized konjac glucomannan microspheres to mould and fill up;Prepare mixed resin liquid;Mixed resin liquid is cast into mould, fills up and solidifies at room temperature;Demolding after solidification, obtains slow-release carbon source.The present invention is by orderly piling up konjac glucomannan microspheres in mould, forms the porous channel of orderly interpenetration, sucrose is more long-lasting in microorganism early stage utilization effective time, to the glucose dissolution in later stage nanopore, microporous channel diameter is large, makes it easier to dissolve, and glucose is monosaccharide, is more easily utilized, has the effect of rapid supply of nutrients, can effectively supplement the intake of carbon source in later stage, improves the utilization rate of carbon source.

Description

Technical Field

[0001] The present 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] Currently, biological methods are widely used in environmental pollution control, such as wastewater nitrogen and phosphorus removal and biogas desulfurization and denitrification. Due to the lack of electron donors (carbon sources), biological treatment often requires the addition of readily degradable supplemental carbon sources. However, these treatments often suffer from issues such as poor timeliness, high costs, complex operation and management, and difficulty achieving standard emissions. Liquid single-carbon organic compounds are often used as supplemental carbon sources. As early as 1991, researchers investigated the effects of methanol, acetic acid, glucose, and brewer's yeast waste on nitrification and denitrification. A comparative study also examined the effect of methanol as an external carbon source on denitrification, investigating the effects of methanol, ethanol, and acetic acid on denitrification. The results showed that acetic acid and ethanol had significantly higher denitrification rates than methanol. However, acetic acid and ethanol have higher operating costs, at seven and two times that of methanol, respectively. Liquid organic carbon sources offer advantages such as ease of removal and rapid reaction rates, but they require frequent replenishment, making them unsuitable for long-term water pollution treatment. Furthermore, incompletely reacted liquid carbon sources may cause secondary water pollution. Therefore, in actual wastewater treatment, the use of liquid organic carbon sources as an additional carbon source for denitrification and phosphorus removal is generally not recommended. Solid carbon sources can serve as both a biofilm support and an electron donor for biological denitrification and phosphorus removal. The entire treatment system is easily controllable, avoiding the risk of uncontrolled carbon source addition in liquid carbon source processes, which can affect effluent quality and promote stable water treatment processes. The use of natural cellulosic materials as solid carbon sources began in the 1990s, with the first study investigating the use of straw-based cellulose as an additional carbon source for groundwater nitrate treatment, achieving a nitrate removal rate of 20%. Because cellulose has a loose structure and large surface area, which facilitates microbial attachment, its use as an additional carbon source can significantly improve nitrate-nitrogen removal efficiency. However, natural cellulosic materials cannot be used for long periods of time and require regular replenishment to maintain high denitrification rates. Furthermore, compared to liquid carbon sources, natural solid carbon sources have lower denitrification efficiency. 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-mentioned technical problems, the purpose of the invention is to provide a slow-release carbon source and its application in wastewater denitrification, by orderly piling konjac glucomannan microspheres in a mould, then bonding load with unsaturated polyester resin to form a slow-release carbon source, after being placed in wastewater, the konjac glucomannan microspheres gradually dissolve to form an orderly interconnected porous channel, first of all, the sucrose in the micropores is dissolved, sucrose is a disaccharide, and the effective time in the early stage of microorganism utilization is longer, and the glucose in the nanopores in the later stage is dissolved, and the microporous channel diameter is large, so it is easier to dissolve, and glucose is a monosaccharide, which is easier to be utilized, with the effect of rapid supply of nutrients, and the intake of the carbon source can be effectively supplemented in the later stage, and the utilization rate of the carbon source is improved.

[0004] Technical solution: A slow-release carbon source, which uses unsaturated polyester resin as a carrier and has built-in konjac gum microspheres coated with an organic carbon source.

[0005] Furthermore, the konjac gum microspheres are micron-sized and nano-sized, the micron-sized particle size is 50-100 μm, and the nano-sized particle size is 50-100 nm.

[0006] Furthermore, the organic carbon source includes sucrose and glucose.

[0007] The method for preparing the above-mentioned slow-release carbon source comprises the following steps:

[0008] (1) Preparation of micron-sized konjac glucomannan microspheres: 20-30 parts of konjac glucomannan, 1-2 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; 5-8 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 1-2 minutes, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0009] (2) Preparation of nano-sized konjac glucomannan microspheres: 15-20 parts of konjac glucomannan, 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 glucomannan 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 glucomannan 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 glucomannan microspheres;

[0010] (3) get micron-sized konjac glucomannan microballoons and pour into mould to 1 / 3 place, continue to add nano-sized konjac glucomannan microballoons to 1 / 2-2 / 3 place, finally add micron-sized konjac glucomannan microballoons to mould and fill up;

[0011] (4) Mix unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline, stir well, and place in a vacuum desiccator to remove bubbles to obtain a mixed resin solution;

[0012] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0013] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0014] Furthermore, the homogenization pressure in step (1) is 40-50 MPa.

[0015] Furthermore, the homogenization pressure in step (2) is 25-35 MPa.

[0016] 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 0.5-2 wt.% of the mixed resin solution.

[0017] Application of the above slow-release carbon source in wastewater denitrification.

[0018] Beneficial effects:

[0019] 1. The present invention orderly deposits konjac glucomannan microspheres in a mould, then carries out bonding load with unsaturated polyester resin, forms a slow-release carbon source, after being placed in waste water, konjac glucomannan microspheres dissolve gradually, form the porous channel of orderly intercommunication, first the sucrose in the micropore is dissolved, sucrose is a disaccharide, and the effective time in the early stage utilization of microorganism is longer, the glucose in the later stage nanopore is dissolved, the microporous channel diameter is large, makes it easier to dissolve, and glucose is a monosaccharide, more easily utilized, there is the effect of fast supply of nutrients, can effectively supplement the intake of carbon source in the later stage, improve the utilization ratio of carbon source.

[0020] 2. The present invention uses konjac gum microspheres to coat the biological carbon source, so that the carbon source can achieve a slow-release effect, can be stably and effectively used by microorganisms, and improve the utilization rate of the carbon source.

[0021] 3. Konjac gum in the present invention, as a high molecular weight polysaccharide, can also be used as a carbon source and has a sustained release effect, and can provide a carbon source over a longer period.

[0022] 4. Nano-zero-valent iron is added to the resin of the present invention. Nano-zero-valent iron has good magnetic responsiveness. After treatment, it can be quickly magnetically separated by a magnetic field, making it easy to recycle and reuse.

[0023] 5, the present invention is compounded with konjac glucomannan and gelatin in the preparation of micron-sized konjac glucomannan microspheres, after adding gelatin, konjac glucomannan microsphere structure is more stable, and the rate of dissolution in water slows down, but the addition of gelatin should not be too much, and solubility reduction also can affect the discharging of carbon source, and the proportioning in this application is the optimum proportion range after multiple tests. Nano-sized konjac glucomannan microspheres are in the same vein. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a graph showing the denitrification performance of slow-release carbon sources in some embodiments;

[0025] Figure 2 The figure shows the COD change of the effluent from the slow-release carbon source of some examples. DETAILED DESCRIPTION

[0026] The present invention provides a slow-release carbon source and its application in wastewater denitrification. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention will be further described in detail with reference to the following examples. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0027] Example 1

[0028] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0029] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0030] (2) Preparation of nano-sized 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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-sized konjac glucomannan microspheres;

[0031] (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, 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;

[0032] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0033] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0034] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0035] Example 2

[0036] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0037] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0038] (2) Preparation of nano-sized 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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-sized konjac glucomannan microspheres;

[0039] (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, 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;

[0040] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0041] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0042] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0043] Example 3

[0044] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0045] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0046] (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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres;

[0047] (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, 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;

[0048] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0049] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0050] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0051] Example 4

[0052] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0053] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0054] (3) Preparation of nano-sized 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 and homogenized for 2 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-sized konjac glucomannan microspheres;

[0055] (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, 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;

[0056] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0057] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0058] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0059] Example 5

[0060] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0061] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0062] (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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres;

[0063] (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 2 / 3, 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;

[0064] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0065] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0066] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0067] Example 6

[0068] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0069] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0070] (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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres;

[0071] (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 2 / 3, 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;

[0072] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator to remove bubbles to obtain a mixed resin solution; 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 solution;

[0073] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0074] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0075] Comparative Example 1

[0076] The difference between this embodiment and embodiment 3 is that gelatin is not added to the preparation of micron-sized konjac gum microspheres, specifically:

[0077] (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, thereby obtaining a konjac glucomannan solution; 6 parts of sucrose were added to 20 parts of water and stirred to dissolve, thereby obtaining a sucrose solution; the konjac glucomannan solution and the sucrose solution were mixed and stirred, added to a homogenizer and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0078] (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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres;

[0079] (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, 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;

[0080] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0081] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0082] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0083] Comparative Example 2

[0084] The difference between this embodiment and Example 3 is that the preparation of nano-scale konjac gum microspheres does not add locust bean gum, specifically:

[0085] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0086] (2) Preparation of nano-sized konjac glucomannan microspheres: 19.5 parts of konjac glucomannan and 80 parts of water were mixed, heated to 85° C. and stirred to dissolve, thereby obtaining a konjac glucomannan solution; 4 parts of glucose were added to 15 parts of water and stirred to dissolve, thereby obtaining a glucose solution; the konjac glucomannan solution and the glucose solution were mixed and stirred, added to a homogenizer and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-sized konjac glucomannan microspheres;

[0087] (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, 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;

[0088] (4) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0089] (5) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (3), and solidified at room temperature;

[0090] (6) After curing, demoulding is performed to obtain a slow-release carbon source.

[0091] The encapsulation efficiency of sucrose and glucose in the micron-sized konjac gum microspheres and the nano-sized konjac gum microspheres was measured respectively, wherein the encapsulation efficiency = the mass of sugar encapsulated in the microspheres / the total amount of sugar × 100%.

[0092] Table 1

[0093] 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

[0094] Note: “-” means not tested

[0095] Comparative Example 3

[0096] The difference between the present embodiment and Example 3 is that nano-level konjac gum microspheres are not adopted, specifically:

[0097] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0098] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0099] (2) Take micron-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;

[0100] (3) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0101] (4) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (2), and solidified at room temperature;

[0102] (5) After curing, demoulding is performed to obtain a slow-release carbon source.

[0103] Comparative Example 4

[0104] The difference between the present embodiment and Example 3 is that micron-level konjac gum microspheres are not adopted, specifically:

[0105] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0106] (1) 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 and homogenized for 1.5 min at a homogenization pressure of 30 MPa, and spray-dried to obtain nano-scale konjac glucomannan microspheres;

[0107] (2) Take nano-scale 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;

[0108] (3) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0109] (4) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (2), and solidified at room temperature;

[0110] (5) After curing, demoulding is performed to obtain a slow-release carbon source.

[0111] Comparative Example 5

[0112] The difference between the present embodiment and Example 5 is that, instead of using nano-sized konjac glucomannan microspheres, sucrose and glucose are coated together in micron-sized konjac glucomannan microspheres, specifically:

[0113] A method for preparing a slow-release carbon source, characterized by comprising the following steps:

[0114] (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 and homogenized for 1.5 min at a homogenization pressure of 45 MPa, and spray-dried to obtain micron-sized konjac glucomannan microspheres;

[0115] (2) Take micron-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;

[0116] (3) Unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline were mixed and stirred uniformly, and placed in a vacuum desiccator 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;

[0117] (4) the mixed resin liquid is cast into the mold filled with konjac glucomannan microspheres in step (2), and solidified at room temperature;

[0118] (5) After curing, demoulding is performed to obtain a slow-release carbon source.

[0119] Application of the above slow-release carbon source in wastewater denitrification.

[0120] Simulated wastewater was prepared using tap water and potassium nitrate as a nitrogen source, with a controlled nitrate nitrogen concentration of 30 mg / L. A certain amount of simulated wastewater, a slow-release carbon source of the present invention (comparative example 6 group added sucrose and glucose calculated to be equivalent to those in Example 3), and acclimated sludge were added to a container at a C / N ratio of 16. The container was sealed to maintain an anoxic environment and incubated in a constant temperature shaker at 28°C and 100 rpm. Samples were taken regularly and filtered through a 0.45% μm filter membrane before measuring COD, nitrate nitrogen concentration, and carbon source utilization. Nitrate nitrogen was determined by UV spectrophotometry, and COD was determined by rapid digestion spectrophotometry.

[0121] Table 2

[0122]

[0123]

[0124] 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, 1.0 wt.% of nano zero-valent iron can be selected.

[0125] Depend on Figure 1 It can be seen that when sucrose and glucose are directly added (Comparative Example 6), the denitrification effect is obvious in the initial stage (1-2 additions), and the nitrate nitrogen removal rate 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, providing sufficient carbon source for denitrification. However, due to the sufficient carbon source, the microorganisms reproduce rapidly, resulting in reduced carbon source utilization efficiency, poor stability in the later stage, decreased nitrate nitrogen removal rate, and insufficient carbon source utilization. The nitrate nitrogen removal rate of 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, characterized in that The slow-release carbon source uses unsaturated polyester resin as a carrier, and has built-in konjac gum microspheres coated with an organic carbon source; The preparation method 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 were mixed, heated to 70°C and stirred to dissolve, to obtain a konjac gum mixed solution; 5-8 parts of sucrose were 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 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, thereby obtaining a konjac gum mixed solution; 3-5 parts of glucose were added to 15 parts of water and stirred to dissolve, thereby obtaining 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) Pour micron-sized konjac gum microspheres into the mold to 1 / 3, continue adding nano-sized konjac gum microspheres to 1 / 2-2 / 3, and finally add micron-sized konjac gum microspheres until the mold is filled; (4) Mix unsaturated polyester resin, nano-zero-valent iron, benzoyl peroxide, and N,N-dimethylaniline, stir them evenly, and place them in a vacuum desiccator to remove bubbles to obtain a mixed resin liquid; (5) casting the mixed resin solution into the mold filled with konjac gum microspheres in step (3), and curing it at room temperature; (6) After curing, demoulding is performed to obtain a slow-release carbon source.

2. A slow-release carbon source according to claim 1, 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, characterized in that: The homogenization pressure in step (1) is 40-50 MPa.

4. A slow-release carbon source according to claim 1, characterized in that The homogenization pressure in step (2) is 25-35 MPa.

5. A slow-release carbon source according to claim 1, characterized in that: In the step (4), the mass ratio of the unsaturated polyester resin, benzoyl peroxide and N,N-dimethylaniline is 100:2:0.

2.

6. A slow-release carbon source according to claim 1, characterized in that: The content of nano zero-valent iron in step (4) is 0.5-2 wt.% of the mixed resin liquid.

7. Use of a slow-release carbon source according to any one of claims 1 to 6 in wastewater denitrification.

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