High-salt low-cod coal chemical wastewater treatment process by tfo coupled with ro

Abstract

The application relates to the field of waste water treatment, and discloses a TFO coupling RO treatment process for high-salt low-COD coal chemical industry waste water. First, the high-salt low-COD coal chemical industry waste water is introduced into a salt-containing waste water adjusting tank to preliminarily pretreat the waste water by adjusting the water volume and the pH value; second, the water out of the adjusting tank is introduced into a flocculation and precipitation tank, a flocculant and a coagulant aid are added into the water to make the particles difficult to precipitate in the water gather each other and form flocculation bodies to precipitate with impurities; then, the supernatant after precipitation is introduced into a targeted Fenton reactor, catalytic ozone is used to generate a targeted active species to realize targeted removal of small-molecule organic matters; next, the water after the targeted oxidation is introduced into a sodium bed system and a reverse osmosis system to remove salts and macromolecular organic matters; finally, the water is further purified through a multi-medium filter to remove micro particles and bacteria which cannot be removed. The water quality of the water out of the application meets the discharge standard.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to a TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater. Background Technology

[0002] In recent years, the treatment of coal chemical wastewater has received widespread attention. This type of wastewater is often characterized by high salt concentration and low COD (Chemical Oxygen Demand) content, making it a difficult-to-degrade organic wastewater. While the organic matter content is low, it may still contain a certain amount of suspended solids, grease, and other pollutants. Due to its low organic matter content, the treatment of low-COD wastewater is relatively challenging. If discharged directly into natural water bodies without effective treatment, the soluble inorganic salts and recalcitrant toxic organic compounds will severely impact soil and water bodies, causing irreversible environmental damage. Currently, the effective treatment of high-salt, low-COD industrial wastewater from coal chemical plants is a major environmental issue facing industrial development. Achieving efficient and comprehensive utilization of this wastewater is a crucial path to solving this bottleneck.

[0003] High-salinity wastewater from coal chemical industry refers to a type of recalcitrant organic wastewater discharged from coal production, with a total salt content greater than 1% but a COD content less than 1000 mg / L. It is characterized by high salt content, strong acidity / alkalinity, high toxicity, complex chemical composition, and poor biodegradability. Currently, the mainstream methods for removing this type of wastewater include incineration, evaporation and concentration, biological methods, and Fenton oxidation and Fenton-like oxidation methods. While incineration is simple to operate, it suffers from high treatment costs, incomplete degradation, and the generation of toxic and harmful gases such as nitrogen oxides and disulfides during incineration, causing secondary pollution to the environment. Biological methods utilize the metabolism of microorganisms to convert organic matter in wastewater into harmless substances, but they suffer from poor stability and ineffective treatment of large-scale high-salinity wastewater. Reverse osmosis (RO) desalination technology uses pressure as a driving force and the selective permeability of the reverse osmosis membrane (which allows only the solvent to pass through, not the solute) to separate the solvent and solute from a solution containing inorganic matter, organic matter, various anions and cations, and microorganisms. It is a phase-change-free physical separation process with significant advantages such as high desalination rate, low pollution, and small footprint. However, it has high requirements for the quality and control of the raw water, necessitating the design of appropriate pretreatment and a professional control system to ensure effluent quality and extend equipment lifespan. Fenton or Fenton-like oxidation methods utilize catalysts to activate oxidants such as hydrogen peroxide, peracetic acid, and ozone under homogeneous or heterogeneous conditions, generating highly oxidizing free radicals to mineralize organic matter without secondary pollution. However, in actual treatment of high-salt, low-COD wastewater, the high salt content and low pollutant concentration mean that high concentrations of chloride and sulfate ions in the wastewater can quench some of the highly oxidizing free radicals, reducing removal efficiency and significantly increasing oxidant dosage, thus increasing treatment costs and energy consumption.

[0004] Therefore, there is an urgent need to develop a specific targeted treatment technology to achieve green, energy-saving, and efficient treatment of this type of coal chemical high-salt, low-COD wastewater. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater.

[0006] A TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater is specifically completed according to the following steps:

[0007] 1. High-salt, low-COD coal chemical wastewater is introduced into a saline wastewater equalization tank, and the pH value of the coal chemical wastewater is adjusted to 6-8 to obtain pH-adjusted coal chemical wastewater.

[0008] 2. The pH-adjusted coal chemical wastewater is introduced into the flocculation sedimentation tank, and then coagulant and coagulant aid are added. After hydraulic retention for a period of time, the supernatant in the flocculation sedimentation tank is introduced into the targeted Fenton reactor, and the settled sludge is introduced into the sludge thickening tank. Then, the sludge is dewatered in the dewatering room, the water is recycled, and the sludge cake is transported off-site.

[0009] 3. A certain concentration of ozone is introduced into the targeted Fenton reactor, and then a targeted catalytic oxidation reaction is carried out under the catalysis of a manganese-based catalyst in the targeted Fenton reactor to obtain water after targeted Fenton oxidation.

[0010] IV. Water after targeted Fenton oxidation enters the sodium bed system through the filter at the top of the sodium bed system, flows through the filter layer, and flows out from the bottom into the reverse osmosis system. After being filtered by the reverse osmosis membrane in the reverse osmosis system, the salt content in the coal chemical wastewater is reduced, resulting in coal chemical wastewater filtered by the reverse osmosis system. The filter layer is filled with ion exchange resin, which undergoes a displacement reaction with cations in the water, causing sodium ions to precipitate out of the water.

[0011] 5. Coal chemical wastewater filtered by the reverse osmosis system enters the multi-media filter. The filter media in the multi-media filter removes small particles and bacteria, resulting in treated water that can be directly discharged or reused.

[0012] Advantages of this invention:

[0013] This invention discloses a TFO-RO coupled process for high-salt, low-COD coal chemical wastewater. The wastewater first enters a saline wastewater equalization tank for preliminary pretreatment, including adjusting the flow rate and pH. The effluent from the equalization tank then enters a flocculation sedimentation tank, where coagulants and flocculants are added to cause particles that are difficult to settle to aggregate and form flocs. The supernatant after sedimentation first enters a targeted Fenton reactor, where a manganese-based catalyst catalyzes ozone to generate targeted active species, achieving targeted removal of small-molecule organic matter. Next, the water after targeted Fenton oxidation enters a sodium bed system, flowing through the top of a filter and exiting from the bottom. Ion exchange resin is placed in the filter layer to exchange with cations in the water, causing sodium ions to precipitate. The wastewater then enters a reverse osmosis system to reduce its salt content. Finally, it undergoes further purification through a multi-media filter to remove unremovable microparticles and bacteria. This invention uses targeted Fenton-like technology coupled with reverse osmosis filtration to treat high-salt, low-COD coal chemical wastewater. Compared with traditional methods, this invention is more environmentally friendly and efficient, and the effluent quality, including TDS, COD, and conductivity, meets emission standards. Attached Figure Description

[0014] Figure 1 This is a flowchart of a TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater, as described in this invention. Detailed Implementation

[0015] Specific Implementation Method 1: This implementation method describes a TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater, which is specifically completed according to the following steps:

[0016] 1. High-salt, low-COD coal chemical wastewater is introduced into a saline wastewater equalization tank, and the pH value of the coal chemical wastewater is adjusted to 6-8 to obtain pH-adjusted coal chemical wastewater.

[0017] 2. The pH-adjusted coal chemical wastewater is introduced into the flocculation sedimentation tank, and then coagulant and coagulant aid are added. After hydraulic retention for a period of time, the supernatant in the flocculation sedimentation tank is introduced into the targeted Fenton reactor, and the settled sludge is introduced into the sludge thickening tank. Then, the sludge is dewatered in the dewatering room, the water is recycled, and the sludge cake is transported off-site.

[0018] 3. A certain concentration of ozone is introduced into the targeted Fenton reactor, and then a targeted catalytic oxidation reaction is carried out under the catalysis of a manganese-based catalyst in the targeted Fenton reactor to obtain water after targeted Fenton oxidation.

[0019] IV. Water after targeted Fenton oxidation enters the sodium bed system through the filter at the top of the sodium bed system, flows through the filter layer, and flows out from the bottom into the reverse osmosis system. After being filtered by the reverse osmosis membrane in the reverse osmosis system, the salt content in the coal chemical wastewater is reduced, resulting in coal chemical wastewater filtered by the reverse osmosis system. The filter layer is filled with ion exchange resin, which undergoes a displacement reaction with cations in the water, causing sodium ions to precipitate out of the water.

[0020] 5. Coal chemical wastewater filtered by the reverse osmosis system enters the multi-media filter. The filter media in the multi-media filter removes small particles and bacteria, resulting in treated water that can be directly discharged or reused.

[0021] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the COD of the high-salt, low-COD coal chemical wastewater described in step one is 0–1000 mg / L, and the salt content is 5000–20000 mg / L; in step one, concentrated sulfuric acid, sodium carbonate, and sodium bicarbonate with a mass fraction of 70%–98% are used to adjust the pH value of the high-salt, low-COD coal chemical wastewater to 6–8. Other steps are the same as in Specific Implementation Method One.

[0022] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the coagulant mentioned in step two is one or a mixture of several of polyacrylamide, polyferric sulfate, activated silica, polyaluminum chloride, and ferric chloride; the dosage of the coagulant mentioned in step two is 50 ppm to 2000 ppm. Other steps are the same as in Specific Implementation Method One or Two.

[0023] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the coagulant aid mentioned in step two is one or a mixture of several of the following: activated silica, clay, activated water glass, sodium silicate, and quicklime; the dosage of the coagulant aid mentioned in step two is 50 ppm to 2000 ppm. The other steps are the same as in Specific Implementation Methods One to Three.

[0024] In this embodiment, the active silica and activated water glass are commercially available products purchased from Aladdin Company.

[0025] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the hydraulic retention time in step two is 1 to 8 hours. The other steps are the same as in Specific Implementation Methods One to Four.

[0026] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One through Five in that the ozone dosage in step three is 200 mg / L to 400 mg / L, and the ozone ventilation rate is 1.0 to 3.0 m³ / h. 3 / h; The temperature of the targeted catalytic oxidation reaction described in step three is 30℃~80℃, and the reaction time is 2h~6h. Other steps are the same as in specific embodiments one to five.

[0027] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the dosage of the manganese-based catalyst in step three is 1 g / L to 100 g / L. The other steps are the same as in Specific Implementation Methods One to Six.

[0028] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that the preparation method of the manganese-based catalyst described in step three is specifically completed according to the following steps:

[0029] ① Dissolve potassium permanganate and ammonium oxalate monohydrate in a mixed solution of anhydrous ethanol and deionized water, stir for 30 min to obtain a mixed solution;

[0030] The mass-to-volume ratio of the mixed solution of potassium permanganate, ammonium oxalate monohydrate, anhydrous ethanol, and deionized water mentioned in step ① is (4g~10g):(4g~10g):(50mL~100mL);

[0031] In step ①, the volume ratio of anhydrous ethanol to deionized water in the mixed solution of anhydrous ethanol and deionized water is 1:5.

[0032] ② The mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, and then subjected to hydrothermal reaction at 150℃~300℃ for 10h~36h to obtain the reaction product; the reaction product is ground, cleaned and dried to obtain a manganese-based catalyst.

[0033] The cleaning described in step ② involves alternating between anhydrous ethanol and deionized water until the reaction product is neutral. The other steps are the same as in specific embodiments one through seven.

[0034] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that: the ion exchange resin mentioned in step four is a copolymer of styrene and divinylbenzene (SDB), consisting of microspheres with an average particle size of 6μm to 10μm, purchased from McLean Company; the reverse osmosis membrane mentioned in step four is a polyester membrane, polyether membrane, polyethersulfone membrane, or polyamide membrane. The other steps are the same as in Specific Implementation Methods One through Eight.

[0035] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the filter media mentioned in step five is one or a mixture of several of gravel, quartz sand, anthracite, and manganese sand; the hydraulic retention time of the multi-media filter mentioned in step five is 1 to 2 hours. Other steps are the same as in Specific Implementation Methods One to Nine.

[0036] The beneficial effects of the present invention are verified using the following embodiments:

[0037] Example 1: A TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater is specifically completed according to the following steps:

[0038] 1. High-salt, low-COD coal chemical wastewater is introduced into a saline wastewater equalization tank, and then the pH value of the coal chemical wastewater is adjusted to 7 using concentrated sulfuric acid, sodium carbonate, and sodium bicarbonate with a mass fraction of 98%, resulting in coal chemical wastewater with a pH value of 7.

[0039] 2. Coal chemical wastewater with a pH of 7 is introduced into a flocculation sedimentation tank, and then coagulant and coagulant aid are added. After hydraulic retention for a period of time, the supernatant in the flocculation sedimentation tank is introduced into a targeted Fenton reactor, and the settled sludge is introduced into a sludge thickening tank. Then, the sludge is dewatered in the dewatering room, the water is recycled, and the sludge cake is transported off-site.

[0040] The coagulant mentioned in step two is polyferric sulfate, and the dosage is 500 ppm;

[0041] The coagulant aid mentioned in step two is active silica, purchased from Aladdin Company, with an addition amount of 700 ppm;

[0042] The hydraulic residence time mentioned in step two is 6 hours;

[0043] 3. A certain concentration of ozone is introduced into the targeted Fenton reactor, and then a targeted catalytic oxidation reaction is carried out under the catalysis of a manganese-based catalyst in the targeted Fenton reactor to obtain water after targeted Fenton oxidation.

[0044] The ozone dosage mentioned in step three is 300 mg / L, and the ozone ventilation rate is 2.0 m³ / h. 3 / h;

[0045] The targeted catalytic oxidation reaction described in step three is carried out at a temperature of 50°C for 4 hours.

[0046] The dosage of the manganese-based catalyst mentioned in step three is 15 g / L;

[0047] The preparation method of the manganese-based catalyst described in step three is specifically carried out according to the following steps:

[0048] ① Dissolve 6g of potassium permanganate and 3g of ammonium oxalate monohydrate in a mixed solution of 80mL of anhydrous ethanol and deionized water, stir and react for 30min to obtain a mixed solution;

[0049] In step ①, the volume ratio of anhydrous ethanol to deionized water in the mixed solution of anhydrous ethanol and deionized water is 1:5.

[0050] ② The mixed solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and then subjected to a hydrothermal reaction at 200°C for 18 hours to obtain the reaction product; the reaction product was then ground, washed, and dried to obtain a manganese-based catalyst.

[0051] The cleaning described in step ② involves alternating between anhydrous ethanol and deionized water until the reaction product is neutral.

[0052] IV. Water after targeted Fenton oxidation enters the sodium bed system through the filter at the top of the sodium bed system, flows through the filter layer, and flows out from the bottom into the reverse osmosis system. After being filtered by the reverse osmosis membrane in the reverse osmosis system, the salt content in the coal chemical wastewater is reduced, resulting in coal chemical wastewater filtered by the reverse osmosis system. The filter layer is filled with ion exchange resin, which undergoes a displacement reaction with cations in the water, causing sodium ions to precipitate out of the water.

[0053] The ion exchange resin mentioned in step four is a copolymer of styrene and divinylbenzene (SDB), which consists of microspheres with an average particle size of 6 μm to 10 μm and was purchased from McLean Company.

[0054] The reverse osmosis membrane mentioned in step four is a polyamide membrane;

[0055] In step four, the conductivity of the effluent is less than 15 μS / cm;

[0056] 5. Coal chemical wastewater filtered by the reverse osmosis system enters the multi-media filter. The filter media in the multi-media filter removes small particles and bacteria, resulting in treated water that can be directly discharged or reused.

[0057] The filter media mentioned in step five are gravel, quartz sand, and anthracite;

[0058] The hydraulic retention time of the multi-media filter described in step five is 1 hour.

[0059] In Example 1, the raw COD of the high-salt, low-COD coal chemical wastewater in step one is 1000 mg / L, the salt content is 10000 mg / L, and the conductivity is 1656 μs / cm. After treatment by the RO-coupled TFO treatment process for high-salt, low-COD coal chemical wastewater in Example 1, the effluent has a COD of 40 mg / L, a salt content of 1000 mg / L, and a conductivity of less than 15 μs / cm.

Claims

1. A TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater, characterized in that... The processing technology is specifically completed according to the following steps:

1. High-salt, low-COD coal chemical wastewater is introduced into a saline wastewater equalization tank, and the pH value of the coal chemical wastewater is adjusted to 6-8 to obtain pH-adjusted coal chemical wastewater.

2. The pH-adjusted coal chemical wastewater is introduced into the flocculation sedimentation tank, and then coagulant and coagulant aid are added. After hydraulic retention for a period of time, the supernatant in the flocculation sedimentation tank is introduced into the targeted Fenton reactor, and the settled sludge is introduced into the sludge thickening tank. Then, the sludge is dewatered in the dewatering room, the water is recycled, and the sludge cake is transported off-site.

3. A certain concentration of ozone is introduced into the targeted Fenton reactor, and then a targeted catalytic oxidation reaction is carried out under the catalysis of a manganese-based catalyst in the targeted Fenton reactor to obtain water after targeted Fenton oxidation. The dosage of the manganese-based catalyst mentioned in step three is 1 g / L to 100 g / L; The preparation method of the manganese-based catalyst described in step three is specifically carried out according to the following steps: ① Dissolve potassium permanganate and ammonium oxalate monohydrate in a mixed solution of anhydrous ethanol and deionized water, stir for 30 min to obtain a mixed solution; The mass-to-volume ratio of the mixed solution of potassium permanganate, ammonium oxalate monohydrate, anhydrous ethanol, and deionized water mentioned in step ① is (4g~10g):(1g~5g):(50mL~100mL); In step ①, the volume ratio of anhydrous ethanol to deionized water in the mixed solution of anhydrous ethanol and deionized water is 1:

5. ② The mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, and then subjected to hydrothermal reaction at 150℃~300℃ for 10h~36h to obtain the reaction product; the reaction product is ground, cleaned and dried to obtain a manganese-based catalyst. The cleaning described in step ② involves alternating between anhydrous ethanol and deionized water until the reaction product is neutral; Fourth, the water after targeted Fenton oxidation enters the sodium bed system through the filter at the top of the sodium bed system, flowing through the filter layer. The wastewater flows out from the bottom and enters the reverse osmosis system. After being filtered by the reverse osmosis membrane in the reverse osmosis system, the salt content in the coal chemical wastewater is reduced, resulting in coal chemical wastewater filtered by the reverse osmosis system. The filter layer contains ion exchange resin, which reacts with cations in the water to cause sodium ions to precipitate out.

5. Coal chemical wastewater filtered by the reverse osmosis system enters the multi-media filter. The filter media in the multi-media filter removes small particles and bacteria, resulting in treated water that can be directly discharged or reused.

2. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The COD of the high-salt, low-COD coal chemical wastewater mentioned in step one is 0~1000mg / L, and the salt content is 5000~20000mg / L. In step one, concentrated sulfuric acid, sodium carbonate, and sodium bicarbonate with a mass fraction of 70%~98% are used to adjust the pH value of the high-salt, low-COD coal chemical wastewater to 6~8.

3. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The coagulant mentioned in step two is one or a mixture of several of polyacrylamide, polyferric sulfate, activated silica, polyaluminum chloride and ferric chloride; the dosage of the coagulant mentioned in step two is 50 ppm to 2000 ppm.

4. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The coagulant aid mentioned in step two is one or a mixture of several of the following: commercially available activated silica, clay, activated water glass, sodium silicate, and quicklime; the dosage of the coagulant aid mentioned in step two is 50 ppm to 2000 ppm.

5. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The hydraulic retention time mentioned in step two is 1 to 8 hours.

6. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The ozone dosage mentioned in step three is 200 mg / L to 400 mg / L, and the ozone ventilation rate is 1.0 to 3.0 m³ / h. 3 / h; The temperature of the targeted catalytic oxidation reaction described in step three is 30℃~80℃, and the reaction time is 2h~6h.

7. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The ion exchange resin mentioned in step four is a copolymer of styrene and divinylbenzene, consisting of microspheres with an average particle size of 6-10 μm; the reverse osmosis membrane mentioned in step four is a polyester membrane, polyether membrane, polyethersulfone membrane, or polyamide membrane.

8. The TFO coupled RO treatment process for high-salt, low-COD coal chemical wastewater according to claim 1, characterized in that... The filter media mentioned in step five is one or a mixture of several of gravel, quartz sand, anthracite, and manganese sand; the hydraulic retention time of the multi-media filter mentioned in step five is 1 to 2 hours.

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