CN104787990B - A treatment method for high-temperature and high-salt refractory oil production wastewater - Google Patents

Abstract

The invention discloses a method for treating high-temperature high-salt degradation-resistant oil extraction wastewater. Microbial inoculant R in oil extraction wastewater₁(4) The degraded organic components are preferentially removed in the first-stage aerobic biochemical tank (2), and the supernatant after solid-liquid separation enters a first-stage ozone pre-oxidation tank (11) for pre-oxidationA secondary aerobic biochemical tank (18) for improving the biodegradability and leading the effluent to flow in, and a microbial agent R added in the tank₂(21) The biochemical organic matters are further degraded, the supernatant fluid flows into an advanced oxidation pond (28) after solid-liquid separation again, the residual organic matters which are difficult to degrade in the water can be thoroughly degraded under the synergistic action of an ozone generator (15), an ultraviolet lamp light-emitting device (29) and an oxidant dosing system (31), and the requirements of the effluent on indexes such as disinfection, chromaticity and the like are met. The process has the advantages of clear and controllable target division of each process section, simple flow operation, less dosage, less sludge output and stable and reliable water outlet. The method is convenient to popularize and use in the field of oilfield wastewater treatment.

Description

A treatment method for high-temperature and high-salt refractory oil production wastewater

technical field

The invention relates to a method for treating high-temperature, high-salt and refractory oil production wastewater by using a combined method of primary aerobic biochemistry-ozone pre-oxidation-secondary aerobic biochemistry-advanced oxidation to obtain wastewater up to standard discharge or recycling .

Background technique

With the development of modern industry, the human demand for oil is also increasing. A large amount of wastewater will be produced in the process of oil exploration and refining. These wastewaters often have high temperature (≥50°C), high salinity (≥3.5%) TDS) and complex residual petroleum components, if discharged directly without treatment, it will inevitably cause serious pollution and damage to the external environment. At present, the traditional treatment methods are mainly coagulation-sedimentation-activated carbon adsorption process or coagulation-filtration-ultrafiltration process, in order to meet the discharge requirements of oil, COD and other indicators in the national discharge or reuse water quality standards. These processes have problems such as many equipments, many control points, large amount of dosing, a large amount of difficult-to-treat sludge generated during operation, high regeneration cost of activated carbon adsorption equipment, and serious secondary pollution.

The biological method of adding high-temperature salt-resistant oleophilic bacteria is considered as a high-tech with broad market prospects because it has low cost for treating petroleum wastewater, can degrade petroleum hydrocarbon pollutants and does not produce secondary pollution. However, at present, there are few reports on the application of high-temperature salt-resistant oleophilic bacteria agents to actual engineering projects. This is mainly because the loss of bacteria agents will make a certain amount of bacteria agents be added regularly in actual engineering projects, thereby greatly increasing The operating cost of the project is high, so finding an efficient way to fix bacteria becomes a prerequisite for its promotion and use.

Oil produced water is difficult to be biochemically oxidized due to low BOD/COD (<0.1), especially after primary biochemical treatment of raw water, most of the remaining organic matter is soluble refractory organic matter, which is difficult to further biochemically degrade, so it is necessary to use Other treatment methods increase BOD/COD, which is convenient for subsequent biochemical treatment units. Ozone has strong oxidizing properties, so it can decompose or degrade various refractory organic pollutants in water. The oxidizing properties of ozone can be used directly, or combined with UV and H ₂ O ₂ for advanced oxidation. The purpose of the existing ozone oxidation process is mainly to allow ozone to completely degrade organic matter at one time, and secondly to improve the biodegradability of wastewater. This treatment method requires a large amount of ozone dosage and high operating costs.

Contents of the invention

In view of the problems existing in the existing high-temperature and high-salt refractory petroleum wastewater treatment methods, such as many equipments, complex control, large dosage of chemicals, high sludge output, unsatisfactory treatment effect on refractory organic matter, and serious secondary pollution, this paper The invention provides a treatment method for discharging or recycling such waste water up to the standard.

Technical scheme of the present invention:

A treatment method for high-temperature and high-salt refractory petroleum wastewater, the steps of the treatment method comprising:

Step 1: The water inlet pump pumps the oil production wastewater into the primary aerobic biochemical pool, and the hydrophilic fiber bundle biological carrier and microbial agent R ₁ are added to the primary aerobic biochemical pool, and the microbial agent is added manually or by gravity The filling ratio of the fiber bundle biological carrier is _Χ1 , and the dosage ratio _of the microbial agent R1 is _{Y1 ;} the dissolved oxygen required for the microbial agent R1 is provided from the aeration head at the bottom by the aeration pump;

Step 2, the mixed solution treated in step 1 enters the first-level solid-liquid separation tank through the water delivery pipe, the settled sludge is discharged through the sludge outlet, and the supernatant overflows from the outlet weir of the first-level solid-liquid separation tank;

Step 3, the supernatant liquid overflowed from step 2 enters the first-level ozone pre-oxidation tank from the top through the water pipe. The first-level ozone pre-oxidation tank is composed of two parts: an ozone reaction zone and a buffer zone. Provided from the titanium alloy aeration head at the bottom, the amount of ozone supplied is q ₁ , the concentration C ₁ , and the reaction time t ₁ ; the ozone reaction zone is connected to the bottom of the buffer zone to form a connector; the aeration at the bottom of the buffer zone is aeration from the bottom by the aeration pump head provides;

Step 4, the water treated in step 3 overflows into the secondary aerobic biochemical pool through the water pipe, and the granular biological carrier and microbial agent R ₂ are added to the secondary aerobic biochemical pool, and the microbial agent is added manually or Dosing by gravity dosing device, the filling ratio of granular biological carrier is Χ2, and the dosage ratio of microbial agent R2 is _{Y2 ;} the dissolved oxygen in the buffer _effluent in the first-level ozone pre _- oxidation tank can meet the requirements of microbial agent R2. Oxygen demand, so there is no need for secondary oxygenation, and the shedding of the biofilm is realized by the agitator;

Step 5: The mixed solution treated in step 4 enters the secondary solid-liquid separation tank through the water pipe, the sedimented sludge is discharged through the sludge discharge port, and the supernatant overflows from the outlet weir of the secondary solid-liquid separation tank;

Step 6: The supernatant liquid overflowed in step 5 enters the advanced oxidation tank from the top through the water delivery pipe. The top of the advanced oxidation tank is equipped with a UV light-emitting device and a dosing port, and the oxidant dosing system passes through the dosing port to feed into the advanced oxidation tank Relevant oxidants, the ozone required by the advanced oxidation tank is provided by the ozone generator through the titanium alloy aeration head at the bottom, the amount of ozone supplied is q ₂ , the concentration is C ₂ , and the reaction time is t ₂ ; the treated water is discharged from the bottom of the advanced oxidation tank.

Compared with existing technology, the present invention has the following effects:

The objectives of each process section of the invention are clear and controllable, the process operation is simple, and the sludge output is small, and can stably and effectively remove microorganisms such as easily degradable organic matter, suspended matter, refractory organic matter, and bacteria in sewage. The function of the primary aerobic biochemical and solid-liquid separation process section is to use the low-cost microbial agent R ₁ to remove organic matter that can be degraded in the influent water, thereby reducing the pressure on the back-end process section. For the petroleum hydrocarbon components in the effluent, add the corresponding high-efficiency bacterial agent R ₁ , which is highly targeted. At the same time, the filler used in the aerobic biochemical tank is a fiber plastic filler with strong adsorption, which has a large specific surface area and is effective against microorganisms and pollutants in the water. Strong fixed capture function, easy to fix microorganisms, and less loss; the main function of the ozone pre-oxidation process section is not to completely oxidize refractory organic matter into carbon dioxide and water, but to control the ozone gas volume q ₁ , concentration C ₁ , Reaction time t ₁ , incomplete oxidation of refractory organic matter, chain breakage of macromolecular organic matter into small molecular organic matter, thereby eliminating its refractory or toxicity, improving its biodegradability, reducing the amount of ozone and reducing operating investment and operating costs. The back-end biochemical process creates better conditions. The aeration buffer zone is added in this process section. The purpose is to blow off the residual ozone in the water and increase the oxygen content in the water to achieve pre-oxygenation. Therefore, the back-end aerobic biochemical area does not need to Carry out aeration and oxygenation; the function of the secondary aerobic biochemical and solid-liquid separation process section is to further biochemically degrade the biodegradable organic matter in the water body after ozone pre _- oxidation through the microbial bacterial agent R2, according to the composition of the organic matter in the water body at this stage Targeted dosing of bacterial agent R ₂ has low operating cost and remarkable effect. The filler used in this process section is hydrophilic granular filler with a density equivalent to _water , which is 0.9ρwater to _1.1ρwater . On the one hand, it is easy to realize The fluidized state of the filler improves the treatment efficiency, and on the other hand, it facilitates the shedding and renewal of the biofilm under the action of stirring; the main function of the advanced oxidation process section is to use ozone, ultraviolet lamps or oxidizing agents (H ₂ O ₂ , KMnO ₄ ) The synergistic oxidation effect thoroughly oxidizes the remaining small amount of refractory biodegradable organic matter in the water body to generate water and carbon dioxide, and at the same time removes bacteria and other microorganisms in the water body to meet the requirements of the effluent index for the number of bacteria.

Case: This process was applied to an oil production wastewater treatment station in Huabei Oilfield for a pilot test. The treated water volume was 1t ^/ h. 50mg/L～100mg/L, COD320mg/L～550mg/L, BOD/COD＜0.1, suspended matter SS80～150mg/L. According to GC-MS analysis, the composition and content of organic matter in the influent water are: saturated linear alkanes (more than 40%), aromatic hydrocarbons (more than 40%), and organic acids (less than 10%), which are refractory organic wastewater. During the pilot test, raw water was used as the only carbon source, and domesticated microorganisms were screened from the oil-water sediment at the project site. The bacteria with good adaptability identified by microorganisms were mainly Bacillus licheniformis and Bacillus subtilis, both of which were Oleophilic bacteria with high temperature resistance and high salt resistance, after separation and purification and amplified culture in fermentation tanks, these two strains are formulated into microbial agent R1 at a ratio of 1:1. The initial MLSS in the pool reaches 400-500mg/L, and the filling ratio of the hydrophilic fiber bundle filler is 60%. After 30 days of domestication and film formation, the converted amount of microorganisms on the fiber bundle filler can be stabilized above 3000mg/L. When the HRT of this process section is in water for 3 hours, the oil removal rate can reach more than 80% stably, and the COD removal rate is 30%.

The reaction time of the ozone reaction zone in the ozone pre-oxidation process section is 15 minutes, the ozone dosing concentration is 80mg/L-110mg/L, and the ozone gas volume is 8L/min. The oil removal rate of this process section is 10%, and the COD removal rate is 20%. The analysis of the ozone pre-oxidized effluent found that its BOD/COD>0.3, the dissolved oxygen DO is close to the state of saturated dissolved oxygen, and the biochemical properties of the effluent are good. At this time, the water temperature also drops from above 45°C of the total influent to 38°C, so the two The microbial agent R2 in the aerobic biochemical stage can be inoculated with low-cost traditional municipal dewatered sludge.

Municipal dewatered activated sludge is used to inoculate the secondary aerobic biochemical tank. The inoculation amount makes the initial MLSS>1000mg/L in the tank, the filling ratio of granular filler is 40%, and the hydraulic retention time HRT is 2h. After 15 days of domestication and film formation, The bioconverted amount on the granular filler can be stabilized at 2500-3000mg/L. The oil removal rate of this process section is 5%, and the COD removal rate can reach 30%-35%. This process section does not require additional aeration , dissolved oxygen DO up to 2 ~ 5mg/L, in line with the requirements of aerobic DO.

The oil content in the water entering the advanced oxidation process section is less than 5mg/L, and the COD is less than 80mg/L. This process section uses 2 135W low-pressure ultraviolet lamps, the concentration of ozone is 80mg/L-110mg/L, and the ozone gas volume is 16L/min. The reaction time was 30 minutes, and no oxidizing agent was added to this process section of the pilot test.

After this process, the effluent indicators: oil is not detected, COD<45mg/L, suspended solids SS<2mg/L, which can stably meet oilfield produced water reinjection (A2, A3) or discharge standards (petroleum<8mg/L, COD<50mg/L, suspended solids<3mg/L), the operating cost of this process can be controlled at 2.5-3.5 yuan/ton of water, and the operating cost of the conventional process to achieve the same effluent index is 4-8 yuan/ton of water. Trial tests have highlighted the characteristics of the present invention with stable operation effect and low operation cost.

Description of drawings

Fig. 1 is a schematic diagram of a treatment method for high temperature and high salinity refractory oil production wastewater.

In the figure, 1. Water inlet pump; 2. Primary aerobic biochemical tank; 3. Hydrophilic fiber bundle biological carrier; 4. Microbial agent R ₁ ; 5. Aeration pump; Gas head; 8. First-level solid-liquid separation tank; 12. First-level ozone pre-oxidation tank; 13. Ozone reaction zone; 14. Buffer zone; 15. Ozone generator; 19. Second-level aerobic biochemical tank; 20. Particles Biological carrier; 21. Microbial agent R ₂ ; 22. Stirrer; 24. Secondary solid-liquid separation tank; 28. Advanced oxidation tank; 29. Ultraviolet light-emitting device; 30. Dosing port; 31. Oxidant dosing system .

detailed description

The present invention will be further described in conjunction with the accompanying drawings.

1. A treatment process for refractory organic waste water, characterized in that: the steps of the treatment process comprise:

Step 1, the water inlet pump 1 pumps the oil production wastewater into the first-level aerobic biochemical pool 2, and the hydrophilic fiber bundle biological carrier 3 and the microbial agent R ₁ 4 are added to the first-level aerobic biochemical pool 2, and the microbial agent is passed through artificially. Dosing or gravity dosing device dosing, fiber bundle biological carrier filling ratio is X ₁ , microbial agent R ₁ 4 dosage ratio is Y ₁ ; microbial agent R ₁ 4 required dissolved oxygen from the bottom through the aeration pump 5 Provided by aeration head 6;

Step 2, the mixed liquid treated in step 1 enters the first-level solid-liquid separation tank 8 through the water delivery pipe 7, and the sedimented sludge is discharged through the sludge discharge port 9, and the supernatant overflows from the outlet weir 10 of the first-level solid-liquid separation tank 8 ;

Step 3, the supernatant that overflows in step 2 enters the first-level ozone pre-oxidation tank 12 from the top through the water pipe 11, and the first-level ozone pre-oxidation tank 12 is composed of two parts, the ozone reaction zone 13 and the buffer zone 14, and the required ozone reaction zone Ozone is provided from the titanium alloy aeration head 16 at the bottom by the ozone generator 15, provided ozone gas quantity q ₁ , concentration C ₁ , and reaction time t ₁ ; the ozone reaction zone 13 and the bottom of the buffer zone 14 are connected to form a connector; the bottom of the buffer zone 14 Aeration is provided by the aeration pump 5 from the bottom aeration head 17;

Step 4, the water treated in step 3 overflows into the secondary aerobic biochemical pool 19 through the water delivery pipe 18, and the granular biological carrier 20 and the microbial bacterial agent R ₂ 21 are added to the secondary aerobic biochemical pool 19, the microbial bacterial agent By manual dosing or gravity dosing device dosing, the filling ratio of granular biological carrier 20 is X ₂ , and the dosing ratio of microbial bacterial agent R ₂ 21 is Y ₂ ; Dissolved oxygen can meet the oxygen demand of the microbial bacterial agent _R221 , so there is no need for secondary oxygenation, and the shedding of the biofilm is realized by the agitator 22;

Step 5, the mixed solution treated in step 4 enters the secondary solid-liquid separation tank 24 through the water delivery pipe 23, and the sedimented sludge is discharged through the mud discharge port 25, and the supernatant overflows from the outlet weir 26 of the secondary solid-liquid separation tank 24 ;

Step 6, the supernatant liquid overflowed in step 5 enters the advanced oxidation tank 28 from the top through the water delivery pipe 27, and the top of the advanced oxidation tank 28 is provided with an ultraviolet light emitting device 29 and a dosing port 30, and the oxidant dosing system 31 passes through the dosing port 30 Dosing relevant oxidants into the advanced oxidation tank 28, the ozone required by the advanced oxidation tank 28 is provided by the ozone generator 15 through the bottom titanium alloy aeration head 32, the supplied ozone gas volume q ₂ , concentration C ₂ , and reaction time t ₂ ; The treated water is discharged from the bottom of the advanced oxidation pond 28 .

The first-stage solid-liquid separation pool 8 and the second-stage solid-liquid separation pool 24 used in the present invention are designed according to the flow rate of the refractory organic wastewater to be treated and the requirements for relevant process sections in the design manual.

The above is a general implementation case of the present invention, and does not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical solution of the present invention. within the scope of protection.

Claims (8)

1. A treatment method for high-temperature and high-salt refractory oil extraction wastewater, characterized in that: the steps of the treatment method comprise: a first-level aerobic biochemical pool (2), a first-level solid-liquid separation tank (8), a first-level ozone pretreatment Oxidation pond (12), secondary aerobic biochemical pond (19), secondary solid-liquid separation pond (24) and advanced oxidation pond (28); Step ₁ , the oil extraction wastewater is pumped into the primary aerobic biochemical pool by the water inlet pump, and the hydrophilic fiber bundle biological carrier and the microbial agent R1 are added into the primary aerobic biochemical pool _; the dissolved oxygen required by the microbial agent R1 passes through The aeration pump is provided from the aeration head of the primary aerobic biochemical zone; Step 2, the mixed solution treated in step 1 enters the first-level solid-liquid separation tank through the water delivery pipe, the settled sludge is discharged through the sludge outlet, and the supernatant overflows from the outlet weir of the first-level solid-liquid separation tank; Step 3, the supernatant that step 2 overflows enters the first-level ozone pre-oxidation tank from the top through the water pipe; the first-level ozone pre-oxidation tank is made up of two parts, the ozone reaction zone (13) and the buffer zone (14), and the ozone reaction zone ( 13) required ozone is provided from bottom titanium alloy aeration head (16) by ozone generator (15), provided ozone gas quantity q ₁ , concentration C ₁ , reaction time t ₁ ; ozone reaction zone (13) and buffer zone ( 14) The bottom is connected to form a connector; the bottom aeration of the buffer zone (14) is provided by the aeration pump (5) from the bottom aeration head (17); Step 4, the water treated in step 3 overflows into the secondary aerobic biochemical pool through the water pipe, and the granular biological carrier and microbial agent R ₂ are added to the secondary aerobic biochemical pool, and the microbial agent is added manually or Dosing by gravity dosing device; the added granular biological carrier is made of hydrophilic plastic material with a density of _0.9ρwater to _1.1ρwater ; Step 5: The mixed solution treated in step 4 enters the secondary solid-liquid separation tank through the water pipe, the sedimented sludge is discharged through the sludge discharge port, and the supernatant overflows from the outlet weir of the secondary solid-liquid separation tank; Step 6: The supernatant liquid overflowed in step 5 enters the advanced oxidation tank from the top through the water pipe, and the treated water is discharged from the bottom of the advanced oxidation tank. 2. the treatment method of high-temperature high-salt refractory oil production wastewater according to claim 1, is characterized in that, in described one-level aerobic biochemical pool (2), add hydrophilic fiber bundle organism with certain filling ratio X ₁ carrier (3). 3. the treatment method of high-temperature high-salt refractory oil extraction wastewater according to claim 1, is characterized in that, for different oilfield oil production water petroleum hydrocarbon components, add corresponding high-efficiency microbial bacterial agent R ₁ (4), microorganism Bacteria agent R ₁ (4) The dosing ratio is Y ₁ , which can be added manually or by a dosing device. 4. The method for treating high-temperature, high-salt and refractory oil production wastewater according to claim 2, characterized in that the hydrophilic fiber bundle biological carrier (3) is made of fiber plastic, with a specific surface area > 2000㎡/m ³ , which has a hydrophilic Oily and absorbent. 5. the treatment method of high-temperature high-salt refractory oil production wastewater according to claim 1, is characterized in that, in described secondary aerobic biochemical pool (19), particle biological carrier (20) is added, and carrier filling ratio is × ₂ . 6. the treatment method of high-temperature high-salt refractory oil production wastewater according to claim 1, is characterized in that, in the described secondary aerobic biochemical pool (19), for the organic component in the wastewater of this stage, add corresponding high-efficiency Microbial agent R ₂ (21), the dosage ratio of high-efficiency microbial agent R ₂ (21) is Y ₂ . 7. the treatment method of high-temperature high-salt refractory oil production wastewater according to claim 1 is characterized in that the dissolved oxygen in the buffer zone (14) effluent in the first stage ozone pre-oxidation tank (12) can meet the requirements of microorganisms. The oxygen demand of the microbial bacterial agent R ₂ (21) does not require secondary aeration and oxygenation, and the shedding and renewal of the biofilm with the microbial microbial bacterial agent R ₂ (21) growing on the granular biological carrier (20) is realized by the agitator (22). 8. The treatment method of high-temperature, high-salt and refractory oil production wastewater according to claim 1, characterized in that, the top of the advanced oxidation tank (28) is provided with an ultraviolet lamp light-emitting device (29) and a dosing port (30), and the oxidizing agent is added The medicine system (31) feeds relevant oxidizing agents into the advanced oxidation tank (28) through the dosing port (30), and the ozone required for the advanced oxidation tank (28) is passed through the bottom titanium alloy aeration head ( 32) Provide, the supplied ozone gas volume q ₂ , concentration C ₂ , and reaction time t ₂ ; the treated water is discharged or reused from the bottom of the advanced oxidation tank (28) up to the standard.