Anaerobic ammonia oxidation biological reaction denitrification method based on electric field enhanced synergistic membrane separation

Abstract

The invention discloses an anaerobic ammonia oxidation biological reaction denitrification method based on electric field intensification synergistic membrane separation. The anaerobic ammonia oxidation biological reaction denitrification method comprises the following steps: S1, inoculating anaerobic ammonia oxidation sludge and injecting wastewater; s2, domesticating the anaerobic ammonia oxidation sludge: controlling the amount-of-substance ratio of ammonia nitrogen to nitrite nitrogen to be (0.8-1): 1 during water feeding, operating in a continuous mode, gradually shortening the hydraulic retention time until the anaerobic ammonia oxidation reaction ratio is 1.20-1.35, and completing domestication; s3, applying an electric field into the reactor, wherein in the first stage, the voltage is controlled to be 0.3 + / -0.05 V, and the operation time is 20-25 days; in the second stage, the control voltage is 0.6 + / -0.05 V, and the operation time is 30-35 days; and in the third stage, the control voltage is 1 + / -0.05 V, and the operation time is 20-25 days. According to the method disclosed by the invention, the ammonia nitrogen can be further removed in an environment lacking nitrous acid by determining the operation parameters of the direct-current electric field, so that the denitrification efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater biological treatment, and in particular to an anaerobic ammonia oxidation biological reaction denitrification method with electric field enhancement and membrane separation. Background Art

[0002] As a country with a large population, my country has been experiencing a continuous increase in the proportion of urban permanent population with the continuous advancement of urbanization, and the amount of domestic water consumption and wastewater discharge have shown a significant growth trend. Nitrogen pollution is one of the main pollutants in domestic wastewater. At present, biological denitrification technology is the core means to solve the problem of nitrogen pollution in water bodies. It can effectively reduce nitrogen-containing pollutants in water bodies and reduce the load for subsequent treatment of water discharge. Among the traditional biological denitrification processes, nitrification-denitrification technology is the most widely used, and the process has been quite mature in domestic engineering practice. However, the process still has obvious shortcomings: First, high energy consumption; mainly because the digestion process relies on a large amount of aeration, resulting in high operating energy consumption. Second, it is highly dependent on carbon sources; additional carbon sources need to be added in the denitrification stage, which not only greatly increases the treatment cost, but also may cause excessive concentration of organic matter in the effluent due to excessive carbon. These technical and economic bottlenecks have seriously restricted the further optimization and promotion and application of nitrification-denitrification processes.

[0003] In the past 20 years, the anaerobic ammonium oxidation process has been widely promoted as a new type of biological denitrification process. The anaerobic ammonium oxidation process is a process in which anaerobic ammonium-oxidizing bacteria directly convert ammonia nitrogen into nitrogen gas under anaerobic conditions, using ammonia nitrogen as an electron donor and nitrite as an electron acceptor. In the biological denitrification process, compared with traditional nitrification-denitrification, anaerobic ammonium oxidation can save about 50-60% of oxygen consumption and 100% of organic carbon sources, but the proliferation rate of anaerobic ammonium-oxidizing bacteria is slow, and they are often lost in the reactor due to drainage, resulting in instability of the reaction system; secondly, nitrogen in wastewater mostly exists in the form of ammonia nitrogen, and nitrite in the anaerobic ammonium oxidation process is provided by ammonia-oxidizing bacteria. There is a problem of nitrite competing with anaerobic ammonium-oxidizing bacteria for nitrite, which also leads to serious limitations of anaerobic ammonium oxidation denitrification. The invention patent with publication number CN104961231A discloses an anaerobic ammonium oxidation reactor device, whose structure includes a water storage tank, a water inlet pump, a water seal device, a constant temperature device, a graphite electrode, an anaerobic ammonium oxidation reactor, a stirring paddle, a flat membrane assembly, a DC power supply, a stirring rotating motor, an AC power supply, etc. The device strengthens the survival characteristics of anaerobic ammonium oxidation bacteria through a built-in DC electric field to increase its proliferation rate; the built-in flat membrane assembly meets the water production while reducing the loss of microorganisms; the membrane assembly is linked with the enhanced electric field to solve the problems of long generation time of anaerobic ammonium oxidation bacteria, slow domestication and reproduction, and easy loss of microorganisms. However, the invention does not give specific parameters on how to apply a DC electric field to achieve the enhancement of the survival characteristics of anaerobic ammonium oxidation bacteria to increase their proliferation rate. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and synergistic membrane separation. The method can further remove ammonia nitrogen in an environment lacking nitrite by clarifying the operating parameters of the direct current electric field, thereby improving the denitrification efficiency of the anaerobic ammonium oxidation process.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation comprises the following steps:

[0007] S1. Inoculating anaerobic ammonium oxidation sludge into the reactor and injecting wastewater: the reactor includes a reactor body, a membrane assembly, an electrode pair and a stirrer are installed in the body, the electrode pair is connected to a DC regulated power supply outside the body, and the wastewater enters the reactor for treatment and is discharged through the outlet pipe of the membrane assembly;

[0008] S2. Domestication of anaerobic ammonium oxidation sludge: Control ammonia nitrogen (NH4 + ) and nitrite (NO2 - ) is 0.8 to 1:1, and the continuous operation is adopted, and the hydraulic retention time (HRT) is gradually shortened until the anaerobic ammonium oxidation reaction ratio is 1.20 to 1.35, and the acclimation is completed;

[0009] S3. Apply an electric field to the reactor in the following order to denitrify the wastewater in the reactor:

[0010] S31. Control the DC regulated power supply voltage to 0.3±0.05V, and the operation time is 20 to 25 days;

[0011] S32. Control the DC regulated power supply voltage to 0.6±0.05V, and the operation time to 30-35 days;

[0012] S33. Control the DC regulated power supply voltage to 1±0.05V, and the operating time is 20 to 25 days.

[0013] In the above method, the reactor is a reactor known to those skilled in the art that can be used for anaerobic ammonia oxidation reaction in the prior art, such as a fluidized bed reactor, a fixed bed reactor, a biofilm reactor, a sequencing batch reactor (SBR reactor, etc.), an air lift reactor, etc.

[0014] Further, in step S2, when the concentrations of ammonia nitrogen and nitrite nitrogen in the wastewater are both between 100 and 1000 mg / L, the anaerobic ammonium oxidation sludge is domesticated in the following two stages:

[0015] Phase 1: Control the water retention time to 18±0.5h and the operation time to 40-50 days;

[0016] In the second stage, the water retention time is controlled to 16±0.5h and the operation time is 20 to 25 days.

[0017] Furthermore, in step S2, under the condition of maintaining the inlet concentrations of ammonia nitrogen and nitrite nitrogen in the reactor stable, the molar ratio of ammonia nitrogen to nitrite nitrogen is preferably controlled to be 1:1.

[0018] Furthermore, in step S1, when the anaerobic ammonium oxidation sludge is inoculated into the reactor, the inoculation amount of the anaerobic ammonium oxidation sludge is preferably 30-40% of the reactor volume.

[0019] Further, in step S1, the electrode pair includes a working electrode (anode) and a counter electrode (cathode), which are respectively connected to the positive electrode and the negative electrode of the DC regulated power supply. More specifically, the working electrode is preferably graphite carbon felt, and the counter electrode is preferably a titanium electrode.

[0020] Furthermore, in step S1, the structure of the membrane assembly is the same as that of the prior art, generally including a filter membrane, a pneumatic joint for fixing the filter membrane, and a water outlet pipe capable of collecting water effluent from the filter membrane, and a hollow fiber membrane is used as the filter membrane in the membrane assembly. Furthermore, the hollow fiber membrane is a microfiltration membrane with a pore size of 0.1 to 1 μm.

[0021] The wastewater (ie, the object to be treated) described in this application is domestic sewage.

[0022] Compared with the prior art, the present invention is characterized in that:

[0023] 1. The anaerobic ammonium oxidation electrochemical process can produce nitrogen gas by using anode electrodes and ammonia nitrogen in a nitrous acid-free environment. The present invention controls the voltage of an external DC regulated power supply to increase in sequence and operate in stages. Even in an environment lacking nitrous acid, the anaerobic ammonium oxidation reaction can be achieved through the electrode, thereby further removing ammonia nitrogen and improving the denitrification efficiency of the anaerobic ammonium oxidation process.

[0024] 2. By setting electrodes in the reactor, the remaining ammonia nitrogen in the reactor can be removed through the action of the electrodes under a suitable voltage, thereby achieving stable operation of the anaerobic ammonium oxidation process.

[0025] 3. The membrane assembly is used for effluent. When effluent is discharged, the tiny pore size of the microfiltration membrane can effectively intercept the microbial sludge, realize the separation of mud and water, slow down the loss of sludge in the reactor, and has a higher anti-pollution load capacity. It can be widely used in denitrification processes such as domestic sewage and industrial wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1The present invention is a schematic diagram of the structure of an anaerobic ammonium oxidation bioreactor device for implementing the method of the present invention.

[0027] Figure 2 NH4 + and NO2 - The content.

[0028] Figure 3 It is the denitrification efficiency and denitrification load during the anaerobic ammonia-oxidizing bacteria domestication process in the method of the present invention.

[0029] The numbers in the figure are:

[0030] 1 water storage tank; 2 water inlet pump; 3 reactor body; 4 membrane assembly; 5 water outlet pump; 6 DC voltage stabilizing source pump; 7 overflow port; 8 working electrode; 9 counter electrode; 10 water outlet tank; 11 agitator. DETAILED DESCRIPTION

[0031] In order to better explain the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0032] Figure 1 The present invention is a schematic diagram of the structure of an anaerobic ammonia oxidation bioreactor device for implementing the method of the present invention, comprising a water storage tank 1, a reactor, a DC regulated power supply 6, a membrane assembly 4, an electrode pair and an agitator 11. The water storage tank 1 is used to store wastewater to be treated, and the water outlet tank 10 is used to store water treated by the reactor device.

[0033] The reactor comprises a reactor body 3, on which a water inlet, a sampling port and an overflow port 7 are provided. The water inlet is connected to the water storage tank by a pipeline, and a water inlet pump 2 is provided on the pipeline path. The membrane assembly 4, the electrode pair and the agitator 11 are installed in the reactor body 3, wherein:

[0034] The membrane assembly 4 includes a filter membrane, a pneumatic joint for fixing the filter membrane, and a water outlet pipe capable of collecting water effluent from the filter membrane. The water outlet pipe extends out of the reactor body 3 and is connected to the water outlet pool 10 through a pipeline. A water outlet pump 5 is arranged on the pipeline path. After the wastewater enters the reactor for treatment, it is discharged to the water outlet pool 10 through the water outlet pipe of the membrane assembly 4. The filter membrane in the membrane assembly 4 is a hollow fiber membrane, specifically a hollow fiber microfiltration membrane with a pore size of 0.1 to 1 μm.

[0035] The electrode pair includes a working electrode 8 (anode) and a counter electrode 9 (cathode), wherein the working electrode 8 is graphite carbon felt, and the counter electrode 9 is a titanium tube. The working electrode 8 and the counter electrode 9 are respectively connected to the positive electrode and the negative electrode of a DC regulated power supply 6 arranged outside the reactor body 3, and the DC regulated power supply 6 provides DC power to form an electric field.

[0036] In the above device, the volume of the reactor is 1.7±0.5L, and the area of ​​the working electrode 8 is 0.0222±0.005m 2 , the area of ​​the electrode 9 is 0.0135±0.005m 2 The water inlet pump 2 and the water outlet pump 5 are peristaltic pumps.

[0037] Example 1

[0038] by Figure 1 The reactor device shown in the figure uses simulated water as test water to carry out a simulated experiment in the laboratory as an example to illustrate the anaerobic ammonia oxidation biological reaction denitrification method of the present invention with electric field enhancement and membrane separation, which includes the following steps:

[0039] S1. Inoculate anaerobic ammonium oxidation sludge into the reactor:

[0040] First, simulated water was prepared according to the common ion concentrations in domestic sewage, NH4 + As the main target pollutant, NO2 - As the electron acceptor in the anaerobic ammonium oxidation process, NaHCO3 was used as the carbon source, and HCl or NaOH was used to adjust the influent pH to 7.5±0.1; other Fe 2+ , Cu 2+ , Mn 2+ 、Zn 2+ 、Ni 2+ Trace elements such as NH4 are needed to meet the normal metabolism of microorganisms. The concentrations of various substances in the simulated water supply are as follows: + Concentration is 180±10mg N / L, NO2 - The concentration is 180±10mg N / L, Fe 2+ The concentration is 2.3mg / L±0.2, Cu 2+ The concentration is 0.08±0.002mg / L, Mn 2+ The concentration is 0.34±0.01mg / L, Zn 2+ The concentration is 0.12±0.01mg / L, Ni 2+ The concentration was 0.065±0.002mg / L, and the pH was 7.5±0.1. The simulated water was stored in a 20L water tank. Nitrogen was introduced before the experiment to remove the dissolved oxygen in the water and control DO (Dissolved Oxygen, environmental monitoring oxygen parameter) below 0.5mg / L. To ensure that the reactor was in an anoxic environment, the water tank was equipped with a nitrogen source. This experiment used a 15L nitrogen bag.

[0041] Then, anaerobic ammonium oxidation sludge was inoculated into the reactor body at an inoculation amount of 33.3% of the reactor volume (anaerobic ammonium oxidation sludge is the bottom sludge in the reactor operating normally in the laboratory, and its MLVSS (Mixed Liquor Volatile Suspended Solids) is 10±2g / L. The volume of the reactor used in this experiment is 1.7±0.5L, and the inoculation amount of anaerobic ammonium oxidation sludge is 600mL.

[0042] Afterwards, inject the prepared simulated water into the reactor body, and stop injecting water after it is full.

[0043] S2. Acclimation of anaerobic ammonium oxidation sludge:

[0044] Turn on the inlet pump and outlet pump, set the inlet flow rate to 1.45mL / min, and the outlet flow rate to 1.6mL / min. + Concentration is 180±10mg N / L, NO2 - The concentration is 180±10mg N / L (the ratio of the amount of ammonia nitrogen to nitrite nitrogen in the inlet water is maintained at 0.8-1:1), and the inlet concentration of ammonia nitrogen and nitrite nitrogen in the reactor is kept stable. The reactor is operated in a continuous flow mode, and samples are taken every 2 days to detect NH4 in the inlet and outlet water. + 、NO2 - Content, running continuously for 130 days, the results are as follows Figure 2 As shown; during operation, the denitrification efficiency and denitrification load are calculated, and the results are as follows Figure 3 shown.

[0045] Depend on Figure 2 It can be seen that after 60 to 75 days of acclimatization, the HRT in the first stage was 18 ± 0.5 h, the HRT was reduced to 16 ± 0.5 h, the nitrogen load increased, the nitrogen removal efficiency gradually stabilized at 65-70%, and △ NO2 - With △NH4 + The ratio is stable at 1.20-1.30, close to the theoretical ratio of 1.32 for anaerobic ammonium oxidation reaction, so it can be considered that the anaerobic ammonium oxidizing bacteria have been domesticated. The domestication is completed when the nitrogen removal efficiency in the reactor is maintained at 60-70% in the final stage.

[0046] Depend on Figure 2 It was found that the anaerobic ammonium oxidation sludge in the reactor body can be domesticated by adopting the following two stages:

[0047] Stage 1: Influent NH4 + Concentration is 180±10mg N / L, NO2 -The concentration is 180±10mg N / L, the inlet flow rate is 1.45mL / min, the outlet flow rate is 1.6mL / min, the HRT is 18±0.5h, and the operation time is 40-50 days;

[0048] The second stage water flow rate is 1.45mL / min, the water flow rate is 1.6mL / min, the HRT is 16±0.5h, the operation time is 20-25 days, and the entire acclimatization process is 60-75 days.

[0049] S3. After the acclimation is completed, the influent concentration of ammonia nitrogen and nitrite nitrogen in the reactor is kept stable, and an electric field is applied to the reactor through the electrode pair. The voltage is controlled by a DC voltage regulator. The anode electrode is the working electrode, and the cathode electrode is the counter electrode. The continuous flow mode is adopted. The voltage intensity is increased in sequence during the operation time. In the first stage, the voltage of the DC voltage regulator is controlled to be 0.3±0.05V, and the voltage of the DC voltage regulator is increased to 0.6±0.05V and 1±0.05V in sequence. Specifically, the electric field is applied to the reactor in the following order to denitrify the wastewater in the reactor:

[0050] S31. Control the DC regulated power supply voltage to 0.3±0.05V, and the operation time is 20 to 25 days;

[0051] S32. Control the DC regulated power supply voltage to 0.6±0.05V, and the operation time to 30-35 days;

[0052] S33. Control the DC regulated power supply voltage to 1±0.05V, and the operating time is 20 to 25 days.

[0053] After 70 to 85 days of operation, the effluent was tested and the results showed that NH4 + Content is 25±5mg N / L, NO2 - The content is <5mg N / L, which meets the secondary sewage discharge requirements of GB 18918-2002 "Pollutant Discharge Standards for Urban Sewage Treatment Plants".

[0054] The principle of using electrodes is that the anaerobic ammonium oxidation process will use electrodes to consume ammonia nitrogen in an environment lacking nitrite. The anaerobic ammonium oxidation process will use nitrite and ammonia nitrogen, and the theoretical reaction ratio is 1.32. In fact, there is competition with nitrite in the reactor, so there will be some ammonia nitrogen remaining. By applying electrodes and gradually increasing the electric field strength, on the one hand, the sludge can be domesticated to adapt to the electrode effect, and on the other hand, the appropriate electrode effect can be used to achieve further removal of ammonia nitrogen, thereby achieving the problem of stable denitrification in the anaerobic ammonium oxidation process.

[0055] When used, nitrogen-containing wastewater enters the anaerobic ammonium oxidation reaction zone. Under the action of a suitable electric field, when the nitrite content in the reaction process is low, the electrode reacts with ammonia nitrogen under the action of anaerobic ammonium oxidizing bacteria. The suitable electric field strength is around 1±0.05V, ensuring the stable operation of the anaerobic ammonium oxidation process.

Claims

1. A method for denitrification by anaerobic ammonium oxidation biological reaction with electric field enhancement and membrane separation, comprising the following steps: S1. Inoculating anaerobic ammonium oxidation sludge into the reactor and injecting wastewater: the reactor includes a reactor body, a membrane assembly, an electrode pair and a stirrer are installed in the body, the electrode pair is connected to a DC regulated power supply outside the body, and the wastewater enters the reactor for treatment and is discharged through the outlet pipe of the membrane assembly; S2. Domestication of anaerobic ammonium oxidation sludge: When the wastewater enters the water, the ratio of ammonia nitrogen to nitrite nitrogen is controlled to be 0.8-1:1, and the continuous operation is adopted, and the hydraulic retention time is gradually shortened until the anaerobic ammonium oxidation reaction ratio is 1.20-1.35, and the domestication is completed; S3. Apply an electric field to the reactor in the following order to denitrify the wastewater in the reactor: S31. Control the DC regulated power supply voltage to 0.3±0.05V, and the operation time is 20 to 25 days; S32. Control the DC regulated power supply voltage to 0.6±0.05V, and the operating time to 30-35 days; S33. Control the DC regulated power supply voltage to 1±0.05V, and the operating time is 20 to 25 days.

2. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 1 is characterized in that: In step S2, when the concentrations of ammonia nitrogen and nitrite nitrogen in the wastewater are both between 100 and 1000 mg / L, the anaerobic ammonium oxidation sludge is domesticated in the following two stages: Phase 1: Control the water retention time to 18±0.5h and the operation time to 40-50 days; In the second stage, the water retention time is controlled to 16±0.5h and the operation time is 20 to 25 days.

3. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 1 or 2 is characterized in that: In step S1, when the anaerobic ammonium oxidation sludge is inoculated into the reactor, the inoculation amount of the anaerobic ammonium oxidation sludge is 30-40% of the volume of the reactor.

4. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 1 or 2, characterized in that: In step S1, the electrode pair includes a working electrode and a counter electrode, which are respectively connected to the positive electrode and the negative electrode of a DC regulated power supply.

5. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 4 is characterized in that: The working electrode is graphite carbon felt, and the counter electrode is a titanium electrode.

6. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 1 or 2, characterized in that: In step S1, a hollow fiber membrane is used as a filter membrane in the membrane assembly.

7. The anaerobic ammonium oxidation biological reaction denitrification method with electric field enhancement and membrane separation according to claim 1 or 2 is characterized in that: In step S2, the molar ratio of ammonia nitrogen to nitrite nitrogen is controlled to be 1:1 when the wastewater enters.

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