Treatment system and method for wastewater containing high salt, high concentration of non-degradable organic matter

Abstract

This invention relates to a treatment system and method for wastewater containing high salt content and high concentration of recalcitrant organic matter, belonging to the field of wastewater treatment technology. It solves the problems of evaporator coking and high treatment costs for hazardous wastewater containing high salt content and high concentration of recalcitrant organic matter in existing methods. The treatment system includes: a dissolved air flotation tank, a comprehensive equalization tank, a biological selection tank, an anoxic tank, a first MBBR tank, a secondary sedimentation tank, a first air flotation filter, an advanced oxidation tank, a second MBBR tank, and a second air flotation filter, arranged sequentially along the material flow direction; it also includes an ozone pretreatment reverse osmosis brine device, the outlet of which is connected to the inlet of the comprehensive equalization tank. This achieves efficient, stable, reliable, and economical treatment of wastewater containing high salt content and high concentration of recalcitrant organic matter.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a treatment system and method for wastewater containing high salt content and high concentration of recalcitrant organic matter. Background Technology

[0002] The petrochemical, coal chemical and other chemical production industries generate a large amount of wastewater containing high salt and high concentration of recalcitrant organic matter during the production process. This type of wastewater has poor biodegradability, high biological toxicity, is difficult to treat and has a long treatment process, which is one of the problems that hinders the output and rapid development of chemical production.

[0003] For example, phenol and acetone production enterprises use phenol and acetone as important organic chemical raw materials, which are mainly used in industries such as petroleum, synthetic resins, oils and fats, and pharmaceuticals. With the rapid development of the economy, the market demand is gradually increasing, and the amount of wastewater generated in the process of producing phenol and acetone is also increasing.

[0004] The wastewater from phenol and acetone production has a complex composition and high concentration of pollutants, mainly containing phenols, ketones, aldehydes, benzene compounds and sulfates. It is a wastewater with high salt content and high organic pollutants, with poor biodegradability, high biological toxicity, great difficulty in treatment and a long treatment process.

[0005] The existing method for treating phenol and acetone production wastewater involves evaporation, but this method has the following drawbacks:

[0006] (1) The wastewater from phenol and acetone production contains organic compounds such as phenols, ketones, aldehydes, and benzene compounds. During the evaporation process, most of these organic compounds will coke inside the heat exchange tubes of the evaporator, leading to a decrease in the evaporator's evaporation capacity and an increase in steam consumption. If the coking reaches a certain level, the evaporator will not be able to operate normally. To ensure the evaporator's evaporation capacity, the cleaning frequency of the evaporator needs to be increased. Therefore, this increases both operating costs and the frequency and difficulty of inspection and maintenance.

[0007] (2) The wastewater from the production of phenol and acetone contains organic compounds such as phenols, ketones, aldehydes, and benzene compounds. Some of these organic compounds are volatile and have low boiling points. The evaporated water also contains organic compounds and has a high COD value. Therefore, the evaporated water needs to undergo biochemical treatment before it can meet discharge standards or be reused.

[0008] (3) After the water evaporates, the concentrated crystal slurry contains most of the organic matter. Therefore, the inorganic salt that crystallizes will be mixed with a lot of organic matter. This inorganic salt is a hazardous waste and needs to be processed by a qualified company. The processing cost is very high. Summary of the Invention

[0009] Based on the above analysis, the embodiments of the present invention aim to provide a treatment system and method for wastewater containing high salt and high concentration of recalcitrant organic matter, in order to solve the problems of evaporator coking and high cost of treating hazardous waste containing miscellaneous salts in existing methods for treating wastewater containing high salt and high concentration of recalcitrant organic matter.

[0010] On one hand, the present invention provides a treatment system for wastewater containing high salt and high concentration of recalcitrant organic matter. The treatment system includes: a dissolved air flotation tank, a comprehensive equalization tank, a biological selection tank, an anoxic tank, a first MBBR tank, a secondary sedimentation tank, a first air flotation filter, an advanced oxidation tank, a second MBBR tank, and a second air flotation filter arranged sequentially along the material flow direction; it also includes an ozone pretreatment reverse osmosis brine device, the outlet of which is connected to the inlet of the comprehensive equalization tank.

[0011] Based on a further improvement of the above method, the treatment system further includes an effluent monitoring tank and an activated carbon filter, wherein the outlet of the second air flotation filter is connected to the inlet of the effluent monitoring tank, and the outlet of the effluent monitoring tank is connected to the inlet of the activated carbon filter.

[0012] Based on a further improvement of the above method, the first MBBR tank is provided with a nitrification liquor return outlet, which is connected to the biological selection tank and the anoxic tank respectively.

[0013] The secondary sedimentation tank is equipped with a sludge return outlet, which is connected to the biological selection tank and the anoxic tank respectively.

[0014] On the other hand, the present invention also provides a method for treating wastewater containing high salt and high concentration of recalcitrant organic matter, using the above-mentioned treatment system for wastewater containing high salt and high concentration of recalcitrant organic matter, the treatment method comprising the following steps:

[0015] Step (1): After petroleum substances and suspended solids are removed in the dissolved air flotation tank, the wastewater containing high salt and high concentration of recalcitrant organic matter enters the integrated equalization tank;

[0016] Step (2): The ozone-oxidized reverse osmosis brine in the ozone pretreatment reverse osmosis brine device enters the integrated equalization tank, mixes and homogenizes with the wastewater treated by the dissolved air flotation tank, and adjusts the pH to 7-8.

[0017] Step (3): The homogenized wastewater enters the biological selection tank, where flocculent activated sludge is optimized to prevent the growth of filamentous bacteria;

[0018] Step (4): The effluent from the biological selection tank enters the anoxic tank, where denitrifying bacteria are used to remove nitrate nitrogen from the wastewater.

[0019] Step (5): The effluent from the anoxic tank enters the first MBBR tank, where ammonia nitrogen and COD are removed through nitrification by aerobic sludge and nitrifying bacteria. MBBR packing is then added to the first MBBR tank to allow high concentrations of microorganisms to attach to the MBBR packing.

[0020] Step (6): The effluent from the first MBBR tank enters the secondary sedimentation tank for mud-water separation;

[0021] Step (7): The supernatant from the secondary sedimentation tank enters the first air flotation filter, and a coagulant is added to the first air flotation filter to remove fine suspended solids and floating oil from the wastewater;

[0022] Step (8): The effluent from the first air flotation filter enters the advanced oxidation tank, where ozone and hydrogen peroxide are added to remove the recalcitrant COD from the wastewater;

[0023] Step (9): The effluent from the advanced oxidation tank enters the second MBBR tank, where MBBR short-cut aeration technology is used to remove most of the degradable COD;

[0024] Step (10): The effluent from the second MBBR tank enters the second air flotation filter, and a coagulant is added to the second air flotation filter to further remove suspended solids from the wastewater.

[0025] Based on a further improvement of the above method, the treatment method further includes: the nitrified liquor treated in the first MBBR tank is returned to the biological selection tank and the anoxic tank through the nitrified liquor return outlet, and the nitrified liquor return ratio is 200% to 300%.

[0026] The sludge treated in the secondary sedimentation tank is returned to the biological selection tank and the anoxic tank through the sludge return outlet, with a sludge return ratio of 100% to 150%.

[0027] Based on further improvements to the above method, in step (1), the flow rate of the wastewater containing high salt and high concentration of recalcitrant organic matter is 10-15 m³ / h. 3 / h; In step (2), the flow rate of the reverse osmosis concentrated brine after ozone oxidation pretreatment is 300-450 m³ / h. 3 / h.

[0028] Based on further improvements to the above method, in step (4), the water temperature of the anoxic pool is 20℃~35℃, the oxidation-reduction potential is between -200mv and -100mv, and the pH value is 7~8.

[0029] Based on further improvements to the above method, in step (5), the water temperature of the first MBBR tank is 20℃~35℃, the dissolved oxygen is 2mg / L~4mg / L, and the pH value is 7~8.

[0030] Based on further improvements to the above method, in step (10), the treatment method further includes: the effluent from the second air flotation filter enters the effluent monitoring tank for monitoring; if it meets the discharge standards, it is discharged; if it does not meet the discharge standards, the effluent enters the activated carbon filter, and part of the COD is removed by activated carbon adsorption before it meets the standards for discharge.

[0031] Based on further improvements to the above method, the wastewater containing high salt and high concentration of recalcitrant organic matter is phenol and acetone production wastewater.

[0032] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0033] 1. This invention removes organic matter from phenol and acetone production wastewater using biochemical and advanced oxidation technologies. The treatment has low operating costs, is simple to operate, and the treated wastewater can be discharged in compliance with standards or reused.

[0034] 2. In the system and method of the present invention, by introducing reverse osmosis concentrated brine pretreated with ozone oxidation, the TDS of wastewater containing high salt and high concentration of recalcitrant organic matter can be reduced, and the water quality fluctuation of the wastewater can be reduced. After mixing, the TDS of the wastewater is kept stable at around 10,000 to 12,000 mg / L for a long time, so that the subsequent biochemical reaction can operate stably.

[0035] 3. In the first MBBR tank, a large number of microorganisms attach and grow on the surface of the MBBR suspended packing, forming a microbial film layer of a certain thickness. Therefore, the sludge concentration in the first MBBR tank is 2 to 4 times that of the traditional activated sludge process, and the sludge concentration can reach 8000 to 12000 mg / L. The high sludge concentration in the first MBBR tank and the unique structure of the MBBR packing make the MBBR process have more efficient COD removal capacity, shock resistance, less sludge production capacity, and reduced land area and construction investment costs.

[0036] 4. The dissolved air flotation (DAF) filter is a novel process that combines dissolved air flotation (DAF) tanks with multi-media filters. It can treat the suspended solids in the secondary sedimentation tank effluent to below 10 mg / L, ensuring that the oxidation efficiency of ozone and hydrogen peroxide in the advanced oxidation tank is not reduced due to high suspended solids in the influent. This guarantees the removal efficiency of recalcitrant COD, improves oxidation efficiency, and reduces the consumption of ozone and hydrogen peroxide. The DAF filter has a rectangular DAF tank at the top and a multi-media filter at the bottom, which requires less land area than conventional DAF + multi-media filter combination processes or coagulation sedimentation + filtration combination processes, saving land and construction investment costs.

[0037] 5. Adding ozone and hydrogen peroxide in a combined manner in the advanced oxidation tank can remove recalcitrant COD through the dual oxidation effect of ozone and hydrogen peroxide, and improve the biodegradability of wastewater, ensuring that the final effluent consistently meets the standards.

[0038] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0039] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0040] Figure 1 The present invention relates to a treatment system for wastewater containing high salt content and high concentration of recalcitrant organic matter.

[0041] Figure label:

[0042] 1- Dissolved air flotation tank; 2- Ozone pretreatment reverse osmosis brine unit; 3- Integrated equalization tank; 4- Biological selection tank and anoxic tank; 5- First MBBR tank; 6- Secondary sedimentation tank; 7- First air flotation filter; 8- Advanced oxidation tank; 9- Second MBBR tank; 10- Second air flotation filter; 11- Effluent monitoring tank; 12- Activated carbon filter; 13- Nitrified liquor return outlet; 14- Sludge return outlet. Detailed Implementation

[0043] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0044] On the one hand, this invention provides a treatment system for wastewater containing high salt content and high concentration of recalcitrant organic matter, such as... Figure 1 As shown, the treatment system includes: a dissolved air flotation tank 1, a comprehensive conditioning tank 3, a biological selection tank and an anoxic tank 4, a first MBBR tank 5, a secondary sedimentation tank 6, a first air flotation filter 7, an advanced oxidation tank 8, a second MBBR tank 9, and a second air flotation filter 10 arranged sequentially along the material flow direction; it also includes an ozone pretreatment reverse osmosis brine device 2, the outlet of which is connected to the inlet of the comprehensive conditioning tank 3.

[0045] During implementation, wastewater containing high salt and high concentration of recalcitrant organic matter is treated in dissolved air flotation tank 1 and then enters integrated equalization tank 3. At the same time, the reverse osmosis brine pretreated by ozone oxidation in ozone pretreatment reverse osmosis brine device 2 enters integrated equalization tank 3. The wastewater containing high salt and high concentration of recalcitrant organic matter is mixed with the reverse osmosis brine pretreated by ozone oxidation. Then, the mixture is sequentially treated in biological selection tank and anoxic tank 4, first MBBR tank 5, secondary sedimentation tank 6, first air flotation filter 7, advanced oxidation tank 8, second MBBR tank 9, and second air flotation filter 10.

[0046] Compared with existing technologies, this invention removes organic matter from phenol and acetone production wastewater through biochemical and advanced oxidation techniques. The treatment process is cost-effective, simple to operate, and the treated wastewater meets discharge standards or can be reused. In the treatment system of this invention, ozone pretreatment reverse osmosis brine pretreated with ozone oxidation is introduced through the ozone pretreatment reverse osmosis brine device 2. This reduces the TDS of wastewater containing high salt and high concentrations of recalcitrant organic matter, and also reduces water quality fluctuations. The TDS of the mixed wastewater remains stable at around 10,000–12,000 mg / L, preventing the subsequent biological system from experiencing large-scale sludge death due to TDS fluctuations and ensuring stable operation of subsequent biological reactions.

[0047] For example, the treatment system further includes an effluent monitoring tank 11 and an activated carbon filter 12. The outlet of the second air flotation filter 10 is connected to the inlet of the effluent monitoring tank 11, and the outlet of the effluent monitoring tank 11 is connected to the inlet of the activated carbon filter 12. The effluent monitoring tank 11 is used to detect the water quality of the effluent from the second air flotation filter 10, and the activated carbon filter 12 is used for further adsorption treatment of effluent that does not meet the discharge standards.

[0048] For example, the first MBBR tank 5 is provided with a nitrification liquor return outlet 13, which is connected to the biological selection tank and the anoxic tank 4 respectively;

[0049] The secondary sedimentation tank 6 is equipped with a sludge return outlet 14, which is connected to the biological selection tank and the anoxic tank 4 respectively.

[0050] Secondly, the present invention also provides a method for treating wastewater containing high salt content and high concentration of recalcitrant organic matter, using the aforementioned treatment system for wastewater containing high salt content and high concentration of recalcitrant organic matter, the treatment method comprising the following steps:

[0051] Step (1): After petroleum substances and suspended solids are removed in the dissolved air flotation tank 1, the wastewater containing high salt and high concentration of recalcitrant organic matter enters the integrated equalization tank 3;

[0052] Step (2): The ozone-oxidized pretreated reverse osmosis brine in the ozone pretreatment reverse osmosis brine device 2 enters the integrated equalization tank 3, where it is mixed and homogenized with the wastewater treated by the dissolved air flotation tank 1, and the pH is adjusted to 7-8.

[0053] Step (3): The homogenized wastewater enters the biological selection tank, where flocculent activated sludge is optimized to prevent the growth of filamentous bacteria;

[0054] Step (4): The effluent from the biological selection tank enters the anoxic tank, where denitrifying bacteria are used to remove nitrate nitrogen from the wastewater.

[0055] Step (5): The effluent from the anoxic tank enters the first MBBR tank 5, where ammonia nitrogen and COD are removed from the wastewater through nitrification by aerobic sludge and nitrifying bacteria. MBBR packing is then added to the first MBBR tank 5 to allow high concentrations of microorganisms to attach to the MBBR packing.

[0056] Step (6): The effluent from the first MBBR tank 5 enters the secondary sedimentation tank 6 for mud-water separation.

[0057] Step (7): The supernatant of the secondary sedimentation tank 6 enters the first air flotation filter 7, and a coagulant is added to the first air flotation filter 7 to remove fine suspended solids and floating oil in the sewage;

[0058] Step (8): The effluent from the first air flotation filter 7 enters the advanced oxidation tank 8, where ozone and hydrogen peroxide are added to remove the recalcitrant COD from the wastewater;

[0059] Step (9): The effluent from the advanced oxidation tank 8 enters the second MBBR tank 9, where MBBR short-cut aeration technology is used to remove most of the degradable COD;

[0060] Step (10): The effluent from the second MBBR tank 9 enters the second air flotation filter 10, and a coagulant is added to the second air flotation filter 10 to further remove suspended solids in the wastewater.

[0061] For example, the wastewater containing high salt and high concentration of recalcitrant organic matter is wastewater from the production of phenol and acetone.

[0062] For example, the wastewater containing high salt and high concentration of recalcitrant organic matter has a COD ≤ 14000 mg / L, petroleum hydrocarbons ≤ 100 mg / L, benzene series compounds ≤ 100 mg / L, and TDS ≤ 47000 mg / L.

[0063] For example, the treatment method further includes: the nitrified liquor treated in the first MBBR tank 5 is returned to the biological selection tank and the anoxic tank 4 through the nitrified liquor return outlet 13, and the nitrified liquor return ratio is 200% to 300%; the sludge treated in the secondary sedimentation tank 6 is returned to the biological selection tank and the anoxic tank 4 through the sludge return outlet 14, and the sludge return ratio is 100% to 150%.

[0064] For example, in step (1), the wastewater treated by the dissolved air flotation tank contains petroleum ≤20mg / L and suspended solids ≤20mg / L.

[0065] Specifically, a coagulant and a flocculant are added to the dissolved air flotation tank 1. The coagulant is an aluminum-based coagulant, with a dosage of 50-60 mg / L, and the flocculant is an anionic polyacrylamide, with a dosage of 1-2 mg / L.

[0066] For example, the dissolved air flotation tank 1 has a dissolved air reflux ratio of 25-30%, an operating pressure of 0.5-0.7 MPa for the dissolved air tank, and a surface hydraulic loading of 4.35-4.4 m. 3 / (m 2 ·h).

[0067] For example, the dissolved air flotation tank 1 includes equipment such as a coagulation tank and a flocculation tank, a dissolved air tank, a dissolved air release device, a dissolved air return pump, and a sludge scraper.

[0068] For example, in step (1), the flow rate of the wastewater containing high salt and high concentration of recalcitrant organic matter is 10-15 m³ / h. 3 / h.

[0069] For example, in step (2), the flow rate of the reverse osmosis brine pretreated with ozone oxidation is 300-450 m³ / h. 3 / h.

[0070] For example, in step (2), the reverse osmosis brine pretreated with ozone oxidation has a COD ≤ 80 mg / L and a TDS ≤ 5000 mg / L.

[0071] For example, the reverse osmosis brine pretreated by ozone oxidation enters the integrated equalization tank 3, where it is mixed and homogenized with the wastewater containing high salt and high concentration of recalcitrant organic matter pretreated by the dissolved air flotation tank 1. This ensures that the concentrations of each pollutant are stabilized within the range of COD≤950mg / L, petroleum ≤20mg / L, benzene series ≤10mg / L, and TDS≤12000mg / L, guaranteeing the stable operation of subsequent biochemical treatment.

[0072] For example, the retention time of wastewater in the integrated equalization tank 3 is 20-25 hours.

[0073] For example, the integrated equalization tank 3 is equipped with an aeration homogenization system to ensure that the wastewater can be completely mixed here to achieve the purpose of homogenization and equal quantity. In the integrated equalization tank, acid and alkali are added to adjust the pH of the wastewater to 7-8.

[0074] For example, in step (3), the biological selection tank is higher than the integrated regulation tank 3, and the sewage treated by the integrated regulation tank 3 is pumped to the biological selection tank.

[0075] For example, the wastewater retention time in the biological selection tank is 0.5 to 1 hour. A submersible mixer is installed in the tank to ensure that the activated sludge is in a suspended state and to ensure that the returned nitrification liquid and sludge are completely mixed with the influent.

[0076] In step (4), the denitrifying bacteria in the anoxic tank reduce nitrite and nitrate to nitrogen gas, and use this ability of the denitrifying bacteria to remove nitrate nitrogen from the wastewater.

[0077] For example, the water temperature in the anoxic tank is 20℃~35℃, the oxidation-reduction potential is -200mv~-100mv, the pH value is 7~8, and the residence time is 16-20h.

[0078] For example, multiple corridors are arranged in the anoxic tank, and a submersible mixer is installed in each corridor to keep the activated sludge in a suspended state, so as to ensure that the activated sludge is in full contact with the organic matter and nitrate nitrogen in the wastewater to complete the biochemical reaction.

[0079] For example, in step (5), high concentrations of microorganisms adhere to the MBBR packing material, forming a microbial film layer of a certain thickness. The sludge concentration is 10,000 to 12,000 mg / L, which is 2 to 4 times that of the traditional activated sludge process. Therefore, the first MBBR tank 5 has a more efficient COD removal capacity, shock resistance capacity, and less sludge production capacity. Compared with the traditional activated sludge process, it reduces the land area by about 2 to 3 times and saves the investment cost of civil construction.

[0080] For example, the water temperature of the first MBBR tank 5 is 20℃~35℃, the dissolved oxygen is 2mg / L~4mg / L, the pH value is 7~8, and the residence time is 40~45h.

[0081] For example, the MBBR packing is a K3 type carrier fluidized bed packing, mainly made of HDPE, with a specific surface area of ​​500 m². 2 / m 3 The filler filling rate is 10-13%.

[0082] For example, the bottom of the first MBBR tank 5 is equipped with an aeration system to keep the MBBR packing material in a fully fluidized state. The outlet of the first MBBR tank 5 is equipped with a packing material interception screen to ensure that the packing material remains in the first MBBR tank 5 and does not flow with the sewage into other tanks.

[0083] For example, a nitrification liquor return pump is installed at the end of the first MBBR tank 5 to return the nitrification liquor treated by the first MBBR tank 5 to the biological selection tank and the anoxic tank for denitrification reaction. The nitrification liquor return ratio is 200% to 300%.

[0084] In step (6), the supernatant of the secondary sedimentation tank 6 enters the first air flotation filter tank 7, and the sludge is returned to the biological selection tank and the anoxic tank.

[0085] For example, the surface loading of the secondary sedimentation tank is 0.5–0.7 m. 3 / (m 2 •h) A sludge scraper is installed in the tank, along with a sludge discharge pump and a sludge return pump. The sludge return ratio is 100% to 150%.

[0086] In step (7), a coagulant is added to the first dissolved air flotation (DAF) filter 7 at a dosage of 20–25 mg / L to remove fine suspended solids and floating oil from the wastewater, thereby improving the oxidation utilization efficiency of ozone and hydrogen peroxide in the advanced oxidation tank. Only coagulant is added to the first DAF filter 7, not flocculants. If a conventional dissolved air flotation tank + multi-media filter combination process or a coagulation sedimentation + filtration combination process is used, coagulant and flocculants need to be added to the dissolved air flotation tank or coagulation sedimentation tank. Therefore, using the DAF filter process can save on flocculant addition and reduce operating costs by 0.01 yuan / ton of water.

[0087] In this invention, the dissolved air flotation (DAF) filter is a process combining a dissolved air flotation (DAF) tank and a multi-media filter. The upper part is a rectangular DAF tank, and the lower part is a multi-media filter. The first DAF filter 7 has dimensions of 16m × 10m × 6m and occupies an area of ​​160m². 2 If a combination of conventional dissolved air flotation tank and multi-media filter or coagulation sedimentation and filtration is used, the land area required for this combination process is at least 320m². 2 Therefore, the air flotation filter process requires a small footprint, which can save on land and civil engineering investment costs.

[0088] For example, the surface loading of the first air flotation filter 7 is 6-8 m³. 3 / (m 2 The dissolved gas reflux ratio is 25-30%, and the operating pressure of the dissolved gas tank is 0.7-0.9 MPa.

[0089] For example, the first air flotation filter 7 is equipped with a coagulation tank and flocculation tank mixer, dissolved air tank, dissolved air releaser, dissolved air return pump, inlet water stabilizing tank, quartz sand and anthracite filter media, filter plate, filter head, backwash air distribution device, backwash outlet tank, backwash water pump, backwash blower, slag scraper and other equipment, and is equipped with automatic backwashing facilities.

[0090] In step (8), ozone and hydrogen peroxide are added in combination in the advanced oxidation tank 8 to further remove the recalcitrant COD in the wastewater. At the same time, the B / C ratio of the wastewater can be increased, and some of the recalcitrant COD substances can be converted into degradable COD.

[0091] For example, an air stripping tank is provided in the advanced oxidation tank 8, and an air stripping device is provided in the air stripping tank to remove residual ozone in the wastewater.

[0092] For example, the ozone dosage in the advanced oxidation tank 8 is 70-80 mg / L, and the dosage of 30% hydrogen peroxide is 70-80 mg / L. If a conventional process of adding only ozone is used, the ozone dosage would be approximately 100-125 mg / L. Therefore, using a combined ozone and hydrogen peroxide dosage can save on the amount of ozone added and reduce the power consumption for ozone production.

[0093] For example, the retention time of the advanced oxidation tank 8 is 1-2 hours, ensuring sufficient retention time for ozone and hydrogen peroxide to react with organic pollutants in the wastewater to generate CO2 and H2O, thereby removing COD, reducing the load on subsequent biochemical treatment, and at the same time converting some of the recalcitrant COD substances into biodegradable COD, thus improving the B / C ratio of the wastewater.

[0094] For example, the exhaust gas in the advanced oxidation tank 8 and the stripping tank contains ozone and cannot be directly discharged into the atmosphere. It needs to be discharged to an ozone exhaust gas destroyer through a collection pipeline for treatment, so that the ozone concentration in the exhaust gas is reduced to below 0.1 mg / L before being discharged into the atmosphere.

[0095] In step (9), in the second MBBR tank 9, the COD in the wastewater is removed by aerobic sludge using MBBR short-cut aeration technology. MBBR packing is added to the tank so that microorganisms attach to the MBBR packing, thereby improving the pollutant removal capacity of the second MBBR tank 9 and preventing sludge loss.

[0096] For example, the water temperature of the second MBBR tank 9 is 20℃~35℃, the dissolved oxygen is 2mg / L~3mg / L, the pH value is 7~8, and the residence time is 4-5h.

[0097] For example, the MBBR packing filler has a filling rate of 15-20%, and the bottom of the tank is equipped with an aeration system specifically for the MBBR packing to keep the MBBR packing in a fully fluidized state. The outlet of the second MBBR tank 9 is equipped with a packing interception screen so that the packing remains in the second MBBR tank 9 and does not flow with the sewage into other tanks.

[0098] In step (10), a coagulant is added to the second flotation filter 10 at a dosage of 30-40 mg / L, mainly to reduce suspended solids in the wastewater and ensure that the suspended solids in the effluent meet the discharge standards. The second flotation filter 10 has dimensions of 16m × 10m × 6m and occupies an area of ​​160m². 2 If a combination of conventional dissolved air flotation tank and multi-media filter or coagulation sedimentation and filtration is used, the land area required for this combination process is at least 320m². 2 Therefore, the air flotation filter process of this invention has a small footprint, which can save land and civil construction investment costs.

[0099] The second air flotation filter 10 of this invention only adds coagulant and not flocculant. If a conventional combined process of dissolved air flotation tank + multi-media filter or coagulation sedimentation + filtration is used, coagulant and flocculant need to be added to the dissolved air flotation tank or coagulation sedimentation tank. Therefore, the air flotation filter process of this invention can save the addition of flocculant and save operating costs of 0.01 yuan / ton of water.

[0100] For example, the surface loading of the second air flotation filter 10 is 6-8 m³. 3 / (m 2 The dissolved gas reflux ratio is 25-30%, and the operating pressure of the dissolved gas tank is 0.7-0.9 MPa.

[0101] For example, the second air flotation filter 10 is equipped with a coagulation tank and flocculation tank mixer, dissolved air tank, dissolved air release device, dissolved air return pump, inlet stabilizing tank, quartz sand and anthracite filter media, filter plates, filter heads, backwashing air distribution device, backwashing effluent tank, sludge scraper, and other equipment, and is equipped with automatic backwashing facilities. The backwashing water pump and backwashing blower are shared with the first air flotation filter 7.

[0102] For example, the treatment method further includes: the effluent from the second air flotation filter 10 enters the effluent monitoring tank 11 for monitoring; if it meets the discharge standards, it is discharged; if it does not meet the discharge standards, the effluent enters the activated carbon filter 12, where some COD is removed by activated carbon adsorption before being discharged in compliance with the standards.

[0103] Specifically, two activated carbon filter tanks 12 are installed, with a filtration rate of 6-8 m / h and a forced filtration rate of 12-15 m / h. Activated carbon filter media is installed in the activated carbon filter tanks 12, and an automatic backwashing system is provided. The backwash air volume for the activated carbon filter tanks comes from the backwash blower of the first air flotation filter tank 7.

[0104] For example, online analyzers for COD, ammonia nitrogen, and total nitrogen are installed in the effluent monitoring tank to detect the values ​​of pollutants such as COD, ammonia nitrogen, and total nitrogen online, ensuring that all indicators meet the emission standards before final discharge or reuse. The retention time in the effluent monitoring tank is 1-2 hours to ensure sufficient buffer time.

[0105] The following detailed description of the treatment system and method for wastewater containing high salt and high concentration of recalcitrant organic matter according to the present invention will be provided through specific embodiments.

[0106] Example 1

[0107] This embodiment provides a treatment system for wastewater containing high salt and high concentration of recalcitrant organic matter, comprising: a dissolved air flotation tank 1, a comprehensive equalization tank 3, a biological selection tank and an anoxic tank 4, a first MBBR tank 5, a secondary sedimentation tank 6, a first air flotation filter 7, an advanced oxidation tank 8, a second MBBR tank 9, and a second air flotation filter 10 arranged sequentially along the material flow direction; it also includes an ozone pretreatment reverse osmosis brine device 2, the outlet of which is connected to the inlet of the comprehensive equalization tank 3; and further includes... The system includes an effluent monitoring tank 11 and an activated carbon filter 12. The outlet of the second air flotation filter 10 is connected to the inlet of the effluent monitoring tank 11, and the outlet of the effluent monitoring tank 11 is connected to the inlet of the activated carbon filter 12. The first MBBR tank 5 is provided with a nitrification liquor return outlet 13, which is connected to the biological selection tank and the anoxic tank 4 respectively. The secondary sedimentation tank 6 is provided with a sludge return outlet 14, which is connected to the biological selection tank and the anoxic tank 4 respectively.

[0108] Example 2

[0109] This embodiment provides a method for treating wastewater containing high salt content and high concentration of recalcitrant organic matter, wherein the wastewater is phenol and acetone production wastewater. The method includes:

[0110] (1) The inflow volume of wastewater from phenol and acetone production is 13m³. 3 The incoming water quality is as follows: COD = 14000 mg / L, petroleum hydrocarbons = 100 mg / L, benzene series compounds = 100 mg / L, TDS = 46000 mg / L. After petroleum hydrocarbons and suspended solids are removed in the dissolved air flotation tank, the petroleum hydrocarbons = 20 mg / L and the suspended solids = 20 mg / L are reduced, and the water flows by gravity into the general equalization tank.

[0111] Coagulants and flocculants were added to the dissolved air flotation (DAF) tank. The coagulant used was an aluminum-based coagulant (purchased from Henan, brand PAC (polyaluminum chloride)), with a dosage of 50 mg / L. The flocculant was anionic polyacrylamide (purchased from Henan, brand PAM (polyacrylamide)), with a dosage of 1 mg / L. The dissolved air reflux ratio of the DAF tank was 25%, the operating pressure of the dissolved air tank was 0.5–0.7 MPa, and the surface hydraulic loading was 4.35 m. 3 / (m 2 •h). Equipped with coagulation and flocculation tanks, mixers, dissolved gas tanks, dissolved gas release devices, dissolved gas reflux pumps, slag scrapers, and other equipment.

[0112] (2) The inflow rate of the reverse osmosis concentrated brine after ozone oxidation pretreatment is 400 m³. 3 The incoming water quality is: COD = 80 mg / L, TDS = 5000 mg / L; the reverse osmosis brine flows by gravity into the integrated equalization tank, where it is mixed and homogenized with the phenol and acetone production wastewater pretreated by the dissolved air flotation tank, so that the concentrations of each pollutant are stabilized at COD = 950 mg / L, petroleum hydrocarbons = 20 mg / L, benzene series compounds = 10 mg / L, and TDS = 12000 mg / L;

[0113] The retention time in the integrated equalization tank is 20 hours. It is equipped with an aeration and homogenization system. The pH of the wastewater is adjusted to 7-8 by adding acid and alkali in the integrated equalization tank.

[0114] (3) The homogenized wastewater is pumped to the biological selection tank, where the retention time is 0.5h and a submersible mixer is installed.

[0115] (4) The effluent from the biological selection tank flows by gravity into the anoxic tank. In the anoxic tank, denitrifying bacteria reduce nitrite and nitrate ions to nitrogen gas, thus removing nitrate nitrogen from the wastewater. The anoxic tank has a water temperature of 25℃, an oxidation-reduction potential between -150mV, a pH between 7 and 8, and a residence time of 16 hours. Multiple corridors are arranged within the anoxic tank, each equipped with a submersible mixer to keep the activated sludge in suspension, ensuring sufficient contact between the activated sludge and the organic matter and nitrate nitrogen in the wastewater to complete the biochemical reaction.

[0116] (5) The effluent from the anoxic tank flows by gravity into the first MBBR tank, where ammonia nitrogen and COD are removed through nitrification by aerobic sludge and nitrifying bacteria. MBBR packing (K3 type carrier fluidized bed packing, mainly made of HDPE, with a specific surface area of ​​500 m²) is added to the first MBBR tank. 2 / m 3 This allows high concentrations of microorganisms to adhere to the MBBR packing material, improving the first MBBR tank's resistance to shock loads and its pollutant removal capacity, while preventing sludge loss.

[0117] The water temperature in the first MBBR tank is 25℃, dissolved oxygen is between 3mg / L, pH value is between 7 and 8, and the retention time is 40h. The MBBR packing material has a filling rate of 10%, and a dedicated aeration system for MBBR packing material is installed at the bottom of the tank to keep the MBBR packing material in a fully fluidized state. A packing material interception screen is installed at the outlet of the first MBBR tank to ensure that the packing material remains in the first MBBR tank and does not flow with the sewage to other tanks.

[0118] A nitrification liquor return pump is installed at the end of the first MBBR tank to return the nitrification liquor treated in the first MBBR tank to the biological selector tank and the anoxic tank for denitrification reaction. The nitrification liquor return ratio is adjustable at 250%.

[0119] (6) The effluent from the first MBBR tank flows by gravity into the second sedimentation tank for sludge-water separation. The sludge is returned to the biological selection tank and the anoxic tank, and the supernatant flows by gravity into the first air flotation filter tank.

[0120] The surface loading of the secondary sedimentation tank is 0.5m. 3 / (m 2 •h) A sludge scraper is installed in the pool, along with a sludge discharge pump and a sludge return pump. The sludge return ratio is 130%.

[0121] (7) Add coagulant (PAC) to the first air flotation filter at a dosage of 20 mg / L to remove fine suspended solids and floating oil in the wastewater, so as to improve the oxidation utilization efficiency of ozone and hydrogen peroxide in the advanced oxidation tank.

[0122] The surface loading of the first air flotation filter is 6m³. 3 / (m 2 •h), the dissolved air reflux ratio is 25%, and the operating pressure of the dissolved air tank is 0.7MPa. The system includes a mixer for the coagulation and flocculation tanks, a dissolved air tank, a dissolved air release device, a dissolved air reflux pump, an inlet stabilizing tank, quartz sand and anthracite filter media, filter plates, filter heads, a backwash air distribution device, a backwash outlet tank, a backwash water pump, a backwash blower, a slag scraper, and other equipment, along with automatic backwashing facilities.

[0123] The influent suspended solids in the first air flotation filter (tank 7) were 20 mg / L, and the effluent suspended solids were 8 mg / L. The removal of suspended solids reduces the consumption of ozone and hydrogen peroxide in the subsequent advanced oxidation tank, thereby improving oxidation efficiency.

[0124] (8) The effluent from the first air flotation filter 7 enters the advanced oxidation tank. By adding ozone and hydrogen peroxide in combination, the COD in the sewage is further removed. At the same time, the B / C ratio of the sewage can be increased, and some of the COD substances that are difficult to degrade can be converted into degradable COD. A stripping tank is set in the advanced oxidation tank. An air source stripping device is set in the stripping tank to remove the residual ozone in the sewage.

[0125] The ozone dosage in the advanced oxidation tank is 70 mg / L, the 30% hydrogen peroxide dosage is 70 mg / L, and the removal rate of recalcitrant COD is 25 mg / L. The retention time in the advanced oxidation tank is 1.3 h, ensuring sufficient retention time for ozone and hydrogen peroxide to react with organic pollutants in the wastewater to generate CO2 and H2O, thereby removing COD, reducing the load on subsequent biological treatment, and simultaneously converting some recalcitrant COD into biodegradable COD, improving the B / C ratio of the wastewater.

[0126] The exhaust gas from the advanced oxidation tank and stripping tank contains ozone and cannot be directly discharged into the atmosphere. It must be discharged through a collection pipeline to an ozone exhaust gas destroyer for treatment, so that the ozone concentration in the exhaust gas is reduced to below 0.1 mg / L before being discharged into the atmosphere.

[0127] (9) The effluent from the advanced oxidation tank enters the second MBBR tank, where MBBR short-cut aeration technology is used to remove most of the degradable COD, and then enters the second air flotation filter tank.

[0128] In the second MBBR tank, COD in the wastewater is removed by aerobic sludge. MBBR packing is added to the tank so that microorganisms attach to the MBBR packing, thereby improving the pollutant removal capacity of the second MBBR tank and preventing sludge loss.

[0129] The water temperature in the second MBBR tank is 30℃, dissolved oxygen is 3mg / L, pH is between 7 and 8, and the retention time is 4h. The MBBR packing material has a filling rate of 15%, and a dedicated aeration system for the MBBR packing material is installed at the bottom of the tank to keep the MBBR packing material in a fully fluidized state. A packing material interception screen is installed at the outlet of the second MBBR tank to ensure that the packing material remains in the second MBBR tank and does not flow with the sewage into other tanks.

[0130] (10) Add coagulant (PAC) to the second air flotation filter at a dosage of 30 mg / L. This is mainly used to reduce suspended solids in the wastewater and ensure that the suspended solids in the effluent meet the discharge standards. The effluent from the second air flotation filter enters the effluent monitoring tank.

[0131] The surface loading of the second air flotation filter is 6m³. 3 / (m 2 The dissolved air recirculation ratio is 25%, and the operating pressure of the dissolved air tank is 0.7 MPa. The system includes a coagulation tank and flocculation tank mixer, dissolved air tank, dissolved air release device, dissolved air recirculation pump, inlet stabilizing tank, quartz sand and anthracite filter media, filter plates, filter heads, backwash air distribution device, backwash effluent tank, slag scraper, and other equipment, along with automatic backwashing facilities. The backwash water pump and backwash blower are shared with the first air flotation filter.

[0132] The suspended solids in the influent of the second air flotation filter were 40 mg / L, and the suspended solids in the effluent were 10 mg / L, which met the discharge requirements.

[0133] (11) If the COD in the effluent monitoring tank exceeds the standard, it can be bypassed to enter the activated carbon filter. The activated carbon in the activated carbon filter will remove part of the COD before it meets the standard and is discharged.

[0134] Two activated carbon filter beds are installed, with a filtration rate of 6 m / h and a forced filtration rate of 12 m / h. Activated carbon filter media is installed, and an automatic backwashing system is provided. The backwashing air volume of the activated carbon filter beds comes from the backwashing fan of the first air flotation filter bed.

[0135] (12) The treated wastewater enters the effluent monitoring tank. Online analyzers for COD, ammonia nitrogen and total nitrogen are installed in the effluent monitoring tank to detect the values ​​of pollutants such as COD, ammonia nitrogen and total nitrogen online. The wastewater is finally discharged or reused only after all indicators meet the emission standards. The retention time in the effluent monitoring tank is 1 hour to ensure sufficient buffer time.

[0136] Table 1 Pollutant removal indicators for each process unit in Example 2

[0137]

[0138] As can be seen from Table 1, the present invention removes organic matter from phenol and acetone production wastewater through biochemical and advanced oxidation methods. The treatment has low operating costs, is simple to operate, and the treated wastewater can be discharged in compliance with standards or reused.

[0139] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating wastewater containing high salt content and high concentration of recalcitrant organic matter, characterized in that, A treatment system is used for wastewater containing high salt content and high concentrations of recalcitrant organic matter. The treatment system includes: a dissolved air flotation tank, a comprehensive conditioning tank, a biological selection tank, an anoxic tank, a first MBBR tank, a secondary sedimentation tank, a first air flotation filter, an advanced oxidation tank, a second MBBR tank, and a second air flotation filter arranged sequentially along the material flow direction; it also includes an ozone pretreatment reverse osmosis brine device, the outlet of which is connected to the inlet of the comprehensive conditioning tank. The first MBBR tank is equipped with a nitrified liquor return outlet, which is connected to the biological selection tank and the anoxic tank respectively. The secondary sedimentation tank is equipped with a sludge return outlet, which is connected to the biological selection tank and the anoxic tank respectively. The processing method includes the following steps: Step (1): After petroleum substances and suspended solids are removed from the dissolved air flotation tank, the wastewater containing high salt and high concentration of recalcitrant organic matter enters the integrated equalization tank. Step (2): The ozone-oxidized pretreated reverse osmosis brine from the ozone pretreatment reverse osmosis brine device enters the integrated equalization tank, where it is mixed and homogenized with the wastewater treated by the dissolved air flotation tank, and the pH is adjusted to 7-8. The ozone-oxidized pretreated reverse osmosis brine has COD ≤ 80 mg / L and TDS ≤ 5000 mg / L. The TDS of the mixed wastewater is stable at 10000~12000 mg / L, COD ≤ 950 mg / L, petroleum hydrocarbons ≤ 20 mg / L, and benzene series compounds ≤ 10 mg / L. Step (3): The homogenized wastewater enters the biological selection tank, where flocculent activated sludge is optimized to prevent the growth of filamentous bacteria; Step (4): The effluent from the biological selection tank enters the anoxic tank, where denitrifying bacteria are used to remove nitrate nitrogen from the wastewater. Step (5): The effluent from the anoxic tank enters the first MBBR tank, where ammonia nitrogen and COD are removed through nitrification by aerobic sludge and nitrifying bacteria. MBBR packing is then added to the first MBBR tank to allow high concentrations of microorganisms to adhere to the packing. The nitrified liquid treated in the first MBBR tank is then returned to the biological selector tank and the anoxic tank through the nitrified liquid return outlet, with a nitrified liquid return ratio of 200%~300%. In step (6), the effluent from the first MBBR tank enters the secondary sedimentation tank for sludge-water separation; the treated sludge in the secondary sedimentation tank is returned to the biological selection tank and the anoxic tank through the sludge return outlet, with a sludge return ratio of 100%~150%. Step (7): The supernatant of the secondary sedimentation tank enters the first air flotation filter, and a coagulant is added to the first air flotation filter to remove fine suspended solids and floating oil in the sewage; the suspended solids in the effluent from the secondary sedimentation tank are treated to below 10 mg / L. Step (8): The effluent from the first air flotation filter enters the advanced oxidation tank, where ozone and hydrogen peroxide are added to remove the recalcitrant COD from the wastewater; at the same time, the B / C ratio of the wastewater is increased to convert some of the recalcitrant COD into biodegradable COD; the ozone dosage is 70~80 mg / L, and the 30% hydrogen peroxide dosage is 70~80 mg / L; the retention time is 1-2 hours. Step (9): The effluent from the advanced oxidation tank enters the second MBBR tank, where MBBR short-cut aeration technology is used to remove most of the degradable COD; Step (10): The effluent from the second MBBR tank enters the second air flotation filter, and coagulant is added to the second air flotation filter to further remove suspended solids in the wastewater; The wastewater containing high salt and high concentration of recalcitrant organic matter is wastewater from the production of phenol and acetone.

2. The processing method according to claim 1, characterized in that, In step (1), the flow rate of the wastewater containing high salt and high concentration of recalcitrant organic matter is 10-15 m³ / h. 3 / h; In step (2), the flow rate of the reverse osmosis concentrated brine after ozone oxidation pretreatment is 300~450m³ / h. 3 / h.

3. The processing method according to claim 1, characterized in that, In step (4), the water temperature of the anoxic pool is 20℃~35℃, the oxidation-reduction potential is between -200mv and -100mv, and the pH value is 7~8.

4. The processing method according to claim 1, characterized in that, In step (5), the water temperature of the first MBBR tank is 20℃~35℃, the dissolved oxygen is 2mg / L~4mg / L, and the pH value is 7~8.

5. The processing method according to claim 1, characterized in that, The treatment method further includes: the effluent from the second air flotation filter enters the effluent monitoring tank for monitoring; if it meets the discharge standards, it is discharged; if it does not meet the discharge standards, the effluent enters the activated carbon filter, where some COD is removed by activated carbon adsorption before being discharged in compliance with the standards.

6. The processing method according to claim 1, characterized in that, The treatment system further includes an effluent monitoring tank and an activated carbon filter. The outlet of the second air flotation filter is connected to the inlet of the effluent monitoring tank, and the outlet of the effluent monitoring tank is connected to the inlet of the activated carbon filter.

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