High-efficiency denitrification method and system for landfill leachate

Abstract

The invention discloses an efficient denitrification method and system for landfill leachate, and the method comprises the following steps: diluting waste molasses, and then adding a compound enzyme preparation containing cellulase, pectinase and alpha-amylase for enzymolysis pretreatment to obtain a pretreatment solution; inoculating the pretreatment liquid with a compound flora containing clostridium butyricum and succinic acid-producing anaerobic spirillum, carrying out 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, and performing pyrolysis to prepare biochar; and synchronously adding the liquid carbon source and the biochar into a denitrification reactor, and carrying out denitrification on the landfill leachate. The total nitrogen removal load of the landfill leachate denitrification system is increased by 60% compared with that of a single carbon source process, and the sugar manufacturing solid waste recycling rate gt is achieved; 95%. According to the method disclosed by the invention, the dual goals of efficient denitrification and solid waste recycling are achieved through cooperative treatment of the waste molasses and the waste sugar residues in the sugar manufacturing process.

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] Landfill leachate is rich in high - concentration ammonia nitrogen and refractory organic matter, and 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 have problems such as high transportation and storage risks and easy exceeding of effluent COD when added in excess, which seriously restricts the economy and stability of the treatment system. Although some studies have tried to utilize the internal carbon source of 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 sugar waste produced by the sugar industry every year 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; sugar waste is 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, and sugar waste contains a large amount of cellulose and ash such as SiO2 and CaO, and theoretically has the potential for collaborative resource utilization.

[0005] Considering 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 there are technical bottlenecks in waste-derived carbon sources, 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 sugar cane residues; (3) Traditional biochar preparation processes have not effectively integrated raw material compatibility and pore structure regulation, resulting in difficulties in synergistically coordinating adsorption, catalysis, and carrier functions; (4) In the existing technology chain, links such as carbon source preparation, residue recycling, and process control are fragmented, and a complete "waste treatment with waste" technical ecosystem has not been formed. 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 solid waste, so as to achieve 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: A method for efficient nitrogen removal from landfill leachate, comprising the following steps: (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; (b) Inoculate the pretreatment solution with a complex 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 sugar cane residues and conduct 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.

[0008] 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.

[0009] As a further improvement, the enzymatic hydrolysis pretreatment in step (a) is carried out at 45 - 55 °C for 4 - 6 hours.

[0010] 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.

[0011] As a further improvement, the anaerobic fermentation in step (b) is carried out at pH = 5.8 - 6.5 and 35 - 38 °C for 48 - 72 hours.

[0012] As a further improvement, in step (b), a liquid carbon source with an acetic acid to propionic acid mass ratio of (1.5 - 2.5):1 is obtained.

[0013] As a further improvement, in step (c), the fermentation residue and the waste sugar residue are mixed at a mass ratio of 1:(0.5 - 2).

[0014] As a further improvement, the pyrolysis 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.

[0015] As a further improvement, the liquid carbon source and the biochar in step (d) are added at a mass ratio of (100 - 200):1.

[0016] The present invention also provides a high-efficiency denitrification system for landfill leachate, comprising: 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 communicated with the residue outlet of the fermentation tank for mixing the fermentation residue and the waste sugar residue; 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 materials discharged 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 to control the dosing rate of the mixing and dosing device.

[0017] 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. Through the coordinated 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.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) For the first time, molasses and waste sugar residue are coordinately treated. After the molasses is fermented to extract VFAs (volatile fatty acids), its residue is mixed with the waste sugar residue 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 the waste in the sugar industry.

[0019] (2) The complex polysaccharides in molasses wastewater were treated synergistically with cellulase, pectinase, and α-amylase, greatly improving the release rate of fermentable sugars. By compounding Clostridium butyricum and Anaerobiospirillum succiniciproducens, the mass ratio of acetic acid to propionic acid in the fermentation products was precisely regulated, resulting in a relatively high and stable denitrifying activity of the carbon source.

[0020] (3) During the pyrolysis process, the cellulose in the waste sugar residue was carbonized to form a microporous structure. The Ca and Fe elements in the ash of the fermentation residue combined with the Si element in the waste sugar residue to in-situ generate Ca-Fe-Si oxides, endowing the biochar with dual functions: adsorbing Cu 2+ and Zn 2+ in the leachate through surface complexation, reducing the inhibition of heavy metals on denitrifying bacteria; accelerating the extracellular electron transfer of denitrifying bacteria and accelerating the denitrification process.

[0021] (4) During the startup period, biochar was added at a high dose of 5 - 8 g / L to rapidly form a biofilm, and the concentration was reduced to 2 - 3 g / L during the stable period to maintain the system stability and avoid the blockage problem caused by excessive dosing.

[0022] (5) By integrating an ORP sensor, a pH probe, and an online nitrate nitrogen analyzer, data on the denitrification process were obtained in real time, and a carbon source dosing prediction model was constructed based on the LSTM neural network. The input parameters included real-time ORP, historical load, temperature fluctuations, etc., and the optimal COD / N ratio was output, greatly reducing the waste of the carbon source and keeping the effluent COD stable at < 100 mg / L.

[0023] The efficient denitrification method and system for landfill leachate based on the resource utilization of sugar industry waste in the present invention have 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 waste sugar residue 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". Brief Description of the Drawings

[0024] In order 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 following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 This is the process flow diagram of the present invention; Figure 2 This is the schematic structural diagram of the system of the present invention. Detailed implementation manners

[0026] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and in detail in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional 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.

[0028] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0029] Refer to Figure 1 , in some specific implementation manners, the method for highly efficient denitrification of landfill leachate of the present invention includes the following steps: (a) Dilute molasses wastewater, and then add a composite enzyme preparation containing cellulase, pectinase, and α-amylase for enzymatic hydrolysis pretreatment to obtain a pretreatment solution.

[0030] Molasses wastewater is a by-product of the sugar industry, which is a thick liquid remaining after extracting sugar from sugarcane or sugar beets, rich in sugars, mainly sucrose, glucose, fructose, etc.

[0031] In some embodiments, the molasses wastewater is diluted to COD = 80 - 150 g / L.

[0032] 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.

[0033] 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%.

[0034] Due to the enzymatic hydrolysis of cellulase, pectinase, and α-amylase, the pretreatment solution mainly contains decomposition products, small molecule substances such as sugars, organic acids, and amino acids.

[0035] (b) Inoculate the pretreatment solution with a compound 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.

[0036] In some embodiments, the inoculation mass ratio of the mixed flora is Clostridium butyricum: Anaerobiospirillum succiniciproducens = 2:1 to 5:1, and during the fermentation process, the alkalinity of the system is maintained at ≥2000 mg / L by adding CaCO3. The inoculation volume fraction is 10-15%.

[0037] In some embodiments, anaerobic fermentation is carried out at pH = 5.8-6.5 and 35-38 °C for 48-72 hours.

[0038] In some embodiments, after fermentation, the fermentation broth is subjected to membrane separation to obtain a liquid carbon source with a mass ratio of acetic acid to propionic acid of (1.5-2.5):1, and the content of volatile fatty acids in the liquid carbon source is ≥25 g / L.

[0039] The main metabolite of Clostridium butyricum is butyric acid, and acetic acid and propionic acid are also produced. The main metabolite of Anaerobiospirillum succiniciproducens is succinic acid, and succinic acid can be further formed into acetic acid and propionic acid. The succinic acid pathway is an important pathway for producing propionic acid.

[0040] 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.

[0041] Using the mixed flora 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. 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 stable, and the energy consumption is low.

[0042] (c) Mix the fermentation residue produced in step (b) with waste sugar residues and carry out pyrolysis to prepare biochar.

[0043] 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 being mixed with the fermentation residue.

[0044] In some embodiments, the fermentation residue and the waste sugar residues are mixed at a mass ratio of 1:(0.5-2).

[0045] In some embodiments, pyrolysis is carried out at 500-600 °C for 1-2 hours under oxygen-limited conditions.

[0046] In some embodiments, the prepared specific surface area is ≥650 m 2 / g, and the pore volume is 0.8-1.2 cm 3Biochar at a rate of / g. The surface of the biochar realizes the dual functions of heavy metal ion (such as Cu) adsorption and electron transfer during the denitrification process through self-generated Ca-Fe-Si oxides during the pyrolysis process, reduces the electron transfer resistance, promotes electron transfer, and accelerates the denitrification process. 2+ ), which reduces the electron transfer resistance, promotes electron transfer, and accelerates the denitrification process.

[0047] The co-pyrolysis of fermentation residue and waste sugar residue has a higher specific surface area and a higher content of surface metal oxides compared to the pyrolysis of a single raw material.

[0048] (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.

[0049] 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.

[0050] In some embodiments, the feeding rate of the liquid carbon source is dynamically adjusted in combination with 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, reduce it to COD / N = 3~4.

[0051] In some embodiments, the biochar is added in stages, with the addition amount being 5~8 g / L during the startup period and decreasing to 2~3 g / L during the stable period.

[0052] Reference Figure 2 , in some specific embodiments, the high-efficiency nitrogen removal system for landfill leachate of the present invention includes: An enzymolysis 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 residue and the waste sugar residue; And 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 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 mixed dosing device.

[0053] In some embodiments, the membrane separation unit uses an ultrafiltration membrane with a molecular weight cut-off of 5000~10000 Da and an operating pressure of 0.2~0.5 MPa.

[0054] In some embodiments, the automatic dosing system is built with a control module based on a machine learning algorithm, and the input parameters include ORP, pH, NO3 --N concentration, output the instruction for adjusting the carbon source feeding rate.

[0055] In view of the problems of low resource utilization rate in the traditional treatment methods of molasses and sugarcane waste residues and high cost of denitrifying carbon sources, the present invention proposes a dual-path collaborative technology of "liquid waste fermentation - solid waste co-pyrolysis": molasses is enzymatically hydrolyzed with a composite enzyme and then directionally fermented with specific anaerobic bacteria to produce 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 hierarchical porous biochar (a porous structure with different pore sizes), and the surface of which spontaneously generates Ca-Fe-Si oxides to simultaneously 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.

[0056] Example 1 Step 1. Enzymatic hydrolysis pretreatment and directional fermentation of molasses Take the molasses from a sugar factory (composition content: sucrose 52 - 58%, glucose 8 - 12%, fructose 5 - 8%, raffinose 4 - 6%, colloid 10 - 15%, ash 8 - 12%, and 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%. Then inoculate 12% by volume of the 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%, 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%.

[0057] Step 2. Preparation of co-pyrolysis biochar from fermentation residue - sugarcane waste residue 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 waste molasses residue (the fiber residue after sugarcane pressing, water content ≤ 15%, composition: cellulose 40 - 45%, hemicellulose 18 - 22%, lignin 15 - 18%, ash 10 - 12%, where the ash contains 50 - 55 wt% SiO2, 8 - 10 wt% CaO, 15 - 20 wt% K2O) at a mass ratio of 1:1.5, crush it to a particle size ≤ 1.5 mm and then place it in a pyrolysis furnace. Heat it to 600 °C at a rate of 10 °C / min under a nitrogen atmosphere and keep it pyrolyzed at a constant temperature for 2 hours. The obtained biochar, after testing, has a specific surface area of 780 m 2 / g, the content of surface Ca-Fe-Si oxides is 14.2 wt%, and the Cu 2+ adsorption capacity is 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.

[0058] Step 3. Operation of the dynamic coupling denitrification system Use the leachate from a certain waste incineration plant (NO3 - -N concentration 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 to link the variable frequency dosing pump, when ORP > -50 mV, increase the carbon source dosing amount to COD / N = 6.0, and when ORP < -100 mV, reduce it to COD / N = 3.5. After operating for 30 days, 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.

[0059] Example 2 Step 1. Enzymatic hydrolysis pretreatment and directional fermentation of waste molasses The difference from Example 1 is that the ratio of Clostridium butyricum to Anaerobiospirillum succinogenes in the compound bacterial solution is changed to 5:1, and other operations and parameters are the same as those in Example 1. After centrifugal separation of the fermentation broth, 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%.

[0060] Steps 2 - 3 are the same as those in Example 1. After operating for 30 days, the TN removal load stabilizes 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.

[0061] Comparative Example 1: Denitrification with traditional sodium acetate carbon source The difference from Example 1 lies in Step 3: Under the same landfill leachate conditions as in Example 1, sodium acetate was added, COD / N = 4.0, and the liquid carbon source and biochar of Example 1 were not used. The initial denitrification rate was 0.78 g NO3 - -N / gCOD, but after 15 days of operation, due to the accelerated biofilm shedding rate, the TN removal load decreased to 2.3 kg N / m 3 ·d, the carbon source consumption reached 1.8 kg COD / kg N, and sodium bicarbonate needed to be supplemented daily to maintain pH > 7.0.

[0062] Comparative Example 2: Pyrolytic biochar from a single raw material The difference from Example 1 lies in Step 2: Only waste molasses (without adding fermentation residues) was pyrolyzed at 600 °C, and the specific surface area of the obtained biochar was only 520 m 2 / g, and the content of surface metal oxides was < 5%. After being added to the system in Step 3 of Example 1, the TN removal load was 2.6 kg N / m 3 ·d, and the dosage needed to be increased to 10 g / L to maintain the effect, resulting in a three-fold increase in the reactor blockage frequency.

[0063] Comparative Example 3: Traditional waste molasses alcohol fermentation The difference from Example 1 lies in Step 1: The homologous waste molasses of Example 1 was used for alcohol fermentation after enzymatic hydrolysis (instead of fermentation with the compound bacterial solution of Example 1), fermented at pH 4.8 and 30 °C for 60 hours, and the alcohol yield was 42 g / L, but the high-COD residual liquid produced needed to be treated additionally, and the comprehensive energy consumption reached 2.6 GJ / ton of waste molasses, which was 136% higher than the directional fermentation process of the present invention.

[0064] The comparison of the effects of the examples and comparative examples is shown in the following table: Table 1 Comparative analysis of the effects of examples and comparative examples

[0065] The present invention realizes the dual goals of efficient nitrogen removal from landfill leachate and resource utilization of sugar production solid waste through a closed-loop process of directional fermentation of molasses wastewater and co-pyrolysis of sugar waste residue. 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 synchronously 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.

[0066] 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 efficiently denitrifying landfill leachate, characterized in that: The following steps are involved: (a) diluting the waste molasses, and then adding a composite enzyme preparation containing cellulase, pectinase and α-amylase to perform enzymatic pretreatment to obtain a pretreated liquid; (b) inoculating the pretreated liquid with a composite bacterial community containing Clostridium butyricum and succinic acid-producing anaerobic spirillum to perform anaerobic fermentation, and separating and obtaining a liquid carbon source containing acetic acid and propionic acid and a fermentation residue; (c) mixing the fermentation residue produced in step (b) with waste sugar residue and performing pyrolysis to prepare biochar; (d) The liquid carbon source obtained in step (b) and the biochar prepared in step (c) are simultaneously added to a denitrification reactor to perform denitrification of the landfill leachate.

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

1.

3. The method for efficient denitrification of landfill leachate according to claim 1, characterized in that: The enzymatic pretreatment in step (a) is performed at 45-55° C. for 4-6 hours.

4. The method for efficient denitrification of landfill leachate according to any one of claims 1 to 3, characterized in that: The inoculation mass ratio of the composite bacterial community in step (b) is Clostridium butyricum: Anaerobic Spirillum succinate-producing = 2:1 to 5:1, and the alkalinity of the system is maintained at ≥ 2000 mg / L during the fermentation process.

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

6. The method for efficient denitrification of landfill leachate according to any one of claims 1 to 3, characterized in that: Step (b) obtains a liquid carbon source with an acetic acid / propionic acid mass ratio of (1.5-2.5):

1.

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

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

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

1.

10. A highly efficient denitrification system for landfill leachate, characterized in that: include: An enzymatic hydrolysis reactor, a fermentation tank, a membrane separation unit and a liquid carbon source storage tank are sequentially connected in series; A mixer, a pyrolysis furnace, and a biochar storage tank are connected in sequence; the mixer is connected to the residue outlet of the fermentation tank and is used to mix the fermentation residue with the waste sugar residue; And a mixing and dosing device, a denitrification reactor with an integrated ORP sensor, and an automatic dosing system interlocked with the sensor; the mixing and dosing device is used to mix the outputs of 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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