A method of treating sewage

Abstract

The application provides a sewage treatment method, which comprises the following steps: contacting sewage with a mixture of a slow-release carbon source material and domesticated sludge, and then performing denitrification treatment on the sewage under denitrification conditions; the slow-release carbon source material comprises a hydrogel framework and a carbon source carried by the hydrogel framework; the carbon source comprises alkali-treated bagasse and sodium acetate; the hydrogel framework comprises a porous structure formed by polyvinyl alcohol and sodium alginate; the amount of the sodium acetate is 0.5-2 parts by weight relative to 1 part by weight of the alkali-treated bagasse, and the amount of the hydrogel framework is 1.5-4 parts by weight; the specific surface area of the slow-release carbon source material is 5-25 m 2 / g; the method has excellent denitrification effect, high nitrogen removal rate, and significantly improved total nitrogen removal amount.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sewage treatment, in particular to a method for treating sewage. BACKGROUND

[0002] The domestic sewage in China mainly presents the characteristics of low carbon-nitrogen ratio, and the lack of carbon source leads to incomplete denitrification, thereby reducing the denitrification effect and increasing the nitrogen concentration in the effluent. At present, biological denitrification technology is widely used in wastewater treatment. In the biological denitrification process, the denitrification step is the key step of denitrification, and sufficient organic carbon source is an essential condition for ensuring biological phosphorus and nitrogen removal of sewage.

[0003] In view of the lack of carbon source in low C / N ratio sewage, adding external carbon source is the most widely used method. At present, the external carbon source mainly includes liquid carbon source, gas carbon source and solid carbon source.

[0004] In the traditional carbon source represented by low-molecular-weight organic matter, theoretically, the smaller the carbon source molecule, the easier it is for denitrifying bacteria to utilize, and the higher the denitrification efficiency. However, the dosage is difficult to control, and often requires complex control devices and continuous monitoring process, thereby increasing the operation cost.

[0005] The natural cellulose material of the solid carbon source has the advantages of low price, low cost, easy availability, no secondary pollution, no biological toxicity and the like, but such carbon source is greatly affected by temperature, and also faces problems such as unstable carbon source release and filler layer blockage. The synthetic degradable polymer as a solid slow-release carbon source is stable, but its preparation process is complex, the price is relatively high, and the composition is relatively single, and lacks trace elements required for growth, which is not conducive to biological diversity, so its application is limited.

[0006] In summary, in view of the trend of low C / N ratio of existing domestic sewage, it is urgent to develop a carbon-releasing stable, long carbon-releasing period, low-cost, high-efficiency denitrification, and biodegradable slow-release carbon source material. SUMMARY

[0007] In view of the above problems existing in the prior art, the present application provides a method for treating sewage. The method of the present application cooperates domesticated sludge and slow-release carbon source material, not only maintains the carbon-nitrogen ratio of the water body at a high level for a long time, but also realizes long-time high-efficiency denitrification, and significantly improves the total nitrogen removal amount. The method of the present application is particularly suitable for biological denitrification treatment of low carbon-nitrogen ratio wastewater.

[0008] The purpose of the present application is mainly realized through the following technical solutions.

[0009] The present application provides a method for treating sewage, which comprises: contacting sewage with a mixture of slow-release carbon source material and domesticated sludge, and then carrying out denitrification treatment on the sewage under denitrification conditions.

[0010] The slow-release carbon source material comprises a hydrogel framework and a carbon source carried by the hydrogel framework.

[0011] The carbon source comprises alkali-treated bagasse and sodium acetate.

[0012] The hydrogel framework comprises a porous structure formed by polyvinyl alcohol and sodium alginate.

[0013] The amount of sodium acetate is 0.5-2 parts by weight relative to 1 part by weight of alkali-treated bagasse, and the amount of hydrogel framework is 1.5-4 parts by weight.

[0014] The specific surface area of the slow-release carbon source material is 5-25 m 2 / g.

[0015] Preferably, the denitrification treatment is carried out in a bioreactor, and the content of the slow-release carbon source material in the bioreactor is 20-35 g / L, preferably 28-32 g / L.

[0016] Preferably, the weight ratio of the slow-release carbon source material to the acclimated sludge in the mixture of the slow-release carbon source material and the acclimated sludge is 1:10-30, preferably 1:15-25.

[0017] Preferably, during the denitrification treatment, the ratio of the sewage to the acclimated sludge is 1L:200-350 mg, preferably 1L:250-300 mg.

[0018] Preferably, the carbon-nitrogen molar ratio of the sewage is 2-8:1, preferably 2-4:1.

[0019] Preferably, the denitrification conditions include: dissolved oxygen content ≤0.5 mg / mL, preferably 0.2-0.4 mg / mL; temperature 25-35°C, preferably 28-32°C; pH 7-7.9, preferably 7-7.5; hydraulic retention time 5-12 h, preferably 6-8 h; stirring speed 130-150 rpm, preferably 135-145 rpm.

[0020] Preferably, the method further comprises: after the denitrification treatment is completed, the obtained denitrified water is allowed to stand and separate into layers, and then the upper layer of denitrified water is discharged.

[0021] Preferably, the acclimated sludge is obtained by the following acclimation method.

[0022] Step (S01) mixes the sludge and the acclimation water under acclimation conditions, stirs for 5-14 h, preferably 6-12 h, then stands, and then removes the supernatant.

[0023] Step (S02) continues to add acclimation water to the sludge removed supernatant, and repeats step (S01).

[0024] Step (S03) repeats step (S02) until the total nitrogen removal rate of the supernatant is > 80%, preferably 85%-95%, and the acclimation is completed.

[0025] Preferably, the mixed liquid after mixing the sludge and the acclimation water has a mixed liquid suspended solid concentration of 7000-8000 mg / L, preferably 7500-8000 mg / L.

[0026] Preferably, the acclimation conditions include: an acclimation temperature of 20-40°C, preferably 25-38°C; a dissolved oxygen content of 0.1-0.5 mg / mL, preferably 0.2-0.5 mg / mL.

[0027] Preferably, the acclimation water includes 90-110 mg / L of COD, preferably 95-105 mg / L of COD; 30-50 mg / L of N-NO3 - , preferably 35-45 mg / L of N-NO3 - ; 6-10 mg / L of total phosphorus, preferably 7-9 mg / L of total phosphorus; 2-5 mg / L of trace elements, preferably 3-5 mg / L of trace elements.

[0028] Preferably, the method further includes: first loading the slow-release carbon source material into a porous hollow suspended ball, and then filling the porous hollow suspended ball loaded with the slow-release carbon source material in the bioreactor to mix with the acclimated sludge in the bioreactor, to obtain a mixture of the slow-release carbon source material and the acclimated sludge.

[0029] Preferably, the diameter of the porous hollow suspended ball is 6-10 cm.

[0030] Preferably, the pore size of the porous hollow suspended ball is 2-4 mm.

[0031] Preferably, the total volume of the slow-release carbon source material in the porous hollow suspended ball is 80%-90% of the volume of the porous hollow suspended ball.

[0032] Preferably, the porosity of the slow-release carbon source material is 20%-80%, preferably 40%-80%.

[0033] Preferably, the porosity of the hydrogel framework is 30%-90%, preferably 50%-90%.

[0034] Preferably, the particle size of the alkali-treated bagasse is 0.1 mm-0.5 mm, preferably 0.1 mm-0.3 mm.

[0035] Preferably, the composition of the alkali-treated bagasse comprises 16-20 wt% lignin, 28-35 wt% cellulose and 15-20 wt% hemicellulose.

[0036] Preferably, the specific surface area of the slow-release carbon source material is 6-22 m 2 / g, preferably 8-20 m 2 / g.

[0037] Preferably, the amount of sodium acetate is 0.7-1.5 parts by weight and the amount of hydrogel framework is 1.6-2.2 parts by weight, relative to 1 part by weight of alkali-treated bagasse.

[0038] Preferably, the weight ratio of polyvinyl alcohol to sodium alginate is 7-10:1.

[0039] Preferably, the preparation method of the slow-release carbon source material comprises the following steps:

[0040] Step (1) alkali treatment of bagasse raw material, drying and crushing to obtain alkali-treated bagasse.

[0041] Step (2) adding 30-50 parts by weight of polyvinyl alcohol and 3-8 parts by weight of sodium alginate to 400-600 parts by volume of water and stirring to prepare a hydrogel precursor.

[0042] Step (3) mixing 10-40 parts by weight of alkali-treated bagasse obtained in step (1) and 10-35 parts by weight of sodium acetate with 30-75 parts by weight of the hydrogel precursor obtained in step (2) to form a slow-release carbon source material precursor, and crosslinking and curing the slow-release carbon source material precursor under the action of a crosslinking agent.

[0043] Preferably, the composition of the bagasse raw material comprises 18-22 wt% lignin, 40-50 wt% cellulose, 25-30 wt% hemicellulose and 1.5-3 wt% sugar.

[0044] Preferably, in step (1), the alkali treatment is carried out in an alkali solution selected from at least one of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution and ammonia water.

[0045] Preferably, the concentration of the alkali solution is 1-5 wt%.

[0046] Preferably, the amount of the alkali solution is 300-500 ml, relative to 20-50 g of bagasse raw material.

[0047] Preferably, in step (1), the conditions of the alkali treatment include a temperature of 20-30°C and a time of 20-24 h.

[0048] Preferably, in step (1), the alkali-treated bagasse raw material is washed to a pH of 6.8-7.2 before drying.

[0049] Preferably, in step (2), the stirring conditions include a temperature of 80-95℃ and a time of 1-3h.

[0050] Preferably, in step (2), the stirring speed is 130-150rpm, the stirring frequency is 1 time / 15-25min, and the stirring time is 10-20min / time.

[0051] Preferably, in step (3), the molding conditions include a temperature of -15~-25℃ and a time of 10-15h.

[0052] Preferably, in step (3), the cross-linking and solidification is performed by immersing the slow-release carbon source material precursor into a cross-linking agent solution, which is a saturated boric acid solution containing 3-5wt% CaCl2.

[0053] Preferably, the cross-linking and solidification conditions include a temperature of 3-5℃ and a time of 20-24h.

[0054] The present application has the following advantages:

[0055] (1) The method of the present application can maintain the carbon-nitrogen ratio of the water body at a high level for a long time, effectively prolonging the time of high-efficiency denitrification and significantly improving the total amount of nitrogen removal; it is very suitable for biological denitrification treatment of wastewater with low carbon-nitrogen ratio;

[0056] (2) The slow-release carbon source material can fully utilize the advantages of alkali-treated bagasse and sodium acetate as carbon sources, and the two together with the hydrogel framework can effectively improve the carbon source slow-release effect of the slow-release carbon source material, and is particularly suitable for biological denitrification treatment of wastewater with low carbon-nitrogen ratio;

[0057] The slow-release carbon source material of the present application has stable carbon source release and long release period;

[0058] The slow-release carbon source material is used in the biological denitrification treatment process of wastewater with low carbon-nitrogen ratio, overcoming the difficulty of low C / N sewage treatment due to insufficient carbon source, and strengthening the denitrification efficiency in the denitrification process;

[0059] (3) The present application realizes the resource utilization of agricultural waste (bagasse raw material). BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1Scanning electron microscope images of the slow-release carbon source material, wherein (A) to (C) are scanning electron microscope images of the slow-release carbon source materials M1, D1 and D2 prepared in Example 1, Comparative Example 1 and Comparative Example 2, respectively, before the release of the carbon source; and (a) to (c) are scanning electron microscope images of the slow-release carbon source materials M1, D1 and D2 prepared in Example 1, Comparative Example 1 and Comparative Example 2, respectively, after the release of the carbon source;

[0061] Figure 2 Elemental scanning images and energy spectrum images of the slow-release carbon source material, wherein (A) to (C) are surface C element scanning images of the slow-release carbon source materials M1, D1 and D2, respectively, before the release of the carbon source; (a) to (c) are surface N element scanning images of the slow-release carbon source materials M1, D1 and D2, respectively, before the release of the carbon source; and (D) to (E) are energy spectrum images of the slow-release carbon source materials M1, D1 and D2, respectively, before the release of the carbon source;

[0062] Figure 3 Quasi-second order fitting curves of the COD curve graphs of the slow-release carbon source materials M1, D1 and D2 during the release of the carbon source in clean water;

[0063] Figure 4 Nitrogen removal rate curve graphs of the biological denitrification processes of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 10;

[0064] Figure 5 Influent COD curve graphs of the biological denitrification processes of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 10;

[0065] Figure 6 Effluent COD curve graphs of the biological denitrification processes of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 10. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present application will be described in detail below with reference to the drawings, in which the same or similar components are denoted by the same reference numerals, and the principle of the present application will be explained with the embodiments thereof.

[0067] The inventors of the present application have found that, by mixing the alkali-treated bagasse and sodium acetate with the hydrogel precursor to prepare the slow-release carbon source material, the carbon release rate of the slow-release carbon source material is stabilized and the carbon release period is prolonged. According to the analysis, in the present application, the alkali-treated bagasse contains a pore structure suitable for the adsorption of microorganisms, especially denitrifying bacteria, to form a biofilm, and the hydrogel framework also has a specific pore structure and folds and gullies. After the alkali-treated bagasse and the hydrogel framework are cross-linked and solidified at a specific composition ratio, the structure of the carbon source (alkali-treated bagasse and sodium acetate) carried by the hydrogel framework is formed, which further improves the carbon source slow-release effect and the carbon release period. Moreover, when the domesticated sludge is used together to treat wastewater, it is more conducive to the attachment of microorganisms, especially denitrifying bacteria, and has excellent carbon source slow-release effect, which synergistically promotes the biological denitrification effect.

[0068] Based on the above research, in a first aspect, the present application provides a method for treating wastewater, which comprises: contacting the wastewater with a mixture of slow-release carbon source material and domesticated sludge, and then performing denitrification treatment on the wastewater under denitrification conditions.

[0069] The slow-release carbon source material comprises a hydrogel framework and a carbon source carried by the hydrogel framework.

[0070] The carbon source comprises alkali-treated bagasse and sodium acetate.

[0071] The hydrogel framework comprises a porous structure formed by polyvinyl alcohol and sodium alginate.

[0072] The amount of sodium acetate is 0.5-2 parts by weight relative to 1 part by weight of alkali-treated bagasse, and the amount of hydrogel framework is 1.5-4 parts by weight.

[0073] The specific surface area of the slow-release carbon source material is 5-25 m 2 / g.

[0074] In a preferred embodiment of the present application, the denitrification treatment is performed in a bioreactor, and the content of the slow-release carbon source material in the bioreactor is 20-35 g / L, preferably 28-32 g / L. The use of this preferred filling amount can further improve the denitrification rate and the denitrification amount.

[0075] In a preferred embodiment of the present application, the weight ratio of the slow-release carbon source material to the acclimated sludge in the mixture of the slow-release carbon source material and the acclimated sludge is 1:10-30, preferably 1:15-25. With the preferred ratio, the nitrogen removal rate and amount in the sewage can be effectively improved. According to analysis, the preferred amount ratio can not only increase the attachment area and amount of denitrifying bacteria on the surface of the slow-release carbon source material, but also make the unattached denitrifying bacteria more evenly distributed in the sewage.

[0076] In a preferred embodiment of the present application, the ratio of the sewage to the acclimated sludge in the denitrification process is 1L:200-350mg, preferably 1L:250-300mg. With the preferred ratio, the nitrogen removal rate and amount of the sewage can be further improved.

[0077] In a preferred embodiment of the present application, the carbon-nitrogen molar ratio of the sewage is 2-8:1, preferably 2-4:1.

[0078] In a preferred embodiment of the present application, the denitrification conditions include: the dissolved oxygen content is ≤0.5mg / mL, preferably 0.2-0.4mg / mL; the temperature is 25-35℃, preferably 28-32℃; the pH value is 7-7.9, preferably 7-7.5; the hydraulic retention time is 5-12h, preferably 6-8h; and the stirring speed is 130-150rpm, preferably 135-145rpm.

[0079] In a preferred embodiment of the present application, the method further includes: after the denitrification process is completed, the obtained denitrified water is allowed to stand and stratify, and then the upper layer of denitrified water is discharged. The standing of the denitrified water can form a low-oxygen or anoxic environment in the lower layer, and on the other hand, the denitrified water and the acclimated sludge are subjected to solid-liquid separation, which is more conducive to the separation and discharge of the denitrified water.

[0080] In the present application, the process from the mixing of the slow-release carbon source material and the acclimated sludge to the contact with the sewage until the ratio of the acclimated sludge to the sewage is 200-350mg:1L is the water inflow stage; the process from the discharge of the denitrified water after the completion of the denitrification to the completion of the water discharge is the water outflow stage; and the sum of the water inflow time and the water outflow time is 1-3h.

[0081] In the present application, the acclimated sludge can be purchased from the market or obtained from the denitrification section of a sewage treatment plant and then acclimated by oneself.

[0082] In a preferred embodiment of the present application, the acclimated sludge is obtained by the following acclimation method:

[0083] Step (S01) mixing sludge with acclimation water under acclimation conditions, stirring for 5-14 hours, preferably 6-12 hours, and then removing supernatant after standing;

[0084] Step (S02) continuing to add acclimation water to the sludge from which the supernatant has been removed, and repeating step (S01);

[0085] Step (S03) repeating step (S02) until the total nitrogen (TN) removal rate of the supernatant is >80%, preferably 85%-95%, and acclimation is completed;

[0086] In the preferred acclimation method, the mixed liquid after mixing the sludge and the acclimation water has a mixed liquid suspended solid concentration of 7000-8000 mg / L, preferably 7500-8000 mg / L.

[0087] The preferred acclimation method can further improve the combined action of microorganisms capable of degrading bagasse and denitrifying bacteria in the acclimated sludge, not only making the carbon-nitrogen ratio in the water body stable at a higher level for a longer time, but also making the denitrification rate and denitrification amount of the denitrifying bacteria at a higher level, effectively improving the denitrification effect on wastewater. According to analysis, the preferred acclimation method can make the denitrifying bacteria in the acclimated sludge microorganisms at a more suitable content, and make the denitrifying bacteria and other microorganisms better play a synergistic effect.

[0088] In a preferred embodiment of the present application, the acclimation conditions include: an acclimation temperature of 20-40℃, preferably 25-38℃; a dissolved oxygen content of 0.1-0.5 mg / mL, preferably 0.2-0.5 mg / mL.

[0089] In a preferred embodiment of the present application, the acclimation water includes 90-110 mg / L of COD, preferably 95-105 mg / L of COD; 30-50 mg / L of N-NO3 - (nitrate nitrogen), preferably 35-45 mg / L of N-NO3 - ; 6-10 mg / L of total phosphorus (TP), preferably 7-9 mg / L of total phosphorus; and 2-5 mg / L of trace elements, preferably 3-5 mg / L of trace elements.

[0090] In the present application, in order to further improve the denitrification effect of the acclimated sludge, preferably, the trace elements include Mg, Ca, Fe, Mn, Zn, Co, Ni, Cu, B, Se and W; more preferably, in the trace elements, relative to 1 part by weight of B, Mg is 2000-2500 parts by weight, Ca is 4500-5200 parts by weight, Fe is 480-550 parts by weight, Mn is 1000-1500 parts by weight, Zn is 250-300 parts by weight, Co is 250-300 parts by weight, Ni is 250-300 parts by weight, Cu is 250-300 parts by weight, Se is 4-8 parts by weight and W is 10-20 parts by weight; and / or, the source of the trace elements includes MgSO4, CaCl2, FeCl2, MnCl2, ZnSO4, CoCl2, NiCl2, CuCl2, H3BO3, Na2SeO3 and Na2WO4.

[0091] In a preferred embodiment of the present application, the method further comprises: first loading the slow-release carbon source material into a porous hollow floating ball, and then filling the porous hollow floating ball loaded with the slow-release carbon source material in a bioreactor to mix with the acclimated sludge in the bioreactor, to obtain a mixture of the slow-release carbon source material and the acclimated sludge. The use of the porous hollow floating ball facilitates the extension of the carbon release period.

[0092] In a preferred embodiment of the present application, the diameter of the porous hollow floating ball is 6-10 cm; and / or, the pore size of the porous hollow floating ball is 2-4 mm.

[0093] In a preferred embodiment of the present application, the total volume of the slow-release carbon source material in the porous hollow floating ball is 80%-90% of the volume of the porous hollow floating ball.

[0094] In the present application, the term "carbon release period" refers to the time from the beginning of the release of the slow-release carbon source material into the water body (containing nitrogen-containing wastewater) (at this time, the carbon source is released quickly, and the carbon-nitrogen molar ratio rises to above 2.5 in a short time) to the time when the carbon-nitrogen molar ratio in the water body is lower than 2.5 due to biological denitrification.

[0095] In the present application, before the release of the carbon source, the slow-release carbon source material has a wrinkle, gully and / or pore structure, which is conducive to the attachment and growth of microorganisms, especially denitrifying bacteria. As the carbon source is gradually released until the water gel skeleton is left, the pores of the slow-release carbon source material gradually increase, and more and more denitrifying bacteria attach to form a uniform biofilm, which can keep the biological denitrification capacity at a high level for wastewater treatment.

[0096] In a preferred embodiment of the present application, the porosity of the slow-release carbon source material is 20%-80%, preferably 40%-80%; and / or, the porosity of the hydrogel framework is 30%-90%, preferably 50%-90%. The slow-release carbon source material and the hydrogel framework having the preferred porosity can further improve the biological denitrification capacity.

[0097] In the present application, the porosity of the slow-release carbon source material is detected before the carbon source is released, and the porosity of the hydrogel framework is detected after the slow-release carbon source material releases carbon for 240 hours in flowing water. The detection method of the porosity in the present application is not particularly limited, and the detection method commonly used in the art can be used, such as the gas adsorption method (BET method).

[0098] In a preferred embodiment of the present application, the particle size of the alkali-treated bagasse is 0.1mm-0.5mm, preferably 0.1mm-0.3mm; the alkali-treated bagasse with the preferred particle size can make the carbon source more evenly distributed in the hydrogel framework, and make the slow-release carbon source material more easily adsorb microorganisms, especially denitrifying bacteria to form a biofilm, thereby improving the denitrification effect.

[0099] In the present application, the alkali-treated bagasse is obtained by alkali treatment of bagasse raw materials, and the bagasse raw materials refer to the residue left after sugar is extracted from sugarcane, the main components of which are cellulose, hemicellulose and lignin, and a small amount of disaccharides and monosaccharides are also left, and a certain amount of impurities such as protein, fat and ash are also included. It has been found through research that the carbon supply sustainability of the bagasse raw materials is insufficient, and the carbon source cannot be continuously provided, which is not suitable for use as a carbon source for denitrification. However, the slow-release carbon source material carried by the hydrogel framework (alkali-treated bagasse and sodium acetate) prepared by mixing the alkali-treated bagasse with a specific amount of polyvinyl alcohol and sodium alginate after being combined with sodium acetate as a carbon source not only shows excellent carbon source slow-release effect, but also effectively promotes biological denitrification. According to the analysis, the alkali-treated bagasse is mainly composed of cellulose, hemicellulose and lignin with a specific content, and the hydrogel formed by cross-linking and solidification of polyvinyl alcohol and sodium alginate has a special wrinkle and gully structure on the surface of the material, and has a pore structure, which is more conducive to the attachment of microorganisms, especially denitrifying bacteria, to form a biofilm, thereby improving the denitrification effect. Moreover, the wrinkle, gully structure and / or pore structure further adjust the slow-release rate and slow-release amount of the carbon source, which not only keeps the carbon-nitrogen ratio in water at a high level, but also prolongs the carbon release period of the slow-release carbon source material.

[0100] In a preferred embodiment of the present application, the alkali-treated bagasse has a component content of 16-20 wt% lignin, 28-35 wt% cellulose and 15-20 wt% hemicellulose, preferably 17-19 wt% lignin, 30-33 wt% cellulose and 16-18 wt% hemicellulose. The alkali-treated bagasse with the preferred component composition can further optimize the structure of the slow-release carbon source material prepared by taking the alkali-treated bagasse as a carbon source, and not only has good slow-release effect and long carbon release period, but also has higher utilization rate of the alkali-treated bagasse.

[0101] In the present application, the alkali-treated bagasse also contains impurities such as protein, fat and ash.

[0102] In the present application, the component content of the bagasse raw material and the alkali-treated bagasse is a dry weight content.

[0103] In a preferred embodiment of the present application, the mass transfer coefficient of the carbon source in the slow-release carbon source material is 5-30 mg·(h·g·L), preferably 7-30 mg·(h·g·L). When the slow-release carbon source material of the present application has the preferred mass transfer coefficient, and cooperates with the wrinkles, grooves and porosity on the surface of the slow-release carbon source material, an unexpected situation occurs when the slow-release carbon source material is used in the biological denitrification process, that is, the denitrification amount first slowly decreases and then increases in the initial stage of biological denitrification. According to analysis, the release rate of the carbon source of the slow-release carbon source material gradually decreases over time, but due to the more wrinkles and grooves on the surface of the slow-release carbon source material and more and more uniform pores that can adsorb and attach more denitrification bacteria, the carbon source can be more efficiently utilized by the attached denitrification bacteria in the release process. Although the denitrification amount decreases in the initial stage, the increase in the amount and area of the attached denitrification bacteria compensates for the decrease in the denitrification amount due to the decrease in the release rate of the carbon source.

[0104] In a preferred embodiment of the present application, the specific surface area of the slow-release carbon source material is 6-22 m 2 / g, preferably 8-20 m 2 / g. The slow-release carbon source material with the preferred specific surface area can control the slow-release rate of the carbon source in a more reasonable range, maintain and stabilize a higher carbon-nitrogen ratio required for denitrification for a longer time, and further take into account the effective utilization of the carbon source by the microorganisms attached to the surface of the slow-release carbon source material and the microorganisms in the water body, thereby improving the denitrification rate and denitrification amount.

[0105] In the present application, the specific surface area can be detected by conventional methods in the art, such as the method of GB / T19587-2017.

[0106] The shape of the slow-release carbon source material is not particularly required in the present application, and any known shape in the art can be used, such as spherical, cubic, cuboid, cylindrical, polygonal, triangular pyramidal, preferably spherical and / or cubic.

[0107] In a preferred embodiment of the present application, the amount of sodium acetate is 0.7-1.5 parts by weight, and the amount of hydrogel framework is 1.6-2.2 parts by weight, relative to 1 part by weight of alkali-treated bagasse. Within the preferred component content ratio range, the slow-release carbon source material has more excellent slow-release effect, and can further improve the denitrification effect for biological denitrification.

[0108] In a preferred embodiment of the present application, the weight ratio of polyvinyl alcohol to sodium alginate in the hydrogel framework is 7-10:1, preferably 7-9:1. The hydrogel framework with the preferred ratio has a more stable structure, and the slow-release carbon source material can continuously maintain good slow-release effect during the process of biological denitrification, so that the amount of biological denitrification is at a higher level.

[0109] The inventors of the present application have found that, due to the high content of lignin and residual disaccharides and monosaccharides in bagasse raw materials, the bagasse raw materials have high carbon release rate and carbon release amount in the early stage in water, and the carbon release amount decreases rapidly in the later stage, resulting in large fluctuation of carbon release rate in the whole carbon release period, which is not conducive to denitrification, and is prone to cause secondary pollution due to excessive carbon release amount in the early stage. However, after alkali treatment, the combination of alkali-treated bagasse and sodium acetate and the slow-release carbon source material prepared from the hydrogel precursor with a specific amount have good carbon source slow-release effect, which can effectively prolong the carbon release period and effectively improve the denitrification effect on wastewater.

[0110] In a preferred embodiment of the present application, the preparation method of the slow-release carbon source material comprises the following steps:

[0111] Step (1): alkali treatment of bagasse raw materials, drying and crushing to obtain alkali-treated bagasse;

[0112] Step (2): adding 30-50 parts by weight of polyvinyl alcohol and 3-8 parts by weight of sodium alginate to 400-600 parts by volume of water and stirring to prepare a hydrogel precursor;

[0113] Step (3): mixing 10-40 parts by weight of alkali-treated bagasse obtained in step (1) and 10-35 parts by weight of sodium acetate with 30-75 parts by weight of the hydrogel precursor obtained in step (2) to form a slow-release carbon source material precursor, and cross-linking and curing the slow-release carbon source material precursor under the action of a cross-linking agent.

[0114] In the present application, the main components of the bagasse raw material are cellulose, hemicellulose and lignin, and a small amount of sugar is also retained, and it also contains a certain amount of protein, fat, ash and other impurities; preferably, the components of the bagasse raw material include 18-22wt% of lignin, 40-50wt% of cellulose, 25-30wt% of hemicellulose and 1.5-3wt% of sugar, preferably including 18-20wt% of lignin, 40-48wt% of cellulose, 25-28wt% of hemicellulose and 1.5-3wt% of sugar. The alkali treatment of the bagasse raw material with the above-mentioned preferred components can more effectively play the synergistic effect of the alkali-treated bagasse and the hydrogel framework in the spatial structure, further improve the slow-release effect of the carbon source, and be more beneficial to the denitrification of the water body. Further, the sugar contained in the bagasse raw material is mainly disaccharides (such as sucrose) and monosaccharides.

[0115] In a preferred embodiment of the present application, in step (1), the alkali treatment is carried out in an alkali solution selected from at least one of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution and ammonia water; more preferably sodium hydroxide solution; and / or the concentration of the alkali solution is 1-5wt% (which can be any one of 1.3wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% and 5wt% or any value between any two adjacent values), preferably 1-3wt%; and / or the amount of the alkali solution is 300-500ml, preferably 350-450ml, relative to 20-50g of the bagasse raw material.

[0116] In a preferred embodiment of the present application, in step (1), the alkali treatment is carried out at a temperature of 20-30℃, preferably 23-27℃, for 20-24h.

[0117] The above-mentioned preferred alkali treatment method can further optimize the pore structure of the obtained alkali-treated bagasse, on the one hand, the carbon source release rate of the obtained alkali-treated bagasse is more stable, on the other hand, the obtained alkali-treated bagasse has better adsorption of microorganisms, especially denitrifying bacteria, and cooperates with the hydrogel framework to synergistically exert more excellent carbon source slow-release effect and biofilm formation effect of microorganisms, especially denitrifying bacteria, to form more uniform biofilm, thereby providing denitrification effect.

[0118] In a preferred embodiment of the present application, in step (1), the alkali-treated bagasse raw material is washed to a pH of 6.8-7.2 before drying. Since the alkali-treated bagasse is washed after the alkali treatment, the alkali-treated bagasse obtained after the alkali treatment basically does not contain disaccharides and monosaccharides, which can be ignored.

[0119] In a preferred embodiment of the present application, in step (2), 35-45 parts by weight of polyvinyl alcohol and 4-6 parts by weight of sodium alginate are added to 450-550 parts by volume of water and stirred to prepare the hydrogel precursor. The hydrogel precursor prepared using the preferred ratio can more uniformly coat the alkali-treated bagasse and sodium acetate, so that the carbon release area is larger and more uniform, and the synergistic carbon release and biofilm formation effects of the alkali-treated bagasse and the hydrogel skeleton are more conducive to being exerted, thereby improving the denitrification effect.

[0120] In a preferred embodiment of the present application, in step (2), the stirring conditions include a temperature of 80-95℃ and a time of 1-3h; and / or, the stirring speed in step (2) is 130-150rpm, preferably 135-145rpm; the stirring frequency is 1 time / 15-25min, preferably 1 time / 18-25min; and the stirring time is 10-20min / time, preferably 15-20min / time. Using the preferred stirring conditions makes the slow-release carbon source material have a more uniform pore structure and more folds and gullies, further improving the adsorption effect of the slow-release carbon source material on denitrifying bacteria and the slow-release effect of the carbon source, thereby improving the biological denitrification effect.

[0121] In a preferred embodiment of the present application, in step (3), 20-30 parts by weight of the alkali-treated bagasse obtained in step (1) and 20-30 parts by weight of sodium acetate are mixed with 32-66 parts by weight of the hydrogel precursor obtained in step (2) to form a slow-release carbon source material precursor, and the slow-release carbon source material precursor is then cross-linked and solidified under the action of a cross-linking agent.

[0122] In a preferred embodiment of the present application, in step (3), the forming conditions include a temperature of -15~-25℃ and a time of 10-15h.

[0123] In a preferred embodiment of the present application, in step (3), the cross-linking and solidification are performed by immersing the slow-release carbon source material precursor into a cross-linking agent solution, and the cross-linking agent solution is a saturated boric acid solution containing 3-5wt% CaCl2; and / or, the cross-linking and solidification conditions include a temperature of 3-5℃ and a time of 20-24h. Using the preferred cross-linking and solidification conditions is more conducive to improving the slow-release effect and structural stability of the slow-release carbon source material.

[0124] In the present application, the weight of the hydrogel skeleton is based on the hydrogel precursor.

[0125] The preferred embodiments of the present application are described below to illustrate the principles of the present application, and are not intended to limit the scope of the present application.

[0126] Cycle (denitrification cycle): the whole process of wastewater completing water inlet, biological denitrification, standing and water outlet is a denitrification cycle;

[0127] Surface structure of slow-release carbon source material: detected and analyzed by scanning electron microscope (model: Hitachi Regulus8100);

[0128] EDS (energy spectrum) and SEM (scanning electron microscope) were used for analysis; the model of EDS was Thermo Kalpha, and the model of SEM was Hitachi Regulus8100;

[0129] Specific surface area: detected and analyzed by the method of GB / T 19587-2017;

[0130] Porosity: gas adsorption method (BET method);

[0131] COD in water: detected by referring to the method in the standard of alkaline potassium persulfate digestion ultraviolet spectrophotometry HJ / T 399-200;

[0132] Nitrogen removal rate: detected by referring to the method in the standard of potassium dichromate rapid digestion spectrophotometry HJ 636-2012;

[0133] Total denitrification amount: when the carbon-nitrogen ratio in water is less than 2.5, stop the denitrification experiment, and at this time, the total denitrification amount = (total nitrogen amount in water before denitrification - total nitrogen amount in water after denitrification) ÷ total nitrogen amount in water before denitrification × 100%.

[0134] Sugarcane bagasse raw material: cellulose content 45wt%, hemicellulose content 27wt%, lignin content 20wt%, sugar content 2wt%, and the balance also includes impurities such as protein, fat, ash, etc;

[0135] Corn stalk: cellulose content 40wt%, hemicellulose content 25wt%, lignin content 20wt%, sugar content 1wt%, and the balance also includes impurities such as protein, fat, ash, etc.

[0136] Corn stalk residue: the product after alkali treatment of corn stalk.

[0137] Preparation example 1

[0138] I. Preparation of slow-release carbon source material:

[0139] Step (1): 40 parts by weight of dried sugarcane bagasse raw material to constant weight was mixed with 400 parts by volume of 1.5wt% sodium hydroxide solution for alkali treatment (alkali treatment temperature was 25℃, and time was 24h);

[0140] After the alkali treatment of the bagasse raw material is completed, the bagasse raw material is washed with water until the pH of the washing liquid is 7, and then dried at 60°C until the weight is constant. The alkali-treated bagasse (cellulose content 32wt%, hemicellulose content 17wt%, lignin content 18wt%, and the rest being protein, fat, ash, etc.) with a particle size distribution of 0.2mm is obtained by crushing and sieving;

[0141] Step (2): 40 parts by weight of polyvinyl alcohol and 5 parts by weight of sodium alginate are added to 500 parts by volume of ultrapure water, and stirring is carried out at a temperature of 95°C, a stirring speed of 140 rpm, a stirring frequency of 1 time / 20 min, and a stirring time of 15 min / time. After 2h, a hydrogel precursor is prepared;

[0142] Step (3): 25 parts by weight of alkali-treated bagasse and 25 parts by weight of sodium acetate are mixed with 50 parts by weight of the hydrogel precursor prepared in step (2), and then poured into a 1cm 3 cubic mold. After 12h at -20°C, the slow-release carbon source material precursor is demolded and formed, and then immersed in a saturated boric acid solution containing 4% CaCl2 for crosslinking and curing (crosslinking and curing temperature is 4°C, and crosslinking and curing time is 24h);

[0143] After crosslinking and curing is completed, the surface is rinsed with ultrapure water to remove residual crosslinking agent, and then dried at 60°C until the material weight is constant to obtain the slow-release carbon source material M1. The surface structure of the slow-release carbon source material M1 is shown in Figure 1 ; The energy spectrum of the slow-release carbon source material M1 is analyzed by EDS and SEM scanning, as shown in Figure 2 ; the C element distribution on the surface is shown in Figure 2 ; the N element distribution is shown in Figure 2 (a); and the O element distribution is shown in

[0144] The specific surface area of M1, the porosity of M1 before carbon release, and the porosity of M1 after carbon release (hydrogel skeleton porosity) are measured and the results are shown in Table 4.

[0145] Preparation Example 2

[0146] I. Preparation of the slow-release carbon source material:

[0147] Step (1): 35 parts by weight of dried bagasse raw material is mixed with 450 parts by volume of 1wt% sodium hydroxide solution for alkali treatment (alkali treatment temperature is 20°C, and time is 20h);

[0148] The alkali-treated bagasse is washed with water until the pH of the washing liquid is 7, then dried at 60°C until the weight is constant, crushed and sieved to obtain alkali-treated bagasse with a particle size distribution of 0.1 mm (cellulose content 35 wt%, hemicellulose content 20 wt%, lignin content 20 wt%, and the balance being protein, fat, ash, etc.);

[0149] Step (2) 36 parts by weight of polyvinyl alcohol and 4 parts by weight of sodium alginate are added to 550 parts by volume of ultrapure water, and stirring is carried out at a temperature of 95°C, with a stirring speed of 130 rpm, a stirring frequency of 1 time / 20 min, and a stirring time of 10 min / time. After 2 h, a hydrogel precursor is prepared;

[0150] Step (3) 20 parts by weight of alkali-treated bagasse and 30 parts by weight of sodium acetate are mixed with 32 parts by weight of the hydrogel precursor prepared in step (2), then poured into a 1 cm 3 cubic mold, and after 12 h at -20°C, the precursor of the slow-release carbon source material is demolded, then immersed in a saturated boric acid solution containing 4% CaCl2 for crosslinking and curing (crosslinking and curing temperature is 4°C, and crosslinking and curing time is 24 h) ;

[0151] After crosslinking and curing, the surface is rinsed with ultrapure water to remove residual crosslinking agent, then dried at 60°C until the weight is constant to obtain the slow-release carbon source material M2;

[0152] The specific surface area of M2, the porosity of M2 before carbon release, and the porosity of M2 after carbon release (hydrogel skeleton porosity) are shown in Table 4.

[0153] Preparation Example 3

[0154] I. Preparation of the slow-release carbon source material:

[0155] Step (1) 45 parts by weight of dried bagasse raw material is mixed with 350 parts by volume of 2 wt% sodium hydroxide solution for alkali treatment (alkali treatment temperature is 20°C, and time is 20 h) ;

[0156] After the alkali treatment of the bagasse raw material is completed, the bagasse is washed with water until the pH of the washing liquid is 7, then dried at 60°C until the weight is constant, crushed and sieved to obtain alkali-treated bagasse with a particle size distribution of 0.3 mm (cellulose content 30 wt%, hemicellulose content 16 wt%, lignin content 17 wt%, and the balance being protein, fat, ash, etc.);

[0157] Step (2) 42 parts by weight of polyvinyl alcohol and 6 parts by weight of sodium alginate were added to 450 parts by volume of ultrapure water, and stirring was carried out at a temperature of 95°C, a stirring speed of 150 rpm, a stirring frequency of 1 time / 20 min, and a stirring time of 20 min / time, to prepare a hydrogel precursor after 2 h;

[0158] Step (3) 30 parts by weight of the alkali-treated bagasse and 20 parts by weight of sodium acetate were mixed with 66 parts by weight of the hydrogel precursor prepared in step (2), and then poured into a 1 cm 3 cubic mold, and demolded to form a shaped slow-release carbon source material precursor after 12 h at a temperature of -20°C, and then the shaped slow-release carbon source material precursor was immersed in a saturated boric acid solution containing 4% CaCl2 to crosslink and solidify (at a temperature of 4°C for 24 h) ;

[0159] After the crosslinking and solidification was completed, the surface residual crosslinking agent was washed with ultrapure water, and then dried at 60°C until the material constant weight to obtain a slow-release carbon source material M3;

[0160] The specific surface area of M3, the porosity of M3 before carbon release, and the porosity of M3 after carbon release (hydrogel skeleton porosity) were determined, and the results are shown in Table 4.

[0161] Preparation Example 4

[0162] The slow-release carbon source material was prepared according to the method of Example 1, except that,

[0163] I. Preparation of a slow-release carbon source material:

[0164] Step (1) 40 parts by weight of a dried bagasse raw material was mixed with 400 parts by volume of 1.5 wt% sodium hydroxide to perform alkali treatment (at a temperature of 25°C for 24 h) ;

[0165] After the alkali treatment of the bagasse raw material was completed, the bagasse raw material was washed with water until the washing liquid PH reached 7, and then dried at 60°C until the constant weight, and then crushed and sieved to obtain alkali-treated bagasse with a particle size distribution of 0.2 mm;

[0166] Step (2) 40 parts by weight of polyvinyl alcohol and 5 parts by weight of sodium alginate were added to 500 parts by volume of ultrapure water, and stirring was carried out at a temperature of 78°C, a stirring speed of 120 rpm, a stirring frequency of 1 time / 30 min, and a stirring time of 10 min / time, to prepare a hydrogel precursor after 2 h;

[0167] Step (3) 25 parts by weight of the alkali-treated bagasse and 25 parts by weight of sodium acetate were mixed with 50 parts by weight of the hydrogel precursor prepared in step (2), and then poured into a 1 cm 3The precursor of the slow-release carbon source material is formed by releasing from the cubic mold at -20°C for 12 h, and then is immersed in a saturated boric acid solution containing 4% CaCl2 for cross-linking and curing (the temperature for cross-linking and curing is 10°C, and the time for cross-linking and curing is 30 h).

[0168] After the cross-linking and curing is completed, the surface residual cross-linking agent is washed with ultrapure water, and then the material is baked at 60°C until the weight is constant to obtain the slow-release carbon source material M4.

[0169] The results of the determination of the specific surface area of M4, the porosity of M4 before carbon release, and the porosity of M4 after carbon release (the porosity of the hydrogel skeleton) are shown in Table 4.

[0170] Preparation Example 5

[0171] The slow-release carbon source material is prepared according to the method of Example 1, except that:

[0172] I. Preparation of the slow-release carbon source material:

[0173] Step (1) 40 parts by weight of the sugarcane bagasse raw material dried to a constant weight is mixed with 400 parts by volume of 1 wt% sodium hydroxide for alkalization treatment (the temperature for alkalization is 25°C, and the time is 12 h).

[0174] After the alkalization treatment of the sugarcane bagasse raw material is completed, the material is washed with water until the washing liquid PH is 7, and then is dried at 60°C to a constant weight, crushed and sieved to obtain the alkalized sugarcane bagasse with a particle size distribution of 0.2 mm (the cellulose content is 40 wt%, the hemicellulose content is 25 wt%, the lignin content is 19 wt%, and the rest is protein, fat, ash, etc.).

[0175] The slow-release carbon source material M5 is obtained.

[0176] The results of the determination of the specific surface area of M5, the porosity of M5 before carbon release, and the porosity of M5 after carbon release (the porosity of the hydrogel skeleton) are shown in Table 4.

[0177] Preparation Example 6

[0178] The slow-release carbon source material is prepared according to the method of Example 1, except that the particle size of the alkalized sugarcane bagasse is 0.8 mm.

[0179] The slow-release carbon source material M6 is obtained.

[0180] The results of the determination of the specific surface area of M6, the porosity of M6 before carbon release, and the porosity of M6 after carbon release (the porosity of the hydrogel skeleton) are shown in Table 4.

[0181] Preparation Example 7

[0182] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that the bagasse was replaced by an equal amount of sodium acetate.

[0183] The slow-release carbon source material D1 was obtained.

[0184] The surface structure of the slow-release carbon source material D1 was analyzed by scanning electron microscopy as shown in Figure 1 The energy spectrum of the slow-release carbon source material D1 was analyzed by EDS and SEM as shown in Figure 2 The C element distribution on the surface of the slow-release carbon source material D1 was as shown in Figure 2 The N element distribution was as shown in Figure 2 (b);

[0185] The specific surface area of D1, the porosity of D1 before carbon release, and the porosity of D1 after carbon release (hydrogel skeleton porosity) were determined as shown in Table 4.

[0186] Preparation Example 8

[0187] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that the sodium acetate was replaced by an equal amount of alkali-treated bagasse.

[0188] The slow-release carbon source material D2 was obtained.

[0189] The surface structure of the slow-release carbon source material D2 was analyzed by scanning electron microscopy as shown in Figure 1 The energy spectrum of the slow-release carbon source material D2 was analyzed by EDS and SEM as shown in Figure 2 The C element distribution on the surface of the slow-release carbon source material D2 was as shown in Figure 2 The N element distribution was as shown in Figure 2 (c);

[0190] The specific surface area of D2, the porosity of D2 before carbon release, and the porosity of D2 after carbon release (hydrogel skeleton porosity) were determined as shown in Table 4.

[0191] Preparation Example 9

[0192] The slow-release carbon source material was prepared according to the method of Example 1, except that

[0193] I. Preparation of the slow-release carbon source material:

[0194] Step (1) 40 parts by weight of the bagasse raw material dried to a constant weight was mixed with 400 parts by volume of sodium hydroxide with a concentration of 1.5 wt% for alkali treatment (the temperature of the alkali treatment was 25°C, and the time was 24h);

[0195] After the alkali treatment of the bagasse raw material was completed, the washing liquid was washed to a pH of 7, and then dried to a constant weight at 60°C, crushed and sieved to obtain alkali-treated bagasse with a particle size distribution of 0.2mm.

[0196] Step (2) 22 parts by weight of polyvinyl alcohol and 2 parts by weight of sodium alginate were added to 500 parts by volume of ultrapure water, and stirring was carried out at a temperature of 95°C, a stirring speed of 120 rpm, a stirring frequency of 1 time / 30 min, and a stirring time of 30 min / time. After 2 h, a hydrogel precursor was prepared;

[0197] Step (3) 42 parts by weight of alkali-treated bagasse and 8 parts by weight of sodium acetate were mixed with 50 parts by weight of the hydrogel precursor prepared in Step (2), and then poured into a 1 cm 3 cubic mold, and after 12 h at a temperature of -20°C, the precursor of the slow-release carbon source material was removed from the mold and then immersed in a saturated boric acid solution containing 4% CaCl2 for crosslinking and curing (at a temperature of 4°C for 24 h) ;

[0198] After the crosslinking and curing were completed, the surface was rinsed with ultrapure water to remove residual crosslinking agent, and then the material was dried at a constant weight at a temperature of 60°C to obtain the slow-release carbon source material D3.

[0199] The specific surface area of D3, the porosity of D3 before carbon release, and the porosity of D3 after carbon release (hydrogel skeleton porosity) were determined, and the results are shown in Table 4.

[0200] Preparation Example 10

[0201] The slow-release carbon source material was prepared according to the method of Example 1, except that the bagasse raw material was replaced with an equal amount of corn stalks.

[0202] The slow-release carbon source material D4 was obtained.

[0203] The specific surface area of D4, the porosity of D4 before carbon release, and the porosity of D4 after carbon release (hydrogel skeleton porosity) were determined, and the results are shown in Table 4.

[0204] Preparation Example 11

[0205] The slow-release carbon source material was prepared according to the method of Example 1, except that the bagasse raw material was replaced with an equal amount of corn stalks, and the sodium acetate was replaced with an equal amount of corn stalks.

[0206] The slow-release carbon source material D5 was obtained.

[0207] The specific surface area of D5, the porosity of D5 before carbon release, and the porosity of D5 after carbon release (hydrogel skeleton porosity) were determined, and the results are shown in Table 4.

[0208] Preparation Example 12

[0209] The slow-release carbon source material was prepared according to the method of Example 1, except that the sodium acetate was replaced with an equal amount of glucose.

[0210] A slow-release carbon source material D6 was obtained.

[0211] The results of measurement of the specific surface area of D6, the porosity of D6 before carbon release, and the porosity of D6 after completion of carbon release (porosity of the hydrogel skeleton) are shown in Table 4.

[0212] Preparation Example 13

[0213] A slow-release carbon source material was prepared according to the method of Example 1, except that sodium acetate was replaced with an equivalent amount of starch.

[0214] A slow-release carbon source material D7 was obtained.

[0215] The results of measurement of the specific surface area of D7, the porosity of D7 before carbon release, and the porosity of D7 after completion of carbon release (porosity of the hydrogel skeleton) are shown in Table 4.

[0216] Preparation Example 14

[0217] A slow-release carbon source material was prepared according to the method of Example 1, except that in step (3), 25 parts by weight of alkali-treated bagasse and 5 parts by weight of sodium acetate were mixed with 70 parts by weight of the hydrogel precursor prepared in step (2).

[0218] A slow-release carbon source material D8 was obtained.

[0219] The results of measurement of the specific surface area of D8, the porosity of D8 before carbon release, and the porosity of D8 after completion of carbon release (porosity of the hydrogel skeleton) are shown in Table 4.

[0220] Preparation Example 15

[0221] A slow-release carbon source material was prepared according to the method of Example 1, except that the bagasse raw material was not subjected to carbonization treatment, but was directly dried at 60°C to a constant weight, pulverized, and sieved to obtain a bagasse raw material having a particle size distribution of 0.2 mm.

[0222] A slow-release carbon source material D9 was obtained.

[0223] The results of measurement of the specific surface area of D9, the porosity of D9 before carbon release, and the porosity of D9 after completion of carbon release (porosity of the hydrogel skeleton) are shown in Table 4.

[0224] Preparation Example 16

[0225] Preparation of acclimated sludge:

[0226] The acclimated sludge was taken from the anoxic section of the A2O biological tank of a sewage treatment plant, and had an MLSS of 7500 mg / L.

[0227] Step (S01) : The sludge to be acclimated was mixed with the acclimation water (composition see Table 1 and Table 2) at a volume ratio of 1 :4 (MLSS after mixing was 7700 mg / L) under the condition of a temperature of 30°C and a dissolved oxygen content of 0.3 mg / mL, stirred for 8 h, and then allowed to stand, after which the supernatant was removed;

[0228] Step (S02) : The acclimation water was continuously added to the sludge from which the supernatant had been removed, and step (S01) was repeated.

[0229] Step (S03) : Step (S02) was repeated until the TN removal rate of the supernatant was 90%, and the acclimation was completed, to obtain acclimated sludge Al.

[0230] Preparation Example 17

[0231] Preparation of acclimated sludge:

[0232] The sludge to be acclimated was taken from the anoxic section of the A2O biological tank of a sewage treatment plant, and the MLSS was 7500 mg / L.

[0233] Step (S01) : The sludge to be acclimated was mixed with the acclimation water (composition see Table 1 and Table 2) at a volume ratio of 1 :4 (MLSS after mixing was 7700 mg / L) under the condition of a temperature of 30°C and a dissolved oxygen content of 0.1 mg / mL, stirred for 16 h, and then allowed to stand, after which the supernatant was removed;

[0234] Step (S02) : The acclimation water was continuously added to the sludge from which the supernatant had been removed, and step (S01) was repeated.

[0235] Step (S03) : Step (S02) was repeated until the TN removal rate of the supernatant was 90%, and the acclimation was completed, to obtain acclimated sludge A2.

[0236] Example 1

[0237] The biological nitrogen removal experiment was performed according to the following method.

[0238] Step (S1) : The slow-release carbon source material Ml was filled into a porous hollow suspended ball (diameter 8 cm, surface porous diameter 3 mm) at a filling rate of 85% (i.e., 85% of the volume of the porous hollow suspended ball was occupied), and then the porous hollow suspended ball filled with the slow-release carbon source material Ml was filled in a bioreactor and mixed with the acclimated sludge of Preparation Example 16 in the bioreactor, and the filling amount of the slow-release carbon source material was 30 g / L of the bioreactor;

[0239] Step (S2) : Wastewater with a C / N ratio (molar ratio) of 2.5: 1 was introduced into the bioreactor to contact the mixture of the slow-release carbon source material and the sludge (the ratio of the acclimated sludge to the incoming wastewater was 280 mg: 1 L);

[0240] After the water feeding in step (S3) is completed, the wastewater is subjected to a denitrification reaction under denitrification conditions (oxygen content of 0.3 mg / mL, temperature of 30°C, pH of 7.2, hydraulic retention time of 7 h, and stirring speed of 140 rpm) to obtain denitrified water, and then the obtained denitrified water is allowed to stand for 1 h;

[0241] Step (S4) water discharge: the denitrified water after standing in step (S3) is discharged from the bioreactor;

[0242] The sum of the water feeding time and the water discharge time is 1 h.

[0243] The water feeding COD, water discharge COD, and nitrogen removal rate of each denitrification cycle are measured, and the measurement results are shown in Table 1. Figures 4-6 The total denitrification amount and carbon release cycle are shown in Table 4.

[0244] Examples 2-6

[0245] The biological denitrification experiment is performed according to the method of Example 1, except that the slow-release carbon source material M1 is replaced by an equal amount of slow-release carbon source materials M2, M3, M4, M5, and M6, respectively.

[0246] The water feeding COD, water discharge COD, and nitrogen removal rate of each denitrification cycle are measured, and the total denitrification amount and carbon release cycle are shown in Table 4.

[0247] Example 7

[0248] The slow-release carbon source material and the biological denitrification experiment are prepared according to the method of Example 1, except that:

[0249] III. Biological denitrification experiment:

[0250] Step (S1) filling of slow-release carbon source material: the slow-release carbon source material M1 is loaded into a porous hollow suspended ball (diameter of 6 cm, and the porous diameter on the surface is 2 mm) at a loading rate of 80% (i.e., occupying 80% of the volume of the porous hollow suspended ball), and then the porous hollow suspended ball loaded with the slow-release carbon source material M1 is filled in the bioreactor and mixed with the acclimated sludge of Preparation Example 1 in the bioreactor (the weight ratio of M1 to the acclimated sludge is 1:15), and the filling amount of the slow-release carbon source material is 32 g / L of the bioreactor;

[0251] Step (S2) water feeding: wastewater with a C / N ratio of 2:1 is introduced into the bioreactor to contact the mixture of the slow-release carbon source material and the acclimated sludge (the ratio of the acclimated sludge to the incoming wastewater is 300 mg:1 L);

[0252] After the water feeding in step (S3) is completed, the wastewater is subjected to a denitrification reaction under denitrification conditions (oxygen content of 0.4, temperature of 28°C, pH of 7, hydraulic retention time of 6 h, and stirring speed of 150 rpm) to obtain denitrified water, and then the obtained denitrified water is allowed to stand for 1 h;

[0253] Step (S4) water discharge: the denitrified water after standing in step (S3) is discharged from the bioreactor;

[0254] The sum of the water feeding time and the water discharge time is 1 h.

[0255] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0256] Example 8

[0257] The slow-release carbon source material and the biological denitrification experiment are prepared according to the method of Example 1, except that:

[0258] III. Biological denitrification experiment:

[0259] Step (S1) filling of slow-release carbon source material: the slow-release carbon source material M1 is loaded into a porous hollow suspended ball (diameter of 10 cm, and the porous diameter on the surface is 4 mm), and the loading rate is 90% (i.e., 90% of the volume of the porous hollow suspended ball is occupied), and then the porous hollow suspended ball loaded with the slow-release carbon source material M1 is filled in the bioreactor and mixed with the acclimated sludge of Preparation Example 1 in the bioreactor (the weight ratio of M1 to the acclimated sludge is 1:25), and the filling amount of the slow-release carbon source material is 28 g / L of the bioreactor;

[0260] Step (S2) water feeding: wastewater with a C / N ratio of 4:1 is introduced into the bioreactor to contact the mixture of the slow-release carbon source material and the acclimated sludge (the ratio of the acclimated sludge to the incoming wastewater is 250 mg:1 L);

[0261] After the water feeding in step (S3) is completed, the wastewater is subjected to a denitrification reaction under denitrification conditions (oxygen content of 0.4, temperature of 28°C, pH of 7, hydraulic retention time of 6 h, and stirring speed of 150 rpm) to obtain denitrified water, and then the obtained denitrified water is allowed to stand for 1 h;

[0262] Step (S4) water discharge: the denitrified water after standing in step (S3) is discharged from the bioreactor;

[0263] The sum of the water feeding time and the water discharge time is 1 h.

[0264] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0265] Example 9

[0266] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that in step (S1), the weight ratio of M1 to the acclimated sludge was 1:35.

[0267] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0268] Example 10

[0269] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that in step (S1), the filling amount of the slow-release carbon source material was 42 g / L of the bioreactor.

[0270] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0271] Example 11

[0272] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that in step (S1), the acclimated sludge of Preparation Example 1 was replaced with an equal amount of the acclimated sludge of Preparation Example 2.

[0273] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0274] Example 12

[0275] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that in step (S2), the ratio of the acclimated sludge in the bioreactor to the incoming sewage was 400 mg:1 L.

[0276] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0277] Example 13

[0278] The slow-release carbon source material and the biological denitrification experiment were prepared according to the method of Example 1, except that in step (S3), the denitrification conditions included an oxygen content of 0.6, a temperature of 22°C, a pH of 8, a hydraulic retention time of 14 h, and a stirring speed of 120 rpm.

[0279] The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0280] Comparative Example 1

[0281] The biological denitrification experiment was performed according to the method of Example 1, except that the slow-release carbon source material M1 was replaced with an equal amount of the slow-release carbon source material D1.

[0282] The influent COD, effluent COD, and nitrogen removal rate for each denitrification cycle were measured, and the measurement results are shown in Table 4. Figures 4-6 The total amount of denitrification and the carbon release cycle are shown in Table 4.

[0283] Comparative Example 2

[0284] The biological denitrification experiment was carried out according to the method of Example 1, except that the slow-release carbon source material M1 was replaced with an equal amount of slow-release carbon source material D2.

[0285] The influent COD, effluent COD and nitrogen removal rate of each denitrification cycle were determined, and the results are shown in Table 4. Figures 4-6

[0286] Comparative Examples 3-9

[0287] The biological denitrification experiment was carried out according to the method of Example 1, except that the slow-release carbon source material M1 was replaced with an equal amount of slow-release carbon source material D3-D9, respectively.

[0288] The influent COD, effluent COD and nitrogen removal rate of each denitrification cycle were determined, and the results are shown in Table 4.

[0289] Comparative Example 10

[0290] Blank group experiment.

[0291] The biological denitrification experiment was carried out according to the method of Example 1, except that no slow-release carbon source material was added.

[0292] The influent COD, effluent COD and nitrogen removal rate of each denitrification cycle were determined, and the results are shown in Table 4. Figures 4-6

[0293] Test Example 1

[0294] The slow-release carbon source materials M1-M6 and D1-D9 were respectively subjected to water carbon release experiments:

[0295] 5 g of each of the above slow-release carbon source materials was weighed and added to a corresponding 500 ml conical flask, 500 ml of distilled water was added to each flask, and the mouth of the flask was sealed with a rubber plug. The conical flasks were placed on a 30°C constant temperature shaker at a speed of 150 rpm for 7 days.

[0296] The leaching liquid was sampled at 0, 1, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120, 144, and 168 h, respectively. After each sampling, the conical flasks were thoroughly replaced with water. The change of COD with time during the carbon release process was simulated using a second-order kinetic equation, and the kinetic characteristics of the carbon release of the slow-release carbon source materials M1-M6 and D1-D9 were recorded.

[0297] The expression of the pseudo-second-order kinetic equation is:

[0298]

[0299] ​​c—COD concentration in solution during carbon release process of slow-release carbon source material per unit mass, mg / (g·L);

[0300] c m —saturated COD concentration released by slow-release carbon source material per unit mass in solution, mg / (g·L);

[0301] K—mass transfer coefficient, mg / (h·g·L), indicating carbon release resistance, the larger K indicates that the carbon release process is less resistant, and the organic carbon is easier to release;

[0302] t 1 / 2 —time used when the released COD reaches half of the saturated concentration, h, t 1 / 2 The smaller t is, the shorter the time used to reach half of the saturated concentration, and the faster the carbon release speed.

[0303] The quasi-second-order kinetics equation expressions of slow-release carbon source materials M1, D1 and D2 are shown in Table 3, and the fitting curves are shown in Table 3.

[0304] Table 1: Acclimation water formula

[0305]

[0306] Table 2: Trace element solution formula

[0307]

[0308] Table 3

[0309]

[0310] Table 4

[0311]

[0312] From Figure 1 (A)-(C) shows that before denitrification, the surfaces of the three carbon sources have more wrinkles and gullies, and have pore structures, which are beneficial to the attachment of microorganisms. Compared with Comparative Examples 1 and 2, the surface of M1 in Example 1 has more dense wrinkles and gullies, and more uniform pores; from Figure 1 (a)-(c) shows that after denitrification, the pore structure of the surface of M1 further increases, and the pore structure of the surface of D1 is less; the wrinkles of the surface of D2 increase; it is shown that when sodium acetate and sugarcane residue are used as carbon sources, M1 can form more dense pore structures after carbon source release, which is more beneficial to the attachment and growth of microorganisms.

[0313] From Figure 2 (A)-(C) shows that the C element of M1, D1 and D2 is uniformly distributed, which is beneficial to the growth of the attached denitrifying bacteria on the surface, and the uneven part may be due to the existence of surface wrinkles and gullies; fromFigure 2 As shown in (a)-(c), the N element in M1, D1, and D2 is uniformly distributed and present in low amounts, having little impact on TN detection during the experiment. Overall, this indicates that the carbon source is uniformly embedded and effectively utilized during the fabrication of the slow-release carbon source material. Figure 2 As shown in (D)-(F), the C content on the surface of the slow-release carbon source material is higher than the N content.

[0314] from Figure 3 It can be seen that when the carbon release process of the slow-release carbon source material is fitted using the pseudo-second-order kinetic equation, the R² values ​​are all above 0.97. Therefore, the carbon release process of each slow-release carbon source material follows the pseudo-second-order kinetic equation. The corresponding kinetic equations and parameter calculations are shown in Table 2. As can be seen from Table 2, the K value of M1 is less than D1 and greater than D2. To a certain extent, this can alleviate the problem of rapid release rate caused by the easy solubility of sodium acetate in water when it is used alone as an encapsulated carbon source. This can reduce the impact of excessive initial carbon release on water quality. At the same time, it can alleviate the shortcomings of large carbon release resistance and slow carbon release when sugarcane bagasse is used alone as a carbon source. Moreover, compared to D1, the mass transfer coefficient K of M1 decreased by 25.2%, but the Cm of M1 decreased by only 12.6% compared to D1. This indicates that the sustained-release carbon source material prepared by combining sodium acetate and alkalized bagasse as carbon sources with the hydrogel framework is not a simple superposition of the carbon release effects when sodium acetate and bagasse are used as carbon sources alone. Instead, it combines the advantages of both to achieve the effect of reducing the carbon source release rate but releasing a large amount of carbon source during the carbon release cycle.

[0315] from Figures 4-6 It can be seen that in the first denitrification cycle, the nitrogen removal rate of Example 1 was slightly lower than that of Comparative Example 1. However, in the second and early stages of the third denitrification cycle, the nitrogen removal rate of Example 1 rebounded and was higher than that of Comparative Example 1. Analysis suggests that in the first denitrification cycle, because the denitrifying bacteria had just begun to attach to the surface of the slow-release carbon source material M1, the amount attached was small, and the carbon release from M1 was less than that from D1 in the initial stage. Therefore, Comparative Example 1 had a higher nitrogen removal rate. However, because M1 has more wrinkles, grooves, and pores on its surface, more denitrifying bacteria were adsorbed on the surface over time. Furthermore, the carbon source release rate of M1 was not significantly different from that of D1, allowing more denitrifying bacteria on the M1 surface to more quickly receive the released carbon source, thus improving the nitrogen removal rate. From the third denitrification cycle onwards, due to the synergistic effect of M1's higher adsorption capacity for denitrifying bacteria and higher carbon source release rate, the nitrogen removal rate of Example 1 was higher than that of Comparative Example 1 and remained at a high level.

[0316] Compared with the Example 4 in which the preparation conditions of the slow-release carbon source material are not in the preferred range, the porosity of the slow-release carbon source material M1 prepared in Example 1 is 58%, the porosity of the hydrogel skeleton is 71%, the specific surface area is 15.8 m2 / g, the total denitrification amount can reach 95%, and the carbon release period can reach 215 h when the slow-release carbon source material M1 is used for biological denitrification of wastewater. 2

[0317] Compared with the Example 5 in which the alkali treatment conditions of the bagasse raw material are not in the preferred range, the alkali treatment of the bagasse raw material in Example 1 is carried out at 25°C for 24 h using a 1.5 wt% sodium hydroxide solution, and the alkali-treated bagasse obtained is used to prepare the slow-release carbon source material M1 for biological denitrification of wastewater, which can effectively improve the total denitrification amount and the carbon release period.

[0318] Compared with the Example 6 in which the particle size of the alkali-treated bagasse is 0.8 mm, the slow-release carbon source material M1 prepared in Example 1 using alkali-treated bagasse with a particle size of 0.2 mm has higher porosity and specific surface area, which effectively improves the total denitrification amount and the carbon release period.

[0319] As can be seen from Example 1 and Examples 7-14, Example 1 using the preferred biological denitrification method of the present application has a higher total denitrification amount and better denitrification effect.

[0320] Compared with Comparative Example 1 in which sodium acetate is used alone to prepare the slow-release carbon source material and Comparative Example 2 in which alkali-treated bagasse is used alone to prepare the slow-release carbon source material, the slow-release carbon source material M1 prepared in Example 1 using a combination of sodium acetate and alkali-treated bagasse has higher porosity and specific surface area, which effectively improves the total denitrification amount and the carbon release period. According to the analysis, although the initial release rate of sodium acetate in D1 is fast and the carbon release amount is large, the lack of alkali-treated bagasse in the combination leads to too low porosity and specific surface area of D1, which is not conducive to the adsorption and biofilm formation of microorganisms, and also makes the attachment area and attachment amount of microorganisms on the material surface low, which is not conducive to the metabolic growth of microorganisms, ultimately resulting in poor denitrification effect. Moreover, due to the fast early release, the carbon release capacity is insufficient in the later period, resulting in a short carbon release period. Although D2 prepared in Comparative Example 2 has a high specific surface area due to the many wrinkles on the material surface, the slow release rate of the alkali-treated bagasse leads to a low carbon release amount, which makes the effect of improving the carbon-nitrogen ratio poor, and overall leads to a short carbon release period and a low total denitrification amount.

[0321] ​Compared with the weight ratio of about 1:0.2 of the comparative example 3 of the alkali-treated bagasse and sodium acetate, the slow-release carbon source material M1 prepared by compounding the alkali-treated bagasse and sodium acetate in a weight ratio of 1:1 in the embodiment 1 has greater porosity and specific surface area, effectively improving the total amount of denitrification and the carbon release period.

[0322] Compared with the comparative example 4 of using corn stalk residue and sodium acetate for compounding and the comparative example 5 of using corn stalk residue alone, the slow-release carbon source material M1 prepared by compounding the alkali-treated bagasse and sodium acetate in the embodiment 1 has higher total amount of denitrification and carbon release period for biological denitrification treatment of wastewater.

[0323] Compared with the comparative example 6 of using glucose and alkali-treated bagasse for compounding and the comparative example 7 of using starch and alkali-treated bagasse for compounding, the slow-release carbon source material M1 prepared by compounding the alkali-treated bagasse and sodium acetate in the embodiment 1 has higher total amount of denitrification for biological denitrification treatment of wastewater.

[0324] Compared with the comparative example 8 of using 25 parts by weight of alkali-treated bagasse and 5 parts by weight of sodium acetate to prepare a slow-release carbon source material with 70 parts by weight of a hydrogel precursor, the slow-release carbon source material M1 prepared by using 25 parts by weight of alkali-treated bagasse and 25 parts by weight of sodium acetate with 50 parts by weight of a hydrogel precursor in the embodiment 1 has higher total amount of denitrification and carbon release period for biological denitrification treatment of wastewater. It is believed that the embodiment 1 adopts a more preferred ratio of raw material usage, not only has a more suitable porosity and specific surface area for adsorbing microorganisms to form more uniform biofilm, but also ensures that the release amount of carbon source is maintained in a more suitable range, while taking into account the longer carbon release period and more stable carbon-nitrogen ratio environment, thereby comprehensively improving the denitrification effect.

[0325] Compared with the comparative example 9 of using bagasse raw material and sodium acetate for compounding to prepare a slow-release carbon source material, the slow-release carbon source material prepared by compounding the alkali-treated bagasse and sodium acetate in the embodiment 1 has more excellent porosity and specific surface area, and has a longer carbon release period, effectively improving the total amount of denitrification. It is believed that the comparative example 9 uses bagasse raw material, which contains a small amount of sugar (such as disaccharides and monosaccharides), although the initial carbon release amount is higher, but the sustained carbon release capacity is poor; and because the structure of the bagasse raw material and the structure of the hydrogel skeleton cannot play a synergistic role, leading to poor biofilm formation ability, poor uniformity of the microbial membrane, small membrane area, and further reducing the denitrification effect.

[0326] It should be noted that the foregoing examples have been provided merely for the purposes of illustration and are not intended to limit the application in any way. Descriptions and examples of materials and processes of the application are intended to be illustrative not limiting. Any modifications of the application and other applications of the application will occur to those skilled in the art to which the application pertains and many options for modification of the application will suggest themselves. The application lies in the broadest aspects of the technological concepts involved. Descriptions and examples of specific chemical materials and processes are intended to be illustrative of the application and it is intended that requests for patent protection be limited to one of the specific embodiments described above, described in the following claims, and any equivalents thereof.

Claims

1. A method of treating sewage, characterised in that, The method comprises: contacting sewage with a mixture of a slow-release carbon source material and acclimated sludge, and then carrying out a denitrification treatment on the sewage under denitrification conditions; The slow-release carbon source material comprises a hydrogel framework and a carbon source carried by the hydrogel framework; The carbon source comprises alkali-treated bagasse and sodium acetate; The hydrogel framework comprises a porous structure formed by polyvinyl alcohol and sodium alginate; The specific surface area of the slow-release carbon source material is 5-25 m 2 / g; The preparation method of the slow-release carbon source material comprises the following steps: Step (1): alkali treatment is performed on bagasse raw material, and after drying and crushing, alkali-treated bagasse is obtained; Step (2): 36-42 parts by weight of polyvinyl alcohol and 4-6 parts by weight of sodium alginate are added to 450-550 parts by volume of water and stirred to prepare a hydrogel precursor; Step (3): 20-30 parts by weight of the alkali-treated bagasse obtained in step (1) and 20-30 parts by weight of sodium acetate are mixed with 32-66 parts by weight of the hydrogel precursor obtained in step (2) to form a slow-release carbon source material precursor, and the slow-release carbon source material precursor is cross-linked and solidified under the action of a cross-linking agent; The composition of the bagasse raw material comprises 18-22 wt% lignin, 40-50 wt% cellulose, 25-30 wt% hemicellulose, and 1.5-3 wt% sugar; In step (1), the alkali treatment is performed in an alkali solution, and the alkali solution is a sodium hydroxide solution; The concentration of the alkali solution is 1-2 wt%; The amount of the alkali solution is 350-450 parts by volume relative to 35-45 parts by weight of the bagasse raw material; In step (1), the conditions of the alkali treatment include a temperature of 20-25°C and a time of 20-24 h; In step (1), the alkali-treated bagasse raw material is washed to a pH of 7 before drying; In step (2), the stirring conditions include a temperature of 95°C and a time of 2 h; The stirring speed in step (2) is 130-150 rpm, the stirring frequency is 1 time / 20 min, and the stirring time is 10-20 min / time; In step (3), the molding conditions include a temperature of -20°C and a time of 12 h; In step (3), the cross-linking and solidification is performed by immersing the slow-release carbon source material precursor into a cross-linking agent solution, and the cross-linking agent solution is a saturated boric acid solution containing 4 wt% CaCl2; The cross-linking and solidification conditions include a temperature of 4°C and a time of 24 h.

2. The method of claim 1, wherein, The denitrification treatment is carried out in a bioreactor, and the content of the slow-release carbon source material in the bioreactor is 20-35 g / L of the bioreactor; And / or, in the mixture of the slow-release carbon source material and the acclimated sludge, the weight ratio of the slow-release carbon source material to the acclimated sludge is 1:10-30; And / or, during the denitrification treatment, the ratio of the sewage to the acclimated sludge is 1L:200-350 mg.

3. The method of claim 2, wherein, The content of the slow-release carbon source material is 28-32 g / L of the bioreactor.

4. The method according to claim 2 or 3, characterized in that, The weight ratio of the slow-release carbon source material to the acclimated sludge is 1:15-25.

5. The method according to claim 2 or 3, characterized in that, The ratio of the sewage to the acclimated sludge is 1L:250-300mg.

6. The method of claim 1 or 2, wherein, The carbon-nitrogen molar ratio of the sewage is 2-8:1; And / or, the denitrification conditions include: dissolved oxygen content ≤0.5mg / mL; temperature is 25-35℃; pH value is 7-7.9; hydraulic retention time is 5-12h; stirring speed is 130-150rpm; And / or, the method further comprises: after the denitrification treatment is completed, the obtained denitrified water is left to stratify, and then the denitrified water in the upper layer is discharged.

7. The method of claim 6, wherein, The carbon-nitrogen molar ratio of the sewage is 2-4:

1.

8. The method of claim 6, wherein, The denitrification conditions include: dissolved oxygen content is 0.2-0.4mg / mL; temperature is 28-32℃; pH value is 7-7.5; hydraulic retention time is 6-8h; stirring speed is 135-145rpm.

9. The method according to any one of claims 1-3 and 7, characterized in that, The acclimated sludge is obtained by the following acclimation method: Step (S01) mixes the sludge with acclimation water under acclimation conditions, stirs for 5-14h, then leaves to stand, and then removes the supernatant; Step (S02) continues to add acclimation water to the sludge from which the supernatant has been removed, and repeats step (S01); Step (S03) repeats step (S02) until the total nitrogen removal rate of the supernatant is >80%, and the acclimation is completed. The mixed liquid after the sludge and the acclimation water are mixed has a suspended solid concentration of 7000-8000mg / L.

10. The method of claim 9, wherein, Step (S01) mixes the sludge with acclimation water under acclimation conditions, stirs for 6-12h, then leaves to stand, and then removes the supernatant.

11. The method of claim 9, wherein, Step (S03) repeats step (S02) until the total nitrogen removal rate of the supernatant is 85%-95%, and the acclimation is completed.

12. The method of claim 9, wherein, The mixed liquid after the sludge and the acclimation water are mixed has a suspended solid concentration of 7500-8000mg / L.

13. The method of claim 9, wherein, The acclimation conditions include: acclimation temperature is 20-40℃; dissolved oxygen content is 0.1-0.5mg / mL; and / or, the acclimation water includes 90-110 mg / L of COD; 30-50 mg / L of N-NO3 - ; 6-10 mg / L of total phosphorus; 2-5 mg / L of trace elements.

14. The method of claim 13, wherein, The acclimation conditions include: acclimation temperature is 25-38℃; dissolved oxygen content is 0.2-0.5mg / mL.

15. The method according to claim 13 or 14, characterized in that, The acclimation water includes 95-105 mg / L of COD; 35-45 mg / L of N-NO3 - ; 7-9 mg / L of total phosphorus; and 3-5 mg / L of trace elements.

16. The method according to any one of claims 1-3, 7 and 10-14, characterized in that, The method further comprises: first loading the slow-release carbon source material into a porous hollow suspended ball, then filling the porous hollow suspended ball loaded with the slow-release carbon source material in a bioreactor, and mixing the slow-release carbon source material and the acclimated sludge in the bioreactor to obtain a mixture of the slow-release carbon source material and the acclimated sludge; And / or, the diameter of the porous hollow suspended ball is 6-10cm; And / or, the pore size of the porous hollow suspended ball is 2-4mm; And / or, the total volume of the slow-release carbon source material in the porous hollow suspended ball is 80%-90% of the volume of the porous hollow suspended ball.

17. The method according to any one of claims 1-3, 7 and 10-14, characterized in that, The porosity of the slow-release carbon source material is 20%-80%; And / or, the porosity of the hydrogel framework is 30%-90%; And / or, the particle size of the alkali-treated bagasse is 0.1mm-0.5mm; And / or, the composition of the alkali-treated bagasse contains 16-20wt% lignin, 28-35wt% cellulose, and 15-20wt% hemicellulose; and / or the specific surface area of the slow-release carbon source material is 6-22 m 2 / g.

18. The method of claim 17, wherein, The porosity of the slow-release carbon source material is 40%-80%.

19. The method of claim 17, wherein, The porosity of the hydrogel skeleton is 50%-90%.

20. The method of claim 17, wherein, The particle size of the alkali-treated bagasse is 0.1mm-0.3mm.

21. The method of claim 17, wherein, The specific surface area of the slow-release carbon source material is 8-20 m 2 / g.

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