High-sulfate-content BDO wastewater treatment process

Abstract

The invention provides a BDO (1, 4-butanediol) wastewater treatment process with high sulfate content, which comprises the following steps: carrying out electrochemical oxidation treatment on BDO (1, 4-butanediol) wastewater with high sulfate content; introducing the obtained BDO wastewater into an anaerobic reaction device for anaerobic reaction to reduce sulfate ions into hydrogen sulfide and oxidize organic matters to reduce COD (Chemical Oxygen Demand); effluent sequentially flows back to the circulating desulfurization device and the air floatation device; carrying out aeration treatment in the circulating desulfurization device so as to oxidize hydrogen sulfide into elemental sulfur; elemental sulfur is recycled in the air flotation device, and part of effluent of the air flotation device and part of effluent of the anaerobic reaction device flow back to inlet water of the anaerobic reaction device; part of effluent of the air floatation device and part of effluent of the anaerobic reaction device are combined and then are sequentially introduced into an aerobic activated sludge tank with a membrane bioreactor and an ozone catalytic oxidation tank. Effluent can enter a subsequent ultrafiltration reverse osmosis membrane system to be purified, and water produced by the membrane system is recycled as reclaimed water.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental engineering and high-concentration refractory wastewater treatment technology, and particularly relates to a BDO wastewater treatment process with high sulfate content. BACKGROUND

[0002] 1,4-butanediol (BDO) is an important organic fine chemical raw material, which is widely used in medicine, chemical industry, textile, papermaking, automobile and daily chemical industry. The commonly used BDO production process is acetylene aldehyde method (Reppe), which uses acetylene and formaldehyde as raw materials, copper / bismuth as catalyst, synthesizes intermediate product 1,4-butynediol, and then hydrogenates to generate BDO. In the production process, because concentrated sulfuric acid is used for resin regeneration, the generated wastewater has the characteristics of high COD content and refractory, high sulfate content and high toxicity, and is difficult to treat.

[0003] At present, the commonly used treatment process for BDO wastewater is the combined process of anaerobic treatment and aerobic treatment. The process for treating BDO wastewater has the problem that the effluent COD does not meet the standard. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a BDO wastewater treatment process with high sulfate content.

[0005] In order to achieve the above purpose, the present application provides a BDO wastewater treatment process with high sulfate content, which comprises the following steps:

[0006] Providing BDO wastewater with high sulfate content; in the BDO wastewater, the concentration of sulfate ions is 5000 mg / L or more; the COD concentration is 3000-5000 mg / L; BOD5 / COD≤0.1;

[0007] Passing the BDO wastewater into an electrochemical oxidation reactor for electrochemical oxidation treatment, so that the organic matter in the BDO wastewater is oxidized and broken;

[0008] Providing an anaerobic reaction device with a circulating desulfurization device and a flotation device; wherein the anaerobic reaction device is provided with an effluent backflow device, and the circulating desulfurization device and the flotation device are sequentially arranged at the effluent end of the effluent backflow device;

[0009] The BDO wastewater treated by electrochemical oxidation is introduced into the anaerobic reaction device for anaerobic reaction, so as to reduce sulfate ions into hydrogen sulfide and oxidize organic matters to reduce COD; the effluent of the effluent return device is sequentially returned to the circulating desulfurization device and the air flotation device; wherein, the air flotation device is subjected to aeration treatment to oxidize hydrogen sulfide into elemental sulfur; part of the effluent of the air flotation device and part of the effluent of the anaerobic reaction device are returned to the water inlet of the anaerobic reaction device;

[0010] Part of the effluent of the air flotation device and part of the effluent of the anaerobic reaction device are sequentially introduced into an aerobic activated sludge tank with a membrane bioreactor and an ozone catalytic oxidation tank.

[0011] In some embodiments, the anaerobic reaction device is an anaerobic tower; the circulating desulfurization device is a circulating desulfurization tower; wherein, in the circulating desulfurization tower, the aeration intensity is 5% to 10% of the volume fraction of air introduced per cubic meter of water, and the residence time per cubic meter of water is 0.3-3h.

[0012] In some embodiments, the influent load of the anaerobic tower is 1-4g·COD / L / d; the BDO wastewater treatment process further comprises: adding trace elements to the water inlet of the anaerobic tower, the trace elements including MgSO410-100mg / L, ZnSO4·7H2O 1-20mg / L, FeCl2·4H2O 10-100mg / L, H3BO3 0.1-10mg / L, NiCl2·6H2O 10-100mg / L, MnSO4·H2O 10-100mg / L, CoCl2·6H2O 10-100mg / L and Na2MoO4·2H2O 0.1-5mg / L.

[0013] In some embodiments, in the electrochemical reactor, the anode is a graphite electrode, a ruthenium-titanium electrode or a ruthenium-iridium-titanium electrode; the cathode is a stainless steel electrode or a graphite electrode.

[0014] In some embodiments, in the electrochemical reactor, the anode is a ruthenium-iridium-titanium electrode, and the cathode is a stainless steel electrode; the applied electric field voltage is 10-20V; the spacing between the plate electrodes is 20-40cm; the reaction residence time is 1.5-2h; the BDO wastewater is BDO wastewater after pH adjustment, and the pH of the BDO wastewater is neutral.

[0015] In some embodiments, the dissolved oxygen concentration in the aerobic activated sludge tank is 3-8 mg / L; the BDO wastewater treatment process further comprises: adding ammonium salt and phosphorus salt in the aerobic activated sludge tank to make the C:N:P ratio in the aerobic activated sludge tank be (50-150):5:1; adding trace elements in the aerobic activated sludge tank, the trace elements comprising CaCl21-5 mg / L, EDTA 1-20 mg / L, CuCl2·2H2O 1-10 mg / L, H3BO30.001-0.1 mg / L, FeSO4·7H2O 0.1-1 mg / L, MnSO4·H2O 0.1-1 mg / L, MgSO4·7H2O 1-10 mg / L, and ZnSO4·7H2O 0.1-0.5 mg / L.

[0016] In some embodiments, the size of the ozone bubbles in the ozone catalytic oxidation tank is 70-100 nm; the gas-liquid volume ratio is 0.15-0.2; the ozone catalyst is an aluminum oxide or iron-cerium activated carbon composite catalyst; and the ozone dosage satisfies the mass ratio of O3 to COD being (1.25-2):1.

[0017] In some embodiments, the BDO wastewater treatment process further comprises: passing the membrane bioreactor effluent into an in-situ oxidation-adsorption tank, adjusting the pH to be 3-6, adding a compounded oxidant and a catalyst to oxidize and modify the residual refractory organic matter and to adsorb the residual refractory organic matter; the mass ratio of the catalyst added per liter of the membrane bioreactor effluent to the COD of per liter of the membrane bioreactor effluent is (0.05-2):1; and the mass ratio of the compounded oxidant to the catalyst is (1-2):1.

[0018] In some embodiments, the compounded oxidant is composed of H2O2, hypochlorite and persulfate.

[0019] In some embodiments, the type of the membrane in the membrane bioreactor is a hollow fiber membrane; the material of the membrane is polytetrafluoroethylene membrane; the pore size of the membrane is 0.1-0.4 μm; and the water feeding mode is continuous water feeding.

[0020] As can be seen from the above, the BDO wastewater treatment process with high sulfate content provided by the application degrades macromolecular organic matter in BDO wastewater into small molecular organic matter by the method of electrochemical oxidation, thereby improving the biodegradability of the BDO wastewater; then COD and sulfate are simultaneously removed by using anaerobic biological treatment and anaerobic effluent recycling stripping measures, the anaerobic effluent is further treated by using aerobic activated sludge and membrane filtration processes to remove COD, and finally, ozone catalytic oxidation process is used to deeply remove COD and decolorize, thereby achieving the wastewater COD discharge standard. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the application or the related art, the drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0022] Figure 1 A flowchart of a BDO wastewater treatment process with high sulfate content according to an embodiment of the application;

[0023] Figure 2 Another flowchart of a BDO wastewater treatment process with high sulfate content according to an embodiment of the application. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to specific embodiments and drawings.

[0025] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the application should be understood as the general meaning understood by those skilled in the art to which the embodiments belong. The terms "first", "second" and the like used in the embodiments of the application do not represent any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and the like mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and the like do not mean physical or mechanical connection, but can include electrical connection, whether direct or indirect. The terms "up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0026] Compared with general high-concentration sulfate wastewater, such as pharmaceutical or food processing wastewater, the BDO production wastewater does not contain chloride and other substances, and the organic matter is mostly large-molecule organic matter that is difficult to degrade, and the COD content is high, usually greater than 3000 mg / L, for example, about 5000 mg / L. The concentration of sulfate ions is greater than 5000 mg / L, i.e. more than 5000 mg / L. The value of BOD5 / COD is usually less than 0.1. At present, the commonly used treatment process for BDO wastewater is a combined process of anaerobic treatment and aerobic treatment, but this process has the problem of being unable to stably meet the standards when treating BDO wastewater.

[0027] The challenges in treating BDO wastewater lie in the following aspects: 1. The organic matter in the wastewater is mostly large molecules (600-3000 Da), which are difficult to biodegrade. Traditional anaerobic and aerobic biological processes have low removal rates. Pretreatment measures are needed to break down the large organic molecules into smaller molecules before biological treatment can be applied. 2. The wastewater has high COD and sulfate content, with a COD / sulfate ratio <1. In this case, the anaerobic system mainly degrades organic matter through sulfate reduction, while also producing hydrogen sulfide. However, when the sulfate content in the wastewater is too high, the free H2S produced by anaerobic processes can enter the anaerobic bacteria cells, inhibiting methanogens (MA), acidogens, and even sulfate-reducing bacteria in the anaerobic system. Therefore, excessively high free H2S concentrations will affect the load and treatment efficiency of the anaerobic reaction. Furthermore, when free H2S dissolves in the effluent of the anaerobic system, it manifests as COD in the effluent, thus increasing the COD content in the anaerobic reactor effluent and reducing the COD removal rate of the anaerobic reactor. Therefore, for wastewater with high levels of recalcitrant organic matter and high sulfate content, the operating efficiency of anaerobic reactors is low, which in turn affects the subsequent degradation of organic matter by aerobic biological processes, ultimately leading to low organic matter removal efficiency and substandard effluent COD.

[0028] Based on this, this application provides a BDO wastewater treatment process with high sulfate content. Electrochemical oxidation pretreatment is used to oxidize and modify the organic matter in the raw water (i.e., the original BDO wastewater), improving its biodegradability. Then, an anaerobic biological process of anaerobic biological treatment followed by circulating stripping is used to simultaneously remove COD and sulfate from the wastewater, reducing the organic load on the subsequent aerobic biological system and improving the effluent quality of the subsequent MBR system. Finally, in-situ oxidation-adsorption and ozone oxidation processes are used for deep COD removal, achieving stable COD compliance in the effluent. Actual engineering verification shows that the high sulfate content BDO wastewater treatment process of this application produces a COD concentration of less than 60 mg / L in the treated wastewater system, allowing it to enter the subsequent ultrafiltration reverse osmosis membrane system for purification, resulting in purified water for recycling as wastewater. Therefore, the high sulfate content BDO wastewater treatment process of this application can, to a certain extent, solve the problem of substandard effluent COD in commonly used BDO wastewater treatment processes.

[0029] This invention provides a BDO wastewater treatment process with high sulfate content, see [link / reference]. Figure 1 The BDO wastewater treatment process with high sulfate content may include:

[0030] S100, providing BDO wastewater with high sulfate content; the concentration of sulfate ions in the BDO wastewater is greater than 5000 mg / L, i.e. 5000 mg / L or more; the COD concentration is 3000-5000 mg / L; and BOD5 / COD≤0.1;

[0031] S200, passing the BDO wastewater into an electrochemical oxidation reactor for electrochemical oxidation treatment, so as to cause the organic matter in the BDO wastewater to be oxidized and broken;

[0032] S300, providing an anaerobic reaction device with a circulating desulfurization device and a flotation device; the anaerobic reaction device is provided with a water outlet backflow device, and the circulating desulfurization device and the flotation device are sequentially arranged at the water outlet end of the water outlet backflow device;

[0033] S400, passing the BDO wastewater treated by electrochemical oxidation into the anaerobic reaction device for anaerobic reaction, so as to reduce sulfate ions to hydrogen sulfide and oxidize organic matter to reduce COD; the water outlet of the water outlet backflow device is sequentially backflowed into the circulating desulfurization device and the flotation device; in the circulating desulfurization device, hydrogen sulfide is oxidized to sulfur element by aeration treatment; in the flotation device, sulfur element is recovered, and part of the water outlet of the flotation device and part of the water outlet of the anaerobic reaction device are backflowed into the water inlet of the anaerobic reaction device;

[0034] S500, sequentially passing part of the water outlet of the flotation device and part of the water outlet of the anaerobic reaction device into an aerobic activated sludge tank with a membrane bioreactor and an ozone catalytic oxidation tank.

[0035] The BDO wastewater with high sulfate content provided by the embodiment of the present application is treated by the method of electrochemical oxidation, so that the macromolecular organic matter in the BDO wastewater is degraded into small molecular organic matter, and the biodegradability of the BDO wastewater is improved; then, the COD and sulfate are synchronously removed by anaerobic biological treatment and anaerobic water outlet circulation stripping measures, the COD is further removed by aerobic activated sludge and membrane filtration processes, and finally, the COD is deeply removed and decolorized by the ozone catalytic oxidation process, so that the wastewater COD meets the discharge standard.

[0036] In some embodiments, in step S100, the BDO wastewater with high sulfate content is usually alkaline, and needs to be adjusted in pH by adding sulfuric acid to avoid affecting the activity of anaerobic bacteria and aerobic bacteria. The concentration of sulfate ions in the wastewater after adjusting the pH value to neutral is usually greater than 8000 mg / L, for example, it can be 8000-9000 mg / L; the COD concentration can be greater than 3000 mg / L, for example, it can be 3000-5000 mg / L, for example, it is about 5000 mg / L; and BOD5 / COD≤0.1.

[0037] In some embodiments, in step S200, the electrochemical oxidation reactor can be an electrochemical oxidation tank. After the BDO wastewater is introduced into the electrochemical oxidation tank, an external voltage can be applied to oxidize and modify the macromolecular organic matter in the BDO wastewater at the anode of the electrode into small-molecule organic matter, thereby improving the biodegradability of the BDO wastewater.

[0038] By using the electrochemical oxidation method, the high-sulfate-content BDO production wastewater can be efficiently oxidized and broken into small-molecule organic matter, and no sludge is produced. This method can avoid the problems of secondary pollution and increased treatment cost caused by the large amount of sludge produced by Fenton oxidation, and can also avoid the problems of low efficiency and high cost of ozone oxidation. Therefore, compared with other oxidation technologies such as Fenton or ozone oxidation, the electrochemical oxidation method has high application potential for pretreating the macromolecular organic matter in the BDO production wastewater.

[0039] In some embodiments, in the electrochemical reactor, the anode can be a graphite electrode, a ruthenium-titanium electrode, or a ruthenium-iridium-titanium electrode. The cathode can be a stainless steel electrode or a graphite electrode. The graphite electrode has the characteristics of low cost, and the ruthenium-titanium electrode or the ruthenium-iridium-titanium electrode can catalyze the anodic oxidation reaction and improve the reaction efficiency.

[0040] In some embodiments, the anode can be a ruthenium-iridium-titanium electrode, and the cathode can be a stainless steel electrode. Correspondingly, before the high-sulfate-content BDO wastewater is introduced into the electrochemical oxidation reactor, the original high-sulfate-content BDO wastewater can be homogenized in a homogenization tank, and acid can be added to adjust the pH of the high-sulfate-content BDO wastewater to neutral, so as to avoid corrosion of the stainless steel electrode. That is, the BDO wastewater is the BDO wastewater after pH adjustment, and the pH of the BDO wastewater is neutral, for example, the pH is 7-8. In the electrochemical oxidation reactor, the applied electric field voltage can be 10-20V, for example, it can be 10V, 11V, 12V, 13V, 14V, 14.5V, 15V, 15.5V, 16V, 17V, 18V, 19V, or 20V. The plate electrode spacing can be 20-40cm, for example, it can be 20cm, 20.5cm, 21cm, 22cm, 24cm, 26cm, 28cm, 30cm, 32cm, 34cm, 36cm, 38cm, or 40cm; the reaction residence time can be 1.5-2.2h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, or 2.2h.

[0041] In some embodiments, the applied electric field voltage can be about 15 V, for example, 14.5 V-15.5 V. The plate electrode spacing can be about 20 cm, for example, 20-20.5 cm. The reaction residence time can be about 2 h, for example, 1.8 h-2.2 h. In this way, better electrochemical oxidation efficiency can be achieved while taking into account the cost.

[0042] In some embodiments, in step S300, the anaerobic reactor generally has methanogens (MA), acidogens, and anaerobic bacteria such as sulfate-reducing bacteria. It should be understood that before the BDO wastewater treated by electrochemical oxidation is treated, the BDO wastewater is generally used to domesticate and cultivate the methanogens (MA), acidogens, and anaerobic bacteria such as sulfate-reducing bacteria in the anaerobic reactor, so that the methanogens (MA), acidogens, and anaerobic bacteria such as sulfate-reducing bacteria can adapt to the BDO wastewater. The anaerobic reactor can be an anaerobic tower. The anaerobic tower is generally configured as an upflow anaerobic sludge bed (UASB) or an improved configuration thereof (such as an expanded granular sludge bed (EGSB) and an internal circulation anaerobic reactor (IC)), which is integrated with a three-phase separator at the top, and the anaerobic tower is configured to have water flowing in from the bottom and out from the top. The three-phase separator can be arranged at the top end of the anaerobic tower, and the water outlet reflux device can be arranged at the lower part of the three-phase separator. The circulating desulfurization device can be a circulating desulfurization tower, the water flow is from top to bottom, and the aeration direction can be from bottom to top. The air flotation device can be an air flotation machine.

[0043] In some embodiments, in step S400, in the anaerobic tower, the methanogens (MA), acidogens, and anaerobic bacteria such as sulfate-reducing bacteria degrade the organic matter in the BDO wastewater. During the degradation of the organic matter, most of the sulfate is reduced to H2S. The main reaction mechanism is that SO4 2-As the final electron acceptor, a small part of the sulfate is used by microorganisms for synthesis of cellular components (i.e. assimilatory sulfate reduction), and a large part of the sulfate is released as H2S outside the cell (termed dissimilatory sulfate reduction). The influent load of the anaerobic tower can be 1-4 g·COD / L / d, for example, can be 1 g·COD / L / d, 1.8 g·COD / L / d, 2 g·COD / L / d, 2.2 g·COD / L / d, 3 g·COD / L / d or 4 g·COD / L / d. The BDO wastewater treatment process can further comprise: adding trace elements in the influent of the anaerobic tower. The trace elements can include MgSO410-100 mg / L, ZnSO4·7H2O 1-20 mg / L, FeCl2·4H2O 10-100 mg / L, H3BO3 0.1-10 mg / L, NiCl2·6H2O 10-100 mg / L, MnSO4·H2O 10-100 mg / L, CoCl2·6H2O 10-100 mg / L and Na2MoO4·2H2O 0.1-5 mg / L. In this way, by adding trace elements, the elemental composition of the BDO wastewater in the anaerobic tower can be adjusted, the anaerobic bacteria in the anaerobic tower can grow well, and have good metabolic activity, thereby improving the biochemical treatment effect of the BDO wastewater in the anaerobic tower.

[0044] In some embodiments, the influent load of the anaerobic tower can be 1.8-2.2 g·COD / L / d. The trace elements can include MgSO4 74 mg / L, ZnSO4·7H2O 10 mg / L, FeCl2·4H2O 84 mg / L, H3BO3 1.0 mg / L, NiCl2·6H2O 20 mg / L, MnSO4·H2O 36 mg / L, CoCl2·6H2O 20 mg / L and Na2MoO4·2H2O 1.0 mg / L. In this way, the anaerobic bacteria in the anaerobic tower can grow better, and have better metabolic activity, thereby further improving the biochemical treatment effect of the BDO wastewater in the anaerobic tower.

[0045] In some embodiments, in step S400, in the circulating desulfurization tower, mainly aeration treatment is carried out, which can oxidize the hydrogen sulfide produced by the reduction of sulfate in the anaerobic tower into elemental sulfur. In the air flotation device, elemental sulfur is mainly recovered by air flotation. In the circulating desulfurization tower, the aeration intensity can be 5%-10% (i.e. 0.05-0.1 m 3 air / m 3The concentration of the BDO wastewater in the water can be 5% to 10%, for example, 5%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, or 10%. The residence time of the water per cubic meter (i.e., the circulating stripping contact time) can be 0.3 to 3 hours, for example, 0.3 hours, 0.5 hours, 0.7 hours, 0.9 hours, 1 hour, 0.3 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3.0 hours. In this way, the concentration of sulfides (free hydrogen sulfide) in the effluent (e.g., the effluent of the flotation device) can be reduced. Part of the effluent wastewater is then recirculated into the influent of the anaerobic tower, and part of the effluent wastewater is passed into the subsequent aerobic activated sludge tank. The recirculation of part of the flotation effluent into the influent of the anaerobic tower can both dilute the COD and sulfate concentrations of the influent of the anaerobic tower and reduce the inhibition of the sulfate-reducing bacteria, methanogens (MA), and acidogens by free hydrogen sulfide in the anaerobic tower, thereby allowing the efficient degradation of organic matter in the anaerobic tower by sulfate reduction and methanogenesis. At the same time, the recirculation of the effluent can also improve the mixing uniformity of the BDO wastewater and the anaerobic bacteria in the anaerobic tower, thereby improving the reaction efficiency of the microorganisms in the anaerobic tower.

[0046] In some embodiments, the aeration intensity can be about 6.5% of the volume fraction of air introduced per cubic meter of water, for example, 6% to 7%. The residence time of the water per cubic meter (i.e., the circulating stripping contact time) can be about 1.2 hours, for example, 1 hour to 1.4 hours. In this way, the efficiency of the oxidation of hydrogen sulfide to elemental sulfur can be improved.

[0047] In some embodiments, an intermediate tank can be provided between the anaerobic reaction device and the aerobic activated sludge tank. The intermediate tank can be used to store part of the effluent of the three-phase separator of the anaerobic reaction device and part of the effluent of the flotation device. The intermediate tank serves as a water quantity and quality adjustment tank, and the water therein can be partially recirculated into the influent of the anaerobic reaction device and partially passed into the aerobic activated sludge tank.

[0048] In some embodiments, in step S500, the aerobic activated sludge tank generally contains aerobic microorganisms. The aerobic microorganisms can further mineralize the residual organic matter in the effluent of the anaerobic tower into carbon dioxide, thereby completely removing the residual biodegradable organic matter in the BDO wastewater. It should be understood that, before the BDO wastewater treated by the anaerobic tower is treated, the BDO wastewater is generally used to acclimate and cultivate the aerobic microorganisms (e.g., aerobic bacteria) in the activated sludge in the aerobic activated sludge tank, so that the aerobic microorganisms (e.g., aerobic bacteria) can adapt to the BDO wastewater.

[0049] In some embodiments, the dissolved oxygen concentration in the aerobic activated sludge tank can be 3-8 mg / L, for example, can be 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L or 8 mg / L. The BDO wastewater treatment process further comprises: adding ammonium salt and phosphorus salt in the aerobic activated sludge tank to make the C:N:P ratio in the aerobic activated sludge tank be (50-150):5:1, for example, can be 50:5:1, 60:5:1, 70:5:1, 80:5:1, 90:5:1, 100:5:1, 110:5:1, 115:5:1, 120:5:1, 125:5:1, 130:5:1, 140:5:1 or 150:5:1; adding trace elements in the aerobic activated sludge tank, the trace elements can include CaCl2 1-5 mg / L, EDTA 1-20 mg / L, CuCl2·2H2O 1-10 mg / L, H3BO3 0.001-0.1 mg / L, FeSO4·7H2O 0.1-1 mg / L, MnSO4·H2O 0.1-1 mg / L, MgSO4·7H2O 1-10 mg / L and ZnSO4·7H2O 0.1-0.5 mg / L. By adding ammonium salt, phosphorus salt and trace elements, the element composition of BDO wastewater in the aerobic activated sludge tank can be adjusted, the aerobic bacteria in the aerobic activated sludge tank can grow well and have good metabolic activity, thereby improving the biochemical treatment effect of BDO wastewater in the aerobic activated sludge tank.

[0050] In some embodiments, the ammonium salt can be (NH4)2SO4, and the phosphorus salt can be KH2PO4. The C:N:P ratio in the aerobic activated sludge tank can be 120:5:1. The trace elements can be CaCl2 1.5 mg / L, EDTA 10 mg / L, CuCl2·2H2O 1.1 mg / L, H3BO3 0.003 mg / L, FeSO4·7H2O 0.25 mg / L, MnSO4·H2O 0.11 mg / L, MgSO4·7H2O 1.2 mg / L and ZnSO4·7H2O 0.2 mg / L. In this way, the aerobic bacteria in the aerobic activated sludge tank can grow better and have better metabolic activity, thereby further improving the biochemical treatment effect of BDO wastewater in the aerobic activated sludge tank.

[0051] In some embodiments, the mixed liquor of the effluent of the aerobic activated sludge tank is introduced into the MBR (membrane bioreactor) tank through the overflow tank, the colloidal COD is intercepted by the ultrafiltration membrane in the MBR (membrane bioreactor) tank, and the sludge and water are separated to improve the water quality of the biochemical effluent. It can be understood that the MBR (membrane bioreactor) tank is the sedimentation tank of the aerobic activated sludge tank. The effluent COD of the MBR tank is the effluent COD of the aerobic activated sludge tank. The type of membrane in the membrane bioreactor can be flat membrane, hollow fiber membrane or tubular membrane, etc. The material of the membrane can be organic polymer membrane, metal membrane or ceramic membrane, etc. The pore size of the membrane can be 0.1-0.4 μm. The water inlet mode can be continuous water inlet or intermittent water inlet.

[0052] In some embodiments, the type of membrane in the membrane bioreactor can be hollow fiber membrane; the material of the membrane can be polytetrafluoroethylene membrane; the pore size of the membrane can be 0.1-0.4 μm; and the water inlet mode is continuous water inlet. In this way, the colloidal COD can be better intercepted, the sludge and water can be better separated, and the water quality of the biochemical effluent can be better improved.

[0053] In some embodiments, referring to Figure 2 , the BDO wastewater treatment process can further include: introducing the effluent of the membrane bioreactor into the in-situ oxidation-adsorption tank, adjusting the pH to 3-6, and adding a compounded oxidizing agent and a compounded catalyst to oxidize and modify the residual refractory organic matter. It should be understood that the in-situ oxidation-adsorption tank can usually be provided with an adsorbent, which can be iron hydroxide and aluminum hydroxide, etc. The mass ratio of the catalyst added per liter of the effluent of the membrane bioreactor to the COD per liter of the effluent of the membrane bioreactor is (0.05-2):1, which can be 0.05:1, 0.1:1, 0.15:1, 0.175:1, 0.2:1, 0.225:1, 0.25:1, 0.275:1, 0.3:1, 0.325:1, 0.35:1, 0.375:1, 0.4:1, 0.425:1, 0.45:1, 0.475:1, 0.5:1, 1:1, 1.5:1 or 2:1, etc. The mass ratio of the compounded oxidizing agent to the catalyst can be less than 10:1, which can be 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1 or 0.5:1. In this way, the residual refractory organic matter can be oxidized and modified by the oxidizing agent, and the COD can be removed by the adsorption of the native metal hydroxide. After sedimentation and clarification, the sludge can be discharged by the filter press, and the upper clear water can overflow into the subsequent ozone catalytic oxidation tank.

[0054] In some embodiments, the in-situ oxidation-adsorption tank can include two tanks with different functions, one being a reaction tank (adsorption tank) and the other being a precipitation tank. Generally, the reaction tank has an adsorbent, and the compounded oxidant and the compounded catalyst are only added to the reaction tank, and the adsorbent is not arranged in the precipitation tank.

[0055] In some embodiments, the mass ratio of the catalyst added per liter of membrane bioreactor effluent to the COD per liter of membrane bioreactor effluent can be (0.15-0.5):1; and the mass ratio of the compounded oxidant to the catalyst can be (1-2):1. In this way, COD can be better removed.

[0056] In some embodiments, the compounded oxidant can be composed of H2O2, hypochlorite, and persulfate; and the catalyst can be composed of FeSO4, CuSO4, MnSO4, and CoSO4. The molar ratio of H2O2, hypochlorite (ClO - ), and persulfate (S2O8 2- ) in the compounded oxidant can be 1:(0.027-0.456):(0.009-0.143), preferably 1:0.14:0.1. The molar ratio of metal ions Fe 2+ , Cu 2+ , Mn 2+ , and Co 2+ in the catalyst can be 100:(0.475-47.5):(0.201-20.1):(0.500-15.0), preferably 100:5:2.49:2.1. In this way, better oxidation and adsorption effects can be achieved.

[0057] In some embodiments, in the ozone catalytic oxidation tank, the size of the ozone bubbles is 50-120 nm; the gas-liquid volume ratio is 0.1-0.3; the ozone catalyst is iron shavings, alumina, or iron-cerium activated carbon composite catalyst; and the ozone dosage satisfies the mass ratio of O3 to COD being (1-3):1. In this way, the ozone can generate hydroxyl radicals under the action of the catalyst, efficiently oxidize residual refractory organic matter, and reduce the color of the wastewater, and the effluent of the ozone catalytic oxidation tank can be directly discharged into the clear water tank.

[0058] In some embodiments, the size of the ozone bubbles can be 70-100 nm, for example 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm or 100 mm. The gas-liquid volume ratio can be 0.15-0.2, for example 0.15, 0.175 or 0.2. The ozone catalyst can be an iron-cerium activated carbon composite catalyst; the ozone dosage satisfies the mass ratio of O3 to COD is (1.25-2):1, for example 1.25:1, 1.5:1, 1.75:1 or 2:1. In this way, higher catalytic activity can be achieved, and the catalysis of ozone to generate hydroxyl radicals can be better, so that the COD removal efficiency is higher.

[0059] The embodiment of the present application aims at the problem that high sulfate and high refractory organic matter in BDO wastewater are difficult to be effectively treated by conventional biochemical treatment. The wastewater biodegradability is improved by electrochemical oxidation, the anaerobic sulfate reduction is strengthened by anaerobic biochemical treatment and effluent recycling stripping, and the wastewater COD removal rate is improved. The biodegradable organic matter is further removed by aerobic biochemical treatment and MBR. Finally, the refractory biodegradable organic matter is deeply removed by in-situ oxidation-adsorption and ozone catalytic oxidation, so as to realize low-cost discharge of BDO wastewater with high sulfate content. The electrochemical oxidation can improve the biodegradability of BDO wastewater without sludge production. The anaerobic biochemical treatment and effluent recycling stripping can efficiently remove the organic matter in BDO wastewater by sulfate reduction, and the anaerobic inhibition caused by hydrogen sulfide accumulation is avoided, so as to improve the anaerobic biochemical efficiency. The combination of aerobic biochemical treatment and MBR can strengthen the removal of biodegradable COD in BDO wastewater, and maximize the utilization of biochemical process to remove COD at low cost. The in-situ oxidation-adsorption tank and ozone catalytic oxidation process have high efficiency, and can realize stable discharge of wastewater COD while reducing the treatment cost compared with the ozone catalytic oxidation process. The process has the advantages of easy control of operating conditions, stable treatment effect and low running cost, and can be widely used in the BDO industry.

[0060] The technical solutions of the present application will be further described in combination with the specific embodiments.

[0061] In the following examples, the experimental methods are conventional methods unless otherwise specified.

[0062] In the following examples, the test materials used are commercially available from conventional biochemical reagent stores unless otherwise specified.

[0063] Example 1: Treatment of BDO wastewater with high sulfate content

[0064] The experiment is carried out for the wastewater of a BDO production enterprise. The electrochemical oxidation pretreatment experiment is carried out in batch mode. The effective volume of the electrochemical oxidation reactor is 10 L. The voltage of the electrochemical oxidation reactor is controlled by an electrochemical workstation. The pH of the BDO wastewater is 12. The concentration of sulfate ions is 5000 mg / L. The COD is 4000 mg / L. The BOD5 / COD of the wastewater is 0.03.

[0065] Step 1: The BDO wastewater is adjusted to pH 7.5 by adding sulfuric acid. The concentration of sulfate ions in the wastewater after adjusting the pH is 8000 mg / L.

[0066] Step 2: The BDO wastewater after adjusting the pH is added to the electrochemical oxidation reactor. The anode of the electrochemical oxidation is a ruthenium-iridium-titanium electrode. The cathode is a stainless steel electrode. The applied electric field voltage is 15 V. The spacing between the plate electrodes is 20 cm. The reaction time is 2 h. The water temperature is room temperature. After the reaction, the concentrations of sulfate ions, COD, and BOD5 in the wastewater are measured. The concentration of sulfate ions is 7908 mg / L. The COD content is 3872 mg / L. The BOD5 / COD is 0.31.

[0067] Step 3: The BDO wastewater after electrochemical oxidation is re-adjusted to pH 7.5. The wastewater is continuously pumped into an anaerobic tower (i.e., an upflow anaerobic sludge bed (UASB)) for anaerobic fermentation. The anaerobic treatment temperature is controlled at 33-36℃. The organic loading of the anaerobic tower influent is controlled at 2 g·COD / L / d. The trace elements added to the anaerobic tower influent are MgSO4 74 mg / L, ZnSO4·7H2O 10 mg / L, FeCl2·4H2O 84 mg / L, H3BO3 1.0 mg / L, NiCl2·6H2O 20 mg / L, MnSO4·H2O 36 mg / L, CoCl2·6H2O 20 mg / L, and Na2MoO4·2H2O 1.0 mg / L. Part of the anaerobic effluent is pumped into a 1 L circulating desulfurization tower using a peristaltic pump. The contact time is 1.2 h. The air volume per cubic meter of water is about 6.5%. After circulating desulfurization, the wastewater is filtered by a flotation machine (it should be understood that the flotation machine is usually a commercial flotation machine, which does not need to be adjusted and can be used directly with the factory-set parameters). The filtrate is returned to the inlet end. After the anaerobic system runs stably for 3 hydraulic retention times, the concentrations of sulfate and COD in the effluent are measured. The concentration of sulfate is reduced to 6334 mg / L (corresponding to a sulfate removal rate of about 20%). The COD is 1703 mg / L (corresponding to a COD removal rate of about 56%).

[0068] Step 4: The anaerobic effluent is pumped into the simulated aerobic activated sludge tank reactor by using a peristaltic pump, and (NH4)2SO4 and KH2PO4 are added to make the C:N:P ratio in the aerobic activated sludge tank 120:5:1. Trace elements CaCl21.5 mg / L, EDTA 10 mg / L, CuCl2·2H2O 1.1 mg / L, H3BO3 0.003 mg / L, FeSO4·7H2O 0.25 mg / L, MnSO4·H2O 0.11 mg / L, MgSO4·7H2O 1.2 mg / L and ZnSO4·7H2O 0.2 mg / L are also added. The hydraulic retention time is 4 days, and the aerobic activated sludge tank reactor is partially aerated by using an aeration pump to increase the dissolved oxygen concentration; the effluent of the aerobic activated sludge tank reactor is subjected to membrane separation by using a hollow fiber membrane module; the COD of the membrane effluent is measured, and the COD is reduced to 279 mg / L.

[0069] Step 5: In-situ oxidation-adsorption is performed by using the membrane effluent, and the mass ratio of the catalyst to the COD of the MBR effluent per liter is 0.2:1; after the oxidant and the catalyst are added at a ratio of 1:1, the pH is adjusted to 5, and after stirring for 30 min, the pH is adjusted to 7 again, 1 ml / L of PAC and 0.2 ml / L of PAM are added, stirring is performed for 10 min, and then the stirring is stopped, the supernatant is measured after standing and precipitating, and the supernatant COD is reduced to 76 mg / L.

[0070] Step 6: The supernatant of the in-situ oxidation-adsorption after separation and precipitation is pumped into an ozone catalytic oxidation reactor by using a pump, the size of the ozone bubbles is sheared to 70-100 nm by using a Venturi shearing device, the gas-liquid ratio is maintained at 0.17, the ozone catalyst is Fe-Ce / GAC, the catalyst dosage is 100 mg / L, the ozone dosage is controlled to O3:COD = 1.5:1 (mass ratio), and after ozone oxidation for 60 min, the final wastewater COD is measured to be 53 mg / L. It can be seen that the final wastewater COD of the embodiment of the present application is 60 mg / L or less, which can enter the subsequent ultrafiltration reverse osmosis membrane system for purification, and the water produced by the membrane system is recycled as reclaimed water.

[0071] Example 2: Treatment of BDO wastewater with high sulfate content

[0072] The difference from Example 1 is that the ozone catalyst in the ozone catalytic oxidation tank in Step 6 is alumina, and the other steps are the same as those in Example 1. That is, the catalyst is changed when the ozone catalytic oxidation tank is treated.

[0073] Experimental results: The COD of the ozone catalytic oxidation effluent is 58 mg / L. It can be seen that the final wastewater COD of the embodiment of the present application is 60 or less, which can enter the subsequent ultrafiltration reverse osmosis membrane system for purification, and the water produced by the membrane system is recycled as reclaimed water.

[0074] Example 1A High Sulfate Content BDO Wastewater Treatment

[0075] The difference between Example 1 and Comparative Example 1A is that step 2 is not performed, and the other steps are the same as Example 1. That is, the electrochemical oxidation treatment is not performed.

[0076] Experimental results: After anaerobic biotreatment, the concentration of sulfate ions was 7400 mg / L, and the COD was 3700 mg / L. The effluent COD of the aerobic activated sludge tank reactor (i.e., the membrane effluent COD) was 3124 mg / L. The effluent COD after in-situ oxidation-adsorption was 1668 mg / L, and the effluent of the ozone catalytic oxidation reactor (i.e., the final effluent COD) was 1505 mg / L.

[0077] Result analysis: Comparing Example 1 and Comparative Example 1A, it can be seen that when the BDO wastewater is not subjected to electrochemical oxidation and is directly subjected to anaerobic biotreatment, there is no significant removal of sulfate and COD in the BDO wastewater. The subsequent aerobic activated sludge tank reactor and MBR also cannot well remove the COD. In-situ oxidation-adsorption and ozone catalytic oxidation also cannot well remove the COD. Therefore, directly subjecting the BDO wastewater to anaerobic treatment, the anaerobic microorganisms cannot hydrolyze the macromolecular organic matter therein into small molecular acids, so that the anaerobic methane production and anaerobic sulfate reduction cannot be normally started. Even if subsequent processes such as the aerobic activated sludge tank reactor, MBR, in-situ oxidation-adsorption, and ozone catalytic oxidation are superimposed, the COD removal effect is limited, and the requirement of entering the subsequent ultrafiltration reverse osmosis membrane system cannot be met. Generally, the requirement of entering the ultrafiltration reverse osmosis membrane system is that the final wastewater COD is below 60 mg / L.

[0078] Example 1B High Sulfate Content BDO Wastewater Treatment

[0079] The difference between Example 1 and Comparative Example 1B is that trace elements are not added to the influent of step 3, and the other steps are the same as Example 1. That is, trace elements are not added to the influent of the anaerobic tower.

[0080] Experimental results: After anaerobic biotreatment, the concentration of sulfate ions was 6100 mg / L, and the COD was 2930 mg / L. The effluent COD of the aerobic activated sludge tank reactor (i.e., the membrane effluent COD) was 921 mg / L. The effluent COD after in-situ oxidation-adsorption was 418 mg / L, and the effluent of the ozone catalytic oxidation reactor (i.e., the final effluent COD) was 400 mg / L.

[0081] Results analysis: By comparing Example 1 with Comparative Example 1B, it can be seen that when trace elements are not added to the anaerobic tower water, the removal effect of sulfate ions and COD after anaerobic biodegradation is poor. The subsequent aerobic activated sludge tank reactor and MBR also cannot well remove COD. In-situ oxidation-adsorption and ozone catalytic oxidation also cannot well remove COD. Therefore, when anaerobic treatment is directly used for BDO wastewater, the nutritional needs of anaerobic microorganisms cannot be met, resulting in low activity and weak sulfate reduction. Even if subsequent processes such as aerobic activated sludge tank reactor, MBR, in-situ oxidation-adsorption, and ozone catalytic oxidation are superimposed, the COD removal effect is limited, and the demand for entering the subsequent ultrafiltration reverse osmosis membrane system cannot be met.

[0082] Comparative Example 1C: High-sulfate-content BDO wastewater treatment

[0083] The difference from Example 1 is only that the step 3 anaerobic tower is not provided with a circulating desulfurization tower and a flotation machine, and the other steps are the same as Example 1. That is, no water circulation stripping treatment is performed during anaerobic treatment.

[0084] Experimental results: After anaerobic biodegradation, the concentration of sulfate ions is 7000 mg / L, and the COD is 3400 mg / L. The COD of the effluent of the aerobic activated sludge tank reactor (i.e., the membrane effluent COD) is 1024 mg / L. The COD of the effluent after in-situ oxidation-adsorption is 568 mg / L, and the COD of the effluent of the ozone catalytic oxidation reactor (i.e., the final effluent COD) is 565 mg / L.

[0085] Results analysis: By comparing Comparative Example 1C with Example 1, it can be seen that when no water circulation stripping treatment is performed during anaerobic treatment, the removal effect of sulfate and COD is poor. The subsequent aerobic activated sludge tank reactor and MBR also cannot well remove COD. In-situ oxidation-adsorption and ozone catalytic oxidation also cannot well remove COD. Therefore, when no water circulation stripping treatment is performed during anaerobic treatment, a large amount of H2S is produced by sulfate-reducing bacteria during the anaerobic biodegradation process, which inhibits methanogenic bacteria and sulfate-reducing bacteria, resulting in the inhibition of sulfate reduction itself. Anaerobic microorganisms cannot hydrolyze it into small-molecule acids, so that anaerobic methanogenesis and anaerobic sulfate reduction cannot be normally started. Even if subsequent processes such as aerobic activated sludge tank reactor, MBR, in-situ oxidation-adsorption, and ozone catalytic oxidation are superimposed, the COD removal effect is limited, and the demand for entering the subsequent ultrafiltration reverse osmosis membrane system cannot be met.

[0086] Comparative Example 1D: High-sulfate-content BDO wastewater treatment

[0087] The difference from Example 1 is only that the trace elements and nutrient solution are not added in the influent in the step 4 aerobic activated sludge treatment stage, and other steps are the same as Example 1. That is, during the aerobic treatment, the trace elements and nutrient solution are not added.

[0088] The experimental results: After running for 2 hydraulic retention times, the aerobic activated sludge changes from brown to grayish white, and the COD removal rate decreases. After running for 3 hydraulic retention times, the effluent COD of the aerobic activated sludge tank is 1024 mg / L, and the MBR effluent COD (i.e. membrane effluent COD) increases to 897 mg / L.

[0089] The result analysis: The normal growth and metabolism of aerobic activated sludge microorganisms requires balanced nutrition such as nitrogen, phosphorus and trace elements. However, BDO wastewater is pure chemical wastewater, and the wastewater lacks the above nutrients. If nitrogen, phosphorus and trace elements are not added for a long time or the amount is insufficient, the activated sludge microorganisms will gradually die, resulting in changes in the appearance of the sludge and loss of COD removal activity. The difference between the effluent COD of the aerobic activated sludge tank and the MBR effluent COD is only 30-50 mg / L. The difference between the effluent COD of the aerobic activated sludge tank of Comparative Example 1D and the MBR effluent COD is significantly greater than this value. It can be seen that when trace elements are not added in the aerobic activated sludge treatment stage and direct aerobic biochemical treatment is performed, the aerobic activated sludge cannot continue its normal metabolism, i.e. it cannot stably treat BDO wastewater. It should be understood that when the aerobic activated sludge tank reactor and the MBR cannot well remove COD, the subsequent in-situ oxidation-adsorption and ozone catalytic oxidation have limited COD removal effect even if the reaction time is adjusted, and cannot meet the requirements of the subsequent ultrafiltration reverse osmosis membrane system.

[0090] BDO wastewater treatment with high sulfate salt content in Comparative Example 1E

[0091] The difference from Example 1 is only that no oxidant and catalyst are added in step 5, and other steps are the same as Example 1. That is, no oxidant and catalyst are added during in-situ oxidation-adsorption treatment.

[0092] The experimental results: After in-situ oxidation-adsorption, the effluent COD is 270 mg / L.

[0093] The result analysis: By comparing Comparative Example 1E with Example 1, it can be seen that when no oxidant and catalyst are added in the in-situ oxidation-adsorption tank, the COD removal effect is poor. It should be understood that when the in-situ oxidation-adsorption tank cannot well remove COD, the subsequent ozone catalytic oxidation has limited COD removal effect even if the reaction time is adjusted, and cannot meet the requirements of the subsequent ultrafiltration reverse osmosis membrane system.

[0094] BDO wastewater treatment with high sulfate salt content in Comparative Example 1F

[0095] The difference from Example 1 is that the ratio of oxidant to catalyst in step 5 is 3.5:1, and other steps are the same as Example 1. That is, the in-situ oxidation-adsorption treatment increases the ratio of oxidant to catalyst.

[0096] Experimental results: After testing, the effluent COD after in-situ oxidation-adsorption is 475 mg / L.

[0097] Result analysis: Comparing Example 1 with Comparative Example 1F, it can be seen that when the ratio of oxidant to catalyst exceeds the ratio of the present application, the effluent COD after in-situ oxidation-adsorption is higher than the MBR effluent COD. Therefore, when the ratio of oxidant to catalyst exceeds the ratio of the present application, the catalytic effect will be reduced. This may be due to insufficient catalyst addition, incomplete reaction of added oxidant, and residual catalyst contributing to COD, thereby causing the effluent COD after in-situ oxidation-adsorption to increase. It should be understood that when the in-situ oxidation-adsorption tank cannot well remove COD, subsequent adjustment of the reaction time of ozone catalytic oxidation has limited effect on COD removal, and cannot meet the requirements of entering the subsequent ultrafiltration reverse osmosis membrane system.

[0098] Comparative Example 1H: Treatment of BDO wastewater with high sulfate content

[0099] The difference from Example 1 is that the pH in step 5 is 7, and other steps are the same as Example 1. That is, the in-situ oxidation-adsorption treatment changes the reaction pH.

[0100] Experimental results: After testing, the effluent COD after in-situ oxidation-adsorption is 189 mg / L.

[0101] Result analysis: Comparing Example 1 with Comparative Example 1G, it can be seen that when the pH of in-situ oxidation-adsorption reaction exceeds the pH of the present application, the COD removal rate of in-situ oxidation-adsorption is low. The final wastewater COD is greater than 60, which cannot meet the requirements of entering the subsequent ultrafiltration reverse osmosis membrane system. Therefore, when the pH of in-situ oxidation-adsorption is higher than the pH of the present application, the catalytic effect will be reduced. This may be due to insufficient reaction of catalyst and oxidant, resulting in low COD removal efficiency due to reagent waste. It should be understood that when the in-situ oxidation-adsorption tank cannot well remove COD, subsequent adjustment of the reaction time of ozone catalytic oxidation has limited effect on COD removal, and cannot meet the requirements of entering the subsequent ultrafiltration reverse osmosis membrane system.

[0102] Comparative Example 1H: Treatment of BDO wastewater with high sulfate content

[0103] The difference from Example 1 is that the size of the ozone bubbles in the ozone catalytic oxidation tank in step 6 is 150-200 nm, and the other steps are the same as those in Example 1. That is, the size of the ozone bubbles is increased during the ozone catalytic oxidation treatment.

[0104] Experimental results: After testing, the effluent COD after ozone catalytic oxidation is 69 mg / L.

[0105] Result analysis: Comparing Comparative Example 1H with Example 1, it can be seen that when the size of the ozone bubbles exceeds the size of the ozone bubbles in the present application, the COD removal rate of the ozone catalytic oxidation treatment is low. The final wastewater COD is greater than 60, which cannot meet the requirements of entering the subsequent ultrafiltration reverse osmosis membrane system. Therefore, when the size of the ozone bubbles is higher than the size of the bubbles in the present application, the ozone catalytic oxidation effect will be reduced. This may be due to the decrease in ozone solubility caused by the increase in the size of the ozone bubbles, which reduces the ozone reaction efficiency.

[0106] Comparative Example 1I: Treatment of BDO wastewater with high sulfate content

[0107] The difference from Example 1 is that the gas-liquid ratio in the ozone catalytic oxidation tank in step 6 is controlled to be 0.1, and the other steps are the same as those in Example 1. That is, the gas-liquid ratio is changed during the treatment in the ozone catalytic oxidation tank.

[0108] Experimental results: After testing, the effluent COD after ozone catalytic oxidation is 65 mg / L.

[0109] Result analysis: Comparing Comparative Example 1G with Example 1, it can be seen that when the gas-liquid ratio is lower than the gas-liquid ratio in the present application, the COD removal rate of the ozone catalytic oxidation is low. The final wastewater COD is greater than 60, which cannot meet the requirements of entering the subsequent ultrafiltration reverse osmosis membrane system. Therefore, when the gas-liquid ratio is lower than the gas-liquid ratio 0.15-0.2 in the present application, the catalytic effect will be reduced.

[0110] Example 1J: Treatment of BDO wastewater with high sulfate content

[0111] The difference from Example 1 is that the ozone dosage in the ozone catalytic oxidation tank in step 6 is controlled to be O3:COD = 1:1, and the other steps are the same as those in Example 1. That is, the ozone dosage is changed during the treatment in the ozone catalytic oxidation tank.

[0112] Experimental results: After testing, the effluent COD after ozone catalytic oxidation is 72 mg / L.

[0113] Result analysis: comparing the comparative example 1J with the example 1, it can be seen that when the ozone dosage is lower than the ozone dosage of the present application, the COD removal rate of ozone catalytic oxidation is reduced. The final wastewater COD is greater than 60, which cannot meet the needs of entering the subsequent ultrafiltration reverse osmosis membrane system. Therefore, when the ozone dosage is lower than the ozone dosage of the present application (1.25-2): 1, the catalytic effect will be reduced.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to suggest that the scope of the disclosure (including the claims) is limited to these examples; under the concept of the present disclosure, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the embodiments of the present disclosure as described above, which are not provided in details for the sake of brevity.

[0115] Although the present disclosure has been described in conjunction with the specific embodiments thereof, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in the light of the foregoing description.

[0116] The embodiments of the present disclosure are intended to cover all such alternatives, modifications and variations as falling within the broad scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A process for the treatment of BDO wastewater with high sulfate content, characterized in that, The application relates to a BDO wastewater treatment method. The BDO wastewater has a high sulfate content, wherein the concentration of sulfate ions is 5000 mg / L or above, the COD concentration is 3000-5000 mg / L, and BOD5 / COD is less than or equal to 0.

1. The BDO wastewater is introduced into an electrochemical oxidation reactor for electrochemical oxidation treatment, so that the organic matters in the BDO wastewater are subjected to oxidative chain breaking. An anaerobic reaction device with a circulating desulfurization device and a gas flotation device is provided; the anaerobic reaction device is provided with a water outlet backflow device, and the circulating desulfurization device and the gas flotation device are sequentially arranged at the water outlet end of the water outlet backflow device. The BDO wastewater treated by electrochemical oxidation is introduced into the anaerobic reaction device for anaerobic reaction, so that the sulfate ions are reduced into hydrogen sulfide, and the organic matters are oxidized to reduce the COD; the water outlet of the water outlet backflow device is sequentially backflowed into the circulating desulfurization device and the gas flotation device; in the circulating desulfurization device, the hydrogen sulfide is oxidized into sulfur single element; in the gas flotation device, the sulfur single element is recovered, and part of the water outlet of the gas flotation device and part of the water outlet of the anaerobic reaction device are backflowed into the water inlet of the anaerobic reaction device. Part of the water outlet of the gas flotation device and part of the water outlet of the anaerobic reaction device are combined and sequentially introduced into an aerobic activated sludge tank with a membrane biological reactor and an ozone catalytic oxidation tank.

2. The BDO wastewater treatment process of claim 1, wherein, The anaerobic reaction device is an anaerobic tower, and the circulating desulfurization device is a circulating desulfurization tower; in the circulating desulfurization tower, the aeration intensity is that the volume fraction of air introduced into per cubic meter of water is 5% to 10%, and the residence time of per cubic meter of water is 0.3 to 3 h.

3. The BDO wastewater treatment process of claim 1, wherein, The water inlet load of the anaerobic tower is 1 to 4 gCOD / L / d; the anaerobic reaction of the BDO wastewater treated by electrochemical oxidation further includes that trace elements are added into the water inlet of the anaerobic tower, and the trace elements include MgSO410-100 mg / L, ZnSO4.7H2O 1-20 mg / L, FeCl2.4H2O 10-100 mg / L, H3BO3 0.1-10 mg / L, NiCl2.6H2O 10-100 mg / L, MnSO4.H2O 10-100 mg / L, CoCl2.6H2O 10-100 mg / L and Na2MoO4.2H2O 0.1-5 mg / L.

4. The BDO wastewater treatment process of claim 1, wherein, In the electrochemical reactor, the anode is a graphite electrode, a ruthenium-titanium electrode or a ruthenium-iridium-titanium electrode; and the cathode is a stainless steel electrode or a graphite electrode.

5. The BDO wastewater treatment process of claim 4, wherein, In the electrochemical reactor, the anode is a ruthenium-iridium-titanium electrode, and the cathode is a stainless steel electrode; the applied electric field voltage is 10-20 V; the spacing between the plate electrodes is 20-40 cm; the reaction residence time is 1.5-2 h; and the BDO wastewater is BDO wastewater after pH adjustment, and the pH is neutral.

6. The BDO wastewater treatment process of claim 1, wherein, The dissolved oxygen concentration in the aerobic activated sludge tank is 3-8 mg / L; the BDO wastewater treatment process further comprises: adding ammonium salt and phosphorus salt in the aerobic activated sludge tank to make the C:N:P ratio in the aerobic activated sludge tank be (50-150):5:1; adding trace elements in the aerobic activated sludge tank, the trace elements comprising CaCl21-5 mg / L, EDTA 1-20 mg / L, CuCl2·2H2O 1-10 mg / L, H3BO30.001-0.1 mg / L, FeSO4·7H2O 0.1-1 mg / L, MnSO4·H2O 0.1-1 mg / L, MgSO4·7H2O 1-10 mg / L and ZnSO4·7H2O 0.1-0.5 mg / L.

7. The BDO wastewater treatment process of claim 1, wherein, In the ozone catalytic oxidation tank, the size of the ozone bubbles is 70-100 nm; the gas-liquid volume ratio is 0.15-0.2; the ozone catalyst is alumina or iron-cerium activated carbon composite catalyst; and the ozone dosage satisfies the mass ratio of O3 to COD being (1.25-2):

1.

8. The BDO wastewater treatment process of claim 1, wherein, The BDO wastewater treatment process further comprises: passing the membrane bioreactor effluent into an in-situ oxidation-adsorption tank, adjusting the pH to be 3-6, adding a compounded oxidant and a catalyst to oxidize and modify the residual refractory organic matter and to carry out adsorption; the mass ratio of the catalyst added per liter of the membrane bioreactor effluent to the COD of the membrane bioreactor effluent is (0.05-2):1; and the mass ratio of the compounded oxidant to the catalyst is (1-2):

1.

9. The BDO wastewater treatment process of claim 8, wherein, The compound oxidant is composed of H2O2, hypochlorite, and persulfate; wherein the molar ratio of H2O2, hypochlorite, and persulfate is 1:(0.027-0.456):(0.009-0.143); the catalyst is composed of FeSO4, CuSO4, MnSO4, and CoSO4; wherein Fe 2+ Cu 2+ Mn 2+ With Co 2+ The molar ratio is 100:(0.475-47.5):(0.201-20.1):(0.500-15.0).

10. The BDO wastewater treatment process of claim 1, wherein, The type of the membrane in the membrane bioreactor is hollow fiber membrane; the material of the membrane is polytetrafluoroethylene membrane; the pore size of the membrane is 0.1-0.4 μm; and the water feeding mode is continuous water feeding.

Images