Integrated treatment method of antibiotic pharmaceutical wastewater

Abstract

The present application relates to the field of wastewater treatment, in particular to an integrated treatment method of antibiotic pharmaceutical wastewater. The present application provides an integrated treatment method of antibiotic pharmaceutical wastewater, which is based on the biochemical-membrane treatment process, and realizes the deep integration of antibiotic adsorption crystallization unit, multi-stage biochemical treatment unit, deep oxidation unit and membrane separation crystallization unit, so as to realize efficient treatment and resource recovery of wastewater, and achieve the double goals of reaching the discharge standard and water resource reuse.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to an integrated treatment method for antibiotic pharmaceutical wastewater. Background Technology

[0002] Antibiotic pharmaceutical wastewater is a typical example of high-concentration organic wastewater in the pharmaceutical industry, characterized by high organic load, high salinity, high color, and high toxicity. This type of wastewater has a complex composition, poor biodegradability, and a strong inhibitory effect on microbial activity. If discharged directly without effective treatment, it will not only pollute surface and groundwater but also induce the spread of antibiotic resistance genes and their accumulation in the environment, further exacerbating ecosystem imbalance and health risks through the food chain.

[0003] While existing traditional technologies such as biological treatment, activated sludge processes, advanced oxidation, and membrane separation have shown some effectiveness, they suffer from problems such as low biological efficiency, severe membrane fouling, high energy consumption, and poor resource utilization, making it difficult to achieve stable discharge compliance and resource recovery. Currently, many factories use the traditional process of "pretreatment + biological treatment + Fenton oxidation + mechanical vapor recompression (MVR)" to treat antibiotic pharmaceutical wastewater. Although this process can remove organic matter and salts to some extent, it suffers from complex processes, large footprints, and high operational and management difficulties. Single biological systems are susceptible to antibiotic inhibition, resulting in low efficiency and unstable effluent; Fenton oxidation produces a large amount of hazardous sludge; evaporation and crystallization consume high energy, have limited salt recovery, and byproducts are often disposed of as solid waste, leading to resource waste. Therefore, existing processes struggle to simultaneously achieve discharge compliance and resource utilization.

[0004] The integrated process developed in this invention, consisting of an antibiotic adsorption crystallization unit, a multi-stage biochemical treatment unit, a deep oxidation unit, and a multi-stage membrane separation crystallization unit, achieves efficient removal of organic matter and synergistic recovery of antibiotics, water, and salts, balancing economic efficiency and stability, and overcoming the bottlenecks of high energy consumption, heavy membrane fouling, and insufficient resource utilization in traditional processes.

[0005] The invention patent CN117843179A proposes a deep treatment process for antibiotic pharmaceutical wastewater based on advanced oxidation and biochemistry. This system can achieve the standard discharge of wastewater, but it does not fully consider the resource utilization of antibiotics, water and salt, and there are still problems with the disposal of oxidation by-products and iron sludge, making it difficult to meet the requirements of green and sustainable processes.

[0006] In summary, the existing technology has the following problems:

[0007] 1. Existing antibiotic pharmaceutical wastewater treatment processes typically involve multiple treatment units, are complex, require a large area, and are difficult to operate and manage.

[0008] 2. Currently, antibiotic recovery mainly relies on methods such as solvent extraction and ion exchange, which have problems such as low recovery efficiency, large solvent consumption, complex operation, high energy consumption, and difficulty in dealing with high-concentration wastewater.

[0009] 3. If wastewater enters the membrane separation unit directly, it is easy for colloids and particulate matter to clog the membrane pores, resulting in a rapid decline in membrane flux and a shortened membrane lifespan.

[0010] 4. Conventional evaporation and crystallization processes have high energy consumption and significant limitations in the resource recovery of salts; concentrated brine and by-products are mostly treated as solid waste, failing to achieve resource recovery and utilization, lacking economically feasible resource recovery pathways, resulting in secondary pollution and resource waste.

[0011] 5. The lack of reasonable reflux and process coupling design results in low overall integration, making it difficult to simultaneously achieve the dual goals of meeting emission standards and reusing antibiotic, water, and salt resources. Summary of the Invention

[0012] This invention proposes an integrated treatment method for antibiotic pharmaceutical wastewater. Based on a biochemical-membrane treatment process, it deeply integrates an antibiotic adsorption crystallization unit, a multi-stage biochemical treatment unit, a deep oxidation unit, and a membrane separation crystallization unit to achieve efficient wastewater treatment and resource recovery, thus achieving the dual goals of compliant discharge and water resource reuse. The specific steps of this invention are as follows:

[0013] An integrated treatment method for antibiotic pharmaceutical wastewater includes the following steps:

[0014] Step 1: The antibiotic pharmaceutical wastewater first enters the equalization tank;

[0015] In step two, the antibiotic wastewater, after being regulated in the equalization tank, flows from bottom to top into a fixed-bed adsorption column filled with activated carbon particles coated with conductive polyaniline (PANI). The saturated adsorption packing enters the next stage elution tower for antibiotic desorption. The wastewater then enters the hydrolysis acidification tank in step six.

[0016] Step 3: The saturated adsorption packing is uniformly loaded into the elution tower. The eluent enters the elution tower from the top and is atomized and sprayed through two layers of full-cone nozzles. At the same time, the agitator inside the tower stirs at low speed to keep the liquid fully mixed. After the regenerated PANI composite packing is vacuum dried, it can be refilled into the adsorption column for continued use. The resulting eluent enters the next stage low-temperature crystallization tank for cooling and crystallization.

[0017] Step 4: After the effluent from the washing tower is filtered to remove suspended solids, it enters a low-temperature crystallizer for temperature-controlled crystallization under set cooling rate and stirring conditions.

[0018] Step 5: The crystallization liquid flowing out of the low-temperature crystallizer enters the solid-liquid separation device, where it is separated to obtain antibiotic crystals and mother liquor. The obtained antibiotic crystals are washed and vacuum dried for recycling. The separated mother liquor is refluxed to the front end of the elution tower. The crystallization wastewater generated during the crystal washing process is neutralized and adjusted before entering the hydrolysis acidification tank in step 6.

[0019] Step 6: Wastewater passing through the fixed-bed adsorption column enters the hydrolysis acidification tank, anaerobic microorganisms are added and suitable conditions are maintained for reaction. Nutrients and buffers are added intermittently during operation. After passing through the hydrolysis acidification system, the wastewater enters the next stage process anoxic-aerobic (AO) tank.

[0020] Step 7: The wastewater that has undergone hydrolysis and acidification pretreatment enters the AO tank. First, the wastewater enters the anaerobic section, and then the wastewater enters the aerobic section. During operation, part of the effluent from the aerobic tank is returned to the anaerobic section at a certain reflux ratio.

[0021] Step 8: The effluent from the AO tank enters the isolated aerated biological filter. When the influent flows in the filter layer, the filter adopts zoned intermittent aeration and is backwashed or air-water combined flushing periodically during operation.

[0022] Step 9: The effluent from the isolated aerated biological filter enters the ozone catalytic tower for deep treatment. The tower is filled with TiO2 / activated carbon composite catalytic packing material, and ozone gas is continuously blown into the bottom of the tower. During operation, a circulating spray distribution method is adopted.

[0023] Step 10: After ozone catalytic oxidation treatment, the water enters the curtain ultrafiltration system, which uses a fabric-reinforced polyvinylidene fluoride (PVDF) hollow fiber membrane module with a pore size of 0.03~0.08μm. The concentrated water from the curtain ultrafiltration system is returned to the front end of the hydrolysis acidification tank.

[0024] Step 11: The permeate from the curtain ultrafiltration system enters the nanofiltration system. As the water flows into the nanofiltration system, divalent cations are retained while monovalent cations permeate, achieving preliminary salt separation. The concentrate from the nanofiltration system enters the subsequent membrane distillation and crystallization system for divalent salt crystallization. The permeate from the nanofiltration system then enters the next stage, the reverse osmosis system.

[0025] Step 12: The reverse osmosis system efficiently retains monovalent cations, and the reverse osmosis permeate is directly reused; the reverse osmosis concentrate enters the subsequent membrane distillation and crystallization system for monovalent salt crystallization.

[0026] Step thirteen: The membrane distillation crystallization system consists of a membrane distillation device and a forced circulation crystallizer. It achieves resource recovery of salts through pre-concentration + crystallization. In the pre-concentration module, a hydrophobic microporous membrane is used. By controlling the temperature of the inlet water and the condenser, water is driven to pass through the hydrophobic membrane in the form of water vapor and condense into product water on the condenser side. The concentrate enters the crystallization module and evaporates in the crystallization tank to make the solution reach a supersaturated state and precipitate crystals. The crystallization slurry is separated into solid and liquid by a centrifuge or vacuum filter to obtain high-purity inorganic salt crystals and mother liquor. The mother liquor is returned to the front end of the membrane distillation module.

[0027] In step one, acid and alkali agents are added to the equalization tank to adjust the pH and stabilize it within the range of 6.5 to 7.5, and a bar screen is installed at the first end of the inlet of the equalization tank.

[0028] In step two, the fixed bed adsorption column adopts a stainless steel vertical cylindrical structure. The inside of the column is provided with a support layer, a uniform distribution layer and an adsorption filler layer from bottom to top. The support layer is filled with quartz sand or porous ceramic particles; the adsorption filler material is PANI-coated activated carbon particles; the influent flow rate is controlled at 2.0~3.5 m / h, and the empty bed contact time is 15~30 min.

[0029] In step three, the washing tower is a vertical cylindrical structure with a spray inlet and a cooling interface at the top. The spray inlet is arranged in a multi-point ring and equipped with multi-layer full-cone nozzles. The saturated adsorption packing is filled to a height of 70-80% of the effective height of the tower.

[0030] In step three, for β-lactam antibiotics, the elution buffer is an ethanol-weak acid mixture; for macrolide antibiotics, the elution buffer is an ethanol-water mixture; for tetracycline antibiotics, the elution buffer is an ethanol-NaCl composite system; for sulfonamide antibiotics, the elution buffer is a weak acid buffer; and for quinolone antibiotics, the elution buffer is an acetonitrile-phosphate buffer system.

[0031] In step three, the elution operation lasts for 30 to 60 minutes; the eluent is collected in a sealed eluent storage tank and the temperature is kept not higher than 25 ℃. When the concentration of antibiotics in the effluent drops to less than 10% of the initial concentration, the elution is considered complete.

[0032] In the low-temperature crystallization tank of step four, the stirring rate of the eluent is 100~300 rpm, and the temperature is slowly cooled to 2~5 ℃ at a cooling rate of 0.1~0.3 ℃ / min. The constant temperature crystallization time is maintained for 4~8 h, which promotes the supersaturation precipitation of antibiotic solute in the solution to form regular crystals. The crystallization recovery rate is 85~90%.

[0033] The solid-liquid separation device in step five uses a vacuum filter with a filter cloth pore size of 10-50 μm, a vacuum degree maintained at 0.05-0.1 MPa, and a temperature not exceeding 10 ℃. The wet crystals obtained after solid separation are washed with pure water to remove antibiotic crystals, with the solvent volume being 1-5 times the volume of the wet crystals, and the washing temperature not exceeding 10 ℃. The antibiotic crystals obtained after solid-liquid separation are then vacuum dried, with the temperature controlled at 35-50 ℃, the pressure controlled at 0.05-0.1 MPa, and the drying time being 2-8 h.

[0034] The multi-stage biochemical treatment unit consisting of steps six, seven, and eight operates at a temperature controlled between 25 and 35°C during the hydrolysis and acidification stage. The AO tank is equipped with an aeration system in the aerobic section, maintaining a dissolved oxygen concentration of 2-3 mg / L. A portion of the effluent from the aerobic tank is returned to the anaerobic section at a recirculation ratio of 200%-300%. The isolated aerated biological filter is filled with biochar and iron-carbon granules as biofilm carriers, with an aeration intensity controlled at 120-150 L / (m³). 3 •h), the air-to-water ratio is set to 5:1 to 8:1, and dissolved oxygen is maintained at 2 to 3 mg / L.

[0035] Steps 10, 11, 12, and 13 constitute a multi-stage membrane separation crystallization unit. The operating pressure of the curtain ultrafiltration system membrane is controlled at -10 to -30 kPa to ensure that the turbidity of the permeate is <1 NTU, the COD of the reverse osmosis permeate is ≤10 mg / L, NH3-N is ≤3 mg / L, and TP is ≤0.5 mg / L. In the membrane distillation crystallization system, the heating side temperature in the pre-concentration module is controlled at 60 to 80°C, the condensation side temperature is controlled at 20 to 30°C, and the conductivity of the condensate is ≤15 μS / cm. The crystallization module temperature is controlled at 65 to 85°C, and the circulation speed is 2 to 4 m / s.

[0036] This invention features a multi-stage reflux mechanism to achieve efficient treatment of antibiotic pharmaceutical wastewater and the resource utilization of antibiotics, water, and salts. In the antibiotic adsorption crystallization unit, the mother liquor after solid-liquid separation is refluxed to the feed end of the fixed-bed adsorption column for resource utilization. In the multi-stage biochemical treatment unit, the nitrified liquor from the aerobic stage of the AO tank is refluxed to the anaerobic stage via an internal reflux path, while the concentrated water from the curtain ultrafiltration system is refluxed to the hydrolysis acidification tank via an external reflux path, forming a closed loop of "front-end pretreatment—membrane separation—reflux enhancement," improving the biodegradability of the wastewater and enhancing its shock resistance. In the membrane distillation crystallization system, the mother liquor from the forced circulation crystallizer is refluxed to the membrane distillation equipment as feed water for further concentration, enabling further fractional recovery of salts.

[0037] This invention addresses the following problems in existing processes: 1. To address the issues of complex processes and large footprint in existing technologies, this invention designs an integrated and modular process consisting of an antibiotic adsorption crystallization unit, a multi-stage biochemical treatment unit, a deep oxidation unit, and a multi-stage membrane separation crystallization unit, thereby shortening the process and improving system compactness and operational efficiency; 2. To address the issues of low recovery efficiency, complex operation, and severe secondary pollution in existing processes, this technology designs an integrated antibiotic adsorption crystallization process consisting of a fixed-bed adsorption column, an elution tower, a low-temperature crystallization tank, and a centrifugal separation device, achieving efficient antibiotic desorption, online regeneration of the packing material, and mother liquor reflux recycling, thereby improving recovery rate and resource utilization efficiency; 3. To address the issues of membrane systems being susceptible to fouling and having short lifespans. This invention designs a multi-stage biochemical treatment system at the front end of the membrane system, consisting of "hydrolysis acidification + AO + isolation aerated biological filter," which effectively reduces the impact of organic matter and colloids on the membrane system, reduces membrane fouling, and extends the service life of the membrane system. 4. Addressing the issues of high energy consumption and limited salt recovery in evaporation crystallization, this invention employs a combination of "dual-membrane separation + membrane distillation crystallization" technology, achieving efficient separation and low-energy recovery of salt substances. This avoids the problems of high energy consumption and low recovery rate in traditional evaporation crystallization processes, promoting the recycling of salt resources. 5. Addressing the lack of a reasonable reflux design in existing processes, this invention enhances the overall stability of the system by setting up a reflux system and optimizing process coupling, achieving efficient wastewater treatment and comprehensive reuse of antibiotics, water, and salt resources.

[0038] This invention has the following advantages:

[0039] 1. This process adopts an integrated and synergistic process of "antibiotic adsorption crystallization unit + multi-stage biochemical treatment unit + deep oxidation unit + multi-stage membrane separation crystallization unit", which is compact, highly automated, energy-efficient, and reduces the number of equipment and floor space.

[0040] 2. A combined process of fixed-bed adsorption column + elution tower + low-temperature crystallization tank + centrifugal separation device is used to construct a closed loop for antibiotic recovery of "adsorption-elution-crystallization-solid-liquid separation", so as to realize the resource recovery of antibiotics and the recycling of mother liquor.

[0041] 3. The combined process of hydrolysis acidification + AO + isolation aeration filter constructs a front-end treatment system of "pretreatment - denitrification - deep purification", which improves biodegradability and achieves denitrification and deep removal of recalcitrant organic matter.

[0042] 4. The isolated aerated biological filter has both degradation and sedimentation functions, which can replace the sedimentation tank, simplify the process and reduce the footprint.

[0043] 5. Through the synergistic effect of multi-stage biochemical treatment units and ozone catalytic reaction, the removal efficiency of recalcitrant organic matter and antibiotic residues is significantly improved.

[0044] 6. The use of membrane distillation (MD) equipment + forced circulation crystallizer (FCC) technology to replace traditional MVR evaporation reduces overall energy consumption by 25-40% compared to the MVR system, achieves high-purity salt recovery, and improves water-salt separation efficiency and resource utilization.

[0045] 7. Set up internal and external reflux to improve denitrification efficiency and resource utilization, extend membrane life, and reduce energy consumption.

[0046] 8. The entire system is highly automated, easy to operate and maintain, and has advantages for industrial promotion. Attached Figure Description

[0047] Figure 1 This is a flowchart of an integrated treatment method for antibiotic pharmaceutical wastewater according to the present invention. Detailed Implementation

[0048] Example 1

[0049] An integrated treatment method for antibiotic pharmaceutical wastewater includes the following steps:

[0050] In the first step, the antibiotic pharmaceutical wastewater first enters the equalization tank. Through hydraulic mixing, homogenization, pH adjustment, and optimization of hydraulic retention time, the influent water quality and quantity are stabilized, and the influent load is balanced, preparing for the subsequent antibiotic recovery and the stable operation of the biochemical and membrane treatment systems.

[0051] In step two, the antibiotic wastewater, after being conditioned in the equalization tank, flows upward into a fixed-bed adsorption column filled with PANI-coated activated carbon particles. As the wastewater flows through the bed, antibiotic molecules are adsorbed and enriched through the hydroxyl and amino groups on the PANI surface and π–π interactions, achieving efficient removal of antibiotics from the solution. The saturated adsorption packing then enters the next stage, the elution tower, for antibiotic desorption; the wastewater then enters the hydrolysis acidification tank in step six.

[0052] Step three: The saturated adsorption packing material is uniformly loaded into the elution tower. The eluent enters the tower from the top and is atomized and sprayed through two layers of full-cone nozzles. Simultaneously, the agitator inside the tower stirs at low speed to maintain thorough mixing of the liquid, ensuring sufficient contact between the eluent and the adsorbent particles and improving adsorption efficiency. The regenerated PANI composite packing material is vacuum dried and can be reloaded into the adsorption column for continued use. The resulting eluent enters the next stage, a low-temperature crystallizer, for cooling and crystallization.

[0053] Step four: After the effluent from the washing tower is filtered to remove suspended solids, it enters a low-temperature crystallizer for temperature-controlled crystallization under set cooling rates and stirring conditions. After crystallization, the crystallized liquid enters the next stage solid-liquid separation unit.

[0054] Step 5: The crystallization liquid flowing out of the low-temperature crystallizer enters the solid-liquid separation device for separation, obtaining antibiotic crystals and mother liquor. The obtained crystals are washed and vacuum dried for recycling; the separated mother liquor is refluxed to the front end of the elution tower to achieve solvent recycling and reduce system operating costs; the crystallization wastewater generated during crystal washing is neutralized and adjusted before entering the hydrolysis acidification tank in step 6.

[0055] Step six: Wastewater passing through the fixed-bed adsorption column enters the hydrolysis acidification tank, where anaerobic microorganisms are added and suitable conditions are maintained for reaction. Nutrients and buffers are intermittently added during operation to maintain system stability. After hydrolysis acidification, the wastewater enters the next stage process AO tank.

[0056] Step seven: The pretreated wastewater undergoing hydrolysis and acidification enters the AO tank. First, the wastewater enters the anaerobic zone, where microorganisms use small-molecule organic acids as a carbon source to decompose antibiotics and organic matter. Some nitrates and sulfates are reduced, and antibiotics are partially degraded into small-molecule intermediates. Subsequently, the wastewater enters the aerobic zone, where aerobic bacteria further decompose and mineralize antibiotic residues under aeration conditions, degrading the complex molecular structure of antibiotics. During operation, a portion of the effluent from the aerobic tank is recycled back to the anaerobic zone at a certain recirculation ratio to further improve denitrification efficiency.

[0057] Step 8: The effluent from the AO tank enters the isolated aerated biological filter, where microorganisms on the biofilm packing remove recalcitrant residual antibiotics and organic matter. As the influent flows through the filter bed, suspended solids and colloidal particles are trapped, achieving a synergistic effect of sedimentation and filtration. The filter employs zoned intermittent aeration to maintain a coexistence of aerobic and facultative anaerobic microenvironments, promoting the synergistic degradation by various microbial communities. Regular backwashing or combined air-water flushing is performed during operation to prevent clogging and sediment accumulation, ensuring stable system operation.

[0058] Step nine: The effluent from the isolated aerated biological filter enters the ozone catalytic tower for further treatment. The tower is filled with TiO2 / activated carbon composite catalytic packing material, utilizing its high specific surface area and catalytic activity to enhance the oxidative decomposition capacity of ozone. Ozone gas is continuously bubbled into the bottom of the tower, and a suitable concentration is maintained through online control. During operation, a circulating spray distribution method is used to ensure uniform distribution of liquid within the packing layer, avoiding short-circuiting and improving mass transfer and reaction efficiency.

[0059] Step 10: The water treated by ozone catalytic oxidation enters the curtain-type ultrafiltration system. A fabric-reinforced PVDF hollow fiber membrane module with a pore size of 0.03~0.08μm is used to physically sieve and remove colloids, suspended solids, and large molecular organic matter, reducing the risk of fouling to subsequent membrane systems. The concentrate from the curtain-type ultrafiltration system is returned to the front end of the hydrolysis acidification tank to reduce the accumulation of pollutants in the system and improve the biodegradability of the wastewater.

[0060] Step 11: The permeate from the curtain ultrafiltration system enters the nanofiltration system. As water flows into the nanofiltration system, divalent cations are retained, while monovalent cations permeate, achieving initial salt separation. The concentrate from the nanofiltration system enters the subsequent membrane distillation and crystallization system #1 for divalent salt crystallization; the permeate from the nanofiltration system enters the next stage, the reverse osmosis system.

[0061] Step 12: The reverse osmosis system efficiently retains monovalent cations. The reverse osmosis permeate is directly reused; the reverse osmosis concentrate enters the subsequent membrane distillation and crystallization system #2 for monovalent salt crystallization.

[0062] Step thirteen: The membrane distillation crystallization system consists of a membrane distillation unit (MD) and a forced circulation crystallizer (FCC). It achieves resource recovery of salts through a pre-concentration + crystallization process. In the pretreatment module, a hydrophobic microporous membrane is used. By controlling the inlet water and condensation temperatures, water is driven to pass through the hydrophobic membrane as steam and condense into product water on the condensation side. This condensate can be directly reused. The concentrated solution enters the crystallization module, where it evaporates in the crystallization tank until the solution reaches a supersaturated state and crystals precipitate. The crystallized slurry undergoes solid-liquid separation via a centrifuge or vacuum filter to obtain high-purity inorganic salt crystals and mother liquor. The mother liquor is returned to the front end of the membrane distillation module.

[0063] The function of the equalization tank in step one is to balance the quality and quantity of the influent to ensure the stable operation of the subsequent biological and membrane treatment systems. Acidic and alkaline reagents are added to adjust the pH and stabilize it within the range of 6.5 to 7.5, and the hydraulic retention time is controlled at 6 hours. A screen is installed at the inlet of the equalization tank to remove large suspended solids or floating matter and improve hydraulic conditions.

[0064] In step two, the fixed-bed adsorption column adopts a stainless steel vertical cylindrical structure. The interior of the column, from bottom to top, consists of a support layer, a uniform distribution layer, and an adsorption packing layer. The support layer is filled with quartz sand or porous ceramsite to support the adsorption layer and prevent fluid short-circuiting. The adsorption packing material is PANI-coated activated carbon particles, which have a certain specificity for antibiotic adsorption and can adsorb and remove 70-85% of antibiotics. The influent flow rate is controlled at 2.0-3.5 m / h, and the empty bed contact time is 15-30 min.

[0065] In step three, the elution tower is a vertical cylindrical structure with a spray inlet and cooling interface at the top. The spray inlet is arranged in a multi-point annular pattern and equipped with multiple layers of full-cone nozzles to achieve uniform spraying and full coverage of the eluent. A liquid collection outlet is located at the bottom to collect and discharge the eluent. The saturated adsorption packing is filled to 70-80% of the effective height of the tower. For β-lactam antibiotics, an ethanol-weak acid mixture is used as the eluent; for macrolide antibiotics, an ethanol-water mixture is used; for tetracycline antibiotics, an ethanol-NaCl composite system is used; for sulfonamide antibiotics, a weakly acidic buffer solution is used; and for quinolone antibiotics, an acetonitrile-phosphate buffer system is used. The elution operation lasts 30-60 minutes. The eluent is collected in a sealed eluent storage tank and kept at a temperature not exceeding 25°C to prevent thermal degradation of the antibiotics. The elution is considered complete when the antibiotic concentration in the effluent drops to below 10% of the initial concentration.

[0066] In step four, the eluent is stirred at 100-300 rpm in the low-temperature crystallization tank and slowly cooled to 2-5 ℃ at a cooling rate of 0.1-0.3 ℃ / min. The constant temperature crystallization time is maintained for 4-8 h, which promotes the supersaturation precipitation of antibiotic solute in the solution to form regular crystals. The crystallization recovery rate is 85-90%.

[0067] In step five, the solid-liquid separation device employs a vacuum filter with a filter cloth pore size of 10–50 μm, maintaining a vacuum level of 0.05–0.1 MPa and a temperature not exceeding 10 °C. The crystallizing liquid is kept at a low temperature during transport to the solid-liquid separation device to prevent crystal dissolution or aggregation. The wet crystals obtained after solid-liquid separation are washed with pure water to remove antibiotic crystals; the solvent volume is 1–5 times the volume of the wet crystals, and the washing temperature does not exceed 10 °C. The antibiotic crystals obtained after solid-liquid separation are then vacuum dried at a temperature controlled at 35–50 °C and a pressure controlled at 0.05–0.1 MPa for 2–8 hours.

[0068] The multi-stage biological treatment unit, consisting of steps six, seven, and eight, is primarily used to improve the biodegradability of wastewater, remove organic matter, and achieve denitrification, thereby effectively reducing the pollution load and improving the treatment efficiency and anti-fouling capabilities of the subsequent membrane separation system. During the hydrolysis and acidification stage, the operating temperature is controlled at 25-35℃. Relying on the action of anaerobic microorganisms, large organic molecules are hydrolyzed into small organic acids, and the structure of antibiotics is destroyed, significantly improving the biodegradability of wastewater and reducing its toxicity. The AO tank achieves the synergistic removal of organic matter and ammonia nitrogen through an alternating anaerobic-aerobic reaction stage, while simultaneously mitigating the inhibitory effect of antibiotics on microbial activity. An aeration system is installed in the aerobic section, maintaining a dissolved oxygen concentration of 2-3 mg / L to promote the nitrification conversion of ammonia nitrogen and the deep degradation of organic pollutants. A portion of the effluent from the aerobic tank is returned to the anaerobic section at a recirculation ratio of 200%-300%, further improving denitrification efficiency. The isolated aerated biological filter is filled with biochar and iron-carbon granules as biofilm packing material, providing a large specific surface area to enhance microbial biomass and strengthen the removal of recalcitrant organic matter. Recalcitrant antibiotics are adsorbed or metabolized by microorganisms and converted into smaller organic molecules. The aeration intensity is controlled at 120~150 L / (m²). 3 The air-to-water ratio is set at 5:1 to 8:1, and dissolved oxygen is maintained at 2 to 3 mg / L to ensure sufficient oxygen supply in the tank and avoid the formation of local anaerobic zones. After passing through multiple biological treatment units, 85% to 95% of antibiotics that have penetrated the fixed bed can be cumulatively removed.

[0069] The ozone catalytic system in step nine is a deep oxidation unit, primarily used for the deep oxidation treatment of the effluent from the multi-stage biological treatment unit. The ozone catalytic tower is filled with a TiO2 / activated carbon composite catalyst, significantly improving ozone mass transfer efficiency and catalytic activity, thus enhancing the removal of recalcitrant organic matter. It thoroughly degrades residual antibiotic molecules and metabolites, converting them into CO2, H2O, and inorganic salts. After passing through the deep oxidation unit, the removal rate of residual antibiotics can reach 99%. This creates favorable influent conditions for the subsequent multi-stage membrane separation and crystallization unit.

[0070] Steps 10, 11, 12, and 13 constitute a multi-stage membrane separation and crystallization unit, primarily used for deep water separation to achieve high-purity salt recovery and water resource utilization. The pre-filter ultrafiltration system operates at a pressure controlled between -10 and -30 kPa to ensure permeate turbidity <1 NTU, providing stable water quality for subsequent units. The nanofiltration system utilizes the pore size sieving effect, Donald effect, and electrostatic repulsion of the nanofiltration membrane to retain approximately 98% of divalent salts. Simultaneously, due to the concentration gradient across the membrane, monovalent salts selectively permeate due to the concentration gradient, achieving preliminary salt separation. The reverse osmosis system further separates water from monovalent salts, producing high-quality permeate that can be directly reused. The reverse osmosis permeate has COD ≤10 mg / L, NH3-N ≤3 mg / L, and TP ≤0.5 mg / L. The system is equipped with online and offline cleaning devices to effectively reduce membrane fouling risk and extend membrane lifespan. In membrane distillation crystallization systems 1# and 2#, the heating side temperature is controlled at 60~80℃ and the condensation side temperature is controlled at 20~30℃, respectively, and the conductivity of the condensate is ≤15 μS / cm; the temperature of the forced circulation crystallization module is controlled at 65~85℃ and the circulation speed is 2~4 m / s.

[0071] Application Example 1

[0072] Wastewater from a large domestic antibiotic pharmaceutical company was used to conduct a laboratory simulation treatment experiment on pharmaceutical wastewater containing amoxicillin. The experimental scale was 10 L / h, with antibiotic concentration of 25 mg / L, COD of 23000 mg / L, ammonia nitrogen of 960 mg / L, and total salt of 31000 mg / L. The wastewater first entered a fixed-bed adsorption unit, with PANI-coated activated carbon as the packing material and a specific surface area of ​​950 m². 2 / g, residence time 30 min. The total antibiotic concentration in the effluent decreased to 4.25 mg / L, with a removal rate of 83%. After ethanol elution and low-temperature crystallization of the adsorption saturated packing, the amoxicillin crystallization recovery rate was 86%, and the purity was 97%. The adsorption effluent entered a multi-stage biological treatment unit, where the antibiotic concentration was further reduced to 0.56 mg / L, with a removal rate of 86%. The biological effluent was treated by an ozone catalytic oxidation reactor with an ozone dosage of 8 mg / L, a contact time of 50 min, and a catalyst dosage of 3 g / L for the TiO2 / activated carbon composite packing. The antibiotic concentration in the effluent decreased to <10 ng / L, COD decreased to 80~120 mg / L, and the antibiotic removal rate reached 99.9%. After a multi-stage membrane separation system, the COD of the reverse osmosis permeate was 5 mg / L, NH3-N was 1.6 mg / L, and TP was 0.3 mg / L. The purity of monovalent salt NaCl reached 99% and the purity of divalent salt MgSO4 reached 96-98% through the membrane distillation crystallization system.

[0073] The entire experimental system operated stably without any adsorption regeneration degradation or membrane fouling issues. It achieved resource utilization of antibiotics, water, and salts with zero pollution discharge, verifying the feasibility of this process for efficient removal and reuse of various types of antibiotic wastewater on a laboratory scale.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated treatment method for antibiotic pharmaceutical wastewater, characterized in that, Includes the following steps: Step 1: The antibiotic pharmaceutical wastewater first enters the equalization tank; In step two, the antibiotic wastewater, after being regulated in the equalization tank, flows from bottom to top into a fixed-bed adsorption column filled with PANI-coated activated carbon particles. The saturated adsorption packing enters the next stage elution tower for antibiotic desorption. The wastewater then enters the hydrolysis acidification tank in step six. Step 3: The saturated adsorption packing is uniformly loaded into the elution tower. The eluent enters the elution tower from the top and is atomized and sprayed through two layers of full-cone nozzles. At the same time, the agitator inside the tower stirs at low speed to keep the liquid fully mixed. After the regenerated PANI composite packing is vacuum dried, it can be refilled into the adsorption column for continued use. The resulting eluent enters the next stage low-temperature crystallization tank for cooling and crystallization. Step 4: After the eluent from the elution tower is filtered to remove suspended solids, it enters a low-temperature crystallization tank for temperature-controlled crystallization under set cooling rate and stirring conditions. Step 5: The crystallization liquid flowing out of the low-temperature crystallizer enters the solid-liquid separation device, where it is separated to obtain antibiotic crystals and mother liquor. The obtained antibiotic crystals are washed and vacuum dried for recycling. The separated mother liquor is refluxed to the front end of the elution tower. The crystallization wastewater generated during the crystal washing process is neutralized and adjusted before entering the hydrolysis acidification tank in step six. Step six: The wastewater enters the hydrolysis acidification tank; Step 7: The wastewater that has undergone hydrolysis and acidification pretreatment enters the AO tank. First, the wastewater enters the anaerobic section, and then the wastewater enters the aerobic section. During operation, part of the effluent from the aerobic tank is returned to the anaerobic section at a certain reflux ratio. Step 8: The effluent from the AO tank enters the isolated aerated biological filter. When the influent flows in the filter layer, the filter adopts zoned intermittent aeration and is backwashed or air-water combined flushing periodically during operation. Step 9: The effluent from the isolated aerated biological filter enters the ozone catalytic tower for deep treatment. The tower is filled with TiO2 / activated carbon composite catalytic packing material, and ozone gas is continuously blown into the bottom of the tower. During operation, a circulating spray distribution method is adopted. Step 10: The water after ozone catalytic oxidation treatment enters the curtain ultrafiltration system, which uses a fabric-reinforced PVDF hollow fiber membrane module with a pore size of 0.03~0.08 μm. The concentrated water from the curtain ultrafiltration system is returned to the front end of the hydrolysis acidification tank. Step 11: The water produced by the curtain ultrafiltration system enters the nanofiltration system. As the water flows into the nanofiltration system, divalent cations are retained while monovalent cations permeate, achieving preliminary separation of salts. The concentrated water from the nanofiltration system enters the subsequent membrane distillation crystallization system for divalent salt crystallization. The water produced by the nanofiltration system enters the next stage of the reverse osmosis system; Step 12: The reverse osmosis system efficiently retains monovalent cations, and the reverse osmosis permeate is directly reused; The reverse osmosis concentrate enters the subsequent membrane distillation crystallization system for monovalent salt crystallization; Step thirteen: The membrane distillation crystallization system consists of a membrane distillation device and a forced circulation crystallizer. It achieves resource recovery of salts through pre-concentration + crystallization. In the pre-concentration module, a hydrophobic microporous membrane is used. By controlling the temperature of the inlet and condensation sides, water is driven to pass through the hydrophobic membrane in the form of water vapor and condense into product water on the condensation side. The concentrate enters the crystallization module and evaporates in the crystallization tank to make the solution reach a supersaturated state and precipitate crystals. The crystallization slurry is separated into solid and liquid by a centrifuge or vacuum filter to obtain high-purity inorganic salt crystals and mother liquor. The mother liquor is returned to the front end of the membrane distillation module.

2. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In step one, acid and alkali agents are added to the equalization tank to adjust the pH and stabilize it within the range of 6.5 to 7.5, and a bar screen is installed at the first end of the inlet of the equalization tank.

3. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In step two, the fixed bed adsorption column adopts a stainless steel vertical cylindrical structure. The inside of the column is provided with a support layer, a uniform distribution layer and an adsorption filler layer from bottom to top. The support layer is filled with quartz sand or porous ceramic particles; the adsorption filler material is PANI-coated activated carbon particles; the influent flow rate is controlled at 2.0~3.5 m / h, and the empty bed contact time is 15~30 min.

4. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In step three, the washing tower is a vertical cylindrical structure with a spray inlet and a cooling interface at the top. The spray inlet is arranged in a multi-point ring and equipped with multi-layer full-cone nozzles. The saturated adsorption packing is filled to a height of 70-80% of the effective height of the tower.

5. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In step three, for β-lactam antibiotics, the elution buffer is an ethanol-weak acid mixture; for macrolide antibiotics, the elution buffer is an ethanol-water mixture; for tetracycline antibiotics, the elution buffer is an ethanol-NaCl composite system; for sulfonamide antibiotics, the elution buffer is a weak acid buffer; and for quinolone antibiotics, the elution buffer is an acetonitrile-phosphate buffer system.

6. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In step three, the elution operation lasts for 30 to 60 minutes; the eluent is collected in a sealed eluent storage tank and kept at a temperature not higher than 25 ℃. When the antibiotic concentration in the effluent drops to less than 10% of the initial concentration, the elution is considered complete.

7. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: In the low-temperature crystallization tank of step four, the stirring rate of the eluent is 100~300 rpm, and the temperature is slowly cooled to 2~5 ℃ at a cooling rate of 0.1~0.3 ℃ / min. The constant temperature crystallization time is maintained for 4~8 h, which promotes the supersaturation precipitation of antibiotic solute in the solution to form regular crystals. The crystallization recovery rate is 85~90%.

8. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: The solid-liquid separation device in step five uses a vacuum filter with a filter cloth pore size of 10-50 μm, a vacuum degree maintained at 0.05-0.1 MPa, and a temperature not exceeding 10 ℃. The wet crystals obtained after solid-liquid separation are washed with pure water to remove antibiotic crystals, with the solvent volume being 1-5 times the volume of the wet crystals, and the washing temperature not exceeding 10 ℃. The antibiotic crystals obtained after solid-liquid separation are then vacuum dried, with the temperature controlled at 35-50 ℃, the pressure controlled at 0.05-0.1 MPa, and the drying time being 2-8 h.

9. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: The multi-stage biochemical treatment unit consisting of steps six, seven, and eight operates at a temperature controlled between 25 and 35°C during the hydrolysis and acidification stage. The AO tank is equipped with an aeration system in the aerobic section, maintaining a dissolved oxygen concentration of 2-3 mg / L. A portion of the effluent from the aerobic tank is returned to the anaerobic section at a recirculation ratio of 200%-300%. The isolated aerated biological filter is filled with biochar and iron-carbon granules as biofilm carriers, with an aeration intensity controlled at 120-150 L / (m³). 3 •h), the air-to-water ratio is set to 5:1 to 8:1, and dissolved oxygen is maintained at 2 to 3 mg / L.

10. The integrated treatment method for antibiotic pharmaceutical wastewater as described in claim 1, characterized in that: Steps 10, 11, 12, and 13 constitute a multi-stage membrane separation crystallization unit. The operating pressure of the curtain ultrafiltration system membrane is controlled at -10 to -30 kPa to ensure that the turbidity of the permeate is <1 NTU, the COD of the reverse osmosis permeate is ≤10 mg / L, NH3-N is ≤3 mg / L, and TP is ≤0.5 mg / L. In the membrane distillation crystallization system, the heating side temperature in the pre-concentration module is controlled at 60 to 80°C, the condensation side temperature is controlled at 20 to 30°C, and the conductivity of the condensate is ≤15 μS / cm. The crystallization module temperature is controlled at 65 to 85°C, and the circulation speed is 2 to 4 m / s.

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