Method and equipment for preparing organic fertilizer by humus and leachate

Abstract

This invention discloses a method and equipment for the synergistic preparation of organic fertilizer from humus and leachate, belonging to the field of organic solid waste resource utilization and pollution control technology. The method includes: humus pretreatment, leachate pretreatment, mixing and composting, aerobic fermentation, and post-treatment; during aerobic fermentation, leachate is added to maintain moisture content, and the precipitated sludge generated from leachate pretreatment is reused in the humus; the equipment includes a fermentation support structure, a forced ventilation system, a temperature monitoring and automatic control system, a turning machine, and a leachate replenishment device. This invention couples the treatment of humus and leachate, achieving "waste-to-waste treatment," using a passivating agent to chemically passivate heavy metals, and using leachate to replace exogenous nitrogen sources and water. The entire process generates no secondary waste, reducing overall costs by 40%–50%, and the resulting organic fertilizer meets standards and is suitable for rapid on-site disposal in landfill remediation projects.

Description

Technical Field

[0001] This invention relates to the field of organic solid waste resource utilization and pollution control technology, specifically to a method and equipment for the synergistic preparation of organic fertilizer from humus and leachate. Background Technology

[0002] With the expiration of service life of my country's municipal solid waste landfills and the advancement of excavation and remediation projects for aged waste, the stock of humus soil generated from landfill screening is enormous. Statistics show that my country's stock of waste exceeds 8 billion tons, with humus soil accounting for 40% to 60%. Humus soil is rich in humus, organic matter, and nitrogen, phosphorus, and potassium nutrients, possessing a basic fertility foundation. However, due to the accumulation of heavy metals, salts, and other pollutants during long-term landfilling, its direct use in farmland poses a high ecological risk. Traditional treatment methods (landfill and incineration) not only occupy land resources but also waste organic matter.

[0003] Meanwhile, landfills and incinerators generate large amounts of leachate during operation. Leachate is a high-concentration organic wastewater with a chemical oxygen demand (COD) concentration of 20,000–80,000 mg / L, containing large amounts of humic acid, fulvic acid, and nitrogen and phosphorus nutrients. The current mainstream treatment process is "biological treatment + membrane separation," but this produces 13%–50% membrane concentrate, which is rich in humus and salts, making disposal costly and difficult. Existing technologies have attempted to utilize leachate to prepare organic fertilizer (e.g., Chinese invention patent CN105601406A), but none have achieved synergistic utilization with humus soil, and the salt and heavy metal content in the leachate is difficult to control effectively.

[0004] In the field of humus resource utilization, Chinese invention patent CN111548233A discloses a bio-organic fertilizer made from humus in existing municipal solid waste and its preparation method. This patent involves screening, washing, and jigging the humus to obtain organic residue and fuel residue, which are then mixed with fly ash and biological agents for granulation. During the curing stage, leachate is sprayed to pretreat the wastewater. Although this method involves both humus and leachate, it still has the following significant drawbacks: (1) The washing process generates secondary wastewater pollution: This patent uses jet water flushing combined with ultrasonic oscillation to wash humus soil, generating a large amount of high-concentration organic mixed mud. Although the filtrate is recycled after dewatering, dissolved organic matter and salt will continue to accumulate during the recycling process, and will eventually need to be discharged as wastewater, which increases the cost of sewage treatment and the environmental burden, and fails to achieve zero discharge throughout the process.

[0005] (2) Heavy metals are only diluted, without chemical passivation: The main method of this patent to solve the problem of excessive heavy metals is to divert the excessive components to the undersize fine material (not used for organic fertilizer), while the heavy metals remaining in the oversize material are physically diluted by adding fly ash. This method does not change the chemical form of heavy metals, and their bioavailability is still high. Long-term application poses a risk of soil pollution. At the same time, fly ash itself may carry a certain amount of heavy metals, introducing new environmental hazards.

[0006] (3) Co-fermentation of humus and leachate was not achieved: This patent only uses leachate tailwater as spray water during the curing stage after granulation. The leachate and humus were not directly mixed during the fermentation process. Humus itself has a low carbon-to-nitrogen ratio (usually 10:1~15:1) and needs to rely on external nitrogen sources for supplementation. Leachate is rich in ammonia nitrogen and organic nitrogen. This patent did not utilize this characteristic to adjust the nutrient balance of compost materials, thus missing the opportunity for synergistic effects between the two wastes in the biochemical reaction.

[0007] (4) The process is complex and the equipment investment is large: This patent requires a variety of special equipment such as tension screen, compound spiral separator (including ultrasonic and pressurized jet device), jigging separator, belt filter press, etc. The equipment chain is long and the investment and operation and maintenance costs are high, which limits its promotion and application in small and medium-sized landfill remediation projects.

[0008] The porous structure of humus soil effectively adsorbs and fixes salts and heavy metals in leachate, while the soluble organic matter and water in the leachate regulate the carbon-nitrogen ratio and moisture content of the humus soil, resulting in a high degree of complementarity in their physicochemical properties. However, a systematic method for the synergistic preparation of organic fertilizer from humus soil and leachate is currently lacking. Developing an organic fertilizer preparation technology that "treats waste with waste and synergistically enhances efficiency" is of significant practical importance in addressing the two major industry pain points: the difficulty in disposing of humus soil and the high cost of leachate treatment. Summary of the Invention

[0009] The purpose of this invention is to provide a method and apparatus for the synergistic preparation of organic fertilizer from humus and leachate, so as to solve the problems mentioned in the background art.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for co-preparing organic fertilizer from humus and leachate includes the following steps: S1 Pretreatment: The humus obtained from the landfill screening is subjected to heavy metal passivation treatment using a passivating agent, and the moisture content is adjusted to 25%~45% to obtain pretreated humus; the landfill leachate is subjected to flocculation and sedimentation treatment using a flocculant to obtain leachate clear liquid and sedimented sludge, and the sedimented sludge is recycled into the pretreated humus. S2 Mixed Composting: The pretreated humus, leachate, carbon source additives and compound microbial agents are mixed evenly, the carbon-nitrogen ratio is adjusted to 20:1~30:1 and the moisture content is 50%~65%, and then piled into a pile. S3 Aerobic Fermentation: Forced ventilation and turning of the pile are carried out; during the fermentation process, the leachate is added to maintain the moisture content, and the pile temperature is controlled at 55℃~65℃ for 7~14 days to obtain mature material. S4 Post-processing: The decomposed material is screened, dried, and granulated to obtain the finished organic fertilizer.

[0011] Furthermore, the passivating agent in S1 includes one or more of superphosphate, phosphate rock powder, zeolite powder, or biochar; the flocculant includes one or more of polyaluminum chloride, polyacrylamide, or polyferric sulfate.

[0012] Furthermore, in S2, the mass ratio of the pretreated humus, leachate, carbon source additive, and compound microbial agent is (50~80):(10~30):(5~20):(0.5~2); the carbon source additive includes one or more of straw powder, rice husk powder, sawdust, or fungal residue; the compound microbial agent contains one or more of Bacillus, Lactobacillus, or Yeast, with an effective viable count ≥1×10⁻⁶. 8 CFU / g.

[0013] Furthermore, the frequency of adding leachate clear liquid as described in S3 is once every 3 to 5 days, and the amount added at one time is 2% to 5% of the mass of the pile.

[0014] Furthermore, the aerobic fermentation described in S3 adopts temperature feedback control: when the pile temperature exceeds 65°C, the ventilation volume is increased, and when it is below 55°C, ventilation is reduced or suspended; in the later stage of fermentation, ventilation is stopped and the pile is turned over regularly, and fermentation is completed when the pile temperature drops below 40°C and the moisture content drops below 30%.

[0015] A second objective of this invention is to provide an apparatus for the co-preparation of organic fertilizer from humus and leachate using the above-described method, comprising: Fermentation tanks are used to support the pile, including trough-type fermentation tanks or windrow-type hardened impermeable flooring. Forced ventilation system, including fan, aeration pipe and air volume regulating valve; A temperature monitoring and automatic control system includes a temperature sensor installed inside the reactor and a PLC controller electrically connected to the temperature sensor. The PLC controller is used to adjust the fan frequency according to a temperature threshold. The turning machine is movably installed on the fermentation tank; The leachate replenishment device includes a leachate clear liquid storage tank, a metering pump, and an atomizing spray pipe arranged above the pile or on the turning machinery. The metering pump is electrically connected to the PLC controller.

[0016] Preferably, when the fermentation tank is a trough-type fermentation tank, the turning machine is a hydraulically driven or chain-plate type turning machine, straddling the tracks on both sides of the trough-type fermentation tank, with a turning roller speed of 80~120 rpm and a turning depth of 1.0~1.5 meters; when the fermentation tank is a windrow-type hardened seepage-proof floor, the turning machine is a tracked or wheeled turning machine, with a turning width of 2~3 meters and a turning depth of 0.8~1.2 meters; the turning machine's step distance for each stroke is 0.8~1.2 meters.

[0017] Preferably, the atomizing spray pipe is equipped with a nozzle, the nozzle orifice diameter is 1~2 mm, the spray pressure is 0.2~0.5 MPa, and the droplet diameter is 30~100 micrometers; Furthermore, when the fermentation tank is a trough-type fermentation tank and the atomizing spray pipe is arranged above the pile, the nozzle is a wide-angle fan-shaped atomizing nozzle with a spray angle of 110°~130°, the spray direction is inclined downward at an angle of 30°~45° with the horizontal plane, the nozzle axis is deflected by 10°~20° from the normal to the pile surface, the spacing between adjacent nozzles along the length of the trough is 1.0~1.5 meters, and 2~3 nozzles are arranged along the width of the trough with a spacing of 0.8~1.2 meters; when the fermentation tank is a trough-type fermentation tank and the atomizing spray pipe is arranged on the turning machine, 6~8 nozzles are evenly distributed along the length of the beam of the turning machine with a spacing of 0.4~0.6 m, the spray direction is perpendicular to the forward direction of the turning machine, and the spray plane is at an angle of 15°~25° with the horizontal plane; Furthermore, when the fermentation tank is a windrow-type hardened impermeable floor and the atomizing spray pipes are arranged above the pile, 5 to 8 nozzles are evenly distributed along the width of the windrow, with a spacing of 0.3 to 0.5 m, and the nozzle axis is vertically downward; when the fermentation tank is a windrow-type hardened impermeable floor and the atomizing spray pipes are arranged on the turning machine, the spraying direction is tilted backward at an angle of 15° to 25° with the horizontal plane.

[0018] Preferably, the aeration pipe is buried at the bottom of the tank or below the pile, with a pipe diameter of DN50~DN100, a pipe wall opening diameter of 3~5 mm, and an opening rate of 8%~12%; the blower is a variable frequency centrifugal blower, with an air volume of 0.2~0.5 cubic meters / hour per cubic meter of material, and an air pressure ≥3 kPa.

[0019] Preferably, at least three sets of temperature sensors are provided, located at different depths within the stack. Beneficial effects

[0020] By adopting the above technical solution, the technical progress achieved by this invention compared to the prior art is as follows: 1. Comprehensive and Collaborative Resource Utilization: This approach couples the treatment of two difficult-to-dispose-of wastes—humus and leachate—with the humus adsorbing salts and heavy metals from the leachate, while the leachate adjusts the carbon-nitrogen ratio and moisture content of the humus, achieving "waste-to-waste treatment." For every ton of humus treated, 0.2-0.5 tons of leachate supernatant can be simultaneously disposed of, avoiding the difficult-to-dispose-of problem of concentrated leachate.

[0021] 2. Excellent product quality: The organic fertilizer produced has an organic matter content of ≥45%, a total nutrient content (nitrogen + phosphorus pentoxide + potassium oxide) of ≥5%, heavy metal indicators that meet the NY / T 525-2021 "Organic Fertilizer" standard, and a seed germination index of ≥85%. It can be directly used for landscaping, soil improvement, etc.

[0022] 3. Significantly reduced costs: Compared with the traditional process of directly composting humus after passivation, which requires the addition of a large amount of commercial nitrogen source and water, this invention uses leachate to replace some auxiliary materials and all process water, reducing the overall cost by 40% to 50%, and has good economic benefits.

[0023] 4. Strong process adaptability: By dynamically adjusting the ratio of humus to leachate and the frequency of replenishment, it can adapt to humus with different landfill years, different pollution levels and leachate with different water quality characteristics, and has a wide range of engineering applicability.

[0024] 5. Environmentally friendly: The entire process has no secondary wastewater or solid waste discharge. The leachate is recycled in the fermentation replenishment stage, and all the precipitated sludge is reused, realizing the full synergistic resource utilization of humus and leachate. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of a trough fermentation device. Figure 3 This is a schematic diagram of a windrow fermentation equipment.

[0026] In the diagram: 1-Fermentation tank; 11-Pile; 12-Retaining wall; 13-Imperile layer; 14-Hardened impermeable floor; 21-Blower; 22-Aeration pipe; 23-Air volume regulating valve; 31-Temperature sensor; 32-PLC controller; 4- Turning machinery; 51-Leachate clear liquid storage tank; 52-Metering pump; 53-Atomizing spray pipe; 54-Nozzle. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments: Example 1 (Typical landfill humus and mid-to-late stage leachate) like Figure 1 In this embodiment, humus soil and late-stage leachate from a municipal solid waste sanitary landfill in Zhejiang (landfill life of 8-12 years) were used as raw materials. The characteristics of the raw materials are as follows: humus soil has an organic matter content of 42.6%, total lead of 62 mg / kg, and a water content of 28%; leachate has a COD of 18000 mg / L, total nitrogen of 850 mg / L, total phosphorus of 120 mg / L, and pH of 7.9.

[0028] A method for co-preparing organic fertilizer from humus and leachate includes the following steps: S1 Pretreatment: Add 1% (by weight of humus) of zeolite powder to humus soil for heavy metal passivation treatment, mix evenly, and adjust the moisture content to 35% to obtain pretreated humus soil; add 1.5% (g / mL) of polyaluminum chloride as a flocculant to leachate, stir and let stand for 6 hours, and separate the solid and liquid to obtain clear leachate (COD reduced to 3500 mg / L) and precipitated sludge, and reuse the precipitated sludge in the pretreated humus soil.

[0029] S2 mixed composting: pretreated humus, leachate, crushed straw powder (particle size 2-3 mm) as carbon source and auxiliary material, compound microbial agent (Bacillus subtilis: lactic acid bacteria = 2:1, effective viable count 2×10⁻⁶). 8 The ingredients (CFU / g) are mixed at a mass ratio of 65:20:10:1, and after thorough mixing, the carbon-nitrogen ratio is 26:1, the moisture content is 58%, and the mixture is stacked in a trough.

[0030] S3 aerobic fermentation: initial ventilation volume is 0.2m³. 3 / (h •m 3 The material was turned over twice daily. On the third day, the pile temperature reached 62℃ and was maintained for 12 days. During this period, when the pile temperature exceeded 65℃, the ventilation rate was increased to 0.5m³. 3 / (h •m 3 Reduce ventilation when the temperature is below 55℃. Add 2kg of leachate every 4 days (approximately 2.1% of the pile mass). Stop forced ventilation after the 15th day. Turn the pile over once every 3 days. On the 25th day, the pile temperature drops to 38℃ and the moisture content drops to 28%, resulting in well-rotted material.

[0031] S4 Post-processing: The composted material is screened by a 15-mesh vibrating sieve. The material passing through the sieve is dried at a low temperature of 70℃ with hot air until the moisture content is 18%. Then, it is extruded and granulated into particles with a particle size of 3~5mm to obtain the finished organic fertilizer product.

[0032] Product testing results: Organic matter 51.3%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) 6.2%, moisture 18%, pH 7.2, total lead 42 mg / kg, total arsenic 8.5 mg / kg, total mercury 0.3 mg / kg, total cadmium 0.8 mg / kg, total chromium 65 mg / kg, seed germination index 85%. All heavy metal indicators meet the limits specified in the NY / T 525-2021 "Organic Fertilizer" standard.

[0033] like Figure 2 The equipment for co-producing organic fertilizer from humus and leachate according to this invention was deployed at the landfill remediation site for continuous operation testing. The equipment includes: Fermentation tank 1 is used to support the pile 11. In this embodiment, a trough-type fermentation tank is used. Each tank is 30m long, 3m wide and 1.5m high. Concrete retaining walls 12 are set on both sides and a seepage-proof layer 13 and drainage ditch are set at the bottom. The forced ventilation system includes a fan 21, an aeration pipe 22, and an air volume regulating valve 23; the fan 21 is a variable frequency centrifugal fan, and the fan 21 is electrically connected to a PLC controller 32, with an initial air volume of 0.2 m³ / h. 3 / (h •m 3 Materials), air pressure 4 kPa; aeration pipe 22 with diameter DN80, buried at the bottom of fermentation tank 1, with pipe wall opening diameter 4 mm and opening rate 10%, each aeration pipe 22 is equipped with air volume regulating valve 23, which is a manual butterfly valve.

[0034] The temperature monitoring and automatic control system includes a temperature sensor 31 installed inside the stack body 11 and a PLC controller 32 electrically connected to the temperature sensor 31. The temperature sensor 31 uses PT100 thermocouples and is set in three sets, which are respectively installed inside the stack body 11 at depths of 0.3m, 0.6m and 0.9m from the surface, and the signals are connected to the PLC controller 32. The turning machine 4 is movably mounted on the fermentation tank 1. In this embodiment, a chain plate turning machine is used, straddling the tracks on both sides of the fermentation tank. The turning roller rotates at 100 rpm, the turning depth is 1.2m, and the step distance for each stroke is 1.2m.

[0035] The leachate replenishment device includes a leachate clear liquid storage tank 51, a metering pump 52, and an atomizing spray pipe 53 arranged on the turning machinery 4. The metering pump 52 is electrically connected to the PLC controller 32. The leachate clear liquid storage tank 51 has a volume of 8m³. 3 Metering pump 52, flow rate 1.0 m³ / h 3 / h, the atomizing spray pipe 53 is installed on the crossbeam of the turning machine 4 to achieve random follow-up spraying. Six nozzles 54 are evenly distributed on the atomizing spray pipe 53. The nozzle 54 has an orifice diameter of 1.5mm, a spraying pressure of 0.3 MPa, a droplet diameter of 30μm, and the spraying direction is perpendicular to the forward direction of the turning machine 4. The spraying plane makes an angle of 15° with the horizontal plane.

[0036] Operating parameters: Approximately 30 tons of material are fed into each tank. During operation, when the temperature sensor 31 detects that the temperature of the pile 11 is below 55℃, the PLC controller 32 automatically increases the frequency of the variable frequency centrifugal fan 21 to increase the ventilation volume; when the temperature of the pile is above 65℃, the ventilation volume is automatically reduced and the turning machine 4 is triggered to start. At the same time, the operator can adjust the opening of the valve 23 according to the air volume and coordinate with the frequency of the fan 21 to finely adjust the air supply of each section of the aeration pipe 22 to avoid local oxygen deficiency or over-ventilation. Leachate is added every 3 days, with a replenishment amount of approximately 800 kg / tank.

[0037] This equipment operated continuously for three months, processing approximately 600 tons of humus and simultaneously disposing of about 180 tons of leachate. No wastewater or solid waste was discharged. The overall cost was 280 yuan per ton of organic fertilizer, a reduction of over 60% compared to traditional landfill disposal methods. Compared to traditional humus composting (which requires the addition of urea to adjust the carbon-to-nitrogen ratio and the use of water to adjust the moisture content), this method shortens the fermentation cycle by 3 days, increases organic matter content by 8%, increases total nutrients by 1.8%, and reduces lead content by 32%. The overall cost is 46% lower than the traditional process of approximately 520 yuan per ton.

[0038] Example 2 (High Humus Content and Young Leachate) This embodiment uses humus soil excavated from a landfill in Anhui Province (landfill age 6 years) and fresh leachate from the same site as raw materials. The humus soil has an organic matter content of 55%, and the heavy metal content does not exceed the limits specified in the NY / T 525-2021 "Organic Fertilizer" standard; the leachate has a COD of 65000 mg / L, total nitrogen of 2200 mg / L, and total phosphorus of 350 mg / L.

[0039] Preparation steps: S1 Pretreatment: Since the heavy metal content of the humus soil did not exceed the standard, no passivating agent was added in this embodiment. The moisture content was directly adjusted to 30% to obtain pretreated humus soil. 1.0% (g / mL) polyferric sulfate and 0.2% (g / mL) polyacrylamide were added to the leachate as flocculants. After standing for 8 hours, a clear leachate was obtained (COD decreased to 5200 mg / L). The precipitated sludge was reused in the pretreated humus soil.

[0040] S2 mixed composting: pretreated humus, leachate, rice husk powder, and sawdust as carbon source and auxiliary materials, and compound microbial agent (yeast: Bacillus subtilis = 1:1, effective viable count 1.5 × 10⁻⁶).8 The ingredients (CFU / g) were mixed in a mass ratio of 80:15:8:2:0.8, and after thorough mixing, the carbon-nitrogen ratio was 22:1, the moisture content was 62%, and the mixture was stacked in a windrow pile with a height of 1.2 m and a width of 2.5 m.

[0041] S3 aerobic fermentation: initial ventilation volume is 0.5m³. 3 / (h •m 3 The material was turned over twice daily. On the 4th day, the pile temperature rose to 65℃ and was maintained for 10 days, with 3 kg of leachate (3.0% of the pile mass) added every 3 days. After 10 days, forced ventilation was stopped, and the pile was turned over once every 2 days. On the 22nd day, the pile temperature dropped to 35℃ and the moisture content dropped to 26%, resulting in well-rotted material.

[0042] S4 Post-processing: The composted material is screened by a 12-mesh vibrating sieve. The material passing through the sieve is dried at a low temperature of 65℃ with hot air until the moisture content is 15%. Then, it is granulated by disc granulation to produce particles with a particle size of 2~4mm, thus obtaining the finished organic fertilizer product.

[0043] Product testing: Organic matter 48.7%, total nutrients 5.6%, moisture 15%, pH 7.5, all heavy metal contents are below the NY / T525-2021 standard limit, and seed germination index 89%.

[0044] like Figure 3 The equipment for co-producing organic fertilizer from humus and leachate according to this invention was deployed at the landfill remediation site for continuous operation testing. The equipment includes: Fermentation tank 1 is used to support pile 11. In this embodiment, windrow fermentation is adopted, and a hardened impermeable floor 14 is set at the bottom. The forced ventilation system includes a fan 21, an aeration pipe 22, and an air volume regulating valve 23; the fan 21 is a variable frequency centrifugal fan, and the fan 21 is electrically connected to a PLC controller 32, with an initial air volume of 0.5 m³ / h. 3 / (h •m 3 Material), air pressure 3 kPa; aeration pipe 22 with a diameter of DN100, buried at the bottom of the pile 11, with a hole diameter of 5 mm and an opening rate of 12% in the pipe wall, and each aeration pipe 22 is equipped with an air volume regulating valve 23, which is a manual butterfly valve.

[0045] The temperature monitoring and automatic control system includes a temperature sensor 31 installed inside the stack body 11 and a PLC controller 32 electrically connected to the temperature sensor 31. The temperature sensor 31 uses PT100 thermocouples and is set in three sets, which are respectively installed inside the stack body 11 at depths of 0.3m, 0.6m and 0.9m from the surface, and the signals are connected to the PLC controller 32. The turning machine 4 is movably installed on the fermentation tank 1; in this embodiment, a tracked turning machine is used, with a turning width of 2.5m, a turning depth of 1.0m, and a step distance of 0.8m for each stroke.

[0046] The leachate replenishment device includes a leachate clear liquid storage tank 51, a metering pump 52, and an atomizing spray pipe 53 arranged on the turning machinery 4. The metering pump 52 is electrically connected to the PLC controller 32. The leachate clear liquid storage tank 51 has a volume of 10m³. 3 Metering pump 52, flow rate 1.0 m³ / h 3 / h, the atomizing spray pipe 53 is installed above the stack body 11 to achieve static spraying. Eight nozzles 54 are evenly distributed on the atomizing spray pipe 53. The nozzle 54 has an orifice diameter of 2mm, a spraying pressure of 0.5 MPa, and a spraying direction of vertically downward.

[0047] Comparative Example 1 (humus soil composted separately using a water washing process) This comparative example uses the humus washing composting process disclosed in Chinese invention patent CN111548233A as a reference, and adopts the same humus raw materials and the same product testing standards as in Example 1.

[0048] Preparation steps: (1) Humus pretreatment (water washing process): Humus is screened in three stages (screen size is 20mm, 10mm and 5mm respectively). The undersized material enters the water washing system. The humus is washed by jet water rinsing combined with ultrasonic oscillation. The water washing temperature is 40℃±2℃, the water washing time is 30min, and the water washing water volume is 2.5 times the mass of humus. After water washing, the material enters the jigging separator for further separation. After dewatering, organic residue (moisture content of about 35%) and water washing wastewater are obtained. The water washing wastewater is recycled after sedimentation and filtration. High-concentration wastewater is discharged every 3 batches.

[0049] (2) Leachate treatment: The leachate is treated by biochemical process to obtain pretreated tailwater. No flocculation and sedimentation treatment is used, and no sludge is reused. The pretreated leachate tailwater is only used for spraying in the subsequent maintenance stage and does not enter the fermentation system.

[0050] (3) Heavy metal treatment: After the humus is washed and screened, the fine particles with excessive heavy metals are diverted to the undersize fine material (not used for organic fertilizer). 8% fly ash by weight of the humus is added to the oversize material for physical dilution, without adding any chemical passivating agent.

[0051] (4) Mixing and composting: Take 60 kg of the above-treated organic residue, 5 kg of fly ash, 10 kg of crushed straw powder, and 1 kg of compound microbial agent (the same agent as in Example 1), mix them evenly, adjust the moisture content to 60%, and pile them into a windrow pile with a height of 1.2 m and a width of 2.5 m. Because a large amount of organic matter is lost after the humus is washed with water, 0.8 kg of urea needs to be added to adjust the carbon-nitrogen ratio to 26:1.

[0052] (5) Aerobic fermentation: The initial ventilation rate was 0.3 L / (min•kg material), and the pile was turned twice a day. During the fermentation process, no leachate was added; instead, clean water was used to maintain the moisture content (approximately 2 kg of clean water was added every 4 days). The pile temperature rose to 60°C on the 4th day and was maintained for 12 days. Forced ventilation was stopped after the 16th day, and the pile was turned once every 3 days. On the 30th day, the pile temperature dropped to 38°C, and the moisture content was 29%, resulting in matured material. The fermentation cycle was extended by 5 days compared to Example 1.

[0053] (6) Post-treatment: During the curing stage, the matured material is sprayed with leachate pretreatment tailings, and then screened by a 15-mesh vibrating screen. The material under the screen is dried at a low temperature of 70°C with hot air until the moisture content is 18%, and then extruded and granulated to produce particles with a particle size of 3-5 mm. Bentonite needs to be added as a binder during the granulation process, and the dosage is 3% of the material mass.

[0054] The washing process generates approximately 110L of high-concentration organic wastewater (including sludge), which is recycled for five batches after sedimentation and filtration. The accumulated dissolved organic matter and salts in the recycled water result in a final discharge of approximately 45L of wastewater, which must be disposed of as industrial wastewater. Each ton of humus treated increases the wastewater treatment cost by approximately 35 yuan. The jigging and sorting process discharges approximately 20L of wastewater containing fine particles.

[0055] Product testing results: Organic matter 38.2%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) 4.1%, moisture 19%, pH 7.4, total lead 50 mg / kg, total arsenic 9.2 mg / kg, total mercury 0.5 mg / kg, total cadmium 1.1 mg / kg, total chromium 72 mg / kg, seed germination index 76%. While the organic matter and total nutrient levels meet the basic requirements of NY / T 525-2021, they are significantly lower than those of the product in Example 1; the lead content is 51 mg / kg, slightly exceeding the standard limit; and the seed germination index of 76% is lower than the recommended value of 85% for high-quality organic fertilizer.

[0056] Cost Accounting: The washing process requires specialized equipment such as a screening system, jet washing device, ultrasonic oscillation equipment, jigging separator, belt filter press, and wastewater treatment facilities. Equipment investment is approximately 1.8 million yuan (based on an annual processing capacity of 10,000 tons of humus, excluding plant and civil engineering costs). The cost of purchased fly ash is approximately 40 yuan / ton of humus, the cost of urea is approximately 75 yuan / ton of humus, the cost of bentonite binder is approximately 18 yuan / ton of product, and the cost of wastewater disposal is approximately 35 yuan / ton of humus. The total cost is approximately 670 yuan / ton of organic fertilizer product.

[0057] Comparative Example 2 (Comparative process without passivating agent and sludge reuse) This comparative example uses the same humus and leachate raw materials as Example 1, but omits the steps of adding passivating agent and reusing precipitated sludge; the rest of the process is the same as in Example 1.

[0058] Preparation steps: (1) Humus pretreatment: Only adjust the moisture content to 35% and do not add any passivating agent to obtain pretreated humus.

[0059] (2) Leachate pretreatment: Same as in Example 1, but the precipitated sludge is not reused and is disposed of as solid waste.

[0060] (3) Mixing and stockpiling: The proportions and mixing methods are the same as in Example 1, and a mixture is obtained.

[0061] (4) Aerobic fermentation: The fermentation parameters and liquid replenishment method are the same as in Example 1, and the fermentation cycle is the same as in Example 1, to obtain the decomposed material.

[0062] (5) Post-processing: Same as in Example 1.

[0063] The sludge, weighing approximately 3.2 kg (with a moisture content of 75%), needs to be transported off-site as solid waste, increasing the disposal cost by approximately 4.5 yuan per ton of humus and resulting in a loss of approximately 0.8 kg of organic matter.

[0064] Product testing results: Organic matter 49.8%, total nutrients 5.9%, moisture 18%, pH 7.3, total lead 55 mg / kg (13 mg / kg higher than Example 1, exceeding the NY / T 525-2021 standard limit of 50 mg / kg), total arsenic 9.1 mg / kg, total mercury 0.4 mg / kg, total cadmium 1.0 mg / kg, total chromium 70 mg / kg, seed germination index 80%. Compared to Example 1: total lead content increased by 10% to 55 mg / kg; total chromium content increased from 65 mg / kg to 70 mg / kg; seed germination index decreased from 85% to 80%. This indicates that without passivating agents, the passivation effect of heavy metals is insufficient, the bioavailability of heavy metals is significantly increased, and product safety is reduced.

[0065] The main process parameters of Example 1, Comparative Example 1, and Comparative Example 2 are shown in Table 1. Table 1

[0066] The product quality of Example 1, Comparative Example 1, and Comparative Example 2 is shown in Table 2. Table 2

[0067] A comparison of Table 1 and Table 2 shows that: (1) Although Comparative Example 1 (water washing process) can produce organic fertilizer products that basically meet national standards, its process is complex and the equipment investment is high. The comprehensive cost of 670 yuan / ton of organic fertilizer products is 2.4 times that of Example 1. Moreover, the water washing process generates a large amount of high-concentration organic wastewater, which needs to be transported and disposed of externally. It does not meet the requirements of zero discharge throughout the process. The organic matter and total nutrients of the product are significantly lower than those of Example 1, with a seed germination index of only 76%, which cannot meet the standard requirements of high-quality organic fertilizer.

[0068] (2) The total lead content of Comparative Example 2 (omitting the addition of passivating agent and sludge reuse) exceeded the limit of NY / T 525-2021 standard, and the seed germination index dropped from 85% to 80%, indicating that the passivation effect of heavy metals was insufficient without passivating agent, the bioavailability of heavy metals could not meet the standards for farmland application, and there were potential safety hazards in the product. At the same time, the off-site disposal of precipitated sludge not only increased the treatment cost, but also caused the waste of organic matter.

[0069] (3) Example 1 of the present invention is significantly superior to the two comparative examples in terms of fermentation cycle, product quality, cost control and environmental protection. It avoids the secondary pollution and high cost of the water washing process, and achieves chemical passivation of heavy metals through the use of passivating agents and full resource utilization through the reuse of precipitated sludge. It ensures the synergistic improvement of product safety and fertilizer efficiency, and fully reflects the technical advantages of "treating waste with waste and synergistic efficiency". It should be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0070] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for synergistically preparing organic fertilizer from humus and leachate, characterized in that, Includes the following steps: S1 Pretreatment: The humus obtained from the landfill screening is subjected to heavy metal passivation treatment using a passivating agent, and the moisture content is adjusted to 25%~45% to obtain pretreated humus. The landfill leachate is treated by flocculation and sedimentation with flocculant to obtain clear leachate and settled sludge, and the settled sludge is reused in the pretreated humus soil. S2 Mixed Composting: The pretreated humus, leachate, carbon source additives and compound microbial agents are mixed evenly, the carbon-nitrogen ratio is adjusted to 20:1~30:1 and the moisture content is 50%~65%, and then piled into a pile. S3 Aerobic Fermentation: Forced ventilation and turning of the pile are carried out; during the fermentation process, the leachate is added to maintain the moisture content, and the pile temperature is controlled at 55℃~65℃ for 7~14 days to obtain mature material. S4 Post-processing: The decomposed material is screened, dried, and granulated to obtain the finished organic fertilizer.

2. The method for synergistic preparation of organic fertilizer from humus and leachate according to claim 1, characterized in that, The passivating agent in S1 includes one or more of superphosphate, phosphate rock powder, zeolite powder, or biochar; the flocculant includes one or more of polyaluminum chloride, polyacrylamide, or polyferric sulfate.

3. The method for synergistic preparation of organic fertilizer from humus and leachate according to claim 1, characterized in that, The mass ratio of the pretreated humus, leachate, carbon source additives, and compound microbial agent in S2 is (50~80):(10~30):(5~20):(0.5~2); the carbon source additives include one or more of straw powder, rice husk powder, sawdust, or fungal residue; the compound microbial agent contains one or more of Bacillus, Lactobacillus, or Yeast, with an effective viable count ≥1×10⁻⁶. 8 CFU / g.

4. The method for synergistic preparation of organic fertilizer from humus and leachate according to claim 1, characterized in that, The frequency of adding leachate clear liquid as described in S3 is once every 3 to 5 days, and the amount added at one time is 2% to 5% of the mass of the pile.

5. The method for synergistic preparation of organic fertilizer from humus and leachate according to claim 1, characterized in that, The aerobic fermentation described in S3 uses temperature feedback control: when the pile temperature exceeds 65℃, increase the ventilation volume; when it is below 55℃, reduce or stop ventilation. In the later stage of fermentation, stop ventilation and turn the pile regularly. Fermentation is completed when the pile temperature drops below 40℃ and the moisture content drops below 30%.

6. An apparatus for the co-preparation of organic fertilizer from humus and leachate using the method described in any one of claims 1-5, characterized in that, include: Fermentation tanks are used to support the pile, including trough-type fermentation tanks or windrow-type hardened impermeable flooring. Forced ventilation system, including fan, aeration pipe and air volume regulating valve; A temperature monitoring and automatic control system includes a temperature sensor installed inside the reactor and a PLC controller electrically connected to the temperature sensor. The PLC controller is used to adjust the fan frequency according to a temperature threshold. The turning machine is movably installed on the fermentation tank; The leachate replenishment device includes a leachate clear liquid storage tank, a metering pump, and an atomizing spray pipe arranged above the pile or on the turning machinery. The metering pump is electrically connected to the PLC controller.

7. The equipment for co-preparing organic fertilizer from humus and leachate according to claim 6, characterized in that, When the fermentation tank is a trough-type fermentation tank, the turning machine is a hydraulically driven or chain-plate type turning machine, straddling the tracks on both sides of the trough-type fermentation tank. The turning roller speed is 80~120 rpm, and the turning depth is 1.0~1.5 meters. When the fermentation tank is a windrow-type hardened seepage-proof floor, the turning machine is a tracked or wheeled turning machine, with a turning width of 2~3 meters and a turning depth of 0.8~1.2 meters. The turning machine's step distance for each stroke is 0.8~1.2 meters.

8. The equipment for co-preparing organic fertilizer from humus and leachate according to claim 6, characterized in that, The atomizing spray pipe is equipped with a nozzle, the nozzle orifice diameter is 1~2 mm, the spray pressure is 0.2~0.5 MPa, and the droplet diameter is 30~100 micrometers; When the fermentation tank is a trough-type fermentation tank and the atomizing spray pipe is arranged above the pile, the nozzle is a wide-angle fan-shaped atomizing nozzle with a spray angle of 110°~130°, the spray direction is inclined downward at an angle of 30°~45° with the horizontal plane, the nozzle axis is deflected by 10°~20° from the normal of the pile surface, the spacing between adjacent nozzles along the length of the trough is 1.0~1.5 meters, and 2~3 nozzles are arranged along the width of the trough with a spacing of 0.8~1.2 meters; when the fermentation tank is a trough-type fermentation tank and the atomizing spray pipe is arranged on the turning machine, 6~8 nozzles are evenly distributed along the length of the beam of the turning machine with a spacing of 0.4~0.6 m, the spray direction is perpendicular to the forward direction of the turning machine, and the spray plane is at an angle of 15°~25° with the horizontal plane; When the fermentation tank is a windrow-type hardened impermeable floor and the atomizing spray pipes are arranged above the pile, 5 to 8 nozzles are evenly distributed along the width of the windrow, with a spacing of 0.3 to 0.5 m, and the nozzle axis is vertically downward; when the fermentation tank is a windrow-type hardened impermeable floor and the atomizing spray pipes are arranged on the turning machine, the spraying direction is tilted backward at an angle of 15° to 25° with the horizontal plane.

9. The equipment for co-preparing organic fertilizer from humus and leachate according to claim 6, characterized in that, The aeration pipe is buried at the bottom of the tank or below the pile, with a pipe diameter of DN50~DN100, a pipe wall opening diameter of 3~5 mm, and an opening rate of 8%~12%; the blower is a variable frequency centrifugal blower, with an air volume of 0.2~0.5 cubic meters / hour per cubic meter of material, and an air pressure ≥3 kPa.

10. The apparatus for co-preparing organic fertilizer from humus and leachate according to claim 6, characterized in that, At least three sets of temperature sensors are provided, located at different depths within the stack.

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