Advanced wastewater purification treatment method based on synergistic oxidation-biological-membrane separation

Abstract

The invention discloses a synergistic oxidation-biological-membrane separation wastewater deep purification treatment method, and aims to solve the problems of incomplete degradation, high energy consumption, secondary pollution and the like in treatment of wastewater containing antibiotics, heterocyclic and halogenated hydrocarbon pollutants in the prior art. Persulfate is activated through the synergistic effect of ultrasonic enhancement and a composite catalyst to generate strong oxidation free radicals, and macromolecular organic matter is decomposed into macromolecular organic matter with the molecular weight of 1t; a small molecule intermediate of 500 Da; efficient degradation of organic matters is realized by adopting a moving bed bio-membrane reactor (MBBR) process controlled by gradient dissolved oxygen; and deep desalination and pollutant interception are realized by combining an ultrafiltration-two-stage reverse osmosis membrane separation technology. The method is suitable for advanced treatment and recycling of industrial wastewater of chemical industry, pharmacy, pesticide and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment, and specifically relates to a wastewater deep treatment method that integrates the synergistic effects of advanced oxidation, biodegradation and membrane separation. It is particularly suitable for the treatment of industrial wastewater containing difficult-to-degrade organic pollutants such as antibiotics, heterocyclic compounds, and halogenated hydrocarbons. Background Art

[0002] With the development of industries like chemical and pharmaceuticals, the treatment of persistent organic pollutants (POPs) in wastewater has become an international challenge. Refractory organic compounds, such as antibiotics, heterocyclic compounds, and halogenated hydrocarbons, pose a significant challenge to existing water treatment technologies due to their high toxicity and bioaccumulation.

[0003] At present, the treatment technologies for wastewater with refractory organic pollutants mainly include physical and chemical methods and biological methods. Among them, physical and chemical methods mainly include adsorption, coagulation and chemical oxidation. Adsorption method (the adsorbent is generally activated carbon, etc.) only realizes the phase transfer of pollutants, and the regeneration cost of saturated adsorbent is high; coagulation method has a high COD Cr ) removal rate is less than 30%; conventional Fenton oxidation has the disadvantages of large iron sludge production (15-20 kg / ton of water) and narrow pH application range (2.5-4.0). Biological methods use the metabolism of microorganisms to convert organic pollutants into harmless substances, thereby achieving the purpose of water purification. Among them, the activated sludge method is the most widely used, but the activated sludge method has a high biochemical oxygen demand / dichromate oxygen demand (BOD5 / COD Cr ) <0.3, the wastewater treatment efficiency drops sharply, the chemical oxygen demand (COD) removal rate is <50%, antibiotics inhibit microbial activity, and anaerobic processes are prone to produce toxic by-products such as hydrogen sulfide.

[0004] Advanced oxidation processes can trigger a series of chain reactions through free radicals to attack target pollutants and degrade them into H2O and CO2, reducing secondary pollution problems. They are also highly efficient, rapid, and have thorough oxidation reactions. Among them, persulfate activation is due to sulfate radicals (SO4 - •) has attracted much attention due to its strong oxidation ability and long half-life (30-40 μs), but traditional persulfate activation relies on a single transition metal (such as Fe 2+ ), the catalyst deactivation rate is fast (half-life < 2 h), and the UV / heat activated persulfate composite activation method has high energy consumption (> 3.5 kWh / m 3), and is sensitive to suspended solids, with efficiency dropping by 65% ​​when turbidity exceeds 50 NTU. While membrane separation technology can effectively intercept organic matter, when used alone in wastewater treatment, membrane fouling is a prominent issue, with rapid flux decay and low operational efficiency. Therefore, using a single process to treat wastewater containing refractory organic matter is unlikely to meet discharge standards or reuse requirements. Summary of the Invention

[0005] The present invention addresses the defects of existing technologies for treating wastewater containing refractory organic matter. By constructing a three-stage coordinated treatment system of "oxidative chain scission-biomineralization-membrane interception", it effectively solves the technical problems of low treatment efficiency, high operating costs and substandard effluent quality of traditional processes.

[0006] The present invention adopts the following technical solution: a synergistic oxidation-biological-membrane separation method for deep purification of wastewater, which specifically comprises the following steps: (1) The wastewater is first removed from the slag by the screen decontamination machine and desanded in the cyclone grit chamber, and then enters the pH adjustment tank to adjust the pH value to 6.5-7.5; (2) The effluent from the pH adjustment tank enters a persulfate advanced oxidation reactor, which is connected to a persulfate addition device and a catalyst addition device. Under the action of persulfate and catalyst, the refractory organic matter in the wastewater is decomposed into small molecular organic matter that is easy to biochemically treat; (3) The wastewater treated by the persulfate advanced oxidation reactor enters the anaerobic tank, the anoxic moving bed biofilm reactor tank (anoxic MBBR tank), the aerobic moving bed biofilm reactor tank (aerobic MBBR tank), and the secondary sedimentation tank in sequence, so that the small molecular organic matter in the wastewater is further biodegraded, thereby reducing the contents of COD, total nitrogen, ammonia nitrogen, and total phosphorus in the wastewater; (4) The supernatant after sedimentation in the secondary sedimentation tank enters the coagulation sedimentation tank, the intermediate water tank, the ultrafiltration module, and the reverse osmosis module in sequence for deep purification treatment to fully remove suspended matter, colloids, pigments, small molecular organic matter, heavy metal ions, and soluble salts in the wastewater. The supernatant then enters the disinfection tank for sterilization and disinfection before being used by reclaimed water users.

[0007] The grid dirt remover has a 5 mm gap between the bars and can intercept suspended solids ≥ 5 mm. It is equipped with an automatic slag cleaning device with a cleaning frequency of 20-30 min / time. The surface load of the cyclone sand settling tank is 5-15 m 3 / (m 2 h), hydraulic retention time 30-60 s, air lift sand removal, aeration intensity 0.05-0.2 m 3 / (m 2 h), the pH regulating tank is equipped with a pH online monitor, linked to an automatic NaOH dosing system, and provided with a two-stage mechanical stirring.

[0008] The persulfate advanced oxidation reactor is equipped with an ultrasonic enhancement device and an anchor propeller composite flow propeller. The ultrasonic enhancement device has an operating frequency of 20-100 kHz and a power density of 0.1-1.0 W / cm 3 , forming a three-dimensional mixed flow field with the anchor propeller composite flow propeller, and forming a collaborative oxidation system together with the persulfate adding device and the catalyst adding device.

[0009] The persulfate addition device contains a persulfate composite oxidant, which is a compound of sodium persulfate and ammonium persulfate in a mass ratio of 3:1-5:1. The addition amount is 1.2-2.5 times the COD equivalent of the wastewater. A COD online monitor is provided at the water inlet of the persulfate advanced oxidation reactor. An intelligent control module is provided between the COD online monitor and the persulfate addition device, and the addition amount of the persulfate composite oxidant is dynamically adjusted according to the measured COD value.

[0010] The catalyst in the catalyst adding device is a ternary nanocomposite catalyst composed of Fe3O4, MnO2 and CuS in a mass ratio of 2:1:0.5, with a particle size of 20-100 nm and a specific surface area of ​​≥150 cm 2 / g, the catalyst dosage is 0.5-2.0 g / L, the persulfate composite oxidant generates hydroxyl radicals (•OH) and sulfate radicals (SO4 - •), and these free radicals trigger a series of chain reactions, causing the macromolecular organic matter in the sewage to break and degrade.

[0011] The anoxic MBBR pool and the aerobic MBBR pool are both equipped with a submerged mixer and an aeration device. The dissolved oxygen concentration of the anoxic MBBR pool is controlled at 0.2-0.5 mg / L, and the dissolved oxygen concentration of the aerobic MBBR pool is controlled at 2.5-4.0 mg / L. Under the control of the dissolved oxygen concentration gradient of the anoxic MBBR pool and the aerobic MBBR pool, the directional enrichment of the functional bacteria genus Flavobacterium and Nitrospira is achieved. The anoxic MBBR pool and the aerobic MBBR pool are both filled with a modified polyethylene MBBR carrier. The surface of the MBBR carrier is modified by plasma grafting carboxyl functional groups, and the specific surface area is ≥500 m 2 / m 3 .

[0012] An online redox potential (ORP) monitor is provided at the outlet of the anoxic MBBR tank to control the amount of carbon source added in a linkage manner, and the ORP value is maintained at -150 mV to -50 mV. An internal reflux pipe and an internal reflux pump are provided between the anoxic MBBR tank and the aerobic MBBR tank to supply the sludge in the aerobic MBBR tank to flow back into the anoxic MBBR tank, and the internal reflux ratio is 150%-400%. An external reflux pipe and an external reflux pump are provided between the anaerobic tank and the secondary sedimentation tank to supply the sludge in the secondary sedimentation tank to flow back into the anaerobic tank, and the external reflux ratio is 40%-150%.

[0013] The ultrafiltration membrane in the ultrafiltration module is made of polyvinylidene fluoride (PVDF) with a molecular weight cutoff of 10-50 kDa and an operating pressure of 0.15-0.25 MPa. The reverse osmosis module adopts a two-stage anti-pollution reverse osmosis membrane, including a low-pressure reverse osmosis membrane section and a high-pressure reverse osmosis membrane section, and adopts a gradient desalination mode. The operating pressure of the low-pressure reverse osmosis membrane section is 1.0-1.5 MPa, and the operating pressure of the high-pressure reverse osmosis membrane section is 4.0-5.0 MPa. The concentrated water discharged from the high-pressure reverse osmosis membrane section is used for flushing the ultrafiltration membrane, road dust reduction, environmental sanitation and cleaning.

[0014] The sludge produced by the persulfate advanced oxidation reactor, the secondary sedimentation tank and the coagulation sedimentation tank is respectively transported to the sludge pool through sludge pumps, and is transported out for harmless disposal after dehydration treatment.

[0015] Compared with the existing technology, the present invention has the following advantages: (1) The treatment efficiency is improved. By constructing a three-stage coordinated treatment system of "oxidative chain scission-biomineralization-membrane interception", the COD removal rate and phenol degradation rate are significantly better than those of traditional processes.

[0016] (2) The operating cost is reduced. By configuring an ultrasonic enhancement device, a three-dimensional mixed flow field is formed inside the persulfate advanced oxidation reactor, which makes the persulfate composite oxidant, catalyst and wastewater mix more evenly and fully react. In addition, through the activation of the catalyst and the ultrasonic cavitation effect of the ultrasonic enhancement device, the utilization rate of the persulfate composite oxidant is effectively improved, and the overall energy consumption of the system is significantly reduced.

[0017] (3) The water quality of the produced water has been significantly improved, which has effectively solved the technical problem of substandard effluent quality in traditional processes, achieved deep treatment and resource utilization of difficult-to-degrade organic wastewater, and increased the wastewater reuse rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0020] A synergistic oxidation-bio-membrane separation method for deep wastewater purification, such as Figure 1 As shown, it specifically includes the following steps: (1) The wastewater is first removed from the slag by the screen decontamination machine and desanded in the cyclone grit chamber, and then enters the pH adjustment tank to adjust the pH value to 6.5-7.5; (2) The effluent from the pH adjustment tank enters the persulfate advanced oxidation reactor, which is connected to a persulfate addition device and a catalyst addition device. Under the action of persulfate and catalyst, the refractory organic matter in the wastewater is decomposed into small molecular organic matter that is easy to biochemically treat; (3) The wastewater treated by the sulfate advanced oxidation reactor enters the anaerobic tank, anoxic MBBR tank, aerobic MBBR tank, and secondary sedimentation tank in sequence, so that the small molecular organic matter in the wastewater is further biodegraded, thereby reducing the content of COD, total nitrogen, ammonia nitrogen, and total phosphorus in the wastewater; (4) The supernatant after sedimentation in the secondary sedimentation tank enters the coagulation sedimentation tank, the intermediate water tank, the ultrafiltration module, and the reverse osmosis module in turn for deep purification treatment to fully remove suspended matter, colloids, pigments, small molecular organic matter, heavy metal ions, and soluble salts in the wastewater. It then enters the disinfection tank for sterilization and disinfection before being used by reclaimed water users.

[0021] The screen dirt remover has a 5 mm gap between the bars and can intercept suspended solids ≥ 5 mm. It is equipped with an automatic slag cleaning device with a cleaning frequency of 20-30 min / time. The surface load of the cyclone grit chamber is 5-15 m 3 / (m 2 h), hydraulic retention time 30-60 s, air lift sand removal, aeration intensity 0.05-0.2 m 3 / (m 2 ·h), the removal rate of sand particles with a particle size of ≥0.2 mm is ≥95%; the pH adjustment tank is equipped with a pH online monitor, linked to the NaOH automatic dosing system, and set with two-stage mechanical stirring, with a mixing time of ≤5 min.

[0022] The persulfate advanced oxidation reactor has an upper cylindrical / lower conical structure and is made of 316L stainless steel. Its mixing system is an anchor-propeller composite flow propeller, which can form a composite flow field of axial flow and radial flow. 4-8 ultrasonic enhancement devices are evenly spaced on the outer wall of the persulfate advanced oxidation reactor. The operating frequency of the ultrasonic enhancement device is 20-100 kHz and the power density is 0.1-1.0 W / cm 3 , forming a three-dimensional mixed flow field with the anchor propeller composite flow propeller, and forming a collaborative oxidation system together with the persulfate adding device and the catalyst adding device.

[0023] The persulfate addition device contains a persulfate composite oxidant, which is a compound of sodium persulfate and ammonium persulfate in a mass ratio of 3:1-5:1. The addition amount is 1.2-2.5 times the COD equivalent of the wastewater, and the reaction time is 60±2 min. A COD online monitor is provided at the water inlet of the persulfate advanced oxidation reactor. An intelligent control module is provided between the COD online monitor and the persulfate addition device, and the dosage of the persulfate composite oxidant is dynamically adjusted according to the measured COD value.

[0024] The catalyst in the catalyst adding device is a ternary nanocomposite catalyst composed of Fe3O4, MnO2 and CuS in a mass ratio of 2:1:0.5, with a particle size of 20-100 nm and a specific surface area of ​​≥150 cm 2 / g, the catalyst dosage is 0.5-2.0 g / L, and the persulfate composite oxidant produces hydroxyl radicals (•OH) and sulfate radicals (SO4 - •), and these free radicals trigger a series of chain reactions, causing the macromolecular organic matter in the sewage to break and degrade.

[0025] Both the anoxic MBBR pool and the aerobic MBBR pool are equipped with a submerged mixer and an aeration device. The dissolved oxygen concentration of the anoxic MBBR pool is controlled at 0.2-0.5 mg / L, and the dissolved oxygen concentration of the aerobic MBBR pool is controlled at 2.5-4.0 mg / L. Under the control of the dissolved oxygen concentration gradient of the anoxic MBBR pool and the aerobic MBBR pool, the directional enrichment of the functional bacteria genus Flavobacterium and Nitrospira is achieved. Both the anoxic MBBR pool and the aerobic MBBR pool are filled with a modified polyethylene MBBR carrier. The surface of the MBBR carrier is modified by plasma grafting carboxyl functional groups, and the specific surface area is ≥500 m 2 / m 3 .

[0026] An ORP online monitor is installed at the outlet of the anoxic MBBR tank to control the amount of carbon source added. The ORP value is maintained at -150mV to -50mV. An internal recirculation pipe and an internal recirculation pump are installed between the anoxic MBBR tank and the aerobic MBBR tank to return the sludge in the aerobic MBBR tank to the anoxic MBBR tank. The internal recirculation ratio is 150%-400%, and the sludge age is controlled at 20-25 days.

[0027] An external return pipe and an external return pump are installed between the anaerobic tank and the secondary sedimentation tank to return the sludge from the secondary sedimentation tank to the anaerobic tank. The external return ratio is 40%-150%. A submersible mixer is installed in the anaerobic tank to mix the sewage and the returned sludge. The dissolved oxygen in the anaerobic tank is controlled at 0.1-0.2 mg / L, and the sludge age is controlled at 5-10 days.

[0028] The ultrafiltration membrane in the ultrafiltration module is made of PVDF material with a molecular weight cutoff of 10-50 kDa and an operating pressure of 0.15-0.25 MPa. The reverse osmosis module adopts a two-stage anti-pollution reverse osmosis membrane, including a low-pressure reverse osmosis membrane section and a high-pressure reverse osmosis membrane section, and adopts a gradient desalination mode. The operating pressure of the low-pressure reverse osmosis membrane section is 1.0-1.5 MPa, and the operating pressure of the high-pressure reverse osmosis membrane section is 4.0-5.0 MPa. The concentrated water discharged from the high-pressure reverse osmosis membrane section is used for flushing the ultrafiltration membrane, road dust reduction, environmental sanitation cleaning and other purposes. The ultrafiltration membrane and reverse osmosis membrane are both cleaned online 1-2 times per hour by air-water flushing and chemically cleaned once every six months to reduce the membrane flux attenuation rate and extend the service life of the membrane.

[0029] The sludge produced by the persulfate advanced oxidation reactor, secondary sedimentation tank and coagulation sedimentation tank is transported to the sludge pool through sludge pumps respectively, and then transported out for harmless disposal after dehydration treatment.

[0030] The present invention constructs a three-stage coordinated treatment system of "oxidative chain scission-biomineralization-membrane interception", which can achieve the efficient degradation of organic pollutants such as antibiotics, heterocyclic compounds and halogenated hydrocarbons in wastewater, as well as the deep purification of other pollutants in wastewater. It effectively solves the technical problems of low treatment efficiency, high operating costs and substandard effluent quality of traditional processes. The produced water quality is excellent and can be used by reclaimed water users.

[0031] The above content describes the technical solution of the present invention in detail, but does not limit the scope of protection of the present invention. Ordinary technicians in this technical field can also make improvements and modifications on this basis, but these improvements and modifications are within the scope of protection of the claims of the present invention.

Claims

1. A method for deep purification of wastewater by synergistic oxidation-biofilm separation, characterized in that The following steps are involved: (1) The wastewater is first removed from the slag by the screen decontamination machine and desanded in the cyclone grit chamber, and then enters the pH adjustment tank to adjust the pH value to 6.5-7.5; (2) The effluent from the pH adjustment tank enters a persulfate advanced oxidation reactor, which is connected to a persulfate addition device and a catalyst addition device. Under the action of persulfate and catalyst, the refractory organic matter in the wastewater is decomposed into small molecular organic matter that is easy to biochemically treat; (3) The wastewater treated by the persulfate advanced oxidation reactor enters the anaerobic tank, the anoxic MBBR tank, the aerobic MBBR tank, and the secondary sedimentation tank in sequence, so that the small molecular organic matter in the wastewater is further biodegraded, thereby reducing the content of COD, total nitrogen, ammonia nitrogen, and total phosphorus in the wastewater; (4) The supernatant after sedimentation in the secondary sedimentation tank enters the coagulation sedimentation tank, the intermediate water tank, the ultrafiltration module, and the reverse osmosis module in sequence for deep purification treatment to fully remove suspended matter, colloids, pigments, small molecular organic matter, heavy metal ions, and soluble salts in the wastewater. The supernatant then enters the disinfection tank for sterilization and disinfection before being used by reclaimed water users.

2. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The grid dirt remover has a 5 mm gap between the bars and can intercept suspended solids ≥ 5 mm. It is equipped with an automatic slag cleaning device with a cleaning frequency of 20-30 min / time. The surface load of the cyclone sand settling tank is 5-15 m 3 / (m 2 h), hydraulic retention time 30-60 s, air lift sand removal, aeration intensity 0.05-0.2 m 3 / (m 2 h), the pH regulating tank is equipped with a pH online monitor, linked to an automatic NaOH dosing system, and provided with a two-stage mechanical stirring.

3. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The persulfate advanced oxidation reactor is equipped with an ultrasonic enhancement device and an anchor propeller composite flow propeller. The ultrasonic enhancement device has an operating frequency of 20-100 kHz and a power density of 0.1-1.0 W / cm 3 , forming a three-dimensional mixed flow field with the anchor propeller composite flow propeller, and forming a collaborative oxidation system together with the persulfate adding device and the catalyst adding device.

4. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The persulfate addition device contains a persulfate composite oxidant, which is a compound of sodium persulfate and ammonium persulfate in a mass ratio of 3:1-5:

1. The addition amount is 1.2-2.5 times the COD equivalent of the wastewater. A COD online monitor is provided at the water inlet of the persulfate advanced oxidation reactor. An intelligent control module is provided between the COD online monitor and the persulfate addition device, and the addition amount of the persulfate composite oxidant is dynamically adjusted according to the measured COD value.

5. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The catalyst in the catalyst adding device is a ternary nanocomposite catalyst composed of Fe3O4, MnO2 and CuS in a mass ratio of 2:1:0.5, with a particle size of 20-100 nm and a specific surface area of ​​≥150 cm 2 / g, and the catalyst dosage is 0.5-2.0 g / L.

6. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The anoxic MBBR pool and the aerobic MBBR pool are both equipped with a submerged mixer and an aeration device. The dissolved oxygen concentration of the anoxic MBBR pool is controlled at 0.2-0.5 mg / L, and the dissolved oxygen concentration of the aerobic MBBR pool is controlled at 2.5-4.0 mg / L. Under the control of the dissolved oxygen concentration gradient of the anoxic MBBR pool and the aerobic MBBR pool, the directional enrichment of the functional bacteria genus Flavobacterium and Nitrospira is achieved. The anoxic MBBR pool and the aerobic MBBR pool are both filled with a modified polyethylene MBBR carrier. The surface of the MBBR carrier is modified by plasma grafting carboxyl functional groups, and the specific surface area is ≥500 m 2 / m 3 .

7. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: An ORP online monitor is provided at the outlet of the anoxic MBBR tank to control the amount of carbon source added in a linkage manner, and the ORP value is maintained at -150 mV to -50 mV. An internal reflux pipe and an internal reflux pump are provided between the anoxic MBBR tank and the aerobic MBBR tank to supply the sludge in the aerobic MBBR tank to flow back into the anoxic MBBR tank, and the internal reflux ratio is 150%-400%. An external reflux pipe and an external reflux pump are provided between the anaerobic tank and the secondary sedimentation tank to supply the sludge in the secondary sedimentation tank to flow back into the anaerobic tank, and the external reflux ratio is 40%-150%.

8. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The ultrafiltration membrane in the ultrafiltration module is made of PVDF material, has a molecular weight cutoff of 10-50 kDa, and an operating pressure of 0.15-0.25 MPa. The reverse osmosis module uses a two-stage anti-pollution reverse osmosis membrane, including a low-pressure reverse osmosis membrane section and a high-pressure reverse osmosis membrane section, and adopts a gradient desalination mode. The operating pressure of the low-pressure reverse osmosis membrane section is 1.0-1.5 MPa, and the operating pressure of the high-pressure reverse osmosis membrane section is 4.0-5.0 MPa. The concentrated water discharged from the high-pressure reverse osmosis membrane section is used for flushing the ultrafiltration membrane, road dust reduction, environmental sanitation and cleaning.

9. The method for deep wastewater purification by synergistic oxidation-biofilm separation according to claim 1, characterized in that: The sludge produced by the persulfate advanced oxidation reactor, the secondary sedimentation tank and the coagulation sedimentation tank is respectively transported to the sludge pool through sludge pumps, and is transported out for harmless disposal after dehydration treatment.

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