Landfill leachate anaerobic-denitrification treatment process and system based on waste molasses synergistic interaction

Abstract

The invention discloses a landfill leachate anaerobic-denitrification treatment process and system based on waste molasses synergistic interaction, and belongs to the technical field of sewage treatment. The process comprises the following steps: (1) carrying out two-stage anaerobic digestion on the landfill leachate to remove organic matters and recover biogas, wherein first-stage anaerobic digestion adopts medium-temperature (35 + / -2 DEG C) anaerobic digestion, and second-stage anaerobic digestion adopts high-temperature (55 + / -1 DEG C) anaerobic digestion; (2) removing impurities from the waste molasses, diluting the waste molasses, mixing the diluted waste molasses with activated sludge, fermenting under an anaerobic condition to generate fermentation liquor rich in volatile fatty acid, and adding the fermentation liquor into a denitrification reactor; and (3) constructing an anaerobic-denitrification synergistic system, and increasing the denitrification rate by using the charcoal-loaded nano zero-valent iron (nZVI at BC) as an electronic mediator. According to the method, resource utilization of the waste molasses is realized, the problem of imbalance of the carbon nitrogen ratio of the landfill leachate is solved, anaerobic digestion and nitrification and denitrification processes are coupled, efficient nitrogen removal and organic matter removal are realized, and meanwhile, the sludge yield and the operation cost are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to an anaerobic-denitrification treatment process and system for landfill leachate based on the synergistic enhancement of waste molasses. Background Art

[0002] As a high-concentration organic wastewater with complex components, the treatment difficulties of landfill leachate mainly focus on characteristics such as high COD, high ammonia nitrogen, and low carbon-nitrogen ratio. Existing treatment technologies generally have problems such as low denitrification efficiency, high operating costs, and risks of secondary pollution, which are specifically manifested as follows:

[0003] First, there is a contradiction between carbon source supply and denitrification efficiency. Traditional denitrification processes mostly use commercial carbon sources such as methanol and sodium acetate. Although a high denitrification rate can be achieved, there are problems such as high reagent costs and potential safety hazards in storage and transportation. Although agricultural waste (such as straw) or industrial by-products (such as molasses) have the potential as carbon sources, direct application is easily inhibited by anti-nutritional factors such as lignin and phenols, resulting in a decrease in the activity of denitrifying bacteria. For example, Patent CN113264588A proposes using molasses and humic acid fermentation broth as a composite carbon source, but the process parameters are not optimized for the characteristics of landfill leachate, and directly adding unfermented molasses can lead to the following problems: First, the macromolecular sugars in molasses need to be hydrolyzed into monosaccharides before they can be utilized by denitrifying bacteria, and the reaction lag is significant; second, the residual colloids, pigments and other impurities increase the effluent chromaticity and COD; third, excessive addition may cause sludge bulking.

[0004] Second, there are defects in the connection between anaerobic treatment and denitrification processes. Existing projects often use single-stage anaerobic digestion (UASB or IC reactor) to reduce COD. Although the organic matter removal rate can reach 80-90%, the contribution to TN removal is limited, and the residual volatile fatty acids (VFAs) will interfere with the subsequent denitrification process. Patent CN102105409A proposes a three-stage anaerobic digestion system for treating brewery waste, which significantly improves the methane production rate, but this process does not introduce any denitrification functional modules (such as nitrification / denitrification), resulting in no substantial improvement in the total nitrogen removal rate.

[0005] Third, there is a bottleneck in electron transfer efficiency. The denitrification process depends on the electron transfer efficiency between microorganisms and electron donors. Although conventional biochar carriers can adsorb pollutants, their low conductivity (conductivity < 10 S / m) results in low electron utilization efficiency. Although nano-zero-valent iron (nZVI) can provide electrons through the oxidation reaction of Fe 0 →Fe 2+ it is prone to agglomeration and surface passivation, and the attenuation rate of the electron supply amount reaches 60% / week in practical applications.

[0006] Fourth, the resource utilization is insufficient. Existing technologies mostly focus on pollutant removal and neglect the value recovery of by-products. For example, the biogas generated in the anaerobic stage is affected by impurities such as hydrogen sulfide, and the methane content is generally lower than 60%. Moreover, as a by-product of the sugar industry, molasses will cause resource waste and environmental pressure if not properly treated.

[0007] The above technical defects result in the common problems faced by existing leachate treatment systems, such as unqualified denitrification, high operating costs, and serious equipment corrosion. Therefore, it is urgent to develop a new treatment process with high efficiency, low consumption, and resource recycling to achieve the synergistic effect of pollutant removal and energy recovery. Summary of the Invention

[0008] Due to problems such as the imbalance of carbon-nitrogen ratio, the high proportion of refractory organic matter, and the high cost of traditional carbon sources in landfill leachate, the biological denitrification efficiency is low and the operating cost remains high. In view of the above pain points, the present invention proposes a synergistic treatment process and system that couples biological enhancement and material regulation, and achieves the dual goals of efficient pollutant removal and energy recovery through the combination of multiple technologies and parameter optimization.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] The present invention provides an anaerobic-denitrification treatment process for landfill leachate with synergistic enhancement based on molasses, comprising the following steps:

[0011] (a) Sequentially introducing the landfill leachate into a first-stage mesophilic anaerobic reactor and a second-stage thermophilic anaerobic reactor for cascade anaerobic digestion, wherein: the first-stage mesophilic anaerobic reactor controls the temperature at 33-37°C and the hydraulic retention time (HRT) at 4-6 days; the second-stage thermophilic anaerobic reactor controls the temperature at 54-56°C and the HRT at 2.5-3.5 days;

[0012] (b) After the molasses is filtered and purified by membrane to remove impurities, it is diluted to a moisture content of 15-45%, added to a fermentation tank and inoculated with activated sludge containing acid-producing bacteria. The mass ratio of the volatile solids (VS) of the activated sludge to the molasses is 1:2. Nitrogen source, phosphorus source, and trace elements are supplemented, and the pH is controlled at 7-10, the temperature at 22-42°C, and the stirring speed at 125-150 revolutions per minute, and anaerobic fermentation is carried out for 3-12 days to obtain a molasses fermentation broth rich in VFAs;

[0013] (c) Adding the molasses fermentation broth obtained in step (b) to the denitrification reactor at a C / N ratio of 4.5-5.5, and simultaneously adding a biochar-supported nano-zero valent iron material (nZVI@BC) with a dosage of 0.8-1.2 g / L. Introducing the effluent from the second-stage thermophilic anaerobic reactor into the denitrification reactor to carry out the nitrification-denitrification process;

[0014] (d) Control the dissolved oxygen (DO) ≤ 0.5 mg / L and the pH value to 7.2-7.8 during the denitrification stage to complete the removal of total nitrogen. The remaining sludge is concentrated and dehydrated and then transported for disposal.

[0015] Preferably, the primary mesophilic anaerobic reactor in step (a) is an upflow anaerobic sludge blanket (UASB), the secondary high-temperature anaerobic reactor is an expanded granular sludge blanket (EGSB), and the volume ratio of the two-stage reactors is 1:0.6-0.8.

[0016] Preferably, the waste molasses in step (b) is selected from one or more mixtures of beet molasses, cane molasses, glucose molasses or corn molasses, the nitrogen source is urea or ammonium chloride, and the addition amount is 0.5-1.5 g / L; the phosphorus source is potassium dihydrogen phosphate or disodium hydrogen phosphate, and the addition amount is 0.2-0.8 g / L; the trace elements are at least three of the sulfates or chlorides of iron, copper, manganese, zinc, magnesium, cobalt and molybdenum, and the total concentration is 0.1-1.0 g / L.

[0017] Preferably, the preparation method of the nZVI@BC material in step (c) comprises: preparing biochar by oxygen-limited pyrolysis of wood waste at 600-800°C, activating the biochar with a mass fraction of 5% KOH solution, and obtaining a biochar with a specific surface area of ​​≥800m 2 / g; Fe was reduced by liquid phase reduction 3+ The zero-valent iron is loaded in the pores of the biochar, with a loading amount of 12 to 15 wt % and a particle size distribution of 20 to 80 nm.

[0018] Preferably, the denitrification reactor in step (c) is a sequencing batch reactor (SBR), which is internally provided with a plurality of inclined guide plates, the guide plate inclination angle is 45 to 60 degrees, the filling rate of the packing area is 30 to 40%, and an online oxidation-reduction potential (ORP) sensor is provided to control the amount of carbon source added in linkage.

[0019] Preferably, the surface of the guide plate is coated with a nitrifying bacteria immobilization gel layer, and the gel is made by embedding a sodium alginate-polyvinyl alcohol composite carrier and an enriched bacterial community in a mass ratio of 1:3.

[0020] The present invention also provides an anaerobic-denitrification treatment system for landfill leachate based on synergistic enhancement of waste molasses, comprising: two-stage anaerobic reaction units (1-UASB, 2-EGSB) connected in sequence; a biogas purification storage unit (3-desulfurization tower, 4-gas cabinet); a waste molasses fermentation unit (5-membrane filtration component, 6-fermentation tank, 7-liquid storage tank) and a denitrification reaction unit (8-SBR, with built-in 9-nZVI@BC filler and 10-guide plate structure).

[0021] Preferably, a microporous aeration disc is arranged at the bottom of the SBR. A gas flow regulating valve is connected between the aeration disc and the air pump, and DO-pH linkage control is realized through a PLC controller, meeting one of the following conditions: when DO > 0.5 mg / L, aeration is automatically turned off and stirring is started; when pH < 7.2, a NaHCO₃ solution with a mass fraction of 0.5% is injected.

[0022] Preferably, for the application of the process in the treatment of industrial wastewater containing high concentrations of nitrates, step (a) is replaced by only retaining the first-stage anaerobic treatment, and the proportion of denitrifying carbon source added is adjusted to C / N = 3.8 - 4.2.

[0023] Preferably, for the application of the nZVI@BC material as an electron mediator in enhancing short-cut denitrification of sewage, the nitrite accumulation rate is ≥ 60% by regulating the material dosage.

[0024] The anaerobic-denitrification treatment process and system for landfill leachate based on the synergistic enhancement of waste molasses of the present invention have the following technical advantages:

[0025] One is the carbon source directional conversion and precise control technology. Active sludge rich in acid-producing bacteria is used to ferment waste molasses, effectively degrading sucrose, glucose, etc., releasing VFAs, and increasing the bioavailability of the carbon source to more than 85%. Based on the real-time monitoring value of ORP (set threshold -50 to -100 mV) in the denitrification reactor, the dosage of the carbon source is adjusted through the PLC controller in linkage to ensure that the C / N ratio is stable within the range of 4.5 - 5.5, avoiding secondary pollution caused by excessive carbon source.

[0026] The second is the electron transfer chain strengthening mechanism. Using high-specific-surface-area biochar as a carrier, nano-zero-valent iron particles are loaded by the liquid-phase reduction method to prepare a nano-zero-valent iron-biochar composite material (nZVI@BC), and a "Fe 0 →Fe 2+ →Fe 3+ " multi-stage electron transfer path is constructed. This material not only directly participates in the denitrification reaction as an electron donor, but its mesoporous structure can also enrich denitrifying bacteria (the biofilm density is increased by 40%), increasing the denitrification rate to 1.8 - 2.1 kg N / (m 3 ·d). An iron-carbon microelectrolysis zone is set in the SBR, and the microcurrent formed by nZVI@BC and Cl - in the leachate is used to continuously activate the activity of denitrifying enzymes, delay the passivation of the iron surface, and extend the material life to more than 120 days.

[0027] Thirdly, it is a two-stage anaerobic energy cascade utilization process. Adopting a temperature grading control strategy, the first-stage mesophilic anaerobic digestion (35±2°C) preferentially decomposes easily degradable organic substances (such as fatty acids and alcohols), and the second-stage thermophilic anaerobic digestion (55±1°C) specifically degrades long-chain fatty acids and refractory substances, achieving a cascade removal of COD (total removal rate ≥ 95%). By controlling the HRT in the high-temperature stage (2.5 - 3.5 days) and regulating the pH (6.8 - 7.2), thermophilic methanogens (such as Methanothermobacter) are enriched, increasing the methane volume fraction in biogas to 68 - 72% and reducing the H2S concentration to <50mg / m 3 .

[0028] Fourthly, it is system integration and intelligent control. In the SBR, multi-layer guide plates with an inclination angle of 55° are set, and the surface is coated with an alginate-polyvinyl alcohol immobilized nitrifying bacteria layer (embedding density ≥ 10 8 CFU / g), realizing the synchronous operation of nitrification-denitrification zones and shortening the hydraulic retention time by 30%.

[0029] The present invention has the following beneficial effects: The COD removal rate of this process is ≥ 95%, the TN removal rate is ≥ 94%, the carbon source cost is reduced by 52%, the biogas production rate reaches 0.5 - 0.6m 3 / kg COD, and the lifespan of the nZVI@BC material is ≥ 120 days. It is applicable to the treatment of high-ammonia-nitrogen wastewater such as landfill leachate and food waste biogas slurry, and has the characteristics of high efficiency, economy and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the process flow chart of the present invention.

[0031] Figure 2 is the system structure schematic diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] In the following embodiments, unless otherwise specified for materials and treatment technologies, it indicates that they are conventional commercially available materials or conventional treatment technologies in the art.

[0034] Example 1

[0035] Take the leachate from a domestic waste landfill with a COD of 12,500 mg / L, a TN of 680 mg / L, and a C / N ratio of 8.2. It passes through a first-stage medium-temperature UASB (35 ± 1 °C, HRT = 5 days, upflow velocity 0.8 m / h) and a second-stage high-temperature EGSB (55 ± 1 °C, HRT = 3 days, upflow velocity 2.5 m / h) in sequence. The COD is reduced to 3,200 mg / L and 420 mg / L in stages, and the total removal rate reaches 96.6%; meanwhile, the biogas production rate is 0.55 m 3 / kg COD, and the methane content is 70%. The waste molasses uses cane molasses, diluted to a water content of 30%. Activated sludge is inoculated according to the VS ratio of waste molasses to activated sludge of 2:1, and urea (1.0 g / L), potassium dihydrogen phosphate (0.5 g / L), FeSO4 (0.3 g / L), and MnCl2 (0.2 g / L) are added. Fermentation is carried out for 7 days at pH 8.5, a temperature of 35 °C, and a stirring speed of 140 revolutions per minute to obtain a fermentation broth with a VFAs concentration of 6,500 mg / L. It is added to the SBR filled with nZVI@BC material (specific surface area 920 m 2 / g, Fe loading 13.5%) at C / N = 5.0 (dosage 1.0 g / L, baffle inclination angle 55°). Control DO = 0.3 mg / L, pH = 7.5. After running for 8 hours, the TN drops from 220 mg / L to 38 mg / L, and the denitrification rate reaches 1.92 kg N / (m 3 ·d), the nitrite accumulation is < 3 mg / L, the sludge production rate is only 0.15 kg DS / ton of water, and the carbon source cost is 18.5 yuan / ton of water, with the best comprehensive performance.

[0036] Example 2

[0037] Adjust the temperature of the first-stage anaerobic reaction to 38 °C (original 35 °C), shorten the HRT of the second-stage anaerobic to 2 days (original 3 days), extend the fermentation time of waste molasses to 9 days (original 7 days), and reduce the C / N dosing ratio to 4.0 (original 5.0). After treatment, the COD of the leachate drops from 12,500 mg / L to 875 mg / L (removal rate 93%), the TN drops from 680 mg / L to 75 mg / L (removal rate 89%), and the biogas production rate drops to 0.48 m 3 / kg COD (methane content 65%), and the denitrification rate drops to 1.65 kgN / (m 3 ·d). Analysis shows that the increase in the temperature of the first-stage anaerobic inhibits the activity of methanogens, and the insufficient C / N causes carbon source competition among denitrifying bacteria, resulting in a decrease in denitrification efficiency. This example verifies the key role of precise regulation of temperature and HRT in the stability of the system.

[0038] Example 3

[0039] For kitchen waste biogas slurry (TN = 820 mg / L, COD = 18000 mg / L, C / N = 5.5), the process was adjusted to only one-stage mesophilic UASB treatment (HRT = 6 days), and the COD decreased to 2100 mg / L; the dosing ratio of molasses fermentation broth was increased to C / N = 6.0, and the dosing amount of nZVI@BC was increased to 1.2 g / L. After 10 hours of operation in the denitrification stage, the TN decreased from 820 mg / L to 82 mg / L (removal rate 90%), the total COD removal rate was 94%, and the biogas production rate was 0.51 m 3 / kg COD (methane content 68%). The sludge production rate was 0.18 kg DS / ton of water, and the carbon source cost was 19.8 yuan / ton of water. The results show that under the condition of low carbon-nitrogen ratio, by increasing the carbon source dosing amount and material loading amount, high-efficiency denitrification can still be maintained, verifying the scenario adaptability of the process.

[0040] Control Example 1

[0041] A single UASB anaerobic reactor (35°C, HRT = 7 days) was used, the carbon source was sodium acetate (C / N = 5.0), and the nZVI@BC material was not used. After treatment, the COD decreased from 12500 mg / L to 1500 mg / L (removal rate 88%), the TN decreased from 680 mg / L to 190 mg / L (removal rate 72%), and the denitrification rate was only 0.85 kg N / (m 3 ·d), and the nitrite accumulation reached 35 mg / L. The biogas production rate was 0.38 m 3 / kg COD (methane content 58%), the carbon source cost was 39.6 yuan / ton of water, and the sludge production rate was 0.30 kg DS / ton of water. This result highlights the significant disadvantages of the traditional process in terms of denitrification efficiency, operating cost, and by-product control.

[0042] Control Example 2

[0043] The two-stage anaerobic digestion treatment step was completely omitted (i.e., the leachate was not treated by UASB and EGSB), and the leachate directly entered the denitrification SBR (initial COD = 12500 mg / L, TN = 680 mg / L), and other conditions were the same as in Example 1. After treatment, the COD removal rate was only 58% (effluent COD = 5250 mg / L): denitrifying bacteria could not effectively degrade high-concentration refractory organic matters (such as long-chain fatty acids, lignin derivatives); the TN removal rate was 67% (TN decreased from 680 mg / L to 224 mg / L): high-concentration COD caused carbon source competition and inhibited the activity of denitrifying bacteria; the biogas production rate was 0: no methane was produced due to the absence of the anaerobic fermentation link; the sludge production rate was 0.45 kg DS / ton of water: high-load shock led to sludge bulking; the operating cost was 32.6 yuan / ton of water: additional carbon source needed to be added to compensate for the COD not anaerobically degraded.

[0044] Control Example 3

[0045] Using commercial sucrose to replace the waste molasses fermentation broth in Example 1, adding it at the same C / N = 5.0, and keeping other conditions exactly the same as in Example 1. The TN removal rate was measured to be 83% (TN decreased from 220 mg / L to 37 mg / L), the denitrification rate was 1.45 kg N / (m 3 ·d), the COD removal rate was 96.2% (the same as in Example 1), but the carbon source cost increased to 52.8 yuan / ton of water.

[0046] Comparative Example 4

[0047] The waste molasses was directly diluted to COD = 52000 mg / L without fermentation treatment, and other conditions were the same as in Example 1. The TN removal rate was only 64%, the COD removal rate decreased to 88%, and the sludge yield increased sharply to 0.38 kg DS / ton of water.

[0048] The effects of the examples and comparative examples are compared as shown in the following table:

[0049] Table 1 Comparative analysis of the effects of each example and comparative example

[0050]

[0051] In Example 1, through two-stage anaerobic digestion temperature grading, waste molasses fermentation pretreatment and the addition of nZVI@BC material, a COD removal rate of 96.6% and a TN removal rate of 94.4% were achieved, and the carbon source cost was reduced by 53.3% (compared with Comparative Example 1). Examples 2 and 3 show that the process still maintains high efficiency (TN removal rate ≥ 89%) in parameter fluctuations (such as temperature, HRT) and scenario expansion (low carbon-nitrogen ratio wastewater), verifying its robustness. Due to the lack of grading treatment and electron transfer enhancement in the comparative examples, the denitrification rate and biogas production rate decreased by 55.7% and 30.9% respectively. The present invention is significantly superior to the traditional process in terms of pollutant removal, resource recovery and economy.

[0052] In Example 1, the stepwise degradation of organic matter in the anaerobic section (UASB removes easily degradable COD → EGSB degrades difficult-to-degrade COD) provides suitable influent conditions (COD = 420 mg / L) for denitrification, avoids carbon source competition, and at the same time recovers biogas energy (0.55 m 3 / kg COD). Due to the lack of this collaborative design in Comparative Example 2, additional carbon source needs to be added (cost increased by 76%), and the sludge production increased sharply to 0.45 kg DS / ton of water. The COD removal rate (58%) and TN removal rate (67%) of Comparative Example 2 are significantly lower than those of Example 1 (96.6%, 92.8%), proving that two-stage anaerobic treatment is the core link to break through the bottleneck of high-concentration organic matter degradation.

[0053] In Example 1, the TN removal rate (92.8%) was significantly higher than that of sucrose (83%) and untreated molasses (64%), demonstrating the necessity of fermentation treatment to break down inhibitors. Although the COD removal rate in Comparative Example 3 was similar to that in Example 1, the carbon source cost increased by 2.85 times, and the denitrification rate decreased by 24.5% due to the lack of trace elements. In Comparative Example 4, phenolic substances caused severe biological inhibition, and the TN removal rate was only 68.9% of that in Example 1, and the sludge disposal cost offset the price advantage of the carbon source. The results of the comparative examples prove that the molasses fermentation process and the addition of nZVI@BC material are essential technical features and are indispensable. If only molasses is used and the pretreatment is omitted (Comparative Example 4), or it is replaced with other carbon sources (Comparative Example 3), the high-efficiency denitrification and low-cost goals claimed in the present invention cannot be achieved.

[0054] Comprehensive comparison shows that the "two-stage anaerobic digestion + carbon source pretreatment + nZVI@BC" technical chain of the present invention is inseparable: if the anaerobic digestion treatment is omitted (Comparative Example 2), the system will collapse; if the carbon source pretreatment is omitted (Comparative Example 4), toxicity inhibition will occur; if nZVI@BC is omitted (Comparative Example 1), the denitrification rate will drop sharply.

[0055] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. The anaerobic-denitrification treatment process of landfill leachate based on synergistic enhancement of waste molasses is characterized by: The following steps are involved: (a) passing the landfill leachate into a primary mesophilic anaerobic reactor and a secondary thermophilic anaerobic reactor in sequence for cascade anaerobic digestion, wherein: the primary mesophilic anaerobic reactor is controlled at a temperature of 33-37° C. and a hydraulic retention time (HRT) of 4-6 days; the secondary thermophilic anaerobic reactor is controlled at a temperature of 54-56° C. and a HRT of 2.5-3.5 days; (b) after removing impurities through membrane filtration, the waste molasses is diluted to a moisture content of 15-45%, added to a fermentation tank and inoculated with activated sludge containing acid-producing bacteria, wherein the mass ratio of volatile solids (VS) of the activated sludge to the waste molasses is 1:2, a nitrogen source, a phosphorus source and trace elements are supplemented, the pH is controlled to 7-10, the temperature is 22-42° C., the stirring speed is 125-150 rpm, and anaerobically fermented for 3-12 days to obtain a waste molasses fermentation liquid rich in volatile fatty acids (VFAs); (c) adding the waste molasses fermentation liquid obtained in step (b) to a denitrification reactor at a C / N ratio of 4.5 to 5.5, and adding biochar-loaded nano zero-valent iron material (nZVI@BC) at a dosage of 0.8 to 1.2 g / L, and introducing the effluent from the secondary high-temperature anaerobic reactor into the denitrification reactor to carry out nitrification and denitrification processes; (d) Control the dissolved oxygen (DO) ≤ 0.5 mg / L and the pH value to 7.2-7.8 during the denitrification stage to complete the removal of total nitrogen. The remaining sludge is concentrated and dehydrated and then transported for disposal.

2. The process according to claim 1, characterized in that The first-stage mesophilic anaerobic reactor in step (a) is an upflow anaerobic sludge blanket (UASB), the second-stage high-temperature anaerobic reactor is an expanded granular sludge blanket (EGSB), and the volume ratio of the two-stage reactors is 1:0.6-0.

8.

3. The process according to claim 1, characterized in that The waste molasses in step (b) is selected from one or more mixtures of beet molasses, cane molasses, glucose molasses or corn molasses; the nitrogen source is urea or ammonium chloride, and the addition amount is 0.5-1.5 g / L; the phosphorus source is potassium dihydrogen phosphate or disodium hydrogen phosphate, and the addition amount is 0.2-0.8 g / L; the trace elements are at least three of the sulfates or chlorides of iron, copper, manganese, zinc, magnesium, cobalt and molybdenum, and the total concentration is 0.1-1.0 g / L.

4. The process according to claim 1, characterized in that The preparation method of the nZVI@BC material in step (c) comprises: preparing biochar by oxygen-limited pyrolysis of wood waste at 600-800°C, activating the biochar with a mass fraction of 5% KOH solution, and obtaining a biochar with a specific surface area of ​​≥800m 2 / g; Fe was reduced by liquid phase reduction 3+ The zero-valent iron is loaded in the pores of the biochar, with a loading amount of 12 to 15 wt % and a particle size distribution of 20 to 80 nm.

5. The process according to claim 1, characterized in that The denitrification reactor in step (c) is a sequencing batch reactor (SBR), which is internally provided with a plurality of inclined guide plates, the guide plate inclination angle is 45 to 60 degrees, the filling rate of the packing area is 30 to 40%, and an online ORP sensor is provided to control the amount of carbon source added in linkage.

6. The sequencing batch reactor according to claim 5, characterized in that: The surface of the guide plate is coated with a nitrifying bacteria immobilized gel layer, and the gel is made by embedding a sodium alginate-polyvinyl alcohol composite carrier and an enriched bacterial community in a mass ratio of 1:

3.

7. The anaerobic-denitrification treatment system of landfill leachate based on synergistic enhancement of waste molasses is characterized by include: Two-stage anaerobic reaction unit (1-UASB, 2-EGSB) connected in sequence; biogas purification and storage unit (3-desulfurization tower, 4-gas cabinet); waste molasses fermentation unit (5-membrane filtration component, 6-fermentation tank, 7-liquid storage tank) denitrification reaction unit (8-SBR, built-in 9-nZVI@BC filler and 10-guide plate structure).

8. The system according to claim 7, characterized in that A microporous aeration plate is arranged at the bottom of the SBR, a gas flow regulating valve is connected between the aeration plate and the air pump, and DO-pH linkage regulation is realized through a PLC controller to meet one of the following conditions: when DO>0.5mg / L, aeration is automatically turned off and stirring is turned on; when pH<7.2, a NaHCO3 solution with a mass fraction of 0.5% is injected.

9. Application of the process according to claim 1 in the treatment of industrial wastewater containing high concentration of nitrates, characterized in that: The step (a) is replaced by retaining only the primary anaerobic treatment, and the addition ratio of the denitrification carbon source is adjusted to C / N=3.8-4.

2.

10. The use of the nZVI@BC material according to claim 4 as an electron mediator in enhancing short-range denitrification of sewage, characterized in that: By adjusting the amount of material added, the nitrite accumulation rate is made ≥60%.

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