Treatment method of petrochemical engineering alkaline residue wastewater

Abstract

The invention provides a treatment method of petrochemical alkali residue wastewater. The treatment method comprises the following steps: (1) adding inorganic acid into the alkali residue wastewater for neutralization; (2) adding sewage into the neutralized alkaline residue wastewater for dilution so as to reduce the COD value of the alkaline residue wastewater; (3) carrying out primary biochemical degradation on the diluted alkaline residue wastewater, wherein a treatment system for the primary biochemical degradation comprises an MABR unit; and (4) enabling effluent of the MABR unit to enter a sedimentation tank, and carrying out secondary biochemical degradation on supernate of the sedimentation tank. According to the treatment method provided by the invention, the aeration membrane of the MABR unit reduces the gas-liquid mass transfer resistance and improves the oxygen utilization rate; oxygen in a biological membrane of the MABR unit and a substrate are transmitted in different directions, the biological membrane is high in adhesive force and not prone to falling off, the microbial activity is high, the pollutant removal efficiency is high, and the system is high in impact resistance and stable in operation; bubble-free aeration is realized, the aeration quantity is small, and the energy consumption is low; and the discharge amount of waste gas is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of biochemical treatment of high-salt and difficult-to-degrade wastewater, and in particular relates to a method for treating petrochemical alkali residue wastewater. Background Art

[0002] A certain amount of alkaline residue wastewater is produced during the oil refining and chemical production process, which is usually dark brown and smelly. This type of wastewater has a high concentration of difficult-to-degrade organic matter, with a COD value of tens of thousands or even hundreds of thousands of mg / L; high alkalinity, with a pH value generally above 13; and extremely high salt content and sulfide concentration, which is a major problem in the field of wastewater treatment at home and abroad.

[0003] At present, incineration, wet oxidation and bioaugmentation are commonly used for the treatment of petrochemical alkali residue wastewater at home and abroad. Incineration is a commonly used method for treating alkali residue wastewater. Its disadvantages are high investment, high energy consumption, secondary pollution, etc., and the treatment of such high-salt wastewater has great damage to the incinerator body; the disadvantages of wet oxidation are high one-time investment, need to operate under high temperature and high pressure, harsh operating conditions, complex operation management, and high operating costs; the investment and operating costs of bioaugmentation are significantly lower than those of incineration and wet oxidation. The bioaugmentation method requires neutralization of alkali residue wastewater before biochemical treatment. The inventor of the present invention used concentrated sulfuric acid to conduct neutralization tests on several petrochemical alkali residue wastewaters with a pH of about 13.7. A large amount of heat is generated during the neutralization process, which causes the wastewater temperature to rise, and generates malodorous gases containing high concentrations of H2S, forming a large amount of foam on the wastewater surface, and generating more precipitation. In this process, due to the overflow of H2S and the generation of precipitation, the COD of the wastewater is significantly reduced.

[0004] CN200710150191.X provides a method for treating alkali residue wastewater by combining a pretreatment system with a biological system. The pretreatment process of the invention requires adding concentrated sulfuric acid to the alkali residue wastewater to acidify the wastewater from a strong alkaline state to a pH of 2 to 4. After recovering cyclohexane acid or phenolic substances, the wastewater enters a conventional bubbling aeration biochemical pool for treatment together with other alkali residue wastewaters. The pH of the biochemical pool is controlled at 6.0 to 7.0. After comprehensive treatment, the COD of the alkali residue wastewater is less than 1000 mg / L. The waste gas generated by the pretreatment and biochemical process is passed through a biological purification tower to remove most of the odor. However, its defects are: first, concentrated sulfuric acid is used to adjust the pH of the alkali residue wastewater to 2-4 during the pretreatment process, so that almost all the sulfides in the wastewater are converted into H2S and enter the waste gas. Sulfides have strong biological toxicity. The lower the pH of the alkali residue wastewater is adjusted, the more complete the H2S overflows, causing a large amount of COD to transfer from the liquid phase to the gas phase. Although the transfer of sulfides greatly reduces the difficulty of wastewater treatment, some engineering cases have shown that the presence of a large amount of H2S in the waste gas has caused tremendous pressure on waste gas treatment, making it difficult for the waste gas treatment system to operate stably, thus creating new and difficult-to-solve problems; second, both experimental studies and actual device operation have shown that as the biochemical degradation of the alkali residue wastewater proceeds, the pH value of the wastewater will decrease. The decrease in pH may be due to the oxidation of sulfides to SO4 in the biochemical process. 2- 2. It is caused by the accumulation of volatile organic acids generated by the degradation of organic pollutants under high COD load and nitrification reaction. Therefore, alkali solution needs to be added for neutralization during the biochemical process to maintain a suitable pH range for microorganisms. The lower the pH of the wastewater at the inlet of the biochemical pool is adjusted, the more alkali is added, thereby increasing the amount of acid and alkali required for pH adjustment, resulting in an increase in treatment costs; third, the biochemical system adopts a traditional bubbling aeration tank, the activated sludge has poor impact resistance, and the aeration volume is large, the oxygen utilization rate is low, the energy consumption is high, and the biochemical pool discharges a large amount of waste gas containing sulfides and volatile organic pollutants, which increases the difficulty and cost of waste gas treatment; finally, the cyclopentane acids and phenols in the wastewater contain more impurities after recovery and need to be refined. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention applies MABR (membrane aerated biofilm reactor) technology to the treatment of petrochemical alkali slag wastewater, realizes bubble-free aeration, low aeration volume, high oxygen utilization rate, further enhances the microbial activity and the impact resistance of the biochemical treatment system, and at the same time greatly reduces waste gas emissions, reduces energy consumption and operating costs.

[0006] To this end, the present invention provides a method for treating petrochemical alkali residue wastewater, comprising the following steps:

[0007] (1) adding inorganic acid to the alkaline residue wastewater for neutralization;

[0008] (2) Adding sewage to dilute the neutralized alkali residue wastewater to reduce its COD value;

[0009] (3) the diluted alkali residue wastewater is subjected to a first biochemical degradation, wherein the first biochemical degradation treatment system includes a MABR unit;

[0010] (4) The effluent from the MABR unit enters the sedimentation tank, and the supernatant in the sedimentation tank undergoes a second biochemical degradation.

[0011] Specifically, the first biochemical degradation treatment system includes an MABR unit, and the first biochemical degradation treatment system can be a separate MABR unit or a MABR unit coupled with a traditional biochemical system (for example, a traditional bubbling aeration biochemical tank); the COD value of the sewage added in step (2) is lower than the COD value of the alkali residue wastewater.

[0012] As a specific embodiment of the present invention, preferably, the MABR unit includes at least one MABR reactor. Further preferably, when the MABR unit includes at least two MABR reactors, the MABR reactors are connected in series. Further preferably, the MABR reactor includes a tank body, a MABR module, an air compression oxygen supply device and a circulation system. The MABR module is arranged in the wastewater in the tank body. The MABR module is connected to the air compression oxygen supply device through an air supply pipeline and a control valve. The circulation system contains a circulation pump to realize the internal circulation of the wastewater in each MABR reactor and the backflow of the activated sludge in the sedimentation tank to each MABR reactor. Further preferably, the MABR module is composed of more than two membrane filaments arranged in parallel and a membrane assembly for fixing the membrane filaments.

[0013] As a specific embodiment of the present invention, preferably, when the MABR unit includes more than two MABR reactors, each MABR reactor shares an air compression oxygen supply device; and / or the air supply pipeline and control valve of each MABR reactor are connected in parallel, and the aeration pressure of the corresponding MABR module is independently adjusted by each control valve to control each MABR reactor to operate independently in anaerobic mode, anoxic mode or aerobic mode.

[0014] Specifically, the anaerobic mode means that anaerobic bacteria account for a high proportion in the biofilm and the dissolved oxygen in the wastewater is in the anaerobic range; the anoxic mode means that anoxic bacteria account for a high proportion in the biofilm and the dissolved oxygen in the wastewater is in the anoxic range; the aerobic mode means that aerobic bacteria account for a high proportion in the biofilm and the dissolved oxygen in the wastewater is in the aerobic range.

[0015] As a specific embodiment of the present invention, preferably, the membrane filament is a tubular hollow fiber membrane with N2 and O2 separation function, and further preferably, a microbial membrane is attached to and grown on the outer surface of the hollow fiber membrane; further preferably, the hollow fiber membrane has the function of permeating O2 and blocking N2.

[0016] As a specific embodiment of the present invention, preferably, the membrane fibers include an aeration membrane, a biofilm and a boundary layer from the inside to the outside in radial direction; further preferably, the biofilm includes an aerobic zone, an anoxic zone and an anaerobic zone from the inside to the outside.

[0017] As a specific embodiment of the present invention, preferably, the dissolved oxygen in the anaerobic mode is 0-0.2 mg / L, and / or the dissolved oxygen in the anoxic mode is 0.2-0.5 mg / L, and / or the dissolved oxygen in the aerobic mode is 1.0-4.0 mg / L.

[0018] As a specific embodiment of the present invention, preferably, the pH value of the alkali residue waste water after neutralization in step (1) is 7.0-9.0, and / or the inorganic acid is sulfuric acid.

[0019] As a specific embodiment of the present invention, preferably, the COD of the alkali residue wastewater after dilution in step (2) is not higher than 30000 mg / L; and / or in step (4), the biochemical degradation is carried out in a conventional biochemical pool, for example, in a conventional bubbling aeration biochemical pool at a pH of 6 to 8 and in an aerobic mode; and / or the COD value of the alkali residue wastewater is 5000-500000 mg / L, preferably 9000-300000 mg / L, the pH value is above 12, preferably above 12.5, and the sulfide is 5000-50000 mg / L, preferably 7000-300000 mg / L.

[0020] As a specific embodiment of the present invention, preferably, in step (3), the hydraulic retention time of the diluted alkali slag wastewater in the MABR unit is 1 to 5 days; and / or in step (3), the COD of the wastewater after biochemical degradation is ≤800 mg / L and the sulfide concentration is ≤10 mg / L.

[0021] As a specific embodiment of the present invention, preferably, the treatment method also includes step (5): the exhaust gas generated in steps (1)-(4) enters the exhaust gas treatment unit for purification and then meets the emission standards; further preferably, the exhaust gas treatment unit includes at least one of an absorption module, an adsorption module, and a catalytic combustion module.

[0022] As a specific embodiment of the present invention, preferably, the processing method comprises the following steps:

[0023] (1) adding inorganic acid to the alkaline residue wastewater to neutralize it to a pH value of 7.0 to 9.0;

[0024] (2) adding sewage to the neutralized alkali residue wastewater to dilute it to a COD of no more than 30,000 mg / L;

[0025] (3) The diluted alkali residue wastewater enters the MABR unit for biochemical degradation. After biochemical degradation, the COD of the wastewater is ≤800 mg / L and the sulfide concentration is ≤10 mg / L;

[0026] (4) The effluent of the MABR unit enters the sedimentation tank, and the supernatant of the sedimentation tank enters the conventional bubbling aeration biochemical tank of the sewage field for biochemical degradation;

[0027] (5) The waste gas generated in the above steps enters the waste gas treatment unit for purification and then meets the emission standards.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The method for treating alkali residue wastewater provided by the present invention applies MABR technology to the treatment of petrochemical alkali residue wastewater. The membrane fibers of the MABR unit adopt hollow fiber membranes with N2 and O2 separation functions, which can reduce the gas-liquid mass transfer resistance and improve the oxygen utilization rate; at the same time, it also improves the pollutant removal efficiency in the alkali residue wastewater, the system impact resistance and the operation stability.

[0030] (2) Since the alkali residue wastewater has a high sulfide content and strong biological toxicity, the biofilm inoculation and domestication are much more difficult than conventional MABR technology. The present invention effectively overcomes this technical difficulty and ensures the high activity and firm adhesion of the biofilm.

[0031] (3) The method for treating alkaline slag wastewater provided by the present invention adjusts the pH of the alkaline slag wastewater entering the MABR reactor to neutral to weak alkalinity, thereby reducing the amount of inorganic acid (such as sulfuric acid) used in the pretreatment system and the amount of alkaline solution used for neutralization after the wastewater is acidified during the biochemical degradation process.

[0032] (4) MABR reactors can operate under aerobic, anoxic or anaerobic conditions, and multi-stage MABR reactors can coordinate biochemical reactions, thereby improving the overall biochemical effect.

[0033] (5) The method for treating alkali residue wastewater provided by the present invention applies MABR technology to the treatment of petrochemical alkali residue wastewater, realizes bubble-free aeration, small aeration volume, low energy consumption, and greatly reduces the emission of waste gas containing H2S and volatile organic pollutants during the biochemical treatment process, thereby reducing the difficulty of subsequent waste gas treatment; it has good economic benefits, significant social benefits and good industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the process flow of the method for treating petrochemical alkali residue wastewater provided by the present invention;

[0035] Figure 2a It is a cross-sectional view of a single membrane fiber in a MABR module; Figure 2bA top view of a single membrane filament in a MABR module.

[0036] Figure 3a Schematic diagram of the diffusion direction of oxygen and substrate in traditional biofilm systems; Figure 3b Schematic diagram of the diffusion direction of oxygen and substrate in the MABR system.

[0037] Among them: 1-a inert carrier; 1-b, aeration membrane; 2, biofilm; 3, boundary layer; 2-1, aerobic zone; 2-2, anoxic zone; 2-3, anaerobic zone; 4, neutralization and dilution tank; 5, pump; 6, air compressor; 7, primary MABR reactor; 8, secondary MABR reactor; 9, sedimentation tank. DETAILED DESCRIPTION

[0038] The technical scheme of the present invention is further described below by specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0039] See also Figure 1 As shown, in the neutralization and dilution tank 4, inorganic acid and dilution sewage are used to neutralize and dilute the alkali residue wastewater; the neutralized and diluted alkali residue wastewater is transported to the primary MABR reactor 7 through a pump 5 for biochemical reaction, and the biochemical wastewater overflows to the secondary MABR reactor 8 for further biochemical reaction. MABR modules are arranged in the alkali residue wastewater in both the primary MABR reactor 7 and the secondary MABR reactor 8, and air compressors 6 are used to supply oxygen to each MABR module in the primary MABR reactor 7 and the secondary MABR reactor 8, and the aeration pressure of the corresponding MABR modules is adjusted by pipeline valves connected in parallel to control The primary MABR reactor 7 and the secondary MABR reactor 8 are independently operated in the anaerobic mode, the anoxic mode or the aerobic mode, and the wastewater in the primary MABR reactor 7 and the secondary MABR reactor 8 are internally circulated by the pump 5; the effluent of the secondary MABR reactor 8 overflows into the sedimentation tank 9, and the activated sludge in the sedimentation tank is pumped back to the primary MABR reactor 7 and the secondary MABR reactor 8 by the pump 5, and the supernatant in the sedimentation tank 9 can enter the conventional biochemical tank for secondary biochemical treatment, for example, in a conventional bubbling aeration biochemical tank under a pH of 6 to 8 and aerobic conditions. Figure 1 Taking a two-stage series MABR that is not coupled with a traditional bubbling aeration biochemical system as an example, in actual application, it can also be a single-stage MABR reactor or a multi-stage series MABR reactor, and can be coupled with a traditional bubbling aeration biochemical system.

[0040] The present invention adopts a tubular hollow fiber membrane (i.e., membrane filament) with N2 and O2 separation functions as a membrane with an aeration function. The membrane with an aeration function can also be used as a biofilm carrier, and microorganisms with different biological functions are inoculated and attached to the outer surface of the hollow fiber membrane wall. MABR technology divides the system into two parts, gas phase (membrane filament lumen) and liquid phase (wastewater) through membrane filaments. During operation, air is passed from one end of the tubular hollow fiber membrane (i.e., membrane filament) into the membrane filament lumen, and O2 in the air enters the liquid phase through the aeration membrane (i.e., the inner wall of the membrane filament), and oxygen is supplied to the microbial membrane attached to the outer surface of the membrane filament wall, so as to achieve bubble-free aeration, and N2 in the air is intercepted by the aeration membrane (i.e., the inner wall of the membrane filament) and discharged from the other end of the tubular hollow fiber membrane (i.e., membrane filament) The inner cavity of the membrane; the wastewater in the liquid phase flows through the entire biofilm, and the pollutants in the wastewater enter the inner side of the biofilm from the outside of the biofilm under the action of concentration drive and microbial adsorption, forming a boundary layer and being utilized by microorganisms through biological metabolism and proliferation, so that the pollutants in the water body are degraded.

[0041] See also Figure 2a , Figure 2b and Figure 3b As shown, the membrane filaments in the MABR module are hollow cylindrical, and the membrane filaments include aeration membrane 1-b, biofilm 2 and boundary layer 3 from the inside to the outside in radial direction; the biofilm 2 includes aerobic zone 2-1, anoxic zone 2-2 and anaerobic zone 2-3 from the inside to the outside. The hollow part (i.e., the inner cavity) of the membrane filaments in the MABR module is the main gas phase (oxygen), and the boundary layer is in contact with the main liquid phase (wastewater).

[0042] See also Figure 3a As shown, the traditional biofilm system includes an inert carrier 1-a, a biofilm 2 and a boundary layer 3 from the inside to the outside; the biofilm 2 includes an anaerobic zone 2-3, an anoxic zone 2-2 and an aerobic zone 2-1 from the inside to the outside.

[0043] See also Figure 3a and Figure 3bAs shown in the figure, the traditional biofilm system uses inert materials as biofilm carriers, and the aeration form is bubbling aeration at the bottom of the biochemical reaction tank. Therefore, the diffusion of oxygen and substrate is from the surface of the biofilm to the inside of the biofilm, and the two are in the same direction. The concentration of oxygen and substrate gradually decreases from the surface of the biofilm to the inside of the biofilm. The traditional biofilm system has the following disadvantages: due to the sufficient substrate and dissolved oxygen on the surface of the biofilm, the biofilm grows too fast and too thick, resulting in increased mass transfer resistance of substrate and oxygen; at the same time, most of the oxygen is consumed on the surface of the biofilm, forming an inert anaerobic layer inside the biofilm, and gaseous metabolic products are constantly escaping, which weakens the fixation of the biofilm on the carrier and makes the biofilm easy to fall off; because the concentration of both oxygen and substrate reaction raw materials is lower as the biofilm moves to the inside, its high activity only appears at the biofilm / wastewater interface. However, the MABR system of the present invention adopts a tubular hollow fiber membrane (i.e., membrane filament) with the function of blocking N2 from penetrating O2 as an aeration membrane and a biofilm carrier (comprising 1-b, a biofilm 2 and a boundary layer 3). O2 enters the liquid phase from the inner cavity of the membrane filament through the inner wall of the membrane filament, and supplies oxygen to the biofilm 2 attached to the outer surface of the aeration membrane 1-b wall, while the substrate enters the inner side of the biofilm 2 from the outside of the biofilm 2 in the wastewater. Therefore, the anisotropic diffusion of oxygen and pollutants in the wastewater in the biofilm 2 is achieved, and the diffusion directions of oxygen and the substrate are opposite, and the concentration change trends are also opposite. The advantages of this diffusion mode are: on the outer surface of the biofilm, there is sufficient substrate but relatively low dissolved oxygen, so the biofilm does not grow too fast or too thick, reducing the mass transfer resistance of the substrate and oxygen; in the inner layer of the biofilm, the organic substrate concentration is the lowest and the dissolved oxygen concentration is the highest, which not only maintains a high organic matter degradation efficiency, but also avoids the biofilm shedding caused by the continuous escape of gaseous metabolic products from the anaerobic inert layer; because oxygen and substrate diffuse in different phases, the biofilm maintains high biological activity from the outside to the inside.

[0044] As can be seen from the above, the MABR unit in the present invention organically integrates the gas separation membrane technology and the biofilm water treatment technology. The aeration membrane 1-b adopts a tubular hollow fiber membrane with N2 and O2 separation functions. The air flows in the lumen of the fiber membrane, and microorganisms with different biological functions are inoculated and attached to the outer surface of the hollow fiber membrane wall. The MABR unit divides the system into two parts: gas phase (aeration membrane lumen) and liquid phase (wastewater) through the aeration membrane. During operation, air is passed into the lumen of the hollow fiber membrane from one end, and the O2 in the air passes through the aeration membrane wall into the liquid phase, supplying oxygen to the microbial membrane attached to the outer surface of the aeration membrane wall, thereby realizing bubble-free aeration, while the N2 in the air is retained in the lumen by the aeration membrane wall and discharged from the other end of the lumen. The biofilm 2 is attached to and grows on one side of the aeration membrane 1-b close to the liquid phase. Under the action of pressure, oxygen diffuses from the gas phase through the aeration membrane wall into the biofilm 2 attached to the outer surface of the aeration membrane 1-b to provide oxygen for the microorganisms. The wastewater in the liquid phase flows through the entire biofilm 2. The pollutants in the wastewater enter the inside of the biofilm 2 from the outside of the biofilm 2 under the action of concentration difference drive and microbial adsorption, and are utilized by the microorganisms through biological metabolism and proliferation. The pollutants in the water body are assimilated into microbial cells and fixed on the biofilm or decomposed into inorganic metabolic products, thereby achieving purification of the water body.

[0045] Unlike the conventional biofilm system where oxygen and pollutants diffuse in the same direction, the MABR system achieves the heterogeneous diffusion of oxygen and pollutants in the biofilm. In the conventional biofilm system, the diffusion of oxygen and substrate is from the surface of the biofilm to the inside of the biofilm, and the two are in the same direction. Due to the sufficient substrate and dissolved oxygen on the surface of the biofilm, the biofilm grows too thick, resulting in an increase in the mass transfer resistance of the substrate and oxygen, and also consuming most of the oxygen, forming an inert anaerobic layer inside the biofilm, and gaseous metabolites continuously escape, weakening the fixation of the biofilm on the carrier, making the biofilm easy to fall off, and its highest activity appears at the biofilm / wastewater interface; while in the MABR system, the diffusion directions of oxygen and substrate are opposite, and the inner layer of the biofilm close to the carrier membrane has a high concentration of dissolved oxygen and a low concentration of organic substrate, while the outer layer of the biofilm close to the liquid phase has a low concentration of dissolved oxygen and a high concentration of substrate. Therefore, the active layer of the heterogeneous mass transfer biofilm can appear at any position of the biofilm thickness, not just at the biofilm-wastewater interface, which greatly improves the biofilm adhesion firmness and biochemical activity.

[0046] The MABR unit used in the method for treating petrochemical alkali residue wastewater provided by the present invention has the following characteristics: (1) a tubular hollow fiber membrane with N2 and O2 separation function is used as an aeration membrane, and oxygen passes through the membrane wall and is directly utilized by the biofilm without passing through the liquid phase boundary layer, which greatly reduces the mass transfer resistance of oxygen and significantly improves the oxygen supply rate; (2) the significant difficulties caused by the extremely high biological toxicity of alkali residue wastewater to the biofilm acclimation process are overcome, and the high activity and adhesion firmness of the biofilm are ensured; (3) the pH value of the alkali residue wastewater at the inlet of the MABR reactor is adjusted to neutral to weakly alkaline, reducing The amount of sulfuric acid used in the pretreatment system and the amount of alkali solution used for neutralization after wastewater acidification during the biochemical degradation process are reduced; (4) Bubble-free aeration is achieved, which not only improves the oxygen utilization rate, but also greatly reduces the aeration volume, overcoming the shortcomings of traditional bubbling aeration, such as large aeration volume, high energy consumption, and large amounts of sulfide and low-molecular organic waste gas produced by sewage pool stripping; (5) Oxygen and substrate diffuse in different directions, which not only enhances the adhesion of the biofilm and makes it difficult for the biofilm to fall off, but also makes any position of the biofilm highly active, significantly improving the degradation effect of pollutants in the wastewater; (6) The sludge output is small, reducing the cost of residual sludge treatment.

[0047] Example 1

[0048] The pH value of the alkali residue wastewater generated by a petrochemical enterprise during the refining and production process is 13.9, the COD is 195600 mg / L, and the sulfide is 16350 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to a pH of about 7.0 with about 92wt% concentrated sulfuric acid; the neutralized alkali residue wastewater is diluted with the effluent from the secondary sedimentation tank of a wastewater biochemical system of a sewage plant (COD is 80 mg / L), and the COD of the alkali residue wastewater after dilution is 22100 mg / L and the sulfide content is 1290 mg / L; the diluted alkali residue wastewater enters the MABR unit for biochemical degradation, and the structure of the MABR reactor is as follows Figure 1 As shown, the difference is that MABR uses a single-stage reactor, the dissolved oxygen is controlled at 2.0-4.0 mg / L, the pH value is controlled in the range of 6.0-8.0, and if the pH is detected to be less than 5.5 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The hydraulic retention time is 5 days. After treatment, the COD of the effluent from the sedimentation tank is 750 mg / L and the sulfide content is 8.1 mg / L; the exhaust gas generated in the above-mentioned acidification, dilution and biochemical processes enters the absorption tower through the induced draft fan, and after the sulfur-containing compounds in the exhaust gas are absorbed by the alkaline absorption liquid, the exhaust gas enters the catalytic combustion system and is discharged into the air after purification meets the standards.

[0049] During the treatment process, due to the fluctuation of the influent indicators of alkaline slag wastewater, the COD of the MABR unit influent once soared to 26050 mg / L, while the effluent COD was still no higher than 800 mg / L and the sulfide was no higher than 10 mg / L.

[0050] Example 2

[0051] The pH value of the alkali residue wastewater generated by a petrochemical enterprise during the refining and production process is 13.7, the COD is 250000 mg / L, and the sulfide is 15000 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to about pH = 9.0 with about 35wt% of waste sulfuric acid liquid generated in the process of the enterprise's device; the neutralized alkali residue wastewater is diluted with the effluent from the sedimentation tank in a wastewater biochemical system of a sewage plant (COD is about 300 mg / L), and the COD of the alkali residue wastewater after dilution is 30000 mg / L and the sulfide content is 1440 mg / L; the diluted alkali residue wastewater enters the MABR unit for biochemical degradation, and the MABR unit adopts the following method: Figure 1 The two-stage reactor shown is connected in series, the dissolved oxygen of the first reactor is controlled at 0-0.2 mg / L, and anaerobic bacteria are mainly present in the biofilm of the first reactor. The dissolved oxygen of the second reactor is controlled at 1.0-2.0 mg / L, and aerobic bacteria are mainly present in the biofilm of the second reactor. The pH control value is 6.0-9.0. If the pH is less than 5.0 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The hydraulic retention time is 4 days. The COD of the effluent from the sedimentation tank after treatment is 720 mg / L and the sulfide content is 8.6 mg / L. The exhaust gas generated in the above-mentioned acidification, dilution and biochemical processes enters the desulfurization tank through the induced draft fan. After the sulfur-containing compounds in the exhaust gas are removed by adsorption with a solid desulfurizer, the exhaust gas enters the catalytic combustion system for treatment, and is discharged into the air after purification meets the standards.

[0052] During the treatment process, due to the fluctuation of the influent indicators of the alkaline slag wastewater, the COD of the MABR unit influent once rose to 33560 mg / L, while the effluent COD was still no higher than 800 mg / L and the sulfide was no higher than 10 mg / L.

[0053] Example 3

[0054] The pH value of the alkali residue wastewater of a petrochemical enterprise is 13.9, the COD is 93050 mg / L, and the sulfide is 15786 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to a pH of about 8.5 with 93wt% concentrated sulfuric acid; the neutralized wastewater is diluted with a sewage with a COD of about 120 mg / L, and the COD of the alkali residue wastewater after dilution is 15060 mg / L and the sulfide content is 2172 mg / L; the diluted alkali residue wastewater enters the MABR unit for biochemical degradation, and the MABR adopts the following method: Figure 1The two-stage reactor shown is connected in series, the dissolved oxygen of the first reactor is controlled at 0.2-0.5 mg / L, and the biofilm of the first reactor is mainly composed of anoxic bacteria. The dissolved oxygen of the second reactor is controlled at 2.0-3.0 mg / L, and the biofilm of the second reactor is mainly composed of aerobic bacteria. The pH control value is 6.0-9.0. If the pH is less than 5.0 detected in the biochemical process, an appropriate amount of alkali solution is used for neutralization. The hydraulic retention time is 3 days. After treatment, the COD of the effluent from the sedimentation tank is 670 mg / L and the sulfide content is 9.3 mg / L; the exhaust gas generated in the above-mentioned acidification, dilution and biochemical processes enters the absorption tower and the desulfurization tank in turn through the induced draft fan, and the sulfur-containing compounds in the exhaust gas are removed by alkaline absorption liquid and solid desulfurizer respectively. After that, the exhaust gas enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0055] During the treatment process, due to the fluctuation of the influent indicators of alkali slag wastewater, the influent COD of the MABR unit fluctuated between 14000 and 18590 mg / L, and the effluent COD was always no higher than 750 mg / L and the sulfide was no higher than 10 mg / L.

[0056] Example 4

[0057] The pH value of the alkali residue wastewater of a petrochemical enterprise refinery is 13.6, the COD is 61780 mg / L, and the sulfide content is 7357 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to a pH of about 8.5 with about 30wt% of waste sulfuric acid produced in the process of the enterprise device; the neutralized alkali residue wastewater is diluted with recycled water with a COD of about 30 mg / L, and the COD of the alkali residue wastewater after dilution is 10930 mg / L and the sulfide content is 1106 mg / L; the diluted alkali residue wastewater enters the MABR unit for biochemical degradation, and the structure of the MABR reactor is as follows Figure 1 As shown, the difference is that three stages of reactors are connected in series. The dissolved oxygen in the first reactor is controlled at 0-0.2 mg / L, and anaerobic bacteria are mainly in the biofilm. The dissolved oxygen in the second reactor is controlled at 0.2-0.5 mg / L, and anoxic bacteria are mainly in the biofilm. The dissolved oxygen control value of the tertiary reactor is 2.0-3.0, and aerobic bacteria are mainly in the biofilm. The pH control value is 6.0-9.0. If the pH is less than 5.5 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The hydraulic retention time is 3 days. After treatment, the COD of the effluent from the sedimentation tank is 630 mg / L and the sulfide content is 7.4 mg / L; the exhaust gas generated in the above-mentioned acidification, dilution and biochemical processes enters the desulfurization tank through the induced draft fan. After the sulfur-containing compounds in the exhaust gas are removed by adsorption with a solid desulfurizer, the exhaust gas enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0058] During the treatment process, due to the fluctuation of the influent indicators of the alkali slag wastewater, the influent COD of the MABR unit fluctuated between 9700 and 12500 mg / L, and the effluent COD was always no higher than 720 mg / L and the sulfide was no higher than 10 mg / L.

[0059] Example 5

[0060] The pH value of the alkali residue wastewater of a petrochemical enterprise is 12.8, the COD is 110200 mg / L, and the sulfide is 8030 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to about pH=8.8 with about 92wt% concentrated sulfuric acid; the neutralized alkali residue wastewater is diluted with recycled water with a COD of 30 mg / L, and the COD of the alkali residue wastewater after dilution is 12360 mg / L and the sulfide content is 810 mg / L; the diluted alkali residue wastewater enters the biochemical unit for treatment, and the biochemical unit adopts the form of coupling the traditional bubbling aeration biochemical tank with the two-stage MABR, and the original traditional bubbling aeration biochemical tank is divided into two areas by a partition, and a MABR reactor is implanted in each area to form a primary and a secondary MABR reactor connected in series, and the MABR reactor structure is as follows Figure 1 As shown, the difference is that the bubbling aeration of the traditional biochemical pool is retained at the bottom of the pool. By adjusting the aeration volume of each pool bottom and the aeration pressure of each MABR module, the dissolved oxygen in the area where the first-level MABR reactor is located is controlled at 0-0.2 mg / L, and anaerobic bacteria are mainly present in the biofilm. The dissolved oxygen in the area where the second-level MABR reactor is located is controlled at 1.0-2.0 mg / L, and aerobic bacteria are mainly present in the biofilm. The pH control values ​​of the two levels are both 6.0-9.0. If the pH is less than 5.5 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The total hydraulic retention time of the biochemical process is 2 days. The biochemical process adopts an aeration method combining MABR membrane aeration and a small amount of bubbling aeration at the bottom of the pool, and the total aeration volume is 0.5m 3 / h, while the aeration volume of a traditional bubbling aeration biochemical pond alone is at least 1.0m 3 / h, therefore, the total aeration volume is reduced to 1 / 2 of the aeration volume of the traditional bubbling aeration biochemical tank. After treatment, the COD of the effluent from the sedimentation tank is 610mg / L and the sulfide content is 5.9mg / L; the waste gas generated in the above-mentioned acidification, dilution and biochemical processes enters the desulfurization tank through the induced draft fan, and after the solid desulfurizer is used to adsorb and remove the sulfur-containing compounds in the waste gas, the waste gas enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0061] During the treatment process, due to the fluctuation of the influent indicators of the alkali slag wastewater, the influent COD of the MABR unit fluctuated between 11000 and 15500 mg / L, and the effluent COD was always no higher than 720 mg / L and the sulfide was no higher than 8 mg / L.

[0062] Example 6

[0063] The pH value of the alkali residue wastewater of a petrochemical enterprise is 14.0, the COD is 75250 mg / L, and the sulfide is 20839 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to pH=7.0 with 92wt% concentrated sulfuric acid; the neutralized alkali residue wastewater is diluted with the effluent of the intermediate sedimentation tank with a COD of 230 mg / L, and the COD of the alkali residue wastewater after dilution is 11380 mg / L and the sulfide content is 2364 mg / L; the diluted alkali residue wastewater enters the biochemical unit for treatment, and the biochemical unit adopts the form of coupling the traditional bubbling aeration biochemical tank with the three-stage MABR, and the original traditional bubbling aeration biochemical tank is divided into three areas by a partition, and a MABR reactor is implanted in each area to form a primary, secondary and tertiary MABR reactors connected in series, and the MABR reactor structure is the same Figure 1 As shown, the difference is that three-stage MABR reactors are used in series, and the bubbling aeration of the traditional biochemical pool is retained at the bottom of the three areas. By adjusting the aeration volume of each pool bottom and the aeration pressure of each MABR module, the dissolved oxygen in the areas where the first, second and third stage MABR reactors are located is controlled at 0-0.2 mg / L, 0.2-0.5 mg / L and 2.0-4.0 mg / L, respectively. The pH control value is 6.0-8.0. If the pH is less than 5.0 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The total hydraulic retention time of the biochemical process is 1 day. The biochemical process adopts an aeration method combining MABR membrane aeration and a small amount of bubbling aeration at the bottom of the pool. The total aeration volume is 0.6m 3 / h, while the aeration capacity of the traditional biochemical pond alone is 1.8m 3 / h, therefore, the total aeration volume is reduced to 1 / 3 of the original aeration volume of the traditional biochemical pool. After treatment, the COD of the effluent from the sedimentation tank is 780mg / L and the sulfide content is 9.2mg / L. The waste gas generated in the above-mentioned acidification, dilution and biochemical processes enters the desulfurization tank through the induced draft fan. After the solid desulfurizer is used to adsorb and remove the sulfur-containing compounds in the waste gas, the waste gas enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0064] During the treatment process, due to the fluctuation of the influent indicators of alkali slag wastewater, the influent COD of the MABR unit fluctuated between 10400 and 14340 mg / L, and the effluent COD was always no higher than 800 mg / L and the sulfide was no higher than 10 mg / L.

[0065] Example 7

[0066] The pH value of the alkali residue wastewater of a petrochemical enterprise is 13.7, the COD is 235800 mg / L, and the sulfide is 13960 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to pH=8.7 with 92wt% concentrated sulfuric acid; the neutralized alkali residue wastewater is diluted with the effluent of the intermediate sedimentation tank with a COD of 230 mg / L, and the COD of the alkali residue wastewater after dilution is 30000 mg / L and the sulfide content is 1598 mg / L; the diluted alkali residue wastewater enters the biochemical unit for treatment, and the biochemical unit adopts the form of coupling the traditional bubbling aeration biochemical tank with the three-stage MABR, and the original traditional bubbling aeration biochemical tank is divided into three areas by a partition, and a MABR reactor is implanted in each area to form a primary, secondary and tertiary MABR reactors connected in series, and the MABR reactor structure is the same as Figure 1 As shown, the difference is that three-stage MABR reactors are used in series, and the bubbling aeration of the traditional biochemical pool is retained at the bottom of the three areas. By adjusting the aeration volume of each pool bottom and the aeration pressure of each MABR module, the dissolved oxygen in the areas where the first, second and third stage MABR reactors are located is controlled at 0-0.2 mg / L, 0.2-0.5 mg / L and 2.0-3.0 mg / L, respectively. The pH control value is 6.0-9.0. If the pH is less than 5.0 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The total hydraulic retention time of the biochemical process is 3 days. The biochemical process adopts an aeration method combining MABR membrane aeration and a small amount of bubbling aeration at the bottom of the pool. The total aeration volume is 0.5m 3 / h, while the aeration capacity of the traditional biochemical pond alone is 1.3m 3 / h, so it can save 61.5% of gas compared with the traditional aerated biochemical pool. After treatment, the COD of the sedimentation tank effluent is 590mg / L and the sulfide content is 1.6mg / L; the waste gas generated in the above acidification, dilution and biochemical process enters the desulfurization tank through the induced draft fan, and the sulfur compounds in the waste gas are removed by adsorption with solid desulfurizer. The waste gas then enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0067] During the treatment process, due to the fluctuation of the inflow index of alkali residue wastewater, the influent COD of the MABR unit fluctuated between 27300 and 34850 mg / L, and the effluent COD was always no higher than 750 mg / L, and the sulfide was no higher than 5 mg / L. During the operation, due to the failure of the air compressor, aeration was forced to stop. In this case, aeration was resumed 4 days later, and the microbial film attached to the aeration membrane had not fallen off. After the aeration was resumed, the treatment effect gradually recovered, proving that the technology of the present invention has good impact resistance.

[0068] Comparative Example 1

[0069] The pH value of the alkali residue wastewater of a petrochemical enterprise is 13.7, the COD is 235800 mg / L, and the sulfide is 13960 mg / L. The method provided by the present invention is used for treatment. The treatment process is as follows: first, the alkali residue wastewater is neutralized to pH=8.7 with 92wt% concentrated sulfuric acid; the neutralized alkali residue wastewater is diluted with the effluent of the intermediate sedimentation tank with a COD of 230 mg / L, and the COD of the alkali residue wastewater after dilution is 30000 mg / L and the sulfide content is 1598 mg / L; the diluted alkali residue wastewater enters the traditional bubbling aeration biochemical tank for treatment, and the dissolution Oxygen is controlled at 2.0-4.0, and pH is controlled at 6.0-9.0. If pH is less than 5.0 during the biochemical process, an appropriate amount of alkali solution is used for neutralization. The biochemical hydraulic retention time is 5 days. After treatment, the COD of the effluent from the sedimentation tank is 987 mg / L and the sulfide content is 18.9 mg / L. The waste gas generated during the above acidification, dilution and biochemical processes enters the absorption tower and desulfurization tank in turn through the induced draft fan. Alkaline absorption liquid and solid desulfurizer are used to remove sulfur-containing compounds in the waste gas respectively. The waste gas then enters the catalytic combustion system for purification and is discharged into the air after meeting the standards.

[0070] During the treatment process, due to the fluctuation of the inflow index of alkali residue wastewater, the COD of the biochemical pool inlet fluctuated between 27550 and 33370 mg / L, the effluent COD once increased to 2730 mg / L, and the sulfide increased to 53 mg / L, which also impacted the waste gas treatment device and affected the stable compliance of the waste gas. We had to control the effluent index and reduce the impact on the waste gas treatment system by reducing the amount of alkali residue treatment and extending the biochemical retention time. In addition, in order to compare with the biochemical impact resistance of the MABR reactor, aeration was stopped. After about 18 hours, abnormalities were observed in the activated sludge. Aeration was immediately resumed, but the biochemical effect could not be restored.

[0071] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for treating petrochemical alkali residue wastewater, characterized in that: The following steps are involved: (1) adding inorganic acid to the alkaline residue wastewater for neutralization; (2) Adding sewage to dilute the neutralized alkali residue wastewater to reduce its COD value; (3) the diluted alkali residue wastewater is subjected to a first biochemical degradation, wherein the first biochemical degradation treatment system includes a MABR unit; (4) The effluent from the MABR unit enters the sedimentation tank, and the supernatant in the sedimentation tank undergoes a second biochemical degradation.

2. The processing method according to claim 1, characterized in that: The MABR unit includes at least one MABR reactor, and preferably, the MABR reactors are connected in series; preferably, the MABR reactor includes a tank body, a MABR module, an air compression oxygen supply device and a circulation system, the MABR module is arranged in the wastewater in the tank body, and is connected to the air compression oxygen supply device through an air supply pipeline and a control valve, and the circulation system contains a circulation pump to realize the internal circulation of the wastewater in each MABR reactor and the backflow of the activated sludge in the sedimentation tank to each MABR reactor; more preferably, the MABR module is composed of more than two membrane filaments arranged in parallel and a membrane assembly for fixing the membrane filaments.

3. The processing method according to claim 2, characterized in that: When the MABR unit includes more than two MABR reactors, the MABR reactors share one air compression oxygen supply device; and / or the air supply pipeline and control valve of each MABR reactor are connected in parallel, and the aeration pressure of the corresponding MABR module is independently adjusted by each control valve to control each MABR reactor to operate independently in anaerobic mode, anoxic mode or aerobic mode.

4. The processing method according to claim 2 or 3, characterized in that: The membrane fibers are tubular hollow fiber membranes with N2 and O2 separation functions. Preferably, a microbial membrane is attached to and grown on the outer surface of the hollow fiber membrane; preferably, the hollow fiber membrane has the function of permeating O2 and blocking N2.

5. The processing method according to any one of claims 2 to 4, characterized in that: The membrane fibers include an aeration membrane, a biological membrane and a boundary layer from the inside to the outside in radial direction; preferably, the biological membrane includes an aerobic zone, an anoxic zone and an anaerobic zone from the inside to the outside.

6. The processing method according to any one of claims 3 to 5, characterized in that: The dissolved oxygen in the anaerobic mode is 0-0.2 mg / L, and / or the dissolved oxygen in the anoxic mode is 0.2-0.5 mg / L, and / or the dissolved oxygen in the aerobic mode is 1.0-4.0 mg / L.

7. The processing method according to any one of claims 1 to 6, characterized in that: The pH value of the alkali residue wastewater after neutralization in step (1) is 7.0-9.0, and / or the inorganic acid is sulfuric acid.

8. The processing method according to any one of claims 1 to 7, characterized in that: The COD of the alkali residue wastewater after dilution in step (2) is not higher than 30000 mg / L; and / or in step (4), the second biochemical degradation is carried out in a conventional biochemical pool; and / or the COD value of the alkali residue wastewater is 5000-500000 mg / L, preferably 9000-300000 mg / L, the pH value is above 12, preferably above 12.5, and the sulfide is 5000-50000 mg / L, preferably 7000-30000 mg / L.

9. The processing method according to any one of claims 1 to 8, characterized in that: In step (3), the hydraulic retention time of the diluted alkali slag wastewater in the MABR unit is 1 to 5 days; and / or in step (3), the COD of the wastewater after the first biochemical degradation is ≤800 mg / L and the sulfide concentration is ≤10 mg / L.

10. The processing method according to any one of claims 1 to 9, characterized in that: It also includes step (5): the exhaust gas generated in steps (1)-(4) enters the exhaust gas treatment unit for purification and then meets the emission standards; preferably, the exhaust gas treatment unit includes at least one of an absorption module, an adsorption module, and a catalytic combustion module.

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