Leachate treatment and regulation process for enhanced denitrification using biogas-purified waste sulfur paste

Abstract

This invention discloses a leachate treatment and control process for enhanced denitrification using waste sulfur paste purified from biogas, comprising: S1, anaerobic biological treatment; S2, preparation of sulfur paste powder or liquid sulfur; S3, synergistic denitrification, including heterotrophic denitrification and sulfur autotrophic denitrification; wherein, sulfur autotrophic denitrification involves the continuous addition of sulfur paste powder or liquid sulfur as an electron donor, with sulfur-oxidizing bacteria enriched around the biological packing material as functional bacteria; S4, aeration; S5, ultrafiltration; S6, deep purification: the deep-purified water after ultrafiltration is sequentially subjected to nanofiltration and reverse osmosis to remove sulfate salts, forming industrial reclaimed water for waste incineration plants. This invention utilizes waste sulfur paste, a byproduct of landfill leachate treatment, in the form of sulfur paste powder or liquid sulfur, as a complete electron donor in the sulfur autotrophic denitrification stage, eliminating the need for external discharge or outsourced disposal, achieving 100% utilization of solid waste, and ensuring that the sulfate and nitrogen concentrations in the produced water simultaneously meet industrial reclaimed water standards.

Description

Technical Field

[0001] This invention relates to the field of landfill leachate treatment technology, and in particular to a leachate treatment and control process that utilizes biogas to purify waste sulfur paste and enhance denitrification. Background Technology

[0002] During the leachate treatment process at waste-to-energy incineration plants, anaerobic digestion removes high concentrations of COD, resulting in the generation of biogas. To improve efficiency and effectiveness, many waste-to-energy incineration plants purify and refine this biogas using processes such as wet complexation iron desulfurization to produce high-value-added biomethane (biogas). This desulfurization process generates a byproduct—waste sulfur paste. Currently, the industry generally regulates and disposes of waste sulfur paste as general industrial solid waste. With the large-scale implementation of biogas purification projects, the annual production of waste sulfur paste continues to increase, not only raising solid waste treatment costs but also failing to effectively recover and utilize the valuable resources, such as elemental sulfur, contained within it.

[0003] The new national standard "Water Quality Standard for Industrial Water Used in Urban Wastewater Reuse" (GB / T19923-2024), implemented in October 2024, added a limit of ≤15 mg / L for total nitrogen in open-loop circulating cooling water. This has created an urgent need for upgrading and retrofitting leachate treatment systems in waste incineration plants that comply with this reuse water standard. Traditional upgrading solutions, such as the two-stage A / O process, have high operating costs and large footprints, while two-stage reverse osmosis (RO) has limited nitrogen removal efficiency. Sulfur autotrophic denitrification technology provides an effective solution to these problems. This technology uses elemental sulfur as an electron donor, requiring no external carbon source, and has advantages such as low operating costs, low sludge production, and stable nitrogen removal efficiency. Synergistic operation of sulfur autotrophic and heterotrophic denitrification can further improve nitrogen removal efficiency, achieving effluent compliance with standards efficiently and at low cost.

[0004] The core of sulfur autotrophic technology lies in the filter media, which requires an annual replenishment rate of approximately 10% to 20%. Its cost accounts for over 90% of the operating cost of a sulfur autotrophic system. Currently, most commercially available sulfur autotrophic filter media are made from pure sulfur, resulting in high sulfur source costs. Furthermore, existing filter media production processes are complex, requiring the addition of various auxiliary agents to promote molding. Traditional processes using fixed filter beds often lead to problems such as caking and uneven mass transfer, affecting system stability.

[0005] It is worth noting that the waste sulfur paste produced from biogas purification is mainly composed of elemental sulfur, and also contains thiosulfates, carbonates, and other components required for sulfur autotrophic filter media. Some projects also contain trace amounts of iron, which can promote the activity of sulfur autotrophic microorganisms. This makes it possible to directly use waste sulfur paste for sulfur autotrophic denitrification.

[0006] In recent years, mixed-nutrient denitrification technology, which synergizes sulfur autotrophic denitrification with heterotrophic denitrification, has attracted widespread attention. Studies have shown that under heterotrophic-sulfur autotrophic synergistic conditions, the relative abundance of sulfur autotrophic denitrifying bacteria (such as *Sulfuritalea*, *Thiobacillus*, and *Methyloversatilis*) increases, and they form synergistic effects with disproportionate denitrifying bacteria. Compared with single denitrification processes, synergistic denitrification exhibits more stable nitrogen removal performance and higher nitrogen removal efficiency.

[0007] However, the existing mixed nutrient denitrification technology still has the following shortcomings: (1) It mainly adopts the slow release method of solid carrier, and the sulfur source release rate is difficult to adjust in real time according to the influent load; (2) The determination of operating parameters mostly depends on experience or static range limitation (such as fixed S / N ratio, fixed hydraulic retention time HRT), and lacks a dynamic and precise control method based on real-time operating data; (3) It does not involve incorporating the quality parameters of sulfur paste solid waste (moisture content, sulfur content, iron content, organic matter content, particle size distribution) into the operation control system; (4) It does not propose a single quantitative indicator that can comprehensively reflect the system's operating status, and it is difficult for operators to quickly judge the overall health status of the system and make targeted adjustments.

[0008] Chinese patent application CN114634247A discloses a sulfur autotrophic denitrification material prepared from sulfur paste or sulfur slag, along with its preparation and application methods. This sulfur autotrophic denitrification material is obtained by mixing industrial waste sulfur paste or sulfur slag with carbonate minerals and then fusing or granulating the mixture into particulate matter. Using this sulfur autotrophic denitrification material as packing material in a deep anaerobic biological filter bed, under a hydraulic retention time of 40–60 minutes, nitrate and nitrite nitrogen levels above 30 mg / L can be reduced to below 5 mg / L. This invention replaces organic carbon sources such as sodium acetate for denitrification, saving over 50% in denitrification costs.

[0009] In the patent application with publication number CN114634247A, sulfur paste is processed into granular filler and used in a fixed bed manner. The preparation process of sulfur autotrophic filter media is complicated, and the fixed bed form makes it difficult to flexibly adjust the amount of sulfur source added according to the changes in the influent water quality, resulting in a high initial investment.

[0010] (1) High cost of adding carbon source: In the traditional treatment process of landfill leachate, the total nitrogen of the effluent is difficult to meet the reuse water standard stipulated by the new national standard without adding carbon source, and the cost of adding carbon source is high.

[0011] (2) The resource utilization of waste sulfur paste is limited: As industrial solid waste, existing waste sulfur paste has disposal costs and its resource utilization is limited. It is usually only used to purify and prepare pure sulfur, and then produce sulfuric acid or sulfur autotrophic filter material. The process is complex and energy consumption is high.

[0012] (3) Insufficient regulation capacity of traditional sulfur autotrophic technology: Traditional sulfur autotrophic technology mostly uses fixed bed filter media, which makes it difficult to flexibly adjust the amount of sulfur source added according to the changes in influent water quality. In addition, the mass transfer effect is poor and it is easy to cause caking or short-circuiting.

[0013] (4) Lack of precise operation and control methods: Existing mixed nutrient denitrification technology mostly adopts static parameter settings and lacks dynamic control methods that take into account the quality of sulfur paste (moisture content, sulfur content, iron content, organic matter content, etc.).

[0014] (5) Lack of quantitative evaluation indicators for system status: There is no existing technology that couples multi-dimensional operating parameters (sulfur source quality, carbon source matching, electron donor allocation, nitrogen and sulfur conversion efficiency) into a single comprehensive control index, making it difficult for operators to judge the overall operating status of the system through a single indicator. Summary of the Invention

[0015] The technical problem this invention aims to solve is to address the shortcomings of the existing technology by providing a leachate treatment and control process that utilizes biogas-purified waste sulfur paste to enhance denitrification. This process treats and controls the waste sulfur paste, a byproduct generated during landfill leachate treatment, as a powdered or liquid sulfur, and adds it entirely to the autotrophic denitrification stage as an electron donor, eliminating the need for external discharge or outsourced disposal. This achieves 100% internal high-value utilization of solid waste. Simultaneously, the sulfate byproducts from autotrophic denitrification are efficiently retained through nanofiltration and reverse osmosis, ensuring that the sulfate and nitrogen concentrations in the treated water meet industrial reuse standards. This solves the bottleneck problem of traditional autotrophic technologies, where the accumulation of sulfate byproducts hinders reuse, and simultaneously realizes a circular economy model of "treating waste with waste."

[0016] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0017] A leachate treatment process for enhancing denitrification by purifying waste sulfur paste using biogas includes the following steps.

[0018] S1. Anaerobic biological treatment: The leachate generated during the storage of waste in the waste incineration power plant is divided into a main pipeline and a branch pipeline. The leachate from the main pipeline is sent to an anaerobic reactor for anaerobic biological treatment to remove organic pollutants and form anaerobic effluent and biogas.

[0019] S2. Preparation of sulfur paste: Biogas is purified using a wet complexing iron desulfurization process to form waste sulfur paste; then, the waste sulfur paste is pretreated to form sulfur paste, which is sulfur paste powder or liquid sulfur.

[0020] S3. Co-nitrification: Anaerobic effluent, branch leachate, and nitrification return liquid are introduced into a co-nitrification denitrification tank for co-nitrification. The co-nitrification denitrification tank includes a heterotrophic denitrification section and a sulfur autotrophic denitrification section arranged sequentially along the water flow direction. The co-nitrification methods include:

[0021] S3-1, Heterotrophic Denitrification: Anaerobic effluent first enters the heterotrophic denitrification section, using the organic carbon source in the leachate as an electron donor to reduce nitrate nitrogen in the nitrified liquid return liquid to nitrogen gas, thus completing heterotrophic denitrification.

[0022] S3-2, Sulfur Autotrophic Denitrification: The effluent from heterotrophic denitrification is introduced into the sulfur autotrophic denitrification section, which is filled with biological packing material, and sulfur-oxidizing bacteria are enriched on the periphery of the biological packing material. The sulfur autotrophic denitrification section continuously adds sulfur paste prepared in S2 as an electron donor through the sulfur dosing port to carry out sulfur autotrophic denitrification. At this time, the elemental sulfur in the sulfur paste is oxidized to sulfate.

[0023] S4. Aeration: The sulfur autotrophic denitrification effluent is introduced into the aeration tank for aerobic reaction, and nitrifying bacteria in the aeration tank oxidize ammonia nitrogen into nitrate nitrogen.

[0024] S5, Ultrafiltration: The aeration effluent is subjected to ultrafiltration. The ultrafiltration effluent is divided into two streams: one stream is used as water for deep purification, and the other stream is used as nitrification liquid return liquid in S3-1.

[0025] S6. Deep purification: The water after ultrafiltration and deep purification is sent to nanofiltration and reverse osmosis systems in sequence for deep desalination treatment. It can retain sulfate ions and the produced water is used as industrial recycled water for waste incineration power plants.

[0026] In S3-2, when sulfur paste is added in the form of sulfur paste powder, the maximum daily processing capacity of leachate does not exceed 800 t / d. At this time, the sulfur paste powder is continuously added using a screw feeder, and the particle size of the sulfur paste powder is ≥100 mesh. When the maximum daily processing capacity of leachate exceeds 800 t / d, a metering pump is used to continuously add liquid sulfur. The liquid sulfur is in a molten state at 119-150℃.

[0027] In S5, the ratio of nitrified liquid reflux to leachate entering the anaerobic reactor in S1 is 50% to 200%.

[0028] In S3-2, the hydraulic retention time of the sulfur autotrophic denitrification section is 12-24 hours, the pH is 7.0-8.5, and the sulfur paste dosage is controlled according to the S / N mass ratio of 1.25-2; the filling ratio of biological packing is 20%-40%; both the inlet and outlet of the sulfur autotrophic denitrification section are equipped with screens, and the screen aperture is smaller than the particle size of the biological packing.

[0029] Heterotrophic denitrification in S3-1 can remove total nitrogen in the effluent of the heterotrophic denitrification section to 150-200 mg / L; sulfur autotrophic denitrification in S3-2 can reduce total nitrogen in the effluent of the sulfur autotrophic denitrification section to below 50 mg / L, achieving cascade synergy between heterotrophic denitrification and sulfur autotrophic denitrification.

[0030] A control process for leachate treatment using biogas-purified waste sulfur paste to enhance denitrification is characterized by: constructing a comprehensive control index (GIDX) to evaluate the operational stability of the landfill leachate treatment process and the compliance of landfill leachate reclaimed water with standards, specifically:

[0031] A. When GIDX>1.5, the landfill leachate treatment process operates stably, the matching efficiency of carbon and sulfur sources within the system is excellent, and the synergistic state of mixed nutrients is optimal.

[0032] B. When 1.2≤GIDX≤1.5, the landfill leachate treatment process is operating normally and the matching efficiency of carbon and sulfur sources within the system is normal. However, there may be local shortcomings. It should be determined whether local adjustments are needed based on the effluent TN test results.

[0033] C. When GIDX < 1.2, the landfill leachate treatment process is unstable, and there are obvious problems with the matching efficiency of carbon and sulfur sources within the system. Problem diagnosis and targeted adjustments are required.

[0034] The method for constructing the comprehensive regulatory index GIDX includes the following steps:

[0035] Step 1: Determine the quality parameters of sulfur paste and calculate the quality correction coefficient of sulfur paste based on quality factors. ;in, This indicates the "effective sulfur equivalent" that each unit mass of sulfur paste can effectively participate in sulfur autotrophic denitrification.

[0036] Step 2: Calculate the contribution rate of heterotrophic denitrification for nitrogen removal. .

[0037] Step 3: Calculate the contribution of sulfur autotrophic denitrification to nitrogen removal. .

[0038] Step 4: Calculate the synergistic denitrification mixing coefficient Specifically:

[0039] .

[0040] Step 5: Calculate the S / N deviation. It is a quantitative indicator for assessing the deviation between actual sulfur source consumption and theoretical demand, and is used to reveal the actual utilization efficiency of elemental sulfur in the system.

[0041] Step 6: Calculate the comprehensive control index GIDX, the specific expression of which is:

[0042] .

[0043] In step 1, the quality parameters of sulfur paste include the moisture content in the sulfur paste. Mass fraction of elemental sulfur iron element mass fraction Organic residual carbon mass fraction The median particle size D50 and the contact angle θ, then The calculation formula is:

[0044] .

[0045] In the formula, This represents the mass fraction of inert impurities in the sulfur paste.

[0046] In step 2, The calculation formula is:

[0047] ;

[0048] In the formula, The amount of carbon source added in the heterotrophic denitrification stage; Increase the carbon source concentration for the heterotrophic denitrification stage; This represents the maximum daily processing capacity of the leachate. The carbon-to-nitrogen ratio designed for the heterotrophic denitrification stage.

[0049] In step 3, The calculation formula is:

[0050] .

[0051] in:

[0052] .

[0053] .

[0054] .

[0055] =1+5×w Fe .

[0056] In the formula, This refers to the daily dosage of sulfur paste. The sulfur-nitrogen ratio designed for the sulfur autotrophic denitrification section.

[0057] This is the utilization rate coefficient of elemental sulfur in sulfur paste.

[0058] Particle size factor; It is a hydrophilic factor; It is an iron catalytic factor.

[0059] In step 5, The calculation formula is:

[0060] .

[0061] in:

[0062] .

[0063] In the formula, The sulfur-nitrogen ratio is calculated based on the actual nitrogen removal consumption in the sulfur autotrophic denitrification section.

[0064] When GIDX < 1.2, the problem diagnosis and targeted adjustment methods include the following steps:

[0065] Step C-1, Inspection Specifically:

[0066] like >0.95 indicates If it's too low, then it needs to be increased. Increase Or reduce the median particle size D50.

[0067] like <0.4 indicates If it's too low, then it needs to be increased. or .

[0068] If 0.4≤ If ≤0.95, then proceed to step C-2.

[0069] Step C-2, Inspection Specifically:

[0070] like A value <0.35 indicates insufficient quality of the sulfur paste, which needs to be replaced. ≥0.35% sulfur paste or increase .

[0071] like If the value is ≥0.35, then proceed to step C-3.

[0072] Step C-3, Inspection And judge If the value is greater than 2, then it indicates that... If the value is too low, the median particle size D50 needs to be reduced, and the stirring in the sulfur autotrophic denitrification section needs to be checked for uniformity and whether there are short-circuit or dead zones.

[0073] If step C-3 makes a judgment If >2 is not true, then check the total nitrogen content of the leachate. and Does it deviate from the design value?

[0074] The present invention has the following beneficial effects:

[0075] 1. This invention constructs a complete closed-loop process of "anaerobic → synergistic denitrification (heterotrophic denitrification tank + sulfur autotrophic denitrification tank) → aerobic tank → UF → NF → RO", placing sulfur autotrophic denitrification before the membrane system and using nanofiltration + reverse osmosis to remove sulfate ions, thus achieving innovation in landfill leachate treatment technology.

[0076] 2. This invention utilizes waste sulfur paste, a byproduct generated during landfill leachate treatment, in the form of sulfur paste powder or liquid sulfur. This paste is added in its entirety to the sulfur autotrophic denitrification stage as an electron donor, eliminating the need for external discharge or outsourced disposal and achieving 100% internal high-value utilization of solid waste. Simultaneously, the sulfate byproduct generated during sulfur autotrophic denitrification is efficiently retained through nanofiltration and reverse osmosis. The sulfate and nitrogen concentrations in the treated water simultaneously meet industrial reuse standards, solving the bottleneck problem of traditional sulfur autotrophic technology where sulfate byproducts accumulate and hinder reuse. This also realizes a circular economy model of "treating waste with waste."

[0077] 3. The sulfur paste in the sulfur autotrophic denitrification stage comes from internal waste, with raw material costs close to zero. No external organic carbon source is required. Compared with the traditional secondary AO technology upgrade scheme, carbon source costs can be saved by 100%.

[0078] 4. This invention is the first to propose incorporating the quality parameters of sulfur paste solid waste (moisture content, sulfur content, iron content, organic matter content, and particle size distribution) into the operation and control system, realizing the engineering coupling of "solid waste resource utilization" and "precise process control". At the same time, the continuous addition of sulfur paste can flexibly adjust the amount of sulfur paste added according to the nitrate nitrogen concentration of the influent, solving the problem of difficult control of fixed-bed reactor operation.

[0079] 5. This invention is the first to propose the Comprehensive Control Index GIDX, which couples multi-dimensional operating parameters into a single quantitative indicator. Operators can quickly judge the overall status of the system and make targeted adjustments through GIDX. Attached Figure Description

[0080] Figure 1 The flowchart of a landfill leachate treatment process for enhancing denitrification by purifying waste sulfur paste using biogas is shown.

[0081] Figure 2The flowchart of the pretreatment of waste sulfur paste into sulfur paste powder in this invention is shown.

[0082] Figure 3 The flowchart of the pretreatment of waste sulfur paste into liquid sulfur in this invention is shown.

[0083] Figure 4 A schematic diagram of the synergistic denitrification tank in this invention is shown.

[0084] Among them are:

[0085] 1. Heterotrophic denitrification section; 2. Sulfate autotrophic denitrification section; 3. Submersible mixer; 4. Baffle wall; 5. Biological packing material; 6. Screen; 7. Sulfate inlet; 8. Alkalinity inlet; 9. Online pH / DO monitoring equipment. Detailed Implementation

[0086] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0087] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0088] like Figure 1 As shown, a landfill leachate treatment process that utilizes biogas to purify waste sulfur paste and enhance denitrification includes the following steps.

[0089] S1. Anaerobic biological treatment: The leachate generated during the storage of waste in the waste incineration power plant is divided into a main pipeline and a branch pipeline. The leachate from the main pipeline is sent to an anaerobic reactor for anaerobic biological treatment to remove organic pollutants and form anaerobic effluent and biogas.

[0090] S2. Preparation of sulfur paste: Biogas is purified by wet complexing iron desulfurization process to form waste sulfur paste. The elemental sulfur content in the waste sulfur paste is preferably 50% to 60%, and the water content is preferably 40% to 55%. Then, the waste sulfur paste is pretreated to form sulfur paste, which is sulfur paste powder or liquid sulfur.

[0091] like Figure 2The diagram shows a flowchart of the pretreatment process for waste sulfur paste into sulfur paste powder. Specifically, the waste sulfur paste stored in the sulfur paste temporary storage silo is dried by a dryer, crushed by a pulverizer, and screened by a sieve to obtain sulfur paste powder with a particle size of ≥100 mesh (preferably D50≤100μm, more preferably D50≤15μm). This powder is then stored in a sulfur powder storage tank and continuously fed in by a screw feeder. This method is typically used in conventional small and medium-sized waste incineration power plants, such as leachate treatment with a maximum daily processing capacity of no more than 800t / d.

[0092] like Figure 3 The flowchart shown illustrates the process of pretreating waste sulfur paste into liquid sulfur. Specifically, the waste sulfur paste stored in the sulfur paste temporary storage silo is pretreated by dehydration / impurity removal and then transported to the sulfur melting kettle and heated to 119-150℃ to melt it into liquid sulfur. The liquid sulfur is then stored under heat preservation through insulated pipes and continuously added to the subsequent sulfur autotrophic denitrification section via a metering pump. Upon contact with water, the liquid sulfur solidifies into sulfur particles with a median particle size D50 of approximately 15μm. This process is suitable for large-scale waste incineration power plants, such as leachate treatment with a maximum daily processing capacity exceeding 800t / d.

[0093] S3. Co-denitrification: Anaerobic effluent, branch leachate and nitrified liquid return liquid are introduced into the co-denitrification denitrification tank for co-denitrification.

[0094] like Figure 4 As shown, the synergistic denitrification tank includes a heterotrophic denitrification section 1 and a sulfur autotrophic denitrification section 2 arranged sequentially along the water flow direction. Submersible mixers 3 are installed in both the heterotrophic denitrification section 1 and the sulfur autotrophic denitrification section 2. A guide wall 4 is installed in the middle of the sulfur autotrophic denitrification section. The sulfur autotrophic denitrification section is filled with biological packing material 5, and sulfur-oxidizing bacteria are enriched on the periphery of the biological packing material. The sulfur autotrophic denitrification section is also equipped with a sulfur inlet 7 and an alkalinity inlet 8. Screens 6 or grids are installed at both the inlet and outlet of the sulfur autotrophic denitrification section, and the pore size of the screens or grids is smaller than the particle size of the biological packing material.

[0095] The hydraulic retention time of the sulfur autotrophic denitrification section is preferably 12-24 hours, the pH is preferably 7.0-8.5, and the sulfur paste dosage is preferably controlled according to an S / N mass ratio of 1.25-2. The biological packing material can be any type such as K1, K3, or K5, and the filling ratio is preferably 20%-40% to facilitate the attachment and growth of sulfur-oxidizing bacteria. The inlet and outlet ends of the sulfur autotrophic denitrification tank are equipped with grids or screens, with the screen aperture smaller than the packing particle size, to prevent packing material loss.

[0096] The alkalinity added through the above-mentioned alkalinity dosing port is preferably at least one of sodium bicarbonate, calcium carbonate, or limestone, which can synergistically stabilize the pH in the denitrification tank within the range of 7.0 to 8.5.

[0097] Furthermore, an online pH / DO monitoring device is installed in the co-denitrification denitrification tank, which can be used to monitor the pH or dissolved oxygen concentration in the co-denitrification denitrification tank.

[0098] The aforementioned synergistic denitrification preferably includes the following steps.

[0099] S3-1, Heterotrophic Denitrification: Anaerobic effluent first enters the heterotrophic denitrification section, using the organic carbon source in the leachate as an electron donor to reduce nitrate nitrogen in the nitrified liquid return liquid to nitrogen gas, thus completing heterotrophic denitrification.

[0100] S3-2, Sulfur Autotrophic Denitrification: The effluent from heterotrophic denitrification is introduced into the sulfur autotrophic denitrification section, where sulfur paste is continuously added as an electron donor through a sulfur inlet to carry out sulfur autotrophic denitrification; at this time, the elemental sulfur in the sulfur paste is oxidized to sulfate ions. Nitrate nitrogen in water is reduced to nitrogen gas, achieving deep denitrification. The specific reaction formula is as follows: Under typical operating conditions, sulfur autotrophic denitrification produces approximately [amount missing] nitrogen per 1 mg / L of total nitrogen removed. Sulfate ions.

[0101] The concentration of hydrogen sulfide in the anaerobic biogas from leachate of waste incineration plants is typically [missing information]. The amount of waste sulfur paste produced by wet complexing iron desulfurization is insufficient relative to the total nitrogen removal required for leachate treatment. Taking a typical operating condition as an example, the scale of leachate from a waste incineration plant... biogas concentration according to The daily production of sulfur paste is approximately 250–350 kg / d, which can only support a sulfur autotrophic denitrification load of about 100–200 mg / L, far below the total nitrogen removal requirement of 1500–2000 mg / L for the anaerobic effluent from the leachate. Therefore, sulfur autotrophic denitrification is positioned as an enhanced rather than the primary denitrification process in this technology. Its core function is to further reduce the total nitrogen in the effluent from 150–200 mg / L to below 50 mg / L, building upon the total nitrogen removal to 150–200 mg / L achieved by heterotrophic denitrification, thus realizing a cascaded synergy between heterotrophic and sulfur autotrophic denitrification. This process positioning means that sulfur paste does not need to be purchased externally or supplemented. The waste sulfur paste generated by the leachate treatment system itself can be fully added to the co-denitrification tank, eliminating the need for external discharge or outsourced disposal, and achieving closed-loop resource utilization of internal solid waste.

[0102] S4. Aeration: The effluent from the sulfur autotrophic denitrification process is introduced into an aeration tank for aerobic reaction. Nitrifying bacteria in the aeration tank oxidize ammonia nitrogen to nitrate nitrogen. The hydraulic retention time in the aeration tank is 4–6 days, and the dissolved oxygen concentration is controlled at 2–5 mg / L. This process oxidizes ammonia nitrogen in the raw water to nitrate nitrogen while removing residual nitrogen. .

[0103] S5. Ultrafiltration: The aeration effluent is introduced into a submerged or external membrane bioreactor for ultrafiltration to achieve mud-water separation. The ultrafiltration effluent is divided into two streams: one stream is used as water for deep purification, and the other stream is used as the nitrification liquid return liquid in S3-1. The ratio of the nitrification liquid return liquid to the leachate entering the anaerobic reactor in S1 is preferably 50%–200%, used for returning nitrate nitrogen, adjusting pH, and supplementing alkalinity. The ultrafiltration membrane pore size is preferably 0.01–0.1 μm.

[0104] S6. Deep Purification: The water after ultrafiltration and deep purification is sequentially sent to nanofiltration and reverse osmosis systems for deep desalination treatment, which can retain sulfate ions. The produced water is used as industrial recycled water for waste incineration power plants. In this invention, the nanofiltration operating pressure is preferably 0.5-1.5 MPa, with a divalent ion removal rate ≥95%; the reverse osmosis operating pressure is preferably 1.0-3.0 MPa, with a desalination rate ≥99%.

[0105] In this process, the sulfate byproduct generated in the sulfur autotrophic denitrification stage is efficiently retained primarily through nanofiltration and reverse osmosis units. Nanofiltration achieves a retention rate of ≥95% for divalent ions (sulfate), and reverse osmosis achieves a desalination rate of ≥99%, ensuring that the final product water sulfate concentration meets the requirements of reuse water standards such as "Water Quality Standard for Industrial Water Use in Urban Wastewater Reuse" (GB / T19923-2024). Simultaneously, some sulfate is discharged as salt along with the nanofiltration and reverse osmosis concentrates. These concentrates can be further treated depending on plant conditions and are typically used for preparing lime slurry from waste incineration.

[0106] A control process for landfill leachate treatment that utilizes biogas to purify waste sulfur paste and enhance denitrification is disclosed. This process assesses the operational stability of the landfill leachate treatment process and the compliance of the leachate return water by constructing a comprehensive control index (GIDX). The preferred method for constructing the GIDX includes the following steps.

[0107] Step 1: First, determine the quality parameters of the sulfur paste, such as the moisture content. Mass fraction of elemental sulfur iron element mass fraction Organic residual carbon mass fraction Median particle size D50 (unit) ) and contact angle θ.

[0108] Then, calculate the quality correction coefficient for sulfur paste based on quality factors. It indicates the "effective sulfur equivalent" that each unit mass of sulfur paste can effectively participate in sulfur autotrophic denitrification. The specific calculation formula is as follows:

[0109] .

[0110] In the formula, This represents the mass fraction of inert impurities in the sulfur paste.

[0111] Step 2: Calculate the contribution rate of heterotrophic denitrification for nitrogen removal. The specific calculation formula is as follows:

[0112] .

[0113] In the formula, The amount of carbon source added in the heterotrophic denitrification stage; Increase the carbon source concentration for the heterotrophic denitrification stage; This represents the maximum daily processing capacity of the leachate. The optimal carbon-to-nitrogen ratio for the heterotrophic denitrification stage is 4.0.

[0114] Step 3: Calculate the contribution of sulfur autotrophic denitrification to nitrogen removal. The specific calculation formula is as follows:

[0115] ;

[0116] in:

[0117] ;

[0118] ;

[0119] ;

[0120] =1+5×w Fe ;

[0121] In the formula, This refers to the daily dosage of sulfur paste. The preferred sulfur-to-nitrogen ratio for the sulfur autotrophic denitrification stage is 1.25 to 1.5. This is the utilization rate coefficient of elemental sulfur in sulfur paste; Particle size factor; It is a hydrophilic factor; It is an iron catalytic factor.

[0122] Step 4: Calculate the synergistic denitrification mixing coefficient Specifically:

[0123] .

[0124] Step 5: Calculate the S / N deviation. It is a quantitative indicator for assessing the deviation between actual sulfur source consumption and theoretical demand, used to reveal the actual utilization efficiency of elemental sulfur within the system. The specific calculation formula is as follows:

[0125] .

[0126] in:

[0127] .

[0128] In the formula, The sulfur-nitrogen ratio is calculated based on the actual nitrogen removal consumption in the sulfur autotrophic denitrification section.

[0129] Step 6: Calculate the comprehensive control index GIDX, the specific expression of which is:

[0130] .

[0131] The present invention uses the Comprehensive Control Index (GIDX) to evaluate the operational stability of landfill leachate treatment processes and the compliance of landfill leachate reclaimed water with standards.

[0132] A. When GIDX>1.5, the landfill leachate treatment process operates stably, the matching efficiency of carbon and sulfur sources within the system is excellent, and the synergistic state of mixed nutrients is optimal.

[0133] B. When 1.2≤GIDX≤1.5, the landfill leachate treatment process is operating normally and the matching efficiency of carbon and sulfur sources within the system is normal. However, there may be local shortcomings. It should be determined whether local adjustments are needed based on the effluent TN test results.

[0134] C. When GIDX < 1.2, the landfill leachate treatment process is unstable and there are obvious problems with the matching efficiency of carbon and sulfur sources within the system. Problem diagnosis and targeted adjustments are required. The preferred adjustment methods include the following steps.

[0135] Step C-1, Inspection Specifically:

[0136] like >0.95 indicates If it's too low, then it needs to be increased. Increase Or reduce the median particle size D50.

[0137] like <0.4 indicates If it's too low, then it needs to be increased. or .

[0138] If 0.4≤ If the value is ≤0.95, then the value is in the optimal range, and we can proceed directly to step C-2.

[0139] Step C-2, Inspection Specifically:

[0140] like A value <0.35 indicates insufficient quality of the sulfur paste, which needs to be replaced. ≥0.35% sulfur paste or increase (Supplement with trace amounts of iron salts) or targeted enhanced drying pretreatment.

[0141] like If the value is ≥0.35, then proceed to step C-3; where 0.35 ≤ ≤0.6 indicates that the quality of sulfur paste is average. A value greater than 0.6 indicates that the sulfur paste is of high quality.

[0142] Step C-3, Inspection And judge Whether >2 is true, specifically:

[0143] If true, it indicates If the value is too low, the median particle size D50 needs to be reduced, and the stirring in the sulfur autotrophic denitrification section needs to be checked for uniformity and whether there are short-circuit or dead zones.

[0144] If this condition is not met, proceed directly to step C-4. Where 0.3 ≤ When the concentration is ≤2.0, the landfill leachate treatment process can still operate normally, but it is necessary to monitor changes in the trend. <0.3 is the preferred range.

[0145] Step C-4, if , and All requirements are met, but GIDX < 1.2. In this case, the total nitrogen content of the leachate needs to be checked. and Check whether the values ​​deviate from the design values, and recalculate the system's denitrification capacity if necessary.

[0146] Through the above step-by-step diagnosis, operators can complete the system health check and formulate a control plan within 30 minutes to ensure that the system can quickly return to efficient operation.

[0147] The present invention provides a detailed description of the above-mentioned landfill leachate treatment process and control method through the following three preferred embodiments.

[0148] Example 1: Sulfur Powder Addition Route – Applicable to Small and Medium-Sized / Renovation Projects

[0149] Project Background: A waste incineration plant has a leachate treatment capacity of 500 t / d, which is the maximum daily leachate treatment capacity. With a capacity of 500 t / d, this is a small to medium-sized project, with a leachate COD of 60,000 mg / L. The anaerobic reactor is equipped with a biogas purification and biogas system, where the biogas undergoes wet complexing iron desulfurization to produce waste sulfur paste as a byproduct. After treatment in the anaerobic reactor, the effluent COD is approximately 1,000 mg / L (virtually non-biodegradable), and the total nitrogen is approximately 1,800 mg / L. Currently, the carbon source replenishment strategy involves daily replenishment of the leachate. (i.e. The raw solution is used as a carbon source for heterotrophic denitrification. However, the quality of the raw solution as a carbon source is poor, and the replenishment of the carbon source is difficult to control precisely. The total nitrogen in the effluent from the biological treatment stage can only be controlled at a minimum of 120-180 mg / L. Excessive replenishment of the raw solution will lead to COD breakthrough, causing the COD in the effluent to rise and affecting the stable operation of the subsequent membrane system. Since the implementation of the new national standard for reclaimed water, although the total nitrogen in the effluent can be controlled at 25-50 mg / L in combination with the downstream membrane system, it is still impossible to consistently meet the limit requirement of ≤15 mg / L for total nitrogen in open circulating cooling water in the 2024 edition of "Water Quality Standard for Industrial Water Reuse of Urban Wastewater" (GB / T19923-2024). Due to the dual constraints of limited available space in the plant area and limited budget for technical upgrade investment, this project plans to adopt the waste sulfur paste-based sulfur autotrophic denitrification process for upgrading and transformation, maximizing the use of existing structures and equipment, and simultaneously achieving the dual goals of resource utilization of general industrial solid waste waste sulfur paste and compliance with total nitrogen standards.

[0150] The concentration of carbon source added to the heterotrophic denitrification stage is the COD concentration in the leachate, which is 60,000 mg / L in this case.

[0151] Waste sulfur paste production and quality: The amount of waste sulfur paste produced is approximately 300 kg / day, with a moisture content of... =42%, mass fraction of elemental sulfur =55%, iron element mass fraction =0.21%, organic residual carbon mass fraction =1.87%, median particle size D50=50μm, contact angle θ≈60°.

[0152] Modification plan and system startup: Divide the original denitrification tank into 1 / 5 to 1 / 4 of its volume as a sulfur autotrophic denitrification section.

[0153] The acclimatization of sulfur-oxidizing bacteria in the sulfur autotrophic denitrification stage includes the following steps.

[0154] A. The effluent from the anaerobic reactor is introduced into the aeration tank, where ammonia nitrogen is converted into nitrate nitrogen through aerobic nitrification, providing sufficient electron acceptors for the subsequent denitrification unit.

[0155] B. Introduce the effluent from the aeration tank into the synergistic denitrification tank, and inoculate the sulfur autotrophic denitrification section with K3 type suspended packing material with a volume filling ratio of 20% and which has been attached with denitrifying sulfur bacteria.

[0156] C. Thiobacillus denitrification culture for 5 days.

[0157] After the sulfur-oxidizing bacteria in the sulfur autotrophic denitrification section have been acclimated, the anaerobic effluent is gradually switched back to direct influent to the co-denitrification denitrification tank. Simultaneously, nitrification liquor recirculation is initiated, with a recirculation ratio controlled at 100%, allowing nitrate nitrogen from the aeration tank effluent to be returned to the co-denitrification unit, maintaining continuous nitrogen removal. Leachate is simultaneously added to the heterotrophic denitrification tank to initiate the heterotrophic denitrification reaction. The hydraulic retention time (HRT) of the co-denitrification process section is a total of 2.8 days, with the reaction pH controlled between 7.5 and 8.5. When the pH falls below 7.5, sodium bicarbonate is added through the alkalinity dosing port to maintain a certain alkalinity before entering the subsequent aeration tank. The HRT of the aeration tank is 5.7 days, dissolved oxygen is controlled at 3-5 mg / L, and the nitrification liquor recirculation ratio is 100%.

[0158] This embodiment employs a powdered sulfur addition route, with core equipment including a dryer, pulverizer, sieve, and screw feeder. Waste sulfur paste is dried and dehydrated (moisture content reduced from 42% to 18%), pulverized to D50=50μm (approximately 270 mesh), sieved, and stored in a sulfur powder storage silo. It is then continuously added to the co-feeding denitrification tank via a screw feeder. This route is simple to operate and easy to maintain, suitable for small to medium-sized projects with low investment sensitivity and low automation requirements. However, it should be noted that the powder addition process requires simple dust removal facilities, and the addition accuracy is limited by the feeder's performance, making it suitable for scenarios with low α value requirements (α=0.178 in this case).

[0159] Synergistic denitrification effect and parameter control: The synergistic denitrification effect of mixed nutrients is significant, with the final effluent total nitrogen at 38.9 mg / L. Regarding parameter control, the synergistic coefficient η of the mixed nutrients... mix The efficiency ratio is 0.937, and the comprehensive control index GIDX is 1.58 > 1.5, which is in the high-efficiency zone. The effluent from the biological system enters the ultrafiltration + nanofiltration + reverse osmosis deep treatment system, and the final product water has TN = 10.13mg / L < 15mg / L and COD < 30mg / L, which meets the GB / T19923-2024 industrial reclaimed water standard.

[0160] Applicability Summary: The powder sulfur route is suitable for upgrading existing facilities with a processing capacity of ≤800t / d and limited investment budget. Its advantages are simple equipment, low investment, quick start-up, and convenient maintenance.

[0161] Example 2: Liquid Sulfur Dosing Route – Applicable to Large-Scale / New Projects

[0162] Project Background: A waste incineration plant has a leachate treatment capacity of Q=1000t / d, which is a large-scale new project with ample site space and high requirements for operational stability and automation. After anaerobic reactor treatment, the influent total nitrogen is 1800mg / L. Approximately 650kg / d of sulfur paste is produced as a byproduct of biogas purification. The sulfur paste quality parameters are: moisture content 36%, elemental sulfur content 58%, iron content 0.25%, and organic carbon content 2.0%. The carbon source replenishment strategy is to replenish leachate daily. (COD=55000mg / L).

[0163] This embodiment employs a liquid sulfur dosing route, with core equipment including a melting tank, an insulated storage tank, a high-temperature metering pump, and an insulated delivery pipeline system. Waste sulfur paste is heated to 120°C to melt into liquid sulfur, which is stored in the insulated storage tank (maintained at 120-130°C) and continuously transported to the co-denitrification tank via the metering pump and insulated pipeline. The liquid sulfur rapidly solidifies into micron-sized sulfur particles (D50≈15μm) upon contact with water, eliminating the need for additional crushing. While this route has a higher equipment investment cost, it offers high dosing accuracy, fully automated continuous operation, and no dust pollution. The naturally formed microparticles from liquid sulfur have extremely small particle sizes and very high surface activity, resulting in a naturally high α value (α=0.816 in this case), making it suitable for large-scale projects with high requirements for denitrification efficiency and operational stability. The liquid sulfur route pretreatment improves the quality of the sulfur paste. The original wet-based sulfur paste has a moisture content of 36% and an elemental sulfur content of 58%. After heating and melting, the moisture is further removed (reducing the moisture content to approximately 5%), resulting in a wet-based sulfur content of approximately 86.1%. It significantly improved the effective sulfur supply per unit mass of sulfur paste.

[0164] Synergistic denitrification effect and parameter control: Calculations show that GIDX≈2.14>1.5, indicating that the system is in the high-efficiency zone, with excellent synergistic mixed nutrient state, appropriate carbon and sulfur source ratios, high utilization rate, and stable effluent meeting standards. After synergistic denitrification, the total nitrogen in the biological treatment stage is 46.5 mg / L. Combined with the downstream ultrafiltration + nanofiltration + reverse osmosis deep treatment system, the final product water TN=12.96 mg / L<15 mg / L and COD<30 mg / L, meeting the GB / T19923-2024 industrial reclaimed water standard.

[0165] Applicability Summary: The liquid sulfur route is suitable for scenarios with a processing scale >800t / d, sufficient investment budget, new projects, high requirements for operational stability and dosing accuracy, and the pursuit of long-term automated operation benefits. Its advantages lie in high dosing accuracy and no dust pollution, and good long-term economic performance.

[0166] Example 3: Optimization Verification of GIDX Regulation—From the Adjustment Area to the High-Efficiency Area

[0167] Project Background: A waste incineration plant has a leachate treatment capacity of Q=600t / d, classifying it as a small to medium-sized project. The raw water has a COD of approximately 58,000 mg / L and total nitrogen of approximately 1,900 mg / L. After anaerobic reactor treatment, the effluent COD is approximately 1,500 mg / L (virtually non-biodegradable). The carbon source replenishment strategy involves daily replenishment of the leachate. As a carbon source for heterotrophic denitrification, approximately 390 kg / d of waste sulfur paste is produced as a byproduct of biogas purification. The quality parameters of the sulfur paste are: moisture content 43.7%, elemental sulfur content 50.4%, iron content 0.19%, and organic carbon content 1.8%. The sulfur paste pretreatment adopts a powder route. The waste sulfur paste is dried and dehydrated (moisture content reduced from 43.7% to 21%), pulverized to D50=70μm, and stored in a sulfur powder storage silo. It is then continuously fed into the co-denitrification tank via a screw feeder.

[0168] Initial operating conditions: During the commissioning period, the total nitrogen in the effluent from the biological system was approximately 64 mg / L. Combined with the downstream ultrafiltration + nanofiltration + reverse osmosis deep treatment system, the final product water TN = 20.2 mg / L > 15 mg / L, which does not yet meet the GB / T19923-2024 industrial reclaimed water standard.

[0169] GIDX Diagnosis and Regulation:

[0170] GIDX≈0.254<1.2, clearly indicating that the system is in a critical state requiring adjustment. Follow the GIDX item-by-item diagnostic process to diagnose the problem points and make targeted adjustments.

[0171] Step C-1, Inspection In this embodiment, η mix The value ≈0.994 > 0.95 indicates that the system over-relies on heterotrophic denitrification, with insufficient contribution from sulfur autotrophic denitrification (only about 0.6%), suggesting that the sulfur source is not functioning effectively. This anomaly suggests the need to increase the amount of sulfur paste added, optimize the grinding fineness, or increase the sulfur content of the sulfur paste. However, in this case, the sulfur paste has already been added at the actual production level (constrained by biogas production), and there is currently no possibility of adjusting or replacing the sulfur paste across projects. Therefore, "optimizing the grinding fineness" is the most convenient control method. While implementing optimization, simultaneous checks are conducted. and To identify whether there are other potential shortcomings besides particle size issues.

[0172] Step C-2, Inspection In this embodiment, k SP The value is approximately 0.403, which is within the normal quality range. This indicates that the basic indicators of the sulfur paste, such as moisture content, sulfur content, and iron content, are acceptable and are not the main reason for the severely low GIDX. This check has passed, and the quality of the sulfur paste itself can be largely ruled out. Further investigation can proceed.

[0173] Step C-3, Inspection In this embodiment, δ SN The value was approximately 8.80, far exceeding the reasonable upper limit, indicating that the amount of sulfur source added was much higher than the theoretical requirement, resulting in extremely low utilization of the sulfur paste. A large amount of sulfur paste was not effectively utilized by microorganisms. δ SN The fundamental reason for the severely elevated value lies in the excessively low value of α (only 0.106). Further analysis of the composition of α: α = φ particle × φ hydro × φ Fe φ hydro Due to the inherent hydrophilicity of sulfur paste, φ Fe Depends on iron content, while φ particle The main limiting factor for the low α value is the excessively large median particle size of sulfur paste (D50=70μm), which results in insufficient specific surface area of ​​sulfur paste particles, limited active sites available to microorganisms, and a large amount of sulfur source fails to participate effectively in the denitrification reaction and is lost or deposited with the effluent.

[0174] Optimized Results: Based on the GIDX control recommendations, the sulfur paste pulverization fineness was adjusted to 270 mesh (D50≈50 μm), keeping other parameters unchanged. Increasing the sulfur paste pulverization fineness to D50=50μm and α=0.178 resulted in a calculated GIDX≈1.52, placing it in the high-efficiency zone. After further adjustments, the total nitrogen in the effluent from the biological system was 21.4 mg / L, 27.6 mg / L, and 19.7 mg / L. Combined with the downstream membrane system, the total nitrogen in the effluent stabilized at 7~11 mg / L (<15 mg / L), fully meeting the GB / T19923-2024 industrial reclaimed water standard.

[0175] Engineering Implications: This case fully validates the core value of GIDX as a system health monitoring instrument. When GIDX is in the adjustment zone, operators can quickly locate the problem (in this case, insufficient fineness of sulfur paste pulverization). Through physical pretreatment optimization (refining particle size), GIDX can be increased from 0.254 to 1.52, enabling the system to transition from the adjustment zone to the high-efficiency zone and achieve effluent compliance. This control path requires no increase in reagent dosage or change in operating parameters; it can be accomplished simply by adjusting the pretreatment process, resulting in low cost and rapid effectiveness. In actual operation, when GIDX shows a continuous downward trend, the steps in the technical solution should be followed first for investigation. Maintenance should be arranged in advance before the effluent quality exceeds the standard, achieving proactive early warning management.

[0176] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A leachate treatment process for enhanced denitrification of waste sulfur paste derived from biogas, characterized in that: include: S1. Anaerobic biological treatment: The leachate generated during the storage of waste in the waste incineration power plant is divided into a main pipeline and a branch pipeline. The leachate from the main pipeline is sent to an anaerobic reactor for anaerobic biological treatment to remove organic pollutants and form anaerobic effluent and biogas. S2. Preparation of sulfur paste: Biogas is purified using a wet complexing iron desulfurization process to form waste sulfur paste; then, the waste sulfur paste is pretreated to form sulfur paste, which is sulfur paste powder or liquid sulfur. S3. Co-nitrification: Anaerobic effluent, branch leachate, and nitrification return liquid are introduced into a co-nitrification denitrification tank for co-nitrification. The co-nitrification denitrification tank includes a heterotrophic denitrification section and a sulfur autotrophic denitrification section arranged sequentially along the water flow direction. The co-nitrification methods include: S3-1, Heterotrophic denitrification: Anaerobic effluent first enters the heterotrophic denitrification section, using the organic carbon source in the leachate as an electron donor to reduce nitrate nitrogen in the nitrified liquid return liquid to nitrogen gas, thus completing heterotrophic denitrification. S3-2, Sulfur Autotrophic Denitrification: The effluent from heterotrophic denitrification is introduced into the sulfur autotrophic denitrification section, which is filled with biological packing material. Sulfur-oxidizing bacteria are enriched on the periphery of the biological packing material. Sulfur autotrophic denitrification section continuously adds sulfur paste prepared in S2 as an electron donor through the sulfur dosing port to carry out sulfur autotrophic denitrification. At this time, the elemental sulfur in the sulfur paste is oxidized to sulfate. S4. Aeration: The sulfur autotrophic denitrification effluent is introduced into the aeration tank for aerobic reaction, and the nitrifying bacteria in the aeration tank oxidize ammonia nitrogen into nitrate nitrogen. S5, Ultrafiltration: The aeration effluent is subjected to ultrafiltration. The ultrafiltration effluent is divided into two streams: one stream is used as water for deep purification, and the other stream is used as nitrification liquid return liquid in S3-1. S6. Deep purification: The water after ultrafiltration and deep purification is sent to nanofiltration and reverse osmosis systems in sequence for deep desalination treatment. It can retain sulfate ions and the produced water is used as industrial recycled water for waste incineration power plants.

2. The leachate treatment process for enhanced denitrification using biogas-purified waste sulfur paste according to claim 1, characterized in that: In S3-2, when sulfur paste is added in the form of sulfur paste powder, the maximum daily processing capacity of leachate does not exceed 800 t / d. At this time, the sulfur paste powder is continuously added using a screw feeder, and the particle size of the sulfur paste powder is ≥100 mesh. When the maximum daily processing capacity of leachate exceeds 800 t / d, a metering pump is used to continuously add liquid sulfur. The liquid sulfur is in a molten state at 119-150℃.

3. The leachate treatment process for enhanced denitrification using biogas-purified waste sulfur paste according to claim 1, characterized in that: In S5, the ratio of nitrified liquid reflux to the main line leachate entering the anaerobic reactor in S1 is 50% to 200%.

4. The leachate treatment process for enhanced denitrification using biogas-purified waste sulfur paste according to claim 1, characterized in that: In S3-2, the hydraulic retention time of the sulfur autotrophic denitrification section is 12-24 hours, the pH is 7.0-8.5, and the sulfur paste dosage is controlled according to the S / N mass ratio of 1.25-2; the filling ratio of biological packing is 20%-40%; both the inlet and outlet of the sulfur autotrophic denitrification section are equipped with screens, and the screen aperture is smaller than the particle size of the biological packing.

5. The leachate treatment process for enhanced denitrification using biogas-purified waste sulfur paste according to claim 1, characterized in that: Heterotrophic denitrification in S3-1 can remove total nitrogen in the effluent of the heterotrophic denitrification section to 150-200 mg / L; sulfur autotrophic denitrification in S3-2 can reduce total nitrogen in the effluent of the sulfur autotrophic denitrification section to below 50 mg / L, achieving cascade synergy between heterotrophic denitrification and sulfur autotrophic denitrification.

6. A control process for the leachate treatment process of enhanced denitrification using biogas-purified waste sulfur paste as described in any one of claims 1 to 5, characterized in that: By constructing a comprehensive control index (GIDX), the operational stability of landfill leachate treatment processes and the compliance of landfill leachate reclaimed water with standards are evaluated, specifically as follows: A. When GIDX>1.5, the landfill leachate treatment process operates stably, the matching efficiency of carbon and sulfur sources within the system is excellent, and the synergistic state of mixed nutrients is optimal. B. When 1.2≤GIDX≤1.5, the landfill leachate treatment process is operating normally and the matching efficiency of carbon source and sulfur source in the system is normal, but there may be local shortcomings. It should be determined whether local adjustments are needed based on the effluent TN test results. C. When GIDX < 1.2, the landfill leachate treatment process is unstable, and there are obvious problems with the matching efficiency of carbon and sulfur sources within the system. Problem diagnosis and targeted adjustments are required.

7. The control process according to claim 6, characterized in that: The method for constructing the comprehensive regulatory index GIDX includes the following steps: Step 1: Determine the quality parameters of sulfur paste and calculate the quality correction coefficient of sulfur paste based on quality factors. ;in, This indicates the "effective sulfur equivalent" that each unit mass of sulfur paste can effectively participate in sulfur autotrophic denitrification; Step 2: Calculate the contribution rate of heterotrophic denitrification for nitrogen removal. ; Step 3: Calculate the contribution of sulfur autotrophic denitrification to nitrogen removal. ; Step 4: Calculate the synergistic denitrification mixing coefficient Specifically: ； Step 5: Calculate the S / N deviation. It is a quantitative indicator for assessing the deviation between actual sulfur source consumption and theoretical demand, and is used to reveal the actual utilization efficiency of elemental sulfur in the system. Step 6: Calculate the comprehensive control index GIDX, the specific expression of which is: 。 8. The control process according to claim 7, characterized in that: In step 1, the quality parameters of sulfur paste include the moisture content in the sulfur paste. Mass fraction of elemental sulfur iron element mass fraction Organic residual carbon mass fraction The median particle size D50 and the contact angle θ, then The calculation formula is: ； In the formula, This represents the mass fraction of inert impurities in the sulfur paste. In step 2, The calculation formula is: ； In the formula, The amount of carbon source added in the heterotrophic denitrification stage; Increase the carbon source concentration for the heterotrophic denitrification stage; This represents the maximum daily processing capacity of the leachate. The carbon-to-nitrogen ratio designed for the heterotrophic denitrification stage; In step 3, The calculation formula is: ； in: ； ； ； =1+5×w Fe ； In the formula, This refers to the daily dosage of sulfur paste. The sulfur-nitrogen ratio designed for the sulfur autotrophic denitrification section; This is the utilization rate coefficient of elemental sulfur in sulfur paste; Particle size factor; It is a hydrophilic factor; It is an iron catalytic factor; In step 5, The calculation formula is: ； in: ； In the formula, The sulfur-nitrogen ratio is calculated based on the actual nitrogen removal consumption in the sulfur autotrophic denitrification section.

9. The control process according to claim 8, characterized in that: When GIDX < 1.2, the problem diagnosis and targeted adjustment methods include the following steps: Step C-1, Inspection Specifically: like >0.95 indicates If it's too low, then it needs to be increased. Increase Or reduce the median particle size D50; like <0.4 indicates If it's too low, then it needs to be increased. or ; If 0.4≤ If ≤0.95, then proceed to step C-2; Step C-2, Inspection Specifically: like A value <0.35 indicates insufficient quality of the sulfur paste, which needs to be replaced. ≥0.35% sulfur paste or increase ; like If the value is ≥0.35, then proceed to step C-3; Step C-3, Inspection And judge If the value is greater than 2, then it indicates that... If the value is too low, the median particle size D50 needs to be reduced, and the stirring in the sulfur autotrophic denitrification section needs to be checked for uniformity and whether there are short-circuit or dead zones.

10. The control process according to claim 9, characterized in that: If step C-3 makes a judgment If >2 is not true, then check the total nitrogen content of the leachate. and Does it deviate from the design value?

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