Method and system for treating medical waste flue gas deacidification wastewater

Abstract

The present application belongs to the technical field of deacidification wastewater treatment, and relates to a medical waste flue gas deacidification wastewater treatment method and system. The treatment method realizes deep purification of new pollutants in deacidification wastewater through hierarchical treatment, realizes recycling of industrial-grade sodium chloride fine salt, and directly uses the industrial-grade sodium chloride fine salt to prepare sodium hypochlorite aqueous solution. The prepared sodium hypochlorite aqueous solution is recycled to the front end of the system for oxidative degradation of new pollutants, forming a recycling path. The present application can not only improve the removal efficiency of new pollutants, but also realize recycling of industrial-grade sodium chloride fine salt and sodium hypochlorite aqueous solution, effectively solve the incomplete impurity removal and equipment scaling problems of traditional processes, and reduce wastewater treatment cost and be green and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of deacidification wastewater treatment technology, specifically, it relates to a method and system for treating medical waste flue gas deacidification wastewater. Background Technology

[0002] During the incineration of medical waste, waste medical plastics, protective consumables, pharmaceuticals and disinfection products are incinerated at high temperatures, and the flue gas desulfurization wastewater will simultaneously accumulate a variety of new pollutants, such as PFAS, PPCPs and microplastics, which increases the difficulty of treating medical waste flue gas desulfurization wastewater.

[0003] PFAS are perfluorinated and polyfluoroalkyl compounds containing strong and stable carbon-fluorine bonds in their molecules. They are characterized by environmental persistence, bioaccumulation, and recalcitrant degradation. Based on carbon chain length, PFAS can be divided into long-chain PFAS and short-chain PFAS. Long-chain PFAS are highly hydrophobic and easily adhere to the surface of particulate impurities, while short-chain PFAS are highly water-soluble and highly mobile. Conventional coagulation, flotation, and ordinary adsorption processes are difficult to remove them effectively, thus easily causing secondary environmental pollution.

[0004] PPCPs are pharmaceuticals and personal care products, mainly derived from residual antibiotics, anti-inflammatory agents, chemotherapy drugs, disinfectants, and skin care ingredients in medical waste. These pollutants are mostly polar trace organic pollutants with low concentrations, persistent toxicity, and poor biodegradability. Conventional water treatment processes cannot effectively degrade and remove them, which can easily induce microbial resistance and disrupt the ecological balance.

[0005] Microplastics mainly originate from the incomplete incineration and pyrolysis of medical disposable plastic consumables, packaging materials, non-woven fabrics, and other materials. They exist in wastewater in the form of micron-sized, nano-sized particles or fibers. They can act as carriers to adsorb pollutants such as PFAS and PPCPs in wastewater, forming a complex pollutant system. At the same time, the fine plastic particles can easily clog membrane treatment units, reducing the stability of the water treatment system and the pollutant removal efficiency.

[0006] Currently, the treatment process for medical waste flue gas deacidification wastewater mostly adopts conventional coagulation sedimentation + filtration + evaporation crystallization processes. However, these processes have many technical shortcomings. On the one hand, this only achieves the harmless treatment of the deacidified wastewater and does not establish a systematic removal system for the aforementioned new pollutants. On the other hand, conventional filtration processes are incomplete in removing calcium and magnesium ions and sulfate ions, which can lead to scaling and clogging of subsequent evaporation crystallization equipment, increasing the difficulty of operation and maintenance and shortening the equipment lifespan. In addition, the high-purity sodium chloride solution after treatment lacks an in-situ resource utilization pathway and is mostly disposed of externally, which cannot be combined with the disinfection needs of medical waste disposal sites. The required sodium hypochlorite disinfectant often needs to be purchased externally, but there are safety hazards in the transportation and storage process. Therefore, the overall process does not form a closed loop and does not meet the green and low-carbon disposal requirements of the hazardous waste industry.

[0007] Therefore, developing a deacidification wastewater treatment system and method that is suitable for medical waste disposal scenarios, has high purification efficiency, meets salt purity standards, has a closed-loop process, and generates no secondary solid waste, while taking into account the purification and treatment of new pollutants and the resource utilization of wastewater, has become an urgent technical challenge to be solved. Summary of the Invention

[0008] The problem to be solved by the present invention is to provide a method and system for treating medical waste flue gas deacidification wastewater, which can realize the purification treatment of new pollutants in deacidification wastewater, the resource recovery of industrial-grade sodium chloride refined salt, and the direct preparation of sodium hypochlorite aqueous solution using the industrial-grade sodium chloride refined salt.

[0009] The problem to be solved by the present invention is to provide a method and system for treating medical waste flue gas deacidification wastewater, in which the prepared sodium hypochlorite aqueous solution is recycled at the front end of the system for the oxidative degradation of new pollutants, forming a resource recycling path.

[0010] To solve the above problems, the present invention is achieved through the following technical solution: This invention provides a method for treating medical waste flue gas deacidification wastewater, wherein the wastewater contains new pollutants, including a first new pollutant, a second new pollutant, and a third new pollutant; The processing method includes the following steps: (1) After stirring and homogenizing, the medical waste flue gas deacidification wastewater is subjected to micro-nano bubble flotation treatment to intercept the first new pollutant in the wastewater and obtain flotation effluent. The first new pollutant includes any one or combination of long-chain PFAS and microplastics. (2) Add a ternary compound coagulant containing amino-modified activated carbon micro powder to the air flotation effluent to carry out coagulation reaction to remove the second new pollutant, then add a flocculant to carry out flocculation reaction, and after settling, adjust the obtained supernatant to the preset pH value, and dewater the precipitated sludge. The second new pollutant includes any one or a combination of dissolved PFAS and dissolved PPCPs. (3) The supernatant is fed into a ceramic ultrafiltration membrane for first-stage filtration to obtain ultrafiltration permeate and ultrafiltration concentrate; the ultrafiltration permeate is preheated to a preset temperature and fed into an organic nanofiltration membrane for second-stage filtration to obtain nanofiltration permeate and nanofiltration concentrate; the obtained nanofiltration permeate is subjected to adsorption of an amino anion exchange resin to remove a third new pollutant to obtain a first sodium chloride solution, wherein the third new pollutant includes short-chain PFAS; (4) The first sodium chloride solution is subjected to vacuum evaporation and crystallization. The resulting crystallized liquid is subjected to solid-liquid separation and drying to obtain refined sodium chloride salt and condensate. (5) Dissolve the sodium chloride refined salt to obtain a second sodium chloride solution, and electrolyze the second sodium chloride solution to obtain an aqueous solution of sodium hypochlorite; (6) At least a portion of the sodium hypochlorite aqueous solution is returned to the inlet of steps (1), (2), and (3) to oxidize and degrade the new pollutants remaining in the system.

[0011] In some embodiments, in step (1), the sodium chloride content in the medical waste flue gas deacidification wastewater is 10% to 20%, the total hardness (calculated as CaCO3) is 3000 mg / L to 6000 mg / L, the sulfate content is 1000 mg / L to 3000 mg / L, and the suspended solids content is 500 mg / L to 1000 mg / L.

[0012] In some embodiments, step (1) of the micro / nano bubble flotation process includes: A magnetically modified chitosan additive was added to the homogenized medical waste flue gas deacidification wastewater. The dosage of the magnetically modified chitosan additive was 0.4 g / L to 6 g / L, and the aeration time was 15 min to 20 min. The magnetically modified chitosan additive is a mixture of chitosan and magnetic nanoparticles; The chitosan and magnetic nanoparticles are added in a ratio of 1:3 to 3:1, and the magnetic nanoparticles are one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, NiFe2O4, and ZnFe2O4.

[0013] In some embodiments, in step (2), the ternary compound coagulant comprises polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micropowder, wherein the mass ratio of polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micropowder is 1.5:1:0.2 to 2.5:1:0.3. The dosage of the ternary compound coagulant is 50 mg / L to 100 mg / L; The flocculant used is anionic polyacrylamide with a molecular weight of 8 million to 12 million and a dosage of 0.5 mg / L to 1.0 mg / L. The coagulation reaction time is 10 min to 15 min, the flocculation reaction time is 8 min to 12 min, and the settling time is 30 min to 45 min. The preset pH value is 7.5 to 8.5.

[0014] In some embodiments, in step (3), the ceramic ultrafiltration membrane includes a porous ceramic support and a separation layer disposed on the surface of the porous ceramic support, wherein the porous ceramic support contains α-Al2O3 and the separation layer contains ZrO2; The α-Al2O3 has a mass percentage content of ≥99% in the porous ceramic support, and the ZrO2 has a mass percentage content of ≥92% in the separation layer; The ceramic ultrafiltration membrane has a pore size of 0.05 μm to 0.1 μm, a compressive strength of ≥50 MPa, and a flux recovery rate of ≥98%. The organic nanofiltration membrane is a polypiperazine amide spiral wound nanofiltration membrane. The organic nanofiltration membrane has a molecular weight cutoff of 200 Da to 400 Da and a flux recovery rate of ≥99%. The concentration of the first sodium chloride solution is 5% to 12%, with calcium ion content ≤5 mg / L, magnesium ion content ≤5 mg / L, and sulfate ion content ≤10 mg / L.

[0015] In some embodiments, step (3) includes: The supernatant is first filtered using a ceramic ultrafiltration membrane to remove flocs, suspended solids, colloidal PFAS, and colloidal PPCPs from the supernatant, resulting in ultrafiltration permeate and ultrafiltration concentrate. The ultrafiltration concentrate is returned to the inlet of step (2); The ultrafiltration permeate is preheated to 45℃~65℃, and then filtered in a second stage using an organic nanofiltration membrane to remove calcium ions, magnesium ions, sulfate ions, residual dissolved PFAS, and residual dissolved PPCPs from the ultrafiltration permeate, thereby obtaining nanofiltration permeate and nanofiltration concentrate. Add calcium chloride to the nanofiltration concentrate, and after precipitation and filtration, return the filtrate to the inlet end of step (2); The nanofiltration permeate is transferred to an amino anion exchange resin adsorption unit to remove short-chain PFAS from the nanofiltration permeate, resulting in a first sodium chloride solution.

[0016] In some embodiments, the operating pressure of the ceramic ultrafiltration membrane is 0.2 MPa to 0.4 MPa, and the operating temperature is 15°C to 40°C. The organic nanofiltration membrane operates at a pressure of 0.8 MPa to 1.2 MPa and at a temperature of 15°C to 70°C.

[0017] In some embodiments, in step (4), the temperature of the vacuum evaporation crystallization is 60°C to 80°C, and the temperature of the drying is 40°C to 50°C.

[0018] In some embodiments, in step (5), the concentration of the second sodium chloride solution is 3% to 5%, the electrolysis voltage is 3.5V to 4.0V, and the effective chlorine content of the sodium hypochlorite aqueous solution is 0.6% to 0.8%.

[0019] Accordingly, the present invention also provides a medical waste flue gas deacidification wastewater treatment system for performing the said treatment method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The method and system for treating medical waste flue gas deacidification wastewater provided by this invention provide a deep purification treatment for medical waste flue gas deacidification wastewater with high salt, high hardness, high impurities and containing new pollutants. Specifically, (1) the wastewater is first subjected to micro-nano bubble flotation treatment to intercept the first new pollutants such as long-chain PFAS and microplastics in the wastewater to obtain flotation effluent; (2) then a ternary compound coagulant is added to the flotation effluent to carry out a coagulation reaction to remove the second new pollutants such as dissolved PFAS and dissolved PPCPs, and then flocculation is added. The agent is used to carry out flocculation reaction, and after standing and settling, the resulting supernatant is adjusted to the preset pH value; (3) the supernatant is filtered in the first stage to obtain ultrafiltration permeate and ultrafiltration concentrate; the ultrafiltration permeate is preheated and then filtered in the second stage to obtain nanofiltration permeate and nanofiltration concentrate; the nanofiltration permeate is adsorbed by amino anion exchange resin to remove short-chain PFAS and other third new pollutants to obtain the first sodium chloride solution; (4) the first sodium chloride solution is vacuum evaporated and crystallized to obtain sodium chloride refined salt; (5) the sodium chloride refined salt is then dissolved and electrolyzed to obtain sodium hypochlorite aqueous solution. Therefore, the present invention removes the first, second and third new pollutants through graded treatment, and simultaneously obtains sodium chloride refined salt and sodium hypochlorite aqueous solution products, realizing the resource recovery of industrial-grade sodium chloride refined salt and sodium hypochlorite aqueous solution.

[0021] Furthermore, the present invention also recirculates at least a portion of the sodium hypochlorite aqueous solution back to the inlet of steps (1), (2), and (3) to oxidize and degrade the new pollutants remaining in the system, forming a resource recycling path. Simultaneously, the ultrafiltration concentrate, nanofiltration concentrate, sludge filtrate, and evaporation condensate generated during the treatment process can be recycled throughout the entire process, and the dewatered sludge can be utilized as a resource. This effectively solves the problem of difficult disposal of mixed salt hazardous waste, achieving full-process resource utilization of deacidification wastewater. Attached Figure Description

[0022] Figure 1 The flowchart illustrates the treatment method for medical waste flue gas deacidification wastewater provided by this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] like Figure 1 As shown, the present invention provides a method for treating medical waste flue gas deacidification wastewater, wherein the medical waste flue gas deacidification wastewater contains new pollutants, the new pollutants including a first new pollutant, a second new pollutant and a third new pollutant; The processing method includes the following steps: S01. After stirring and homogenizing, the medical waste flue gas deacidification wastewater is subjected to micro-nano bubble flotation treatment to intercept the first new pollutant in the wastewater and obtain flotation effluent, wherein the first new pollutant includes any one or combination of long-chain PFAS and microplastics. In some embodiments, in step S01, the sodium chloride content in the medical waste flue gas deacidification wastewater is 10% to 20%, the total hardness (calculated as CaCO3) is 3000 mg / L to 6000 mg / L, the sulfate content is 1000 mg / L to 3000 mg / L, and the suspended solids content is 500 mg / L to 1000 mg / L.

[0025] Specifically, the present invention introduces the medical waste flue gas deacidification wastewater into the homogenization adjustment tank of the homogenization adjustment unit, and stirs it for 15 min to 30 min by a stirring device to equalize the water quality of the deacidification wastewater, so that the sodium chloride concentration, calcium and magnesium ion content, pH value and suspended solids concentration in the deacidification wastewater reach a stable level, and avoids water quality fluctuations from affecting the subsequent treatment effect.

[0026] In some embodiments, step S01, the micro / nano bubble flotation treatment includes: A magnetically modified chitosan additive was added to the homogenized medical waste flue gas deacidification wastewater. The dosage of the magnetically modified chitosan additive was 0.4 g / L to 6 g / L, and the aeration time was 15 min to 20 min. The magnetically modified chitosan additive is a mixture of chitosan and magnetic nanoparticles; The chitosan and magnetic nanoparticles are added in a ratio of 1:3 to 3:1, and the magnetic nanoparticles are one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, NiFe2O4, and ZnFe2O4.

[0027] Specifically, the present invention simultaneously sets up a micro-nano bubble flotation module, adds a magnetic modified chitosan additive, and aerates for 15 min to 20 min to aggregate and intercept the first new pollutants in the wastewater. At the same time, the scum is discharged into the sludge system for high-temperature incineration and mineralization.

[0028] It should be noted that the first novel pollutant of this invention includes any one or a combination of long-chain PFAS and microplastics. This invention utilizes the amino and hydroxyl groups abundant in chitosan molecules to bind with negatively charged long-chain PFAS molecules through electrostatic interaction, and captures microplastic particles through micro-nano bubble flotation and hydrogen bonding. At the same time, magnetic nanoparticles are introduced to endow the magnetically modified chitosan additive with magnetic responsiveness, so that it can be quickly and conveniently separated and recovered from wastewater by an external magnetic field after adsorption is completed.

[0029] Furthermore, by controlling the dosage of the magnetically modified chitosan additive to 0.4 g / L to 25 g / L and the ratio of chitosan to magnetic nanoparticles to 1:3 to 3:1, the present invention achieves effective removal of the first new pollutant, reducing the new pollutant by more than 70% at the source.

[0030] S02. A ternary compound coagulant containing amino-modified activated carbon micropowder is added to the air flotation effluent to carry out a coagulation reaction to remove the second new pollutant. Then, a flocculant is added to carry out a flocculation reaction. After settling, the resulting supernatant is adjusted to a preset pH value, and the precipitated sludge is dewatered. The second new pollutant includes any one or a combination of dissolved PFAS and dissolved PPCPs. In some embodiments, in step S02, the ternary compound coagulant comprises polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micropowder, wherein the mass ratio of polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micropowder is 1.5:1:0.2 to 2.5:1:0.3. The dosage of the ternary compound coagulant is 50 mg / L to 100 mg / L; The flocculant used is anionic polyacrylamide with a molecular weight of 8 million to 12 million and a dosage of 0.5 mg / L to 1.0 mg / L. The coagulation reaction time is 10 min to 15 min, the flocculation reaction time is 8 min to 12 min, and the settling time is 30 min to 45 min. The preset pH value is 7.5 to 8.5.

[0031] Specifically, in the coagulation reaction tank of the coagulation sedimentation unit, this invention adds a ternary compound coagulant containing polyaluminum chloride, polyferric sulfate, and amino-modified activated carbon micropowder to the air flotation effluent, and the coagulation reaction lasts for 10 to 15 minutes. Preferably, the mass ratio of polyaluminum chloride, polyferric sulfate, and amino-modified activated carbon micropowder is 1.5:1:0.2 to 2.5:1:0.3, and the dosage is 0.5 mg / L to 1.0 mg / L. Within the above range, through the synergistic effect of aluminum and iron salts, the removal efficiency of the coagulation reaction for suspended particulate matter, colloidal impurities, some heavy metals, and organic matter in deacidification wastewater can be effectively improved, while the amino-modified activated carbon micropowder, with its porous adsorption structure, can effectively capture secondary pollutants.

[0032] Furthermore, this invention selects anionic polyacrylamide as a flocculant, and the flocculation reaction in the flocculation reaction tank is carried out for 8 min to 12 min. The molecular weight of the anionic polyacrylamide is 8 million to 12 million, and the dosage is 0.5 mg / L to 1.0 mg / L. Within the above range, the anionic polyacrylamide can utilize its ultra-high molecular weight and strong adsorption bridging effect to quickly aggregate the fine flocs formed after coagulation into large and dense flocs at a relatively low dosage, thereby accelerating sedimentation and improving solid-liquid separation efficiency.

[0033] Furthermore, in this invention, the supernatant is allowed to settle in an inclined tube sedimentation tank for 30-45 minutes. Using a pH adjustment and dosing device, the pH of the supernatant is precisely controlled to 7.5-8.5 to provide suitable water quality for the subsequent membrane separation unit. Simultaneously, some free calcium and magnesium ions are initially removed, reducing the load on subsequent membrane treatment. Meanwhile, the bottom sedimented sludge is dewatered to a moisture content of ≤60% using a plate and frame filter press and then sent to a medical waste incinerator for high-temperature mineralization at 1100℃ to thoroughly decompose the enriched new pollutants. The sludge filtrate is then returned to the homogenization and conditioning unit.

[0034] It should be noted that the second new pollutant in this invention includes any one or a combination of dissolved PFAS and dissolved PPCPs. This invention uses a ternary modified composite coagulant to adsorb the second new pollutants such as dissolved PFAS and dissolved PPCPs, and then achieves solid-liquid separation through flocculation and sedimentation. After static sedimentation, a supernatant and precipitated sludge are obtained. The obtained precipitated sludge can be further eliminated by high-temperature incineration. Therefore, through the above treatment, the cumulative removal rate of the new pollutants in this invention can be increased to more than 80%.

[0035] S03. The supernatant is fed into a ceramic ultrafiltration membrane for first-stage filtration to obtain ultrafiltration permeate and ultrafiltration concentrate; the ultrafiltration permeate is preheated to a preset temperature and fed into an organic nanofiltration membrane for second-stage filtration to obtain nanofiltration permeate and nanofiltration concentrate; the obtained nanofiltration permeate is subjected to adsorption of an amino anion exchange resin to remove a third new pollutant to obtain a first sodium chloride solution, wherein the third new pollutant includes short-chain PFAS; In some embodiments, step S03 includes: The supernatant is first filtered using a ceramic ultrafiltration membrane to remove flocs, suspended solids, colloidal PFAS, and colloidal PPCPs from the supernatant, resulting in ultrafiltration permeate and ultrafiltration concentrate. The ultrafiltration concentrate is returned to the inlet end of step S02; The ultrafiltration permeate is preheated to 45℃~65℃, and then filtered in a second stage using an organic nanofiltration membrane to remove calcium ions, magnesium ions, sulfate ions, residual dissolved PFAS, and residual dissolved PPCPs from the ultrafiltration permeate, thereby obtaining nanofiltration permeate and nanofiltration concentrate. Add calcium chloride to the nanofiltration concentrate, and after precipitation and filtration, return the filtrate to the inlet end of step (2); The nanofiltration permeate is transferred to an amino anion exchange resin adsorption unit to remove short-chain PFAS from the nanofiltration permeate, resulting in a first sodium chloride solution.

[0036] Specifically, this invention uses ceramic ultrafiltration to trap colloidal new pollutants and suspended solids, employs a high-temperature resistant organic nanofiltration membrane to trap residual dissolved new pollutants and divalent scaling ions, and then uses an amino anion exchange resin to remove short-chain PFAS that are difficult to trap by ceramic ultrafiltration and organic nanofiltration, resulting in a high-purity first sodium chloride solution. Furthermore, this invention recirculates the ultrafiltration concentrate to the front end of the coagulation reaction to achieve the cyclic adsorption and removal of new pollutants. The nanofiltration concentrate is then precipitated by adding calcium chloride, allowing residual new pollutants to be completely decomposed along with the resulting precipitated sludge in the incineration system. The filtrate is then recirculated to the front end of the coagulation reaction for adsorption, resulting in a system water recovery rate >97%.

[0037] It should be noted that the present invention utilizes the waste heat energy of medical waste incineration flue gas to preheat the ultrafiltration permeate to 45℃~65℃, thereby increasing the solubility of sulfate and inhibiting the crystallization of sulfate on the surface of organic nanofiltration membrane, thus improving the feed flux and the filtration efficiency of organic nanofiltration membrane.

[0038] In some embodiments, in step S03, the ceramic ultrafiltration membrane includes a porous ceramic support and a separation layer disposed on the surface of the porous ceramic support, wherein the porous ceramic support comprises α-Al2O3 and the separation layer comprises ZrO2; The α-Al2O3 has a mass percentage content of ≥99% in the porous ceramic support, and the ZrO2 has a mass percentage content of ≥92% in the separation layer; The ceramic ultrafiltration membrane has a pore size of 0.05μm to 0.1μm, a compressive strength of ≥50MPa, and a flux recovery rate of ≥98%.

[0039] Specifically, the α-Al2O3 porous ceramic support provides good compressive strength and resistance to acid and alkali corrosion, enabling the membrane module to operate stably for a long time without irreversible fouling. Meanwhile, the ZrO2 separation layer, with its excellent hydrophilicity and antifouling properties, can effectively reduce the adsorption of flocs, suspended solids, colloids and organic matter on the membrane surface, thus significantly improving the chemical stability and cleaning resistance of the ceramic ultrafiltration membrane.

[0040] Preferably, the compressive strength of the ceramic ultrafiltration membrane is ≥50MPa, within the above-mentioned compressive strength range, so that the ceramic ultrafiltration membrane can withstand repeated high-pressure washing.

[0041] Preferably, the ceramic ultrafiltration membrane is cleaned with 2% NaOH and 0.8% sodium hypochlorite. After cleaning, the flux recovery rate of the ceramic ultrafiltration membrane is ≥98%, and its service life is as long as 8 to 10 years.

[0042] Preferably, the ceramic ultrafiltration membrane used in this invention has the characteristics of high salt resistance, corrosion resistance, and pollution resistance, and its pore size is 0.05μm to 0.1μm. Within the above range, the ceramic ultrafiltration membrane performs the first stage filtration of the supernatant, which can effectively intercept the fine flocs, suspended solids, colloids and macromolecular organic matter remaining in the deacidification wastewater. At the same time, it can also initially remove some particulate calcium and magnesium compounds, ensuring that the subsequent nanofiltration membrane is not contaminated and operates stably.

[0043] In some embodiments, the organic nanofiltration membrane is selected as a polypiperazine amide spiral wound nanofiltration membrane; The organic nanofiltration membrane has a molecular weight cutoff of 200 Da to 400 Da and a flux recovery rate of ≥99%. Specifically, the present invention uses a high-temperature resistant spiral-wound organic nanofiltration membrane for the second stage filtration of the ultrafiltration permeate, with a molecular weight cutoff of 200 Da to 400 Da. This not only accurately retains divalent calcium ions, divalent magnesium ions, and divalent sulfate ions, but also allows monovalent sodium ions and monovalent chloride ions to pass through efficiently, while improving the removal rate of new pollutants.

[0044] Preferably, the organic nanofiltration membrane is a polypiperazine amide spiral wound nanofiltration membrane, which can operate stably at temperatures ranging from 15°C to 70°C. Furthermore, by using a 2% NaOH and 0.8% sodium hypochlorite aqueous solution at 75°C to 80°C and then briefly cleaning it at 80°C to 90°C, newly attached pollutants on the surface of the nanofiltration membrane can be degraded, resulting in a membrane flux recovery rate of ≥99%.

[0045] In some embodiments, the operating pressure of the ceramic ultrafiltration membrane is 0.2 MPa to 0.4 MPa, and the operating temperature is 15°C to 40°C. The organic nanofiltration membrane operates at a pressure of 0.8 MPa to 1.2 MPa and a temperature of 15°C to 70°C. Specifically, the present invention sets the operating pressure of the first-stage filtration to 0.2 MPa to 0.4 MPa and the operating temperature to 15°C to 40°C. Within the above range, it effectively retains flocs, suspended solids, colloidal PFAS, and colloidal PPCPs with low energy consumption, achieving a retention rate of ≥99%, which can reduce subsequent membrane fouling.

[0046] Furthermore, this invention sets the operating pressure of the second-stage filtration to 0.8MPa~1.2MPa and the operating temperature to 15℃~70℃. Utilizing the charge repulsion and sieving effect of the organic nanofiltration membrane, it ensures efficient permeation of sodium chloride while fully retaining magnesium sulfate or calcium sulfate. The retention rate for calcium and magnesium ions is ≥98%, the retention rate for sodium and chloride ions is ≤5%, and the retention rate for residual dissolved PFAS and PPCPs is ≥96%. At the same time, it lays the foundation for subsequent evaporation and crystallization to obtain high-purity industrial-grade sodium chloride refined salt.

[0047] In some embodiments, the concentration of the first sodium chloride solution is 5% to 12%, the calcium ion content is ≤5 mg / L, the magnesium ion content is ≤5 mg / L, and the sulfate ion content is ≤10 mg / L.

[0048] It should be noted that the third new pollutant described in this invention includes short-chain PFAS. Because short-chain PFAS are too small in size, they can easily penetrate membrane pores. Therefore, ceramic ultrafiltration and organic nanofiltration are difficult to completely remove them. However, this invention utilizes the adsorption energy of amino anion exchange resin to effectively remove short-chain PFAS through multiple synergistic effects such as electrostatic attraction or hydrogen bonding, thereby increasing the cumulative removal rate of new pollutants in wastewater to over 99%.

[0049] Therefore, this invention employs a two-stage tandem membrane separation process of ceramic ultrafiltration and high-temperature resistant organic nanofiltration to effectively remove calcium ions, magnesium ions, sulfate ions, and residual new pollutants from deacidification wastewater. Short-chain PFAS are removed using an amino anion exchange resin to obtain a high-purity first sodium chloride solution, laying the foundation for the subsequent preparation of industrial-grade sodium chloride refined salt and sodium hypochlorite aqueous solution.

[0050] S04. The first sodium chloride solution is subjected to vacuum evaporation and crystallization. The resulting crystallized liquid is subjected to solid-liquid separation and drying to obtain refined sodium chloride salt and condensate. In some embodiments, in step S04, the temperature of the vacuum evaporation crystallization is 60°C to 80°C, and the temperature of the drying is 40°C to 50°C.

[0051] Specifically, this invention delivers a high-purity first sodium chloride solution to an evaporator crystallizer, utilizing the waste heat from medical waste incineration as a heat source. A vacuum evaporation crystallization process is employed, setting the evaporation concentration crystallization temperature to 60℃~80℃ and the vacuum degree to 0.02MPa~0.09MPa. Under this low-temperature vacuum thermal environment, residual trace amounts of new pollutants can be effectively decomposed. Subsequently, the crystallized liquid is centrifuged for dehydration and dried at a low temperature of 40℃~50℃ to obtain industrial-grade sodium chloride refined salt and condensate. The purity of the industrial-grade sodium chloride refined salt is ≥98.5%, meeting the requirements of the national standard GB / T 5462-2015 "Industrial Salt".

[0052] It should be noted that the industrial-grade sodium chloride refined salt and condensate obtained by this invention do not have any new pollutant accumulation, and the condensate produced by evaporation and crystallization is pure water, which can be recycled back to the medical waste disposal workshop to achieve zero water discharge.

[0053] S05. Dissolve the sodium chloride refined salt to obtain a second sodium chloride solution, and electrolyze the second sodium chloride solution to obtain an aqueous solution of sodium hypochlorite; In some embodiments, in step S05, the concentration of the second sodium chloride solution is 3% to 5%, the electrolysis voltage is 3.5V to 4.0V, and the chlorine content of the sodium hypochlorite aqueous solution is 0.6% to 0.8%.

[0054] Specifically, the present invention quantitatively delivers the industrial-grade sodium chloride refined salt to a salt dissolving tank to prepare a second sodium chloride solution with a concentration of 3% to 5%, and then delivers it to a sodium hypochlorite generator to prepare an aqueous sodium hypochlorite solution with an effective chlorine content of 0.6% to 0.8% by electrolysis. The hydrogen gas obtained by electrolysis is collected in a sealed manner and sent to the incineration unit for combustion and heating, eliminating the risk of explosion and recovering heat energy at the same time.

[0055] Preferably, the electrolysis voltage of the sodium hypochlorite generator is 3.5V to 4.0V, the coating of the anode used for electrolysis is a composite coating of metal oxides containing ruthenium, iridium, tin and cerium oxide, and the cathode used for electrolysis is a titanium mesh with a nickel-cobalt alloy plated on its surface. This can reduce the oxygen evolution side reaction in the electrolysis process, increase the current efficiency by more than 12%, and extend the service life of the electrodes to more than 5 years.

[0056] S06. At least a portion of the sodium hypochlorite aqueous solution is returned to the inlet of steps (1), (2), and (3) to oxidize and degrade the new pollutants remaining in the system; Specifically, the present invention uses the obtained sodium hypochlorite aqueous solution as an oxidant and refluxes it to the homogenization adjustment unit, the front end of the coagulation reaction, and the front end of the ceramic ultrafiltration. The strong oxidizing properties of sodium hypochlorite are used to oxidize and degrade the trace amounts of new pollutants remaining in the system. There is no need to purchase oxidizing reagents such as ozone or hydrogen peroxide. Moreover, the obtained sodium hypochlorite aqueous solution has a concentration of 0.6% to 0.8%, which is low and does not require additional dilution.

[0057] In addition, the obtained sodium hypochlorite aqueous solution can be transported to medical waste disposal workshops, wastewater treatment units, flue gas desulfurization systems, and other locations through disinfectant dosing pipelines to achieve in-situ disinfection, wastewater pretreatment oxidation, and flue gas desulfurization assistance, forming a complete resource utilization closed loop.

[0058] Accordingly, the present invention also provides a medical waste flue gas deacidification wastewater treatment system for performing the said treatment method.

[0059] The medical waste flue gas deacidification wastewater treatment system of the present invention includes a homogenization and conditioning unit, a coagulation and sedimentation reaction unit, a membrane separation and purification unit, an amino anion exchange resin adsorption unit, a salt crystallization preparation unit, a sodium hypochlorite generation unit, and a sludge treatment system. Wastewater sequentially enters the homogenization and conditioning unit, the coagulation and sedimentation reaction unit, the membrane separation and purification unit, and the amino anion exchange resin adsorption unit for new pollutant treatment. Subsequently, sodium chloride refined salt is prepared in the salt crystallization preparation unit. The sodium hypochlorite generation unit uses the sodium chloride refined salt prepared by the salt crystallization preparation unit to prepare sodium hypochlorite aqueous solution, and at least a portion of the sodium hypochlorite aqueous solution is returned to the front end of the system to oxidize and degrade the new pollutants remaining in the system.

[0060] Specifically, the homogenization and conditioning unit includes a homogenization and conditioning tank and a stirring device disposed therein, for equalizing the water quality of the wastewater. The homogenization and conditioning tank is also equipped with a micro-nano air flotation bubble module for removing the first new pollutants from the wastewater.

[0061] The coagulation and sedimentation reaction unit comprises a coagulation reaction tank, a flocculation reaction tank, and an inclined tube sedimentation tank connected in sequence. Wastewater first enters the coagulation reaction tank for coagulation to remove secondary pollutants. The effluent then enters the flocculation reaction tank for flocculation, causing fine particles to aggregate into flocs. Subsequently, it enters the inclined tube sedimentation tank for static sedimentation, achieving solid-liquid separation. The bottom of the inclined tube sedimentation tank is equipped with a sludge discharge outlet, which is connected to the sludge treatment system. The sludge produced during sedimentation is sent to the sludge treatment system for dewatering treatment through the discharge outlet.

[0062] The membrane separation and purification unit includes a ceramic ultrafiltration membrane and an organic nanofiltration membrane connected in sequence. The supernatant first enters the ceramic ultrafiltration membrane and is filtered through the first stage to remove flocs, colloidal PFAS, and colloidal PPCPs from the supernatant, resulting in ultrafiltration permeate and ultrafiltration concentrate. The ultrafiltration concentrate is refluxed to the inlet of the coagulation and sedimentation reaction unit. The ultrafiltration permeate is preheated and then enters the organic nanofiltration membrane. After the second stage of filtration, calcium ions, magnesium ions, sulfate ions, residual dissolved PFAS, and residual dissolved PPCPs from the ultrafiltration permeate are removed, resulting in nanofiltration permeate and nanofiltration concentrate. The nanofiltration concentrate is treated with calcium chloride precipitation, and the precipitate filtrate is refluxed to the inlet of the coagulation and sedimentation reaction unit.

[0063] The amino anion exchange resin adsorption unit contains amino anion exchange resin, which is used to adsorb and remove a third new pollutant from nanofiltration permeate to obtain a first sodium chloride solution.

[0064] The salt crystallization preparation unit includes an evaporator crystallizer, a centrifugal dehydrator, and a dryer. The first sodium chloride solution first enters the evaporator crystallizer, and after evaporation and concentration, it enters the centrifugal dehydrator for solid-liquid separation. The separated solid salt is then dried by the dryer to obtain industrial-grade refined sodium chloride salt.

[0065] The sodium hypochlorite generating unit includes a salt dissolving tank, a sodium hypochlorite generator, a disinfectant storage tank, and a disinfectant dosing pipeline. The salt dissolving tank is connected to the sodium chloride refined salt outlet of the salt crystallization preparation unit. It is used to prepare a second sodium chloride solution in the salt dissolving tank using the industrial-grade sodium chloride refined salt as raw material. The solution is then sent to the sodium hypochlorite generator for electrolysis to prepare an aqueous sodium hypochlorite solution, which is stored in the disinfectant storage tank and returned to the front end of the system through the disinfectant dosing pipeline. This solution is used to oxidize and degrade any new pollutants remaining in the system, forming a complete resource recovery closed loop.

[0066] Therefore, the treatment method and system for medical waste flue gas deacidification wastewater provided by this invention removes the first, second, and third new pollutants through staged treatment, while simultaneously obtaining sodium chloride refined salt and sodium hypochlorite aqueous solution products. This achieves the resource recovery of industrial-grade sodium chloride refined salt and sodium hypochlorite aqueous solution, and at least a portion of the obtained sodium hypochlorite aqueous solution is recycled back to the front end of the system, forming a resource recycling path. Simultaneously, the ultrafiltration concentrate, nanofiltration concentrate, sludge filtrate, and evaporation condensate generated during the treatment process can be recycled throughout the entire process, and the dewatered sludge can be utilized as a resource. This effectively solves the problem of difficult disposal of mixed salt hazardous waste, achieving full-process resource recovery of deacidification wastewater.

[0067] The following will provide further details with reference to specific embodiments.

[0068] Example 1 A medical waste disposal center processes 50 tons of medical waste per day, equipped with a wet deacidification process, generating 20 cubic meters of deacidification wastewater daily. 3 The medical waste flue gas deacidification wastewater contains new pollutants. The sodium chloride content in the medical waste flue gas deacidification wastewater is 10%, the total hardness (calculated as CaCO3) is 4500 mg / L, the sulfate content is 2200 mg / L, and the suspended solids content is 750 mg / L.

[0069] Embodiment 1 of the present invention provides a method for treating medical waste flue gas deacidification wastewater, wherein the medical waste flue gas deacidification wastewater contains new pollutants, the new pollutants including a first new pollutant, a second new pollutant and a third new pollutant; The processing method includes the following steps: S01. After stirring and homogenizing, the medical waste flue gas deacidification wastewater is subjected to micro-nano bubble flotation treatment to intercept the first new pollutant in the wastewater and obtain flotation effluent, wherein the first new pollutant includes long-chain PFAS and microplastics. The medical waste flue gas deacidification wastewater enters the homogenization and conditioning tank of the homogenization and conditioning unit. After homogenization treatment by stirring with a stirring device for 20 minutes, 5 g / L of magnetic modified chitosan additive is added to the homogenized medical waste flue gas deacidification wastewater. The magnetic modified chitosan additive is a mixture of chitosan and Fe3O4 nanoparticles. The addition ratio of chitosan to Fe3O4 nanoparticles is 1:3. Then, aeration is carried out for 20 minutes to intercept long-chain PFAS and microplastics in the wastewater, and air flotation effluent is obtained. S02. A ternary compound coagulant containing amino-modified activated carbon micro powder is added to the air flotation effluent to carry out a coagulation reaction to remove the second new pollutant. Then, a flocculant is added to carry out a flocculation reaction. After settling, the resulting supernatant is adjusted to a preset pH value, and the precipitated sludge is dewatered. The second new pollutant includes dissolved PFAS and dissolved PPCPs. The flotation effluent enters the coagulation reaction tank of the coagulation sedimentation reaction unit. A ternary composite coagulant is added to the flotation effluent and reacts for 15 minutes. The mass ratio of polyaluminum chloride, polyferric sulfate, and amino-modified activated carbon micropowder in the composite coagulant is 1.5:1:0.2. The dosage of the ternary composite coagulant is 80 mg / L. The coagulation reaction is carried out to remove dissolved PFAS and dissolved PPCPs. After the coagulation reaction, the mixture enters the flocculation reaction tank, where a flocculant is added and reacted for 10 minutes. The flocculant used is anionic polyacrylamide with a molecular weight of 8 million and a dosage of 0.8 mg / L. After flocculation, the sludge enters the inclined tube sedimentation tank, where it is allowed to settle for 40 minutes. The resulting supernatant is then adjusted to pH 7.5, and the settled sludge is dewatered before entering the membrane separation and purification unit. S03. The supernatant is fed into a ceramic ultrafiltration membrane for first-stage filtration to obtain ultrafiltration permeate and ultrafiltration concentrate; the ultrafiltration permeate is preheated to a preset temperature and fed into an organic nanofiltration membrane for second-stage filtration to obtain nanofiltration permeate and nanofiltration concentrate; the obtained nanofiltration permeate is subjected to adsorption of an amino anion exchange resin to remove a third new pollutant to obtain a first sodium chloride solution, wherein the third new pollutant includes short-chain PFAS; The supernatant was first-stage filtered using a ceramic ultrafiltration membrane. The porous ceramic support of the ceramic ultrafiltration membrane contained α-Al2O3, with the α-Al2O3 comprising 99% by mass. The separation layer contained ZrO2, with the ZrO2 comprising 93% by mass. The ceramic ultrafiltration membrane had a pore size of 0.1 μm, a compressive strength of 65 MPa, and a flux recovery rate of 98.5%. The operating pressure of the first-stage filtration was set at 0.3 MPa, and the operating temperature at 35°C. The ceramic ultrafiltration membrane removed flocs, colloidal PFAS, and colloidal PPCPs from the supernatant with a rejection rate of 99%, yielding ultrafiltration permeate and ultrafiltration concentrate. The ultrafiltration concentrate is returned to the inlet of SO2 for the cyclic adsorption and removal of new pollutants; The ultrafiltration permeate is preheated to 65°C using waste heat from medical waste incineration flue gas. A second stage of filtration is then performed using an organic nanofiltration membrane. This organic nanofiltration membrane is a high-temperature resistant polypiperazine amide spiral wound organic nanofiltration membrane with a molecular weight cutoff of 200 Da and a flux recovery rate of 99%. The operating pressure of the second stage filtration is set at 1.0 MPa, and the operating temperature at 65°C. The organic nanofiltration membrane removes calcium ions, magnesium ions, sulfate ions, residual dissolved PFAS, and residual dissolved PPCPs from the ultrafiltration permeate. The membrane achieves a rejection rate of 98.8% for calcium and magnesium ions, a rejection rate of 3% for sodium and chloride ions, and a rejection rate of 98% for residual dissolved PFAS and PPCPs, yielding nanofiltration permeate and nanofiltration concentrate. Calcium chloride is added to the nanofiltration concentrate, and after precipitation and filtration, the filtrate is returned to the SO2 inlet to remove new pollutants through cyclic adsorption. The nanofiltration permeate is transferred to an amino anion exchange resin adsorption unit to remove short-chain PFAS from the nanofiltration permeate, resulting in a first sodium chloride solution.

[0070] S04. The first sodium chloride solution is subjected to vacuum evaporation and crystallization. The resulting crystallized liquid is subjected to solid-liquid separation and drying to obtain refined sodium chloride salt and condensate. The first sodium chloride solution was transferred to the evaporator crystallizer of the salt crystallization preparation unit for evaporation, concentration and crystallization. The evaporation and crystallization temperature was set at 70°C. Then the obtained crystallized liquid was put into a centrifugal dehydrator for solid-liquid separation, and then dried by a dryer at a drying temperature of 45°C to obtain industrial grade sodium chloride refined salt. S05. Dissolve the sodium chloride refined salt to obtain a second sodium chloride solution, and electrolyze the second sodium chloride solution to obtain an aqueous solution of sodium hypochlorite; The industrial-grade sodium chloride refined salt is transferred to the salt dissolving tank of the sodium hypochlorite generating unit. After dissolution, a second sodium chloride solution with a concentration of 4% is obtained. The second sodium chloride solution is then transferred to the sodium hypochlorite generator. The electrolysis voltage of the sodium hypochlorite generator is set to 3.8V. The anode used for electrolysis is coated with a ruthenium-iridium-tin / cerium oxide composite coating, and the cathode is a titanium mesh with a nickel-cobalt alloy plated on its surface. The second sodium chloride solution is electrolyzed to obtain an aqueous sodium hypochlorite solution.

[0071] (6) A portion of the sodium hypochlorite aqueous solution is returned to the inlet of steps S01, S02 and S03 to oxidize and degrade the new pollutants remaining in the system.

[0072] Comparative Example 1 The medical waste flue gas deacidification wastewater treated in Comparative Example 1 of this invention is the same as that in Example 1.

[0073] Comparative Example 1 of this invention provides a method for treating medical waste flue gas deacidification wastewater, which employs a conventional coagulation sedimentation + sand filtration + evaporation crystallization process, including the following steps: S101. Add lime to the medical waste flue gas deacidification wastewater to cause calcium and magnesium ions, suspended solids, colloids, etc. to form precipitates, and then separate the precipitates to obtain the supernatant; S102. Pass the supernatant through a filter device containing filter media such as quartz sand to further remove fine suspended solids and colloids from the deacidification wastewater; S103. The filtered deacidified wastewater is added to an evaporator, and concentrated and crystallized by heating and evaporation to obtain crystalline salt, which is then dehydrated and transported for disposal.

[0074] The results show that the concentration of the first sodium chloride solution obtained in Example 1 of this invention is 10%, the calcium ion content is 3.2 mg / L, the magnesium ion content is 3.2 mg / L, the sulfate content is 6.8 mg / L, the removal rate of new pollutants is 99.5%, the purity of the obtained industrial-grade sodium chloride refined salt is 99.1%, there is no enrichment of new pollutants, which meets the GB / T 5462-2015 "Industrial Salt" standard, and the effective chlorine content of the obtained sodium hypochlorite aqueous solution is 0.8%, which fully meets the requirements for oxidative degradation of residual new pollutants in the system and on-site disinfection.

[0075] Furthermore, the medical waste flue gas deacidification wastewater treatment system described in Embodiment 1 of this invention has no wastewater discharge, and the dewatered sludge can be harmlessly incinerated at high temperatures, simultaneously meeting the environmental protection requirements for hazardous waste disposal and new pollutants. Embodiment 1 of this invention recovers approximately 1.6 tons of industrial-grade sodium chloride daily, producing approximately 2 tons of sodium hypochlorite aqueous solution, which can completely replace purchased disinfectants or oxidants, saving over 300,000 yuan annually. The equipment has operated continuously for 6 months without scaling or clogging.

[0076] In contrast, Comparative Example 1 can only achieve wastewater harmlessness. The crystalline salt obtained from evaporation and crystallization is a mixed salt with a purity of 83%, which is classified as hazardous waste and requires paid disposal. The retention rate of calcium ions, magnesium ions, and sulfate ions is 70%, and the removal rate of new pollutants is 48%. The evaporator develops severe scaling after 30 days of use, resulting in high operation and maintenance costs. There is no resource recovery path, and it cannot achieve the resource recovery of industrial-grade sodium chloride refined salt, nor can it prepare sodium hypochlorite aqueous solution. It can only achieve wastewater discharge that meets standards, resulting in resource waste and high environmental protection costs.

[0077] Therefore, the treatment method and system for medical waste flue gas deacidification wastewater provided by the present invention can achieve deep purification of new pollutants in deacidification wastewater by removing new pollutants in stages, resource recovery of industrial-grade sodium chloride refined salt, and direct use of the industrial-grade sodium chloride refined salt to prepare sodium hypochlorite aqueous solution and reuse it at the front end of the system, forming a resource recycling path. This effectively solves the problems of incomplete impurity removal and equipment scaling in traditional processes, while reducing wastewater treatment costs and being green and environmentally friendly.

[0078] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for treating medical waste flue gas deacidification wastewater, characterized in that, The medical waste flue gas deacidification wastewater contains new pollutants, including a first new pollutant, a second new pollutant, and a third new pollutant. The processing method includes the following steps: (1) After stirring and homogenizing, the medical waste flue gas deacidification wastewater is subjected to micro-nano bubble flotation treatment to intercept the first new pollutant in the wastewater and obtain flotation effluent. The first new pollutant includes any one or combination of long-chain PFAS and microplastics. (2) Add a ternary compound coagulant containing amino-modified activated carbon micro powder to the air flotation effluent to carry out coagulation reaction to remove the second new pollutant, then add a flocculant to carry out flocculation reaction, and after settling, adjust the obtained supernatant to the preset pH value, and dewater the precipitated sludge. The second new pollutant includes any one or a combination of dissolved PFAS and dissolved PPCPs. (3) The supernatant is fed into a ceramic ultrafiltration membrane for first-stage filtration to obtain ultrafiltration permeate and ultrafiltration concentrate; the ultrafiltration permeate is preheated to a preset temperature and fed into an organic nanofiltration membrane for second-stage filtration to obtain nanofiltration permeate and nanofiltration concentrate; the obtained nanofiltration permeate is subjected to adsorption of an amino anion exchange resin to remove a third new pollutant to obtain a first sodium chloride solution, wherein the third new pollutant includes short-chain PFAS; (4) The first sodium chloride solution is subjected to vacuum evaporation and crystallization. The resulting crystallized liquid is subjected to solid-liquid separation and drying to obtain refined sodium chloride salt and condensate. (5) Dissolve the sodium chloride refined salt to obtain a second sodium chloride solution, and electrolyze the second sodium chloride solution to obtain an aqueous solution of sodium hypochlorite; (6) At least a portion of the sodium hypochlorite aqueous solution is returned to the inlet of steps (1), (2), and (3) to oxidize and degrade the new pollutants remaining in the system.

2. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (1), the sodium chloride content in the medical waste flue gas deacidification wastewater is 10% to 20%, the total hardness (calculated as CaCO3) is 3000 mg / L to 6000 mg / L, the sulfate content is 1000 mg / L to 3000 mg / L, and the suspended solids content is 500 mg / L to 1000 mg / L.

3. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (1), the micro / nano bubble flotation treatment includes: A magnetically modified chitosan additive was added to the homogenized medical waste flue gas deacidification wastewater. The dosage of the magnetically modified chitosan additive was 0.4 g / L to 6 g / L, and the aeration time was 15 min to 20 min. The magnetically modified chitosan additive is a mixture of chitosan and magnetic nanoparticles; The chitosan and magnetic nanoparticles are added in a ratio of 1:3 to 3:1, and the magnetic nanoparticles are one or more of Fe3O4, γ-Fe2O3, MnFe2O4, CoFe2O4, NiFe2O4, and ZnFe2O4.

4. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (2), the ternary compound coagulant comprises polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micro powder, and the mass ratio of polyaluminum chloride, polyferric sulfate and amino-modified activated carbon micro powder is 1.5:1:0.2 to 2.5:1:0.

3. The dosage of the ternary compound coagulant is 50 mg / L to 100 mg / L; The flocculant used is anionic polyacrylamide with a molecular weight of 8 million to 12 million and a dosage of 0.5 mg / L to 1.0 mg / L. The coagulation reaction time is 10 min to 15 min, the flocculation reaction time is 8 min to 12 min, and the settling time is 30 min to 45 min. The preset pH value is 7.5 to 8.

5.

5. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (3), the ceramic ultrafiltration membrane includes a porous ceramic support and a separation layer disposed on the surface of the porous ceramic support. The porous ceramic support contains α-Al2O3, and the separation layer contains ZrO2. The α-Al2O3 has a mass percentage content of ≥99% in the porous ceramic support, and the ZrO2 has a mass percentage content of ≥92% in the separation layer; The ceramic ultrafiltration membrane has a pore size of 0.05 μm to 0.1 μm, a compressive strength of ≥50 MPa, and a flux recovery rate of ≥98%. The organic nanofiltration membrane is a polypiperazine amide spiral wound nanofiltration membrane. The organic nanofiltration membrane has a molecular weight cutoff of 200 Da to 400 Da and a flux recovery rate of ≥99%. The concentration of the first sodium chloride solution is 5% to 12%, with calcium ion content ≤5 mg / L, magnesium ion content ≤5 mg / L, and sulfate ion content ≤10 mg / L.

6. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, Step (3) includes: The supernatant is first filtered using a ceramic ultrafiltration membrane to remove flocs, suspended solids, colloidal PFAS, and colloidal PPCPs from the supernatant, resulting in ultrafiltration permeate and ultrafiltration concentrate. The ultrafiltration concentrate is returned to the inlet of step (2); The ultrafiltration permeate is preheated to 45℃~65℃, and then filtered in a second stage using an organic nanofiltration membrane to remove calcium ions, magnesium ions, sulfate ions, residual dissolved PFAS, and residual dissolved PPCPs from the ultrafiltration permeate, thereby obtaining nanofiltration permeate and nanofiltration concentrate. Add calcium chloride to the nanofiltration concentrate, and after precipitation and filtration, return the filtrate to the inlet end of step (2); The nanofiltration permeate is transferred to an amino anion exchange resin adsorption unit to remove short-chain PFAS from the nanofiltration permeate, resulting in a first sodium chloride solution.

7. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, The ceramic ultrafiltration membrane operates at a pressure of 0.2 MPa to 0.4 MPa and at a temperature of 15°C to 40°C. The organic nanofiltration membrane operates at a pressure of 0.8 MPa to 1.2 MPa and at a temperature of 15°C to 70°C.

8. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (4), the temperature of vacuum evaporation crystallization is 60℃~80℃, and the temperature of drying is 40℃~50℃.

9. The method for treating medical waste flue gas deacidification wastewater according to claim 1, characterized in that, In step (5), the concentration of the second sodium chloride solution is 3% to 5%, the electrolysis voltage is 3.5V to 4.0V, and the effective chlorine content of the sodium hypochlorite aqueous solution is 0.6% to 0.8%.

10. A medical waste flue gas deacidification wastewater treatment system for performing the treatment method as described in any one of claims 1 to 9.

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