CN111186961B - Electrochemical bubble-free aeration membrane bioreactor and application thereof - Google Patents

Abstract

The invention discloses an electrochemical bubble-free aeration membrane bioreactor and an application thereof, belonging to the technical field of sewage treatment. The reactor includes a water inlet pipe, an inlet water pump, a reactor shell, a graphite plate anode, an electrochemical bubble-free aeration membrane assembly, a power source, an aeration system, a water outlet pipe and a circulation device. The invention adopts graphite plate as anode, adopts electrochemical bubble-free aeration membrane assembly as cathode in electrochemical system directly, and applies external electric field through regulated DC power supply. The removal of pollutants, and the strong oxidizing substances produced by electrocatalysis can be used to achieve the removal of refractory organic pollutants in sewage without adding any chemical agents, and the efficient coupling of electrochemical oxidation and bubble-free aeration membrane bioreactors can be realized. .

Description

An electrochemical bubble-free aerated membrane bioreactor and its application

technical field

The invention relates to a membrane bioreactor and applications thereof, in particular to an electrochemical non-foam aeration membrane bioreactor and applications thereof, belonging to the technical field of sewage treatment.

Background technique

With the wide application of drugs, antibiotics, personal care products, etc., a large number of refractory organic pollutants enter the municipal pipeline network through various channels. Since most of these micropollutants have poor biodegradability, and conventional sewage treatment plants have not specially designed corresponding treatment processes, these micropollutants can enter the receiving water body through the sewage treatment unit, which seriously threatens the safety of drinking water and the human health.

The bubble-free aerated membrane bioreactor is a biofilm reactor used in water treatment. It uses a gas-permeable membrane as a microbial growth carrier, and at the same time uses a gas-permeable membrane to supply oxygen to the attached and growing microorganisms. The technical advantages of the bubble-free aerated membrane bioreactor are mainly reflected in the heterogeneous mass transfer of pollutants and oxygen, the oxygen supply of the aeration membrane in the form of no bubbles, and the functional layering of the biofilm structure. However, the removal efficiency of refractory pollutants by bubble-free aerated membrane bioreactors is still very limited.

Electrochemical advanced oxidation is an environmentally friendly technology for the treatment of refractory pollutants in sewage. By applying an electric field, oxidant species (such as hydroxyl radicals, superoxide anions, H ₂ O ₂ , etc.) can be generated in situ, thereby degrading the refractory organic pollutants in water. Therefore, how to reasonably design the structure of the electrochemical reactor and develop the corresponding process to realize the efficient coupling of the electrochemical oxidation and the bubble-free aerated membrane bioreactor, so as to realize the efficient removal of the refractory pollutants, is an urgent problem to be solved at present. .

SUMMARY OF THE INVENTION

In view of the problems in the prior art, the present invention provides an electrochemical bubble-free aeration membrane bioreactor and its application. The invention has a simple structure, uses a graphite plate as an anode, and adopts an electrochemical bubble-free aeration membrane assembly directly as a battery The cathode in the chemical system applies an external electric field through a regulated DC power supply. When operating in a continuous flow mode, it can not only achieve the removal of conventional pollutants in sewage, but also use the strong oxidation generated by electrocatalysis without adding any chemicals. It can realize the removal of refractory organic pollutants in sewage, and realize the efficient coupling of electrochemical oxidation and bubble-free aerated membrane bioreactor.

For realizing the above technical purpose, the technical scheme of the present invention is:

An electrochemical bubble-free aeration membrane bioreactor, comprising a water inlet pipe, an inlet pump, a reactor shell, a graphite plate anode, an electrochemical bubble-free aeration membrane assembly, a power source, an aeration system, a water outlet pipe and a circulation device; One end of the water inlet pipe is placed in the reactor shell; the graphite plate anode and the electrochemical bubble-free aeration membrane assembly are located in the reactor shell; the graphite plate anode is connected to the positive electrode of the power supply through a wire; The bubble aeration membrane assembly is connected to the negative electrode of the power supply through a wire. The electrochemical bubble-free aeration membrane assembly includes a membrane frame, a stainless steel wire mesh and a hollow fiber membrane. The membrane frame includes an upper air duct and a lower air duct. There is an air inlet, an exhaust port is arranged on the lower air duct, the hollow fiber membrane is woven on the stainless steel wire mesh in the form of a curtain arrangement, and the upper and lower ends of the hollow fiber membrane are sealed and fixed on the upper air duct and the lower guide respectively. In the trachea, the inner cavity of the hollow fiber membrane is communicated with the inner cavity of the upper airway and the lower airway, and the surface of the hollow fiber membrane is loaded with a biofilm; the aeration system includes an aeration pump, an aeration pipe and an exhaust pipe, The aeration pipe is provided with a gas flow meter for adjusting the intake air volume and a pressure gauge for adjusting the aeration pressure, the aeration pipe is connected with the air inlet, the exhaust pipe is connected with the exhaust port; the water outlet pipe is connected with the device. The overflow weir at the top of the reactor shell is communicated; the circulation device includes a circulation pump and a circulation pipe, and the two ends of the circulation pipe are respectively communicated with the lower end and the upper end of the reactor shell.

Preferably, the biofilm is a heterogeneous mass transfer biofilm formed by a cyclic hanging film method.

Further preferably, the steps of the circulating film hanging method are:

(1) First prepare simulated micro-polluted surface water with COD content of 50 mg/L and NH4 ⁺ -N content of 5 mg/L, then the activated sludge collected from the sewage treatment plant and the prepared simulated micro-polluted surface water according to The volume ratio is 1:2 and mixed to form a mixed water body. The water inlet pump is turned off, and the mixed water body is poured into the reactor. Among them, the reactor used in the circulating film method has the same structure as the electrochemical non-foam aeration membrane bioreactor. , the difference is only that the surface of the hollow fiber membrane in the reactor used in the circulating membrane method is not loaded with biofilm, and the circulating pump is turned on to make the activated sludge at the bottom of the reactor flow from the top of the reactor to the bottom through the circulating pipe. The circulating flow rate was set to 1.50 mL/min, and the hydraulic retention time was 24 h. After a layer of biofilm visible to the naked eye was attached to the surface of the hollow fiber membrane, all the activated sludge and simulated pollutant surface water in the reactor were discharged;

(2) Turn on the water inlet pump, and use the nutrient solution to continuously feed water until a yellow-brown biofilm with uniform thickness grows on the surface of the hollow fiber membrane. The composition of the solution is sodium humate 40 mg/L, NH ₄ Cl 19.11 mg/L, KCl 0.58 mg/L, MgSO ₄ ∙7H2O 12.3 mg/L, CaCl ₂ ∙2H ₂ O 29.4 mg/L, Na ₂ SO ₃ 50 mg/L.

Preferably, the hollow fiber membrane is any one of polyvinylidene fluoride hollow fiber membrane, polypropylene hollow fiber membrane, polytetrafluoroethylene hollow fiber membrane, and polyethersulfone hollow fiber membrane.

Preferably, the outer diameter of the hollow fiber membrane is 0.5-1.5 mm.

Preferably, the power supply is a regulated DC power supply, and the voltage range of the power supply is 0.5-2 V.

Preferably, the distance between the graphite plate anode and the electrochemical bubble-free aeration membrane assembly is 0.5-5 cm.

Application of the above reactor in sewage treatment.

Preferably, the hydraulic retention time is 2-8 h.

Principle of the present invention:

The sewage enters the electrochemical bubble-free aeration membrane bioreactor from the water inlet pipe, and the refractory organic matter is first oxidized and degraded by the oxidizing substances (hydroxyl radicals) generated on the anode surface of the graphite plate. The pollutants reach the surface of the cathode electrochemical bubble-free aeration membrane module, and the intermediate products obtained from the anode degradation and the easily degradable pollutants in the water are degraded and removed by the biofilm on the cathode membrane module. At the same time, the _O2 released by the hollow fiber membrane is on the cathode surface. The obtained electrons are reduced to form H ₂ O ₂ , and H ₂ O ₂ and O ₂ promote the production of Fe(II) on the surface of the stainless steel wire of the cathode membrane module through corrosion, so that the Fenton reaction occurs at the cathode interface, and at the same time, Fe(III) can pass through. It accepts electrons and is reduced to Fe(II), thereby ensuring the continuous generation of oxidant species and improving the removal rate of refractory organic matter. The treated water flows out through overflow weirs and outlet pipes.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention adopts graphite plate as anode, adopts electrochemical bubble-free aeration membrane assembly as cathode directly, and when operating under the continuous flow mode of external electric field, the hydroxyl radical generated by anode can realize the preliminary oxidation of refractory organic matter, The oxidized intermediate products can be further degraded and removed by the biofilm on the cathode membrane module, and the intermediate products that are not completely degraded and removed can be further degraded by the strong oxidizing substances produced on the surface of the cathode membrane module. The present invention can be used without the addition of any chemical agent. The strong oxidizing substances produced by electrocatalysis realize the efficient removal of refractory organic pollutants, and realize the efficient coupling of electrochemical oxidation and bubble-free aerated membrane bioreactor.

2. In the present invention, through the bubble-free aeration membrane, oxygen enters the biofilm through the membrane wall in a bubble-free form, and can be directly utilized by microorganisms. The oxygen utilization rate is high, and the low oxygen supply can meet the needs of aeration. Conducive to reducing energy consumption. In addition, the bubble-free aeration does not generate bubbles, and the biofilm on the surface of the electrochemical bubble-free aeration membrane module will not be rubbed by the bubbles, so it is not easy to fall off. The unique double-membrane structure and anisotropic mass transfer process make it have many advantages such as simultaneous nitrification and denitrification, flexible oxygen control, long biofilm sludge age, high activity, and low cost of infrastructure and operation.

3. The reactor of the present invention has simple structure, convenient operation, stable effluent quality, and high efficiency in sewage treatment.

4. The reactor of the present invention is used to treat the sewage without chemical addition and will not cause secondary pollution.

Description of drawings

Fig. 1 is the structural representation of the reactor of the present invention;

Fig. 2 is the structural representation of the electrochemical bubble-free aeration membrane assembly in the present invention;

Reference number:

11. Water inlet pipe 12. Inlet water pump 2. Reactor shell 3. Graphite plate anode 4. Electrochemical bubble-free aeration membrane module 41. Stainless steel wire mesh 42. Hollow fiber membrane 43. Membrane frame 44. Upper air duct 45. Lower air pipe 51. Circulation pipe 52. Circulation pump 6. Power supply 71. Aeration pipe 72. Aeration pump 73. Gas flow meter 74. Pressure gauge 75. Exhaust pipe 8. Water outlet pipe

Detailed ways

The features of the present invention are further described below through examples, but the claims of the present invention are not limited in any way.

Example 1:

An electrochemical bubble-free aeration membrane bioreactor, comprising a water inlet pipe 11, an inlet pump 12, a reactor shell 2, a graphite plate anode 3, an electrochemical bubble-free aeration membrane assembly 4, a power source 6, an aeration system, The water outlet pipe 8 and the circulation device; one end of the water inlet pipe 11 is placed in the reactor shell 2; the graphite plate anode 3 and the electrochemical bubble-free aeration membrane assembly 4 are located in the reactor shell 2; the graphite plate The anode 3 is connected to the positive electrode of the power source 6 through a wire; the electrochemical bubble-free aeration membrane assembly is connected to the negative electrode of the power source 6 through a wire, and the distance between the electrochemical bubble-free aeration membrane assembly and the graphite plate anode 3 is 50 mm, and the The electrochemical bubble-free aeration membrane module 4 includes a membrane frame 43, a stainless steel wire mesh 41 and a hollow fiber membrane 42. The membrane frame 43 includes an upper air duct 44 and a lower air duct 45, and the upper air duct 44 is provided with an air inlet , the lower air duct 45 is provided with an exhaust port, the hollow fiber membrane 42 is woven on the stainless steel wire mesh 41 in a curtain arrangement, and the upper and lower ends of the hollow fiber membrane 42 are sealed and fixed to the upper air duct 44 and the lower In the airway tube 45, the inner cavity of the hollow fiber membrane 42 is communicated with the inner cavity of the upper airway tube 44 and the lower airway tube 45, and the hollow fiber membrane material can be polyvinylidene fluoride hollow fiber membrane, polypropylene hollow fiber membrane, polytetrafluoroethylene Either a hollow fiber membrane or a polyethersulfone hollow fiber membrane, the outer diameter of which is 1.0 mm, and the surface of the hollow fiber membrane is loaded with a biological membrane (not shown in the figure), wherein the biological membrane is formed by circulating the membrane The anisotropic mass transfer biofilm formed by the method; the power supply 6 is a regulated DC power supply 6; the aeration system includes an aeration pump 72, an aeration pipe 71 and an exhaust pipe 75, and the aeration pipe 71 is provided with a A gas flow meter 73 for adjusting the intake air volume and a pressure gauge 74 for detecting the air pressure of the aeration pipe 71, the aeration pipe 71 is connected with the air inlet, and the exhaust pipe 75 is connected with the exhaust port; The overflow weir at the top of the reactor shell 2 is communicated; the circulation device includes a circulation pump 52 and a circulation pipe 51, and the two ends of the circulation pipe 51 are communicated with the lower end and the upper end of the reactor shell 2 respectively.

The structure of the reactor used in the cyclic film hanging method mentioned in this embodiment is the same as that of the electrochemical non-foam aerated membrane bioreactor mentioned above, and the difference is only in the hollow fibers in the reactor used in the cyclic film hanging method. The surface of the membrane is not loaded with biofilm, and the specific steps of the cyclic film hanging method are as follows:

(1) First prepare simulated micro-polluted surface water with COD content of 50 mg/L and NH4 ⁺ -N content of 5 mg/L, then the activated sludge collected from the sewage treatment plant and the prepared simulated micro-polluted surface water according to The volume ratio is 1:2 and mix to form a mixed water body, close the water inlet pump, pour the mixed water body into the reactor, turn on the circulating pump to make the activated sludge at the bottom of the reactor flow from the top of the reactor to the bottom through the circulating pipe, and the circulation of the reactor The flow rate was set to 1.50 mL/min, and the hydraulic retention time was 24 h. After a layer of biofilm visible to the naked eye was attached to the surface of the hollow fiber membrane, all the activated sludge and simulated pollutant surface water in the reactor were discharged;

(2) Turn on the inlet water pump, and use the nutrient solution to continuously feed water until a yellow-brown biofilm with uniform thickness grows on the surface of the hollow fiber membrane. The composition of the solution is sodium humate 40 mg/L, NH ₄ Cl 19.11 mg/L, KCl 0.58 mg/L, MgSO ₄ ∙7H2O 12.3 mg/L, CaCl ₂ ∙2H ₂ O 29.4 mg/L, Na ₂ SO ₃ 50 mg/L.

The above electrochemical bubble-free aerated membrane bioreactor was used to treat simulated micro-polluted surface water containing sulfamethoxazole (SMX) and trimethoprim (TMP). The experimental conditions were set as: influent COD 50 mg/L, NH ₄ ⁺ -N 5 mg/L, sulfamethoxazole 100 μg/L, trimethoprim 100 μg/L, the hydraulic retention time was 2 h, and the regulated DC power supply voltage was 1 V. Other conditions were the same, and the unpowered reactor was set as the blank control group. After 20 days of operation in continuous flow mode, the effluent condition of the reactor was detected. The results showed that the effluent COD of the two reactors was lower than 10 mg/L, and the removal rate of sulfamethoxazole and trimethoprim in the blank group was only The removal rate of sulfamethoxazole and trimethoprim can be stably maintained at about 70% in the electrochemical bubble-free aerated membrane bioreactor with an external voltage of 1.0 V.

Example 2:

The same electrochemical bubble-free aerated membrane bioreactor as in Example 1 was used to treat the simulated micro-polluted surface water containing sulfamethoxazole (SMX) and trimethoprim (TMP), and the experimental conditions were set as: influent COD 50 mg/L, NH ₄ ⁺ -N 5 mg/L, sulfamethoxazole 100 μg/L, trimethoprim 100 μg/L, the hydraulic retention time was 4 h, and the regulated DC power supply voltage was 1.5 V. Other conditions were the same, and the unpowered reactor was set as the blank control group. After 20 days of operation in continuous flow mode, the effluent condition of the reactor was detected. The results showed that the effluent COD of the two reactors was lower than 10 mg/L, and the removal rate of sulfamethoxazole and trimethoprim in the blank group was only The removal rate of sulfamethoxazole and trimethoprim can be stably maintained at more than 80% by the electrochemical bubble-free aerated membrane bioreactor with an external voltage of 1.5 V.

Example 3:

The same electrochemical bubble-free aerated membrane bioreactor as in Example 1 was used to treat the simulated micro-polluted surface water containing sulfamethoxazole (SMX) and trimethoprim (TMP), and the experimental conditions were set as: influent COD 50 mg/L, NH ₄ ⁺ -N 5 mg/L, sulfamethoxazole 100 μg/L, trimethoprim 100 μg/L, the hydraulic retention time was 8 h, and the regulated DC power supply voltage was 2 V. Other conditions were the same, and the unpowered reactor was set as the blank control group. After 20 days of operation in continuous flow mode, the effluent condition of the reactor was detected. The results showed that the effluent COD of the two reactors was lower than 10 mg/L, and the removal rate of sulfamethoxazole and trimethoprim in the blank group was only The removal rate of sulfamethoxazole and trimethoprim was stably maintained at more than 90% in the electrochemical bubble-free aerated membrane bioreactor with an external voltage of 2 V.

It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effect; as long as it meets the needs of use, it is within the protection scope of the present invention.

Claims (7)

1. an electrochemical bubble-free aeration membrane bioreactor, is characterized in that, comprises water inlet pipe, inlet pump, reactor shell, graphite plate anode, electrochemical bubble-free aeration membrane assembly, power supply, aeration system, A water outlet pipe and a circulation device; one end of the water inlet pipe is placed in the reactor shell; the graphite plate anode and the electrochemical bubble-free aeration membrane assembly are located in the reactor shell; the graphite plate anode is connected to the positive electrode of the power supply through a wire ; The electrochemical bubble-free aeration membrane assembly is connected with the negative electrode of the power supply through a wire, the electrochemical bubble-free aeration membrane assembly is in the shape of a plate grid, and the electrochemical bubble-free aeration membrane assembly includes a membrane frame, a stainless steel wire net and hollow fiber membrane, the membrane frame includes an upper air duct and a lower air duct, the upper air duct is provided with an air inlet, and the lower air duct is provided with an exhaust port, the hollow fiber membranes are arranged in the form of curtains Braided on stainless steel wire mesh, the upper and lower ends of the hollow fiber membrane are sealed and fixed in the upper airway and the lower airway respectively, the inner cavity of the hollow fiber membrane is communicated with the upper airway and the lower airway, and the surface of the hollow fiber membrane A biofilm is loaded; the aeration system includes an aeration pump, an aeration pipe and an exhaust pipe, and the aeration pipe is provided with a gas flow meter for adjusting the intake air volume and a pressure gauge for adjusting the aeration pressure. The gas pipe is connected with the air inlet, and the exhaust pipe is connected with the exhaust port; the water outlet pipe is connected with the overflow weir arranged on the top of the reactor shell; the circulation device includes a circulation pump and a circulation pipe, and the two parts of the circulation pipe are The ends are respectively communicated with the lower end and the upper end of the reactor shell, and there is no gas diffuser at the bottom of the reactor; The biofilm is a heterogeneous mass transfer biofilm formed by a cyclic film hanging method; the steps of the circulating film hanging method are: (1) First prepare simulated micro-polluted surface water with COD content of 50 mg/L and NH ₄ ⁺ -N content of 5 mg/L, and then prepared simulated micro-polluted surface water with activated sludge collected from the sewage treatment plant Mix well according to the volume ratio of 1:2 to form a mixed water body, turn off the water inlet pump, pour the mixed water body into the reactor, turn on the circulating pump to make the activated sludge at the bottom of the reactor flow from the top of the reactor to the bottom through the circulating pipe, and the The circulating flow rate was set to 1.50 mL/min, and the hydraulic retention time was 24 h. After a layer of biofilm visible to the naked eye was attached to the surface of the hollow fiber membrane, all the activated sludge and simulated pollutant surface water in the reactor were discharged; (2) Turn on the water inlet pump, and use the nutrient solution to continuously feed water until a yellow-brown biofilm with uniform thickness grows on the surface of the hollow fiber membrane. The composition of the solution is sodium humate 40 mg/L, NH ₄ Cl 19.11 mg/L, KCl 0.58 mg/L, MgSO ₄ ∙7H ₂ O 12.3 mg/L, CaCl ₂ ∙ 2H ₂ O 29.4 mg/L, Na ₂ SO ₃ 50 mg/L. 2. The reactor according to claim 1, wherein the hollow fiber membrane is a polyvinylidene fluoride hollow fiber membrane, a polypropylene hollow fiber membrane, a polytetrafluoroethylene hollow fiber membrane, and a polyethersulfone hollow fiber membrane any of the . 3. The reactor according to claim 1, wherein the outer diameter of the hollow fiber membrane is 0.5-1.5 mm. 4 . The reactor according to claim 1 , wherein the power supply is a regulated DC power supply, and the voltage range of the power supply is 0.5-2 V. 5 . 5 . The reactor according to claim 1 , wherein the distance between the graphite plate anode and the electrochemical bubble-free aeration membrane assembly is 0.5-5 cm. 6 . 6. The application of the reactor according to claim 1 in sewage treatment. 7. The application according to claim 6, wherein the hydraulic retention time is 2-8 h.

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