Photocatalytic Fenton wastewater treatment method and device for synchronous denitrification and removal of refractory organic matter

Abstract

The present invention provides a photo-Fenton wastewater treatment method and device for synchronous denitrification and removal of refractory organic matter. The method comprises the following steps: adding wastewater and H₂O₂ into a reactor containing a photo-Fenton catalyst and anaerobic ammonium oxidation bacteria, and reacting under light conditions to remove nitrogen and refractory organic matter in the wastewater. This application realizes the removal of refractory organic matter through photo-Fenton, and through multi-species community denitrification with Anammox as the core and enhanced carbon reduction, a more sustainable method is proposed for treating wastewater with high nitrogen content and refractory organic matter.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a photo-Fenton wastewater treatment method and device for synchronously removing nitrogen and refractory organic compounds. Background Art

[0002] Wastewater contains a large amount of refractory organic compounds, such as landfill leachate, livestock wastewater and pharmaceutical wastewater. Due to the toxicity and environmental persistence of these compounds, they have attracted extensive attention in wastewater treatment. The combination of Fenton reaction and biological method is considered to be an ideal method for effectively removing refractory organic compounds and ammonia nitrogen. In the traditional Fenton reaction, Fe(II) is used as a catalyst to react with hydrogen peroxide (H2O2) to generate hydroxyl radicals (·OH), which can degrade complex organic compounds into small molecules, improve biodegradability and reduce biotoxicity. However, the Fenton reaction using FeSO4 as a catalyst faces the disadvantages of Fe(III) removal, iron sludge generation and pH adjustment. In addition, traditional biological nitrogen removal processes require a large amount of dissolved oxygen and carbon sources, and the operating cost is high.

[0003] The photo-Fenton combined with biological treatment technology based on solid iron catalysts is undoubtedly the best solution to the above problems. The photo-Fenton technology can utilize solar energy to accelerate the Fe(III) / Fe(II) redox cycle, realize the continuous catalysis of H2O2 by a low-dose catalyst to generate ·OH, improve the catalytic efficiency and save the chemical cost. Compared with dissolved FeSO4, the solid iron catalyst overcomes the disadvantages of pH adjustment and sludge disposal, and can save 20-30% of the operating cost in industrial-scale applications. Anaerobic ammonium oxidation (Anammox) is an alternative nitrogen removal strategy that has received extensive attention in the field of biological nitrogen removal. Compared with traditional nitrogen removal processes, the Anammox process has the advantages of low aeration demand, short nitrogen removal pathway, no need for external carbon source and low greenhouse gas production, and can reduce 90% of the operating cost and save 50% of the space area. Summary of the Invention

[0004] In order to combine the advantages of the photo-Fenton reaction and Anammox, the present invention proposes a photo-Fenton-Anammox one-stage nitrogen removal and carbon reduction system, which realizes the removal of refractory organic compounds through photo-Fenton, and uses a multi-species community with Anammox as the core for nitrogen removal and enhanced carbon reduction, forming a more sustainable method for treating wastewater with high nitrogen content and refractory organic compounds.

[0005] The present invention is realized by adopting the following technical solutions:

[0006] A photo-Fenton wastewater treatment method for synchronously removing nitrogen and refractory organic compounds, comprising the following steps:

[0007] Wastewater and H2O2 are introduced into a photo-Fenton catalyst and anaerobic ammonium oxidizing bacteria to form a reaction system. The reaction system reacts under light conditions to remove nitrogen and refractory organic matter in the wastewater.

[0008] The molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater is 1-1.3.

[0009] Optionally, the wastewater is subjected to a short-cut nitrification treatment and / or a short-cut denitrification treatment so that the molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater reaches 1-1.3.

[0010] The substrates of Anammox are ammonia nitrogen and nitrite, with ammonia nitrogen as the electron donor and nitrite as the electron acceptor, and the two react in a ratio of 1:1.32 to produce nitrogen gas (1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O), so the molar ratio of ammonia nitrogen to nitrite should be maintained at 1-1.3. However, the nitrite content in actual wastewater is very low, so the wastewater must be subjected to short-cut nitrification or short-cut denitrification treatment to achieve this ratio.

[0011] Optionally, the photo-Fenton catalyst is NH2-MIL-101(Fe) catalyst;

[0012] Optionally, the photo-Fenton catalyst is combined with the anaerobic ammonium oxidation granular sludge by self-precipitation. The catalyst is added to the reactor once before starting the reaction and combined with the anaerobic ammonium oxidation granular sludge.

[0013] Optionally, the concentration of the photo-Fenton catalyst in the reactor during the reaction is 50 to 200 mg / L.

[0014] Optionally, the mass fraction of H2O2 introduced into the reaction system is 0.08 to 0.3‰.

[0015] Optionally, the hydraulic retention time during the reaction is 3-5 h.

[0016] Optionally, the reaction temperature during the reaction is 33-35°C.

[0017] Optionally, the pH of the wastewater during the reaction is 7.5-8.0.

[0018] Optionally, the illumination intensity during the reaction process is 8500-10000 lux.

[0019] Optionally, before the reaction, the method further includes the following steps:

[0020] Seeding sludge: Inject granular sludge containing anaerobic ammonium oxidation bacteria into the reactor to make the total sludge concentration 5000 - 6000 mg / L;

[0021] Sludge acclimation: Cultivate until the total nitrogen removal load reaches more than 3.0 kg / (m 3 ·d), and the acclimation ends after the total nitrogen removal rate of the effluent reaches more than 85%.

[0022] The sludge concentration is detected by the oven method according to the sludge inspection method of CJ 221 - 2005 for urban sewage treatment plants.

[0023] Optionally, after the sludge acclimation culture ends, NH2-MIL-101(Fe) is combined with anaerobic ammonium oxidation granular sludge by self-precipitation. After adding, nitrogen gas is introduced from the bottom of the reactor at a flow rate of 100 ml / min and maintained for 1 - 2 h to achieve full contact between NH2-MIL-101(Fe) and anaerobic ammonium oxidation granules.

[0024] The present invention also provides a photo-Fenton wastewater treatment device for synchronous denitrification and removal of refractory organic matter, including:

[0025] Photo-Fenton - Anammox reactor, which is provided with a photo-Fenton catalyst and anaerobic ammonium oxidation bacteria inside;

[0026] H2O2 storage tank, which is connected to the photo-Fenton - Anammox reactor through an H2O2 dosing pump;

[0027] Lighting system, which is arranged on the photo-Fenton - Anammox reactor to provide lighting conditions for it;

[0028] Intermediate inlet water tank, which is connected to the photo-Fenton - Anammox reactor for wastewater input.

[0029] Optionally, the intermediate inlet water tank is connected with a shortcut nitrification reactor and / or a shortcut denitrification reactor to adjust the molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater input into the photo-Fenton - Anammox reactor to 1 - 1.3.

[0030] Optionally, the shortcut nitrification reactor is internally provided with an aeration head, a stirrer, suspended packing, and a heater; the suspended packing is a plastic cylindrical material; the diameter of the suspended packing is 10 - 30 mm, and the effective surface area is 300 - 800 m 2 / m 3 , the dosage of the suspended packing accounts for 30 - 50% of the effective volume of the reactor, and the dissolved oxygen content in the shortcut nitrification reactor is below 0.3 mg / L.

[0031] Optionally, a heating rod, a stirrer, and polyurethane biological sponge fillers are provided inside the short-cut denitrification reactor; the specific surface area of the polyurethane biological sponge fillers is 13,000-15,000 m 2 / m 3 and the specific gravity is 0.86-0.91 g / cm 3 .

[0032] Optionally, the device further includes a sewage inlet water tank, which is connected to the short-cut nitrification reactor and the short-cut denitrification reactor;

[0033] Water quality detection devices are provided in both the sewage inlet water tank and the intermediate inlet water tank.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The present invention constructs a photo-Fenton-Anammox one-stage nitrogen and carbon removal system for the first time. The removal of refractory organic matter is achieved through photo-Fenton, and nitrogen removal and enhanced carbon removal are realized through a multi-species community with Anammox as the core, and a more sustainable method is proposed for treating wastewater with high nitrogen content and refractory organic matter.

[0036] Since the nitrite content in the wastewater is very low in actual situations, for the device for synchronously removing nitrogen and refractory organic matter in the wastewater provided by the present invention, in order to achieve a stable supply of nitrite for the Anammox reaction, a water quality identification device is provided at the front end of the photo-Fenton-Anammox reactor. Through water quality discrimination for diversion, the high ammonia nitrogen wastewater is diverted to the short-cut nitrification reactor, and the high nitrate wastewater is diverted to the short-cut denitrification reactor. The flow rate is controlled in real time through online detection data to achieve a ratio of ammonia nitrogen to nitrite in the inlet water of the photo-Fenton-Anammox reactor of 1-1.3.

[0037] In the present invention, Anammox bacteria promote the Fe(II) / Fe(III) cycle by improving electron-hole separation, achieving efficient removal of refractory organic matter with a low H2O2 dosage and ensuring high metabolic activity of Anammox in an oxidative environment. The photo-Fenton reaction activates H2O2 through the Fe(II) / Fe(III) redox cycle to generate highly reactive free radicals to effectively attack and degrade target pollutants. Specifically, the photo-generated electrons produced by photo-exciting NH2-MIL-101(Fe) reduce Fe(III) to Fe(II), and the generated Fe(II) reacts with H2O2 as the active center to generate ·OH, while Fe(II) itself is oxidized to Fe(III). However, the rapid recombination of electron-hole pairs limits the Fe(II) / Fe(III) redox in the photo-Fenton process. But in the present invention, through the cooperation of Anammox bacteria and the photo-Fenton reaction, the photo-generated electrons can be transferred to the interior of the cell through the electron transport chain, forming a large spatial separation between the reduced electrons and the oxidized holes, promoting long-lived charge separation; meanwhile, the redox-active functional groups in the extracellular polymeric substances can act as electron shuttles to play an electron transfer role, increasing the cell's ability to accept external electrons. In addition, Anammox bacteria have the characteristic of secreting a large amount of extracellular polymeric substances (EPS), and studies have shown that the reducing proteins and polysaccharides in the EPS extract can act as hole scavengers to improve the photocatalytic efficiency. Therefore, the ability of Anammox bacteria in the present invention to uptake photo-generated electrons and the hole scavenging effect of the secreted EPS can improve the separation of electron-hole pairs in the photo-Fenton process, making the generation rate of Fe(II) much greater than the consumption rate, which can achieve the purpose of enhancing the H2O2 activation efficiency and realizing efficient removal of refractory organic matter with a low H2O2 dosage; and the low H2O2 dosage not only reduces the operating cost of the photo-Fenton reaction, but more importantly, minimizes the toxic effect of H2O2 on Anammox. In summary, the photo-Fenton-Anammox one-stage denitrification and carbon reduction system can not only meet the low-cost and high-efficiency decomposition of refractory organic matter by photo-Fenton, but also ensure the denitrification activity of Anammox, achieving simultaneous denitrification and carbon reduction.

[0038] In the present invention, the synergistic effect of multiple populations with Anammox as the core is fully exerted to achieve the hierarchical treatment of organic matter by "chemical oxidation + biological reduction + heterotrophic metabolism" and improve the nitrogen removal efficiency. Photo-Fenton can degrade complex organic compounds into small molecules, improve biodegradability and reduce biological toxicity, promote the growth of heterotrophic denitrifying bacteria in the Anammox community, facilitate the further removal of Anammox nitrate by-products, and improve the nitrogen removal efficiency. At the same time, the low redox potential and sufficient photo-generated electrons are beneficial to the electron acquisition ability of Anammox-DNRA when Anammox bacteria coexist with denitrifying bacteria, thus defeating heterotrophic denitrifying bacteria, ensuring the dominant position of Anammox bacteria, and in-situ eliminating Anammox nitrate by-products. Thaueraspp. is a common microorganism in sewage treatment and has the ability to reduce humus. Research shows that Thauera spp. can grow and enrich well under electrode stimulation and has the characteristics of electricity generation and extracellular electron transfer. The low redox potential generated by the Fe(II) / Fe(III) redox cycle in NH2-MIL-101(Fe) can stimulate the electrochemical characteristics of Thauera spp. and stimulate the in-situ enrichment of Thauera spp. The respiratory process driven by Thauera spp. (such as Thauera humireducens) can achieve the reduction and transformation of various organic matters such as aromatic and polyhalogenated compounds, form complementary advantages of "chemical oxidation + biological reduction + heterotrophic metabolism" with photo-Fenton and heterotrophic denitrifying bacteria, and realize the balanced operation of the nitrogen and carbon removal system under the coexistence of multiple populations.

[0039] In the present invention, the alkalinity-causing characteristics of Anammox are utilized to overcome the pH fluctuation of the photo-Fenton reaction and achieve the pH self-balance of the combined process. The quantum yield generated in the photo-Fenton reaction largely depends on the pH value used in the reaction process. Research shows that when the pH ranges from 2 to 7, the content of ·OH increases with the increase of pH. However, when the Fenton reaction is used to treat wastewater from refineries, petrochemical plants, pharmaceuticals, etc., the generation of small molecule acids often occurs, which will lead to a decrease in the effluent pH and weaken the treatment efficiency of the neutral photo-Fenton reaction. Anammox is an alkalinity-causing reaction, and the reaction will cause an increase in pH. Therefore, when photo-Fenton is combined with Anammox, the metabolism of Anammox bacteria can maintain the neutral pH required for the photo-Fenton reaction to efficiently remove refractory organic matter, while avoiding the environmental and economic disadvantages related to adjusting the pH value of the effluent.

[0040] In the present invention, in-situ stimulation is used to cause Anammox to secrete a large amount of EPS, improving its tolerance to the oxidation environment and denitrification metabolic activity. In the photo-Fenton system, EPS can be enhanced in its assembly and durability due to consumption caused by hole scavenging and oxidation stimulation by H2O2. In addition, photo-generated electrons can enhance the permeability of the bacterial membrane by inducing physical and chemical reactions in the microbial membrane lipid composition, including the redirection of lipid lipids and peroxidation of unsaturated lipids, which also leads to an increase in EPS secretion. Therefore, when photo-Fenton is combined with Anammox, Anammox bacteria can produce a large amount of EPS for hole scavenging and resistance to the oxidation environment, ensuring its denitrification ability under H2O2 oxidation stress. In addition, the large amount of EPS secretion is beneficial to enhancing the electron transfer effect of redox-active functional groups, accelerating the transfer of photo-generated electrons, and thus improving the metabolic activity of Anammox bacteria. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] As Figure 1 shown is a schematic structural diagram of a novel device for synchronously removing nitrogen and refractory organic matter from wastewater according to the present invention;

[0043] Among them, the reference numerals are:

[0044] 1 - water quality identification device, 2 - sewage inlet water tank, 3 - shortcut nitrification reactor, 4 - shortcut denitrification reactor, 5 - intermediate inlet water tank, 6 - photo-Fenton-Anammox reactor, 7 - outlet water tank, 8 - first water quality detection device, 9 - shortcut nitrification inlet water pump, 10 - aeration pump, 11 - gas flowmeter, 12 - suspended packing, 13 - heating rod, 14 - aeration head, 15 - magnetic stirrer, 16 - shortcut denitrification inlet water pump, 17 - mechanical stirrer, 18 - polyurethane biological sponge packing, 19 - second water quality detection device, 20 photo-Fenton-Anammox inlet water pump, 21 - constant temperature water jacket, 22 - lighting system, 23 - H2O2 dosing pump, 24 - H2O2 storage tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following embodiments are provided to better further understand the present invention. They are not limited to the best embodiments described, and do not limit the content and protection scope of the present invention. Any product obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts and being the same as or similar to the present invention falls within the protection scope of the present invention.

[0046] For those not specifying specific experimental procedures or conditions in the examples, the operations or conditions of the conventional experimental procedures described in the literature in this field can be followed. For the reagents or instruments without indicating the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0047] The photocatalytic Fenton catalysts used in each example are all conventional solid iron catalysts, preferably NH2-MIL-101(Fe). The synthesis preparation method of NH2-MIL-101(Fe) includes the following steps: FeCl3·6H2O (3.22 g, 11.92 mmol) is first dissolved in 144 mL of N,N-dimethylformamide (DMF). 2-Aminoterephthalic acid (NH2-BDC) (1.08 g, 5.96 mmol) is added to the above suspension, and ultrasonic treatment is carried out at room temperature for 1 h until NH2-BDC is dissolved. Subsequently, the mixture is maintained in a reaction kettle (200 mL) at 110 °C for 24 h. After cooling to room temperature, the precipitate is separated from the reaction mixture by centrifugation (4000 r / min), and washed thoroughly three times with DMF and ethanol respectively to remove unreacted raw materials. Finally, the obtained solid is dried in a vacuum furnace at 80 °C for 12 h.

[0048] Example 1

[0049] This example provides a method for synchronously removing nitrogen and refractory organic matter from wastewater. This method constructs a photocatalytic Fenton-Anammox one-stage denitrification and carbon reduction system, including the following steps: adding wastewater, photocatalytic Fenton catalyst, and H2O2 into a reactor containing anaerobic ammonium oxidation bacteria, and reacting under light conditions to remove nitrogen and refractory organic matter in the wastewater.

[0050] The control method in this example includes the following steps:

[0051] 1) Using simulated wastewater, ammonium sulfate and sodium nitrite are added to tap water at a molar ratio of 1:1.15 to prepare wastewater, and the total nitrogen concentration of the prepared wastewater is 500 - 600 mg / L (calculated as N); fulvic acid is used to simulate refractory organic matter, and the concentration of refractory organic matter is 50 - 100 mg / L (calculated as C); CaCl2·2H2O 30 mg / L, MgSO4·7H2O 25 mg / L, FeSO4·7H2O 20 mg / L. At this time, 1 mL of trace elements is added to each liter of simulated wastewater: H3BO3 0.05 g / L, ZnCl2 0.05 g / L, CuCl2 0.03 g / L, MnSO4·H2O 0.05 g / L, (NH4)6Mo 24· 4H2O 0.05 g / L, AlCl3 0.05 g / L, CoCl2·6H2O 0.05 g / L, NiCl2 0.05 g / L. The pH of the sewage was adjusted to 7.0 - 7.5 using KHCO3.

[0052] 2) Inoculated sludge: Granular sludge was taken from a stable anaerobic ammonium oxidation anaerobic reactor and injected into the photo-Fenton - Anammox reactor. Wastewater was introduced into the reactor to maintain the total sludge concentration in the photo-Fenton - Anammox reactor within the range of 5000 - 6000 mg / L.

[0053] 3) Sludge acclimation stage: During the sludge acclimation stage, the photo-Fenton - Anammox reactor was operated in continuous flow. The total nitrogen removal load of the device was adjusted by controlling the hydraulic retention time (HRT). When the total nitrogen removal load of the entire device reached 3.0 kg / (m 3 ·d), and the total nitrogen removal rate of the effluent was up to 85% or more, the sludge acclimation and cultivation ended, and the next step was carried out.

[0054] 4) Photo-Fenton stage: After the sludge acclimation and cultivation ended, NH2-MIL-101(Fe) and H2O2 were added. NH2-MIL-101(Fe) was combined with anaerobic ammonium oxidation granular sludge through self-precipitation. After adding, nitrogen gas was introduced from the bottom of the reactor at a flow rate of 100 ml / min and maintained for 1 - 2 h to ensure full contact between NH2-MIL-101(Fe) and anaerobic ammonium oxidation bacteria in the granular sludge. The photo-Fenton - Anammox reactor was operated in continuous flow, with an internal reflux ratio of 500% - 600%, an HRT of 3 h, an NH2-MIL-101(Fe) dosage of 150 mg / L, and an H2O2 addition mass fraction of 0.1‰.

[0055] The contents of NO3 - -N, NO2 - -N, and NH4 + -N in the influent and effluent of the reactor in Example 2 were detected daily, and the results are shown in Table 1. The results show that the one-stage device for treating refractory organic wastewater by coupling MOF photo-Fenton and Anammox proposed in the present invention can achieve efficient treatment of wastewater with high nitrogen content and refractory organic matter, and has a wide range of applications.

[0056] Table 1 Nitrogen compound contents in the influent and effluent of the photo-Fenton - Anammox reactor

[0057]

[0058] The TOC content in the effluent of the reactor in Example 2 was detected, and the results are shown in Table 2.

[0059] Table 2 TOC content in the effluent of the photo-Fenton-Anammox reactor

[0060]

[0061]

[0062] 150 mg / L of NH2-MIL-101(Fe) and 0.1‰ H2O2 were added to the Anammox reactor to start the photo-Fenton-Anammox reactor, and the photo-Fenton-Anammox reactor was continuously and stably operated for 20 days. The nitrogen compound contents in the influent and effluent of the photo-Fenton-Anammox reactor are shown in Table 1. The influent ammonia nitrogen of the reactor was 201.5 ± 8.6 mg / L, nitrite was 230.6 ± 5.6 mg / L, nitrate was 4.2 ± 1.2 mg / L, the effluent ammonia nitrogen was 14.8 ± 5.9 mg / L, nitrite was 7.7 ± 5.8 mg / L, nitrate was 33.1 ± 4.0 mg / L, and the denitrification efficiency was 87.3 ± 1.9%, close to the theoretical removal rate of 89%. The denitrification performance of the reactor was good. The results showed that the activity of anaerobic ammonium-oxidizing bacteria was not affected by the oxidation free radicals such as H2O2 and ·OH in the photo-Fenton system. The TOC content in the effluent of the photo-Fenton-Anammox reactor is shown in Table 2. The influent TOC concentration was 23.9 ± 1.0 mg / L, and the effluent was 3.5 ± 0.6 mg / L. The TOC removal rate was 85.4 ± 2.2%. The results showed that the photo-Fenton-Anammox reactor had good ability to remove refractory organic compounds. The study on the denitrification performance and the ability to remove refractory organic compounds of the photo-Fenton-Anammox reactor for 20 consecutive days showed that the process had high-efficiency synchronous denitrification and carbon reduction performance.

[0063] Example 2

[0064] In this example, by adjusting the dosage of the photo-Fenton catalyst and the dosage of H2O2, the optimal usage amounts of the photo-Fenton catalyst and H2O2 were determined. In this example, a sewage treatment experiment was carried out in a 150 ml serum bottle. Granular sludge was taken from the anaerobic ammonium-oxidation anaerobic reactor, and the inoculated sludge volume accounted for 20% of the total volume of the reactor. The temperature was maintained at 35 ± 1 °C during the experiment. In this example, deionized water was used to prepare artificial wastewater containing 60 mg / L NH4 + -N, 80 mg / L NO2 - -N, 1000 mg / L KHCO3 and added to the serum bottle, and the pH of the artificial wastewater was maintained at 7.5.

[0065] First, set up the NH2-MIL-101(Fe) concentration gradient experiment. The dosing amounts of NH2-MIL-101(Fe) into the serum bottles were 50, 100, 150, and 200 mg / L respectively. The light-exposed group without the addition of NH2-MIL-101(Fe) was used as the blank control group, and replicates (experimental group 1 and experimental group 2) were set under the same experimental conditions. Detect the contents of NH4 + -N and NO2 - -N in the effluents of different serum bottles, and the results are shown in Table 3.

[0066] Table 3 Contents of NH4 + -N and NO2 - -N

[0067]

[0068]

[0069] From the above experimental results, it can be seen that the dosing amount of NH2-MIL-101(Fe) shows a phenomenon of low-dose promotion and high-concentration inhibition on the anaerobic ammonium oxidation denitrification efficiency. After dosing 50, 100, and 150 mg / L of NH2-MIL-101(Fe), with the increase of the dosing concentration, the anaerobic ammonium oxidation denitrification efficiency gradually increases and reaches the highest denitrification efficiency at a concentration of 150 mg / L. Anaerobic ammonium-oxidizing bacteria can utilize the photogenerated electrons excited by photocatalytic NH2-MIL-101(Fe) to optimize their own metabolic ability and improve the denitrification efficiency. When the dosing amount continues to increase (200 mg / L), the anaerobic ammonium oxidation denitrification efficiency decreases significantly, which may be related to the biological toxicity of NH2-MIL-101(Fe). A high dosing amount of NH2-MIL-101(Fe) may cause a decrease in cell viability. Therefore, the optimal dosing amount of NH2-MIL-101(Fe) is 150 mg / L.

[0070] Then, conduct the H2O2 dosing amount experiment. Take granular sludge from the anaerobic ammonium oxidation anaerobic reactor, and the inoculated sludge volume accounts for 20% of the total volume of the reactor. During the experiment, the temperature is maintained at 35 ± 1 °C. In this example, deionized water is used to prepare artificial wastewater containing 60 mg / L NH4 + -N, 80 mg / L NO2 - -N, and 1000 mg / L KHCO3 and add it to the serum bottle, and keep the pH of the artificial wastewater at 7.5. Set up the light-Fenton H2O2 dosing mass fraction gradient experiment, which are 0, 0.08‰, 0.1‰, 0.3‰, and 0.5‰ respectively. The dosing amount of NH2-MIL-101(Fe) is 150 mg / L, and the concentration of refractory organic matter is 15 mg / L. Replicates (experimental group 1 and experimental group 2) are set under the same experimental conditions.

[0071] The TOC content in the effluent of different serum bottles was detected, and the results are shown in Table 4. In the table, MOF indicates the addition of 150 mg / L of NH2-MIL-101(Fe).

[0072] Table 4 TOC content in the effluent of different serum bottles

[0073]

[0074] From the above experimental results, it can be seen that the removal rate of TOC by Anammox is 14.7 ± 1.63%. After adding NH2-MIL-101(Fe), the TOC removal rate is increased to 25.87 ± 5.67%. When photo-Fenton is combined with Anammox, when the mass fraction of H2O2 added is 0.08‰, 0.1‰, 0.3‰, and 0.5‰, the TOC removal rates are 60.03 ± 4.83%, 78.17 ± 10.57%, 61.96 ± 7.63%, and 44.63 ± 5.43% respectively. Compared with the single Anammox treatment, the TOC removal rate is increased by 3.0 - 5.3 times, and compared with the single photo-Fenton treatment, the TOC removal rate is increased by 2.9 - 4.5 times. When the dosage of NH2-MIL-101(Fe) is 150 mg / L and the mass fraction of H2O2 added is 0.1‰, the removal rate of refractory organic compounds by the MOF photo-Fenton coupled with Anammox is the highest, which is 3.7 - 4.3 times that of the single photo-Fenton treatment under the same conditions. Compared with the single Anammox biological treatment, the removal rate of refractory organic compounds by the combination of MOF photo-Fenton and Anammox is increased by 3.1 - 3.3 times. Therefore, the combination of MOF photo-Fenton and Anammox has a high ability to remove refractory organic compounds and can become an economical and effective technology for refractory organic compounds.

[0075] Example 3

[0076] This embodiment provides a device for synchronously removing nitrogen and refractory organic matter from wastewater based on the method for synchronously removing nitrogen and refractory organic matter from wastewater in Embodiment 1. The continuous flow reaction process is used to treat sewage. The device includes an intermediate inlet water tank 5, and the intermediate inlet water tank 5 is connected to a photo-Fenton-Anammox reactor 6. The photo-Fenton-Anammox reactor 6 includes a photo-Fenton-Anammox inlet water pump 20, a constant temperature jacket 21, a lighting system 22, an H2O2 dosing pump 23, and an H2O2 storage tank 24. Among them, the intermediate inlet water tank 5 is connected to the bottom inlet valve of the photo-Fenton-Anammox reactor 6 through the photo-Fenton-Anammox inlet water pump 20; the H2O2 storage tank 24 is connected to the bottom inlet valve of the photo-Fenton-Anammox reactor 6 through the H2O2 dosing pump 23; the sludge inoculated in the photo-Fenton-Anammox reactor 6 comes from an anaerobic ammonia oxidation anaerobic reactor; the photo-Fenton-Anammox reactor 6 is provided with an internal reflux pump to provide shear force to maintain the stability of granular sludge. A constant temperature jacket 21 is also provided outside the photo-Fenton-Anammox reactor to control the internal temperature of the reactor. The lighting system 22 is the light source for the photo-Fenton reaction, and its lighting intensity is 8500-10000 lux.

[0077] During the reaction process, it is necessary to maintain the ratio of ammonia nitrogen to nitrite nitrogen in the intermediate inlet water tank 5 at 1-1.3 to enable the photo-Fenton-Anammox reactor to react stably and efficiently. In order to make the wastewater treated by the system reach this ratio, the device is also provided with a shortcut nitrification reactor 3 and a shortcut denitrification reactor 4. As Figure 1 shown, the intermediate inlet water tank 5 is connected to the shortcut nitrification reactor 3 and the shortcut denitrification reactor 4.

[0078] The shortcut nitrification reactor 3 includes a shortcut nitrification inlet water pump 9, an aeration pump 10, a gas flow meter 11, suspended packing 12, a heating rod 13, an aeration head 14, and a magnetic stirrer 15; among them, the aeration head 14 is connected to the external aeration pump 10 through the gas flow meter 11 by an air delivery pipe. The suspended packing is a plastic cylindrical material with a diameter of 10-30 mm and an effective surface area of 300-800 m 2 / m 3 , and the dosage accounts for 30-50% of the effective volume of the reactor, and the dissolved oxygen content is below 0.3 mg / L.

[0079] The shortcut denitrification reactor 4 includes a shortcut denitrification inlet water pump 16, a heating rod 13, a mechanical stirrer 17, and a polyurethane biological sponge packing 18. Shortcut denitrification reactor: 4 groups of packings are vertically placed in the reactor. The specific surface area of the polyurethane biological sponge packing is 15000 m 2 / m 3 , specific gravity is 0.91 g / cm 3 .

[0080] The sewage inlet tank 2 and the intermediate inlet tank 5 are respectively equipped with a first water quality detection device 8 and a second water quality detection device 19. The water quality identification device 1 analyzes the water quality through the first water quality detection device 8 and the second water quality detection device 19, diverts the high ammonia nitrogen wastewater (ammonia nitrogen / total nitrogen > 90%) to the shortcut nitrification reactor, diverts the high nitrate wastewater (nitrate / total nitrogen > 90%) to the shortcut denitrification reactor, and controls the diversion flow rate in real time through the on-line detection data to achieve an ammonia nitrogen to nitrite molar ratio of 1 - 1.3 in the intermediate inlet tank 5.

[0081] The steps of wastewater treatment using the above device are as follows:

[0082] 1) Shortcut nitrification reactor: The suspended packing is a plastic cylindrical material with a diameter of 10 - 30 mm and an effective surface area of 300 - 800 m 2 / m 3 , the dosage accounts for 30 - 50% of the effective volume of the reactor, the initial sludge concentration is 3500 - 4000 mg / L, and a low dissolved oxygen anoxic-aerobic alternating strategy is adopted to inhibit the activity of NOB. The dissolved oxygen content is below 0.5 mg / L, and the anoxic-aerobic alternating time ratio is 2 - 2.3;

[0083] 2) Shortcut denitrification reactor: 4 groups of packings are vertically placed in the reactor. The polyurethane biological sponge packing has a specific surface area of 15000 m 2 / m 3 and a specific gravity of 0.91 g / cm 3 . The inoculated sludge is heterotrophic shortcut denitrification. The initial sludge concentration is 5000 - 6000 mg / L, and the volume of the inoculated sludge accounts for 30 - 40% of the total volume of the reactor. The pH is controlled at 7.0 - 7.5;

[0084] 3) Photo-Fenton - Anammox reactor:

[0085] Inoculated sludge: Granular sludge is taken from a stable anaerobic ammonia oxidation anaerobic reactor and injected into the photo-Fenton - Anammox reactor, and the total sludge concentration is increased to the range of 5000 - 6000 mg / L.

[0086] Sludge acclimation stage: In the sludge acclimation stage, the photo-Fenton - Anammox reactor operates in continuous flow, and the total nitrogen removal load of the device is adjusted by controlling the hydraulic retention time (HRT). When the total nitrogen removal load of the entire device reaches 3.0 kg / (m 3 ·d), and the total nitrogen removal rate of the effluent is as high as over 85%, the sludge acclimation and cultivation are completed, and the next step is carried out.

[0087] Photocatalysis Fenton stage: After the sludge acclimation and cultivation were completed, NH2-MIL-101(Fe) was combined with anaerobic ammonium oxidation granular sludge through self-precipitation. After addition, nitrogen gas was introduced from the bottom of the reactor at a flow rate of 100 ml / min and maintained for 1-2 h to achieve sufficient contact between NH2-MIL-101(Fe) and anaerobic ammonium oxidation granules. The photocatalysis Fenton-Anammox reactor was operated in continuous flow, with an HRT of 3-5 h, a dosing amount of NH2-MIL-101(Fe) of 150 mg / L, and a dosing mass fraction of H2O2 of 0.1‰.

[0088] It should be noted that although a shortcut nitrification reactor and a shortcut denitrification reactor were used simultaneously in this embodiment. However, in actual work, for wastewater with stable components, only one of the shortcut nitrification reactor or the shortcut denitrification reactor needs to be used, and the ammonia-nitrogen to nitrite ratio in the wastewater can be adjusted to 1-1.3, without the need to use both simultaneously.

[0089] Obviously, the above embodiments are merely examples given for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for treating wastewater by photo-Fenton for synchronous denitrification and removal of refractory organic matter, characterized in that, It includes the following steps: Introduce wastewater and H2O2 into a reaction system formed by mixing a photo-Fenton catalyst and anaerobic ammonium oxidation bacteria. The reaction system reacts under light conditions to remove nitrogen and refractory organic matter in the wastewater. The photo-Fenton catalyst is an NH2-MIL-101(Fe) catalyst; The molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater is 1 - 1.

3.

2. The method according to claim 1, wherein The wastewater undergoes partial nitrification treatment and / or partial denitrification treatment to make the molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater reach 1 - 1.

3.

3. The method according to claim 1, characterized in that, During the reaction process, the concentration of the photo-Fenton catalyst in the reactor is 50 - 200 mg / L.

4. The method according to claim 1, wherein The mass fraction of H2O2 introduced into the reaction system is 0.08 - 0.3‰.

5. The method according to claim 1, characterized in that, During the reaction process, the hydraulic retention time is 3 - 5 h; and / or, the reaction temperature during the reaction process is 33 - 35 °C; and / or, the pH of the wastewater during the reaction process is 7.5 - 8.0; and / or, the illumination intensity during the reaction process is 8500 - 10000 lux.

6. The method according to claim 1, wherein Before the reaction, it also includes the following steps: Inoculate sludge: Inject granular sludge containing anaerobic ammonium oxidation bacteria into the reactor to make the total sludge concentration 5000 - 6000 mg / L; Perform sludge acclimation: Cultivate until the total nitrogen removal load reaches 3.0 kg / (m 3 ·d) or more, and the acclimation ends after the total nitrogen removal rate of the effluent reaches 85% or more.

7. A photocatalytic Fenton wastewater treatment device for synchronous denitrification and removal of refractory organic compounds, characterized in that, It includes: A photo-Fenton - Anammox reactor, which is provided with a photo-Fenton catalyst and anaerobic ammonium oxidation bacteria inside; An H2O2 storage tank, which is connected to the photo-Fenton - Anammox reactor through an H2O2 dosing pump; A lighting system, which is arranged on the photo-Fenton - Anammox reactor to provide light conditions for it; An intermediate water inlet tank, which is connected to the photo-Fenton - Anammox reactor for realizing the input of wastewater; The photo-Fenton catalyst is an NH2-MIL-101(Fe) catalyst; The molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater is 1 - 1.

3.

8. The device according to claim 7, wherein The intermediate water inlet tank is connected with a partial nitrification reactor and / or a partial denitrification reactor to adjust the molar ratio of ammonia nitrogen to nitrite nitrogen in the wastewater input into the photo-Fenton - Anammox reactor to 1 - 1.

3.

9. The device according to claim 8, wherein The internal of the shortcut nitrification reactor is equipped with an aeration head, a stirrer, suspended packing, and a heater; the suspended packing is a plastic cylindrical material; the diameter of the suspended packing is 10 - 30 mm, and the effective surface area is 300 - 800 m 2 / m 3 , the dosage of the suspended packing accounts for 30 - 50% of the effective volume of the reactor, and the dissolved oxygen content in the shortcut nitrification reactor is below 0.3 mg / L; And / or, a heating rod, a stirrer and polyurethane biological sponge fillers are arranged inside the short-cut denitrification reactor; the specific surface area of the polyurethane biological sponge fillers is 13,000-15,000 m 2 / m 3 , and the density is 0.86-0.91 g / cm 3 .

10. The device according to claim 8, characterized in that, It also includes a sewage inlet tank, which is connected to the partial nitrification reactor and the partial denitrification reactor; Both the sewage inlet tank and the intermediate water inlet tank are equipped with water quality detection devices.

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