A composite carbon source for sewage denitrification and its application

Abstract

The present invention discloses a composite carbon source for wastewater denitrification and its application in the field of sewage treatment technology. The composite carbon source comprises the following components by weight: 16-18 parts wheat straw, 22-26 parts soybean straw, 8-15 parts rice husk, 12-16 parts corn cobs, 3-4 parts sodium alginate, and 7-9 parts composite shell material. The present invention proposes a method of preparing a mixed carbon source using agricultural waste, achieving waste recycling and reducing product costs. The composite shell material is coated with montmorillonite and corn starch and loaded with zinc ferrite. This provides a good slow-release carbon source while providing chemical reduction sites to further enhance the denitrification effect of the composite carbon source.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a composite carbon source for sewage denitrification and application thereof. Background Art

[0002] With the rapid development of society and the gradual improvement of residents' living standards, the amount of sewage discharged is also increasing, and the problem of water pollution is becoming increasingly serious. In order to meet the sewage discharge standards and solve the problem of eutrophication of water bodies, sewage treatment plants mostly need to add external carbon sources when using biological denitrification technology for deep denitrification. At present, the external carbon sources in industrial applications are mainly methanol, sodium acetate, and glucose. Due to unbalanced addition, it is easy to cause problems such as increased sludge production in the water treatment system and secondary pollution. External carbon sources can be divided into two categories: liquid carbon sources and solid carbon sources. Liquid carbon sources are mainly water-soluble substances or liquid substances such as methanol, ethanol, acetate, and glucose. Solid carbon sources can be divided into three categories: natural high molecular substances, degradable polymers, and composite substances. Among them, the denitrification effect of natural high molecular substances is unstable, and the cost of degradable polymers is high, so they are difficult to use on a large scale. The cellulose and hemicellulose contained in plants will undergo further hydrolysis reactions when soaked in water for a long time, and produce various monosaccharides and polysaccharides, which are easily decomposed and utilized by microorganisms in the water.

[0003] The existing technologies currently have the following main problems: the cost of the external carbon source currently used is high, the denitrification performance is poor, and it is easy to cause secondary pollution. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a composite carbon source for wastewater denitrification and its application. In order to solve the problems of high cost of external carbon sources, poor denitrification performance, and easy secondary pollution, the present invention proposes a method of preparing a mixed carbon source by using agricultural waste, thereby realizing waste recycling and reducing product costs. At the same time, montmorillonite and corn starch are used as composite shell materials and loaded with zinc ferrite to coat the mixed carbon source. While obtaining a good slow-release carbon source, chemical reduction sites are provided to further enhance the denitrification effect of the composite carbon source.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: The present invention proposes a composite carbon source for sewage denitrification, which is composed of the following components in parts by weight: 16-18 parts of wheat straw, 22-26 parts of soybean straw, 8-15 parts of rice husks, 12-16 parts of corn cobs, 3-4 parts of sodium alginate and 7-9 parts of composite shell materials.

[0006] Preferably, the composite shell material comprises the following components in parts by weight: 10-12 parts of ferric chloride hexahydrate, 17-20 parts of zinc acetate, 96-112 parts of montmorillonite and 150-160 parts of corn starch.

[0007] Preferably, the method for preparing the composite shell material specifically comprises the following steps:

[0008] S1. Add ferric chloride hexahydrate to ethylene glycol, then add zinc acetate, and stir to dissolve to obtain a mixed solution;

[0009] S2, adding montmorillonite to water, adding 3-aminopropyltriethoxysilane, dispersing evenly, stirring in a water bath, filtering, washing, and drying to obtain modified montmorillonite;

[0010] S3, adding the modified montmorillonite obtained in S2 to deionized water, ultrasonically dispersing to obtain a dispersion, dropping the mixed solution into the dispersion, sealing and heating the autoclave, cooling, filtering, washing, and drying to obtain zinc ferrite / modified montmorillonite;

[0011] S4. Add the zinc ferrite / modified montmorillonite obtained in S3 to a 5-6 wt% corn starch solution, stir in a water bath, and obtain a composite shell material.

[0012] Preferably, in S1, the amount of ferric chloride hexahydrate added to ethylene glycol is 0.08-0.1 g / mL.

[0013] Preferably, in S2, the amount of 3-aminopropyltriethoxysilane added to water is 0.8-1 mg / mL.

[0014] Preferably, in S2, the water bath is stirred at a temperature of 70-80°C, a speed of 100-120 rpm, and a time of 3-5 hours.

[0015] Preferably, in S3, the modified montmorillonite is added to deionized water in an amount of 10-15 mg / mL.

[0016] Preferably, in S3, the autoclave is sealed and heated at a temperature of 176-183°C for 5-6 hours.

[0017] Preferably, in S4, the stirring in the water bath is performed at a temperature of 50-60° C., a speed of 160-180 rpm, and a time of 3-4 h.

[0018] The present invention provides a method for preparing a composite carbon source for wastewater denitrification, which specifically comprises the following steps:

[0019] (1) Wheat straw, soybean straw, rice husk and corn cob are washed and air-dried, and then crushed through a 50-mesh sieve to obtain a mixed powder, and the mixed powder is subjected to alkaline leaching treatment with a 1.5-2.5 wt% sodium hydroxide solution for 20-30 h to obtain a mixed carbon source;

[0020] (2) uniformly mixing the mixed carbon source obtained in step (1) with sodium alginate, adding the mixture to a granulator for granulation, and drying at 30-50° C. to obtain a composite inner core material;

[0021] (3) The composite inner core material obtained in step (2) is added to a granulation machine, and a composite coating material is added to wrap the composite inner core material until the coating thickness is 1-1.5 mm, thereby obtaining a composite carbon source for wastewater denitrification.

[0022] The present invention provides an application of a composite carbon source for wastewater denitrification, specifically as follows: the composite carbon source for wastewater denitrification provided by the present invention can be used for the treatment of urban sewage, and the dosage is determined by the total nitrogen index of the water body, the addition point and the test conditions. The dosage of the composite carbon source used for wastewater denitrification in urban sewage is usually 300-400 mg / L.

[0023] The beneficial effects achieved by the present invention are as follows: agricultural waste is used to prepare a mixed carbon source, thereby realizing waste recycling; wheat straw, soybean straw, rice husk, and corn cob are crushed and alkali-leached to destroy the surface structure of the plant, increase its specific surface area, enable the plant to decompose and release organic matter more effectively and regularly, improve the decomposition rate in water, and reduce product cost; montmorillonite and corn starch are used as composite shell materials and loaded with zinc ferrite, and zinc ferrite is synthesized on the montmorillonite by hydrothermal synthesis, thereby enhancing the denitrification effect of the composite carbon source in the early stage of input; at the same time, the magnetism of zinc ferrite makes it easy to recycle, reduces resource consumption, and avoids secondary pollution; 3-aminopropyltriethoxysilane is used to combine corn starch with montmorillonite, while retaining the advantages of large specific surface area and easy film formation, reducing the decomposition rate of corn starch and achieving a slow-release effect; the composite shell material is used to coat the mixed carbon source, while obtaining a good slow-release effect, providing chemical reduction sites, and further ensuring the continuous and stable denitrification effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The carbon release performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention are shown;

[0025] Figure 2 For the denitrification test of Examples 1-3 and Comparative Examples 1-3 of the present invention, NO3 - -N removal rate result graph;

[0026] Figure 3 For the denitrification test of Examples 1-3 and Comparative Examples 1-3 of the present invention, NO2 - -N removal rate results graph.

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0031] Example 1

[0032] A composite carbon source for wastewater denitrification is composed of the following components in parts by weight: 18 parts of wheat straw, 26 parts of soybean straw, 15 parts of rice husk, 16 parts of corn cobs, 4 parts of sodium alginate and 9 parts of composite shell material.

[0033] The composite shell material includes the following components in parts by weight: 12 parts of ferric chloride hexahydrate, 20 parts of zinc acetate, 112 parts of montmorillonite and 160 parts of corn starch.

[0034] The preparation method of the composite shell material specifically comprises the following steps:

[0035] S1. Add 0.1 g / mL of ferric chloride hexahydrate to ethylene glycol, then add zinc acetate, and stir to dissolve to obtain a mixed solution;

[0036] S2. Add montmorillonite to water, add 3-aminopropyltriethoxysilane at a dosage of 1 mg / mL, disperse evenly, stir in a water bath at 80°C at 120 rpm for 5 h, filter, wash, and dry to obtain modified montmorillonite;

[0037] S3, adding the modified montmorillonite obtained in S2 to deionized water at an addition amount of 15 mg / mL, ultrasonically dispersing to obtain a dispersion, dropping the mixed solution into the dispersion, heating in a sealed autoclave at 183°C for 6 h, cooling, filtering, washing, and drying to obtain zinc ferrite / modified montmorillonite;

[0038] S4. Add the zinc ferrite / modified montmorillonite obtained in S3 to a 6 wt % corn starch solution, stir at 180 rpm in a 60° C. water bath for 4 h to obtain a composite shell material.

[0039] The present invention provides a method for preparing a composite carbon source for wastewater denitrification, which specifically comprises the following steps:

[0040] (1) Wheat straw, soybean straw, rice husk and corn cob were washed and air-dried, and then crushed through a 50-mesh sieve to obtain a mixed powder. The mixed powder was alkali-leached with a 2.5 wt% sodium hydroxide solution for 30 h to obtain a mixed carbon source;

[0041] (2) uniformly mixing the mixed carbon source obtained in step (1) with sodium alginate, adding the mixture to a granulator for granulation, and drying at 50° C. to obtain a composite inner core material;

[0042] (3) The composite inner core material obtained in step (2) is added to a granulation machine, and a composite coating material is added to wrap the composite inner core material until the coating thickness reaches 1.5 mm, thereby obtaining a composite carbon source for wastewater denitrification.

[0043] The present invention provides an application of a composite carbon source for sewage denitrification in sewage treatment, specifically as follows: the composite carbon source for sewage denitrification provided by the present invention can be used for the treatment of urban sewage, and the dosage is determined by the total nitrogen index of the water body, the addition point and the test conditions. The dosage of the composite carbon source used for sewage denitrification in urban sewage is usually 300 mg / L.

[0044] Example 2

[0045] A composite carbon source for wastewater denitrification is composed of the following components in parts by weight: 16 parts of wheat straw, 22 parts of soybean straw, 8 parts of rice husk, 12 parts of corn cobs, 3 parts of sodium alginate and 7 parts of composite shell material.

[0046] The composite shell material includes the following components in parts by weight: 10 parts of ferric chloride hexahydrate, 17 parts of zinc acetate, 96 parts of montmorillonite and 150 parts of corn starch.

[0047] The preparation method of the composite shell material specifically comprises the following steps:

[0048] S1. Add 0.08 g / mL of ferric chloride hexahydrate to ethylene glycol, then add zinc acetate, and stir to dissolve to obtain a mixed solution;

[0049] S2. Add montmorillonite to water, add 3-aminopropyltriethoxysilane at a dosage of 0.8 mg / mL, disperse evenly, stir at 100 rpm in a 70°C water bath for 3 h, filter, wash, and dry to obtain modified montmorillonite;

[0050] S3, adding the modified montmorillonite obtained in S2 to deionized water at an addition amount of 10 mg / mL, ultrasonically dispersing to obtain a dispersion, dropping the mixed solution into the dispersion, heating in a sealed autoclave at 176° C. for 5 h, cooling, filtering, washing, and drying to obtain zinc ferrite / modified montmorillonite;

[0051] S4. Add the zinc ferrite / modified montmorillonite obtained in S3 to a 5 wt % corn starch solution, and stir at 160 rpm in a 50° C. water bath for 3 h to obtain a composite shell material.

[0052] The present invention provides a method for preparing a composite carbon source for wastewater denitrification, which specifically comprises the following steps:

[0053] (1) Wheat straw, soybean straw, rice husk and corn cob were washed and air-dried, and then crushed through a 50-mesh sieve to obtain a mixed powder, which was then leached with a 1.5 wt% sodium hydroxide solution for 20 h to obtain a mixed carbon source;

[0054] (2) uniformly mixing the mixed carbon source obtained in step (1) with sodium alginate, adding the mixture into a granulator for granulation, and drying at 30° C. to obtain a composite inner core material;

[0055] (3) The composite inner core material obtained in step (2) is added to a granulation machine, and a composite coating material is added to wrap the composite inner core material until the coating thickness is 1 mm, thereby obtaining a composite carbon source for wastewater denitrification.

[0056] The present invention provides an application of a composite carbon source for sewage denitrification in sewage treatment, specifically as follows: the composite carbon source for sewage denitrification provided by the present invention can be used for the treatment of urban sewage, and the dosage is determined by the total nitrogen index of the water body, the addition point and the test conditions. The dosage of the composite carbon source used for sewage denitrification in urban sewage is usually 300 mg / L.

[0057] Example 3

[0058] A composite carbon source for wastewater denitrification is composed of the following components in parts by weight: 17 parts of wheat straw, 24 parts of soybean straw, 10 parts of rice husk, 14 parts of corn cob, 3.5 parts of sodium alginate and 8 parts of composite shell material.

[0059] The composite shell material includes the following components in parts by weight: 11 parts of ferric chloride hexahydrate, 18 parts of zinc acetate, 105 parts of montmorillonite and 155 parts of corn starch.

[0060] The preparation method of the composite shell material specifically comprises the following steps:

[0061] S1. Add 0.09 g / mL of ferric chloride hexahydrate to ethylene glycol, then add zinc acetate, and stir to dissolve to obtain a mixed solution;

[0062] S2. Add montmorillonite to water, add 3-aminopropyltriethoxysilane at a dosage of 0.9 mg / mL, disperse evenly, stir in a 75°C water bath at 110 rpm for 4 h, filter, wash, and dry to obtain modified montmorillonite;

[0063] S3, adding the modified montmorillonite obtained in S2 to deionized water at an addition amount of 12.5 mg / mL, ultrasonically dispersing to obtain a dispersion, dropping the mixed solution into the dispersion, heating in a sealed autoclave at 180° C. for 5.5 h, cooling, filtering, washing, and drying to obtain zinc ferrite / modified montmorillonite;

[0064] S4. Add the zinc ferrite / modified montmorillonite obtained in S3 to a 5.5 wt% corn starch solution, stir at 170 rpm in a 55° C. water bath for 3.5 h to obtain a composite shell material.

[0065] The present invention provides a method for preparing a composite carbon source for wastewater denitrification, which specifically comprises the following steps:

[0066] (1) Wheat straw, soybean straw, rice husk and corn cob were washed and air-dried, and then crushed through a 50-mesh sieve to obtain a mixed powder, which was then leached with a 2 wt% sodium hydroxide solution for 25 h to obtain a mixed carbon source;

[0067] (2) uniformly mixing the mixed carbon source obtained in step (1) with sodium alginate, adding the mixture into a granulator for granulation, and drying at 40° C. to obtain a composite inner core material;

[0068] (3) The composite inner core material obtained in step (2) is added to a granulation machine, and a composite coating material is added to wrap the composite inner core material until the coating thickness reaches 1.2 mm, thereby obtaining a composite carbon source for wastewater denitrification.

[0069] The present invention provides an application of a composite carbon source for sewage denitrification in sewage treatment, specifically as follows: the composite carbon source for sewage denitrification provided by the present invention can be used for the treatment of urban sewage, and the dosage is determined by the total nitrogen index of the water body, the addition point and the test conditions. The dosage of the composite carbon source used for sewage denitrification in urban sewage is usually 300 mg / L.

[0070] Comparative Example 1

[0071] This comparative example provides a composite carbon source, which differs from Example 1 only in that all components do not contain the composite shell material, and the remaining components and component contents are the same as those in Example 1.

[0072] Comparative Example 2

[0073] This comparative example provides a composite carbon source, which differs from Example 1 only in that 3-aminopropyltriethoxysilane is not included in all components, and the remaining components and component contents are the same as those in Example 1.

[0074] Comparative Example 3

[0075] This comparative example provides a composite carbon source, which differs from Example 1 only in that ferric chloride hexahydrate and zinc acetate are not included in all components, and the remaining components and component contents are the same as those in Example 1.

[0076] Experimental example

[0077] 1. Carbon release performance test

[0078] 20 mL of anaerobic sludge with a concentration of 8 g / L was added to the reactor, and then 300 mg of the composite carbon source material prepared in Example 1-3 and Comparative Example 1-2 was added to the reactor, distilled water was added to 1 L, the pH was adjusted to 7, and the solution was sealed and slowly stirred for 24 h to obtain the clear liquid. The chemical oxygen demand (COD) concentration was determined after filtration through a 0.45 μm filter membrane, and the measured data at 5 d, 10 d, 12 d, 20 d, 25 d, 30 d, and 35 d were recorded. After each liquid was taken, distilled water was added to 1 L and the experiment was continued.

[0079] Figure 1 This is a graph showing the carbon release performance test results of Examples 1-3 and Comparative Example 1-2 of the present invention; as shown in the figure, the COD concentration of Example 1-3 tends to be stable at 5 days, reaches a maximum value at 25 days, and is stable at about 43 mg / L for a long time within 30 days, continuously and stably releasing organic matter. The carbon release performance of Example 1-3 is significantly better than that of Comparative Example 1-2, indicating that the use of the composite shell material and 3-aminopropyltriethoxysilane improves the carbon release performance of the composite carbon source, which is beneficial to reducing the amount of carbon source used to avoid waste and secondary pollution.

[0080] 2. Denitrification test

[0081] Simulated wastewater: COD is 30.26 mg / L, TN is 18.21 mg / L, of which NO3 - -N concentration is 18.19 mg / L, NO2 - -N is 0.36mg / L, NH4 + -N concentration was 9.13 mg / L and TP was 1.55 mg / L.

[0082] 15 mL of activated sludge with a concentration of 8 g / L after denitrification acclimation was added to the reactor, and simulated wastewater was added to 800 mL. 320 mg of Example 1-3 and Comparative Example 1-3 were added respectively, and the pH was adjusted to about 7.5. The conical flask was sealed and placed in an oscillator at a speed of 70 rpm. The supernatant was taken at 0 h and 48 h to determine NO3 - -N, NO2- -N, 0 h as the initial concentration and 48 h as the final concentration;

[0083] Calculate NO3 using the following formula - -N removal rate:

[0084] NO3 - -N removal rate = (NO3 - -N initial concentration-NO3 - -N final concentration) / NO3 - -N initial concentration × 100%; calculate NO2 in the same way - -N removal rate;

[0085] Figure 2 For the denitrification test of Examples 1-3 and Comparative Examples 1-3 of the present invention, NO3 - -N removal rate results, as shown in Figure 1-3 of NO3 - -N removal rate was significantly higher than that of comparative examples 1-3; Figure 3 For the denitrification test of Examples 1-3 and Comparative Examples 1-3 of the present invention, NO2 - -N removal rate results, as shown in Figure 1-3 of the NO2 - -N removal rate is significantly higher than that of comparative examples 1-3, indicating that the use of composite shell material, 3-aminopropyltriethoxysilane and zinc ferrite improves the denitrification effect of composite carbon source.

[0086] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

[0087] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and actual applications are not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, any method and embodiment similar to the technical solution without creative design shall fall within the scope of protection of the present invention.

Claims

1. A composite carbon source for wastewater denitrification, characterized in that: The invention is composed of the following components in parts by weight: 16-18 parts of wheat straw, 22-26 parts of soybean straw, 8-15 parts of rice husk, 12-16 parts of corn cob, 3-4 parts of sodium alginate and 7-9 parts of composite shell material; The composite shell material comprises the following components in parts by weight: 10-12 parts of ferric chloride hexahydrate, 17-20 parts of zinc acetate, 96-112 parts of montmorillonite and 150-160 parts of corn starch; The preparation method of the composite shell material specifically comprises the following steps: S1. Add ferric chloride hexahydrate to ethylene glycol, then add zinc acetate, and stir to dissolve to obtain a mixed solution; S2, adding montmorillonite to water, adding 3-aminopropyltriethoxysilane, dispersing evenly, stirring in a water bath, filtering, washing, and drying to obtain modified montmorillonite; S3, adding the modified montmorillonite obtained in S2 to deionized water, ultrasonically dispersing to obtain a dispersion, dropping the mixed solution into the dispersion, sealing and heating the autoclave, cooling, filtering, washing, and drying to obtain zinc ferrite / modified montmorillonite; S4, adding the zinc ferrite / modified montmorillonite obtained in S3 to a 5-6 wt% corn starch solution, stirring in a water bath, to obtain a composite shell material; The method for preparing the composite carbon source for wastewater denitrification specifically comprises the following steps: (1) Wheat straw, soybean straw, rice husk and corn cob are washed and air-dried, and then crushed through a 50-mesh sieve to obtain a mixed powder, and the mixed powder is subjected to alkaline leaching treatment with a 1.5-2.5 wt% sodium hydroxide solution for 20-30 h to obtain a mixed carbon source; (2) uniformly mixing the mixed carbon source obtained in step (1) with sodium alginate, adding the mixture to a granulator for granulation, and drying at 30-50° C. to obtain a composite inner core material; (3) The composite inner core material obtained in step (2) is added to a granulation machine, and a composite coating material is added to wrap the composite inner core material until the coating thickness is 1-1.5 mm, thereby obtaining a composite carbon source for wastewater denitrification.

2. The composite carbon source for wastewater denitrification according to claim 1, characterized in that: In S1, the amount of ferric chloride hexahydrate added to ethylene glycol is 0.08-0.1 g / mL.

3. The composite carbon source for wastewater denitrification according to claim 2, characterized in that: In S2, the amount of 3-aminopropyltriethoxysilane added to water is 0.8-1 mg / mL.

4. The composite carbon source for wastewater denitrification according to claim 3, characterized in that: In S2, the water bath is stirred at a temperature of 70-80°C, a speed of 100-120 rpm, and a time of 3-5 hours.

5. The composite carbon source for wastewater denitrification according to claim 4, characterized in that: In S3, the modified montmorillonite is added to deionized water in an amount of 10-15 mg / mL.

6. The composite carbon source for wastewater denitrification according to claim 5, characterized in that: In S3, the autoclave is sealed and heated at a temperature of 176-183°C for 5-6 hours.

7. The composite carbon source for wastewater denitrification according to claim 6, characterized in that: In S4, the water bath is stirred at a temperature of 50-60° C., a speed of 160-180 rpm, and a time of 3-4 h.

8. Use of the composite carbon source for wastewater denitrification according to any one of claims 1 to 7 in municipal wastewater treatment.

Images