Method for enhancing degradation of volatile degradation-resistant compound wastewater by using tubular biological membrane electrode

Abstract

The invention discloses a method for enhancing degradation of volatile degradation-resistant compound wastewater by microorganisms by using a tubular biological membrane electrode. The method comprises the following steps: preparing a tubular oxygen evolution electrode with high biocompatibility, placing the tubular oxygen evolution electrode in a reactor chamber, enabling wastewater to enter the reactor from the top of the tubular electrode, reaching an oxygen evolution potential through external voltage, and constructing a micro-aerobic biological membrane to strengthen degradation of volatile refractory compounds. The tubular biological membrane electrode is introduced into a microbial system to construct a micro-aerobic environment, so that the external environment fluctuation resistance of organisms is effectively improved, and the long-term stability of a biological system is promoted. Under the optimal operation condition, the removal rate of volatile refractory compounds in the wastewater can reach 98% or above. The method is low in cost, efficient and simple, high energy consumption under conventional mechanical aeration is reduced, and volatilization of organic pollutants is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of volatile refractory compound wastewater treatment, and relates to a method for utilizing tubular biofilm electrodes to enhance microbial degradation of volatile refractory compound wastewater. Background Art

[0002] Volatile organic compounds are a class of pollutants that are volatile and have high vapor pressure at room temperature and pressure. These substances are widely used in many industrial fields such as chemical industry, coating, printing, and pharmaceuticals. For example, nitrogen-containing heterocyclic compounds are an important class of organic compounds that are often used as solvents and chemical raw materials and are indispensable in the synthesis of plastics, rubber, fibers, etc. These heterocyclic compounds exhibit special chemical and physical properties, and the strong bonds formed by nitrogen atoms and carbon atoms make them highly chemically stable.

[0003] At present, the main treatment methods for volatile organic compound wastewater are recovery method and destruction method. Recovery methods include adsorption method, absorption method, condensation method, etc. The adsorption method uses adsorbents such as activated carbon and molecular sieves to adsorb volatile organic compounds. Although the equipment is simple and easy to operate, the adsorbent regeneration cost is high and it is easy to saturate, and the treatment efficiency will decrease over time; the absorption method absorbs volatile organic compounds through specific solvents, and valuable components can be recycled, but the selection and subsequent treatment of absorbents are relatively complicated, and secondary pollution may also be generated. The destruction methods mainly include combustion method and biodegradation method. The combustion method is divided into direct combustion and catalytic combustion. Direct combustion needs to be carried out at high temperature, with high energy consumption and may produce secondary pollutants such as nitrogen oxides. Although catalytic combustion can reduce the reaction temperature, the catalyst cost is high and it is easy to be poisoned and inactivated; the biodegradation method uses microorganisms to decompose volatile organic compounds into harmless substances. It is low-cost and environmentally friendly, but the degradation rate is slow, and the microbial cultivation and domestication are difficult. The treatment effect of high-concentration or difficult-to-biodegrade volatile organic compounds is not good.

[0004] Although aerobic biological methods can achieve efficient removal of volatile organic compounds, they also have certain defects, such as high energy consumption. Since a large amount of oxygen is required to maintain aerobic conditions, the operating cost is high; pollutants are volatile and can easily escape into the air during aerobic treatment, causing secondary pollution. Currently, there are sewage treatment methods that combine electrochemistry with microorganisms, mainly using electrically assisted anaerobic technology to treat pollutants. Adding electricity can enhance the anaerobic degradation process of microorganisms, but it is difficult to achieve complete mineralization when treating pollutant wastewater, resulting in the effluent failing to meet standards. From the above, it can be seen that research and treatment of volatile organic compound wastewater is very necessary.

[0005] Chinese patent application 202311637111.9 discloses a method for strengthening the degradation of nitrogen-containing heterocyclic compounds by constructing an aerobic / anoxic microenvironment through electrocatalytic coupling of nitrate nitrogen. Electrode materials loaded with transition metal oxides are used for oxygen evolution by electrocatalysis. Oxygen directly passes through the biofilm loaded on the anode surface to achieve in-situ mass transfer of oxygen, forming an aerobic / anoxic environment. Nitrate nitrogen can be used as an electron acceptor under anoxic conditions to achieve aerobic / anoxic biodegradation of nitrogen-containing heterocyclic compound wastewater. The cross-flow rising reactor used reduces the volume of the reactor, improves the reactor's ability to resist shock loads, promotes more contact between organic pollutants and microorganisms on the electrode surface, and improves degradation efficiency. The above device improves the biodegradability of nitrogen-containing heterocyclic compounds to a certain extent. However, the electrode used in the above device is a plate electrode, which has the problem of insufficient contact between the pollutant and the electrode surface. The pollutant first contacts the anoxic environment in the aerobic / anoxic microenvironment of the biofilm. The oxygen mass transfer efficiency is not efficient enough, and the degradation efficiency cannot be guaranteed. Summary of the invention

[0006] In view of the problems of large mechanical aeration energy consumption, high gas loss, gas volatilization pollution, poor oxygen evolution capacity, etc. in the existing aerobic biological treatment of wastewater containing volatile organic compounds, the present invention provides a method for enhancing microbial degradation of wastewater containing volatile and difficult-to-degrade compounds by using tubular biofilm electrodes. The method utilizes electrodes with good biocompatibility for electrocatalytic oxygen evolution. Oxygen directly passes through the biofilm loaded on the surface of the tubular anode to achieve in-situ mass transfer of oxygen, form a microaerobic microenvironment, and achieve microaerobic biodegradation of wastewater containing volatile and difficult-to-degrade compounds.

[0007] The method of using tubular biofilm electrodes to enhance the degradation of volatile refractory compound wastewater by microorganisms comprises the following steps: firstly preparing an electrocatalytic electrode with good biocompatibility, then constructing an electrocatalytic microaerobic biofilm system, and passing the oxygen generated by decomposing water by the electrocatalytic electrode through the biofilm loaded on the surface of the electrode material to construct a microaerobic environment, coupling microorganisms to degrade volatile refractory compound wastewater, and simultaneously using the method of water seepage from the top of the anode into the reactor to promote better contact between organic pollutants and microorganisms on the electrode surface. When the pollutants enter the reactor, they first come into contact with the aerobic layer, and realizing the open loop of the pollutants is beneficial to the subsequent degradation of the pollutants, improving the reactor's ability to resist shock loads, and improving the degradation efficiency. The specific steps are as follows:

[0008] Step 1, spraying a catalyst on the surface of a hollow tubular foam metal substrate material to obtain an anode, and weaving a conductive material into a mesh to obtain a cathode;

[0009] Step 2, using a three-electrode system, the reference electrode is an Ag / AgCl electrode, and a constant potential is applied to the three-electrode system using an electrochemical workstation; the anode is placed in the middle of the seepage rising microbial reactor, the cathode is placed around the anode, the reference electrode is placed between the cathode and the anode, anaerobic sludge is added to cover the anode, a biofilm is formed on the surface of the anode, a voltage is applied to reach the oxygen evolution potential, and at the same time, wastewater containing volatile and difficult-to-degrade compounds is infiltrated from the water inlet at the top of the anode, and water is discharged from the top of the reactor, so as to realize electrocatalytic oxygen evolution to build a microaerobic environment to enhance microbial degradation.

[0010] Furthermore, in step 1, the catalyst is a compound with electrocatalytic oxygen evolution capability conventionally used in the art, including but not limited to Ru 0.5 Ir 0.5 O 2 、RuO 2 、IrO 2 wait.

[0011] Furthermore, in step 1, the hollow tubular foam metal substrate includes but is not limited to foam metals such as foam titanium and foam nickel.

[0012] Furthermore, in step 1, the conductive material is a metal wire with conductive properties conventionally used in the art, including but not limited to titanium, nickel, etc.

[0013] Furthermore, in step 1, the pores of the hollow tubular metal foam base material are 50 μm.

[0014] Furthermore, in step 1, the pores of the cathode are 4 meshes.

[0015] Furthermore, in step 2, the anaerobic sludge is taken from a bioreactor for treating wastewater containing volatile recalcitrant compounds, and the initial inoculum size of the anaerobic sludge is 10 to 30 mg L -1 MLSS -1 .

[0016] Furthermore, in step 2, the applied voltage is 0.9-1.8 V, and the concentration of the influent water is 100-200 mg L -1 .

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The tubular oxygen electrolysis electrode constructed by the present invention has a hollow tubular structure with the function of water intake. Therefore, the water intake method of the tubular electrode oxygen electrolysis microaerobic biofilm reactor is different from that of the traditional plate electrode oxygen electrolysis microaerobic bioreactor, and the two pyridines flow in opposite directions. The way of water intake through the tubular electrode and seepage into the reactor allows the pollutants to first contact the aerobic layer of the biofilm, and the oxygen generated by oxygen electrolysis is directly transferred to the aerobic layer of the biofilm, which improves the oxygen mass transfer efficiency, is conducive to the ring opening of volatile compounds, and is converted from large molecular organic matter to small molecular inorganic matter, and increases the contact time between pollutants and microorganisms, which is conducive to the degradation of pollutants;

[0019] (2) The present invention couples electrocatalytic technology with biotechnology to construct a microaerobic microenvironment through electrocatalytic oxygen evolution to enhance the degradation of volatile compound wastewater. 0.5 Ir 0.5 O 2 Under a certain applied voltage, water is decomposed to release oxygen. Since the electrode material has strong hydrophilicity, looseness, porosity and other characteristics, it has better biocompatibility. Therefore, the oxygen produced directly reaches the biofilm in the microbial reaction system, forming an aerobic-anoxic-anaerobic microbial layer structure, which is conducive to the in-situ utilization of aerobic microorganisms and the rapid decomposition of organic matter, changing the traditional oxygen supply mode and improving O 2 The utilization rate of the microorganisms is improved. After a period of selection, the microbial structure evolves in a direction that is more conducive to the degradation of pollutants, which improves the system's tolerance and activity to pollutants and greatly improves the stability of the system, solving the problem that traditional volatile compounds such as pyridine are easy to volatilize and aerobic biological treatment has large gas loss and high cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a simplified schematic diagram of the structure of a tubular oxygen electrolysis micro-aerobic biofilm reactor, wherein a water inlet ④ is arranged at the top of the electrode, and a water outlet ⑤ is arranged at the other end of the reactor top, and an anode ①, a reference electrode ③ and a cathode ② are arranged inside the reactor and filled with anaerobic sludge.

[0021] Figure 2 The figures are (a) and (b) a cross-sectional view of a hollow tubular metal foam anode with a catalyst sprayed on the surface.

[0022] Figure 3 3 is a graph showing the pyridine removal performance of different reaction systems in Example 1. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below in conjunction with specific embodiments and drawings. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0024] The hollow tubular titanium foam used in the following examples was purchased from Nantong New Phoenix Materials Co., Ltd.

[0025] Example 1

[0026] Spraying Ru on the surface of hollow tubular titanium foam 0.5 Ir 0.5 O 2 The anode is prepared, and the electrode material has the characteristics of easy synthesis, high biocompatibility, containing electrocatalytic materials and strong hydrophilicity. The cathode is prepared by weaving titanium wire into a mesh. The reference electrode is Ag / AgCl.

[0027] Five groups of reactors were set up: a tubular electrooxygen microaerobic biofilm reactor, a tubular electrooxygen reactor, an aerobic bioreactor, an anaerobic bioreactor, and a plate electrooxygen microaerobic bioreactor (prepared with reference to Chinese patent application 202311637111.9), and pyridine degradation experiments were carried out respectively.

[0028] Tubular electro-oxygen micro-aerobic biofilm reactor: The structural diagram of the tubular electro-oxygen micro-aerobic biofilm reactor is shown in Figure 1 .like Figure 1 As shown, a water inlet ④ is set at the top of the electrode, and a water outlet ⑤ is set at the other end of the reactor top. The reactor is provided with an anode ①, a reference electrode ③ and a cathode ② and filled with anaerobic sludge. 0.5 Ir 0.5 O 2 / Foam titanium electrode composition, tubular Ru 0.5 Ir 0.5 O 2 / The foamed titanium electrode is placed in the middle of the bioreactor as the anode, the middle of the anode is the Ag / AgCl reference electrode, and the titanium mesh surrounding the anode is the cathode. The wastewater containing volatile compounds is introduced into the microbial reaction system and a voltage is applied to the oxygen evolution potential. The applied voltage is 1.3V.

[0029] The microbial reaction system of the reactor is composed of the same amount of simulated wastewater and inoculated sludge. The simulated wastewater is 100 mg L -1 pyridine solution, pH 7 phosphate buffer, and 1 mL L -1 The anaerobic sludge inoculated was taken from the bioreactor treating pyridine-containing wastewater. The initial anaerobic sludge inoculation amount was 10-30 mg L -1 MLSS.

[0030] The pyridine removal performance of different reaction systems is shown in Figure 2. Figure 3As shown in the figure, it can be seen that the pyridine degradation rate in the tubular electro-oxygen micro-aerobic biofilm reactor under an applied voltage of 1.3 V is significantly higher than that in the other two groups of reactors, and the degradation rate is comparable to that of the aerobic bioreactor. Comparing the tubular electro-oxygen reactor and the anaerobic bioreactor under the same conditions, it is found that their pyridine degradation rates are relatively slow. It is speculated that the removal of this part of pyridine may be due to the oxygen generated by electrocatalysis reaching the microbial layer, which helps aerobic microorganisms to use it in situ and quickly decompose organic matter.

[0031] In a tubular electro-oxygen micro-aerobic biofilm reactor, the electrocatalytic Ru 0.5 Ir 0.5 O 2 / The oxygen produced by the decomposition of water by titanium foam is transferred to the biofilm on the electrode surface, forming an aerobic-anoxic-anaerobic biolayer structure. Pyridine is oxidized and decomposed in the aerobic layer, and then reaches the anoxic layer to be further decomposed and mineralized, achieving the purpose of electro-oxygen coupling biodegradation of volatile compound wastewater. It not only promotes the growth of functional microorganisms and strengthens the electron transfer between pollutants and microorganisms, but also reduces the energy waste and gas pollution caused by the use of mechanical aeration in traditional biodegradation. At the same time, it increases the system's ability to resist shock loads, providing a certain theoretical and practical basis for industrial application.

[0032] The comparative reactor setup is shown below:

[0033] Comparative Example 1

[0034] Tubular electrooxygen reactor: It has the same structure as the tubular electrooxygen micro-aerobic biofilm reactor, with an applied voltage of 1.3V. The difference from the tubular electrooxygen micro-aerobic biofilm reactor is that no anaerobic sludge is added.

[0035] Comparative Example 2

[0036] Aerobic bioreactor: The structure is the same as that of the tubular electro-oxygen micro-aerobic biofilm reactor. The difference from Example 1 is that the applied voltage is 0 and aeration is performed by an aeration pump to maintain the dissolved oxygen in the reactor at 2.0-3.0 mg L -1 .

[0037] Comparative Example 3

[0038] Anaerobic bioreactor: The structure is the same as that of the tubular electro-oxygen micro-aerobic biofilm reactor, and the difference from Example 1 is that the applied voltage is 0.

[0039] Comparative Example 4

[0040] Plate-type oxygen electrolysis microaerobic bioreactor: prepared with reference to Chinese patent application 202311637111.9. The difference from Example 1 is that the electrode structure is a plate electrode, and the water inlet method is different, that is, water is introduced from the lower end of the anode.

[0041] Among the control reactor systems, only the aerobic bioreactor has a pyridine removal rate comparable to that of the tubular electro-oxygen micro-aerobic biofilm reactor system. The aerobic bioreactor can cause problems such as pyridine volatilization and energy waste. Under the same voltage, the plate-type electro-oxygen micro-aerobic bioreactor has a lower pyridine removal rate than the tubular electro-oxygen micro-aerobic biofilm reactor due to the low oxygen mass transfer efficiency. 0.5 Ir 0.5 O 2 / The foam titanium electrode is used as an oxygen evolution electrode. A layer of biofilm is attached to the surface of the electrode. The oxygen produced by the oxygen evolution electrode forms an aerobic-anoxic-anaerobic microenvironment through the surface of the biofilm. On the other hand, the way in which water seeps into the reactor through the tubular electrode is more in line with the degradation path of volatile pollutants.

[0042] Obviously, the above implementation cases are only examples for the purpose of clearly illustrating the embodiments, and are not intended to limit the embodiments. For ordinary technicians in the relevant field, 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 methods here. The obvious changes or modifications derived from this still fall within the scope of protection of the claims of the present invention.

Claims

1. A method for enhancing the degradation of volatile and difficult-to-degrade compound wastewater by microorganisms using tubular biofilm electrodes, characterized in that: The specific steps are as follows: Step 1, spraying a catalyst on the surface of a hollow tubular foam metal substrate material to obtain an anode, and weaving a conductive material into a mesh to obtain a cathode; Step 2, using a three-electrode system, the reference electrode is an Ag / AgCl electrode, and a constant potential is applied to the three-electrode system using an electrochemical workstation; the anode is placed in the middle of the seepage rising microbial reactor, the cathode is placed around the anode, the reference electrode is placed between the cathode and the anode, anaerobic sludge is added to cover the anode, a biofilm is formed on the surface of the anode, a voltage is applied to reach the oxygen evolution potential, and at the same time, wastewater containing volatile and difficult-to-degrade compounds is infiltrated from the water inlet at the top of the anode, and water is discharged from the top of the reactor, so as to realize electrocatalytic oxygen evolution to build a microaerobic environment to enhance microbial degradation.

2. The method according to claim 1, characterized in that In step 1, the catalyst is Ru 0.5 Ir 0.5 O2, RuO2 or IrO2.

3. The method according to claim 1, characterized in that: In step 1, the hollow tubular foam metal substrate is foamed titanium or foamed nickel.

4. The method according to claim 1, characterized in that: In step 1, the conductive material is titanium or nickel.

5. The method according to claim 1, characterized in that In step 1, the pores of the hollow tubular metal foam substrate material are 50 μm.

6. The method according to claim 1, characterized in that In step 1, the pores of the cathode are 4 meshes.

7. The method according to claim 1, characterized in that In step 2, anaerobic sludge is taken from a bioreactor treating wastewater containing volatile recalcitrant compounds.

8. The method according to claim 1, characterized in that In step 2, the initial inoculum size of anaerobic sludge is 10-30 mg L -1 MLSS -1 .

9. The method according to claim 1, characterized in that In step 2, the applied voltage was 0.9–1.8 V and the influent concentration was 100–200 mg L -1 .

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