Sludge and fly ash mixed filling treatment process

Abstract

The invention relates to the technical field of waste landfill treatment, and discloses a sludge and fly ash mixed filling treatment process which comprises the steps of porous medium composite adsorption medium preparation, ion exchange pre-activation modification, osmotic pressure gradient layer construction, electrochemical activation field formation, ion channel dredging treatment, osmotic pressure self-repairing adjustment, electrochemical self-cleaning maintenance and the like. According to the method, efficient removal and long-term stable treatment of heavy metal pollutants are achieved through the synergistic effect of porous medium enhanced permeation adsorption and ion exchange pre-activation in combination with osmotic pressure gradient directional migration and electrochemical activation, the heavy metal removal rate is high, the landfill system stably operates for a long time, manpower is reduced, and the environmental pollution risk is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste landfill treatment, more particularly, it relates to a sludge and fly ash mixed filling treatment process. BACKGROUND

[0002] Garbage incineration fly ash contains a large amount of heavy metals and dioxin and other harmful substances as hazardous waste, sewage treatment sludge has good adsorption performance, and the mixed landfill of the two is the main current collaborative disposal method.

[0003] In the prior art, the traditional sludge and fly ash mixed filling process mainly adopts a simple physical mixing method, but has significant technical defects: the adsorption capacity of the porous medium is limited and is easy to reach saturation state, local uneven permeation leads to unstable pollutant treatment effect; in a complex landfill environment, a plurality of heavy metal ions compete for limited adsorption sites, organic substances shield and interfere with ion exchange, and the selective adsorption effect is poor; in the long-term operation process, the ion migration channel is blocked by sediments, the osmotic pressure gradient gradually decays and fails, and the electrochemical system performance continuously decreases, which requires frequent manual maintenance.

[0004] How to realize efficient directional migration and long-term stable removal of heavy metal pollutants in the process of sludge and fly ash mixed filling, and at the same time have self-maintenance ability to reduce operation cost, is a problem to be solved at present. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a sludge and fly ash mixed filling treatment process, comprising the following steps: Step 1: mixing modified zeolite and bentonite to obtain a porous material composition, and mixing and stirring the porous material composition with dry sludge with a water content of less than 60% to obtain a composite adsorption medium; Step 2: pre-activating the composite adsorption medium with a calcium chloride solution to obtain a pre-activated composite adsorption medium; Step 3: constructing an osmotic pressure gradient system in layers in the landfill area, sequentially laying a high concentration gradient layer, a medium concentration gradient layer and a low concentration gradient layer from top to bottom to form a directional osmotic pressure gradient field; Step 4: arranging electrodes in the landfill body, applying a direct current voltage to form an electric field environment, so that heavy metal cations migrate towards the cathode and combine with active sites in the pre-activated composite adsorption medium; Step 5: periodically adding a biological enzyme mixture to the landfill body to decompose organic sediments and biofilms accumulated in the ion migration channel; Step 6: embedding an osmotic pressure sensing unit in the osmotic pressure gradient layer, and when the osmotic pressure gradient deviates from the preset value, automatically releasing a regulator to restore the osmotic pressure gradient; Step 7: Electrode self-cleaning is performed in an alternating electric field mode to prevent continuous aggregation of ions on the electrode surface.

[0006] Preferably, in step 1, the modified zeolite and the bentonite are mixed in a weight ratio of 1:1, the pore size of the modified zeolite is 0.5-2.0 nm, and the specific surface area of the bentonite is greater than 300 m² / g;The porous material composition is mixed and stirred with the dried sludge in a weight ratio of 1:3, and the stirring time is 30-45 minutes.

[0007] Preferably, in step 2, the concentration of the calcium chloride solution is 0.1-0.5 mol / L, and the pre-activation treatment time is 2-4 hours.

[0008] Preferably, in step 3, the high-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 2-3 mol / L and a thickness of 20-30 cm;The medium-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 1-1.5 mol / L and a thickness of 30-40 cm;The low-concentration gradient layer is infiltrated with deionized water with a thickness of 40-50 cm.

[0009] Preferably, in step 4, the electrodes are arranged in a grid pattern, the electrode spacing is 1-2 meters, and the electrode material is graphite or titanium alloy;The direct current voltage is 3-5 V, and the current density is controlled in the range of 0.1-0.5 A / m².

[0010] Preferably, in step 5, the biological enzyme mixed solution includes cellulase and protease, and the enzyme concentration is 50-100 U / mL, and the dosing period is once a month.

[0011] Preferably, in step 6, the osmotic pressure sensing unit includes a semi-permeable membrane and an indicator solution, and the regulator is a coated slow-release sodium chloride particle, and the diameter of the sodium chloride particle is 0.5-1.0 mm.

[0012] Preferably, in step 7, the alternating electric field mode refers to the alternating application of a forward electric field and a reverse electric field, and the alternating period is 24 hours.

[0013] Preferably, it further comprises step 8: mixing the pre-activated composite adsorption medium with fly ash in a weight ratio of 3:1, and constructing the landfill in a layered landfill manner, and the thickness of each layer is controlled in the range of 50-80 cm.

[0014] Preferably, it further comprises step 9: regularly monitoring the heavy metal concentration and pH value in the leachate, the monitoring frequency is once a week, the heavy metal concentration is monitored by atomic absorption spectrometry or inductively coupled plasma mass spectrometry, the pH value is monitored by electrode method, and the recording range is 6.0-9.0.

[0015] The present application provides a sludge and fly ash mixed landfill treatment process, comprising: The present application has the following advantages: The processing efficiency is significantly improved: the synergistic effect of composite adsorption medium and ion exchange pre-activation makes the heavy metal removal rate reach 85-95%, which is more than 70% higher than that of the traditional mixed filling process. The osmotic pressure gradient directional migration technology realizes the active collection of pollutants, avoiding the loss of processing efficiency caused by disordered diffusion.

[0016] The long-term stability is greatly improved: through the osmotic pressure self-repairing mechanism and the electrochemical self-cleaning system, the landfill system can be stably operated for more than 20 years, which is much longer than the effective period of 5-8 years of the traditional process. The directional migration efficiency is maintained above 90% in long-term operation, overcoming the problem of decreasing efficiency year by year of the traditional process.

[0017] The self-maintenance ability is outstanding: the integration of ion channel dredging, osmotic pressure self-repairing and electrochemical self-cleaning three self-maintenance functions makes the demand for artificial maintenance decrease by more than 90%. The biological enzyme cleaning method has the characteristics of environmental friendliness, avoiding the secondary pollution risk caused by chemical cleaning.

[0018] The environmental safety is enhanced: through the dual effects of electrochemical activation and complex stabilization, the harmful substances such as heavy metals and dioxins in fly ash are effectively fixed, and the pollutant concentration in the leachate is reduced to below the environmental protection standard. The long-term stability of the landfill system ensures the continuous control of environmental risks.

[0019] The adaptability and practicality are strong: the process is suitable for fly ash and sludge combination of different components, and can maintain stable treatment effect under complex ion environment and climate change conditions. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the heavy metal ion removal rate trend comparison chart of the present invention.

[0021] Figure 2 is the long-term stability comparison chart of the key performance indicators of the landfill system of the present invention.

[0022] Figure 3 is the porosity change trend comparison of the landfill system of the present invention.

[0023] Figure 4 is the system performance self-recovery curve comparison chart of the present invention.

[0024] Figure 5 is the dioxin degradation / fixation effect comparison chart of the present invention.

[0025] Figure 6 is the heavy metal removal effect comparison under complex ion environment of the present invention. DETAILED DESCRIPTION

[0026] The subject matter described herein will now be discussed with reference to example implementations. It should be understood that the discussion of these implementations is merely meant to provide a better understanding of the subject matter described herein and can be changed in ways that do not depart from the scope of the subject matter contained in this specification. Various examples can omit, substitute, or add various procedures or components as appropriate. Also, it should be understood that some features described with respect to one example can be combined in other examples.

[0027] Embodiment 1 A sludge and fly ash mixed filling treatment process, comprising the following steps: Step 1: mixing modified zeolite and bentonite to obtain a porous material composition, and mixing the porous material composition with dry sludge with a water content of less than 60% to obtain a composite adsorption medium; The modified zeolite and the bentonite are mixed at a weight ratio of 1:1, the pore size of the modified zeolite is 1.2 nm, and the specific surface area of the bentonite is greater than 300 m² / g; the porous material composition is mixed with the dry sludge at a weight ratio of 1:3, and the stirring time is 38 minutes.

[0028] Step 2: pre-activating the composite adsorption medium with a calcium chloride solution to obtain a pre-activated composite adsorption medium; The concentration of the calcium chloride solution is 0.3 mol / L, and the pre-activation time is 3 hours.

[0029] Step 3: constructing a permeation pressure gradient system in a landfill area in layers, sequentially laying a high-concentration gradient layer, a medium-concentration gradient layer, and a low-concentration gradient layer from top to bottom to form a directional permeation pressure gradient field; The high-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 2.5 mol / L and a thickness of 25 cm; the medium-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 1.25 mol / L and a thickness of 35 cm; and the low-concentration gradient layer is infiltrated with deionized water with a thickness of 45 cm.

[0030] Step 4: arranging electrodes in the landfill body, applying a direct current voltage to form an electric field environment, and causing heavy metal cations to migrate towards the cathode and combine with active sites in the pre-activated composite adsorption medium; The electrodes are arranged in a grid pattern with an electrode spacing of 1.5 meters, and the electrode material is graphite; the direct current voltage is 4 V, and the current density is controlled within the range of 0.3 A / m².

[0031] Step 5: periodically adding a biological enzyme mixture to the landfill body to decompose organic sediments and biological membranes accumulated in the ion migration channel; The biological enzyme mixture includes cellulase and protease, and the enzyme concentration is 75 U / mL, and the addition cycle is once a month.

[0032] Step 6: The osmotic pressure sensing unit is buried in the osmotic pressure gradient layer, and when the osmotic pressure gradient deviates from the preset value, the adjusting agent is automatically released to restore the osmotic pressure gradient; The osmotic pressure sensing unit comprises a semi-permeable membrane and an indicating solution, and the adjusting agent is a coated slow-release sodium chloride particle with a diameter of 0.7 mm.

[0033] Step 7: Electrode self-cleaning is performed in an alternating electric field mode to prevent continuous aggregation of ions on the electrode surface. The alternating electric field mode refers to the alternating application of a forward electric field and a reverse electric field with an alternating period of 24 hours.

[0034] Step 8: The pre-activated composite adsorption medium is mixed with fly ash at a weight ratio of 3:1, and a landfill site is constructed using a layered landfill method, with each layer controlled to a thickness of 65 cm.

[0035] Step 9: Regularly monitor the heavy metal concentration and pH value in the leachate, with a monitoring frequency of once a week. The heavy metal concentration is monitored using atomic absorption spectrometry or inductively coupled plasma mass spectrometry, and the pH value is monitored using an electrode method, with a recording range of 7.5.

[0036] Example 2 The difference between this example and Example 1 is: Step 1: The pore size of the modified zeolite is 0.5 nm, and the stirring time is 30 minutes.

[0037] Step 2: The calcium chloride solution concentration is 0.1 mol / L, and the pre-activation treatment time is 2 hours.

[0038] Step 3: The high-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 2 mol / L and a thickness of 20 cm; the medium-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 1 mol / L and a thickness of 30 cm; and the low-concentration gradient layer is infiltrated with deionized water with a thickness of 40 cm.

[0039] Step 4: The electrodes are arranged in a grid pattern with an electrode spacing of 1 meter, and the electrode material is titanium alloy; the direct current voltage is 3V, and the current density is controlled within the range of 0.1 A / m².

[0040] Step 5: The biological enzyme mixture includes cellulase and protease, with an enzyme concentration of 50 U / mL and a dosing period of once a month.

[0041] Step 6: The sodium chloride particle diameter is 0.5 mm.

[0042] Step 8: Each layer is controlled to a thickness of 50 cm.

[0043] Step 9: The pH value is monitored using an electrode method, with a recording range of 6.0.

[0044] Example 3 The difference between this embodiment and embodiment 1 is that: Step 1: The pore size of the modified zeolite is 2.0 nm, and the stirring time is 45 minutes.

[0045] Step 2: The concentration of the calcium chloride solution is 0.5 mol / L, and the pre-activation treatment time is 4 hours.

[0046] Step 3: The high-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 3 mol / L and a thickness of 30 cm; the medium-concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 1.5 mol / L and a thickness of 40 cm; and the low-concentration gradient layer is infiltrated with deionized water with a thickness of 50 cm.

[0047] Step 4: The electrodes are arranged in a grid pattern with an electrode spacing of 2 meters; the direct current voltage is 5 V, and the current density is controlled within the range of 0.5 A / m².

[0048] Step 5: The biological enzyme mixture includes cellulase and protease, and the enzyme concentration is 100 U / mL, with a dosing period of once a month.

[0049] Step 6: The sodium chloride particles have a diameter of 1.0 mm.

[0050] Step 8: The thickness of each layer is controlled to be 80 cm.

[0051] Step 9: The pH value is monitored using the electrode method, and the recording range is 9.0.

[0052] Example 4 In this embodiment, a sludge and fly ash mixed filling treatment process is proposed, which includes the following specific steps: Step S1: Preparation of porous medium composite adsorption medium The modified zeolite and bentonite are mixed in a weight ratio of 1:1 to obtain a porous material composition, wherein the pore size of the modified zeolite is 1.3 nm, and the specific surface area of the bentonite is greater than 300 m² / g. The porous material composition is mixed and stirred with dried sludge with a water content of less than 60% at a weight ratio of 1:3, and the stirring time is 40 minutes to obtain a composite adsorption medium.

[0053] This step forms a composite medium with different pore sizes and adsorption properties through the synergistic effect of double porous materials, which realizes the graded capture of heavy metal ions with different particle sizes compared with the single adsorption material of the prior art.

[0054] The modified zeolite refers to a natural zeolite after acid treatment or cation exchange treatment, and the Al 3+The mesoporous structure is formed by partial removal, and the pore size range is 1.3 nm, mainly used for adsorbing medium-sized heavy metal ions such as copper ions and zinc ions. Bentonite is a clay mineral with montmorillonite as the main component, which has a layered silicate structure, a specific surface area greater than 300 m² / g, and good cation exchange capacity, mainly adsorbing large-sized heavy metal ions such as lead ions and cadmium ions. During the mixing process, the mesoporous structure of the modified zeolite and the interlayer space of the bentonite form a continuous pore network, and the organic matter in the sludge fills the gap between the pores, enhancing the overall stability of the composite medium. The weight ratio of 1:3 ensures that the sludge matrix can carry enough porous materials, and the stirring time of 40 minutes ensures that the porous materials are uniformly dispersed in the sludge, forming a stable composite adsorption medium.

[0055] Step S2: Ion exchange pre-activation modification The composite adsorption medium is pre-activated by calcium chloride solution, and the concentration of calcium chloride solution is 0.3 mol / L, and the treatment time is 3 hours. During the pre-activation process, calcium ions exchange with the original cations in the porous medium, replacing sodium ions, potassium ions and other monovalent ions, and forming calcium ion active sites on the surface of the porous medium. The ion exchange capacity of the pre-activated composite adsorption medium is increased by 40-60% compared with the untreated medium.

[0056] This step breaks through the limitations of traditional passive adsorption and creates preferential binding sites for heavy metal ions through active ion pre-displacement.

[0057] Ion exchange pre-activation is based on the principle of ion exchange equilibrium, and calcium ions (Ca 2+ ) are used to displace the exchangeable cations (mainly Na + , K + ) on the surface of zeolite and bentonite: 2Na + + Ca 2+ → Ca 2+ + 2Na + . As a divalent ion, calcium ion has higher charge density than monovalent ion, and has stronger electrostatic binding force with silicon-oxygen tetrahedral framework, forming stable Ca 2+ -silicon-oxygen bond sites. The concentration of calcium chloride solution is 0.3 mol / L, which provides sufficient calcium ion concentration to drive the exchange reaction. If the concentration is too low, the exchange will not be sufficient, and if the concentration is too high, calcium ions will precipitate on the surface. The treatment time of 3 hours ensures that the ion exchange reaches equilibrium state, and the exchange reaction follows Langmuir adsorption isotherm. The surface calcium ion density of the pre-activated composite adsorption medium increases, providing more binding sites for subsequent heavy metal ion adsorption, and the ion exchange capacity increases by 40-60%, which means that the number of moles of cations exchanged per unit mass of adsorption medium increases.

[0058] Step S3: osmotic pressure gradient layer construction The osmotic pressure gradient system is constructed in layers in the landfill area. From top to bottom, a high concentration gradient layer, a medium concentration gradient layer, and a low concentration gradient layer are laid in turn. The high concentration gradient layer is soaked with a sodium chloride solution with a concentration of 2.5 mol / L and a thickness of 25 cm. The medium concentration gradient layer is soaked with a sodium chloride solution with a concentration of 1.2 mol / L and a thickness of 35 cm. The low concentration gradient layer is soaked with deionized water and has a thickness of 45 cm. Through the osmotic pressure difference between the layers of different concentrations, an osmotic driving force from high concentration to low concentration is formed, and a directional osmotic pressure gradient field is obtained. This construction method is different from the uniform distribution method of the prior art, and creates a controllable liquid directional flow condition.

[0059] The osmotic pressure gradient is a driving force generated based on the chemical potential difference of the solution, which follows the Van't Hoff equation π = iMRT, where π is the osmotic pressure, i is the electrolyte dissociation degree, M is the molar concentration, R is the gas constant, and T is the absolute temperature. Sodium chloride is completely ionized into Na + and Cl - , and the value of i is 2. Therefore, the osmotic pressure of a 2.5 mol / L sodium chloride solution is about 150 atm, the osmotic pressure of a 1.2 mol / L solution is about 72 atm, and the osmotic pressure of deionized water is close to 0. The osmotic pressure difference drives water molecules to migrate from the low concentration area to the high concentration area, while carrying dissolved heavy metal ions to migrate directionally. The thickness of the layers is set according to the law of osmotic migration distance. The high concentration layer (25 cm) is used as the driving source, the medium concentration layer (35 cm) is used as the buffer transition zone, and the low concentration layer (45 cm) is used as the pollutant enrichment zone. The osmotic pressure gradient field refers to the continuous osmotic pressure distribution formed in the vertical direction of the landfill. The osmotic driving force is: ; The negative gradient indicates that the driving force is directed from high concentration to low concentration.

[0060] Step S4: electrochemical activation field formation Electrodes are arranged in a grid pattern in the landfill. The electrode spacing is 1.5 meters, and the electrode material is graphite or titanium alloy. A direct current voltage of 4V is applied, and the current density is controlled within the range of 0.3 A / m², forming a weak electric field environment. Under the action of the electric field, heavy metal cations migrate towards the cathode and combine with active sites in the pre-activated composite adsorption medium. The electrochemically activated ion directional migration condition is obtained, and the electric field strength can effectively drive ion migration while avoiding adverse effects on microbial activity.

[0061] Electrochemical activation is based on the principle of electrokinetics, which uses an external electric field to exert a Coulomb force on charged ions to achieve directional migration. Graphite electrodes have good electrical conductivity and chemical stability, and titanium alloy electrodes have excellent corrosion resistance. Both materials are suitable for long-term electrochemical reactions in landfill environments. Grid arrangement refers to the arrangement of electrodes in a rectangular grid, with positive and negative electrodes alternating. The electrode spacing is 1.2 meters to ensure uniform distribution of the electric field strength and avoid excessive local electric field strength that can cause electrolytic water reactions. The electric field strength E = U / d = 4V / (1.5m) = 2.7V / m generated by a direct current voltage of 4V. The migration rate of heavy metal ions v = μE under this intensity, where μ is the ion electrophoretic mobility. The current density of 0.3A / m² controls the rate of electrochemical reaction to avoid the production of excess H2 and O2 gas affecting the structure of the landfill. Heavy metal cations migrate to the cathode under the action of the electric field, and during the migration process, they compete with calcium ions on the surface of the pre-activated composite adsorption medium: Ca 2+ + Pb 2+ → Pb 2+ + Ca 2+ Heavy metal ions such as lead ions preferentially occupy adsorption sites to form stable combinations.

[0062] Step S5: Ion channel dredging treatment Periodically add a mixture of cellulase and protease to the landfill, with an enzyme concentration of 75U / mL and a dosing period of once a month. Enzyme solution reaches the ion migration channel guided by osmotic pressure gradient, decomposes organic deposits and biofilms accumulated in the channel, and removes shielding materials for ion exchange. At the same time, small organic molecules produced by enzymatic hydrolysis further form stable complexes with heavy metal ions. A smooth ion migration channel and enhanced complex stabilization effect are obtained. This biological enzymatic method is different from existing physical or chemical cleaning methods, with the characteristics of high selectivity and environmental friendliness.

[0063] Ion channel dredging is a biochemical process that uses the catalytic action of biological enzymes to remove organic blockages. Cellulase (EC 3.2.1.4) can hydrolyze β-1,4-glucosidic bonds to decompose cellulose organic deposits, and the decomposition reaction is: (C6H 10 O5) n + nH2O → nC6H 12O6. Proteases (EC 3.4) are able to hydrolyze peptide bonds in protein molecules, breaking down protein components in biological membranes, with the reaction: Protein + H2O → Polypeptide + Amino acid. Enzyme concentration 75 U / mL is the enzyme activity unit, 1 U represents the amount of enzyme that catalyzes the conversion of 1 μmol of substrate per minute under standard conditions. The dosing cycle is determined based on the accumulation rate of organic sediments and the efficiency of enzymatic hydrolysis once a month. Enzyme solution reaches the ion migration channel through the directional flow of osmotic pressure gradient, which refers to the pore network in the pre-activated composite adsorption medium, including the mesopores (0.5-2.0 nm) of modified zeolite and the interlayer voids (1.5 nm) of bentonite. Small molecule organics such as glucose and amino acids produced by enzymatic hydrolysis contain coordination groups such as carboxyl and amino groups, which can form coordination complexes with heavy metal ions. The complexation reaction is: M 2+ + 2L - → ML2, where M 2+ is a heavy metal ion, and L - is a ligand.

[0064] Step S6: Osmotic pressure self-repairing adjustment Osmotic pressure sensing units are embedded in each osmotic pressure gradient layer, and the sensing units are filled with semi-permeable membranes and indicator solutions. When the osmotic pressure gradient deviates from the preset value, the pressure change in the sensing unit triggers the automatic release of the adjusting agent. The adjusting agent is sodium chloride particles wrapped in a slow-release manner, and the outer coating material breaks under pressure to release the contents. The osmotic pressure recovery function is automatically adjusted to maintain the long-term stability of the gradient field. This self-triggering adjustment method realizes autonomous repair without manual monitoring and intervention.

[0065] Osmotic pressure self-repairing is a physical and chemical adjustment process based on osmotic pressure sensing and trigger release. The osmotic pressure sensing unit is a sealed container made of a semi-permeable membrane, which is filled with a known concentration of sodium chloride indicator solution inside. The semi-permeable membrane only allows water molecules to pass through while preventing ions from passing through. When the external osmotic pressure changes, according to the osmotic balance principle, water molecules will enter or leave the sensing unit through the semi-permeable membrane, causing internal pressure changes. The pressure change ΔP = πext- πint, when ΔP exceeds the set threshold, the pressure acts on the surface of the coating material to generate mechanical stress. The coating material uses pressure-sensitive polymers such as polylactic acid (PLA) or polyethylene glycol (PEG), which break at a pre-set pressure. Sodium chloride particles are released and dissolved in the surrounding environment, replenishing the concentration loss caused by ion migration and dilution, restoring the original osmotic pressure gradient. The slow-release effect is controlled by the particle size, with a particle diameter of 0.7 mm and a dissolution time of about 3 hours, ensuring the gradual recovery of osmotic pressure rather than an instantaneous impact.

[0066] Step S7: Electrochemical self-cleaning maintenance Electrode self-cleaning is carried out in an alternating electric field mode, with positive and negative electric fields applied alternately, with an alternating period of 24 hours. During the electric field conversion, active substances such as hydroxyl radicals and ozone produced by electrolytic reaction clean the deposits and biological contamination layer on the electrode surface. At the same time, the periodic change of electric field direction prevents the continuous accumulation of ions on the electrode surface. A continuously clean electrode surface and stable electrochemical activation effect are obtained. This alternating cleaning method avoids the electrode polarization and pollution problems caused by traditional unidirectional electric field.

[0067] Electrochemical self-cleaning is an electrochemical process that uses electrolytic reaction to produce active oxidizing substances to remove pollutants on the electrode surface. Alternating electric field refers to the positive and negative conversion of electrode polarity according to the set period, the original anode becomes cathode, and the original cathode becomes anode, with an alternating period of 24 hours to ensure sufficient cleaning effect without affecting the continuity of ion migration. Electrolytic reaction occurs on the surface of the anode: 2H2O → O2 + 4H + + 4e - , and hydroxyl radicals are produced simultaneously: H2O → ·OH + H + + e - . Reduction of water occurs on the surface of the cathode: 2H2O + 2e - → H2 + 2OH - . Hydroxyl radicals (·OH) are strong oxidizing substances with an oxidation potential of 2.80V, which can oxidize and decompose organic pollutants and biological membranes on the electrode surface. Ozone (O3) is produced by the electrochemical synthesis of oxygen: 3O2 → 2O3, with an oxidation potential of 2.07V, which has a strong oxidizing effect on bacteria and organic matter. The conversion of electric field direction prevents the continuous accumulation of heavy metal ions on a single electrode surface, avoiding the increase in resistance and reduction in activity caused by the formation of metal deposition layer on the electrode surface. Continuous cleaning means that the concentration of pollutants on the electrode surface is maintained at a low level, and the electrode conductivity and catalytic activity remain stable.

[0068] Step S8: Construction and operation maintenance of mixed filling system The composite adsorption medium treated by the above method is mixed with fly ash at a weight ratio of 3:1, and a layered landfill method is used to construct the landfill. The concentration of heavy metals and pH value in the leachate are monitored regularly to evaluate the treatment effect.

[0069] The mixed filling system is constructed by mixing the pre-activated composite adsorption medium with the waste incineration fly ash according to the weight ratio and laying them in layers. The weight ratio of 3:1 ensures sufficient adsorption medium capacity to treat the heavy metal pollutants in the fly ash, and the ratio is based on the best mixing ratio determined in the foregoing experiment. The layered landfill refers to laying the composite adsorption medium layer and the fly ash layer alternately according to the set thickness, and the thickness of each layer is controlled to be 50-80 cm, so as to ensure the effective establishment of the osmotic pressure gradient and the uniform distribution of the electric field. The operation and maintenance include regular monitoring and data recording, the heavy metal concentration monitoring adopts the atomic absorption spectrometry (AAS) or the inductively coupled plasma mass spectrometry (ICP-MS), and the detection limit reaches the μg / L level. The pH value monitoring adopts the electrode method, and the recording range is 6.0-9.0. The monitoring frequency is once a week, and the continuous monitoring data are used to evaluate the treatment effect and the system stability.

[0070] In order to verify the technical effect of the present application, the following experimental tests are carried out.

[0071] Experiment one: comparison test of heavy metal removal efficiency 1. Experimental purpose The improvement effect of the composite adsorption medium and the ion exchange pre-activation technology of the present application on the heavy metal removal efficiency is verified, and the traditional mixed filling process is compared.

[0072] 2. Experimental materials and equipment Modified zeolite (pore size 0.5-2.0 nm); Bentonite (specific surface area 350 m² / g); Dried sludge (moisture content 55%); Waste incineration fly ash (total heavy metal content 15000 mg / kg); Calcium chloride solution (0.3 mol / L); Sodium chloride solution (2.5 mol / L, 1.2 mol / L); Deionized water; Experimental columnar landfill simulation device (diameter 30 cm, height 200 cm); Graphite electrode (diameter 5 mm); Direct current power supply (0-10V adjustable); Atomic absorption spectrophotometer; Inductively coupled plasma mass spectrometer (ICP-MS); pH meter; Experimental stirring device.

[0073] 3. Experimental steps Experimental group preparation: The pre-activated composite adsorption medium is prepared according to the process steps S1-S4 of the present application; Osmotic pressure gradient layer is constructed; The electrode grid is arranged with an electrode spacing of 1.5 meters; A direct current electric field is set with a voltage of 4V and a current density of 0.3A / m².

[0074] The control group is prepared: The dried sludge and fly ash are directly mixed in a weight ratio of 3:1 by using a traditional process; No osmotic pressure gradient and electric field are set.

[0075] Test method: The same amount of simulated leachate containing Pb 2+ , Cd 2+ , Zn 2+ , Cu 2+ , Hg 2+ and other heavy metal ions with a total concentration of 500mg / L is uniformly injected into the top of the two groups of landfill columns; Leachate samples are collected from the bottom of the two groups of landfill columns every 24 hours; The concentrations of heavy metal ions in each leachate sample are determined; Continuous monitoring is performed for 10 days.

[0076] Data processing: The removal rate of each metal ion is calculated: removal rate (%) = (initial concentration - leaching concentration) / initial concentration x 100%; The total heavy metal removal rate is calculated; The data of the two groups are compared.

[0077] 4. Experimental results See the following table:

[0078] Figure 1 : Comparison chart of the removal rate of heavy metal ions with time.

[0079] 5. Result analysis The removal rate of the five typical heavy metals by the process of the application is significantly higher than that by the traditional mixing process, and the total average removal rate reaches 92.6%, which is about 42 percentage points higher than that by the traditional process.

[0080] The results of 10 days of continuous monitoring show that the heavy metal removal efficiency of the process of the application remains stable, and the total average removal rate still maintains at 91.6% after 10 days, only decreasing by 1 percentage point; while the removal efficiency of the traditional process significantly decreases with time, from the initial 50.6% to 42.0%, with a decrease of 17%.

[0081] The removal effect of heavy metal ions shows a poor selectivity difference, and the removal rate of Pb 2+ and Hg 2+The heavy metal removal effect is most obvious for the heavy metal with equal ionic radius, which is consistent with the multi-level adsorption mechanism of the composite adsorption medium with different pore size distribution.

[0082] The experimental results prove that the synergistic effect of ion exchange pre-activation and osmotic pressure gradient directional migration significantly improves the heavy metal removal efficiency, especially for Pb 2+ and Hg 2+ which are more harmful to the environment.

[0083] Experiment two: long-term stability accelerated test 1. Experimental purpose Verify the improvement effect of the osmotic pressure self-repairing and electrochemical self-cleaning technology of the application on the long-term stability of the landfill system, and evaluate the performance change of the system under the simulated long-term operation conditions.

[0084] 2. Experimental materials and equipment The experimental group and the control group landfill systems prepared in experiment one; Accelerated aging test device (temperature and humidity controllable); Simulated rainfall device; Circulating percolation device; Osmotic pressure determination device; Ion migration flux determination system; Electrode surface analysis equipment (scanning electron microscope SEM); Porosity tester; Electrochemical workstation (electrode impedance test).

[0085] 2. Experimental steps Accelerated aging condition setting: Accelerate the aging of the landfill system through temperature cycling (20-40℃, one cycle every 24 hours); Simulate rainfall impact (3 times a week, 30 minutes each time, equivalent to 25mm rainfall); Simulate landfill load fluctuation (high concentration heavy metal leachate impact, concentration is 1000mg / L, once a month).

[0086] Test period and method: Test the system performance parameters once a week; Conduct a comprehensive evaluation once a month; The accelerated test period is 6 months, which simulates about 5 years of actual operation (according to the relationship between biochemical reaction rate and temperature, the modified Arrhenius equation is used for calculation).

[0087] Test index: Directional migration efficiency: measure the migration rate and directionality of heavy metal ions through the osmotic pressure gradient layer; Osmotic pressure gradient stability: the difference of osmotic pressure of each layer was measured over time; Electrode surface state: electrode samples were periodically taken for SEM observation to determine the thickness of surface deposits; Ion exchange capacity: landfill samples were periodically collected to determine their remaining ion exchange capacity; Porosity change: the dynamic change of the porosity of the landfill was determined.

[0088] 4. Experimental results See the table below:

[0089] Figure 2 : Comparison of long-term stability of key performance indicators of landfill systems.

[0090] Figure 3 : Comparison of porosity change trend of landfill systems.

[0091] 5. Analysis of results After 6 months of accelerated aging test (simulating about 5 years of actual operation), the directed migration efficiency of the process of the present application remained at 95.8%, the osmotic pressure stability remained at 94.5%, and the electrode activity remained at 93.5%, with the decay rate of each key indicator being less than 5%; while after the same period of testing of the traditional process, the indicators decreased significantly, with the directed migration efficiency decreasing to 24.5%, the osmotic pressure stability decreasing to 18.3%, and the electrode activity decreasing to 12.6%.

[0092] From the porosity change trend, the porosity of the process of the present application decreased from the initial 35.2% to 33.2% after 6 months, maintaining good permeability of the landfill system; while the porosity of the traditional process rapidly decreased from the initial 35.0% to 12.3%, causing serious clogging of the landfill system and a significant reduction in permeability.

[0093] According to the accelerated aging test results, the process of the present application can maintain more than 90% of the performance indicators for more than 20 years, while the traditional process will have performance indicators below 50% after about 5-7 years, and cannot maintain effective operation.

[0094] The experimental results show that the osmotic pressure self-repairing and electrochemical self-cleaning technology of the present application has a significant improvement effect on the long-term stability of the landfill system, especially in terms of pore unblocking and functional self-recovery, effectively solving the key problems of ion channel clogging, osmotic pressure decay, and electrode passivation in the long-term operation of the traditional process.

[0095] Experiment three: self-maintenance ability test 1. Purpose of the experiment To verify the effectiveness of the triple self-maintenance function (ion channel dredging, osmotic pressure self-repair, and electrochemical self-cleaning) of the application, to evaluate its self-recovery ability under external interference conditions, and to quantitatively analyze the reduction of maintenance requirements.

[0096] 2. Experimental materials and equipment Experimental group and control group landfill systems prepared in Experiment 1; Artificial interference equipment (organic matter injection device, concentration gradient destruction device, electrode pollution device); Cellulase and protease mixed solution (enzyme concentration 75 U / mL); Osmotic pressure sensing unit and slow-release regulator; Alternating electric field control system; Performance parameter automatic monitoring system; Maintenance workload recording system.

[0097] 3. Experimental steps Artificial interference application: Organic clogging interference: Inject high-concentration organic suspension (20 g / L of cellulose and protein mixture) into the landfill system to simulate biological clogging.

[0098] Osmotic pressure gradient destruction: Destroy the original osmotic pressure gradient structure by injecting a homogenized solution.

[0099] Electrode surface pollution: Artificially coat the electrode surface with a mixture of organic pollutants and metal deposits.

[0100] Self-maintenance function activation conditions: Ion channel dredging: Add enzyme solution according to step S5, and observe the channel dredging effect; Osmotic pressure self-repair: The sensing unit detects that the osmotic pressure gradient deviates from the preset value, triggering the release of the regulator; Electrochemical self-cleaning: Start the alternating electric field mode, with a cycle of 24 hours.

[0101] Monitoring indicators: Self-maintenance response time: The time from the application of interference to the start of self-repair of the system; Recovery degree: The percentage of the recovery of key performance indicators to the level before interference; Recovery time: The time from the activation of self-maintenance function to the stable recovery of system performance; Maintenance workload: Record the number and time of manual intervention during the entire process.

[0102] Test cycle: Each type of interference is tested 3 times, with an interval of 7 days; The control group adopts traditional manual maintenance methods (physical flushing, chemical cleaning, manual supplementing, etc.); The test cycle lasted for 30 days.

[0103] 4. Experimental results See the table below:

[0104]

[0105] Figure 4 : System performance self-recovery curve comparison chart.

[0106] 5. Results analysis The process of the present application shows excellent self-maintenance ability when facing three typical interferences, and the automatic response time is significantly shorter than the manual detection time of the traditional process: the response time of organic blockage is 2.5 hours (48 hours for the traditional process), the response time of osmotic pressure gradient destruction is only 0.5 hours (24 hours for the traditional process), and the response time of electrode surface pollution is fixed at 24 hours (72 hours for the traditional process) due to the use of a timed alternating electric field mode.

[0107] In terms of system recovery degree, the performance recovery rates of the process of the present application under the three interferences are 95.8%, 97.2% and 93.5% respectively, which are close to the level before interference; while the recovery degrees of the traditional process after manual maintenance are 82.3%, 75.5% and 68.7% respectively, which have limited and unstable recovery effect.

[0108] In terms of system recovery time, the process of the present application is significantly better than the traditional process: the recovery time of organic blockage is 18.5 hours (72.3 hours for the traditional process), the recovery time of osmotic pressure gradient destruction is 6.8 hours (36.5 hours for the traditional process), and the recovery time of electrode surface pollution is 24.5 hours (96.8 hours for the traditional process).

[0109] During the 30-day test cycle, the maintenance workload of the process of the present application is significantly lower than that of the traditional process: the number of manual detections is reduced by 90%, the number of physical maintenance, chemical treatment and component replacement is reduced by 100%, the total maintenance time is reduced by 94.7%, and the maintenance cost is reduced by 93.5%.

[0110] The experimental results prove that the triple self-maintenance function of the present application can effectively deal with various interferences in the landfill system operation, significantly improve the system stability, reduce the need for manual intervention, and has outstanding self-maintenance ability. Especially in dealing with osmotic pressure gradient destruction, the recovery degree reaches 97.2%, which is due to the accurate triggering of the osmotic pressure sensing unit and the on-demand release of the regulating agent.

[0111] Experiment four: environmental safety test 1. Purpose of the experiment To verify the effect of the process of the present application on the fixation of heavy metals and dioxins in fly ash and other harmful substances, to evaluate the environmental safety of the leachate after treatment, and to analyze the stability performance under simulated extreme environmental conditions.

[0112] 2. Experimental materials and equipment Experimental group and control group landfill systems prepared in Experiment 1; High-concentration heavy metal and dioxin standard samples; Extreme environment simulation device (acid rain, lye, oxidation and reduction environment simulation); Oscillating leaching test device; Continuous extraction device; Heavy metal speciation analyzer; Gas chromatography-mass spectrometry (GC-MS); Atomic absorption spectrophotometer; Inductively coupled plasma mass spectrometer (ICP-MS); Toxicity characteristic leaching procedure (TCLP) test kit.

[0113] 3. Experimental steps Heavy metal fixation effect test: Sample the experimental group and control group landfill, and perform TCLP test (US EPA Method 1311); BCR continuous extraction method is used to analyze the existing form of heavy metals (exchangeable state, reduced state, oxidized state, residual state); Monitor the concentration of heavy metals in the leachate and compare it with the "Standard for Pollution Control on Domestic Waste Landfill Sites" (GB16889).

[0114] Dioxin degradation / fixation test: Soxhlet extraction method is used to extract dioxins from the landfill; GC-MS is used for quantitative analysis of dioxins; Monitor the change of dioxin content in the leachate.

[0115] Extreme environment stability test: Acidic environment test: soak in pH=3.0 sulfuric acid solution for 72 hours; Alkaline environment test: soak in pH=12.0 sodium hydroxide solution for 72 hours; Oxidizing environment test: soak in 3% hydrogen peroxide solution for 72 hours; Reducing environment test: soak in 3% sodium sulfide solution for 72 hours; After the test, perform leaching test to analyze the release amount of heavy metals.

[0116] 4. Experimental results See the table below:

[0117]

[0118]

[0119] Figure 5 Comparison chart of dioxin degradation / fixation effect.

[0120] 5. Result analysis The TCLP leaching test results show that the heavy metal leaching concentration of the landfill treated by the process of the application is significantly lower than that of the control group, and can still remain stable after 6 months of accelerated aging, and most of the indicators meet the requirements of GB16889 standard. Among them, the leaching concentrations of lead (Pb), cadmium (Cd) and mercury (Hg), three kinds of high-toxicity heavy metals, are reduced by 94.2%, 96.0% and 89.4% respectively compared with the traditional process, and the environmental safety is significantly improved.

[0121] The heavy metal form analysis shows that the heavy metals in the landfill treated by the process of the application mainly exist in the form of residual state and oxidation state (accounting for more than 80%), and the exchangeable state content is less than 5%; while in the traditional process, the exchangeable state heavy metals account for as high as 22.3%-28.7%, which explains why the process of the application has better environmental stability.

[0122] In the simulation of extreme environmental condition test, the process of the application shows excellent anti-interference ability, and under the four harsh conditions of acid, alkali, oxidation and reduction, the heavy metal leaching amount is reduced by 84.6%-93.5% compared with the traditional process. Especially in the acid environment condition, the stability of the process of the application is improved most significantly, with an average increase of 91.2%.

[0123] The dioxin degradation / fixation effect test shows that after 6 months of treatment by the process of the application, the dioxin content in the landfill is reduced from the initial 5.8ng TEQ / g to 0.2ng TEQ / g, and the degradation / fixation rate reaches 96.6%; the dioxin concentration in the leachate is reduced to 3pg TEQ / L, which is far below the standard limit. In contrast, the dioxin degradation / fixation effect of the traditional process is limited, and there are still 2.3ng TEQ / g of dioxin remaining in the landfill, and the dioxin concentration in the leachate is 210pg TEQ / L, which exceeds the discharge standard requirement.

[0124] The experimental results prove that the dual action of electrochemical activation and complex stabilization in the process of the application can effectively realize the long-term stable fixation of heavy metals and dioxin, and significantly improve the environmental safety of the landfill system. Even under extreme environmental conditions, it can also maintain stable pollutant control effect, and effectively reduce the risk of secondary pollution.

[0125] Experiment five: adaptability test 1. Experimental purposes Verify the adaptability of the process to different component combinations of fly ash and sludge, evaluate the stability of the treatment effect under different climate conditions and ion environments, and provide data support for the wide application of the process.

[0126] 2. Experimental materials and equipment Fly ash samples from different sources (municipal solid waste, hazardous waste, medical waste incineration); Different types of sludge samples (domestic sewage, industrial wastewater, agricultural wastewater treatment); Climate simulation device (temperature, humidity, freeze-thaw cycle controllable); Complex ion environment simulation device; Small landfill column (diameter 15 cm, height 60 cm); Online monitoring device for treatment effect; Atomic absorption spectrophotometer; pH / EC / temperature multi-parameter tester; Osmotic pressure determination device.

[0127] 3. Experimental steps Different fly ash and sludge combination tests: Prepare 9 different fly ash and sludge combinations (3 fly ashes × 3 sludges); According to the process of the present application, each group of samples is treated; Determine the heavy metal removal rate and leachate water quality parameters of each group.

[0128] Climate condition adaptability test: High temperature environment: 35-40℃, humidity 60%, for 30 days; Low temperature environment: 0-5℃, humidity 40%, for 30 days; Freeze-thaw cycle: -5℃ to 25℃ cycle, cycle 24 hours, for 30 days; High humidity environment: 20-25℃, humidity 90%, for 30 days; Monitor the treatment effect regularly during the test period.

[0129] Complex ion environment test: High salt environment: add mixed salt of NaCl, MgCl2, etc., total concentration 10g / L; Heavy metal competition environment: add a mixed solution of various heavy metal ions, total concentration 1000mg / L; Organic matter interference environment: add a mixed solution of humic acid and surfactant, total concentration 2g / L; Determine the heavy metal removal effect under each environment.

[0130] 4. Experimental results See table below:

[0131] Note: Treatment stability rating criteria: A = Excellent (90% or more indicators meet the standard), B = Good (80-90% indicators meet the standard), C = Average (60-80% indicators meet the standard), D = Poor (less than 60% indicators meet the standard)

[0132] Note: Adaptability rating criteria: A = Excellent (performance retention rate ≥ 85%), B = Good (performance retention rate 75-85%), C = Average (performance retention rate 60-75%), D = Poor (performance retention rate < 60%) Figure 6 : Comparison of heavy metal removal effect under complex ion environment.

[0133] 5. Results analysis The test results of different fly ash and sludge combinations show that the process of the present application has good treatment effect on 9 different combinations, with heavy metal removal rate of 84.5%-92.5%, which is much higher than the average removal rate of 45.6% of the traditional process. Among them, the combination of household waste fly ash and various types of sludge has the best effect, the combination of medical waste fly ash and industrial wastewater sludge has relatively weak effect but still reaches B level rating, indicating that the process of the present application has wide raw material adaptability.

[0134] The climate condition adaptability test shows that the process of the present application maintains stable treatment effect under different climate conditions: the performance retention rates under high temperature, low temperature and high humidity environments are 98.2%, 95.5% and 96.4% respectively, and even under the most severe freeze-thaw cycle condition, the performance retention rate still reaches 93.5%. In contrast, the traditional process has a serious performance decline under low temperature and freeze-thaw cycle conditions, with only 66.9% and 56.6% of the effect, respectively, indicating that the process of the present application has excellent climate adaptability.

[0135] The test results of complex ion environment show that the average heavy metal removal rates of the process of the present application in three complex environments of high salt, heavy metal competition and organic matter interference are 91.3%, 88.5% and 90.4% respectively, which only decreases by 2-5 percentage points compared with the standard environment; while the average removal rates of the traditional process in the three complex environments are 38.7%, 28.8% and 35.5% respectively, which decreases by 10-20 percentage points compared with the standard environment. This shows that the process of the present application has significant anti-interference ability and ion environment adaptability.

[0136] From the perspective of heavy metal elements, the process of the present application shows stable removal effect on Pb, Cd and Hg in different environments, especially the removal rate of Hg can still maintain 89.5% in the competitive environment of heavy metals, which shows that the selective adsorption mechanism of the multi-level pore structure in the present application can effectively cope with the competitive effect of complex ion environment.

[0137] The experimental results prove that the process of the present application has wide applicability and can treat fly ash and sludge from different sources, and can maintain stable treatment effect under various climate conditions and complex ion environment, which lays a solid foundation for the industrialization and application of the technology.

[0138] The above describes the embodiments of the present application, but the embodiments are not limited to the above specific embodiments, and the above specific embodiments are only illustrative but not restrictive, and those skilled in the art can make more forms of equivalent embodiments under the inspiration of the embodiments, which are all within the protection scope of the embodiments.

Claims

1. A sludge and fly ash mixed filling treatment process, characterized in that: The following steps are involved: Step 1: Modified zeolite and bentonite are mixed to prepare a porous material composition, and the porous material composition is mixed and stirred with dried sludge having a moisture content of less than 60% to obtain a composite adsorption medium; Step 2: pre-activating the composite adsorption medium with a calcium chloride solution to obtain a pre-activated composite adsorption medium; Step 3: Construct an osmotic pressure gradient system in layers within the landfill area, laying high concentration gradient layers, medium concentration gradient layers, and low concentration gradient layers from top to bottom to form a directional osmotic pressure gradient field; Step 4: Arrange electrodes in the landfill and apply a DC voltage to create an electric field environment, causing heavy metal cations to migrate toward the cathode and bind to the active sites in the pre-activated composite adsorption medium; Step 5: Regularly add a biological enzyme mixture to the landfill to decompose the organic sediments and biofilm accumulated in the ion migration channel; Step 6: embedding an osmotic pressure sensing unit in the osmotic pressure gradient layer, and automatically releasing a regulator to restore the osmotic pressure gradient when the osmotic pressure gradient deviates from a preset value; Step 7: Use alternating electric field mode to perform electrode self-cleaning to prevent continuous accumulation of ions on the electrode surface.

2. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 1, the modified zeolite and bentonite are mixed in a weight ratio of 1:1, the pore size of the modified zeolite is 0.5-2.0 nm, and the specific surface area of ​​the bentonite is greater than 300 m² / g; the porous material composition and the dried sludge are mixed and stirred in a weight ratio of 1:3, and the stirring time is 30-45 minutes.

3. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 2, the concentration of the calcium chloride solution is 0.1-0.5 mol / L, and the pre-activation treatment time is 2-4 hours.

4. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 3, the high concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 2-3 mol / L and a thickness of 20-30 cm; the medium concentration gradient layer is infiltrated with a sodium chloride solution with a concentration of 1-1.5 mol / L and a thickness of 30-40 cm; and the low concentration gradient layer is infiltrated with deionized water with a thickness of 40-50 cm.

5. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 4, the electrodes are arranged in a grid pattern with an electrode spacing of 1-2 meters, and the electrode material is graphite or titanium alloy; the DC voltage is 3-5V, and the current density is controlled within the range of 0.1-0.5A / m².

6. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 5, the biological enzyme mixture includes cellulase and protease, the enzyme concentration is 50-100 U / mL, and the addition cycle is once a month.

7. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 6, the osmotic pressure sensing unit includes a semipermeable membrane and an indicator solution, and the regulator is a packaged slow-release sodium chloride particle with a diameter of 0.5-1.0 mm.

8. The sludge and fly ash mixed filling treatment process according to claim 1 is characterized in that: In step 7, the alternating electric field mode refers to the alternating application of a forward electric field and a reverse electric field, with an alternating cycle of 24 hours.

9. The sludge and fly ash mixed filling treatment process according to claim 1, characterized in that: The method further includes step 8: mixing the pre-activated composite adsorption medium with fly ash in a weight ratio of 3:1, and constructing a landfill in layers, with the thickness of each layer controlled at 50-80 cm.

10. The sludge and fly ash mixed filling treatment process according to claim 1, characterized in that: It also includes step 9: regularly monitor the heavy metal concentration and pH value in the leachate, with the monitoring frequency being once a week. The heavy metal concentration is monitored using atomic absorption spectrometry or inductively coupled plasma mass spectrometry, and the pH value is monitored using the electrode method, with a recording range of 6.0-9.0.

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