A method for treating oil sand retort industrial wastewater

Abstract

The application provides a treatment method of oil sand dry distillation industrial wastewater. Cr The application takes "acid neutralization-organic pollutant degradation-deep adsorption" as the core, and a treatment system thereof comprises a regulating and neutralizing unit, a coagulation air flotation unit, a biochemical treatment unit, a deep adsorption unit and a disinfection and discharge unit connected in sequence; compared with a traditional oil field water treatment process, the application focuses on solving the problems of acid neutralization and organic pollutant removal, rather than high mineralization treatment, and has the advantages of strong pertinence, high treatment efficiency, stable operation and the like, and can ensure that the oil sand dry distillation wastewater meets the discharge standard.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for treating industrial wastewater from oil sands dry distillation. Background Technology

[0002] Oil sands dry distillation industrial wastewater is a special type of wastewater generated during the oil sands processing. Its core source is a mixture of liquid products and water vapor released during the high-temperature dry distillation (pyrolysis) of oil sands. This type of wastewater is biologically toxic and difficult to degrade naturally. The benzene compounds it contains pose a serious threat to aquatic life and human health, and it must be treated to meet standards before it can be discharged.

[0003] Traditional oilfield water treatment processes are primarily designed for water with high mineralization and high suspended solids, targeting water with a pH of neutral to slightly alkaline and a COD level of [missing information]. Cr <50mg / L, total salt content 10000-100000mg / L, high concentration of inorganic ions such as chloride and sulfate, suspended solids often >500mg / L. Generally, processes such as oil separation, sedimentation, desalination (such as electrodialysis / reverse osmosis), and chemical precipitation are adopted. The logic is "oil separation and sedimentation - desalination and softening - mineral removal". The focus is on inorganic ion and salinity control. The core is to remove high suspended solids and inorganic minerals, reduce salinity and reduce mineralization. The typical process route is pretreatment tank → oil separation → sedimentation → electrodialysis → ion exchange → reinjection / discharge.

[0004] The water quality characteristics of oil sands dry distillation wastewater are quite unique, with low pH and high chemical oxygen demand (COD). Cr This wastewater contains high levels of organic pollutants such as benzene compounds, petroleum hydrocarbons, and volatile phenols, but has a lower concentration of inorganic ions. It differs significantly from oilfield water in terms of pollutant properties, concentration, and acidity / alkalinity. Traditional oilfield water treatment processes are ineffective in treating acidic substances and organic pollutants in oil sands distillation wastewater, resulting in water quality that fails to meet standards after treatment.

[0005] Therefore, there is an urgent need to develop a treatment process specifically for wastewater from oil sands dry distillation industry in order to address the shortcomings of existing technologies. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for treating industrial wastewater from oil sands dry distillation, which is particularly suitable for treating oil sands dry distillation wastewater containing benzene compounds, with high COD and acidity.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for treating industrial wastewater from oil sands dry distillation, comprising a regulating and neutralizing unit, a coagulation and flotation unit, a biochemical treatment unit, a deep adsorption unit, and a disinfection and discharge unit connected in sequence, the specific steps of which are as follows: S1. Adjustment and neutralization unit: including an equalization tank, used to adjust the pH value of wastewater to 6.5-7.5, and the wastewater stays in the tank for no less than 12 hours; S2, Coagulation and Flotation Unit: Includes a coagulation sedimentation tank, where polyaluminum chloride (PAC) solution and polyacrylamide (PAM) solution are first added for coagulation, and then dissolved air flotation is used to remove petroleum and suspended solids from the wastewater. S3, Biochemical treatment unit: including hydrolysis acidification tank and contact oxidation tank, used to degrade organic matter; S4: Deep adsorption unit: Employs an activated carbon adsorption tower for the removal of benzene compounds; S5. Disinfection and emission unit: Add sodium hypochlorite solution to kill microorganisms.

[0008] Preferably, NaOH solution is added to the adjustment and neutralization unit for pH adjustment, and the mass concentration of the NaOH solution is 30%, with an addition amount of 5-10 kg / ton of wastewater.

[0009] Preferably, the PAC solution in the coagulation flotation unit has a mass concentration of 10% and an addition amount of 200-300 mg / L, and the PAM solution has a mass concentration of 0.1% and an addition amount of 5-10 mg / L.

[0010] Preferably, the dissolved air pressure of the dissolved air flotation machine in the coagulation flotation unit is 0.3-0.4 MPa, and the residence time is 30 min.

[0011] Preferably, the hydraulic retention time of the hydrolysis acidification tank in the biochemical treatment unit is 4 hours, and the dissolved oxygen is <0.5 mg / L; the hydraulic retention time of the contact oxidation tank is 6 hours, and the aeration intensity is 10-15 L / (m²). 2 (·min), sludge concentration 2000-3000 mg / L.

[0012] Preferably, the activated carbon adsorption tower in the deep adsorption unit is filled with coconut shell activated carbon with an iodine value ≥800mg / g, and the empty bed contact time is 20min.

[0013] Preferably, the sodium hypochlorite solution in the disinfection and discharge unit has a mass concentration of 10%, an addition amount of 5-10 mg / L, and a disinfection residence time of 15 min.

[0014] Technical effect This invention has significant technical advantages compared to existing technologies: This invention provides a method for treating industrial wastewater from oil sands dry distillation, specifically targeting wastewater with low pH and high COD. CrCharacterized by high mineralization and the presence of benzene compounds, this invention focuses on "acid neutralization - organic pollutant degradation - deep adsorption" to remove organic matter. The process route is: neutralization → coagulation and flotation → hydrolysis and acidification → contact oxidation → activated carbon adsorption → disinfection. Compared with traditional oilfield water treatment processes, this invention focuses on solving the problems of acid neutralization and organic pollutant removal, rather than treating high mineralization. It has the advantages of being highly targeted, having high treatment efficiency, and stable operation, and can ensure that oil sands distillation wastewater meets discharge standards.

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the treatment process for industrial wastewater from oil sands dry distillation according to the present invention. Detailed Implementation

[0017] This invention provides a method for treating industrial wastewater from oil sands dry distillation, comprising a conditioning and neutralization unit, a coagulation and flotation unit, a biochemical treatment unit, a deep adsorption unit, and a disinfection and discharge unit connected in sequence; the specific steps are as follows: S1. Adjustment and Neutralization Unit: Used to adjust the wastewater volume and neutralize acidity. An adjustment tank is installed, equipped with a stirring device. A 30% NaOH solution is added via an online pH monitor and a linked dosing system to adjust the wastewater pH to 6.5-7.5. The volume of the adjustment tank is designed according to the treatment scale to ensure that the wastewater retention time in the tank is no less than 12 hours to balance the water quality and quantity.

[0018] S2. Coagulation and Flotation Unit: Used to remove petroleum hydrocarbons and suspended solids from wastewater. The adjusted wastewater enters the coagulation sedimentation tank, where a 10% (w / w) polyaluminum chloride (PAC) solution and a 0.1% (w / w) polyacrylamide (PAM) solution are added. The PAC solution dosage is 200-300 mg / L, and the PAM solution dosage is 5-10 mg / L. After mixing and reaction, the solution enters the dissolved air flotation (DAF) machine. The DAF machine operates at a dissolved air pressure of 0.3-0.4 MPa and a residence time of 30 minutes. It removes oil and suspended solids by releasing microbubbles, bringing them to the surface for removal, ensuring a suspended solids removal rate ≥80% and reducing the petroleum hydrocarbon concentration to below 0.5 mg / L.

[0019] S3, Biological Treatment Unit: Used to degrade organic matter in wastewater. Air flotation effluent sequentially enters the hydrolysis acidification tank and the contact oxidation tank. The hydrolysis acidification tank is equipped with combined packing material, controlling dissolved oxygen (DO) < 0.5 mg / L and hydraulic retention time (HRT) 4 h, decomposing large organic molecules into smaller molecules and improving the biodegradability of the wastewater. The contact oxidation tank uses an aeration system with an aeration intensity of 10-15 L / (m³). 2The sludge concentration is controlled at 2000-3000 mg / L, and the hydraulic retention time (HRT) is 6 h, with COD removed through microbial action. Cr And BOD5, making COD Cr The removal rate reaches 60-70%, and the BOD5 removal rate is over 80%.

[0020] S4: Deep Adsorption Unit: Used to remove residual benzene and other recalcitrant organic compounds. The biochemical effluent enters the activated carbon adsorption tower, which is filled with coconut shell activated carbon. The empty bed contact time is 20 minutes, and through physical adsorption, the removal rate of benzene and other compounds such as toluene is increased to over 90%.

[0021] S5. Disinfection and Discharge Unit: Used to kill microorganisms. A 10% sodium hypochlorite solution is used for disinfection, with a dosage of 5-10 mg / L. The solution is thoroughly mixed with wastewater through a pipeline mixer before entering the disinfection tank, where it remains for 15 minutes to kill microorganisms and ensure that the effluent meets discharge standards.

[0022] Figure 1 This is a process flow diagram of the treatment process for industrial wastewater from oil sands dry distillation according to the present invention. Example 1

[0023] This example focuses on the industrial wastewater from the oil sands dry distillation of a certain factory. Testing showed that the wastewater had a pH value as low as 4.0, indicating strong acidity, and a high chemical oxygen demand (COD). Cr The concentration of organic pollutants was 254 mg / L, containing benzene series compounds (toluene 374 μg / L, m-xylene 258 μg / L), petroleum products (1.28 mg / L), and volatile phenols (0.180 mg / L). The total salt content was 70 mg / L, and the concentration of inorganic ions was low.

[0024] The treatment method for industrial wastewater from oil sands dry distillation includes a series of interconnected units: a neutralization and conditioning unit, a coagulation and flotation unit, a biochemical treatment unit, a deep adsorption unit, and a disinfection and discharge unit. The treatment capacity is 2 tons / day. The specific steps are as follows: S1, Adjustment and Neutralization Unit: Introduce wastewater into a 1m... 3 In the equalization tank, the stirring device is turned on, and the pH is monitored in real time by an online pH monitor. The dosing pump is then activated to add a 30% NaOH solution at a rate of 8 kg / ton of water until the pH is adjusted to 6.5. The wastewater is then left in the tank for 12 hours.

[0025] S2, Coagulation and Flotation Unit: The wastewater adjusted in S1 enters the coagulation sedimentation tank, and a 10% PAC solution (250 mg / L) and a 0.1% PAM solution (8 mg / L) are added. After mixing and reaction, the mixture enters the dissolved air flotation machine, where the dissolved air pressure is controlled at 0.3 MPa and the solution is retained for 30 minutes to remove petroleum and suspended solids. Result: The suspended solids concentration decreased from 100 mg / L to below 20 mg / L, and the petroleum concentration decreased to below 0.5 mg / L.

[0026] S3, Biochemical Treatment Unit: The air flotation effluent after S2 treatment first enters a 2m... 3 Hydrolysis acidification tank, equipped with combined packing material, controlled DO < 0.5 mg / L, HRT 4h; then enters 3m 3 Contact oxidation tank, aeration intensity 12 L / (m²) 2 •min), sludge concentration 2500 mg / L, HRT 6 h, COD after treatment Cr The concentration decreased from 254 mg / L to below 100 mg / L, and BOD5 decreased from 18.9 mg / L to below 3.78 mg / L.

[0027] S4: Deep Adsorption Unit: The biochemical effluent after S3 treatment enters an activated carbon adsorption tower with a diameter of 0.5m and a height of 1.5m, filled with coconut shell activated carbon (iodine value ≥800mg / g). The empty bed contact time is 20min to remove benzene series compounds, reducing toluene from 374μg / L to below 37.4μg / L and m-xylene from 258μg / L to below 25.8μg / L.

[0028] S5. Disinfection and Discharge Unit: A 10% sodium hypochlorite solution (8 mg / L) is added to the adsorption effluent after S4 treatment. The mixture is then passed through a pipeline mixer before entering a 1m... 3 Disinfection tank, retention time 15 minutes. Final effluent pH = 6.5-7.5, COD... Cr ≤100mg / L, petroleum hydrocarbons ≤0.5mg / L, toluene ≤37.4μg / L, m-xylene ≤25.8μg / L, meeting the Class III standard requirements of the Integrated Wastewater Discharge Standard (GB8978-1996). Example 2

[0029] This example describes the treatment of carbonization wastewater from a medium-sized oil sands processing plant. The test data are: pH 5.0, COD... Cr The concentration of pollutants is 380 mg / L, containing benzene compounds (benzene 210 μg / L, ethylbenzene 180 μg / L), petroleum hydrocarbons 2.5 mg / L, volatile phenols 0.32 mg / L, and total salt content 95 mg / L. The processing capacity is 5 tons / day, and the specific steps are as follows: S1, Adjustment and Neutralization Unit: Wastewater is introduced into a 3m... 3In the equalization tank, the stirring device is turned on, and the pH is monitored in real time by an online pH monitor. A 30% NaOH solution is added by the linkage dosing pump at a dosage of 5 kg / ton of water to adjust the pH to 7.0. The wastewater stays in the tank for 14 hours.

[0030] S2, Coagulation and Flotation Unit: The wastewater adjusted in S1 enters the coagulation sedimentation tank, where a 10% PAC solution (200 mg / L) and a 0.1% PAM solution (5 mg / L) are added. After mixing and reaction, the mixture enters the dissolved air flotation unit, with the dissolved air pressure controlled at 0.35 MPa and a residence time of 30 minutes. After treatment, the suspended solids concentration decreases from 150 mg / L to below 25 mg / L, and petroleum hydrocarbons decrease to below 0.4 mg / L.

[0031] S3, Biochemical Treatment Unit: The air flotation effluent after S2 treatment first enters a 5m... 3 Hydrolysis acidification tank, DO < 0.5 mg / L, HRT 4 h; then enter 8 m 3 Contact oxidation tank, aeration intensity 10 L / (m²) 2 •min), sludge concentration 2000 mg / L, HRT 6 h. COD after treatment Cr The concentration of BOD5 decreased from 380 mg / L to below 110 mg / L, and BOD5 decreased from 35 mg / L to below 6 mg / L.

[0032] S4, Deep Adsorption Unit: The biochemical effluent after S3 treatment enters an activated carbon adsorption tower with a diameter of 0.8m and a height of 2m, filled with coconut shell activated carbon (iodine value ≥800mg / g), with an empty bed contact time of 20min. After treatment, benzene decreased from 210μg / L to below 20μg / L, and ethylbenzene decreased from 180μg / L to below 15μg / L.

[0033] S5. Disinfection and Discharge Unit: A 10% sodium hypochlorite solution (5 mg / L) is added to the adsorption effluent after S4 treatment. The mixture is then passed through a pipeline mixer before entering a 2m... 3 Disinfection tank, retention time 15 minutes. Final effluent pH = 6.5-7.5, COD... Cr ≤110mg / L, petroleum ≤0.4mg / L, benzene ≤20μg / L, ethylbenzene ≤15μg / L, meeting the Class III standard requirements of the Integrated Wastewater Discharge Standard (GB8978-1996). Example 3

[0034] This example describes the treatment of wastewater from a large oil sands carbonization plant. The wastewater quality is as follows: pH 3.5, COD... CrThe concentrations of pollutants are as follows: 520 mg / L for benzene series compounds (o-xylene 420 μg / L, styrene 310 μg / L), 3.8 mg / L for petroleum products, 0.55 mg / L for volatile phenols, and 120 mg / L for total salts. The treatment capacity is 10 tons / day. The specific steps are as follows: S1, Adjustment and Neutralization Unit: Wastewater is introduced into an 8m... 3 In the equalization tank, the stirring device is turned on, and the pH is monitored in real time by an online pH monitor. The dosing pump is linked to add a 30% NaOH solution at a dosage of 10 kg / ton of water to adjust the pH to 7.5. The wastewater retention time is 16 hours.

[0035] S2, Coagulation and Flotation Unit: The wastewater adjusted in S1 enters the coagulation sedimentation tank, where a 10% PAC solution (300 mg / L) and a 0.1% PAM solution (10 mg / L) are added. After mixing and reaction, the mixture enters the dissolved air flotation unit at a dissolved air pressure of 0.4 MPa for 30 minutes. After treatment, the suspended solids concentration decreases from 220 mg / L to below 30 mg / L, and petroleum hydrocarbons decrease to below 0.45 mg / L.

[0036] S3, Biochemical Treatment Unit: The air flotation effluent after S2 treatment first enters a 10m... 3 Hydrolysis acidification tank, DO < 0.5 mg / L, HRT 4 h; then enter 15 m 3 Contact oxidation tank, aeration intensity 15 L / (m²) 2 •min), sludge concentration 3000 mg / L, HRT 6 h. COD after treatment Cr The concentration of BOD5 decreased from 520 mg / L to below 130 mg / L, and BOD5 decreased from 60 mg / L to below 10 mg / L.

[0037] S4, Deep Adsorption Unit: The biochemical effluent after S3 treatment enters an activated carbon adsorption tower with a diameter of 1.2m and a height of 2.5m, filled with coconut shell activated carbon (iodine value ≥800mg / g), with an empty bed contact time of 20min. After treatment, o-xylene decreased from 420μg / L to below 40μg / L, and styrene decreased from 310μg / L to below 30μg / L.

[0038] S5. Disinfection and Discharge Unit: A 10% sodium hypochlorite solution (10 mg / L) is added to the adsorption effluent after S4 treatment. The mixture is then passed through a pipeline mixer before entering a 5m... 3 Disinfection tank, retention time 15 minutes. Final effluent pH = 6.5-7.5, COD... Cr ≤130mg / L, petroleum hydrocarbons ≤0.45mg / L, o-xylene ≤40μg / L, styrene ≤30μg / L, meeting the Class III standard requirements of the Integrated Wastewater Discharge Standard (GB8978-1996).

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for treating industrial wastewater from oil sands dry distillation, characterized in that, The system comprises a regulating and neutralizing unit, a coagulation and flotation unit, a biochemical treatment unit, a deep adsorption unit, and a disinfection and emission unit, connected in sequence. The specific steps are as follows: S1. Adjustment and neutralization unit: including an equalization tank, used to adjust the pH value of wastewater to 6.5-7.5, and the wastewater stays in the tank for no less than 12 hours; S2, Coagulation and Flotation Unit: Includes a coagulation sedimentation tank, where polyaluminum chloride (PAC) solution and polyacrylamide (PAM) solution are first added for coagulation, and then dissolved air flotation is used to remove petroleum and suspended solids from the wastewater. S3, Biochemical treatment unit: including hydrolysis acidification tank and contact oxidation tank, used to degrade organic matter; S4, Deep Adsorption Unit: Employs an activated carbon adsorption tower for the removal of benzene compounds; S5. Disinfection and emission unit: Add sodium hypochlorite solution to kill microorganisms.

2. The method according to claim 1, characterized in that, The pH is adjusted by adding NaOH solution in the adjustment and neutralization unit. The mass concentration of the NaOH solution is 30%, and the dosage is 5-10 kg / ton of wastewater.

3. The method according to claim 1, characterized in that, The PAC solution in the coagulation-flotation unit has a mass concentration of 10% and a dosage of 200-300 mg / L, while the PAM solution has a mass concentration of 0.1% and a dosage of 5-10 mg / L.

4. The method according to claim 1, characterized in that, The dissolved air flotation unit in the coagulation and flotation unit has a dissolved air pressure of 0.3-0.4 MPa and a residence time of 30 min.

5. The method according to claim 1, characterized in that, The hydrolysis acidification tank in the biochemical treatment unit has a hydraulic retention time of 4 hours and dissolved oxygen < 0.5 mg / L; the contact oxidation tank has a hydraulic retention time of 6 hours and an aeration intensity of 10-15 L / (m²). 2 (·min), sludge concentration 2000-3000 mg / L.

6. The method according to claim 1, characterized in that, The activated carbon adsorption tower in the deep adsorption unit is filled with coconut shell activated carbon with an iodine value ≥800mg / g, and the empty bed contact time is 20min.

7. The method according to claim 1, characterized in that, The sodium hypochlorite solution in the disinfection and discharge unit has a mass concentration of 10%, an addition amount of 5-10 mg / L, and a disinfection residence time of 15 min.

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