A method and system for efficient denitrification of landfill leachate

Abstract

The present invention discloses a method and system for efficient denitrification of landfill leachate, comprising the following steps: diluting molasses wastewater, then adding a composite enzyme preparation containing cellulase, pectinase, and α-amylase for enzymatic hydrolysis pretreatment to obtain a pretreatment solution; inoculating the pretreatment solution with a compound microbial community containing Clostridium butyricum and Anaerobiospirillum succiniciproducens for anaerobic fermentation, and separating to obtain a liquid carbon source containing acetic acid and propionic acid and fermentation residues; mixing the fermentation residues with waste sugar residues for pyrolysis to prepare biochar; synchronously adding the liquid carbon source and biochar to a denitrification reactor for denitrification of landfill leachate. The present invention enables the total nitrogen removal load of the landfill leachate denitrification system to be increased by 60% compared with a single carbon source process, and realizes a resource utilization rate of sugar-making solid waste > 95%. The present invention achieves the dual goals of efficient denitrification and solid waste resource utilization through the coordinated treatment of molasses wastewater and waste sugar residues.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial solid waste co - treatment and wastewater deep denitrification, and specifically relates to a method and system for efficient denitrification of landfill leachate. Background Art

[0002] Due to the high concentration of ammonia nitrogen and refractory organic matter in landfill leachate, its deep denitrification treatment has always been a technical difficulty in the field of environmental engineering. Traditional processes mostly adopt the "nitrification - denitrification" biological treatment route. In the denitrification stage, since the carbon - nitrogen ratio (C / N) of leachate is generally lower than 2:1, a large amount of exogenous carbon source needs to be added to maintain the metabolic requirements of denitrifying bacteria. According to statistics, the carbon source procurement cost accounts for 35 - 45% of the total cost of leachate treatment. Commercial carbon sources such as sodium acetate and methanol seriously restrict the economy and stability of the treatment system due to problems such as high transportation and storage risks and easy exceeding of effluent COD when added in excess. Although some studies have tried to utilize the internal carbon source in landfill leachate, for example, CN114956485A discloses a biological denitrification method for enhancing the utilization of internal carbon source, but it is extremely sensitive to the fluctuation of influent water quality, and the total nitrogen removal rate is often lower than 70% in actual engineering.

[0003] To reduce the carbon source cost, in recent years, researchers have turned to developing organic waste fermentation broth as an alternative carbon source. For example, CN104324930A proposes to use volatile fatty acids (VFAs) produced by anaerobic fermentation of food waste as a denitrification carbon source. However, the proportion of propionic acid in its fermentation products is too high, resulting in a reduction of about 30% in the denitrification rate compared with sodium acetate, and it is easy to cause a sudden drop in the system pH. Another type of solution such as CN106145348A uses the fermentation broth of sewage treatment plant sludge, but there are risks of heavy metal accumulation and pathogen residues, which limit its large - scale application.

[0004] The mainstream disposal methods of molasses and sugarcane residues generated annually in the sugar industry are as follows: molasses is used to produce alcohol or feed additives. However, alcohol fermentation consumes a large amount of steam energy, and the viscosity characteristics of molasses in feed additive processing lead to high drying energy consumption problems; sugarcane residues are mostly directly incinerated as fuel or simply composted, resulting in problems such as greenhouse gas emissions and limited land use. It is worth noting that molasses is rich in fermentable sugars such as sucrose and glucose, while sugarcane residues contain a large amount of cellulose and ash such as SiO2 and CaO, and theoretically have the potential for co - resource utilization.

[0005] Based on the current state of the art, the following problems exist in the fields of denitrification and nitrogen removal from landfill leachate and resource utilization of sugar industry solid waste: (1) The cost of commercial carbon sources is high, while waste-derived carbon sources have technical bottlenecks such as low activity and poor stability; (2) The treatment of sugar industry waste remains at the level of single-component utilization, lacking a collaborative treatment plan for molasses and sugarcane bagasse; (3) Traditional biochar preparation processes have not effectively integrated raw material compatibility and pore structure regulation, resulting in difficulty in synergistically coordinating adsorption-catalysis-carrier functions; (4) In the existing technology chain, links such as carbon source preparation, residue reuse, and process regulation are fragmented and have not formed a complete technical ecosystem of "treating waste with waste". Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background technology and provide a method and system for efficient nitrogen removal from landfill leachate based on the resource utilization of sugar industry waste, achieving the dual goals of efficient nitrogen removal and solid waste resource utilization.

[0007] To solve the above technical problems, the technical solution proposed by the present invention is as follows:

[0008] A method for efficient nitrogen removal from landfill leachate, comprising the following steps:

[0009] (a) Dilute molasses, and then add a composite enzyme preparation containing cellulase, pectinase, and α-amylase for enzymatic hydrolysis pretreatment to obtain a pretreatment solution;

[0010] (b) Inoculate the pretreatment solution with a complex microbial community containing Clostridium butyricum and Anaerobiospirillum succiniciproducens, carry out anaerobic fermentation, and separate to obtain a liquid carbon source containing acetic acid and propionic acid and fermentation residues;

[0011] (c) Mix the fermentation residues produced in step (b) with sugarcane bagasse and carry out pyrolysis to prepare biochar;

[0012] (d) Synchronously add the liquid carbon source obtained in step (b) and the biochar prepared in step (c) to a denitrification reactor for denitrification of landfill leachate.

[0013] As a further improvement, in the composite enzyme preparation in step (a), the enzyme activity ratio of cellulase, pectinase, and α-amylase is (3-5):(2-3):1.

[0014] As a further improvement, the enzymatic hydrolysis pretreatment in step (a) is carried out at 45-55 °C for 4-6 hours.

[0015] As a further improvement, the inoculation mass ratio of the complex microbial community in step (b) is Clostridium butyricum: Anaerobiospirillum succiniciproducens = 2:1 to 5:1, and the system alkalinity is maintained ≥ 2000 mg / L during the fermentation process.

[0016] As a further improvement, the anaerobic fermentation described in step (b) is carried out at pH = 5.8 - 6.5 and 35 - 38 °C for 48 - 72 hours.

[0017] As a further improvement, the liquid carbon source obtained in step (b) has a mass ratio of acetic acid to propionic acid of (1.5 - 2.5):1.

[0018] As a further improvement, the fermentation residue and the waste sugar residue described in step (c) are mixed at a mass ratio of 1:(0.5 - 2).

[0019] As a further improvement, the pyrolysis described in step (c) is carried out at 500 - 600 °C for 1 - 2 hours under oxygen-limited conditions to prepare biochar with a specific surface area ≥ 650 m 2 / g and a pore volume of 0.8 - 1.2 cm 3 / g.

[0020] As a further improvement, the liquid carbon source and the biochar described in step (d) are added at a mass ratio of (100 - 200):1.

[0021] The present invention also provides a high-efficiency denitrification system for landfill leachate, comprising:

[0022] An enzymatic hydrolysis reactor, a fermentation tank, a membrane separation unit and a liquid carbon source storage tank connected in series in sequence;

[0023] A mixer, a pyrolysis furnace and a biochar storage tank connected in sequence; the mixer is communicated with the residue outlet of the fermentation tank and is used for mixing the fermentation residue and the waste sugar residue;

[0024] And a mixing and dosing device, a denitrification reactor integrated with an ORP sensor and an automatic dosing system interlocked with the sensor; the mixing and dosing device is used for mixing the discharges from the liquid carbon source storage tank and the biochar storage tank and dosing them into the denitrification reactor; the automatic dosing system is used for controlling the dosing rate of the mixing and dosing device.

[0025] The present invention aims to solve the technical problems of high cost of external carbon sources, single resource utilization path of traditional waste and poor system stability in the denitrification process of landfill leachate. By the collaborative treatment of molasses and waste sugar residue in the sugar industry, a closed-loop technology system of "directed fermentation - residue pyrolysis - functional coupling" is constructed to achieve the dual goals of high-efficiency denitrification and solid waste resource utilization.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1)For the first time, molasses wastewater and sugarcane waste residues are co-treated. After molasses wastewater is fermented to extract VFAs (volatile fatty acids), its residue is mixed with sugarcane waste residues for pyrolysis, solving the problem of single pore structure, improving the total nitrogen removal load of the landfill leachate denitrification system, and realizing the resource utilization of sugar industry waste.

[0028] (2)Cellulase, pectinase, and α-amylase are used to co-treat the complex polysaccharides in molasses wastewater, greatly improving the release rate of fermentable sugars; through the compounding of Clostridium butyricum and Anaerobiospirillum succiniciproducens, the mass ratio of acetic acid to propionic acid in the fermentation products is precisely regulated, making the denitrification activity of the carbon source high and stable.

[0029] (3)During the pyrolysis process, the cellulose in sugarcane waste residues is carbonized to form a microporous structure. The Ca and Fe elements in the ash of the fermentation residue combine with the Si element in the sugarcane waste residues to in-situ generate Ca-Fe-Si oxides, endowing the biochar with dual functions: adsorbing Cu in the leachate through surface complexation 2+ 、Zn 2+ , reducing the inhibition of heavy metals on denitrifying bacteria; accelerating the extracellular electron transfer of denitrifying bacteria and accelerating the denitrification process.

[0030] (4)During the startup period, biochar is added at a high dose of 5 - 8 g / L to quickly form a biofilm, and the concentration is reduced to 2 - 3 g / L during the stable period to maintain the system stability and avoid the blockage problem caused by excessive dosing.

[0031] (5)By integrating an ORP sensor, a pH probe, and an on-line nitrate nitrogen analyzer, data on the denitrification process are obtained in real time, and a carbon source dosing prediction model is constructed based on the LSTM neural network. The input parameters include real-time ORP, historical load, temperature fluctuations, etc., and the optimal COD / N ratio is output, greatly reducing the waste of carbon source and making the effluent COD stable < 100 mg / L.

[0032] The efficient denitrification method and system for landfill leachate based on the resource utilization of sugar industry waste of the present invention has the following advantages: First, the denitrification efficiency is significantly improved. The total nitrogen removal load of the system reaches 3.5 kg N / m 3 ·d, which is 67% higher than that of the traditional sodium acetate carbon source system, and the denitrification efficiency > 95%; Second, the operating cost is greatly reduced. The carbon source cost is reduced from 1.8 - 2.2 yuan / kg N in the traditional process to 0.5 - 0.7 yuan / kg N, and the comprehensive energy consumption is reduced by 60%; Third, the environmental benefits are prominent. Treating 10,000 tons of molasses wastewater and 20,000 tons of sugarcane waste residues per year can reduce CO2 emissions by about 36,000 tons, and simultaneously treat 50,000 cubic meters of leachate, realizing a circular economy model of "treating waste with waste". Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 is the process flow chart of the present invention;

[0035] Figure 2 is the structural schematic diagram of the system of the present invention. Specific Embodiments

[0036] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and the preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0039] Reference Figure 1 , in some specific embodiments, the method for highly efficient denitrification of landfill leachate of the present invention includes the following steps:

[0040] (a) Dilute the molasses wastewater, and then add a composite enzyme preparation containing cellulase, pectinase, and α - amylase for enzymatic hydrolysis pretreatment to obtain a pretreatment solution.

[0041] Molasses wastewater is a by - product of the sugar industry, a thick liquid remaining after extracting sugar from sugarcane or sugar beets, rich in sugars, mainly sucrose, glucose, fructose, etc.

[0042] In some embodiments, the molasses wastewater is diluted to COD = 80 - 150 g / L.

[0043] In some embodiments, in the added composite enzyme preparation, the enzyme activity ratio of cellulase, pectinase, and α - amylase is (3 - 5):(2 - 3):1.

[0044] In some embodiments, enzymatic hydrolysis pretreatment is carried out at 45 - 55 °C for 4 - 6 hours to increase the reducing sugar release rate to more than 90%.

[0045] Due to the enzymatic hydrolysis of cellulase, pectinase, and α-amylase, the pretreatment liquid mainly contains decomposition products, small-molecule substances such as sugars, organic acids, and amino acids.

[0046] (b) Inoculate the pretreatment liquid with a complex microbial community containing Clostridium butyricum and Anaerobierspirillum succiniproducens, carry out anaerobic fermentation, and separate to obtain a liquid carbon source containing acetic acid and propionic acid and fermentation residues.

[0047] In some embodiments, the inoculation mass ratio of the complex microbial community is Clostridium butyricum: Anaerobierspirillum succiniproducens = 2:1 to 5:1, and the alkalinity of the system is maintained ≥ 2000 mg / L by adding CaCO3 during the fermentation process. The inoculation volume fraction is 10 - 15%.

[0048] In some embodiments, anaerobic fermentation is carried out at pH = 5.8 - 6.5 and 35 - 38 °C for 48 - 72 hours.

[0049] In some embodiments, after fermentation, the fermentation broth is subjected to membrane separation to obtain a liquid carbon source with an acetic acid / propionic acid mass ratio of (1.5 - 2.5):1, and the content of volatile fatty acids in the liquid carbon source is ≥ 25 g / L.

[0050] The main metabolite of Clostridium butyricum is butyric acid, and acetic acid and propionic acid are also produced. The main metabolite of Anaerobierspirillum succiniproducens is succinic acid, and succinic acid can be further converted into acetic acid and propionic acid. The succinic acid pathway is an important pathway for the production of propionic acid.

[0051] Among organic acids, short-chain fatty acids (such as acetic acid, propionic acid, etc.) are easy to be utilized by microorganisms due to their short chains and small molecules, and can be used as carbon sources for biological denitrification. Especially acetic acid and propionic acid (acetic acid has the best effect) are easy to be absorbed and utilized by microorganisms, and are of better quality than butyric acid, etc., so it is necessary to produce acetic acid and propionic acid directionally.

[0052] Using the complex microbial community can achieve directional fermentation, that is, the main fermentation products are acetic acid and propionic acid, and the mass ratio of the two is (1.5 - 2.5):1. When acetic acid and propionic acid are mixed in the above ratio, the microbial community is richer and the denitrification effect is more stable. Compared with other fermentation products (such as alcohol), the denitrification activity is higher and more stable, and the energy consumption is low.

[0053] (c) Mix the fermentation residues produced in step (b) with waste sugar residues and carry out pyrolysis to prepare biochar.

[0054] In some embodiments, the waste sugar residues are the fiber residues after sugarcane pressing, with a moisture content ≤ 15%, a cellulose content ≥ 40%, and are crushed to a particle size ≤ 2 mm before mixing with the fermentation residues.

[0055] In some embodiments, the fermentation residue and the waste sugar residue are mixed at a mass ratio of 1:(0.5 - 2).

[0056] In some embodiments, pyrolysis is carried out at 500 - 600 °C for 1 - 2 hours under oxygen-limited conditions.

[0057] In some embodiments, biochar with a specific surface area ≥ 650 m 2 / g and a pore volume of 0.8 - 1.2 cm 3 / g is prepared. The surface of the biochar realizes the dual functions of heavy metal ion (such as Cu 2+ ) adsorption and electron transfer during the denitrification process through the self-generated Ca-Fe-Si oxides during the pyrolysis process, reducing the electron transfer resistance, promoting electron transfer, and accelerating the denitrification process.

[0058] The co-pyrolysis of fermentation residue - waste sugar residue has a higher specific surface area and a higher content of surface metal oxides compared with the pyrolysis of a single raw material.

[0059] (d) Synchronously add the liquid carbon source obtained in step (b) and the biochar prepared in step (c) to the denitrification reactor for the denitrification of landfill leachate.

[0060] In some embodiments, the liquid carbon source and the biochar are added at a mass ratio of (100 - 200):1. Alternatively, the biochar is added at 1 - 2% of the COD mass of the liquid carbon source.

[0061] In some embodiments, the feeding rate of the liquid carbon source is dynamically adjusted in combination with the on-line monitoring of ORP. The specific dynamic adjustment is as follows: when the ORP value is higher than -50 mV, increase the feeding amount of the liquid carbon source to COD / N = 5 - 6; when the ORP value is lower than -100 mV, decrease it to COD / N = 3 - 4.

[0062] In some embodiments, the biochar is added in stages, with the feeding amount in the startup period being 5 - 8 g / L and decreasing to 2 - 3 g / L in the stable period.

[0063] Reference Figure 2 In some specific embodiments, the high-efficiency nitrogen removal system for landfill leachate of the present invention includes:

[0064] An enzymatic hydrolysis reactor, a fermentation tank, a membrane separation unit, and a liquid carbon source storage tank connected in series in sequence;

[0065] A mixer, a pyrolysis furnace, and a biochar storage tank connected in sequence; the mixer is connected to the residue outlet of the fermentation tank and is used to mix the fermentation residue and the waste sugar residue;

[0066] as well as a mixed dosing device, a denitrification reactor integrated with an ORP sensor, and an automatic dosing system interlocked with the sensor; the mixed dosing device is used to mix the discharges from the liquid carbon source storage tank and the biochar storage tank and dose them into the denitrification reactor; the automatic dosing system is used to control the dosing rate of the mixed dosing device.

[0067] In some embodiments, the membrane separation unit uses an ultrafiltration membrane with a molecular weight cut-off of 5000 - 10000 Da, and the operating pressure is 0.2 - 0.5 MPa.

[0068] In some embodiments, the automatic dosing system is built-in with a control module based on a machine learning algorithm, and the input parameters include ORP, pH, NO3 - -N concentration, and an instruction for adjusting the carbon source dosing rate is output.

[0069] In view of the problems of low resource utilization rate of the traditional treatment methods for molasses and sugarcane waste residues and high cost of denitrification carbon sources, the present invention proposes a dual-path collaborative technology of "liquid waste fermentation - solid waste co-pyrolysis": molasses is subjected to composite enzymatic hydrolysis and then directionally fermented with specific anaerobic bacteria to obtain a liquid carbon source with an optimized acetic acid / propionic acid ratio; simultaneously, the fermentation residue is mixed with sugarcane waste residues for co-pyrolysis to prepare hierarchically porous biochar (a porous structure with different pore sizes), and the surface of which self-generates Ca-Fe-Si oxides to synchronously adsorb heavy metals and enhance electron transfer. Through the above technology, the total nitrogen removal load of the landfill leachate denitrification system is increased by 60% compared with the single carbon source process, and the resource utilization rate of sugar-making solid waste is > 95%. The present invention realizes the dual goals of efficient denitrification and solid waste resource utilization through the collaborative treatment of molasses and sugarcane waste residues.

[0070] Example 1

[0071] Step 1. Enzymatic hydrolysis pretreatment and directional fermentation of molasses

[0072] Take the molasses from a certain sugar factory (composition content: sucrose 52 - 58%, glucose 8 - 12%, fructose 5 - 8%, raffinose 4 - 6%, colloid 10 - 15%, ash 8 - 12%, where the ash contains 1.2 - 1.8 wt% Ca and 0.3 - 0.5 wt% Fe), dilute it to a COD of 90 g / L, add a composite enzyme preparation (cellulase 18 U / mL, pectinase 12 U / mL, α-amylase 6 U / mL, enzyme activity ratio 3:2:1), pretreat it at 50°C for 5 hours to increase the reducing sugar release rate to 94%. Subsequently, inoculate 12% by volume of a compound bacterial solution (Clostridium butyricum: Anaerobiospirillum succiniciproducens = 3:1), adjust the initial pH to 6.2, and anaerobically ferment at 36°C for 65 hours. After centrifugal separation of the fermentation broth, the total amount of VFAs is measured to be 27.8 g / L (acetic acid accounts for 63% and propionic acid accounts for 29%), the acetic acid / propionic acid mass ratio is 2.17, and the content of residual macromolecular organic matter is < 3%.

[0073] Step 2. Preparation of biochar by co-pyrolysis of fermentation residue and molasses residue

[0074] Mix the fermentation residue from Step 1 (ash containing 6.8 - 7.5 wt% CaO, 3.2 - 3.8 wt% Fe2O3, 2.1 - 2.8 wt% SiO2) with molasses residue (fibrous residue after sugarcane pressing, water content ≤ 15%, composition: 40 - 45% cellulose, 18 - 22% hemicellulose, 15 - 18% lignin, 10 - 12% ash, where ash contains 50 - 55 wt% SiO2, 8 - 10 wt% CaO, 15 - 20 wt% K2O) at a mass ratio of 1:1.5, crush to a particle size ≤ 1.5 mm, and place in a pyrolysis furnace. Heat to 600 °C at a rate of 10 °C / min under a nitrogen atmosphere and pyrolyze isothermally for 2 hours. The resulting biochar is tested to have a specific surface area of 780 m 2 / g, surface Ca-Fe-Si oxide content of 14.2 wt%, and Cu 2+ adsorption capacity of 145 mg / g. When this biochar is added to the denitrification system at 5 g / L, the electron transfer resistance can be reduced to 28 Ω·cm 2 , which is 42% less than that of traditional biochar.

[0075] Step 3. Operation of the dynamic coupling denitrification system

[0076] Use the leachate from a certain waste incineration plant (NO3 - -N concentration of 420 mg / L, C / N = 1.5), add the liquid carbon source obtained in Step 1 (initial COD / N = 5.5) and the biochar obtained in Step 2 (added at 1.5% of the COD mass of the liquid carbon source) to a 1.5 m 3 denitrification reactor. Through the ORP sensor linked to the variable frequency dosing pump, when ORP > -50 mV, increase the carbon source dosage to COD / N = 6.0, and when ORP < -100 mV, reduce it to COD / N = 3.5. After 30 days of operation, the TN removal load stabilizes at 3.6 kg N / m 3 ·d, the effluent TN < 10 mg / L, and the carbon source consumption is 0.65 kg COD / kg N, which is 72% lower than that of Comparative Example 1.

[0077] Example 2

[0078] Step 1. Enzymatic pretreatment and directional fermentation of molasses

[0079] The difference from Example 1 is that the ratio of Clostridium butyricum to Anaerobiospirillum succiniciproducens in the compound bacterial liquid is changed to 5:1, and other operations and parameters are the same as those in Example 1. After the fermentation broth is centrifuged and separated, the total amount of VFAs is measured to be 26.5 g / L (acetic acid accounts for 59%, propionic acid accounts for 31%), the mass ratio of acetic acid to propionic acid is 1.9, and the content of residual macromolecular organic matter is <3%.

[0080] Step 2-3 is the same as that in Example 1. After operating for 30 days, the TN removal load is stabilized at 3.4 kg N / m 3 ·d, the effluent TN < 10 mg / L, and the carbon source consumption is 0.7 kg COD / kg N.

[0081] Comparative Example 1: Denitrification with traditional sodium acetate carbon source

[0082] The difference from Example 1 lies in Step 3: Under the same landfill leachate conditions as in Example 1, sodium acetate is added, COD / N = 4.0, and the liquid carbon source and biochar of Example 1 are not used. The initial denitrification rate is 0.78 g NO3 - -N / gCOD, but after operating for 15 days, due to the accelerated biofilm shedding rate, the TN removal load drops to 2.3 kg N / m 3 ·d, the carbon source consumption reaches 1.8 kg COD / kg N, and sodium bicarbonate needs to be supplemented daily to maintain pH > 7.0.

[0083] Comparative Example 2: Pyrolysis biochar from a single raw material

[0084] The difference from Example 1 lies in Step 2: Only waste sugar residues (without adding fermentation residues) are pyrolyzed at 600 °C, and the specific surface area of the obtained biochar is only 520 m 2 / g, and the content of surface metal oxides is <5%. After being added to the system in Step 3 of Example 1, the TN removal load is 2.6 kg N / m 3 ·d, and the dosage needs to be increased to 10 g / L to maintain the effect, resulting in a three-fold increase in the reactor blockage frequency.

[0085] Comparative Example 3: Traditional molasses alcohol fermentation

[0086] The difference from Example 1 lies in Step 1: The homologous molasses in Example 1 is used for alcohol fermentation after enzymatic hydrolysis (instead of using the compound bacterial liquid fermentation in Example 1), fermented at pH 4.8 and 30 °C for 60 hours, the alcohol yield is 42 g / L, but the high-COD residual liquid needs to be treated additionally, and the comprehensive energy consumption reaches 2.6 GJ / ton of molasses, which is 136% higher than the directional fermentation process of the present invention.

[0087] The comparison of the effects of the examples and comparative examples is shown in the following table:

[0088] Table 1 Comparative Analysis of the Effects of Examples and Comparative Examples

[0089]

[0090] Through the closed-loop process of directional fermentation of molasses wastewater and co-pyrolysis of sugarcane waste, the present invention realizes the dual goals of efficient nitrogen removal from landfill leachate and resource utilization of sugarcane solid waste. The data of the examples show that the TN removal load is increased by 56% compared with the traditional sodium acetate process, and the long-term operation stability is significantly enhanced; the carbon source cost is reduced to 32% of the traditional process, and the dosage of biochar is reduced by 50%; the solid waste resource utilization rate > 96%, and the risks of heavy metal pollution and CO2 emissions are simultaneously reduced. The comparative examples verify the necessity of core innovations such as co-pyrolysis and dynamic dosing, highlighting the technical advancement and industrialization potential of the present invention.

[0091] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for efficient denitrification of landfill leachate, characterized in that, It includes the following steps: (a) Dilute the waste molasses, and then add a composite enzyme preparation containing cellulase, pectinase, and α-amylase for enzymatic hydrolysis pretreatment to obtain a pretreatment liquid; (b) Inoculate the pretreatment liquid with a compound microbial community containing Clostridium butyricum and Anaerobiospirillum succiniciproducens for anaerobic fermentation, and separate to obtain a liquid carbon source containing acetic acid and propionic acid and fermentation residues; (c) Mix the fermentation residues produced in step (b) with waste sugar residues and perform pyrolysis to prepare biochar; (d) Synchronously add the liquid carbon source obtained in step (b) and the biochar prepared in step (c) to a denitrification reactor for denitrification of landfill leachate.

2. The efficient denitrification method for landfill leachate according to claim 1, characterized in that In the composite enzyme preparation described in step (a), the enzyme activity ratio of cellulase, pectinase, and α-amylase is (3-5):(2-3):

1.

3. The high-efficiency nitrogen removal method for landfill leachate according to claim 1, characterized in that The enzymatic hydrolysis pretreatment described in step (a) is carried out at 45-55°C for 4-6 hours.

4. The method for highly efficient denitrification of landfill leachate according to any one of claims 1 to 3, characterized in that, The inoculation mass ratio of the compound microbial community described in step (b) is Clostridium butyricum: Anaerobiospirillum succiniciproducens = 2:1 to 5:1, and the system alkalinity is maintained ≥2000 mg / L during the fermentation process.

5. The method for highly efficient denitrification of landfill leachate according to any one of claims 1 to 3, characterized in that, The anaerobic fermentation described in step (b) is carried out at pH = 5.8-6.5 and 35-38°C for 48-72 hours.

6. The method for efficiently denitrifying landfill leachate according to any one of claims 1 to 3, characterized in that, A liquid carbon source with an acetic acid / propionic acid mass ratio of (1.5-2.5):1 is obtained in step (b).

7. The method for highly efficient denitrification of landfill leachate according to any one of claims 1 to 3, characterized in that In step (c), the fermentation residues and waste sugar residues are mixed at a mass ratio of 1:(0.5-2).

8. The high-efficiency denitrification method for landfill leachate according to any one of claims 1 to 3, characterized in that, The pyrolysis described in step (c) is carried out under oxygen-limited conditions at 500-600 °C for 1-2 hours to prepare biochar with a specific surface area ≥ 650 m 2 / g and a pore volume of 0.8-1.2 cm 3 / g.

9. The method for efficiently denitrifying landfill leachate according to any one of claims 1 to 3, characterized in that, The liquid carbon source and biochar described in step (d) are added at a mass ratio of (100-200):

1.

10. An efficient denitrification system for landfill leachate, characterized in that, It includes: An enzymatic hydrolysis reactor, a fermentation tank, a membrane separation unit, and a liquid carbon source storage tank connected in series in sequence; A mixer, a pyrolysis furnace, and a biochar storage tank connected in sequence; the mixer is connected to the residue outlet of the fermentation tank and is used to mix the fermentation residues with waste sugar residues; And a mixing and dosing device, a denitrification reactor integrated with an ORP sensor, and an automatic dosing system interlocked with the sensor; the mixing and dosing device is used to mix the materials discharged from the liquid carbon source storage tank and the biochar storage tank and add them to the denitrification reactor; the automatic dosing system is used to control the dosing rate of the mixing and dosing device.

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