Anaerobic-denitrification treatment process and system for landfill leachate based on synergistic effect of waste molasses

Abstract

This invention discloses an anaerobic-denitrification treatment process and system for landfill leachate based on the synergistic effect of waste molasses, belonging to the field of wastewater treatment technology. The process includes the following steps: (1) Landfill leachate undergoes two-stage anaerobic digestion to remove organic matter and recover biogas, wherein the first-stage anaerobic digestion adopts mesophilic (35±2℃) anaerobic digestion, and the second-stage anaerobic digestion adopts high-temperature (55±1℃) anaerobic digestion; (2) Waste molasses is mixed with activated sludge after impurity removal and dilution, and fermented under anaerobic conditions to generate a fermentation broth rich in volatile fatty acids, which is then added to the denitrification reactor; (3) An anaerobic-denitrification synergistic system is constructed, and the denitrification rate is enhanced by using biochar-supported nano-zero-valent iron (nZVI@BC) as an electron mediator. This invention realizes the resource utilization of waste molasses, and at the same time solves the problem of carbon-nitrogen ratio imbalance in landfill leachate. It couples anaerobic digestion with nitrification and denitrification processes to achieve efficient denitrification and organic matter removal, while reducing sludge production and operating costs.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an anaerobic-denitrification treatment process and system for landfill leachate based on the synergistic effect of waste molasses. Background Technology

[0002] Landfill leachate, a complex and high-concentration organic wastewater, presents significant challenges in treatment primarily due to its high COD, high ammonia nitrogen, and low carbon-to-nitrogen ratio. Existing treatment technologies generally suffer from low nitrogen removal efficiency, high operating costs, and the risk of secondary pollution, specifically manifested in the following ways:

[0003] First, there is a contradiction between carbon source supply and denitrification efficiency. Traditional denitrification processes often use commercial carbon sources such as methanol and sodium acetate, which can achieve high nitrogen removal rates, but have problems such as high reagent costs and safety hazards in storage and transportation. Agricultural waste (such as straw) or industrial by-products (such as molasses) have carbon source potential, but direct application is easily inhibited by anti-nutritional factors such as lignin and phenols, leading to a decrease in the activity of denitrifying bacteria. For example, patent CN113264588A proposes to use molasses and humic acid fermentation liquid as a composite carbon source, but it does not optimize process parameters for the characteristics of landfill leachate, and directly adding unfermented molasses can easily lead to the following problems: First, the large sugar molecules in molasses need to be hydrolyzed into monosaccharides before they can be utilized by denitrifying bacteria, resulting in a significant reaction lag; second, residual colloids, pigments and other impurities increase the color and COD of the effluent; third, excessive addition may cause sludge bulking.

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

[0005] Thirdly, the bottleneck of electron transfer efficiency. The denitrification process depends on the electron transfer efficiency between microorganisms and electron donors. While conventional biochar carriers can adsorb pollutants, their insufficient conductivity (<10 S / m) leads to low electron utilization. Although nano-zero-valent iron (nZVI) can transfer electrons through Fe... 0 →Fe 2+ The oxidation reaction provides electrons, but it is prone to aggregation and surface passivation. In practical applications, the electron supply decay rate reaches 60% / week.

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

[0007] The aforementioned technical deficiencies have led to widespread problems in existing leachate treatment systems, including inadequate nitrogen removal, high operating costs, and severe equipment corrosion. Therefore, there is an urgent need to develop a new, highly efficient, low-consumption, and resource-recycling treatment process to achieve synergistic effects in pollutant removal and energy recovery. Summary of the Invention

[0008] Landfill leachate suffers from problems such as an imbalanced carbon-to-nitrogen ratio, a high proportion of recalcitrant organic matter, and high costs of traditional carbon sources, resulting in low efficiency and high operating costs for biological nitrogen removal. This invention addresses these pain points by proposing a synergistic treatment process and system that couples bioaugmentation and material regulation. Through the combined use of multiple technologies and parameter optimization, it achieves the dual goals of efficient pollutant removal and energy recovery.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] This invention provides an anaerobic-denitrification treatment process for landfill leachate based on the synergistic effect of waste molasses, comprising the following steps:

[0011] (a) The landfill leachate is sequentially fed into a primary mesophilic anaerobic reactor and a secondary hyperthermic anaerobic reactor for cascade anaerobic digestion. The temperature of the primary mesophilic anaerobic reactor is controlled at 33–37°C, and the hydraulic retention time (HRT) is 4–6 days. The temperature of the secondary hyperthermic anaerobic reactor is controlled at 54–56°C, and the HRT is 2.5–3.5 days.

[0012] (b) After impurities are removed by membrane filtration, the waste molasses is diluted to a moisture content of 15-45%, added to a fermenter and inoculated with activated sludge containing acid-producing bacteria. The mass ratio of volatile solids (VS) of the activated sludge to waste molasses is 1:2. Nitrogen, phosphorus and trace elements are added, and the pH is controlled to 7-10, the temperature to 22-42℃, and the stirring speed to 125-150 rpm. Anaerobic fermentation is carried out for 3-12 days to obtain waste molasses fermentation liquid rich in VFAs.

[0013] (c) The waste molasses fermentation liquid obtained in step (b) is added to the denitrification reactor at a C / N ratio of 4.5 to 5.5. At the same time, biochar-supported nano zero-valent iron material (nZVI@BC) is added at a dosage of 0.8 to 1.2 g / L. The effluent from the secondary high-temperature anaerobic reactor is introduced into the denitrification reactor to carry out the nitrification-denitrification denitrification process.

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

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

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

[0017] Preferably, the preparation method of the nZVI@BC material in step (c) includes: preparing biochar from wood waste by oxygen-limited pyrolysis at 600-800℃, and activating it with a 5% KOH solution to achieve a specific surface area ≥800m². 2 / g; Fe was reduced using a liquid-phase reduction method. 3+ Loaded within the pores of biochar, the zero-valent iron loading is 12–15 wt%, and the particle size distribution is 20–80 nm.

[0018] Preferably, the denitrification reactor in step (c) is a sequencing batch reactor (SBR), which has multiple layers of inclined guide plates with an inclination angle of 45-60°, a packing rate of 30-40%, and is equipped with an online oxidation-reduction potential (ORP) sensor to control the carbon source addition.

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

[0020] This invention also provides an anaerobic-denitrification treatment system for landfill leachate based on the synergistic effect of waste molasses, comprising: a two-stage anaerobic reaction unit (1-UASB, 2-EGSB) connected in sequence; a biogas purification and storage unit (3-desulfurization tower, 4-gas holder); a waste molasses fermentation unit (5-membrane filter assembly, 6-fermentation tank, 7-storage tank); and a denitrification reaction unit (8-SBR, with built-in 9-nZVI@BC packing and 10-baffle structure).

[0021] Preferably, the SBR is equipped with a microporous aeration disc at the bottom, and a gas flow regulating valve is connected between the aeration disc and the air pump. The DO-pH linkage is controlled by a PLC controller to meet one of the following conditions: when DO>0.5mg / L, the aeration is automatically turned off and the stirring is turned on; when pH<7.2, a 0.5% NaHCO3 solution is injected.

[0022] Preferably, in the application of the process in the treatment of industrial wastewater containing high concentrations of nitrates, step (a) is replaced by retaining only the primary anaerobic treatment, and the denitrification carbon source addition ratio is adjusted to C / N = 3.8 to 4.2.

[0023] Preferably, the nZVI@BC material is used as an electron mediator in the enhanced short-cut denitrification of wastewater, and the nitrite accumulation rate is ≥60% by adjusting the amount of material added.

[0024] The anaerobic-denitrification treatment process and system for landfill leachate based on the synergistic effect of waste molasses, as described in this invention, has the following technical advantages:

[0025] Firstly, there is the technology for targeted carbon source conversion and precise control. Activated sludge rich in acid-producing bacteria is used to ferment waste molasses, effectively degrading sucrose, glucose, and other substances, releasing VFAs, and increasing the bioavailability of the carbon source to over 85%. Based on real-time monitoring values ​​of ORP (set threshold -50 to -100 mV) within the denitrification reactor, the carbon source dosage is adjusted via a PLC controller to ensure the C / N ratio remains stable within the range of 4.5 to 5.5, avoiding secondary pollution caused by excessive carbon source.

[0026] Second, the electron transport chain enhancement mechanism. Using high specific surface area biochar as a carrier, nano-zero-valent iron particles were loaded onto the biochar using a liquid-phase reduction method to prepare a nano-zero-valent iron-biochar composite material (nZVI@BC), constructing a "Fe 0 →Fe 2+ →Fe 3+ "Multi-level electron transport pathways. This material not only directly participates in the denitrification reaction as an electron donor, but its mesoporous structure can also enrich denitrifying bacteria (increasing biofilm density by 40%), thereby increasing the nitrogen removal rate to 1.8–2.1 kg N / (m²)." 3 ·d). An iron-carbon micro-electrolysis zone is set up inside the SBR, utilizing nZVI@BC to react with Cl in the leachate. - The generated microcurrent continuously activates denitrifying enzyme activity, delays iron surface passivation, and extends the material life to more than 120 days.

[0027] Thirdly, a two-stage anaerobic energy cascade utilization process is employed. A temperature-stage control strategy is used: the first stage, mesophilic anaerobic digestion (35±2℃), preferentially decomposes easily degradable organic matter (such as fruit acids and alcohols); the second stage, thermophilic anaerobic digestion (55±1℃), specifically degrades long-chain fatty acids and recalcitrant substances, achieving cascaded COD removal (total removal rate ≥95%). Through high-temperature stage HRT control (2.5–3.5 days) and pH adjustment (6.8–7.2), thermophilic methanogenic bacteria (such as *Methanothermobacter*) are enriched, increasing the methane volume fraction in biogas to 68–72% and reducing the H2S concentration to <50 mg / m³. 3 .

[0028] Fourthly, system integration and intelligent control. A multi-layered baffle plate with a 55° inclination is installed inside the SBR, and its surface is coated with a sodium alginate-polyvinyl alcohol immobilized nitrifying bacteria layer (embedding density ≥10). 8 (CFU / g) enables simultaneous operation of nitrification and denitrification zones, reducing hydraulic retention time by 30%.

[0029] This invention has the following beneficial effects: the COD removal rate is ≥95%, the TN removal rate is ≥94%, the carbon source cost is reduced by 52%, and the biogas production rate reaches 0.5-0.6m³. 3 With a COD of / kg and a material lifespan of ≥120 days, nZVI@BC is suitable for treating high ammonia nitrogen wastewater such as landfills and kitchen wastewater, combining high efficiency, economy and environmental friendliness. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the present invention.

[0031] Figure 2 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the following embodiments, unless otherwise specified, the materials and processing techniques are commercially available materials or conventional processing techniques in the art.

[0034] Example 1

[0035] Leachate from a municipal solid waste landfill had a COD of 12500 mg / L, TN of 680 mg / L, and a C / N ratio of 8.2. After sequentially passing it through a first-stage mesophilic UASB reactor (35±1℃, HRT=5 days, upflow velocity 0.8 m / h) and a second-stage high-temperature EGSB reactor (55±1℃, HRT=3 days, upflow velocity 2.5 m / h), the COD was reduced to 3200 mg / L and 420 mg / L in stages, achieving a total removal rate of 96.6%. Simultaneously, the biogas production rate was 0.55 m³ / L. 3 / kg COD, methane content 70%. Waste molasses was obtained by diluting sugarcane molasses to a moisture content of 30%. Activated sludge was inoculated with waste molasses at a VS ratio of 2:1. Urea (1.0 g / L), potassium dihydrogen phosphate (0.5 g / L), FeSO4 (0.3 g / L), and MnCl2 (0.2 g / L) were added. Fermentation was carried out for 7 days at pH 8.5, 35℃, and a stirring speed of 140 rpm to obtain a fermentation broth with a VFA concentration of 6500 mg / L. The broth was added to the nZVI@BC material (specific surface area 920 m²) at a C / N ratio of 5.0. 2 An SBR (dosage 1.0 g / L, baffle angle 55°) with Fe loading of 13.5% and DO = 0.3 mg / L and pH = 7.5 was run for 8 hours. TN decreased from 220 mg / L to 38 mg / L, and the denitrification rate reached 1.92 kg N / (m³). 3 •d) The cumulative nitrite content is <3mg / L, the sludge yield is only 0.15kg DS / ton of water, and the carbon source cost is 18.5 yuan / ton of water, making it the best in terms of overall performance.

[0036] Example 2

[0037] The treatment employed several methods: adjusting the primary anaerobic reaction temperature to 38℃ (from 35℃), shortening the secondary anaerobic HRT to 2 days (from 3 days), extending the waste molasses fermentation time to 9 days and hours (from 7 days), and reducing the C / N dosage ratio to 4.0 (from 5.0). After treatment, the leachate COD decreased from 12500 mg / L to 875 mg / L (removal rate 93%), TN decreased from 680 mg / L to 75 mg / L (removal rate 89%), and biogas production decreased to 0.48 m³ / L. 3 / kg COD (methane content 65%), denitrification rate drops to 1.65kgN / (m³). 3 (d) Analysis showed that increased primary anaerobic temperature inhibited methanogenic bacteria activity, and insufficient C / N ratio led to carbon source competition by denitrifying bacteria, resulting in decreased nitrogen removal efficiency. This example verifies the crucial role of precise temperature and HRT control in system stability.

[0038] Example 3

[0039] For the biogas slurry from kitchen waste (TN = 820 mg / L, COD = 18000 mg / L, C / N = 5.5), the process was adjusted to a single-stage mesophilic UASB treatment (HRT = 6 days), reducing COD to 2100 mg / L; the proportion of waste molasses fermentation liquid added was increased to C / N = 6.0, and the nZVI@BC dosage was increased to 1.2 g / L. After 10 hours of denitrification, 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 m³ / L. 3 / kg COD (methane content 68%). Sludge yield 0.18 kg DS / ton of water, carbon source cost 19.8 yuan / ton of water. The results show that under low carbon-to-nitrogen ratio conditions, high-efficiency denitrification can still be maintained by increasing the carbon source dosage and material loading, verifying the scenario adaptability of the process.

[0040] Comparative Example 1

[0041] A single UASB anaerobic reactor (35℃, HRT = 7 days) was used with sodium acetate as the carbon source (C / N = 5.0), and nZVI@BC material was not used. After treatment, COD decreased from 12500 mg / L to 1500 mg / L (removal rate 88%), TN decreased from 680 mg / L to 190 mg / L (removal rate 72%), and the nitrogen removal rate was only 0.85 kg N / (m³). 3 (d) Nitrite accumulation reached 35 mg / L. Biogas yield was 0.38 m³ / L. 3 The results show that the traditional process has significant disadvantages in terms of denitrification efficiency, operating costs, and byproduct control. The COD (58% methane content) is 0.30 kg / ton of water, the carbon source cost is 39.6 yuan / ton of water, and the sludge yield is 0.30 kg DS / ton of water.

[0042] Comparative Example 2

[0043] The two-stage anaerobic digestion process is completely omitted (i.e., the leachate is not treated by UASB and EGSB), and the leachate directly enters the denitrification SBR (initial COD = 12500 mg / L, TN = 680 mg / L), with other conditions the same as in Example 1. The COD removal rate after treatment is only 58% (effluent COD = 5250 mg / L): denitrifying bacteria cannot effectively degrade high concentrations of recalcitrant organic matter (such as long-chain fatty acids and lignin derivatives); the TN removal rate is 67% (TN decreased from 680 mg / L to 224 mg / L): high COD concentrations cause carbon source competition, inhibiting denitrifying bacteria activity; biogas production is 0: no methane is produced due to the absence of anaerobic fermentation; sludge production is 0.45 kg DS / ton of water: high load shocks cause sludge bulking; operating cost is 32.6 yuan / ton of water: additional carbon source needs to be added to compensate for the COD that was not anaerobicly degraded.

[0044] Comparative Example 3

[0045] Commercial sucrose was used instead of the waste molasses fermentation broth in Example 1, and added at the same C / N ratio of 5.0, with all other conditions identical to Example 1. The measured TN removal rate was 83% (TN decreased from 220 mg / L to 37 mg / L), and the denitrification rate was 1.45 kgN / (m³). 3 ·d), COD removal rate was 96.2% (the same as in Example 1), but carbon source cost rose to 52.8 yuan / ton of water.

[0046] Comparative Example 4

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

[0048] The following table shows a comparison of the effects of the examples and comparative examples:

[0049] Table 1 Comparison and analysis of the effects of each embodiment and comparative example.

[0050]

[0051] Example 1, through two-stage anaerobic digestion with temperature staggered treatment, waste molasses fermentation pretreatment, and nZVI@BC material addition, achieved a COD removal rate of 96.6% and a TN removal rate of 94.4%, while reducing carbon source costs by 53.3% (compared to Comparative Example 1). Examples 2 and 3 show that the process remains highly efficient (TN removal rate ≥89%) even with parameter fluctuations (such as temperature and HRT) and expanded scenarios (low C / N ratio wastewater), verifying its robustness. The comparative example, lacking staggered treatment and electron transfer enhancement, experienced a 55.7% reduction in denitrification rate and a 30.9% reduction in biogas yield, respectively. This invention significantly outperforms traditional processes in terms of pollutant removal, resource recovery, and economic efficiency.

[0052] Example 1 utilizes a cascaded degradation process of organic matter in the anaerobic stage (UASB removes readily biodegradable COD → EGSB degrades recalcitrant COD) to provide suitable influent conditions for denitrification (COD = 420 mg / L), avoiding carbon source competition, and simultaneously recovering biogas energy (0.55 m³ / L). 3 / kg COD). Comparative Example 2, lacking this synergistic design, required additional carbon source addition (increasing cost by 76%), and sludge production surged to 0.45 kg DS / ton of water. The COD removal rate (58%) and TN removal rate (67%) of Comparative Example 2 were significantly lower than those of Example 1 (96.6% and 92.8%), demonstrating that two-stage anaerobic treatment is the core step in overcoming 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 waste molasses (64%), demonstrating the necessity of fermentation treatment to break down inhibitors. Although the COD removal rate of Comparative Example 3 was similar to that of 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 bioinhibition, and the TN removal rate was only 68.9% of that of Example 1, and the cost of sludge disposal offset the price advantage of the carbon source. The results of the comparative examples demonstrate that the waste molasses fermentation process and the addition of nZVI@BC material are essential technical features, and neither can be omitted. If only waste molasses is used without pretreatment (Comparative Example 4), or if other carbon sources are replaced (Comparative Example 3), the high-efficiency denitrification and low-cost goals claimed by this invention cannot be achieved.

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

[0055] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An anaerobic-denitrification treatment process for landfill leachate based on the synergistic effect of waste molasses, characterized in that, Includes the following steps: (a) The landfill leachate is sequentially fed into a primary mesophilic anaerobic reactor and a secondary hyperthermic anaerobic reactor for cascade anaerobic digestion. The primary mesophilic anaerobic reactor is an upflow anaerobic sludge blanket (UASB) reactor, and the secondary hyperthermic anaerobic reactor is an expanded granular sludge blanket (EGSB) reactor. The volume ratio of the two reactors is 1:0.6~0.

8. The temperature of the primary mesophilic anaerobic reactor is controlled at 33~37℃, and the hydraulic retention time is 4~6 days. The temperature of the secondary hyperthermic anaerobic reactor is controlled at 54~56℃, and the hydraulic retention time is 2.5~3.5 days. (b) After the waste molasses is filtered through a 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 volatile solids (VS) of the activated sludge to waste molasses is 1:

2. Nitrogen source, phosphorus source and trace elements are added, and the pH is controlled to 7-10, the temperature is 22-42℃, the stirring speed is 125-150 rpm, and the anaerobic fermentation is carried out for 3-12 days to obtain waste molasses fermentation broth rich in volatile fatty acids (VFAs). (c) The waste molasses fermentation liquid obtained in step (b) is added to the denitrification reactor at a C / N ratio of 4.5 to 5.

5. At the same time, biochar-supported nano-zero-valent iron material nZVI@BC is added at a dosage of 0.8 to 1.2 g / L. An iron-carbon micro-electrolysis zone is set up in the denitrification reactor to form a micro-current with chloride ions in the landfill leachate using nZVI@BC. The effluent from the secondary high-temperature anaerobic reactor is introduced into the denitrification reactor to carry out the nitrification-denitrification denitrification process. (d) Control the dissolved oxygen (DO) during the denitrification stage to ≤0.5 mg / L and the pH value to 7.2~7.8 to complete the removal of total nitrogen. The remaining sludge is concentrated, dewatered, and then transported off-site for disposal.

2. The process according to claim 1, characterized in that, The waste molasses mentioned in step (b) is selected from one or more of beet molasses, sugarcane molasses, glucose molasses or corn molasses. The nitrogen source is urea or ammonium chloride, and the dosage is 0.5~1.5 g / L. The phosphorus source is potassium dihydrogen phosphate or disodium hydrogen phosphate, and the dosage 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, with a total concentration of 0.1~1.0 g / L.

3. The process according to claim 1, characterized in that, The preparation method of the nZVI@BC material in step (c) includes: preparing biochar by oxygen-limited pyrolysis of wood waste at 600~800℃, activating it with 5% KOH solution, and achieving a specific surface area ≥800 m² / g; loading Fe³⁺ into the pores of the biochar using a liquid-phase reduction method, with a zero-valent iron loading of 12~15wt% and a particle size distribution of 20~80 nm.

4. The process according to claim 1, characterized in that, The denitrification reactor mentioned in step (c) is a sequencing batch reactor (SBR), which is equipped with multiple layers of inclined guide plates with an inclination angle of 45~60° and a packing rate of 30~40%. It is also equipped with an online oxidation-reduction potential (ORP) sensor. Based on the real-time monitoring value of ORP in the denitrification reactor, which is -50~-100 mV, the carbon source dosage is adjusted in linkage with the PLC controller to stabilize the C / N ratio at 4.5~5.

5.

5. The process according to claim 4, characterized in that, The surface of the flow guide plate is coated with a nitrifying bacteria immobilized gel layer, which is made by embedding sodium alginate-polyvinyl alcohol composite carrier and enriched bacterial groups at a mass ratio of 1:

3.

6. An anaerobic-denitrification treatment system for landfill leachate based on the synergistic effect of waste molasses, characterized in that, include: The two-stage anaerobic reaction unit is connected in sequence, including the first-stage mesothermal upflow anaerobic sludge blanket (UASB) and the second-stage high-temperature expanded granular sludge blanket (EGSB). The biogas purification and storage unit includes a desulfurization tower and a gas holder; the waste molasses fermentation unit includes a membrane filtration assembly, a fermentation tank and a storage tank; and the denitrification reaction unit is a sequencing batch reactor (SBR), which incorporates nZVI@BC packing and a baffle plate structure.

7. The system according to claim 6, characterized in that, The SBR is equipped with a microporous aeration disc at the bottom. The aeration disc is connected to the air pump by a gas flow regulating valve, and the DO-pH linkage is controlled by a PLC controller to meet one of the following conditions: when DO>0.5 mg / L, the aeration is automatically turned off and the stirring is turned on; when pH<7.2, a 0.5% NaHCO3 solution is injected.

8. The application of the process according to claim 1 in the treatment of industrial wastewater containing high concentrations of nitrates, characterized in that, Replace step (a) with only primary anaerobic treatment, and adjust the denitrification carbon source addition ratio to C / N = 3.8~4.

2.

9. The application of the nZVI@BC material as an electron mediator in enhanced short-cut denitrification of wastewater according to claim 3, characterized in that, By adjusting the amount of material added, the nitrite accumulation rate can be ≥60%.

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